Circulation research最新文献

Background: Sex and atherosclerotic plaque histology are intertwined, with fibrous plaques being more prevalent in women. Plaque erosion, a significant contributor to acute coronary syndromes, is linked to fibrous plaques and is more prevalent in women than men. We hypothesize that the molecular drivers of histologically determined fibrous plaques differ between men and women.

Methods: Human end-stage atherosclerotic plaques were isolated from carotid endarterectomy patients included in the Athero-Express Biobank. Fibrous plaques were histologically assessed, linked to clinical characteristics, and processed for protein, bulk RNA, single-cell RNA, and DNA methylation data. We leveraged sex-differential gene expression and deconvolution analyses to uncover sex-biased molecular and cellular mechanisms. Spatial transcriptomics localized gene expression patterns in plaques. Furthermore, we studied the female-biased processes in human plaque endothelial cells and vascular smooth muscle cells stimulated with TGF-β (transforming growth factor-β), with or without SMAD3 (SMAD family member 3) inhibition.

Results: Of 1889 atherosclerotic plaques (1309 male and 580 female), fibrous lesions were observed in 50% of female and 31% of male patients. Compared with patients with atheromatous plaques (n=494), women with fibrous plaques exhibited a high prevalence of smoking, while men with fibrous plaques presented more often with diabetes. Female fibrous plaques were characterized by smooth muscle cell-driven ECM (extracellular matrix) remodeling, TGF-β response, and endothelial-to-mesenchymal transition, localized to the fibrous cap. Conversely, male plaques were linked to macrophage-mediated inflammation proximal to the core, dependent on diabetes. Finally, we experimentally confirmed these female-biased mechanisms, showing that TGF-β induced endothelial-to-mesenchymal transition in endothelial cells and ECM remodeling in vascular smooth muscle cells, both partly reversed by SMAD3 inhibition.

Conclusions: Women and men with end-stage fibrous atherosclerotic plaques exhibit distinct clinical and molecular profiles. These mechanisms might be candidate pathways to understand plaque erosion from a molecular point of view and may provide promising targets for atherosclerosis therapies, as they account for both sex and plaque phenotype.

Background: Lmods (leiomodins) are critical for the assembly and maintenance of thin filaments in striated muscles by allowing thin filament elongation at the pointed ends. Lmod2's elongation function has been linked to both actin-binding sites (ABSs) 2 and 3, while the existence and function of an N-terminal ABS1 has been debated.

Methods: To elucidate the little-known role of Lmod2's ABS1, we created a mutant (F64D/L69D/W72D/W73D: Lmod2-quadruple mutant) predicted to decrease the binding of ABS1 to actin. We analyzed the effect of the mutations using several in vitro, cellular, and in vivo assays.

Results: By disrupting the interaction of Lmod2 ABS1 with actin in isolated cardiomyocytes and in mice, we engineered a super Lmod2 that results in remarkably longer thin filaments. Structural analysis determined that ABS1 of Lmod2 binds to actin through a disordered region and an amphipathic α-helix. Analysis of the mutated ABS1 revealed that the helix is destroyed, and binding to actin is maintained only in the N-terminal disordered region of Lmod2 ABS1.

Conclusions: These discoveries support a model of controlled thin filament pointed end elongation by Lmod2 and provide the first direct evidence of, as well as the structural and functional mechanistic basis for, Lmod2's physiological leaky cap activity.

Background: The adult mammalian heart lacks the significant regenerative potential needed to cope with the massive loss of cardiomyocytes following myocardial infarction. Ultimately, irreversible cardiac damage leads to heart failure, which is associated with a poor prognosis. Given this, reactivating dormant regenerative processes in the injured heart represents an attractive therapeutic approach. When regeneration does occur, newly formed cardiomyocytes are derived from preexisting ones.

Methods: We aimed to identify novel regulators of cardiomyocyte proliferation. In this context, the genome is transcribed for a large part into RNAs with little or no protein-coding potential. Among noncoding RNAs, long noncoding RNAs represent the most diverse class of molecules and are implicated in numerous epigenetic mechanisms, making them ideal targets for controlling cell identity and behavior. In this project, we developed a high-throughput screening assay to identify long noncoding RNAs that promote cardiomyocyte proliferation upon knockdown. Using a stringent selection pipeline, we identified Clipper, an enhancer-associated long noncoding RNA regulating the expression of its cognate protein-coding gene Lpin1 in cis.

