Advanced Magnetic Resonance Imaging to Define the Microvascular Injury Driven by Neuroinflammation in the Brain of a Mouse Model of Hypertension.

BACKGROUND: Hypertension is one of the main risk factors for dementia and cognitive impairment. METHODS: We used the model of transverse aortic constriction to induce chronic pressure overload in mice. We characterized brain injury by advanced translational applications of magnetic resonance imaging. In parallel, we analyzed peripheral target organ damage induced by chronic pressure overload by ultrasonography. Microscopical characterization of brain vasculature was performed as well, together with the analysis of immune and inflammatory markers. RESULTS: We identified a specific structural, microstructural, and functional brain injury. In particular, we highlighted a regional enlargement of the hypothalamus, microstructural damage in the white matter of the fimbria, and a reduction of the cerebral blood flow. A parallel analysis performed by confocal microscopy revealed a correspondent tissue damage evidenced by a reduction of cerebral capillary density, paired with loss of pericyte coverage. We assessed cognitive impairment and cardiac damage induced by hypertension to perform correlation analyses with the brain injury severity. At the mechanistic level, we found that CD8+T cells, producing interferon-γ, infiltrated the brain of hypertensive mice. By neutralizing this proinflammatory cytokine, we obtained a rescue of the phenotype, demonstrating their crucial role in establishing the microvascular damage. CONCLUSIONS: Overall, we have used translational tools to comprehensively characterize brain injury in a mouse model of hypertension induced by chronic pressure overload. We have identified early cerebrovascular damage in hypertensive mice, sustained by CD8+IFN-γ+T lymphocytes, which fuel neuroinflammation to establish the injury of brain capillaries.

La inhibición de la PI3Kγ protege contra la miocardiopatía diabética en ratones / PI3Kγ inhibition protects against diabetic cardiomyopathy in mice

Introducción y objetivos: Las enfermedades cardiovasculares, incluida la miocardiopatía, son las principales complicaciones de la diabetes mellitus. Un conocimiento más profundo de los mecanismos moleculares que conducen a la miocardiopatía es crucial para el desarrollo de nuevos tratamientos. Se propuso la fosfoinosítido 3-cinasa gamma (PI3Kγ) como objetivo molecular contra la miocardiopatía diabética, dado el papel que desempeña la PI3Kγ en el remodelado cardiaco frente a la sobrecarga de presión. Dada la disponibilidad de un inhibidor farmacológico de este objetivo molecular, el GE21, se ha investigado la validez de nuestra hipótesis induciendo la diabetes a ratones con ablación genética de la PI3Kγ, o knock-in, para una PI3Kγ catalíticamente inactiva. Métodos: Se provocó la diabetes a los ratones empleando estreptozotocina. Se evaluó la función cardiaca mediante exámenes ecocardiográficos secuenciales, mientras que la fibrosis y la inflamación se evaluaron mediante examen histológico. Resultados: La diabetes mellitus indujo disfunción cardiaca en los ratones genéticamente intactos (wild-type). La disfunción sistólica se previno completamente y la diastólica parcialmente, tanto en ratones con PI3Kγ inactivada como ratones sin actividad de cinasa. La disfunción cardiaca se recuperó en la misma medida administrando el inhibidor de la PI3Kγ GE21, de manera dependiente de la dosis. Estas acciones de inhibición genética o farmacológica de la PI3Kγ se asociaron con una reducción de la fibrosis y la inflamación en el corazón diabético. Conclusiones: Nuestro estudio demuestra un papel fundamental de la PI3Kγ en la miocardiopatía diabética en ratones y el efecto beneficioso de la inhibición farmacológica de la PI3Kγ; destaca su potencial como estrategia prometedora para el tratamiento clínico de las complicaciones cardiacas de los pacientes diabéticos (AU)

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 (AU)

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.

A cholinergic-sympathetic pathway primes immunity in hypertension and mediates brain-to-spleen communication.

The crucial role of the immune system in hypertension is now widely recognized. We previously reported that hypertensive challenges couple the nervous drive with immune system activation, but the physiological and molecular mechanisms of this connection are unknown. Here, we show that hypertensive challenges activate splenic sympathetic nerve discharge to prime immune response. More specifically, a vagus-splenic nerve drive, mediated by nicotinic cholinergic receptors, links the brain and spleen. The sympathetic discharge induced by hypertensive stimuli was absent in both coeliac vagotomized mice and in mice lacking α7nAChR, a receptor typically expressed by peripheral ganglionic neurons. This cholinergic-sympathetic pathway is necessary for T cell activation and egression on hypertensive challenges. In addition, we show that selectively thermoablating the splenic nerve prevents T cell egression and protects against hypertension. This novel experimental procedure for selective splenic denervation suggests new clinical strategies for resistant hypertension.

TIMP3 interplays with apelin to regulate cardiovascular metabolism in hypercholesterolemic mice.

