Arginase in parasitic infections: macrophage activation, immunosuppression, and intracellular signals. J Biomed Biotechnol. 2010;2010:683485. [PMID: 20029630 PMCID: PMC2792949 DOI: 10.1155/2010/683485]

Diphenyl diselenide-modulation of macrophage activation: down-regulation of classical and alternative activation markers

Diphenyl diselenide (PhSe)(2), a simple organoselenium compound, possesses interesting pharmacological properties that are under extensive research. As macrophages respond to microenvironmental stimuli and can display activities engaged in the initiation and the resolution of inflammation, in the present report we describe the ability of (PhSe)(2) to modulate the macrophage activation. Our data indicate that (PhSe)(2) could inhibit the NO production in a dose-dependent fashion in peritoneal macrophages activated by LPS or treated with vehicle alone. We could demonstrate that this effect correlated with a reduction in the expression of the inducible NO synthase in (PhSe)(2)-treated cells. Furthermore, (PhSe)(2) suppressed the production of reactive oxygen species, diminished the activity of the arginase enzyme, and the accumulation of nitrotyrosine modified proteins in LPS-stimulated macrophages. This compound also diminished the antigen presentation capacity of classically activated macrophages, as it reduced MHCII and CD86 expression. In addition, (PhSe)(2) modulated the alternative activation phenotype of macrophages. Dexamethasone-activated macrophages presented higher production of IL-10 and CD206, which were both down-regulated by the addition of (PhSe)(2). These results suggest that (PhSe)(2) possesses antioxidant and anti-inflammatory activities in classically-activated macrophages. We could demonstrate that (PhSe)(2) can be also utilized to modulate the alternative activation phenotype of macrophages.

Th2-associated alternative Kupffer cell activation promotes liver fibrosis without inducing local inflammation

Cirrhosis is the final outcome of liver fibrosis. Kupffer cell-mediated hepatic inflammation is considered to aggravate liver injury and fibrosis. Alternatively-activated macrophages are able to control chronic inflammatory events and trigger wound healing processes. Nevertheless, the role of alternative Kupffer cell activation in liver harm is largely unclear. Thus, we evaluated the participation of alternatively-activated Kupffer cells during liver inflammation and fibrosis in the murine model of carbon tetrachloride-induced hepatic damage. To stimulate alternative activation in Kupffer cells, 20 Taenia crassiceps (Tc) larvae were inoculated into BALBc/AnN female mice. Six weeks post-inoculation, carbon tetrachloride or olive oil were orally administered to Tc-inoculated and non-inoculated mice twice per week during other six weeks. The initial exposure of animals to T. crassiceps resulted in high serum concentrations of IL-4 accompanied by a significant increase in the hepatic mRNA levels of Ym-1, with no alteration in iNOS expression. In response to carbon tetrachloride, recruitment of inflammatory cell populations into the hepatic parenchyma was 5-fold higher in non-inoculated animals than Tc-inoculated mice. In contrast, carbon tetrachloride-induced liver fibrosis was significantly less in non-inoculated animals than in the Tc-inoculated group. The latter showed elevated IL-4 serum levels and low IFN-γ concentrations during the whole experiment, associated with hepatic expression of IL-4, TGF-β, desmin and α-sma, as well as increased mRNA levels of Arg-1, Ym-1, FIZZ-1 and MMR in Kupffer cells. These results suggest that alternative Kupffer cell activation is favored in a Th2 microenvironment, whereby such liver resident macrophages could exhibit a dichotomic role during chronic hepatic damage, being involved in attenuation of the inflammatory response but at the same time exacerbation of liver fibrosis.

The increase in mannose receptor recycling favors arginase induction and Trypanosoma cruzi survival in macrophages

The macrophage mannose receptor (MR) is a pattern recognition receptor of the innate immune system that binds to microbial structures bearing mannose, fucose and N-acetylglucosamine on their surface. Trypanosoma cruzi antigen cruzipain (Cz) is found in the different developmental forms of the parasite. This glycoprotein has a highly mannosylated C-terminal domain that participates in the host-antigen contact. Our group previously demonstrated that Cz-macrophage (Mo) interaction could modulate the immune response against T. cruzi through the induction of a preferential metabolic pathway. In this work, we have studied in Mo the role of MR in arginase induction and in T. cruzi survival using different MR ligands. We have showed that pre-incubation of T. cruzi infected cells with mannose-Bovine Serum Albumin (Man-BSA, MR specific ligand) biased nitric oxide (NO)/urea balance towards urea production and increased intracellular amastigotes growth. The study of intracellular signals showed that pre-incubation with Man-BSA in T. cruzi J774 infected cells induced down-regulation of JNK and p44/p42 phosphorylation and increased of p38 MAPK phosphorylation. These results are coincident with previous data showing that Cz also modifies the MAPK phosphorylation profile induced by the parasite. In addition, we have showed by confocal microscopy that Cz and Man-BSA enhance MR recycling. Furthermore, we studied MR behavior during T. cruzi infection in vivo. MR was up-regulated in F4/80+ cells from T. cruzi infected mice at 13 and 15 days post infection. Besides, we investigated the effect of MR blocking antibody in T. cruzi infected peritoneal Mo. Arginase activity and parasite growth were decreased in infected cells pre-incubated with anti-MR antibody as compared with infected cells treated with control antibody. Therefore, we postulate that during T. cruzi infection, Cz may contact with MR, increasing MR recycling which leads to arginase activity up-regulation and intracellular parasite growth.

