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Our understanding of the diversity of life on our planet and the possibility of finding or sustaining life elsewhere in the universe plays a central role in supporting human space settling and exploration. Astrobiology and its outcomes require a multidisciplinary and comprehensive approach, in which the microbial, geological, chemical, astronomical, and physical domains of research are interlinked. An example of the applications of astrobiology and space microbiology is the use of extremophiles for in-situ resource utilization through biomining and bioleaching. To better understand the multidisciplinary research landscape in this area, we have quantitatively reviewed the global scientific literature on astrobiology with a focus on biomining and bioleaching through bibliometric network analysis, investigating patterns and trends in its development over time. The network analysis of the keywords co-occurrence highlights different connecting and overlapping clusters, illustrating the multidisciplinary character of astrobiology. Temporal analyses show a recent focus on topics related to microbiology and geomicrobiology, emphasizing the role that these fields will play in future astrobiology research. In conclusion, astrobiology, biomining, and bioleaching research are timely responding to the identification of these techniques as tools for biotechnological applications, expected to play a crucial role in long-term human space exploration.

The antioxidant role of mitochondrial uncoupling protein 3 (UCP3) is controversial. This work aimed to investigate the effects of UCP3 on the heart of mice housed at thermoneutral temperature, an experimental condition that avoids the effects of thermoregulation on mitochondrial activity and redox homeostasis, preventing the alterations related to these processes from confusing the results caused by the lack of UCP3. WT and KO UCP3 mice were acclimatized at 30 °C for 4 weeks and hearts were used to evaluate metabolic capacity and redox state. Tissue and mitochondrial respiration, the activities of the mitochondrial complexes, and the protein expression of mitochondrial complexes markers furnished information on mitochondrial functionality. The levels of lipid and protein oxidative damage markers, the activity of antioxidant enzymes, the reactive oxygen species levels, and the susceptibility to in vitro Fe-ascorbate-induced oxidative stress furnished information on redox state. UCP3 ablation reduced tissue and mitochondrial respiratory capacities, not affecting the mitochondrial content. In KO UCP3 mice, the mitochondrial complexes activities were lower than in WT without changes in their content. These effects were accompanied by an increase in the level of oxidative stress markers, ROS content, and in vitro susceptibility to oxidative stress, notwithstanding that the activities of antioxidant enzymes were not affected by UCP3 ablation. Such modifications are also associated with enhanced activation/phosphorylation of EIF2α, a marker of integrated stress response and endoplasmic reticulum stress (GRP778 BIP). The lack of UCP3 makes the heart more prone to oxidative insult by reducing oxygen consumption and increasing ROS. Our results demonstrate that UCP3 helps the cell to preserve mitochondrial function by mitigating oxidative stress.

The growing environmental spreading of food synthetic dyes and bio-colors have the potential for altering organisms’ redox states. Here, three model species for aquatic pollution trials, Cucumis sativus seeds, Artemia salina cysts, and Danio rerio embryos, were short-term exposed to a fixed concentration of the artificial red E124, and two red bio-colors, cochineal E120, and vegan red (VEGR). In the animal models, we evaluated the total reactive oxygen species (ROS) and the susceptibility to in vitro oxidative stress, and in C. sativus, H2O2 production and antioxidant capacity. We also measured organismal performance indices (routine oxygen consumption in the animal models, dark oxygen consumption, and photosynthetic efficiency in C. sativus). In C. sativus, only E124 increased ROS and affected dark oxygen consumption and photosynthetic efficiency, while all dyes enhanced the antioxidant defenses. In the A. salina nauplii, all dyes increased ROS, while E120 and E124 reduced the susceptibility to oxidative stress. In D. rerio, treatments did not affect ROS content, and reduced oxidative stress susceptibility. Our data show that red food dyes affect the redox state of the developing organisms, in which ROS plays a significant role. We suggest a potentially toxic role for red food dyes with environmentally relevant consequences.

