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Shridas P, Ji A, Trumbauer AC, Noffsinger VP, Meredith LW, de Beer FC, Mullick AE, Webb NR, Karounos DG, Tannock LR. Antisense oligonucleotide targeting hepatic Serum Amyloid A limits the progression of angiotensin II-induced abdominal aortic aneurysm formation. Atherosclerosis 2024; 391:117492. [PMID: 38461759 PMCID: PMC11006562 DOI: 10.1016/j.atherosclerosis.2024.117492] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Revised: 02/07/2024] [Accepted: 02/23/2024] [Indexed: 03/12/2024]
Abstract
BACKGROUND AND AIMS Obesity increases the risk for abdominal aortic aneurysms (AAA) in humans and enhances angiotensin II (AngII)-induced AAA formation in C57BL/6 mice. We reported that deficiency of Serum Amyloid A (SAA) significantly reduces AngII-induced inflammation and AAA in both hyperlipidemic apoE-deficient and obese C57BL/6 mice. The aim of this study is to investigate whether SAA plays a role in the progression of early AAA in obese C57BL/6 mice. METHODS Male C57BL/6J mice were fed a high-fat diet (60% kcal as fat) throughout the study. After 4 months of diet, the mice were infused with AngII until the end of the study. Mice with at least a 25% increase in the luminal diameter of the abdominal aorta after 4 weeks of AngII infusion were stratified into 2 groups. The first group received a control antisense oligonucleotide (Ctr ASO), and the second group received ASO that suppresses SAA (SAA-ASO) until the end of the study. RESULTS Plasma SAA levels were significantly reduced by the SAA ASO treatment. While mice that received the control ASO had continued aortic dilation throughout the AngII infusion periods, the mice that received SAA-ASO had a significant reduction in the progression of aortic dilation, which was associated with significant reductions in matrix metalloprotease activities, decreased macrophage infiltration and decreased elastin breaks in the abdominal aortas. CONCLUSIONS We demonstrate for the first time that suppression of SAA protects obese C57BL/6 mice from the progression of AngII-induced AAA. Suppression of SAA may be a therapeutic approach to limit AAA progression.
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Affiliation(s)
- Preetha Shridas
- Department of Internal Medicine, University of Kentucky, Lexington, 40536, Kentucky, USA; Saha Cardiovascular Research Center, University of Kentucky, Lexington, 40536, Kentucky, USA.
| | - Ailing Ji
- Saha Cardiovascular Research Center, University of Kentucky, Lexington, 40536, Kentucky, USA
| | - Andrea C Trumbauer
- Saha Cardiovascular Research Center, University of Kentucky, Lexington, 40536, Kentucky, USA
| | - Victoria P Noffsinger
- Saha Cardiovascular Research Center, University of Kentucky, Lexington, 40536, Kentucky, USA
| | - Luke W Meredith
- Saha Cardiovascular Research Center, University of Kentucky, Lexington, 40536, Kentucky, USA
| | - Frederick C de Beer
- Department of Internal Medicine, University of Kentucky, Lexington, 40536, Kentucky, USA; Saha Cardiovascular Research Center, University of Kentucky, Lexington, 40536, Kentucky, USA
| | | | - Nancy R Webb
- Saha Cardiovascular Research Center, University of Kentucky, Lexington, 40536, Kentucky, USA; Pharmacology and Nutritional Sciences, University of Kentucky, Lexington, 40536, Kentucky, USA
| | - Dennis G Karounos
- Department of Internal Medicine, University of Kentucky, Lexington, 40536, Kentucky, USA; Pharmacology and Nutritional Sciences, University of Kentucky, Lexington, 40536, Kentucky, USA; Department of Veterans Affairs, Lexington, 40536, Kentucky, USA
| | - Lisa R Tannock
- Department of Internal Medicine, University of Kentucky, Lexington, 40536, Kentucky, USA; Saha Cardiovascular Research Center, University of Kentucky, Lexington, 40536, Kentucky, USA
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Ji A, Trumbauer AC, Noffsinger VP, Meredith LW, Dong B, Wang Q, Guo L, Li X, De Beer FC, Webb NR, Tannock LR, Starr ME, Waters CM, Shridas P. Deficiency of Acute-Phase Serum Amyloid A Exacerbates Sepsis-Induced Mortality and Lung Injury in Mice. Int J Mol Sci 2023; 24:17501. [PMID: 38139330 PMCID: PMC10744229 DOI: 10.3390/ijms242417501] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2023] [Revised: 12/11/2023] [Accepted: 12/13/2023] [Indexed: 12/24/2023] Open
Abstract
Serum amyloid A (SAA) is a family of proteins, the plasma levels of which may increase >1000-fold in acute inflammatory states. We investigated the role of SAA in sepsis using mice deficient in all three acute-phase SAA isoforms (SAA-TKO). SAA deficiency significantly increased mortality rates in the three experimental sepsis mouse models: cecal ligation and puncture (CLP), cecal slurry (CS) injection, and lipopolysaccharide (LPS) treatments. SAA-TKO mice had exacerbated lung pathology compared to wild-type (WT) mice after CLP. A bulk RNA sequencing performed on lung tissues excised 24 h after CLP indicated significant enrichment in the expression of genes associated with chemokine production, chemokine and cytokine-mediated signaling, neutrophil chemotaxis, and neutrophil migration in SAA-TKO compared to WT mice. Consistently, myeloperoxidase activity and neutrophil counts were significantly increased in the lungs of septic SAA-TKO mice compared to WT mice. The in vitro treatment of HL-60, neutrophil-like cells, with SAA or SAA bound to a high-density lipoprotein (SAA-HDL), significantly decreased cellular transmigration through laminin-coated membranes compared to untreated cells. Thus, SAA potentially prevents neutrophil transmigration into injured lungs, thus reducing exacerbated tissue injury and mortality. In conclusion, we demonstrate for the first time that endogenous SAA plays a protective role in sepsis, including ameliorating lung injury.
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Affiliation(s)
- Ailing Ji
- Saha Cardiovascular Research Center, University of Kentucky, Lexington, KY 40536, USA; (A.J.); (A.C.T.); (V.P.N.); (L.W.M.); (Q.W.); (L.G.); (X.L.); (N.R.W.); (L.R.T.)
| | - Andrea C. Trumbauer
- Saha Cardiovascular Research Center, University of Kentucky, Lexington, KY 40536, USA; (A.J.); (A.C.T.); (V.P.N.); (L.W.M.); (Q.W.); (L.G.); (X.L.); (N.R.W.); (L.R.T.)
| | - Victoria P. Noffsinger
- Saha Cardiovascular Research Center, University of Kentucky, Lexington, KY 40536, USA; (A.J.); (A.C.T.); (V.P.N.); (L.W.M.); (Q.W.); (L.G.); (X.L.); (N.R.W.); (L.R.T.)
| | - Luke W. Meredith
- Saha Cardiovascular Research Center, University of Kentucky, Lexington, KY 40536, USA; (A.J.); (A.C.T.); (V.P.N.); (L.W.M.); (Q.W.); (L.G.); (X.L.); (N.R.W.); (L.R.T.)
| | - Brittany Dong
- Department of Physiology, University of Kentucky, Lexington, KY 40536, USA; (B.D.); (C.M.W.)
| | - Qian Wang
- Saha Cardiovascular Research Center, University of Kentucky, Lexington, KY 40536, USA; (A.J.); (A.C.T.); (V.P.N.); (L.W.M.); (Q.W.); (L.G.); (X.L.); (N.R.W.); (L.R.T.)
| | - Ling Guo
- Saha Cardiovascular Research Center, University of Kentucky, Lexington, KY 40536, USA; (A.J.); (A.C.T.); (V.P.N.); (L.W.M.); (Q.W.); (L.G.); (X.L.); (N.R.W.); (L.R.T.)
| | - Xiangan Li
- Saha Cardiovascular Research Center, University of Kentucky, Lexington, KY 40536, USA; (A.J.); (A.C.T.); (V.P.N.); (L.W.M.); (Q.W.); (L.G.); (X.L.); (N.R.W.); (L.R.T.)
- Department of Physiology, University of Kentucky, Lexington, KY 40536, USA; (B.D.); (C.M.W.)
- Pharmacology and Nutritional Sciences, University of Kentucky, Lexington, KY 40536, USA;
| | - Frederick C. De Beer
- Department of Internal Medicine, University of Kentucky, Lexington, KY 40536, USA;
| | - Nancy R. Webb
- Saha Cardiovascular Research Center, University of Kentucky, Lexington, KY 40536, USA; (A.J.); (A.C.T.); (V.P.N.); (L.W.M.); (Q.W.); (L.G.); (X.L.); (N.R.W.); (L.R.T.)
- Pharmacology and Nutritional Sciences, University of Kentucky, Lexington, KY 40536, USA;
| | - Lisa R. Tannock
- Saha Cardiovascular Research Center, University of Kentucky, Lexington, KY 40536, USA; (A.J.); (A.C.T.); (V.P.N.); (L.W.M.); (Q.W.); (L.G.); (X.L.); (N.R.W.); (L.R.T.)
- Department of Internal Medicine, University of Kentucky, Lexington, KY 40536, USA;
| | - Marlene E. Starr
- Pharmacology and Nutritional Sciences, University of Kentucky, Lexington, KY 40536, USA;
- Department of Surgery, College of Medicine, University of Kentucky, Lexington, KY 40536, USA
| | - Christopher M. Waters
- Department of Physiology, University of Kentucky, Lexington, KY 40536, USA; (B.D.); (C.M.W.)
| | - Preetha Shridas
- Saha Cardiovascular Research Center, University of Kentucky, Lexington, KY 40536, USA; (A.J.); (A.C.T.); (V.P.N.); (L.W.M.); (Q.W.); (L.G.); (X.L.); (N.R.W.); (L.R.T.)
- Department of Internal Medicine, University of Kentucky, Lexington, KY 40536, USA;
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Shridas P, Ji A, Trumbauer AC, Noffsinger VP, Meredith LW, de Beer FC, Mullick AE, Webb NR, Karounos DG, Tannock LR. Antisense Oligonucleotide Targeting Hepatic Serum Amyloid A Limits the Progression of Angiotensin II-Induced Abdominal Aortic Aneurysm Formation. bioRxiv 2023:2023.08.22.554377. [PMID: 37662383 PMCID: PMC10473661 DOI: 10.1101/2023.08.22.554377] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/05/2023]
Abstract
OBJECTIVE Obesity increases the risk for abdominal aortic aneurysms (AAA) in humans and enhances angiotensin II (AngII)-induced AAA formation in C57BL/6 mice. Obesity is also associated with increases in serum amyloid A (SAA). We previously reported that deficiency of SAA significantly reduces AngII-induced inflammation and AAA in both hyperlipidemic apoE-deficient and obese C57BL/6 mice. In this study, we investigated whether SAA plays a role in the progression of early AAA in obese C57BL/6 mice. APPROACH AND RESULTS Male C57BL/6J mice were fed a high-fat diet (60% kcal as fat) throughout the study. After 4 months of diet, the mice were infused with angiotensin II (AngII) until the end of the study. Mice with at least a 25% increase in the luminal diameter of the abdominal aorta after 4 weeks of AngII infusion were stratified into 2 groups. The first group received a control antisense oligonucleotide (Ctr ASO), and the second group received ASO that suppresses SAA (SAA-ASO) until the end of the study. Plasma SAA levels were significantly reduced by the SAA ASO treatment. While mice that received the control ASO had continued aortic dilation throughout the AngII infusion periods, the mice that received SAA-ASO had a significant reduction in the progression of aortic dilation, which was associated with significant reductions in matrix metalloprotease activities, decreased macrophage infiltration and decreased elastin breaks in the abdominal aortas. CONCLUSION We demonstrate for the first time that suppression of SAA protects obese C57BL/6 mice from the progression of AngII-induced AAA. Suppression of SAA may be a therapeutic approach to limit AAA progression.
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Ji A, Trumbauer AC, Noffsinger VP, de Beer FC, Webb NR, Tannock LR, Shridas P. Serum Amyloid A augments the atherogenic effects of Cholesteryl Ester Transfer Protein. J Lipid Res 2023; 64:100365. [PMID: 37004910 PMCID: PMC10165456 DOI: 10.1016/j.jlr.2023.100365] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2023] [Revised: 03/24/2023] [Accepted: 03/27/2023] [Indexed: 04/03/2023] Open
Abstract
Serum Amyloid A (SAA) is predictive of cardiovascular disease (CVD) in humans and causes atherosclerosis in mice. SAA has many pro-atherogenic effects in vitro. However, HDL, the major carrier of SAA in the circulation, masks these effects. The remodeling of HDL by CETP liberates SAA restoring its pro-inflammatory activity. Here, we investigated whether deficiency of SAA suppresses the previously described pro-atherogenic effect of Cholesteryl Ester Transfer Protein (CETP). ApoE-/- mice and apoE-/- mice deficient in the three acute-phase isoforms of SAA (SAA1.1, SAA2.1, and SAA3; "apoE-/- SAA-TKO") with and without AAV-mediated expression of CETP were studied. There was no effect of CETP expression or SAA genotype on plasma lipids or inflammatory markers. Atherosclerotic lesion area in the aortic arch of apoE-/- mice was 5.9 ± 1.2%, CETP expression significantly increased atherosclerosis in apoE-/- mice (13.1 ± 2.2%). However, atherosclerotic lesion area in the aortic arch of apoE-/- SAA-TKO mice (5.1±1.1%) was not significantly increased by CETP expression (6.2 ± 0.9%). The increased atherosclerosis in apoE-/- mice expressing CETP was associated with markedly increased SAA immunostaining in aortic root sections. Thus, SAA augments the atherogenic effects of CETP, which suggests that inhibiting CETP may be of particular benefit in patients with high SAA.
