Effect of telmisartan on VEGF-induced and VEGF-independent angiogenic responsiveness of coronary endothelial cells in normal and streptozotocin (STZ)-induced diabetic rats

Telmisartan possesses endothelial protective effects due to angiotensin II type 1 receptor antagonist, peroxisome proliferator-activated receptor gamma (PPAR gamma) agonist and antioxidant action. Therefore, our objective was to study effect of telmisartan on angiogenic responsiveness of coronary endothelial cells (cECs) of normal and diabetic rats. Male Wistar rats were divided into six groups, normal rats, diabetic rats 30 d. (30 days after administration of STZ), diabetic rats 60 ds. (60 days after administration of STZ), telmisartan-treated normal rats (2 mg/kg, p.o., for 15 days before isolation of hearts), telmisartan-treated diabetic rats 30 ds, and telmisartan-treated diabetic rats 60 ds. Each group was further divided into two subgroups, sham rat hearts and ischemia-reperfused rat hearts. After isolation of cEC from each subgroup, angiogenic responsiveness and nitric oxide releasing properties were studied using chorioallantoic membrane (CAM) assay and Griess method, respectively. cEC of normal rats showed significant increase in angiogenic responsiveness in presence of vascular endothelial growth factor (VEGF) but not in absence of it. This activity was attenuated by pretreatment of cEC with L-NAME, wortmannin and chelerythrine. Diabetes and ischemia reperfusion injury suppressed angiogenic responsiveness of cEC. Telmisartan treatment showed significant increase in VEGF-induced angiogenic responsiveness and nitric oxide releasing properties of cECs of all subgroups as compared to their respective non-treated subgroups. These effects of telmisartan were significantly inhibited by pretreatment of cECs with L-NAME and wortmannin but not with chelerythrine. Our data suggest that telmisartan improves VEGF-induced coronary angiogenic activity in normal and diabetic rats via stimulation of PI3K/eNOS/NO pathway.