High-density lipoprotein (HDL) is an anti-atherosclerotic lipoprotein. Thanks to the activity of apolipoprotein ApoA1, the principal protein component of HDL, this last is responsible for converting cholesterol into ester form and transporting excessive cholesterol to the liver (“reverse cholesterol transport” RCT). When HDL undergoes oxidation, it becomes dysfunctional and proatherogenic. ApoA1 is a target of oxidation, and its alteration affects RCT and contributes to atherosclerosis development. Until now, the mechanism of HDL oxidation is not fully understood and only hydroxyl radicals seem to induce direct oxidation of protein and lipidic components of lipoproteins. Here we demonstrate that superoxide radical, widely produced in early atherosclerosis, directly oxidizes HDL, and as a consequence, ApoA1 undergoes structural alterations impairing its anti-atherosclerotic functions. Our results highlight in an in vitro system the potential mechanism by which O2·− triggers atherosclerotic pathogenesis in vivo. Our study gets the basis for therapeutic approaches focused on the management of superoxide generation in early atherosclerosis onset.

Benzodiazepines, psychotropics drugs used for treating sleep disorders, anxiety and epilepsy, represent a major class of emerging water pollutants. As occurs for other pharmaceutical residues, they are not efficiently degraded during sewage treatment and persist in effluent waters. Bioaccumulation is already reported in fish and small crustaceans, but the impact and consequences on other "non-target" aquatic species are still unclear and nowadays of great interest. In this study, we investigated the effects of a pharmaceutical preparation containing the benzodiazepine delorazepam on the embryogenesis of Xenopus laevis, amphibian model species, taxa at high risk of exposure to water contaminants. Environmental (1 μg/L) and two higher (5 and 10 μg/L) concentrations were tested on tadpoles up to stage 45/46. Results demonstrate that delorazepam interferes with embryo development and that the effects are prevalently dose-dependent. Delorazepam reduces vitality by decreasing heart rate and motility, induces marked cephalic and abdominal edema, as well as intestinal and retinal defects. At the molecular level, delorazepam increases ROS production, modifies the expression of some master developmental genes and pro-inflammatory cytokines. The resulting stress condition significantly affects embryos' development and threatens their survival. Similar effects should be expected as well in embryos belonging to other aquatic species that have not been yet considered targets for these pharmaceutical residues.

The abuse of artificial food dyes and the evidence that they harm human health recently prompted a significant effort to introduce vegan substitutes prepared from fruits and vegetables. Not much information, however, has been collected on their possible effects on aquatic and terrestrial ecosystems once released as waste in surface waters. For this purpose, we analyzed the effects of a vegan red (VEG) preparation (concentration 1.2 g/L) on three rapidly proliferating models for terrestrial and aquatic ecosystem contamination. In particular, in vitro cells cultures (exposure for 24 h), Artemia salina nauplii and Cucumis sativus seedlings (exposure 5 days). A comparison was made with the effects exerted by the two dyes that vegan red is intended to replace: an animal dye, cochineal E120 and an artificial dye E124. The analyses of conventional endpoints, indicative of cell proliferation, differentiation, and growth rate, demonstrate that the three dyes affect development and that the vegan substitute is as unsafe as the E124 and E120. Vegan red in fact impairs cell growth in in vitro cells, delays naupliar hatching and early growth in Artemia, and reduces shoot/root biomass in Cucumis. Marked hyperplasia and hypertrophy of mesophyll are also observed in Cucumis leaves. Substitution in food and beverages, therefore, should be carefully reconsidered to avoid unnecessary environmental contamination.

Following the discovery of superoxide dismutase enzymes [...]

This chapter describes the main processes by which mitochondria produce and manage reactive species by eliminating them or allowing their use as signaling molecules. It starts by describing mitochondria as the sites of oxidative phosphorylation, which allows the ATP synthesis. It then depicts how mitochondria cause the formation of oxidant species (radicals and other reactive oxygen species, ROS) involved in diseases and aging. It also describes the mitochondrial antioxidant system and the main factors involved in its regulation. Besides, it illustrates how the antioxidant system allows mitochondria not only to protect themselves from oxidative damage but also to detoxify the ROS produced in other cellular sites, which renders mitochondria a sink of ROS. The information reported in this chapter highlights the importance of the mitochondrial antioxidant system that can affect the processes regulated by ROS such as cell signaling and metabolic and neurodegenerative disease progression.