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Affiliation(s)
- Ailing Ji
- Barnstable Brown Diabetes Center, University of Kentucky, Lexington, KY, USA; Saha Cardiovascular Research Center, University of Kentucky, Lexington, KY, USA
| | - Andrea C Trumbauer
- Barnstable Brown Diabetes Center, University of Kentucky, Lexington, KY, USA; Saha Cardiovascular Research Center, University of Kentucky, Lexington, KY, USA
| | - Victoria P Noffsinger
- Barnstable Brown Diabetes Center, University of Kentucky, Lexington, KY, USA; Saha Cardiovascular Research Center, University of Kentucky, Lexington, KY, USA
| | - Frederick C de Beer
- Barnstable Brown Diabetes Center, University of Kentucky, Lexington, KY, USA; Saha Cardiovascular Research Center, University of Kentucky, Lexington, KY, USA; Department of Internal Medicine, University of Kentucky, Lexington, KY, USA
| | - Nancy R Webb
- Barnstable Brown Diabetes Center, University of Kentucky, Lexington, KY, USA; Saha Cardiovascular Research Center, University of Kentucky, Lexington, KY, USA; Department of Pharmacology and Nutritional Sciences, University of Kentucky, Lexington, KY, USA
| | - Lisa R Tannock
- Barnstable Brown Diabetes Center, University of Kentucky, Lexington, KY, USA; Saha Cardiovascular Research Center, University of Kentucky, Lexington, KY, USA; Department of Internal Medicine, University of Kentucky, Lexington, KY, USA; Lexington Veterans Affairs Medical Center, Lexington, KY, USA
| | - Preetha Shridas
- Barnstable Brown Diabetes Center, University of Kentucky, Lexington, KY, USA; Saha Cardiovascular Research Center, University of Kentucky, Lexington, KY, USA; Department of Internal Medicine, University of Kentucky, Lexington, KY, USA.
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Shridas P, Ji A, Trumbauer AC, Noffsinger VP, Leung SW, Dugan AJ, Thatcher SE, Cassis LA, de Beer FC, Webb NR, Tannock LR. Adipocyte-Derived Serum Amyloid A Promotes Angiotensin II-Induced Abdominal Aortic Aneurysms in Obese C57BL/6J Mice. Arterioscler Thromb Vasc Biol 2022; 42:632-643. [PMID: 35344382 PMCID: PMC9050948 DOI: 10.1161/atvbaha.121.317225] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Obesity increases the risk for human abdominal aortic aneurysms (AAAs) and enhances Ang II (angiotensin II)-induced AAA formation in C57BL/6J mice. Obesity is also associated with increases in perivascular fat that expresses proinflammatory markers including SAA (serum amyloid A). We previously reported that deficiency of SAA significantly reduces Ang II-induced inflammation and AAA in hyperlipidemic apoE-deficient mice. In this study. we investigated whether adipose tissue-derived SAA plays a role in Ang II-induced AAA in obese C57BL/6J mice. METHODS The development of AAA was compared between male C57BL/6J mice (wild type), C57BL/6J mice lacking SAA1.1, SAA2.1, and SAA3 (TKO); and TKO mice harboring a doxycycline-inducible, adipocyte-specific SAA1.1 transgene (TKO-Tgfat; SAA expressed only in fat). All mice were fed an obesogenic diet and doxycycline to induce SAA transgene expression and infused with Ang II to induce AAA. RESULTS In response to Ang II infusion, SAA expression was significantly increased in perivascular fat of obese C57BL/6J mice. Maximal luminal diameters of the abdominal aorta were determined by ultrasound before and after Ang II infusion, which indicated a significant increase in aortic luminal diameters in wild type and TKO-TGfat mice but not in TKO mice. Adipocyte-specific SAA expression was associated with MMP (matrix metalloproteinase) activity and macrophage infiltration in abdominal aortas of Ang II-infused obese mice. CONCLUSIONS We demonstrate for the first time that SAA deficiency protects obese C57BL/6J mice from Ang II-induced AAA. SAA expression only in adipocytes is sufficient to cause AAA in obese mice infused with Ang II.
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Affiliation(s)
- Preetha Shridas
- Departments of Internal Medicine (P.S., A.J., V.P.N., S.W.L., F.C.d.B., L.R.T.), University of Kentucky, Lexington
- Saha Cardiovascular Research Center (P.S., A.C.T., S.W.L., F.C.d.B., N.R.W., L.R.T.), University of Kentucky, Lexington
- Barnstable Brown Diabetes Center (P.S., F.C.d.B., N.R.W., L.R.T.), University of Kentucky, Lexington
| | - Ailing Ji
- Departments of Internal Medicine (P.S., A.J., V.P.N., S.W.L., F.C.d.B., L.R.T.), University of Kentucky, Lexington
| | - Andrea C Trumbauer
- Saha Cardiovascular Research Center (P.S., A.C.T., S.W.L., F.C.d.B., N.R.W., L.R.T.), University of Kentucky, Lexington
| | - Victoria P Noffsinger
- Departments of Internal Medicine (P.S., A.J., V.P.N., S.W.L., F.C.d.B., L.R.T.), University of Kentucky, Lexington
| | - Steve W Leung
- Departments of Internal Medicine (P.S., A.J., V.P.N., S.W.L., F.C.d.B., L.R.T.), University of Kentucky, Lexington
- Saha Cardiovascular Research Center (P.S., A.C.T., S.W.L., F.C.d.B., N.R.W., L.R.T.), University of Kentucky, Lexington
| | - Adam J Dugan
- Biostatistics (A.J.D.), University of Kentucky, Lexington
| | - Sean E Thatcher
- Department of Pharmacology, Temple University, Philadelphia, PA (S.E.T.)
| | - Lisa A Cassis
- Pharmacology and Nutritional Sciences (L.A.C., N.R.W.), University of Kentucky, Lexington
| | - Frederick C de Beer
- Departments of Internal Medicine (P.S., A.J., V.P.N., S.W.L., F.C.d.B., L.R.T.), University of Kentucky, Lexington
- Saha Cardiovascular Research Center (P.S., A.C.T., S.W.L., F.C.d.B., N.R.W., L.R.T.), University of Kentucky, Lexington
- Barnstable Brown Diabetes Center (P.S., F.C.d.B., N.R.W., L.R.T.), University of Kentucky, Lexington
| | - Nancy R Webb
- Pharmacology and Nutritional Sciences (L.A.C., N.R.W.), University of Kentucky, Lexington
- Saha Cardiovascular Research Center (P.S., A.C.T., S.W.L., F.C.d.B., N.R.W., L.R.T.), University of Kentucky, Lexington
- Barnstable Brown Diabetes Center (P.S., F.C.d.B., N.R.W., L.R.T.), University of Kentucky, Lexington
| | - Lisa R Tannock
- Departments of Internal Medicine (P.S., A.J., V.P.N., S.W.L., F.C.d.B., L.R.T.), University of Kentucky, Lexington
- Saha Cardiovascular Research Center (P.S., A.C.T., S.W.L., F.C.d.B., N.R.W., L.R.T.), University of Kentucky, Lexington
- Barnstable Brown Diabetes Center (P.S., F.C.d.B., N.R.W., L.R.T.), University of Kentucky, Lexington
- Department of Veterans Affairs, Lexington, KY (L.R.T.)
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Ji A, Trumbauer A, Noffsinger V, Guo L, Wang Q, Li XA, Debeer FC, Webb N, Tannock LR, Starr M, Waters C, Shridas P. Abstract 447: Deficiency Of Serum Amyloid A Exacerbates Sepsis-induced Acute Lung Injury In Mice. Arterioscler Thromb Vasc Biol 2022. [DOI: 10.1161/atvb.42.suppl_1.447] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
Abstract
Objectives:
Serum Amyloid A (SAA) is a family of proteins whose plasma levels increase > 1000-fold in acute inflammatory states such as sepsis. We and others have demonstrated that SAA plays a causal role in mouse models of atherosclerosis. However, SAA may not be a valid therapeutic target if it is needed for host defense in inflammation. Here, we investigated the role of SAA in sepsis using mice deficient in all three acute-phase SAA isoforms (TKO).
Approach and results:
SAA deficiency significantly increased mortality rates in three experimental sepsis models. Survival rates in TKO and wild-type (WT) mice were: 25% and 55% after cecal ligation and puncture (CLP; p=0.02; n=10 each strain/gender); 0% and 45% after cecal slurry injection (p<0.0001; n=9 each strain); and 55% and 90 % after lipopolysaccharide injection (p<0.0001; n=10 each strain/gender). 24-hours after CLP, there were no apparent differences in liver, heart or kidney histology between genotypes. However, TKO mice had exacerbated lung pathology, including consolidation of lung tissues and atelectasis, compared to WT mice. RNAseq analysis of lungs excised 24-hours after CLP identified 664 genes differentially expressed (404 upregulated and 260 downregulated) in TKO compared to WT (p<0.05). Some of the genes that showed profound induction in the lungs of TKO compared to the WT were
Proz, Dbp, Cxcl1, Cxcl2, Arg1
and
Ackr1
. Gene ontology analysis revealed a significant enrichment of differentially expressed genes associated with chemokine production, chemokine and cytokine-mediated signaling, neutrophil chemotaxis and neutrophil migration in TKO lung tissues compared to WT tissues (p<0.01).
Conclusions:
SAA protects mice against sepsis-induced mortality, potentially by protecting the lung from tissue damage. Thus, the risk of infection should be considered when targeting SAA to ameliorate atherosclerosis.
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Affiliation(s)
| | | | | | | | | | - Xiang-An Li
- UNIVERSITY KENTUCKY SAHA CRVC, Lexington, KY
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Shridas P, Patrick AC, Tannock LR. Role of Serum Amyloid A in Abdominal Aortic Aneurysm and Related Cardiovascular Diseases. Biomolecules 2021; 11:biom11121883. [PMID: 34944527 PMCID: PMC8699432 DOI: 10.3390/biom11121883] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Revised: 12/07/2021] [Accepted: 12/13/2021] [Indexed: 01/02/2023] Open
Abstract
Epidemiological data positively correlate plasma serum amyloid A (SAA) levels with cardiovascular disease severity and mortality. Studies by several investigators have indicated a causal role for SAA in the development of atherosclerosis in animal models. Suppression of SAA attenuates the development of angiotensin II (AngII)-induced abdominal aortic aneurysm (AAA) formation in mice. Thus, SAA is not just a marker for cardiovascular disease (CVD) development, but it is a key player. However, to consider SAA as a therapeutic target for these diseases, the pathway leading to its involvement needs to be understood. This review provides a brief description of the pathobiological significance of this enigmatic molecule. The purpose of this review is to summarize the data relevant to its role in the development of CVD, the pitfalls in SAA research, and unanswered questions in the field.
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Affiliation(s)
- Preetha Shridas
- Department of Internal Medicine, University of Kentucky, Lexington, KY 40536, USA
- Saha Cardiovascular Research Center, University of Kentucky, Lexington, KY 40536, USA
- Barnstable Brown Diabetes Center, University of Kentucky, Lexington, KY 40536, USA
| | - Avery C Patrick
- Pharmacology and Nutritional Sciences, University of Kentucky, Lexington, KY 40536, USA
| | - Lisa R Tannock
- Department of Internal Medicine, University of Kentucky, Lexington, KY 40536, USA
- Saha Cardiovascular Research Center, University of Kentucky, Lexington, KY 40536, USA
- Barnstable Brown Diabetes Center, University of Kentucky, Lexington, KY 40536, USA
- Veterans Affairs Lexington, University of Kentucky, Lexington, KY 40536, USA
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Trumbauer A, Noffsinger V, Ji A, DEBEER FC, Dugan A, Mullick AE, Webb NR, Shridas P, Tannock LR. Abstract P101: Suppression Of Serum Amyloid A Limits Progression Of Obesity Associated Abdominal Aortic Aneurysms. Arterioscler Thromb Vasc Biol 2021. [DOI: 10.1161/atvb.41.suppl_1.p101] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Obesity increases the risk for abdominal aortic aneurysms (AAA) in humans, and enhances angiotensin II (AngII)-induced AAA formation in C57BL/6 mice. Obesity is also associated with increases in serum amyloid A (SAA). We previously reported that deficiency of SAA significantly reduces AngII-induced inflammation and AAA in apoE-deficient mice. In this study we investigated whether SAA plays a role in progression of an established AAA in obese C57BL/6 mice.
Approach and Results:
Male C57BL/6 mice were fed a high fat diet (60% kcal as fat) throughout the study. After 4 months of diet the mice were infused with angiotensin II (AngII) at 1000ng/kg/min until the end of the study. Ultrasound (US) was performed in all mice before and after 28 days of AngII infusion, and mice that had at least a 25% increase in the luminal diameter of the abdominal aorta were stratified by luminal diameter into 3 groups. Group 1 was killed to establish baseline AAA. Groups 2 and 3 continued to receive AngII for a further 8 weeks along with an antisense oligonucleotide (ASO) that suppresses all 3 acute phase SAA isoforms (SAA-ASO), or a control ASO (5 mg/kg/wk). US was repeated at study end to assess AAA progression. Plasma SAA at the end of the experiment was 89.2±83.2 mg/L in the control ASO group, and 18.6±0.7 mg/L in the SAA-ASO group (mean±SD , p=0.008). There was no impact of SAA suppression on body weight, body fat, or blood pressure. After the first 4 weeks of AngII infusion, the average luminal diameter in all mice was 1.81±0.40 mm (mean±SD). Mice that received the control ASO had continued aortic dilation (average luminal aortic diameter 2.06±0.42 mm), whereas the mice that received the SAA-ASO had a significant reduction in progression of aortic dilation (average luminal diameter 1.64±0.43 mm, p=0.0015 for interaction between time and group).
