Author + information
Hirsutine, a compound extracted from Uncaria rhynchophylla, has been proven to be able to exert vasodilatory effects and cardioprotective effects on hypoxic neonatal rat cardiomyocytes. In order to acquire a deeper insight into the pharmacological functions and clinical applications of hirsutine, we synthesized its analogue, G2, to serve as our drug candidate for the treatment of microvascular dysfunction.
Superior mesenteric arteries isolated from male Sprague-Dawley rats was mounted in myograph chambers (Danish Myo Technology, Aarhus, Denmark) for further functional study. G2, including the enantiomers G2-a and G2-b in G2, was separately subjected to superior mesenteric arteries from rats pre-exposed to 60 mM KCl or 10 μM phenylephrine to confirm their vasorelaxant effects. Rat diabetic model was also established to assess the in vitro vasodilatory effect of G2. G2 was also subjected to SD diabetic rats for in vivo measurement of endothelium protection and histological assessment.
G2 and its enantiomers G2-a and G2-b could stimulate apparent vasodilatory effects on KCl and phenylephrine pre-treated mesenteric arteries. Meanwhile, the G2-a (IC50=0.092 μM) was 100 fold and 10 fold stronger in vasodilation than the enantiomer G2-b (IC50=7.9 uM) and the racemate G2 (IC50=0.499 μM) respectively. Endothelium denudation could reduce G2, G2-a, and G2-binduced vasorelaxant effects. Diabetes triggered endothelium dysfunction and L-NAME pretreatment could lead to similar vasorelaxant effect reduction, which meant that G2-evoked vasodilatory effect was endothelium-dependent. G2 subjected to diabetic rats could attenuate diabetes-damaged acetylcholine-induced endothelium-dependent relaxations. Immunohistochemical staining and western blot showed that eNOS was upregulated and no concentration was increased in diabetic vessels.
G2, and its enantiomers G2-a and G2-b could exert endothelium-dependent vasodilatory effects in vitro through and endothelial protection in vivo. Meanwhile, the effectiveness of G2-a and G2-b was highly distinguishing in wire myograph assay.