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Mahaling B, Low SWY, Beck M, Kumar D, Ahmed S, Connor TB, Ahmad B, Chaurasia SS. Damage-Associated Molecular Patterns (DAMPs) in Retinal Disorders. Int J Mol Sci 2022; 23:ijms23052591. [PMID: 35269741 PMCID: PMC8910759 DOI: 10.3390/ijms23052591] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2022] [Revised: 02/22/2022] [Accepted: 02/25/2022] [Indexed: 12/13/2022] Open
Abstract
Damage-associated molecular patterns (DAMPs) are endogenous danger molecules released from the extracellular and intracellular space of damaged tissue or dead cells. Recent evidence indicates that DAMPs are associated with the sterile inflammation caused by aging, increased ocular pressure, high glucose, oxidative stress, ischemia, mechanical trauma, stress, or environmental conditions, in retinal diseases. DAMPs activate the innate immune system, suggesting their role to be protective, but may promote pathological inflammation and angiogenesis in response to the chronic insult or injury. DAMPs are recognized by specialized innate immune receptors, such as receptors for advanced glycation end products (RAGE), toll-like receptors (TLRs) and the NOD-like receptor family (NLRs), and purine receptor 7 (P2X7), in systemic diseases. However, studies describing the role of DAMPs in retinal disorders are meager. Here, we extensively reviewed the role of DAMPs in retinal disorders, including endophthalmitis, uveitis, glaucoma, ocular cancer, ischemic retinopathies, diabetic retinopathy, age-related macular degeneration, rhegmatogenous retinal detachment, proliferative vitreoretinopathy, and inherited retinal disorders. Finally, we discussed DAMPs as biomarkers, therapeutic targets, and therapeutic agents for retinal disorders.
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Affiliation(s)
- Binapani Mahaling
- Ocular Immunology and Angiogenesis Lab, Department of Ophthalmology and Visual Sciences, Froedtert and MCW Eye Institute, Medical College of Wisconsin, Milwaukee, WI 53226, USA; (B.M.); (S.W.Y.L.); (M.B.); (D.K.); (S.A.); (T.B.C.); (B.A.)
| | - Shermaine W. Y. Low
- Ocular Immunology and Angiogenesis Lab, Department of Ophthalmology and Visual Sciences, Froedtert and MCW Eye Institute, Medical College of Wisconsin, Milwaukee, WI 53226, USA; (B.M.); (S.W.Y.L.); (M.B.); (D.K.); (S.A.); (T.B.C.); (B.A.)
| | - Molly Beck
- Ocular Immunology and Angiogenesis Lab, Department of Ophthalmology and Visual Sciences, Froedtert and MCW Eye Institute, Medical College of Wisconsin, Milwaukee, WI 53226, USA; (B.M.); (S.W.Y.L.); (M.B.); (D.K.); (S.A.); (T.B.C.); (B.A.)
| | - Devesh Kumar
- Ocular Immunology and Angiogenesis Lab, Department of Ophthalmology and Visual Sciences, Froedtert and MCW Eye Institute, Medical College of Wisconsin, Milwaukee, WI 53226, USA; (B.M.); (S.W.Y.L.); (M.B.); (D.K.); (S.A.); (T.B.C.); (B.A.)
| | - Simrah Ahmed
- Ocular Immunology and Angiogenesis Lab, Department of Ophthalmology and Visual Sciences, Froedtert and MCW Eye Institute, Medical College of Wisconsin, Milwaukee, WI 53226, USA; (B.M.); (S.W.Y.L.); (M.B.); (D.K.); (S.A.); (T.B.C.); (B.A.)
| | - Thomas B. Connor
- Ocular Immunology and Angiogenesis Lab, Department of Ophthalmology and Visual Sciences, Froedtert and MCW Eye Institute, Medical College of Wisconsin, Milwaukee, WI 53226, USA; (B.M.); (S.W.Y.L.); (M.B.); (D.K.); (S.A.); (T.B.C.); (B.A.)
