Focus on translational vascular biology: new therapeutic targets in hypertension, aortic aneurysm, and atherosclerosis

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This Focus Issue on vascular biology contains the Special Article ‘Balloon pulmonary angioplasty for chronic thromboembolic pulmonary hypertension: a Clinical Consensus Statement of the ESC Working Group on Pulmonary Circulation and Right Ventricular Function’ by Irene Lang from the Medical University of Vienna in Austria, and colleagues.1 The authors point out that the current treatment algorithm for chronic thrombo-embolic pulmonary hypertension (CTEPH) as depicted in the 2022 European Society of Cardiology (ESC)/European Respiratory Society (ERS) guidelines on the diagnosis and treatment of pulmonary hypertension (PH) includes a multimodal approach of combinations of pulmonary endarterectomy (PEA), balloon pulmonary angioplasty (BPA), and medical therapies to target major vessel pulmonary vascular lesions, and microvasculopathy.2–6 Today, BPA of >1700 patients has been reported in the literature from centres in Asia, USA, and Europe, and many more patients have been treated outside literature reports. As BPA becomes part of routine care of patients with CTEPH, benchmarks for safe and effective care delivery become increasingly important. In light of this development, the ESC Working Group on Pulmonary Circulation and Right Ventricular Function has decided to publish a document that helps standardize BPA to meet the need of uniformity in patient selection, procedural planning, the technical approach, materials and devices, treatment goals, complications including their management, and patient follow-up, thus complementing the guidelines. Delphi methodology was utilized for statements that were not evidence based. First, an anatomical nomenclature and a description of vascular lesions is provided. Second, treatment goals and definitions of complete BPA are outlined. Third, definitions of complications are presented which may be the basis for a standardized reporting in studies involving BPA. The document is intended to serve as a companion to the official ESC/ERS guidelines. In a State of the Art Review article entitled ‘Novel mechanisms and therapeutic targets in atherosclerosis: inflammation and beyond’, Christian Weber from the Ludwig-Maximilians-Universität München in Germany, and colleagues note that their review, based on the ESC William Harvey Lecture in Basic Science 2022, highlights recent experimental and translational progress on the therapeutic targeting of the inflammatory components in atherosclerosis, introducing novel strategies to limit side effects and to increase efficacy.7 Since the validation of the inflammatory paradigm in CANTOS and COLCOT, efforts to control the residual risk conferred by inflammation have centred on the NLRP3 inflammasome-driven interleukin (IL)-1β–IL-6 axis.8,9 Interference with the co-stimulatory dyad CD40L–CD40 and selective targeting of tumour necrosis factor-receptor associated factors (TRAFs), namely the TRAF6–CD40 interaction in macrophages by small molecule inhibitors, harbour intriguing options to reduce established atherosclerosis and plaque instability without immune side effects. The chemokine system crucial for shaping immune cell recruitment and homoeostasis can be fine-tuned and modulated by its heterodimer interactome. Structure–function analysis enabled the design of cyclic, helical, or linked peptides specifically targeting or mimicking these interactions to limit atherosclerosis or thrombosis by blunting myeloid recruitment, boosting regulatory T cells, inhibiting platelet activity, or specifically blocking the atypical chemokine macrophage inhibitory factor without notable side effects. Finally, adventitial neuroimmune cardiovascular interfaces in advanced atherosclerosis show robust restructuring of innervation from perivascular ganglia and employ sensory neurons of dorsal root ganglia to enter the central nervous system and to establish an atherosclerosis–brain circuit sensor, while sympathetic and vagal efferents project to the coeliac ganglion to create an atherosclerosis–brain circuit effector. Disrupting this circuitry by surgical or chemical sympathectomy limited disease progression and enhanced plaque stability, opening up exciting perspectives for selective and tailored intervention beyond anti-inflammatory strategies. Potential medical therapies to limit abdominal aortic aneurysm growth or rupture. VSMC, vascular smooth muscle cell.10 In another State of the Art Review article entitled ‘Pathogenesis and management of abdominal aortic aneurysm’, Jonathan Golledge from the James Cook University in Townsville, Australia, and colleagues remind us that abdominal aortic aneurysm (AAA) causes ∼170 000 deaths annually worldwide. Most guidelines recommend that asymptomatic small AAAs (<50 mm in women; < 55 mm in men) are monitored by imaging, and large asymptomatic, symptomatic, and ruptured AAAs are considered for surgical repair.10 Advances in AAA repair techniques have occurred, but a remaining priority is therapies to limit AAA growth and rupture. This review outlines research on AAA pathogenesis and therapies