Hyperoside ameliorates cerebral ischaemic–reperfusion injury by opening the TRPV4 channel in vivo through the IP(3)-PKC signalling pathway

CONTEXT: Hyperoside (Hyp), one of the active flavones from Rhododendron (Ericaceae), has beneficial effects against cerebrovascular disease. However, the effect of Hyp on vasodilatation has not been elucidated. OBJECTIVE: To explore the effect of Hyp on vasodilatation in the cerebral basilar artery (CBA) of Sprague-Dawley (SD) rats suffering with ischaemic–reperfusion (IR) injury. MATERIALS AND METHODS: Sprague-Dawley rats were randomly divided into sham, model, Hyp, Hyp + channel blocker and channel blocker groups. Hyp (50 mg/kg, IC(50) = 18.3 μg/mL) and channel blocker were administered via tail vein injection 30 min before ischaemic, followed by 20 min of ischaemic and 2 h of reperfusion. The vasodilation, hyperpolarization, ELISA assay, haematoxylin–eosin (HE), Nissl staining and channel-associated proteins and qPCR were analysed. Rat CBA smooth muscle cells were isolated to detect the Ca(2+) concentration and endothelial cells were isolated to detect apoptosis rate. RESULTS: Hyp treatment significantly ameliorated the brain damage induced by IR and evoked endothelium-dependent vasodilation rate (47.93 ± 3.09% vs. 2.99 ± 1.53%) and hyperpolarization (–8.15 ± 1.87 mV vs. −0.55 ± 0.42 mV) by increasing the expression of IP3R, PKC, transient receptor potential vanilloid channel 4 (TRPV4), IK(Ca) and SK(Ca) in the CBA. Moreover, Hyp administration significantly reduced the concentration of Ca(2+) (49.08 ± 7.74% vs. 83.52 ± 6.93%) and apoptosis rate (11.27 ± 1.89% vs. 23.44 ± 2.19%) in CBA. Furthermore, these beneficial effects of Hyp were blocked by channel blocker. DISCUSSION AND CONCLUSIONS: Although Hyp showed protective effect in ischaemic stroke, more clinical trial certification is needed due to the difference between animals and humans.