Shikonin Attenuates Chronic Cerebral Hypoperfusion-Induced Cognitive Impairment by Inhibiting Apoptosis via PTEN/Akt/CREB/BDNF Signaling

Abstract

Shikonin (SK) exerts neuroprotective effects; however, to date, its protective effect against chronic cerebral hypoperfusion- (CCH-) induced vascular dementia (VaD) has not been investigated. Therefore, the current study investigated whether SK could mitigate the cognitive deficits caused by CCH. The effects of SK treatment on the PTEN/Akt/CREB/BDNF signaling pathway and apoptosis in hippocampal neurons were examined in a rat model of VaD established via bilateral common carotid artery occlusion (BCCAO). Fifty-two rats were randomly divided into 4 groups: sham, vehicle, SK-L (10 mg/kg SK per day), and SK-H (25 mg/kg SK per day). SK was regularly administered by gavage for 2 weeks. The results of the water maze test revealed that the escape latency in the vehicle group was significantly longer than that in the sham group, and rats in the vehicle group spent a smaller proportion of time in the target quadrant than those in the sham group. SK treatment reduced the escape latencies and increased the proportion of time spent in the target quadrant. Nissl staining showed morphological damage in the CA1 areas of the hippocampus in the vehicle group. SK treatment alleviated the injuries to hippocampal neurons. Western blot analysis showed higher p-PTEN and lower p-Akt, p-CREB, and BDNF expression in the vehicle group than in the sham group. SK administration reversed the upregulation of p-PTEN and the downregulation of p-Akt, p-CREB, and BDNF. The number of terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling- (TUNEL-) positive cells in the hippocampal CA1 region of the vehicle group was significantly increased. Treatment with SK decreased the number of positive cells. Furthermore, as marker proteins of apoptosis, bcl-2 expression was decreased and bax expression was increased; thus, the ratio of bcl-2/bax was decreased in the vehicle group. SK treatment upregulated the expression of bcl-2 and downregulated the expression of bax, thereby elevating the bcl-2/bax ratio. Moreover, the aforementioned effects of SK were dose-dependent. The effect of 25 mg/kg per day was more obvious than that of 10 mg/kg per day. In conclusion, SK inhibited hippocampal neuronal apoptosis to protect against CCH-induced injury by regulating the PTEN/Akt/CREB/BDNF signaling pathway, consequently improving cognitive impairment.