Epsins Negatively Regulate Aortic Endothelial Cell Function by Augmenting Inflammatory Signaling

Abstract

Background: The endothelial epsin 1 and 2 endocytic adaptor proteins play an important role in atherosclerosis by regulating the degradation of the calcium release channel inositol 1,4,5-trisphosphate receptor type 1 (IP3R1). In this study, we sought to identify additional targets responsible for epsin-mediated atherosclerotic endothelial cell activation and inflammation in vitro and in vivo. Methods: Atherosclerotic ApoE−/− mice and ApoE−/− mice with an endothelial cell-specific deletion of epsin 1 on a global epsin 2 knock-out background (EC-iDKO/ApoE−/−), and aortic endothelial cells isolated from these mice, were used to examine inflammatory signaling in the endothelium. Results: Inflammatory signaling was significantly abrogated by both acute (tumor necrosis factor-α (TNFα) or lipopolysaccharide (LPS)) and chronic (oxidized low-density lipoprotein (oxLDL)) stimuli in EC-iDKO/ApoE−/− mice and murine aortic endothelial cells (MAECs) isolated from epsin-deficient animals when compared to ApoE−/− controls. Mechanistically, the epsin ubiquitin interacting motif (UIM) bound to Toll-like receptors (TLR) 2 and 4 to potentiate inflammatory signaling and deletion of the epsin UIM mitigated this interaction. Conclusions: The epsin endocytic adaptor proteins potentiate endothelial cell activation in acute and chronic models of atherogenesis. These studies further implicate epsins as therapeutic targets for the treatment of inflammation of the endothelium associated with atherosclerosis.

Targeting Epsins by nanotherapy regulates lipid metabolism and promotes ABCG1-mediated cholesterol efflux to fortify atheroma regression

“…As we show that silencing of lesional macrophage Epsins reduces necrotic core size, we reasoned that inhibiting Epsins may reinforce efferocytosis in macrophages, analogous to our observations in DKO macrophages (Brophy et al, 2019) given that efferocytosis plays a central role in regulating necrotic core formation (Gerlach et al, 2021; Kojima et al, 2017; Thorp et al, 2008). Despite the fact that S2P-NPs have been shown to only negligibly target the endothelium (Tao et al, 2020), whether S2PNP-siEpsin1/2 prohibits endothelial Epsins to synergistically curb atherosclerosis may require further investigation as deletion of endothelial Epsins also reduces inflammation and atherogenesis (Dong et al, 2020; Dong et al, 2021). Interestingly, we did not observe significant changes of the lipid profiles in the plasma from S2PNP-siCtrl and S2PNP-siEpsin1/2 treated ApoE -/- mice, suggesting either a minor liver targeting by S2PNP-siEpsin1/2 or that S2PNP-siEpsin1/2-mediated silencing of Epsins in liver could be inconsequential.…”

“…Despite their multifaceted functions, our previous work demonstrates that Epsins possess a vast degree of specificity and selectivity in choosing their binding partners. Therefore, the actions of Epsins are cell context-dependent (Brophy et al, 2019; Chang et al, 2015; Chen et al, 2009; Dong et al, 2020; Dong et al, 2021; Liu et al, 2014; Pasula et al, 2012; Tessneer et al, 2014). Notably, we demonstrated that myeloid-specific Epsins loss downregulated inflammation and impeded atheroma formation in an atherogenic mouse model by stabilizing macrophage LRP-1 (Brophy et al, 2019).…”

Targeting Epsins to Inhibit FGF Signaling while Potentiating TGF-β Signaling Constrains Endothelial-to-Mesenchymal-Transition in Atherosclerosis

“…Our data showed that atherosclerotic plaques can be significantly reduced by API peptide administration (Figure 7). However, we could not completely rule out the possibility that some of the API peptide targeted macrophages, which could provide additional anti-inflammatory benefits 30,[42][43][44] .…”

“…We previously reported that epsins bind to numerous receptors ( e.g., IP3R1, TNFR1, TLR2/4, and LRP1) via the UIM domain 30, 42–44 . This suggests that epsin UIM was a critical domain to regulate inflammatory receptors, which was the basis for the development of our therapeutic peptide.…”

“…Deletion of epsins in endothelial cells attenuates atherosclerosis by stabilizing IP3R1 degradation 29 and by blunting inflammatory signaling through TLR2/4 30 in the Apoe −/− atherosclerosis mouse model, suggesting that epsins promote atherosclerosis by modulating inflammatory signaling pathways. Macrophage-deficient epsins also reduce atherosclerosis by binding to the LDL Receptor-related Protein 1 (LRP-1) to increase efferocytosis 31 .…”