Allosteric inhibition of rat liver and kidney arginase by copper and mercury ions

Arginase Activity in Eisenia andrei Coelomocytes: Function in the Earthworm Innate Response

Arginase is the manganese metalloenzyme catalyzing the conversion of l-arginine to l-ornithine and urea. In vertebrates, arginase is involved in the immune response, tissue regeneration, and wound healing and is an important marker of alternative anti-inflammatory polarization of macrophages. In invertebrates, data concerning the role of arginase in these processes are very limited. Therefore, in the present study, we focused on the changes in arginase activity in the coelomocytes of Eisenia andrei. We studied the effects of lipopolysaccharide (LPS), hydrogen peroxide (H₂O₂), heavy metals ions (e.g., Mn²⁺), parasite infection, wound healing, and short-term fasting (5 days) on arginase activity. For the first time in earthworms, we described arginase activity in the coelomocytes and found that it can be up-regulated upon in vitro stimulation with LPS and H₂O₂ and in the presence of Mn²⁺ ions. Moreover, arginase activity was also up-regulated in animals in vivo infected with nematodes or experiencing segment amputation, but not in fasting earthworms. Furthermore, we confirmed that the activity of coelomocyte arginase can be suppressed by l-norvaline. Our studies strongly suggest that similarly to the vertebrates, also in the earthworms, coelomocyte arginase is an important element of the immune response and wound healing processes.

Colorimetric and electrochemical detection of pathogens in water using silver ions as a unique probe

The manuscript highlights the efficacy of silver ions to act as a unique probe for the detection of bacterial contamination in water samples. The bacterial cell membrane adherence property of the silver ions was employed to develop two different bacterial detection assays employing colorimetric and electrochemical techniques. In one of the schemes, silver ion was used directly as a detector of bacteria in a colorimetric assay format, and in the other scheme surface-functionalized antibodies were used as a primary capture for specific detection of Salmonella enterica serovar Typhi. The colorimetric detection is based on silver-induced inhibition of urease activity and silver ion utilization by bacteria for the rapid screening of enteric pathogens in water. The specific detection of bacteria uses an antibody-based electrochemical method that employs silver as an electrochemical probe. The ability of silver to act as an electrochemical probe was investigated by employing Anodic Stripping Voltammetry (ASV) for targeted detection of Salmonella Typhi. For further insights into the developed assays, inductively coupled plasma mass spectrometry (ICP-MS) and transmission electron microscopy (TEM) studies were performed. The sensitivity of the developed assay was found to be 100 cfu mL⁻¹ for colorimetric and 10 cfu mL⁻¹ for electrochemical assay respectively.

Imbalance of dietary nutrients and the associated differentially expressed genes and pathways may play important roles in juvenile Kashin-Beck disease

BACKGROUND

Kashin-Beck disease (KBD) is a childhood-onset endemic osteoarthropathy in China. Nutrients including trace elements may play active roles in the development of KBD.

OBJECTIVE

This study aimed to estimate the nutrient intakes of children in endemic areas and to identify the imbalanced nutrients associated differentially expressed genes in the juvenile patients with KBD.

METHODS

In this cross-sectional study, a consecutive 3 day 24 h semi-quantitative dietary retrospect questionnaire was conducted to estimate the daily nutrient intakes of children using CDGSS 3.0 software. Gene profile analysis was employed to identify differentially expressed genes in peripheral blood mononuclear cells of children with KBD. GOC, CTD, KEGG, and REACTOME databases were used to establish the relationship between nutrients and nutrients-associated differentially expressed genes and pathways. Statistical analyses were accomplished by SPSS 18.0 software.

