Glycyrrhizic acid attenuates cerebral ischemia-reperfusion injury in rats by inhibiting HMGB1-mediated pyroptosis

Objective To explore the protective impact of glycyrrhizic acid on rats experiencing cerebral ischemia-reperfusion, and to elaborate its mechanism of action via high mobility group box-1 protein (HMGB1)- mediated pyroptosis. Methods Forty five male Sprague-Dawley (SD) rats were randomly assigned to three groups: a sham-operated group (sham group), a middle cerebral artery occlusion/reperfusion group (MCAO/R group), and a glycyrrhizic acid group. The MCAO/R group and glycyrrhizic acid group had the MCAO/R model established using Longa's modified wire bolus method, and the glycyrrhizic acid group was administered 20 mg/ kg glycyrrhizic acid solution by gavage for 7 d. The neurological deficits in rats were evaluated using the modified neurological severity score (mNSS); the percentage of cerebral infarct volume in rats was detected by 2, 3, 5-triphenyltetrazolium chloride (TTC) staining; the pathologic changes in neurons and other cells in the infarcted areas of rat brain tissue were detected by hematoxylin-eosin (HE) staining and Nissl staining; the levels of tumor necrosis factor- α (TNF- α) and interleukin-1β (IL-1β) in the infarcted areas of rat brain tissue were detected by enzyme-linked immunosorbent assay (ELISA); the protein expression of HMGB1, pyroptosis-related nucleotidebinding oligomerization domain-like receptor protein 3 (NLRP3), GSDMD, and caspase-1 in the infarcted area of rat brain tissue was detected by western blotting. Results Rats in the MCAO/R group exhibited significantly higher mNSS scores compared with those in the sham group (P < 0.05). The morphology of neurons in the infarcted area of rat brain tissue was impaired, disorganized and structurally disrupted. Moreover, the expression levels of HMGB1, NLRP3, GSDMD, and caspase-1 proteins were significantly elevated (P < 0.05), and the expression levels of TNF-α and IL-1β were also significantly increased (P < 0.05). Compared with the MCAO/R group, the mNSS scores of rats in the glycyrrhizic acid group were significantly decreased (P < 0.05), the number of necrotic neurons in the infarcted area of rat brain tissue was significantly reduced and the nerve fibers were arranged orderly. Additionally, the expression levels of HMGB1, NLRP3, GSDMD, caspase-1 proteins, as well as TNF-α and IL-1β were significantly decreased (P < 0.05). Conclusion Glycyrrhizic acid can significantly ameliorate cerebral ischemia-reperfusion- injury in rats, and its mechanism may be related to the HMGB1-mediated pyroptosis pathway.