ABSTRACT
OBJECTIVES: The direct-acting protease inhibitor paritaprevir is a new pharmaco-logic option available for treatment of chronic hepatitis C (HCV). Paritaprevir is reported to inhibit human UGT 1A1, but the mechanism of inhibition and its possible clinical consequences are not established. Our objective was to evaluate the in-vitro metabolic interaction between paritaprevir and the oral contraceptive steroid ethinyl estradiol (EE), a UGT 1A1 substrate. METHODS: Enzyme kinetic parameters were determined using human liver microsomes for the biotransformation of EE to its glucuronide metabolites, and the potency and mechanism of inhibition by paritaprevir. Probenecid was used as a reference inhibitor for purposes of assay validation. KEY FINDINGS: The underlying pattern of EE kinetics was complex, with evidence of substrate inhibition. The in-vitro inhibition constant (Ki ) value for paritaprevir vs EE on average was 20 µm and was consistent with a competitive inhibition mechanism. The ratio of in-vivo maximum plasma concentration of paritaprevir to in-vitro Ki was <0.1. CONCLUSIONS: Paritaprevir is an in-vitro inhibitor of UGT 1A1. However, the in-vitro Ki value relative to maximum clinical plasma concentrations is below the threshold to trigger a recommendation for pharmacokinetic drug interaction studies.
Subject(s)
Antiviral Agents/pharmacology , Glucuronosyltransferase/antagonists & inhibitors , Macrocyclic Compounds/pharmacology , Microsomes, Liver/drug effects , Adolescent , Adult , Aged , Antiviral Agents/pharmacokinetics , Child , Child, Preschool , Cyclopropanes , Drug Interactions , Enzyme Inhibitors/pharmacology , Ethinyl Estradiol/metabolism , Humans , Lactams, Macrocyclic , Macrocyclic Compounds/pharmacokinetics , Male , Microsomes, Liver/enzymology , Middle Aged , Probenecid/pharmacology , Proline/analogs & derivatives , Sulfonamides , Young AdultABSTRACT
Secreted Frizzled-related protein 2 (sFRP2) plays a key role in chronic fibrosis after myocardial infarction and in heart failure. The aim of this study was to elucidate the mechanisms through which sFRP2 may regulate the growth and extracellular matrix (ECM) remodeling of adult mouse cardiac fibroblasts (CFs). We found that sFRP2 activates CFs in part through canonical Wnt/ß-catenin signaling, as evidenced by increased expression of Axin2 and Wnt3a, but not Wnt5a, as well as accumulation of nuclear ß-catenin. In response to sFRP2, CFs exhibited robust cell proliferation associated with increased glucose consumption and lactate production, a phenomenon termed "the Warburg effect" in oncology. The coupling between CF expansion and anaerobic glycolysis is marked by upregulation of glyceraldehyde-3-phosphate dehydrogenase and tissue-nonspecific alkaline phosphatase. In conjunction with these phenotypic changes, CFs accelerated ECM remodeling through upregulation of expression of the matrix metalloproteinase (MMP) 1 and MMP13 genes, two members of the collagenase subfamily, and enzyme activities of MMP2 and MMP9, two members of the gelatinase subfamily. Consistent with the induction of multiple MMPs possessing collagenolytic activities, the steady-state level of collagen type 1 in CF-spent medium was reduced by sFRP2. Analysis of non-CF cell types revealed that the multifaceted effects of sFRP2 on growth control, glucose metabolism, and ECM regulation are largely restricted to CFs and highly sensitive to Wnt signaling perturbation. The study provides a molecular framework on which the functional versatility and signaling complexity of sFRP2 in cardiac fibrosis may be better defined.
