Ping Song

Thoracic aortic aneurysm and dissection (TAAD) is a life-threatening vascular disease lacking therapies that target underlying cell death pathways. Ferroptosis, an iron-dependent form of lipid peroxidation-driven cell death, has emerged as a key mechanism in vascular remodeling. We investigated whether exogenous ketosis induced by ketone ester (KE) supplementation can suppress ferroptosis and prevent TAAD. TAAD was induced in C57BL/6 mice using β-aminopropionitrile (BAPN). A subset of these mice received KE [(R)-3-hydroxybutyl (R)-3-hydroxybutyrate, 20 g/L] in their drinking water starting on day 15 of the BAPN treatment. Human aortic smooth muscle cells (HASMCs) were treated with the GPX4 inhibitor Ras-Selective Lethal 3 (RSL3) and β-hydroxybutyrate (β-OHB) to investigate ferroptotic markers, lipid peroxidation, and labile iron levels. KE supplementation significantly reduced TAAD incidence (69% → 43%) and improved survival rate (52% → 73%), while preserving aortic structure and reducing elastic fiber fragmentation. Transcriptomic analyses of human TAAD datasets (GSE153434 and GSE52093) and single-cell RNA sequencing data (GSE155468) revealed ferroptosis signatures characterized by decreased GPX4 and increased expression of iron metabolism genes. Mechanistically, KE suppressed BAPN-induced iron accumulation and lipid peroxidation in vivo. In HASMCs, β-OHB inhibited ferroptosis induced by GPX4 inhibition, decreasing lipid peroxidation and labile iron levels. KE restored GPX4 and SLC7A11 expression while suppressing HO-1 in vivo, with effects dependent on Nrf2 signaling in vitro. In summary, ketone ester supplementation protects against TAAD by inhibiting VSMC ferroptosis via GPX4 induction and HO-1 suppression, highlighting a potential therapeutic strategy for aortic disease.

Ketones are metabolites primarily produced by the liver and are utilized by various organs outside of the liver. Recent advances have demonstrated that ketones serve not only as alternative energy sources but also as signaling molecules. Research indicates that ketones can influence cancer development and metastasis, cardiac metabolic and structural remodeling, physical performance, vascular function, inflammation, and the aging process. Emerging evidence from preclinical and early-phase clinical studies suggests that strategies such as ketone salts, ketone esters, and the ketogenic diet may offer therapeutic benefits for conditions like heart failure, acute cardiac injury, diabetic cardiomyopathy, vascular complications, atherosclerosis, hypertension, and aortic aneurysm. This literature review updates the current understanding of ketone metabolism and its contributions to cardiovascular health and diseases. We highlight the underlying molecular mechanism with post-translational modification known as β-hydroxybutyrylation, which affects the fate and function of target proteins. Additionally, we discuss the therapeutic challenges associated with ketone therapy, the potential of using ketone levels as biomarkers for cardiovascular diseases, as well as gender- and age-specific differences in ketone treatment. Finally, we explore future research directions and what is needed to translate these new insights into cardiovascular medicine.

During the maturation of hematopoietic stem/progenitor cells (HSPCs) to fully differentiated mature B lymphocytes, developing lymphocytes may undergo malignant transformation and produce B-cell lymphomas. Emerging evidence shows that through the endothelial-hematopoietic transition, specialized endothelial cells called the hemogenic endothelium can differentiate into HSPCs. However, the contribution of genetic defects in hemogenic endothelial cells to B-cell lymphomagenesis has not yet been investigated. Here, we report that mice with endothelial cell-specific deletion of Fbw7 spontaneously developed diffuse large B-cell lymphoma (DLBCL) following Bcl6 accumulation. Using lineage tracing, we showed that B-cell lymphomas in Fbw7 knockout mice were hemogenic endothelium-derived. Mechanistically, we found that FBW7 directly interacted with Bcl6 and promoted its proteasomal degradation. FBW7 expression levels are inversely correlated with BCL6 expression. Additionally, pharmacological disruption of Bcl6 abolished Fbw7 deletion-induced B-cell lymphomagenesis. We conclude that selective deletion of E3 ubiquitin ligase FBW7 in VE-cadherin positive endothelial cells instigates diffuse large B-cell lymphoma via upregulation of BCL6 stability. In addition, the mice with endothelial cell-specific deletion of Fbw7 provide a valuable preclinical platform for in vivo development and evaluation of novel therapeutic interventions for the treatment of DLBCL.

(1) Background: Apolipoprotein E (ApoE) is a critical plasma apolipoprotein for lipid transport and nonlipid-related functions. Humans possess three isoforms of ApoE (2, 3, and 4). ApoE2, which exhibits beneficial effects on cardiac health, has not been adequately studied. (2) Methods: We investigated the cardiac phenotypes of the humanized ApoE knock-in (hApoE KI) rats and compared to wild-type (WT) and ApoE knock-out (ApoE KO) rats using echocardiography, ultrasound, blood pressure measurements, histology strategies, cell culture, Seahorse XF, cardiomyocyte contractility and intracellular Ca²⁺ tests, and Western blotting; (3) Results: hApoE2 rats exhibited enhanced heart contractile function without signs of detrimental remodeling. Isolated adult hApoE2 cardiomyocytes had faster and stronger sarcomere contractility because of more mitochondrial energy generation and stimulation-induced fast and elevated intracellular Ca²⁺ transient. The abundant energy is a result of elevated mitochondrial function via fatty acid β-oxidation. The fast and elevated Ca²⁺ transient is associated with decreased sarcoplasmic reticulum (SR) Ca²⁺ ATPase (SERCA2) and increased expression of cardiac ryanodine receptor 2 (RyR2) conducting a potent Ca²⁺ release from SR.; (4) Conclusions: Our studies validated the association of polymorphic ApoEs with cardiac health in the rat model, and revealed the possible mechanisms of the protective effect of ApoE2 against heart diseases.

