Atsushi Hirotani

Lysophosphatidylcholine causes Ca2+ influx, enhanced DNA synthesis and cytotoxicity in cultured vascular smooth muscle cells

The effects of lysophosphatidylcholine (LPC), a vasoactive phospholipid, on intracellular free calcium concentration ([Ca2+]i), DNA synthesis and cytotoxicity of vascular smooth muscle cells (VSMC) were studied. LPC from 10(-7) to 10(-5) mol/l dose-dependently induced a sustained increase in [Ca2+]i. In contrast to the response of [Ca2+]i induced by angiotensin II, that induced by LPC was totally abolished when extracellular Ca2+ was removed, was not affected by pretreatment of the cells with islet-activating protein, and was not desensitized by repeated addition. 8-(N,N-Diethylamino)octyl 3,4,5-trimethoxybenzoic acid (TMB-8), an inhibitor of Ca2+ release from intracellular Ca2+ stores, 1-(5-isoquinolinesulfonyl)-2-methylpiperadine dihydrochloride (H-7), an inhibitor of protein kinase C, KT5823, an inhibitor of protein kinase G, and Ca2+ channel blockers failed to suppress the LPC-induced increase in [Ca2+]i. LPC at 10(-5) mol/l caused significant stimulation of [3H]thymidine incorporation into VSMC, and at concentrations of 10(-5) mol/l and higher dose-dependently stimulated release of lactate dehydrogenase in cell culture supernatants. Moreover, digitonin mimicked the effects of LPC on [Ca2+]i, and also caused similar effects to those of LPC on DNA synthesis and cytotoxicity in VSMC. These observations suggest that LPC causes both cell growth and cell injury of VSMC, at least partly, through its detergent action, causing membrane leakiness and resultant [Ca2+]i overload in vitro, thus indicating the possible participation of LPC in atherosclerosis and/or injury of the vascular wall.

Prognostic predictors for survival in patients with COPD using cardiopulmonary exercise testing

We studied the relationship between physiologic parameters in cardiopulmonary exercise testing (CPET) and prognosis in terms of survival time in patients with chronic obstructive pulmonary disease (COPD) in order to accurately assess the severity of the disease. From a group of 195 patients with COPD who had consecutively undergone CPET between July 1989 and October 1997, we enrolled 120 subjects (mean age 67·6 years, 104 males) with exertional dyspnoea into a cohort protocol. Of these subjects, 34 (28·3%) died during the 3–5‐year follow‐up period after CPET. By univariate analysis, the following factors were significantly associated with survival time: age, body mass index, %FVC, %FEV1, FEV1%, Paco2 at rest, severity of exercise‐induced hypoxemia evaluated by ΔPao2/ΔV̇o2 (Pao2‐slope), oxygen uptake, ventilation, tidal volume, Paco2 and oxygen pulse at maximum exercise, as well as prescribing long‐term oxygen therapy. By multivariate analysis, age and the Pao2‐slope showed significance as independent prognostic factors, and the Pao2‐slope was most closely associated with the survival time. These results reveal that CPET is a useful technique to accurately assess the relationship between the functional impairments and the prognosis of patients with COPD.

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.

Prospective Clinical Evaluation of the Serologic Tuberculous Glycolipid Test in Combination with the Nucleic Acid Amplification Test

ABSTRACT We have conducted a prospective controlled multicenter study to evaluate differences in the levels of clinical utility of the tuberculous glycolipid (TBGL) serodiagnostic test and the nucleic acid amplification test in patients with smear-negative active pulmonary tuberculosis (TB). The TBGL test and the PCR test were individually not so useful for the rapid diagnosis of smear-negative active pulmonary TB. However, clinical utility was considerably improved by using the TBGL test and the PCR test in combination, especially in patients with smear-negative and culture-negative active pulmonary TB and in patients with minimally advanced lesions.

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.

