Anemoside B4 alleviates neuropathic pain through inhibiting inflammation

Abstract

Research background: Neuropathic pain (NP), which is caused by nerve injury or other diseases damages patients’ life quality seriously. Anemoside B4 (AB4) is the active component of triterpenoid saponins in traditional Chinese medicine Pulsatilla, with prominent effects of anti-inflammation and analgesia. However, its pharmacological mechanisms acting on NP remains unclear.Methods: The analgesia effects of AB4 against NP were investigated on the basis of the spinal nerve ligation (SNL) rat model by detecting the thresholds of mechanical pain and response times to cold stimulate. The key targets of AB4 acting on NP is selected based on the transcriptomic analysis, and their relative expression level was further verified by RT-qPCR. The binding sites of AB4 to the targets were searched by molecular docking. The regulation effects of AB4 on cytokines including IL-1β, IL-6 and TNF-α in the serum of SNL rats were tested by ELISA.Results: In contrast with normal rats, the thresholds of mechanical pain was decreased, whereas the response times to cold stimulate was increased in SNL rats, and the above phenomenon was reversed by AB4 treatment. The transcriptome sequencing results revealed that AB4 mainly regulated the serotonergic synapse, glutamatergic synapse, GABAergic synapse, dopaminergic synapse and cholinergic synapse pathways which was closely related to neuroinflammation and central pain sensitization. Further overlap analysis selected five genes in the pathway, named Alox15, Gngt1, Gngt2, Gnb3 and Tph1 respectively. Further RT-qPCR confirmed that the gene expression of them was down-regulated in the hippocampus of SNL rats, and up-regulated by AB4 administration. According to the molecular docking results, Anemoside B4 forms tightly bonded hydrogen bonding forces with key target molecules of the synaptic pathway, including Alox15, Gngt1, Gngt2, Gnb3 and Tph1. In addition, AB4 treatment also decreased the contents of inflammatory cytokines IL-1β, IL-6 and TNF-α in the serum of SNL rats.Conclusion: Our findings suggested the possibility of AB4 as a promising candidate for NP treatment by inhibiting inflammation.