Vagal afferents contribute to sympathoexcitation-driven metabolic dysfunctions.

Multiple crosstalk between peripheral organs and the nervous system are required to maintain physiological and metabolic homeostasis. Using Vav3-deficient mice as a model for chronic sympathoexcitation-associated disorders, we report here that afferent fibers of the hepatic branch of the vagus nerve are needed for the development of the peripheral sympathoexcitation, tachycardia, tachypnea, insulin resistance, liver steatosis and adipose tissue thermogenesis present in those mice. This neuronal pathway contributes to proper activity of the rostral ventrolateral medulla, a sympathoregulatory brainstem center hyperactive in Vav3-/- mice. Vagal afferent inputs are also required for the development of additional pathophysiological conditions associated with deregulated rostral ventrolateral medulla activity. By contrast, they are dispensable for other peripheral sympathoexcitation-associated disorders sparing metabolic alterations in liver.

Vav proteins maintain epithelial traits in breast cancer cells using miR-200c-dependent and independent mechanisms.

The bidirectional regulation of epithelial-mesenchymal transitions (EMT) is key in tumorigenesis. Rho GTPases regulate this process via canonical pathways that impinge on the stability of cell-to-cell contacts, cytoskeletal dynamics, and cell invasiveness. Here, we report that the Rho GTPase activators Vav2 and Vav3 utilize a new Rac1-dependent and miR-200c-dependent mechanism that maintains the epithelial state by limiting the abundance of the Zeb2 transcriptional repressor in breast cancer cells. In parallel, Vav proteins engage a mir-200c-independent expression prometastatic program that maintains epithelial cell traits only under 3D culture conditions. Consistent with this, the depletion of endogenous Vav proteins triggers mesenchymal features in epithelioid breast cancer cells. Conversely, the ectopic expression of an active version of Vav2 promotes mesenchymal-epithelial transitions using E-cadherin-dependent and independent mechanisms depending on the mesenchymal breast cancer cell line used. In silico analyses suggest that the negative Vav anti-EMT pathway is operative in luminal breast tumors. Gene signatures from the Vav-associated proepithelial and prometastatic programs have prognostic value in breast cancer patients.

Zofenopril exerts a cardiovascular protective effect on rats infused with angiotensin II beyond angiotensin-converting enzyme inhibition.

OBJECTIVES: Elevated levels of angiotensin II are implicated in the hypertensive pathophysiological process. Zofenopril has a sulphydryl group which gives it antioxidant properties. The aim of this study was to investigate its beneficial effects beyond angiotensin-converting enzyme (ACE) inhibition using angiotensin II-infused rats as hypertension model. METHODS: Zofenopril was added in drinking water. Systolic blood pressure was assessed by the tail-cuff method. Left ventricular weight/body weight ratio was calculated as cardiac hypertrophy index. An estimate of the cardiac collagen was performed by measuring the content of hydroxyproline. Vascular reactivity was evaluated on aortic rings and isolated perfused kidney, and vascular structure in thoracic aorta was studied. Superoxide anion generation was quantified in aorta by lucigenin-enhanced chemiluminescence. KEY FINDINGS: Zofenopril partially prevented the increase in systolic blood pressure and cardiac hypertrophy induced by angiotensin II and avoided the increase in collagen deposition. The treatment improved vasorelaxing responses, reversed the vascular remodelling and abolished the effects of angiotensin II on the production of ·O2-. It is worth to mention that all these results are observed even with high levels of plasma angiotensin. CONCLUSION: Zofenopril could exert additional beneficial effects beyond ACE inhibition that would justify the improvement of pathophysiological processes triggered by angiotensin II.

Genetic dissection of the vav2-rac1 signaling axis in vascular smooth muscle cells.

Vascular smooth muscle cells (vSMCs) are key in the regulation of blood pressure and the engagement of vascular pathologies, such as hypertension, arterial remodeling, and neointima formation. The role of the Rac1 GTPase in these cells remains poorly characterized. To clarify this issue, we have utilized genetically engineered mice to manipulate the signaling output of Rac1 in these cells at will using inducible, Cre-loxP-mediated DNA recombination techniques. Here, we show that the expression of an active version of the Rac1 activator Vav2 exclusively in vSMCs leads to hypotension as well as the elimination of the hypertension induced by the systemic loss of wild-type Vav2. Conversely, the specific depletion of Rac1 in vSMCs causes defective nitric oxide vasodilation responses and hypertension. Rac1, but not Vav2, also is important for neointima formation but not for hypertension-driven vascular remodeling. These animals also have allowed us to dismiss etiological connections between hypertension and metabolic disease and, most importantly, identify pathophysiological programs that cooperate in the development and consolidation of hypertensive states caused by local vascular tone dysfunctions. Finally, our results suggest that the therapeutic inhibition of Rac1 will be associated with extensive cardiovascular system-related side effects and identify pharmacological avenues to circumvent them.