- Vitreoretinal Surgery, Froedtert and MCW Eye Institute, Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | - Baseer Ahmad
- Ocular Immunology and Angiogenesis Lab, Department of Ophthalmology and Visual Sciences, Froedtert and MCW Eye Institute, Medical College of Wisconsin, Milwaukee, WI 53226, USA; (B.M.); (S.W.Y.L.); (M.B.); (D.K.); (S.A.); (T.B.C.); (B.A.)
- Vitreoretinal Surgery, Froedtert and MCW Eye Institute, Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | - Shyam S. Chaurasia
- Ocular Immunology and Angiogenesis Lab, Department of Ophthalmology and Visual Sciences, Froedtert and MCW Eye Institute, Medical College of Wisconsin, Milwaukee, WI 53226, USA; (B.M.); (S.W.Y.L.); (M.B.); (D.K.); (S.A.); (T.B.C.); (B.A.)
- Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, Milwaukee, WI 53226, USA
- Correspondence: ; Tel.: +1-414-955-2050
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Murata M, Noda K, Yoshida S, Saito M, Fujiya A, Kanda A, Ishida S. Unsaturated Aldehyde Acrolein Promotes Retinal Glial Cell Migration. Invest Ophthalmol Vis Sci 2020; 60:4425-4435. [PMID: 31652327 DOI: 10.1167/iovs.19-27346] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose To investigate the effect of the unsaturated aldehyde acrolein on retinal glial cell migration. Methods Müller glial cell markers expression in TR-MUL5 were confirmed by RT-PCR and immunostaining. Cell viability and migration rate of TR-MUL5 cells were assessed after the stimulation with acrolein. DNA microarray analysis was performed to analyze changes in the expression levels of migration-related genes in Müller glial cells stimulated with acrolein. Real-time PCR and ELISA were performed to validate DNA microarray analysis results. Inhibitors of C-X-C motif chemokine ligand 1 (CXCL1), one of the genes highly upregulated after the exposure to acrolein, and blockers of its receptor, CXCR2, were used to investigate the role of the CXCL1-CXCR2 axis on glial cell migration. CXCL1 concentration was measured in vitreous fluid samples obtained from proliferative diabetic retinopathy (PDR) and nondiabetic control eyes. CXCL1 and CXCR2 expression in glial cells of fibrovascular tissues obtained from PDR patients was examined by immunostaining. Results At a high concentration, acrolein (100 μM) significantly decreased cell viability. However, in moderate, sublethal concentrations (25-50 μM), acrolein induced cell migration and substantially increased the production of CXCL1 in TR-MUL5 cells. CXCL1 concentration was significantly elevated in vitreous fluids of PDR patients, and CXCL1 and CXCR2 were present in glial cells in fibrovascular tissues of PDR patients. CXCL1 stimulation increased glial cell migration in a dose-dependent manner, which was abrogated by the neutralization of the CXCL1-CXCR2 axis. Conclusions Our data demonstrate that acrolein promotes retinal Müller glial cell migration by enhancing CXCL1 production.
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Affiliation(s)
- Miyuki Murata
- Laboratory of Ocular Cell Biology and Visual Science, Faculty of Medicine and Graduate School of Medicine, Hokkaido University, Sapporo, Japan.,Department of Ophthalmology, Faculty of Medicine and Graduate School of Medicine, Hokkaido University, Sapporo, Japan
| | - Kousuke Noda
- Laboratory of Ocular Cell Biology and Visual Science, Faculty of Medicine and Graduate School of Medicine, Hokkaido University, Sapporo, Japan.,Department of Ophthalmology, Faculty of Medicine and Graduate School of Medicine, Hokkaido University, Sapporo, Japan
| | - Shiho Yoshida
- Laboratory of Ocular Cell Biology and Visual Science, Faculty of Medicine and Graduate School of Medicine, Hokkaido University, Sapporo, Japan.,Department of Ophthalmology, Faculty of Medicine and Graduate School of Medicine, Hokkaido University, Sapporo, Japan
| | - Michiyuki Saito
- Department of Ophthalmology, Faculty of Medicine and Graduate School of Medicine, Hokkaido University, Sapporo, Japan
| | - Akio Fujiya
- Department of Ophthalmology, Faculty of Medicine and Graduate School of Medicine, Hokkaido University, Sapporo, Japan
| | - Atsuhiro Kanda
- Laboratory of Ocular Cell Biology and Visual Science, Faculty of Medicine and Graduate School of Medicine, Hokkaido University, Sapporo, Japan.,Department of Ophthalmology, Faculty of Medicine and Graduate School of Medicine, Hokkaido University, Sapporo, Japan
| | - Susumu Ishida
- Laboratory of Ocular Cell Biology and Visual Science, Faculty of Medicine and Graduate School of Medicine, Hokkaido University, Sapporo, Japan.,Department of Ophthalmology, Faculty of Medicine and Graduate School of Medicine, Hokkaido University, Sapporo, Japan
