Studies on the effect of copper deficiency on rat liver mitochondria. III. Effects on adenine nucleotide translocase

Water-soluble extract of Salvia miltiorrhiza ameliorates carbon tetrachloride-mediated hepatic apoptosis in rats

Apoptosis is one of the events that are involved in liver fibrogenesis. Thus, factors that affect apoptosis may be used to modulate liver fibrosis. We have recently reported that Salvia miltiorrhiza plays a protective role in carbon tetrachloride (CCl4)-induced hepatic fibrosis. In this study, we aimed to evaluate whether S. miltiorrhiza modulated CCl4-induced hepatic apoptosis in rats. Male Wistar rats were given orally either vehicle or water-extract of S. miltiorrhiza (50 mg kg(-1) twice daily) for nine weeks beginning from the start of CCl4 administration. A group of normal rats was included for comparison. Hepatocyte DNA fragmentation and cytosolic caspase-3 and caspase-8 activity were determined in the experimental animals. Hepatic cytosolic Bax, Bcl-2, cytochrome c, and calpain-mu expressions were measured by Western blot analysis. Hepatic mitochondrial glutathione levels were assessed by colorimetric assay. Compared with normal rats, rats receiving CCl4 alone showed profound DNA fragmentation associated with an increased cytosolic fraction of cytochrome c and calpain-mu protein expressions and a decreased mitochondrial glutathione level. In contrast, a decreased laddering of DNA fragmentation was noted in rats receiving CCl4 plus S. miltiorrhiza extract. The mitochondrial glutathione level was significantly increased in rats receiving CCl4 plus S. miltiorrhiza extract compared with those receiving CCl4 alone. Additionally, cytosolic caspase-3 activity and cytosolic fractions of Bax, Bcl-2, cytochrome c, and calpain-mu protein expressions were decreased in rats receiving CCl4 plus S. miltiorrhiza extract compared with those receiving CCl4 alone. The cytosolic caspase-8 activity in rats receiving CCl4 alone was no different from those receiving CCl4 plus S. miltiorrhiza extract. These results indicated that chronic administration of S. miltiorrhiza ameliorated CCl4-mediatd hepatic apoptosis in rats. This effect may be related to the antioxidant properties of S. miltiorrhiza.

Identification of the mitochondrial ATP-Mg/Pi transporter. Bacterial expression, reconstitution, functional characterization, and tissue distribution

The mitochondrial carriers are a family of transport proteins that, with a few exceptions, are found in the inner membranes of mitochondria. They shuttle metabolites, nucleotides, and cofactors through this membrane and thereby connect and/or regulate cytoplasm and matrix functions. ATP-Mg is transported in exchange for phosphate, but no protein has ever been associated with this activity. We have isolated three human cDNAs that encode proteins of 458, 468, and 489 amino acids with 66-75% similarity and with the characteristic features of the mitochondrial carrier family in their C-terminal domains and three EF-hand Ca(2+)-binding motifs in their N-terminal domains. These proteins have been overexpressed in Escherichia coli and reconstituted into phospholipid vesicles. Their transport properties and their targeting to mitochondria demonstrate that they are isoforms of the ATP-Mg/Pi carrier described in the past in whole mitochondria. The tissue specificity of the three isoforms shows that at least one isoform was present in all of the tissues investigated. Because phosphate recycles via the phosphate carrier in mitochondria, the three isoforms of the ATP-Mg/Pi carrier are most likely responsible for the net uptake or efflux of adenine nucleotides into or from the mitochondria and hence for the variation in the matrix adenine nucleotide content, which has been found to change in many physiopathological situations.

