Cyclic AMP reverses radiocontrast media-induced apoptosis in LLC-PK1 cells by activating A kinase/PI3 kinase.
BACKGROUND
Radiographic contrast material is one of agents that are prone to cause nephropathy, although little is known about cellular mechanisms underlying contrast media-induced renal failure. The present study was designed to determine the role of caspase in contrast media-induced renal injury. The modulation by cyclic adenosine monophosphate (cAMP) of cell injury was subsequently examined.


METHODS
LLC-PK1 cells (a proximal renal tubular cell line of porcine origin) were exposed to diverse contrast media for 30 minutes followed by incubation for 24 hours in normal medium. Cell viability was assessed by mitochondrial enzyme activity and propidium iodide stain. Apoptosis was determined by DNA electrophoresis and annexin V stain. Caspase activity was measured fluorometrically. The mRNA for bax and bcl-2 was determined by reverse transcription-polymerase chain reaction (RT-PCR).


RESULTS
Iodinated and magnetic resonance contrast media reduced cell viability due to apoptosis. The cell damage induced by a non-ionic contrast medium ioversol was inhibited by specific inhibitors for caspase-3 and -9 but not caspase-8. Ioversol enhanced the activities of caspase-3 and -9, but to a lesser extent, caspase-8. The bax mRNA was enhanced, while bcl-2 mRNA was reduced, after exposure to ioversol. All of these actions of ioversol were reversed by dibutyl cAMP in the manner sensitive to a protein kinase A inhibitor H89 and a phosphatidylinositol 3 (PI3) kinase inhibitor wortmannin.


CONCLUSIONS
We demonstrated for the first time that cAMP reversed caspase-dependent apoptotic renal cell damage caused by contrast media. Both protein kinase A and PI3 kinase might be involved in protective effect of cAMP.
Yano
Takahisa
T
Department of Hospital Pharmacy, Faculty of Medicine, Kyushu University, Higashi-ku, Fukuoka, Japan. tyano@pharm.med.kyushu-u.ac.jp
Itoh
Yoshinori
Y
Sendo
Toshiaki
T
Kubota
Toshio
T
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 / Q000494:pharmacology*; D000242:Cyclic AMP / Q000494:pharmacology*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D004789:Enzyme Activation; D007457:Iodine Radioisotopes / Q000494:pharmacology*; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D018374:LLC-PK1 Cells / Q000187:drug effects / Q000201:enzymology / Q000502:physiology*; D009994:Osmolar Concentration; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000235:genetics; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism; D013552:Swine; D013997:Time Factors; D014283:Triiodobenzoic Acids / Q000037:antagonists & inhibitors / Q000494:pharmacology; D051028:bcl-2-Associated X Protein
D003287:Contrast Media; D007457:Iodine Radioisotopes; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D014283:Triiodobenzoic Acids; D051028:bcl-2-Associated X Protein; D003994:Bucladesine; D000242:Cyclic AMP; D019869:Phosphatidylinositol 3-Kinases; D017868:Cyclic AMP-Dependent Protein Kinases; D020169:Caspases; C054871:ioversol