The Effect Of Transient Global Cerebral Ischemia On Expression Of Heat Shock Protein Hsp40of Hippocampal CA1Neurons

Hsp40is one important member of the heat shock protein family. Hsp40belongs to peptide protein family，with highly conserved structure and importantphysiological functions. It is widespread from bacteria to mammals.It was reported by Kirino in1982that transient global cerebral ischemiaexperiments led to delayed death of the gerbil hippocampal CA1neurons.Cerebral ischemia triggered a series of changes on the molecular level. The timethese changes occurred within ranged from a few hours to a few days afterischemia. And one of the main causes of the delayed neuronal death was theproduction of protein aggregates. But in normal, the generation of proteins isalways monitored by the intracellular protein quality-control system andabnormal generated proteins will be cleared in time once it happens, to insurethere would be no cytotoxic protein aggregates formation. Hsp40is oneimportant part of intracellular protein-quality system. The two major aspects ofthe biological roles of Hsp40are as follows: Firstly, Hsp40can combine withthe hydrophobic parts which is exposed externally of the abnormal protein andprevent mutual adhesion of abnormal proteins, as well as the formation ofprotein aggregates. In addition, Hsp40participates in the repairment ofdenatured proteins. Secondly, Hsp40can play a synergic physiological role withHsp70and it can also regulate the function of Hsp70. It was also reported thatHsp40may assist Hsp70to traffic the abnormal protein into the proteindegradation system.Objective: To clarify the Hsp40protein expression changes after thetransient cerebral ischemia and reperfusion damage in hippocampal CA1 neurons and to investigate the effect of Hsp40on the protein aggregatesformation.Methods: Rats20min experiment was used to establish a global cerebralischemic rat model.28male Wistar rats, were divided into4groups by differentreperfusion time points: sham group,4hour recovery group,24hour recoverygroup,72hour recovery group. There were averagely7rats in each group.Immunohistochemical method combined with laser scanning confocalmicroscopy was used to observe the distribution of heat shock protein Hsp40inthe hippocampal CA1neurons, and differential centrifuge combined withWestern blot analysis was used to further analyze the neuron intracellular changeof heat shock protein Hsp40after transient cerebral ischemia and reperfusion.Results:（1）Immunohistochemical laser scanning confocal microscopystudies showed that in hippocampal CA1neurons, Hsp40in cytoplasmdecreased at the earliest time after the transient cerebral ischemia-reperfusion,and then followed by Hsp40in the nucleus decreased, until the neurons were alldead.（2）Differential centrifugate and Western blot analysis showed that Hsp40within the cytoplasm of neurons in hippocampal CA1region graduallydecreased after transient cerebral ischemia-reperfusion from1.00±0.08to0.24±0.06（P<0.01）after24h reperfusion; Hsp40in protein aggregates increasedfrom1.00±0.19to8.42±1.38（P<0.01）after24h reperfusion.Conclusion: The siginficant reduction of Hsp40in hippocampal CA1neurons is one of the important cause of the formation of cytotoxic proteinaggregates, which lead to the delayed neuronal death.