Shigeki Hata

Reduction of risk of pneumonia associated with use of angiotensin I converting enzyme inhibitors in elderly inpatients

Pneumonia is a major direct cause of death in the elderly. Although aspiration based on a reduced cough reflex is one of the causes of pneumonia in the elderly, there are few studies of angiotensin-I converting enzyme inhibitors (ACE inhibitors), which are antihypertensive drugs that induce cough, as a factor influencing the incidence of pneumonia in institutionalized elderly subjects. To assess the effect of ACE inhibitors and dihydropiridine calcium-channel blockers on the incidence of pneumonia, we conducted a hospital-based case-control study. Cases were 55 pneumonia patients aged > or = 65 years during a 1-year period. The controls were elderly subjects, frequency matched to the cases by age and gender (n = 220). Data were collected on known risk factors and on medication for hypertension, consisting of ACE inhibitors, calcium-channel blockers, and nonantihypertensive medication. The significance of differences in risk factors was analyzed using univariate and multivariate comparisons of cases and controls. After adjustment for potential confounding factors, the relative risk estimates for pneumonia were 0.38 (95% confidence interval [CI], 0.15-0.97) and 1.84 (95% CI, 0.89-3.78) for ACE inhibitors and calcium-channel blockers, respectively, relative to nonantihypertensive medication. The preventive effect of ACE inhibitors on pneumonia was apparent in long-acting ACE inhibitor users (0.24; 95% CI, 0.07-0.88). We conclude that ACE inhibitor use is an independent factor reducing risk of pneumonia among elderly inpatients.

Possible participation of Fas-mediated apoptosis in the mechanism of atherosclerosis

Apoptosis is a programmed cell death that plays a major role during development, homeostasis, and in many diseases. Recent evidence has demonstrated the death of vascular smooth muscle cells (VSMCs) within advanced human atheroma. In the rat balloon-injury model, apoptotic cells were specifically identified in the neointima. The presence of apoptotic cells was demonstrated by in situ terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL). To clarify the mechanisms that trigger apoptosis in atherosclerotic lesions, we examined whether cytokines released from macrophages can modulate Fas, a death signal, in cultured human VSMCs. Simultaneous treatment with interleukin-1 (IL-1) and tumor necrosis factor-alpha (TNF-alpha) but not with each cytokine alone induced upregulation of Fas in VSMCs. However, coincubation with NG-monomethyl-L-arginine, an inhibitor of nitric oxide (NO) synthesis, inhibited the upregulation of Fas induced by IL-1 and TNF-alpha. Incubation with sodium nitroprusside, a NO donor, also induced upregulation of Fas in VSMCs. Furthermore, fluorescent nuclear staining with Hoechst 33258 revealed that monoclonal antibody to human Fas significantly enhanced NO-induced apoptotis in VSMCs. These findings suggest that macrophage-derived cytokines can induce upregulation of Fas through a NO-dependent mechanism in VSMCs. Thus, Fas-mediated apoptosis may regulate apoptotic death of VSMCs during atherogenesis.

Parathyroid Hormone–Related Protein Inhibits Endothelin-1 Production

Abstract The effect of human parathyroid hormone–related protein, a powerful vasodilator, on endothelin-1 production in cultured bovine pulmonary arterial endothelial cells was studied. Treatment with parathyroid hormone–related protein(1-34) at concentrations of 10−9 to 10−6 mol/L for 24 hours caused dose-dependent suppression of the secretion of endothelin-1, with maximal suppression at 10−7 mol/L to 74% of the control value. This inhibitory effect was completely abolished by coincubation with 100 ng/mL pertussis toxin, an inhibitor of GTP binding protein. Furthermore, addition of N G-monomethyl-l-arginine, an inhibitor of nitric oxide synthase, at 10−3 mol/L significantly blocked the suppressive effect of parathyroid hormone–related protein(1-34) on endothelin-1 secretion, and further addition of 5×10−3 mol/L l-arginine significantly attenuated the blocking effect of N G-monomethyl-l-arginine. Parathyroid hormone–related protein(1-34) at 10−7 mol/L resulted in an approximately fivefold increase in intracellular cGMP level. Northern blot analysis revealed that parathyroid hormone–related protein(1-34) inhibited both basal and thrombin-induced endothelin-1 gene expression. These findings suggest that the vasodilating property of parathyroid hormone–related protein may be mediated in part through its inhibitory effect on endothelin-1 production, which is probably mediated through nitric oxide and cGMP in endothelial cells. Thus, a feedback regulatory mechanism may exist between parathyroid hormone–related protein and endothelin-1 in the vascular wall.

Endothelin-1 Enhances Nitric Oxide–Induced Cytotoxicity in Vascular Smooth Muscle

Prolonged incubation with 1 nmol/L interleukin-1 induced high levels of nitric oxide release and cytotoxicity in vascular smooth muscle cells. NG-Monomethyl-L-arginine, an inhibitor of nitric oxide synthesis, inhibited interleukin-1-induced cytotoxicity at a concentration of 3 mmol/L. Furthermore, prolonged incubation with 0.1 mmol/L sodium nitroprusside, a nitric oxide donor, also induced cytotoxicity. On the other hand, endothelin-1 at concentrations from 10(-10) to 10(-7) mol/L induced a concentration-dependent enhancement of cytotoxicity induced by interleukin-1. However, endothelin-1 did not affect interleukin-1-induced nitric oxide production. Coculture study of vascular smooth muscle cells and endothelial cells without direct cell contact revealed that incubation for 72 hours with interleukin-1 induced high levels of nitric oxide release from cocultured vascular smooth muscle cells to the same degree as release from vascular smooth muscle cells alone. However, interleukin-1-induced cytotoxicity was more enhanced in cocultured vascular smooth muscle cells than in vascular smooth muscle cells alone. Furthermore, coincubation with 20 nmol/L BQ-485, an antagonist of one type of endothelin receptor (ETA), prevented the enhancement of interleukin-1-induced cytotoxicity in cocultured vascular smooth muscle cells. These findings suggest that endothelin-1 secreted from endothelial cells may enhance nitric oxide-induced cytotoxicity by means of the ETA receptor in vascular smooth muscle cells.

