You are here:
Propiconazole enhanced hepatic cell proliferation is associated with dysregulation of the cholesterol biosynthesis pathway leading to activation of Erk1/2 through Ras famesylation
Citation:
MURPHY, L. A., T. MOORE, AND S. NESNOW. Propiconazole enhanced hepatic cell proliferation is associated with dysregulation of the cholesterol biosynthesis pathway leading to activation of Erk1/2 through Ras famesylation. TOXICOLOGY AND APPLIED PHARMACOLOGY. Academic Press Incorporated, Orlando, FL, 260(2):146-54, (2012).
Impact/Purpose:
Propiconazole is a mouse hepatotumorigenic fungicide designed to inhibit CYP51, a key enzyme in the biosynthesis of ergosterol in fungi and is widely used in agriculture to prevent fungal gr
Description:
Propiconazole is a mouse hepatotumorigenic fungicide designed to inhibit CYP51, a key enzyme in the biosynthesis of ergosterol in fungi and is widely used in agriculture to prevent fungal growth. Metabolomic studies in mice revealed that propiconazole increased levels of hepatic cholesterol metabolites and bile acids, and transcriptomic studies revealed that genes within the cholesterol biosynthesis, cholesterol metabolism and bile acid biosyntheses pathways were up-regulated. Hepatic cell proliferation was also increased by propiconazole. AML12 immortalized hepatocytes were used to study propiconazole's effects on cell proliferation focusing on the dysregulation of cholesterol biosynthesis and resulting effects on Ras farnesylation and Erkl/2 activation as a primary pathway. Mevalonate, a key intermediate in the cholesterol biosynthesis pathway, increases cell proliferation in several cancer cell lines and tumors in vivo and serves as the precursor for isoprenoids (e.g. farnesyl pyrophosphate) which are crucial in the farnesylation of the Ras protein by farnesyl transferase. Farnesylation targets Ras to the cell membrane where it is involved in signal transduction, including the mitogenactivated protein kinase (MAPK) pathway. In our studies, mevalonic acid lactone (MVAL), a source of mevalonic acid, increased cell proliferation in AML12 cells which was reduced by farnesyl transferase inhibitors (L-744,832 or manumycin) or simvastatin, an HMG-CoA reductase inhibitor, indicating that this cell system responded to alterations in the cholesterol biosynthesis pathway. Cell proliferation in AML12 cells was increased by propiconazole which was reversed by co-incubation with L-744,832 or simvastatin. Increasing concentrations of exogenous cholesterol muted the proliferative effects of propiconazole, a result ascribed to reduced stimulation of the endogenous cholesterol biosynthesis pathway. Western analysis of subcellular fractions from control, MVAL or propiconazole-treated cells revealed increased Ras.
