1
|
Xiang B, Zhang Y, Li YM, Zhang K, Zhang YY, Wu LL, Yu GY. Effects of Phenylephrine on Transplanted Submandibular Gland. J Dent Res 2016; 85:1106-11. [PMID: 17122163 DOI: 10.1177/154405910608501208] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Autotransplantation of the submandibular gland is a potential treatment for severe kerato-conjunctivitis sicca. However, one of the major barriers to this procedure is that secretions from the transplanted gland decrease shortly after the operation, which may lead to obstruction of Wharton’s duct, or even to transplantation failure. Using a rabbit model, we investigated whether phenylephrine could improve the secretion from the transplanted gland. We found that phenylephrine treatment significantly reversed the decrease in salivary secretion after transplantation, enhanced the expressions of α1A-, α1B-, and α1D-adrenoceptor mRNA, and ameliorated atrophy of acinar cells. Furthermore, phenylephrine also induced translocation of aquaporin-5 from the cytoplasm to the apical membrane, and increased the levels of phospho-ERK1/2, ERK1/2, phospho-PKCζ, and PKCζ in the transplanted gland. These results indicate that phenylephrine treatment moderates structural injury and improves secretory function in the transplanted submandibular gland through promoting α1-adrenoceptor expression and post-receptor signal transduction.
Collapse
Affiliation(s)
- B Xiang
- Department of Oral and Maxillofacial Surgery, Peking University School and Hospital of Stomatology, Zhong Guan Cun South St. 22, 100081, Beijing, PRC
| | | | | | | | | | | | | |
Collapse
|
2
|
Velazquez-Garcia S, Valle S, Rosa TC, Takane KK, Demirci C, Alvarez-Perez JC, Mellado-Gil JM, Ernst S, Scott DK, Vasavada RC, Alonso LC, Garcia-Ocaña A. Activation of protein kinase C-ζ in pancreatic β-cells in vivo improves glucose tolerance and induces β-cell expansion via mTOR activation. Diabetes 2011; 60:2546-59. [PMID: 21911744 PMCID: PMC3178296 DOI: 10.2337/db10-1783] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
OBJECTIVE PKC-ζ activation is a key signaling event for growth factor-induced β-cell replication in vitro. However, the effect of direct PKC-ζ activation in the β-cell in vivo is unknown. In this study, we examined the effects of PKC-ζ activation in β-cell expansion and function in vivo in mice and the mechanisms associated with these effects. RESEARCH DESIGN AND METHODS We characterized glucose homeostasis and β-cell phenotype of transgenic (TG) mice with constitutive activation of PKC-ζ in the β-cell. We also analyzed the expression and regulation of signaling pathways, G1/S cell cycle molecules, and β-cell functional markers in TG and wild-type mouse islets. RESULTS TG mice displayed increased plasma insulin, improved glucose tolerance, and enhanced insulin secretion with concomitant upregulation of islet insulin and glucokinase expression. In addition, TG mice displayed increased β-cell proliferation, size, and mass compared with wild-type littermates. The increase in β-cell proliferation was associated with upregulation of cyclins D1, D2, D3, and A and downregulation of p21. Phosphorylation of D-cyclins, known to initiate their rapid degradation, was reduced in TG mouse islets. Phosphorylation/inactivation of GSK-3β and phosphorylation/activation of mTOR, critical regulators of D-cyclin expression and β-cell proliferation, were enhanced in TG mouse islets, without changes in Akt phosphorylation status. Rapamycin treatment in vivo eliminated the increases in β-cell proliferation, size, and mass; the upregulation of cyclins Ds and A in TG mice; and the improvement in glucose tolerance-identifying mTOR as a novel downstream mediator of PKC-ζ-induced β-cell replication and expansion in vivo. CONCLUSIONS PKC:-ζ, through mTOR activation, modifies the expression pattern of β-cell cycle molecules leading to increased β-cell replication and mass with a concomitant enhancement in β-cell function. Approaches to enhance PKC-ζ activity may be of value as a therapeutic strategy for the treatment of diabetes.
