Cell- and isoform-specific increases in arginase expression in acute silica-induced pulmonary inflammation

Arginase induction was reported in several inflammatory lung diseases, suggesting that this may be a common feature underlying the pathophysiology of such diseases. As little is known regarding arginase expression in silicosis, the induction and cellular localization of arginase were elucidated in lungs of Sprague-Dawley rats 24 h following exposure to varying doses of silica by intratracheal instillation. Arginase expression was evaluated by activity assay, quantification of arginase I and arginase II mRNA levels using real-time polymerase chain reaction (PCR), and immunohistochemistry. Analyses of cells and fluid obtained by bronchoalveolar lavage (BAL) showed that markers of pulmonary inflammation, tissue damage, activation of alveolar macrophages (AM) and NO production were significantly increased by all silica doses. Arginase activity was increased also in AMs isolated from BAL fluid of silica-treated rats. Silica produced two- and three-fold increases in arginase activity of whole lung at doses of 1 and 5 mg/100 g body weight, respectively. Levels of arginase I mRNA, but not of arginase II mRNA, were similarly elevated. In control lungs, arginase I immunoreactivity was observed only in AMs sparsely dispersed throughout the lung; no inducible nitric oxide synthase (iNOS) immunoreactivity was detected. In silica-treated lungs, arginase I and iNOS were co-expressed in most AMs that were abundantly clustered at inflammatory foci. The rapid induction of arginase I expression in inflammatory lung cells, similar to induction of arginase in other inflammatory lung diseases, implicates elevated arginase activity as a factor in the development of lung damage following exposure to silica.     

Arginases I and II in lungs of ovalbumin-sensitized mice exposed to ovalbumin: sources and consequences

Arginase gene expression in the lung has been linked to asthma both in clinical studies of human patients and in the well-studied mouse model of ovalbumin-induced airway inflammation. Arginase is thought to regulate NO levels in the lung by its ability to divert arginine, the substrate for nitric oxide synthases that produce citrulline and NO, into an alternative metabolic pathway producing ornithine and urea. In the present study arginase I and arginase II concentrations were measured in isolated microdissected airway preparations from sensitized Balb/c mice exposed to ovalbumin aerosol. We found that arginase II was constitutively expressed in the airways of normal mice, whereas arginase I was undetectable in normal airways, while its expression was increased in airways of mice exposed to ovalbumin. The expression of arginase I strongly correlated with the presence of lung inflammation, as quantified by differential cell counts in lung lavage, suggesting that most, or all, of the arginase I in lungs of mice exposed to ovalbumin is present in the inflammatory cells rather than in the airway epithelium. There was also a significant correlation between increased expression of arginase I in the isolated airways and decreased lung compliance. On the other hand, while we found arginase II expression to also be significantly increased in airways from mice exposed to ovalbumin as compared with normal airways, the relative increase was much less than that observed for arginase I, suggesting that there was a smaller contribution of inflammatory cells to the arginase II content of the airways in mice exposed to ovalbumin. There was no apparent correlation between the content of arginase in isolated airways and exhaled NO concentration in the expired air from mice exposed to ovalbumin. However, there was a correlation between exhaled NO concentration from mice exposed to ovalbumin and the lymphocyte content of the lung lavage. The concentration of arginine found in isolated airways from Balb/c mice exposed for 2 weeks to ovalbumin was about half of the value found in isolated microdissected airways from normal mice. Treatment of mice systemically with an arginase inhibitor significantly increased the amount of NO produced, as measured as the amount of nitrite+nitrate (NOx) in lung lavage supernatant prepared from mice exposed to ovalbumin. Our results are consistent with the hypothesis that the response of the lung to ovalbumin challenge includes an adaptive response in the large airways regulating the concentration of arginine within cells of the airway epithelium and subepithelial layer, by shunting of arginine into the metabolic pathway for increased synthesis of NO.     