Conclusions:
We demonstrate for the first time that suppression of SAA protects obese C57BL/6 mice from progression of AngII-induced AAA. Suppression of SAA may be a therapeutic approach to limit AAA progression.
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Davis TA, Conradie D, Shridas P, de Beer FC, Engelbrecht AM, de Villiers WJS. Serum Amyloid A Promotes Inflammation-Associated Damage and Tumorigenesis in a Mouse Model of Colitis-Associated Cancer. Cell Mol Gastroenterol Hepatol 2021; 12:1329-1341. [PMID: 34217896 PMCID: PMC8463861 DOI: 10.1016/j.jcmgh.2021.06.016] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Revised: 06/20/2021] [Accepted: 06/21/2021] [Indexed: 12/20/2022]
Abstract
BACKGROUND & AIMS Identifying new approaches to lessen inflammation, as well as the associated malignant consequences, remains crucial to improving the lives and prognosis of patients diagnosed with inflammatory bowel diseases. Although it previously has been suggested as a suitable biomarker for monitoring disease activity in patients diagnosed with Crohn's disease, the role of the acute-phase protein serum amyloid A (SAA) in inflammatory bowel disease remains unclear. In this study, we aimed to assess the role of SAA in colitis-associated cancer. METHODS We established a model of colitis-associated cancer in wild-type and SAA double-knockout (Saa1/2-/-) mice by following the azoxymethane/dextran sulfate sodium protocol. Disease activity was monitored throughout the study while colon and tumor tissues were harvested for subsequent use in cytokine analyses, Western blot, and immunohistochemistry +experiments. RESULTS We observed attenuated disease activity in mice deficient for Saa1/2 as evidenced by decreased weight loss, increased stool consistency, decreased rectal bleeding, and decreased colitis-associated tissue damage. Macrophage infiltration, including CD206+ M2-like macrophages, also was attenuated in SAA knockout mice, while levels of interleukin 4, interleukin 10, and tumor necrosis factor-ɑ were decreased in the distal colon. Mice deficient for SAA also showed a decreased tumor burden, and tumors were found to have increased apoptotic activity coupled with decreased expression for markers of proliferation. CONCLUSION Based on these findings, we conclude that SAA has an active role in inflammatory bowel disease and that it could serve as a therapeutic target aimed at decreasing chronic inflammation and the associated risk of developing colitis-associated cancer.
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Affiliation(s)
| | | | - Preetha Shridas
- Department of Internal Medicine, University of Kentucky, Lexington, Kentucky
| | - Frederick C de Beer
- Department of Internal Medicine, University of Kentucky, Lexington, Kentucky
| | - Anna-Mart Engelbrecht
- Department of Physiological Sciences; African Cancer Institute, Department of Global Health
| | - Willem J S de Villiers
- African Cancer Institute, Department of Global Health; Department of Internal Medicine, Stellenbosch University, Stellenbosch, South Africa.
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10
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Fourie C, Shridas P, Davis T, de Villiers WJ, Engelbrecht AM. Serum amyloid A and inflammasome activation: A link to breast cancer progression? Cytokine Growth Factor Rev 2021; 59:62-70. [DOI: 10.1016/j.cytogfr.2020.10.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Revised: 10/16/2020] [Accepted: 10/20/2020] [Indexed: 12/13/2022]
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11
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Abstract
PURPOSE OF REVIEW Acute phase serum amyloid A (SAA) is persistently elevated in chronic inflammatory conditions, and elevated levels predict cardiovascular risk in humans. More recently, murine studies have demonstrated that over-expression of SAA increases and deficiency/suppression of SAA attenuates atherosclerosis. Thus, beyond being a biomarker, SAA appears to play a causal role in atherogenesis. The purpose of this review is to summarize the data supporting SAA as a key player in atherosclerosis development. RECENT FINDINGS A number of pro-inflammatory and pro-atherogenic activities have been ascribed to SAA. However, the literature is conflicted, as recombinant SAA, and/or lipid-free SAA, used in many of the earlier studies, do not reflect the activity of native human or murine SAA, which exists largely lipid-associated. Recent literatures demonstrate that SAA activates the NLRP3 inflammasome, alters vascular function, affects HDL function, and increases thrombosis. Importantly, SAA activity appears to be regulated by its lipid association, and HDL may serve to sequester and limit SAA activity. SUMMARY SAA has many pro-inflammatory and pro-atherogenic activities, is clearly demonstrated to affect atherosclerosis development, and may be a candidate target for clinical trials in cardiovascular diseases.
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Affiliation(s)
- Preetha Shridas
- Department of Internal Medicine
- Saha Cardiovascular Research Center
- Barnstable Brown Diabetes Center and University of Kentucky
| | - Lisa R Tannock
- Department of Internal Medicine
- Saha Cardiovascular Research Center
- Barnstable Brown Diabetes Center and University of Kentucky
- Veterans Affairs Lexington, Lexington, Kentucky, USA
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12
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Wilson PG, Thompson JC, Shridas P, McNamara PJ, de Beer MC, de Beer FC, Webb NR, Tannock LR. Serum Amyloid A Is an Exchangeable Apolipoprotein. Arterioscler Thromb Vasc Biol 2018; 38:1890-1900. [PMID: 29976766 PMCID: PMC6202200 DOI: 10.1161/atvbaha.118.310979] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Objective- SAA (serum amyloid A) is a family of acute-phase reactants that have proinflammatory and proatherogenic activities. SAA is more lipophilic than apoA-I (apolipoprotein A-I), and during an acute-phase response, <10% of plasma SAA is found lipid-free. In most reports, SAA is found exclusively associated with high-density lipoprotein; however, we and others have reported SAA on apoB (apolipoprotein B)-containing lipoproteins in both mice and humans. The goal of this study was to determine whether SAA is an exchangeable apolipoprotein. Approach and Results- Delipidated human SAA was incubated with SAA-free human lipoproteins; then, samples were reisolated by fast protein liquid chromatography, and SAA analyzed by ELISA and immunoblot. Both in vitro and in vivo, we show that SAA associates with any lipoprotein and does not remain in a lipid-free form. Although SAA is preferentially found on high-density lipoprotein, it can exchange between lipoproteins. In the presence of CETP (cholesterol ester transfer protein), there is greater exchange of SAA between lipoproteins. Subjects with diabetes mellitus, but not those with metabolic syndrome, showed altered SAA lipoprotein distribution postprandially. Proteoglycan-mediated lipoprotein retention is thought to be an underlying mechanism for atherosclerosis development. SAA has a proteoglycan-binding domain. Lipoproteins containing SAA had increased proteoglycan binding compared with SAA-free lipoproteins. Conclusions- Thus, SAA is an exchangeable apolipoprotein and increases apoB-containing lipoproteins' proteoglycan binding. We and others have previously reported the presence of SAA on low-density lipoprotein in individuals with obesity, diabetes mellitus, and metabolic syndrome. We propose that the presence of SAA on apoB-containing lipoproteins may contribute to cardiovascular disease development in these populations.
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Affiliation(s)
- Patricia G Wilson
- Department of Veterans Affairs, Lexington, KY
- Saha Cardiovascular Research Center, College of Medicine, University of Kentucky
- Barnstable Brown Diabetes Center, College of Medicine, University of Kentucky
| | - Joel C Thompson
- Department of Veterans Affairs, Lexington, KY
- Saha Cardiovascular Research Center, College of Medicine, University of Kentucky
- Barnstable Brown Diabetes Center, College of Medicine, University of Kentucky
| | - Preetha Shridas
- Department of Internal Medicine, College of Medicine, University of Kentucky
- Saha Cardiovascular Research Center, College of Medicine, University of Kentucky
- Barnstable Brown Diabetes Center, College of Medicine, University of Kentucky
| | - Patrick J McNamara
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky
| | - Maria C de Beer
- Department of Physiology, College of Medicine, University of Kentucky
- Saha Cardiovascular Research Center, College of Medicine, University of Kentucky
- Barnstable Brown Diabetes Center, College of Medicine, University of Kentucky
| | - Frederick C de Beer
- Department of Internal Medicine, College of Medicine, University of Kentucky
- Saha Cardiovascular Research Center, College of Medicine, University of Kentucky
- Barnstable Brown Diabetes Center, College of Medicine, University of Kentucky
| | - Nancy R Webb
- Department of Veterans Affairs, Lexington, KY
- Department of Pharmacology and Nutritional Sciences, College of Medicine, University of Kentucky
- Saha Cardiovascular Research Center, College of Medicine, University of Kentucky
- Barnstable Brown Diabetes Center, College of Medicine, University of Kentucky
| | - Lisa R Tannock
- Department of Veterans Affairs, Lexington, KY
- Department of Internal Medicine, College of Medicine, University of Kentucky
- Saha Cardiovascular Research Center, College of Medicine, University of Kentucky
- Barnstable Brown Diabetes Center, College of Medicine, University of Kentucky
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13
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Shridas P, De Beer MC, Webb NR. High-density lipoprotein inhibits serum amyloid A-mediated reactive oxygen species generation and NLRP3 inflammasome activation. J Biol Chem 2018; 293:13257-13269. [PMID: 29976759 DOI: 10.1074/jbc.ra118.002428] [Citation(s) in RCA: 56] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2018] [Revised: 06/18/2018] [Indexed: 12/11/2022] Open
Abstract
Serum amyloid A (SAA) is a high-density apolipoprotein whose plasma levels can increase more than 1000-fold during a severe acute-phase inflammatory response and are more modestly elevated in chronic inflammation. SAA is thought to play important roles in innate immunity, but its biological activities have not been completely delineated. We previously reported that SAA deficiency protects mice from developing abdominal aortic aneurysms (AAAs) induced by chronic angiotensin II (AngII) infusion. Here, we report that SAA is required for AngII-induced increases in interleukin-1β (IL-1β), a potent proinflammatory cytokine that is tightly controlled by the Nod-like receptor protein 3 (NLRP3) inflammasome and caspase-1 and has been implicated in both human and mouse AAAs. We determined that purified SAA stimulates IL-1β secretion in murine J774 and bone marrow-derived macrophages through a mechanism that depends on NLRP3 expression and caspase-1 activity, but is independent of P2X7 nucleotide receptor (P2X7R) activation. Inhibiting reactive oxygen species (ROS) by N-acetyl-l-cysteine or mito-TEMPO and inhibiting activation of cathepsin B by CA-074 blocked SAA-mediated inflammasome activation and IL-1β secretion. Moreover, inhibiting cellular potassium efflux with glyburide or increasing extracellular potassium also significantly reduced SAA-mediated IL-1β secretion. Of note, incorporating SAA into high-density lipoprotein (HDL) prior to its use in cell treatments completely abolished its ability to stimulate ROS generation and inflammasome activation. These results provide detailed insights into SAA-mediated IL-1β production and highlight HDL's role in regulating SAA's proinflammatory effects.
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Affiliation(s)
- Preetha Shridas
- From the Departments of Internal Medicine, .,Barnstable Brown Diabetes Center, University of Kentucky, Lexington, Kentucky 40536
| | - Maria C De Beer
- Barnstable Brown Diabetes Center, University of Kentucky, Lexington, Kentucky 40536.,Physiology, and.,Pharmacology and Nutritional Sciences
| | - Nancy R Webb
- Barnstable Brown Diabetes Center, University of Kentucky, Lexington, Kentucky 40536.,Pharmacology and Nutritional Sciences.,Saha Cardiovascular Research Center, and
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14
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Shridas P, de Beer MC, Webb NR. Abstract 566: High-density Lipoprotein Inhibits Serum Amyloid a -Mediated Inflammasome Activation. Arterioscler Thromb Vasc Biol 2018. [DOI: 10.1161/atvb.38.suppl_1.566] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Objectives:
Interleukin-1beta (IL-1β) has been implicated in inflammatory diseases, including atherosclerosis and abdominal aortic aneurysm (AAA). Production of bioactive IL-1β is controlled by the inflammasome, a multi-protein complex that regulates caspase-1 activity. Serum Amyloid A (SAA) is an acute-phase protein whose levels in circulation is elevated in individuals with chronic inflammation. We previously reported that deficiency of SAA protects mice from angiotensin II (AngII)-induced AAA. Here we report that reduced AngII-induced AAA in SAA-deficient mice is accompanied by significant reductions in plasma IL-1β, indicating that SAA is required for inflammasome activation in AngII-infused mice. The objective of this study is to investigate mechanisms involved in SAA-mediated inflammasome activation.
Methods/Results:
SAA dose-dependently induced both caspase-1 activation and IL-1β secretion in J774 macrophage-like cells incubated with 0-25 μg/ml purified mouse SAA. The ability of SAA to induce IL-1β secretion was significantly reduced in bone marrow-derived macrophages deficient in NLRP3. A caspase-1inhibitor, Z-YVAD-FMK, significantly suppressed IL-1β secretion induced by SAA, whereas the P2X7-receptor antagonist, AA38079, had no effect. Inhibition of reactive oxygen species (ROS), cathepsin-B activation, and cellular potassium efflux by N-acetyl-L-cysteine, CA-074, and glyburide, respectively, blocked NLRP3 inflammasome activation by SAA. Pre-incubating SAA with HDL prior to cell treatments completely abrogated SAA-mediated inflammasome activation. In contrast, HDL did not alter inflammasome activation triggered by ATP.
Conclusions:
SAA-mediated NLRP3 inflammasome activation in macrophages is dependent on ROS generation, release of cathepsin-B, and potassium efflux, and is independent of the P2X7 receptor. Moreover, our data identify a novel mechanism by which HDL may exert cardioprotective effects.
