tetracycline and tianeptine

The small heterodimer partner (SHP) (NR0B2) is an atypical nuclear receptor that lacks a DNA-binding domain. It interacts with and inhibits many transcription factors, affecting key metabolic processes, including bile acid, cholesterol, fatty acid, and drug metabolism. Our aim was to determine the influence of steatotic drugs and nonalcoholic fatty liver disease (NAFLD) on SHP expression and investigate the potential mechanisms. SHP was found to be repressed by steatotic drugs (valproate, doxycycline, tetracycline, and cyclosporin A) in cultured hepatic cells and the livers of different animal models of NAFLD: iatrogenic (tetracycline-treated rats), genetic (glycine N-methyltransferase-deficient mice), and nutritional (mice fed a methionine- and choline-deficient diet). Among the different transcription factors investigated, CCAAT-enhancer-binding protein α (C/EBPα) showed the strongest dominant-repressive effect on SHP expression in HepG2 and human hepatocytes. Reporter assays revealed that the inhibitory effect of C/EBPα and steatotic drugs colocalize between -340 and -509 base pair of the SHP promoter, and mutation of a predicted C/EBPα response element at -473 base pair abolished SHP repression by both C/EBPα and drugs. Moreover, inhibition of major stress signaling pathways demonstrated that the mitogen-activated protein kinase kinase 1/2 pathway activates, while the phosphatidylinositol 3 kinase pathway represses SHP in a C/EBP-dependent manner. We conclude that SHP is downregulated by several steatotic drugs and in advanced NAFLD. These conditions can activate signals that target C/EBPα and consequently repress SHP, thus favoring the progression and severity of NAFLD.

Topics: Animals; CCAAT-Enhancer-Binding Protein-alpha; Cells, Cultured; Cyclosporine; Doxycycline; Fatty Liver; Humans; Male; Mice; Mitogen-Activated Protein Kinase 1; Non-alcoholic Fatty Liver Disease; Promoter Regions, Genetic; Receptors, Cytoplasmic and Nuclear; Signal Transduction; Tetracycline; Thiazepines; Transcription, Genetic; Valproic Acid

Although many steatogenic drugs inhibit mitochondrial fatty acid beta-oxidation, limited information is available on possible effects on hepatic lipoprotein secretion. In the endoplasmic reticulum (ER) lumen, microsomal triglyceride transfer protein (MTP) lipidates apolipoprotein B (Apo B), to form triglyceride (TG)-rich very low density lipoprotein (VLDL) particles, which follow vesicular flow to the plasma membrane to be secreted, whereas incompletely lipidated Apo B particles are partly degraded. We studied hepatic MTP activity, the lipoproteins present in the ER lumen, and hepatic lipoprotein secretion 4 hours after administration of a single dose of amineptine (1 mmol/kg), amiodarone (1 mmol/kg), doxycycline (0.25 mmol/kg), tetracycline (0.25 mmol/kg), tianeptine (0.5 mmol/kg), or pirprofen (2 mmol/kg) in mice. These various doses have been shown previously to markedly inhibit fatty acid oxidation after a single dose, and to trigger steatosis either after repeated doses (doxycycline) or a single dose (other compounds) in mice. In the present study, amineptine, amiodarone, pirprofen, tetracycline, and tianeptine, but not doxycycline, inhibited MTP activity in vitro, decreased ex vivo MTP activity in the hepatic homogenate of treated mice, decreased TG in the luminal VLDL fraction of hepatic microsomes of treated mice, and decreased in vivo hepatic lipoprotein secretion (TG and Apo B). In conclusion, several steatogenic drugs inhibit not only mitochondrial beta-oxidation, as previously shown, but also MTP activity, Apo B lipidation into TG-rich VLDL particles, and hepatic lipoprotein secretion. Drugs with these dual effects may be more steatogenic than drugs acting only on beta-oxidation or only MTP.

Topics: Amiodarone; Animals; Anti-Bacterial Agents; Anti-Inflammatory Agents, Non-Steroidal; Antidepressive Agents, Tricyclic; Apolipoproteins B; Carrier Proteins; Dibenzocycloheptenes; Doxycycline; Enzyme Inhibitors; Fatty Liver; Lipoproteins, VLDL; Mice; Microsomes, Liver; Mitochondria, Liver; Oxidation-Reduction; Phenylpropionates; Sonication; Tetracycline; Thiazepines; Triglycerides

Human lymphocytes were assessed as a cellular model for determining the effects of drugs on human mitochondria. Formation of total oxidized 14C-products was maximal with 1 mM [U-14C]palmitic acid, was linear for 90 min, linear with the number of lymphocytes, and decreased by 95% and 77% in the presence of 30 microM rotenone and 2 mM KCN. Seven drugs were tested which had previously been shown to inhibit beta-oxidation in animals; all decreased formation of total oxidized 14C-products by human lymphocytes, but with different IC50 values: 35 microM with amiodarone, 2.75 mM with tetracycline and amineptine, 3.75 mM with tianeptine, and more than 10 mM for valproic acid and the ibuprofen enantiomers. Formation of [14C]CO2 either increased or decreased, in relation to the various effects of these drugs on coupling, beta-oxidation, and the tricarboxylic acid cycle. There was a general trend for some relationship between inhibition of fatty acid oxidation and loss of cellular ATP. Those compounds, however, which uncoupled oxidative phosphorylation (2,4-dinitrophenol, amiodarone, ibuprofen) and/or inhibited the mitochondrial respiratory chain (amiodarone, rotenone, KCN) resulted in comparatively higher ATP depletion. Amiodarone, a drug which produces several effects (uncoupling, inhibition of beta-oxidation, of the tricarboxylic acid cycle and of the respiratory chain), caused a dramatic decrease in cellular ATP and cell viability at low concentrations (20-100 microM). Both these effects were prevented by the addition of 5 mM glucose, a substrate for anaerobic glycolysis. We conclude that human lymphocytes may be a useful model for assessing the effects of drugs on human mitochondrial function. IC50 values determined with this model may not necessarily apply, however, to other cells.

Topics: Adenosine Triphosphate; Amiodarone; Carbon Radioisotopes; Cell Survival; Dibenzocycloheptenes; Fatty Acids; Humans; Lymphocytes; Mitochondria; Models, Biological; Oxidation-Reduction; Tetracycline; Thiazepines