Hypertension and hyperglycemia synergize to cause incipient renal tubular alterations resulting in increased NGAL urinary excretion in rats.

BACKGROUND: Hypertension and diabetes are the two leading causes of chronic kidney disease (CKD) eventually leading to end stage renal disease (ESRD) and the need of renal replacement therapy. Mortality among CKD and ESRD patients is high, mostly due to cardiovascular events. New early markers of risk are necessary to better anticipate the course of the disease, to detect the renal affection of additive risk factors, and to appropriately handle patients in a pre-emptive and personalized manner. METHODS: Renal function and NGAL urinary excretion was monitored in rats with spontaneous (SHR) or L-NAME induced hypertension rendered hyperglycemic (or not as controls). RESULTS: Combination of hypertension and hyperglycemia (but not each of these factors independently) causes an increased urinary excretion of neutrophil gelatinase-associated lipocalin (NGAL) in the rat, in the absence of signs of renal damage. Increased NGAL excretion is observed in diabetic animals with two independent models of hypertension. Elevated urinary NGAL results from a specific alteration in its tubular handling, rather than from an increase in its renal expression. In fact, when kidneys of hyperglycaemic-hypertensive rats are perfused in situ with Krebs-dextran solution containing exogenous NGAL, they excrete more NGAL in the urine than hypertensive rats. We also show that albuminuria is not capable of detecting the additive effect posed by the coexistence of these two risk factors. CONCLUSIONS: Our results suggest that accumulation of hypertension and hyperglycemia induces an incipient and quite specific alteration in the tubular handling of NGAL resulting in its increased urinary excretion.

Pravastatin improves endothelial function in arteries used in coronary bypass grafting.

Internal mammary artery (IMA) and radial artery (RA) are the 2 main arterial conduits used in coronary artery bypass grafting (CABG). The aim of this study was to analyze in vitro the vasoreactive properties in both vessels and to investigate the effects of pravastatin incubation on vascular function. IMA and RA rings obtained from patients undergoing CABG were studied in organ baths. We examined the contractile responses to phenylephrine and U46619 and the relaxation to acetylcholine (ACh) and sodium nitroprusside. In another series of experiments, the vascular reactivity and the superoxide anion production were studied after incubation with pravastatin. The effect of mevalonic acid on such responses was also assessed. Our results show that RA significantly evoked greater tension in response to vasoconstrictor agents and higher relaxation to ACh than IMA. In contrast, relaxation induced by sodium nitroprusside was not significantly different. Incubation with pravastatin reduced the contractile response to U46619 and improved the endothelium-dependent relaxation to ACh in both arteries. Whereas the effect of pravastatin on response to U46619 was completely abolished by coincubation with mevalonic acid, only a partial inhibition on ACh relaxation was observed. In conclusion, in vitro incubation with pravastatin enhanced endothelial function in IMA and RA. This suggests that postoperative (may include intraoperative) administration of statins could improve the endothelial function of arterial grafts in patients undergoing CABG.

Transcriptional factor aryl hydrocarbon receptor (Ahr) controls cardiovascular and respiratory functions by regulating the expression of the Vav3 proto-oncogene.

Aryl hydrocarbon receptor (Ahr) is a transcriptional factor involved in detoxification responses to pollutants and in intrinsic biological processes of multicellular organisms. We recently described that Vav3, an activator of Rho/Rac GTPases, is an Ahr transcriptional target in embryonic fibroblasts. These results prompted us to compare the Ahr(-/-) and Vav3(-/-) mouse phenotypes to investigate the implications of this functional interaction in vivo. Here, we show that Ahr is important for Vav3 expression in kidney, lung, heart, liver, and brainstem regions. This process is not affected by the administration of potent Ahr ligands such as benzo[a]pyrene. We also report that Ahr- and Vav3-deficient mice display hypertension, tachypnea, and sympathoexcitation. The Ahr gene deficiency also induces the GABAergic transmission defects present in the Vav3(-/-) ventrolateral medulla, a main cardiorespiratory brainstem center. However, Ahr(-/-) mice, unlike Vav3-deficient animals, display additional defects in fertility, perinatal growth, liver size and function, closure, spleen size, and peripheral lymphocytes. These results demonstrate that Vav3 is a bona fide Ahr target that is in charge of a limited subset of the developmental and physiological functions controlled by this transcriptional factor. Our data also reveal the presence of sympathoexcitation and new cardiorespiratory defects in Ahr(-/-) mice.

