Whole Body Hyperthermia-Induced Brain Injury in Rats: Forensic Biochemical, Pathological, and Immunohistochemical Investigations

Abstract

Episodes of hyperthermia occur frequently from exposure to infections or adverseclimatic changes. Such hyperthermia has been linked to various detrimental healtheffects. This study aimed to investigate the pathophysiological responses to acuteversus subacute whole-body hyperthermia (WBH) in rats, particularly on the brain,with special reference to their medicolegal importance. Rats were randomly assigned tothree equal groups. The normothermic group was kept at room temperature, the acutewhole-body hyperthermic (AWBH) group was subjected to long-period WBH as a singlebout of 4 hours at 43 °C, and the subacute whole-body hyperthermic (SWBH) group wassubjected to repeated short-period WBH;2 hours daily for 7 successive days at 43°C. Asignificant increase in body temperature and a significant decrease in body weight wererecorded in both the acute and subacute hyperthermic groups. However, significantelevations in the serum glucose and cortisol levels and in the brain malondialdehydeand 8-hydroxy-2'-desoxyguanosinelevels, with a significant reduction in brain totalantioxidant capacity, were observed only in the AWBH group. Moreover, exposure toWBH induced various degrees of pathological changes, along with positive immunereactivity for heat shock protein 70 and glial fibrillary acidic protein in the cerebrumand cerebellum of rats in both hyperthermic groups. Overall, WBH induced variousadverse health effects, mediated by the induction of oxidative damage, particularlyfollowing acute exposure. Hence, these findings provide evidence that acute exposure tolong-term WBH may markedly exacerbate brain injury more than repeated short-termexposure, reflecting the role of the adaptive mechanisms to repeated heat exposure.Interestingly, the obtained findings may be valuable in the forensic antemortem andpostmortem diagnosis of WBH and heat-related deaths.