Increase In Arginase Research Articles

Mitochondrial Fragmentation Promotes Inflammation Resolution Responses in Macrophages via Histone Lactylation.

During the inflammatory response, macrophage phenotypes can be broadly classified as pro-inflammatory/classically activated "M1", or pro-resolving/alternatively "M2" macrophages. Although the classification of macrophages is general and assumes there are distinct phenotypes, in reality macrophages exist across a spectrum and must transform from a pro-inflammatory state to a proresolving state following an inflammatory insult. To adapt to changing metabolic needs of the cell, mitochondria undergo fusion and fission, which have important implications for cell fate and function. We hypothesized that mitochondrial fission and fusion directly contribute to macrophage function during the pro-inflammatory and proresolving phases. In the present study, we find that mitochondrial length directly contributes to macrophage phenotype, primarily during the transition from a pro-inflammatory to a proresolving state. Phenocopying the elongated mitochondrial network (by disabling the fission machinery using siRNA) leads to a baseline reduction in the inflammatory marker IL-1β, but a normal inflammatory response to LPS, similar to control macrophages. In contrast, in macrophages with a phenocopied fragmented phenotype (by disabling the fusion machinery using siRNA) there is a heightened inflammatory response to LPS and increased signaling through the ATF4/c-Jun transcriptional axis compared to control macrophages. Importantly, macrophages with a fragmented mitochondrial phenotype show increased expression of proresolving mediator arginase 1 and increased phagocytic capacity. Promoting mitochondrial fragmentation caused an increase in cellular lactate, and an increase in histone lactylation which caused an increase in arginase 1 expression. These studies demonstrate that a fragmented mitochondrial phenotype is critical for the proresolving response in macrophages and specifically drive epigenetic changes via lactylation of histones following an inflammatory insult.

In Vitro Functional Characterization of Type-I Taste Bud Cells as Monocytes/Macrophages-like Which Secrete Proinflammatory Cytokines.

The sense of taste determines the choice of nutrients and food intake and, consequently, influences feeding behaviors. The taste papillae are primarily composed of three types of taste bud cells (TBC), i.e., type I, type II, and type III. The type I TBC, expressing GLAST (glutamate--aspartate transporter), have been termed as glial-like cells. We hypothesized that these cells could play a role in taste bud immunity as glial cells do in the brain. We purified type I TBC, expressing F4/80, a specific marker of macrophages, from mouse fungiform taste papillae. The purified cells also express CD11b, CD11c, and CD64, generally expressed by glial cells and macrophages. We further assessed whether mouse type I TBC can be polarized toward M1 or M2 macrophages in inflammatory states like lipopolysaccharide (LPS)-triggered inflammation or obesity, known to be associated with low-grade inflammation. Indeed, LPS-treatment and obesity state increased TNFα, IL-1β, and IL-6 expression, both at mRNA and protein levels, in type I TBC. Conversely, purified type I TBC treated with IL-4 showed a significant increase in arginase 1 and IL-4. These findings provide evidence that type I gustatory cells share many features with macrophages and may be involved in oral inflammation.

The Innate and Adaptive Immune Landscape of SARS-CoV-2-Associated Multisystem Inflammatory Syndrome in Children (MIS-C) From Acute Disease to Recovery

Multisystem inflammatory syndrome in children (MIS-C) is a life-threatening disease occurring several weeks after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Deep immune profiling showed acute MIS-C patients had highly activated neutrophils, classical monocytes and memory CD8+ T-cells; increased frequencies of B-cell plasmablasts and double-negative B-cells. Post treatment samples from the same patients, taken when symptoms were resolving, identified recovery-associated immune features including CD163+ monocytes, emergence of a new population of immature neutrophils and, in some patients, a transient increase in arginase. Plasma profiling identified multiple features shared by MIS-C, Kawasaki Disease and COVID-19 and that therapeutic inhibition of IL6 may be preferable to IL1 or TNF-a. We identified potential new mechanisms of action for IVIG, the most commonly used drug to treat MIS-C. Finally, we showed systemic complement activation with high plasma C5b-9 levels is common in MIS-C, suggesting complement inhibitors could be used to treat the disease.Funding Information: Birmingham Women’s and Children’s Hospital Charity funded the single cell RNA sequencing analysis. No other external funding was received. Declaration of Interests: None declared.Ethics Approval Statement: Reviewed and approved by South of Birmingham Research Ethics Committee (REC: 17/WM/0453, IRAS: 233593).

