Oxidative stress in rats with heatstroke-induced cerebral ischemia

Enniatin B1 induces damage to Leydig cells via inhibition of the Nrf2/HO-1 and JAK/STAT3 signaling pathways

Enniatin B1 (ENN B1) is a mycotoxin that can be found in various foods. However, whether ENN B1 is hazardous to the reproductive system is still elusive. Leydig cells are testosterone-generating cells that reside in the interstitial compartment between seminiferous tubules. Dysfunction of Leydig cells could result in male infertility. This study aimed to examine the toxicological effects of ENN B1 against TM3 Leydig cells. ENN B1 significantly inhibited cell viability in a dose-dependent manner. ENN B1 treatment also decreased the expression of functional genes in Leydig cells. Moreover, ENN B1 induced Leydig cells apoptosis and oxidative stress. Mechanistically, ENN B1 leads to the upregulation of Bax and downregulation of Bcl-2 in Leydig cells. In addition, ENN B1 inhibited the Nrf2/HO-1 pathway, which is critical for the induction of oxidative stress. Additionally, ENN B1 treatment repressed the JAK/STAT3 signaling pathway in Leydig cells. Rescue experiments showed that activation of STAT3 resulted in alleviation of ENN B1-induced damage in Leydig cells. Collectively, our study demonstrated that ENN B1 induced Leydig cell dysfunction via multiple mechanisms.

Graduate Student Literature Review: Mitochondrial response to heat stress and its implications on dairy cattle bioenergetics, metabolism, and production

The dairy industry depends upon the cow's successful lactation for economic profitability. Heat stress compromises the economic sustainability of the dairy industry by reducing milk production and increasing the risk of metabolic and pathogenic disease. Heat stress alters metabolic adaptations, such as nutrient mobilization and partitioning, that support the energetic demands of lactation. Metabolically inflexible cows are unable to enlist the necessary homeorhetic shifts that provide the needed nutrients and energy for milk synthesis, thereby impairing lactation performance. Mitochondria provide the energetic foundation that enable a myriad of metabolically demanding processes, such as lactation. Changes in an animal's energy requirements are met at the cellular level through alterations in mitochondrial density and bioenergetic capacity. Mitochondria also act as central stress modulators and coordinate tissues' energetic responses to stress by integrating endocrine signals, through mito-nuclear communication, into the cellular stress response. In vitro heat insults affect mitochondria through a compromise in mitochondrial integrity, which is linked to a decrease in mitochondrial function. However, limited evidence exists linking the in vivo metabolic effects of heat stress with parameters of mitochondrial behavior and function in lactating animals. This review summarizes the literature describing the cellular and subcellular effects of heat stress, with a focus on the effect of heat stress on mitochondrial bioenergetics and cellular dysfunction in livestock. Implications for lactation performance and metabolic health are also discussed.

Inflammation, coagulation, and cellular injury in heat-induced shock

BACKGROUND

The number of heatstroke victims hit record numbers in 2022 as global warming continues. In heat-induced injuries, circulatory shock is the most severe and deadly complication. This review aims to examine the mechanisms and potential approaches to heat-induced shock and the life-threatening complications of heatstroke.

METHODS

A computer-based online search was performed using the PubMed database and Web of Science database for published articles concerning heatstroke, shock, inflammation, coagulopathy, endothelial cell, cell death, and heat shock proteins.

RESULTS

Dehydration and heat-induced cardiomyopathy were reported as the major causes of heat-induced shock, although other heat-induced injuries are also involved in the pathogenesis of circulatory shock. In addition to dehydration, the blood volume decreases considerably due to the increased vascular permeability as a consequence of endothelial damage. Systemic inflammation is induced by factors that include elevated cytokine and chemokine levels, dysregulated coagulation/fibrinolytic responses, and the release of damage-associated molecular patterns (DAMPs) from necrotic cell death that cause distributive shock. The cytoprotective heat shock proteins can also facilitate circulatory disturbance under excess heat stress.

CONCLUSIONS

Multiple mechanisms are involved in the pathogenesis of heat-induced shock. In addition to dehydration, heat stress-induced cardiomyopathy due to the thermal damage of mitochondria, upregulated inflammation via damage-associated molecular patterns released from oncotic cells, unbalanced coagulation/fibrinolysis, and endothelial damage are the major factors that are related to circulatory shock.

Application of diffusion tensor imaging and functional alterations in evaluating brain alterations related to heatstroke in a rat model

OBJECTIVES

To assess the alterations in resting-state functions and neural structures in the brain of a heatstroke rat model and explore the underlying relationship.

METHODS

In total, 17 male Sprague Dawley rats were randomly divided into a control group (CTRL, n = 7) and a heatstroke group (HS, n = 10). All rats underwent 7.0 T magnetic resonance imaging (MRI). T2-weighted imaging, resting-state functional MRI (rs-fMRI), and diffusion tensor imaging (DTI) were obtained. On day 25, the surviving HS group rats (the follow-up group, FU, n = 7) were scanned again.

RESULTS

Heatstroke resulted in functional alterations and structural damage in the cerebellar molecular layer (CML), right perirhinal area (PA), pretectal region (PR), right dentate gyrus, and external cortex of the inferior colliculus (ECIC). Further functional changes occur in the right temporal associative cortex (TAC), left retrosplenial cortex (RC), and CML during convalescence. The fractional anisotropy values were significantly positively correlated with the amplitude of low-frequency fluctuation (ALFF) (HS-CML: r = 0.746, p = 0.034; right PR: r = 0.648, p = 0.049; FU-right PA: r = 0.817, p = 0.025)/regional homogeneity (ReHo) ratio (HS-CML: r = 0.833, p = 0.008; ECIC: r = 0.678, p = 0.045) and negatively correlated with the ALFF (FU-left RC: r = -0.818, p = 0.024; right TAC: r = -0.813, p = 0.049).

CONCLUSION

DTI and rs-fMRI allow meticulous monitoring of the progression of neurological and functional alterations in the brain after heatstroke.

Redox Implications of Extreme Task Performance: The Case in Driver Athletes

Redox homeostasis and redox-mediated signaling mechanisms are fundamental elements of human biology. Physiological levels of reactive oxygen species (ROS) and reactive nitrogen species (RNS) modulate a range of functional processes at the cellular, tissue, and systemic levels in healthy humans. Conversely, excess ROS or RNS activity can disrupt function, impairing the performance of daily activities. This article analyzes the impact of redox mechanisms on extreme task performance. Such activities (a) require complex motor skills, (b) are physically demanding, (c) are performed in an extreme environment, (d) require high-level executive function, and (e) pose an imminent risk of injury or death. The current analysis utilizes race car driving as a representative example. The physiological challenges of this extreme task include physical exertion, g loading, vibration, heat exposure, dehydration, noise, mental demands, and emotional factors. Each of these challenges stimulates ROS signaling, RNS signaling, or both, alters redox homeostasis, and exerts pro-oxidant effects at either the tissue or systemic levels. These redox mechanisms appear to promote physiological stress during race car driving and impair the performance of driver athletes.

Fermentation quality of herbal tea residue and its application in fattening cattle under heat stress

Background

Herbal tea residue (HTR) is generally considered to be the waste of herbal tea beverage production while it still retains rich nutrients and active substances. The main aim of the present study was to investigate the effect of fermentation technology on improving the quality of HTRs, and focus on the fermented HTR-induced alleviation of summer heat stress in fattening cattle.

Results

In this study, the waste HTR was fermented and then fed to a total of 45 fattening cattle that were divided into 3 groups (fermented HTR replaced 0, 15, 30% of the forage component of the diet), and the feeding experiment was lasted for 40 days. The physiological indexes, growth performance and fecal microbiota of fattening cattle were evaluated and results showed that fermented HTR could effectively reduce the respiratory rate and rectal temperature of fattening cattle under heat stress, increase the daily feed intake and daily gain, and improve the antioxidant content and blood immune index. In addition, we studied the fecal microbiota composition of 6 fattening cattle in control and 30% HTR substitution groups and found fermented HTR significantly changed the composition of fecal microbiota and increased microbial diversity, and correlation analysis suggested that the bacteria were closely related to fecal SCFA levels of fattening cattle under heat stress.

Conclusions

In this study, fermented HTR replaced 30% of the forage component of the diet that can change the intestine microorganisms, maintain health and alleviate the heat stress of fattening cattle.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12917-021-03061-y.