Vav3 is involved in GABAergic axon guidance events important for the proper function of brainstem neurons controlling cardiovascular, respiratory, and renal parameters.

Vav3 is a phosphorylation-dependent activator of Rho/Rac GTPases that has been implicated in hematopoietic, bone, cerebellar, and cardiovascular roles. Consistent with the latter function, Vav3-deficient mice develop hypertension, tachycardia, and renocardiovascular dysfunctions. The cause of those defects remains unknown as yet. Here, we show that Vav3 is expressed in GABAegic neurons of the ventrolateral medulla (VLM), a brainstem area that modulates respiratory rates and, via sympathetic efferents, a large number of physiological circuits controlling blood pressure. On Vav3 loss, GABAergic cells of the caudal VLM cannot innervate properly their postsynaptic targets in the rostral VLM, leading to reduced GABAergic transmission between these two areas. This results in an abnormal regulation of catecholamine blood levels and in improper control of blood pressure and respiration rates to GABAergic signals. By contrast, the reaction of the rostral VLM to excitatory signals is not impaired. Consistent with those observations, we also demonstrate that Vav3 plays important roles in axon branching and growth cone morphology in primary GABAergic cells. Our study discloses an essential and nonredundant role for this Vav family member in axon guidance events in brainstem neurons that control blood pressure and respiratory rates.

The Rho/Rac exchange factor Vav2 controls nitric oxide-dependent responses in mouse vascular smooth muscle cells.

The regulation of arterial contractility is essential for blood pressure control. The GTPase RhoA promotes vasoconstriction by modulating the cytoskeleton of vascular smooth muscle cells. Whether other Rho/Rac pathways contribute to blood pressure regulation remains unknown. By studying a hypertensive knockout mouse lacking the Rho/Rac activator Vav2, we have discovered a new signaling pathway involving Vav2, the GTPase Rac1, and the serine/threonine kinase Pak that contributes to nitric oxide-triggered blood vessel relaxation and normotensia. This pathway mediated the Pak-dependent inhibition of phosphodiesterase type 5, a process that favored RhoA inactivation and the subsequent depolymerization of the F-actin cytoskeleton in vascular smooth muscle cells. The inhibition of phosphodiesterase type 5 required its physical interaction with autophosphorylated Pak1 but, unexpectedly, occurred without detectable transphosphorylation events between those 2 proteins. The administration of phosphodiesterase type 5 inhibitors prevented the development of hypertension and cardiovascular disease in Vav2-deficient animals, demonstrating the involvement of this new pathway in blood pressure regulation. Taken together, these results unveil one cause of the cardiovascular phenotype of Vav2-knockout mice, identify a new Rac1/Pak1 signaling pathway, and provide a mechanistic framework for better understanding blood pressure control in physiological and pathological states.

Vav3 proto-oncogene deficiency leads to sympathetic hyperactivity and cardiovascular dysfunction.

Although much is known about environmental factors that predispose individuals to hypertension and cardiovascular disease, little information is available regarding the genetic and signaling events involved. Indeed, few genes associated with the progression of these pathologies have been discovered despite intensive research in animal models and human populations. Here we identify Vav3, a GDP-GTP exchange factor that stimulates Rho and Rac GTPases, as an essential factor regulating the homeostasis of the cardiovascular system. Vav3-deficient mice exhibited tachycardia, systemic arterial hypertension and extensive cardiovascular remodeling. These mice also showed hyperactivity of sympathetic neurons from the time of birth. The high catecholamine levels associated with this condition led to the activation of the renin-angiotensin system, increased levels of kidney-related hormones and the progressive loss of cardiovascular and renal homeostasis. Pharmacological studies with drugs targeting sympathetic and renin-angiotensin responses confirmed the causative role and hierarchy of these events in the development of the Vav3-null mouse phenotype. These observations uncover the crucial role of Vav3 in the regulation of the sympathetic nervous system (SNS) and cardiovascular physiology, and reveal a signaling pathway that could be involved in the pathophysiology of human disease states involving tachycardia and sympathetic hyperactivity with unknown etiologies.

Cardiovascular effects of nebivolol in spontaneously hypertensive rats persist after treatment withdrawal.

