Alteration of Mrp2 and P-gp expression, including expression in remote organs, after intestinal ischemia-reperfusion

Potential role of bile acids in the pathogenesis of necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is one of the most common acute gastrointestinal diseases in preterm infants. Recent studies have found that NEC is not only caused by changes in the intestinal environment but also by the failure of multiple systems and organs, including the liver. The accumulation of bile acids (BAs) in the ileum and the disorder of ileal BA transporters are related to the ileum injury of NEC. Inflammatory factors such as tumor necrosis factor (TNF)-α and interleukin (IL)-18 secreted by NEC also play an important role in regulating intrahepatic BA transporters. As an important link connecting the liver and intestinal circulation, the bile acid metabolic pathway plays an important role in the regulation of intestinal microbiota, cell proliferation, and barrier protection. In this review, we focus on how bile acids explore the dynamic changes of bile acid metabolism in necrotizing enterocolitis and the potential therapeutic value of targeting the bile acid signaling pathways.

Association between α-defensin 5 and the expression and function of P-glycoprotein in differentiated intestinal Caco-2 cells

α-Defensin 5 is known to be secreted by Paneth cells in the small intestine and plays an important role in eliminating pathogenic microorganisms. It has been reported that a decrease in α-defensin 5 level in the human small intestine is a risk of inflammatory bowel disease (IBD). Furthermore, P-glycoprotein (P-gp), a member of the ATP-binding cassette transporter superfamily, encoded by the ABCB1/MDR1 gene, plays an important role in the front line of host defense by protecting the gastrointestinal barrier from xenobiotic accumulation and may contribute to the development and persistence of IBD. Therefore, we examined the relationship between α-defensin 5 and the expression and function of P-gp using a human gastrointestinal model cell line (Caco-2). We found that MDR1 mRNA and P-gp protein level were increased in Caco-2 cells as well as α-defensin 5 secretion corresponded with the duration of cell culture. Exposure to α-defensin 5 peptide and recombinant tumor necrosis factor-α (TNF-α) significantly increased the expression and function P-gp. The mRNA levels of interleukin (IL)-8, IL-6, TNF-α, IL-1β, and IL-2 were also increased following exposure to TNF-α, similar to α-defensin 5 treatment. These results suggest that α-defensin 5 regulates P-gp expression and function by increasing TNF-α expression in Caco-2 cells.

Expression of oxidative stress and antioxidant defense genes in the kidney of inbred mice after intestinal ischemia and reperfusion

PURPOSE

To determine the gene expressions profile related to the oxidative stress and the antioxidant response in the kidneys of mice subjected to intestinal ischemia and reperfusion.

METHODS

Twelve inbred mice (C57BL/6) were randomly assigned to one of two groups: the control group (CG) underwent anesthesia and was observed for 120 min and the ischemia/reperfusion group (IRG), animals were anesthetized and subjected to laparotomy and ischemia for 60 minutes followed by 60 minutes of reperfusion. The expressions of 84 genes from the kidney were determined by the Reverse Transcription qualitative Polymerase Chain Reaction (RT-qPCR). All genes that were up regulated by more than threefold using the algorithm [2(ΔΔCt)] were considered statically significant (p<0.05).

RESULTS

In the IRG group 29 (34.52%) of 84 genes, were up regulated by more than threefold. The genes that were differentially up regulated in the glutathione peroxidase cluster (10 genes): were Gpx2 and Gpx7. The genes that were up regulated in the peroxidase cluster (16 genes) were following: Duox1, Epx, Lpo, Mpo, Ptgs2, Rag2, Serpinb1b, Tmod1 and Tpo. The genes that up regulated in the reactive oxygen species cluster (16 genes): Il19, Il22, Nos2, Nox1, Noxa1, Noxo1, Recql4 and Sod2. The genes that were up regulated in the oxidative stress cluster (22 genes) were: Mpp4, Nudt15, Upc3 and Xpa. The genes that were up regulated in the oxygen carriers cluster (12 genes) were: Hbq1, Mb, Ngb, Slc38a1 and Xirp1. The peroxiredoxins genes (10) showed no consistent differential regulation.

CONCLUSION

The genes related to oxidative stress and antioxidant defense showed increased expression in renal tissue trigged intestinal ischemia and reperfusion.

Distinct alterations in ATP-binding cassette transporter expression in liver, kidney, small intestine, and brain in adjuvant-induced arthritic rats

Pathophysiological changes of infection or inflammation are associated with alterations in the production of numerous absorption, distribution, metabolism and excretion-related proteins. However, little information is available on the effects of inflammation on the expression levels and activities of ATP-binding cassette (ABC) transporters. We examined the effect of acute (on day 7) and chronic (on day 21) inflammation on the expression of ABC transporters in some major tissues in rat. Adjuvant-induced arthritis (AA) in rats was used as an animal model for inflammation. The mRNA levels of mdr1a and mdr1b encoding P-glycoprotein (P-gp) decreased significantly in livers of AA rats on day 21. Hepatic protein levels of P-gp, Mrp2, and Bcrp decreased significantly in membranes but not homogenates of AA rats after 7 days and after 21 days of treatment with adjuvant. Contrary to liver, protein levels of P-gp and Mrp2, but not Bcrp in kidney, increased significantly in membranes. The biliary excretion of rhodamine 123 was decreased in rats with chronic inflammation owing to decreases in efflux activities of P-gp. Our results showed that the expression of transporters in response to inflammation was organ dependent. In particular, hepatic and renal P-gp and Mrp2 exhibited opposite changes in membrane protein levels.

