Association between Apolipoprotein E Polymorphism and Clinical Outcome after Ischemic Stroke, Intracerebral Hemorrhage, and Subarachnoid Hemorrhage

Apolipoproteins in ischemic stroke progression and recovery: Key molecular mechanisms and therapeutic potential

Ischemic stroke, responsible for 80 % of all strokes, is a leading cause of mortality globally. While altered lipids profiles are recognized as modifiable risk factors, their direct impact on stroke outcomes is less understood due to the brain's distinct lipid metabolism and the selective permeability of the blood-brain barrier for lipoproteins. As key components of lipoproteins, apolipoproteins are essential for lipid transport, redistribution and metabolism in both the central nervous system and peripheral blood circulation. This review provides an updated perspective on the influence of brain-expressed apolipoproteins (such as ApoE, ApoA-I, ApoJ, ApoD, and others) and those that cross the damaged blood-brain barrier following ischemic stroke. We explore hypotheses regarding their involvement in molecular pathways related to lipid metabolism, inflammation, oxidative stress, mitochondrial function and blood-brain barrier integrity. Through this synthesis, we aim to identify potential biomarkers and therapeutic targets, thereby enhancing our understanding of apolipoproteins in ischemic stroke progression and contributing to improved clinical outcomes.

Intervention Role of APOE in CNS Diseases: APOE Actions and APOE Neurogenesis Capability

Neurogenesis is a biological process in which new neurons are generated from neural stem cells (NSCs) in specific neural niches in the brain. Impaired neurogenesis, characterized by the progressive loss of neurons, leads to cognitive and motor disabilities and is a hallmark of central nervous system (CNS) diseases. Conversely, enhancing neurogenesis has been shown to alleviate the symptoms of CNS diseases. Apolipoprotein E (APOE) is a protein that plays various biological roles in CNS diseases. Emerging research indicates that APOE is involved in adult neurogenesis, which is crucial for maintaining the neural progenitor pool in the dentate gyrus (DG) and synaptic activity. Therefore, APOE could be a therapeutic target for promoting neurogenesis in the treatment and intervention of CNS diseases. In this context, we present a comprehensive overview of the clinical evidence supporting the role of APOE in CNS diseases on the basis of a meta-analysis. We also discuss the neurogenic potential of APOE, which has significant implications not only for understanding the biological underpinnings of neurological diseases but also for developing novel treatment strategies for CNS diseases.

Apolipoprotein E-ε4 allele is associated with perihematomal brain edema and poor outcomes in patients with intracerebral hemorrhage

Intracerebral hemorrhage (ICH) poses significant disability and mortality risks and perihematomal edema (PHE) plays a crucial role in ICH prognosis. The ApoE-ε4 allele has been implicated in exacerbating PHE and influencing neurological recovery post-ICH, yet, this specific association has not been explored much. This study aimed to investigate the correlation between ApoE-ε4 allele, PHE, and clinical prognosis in patients with ICH. We conducted a prospective observational cohort study at the Affiliated Hospital of Guizhou Medical University from January 2020 to December 2023. We enrolled patients with supratentorial ICH patients and analyzed ApoE gene alleles, clinical baseline data, blood biochemical indices, and imaging findings. We considered ApoE-ε4 carrier status as an exposure variable and compared PHE volumes between ApoE-ε3 (ε3/ε3) and ApoE-ε4 (ε2/ε4, ε3/ε4, ε4/ε4) carriers. We also compared clinical and imaging characteristics between the good prognosis group (modified Rankin score 0-3) and the poor prognosis group (modified Rankin score 4-6). Finally, we examined the association between ApoEε4 and PHE volume and poor prognosis at discharge. Among 153 patients, 63 (41%) carried ApoE-ε4. ApoE-ε4 carriers had significantly higher PHE volumes at 24 h and on days 5-7 compared to ApoE-ε3 carriers. The poor prognosis group had a higher proportion of ApoE-ε4 carriers (53.9% vs. 28.6%, p = 0.001) and increased PHE volumes. ApoE-ε4 (OR 2.438, p = 0.02) and PHE (OR 1.048, p = 0.015) were independent predictors of poor prognosis. The area under the curve for ApoE-ε4 was 0.627, and for PHE volume, it was 0.698. The ICH patients carrying the ApoE-ε4 allele show severe PHE and poorer outcomes. Carrying ApoE-ε4 gene is an independent predictor for poor outcomes in patients with ICH.Trial registration: ClinicalTrials.gov, NCT05687201. Registered June 1, 2023, Effect of Apolipoprotein E on the Prognosis of Patients with Intracerebral Hemorrhage-Full Text View-ClinicalTrials.gov "prospective registered".

