Variations in oxidative stress and antioxidant defense level during different phases of hibernation in common Asian toad, Duttaphrynus melanostictus

Preparation for oxidative stress in Chinese toads (Bufo gargarizans) living under natural conditions along an altitudinal gradient

Preparation for oxidative stress (POS) has been widely reported in animals under controlled laboratory conditions, but whether this phenomenon is visible in animals under natural conditions remains to be explored. Altitudinal gradients provide a good opportunity to address this question, since environmental conditions become more hostile with increasing altitude. Here, we investigated the levels of oxidative stress, oxidative damage, and antioxidant defenses in Chinese toads (Bufo gargarizans) along an altitudinal gradient (50 m, 1200 m, 2300 m, 3400 m above sea level). The results show that changing altitude led to a significantly lower ratio of oxidized to reduced glutathione in liver, with a higher value at 50 m. This ratio in muscle tissues did not differ significantly between altitudes of 50 m, 2300 m, and 3400 m. However, reduced glutathione content increased significantly along the altitude, with higher values in liver at 2300 m and higher values in skeletal muscle at 3400 m. Malondialdehyde (MDA) content in liver did not change significantly with increasing altitude. Brain and muscle tissues showed a higher MDA content at 50 m than the other three altitudes. The activities of superoxide dismutase, catalase, glutathione peroxidase, and glutathione-S-transferase, as well as total antioxidant capacity, also displayed tissue-specific upregulation in heart, skeletal muscle, and brain, but all of these antioxidant enzymes except for glutathione-S-transferase were significantly reduced in liver along the altitudinal gradient. In summary, environmental factors at higher altitude did not lead to higher levels of oxidative stress and oxidative damage in B. gargarizans, mainly due to stronger antioxidant defenses. This study corroborates the occurrence of POS in high-altitude toads living under field conditions and contributes to revealing the biochemical adaptations to extreme environments at higher altitude.

Application of artificial hibernation technology in acute brain injury

Controlling intracranial pressure, nerve cell regeneration, and microenvironment regulation are the key issues in reducing mortality and disability in acute brain injury. There is currently a lack of effective treatment methods. Hibernation has the characteristics of low temperature, low metabolism, and hibernation rhythm, as well as protective effects on the nervous, cardiovascular, and motor systems. Artificial hibernation technology is a new technology that can effectively treat acute brain injury by altering the body's metabolism, lowering the body's core temperature, and allowing the body to enter a state similar to hibernation. This review introduces artificial hibernation technology, including mild hypothermia treatment technology, central nervous system regulation technology, and artificial hibernation-inducer technology. Upon summarizing the relevant research on artificial hibernation technology in acute brain injury, the research results show that artificial hibernation technology has neuroprotective, anti-inflammatory, and oxidative stress-resistance effects, indicating that it has therapeutic significance in acute brain injury. Furthermore, artificial hibernation technology can alleviate the damage of ischemic stroke, traumatic brain injury, cerebral hemorrhage, cerebral infarction, and other diseases, providing new strategies for treating acute brain injury. However, artificial hibernation technology is currently in its infancy and has some complications, such as electrolyte imbalance and coagulation disorders, which limit its use. Further research is needed for its clinical application.

REVIEW: Evidence supporting the 'preparation for oxidative stress' (POS) strategy in animals in their natural environment

Hypometabolism is a common strategy employed by resilient species to withstand environmental stressors that would be life-threatening for other organisms. Under conditions such as hypoxia/anoxia, temperature and salinity stress, or seasonal changes (e.g. hibernation, estivation), stress-tolerant species down-regulate pathways to decrease energy expenditures until the return of less challenging conditions. However, it is with the return of these more favorable conditions and the reactivation of basal metabolic rates that a strong increase of reactive oxygen and nitrogen species (RONS) occurs, leading to oxidative stress. Over the last few decades, cases of species capable of enhancing antioxidant defenses during hypometabolic states have been reported across taxa and in response to a variety of stressors. Interpreted as an adaptive mechanism to counteract RONS formation during tissue hypometabolism and reactivation, this strategy was coined "Preparation for Oxidative Stress" (POS). Laboratory experiments have confirmed that over 100 species, spanning 9 animal phyla, apply this strategy to endure harsh environments. However, the challenge remains to confirm its occurrence in the natural environment and its wide applicability as a key survival element, through controlled experimentation in field and in natural conditions. Under such conditions, numerous confounding factors may complicate data interpretation, but this remains the only approach to provide an integrative look at the evolutionary aspects of ecophysiological adaptations. In this review, we provide an overview of representative cases where the POS strategy has been demonstrated among diverse species in natural environmental conditions, discussing the strengths and weaknesses of these results and conclusions.

