Macrophage ALDH2 (Aldehyde Dehydrogenase 2) Stabilizing Rac2 Is Required for Efferocytosis Internalization and Reduction of Atherosclerosis Development.

BACKGROUND: Clinical studies show that the most common single-point mutation in humans, ALDH2 (aldehyde dehydrogenase 2) rs671 mutation, is a risk factor for the development and poor prognosis of atherosclerotic cardiovascular diseases, but the underlying mechanism remains unclear. Apoptotic cells are phagocytosed and eliminated by macrophage efferocytosis during atherosclerosis, and enhancement of arterial macrophage efferocytosis reduces atherosclerosis development. METHODS: Plaque areas, necrotic core size, apoptosis, and efferocytosis in aortic lesions were investigated in APOE-/- mice with bone marrow transplanted from APOE-/-ALDH2-/- and APOE-/- mice. RNA-seq, proteomics, and immunoprecipitation experiments were used to screen and validate signaling pathways affected by ALDH2. Efferocytosis and protein levels were verified in human macrophages from wild-type and rs671 mutation populations. RESULTS: We found that transplanting bone marrow from APOE-/-ALDH2-/- to APOE-/- mice significantly increased atherosclerosis plaques compared with transplanting bone marrow from APOE-/- to APOE-/- mice. In addition to defective efferocytosis in plaques of APOE-/- mice bone marrow transplanted from APOE-/-ALDH2-/- mice in vivo, macrophages from ALDH2-/- mice also showed significantly impaired efferocytotic activity in vitro. Subsequent RNA-seq, proteomics, and immunoprecipitation experiments showed that wild-type ALDH2 directly interacted with Rac2 and attenuated its degradation due to decreasing the K48-linked polyubiquitination of lysine 123 in Rac2, whereas the rs671 mutant markedly destabilized Rac2. Furthermore, Rac2 played a more crucial role than other Rho GTPases in the internalization process in which Rac2 was up-regulated, activated, and clustered into dots. Overexpression of wild-type ALDH2 in ALDH2-/- macrophages, rather than the rs671 mutant, rescued Rac2 degradation and defective efferocytosis. More importantly, ALDH2 rs671 in human macrophages dampened the apoptotic cells induced upregulation of Rac2 and subsequent efferocytosis. CONCLUSIONS: Our study has uncovered a pivotal role of the ALDH2-Rac2 axis in mediating efferocytosis during atherosclerosis, highlighting a potential therapeutic strategy in cardiovascular diseases, especially for ALDH2 rs671 mutation carriers.

Prevention of aortic dissection and aneurysm via an ALDH2-mediated switch in vascular smooth muscle cell phenotype.

AIMS: Aortic aneurysm/dissection (AAD) is a life-threatening disorder lacking effective pharmacotherapeutic remedies. Aldehyde dehydrogenase 2 (ALDH2) polymorphism is tied with various risk factors for AAD including hypertension, atherosclerosis, and hypercholesterolaemia although direct correlation between the two remains elusive. METHODS AND RESULTS: Two independent case-control studies were conducted involving 307 AAD patients and 399 healthy controls in two geographically distinct areas in China. Our data revealed that subjects carrying mutant ALDH2 gene possessed a ∼50% reduced risk of AAD compared with wild-type (WT) alleles. Using 3-aminopropionitrile fumarate (BAPN)- and angiotensin II (Ang II)-induced AAD animal models, inhibition of ALDH2 was found to retard development of AAD. Mechanistically, ALDH2 inhibition ablated pathological vascular smooth muscle cell (VSMC) phenotypical switch through interaction with myocardin, a determinant of VSMC contractile phenotype. Using microarray and bioinformatics analyses, ALDH2 deficiency was found to down-regulate miR-31-5p, which further altered myocardin mRNA level. Gain-of-function and loss-of-function studies verified that miR-31-5p significantly repressed myocardin level and aggravated pathological VSMC phenotypical switch and AAD, an effect that was blunted by ALDH2 inhibition. We next noted that ALDH2 deficiency increased Max expression and decreased miR-31-5p level. Moreover, ALDH2 mutation or inhibition down-regulated levels of miR-31-5p while promoting myocardin downstream contractile genes in the face of Ang II in primary human VSMCs. CONCLUSIONS: ALDH2 deficiency is associated with a lower risk of AAD in patients and mice, possibly via suppressing VSMC phenotypical switch in a miR-31-5p-myocardin-dependent manner. These findings favour a role for ALDH2 and miR-31-5p as novel targets for AAD therapy.

