Background: The development of thoracic aortic dissection (TAD) is closely related to extracellular matrix degradation and vascular smooth muscle cell (VSMC) transformation from contractile to synthetic type. LGMN (legumain) degrades extracellular matrix components directly or by activating downstream signals. The role of LGMN in VSMC differentiation and the occurrence of TAD remains elusive. Methods: Microarray datasets concerning vascular dissection or aneurysm were downloaded from the Gene Expression Omnibus database to screen differentially expressed genes. Four-week-old male Lgmn knockout mice (Lgmn ^–/– ), macrophage-specific Lgmn knockout mice (Lgmn ^F/F ;LysM ^Cre ), and RR-11a–treated C57BL/6 mice were given BAPN (β-aminopropionitrile monofumarate; 1 g/kg/d) in drinking water for 4 weeks for TAD modeling. RNA sequencing analysis was performed to recapitulate transcriptome profile changes. Cell interaction was examined in macrophage and VSMC coculture system. The reciprocity of macrophage-derived LGMN with integrin αvβ3 in VSMCs was tested by coimmunoprecipitation assay and colocalization analyses. Results: Microarray datasets from the Gene Expression Omnibus database indicated upregulated LGMN in aorta from patients with TAD and mice with angiotensin II–induced AAA. Elevated LGMN was evidenced in aorta and sera from patients with TAD and mice with BAPN-induced TAD. BAPN-induced TAD progression was significantly ameliorated in Lgmn-deficient or inhibited mice. Macrophage-specific deletion of Lgmn alleviated BAPN-induced extracellular matrix degradation. Unbiased profiler polymerase chain reaction array and Gene Ontology analysis displayed that LGMN regulated VSMC phenotype transformation. Macrophage-specific deletion of Lgmn ameliorated VSMC phenotypic switch in BAPN-treated mice. Macrophage-derived LGMN inhibited VSMC differentiation in vitro as assessed by macrophages and the VSMC coculture system. Macrophage-derived LGMN bound to integrin αvβ3 in VSMCs and blocked integrin αvβ3, thereby attenuating Rho GTPase activation, downregulating VSMC differentiation markers and eventually exacerbating TAD development. ROCK (Rho kinase) inhibitor Y-27632 reversed the protective role of LGMN depletion in vascular dissection. Conclusions: LGMN signaling may be a novel target for the prevention and treatment of TAD.

Macrophages play a vital role in cardiac repair following myocardial infarction (MI). An enriched environment (EE) is involved in the regulation of macrophage-related activities and disease progression; however, whether EE affects the phenotype and function of macrophages to improve postinfarction cardiac repair remains unknown. In this study, we found that EE improved cardiac function, decreased mortality, and ameliorated adverse ventricular remodeling in mice after MI, with these outcomes closely related to the increased survival of Ly6C ^low macrophages and their CCR2 ⁻ MHCII ^low subsets. EE increased the expression of brain-derived neurotrophic factor (BDNF) in the hypothalamus, leading to higher circulating levels of BDNF, which, in turn, regulated the cardiac macrophages. BDNF bound to tropomyosin receptor kinase B to activate downstream ERK1/2 and AKT pathways, promoting macrophage survival. These findings demonstrate that EE optimizes postinfarction cardiac repair and highlights the significance of EE as a previously unidentified strategy for impeding adverse ventricular remodeling.

BACKGROUND: Vascular smooth muscle cells (VSMCs) undergo phenotypic changes during the development of aortic aneurysm and dissection (AAD). Metabolism shifts from oxidative phosphorylation to glycolysis. Recent studies suggest that epigenetics plays a crucial role in AAD. METHODS: The epigenetic regulation of histone lactylation was analyzed in the aorta of patients with aortic aneurysm and in a murine model of AAD. Histone lactylation was also studied in VSMCs treated with angiotensin II. The epigenetic pathway involving H4K16 lactylation (H4K16la) was explored in vitro and in vivo. To examine the role of H4K16la in AAD formation, mice lacking Pdk1 or Kat7 in VSMCs were created. Mice were treated with pharmacological inhibitors of Pdk1 or Kat7. The levels of blood lactate, aortic lactate, and aortic H4K16la were compared between patients with aortic aneurysm and controls. RESULTS: Histone lactylation (H4K16la) was increased in the aortic tissues of patients with AAD and mice. Enhanced histone lactylation was linked to increased pyruvate dehydrogenase kinase 1 (PDK1) transcription, which accelerated lactate production in VSMCs. A positive feedback loop was identified involving H4K16la, PDK1, and lactate; this pathway alters the metabolism and phenotype of VSMCs. KAT7 (lysine acetyltransferase 7) was found to be a histone lactyltransferase for histone lactylation in VSMCs. Genetic or pharmacological inhibition of PDK1 or KAT7 decreased AAD injury by disrupting the H4K16la/PDK1/lactate pathway. Patients with AAD have elevated lactate in blood and aortic tissues and elevated H4K16la in aortic tissues compared with control patients. CONCLUSIONS: Histone lactylation changes the metabolism and phenotype of VSMC in AAD. Inhibition of PDK1 or KAT7 may be a novel approach to treat or prevent AAD.

BACKGROUND: Cardiac inflammation is a key driver of cardiac fibrosis and heart failure. Cytotoxic CD8⁺ T cells play important roles in modulating inflammatory responses, especially during infections and autoimmune diseases. HIFs (hypoxia-inducible factors) regulate CD8⁺ T cell function and cardiac remodeling. However, the role of HIF in CD8⁺ T cells during heart failure development remains unclear. METHODS: We generated CD8⁺ T cell-specific PHD2 (prolyl hydroxylase domain protein 2)-deficient mice (PHD2 ^CKO ), in which HIF bioavailability is increased due to the loss of PHD2. PHD2 ^CKO and wild-type littermates were subjected to pressure overload via transverse aortic constriction. Cardiac function, inflammation, and CD8⁺ T cell responses were assessed. CD8⁺ T cell metabolism was analyzed using Seahorse assays to measure extracellular acidification rate and oxygen consumption rate. HIF1α and HIF2α protein levels were measured by Western blotting. RESULTS: Under baseline conditions, PHD2 deletion in CD8⁺ T cells had no effect on heart function or effector molecule expression. Following transverse aortic constriction, PHD2 ^CKO mice showed exacerbated cardiopulmonary inflammation, fibrosis, and dysfunction. These effects were associated with enhanced CD8⁺ T cell activation and cytokine production. In vitro, PHD2-deficient CD8⁺ T cells exhibited increased glycolysis (extracellular acidification rate), reduced oxidative phosphorylation (oxygen consumption rate), and elevated HIF1α—but not HIF2α—levels. Pharmacological inhibition of HIF1α, but not HIF2α, reversed these metabolic and functional changes. CONCLUSIONS: PHD2 deletion in CD8⁺ T cells aggravates cardiopulmonary remodeling after pressure overload by enhancing CD8⁺ T cell activation and cytokine release via a HIF1α-dependent mechanism.