Anti-Inflammatory And Immunomodulatory Mechanisms Of Atorvastatin In Mice Subjected To Traumatic Brain Injury

Backgroud: Excessive inflammation is an important secondary brain injury in the pathological mechanism of Traumatic Brain Injury(TBI).It has both beneficial and harmful effects.A large number of data indicate that statin drugs have a wide range of immunoregulatory and anti-inflammatory properties in addition to lipid-lowering effects.Among statins,atorvastatin has been shown to be neuroprotective in the experimental TBI model;however,there is insufficient evidence regarding its effect on neurological inflammation in the acute phase of TBI.Objective: The purpose of the present study is to evaluate the effect of atorvastatin on the immune response in the acute phase of traumatic brain injury and to investigate the possible involvement of leukocyte infiltration in peripheral blood and polarization of microglia/macrophages after TBI.Methods: The C57BL/6 mice TBI model was established using an electronically controlled cerebral cortical impact instrument(eCCI).Atorvastatin or saline was administered orally starting 1 h post-TBI for three consecutive days.Modified neurological severity scores(mNSS)and Rota-rod were used to assess the degree of short-term neurological deficits in TBI mice.The leukocyte subpopulations of invading brain tissue were analyzed by immunohistochemistry and flow cytometry.Enzymelinked immunosorbent assay(ELISA)was used to detect proinflammatory and antiinflammatory cytokines and chemokines.The transformation of M1 and M2 microglia/macrophages was detected by quantitative real-time PCR(qRT-PCR)and flow cytometry.Apoptotic neurons were labeled and identified by double staining of terminal deoxynucleotidyl transferase-dUTP nick end labeling(TUNEL)staining and immunofluorescence labeling for neuronal nuclei(NeuN).Results: Treatment with atorvastatin at a dose of 1 mg/kg/day decreased neuronal apoptosis and improved functional deficits in TBI mice.After atorvastatin treatment,the invasion of T cells,neutrophils/and natural killer(NK)cells was also significantly reduced,as was the production of pro-inflammatory/cytokines(IFN-? and IL-6)and /chemokines(RANTES and IP-10).It is noteworthy that atorvastatin treatment significantly increased the proportion of regulatory T cells(Tregs)in the peripheral spleen and brain and increased the levels of its major effector cytokines IL-10 and TGF-?1.We have also found that atorvastatin significantly attenuates the activation of total microglia/macrophages but increase the M2/M1 ratio by inhibiting M1 microglial/macrophage polarization and enhancing M2 microglia/macrophage polarization.Conclusion: Our data suggest that acute administration of/atorvastatin can effectively modulate excessive inflammatory after TBI,and its mechanisms include regulating peripheral leukocyte invasion and regulating the polarization state of microglia/macrophages.