Role of nitric oxide in the progression of cardiovascular remodeling induced by carotid arterio-venous shunt in rabbits

Protective and Therapeutic Effects of Chinese Medicine Formula Jiajian Yunvjian on Experimental Cardiac Remodeling after Myocardial Infarction Induced by Coronary Artery Ligation

Introduction. This study was designed to explore the effect and mechanism of a classic Chinese medicine formula Jiajian Yunvjian (JJYNJ) on cardiac remodeling. Cardiac remodeling after myocardial infarction (MI) model was achieved by coronary artery ligation (CAL). Methodology. When dosed orally once daily, the effects of JJYNJ on hemodynamics, left ventricular weight index (LVWI), heart weight index (HWI), concentration, and gene expression of neuroendocrine factors as well as the histomorphological observation were determined. Results. After 4 weeks, mild cardiac remodeling in CAL group was characterized compared with sham group, but after 4 weeks of treatment of JJYNJ, hemodynamics improved, HWI reduced, and circulating angiotensin II (Ang II), endothelin-1 (ET-1), tumor necrosis factor-α (TNF-α), and hydroxyproline (Hyp) concentrations as well as Ang II receptor type 1 (AT₁R) mRNA, transforming growth factor β₁ (TGF-β₁) mRNA, and TNF-α mRNA levels in myocardium were lower than in CAL group. Decreased plasma aldosterone (ALD) concentration, cross-sectional area of cardiomyocyte, collagen volume fraction (CVF), collagen types I and III, perivascular collagen area (PVCA), and upregulated nitric oxide (NO) levels were observed at the same time. Conclusions. These findings suggest that JJYNJ may have a protective and therapeutic function on cardiac remodeling related to MI.

Fibrosis of pulmonary vascular remodeling in carotid artery-jugular vein shunt pulmonary artery hypertension model of rats

OBJECTIVE

The aim of the present study was to observe the changes of hemodynamics, stereology in pulmonary vascular remodeling and messenger RNA (mRNA) expressions of transforming growth factor beta 1, and receptors in carotid artery-jugular vein (CA-JV) shunt pulmonary artery hypertension model of rats.

METHODS

Thirty-six Sprague-Dawley rats were randomized into three groups: CA-JV group, monocrotaline (MCT) administration group, and control group. Left CA-JV shunts were established in CA-JV group. Dorsal subcutaneous injections of MCT (60 mg kg(-1)) were received in MCT group. Ligations of left common carotid artery and external jugular vein were performed in control group. Right ventricular systolic pressure (RVSP) measurement, histological evaluation of the pulmonary tissue, and mRNA levels of transforming growth factor beta 1 (TGFß1), receptor 1 and receptor 2, were investigated after 6 weeks on MCT group, and after 12 weeks on both control and CA-JV groups.

RESULTS

Compared with control group, RVSP, percentage of fibrous tissue (F%) in pulmonary arterioles, mRNA levels of TGFß1, and receptors of CA-JVand MCT groups increased significantly. Severe hemodynamics change was found in MCT groups. On the other hand, CA-JV group demonstrated more obvious fibrogenesis and TGFß1 signals' upregulation in two pulmonary artery hypertension (PAH) models.

CONCLUSIONS

CA-JV shunt model of rats was a well-established PAH animal model simulating congenital heart disease with systemic-pulmonary shunt.

Cardiovascular function in mice during normal pregnancy and in the absence of endothelial NO synthase

In humans, the increased cardiovascular demands of pregnancy are met by increases in cardiac output (CO), stroke volume (SV), plasma volume (PV), and cardiac and aortic inner dimensions and a concurrent decrease in arterial pressure that indicates a fall in total peripheral vascular resistance. The mechanisms responsible for these changes are incompletely understood, but NO synthase (NOS) is believed to play a central role. We assessed whether C57Bl/6J (B6) mice show similar changes and whether these changes are altered in mice lacking the gene for endothelial NOS (eNOS). The CO of B6 mice increased 28% by day 9.5 of gestation because of a 25% increase in SV, and increased 48% by day 17.5 because of a 41% increase in SV. The increase in SV at day 17.5 was associated with a 27% increase in PV, a 15% decrease in arterial pressure, and 10% to 15% increases in aortic and left-ventricular inner dimensions. In the absence of eNOS, CO increased 22% by day 9.5 because of increases in SV (14%) and heart rate (9%), but increased no further by day 17.5. SV near term was lower than B6 mice despite similar 26% increases in PV and 14% decreases in arterial pressure in association with blunted left-ventricular chamber enlargement. All reported changes are P<0.05. We conclude that cardiovascular changes during pregnancy are similar in B6 mice and humans. eNOS plays a critical role in increasing stroke volume in late gestation by promoting cardiac remodeling.

