Acute changes of biventricular gene expression in volume and right ventricular pressure overload.

OBJECTIVE: We investigated the effects of acute volume and RV pressure overload on biventricular function and gene expression of BNP, pro-inflammatory cytokines (IL-6 and TNF-alpha), iNOS, growth factors (IGF-1, ppET-1), ACE and Ca2+-handling proteins (SERCA2a, phospholamban and calsequestrin). METHODS: Male Wistar rats (n=45) instrumented with pressure tip micromanometers in right (RV) and left ventricular (LV) cavities were assigned to one of three protocols: i) Acute RV pressure overload induced by pulmonary trunk banding in order to double RV peak systolic pressure, during 120 or 360 min; ii) acute volume overload induced by dextran40 infusion (5 ml/h), during 120 or 360 min; iii) Sham. RV and LV samples were collected for mRNA quantification. RESULTS: BNP upregulation was restricted to the overloaded ventricles. TNF-alpha, IL-6, ppET-1, SERCA2a and phospholamban gene activation was higher in volume than in pressure overload. IGF-1 overexpression was similar in both types of overload, but was limited to the RV. TNF-alpha and CSQ mRNA levels were increased in the non-overloaded LV after pulmonary trunk banding. No significant changes were detected in ACE or iNOS expression. RV end-diastolic pressures positively correlated with local expression of BNP, TNF-alpha, IL-6, IGF-1, ppET-1 and SERCA2a, while RV peak systolic pressures correlated only with local expression of IL-6, IGF-1 and ppET-1. CONCLUSIONS: Acute cardiac overload alters myocardial gene expression profile, distinctly in volume and pressure overload. These changes correlate more closely with diastolic than with systolic load. Nonetheless, gene activation is also present in the non-overloaded LV of selectively RV overloaded hearts.

Antenatal vitamin A administration attenuates lung hypoplasia by interfering with early instead of late determinants of lung underdevelopment in congenital diaphragmatic hernia.

BACKGROUND/PURPOSE: Early and late lung underdevelopment in congenital diaphragmatic hernia (CDH) is likely caused by nonmechanical (directly mediated by nitrofen) and mechanical (mediated by thoracic herniation) factors, respectively. The authors investigated if vitamin A enhances lung growth because of effects on both early and late determinants of lung hypoplasia. METHODS: Twenty-seven pregnant Wistar rats were exposed on embryonic day (E)9.5 to 100 mg of nitrofen or just olive oil. From nitrofen-exposed pregnant rats, 12 were treated at day 9.5 or 18.5 with 15,000 IU of vitamin A. Lungs were harvested at E18, E20, and E22, weighed, and analyzed for DNA and protein contents. Left and/or right lung hypoplasia was estimated by assessment of the ratios of lung to body weight and left to right lung weight. Fetuses were assigned to 5 experimental groups: baseline (exposed neither to nitrofen nor vitamin A), nitrofen (exposed to nitrofen without CDH), CDH (exposed to nitrofen with CDH), nitr+vitA (exposed to nitrofen without CDH and treated with vitamin A), and CDH+vitA (exposed to nitrofen with CDH and treated with vitamin A). RESULTS: Incidence of hernia was significantly reduced in fetuses treated with vitamin A. When vitamin A was administered at E9.5, the authors observed similar effect on lung hypoplasia measured through ratio of lung to body weight at E18 in the nitrofen and CDH groups (nitrofen 1.92% +/- 0.05%, CDH 1.92% +/- 0.04%), whereas lung hypoplasia was attenuated relative to baseline (2.45% +/- 0.05%) in 5% and 4% in nitrofen (nitr+vitA 2.05% +/- 0.03%) and CDH (CDH+vitA 2.08% +/- 0.04%) groups, respectively. At E20, lung hypoplasia was increased in CDH compared with nitrofen groups (nitrofen 2.52% +/- 0.1%, CDH 2.39% +/- 0.05%), whereas vitamin A attenuated lung hypoplasia, in relation to baseline (3.20% +/- 0.07%), 14% in both nitrofen-exposed groups (nitr+vitA 2.96% +/- 0.03%, CDH+vitA 2.83% +/- 0.03%). At E22, lung hypoplasia was significantly higher in CDH group than nitrofen group (nitrofen 2.13% +/- 0.06%, CDH 1.48% +/- 0.03%), whereas lung hypoplasia was attenuated in 9% of both nitrofen-exposed groups (nitr+vitA 2.35% +/- 0.06%, CDH+vitA 1.69% +/- 0.05%) in relation to baseline group (2.38% +/- 0.04%). Administration of vitamin A at E18.5 produced no significant effects on lung growth. CONCLUSIONS: The authors conclude from these results that antenatal administration of vitamin A attenuates lung hypoplasia in CDH by interfering with early determinants of lung underdevelopment. This finding may have clinical implications because prenatal diagnosis of human CDH commonly occurs after 16 weeks' gestation when late determinants of lung hypoplasia likely predominate.

