Inhibiting Virus Replication and Excessive Inflammatory Response: Mechanism of Combined Prescription of Ma-Xing-Shi-Gan Decoction and Xiao-Chai-Hu Decoction Against Influenza Virus

Ethnopharmacological relevance: The combined prescription of two classical decoctions (Ma-Xing-Shi-Gan decoction with Xiao-Chai-Hu decoction), named as San-Yang-He-Zhi (SYHZ) decoction, has been widely used for the treatment of influenza virus (IFV) infections for decades.Aim of the study: This study aimed to evaluate the anti-influenza effect of SYHZ decoction and explore the un-derlying mechanism. Materials and methods: The ingredients of SYHZ decoction were analyzed by mass spectrometry. An animal model of IFV infection was established by challenging C57BL/6J mice with PR8 virus. Three groups of mice were infected with lethal or non-lethal doses of IFV, then followed by oral administration of phosphate-buffered saline (PBS), or SYHZ, or oseltamir; blank control mice (without IFV infection) were treated with PBS. Survival rate, Lung index, colon length, body weight loss and IFV viral load were measured 7 days post infection; histology and electron-microscopy examinations of lung tissue were performed; cytokine and chemokine levels in lung and serum were measured; and the intestinal metagenome, the cecum metabolome, and the lung transcriptome were analyzed. Results: SYHZ treatment significantly improved survival rate compared with PBS (40% vs 0%); improved lung index, colon length, and body weight loss; and alleviated lung histological damage and viral load. SYHZ-treated mice had significantly lower levels of IL-1 beta, TNF-alpha, IL-6, CCL2, CXCL10 in lung and serum, and increased levels of multiple bioactive components in cecum. Pro-inflammatory cytokines, Toll-and NOD-like receptors, pro-apoptosis molecules, and lung-injury-related proteins were downregulated in SYHZ mice, whereas surfactant protein and mucin were upregulated. The NOD-like receptor pathway, Toll-like receptor pathway, and NF-kappa B pathway were downregulated by SYHZ treatment.Conclusions: SYHZ decoction alleviated IFV infection in a mouse model. Multiple bioactive ingredients of SYHZ may inhibit replication of IFV and suppress excessive immune response.