N‐acetylneuraminic acid modulates SQSTM1/p62 sialyation‐mediated ubiquitination degradation contributing to vascular endothelium dysfunction in experimental atherosclerosis mice

Abstract

Sialic acid (SIA) has been reported to be a risk factor for atherosclerosis (AS) due to its high plasma levels in such patients. However, the effect of increasing SIA in circulation on endothelial function during AS progression remains unclear. In the present study, ApoE−/− mice and endothelial cells line (HUVEC cells) were applied to investigate the effect of SIA on AS progression and its potential molecular mechanism. In vivo, mice were injected intraperitoneally with Neu5Ac (main form of SIA) to keep high‐level SIA in circulation. ORO, H&E, and Masson staining were applied to detect the plaque progression. In vitro, HUVECs were treated with Neu5Ac at different times, CCK‐8, RT‐PCR, western blot, and immunoprecipitation methods were used to analyze its effects on endothelial function and the potential involved mechanism. Results from the present study showed that high plasma levels of Neu5Ac in ApoE−/− mice could aggravate the plaque areas as well as increase necrotic core areas and collagen fiber contents. Remarkably, Neu5Ac levels in circulation displayed a positive correlation with AS plaque areas. Furthermore, results from HUVECs showed that Neu5Ac inhibited cells viability in a time/dose‐dependent manner, by then induced the activation of inflammation makers such as ICAM‐1 and IL‐1β. Mechanism study showed that the activation of excessive autophagy medicated by SQSTM1/p62 displayed an important role in endothelium inflammatory injury. Neu5Ac could modify SQSTM1/p62 as a sialylation protein, and then increase its level with ubiquitin binding, further inducing ubiquitination degradation and being involved in the excessive autophagy pathway. Inhibition of sialylation by P‐3Fax‐Neu5Ac, a sialyltransferase inhibitor, reduced the binding of SQSTM1/p62 to ubiquitin. Together, these findings indicated that Neu5Ac increased SQSTM1/p62‐ubiquitin binding through sialylation modification, thereby inducing excessive autophagy and subsequent endothelial injury. Inhibition of SQSTM1/p62 sialylation might be a potential strategy for preventing such disease with high levels of Neu5Ac in circulation.

Single-Cell Transcriptomic Profiling Unveils Critical Metabolic Alterations and Signatures in Progression of Atherosclerosis

“…Several studies have investigated sialic acid levels in individuals with AS or those at high risk of AS [30,31,[33][34][35][36][37][38][39]. The results showed that sialic acid levels in patients with heart failure, acute coronary syndrome, coronary atherosclerosis, type 2 diabetes mellitus and hyperlipidemic were higher than the relative control group (Table 1), further confirmed that sialic acid could be a potential metabolic maker to indicate the disease progression as we reported previously.…”

“…Epidemiological studies have revealed that the elevated plasma sialic acid especially Neu5Ac was highly associated with the increased risk of cardiovascular events [47]. And our previous results also pointed out the pro-atherosclerotic effect of sialic acid through inducing endothelial inflammatory injury or promoting macrophage M1 polarization [30, 33, 48]. However, the mechanism underlying the accumulation of sialic acid in AS plaque still needs further explore.…”

“…Specially, our present results have indicated that the intermediate metabolites from glycolysis/hexosamine/sialic acid metabolism displayed an obvious increase in myeloid cells and ECs, indicating that dysfunction of glucose to sialic acid metabolism might play essential roles in maintaining the homeostasis of those cells. Moreover, sialic acid is a component of cell surface sugar moieties, and accumulation of sialic acid in plasma has been reported to be highly associated with AS progression [33].…”