INFLUENCE OF NITRIC OXIDE, HYDROGEN SULFIDE, MARKERS OF ANTIOXIDANT HOMEOSTASIS AND BONE METABOLISM OF ORAL FLUID ON THE DENTAL HEALTH OF CHILDREN WITH MILD IODINE DEFICIENCY, LATENT IRON DEFICIENCY AND ASSOCIATED MICROELEMENTOSIS

The article analyzes the metabolism of nitric oxide (NO), hydrogen sulfide (H2S), markers of antioxidant protection, bone metabolism of oral fluid and features of dental status in children with mild iodine deficiency (МІD), latent iron deficiency and combined (LID); a combination of trace elements was examined.
 As a result of the study (age group from 6 to 11 years) under the conditions of МІD in boys there was an increase in the level of NO2, NO2- + NO3-, and in girls - peroxynitrite in the oral fluid. In schoolchildren with LІD changes in the studied parameters were less pronounced (in the oral fluid increased NO2 concentration regardless of gender and increased peroxynitrite content only in girls). Under conditions of combined micronutrient imbalance in the oral fluid levels of NO2 increased, the amount of NO2- and NO3-, peroxynitrite, regardless of gender, and girls, in addition, levels of arginase decreased. Such changes were observed against the background of weakening of antioxidant protection of oral fluid. In particular, acid phosphatase (АсР) was activated under the conditions of LD in boys against the background of alkaline phosphatase (АР) inhibition and reduction of total calcium levels in oral fluid. The same tendency was observed in girls of this group, in addition, they found inhibition of superoxide dismutase (SOD) activity of oral fluid. Under the conditions of LІD, regardless of gender, KF activation was observed against the background of АсР suppression (in boys), decrease in SOD activity (in girls). The most pronounced changes were observed in the oral fluid of children with combined iodine and iron deficiency: increased activity of АР regardless of gender, glutathione peroxidase (GP), LF in girls, inhibition of АсР activity in boys, decreased total calcium regardless of gender. The level of ionized calcium in the oral fluid increased only in girls.
 In children aged 12 to 18 years under the conditions of МІD, an increase in the concentration of peroxynitrite in the oral fluid regardless of gender and a decrease in arginase levels were found only in girls. In the oral fluid of boys with LІD found a decrease in L-arginine, in girls - and an increase in L-arginine, NO2 concentration on the background of a decrease in arginase and peroxynitrite. In high school students with combined microelements, regardless of gender, the content of peroxynitrite in the oral fluid and a decrease in the level of L-arginine in boys and an increase in arginase in girls. In this group, a significant increase in the concentration of H2S in schoolgirls, which can perform a protective function in oxidative stress or impaired blood supply, attracts attention. The results of the level of total, ionized calcium and phosphatase activity indicate an increase in the resorptive process in periodontal tissues in all experimental groups.
 During the dental examination, a high level of caries prevalence, a decrease in the level of hygiene, and a higher PMA index were found in older schoolchildren with a combination of microelements. The poorer level of dental health among boys concerning girls attracts attention, which can be explained by the better level of care and daily rehabilitation of the oral cavity in girls.
 Thus, under the conditions of preclinical microelements the indicators of NO metabolism change, the antioxidant reserve of oral fluid decreases, and markers of bone metabolism are disturbed. Such biochemical changes in the composition of oral fluid are compared with indicators of dental status.

Metagenomic insights into the taxonomy, function, and dysbiosis of prokaryotic communities in octocorals

BackgroundIn octocorals (Cnidaria Octocorallia), the functional relationship between host health and its symbiotic consortium has yet to be determined. Here, we employed comparative metagenomics to uncover the distinct functional and phylogenetic features of the microbiomes of healthy Eunicella gazella, Eunicella verrucosa, and Leptogorgia sarmentosa tissues, in contrast with the microbiomes found in seawater and sediments. We further explored how the octocoral microbiome shifts to a pathobiome state in E. gazella.ResultsMultivariate analyses based on 16S rRNA genes, Clusters of Orthologous Groups of proteins (COGs), Protein families (Pfams), and secondary metabolite-biosynthetic gene clusters annotated from 20 Illumina-sequenced metagenomes each revealed separate clustering of the prokaryotic communities of healthy tissue samples of the three octocoral species from those of necrotic E. gazella tissue and surrounding environments. While the healthy octocoral microbiome was distinguished by so-far uncultivated Endozoicomonadaceae, Oceanospirillales, and Alteromonadales phylotypes in all host species, a pronounced increase of Flavobacteriaceae and Alphaproteobacteria, originating from seawater, was observed in necrotic E. gazella tissue. Increased abundances of eukaryotic-like proteins, exonucleases, restriction endonucleases, CRISPR/Cas proteins, and genes encoding for heat-shock proteins, inorganic ion transport, and iron storage distinguished the prokaryotic communities of healthy octocoral tissue regardless of the host species. An increase of arginase and nitric oxide reductase genes, observed in necrotic E. gazella tissues, suggests the existence of a mechanism for suppression of nitrite oxide production by which octocoral pathogens may overcome the host’s immune system.ConclusionsThis is the first study to employ primer-less, shotgun metagenome sequencing to unveil the taxonomic, functional, and secondary metabolism features of prokaryotic communities in octocorals. Our analyses reveal that the octocoral microbiome is distinct from those of the environmental surroundings, is host genus (but not species) specific, and undergoes large, complex structural changes in the transition to the dysbiotic state. Host-symbiont recognition, abiotic-stress response, micronutrient acquisition, and an antiviral defense arsenal comprising multiple restriction endonucleases, CRISPR/Cas systems, and phage lysogenization regulators are signatures of prokaryotic communities in octocorals. We argue that these features collectively contribute to the stabilization of symbiosis in the octocoral holobiont and constitute beneficial traits that can guide future studies on coral reef conservation and microbiome therapy.CGE-K3mkWRXvLuipSC6CFkVideo

