Effect of mild hypothermia treatment on rat RIPK-1 expression following traumatic brain injury

Objective To investigate the correlationbetween mild hypothermia treatment and gene transcription and protein expression of receptor-interacting protein kinase-1 (RIPK-1) following by traumatic brain injury (TBI) in rats.Methods Forty adult male Wistar rats were randomly divided into 5 equal groups (normal,sham,sham + hypothermia,TBI,and TBI + hypothermia).After TBI induced by fluid percussion injury (FPI),group TBI remained at normal temperature (37℃),and group (TBI + hypothermia) underwent mild hypothermia (32℃) for 4 h.Neurological severity scores (NSS) were then assessed.All rats were sacrificed at 48 h and brain tissues were harvested,stained with hematoxylin and eosin (HE).mRNA and protein expressions of RIPK-1 were analyzed by reverse transcription-polymerase chain reaction (RT-PCR),real-time PCR,Western-blot,and immunohistochemistry (IHC),respectively.Results Significantly decreased NSS scores were observed in group TBI + hypothermia compared to group TBI (P ＜ 0.01).Additionally,group TBI increased RIPK-1 levels compared to group sham (P ＜ 0.05).Reduced expression of RIPK-1 were apparent in group TBI + hypothermia compare to group TBI (P ＜ 0.05).However,no statistically significant difference was observed among groups normal,sham,and sham + hypothermia in NSS scores and the expression of RIPK-1 (P ＞ 0.05).Conclusion Mild hypothermia treatment significantly reduced NSS score and RIPK-1 upregulation after TBI,which may provide a better understanding of the mechanisms by which hypothermia reduces secondary brain injury in TBI patients. Key words: Traumatic brain injury;  Hypothermia;  Receptor interacting protein kinase 1 ; Necroptosis