Arginase enzymes in isolated airways from normal and nitric oxide synthase 2-knockout mice exposed to ovalbumin

Arginase has been suggested to compete with nitric oxide synthase (NOS) for their common substrate, l-arginine. To study the mechanisms underlying this interaction, we compared arginase expression in isolated airways and the consequences of inhibiting arginase activity in vivo with NO production, lung inflammation, and lung function in both C57BL/6 and NOS2 knockout mice undergoing ovalbumin-induced airway inflammation, a mouse model of asthma.Arginases I and II were measured by western blot in isolated airways from sensitized C57BL/6 mice exposed to ovalbumin aerosol. Physiological and biochemical responses - inflammation, lung compliance, airway hyperreactivity, exhaled NO concentration, arginine concentration - were compared with the responses of NOS2 knockout mice. NOS2 knockout mice had increased total cells in lung lavage, decreased lung compliance, and increased airway hyperreactivity. Both arginase I and arginase II were constitutively expressed in the airways of normal C57BL/6 mice. Arginase I was up-regulated approximately 8-fold in the airways of C57BL/6 mice exposed to ovalbumin. Expression of both arginase isoforms were significantly upregulated in NOS2 knockout mice exposed to ovalbumin, with about 40- and 4-fold increases in arginases I and II, respectively. Arginine concentration in isolated airways was not significantly different in any of the groups studied. Inhibition of arginase by systemic treatment of C57BL/6 mice with a competitive inhibitor, Nω-hydroxy-nor-l-arginine (nor-NOHA), significantly decreased the lung inflammatory response to ovalbumin in these animals.We conclude that NOS2 knockout mice are more sensitive to ovalbumin-induced airway inflammation and its sequelae than are C57BL/6 mice, as determined by increased total cells in lung lavage, decreased lung compliance, and increased airway hyperreactivity, and that these findings are strongly correlated with increased expression of both arginase isoforms in the airways of the NOS2 knockout mice exposed to ovalbumin.     

Mitochondrial function in carbon tetrachloride-induced cirrhosis in the rat. Qualitative and quantitative defects

Mitochondrial function is impaired in patients and experimental animals with liver cirrhosis. The relationship between mitochondrial impairment and severity of cirrhosis is unknown, however. We therefore characterized the severity of cirrhosis in rats with phenobarbital/CCl4-induced cirrhosis by the aminopyrine breath test, a microsomal function test reflecting hepatocellular mass. Mitochondrial function was evaluated by measuring oxygen consumption, enzyme activities and ATP production in mitochondria isolated from cirrhotic (N = 8) and control livers (N = 4). Oxygen consumption and mitochondrial enzyme activities calculated per liver were significantly reduced in the presence of cirrhosis. This decrease corresponded to the loss of hepatocytes calculated from the reduction in aminopyrine breath test. The effect of atractylate, oligomycin and dinitrophenol on state 3 respiration was equal between the two groups. The respiratory control ratio was significantly reduced in mitochondria from cirrhotic livers with beta-hydroxybutyrate (4.01 +/- 0.94 vs 5.45 +/- 0.40), but not with succinate as substrate. The rate of ATP production was significantly decreased in mitochondria from cirrhotic rats for both substrates. In contrast, the static head (state 4) phosphate potential was fully developed after 10 min and was equal between the two groups. We conclude that cirrhosis of the liver leads to a loss of hepatocytes which is paralleled by reduced oxygen uptake and reduced mitochondrial enzyme activities.     

Glucocorticoids inhibit lipopolysaccharide-induced up-regulation of arginase in rat alveolar macrophages

1. As arginase by limiting nitric oxide (NO) synthesis may play a role in airway hyperresponsiveness and glucocorticoids are known to induce the expression of arginase I in hepatic cells, glucocorticoid effects on arginase in alveolar macrophages (AM Phi) were studied. 2. Rat AM Phi were cultured in absence or presence of test substances. Thereafter, nitrite accumulation, arginase activity, and the expression pattern of inducible NO synthase, arginase I and II mRNA (RT - PCR) and proteins (immunoblotting) were determined. 3. Lipopolyssacharides (LPS, 20 h) caused an about 2 fold increase in arginase activity, whereas interferon-gamma (IFN-gamma), like LPS a strong inducer of NO synthesis, had no effect. 4. Dexamethasone decreased arginase activity by about 25% and prevented the LPS-induced increase. Mifepristone (RU-486) as partial glucocorticoid receptor agonist inhibited LPS-induced increase by 45% and antagonized the inhibitory effect of dexamethasone. 5. Two different inhibitors of the NF-kappa B-pathway also prevented LPS-induced increase in arginase activity. 6. Rat AM Phi expressed mRNA and protein of arginase I and II, but arginase I expression was stronger. Arginase I mRNA and protein was not affected by IFN-gamma, but increased by LPS and this effect was prevented by dexamethasone. Both, LPS and IFN-gamma enhanced the levels of arginase II mRNA and protein, effects also inhibited by dexamethasone. As IFN-gamma did not affect total arginase activity, arginase II may represent only a minor fraction of total arginase activity. 7. In rat AM Phi glucocorticoids inhibit LPS-induced up-regulation of arginase activity, an effect which may contribute to the beneficial effects of glucocorticoids in the treatment of inflammatory airway diseases.     