Arginase I Attenuates Inflammatory Cytokine Secretion Induced by Lipopolysaccharide in Vascular Smooth Muscle Cells

Objective—

Inflammation plays an important role in atherosclerosis. Arginase I (Arg I) promotes the proliferation of vascular smooth muscle cells; however, the effect of Arg I on inflammation remains unknown. The present study investigated the role of Arg I in inflammation in vitro and in vivo.

Methods and Results—

Quantitative reverse transcription–polymerase chain reaction and Western blot analysis demonstrated that Arg I inhibited tumor necrosis factor-α production induced by lipopolysaccharide in human aortic smooth muscle cells. Inducible nitric oxide synthase substrate competition and nuclear factor-κB activation were main contributors to lipopolysaccharide-mediated inflammatory cytokine generation. However, Arg I could attenuate the function of inducible nitric oxide synthase and inhibit the subsequent nuclear factor-κB activation, leading to inhibition of tumor necrosis factor-α generation. Furthermore, upregulation of Arg I significantly decreased macrophage infiltration and inflammation in atherosclerotic plaque of rabbits, whereas downregulation of Arg I aggravated these adverse effects.

Conclusion—

The results indicate the antiinflammatory effects of Arg I and suggest an unexpected beneficial role of Arg I in inflammatory disease.

Trypanosoma cruzi Coexpressing Ornithine Decarboxylase and Green Fluorescence Proteins as a Tool to Study the Role of Polyamines in Chagas Disease Pathology

Polyamines are essential for Trypanosoma cruzi, the causative agent of Chagas disease. As T. cruzi behaves as a natural auxotrophic organism, it relies on host polyamines biosynthesis. In this paper we obtained a double-transfected T. cruzi parasite that expresses the green fluorescent protein (GFP) and a heterologous ornithine decarboxylase (ODC), used itself as a novel selectable marker. These autotrophic and fluorescent parasites were characterized; the ODC presented an apparent Km for ornithine of 0.51 ± 0.16 mM and an estimated V_max value of 476.2 nmoles/h/mg of protein. These expressing ODC parasites showed higher metacyclogenesis capacity than the auxotrophic counterpart, supporting the idea that polyamines are engaged in this process. This double-transfected T. cruzi parasite results in a powerful tool—easy to follow by its fluorescence—to study the role of polyamines in Chagas disease pathology and in related processes such as parasite survival, invasion, proliferation, metacyclogenesis, and tissue spreading.

Modulation of mouse macrophage proteome induced by Toxoplasma gondii tachyzoites in vivo

Toxoplasma gondii is an obligate intracellular protozoan parasite, which can invade and multiply within the macrophages of humans and most warm-blooded animals. Macrophages are important effector cells for the control and killing of intracellular T. gondii, and they may also serve as long-term host cells for the replication and survival of the parasite. In the present study, we explored the proteomic profile of macrophages of the specific pathogen-free Kunming mice at 24 h after infection with tachyzoites of the virulent T. gondii RH strain using two-dimensional gel electrophoresis combined with matrix-assisted laser desorption ionization time-of-flight (TOF)/TOF tandem mass spectrometry. Totally, 60 differentially expressed protein spots were identified. Among them, 52 spots corresponded to 38 proteins matching to proteins of the mouse, including actin, enolase, calumenin, vimentin, plastin 2, annexin A1, cathepsin S, arginase-1, arachidonate 12-lipoxygenase, and aminoacylase-1. Functional prediction using Gene Ontology database showed that these proteins were mainly involved in metabolism, structure, protein fate, and immune responses. The findings provided an insight into the interactive relationship between T. gondii and the host macrophages, and will shed new lights on the understanding of molecular mechanisms of T. gondii pathogenesis.

