Measuring the oxidation of heme compounds in heart homogenates from rats supplemented with dietary antioxidants

Exercise, antioxidants, and HSP72: protection against myocardial ischemia/reperfusion

Endurance exercise is associated with protection against myocardial ischemia/reperfusion (I/R) injury and has been shown to increase heat shock protein 72 (HSP72). Dietary antioxidants have also been reported to decrease I/R-induced injury. Because exercise and antioxidants may provide cardioprotection via different mechanisms, combining these countermeasures could provide additive protection. Alternatively, because exercise-induced oxidant production may promote expression of HSP72, antioxidants could attenuate exercise-induced HSP72 expression and decrease exercise-related cardioprotection. These experiments examined the individual and combined effects of exercise and antioxidants on myocardial I/R injury (in vivo). Rats receiving a mixed antioxidant diet or control diet were assigned to exercise or sedentary groups and randomized to receive: (i) short I/R (myocardial stunning), (ii) long I/R (myocardial infarction), or (iii) sham surgery. Antioxidants significantly increased total antioxidant capacity and attenuated exercise-related HSP72 accumulation. Nonetheless, during short I/R, exercise-trained animals demonstrated improved left ventricular developed pressure (LVDP), independent of diet. Further, antioxidants alone resulted in improved LVDP. Finally, compared to control diet/sedentary animals, both exercise groups (control and antioxidant diets) and the antioxidant diet/sedentary group sustained smaller infarctions. We conclude that exercise and antioxidants can independently provide protection against myocardial contractile dysfunction and infarction, and the combination of these two strategies does not enhance or inhibit the protection observed with each individual countermeasure.

Increased antioxidant capacity does not attenuate muscle atrophy caused by unweighting

Previous studies have increased antioxidant capacity in skeletal muscle to attenuate oxidative stress and muscle atrophy during limb immobilization (Appell HJ, Duarte JAR, and Soares JMC. Int J Sports Med 18: 157-160, 1997; Kondo H, Miura M, Nakagaki I, Sasaki S, and Itokawa Y. Am J Physiol Endocrinol Metab 262: E583-E590, 1992). The purpose of this study was to determine the level of oxidative stress in muscle during hindlimb unweighting (HLU) and whether antioxidant supplementation can attenuate the atrophy and changes in contractile properties resulting from 14 days of unweighting. Muscle unweighting caused a 44% decrease in soleus (Sol) and a 30% decrease in gastrocnemius (GS) mass, a 7% decrease in body weight, and 28% decrease in tetanic force in the GS. Protein carbonyls increased by 44% in the Sol with HLU. Antioxidant supplementation did not attenuate the GS or Sol atrophy or the decrease in GS force generation during HLU. Sol and GS protein concentration was not different between groups. The GS was also subjected to three different oxidative challenges to determine whether the supplement increased the antioxidant capacity of the muscle. In all cases, muscles exhibited an increased antioxidant capacity. These data indicate that antioxidant supplementation was not an effective countermeasure to the atrophy associated with HLU.

Analysis of oxidized heme proteins and its application to multiple antioxidant protection

Oxidation in tissues and homogenates can be determined by the analysis of oxidized heme proteins. Oxidation of heme proteins can be measured by spectral changes and the deconvolution of the spectra of mixtures of heme proteins by a spreadsheet heme spectra analysis program (HSAP), incorporating the spectra of the individual pure heme proteins. HSAP also is used to analyze the spectra of mixtures of heme proteins found in the literature. HSAP is applied in measuring the protective effects in rats of multiple antioxidants suitable for use in humans for protection against diseases.