OBJECTIVE: Tissue inhibitor of metalloproteinase 3 (TIMP3) is an extracellular matrix (ECM) bound protein, which has been shown to be downregulated in human subjects and experimental models with cardiometabolic disorders, including type 2 diabetes mellitus, hypertension and atherosclerosis. The aim of this study was to investigate the effects of TIMP3 on cardiac energy homeostasis during increased metabolic stress conditions. METHODS: ApoE(-/-)TIMP3(-/-) and ApoE(-/-) mice on a C57BL/6 background were subjected to telemetric ECG analysis and experimental myocardial infarction as models of cardiac stress induction. We used Western blot, qRT-PCR, histology, metabolomics, RNA-sequencing and in vivo phenotypical analysis to investigate the molecular mechanisms of altered cardiac energy metabolism. RESULTS: ApoE(-/-)TIMP3(-/-) revealed decreased lifespan. Telemetric ECG analysis showed increased arrhythmic episodes, and experimental myocardial infarction by left anterior descending artery (LAD) ligation resulted in increased peri-operative mortality together with increased scar formation, ventricular dilatation and a reduction of cardiac function after 4 weeks in the few survivors. Hearts of ApoE(-/-)TIMP3(-/-) exhibited accumulation of neutral lipids when fed a chow diet, which was exacerbated by a high fat, high cholesterol diet. Metabolomics analysis revealed an increase in circulating markers of oxidative stress with a reduction in long chain fatty acids. Using whole heart mRNA sequencing, we identified apelin as a putative modulator of these metabolic defects. Apelin is a regulator of fatty acid oxidation, and we found a reduction in the levels of enzymes involved in fatty acid oxidation in the left ventricle of ApoE(-/-)TIMP3(-/-) mice. Injection of apelin restored the hitherto identified metabolic defects of lipid oxidation. CONCLUSION: TIMP3 regulates lipid metabolism as well as oxidative stress response via apelin. These findings therefore suggest that TIMP3 maintains metabolic flexibility in the heart, particularly during episodes of increased cardiac stress.

Lack of kinase-independent activity of PI3Kγ in locus coeruleus induces ADHD symptoms through increased CREB signaling.

Although PI3Kγ has been extensively investigated in inflammatory and cardiovascular diseases, the exploration of its functions in the brain is just at dawning. It is known that PI3Kγ is present in neurons and that the lack of PI3Kγ in mice leads to impaired synaptic plasticity, suggestive of a role in behavioral flexibility. Several neuropsychiatric disorders, such as attention-deficit/hyperactivity disorder (ADHD), involve an impairment of behavioral flexibility. Here, we found a previously unreported expression of PI3Kγ throughout the noradrenergic neurons of the locus coeruleus (LC) in the brainstem, serving as a mechanism that regulates its activity of control on attention, locomotion and sociality. In particular, we show an unprecedented phenotype of PI3Kγ KO mice resembling ADHD symptoms. PI3Kγ KO mice exhibit deficits in the attentive and mnemonic domains, typical hyperactivity, as well as social dysfunctions. Moreover, we demonstrate that the ADHD phenotype depends on a dysregulation of CREB signaling exerted by a kinase-independent PI3Kγ-PDE4D interaction in the noradrenergic neurons of the locus coeruleus, thus uncovering new tools for mechanistic and therapeutic research in ADHD.

The angiogenic factor PlGF mediates a neuroimmune interaction in the spleen to allow the onset of hypertension.

Hypertension is a health problem affecting over 1 billion people worldwide. How the immune system gets activated under hypertensive stimuli to contribute to blood pressure elevation is a fascinating enigma. Here we showed a splenic role for placental growth factor (PlGF), which accounts for the onset of hypertension, through immune system modulation. PlGF repressed the expression of the protein Timp3 (tissue inhibitor of metalloproteinases 3), through the transcriptional Sirt1-p53 axis. Timp3 repression allowed costimulation of T cells and their deployment toward classical organs involved in hypertension. We showed that the spleen is an essential organ for the development of hypertension through a noradrenergic drive mediated by the celiac ganglion efferent. Overall, we demonstrate that PlGF mediates the neuroimmune interaction in the spleen, organizing a unique and nonredundant response that allows the onset of hypertension.

Hypertension induces brain ß-amyloid accumulation, cognitive impairment, and memory deterioration through activation of receptor for advanced glycation end products in brain vasculature.

Although epidemiological data associate hypertension with a strong predisposition to develop Alzheimer disease, no mechanistic explanation exists so far. We developed a model of hypertension, obtained by transverse aortic constriction, leading to alterations typical of Alzheimer disease, such as amyloid plaques, neuroinflammation, blood-brain barrier dysfunction, and cognitive impairment, shown here for the first time. The aim of this work was to investigate the mechanisms involved in Alzheimer disease of hypertensive mice. We focused on receptor for advanced glycation end products (RAGE) that critically regulates Aß transport at the blood-brain barrier and could be influenced by vascular factors. The hypertensive challenge had an early and sustained effect on RAGE upregulation in brain vessels of the cortex and hippocampus. Interestingly, RAGE inhibition protected from hypertension-induced Alzheimer pathology, as showed by rescue from cognitive impairment and parenchymal Aß deposition. The increased RAGE expression in transverse aortic coarctation mice was induced by increased circulating advanced glycation end products and sustained by their later deposition in brain vessels. Interestingly, a daily treatment with an advanced glycation end product inhibitor or antioxidant prevented the development of Alzheimer traits. So far, Alzheimer pathology in experimental animal models has been recognized using only transgenic mice overexpressing amyloid precursor. This is the first study demonstrating that a chronic vascular insult can activate brain vascular RAGE, favoring parenchymal Aß deposition and the onset of cognitive deterioration. Overall we demonstrate that RAGE activation in brain vessels is a crucial pathogenetic event in hypertension-induced Alzheimer disease, suggesting that inhibiting this target can limit the onset of vascular-related Alzheimer disease.