Programmed death ligand 2 regulates arginase induction and modifies Trypanosoma cruzi survival in macrophages during murine experimental infection

The programmed death ligands 1 (PD-L1) and 2 (PD-L2) that bind to programmed death 1 (PD-1) have been involved in peripheral tolerance and in the immune escape mechanisms during chronic viral infections and cancer. However, there are no reports about the role of these molecules during Trypanosoma cruzi infection. We have studied the role of PD-L1 and PD-L2 in T. cruzi infection and their importance in arginase/inducible nitric oxide synthase (iNOS) balance in the immunomodulatory properties of macrophages (Mφ). In this work, we have demonstrated that expression of the PD-1/PD-L pathway is modified during T. cruzi infection on Mφs obtained from peritoneal cavity. The Mφs from T. cruzi-infected mice suppressed T-cell proliferation and this was restored when anti-PD-1 and anti-PD-L1 antibodies were added. Nevertheless, anti-PD-L2 antibody treatment did not re-establish T-cell proliferation. PD-L2 blockade on peritoneal cells from infected mice showed an increase in arginase expression and activity and a decrease in iNOS expression and in nitric oxide (NO) production. Additionally, interleukin-10 production increased whereas interferon-γ production was reduced. As a result, this microenvironment enhanced parasite proliferation. In contrast, PD-1 and PD-L1 blockage increased iNOS expression and NO production on peritoneal Mφs from T. cruzi-infected mice. Besides, PD-L2 knockout infected mice showed an increased in parasitaemia as well as in arginase activity, and a reduction in NO production. Taken together, our results demonstrate that PD-L2 is involved in the arginase/iNOS balance during T. cruzi infection having a protective role in the immune response against the parasite.

Arginase-1: a new immunohistochemical marker of hepatocytes and hepatocellular neoplasms

The distinction of hepatocellular carcinoma (HCC) from metastatic tumor in the liver often presents a diagnostic challenge that carries significant impact on prognostication and therapy. The number of diagnostically useful immunohistochemical markers of hepatocytes is limited to hepatocyte paraffin antigen (HepPar-1), polyclonal carcinoembryonic antigen, and CD10, with alpha-fetoprotein and glypican-3 labeling HCCs. Arginase-1 (Arg-1) is a binuclear manganese metalloenzyme that catalyzes the hydrolysis of arginine to ornithine and urea. We used immunohistochemistry to compare the sensitivity of Arg-1 to that of HepPar-1 in 151 HCCs. We found that the overall sensitivities of Arg-1 and HepPar-1 are 96.0% and 84.1%, respectively. The sensitivities of Arg-1 in well, moderately, and poorly differentiated HCCs are 100%, 96.2%, and 85.7%, respectively, whereas, in comparison, HepPar-1 demonstrated sensitivities of 100%, 83.0%, and 46.4% for well, moderately, and poorly differentiated tumors, respectively. There were no HCCs in our study that were reactive for HepPar-1 but nonreactive for Arg-1. We also examined Arg-1 expression in nonhepatocellular tumors, including many that are potential mimics of HCC (renal cell carcinomas, neuroendocrine tumors, melanomas, gastric adenocarcinomas, and adrenocortical carcinomas) and found that only 2 non-HCC tumors were reactive for Arg-1. Arg-1 represents a sensitive and specific marker of benign and malignant hepatocytes that may ultimately prove to be a useful diagnostic tool in routine surgical pathology practice.

Proinflammatory clearance of apoptotic neutrophils induces an IL-12(low)IL-10(high) regulatory phenotype in macrophages

Clearance of apoptotic exudate neutrophils (efferocytosis) induces either pro- or anti-inflammatory responses in mouse macrophages depending on host genetic background. In this study, we investigated whether neutrophil efferocytosis induces a stable macrophage phenotype that could be recalled by late restimulation with LPS. Bone marrow-derived macrophages previously stimulated by pro- but not anti-inflammatory neutrophil efferocytosis expressed a regulatory/M2b phenotype characterized by low IL-12 and high IL-10 production following restimulation, increased expression of LIGHT/TNF superfamily 14, Th2-biased T cell responses, and permissive replication of Leishmania major. Induction of regulatory/M2b macrophages required neutrophil elastase activity and was partially dependent on TLR4 signaling. These results suggested that macrophage differentiation to a regulatory phenotype plays a role in resolution of inflammation but could contribute to increased humoral Ab responses and parasite persistence in the infected host.

Subsets, expansion and activation of myeloid-derived suppressor cells

Tumor cells and microorganisms manipulate the immune system to minimize any counter response in order to survive. Myeloid-derived suppressor cells (MDSC) in the mouse represent activated Gr-1(+) CD11b(+) myeloid precursor cells. Activation may occur through endogenous or exogenous factors leading to the suppression of immune responses. Under steady state conditions the same precursors differentiate into dendritic cells, macrophages and neutrophils. Their linkage to tumor progression and several suppression mechanisms employing the arginine metabolism are well documented, but knowledge of their role in chronic infections, autoimmune diseases and graft-versus-host reactions is just emerging. Several factors have been described to promote MDSC expansion and activation in bone marrow, spleen and tumor sites. New evidence suggests that the Gr-1 antibody itself may differentially trigger myelopoiesis under steady state conditions or induce apoptosis in inflammatory situations after binding to a common epitope expressed on Ly-6C and Ly-6G molecules, respectively. Moreover, two subsets of neutrophil- and monocyte-related MDSC have been described in tumor-bearing and healthy mice. In the present review, we summarize some early work leading to recent findings on these two MDSC subsets, the factors supporting MDSC expansion and activation, as well as novel insights on Gr-1 antibody functions.