Alterações metabólicas e funcionais do cobre em diabetes mellitus

O objetivo desta revisão foi discutir aspectos que envolvem as alterações metabólicas e funcionais do cobre em Diabetes Mellitus. Na presença desta doença, alguns distúrbios funcionais de cobre têm sido caracterizados e explicados em parte por alterações nos processos de absorção, circulação e utilização do elemento. O estado hormonal pode modificar a secreção biliar de cobre e assim repercutir na regulação homeostática da absorção. A redução na atividade da lisil-oxidase, uma cuproenzima, altera a síntese de colágeno e de elastina, comprometendo assim a integridade dos vasos sangüíneos. Tal fato pode agravar o desenvolvimento de complicações vasculares nos diabéticos. Os estudos com diabetes experimental apontam um acúmulo tecidual de cobre nos rins, o que conduz à especulações quanto à gênese da nefropatia diabética. Os experimentos com pacientes diabéticos demonstram irregularidades no cobre circulante, aumento de peroxidação lipídica e estado nutricional inadequado deste micronutriente.

Ultrastructure of hepatocytes in copper-deficient Sika deer (Cervus nippon Temminck)

The livers of 13 Sika deer (Cervus nippon Temminck) aged 4 to 9 years and suffering from copper deficiency (enzootic ataxia) were examined histologically, histochemically and by electron microscopy. In addition, the serum and liver copper concentrations, measured in three animals, were found to be low. Histologically, the hepatocytes exhibited cloudy swelling, and numerous haemosiderin deposits were seen in the hepatocytes and Kupffer cells. Staining with p-dimethyl amino-benzylidene-rhodamine revealed distinctly fewer copper granules than normal. Histochemically, 3,3'-diaminobenzidine-H2O2 staining revealed increased numbers of catalase-positive granules around nuclei. Electron microscopically, "giant" and bizarre-shaped mitochondria, irregular depression of the mitochondrial membrane, and fusion of cristae were noted. Disorders of copper-containing enzymes, including cytochrome oxidase, caeruloplasmin and monoamine oxidase, may have been responsible for the mitochondrial abnormalities.

Increase of flux control of cytochrome c oxidase in copper-deficient mottled brindled mice

The brindled mottled mouse (Mobr), an animal model of the Menkes' copper deficiency syndrome, was used for the investigation of changes in respiratory flux control associated with cytochrome c oxidase deficiency in muscle. Enzymatic analysis of cardiac and skeletal muscles showed an approximately 2-fold decrease in cytochrome c oxidase activity of brindled mutants in both types of muscles as compared with controls. The activities of NADH-cytochrome c oxidoreductase (respiratory chain segment I-III) and succinate-cytochrome c oxidoreductase (segment II-III) were normal. Assessment of mitochondrial respiratory function was performed using chemically skinned musculus quadriceps or heart muscle fibers isolated from control and brindled mottled mice. In skeletal muscle, there was no difference found in maximal rates of respiration. In the Mobr hearts, this parameter was slightly lower than control. Alternately, the determination of flux control coefficients of cytochrome c oxidase performed by a step by step inhibition of respiration with increasing concentrations of azide or cyanide revealed significantly sharper inhibition curves for brindled mice than for control, indicating more than 2-fold elevated flux control coefficients of cytochrome c oxidase. This investigation proved essential in characterizing the metabolic effect of a cytochrome c oxidase deficiency. We conclude, therefore, that application of metabolic control analysis can be a valuable approach to study defects of mitochondrial oxidative phosphorylation.

Biochemical study on the critical period for treatment of the mottled brindled mouse

Hemizygous mottled brindled mice (Mobr/y mice) were treated by subcutaneous injection of copper and were decapitated on postnatal day 14. Cytochrome c oxidase (COX) activity of the brain mitochondria in the mice given 10 micrograms of copper/g on day 4 or 7 showed significant increases compared with that of untreated Mobr/y animals, and these mice had no neurological symptoms. Mice given 10 micrograms of copper/g on day 12 showed neither increases in COX activity nor clinical improvement. The brain levels of copper, noradrenaline, and dopamine in the mice treated on day 12 were the same as those in animals treated on day 4 or 7. The in vitro activities of dopamine-beta-hydroxylase of the brain were also the same among the treated mice, irrespective of the date of treatment. The results indicate that delays in copper treatment produce irreversible changes in COX activity of the brain and lead to clinical unresponsiveness to treatment.

