Potentiation of hydrogen peroxide, nitric oxide, and cytokine production in RAW 264.7 macrophage cells exposed to human and commercial isolates of Bifidobacterium

Bifidobacteria have been previously shown to stimulate immune function and this may be mediated by macrophages. The RAW 264.7 cell line was used here as a macrophage model to assess the effects of human and commercial Bifidobacterium isolates on the production nitric oxide (NO), hydrogen peroxide (H2O2) and the cytokines IL-6 and tumor necrosis factor (TNF)-α. Thirty three Bifidobacterium strains differentially stimulated the production of H2O2 NO, TNF-α, and IL-6 in a dose-dependent manner in 24-h cultures. In the presence of lipopolysaccharide (LPS) the effects of bifidobacteria on NO and H2O2 were masked and were less pronounced at the later stage of incubation. Co-stimulation of macrophages with both LPS and Bifidobacterium increased the production of IL-6 synergistically. In contrast, LPS reduced the ability of the bifidobacteria-induced macrophages to produce TNF-α. Our results demonstrated that both human and commercial Bifidobacterium strains can stimulate H2O2, NO, TNF-α, and IL-6 production, and this effect was strain-dependent. The in vitro approaches employed here should be useful in further characterization of the effects of bifidobacteria on gastrointestinal and systemic immunity.