Regulatory Effects of Dexamethasone on the Expression of HSP 70 mRNA in Neonatal Rats Following Cerebral Hypoxia-ischemia

Objective To investigate the expression of HSP70 gene in the brain of neonatal rats following cerebral hypoxia ischemia (HI) and the effect of dexamethasone (DEX) on the expression of HSP70 mRNA. Methods Rapid competitive reverse transcriptase PCR was used to semi quantitatively analyze the expression of HSP70 mRNA in the ipsilateral cerebral hemisphere in a neonatal rat model of hypoxia ischemia. Groups were divided into those pre treated with DEX prior to hypoxia ischemia, those treated with DEX immediately following hypoxia ischemia, those pre treated with DEX prior to sham, and normal controls, respectively. Results Cerebral HI increased HSP70 mRNA expression. The peak time of overexpression was 12 h after HI(3.868±1.421), and maintained at a higher level during 12～48 h(3.186±0.803, 2.568±0.709). The intensity of HSP70 mRNA expression was greatly decreased or almost abolished completely by the pretreatment with DEX. At 12 h, 24 h and 48 h after this treatment, HSP 70 mRNA expression were 0.526±0.593, 0.492±0.450 and 0.434±0.428, respectively, while the treatment with DEX after the insults had no evident effect on the expression of HSP70 mRNA. AT 12 h, 24 h and 48 h, HSP 70 mRNA expression were 3.460± 1.309 , 3.020±0.565 and 2.242±0.504, respectively. Conclusions DEX prophylaxis could suppress the overexpression of HSP70 mRNA following cerebral HI. Inhibition of HSP70 mRNA expression by DEX prophylaxis could be related to the suppression of overexcitation of neurons. [