Role of endothelial nitric oxide synthase in aggravation of indomethacin-induced gastric damage in adjuvant arthritic rats.

The role of nitric oxide synthase (NOS) isozymes in the aggravation of indomethacin-induced gastric damage in adjuvant arthritic rats was investigated. Two weeks after injection of Freund's complete adjuvant, the animals were given indomethacin, and the stomach was examined for damage 4 h later. Indomethacin caused hemorrhagic lesions in the normal rat stomach, and these lesions were markedly aggravated in arthritic rats. Pretreatment with L-NAME (a nonselective inhibitor of NOS) and aminoguanidine (a relative selective inhibitor of iNOS) did not affect the ulcerogenic response in normal rats but dose-dependently prevented the aggravation of lesions in arthritic rats, but the effect of aminoguanidine was apparently less than that of L-NAME. The increased ulcerogenic response in arthritic rats was significantly suppressed by 1400 W (a selective inhibitor of iNOS) and L-NIO (a selective inhibitor of eNOS) but not by L-NPA (a selective inhibitor of nNOS). The concurrent administration of 1400 W and L-NIO almost totally abolished the aggravation of damage in arthritic rats. The expressions of eNOS and iNOS but not nNOS in the gastric mucosa were clearly enhanced in arthritic rats. Mucosal levels of non-protein sulfhydryls were significantly lower in arthritic rats than those in normal rats. The aggravation of damage in arthritic rats was significantly prevented by glutathione. These results suggest that the increased ulcerogenic response to indomethacin in arthritic rat stomachs is mediated by NO derived from eNOS in addition to iNOS. It is assumed that eNOS/NO may act harmfully on the gastric mucosa of arthritic rats with mucosal SH deficiency.

Plasma cytokine levels in cardiac chambers of patients with mitral stenosis with congestive heart failure.

To ascertain whether elevated levels of circulating proinflammatory cytokines in patients with advanced heart failure are due to congestive heart failure or due to cachexia or infection complicating heart failure, we measured prospectively plasma concentrations of tumor necrosis factor-alpha (TNF-alpha), interleukin-1 beta (IL-1 beta), interleukin 2 (IL-2), and interleukin-6 (IL-6) in 12 patients with mitral stenosis with moderate congestive heart failure, but not with cachexia or infection. Blood samples were obtained from the peripheral vein and right and left atria of the patients during percutaneous mitral valvuloplasty. Levels of TNF-alpha, IL-1 beta, IL-2, and IL-6 in the plasma form the peripheral vein and right and left atria of these patients were not elevated compared with those from the peripheral vein of a control group of 10 normal subjects. On the other hand, plasma levels of TNF-alpha but not IL-1 beta, IL-2 or IL-6, were elevated in 4 of 9 patients with congestive heart failure complicated with cachexia and/or infection. Our results suggest that proinflammatory cytokine levels are not elevated in congestive heart failure uncomplicated with cachexia or infection.

Cyclic AMP augments cytokine-stimulated nitric oxide synthesis in rat cardiac myocytes.

We investigated the effect of adenosine 3', 5'-cyclic monophosphate (cAMP) on inducible nitric oxide synthase (iNOS) expression in cultured neonatal rat cardiac myocytes. Incubation of cardiac myocytes for 24 h with interleukin-1 beta (IL-1 beta) caused a significant increase in the production of nitrite, a stable metabolite of nitric oxide. Dibutyl cAMP (db-cAMP) significantly augmented nitrite production by IL-1 beta-stimulated, but not by unstimulated cells, in a dose-dependent manner. db-cAMP also dose dependently increased nitrite production by tumor necrosis factor-alpha(TNF-alpha)-stimulated cells. Simultaneous incubation with NG-monomethyl-L-arginine completely inhibited the effect of db-cAMP on nitrite production. cAMP-induced nitrite production by cytokine-stimulated cells was accompanied by increased iNOS mRNA accumulation. The synergistic effect of cAMP on IL-1 beta-induced nitrite accumulation was mimicked by cAMP-generating agonists forskolin and isoproterenol. These results indicate that cAMP upregulates cytokine-induced iNOS expression in cardiac myocytes.

Effects of inflammatory cytokines on vascular tone.

