Is there a new treatment for hypertensive disease in the horizon? Role of soluble guanylate cyclase.
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Biomedical subjects
Publications and source records attributed to Veronica Franco.
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High dietary sodium has been adduced as a cause of hypertension and its target organ damage for millennia; yet careful observations using sophisticated techniques have revealed only a weak relationship between sodium intake/excretion and blood pressure in the general population. Further, studies of the effects of dietary sodium reduction on blood pressure have revealed minimal achieved reductions in blood pressure, no relationship between the magnitude of reduction in sodium intake/excretion and the blood pressure effect, and no evidence of an effect of sodium reduction on death or cardiovascular events. While blood pressure in the population as a whole is only modestly responsive to alterations in sodium intake, some individuals manifest large blood pressure changes in response to acute or chronic salt depletion or repletion, and are termed "salt sensitive". Salt sensitivity and resistance have a large variety of determinants, including genetic factors, race/ethnicity, age, body mass and diet (overall diet quality, macro- and micronutrient content), as well as associated disease states, e.g. hypertension, diabetes and renal dysfunction. Salt sensitivity can be modulated by improving the quality of the diet, e.g. the DASH diet reduced salt sensitivity by increasing the slope of the pressure-natriuresis curve. Mechanisms that appear to contribute to salt sensitivity include blunted activity of the renin-angiotensin-aldosterone system, deficiency in atrial natriuretic peptide expression, and blunted arterial baroreflex sensitivity. Salt sensitivity in both normotensive and hypertensive persons has been associated with increased cardiovascular disease events and reduced survival. Increased attention to strategies that reduce salt sensitivity, i.e. improvement in diet quality and weight loss, particularly in high risk persons, is urgently needed.
1. Atrial natriuretic peptide (ANP)-null mice (Nppa(-/-)) exhibit cardiac hypertrophy at baseline and adverse cardiac remodelling in response to transverse aortic constriction (TAC)-induced pressure overload stress. Previous studies have suggested that natriuretic peptides could potentially oppose mineralocorticoid signalling at several levels, including suppression of adrenal aldosterone production, inhibition of mineralocorticoid receptor (MR) activation or suppression of MR-mediated production of pro-inflammatory factors. Thus, we hypothesized that the MR blocker eplerenone would prevent the exaggerated left ventricular (LV) remodelling/fibrosis and dysfunction after TAC in Nppa(-/-). 2. In the present study, Nppa(-/-) and wild-type Nppa(+/+) mice fed eplerenone- or vehicle (oatmeal)-supplemented chow since weaning were subjected to TAC or sham operation. The daily dose of eplerenone administered was approximately 200 mg/kg. At 1 week after TAC, LV size and function were evaluated by echocardiogram and LV cross-sections were stained with picrosirius red for collagen volume measurement. Total RNA was extracted from the LV for real-time polymerase chain reaction analysis of osteopontin. 3. Eplerenone had no effect on baseline hypertrophy observed in sham-operated Nppa(-/-) compared with Nppa(+/+) mice. Eplerenone attenuated the TAC-induced increase in LV weight in both genotypes and completely prevented LV dilation, systolic dysfunction and interstitial collagen deposition seen in Nppa(-/-) mice after TAC. However, serum aldosterone levels were lower in Nppa(-/-) compared with Nppa(+/+) wild types. No interaction between eplerenone and genotype in osteopontin mRNA levels was observed. 4. Eplerenone prevents adverse cardiac remodelling related to pressure overload in ANP-deficient mice, mainly due to an antifibrotic effect. The mechanism whereby ANP deficiency leads to excess hypertrophy, fibrosis and early failure following TAC is increased profibrotic signals resulting from excess or unopposed MR activation, rather than increased levels of aldosterone.
We hypothesized that a single copy of the proatrial natriuretic peptide gene (Nppa+/-) would not be adequate to protect heterozygous mice against exaggerated cardiac hypertrophy and remodeling after pressure-overload stress. Nppa+/+, Nppa+/-, and Nppa-/- mice were subjected to sham surgery or transverse aortic constriction and fed a basal salt diet. Heart weight varied inversely with Nppa gene load by 1 week after either surgery. Fractional shortening did not differ among genotypes at baseline and fell in Nppa-/- mice only after transverse aortic constriction. There was a graded response in collagen deposition related to atrial natriuretic peptide (ANP) expression after either surgery. A robust interstitial and perivascular fibrosis was noted in Nppa-/- and Nppa+/- but not in Nppa+/+ mice after transverse aortic constriction. Our findings are consistent with a growing body of evidence that ANP is an important modulator of cardiac hypertrophy and remodeling in response to hemodynamic stress. The observation that partial ANP deficiency results in exaggerated hypertrophy and remodeling after pressure overload suggests that genetic or environmental variation in ANP levels may play a role in the development of cardiac hypertrophy, remodeling, and failure in humans.
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Hypertension, particularly systolic hypertension, affects postmenopausal women and is an important risk factor for cardiovascular disease in this group. In the last year, several papers have better defined the mechanisms by which hormone replacement therapy influences blood pressure in postmenopausal women, including effects on nitric oxide, angiotensin II and vascular stiffness (compliance). Currently, data concerning the influence of hormone replacement therapy on blood pressure in postmenopausal women are inconclusive because of the limitations of published studies. It is clear, however, that hypertension is not a contraindication to starting hormone replacement therapy.