Inhibition of mitochondrial activity ameliorates atherosclerosis in ApoE −/− mice via suppressing vascular smooth cell activation and macrophage foam cell formation

Rotenone activates the LKB1-AMPK-ULK1 signaling pathway to induce autophagy and apoptosis in rat thoracic aortic endothelial cells

BACKGROUND

The specific mechanism by which rotenone impacts thoracic aortic autophagy and apoptosis is unknown. We aimed to investigate the regulatory effects of rotenone on autophagy and apoptosis in rat thoracic aortic endothelial cells (RTAEC) via activation of the LKB1-AMPK-ULK1 signaling pathway and to elucidate the molecular mechanisms of rotenone on autophagy and apoptosis in vascular endothelial cells.

METHODS

In vivo, 60 male SD rats were randomly selected and divided into 5 groups: control (Con), DMSO, 1, 2, and 4 mg/kg groups, respectively. After 28 days of treatment, histopathological and ultrastructural changes in each group were observed using HE and transmission electron microscopy; Autophagy, apoptosis, and LKB1-AMPK-ULK1 pathway-related proteins were detected by Western blot; Apoptosis levels in the thoracic aorta were detected by TUNEL. In vitro, RTAEC were cultured and divided into control (Con), DMSO, 20, 100, 500, and 1000 nM groups. After 24 h of intervention, autophagy, apoptosis, and LKB1-AMPK-ULK1 pathway-related factors were detected by Western blot and qRT-PCR; Flow cytometry to detect apoptosis levels; Autophagy was inhibited with 3-MA and CQ to detect apoptosis levels, and changes in autophagy, apoptosis, and downstream factors were detected by the AMPK inhibitor CC intervention.

RESULTS

Gavage in SD rats for 28 days, some degree of damage was observed in the thoracic aorta and heart of the rotenone group, as well as the appearance of autophagic vesicles was observed in the thoracic aorta. TUNEL analysis revealed higher apoptosis in the rotenone group's thoracic aorta; RTAEC cultured in vitro, after 24 h of rotenone intervention, showed increased ROS production and significantly decreased ATP production. The flow cytometry data suggested an increase in the number of apoptotic RTAEC. The thoracic aorta and RTAEC in the rotenone group displayed elevated levels of autophagy and apoptosis, and the LKB1-AMPK-ULK1 pathway proteins were activated and expressed at higher levels. Apoptosis and autophagy were both suppressed by the autophagy inhibitors 3-MA and CQ. The AMPK inhibitor CC reduced autophagy and apoptosis in RTAEC and suppressed the production of the AMPK downstream factors ULK1 and P-ULK1.

CONCLUSIONS

Rotenone may promote autophagy in the thoracic aorta and RTAEC by activating the LKB1-AMPK-ULK1 signaling pathway, thereby inducing apoptosis.

Explore the role of long noncoding RNAs and mRNAs in intracranial atherosclerotic stenosis: From the perspective of neutrophils

CONTEXT

Circulating neutrophils and long noncoding RNAs (lncRNAs) play various roles in intracranial atherosclerotic stenosis (ICAS).

OBJECTIVE

Our study aimed to detect differentially expressed (DE) lncRNAs and mRNAs in circulating neutrophils and explore the pathogenesis of atherosclerosis from the perspective of neutrophils.

METHODS

Nineteen patients with ICAS and 15 healthy controls were enrolled. The peripheral blood of the participants was collected, and neutrophils were separated. The expression profiles of lncRNAs and mRNAs in neutrophils from five patients and five healthy controls were obtained, and DE lncRNAs and mRNAs were selected. Six lncRNAs were selected and validated using quantitative reverse transcription-polymerase chain reaction (qRT-PCR), and ceRNA and lncRNA-RNA binding protein (RBP)-mRNA networks were constructed. Correlation analysis between lncRNAs and mRNAs was performed. Functional enrichment annotations were also performed.