Arginase: a critical regulator of nitric oxide synthesis and vascular function

1. Arginase is the focal enzyme of the urea cycle hydrolysing L-arginine to urea and L-ornithine. Emerging studies have identified arginase in the vasculature and have implicated this enzyme in the regulation of nitric oxide (NO) synthesis and the development of vascular disease. 2. Arginase inhibits the production of NO via several potential mechanisms, including competition with NO synthase (NOS) for the substrate L-arginine, uncoupling of NOS resulting in the generation of the NO scavenger, superoxide and peroxynitrite, repression of the translation and stability of inducible NOS protein, inhibition of inducible NOS activity via the generation of urea and by sensitization of NOS to its endogenous inhibitor asymmetric dimethyl-L-arginine. 3. Upregulation of arginase inhibits endothelial NOS-mediated NO synthesis and may contribute to endothelial dysfunction in hypertension, ageing, ischaemia-reperfusion and diabetes. 4. Arginase also redirects the metabolism of L-arginine to L-ornithine and the formation of polyamines and L-proline, which are essential for smooth muscle cell growth and collagen synthesis. Therefore, the induction of arginase may also promote aberrant vessel wall remodelling and neointima formation. 5. Arginase represents a promising novel therapeutic target that may reverse endothelial and smooth muscle cell dysfunction and prevent vascular disease.     

Tissue-specific up-regulation of arginase I and II induced by p38 MAPK mediates endothelial dysfunction in type 1 diabetes mellitus

Background and Purpose

Emerging evidence suggests a selective up-regulation of arginase I in diabetes causing coronary artery disease; however, the mechanisms behind this up-regulation are still unknown. Activated p38 MAPK has been reported to increase arginase II in various cardiovascular diseases. We therefore tested the role of p38 MAPK in the regulation of arginase I and II expression and its effect on endothelial dysfunction in diabetes mellitus.

Experimental Approach

Endothelial function was determined in septal coronary (SCA), left anterior descending coronary (LAD) and mesenteric (MA) arteries from healthy and streptozotocin-induced diabetic Wistar rats by wire myographs. Arginase activity and protein levels of arginase I, II, phospho-p38 MAPK and phospho-endothelial NOS (eNOS) (Ser¹¹⁷⁷) were determined in these arteries from diabetic and healthy rats treated with a p38 MAPK inhibitor in vivo.

Key Results

Diabetic SCA and MA displayed impaired endothelium-dependent relaxation, which was prevented by arginase and p38 MAPK inhibition while LAD relaxation was not affected. Arginase I, phospho-p38 MAPK and eNOS protein expression was increased in diabetic coronary arteries. In diabetic MA, however, increased expression of arginase II and phospho-p38 MAPK, increased arginase activity and decreased expression of eNOS were observed. All these effects were reversed by p38 MAPK inhibition.

Conclusions and Implications

Diabetes-induced activation of p38 MAPK causes endothelial dysfunction via selective up-regulation of arginase I expression in coronary arteries and arginase II expression in MA. Therefore, regional differences appear to exist in the arginase isoforms contributing to endothelial dysfunction in type 1 diabetes mellitus.     

Evaluation of the protective effects of quercetin in the hepatopulmonary syndrome.