OBJECTIVES: We observed previously that nebivolol treatment for 2 months reduced cardiovascular lesions in spontaneously hypertensive rats (SHR). Therefore, we investigated whether this beneficial effect is increased with a longer treatment, and its persistence after withdrawal. METHODS: Male SHR were treated with 8 mg/kg per day of nebivolol (N-SHR) for 6 months. A separate group was also given identical treatment but they were then monitored for a further 3 months after drug withdrawal. SHR and Wistar-Kyoto rats (WKY) receiving vehicle were used as controls. Systolic blood pressure and heart rate were measured using the tail-cuff method. Left ventricular weight/body weight ratio was calculated as the hypertrophy index. Cardiac and vascular fibrosis was evaluated on sections stained with sirious red. Vascular reactivity was evaluated on aortic rings through acetylcholine and sodium nitroprusside responses. The effect of treatment on vascular structure was assessed by lumen diameter, wall thickness and medial cross-sectional area determination. RESULTS: Blood pressure was reduced in N-SHR. After withdrawal it increased progressively, without reaching the values of the hypertensive controls. Cardiac hypertrophy and collagen content both in heart and aorta were significantly reduced, and these changes persisted after nebivolol suppression. Acetylcholine-induced relaxant response was improved by nebivolol and maintained after withdrawal. Medial thickness and cross-sectional area were significantly reduced in both conductance and resistance arteries, and these effects persisted after withdrawal. CONCLUSION: The nebivolol antihypertensive effect was accompanied by an important reduction of hypertrophy and collagen deposition in both vascular and left ventricle tissue, which was maintained after a long period of therapy withdrawal.

Amlodipine decreases fibrosis and cardiac hypertrophy in spontaneously hypertensive rats: persistent effects after withdrawal.

Our objective was to examine the effect of chronic treatment with amlodipine on blood pressure, left ventricular hypertrophy, and fibrosis in spontaneously hypertensive rats and the persistence of such an effect after drug withdrawal. We investigated the effects of treatment with 2, 8 and 20 mg/kg/day of amlodipine given orally for six months and at three months after drug withdrawal. Systolic blood pressure was measured using the tail-cuff method. At the end of the study period, the heart was excised, the left ventricle was isolated, and the left ventricle weight/body weight ratio was calculated as a left ventricular hypertrophy index. Fibrosis, expressed as collagen volume fraction, was evaluated using an automated image-analysis system on sections stained with Sirius red. Age-matched untreated Wistar-Kyoto and SHR were used as normotensive and hypertensive controls, respectively. Systolic blood pressure was reduced in the treated SHR in a dose-dependent way and after amlodipine withdrawal it increased progressively, without reaching the values of the hypertensive controls. Cardiac hypertrophy was reduced by 8 and 20 mg/kg/day amlodipine, but when treatment was withdrawn only the group treated with 8 mg/kg/day maintained significant differences versus the hypertensive controls. All three doses of amlodipine reduced cardiac fibrosis and this regression persisted with the two highest doses after three months without treatment. We concluded that antihypertensive treatment with amlodipine is accompanied by a reduction in left ventricular hypertrophy and regression in collagen deposition. Treatment was more effective in preventing fibrosis than in preventing ventricular hypertrophy after drug withdrawal.

Beneficial effects of trandolapril in uninephrectomized spontaneously hypertensive rats: role of cyclooxygenase pathway.

The antihypertensive efficacy of the angiotensin-converting enzyme inhibitor trandolapril was evaluated in uninephrectomized spontaneously hypertensive rats. After 5 weeks of treatment, blood pressure, cardiac and aortic mass, as well as the functional status of the aortic endothelium, and the role played by the cyclooxygenase pathway were investigated. In addition, the effect of a sub-antihypertensive dose of the calcium antagonist verapamil, in combination with trandolapril, was also investigated. As compared to placebo, trandolapril returned blood pressure and aortic lamina media cross sectional area to normotensive values, significantly reduced the heart-to-body weight, and improved the acetylcholine-induced relaxation of aortic rings. This latter effect is thought to be mediated by the elimination of a substance derived from the cyclooxygenase pathway. Verapamil, in single therapy, did not reduce blood pressure, or heart-to-body weight, increased aortic lamina media cross sectional area and impaired acetylcholine-induced relaxation. When combined with trandolapril in dual therapy, some of the beneficial effects of trandolapril remained, whereas others were counterbalanced by verapamil. In conclusion, trandolapril proved to be an effective therapeutic drug in this animal model of hypertension. Combination of trandolapril with a sub-antihypertensive dose of verapamil did not show any positive synergistic effect; on the contrary, it outweighed some of the beneficial effects of trandolapril.