Hypomethylated leptin receptor reduces cerebral ischaemia–reperfusion injury by activating the JAK2/STAT3 signalling pathway

Objective To investigate the cerebroprotective effects of leptin in vitro and in vivo via the Janus kinase-2 (JAK2)/transcription factor signal transducer and activators of transcription-3 (STAT3) pathway and leptin receptors (LEPR). Methods The study used the cellular oxygen-glucose deprivation (OGD) model in PC12 cells and the middle cerebral artery occlusion (MCAO) rat model of cerebral ischaemia–reperfusion injury (CIRI) to assess changes in gene expression and protein levels following leptin pretreatment. The methylated DNA immunoprecipitation (MeDIP) assay measured DNA methylation levels. Results The optimal leptin concentration for exerting neuroprotective effects against ischaemia–reperfusion injury in PC12 cells was 200 ng/ml in vitro, but excessive leptin diminished this effect. Leptin pretreatment in the MCAO rat model demonstrated a similar effect to previously reported leptin administration post-CIRI. In addition to regulating the expression of inflammation-related cytokines, Western blot analysis showed that leptin pretreatment upregulated BCL-2 and downregulated caspase 3 levels. The MeDIP analysis demonstrated that DNA methylation regulated LEPR gene expression in the MCAO rat model when leptin pretreatment was used. Conclusion Exogenous leptin might bind to extra-activated LEPR by reducing the methylation level of the LEPR gene promoter region, which leads to an increase in phosphorylated JAK2/STAT3 and apoptotic signalling pathways.