RESULTS

Volcano plots and heat maps displayed the expression profiles and DE lncRNAs and mRNAs, respectively. The qRT-PCR results revealed that the four lncRNAs showed a tendency consistent with the expression profile, with statistical significance. The ceRNA network revealed three pairs of regulatory networks: lncRNA RP3-406A7.3-NAGLU, lncRNA HOTAIRM1-MVK/IL-25/GBF1/CNOT4/ANKK1/PLEKHG6, and lncRNA RP11-701H16.4-ZNF416. The lncRNA-RBP-mRNA network showed five pairs of regulatory networks: lncRNA RP11-701H16.4-TEK, lncRNA RP11-701H16.4-MED17, lncRNA SNHG19-NADH-ubiquinone oxidoreductase core subunit V1, lncRNA RP3-406A7.3-Angel1, and lncRNA HOTAIRM1-CARD16.

CONCLUSIONS

Our study identified and verified four lncRNAs in neutrophils derived from peripheral blood, which may explain the transcriptional alteration of neutrophils during the pathophysiological process of ICAS. Our results provide insights for research related to the pathogenic mechanisms and drug design of ICAS.

Vascular smooth muscle cell c-Fos is critical for foam cell formation and atherosclerosis

BACKGROUND

Hyperlipidemia-induced vascular smooth muscle cell (VSMC)-derived foam cell formation is considered a crucial event in the development of atherosclerosis. Since c-Fos emerges as a key modulator of lipid metabolism, we investigated whether c-Fos plays a role in hyperlipidemia-induced VSMC-derived foam cell formation and atherosclerosis.

APPROACH AND RESULTS

c-Fos expression was observed in VSMCs in atherosclerotic plaques from patients and western diet-fed atherosclerosis-prone LDLR^-/- and ApoE^-/- mice by immunofluorescence staining. To ascertain c-Fos's function in atherosclerosis development, VSMC-specific c-Fos deficient mice in ApoE^-/- background were established. Western diet-fed c-Fos^VSMCKOApoE^-/- mice exhibited a significant reduction of atherosclerotic lesion formation as measured by hematoxylin and eosin staining, accompanied by decreased lipid deposition within aortic roots as determined by Oil red O staining. Primary rat VSMCs were isolated to examine the role of c-Fos in lipid uptake and foam cell formation. oxLDL stimulation resulted in VSMC-derived foam cell formation and elevated intracellular mitochondrial reactive oxygen species (mtROS), c-Fos and LOX-1 levels, whereas specific inhibition of mtROS, c-Fos or LOX-1 lessened lipid accumulation in oxLDL-stimulated VSMCs. Mechanistically, oxLDL acts through mtROS to enhance transcription activity of c-Fos to facilitate the expression of LOX-1, exerting a feedforward mechanism with oxLDL to increase lipid uptake and propel VSMC-derived foam cell formation and atherogenesis.

CONCLUSION

Our study demonstrates a fundamental role of mtROS/c-Fos/LOX-1 signaling pathway in promoting oxLDL uptake and VSMC-derived foam cell formation during atherosclerosis. c-Fos may represent a promising therapeutic target amenable to clinical translation in the future.

Mathematical modeling of plaque progression and associated microenvironment: How far from predicting the fate of atherosclerosis?

Mathematical modeling contributes to pathophysiological research of atherosclerosis by helping to elucidate mechanisms and by providing quantitative predictions that can be validated. In turn, the complexity of atherosclerosis is well suited to quantitative approaches as it provides challenges and opportunities for new developments of modeling. In this review, we summarize the current 'state of the art' on the mathematical modeling of the effects of biomechanical factors and microenvironmental factors on the plaque progression, and its potential help in prediction of plaque development. We begin with models that describe the biomechanical environment inside and outside the plaque and its influence on its growth and rupture. We then discuss mathematical models that describe the dynamic evolution of plaque microenvironmental factors, such as lipid deposition, inflammation, smooth muscle cells migration and intraplaque hemorrhage, followed by studies on plaque growth and progression using these modelling approaches. Moreover, we present several key questions for future research. Mathematical models can complement experimental and clinical studies, but also challenge current paradigms, redefine our understanding of mechanisms driving plaque vulnerability and propose future potential direction in therapy for cardiovascular disease.

