Polygonum multiflorum is a traditional Korean medicine that has been utilized widely in East Asian countries as a longevity agent. Clinical studies have demonstrated that Polygonum multiflorum improves
hypercholesterolemia,
coronary heart disease, neurosis and other diseases commonly associated with aging. However, scientific evidence defining the protective effects and mechanisms of Polygonum multiflorum against
ischemic stroke is incomplete. In the present study, we investigated the cerebrovascular protective effects of Polygonum multiflorum against ischemic
brain injury using an in vivo photothrombotic mouse model. To examine the underlying mechanism of action, we utilized an in vitro human brain microvascular endothelial cell (HBMEC) culture system.
Hexane extracts (HEPM),
ethyl acetate extracts (EAEPM) and
methanol extracts (MEPM) of Polygonum multiflorum (100 mg/kg) were administered intraperitoneally 30 min prior to ischemic insult. Focal
cerebral ischemia was induced in C57BL/6J mice and
endothelial nitric oxide synthase knockout (eNOS KO) mice by photothrombotic cortical occlusion. We evaluated the
infarct volume, as well as neurological and motor function, 24 h after ischemic
brain injury. Following ischemic insult, HEPM induced a significant reduction in
infarct volume and subsequent neurological deficits, compared with EAEPM and MEPM. HEPM significantly decreased
infarct size and improved neurological and motor function, which was not observed in eNOS KO mice, suggesting that this cerebroprotective effect is primarily an eNOS-dependent mechanism. In vitro, HEPM effectively promoted NO production, however these effects were inhibited by the NOS inhibitor,
L-NAME and the PI3K/Akt inhibitor,
LY-294002. Furthermore, HEPM treatment resulted in increased phosphorylation-dependent activation of Akt and eNOS in HBMEC, suggesting that HEPM increased NO production via phosphorylation-dependent activation of Akt and eNOS. In conclusion, HEPM prevents cerebral ischemic damage through an eNOS-dependent mechanism, and thus may have clinical applications as a
protective agent against neurological injury in
stroke.