Ischemia/Reperfusion-Inducible Protein Modulates the Function of Organic Cation Transporter 1 and Multidrug and Toxin Extrusion 1

Abstract

The recently identified ischemia/reperfusion-inducible protein (IRIP) has been reported to negatively modulate the activities of several transporters in cell culture systems. The goal of this study is to determine whether IRIP regulates the activities of OCT1 and MATE1, and hence the disposition in vivo of their substrate metformin, a therapeutic drug for diabetes and other obesity-related syndromes. In the uptake studies in the human embryonic kidney 293 cells overexpressing IRIP with and without OCT1 or MATE1, IRIP overexpression was found to significantly inhibit the uptake of 1-methyl-4-phenylpyridinium mediated by OCT1 or MATE1. In contrast, knockdown of IRIP by small hairpin RNA (shRNA) increased the transporter activities in vitro. IRIP overexpression decreased the membrane localization of transporter proteins without any changes in transcript levels in cells. By overexpressing IRIP in mouse liver via hydrodynamic tail vein injection, we demonstrated that increased IRIP expression could cause a significant reduction in hepatic accumulation of metformin (P < 0.01). In addition, we observed that the expression of IRIP was approximately half (P < 0.01) in ob/ob mice when compared to their lean littermates, with significant increases in hepatic Oct1 protein expression and metformin accumulation. In conclusion, IRIP negatively modulates the function of OCT1 and MATE1 in cells. Importantly, we provide in vivo evidence for such modulation that may cause an alteration in drug disposition. The regulation by IRIP on transporter activities likely occurs at a post-transcriptional level, and future studies are needed to characterize the exact mechanism.

Metformin‐associated lactic acidosis (MALA): Moving towards a new paradigm

“…Lastly, proteins released during acute ischemia (e.g. ischemia/reperfusion‐inducible protein) may interfere with the uptake of cationic compounds such as metformin …”

The Impact of Solute Carrier (SLC) Drug Uptake Transporter Loss in Human and Rat Cryopreserved Hepatocytes on Clearance Predictions

“…The downregulation of hepatic uptake transporters is initiated by proinflammatory cytokines released upon tissue damage, and the signaling pathways involved are being elucidated (Donner et al, 2013;Li et al, 2013). There are also indications that this downregulation of uptake transporters can be minimized, for example, by limiting the time of tissue ischemia during cell isolation or by induction of heme oxygenase-1 (Donner et al, 2013).…”

Incorporation of a Biguanide Scaffold Enhances Drug Uptake by Organic Cation Transporters 1 and 2

“…The uptake of prototypical substrates, MPP + and metformin, was used to assess the function of these transporters as described previously. 28 The uptake was higher in the HEK-OCT1 and HEK-OCT2 cells than the empty vector controls (HEK-P5) and was linear up to 10 min prior to plateau (Figure 2). Subsequent uptake experiments were then carried out for 10 min, all in room temperature.…”