HSP70 Effect On Febrile Response And PGE₂ Content In Hypothalamus Induced By TNF-α In Rats

IntroductionHeat shock protein (HSP) is highly distributed in cells of body. The expressing of HSP and its genes can increased rapidly when faced to some stimula that can hurt organ cells, and it is important for stress response.Body temperature of organisms can't exceed 41℃ in physiological or pathological conditions. This phenomenon is called febrile ceiling. It is reported that the increasing of HSP70 expression is company with the limited of fever. Several studies have demonstrated that HSP70 has an important role in cell protection, inflammatory reaction and immunization, but the probably mechanism is still unclear. This study observed the effects of HSP70 induced by heat stress on TNF - a - induced fever, and measured the change of PGE2 level in hypothalamus, so as to explore whether HSF70 participates febrile ceiling and the possible mechanism.Materials and Methods1. Animals and surgeryMale Sprague - Dawley rats, weighting 200 - 250g, purchased from China Medical University Animal Center, were housed individually. Room temperature was kept at (22 ± 2) ℃. Food and water were available ad libitum. Under intraperitoneal anesthesia (ketamine hydrochloride and xylazine) , a 23 bugle stainless steel was implanted into POA area by stereotaxic apparatus according to the rat brain atlas, and the cannula was anchored with dental acrylic. Rats were individually housed a week before experiments. Before experiment, rats were ex-ercised for 7 days. Examine body temperature: digital thermometer probe was inserted 6 centimeters in rats' rectum. Value was recorded after stabilization. Mean of three values 1 hour before administration was taken as baseline of pre -handling. Record body temperature of rats after administration. When the experiment was over, cannulas positions were checked to discard incorrect ones.2. The expression of HSP70 in rat hypothalamus tissue assay Hypothalamus tissue was homogenated, centrifuged and the supernatantswere used to measure the expression of HSP70 by Western blotting assay3. PGE2 level assayRat brain tissue was put into liquid nitrogen simultaneously. 10 mg hypothalamus tissue was weighted, homogenate, centrifuged and assay concentration of PGE2 with radioimmunoassay.4. Statistical analysisResults were presented as mean ± SD ( x ± s ). Data were analyzed using t - test.Results1. The maximum expression of HSP70 in hypothalamus was attained at 12h after heat stress.2. HSP70 prevents the body temperature rise induced by TNF - a.3. The PGE2 content in hypothalamus were reduced in HS group.DisscussionExposed to high temperature, cells, tissues or bodies can be induced to produce heat shock proteins ( HSPs). This process is called heat shock reaction ( HSR). Several studies have demonstrated that HSP can increase the thermotol-erance. HSP70 has an important role in cell protection, inflammatory reaction and immunization.PGE2 is a kind of important central mediator in febrile response. It is deeply concerned by researchers for thermoregulation. It has been demonstrated that...