Immunohistochemical detection of arginase-I expression in formalin-fixed lung and other tissues

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 one 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.

Arginase-II Deficiency Extends Lifespan in Mice

“…It has been reported that both Arg-I and Arg-II are present in skin. Arg-I is mainly expressed in bulbs of anagen follicles along with lower expression in the adnexal sebaceous glands and surface epithelium (Hochstedler et al, 2013 ), whereas Arg-II is mainly expressed in skin keratinocytes and fibroblasts (Debats et al, 2009 ). Our current work confirms the observation that Arg-II is expressed in keratinocytes and in fibroblasts (co-localized with α-SMA positive cells) but also in α-SMA negative cells, probably resident immune cells (Figure 4B ).…”

Arginase‐2, a miR‐1299 target, enhances pigmentation in melasma by reducing melanosome degradation via senescence‐induced autophagy inhibition

“…There are two distinct isoenzymes of mammalian arginase: arginase‐1 (ARG1) and ARG2. ARG1, which plays a critical role in urea biogenesis, is highly expressed in the liver, but not in skin (Hochstedler, Leidinger, Maher‐Sturm, Gibson‐Corley, & Meyerholz, ). On the other hand, ARG2 is expressed in diverse extrahepatic tissues lacking a complete urea cycle, including skin keratinocytes and fibroblasts (Debats et al., ).…”

Arginase 1 is negatively regulated by β-catenin signaling in the lung

“…Outside the liver, Arg1 is expressed in macrophages [6, 7, 34], where it has been reported to be a marker of an alternatively activated macrophage phenotype [9, 11, 35, 36]. To determine whether the increase in Arg1 observed 14 days post-bleomycin injury was due to an increase in the number of alternatively activated macrophages in the lungs, we analyzed macrophage differentiation by flow cytometry using standard markers for myeloid cell activation.…”