to limit AAA growth. Genome-wide association studies have identified novel drug targets, e.g. IL-6 blockade. Mendelian randomization analyses suggest that treatments to reduce LDL-cholesterol such as proprotein convertase subtilisin/kexin type 9 inhibitors and smoking reduction or cessation are also treatment targets. Thirteen placebo-controlled randomized trials have tested whether a range of antibiotics, blood pressure-lowering drugs, a mast cell stabilizer, an antiplatelet drug, or fenofibrate slow AAA growth. None of these trials has shown convincing evidence of drug efficacy and they have been limited by small sample sizes, limited drug adherence, poor participant retention, and overoptimistic AAA growth reduction targets. Data from some large observational cohorts suggest that blood pressure reduction, particularly by angiotensin-converting enzyme inhibitors, could limit aneurysm rupture, but this has not been evaluated in randomized trials. Some observational studies suggest that metformin may limit AAA growth, and this is currently being tested in randomized trials (Figure 1). In conclusion, no drug therapy has been shown to convincingly limit AAA growth in randomized controlled trials. Further large prospective studies on other targets are needed. Epigenetic age is emerging as a personalized and accurate predictor of biological age. In a Clinical Research article entitled ‘Subclinical atherosclerosis and accelerated epigenetic age mediated by inflammation: a multi-omics study’, Fátima Sánchez-Cabo from the Centro Nacional de Investigaciones Cardiovasculares (CNIC) in Madrid, Spain, and colleagues assess the association of subclinical atherosclerosis (SA) with accelerated epigenetic age and investigate the underlying mechanisms mediating this association.11 Whole-blood methylomics, transcriptomics, and plasma proteomics were obtained for 391 participants of the Progression of Early Subclinical Atherosclerosis study. Epigenetic age was calculated from methylomics data for each participant. Its divergence from chronological age is termed epigenetic age acceleration. Subclinical atherosclerosis (SA) burden was estimated by multiterritory 2D/3D vascular ultrasound and by coronary artery calcification. In healthy individuals, the presence, extension, and progression of SA were associated with a significant acceleration of the Grim epigenetic age, a predictor of health and life span, regardless of traditional cardiovascular risk factors. Individuals with an accelerated Grim epigenetic age were characterized by an increased systemic inflammation and associated with a score of low-grade, chronic inflammation. Mediation analysis using transcriptomics and proteomics data revealed key pro-inflammatory pathways (IL-6, inflammasome, and IL-10) and genes (IL1B, OSM, TLR5, and CD14) mediating the association between SA and epigenetic age acceleration. The authors conclude that the presence, extension, and progression of SA in middle-aged asymptomatic individuals are associated with an acceleration in the Grim epigenetic age. Mediation analysis using transcriptomics and proteomics data suggests a key role for systemic inflammation in this association, reinforcing the relevance of interventions on inflammation to prevent cardiovascular disease. This manuscript is accompanied by an Editorial by Nivedhitha Velayutham and Richard Lee from Harvard University in Cambridge, MA, USA.12 The authors highlight that the study by Sanchez-Cabo et al. certainly does not exclude other factors beyond known inflammatory pathways in the presence and progression of SA. Also, while the authors identified a strong association between SA and Grim epigenetic age acceleration (EAA), a causal effect cannot be established due to the study design. Further longitudinal studies designed to assess the effect and directionality of SA on health and life span, as well as the viability of modulating inflammatory signalling to prevent progression of SA, are needed. Nevertheless, the findings of Sanchez-Cabo et al. strengthen the role of inflammatory mechanisms in SA and its impact on EAA. The study also provides more mechanistic evidence for strategies aiming at attenuating systemic inflammation for the delay of atherosclerosis progression in cardiovascular disease. The role of smooth muscle cells (SMCs) in coronary artery disease has long been underestimated.13,14 The variant p.Arg149Cys in ACTA2, which encodes SMC-specific α-actin, predisposes to thoracic aortic disease and early-onset coronary artery disease in individuals without cardiovascular risk factors. In a Translational Research article entitled ‘Smooth muscle α-actin missense variant promotes atherosclerosis through modulation of intracellular cholesterol in smooth muscle cells’, Kaveeta Kaw from the University of Texas Health Science Center in Houston, TX, USA, and colleagues investigated how this variant drives increased atherosclerosis.15Apoe−/− mice with and without the variant were fed a high-fat diet for 12 weeks, followed by evaluation of atherosclerotic plaque formation and single-cell transcriptomics analysis. SMCs explanted from Acta2R149C/+ and wild-type (WT) ascending aortas were used to investigate