C Van den Branden

Peroxisomal proliferation in heart and liver of mice receiving chlorpromazine, ethyl 2(5(4-chlorophenyl)pentyl) oxiran-2-carboxylic acid or high fat diet: a biochemical and morphometrical comparative study.

ABSTRACT. Chlorpromazine and related drugs including trifluoperazine, clopenthixol, and fluphenazine are in vitro inhibitors of mitochondrial carnitine palmitoyltransferase and cytochrome c oxidase and of peroxisomal carnitine octanoyltransferase from mouse heart and liver. By contrast with 0.1% ethyl 2(5(4-chlorophenyl)pentyl) oxiran- 2-carboxylic acid or 0.1% clofibrate-containing diets, the treatment of mice with 0.1% chlorpromazine-containing diet fails to induce peroxisomal proliferation in liver and heart. An 0.5% chlorpromazine-containing diet did induce peroxisomal proliferation. Inhibition of peroxisomal 0- oxidation presumably via the reduction of carnitine octanoyltransferase by chlorpromazine elicits the appearance in liver of lamellar structures resembling those seen in human peroxisomal disorders and induces accumulation of very long-chain fatty acids in plasma. The peroxisomal proliferation induced by administration of high dose chlorpromazine is ascribed to its ability to depress mitochondrial fatty acid oxidation by impairing cytochrome c oxidase and carnitine palmitoyltransferase activities.

Antioxidant enzyme gene expression in rats with remnant kidney induced chronic renal failure

Reactive oxygen intermediates play a role in chronic renal injury and glomerulosclerosis. We investigate changes in renal cortex antioxidant enzyme gene expression in the rat remnant-kidney model of chronic renal failure and compare the new data to enzyme activities published earlier. Antioxidant enzyme gene expression is evaluated by Northern blot analysis of cortex mRNA, using cDNA probes for catalase, copper/zinc-containing superoxide dismutase, and glutathione peroxidase. Catalase gene expression decreases during development of renal failure; this decrease is accompanied by decreased catalase activity during the glomerulosclerosis phase of the remnant-kidney model. Copper/zinc superoxide dismutase and glutathione peroxidase gene expression remain at a normal level during progression of the model, whereas their activities show a temporary decrease in the early remnant kidney. In the remnant-kidney model, catalase seems to be more vulnerable to reactive oxygen intermediates than superoxide dismutase and glutathione peroxidase. Our results show that antioxidant enzyme activity and gene expression do not change in the same direction at all times during disease development and that all antioxidant enzymes do not respond in the same way.

Short and Long-term Influence of Phenothiazines On Liver Peroxisomal Fatty-acid Oxidation in Rodents

Evidence is given that phenothiazines depress hepatic peroxisomal fatty acid oxidation in vivo. After oral administration to rats thioridazine and chlorpromazine inhibit peroxisomal β‐oxidation, evaluated by H2O2 production, during 2 weeks. In mice, this effect could not be demonstrated. However, in both species VLCFA are increased after short and long term drug administration. Electron microscopy reveals the presence of membranous structures in liver cytoplasm or lysosomes. The inhibition by thioridazine of peroxisomal β‐oxidation does not lead to hepatic peroxisome proliferation. The activities of enzymes related to fatty acid breakdown are not increased and liver peroxisomes are microscopically normal.

Peroxisomes in mice fed a diet supplemented with low doses of fish oil

The influence of low dietary doses (0.1 and 0.8% w/w) of a commercial fish oil preparation on peroxisomes in normal mice was studied and compared to the known strong inductive effects of high (10%) fish oil diets. Low fish oil doses were chosen to supply the mice with a concentration of docosahexaenoic acid, which was beneficial to patients with a peroxisomal disease. Peroxisomes were evaluated by cytochemical, morphometric, and enzymological techniques. The 0.1% fish oil diet had no effect on peroxisomes in liver, heart, and kidney even after prolonged treatment. The 0.8% diet did not change the peroxisomal number nor the catalase (EC 1.11.1.6) activity in the liver. Hepatic peroxisomal β-oxidation, however, was increased by 50% after 14 d. This was accompanied by reduced peroxisomal size. The 0.8% diet also caused a small increase (+25%) in myocardial catalase activity. No effect was observed in kidneys. Our results indicate that in mice a low (<0.8%) dietary fish oil dose has no or only a slight effect on hepatic peroxisomal β-oxidation. This may be of particular interest to patients with a peroxisomal fatty acid β-oxidation defect and who display a severe deficiency of docosahexaenoic acid—diets supplemented with low fish oil doses will improve the docosahexaenoic acid level without adding a strong load to the disturbed fatty acid metabolism.

Peroxisome proliferation associated with fibrinogen storage in the liver

We report a patient with fibrinogen storage disease in which there was proliferation of normal‐sized peroxisomes in the hepatocytes. This phenomenon has previously been described in several acquired liver diseases. We believe that this is an adaptation response due to decreased microsomal isoenzyme activity as a result of the excess accumulation of fibrinogen in the endoplasmic reticulum.

Altered Adrenocortical Response under the Influence of Experimentally Increased Serum Very Long Chain Fatty Acids in Rats

C 26:0/C 22:0 ratio can be experimentally increased in serum of normal rats by oral administration of hexacosanoic acid (C 26:0) or of thioridazine, an inhibitor of peroxisomal beta-oxidation. This causes a decreased corticosterone response as well as decreased mobilization of cholesterol esters in zona fasciculata interna cells following ACTH administration. Zona fasciculata interna cells and their nuclei are enlarged and contain more Feulgen DNA in thioridazine-fed rats. The similarity of adrenocortical response to inhibition of peroxisomal beta-oxidation and to C 26:0 administration points to raised VLCFA as the common factor which is also operative in many peroxisomal diseases accompanied by adrenocortical function defects.

Demonstration of H2O2 production in vivo during aminopyrine metabolism and phenobarbital induction

It has been shown previously that, by using methanol and a catalase inhibitor, 3-amino-1, 2, 4,-triazole, changes in hepatic H2O2 production in vivo can be detected. Using this method in guinea pigs and rats we could demonstrate increased H2O2 production during metabolism in vivo of aminopyrine, especially in phenobarbital-pretreated animals. In contrast, administration of antipyrine does not lead to H2O2 production. In the guinea pigs, phenobarbital induction also stimulates the H2O2 production in vivo without administration of exogenous substrates. The rate and extent of this additional H2O2 production depend on the induction state, drug metabolism and species; the major findings are in agreement with and extend previous research in vitro on microsomes, isolated hepatocytes and perfused liver.

Particulate Cytochrome c in Agrobacterium tumefaciens

: In Agrobacterium tumefaciens the main part of c-type cytochromes is tightly bound to the bacterial cell envelope structures. Several techniques were attempted to solubilize these cytochromes. The highest yield of cytochromes released is obtained by treatment of particle suspensions with 5% Triton X-100. Further purification confirms that the proteins are not really solubilized, but still aggregated in small heterogeneous complexes. Chromatography on a CM-cellulose column demonstrates that at least three different c-type cytochromes are present: cyt c-550, cyt c-552 and cyt c-556.