We investigated the effects of thyroid state on the mechanisms underlying rat heart mitochondrial capacity to remove H2O2 produced by an exogenous source. The removal rates were higher in the presence of respiratory substrates independently from thyroid state and were higher in hyperthyroid than in hypothyroid preparations. The thyroid state-linked changes in H2O2 removal rates, mirrored those in H2O2 release rates, showing that endogenous and exogenous H2O2 do not compete for the removing system. Mitochondrial content of coenzyme Q9 and Q10 was lower in hypothyroidism and higher in hyperthyroidism suggesting that the thyroid state-linked changes in the rates of H2O2 production are due to changes in the ubiquinone mitochondrial content. The rates of H2O2 removal in the presence of antioxidant enzyme inhibitors indicated that the contribution of each antioxidant is dependent on the thyroid state. This was supported by enzymatic activity measurements. Pharmacological inhibition also showed that the overall percentage contribution of the enzymatic processes, as well as that of non-enzymatic processes, is not affected by thyroid state. Cytochrome levels, inferred by light emission measurements, and western blot determination of cytochrome c, were lower in hypothyroid and higher in hyperthyroid preparations supporting the idea that the levels of reducing compounds were modified in opposite way by the changes in thyroid state. Further support was obtained showing that the whole antioxidant capacity, which provides an evaluation of capacity of the systems, different from cytochromes, assigned to H2O2 scavenging, was lower in hyperthyroid than in hypothyroid state.

Background: In recent years, the concern has been growing on increasing aquatic nitrite levels due to anthropogenic activities. Crustaceans and fish easily uptake nitrite via the chloride uptake system of gills. High nitrite body levels may interfere with nitric oxide (NO) production by nitric oxide synthase (NOS). The arginase, which catalyzes arginine conversion to ornithine and urea, is central to NO homeostasis. In vivo, changes in the arginase activity alter urea body levels and urea excretion and modulate NOS by altering arginine availability for NO synthesis. Excess arginase activity may uncouple NOS and induce oxidative stress. Methods: We tested muscle arginase activity and urea excretion in two fish species, zebrafish and convict cichlid, and the crustacean Yamato shrimp, under sub-lethal nitrite stress. Results: Exposure to nitrite (2 mM in the fish, 1 mM in the shrimp) significantly increased blood nitrite concentration in all species. Concomitantly, nitrite stress significantly increased arginase activity, urea excretion, and urea levels in the blood. In Yamato shrimp, urea levels also increased in muscle. Conclusion: Our results agree with the hypothesis that nitrite stress affects NO homeostasis by arginase stimulation and urea excretion. These parameters might function as markers of sub-lethal nitrite stress in freshwater fish and crustaceans.

Rapid fluctuations of the oxygen content of both natural and anthropogenic origin are relatively common in freshwater environments. Fish adaptation to these conditions implies tolerance of both low levels of oxygen availability and reoxygenation. Hypoxia tolerance in fish has been widely studied, but the involvement of mitochondria in the response of fish to rapid hypoxia/reoxygenation stress is less known. Zebrafish, a floodplain species, is likely facing significant changes in dissolved oxygen in its natural environment and displays a moderate ability to tolerate hypoxia. In the present study, we report the effects of an acute hypoxia/reoxygenation stress (H/R) protocol on mitochondrial functionality (respiration, complex activities, rate of H2O2 release) and redox state (level of HPs and protein oxidation) of muscle tissue. In parallel, the animal metabolic performance (routine metabolism, nitrogen excretion and swimming performance) was measured. Additionally, the recovery from H/R was tested 20 h after treatment. A significant stimulation by H/R of muscle mitochondrial respiration and H2O2 release was observed, which was only in part counteracted by stimulation of the antioxidant system, resulting in an increased level of lipid peroxides and protein carbonyls. In parallel, H/R increased the animal oxygen consumption and urea excretion rate and reduced routine activity. A significant strong reduction of endurance at 80% Ucrit was also observed. Most of the altered parameter did not recover 20 h after reoxygenation. These data indicate a significant alteration of zebrafish muscle mitochondrial state after acute H/R, associated with changes in tissue redox state and locomotor performance.

From their discovery in biological systems, reactive oxygen species (ROS) have been considered key players in tissue injury for their capacity to oxidize biological macromolecules [...]

