A nonsense mutation in the NDUFS4 gene encoding the 18 kDa (AQDQ) subunit of complex I abolishes assembly and activity of the complex in a patient with Leigh-like syndrome.

Sequence analysis of mitochondrial and nuclear candidate genes of complex I in children with deficiency of this complex and exhibiting Leigh-like syndrome has revealed, in one of them, a novel mutation in the NDUFS4 gene encoding the 18 kDa subunit. Phosphorylation of this subunit by cAMP-dependent protein kinase has previously been found to activate the complex. The present mutation consists of a homozygous G-->A transition at nucleotide position +44 of the coding sequence of the gene, resulting in the change of a tryptophan codon to a stop codon. Such mutation causes premature termination of the protein after only 14 amino acids of the putative mitochondrial targeting peptide. Fibroblast cultures from the patient exhibited severe reduction of the rotenone-sensitive NADH-->UQ oxidoreductase activity of complex I, which was insensitive to cAMP stimulation. Two-dimensional electrophoresis showed the absence of detectable normally assembled complex I in the inner mitochondrial membrane. These findings show that the expression of the NDUFS4 gene is essential for the assembly of a functional complex I.

Chronic low dose ethanol intake: biochemical characterization of liver mitochondria in rats.

Liver mitochondria were isolated from male rats exposed for 2 months to low doses of ethanol (3% v/v in drinking water), a condition not associated with tolerance or dependence. The results show no significant changes in the content of reduced or oxidized glutathione in the liver mitochondria of ethanol treated rats with respect to controls. However, a slight but significant increase in lipid peroxidation, accompanied by an increased content of oxidized proteins, was found in ethanol exposed animals. Mitochondrial content of cytochrome complexes was not significantly affected by ethanol intake. The specific enzymatic activity of cytochrome oxidase showed, however, a significant decrease in ethanol-treated rats. The slight mitochondrial alterations found in the liver of rats exposed chronically to low doses of ethanol might represent the beginning of a more extensive damage previously observed in rats exposed to high doses of this substance.

Oxidative burst and lysosomal enzyme release by polymorphonuclear cells in type IIa, type IIb and type IV primary hyperlipoproteinaemia.

Several findings pint out the occurrence of a strict relationship between lipoproteins and immunoresponsiveness. In this regard, in vitro lipoproteins pretreatment of mononuclear cell suspensions leads to an inhibition of Natural Killer (NK) cytotoxicity or T- and B-mediated immune functions. These results have an in vivo counterpart, since an impairment of either T-driven B cell polyclonal differentiation or phagocyte chemotaxis, phagocytosis and killing has been shown in patients with type IIa and type IIb primary hyperlipoproteinaemia. On the contrary, these activities fall within normal range in type IV hyperlipoproteinaemic subjects. To further address the potential role of polymorphonuclear cells (PMN) in atherosclerotic process, in the present report PMN-mediated superoxide anion (O2-) generation, hydrogen peroxide (H2O2) production, beta-glucuronidase and myeloperoxidase release have been assessed in similar groups of patients. Results provide a clearcut evidence for a significant enhancement of oxidative metabolism by either suspended or adherent to plastic PMN in type IIa primary hyperlipoproteinaemia only. These data were further confirmed by the observation that the same cell suspensions exhibit a significant increase of H2O2 generation and/or beta-glucuronidase and myeloperoxidase release. By contrast, PMN metabolic pathway in type IIb and type IV patients mimics that observed in healthy individuals. In the light of the well known increase of serum low-density lipoproteins (LDL) in type IIa primary hyperlipoproteinaemia, these findings suggest that also PMN may play an important role in the development of atherosclerosis. The augmented oxidative responsiveness may, in fact, give rise to LDL oxidation, which is in turn responsible for foam cell generation through an exaggerated uptake of oxidized LDL by macrophages.(ABSTRACT TRUNCATED AT 250 WORDS)