The hepatic bile acid transporters Ntcp and Mrp2 are downregulated in experimental necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is the most common gastrointestinal emergency of premature infants and is characterized by an extensive hemorrhagic inflammatory necrosis of the distal ileum and proximal colon. We have previously shown that, during the development of experimental NEC, the liver plays an important role in regulating inflammation in the ileum, and accumulation of ileal bile acids (BA) along with dysregulation of ileal BA transporters contributes to ileal damage. Given these findings, we speculated that hepatic BA transporters would also be altered in experimental NEC. Using both rat and mouse models of NEC, levels of Cyp7a1, Cyp27a1, and the hepatic BA transporters Bsep, Ntcp, Oatp2, Oatp4, Mrp2, and Mrp3 were investigated. In addition, levels of hepatic BA transporters were also determined when the proinflammatory cytokines tumor necrosis factor (TNF)-α and interleukin (IL)-18, which are both elevated in NEC, are neutralized during disease development. Ntcp and Mrp2 were decreased in NEC, but elevated ileal BA levels were not responsible for these reductions. However, neutralization of TNF-α normalized Ntcp, whereas removal of IL-18 normalized Mrp2 levels. These data show that the hepatic transporters Ntcp and Mrp2 are downregulated, whereas Cyp27a1 is increased in rodent models of NEC. Furthermore, increased levels of TNF-α and IL-18 in experimental NEC may play a role in the regulation of Ntcp and Mrp2, respectively. These data suggest the gut-liver axis should be considered when therapeutic modalities for NEC are developed.

Regulation of hepatic ABCC transporters by xenobiotics and in disease states

The subfamily of ABCC transporters consists of 13 members in mammals, including the multidrug resistance-associated proteins (MRPs), sulfonylurea receptors (SURs), and the cystic fibrosis transmembrane conductance regulator (CFTR). These proteins play roles in chemical detoxification, disposition, and normal cell physiology. ABCC transporters are expressed differentially in the liver and are regulated at the transcription and translation level. Their expression and function are also controlled by post-translational modification and membrane-trafficking events. These processes are tightly regulated. Information about alterations in the expression of hepatobiliary ABCC transporters could provide important insights into the pathogenesis of diseases and disposition of xenobiotics. In this review, we describe the regulation of hepatic ABCC transporters in humans and rodents by a variety of xenobiotics, under disease states and in genetically modified animal models deficient in transcription factors, transporters, and cell-signaling molecules.

Effects of intestinal ischemia/reperfusion on P-glycoprotein mediated biliary and renal excretion of rhodamine123 in rat

To analyze the effects of I/R on P-gp function in liver and kidney, biliary and urinary excretions of rhodamine123 as a substrate of P-gp were examined in rats. The effects of reperfusion time on change and recovery of P-gp function were also examined. The biliary and renal clearance of rhodamine123 significantly decreased at 3 hr after reperfusion, but returned to control levels at 24 hr after reperfusion. These results suggest that intestinal I/R-induced decrease in P-gp-mediated biliary and renal excretion of rhodamine123 is litely due to impairment of P-gp-mediated transport ability. The level of P-gp protein in liver decreased and that of iNOS mRNA increased at 3 hr after reperfusion and both levels returned to control levels at 24 hr after reperfusion. No marked change in the levels of P-gp protein and iNOS mRNA was observed in kidney at 3 hr and 24 hr after reperfusion. Thus, decrease in biliary excretion of rhodamine123 would appear due in part to decrease in expression of P-gp, caused by increase in lipid peroxidation levels through iNOS mRNA.

Effect of intestinal ischaemia/reperfusion on P-glycoprotein-mediated ileal excretion of rhodamine 123 in the rat

Objectives

We have shown that ischaemia/reperfusion in the small intestine at an early phase, such as 1 h after reperfusion, induced not only functional changes in the membrane, such as P-glycoprotein (P-gp) dysfunction, but also decreased expression of P-gp protein and mdr1a mRNA. In the present study we examined whether intestinal ischaemia/reperfusion modifies the P-gp-mediated ileal excretion transport system in rats beyond 1 h after reperfusion.

Methods

To evaluate the contribution of P-gp-mediated transport to the ileal excretion of rhodamine 123, we used Western blotting to measure the expression of P-gp protein levels isolated from the ileum at different reperfusion times after 60 min of ischaemia. We also measured the expression of inducible nitric oxide synthase (iNOS) mRNA using real-time RT-PCR.

Key findings

Ileal excretion of rhodamine 123 decreased at 3 h after reperfusion and had recovered at 24 h. Changes in villi structure at 3 h and its recovery at 24 h were also observed. Verapamil, a competitive inhibitor of P-gp, significantly inhibited ileal clearance of rhodamine 123 to the lumen at 24 h after reperfusion, suggesting that P-gp was working at this time. These results suggest that intestinal ischaemia/reperfusion-induced decrease in P-gp-mediated ileal excretion of rhodamine 123 was probably due to impaired P-gp-mediated transport. Levels of P-gp protein and iNOS mRNA in the ileum decreased 3 h after ischaemia/reperfusion and returned to control levels after 24 h.

Conclusions

These findings suggest that intestinal ischaemia/reperfusion markedly decreases P-gp-mediated ileal excretion of rhodamine 123, probably by decreasing the expression of P-gp protein, which is likely to be due to increased lipid peroxidation via iNOS.