The Innate and Adaptive Immune Landscape of SARS-CoV-2-Associated Multisystem Inflammatory Syndrome in Children (MIS-C) from Acute Disease to Recovery

Multisystem inflammatory syndrome in children (MIS-C) is a life-threatening disease occurring several weeks after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. MIS-C has overlapping clinical features with Kawasaki Disease (KD), a rare childhood vasculitis, but whether these diseases share underpinning immunological perturbations is unknown. Deep immune profiling showed acute MIS-C patients had highly activated neutrophils, classical monocytes and memory CD8+ T-cells; increased frequencies of B-cell plasmablasts and double-negative B-cells; and increased cytokine levels. Post treatment samples from the same patients, taken when symptoms were resolving, identified recovery-associated immune features including CD163+ monocytes, emergence of a new population of immature neutrophils and, in some patients, a transient increase in arginase. Our data show MIS-C and KD share substantial immunopathology during the acute and recovery stages of disease and identify potential new mechanisms of action for IVIG, a widely used anti-inflammatory drug used to treat MIS-C, KD and other inflammatory diseases.

Derangement of Arginine and Related Amino Acids in Children Undergoing Surgery for Congenital Heart Disease With Cardiopulmonary Bypass.

Prospective observational study. The study was conducted in the Heart Center at Texas Children's Hospital. Children undergoing surgery for congenital heart disease with cardiopulmonary bypass. None. Serial perioperative blood samples were collected for quantification of amino acids, arginase, nitric oxide metabolites, and markers of organ function (lactate, Pao2/Fio2 ratio, and creatinine clearance). Thirty children (18 males) were included in the study; median (interquartile range) age 0.5 years (0.3-0.9 yr). The mean ± sd for plasma amino acid concentrations before cardiopulmonary bypass: arginine 62 ± 20 µmol/L, citrulline 24 ± 6 µmol/L, ornithine 53 ± 32 µmol/L, and glutamine 591 ± 126 µmol/L. Arginine concentration was decreased within the first 24 hours (43 ± 15 µmol/L; p = 0.004), citrulline and glutamine concentrations decreased over the first 48 hours (11 ± 4 µmol/L; p < 0.001 and 493 ± 131 µmol/L; p = 0.019, respectively) and were associated with an increase in arginase (3.8 ± 3 µg/mL; p < 0.05). There was an increase in Vasoactive-Inotropic Score (5.9 ± 19 vs 0.5 ± 2; p < 0.001), decrease in creatinine clearance (76 ± 24 vs 93 ± 31; p = 0.002), and Pao2/Fio2 ratio (243 ± 138 vs 374 ± 200; p = 0.007) comparing to baseline. A widely variable degree of arginine, citrulline, and glutamine depletion occurs in children after surgery for congenital heart disease. These findings were associated with increased arginase and coincide with some of the markers of organ perfusion.

Curcumin Improves Biomolecules Associated with Renal Function and Attenuates Oxidative Injury and Histopathological Changes in Potassium-Induced Toxicity in Rats' Kidney.