Aldehyde dehydrogenase 2 inhibited oxidized LDL-induced NLRP3 inflammasome priming and activation via attenuating oxidative stress.

Oxidized low-density lipoprotein (ox-LDL)-mediated NLRP3 inflammasome activation is crucial in atherosclerosis (AS) initiation and progression. Aldehyde dehydrogenase 2 (ALDH2) has been reported to display protective effects during AS development; however, the underlying mechanisms are largely unknown. Here we investigate the role of ALDH2 in ox-LDL-induced NLRP3 inflammasome priming and activation. We treated RAW264.7 murine macrophages with ox-LDL with or without ALDH2 activator Alda-1 and measured NLRP3 inflammasome priming and activation, ALDH2 protein expression and enzyme activity, IL-1ß release, and DNA damage. It was found that ox-LDL impaired ALDH2 activity and induced NLRP3 inflammasome priming and activation. Alda-1 inhibited both of the priming and activation steps of NLRP3 inflammasome as well as subsequent cell pyroptosis and attenuated ROS and 4-HNE levels in ox-LDL-treated macrophages. Taken together, ALDH2 activation inhibits priming and activation of NLRP3 inflammasome via reducing oxidative stress, which suggests that ALDH2 may be a potential target for anti-inflammatory therapies in AS treatment.

Aldehyde dehydrogenase 2 protects against sympathetic excitation-induced cardiac fibrosis.

Sympathetic stimulated-cardiac fibrosis imposes great significance on both disease progression and survival in the pathogenesis of many cardiovascular diseases. However, there are few effective therapies targeting it clinically. The cardioprotective effect of aldehyde dehydrogenase 2 (ALDH2) has been explored in many pathological conditions, whether it can exert benefit effects on chronic sympathetic stimulus-induced cardiac fibrosis remains unclear. In this study, we determined to explore the role of ALDH2 on isoproterenol (ISO)-induced cardiac fibroblasts (CF) proliferation and cardiac fibrosis. It was found that ALDH2 enzymatic activity was impaired in ISO-induced HCF proliferation and Aldh2 deficiency promoted mouse CF proliferation. Alda-1, an ALDH2 activator, exerted obvious suppressive effect on ISO-induced HCF proliferation, together with the induction of cell cycle arrest at G0/G1 phase and decreased expression of cyclin E1 and cyclin-dependent kinase 2 (CDK2). Mechanistically, the inhibitory role of Alda-1 on HCF proliferation was achieved by decreasing mitochondrial reactive oxygen species (ROS) production, which was partially reversed by rotenone, an inducer of ROS. In addition, wild-type mice treated with Alda-1 manifested with reduced fibrosis and better cardiac function after ISO pump. In summary, Alda-1 alleviates sympathetic excitation-induced cardiac fibrosis via decreasing mitochondrial ROS accumulation, highlighting ALDH2 activity as a promising drug target of cardiac fibrosis.

Mitochondrial Ca2+ regulation in the etiology of heart failure: physiological and pathophysiological implications.