Defining and Addressing Research Priorities in Cancer Cachexia through Transdisciplinary Collaboration

For many patients, the cancer continuum includes a syndrome known as cancer-associated cachexia (CAC), which encompasses the unintended loss of body weight and muscle mass, and is often associated with fat loss, decreased appetite, lower tolerance and poorer response to treatment, poor quality of life, and reduced survival. Unfortunately, there are no effective therapeutic interventions to completely reverse cancer cachexia and no FDA-approved pharmacologic agents; hence, new approaches are urgently needed. In May of 2022, researchers and clinicians from Moffitt Cancer Center held an inaugural retreat on CAC that aimed to review the state of the science, identify knowledge gaps and research priorities, and foster transdisciplinary collaborative research projects. This review summarizes research priorities that emerged from the retreat, examples of ongoing collaborations, and opportunities to move science forward. The highest priorities identified include the need to (1) evaluate patient-reported outcome (PRO) measures obtained in clinical practice and assess their use in improving CAC-related outcomes; (2) identify biomarkers (imaging, molecular, and/or behavioral) and novel analytic approaches to accurately predict the early onset of CAC and its progression; and (3) develop and test interventions (pharmacologic, nutritional, exercise-based, and through mathematical modeling) to prevent CAC progression and improve associated symptoms and outcomes.

Glutathione Depletion Disrupts Redox Homeostasis in an Anoxia-Tolerant Invertebrate

The upregulation of endogenous antioxidants is a widespread phenomenon in animals that tolerate hypoxia/anoxia for extended periods. The identity of the mobilized antioxidant is often context-dependent and differs among species, tissues, and stresses. Thus, the contribution of individual antioxidants to the adaptation to oxygen deprivation remains elusive. This study investigated the role of glutathione (GSH) in the control of redox homeostasis under the stress of anoxia and reoxygenation in Helix aspersa, an animal model of anoxia tolerance. To do so, the total GSH (tGSH) pool was depleted with l-buthionine-(S, R)-sulfoximine (BSO) before exposing snails to anoxia for 6 h. Then, the concentration of GSH, glutathione disulfide (GSSG), and oxidative stress markers (TBARS and protein carbonyl) and the activity of antioxidant enzymes (catalase, glutathione peroxidase, glutathione transferase, glutathione reductase, and glucose 6-phosphate dehydrogenase) were measured in foot muscle and hepatopancreas. BSO alone induced tGSH depletion by 59-75%, but no other changes happened in other variables, except for foot GSSG. Anoxia elicited a 110-114% increase in glutathione peroxidase in the foot; no other changes occurred during anoxia. However, GSH depletion before anoxia increased the GSSG/tGSH ratio by 84-90% in both tissues, which returned to baseline levels during reoxygenation. Our findings indicate that glutathione is required to withstand the oxidative challenge induced by hypoxia and reoxygenation in land snails.