The hepatopulmonary syndrome (HPS) occurs when intrapulmonary dilatation causes hypoxemia in cirrhosis. The free radicals may play a significant contributory role in the progression of HPS, and flavonoid agents could protect against deleterious effects of free radicals. The flavonoid quercetin was evaluated in an experimental model of biliary cirrhosis induced by bile duct ligation (BDL) in rats. Quercetin was administered at 50mg/kg for 14 days to cirrhotic and non-cirrhotic rats. Bone marrow was extracted from animals to analyze micronuclei. Lung, liver and blood were extracted to detect DNA damage using the comet assay. The results showed that the micronuclei and DNA damages to lung and liver were increased in BDL rats. Quercetin caused no damage to the DNA while decreasing the occurrence of micronucleated cells in bone marrow as well as DNA damage to lung and liver in cirrhotic rats. Quercetin showed antimutagenic activity against hydroperoxides as evaluated by the oxidative stress sensitive bacterial strains TA102 Salmonella typhimurium and IC203 Escherichia coli, suggesting protection by free radical scavenging. In Saccharomyces cerevisie yeast strains lacking mitochondrial or cytosolic superoxide dismutase, these results indicate that quercetin protects cells by induction of antioxidant enzymes. The present study is the first report of genotoxic/antigenotoxic effects of quercetin in a model of animal cirrhosis. In this model, quercetin was not able to induce genotoxicity and, conversely, it increased the genomic stability in the cirrhotic rats, suggesting beneficial effects, probably by its antioxidant properties.     

AUGMENTED ENDOGENOUS NITRIC OXIDE PRODUCTION IN PARTIAL PORTAL VEIN-LIGATED RATS

1. Endothelium-derived nitric oxide (NO) is a potent vasodilator. Because the body oxidizes it to nitrate ions, NO₃-, measurement of the serum concentration and the urinary excretion of NO₃- may be an index for endogenous NO. We investigated the role of NO on hyperdynamic circulation in cirrhotic and partial portal vein-ligated rats by measuring NO₃. 2. Liver cirrhosis was induced by administration of thioacetamide. Systemic and splanchnic haemodynamics and splenic-systemic shunting were determined by tracer microspheres. The concentration of NO₃- was measured by using high-performance liquid chromatography with an anion-column. 3. We found that systemic and splanchnic hyperdynamic circulation existed to almost the same extent in cirrhotic and in portal vein-ligated rats as compared to the controls and sham-operated rats, respectively. Splenic-systemic shunting was markedly greater in portal vein-ligated rats than in cirrhotic rats. 4. Serum NO₃- levels and urinary excretion of NO₃- in cirrhotic rats tended to increase as compared to the controls. On the other hand, the levels in portal vein-ligated rats were significantly increased as compared to those of the sham-operated rats, and were significantly and negatively correlated to the splanchnic arterial resistance and total vascular resistance. The amount of urinary excretion of NO₃- significantly correlated to splenic-systemic shunting (r = 0.61, P<0.05) only in portal vein-ligated rats. 5. We suggest that these high levels of NO₃- in portal vein-ligated rats relate to the extensive formation of porto-collateral vasculature or acute changes in systemic and splanchnic haemodynamics due to portal vein-ligation.     

Arginase Inhibition by Ethylacetate Extract of Caesalpinia sappan Lignum Contributes to Activation of Endothelial Nitric Oxide Synthase

Caesalpinia sappan (C. sappan) is a medicinal plant used for promoting blood circulation and removing stasis. During a screening procedure on medicinal plants, the ethylacetate extract of the lignum of C. sappan (CLE) showed inhibitory activity on arginase which has recently been reported as a novel therapeutic target for the treatment of cardiovascular diseases such as atherosclerosis. CLE inhibited arginase II activity prepared from kidney lysate in a dose-dependent manner. In HUVECs, inhibition of arginase activity by CLE reciprocally increased NOx production through enhancement of eNOS dimer stability without any significant changes in the protein levels of eNOS and arginase II expression. Furthermore, CLE-dependent arginase inhibition resulted in increase of NO generation and decrease of superoxide production on endothelium of isolated mice aorta. These results indicate that CLE augments NO production on endothelium through inhibition of arginase activity, and may imply their usefulness for the treatment of cardiovascular diseases associated with endothelial dysfunction.     