Interleukin-2 modulates the responsiveness to angiotensin II in cultured vascular smooth muscle cells.

Preincubation with interleukin-2 (IL-2), a T cell-derived cytokine, enhanced the increase in intracellular Ca2+ ([Ca2+]i) induced by angiotensin II (AII) in vascular smooth muscle cells (VSMC). IL-2 itself did not affect the basal [Ca2+]i level or the maximal response of [Ca2+]i increase induced by AII. Furthermore, IL-2-induced enhancement was not observed in the absence of extracellular Ca2+, suggesting that IL-2 enhances Ca2+ influx induced by AII. IL-2 also enhanced the stimulation of DNA synthesis induced by AII, although IL-2 alone did not stimulate DNA synthesis. Genistein, an inhibitor of protein tyrosine kinases, significantly inhibited IL-2-induced enhancement of both Ca2+ influx and DNA synthesis induced by AII. A neutralizing antibody against heparin-binding epidermal growth factor-like growth factor (HB-EGF) partially inhibited IL-2-induced enhancement of DNA synthesis induced by AII. These findings suggest that autocrine HB-EGF is partially involved in the mechanism of IL-2-induced enhancement of DNA synthesis. On the other hand IL-2 stimulated both glycosaminoglycan (GAG) and prostacyclin syntheses and enhanced the stimulation of both GAG and prostacyclin syntheses induced by AII. Therefore, IL-2 may play important roles in the pathogenesis of atherosclerosis and vascular disease by modulating the responsiveness to AII in VSMC.

Vascular smooth muscle maintains the levels of Bcl-2 in endothelial cells.

Endothelial cells (ECs) play important roles in maintaining vascular homeostasis. Therefore, dysregulation of EC apoptosis may be involved in the mechanism of atherogenesis. Since recent evidence has shown that vascular endothelial growth factor (VEGF), an EC-specific growth factor, is released from vascular smooth muscle cells (VSMCs), we examined whether VSMCs can modulate EC apoptosis using a coculture system. Incubation of ECs with high levels of nitric oxide (NO) released by N-ethyl-2-[1-ethyl-2-hydroxy-2-nitrosohydrazino]-ethanamine, a NO releasing agent, resulted in apoptosis in association with decreased levels of Bcl-2, and increased levels of Bax, an accelerator of aoptosis. Exogenously added VEGF partially inhibited apoptosis and alterations of these bcl-2 family proteins induced by NO. On the other hand, NO-induced apoptosis and down-regulation of Bcl-2 in ECs were almost completely inhibited by coculturing with VSMCs. However, these inhibitory effects by VSMCs were suppressed by a neutralizing antibody against VEGF. In addition, overexpression of Bcl-2 prevented from NO-induced apoptosis in ECs. These findings indicate that VSMCs protect ECs from NO-induced apoptosis through inhibiting down-regulation of Bcl-2. Thus, vascular smooth muscle which releases EC survival factors including VEGF may play important roles in maintaining the levels of Bcl-2 in ECs.

Endothelin-1 enhances nitric oxide-induced cell death in cultured vascular smooth-muscle cells

Increased expression of endothelin-1 (ET-1) immunoreactivity is demonstrated in the active atherosclerotic plaque. Here we show that both ETA and ETB receptors are expressed in rat vascular smooth-muscle cells (VSMCs). ET-1 binding to ETB receptors enhances nitric oxide-induced cell death in VSMCs. These findings suggest that ET-1 may participate in the mechanism of cell death (apoptosis) in the plaque through activation of ETB-mediated pathways and that a selective ETB receptor antagonist could be useful in preventing acute plaque alterations, such as plaque rupture.

Hyperparathyroidism as a cause of calcification of the abdominal aorta in elderly female subjects

We evaluated serum levels of calcium-related factors and bone mineral content in 40 healthy elderly female subjects (mean age ± SD, 79 ± 7 years) as possible factors relating to calcification of the abdominal aorta. There were no significant differences in serum levels of total cholesterol, triglycerides, and estradiol between elderly female subjects with and without calcification of the abdominal aorta. Elderly female subjects with calcification of the abdominal arota, when compared to those without calcification, showed significantly reduced values of bone mineral content of the distal radius. Moreover, the elderly female subjects with calcification of the abdominal aorta showed significant increases in serum levels of parathyroid hormone and calcitonin, and significantly decreased levels of 24,25-dihydroxyvitamin D3. There were no significant differences in serum levels of 25-hydroxyvitamin D3 and 1,25-dihydroxyvitamin D3. These data suggest that elevated secretion of parathyroid hormone plays an important role in the development of calcification of the abdominal aorta.