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15
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Thompson JC, Wilson PG, Shridas P, Ji A, de Beer M, de Beer FC, Webb NR, Tannock LR. Serum amyloid A3 is pro-atherogenic. Atherosclerosis 2018; 268:32-35. [PMID: 29175652 PMCID: PMC5839639 DOI: 10.1016/j.atherosclerosis.2017.11.011] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/09/2017] [Revised: 10/24/2017] [Accepted: 11/15/2017] [Indexed: 11/26/2022]
Abstract
BACKGROUND AND AIMS Serum amyloid A (SAA) predicts cardiovascular events. Overexpression of SAA increases atherosclerosis development; however, deficiency of two of the murine acute phase isoforms, SAA1.1 and SAA2.1, has no effect on atherosclerosis. SAA3 is a pseudogene in humans, but is an expressed acute phase isoform in mice. The goal of this study was to determine if SAA3 affects atherosclerosis in mice. METHODS ApoE-/- mice were used as the model for all studies. SAA3 was overexpressed by an adeno-associated virus or suppressed using an anti-sense oligonucleotide approach. RESULTS Over-expression of SAA3 led to a 4-fold increase in atherosclerosis lesion area compared to control mice (p = 0.01). Suppression of SAA3 decreased atherosclerosis in mice genetically deficient in SAA1.1 and SAA2.1 (p < 0.0001). CONCLUSIONS SAA3 augments atherosclerosis in mice. Our results resolve a previous paradox in the literature and support extensive epidemiological data that SAA is pro-atherogenic.
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Affiliation(s)
- Joel C Thompson
- Department of Veterans Affairs, Lexington, KY 40502, USA; Department of Internal Medicine, University of Kentucky, Lexington, KY, 40536, USA; Barnstable Brown Diabetes Center, University of Kentucky, Lexington, KY, 40536, USA; Saha Cardiovascular Research Center, University of Kentucky, Lexington, KY, 40536, USA
| | - Patricia G Wilson
- Department of Veterans Affairs, Lexington, KY 40502, USA; Department of Internal Medicine, University of Kentucky, Lexington, KY, 40536, USA; Barnstable Brown Diabetes Center, University of Kentucky, Lexington, KY, 40536, USA; Saha Cardiovascular Research Center, University of Kentucky, Lexington, KY, 40536, USA
| | - Preetha Shridas
- Department of Internal Medicine, University of Kentucky, Lexington, KY, 40536, USA; Barnstable Brown Diabetes Center, University of Kentucky, Lexington, KY, 40536, USA; Saha Cardiovascular Research Center, University of Kentucky, Lexington, KY, 40536, USA
| | - Ailing Ji
- Department of Veterans Affairs, Lexington, KY 40502, USA; Department of Internal Medicine, University of Kentucky, Lexington, KY, 40536, USA; Barnstable Brown Diabetes Center, University of Kentucky, Lexington, KY, 40536, USA; Saha Cardiovascular Research Center, University of Kentucky, Lexington, KY, 40536, USA
| | - Maria de Beer
- Department of Physiology, University of Kentucky, Lexington, KY, 40536, USA; Barnstable Brown Diabetes Center, University of Kentucky, Lexington, KY, 40536, USA; Saha Cardiovascular Research Center, University of Kentucky, Lexington, KY, 40536, USA
| | - Frederick C de Beer
- Department of Internal Medicine, University of Kentucky, Lexington, KY, 40536, USA; Barnstable Brown Diabetes Center, University of Kentucky, Lexington, KY, 40536, USA; Saha Cardiovascular Research Center, University of Kentucky, Lexington, KY, 40536, USA
| | - Nancy R Webb
- Department of Veterans Affairs, Lexington, KY 40502, USA; Department of Pharmacology and Nutritional Sciences, University of Kentucky, Lexington, KY, 40536, USA; Barnstable Brown Diabetes Center, University of Kentucky, Lexington, KY, 40536, USA; Saha Cardiovascular Research Center, University of Kentucky, Lexington, KY, 40536, USA
| | - Lisa R Tannock
- Department of Veterans Affairs, Lexington, KY 40502, USA; Department of Internal Medicine, University of Kentucky, Lexington, KY, 40536, USA; Barnstable Brown Diabetes Center, University of Kentucky, Lexington, KY, 40536, USA; Saha Cardiovascular Research Center, University of Kentucky, Lexington, KY, 40536, USA.
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16
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Tannock LR, De Beer MC, Ji A, Shridas P, Noffsinger VP, den Hartigh L, Chait A, De Beer FC, Webb NR. Serum amyloid A3 is a high density lipoprotein-associated acute-phase protein. J Lipid Res 2017; 59:339-347. [PMID: 29247043 DOI: 10.1194/jlr.m080887] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2017] [Revised: 11/22/2017] [Indexed: 12/20/2022] Open
Abstract
Serum amyloid A (SAA) is a family of acute-phase reactants. Plasma levels of human SAA1/SAA2 (mouse SAA1.1/2.1) can increase ≥1,000-fold during an acute-phase response. Mice, but not humans, express a third relatively understudied SAA isoform, SAA3. We investigated whether mouse SAA3 is an HDL-associated acute-phase SAA. Quantitative RT-PCR with isoform-specific primers indicated that SAA3 and SAA1.1/2.1 are induced similarly in livers (∼2,500-fold vs. ∼6,000-fold, respectively) and fat (∼400-fold vs. ∼100-fold, respectively) of lipopolysaccharide (LPS)-injected mice. In situ hybridization demonstrated that all three SAAs are produced by hepatocytes. All three SAA isoforms were detected in plasma of LPS-injected mice, although SAA3 levels were ∼20% of SAA1.1/2.1 levels. Fast protein LC analyses indicated that virtually all of SAA1.1/2.1 eluted with HDL, whereas ∼15% of SAA3 was lipid poor/free. After density gradient ultracentrifugation, isoelectric focusing demonstrated that ∼100% of plasma SAA1.1 was recovered in HDL compared with only ∼50% of SAA2.1 and ∼10% of SAA3. Thus, SAA3 appears to be more loosely associated with HDL, resulting in lipid-poor/free SAA3. We conclude that SAA3 is a major hepatic acute-phase SAA in mice that may produce systemic effects during inflammation.
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Affiliation(s)
- Lisa R Tannock
- Departments of Internal Medicine, University of Kentucky, Lexington, KY.,Saha Cardiovascular Research Center, University of Kentucky, Lexington, KY.,Barnstable Brown Diabetes Center, University of Kentucky, Lexington, KY.,Veterans Affairs Lexington, University of Kentucky, Lexington, KY
| | - Maria C De Beer
- Saha Cardiovascular Research Center, University of Kentucky, Lexington, KY.,Barnstable Brown Diabetes Center, University of Kentucky, Lexington, KY.,Departments of Physiology, University of Kentucky, Lexington, KY
| | - Ailing Ji
- Departments of Internal Medicine, University of Kentucky, Lexington, KY.,Saha Cardiovascular Research Center, University of Kentucky, Lexington, KY
| | - Preetha Shridas
- Departments of Internal Medicine, University of Kentucky, Lexington, KY.,Saha Cardiovascular Research Center, University of Kentucky, Lexington, KY.,Barnstable Brown Diabetes Center, University of Kentucky, Lexington, KY
| | - Victoria P Noffsinger
- Departments of Internal Medicine, University of Kentucky, Lexington, KY.,Saha Cardiovascular Research Center, University of Kentucky, Lexington, KY
| | - Laura den Hartigh
- Department of Medicine University of Washington, Seattle, WA.,University of Washington Diabetes Institute, University of Washington, Seattle, WA
| | - Alan Chait
- Department of Medicine University of Washington, Seattle, WA.,University of Washington Diabetes Institute, University of Washington, Seattle, WA
| | - Frederick C De Beer
- Departments of Internal Medicine, University of Kentucky, Lexington, KY.,Saha Cardiovascular Research Center, University of Kentucky, Lexington, KY.,Barnstable Brown Diabetes Center, University of Kentucky, Lexington, KY
| | - Nancy R Webb
- Saha Cardiovascular Research Center, University of Kentucky, Lexington, KY .,Barnstable Brown Diabetes Center, University of Kentucky, Lexington, KY.,Veterans Affairs Lexington, University of Kentucky, Lexington, KY.,Departments of Pharmacology and Nutritional Sciences, University of Kentucky, Lexington, KY
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17
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Abstract
PURPOSE Group X (GX) and group V (GV) secretory phospholipase A2 (sPLA2) potently release arachidonic acid (AA) from the plasma membrane of intact cells. We previously demonstrated that GX sPLA2 negatively regulates glucose-stimulated insulin secretion (GSIS) by a prostaglandin E2 (PGE2)-dependent mechanism. In this study we investigated whether GV sPLA2 similarly regulates GSIS. METHODS GSIS and pancreatic islet-size were assessed in wild-type (WT) and GV sPLA2-knock out (GV KO) mice. GSIS was also assessed ex vivo in isolated islets and in vitro using MIN6 pancreatic beta cell lines with or without GV sPLA2 overexpression or silencing. RESULTS GSIS was significantly decreased in islets isolated from GV KO mice compared to WT mice and in MIN6 cells with siRNA-mediated GV sPLA2 suppression. MIN6 cells overexpressing GV sPLA2 (MIN6-GV) showed a significant increase in GSIS compared to control cells. Though the amount of AA released into the media by MIN6-GV cells was significantly higher, PGE2 production was not enhanced or cAMP content decreased compared to control MIN6 cells. Surprisingly, GV KO mice exhibited a significant increase in plasma insulin levels following i.p. injection of glucose compared to WT mice. This increase in GSIS in GV KO mice was associated with a significant increase in pancreatic islet size and number of proliferating cells in β-islets compared to WT mice. CONCLUSIONS Deficiency of GV sPLA2 results in diminished GSIS in isolated pancreatic beta-cells. However, the reduced GSIS in islets lacking GV sPLA2 appears to be compensated by increased islet mass in GV KO mice.
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Affiliation(s)
- Preetha Shridas
- Saha Cardiovascular Research Center, University of Kentucky Medical Center, Lexington, KY, 40536, USA.
- Departments of Internal Medicine, University of Kentucky Medical Center, Lexington, KY, 40536, USA.
| | - Victoria P Noffsinger
- Saha Cardiovascular Research Center, University of Kentucky Medical Center, Lexington, KY, 40536, USA
- Departments of Internal Medicine, University of Kentucky Medical Center, Lexington, KY, 40536, USA
| | - Andrea C Trumbauer
- Saha Cardiovascular Research Center, University of Kentucky Medical Center, Lexington, KY, 40536, USA
| | - Nancy R Webb
- Saha Cardiovascular Research Center, University of Kentucky Medical Center, Lexington, KY, 40536, USA
- Pharmacology and Nutritional Sciences, Division of Nutritional Sciences, University of Kentucky Medical Center, Lexington, KY, 40536, USA
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18
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Wilson PG, Thompson JC, Shridas P, de Beer FC, Webb NR, Tannock LR. Abstract 15: Serum Amyloid A is Not Just an HDL-Associated Lipoprotein. Arterioscler Thromb Vasc Biol 2017. [DOI: 10.1161/atvb.37.suppl_1.15] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Serum Amyloid A (SAA) is traditionally thought to be only found with HDL; however, recently several groups have found that SAA is found on apoB-containing lipoproteins (LDL and VLDL) under some circumstances. The goal of this study was to determine the relative lipoprotein association of SAA. Native human acute phase SAA was isolated from acute phase plasma collected from patients undergoing cardiovascular bypass surgery; the SAA was purified and delipidated. Plasma was collected from a group of healthy, non-obese humans with low levels of SAA (< 2 mg/L) and lipoproteins (VLDL, LDL and HDL) were isolated by density gradient ultracentrifugation. The delipidated SAA (at 2 concentrations) was incubated in vitro with the various lipoprotein preparations then samples were re-isolated by fast protein liquid chromatography and SAA was analyzed by ELISA and immunoblot. When SAA was incubated with any single lipoprotein all of the SAA was found associated with that lipoprotein and none remained in a lipid-free form. When SAA was incubated with a mixture of VLDL, LDL and HDL (based on equal protein and corresponding to concentrations in plasma) a majority of SAA (50-60%) was found on HDL with the remaining SAA found on VLDL and LDL. When SAA first complexed to HDL was added to a mixture of SAA-free LDL and VLDL the majority of SAA remained with the HDL (76-86%) but 5-10% of the SAA was found on each of LDL and VLDL. When SAA first complexed to either apoB-containing lipoprotein was then added to a mixture of HDL and the other apoB-containing lipoprotein most SAA moved to HDL (55-70%) but the remainder was found on the apoB-containing particles. Thus, SAA can move between lipoprotein particles in vitro. To determine if the presence of SAA on apoB-containing lipoproteins had a functional effect we evaluated lipoprotein-proteoglycan binding affinity. Proteoglycan mediated lipoprotein retention in the vessel wall is thought to be one of the key steps in initiation of atherosclerosis. Compared to SAA-free LDL or VLDL, the presence of SAA on apoB-containing lipoproteins caused increased proteoglycan binding affinity. Thus, SAA is not simply an HDL lipoprotein, but SAA can move between lipoprotein particles, and the presence of SAA on apoB particles may increase their atherogenicity.
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Shridas P, Noffsinger VP, Webb NR. Abstract 483: Non-redundant and Opposing Roles of Group X and Group V Secretory Phospholipase A2s on Pancreatic Beta-cell Function. Arterioscler Thromb Vasc Biol 2015. [DOI: 10.1161/atvb.35.suppl_1.483] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Background:
Group X and group V secretory phospholipase A2s (GX and GV sPLA2s) potently release arachidonic acid (AA) from the plasma membrane of intact cells. AA is an activator of glucose-stimulated insulin secretion (GSIS) by β-islet cells. However, the AA metabolite prostaglandin E2 (PGE2) is a known inhibitor of GSIS. Both GX and GV sPLA2s are expressed in mouse pancreatic islet cells. We previously demonstrated that GX sPLA2 negatively regulates GSIS by a PGE2-dependent mechanism. In this study we investigated whether GV sPLA2 similarly regulates GSIS.