The cholesterol metabolite 24(S)-hydroxycholesterol (24S-OHC) allows cholesterol excretion from the brain and was suggested to be critically involved in physiological as well as neurodegenerative processes. It induces on human neuronal cell cultures a dose dependent toxicity associated with increased reactive oxygen species production. Since glial cells play a key role in assisting neuronal function, here we investigated the effects of increased concentrations of 24S-OHC on a glial cell model (human glioblastoma U-87 MG cells). We determined the content of PGC-1α and TFAM, involved in the biogenesis of mitochondria, both mitochondrial complexes activity and protein amount, lipid and protein oxidative damage, cellular reactive oxygen species (ROS) release and both the activities and amount of the antioxidant enzymes glutathione peroxidase and catalase. Low concentration of 24S-OHC increased cellular content of PGC-1α and TFAM and the activities of mitochondrial complexes I and II, with no marked changes in their protein amount. Interestingly, 24S-OHC at lower concentrations reduced while at higher concentration increased lipid and protein oxidative damage. Conversely, the content of nitro-tyrosine increased only with the highest 24S-OHC concentration. Also, cell H2O2 release was reduced by lower and increased by higher 24S-OHC used concentrations. The cell activity of glutathione peroxidase was reduced by 24S-OHC at higher concentration while that of catalase was reduced by all the assayed concentrations. Further, a dose dependent decrease of both enzymes levels was observed. In conclusion, we demonstrated that 24S-OHC exerts different effects on U-87 MG cells depending on its level. At lower concentrations it stimulates cellular processes critical to maintain redox homeostasis, while at higher dose its effect on the glial cell here used resemble its action on neurons.

Mitochondria are both the main sites of production and the main target of reactive oxygen species (ROS). This can lead to mitochondrial dysfunction with harmful consequences for the cells and the whole organism, resulting in metabolic and neurodegenerative disorders such as type 2 diabetes, obesity, dementia, and aging. To protect themselves from ROS, mitochondria are equipped with an efficient antioxidant system, which includes low-molecular-mass molecules and enzymes able to scavenge ROS or repair the oxidative damage. In the mitochondrial membranes, a major role is played by the lipid-soluble antioxidant vitamin E, which reacts with the peroxyl radicals faster than the molecules of polyunsaturated fatty acids, and in doing so, protects membranes from excessive oxidative damage. In the present review, we summarize the available data concerning the capacity of vitamin E supplementation to protect mitochondria from oxidative damage in hyperthyroidism, a condition that leads to increased mitochondrial ROS production and oxidative damage. Vitamin E supplementation to hyperthyroid animals limits the thyroid hormone-induced increases in mitochondrial ROS and oxidative damage. Moreover, it prevents the reduction of the high functionality components of the mitochondrial population induced by hyperthyroidism, thus preserving cell function.

Unaccustomed and/or exhaustive exercise generates excessive free radicals and reactive oxygen and nitrogen species leading to muscle oxidative stress-related damage and impaired contractility. Conversely, a moderate level of free radicals induces the body’s adaptive responses. Thus, a low oxidant level in resting muscle is essential for normal force production, and the production of oxidants during each session of physical training increases the body’s antioxidant defenses. Mitochondria, NADPH oxidases and xanthine oxidases have been identified as sources of free radicals during muscle contraction, but the exact mechanisms underlying exercise-induced harmful or beneficial effects yet remain elusive. However, it is clear that redox signaling influences numerous transcriptional activators, which regulate the expression of genes involved in changes in muscle phenotype. The mitogen-activated protein kinase family is one of the main links between cellular oxidant levels and skeletal muscle adaptation. The family components phosphorylate and modulate the activities of hundreds of substrates, including transcription factors involved in cell response to oxidative stress elicited by exercise in skeletal muscle. To elucidate the complex role of ROS in exercise, here we reviewed the literature dealing on sources of ROS production and concerning the most important redox signaling pathways, including MAPKs that are involved in the responses to acute and chronic exercise in the muscle, particularly those involved in the induction of antioxidant enzymes.

