Probiotic Bacteria Alter Pattern-Recognition Receptor Expression and Cytokine Profile in a Human Macrophage Model Challenged with Candida albicans and Lipopolysaccharide

Probiotics are live microorganisms that confer benefits to the host health. The infection rate of potentially pathogenic organisms such as , the most common agent associated with mucosal candidiasis, can be reduced by probiotics. However, the mechanisms by which the probiotics interfere with the immune system are largely unknown. We evaluated the effect of probiotic bacteria on challenged human macrophages. Macrophages were pretreated with lactobacilli alone ( LR32, L324m, or NCFM) or associated with lipopolysaccharide (LPS), followed by the challenge with or LPS in a co-culture assay. The expression of pattern-recognition receptors genes ( , and ) was determined by RT-qPCR, and dectin-1 reduced levels were confirmed by flow cytometry. The cytokine profile was determined by ELISA using the macrophage cell supernatant. Overall probiotic lactobacilli down-regulated the transcription of ( < 0.05), resulting in the decreased expression of dectin-1 on probiotic pretreated macrophages. The tested species down-regulated , and increased mRNA levels in macrophages challenged with . The cytokines profile of macrophages challenged with or LPS were altered by the probiotics, which generally led to increased levels of IL-10 and IL-1β, and reduction of IL-12 production by macrophages ( < 0.05). Our data suggest that probiotic lactobacilli impair the recognition of PAMPs by macrophages, and alter the production of pro/anti-inflammatory cytokines, thus modulating inflammation.