HIF1α activation is associated with increased CaV3.2 expression and hypoxia-induced neuronal hyperexcitability.

Transient insults to the brain can convert neurons chronically hyperexcitable. Key molecular mechanisms that link hypoxic events, e.g. in the context of episodic ischemia, to neuronal hyperexcitability remain vague. The transcription factor hypoxia-inducible factor 1α (HIF1α) is a central mediator of the cellular response to hypoxia and may contribute to epileptogenesis by regulating ion channel expression. Here, we identify the T-type calcium channel CaV3.2 (encoded by Cacna1h) as a putative transcriptional target of HIF1α and investigate its role in hypoxia-associated changes in neuronal excitability. Oxygen deprivation followed by reoxygenation (OD/R) induced a persistent increase in neuronal firing rate. In murine organotypic brain slices, hypoxic conditions increased HIF1α and Cacna1h expression at the transcript level, and in human organotypic brain slices hypoxia increased HIF1α and Cacna1h protein expression. Using neuronal cell lines and primary cortical neurons we show that HIF1α activation through HIF1α overexpression, consistently increases Cacna1h expression. In NS20Y cells, overexpression of a normoxia-stable HIF1α variant increased Cacna1h promoter activity in both fluorescent and dual-luciferase reporter assays. The same effect was observed in primary cortical neurons, where HIF1α overexpression also elevated network activity measured by multielectrode array recordings, replicating the effect of the OD/R model. Together, these findings identify HIF1α as a putative transcriptional regulator of CaV3.2 in neurons and reveal a conserved hypoxia-responsive HIF1α-CaV3.2 pathway that promotes neuronal excitability across experimental models. This pathway may represent a potential molecular entry point for future studies aimed at understanding and ultimately modulating hypoxia-associated epileptogenic processes.