Intestinal barrier is essential for dietary products and microbiota compartmentalization and therefore gut homeostasis. When this barrier is broken, cecal content overflows into the peritoneal cavity, leading to local and systemic robust inflammatory response, characterizing
peritonitis and
sepsis. It has been shown that IL-1β contributes with inflammatory storm during
peritonitis and
sepsis and its inhibition has beneficial effects to the host. Therefore, we investigated the mechanisms underlying IL-1β secretion using a widely adopted murine model of experimental
peritonitis. The combined injection of sterile cecal content (SCC) and the gut commensal bacteria Bacteroides fragilis leads to IL-1β-dependent
peritonitis, which was mitigated in mice deficient in NLRP3 (nucleotide-binding domain, leucine-rich-containing family, pyrin domain-containing-3)
inflammasome components. Typically acting as a damage signal, SCC, but not B. fragilis, activates canonical pathway of NLRP3 promoting IL-1β secretion in vitro and in vivo. Strikingly, absence of fiber in the SCC drastically reduces IL-1β production, whereas high-fiber SCC conversely increases this response in an NLRP3-dependent manner. In addition, NLRP3 was also required for IL-1β production induced by purified
dietary fiber in primed macrophages. Extending to the in vivo context, IL-1β-dependent
peritonitis was worsened in mice injected with B. fragilis and high-fiber SCC, whereas zero-fiber SCC ameliorates the pathology. Corroborating with the proinflammatory role of
dietary fiber, IL-1R-deficient mice were protected from
peritonitis induced by B. fragilis and particulate bran. Overall, our study highlights a function, previously unknown, for
dietary fibers in fueling
peritonitis through NLRP3 activation and IL-1β secretion outside the gut.