title: Involvement of de novo ceramide synthesis in radiocontrast-induced renal tubular cell injury.
abstract: We reported previously that various radiocontrast media cause apoptosis in porcine proximal tubular (LLC-PK(1)) cells, in which reduction in B-cell lymphoma (Bcl)-2 expression and caspase-3 activation are implicated. In the present study, we investigated a role for ceramide in radiocontrast media-induced apoptosis in renal tubular cells. LLC-PK(1) cells were exposed to radiocontrast media for 30 min, followed by incubation for 24 h in normal medium. Cell viability was assessed by 2-(2-methoxy-4-nitrophenyl)-3-(4-nitrophenyl)-5-(2,4-disulfophenyl)-2H-tetrazolium monosodium salt assay, while apoptosis was determined by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling stain. Immunofluorescent stains were performed using antibodies against phosphorylated Akt (pAkt) and cAMP response element binding protein (CREB) (pCREB), and ceramide. The mRNA expression and protein content of Bcl-2 were determined by reverse transcriptase-polymerase chain reaction and enzyme immunoassay, respectively. In vivo model of contrast-induced renal injury was induced in mice with unilateral renal occlusion. The cell injury induced by the nonionic radiocontrast medium ioversol was reversed by inhibiting de novo ceramide synthesis with fumonisin B(1) (FB(1)) and L-cycloserine, but not by suppressing sphingomyelin breakdown with D609. FB(1) reversed ioversol-induced decrease in the immunoreactivities of pAkt and pCREB, reduction in Bcl-2 expression and caspase-3 activation. Like ioversol, C2 ceramide and the Akt inhibitor Src homology-6 induced apoptosis by reducing pAkt and pCREB-like immunoreactivities, lowering Bcl-2 expression and enhancing caspase-3 activity. Indeed, various radiocontrast media, excluding iodixanol which showed the least nephrotoxicity, enhanced ceramide-like immunoreactivity. The role for de novo ceramide synthesis was also shown in the in vivo model of radiocontrast nephropathy. We demonstrated here for the first time that the enhancement of de novo ceramide synthesis contributes to radiocontrast nephropathy.
authors.affiliation: Department of Pharmacy, Kyushu University Hospital, Higashi-ku, Fukuoka, Japan. yositou@st.hosp.kyushu-u.ac.jp
authors.forename: Y
authors.initials: Y
authors.lastname: Itoh
authors.forename: T
authors.initials: T
authors.lastname: Yano
authors.forename: T
authors.initials: T
authors.lastname: Sendo
authors.forename: M
authors.initials: M
authors.lastname: Sueyasu
authors.forename: K
authors.initials: K
authors.lastname: Hirano
authors.forename: H
authors.initials: H
authors.lastname: Kanaide
authors.forename: R
authors.initials: R
authors.lastname: Oishi
mesh_terms: D000117:Acetylglucosamine / Q000652:urine; D000818:Animals; D017209:Apoptosis; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D002518:Ceramides / Q000096:biosynthesis*; D003287:Contrast Media / Q000633:toxicity*; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D037341:Fumonisins / Q000494:pharmacology; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D007684:Kidney Tubules / Q000187:drug effects* / Q000473:pathology; D051379:Mice; D008928:Mitochondria / Q000187:drug effects; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000032:analysis / Q000235:genetics; D017382:Reactive Oxygen Species; D013552:Swine; D014283:Triiodobenzoic Acids / Q000633:toxicity*
chemical_list: D002518:Ceramides; D003287:Contrast Media; D017362:Cyclic AMP Response Element-Binding Protein; D037341:Fumonisins; D019253:Proto-Oncogene Proteins c-bcl-2; D017382:Reactive Oxygen Species; D014283:Triiodobenzoic Acids; C056933:fumonisin B1; D007334:Insulin-Like Growth Factor I; D051057:Proto-Oncogene Proteins c-akt; C054871:ioversol; D000117:Acetylglucosamine