When rats were exposed to high environmental temperature (e.g., 42 or 43 degrees C),
hyperthermia,
hypotension, and
cerebral ischemia and damage occurred during
heat stroke were associated with increased production of
free radicals (specifically
hydroxyl radicals and
superoxide anions), higher lipid peroxidation, lower enzymatic
antioxidant defenses, and higher enzymatic
pro-oxidants in the brain of
heat stroke-affected rats. Pretreatment with conventional
hydroxyl radical scavengers (e.g.,
mannitol or
alpha-tocopherol) prevented increased production of
hydroxyl radicals, increased levels of lipid peroxidation, and ischemic neuronal damage in different brain structures attenuated with
heat stroke and increased subsequent survival time. Heat shock preconditioning (a mild sublethal heat exposure for 15min) or regular, daily exercise for at least 3 weeks, in addition to inducing overproduction of
heat shock protein 72 in multiple organs including brain, significantly attenuated the
heat stroke-
induced hyperthermia,
hypotension,
cerebral ischemia and damage, and overproduction of
hydroxyl radicals and lipid peroxidation. The precise function of
heat shock protein 72 are unknown, but there is considerable evidence that these
proteins are essential for survival at both normal and elevated temperatures. They also play a critical role in the development of thermotolerance and protection from oxidative damage associated with
cerebral ischemia and energy depletion during
heat stroke. In addition,
Shengmai San or
magnolol (Chinese
herbal medicines) or hypervolemic
hemodilution (produced by
intravenous infusion of 10%
human albumin) is effective for prevention and repair of ischemic and oxidative damage in the brain during
heat stroke. Thus, it appears that
heat shock protein 72 preconditioning induced by prior heat shock or regular exercise training, as well as pretreatment with
Shengmai San or
magnolol is able to prevent the oxidative damage during
heat stroke. On the other hand, hypervolemic
hemodilution,
Shengmai San, or
magnolol is able to treat the oxidative damage after
heat stroke onset.