Collapse
Affiliation(s)
- Silvia Velazquez-Garcia
- Department of Medicine, Division of Endocrinology and Metabolism, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Shelley Valle
- Department of Medicine, Division of Endocrinology and Metabolism, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Taylor C. Rosa
- Department of Medicine, Division of Endocrinology and Metabolism, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Karen K. Takane
- Department of Medicine, Division of Endocrinology and Metabolism, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Cem Demirci
- Department of Pediatrics, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Juan C. Alvarez-Perez
- Department of Medicine, Division of Endocrinology and Metabolism, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Jose M. Mellado-Gil
- Department of Medicine, Division of Endocrinology and Metabolism, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Sara Ernst
- Department of Medicine, Division of Endocrinology and Metabolism, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Donald K. Scott
- Department of Medicine, Division of Endocrinology and Metabolism, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Rupangi C. Vasavada
- Department of Medicine, Division of Endocrinology and Metabolism, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Laura C. Alonso
- Department of Medicine, Division of Endocrinology and Metabolism, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Adolfo Garcia-Ocaña
- Department of Medicine, Division of Endocrinology and Metabolism, University of Pittsburgh, Pittsburgh, Pennsylvania
- Corresponding author: Adolfo Garcia-Ocaña,
| |
Collapse
|
3
|
Li L, Zhou Y, Wang C, Zhao YL, Zhang ZG, Fan D, Cui XB, Wu LL. Src tyrosine kinase regulates angiotensin II-induced protein kinase Czeta activation and proliferation in vascular smooth muscle cells. Peptides 2010; 31:1159-64. [PMID: 20307614 DOI: 10.1016/j.peptides.2010.03.014] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/20/2010] [Revised: 03/12/2010] [Accepted: 03/12/2010] [Indexed: 11/25/2022]
Abstract
Protein kinase Czeta (PKCzeta) isoform plays a critical role in angiotensin II (AngII)-elicited extracellular signal-regulated kinase 1/2 (ERK1/2) activation and proliferation in vascular smooth muscle cells (VSMCs). However, the exact signal transduction mechanism by which AngII activates PKCzeta has not been clarified. In this study, we investigated the role of Src in PKCzeta activation and VSMCs proliferation induced by AngII. AngII-induced rapid activation of PKCzeta, which was associated with its phosphorylation and nuclear translocation. AngII not only induced Src activation but also promoted the physical association between Src and PKCzeta, which was abolished by Src inhibition with PP2. Src inhibition also abrogated AngII-stimulated PKCzeta activation, ERK1/2 phosphorylation and VSMCs proliferation. In conclusion, Src kinase plays an important role in AngII-elicited PKCzeta activation and the subsequent downstream signaling including ERK1/2 activation and VSMCs proliferation.
Collapse
Affiliation(s)
- Li Li
- Department of Physiology and Pathophysiology, Peking University Health Science Center and Key Laboratory of Molecular Cardiovascular Sciences, Ministry of Education, Beijing 100191, China
| | | | | | | | | | | | | | | |
Collapse
|
4
|
Ford SP, Zhang L, Zhu M, Miller MM, Smith DT, Hess BW, Moss GE, Nathanielsz PW, Nijland MJ. Maternal obesity accelerates fetal pancreatic beta-cell but not alpha-cell development in sheep: prenatal consequences. Am J Physiol Regul Integr Comp Physiol 2009; 297:R835-43. [PMID: 19605766 DOI: 10.1152/ajpregu.00072.2009] [Citation(s) in RCA: 130] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Maternal obesity affects offspring weight, body composition, and organ function, increasing diabetes and metabolic syndrome risk. We determined effects of maternal obesity and a high-energy diet on fetal pancreatic development. Sixty days prior to breeding, ewes were assigned to control [100% of National Research Council (NRC) recommendations] or obesogenic (OB; 150% NRC) diets. At 75 days gestation, OB ewes exhibited elevated insulin-to-glucose ratios at rest and during a glucose tolerance test, demonstrating insulin resistance compared with control ewes. In fetal studies, ewes ate their respective diets from 60 days before to 75 days after conception when animals were euthanized under general anesthesia. OB and control ewes increased in body weight by approximately 43% and approximately 6%, respectively, from diet initiation until necropsy. Although all organs were heavier in fetuses from OB ewes, only pancreatic weight increased as a percentage of fetal weight. Blood glucose, insulin, and cortisol were elevated in OB ewes and fetuses on day 75. Insulin-positive cells per unit pancreatic area were 50% greater in fetuses from OB ewes as a result of increased beta-cell mitoses rather than decreased programmed cell death. Lambs of OB ewes were born earlier but weighed the same as control lambs; however, their crown-to-rump length was reduced, and their fat mass was increased. We conclude that increased systemic insulin in fetuses from OB ewes results from increased glucose exposure and/or cortisol-induced accelerated fetal beta-cell maturation and may contribute to premature beta-cell function loss and predisposition to obesity and metabolic disease in offspring.
