NRF1 alleviates cerebral ischemia-reperfusion injury by transcriptionally activating FTO and downregulating m6A-mediated FOXO1 expression.

BACKGROUND: Studies show that upregulation of Nuclear respiratory factor 1 (NRF1) inhibits cerebral ischemia-reperfusion injury (CIRI). However, the molecular mechanism of NRF1 in CIRI remains to be largely unrevealed. Therefore, in this study, we aimed to investigate the potential mechanisms by which NRF1 regulates OGD/R-mediated neuronal apoptosis and its effects on CIRI in rats.

METHODS: A middle cerebral artery occlusion/reperfusion (MCAO/R) rat model was established to detect the expression of NRF1 in brain tissues of MCAO/R rats. Next, neuronal cells were treated with oxygen-glucose deprivation/reperfusion (OGD/R) and transfected with NRF1 overexpression vectors (pcDNA-NRF1), and cell apoptosis, inflammatory reaction and oxidative stress were evaluated. Furthermore, the enrichment of NRF1 in the promoter of fat mass and obesity-related genes (FTO) was evaluated with ChIP analysis, and the transcriptional activation of FTO by NRF1 was evaluated with luciferase reporter gene analysis. The m6A level of forkhead box O1 (FOXO1) mRNA was evaluated by MeRIP analysis, and the binding of FTO to FOXO1 mRNA was evaluated by RIP analysis. FTO siRNA and FOXO1 overexpression vectors (pcDNA-FOXO1) were transfected into NRF1 overexpressing neuronal cells to perform reversal experiments. Finally, MCAO/R rats were intracranially injected with NRF1 lentiviral vectors (LV-NRF1), and the volume of cerebral infarction, pathological damage and neuronal apoptosis were determined.

RESULTS: NRF1 was downregulated in brain tissues of MCAO/R rats and OGD/R-treated neurons. Overexpression of NRF1 inhibited cell apoptosis and reduced inflammatory factor secretion (IL-1β and TNF-α) and oxidative stress (SOD activity was increased and MDA content was decreased) in OGD/R-treated neuronal cells. Mechanistic studies shown that NRF1 promotes FTO transcriptional activation by binding to the FTO promoter, while FTO interference upregulates FOXO1 expression by increasing the m6A level of FOXO1 mRNA. Silencing FTO or overexpression of FOXO1 reversed the inhibitory effect of NRF1 overexpression on OGD/R-induced neuronal damage. In addition, upregulation of NRF1 reduced the volume of cerebral infarction and alleviated neurological impairment and neuronal apoptosis in MCAO/R rats.

CONCLUSIONS: This study revealed that NRF1 inhibited neuronal apoptosis and alleviated neurological deficits and neuro-inflammation in MCAO/R rats by promoting FTO-m6A-mediated downregulation of FOXO1, which may provide a potential therapeutic strategy for CIRI.