Lactobacillus johnsonii N6.2 Stimulates the Innate Immune Response through Toll-Like Receptor 9 in Caco-2 Cells and Increases Intestinal Crypt Paneth Cell Number in BioBreeding Diabetes-Prone Rats

Abstract

Lactobacillus johnsonii (Ljo) N6.2 has been shown to mitigate the development of type 1 diabetes when administered to diabetes-prone rats. The specific mechanisms underlying this observed response remain under investigation. The objective of this study was to assess the effect of Ljo N6.2 on mucosal inflammatory response using differentiated Caco-2 monolayers. The mRNA expression levels of CCL20, CXCL8, and CXCL10 chemokines were determined by qRT-PCR. Ljo at 10(11) CFU/L induced a strong response in all chemokines examined. To assess the specific host-signaling pathways involved, we performed RT-PCR amplification of Toll-like receptors (TLR) and nucleotide-binding oligomerization domain-like receptors. TLR7 and TLR9 expression levels were induced 4.2- and 9-fold, respectively, whereas other TLR and nucleotide-binding oligomerization domain receptors were not modified. A similar effect was observed in Caco-2 monolayers treated with Ljo cell-free extract or purified nucleic acids (NA). Increased levels of IFN type 1 and IFN regulators Stat1 and IRF7 followed the upregulation of TLR9. Activation of TLR9 was also evidenced by increased Frizzled 5 expression in Ljo-treated Caco-2 cells and an increase in the number of Paneth cells in Ljo-fed, diabetes-prone rats. These results are in agreement with the polarizing-tolerizing mechanism recently described in which the apical stimulation of TLR9 in intestinal epithelial cells leads to a higher state of immunologic alertness. Furthermore, these results suggest that live probiotics could be, in the future, replaced with select cellular components.

Gut Microbiota and Type 1 Diabetes

“…Diabetes prevention, in association with the upregulation of IL-17 immunity, could be explained by the ability of IL-17 to activate the anti-microbial response in combination with mucosal repair mechanisms [15]. It is also possible that other mechanisms are involved because Lactobacillus johnsonii affects epithelial integrity directly [16]. However, in NOD-mice, increased expression of colonic IL-17 was associated with the development of diabetes, and dietary prevention of diabetes was associated with down-regulation of colonic IL-17 [17].…”

Intestinal Epithelial Cells Modulate Antigen-Presenting Cell Responses to Bacterial DNA

“…TLR9 signaling is associated with gut homeostasis, where loss of TLR9 signaling results in increased susceptibility to colonic inflammation (17). Further, TLR9 has been shown to be involved in the antiinflammatory effects of probiotics (13,20), demonstrating a role for probiotic bacteria DNA as an active factor that imparts a beneficial effect. More recently, Hall et al (8) have shown a role for TLR9 signaling and gut flora DNA in modulating the levels of T-regulatory and T-effector cells in the gut.…”

Evaluation of the Effect of Probiotic Administration on Gene Expression in Goat Blood

“…Most effects have been attributed to an increase in the innate immune response and to others an increase in the acquired immune response. The innate immune system initiates a response to microorganisms or their components via pattern recognition receptors such as Toll-like receptors (TLR) or nucleotide-binding oligomerization domain-like receptors (Kingma et al, 2011) and previous studies have reported TLRs expression in blood Worku & Morris 2009). In our study, probiotics had an effect in the expression of TLR3 and TLR8 in goats, and increase in expression of TLR4, TLR6, TLR7 and TLR9.…”