Hyperbaric hyperoxia exaggerates respiratory membrane defects in the copper-deficient rat lung

Copper deficiency and cardiovascular disease: role of peroxidation, glycation, and nitration

Dietary copper deficiency causes a variety of cardiovascular deficits. Systemic effects include high blood pressure, enhancement of inflammation, anemia, reduced blood clotting, and possibly arteriosclerosis. Effects on specific organs or tissues include weakened structural integrity of the heart and blood vessels, impairment of energy use by the heart, reduced ability of the heart to contract, altered ability of blood vessels to control their diameter and grow, and altered structure and function of circulating blood cells. In some instances, the cause of a defect can be directly attributed to reduced activity of a specific copper-dependent enzyme. However, three nonspecific mechanisms of damage have been implicated in cardiovascular defects of copper deficiency. They are peroxidation, the interaction of oxygen-derived free radicals with lipids and proteins (possibly DNA); glycation, the nonenzymatic glycosylation of proteins; and nitration, the interaction of nitric oxide and its metabolites with peptides and proteins. Though independently these mechanisms present great potential for damage, the possibility that they may interact presents an added reason for concern. Furthermore, the fact that at least two of these mechanisms are associated with diabetes and aging suggests that copper deficiency may exacerbate deficits associated with these two conditions.Key words: copper, heart, circulation, peroxidation, glycation, nitric oxide.

Metallothionein inhibits myocardial apoptosis in copper-deficient mice: role of atrial natriuretic peptide

Dietary copper restriction causes heart hypertrophy in animal models. Several studies have indicated that this cardiomyopathy is mediated by oxidative stress. Metallothionein (MT), a low molecular weight and cysteine-rich protein, functions in protecting the heart from oxidative injury. We therefore used a cardiac-specific MT-overexpressing transgenic mouse model to test the hypothesis that MT inhibits copper deficiency-induced heart hypertrophy. Dams of both transgenic pups and non-transgenic littermates were fed a copper-adequate or copper-deficient diet, starting on the fourth day post-delivery, and the weanling mice were continued on the dams' diets until they were killed. Heart hypertrophy developed in copper-deficient pups by the fourth week of the combined pre- and post-weaning feeding and aggressively progressed until the end of the experiment (6 weeks). MT overexpression did not prevent the occurrence of heart hypertrophy, but inhibited the progression of this cardiomyopathy, which correlated with its suppression of cardiac lipid peroxidation. Corresponding to the progression of heart hypertrophy, myocardial apoptosis and atrial natriuretic peptide (ANP) production in the left ventricle were detected in non-transgenic copper-deficient mice; these effects were significantly suppressed in transgenic copper-deficient mice. Measurement of apoptosis by TUNEL assay and Annexin V-FITC confocal microscopy in primary cultures of cardiomyocytes revealed that ANP was largely responsible for the myocyte apoptosis and that MT inhibited ANP-induced apoptosis. The data clearly demonstrate that elevation of MT in the heart inhibits oxidative injury and suppresses the progression of heart hypertrophy in copper deficiency, although it does not block its initiation. The results suggest that MT inhibits the transition from heart hypertrophy to failure by suppressing apoptosis through inhibition of both cardiac ANP production and its apoptotic effect.

Cardiovascular effects of dietary copper deficiency

Dietary copper deficiency may impair cardiovascular health by contributing to high blood pressure, enhancement of inflammation, anemia, reduced blood clotting and arteriosclerosis. The purpose of this review is to compile information on the numerous changes of the heart, blood and blood vessels that may contribute to these cardiovascular defects. These alterations include weakened structural integrity of the heart and blood vessels, impairment of the use of energy by the heart, reduced ability of the heart to contract, altered ability of blood vessels to control their diameter and to grow, and altered structure and function of circulating blood cells. The fundamental causes of these changes rest largely on reduced effectiveness of enzymes that depend on copper for their activity.

