title: Role of mitochondrial Bax, caspases, and MAPKs for ceramide-induced apoptosis in renal proximal tubular cells.
abstract: It remains elusive whether crosstalk exists among mitochondrial Bax, caspases, and mitogen-activated protein kinases (MAPKs), and whether epidermal growth factor (EGF), which may activate MAPKs, affects ceramide-induced apoptosis through the crosstalk in renal proximal tubular cells (RPTCs). Effect of ceramide on expression of mitochondrial Bax and phosphorylated (p)-ERK, p38MAPK and JNK, that of MAPKs inhibition, and of EGF in the presence or absence of MAPKs inhibition on ceramide-induced apoptosis were examined in HK-2 cells. Apoptosis and expression of mitochondrial Bax and p-MAPKs were measured by Hoechst 33258 staining and Western blotting. C2-ceramide, but not dihydroC2-ceramide, inactive C2-ceramide, induced apoptosis at 24 h. C2-ceramide enhanced the mitochondrial Bax expression at 1 h, which was peaked at 3-6 h and decreased at 24 h, but remained increased, compared to control. An inhibitor of caspases, zVAD-fmk, ameliorated ceramide-induced apoptosis, suggesting a role of caspases for ceramide-induced apoptosis. C2-ceramide enhanced the expression of p-ERK and p-p38MAPK, but not p-JNK, at 1 h, which was increased till 24 h. An inhibitor of ERK, PD98059, or of p38MAPK, SB202190, failed to affect C2-ceramide-induced apoptosis. EGF, which enhanced the expression of p-ERK and p-p38MAPK but not p-JNK, ameliorated C2-ceramide-induced apoptosis without affecting mitochondrial Bax. Inhibition of ERK or p38MAPK failed to abolish the protective effect of EGF on C2-ceramide-induced apoptosis. Mitochondrial Bax and caspases, but not MAPKs, play a role for ceramide-induced apoptosis in RPTCs. EGF ameliorates ceramide-induced apoptosis in Bax- and MAPKs-independent pathways. The mechanism of ceramide-induced apoptosis and anti-apoptotic effect of EGF deserves further investigations.
authors.affiliation: Department of Pediatrics, Nagoya University Graduate School of Medicine, Nagoya, Aichi, Japan.
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Iwayama
authors.forename: Norishi
authors.initials: N
authors.lastname: Ueda
mesh_terms: D017209:Apoptosis; D061945:Caspase Inhibitors / Q000494:pharmacology; D020169:Caspases / Q000378:metabolism*; D002460:Cell Line; D004789:Enzyme Activation; D004815:Epidermal Growth Factor / Q000502:physiology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D007687:Kidney Tubules, Proximal / Q000166:cytology*; D008928:Mitochondria / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D011725:Pyridines / Q000494:pharmacology; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000502:physiology; D051028:bcl-2-Associated X Protein / Q000502:physiology*; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: C494826:BAX protein, human; D061945:Caspase Inhibitors; D007093:Imidazoles; C064769:N-acetylsphingosine; D011725:Pyridines; D051028:bcl-2-Associated X Protein; D004815:Epidermal Growth Factor; D048049:Extracellular Signal-Regulated MAP Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D020169:Caspases; D013110:Sphingosine; C090942:4-(4-fluorophenyl)-2-(4-hydroxyphenyl)-5-(4-pyridyl)imidazole
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