Results: Clipper was found to control mitochondrial biogenesis via LPIN1. Specifically, productive mitochondrial division, characterized by fission site positioning at the midzone of the mitochondrion, was stimulated by Clipper or Lpin1 silencing. The process was associated with a change in mitochondrial bioenergetics, particularly decreased oxidative metabolism, reduced production of reactive oxygen species, and dampened DNA damage, creating favorable conditions for cardiomyocyte proliferation. Importantly, Clipper knockdown in vivo following myocardial infarction stimulated cardiac regeneration in the damaged myocardium, leading to the restoration of heart function. Importantly, CLIPPER is positionally and functionally conserved in humans.

Conclusions: Our data identify CLIPPER as a promising therapeutic target for heart regeneration, acting through control of LPIN1-dependent mitochondrial biogenesis and cardiomyocyte proliferation.

Background: Cardiovascular disease remains the leading cause of death worldwide, with coronary artery disease being the primary contributor. Our recent studies suggest that activation of LepRs (leptin receptors) in the brain can improve cardiac function after myocardial infarction. However, the mechanism by which this cardioprotective effect is transmitted from the brain to the heart remains unclear. We hypothesize that brain LepR activation stimulates brown adipose tissue (BAT) to secrete extracellular vesicles (EVs) enriched with cardioprotective factors. These EVs may safeguard the heart by modulating cardiac mitochondrial function and collagen deposition.

Methods: Sprague-Dawley rats with BAT intact, BAT ablation, or BAT sympathetic denervation were implanted with an intracerebroventricular cannula for continuous leptin or vehicle delivery over 28 days after cardiac ischemia-reperfusion injury. Cardiac function was assessed weekly via echocardiography and by ventricular catheterization at the end of the protocol. EVs were isolated from BAT for analysis. Rab27a, a protein required for EV release, was knocked down using adeno-associated virus, and EV tracking was conducted using a double fluorescent reporter mouse model.

Results: Our findings indicate that BAT ablation or BAT sympathetic denervation diminishes the cardioprotective effects of brain LepR activation. We also observed an increased concentration of EVs within the BAT of rats treated with intracerebroventricular leptin compared with vehicle-treated controls, an effect abolished by BAT denervation. Furthermore, knockdown of Rab27a in BAT reduced the cardioprotective benefits of brain LepR activation. MicroRNA-29c-3p was identified as a cargo of leptin-stimulated BAT-derived EVs and appears to play a key role in mitigating cardiac fibrosis after ischemia-reperfusion injury in leptin-treated animals.

Conclusions: Activation of LepR in the brain protects the heart after ischemia-reperfusion injury via sympathetic-mediated BAT-derived EVs enriched with microRNA-29c-3p.

Background: Pulmonary interstitial macrophages can be divided into 2 distinct subsets with different origins: resident macrophages (resMФs) and recruited macrophages (recMФs). However, their specific roles in pulmonary arterial hypertension remain unclear.

Methods: Bone marrow transplantation, the DT (diphtheria toxin) receptor system, and genetically modified murine models were utilized to explore how key TFs (transcription factors) regulate phenotype alterations in pulmonary resMФs and recMФs in an SU5416/hypoxia murine model of pulmonary hypertension (PH). Therapeutic approaches included DNA aptamer-based proteolysis-targeting chimera and small interfering RNA-loaded lipid nanoparticle for treating SU5416/hypoxia-exposed rats.

Results: Depletion of either resMФs or recMФs using DT treatment significantly reduced SU5416/hypoxia-induced PH in mice. Pulmonary recMФs exhibited a proinflammatory phenotype during PH, driven by the TF Hic1 (hypermethylated in cancer 1). Bone marrow transplantation with Hic1^-/- recMФs ameliorated PH in mice. Hic1 enhanced proinflammatory gene transcription by inhibiting Sirt1 (sirtuin 1)-mediated H3K9ac (histone H3 lysine 9 acetylation) deacetylation in the promoter regions. In contrast, pulmonary resMФs demonstrated a profibrotic transcriptome characterized by upregulation of MMP genes that are, in turn, regulated by Prrx2 (paired-related homeobox 2). Prrx2 deletion in resMФs protected against PH in mice by reducing perivascular fibrosis. Simultaneously targeting Prrx2 and Hic1 in macrophages significantly alleviated SU5416/hypoxia-induced PH in rats.

Conclusions: The differential roles of pulmonary resMФs and recMФs in pulmonary vascular remodeling highlight novel therapeutic targets for pulmonary arterial hypertension treatment, specifically through inhibition of Hic1 and Prrx2 in macrophages.

