PARP, Na+/H+‐exchanger‐1, and early diabetes‐induced retinal changes

Abstract

Abstract Purpose To evaluate the roles for PARP and Na+/H+‐exchanger‐1 (NHE‐1) in early diabetes‐induced changes in the retina and retinal capillary cells Methods Control (C) and STZ‐diabetic (D) rats were treated with/without the PARP inhibitors, 1,5‐isoquinolinediol (ISO, 3 mgkg‐1d‐1 i.p.) or 10‐(4‐Methyl‐piperazin‐1‐ylmethyl)‐2H‐7‐oxa‐1,2‐diaza‐benzo[de]‐anthracen‐3‐one (GPI 15427, 30 mgkg‐1d‐1), for 10 wks after 2 wks without treatment. Apoptosis was evaluated in flat‐mounted retinas by TUNEL assay, and nitrotyrosine (NT), poly(ADP‐ribose) (PAR), GFAP, BiP/GRP78 and GRP94 expressions by immunohistochemistry and Western blot analyses. Primary bovine retinal pericytes and endothelial cells were cultured with/without 0.6 mM palmitate, or in 5 mM or 30 mM glucose. Apoptosis was assessed by TUNEL and caspase‐3 assays, superoxide production by ethidium fluorescence, and NT and PAR by immunocytochemistry. Results In the PARP study, the number of TUNEL‐positive nuclei was increased ~4‐fold in D, and this increase was prevented in D+ISO and D+GPI 15427. PARP inhibitors counteracted oxidative‐nitrosative and endoplasmic reticulum stresses, and glial activation. Palmitate dose dependently increased superoxide production in cultured retinal cells. GPI 15427, 20 microM, prevented FFA‐induced increase in the rate of apoptosis, and alleviated NT and PAR accumulation in both pericytes and endothelial cells. In the NHE‐1 study, the specific NHE‐1 inhibitor cariporide (10 microM) prevented high glucose‐induced apoptosis, and alleviated oxidative‐nitrosative stress and PAR accumulation in bovine retinal pericytes. In vivo studies in the STZ‐diabetic rat model are in progress. Conclusion PARP and NHE‐1 play an important role in early diabetes‐induced changes in retina and retinal capillary cells.