Rapid Reversal of the Diabetic Endothelial Dysfunction by Pharmacological Inhibition of Poly(ADP-Ribose) Polymerase

Abstract

Abstract-Oxygen-and nitrogen-derived free radicals and oxidants play an important role in the pathogenesis of diabetic endothelial dysfunction. Recently we proposed the importance of oxidant-induced DNA strand breakage and activation of the nuclear enzyme poly(ADP-ribose) polymerase (PARP) in the pathogenesis of diabetic endothelial dysfunction.In this study, we tested whether established diabetic endothelial dysfunction is reversible by PARP inhibition. The novel PARP inhibitor PJ34 (10 mg/kg per day PO) was given at various lengths (4 weeks or 3 days) for established streptozotocin-diabetic animals. In addition, we also tested whether incubation of the aortic rings with PJ34 (3 mol/L) or a variety of other PARP inhibitors for 1 hour affects the diabetic vascular changes. Both 4-week and 3-day PARP-inhibitor treatment of streptozotocin-diabetic mice with established endothelial dysfunction fully reversed the acetylcholine-induced endothelium-dependent relaxations in vitro. Furthermore, 1-hour in vitro incubation of aortae from streptozotocin-diabetic mice with various PARP inhibitors was able to reverse the endothelial dysfunction. ATP, NAD ϩ , and NADPH levels were markedly reduced in diabetic animals, and PARP-inhibitor treatment was able to restore these alterations. Unexpectedly, pharmacological inhibition of PARP not only prevents the development of the endothelial dysfunction but is also able to rapidly reverse it. Thus, PARP activation and the associated metabolic compromise represent an ongoing process in diabetic blood vessels. Pharmacological inhibition of this process is able to reverse diabetic endothelial dysfunction. Key Words: diabetes Ⅲ endothelium Ⅲ nitric oxide Ⅲ necrosis Ⅲ apoptosis P oly(ADP-ribose) polymerase (PARP) is an abundant nuclear enzyme that has been implicated in the cellular response to DNA injury. 1 We recently proposed a role for PARP activation in the pathogenesis of diabetic endothelial dysfunction. Endothelial cells and vascular rings from PARP ϩ/ϩ mice incubated in high glucose were found to exhibit metabolic suppression and loss of endotheliumdependent relaxant function, effects that did not develop in the vascular rings from PARP Ϫ/Ϫ mice and were prevented by pharmacological inhibition of PARP. 2 Ex vivo experiments, examining the immunohistochemical profile and the endothelium-dependent relaxant function of diabetic aortae, demonstrated intravascular production of reactive nitrogen species, the development of DNA strand breakage, and the activation of PARP. 2 Finally, in vivo treatment with PJ34, a novel potent phenanthridinone PARP inhibitor, was found to prevent the development of diabetic endothelial dysfunction in streptozotocin-diabetic mice. 2 In this study we report our recent, unexpected findings that demonstrate that pharmacological PARP inhibition not only prevents the development of diabetic vascular dysfunction but also rapidly restores the function of established diabetic blood vessels.

Endothelial nitric oxide synthase dysfunction in diabetic mice: importance of tetrahydrobiopterin in eNOS dimerisation

“…To ensure that our findings were not specific to the C57BL/6 strain, we carried out similar experiments in Balb/c mice. Diabetes was induced by peritoneal injection of STZ (Sigma-Aldrich, Gillingham, UK), 200 mg/kg for Balb/c and 160 mg/kg for C57BL/6 and GCH-Tg, or of STZ vehicle (citrate buffer; control), as previously described [22][23][24]. Blood glucose was monitored weekly using a one-touch blood glucose meter (Lifescan, High Wycombe, UK); body weight was also measured weekly.…”

Vascular endothelial growth factor in eye disease

“…This concept has been supported by research showing nitrotyrosine formation in the plasma of diabetic patients (Ceriello et al, 2001). Elevated nitrotyrosine levels have also been observed in blood vessels and retinas from diabetic rats (El-Remessy, 2003b;ElRemessy et al, 2006;Kowluru, 2003;Kowluru and Koppolu, 2002;Soriano et al, 2001). Moreover, exogenous peroxynitrite increases VEGF expression in cultured RECs (Platt et al, 2005).…”

The pathogenesis of diabetic complications: the role of DNA injury and poly(ADP-ribose) polymerase activation in peroxynitrite-mediated cytotoxicity

“…Activation of PARP and beneficial effects of various PARP inhibitors have been demonstrated in various forms of endothelial dysfunction such as the one associated with circulatory shock, hypertension, atherosclerosis, preeclampsia and aging (Szabó et al 1997, Hung et al 2002, Martinet et al 2002. Furthermore, recent data suggest that activation of PARP importantly contributes to the development of endothelial dysfunction in various experimental models of diabetes and also in humans (Garcia Soriano et al 2001, Soriano et al 2001a, Pacher et al 2002d, Szabó et al 2002b). In addition, it has recently been demonstrated that PARP activation plays a pathogenetic role in diabetic nephropathy, neuropathy and retinopathy , Minchenko et al 2003, Li et al 2004.…”