Effects of Some Metal Ions on Human Erythrocyte Glutathione Reductase:An In Vitro Study

The intersection of host in vivo metabolism and immune responses to infection with kinetoplastid and apicomplexan parasites

SUMMARYProtozoan parasite infection dramatically alters host metabolism, driven by immunological demand and parasite manipulation strategies. Immunometabolic checkpoints are often exploited by kinetoplastid and protozoan parasites to establish chronic infection, which can significantly impair host metabolic homeostasis. The recent growth of tools to analyze metabolism is expanding our understanding of these questions. Here, we review and contrast host metabolic alterations that occur in vivo during infection with Leishmania, trypanosomes, Toxoplasma, Plasmodium, and Cryptosporidium. Although genetically divergent, there are commonalities among these pathogens in terms of metabolic needs, induction of the type I immune responses required for clearance, and the potential for sustained host metabolic dysbiosis. Comparing these pathogens provides an opportunity to explore how transmission strategy, nutritional demand, and host cell and tissue tropism drive similarities and unique aspects in host response and infection outcome and to design new strategies to treat disease.

Nanoparticle Effects on Stress Response Pathways and Nanoparticle-Protein Interactions

Nanoparticles (NPs) are increasingly used in a wide variety of applications and products; however, NPs may affect stress response pathways and interact with proteins in biological systems. This review article will provide an overview of the beneficial and detrimental effects of NPs on stress response pathways with a focus on NP-protein interactions. Depending upon the particular NP, experimental model system, and dose and exposure conditions, the introduction of NPs may have either positive or negative effects. Cellular processes such as the development of oxidative stress, the initiation of the inflammatory response, mitochondrial function, detoxification, and alterations to signaling pathways are all affected by the introduction of NPs. In terms of tissue-specific effects, the local microenvironment can have a profound effect on whether an NP is beneficial or harmful to cells. Interactions of NPs with metal-binding proteins (zinc, copper, iron and calcium) affect both their structure and function. This review will provide insights into the current knowledge of protein-based nanotoxicology and closely examines the targets of specific NPs.

Deciphering of The Effect of Chemotherapeutic Agents on Human Glutathione S-Transferase Enzyme and MCF-7 Cell Line

BACKGROUND

Cancer is the disease that causes the most death after cardiovascular diseases all over the world these days. Breast cancer is the most common type of cancer among women and ranks the second among cancer-related deaths after lung cancer. Chemotherapeutics act by killing cancer cells, preventing their spread and slowing their growth. Recent studies focus on the effects of chemotherapeutics on cancer cells and new chemotherapy approaches that targeting enzymes that catalyze important metabolic reactions in the cell.

OBJECTIVE

The aim of this study was to investigate the effects of chemotherapeutic agents, Tamoxifen and 5-FU, on MCF-7 cell line and human erythrocyte GST, an important enzyme of intracellular antioxidant metabolism.

METHODS

In this study, it was investigated that the effect of chemotherapeutic agents, Tamoxifen and 5-FU, on MCF-7 breast cancer cell line and performed ROS analyzes. In addition, it was purified glutathione S-transferase (GST), one of the important enzymes of intracellular antioxidant mechanism, from human erythrocytes by using ammonium sulfate precipitation and glutathione agarose affinity chromatography, and investigated in vitro effects of chemotherapeutic agents, 5 - FU and Tamoxifen, on the activity of this enzyme for the first time.

RESULTS

it was determined that Tamoxifen and 5-FU inhibited cellular viability and 5-FU increased intracellular levels of ROS, whereas Tamoxifen reduced intracellular levels of ROS. In addition, human erythrocyte GST enzyme with 16.2 EU/mg specific activity was purified 265.97-fold with a yield of 35% using ammonium sulfate precipitation and glutathione agarose affinity chromatography. The purity of the enzyme was checked by the SDS-PAGE method. In vitro effects of chemotherapeutics, 5-FU and Tamoxifen, on GST activity purified from human erythrocytes were investigated. The results showed that 5-FU increased the activity of GST in the concentration range of 77 to 1155 μM and that Tamoxifen increased the activity of GST in the concentration range of 0.54 to 2.70 μM.

