Estrogen and propofol combination therapy inhibits endoplasmic reticulum stress and remarkably attenuates cerebral ischemia-reperfusion injury and OGD injury in hippocampus

Aim: Endoplasmic reticulum stress (ERS) is vital in inducing apoptosis via caspase-12 and C/EBP homologous protein (CHOP) apoptotic pathway in the hippocampus after ischemia-reperfusion injury. The study aimed to estimate the efficacy of estrogen and propofol combination therapy against ERS-induced apoptosis after cerebral ischemia-reperfusion injury and oxygen-glucose deprivation (OGD) injury in the hippocampus in vivo and in vitro.

Methods: Rat model of cerebral ischemia-reperfusion injury was generated by middle cerebral artery occlusion (MCAO) strategy with ischemic intervention for 90 min and reperfusion for 24 h. Propofol processing ischemia-reperfusion group (Propofol group) infused 50 mg/kg/h of propofol via the femoral vein at the onset of reperfusion for 30 min. Estrogen processing ischemia-reperfusion group (estrogen group) received 0.0125 mg/kg of estrogen via tail vein at 30 min prior to MCAO. Combination therapy for ischemia-reperfusion group (combination group) received simultaneous processing with propofol and estrogen. In vitro, brain slices were randomly exposed to dimethylsulfoxide (DSMO), 10 μm of propofol, 10 nm of estrogen, or propofol and estrogen. Changes in the orthodromic population spike (OPS) at the end of reoxygenation were recorded. Neurological deficit examination, Nissl staining, and 2,3,5-triphenyltetrazolium chloride (TTC) staining were employed to evaluate the level of cerebral ischemia-reperfusion injury. The expression of caspase-3, caspase-12, glucose-regulated protein 78 (GRP78), and CHOP were investigated by Western blot and immunofluorescence staining assays. Neural apoptotic rate in hippocampus was detected by the flow cytometry trial.

Results: Neurological deficit score, infarct volume, the expression of caspase-3 (P < 0.05), caspase-12, GRP78, CHOP, and neural apoptotic rate of I/R group increased markedly (P < 0.01). When obtaining drug treatment, neurological deficit score (P < 0.05), infarct volume, the expression levels of caspase-12 and GRP78, and neural apoptotic rate of the propofol group decreased significantly (P < 0.01). Furthermore, neurological deficit score, infarct volume, expression levels of caspase-3, caspase-12, GRP78, and CHOP (P < 0.05), and neural apoptotic rate decreased in the estrogen group (P < 0.01) and especially in the combination group (P < 0.01). Compared with the propofol group, the neurological deficit score (P < 0.05), infarct volume, caspase-3, caspase-12, GRP78, CHOP, and neural apoptotic rate of the combination group decreased (P < 0.01). Compared with the estrogen group, the infarct volume, caspase-3 (P < 0.05), GRP78, CHOP, and neural apoptotic rate (P < 0.05) of the combination group decreased (P < 0.01). Compared with the propofol group, the infarct volume, caspase-3, caspase-12 (P < 0.05), and GRP78 (P < 0.05) of the estrogen group decreased (P < 0.01). Propofol and estrogen treatment can delay the abolishing time of OPS and increase the recovery rate and amplitude of OPS, compared with OGD group (P < 0.01), especially in the combination therapy (P < 0.01).

Conclusion: The neuroprotection of propofol and estrogen combination therapy inhibited excessive ERS-induced apoptosis against cerebral ischemia-reperfusion injury and OGD injury in the hippocampus of rats. Furthermore, the outcomes demonstrated that combination therapy yielded synergistic effects.