Dataset Information

Nitrosative stress plays an important role in Wnt pathway activation in diabetic retinopathy.

ABSTRACT:

Aims

Diabetes is associated with nitrosative stress in multiple tissues. Overactivation of the Wnt pathway has been shown to play a pathogenic role in diabetic retinopathy (DR). The purpose of this study was to investigate whether nitrosative stress contributes to aberrant activation of Wnt signaling in diabetes.

Results

Nitrosative stress induced by peroxynitrite (PN), 4-hydroxynonenal (HNE), or high glucose (HG) in retinal cells was assessed by a dichlorofluorescein fluorescence assay or by Western blot analysis and enzyme-linked immunosorbent assay of 3-nitrotyrosine (3-NT). These nitrosative stress inducers activated the canonical Wnt pathway, as shown by Western blot analysis of phosphorylated low-density lipoprotein receptor-related protein 6 (pLRP6), total and nuclear ?-catenin levels, Luciferase reporter assay, and expression of the Wnt target genes intercellular adhesion molecule 1 (ICAM-1) and vascular endothelial growth factor (VEGF). Uric acid (UA), a PN scavenger, and 5,10,15,20-Tetrakis (4-sulfonatophenyl) porphyrinato Iron III Chloride (FeTPPS), a PN decomposition catalyst, suppressed Wnt signaling and ICAM-1 and VEGF overexpression induced by PN, HNE, and HG. Furthermore, UA and FeTPPS also inhibited Wnt signaling induced by the Wnt ligand. In streptozotocin-induced diabetic rats, retinal levels of 3-NT, ?-catenin, nuclear ?-catenin, pLRP6, VEGF, and ICAM-1 were markedly increased. UA treatment for 6 weeks ameliorated diabetes-induced Wnt signaling in the diabetic rat retina. The UA treatment also decreased inflammatory cell infiltration and extraverted serum albumin in the perfused retina of diabetic rats, suggesting decreased retinal inflammation and vascular leakage.

Innovation and conclusion

Nitrosative stress in diabetes contributes to Wnt pathway activation in the retina, and Wnt signaling may mediate the pathogenic effects of nitrosative stress in DR.

SUBMITTER: Liu Q

PROVIDER: S-EPMC3579458 | biostudies-literature | 2013 Apr

REPOSITORIES: biostudies-literature

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Nitrosative stress plays an important role in Wnt pathway activation in diabetic retinopathy.

Liu Qiuping Q Li Jingming J Cheng Rui R Chen Ying Y Lee Kyungwon K Hu Yang Y Yi Jinglin J Liu Zuguo Z Ma Jian-xing JX

Antioxidants & redox signaling 20121015 10

<h4>Aims</h4>Diabetes is associated with nitrosative stress in multiple tissues. Overactivation of the Wnt pathway has been shown to play a pathogenic role in diabetic retinopathy (DR). The purpose of this study was to investigate whether nitrosative stress contributes to aberrant activation of Wnt signaling in diabetes.<h4>Results</h4>Nitrosative stress induced by peroxynitrite (PN), 4-hydroxynonenal (HNE), or high glucose (HG) in retinal cells was assessed by a dichlorofluorescein fluorescence ...[more]

PMID: 23066786

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Project description:Aims/introductionThe role of the renal nitric oxide (NO) system in the pathophysiology of diabetic nephropathy constitutes a very challenging and fertile field for future investigation. The purpose of the present study was to investigate whether NO donors can attenuate diabetic renal fibrosis and apoptosis through modulating oxidative-and nitrosative-stress, and Wnt signaling using in vivo diabetic models.Materials and methodsDiabetic rat was induced by a single intraperitoneal injection of streptozotocin. Rats in each group were intraperitoneally given 2,2'-(hydroxynitrosohydrazino)bis-ethanamine (1 U/kg/day) and vehicle for 28 and 56 consecutive days. Expression of the oxidative-and nitrosative-stress, and Wnt signaling components were examined in kidneys from diabetic animals by quantitative reverse transcription polymerase chain reaction, western blot analysis and immunohistochemical staining.ResultsNO donor treatment significantly reduced the ratio of kidney weight to bodyweight and proteinuria. This treatment also significantly restored the suppressive effect of diabetes on urinary NO2 + NO3 levels. Immunohistochemistry showed that NO donor treatment significantly reduced transforming growth factor (TGF)-?1, fibronectin, cleaved caspase-3 and triphosphate-biotin nick end-labeling expression in the glomeruli of diabetic rats. We found that diabetes promoted 8-hydroxy-2'-deoxyguanosine, and peroxynitrite expression coincided with reduced endothelial NO synthase expression in glomeruli. Interestingly, NO donor treatment completely removed oxidative stress and nitrosative stress, and restored endothelial NO synthase expression in diabetic renal glomeruli. Immunohistomorphometry results showed that NO donor treatment significantly restored suppressed Wnt5a expression and ?-catenin immunoreactivities in glomeruli. Based on laser-captured microdissection for quantitative reverse transcription polymerase chain reaction, diabetes significantly increased TGF-?1, and fibronectin expression coincided with depressed Wnt5a expression. NO donor treatment reduced TGF-?1, fibronectin activation, and the suppressing effect of diabetes on Wnt5a and ?-catenin expression in renal glomeruli.ConclusionsNO donor treatment alleviates extracellular matrix accumulation and apoptosis in diabetic nephropathy in vivo by not only preventing the diabetes-mediated oxidative and nitrostative stress, but also restoring downregulation of endothelial NO synthase expression and Wnt/?-catenin signaling. These findings suggest that modulation of NO is a viable alternative strategy for rescuing diabetic renal injury.

