The Research Of Effects On Brains And Mechanism Of Different Hypothermic Circulatory Arrests

Objective Deep hypothermic circulatory arrest (DHCA) is widely used in aortic and complex congenital heart operations, in order to provide bloodless surgery field by arresting circulation, and to protect organs by lowering body temperature. However, the mechanism of cerebral injury after DHCA is still far away from fully understood. We evaluated the injury of different arrest temperature to search for new aspect of cerebral protection during DHCA.Methods24SD rats were randomly divided to4groups:deep hypothermic circulatory arrest (15～20℃), moderate hypothermic circulatory arrest (20～25℃), mild hypothermic circulatory arrest (25～30℃) and sham group. Brains of rats were harvest after surgery. Injury of neurons was evaluated after HE staining. The expression pattern of HIF-1α was observed by immunohistochemical staining. TUNEL technique was used for evaluate apoptosis. Transmission electronic microscope was used to observe the ultrastructure injury of neuro (corpus neuroni, dendrite and axon) and blood brain barrier.Results Neuron injury appeared in3hypothermic circulatory arrest groups, but there was no apparent difference after HE staining. There was no apparent apoptosis neuron observed after TUNEL. HIF-1a was over-expressed in deep hypothermic circulatory arrest, moderate hypothermic circulatory arrest and mild hypothermic circulatory arrest group, but there was no different. Microtubules and mitochondrial cristaes were dissolved in dendrite and axon. Podocyticprocess of astrocyte which constitutes blood brain barrier swelled.Conclusion Different hypothermic circulatory arrests contributed to cerebral injury, but there was no linear correlation between the injury severity and temperature. This indicated that the mechanism of cerebral injury after DHCA was complicated. Objective Our previous research indicated that miR-194dramaticlly decreased in hippocampus after DHCA. And the target predicted web inferred micro-tubule associated protein2is the modulated target of miR-194. In addition, we also observed the microtubule of rat dissolved after hypothermic circulatory arrest. We researched for a profound understanding of molecular mechanism of cerebral injury and protection associated with MAP2after DHCA.Methods30SD rats were randomly divided to5groups:deep hypothermic circulatory arrest (15～20℃), moderate hypothermic circulatory arrest (20～25℃), mild hypothermic circulatory arrest (25～30℃), normal temperature cardiopulmonary bypass, and sham group. Brains and blood of rats were harvest after surgery, and the hippocampus was isolated. Elisa test was used to measure the plasma concentration of MAP2and S100B, which is a classical biomarker for cerebral injury. The mRNA and protein content of hippocampus was tested with PCR and western blot. Wild type and mutant type of MAP23’ UTR vector were established, Dual Luciferase Reporter system was used to verify the modulate relationship between miR-194and MAP2.Results There was no statistical difference between the groups on plasma concentration of S100B after DHCA. But the plasma MAP2was dramatically increased in mild hypothermic circulatory arrest group compared with normal cardiopulmonary bypass group and sham group. The MAP2mRNA content was also increased in mild hypothermic circulatory arrest group compared with sham group. But the MAP2protein content showed no difference. The activity of luciferase showed that miR-194did not modulate the expression.of MAP2.Conclusion Microtubules were dissolved after hypothermic circulatory arrest, the plasma concentration of MAP2was increased dramatically in mild hypothermic circulatory arrest when S100B didn’t show difference. MiR-194did not modulate the expression of MAP2, despite that miR-194and MAP2both changed after DHCA. Objective Sumolytion is up-regulated after hypothermic condition, in order to increase the cerebral tolerance to ischemia and reperfusion injury. However, the pattern of sumolytion, the expression and modulation of SUM02, and the relationship between sumolytion and other pathway are still unkown.Methods30SD rats were randomly divided to5groups:deep hypothermic circulatory arrest (15～20℃), moderate hypothermic circulatory arrest (20～25℃), mild hypothermic circulatory arrest (25～30℃), normal temperature cardiopulmonary bypass, and sham group. Brains of rats were harvest after surgery, and the hippocampus was isolated. PCR was used to test the content of SUM02mRNA. Western blot was used to quantify SUM02/3, Caspase3, Bax, Bcl-2, CytC, Beclinl, HIF-la, Akt, p44/42MAPK (Erkl/2) and pMEK.Results Free SUM02/3and total SUM02/3decreased in moderate hypothermic circulatory arrest group compared with normal temperature cardiopulmonary bypass group. Total SUM02/3of mild hypothermic circulatory arrest group was also decreased compared with normal temperature cardiopulmonary bypass group. There was no statistical difference on other results.Conclusion The content of SUM02/3changed after DHCA, but the effects and mechanism were still unknown.