Effect of diltiazem on cardiac function assessed by echocardiography and neurohumoral factors after reperfused myocardial infarction without congestive heart failure

Suppression of collagen production in norepinephrine stimulated cardiac fibroblasts culture: differential effect of alpha and beta-adrenoreceptor antagonism

OBJECTIVES

Prolonged sympathetic activation is damaging to the heart and experimental norepinephrine (NE) infusion induces the deposition of myocardial collagen. This study investigated the effects of NE on collagen and transforming growth factor-beta1 (TGF-beta1) gene expression in rat cardiac fibroblasts (CF) culture, and compared the anti-fibrotic effect of alpha and beta (both selective and non-selective adrenergic receptor antagonists) receptors.

METHODS AND RESULTS

Rat CF were cultured in the presence of NE (0.01 to 100 muM) for 24 hours. Procollagen types I and III as well as TGF-beta1 gene expressions were measured by real-time quantitative PCR method. Collagen protein level was measured by Sirius red-based colorimetric method and Western blot analysis. The optimal dose of NE on fibrogenesis was 0.1 muM. Incubation for 24 hours increased procollagen I, III and TGF-beta1 gene expression by 1.35 +/- 0.23, 1.26 +/- 0.16 and 1.35 +/- 0.21 fold, respectively (all p < 0.05). The collagen protein was increased by both Sirius-red assay (0.120 +/- 0.03 vs 0.093 +/- 0.04 microg/total microg of protein, p < 0.05) and Western blot analysis (1.29 +/- 0.26 fold, p < 0.05), when compared with the control group. Addition of carvedilol (a non-selective beta-blocker with alpha-blockage activity) inhibited the effect of NE on procollagen I (0.64 +/- 0.17 vs 1.28 +/- 0.08 fold, p < 0.01), procollagen III gene (0.47 +/- 0.16 vs 1.45 +/- 0.29 fold, p < 0.01) and collagen protein expressions (0.99 +/- 0.12 vs 1.26 +/- 0.31 fold, p < 0.05, respectively). Doxazosin (an alpha-blocker) also inhibited the effect of NE on procollagen I (0.88 +/- 0.30 vs 1.28 +/- 0.08 fold, p < 0.01), procollagen III gene (0.64 +/- 0.13 vs 1.45 +/- 0.29 fold, p < 0.01) and collagen protein expression (0.90 +/- 0.11 vs 1.26 +/- 0.31 fold, p < 0.01 respectively). Such inhibitory effects were not seen in metoprolol (a beta1-selective blocker) and propranolol (a non-selective beta blocker). Furthermore, all the 4 drugs were unable to inhibit the NE induced TGF-beta1 gene over-expression.

CONCLUSIONS

In conclusion, NE increased collagen gene and protein expressions in CF culture. This effect is likely mediated through alpha-receptor as they were normalized by pretreatment with carvedilol and doxazosin, but not beta-blockers such as propranolol and metoprolol. Also, TGF-beta1 doesn't seem to play a role in carvedilol inhibition of NE induced fibrogenesis.

The effects of medications on circulating levels of cardiac natriuretic peptides

Circulating cardiac natriuretic peptide levels are being used increasingly in a range of clinical circumstances. Since it is evident that drugs used in the treatment of cardiovascular disorders can modulate natriuretic peptide levels, we here review the literature documenting these effects. Diuretics, blockers of the renin-angiotensin system, vasodilator agents, dopamine-like agonists, amiodarone, and perhaps allopurinol and statins suppress natriuretic peptide levels, most obviously in heart failure. Beta-blockers stimulate natriuretic peptide concentrations in hypertensive subjects, whereas in heart failure they have little effect or are stimulatory in the short term and inhibitory with sustained therapy. Digitalis compounds and aspirin tend to increase natriuretic peptide levels, and calcium channel blocking agents have varying effects depending on the individual drug and duration of administration. The effects of other drugs are less clear. Additional information is needed regarding the effects of medications along with dissection of the role of altered cardiac secretion versus changes in plasma clearance as explanation for drug-induced perturbations in natriuretic peptide concentrations. In the meantime, clinicians need to consider the known effects of medications when interpreting plasma levels of the cardiac natriuretic peptides.