Heart failure (HF) represents one of the leading causes of cardiovascular diseases with high rates of hospitalization, morbidity and mortality worldwide. Ample evidence has consolidated a crucial role for mitochondrial injury in the progression of HF. It is well established that mitochondrial Ca2+ participates in the regulation of a wide variety of biological processes, including oxidative phosphorylation, ATP synthesis, reactive oxygen species (ROS) generation, mitochondrial dynamics and mitophagy. Nonetheless, mitochondrial Ca2+ overload stimulates mitochondrial permeability transition pore (mPTP) opening and mitochondrial swelling, resulting in mitochondrial injury, apoptosis, cardiac remodeling, and ultimately development of HF. Moreover, mitochondria possess a series of Ca2+ transport influx and efflux channels, to buffer Ca2+ in the cytoplasm. Interaction at mitochondria-associated endoplasmic reticulum membranes (MAMs) may also participate in the regulation of mitochondrial Ca2+ homeostasis and plays an essential role in the progression of HF. Here, we provide an overview of regulation of mitochondrial Ca2+ homeostasis in maintenance of cardiac function, in an effort to identify novel therapeutic strategies for the management of HF.

Inhibition of cardiac hypertrophy by aromadendrin through down-regulating NFAT and MAPKs pathways.

Cardiac hypertrophy is a maladaptive response to pressure overload and it's an important risk factor for heart failure and other adverse cardiovascular events. Aromadendrin (ARO) has remarkable anti-lipid peroxidation efficacy and is a potential therapeutic medicine for the management of diabetes and cardiovascular diseases. In this study, we established the cardiac hypertrophy cell model in rat neonatal ventricular cardiomyocytes (RNVMs) with phenylephrine. The cell model was characterized by the increased protein synthesis and cardiomyocyte size, which can be normalized by ARO treatment in both concentration- and time-dependent manner. In transverse aortic constriction (TAC) induced cardiac hypertrophy model, ARO administration improved the impairment of cardiac function and alleviated the cardiac hypertrophy indicators, like ventricular mass/body weight, myocyte cross-sectional area, and the expression of ANP, BNP and Myh7. ARO treatment also suppressed the cardiac fibrosis and the correlated fibrogenic genes. Our further investigation revealed ARO could down-regulate pressure overload-induced Malondialdehyde (MDA) and 4-HNE expression, restore the decrease of GSH/GSSG ratio, meanwhile prevent nuclear translocation of NFAT and the activation of MAPKs pathways. Collectively, ARO has a protective effect against experimental cardiac hypertrophy in mice, suggesting its potential as a novel therapeutic drug for pathological cardiac hypertrophy.

ALDH2 mediates the dose-response protection of chronic ethanol against endothelial senescence through SIRT1/p53 pathway.

Aldehyde dehydrogenase 2 (ALDH2) plays essential roles in drinking-associated diseases or effects. As we have previously reported, ALDH2 mediates acute ethanol-induced eNOS activation in vitro. However, whether chronic ethanol treatment has a dose-response endothelial protection, as well as the possible mediating role of ALDH2 involved, is unclear. Here, we show that appropriate dose of ethanol preserved the expression and activity of ALDH2 and eNOS, and alleviated senescence-associated phenotypes in human aortic endothelial cells. Furthermore, ALDH2 deficiency impairs the dose-response protection of ethanol against endothelial senescence by promoting the accumulation of 4-HNE, the formation of 4-HNE-SIRT1 protein adducts and the subsequent decrease in SIRT1-dependent p53 deacetylation. Collectively, our data indicate that ALDH2 mediates the protection of appropriate ethanol by modulating SIRT1/p53-dependent endothelial senescence.

Bottom-up synthesis of MoS2 nanospheres for photothermal treatment of tumors.

Photothermal therapy (PTT) is providing new opportunities for killing cancer cells. In this work, we introduce a new nanomedicine based on spherical MoS2 nanoparticles for PTT treatment of tumors, prepared using "green" bottom-up technology. To increase water solubility and avoid rapid clearance by the reticuloendothelial system, polyethylene glycol (PEG) was used to coat them. These MoS2-PEG nanospheres with an appropriate size (∼100 nm) exhibit high photothermal conversion efficiency (26.7%). In vitro cellular studies revealed that the MoS2-PEG nanospheres showed negligible cytotoxicity. Additionally, through combining the MoS2-PEG nanosphere samples with NIR irradiation at 808 nm, excellent in vitro tumor cell killing efficacy was achieved. In the 4T1 tumor model, the MoS2-PEG nanospheres exhibited good antitumor efficiency in vivo, displaying complete tumor inhibition over 16 days after treatment. Therefore, MoS2-PEG nanospheres played an important role in tumor destruction, and this concept for developing spherical MoS2-based nanomedicines can serve as a platform technology for the next generation of in vivo PTT agents.

