The Role And Mechanism Of Profilin-1 In Diabetic Retinopathy

Part Ⅰ Profilin-1 mediates microvascular endothelial dysfunction in diabetic retinopathy through HIF-la-dependent pathwayBackground:Diabetic retinopathy(DR),a well-known serious complication of diabetes mellitus,can eventually advance to end-stage blindness.Objective:To investigate the role of profilin-1(PFN1)in microvascular endothelial dysfunction(MVED)triggered by DR.Methods:We assessed the expression of PFN1 and hypoxia inducible factor-la(HIF-1α)in human retinal microvascular endothelial cells(HRMECs)determined by real-time quantitative PCR;Establishment of 6-month-old SD mouse DR model,assessed the expression of PFN1 and the function of metformin in PFN1-mediated MVED by immunofluorescence and immunoblotting.Results:High glucose upregulated PFN1 and HIF-1α expression levels.These changes were associated with increased permeability,apoptosis,and angiogenesis in vivo and in vitro.Metformin prevented high glucose or hyperglycemia-induced MVED by inhibition of HIF-1α/PFN1 signaling in cultured HRMECs and in SD rats with DR.Conclusions:Our results indicate that activation of HIF-1α/PFN1 by high glucose mediates permeability,apoptosis,and angiogenesis and that metformin alleviates MVED by suppressing HIF-1α/PFN1 signaling during DR.These results suggest a potential therapeutic strategy for preventing the onset of PFN1 in early-stage of DR.Part Ⅱ ANGPTL-8 induces diabetic retinal inflammation by activating Profilin-1Background:Diabetic retinopathy(DR),the most common cause of irreversible blindness in working-age adults,results in central vision loss that is caused by microvascular damage to the inner lining of the back of the eye,the retina.Objective The aim of this work was to assess the temporal relationships between angiopoietin-like protein-8(ANGPTL-8),a novel adipocytokine factor,and diabetic retinal inflammation and microvascular dysfunction.The downstream pathway(s)and upstream mediator(s)of ANGPTL-8 were then determined under high glucose(HG)conditions.Methods:Diabetic rats and control animals were randomly assigned to receive hypoxia inducible factor-1 alpha(HIF-1α)blockade(doxorubicin or shRNA)or vehicle for 8 weeks.Human retinal microvascular endothelial cells(HRMECs)were incubated with normal or high glucose,with or without blockade or recombinant proteins,for ANGPTL-8,HIF-la,and vascular endothelial growth factor(VEGF).The levels of ANGPTL-8,profilin-1,HIF-1 a,VEGF,interleukin 1 beta(IL-1β),IL-6,and intercellular adherent molecule 1(ICAM-1)in the rat retinas and HRMEC extracts were examined by Western blotting and real-time RT-PCR.Results:The levels of ANGPTL-8,profilin-1,HIF-1α,and VEGF protein and mRNA were significantly higher in the diabetic rats and HG-exposed HRMECs.ANGPTL-4 was a potent modulator of increased inflammation,permeability,and angiogenesis via activation of the profilin-1 signaling pathway.Our results showed that ANGPTL-8 upregulation was induced by HG,which was dependent on HIF-1α activation that was also triggered by HG,both in vivo and in vitro.Conclusions:Our results suggest that targeting ANGPTL-8,alone or in combination with profilin-1,may be an effective therapeutic strategy and diagnostic screening biomarker for proliferative diabetic retinopathy and other vitreous-retinal inflammatory diseases.