Role of pyroptosis in brain injury in a rat model of hepatic ischemia-reperfusion

Objective To evaluate the role of pyroptosis in brain injury in a rat model of hepatic ischemia-reperfusion (I/R). Methods Thirty clean-grade healthy male Sprague-Dawley rats of both sexes, aged 6-8 weeks, weighing 180-200 g, were divided into 3 groups (n=10 each) using a random number table method: sham operation group (group S, n=10), hepatic I/R plus dimethyl sulfoxide (DMSO) group (group I/R+ DMSO, n=10), and hepatic I/R plus caspase-1 inhibitor Ac-YVAD-cmk group (group I/R+ YVAD, n=10). Hepatic I/R was produced by occluding the left hepatic artery and portal vein for 90 min followed by 6-h reperfusion in anesthetized rats.At 2 h before reperfusion, Ac-YVAD-cmk 5 mg/kg was intraperitoneally injected in group I/R+ YVAD, and the equal volume of DMSO was given instead in group I/R+ DMSO.Hippocampal and cortical samples were obtained at the end of reperfusion for determination of reactive oxygen species (ROS) content (using DCFH-DA fluorescence probe), malondialdehyde (MDA) content (using thiobarbituric acid method), superoxide dismutase (SOD) activity (by xanthine oxidase method), expression of NLRP3, cleaved-caspase-1 and apoptosis-associated speck-like protein containing a CAR (ASC) (by Western blot), nucleotide-binding domain, leucine rich family (NLR) pyrin domain containing 3 (NLRP3) expression (by immunohistochemical staining), and concentrations of IL-1β, IL-18, S100-β protein and neuron-specific enolase (NSE) in serum (by enzyme-linked immunosorbent assay). Results Compared with group S, the contents of ROS and MDA in hippocampus and cortex were significantly increased, the activity of SOD in hippocampus and cortex was decreased, the expression of NLRP3, cleaved-caspase-1 and ASC was up-regulated, and the concentrations of IL-1β, IL-18, S-100β protein and NSE in serum were increased in group I/R+ DMSO (P<0.05). Compared with group I/R+ DMSO, the contents of ROS and MDA in hippocampus and cortex were significantly decreased, the activity of SOD in hippocampus and cortex was increased, the expression of NLRP3, cleaved-caspase-1 and ASC was down-regulated, and the concentrations of IL-1β, IL-18, S-100β protein and NSE in serum were decreased in group I/R+ YVAD (P<0.05). Conclusion Pyroptosis is involved in the pathophysiological mechanism of brain injury induced by hepatic I/R injury in rats. Key words: Pyroptosis; Reperfusion injury; Liver; Brain injuries