Poly(ADPribose)polymerase inhibition counteracts renal hypertrophy and multiple manifestations of peripheral neuropathy in diabetic Akita mice

PURPOSE. This study evaluated the role for poly(ADP-ribose) polymerase (PARP) in diabetes-induced cataractogenesis and early retinal changes. METHODS. Control and streptozotocin (STZ)-diabetic rats were treated with or without the PARP inhibitors 1,5-isoquinolinediol (ISO; 3 mg kg Ϫ1 d Ϫ1 intraperitoneally) and 10-(4-methyl-piperazin-1-ylmethyl)-2H-7-oxa-1,2-diaza-benzo- [de]anthracen-3-1 (GPI-15427, 30 mg kg Ϫ1 d Ϫ1 orally) for 10 weeks after the first 2 weeks without treatment. Lens clarity was evaluated by indirect ophthalmoscopy and slit lamp examination, and retinal changes were evaluated by immunohistochemistry and Western blot analysis. In in vitro studies, cultured human lens epithelial cells and bovine retinal pericytes and endothelial cells were exposed to high glucose or palmitate. RESULTS. PARP is expressed in lens, and poly(ADP-ribosyl)ated proteins are primarily localized in the 38-to 87-kDa range of the protein spectrum, with several minor bands at 17 to 38 kDa. The 38-to 87-kDa and the 17-to 38-kDa poly(ADPribosyl)ated protein expression increased by 74% and 275%, respectively, after 4 weeks of diabetes and by approximately 65% early after exposure of lens epithelial cells to 30 mM glucose. Both PARP inhibitors delayed, but did not prevent, the formation of diabetic cataract. The number of TUNEL-positive nuclei in flatmounted retinas increased approximately 4-fold in STZ diabetic rats, and this increase was prevented by ISO and GPI-15427. Both PARP inhibitors reduced diabetes-induced retinal oxidative-nitrosative and endoplasmic reticulum stress and glial activation. GPI-15427 (20 M) prevented oxidative-nitrosative stress and cell death in palmitate-exposed pericytes and endothelial cells. CONCLUSIONS. PARP activation is implicated in the formation of diabetic cataract and in early retinal changes. These findings provide a rationale for the development of PARP inhibitors for the prevention of diabetic ocular complications. (Invest Ophthalmol Vis Sci

New Therapeutic and Biomarker Discovery for Peripheral Diabetic Neuropathy: PARP Inhibitor, Nitrotyrosine, and Tumor Necrosis Factor-α

This study evaluated poly(ADP-ribose) polymerase (PARP) inhibition as a new therapeutic approach for peripheral diabetic neuropathy using clinically relevant animal model and endpoints, and nitrotyrosine (NT), TNF-α, and nitrite/nitrate as potential biomarkers of the disease. Control and streptozotocin-diabetic rats were maintained with or without treatment with orally active PARP inhibitor 10-(4-methyl-piperazin-1-ylmethyl)-2H-7-oxa-1,2-diaza-benzo[de]anthracen-3-one (GPI-15,427), 30 mg kg−1 d−1, for 10 wk after first 2 wk without treatment. Therapeutic efficacy was evaluated by poly(ADP-ribosyl)ated protein expression (Western blot analysis), motor and sensory nerve conduction velocities, and tibial nerve morphometry. Sciatic nerve and spinal cord NT, TNF-α, and nitrite/nitrate concentrations were measured by ELISA. NT localization in peripheral nervous system was evaluated by double-label fluorescent immunohistochemistry. A PARP inhibitor treatment counteracted diabetes-induced motor and sensory nerve conduction slowing, axonal atrophy of large myelinated fibers, and increase in sciatic nerve and spinal cord NT and TNF-α concentrations. Sciatic nerve NT and TNF-α concentrations inversely correlated with motor and sensory nerve conduction velocities and myelin thickness, whereas nitrite/nitrate concentrations were indistinguishable between control and diabetic groups. NT accumulation was identified in endothelial and Schwann cells of the peripheral nerve, neurons, astrocytes, and oligodendrocytes of the spinal cord, and neurons and glial cells of the dorsal root ganglia. The findings identify PARP as a compelling drug target for prevention and treatment of both functional and structural manifestations of peripheral diabetic neuropathy and provide rationale for detailed evaluation of NT and TNF-α as potential biomarkers of its presence, severity, and progression