RESULTS

Daily Se intakes without supplementation of children were significantly lower in Se-supplemented (Se + ) KBD areas (29.3 ∼ 29.6 mg/d) and non-endemic area (27.8 ± 7.9 mg/d) compared to non-Se-supplemented (Se-) KBD area (32.9 ± 7.9 mg/d, c² = 20.24, P < .01). Children in Se+ KBD areas were suffering more serious insufficient intake of multiple nutrients, including vitamins-B₂/-C/-E, Ca, Fe, Zn and I. Gene profile analysis combined with bioinformatics technique identified 34 nutrients associated differentially expressed genes and 10 significant pathways which are related to the pathological changes in juvenile KBD.

CONCLUSIONS

Imbalance of dietary nutrients and nutrients-associated differentially expressed genes and pathways may play important roles in the development of juvenile KBD.

Evidence of metabolic microevolution of the limpet Nacella concinna to naturally high heavy metal levels in Antarctica

The gastropod Nacella concinna is the most conspicuous macroinvertebrate of the intertidal zone of the Antarctic Peninsula and adjacent islands. Naturally high levels of copper and cadmium in coastal marine ecosystems are accumulated in N. concinna tissues. We aimed to study the effects of metal cations on N. concinna arginase in the context of possible adaptive microevolution. Gills and muscle had the highest argininolytic activity, which was concentrated in the cytosol in both tissues. Gills had the highest levels of arginase and may be involved in the systemic control of l-arginine levels. The relatively high argininolytic activity of the N. concinna muscular foot, with K_M=25.3±3.4mmolL^-1, may be involved in the control of l-arginine levels during phosphagen breakdown. N. concinna arginases showed the following preferences for metal cations: Ni²⁺>Mn²⁺>Co²⁺>Cu²⁺ in muscle and Mn²⁺>Cu²⁺ in gills. Cu²⁺ activation is a unique characteristic of N. concinna arginases, as copper is a potent arginase inhibitor. Cu²⁺ partly neutralized N. concinna arginase inhibition by Cd²⁺, worked synergistically in muscle arginase activation by Co²⁺ and neutralized muscle arginase activation by Ni²⁺. Mn²⁺ was able to activate muscle arginase in the presence of Fe³⁺ and Pb²⁺. The selection of arginases that are activated by Cu²⁺ and resistant to inhibition by Cd²⁺ in the presence of Cu²⁺ over evolutionary timescales may have favored N. concinna occupation of copper- and cadmium-rich niches.

Copper oxide nanoparticles recruit macrophages and modulate nitric oxide, proinflammatory cytokines and PGE2 production through arginase activation

AIM

In the present study, we examine the effects of copper oxide nanoparticles (CuNP) on macrophage immune response and the signaling pathways involved.

MATERIALS & METHODS

A peritonitis model was used to determine in vivo immune cells recruitment, while primary macrophages were used as an in vitro model for the cellular and molecular analysis.

RESULTS

In vivo, CuNP induce significant macrophages recruitment to the site of injection. In vitro, in LPS-stimulated primary macrophages, the co-treatment with CuNP inhibited the production of NO in a dose-dependent manner. The mechanism underlying NO and proinflammatory cytokines inhibition was associated with an increased arginase activity. Macrophage stimulation with CuNP did not provoke any cytokine secretion; however, arginase inhibition promoted TNFα and MIP-1β production. In addition, CuNP induced the expression of COX-2 and the production of PGE2 through arginase activation.

CONCLUSION

Our results demonstrate that CuNP activate arginase and suppress macrophage innate immune response.

Expression, purification and characterization of arginase from Helicobacter pylori in its apo form

