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Yes-associated protein (YAP) and its associated coactivator of PDZ-binding motif (TAZ) are co-transcriptional regulators and down effectors of the Hippo signaling pathway. Recent studies have shown that the Hippo/YAP signaling pathway may play a role in mediating vascular homeostasis. This study investigated the role of YAP/TAZ in endothelial dysfunction and vascular inflammation in angiotensin (Ang)II hypertensive mice. The infusion of AngII (1.1 mg/kg/day by mini-pump) for 3 weeks induced the activation of YAP/TAZ, manifested by decreased cytosolic phosphor-YAP and phosphor-TAZ, and increased YAP/TAZ nuclear translocation, which were prevented by YAP/TAZ inhibitor verteporfin. AngII significantly increased systolic blood pressure (SBP), macrophage infiltration, and expressions of proinflammatory cytokines, and impaired endothelial function in the aorta of the mice. Treatment with verteporfin improved endothelial function and reduced vascular inflammation with a mild reduction in SBP. AngII also induced YAP/TAZ activation in human umbilical vein endothelial cells in vitro, which were prevented by LB-100, an inhibitor of protein phosphatase 2A (PP2A, a major dephosphorylase). Treatment with LB-100 reversed AngII-induced proinflammatory cytokine expression and impairment of phosphor-eNOS expression in vitro. Our results suggest that AngII induces YAP/TAZ activation via PP2A-dependent dephosphorylation, which may contribute to the impairment of endothelial function and the induction of vascular inflammation in hypertension. YAP/TAZ may be a new target for hypertensive vascular injury.

Vascular endothelial insulin signaling is critical for the maintenance of vascular and metabolic homeostasis. We have previously shown that in hypertensive Dahl rats, impaired vascular insulin action is linked to angiotensin II activation of the NFκB inflammatory pathway. Macrophage polarization (M1) has implicated in hypertensive and metabolic diseases. Here, we investigated the effect of macrophage depletion using liposome-encapsulated clodronate (LEC) on endothelial insulin resistance and cardiovascular remodeling in Dahl salt-sensitive (DS) rats. High salt intake (HS) for 5 weeks increased systolic blood pressure (SBP: 192±5 vs. 144±4 mmHg in NS, p<0.05), aortic and cardiac hypertrophy, cardiac fibrosis, and impaired acetylcholine- and insulin-induced vasorelaxation, accompanied by impaired insulin activation of endothelial nitric oxide synthases (eNOS)/NO signaling. HS rats had a significant increase in CD68 (a monocyte/macrophage marker) expression in the aorta and the heart. LEC reduced SBP (168±5 mmHg, p<0.05) and cardiovascular injury and improved acetylcholine- and insulin-mediated vasorelaxation and insulin signaling molecules with a reduction in the macrophage infiltration in the aorta and the heart. HS rats also manifested an increase in the aortic expressions of inflammatory cytokines, including the ratio of phosphorylated inhibitory kappa B (Iκb)/Iκb, tumor necrosis factor α, and phosphorylated c-Jun N-terminal kinase (JNK) and oxidative stress, which were reduced in HS/LEC rats. Our results suggest that in salt-sensitive hypertension, macrophage may importantly contribute to endothelial insulin resistance, vascular inflammation, and injury. These findings support the idea that macrophages may be a new target for immunotherapy of vasculopathy in hypertensive and metabolic disorders.

Obesity and cigarette smoke are major cardiovascular (CV) risk factors and, when coexisting in the same individuals, have additive/synergistic effects upon CVD. We studied the mechanisms involved in nicotine enhancement of CVD in Sprague Dawley rats with diet-induced obesity. The rats were fed either a high fat (HFD) or normal rat chow diet with or without nicotine (100 mg/L in drinking water) for 20 weeks. HFD rats developed central obesity, increased systolic blood pressure (SBP), aortic superoxide (O2-) production, and impaired endothelial nitric oxide synthase (eNOS) and endothelium-dependent relaxation to acetylcholine (EDR). Nicotine further increased SBP, O2- and impaired eNOS and EDR in obese rats. In the peritoneal macrophages from obese rats, tumor necrosis factor (TNF) α, interleukin 1β and CD36 were increased, and were further increased in nicotine-treated obese rats. Using PCR array we found that 3 of 84 target proinflammatory genes were increased by 2-4 fold in the aorta of obese rats, 11 of the target genes were further increased in nicotine-treated obese rats. HUVECs, incubated with conditioned medium from the peritoneal macrophages of nicotine treated-obese rats, exhibited reduced eNOS and increased NADPH oxidase subunits gp91phox and p22phox expression. Those effects were partially prevented by adding anti-TNFα antibody to the conditioned medium. Our results suggest that nicotine aggravates the CV effects of diet-induced obesity including the oxidative stress, vascular inflammation and endothelial dysfunction. The underlying mechanisms may involve in targeting endothelium by enhancement of macrophage-derived TNFα.

Reduced numbers and activity of circulating progenitor cells are associated with aging and have been linked with coronary artery disease. To determine the impact of aging and atherosclerotic disease on the chemotaxic activity of bone marrow derived cells (BMCs), we examined CXCR4 surface expression on BMCs from aged and atherosclerotic mice.CXCR4 expression and cellular mobility were compared between BMCs of young (6-week old) ApoE null mice (ApoE(-/-)) and aged ApoE(-/-) mice that had been fed with a high-fat, high-cholesterol diet for 6-months.Age and atherosclerosis correlated with significantly lower surface expression of CXCR4 that was less inducible by calcium. The impaired calcium response was associated with defective calcium influx and was partially recovered by treatment with the calcium ionophore ionomycin. ApoE(-/-) mice fed high fat diet for 6-months had defective CXCR4 expression and SDF-1 regulation that is equivalent to that of 24-month old wild type mice. BMCs from aged, atherogenic ApoE(-/-) mice also displayed defective homing to SDF-1, and the animals had lower serum and bone marrow levels of SDF-1.Evolution of atherosclerosis in ApoE(-/-) mice is paralleled by progressive loss of mobility of BMCs with reductions of CXCR4 expression, and reduced levels of SDF-1 in both serum and bone marrow. These changes mute the homing capability of BMCs and may contribute to the progression of atherosclerosis in this model.

Insulin resistance and hypertension are considered as prototypical “diseases of civilization” that are manifested in the modern environment as plentiful food and sedentary life. The human propensity for insulin resistance and hypertension is a product, at least in part, of our evolutionary history. Adaptation to ancient lifestyle characterized by a low sodium, low-calorie food supply and physical stress to injury response has driven our evolution to shape and preserve a thrifty genotype, which is favorite with energy-saving and sodium conservation. As our civilization evolved, a sedentary lifestyle and sodium- and energy-rich diet, the thrifty genotype is no longer advantageous, and may be maladaptive to disease phenotype, such as hypertension, obesity and insulin resistance syndrome. This article reviews human evolution and the impact of the modern environment on hypertension and insulin resistance.