CONCLUSION

In this study, the effects of tamoxifen and 5-FU chemotherapeutic agents on both MCF-7 cell line and human GST enzyme were examined together for the first time. Our study showed that chemotherapeutic agents (5-FU and Tamoxifen) inhibited cellular viability and Tamoxifen reduced intracellular levels of ROS whereas 5-FU increased intracellular levels of ROS. In addition, 5-FU and Tamoxifen were found to increase the activity of GST enzyme purified from the human erythrocyte.

Purification and characterization of the carbonic anhydrase enzyme from horse mackerel (Trachurus trachurus) muscle and the impact of some metal ions and pesticides on enzyme activity

In this paper, the total carbonic anhydrase (CA) enzyme was purified from horse mackerel (Trachurus trachurus) muscle with a specific activity of 23,063.93 EU/mg, purification fold of 551.08, total activity of 1522.22 EU/mL and a yield of 18.50% using sulfanilamide affinity column chromatography. For obtaining the subunit molecular mass and enzyme purity, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) for this part was performed and a single band was clearly recorded. The molecular mass of this enzyme was found approximately 35 kDa. The optimum temperature and pH values were obtained from Arrhenius plot. In addition, the inhibitory effects of different heavy metal ions (Fe²⁺, Cu²⁺, Co²⁺, Pb²⁺ Hg²⁺ and As³⁺) and some pesticides (thiram, clofentezine, propineb, deltamethrin, azoxystrobin and thiophanate) on horse mackerel (Trachurus trachurus) muscle tissue CA enzyme activities were investigated by utilizing esterase assay activity. The used metal ions and pesticides had IC₅₀ values in the range of 0.21-13.84 mM and 3.78-70.58 mM, respectively.

Diabetes and Exposure to Environmental Lead (Pb)

Although the increased incidence of type 2 diabetes since the 1950s is thought to be primarily due to coincident alterations in lifestyle factors, another potential contributing factor in industrialized countries is exposure of the population to environmental pollutants and industrial chemicals. Exposure levels of many environmental toxicants have risen in the same time-frame as the disease incidence. Of particular interest in this regard is the metal lead. Although overall lead exposure levels have diminished in recent decades, there is an under-recognized but persistent occurrence of lead exposure in poor underserved urban populations. Although the neural developmental pathologies induced by lead exposures have been well documented, very little is known about the effect of lead exposure on the incidence of chronic metabolic diseases such as type 2 diabetes. Although our understanding of the metabolic health effects of lead exposure is incomplete, there are studies in model systems and a small amount of epidemiological data that together suggest a deleterious effect of environmental lead exposure on metabolic health. This article reviews the human, animal and in vitro studies that have examined the effects of lead exposure on the development of diabetes and related metabolic conditions.

In vitro thrombolytic activity of a purified fibrinolytic enzyme from Chlorella vulgaris

A fibrinolytic enzyme was produced by microalga Chlorella vulgaris cultivated in autotrophic and mixotrophic conditions added corn steep liquor, purified by a single chromatographic step, then biochemical characterization and in vitro thrombolytic activity was performed. Maximum cell concentration (1637.45 ± 15 mg L^-1) and productivity (181.93 mg L^-1 day^-1) was obtained in mixotrophic culture using 1% corn steep liquor. Enzyme-extracted microalgal biomass was purified by acetone precipitation and DEAE Sephadex anion exchange chromatography up to 2 fold with recovery of 4.0%. After purification, fibrinolytic activity was 1834.6 U mg^-1 and 226.86 mm² by spectrophotometry and fibrin plate assays, respectively. SDS-PAGE results exhibited a protein band of about 45 kDa and fibrinolytic band was detected by fibrin zymography. Enzyme activity was enhanced in the presence of Fe²⁺ and inhibited by phenylmethane sulfonyl fluoride (PMSF) and ethylenediamine tetracetic acid (EDTA), which suggest it to be a metal-dependent serine protease. The extract also showed a red blood cell lysis <4% and in vitro thrombolytic activity of 25.6% in 90 min of reaction. These results indicate that the fibrinolytic enzyme from C. vulgaris may have potential applications in the prevention and treatment of thrombosis.

