Glycyrrhizic Acid alleviate the Neurotoxicity of Semen Strychni through inhibition of HMGB1 phosphorylation and inflammatory

Backgrounds: In recent years, the neurotoxicity of Semen Strychni was reported in many clinical cases. Hence，this study was conducted to investigate the role of HMGB1 in the model of neurotoxicity induced by Semen Strychni and the alleviation of glycyrrhizic acid, which is related to the regulation of HMGB1 release. Methods: The rats were intraperitoneally injected with Semen Strychni extract (175mg/kg), followed by oral administration ofglycyrrhizic acid (50 mg/kg) for 4 days. After treatment, neuronal degeneration, apoptosis, and necrosis were observed by Nissl, FJB, and Tunel. ELISA was used to detect related inflammatory indicators TNF-α, IL-1β, HMGB1, and neurotransmitter enzymes MAO, AChE. IF and Western Blot were used to determine the localization of HMGB1, p-HMGB1, and NF-κB in the nucleus and cytoplasm; CO-IP was used to determine the interaction between PP2A, PKC, CaMKIV and HMGB1. The expression of ERK, p-ERK, JNK, p-JNK, p38, p-p38, was detected by Western Blot . Results: After neurotoxic model rats were treated with glycyrrhizic acid neuronal damage and apoptosis were improved to a certain extent, the inhibitory effect of Semen Strychni on neurotransmitter metabolic enzymes was removed, and the levels of inflammatory indexes TNF-α and IL-1β were also significantly down-regulated. The results of IF and Western Blot showed that Semen Strychni reduced the nucleus level of HMGB1, significantly increased the cytoplasm and serum release levels, and increased the level of p-HMGB1, while glycyrrhizic acid could down-regulate the level of p-HMGB1, inhibit the nucleoplasmic shuttle and extracellular release process of HMGB1. Glycyrrhizic acid could strengthen the interaction between HMGB1 and PP2A and reduce the combination of HMGB1 and PKC. Glycyrrhizic acid significantly down-regulated the expression levels of p-ERK, p-JNK, and p-p38 proteins, and inhibited the transfer of NF-κB from the cytoplasm to the nucleus. Conclusions: Glycyrrhizic acid has a certain ameliorating effect on the neurotoxicity induced by Semen Strychni, and its mechanism is related to the inhibition of HMGB1 phosphorylation, the reduction of nucleoplasmic shuttle, and the inhibition of downstream inflammatory pathways of HMGB1.