The Role And Mechanisms Of Cytoplasmic Gelsolin (GSN) In Brain Injury After Experimental Subarachnoid Hemorrhage

Subarachnoid hemorrhage(SAH),especially aneurysm subarachnoid hemorrhage,is a life-threatening disease of central nervous system(CNS).Although its relatively low incidence,its early age of onset and poor outcome results in a lot of life years lost.Clinical studies have shown that increased levels of pro-inflammatory factors in cerebrospinal fluid(CSF)and serum of SAH patients are associated with poor outcome.Elevated inflammatory factors contribute to the breakage of blood brain barrier(BBB),brain edema,neuroglia cells apoptosis and death.Administration of the antagonists of the pro-inflammatory factors confers neuroprotective effect in experimental studies.However,how the inflammatory response is initiated and the upstream of the inflammatory response is still poorly investigated.Gelsolin(GSN)is a Ca2+-dependent actin filament severing,capping,and nucleating protein,as well as multifunctional regulator of cell structure and metabolism,including apoptosis.In the present study,we intended to investigate the expression pattern and cell distribution of GSN in rat brain after experimental SAH.GSN expression was examined in sham group and at 3 h,6 h,12 h,day 1(1 d)5 2 d,3 d,5 d and 7 d after SAH by western blot analysis as well as real-time polymerase chain reaction(PCR).Immunohistochemistry and immunofluorescence were performed to detect the localization of GSN.The level of GSN protein expression was significantly decreased in SAH group and reached a bottoming point on 1 d after SAH.GSN mRNA level was significantly decreased in SAH groups in comparison with the sham group,and reached a minimum value at 12 h after SAH.Immunohistochemistryshowed that GSN was constitutively and obviously expressed in the cortex of the normal rat brain and significantly decreased in the rat cortex after SAH.In addition,immunofluorescence results revealed that GSN expression could be found in both neurons and microglias,as well as in GFAP-positive astrocytes.The decreased expression of GSN could mainly be found in neurons and astrocytes as well,and GSN-positive micoglias showed different cell morphological characteristics.Interestingly,the protein and gene levels of GSN seemed to be constant in the rat hippocampus of sham and SAH groups.These findings suggested a potential role of GSN in the pathophysiology of the brain at the early stage of SAH.To find a treatment which targeted GSN,we used the GSN over-expression lentivirus,which was reported to have benefical effect in brain ischemia models.GSN over-expression lentiviruses were injected intracerebroventricularly.Our result indicated that GSN over-expression lentiviruses treatment could enhance the expression of GSN,and down-regulate cell apoptosis induced by SAH.Further,GSN over-expression lentiviruses treatment could reduce the brain edema significantly.Thus,numbers of TUNEL-positive staining positive cells were reduced after GSN over-expression lentiviruses treatment.These results suggested that lentiviruses can attenuate the early brain injury following SAH in rats.In summary,the present study is the first to characterize the cerebral cortical and hippocampus cGSN expression pattern after SAH to our knowledge.We found that SAH caused an obvious down-regulation of cGSN in the brain cortex.GSN played an important role in the early brain injury after SAH.GSN could be an important regulator of the apoptosis after SAH.