Yoshio Tomoda

Regulation of adrenomedullin secretion from cultured cells

Characterization of immunoreactive adrenomedullin (AM) secreted from cultured human vascular smooth muscle cells and 7 other cells indicates that AM is synthesized and secreted from all cultured cells we surveyed. The secretion rate of AM measured ranges from 0.001-6.83 fmol/10(5) cells/h, and endothelial cells, vascular smooth muscle cells and fibroblasts generally secrete AM at high rates. Based on the results of regulation of AM secretion from vascular wall cells, fibroblasts, macrophages and other cells measured in this and previous studies, AM secretion is found to be generally stimulated by inflammatory cytokines, lipopolysaccharide (LPS) and hormones. Especially, vascular smooth muscle cells and fibroblasts elicited uniform and strong stimulatory responses of AM secretion to tumor necrosis factor (TNF), interleukin-1 (IL-1), LPS and glucocorticoid, but endothelial cells did not elicit such prominent responses. AM secretion of monocyte-macrophage was mainly regulated by the degree of differentiation into macrophage and activation by LPS and inflammatory cytokines including interferon-gamma. The other examined cells showed weaker responses to LPS and IL-1. Although cultured cells may have been transformed as compared with those in the tissue, these data indicate that AM is widely synthesized and secreted from most of the cells in the body and functions as a local factor regulating inflammation and related reactions in addition to as a potent vasodilator. The responses of AM secretion to LPS and inflammatory cytokines suggest that fibroblasts, vascular smooth muscle cells and macrophage are the major sources of AM in the septic shock.

Cardiac fibroblasts are major production and target cells of adrenomedullin in the heart in vitro

OBJECTIVE Adrenomedullin (AM) is a potent vasodilator peptide. Plasma AM concentration is increased in patients with various heart diseases, and both myocytes (MCs) and non-myocytes (NMCs) secrete AM and express its receptors. These facts suggest that cardiac cells possess an autocrine/paracrine capability mediated by AM. METHODS MCs and NMCs were prepared from cardiac ventricles of neonatal rats. AM and endothelin-1 concentrations were measured by radioimmunoassays, and interleukin-6 level by a specific bioassay. Total nitrite/nitrate contents were measured with a fluorescence assay kit. RESULTS A basal secretion rate of AM from NMCs was 2.8-fold higher than that from MCs. Interleukin-1beta, tumor necrosis factor-alpha and lipopolysaccharide stimulated AM secretion from NMCs but not from MCs. AM stimulated interleukin-6 production in the presence of these cytokines or lipopolysaccharide, which was more prominent in NMCs. In the presence of interleukin-1beta, AM augmented nitric oxide synthesis 2.7-fold in NMCs, but slightly in MCs. NMCs secreted endothelin-1 at a rate nine times higher than MCs, and AM inhibited endothelin-1 secretion from NMCs. CONCLUSION This in vitro study suggests that AM in the heart is mainly produced in NMCs and exerts its effects through NMCs, especially under inflammatory conditions.

C-type natriuretic peptide is synthesized and secreted from leukemia cell lines, peripheral blood cells, and peritoneal macrophages

OBJECTIVE C-type natriuretic peptide (CNP) is the third member of the natriuretic peptide family. Cultured endothelial cells secrete CNP, and its secretion rate from the endothelial cells is augmented by lipopolysaccharide, interleukin-1beta, and tumor necrosis factor-alpha, which participate in the pathophysiology of inflammation. In this study, we investigated the regulation of CNP secretion from monocytes and macrophages to estimate its contribution to the progression of inflammation. MATERIALS AND METHODS CNP secretion rates from two human leukemia cell lines (THP-1 and HL-60), human peripheral blood lymphocytes, granulocytes, monocytes, monocyte-derived macrophages, and mouse peritoneal macrophages were measured under conditions with or without stimulation. Immunoreactive CNP levels in the culture media of these cells were measured by a specific radioimmunoassay. RESULTS The secretion rates of CNP from THP-1 and HL-60 cells were augmented according to the degree of their differentiation into macrophage-like cells under the stimulation with phorbol ester. Peripheral blood monocytes also increased the CNP secretion rate after their differentiation into macrophages. Retinoic acid elicited synergistic effects on the CNP secretion rate from HL-60 cells when administered with lipopolysaccharide, interferon-gamma, interleukin-1beta, tumor necrosis factor-alpha, or phorbol ester. In contrast, the phorbol ester-stimulated CNP secretion rate from THP-1 cells was suppressed with dexamethasone, which inhibits monocyte differentiation into macrophage. CONCLUSIONS The secretion rate of CNP from monocytes was shown to be regulated based on the degree of their differentiation. This study provides evidence that the monocyte/macrophage system is one of the sources of CNP, especially under inflammatory conditions.

Transcardiac gradient of soluble adhesion molecules predicts progression of coronary artery disease

BACKGROUND During the development of atherosclerotic lesion, several types of cellular adhesion molecules (CAMs) are overexpressed on the surface of vascular endothelium. Some parts of these membrane proteins are proteolysed and are detected in blood as soluble forms. AIMS The purpose of this study is to investigate the relationship between the transcardiac gradient of soluble cellular adhesion molecules (sCAMs) and the clinical characteristics of coronary artery disease (CAD). METHODS We studied 46 patients with clinically stable CAD. Serum sCAM levels in both aortic sinus and coronary sinus were measured using enzyme-linked immunosorbent assay, and the transcardiac gradient of sCAMs was calculated. We also evaluated the angiographic severity of CAD, response of coronary artery to acetylcholine (Ach), as well as progression of coronary atherosclerosis over a 6-month period. RESULTS The transcardiac gradient of sCAMs did not correlate to the angiographic severity of coronary atherosclerosis. The transcardiac gradient of sVCAM-1 was significantly higher in patients with vasoconstrictive response to Ach than patients without vasoconstrictive response to Ach (191.5+/-98.2 vs. -9.2+/-14.1 ng/ml, P<0.05). Furthermore, patients who exhibited progression of coronary atherosclerosis had a higher transcardiac gradient of sVCAM-1 at the initial study than patients without progression (47.8+/-24.5 vs. -6.4+/-12.3 ng/ml, P<0.05). CONCLUSIONS An elevated transcardiac gradient of sVCAM-1 may represent the persistent activation of coronary artery that is accompanied by endothelial dysfunction, and may be a predictive index of progression of coronary atherosclerosis. Measurement of coronary circulating sVCAM-1 could provide important functional and predictive information about atherosclerosis.