Haruya Kawase

The neuropeptide neurotensin (NTS) is up-regulated in cardiac lymphatic endothelial cells (LECs) in response to ischemic or mechanical damage, but its role in cardiac remodeling is unknown. Here, we aimed to define the role of LEC-derived NTS in cardiac injury responses and to assess the therapeutic potential of targeting cardiac NTS signaling. In cultured murine and human cells, NTS reduced cardiomyocyte hypertrophy and fibroblast activation, and these effects were mediated by NTS receptor 2 (NTSR2)–dependent guanosine 3′,5′-monophosphate (cGMP) production. Consistent with an antihypertrophic and antifibrotic role of NTS, mice with LEC-specific Nts deletion exhibited aggravated hypertrophy and fibrosis after transverse aortic constriction (TAC) and myocardial infarction (MI). Similarly, cardiomyocyte-specific or activated fibroblast-specific inactivation of Ntsr2 led to enhanced cardiac remodeling after TAC. NTSR2 agonist NT150 reproduced the beneficial effects of NTS in cultured human and murine cells and ameliorated cardiac remodeling and dysfunction in both TAC and MI. Additionally, in freshly isolated cardiac tissues from patients with heart failure, NT150 induced cGMP production and suppressed prohypertrophic signaling. These findings identify NTS as an endogenous inhibitor of adverse cardiac remodeling and suggest NTSR2 agonism as a therapeutic strategy in heart failure.

Amyloid precursor protein (APP) gives rise to amyloid-β, a pathological factor in Alzheimer’s disease. However, the physiological role of APP and its homolog amyloid precursor–like protein 2 (APLP2), which are also widely expressed outside the nervous system, is largely unknown. Here, we show that endothelial APP and APLP2 are required for postischemia angiogenesis after myocardial infarction (MI). We found that hypoxia induced the endothelial expression of α-secretases, resulting in nonamyloidogenic processing of APP and APLP2 into the soluble forms APPsα and APLP2sα. Loss of endothelial APP and APLP2 led to decreased neovascularization as well as increased heart failure and mortality after MI, a phenotype that could be rescued by endothelial expression of APPsα. APPsα and APLP2sα exerted their proangiogenic effect by positive allosteric modulation of the endothelial receptor tyrosine kinase KIT, which promotes postischemia neovascularization. Our data identify a function of APP and APLP2 in endothelial cells, which is required for postischemia tissue repair, and suggest approaches to improve regeneration after MI and other ischemic diseases.

Macrophages express numerous G protein-coupled receptors (GPCRs) that regulate adhesion, migration, and activation, but the function of orphan receptor GPRC5B in macrophages is unknown. Both resident peritoneal and bone marrow-derived macrophages from myeloid-specific GPRC5B-deficient mice show increased migration and phagocytosis, resulting in improved bacterial clearance in a peritonitis model. In other models such as myocardial infarction, increased myeloid cell recruitment has adverse effects. Mechanistically, we found that GPRC5B physically interacts with GPCRs of the prostanoid receptor family, resulting in enhanced signaling through the prostaglandin E receptor 2 (EP2). In GPRC5B-deficient macrophages, EP2-mediated anti-inflammatory effects are diminished, resulting in hyperactivity. Using in silico modelling and docking, we identify residues potentially mediating GPRC5B/EP2 dimerization and show that their mutation results in loss of GPRC5B-mediated facilitation of EP2 signaling. Finally, we demonstrate that decoy peptides mimicking the interacting sequence are able to reduce GPRC5B-mediated facilitation of EP2-induced cAMP signaling in macrophages.