Activation profile of pro-inflammatory cytokines in acute cardiac overload.

INTRODUCTION: Pro-inflammatory cytokines have been implicated in ventricular remodeling during heart failure progression. In the present study, we investigated the effects of acute volume and RV pressure overload on biventricular hemodynamics and myocardial gene expression of IL-6 and TNF-alpha. METHODS: Male Wistar rats (n = 45) instrumented with RV and LV tip micromanometers were randomly assigned to one of three protocols: i) acute RV pressure overload (PrOv) induced by pulmonary trunk banding in order to double RV peak systolic pressure, for 120 or 360 min; ii) acute volume overload (VolOv) induced by dextran40 infusion (5 ml/h), for 120 or 360 min; iii) Sham. Free wall samples from the RV and LV were collected for mRNA quantification. RESULTS: In the RV, acute overload induced IL-6 and TNF-alpha gene expression, higher in VolOv (IL-6: + 669.7 +/- 263.4%; TNF-alpha: + 5149.9 +/- 1099.0%; 360 min) than in PrOv (IL-6: + 64.9 +/- 44.2%; TNF-alpha: + 628.1 +/- 229.3%; 360 min). In PrOv, TNF-alpha mRNA levels in the LV were increased, in the absence of ventricular overload. IL-6 and TNF-alpha mRNA levels did not correlate in the LV, while in the RV a positive correlation was found (r = 0.574; p < 0.001). CONCLUSIONS: Acute cardiac overload induces overexpression of pro-inflammatory cytokines. This gene activation is not uniform, being higher in volume overload and involving both load-dependent and load-independent mechanisms.

Ventricular BNP gene expression in acute cardiac overload.

INTRODUCTION: B-type natriuretic peptide (BNP) plasma levels have important diagnostic and prognostic implications in heart failure (HF). Recently, aside from its natriuretic effect, antiproliferative and antifibrotic actions of BNP on the cardiovascular system have been described. Under physiological conditions the atria are the main source of this peptide, while its ventricular expression is still controversial. The aim of this work was to evaluate, in an animal model, the ventricular expression of BNP in normal hearts, at baseline and under acute cardiac overload. METHODS: Anesthetized open chest male Wistar rats (n=18) were instrumented with a micromanometer in the right ventricular cavity for pressure assessment. Randomization for three different protocols was then performed: (i) pressure overload for a period of 6 hours (SPr; n = 6), by pulmonary trunk banding, in order to double basal right ventricular systolic pressure; (ii) volume overload with a six-hour perfusion of Dextran 40 (SVol; n = 6), to raise end-diastolic right ventricular pressure fourfold; (iii) sham operated rats (n = 6). Transmural samples from the right ventricular free wall were then obtained for quantification of BNP mRNA by RT and quantitative real-time PCR. The results are expressed as mean+/-SEM (number molecules of mRNA BNP)/(ng total mRNA); p < 0.05. RESULTS: A basal expression of BNP was identified in the sham group (3.6x10(7) +/- 1.7x10(7)). BNP mRNA levels were elevated in both the SPr and SVol groups (+123.1 +/- 46.3% SPr and +171.6 +/- 87.7% SVol). CONCLUSIONS: Acute cardiac pressure and volume overload are associated with increased ventricular BNP gene expression. Our results suggest that BNP may be involved in early ventricular remodeling.

Endogenous production of ghrelin and beneficial effects of its exogenous administration in monocrotaline-induced pulmonary hypertension.

We investigated the endogenous production of ghrelin as well as cardiac and pulmonary vascular effects of its administration in a rat model of monocrotaline (MCT)-induced pulmonary hypertension (PH). Adult Wistar rats randomly received a subcutaneous injection of MCT (60 mg/kg) or an equal volume of vehicle. One week later, animals were randomly assigned to receive a subcutaneous injection of ghrelin (100 mug/kg bid for 2 wk) or saline. Four groups were analyzed: normal rats treated with ghrelin (n=7), normal rats injected with saline (n=7), MCT rats treated with ghrelin (n=9), and MCT rats injected with saline (n=9). At 22-25 days, right (RV) and left ventricular (LV) pressures were measured, heart and lungs were weighted, and samples were collected for histological and molecular analysis. Endogenous production of ghrelin was almost abolished in normal rats treated with ghrelin. In MCT-treated animals, pulmonary expression of ghrelin was preserved, and RV myocardial expression was increased more than 20 times. In these animals, exogenous administration of ghrelin attenuated PH, RV hypertrophy, wall thickening of peripheral pulmonary arteries, and RV diastolic disturbances and ameliorated LV dysfunction, without affecting its endogenous production. In conclusion, decreased tissular expression of ghrelin in healthy animals but not in PH animals suggests a negative feedback in the former that is lost in the latter. A selective increase of ghrelin mRNA levels in the RV of animals with PH might indicate distinct regulation of its cardiac expression. Finally, ghrelin administration attenuated MCT-induced PH, pulmonary vascular remodeling, and RV hypertrophy, indicating that it may modulate PH.