Effect Of Hyperthermia On Tight Junction Claudin-1Expression Of BBB After Focal Cerebral Ischemia In Rat

[Objective] Because of its high incidence, high morbidity and high mortality, cerebral vascular disease(ICVD) has deep influence on people’s health and makes it a heavy burden to the society and family. Therefore, the study of its pathophysiology becomes extremely important. Fever or hyperthermia is a common complication of ischemic cerebral vascular disease.Studies have shown fever can aggravate ischemic brain damage, but the specific mechanism has not been fully elucidated. The damaging of tight junction (TJ) proteins of the blood brain barrier (BBB) leads to brain edema, hemorrhage and so on after cerebral ischemia and reperfusion injury (I/R). Claudin-1is one of the TJ proteins between BBB endothelial cells. It is not known whether the hyperthermia will aggravate the BBB damage by disrupting claudin-1after cerebral ischemia, and then exacerbating the brain edema and necrosis of neurons. In the present study, we have examined the changing of claudin-1by the time after hyperthermia and try to find its possible role on the brain edema, cerebral neurological function and cerebral infarction.[Methods] The male Sprague-Dawley rats, weight250-300g, offered by the Kunming Medical University, were randomly divided into sham group, normothermia ischemic (No+Is)3h,6h and24h groups; hyperthermia ischemia(Hp+Is)3h,6h and24h group. Middle cerebral artery occlusion (MCAo) was induced according to Longa way. After focal cerebral ischemia was successfully established, rats in Hp+Is group received hyperthermia treatment for3hours, whose rectal temperature was kept at39.0℃by a multifunctional small pet electric blanket.Rats in No+ls group received normothermia treatment, whose rectal temperature was kept at37.5℃by multifunctional small pet electric blanket.Neurologic score and infract size were evaluated at24h after the MCAo. Brain edema was measured by wet and dry weight method at24h after the MCAo. The cerebral infarrction volume was evaluated by TTC(2,3,5-triphenyltertrazolium,chloride) staining method at24h after ischemic/reperfusion. Claudin-1expression was detected by western blot and immunohistochemistry.[Results]1. The neurologic score is much more higher in hyperthermia ischemia group than the one in normothermia ischemia group at24h(P<0.01).2. At24h after brain ischemia and reperfusion, ischemia increased the water content of brain in normothermia ischemia group compared to the sham (P<0.01).The water content of brain in hyperthermia ischemia group was higher than that of normothermia ischemia group (P<0.01).3.Infarct volume of hyperthermia ischemia group increased compared with that of normothermia ischemia group at24h after ischemia and reperfusion(P<0.01).4. At3h,6h and24h after brain ischemia and reperfusion, claudin-1expression of normothermia ischemia group and hyperthermia ischemia group decreased compared with that of sham(P<0.01), and decreased with the reperfusion time (P<0.05), and reach to the lowest at24h.At each time point, claudin-1expressions in hyperthermia ischemia group were lower than those in normothermia ischemia group respectively(P<0.01).5. At3h and6h after brain ischemia and reperfusion, the positive cells count of tight junction protein claudin-1declined gradually(P<0.01)and disappeared at24.6. At3h and6h after brain ischemia and reperfusion, the IOD/Area of claudin-1protein of normothermia ischemia group and hyperthermia ischemia group decreased compared with that of sham(P<0.01), and decreased with the reperfusion time (P<0.01), and reach to the zero at24h. At3h and6h after reperfusion, IOD/Area of claudin-1of hyperthermia ischemia group were lower than that of normothermia ischemia group respectively (P<0.01).[Conclusions]1.Hyperthermia increase the nerve damage after ischemia/reperfusion.2. Hyperthermia aggravate brain edema and brain infarct volume after the onset of ischemia and reperfusion.3.Claudin-1expression decreased with the prolongation of time and fell to the lowest at24h after ischemia and reperfusion, Hyperthermia aggravate claudin-1damaged.4. Hyperthermia can probably make brain edema and brain damage worse by exacerbate claudin-1damage after ischemia and reperfusion.