Arginases I and II in lungs of ovalbumin-sensitized mice exposed to ovalbumin: sources and consequences.
ABSTRACT 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.
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ABSTRACT: Neutrophils are the predominant cells recruited in the airways of horses suffering from heaves. These cells have been shown to express arginase in some species. The metabolism of L-arginine is thought to be involved in chronic inflammation, and airway obstruction and remodeling. The aim of this study was to assess the expression, regulation, activity, and functional role of arginase isoforms in equine neutrophils. Arginase I, arginase II, ornithine decarboxylase (ODC) and ornithine aminotransferase (OAT) expression were assessed in resting and stimulated (IL-4, LPS/fMLP, PMA; 5 and 18 h) blood neutrophils using quantitative PCR. Arginase expression was also studied by western blot and enzyme activity assay. The effect of nor-NOHA (1 mM), a specific arginase inhibitor, was assessed on arginase activity in vitro and ex vivo on neutrophil's inflammatory gene expression and viability. Results showed that equine neutrophils constitutively express arginase isoform 2,ODC and OAT. Neutrophil ex vivo stimulation did not induce arginase I nor influence arginase II mRNA expression. Ex vivo inhibition of arginase activity by nor-NOHA had no effect on neutrophils inflammatory gene expression induced by LPS/fMLP (5 h) but significantly reversed the cell loss observed after this stimulation.Veterinary Immunology and Immunopathology 01/2013; · 1.88 Impact Factor
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ABSTRACT: Arginases are a family of enzymes that convert L-arginine to L-ornithine and urea. Alterations in expression of the isoform arginase-I are increasingly recognized in lung diseases such as asthma and cystic fibrosis. To define expression of murine arginase-I in formalin-fixed tissues, including lung, an immunohistochemical protocol was validated in murine liver, a tissue that has distinct zonal arginase-I expression, making it a useful control. In the lung, arginase-I immunostaining was observed in airway surface epithelium and this decreased from large to small airways, with a preferential staining of ciliated epithelium versus Clara cells and alveolar epithelia. In submucosal glands, the ducts and serous acini had moderate immunostaining, which was absent in mucous cells. Focal immunostaining was observed in alveolar macrophages, endothelial cells, pulmonary vein cardiomyocytes, pulmonary artery smooth muscle, airway smooth muscle, and neurons of ganglia of the lung. Arginase-I immunostaining was also detected in other tissues including salivary glands, pancreas, liver, skin, and intestine. Differential immunostaining was observed between sexes in submandibular salivary glands; arginase-I was diffusely expressed in the convoluted granular duct cells of females, but was rarely noted in males. Strain specific differences were not detected. In a mouse with an incidental case of lymphoma, neoplastic lymphocytes lacked arginase-I immunostaining, in contrast to immunostaining detected in non-neoplastic lymphocytes of lymphoid tissues. The use of liver tissue to validate arginase-I immunohistochemistry produced consistent expression patterns in mice,and this approach can be useful to enhance consistency of arginase-I immunohistochemical studies.Journal of histotechnology 12/2013; 36(4):128-134. · 0.15 Impact Factor
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ABSTRACT: We have shown that expression of Human Papillomavirus type 16 E7 (HPV16.E7) protein within epithelial cells, as occurs in HPV associated-premalignancy and cancers, results in local immune suppression, and a weak and ineffective immune response to E7 protein. However, a robust acute inflammatory stimulus can overcome this to enable immune elimination of HPV16.E7 transformed epithelial cells. 2,4-Dinitrochlorobenzene (DNCB) can elicit acute inflammation and has been shown to initiate the regression of HPV-associated genital warts. Although clinical use of DNCB is discouraged due to its mutagenic potential, understanding how DNCB induced acute inflammation alters local HPV16.E7 mediated-immune suppression might lead to better treatments. Here, we show that topical DNCB application to skin expressing HPV16.E7 as a transgene induces a hyperinflammatory response, not seen in non-transgenic control animals. The E7 associated-inflammatory response is characterized by enhanced expression of Th2 cytokines and increased infiltration of CD11b(+)Gr1(int)F4/80(+)Ly6C(hi)Ly6G(low) myeloid cells, producing arginase-1. Inhibition of arginase with an arginase specific inhibitor, N(omega)-hydroxy-nor-L-arginine, ameliorates the DNCB-induced inflammatory response. Our results demonstrate that HPV16.E7 protein enhances DNCB associated-production of arginase-1 by myeloid cells and consequent inflammatory cellular infiltration of skin.Journal of Investigative Dermatology accepted article peview online, 14 April 2014. doi:10.1038/jid.2014.186.Journal of Investigative Dermatology 04/2014; · 6.19 Impact Factor