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Xu WQ, Wang YS. The role of Toll-like receptors in retinal ischemic diseases. Int J Ophthalmol 2016; 9:1343-51. [PMID: 27672603 DOI: 10.18240/ijo.2016.09.19] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2015] [Accepted: 03/01/2016] [Indexed: 02/08/2023] Open
Abstract
Toll-like receptors (TLRs) are commonly referred to a series of evolutionary conserved receptors which recognize and respond to various microbes and endogenous ligands. Growing evidence has demonstrated that the expression of TLRs in the retina is regulated during retinal ischemic diseases, including ischemia-reperfusion injury, glaucoma, diabetic retinopathy (DR) and retinopathy of prematurity (ROP). TLRs can be expressed in multiple cells in the retina, such as glial cells, retinal pigment epithelium (RPE), as well as photoreceptor cells and endothelium cells. Activation of TLRs in retina could initiate a complex signal transduction cascade, induce the production of inflammatory cytokines and regulate the level of co-stimulatory molecules, which play prominent roles in the pathogenesis of retinal ischemic diseases. In this review, we summarized current studies about the relationship between TLRs and ischemic retinopathy. A greater understanding of the effect of TLRs on ischemic injuries may contribute to the development of specific TLR targeted therapeutic strategies in these conditions.
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Affiliation(s)
- Wen-Qin Xu
- Department of Ophthalmology, Eye Institute of Chinese PLA, Xijing Hospital, Fourth Military Medical University, Xi'an 710032, Shaanxi Province, China
| | - Yu-Sheng Wang
- Department of Ophthalmology, Eye Institute of Chinese PLA, Xijing Hospital, Fourth Military Medical University, Xi'an 710032, Shaanxi Province, China
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Chi W, Chen H, Li F, Zhu Y, Yin W, Zhuo Y. HMGB1 promotes the activation of NLRP3 and caspase-8 inflammasomes via NF-κB pathway in acute glaucoma. J Neuroinflammation 2015. [PMID: 26224068 PMCID: PMC4518626 DOI: 10.1186/s12974-015-0360-2] [Citation(s) in RCA: 148] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Background Acute glaucoma is a significantly sight-threatening cause of irreversible blindness in the world characterized by a sudden and substantial intraocular pressure (IOP) increase and subsequent retinal ganglion cell (RGC) death. This study aims to explore the role of high-mobility group box 1 (HMGB1) in an acute glaucoma mouse model. Methods An acute glaucoma model was induced by a rapid and substantial increase IOP to 70 mmHg for 60 min via anterior chamber punctured and affused with Balance Salt Solution in C57BL/6 mice. Retinal tissue ischemic damage and loss of RGCs were assessed at 6, 24, 48, 72 h after high IOP treatment, and at 48 h, group with or without recombinant high-mobility group box 1 (rHMGB1), the HMGB1 inhibitor, glycyrrhizic acid (GA), and by HE and immunofluorescent staining. The nuclear factor κB (NF-κB) inhibitor, JSH-23, and caspase-8 inhibitor, Z-IETD-fmk, were injected into vitreous. Reverse transcription and semi-quantitative reverse transcription polymerase chain reaction (RT-PCR), western blotting, and immunoprecipitation were performed to evaluate the expression level of nucleotide-binding domain, leucine-rich repeat containing protein 3 (NLRP3), phosphor-NF-κB p65, caspase-8, caspase-1, apoptosis-associated speck-like protein containing a CARD (ASC), and interleukin-1β (IL-1β). Results HMGB1 was increased in ischemic retinal tissue during acute glaucoma as early as 6 h after rapid IOP elevation. Exogenous HMGB1 exacerbated retinal ischemic damage, RGC loss, and inhibition of endogenous HMGB1 significantly reduced the severity of disease. HMGB1 significantly induced the elevation of canonical NLRP3, ASC, caspase-1, and non-canonical capase-8-ASC inflammasome and promoted the processing of IL-1β. Furthermore, the effect of HMGB1 on NLRP3 inflammasome activation and IL-1β production was dependent on NF-κB pathway. Thus, HMGB1/caspase-8 pathway promoted the processing of IL-1β via NF-κB pathway. Conclusion The findings of this study identified a novel signaling pathway in which HMGB1, in response to acutely elevated intraocular pressure, activated the canonical NLRP3 and non-canonical caspase-8 inflammasomes and production of IL-1β during acute glaucoma development. These results provide new insights to the understanding of the innate response that contributes to pathogenesis of acute glaucoma.
