Anti-inflammatory effect of Lactiplantibacillus plantarum T1 cell-free supernatants through suppression of oxidative stress and NF-κB- and MAPK-signaling pathways.

Lactiplantibacillus plantarum T1 is an isolated probiotic lactic acid bacterium (LAB) from pickled vegetables in Chongqing, China. In this study, we evaluated the anti-inflammatory activity and the underlying mechanisms of L. plantarum T1 cell-free supernatant (CFS) on lipopolysaccharide (LPS)-stimulated murine RAW264.7 macrophages in vitro . Reverse transcription quantitative PCR (RT-qPCR), immunofluorescence, Griess methods, and western blotting were utilized to assess the anti-inflammatory cytokines and antioxidative effect of L. plantarum T1 CFS. Our results showed that L. plantarum T1 CFS pretreatment significantly reduced pro-inflammatory cytokine levels, including nitric oxide, inducible nitric oxide synthase, cyclooxygenase-2, tumor necrosis factor, interleukin (IL)-1β, and IL-6, as well as reactive oxygen species. Interestingly, L. plantarum T1 CFS unregulated the antioxidant indicators, including superoxide dismutase, catalase, and glutathione in RAW264.7 cells. Furthermore, L. plantarum T1 CFS activated the nuclear factor kappa-B (NF-κB) and mitogen-activated protein kinase (MAPK) pathway. This study showed the excellent antioxidant and anti-inflammatory properties of L. plantarum T1 through multiple pathways, highlighting its potential for further research and application as a probiotic strain. IMPORTANCE L. plantarum T1 stood out in a series of acid and bile salt tolerance and bacterial inhibition tests as a probiotic isolated from paocai, which provides many health benefits to the host by inhibiting the growth of harmful pathogenic microorganisms and suppressing excessive levels of oxidative stress and inflammation. Not all LAB have good probiotic functions and are used in various applications. The anti-inflammatory antioxidant potential and mechanisms of L. plantarum T1 CFS have not been described and reported. By using RT-qPCR, Griess method, and western blotting, we showed that L. plantarum T1 CFS had anti-inflammatory and antioxidant effects. Griess assay, TBA assay, WST-8 assay, immunofluorescence assay, RT-qPCR, and western blotting data revealed that its anti-inflammatory and antioxidant mechanisms were associated with oxidative stress and NF-κB and MAPK signaling pathways. The anti-inflammatory and antioxidant effects of L. plantarum T1 CFS in paocai generates opportunities for probiotic product development.