Inhibition Of AP-1 Attenuates Neuroinflammation And Brain Injury After Intracerebral Hemorrhage

Background and purpose Intracerebral hemorrhage(ICH)is a common but devastating stoke subtype and lacks effective treatment.After the rupture of the parenchymal blood vessel,the blood component enters the brain tissue and forms a hematoma,which causes mechanical damage to adjacent tissues.Increasing evidence has shown that inflammation is the key factors contribute to ICH-induced secondary brain injury.The hematoma components and damaged cells triggered brain inherent or adaptive immune response,and the resident microglia is believed to be the first inflammatory cells in response to the extravascular blood components.Subsequently,the activated microglia release a variety of proinflammatory cytokines,chemokines and radicals.The circulating leukocytes then infiltrate the hemorrhagic brain and release varies proinflammatory mediators,contributing to a severe ICH-induced brain injury by increasing the brain edema formation,the permeability of the blood-brain barrier(BBB)and the apoptosis of neurons.Activator protein 1(AP‐1)is a transcription factor,plays an important role in cell proliferation,differentiation and apoptosis.AP-1 is a ubiquitous dimeric protein complex composed of Jun and Fos subfamilies,and it is an important molecular switch mediating the inflammation signaling pathway.SR11302,is a chemical compound which can inhibit the activity of AP-1.By inducing two types of experimental hemorrhage mice models and using SR11302 to inhibit the AP-1,to demonstrate the effective protection in hemorrhagic brain through the inhibition of AP-1,and further investigated the association between the AP-1 and the neuroinflammation after ICH onset.Methods Intracerebral hemorrhage mice were developed by autologous blood or collagenase infusion.SR11032(100mmol/L,1μl)or vehicle(dimethyl sulfoxide,DMSO)was administered through brain parenchymal injection 1 hour before ICH induction.We measured the dynamics of AP-1(c-Jun,c-Fos)in mouse brain after ICH onset via flow cytometry or Rt-PCR,and also measured the m RNA levels of cytokines,including interleukin(IL)‐6,IL‐1β and tumor necrosis factor(TNF)‐α.According to the above results,using the immunofluorescence to verify the AP-1 expression in microglia after ICH.Neurological deficient tests were performed at day 1 and day 3 after ICH,including m NSS,corner-turn test and mortality rate.In addition,the brain water content was accessed by dry-weight at day 3 after ICH.Flow cytometry were used to measure the amount of circulating leukocytes,including neutrophils,T cells and natural killer(NK)cells,and resident microglia in mouse brain at 24 h after ICH,which administrated with SR11302 or vehicle,and also measured the amount of IL-6 or TNF-α positive microglia in vivo or in vitro.Results AP-1 was significantly upregulated in mice brain at 6 hours after ICH,especially in microglia,accompanied by increased in proinflammatory cytokines,including IL-1β,IL-6 and TNF-α.Inhibition of AP‐1 using SR11302 reduced neurological function deficits and brain edema at day 3 after ICH.SR11302 decreased the resident microglia and its production of IL-6 or TNF-α,and reduced brain infiltrated leukocytes in ICH mice.In addition,SR11302 treatment ablated the production of IL-6 or TNF-αin cultured microglia which exposed to thrombin.Conclusion Inhibition of AP-1 can attenuate the neuroinflammation after ICH in experimental hemorrhage model,reduce the brain edema and neurological function deficient,improve the ICH-induced brain injury.And may provide a potential therapy for intracerebral hemorrhage.