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Affiliation(s)
- Wei Chi
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, 3#925 Xianlienan Road, Guangzhou, 510060, China.
| | - Hongrui Chen
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, 3#925 Xianlienan Road, Guangzhou, 510060, China.
| | - Fei Li
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, 3#925 Xianlienan Road, Guangzhou, 510060, China.
| | - Yingting Zhu
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, 3#925 Xianlienan Road, Guangzhou, 510060, China.
| | - Wei Yin
- Zhongshan medical college, Sun Yat-sen University, Guangzhou, 510030, China.
| | - Yehong Zhuo
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, 3#925 Xianlienan Road, Guangzhou, 510060, China.
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Sakamoto K, Mizuta A, Fujimura K, Kurauchi Y, Mori A, Nakahara T, Ishii K. High-mobility group Box-1 is involved in NMDA-induced retinal injury the in rat retina. Exp Eye Res 2015; 137:63-70. [PMID: 26079740 DOI: 10.1016/j.exer.2015.06.003] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2014] [Revised: 05/16/2015] [Accepted: 06/03/2015] [Indexed: 12/20/2022]
Abstract
High-mobility group Box-1 (HMGB1) is known to be released from injured cells and to induce an inflammatory response. Although HMGB1 was reported to mediate ischemia-reperfusion injury of the brain, its role in glutamate excitotoxicity of the retina remains controversial. Here, the authors demonstrated the evidence that HMGB1 is involved in the retinal damage induced by NMDA. Under ketamine/xylazine anesthesia, male Sprague-Dawley rats were subjected to intravitreal injection of NMDA (200 nmol/eye) or HMGB1 protein derived from bovines (5-15 μg/eye). Intravitreal anti-HMGB1 IgY (5 μg/eye) was simultaneously administered with NMDA or HMGB1. Seven days later, animals were killed and 5-μm retinal sections through the optic nerve head were obtained. These specimens were subjected to morphometry. Intravitreal NMDA and HMGB1 protein evoked cell loss in the ganglion cell layer 7 days later. Intravitreal anti-HMGB1 IgY reduced these damages. Anti-HMGB1 IgY reduced the number of 8-hydroxy-deoxyguanosine (8-OHdG)-positive cells induced by intravitreal NMDA. Toll-like receptor 2/4 antagonist peptide, receptor for advanced glycation end-products (RAGE) antagonist peptide, and FPS-ZM1 significantly reduced the retinal damage induced by HMGB1 protein. The results in the present study suggest that HMGB1 is at least in part involved in NMDA-induced retinal injury, and probably induces cell death of retinal ganglion cells with increase of oxidative stress, via activation of toll-like receptor 2/4 and RAGE in the rat retina.