OBJECTIVE: To assess the direct effects of the inflammatory cytokines interleukin-2 (IL-2), interleukin-6 (IL-6) and interleukin-8 (IL-8) on vascular smooth muscle contraction. METHODS: Smooth muscle contractility was studied in the thoracic aorta isolated from male Sprague-Dawley rats. Syntheses of cAMP and nitric oxide (NO) were investigated in cultured rat vascular smooth muscle cells (VSMC). RESULTS: Pretreatment of the rings with IL-6 (10 ng/ml) for 180 min caused a significant inhibition of their contraction in response to 10(-5) M phenylephrine, wile Il-2 (10 ng/ml) and IL-8 (100 ng/ml) showed no significant effect on the contraction. The inhibitory effect of IL-6 exhibited a dose-dependency (0.1 approximately 10 ng/ml). In cultured rat VSMC, synthesis of cAMP was increased time-dependently by IL-6, while IL-2 and IL-8 failed to show any significant effects. IL-2, IL-6 and IL-8 did not affect the production of nitrite, a stable metabolite of NO, by VSMC. CONCLUSIONS: IL-6, but not IL-2 and IL-8, is a potent inhibitor of vascular contraction, which effect is mediated through the increased cAMP synthesis.

Nitric oxide synthesis in cardiac myocytes and fibroblasts by inflammatory cytokines.

OBJECTIVE: The aim was to investigate nitric oxide (NO) synthase activity in cultured neonatal rat cardiac myocytes and fibroblasts upon treatment with inflammatory cytokines interleukin 1 beta (IL-1 beta), tumour necrosis factor alpha (TNF-alpha), IL-2, IL-6, IL-8, transforming growth factor beta (TGF-beta) and gram negative bacterial lipopolysaccharide (LPS). METHODS: NO and guanosine 3',5'-cyclic monophosphate (cGMP) synthesis was measured in cultured neonatal rat cardiac myocytes and fibroblasts, using Griess reagent and an enzyme immunoassay kit, respectively. The expression of inducible NO synthase (iNOS) mRNA and protein was assayed by northern and western blotting, respectively. RESULTS: Incubation of cardiac myocytes for 24 h with IL-1 beta (10 ng.ml-1) or LPS (1 microgram.ml-1) caused significant increases in NO and cGMP production. TNF-alpha, IL-2, IL-6, IL-8, and TGF-beta showed no significant effect on their production. IL-1 beta induced NO and cGMP production in a time and dose dependent manner. IL-1 beta also increased iNOS mRNA and protein accumulation in cardiac myocytes. Simultaneous incubation of IL-1 beta with NG-monomethyl-L-arginine, genistein, calphostin C, cycloheximide, or actinomycin D completely inhibited the IL-1 beta induced NO production by cardiac myocytes. TGF-beta, dexamethasone, or cyclosporin A also dose dependently inhibited the IL-1 beta induced NO production. Exposure to IL-1 beta for 12-24 h decreased the beating rate of cardiac myocytes, but addition of dexamethasone completely overcame this inhibition. In contrast to cardiac myocytes, incubation of cardiac fibroblasts for 24 h with IL-1 beta or LPS showed no significant effect on NO or cGMP production. CONCLUSIONS: These observations suggest that IL-1 beta/LPS responsive iNOS, which is an important regulator of contractile function of the heart, is present in cardiac myocytes but not in cardiac fibroblasts.

Inflammatory cytokines and rat vascular tone.

1. Experiments were performed to examine the effect of inflammatory cytokines, interleukin-2 (IL-2), IL-6 and IL-8, on the contractility of rat aorta. 2. Pretreatment of the endothelium-denuded aortic ring with IL-6 for 3 h caused a significant inhibition of its contraction (58.9 +/- 7.8%, n = 9, P < 0.01) when induced by 10(-6) mol/L phenylephrine. 3. On the other hand, IL-2 and IL-8 failed to show significant effects on the contractility of the aorta. 4. This inhibitory effect of IL-6 on phenylephrine-induced contraction showed dose-dependency, and completely disappeared in the presence of 10(-5) mol/L indomethacin. 5. In cultured rat vascular smooth muscle cells (VSMC), the release of 6-keto-prostaglandin F1alpha into the extracellular medium was significantly increased by exposure to IL-6, but not by exposure to IL-2 or IL-8. 6. IL-2, IL-6 and IL-8 showed no effects on the release of nitrite, a stable metabolite of nitric oxide (NO), from VSMC. 7. These results indicate that IL-6, not IL-2 or IL-8, is a potent inhibitor of the alpha-adrenergic-stimulated contraction of vascular smooth muscle and its action is mediated by the increased synthesis of prostacyclin rather than NO.

Nitric oxide synthesis in rat mesangial cells induced by cytokines.

