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)-1ß, 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.

[Immunohistochemical study of tumor necrosis factor-alpha expression in the lungs and small intestines in hyperthermia-LPS co-stressed rats].

OBJECTIVE: To investigate the effects of co-exposure to hyperthermia and lipopolysaccharides (LPS) on tumor necrosis factor-alpha (TNF-alpha) expression in the lungs and small intestines of rats. METHODS: Male pathogen-free Wistar rats were randomly assigned into saline-injected normothermic control (C), saline heat exposure (H), LPS normothermic control (L), and LPS plus heat exposure (HL) groups. The rats in H and HL groups were exposed in a chamber at an ambient dry bulb temperature (Tdb) of 35.0-/+0.5 degrees celsius;, and those in C and L groups to 26-/+0.5 degrees celsius;. In L and HL groups, the rats were given an intravenous injection of LPS 10 mg/kg via the tail vein to induce endotoxemia, and those in C and H group received 10 ml/kg injection. The plasma levels of sTNFrI and sTNFrII were detected at different time points using ELISA. The expression of TNF-alpha in the lungs and small intestines was detected by immunohistochemical SABC method, and the damage of the lungs and small intestines evaluated histologically 120 min after the treatment. RESULTS: Co-exposure to hyperthermia and LPS caused significantly enhanced expressions of TNF-alpha and its receptor sTNFrI and sTNFrII in the plasma and tissues and obvious histopathological damage in the lung and small intestines. CONCLUSION: Co-stress of hyperthermia and LPS-induced toxicity is associated with the expression of TNF-alpha in the lung and small intestines.

[Immunohistochemical study of TNF-alpha expression in the kidney of rats with lipopolysaccharide and heat stresses].

OBJECTIVE: To investigate the effects of co-exposure of LPS and heat on TNF-alpha expression in rat kidneys. METHODS: Male pathogen-free Wistar rats were randomly assigned in saline-injected normothermic control (C group), saline-injected heat exposure (H group), LPS-injected normothermic control (L group), and LPS-injected heat exposure (HL group). The rats in H and HL groups were exposed in a chamber at an ambient dry bulb temperature (Tdb) of 35.0-/+0.5 degrees, and those in C and L groups were exposed to a Tdb of 26-/+0.5 degrees. The rats in L and HL groups were given an intravenous injection of LPS (10 mg/kg) via the tail vein to induce endotoxemia, and equivalent normal saline was injected in C and H groups. TNF-alpha expression in the kidney was detected by immunohistochemical SABC method, and the renal damage was evaluated histologically at 120 min after the treatment. RESULTS: Co-exposure of the rats with LPS and heat caused significantly enhanced TNF-alpha expression and histopathological damage in the kidneys. CONCLUSION: LPS combined with heat exposure causes renal toxicity, while is closely associated with the expression of TNF-alpha in the kidneys.

Activated protein C can be used as a prophylactic as well as a therapeutic agent for heat stroke in rodents.

The present study was attempted to assess the prophylactic and the therapeutic effect of human recombinant activated protein C (APC; drotrecogin-alpha, activated) in experimental heat stroke. Anesthetized rats were divided into two groups and given vehicle solution 1 h before the start or immediately after the termination of heat stress (isotonic sodium chloride solution, 2 mL kg(-1) of body weight, i.v.) or APC (1-10 mg in 2 mL of isotonic sodium chloride solution per kilogram of body weight, i.v.). They were exposed to ambient temperature of 40 degrees C for 100 min to induce heat stroke. When the vehicle-pretreated rats underwent heat stress, their survival time values were found to be 57 to 71 min. Pretreatment or treatment with APC significantly increased survival time (122-221 min). All vehicle-pretreated heat stroke animals displayed systemic inflammation (evidenced by increased TNF-alpha, IL-1alpha, and IL-6) and activated coagulation (evidenced by increased levels of activated partial thromboplastin time, prothrombin time, and D-dimer and decreased levels of both platelet count and protein C). Biochemical assay also revealed that both renal and hepatic dysfunction (e.g., increased plasma levels of blood urea nitrogen, creatinine, adenine aminotransferase, aspartate aminotransferase, and alkaline phosphatase) were noted during heat stroke. A significant decrease in both cerebral blood flow and partial pressure of oxygen in hypothalamus were also observed in vehicle-pretreated heat stroke animals. These heat stroke reactions were all significantly reduced by pretreatment or treatment with human recombinant APC. The results indicate that human recombinant APC can be used as a prophylactic and a therapeutic agent for experimental heat stroke by ameliorating systemic inflammation, hypercoagulable state, and multiple organ dysfunction.