Expressions of chemokines and their receptors in the brain after heat stroke-induced cortical damage.

Despite growing evidence that cytokines and chemokines are expressed in humans and rats after heat stress, the cellular mechanisms underlying the effects on the brain after heatstroke (HS) are not fully understood. In this study, we observed time course changes of chemokines in rat brain tissues and elucidated what kinds of cortical cells were affected after HS. Male SD rats were anesthetized and randomly separated into two groups as follows: (a) normothermic sham and (b) HS rats. Rats were sacrificed at different time points (0, 1, 3, 6, and 12h after heat exposure, n=5 in each group) to the end of the experiment in order to extract the mRNA/proteins of cortical tissues. Cerebrospinal fluid (CSF) of sham and HS rats was also collected before sacrifice. In the HS group, an elevated body temperature (Tco>40°C) and abnormality of cortical cells (e.g., pyknotic nuclei) were observed. When compared to the sham group, expression levels of either mRNAs or proteins of chemokines and their receptors (including CXCL1, MIP2, MCP1, CXCR1, CXCR2, and CCR2) peaked at different time points after heat exposure. We also found that CXCR2 was expressed in the cortex of rat brain and was colocalized with neurons and microglia after HS. Hence, MCP1, MIP2, and CXCR2 might play important roles in the brain after HS, possibly indicating a new direction for treating HS.