Regulation of MDR-1 (P-glycoprotein) by cyclooxygenase-2.
Cyclooxygenase-2 (Cox-2), an inducible form of the enzyme that catalyzes the first step in the synthesis of prostanoids, has been shown to be overexpressed in a wide range of tumors and possesses proangiogenic and antiapoptotic properties. To understand the molecular mechanism of Cox-2 action we used adenovirus-mediated transfer of rat Cox-2 cDNA into renal rat mesangial cells and determined the differential gene expression using cDNA microarrays. One of the several genes that were highly up-regulated by over expressed Cox-2 was MDR1. MDR1 or P-glycoprotein (P-gp), the product of the MDR1 gene, is implicated as the primary cause of multidrug resistance (MDR) in tumors where it acts as an efflux pump for chemotherapeutic agents. It is also expressed in normal tissues of the liver and kidney where it functions to actively transport lipophilic xenobiotics. Reverse transcriptase-PCR analysis confirmed the results of the microarray, showing increased mRNA levels for MDR1 in Cox-2 overexpressing cells. This increase in mRNA translated to an increase in MDR1 protein expression, which was dose-dependent on Cox-2 expression. Furthermore, using rhodamine 123 efflux assay we observed a significant increase in P-gp activity in Cox-2 overexpressing renal mesangial cells. The specific Cox-2 inhibitor NS398 was able to block the Cox-2-mediated increase in MDR1 expression and activity, suggesting that Cox-2 products may be implicated in this response. These results prove the existence of a causal link between Cox-2 and P-gp activity, which would have implications for kidney function and multidrug resistance in tumors where Cox-2 is overexpressed.
Department of Medicine, Division of Nephrology and the Cardiovascular Research Center, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA.
Vimal A
VA
Patel
Michael J
MJ
Dunn
Andrey
A
Sorokin
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics / Q000378:metabolism*; D000256:Adenoviridae / Q000235:genetics / Q000378:metabolism; D000818:Animals; D002478:Cells, Cultured; D051546:Cyclooxygenase 2; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005456:Fluorescent Dyes / Q000378:metabolism; D018014:Gene Transfer Techniques; D017930:Genes, Reporter; D005920:Glomerular Mesangium / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D008297:Male; D020411:Oligonucleotide Array Sequence Analysis; D011451:Prostaglandin-Endoperoxide Synthases / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D020112:Rhodamine 123 / Q000378:metabolism; D019076:Transgenes
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D004791:Enzyme Inhibitors; D005456:Fluorescent Dyes; D007527:Isoenzymes; D020112:Rhodamine 123; D051546:Cyclooxygenase 2; D011451:Prostaglandin-Endoperoxide Synthases