Crystalline silica (cSiO2) particles are naturally existing environmental toxicants. Exposure to cSiO2 could cause local or systemic inflammation and aggregate inflammation-associated diseases. Dietary postbiotics are reported to possess anti-inflammatory activities; however, their effects on cSiO2-triggered inflammation are unknown. Here, we investigate the impact of postbiotics from Lacticaseibacillus rhamnosus (LGG), Limosilactobacillus reuteri (L.reu), and Bifidobacterium animalis subsp. lactis Bb12 (BB12) on cSiO2-induced cytotoxicity and IL-1 cytokines in vitro using macrophages. The postbiotics used in this study were cell-free fractions of a probiotic growth medium collected at different time points. The in vitro model used was the wild-type murine macrophage RAW 264.7 cell line stably transfected with the inflammasome adapter protein, ASC. Our results indicate that all the postbiotics could reduce cSiO2-induced cytotoxicity in the wild-type and ASC macrophages and the effects were OD-dependent. Following priming with a lipopolysaccharide, cSiO2 treatment resulted in robust inflammasome activation in ASC, as reflected by the IL-1β release. These responses were minimal or absent in the wild-type RAW cells. All the postbiotics decreased the release of IL-1β from ASC; however, only LGG and BB12 reduced the IL-1β secretion from wild-type cells. Only the L.reu postbiotics reduced the IL-1α release from ASC. We conclude that the postbiotics from LGG, BB12, and L.reu can protect macrophages against cSiO2-induced cytotoxicity and suppress IL-1β activation.
Keywords: IL-1α; IL-1β; NLRP3 inflammasome; cytotoxicity; macrophage; postbiotics; silica.