The role of solar radiation and tidal emersion on oxidative stress and glutathione synthesis in mussels exposed to air

Preparation for oxidative stress (POS) is a widespread adaptive response to harsh environmental conditions, whose hallmark is the upregulation of antioxidants. In contrast to controlled laboratory settings, animals are exposed to multiple abiotic stressors under natural field conditions. Still, the interplay between different environmental factors in modulating redox metabolism in natural settings remains largely unexplored. Here, we aim to shed light on this topic by assessing changes in redox metabolism in the mussel Brachidontes solisianus naturally exposed to a tidal cycle. We compared the redox biochemical response of mussels under six different natural conditions in the field along two consecutive days. These conditions differ in terms of chronology, immersion/emersion, and solar radiation, but not in terms of temperature. Animals were collected after being exposed to air early morning (7:30), immersed during late morning and afternoon (8:45-15:30), and then exposed to air again late afternoon towards evening (17:45-21:25), in two days. Whole body homogenates were used to measure the activity of antioxidant (catalase, glutathione transferase and glutathione reductase) and metabolic (glucose 6-phosphate dehydrogenase, malate dehydrogenase, isocitrate dehydrogenase and pyruvate kinase) enzymes, reduced (GSH) and disulfide (GSSG) glutathione levels, and oxidative stress markers (protein carbonyl and thiobarbituric acid reactive substances). Air and water temperature remained stable between 22.5 °C and 26 °C during both days. Global solar radiation (GSR) greatly differed between days, with a cumulative GSR of 15,381 kJ/m² for day 1 and 5,489 kJ/m² for day 2, whose peaks were 2,240 kJ/m²/h at 14:00 on day 1 and 952 kJ/m²/h at 12:00 on day 2. Compared with animals underwater, emersion during early morning did not elicit any alteration in redox biomarkers in both days. Air exposure for 4 h in the late afternoon towards evening caused oxidative damage to proteins and lipids and elicited GSH synthesis in animals that had been previously exposed to high GSR during the day. In the following day, when GSR was much lower, exposure to air under the same conditions (duration, time, and temperature) had no effect on any redox biomarker. These findings suggest that air exposure under low-intensity solar radiation is not sufficient to trigger POS in B. solisianus in its natural habitat. Thus, natural UV radiation is possibly a key environmental factor that combined to air exposure induces the POS-response to the stressful event of tidal variation in this coastal species.

Metabolic and Redox Biomarkers in Skeletal Muscle Underlie Physiological Adaptations of Two Estivating Anuran Species in a South American Semi-arid Environment

The upregulation of endogenous antioxidants (i.e., preparation for oxidative stress, POS) is part of the biochemical responses underlying the adaptation of animals to adverse environments. Despite the phylogenetic diversity of animals in which POS has been described, most studies focus on animals under controlled laboratory conditions. To address this limitation, we have recently assessed the redox metabolism in the skeletal muscle of Proceratophrys cristiceps estivating under natural settings in the Caatinga. Here, we analyzed biochemical biomarkers in the muscle of another Caatinga species, Pleurodema diplolister, during the rainy (active) and dry (estivating frogs) seasons. We aimed to determine whether P. diplolister enhances its antioxidants during estivation under field conditions and to identify any effect of species on the biochemical responses of P. diplolister and P. cristiceps associated with estivation. To do so, we measured the activities of representative enzymes of intermediary metabolism and antioxidant systems, as well as glutathione and protein carbonyl levels, in the skeletal muscle of P. diplolister. Our findings revealed the suppression of oxidative metabolism and activation of antioxidant enzymes in estivating P. diplolister compared with active specimens. No changes in oxidative damage to proteins were observed and estivating P. diplolister had lower levels of disulfide glutathione (GSSG) and disulfide-to-total glutathione ratio (GSSG/tGSH) than those observed in active individuals. When data for P. diplolister and P. cristiceps were assembled and analyzed, significant effects of species were detected on the activities of metabolic enzymes (citrate synthase, isocitric dehydrogenase, malic enzyme, and creatine kinase) and antioxidant enzymes (catalase, glutathione peroxidase and glutathione transferase), as well as on GSSG/tGSH ratio. Such effects might underlie the physiological and behavioral differences between these two species that share the same microhabitat and survival strategy (i.e., to estivate) during the dry season. Despite some peculiarities, which reflect the physiological diversity of the mechanisms associated with estivation in the Brazilian Caatinga, both P. diplolister and P. cristiceps seem to balance the suppression of oxidative pathways, the maintenance of the capacity of oxygen-independent pathways, and the activation of endogenous antioxidants to preserve muscle function and be ready to resume activity whenever the unpredictable rainy period arrives.