Chronic Nitric Oxide Synthase Inhibition Prevents New Coronary Capillary Generation

L-NAME-induced hypertension has been shown to produce concentric (eutrophic) remodeling of the heart despite an enhanced afterload. We postulated that nitric oxide synthase inhibition could limit coronary capillary growth to explain the nature of remodeling. To test our hypothesis, we aimed at determining the effect of endogenous and exogenous nitric oxide on coronary neovascularization. Aortic and coronary rings from normotensive animals were incubated in a three-dimensional type I collagen matrix in the presence of L-NAME or the nitric oxide donor SNAP. L-NAME inhibited, while SNAP stimulated, neovascularization from aortic and coronary rings after 12 days of in vitro incubation. In arterial rings harvested from rats treated with L-NAME for 14 days and in which no further in vitro treatment was added, only coronary rings showed a reduction in new capillary generation. While confirming that chronic L-NAME-treated rats develop concentric remodeling, the evaluation of capillary density did not reveal any difference as compared with the controls in 3 areas of the myocardium. In conclusion, chronic inhibition of nitric oxide synthesis in vivo produces a long-lasting reduction in the capacity of coronary arteries to generate new capillaries in vitro. Thus, our results lend support to the hypothesis that an inhibition of new capillary formation could prevent the development of compensatory ventricular hypertrophy, in favor of concentric remodeling.

Fatty acid metabolism assessed by 125I-iodophenyl 9-methylpentadecanoic acid (9MPA) and expression of fatty acid utilization enzymes in volume-overloaded hearts

BACKGROUND

The peroxisome proliferator-activated receptor (PPAR) alpha is a member of the nuclear receptor superfamily and regulates gene expression of fatty acid utilization enzymes. In cardiac hypertrophy and heart failure by pressure-overload, myocardial energy utilization reverts to the fetal pattern, and metabolic substrate switches from fatty acid to glucose. However, myocardial metabolism in volume-overloaded hearts has not been rigorously studied. The aim of the present study was to examine fatty acid metabolism and protein expressions of PPARalpha and fatty acid oxidation enzymes in volume-overloaded rabbit hearts.

METHODS

Volume-overload was induced by carotid-jugular shunt formation. Sham-operated rabbits were used as control. Chronic volume-overload increased left ventricular weight and ventricular cavity size, and relative wall thickness was decreased, indicating eccentric cardiac hypertrophy. (125)I-iodophenyl 9-methylpentadecanoic acid (9MPA) was intravenously administered, and animals were sacrificed at 5 min after injection. The 9MPA was rapidly metabolized to iodophenyl-3-methylnonanoic acid (3MNA) by beta-oxidation. Lipid extraction from the myocardium was performed by the Folch method, and radioactivity distribution of metabolites was assayed by thin-layer chromatography. The protein was extracted from the left ventricular myocardium, and levels of PPARalpha and fatty acid oxidation enzymes were examined by Western blotting.

RESULTS

Myocardial distribution of 9MPA tended to be more heterogeneous in shunt than in sham rabbits (P = 0.06). In volume-overloaded hearts by shunt, the conversion from 9MPA to 3MNA by beta-oxidation was faster than the sham-control hearts (P < 0.05). However, protein levels of PPARalpha and fatty acid utilization enzymes were unchanged in shunt rabbits compared with sham rabbits.

CONCLUSIONS

These data suggest that myocardial fatty acid metabolism is enhanced in eccentric cardiac hypertrophy by volume-overload without changes in protein expressions of PPARalpha and fatty acid utilization enzymes. Our data may provide a novel insight into the subcellular mechanisms for the pathological process of cardiac remodelling in response to mechanical stimuli.