Analysis of lung damage induced by trichloroethylene inhalation in mice fed diets with low, normal, and high copper content

Copper is both an essential nutrient required for the activity of several enzymes and a toxic element able to catalyze free radical formation. Trichloroethylene (TCE) is a xenobiotic that generates epoxidic intermediates by bioactivation through the cytochrome P-450 system. In this study, the influence of a dietary copper imbalance on the TCE-induced lung damage was investigated. Weaning mice were fed copper-deficient, copper-sufficient, and copper-excessive diets. After 4 wk, mice were exposed for 30 min to 6,500 ppm of TCE and euthanatized 48 hr later. Lung damage in the TCE-treated mice consisted of vacuolations of Clara cells and was quantitatively evaluated by counting the vacuolated cells per micrometer of basal lamina. At the ultrastructural level, vacuolations appeared as the result of hydropic swelling of the endoplasmic reticulum cisternae. The copper-deficient mice presented the highest number of vacuolated Clara cells. These mice also showed alteration of the capillary endothelium and interstitium and decreased pulmonary copper-zinc-superoxide dismutase activity. Occurrence of oxidative stress in lungs of both copper-sufficient and copper-deficient mice following TCE treatment was indicated by a decrease in reduced glutathione and an increase in its oxidized form.

Von Willebrand factor restores impaired platelet thrombogenesis in copper-deficient rats

Dietary copper restriction reduces microvascular thrombogenesis. We have now examined the roles of shear forces and von Willebrand factor (vWF) in in vivo thrombus formation in the cremaster microcirculation of copper-deficient rats. Male weanling Sprague-Dawley rats were fed purified diets that were either copper-adequate (6.3 mg Cu/kg) or copper-deficient (0.3 mg Cu/kg) for 4 wk. Intravascular fluorescein isothiocyanate tagged to bovine serum albumin was activated with 450-490 nm light to induce thrombus formation in microvessels. Thrombus initiation time was significantly prolonged in copper-deficient rats; after thrombus appearance, however, vessel occlusion was significantly accelerated. The greater shear rates of arterioles compared with venules significantly increased the thrombus initiation time in both groups. However, vessel occlusion time and thrombus growth time were independent of shear rate. Intravascular vWF (0.2 u/100 g body wt) decreased thrombus initiation time in the CuD group without affecting thrombus growth time. The data suggest that decreased thrombogenesis in copper-deficient rats is not a result of altered rheological factors or arteriolar-venular differences, but appears to result from decreased platelet-to-endothelial cell adhesion.

Weak antioxidant defenses make the heart a target for damage in copper-deficient rats

Copper deficiency causes more salient pathologic changes in the heart than in the liver of rats. Although oxidative stress has been implicated in copper deficiency-induced pathogenesis, little is known about the selective toxicity to the heart. Therefore, we examined the relationship between the severity of copper deficiency-induced oxidative damage and the capacity of antioxidant defense in heart and liver to investigate a possible mechanism for the selective cardiotoxicity. Weanling rats were fed a purified diet deficient in copper (0.4 microgram/g diet) or one containing adequate copper (6.0 microgram/g diet) for 4 weeks. Copper deficiency induced a 2-fold increase in lipid peroxidation in the heart (thiobarbituric assay) but did not alter peroxidation in the liver. The antioxidant enzymatic activities of superoxide dismutase, catalase, and glutathione peroxidase were, respectively, 3-, 50- and 1.5-fold lower in the heart than in the liver, although these enzymatic activities were depressed in both organs by copper deficiency. In addition, the activity of glutathione reductase was 4 times lower in the heart than in the liver. The data suggest that a weak antioxidant defense system in the heart is responsible for the relatively high degree of oxidative damage in copper-deficient hearts.

Newer aspects of micronutrients in chronic disease: copper

Cu ions are pro-oxidants when added to biological material in vitro and excessive levels of Cu in the body, such as in Wilson's Disease (Yarze et al. 1992) promote oxidant-related pathologies. In contrast there is now substantial evidence that an optimum level of Cu is required to maintain antioxidant defence and that Cu deficiency in animals increases oxidant stress. There are abundant mechanistic relationships linking Cu deficiency and processes associated with IHD, some of which do not directly involve oxidant damage. These mechanistic relationships, however, have mostly been demonstrated in animal models and more information is urgently required concerning possible chronic mild Cu deficiencies in human populations. A major hurdle to advances in this area is the lack of indices of Cu status which are sensitive enough to detect marginal Cu deficiency in humans. The question, therefore, of whether or not there is a role for mild Cu deficiency in the onset of chronic disease processes, including IHD, remains unanswered.