Insulin resistance is a hallmark of obesity-associated type 2 diabetes. Insulin’s actions go beyond metabolic cells and also involve blood vessels, where insulin increases capillary blood flow and delivery of insulin and nutrients. We show that adrenomedullin, whose plasma levels are increased in obese humans and mice, inhibited insulin signaling in human endothelial cells through protein-tyrosine phosphatase 1B–mediated dephosphorylation of the insulin receptor. In obese mice lacking the endothelial adrenomedullin receptor, insulin-induced endothelial nitric oxide–synthase activation and skeletal muscle perfusion were increased. Treating mice with adrenomedullin mimicked the effect of obesity and induced endothelial and systemic insulin resistance. Endothelial loss or blockade of the adrenomedullin receptor improved obesity-induced insulin resistance. These findings identify a mechanism underlying obesity-induced systemic insulin resistance and suggest approaches to treat obesity-associated type 2 diabetes.

Protein phosphorylation, controlled by protein kinases, is central to regulating various pathophysiological processes, including cardiac systolic function. The dysregulation of protein kinase activity plays a significant role in the pathogenesis of cardiac systolic dysfunction. While cardiac contraction mechanisms are well documented, the mechanisms underlying cardiac diastole remain elusive. This gap persists owing to the historical focus on systolic dysfunction in heart failure research. Recently, heart failure with preserved ejection fraction (HFpEF), an age‐related disease characterized by cardiac diastolic dysfunction, has emerged as a major public health concern. However, its underlying mechanism remains unclear. In this study, we investigated cardiac protein kinases by analyzing the gene expression of 518 protein kinases in human tissues. We identified alpha‐kinase 2 (ALPK2) as a novel cardiac‐specific atypical kinase and generated tamoxifen‐inducible, cardiomyocyte‐specific Alpk2 ‐knockout mice and Alpk2 ‐overexpressing mice. Alpk2 deficiency did not affect cardiac systolic dysfunction in the myocardial infarction model or the pressure‐overload‐induced heart failure model. Notably, cardiomyocyte‐specific Alpk2 deficiency exacerbated cardiac diastolic dysfunction induced by aging and in the HFpEF model. Conversely, Alpk2 overexpression increased the phosphorylation of tropomyosin 1, a major regulator that binds myosin to actin, and mitigated cardiac stiffness in HFpEF. This study provides novel evidence that ALPK2 represents a potential therapeutic target for cardiac diastolic dysfunction in HFpEF and age‐related cardiac impairments.

Chronic fibrotic tissue disrupts various organ functions. Despite significant advances in therapies, mortality and morbidity due to heart failure remain high, resulting in poor quality of life. Beyond the cardiomyocyte-centric view of heart failure, it is now accepted that alterations in the interstitial extracellular matrix (ECM) also play a major role in the development of heart failure. Here, we show that protein kinase N (PKN) is expressed in cardiac fibroblasts. Furthermore, PKN mediates the conversion of fibroblasts into myofibroblasts, which plays a central role in secreting large amounts of ECM proteins via p38 phosphorylation signaling. Fibroblast-specific deletion of PKN led to a reduction of myocardial fibrotic changes and cardiac dysfunction in mice models of ischemia-reperfusion or heart failure with preserved ejection fraction. Our results indicate that PKN is a therapeutic target for cardiac fibrosis in heart failure.