Arginase, a manganese-dependent enzyme that widely distributed in almost all creatures, is a urea cycle enzyme that catalyzes the hydrolysis of L-arginine to generate L-ornithine and urea. Compared with the well-studied arginases from animals and yeast, only a few eubacterial arginases have been characterized, such as those from H. pylori and B. anthracis. However, these enzymes used for arginase activity assay were all expressed with LB medium, as low concentration of Mn²⁺ was detectable in the medium, protein obtained were partially Mn²⁺ bonded, which may affect the results of arginase activity assay. In the present study, H. pylori arginase (RocF) was expressed in a Mn²⁺ and Co²⁺ free minimal medium, the resulting protein was purified through affinity and gel filtration chromatography and the apo-form of RocF was confirmed by flame photometry analysis. Gel filtration indicates that the enzyme exists as monomer in solution, which was unique as compared with homologous enzymes. Arginase activity assay revealed that apo-RocF had an acidic pH optimum of 6.4 and exhibited metal preference of Co²⁺>Ni²⁺>Mn²⁺. We also confirmed that heat-activation and reducing regents have significant impact on arginase activity of RocF, and inhibits S-(2-boronoethyl)-L-Cysteine (BEC) and Nω-hydroxy-nor-Arginine (nor-NOHA) inhibit the activity of RocF in a dose-dependent manner.

Inhibition of rat liver and kidney arginase by cadmium ion

Cadmium ion activates arginase from many species of organisms but is an inhibitor of arginase from many other species. The purpose of this study was to investigate the inhibition of rat liver and kidney arginase by cadmium ion. Rat kidney arginase was inhibited by much lower concentrations of cadmium ion than rat liver arginase. Cadmium ion was a mixed noncompetitive inhibitor of both rat liver and kidney arginase. Cadmium ion enhanced the substrate activation of rat kidney arginase while still inhibiting the enzyme. Cadmium ion prevented the substrate inhibition of rat kidney arginase by fluoride while still inhibiting the enzyme. Cadmium ion also inhibited rat kidney arginase in the presence of manganese ion.

Urea cycle of Fasciola gigantica: Purification and characterization of arginase

The ornithine-urea cycle has been investigated in Fasciola gigantica. Agrinase had very high activity compared to the other enzymes. Carbamoyl phosphate synthetase and ornithine carbamoyltransferase had very low activity. A moderate enzymatic activity was recorded for argininosuccinate synthetase and argininosuccinate lyase. The low levels of F. gigantica urea cycle enzymes except to the arginase suggest the urea cycle is operative but its role is of a minor important. The high level of arginase activity may benefit for the hydrolysis of the exogenous arginine to ornithine and urea. Two arginases Arg I and Arg II were separated by DEAE-Sepharose column. Further purification was restricted to Arg II with highest activity. The molecular weight of Arg II, as determined by gel filtration and SDS-PAGE, was 92,000. The enzyme was capable to hydrolyze l-arginine and to less extent l-canavanine at arginase:canavanase ratio (>10). The enzyme exhibited a maximal activity at pH 9.5 and Km of 6 mM. The optimum temperature of F. gigantica Arg II was 40 degrees C and the enzyme was stable up to 30 degrees C and retained 80% of its activity after incubation at 40 degrees C for 15 min and lost all of its activity at 50 degrees C. The order of effectiveness of amino acids as inhibitors of enzyme was found to be lysine>isoleucine>ornithine>valine>leucine>proline with 67%, 43%, 31%, 25%, 23% and 15% inhibition, respectively. The enzyme was activated with Mn2+, where the other metals Fe2+, Ca2+, Hg2+, Ni2+, Co2+ and Mg2+ had inhibitory effects.

Substrate inhibition of rat liver and kidney arginase with fluoride

Fluoride is an uncompetitive inhibitor of rat liver arginase. This study has shown that fluoride caused substrate inhibition of rat liver arginase at substrate concentrations above 4 mM. Rat kidney arginase was more sensitive to inhibition by fluoride than liver arginase. For both liver and kidney arginase preincubation with fluoride had no effect on the inhibition. When assayed with various concentrations of L-arginine, rat kidney arginase did not have Michaelis-Menten kinetics. Lineweaver-Burk and Eadie-Hofstee plots were nonlinear. Kidney arginase showed strong substrate activation at concentrations of L-arginine above 4 mM. Within narrow concentrations of L-arginine, the inhibition of kidney arginase by fluoride was uncompetitive. Fluoride caused substrate inhibition of kidney arginase at L-arginine concentrations above 1 mM. The presence of fluoride prevented the substrate activation of rat kidney arginase.