Background: Abdominal aortic aneurysms (AAAs) are characterized by ECM (extracellular matrix) degradation and chronic vascular inflammation, with macrophages playing a key role. The mechanisms regulating macrophage activation in AAA remain incompletely understood. Vascular macrophages express Olfr2 (olfactory receptor 2), a GPCR (G-protein-coupled receptor) implicated in inflammation, but its role in AAA development is unknown.

Methods: We investigated the role of Olfr2 in AAA using PPE (porcine pancreatic elastase) infusion in Olfr2-deficient (Olfr2^-/-), Ang II (angiotensin II) infusion in Apoe^-/- Olfr2^-/-mice, bone marrow transplantation, and pharmacological modulation experiments. Echocardiography and histology were complemented by spectral flow cytometry, transcriptional profiling, and functional in vivo and ex vivo assays.

Results: Microarray analysis revealed increased expression of the human Olfr2 orthologue OR6A2 (olfactory receptor family 6 subfamily A member 2) in AAA tissue. Flow cytometry showed OR6A2 upregulation in monocytes from patients with large versus small AAAs. In both human and murine tissues, up to 30% of vascular macrophages expressed OR6A2/Olfr2, which peaked in MHCII^high CCR2^low monocytes/macrophages on day 7 of experimental AAA. Both whole-body and hematopoietic Olfr2 deficiency protected mice from AAA formation, with reduced ECM degradation, decreased macrophage infiltration, and preserved smooth muscle cell content. Treatment with the Olfr2 agonist octanal exacerbated, while the antagonist citral reduced AAA and inflammation. In Olfr2^-/- mice, inflammatory gene expression and aortic leukocyte accumulation were diminished. Despite a similar total leukocyte count, Ly6C^high monocytes displayed reduced CX3CR1 (CX3C motif chemokine receptor 1) expression and impaired migration toward CX3CL1 in vitro. Competitive transfer confirmed reduced migratory capacity of Olfr2^-/- monocytes, while pharmacological CX3CR1 inhibition mitigated the proinflammatory effects of octanal in AAA.

Conclusions: Olfr2 regulates monocyte recruitment and macrophage-driven inflammation during AAA. Its genetic deletion or pharmacological inhibition protects against AAA, whereas receptor activation worsens the disease. Olfr2 represents a critical modulator of vascular inflammation and a potential therapeutic target in AAA.

Background: Truncating variants in the TTN gene (TTNtv), encoding the giant sarcomeric protein titin, cause a range of human cardiac and skeletal muscle disorders of varying penetrance and severity. The effects of variant location on clinical manifestations are incompletely understood.

Methods: We generated 6 zebrafish lines carrying truncating ttn.2 variants in the Z-disk, I-band, A-band, and M-band titin regions. Expression of titin transcripts and protein levels was evaluated using quantitative polymerase chain reaction and proteomics. Phenotype analysis was performed during embryonic development and in adult hearts.

Results: Homozygous embryos from all lines except the C-terminal line, e232, showed a significant reduction of Z-disk and I-band ttn.2 transcripts, but A-band and M-band transcript levels were reduced only in lines with truncations distal to the cronos promoter. These homozygous embryos uniformly died by 7 to 10 days postfertilization with marked impairment of cardiac morphology and function. Skeletal muscle motility and sarcomere organization were more disrupted in mutants with truncations distal to the cronos promoter compared with those proximal. In contrast, homozygous e232 embryos, which lacked only the titin kinase and M-band regions, had relatively preserved cardiac function with incorporation of truncated Ttn.2/Cronos protein and normal sarcomere assembly, but selective degradation of fast skeletal muscle sarcomeres. All heterozygous embryos were phenotypically indistinguishable from wild type. High-frequency echocardiography in adult heterozygous fish showed reduced ventricular contraction under resting conditions in A-band mutants. Heterozygous Z-disk and I-band mutants had no significant baseline impairment but were unable to augment ventricular contraction in response to acute adrenaline exposure, indicating a lack of cardiac reserve.

Conclusions: Our data suggest that cardiac and skeletal muscle dysfunction associated with truncating ttn.2 variants is influenced by age, variant location, and the amount of functional titin protein. The distinctive phenotype associated with distal C-terminal truncations may reflect different requirements for C-terminal titin for maintenance of fast, slow, and cardiac muscle sarcomeres.