atherosclerosis-associated SMC phenotypic modulation. Hyperlipidaemic Acta2R149C/+Apoe−/− mice had a 2.5-fold increase in atherosclerotic plaque burden compared with Apoe−/− mice, with no differences in serum lipid levels. At the cellular level, misfolding of the R149C α-actin activated heat shock factor 1, which increased endogenous cholesterol biosynthesis and intracellular cholesterol levels through increased HMG-CoA reductase (HMG-CoAR) expression and activity. The increased cellular cholesterol in Acta2R149C/+ SMCs induced endoplasmic reticulum stress and activated PERK–ATF4–KLF4 signalling to drive atherosclerosis-associated phenotypic modulation in the absence of exogenous cholesterol, while WT cells required higher levels of exogenous cholesterol to drive phenotypic modulation. Treatment with the HMG-CoAR inhibitor pravastatin successfully reversed the increased atherosclerotic plaque burden in Acta2R149C/+Apoe−/− mice. The authors conclude that these data establish a novel mechanism by which a pathogenic missense variant in a smooth muscle-specific contractile protein predisposes to atherosclerosis in individuals without hypercholesterolaemia or other risk factors. The results emphasize the role of increased intracellular cholesterol levels in driving SMC phenotypic modulation and atherosclerotic plaque burden. The contribution is accompanied by an Editorial by Hanrui Zhang from Columbia University Irving Medical Center in New York, NY, USA and Marit Westerterp and Benedek Halmos from the University of Groningen in the Netherlands.16 The authors highlight that Kaw et al. discover that expression of the ACTA2 p.R149C variant drives atherosclerosis by increasing SMC cholesterol synthesis, even in the absence of hypercholesterolaemia, probably explaining the premature coronary artery disease in carriers of the p.R149C variant in the absence of cardiovascular risk factors. Statins decreased atherosclerosis in mice expressing the p.R149C variant, suggesting additional therapeutic benefits. Further, employing nanoparticles to target statins to the atherosclerotic plaque reduced atherosclerosis to a larger extent than oral administration of statins in Apoe−/− mice. Future studies will be needed to explore whether suppressing cholesterol synthesis in SMCs is a novel therapeutic target. Impaired dermal lymphangiogenesis and lymphatic dysfunction contribute to the pathogenesis of salt-sensitive hypertension. Modulation of lymphatic endothelial A2AR-mediated VEGF-independent activation of VEGFR2 signalling, to regulate dermal lymphangiogenesis and sodium balance, might be a potential therapeutic target in salt-sensitive hypertension. A2AR, adenosine A2A receptor; KO, knockout; LEC, lymphatic endothelial cell; MSK1, mitogen- and stress-activated kinase 1; Na+, sodium; VEGF, vascular endothelial growth factor; VEGFR2, vascular endothelial growth factor receptor 2.25 Excess dietary sodium intake and retention lead to hypertension.17–24 In a Translational Research article entitled ‘A2AR-mediated lymphangiogenesis via VEGFR2 signalling prevents salt-sensitive hypertension’, Tao Zhuang from Fudan University in Shanghai, China and colleagues note that impaired dermal lymphangiogenesis and lymphatic dysfunction-mediated sodium and fluid imbalance are pathological mechanisms. The adenosine A2A receptor (A2AR) is expressed in lymphatic endothelial cells (LECs), while the roles and mechanisms of LEC–A2AR in skin lymphangiogenesis during salt-induced hypertension are not clear.25 The expression of LEC–A2AR correlated with lymphatic vessel density in both high-salt diet (HSD)-induced hypertensive mice and hypertensive patients. Lymphatic endothelial cell-specific A2AR knockout mice fed HSD exhibited a 17% ± 2% increase in blood pressure and a 17% ± 3% increase in sodium content associated with decreased lymphatic density (−19% ± 2%) compared with HSD-WT mice. A2AR activation by the agonist CGS21680 increased lymphatic capillary density and decreased blood pressure in HSD-WT mice. Furthermore, this A2AR agonist activated MSK1 directly to promote VEGFR2 activation and endocytosis independently of VEGF, as assessed by phosphoprotein profiling and immunoprecipitation assays in LECs. The VEGFR2 kinase activity inhibitor fruquintinib or VEGFR2 knockout in LECs but not the VEGF-neutralizing antibody bevacizumab suppressed A2AR activation-mediated decrease in blood pressure. Immunostaining revealed that phosphorylated VEGFR2 and MSK1 expression in the LECs were positively correlated with skin lymphatic vessel density and A2AR level in hypertensive patients (Figure 2). The authors conclude that their study highlights a novel A2AR-mediated VEGF-independent activation of VEGFR2 signalling in dermal lymphangiogenesis and sodium balance, which might be a potential therapeutic target in salt-sensitive hypertension (SSHTN). The manuscript is accompanied by an Editorial by Ryszard Nosalski and Tomasz Guzik from the University of Edinburgh, UK.26 The authors summarize that numerous studies, including the current study by Zhuang et al., propose that targeting lymphangiogenesis pathology could be a promising strategy to develop new treatments SSHTN. However, this option is also opposed