Molecular identification and functional delineation of a glutathione reductase homolog from disk abalone (Haliotis discus discus): Insights as a potent player in host antioxidant defense

Glutathione reductase (GSR) is an enzyme that catalyzes the biochemical conversion of oxidized glutathione (GSSG) into the reduced form (GSH). Since the ratio between the two forms of glutathione (GSH/GSSG) is important for the optimal function of GSH to act as an antioxidant against H₂O₂, the contribution of GSR as an enzymatic regulatory agent to maintain the proper ratio is essential. Abalones are marine mollusks that frequently encounter environmental factors that can trigger the overproduction of reactive oxygen species (ROS) such as H₂O₂. Therefore, we conducted the current study to reveal the molecular and functional properties of a GSR homolog in the disk abalone, Haliotis discus discus. The identified cDNA sequence (2325 bp) has a 1356 bp long open reading frame (ORF), coding for a 909 bp long amino acid sequence, which harbors a pyridine nucleotide-disulfide oxidoreductase domain (171-246 aa), a pyridine nucleotide-disulfide oxidoreductase dimerization domain, and a NAD(P)(+)-binding Rossmann fold superfamily signature domain. Four functional residues: the FAD binding site, glutathione binding site, NADPH binding motif, and assembly domain were identified to be conserved among the other species. The recombinant abalone GSR (rAbGSR) exhibited detectable activity in a standard glutathione reductase activity assay. The optimum pH and optimal temperature for the reaction were found to be 7.0 and 50 °C, respectively, while the ionic strength of the medium had no effect. The enzymatic reaction was vastly inhibited by Cu⁺² and Cd⁺² ions. A considerable effect of cellular protection was detected with a disk diffusion assay conducted with rAbGSR. Moreover, an MTT assay and flow cytometry confirmed the significance of the protective role of rAbGSR in cell function. Furthermore, AbGSR was found to be ubiquitously distributed in different types of abalone tissues. AbGSR mRNA expression was significantly upregulated in response to three immune challenges: Vibrio parahaemolyticus, Listeria monocytogenes, and lipopolysaccharide (LPS), thus indicating its possible involvement in host defense mechanisms during pathogenic infections. Taken together, the results of the current study suggest that AbGSR plays an important role in antioxidant-mediated host defense mechanisms and also provide insights into the immunological contribution of AbGSR.

Investigation of inhibition of human glucose 6-phosphate dehydrogenase by some 99mTc chelators by in silico and in vitro methods

The inhibitory effects of methoxyisobutylisonitrile (MIBI), diethylene triamine pentaacetic acid (DTPA), dimercaptosuccinic acid (DMSA) and metilendifosfonat (MDP) on human erythrocyte glucose 6-phosphate dehydrogenase (hG6PD) activity were investigated. For this purpose, hG6PD was initially purified 557-fold at a yield of 51.43% using 2',5'-adenosine diphosphate (ADP) sepharose 4B affinity gel chromatography. The in vitro effects of these chelators on hG6PD enzyme were studied. IC₅₀ values of MIBI, DTPA, DMSA and MDP were 0.056, 0.172, 0.274 and 0.175 mM, of hG6PD, respectively. It was detected in in vitro studies that the hG6PD enzyme is inhibited due to these radiopharmaceutical chelators. In addition to in vitro studies, in order to better understand the molecular mechanism of studied compounds, combined in silico approaches, including molecular docking and molecular dynamics (MD), simulations were successfully performed. MD simulations shed light on inhibition mechanisms of the individual inhibitors into the ligand-binding pocket of hG6PD. Essential amino acids for binding are also investigated using per-residue interaction analysis studies.