Collapse
Affiliation(s)
- Stephen P Ford
- Center for the Study of Fetal Programming, Department of Animal Science, University of Wyoming, Laramie, Wyoming, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
5
|
Abstract
Members of the serine/threonine PKC (protein kinase C) family perform diverse functions in multiple cell types. All members of the family are activated in signalling cascades triggered by occupation of cell surface receptors, but the cPKC (conventional PKC) and nPKC (novel PKC) isoforms are also responsive to fatty acid metabolites. PKC isoforms are involved in various aspects of pancreatic beta-cell function, including cell proliferation, differentiation and death, as well as regulation of secretion in response to glucose and muscarinic receptor agonists. Recently, the nPKC isoform, PKCepsilon, has also been implicated in the loss of insulin secretory responsiveness that underpins the development of Type 2 diabetes.
Collapse
|
6
|
Schmitz-Peiffer C, Biden TJ. Protein kinase C function in muscle, liver, and beta-cells and its therapeutic implications for type 2 diabetes. Diabetes 2008; 57:1774-83. [PMID: 18586909 PMCID: PMC2453608 DOI: 10.2337/db07-1769] [Citation(s) in RCA: 107] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/16/2008] [Accepted: 04/15/2008] [Indexed: 01/27/2023]
Affiliation(s)
| | - Trevor J. Biden
- From the Garvan Institute of Medical Research, Darlinghurst, Australia
| |
Collapse
|
7
|
Vasavada RC, Wang L, Fujinaka Y, Takane KK, Rosa TC, Mellado-Gil JMD, Friedman PA, Garcia-Ocaña A. Protein kinase C-zeta activation markedly enhances beta-cell proliferation: an essential role in growth factor mediated beta-cell mitogenesis. Diabetes 2007; 56:2732-43. [PMID: 17686945 DOI: 10.2337/db07-0461] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
OBJECTIVE Diabetes results from a deficiency of functional beta-cells. Previous studies have identified hepatocyte growth factor (HGF) and parathyroid hormone-related protein (PTHrP) as two potent beta-cell mitogens. The objective of this study is to determine 1) whether HGF and PTHrP have additive/synergistic effects on beta-cell growth and proliferation; 2) the signaling pathways through which these growth factors mediate beta-cell mitogenesis; and 3) whether activation of this/these signaling pathway(s) enhances human beta-cell replication. RESEARCH DESIGN AND METHODS We generated and phenotypically analyzed doubly transgenic mice overexpressing PTHrP and HGF in the beta-cell. INS-1 and primary mouse and human islet cells were used to identify mitogenic signaling pathways activated by HGF and/or PTHrP. RESULTS Combined overexpression of HGF and PTHrP in the beta-cell of doubly transgenic mice did not result in additive/synergistic effects on beta-cell growth and proliferation, suggesting potential cross-talk between signaling pathways activated by both growth factors. Examination of these signaling pathways in INS-1 cells revealed atypical protein kinase C (PKC) as a novel intracellular target activated by both HGF and PTHrP in beta-cells. Knockdown of PKC zeta, but not PKC iota/lambda, expression using specific small-interfering RNAs blocked growth factor-induced INS-1 cell proliferation. Furthermore, adenovirus-mediated delivery of kinase-dead PKC zeta completely inhibited beta-cell proliferation in primary islet cells overexpressing PTHrP and/or HGF. Finally, adenovirus-mediated delivery of constitutively active PKC zeta in mouse and human primary islet cells significantly enhanced beta-cell proliferation. CONCLUSIONS PKC zeta is essential for PTHrP- and HGF-induced beta-cell proliferation. PKC zeta activation could be useful in therapeutic strategies for expanding beta-cell mass in vitro and in vivo.
