Probiotic Bacterium Prevents Cytokine-induced Apoptosis in Intestinal Epithelial Cells

Fang Yan,D Brent Polk

doi:10.1074/jbc.m207050200

Abstract

Probiotic bacteria are microorganisms that benefit the host by preventing or ameliorating disease. However, little information is known regarding the scientific rationale for using probiotics as alternative medicine. The purpose of this paper is to investigate the mechanisms of probiotic beneficial effects on intestinal cell homeostasis. We now report that one such probiotic, Lactobacillus rhamnosus GG (LGG), prevents cytokine-induced apoptosis in two different intestinal epithelial cell models. Culture of LGG with either mouse or human colon cells activates the anti-apoptotic Akt/protein kinase B. This model probiotic also inhibits activation of the pro-apoptotic p38/mitogen-activated protein kinase by tumor necrosis factor, interleukin-1alpha, or gamma-interferon. Furthermore, products recovered from LGG culture broth supernatant show concentration-dependent activation of Akt and inhibition of cytokine-induced apoptosis. These observations suggest a novel mechanism of communication between probiotic microorganisms and epithelia that increases survival of intestinal cells normally found in an environment of pro-apoptotic cytokines.

Highlights

The human gastrointestinal microflora establishes at birth and acquires through a series of colonizations more than 400 bacterial species in the adult [1]
Because dominant-negative kiKSR expression induces apoptosis in tumor necrosis factor (TNF)-treated intestinal cells [29], we used kiKSR-expressing colon cells to test our hypothesis that probiotics prevent TNF-induced apoptosis through regulation of signal transduction pathways
We found that TNF-stimulated apoptosis detected by terminal deoxynucleotidyltransferase-mediated dUTP nick-end-labeling (TUNEL) staining in kiKSR-expressing YAMC cells was inhibited by co-culture with viable Lactobacillus rhamnosus GG (LGG) but was not hkLGG (Fig. 1, A and B)

Summary

Introduction

The human gastrointestinal microflora establishes at birth and acquires through a series of colonizations more than 400 bacterial species in the adult [1]. In human clinical trials the non-pathogenic Gram-positive commensal Lactobacilli found in the human and mouse gastrointestinal tracts have been considered as probiotics with beneficial health effects, including enhanced lymphocyte proliferation [5], innate and acquired immunity [6], and anti-inflammatory cytokine production [7]. There is increasing evidence that probiotic Lactobacillus species play a role in the treatment of inflammatory bowel disease (IBD). In this disease, abnormal immune responses cause inflammation that appears to be stimulated by elements of the enteric microenviroment, including normal and pathogenic organisms [12]. Culture of LGG with colon cells activates the anti-apoptotic Akt/protein nase suppressor of Ras; LGG-cm, LGG conditioned medium; LGG-s, supernatant recovered from LGG culture broth; MAP, mitogen activated protein; NF␬B, nuclear factor ␬B; PI, phosphoinositide; SAPK/ JNK, stress-activated protein kinase/c-Jun amino-terminal kinase; TNF, tumor necrosis factor; YAMC, young adult mouse colon; hk, heat killed; DAPI, 4,6-diamidino-2-phenylindole; TUNEL, terminal deoxynucleotidyltransferase-mediated dUTP nick-end labeling

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