Low-dose dipyridamole treatment partially prevents diabetes mellitus-induced vascular endothelial and renal abnormalities in rats

Abstract

Dipyridamole is a conventionally used platelet inhibitor employed for the secondary prevention of transient ischemic attack. Dipyridamole could potentiate some of the vascular protective effects of nitric oxide (NO) [1]. Intriguingly, the vascular protective action of dipyridamole was reported to be mediated by its stimulatory action on endothelial nitric oxide synthase (eNOS) activity [2]. However, the effect of dipyridamole in diabetes mellitus-induced vascular endothelial dysfunction (VED) is not yet known. There are strong associations between diabetic VED and nephropathy [3,4]. Administration of dipyridamole either alone or in combination with aspirin reduced the incidence of proteinuria in patients with diabetic nephropathy [5]. Dipyridamole at high-dose is considered proischemic, and it could cause a marked coronary steal effect. Dipyridamole, however, at lowdose orallymight have aminimal hemodynamic effect [6]. The present study investigated the effect of low-dose dipyridamole in diabetes mellitus-induced VED and nephropathy in rats. The experimental protocol of this study was approved by the ‘Institutional Animal Ethics Committee’. Wistar albino rats of either sex (n = 6) weighing about 250 to 350 g were used. Group I (Normal Control), rats were maintained on standard food and water, and no treatment was given. Group II (Diabetic Control), rats were administered streptozotocin (STZ) (50 mg/kg, i.p., once), andwere allowed for 8 weeks to develop experimental VED and nephropathy (rats showing blood glucose level of greater than 200 mg/dl after 72 h of STZ administration were selected and named as diabetics). Group III (Dipyridamole per se), normal rats were administered low-dose dipyridamole (30 mg/kg/day, p.o.) for 4 weeks. Group IV (Dipyrida), the diabetic rats after 4 weeks of STZ-administration were treated with low-dose dipyridamole (30 mg/kg/day, p.o.) for 4 weeks. Groups V and VI (Wortmannin or L-NAME Incubated Aortic Ring of Dipyridamole Treated), the diabetic rats were treated with low-dose dipyridamole (30 mg/kg/day, p.o., 4 weeks) as mentioned in group IV. The in vitro effects of wortmannin (100 nM) or L-NAME (100 μM) (the aortic ring was incubated with either wortmannin or L-NAME for 30-min) on endothelium-dependent and -independent relaxation in the phenylephrine (3 × 10−6 M)-precontracted isolated aortic ring preparation were evaluated. One way ANOVA, followed by Tukey's multiple comparison test was employed to analyse the data. STZ-induced diabetic rats developed VED and nephropathy in 8 weeks. Diabetes mellitus-induced VED was associated with marked reduction in acetylcholine-induced endothelium-dependent relaxation, decrease in aortic and serum nitrite/nitrate concentration, and induction of oxidative stress and lipid alteration. Scanning electron microscopic and histological studies on thoracic aorta revealed a marked impairment in vascular endothelial integrity. Moreover, elevation of serum creatinine and blood urea nitrogen, and induction of proteinuria accompanying with renal oxidative stress were noted in diabetic rats. However, treatment with low-dose dipyridamole partially, but substantially prevented aforementioned vascular endothelial and renal abnormalities in diabetic rats without affecting the elevated glucose concentration. Interestingly, incubation of aortic rings, isolated from dipyridamole-treated diabetic rats, with either wortmannin (inhibitor of phosphatidylinositide 3-kinase, PI3-K) or LNAME (inhibitor of nitric oxide synthase, NOS) markedly abolished dipyridamole-associated improvement in acetylcholine-induced endothelium-dependent relaxation (Table 1, Figs. 1 and 2). To summarize, dipyridamole in low-dose partially, but significantly prevents diabetes mellitus-induced VED by activating endothelial PI3K-eNOS-NO signalling pathways. The renovascular reduction of oxidative stress might explain the mechanism pertaining to the partial renoprotective action of low-dose dipyridamole in diabetes mellitus. We express our gratitude to the management of RITS, Sirsa, Haryana, India for the support. The authors of this manuscript have certified that