LACTOBACILLUS PROBIOTIC SPECIES STRENGTHEN INTESTINAL BARRIER FUNCTION AND TIGHT JUNCTION INTEGRITY

Brian Blackwood, Ann and Robert H. Lurie Children's Hospital of Chicago, Rush University Medical Center; Carrie Yuan, Northwestern University Feinberg School of Medicine; Joseph Nicolas, Northwestern University Feinberg School of Medicine; Douglas Wood, Northwestern University Feinberg School of Medicine; Catherine Hunter, Ann and Robert H. Lurie Children's Hospital of Chicago, Northwestern University Feinberg School of Medicine

Necrotizing Enterocolitis (NEC) is the most common gastrointestinal emergency of premature infants. Probiotics have shown efficacy in the prevention of NEC, but the underlying mechanisms remain unknown. Tight junctions (TJ) are protein complexes that maintain epithelial barrier integrity. 

We hypothesized that Lactobacillus sp. (rhamnosus (LR) and plantarum (LP)) strengthen intestinal barrier function, promote TJ integrity, and protect against experimental NEC.

Monolayers of polarized intestinal epithelial cells (Caco-2) were pretreated with various doses of LR and LP. Transepithelial resistance (TER) was measured over a time course.  TJ were disrupted by 1) EGTA calcium switch, or 2) LPS treatment. The ability of LR and LP to maintain TER was measured. Transmembrane flux of fitc dextran assessed permeability. TJ structure was evaluated by ZO-1 immunofluorescence. The in vivo effect of Lactobacillus was assessed with the Cronobacter sakazakii (CS) rat pup model of NEC. Pups were subject to hypoxia and CS-formula feeding +/- LR. The enteral to serum ratio of gavaged fitc dextran was measured. Intestinal segments were processed for histology and protein analysis. Intestinal injury scores were measured by a blinded pathologist. Differences were analyzed with ANOVA.

TER increased by 163 ohms (62%) when treated with LR, and by 20 ohms (8%) when treated with LP (p< 0.01, p<0.05). Cells treated with LP and LR had decreased permeability to fitc dextran (p<0.0001). ZO-1 immunofluorescence confirmed TJ structural stability in cells that received probiotic treatment compared with controls. Pup intestinal injury scoring revealed a significant decrease in intestinal injury in the pups that received Lactobacillus sp. compared to controls (p<0.03). There was a significant increase in permeability to fitc dextran in those pups that did not receive probiotics as compared to those that did (p<0.0004).

Lactobacillus sp. strengthen intestinal barrier function and preserves TJ integrity in experimental models of NEC. The mechanisms by which this effect takes place represent an exciting area of future research.