Methods and Results:
GSIS was measured in pancreatic islet cells isolated from WT and GV sPLA2-deficient (GV KO) mice. To complement these studies, GSIS was also assessed in vitro using MIN6 pancreatic beta cell lines with or without GV sPLA2 overexpression or silencing. In marked contrast to our findings in GX KO mice, GSIS was significantly decreased in islets isolated from GV KO mice compared to WT mice. Similarly, there was a significant decrease in GSIS in MIN6 cells with siRNA-mediated GV sPLA2 suppression. Consistent with these findings, MIN6 cells overexpressing GV sPLA2 (MIN6-GV) showed a significant increase in GSIS compared to control cells. As expected, the amount of AA released into the media by MIN6-GV cells was significantly increased compared to control MIN6 cells. However, unlike MIN6 cells overexpressing GX sPLA2, MIN6-GV cells did not exhibit enhanced PGE2 production or decreased cAMP content compared to control MIN6 cells, despite similar amounts of sPLA2 activity produced by the two cell lines.
Conclusions:
We conclude that GX and GV sPLA2s play opposing and non-redundant roles in pancreatic β-cell function. Whereas GV sPLA2 activates GSIS, GX sPLA2 suppresses this process. This functional difference appears to be due to the extent to which AA generated by the respective sPLA2’s is coupled to PGE2 production.
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Affiliation(s)
| | | | - Nancy R Webb
- Molecular and Biomedical Pharmacology, Univ of Kentucky, Lexington, KY
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20
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Webb NR, De Beer MC, Wroblewski JM, Ji A, Bailey W, Shridas P, Charnigo RJ, Noffsinger VP, Witta J, Howatt DA, Balakrishnan A, Rateri DL, Daugherty A, De Beer FC. Deficiency of Endogenous Acute-Phase Serum Amyloid A Protects apoE-/- Mice From Angiotensin II-Induced Abdominal Aortic Aneurysm Formation. Arterioscler Thromb Vasc Biol 2015; 35:1156-65. [PMID: 25745063 DOI: 10.1161/atvbaha.114.304776] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2014] [Accepted: 02/13/2015] [Indexed: 11/16/2022]
Abstract
OBJECTIVE Rupture of abdominal aortic aneurysm (AAA), a major cause of death in the aged population, is characterized by vascular inflammation and matrix degradation. Serum amyloid A (SAA), an acute-phase reactant linked to inflammation and matrix metalloproteinase induction, correlates with aortic dimensions before aneurysm formation in humans. We investigated whether SAA deficiency in mice affects AAA formation during angiotensin II (Ang II) infusion. APPROACH AND RESULTS Plasma SAA increased ≈60-fold in apoE(-/-) mice 24 hours after intraperitoneal Ang II injection (100 μg/kg; n=4) and ≈15-fold after chronic 28-day Ang II infusion (1000 ng/kg per minute; n=9). AAA incidence and severity after 28-day Ang II infusion was significantly reduced in apoE(-/-) mice lacking both acute-phase SAA isoforms (SAAKO; n=20) compared with apoE(-/-) mice (SAAWT; n=20) as assessed by in vivo ultrasound and ex vivo morphometric analyses, despite a significant increase in systolic blood pressure in SAAKO mice compared with SAAWT mice after Ang II infusion. Atherosclerotic lesion area of the aortic arch was similar in SAAKO and SAAWT mice after 28-day Ang II infusion. Immunostaining detected SAA in AAA tissues of Ang II-infused SAAWT mice that colocalized with macrophages, elastin breaks, and enhanced matrix metalloproteinase activity. Matrix metalloproteinase-2 activity was significantly lower in aortas of SAAKO mice compared with SAAWT mice after 10-day Ang II infusion. CONCLUSIONS Lack of endogenous acute-phase SAA protects against experimental AAA through a mechanism that may involve reduced matrix metalloproteinase-2 activity.
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Affiliation(s)
- Nancy R Webb
- From the Departments of Pharmacology Division of Nutritional Sciences (N.R.W.), Physiology (M.C.D.B.) and Internal Medicine (J.M.W., A.J., W.B., P.S., V.P.N., D.A.H., A.B., D.L.R., A.D., F.C.D.B.), and Saha Cardiovascular Research Center (N.R.W., M.C.D.B., J.M.W., A.J., P.S., V.P.N., D.A.H., A.B., D.L.R., A.D., F.C.D.B.), and Departments of Statistics and Biostatistics (R.J.C.), University of Kentucky, Lexington; and Foundation Gastroenterology, Nashua, NH (J.W.).
| | - Maria C De Beer
- From the Departments of Pharmacology Division of Nutritional Sciences (N.R.W.), Physiology (M.C.D.B.) and Internal Medicine (J.M.W., A.J., W.B., P.S., V.P.N., D.A.H., A.B., D.L.R., A.D., F.C.D.B.), and Saha Cardiovascular Research Center (N.R.W., M.C.D.B., J.M.W., A.J., P.S., V.P.N., D.A.H., A.B., D.L.R., A.D., F.C.D.B.), and Departments of Statistics and Biostatistics (R.J.C.), University of Kentucky, Lexington; and Foundation Gastroenterology, Nashua, NH (J.W.)
| | - Joanne M Wroblewski
- From the Departments of Pharmacology Division of Nutritional Sciences (N.R.W.), Physiology (M.C.D.B.) and Internal Medicine (J.M.W., A.J., W.B., P.S., V.P.N., D.A.H., A.B., D.L.R., A.D., F.C.D.B.), and Saha Cardiovascular Research Center (N.R.W., M.C.D.B., J.M.W., A.J., P.S., V.P.N., D.A.H., A.B., D.L.R., A.D., F.C.D.B.), and Departments of Statistics and Biostatistics (R.J.C.), University of Kentucky, Lexington; and Foundation Gastroenterology, Nashua, NH (J.W.)
| | - Ailing Ji
- From the Departments of Pharmacology Division of Nutritional Sciences (N.R.W.), Physiology (M.C.D.B.) and Internal Medicine (J.M.W., A.J., W.B., P.S., V.P.N., D.A.H., A.B., D.L.R., A.D., F.C.D.B.), and Saha Cardiovascular Research Center (N.R.W., M.C.D.B., J.M.W., A.J., P.S., V.P.N., D.A.H., A.B., D.L.R., A.D., F.C.D.B.), and Departments of Statistics and Biostatistics (R.J.C.), University of Kentucky, Lexington; and Foundation Gastroenterology, Nashua, NH (J.W.)
| | - William Bailey
- From the Departments of Pharmacology Division of Nutritional Sciences (N.R.W.), Physiology (M.C.D.B.) and Internal Medicine (J.M.W., A.J., W.B., P.S., V.P.N., D.A.H., A.B., D.L.R., A.D., F.C.D.B.), and Saha Cardiovascular Research Center (N.R.W., M.C.D.B., J.M.W., A.J., P.S., V.P.N., D.A.H., A.B., D.L.R., A.D., F.C.D.B.), and Departments of Statistics and Biostatistics (R.J.C.), University of Kentucky, Lexington; and Foundation Gastroenterology, Nashua, NH (J.W.)
| | - Preetha Shridas
- From the Departments of Pharmacology Division of Nutritional Sciences (N.R.W.), Physiology (M.C.D.B.) and Internal Medicine (J.M.W., A.J., W.B., P.S., V.P.N., D.A.H., A.B., D.L.R., A.D., F.C.D.B.), and Saha Cardiovascular Research Center (N.R.W., M.C.D.B., J.M.W., A.J., P.S., V.P.N., D.A.H., A.B., D.L.R., A.D., F.C.D.B.), and Departments of Statistics and Biostatistics (R.J.C.), University of Kentucky, Lexington; and Foundation Gastroenterology, Nashua, NH (J.W.)
| | - Richard J Charnigo
- From the Departments of Pharmacology Division of Nutritional Sciences (N.R.W.), Physiology (M.C.D.B.) and Internal Medicine (J.M.W., A.J., W.B., P.S., V.P.N., D.A.H., A.B., D.L.R., A.D., F.C.D.B.), and Saha Cardiovascular Research Center (N.R.W., M.C.D.B., J.M.W., A.J., P.S., V.P.N., D.A.H., A.B., D.L.R., A.D., F.C.D.B.), and Departments of Statistics and Biostatistics (R.J.C.), University of Kentucky, Lexington; and Foundation Gastroenterology, Nashua, NH (J.W.)
| | - Victoria P Noffsinger
- From the Departments of Pharmacology Division of Nutritional Sciences (N.R.W.), Physiology (M.C.D.B.) and Internal Medicine (J.M.W., A.J., W.B., P.S., V.P.N., D.A.H., A.B., D.L.R., A.D., F.C.D.B.), and Saha Cardiovascular Research Center (N.R.W., M.C.D.B., J.M.W., A.J., P.S., V.P.N., D.A.H., A.B., D.L.R., A.D., F.C.D.B.), and Departments of Statistics and Biostatistics (R.J.C.), University of Kentucky, Lexington; and Foundation Gastroenterology, Nashua, NH (J.W.)
| | - Jassir Witta
- From the Departments of Pharmacology Division of Nutritional Sciences (N.R.W.), Physiology (M.C.D.B.) and Internal Medicine (J.M.W., A.J., W.B., P.S., V.P.N., D.A.H., A.B., D.L.R., A.D., F.C.D.B.), and Saha Cardiovascular Research Center (N.R.W., M.C.D.B., J.M.W., A.J., P.S., V.P.N., D.A.H., A.B., D.L.R., A.D., F.C.D.B.), and Departments of Statistics and Biostatistics (R.J.C.), University of Kentucky, Lexington; and Foundation Gastroenterology, Nashua, NH (J.W.)
| | - Deborah A Howatt
- From the Departments of Pharmacology Division of Nutritional Sciences (N.R.W.), Physiology (M.C.D.B.) and Internal Medicine (J.M.W., A.J., W.B., P.S., V.P.N., D.A.H., A.B., D.L.R., A.D., F.C.D.B.), and Saha Cardiovascular Research Center (N.R.W., M.C.D.B., J.M.W., A.J., P.S., V.P.N., D.A.H., A.B., D.L.R., A.D., F.C.D.B.), and Departments of Statistics and Biostatistics (R.J.C.), University of Kentucky, Lexington; and Foundation Gastroenterology, Nashua, NH (J.W.)
| | - Anju Balakrishnan
- From the Departments of Pharmacology Division of Nutritional Sciences (N.R.W.), Physiology (M.C.D.B.) and Internal Medicine (J.M.W., A.J., W.B., P.S., V.P.N., D.A.H., A.B., D.L.R., A.D., F.C.D.B.), and Saha Cardiovascular Research Center (N.R.W., M.C.D.B., J.M.W., A.J., P.S., V.P.N., D.A.H., A.B., D.L.R., A.D., F.C.D.B.), and Departments of Statistics and Biostatistics (R.J.C.), University of Kentucky, Lexington; and Foundation Gastroenterology, Nashua, NH (J.W.)
| | - Debra L Rateri
- From the Departments of Pharmacology Division of Nutritional Sciences (N.R.W.), Physiology (M.C.D.B.) and Internal Medicine (J.M.W., A.J., W.B., P.S., V.P.N., D.A.H., A.B., D.L.R., A.D., F.C.D.B.), and Saha Cardiovascular Research Center (N.R.W., M.C.D.B., J.M.W., A.J., P.S., V.P.N., D.A.H., A.B., D.L.R., A.D., F.C.D.B.), and Departments of Statistics and Biostatistics (R.J.C.), University of Kentucky, Lexington; and Foundation Gastroenterology, Nashua, NH (J.W.)
| | - Alan Daugherty
- From the Departments of Pharmacology Division of Nutritional Sciences (N.R.W.), Physiology (M.C.D.B.) and Internal Medicine (J.M.W., A.J., W.B., P.S., V.P.N., D.A.H., A.B., D.L.R., A.D., F.C.D.B.), and Saha Cardiovascular Research Center (N.R.W., M.C.D.B., J.M.W., A.J., P.S., V.P.N., D.A.H., A.B., D.L.R., A.D., F.C.D.B.), and Departments of Statistics and Biostatistics (R.J.C.), University of Kentucky, Lexington; and Foundation Gastroenterology, Nashua, NH (J.W.)
| | - Frederick C De Beer
- From the Departments of Pharmacology Division of Nutritional Sciences (N.R.W.), Physiology (M.C.D.B.) and Internal Medicine (J.M.W., A.J., W.B., P.S., V.P.N., D.A.H., A.B., D.L.R., A.D., F.C.D.B.), and Saha Cardiovascular Research Center (N.R.W., M.C.D.B., J.M.W., A.J., P.S., V.P.N., D.A.H., A.B., D.L.R., A.D., F.C.D.B.), and Departments of Statistics and Biostatistics (R.J.C.), University of Kentucky, Lexington; and Foundation Gastroenterology, Nashua, NH (J.W.)
