Inhibition of Rho family GTPases results in increased TNF-alpha production after lipopolysaccharide exposure.
These studies demonstrate that treatment of macrophages with lovastatin, a cholesterol-lowering drug that blocks farnesylation and geranylgeranylation of target proteins, increases LPS-induced TNF-alpha production. This is reversed by the addition of mevalonate, which bypasses the lovastatin block. Examination of membrane localization of RhoA, Cdc42, Rac1, and Ras demonstrated decreased membrane localization of the geranylgeranylated Rho family members (RhoA, Cdc42, and Rac1) with no change in the membrane localization of farnesylated Ras. LPS-induced TNF-alpha production in the presence of the Rho family-specific blocker (toxin B from Clostridium difficile) was significantly enhanced consistent with the lovastatin data. One intracellular signaling pathway that is required for TNF-alpha production by LPS is the extracellular signal-regulated kinase (ERK). Significantly, we found prolonged ERK activation after LPS stimulation of lovastatin-treated macrophages. When we inhibited ERK, we blocked the lovastatin-induced increase in TNF-alpha production. As a composite, these studies demonstrate a negative role for one or more Rho family GTPases in LPS-induced TNF-alpha production.
Monick
Martha M
MM
Division of Pulmonary, Critical Care, and Occupational Medicine, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Room 100, Ekstein Medical Research Building, Iowa City, IA 52242, USA. martha-monick@uiowa.edu
Powers
Linda S
LS
Butler
Noah S
NS
Hunninghake
Gary W
GW
D000818:Animals; D002460:Cell Line; D004338:Drug Combinations; D004789:Enzyme Activation / Q000187:drug effects / Q000276:immunology; D007108:Immune Tolerance / Q000187:drug effects; D007166:Immunosuppressive Agents / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008148:Lovastatin / Q000494:pharmacology; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000276:immunology; D008264:Macrophages / Q000187:drug effects / Q000201:enzymology / Q000276:immunology / Q000378:metabolism; D008798:Mevalonic Acid / Q000378:metabolism / Q000494:pharmacology; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis*; D015854:Up-Regulation / Q000187:drug effects / Q000276:immunology*; D020741:rho GTP-Binding Proteins / Q000037:antagonists & inhibitors* / Q000502:physiology*
D004338:Drug Combinations; D007166:Immunosuppressive Agents; D008070:Lipopolysaccharides; D014409:Tumor Necrosis Factor-alpha; D008148:Lovastatin; D020928:Mitogen-Activated Protein Kinases; D020741:rho GTP-Binding Proteins; D008798:Mevalonic Acid