Motoyoshi Tsujino

Endothelin-1 induces hypertrophy with enhanced expression of muscle-specific genes in cultured neonatal rat cardiomyocytes.

To determine whether endothelin-1 (ET-1) induces hypertrophy of cardiomyocytes, the effects of ET-1 on the expression of muscle-specific genes and a proto-oncogene, c-fos, in cultured neonatal rat cardiomyocytes were examined by Northern blot analysis. ET-1 (10(-7) M) induced about twofold to fourfold increases in the gene expression of myosin light chain 2, alpha-actin, and troponin I after 6 hours, which continued up to 24 hours. The ET-1-induced increases in mRNA levels for these muscle-specific genes were dose dependent (10(-9) to 10(-7) M). Run-on transcriptional assay showed that the changes in mRNA level for three muscle-specific genes were regulated, at least in part, at the transcriptional level. 12-O-Tetradecanoylphorbol 13-acetate (TPA), a potent protein kinase C activator, and the Ca2+ ionophore ionomycin also increased mRNA levels of three muscle-specific genes. ET-1, TPA, and ionomycin similarly induced the expression of c-fos after 30 minutes, which returned to an undetectable level after 6 hours. ET-1 remarkably and dose-dependently stimulated accumulation of total inositol phosphates in cardiomyocytes. Morphometrical evaluation showed that ET-1 significantly increased surface area of cardiomyocytes without cell proliferation. ET-1 also dose-dependently stimulated the synthesis of protein and DNA, which was unaffected by the L-type calcium channel blocker nicardipine. These data suggest that ET-1 induces hypertrophy of cardiomyocytes associated with the induction of muscle-specific gene transcripts through the possible involvement of protein kinase C activation or intracellular Ca2+ mobilization.

Insulin-like growth factor-I induces hypertrophy with enhanced expression of muscle specific genes in cultured rat cardiomyocytes.

BackgroundCardiac hypertrophy is commonly observed in acromegalic patients, in whom serum insulinlike growth factor-I (IGF-I) levels are elevated. In the present study, we examined whether IGF-I induces hypertrophy in cultured neonatal rat cardiomyocytes through its specific receptor and whether IGF binding protein-3 (IGFBP-3), which is a major circulating carrier protein for IGF-I, inhibits IGF-I-induced cardiac hypertrophy in vitro. Methods and ResultsBecause the response of cardiac hypertrophy is characterized by the induction of expression for muscle-specific genes, the effect of IGF-I on steady-state levels of mRNA for myosin light chain-2 (MLC-2) and troponin I and for skeletal and cardiac a-actin isoforms was evaluated by Northern blot analysis. IGF-I (10-7 M) increased mRNA levels for MLC-2 and troponin I as early as 60 minutes with maximum levels by 6 hours, which were maintained for as long as 24 hours. IGF-I (10-7 M) also increased transcripts for skeletal a-actin but not for cardiac a-actin. The cell size as evaluated morphometrically was almost doubled after 48-hour treatment with IGF-I. IGF-I induction of protein synthesis was dose dependent (10-10 to 10-7 M) with a maximal 2.2-fold increase seen at 10-8 M. In contrast to the hypertrophic effect of IGF-I, growth hormone affected neither protein synthesis nor expression for muscle-specific genes. Binding study using125IIGF-I revealed the presence of specific binding sites for IGF-I in rat cardiomyocytes. IGFBP-3 induced a dose-dependent inhibition of protein synthesis stimulated by IGF-I; IGFBP-3 (10-7 M) completely inhibited the [3HIleucine uptake stimulated by IGF-I 10-8 M). IGFBP-3 similarly inhibited the IGF-I-stimulated gene expressions for MLC-2 and troponin I. ConclusionsThese results suggest that IGF-I directly causes cardiac hypertrophy and that its effect can be blocked by IGFBP-3.

Induction of nitric oxide synthase gene by interleukin-1 beta in cultured rat cardiocytes.