Heat stress aggravates oxidative stress, apoptosis, and endoplasmic reticulum stress in the cerebellum of male C57 mice

BACKGROUND

The current study was set to assess the effect of heat stress exposure on oxidative stress, apoptosis, and endoplasmic reticulum stress markers in the cerebellum of male mice.

METHODS

Fifty male C57BL/6 mice were assigned to five groups of (I) control, (II) heat stress (HS)7, (III) HS14, (IV) HS21, and (V) HS42 groups. Animals in the control group were not exposed to HS. Mice in the II-V groups were exposed to HS once a day over 7, 14, 21, and 42 days, respectively. Cerebellar reactive oxygen species (ROS) levels, expression of heat shock protein (HSP)70 and caspase 3 as well as endoplasmic reticulum stress-related proteins (PERK, p-PERK, CHOP, and Full-length ATF-6) expression were determined on the 7th, 14th, 21st, and 42nd days.

RESULTS

ROS levels and HSP70 expression increased following HS on the 14th, 21st, and 42nd days and the 7th, and 14th days with a peak level of expression on the 14th day following HS. HSP70 levels decreased afterward on the 21st and 42nd days compared with the control group. Besides, exposure to HS for 14, 21, and 42 days resulted in a significant increase in the CHOP and p-PERK levels in the cerebellum compared with the control group. Heat exposure also increased protein expression of cleaved caspase 3 and active ATF-6/Full-length ATF-6 on the 21st and 42nd days in the cerebellum compared with the control animals.

CONCLUSION

These findings indicated that chronic HS augmented oxidative stress, endoplasmic reticulum stress, and apoptosis pathways in the cerebellum of mice.

Choline attenuates heat stress-induced oxidative injury and apoptosis in bovine mammary epithelial cells by modulating PERK/Nrf-2 signaling pathway

Heat stress-induced decline in milk production and mammary glands dysfunction are economically important challenges facing the dairy industry, especially in summer. Choline is an organic water-soluble compound that can regulate a series of vital biological process, including cellular structural integrity and oxidative stress. However, it is unclear whether choline plays an anti-apoptosis and antioxidant effect in heat stress-induced mammary epithelial cells. This study aimed to determine the antioxidant effect of choline on heat stress-induced apoptosis and oxidative stress and its underlying molecular mechanism in bovine mammary epithelial cells (MAC-T cells). The MAC-T cells were divided into four treatment groups: control (37℃), choline (37℃), heat stress (HS, 42℃), and HS + choline. The results showed that heat stress up-regulated the HSP70 and HSP90 expression both in mRNA and protein, enhanced ROS accumulation, increased malondialdehyde (MDA) content, reduced the superoxide dismutase (SOD) and glutathione peroxidase (GSH-PX) activity, significantly increased the expression of caspase-3 and upregulated the ratio of Bax/Bcl-2 and ultimately lead to oxidative stress and apoptosis in MAC-T cells. However, choline pretreatment reversed the above phenomenon compared with the HS group. The HS + choline group inhibited heat stress-induced phosphorylation of PERK, nuclear translocation of Nrf-2 and the protein expression of GRP78. In addition, the ratio of Bax/Bcl-2 and the expression of caspase-3 were significantly reduced in HS + choline group, thereby reduced the HS-induced oxidative stress and apoptosis in MAC-T cells. In conclusion, choline attenuates heat stress-induced oxidative stress and apoptosis of MAC-T cells by modulating PERK/Nrf-2 pathway.

Attenuation of Heat-Induced Hypothalamic Ischemia, Inflammation, and Damage by Hyperbaric Oxygen in Rats

The present study was attempted to assess the mechanisms underlying the beneficial effects of hyperbaric oxygen (HBO₂; 100% O₂ at 253 kpa) in treating experimental heatstroke. Anesthetized rats were divided into five major groups: normothermic control (NC) rats treated with normobaric air (NBA; 21% O₂ at 101 kpa; NC + NBA); NC rats treated with HBO₂ (NC + HBO₂); heatstroke (HS) rats treated with NBA (HS + NBA); HS rats treated with hyperbaric air (HBA; 21% at 253 kpa; HS + HBA); and HS rats treated with HBO₂ (HS + HBO₂). HS groups were exposed to heat (43°C) for exactly 68 min and then allowed to recover at 26°C. HBA or HBO₂ was adopted 68 or 78 min after the start of heat exposure. Survival time values for (HS + NBA) rats, (HS + HBA) rats at 68 min, (HS + HBA) rats at 78 min, (HS + HBO₂) rats at 68 min, and (HS + HBO₂) rats at 78 min were found to be 90 ± 3, 133 ± 12, 109 ± 9, 240 ± 18, and 170 ± 15 min, respectively. Resuscitation with HBA or HBO₂ at 68 min was superior to those treated at 78 min in prolonging the survival time values. All (HS + NBA) animals displayed hyperthermia, hypotension, and increased cellular levels of ischemia, oxidative stress and damage markers, pro-inflammatory cytokines, and an indicator of polymorphonuclear cell accumulation in their hypothalamus as compared to those of NCs. Heat-induced hyperthermia was not affected by HBA or HBO₂ treatment. However, heat-induced hypotension and hypothalamic ischemia, oxidative stress, neuronal damage, and inflammation were all significantly reduced by HBA or HBO₂ therapy. Compared to those of HBA therapy, HBO₂ therapy had a significantly higher beneficial effect in treating heatstroke. Our results suggested that HBO₂ improved heatstroke outcomes, in part, by restoring normal hypothalamic function. Delaying the onset of HBO₂ therapy reduced the therapeutic efficiency.

Oxidative stress in response to heat stress in wild caught Namaqua rock mice, Micaelamys namaquensis

Modelling of anthropogenic induced climate suggests more frequent and severe heatwaves in the future, which are likely to result in the mass die-off of several species of organisms. Oxidative stress induced by severe heat stress has previously been associated with a reduction in animal cognitive performance, depressed reproduction and lower life expectancy. Little is known about the non-lethal consequences of species should they survive extreme heat exposure. We investigated the oxidative stress experienced by the Namaqua rock mouse, a nocturnal rodent, using two experimental heat stress protocols, a 6 hour acute heat stress protocol without access to water and a 3-day heatwave simulation with ad libitum water. Oxidative stress was determined in the liver, kidney and brain using malondialdehyde (MDA) and protein carbonyl (PC) as markers of oxidative damage, and superoxide dismutase (SOD) and total antioxidant capacity (TAC) as markers of antioxidant defence. Incubator heat stress (heat and dehydration stress) was brought about by increasing the body temperatures of animals to 39-40.8 °C for 6 hours. Following incubator heat stress, significantly higher levels of MDA were observed in the liver. Dehydration did not explain the variation in oxidative markers and is likely a combined effect of thermal and dehydration stress. Individual body mass was significantly negatively correlated to kidney SOD and lipid peroxidation. A heatwave was simulated using a temperature cycle that would naturally occur during a heatwave in the species' local habitat, with a maximal ambient temperature of 38 °C. Following the simulated heatwave, SOD activity of the kidney demonstrated significantly lowered activity suggesting oxidative stress. Current heat waves in this species have the potential of causing oxidative stress. Heat and dehydration stress following exacerbated temperatures are likely to incur significant oxidative stress in multiple tissues demonstrating the importance of water availability to allow for rehydration to prevent oxidative stress.

Physcion Protects Rats Against Cerebral Ischemia-Reperfusion Injury via Inhibition of TLR4/NF-kB Signaling Pathway

Background

Ischemic stroke (IS) is characterized by the rapid loss of brain function due to ischemia. Physcion has been found to have a neuroprotective effect against cerebral ischemia-reperfusion (I/R) injury. However, the mechanism by which physcion regulates cerebral I/R injury remains largely unknown.

Methods

An oxygen-glucose deprivation/reperfusion (OGD/R) model in SH-SY5Y cells and a rat cerebral ischemia-reperfusion (I/R) model were established, respectively. CCK-8 and flow cytometry assays were used to detect the viability and apoptosis of SH-SY5Y cells. Moreover, enzyme-linked immunosorbent assay (ELISA) was used to measure the levels of SOD, MDA, GSH-Px, TNF-α, IL-1β, IL-6 and IL-10 in the supernatant of SH-SY5Y cells. Meanwhile, Western blot assay was used to detect the expressions of TLR4, p-p65 and p-IκB in SH-SY5Y cells and I/R rats.