Gamma irradiation leads to two waves of apoptosis in distinct cell populations of the retina of newborn rats

Gamma radiation induces apoptosis in the proliferative zone (neuroblastic layer) of the developing rat retina. We asked whether sensitivity to apoptosis might be related to distinct phases of the cell cycle. Explants of newborn rat retina or newborn pups were gamma-irradiated and apoptosis was detected by chromatin condensation, DNA fragmentation in situ and DNA electrophoresis. After 6 hours, early appearing apoptotic bodies were located mainly towards the outer tier of the neuroblastic layer. In contrast, after 24 hours, late-appearing apoptotic cells were located towards the inner margin of the neuroblastic layer, a region associated with the S phase of the cell cycle. Labeling of a cohort of cells with the nucleotide analog bromo-deoxyuridine (BrdU) at the time of irradiation, showed that these cells die in the late wave of apoptosis. BrdU given 3 hours before fixation labeled a large number of late apoptotic cells, but no early apoptotic cells. After labeling of all cycling cells with BrdU, 40% of the early apoptotic profiles were unlabeled, and thus post-mitotic. The same schedules of cell death were identified after gamma irradiation in vivo. The results show that irradiation leads to two waves of apoptosis in distinct cell populations. An early wave comprises both post-mitotic cells and proliferating cells out of the S phase. The late wave comprises cells in S phase, which pass through this phase again to die. The antioxidant pyrrolidinedithiocarbamate prevented the early but not the late wave of apoptosis following irradiation, and blocked lipid peroxidation at 6 hours after the insult, suggesting that the two waves of apoptosis are indeed mediated by distinct mechanisms.

Antioxidant potentials of vitamin A and carotenoids and their relevance to heart disease

Despite being one of the first vitamins to be discovered, the full range of biological activities for vitamin A remains to be defined. Structurally similar to vitamin A, carotenoids are a group of nearly 600 compounds. Only about 50 of these have provitamin A activity. Recent evidence has shown vitamin A, carotenoids and provitamin A carotenoids can be effective antioxidants for inhibiting the development of heart disease. Vitamin A must be obtained from the diet: green and yellow vegetables, dairy products, fruits and organ meats are some of the richest sources. Within the body, vitamin A can be found as retinol, retinal and retinoic acid. Because all of these forms are toxic at high concentrations, they are bound to proteins in the extracellular fluids and inside cells. Vitamin A is stored primarily as long chain fatty esters and as provitamin carotenoids in the liver, kidney and adipose tissue. The antioxidant activity of vitamin A and carotenoids is conferred by the hydrophobic chain of polyene units that can quench singlet oxygen , neutralize thiyl radicals and combine with and stabilize peroxyl radicals. In general, the longer the polyene chain, the greater the peroxyl radical stabilizing ability. Because of their structures, vitamin A and carotenoids can autoxidize when O2 tension increases, and thus are most effective antioxidants at low oxygen tensions that are typical of physiological levels found in tissues. Overall, the epidemiological evidence suggests that vitamin A and carotenoids are important dietary factors for reducing the incidence of heart disease. Although there is considerable discrepancy in the results from studies in humans regarding this relationship, carefully controlled experimental studies continue to indicate that these compounds are effective for mitigating and defending against many forms of cardiovascular disease. More work, especially concerning the relevance of how tissue concentrations, rather than plasma levels, relate to the progression of tissue damage in heart disease is required. This review assembles information regarding the basic structure and metabolism of vitamin A and carotenoids as related to their antioxidant activities. Epidemiological, intervention trials and experimental evidence about the effectiveness of vitamin A and carotenoids for reducing cardiovascular disease is also reviewed.

Formation of fluorescent heme degradation products during the oxidation of hemoglobin by hydrogen peroxide

Hemoglobin and methemoglobin oxidized by hydrogen peroxide generate ferrylhemoglobin and oxoferrylhemoglobin, respectively. Two fluorescent compounds were found to be produced during the reaction of oxyhemoglobin, but not methemoglobin, with H2O2. These two compounds had excitation wavelengths of 321 nm and 460 nm, respectively, with emission wavelengths of 465 nm and 525 nm, respectively. The formation of the same fluorescent products during the reaction of H2O2 with ferroprotoporphyrin-IX and ferriprotoporphyrin-IX demonstrate that these compounds originate from the heme moiety. The release of heme iron during the formation of these fluorescent compounds indicates that they are associated with heme degradation. The time course for the formation of fluorescent products show that the extent of heme degradation is dependent on H2O2 concentration. The results of this investigation indicate that the heme moiety of Fe(II) hemoglobin undergoes degradation in presence of H2O2. The ability to detect this process by fluorescence provides a sensitive marker in order to asses hemoglobin and RBC oxidative stress under pathological conditions.