The ability of aerobic organisms to cope with the attack of radicals and other reactive oxygen species improves by feeding on foods containing antioxidants. Microalgae contain many molecules showing in vitro antioxidant capacity, and their food consumption can protect cells from oxidative insults. We evaluated the capacity of dietary supplementation with 1% dried Chlorella sorokiniana strain 211/8k, an alga rich in glutathione, &alpha, tocopherol, and carotenoids, to counteract an oxidative attack in vivo. We used the hyperthyroid rat as a model of oxidative stress, in which the increase in metabolic capacities is associated with an increase in the release of mitochondrial reactive oxygen species (ROS) and the susceptibility to oxidative insult. Chlorella sorokiniana supplementation prevents the increases in oxidative stress markers and basal oxygen consumption in hyperthyroid rat livers. It also mitigates the thyroid hormone-induced increase in maximal aerobic capacities, the mitochondrial ROS release, and the susceptibility to oxidative stress. Finally, alga influences the thyroid hormone-induced changes in the factors involved in mitochondrial biogenesis peroxisomal proliferator-activated receptor-&gamma, coactivator (PGC1-1) and nuclear respiratory factor 2 (NRF-2). Our results suggest that Chlorella sorokiniana dietary supplementation has beneficial effects in counteracting oxidative stress and that it works primarily by preserving mitochondrial function. Thus, it can be useful in preventing dysfunctions in which mitochondrial oxidative damage and ROS production play a putative role.

We investigated the effects of thyroid state on the mechanisms underlying rat heart mitochondrial capacity to remove H

We investigated thyroid state effect on capacity of rat liver mitochondria to remove exogenously produced H2O2, determining their ability to decrease fluorescence generated by an H2O2 detector system. The rate of H2O2 removal by both non respiring and respiring mitochondria was increased by hyperthyroidism and decreased by hypothyroidism. However, the rate was higher in the presence of respiratory substrates, in particular pyruvate/malate, indicating a respiration-dependent process. Generally, the changes in H2O2 removal rates mirrored those in H2O2 release rates excluding the possibility that endogenous and exogenous H2O2 competed for the removing system. Pharmacological inhibition revealed thyroid state-linked differences in antioxidant enzyme contribution to H2O2 removal which were consistent with those in antioxidant system activities. The H2O2 removal was only in part due to enzymatic systems and that imputable to non-enzymatic processes was higher in hyperthyroid and lower in hypothyroid mitochondria. The levels of cytochrome c and the light emissions, due to luminol oxidation catalyzed by cytochrome/H2O2, exhibited similar changes with thyroid state supporting the idea that non-enzymatic scavenging was mainly due to hemoprotein action, which produces hydroxyl radicals. Further support was obtained showing that the whole antioxidant capacity, which provides an evaluation of capacity of the systems, different from cytochromes, assigned to H2O2 scavenging, was lower in hyperthyroid than in hypothyroid state. In conclusion, our results show that mitochondria from hyperthyroid liver have a high capacity for H2O2 removal, which, however, leading in great part to more reactive oxygen species, results harmful for such organelles.

We compared the capacity of rat liver and heart mitochondria to remove exogenously produced H2O2, determining their ability to decrease fluorescence generated by H2O2 detector system. In the absence of substrates, liver and heart mitochondria removed H2O2 at similar rates. Respiratory substrate addition increased removal rates, indicating a respiration-dependent process. Moreover, the rates were higher with pyruvate/malate than with succinate and in heart than in liver mitochondria. Generally, the changes in H2O2 removal rates mirrored those of H2O2 release rates excluding the possibility that endogenous and exogenous H2O2 competed for the removing system. This idea was supported by the observation that the heaviest of three liver mitochondrial fractions exhibited the highest rates of both H2O2 release and removal. Pharmacological inhibition showed tissue-linked differences in antioxidant enzyme contribution to H2O2 removal which were consistent with the differences in antioxidant system activities. The enzymatic processes accounted only in part for net H2O2 removal and the non-enzymatic ones participated to H2O2 scavenging to a degree that was higher for heart than for liver mitochondria. The idea that non-enzymatic scavenging was due in great part to hemoproteins action was consistent with observation that the concentration of cytochromes, in particular cytochrome c, was higher in heart mitochondria. Indirect support was also obtained by a technique of enhanced luminescence, utilizing the capacity of cytochrome c/H2O2 to catalyze the luminol oxidation, which showed that luminescence response to an oxidative challenge was higher in heart mitochondria.