Results

In this study, physcion treatment significantly rescued OGD/R-induced neuronal injury. In addition, physcion decreased inflammatory response in SH-SY5Y cells after OGD/R insult, as shown by the decreased levels of the pro-inflammatory factors TNF-α, IL-1β, IL-6 and IL-10. Moreover, physcion attenuated the oxidative stress in OGD/R-treated SY-SY5Y cells, as evidenced by the increased SOD and GSH levels and the decreased ROS and MDA levels. Meanwhile, physcion significantly reduced cerebral infarction, attenuated neuronal injury and apoptosis in I/R rats. Furthermore, physcion markedly decreased the expressions of TLR4, p-NF-κB p65 and p-IκB in the brain tissues of rats subjected to I/R and in SH-SY5Y cells exposed to OGD/R.

Conclusion

In conclusion, our study indicated that physcion protected neuron cells against I/R injury in vitro and in vivo by inhibition of the TLR4/NF-kB pathway; thus, physcion might serve as a promising therapeutic candidate for IS.

Protective effects of the phytogenic feed additive "comfort" on growth performance via modulation of hypothalamic feeding- and drinking-related neuropeptides in cyclic heat-stressed broilers

Identification of alternatives to antibiotics in livestock and poultry is necessary. Fueled by consumer preferences, phytogenic feed additives are increasingly used in the food system; however, their mode of action is not well defined. Here, we used broiler chickens, in which appetite and feeding behavior regulation are controlled by complex mechanisms, to determine the effect of the phytogenic feed additive "comfort" (PFA-C) as well as its underlying molecular mechanisms on growth performance in heat-stressed broiler chickens. Heat stress significantly increased birds' core body temperature, water intake, and the hypothalamic expression of heat shock protein (HSP) 70, whereas it decreased feed intake, BW, and woody breast incidence. Phytogenic feed additive "comfort" supplementation downregulated the hypothalamic expression of HSP70, reduced core body temperature, increased feed and water intake, and improved BW in HS broilers. At molecular levels, the effect of PFA-C on growth performance seemed to be mediated by modulation of hypothalamic expression of melanocortin receptor 2, arginine vasopressin, aquaporin 2, and sodium and potassium-transporting ATPase subunit beta 1 polypeptides. In summary, PFA-C supplementation ameliorates heat stress productivity losses via a potential cytoprotective effect, reduction of hypothalamic intracellular stress, and modulation of hypothalamic feeding- and drinking-related polypeptide expression.

Heat and dehydration induced oxidative damage and antioxidant defenses following incubator heat stress and a simulated heat wave in wild caught four-striped field mice Rhabdomys dilectus

Heat waves are known for their disastrous mass die-off effects due to dehydration and cell damage, but little is known about the non-lethal consequences of surviving severe heat exposure. Severe heat exposure can cause oxidative stress which can have negative consequences on animal cognition, reproduction and life expectancy. We investigated the current oxidative stress experienced by a mesic mouse species, the four striped field mouse, Rhabdomys dilectus through a heat wave simulation with ad lib water and a more severe temperature exposure with minimal water. Wild four striped field mice were caught between 2017 and 2019. We predicted that wild four striped field mice in the heat wave simulation would show less susceptibility to oxidative stress as compared to a more severe heat stress which is likely to occur in the future. Oxidative stress was determined in the liver, kidney and brain using malondialdehyde (MDA) and protein carbonyl (PC) as markers for oxidative damage, and superoxide dismutase (SOD) and total antioxidant capacity (TAC) as markers of antioxidant defense. Incubator heat stress was brought about by increasing the body temperatures of animals to 39-40.8°C for 6 hours. A heat wave (one hot day, followed by a 3-day heatwave) was simulated by using temperature cycle that wild four striped field mice would experience in their local habitat (determined through weather station data using temperature and humidity), with maximal ambient temperature of 39°C. The liver and kidney demonstrated no changes in the simulated heat wave, but the liver had significantly higher SOD activity and the kidney had significantly higher lipid peroxidation in the incubator experiment. Dehydration significantly contributed to the increase of these markers, as is evident from the decrease in body mass after the experiment. The brain only showed significantly higher lipid peroxidation following the simulated heat wave with no significant changes following the incubator experiment. The significant increase in lipid peroxidation was not correlated to body mass after the experiment. The magnitude and duration of heat stress, in conjunction with dehydration, played a critical role in the oxidative stress experienced by each tissue, with the results demonstrating the importance of measuring multiple tissues to determine the physiological state of an animal. Current heat waves in this species have the potential of causing oxidative stress in the brain with future heat waves to possibly stress the kidney and liver depending on the hydration state of animals.

Heat stress induced oxidative damage and perturbation in BDNF/ERK1/2/CREB axis in hippocampus impairs spatial memory

Heat exposure is an environmental stress that causes diverse heat related pathophysiological changes under extreme conditions. The brain including hippocampal region which is associated with learning and memory is significantly affected by heat stress resulting in memory impairment. However, the effect of heat on the spatial memory remains unclear. The present study aimed to explore the effect of heat stress on hippocampus and spatial memory in rats. Rat model of acute heat stress was used which was divided into two groups, viz. moderate heat stress (MHS) and severe heat stress (SHS). Redox parameters evaluation revealed that MHS and SHS exposure markedly increase the production of malondialdehyde (MDA), oxidised glutathione (GSSG), reactive oxidative species (ROS), protein oxidation level and decrease the reduced glutathione (GSH) levels in the hippocampal tissue. Furthermore, Cresyl Violet (CV) staining of hippocampal region showed higher pyknosis in rats exposed to SHS. Pronounced increase of caspase3 expression and Fluoro Jade-C (FJ-C) positive cells were observed in SHS resulting in neuronal injury and apoptosis in CA3 region of hippocampus culminating in spatial memory deficit. Our data also suggest that heat stress induces phospho Extracellular signal-regulated kinases (pERK)1/2 activation induced by Brain-derived neurotrophic factor (BDNF) leading to further activation of phospho cAMP-response element binding protein (pCREB) under MHS. However, during SHS, BDNF and pCREB expression were completely dysregulated and not sufficient to rescue cognitive decline in rats. In conclusion, SHS induces pathological alterations that include oxidative damage and apoptosis of hippocampal neurons, disturbing BDNF/ERK1/2/CREB axis that may affect spatial memory.

Transcriptomic and biochemical effects of pycnogenol in ameliorating heat stress-related oxidative alterations in rats

BACKGROUND

Heat stress is a condition that is due to extreme heat exposure. It occurs when the body cannot keep its temperature healthy in response to a hot climate and associated with oxidative stress. Testicular hyperthermia can induce apoptosis of sperm cells, affect sperm production and decrease sperm concentration, leading to sperm disorder, for this reason, we examined the protective impact of pycnogenol that it has a wide range of biological benefits, including antioxidant, anti-inflammatory and anti-cancer activities against the oxidative alterations that happen in testicular and brain tissues due to heat stress in rats.

STUDY DESIGN

Forty-eight Wistar male rats, approximately around 6 weeks age were allocated randomly into four groups (12 in each) of control, HS (subjected to heat stress and supplemented orally with 50 mg of pycnogenol/kg b. w./day dissolved in saline for 21 days), and pycnogenol (rats supplemented orally with 50 mg of pycnogenol/kg b. w./day dissolved in saline for 21 days).

RESULTS

Data revealed a promising role of pycnogenol as an antioxidant, natural product to successfully reverse the heat-induced oxidative alterations in testicular and brain tissues of rats through significant upregulation of superoxide dismutase-2, catalase, reduced glutathione, and anti-apoptotic gene, while downregulating pro-apoptotic, and heat shock protein70. Pycnogenol treatment also reversed the reproductive hormone level and spermatogenesis to their normal values.

CONCLUSION

Pycnogenol as a natural protective supplement could recover these heat stress-induced oxidative changes in testes and hypothalamus.

Myricetin against myocardial injury in rat heat stroke model

BACKGROUND

Heat stroke-induced mortality is rising across the globe. So, the design of prophylactic and/or therapeutic modalities for heat stroke is pressing need. The common plant derived flavonoid exhibits strong anti-oxidant and anti-inflammatory activities; however, its effects in heat stroke remain unknown. The study aimed to investigate the cardioprotective effects of myricetin on heat stroke induced acute myocardial injury as well as lethality in rats and to explore the underlying mechanisms.