The protective effect of curcumin on potassium bromate (KBrO3)-induced renal damage was investigated in vivo. Treatment with KBrO3 (20mg/kgbw) caused a significant increase in arginase and adenosine deaminase (ADA) activities in rats' kidney. However, oral administration of curcumin (20mg/kg bw) caused a significant reduction in ADA and arginase activities in KBrO3 + CUR group. Furthermore, nitric oxide level was significantly low in KBrO3 group compared with the control. After treatment with curcumin in KBrO3 + CUR group, nitric oxide levels increased significantly (P < 0.05). Determination of some kidney biomarkers revealed elevated levels of creatinine, serum urea, and electrolytes (Na+ and Cl-) in KBrO3-treated rats. Curcumin effectively reduced the levels of these renal function parameters in KBrO3 + CUR groups and were not significantly different from the control. Antioxidant enzyme activities such as superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPX) activities as well as glutathione (GSH) levels were significantly low with concomitant higher levels of malondialdehyde (MDA) after treatment with KBrO3. Curcumin caused a significant increase in SOD, CAT, and GPX activities including GSH levels with lower production of MDA in kidney homogenates of rats in KBrO3 + CUR. Curcumin ameliorated corpuscular degeneration in the kidney tissue and exhibited protection against tubular necrosis. These results revealed the protective effect of curcumin against KBrO3-induced renal toxicity by preventing degradation of ADA and arginine, improving antioxidant status and histopathological changes in rats' kidney.

Extracellular Vesicles Shedding Promotes Melanoma Growth in Response to Chemotherapy

Extracellular vesicles (EVs) are emerging as key players in intercellular communication. EVs can transfer biological macromolecules to recipient cells, modulating various physiological and pathological processes. It has been shown that tumor cells secrete large amounts of EVs that can be taken up by malignant and stromal cells, dictating tumor progression. In this study, we investigated whether EVs secreted by melanoma cells in response to chemotherapy modulate tumor response to alkylating drugs. Our findings showed that human and murine melanoma cells secrete more EVs after treatment with temozolomide and cisplatin. We observed that EVs shed by melanoma cells after temozolomide treatment modify macrophage phenotype by skewing macrophage activation towards the M2 phenotype through upregulation of M2-marker genes. Moreover, these EVs were able to favor melanoma re-growth in vivo, which was accompanied by an increase in Arginase 1 and IL10 gene expression levels by stromal cells and an increase in genes related to DNA repair, cell survival and stemness in tumor cells. Taken together, this study suggests that EVs shed by tumor cells in response to chemotherapy promote tumor repopulation and treatment failure through cellular reprogramming in melanoma cells.

Orange peels modulate antioxidant markers and key enzymes relevant to erection in the penile tissue of paroxetine-treated rats.

In comparison to other antidepressant drugs, erectile dysfunction (ED) is more pronounced in paroxetine use. On the other hand, orange (Citrus sinensis) peels commonly consumed in various forms are used in folkloric medicine for ED management. Thus, this study evaluated the effect of orange peels infusion on sexual behaviour, nitric oxide (NO) level and some enzymes (arginase, phosphodiesterase-5 [PDE-5], acetylcholinesterase [AChE] and adenosine deaminase [ADA]) in paroxetine-treated rats. Erectile dysfunction was induced with paroxetine (10mg/kg body weight). The animals were grouped into five (n=6): normal rats; paroxetine-induced rats; paroxetine-induced rats treated with sildenafil citrate (5mg/kg); paroxetine-induced rats treated with orange peels infusion (50mg/kg); Paroxetine induced rats treated with orange peel infusions (100 mg/kg). The results revealed a significant decrease in sexual behaviour, NO level and the activities of antioxidant enzymes, while there was a significant increase in arginase, PDE-5, AChE and ADA activities in paroxetine-induced rats. However, orange peel infusions ameliorated erectile dysfunction in paroxetine-treated rats. This study showed some possible biochemical basis underlying the use of orange peels infusion in erectile dysfunction management.

Regulation of MAP kinase-mediated endothelial dysfunction in hyperglycemia via arginase I and eNOS dysregulation

Emerging evidence suggests that arginase contributes to endothelial dysfunction in diabetes. Intracellular signaling pathways, which interplay between arginase and eNOS enzyme activity leading to the development of endothelial dysfunction in hyperglycemia are not fully understood. Here, we analyzed the possible involvement of hyperglycemia (HG) induced arginase expression in eNOS protein regulation and activity and also the impact of arginase inhibition on eNOS activity. Furthermore, the roles of p38 MAPK and Erk1/2 phosphorylation in upregulation of arginase expression and eNOS dysregulation in endothelial cells (ECs) under hyperglycemia were evaluated. Protein analysis showed a concurrent increase in arginase I expression and decrease in eNOS expression and phosphorylation at Ser1177 under HG conditions. There was no simultaneous change in phosphorylation of eNOS at Thr495 in HG. Arginase inhibition prevented increased arginase activity, restored impaired NO bioavailability and reduced superoxide anion generation. Inhibition of MAP-kinases demonstrated that, unlike Erk1/2, p38 MAPK is an upstream activator in a signaling cascade leading to increased arginase I in HG conditions. P38 MAPK protein expression and phosphorylation were increased in response to HG. In the presence of a p38 MAPK inhibitor, HG-induced arginase expression was blunted. Although Erk1/2 was activated in HG, increased arginase expression was not blocked by co-treatment with an Erk1/2 inhibitor. Activation of both, p38 MAPK and Erk1/2 in HG, induced a downregulation in eNOS activity. Hence, applying MAPK inhibitors increased eNOS phosphorylation in HG.In conclusion, these findings demonstrate contributions of arginase I in the development of endothelial cell dysfunction under HG conditions via impaired eNOS regulation, which maybe mediated by p38 MAPK.