Collapse
Affiliation(s)
- Rupangi C Vasavada
- Department of Medicine, Division of Endocrinology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, USA
| | | | | | | | | | | | | | | |
Collapse
|
8
|
Fernández E, Martín MA, Fajardo S, Escrivá F, Alvarez C. Increased IRS-2 content and activation of IGF-I pathway contribute to enhance beta-cell mass in fetuses from undernourished pregnant rats. Am J Physiol Endocrinol Metab 2007; 292:E187-95. [PMID: 16912057 DOI: 10.1152/ajpendo.00283.2006] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
We have previously shown that fetuses from undernourished (U) pregnant rats exhibited an increased beta-cell mass probably related to an enhanced IGF-I replicative response. Because IGF-I signaling pathways have been implicated in regulating beta-cell growth, we investigated in this study the IGF-I transduction system in U fetuses. To this end, an in vitro model of primary fetal islets was developed to characterize glucose/IGF-I-mediated signaling that specially influences beta-cell proliferation. We found that U fetal islets showed a greater replicative response to glucose and IGF-I than controls. Furthermore, insulin receptor substrate (IRS)-2 protein and its association with p85 were also increased. In the complete absence of IGF-I or stimulatory glucose, U islets presented an increased basal phosphorylation of downstream signals of the phosphatidylinositol 3-kinase (PI3K) pathway such as PKB, glycogen synthase kinase (GSK)3alpha/beta, PKCzeta, and mammalian target of rapamycin (mTOR). Similarly, phosphorylation of these proteins (except GSK3alpha/beta) by glucose and IGF-I was augmented even though total protein content remained unchanged. Downstream of PKB, direct glucose activation of mTOR was increased as well. In contrast, ERK1/2 phosphorylation was unaffected by undernutrition, but ERK activation seemed to be required to induce a higher proliferative response in U islets. In conclusion, we have demonstrated that fetal U islets show increased IRS-2 content and an enhancement in both basal and glucose/IGF-I activations of the IRS-2/PI3K/PKB pathway. These molecular changes may be responsible for the greater glucose/IGF-I islet replication and contribute to the increased beta-cell mass found in these fetuses.
Collapse
Affiliation(s)
- Elisa Fernández
- Departamento de Bioquímica y Biología Molecular, Facultad de Farmacia, Universidad Complutense, Ciudad Universitaria, 28040 Madrid, Spain
| | | | | | | | | |
Collapse
|
9
|
Zhao Y, Liu J, Li L, Liu L, Wu L. Role of Ras/PKCζ/MEK/ERK1/2 signaling pathway in angiotensin II-induced vascular smooth muscle cell proliferation. ACTA ACUST UNITED AC 2005; 128:43-50. [PMID: 15721486 DOI: 10.1016/j.regpep.2004.12.012] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2004] [Accepted: 12/10/2004] [Indexed: 10/26/2022]
Abstract
The role of protein kinase C (PKC) and its cross talk with extracellular signal-regulated kinase (ERK) cascade in angiotensin II (AngII)-elicited vascular smooth muscle cell (VSMC) proliferation are still unclear. In this study, the PKC pathway of AngII to activate ERK1/2 and induce cell proliferation was investigated in rat aortic smooth muscle cells. The proliferation of VSMCs was tested by [3H]-thymidine incorporation assay. Phosphorylated and non-phosphorylated PKCzeta, ERK1/2, Elk-1, and mitogen-activated ERK-activating kinase (MEK) were estimated by Western blot analysis. The interactions of signal molecules were examined by immunoprecipitation. AngII-induced VSMC proliferation and activation of ERK1/2 and nuclear transcription factor Elk-1 were all down-regulated by PKC non-specific inhibitor (staurosporine) and PKCzeta pseudosubstrate inhibitor (PS-PKCzeta). Dominant negative Ras transfection into VSMCs decreased AngII-induced PKCzeta and ERK1/2 phosphorylation. AngII stimulated the association of PKCzeta with Ras. AngII-induced MEK phosphorylation was inhibited by PKCzeta pseudosubstrate inhibitor and the PKCzeta-MEK complex was detected by immunoprecipitation. These results suggest that PKCzeta isoform is involved in VSMC proliferation and Elk-1 activation. AngII can activate ERK1/2 by Ras/PKCzeta/MEK pathway, which may be one of the important signal transduction pathways in AngII-induced VSMC proliferation.