Effect of aging on the oxidative phosphorylation pathway

The proposed study was undertaken to investigate the effect of aging on control of the oxidative phosphorylation pathway. Flux control coefficients for adenine nucleotide translocase and cytochrome c oxidase were determined using the procedure of Groen et al. [J. Biol. Chem., 257 (1982) 137-144]. Hepatic mitochondrial fractions from Fischer 344 rats were isolated from control (average age 6.5 months), and aged (average age 27.3 months) groups. No aging-related changes in the extent of control of respiration by the oxidase were obtained, however, differences were observed for the translocase. For the control group of animals, the greatest regulation occurred at 80-85% maximal respiratory rates, and declined at higher rates. For the aged group, a similar flux control coefficient was obtained at 80-85% respiration, but was maintained as respiration increased to maximal rates. It is proposed that changes in the flux control coefficients at maximal respiratory rates are associated with an aging-related decrease in translocase activity. Evaluation of translocase content revealed no significant differences between the two groups supporting the concept that the decreased activity was not due to decreased content. During the course of these experiments, it also became apparent that there was a significant aging-related decrease in the rate of succinate oxidation providing an adequate supply of ADP was present. No significant changes in respiratory rates, or RCR, were evident at suboptimal concentrations of ADP as reported previously from this laboratory [Vorbeck, M.L. et al., Arch. Biochem. Biophys., 214 (1982) 67-79]. Since similar decreases in respiration were obtained upon addition of an uncoupler, the aging-related changes in respiration are attributed to differences at the level of the electron transport system, including its associated reactions. The aging-related differences in respiratory rates, and extent of control of respiration, were both observed under conditions of maximal stimulation of respiration. This suggests an inability of mitochondria from aged animals to respond to the increased demands of oxidation. Basic to these differences may be the lipid-membrane associated changes seen during aging.

Studies on the roles of apotransferrin and caeruloplasmin (EC 1.16.3.1) on iron absorption in copper-deficient rats using an isolated vascularly- and luminally-perfused intestinal preparation

1. Studies have been made on the effects of dietary copper on the iron and Cu distribution in rats and on the metabolic activity and absorptive capacity of intestines perfused both vascularly and luminally. 2. Rats maintained for 4-5 weeks on a Cu-deficient diet (0.4 microgram Cu/kg) had significantly lower plasma, liver and intestinal Cu concentrations and significantly reduced plasma caeruloplasmin and liver cytochrome c oxidase (EC 1.9.3.1) activity compared with controls receiving a Cu-supplemented diet (5 micrograms Cu/kg). Disturbances in Fe metabolism in Cu-deficient rats were evident as shown by a mild anaemia, significantly elevated hepatic Fe concentrations and hypoferraemia. 3. Intestinal glucose uptake from both the luminal perfusion medium (LPM) and vascular perfusion medium (VPM) was unaffected by Cu deficiency despite a significant (25-30%) reduction in oxygen consumption. This was associated with a 40% decline in mucosal cytochrome c oxidase activity. 4. In studies of Fe absorption, Fe uptake from the LPM was unaffected by Cu deficiency while transfer of Fe to VPM was significantly reduced (50%) compared with control preparations. Addition of apotransferrin (1 g/l) to the VPM was without effect in preparations from control rats but significantly increased the transfer of Fe to the VPM in preparations from Cu-deficient rats without affecting Fe uptake from the LPM. 5. The addition of either human or porcine caeruloplasmin (together with apotransferrin) to the VPM, such that the resultant ferroxidase (EC 1.16.3.1) activity of the VPM supernatant fraction was four to five times that of normal rat plasma, was without effect on either Fe uptake, tissue retention or Fe transfer to the VPM by preparations from either Cu-deficient or control rats. 6. These findings offer no evidence in support of the proposed role for caeruloplasmin with its associated ferroxidase activity in Fe absorption in the rat.