by some observations. Hence, further research is necessary to establish the relationship between lymphangiogenesis and HTN to determine the therapeutic potential. Thus, when considering a clinical approach, it is crucial to gain a comprehensive understanding of the intricate connections between skin sodium, lymphatic vessels, and blood pressure before developing any large-scale clinical trials targeting lymphangiogenesis in humans. A deeper understanding of these links will enable the development of more targeted and effective treatment strategies for SSHTN, ultimately leading to better clinical outcomes. The mechanisms underlying ageing-induced vascular remodelling remain unclear. In a Translational Research article entitled ‘Sirtuin 2 deficiency aggravates ageing-induced vascular remodelling in humans and mice’, Yang Zhang from the Chinese Academy of Medical Sciences & Peking Union Medical College in China, and colleagues investigate the role and underlying mechanisms of the cytoplasmic deacetylase sirtuin 2 (SIRT2) in ageing-induced vascular remodelling.27 Young and old WT and Sirt2 knockout mice were used to explore vascular function and pathological remodelling. RNA-seq, histochemical staining, and biochemical assays were used to evaluate the effects of Sirt2 knockout on the vascular transcriptome and pathological remodelling, and explore the underlying biochemical mechanisms. Among the sirtuins, SIRT2 had the highest levels in human and mouse aortas. SIRT2 activity was reduced in aged aortas, and loss of SIRT2 accelerated vascular ageing. In old mice, SIRT2 deficiency aggravated ageing-induced arterial stiffness and constriction–relaxation dysfunction, accompanied by aortic remodelling (thickened vascular medial layers, breakage of elastin fibres, collagen deposition, and inflammation). Transcriptome and biochemical analyses revealed that the ageing-controlling protein p66Shc and metabolism of mitochondrial reactive oxygen species (mROS) contributed to SIRT2 function in vascular ageing. SIRT2 repressed p66Shc activation and mROS production by deacetylating p66Shc at lysine 81. Elimination of reactive oxygen species by MnTBAP repressed the SIRT2 deficiency-mediated aggravation of vascular remodelling and dysfunction in angiotensin II-challenged and aged mice. The SIRT2 co-expression module in aortas was reduced with ageing across species, and was a significant predictor of age-related aortic diseases in humans. The authors conclude that SIRT2 is a response to ageing that delays vascular ageing, and the cytoplasm–mitochondria axis is important for vascular ageing. Therefore, SIRT2 may serve as a potential therapeutic target for vascular rejuvenation. The contribution is accompanied by an Editorial by Yustina Puspitasari from the University of Zurich in Switzerland.28 The author concludes that the results presented by Zhang and colleagues are thought-provoking, particularly regarding the role of SIRT2 in vascular ageing. The use of the public transcriptome dataset in this study provides insights into the potential predictive value of SIRT2 on the incidence of aortic aneurysms. Yet, using public transcriptome databases presents some limitations due to the lack of detailed information on patient characteristics, as correctly mentioned by the authors. Of course, these findings will require validation in real patient populations while also investigating the potential correlation of SIRT2 with other age-related vascular diseases, such as atherosclerosis, arterial stiffness, and ischaemic stroke. Even though analysis of the molecular mechanism of SIRT2 will warrant further investigations, the current study provides an important additional contribution to solve the mystery of vascular ageing and to embark on the future where growing old is inevitable, but ageing is optional. Blood eosinophil count and eosinophil cationic protein (ECP) concentration are risk factors of cardiovascular diseases. In a Translational Research article entitled ‘Cationic proteins from protein vascular and from and and Harvard Medical in MA, USA and colleagues tested whether and how and contribute to vascular and Immunostaining revealed eosinophil in human and mouse atherosclerotic deficiency in mice with increased SMC content and reduced calcification. This in mice was when mice from and mice or mouse a of or but not or increased the of SMC from WT mice but not from knockout mice. analyses that and activated but not activation or expression of protein or growth factor in SMC from WT and knockout mice. that immune with but not and analysis that to and with human and also to on human vascular SMCs and SMC In a of from the and its of blood eosinophil and levels correlated with the of arterial from coronary to The authors conclude that cationic proteins that can promote SMC and using the signalling The contribution is accompanied by an Editorial by from the University in note that the study by et al. important novel into the cellular and molecular pathways by in atherosclerosis and vascular calcification. targeting cationic proteins may a more therapeutic strategy in cardiovascular disease. The that this of the European will be of to its from outside the to and for with of this