Intestinal P Glycoprotein Acts as a Natural Defense Mechanism againstListeria monocytogenes

Abstract

Mechanisms by which the intestinal epithelium resists invasion by food-borne pathogens such as Listeria monocytogenes are an evolving area of research. Intestinal P glycoprotein is well known to limit the absorption of xenobiotics and is believed to act as a cytotoxic defense mechanism. The aim of this study was to determine if intestinal P glycoprotein is involved in host defense against L. monocytogenes. Caco-2 cells and a Pglycoprotein-overexpressing subclone (Caco-2/MDR) were employed in addition to mdr1a ؊/؊ mice and wildtype controls. In vitro invasion assays and in vivo experiments were employed to measure bacterial invasion and dissemination. In addition, L. monocytogenes proteins were labeled with [35 S]methionine, and the transepithelial transport across Caco-2 monolayers was characterized in both directions. Overexpression of P glycoprotein in Caco-2/MDR cells led to increased resistance to L. monocytogenes invasion, whereas P-glycoprotein inhibition led to increased invasion. Flux of [35 S]methionine-labeled L. monocytogenes proteins was significantly greater in the basolateral-to-apical direction than in the apical-to-basolateral direction, indicating dependence on an apically located efflux transporter. Moreover, inhibiting P glycoprotein reduced the basolateral-to-apical flux of the proteins. Early dissemination of L. monocytogenes from the gastrointestinal tract was significantly greater in the mdr1a ؊/؊ mice than in wild-type controls. Expression and function of intestinal P glycoprotein is an important determinant in resistance to early invasion of L. monocytogenes.P glycoprotein is the 170-kDa product of the human MDR1 gene and is arguably one of the most extensively studied members of the ATP-binding cassette superfamily of transport proteins (28). P glycoprotein is best known for its ability to transport drug substrates out of cells in a variety of tissues, including the intestine (1,12,27). Both the expression and the function of P glycoprotein have been linked to considerable variability in oral drug absorption; however, the precise physiological role of intestinal P glycoprotein is unknown. Because P glycoprotein is well conserved throughout evolution and has a broad substrate affinity, it is widely believed to act as a cytotoxic protection mechanism. Given its apical distribution on the enterocyte, P glycoprotein is exquisitely positioned to limit the absorption of substances that the cell perceives as harmful. Thus, it is conceivable that P glycoprotein restricts the absorption of other, nondrug substances in the intestine. Proteins facilitating invasion of pathogenic bacteria would be ideal candidates given the purported mechanism of action of P glycoprotein.Listeria monocytogenes is a food-borne pathogen responsible for considerable morbidity and mortality (11,24). Although multiple sites of invasion have been proposed, the vanguard of the body's interaction with L. monocytogenes is the intestinal epithelial barrier. Intestinal epithelial cells come in contact with not only the bacter...

Loss of TLR2 Worsens Spontaneous Colitis in MDR1A Deficiency through Commensally Induced Pyroptosis

“…Cells deficient in TLR2 show defective autophagic defense against intracellular Listeria monocytogenes (57). Loss of MDR1A may allow increased pathogen invasion (58), thus possibly overstraining the autophagic machinery. Autophagosomes fuse with lysosomes to efficiently kill the ingested microorganism.…”

Bacteria in the Intestine, Helpful Residents or Enemies from Within?

“…Conversely, bacteria and LPS can cause the induction of HIF-1 in human and murine epithelial cells (70). In addition, P-glycoprotein, a HIF-1-inducible protein, has been demonstrated to play a role in the inhibition of invasion of enterocytes by Listeria monocytogenes (103). Indeed, the intestine is thought to be hypoxic in the physiologic state (140), and the colonic epithelium has been shown to be severely oxygen deprived during inflammation (62).…”

The interaction of gut microbes with host ABC transporters

“…These results imply that expression and function of P-gp is an important determinant in resistance to early invasion of L. monocytogenes. 16 Their findings also invite speculation that that P-gp plays a novel role in host defense by its ability to efflux bacterial virulence proteins out from the host cell. Further studies will be required to validate this fascinating concept.…”

“…Apical localization of P-gp also affords the opportunity for interactions with enteric bacteria. To this end, recent investigations have revealed an intriguing interaction between P-gp expressed on intestinal epithelial cells and enteric pathogens Listeria monocytogenes, 16 Salmonella enterica serovar Typhimurium, 17 and also perhaps unidentified members of the residential microbial community. For example, L. monocytogenes is a ubiquitous Gram-positive food-borne pathogen that causes listeriosis, a disease characterized by severe gastroenteritis, encephalitis, meningitis or septicemia, as well as miscarriage and is responsible for considerable morbidity and mortality.…”

“…12 This expression invasion by food-borne pathogens through the action of ABC efflux transporters. To test the hypothesis that intestinal P-gp is involved in host defense against L. monocytogenes, Neudeck et al used complementary in vitro (Caco-2/MDR) and in vivo (mdr1a -/-mice) models 16 and found that overexpression of P-gp led to increased resistance to L. monocytogenes invasion, whereas P-gp protein inhibition led to increased invasion. These results imply that expression and function of P-gp is an important determinant in resistance to early invasion of L. monocytogenes.…”