A potential early-atheroprotective target: Irgm1 mediates lymphangiogenesis through LEC autophagy by Tfeb translocation.

Lymphatic dysfunction is a pivotal pathological mechanism underlying the development of early atherosclerotic plaques. Potential targets of lymphatic function must be identified to realize the early prevention and treatment of atherosclerosis (AS). The immunity-related GTPase Irgm1 is involved in orchestrating cellular autophagy and apoptosis. However, the effect of Irgm1 on early AS progression, particularly through alterations in lymphatic function, remains unclear. In this study, we confirmed the protective effect of lymphangiogenesis on early-AS in vivo. Subsequently, an in vivo model of early AS mice with Irgm1 knockdown shows that Irgm1 reduces early atherosclerotic plaque burden by promoting lymphangiogenesis. Given that lymphatic endothelial cell (LEC) autophagy significantly contributes to lymphangiogenesis, Irgm1 may enhance lymphatic circulation by promoting LEC autophagy. Moreover, Irgm1 orchestrates autophagy in LECs by inhibiting mTOR and facilitating nuclear translocation of Tfeb. Collectively, these processes lead to lymphangiogenesis. Thus, this study establishes a link between Irgm1 and early AS, thus revealing a novel mechanism by which Irgm1 exerts an early protective influence on AS within the context of lymphatic circulation. The insights gained from this study have the potential to revolutionize the approach and management of AS onset.

Arsenic trioxide alleviates atherosclerosis by inhibiting CD36-induced endocytosis and TLR4/NF-κB-induced inflammation in macrophage and ApoE-/- mice.

BACKGROUND: Inflammation and lipid accumulation are key events in atherosclerosis progression. Despite arsenic trioxide's (ATO) toxicity, at appropriate doses, it is a useful treatment for various diseases treatment. ATO prevents vascular restenosis; however, its effects on atherosclerotic plaque development and instability remain unclear. METHODS: ApoE-/- mice were fed high-fat diet for 4 months, and starting at the third month, ATO was intravenously administered every other day. Atherosclerotic lesion size, histological characteristics, and related protein and lipid profiles were assessed using samples from the aorta, carotid artery, and serum. The anti-inflammatory and anti-pyroptosis effects of ATO were investigated by stimulating RAW264.7 and THP-1 cell lines with oxidized low-density lipoprotein (ox-LDL) or lipopolysaccharide (LPS). RESULTS: ATO reduced atherosclerotic lesion formation and plasma lipid levels in ApoE-/- mice. In the serum and aortic plaques, ATO reduced the levels of pro-inflammatory factors, including interleukin (IL) 6 and tumor necrosis factor α, but increased IL-10 levels. Mechanistically, ATO promoted the CD36-mediated internalization of ox-LDL in a peroxisome proliferator-activated receptor γ-dependent manner. Furthermore, ATO downregulated Toll-like receptor 4 (TLR4) expression in plaques and macrophages and inhibited p65 nuclear translocation and IκBα degradation. ATO reduced macrophage pyroptosis by downregulating NLR family pyrin domain-containing 3 (NLRP3) expression and caspase 1 activation. CONCLUSION: ATO has potential atheroprotective effects, especially in macrophages. The mechanisms were inhibition of CD36-mediated foam cell formation and suppression of inflammatory responses and pyroptosis mediated by TLR4/nuclear factor κB and NLRP3 activation. Our findings provide evidence supporting the potential atheroprotective value of ATO.

Methylmalonic acid, vitamin B12, and mortality risk in patients with preexisting coronary heart disease: a prospective cohort study.

BACKGROUND: The inconsistent relationship between Vitamin B12 (B12), methylmalonic acid (MMA, marker of B12 deficiency) and mortality was poorly understood, especially in patients with coronary heart disease (CHD). This study aims to investigate the association of serum MMA, and B12-related biomarkers (serum level, dietary intake, supplement use, and sensibility to B12) with all-cause and cardiovascular mortality in adults with CHD. METHODS: The data of this study were from a subcohort within the US National Health and Nutrition Examination Survey (NHANES). We included adults with preexisting CHD with serum MMA and B12, and dietary B12 intake measurements at recruitment. All participants were followed up until 31 December 2019. Weighted Cox proportional hazard regression was used to estimate hazard ratios (HR) and 95% CI of mortality risk. RESULTS: Overall, 1755 individuals (weighted mean [SE] age, 65.2 [0.5] years; 1047 men [weighted 58.5%]) with CHD were included, with geometric mean levels of serum MMA 182.4 nmol/L, serum B12 494.5 pg/ml, and dietary B12 intake 4.42 mg/day, and percentage of B12 supplements use 39.1%. During a median follow-up of 7.92 years, 980 patients died. Serum B12 concentration, dietary B12 intake and supplements use were not significantly associated with mortality risk (each p ≥ 0.388). In contrast, individuals in the top tertile of MMA had multivariable-adjusted HRs (95% CIs) of 1.70 (1.31-2.20) for all-cause mortality, and 2.00 (1.39-2.89) for cardiovascular mortality (both p trend < 0.001) compared to those in the bottom tertile of MMA. MMA-related mortality risk was particularly higher among participants with sufficient serum B12 (p < 0.001). CHD patients with increased levels of both MMA and B12 had a doubled mortality risk compared to those with lower MMA and B12 (p < 0.001). CONCLUSION: MMA accumulation but not serum or dietary vitamin B12 was associated with increased cardiovascular mortality risk among patients with CHD. This paradox may be related to decreased response to vitamin B12.

IRGM/Irgm1 deficiency inhibits neutrophil-platelet interactions and thrombosis in experimental atherosclerosis and arterial injury.

BACKGROUND: Neutrophil extracellular traps (NETs) closely link inflammation and thrombosis. The immune-related GTPase family M protein (IRGM) and its ortholog of mouse IRGM1 are positively correlated with plaque rupture during atherosclerosis process. However, whether and how IRGM/IRGM1 affects NETs formation and atherosclerotic thrombosis remains unknown, which will further promote the development of antithrombotic treatment tools. METHODS: The thrombi images, platelet activation makers and NETs makers were detected in the serum of STEMI patients and controls. To futher investigate IRGM/IRGM1 affects NETs formation and atherothrombosis in vivo, ApoE-/-Irgm1+/- and ApoE-/- mice received diets rich in fat and 2.5% FeCl3 was then used to induce experimental arterial thrombosis in an atherosclerosis background. In vitro, PMA and thrombin were used to stimulate neutrophils and platelets, respectively, and the expression of IRGM/IRGM1 were modified. To reveal the molecular mechanisms, MAPK-cPLA2 signals inhibitors were used. RESULTS: Serum IRGM was positively correlated with PF4 and neutrophil elastase. Subsequently, Irgm1 deficient mice have a longer occlusion time and lower growth rate. In vitro, as expected, IRGM/Irgm1 deficiency inhibits platelet activation and platelet-neutrophil interaction. More importantly, IRGM promoted NETs production through activating MAPK-cPLA2 signals in PMA stimulated neuropils, whereas inhibiting the production of NETs eliminated the difference in platelet activation and thrombosis caused by IRGM/Irgm1 modification in vivo and vitro. Similarly, inhibition of platelet activation also eliminated the influence of IRGM/Irgm1 modification on NETs production. CONCLUSIONS: Overall, our data indicate that IRGM/Irgm1 deficiency in neuropils inhibits the intense interaction between neutrophils and platelets, and ultimately inhibits thrombosis.