Purification and characterization of glucose 6-phosphate dehydrogenase enzyme from rainbow trout (Oncorhynchus mykiss) liver and investigation of the effects of some metal ions on enzyme activity

Glucose 6-phosphate dehydrogenase (d-glucose 6-phosphate: NADP+ oxidoreductase, EC 1.1.1.49; G6PD) is a key enzyme that is localized in all mammal tissues, especially in cytoplasmic sections and that catalyzes the first step of pentose phosphate metabolic pathway. In this study, G6PD enzyme was purified 1444-fold with a yield of 77% from rainbow trout liver using 2′,5′-ADP-sepharose-4B affinity chromatography. Moreover, a purity check of the enzyme was performed with sodium dodecyl sulfate–polyacrylamide gel electrophoresis. Some characteristic features like optimal pH, stable pH, optimal temperature and optimal ionic strength were determined for the purified enzyme. In addition to this, in vitro effects of ions like silver nitrate (Ag+), thallium sulphate (TI+), cobalt (II) nitrate (Co2+) and arsenic (V) oxide (As5+) on enzyme activity were researched. Half-maximal inhibitory concentration (IC50) values of Ag+, Co2+ and As5+ metal ions, which showed an inhibitory effect, were found to be 0.0044, 0.084 and 4.058 mM, respectively; and their inhibition constants ( Ki) were found to be 0.0052 ± 0.00042, 0.087 ± 0.015700 and 4.833 ± 1.753207 mM, respectively. Tl+ not exhibited inhibitory effect on the enzyme activity.

In vitro enzymatic response of Turkish native chicken "Gerze" to heavy metal exposure

Glucose-6-phosphate dehydrogenase (G6PD) was purified and characterized from the Turkish native chicken, Gerze, erythrocytes for the first time, and some characteristics were investigated. Purification procedure consisted of ammonium sulphate fractionation and affinity chromatography on 29, 59-ADP Sepharose-4B. The enzyme was purified 1063.22-fold with a yield of 43.27% and specific activity of 93.5 EU/mg proteins. Kinetic parameters of the enzyme were determined with glucose-6-phosphate (G6P) as substrate and purified enzyme had an apparent K(M) and V(max) values of 0.222 mM and 0.097 U/ml, respectively. The same parameters were determined with NADP(+) and the K(M) and V(max) values were 0.0603 mM and 0.153 U/ml, respectively. The following metals, Cd(+2), Pb(+2), Hg(+2), Cu(+2), Zn(+2) and Fe(+3) showed inhibitory effects on the enzyme. Cd(+2) and Pb(+2) exhibited the strongest inhibitory action. Hg(+2) and Cu(+2) were moderate inhibitors, whereas Zn(+2) and Fe(+3) showed weaker actions. All tested metals inhibited the enzyme in competitive manner.

The effects of chemical and radioactive properties of Tl-201 on human erythrocyte glutathione reductase activity

AIM

The aim of the study was to evaluate the inhibitory effects of thallium-201 ((201)Tl) solution on human erythrocyte glutathione reductase (GR) activity.

METHODS

Erythrocyte GR was initially purified by 2',5'-adenosine diphosphate Sepharose-4B affinity and Sephadex G-200 gel filtration chromatography. The purification was monitored by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, which showed a single band for the final enzyme preparation. The in vitro and in vivo effects of the (201)Tl solution including Tl(+), Fe(+3) and Cu(+2) metals and the in vitro effects of the radiation effect of the (201)Tl solution and nonradioactive Tl(+), Fe(+3) and Cu(+2) metals on human erythrocyte GR enzyme were studied. Enzyme activity was determined with the Beutler method at 340 nm using a spectrophotometer. All purification procedures were carried out at (+)4 °C.