Collapse
Affiliation(s)
- Yali Zhao
- Department of Physiology and Pathophysiology, Peking University Health Science Center, Beijing, 100083, China
| | | | | | | | | |
Collapse
|
10
|
Hurbin A, Coll JL, Dubrez-Daloz L, Mari B, Auberger P, Brambilla C, Favrot MC. Cooperation of amphiregulin and insulin-like growth factor-1 inhibits Bax- and Bad-mediated apoptosis via a protein kinase C-dependent pathway in non-small cell lung cancer cells. J Biol Chem 2005; 280:19757-67. [PMID: 15767261 PMCID: PMC2685917 DOI: 10.1074/jbc.m413516200] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Amphiregulin (AR) and insulin-like growth factor-1 (IGF1) are growth factors known to promote non-small cell lung cancer (NSCLC) survival. We have previously published that 1) AR and IGF1, secreted by H358 NSCLC cells, cooperate to protect those cells and H322 NSCLC cells from serum-starved apoptosis; 2) H358 cells resist Bax-induced apoptosis through an inhibition of Bax conformational change. We show here that the antiapoptotic activity of the AR/IGF1 combination is specifically abolished by the PKC inhibitors calphostin C and staurosporine, but not by the MAPK and phosphatidylinositol 3-kinase inhibitors PD98059 and wortmannin, suggesting the involvement of a PKC-dependent and MAPK- and phosphatidylinositol 3-kinase-independent survival pathway. The PKCdelta inhibitor rottlerin restores apoptosis induced by serum deprivation. In addition, phosphorylation of PKCdelta and PKCzeta/lambda, but not of PKCalpha/beta(II), increases in serum-starved H358 cells and in H322 cells treated with an AR/IGF1 combination and is blocked by calphostin C. The combination of AR and IGF1 increases p90(rsk) and Bad phosphorylation as well as inhibiting the conformational change of Bax by a PKC-dependent mechanism. Finally, PKCdelta, PKCzeta, or p90(rsk) small interfering RNAs block the antiapoptotic activity of AR/IGF1 combination but have no effect on partial apoptosis inhibition observed with each factor used alone. Constitutively active PKC expression inhibits serum deprivation-induced apoptosis, whereas a catalytically inactive form of p90(rsk) restores it. Thus, AR and IGF1 cooperate to prevent apoptosis by activating a specific PKC-p90(rsk)-dependent pathway, which leads to Bad and Bax inactivation. This signaling pathway is different to that used by single factor.
Collapse
Affiliation(s)
- Amandine Hurbin
- Groupe de Recherche Sur Le Cancer du Poumon : Bases Moléculaires de la Progression Tumorale, Dépistage et Thérapie Génique
INSERM : U578Institut Albert BonniotRond Point de La Chantourne
38706 LA TRONCHE CEDEX,FR
| | - Jean-Luc Coll
- Groupe de Recherche Sur Le Cancer du Poumon : Bases Moléculaires de la Progression Tumorale, Dépistage et Thérapie Génique
INSERM : U578Institut Albert BonniotRond Point de La Chantourne
38706 LA TRONCHE CEDEX,FR
| | - Laurence Dubrez-Daloz
- Mort cellulaire et cancer
INSERM : U517IFR100Université de BourgogneFaculte de Medecine
7, Boulevard Jeanne D'Arc
21079 DIJON CEDEX,FR
| | - Bernard Mari
- Physiopathologie de la survie et de la mort cellulaire et infection virale
INSERM : U526IFR50Université de Nice Sophia-AntipolisFaculte de Médecine
28, Avenue de Valombrose
06107 NICE CEDEX 2,FR
| | - Patrick Auberger
- Physiopathologie de la survie et de la mort cellulaire et infection virale
INSERM : U526IFR50Université de Nice Sophia-AntipolisFaculte de Médecine
28, Avenue de Valombrose
06107 NICE CEDEX 2,FR
| | - Christian Brambilla
- Groupe de Recherche Sur Le Cancer du Poumon : Bases Moléculaires de la Progression Tumorale, Dépistage et Thérapie Génique
INSERM : U578Institut Albert BonniotRond Point de La Chantourne
38706 LA TRONCHE CEDEX,FR
| | - Marie-Christine Favrot
- Groupe de Recherche Sur Le Cancer du Poumon : Bases Moléculaires de la Progression Tumorale, Dépistage et Thérapie Génique
INSERM : U578Institut Albert BonniotRond Point de La Chantourne
38706 LA TRONCHE CEDEX,FR
- * Correspondence should be adressed to: Marie-Christine Favrot
| |
Collapse
|
11
|