METHODS

Myocardial injury was induced by subjecting the anesthetized rats to a high ambient temperature of 43 °C for 70 min. An intragastrical dose of myricetin (5-25 mg/kg body weight) was given to rats once per day for one week prior to the start of heat stress. Heat shock protein 72 antibodies was given intraperitoneally to rats 24 h before the start of heat stress. Myocardial injury severity was estimated by determing myocardial damage scores, myocardial injury indicators, myocardial oxidative and inflammatory factors. Western blot analysis was used for cardiac expression of heat shock protein (HSP)72.

RESULTS

Significant (P < 0.05) up-regulation of HSP-72 after chronic administration of myricetin coincided with significant (P < 0.05) reduction in hyperthermia, hypotension, cardiac inflammatory and oxidative damage and lethality. Inhibition of HSP-72 showed a significant (P < 0.05) reversal in the cardiaprotection as well as survival.

CONCLUSIONS

Our results indicate that myricetin diminishes myocardial injury as well as lethality in heat stroke by up-regulating HSP-72 and show promise as a novel prevention therapeutic for heat stroke.

Protective Effects of Hyperbaric Oxygen Therapy on Brain Injury by Regulating the Phosphorylation of Drp1 Through ROS/PKC Pathway in Heatstroke Rats

This study aimed to elucidate the neurotherapeutic effect of hyperbaric oxygen (HBO) on brain injury and the potential role of dynamin-related protein 1 (Drp1) and its regulatory pathway in heatstroke (HS) rats. In in vivo experiments, rats were exposed to HBO after the onset of HS, or the same pressure but normal air as a control. The results indicated that HBO decreased the mortality and thermoregulatory dysfunction and prolonged the survival time of HS rats. Neurological dysfunction induced by HS was attenuated by HBO through assessment of modified neurological severity score and Morris water maze. HBO also alleviated histopathologic changes and oxidative injury (malondialdehyde and 8-hydroxyguanine), increased activities of superoxide dismutase (SOD) and glutathione/oxidized glutathione and ameliorated apoptotic parameters (caspase-3/6 activities and the number of apoptotic cells) of the hippocampus, hypothalamus and brain stem in rats compared to the HS group. Phosphorylation of Drp^Ser616 was increased by HS but decreased by HBO in the brains of rats determined by Western blot and immunohistochemical staining. In experiments in vitro, rat hippocampal neurons were used as a heat stress (HS) cellular model to examine the effects of HBO. As the results, HBO attenuated HS-induced cytotoxicity, oxidative injury (malondialdehyde), reactive oxygen species (ROS) generation, decreasing SOD activity and apoptosis. Drp1 inhibitor (Mdivi-1) treatment produced the same effects and had a trend to decrease oxidative injury. But the difference is not statistically significant. HBO and Mdivi-1decreased the phosphorylation of Drp^Ser616 induced by HS and HBO decreased the phosphorylation of protein kinase C (PKC) induced by HS. Moreover, both PKC inhibitor and ROS scavenger inhibited HS-induced p-Drp^Ser616. In conclusion, HBO may alleviate the brain injury caused by HS by decreasing ROS/PKC-regulated p-Drp^Ser616.

Hypothalamic impairment underlying heat intolerance in pregnant mice

Pregnant women are vulnerable to heat stroke reactions caused by high environmental temperatures. Heat intolerance is associated with hypothalamic impairment. Here, we aim to ascertain whether pregnancy causes heat intolerance by inducing hypothalamic impairment in mice. In the heated groups, mice were exposed to whole body heating (WBH; 41.2 °C for 1 h) in an environment-controlled chamber. Then, they were returned to normal room temperature (26 °C) immediately after WBH. In the hyperbaric oxygen therapy (HBO₂T) groups, mice were exposed to 100% O₂ at 2.0 atm absolute (ATA) for 4 h immediately post-WBH. Mice that survived after 4 h of WBH were considered survivors. Here, we show that when pregnant mice underwent non-HBO₂T (21% O₂ at 1.0 ATA for 4 h) after WBH, the survival rate was 4/20, and the core temperature at 4 h post-WBH was 31.2 ± 0.2 °C. Both the survival rate and core temperature of HBO₂T pregnant mice (10/10 and 35.2 ± 0.3 °C, respectively) were significantly greater than those in non-HBO₂T pregnant mice. Compared to non-HBO₂T heated mice, the HBO₂T heated mice exhibited lower neurological severity scores, reduced hypothalamic neuronal damage, fewer apoptotic cells, reduced multiorgan damage scores, and lower hypothalamic levels of proinflammatory cytokines and nitrogen and oxygen radical species. Compared to non-HBO₂T heated mice, the HBO₂T-treated heated mice had significantly higher hypothalamic-pituitary-adrenal axis activity (evidenced by higher serum levels of both adrenocorticotrophic hormone and corticosterone). In conclusion, pregnancy induces heat intolerance by inducing hypothalamic impairment in mice. Additionally, HBO₂T protects against heat intolerance in pregnant mice by preserving hypothalamic integrity.

Structural changes in liver under conditions of experimental hemorrhagic stroke

The article describes the results of histological and morphometric studies of liver in Balb/c mice with hemorrhagic stroke. The hemorrhagic stroke was modeled in the animals by administering autoblood in volume of 0.1 ml in the right hemisphere, and within 5, 10 and 30 days an analysis of structural changes in the liver was performed. Progressive changes were established in terms of 5-10 days of the experiment. This consisted of changes in the sinusoidal capillaries and notable changes in the central veins of the liver lobuli. Herein, acute dilatation and erythrocytal stasis were most pronounced around the lumen of the central veins, while hepatocytes with signs of necrosis (severe cytoplasmic swelling, vacuolar dystrophic changes) were detected in the sinusoid capillaries. The results of the morphometry indicated an increase in the area of the nucleus and the cells caused by intracellular swelling, domination of euchromatin and decrease of total density of chromatin in nuclei. Partial regression of the diameter of sinusoidal capillaries and the area of hepatocytes were detected on the 30th day of the experiment. The changes in the sinusoidal capillaries of the liver lobules are assessed as secondary to stroke, as well as to changes in organ microcirculation, and are associated with dystrophic changes in the hepatocytes.

Betaine protects against heat exposure-induced oxidative stress and apoptosis in bovine mammary epithelial cells via regulation of ROS production

Heat stress is one of the wide varieties of factors which cause oxidative stress in vivo; elevated temperature can lead to oxidative stress of dairy cows that affects milk production. The aim of this study was to determine the capacity of the betaine to act as an antioxidant against oxidative stress induced by heat exposure and apoptosis in mammary epithelial cells (mammary alveolar cells, MAC-T). The MAC-T were divided into four treatment groups: control (37 °C), heat stress (HS, 42 °C), betaine (37 °C), and HS + betaine. MAC-T under heat stress (HS) showed increased ROS accumulation, malondialdehyde (MDA) content, superoxide dismutase (SOD) concentration, and catalase (CAT) activity. During heat stress, betaine decreased the mRNA expression level of HSP70 and HSP27 in MAC-T. Bax/Bcl-2 ratio and caspase-3, the markers of apoptosis, were also elevated in MAC-T under heat stress. The markers of oxidative stress Nrf-2/HO-1 genes were also elevated in MAC-T under heat stress. Pretreatment of betaine reversed the heat-induced depletion in total antioxidant status, ROS accumulation, and SOD and CAT contents in MAC-T. Bax/Bcl-2 ratio and Nrf-2/HO-1 expression of heat-exposed MAC-T were also reduced with betaine supplementation. In conclusion, betaine alleviated oxidative stress and apoptosis of MAC-T by inhibiting ROS accumulation.

Application of spatially modulated near-infrared structured light to study changes in optical properties of mouse brain tissue during heatstress

Heat stress (HS) is a medical emergency defined by abnormally elevated body temperature that causes biochemical, physiological, and hematological changes. The goal of the present research was to detect variations in optical properties (absorption, reduced scattering, and refractive index coefficients) of mouse brain tissue during HS by using near-infrared (NIR) spatial light modulation. NIR spatial patterns with different spatial phases were used to differentiate the effects of tissue scattering from those of absorption. Decoupling optical scattering from absorption enabled the quantification of a tissue's chemical constituents (related to light absorption) and structural properties (related to light scattering). Technically, structured light patterns at low and high spatial frequencies of six wavelengths ranging between 690 and 970 nm were projected onto the mouse scalp surface while diffuse reflected light was recorded by a CCD camera positioned perpendicular to the mouse scalp. Concurrently to pattern projection, brain temperature was measured with a thermal camera positioned slightly off angle from the mouse head while core body temperature was monitored by thermocouple probe. Data analysis demonstrated variations from baseline measurements in a battery of intrinsic brain properties following HS.