Indoleamine 2,3 dioxygenase-1 (IDO1) catalyzes tryptophan-kynurenine metabolism in many inflammatory and cancer diseases. Of note, acute inflammation that occurs immediately after heart injury is essential for neonatal cardiomyocyte proliferation and heart regeneration. However, the IDO1-catalyzed tryptophan metabolism during heart regeneration is largely unexplored. Here, we find that apical neonatal mouse heart resection surgery led to rapid and consistent increases in cardiac IDO1 expression and kynurenine accumulation. Cardiac deletion of Ido1 gene or chemical inhibition of IDO1 impairs heart regeneration. Mechanistically, elevated kynurenine triggers cardiomyocyte proliferation by activating the cytoplasmic aryl hydrocarbon receptor-SRC-YAP/ERK pathway. In addition, cardiomyocyte-derived kynurenine transports to endothelial cells and stimulates cardiac angiogenesis by promoting aryl hydrocarbon receptor nuclear translocation and enhancing vascular endothelial growth factor A expression. Notably, Ahr deletion prevents indoleamine 2,3 dioxygenase -kynurenine–associated heart regeneration. In summary, increasing indoleamine 2,3 dioxygenase-derived kynurenine level promotes cardiac regeneration by functioning as an endogenous regulator of cardiomyocyte proliferation and cardiac angiogenesis.

Editorial: Vascular smooth muscle cell fate and vascular remodeling: Mechanisms, therapeutic targets, and drugs, volume I

Background: IDO1 (indoleamine 2,3-dioxygenase 1) is the rate-limiting enzyme for tryptophan metabolism. IDO1 malfunction is involved in the pathogenesis of atherosclerosis. Vascular smooth muscle cells (VSMCs) with an osteogenic phenotype promote calcification and features of plaque instability. However, it remains unclear whether aberrant IDO1-regulated tryptophan metabolism causes VSMCs osteogenic reprogramming and calcification. Methods: We generated global Apoe ( apolipoprotein E ) and Ido1 double knockout mice, and Apoe knockout mice with specific deletion of IDO1 in VSMCs or macrophages. Arterial intimal calcification was evaluated by a Western diet–induced atherosclerotic calcification model. Results: Global deficiency of IDO1 boosted calcific lesion formation without sex bias in vivo. Conditional IDO1 loss of function in VSMCs rather than macrophages promoted calcific lesion development and the abundance of RUNX2 (runt-related transcription factor 2). In contrast, administration of kynurenine via intraperitoneal injection markedly delayed the progression of intimal calcification in parallel with decreased RUNX2 expression in both Apoe ^−/− and Apoe ^−/− Ido1 ^−/− mice. We found that IDO1 deletion restrained RUNX2 from proteasomal degradation, which resulted in enhanced osteogenic reprogramming of VSMCs. Kynurenine administration downregulated RUNX2 in an aryl hydrocarbon receptor–dependent manner. Kynurenine acted as the endogenous ligand of aryl hydrocarbon receptor, controlled resultant interactions between cullin 4B and aryl hydrocarbon receptor to form an E3 ubiquitin ligase that bound with RUNX2, and subsequently promoted ubiquitin-mediated instability of RUNX2 in VSMCs. Serum samples from patients with coronary artery calcification had impaired IDO1 activity and decreased kynurenine catabolites compared with those without calcification. Conclusions: Kynurenine, an IDO1-mediated tryptophan metabolism main product, promotes RUNX2 ubiquitination and subsequently leads to its proteasomal degradation via an aryl hydrocarbon receptor–dependent nongenomic pathway. Insufficient kynurenine exerts the deleterious role of IDO1 ablation in promoting RUNX2-mediated VSMCs osteogenic reprogramming and calcification in vivo.

In the bone marrow, classical and plasmacytoid dendritic cells (DC) develop from the macrophage-DC precursor (MDP) through a common DC precursor (CDP) step. This developmental process receives essential input from the niche in which it takes place, containing endothelial cells (EC) among other cell types. Here we show that targeted deletion of serine/threonine kinase 11 (Stk11) encoding tumor suppressor liver kinase b1 (Lkb1) in mouse ECs but not DCs, results in disrupted differentiation of MDPs to CDPs, severe reduction in mature DC numbers and spontaneous tumorigenesis. In wild type ECs, Lkb1 phosphorylates polypyrimidine tract binding protein 1 (Ptbp1) at threonine 138, which regulates stem cell factor (Scf) pre-mRNA splicing. In the absence of Lkb1, exon 6 of Scf is spliced out, leading to the loss of Scf secretion. Adeno-associated-virus-mediated delivery of genes encoding either soluble Scf or the phosphomimetic mutant Ptbp1^T138E proteins rescued the defects of MDP to CDP differentiation and DC shortage in the endothelium specific Stk11 knockout mice. In summary, endothelial Stk11 expression regulates DC differentiation via modulation of Scf splicing, marking the Stk11-soluble-Scf axis as a potential cause of DC deficiency syndromes.