mdl-100907 and Cardiomegaly

Serotonin, in addition to its fundamental role as a neurotransmitter, plays a critical role in the cardiovascular system, where it is thought to be involved in the development of cardiac hypertrophy and failure. Indeed, we recently found that mice with deletion of monoamine oxidase A had enhanced levels of blood and cardiac 5-HT, which contributed to exacerbation of hypertrophy in a model of experimental pressure overload. 5-HT2A receptors are expressed in the heart and mediate a hypertrophic response to 5-HT in cardiac cells. However, their role in cardiac remodeling in vivo and the signaling pathways associated are not well understood. In the present study, we evaluated the effect of a selective 5-HT2A receptor antagonist, M100907, on the development of cardiac hypertrophy induced by transverse aortic constriction (TAC). Cardiac 5-HT2A receptor expression was transiently increased after TAC, and was recapitulated in cardiomyocytes, as observed with 5-HT2A in situ labeling by immunohistochemistry. Selective blockade of 5-HT2A receptors prevented the development of cardiac hypertrophy, as measured by echocardiography, cardiomyocyte area and heart weight-to-body weight ratio. Interestingly, activation of calmodulin kinase (CamKII), which is a core mechanism in cardiac hypertrophy, was reduced in cardiac samples from M100907-treated TAC mice compared to vehicle-treated mice. In addition, phosphorylation of histone deacetylase 4 (HDAC4), a downstream partner of CamKII was significantly diminished in M100907-treated TAC mice. Thus, our results show that selective blockade of 5-HT2A receptors has beneficial effect in the development of cardiac hypertrophy through inhibition of the CamKII/HDAC4 pathway.

Topics: Age Factors; Analysis of Variance; Animals; Aorta; Calcium-Calmodulin-Dependent Protein Kinase Type 2; Cardiomegaly; Constriction, Pathologic; Disease Models, Animal; Echocardiography; Fluorobenzenes; Gene Expression Regulation; Hemodynamics; Histone Deacetylases; Male; Mice; Mice, Inbred C57BL; Myocardium; Piperidines; Receptor, Serotonin, 5-HT2A; RNA, Messenger; Serotonin Antagonists

Herein, we studied the cross talk between 5-HT(2B) receptor blocker (SB-204741) and GSK-3β inhibitor (SB-216763) in isoproterenol-induced cardiac hypertrophy for 28 days. SB-204741 treatment significantly ameliorated (P<0.05) myocardial dysfunction, myocyte area, fibrosis and myocardial architecture in isoproterenol insulted myocardium. Moreover, this improvement in functional and morphological changes was associated with suppression of hypertrophic (BNP and CK-MB), inflammatory (IKK-β/NF-κB/TNF-α and CRP), and apoptotic markers (TUNEL positivity and Bax expression) along with phosphorylation of Akt/GSK-3β/β-catenin/eNOS. Intriguingly, co-treatment with GSK-3β inhibitor (P<0.01) further amplified the anti-hypertrophic effect of SB-204741 (P<0.05) such that the effect was indistinguishable from that of vehicle treated rats. Thus, 5-HT(2B) receptor blockade mediated anti-hypertrophic effect is atleast in part is governed through phosphorylation of Akt/GSK-3β/β-catenin/eNOS via attenuating inflammatory and apoptotic pathways.

Topics: Animals; Cardiomegaly; Drug Evaluation, Preclinical; Drug Synergism; Glycogen Synthase Kinase 3; Glycogen Synthase Kinase 3 beta; Indoles; Isoproterenol; Male; Maleimides; Myocardium; Nitric Oxide Synthase Type III; Phosphorylation; Protein Kinase Inhibitors; Proto-Oncogene Proteins c-akt; Rats; Rats, Wistar; Receptor, Serotonin, 5-HT2B; Serotonin 5-HT2 Receptor Antagonists; Signal Transduction; Thiophenes

1. Serotonin (5-hydroxytryptamine; 5-HT) plays important roles in the development of cardiac hypertrophy via activation of 5-HT receptors. The aim of the present study was to investigate the role of 5-HT(2B) receptors in the development of cardiomyocyte apoptosis and hypertrophy associated with noradrenaline (NA) overload. 2. Cardiac hypertrophy was induced in rats by intraperitoneal injection of 1.5 mg/kg NA for 4 weeks. Starting from Day 15, 5-HT2B receptor antagonist SB 204741 (i.p., 0.5 or 2 mg/kg) or SDZ SER 082 (i.p., 1 mg/kg) was injected twice daily for another 14 days. Whole-cell patch-clamp techniques were used to record ionic currents in freshly isolated ventricular cardiomyocytes. Western blot and terminal deoxyribonucleotidyl transferase-mediated dUTP-digoxigenin nick end-labelling (TUNEL) assays were used to assess myocardial apoptosis. 3. Expression of 5-HT(2B) receptors was enhanced in the hypertrophic left ventricle induced by NE overload in vivo. The 5-HT(2B) receptor antagonist SB 204741 partially reversed cardiac hypertrophy induced by NE overload (P < 0.05) and decreased L-type calcium currents in ventricular cardiomyocytes (P < 0.05). In addition, SB 204741 notably attenuated myocardial apoptosis, as evidenced by downregulation of Bax and caspase 3 (P < 0.05) and upregulation of the anti-apoptotic Bcl-2 protein (P < 0.05). 4. In conclusion, the data suggest an involvement of 5-HT(2B) receptors in the generation of apoptotic events associated with cardiac remodelling during increased adrenergic stimulation.