Project description:The complement system plays a crucial role in retinal homeostasis. While the proteomic analysis of ocular tissues in diabetic retinopathy (DR) has shown the deposition of complement proteins, their exact role in the pathogenesis of DR is yet unclear. We performed a detailed investigation of the role of the complement system by evaluating the levels of major complement proteins including C3, C1q, C4b, Complement Factor B (CFB), and Complement Factor H (CFH) and their activated fragments from both the classical and alternative pathways in vitreous humor and serum samples from proliferative DR (PDR) patients and controls. Further, the expressions of complements and several other key pro- and anti-angiogenic genes in the serum and vitreous humor were analyzed in the blood samples of PDR and non-PDR (NPDR) patients along with controls without diabetes. We also assessed the pro-inflammatory cytokines and matrix metalloproteinases in the vitreous humor samples. There was a significant increase in C3 and its activated fragment C3bα' (110 kDa) along with a corresponding upregulation of CFH in the vitreous of PDR patients, which confirmed the increased activation of the alternative complement pathway in PDR. Likewise, a significant upregulation of angiogenic genes and downregulation of anti-angiogenic genes was seen in PDR and NPDR cases. Increased MMP9 activity and upregulation of inflammatory markers IL8 and sPECAM with a downregulation of anti-inflammatory marker IL-10 in PDR vitreous indicated the possible involvement of microglia in DR pathogenesis. Further, a significantly high C3 deposition in the capillary wall along with thickening of basement membranes and co-localization of CFH expression with CD11b+ve activated microglial cells in diabetic retina suggested microglia as a source of CFH in diabetic retina. The increased CFH levels could be a feedback mechanism for arresting excessive complement activation in DR eyes. A gradual increase of CFH and CD11b expression in retina with early to late changes in epiretinal membranes of DR patients indicated a major role for the alternative complement pathway in disease progression.

Project description:IntroductionIn response to gamma-irradiation (IR)-induced double-strand DNA breaks, cells undergo cell-cycle arrest, allowing time for DNA repair before reentering the cell cycle. G2/M checkpoint activation involves activation of ataxia telangiectasia mutated (ATM)/ATM- and rad3-related (ATR) kinases and inhibition of Cdc25 phosphatases, resulting in inhibition of Cdc2 kinase and subsequent G2/M cell-cycle arrest. Previous studies from our laboratory showed that the G2/M checkpoint activation after IR exposure of MCF-7 breast cancer cells is dependent on the activation of extracellular signal-regulated protein kinase 1 and 2 (ERK1/2) signaling. In the present studies, we investigated the role of Ras-related C3 botulinum toxin substrate 1 (Rac1) guanosine triphosphatase (GTPase) in IR-induced G2/M checkpoint response and ERK1/2 activation, as well as in cell survival after IR.MethodsWith Rac1-specific inhibitor, dominant negative mutant Rac1 (N17Rac1) and specific small interfering RNA, the effect of Rac1 on IR-induced G2/M checkpoint response and ERK1/2 activation was examined in human breast cancer cells. In addition, the effect of Rac1 on cell survival after irradiation was assessed by using Rac1-specific inhibitor.ResultsIR exposure of MCF-7 breast cancer cells was associated with a marked activation of Rac1 GTPase. Furthermore, inhibition of Rac1 by using specific inhibitor, dominant-negative Rac1 mutant, or specific siRNA resulted in attenuation of IR-induced G2/M arrest and concomitant diminution of IR-induced activation of ATM, ATR, Chk1, and Chk2 kinases, as well as phosphorylation of Cdc2-Tyr15. Moreover, Rac1 inhibition or decreased Rac1 expression also abrogated IR-induced phosphorylation of mitogen-activated protein kinase kinase 1 and 2 (MEK1/2) and ERK1/2. Ultimately, inhibition of Rac1 markedly increased cellular sensitivity to IR exposure, which involves induction of apoptosis.ConclusionStudies in this report suggest that Rac1 GTPase plays an essential role in the activation of IR-induced ERK1/2 signaling and subsequent G2/M checkpoint response. Furthermore, results also support a role for Rac1 in promoting cell survival after irradiation treatment.

Dataset Information

Nitrosative stress plays an important role in Wnt pathway activation in diabetic retinopathy.

Aims

Results

Innovation and conclusion

Publications

Nitrosative stress plays an important role in Wnt pathway activation in diabetic retinopathy.

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