Changes in the Localization of Ileal P-Glycoprotein Induced by Intestinal Ischemia/Reperfusion

Abstract

ATP binding cassette (ABC) transporters form one of the largest families of membrane transport proteins and are expressed in all organisms. They have been studied extensively and play a vital role in many cellular processes. ABC transporters are responsible for the multidrug resistance of cancer cells 1) but may also be capable of transporting several substrates such as metal ions, peptides, amino acids, sugars, and a large number of hydrophobic compounds and metabolites across the plasma membrane as well as intracellular membranes.2) ABC transporters play important roles in the defense mechanisms of several tissues through the excretion of toxic compounds and their metabolites. 3,4) In addition, the expression levels of the transporters are tightly regulated during tissue defense. 5)P-Glycoprotein (P-gp) is a typical ABC transporter. P-gp, which plays a very important role in drug therapy, was first discovered in 1976 as an efflux pump in a colchicine-resistant cell line, and 10 years later, the gene for P-gp was encoded. It is the most extensively studied of all of the ABC transporters.During small intestine grafting, rejection and ischemia/ reperfusion (I/R) injury are important problems. Immunosuppressive therapy is always required after transplantation. Since transplantation depends on a delicate balance between immunosuppression and rejection, the maintenance of adequate blood concentrations of immunosuppressants is critical. Cyclosporine A and tacrolimus are representative P-gp substrates. Therefore, P-gp controls the efficacies of these immunosuppressants. Information about the changes in P-gp induced by intestinal I/R would be useful for clinicians performing immunosuppressive therapy. We previously reported in in vitro 6) and in vivo 7-9) studies that I/R influences the function and expression of P-gp. In these reports, a correlation was found between the function of P-gp 1 h after reperfusion and the expression level of P-gp, but no such relationship was recognized 24 h after reperfusion. 7,8) It was suggested that this was due to functional abnormalities or abnormal localization of P-gp.In the present study, we examined whether abnormal P-gp localization is induced by intestinal I/R. Moreover, the mechanism and factors responsible for this phenomenon were also examined. MATERIALS AND METHODS MaterialsAll reagents were of analytical grade or better. Animals and Experimental Design Male Wistar/ST rats (8 weeks old) were purchased from Japan SLC Ltd. (Shizuoka, Japan). All animal experiments were performed according to the guidelines of Tokyo University of Pharmacy and Life Sciences. The animals were fasted for 18 h before the start of the experiment. Water was given freely during fasting. We have previously reported an in vivo intestinal I/R model that was produced using a spring scale and surgical sutures.7-9) Briefly, the superior mesenteric artery and vein in rats were occluded by lifting them using surgical-sutures (Natsume No. 3) connected to a spring balance for 1 h (ischemia condition), before r...

Intestinal P-glycoprotein Expression is Multimodally Regulated by Intestinal Ischemia-Reperfusion

“…6A and 6B) and P-gp protein expression in the ileal homogenate (data not shown) were not decreased. Takizawa et al (23) reported abnormal localization of P-gp in the ileal membrane during intestinal I/R. This finding suggests that abnormal localization of P-gp also occurs in our intestinal I/R-15 model rats.…”

Effect of Aminoguanidine on Ischemia/Reperfusion Injury in Rat Small Intestine

“…We have already reported that changes in the function and expression of ileal P-gp, which is an important ATP-binding cassette transporter, by intestinal I/R. 11,12,20,21) Moreover, we reported AG significantly inhibited the decrease of ileal P-gp function to excrete P-gp substrate, rhodamine 123, into the ileal lumen and expression by intestinal I/R until 1 h after reperfusion. 13) These results showed that AG can inhibit intestinal I/R injury until 1 h after reperfusion.…”