Topics: Animals; Apoptosis; bcl-2-Associated X Protein; Calcium Channels, L-Type; Cardiomegaly; Cardiomyopathies; Caspase 3; Down-Regulation; Indoles; Myocytes, Cardiac; Naphthyridines; Norepinephrine; Proto-Oncogene Proteins c-bcl-2; Rats; Rats, Sprague-Dawley; Receptor, Serotonin, 5-HT2B; Serotonin; Serotonin 5-HT2 Receptor Antagonists; Up-Regulation; Urea

Topics: Angiotensin II; Angiotensin II Type 1 Receptor Blockers; Animals; Cardiomegaly; Cytokines; Drug Delivery Systems; ErbB Receptors; Fibroblasts; Heart Failure; Heparin-binding EGF-like Growth Factor; Humans; Intercellular Signaling Peptides and Proteins; Isoproterenol; Matrix Metalloproteinase Inhibitors; Matrix Metalloproteinases; Mice; Mice, Transgenic; Myocardium; Rats; Receptor, Angiotensin, Type 1; Receptor, Serotonin, 5-HT2B; Serotonin 5-HT2 Receptor Antagonists; Serotonin Antagonists; Signal Transduction

The potential role of serotonin (5-HT) in cardiac function has generated much interest in recent years. In particular, the need for a tight regulation of 5-HT to maintain normal cardiovascular activity has been demonstrated in different experimental models. However, it remains unclear how increased levels of 5-HT could contribute to the development of cardiac hypertrophy. Availability of 5-HT depends on the mitochondrial enzyme monoamine oxidase A (MAO-A). Therefore, we investigated the consequences of MAO-A deletion on ventricular remodeling in the model of aortic banding in mice. At baseline, MAO-A deletion was associated with an increase in whole blood 5-HT (39.4+/-1.9 microM vs. 24.0+/-0.9 microM in KO and WT mice, respectively). Cardiac 5-HT(2A), but not 5-HT(2B) receptors were overexpressed in MAO-A KO mice, as demonstrated by real-time PCR and Western-blot experiments. After aortic banding, MAO-A KO mice demonstrated greater increase in heart wall thickness, heart to body weight ratios, cardiomyocyte cross-section areas, and myocardial fibrosis compared to WT. Exacerbation of hypertrophy in KO mice was associated with increased amounts of 5-HT in the heart. In order to determine the role of 5-HT and 5-HT(2A) receptors in ventricular remodeling in MAO-A KO mice, we administered the 5-HT(2A) receptor antagonists ketanserin (1 mg/kg/day) or M100907 (0.1 mg/kg/day) during 4 weeks of aortic banding. Chronic administration of these antagonists strongly prevented exacerbation of ventricular hypertrophy in MAO-A KO mice. These results show for the first time that regulation of peripheral 5-HT by MAO-A plays a role in ventricular remodeling via activation of 5-HT(2A) receptors.

Topics: Animals; Aorta; Blood Pressure; Cardiomegaly; Fibrosis; Fluorobenzenes; Gene Deletion; Gene Expression Regulation; Heart Ventricles; Ketanserin; Mice; Mice, Knockout; Monoamine Oxidase; Myocardium; Piperidines; Pressure; Receptors, Serotonin; Serotonin; Stress, Physiological; Ultrasonography

The serotonergic 5-HT2B receptor regulates cardiomyocyte development and growth. A putative contribution of this receptor to fibroblast-dependent cardiac function has not been identified.. By mimicking sympathetic stimulation with chronic isoproterenol perfusion in vivo, we found that mice developed a cardiac hypertrophy, which was prevented by exposure to the 5-HT2B receptor antagonists SB206553 or SB215505 or in 5-HT2B receptor-knockout mice. The isoproterenol-induced hypertrophy was associated with an increase in the plasma levels of interleukin-1beta and tumor necrosis factor-alpha but not interleukin-6. In contrast, the plasma isoproterenol-induced cytokine increase was not observed in either 5-HT2B receptor-mutant or wild-type mice perfused with isoproterenol+SB206553. We demonstrated that stimulation of wild-type cardiac fibroblasts by isoproterenol markedly increased the production of the interleukin-6, interleukin-1beta, and tumor necrosis factor-alpha cytokines. Strikingly, we found that this isoproterenol-induced cytokine production was abolished by SB206553 or in 5-HT2B receptor-knockout fibroblasts. Serotonin also stimulated production of the 3 cytokines in wild-type fibroblasts, which was effectively reduced in 5-HT2B receptor-knockout fibroblasts.. Our results demonstrate for the first time that 5-HT2B receptors are essential for isoproterenol-induced cardiac hypertrophy, which involves the regulation of interleukin-6, interleukin-1beta, and tumor necrosis factor-alpha cytokine production by cardiac fibroblasts.

Topics: Adrenergic beta-1 Receptor Antagonists; Adrenergic beta-2 Receptor Antagonists; Adrenergic beta-Agonists; Animals; Cardiomegaly; Cells, Cultured; Drug Evaluation, Preclinical; Fibroblasts; Gene Expression Regulation; Heart Ventricles; Imidazoles; Indoles; Interleukin-1; Interleukin-6; Isoproterenol; Mice; Mice, Knockout; Myocytes, Cardiac; Propanolamines; Pyridines; Quinolines; Receptor, Serotonin, 5-HT2B; Receptors, Adrenergic, beta-1; Receptors, Adrenergic, beta-2; Serotonin 5-HT2 Receptor Antagonists; Serotonin Antagonists; Sympathetic Nervous System; Sympathomimetics; Tumor Necrosis Factor-alpha