Abstract
Probiotic bacteria have the ability to modulate host immune responses and have potent therapeutic functional effects against several diseases, including inflammatory diseases. However, beneficial effects of probiotics are strain specific and their interactions with host immune cells to modulate inflammatory response are largely unknown. Intestinal epithelial cells (IECs), which are the first line of defense against invading pathogens, and connects between commensals/probiotics and immune system; therefore, in this study, we used human IECs to assess the probiotic effects of three selected Lactobacillus strains in vitro. An HT-29 colonic epithelial cell and HT-29/blood mononuclear cells co-culture system were stimulated with Lactobacillus followed by Salmonella for different hours, after which the mRNA level of cytokines, β-defensin-2 and negative regulators for TLR signaling and protein levels of ZO-1 and IκB-α were analyzed by real-time polymerase chain reaction and western blot analysis. L. brevis decreased Salmonella induced IL-6, IL-8, MCP-1 and IL-1β levels, whereas L. pentosus suppressed IL-6 and MCP-1 in HT-29 cells. Moreover, L. brevis was able to increase the mRNA levels of A20, Tollip, SIGIRR and IRAKM, while L. pentosus reduced the levels of A20, and IRAKM in response to Salmonella. In addition, decrease in protein level of TNF-α and increase in mRNA level of IL-10 was observed in L. brevis and L. pentosus treated HT-29 cells. Lactobacillus strains were differentially modulated ZO-1 and p-IκB-α in HT-29 cells treated with Salmonella. Overall, the results of this study indicate that Lactobacillus strains attenuate Salmonella induced inflammatory responses through beneficial modulation of TLR negative regulators and the NF-κB pathway.
Highlights
The human intestine is a home to diverse microbial populations that are known to play crucial roles in human health, such as regulation of immune and metabolic homeostasis, digestion of dietary fibers, and protection against pathogenic invaders [1, 2]
Stimulation of HT-29 cells with L. brevis, L. curvatus and L. pentosus altered the mRNA level of IL-6 and MCP-1 at 3 h, whereas IL-8 and IL-1β were not altered by LABs in HT-29 cells under inflammatory conditions
Intestinal ECs (IECs) are the dominant cell types in the guts of humans and animals that are continually exposed to gut microbes and mediate signaling to maintain host innate immunity by sensing gut bacteria, including Lactobacillus, and their molecular patterns via pattern recognition receptors (PRRs) such as Toll-like receptors (TLRs) [25]
Summary
The human intestine is a home to diverse microbial populations that are known to play crucial roles in human health, such as regulation of immune and metabolic homeostasis, digestion of dietary fibers, and protection against pathogenic invaders [1, 2]. Lactobacilli are natural inhabitants in the gut of human where they exert potent probiotic effects including competitive. Immunobiotics attenuates Salmonella induced inflammatory response study design, data collection and analysis, decision to publish, or preparation of the manuscript
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