血红素加氧酶-1的表达对实验性肝硬化内毒素血症大鼠的影响

目的:探讨血红素加氧酶-1(HO-1)的表达对实验性肝硬化内毒素血症大鼠的影响。方法:32只健康雄性wistar大鼠,随机分为4组,正常+脂多糖(LPS)(对照组)、肝硬化+生理盐水对照组(TAA组)、肝硬化+LPS组(TAA+LPS组)、肝硬化+LPS+hemin(氯化高铁血红素)(HM组)。用硫代乙酰胺(TAA)诱导肝硬化模型时间共计10周,对照组自由饮清水。于模型造成后,向对照组、TAA+LPS组、HM组大鼠腹腔内注入LPS3 mg/kg;TAA组大鼠腹腔内注入等量的生理盐水;HM组于注射LPS 12 h前,腹腔注射HM(40 mg/kg),并在注入LPS 6 h后,各组动物经腹主动脉穿刺采全血观察血浆中丙氨酸氨基转移酶(ALT)、天门冬氨基酸转移酶(AST)、一氧化氮(NO)及丙二醛(MDA)的表达。留肝组织用免疫组织化学法观察HO-1的表达。结果:对照组、TAA组、TAA+LPS组、HM组血浆中的ALT/AST、MDA、NO依次升高差异有显著性(P<0.05),对照组、TAA、TAA+LPS、HM组各组大鼠的灰阶值显著依次降低,且有明显差别(P<0.05)。结论:在实验性的肝硬化内毒素中尽管HO-1的表达增加,但它未起到保护作用,它与内毒素对机体的损伤有关。     

Paracrine renal endothelin system in rats with liver cirrhosis.

1. Liver cirrhosis was induced in rats by CCl4 administration. We analysed the expression of endothelin receptor subtypes in the renal cortex and medulla using Scatchard analysis and receptor autoradiography, and measured plasma as well as renal-tissue endothelin-1 concentrations using a specific radioimmunoassay. Furthermore, we analysed the effects of the non-selective (A/B) endothelin receptor antagonist, bosentan (6 and 100 mg kg-1 day-1) on mean arterial blood pressure, water and sodium excretion and glomerular filtration rate. 2. Our study revealed an overexpression of the endothelin B receptor (ETB) in the renal medulla of rats with liver cirrhosis (Cir: 2775 +/- 299 fmol mg-1; Con: 1695 +/- 255 fmol mg-1; n = 8; means +/- s.d., P < 0.01), whereas the density of ETB in the cortex and the endothelin A receptor (ETA) in the cortex and medulla were similar in both cirrhotic and control rats. Receptor autoradiography showed that the upregulation of medullary ETB in cirrhotic rats was due to an upregulation of ETB in the inner medullary collecting duct cells. 3. The tissue endothelin-1 concentrations were increased in the renal medulla of cirrhotic rats (Cir: 271 +/- 68 pg g-1wet wt.; Con: 153 +/- 36 pg g-1 wet wt., n = 8; means +/- s.d., P < 0.01). 4. The glomerular filtration rate was slightly decreased in cirrhotic rats but not altered after bosentan treatment in either cirrhotic or control rats. Bosentan decreased sodium excretion to a similar extent in both cirrhotic and control rats, whereas water excretion was significantly reduced by both dosages of bosentan in cirrhotic rats only (Cir + vehicle: 12.5 +/- 0.62 m day-1, Cir + 6 mg kg-1 day-1 bosentan: 8.6 +/- 1.0 ml day-1; Cir + 100 mg kg-1 day-1 bosentan: 7.4 +/- 0.6 ml day-1; n = 10; means +/- s.e.mean). 5. We therefore suggest that the upregulation of the medullary ETB in cirrhotic rats is involved in the regulation of water excretion in rats with CCl4-induced liver cirrhosis.     

