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Intolerance to heat exposure is believed to be associated with hypothalamo-pituitary-adrenocortical (HPA) axis impairment [reflected by decreases in blood concentrations of both adrenocorticotrophic-hormone (ACTH) and corticosterone]. The purpose of this study was to determine the effect of human recombinant factor VIIa (rfVIIa) on heat intolerance, HPA axis impairment, and hypothalamic inflammation, ischemic and oxidative damage, and apoptosis in mice under heat stress. Immediately after heat stress (41.2 °C for 1 h), mice were treated with vehicle (1 mL/kg of body weight) or rfVIIa (65-270 µg/kg of body weight) and then returned to room temperature (26 °C). Mice still alive on day 4 of heat exposure were considered survivors. Cellular ischemia markers (e.g., glutamate, lactate-to-pyruvate ratio), oxidative damage markers (e.g., nitric oxide metabolite, hydroxyl radials), and pro-inflammatory cytokines (e.g., interleukin-6, interleukin-1β, tumor necrosis factor-α) in hypothalamus were determined. In addition, blood concentrations of both ACTH and corticosterone were measured. Hypothalamic cell damage was assessed by determing the neuronal damage scores, whereas the hypothalamic cell apoptosis was determined by assessing the numbers of cells stained with terminal deoxynucleotidyl transferase-mediated αUTP nick-end labeling, caspase-3-positive cells, and platelet endothelial cell adhesion molecula-1-positive cells in hypothalamus. Compared with vehicle-treated heated mice, rfVIIa-treated heated mice had significantly higher fractional survival (8/10 vs 1/10), lesser thermoregulatory deficit (34.1 vs 24.8 °C), lesser extents of ischemic, oxidative, and inflammatory markers in hypothalamus, lesser neuronal damage scores and apoptosis in hypothalamus, and lesser HPA axis impairment. Human recombinant factor VIIa appears to exert a protective effect against heatstroke by attenuating hypothalamic cell apoptosis (due to ischemic, inflammatory, and oxidative damage) 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., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Heatstroke is a form of excessive hyperthermia associated with a systemic inflammatory response that leads to multi-organ dysfunction in which central nervous system disorders predominate. Herein we determined to ascertain whether heat-induced multi-organ dysfunction in rats could be attenuated by granulocyte-colony stimulating factor (G-CSF) preconditioning. Anesthetized rats were divided into 2 major groups and given vehicle solution (isotonic saline, 0.3 ml, subcutaneously) or G-CSF (50-200 μg/kg body weight in 0.3 ml normal saline, subcutaneously) daily and consecutively for 5 days before the start of thermal experiments. They were exposed to an ambient temperature of 43°C for 68 min to induce heatstroke. G-CSF preconditioning significantly prolonged the survival time in heatstroke rats in a dose-related way (82-98 min vs 127-243 min). The non-preconditioning heatstroke animals showed hyperthermia, arterial hypotension, increased serum levels of systemic inflammatory response molecules, increased hypothalamic apoptotic cell numbers as well as neuronal damage scores, and increased serum levels of renal and hepatic dysfunction indicators. These heatstroke syndromes could be significantly reduced by G-CSF preconditioning. Thus our results revealed a potential for G-CSF used as a prophylactic agent for heatstroke in rats., (Copyright © 2011. Published by Elsevier B.V.)

The present study was attempted to evaluate the therapeutic effects of activated protein C and/or hyperbaric oxygen in an animal model of heatstroke. Sixty-eight minutes heat stress (43 degrees C) initiated, the anesthetized rats were randomized to several groups and administered: 1) no resuscitation (vehicle solution plus normabaric air, 2) intravenous activated protein C (1mg in 1ml of normal saline per kg of body weight), 3) hyperbaric oxygen (100% oxygen at 202kpa for 17min), and 4) intravenous activated protein C plus hyperbaric oxygen. Another group of rats exposed to room temperature (26 degrees C) was used as normothermic controls. Blood sampling was 0min, 70min, and 85min after heat stress initiated. When the vehicle-treated rats underwent heat exposure, their survival time values found were to be 19-25min. Resuscitation with activated protein C or hyperbaric oxygen significantly and equally improved survival during heatstroke (134-159min). As compared with those of activated protein C or hyperbaric oxygen alone, combined activated protein C and hyperbaric oxygen significantly had higher survival time values (277-347min). All vehicle-treated heatstroke animals displayed systemic response, hypercoagulable state, and hepatic and renal dysfunction. Combined activated protein C and hyperbaric oxygen therapy reduced these heatstroke reactions better than activated protein C or hyperbaric oxygen alone. The results indicate consequently, combined activated protein C and hyperbaric oxygen therapy heightens benefit in combating heatstroke reactions.