Parathyroid Hormone–Related Protein Upregulates Interleukin-1β–Induced Nitric Oxide Synthesis

Abstract The effect of parathyroid hormone–related protein on interleukin-1β–induced nitric oxide production was studied in rat vascular smooth muscle cells. Interleukin-1β time- and dose-dependently enhanced the production of nitrite, a stable metabolite of nitric oxide. Parathyroid hormone–related protein(1-34) alone up to 10 −7 mol/L had no obvious effect, but significantly increased the cytokine-induced nitrite production. RNA analysis revealed that the synergistic effect of parathyroid hormone–related protein(1-34) resulted from a potentiation of the expression of inducible nitric oxide synthase and GTP-cyclohydrolase I, the rate-limiting enzyme in the synthesis of tetrahydrobiopterin, which is a cofactor of nitric oxide synthase. The increased nitric oxide release induced by interleukin-1β or interleukin-1β with parathyroid hormone–related protein(1-34) was completely inhibited by coincubation with 3×10 −3 mol/L N G -monomethyl-l-arginine, a competitive inhibitor of nitric oxide synthase, or with 10 −3 mol/L 2,4-diamino-6-hydroxypyrimidine, an inhibitor of GTP-cyclohydrolase I. Endothelin-1 potentiated interleukin-1β induction of nitric oxide, which might be mediated by endogenous parathyroid hormone–related protein. Neutralization of exogenous or endogenous parathyroid hormone–related protein with antibody attenuated the synergistic effect of parathyroid hormone–related protein, but did not affect interleukin-1β induction of nitric oxide. These results suggest that locally produced parathyroid hormone–related protein acts as a synergistic regulator upregulating interleukin-1β–induced nitric oxide synthesis in the cardiovascular system, and thereby may affect vascular tone and/or vascular remodeling after vascular injury in some pathological processes such as atherosclerosis and hypertension.

Circulating Suppressing Factor for the Muscarinic Acetylcholine Receptor in Patients with Senile Dementia of the Alzheimer Type

Circulating suppressing factor for the binding of quinuclidinyl benzilate (QNB), an antagonist for the muscarinic acetylcholine receptor, to the synaptic membranes was evaluated in 48 patients with senile dementia of the Alzheimer type (SDAT), in 17 patients with the vascular type dementia (VTD) and in 11 nondemented elderly subjects (NE). The mean suppression rate on the binding in the SDAT group was significantly greater than that in the NE group, although that in the VTD group was similar to that in the NE group. Moreover, the percent QNB binding was significantly (p < 0.05) correlated with the score of the mini-mental state in the SDAT group. The circulating suppressing factor may participate in the pathogenesis of SDAT.

Effect of tablets with a combination of telmisartan and amlodipine on patients with hypertension: the Cotalo study

Fixed-dose combination (FDC) therapy with telmisartan 40 mg+amlodipine 5 mg (T40/A5) is expected to achieve tight blood pressure (BP) control because of the strong efficacy and long half-life of each drug. The aims of this study were to evaluate the 24-h antihypertensive efficacy of T40/A5 FDC therapy and to explore differences that may arise owing to different administration times in Japanese patients whose hypertension was not controlled by 5 mg of amlodipine per day. In this randomized clinical trial, 44 patients who had been taking amlodipine 5 mg per day and did not achieve their optimal BP target were enrolled (mean age: 67.8±10.2 years). The subjects were then randomly assigned to a T40/A5 morning or evening administration group (22 patients per group). At baseline and 8 weeks after randomization, we evaluated clinical BP and various laboratory values and performed ambulatory BP monitoring (ABPM). Clinical and mean BP evaluated with ABPM at 8 weeks (24 h, daytime, nighttime and early morning) were significantly decreased compared with BP at baseline. There were no significant differences in the diurnal BP profile change from baseline to 8 weeks between subjects in the morning and evening administration groups. There were also no significant differences in the diurnal BP profile change from baseline to 8 weeks between subjects with or without metabolic syndrome. We conclude that T40/A5 FDC therapy significantly decreased the 24-h mean and clinical BP, independent of administration time, in patients whose hypertension was not controlled by 5 mg of amlodipine.

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.