一氧化氮对大鼠全胃肠外营养肝脂肪变性的防护作用

目的:探讨一氧化氮(N0)在全胃肠外营养(TPN)引起的肝脂肪变性中的作用.方法:30只正常Wistar大鼠随机分为5组:A组,自由进食和水;B组,TPN;C组,TPN 精氨酸;D组,TPN N~G-硝基-L-精氨酸甲酯(N~G-nitrio-L-arginine methyl ester,L-NAME);E组,TPN 精氨酸 L-NAME.实验7天后测肝功能、肝内脂肪、肝脏NO含量及NOS活性并进行肝脏组织学检查.结果:B组肝内脂肪[甘油三酯、胆固醇(mmol·g~(-1))](39.3±2.4和 13.1±1.1)较A组(6.9±0.8和5.6±0.6)明显增加(P<0.05),D组肝内脂肪(50±6和14.1±1.7)较B组增加更显著(P<0.05),C组肝内脂肪(18±4和 7±3)较B组明显减少(P<0.05),肝内NOS活性及分布与肝内脂肪含量及分布相平行.结论:一氧化氮在TPN引起的肝脂肪变性中起防护作用.     

Decreased hepatic elimination of pyrimethamine during malaria infection. Studies in the isolated perfused rat liver

The elimination of the antimalarial drug pyrimethamine was studied in isolated liver preparations from young rats (80-100 g) infected with merozoites of Plasmodium berghei two weeks earlier. Perfusate half-life of pyrimethamine was increased in livers from M.I. rats (t1/2 beta control group = 56 +/- 11 min vs M.I. group = 101 +/- 12, P less than 0.01), reflecting a decrease in hepatic clearance (3.6 +/- 1.1 ml/min vs 1.9 +/- 0.5 ml/min, P less than 0.01). There was no significant difference in volume of distribution between livers from M.I. and control groups. Intrahepatic concentration of unchanged drug at 3 hr was 4-5-fold greater in livers from infected rats (control group = 4725 +/- 2287 ng/ml vs M.I. group = 22,324 +/- 6824 ng/ml), while liver: perfusate concentration ratios were not significantly different (control group = 30.8 +/- 24.1 vs M.I. group = 35.6 +/- 20.3). We conclude that the hepatic elimination of pyrimethamine is substantially impaired in the malaria-infected rat.     

一氧化氮与内皮素在肝硬化发生发展中的作用

目的 :研究一氧化氮和内皮素在肝硬化发生发展中的作用。方法 :用放射免疫法 ,镀铜镉还原法和火箭电泳法测定 74例肝硬化患者和 5 1例正常对照组血浆内皮素 (ET)、肿瘤坏死因子 α(TNFα)、一氧化氮 (NO)和纤维联结蛋白 (FN)的含量。结果 :肝硬化患者血浆 ET和 NO明显升高 ,二者均与 TNFα呈正相关 ,与 FN呈负相关。ET和 NO水平随肝功能受损加重、腹水量增加和食管静脉曲张程度加重而增加 ,正常对照组和肝硬化 A级时 ,ET与 NO无相关性 ,而 B级和 C级 ,中大量腹水组及食管静脉曲张组 ET和 NO呈明显正相关。结论 :NO和 ET在肝硬化发生发展中均具有重要作用 ,二者共同促进了肝硬化的失代偿及并发症发生     

NO和iNOS在肝硬化患者肝组织中的表达及与门静脉压力的关系

目的：观察NOS-NO系统在肝硬化患者肝组织中的表达及与门静脉压力的关系，以探讨其在肝硬化门脉高压中的作用。方法：随机抽取20例正常志愿者及20例肝硬化患者，在B超引导下经皮经肝穿刺分别测定门静脉压力、抽取门静脉血和外周血并留取肝组织，测定血液中NO浓度，观察肝组织iNOS的表达。结果：肝硬化患者下腔静脉及门静脉血中NO浓度、肝组织iNOS的表达及门静脉压力均分别显著高于正常对照组。正常对照组的外周血和门静脉血中NO浓度水平接近．差异无统计学意义；但肝硬化患者的门静脉血NO浓度显著高于外周血NO浓度。门静脉压力与外周静脉血NO浓度、门脉血NO浓度及肝组织中iNOS的表达呈直线相关关系。结论：门静脉压力与门脉血NO浓度、肝组织中iNOS的表达密切相关。     

Korean Red Ginseng Water Extract Restores Impaired Endothelial Function by Inhibiting Arginase Activity in Aged Mice