CAT-1 as a novel CAM stabilizes endothelial integrity and mediates the protective actions of L-Arg via a NO-independent mechanism.

Interendothelial junctions play an important role in the maintenance of endothelial integrity and the regulation of vascular functions. We report here that cationic amino acid transporter-1 (CAT-1) is a novel interendothelial cell adhesion molecule (CAM). We identified that CAT-1 protein localized at cell-cell adhesive junctions, similar to the classic CAM of VE-cadherin, and knockdown of CAT-1 with siRNA led to an increase in endothelial permeability. In addition, CAT-1 formed a cis-homo-dimer and showed Ca(2+)-dependent trans-homo-interaction to cause homophilic cell-cell adhesion. Co-immunoprecipitation assays showed that CAT-1 can associate with ß-catenin. Furthermore, we found that the sub-cellular localization and function of CAT-1 are associated with cell confluency, in sub-confluent ECs CAT-1 proteins distribute on the entire surface and function as L-Arg transporters, but most of the CAT-1 in the confluent ECs are localized at interendothelial junctions and serve as CAMs. Further functional characterization has disclosed that extracellular L-Arg exposure stabilizes endothelial integrity via abating the cell junction disassembly of CAT-1 and blocking the cellular membrane CAT-1 internalization, which provides the new mechanisms for L-Arg paradox and trans-stimulation of cationic amino acid transport system (CAAT). These results suggest that CAT-1 is a novel CAM that directly regulates endothelial integrity and mediates the protective actions of L-Arg to endothelium via a NO-independent mechanism.

SALVIANOLIC ACID A ATTENUATES ANGIOTENSIN II-INDUCED CARDIAC FIBROSIS THROUGH REGULATING THE TXNIP SIGNALING PATHWAY.

ABSTRACT: Cardiac fibrosis, characterized by excessive collagen accumulation in heart tissues, poses a significant clinical challenge in various heart diseases and complications. Although salvianolic acid A (Sal A) from Danshen ( Salvia miltiorrhiza ) has shown promise in the treatment of ischemic heart disease, myocardial infarction, and atherosclerosis, its effects on cardiac fibrosis remain unexplored. Our study investigated the efficacy of Sal A in reducing cardiac fibrosis and elucidated its underlying molecular mechanisms. We observed that Sal A demonstrated significant cardioprotective effects against Angiotensin II (Ang II)-induced cardiac remodeling and fibrosis, showing a dose-dependent reduction in fibrosis in mice and suppression of cardiac fibroblast proliferation and fibrotic protein expression in vitro . RNA sequencing revealed that Sal A counteracted Ang II-induced upregulation of Txnip, and subsequent experiments indicated that it acts through the inflammasome and ROS pathways. These findings establish the antifibrotic effects of Sal A, notably attenuated by Txnip overexpression, and highlight its significant role in modulating inflammation and oxidative stress pathways. This underscores the importance of further research on Sal A and similar compounds, especially regarding their effects on inflammation and oxidative stress, which are key factors in various cardiovascular diseases.

Early Progression of Abdominal Aortic Aneurysm is Decelerated by Improved Endothelial Barrier Function via ALDH2-LIN28B-ELK3 Signaling.

