title: ERK signaling mediates the induction of inflammatory cytokines by bufalin in human monocytic cells.
abstract: Treatment of human leukemia THP-1 cells with bufalin, a specific inhibitor of Na(+)-K(+)-ATPase, sequentially induces c-fos and inflammatory cytokines interleukin-1 beta (IL-1 beta) and tumor necrosis factor-alpha (TNF-alpha) gene expressions before the appearance of mature phenotypes of monocytic cells. In this study we examined the signal transduction leading to bufalin-induced gene expressions. Bufalin selectively activated extracellular signal-regulated kinase (ERK), compared with other mitogen-activated protein (MAP) kinase family members. Pretreatment of THP-1 cells with PD-98059, an inhibitor of the ERK-kinase cascade, abolished bufalin-induced c-fos and IL-1 beta gene expressions, indicating that the ERK-kinase cascade mediates the induction of inflammatory cytokines by bufalin. Inhibition of the Na(+)/Ca(2+) exchanger by KB-R7943 and of protein kinase C (PKC) by Ro-31-8220 suppressed ERK activation and gene expressions of c-fos and IL-1 beta. These findings suggest that Na(+)-K(+)-ATPase inhibition by bufalin induces calcium influx and thereby activates PKC and ERK. In cells treated with an inhibitor of p38 MAP kinases, SB-203580, bufalin-mediated ERK activation became persistent and the induction of IL-1 beta and TNF-alpha expressions was significantly augmented. These results suggest that cross talk in bufalin-mediated ERK activation is negatively regulated by endogenous p38 MAP kinase activations.
authors.affiliation: Department of Biochemical Toxicology, School of Pharmaceutical Sciences, Showa University, Tokyo 142-8555, Japan. kuromasa@pharm.showa-u.ac.jp
authors.forename: M
authors.initials: M
authors.lastname: Kurosawa
authors.forename: S
authors.initials: S
authors.lastname: Numazawa
authors.forename: Y
authors.initials: Y
authors.lastname: Tani
authors.forename: T
authors.initials: T
authors.lastname: Yoshida
mesh_terms: D002018:Bufanolides / Q000494:pharmacology*; D016207:Cytokines / Q000235:genetics*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology*; D016762:Genes, fos; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D007375:Interleukin-1 / Q000235:genetics; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009000:Monocytes / Q000502:physiology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D019831:Sodium-Calcium Exchanger / Q000037:antagonists & inhibitors; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors; D013890:Thiourea / Q000031:analogs & derivatives / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics
chemical_list: C101670:2-(2-(4-(4-nitrobenzyloxy)phenyl)ethyl)isothiourea methanesulfonate; D002018:Bufanolides; D016207:Cytokines; D004791:Enzyme Inhibitors; D007211:Indoles; D007375:Interleukin-1; D019831:Sodium-Calcium Exchanger; D014409:Tumor Necrosis Factor-alpha; D011493:Protein Kinase C; D020928:Mitogen-Activated Protein Kinases; D000254:Sodium-Potassium-Exchanging ATPase; D013890:Thiourea; C022777:bufalin; C064758:Ro 31-8220