Esculetin improves cognitive impairments induced by transient cerebral ischaemia and reperfusion in mice via regulation of mitochondrial fragmentation and mitophagy

Mitochondrial dynamics regulate mitochondrial autophagy (mitophagy) and apoptosis, which are important events for the quality control of mitochondria and mitochondrial-associated diseases. Esculetin (ESC) is a natural coumarin that exhibits inspiring biological activities in a variety of animal models, but its neuroprotective effects on cerebral ischaemia have not been clearly elucidated. In this paper, we demonstrated the effects of ESC on transient cerebral ischaemia and reperfusion injury induced in a mouse model and examined the possible underlying mechanisms by investigating mitochondrial fragmentation-regulated mitochondrial autophagy and apoptosis. The experimental results showed that ESC treatment alleviated neurological defects and improved cognitive impairments in transient bilateral common carotid artery occlusion (tBCCAO)-treated mice. Further mechanism studies showed that tBCCAO induced mitochondrial oxidative stress injuries and triggered mitochondrial fragmentation, which were evident by the elevated levels of malondialdehyde and mitochondrial dynamin-related protein 1 (Drp1) and the downregulated activities of superoxide dismutase and nuclear transcription factor E2-related factor 2 (Nrf2). ESC treatment significantly alleviated tBCCAO-induced mitochondrial stress and mitochondrial fragmentation. Moreover, mitophagy and mitochondrial apoptosis were stimulated in response to the mitochondrial oxidative stress in the hippocampus of tBCCAO-treated mice, and ESC treatment regulated the expression of mitophagy-related factors, including Bnip3, Beclin1, Pink1, and parkin, the LC-3 II/I ratio, and apoptosis-related factors, including p53, Bax, and caspase 3. Taken together, our results suggest that ESC treatment regulated hippocampal mitophagy and mitochondrial apoptosis triggered by mitochondrial stress via the mediation of mitochondrial fragmentation during transient cerebral ischaemia and reperfusion injury, which provides insight into the potential of ESC for further therapeutic implications.