Apolipoprotein E Polymorphism Impacts White Matter Injury Through Microglial Phagocytosis After Experimental Subarachnoid Hemorrhage

Apolipoprotein E (apoE, protein; APOE, gene), divided into three alleles of E2, E3 and E4 in humans, is associated with the progression of white matter lesion load. However, mechanism evidence has not been reported regarding the APOE genotype in early white matter injury (WMI) under subarachnoid hemorrhage (SAH) conditions. In the present study, we investigated the effects of APOE gene polymorphisms, by constructing microglial APOE3 and APOE4-specific overexpression, on WMI and underlying mechanisms of microglia phagocytosis in a mice model of SAH. A total of 167 male C57BL/6J mice (weight 22-26 g) were used. SAH and bleeding environment were induced by endovascular perforation in vivo and oxyHb in vitro, respectively. Multi-technology approaches, including immunohistochemistry, high throughput sequencing, gene editing for adeno-associated viruses, and several molecular biotechnologies were used to validate the effects of APOE polymorphisms on microglial phagocytosis and WMI after SAH. Our results revealed that APOE4 significantly aggravated the WMI and decreased neurobehavioral function by impairing microglial phagocytosis after SAH. Indicators negatively associated with microglial phagocytosis increased like CD16, CD86 and the ratio of CD16/CD206, while the indicators positively associated with microglial phagocytosis decreased like Arg-1 and CD206. The increased ROS and aggravating mitochondrial damage demonstrated that the damaging effects of APOE4 in SAH may be associated with microglial oxidative stress-dependent mitochondrial damage. Inhibiting mitochondrial oxidative stress by Mitoquinone (mitoQ) can enhance the phagocytic function of microglia. In conclusion, anti-oxidative stress and phagocytosis protection may serve as promising treatments in the management of SAH.

Association between Apolipoprotein E genotype and functional outcome in acute ischemic stroke

This study aims to determine whether APOE alleles would affect the functional outcome in acute ischemic stroke (AIS) and whether the relationship between inflammation and stroke-related disability varies according to APOE genotypes. We retrospectively collected the demographic and clinical data of AIS patients within one week of symptom-onset through medical records review. The primary outcome was dependence or death, defined as modified Rankin scale (mRS) score of 2-6, which was assessed at 3 months. Among 1929 enrolled patients, the prevalence of APOE ε4 carriers was 17.73% (342/1929). There were 394 AIS patients (394/1929, 20.43%) showed poor function outcome of 90-day mRS (2-6), of whom 147 (147/342, 42.98%) were APOE ε4 carriers and 247 (247/1587, 15.56%) were non-ε4 carriers. There was a significant increased probability of poor functional outcome after AIS among APOE ε4 carriers versus non-ε4 carriers (adjusted-OR 4.62, 95% CI 3.51 to 6.09, P < 0.001). Among ε4 carriers, high neutrophil-to-lymphocyte ratio (NLR) was significantly associated with stroke-related disability (Ptrend = 0.035); however, no significant association was observed among non-ε4 carriers. Our study showed that the APOE ε4 carriers had worse functional outcome after AIS as compared with non-ε4 carriers. APOE genotype may modify the relationship between NLR and 3-month stroke outcome.