LncRNA CDKN2B-AS1 hinders the proliferation and facilitates apoptosis of ox-LDL-induced vascular smooth muscle cells via the ceRNA network of CDKN2B-AS1/miR-126-5p/PTPN7

OBJECTIVE

The patterns of lncRNA CDKN2B-AS1 in coronary heart disease (CHD) have been extensively studied. This study investigated the competing endogenous RNA (ceRNA) network of CDKN2B-AS1 in coronary atherosclerosis (CAS).

METHODS

Microarray analyses were performed to screen out the CHD-related lncRNAs (CDKN2B-AS1) and the downstream microRNAs (miR-126-5p). The expression of CDKN2B-AS1 in serum of patients with CHD and healthy volunteers was detected. Vascular smooth muscle cells (VSMCs) were treated with oxidized low density lipoprotein (ox-LDL) to establish the cell model. Then pcDNA-CDKN2B-AS1 and/or miR-126-5p mimic were transfected into ox-LDL-treated VSMCs to estimate cell proliferation, apoptosis and inflammation. The ceRNA network of CDKN2B-AS1 along with the possible pathway in CHD was testified.

RESULTS

CDKN2B-AS1 expression was low in patients with CHD and ox-LDL-treated VSMCs. Upon CDKN2B-AS1 overexpression, TNF-α, NF-κB and IL-1β levels in VSMCs were decreased, the proliferation of VSMCs was inhibited and the apoptosis rate was increased. Overexpression of miR-126-5p could reverse these trends. CDKN2B-AS1 as a ceRNA competitively bound to miR-126-5p to upregulate PTPN7. CDKN2B-AS1 inhibited VSMC proliferation and accelerated apoptosis by inhibiting the PI3K-Akt pathway.

CONCLUSION

LncRNA CDKN2B-AS1 upregulates PTPN7 by absorbing miR-126-5p and inhibits the PI3K-Akt pathway, thus hindering the proliferation and accelerating apoptosis of VSMCs induced by ox-LDL, thus being a therapeutic approach for CAS.

Lactate accelerates vascular calcification through NR4A1-regulated mitochondrial fission and BNIP3-related mitophagy

Arterial media calcification is related to mitochondrial dysfunction. Protective mitophagy delays the progression of vascular calcification. We previously reported that lactate accelerates osteoblastic phenotype transition of VSMC through BNIP3-mediated mitophagy suppression. In this study, we investigated the specific links between lactate, mitochondrial homeostasis, and vascular calcification. Ex vivo, alizarin S red and von Kossa staining in addition to measurement of calcium content, RUNX2, and BMP-2 protein levels revealed that lactate accelerated arterial media calcification. We demonstrated that lactate induced mitochondrial fission and apoptosis in aortas, whereas mitophagy was suppressed. In VSMCs, lactate increased NR4A1 expression, leading to activation of DNA-PKcs and p53. Lactate induced Drp1 migration to the mitochondria and enhanced mitochondrial fission through NR4A1. Western blot analysis of LC3-II and p62 and mRFP-GFP-LC3 adenovirus detection showed that NR4A1 knockdown was involved in enhanced autophagy flux. Furthermore, NR4A1 inhibited BNIP3-related mitophagy, which was confirmed by TOMM20 and BNIP3 protein levels, and LC3-II co-localization with TOMM20. The excessive fission and deficient mitophagy damaged mitochondrial structure and impaired respiratory function, determined by mPTP opening rate, mitochondrial membrane potential, mitochondrial morphology under TEM, ATP production, and OCR, which was reversed by NR4A1 silencing. Mechanistically, lactate enhanced fission but halted mitophagy via activation of the NR4A1/DNA-PKcs/p53 pathway, evoking apoptosis, finally accelerating osteoblastic phenotype transition of VSMC and calcium deposition. This study suggests that the NR4A1/DNA-PKcs/p53 pathway is involved in the mechanism by which lactate accelerates vascular calcification, partly through excessive Drp-mediated mitochondrial fission and BNIP3-related mitophagy deficiency.

