Effects Of Apolipoprotein E And Apoe-derived Mimic Pepetide, COG1410, On Early Brain Injury And Neuroinflammation After Subarachnoid Hemorrhage

ObjectiveSubarachnoid hemorrhage(SAH) is a subtype of hemorrhagic stroke with high mortality and morbidity. Early brain injury(EBI) refers to the acute pathological events that occur within the first 72 h after SAH.Apolipoprotein E(apoE) is the major apolipoprotein in the central nervous system(CNS). ApoE not only participates in lipids metabolism but also exerts neuroprotective effects via suppressing neuroinflammation.COG1410, a mimic peptide from the receptor binding region of apoE holoprotein, binds to the functional receptors of apoE. COG1410 is blood brain barrier(BBB) permeable, which makes it a promising neuroprotective agent for translational application. The role of apoE in the pathological process of SAH remains unclear. The present study aimed to investigate the role of endogenous apoE and COG1410 in the EBI and neuroinflammation after SAH, as well as to explore the preliminary mechanisms.Methods1. Mouse SAH model was induced in C57BL/6J wild type(WT) andAPOE knock out(APOE-/-) mice using endovascular perforation. The expression of endogenous apoE was evaluated within 72 h after SAH. To evaluate the roles of endogenous apoE in EBI and neuroinflammation, the cortical apoptosis was detected by TUNEL. White matter injury was detected by immunohistochemistry(IHC) and 7.0T MRI. Microglial activation was detected by IHC. The expression of IL-1β 、 IL-6 、 TNF-αwere detected by ELISA. Phosphorylation of JNK, c-Jun and NF-κB were detected by western blot in WT and APOE-/- mice at 24 h after SAH.2. WT mice were treated with COG1410 or saline after SAH. The timing and dosing of COG1410 were determined by weight loss, rotarod test and neurological score. The cortical apoptosis was detected by TUNEL.White matter injury was detected by immunohistochemistry(IHC) and7.0T MRI. Microglial activation was detected by IHC. The expression of IL-1β 、 IL-6 、 TNF-α were detected by ELISA. Phosphorylation of JNK,c-Jun and NF-κB were detected by western blot in COG1410 or saline treated mice at 24 h after SAH.3. BV-2 microglia cell line was activated by hemoglobin(Hb). The nitric oxide(NO) release was detected by Griess method. Microglial polarization was detected by flow cytometry. JNK phosphorylation was detected by western blot. The HT-22 neuron cell line was treated with the conditioned medium from Hb or Hb+COG1410 treated BV-2 cells. The apoptosis of HT-22 was detected by flow cytometry. BV-2 cells weretreated by SP600125, a JNK inhibitor. The NO release was detected by Griess method. Microglial polarization was detected by flow cytometry.Results1. The expression of apoE increased from 6h after SAH. The survival rate and rotarod latencies of APOE-/- mice were lower than WT mice. The cortical apoptosis and white matter injury of APOE-/- mice were more severe than that of WT mice. The microglial activation, expression of IL-1β、IL-6 、 TNF-α, and the phosphorylation levels of JNK, c-Jun and NF-κB were higher in APOE-/- mice than that of WT mice.2. The effective dose of COG1410 for treating SAH mice was 2mg/kg,and the timing was within 2h after SAH. The cortical apoptosis and white matter injury was attenuated by COG1410. COG1410 suppressed the microglial activation, regulated microglial polarization, reduced IL-1β 、IL-6、TNF-α expression, and inhibited the phosphorylation of JNK, c-Jun and NF-κB.3. COG1410 reduced the NO release from Hb-induced BV-2 cells.COG1410 inhibited M1 and promoted M2 polarization of BV-2 cells. The apoptotic rate of HT-22 cells treated by conditioned medium from Hb+COG1410 treated BV-2 cells was lower than that from Hb treated BV-2 cells. JNK phosphorylation of BV-2 cells was inhibited by COG1410.SP600125 reduced NO production from BV-2 cells and inhibited their M1 polarization. However, M2 polarization of BV-2 cells remained unchangedafter SP600125 treatment.ConclusionEndogenous apoE and apoE-derived mimic peptide, COG1410, reduce cortical apoptosis, white matter injury and neuroinflammation after SAH,which may account for the improved neurological functions of mice.COG1410 alleviates neuronal injury by suppressing microglial M1 polarization via inhibiting JNK signaling pathway.