Semen Strychni Pulveratum and vomicine alleviate neuroinflammation in amyotrophic lateral sclerosis through cGAS-STING-TBK1 pathway

Ethnopharmacological relevance: Amyotrophic lateral sclerosis (ALS) is a fetal neuromuscular disorder characterized by the gradual deterioration of motor neurons. Semen Strychni pulveratum (SSP), a processed version of Semen Strychni (SS) powder, is widely used to treat ALS in China. Vomicine is one of the most primary components of SS. However, their pharmacological effects and mechanisms for ALS remain elusive.

Aim of the study: This study aimed to evaluate the neuroprotective and anti-neuroinflammatory effects of SSP and vomicine, as well as to explore their protective roles in ALS and the underlying mechanisms.

Materials and methods: In vivo, 8-week-old hSOD1-WT mice and hSOD1-G93A mice were orally administered different concentrations of SSP (SSP-L = 5.46 mg/ml, SSP-M = 10.92 mg/ml or SSP-H = 16.38 mg/ml) once every Other day for 8 weeks. A series of experiments, including body weight measurement, footprint tests, Hematoxylin & Eosin staining, and Nissl staining, were performed to evaluate the preventive effect of SSP. Immunofluorescence staining, western blotting, and RT-qPCR were subsequently performed to evaluate activation of the cGAS-STING-TBK1 pathway in the spinal cord. In vitro, hSOD1^G93A NSC-34 cells were treated with vomicine to further explore the pharmacological mechanism of vomicine in the treatment of ALS via the cGAS-STING-TBK1 pathway.

Results: SSP improved motor function, body weight loss, gastrocnemius muscle atrophy, and motor neuron loss in the spine and cortex of hSOD1-G93A mice. Furthermore, the cGAS-STING-TBK1 pathway was activated in the spinal cord of hSOD1-G93A mice, with activation predominantly observed in neurons and microglia. However, the levels of cGAS, STING, and pTBK1 proteins and cGAS, IRF3, IL-6, and IL-1β mRNA were reversed following intervention with SSP. Vomicine not only downregulated the levels of cGAS, TBK1, IL-6 and IFN-β mRNA, but also the levels of cGAS and STING protein in hSOD1^G93A NSC-34 cells.

Conclusion: This study demonstrated that SSP and vomicine exert neuroprotective and anti-neuroinflammatory effects in the treatment of ALS. SSP and vomicine may reduce neuroinflammation by regulating the cGAS-STING-TBK1 pathway, and could thereby play a role in ALS treatment.

Amyotrophic lateral sclerosis; Neuroinflammation; Semen strychni pulveratum; Vomicine; cGAS-STING-TBK1 pathway.