RESULTS

Glutathione reductase was purified 2033-fold at a yield of 28.17%. (201)Tl solution and radiation exposure had inhibitory effects on the enzyme activity. Besides, effects of nonradioactive Tl(+), Fe(+3) and Cu(+2) were studied on enzyme activity in vitro. Furthermore, seven human patients were also used for in vivo studies of (201)Tl solution.

CONCLUSION

It was detected in in vitro and in vivo studies that the human erythrocyte GR enzyme is inhibited due to the radiation effect of (201)Tl solution.

Design, synthesis and biological evaluation of novel nitroaromatic compounds as potent glutathione reductase inhibitors

Discovery of GR inhibitors has become very popular recently due to antimalarial and anticancer activities. In this study, the synthesis and GR inhibitory capacities of novel nitroaromatic compounds (NCs) (1-3) were reported. Some commercially available molecules were also tested for comparison reasons. The novel NCs were obtained in high yields using simple chemical procedures and exhibited much potent inhibitory activities against GR at low micromolar concentrations with K(i) values ranging from 0.211 to 4.57 μM as compared with well-known agents. Inhibition mechanism was assessed as being due to occlusion of the active site entrance by means of the NCs. Molecular docking results have shown that docking poses of ligands are able to construct binding interactions with the essential amino acids.

Purification and characterization of carbonic anhydrase from the teleost fish Dicentrarchus labrax (European seabass) liver and toxicological effects of metals on enzyme activity

Carbonic anhydrase (EC 4.2.1.1; CA) was purified and characterized from the liver of the teleost fish Dicentrarchus labrax (European seabass) for the first time. The purification procedure consisted of a single step affinity chromatography on Sepharose 4B-tyrosine-sulfanilamide. The enzyme was purified 78.8-fold with a yield of 46%, and a specific activity of 751.72U/mg proteins. It has an optimum pH at 7.5; an optimum temperature at 25°C; an optimum ionic strength at 10mM and a stable pH at 8.5. The kinetic parameters of this enzyme were determined for its esterase activity, with 4-nitrophenyl acetate (NPA) as substrate and the purified enzyme had an apparent K(M) and V(max) values of 0.44 mM and 0.249 μmolxmin(-1), respectively. The following metals, Al(+3), Cu(+2), Pb(+2), Co(+3), Ag(+1), Zn(+2) and Hg(+2) showed inhibitory effects on the enzyme. Al(+3) and Cu(+2) exhibited the strongest inhibitory action. Pb(+2) was moderate inhibitor, whereas other metals showed weaker actions. All tested metals inhibited the enzyme in a competitive manner. Our findings indicate that these metals inhibit the fish enzyme in a similar manner to other α-CAs from mammals investigated earlier, but the susceptibility to various metals differ between the fish and mammalian enzymes. Our results also demonstrate that these metals might be dangerous at low micromolar concentrations for fish CA enzymes.

Deltamethrin attenuates antioxidant defense system and induces the expression of heat shock protein 70 in rainbow trout

The current research aims to determine alterations in gene expression and enzymatic activity of fish antioxidant metabolism in response to pesticide administration. To this end, three different deltamethrin concentrations (0.25, 1, 2.5mug/L) were administrated to rainbow trout (Oncorhynchus mykiss) at different time intervals (6, 12, 24, 48 and 72h) in order to observe the influences of the pesticide on the activity of glutathione reductase, glucose 6-phosphate dehydrogenase, 6-ghosphogluconate dehydrogenase, and the expression of Hsp70 gene. We observed that the activities of the enzymes decreased with increasing deltamethrin concentrations and exposure time. The pesticide had more inhibitory effects on gill enzymes than those of muscle, liver and kidney. In addition, we detected that deltamethrin increased the expression of the stress-related protein Hsp70 with significant fold-chance values. The efficiency rate was 96.4% which is equal to 1.96 calculated via conversion formula used to calculate fold-chance value. We conclude that deltamethrin causes oxidative stress in fish both at protein and mRNA levels.