Background: Transgenic mice have been used to examine the role of heat shock protein (HSP)72 in experimental heatstroke. Transgenic mice that were heterozygous for a porcine HSP70beta gene ([+] HSP72) and transgene-negative littermate controls ([-] HSP72), under pentobarbital sodium anesthesia, were subjected to heat stress to induce heatstroke. It was found that the overexpression of HSP72 in multiple organs improved survival during heatstroke by reducing hypotension and cerebral ischemia and damage in mice. Herein we attempted to further assess the effect of heat exposure on thermoregulatory function, hypothalamic integration, and survival in unrestrained, unanesthetized [+]HSP72 and compare with those of [-]HSP72. In this research with the transgenic mice, we first conducted several biochemical, physiologic and histological determinations and then investigated the beneficial effects of HSP72 overexpression on the identified hypothalamic deficits, thermoregulatory dysfunction, and mortality during heatstroke., Results: We report here that when [-]HSP72 mice underwent heat stress (ambient temperature 42.4 degrees C for 1 h), the fraction survival and core temperature at 4 h after heat stress were found to be 0 of 12 and 34.2 degrees C +/- 0.4 degrees C, respectively. Mice that survived to day 4 after heat stress were considered as survivors. In [+]HSP72 mice, when exposed to the same heat treatment, both fraction survival and core temperature values were significantly increased to new values of 12/12 and 37.4 degrees C +/- 0.3 degrees C, respectively. Compared to [-]HSP mice, [+]HSP72 mice displayed lower hypothalamic values of cellular ischemia (e.g., glutamate and lactate-to-pyruvate ratio) and damage (e.g., glycerol) markers, pro-oxidant enzymes (e.g., lipid peroxidation and glutathione oxidation), pro-inflammatory cytokines (e.g., interleukin-1beta and tumor necrosis factor-alpha), and neuronal damage score evaluated 4 h after heat stress. In contrast, [+]HSP72 mice had higher hypothalamic values of antioxidant defences (e.g., glutathione peroxidase and glutathione reductase), ATP, and HSP72 expression., Conclusion: This study indicates that HSP72 overexpression appears to be critical to the development of thermotolerance and protection from heat-induced hypothalamic ischemic and oxidative damage.

The present study was conducted to assess the effects of whole body cooling on multiorgan dysfunction that occurred during heatstroke in streptozotocin (STZ)-induced diabetic rats. The rats were randomly divided into four groups: [1] the normal control, [2] diabetic control, [3] diabetic heatstroke, and [4] diabetic heatstroke-whole body cooling (WBC). They were exposed to ambient temperature of 43 degrees C for exactly 58 min to induce heatstroke. When the diabetic heatstroke rats underwent heat stress, their survival time values were found to be 11-13 min. Immediately after the onset of heatstroke, resuscitation with body cooling greatly improved survival (221-257 min). Compared with the diabetic (STZ-treated) controls, the diabetic-heatstroke rats displayed higher levels of body temperature, intracranial pressure, serum nitric oxide metabolite, tumor necrosis factor-alpha and dihydroxybenzoic acid, blood urea nitrogen, creatinine, alanine aminotransferase, aspartate aminotransferase, and alkaline phosphatase. In contrast, the values of mean arterial pressure, cerebral perfusion pressure, and brain levels of local blood flow, and partial pressure of oxygen were all significantly lower during heatstroke. The cerebrovascular, renal, and hepatic dysfunction, the increased levels of nitric oxide metabolites, tumor necrosis factor-alpha, and dihydroxybenzoic acid in the serum during heatstroke were significantly reduced by WBC. Although the serum interleukin-10 maintained at a negligible levels before heat stress, they were significantly elevated by WBC in diabetic-heatstroke rats. The data demonstrate that heatstroke-induced multiorgan dysfunction in streptozotocin-induced diabetic rats can be decreased by WBC.

Abstract: The present study was performed to assess the prophylactic effect of baicalin, a flavonoid compound, in an animal model of heatstroke. Anesthetized rats, immediately before the start of heat stress, were divided into two major groups and given the following: vehicle solution (1mL per kg body weight) or baicalin (10–40mg per kg body weight) intravenously. They were exposed to ambient temperature of 43°C to induce heatstroke. Another group of rats was exposed to room temperature (24°C) and used as normothermic controls. Their physiologic and biochemical parameters were continuously monitored. When the vehicle-pretreated rats underwent heat stress, their survival time values were found to be 20–28min. Pretreatment with intravenous doses of baicalin significantly improved survival during heatstroke (65–248min). As compared to those of normothermic controls, all vehicle-pretreated heatstroke animals displayed higher levels of core temperature, intracranial pressure, and nitric oxide metabolite (NO2 −), glutamate, glycerol, lactate/pyruvate ratio, and dihydroxybenzoic acid (DHBA) in hypothalamus. In addition, both serum and hypothalamic levels of interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) as well as plasma levels of creatinine, serum urea nitrogen, glutamic oxaloacetic transaminase, glutamic pyruvic transaminase and alkaline phosphatase were elevated after heatstroke onset. In contrast, all vehicle-pretreated heatstroke animals had lower levels of mean arterial pressure, cerebral perfusion pressure, cerebral blood flow, and brain PO2. Administration of baicalin before the start of heat exposure significantly reduced the hyperthermia, intracranial hypertension, and the increased levels of NO2 −, glutamate, glycerol, lactate/pyruvate ratio, and DHBA in the hypothalamus that occurred during heatstroke. The heatstroke-induced increased levels of IL-1β and TNF-α in both the serum and hypothalamus, and renal and hepatic dysfunction were suppressed by baicalin pretreatment. In contrast, both the serum and hypothalamic levels of IL-10 were significantly elevated by baicalin during heatstroke. We successfully demonstrated that baicalin can be used as a prophylactic agent for heatstroke. In particular, baicalin may protect against cerebrovascular dysfunction and brain inflammation in heatstroke. [Copyright &y& Elsevier]