Interferon-γ drives macrophage reprogramming, cerebrovascular remodelling, and cognitive dysfunction in a zebrafish and a mouse model of ion imbalance and pressure overload.

AIMS: Dysregulated immune response contributes to inefficiency of treatment strategies to control hypertension and reduce the risk of end-organ damage. Uncovering the immune pathways driving the transition from the onset of hypertensive stimulus to the manifestation of multi-organ dysfunction are much-needed insights for immune targeted therapy. METHODS AND RESULTS: To aid visualization of cellular events orchestrating multi-organ pathogenesis, we modelled hypertensive cardiovascular remodelling in zebrafish. Zebrafish larvae exposed to ion-poor environment exhibited rapid angiotensinogen up-regulation, followed by manifestation of arterial hypertension and cardiac remodelling that recapitulates key characteristics of incipient heart failure with preserved ejection fraction. In the brain, time-lapse imaging revealed the occurrence of cerebrovascular regression through endothelial retraction and migration in response to the ion-poor treatment. This phenomenon is associated with macrophage/microglia-endothelial contacts and endothelial junctional retraction. Cytokine and transcriptomic profiling identified systemic up-regulation of interferon-γ and interleukin 1ß and revealed altered macrophage/microglia transcriptional programme characterized by suppression of innate immunity and vasculo/neuroprotective gene expression. Both zebrafish and a murine model of pressure overload-induced brain damage demonstrated that the brain pathology and macrophage/microglia phenotypic alteration are dependent on interferon-γ signalling. In zebrafish, interferon-γ receptor 1 mutation prevents cerebrovascular remodelling and dysregulation of macrophage/microglia transcriptomic profile. Supplementation of bone morphogenetic protein 5 identified from the transcriptomic approach as a down-regulated gene in ion-poor-treated macrophages/microglia that is rescued by interferon-γ blockage, mitigated cerebral microvessel loss. In mice subjected to transverse aortic constriction-induced pressure overload, typically developing cerebrovascular injury, neuroinflammation, and cognitive dysfunction, interferon-γ neutralization protected them from blood-brain barrier disruption, cerebrovascular rarefaction, and cognitive decline. CONCLUSIONS: These findings uncover cellular and molecular players of an immune pathway communicating hypertensive stimulus to structural and functional remodelling of the brain and identify anti-interferon-γ treatment as a promising intervention strategy capable of preventing pressure overload-induced damage of the cerebrovascular and nervous systems.

Bone marrow adipocytes fuel emergency hematopoiesis after myocardial infarction.

After myocardial infarction (MI), emergency hematopoiesis produces inflammatory myeloid cells that accelerate atherosclerosis and promote heart failure. Since the balance between glycolysis and mitochondrial metabolism regulates hematopoietic stem cell homeostasis, metabolic cues may influence emergency myelopoiesis. Here, we show in humans and female mice that hematopoietic progenitor cells increase fatty acid metabolism after MI. Blockade of fatty acid oxidation by deleting carnitine palmitoyltransferase (Cpt1A) in hematopoietic cells of Vav1Cre/+Cpt1Afl/fl mice limited hematopoietic progenitor proliferation and myeloid cell expansion after MI. We also observed reduced bone marrow adiposity in humans, pigs and mice following MI. Inhibiting lipolysis in adipocytes using AdipoqCreERT2Atglfl/fl mice or local depletion of bone marrow adipocytes in AdipoqCreERT2iDTR mice also curbed emergency hematopoiesis. Furthermore, systemic and regional sympathectomy prevented bone marrow adipocyte shrinkage after MI. These data establish a critical role for fatty acid metabolism in post-MI emergency hematopoiesis.

Targeting Interleukin-1ß Protects from Aortic Aneurysms Induced by Disrupted Transforming Growth Factor ß Signaling.

Aortic aneurysms are life-threatening conditions with effective treatments mainly limited to emergency surgery or trans-arterial endovascular stent grafts, thus calling for the identification of specific molecular targets. Genetic studies have highlighted controversial roles of transforming growth factor ß (TGF-ß) signaling in aneurysm development. Here, we report on aneurysms developing in adult mice after smooth muscle cell (SMC)-specific inactivation of Smad4, an intracellular transducer of TGF-ß. The results revealed that Smad4 inhibition activated interleukin-1ß (IL-1ß) in SMCs. This danger signal later recruited innate immunity in the adventitia through chemokine (C-C motif) ligand 2 (CCL2) and modified the mechanical properties of the aortic wall, thus favoring vessel dilation. SMC-specific Smad4 deletion in Il1r1- or Ccr2-null mice resulted in milder aortic pathology. A chronic treatment with anti-IL-1ß antibody effectively hampered aneurysm development. These findings identify a mechanistic target for controlling the progression of aneurysms with compromised TGF-ß signaling, such as those driven by SMAD4 mutations.

PI3Kγ Inhibition Protects Against Diabetic Cardiomyopathy in Mice.

INTRODUCTION AND OBJECTIVES: Cardiovascular diseases, including cardiomyopathy, are the major complications in diabetes. A deeper understanding of the molecular mechanisms leading to cardiomyopathy is critical for developing novel therapies. We proposed phosphoinositide3-kinase gamma (PI3Kγ) as a molecular target against diabetic cardiomyopathy, given the role of PI3Kγ in cardiac remodeling to pressure overload. Given the availability of a pharmacological inhibitor of this molecular target GE21, we tested the validity of our hypothesis by inducing diabetes in mice with genetic ablation of PI3Kγ or knock-in for a catalytically inactive PI3Kγ. METHODS: Mice were made diabetic by streptozotocin. Cardiac function was assessed by serial echocardiographic analyses, while fibrosis and inflammation were evaluated by histological analysis. RESULTS: Diabetes induced cardiac dysfunction in wild-type mice. Systolic dysfunction was completely prevented, and diastolic dysfunction was partially blocked, in both PI3Kγ knock-out and kinase-dead mice. Cardiac dysfunction was similarly rescued by administration of the PI3Kγ inhibitor GE21 in a dose-dependent manner. These actions of genetic and pharmacological PI3Kγ inhibition were associated with a decrease in inflammation and fibrosis in diabetic hearts. CONCLUSIONS: Our study demonstrates a fundamental role of PI3Kγ in diabetic cardiomyopathy in mice and the beneficial effect of pharmacological PI3Kγ inhibition, highlighting its potential as a promising strategy for clinical treatment of cardiac complications of diabetic patients.