Continuous exposure of homeothermic animals to low environmental temperatures elicits physiological adaptations necessary for animal survival, which are associated to higher generation of pro-oxidants in thermogenic tissues. It is not known whether intermittent cold exposure (cold training) is able to affect tissue responses to continuous cold exposure. Therefore, we investigated whether rat liver responses to continuous cold exposure of 2 days are modified by cold training (1h daily for 5 days per week for 3 consecutive weeks). Continuous cold increased liver oxidative metabolism by increasing tissue content of mitochondrial proteins and mitochondrial aerobic capacity. Cold training did not affect such parameters, but attenuated or prevented the changes elicited by continuous cold exposure. Two-day cold exposure increased lipid hydroperoxide and protein-bound carbonyl levels in homogenates and mitochondria, whereas cold training decreased such effects although it decreased only homogenate protein damage in control rats. The activities of the antioxidant enzymes GPX and GR and H2O2 production were increased by continuous cold exposure. Despite the increase in GPX and GR activities, livers from cold-exposed rats showed increased susceptibility to in vitro oxidative challenge. Such cold effects were decreased by cold training, which in control rats reduced only H2O2 production and susceptibility to stress. The changes of PGC-1, NRF-1, and NRF-2 expression levels were consistent with those induced by cold exposure and cold training in mitochondrial protein content and antioxidant enzyme activities. However, the mechanisms by which cold training attenuates the effects of the continuous cold exposure remain to be elucidated.

In both 3,5,3-triiodothyronine (T(3))-induced hyperthyroidism and cold-induced functional hyperthyroidism, the heart displays an increased susceptibility to oxidative challenge in vitro. Hearts from T(3)-treated rats also exhibit an increased susceptibility to ischaemia-reperfusion, a condition that raises free radical production. The present study was designed to establish whether cold-exposed rats exhibit an increased cardiac susceptibility to ischaemia-reperfusion which can be attenuated by vitamin E. The following four groups of animals were used: C, control rats (n = 8, temperature 24°C); C+VE, vitamin E-treated rats (n = 8, temperature 24°C); CE, cold-exposed rats (n = 8, temperature 4°C); and CE+VE, cold-exposed vitamin E-treated rats (n = 8, temperature 4°C). Langendorff preparations from these animals were submitted to 20 min ischaemia followed by 25 min reperfusion. At the end of the ischaemia-reperfusion protocol, homogenates and mitochondria were prepared and used for analytical procedures. With respect to control hearts, cold hearts showed a lower inotropic recovery and a higher oxidative stress, as inferred by higher levels of oxidized proteins and lipids and lower reduced glutathione levels. These changes were prevented when cold rats were treated with vitamin E. Evidence was also obtained that mitochondria are involved in the tissue derangement of cold hearts. Indeed, they display a faster production of reactive oxygen species, which causes mitochondrial oxidative damage and functional decline that parallel the tissue dysfunction. Moreover, vitamin E-linked improvement of tissue function was associated with a lower oxidative damage and a restored function of mitochondria. Finally, the mitochondrial population composition and Ca(2+)-induced swelling data indicate that the decline in mitochondrial function is in part due to a decrease in the amount of the highly functional heavy mitochondria linked to their higher susceptibility to oxidative damage and swelling. In conclusion, our work shows that vitamin E treatment attenuates harmful side-effects of the cardiac response to cold, such as oxidative damage and susceptibility to oxidants, thus preserving mitochondrial function and tissue recovery from ischaemia-reperfusion.

Specific tissue responses to thyroid hormone are mediated by the hormone binding to two subtypes of nuclear receptors, TRα and TRβ. We investigated the relationship between TRβ activation and liver oxidative metabolism in hypothyroid rats treated with equimolar doses of triiodothyronine (T3) and GC-1, a TRβ agonist. T3 treatment produces increases in O2 consumption and H2O2 production higher than those elicited by GC-1. The greater effects of T3 on oxidative processes are linked to the higher hormonal stimulation of the content of respiratory chain components including autoxidizable electron carriers as demonstrated by the measurement of activities of respiratory complexes and H2O2 generation in the presence of respiratory inhibitors. It is conceivable that these differential effects are dependent on the inability of GC-1 to stimulate TRα receptors that are likely involved in the expression of some components of the respiratory chain. The greater increases in reactive oxygen species production and susceptibility to oxidants exhibited by mitochondria from T3-treated rats are consistent with their higher lipid and protein oxidative damage and lower resistance to Ca2+ load. The T3 and GC-1 effects on the expression levels of nuclear respiratory factor-1 and -2 and peroxisome proliferator-activated receptor-γ coactivator-1α suggest the involvement of respiratory factors in the agonist-linked changes in mitochondrial respiratory capacities and H2O2 production.

