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 adverse climatic changes. Such hyperthermia has been linked to various detrimental health effects. This study aimed to investigate the pathophysiological responses to acute versus subacute whole-body hyperthermia (WBH) in rats, particularly on the brain, with special reference to their medicolegal importance. Rats were randomly assigned to three equal groups. The normothermic group was kept at room temperature, the acute whole-body hyperthermic (AWBH) group was subjected to long-period WBH as a single bout of 4 hours at 43 °C, and the subacute whole-body hyperthermic (SWBH) group was subjected to repeated short-period WBH;2 hours daily for 7 successive days at 43 °C. A significant increase in body temperature and a significant decrease in body weight were recorded in both the acute and subacute hyperthermic groups. However, significant elevations in the serum glucose and cortisol levels and in the brain malondialdehyde and 8-hydroxy-2'-desoxyguanosine levels, with a significant reduction in brain total antioxidant capacity, were observed only in the AWBH group. Moreover, exposure to WBH induced various degrees of pathological changes, along with positive immune reactivity for heat shock protein 70 and glial fibrillary acidic protein in the cerebrum and cerebellum of rats in both hyperthermic groups. Overall, WBH induced various adverse health effects, mediated by the induction of oxidative damage, particularly following acute exposure. Hence, these findings provide evidence that acute exposure to long-term WBH may markedly exacerbate brain injury more than repeated short-term exposure, reflecting the role of the adaptive mechanisms to repeated heat exposure. Interestingly, the obtained findings may be valuable in the forensic antemortem and postmortem diagnosis of WBH and heat-related deaths.