EFFECTS of Zoledronic ACID On eNOS Exppression and Vascular Contractility IN Rat Aorta

Abstract 4318

Zoledronic acid (ZOL) is a potent nitrogen-containing bisphosphonate used in the treatment of skeletal metabolic disorders and bone metastatic diseases. It has been shown that the nitrogenous bisphosphonates inhibits enzymes of mevalonate pathway. Similar with statin derivatives, ZOL affects the biological activity of geranyl-geranylated proteins in mevalonate pathway, as shown for the small GTPase RhoA. Although, beneficial effects of statin derivatives on vascular tissue have been reported, there is no study on effects and of ZOL on endothelial functions in vascular tissue and mechanisms of its action. It is important to elucidate the mechanism regulating NO production for endothelial cells to develop new therapeutic strategies for the treatment of impaired endothelial function associated with the vascular diseases. The aim of this study is to demonstrate the molecular mechanism of ZOL in the regulation of endothelial responses and eNOS expression in rat aorta. For his aim, potassium chloride and phenyleprine induced vasoconstriction was evaluated in endothelium intact and denuded isolated rat aorta preparations (n=6) after incubation with ZOL 100 μM and the results were compared with those without ZOL incubation. In addition, to evaluate endothelium dependent or independent effects of ZOL, vasodilator effects of acetylcholine and sodium nitroprussid were tested in the presence and absence of ZOL. To evaluate the influence of protein geranylation in effect of ZOL, contractile effect of phenylephrine vasocontractions was tested after incubation with ZOL in the presence of geranylgeranyl pyrophosphate and farnesyl pyrophosphate, important enzymes of mevolonate pathway. In addition, eNOS mRNA expressions were evaluated with RT-PCR in intact rat aorta or after incubation with ZOL. According to our results, incubation with ZOL decreased potassium chloride and phenylephrine-induced contractions significantly. This decrease was reversed NO-syntase inhibitor N^ı,-nitro-L-arginine methyl esther (L-NAME) 0.1mM. Additionally, incubation with ZOL, increased endothelium-dependent acethycholine-induced relaxations and this effect of ZOL was inhibited by L-NAME. In rat aorta preparations incubated with ZOL, eNOS mRNA expression was increased significantly (1.52 fold) compared with control group. According to these results, we herein provide the first experimental evidence for the physiological role of ZOL in the regulation of eNOS expression and the contractility in the vascular tissues. This effect of ZOL is probably via its influence on RhoA. Since the restoration of NO bioactivity is a major target of present pharmacological and non-pharmacological treatments in cardiovascular medicine, further laboratory and clinical studies to explore the effect of ZOL on vascular endothelium may be helpful to demonstrate the possible benefits.