We investigated whether reactive oxygen species (ROS) are involved in heart adaptive responses administering a vitamin E-enriched diet to trained rats. Using the homogenates and/or mitochondria from rat hearts we determined the aerobic capacity, tissue level of mitochondrial proteins, and expression of cytochrome c and factors (PGC-1, NRF-1, and NRF-2) involved in mitochondrial biogenesis. We also determined the oxidative damage, glutathione peroxidase (GPX) and reductase activities, glutathione content, mitochondrial ROS release rate, and susceptibility to in vitro oxidative challenge. Glutathione (GSH) content was not affected by both training and antioxidant supplementation. Conversely, antioxidant supplementation prevented metabolic adaptations to training, such as the increases in oxidative capacity, tissue content of mitochondrial proteins, and cytochrome c expression, attenuated some protective adaptations, such as the increase in antioxidant enzyme activities, and did not modify the decrease in ROS release by succinate supplemented mitochondria. Moreover, vitamin E prevented the training-linked increase in tissue capacity to oppose an oxidative attach. The antioxidant effects were associated with decreased levels of PGC-1, NRF-1, and NRF-2 expression. Our results support the idea that some heart adaptive responses to training depend on ROS produced during the exercise sessions and are mediated by the increase in PGC-1 expression which is involved in both the regulation of respiratory capacity and antioxidant protection. However, vitamin inability to prevent some adaptations suggests that other signaling pathways impinging on PGC-1 can modify the response to the antioxidant integration.

Thyroid hormones affect growth, development and metabolism of vertebrates, and are considered the main regulators of their homeostasis. On the other hand, elevated circulating levels of thyroid hormones are associated with modifications in the whole organism (weight loss and increased metabolism and temperature) and in several body regions. Indeed, tachycardia, atrial arrhythmias, heart failure, muscle weakness and wasting, bone mass loss, and hepatobiliary complications are commonly found in hyperthyroid animals and humans. Most of the thyroid hormone actions result from influences on transcription of T3-responsive genes, which are mediated through nuclear receptors. However, there is significant evidence for involvement of tissue oxidative stress in some dysfunctions shown in hyperthyroid state. Mitochondria have been thought to both play a major role in tissue oxidative damage and dysfunction and provide protection against excessive tissue dysfunction, through several mechanisms including increased expression of uncoupling proteins, proteolytic enzymes and transcriptional coactivator PGC-1, and stimulated opening of permeability transition pores. Actually, examination of the most recent data confirms that, in hyperthyroid state, mitochondria play a major role in tissue oxidative stress and rescue from excessive dysfunction. However, such data have also shown the substantial interplay between mitochondria and other sources of ROS and the role that, in pathological conditions, such sources play in generating oxidative stress and promoting survival mechanisms, such as autophagy and apoptosis. These observations suggest that cellular ROS producers could provide a significant contribution to processes that, in hyperthyroid state, oxidatively damage tissues and assure their survival.

We studied the effects of ten-day 1%Galdieria sulphurariadietary supplementation on oxidative damage and metabolic changes elicited by acute exercise (6-hour swimming) determining oxygen consumption, lipid hydroperoxides, protein bound carbonyls in rat tissue (liver, heart, and muscle) homogenates and mitochondria, tissue glutathione peroxidase and glutathione reductase activities, glutathione content, and rates of H2O2mitochondrial release. Exercise increased oxidative damage in tissues and mitochondria and decreased tissue content of reduced glutathione. Moreover, it increased State 4 and decreased State 3 respiration in tissues and mitochondria.G. sulphurariasupplementation reduced the above exercise-induced variations. Conversely, alga supplementation was not able to modify the exercise-induced increase in mitochondrial release rate of hydrogen peroxide and in liver and heart antioxidant enzyme activities. The alga capacity to reduce lipid oxidative damage without reducing mitochondrial H2O2release can be due to its high content of C-phycocyanin and glutathione, which are able to scavenge peroxyl radicals and contribute to phospholipid hydroperoxide metabolism, respectively. In conclusion,G. sulphurariaability to reduce exercise-linked oxidative damage and mitochondrial dysfunction makes it potentially useful even in other conditions leading to oxidative stress, including hyperthyroidism, chronic inflammation, and ischemia/reperfusion.