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Layne JD, Shridas P, Webb NR. Ectopically expressed pro-group X secretory phospholipase A2 is proteolytically activated in mouse adrenal cells by furin-like proprotein convertases: implications for the regulation of adrenal steroidogenesis. J Biol Chem 2015; 290:7851-60. [PMID: 25623068 DOI: 10.1074/jbc.m114.634667] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Group X secretory phospholipase A2 (GX sPLA2) hydrolyzes mammalian cell membranes, liberating free fatty acids and lysophospholipids. GX sPLA2 is produced as a pro-enzyme (pro-GX sPLA2) that contains an N-terminal 11-amino acid propeptide ending in a dibasic motif, suggesting cleavage by a furin-like proprotein convertase (PC). Although propeptide cleavage is clearly required for enzymatic activity, the protease(s) responsible for pro-GX sPLA2 activation have not been identified. We previously reported that GX sPLA2 negatively regulates adrenal glucocorticoid production, likely by suppressing liver X receptor-mediated activation of steroidogenic acute regulatory protein expression. In this study, using a FLAG epitope-tagged pro-GX sPLA2 expression construct (FLAG-pro-GX sPLA2), we determined that adrenocorticotropic hormone (ACTH) enhanced FLAG-pro-GX sPLA2 processing and phospholipase activity secreted by Y1 adrenal cells. ACTH increased the expression of furin and PCSK6, but not other members of the PC family, in Y1 cells. Overexpression of furin and PCSK6 in HEK 293 cells significantly enhanced FLAG-pro-GX sPLA2 processing, whereas siRNA-mediated knockdown of both PCs almost completely abolished FLAG-pro-GX sPLA2 processing in Y1 cells. Expression of either furin or PCSK6 enhanced the ability of GX sPLA2 to suppress liver X receptor reporter activity. The PC inhibitor decanoyl-Arg-Val-Lys-Arg-chloromethyl ketone significantly suppressed FLAG-pro-GX sPLA2 processing and sPLA2 activity in Y1 cells, and it significantly attenuated GX sPLA2-dependent inhibition of steroidogenic acute regulatory protein expression and progesterone production. These findings provide strong evidence that pro-GX sPLA2 is a substrate for furin and PCSK6 proteolytic processing and define a novel mechanism for regulating corticosteroid production in adrenal cells.
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Affiliation(s)
- Joseph D Layne
- From the Department of Pharmacology and Nutritional Sciences, Division of Nutritional Sciences, the Saha Cardiovascular Research Center, and
| | - Preetha Shridas
- the Department of Internal Medicine, University of Kentucky Medical Center, Lexington, Kentucky 40536
| | - Nancy R Webb
- the Department of Internal Medicine, University of Kentucky Medical Center, Lexington, Kentucky 40536
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22
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Shridas P, Zahoor L, Forrest KJ, Layne JD, Webb NR. Group X secretory phospholipase A2 regulates insulin secretion through a cyclooxygenase-2-dependent mechanism. J Biol Chem 2014; 289:27410-7. [PMID: 25122761 DOI: 10.1074/jbc.m114.591735] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Group X secretory phospholipase A2 (GX sPLA2) potently hydrolyzes membrane phospholipids to release arachidonic acid (AA). While AA is an activator of glucose-stimulated insulin secretion (GSIS), its metabolite prostaglandin E2 (PGE2) is a known inhibitor. In this study, we determined that GX sPLA2 is expressed in insulin-producing cells of mouse pancreatic islets and investigated its role in beta cell function. GSIS was measured in vivo in wild-type (WT) and GX sPLA2-deficient (GX KO) mice and ex vivo using pancreatic islets isolated from WT and GX KO mice. GSIS was also assessed in vitro using mouse MIN6 pancreatic beta cells with or without GX sPLA2 overexpression or exogenous addition. GSIS was significantly higher in islets isolated from GX KO mice compared with islets from WT mice. Conversely, GSIS was lower in MIN6 cells overexpressing GX sPLA2 (MIN6-GX) compared with control (MIN6-C) cells. PGE2 production was significantly higher in MIN6-GX cells compared with MIN6-C cells and this was associated with significantly reduced cellular cAMP. The effect of GX sPLA2 on GSIS was abolished when cells were treated with NS398 (a COX-2 inhibitor) or L-798,106 (a PGE2-EP3 receptor antagonist). Consistent with enhanced beta cell function, GX KO mice showed significantly increased plasma insulin levels following glucose challenge and were protected from age-related reductions in GSIS and glucose tolerance compared with WT mice. We conclude that GX sPLA2 plays a previously unrecognized role in negatively regulating pancreatic insulin secretion by augmenting COX-2-dependent PGE2 production.
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Affiliation(s)
- Preetha Shridas
- From Saha Cardiovascular Research Center and Departments of Internal Medicine and
| | - Lubna Zahoor
- From Saha Cardiovascular Research Center and Departments of Internal Medicine and
| | - Kathy J Forrest
- From Saha Cardiovascular Research Center and Departments of Internal Medicine and
| | - Joseph D Layne
- From Saha Cardiovascular Research Center and Pharmacology and Nutritional Sciences, Division of Nutritional Sciences, University of Kentucky Medical Center, Lexington Kentucky 40536
| | - Nancy R Webb
- From Saha Cardiovascular Research Center and Pharmacology and Nutritional Sciences, Division of Nutritional Sciences, University of Kentucky Medical Center, Lexington Kentucky 40536
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23
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De Beer MC, Wroblewski JM, Noffsinger VP, Rateri DL, Howatt DA, Balakrishnan A, Ji A, Shridas P, Thompson JC, van der Westhuyzen DR, Tannock LR, Daugherty A, Webb NR, De Beer FC. Deficiency of endogenous acute phase serum amyloid A does not affect atherosclerotic lesions in apolipoprotein E-deficient mice. Arterioscler Thromb Vasc Biol 2013; 34:255-61. [PMID: 24265416 DOI: 10.1161/atvbaha.113.302247] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE Although elevated plasma concentrations of serum amyloid A (SAA) are associated strongly with increased risk for atherosclerotic cardiovascular disease in humans, the role of SAA in the pathogenesis of lesion formation remains obscure. Our goal was to determine the impact of SAA deficiency on atherosclerosis in hypercholesterolemic mice. APPROACH AND RESULTS Apolipoprotein E-deficient (apoE(-/-)) mice, either wild type or deficient in both major acute phase SAA isoforms, SAA1.1 and SAA2.1, were fed a normal rodent diet for 50 weeks. Female mice, but not male apoE-/- mice deficient in SAA1.1 and SAA2.1, had a modest increase (22%; P≤0.05) in plasma cholesterol concentrations and a 53% increase in adipose mass compared with apoE-/- mice expressing SAA1.1 and SAA2.1 that did not affect the plasma cytokine levels or the expression of adipose tissue inflammatory markers. SAA deficiency did not affect lipoprotein cholesterol distributions or plasma triglyceride concentrations in either male or female mice. Atherosclerotic lesion areas measured on the intimal surfaces of the arch, thoracic, and abdominal regions were not significantly different between apoE-/- mice deficient in SAA1.1 and SAA2.1 and apoE-/- mice expressing SAA1.1 and SAA2.1 in either sex. To accelerate lesion formation, mice were fed a Western diet for 12 weeks. SAA deficiency had effect neither on diet-induced alterations in plasma cholesterol, triglyceride, or cytokine concentrations nor on aortic atherosclerotic lesion areas in either male or female mice. In addition, SAA deficiency in male mice had no effect on lesion areas or macrophage accumulation in the aortic roots. CONCLUSIONS The absence of endogenous SAA1.1 and 2.1 does not affect atherosclerotic lipid deposition in apolipoprotein E-deficient mice fed either normal or Western diets.
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Affiliation(s)
- Maria C De Beer
- From the Graduate Center for Nutritional Science (M.C.D.B., J.M.W., V.P.N., A.J., P.S., J.C.T., D.R.v.d.W., L.R.T., N.R.W., F.C.D.B.), Saha Cardiovascular Research Center (M.C.D.B., J.M.W., V.P.N., D.L.R., D.A.H., A.B., A.J., P.S., J.C.T., D.R.v.d.W., L.R.T., A.D., N.R.W., F.C.D.B.), and the Departments of Physiology (M.C.D.B.) and Internal Medicine (J.M.W., V.P.N., D.L.R., D.A.H., A.B., A.J., P.S., J.C.T., D.R.v.d.W., L.R.T., A.D., N.R.W., F.C.D.B.), University of Kentucky Medical Center, Lexington, KY; and Department of Veterans Affairs Medical Center, Lexington, KY (D.R.v.d.W., L.R.T.)
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24
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Carter LG, Lewis KN, Wilkerson DC, Tobia CM, Ngo Tenlep SY, Shridas P, Garcia-Cazarin ML, Wolff G, Andrade FH, Charnigo RJ, Esser KA, Egan JM, de Cabo R, Pearson KJ. Perinatal exercise improves glucose homeostasis in adult offspring. Am J Physiol Endocrinol Metab 2012; 303:E1061-8. [PMID: 22932781 PMCID: PMC3469606 DOI: 10.1152/ajpendo.00213.2012] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Emerging research has shown that subtle factors during pregnancy and gestation can influence long-term health in offspring. In an attempt to be proactive, we set out to explore whether a nonpharmacological intervention, perinatal exercise, might improve offspring health. Female mice were separated into sedentary or exercise cohorts, with the exercise cohort having voluntary access to a running wheel prior to mating and during pregnancy and nursing. Offspring were weaned, and analyses were performed on the mature offspring that did not have access to running wheels during any portion of their lives. Perinatal exercise caused improved glucose disposal following an oral glucose challenge in both female and male adult offspring (P < 0.05 for both). Blood glucose concentrations were reduced to lower values in response to an intraperitoneal insulin tolerance test for both female and male adult offspring of parents with access to running wheels (P < 0.05 and P < 0.01, respectively). Male offspring from exercised dams showed increased percent lean mass and decreased fat mass percent compared with male offspring from sedentary dams (P < 0.01 for both), but these parameters were unchanged in female offspring. These data suggest that short-term maternal voluntary exercise prior to and during healthy pregnancy and nursing can enhance long-term glucose homeostasis in offspring.
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Affiliation(s)
- Lindsay G Carter
- Graduate Center for Nutritional Sciences, College of Medicine, University of Kentucky, Lexington, Kentucky 40536-0200, USA
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25
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Boyanovsky BB, Bailey W, Dixon L, Shridas P, Webb NR. Group V secretory phospholipase A2 enhances the progression of angiotensin II-induced abdominal aortic aneurysms but confers protection against angiotensin II-induced cardiac fibrosis in apoE-deficient mice. Am J Pathol 2012; 181:1088-98. [PMID: 22813854 DOI: 10.1016/j.ajpath.2012.05.037] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2011] [Revised: 05/02/2012] [Accepted: 05/17/2012] [Indexed: 01/23/2023]
Abstract
Abdominal aortic aneurysms (AAAs) and heart failure are complex life-threatening diseases whose etiology is not completely understood. In this study, we investigated whether deficiency of group V secretory phospholipase A(2) (GV sPLA(2)) protects from experimental AAA. The impact of GV sPLA(2) deficiency on angiotensin (Ang) II-induced cardiac fibrosis was also investigated. Apolipoprotein E (apoE)(-/-) mice and apoE(-/-) mice lacking GV sPLA(2) (GV DKO) were infused with 1000 ng/kg per minute Ang II for up to 28 days. Increases in systolic blood pressure, plasma aldosterone level, and urinary and heart prostanoids were similar in apoE(-/-) and GV DKO mice after Ang II infusion. The incidence of aortic rupture in Ang II-infused GV DKO mice (10%) was significantly reduced compared with apoE(-/-) mice (29.4%). Although the incidence of AAA in GV DKO mice (81.3%) and apoE(-/-) mice (100%) was similar, the mean percentage increase in maximal luminal diameter of abdominal aortas was significantly smaller in GV DKO mice (68.5% ± 7.7%) compared with apoE(-/-) mice (92.6% ± 8.3%). Deficiency of GV sPLA(2) resulted in increased Ang II-induced cardiac fibrosis that was most pronounced in perivascular regions. Perivascular collagen, visualized by picrosirius red staining, was associated with increased TUNEL staining and increased immunopositivity for macrophages and myofibroblasts and nicotinamide adenine dinucleotide phosphate oxidase (NOX)-2 and NOX-4, respectively. Our findings indicate that GV sPLA(2) modulates pathological responses to Ang II, with different outcomes for AAA and cardiac fibrosis.
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Affiliation(s)
- Boris B Boyanovsky
- Endocrinology Division, the Department of Internal Medicine, University of Kentucky, Lexington, USA.
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Shridas P, Zahoor L, Bailey W, Forrest K, Webb NR. Abstract 143: Group X Secretory Phospholipase A2 Regulates Insulin Secretion by Mouse Pancreatic Beta Cells. Arterioscler Thromb Vasc Biol 2012. [DOI: 10.1161/atvb.32.suppl_1.a143] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Background:
Group X secretory phospholipase A2 (GX sPLA2) potently releases arachidonic acid (AA) from the plasma membrane of intact cells. AA is a precursor of bioactive prostaglandins that are known to modulate insulin secretion by β-islet cells. C57BL/6 mice deficient in GX sPLA2 (GX KO) are protected from age-related defect in glucose tolerance. GX sPLA2 is expressed in mouse pancreatic islet cells. In this study we tested the hypothesis that GX sPLA2 regulates pancreatic insulin secretion.
Methods and results:
Glucose stimulated insulin secretion (GSIS) was measured in vivo in WT and GX KO mice and ex vivo using pancreatic islet cells isolated from WT and GX KO mice. To complement these studies, GSIS was also assessed in vitro using Min6 pancreatic beta cell lines with or without GX sPLA2 overexpression. GSIS was significantly increased in GX KO mice compared to WT mice, and in islet cells isolated from GX KO mice compared to WT mice. Consistent with this finding, Min6 cells overexpressing GX sPLA2 demonstrated significantly decreased GSIS compared to control cells. Expression of ABCA1 and ABCG1 mRNAs were significantly upregulated in islet cells from GX KO mice compared to WT mice, consistent with our previous report that GX sPLA2 negatively regulates LXR activity. However, there was no significant difference in cholesterol content between islets from WT and GX KO mice suggesting that altered LXR activity may not be the mechanism. Min6 cells overexpressing GX sPLA2 secrete significantly increased levels of PGE2- a known negative regulator of GSIS, in the medium compared to control cells. Treatment of these cells with NS398- an inhibitor of COX2 enzyme, abolished the decrease in GSIS shown by these cells.