D'Alessandris C, Andreozzi F, Federici M, Cardellini M, Brunetti A, Ranalli M, Del Guerra S, Lauro D, Del Prato S, Marchetti P, Lauro R, Sesti G. IncreasedO‐glycosylation of insulin signaling proteins results in their impaired activation and enhanced susceptibility to apoptosis in pancreatic β‐cells. FASEB J 2004; 18:959-61. [PMID: 15059979 DOI: 10.1096/fj.03-0725fje] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Because adverse effects of glucose were attributed to its increased routing through the hexosamine pathway (HBP), we inquired whether HBP activation affects pancreatic beta-cell survival. Exposure of human islets to high glucose resulted in increased apoptosis of beta-cells upon serum deprivation that was reversed by azaserine. Also, glucosamine, a direct precursor of the downstream product of the HBP, increased human beta-cells apoptosis upon serum deprivation, which was reversed by benzyl-2-acetamido-2-deoxy-alpha-d-galactopyranoside (BADGP), an inhibitor of protein O-glycosylation. These results were reproduced in RIN rat beta-cells. Glucosamine treatment resulted in inhibition of tyrosine-phosphorylation of the insulin receptor (IR), IRS-1, and IRS-2, which was associated with increased O-glycosylation. These changes caused impaired activation of the PI 3-kinase/Akt survival signaling that resulted in reduced GSK-3 and FOXO1a inactivation. BADGP reversed the glucosamine-induced reduction in insulin-stimulated phosphorylation of IR, IRS-1, IRS-2, Akt, GSK-3, and FOXO1a. Impaired FOXO1a inactivation sustained expression of the pro-apoptotic protein Bim, without affecting Bad, Bcl-XL, or Bcl-2 expression. These results indicate that hyperglycemia may increase susceptibility to apoptosis of human and rat beta-cell through activation of the HBP. Increased routing of glucose through this metabolic pathway results in impaired activation of the IR/IRSs/PI3-kinase/Akt survival pathway by induction of O-glycosylation of signaling molecules.
Collapse
Affiliation(s)
- Cristina D'Alessandris
- Laboratory of Molecular Medicine, Department of Internal Medicine, University of Rome-Tor Vergata, Rome, Italy
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
12
|
Friedrichsen BN, Richter HE, Hansen JA, Rhodes CJ, Nielsen JH, Billestrup N, Møldrup A. Signal transducer and activator of transcription 5 activation is sufficient to drive transcriptional induction of cyclin D2 gene and proliferation of rat pancreatic beta-cells. Mol Endocrinol 2003; 17:945-58. [PMID: 12586844 DOI: 10.1210/me.2002-0356] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Signal transducer and activator of transcription 5 (STAT5) activation plays a central role in GH- and prolactin-mediated signal transduction in the pancreatic beta-cells. In previous experiments we demonstrated that STAT5 activation is necessary for human (h)GH-stimulated proliferation of INS-1 cells and hGH-induced increase of mRNA-levels of the cell cycle regulator cyclin D2. In this study we have further characterized the role of STAT5 in the regulation of cyclin D expression and beta-cell proliferation by hGH. Cyclin D2 mRNA and protein levels (but not cyclin D1 and D3) were induced in a time-dependent manner by hGH in INS-1 cells. Inhibition of protein synthesis by coincubation with cycloheximide did not affect the hGH-induced increase of cyclin D2 mRNA levels at 4 h. Expression of a dominant negative STAT5 mutant, STAT5aDelta749, partially inhibited cyclin D2 protein levels. INS-1 cells transiently transfected with a cyclin D2 promoter-reporter construct revealed a 3- to 5-fold increase of transcriptional activity in response to hGH stimulation. Furthermore, coexpression of a constitutive active STAT5 mutant (either CA-STAT5a or CA-STAT5b) was sufficient to drive transactivation of the promoter. CA-STAT5b was stably expressed in INS-1 cells under the control of a doxycycline-inducible promoter. Gel retardation experiments using a probe representing a putative STAT5 binding site in the cyclin D2 promoter revealed binding of the doxycycline-induced CA-STAT5b. Furthermore, induction of CA-STAT5b stimulated transcriptional activation of the cyclin D2 promoter and induced hGH-independent proliferation in these cells. In primary beta-cells, adenovirus-mediated expression of CA-STAT5b profoundly stimulated DNA-synthesis (5.3-fold over control) in the absence of hGH. Our studies indicate that STAT5 activation is sufficient to drive proliferation of the beta-cells and that cyclin D2 may be a critical target gene for STAT5 in this process.