PDK4 promotes vascular calcification by interfering with autophagic activity and metabolic reprogramming

Pyruvate dehydrogenase kinase 4 (PDK4) is an important mitochondrial matrix enzyme in cellular energy regulation. Previous studies suggested that PDK4 is increased in the calcified vessels of patients with atherosclerosis and is closely associated with mitochondrial function, but the precise regulatory mechanisms remain largely unknown. This study aims to investigate the role of PDK4 in vascular calcification and the molecular mechanisms involved. Using a variety of complementary techniques, we found impaired autophagic activity in the process of vascular smooth muscle cells (VSMCs) calcification, whereas knocking down PDK4 had the opposite effect. PDK4 drives the metabolic reprogramming of VSMCs towards a Warburg effect, and the inhibition of PDK4 abrogates VSMCs calcification. Mechanistically, PDK4 disturbs the integrity of the mitochondria-associated endoplasmic reticulum membrane, concomitantly impairing mitochondrial respiratory capacity, which contributes to a decrease in lysosomal degradation by inhibiting the V-ATPase and lactate dehydrogenase B interaction. PDK4 also inhibits the nuclear translocation of the transcription factor EB, thus inhibiting lysosomal function. These changes result in the interruption of autophagic flux, which accelerates calcium deposition in VSMCs. In addition, glycolysis serves as a metabolic adaptation to improve VSMCs oxidative stress resistance, whereas inhibition of glycolysis by 2-deoxy-D-glucose induces the apoptosis of VSMCs and increases the calcium deposition in VSMCs. Our results suggest that PDK4 plays a key role in vascular calcification through autophagy inhibition and metabolic reprogramming.

Macrophage-Enriched lncRNA RAPIA: A Novel Therapeutic Target for Atherosclerosis

OBJECTIVE

Despite the current antiatherosclerotic and antithrombotic therapies, the incidence of advanced atherosclerosis-associated clinical events remains high. Whether long noncoding RNAs (lncRNAs) affect the progression of atherosclerosis and whether they are potential targets for the treatment of advanced atherosclerosis are poorly understood. Approach and Results: The progression of atherosclerotic lesions was accompanied by dynamic alterations in lncRNA expression, as revealed by RNA sequencing and quantitative polymerase chain reaction. Among the dynamically changing lncRNAs, we identified a novel lncRNA, lncRNA Associated with the Progression and Intervention of Atherosclerosis (RAPIA), that was highly expressed in advanced atherosclerotic lesions and in macrophages. Inhibition of RAPIA in vivo not only repressed the progression of atherosclerosis but also exerted atheroprotective effects similar to those of atorvastatin on advanced atherosclerotic plaques that had already formed. In vitro assays demonstrated that RAPIA promoted proliferation and reduced apoptosis of macrophages. A molecular sponge interaction between RAPIA and microRNA-183-5p was demonstrated by dual-luciferase reporter and RNA immunoprecipitation assays. Rescue assays indicated that RAPIA functioned at least in part by targeting the microRNA-183-5p/ITGB1 (integrin β1) pathway in macrophages. In addition, the transcription factor FoxO1 (forkhead box O1) could bind to the RAPIA promoter region and facilitate the expression of RAPIA.

CONCLUSIONS

The progression of atherosclerotic lesions was accompanied by dynamic changes in the expression of lncRNAs. Inhibition of the pivotal lncRNA RAPIA may be a novel preventive and therapeutic strategy for advanced atherosclerosis, especially in patients resistant or intolerant to statins.