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Affiliation(s)
- Kenji Sakamoto
- Department of Molecular Pharmacology, Kitasato University School of Pharmaceutical Sciences, Tokyo 108-8641, Japan.
| | - Aya Mizuta
- Department of Molecular Pharmacology, Kitasato University School of Pharmaceutical Sciences, Tokyo 108-8641, Japan
| | - Kyosuke Fujimura
- Department of Molecular Pharmacology, Kitasato University School of Pharmaceutical Sciences, Tokyo 108-8641, Japan
| | - Yuki Kurauchi
- Department of Molecular Pharmacology, Kitasato University School of Pharmaceutical Sciences, Tokyo 108-8641, Japan
| | - Asami Mori
- Department of Molecular Pharmacology, Kitasato University School of Pharmaceutical Sciences, Tokyo 108-8641, Japan
| | - Tsutomu Nakahara
- Department of Molecular Pharmacology, Kitasato University School of Pharmaceutical Sciences, Tokyo 108-8641, Japan
| | - Kunio Ishii
- Department of Molecular Pharmacology, Kitasato University School of Pharmaceutical Sciences, Tokyo 108-8641, Japan
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Semeraro F, Cancarini A, dell'Omo R, Rezzola S, Romano MR, Costagliola C. Diabetic Retinopathy: Vascular and Inflammatory Disease. J Diabetes Res 2015; 2015:582060. [PMID: 26137497 PMCID: PMC4475523 DOI: 10.1155/2015/582060] [Citation(s) in RCA: 253] [Impact Index Per Article: 28.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/11/2014] [Revised: 05/03/2015] [Accepted: 05/13/2015] [Indexed: 02/06/2023] Open
Abstract
Diabetic retinopathy (DR) is the leading cause of visual impairment in the working-age population of the Western world. The pathogenesis of DR is complex and several vascular, inflammatory, and neuronal mechanisms are involved. Inflammation mediates structural and molecular alterations associated with DR. However, the molecular mechanisms underlying the inflammatory pathways associated with DR are not completely characterized. Previous studies indicate that tissue hypoxia and dysregulation of immune responses associated with diabetes mellitus can induce increased expression of numerous vitreous mediators responsible for DR development. Thus, analysis of vitreous humor obtained from diabetic patients has made it possible to identify some of the mediators (cytokines, chemokines, and other factors) responsible for DR pathogenesis. Further studies are needed to better understand the relationship between inflammation and DR. Herein the main vitreous-related factors triggering the occurrence of retinal complication in diabetes are highlighted.
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Affiliation(s)
- F. Semeraro
- Department of Medical and Surgical Specialties, Radiological Sciences and Public Health, University of Brescia, Brescia, Italy
| | - A. Cancarini
- Department of Medical and Surgical Specialties, Radiological Sciences and Public Health, University of Brescia, Brescia, Italy
| | - R. dell'Omo
- Department of Medicine and Health Sciences, University of Molise, Campobasso, Italy
| | - S. Rezzola
- Department of Molecular and Translational Medicine, University of Brescia, Brescia, Italy
| | - M. R. Romano
- Department of Neuroscience, Reproductive Sciences and Dentistry, University of Naples, Italy
| | - C. Costagliola
- Department of Medicine and Health Sciences, University of Molise, Campobasso, Italy
- ICRRS Neuromed, Pozzilli, Isernia, Italy
- *C. Costagliola:
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Janko C, Filipović M, Munoz LE, Schorn C, Schett G, Ivanović-Burmazović I, Herrmann M. Redox modulation of HMGB1-related signaling. Antioxid Redox Signal 2014; 20:1075-85. [PMID: 23373897 PMCID: PMC3928832 DOI: 10.1089/ars.2013.5179] [Citation(s) in RCA: 122] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
SIGNIFICANCE In the cells' nuclei, high-mobility group box protein 1 (HMGB1) is a nonhistone chromatin-binding protein involved in the regulation of transcription. Extracellularly, HMGB1 acts as a danger molecule with properties of a proinflammatory cytokine. It can be actively secreted from myeloid cells or passively leak from any type of injured, necrotic cell. Increased serum levels of active HMGB1 are often found in pathogenic inflammatory conditions and correlate with worse prognoses in cancer, sepsis, and autoimmunity. By damaging cells, superoxide and peroxynitrite promote leakage of HMGB1. RECENT ADVANCES The activity of HMGB1 strongly depends on its redox state: Inflammatory-active HMGB1 requires an intramolecular disulfide bond (Cys23 and Cys45) and a reduced Cys106. Oxidation of the latter blocks its stimulatory activity and promotes immune tolerance. CRITICAL ISSUES Reactive oxygen and nitrogen species create an oxidative environment and can be detoxified by superoxide dismutase (SOD), catalase, and peroxidases. Modifications of the oxidative environment influence HMGB1 activity. FUTURE DIRECTIONS In this review, we hypothesize that manipulations of an oxidative environment by SOD mimics or by hydrogen sulfide are prone to decrease tissue damage. Both the concomitant decreased HMGB1 release and its redox chemical modifications ameliorate inflammation and tissue damage.