Collapse
|
13
|
Eitel K, Staiger H, Rieger J, Mischak H, Brandhorst H, Brendel MD, Bretzel RG, Häring HU, Kellerer M. Protein kinase C delta activation and translocation to the nucleus are required for fatty acid-induced apoptosis of insulin-secreting cells. Diabetes 2003; 52:991-7. [PMID: 12663471 DOI: 10.2337/diabetes.52.4.991] [Citation(s) in RCA: 115] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Insulin resistance as well as pancreatic beta-cell failure can be induced by elevated free fatty acid (FFA) levels. We studied the mechanisms of FFA-induced apoptosis in rat and human beta-cells. Chronic treatment with high physiological levels of saturated fatty acids (palmitate and stearate), but not with monounsaturated (palmitoleate and oleate) or polyunsaturated fatty acids (linoleate), triggers apoptosis in approximately 20% of cultured RIN1046-38 cells. Apoptosis restricted to saturated FFAs was also observed in primary cultured human beta-cells, suggesting that this mechanism is potentially relevant in vivo in humans. To further analyze FFA-induced signaling pathways leading to apoptosis, we used RIN1046-38 cells. Apoptosis was accompanied by a rapid (within 15 min) nuclear translocation of protein kinase C (PKC)-delta and subsequent lamin B1 disassembly. This translocation was impaired by the phospholipase C inhibitor U-73122, which also substantially reduced apoptosis. Furthermore, lamin B1 disassembly and apoptosis were decreased by cell transfection with a dominant-negative mutant form of PKC-delta. These data suggest that nuclear translocation and kinase activity of PKC-delta are both necessary for saturated fatty acid-induced apoptosis.
Collapse
Affiliation(s)
- Katrin Eitel
- Internal Medicine IV, University of Tübingen, Tübingen, Germany
| | | | | | | | | | | | | | | | | |
Collapse
|
14
|
Kuemmerle JF. IGF-I elicits growth of human intestinal smooth muscle cells by activation of PI3K, PDK-1, and p70S6 kinase. Am J Physiol Gastrointest Liver Physiol 2003; 284:G411-22. [PMID: 12444011 DOI: 10.1152/ajpgi.00310.2002] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Endogenous IGF-I regulates growth of human intestinal smooth muscle cells by jointly activating phosphatidylinositol 3-kinase (PI3K) and ERK1/2. The 70-kDa ribosomal S6 kinase (p70S6 kinase) is a key regulator of cell growth activated by several independently regulated kinases. The present study characterized the role of p70S6 kinase in IGF-I-induced growth of human intestinal smooth muscle cells and identified the mechanisms of p70S6 kinase activation. IGF-I-induced growth elicited via either the PI3K or ERK1/2 pathway required activation of p70S6 kinase. IGF-I elicited concentration-dependent activation of PI3K, 3-phosphoinositide-dependent kinase-1 (PDK-1), and p70S6 kinase that was sequential and followed similar time courses. IGF-I caused time-dependent and concentration-dependent phosphorylation of p70S6 kinase on Thr(421)/Ser(424), Thr(389), and Thr(229) that paralleled p70S6 kinase activation. p70S6 kinase(Thr(421)/Ser(424)) phosphorylation was PI3K dependent and PDK-1 independent, whereas p70S6 kinase(Thr(389)) and p70S6 kinase(Thr(229)) phosphorylation and p70S6 kinase activation were PI3K dependent and PDK-1 dependent. IGF-I elicited sequential Akt(Ser(308)), Akt(Ser(473)), and mammalian target of rapamycin(Ser(2448)) phosphorylation; however, transfection of muscle cells with kinase-inactive Akt1(K179M) showed that these events were not required for IGF-I to activate p70S6 kinase and stimulate proliferation of human intestinal muscle cells.
Collapse
Affiliation(s)
- John F Kuemmerle
- Departments of Medicine and Physiology, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, VA 23298-0711, USA.
| |
Collapse
|