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Olga Rafikova, Folami Lamoke, Diana Gutsaeva, Wan Jin Jahng, Andrea Repossi, Francesco Facchiano, Manuela Bartoli; Modulation of toll-like receptor 4 signaling in human diabetic retina by peroxiredoxin 1 . Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):4288.
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© ARVO (1962-2015); The Authors (2016-present)
Toll-like receptor 4 (TLR4) has been shown to promote retinal inflammation in ischemic retinopathies, however its regulation in these pathological conditions still remain unclear and understudied. The redox protein peroxiredoxin 1 (Prx1) is oxidized in response to several oxidative insults and when oxidized promotes TLR4 maturation. More recently our group and others have shown that oxidized Prx-1 can be secreted and can work as an alarmin by activating/phosphorylating TLR4. Due to the potential relevance of TLR4 expression in inflammatory retinal diseases, here we wanted to investigate the potential role of Prx-1 in human diabetic retinopathy (DR).
Vitreous and retinal samples of post-mortem diabetic (n=9) and not diabetic (n=6) donors were obtained from Georgia Eye Bank. Vitreous of diabetic (n=10) and not diabetic (n=7) patients undergoing pars plan vitrectomy for different ocular pathologies were also analyzed. Western blotting analysis was conducted to assess retinal expression of total and phosphorylated TLR4 as well as Prx-1 levels and oxidation state in retinal and vitreal samples (respectively). Human retinal endothelial cells (HuREC) were subjected to different stressors including hydrogen peroxide (H2O2), high glucose (HG, 25mM) and control conditions (5mM glucose and the osmotic control 25mM L-glucose). Secretion of Prx-1 and activation/phosphorylation of TLR4 was also monitored by Western blotting analysis.
Western blotting analysis showed increased TLR4 expression and phosphorylation in diabetic donor retinas as compared to not diabetic donors. Prx-1 expression was also up-regulated, however there was a significant increase in oxidized and oligomeric forms of Prx-1 in the diabetic donors as compared to not diabetic retinas. Furthermore, Prx-1 was present in the vitreous of all the diabetic donors and patients while it was almost absent in the vitreous of not diabetic subjects. Stimulation of HuREC with HG and H2O2 promoted secretion of Prx-1 and activation/phosphorylation of TLR4. Blockade of Prx-1 in the cell media with neutralizing antibodies blocked HG and H2O2-induced TLR4 phosphorylation/activation.
We have identified Prx-1 as a new contributing factor to the induction of chronic inflammation in human diabetic retinopathy through its modulation of TLR4 phosphorylation/activation.
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