Non-Exertional Heatstroke: A Case Report and Review of the Literature

BACKGROUND Heatstroke (HS) is a life-threatening condition characterized by an elevation of the core body temperature above 40°C, central nervous system dysfunction, and possible multi-organ failure. HS can trigger systemic inflammation, disseminated intravascular coagulation (DIC), rhabdomyolysis, cerebral edema and seizures, pulmonary edema, heart dysfunctions, and renal and hepatic failure. CASE REPORT We report the case of a 41-year-old Romanian woman with a history of alcoholism who developed HS after arriving by bus in Verona, Italy in June 2016. The patient developed consecutive multi-organ dysfunction, including liver and renal failure, rhabdomyolysis, DIC, and arrhythmia. The patient was successfully treated with conservative measures. After 17 days, she recovered completely. CONCLUSIONS The exact mechanism of HS-related multiple organ dysfunction is not completely understood and its pathogenesis is complex. It involves inflammation, oxidative stress, endoplasmic reticulum (ER) stress, and mitochondrial dysfunction. Development of a model in which chronic alcohol abuse alters oxidative, inflammatory, and ER stress response could also be a conceivable solution to the positive prognosis of severe HS patients, in which liver failure has a prominent role.

In vivo immunoprotective role of Indigofera tinctoria and Scoparia dulcis aqueous extracts against chronic noise stress induced immune abnormalities in Wistar albino rats

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Chronic noise stress was suppressed both innate and adaptive immune response of wistar albino rats.

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Noise stress also caused DNA damage in the liver and spleen tissues.

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Aqueous extracts of I. tinctoria and S. dulcis prevent the immune abnormalities caused by noise stress.

Indigofera tinctoria and Scoparia dulcis are being widely used in Indian folk medicine for the treatment of various disorders. Environmental noise pollution is thought to be an important factor for many health problems and it causes immune abnormalities. In the present study immune-regulating potential of I. tinctoria and S. dulcis aqueous extracts on innate and adaptive immune system of wistar albino rats was evaluated during normal and chronic noise induced stress conditions. The results demonstrated that both I. tinctoria and S. dulcis aqueous extracts (200 mg/kg b.w) showed immunostimulant effect on both innate and adaptive immune response of wistar albino rat compared to control group under normal condition. The noise stress (100 dB for 1 h, 20 days) induced animals showed suppressive effects on immune response by decreasing macrophage phagocytosis, antibody secretion by spleen cells, humoral immune response, proliferation of lymphocytes, cytotoxicity, TNF α expression, granzyme B and perforin expression in splenic NK cells. Similarly, noise stress also caused DNA damage in tissues. However, the suppressed effects induced by noise stress on rat immune system were significantly prevented by oral administration of both I. tinctoria and S. dulcis aqueous extracts. Considering all these results it is suggested that the selected medicinal plant’s aqueous extracts have the potential to prevent the effects of noise stress induced rat immune system and explore a strong immunostimulant potential applicable to clinical practices.

Oxidative stress and glutamate excitotoxicity contribute to apoptosis in cerebral venous sinus thrombosis

Cerebral venous sinus thrombosis (CVST) is an important cause of stroke in young especially in the developing countries. There is paucity of studies on the mechanism of cell damage in CVST. Aim of this study is to explore the role of glutamate excitotoxicity, oxidative stress; and apoptosis in an experimental model of CVST. Cerebral venous sinus thrombosis was induced by putting a strip of filter paper soaked in 40% ferric chloride on superior sagittal sinus. Brain was removed on day 1, 2 and 7 and oxidative stress markers (Mn-SOD, Catalase, GPx, LPO and GSH) were estimated spectrophotometrically. Glutamate level and its receptors NR1, NR2A and NR2B were estimated by real time polymerase chain reaction. The markers of apoptosis were evaluated by expression of cleaved Caspase-3 and specrtin break down product (SBDP) by western blot. In CVST, the evidence of oxidative stress (reduced activity of Mn-SOD, Catalase, GPx, GSH and increased level of LPO) was noted. Glutamate level was elevated and its receptors NR1, NR2A and NR2B were reduced. Increased expression of cleaved Caspase-3 on day 2 and 7 and SBDP on day 1 and 2 were noted. Oxidative stress, glutamate excitotoxicity and apoptosis seem to have important role in CVST induced cell damage.

Cerebral Vascular Control and Metabolism in Heat Stress

This review provides an in-depth update on the impact of heat stress on cerebrovascular functioning. The regulation of cerebral temperature, blood flow, and metabolism are discussed. We further provide an overview of vascular permeability, the neurocognitive changes, and the key clinical implications and pathologies known to confound cerebral functioning during hyperthermia. A reduction in cerebral blood flow (CBF), derived primarily from a respiratory-induced alkalosis, underscores the cerebrovascular changes to hyperthermia. Arterial pressures may also become compromised because of reduced peripheral resistance secondary to skin vasodilatation. Therefore, when hyperthermia is combined with conditions that increase cardiovascular strain, for example, orthostasis or dehydration, the inability to preserve cerebral perfusion pressure further reduces CBF. A reduced cerebral perfusion pressure is in turn the primary mechanism for impaired tolerance to orthostatic challenges. Any reduction in CBF attenuates the brain's convective heat loss, while the hyperthermic-induced increase in metabolic rate increases the cerebral heat gain. This paradoxical uncoupling of CBF to metabolism increases brain temperature, and potentiates a condition whereby cerebral oxygenation may be compromised. With levels of experimentally viable passive hyperthermia (up to 39.5-40.0 °C core temperature), the associated reduction in CBF (∼ 30%) and increase in cerebral metabolic demand (∼ 10%) is likely compensated by increases in cerebral oxygen extraction. However, severe increases in whole-body and brain temperature may increase blood-brain barrier permeability, potentially leading to cerebral vasogenic edema. The cerebrovascular challenges associated with hyperthermia are of paramount importance for populations with compromised thermoregulatory control--for example, spinal cord injury, elderly, and those with preexisting cardiovascular diseases.

Reactive oxygen species, heat stress and oxidative-induced mitochondrial damage. A review

In recent years there has been enormous interest in researching oxidative stress. Reactive oxygen species (ROS) are derived from the metabolism of oxygen as by-products of cell respiration, and are continuously produced in all aerobic organisms. Oxidative stress occurs as a consequence of an imbalance between ROS production and the available antioxidant defence against them. Nowadays, a variety of diseases and degenerative processes such as cancer, Alzheimer's and autoimmune diseases are mediated by oxidative stress. Heat stress was suggested to be an environmental factor responsible for stimulating ROS production because of similarities in responses observed following heat stress compared with that occurring following exposure to oxidative stress. This manuscript describes the main mitochondrial sources of ROS and the antioxidant defences involved to prevent oxidative damage in all the mitochondrial compartments. It also deals with discussions concerning the cytotoxic effect of heat stress, mitochondrial heat-induced alterations, as well as heat shock protein (HSP) expression as a defence mechanism.

Nutritional strategies to alleviate heat stress in pigs

Pigs are comparatively less heat tolerant than other species of production animals, which poses challenges for stock productivity and management during seasonal heat waves that occur in summer. The issues surrounding heat and pig production are predicted to increase, based on the actions of climate change increasing the intensity, frequency and duration of heat waves. Furthermore, future growth areas of pig production are going to be in tropical regions such as South-east Asia and Latin America. Efforts by the pig to dissipate excess body heat come at a cost to health and divert energy away from growth, compromising efficient pig production. Management of heat stress requires multiple strategies, and recent research is improving the understanding of the application of nutritional strategies to ameliorate the effects of heat stress. In particular the use of feed additives is an important, flexible and economical method to alleviate heat stress and the intensive nature of pig production lends itself to the use of additives. Some specific examples include antioxidants, betaine and chromium, which have been proved effective or being tested in mitigating some certain impacts of heat stress in pigs. The aim of this review is to summarise recent advances in the nutritional management of heat stress in pigs.