Cardiovascular disease is the prime cause of morbidity and mortality and the population ages that may contribute to increase in the occurrence of cardiovascular disease. Arginase upregulation is associated with impaired endothelial function in aged vascular system and thus may contribute to cardiovascular disease. According to recent research, Korean Red Ginseng water extract (KRGE) may reduce cardiovascular disease risk by improving vascular system health. The purpose of this study was to examine mechanisms contributing to age-related vascular endothelial dysfunction and to determine whether KRGE improves these functions in aged mice. Young (10±3 weeks) and aged (55±5 weeks) male mice (C57BL/6J) were orally administered 0, 10, or 20 mg/mouse/day of KRGE for 4 weeks. Animals were sacrificed and the aortas were removed. Endothelial arginase activity, nitric oxide (NO) generation and reactive oxygen species (ROS) production, endothelial nitric oxide synthase (eNOS) coupling, vascular tension, and plasma peroxynitrite production were measured. KRGE attenuated arginase activity, restored nitric oxide (NO) generation, reduced ROS production, and enhanced eNOS coupling in aged mice. KRGE also improved vascular tension in aged vessels, as indicated by increased acetylcholine-induced vasorelaxation and improved phenylephrine-stimulated vasoconstriction. Furthermore, KRGE prevented plasma peroxynitrite formation in aged mice, indicating reduced lipid peroxidation. These results suggest KRGE exerts vasoprotective effects by inhibiting arginase activity and augmenting NO signaling and may be a useful treatment for age-dependent vascular diseases.     

Hyperoxia increases hepatic arginase expression and ornithine production in mice

Hyperoxic exposure affects the levels and activities of some hepatic proteins. We tested the hypothesis that hyperoxic exposure would result in greater hepatic .NO concentrations. C3H/HeN mice were exposed to >95% O(2) for 72 or 96 h and compared to room air-breathing controls. In contrast to our working hypothesis, exposure to >95% O(2) for 96 h decreased hepatic nitrite/nitrate NO(X) concentrations (10.9 +/- 2.2 nmol/g liver versus 19.3 +/- 2.4 nmol/g liver in room air, P < 0.05). The hepatic levels of endothelial NO synthase (eNOS) and inducible NOS (iNOS) proteins were not different among the groups. The arginases, which convert L-arginine to urea and L-ornithine, may affect hepatic NOS activities by decreasing L-arginine bioavailability. Hepatic ornithine concentrations were greater in hyperoxic animals than in controls (318 +/- 18 nmol/g liver in room air, and 539 +/- 64, and 475 +/- 40 at 72 and 96 h of hyperoxia, respectively, P < 0.01). Hepatic arginase I protein levels were greater in hyperoxic animals than in controls. Hepatic carbamoyl phosphate synthetase (CPS) protein levels and activities were not different among groups. These results indicate that increases in hepatic levels of arginase I in mice exposed to hyperoxia may diminish .NO production, as reflected by lower liver levels of NO(X). The resultant greater hepatic ornithine concentrations may represent a mechanism to facilitate tissue repair, by favoring the production of polyamines and/or proline.     

Pharmacokinetics of molsidomine and its active metabolite, linsidomine, in patients with liver cirrhosis.

The pharmacokinetics of molsidomine were investigated in six healthy volunteers and in seven patients with alcoholic cirrhosis. After a 2 mg oral dose, molsidomine elimination half-life was prolonged in cirrhotic patients (13.1 +/- 10.0 h vs 1.2 +/- 0.2 h, P less than 0.01) because of a decrease in its apparent plasma clearance (CL/F) (39.8 +/- 31.9 ml h-1 kg-1 in patients with cirrhosis vs 590 +/- 73 ml h-1 kg-1 in volunteers). The elimination half-life of the active metabolite, linsidomine (SIN-1) was also prolonged in cirrhotic patients (7.5 +/- 5.4 h vs 1.0 +/- 0.19 h, P less than 0.05). The AUC values of both molsidomine and linsidomine were increased in the cirrhotic group, but the increase in the former was considerably greater than in the latter as shown by the significant decrease of the ratio AUClinsidomine/AUCmolsidomine x 100 (4.5 +/- 6.1 in cirrhotic patients vs 23.5 +/- 3.4 in healthy volunteers, P less than 0.001). These results suggest that liver cirrhosis profoundly alters the pharmacokinetics and metabolism of molsidomine.