Effect of glycyrrhizin on traumatic brain injury in rats and its mechanism

Abstract

ObjectiveTo investigate the neuroprotective effects of glycyrrhizin (Gly) as well as its effect on expression of high-mobility group box 1 (HMGB1) in rats after traumatic brain injury (TBI) MethodsMale Sprague-Dawley rats were randomly divided into three groups: sham group TBI group and TBI+Gly group (n=36 per group). Rat TBI model was made by using the modified Feeney’s method. In TBI+Gly group Gly was administered intravenously at a dosage of 10mg/kg 30min after TBI. At 24h after TBI motor function and brain water content were evaluated. Meanwhile HMGB1/HMGB1 receptors including toll-like receptor 4 (TLR4) and receptor for advanced glycation end products (RAGE)/nuclear factor- κ B(NF- κ B) signaling pathway and inflammatory cytokines in the injured brain tissues were detected using quantitative real-time polymerase chain reaction western blot electrophoretic mobility shift assay and enzyme-linked immunosorbent assay. Furthermore HMGB1 RAGE and TLR4 immunohistochemistry and apoptosis were analyzed ResultsBeam walking performance impairment and brain edema were significantly reduced in TBI+Gly group compared with TBI group; meanwhile, the over-expressions of HMGB1/HMGB1 receptors (TLR4 and RAGE)/NF-κB DNA-binding activity and inflammatory cytokines were inhibited. The percentages of HMGB1, RAGE and TLR4-positive cells and apoptotic cells were respectively 58.37%±5.06%, 54.15%±4.65%, 65.50%±4.83%, 52.02%±4.63% in TBI group and 39.99%±4.99%, 34.87%±5.02%, 43.33%±4.54%, 37.84%±5.16% in TBI+Gly group (all P<0.01 compared with TBI group). ConclusionGly can reduce secondary brain injury and improve outcomes in rat following TBI by down-regulation of HMGB1/HMGB1 receptors (TLR4 and RAGE)/NF-κ B-mediated inflammatory responses in the injured rat brain.