Hypoxic Pulmonary Endothelial Cells Release Epidermal Growth Factor which Results in Vascular Smooth Muscle Cell Arginase 2 Expression and Proliferation

The hallmark of pulmonary hypertension (PH) is vascular remodeling leading to alterations in hemodynamics and vasoreactivity. Endothelial cells (EC) are central in the response of a vessel to stimuli associated with PH. EC can proliferate contributing to vascular remodeling, but likely a more important role of EC is the release of factors that induce proliferation in the underlying smooth muscle cells (SMC) leading to intimal thickening. Hypoxia is associated with the development of PH in certain human diseases. We have previously shown that human pulmonary microvascular EC (hPMVEC) respond to hypoxia with proliferation that is dependent on arginase 2 up‐regulation. This arginase 2 up‐regulation is mediated by the release of epidermal growth factor (EGF) and resultant activation of EGF receptors (EGFR) on hPMVEC. We hypothesized that the release of EGF by hPMVEC would also result in proliferation of human pulmonary arterial SMC (hPASMC) via EGFR‐mediated arginase 2 up‐regulation. To test this hypothesis, we used conditioned media (CM) from hPMVEC grown either in normoxia or hypoxia to study the role of EGF released by hPMVEC on the regulation of arginase 2 and proliferation in hPASMC. When hPASMC were grown with CM from hypoxic hPMVEC there was a 9‐fold induction of arginase 2 protein levels and more than a doubling of viable hPASMC numbers compared to hPASMC grown with CM from normoxic hPMVEC. In another experiment, hPVMEC were transfected with a scramble siRNA (scramble) or an siRNA against EGF (siEGF) and then the hPMVEC placed in hypoxia to generate conditioned media. In the hPASMC treated with the CM from siEGF‐treated hypoxic hPMVEC there were lower levels of arginase 2 protein than in the hPASMC grown in CM from hPMVEC grown in normoxia; and substantially less arginase 2 than in hPASMC treated with CM from hypoxic hPMVEC treated with scramble. Furthermore, hPASMC treated with hypoxic CM from siEGF‐treated hPMVEC had substantially lower viable cell numbers than in hPASMC treated with hypoxic CM from scramble‐treated hPMVEC. When hPASMC were treated with hypoxic CM from hPMVEC the addition of an EGF neutralizing antibody to the CM prevented the increase in viable cell numbers seen with hypoxic CM. When hPASMC were transfected with siRNA against EGFR and then treated with hypoxic CM from hPMVEC the hypoxia‐induced increase in arginase 2 protein levels and viable cell numbers were prevented. These data demonstrate that hPMVEC release EGF, which can activate EGFR on hPASMC to induce arginase 2 protein expression and increase viable cell numbers. We speculate that EGF neutralizing antibodies or EGFR blocking antibodies are potential therapeutics to prevent and/or attenuate the vascular remodeling seen in PH associated with hypoxia.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Transforming growth factor β neutralization finely tunes macrophage phenotype in elastase-induced abdominal aortic aneurysm and is associated with an increase of arginase 1 expression in the aorta