Conclusions:
We conclude that GX sPLA2 plays a previously unrecognized role in negatively regulating pancreatic insulin secretion most likely by enhancing PGE2 production.
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Shridas P, Bailey WM, Talbott KR, Oslund RC, Gelb MH, Webb NR. Group X secretory phospholipase A2 enhances TLR4 signaling in macrophages. J Immunol 2011; 187:482-9. [PMID: 21622863 DOI: 10.4049/jimmunol.1003552] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Secretory phospholipase A(2)s (sPLA(2)) hydrolyze glycerophospholipids to liberate lysophospholipids and free fatty acids. Although group X (GX) sPLA(2) is recognized as the most potent mammalian sPLA(2) in vitro, its precise physiological function(s) remains unclear. We recently reported that GX sPLA(2) suppresses activation of the liver X receptor in macrophages, resulting in reduced expression of liver X receptor-responsive genes including ATP-binding cassette transporters A1 (ABCA1) and G1 (ABCG1), and a consequent decrease in cellular cholesterol efflux and increase in cellular cholesterol content (Shridas et al. 2010. Arterioscler. Thromb. Vasc. Biol. 30: 2014-2021). In this study, we provide evidence that GX sPLA(2) modulates macrophage inflammatory responses by altering cellular cholesterol homeostasis. Transgenic expression or exogenous addition of GX sPLA(2) resulted in a significantly higher induction of TNF-α, IL-6, and cyclooxygenase-2 in J774 macrophage-like cells in response to LPS. This effect required GX sPLA(2) catalytic activity, and was abolished in macrophages that lack either TLR4 or MyD88. The hypersensitivity to LPS in cells overexpressing GX sPLA(2) was reversed when cellular free cholesterol was normalized using cyclodextrin. Consistent with results from gain-of-function studies, peritoneal macrophages from GX sPLA(2)-deficient mice exhibited a significantly dampened response to LPS. Plasma concentrations of inflammatory cytokines were significantly lower in GX sPLA(2)-deficient mice compared with wild-type mice after LPS administration. Thus, GX sPLA(2) amplifies signaling through TLR4 by a mechanism that is dependent on its catalytic activity. Our data indicate this effect is mediated through alterations in plasma membrane free cholesterol and lipid raft content.
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Affiliation(s)
- Preetha Shridas
- University of Kentucky Medical Center, Lexington, KY 40536, USA.
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Shridas P, Bailey WM, Gizard F, Oslund RC, Gelb MH, Bruemmer D, Webb NR. Group X secretory phospholipase A2 negatively regulates ABCA1 and ABCG1 expression and cholesterol efflux in macrophages. Arterioscler Thromb Vasc Biol 2010; 30:2014-21. [PMID: 20844270 DOI: 10.1161/atvbaha.110.210237] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE GX sPLA(2) potently hydrolyzes plasma membranes to generate lysophospholipids and free fatty acids; it has been implicated in inflammatory diseases, including atherosclerosis. To identify a novel role for group X (GX) secretory phospholipase A(2) (sPLA(2)) in modulating ATP binding casette transporter A1 (ABCA1) and ATP binding casette transporter G1 (ABCG1) expression and, therefore, macrophage cholesterol efflux. METHODS AND RESULTS The overexpression or exogenous addition of GX sPLA(2) significantly reduced ABCA1 and ABCG1 expression in J774 macrophage-like cells, whereas GX sPLA(2) deficiency in mouse peritoneal macrophages was associated with enhanced expression. Altered ABC transporter expression led to reduced cholesterol efflux in GX sPLA(2)-overexpressing J774 cells and increased efflux in GX sPLA(2)-deficient mouse peritoneal macrophages. Gene regulation was dependent on GX sPLA(2) catalytic activity, mimicked by arachidonic acid and abrogated when liver X receptor (LXR)α/β expression was suppressed, and partially reversed by the LXR agonist T0901317. Reporter assays indicated that GX sPLA(2) suppresses the ability of LXR to transactivate its promoters through a mechanism involving the C-terminal portion of LXR spanning the ligand-binding domain. CONCLUSIONS GX sPLA(2) modulates gene expression in macrophages by generating lipolytic products that suppress LXR activation. GX sPLA(2) may play a previously unrecognized role in atherosclerotic lipid accumulation by negatively regulating the genes critical for cellular cholesterol efflux.
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Affiliation(s)
- Preetha Shridas
- Graduate Center for Nutritional Sciences, Saha Cardiovascular Research Center, University of Kentucky Medical Center, Lexington 40536-0200, USA
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Zack M, Boyanovsky BB, Shridas P, Bailey W, Forrest K, Howatt DA, Gelb MH, de Beer FC, Daugherty A, Webb NR. Group X secretory phospholipase A(2) augments angiotensin II-induced inflammatory responses and abdominal aortic aneurysm formation in apoE-deficient mice. Atherosclerosis 2010; 214:58-64. [PMID: 20833395 DOI: 10.1016/j.atherosclerosis.2010.08.054] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/27/2010] [Revised: 07/15/2010] [Accepted: 08/09/2010] [Indexed: 12/22/2022]
Abstract
OBJECTIVE Abdominal aortic aneurysm (AAA) is a complex vascular disease characterized by matrix degradation and inflammation and is a major cause of mortality in older men. Specific interventions that prevent AAA progression remain to be identified. In this study, we tested the hypothesis that Group X secretory phospholipase A(2) (GX sPLA(2)), an enzyme implicated in inflammatory processes, mediates AAA. METHODS AND RESULTS GX sPLA(2) was detected by immunostaining in human aneurysmal tissue and in angiotensin II (Ang II)-induced AAAs in apolipoprotein E-deficient (apoE(-/-)) mice. GX sPLA(2) mRNA was increased significantly (11-fold) in abdominal aortas of apoE(-/-) mice in response to Ang II infusion. To define the role of GX sPLA(2) in experimental AAAs, apoE(-/-) and apoE(-/-) x GX sPLA(2)(-/-) (GX DKO) mice were infused with Ang II for either 10 (n=7) or 28 (n=24-26) days. Deficiency of GX sPLA(2) significantly reduced the incidence and severity of AAAs, as assessed by ultrasound measurements in vivo of aortic lumens and by computer-assisted morphometric analyses ex vivo of external diameter. Results from gene expression profiling indicated that the expression of specific matrix metalloproteinases and inflammatory mediators was blunted in aortas from GX DKO mice compared to apoE(-/-) mice after 10-day Ang II infusion. Ang II induction of cyclooxygenase-2, interleukin-6, matrix metalloproteinase (MMP)-2, MMP-13 and MMP-14 was reduced significantly in GX DKO mice compared to apoE(-/-) mice. CONCLUSION GX sPLA(2) promotes Ang II-induced pathological responses leading to AAA formation.
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Affiliation(s)
- Melissa Zack
- Graduate Center for Nutritional Sciences, University of Kentucky, Lexington, KY 40536-0200, USA
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Abstract
Studies in vitro indicate that group X secretory phospholipase A(2) (GX sPLA(2)) potently releases arachidonic acid (AA) and lysophosphatidylcholine from mammalian cell membranes. To define the function of GX sPLA(2) in vivo, our laboratory recently generated C57BL/6 mice with targeted deletion of GX sPLA(2) (GX(-/-) mice). When fed a normal rodent diet, GX(-/-) mice gained significantly more weight and had increased adiposity compared to GX(+/+) mice, which was not attributable to alterations in food consumption or energy expenditure. When treated with adipogenic stimuli ex vivo, stromal vascular cells isolated from adipose tissue of GX(-/-) mice accumulated significantly more (20%) triglyceride compared to cells from GX(+/+) mice. Conversely, overexpression of GX sPLA(2), but not catalytically inactive GX sPLA(2), resulted in a significant 50% reduction in triglyceride accumulation in OP9 adipocytes. The induction of genes encoding adipogenic proteins (PPARγ, SREBP-1c, SCD1, and FAS) was also significantly blunted by 50-80% in OP9 cells overexpressing GX sPLA(2). Activation of the liver X receptor (LXR), a nuclear receptor known to up-regulate adipogenic gene expression, was suppressed in 3T3-L1 and OP9 cells when GX sPLA(2) was overexpressed. Thus, hydrolytic products generated by GX sPLA(2) negatively regulate adipogenesis, possibly by suppressing LXR activation.
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Affiliation(s)
- Xia Li
- Graduate Center for Nutritional Sciences, University of Kentucky Medical Center, Lexington, KY 40536-0200, USA
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Shridas P, Bailey WM, Boyanovsky BB, Oslund RC, Gelb MH, Webb NR. Group X secretory phospholipase A2 regulates the expression of steroidogenic acute regulatory protein (StAR) in mouse adrenal glands. J Biol Chem 2010; 285:20031-9. [PMID: 20421306 DOI: 10.1074/jbc.m109.090423] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We developed C57BL/6 mice with targeted deletion of group X secretory phospholipase A(2) (GX KO). These mice have approximately 80% higher plasma corticosterone concentrations compared with wild-type (WT) mice under both basal and adrenocorticotropic hormone (ACTH)-induced stress conditions. This increased corticosterone level was not associated with increased circulating ACTH or a defect in the hypothalamic-pituitary axis as evidenced by a normal response to dexamethasone challenge. Primary cultures of adrenal cells from GX KO mice exhibited significantly increased corticosteroid secretion compared with WT cells. Conversely, overexpression of GX secretory phospholipase A(2) (sPLA(2)), but not a catalytically inactive mutant form of GX sPLA(2), significantly reduced steroid production 30-40% in Y1 mouse adrenal cell line. This effect was reversed by the sPLA(2) inhibitor, indoxam. Silencing of endogenous M-type receptor expression did not restore steroid production in GX sPLA(2)-overexpressing Y1 cells, ruling out a role for this sPLA(2) receptor in this regulatory process. Expression of steroidogenic acute regulatory protein (StAR), the rate-limiting protein in corticosteroid production, was approximately 2-fold higher in adrenal glands of GX KO mice compared with WT mice, whereas StAR expression was suppressed in Y1 cells overexpressing GX sPLA(2). Results from StAR-promoter luciferase reporter gene assays indicated that GX sPLA(2) antagonizes StAR promoter activity and liver X receptor-mediated StAR promoter activation. In summary, GX sPLA(2) is expressed in mouse adrenal glands and functions to negatively regulate corticosteroid synthesis, most likely by negatively regulating StAR expression.
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Affiliation(s)
- Preetha Shridas
- Graduate Center for Nutritional Sciences, the Cardiovascular Research Center, University of Kentucky Medical Center, Lexington, Kentucky 40536, USA
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Boyanovsky BB, Li X, Shridas P, Sunkara M, Morris AJ, Webb NR. Bioactive products generated by group V sPLA(2) hydrolysis of LDL activate macrophages to secrete pro-inflammatory cytokines. Cytokine 2010; 50:50-7. [PMID: 20138782 DOI: 10.1016/j.cyto.2009.12.009] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2009] [Revised: 12/16/2009] [Accepted: 12/18/2009] [Indexed: 01/02/2023]
Abstract
OBJECTIVE Previous studies have established that hydrolysis of LDL by Group V secretory phospholipase A(2) (GV sPLA(2)) generates a modified particle capable of inducing macrophage foam cell formation. The aim of the present study was to determine whether GV sPLA(2)-hydrolyzed LDL (GV-LDL) produces pro-atherogenic effects in macrophages independent of cholesterol accumulation. METHODS AND RESULTS J-774 cells incubated with GV-LDL produced more TNF-alpha and IL-6 compared to cells incubated with control-LDL. Indirect immunofluorescence showed that GV-LDL but not control-LDL induced nuclear translocation of NFkappaB. Inhibitors of NFkappaB activation, effectively blocked cytokine production induced by GV-LDL. Control-LDL and GV-LDL were separated from albumin present in reaction mixtures by ultracentrifugation. The albumin fraction derived from GV-LDL contained 80% of the FFA generated and was more potent than the re-isolated GV-LDL in inducing pro-inflammatory cytokine secretion. Linoleic acid (18:2) and oleic acid (18:1) were the most abundant FFAs generated, whereas newly formed lyso-PCs contained 14:0 (myristic), 16:1 (palmitic), and 18:2 fatty acyl groups. Experiments with synthetic FFA showed that 18:1 induced J-774 cells to secrete TNF-alpha and IL-6. CONCLUSIONS These results indicate that in addition to promoting atherosclerotic lipid accumulation in macrophages, GV sPLA(2) hydrolysis of LDL leads to activation of NFkappaB, a key regulator of inflammation.
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Affiliation(s)
- Boris B Boyanovsky
- Department of Internal Medicine Endocrinology Division, University of Kentucky, Lexington, 40536, USA.
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Boyanovsky BB, Shridas P, Simons M, van der Westhuyzen DR, Webb NR. Syndecan-4 mediates macrophage uptake of group V secretory phospholipase A2-modified LDL. J Lipid Res 2008; 50:641-50. [PMID: 19056705 DOI: 10.1194/jlr.m800450-jlr200] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We previously reported that LDL modified by group V secretory phospholipase A2 (GV-LDL) promotes macrophage foam cell formation through a mechanism independent of scavenger receptors SR-A and CD36, and dependent on cellular proteoglycans. This study investigates the role of syndecans, a family of cell surface proteoglycans known to mediate endocytosis through macropinocytosis, in macrophage uptake of GV-LDL. LY 294002, a phosphatidylinositol 3-kinase inhibitor, significantly reduced internalization of (125)I-labeled GV-LDL in J-774 macrophages, consistent with a macropinocytic uptake pathway. Using small, interfering RNA-directed gene silencing, we demonstrated a direct relationship between (125)I-labeled GV-LDL binding and the level of syndecan-3 and syndecan-4 expression in J-774 cells. However, (125)I-labeled GV-LDL uptake was significantly reduced only when syndecan-4 expression was suppressed. Peritoneal macrophages from syndecan-4-deficient mice exhibited markedly reduced uptake of fluorescently labeled GV-LDL compared with wild-type cells. Furthermore, cholesteryl ester accumulation induced by GV-LDL was dependent on syndecan-4 expression. Syndecan-4 expression and GV-LDL binding were significantly increased in J-774 cells treated with lipopolysaccharide, suggesting that GV-LDL uptake via this pathway may be enhanced during inflammation. Taken together, our data point to a novel role for syndecan-4 in mediating the uptake of GV-LDL, a process implicated in atherosclerotic lesion progression.