The production of nitric oxide (NO) is increased in experimental nephritis, with NO thought to be an important mediator of cell damage. The cytokines interleukin 1 beta (IL-1 beta), IL-6, IL-8, monocyte chemotactic protein-1 (MCP-1) and transforming growth factor-beta (TGF-beta) are released from mesangial cells in vitro or are expressed in various forms of glomerulonephritis. We investigated the effects of these cytokines on NO synthesis in cultured rat mesangial cells. Incubation of mesangial cells with IL-1 beta (10 ng/ml) for 24 h increased the accumulation of NO and guanosine 3',5'-cyclic monophosphate (cGMP). IL-6, IL-8, MCP-1 and TGF-beta showed no significant effect on the production of NO or cGMP. Transcripts of the inducible NO synthase (iNOS) gene were not detected in unstimulated mesangial cells. However, exposure of cells to IL-1 beta (10 ng/ml) for 24 h resulted in the appearance of iNos mRNA. IL-1 beta-induced NO synthesis was significantly inhibited by NG-monomethyl-L-arginine, cycloheximide, actinomycin D, dexamethasone, and TGF-beta. These results indicate that, of the various cytokines studied, only IL-1 beta stimulates iNOS mRNA accumulation and NO synthesis in mesangial cells. NO may function in an autocrine manner to modulate the glomerular response to inflammation.

Inhibitory effect of interleukin-6 on vascular smooth muscle contraction.

Our objective was to investigate the direct effect of interleukin-6 (IL-6) on the vascular smooth muscle contraction. We measured the contraction of endothelium-denuded aortic rings isolated from Sprague-Dawley rats. We also investigated the involvement of vasodilator prostaglandin and guanosine 3',5'-cyclic monophosphate (cGMP) productions in the effect of IL-6 using cultured rat vascular smooth muscle cells (VSMC). Exposing the aortic rings to recombinant murine IL-6 (50 U/ml) for 180 min significantly suppressed the phenylephrine (10(-9)-10(-5) M)-induced contraction. This inhibitory effect of IL-6 on the contraction tended to exhibit a dose-dependent relationship (0.5-50 U/ml). The effect of IL-6 was totally eliminated in the presence of indomethacin (10(-5) M). The release of immunoreactive 6-ketoprostaglandin F1 alpha from cultured rat VSMC was significantly increased by exposure to IL-6. Intracellular cGMP concentration in VSMC was not affected by IL-6. In conclusion, IL-6 is a potent inhibitor of the alpha-adrenergic-stimulated contraction of vascular smooth muscle. Its action is endothelium independent and mediated by the increased synthesis of prostacyclin in VSMC.

Nitric oxide synthesis in rat cardiac myocytes and fibroblasts.

We investigated nitric oxide (NO) synthase activity in cultured neonatal rat cardiac myocytes and fibroblasts upon treatment with interleukin 1 beta (IL-1 beta) and lipopolysaccharide (LPS). Incubation of cardiac myocytes for 24 h with IL-1 beta or LPS caused a significant increase in NO and cGMP production. Simultaneous incubation of IL-1 beta with NG-monomethyl-L-arginine or transforming growth factor beta (TGF-beta) completely inhibited the IL-1 beta-induced NO and cGMP production in cardiac myocytes. In contrast, incubation of cardiac fibroblasts for 24 h with IL-1 beta or LPS showed no significant effect on NO or cGMP production. Addition of IL-1 beta decreased the beating rate of cardiac myocytes, but TGF-beta overcame that inhibition. These observations suggest the presence of iNOS in cardiac myocytes, which is an important regulator of contractile function of the heart.

Serum interleukin 6 levels become elevated in acute myocardial infarction.

We have examined serum interleukin 6 (IL-6) levels in 12 patients with acute myocardial infarction (AMI). IL-6 levels became elevated in all patients, following the rise of serum creatine kinase (CK) activity. Peak IL-6 levels showed a good correlation with peak serum C-reactive protein (CRP) levels, while there was no direct relationship between peak IL-6 levels and peak CK activity. IL-6 mRNA was not detected in unstimulated "quiescent" rat cardiocytes cultured in serum-free medium, but its expression was induced by exposure of the cells to serum or ionomycin. These results show that IL-6 is synthesized in the myocardium and serum IL-6 levels become elevated in AMI, suggesting that IL-6 could affect the progression and/or healing processes of AMI.

[Anterior ST-segment deviation during inferior myocardial infarction: arteriographic correlations during the acute phase].

Electrocardiographic changes in the anterior wall lead in inferior myocardial infarction were studied in coronary angiographic findings in the acute stage. The subjects were 40 patients with initial inferior myocardial infarction due to right coronary lesions. ST segments were elevated in 7 patients, remained unchanged in 11 and were depressed in 22. Two patients predominantly perfused in the left coronary artery showed ST elevation. All seven patients who showed elevation of the ST segments had occlusion of the ventricular branch proximal to right. However, another 15 (68%) of the patients with occlusion of the same lesion did not show elevation of any ST segment. There was no difference in left ventricular ejection fraction between the groups. The regional ejection fraction at the left ventricular inferior wall was significantly (p less than 0.01) higher in the ST elevated group than in the ST depressed group. Elevation of the ST segments in the anterior wall lead was observed only when the right ventricular free wall sustained injury, and no elevation of any ST segment was observed when the range of injury in the inferoposterior wall was wide, even in the presence of injury to the right ventricular free wall.