ObjectiveMacrophages play a critical role in the initiation and progression of abdominal aortic aneurysm (AAA) and are classically distinguished into M1 “proinflammatory” and M2 “anti-inflammatory” macrophages. Topical application of elastase associated with transforming growth factor β (TGF-β) systemic neutralization reproduces the main pathologic features of human AAA, offering a new model to investigate their role. The aim of this study was to investigate whether macrophages contribute to the expression of canonical M1/M2 markers in the aorta in the AAA model induced by elastase and systemic blockade of TGF-β and whether blocking of TGF-β activity affects macrophage phenotype and the expression of the M2 marker arginase 1 (ARG1). MethodsC57Bl/6J male mice (6-8 weeks old) were randomly assigned to three experimental groups: mice that had local application of heat-inactivated elastase or elastase and mice that had elastase application and received injection of anti-TGF-β (elastase + anti-TGF-β group). Monocyte-macrophage depletion was achieved in the elastase + anti-TGF-β group using liposome clodronate. Macrophage phenotype was characterized by quantitative polymerase chain reaction, flow cytometry, and immunohistochemistry. Human infrarenal AAA tissues (n = 10) were obtained to analyze ARG1 expression. ResultsAnalysis of gene expression in the infrarenal aortic wall revealed that after 14 days, no significant difference for the expression of CCL2, NOS2, and Ym1/2 was observed in the elastase group compared with the elastase + anti-TGF-β group, whereas the expression of ARG1, interleukin (IL) 1β, and IL-6 was significantly increased. Macrophage depletion in the elastase + anti-TGF-β group led to a significant decrease of IL-1β, IL-6, ARG1, and Ym1/2 gene expression. Immunofluorescent staining confirmed that TGF-β neutralization significantly enhanced ARG1 protein expression in the aneurysmal tissue. Flow cytometry analysis revealed an increase of macrophages expressing ARG1 in the aorta of mice treated with elastase + anti-TGF-β compared with the elastase group, and their proportion increased with aneurysmal dilation. In humans, ARG1 protein expression was increased in aneurysmal tissues compared with controls, and positive cells were mainly found in the adventitia. ConclusionsTGF-β neutralization finely tunes macrophage phenotype in elastase-induced AAA and leads to an increase in ARG1 gene and protein expression in the aortic wall. Even if further studies are required to elucidate its role in AAA development, ARG1 could represent a new prognostic or therapeutic target in aneurysmal disease.

Poly (ADP-Ribose) Polymerase 1 Mediated Arginase II Activation Is Responsible for Oxidized LDL-Induced Endothelial Dysfunction.

It is well known that arginase II leads to decreased synthesis of nitric oxide (NO) by competing with endothelial nitric oxide synthase (eNOS) for their same substrate L-arginine. However, the regulatory mechanisms of arginase II production remain unclear. In this study, we hypothesized that poly- (ADP-ribose) transferase/polymerase-1 (PARP-1) may be a critical factor responsible for ox-LDL (oxidized Low Density Lipoprotein)-enhanced arginase II activity. We used serial deletions within plasmid constructs and found that a core promoter region of arginase II was located at the element of -774 to -738 bp and PARP-1 was identified specifically binding to this region. Inhibition of PARP-1 markedly reduced the endogenous arginase II expression and enhanced eNOS and NO production. Similarly, ox-LDL-induced increase in arginase II production and eNOS and NO reduction was substantially abolished by PARP-1 inhibition both in vitro and in vivo. Significant decrease in arginase II expression and increase in eNOS expression and NO levels, as well as improved endothelial function were observed in PARP-1-/- mice. The underlying mechanisms of ox-LDL-induced changes of PARP-1 expression involved migration of phosphorylated ERK2 into nuclei and direct interaction with PARP-1 which dramatically enhanced PARP-1 production, followed by histone acetylation to activate arginase II transcription process. Our studies demonstrated for the first time that PARP-1 regulates basal transcription process and ox-LDL-induced up-regulation of arginase II. These results demonstrated that PARP-1 offers a promising therapeutic target for endothelial dysfunction and atherosclerosis.

Histamine Regulates the Inflammatory Profile of SOD1-G93A Microglia and the Histaminergic System Is Dysregulated in Amyotrophic Lateral Sclerosis.

Amyotrophic lateral sclerosis (ALS) is a late-onset motor neuron disease where activated glia release pro-inflammatory cytokines that trigger a vicious cycle of neurodegeneration in the absence of resolution of inflammation. Given the well-established role of histamine as a neuron-to-glia alarm signal implicated in brain disorders, the aim of this study was to investigate the expression and regulation of the histaminergic pathway in microglial activation in ALS mouse model and in humans. By examining the contribution of the histaminergic system to ALS, we found that particularly via H1 and H4 receptors, histamine promoted an anti-inflammatory profile in microglia from SOD1-G93A mice by modulating their activation state. A decrease in NF-κB and NADPH oxidase 2 with an increase in arginase 1 and P2Y12 receptor was induced by histamine only in the ALS inflammatory environment, but not in the healthy microglia, together with an increase in IL-6, IL-10, CD163, and CD206 phenotypic markers in SOD1-G93A cells. Moreover, histaminergic H1, H2, H3, and H4 receptors, and histamine metabolizing enzymes histidine decarboxylase, histamine N-methyltransferase, and diamine oxidase were found deregulated in spinal cord, cortex, and hypothalamus of SOD1-G93A mice during disease progression. Finally, by performing a meta-analysis study, we found a modulated expression of histamine-related genes in cortex and spinal cord from sporadic ALS patients. Our findings disclose that histamine acts as anti-inflammatory agent in ALS microglia and suggest a dysregulation of the histaminergic signaling in ALS.

