Lactobacillus rhamnosus GG attenuates interferon-γ and tumour necrosis factor-α-induced barrier dysfunction and pro-inflammatory signalling

Abstract

The intestinal epithelium forms a protective barrier against luminal contents and the external environment, mediated via intercellular tight junctions (TJs). The TJ can be disrupted via cell signalling induced by either enteric pathogens or pro-inflammatory cytokines, thereby contributing to various intestinal disorders ranging from acute infectious diarrhoea to chronic inflammatory bowel diseases. Probiotics, such as Lactobacillus rhamnosus GG (LGG), are reported to confer beneficial effects on epithelial cells, including antagonizing infections and reducing overt proinflammatory responses, but the underlying mechanisms of these observed effects require further characterization. We hypothesized that probiotics preserve barrier function by interfering with proinflammatory cytokine signalling. Caco-2bbe cells were seeded into Transwells to attain polarized monolayers with intercellular TJs. Monolayers were inoculated apically with the probiotic LGG 3 h prior to the addition of IFN-c (100 ng ml "1 ) to the basolateral medium overnight. The monolayers were then placed in fresh basal medium±TNF-a (10 ng ml "1) and transepithelial electrical resistance (TER) measurements were taken over the time-course of TNF-a stimulation. To complement the TER findings, cells were processed for zona occludens-1 (ZO-1) immunofluorescence staining. As a measure of TNF-a downstream signalling, cells were immunofluorescently stained for NF-kB p65 subunit and CXCL-8 mRNA was quantified by qRT-PCR. Basal cell culture medium was collected after overnight TNF-a stimulation to measure secreted chemokines, including CXCL-8 (interleukin-8) and . Following LGG inoculation, IFN-c priming and 24 h TNF-a stimulation, epithelial cells maintained TER and ZO-1 distribution.LGG diminished the nuclear translocation of p65, demonstrated by both immunofluorescence and CXCL-8 mRNA expression. CXCL-8 and CCL-11 protein levels were decreased in LGG-inoculated, cytokine-challenged cells. These findings indicate that LGG alleviates the effects of pro-inflammatory cytokines on epithelial barrier integrity and inflammation, mediated, at least in part, through inhibition of NF-kB signalling. INTRODUCTIONThe intestinal epithelium forms a protective barrier against luminal contents, such as microbes and dietary food antigens, present in the external environment. Barrier function is mediated through apical junction complexes, which consist of paracellular proteins integrated into tight junctions (TJs) (Van Itallie & Anderson, 2006). Abnormalities of intercellular TJs contribute to a variety of intestinal disorders, including acute diarrhoeal illness, gluten-sensitive enteropathy (coeliac disease) and chronic inflammatory bowel disease (McGuckin et al., 2009). The challenging of intact polarized epithelia with either proinflammatory cytokines or pathogenic bacteria dismantles the TJ protein structure and thereby disrupts barrier function (Donato et al., 2008; Wang et al., 2005Wang et al., , 2006 Zareie et al., 2005).We have shown that probiotic lactobacilli antago...

Strain-Dependent Augmentation of Tight-Junction Barrier Function in Human Primary Epidermal Keratinocytes by Lactobacillus and Bifidobacterium Lysates

“…Additionally, L. rhamnosus GG has been demonstrated to inhibit NF-B signaling, which led to enhanced barrier integrity in a model of cytokine-induced barrier dysfunction (5). The soluble factor p40, derived from L. rh-amnosus GG, has also been implicated in protection of the gut epithelial barrier from peroxide-induced damage.…”

“…Ingestion of probiotic bacteria has been claimed to prevent or treat a variety of disorders of the gut, ranging from travelers' diarrhea to the chronic relapsing inflammatory condition Crohn's disease (1, 2) through mechanisms that are incompletely understood. However, evidence suggests that one mechanism may be via protection or augmentation of gut epithelial barrier function (3,4,5). This is provided for in the most part by tight junctions (TJs), which are multiprotein complexes sealing the paracellular space between adjacent epithelial cells and limiting transport through this pathway to small, hydrophilic molecules and ions (reviewed in reference 6).…”

VSL#3 probiotics regulate the intestinal epithelial barrier in�vivo and in vitro via the p38 and ERK signaling pathways

“…Tight junctions are the major determinants of paracellular permeability. Although changes in epithelial tight junction protein expression have been studied extensively in monolayers stimulated by cytokines, challenged by bacteria, or exposed to aspirin (16)(17)(18)(19)(20)(21)(22), much remains to be understood about barrier disruptive changes under inflammatory conditions in vivo. Our results have indicated that the probiotic mixture VSL#3 protects colonic epithelial barrier function in acute DSS colitis, as demonstrated by effective prevention of increased Evans blue dye uptake.…”

Preparation and characterization of alginate and gelatin microcapsules containing Lactobacillus rhamnosus

“…A number of health benefits have been claimed for Lact. rhamnosus, such as alleviation of inflammation or pathogen-induced barrier dysfunction (Lebeer et al 2010, Donato et al 2010, prevention of intestinal injuries induced by rotavirus diarrhea (Liu et al 2013a), a decrease in the symptoms of atopic dermatitis in children aged 4-48 months (Wu et al 2015) and prevention of gastrointestinal infectious (Hojsak et al 2010).…”