Combination treatment with Gua Sha and Blood-letting causes attenuation of systemic inflammation, activated coagulation, tissue ischemia and injury during heatstroke in rats

OBJECTIVE

Gua Sha and Blood-letting at the acupoints were Chinese traditional therapies for heatstroke. The purpose of present study was to assess the therapeutic effect of Gua Sha on the DU Meridian and Bladder Meridian combined with Blood-letting acupoints at Shixuan (EX-UE 11) and Weizhong (BL 40) on heatstroke.

METHODS

Anesthetized rats, immediately after the onset of heatstroke, were divided into four major groups: Gua Sha group, Blood-letting group, Gua Sha combined with Blood-letting group and model group. They were exposed to ambient temperature of 43 °C to induce heatstroke. Another group of rats were exposed to room temperature (26 °C) and used as normal control group. Their survival times were measured. In addition, their physiological and biochemical parameters were continuously monitored.

RESULTS

When rats underwent heatstroke, their survival time values were found to be 21-25 min. Treatment of Gua Sha combined with Bloodletting greatly improved the survival time (230±22 min) during heatstroke. All heatstoke animals displayed and activated coagulation evidenced by increased prothrombin time (PT), activated partial thromboplastin time (aPTT), D-dimer, and decreased platelet count, protein C. Furthermore, the animals displayed systemic inflammation evidenced by increased the serum levels of cytokines interleukin-1ß (IL-1ß), tumor necrosis factor α (TNF-α) and malondialdehyde (MDA). Biochemical markers evidenced by cellular ischemia and injury/dysfunction included increased plasma levels of blood urea nitrogen (BUN), creatinine, serum glutamic oxaloacetic transaminase (SGOT), serum glutamic pyruvic transaminase (SGPT), and alkaline phosphatase (ALP) were all elevated during heatstroke. Core temperatures (Tco) were also increased during heatstroke. In contrast, the values of mean arterial pressure were signifificantly lower during heatstroke. These heatstroke reactions were all signifificantly suppressed by treatment of Gua Sha and Blood-letting, especially the combination therapy.

CONCLUSION

Gua Sha combined with Blood-letting after heatstroke may improve survival by ameliorating systemic inflflammation, hypercoagulable state, and tissue ischemia and injury in multiple organs.

Honokiol Protected against Heatstroke-Induced Oxidative Stress and Inflammation in Diabetic Rats

We aimed at investigating the effect of honokiol on heatstroke in an experimental rat model. Sprogue-Dawley rats were divided into 3 groups: normothermic diabetic rats treated with vehicle solution (NTDR+V), heatstroke-diabetic rats treated with vehicle (HSDR+V), and heatstroke rats treated with konokiol (0.5-5 mg/ml/kg) (HSDR+H). Sixty minutes before the start of heat stress, honokiol or vehicle solution was administered. (HSDR+H) significantly (a) attenuated hyperthermia, hypotension and hypothalamic ischemia, hypoxia, and neuronal apoptosis; (b) reduced the plasma index of the toxic oxidizing radicals; (c) diminished the indices of hepatic and renal dysfunction; (d) attenuated the plasma systemic inflammatory response molecules; (e) promoted plasma levels of an anti-inflammatory cytokine; (f) reduced the index of infiltration of polymorphonuclear neutrophils in the serum; and (g) promoted the survival time fourfold compared with the (HSDR+V) group. In conclusion, honokiol protected against the outcome of heatstroke by reducing inflammation and oxidative stress-mediated multiple organ dysfunction in diabetic rats.

Attenuating heatstroke-induced acute lung inflammation, edema, and injury in rats by exercise preconditioning

BACKGROUND

This study aimed to ascertain whether heat-induced acute lung edema, inflammation, and ischemic damage can be affected by heat shock protein 70 (HSP-70)-mediated exercise preconditioning (EP) in rats.

METHODS

Wistar rats were assigned to one of the following four groups: the non-EP + nonheated group, the non-EP + heated group, the EP + heated group, and the EP + HSP-70 antibodies + heated group. EP groups of animals were subjected to a protocol of running on a treadmill for 30 minutes at 20 m/min, 30 minutes at 30 m/min, and 60 minutes at 30 m/min after 1, 2, and 3 weeks of training, respectively. Heated group of animals, under general anesthesia, were put in a folded heating pad of 43°C for 68 minutes. Then, the heated animals were allowed to recover at room temperature. HSP-70 antibodies were injected intravenously 24 hours before heat exposure.

RESULTS

As compared with the non heated + non-EP rats, the heated + non-EP rats had significantly higher scores of alveolar edema, neutrophil infiltration, and hemorrhage, acute pleurisy, and increased bronchoalveolar fluid levels of proinflammatory cytokines and ischemic and oxidative damage markers. EP, in addition to inducing overexpression of HSP-70 in lung tissues, significantly attenuated heat-induced acute pulmonary edema, inflammation, and ischemic and oxidative damage in the lungs. HSP-70 antibodies, in addition to reducing HSP-70 expression in the lungs, significantly attenuated the beneficial effects of EP in reducing acute lung inflammation and injury.

CONCLUSION

EP may attenuate the occurrence of pulmonary edema, inflammation, as well as ischemic and oxidative damage caused by heatstroke by up-regulating HSP-70 in the lungs.

Tetramethylpyrazine decreases hypothalamic glutamate, hydroxyl radicals and prostaglandin-E2 and has antipyretic effects

OBJECTIVE

We studied the effects of tetramethylpyrazine (TMP) on the fever, increased plasma levels of tumor necrosis factor-α (TNF-α) and increased hypothalamic levels of glutamate, hydroxyl radicals and prostaglandin-E2 (PGE2) induced by lipopolysaccharide (LPS).

MATERIALS AND METHODS

The microdialysis probes were stereotaxically and chronically implanted into the hypothalamus of rabbit brain for determining extracellular levels of glutamate, hydroxyl radials, and PGE2. In addition, both the body core temperature and plasma levels of TNF-α were measured.

RESULTS

All the body core temperature, plasma levels of TNF-α, and hypothalamic levels of glutamate, hydroxyl radicals, and PGE2 were up-graded by an intravenous dose of LPS (2 μg/kg). Pretreatment with intravenous TMP (10-40 mg/kg) or intracerebroventricular TMP (130 μg in 20 μl per animal) 1 h before LPS administration significantly attenuated the LPS-induced fever as well as the increased hypothalamic levels of glutamate, hydroxyl radicals, and PGE2. LPS-induced fever could also be attenuated by intravenous or intracerebroventricular TMP 1 h after LPS injection.

CONCLUSION

TMP preconditioning may cause its antipyretic action by reducing plasma levels of TNF-α as well as hypothalamic levels of glutamate, hydroxyl radicals, and PGE2 in rabbits.

Attenuating systemic inflammatory markers in simulated high-altitude exposure by heat shock protein 70-mediated hypobaric hypoxia preconditioning in rats

BACKGROUND/PURPOSE

The primary goal of this study was to test whether high-altitude exposure (HAE: 0.9% O(2) at 0.47 ATA for 24 hours) was capable of increasing the systemic inflammatory markers as well as the toxic organ injury indicators in rats, with a secondary goal to test whether preinduction of heat shock protein (HSP) 70 by hypobaric hypoxia preconditioning (HHP: 18.3% O(2) at 0.66 ATA for 5 h/day on 5 days consecutively for 2 weeks) attenuated the proposed increased serum levels of both the systemic inflammatory markers and the toxic organ injury indicators.

METHODS

Rats were assigned to: (1) non-HHP (21% O(2) at 1.0 ATA)+non-HAE (21% O(2) at 1.0 ATA) group; (2) non-HHP+HAE group; (3) HHP+non-HAE group; (4) HHP+HAE group; and (5) HHP+HSP70 antibodies (Ab)+HAE group. For the HSP70Ab group, a neutralizing HSP70Ab was injected intravenously at 24 hours prior to HAE. All the physiological and biochemical parameters were obtained at the end of HAE or the equivalent time period of non-HAE. Blood samples were obtained for determination of both the systemic inflammatory markers (e.g., serum tumor necrosis factor-α, interleukin-1β, E-selectin, intercellular adhesion molecule-1, and liver myeloperoxidase activity) and the toxic organ injury indicators (e.g., nitric oxide metabolites, 2,3-dihydroxybenzoic acid, and lactate dehydrogenase).

