The Role And Mechanism Of Blood Components In Acute White Matter Injury After Intraventricular Hemorrhage

BackgroundIntraventricular hemorrhage(IVH)refers to blood within the ventricular system of the brain,which could be classified as primary IVH and secondary IVH.The primary IVH is extremely rare,whereas secondary IVH is more common,relatively.About 40%ICH patients and up to 70%SAH patients exhibit complication of IVH,and the presence of IVH is closely related to high mortality and negative outcomes for both ICH and SAH patients.However,the mechanisms of IVH have not been well studied.Exploring the potential mechanisms may provide a new target for IVH patient treatment.The central nervous system consists of the following two types of brain tissue:gray matter and white matter.In humans,nearly half of the brain is composed of gray matter and half is composed of white matter.The gray matter is mainly composed of neuronal cell bodies and unmyelinated axons while the white matter contains myelinated axon tracts and,supporting glia cells,including oligodendrocytes,astrocytes and microglia.White matter is believed to be passive tissue that acts as a relay and coordinates communication among different regions of gray matter.More and more clinicians and researchers realize that white matter injury occurred in many neurological diseases,and related to function outcome.However,the role and mechanisms of WMI after IVH remain unknown.Blood components and subsequent metabolites play an important role in brain injury after hemorrhagic stroke.Complement activation and MAC formation induced red blood cells lysis and subsequent release of hemoglobin and iron,which cause brain injury.minocycline is a chelator of iron,which blocks the iron-induced injury.Thrombin also induced brain injury after hemorrhagic stroke.SCH79797 is an inhibitor of PAR-1,which is a critical effector of thrombin.However,the role of these blood component in WHI remain unknown.With the increasing awareness of blood metabolism in hemorrhagic stroke,more and more studies have discovered drugs that targeting different blood components.Heparin is well-known to bind the complement proteins and regulate the complement cascade,which initiates the erythrocytes lysis.Heparin may also bind and inactivate thrombin.However,whether these drugs could alleviate WMI after IVH remain unknown.In the current study,we investigated whether intraventricular injection of autologous blood induced white matter injury and the role of blood components such as thrombin and iron as well as the effects of heparin,SCH79797 and minocycline in WMI after IVH.MethodsPart 11.Male SD rats received a 200-?L injection of saline or autologous blood into the right lateral ventricle.7.0T MRI scanning was performed at 24h after IVH induction.The sequence is T2 WI,the T2-hyperintensity volume was measured by Image J.Immunohistochemistry,HE staining,RT-PCR and western blot were performed to measure the expression of markers of WMI,such as MBP,and inflammation as well as apoptosis.2.Male SD rats had an intraventricular injection of 50-?L packed red blood cells(RBC)or lysed RBC.7.0T MRI scanning was performed at 24h after IVH induction.The sequence is T2 WI,the T2-hyperintensity volume was measured by Image J.Immunohistochemistry was performed to measure the expression of markers of WMI,such as MBP,dMBP and ?-APP.Part 21.Male SD rats received intraventricular injection of 200-?L of saline,iron(0.5mM)or minocycline(1.5mM).7.0T MRI scanning was performed at 24h after IVH induction.The sequence is T2 WI,the T2-hyperintensity volume was measured by Image J.Immunohistochemistry was performed to measure the expression of markers of WMI,such as MBP,dMBP and ?-APP.2.Male SD rats had an intraventricular injection of 50-?L saline,Thrombin(3 units)or SCH79797(0.15Nm).7.0T MRI scanning was performed at 24h after IVH induction.The sequence is T2 WI,the T2-hyperintensity volume was measured by Image J.Immunohistochemistry and western blot was performed to measure the expression of markers of WMI,such as MBP,dMBP and p-APPPart 31.Male SD rats had an intraventricular injection of 200-?Lsaline,autologous blood or heparinized blood(5 units heparin).7.0T MRI scanning was performed at 24h after IVH induction.The sequence is T2 WI,the T2-hyperintensity volume was measured by Image J.Western blot and TUNEL staining were performed to measure markers of WMI,such as MBP,dMBP and ?-APP,and apoptosis in white matter.ResultPart 11.Intraventricular injection of autologous blood(200-?l)resulted in overload of red blood cells and broken white matter,disrupted blood brain barrier;increased T2-hyperintensity volume in white matter.MBP expression is significantly reduced,while levels of dMBP,?-APP;NLRP3 inflammmasome activation and proinflammatory cytokines increased;apoptosis of mature oligodendrocytes increased compared with the vehicle group.2.Intraventricular injection of lysed RBC(50-?l)increased T2-hyperintensity volume in white matter.MBP expression is significantly reduced,while levels of dMBP,?-APP,indicating that intraventricular injection of lysed RBC resulted in white matter injury.Part 21.Intraventricular injection of iron(0.5mM)increased T2-hyperintensity volume in white matter.MBP expression is significantly reduced,while levels of dMBP,?-APP increased compared with the vehicle group.Minocycline blocked iron-induced white matter injury.2.Intraventricular injection of thrombin(3 units)increased T2-hyperintensity volume in white matter.MBP expression is significantly reduced,while levels of dMBP,?-APP increased compared with the vehicle group.SCH79797 reduced thrombin-induced white matter injuryPart 31.Compared with autologous blood injection,injection of heparinized blood reduced the T2-hyperintensity areas in white matter,increased MBP levels and reduced dMBP and ?-APP levels.Heparin also reduced apoptotic cells in white matter.ConclusionPart 1Experimental IVH resulted in severe white matter injury.NLRP3 inflammasome activation and apoptosis of mature oligodendrocytes were involved in white matter injury after IVH.RBC lysis play an important role in white matter injury after IVHPart 2Iron and thrombin injection induced white matter injury,minocycline and SCH79797 reduced iron and thrombin-induced white matter injury,indicating that iron and thrombin play an important role in white matter injury after IVH.a promising treatment target for WMI after IVH.Part 3Heparin reduced the severe white matter injury,providing a potent treatment for white matter injury after IVH.