Apolipoprotein E4 Expression Causes Gain of Toxic Function in Isogenic Human Induced Pluripotent Stem Cell-Derived Endothelial Cells

Abstract

Objective: The ApoE (apolipoprotein) allele epsilon 4 is a major genetic risk factor for Alzheimer disease, cardiovascular disorders, and stroke, indicating that it significantly impacts cerebral and vascular systems. However, very little is known about how APOE genotype affects brain endothelial cells, which form a network of tight junctions to regulate communication between the brain and circulating blood factors. Approach and Results: Here, we present a novel model of endothelial dysfunction using isogenic human induced pluripotent stem cell-derived cells harboring different alleles of the APOE gene, specifically ApoE 3/3, 3/4, and 4/4. We show for the first time that ApoE4 expression by endothelial cells is sufficient to cause a toxic gain of cellular dysfunction. Using RNAseq, we found significant effects of ApoE4 on signaling pathways involved in blood coagulation and barrier function. These changes were associated with altered cell function, including increased binding of platelets to ECs with the 3/4 or 4/4 genotype. ApoE4-positive cells exhibited a proinflammatory state and prothrombotic state, evidenced by higher secretion of Aβ (amyloid-β) 40 and 42, increased release of cytokines, and overexpression of the platelet-binding protein VWF (vonWillebrand factor). Immunohistochemistry of human brain Alzheimer disease brains also showed increased VWF expression with the ApoE4/4 genotype. Finally, pharmacological inhibition of inflammation in ECs by celastrol rescued overexpression of VWF in cells expressing ApoE4. Conclusions: These cells provide novel insight into ApoE4-mediated endothelial dysfunction and provide a new platform to test potential therapies for vascular disorders.

Lipoprotein(a) and Its Potential Association with Thrombosis and Inflammation in COVID-19: a Testable Hypothesis

“…Relative to those of European and Asian descent, individuals of African descent may have up to twice the frequency of the E4 allele [ 65 , 66 ••]. APOE4 is also associated with a higher level of proinflammatory cytokines and promotes prothrombotic properties [ 67 ]. Furthermore, in an analysis of > 400,000 individuals, apoE4 isoforms strongly influenced mass levels of Lp(a) with 65% higher Lp(a) levels in APOE4/4 subjects (Fig.…”

Leaky memories: Impact of APOE4 on blood–brain barrier and dementia

“…5 Evidence from human induced pluripotent stem cell-derived endothelial cells harboring different APOE genotypes suggests endothelial cells themselves contribute to vascular dysfunction in APOE4 carriers. 6 Other pathways beyond MMP9 can also contribute. Robo4-paxillin-ARF6 signaling in endothelial cells has recently been identified as a key pathway for maintaining vascular integrity.…”

Human Induced Pluripotent Stem Cells as a Screening Platform for Drug-Induced Vascular Toxicity

“…To test the toxicity of a compound, the conventional approach is to apply it directly to a monolayer culture of target cells. Although they lack the sophisticated tissue architecture or biophysical stimulation (e.g., shear stress) present in vivo, numerous studies have demonstrated that iPSC-ECs or iPSC-SMCs cultured in monolayers respond to chemical or genetic stress in ways that are largely consistent with clinical observations or data from primary cells (Zhang et al, 2011;Cheung et al, 2012;Biel et al, 2015;Belair et al, 2016;Tang et al, 2017;Rieker et al, 2019;Chu et al, 2020). For instance, our lab recently found that e-cigarette liquid (e-liquid) triggered a broad array of molecular and functional disorders in iPSC-ECs, including activation of cell apoptosis, increased reactive oxygen species (ROS) production and LDL uptake, as well as reduced cell migration (Lee et al, 2019).…”