A prostacyclin analog prevents radiocontrast nephropathy via phosphorylation of cyclic AMP response element binding protein.
We reported previously that radiocontrast medium induces caspase-dependent apoptosis and that cAMP analogs inhibit cell injury in cultured renal tubular cells. In the present study, cellular mechanisms underlying the protective effects of cAMP were determined. Ioversol, a radiocontrast medium, caused cell injury accompanied by decreases in Bcl-2, increases in Bax, and caspase activation in LLC-PK1 cells. Both cell injury and cellular events induced by ioversol were inhibited by dibutyryl cAMP and the prostacyclin analog beraprost. Dibutyryl cAMP increased phosphorylation of Akt and CREB, both of which were reversed by H89, wortmannin and the Akt inhibitor SH-6. The protective effect of dibutyryl cAMP was also reversed by these kinase inhibitors. In dominant-negative CREB-transfected cells, dibutyryl cAMP no longer prevented cell injury or inhibited changes in mRNA expression of Bcl-2 and Bax. In mice with unilateral renal occlusion, ioversol increased urinary excretion of N-acetyl-beta-d-glucosaminidase with concomitant decreases in Bcl-2 mRNA, increases in Bax mRNA, activation of caspase-3, and induction of apoptosis in tubular and interstitial cells. Beraprost completely reversed these in vivo effects of ioversol. These findings suggest that elevation of endogenous cAMP effectively prevents radiocontrast nephropathy through activation of A kinase/PI 3-kinase/Akt followed by CREB phosphorylation and enhanced expression of Bcl-2.
Yano
Takahisa
T
Department of Pharmacy, Kyushu University Hospital, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan. tyano@pharm.med.kyushu-u.ac.jp
Itoh
Yoshinori
Y
Kubota
Toshio
T
Sendo
Toshiaki
T
Koyama
Tatsuya
T
Fujita
Takuya
T
Saeki
Kumiko
K
Yuo
Akira
A
Oishi
Ryozo
R
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D003994:Bucladesine / Q000494:pharmacology; D020169:Caspases / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D003287:Contrast Media; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D011464:Epoprostenol / Q000031:analogs & derivatives* / Q000494:pharmacology*; D007668:Kidney / Q000378:metabolism / Q000473:pathology; D007674:Kidney Diseases / Q000139:chemically induced* / Q000473:pathology / Q000517:prevention & control*; D018374:LLC-PK1 Cells; D051379:Mice; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation; D010770:Phosphotransferases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D013552:Swine; D014283:Triiodobenzoic Acids
D003994:Bucladesine; D020169:Caspases; D003287:Contrast Media; D017362:Cyclic AMP Response Element-Binding Protein; D011464:Epoprostenol; D019869:Phosphatidylinositol 3-Kinases; D010770:Phosphotransferases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D019253:Proto-Oncogene Proteins c-bcl-2; D014283:Triiodobenzoic Acids; C048081:beraprost; C054871:ioversol