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Plasma Exosomes Contribute to Microvascular Damage in Diabetic Retinopathy by Activating the Classical Complement Pathway.

ABSTRACT: Diabetic retinopathy (DR) is a microvascular complication of diabetes and is the leading cause of vision loss in working-age adults. Recent studies have implicated the complement system as a player in the development of vascular damage and progression of DR. However, the role and activation of the complement system in DR are not well understood. Exosomes, small vesicles that are secreted into the extracellular environment, have a cargo of complement proteins in plasma, suggesting that they can participate in causing the vascular damage associated with DR. We demonstrate that IgG-laden exosomes in plasma activate the classical complement pathway and that the quantity of these exosomes is increased in diabetes. Moreover, we show that a lack of IgG in exosomes in diabetic mice results in a reduction in retinal vascular damage. The results of this study demonstrate that complement activation by IgG-laden plasma exosomes could contribute to the development of DR.

SUBMITTER: Huang C

PROVIDER: S-EPMC6054433 | biostudies-literature | 2018 Aug

REPOSITORIES: biostudies-literature

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Plasma Exosomes Contribute to Microvascular Damage in Diabetic Retinopathy by Activating the Classical Complement Pathway.

Huang Chao C Fisher Kiera P KP Hammer Sandra S SS Navitskaya Svetlana S Blanchard Gary J GJ Busik Julia V JV

Diabetes 20180604 8

Diabetic retinopathy (DR) is a microvascular complication of diabetes and is the leading cause of vision loss in working-age adults. Recent studies have implicated the complement system as a player in the development of vascular damage and progression of DR. However, the role and activation of the complement system in DR are not well understood. Exosomes, small vesicles that are secreted into the extracellular environment, have a cargo of complement proteins in plasma, suggesting that they can p ...[more]

PMID: 29866771

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Project description:BackgroundProliferative diabetic retinopathy (PDR), a sight-threatening retinopathy, is the leading cause of irreversible blindness in adults. Despite strict control of systemic risk factors, a fraction of patients with diabetes develop PDR, suggesting the existence of other potential pathogenic factors underlying PDR. This study aimed to investigate the plasma metabotype of patients with PDR and to identify novel metabolite markers for PDR. Biomarkers identified from this study will provide scientific insight and new strategies for the early diagnosis and intervention of diabetic retinopathy.MethodsA total of 1024 patients with type 2 diabetes were screened. To match clinical parameters between case and control subjects, patients with PDR (PDR, n = 21) or those with a duration of diabetes of ≥10 years but without diabetic retinopathy (NDR, n = 21) were assigned to the present case-control study. Distinct metabolite profiles of serum were examined using liquid chromatography-mass spectrometry (LC-MS).ResultsThe distinct metabolites between PDR and NDR groups were significantly enriched in 9 KEGG pathways (P < 0.05, impact > 0.1), namely, alanine, aspartate and glutamate metabolism, caffeine metabolism, beta-alanine metabolism, purine metabolism, cysteine and methionine metabolism, sulfur metabolism, sphingosine metabolism, and arginine and proline metabolism. A total of 63 altered metabolites played important roles in these pathways. Finally, 4 metabolites were selected as candidate biomarkers for PDR, namely, fumaric acid, uridine, acetic acid, and cytidine. The area under the curve for these biomarkers were 0.96, 0.95, 1.0, and 0.95, respectively.ConclusionsThis study suggested that impairment in the metabolism of pyrimidines, arginine and proline were identified as metabolic dysregulation associated with PDR. And fumaric acid, uridine, acetic acid, and cytidine might be potential biomarkers for PDR. Fumaric acid was firstly reported as a novel metabolite marker with no prior reports of association with diabetes or diabetic retinopathy, which might provide insights into potential new pathogenic pathways for diabetic retinopathy.

Project description:ObjectivesTo determine the risk factors for retinal microvascular impairment on optical coherence tomography angiography (OCT-A) in type 2 diabetic patients without clinical diabetic retinopathy (DR).MethodsThis retrospective and cross-sectional study enrolled 74 diabetic patients without clinically evident DR for the study group and 34 healthy subjects for the control group. OCT-A parameters were measured to determine vascular density (VD) and the foveal avascular zone (FAZ) size in the superficial and deep capillary plexuses (SCP/DCP) of the retina. Clinical data were collected on sex, age, diabetes duration, hemoglobin A1c (HbA1c), hypertension, dyslipidemia, low-density lipoprotein cholesterol (LDL-C), estimated glomerular filtration rate (eGFR) and smoking status. Multiple linear regression analyses were performed to represent the associated clinical variables with OCT-A parameters in diabetic patients.ResultsIn comparison between the study and control groups, the VD in the SCP and DCP were significantly lower in diabetic patients compared to the controls (P = 0.022 and 0.003, respectively). The FAZ size in the SCP and DCP were significantly greater in diabetic patients compared to the controls (P = 0.035 and <0.001, respectively). In age- and sex-adjusted multiple regression analyses for the diabetic patients, dyslipidemia and hypertension were negatively associated with SCP-VD (β = -0.357, P = 0.002; β = -0.239, P = 0.039, respectively). Current smoking was correlated with lower DCP-VD (β = -0.255, P = 0.043). Greater SCP-FAZ size was associated with dyslipidemia and greater LDL-C (β = 0.254, P = 0.013; β = 0.232, P = 0.029, respectively), and greater DCP-FAZ size, with lower eGFR and greater LDL-C (β = -0.355, P = 0.004; β = 0.235, P = 0.037, respectively).ConclusionsDiabetic patients without clinical DR showed lower VD and greater FAZ size in the SCP and DCP compared to healthy controls. In diabetic patients without clinical DR, dyslipidemia and/or high LDL-C were important risk factors for retinal microvascular impairment. Hypertension, current smoking and lower eGFR also contributed to microvascular impairment.

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.

Dataset Information

Plasma Exosomes Contribute to Microvascular Damage in Diabetic Retinopathy by Activating the Classical Complement Pathway.

Publications

Plasma Exosomes Contribute to Microvascular Damage in Diabetic Retinopathy by Activating the Classical Complement Pathway.

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