The Bacterial Fermentation Product Butyrate Influences Epithelial Signaling via Reactive Oxygen Species-Mediated Changes in Cullin-1 Neddylation

Abstract

The human enteric flora plays a significant role in intestinal health and disease. Populations of enteric bacteria can inhibit the NF-κB pathway by blockade of IκB-α ubiquitination, a process catalyzed by the E3-SCFβ-TrCP ubiquitin ligase. The activity of this ubiquitin ligase is regulated via covalent modification of the Cullin-1 subunit by the ubiquitin-like protein NEDD8. We previously reported that interaction of viable commensal bacteria with mammalian intestinal epithelial cells resulted in a rapid and reversible generation of reactive oxygen species (ROS) that modulated neddylation of Cullin-1 and resulted in suppressive effects on the NF-κB pathway. Herein, we demonstrate that butyrate and other short chain fatty acids supplemented to model human intestinal epithelia in vitro and human tissue ex vivo results in loss of neddylated Cul-1 and show that physiological concentrations of butyrate modulate the ubiquitination and degradation of a target of the E3- SCFβ-TrCP ubiquitin ligase, the NF-κB inhibitor IκB-α. Mechanistically, we show that physiological concentrations of butyrate induces reactive oxygen species that transiently alters the intracellular redox balance and results in inactivation of the NEDD8-conjugating enzyme Ubc12 in a manner similar to effects mediated by viable bacteria. Because the normal flora produces significant amounts of butyrate and other short chain fatty acids, these data provide a functional link between a natural product of the intestinal normal flora and important epithelial inflammatory and proliferative signaling pathways.

The importance of oxygen free radicals in the etiopathogenesis of diversion colitis in rats

“…It has been demonstrated that 70% of the oxygen consumption in colonic cells comes from the oxidation of SFCAs, particularly butyrate 29 . In segments without a fecal stream, the absence of dietetic fibers and changes to the normal bacterial flora decrease the production, absorption and use of SFCAs by the epithelial cells, leading to the overproduction of ROS 30 . The importance of adequate oxidation of SCFAs in the prevention of DC is known through clinical and experimental studies showing that rectal instillation with SCFAs in diverted colon segments reduces the inflammatory process 14,16 .…”

DUOX2-derived reactive oxygen species are effectors of NOD2-mediated antibacterial responses

“…For example, it has been shown recently that Mycobacterium ulcerans induces ROS formation in epidermal keratinocytes via TLRdependent pathways (Lee et al, 2009). By contrast, fermentation products derived from commensal bacteria of the gut flora also induce ROS production in intestinal epithelial cells resulting in neddylation of cullin 1 and suppression of NFκB signalling (Kumar et al, 2007;Kumar et al, 2009). Thus generation of ROS is a common event, initiated by both harmless bacteria and pathogens.…”

Epithelial Adhesion Mediated by Pilin SpaC Is Required for Lactobacillus rhamnosus GG-Induced Cellular Responses

“…This bacterium-induced ROS generation modulates numerous cellular functions, including transient oxidative inactivation of enzymes required for modulating cullin-dependent signaling (10,11), inducing extracellular signal-regulated kinase (ERK)-specific signaling (12), and potentiating epithelial restitution via redox inactivation of focal adhesion kinase phosphatases (13). We also showed that specific taxa composing the microbiota, especially those within the genus Lactobacillus, can directly stimulate intestinal stem cell growth and accelerate epithelial growth during homeostasis (8) or wound healing by redox-dependent mechanisms involving NADPH oxidase 1 (14).…”