RESULTS

HHP, in addition to inducing overexpression of tissue HSP70, significantly attenuated the HAE-induced hypotension, bradycardia, hypoxia, acidosis, and increased tissue levels of both the systemic inflammatory markers and the toxic organ injury indicators. The beneficial effects of HHP in inducing tissue overexpression of HSP70 as well as in preventing the HAE-induced increased levels of the systemic inflammatory markers and the toxic organ injury indicators could be significantly reduced by HSP70Ab preconditioning.

CONCLUSION

These results suggest that HHP may downgrade both the systemic inflammatory markers and the toxic organ injury indicators in HAE by upregulating tissue HSP70.

Hypobaric hypoxia preconditioning attenuates experimental heatstroke syndromes via preinduction of heat shock protein 70

INTRODUCTION

Heatstroke has been defined as a form of hyperthermia associated with a systemic inflammatory response that leads to multiple organ dysfunction syndrome (MODS). It has also been documented that heat shock protein 70 (HSP70) preconditioning is able to induce thermotolerance. Here, the authors further investigated whether hypobaric hypoxia preconditioning (HHP) improved the MODS in heatstroke by up-regulation of HSP70.

METHODS

Anesthetized rats were randomly assigned to (a) non-HHP + nonheated group, (b) non-HHP + heated group, (c) HHP + heated group and (d) HHP + HSP70 antibodies (Abs) + heated groups. All heated groups were exposed to heat stress (43°C, 70 minutes) to induce heatstroke. For HHP, animals were exposed to 0.66 atmosphere absolute (18.3% O2) for 5 hours daily for consecutive 5 days per week for 2 weeks before the start of heat exposure.

RESULTS

HHP significantly (i) attenuated hypotension, (ii) reduced plasma index of the toxic oxidizing radicals and the organ injury indicator, (iii) attenuated plasma systemic inflammatory response molecules, (iv) reduced an index of infiltration of polymorphonuclear neutrophils in the lung like myeloper-oxidase activity, (v) promoted plasma levels of an anti-inflammatory cytokine, interleukin-10, (vi) promoted the survival time to fourfold compared with non-HHP group and (vii) promoted the overexpression of HSP70 in different organs (eg, the lung) during heatstroke. The beneficial effects of HHP could be significantly attenuated by HSP70 Ab preconditioning.

CONCLUSION

Our results show that HHP protects rats from heat-induced MODS via up-regulating HSP70. Thus, HHP could be a novel strategy for the prevention of heatstroke animals or patients before heat exposure.

Attenuating brain inflammation, ischemia, and oxidative damage by hyperbaric oxygen in diabetic rats after heat stroke

BACKGROUND/PURPOSE

Alternating hypothalamic-pituitary-adrenal axis mechanisms would lead to multiple organs dysfunction or failure. Herein, we attempt to assess whether hypothalamic inflammation and ischemic and oxidative damage that occurred during heatstroke (HS) can be affected by hyperbaric oxygen (HBO₂) therapy in streptozotocin-induced diabetic rats.

METHODS

In this study, anesthetized diabetic rats, immediately after the onset of HS, were divided into two major groups and given the normobaric air (21% O₂ at 1.0 atmospheres absolute) or HBO₂ (100% O₂ at 2.0 atmospheres absolute). HS was induced by exposing the animals to heat stress (43°C). Another group of anesthetized diabetic rats was kept at normothermic state and used as controls.

RESULTS

The survival time values for the HBO2-treated HS-diabetic rats increased form the control values of 78-82 minutes to new values of 184-208 minutes. HBO₂ therapy caused a reduction of HS-induced cellular ischemia (e.g., increased cellular levels of glutamate and lactate/pyruvate ratio), hypoxia (e.g., decreased cellular levels of PO₂), inflammation (e.g., increased cellular levels of interleukin-1β, tumor necrosis factor-alpha, interleukin-6, and myeloperoxidase), and oxidative damage (e.g., increased values of nitric oxide, 2,3-dihydroxybenzoic acid, glycerol, and neuronal damage score) in the hypothalamus of the diabetic rats.

CONCLUSION

Our results suggest that, in diabetic animals, HBO2 therapy may improve outcomes of HS in part by reducing heat-induced activated inflammation and ischemic and oxidative damage in the hypothalamus and other brain regions.

Melatonin reduces acute lung inflammation, edema, and hemorrhage in heatstroke rats

AIM

To assess the therapeutic effect of melatonin on heat-induced acute lung inflammation and injury in rats.

METHODS

Heatstroke was induced by exposing anesthetized rats to heat stress (36 °C, 100 min). Rats were treated with vehicle or melatonin (0.2, 1, 5 mg/kg) by intravenous administration 100 min after the initiatioin of heatstroke and were allowed to recover at room temperature (26 °C). The acute lung injury was quantified by morphological examination and by determination of the volume of pleural exudates, the number of polymorphonuclear (PMN) cells, and the myeloperoxidase (MPO) activity. The concentrations of tumor necrosis factor, interleukin (IL)-1β, IL-6, and IL-10 in bronchoalveolar fluid (BALF) were measured by ELISA. Nitric oxide (NO) level was determined by Griess method. The levels of glutamate and lactate-to-pyruvate ratio were analyzed by CMA600 microdialysis analyzer. The concentrations of hydroxyl radicals were measured by a procedure based on the hydroxylation of sodium salicylates leading to the production of 2,3-dihydroxybenzoic acid (DHBA).

RESULTS

Melatonin (1 and 5 mg/kg) significantly (i) prolonged the survival time of heartstroke rats (117 and 186 min vs 59 min); (ii) attenuated heatstroke-induced hyperthermia and hypotension; (iii) attenuated acute lung injury, including edema, neutrophil infiltration, and hemorrhage scores; (iv) down-regulated exudate volume, BALF PMN cell number, and MPO activity; (v) decreased the BALF levels of lung inflammation response cytokines like TNF-alpha, interleukin (IL)-1β, and IL-6 but further increased the level of an anti-inflammatory cytokine IL-10; (vi) reduced BALF levels of glutamate, lactate-to-pyruvate ratio, NO, 2,3-DHBA, and lactate dehydrogenase.

CONCLUSION

Melatonin may improve the outcome of heatstroke in rats by attenuating acute lung inflammation and injury.

Flutamide, an androgen receptor antagonist, improves heatstroke outcomes in mice

Flutamide has been used as an adjunct for decreasing the mortality from subsequent sepsis. Heatstroke resembles septic shock in many aspects. We hypothesized that heat-induced multiple organ dysfunction syndromes and lethality could be reduced by flutamide therapy. In heatstroke groups, mice were exposed to whole body heating (41.2°C, for 1h) in a controlled-environment chamber. The heat-stressed mice were returned to normal room temperature (24°C) after whole body heating. Mice still alive on day 4 of WBH treatment were considered survivors. Physiological and biochemical parameters were monitored for 2.5h post-WBH. Heatstroke mice were subcutaneously treated with flutamide (12.5-50mg/kg body weight in 0.05 ml) or vehicle solution (0.05 ml/kg body weight) once daily for 3 consecutive days post-WBH. We evaluated the effect of flutamide in heatstroke mice and showed that flutamide significantly (i) attenuated hypothermia, (ii) reduced the number of apoptotic cells in the hypothalamus, the spleen, the liver, and the kidney, (iii) attenuated the plasma index of toxic oxidizing radicals (e.g., nitric oxide metabolites and hydroxyl radicals), (iv) diminished the plasma index of the organ injury index (e.g., lactate dehydrogenase), (v) attenuated plasma systemic inflammation response molecules (e.g., tumor necrosis factor-α and interleukin-6), (vi) reduced the index of infiltration of polymorphonuclear neutrophils in the lung (e.g., myeloperoxidase activity), and (vii) allowed three times the fractional survival compared with vehicle. Thus, flutamide appears to be a novel agent for the treatment of mice with heatstroke or patients in the early stage of heatstroke.

