Brain-specific Loss Of Abcg1 Disturbs Cholesterol Metabolism And Aggravates Pyroptosis And Neurological Deficits After Traumatic Brain Injury

Background:Traumatic brain injury(TBI)consists of two types of injuries,primary injury caused by physical impact and secondary injury caused by inflammation.Injury time estimation and cognitive function assessment related to traumatic brain injury are difficulties in forensic research.Epidemiological studies indicate that traumatic brain injury is one of the most serious medical problems worldwide.At the same time,accumulating evidence indicates that the imbalance of cholesterol metabolism homeostasis is involved in the pathophysiological process of TBI and leads to neurological dysfunction.As key transporters regulating intracellular cholesterol efflux,the ATP-binding cassette(ABC)transporter family has many beneficial effects on central nervous system(CNS)diseases.In this study,by constructing brain-specific Abcg1 knockout(Abcg1-KO)mice,the aim was to explore the role and mechanism of Abcg1 on TBI,and to provide new research ideas for forensic TBI cognitive function assessment and clinical treatment.Methods:In this subject,a mouse TBI model was first established using a controlled cortical impact(CCI)craniocerebral injury device,and the temporal changes of molecules related to cholesterol metabolism in the damaged cortex were detected(Sham,multiple time points from 6h to 14d).Then through molecular biology such as immunofluorescence(Immunofluorescence,IF)and Western blot(Western blot,WB),morphology such as Nissl staining(Nissl Staining),hematoxylin and eosin(HE)staining,immunohistochemical staining(immunohistochemical Staining)and behavioral tests such as motor function test(Wire-grip Test),water maze(Morris water Maze),open field test(Open Field Test)to study the role of Abcg1 on cognitive function after TBI and related mechanisms.Considering that ABCG1 is expressed in neurons and glial cells after TBI,Nestin-specific Abcg1 knockout(Abcg1-KO)mice were generated using the Cre/loxP recombinant system,and Abcg1 knockout mice were studied using molecular biology and morphological methods.What is the difference in the level of cholesterol metabolism in mice under physiological and pathological conditions?Finally,the retinoid X receptor(RXR,the upstream molecule of ABCG1)agonist bexarotene(Bex)was used for Abcg1 knockout mice,and further to explore the mechanism of ABCG1 in cholesterol metabolism,secondary cell death and cognitive dysfunction after TBI.Results:(1)After TBI,cholesterol metabolism-related proteins ABCA1,ABCG1,ABCG4,SCARB1,ApoE,LCAT,RXRalpha,PPARgamma and LXRalpha were expressed sequentially,and the expressions of almost all proteins 3 days after TBI were statistically similar to those in the Sham group.(2)Under physiological conditions,Abcg1-KO mice showed cholesterol metabolism disorder,and Abcg1-KO aggravated cholesterol metabolism disorder,cell pyroptosis and cell apoptosis induced by TBI.(3)Abcg1-KO aggravated TBIinduced motor dysfunction,memory deficits,depression-like behaviors,and brain defect volume.(4)Whether in wild-type mice or in Abcg1-KO mice,Bex can alleviate TBI-induced cholesterol metabolism disorders,cell pyroptosis,plasma membrane damage,and nerve dysfunction,but it does not inhibit the apoptosis of Abcg1-KO mice death,cerebral edema,and brain defect volume.Conclusions:We provide experimental evidence that brain-specific knockdown of Abcg1 exacerbates cholesterol metabolism imbalance after TBI.In addition to regulating cholesterol metabolism in the brain,Abcg1 can improve neurological deficits and reduce the volume of brain damage by inhibiting pyroptosis,apoptosis,neuronal damage,and brain edema.Moreover,the brain protective effect of Abcg1 on TBI is partially dependent on the activation of the RXRalpha/PPARgamma pathway,which provides a potential target for the treatment of TBI.Therefore,this study provides a new idea for understanding the multiple biological functions of Bex,and provides a way to study the anti-pyrotic effect of Bex after TBI.