Purification of PON1 from human serum and assessment of enzyme kinetics against metal toxicity

Paraoxonase-1 (PON1) is an organophosphate hydrolyser enzyme which has also antioxidant properties in metabolism. Due to its crucial functions, inhibition of the enzyme is undesirable and very dangerous. PON1 enzyme activity should not be altered in any case. Inhibitory investigations of this enzyme are therefore important and useful. Metal toxicology of enzymes has become popular in the recent years. Here, we report the in vitro inhibitory effects of some metal ions, including Pb(+2), Cr(+2), Fe(+2), and Zn(+2), on the activity of human serum PON1 (hPON1; EC 3.1.8.1.). For this purpose, we purified the enzyme from human serum and analyzed the alterations in the enzyme activity in the presence of metal ions. The results show that metal ions exhibit inhibitory effects on hPON1 at low concentrations with IC (50) values ranging from 0.838 to 7.410 mM. Metal ions showed different inhibition mechanisms: lead and iron were competitive, chrome was noncompetitive, and zinc was uncompetitive. Lead was determined to be the most effective inhibitor.

Effects of glutathione reductase inhibition on cellular thiol redox state and related systems

Although inhibition of glutathione reductase (GR) has been demonstrated to cause a decrease in reduced glutathione (GSH) and increase in glutathione disulfide (GSSG), a systematic study of the effects of GR inhibition on thiol redox state and related systems has not been noted. By employing a monkey kidney cell line as the cell model and 2-acetylamino-3-[4-(2-acetylamino-2-carboxy-ethylsulfanylthio carbonylamino)phenylthiocarbamoylsulfanyl]propionic acid (2-AAPA) as a GR inhibitor, an investigation of the effects of GR inhibition on cellular thiol redox state and related systems was conducted. Our study demonstrated that, in addition to a decrease in GSH and increase in GSSG, 2-AAPA increased the ratios of NADH/NAD(+) and NADPH/NADP(+). Significant protein glutathionylation was observed. However, the inhibition did not affect the formation of reactive oxygen species or expression of antioxidant defense enzyme systems [GR, glutathione peroxidase, catalase, and superoxide dismutase] and enzymes involved in GSH biosynthesis [gamma-glutamylcysteine synthetase and glutathione synthetase].

Purification and characterization of glutathione reductase from rainbow trout (Oncorhynchus mykiss) liver and inhibition effects of metal ions on enzyme activity

Glutathione reductase (E C: 1.8.1.7; GR) was purified from rainbow trout (Oncorhynchus mykiss) liver, and some characteristics of the enzyme were investigated. The purification procedure consisted of four steps: preparation of homogenate, ammonium sulfate fractionation, affinity chromatography on 2',5'-ADP Sepharose-4B and gel filtration chromatography on Sephadex G-200. The enzyme, with a specific activity of 27.45 U/mg protein, was purified 1,654-fold with a yield of 41%. Optimal pH, stable pH, optimal temperature, optimum ionic strength, molecular mass, KM and Vmax values for GSSG and NADPH were also determined for the enzyme. In addition, Ki values and inhibition types were determined for GSH and NADP+. Additionally, inhibitory effects of metal ions (Cd+2, Cu+2, Pb+2, Hg+2, Fe+3 and Al+3) on glutathione reductase were investigated. Ki constants and IC50 values for metal ions were determined by Lineweaver-Burk graphs and plotting activity % vs. [I], respectively. IC50 values of Cd+2,Cu+2, Pb+2, Hg+2, Fe+3 and Al+3 were 0.0655, 0.082, 0.122, 0.509, 0.797 and 0.804 mM, and the Ki constants for Cd+2 and Cu+2 were 0.104+/-0.001, 0.117+/-0.001, respectively.