Nanowired drug delivery for neuroprotection in central nervous system injuries: modulation by environmental temperature, intoxication of nanoparticles, and comorbidity factors

Recent developments in nanomedicine resulted in targeted drug delivery of active compounds into the central nervous system (CNS) either through encapsulated material or attached to nanowires. Nanodrug delivery by any means is supposed to enhance neuroprotection due to rapid accumulation of drugs within the target area and a slow metabolism of the compound. These two factors enhance neuroprotection than the conventions drug delivery. However, this is still uncertain whether nanodrug delivery could alter the pharmacokinetics of compounds making it more effective or just longer exposure of the compound for extended period of time is primarily responsible for enhanced effects of the drugs. Our laboratory is engaged in understanding of the nanodrug delivery using TiO(2) nanowires in CNS injuries models, for example, spinal cord injury (SCI), hyperthermia and/or intoxication of nanoparticles with or without other comorbidity factors, that is, diabetes or hypertension in rat models. Our observations suggest that nanowired drug delivery is effective under normal situation of SCI and hyperthermia as evidenced by significant reduction in the blood-brain barrier (BBB) breakdown, brain edema formation, cognitive disturbances, neuronal damages, and brain pathologies. However, when the pathophysiology of these CNS injuries is aggravated by nanoparticles intoxication or comorbidity factors, adjustment in dosage of nanodrug delivery is needed. This indicates that further research in nanomedicine is needed to explore suitable strategies in achieving greater neuroprotection in CNS injury in combination with nanoparticles intoxication or other comorbidity factors for better clinical practices.

Hypobaric hypoxia preconditioning attenuates acute lung injury during high-altitude exposure in rats via up-regulating heat-shock protein 70

HHP (hypobaric hypoxia preconditioning) induces the overexpression of HSP70 (heat-shock protein 70), as well as tolerance to cerebral ischaemia. In the present study, we hypothesized that HHP would protect against HAE (high-altitude exposure)-induced acute lung injury and oedema via promoting the expression of HSP70 in lungs prior to the onset of HAE. At 2 weeks after the start of HHP, animals were exposed to a simulated HAE of 6000 m in a hypobaric chamber for 24 h. Immediately after being returned to ambient pressure, the non-HHP animals had higher scores of alveolar oedema, neutrophil infiltration and haemorrhage, acute pleurisy (e.g. increased exudate volume, increased numbers of polymorphonuclear cells and increased lung myeloperoxidase activity), increased pro-inflammatory cytokines [e.g. TNF-α (tumour necrosis factor-α), IL (interleukin)-1β and IL-6], and increased cellular ischaemia (i.e. glutamate and lactate/pyruvate ratio) and oxidative damage [glycerol, NOx (combined nitrate+nitrite) and 2,3-dihydroxybenzoic acid] markers in the BALF (bronchoalveolar fluid). HHP, in addition to inducing overexpression of HSP70 in the lungs, significantly attenuated HAE-induced pulmonary oedema, inflammation, and ischaemic and oxidative damage in the lungs. The beneficial effects of HHP in preventing the occurrence of HAE-induced pulmonary oedema, inflammation, and ischaemic and oxidative damage was reduced significantly by pretreatment with a neutralizing anti-HSP70 antibody. In conclusion, HHP may attenuate the occurrence of pulmonary oedema, inflammation, and ischaemic and oxidative damage caused by HAE in part via up-regulating HSP70 in the lungs.

Effects of combination treatment with dexamethasone and mannitol on neuronal damage and survival in experimental heat stroke

There is evidence that increased plasma cytokines, elevated brain levels of monoamines and hydroxyl radical production may be implicated in pathogenesis during heat stroke in rats. Acute treatment with a combined therapeutic approach has been repeatedly advocated in cerebral ischemia experiments. The aim of this study was to investigate whether the combined agent (mannitol and dexamethasone) has beneficial efficacy to improve the survival time (ST) and heat stroke-induced damage in experimental heat stroke. Urethane-anesthetized rats underwent instrumentation for the measurement of colonic temperature, mean arterial pressure (MAP), striatal cerebral blood flow (CBF), heart rate, and neuronal damage score. The rats were exposed to an ambient temperature (43 degrees C) to induce heat stroke. Concentrations of the ischemic and damage markers, dopamine, serotonin, and hydroxyl radical production in corpus striatum, and the plasma levels of tumor necrosis factor-alpha (TNF-alpha) were observed during heat stroke. After the onset of heat stroke, the heat stroke rats display decreased MAP, decreased CBF, increased the plasma levels of TNF-alpha, increased cerebral striatal monoamines and hydroxyl radical production release, and severe cerebral ischemia and neuronal damage compared with those of normothermic control rats. However, immediate treatment with the combined agent confers significant protection against heat stroke-induced arterial hypotension, systemic inflammation, cerebral ischemia, cerebral monoamines and hydroxyl radical production overloads, and improves neuronal damage and the ST in heat stroke rats. Our data suggest that administration of this combined agent seems to have more effective to ameliorate the heat stroke-induced neuronal damage and prolong the ST.

Low ambient temperature reveals distinct mechanisms for MDMA-induced serotonergic toxicity and astroglial Hsp27 heat shock response in rat brain

3,4-Methylenedioxymethamphetamine (MDMA, 'ecstasy') is a widely used recreational drug known to cause selective long-term serotonergic damage. In our recent paper we described region-specific, dose-dependent increase in the protein expression of astroglial Hsp27 and neuronal Hsp72 molecular chaperones after MDMA administration of rats. Here, we examined the possible interaction of elevated Hsp27 protein level to hyperthermic responses after MDMA administration and its separation from drug-induced serotonergic neurotoxicity. For this, 7-8 week old male Dark Agouti rats were treated with 15 mg/kg i.p. MDMA. Treatment at an ambient temperature of 22 ± 1°C caused a significant elevation of the rectal temperature, an increase of Hsp27 immunoreactive protoplasmic astrocytes in the hippocampus, the parietal and cingulate cortices, and a significant decrease in the density of tryptophan hydroxylase immunoreactive fibers in the same brain regions, 8h as well as 24h after drug administrations. In addition, serotonergic axons exhibited numerous swollen varicosities and fragmented morphology. MDMA treatment at low ambient temperature (10 ± 2°C) almost completely abolished the elevation of body temperature and the increased astroglial Hsp27 expression but failed to alter - or just slightly attenuated - the depletion in the density of tryptophan hydroxylase immunoreactive fibers. These results suggest that the increased astroglial Hsp27 protein expression is rather related to the hyperthermic response after the drug administration and it could be separated from the serotonergic neurotoxicity caused by MDMA. In addition, the induction of Hsp27 per se is uneffective to protect serotonergic fibers after MDMA administration. Our results also suggest that Tph immunohistochemistry is an early and sensitive method to demonstrate MDMA-caused vulnerability.

Therapeutic effects of melatonin on heatstroke-induced multiple organ dysfunction syndrome in rats

Melatonin reportedly exerts beneficial effects to attenuate multiple organ dysfunction syndrome (MODS) in septic shock. Heatstroke resembles septic shock in many aspects. Thus, this study was performed on the anesthetized rats by using heat exposure to induce heatstroke-associated MODS. We evaluated the effect of melatonin, a versatile molecule synthesized in the pineal gland and in many organs, in heatstroke rats and showed that melatonin (0.2-5.0 mg/kg of body weight, i.v., immediately after the start of heat stress) significantly (i) attenuated hyperthermia, hypotension and hypothalamic ischemia and hypoxia, (ii) reduced plasma index of the toxic oxidizing radicals like nitric oxide metabolites and hydroxyl radicals, (iii) diminished plasma index of hepatic and renal dysfunction like creatinine, blood urea nitrogen, alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, and lactate dehydrogenase, (iv) attenuated plasma systemic inflammation response molecules like soluble intercellular and lesion molecule-1, E-selectin, tumor necrosis factor-alpha, interleukin (IL)-1β, and IL-6, (v) promoted plasma levels of an anti-inflammatory cytokine IL-10, (vi) reduced an index of infiltration of polymorphonuclear neutrophils in the lung like myeloperoxidase activity, and (vii) promoted the survival time to fourfold compared with the heatstroke alone group. Thus, melatonin could be a novel agent for the treatment of heatstroke animals or patients in the early stage.

Hyperpyrexia resulting in encephalopathy in a 14-month-old patient with cblC disease

Cobalamin C (cblC) defect, the most common inborn error of cobalamin metabolism, is a multisystem disorder usually presenting with progressive neurological, haematological and ophthalmological signs. We report on a cblC patient diagnosed in the newborn age who developed nearly normal during the first year of life. During an upper respiratory tract infection with severe hyperpyrexia at the age of 14months he developed an acute encephalopathic crisis resulting in severe mental retardation and marked internal and external cerebral atrophy. Hyperacute encephalopathic crises have not been observed so far in patients with cblC defect. It remains unclear, if this association is incidental or if the underlying metabolic defect may have predisposed the brain tissue to hyperpyrexia-induced damage.