BACKGROUND: Vascular smooth muscle cells (VSMCs) are highly plastic. Vessel injury induces a phenotypic transformation from differentiated to dedifferentiated VSMCs, which involves reduced expression of contractile proteins and increased production of extracellular matrix and inflammatory cytokines. This transition plays an important role in several cardiovascular diseases such as atherosclerosis, hypertension, and aortic aneurysm. TGF-β (transforming growth factor-β) is critical for VSMC differentiation and to counterbalance the effect of dedifferentiating factors. However, the mechanisms controlling TGF-β activity and VSMC phenotypic regulation under in vivo conditions are poorly understood. The extracellular matrix protein TN-X (tenascin-X) has recently been shown to bind TGF-β and to prevent it from activating its receptor. METHODS: We studied the role of TN-X in VSMCs in various murine disease models using tamoxifen-inducible SMC-specific knockout and adeno-associated virus–mediated knockdown. RESULTS: In hypertensive and high-fat diet–fed mice, after carotid artery ligation as well as in human aneurysmal aortae, expression of Tnxb , the gene encoding TN-X, was increased in VSMCs. Mice with smooth muscle cell–specific loss of TN-X (SMC-Tnxb-KO) showed increased TGF-β signaling in VSMCs, as well as upregulated expression of VSMC differentiation marker genes during vascular remodeling compared with controls. SMC-specific TN-X deficiency decreased neointima formation after carotid artery ligation and reduced vessel wall thickening during Ang II (angiotensin II)–induced hypertension. SMC-Tnxb-KO mice lacking ApoE showed reduced atherosclerosis and Ang II–induced aneurysm formation under high-fat diet. Adeno-associated virus–mediated SMC-specific expression of short hairpin RNA against Tnxb showed similar beneficial effects. Treatment with an anti-TGF-β antibody or additional SMC-specific loss of the TGF-β receptor reverted the effects of SMC-specific TN-X deficiency. CONCLUSIONS: In summary, TN-X critically regulates VSMC plasticity during vascular injury by inhibiting TGF-β signaling. Our data indicate that inhibition of vascular smooth muscle TN-X may represent a strategy to prevent and treat pathological vascular remodeling.

Activation of endothelial YAP/TAZ signaling is crucial for physiological and pathological angiogenesis. The mechanisms of endothelial YAP/TAZ regulation are, however, incompletely understood. Here we report that the protocadherin FAT1 acts as a critical upstream regulator of endothelial YAP/TAZ which limits the activity of these transcriptional cofactors during developmental and tumor angiogenesis by promoting their degradation. We show that loss of endothelial FAT1 results in increased endothelial cell proliferation in vitro and in various angiogenesis models in vivo. This effect is due to perturbed YAP/TAZ protein degradation, leading to increased YAP/TAZ protein levels and expression of canonical YAP/TAZ target genes. We identify the E3 ubiquitin ligase Mind Bomb-2 (MIB2) as a FAT1-interacting protein mediating FAT1-induced YAP/TAZ ubiquitination and degradation. Loss of MIB2 expression in endothelial cells in vitro and in vivo recapitulates the effects of FAT1 depletion and causes decreased YAP/TAZ degradation and increased YAP/TAZ signaling. Our data identify a pivotal mechanism of YAP/TAZ regulation involving FAT1 and its associated E3 ligase MIB2, which is essential for YAP/TAZ-dependent angiogenesis.

The force-frequency relation (FFR) is a hemodynamic index of the chronotropic relationship between left ventricular (LV) systolic function (percent change in dP/dt_max) and elevation of heart rate. FFR is a marker of myocardial contractile reserve and follows an upward slope in healthy myocardium [monophasic FFR (MoF)], a pattern that becomes biphasic (BiF) under pathological conditions. However, it remains uncertain whether the FFR determines a patient's prognosis. We investigated the promising role of the FFR as a predictor of cardiac events in the setting of hypertrophic cardiomyopathy (HCM).Methods and Results:A total of 113 consecutive patients with HCM (New York Heart Association (NYHA) class I-II) were retrospectively evaluated; 27 (23.9%) had a BiF pattern and they experienced a higher incidence of cardiac events compared with those showing an MoF pattern (median follow-up, 4.7 years; P<0.001). Furthermore, Cox proportional hazard regression analysis revealed that the LV end-diastolic volume index (hazard ratio: 1.051, P=0.014) and BiF pattern (hazard ratio: 15.260, P=0.001) were independent predictors of primary cardiac events. Interestingly, abnormal reductions in myocardial regulatory molecules related to contractility (SERCA2α) were observed exclusively in the patients exhibiting a BiF pattern. The FFR reflects latent myocardial abnormalities and predicts cardiac events in the setting of HCM, even during the asymptomatic stages of the disease.