Hepatocellular carcinomas promote tumor-associated macrophage M2-polarization via increased B7-H3 expression.

B7 family members are aberrantly expressed on the human hepatocellular carcinoma (HCC) cell surface, and induce local and systemic immunosuppression. Tumor-associated macrophages (TAMs) are a significant immune cell subpopulation in HCC and may be induced to express co-inhibitory molecules including B7 homologue 3 (B7-H3). In the present study, 79.3% of the HCC tissue samples showed high expression of B7-H3 which was positively correlated with the number of TAMs in the evaluated cancer tissues. Furthermore, high levels of TAMs or B7-H3 were associated with a shorter survival time of the HCC patients. In vitro, B7-H3 expression was upregulated at both the mRNA and protein levels in phorbol 12-myristate 13-acetate (PMA)-induced THP-1 cells cocultured with HepG2 cells in a Transwell system. In addition, B7-H3 promoted PMA-induced THP-1 cells to differentiate into the M2 phenotype, with evidence of increases in arginase 1 (Arg1), vascular endothelial cell growth factor (VEGF) and macrophage-derived chemokine (CCL22) mRNA following coculture with HepG2 cells. However, this phenomenon was abrogated through knockdown of B7-H3 by RNA interference or by blocking the signal transducer and activator of trans-cription 3 (STAT3) signaling pathway. Overall, these results suggest that the B7-H3-mediated STAT3 signaling pathway is an important mechanism for inducing M2-type polarization of TAMs, which accelerates HCC development. Our findings may support the development of novel therapeutic strategies for HCC patients through the skewing of the TAM phenotype by targeting the B7-H3 signaling pathway.

Arginase inhibition augments nitric oxide production and facilitates left ventricular systolic function in doxorubicin-induced cardiomyopathy in mice.

A metabolizing enzyme arginase can decrease nitric oxide (NO) production by competing with NO synthase for arginine as a substrate, but its pathophysiological role in heart failure remains unknown. We aimed to investigate the effect of pharmacological inhibition of arginase on left ventricular function in doxorubicin‐induced cardiomyopathy in mice. Doxorubicin administration for 5 weeks significantly increased protein expression levels or activity of arginase in the lungs and liver, and caused moderate increase in arginase 2 expression in the aorta. In the lungs, accumulated interstitial cells strongly expressed both arginase 1 and arginase 2 by doxorubicin administration. Echocardiography revealed that administration of a potent, reversible arginase inhibitor N‐omega‐hydroxy‐nor‐l‐arginine completely reversed doxorubicin‐induced decrease in the ejection fraction, in parallel with expression levels of BNP mRNA, without affecting apoptosis, hypertrophy, fibrosis, or macrophage infiltration in the left ventricle. Arginase inhibition reversibly lowered systolic blood pressure, and importantly, it recovered doxorubicin‐induced decline in NO concentration in the serum, lungs, and aorta. Furthermore, arginase inhibition stimulated NO secretion from aortic endothelial cells and peritoneal macrophages in vitro. In conclusion, pharmacological inhibition of arginase augmented NO concentration in the serum, lungs, and aorta, promoted NO‐mediated decrease in afterload for left ventricle, and facilitated left ventricular systolic function in doxorubicin‐induced cardiomyopathy in mice.

Effects of acute‐liver‐failure‐plasma exposure on hepatic functionality of HepaRG‐AMC‐Bioartificial Liver

The AMC-bioartificial liver loaded with the human hepatoma cell line HepaRG as biocomponent (HepaRG-AMC-BAL) has recently proven efficacious in rats with acute liver failure (ALF). However, its efficacy may be affected by cytotoxic components of ALF plasma during treatment. In this study, we investigated the effects of ALF-plasma on the HepaRG-AMC-BAL. HepaRG-AMC-BALs were connected to the blood circulation of rats with total liver ischaemia, either during the first 5h after induction of ischaemia (mild ALF group), or during the following 10h (severe ALF group). After disconnection, the BALs were assessed for cell leakage, gene transcript levels, ammonia elimination, urea production, cytochrome P450 3A4 activity, apolipoprotein A 1 production, glucose and amino acid metabolism. Cell leakage increased 2.5-fold in the severe ALF group, but remained limited in all groups. Hepatic gene transcript levels decreased (max 40-fold) or remained stable. In contrast, hepatic functions increased slightly or remained stable. Particularly, urea production increased 1.5-fold, with a concurrent increase in arginase 2 transcription and arginine consumption, with a trend towards reduced conversion of ammonia into urea. The amino acid consumption increased, however, the net glucose consumption remained stable. The HepaRG-AMC-BAL retains functionality after both mild and severe exposure to ALF plasma, but urea production may be increasingly derived from arginase 2 activity instead of urea cycle activity. Nevertheless, the increase in cell leakage and decrease in various hepatic transcript levels suggest that a decrease in hepatic functionality may follow upon extended exposure to ALF plasma.