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Affiliation(s)
- Christina Janko
- 1 Department of Internal Medicine 3, Rheumatology and Immunology, Friedrich-Alexander-University of Erlangen-Nuremberg , Erlangen, Germany
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Vitreous mediators in retinal hypoxic diseases. Mediators Inflamm 2013; 2013:935301. [PMID: 23365490 PMCID: PMC3556845 DOI: 10.1155/2013/935301] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2012] [Revised: 10/19/2012] [Accepted: 12/01/2012] [Indexed: 12/31/2022] Open
Abstract
The causes of retinal hypoxia are many and varied. Under hypoxic conditions, a variety of soluble factors are secreted into the vitreous cavity including growth factors, cytokines, and chemokines. Cytokines, which usually serve as signals between neighboring cells, are involved in essentially every important biological process, including cell proliferation, inflammation, immunity, migration, fibrosis, tissue repair, and angiogenesis. Cytokines and chemokines are multifunctional mediators that can direct the recruitment of leukocytes to sites of inflammation, promote the process, enhance immune responses, and promote stem cell survival, development, and homeostasis. The modern particle-based flow cytometric analysis is more direct, stable and sensitive than the colorimetric readout of the conventional ELISA but, similar to ELISA, is influenced by vitreous hemorrhage, disruption of the blood-retina barrier, and high serum levels of a specific protein. Finding patterns in the expression of inflammatory cytokines specific to a particular disease can substantially contribute to the understanding of its basic mechanism and to the development of a targeted therapy.
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Watanabe T, Kobata A, Tanigawa T, Nadatani Y, Yamagami H, Watanabe K, Tominaga K, Fujiwara Y, Takeuchi K, Arakawa T. Activation of the MyD88 signaling pathway inhibits ischemia-reperfusion injury in the small intestine. Am J Physiol Gastrointest Liver Physiol 2012; 303:G324-34. [PMID: 22628037 DOI: 10.1152/ajpgi.00075.2012] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Toll-like receptors (TLRs) recognize microbial components and trigger the signaling cascade that activates innate and adaptive immunity. Recent studies have shown that the activation of TLR-dependent signaling pathways plays important roles in the pathogenesis of ischemia-reperfusion (I/R) injuries in many organs. All TLRs, except TLR3, use a common adaptor protein, MyD88, to transduce activation signals. We investigated the role of MyD88 in I/R injury of the small intestine. MyD88 and cyclooxygenase-2 (COX-2) knockout and wild-type mice were subjected to intestinal I/R injury. I/R-induced small intestinal injury was characterized by infiltration of inflammatory cells, disruption of the mucosal epithelium, destruction of villi, and increases in myeloperoxidase activity and mRNA levels of TNF-α and the IL-8 homolog KC. MyD88 deficiency worsened the severity of I/R injury, as assessed using the histological grading system, measuring luminal contents of hemoglobin (a marker of intestinal bleeding), and counting apoptotic epithelial cells, while it inhibited the increase in mRNA expression of TNF-α and KC. I/R significantly enhanced COX-2 expression and increased PGE(2) concentration in the small intestine of wild-type mice, which were markedly inhibited by MyD88 deficiency. COX-2 knockout mice were also highly susceptible to intestinal I/R injury. Exogenous PGE(2) reduced the severity of injury in both MyD88 and COX-2 knockout mice to the level of wild-type mice. These findings suggest that the MyD88 signaling pathway may inhibit I/R injury in the small intestine by inducing COX-2 expression.
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Affiliation(s)
- Toshio Watanabe
- Department of Gastroenterology, Osaka City University Graduate School of Medicine, Osaka Japan.
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