Immunomodulatory effect of molecules secreted by the probiotic strain of Escherichia coli O83:K24:H31.
TL;DR
The findings suggest that probiotics may exert beneficial effects through the content of their secreted supernatants rather than solely through the presence of bacterial cells, highlighting the potential of such preparations and their component molecules as a postbiotic therapeutic solution.
Abstract
Bacteria and their metabolic products profoundly affect the immune system. Research has shown that early postnatal supplementation with specific probiotic strains, such as Escherichia coli O83:K24:H31 (EcO83), can provide health benefits. EcO83 is a facultative anaerobe capable of generating energy through multiple metabolic pathways, an adaptation that allows it to thrive in the gastrointestinal tract, where oxygen availability can vary. However, the precise mechanisms through which this probiotic, and in particular its metabolites, functions remain largely unknown. Short-chain fatty acids (SCFAs) represent an important class of metabolites with known immunoregulatory effects. In this exploratory study, we aimed to test the impact of aerobic and anaerobic conditions on SCFA production and evaluate the immunomodulatory capacity of postbiotics derived from EcO83 under aerobic and anaerobic conditions on human peripheral blood mononuclear cells (PBMCs), mouse splenocytes, and bone marrow-derived dendritic cells (BMDCs) in vitro. Our results revealed that supernatants from aerobic cultures preferentially induced Th1 cytokines, such as IFN-γ, in PBMCs, whereas those from anaerobic cultures more prominently triggered the Th2 cytokine IL-13. Similarly, murine splenocytes produced more IFN-γ when stimulated with aerobic supernatants. Additionally, both aerobic and anaerobic EcO83 supernatants promoted the release of proinflammatory (TNF-α) and anti-inflammatory (IL-10) cytokines from BMDCs, as well as their maturation, evidenced by upregulation of the surface marker CD80. We detected SCFA, specifically acetate and propionate, in the supernatants of both aerobic and anaerobic EcO83 cultures, with no statistically significant differences between them. In conclusion, our findings suggest that probiotics may exert beneficial effects through the content of their secreted supernatants rather than solely through the presence of bacterial cells, highlighting the potential of such preparations and their component molecules as a postbiotic therapeutic solution. To our knowledge, this is the first report demonstrating that EcO83 produces SCFAs, including acetate and propionate, under different oxygen conditions.