Schisandrol A Alleviates Allergic Asthma in Mice via Regulating the NF-κB/IκBα and Nrf2/HO-1 Signaling Pathways

Schisandra chinensis (Turcz) Baill (S. chinensis) is the key traditional Chinese medicine for the treatment of asthma used by ancient and modern medical practitioners. However, the material basis and the main mechanism of its antiasthmatic effect remain unclear. Our preliminary results showed that schisandrol A (SCA), a representative monomer of Schisandra lignans, had the best relaxation effect on tracheal rings in isolated rats. In this research, a mouse asthma model was prepared by combining ovalbumin (OVA) with Al (OH)₃ for exploring the antiasthmatic action and the underlying mechanism of SCA. The study results demonstrated that SCA improved the behavior of mice with asthma and pathological changes in their lung tissues and airways, decreased serum immunoglobulin E (IgE) and OVA-IgE levels, interleukin-4 (IL-4), IL-5, IL-13, and eotaxin contents, and leukocytes number in bronchoalveolar lavage fluid. SCA downregulated the gene expressions of keratinocyte-derived protein chemokines and ILs and reduced the expressions of phosphorylated IκB kinase α (p-IKKα) and p-nuclear factor kappa-B (NF-κB) proteins in lung tissues. In addition, it was found that SCA could significantly increase T-superoxide dismutase and catalase activities, decrease malondialdehyde content, and elevate p-IκBα, NF-E2-related-factor 2 (Nrf2), and heme oxygenase-1 (HO-1) protein expressions. In summary, SCA treatment resulted in a significant improvement in the allergic bronchial asthma in mice, and its mechanisms may involve the regulation of the NF-κB/IκBα pathway to reduce inflammatory response and the Nrf2/HO-1 pathway to improve the body's antioxidant capacity. These results suggest that SCA is a key component of S. chinensis in exerting antiasthmatic effects.