ABSTRACT
Inhibition of hepatic transporters such as organic anion transporting polypeptides (OATPs) 1B can cause drug-drug interactions (DDIs). Determining the impact of perpetrator drugs on the plasma exposure of endogenous substrates for OATP1B could be valuable to assess the risk for DDIs early in drug development. As OATP1B orthologs are well conserved between human and monkey, we assessed in cynomolgus monkeys the endogenous OATP1B substrates that are potentially suitable to assess DDI risk in humans. The effect of rifampin (RIF), a potent inhibitor for OATP1B, on plasma exposure of endogenous substrates of hepatic transporters was measured. From the 18 biomarkers tested, RIF (18 mg/kg, oral) caused significant elevation of plasma unconjugated and conjugated bilirubin, which may be attributed to inhibition of cOATP1B1 and cOATP1B3 based on in vitro to in vivo extrapolation analysis. To further evaluate whether cynomolgus monkeys are a suitable translational model to study OATP1B-mediated DDIs, we determined the inhibitory effect of RIF on in vitro transport and pharmacokinetics of rosuvastatin (RSV) and atorvastatin (ATV). RIF strongly inhibited the uptake of RSV and ATV by cOATP1B1 and cOATP1B3 in vitro. In agreement with clinical observations, RIF (18 mg/kg, oral) significantly decreased plasma clearance and increased the area under the plasma concentration curve (AUC) of intravenously administered RSV by 2.8- and 2.7-fold, and increased the AUC and maximum plasma concentration of orally administered RSV by 6- and 10.3-fold, respectively. In contrast to clinical findings, RIF did not significantly increase plasma exposure of either intravenous or orally administered ATV, indicating species differences in the rate-limiting elimination pathways.
Subject(s)
Cytochrome P-450 Enzyme Inducers/adverse effects , Hydroxymethylglutaryl-CoA Reductase Inhibitors/pharmacokinetics , Membrane Transport Modulators/adverse effects , Microsomes, Liver/drug effects , Models, Biological , Organic Anion Transporters/antagonists & inhibitors , Administration, Oral , Animals , Bilirubin/analogs & derivatives , Bilirubin/blood , Bilirubin/metabolism , Biomarkers/blood , Biomarkers/metabolism , Cytochrome P-450 Enzyme Inducers/administration & dosage , Drug Evaluation, Preclinical , Drug Interactions , HEK293 Cells , Humans , Hydroxymethylglutaryl-CoA Reductase Inhibitors/administration & dosage , Hydroxymethylglutaryl-CoA Reductase Inhibitors/blood , Hydroxymethylglutaryl-CoA Reductase Inhibitors/pharmacology , Injections, Intravenous , Macaca fascicularis , Male , Membrane Transport Modulators/administration & dosage , Metabolic Clearance Rate , Microsomes, Liver/enzymology , Microsomes, Liver/metabolism , Organic Anion Transporters/genetics , Organic Anion Transporters/metabolism , Protein Isoforms/antagonists & inhibitors , Protein Isoforms/genetics , Protein Isoforms/metabolism , Random Allocation , Recombinant Proteins/chemistry , Recombinant Proteins/metabolism , Species SpecificityABSTRACT
Troglitazone, a first-generation thiazolidinedione of antihyperglycaemic properties, was withdrawn from the market due to unacceptable idiosyncratic hepatotoxicity. Despite intensive research, the underlying mechanism of troglitazone-induced liver toxicity remains unknown. Here we report the use of the Sod2(+/-) mouse model of silent mitochondrial oxidative-stress-based and quantitative mass spectrometry-based proteomics to track the mitochondrial proteome changes induced by physiologically relevant troglitazone doses. By quantitative untargeted proteomics, we first globally profiled the Sod2(+/-) hepatic mitochondria proteome and found perturbations including GSH metabolism that enhanced the toxicity of the normally nontoxic troglitazone. Short- and long-term troglitazone administration in Sod2(+/-) mouse led to a mitochondrial proteome shift from an early compensatory response to an eventual phase of intolerable oxidative stress, due to decreased mitochondrial glutathione (mGSH) import protein, decreased dicarboxylate ion carrier (DIC), and the specific activation of ASK1-JNK and FOXO3a with prolonged troglitazone exposure. Furthermore, mapping of the detected proteins onto mouse specific protein-centered networks revealed lipid-associated proteins as contributors to overt mitochondrial and liver injury when under prolonged exposure to the lipid-normalizing troglitazone. By integrative toxicoproteomics, we demonstrated a powerful systems approach in identifying the collapse of specific fragile nodes and activation of crucial proteome reconfiguration regulators when targeted by an exogenous toxicant.
Subject(s)
Chromans/toxicity , Glutathione/antagonists & inhibitors , Hypoglycemic Agents/toxicity , Mitochondria/drug effects , Mitochondrial Proteins/genetics , Proteomics , Thiazolidinediones/toxicity , Animals , Dicarboxylic Acid Transporters/antagonists & inhibitors , Dicarboxylic Acid Transporters/genetics , Dicarboxylic Acid Transporters/metabolism , Female , Forkhead Box Protein O3 , Forkhead Transcription Factors/agonists , Forkhead Transcription Factors/genetics , Forkhead Transcription Factors/metabolism , Gene Expression Regulation/drug effects , Glutathione/metabolism , Humans , Ion Transport/drug effects , MAP Kinase Kinase 4/genetics , MAP Kinase Kinase 4/metabolism , MAP Kinase Kinase Kinase 5/genetics , MAP Kinase Kinase Kinase 5/metabolism , Male , Mice , Mice, Knockout , Mitochondria/genetics , Mitochondria/metabolism , Mitochondrial Proteins/metabolism , Oxidative Stress/drug effects , Signal Transduction , Superoxide Dismutase/deficiency , Superoxide Dismutase/genetics , TroglitazoneABSTRACT
Adenosine-to-inosine RNA editing is crucial for generating molecular diversity, and serves to regulate protein function through recoding of genomic information. Here, we discover editing within Ca(v)1.3 Ca²âº channels, renown for low-voltage Ca²âº-influx and neuronal pacemaking. Significantly, editing occurs within the channel's IQ domain, a calmodulin-binding site mediating inhibitory Ca²âº-feedback (CDI) on channels. The editing turns out to require RNA adenosine deaminase ADAR2, whose variable activity could underlie a spatially diverse pattern of Ca(v)1.3 editing seen across the brain. Edited Ca(v)1.3 protein is detected both in brain tissue and within the surface membrane of primary neurons. Functionally, edited Ca(v)1.3 channels exhibit strong reduction of CDI; in particular, neurons within the suprachiasmatic nucleus show diminished CDI, with higher frequencies of repetitive action-potential and calcium-spike activity, in wild-type versus ADAR2 knockout mice. Our study reveals a mechanism for fine-tuning Ca(v)1.3 channel properties in CNS, which likely impacts a broad spectrum of neurobiological functions.