Impaired myocardial contractility in septic shock is protracting, which may be caused by cytokine-induced nitric oxide (NO) synthesis in the heart. However, the cellular mechanism by which cytokines induce nitric oxide synthase (NOS) in cardiocytes remains obscure. Methods and ResultsWe studied the effect of human recombinant interleukin-1β (IL-1β) on synthesis of NO2−NO3− (NOx) and the expression of NOS mRNA and protein in cultured neonatal rat cardiocytes. IL-1β dose-dependently (0.1 to 10 ng/mL) stimulated NOx production as a function of time (6 to 48 hours). Northern blot analysis using complementary DNAs for rat brain-type constitutive (c) NOS and mouse macrophage-type inducible (i) NOS as probes showed that IL-1β induced expression of mRNA for iNOS but not for cNOS, starting after 6 hours and reaching a maximum after 48 hours in cardiocytes. IL-1β similarly induced iNOS mRNA expression in cultured adult rat cardiocytes in a time-dependent manner. Western blot analysis using specific antibody against the N-terminal fragment of mouse iNOS revealed the expression of 130-kD iNOS-like protein in IL-1β-treated cardiocytes. Northern blotting and immunocytochemical study revealed that IL-1β-induced iNOS mRNA and iNOS-like immunoreactivity were exclusively localized to cardiac myocytes but also to nonmyocytes, to a lesser extent. N−monomethyl- L-arginine, an NOS inhibitor, completely blocked the IL-1β-induced NOx production, whose effect was reversed by L-arginine but not by D-arginine. Dexamethasone inhibited the IL-1β-induced NO2, production as well as iNOS mRNA expression. Cycloheximide and actinomycin D completely inhibited the IL-1β-induced NOx production and iNOS mRNA expression. Neither a calmodulin inhibitor (W-7), a protein kinase C inhibitor (calphostin C), nor a Ca2+ channel antagonist (nicardipine) showed any effect on the IL-1β-induced NOx production. ConclusionsThese data demonstrate that IL-1β induces macrophage-type iNOS mRNA expression mainly by cardiac myocytes but also by nonmyocytes to a lesser extent, and subsequent de novo protein synthesis of iNOS leads to excessive local production of NO by cardiocytes.

Plasma Endothelin- 1 Levels in Idiopathic Dilated Cardiomyopathy

Abstract Endothelin is a novel endothelium-derived vasoconstrictive peptide. 1,2 Circulating immunoreactive endothelin-1 levels have been shown to increase in patients with acute myocardial infarction, 3 hypertension 4 and cardiogenic shock, 5 suggesting its paracrine or autocrine role in certain cardiovascular diseases. In congestive heart failure, a number of neurohormonal factors including sympathetic nervous activity and renin-angiotensin-aldosterone system 6 are known to be activated for compensatory mechanisms against the failing heart. To elucidate whether endogenous endothelin-1 is involved in heart failure, this study was designed to measure circulating endothelin-1 levels in patients with idiopathic dilated cardiomyopathy of various severities.

Regression of left ventricular hypertrophy in patients with essential hypertension: outcome of 12 years antihypertensive treatment.

To assess the regression of cardiac hypertrophy during long-term (12 years) antihypertensive treatment, the following parameters were determined in 93 patients with essential hypertension: SV1 + RV5 by electrocardiography (ECG), and septal wall (SW) and posterior wall (PW) thickness by echocardiography (UCG). The patients were treated with a thiazide diuretic alone (group 1), thiazide + beta-blocker (group 2), thiazide + methyldopa or nifedipine (group 3) or nifedipine or methyldopa alone (group 4). The blood pressure decreased gradually within 6 months of treatment. According to ECG, regression of left ventricular hypertrophy occurred during the initial 7 years in all groups, whereas in the subsequent 5 years, statistically significant regression was found only in the patients treated with thiazide + other drugs (group 3). By UCG, which was taken only at the 7th and 12th year, regression was detectable during the last 5 years in all groups. The apparent incidence of regression of hypertrophy was lower in the thiazide-alone group (group 1) than in the thiazide + beta-blocker group (group 2), most likely due to mild hypertension in group 1. A cardiovascular accident (nonfatal myocardial infarction) occurred only in 1 patient. We conclude that during long-term antihypertensive treatment, persistent, progressive reversal of cardiac hypertrophy takes place.

A partial defect in technetium-99m pyrophosphate image suggesting cardiac rupture following acute myocardial infarction

We present the case of a 70-year-old woman with acute myocardial infarction who died of cardiac rupture on the 2nd hospital day. Dual isotope single photon emission computed tomography (SPECT) using thallium-201 chloride and technetium-99m pyrophosphate (PYP) performed on the 2nd hospital day showed a large perfusion defect in the anteroseptal wall on 201Tl image and a increased accumulation on 99mTc-PYP image in the anterior area consistent with a partial defect. Autopsy performed 1 h after death revealed a tear in the left ventricular anterior wall consistent with the defect on the 99mTc-PYP image. We propose that the finding of a partial defect in 99mTc-PYP is an interesting finding which may be associated with cardiac rupture following acute myocardial infarction.

IgG4-related hypophysitis with subtle hypopituitarism in an elderly diabetic patient: Is treatment or observation preferable?

A 70-year-old man with diabetes mellitus presented with an enlarged pituitary stalk in 2014. IgG4-related parotitis and submandibular sialoadenitis were diagnosed in 2012. He denied any symptoms related to a pituitary mass. His visual field was intact, and his hypopituitarism was subtle. The serum IgG4 level was elevated. A lip biopsy revealed strong fibrosis and hyper-infiltration of IgG4-positive plasma cells. Based on these findings, IgG4-related hypophysitis was diagnosed. The patient was carefully followed without specific intervention. His clinical condition showed no change until December 2016, suggesting a stable, natural course. Care should be taken when considering glucocorticoid therapy, especially for elderly diabetic patients, given possible side effects.