Isorhynchophylline exerts anti-inflammatory and anti-oxidative activities in LPS-stimulated murine alveolar macrophages

Excessive inflammatory response and oxidative stress are considered as important pathogenic factors in the development of acute lung injury. Isorhynchophylline (IRN), a tetracyclic oxindole alkaloid isolated from Uncaria rhynchophylla, possesses anti-inflammatory and anti-oxidant activities. Our study aimed to investigate the effects and potential mechanisms of IRN on lipopolysaccharide (LPS)-stimulated murine alveolar macrophage cell lines MH-S and NR8383. CCK-8 assay was used to evaluate the cytotoxicity of IRN and LPS. Inflammatory response was assessed by detecting the mRNA expressions and release of tumor necrosis factor α (TNF-α), interleukin (IL)-1β, IL-6, and plasminogen activator inhibitor-1 (PAI-1) using qRT-PCR and ELISA. The expressions of inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX)-2 were examined by qRT-PCR and western blot. Oxidative stress was evaluated by detecting malondialdehyde (MDA) level and the activities of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and catalase (CAT). The changes of the toll like receptor (TLR4)/nuclear factor-kappa B (NF-κB)/nod-like receptor protein 3 (NLRP3) inflammasome pathway was detected by western blot. Treatment with LPS or IRN for 24 h showed no cytotoxicity on MH-S and NR8383 cells. IRN pretreatment inhibited LPS-induced production of inflammatory cytokines, expressions of iNOS and COX-2, and oxidative stress in murine alveolar macrophages. Additionally, IRN inhibited LPS-induced activation of TLR4/NF-κB/NLRP3 inflammasome pathway in MH-S cells. Mechanistically, inhibition of TLR4/NF-κB/NLRP3 inflammasome pathway by si-TLR4 suppressed LPS-induced inflammation and oxidative stress in murine alveolar macrophages. IRN exerted anti-inflammatory and anti-oxidant effects on LPS-stimulated murine alveolar macrophages via inhibition of the TLR4/NF-κB/NLRP3 inflammasome pathway.