Histone deacetylase 9 plays a role in sevoflurane‐induced neuronal differentiation inhibition by inactivating cAMP ‐response element binding protein transcription and inhibiting the expression of neurotrophin‐3

Abstract Postoperative cognitive decline (POCD) is a common and serious complication following anesthesia and surgery; however, the precise mechanisms of POCD remain unclear. Our previous research showed that sevoflurane impairs adult hippocampal neurogenesis (AHN) and thus cognitive function in the aged brain by affecting neurotrophin‐3 (NT‐3) expression; however, the signaling mechanism involved remains unexplored. In this study, we found a dramatic decrease in the proportion of differentiated neurons with increasing concentrations of sevoflurane, and the inhibition of neural stem cell differentiation was partially reversed after the administration of exogenous NT‐3. Understanding the molecular underpinnings by which sevoflurane affects NT‐3 is key to counteracting cognitive dysfunction. Here, we report that sevoflurane administration for 2 days resulted in upregulation of histone deacetylase 9 (HDAC9) expression, which led to transcriptional inactivation of cAMP‐response element binding protein (CREB). Due to the colocalization of HDAC9 and CREB within cells, this may be related to the interaction between HDAC9 and CREB. Anyway, this ultimately led to reduced NT‐3 expression and inhibition of neural stem cell differentiation. Furthermore, knockdown of HDAC9 rescued the transcriptional activation of CREB after sevoflurane exposure, while reversing the downregulation of NT‐3 expression and inhibition of neural stem cell differentiation. In summary, this study identifies a unique mechanism by which sevoflurane can inhibit CREB transcription through HDAC9, and this process reduces NT‐3 levels and ultimately inhibits neuronal differentiation. This finding may reveal a new strategy to prevent sevoflurane‐induced neuronal dysfunction.