Deletion of STAT5a/b in vascular smooth muscle abrogates the male bias in hypoxic pulmonary hypertension in mice: implications in the human disease.

Chronic hypoxia typically elicits pulmonary hypertension (PH) in mice with a male-dominant phenotype. There is an opposite-sex bias in human PH, with a higher prevalence in women, but greater survival (the "estrogen paradox"). We investigated the involvement of the STAT5a/b species, previously established to mediate sexual dimorphism in other contexts, in the sex bias in PH. Mice with heterozygous or homozygous deletions of the STAT5a/b locus in vascular smooth muscle cells (SMCs) were generated in crosses between STAT5a/b(fl/fl) and transgelin (SM22α)-Cre(+/+) parents. Wild-type (wt) males subjected to chronic hypoxia showed significant PH and pulmonary arterial remodeling, with wt females showing minimal changes (a male-dominant phenotype). However, in conditional STAT5(+/-) or STAT5(-/-) mice, hypoxic females showed the severest manifestations of PH (a female-dominant phenotype). Immunofluorescence studies on human lung sections showed that obliterative pulmonary arterial lesions in patients with idiopathic pulmonary arterial hypertension (IPAH) or hereditary pulmonary arterial hypertension (HPAH), both male and female, overall had reduced STAT5a/b, reduced PY-STAT5 and reduced endoplasmic reticulum (ER) GTPase atlastin-3 (ATL3). Studies of SMCs and endothelial cell (EC) lines derived from vessels isolated from lungs of male and female IPAH patients and controls revealed instances of coordinate reductions in STAT5a, STAT5b and ATL3 in IPAH-derived cells, including SMCs and ECs from the same patient. Taken together, these data provide the first definitive evidence for a contribution of STAT5a/b to the sex bias in PH in the hypoxic mouse and implicate reduced STAT5 in the pathogenesis of the human disease.

Potential mechanisms of low-sodium diet-induced cardiac disease: superoxide-NO in the heart.

RATIONALE: Patients on a low salt (LS) diet have increased mortality. OBJECTIVE: To determine whether reduction in NO bioactivity may contribute to the LS-induced cardiac dysfunction and mortality. METHODS AND RESULTS: Adult male mongrel dogs were placed on LS (0.05% sodium chloride) for 2 weeks. Body weight (25.4 + or - 0.4 to 23.6 + or - 0.4 kg), left ventricular systolic pressure (137.0 + or - 3.4 to 124.0 + or - 6.7 mm Hg), and mean aortic pressure (111 + or - 3.1 to 98 + or - 4.3 mm Hg) decreased. Plasma angiotensin II concentration increased (4.4 + or - 0.7 to 14.8 + or - 3.7 pg/mL). Veratrine-induced (5 microg/kg) NO-mediated vasodilation was inhibited by 44% in LS; however, the simultaneous intravenous infusion of ascorbic acid or apocynin acutely and completely reversed this inhibition. In LS heart tissues, lucigenin chemiluminescence was increased 2.3-fold to angiotensin II (10(-8) mol/L), and bradykinin (10(-4) mol/L) induced reduction of myocardial oxygen consumption in vitro was decreased (40 + or - 1.3% to 16 + or - 6.3%) and completely restored by coincubation with tiron, tempol or apocynin. Switching of substrate uptake from free fatty acid to glucose by the heart was observed (free fatty acid: 8.97 + or - 1.39 to 4.53 + or - 1.12 micromol/min; glucose: 1.31 + or - 0.52 to 6.86 + or - 1.78 micromol/min). Western blotting indicated an increase in both p47(phox) (121%) and gp91(phox) (44%) as did RNA microarray analysis (433 genes changed) showed an increase in p47(phox) (1.6-fold) and gp91(phox) (2.0 fold) in the LS heart tissue. CONCLUSIONS: LS diet induces the activation of the renin-angiotensin system, which increases oxidative stress via the NADPH oxidase and attenuates NO bioavailability in the heart.

Tumor necrosis factor alpha alters Na+-K+ ATPase activity in rat cardiac myocytes: involvement of NF-kappaB, AP-1 and PGE2.

There has been increasing evidence that tumor necrosis factor alpha (TNF-alpha) is synthesized by cardiomyoctes and contributes to their impaired function and to cardiac failure. Because the Na(+)-K(+) ATPase is a key player in the contraction of cardiomyocytes, this work was undertaken to study the effect of TNF-alpha on the Na(+)-K(+) ATPase in rat heart. Sprague Dawley rats (Rattus norvegicus) were injected with TNF-alpha (270 ng/100 g body weight) and 4 h later the ventricles were isolated, homogenized and assayed for their Na(+)-K(+) ATPase activity. The effect of TNF-alpha on the pump was studied also in isolated myocytes treated in suspension. The involvement of PGE2 was investigated by pre-treating animals or cells with indomethacin, an inhibitor of COX enzymes. The involvement of NF-kappaB and AP-1 was studied using their respective inhibitors PDTC and curcumin. A time response study showed an increase in the activity of the Na(+)-K(+) ATPase in the left and right ventricles of animals treated with the cytokine, with no change in its protein expression. This effect disappeared in the presence of indomethacin suggesting an involvement of PGE(2) in the action of TNF-alpha. Rats and cells treated directly with PGE(2) showed a dose-dependent response. A decrease in the activity of the Na(+)-K(+) ATPase was observed at a low dose and an increase at a high dose in both ventricles. Since PGE(2) is suspected to be the active mediator in TNF-alpha signaling, inhibiting its synthesis by inhibiting some suspected transcription factors was attempted. PDTC abrogated fully, and curcumin partially the effect of the cytokine. It was concluded that TNF-alpha activates NF-kappaB and AP-1 and induces PGE(2) release which alters dose-dependently the activity of the pump by activating different EP receptors with different affinities for PGE(2).