The involvement of endothelial barrier function in abdominal aortic aneurysm (AAA) and its upstream regulators remains unknown. Single-cell RNA sequencing shows that disrupted endothelial focal junction is an early (3 days) and persistent (28 days) event during Angiotensin II (Ang II)-induced AAA progression. Consistently, mRNA sequencing on human aortic dissection tissues confirmed downregulated expression of endothelial barrier-related genes. Aldehyde dehydrogenase 2 (ALDH2), a negative regulator of AAA, is found to be upregulated in the intimal media of AAA samples, leading to testing its role in early-stage AAA. ALDH2 knockdown/knockout specifically in endothelial cells (ECs) significantly increases expression of EC barrier markers related to focal adhesion and tight junction, restores endothelial barrier integrity, and suppresses early aortic dilation of AAA (7 and 14 days post-Ang II). Mechanically, ELK3 acts as an ALDH2 downstream regulator for endothelial barrier function preservation. At the molecular level, ALDH2 directly binds to LIN28B, a regulator of ELK3 mRNA stability, hindering LIN28B binding to ELK3 mRNA, thereby depressing ELK3 expression and impairing endothelial barrier function. Therefore, preserving vascular endothelial barrier integrity via ALDH2-specific knockdown in ECs holds therapeutic potential in the early management of AAAs.

The upregulated scavenger receptor CD36 is associated with the progression of nontarget lesions after stent implantation in atherosclerotic rabbits.

BACKGROUND: The incidence of recurrent cardiovascular events from the progression of nontarget lesions (NTLs) is high for percutaneous coronary intervention-treated patients. However, the underlying mechanisms have not been thoroughly elucidated. METHODS: In this study, ten atherosclerotic rabbits with multiple plaques in the upper and lower segments of abdominal aorta (group A) were randomly divided into two subgroups: group A1 underwent intravascular ultrasound examination and stent implantation in the lower segments of the abdominal aorta (n=5), whereas group A2 was without stenting (n=5). Group B was a control group without balloon injury. The serum levels of high-sensitivity CRP, interleukin-6 (IL-6), oxidized low-density lipoprotein, and CD36 were assessed via ELISA at five time points between the 10th and 18th weeks. The upper abdominal aorta was examined via the immunohistochemical stain and Western blotting of matrix metallopeptidase 9 (MMP-9), CD36, IL-6, and tumor necrosis factor α. RESULTS: As a result, we found that stent implantation aggravated serum levels of CD36, oxidative stress, and inflammatory cytokines. Meanwhile, the upper abdominal arterial plaque burden significantly increased after stenting by intravascular ultrasound. Immunohistochemistry and Western blotting showed that the local NTLs' matrix metallopeptidase 9, CD36, IL-6, and tumor necrosis factor α expressions in group A1 were significantly higher than those in groups A2 and B (P<0.05-0.01). More importantly, a strong correlation was identified between CD36 expression and NTLs' plaque burden before the rabbits were killed. CONCLUSION: Taken together, stent implantation accelerated inflammation, induced oxidative stress, and increased the NTLs' progression, which were associated with the upregulated CD36 expression.

Postinfarction Hearts Are Protected by Premature Senescent Cardiomyocytes Via GATA 4-Dependent CCN 1 Secretion.

Background Stress-induced cell premature senescence participates in a variety of tissue and organ remodeling by secreting such proteins as proinflammatory cytokines, chemokines, and growth factors. However, the role of cardiomyocyte senescence in heart remodeling after acute myocardial infarction has not been thoroughly elucidated to date. Therefore, we sought to clarify the impact of premature myocardial senescence on postinfarction heart function. Methods and Results Senescence markers, including p16 INK4a, p21 CIP1/WAF1, and SA -ß-gal staining, were analyzed in several heart disease models by immunostaining. Both postinfarction mouse hearts and ischemic human myocardium demonstrated increased senescence markers. Additionally, senescence-related secretory phenotype was activated after acute myocardial infarction, which upregulated senescence-related secretory phenotype factors, including CCN family member 1 ( CCN 1), interleukin-1α, tumor necrosis factor α, and monocyte chemoattractant protein-1. In vivo, a tail vein injection of AAV 9- Gata4-sh RNA significantly attenuated senescence-related secretory phenotype secretion and aggravated postinfarction heart dysfunction. Furthermore, among activated senescence-related secretory phenotype factors, CCN 1 administration reduced myofibroblast viability in vitro and rescued the deleterious effect of AAV 9- Gata4-sh RNA in vivo. Conclusions Myocardial premature senescence was observed in the ischemic hearts and improved postinfarction heart function, partly through the GATA-binding factor 4- CCN 1 pathway.