Ginkgo biloba Extract Prevents Female Mice from Ischemic Brain Damage and the Mechanism Is Independent of the HO1/Wnt Pathway

Jatin Tulsulkar, Bryan Glueck, Terry D. Hinds, Zahoor A. Shah

It is well known that gender differences exist in experimental or clinical stroke with respect to brain damage and loss of functional outcome. We have previously reported neuroprotective properties of Ginkgo biloba/EGb 761® (EGb 761) in transient and permanent mouse models of brain ischemia using male mice, and the mechanism of action was attributed to the upregulation of the heme oxygenase 1 (HO1)/Wnt pathway. Here, we sought to investigate whether EGb 761's protective effect in ovariectomized female mice following stroke is also mediated by the HO1/Wnt pathway. Female mice were ovariectomized (OVX) to remove the protective effect of estrogen and were treated with EGb 761 for 7 days prior to inducing permanent middle cerebral artery occlusion (pMCAO) and allowed to survive for an additional 7 days. At day 8, animals were sacrificed, and the brains were harvested for infarct volume analysis, western blots, and immunohistochemistry. The OVX female mice treated with EGb 761 showed significantly lower infarct size as compared to Veh/OVX animals. EGb 761 treatment in female mice inhibited apoptosis by preventing caspase-3 cleavage and blocking the extrinsic apoptotic pathway. EGb 761 pretreatment significantly enhanced neurogenesis in OVX mice as compared to the Veh/OVX group and significantly upregulated androgen receptor expression with no changes in HO1/Wnt signaling. These results suggest that EGb 761 prevented brain damage in OVX female mice by improving grip strength and neurological deficits, and the mechanism of action is not through HO1/Wnt but via blocking the extrinsic apoptotic pathway.