Arginase Promotes Skeletal Muscle Arteriolar Endothelial Dysfunction in Diabetic Rats

Endothelial dysfunction is a characteristic feature in diabetes that contributes to the development of vascular disease. Recently, arginase has been implicated in triggering endothelial dysfunction in diabetic patients and animals by competing with endothelial nitric oxide synthase for substrate l-arginine. While most studies have focused on the coronary circulation and large conduit blood vessels, the role of arginase in mediating diabetic endothelial dysfunction in other vascular beds has not been fully investigated. In the present study, we determined whether arginase contributes to endothelial dysfunction in skeletal muscle arterioles of diabetic rats. Diabetes was induced in male Sprague Dawley rats by streptozotocin injection. Four weeks after streptozotocin administration, blood glucose, glycated hemoglobin, and vascular arginase activity were significantly increased. In addition, a significant increase in arginase I and II mRNA expression was detected in gracilis muscle arterioles of diabetic rats compared to age-matched, vehicle control animals. To examine endothelial function, first-order gracilis muscle arterioles were isolated, cannulated in a pressure myograph system, exposed to graded levels of luminal flow, and internal vessel diameter measured. Increases in luminal flow (0–50 μL/min) caused progressive vasodilation in arterioles isolated from control, normoglycemic animals. However, flow-induced vasodilation was absent in arterioles obtained from streptozotocin-treated rats. Acute in vitro pretreatment of blood vessels with the arginase inhibitors Nω-hydroxy-nor-l-arginine or S-(2-boronoethyl)-l-cysteine restored flow-induced responses in arterioles from diabetic rats and abolished differences between diabetic and control animals. Similarly, acute in vitro pretreatment with l-arginine returned flow-mediated vasodilation in vessels from diabetic animals to that of control rats. In contrast, d-arginine failed to restore flow-induced dilation in arterioles isolated from diabetic animals. Administration of sodium nitroprusside resulted in a similar degree of dilation in arterioles isolated from control or diabetic rats. In conclusion, the present study identifies arginase as an essential mediator of skeletal muscle arteriolar endothelial dysfunction in diabetes. The ability of arginase to induce endothelial dysfunction in skeletal muscle arterioles may further compromise glucose utilization and facilitate the development of hypertension in diabetes.

The role of arginase I in diabetes-induced retinal vascular dysfunction in mouse and rat models of diabetes

A reduction in retinal blood flow occurs early in diabetes and is likely to be involved in the development of diabetic retinopathy. We hypothesise that activation of the arginase pathway could have a role in the vascular dysfunction of diabetic retinopathy. Experiments were performed using a mouse and rat model of streptozotocin (STZ)-induced diabetes for in vivo and ex vivo analysis of retinal vascular function. For in vivo studies, mice were infused with the endothelial-dependent vasodilator acetylcholine (ACh) or the endothelial-independent vasodilator sodium nitroprusside (SNP), and vasodilation was assessed using a fundus microscope. Ex vivo assays included pressurised vessel myography, western blotting and arginase activity measurements. ACh-induced retinal vasodilation was markedly impaired in diabetic mice (40% of control values), whereas SNP-induced dilation was not altered. The diabetes-induced vascular dysfunction was markedly blunted in mice lacking one copy of the gene encoding arginase I and in mice treated with the arginase inhibitor 2(S)-amino-6-boronohexanoic acid. Ex vivo studies performed using pressure myography and central retinal arteries isolated from rats with STZ-induced diabetes showed a similar impairment of endothelial-dependent vasodilation that was partially blunted by pretreatment of the isolated vessels with another arginase inhibitor, (S)-2-boronoethyl-L-cysteine. The diabetes-induced vascular alterations were associated with significant increases in both arginase I protein levels and total arginase activity. These results indicate that, in the mouse and rat model, diabetes-induced increases in arginase I were involved in the diabetes-induced impairment of retinal blood flow by a mechanism involving vascular endothelial cell dysfunction.