Lactobacillus plantarum Lac16 alleviates dextran sodium sulfate-induced colitis in mice by suppressing NLRP3 inflammasome overactivation through microbiota-derived isobutyric acid

ABSTRACT Inflammatory bowel disease (IBD) is a chronic intestinal inflammatory disorder characterized by immune dysregulation. Therapeutic strategies targeting gut microbiota modulation have been proven to be effective against IBD. This study sought to explore the protective effects of Lactobacillus plantarum Lac16 against dextran sulfate sodium (DSS)-induced colitis and to elucidate its underlying mechanisms. Results illustrated that Lac16 administration significantly ameliorated colitis symptoms, as evidenced by reduced weight loss, attenuated colon shortening, and decreased disease activity index scores. Furthermore, Lac16 treatment restored intestinal barrier integrity, modulated inflammatory cytokine levels, promoted macrophage polarization toward an anti-inflammatory phenotype, and suppressed NOD-like receptor protein 3 (NLRP3) inflammasome overactivation in the colon. Lac16 treatment effectively remodeled gut microbiota composition by significantly increasing the abundance of beneficial bacteria, particularly Alloprevotella and Dubosiella , while reducing the abundance of potentially pathogenic bacteria such as Bacteroides and Helicobacter . It also elevated acetic acid and isobutyric acid levels among microbiota-derived short-chain fatty acids. The pseudo-germ-free mouse model confirmed that Lac16 inhibits NLRP3 inflammasome overactivation and ameliorates colitis symptoms by modulating the gut microbiota. Moreover, the fecal microbiota transplantation (FMT) mouse model demonstrated that these protective benefits are transferable through FMT. Subsequently, isobutyric acid was found to suppress NLRP3 inflammasome overactivation and ameliorate colitis in vivo while also attenuating inflammatory injury in vitro . Collectively, these findings illustrate that Lac16 alleviates colitis and provides gastrointestinal protection by suppressing NLRP3 inflammasome overactivation through a gut microbiota-dependent mechanism, with microbiota-derived isobutyric acid identified as the pivotal mediator in this protective process. IMPORTANCE This study establishes that Lactobacillus plantarum Lac16 alleviates DSS-induced colitis through gut microbiota-dependent mechanisms. Lac16 administration significantly ameliorated colitis symptoms while restoring intestinal barrier integrity, promoting anti-inflammatory macrophage polarization, and suppressing NLRP3 inflammasome overactivation. The pseudo-germ-free mouse model provided definitive evidence that Lac16’s suppression of NLRP3 inflammasome overactivation requires gut microbiota. Fecal microbiota transplantation verified the causal role of microbiota in mediating Lac16’s therapeutic benefits. Notably, Lac16 reshaped microbial composition, elevating beneficial genera ( Alloprevotella and Dubosiella ) while suppressing pathogenic genera ( Bacteroides and Helicobacter ). Crucially, Lac16 increased microbiota-derived short-chain fatty acids, particularly isobutyric acid. Both in vivo and in vitro experiments confirmed that isobutyric acid significantly contributes to anticolitic effects and suppresses NLRP3 activation. These findings elucidate a novel mechanism by which Lac16 ameliorates colitis via (i) microbiota-dependent NLRP3 inflammasome modulation and (ii) isobutyric acid-mediated protective effects. This work provides important insights into probiotic mechanisms and supports targeting microbial metabolic networks for IBD intervention.