We studied vitamin E eff ects on metabolic changes and oxidative damage elicited by swim training in rat liver. Training reduced mitochondrial aerobic capacity but increased liver content of mitochondrial proteins, so that tissue aerobic capacity was not diff erent in trained and sedentary animals. Vitamin E supplementation prevented the training-induced mitochondrial changes. Training and vitamin E eff ects were consistent with the changes in tissue content of factors involved in mitochondrial biogenesis (peroxisomal proliferator-activated receptor- γ coactivator and nuclear respiratory factors 1 and 2). Tissue and mitochondrial oxidative damage was reduced by training decreasing the rate of mitochondrial reactive oxygen species (ROS) production and enhancing glutathione levels and glutathione peroxidase and glutathione reductase activities. The eff ects of vitamin E were diff erent when it was administered to sedentary or trained rats. In the former, vitamin E reduced liver preparations oxidative damage decreasing ROS production rate and increasing GSH content without any eff ect on antioxidant enzyme activities. In the latter, vitamin E did not modify ROS production and oxidative damage but decreased antioxidant levels. This decrease was likely responsible for the enhanced susceptibility to in vitro oxidative attack of the hepatic tissue from trained rats following vitamin E supplementation. These results indicate that vitamin E integration, which can be healthy for animals subjected to acute exercise, is not advisable during training because it prevents or reduces the favourable eff ects of the physical activity. They also support the idea that the stimulus for training-induced adaptive responses can derive from the increased ROS production that accompanies the single sessions of the training program.

In cold exposed rats, it is known that vitamin E induces an increase in the respiration of the whole mitochondrial population isolated from liver. To obtain information on the effects of cold exposure and vitamin E treatment on the dynamics of mitochondrial population, we determined characteristics of rat liver mitochondrial fractions, resolved at 1,000 (M(1)), 3,000 (M(3)), and 10,000 g (M(10)). We found that cold exposure increased the liver content of total mitochondrial proteins irrespective of vitamin E treatment. Conversely, protein distribution among the mitochondrial subpopulations was differentially affected by cold and antioxidant integration. In a cold environment, the M(1) fraction, characterized by the highest O(2) consumption and H(2)O(2) production rates, underwent a remarkable protein content reduction, which was attenuated by vitamin E. These changes were dependent on the opposite effects of the two treatments on mitochondrial oxidative damage and susceptibility to swelling. The proteins of the other fractions, in which the above effects were lower, underwent smaller (M(3)) or no change (M(10)) in the treatment groups. The cold also led to an increase in O(2) consumption of the M(1) fraction which was accentuated by vitamin E treatment. This phenomenon and the vitamin-induced recovery of the M(1) proteins supply an explanation of the previously reported increase in the respiration of the whole mitochondrial population induced by vitamin E in the liver from cold exposed rats.

Thyronamines T 0 AM and T 1 AM are naturally occurring decarboxylated thyroid hormone derivatives. Their in vivo administration induces effects opposite to those induced by thyroid hormone, including lowering of body temperature. Since the mitochondrial energy-transduction apparatus is known to be a potential target of thyroid hormone and its derivatives, we investigated the in vitro effects of T 0 AM and T 1 AM on the rates of O 2 consumption and H 2 O 2 release by rat liver mitochondria. Hypothyroid animals were used because of the low levels of endogenous thyronamines. We found that both compounds are able to reduce mitochondrial O 2 consumption and increase H 2 O 2 release. The observed changes could be explained by a partial block, operated by thyronamines, at a site located near the site of action of antimycin A. This hypothesis was confirmed by the observation that thyronamines reduced the activity of Complex III where the site of antimycin action is located. Because thyronamines exerted their effects at concentrations comparable to those found in hepatic tissue, it is conceivable that they can affect in vivo mitochondrial O 2 consumption and H 2 O 2 production acting as modulators of thyroid hormone action.