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Affiliation(s)
- Boris B Boyanovsky
- Department of Internal Medicine, Endocrinology Division, University of Kentucky Medical Center, Lexington, KY 40536, USA
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Sun B, Boyanovsky BB, Connelly MA, Shridas P, van der Westhuyzen DR, Webb NR. Distinct mechanisms for OxLDL uptake and cellular trafficking by class B scavenger receptors CD36 and SR-BI. J Lipid Res 2007; 48:2560-70. [PMID: 17876058 DOI: 10.1194/jlr.m700163-jlr200] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Modified forms of LDL, including oxidized low density lipoprotein (OxLDL), contribute to macrophage lipid accumulation in the vessel wall. Despite the pathophysiological importance of uptake pathways for OxLDL, the molecular details of OxLDL endocytosis by macrophages are not well understood. Studies in vitro demonstrate that the class B scavenger receptor CD36 mediates macrophage uptake and degradation of OxLDL. Although the closely related scavenger receptor class B type I (SR-BI) binds OxLDL with high affinity, evidence that SR-BI plays a role in OxLDL metabolism is lacking. In this study, we directly compared OxLDL uptake and degradation by CD36 and SR-BI. Our results indicate that although CD36 and SR-BI internalize OxLDL, SR-BI mediates significantly less OxLDL degradation. Endocytosis of OxLDL by both SR-BI and CD36 is independent of caveolae, microtubules, and actin cytoskeleton. However, OxLDL uptake by CD36, but not SR-BI, is dependent on dynamin. The analysis of chimeric SR-BI/CD36 receptors shows that the CD36 C-terminal cytoplasmic tail is necessary and sufficient for dynamin-dependent OxLDL internalization by class B scavenger receptors. These findings indicate that different mechanisms are involved in OxLDL uptake by SR-BI and CD36, which may segregate these two structurally homologous receptors at the cell surface, leading to differences in intracellular trafficking and degradation.
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Affiliation(s)
- Bing Sun
- Graduate Center for Nutritional Sciences, University of Kentucky Medical Center, Lexington, KY 40536, USA
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Shridas P, Waechter CJ. Human dolichol kinase, a polytopic endoplasmic reticulum membrane protein with a cytoplasmically oriented CTP-binding site. J Biol Chem 2006; 281:31696-704. [PMID: 16923818 DOI: 10.1074/jbc.m604087200] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Dolichol kinase (DK) catalyzes the CTP-dependent phosphorylation of dolichol in the biosynthesis de novo and possibly the recycling of dolichyl monophosphate in yeast and mammals. A cDNA clone from human brain encoding the mammalian homologue, hDKp, of the yeast enzyme has recently been identified. In this study hDK has been overexpressed in Chinese hamster ovary cells and shown to be a polytopic membrane protein localized in the endoplasmic reticulum with an N terminus extended into the lumen and a cytoplasmically oriented C terminus. A conserved sequence, DXXAXXXGXXXGX(8)KKTXEG, found in several enzymes utilizing CTP as substrate including DKs, phytol kinases, and several CDP-diacylglycerol synthetases has been identified, and the possibility that it is part of the CTP-binding domain of hDKp has been investigated. Topological studies indicate that the loop between transmembrane domains (TMD) 11 and TMD12 of hDKp, containing the putative CTP binding domain, faces the cytoplasm. Deletion of the loop between TMD11-12, hDK(Delta459-474), or mutation of selected conserved residues within the cytoplasmic loop results in either a partial or total loss of activity and significant reductions in the affinity for CTP. In addition, the SEC59 gene in the yeast DK mutant was sequenced, and a G420D substitution was found. Conversion of the corresponding residue Gly-443 in hDKp to aspartic acid resulted in inactivation of the mammalian enzyme. These results extend the information on the topological arrangement of hDKp and indicate that the cytoplasmic loop between TMDs 11-12, containing the critical conserved residues, lysine 470 and lysine 471 in the (470)KKTXEG(475) motif, is part of the CTP-binding site in hDK.
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Affiliation(s)
- Preetha Shridas
- Department of Molecular and Cellular Biochemistry, University of Kentucky College of Medicine, Lexington, Kentucky 40536, USA
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Shridas P, Rush JS, Waechter CJ. Identification and characterization of a cDNA encoding a long-chain cis-isoprenyltranferase involved in dolichyl monophosphate biosynthesis in the ER of brain cells. Biochem Biophys Res Commun 2003; 312:1349-56. [PMID: 14652022 DOI: 10.1016/j.bbrc.2003.11.065] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
A long-chain cis-isoprenyltransferase (cis-IPTase) located in the endoplasmic reticulum (ER) catalyzes the chain elongation stage in the pathway for the de novo biosynthesis of dolichyl monophosphate (Dol-P) in eukaryotic cells. In Saccharomyces cerevisiae, the ER-associated cis-IPTase is encoded by the RER2 gene. Mutations in the RER2 gene result in defects in growth and protein N-glycosylation. In this study a cDNA isolated from human brain (Accession No. AK023164.1), which has substantial homology to cis-IPTases from bacteria, Arabidopsis, and S. cerevisiae, has been shown to: (1) complement the growth defect; (2) restore cis-IPTase activity; dolichol and Dol-P synthesis; and (3) restore normal N-glycosylation of carboxypeptidase Y (CPY) in the yeast rer2Delta mutant. Consistent with a role in Dol-P biosynthesis, overexpression of the human cis-isoprenyltransferase (hCIT) cDNA also suppresses the temperature-sensitive growth and CPY hypoglycosylation phenotypes in sec59-1 cells which are defective in Dol-P biosynthesis due to a temperature-sensitive mutation in dolichol kinase. Overexpression of hCIT in Chinese hamster ovary (CHO) cells results in a modest increase in cis-IPTase activity associated with microsomal fractions and the appearance of a new 38kDa polypeptide that co-localizes with calnexin in the ER, the site of Dol-P biosynthesis, even though no transmembrane domains are predicted by a hydropathy plot.
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Affiliation(s)
- Preetha Shridas
- Department of Molecular and Cellular Biochemistry, University of Kentucky College of Medicine, Lexington, KY 40536, USA
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Fernandez F, Shridas P, Jiang S, Aebi M, Waechter CJ. Expression and characterization of a human cDNA that complements the temperature-sensitive defect in dolichol kinase activity in the yeast sec59-1 mutant: the enzymatic phosphorylation of dolichol and diacylglycerol are catalyzed by separate CTP-mediated kinase activities in Saccharomyces cerevisiae. Glycobiology 2002; 12:555-62. [PMID: 12213788 DOI: 10.1093/glycob/cwf068] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Dolichol kinase (DK) catalyzes the CTP-mediated phosphorylation of dolichol in eukaryotic cells, the terminal step in dolichyl monophosphate (Dol-P) biosynthesis de novo. In S. cerevisiae, the SEC59 gene encodes a protein essential for the expression of DK, an enzyme activity that is required for cell viability and normal rates of lipid intermediate synthesis and protein N-glycosylation. This study identifies a cDNA clone from human brain that encodes the mammalian homolog of DK (hDK1p). hDK1 is capable of complementing the growth defect, elevating DK activity, and consequently increasing Dol-P levels in vivo and restoring normal N-glycosylation of carboxypeptidase Y at the restrictive temperature in the temperature-sensitive mutant sec59-1. The CTP-mediated phosphorylation of diacylglycerol (DAG) is unaffected by either the temperature-sensitive mutation in the sec59-1 strain, overexpression of the SEC59 gene, or the mammalian homolog hDK1 under conditions that produced a loss or elevation in the level of DK activity. Additionally, overexpression of hDK1p in Sf-9 cells resulted in a 15-fold increase in DK activity but not DAG kinase activity in crude microsomal fractions. The cloned cDNA contains an open reading frame that would encode a protein with 538 amino acids and a molecular weight of 59,268 kDa. Consistent with this prediction, new polypeptides were detected with an apparent molecular weight of 59-60 kDa when His(6)-tagged constructs of hDK1 or the SEC59 gene were expressed in Sf-9 cells or the temperature-sensitive sec59-1 mutant cells, respectively. These results identify the first cDNA clone encoding a protein required for the expression of DK activity, possibly the catalytic subunit, in a mammalian cell, and establish that the phosphorylation of dolichol and DAG are catalyzed by separate kinase activities in yeast.
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Affiliation(s)
- Fabiana Fernandez
- Institut fur Mikrobiologie, ETH Zentrum, CH-8092 Zurich, Switzerland
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Rajini B, Shridas P, Sundari CS, Muralidhar D, Chandani S, Thomas F, Sharma Y. Calcium binding properties of gamma-crystallin: calcium ion binds at the Greek key beta gamma-crystallin fold. J Biol Chem 2001; 276:38464-71. [PMID: 11502736 DOI: 10.1074/jbc.m102164200] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The beta- and gamma-crystallins are closely related lens proteins that are members of the betagamma-crystallin superfamily, which also include many non-lens members. Although beta-crystallin is known to be a calcium-binding protein, this property has not been reported in gamma-crystallin. We have studied the calcium binding properties of gamma-crystallin, and we show that it binds 4 mol eq of calcium with a dissociation constant of 90 microm. It also binds the calcium-mimic spectral probes, terbium and Stains-all. Calcium binding does not significantly influence protein secondary and tertiary structures. We present evidence that the Greek key crystallin fold is the site for calcium ion binding in gamma-crystallin. Peptides corresponding to Greek key motif of gamma-crystallin (42 residues) and their mutants were synthesized and studied for calcium binding. These peptides adopt beta-sheet conformation and form aggregates producing beta-sandwich. Our results with peptides show that, in Greek key motif, the amino acid adjacent to the conserved aromatic corner in the "a" strand and three amino acids of the "d" strand participate in calcium binding. We suggest that the betagamma superfamily represents a novel class of calcium-binding proteins with the Greek key betagamma-crystallin fold as potential calcium-binding sites. These results are of significance in understanding the mechanism of calcium homeostasis in the lens.
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Affiliation(s)
- B Rajini
- Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad-500007, India
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Abstract
Aggregation and covalent cross-linking of the crystallins, the major structural proteins of the eye lens, increase light scattering by the lens leading to opacification and cataract. Disturbance of calcium homeostasis in the tissue is one of the factors implicated in cataractogenesis. Calcium-activated transglutaminase (TG)-catalyzed cross-linking of some lens proteins has been reported earlier. We show here that alpha-crystallin, a major structural protein in the lens and a member of the small heat shock protein family, is also a substrate for TG-mediated cross-linking, indicating the presence of donor Lys and acceptor Gln residues in the protein. Upon TG-catalyzed dimerization, the secondary and tertiary structures of the protein are altered, and its surface hydrophobicity reduced. The chaperone-like property of the protein, suspected to be one of its functions in situ, is substantially reduced upon such cross-linking. These results, taken together with earlier ones on lens beta-crystallins and vimentin, suggest that TG-mediated events might compromise lens function. Also, since alpha-crystallin occurs not only in the lens but in other tissues as well, such TG-catalyzed cross-linking and the associated alterations in its structure and activity would be of general pathological interest.
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Affiliation(s)
- P Shridas
- Centre for Cellular and Molecular Biology, Hyderabad, India
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Shridas P, Boopathy R. Chemical modification studies of Rhizomucor miehei protease: evidence for the role of basic amino acids in enzyme catalysis. Indian J Biochem Biophys 1998; 35:339-45. [PMID: 10412227] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/13/2023]
Abstract
The effect of chemical modification on milk clotting and proteolytic activities of aspartyl protease obtained from Rhizomucor miehei NRRL 3500 was examined in the absence and the presence of its specific inhibitor pepstatin A. The effect on the ratio of milk clotting activity (MC) to proteolytic activity (PA), an index of the quality of milk clotting proteases was also determined. Modification of the enzyme with trinitrobenzenesulfonic acid, diethylpyrocarbonate and phenylglyoxal produced an increase in the ratio of MC/PA, while modification with 2- hydroxy-5-nitrobenzyl bromide did not affect the ratio. Modification with N-acetylimidazole resulted in a marginal increase in MC/PA ratio. Protection using pepstatin A during modification with phenylglyoxal, N-acetylimidazole and 2-hydroxy-5-nitrobenzyl bromide, protected both MC and PA. In the case of modification by diethylpyrocarbonate, pepstatin A protected only MC. Pepstatin A did not protect both the activities on the modification of the enzyme by trinitrobenzene sulfonic acid. These observations indicate the presence of arginine, tyrosine and tryptophan at the catalytic site of the enzyme, for eliciting MC and PA of the enzyme. In general, modification of the positively charged residues increases the MC/PA ratio of the enzyme. In addition the modified lysine residues responsible for the inactivation of the enzyme were not involved in the active site of the enzyme. Thus the lysine residues might have a secondary role in enzyme catalysis. Further, histidine at the catalytic site was found to be exclusively involved in milk clotting activity. The enzyme with modified histidine residues were more susceptible to autocatalysis, indicating that histidine residues protect the enzyme against autolysis.
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Affiliation(s)
- P Shridas
- Department of Biotechnology, Bharathiar University, Coimbatore, India.
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