Inhibition Of Glutathione S-transferase Research Articles

Abstract 14532: Computational Drug Repurposing Identifies a Piperlongumine Analog That Controls a Gstp1-iscu Pathogenic Axis in Pulmonary Hypertension

Background and Hypothesis: Pulmonary arterial hypertension (PAH) is an incurable vascular disease for which chemotherapies are being considered for therapeutic development. There is no method reported to date for effective computational screening of these drugs for this disease. Big data analyses that leverage the molecular parallels between cancer and PH may define novel pathogenic mechanisms and facilitate repurposing of chemotherapies for PAH. More specifically, while functional deficiency of the iron-sulfur (Fe-S) biogenesis gene ISCU and oxidative metabolism in human pulmonary arterial endothelial cells (PAECs) is known to drive PAH, the pathogenic regulation of ISCU is not fully defined, and no tailored drugs have been identified to bolster ISCU activity. Methods and Results: We applied a computational algorithm EDDY (Evaluating Differential DependencY), which analyzes RNA sequencing data from 810 cancer cell lines exposed to 368 small molecules, in order to identify chemotherapeutics that depended upon rewired PH-related gene clusters. The top ranked drug was a piperlongumine (PL) analog (BRD2889) that was predicted to extensively rewire dependencies across PH gene clusters, mediated by ISCU. In vitro, coupling gain- and loss-of-function analyses of GSTP1 with BRD2889 exposure in PAECs, we found that BRD2889 inhibits glutathione S-transferase P1 (GSTP1), an enzyme which in turn catalyzes ISCU glutathionylation and increases its stability in hypoxia. Consequently, BRD2889 and GSTP1 knockdown phenocopy one another by increasing Fe-S-dependent Complex I activity and mitochondrial oxygen consumption while ameliorating pathogenic apoptosis. Consistent with these computational and in vitro results, in a mouse model of PAH (IL-6 transgenic mice in hypoxia), BRD2889 improved hemodynamic and molecular disease manifestations in vivo. Conclusions: Using a novel computational platform, we identified a coordinated connection between BRD342289 and GSTP1-ISCU axis, crucial to PAEC metabolism. This study offers insight to fundamental PH pathobiology and sets the stage for accelerated repurposing of chemotherapies such as BRD342289 in PH.

A bi-functional fluorescent probe for visualized and rapid natural drug screening via GSTs activity monitoring

Glutathione S-transferase (GSTs), as an important target for drug screening, is closely associated with physiological and pathological process regulation. Hence, effective monitoring of GSTs activity is benificial for GSTs-induced diseases diagnosis and therapeutic drugs discovery. Resorufin-typed probes with high sensitivity, excellent selectivity, and low cytotoxicity have become a powerful tool for target monitoring. In this study, a bi-functional fluorescent probe, resorufin-typed probe (RP) with resorufin as a fluorophore was designed as the GSTs substrate and drug screening tool. GSTs can trigger significant fluorescence signal enhancement of RP by catalyzing the combination of glutathione (GSH) and its recognition site in RP. Meaningfully, the change of fluorescence signal positively correlated with GSTs activity can be used to monitor the regulatory effect of natural drugs on GSTs. Based on the axis relation of “drug-GSTs activity-fluorescence signal”, this powerful probe was successfully employed for visual and rapid screening GSTs-targeted natural compounds in vitro by monitoring the change of GSTs activity. Natural compound 1, 2 and 7 (C1, C2 and C7) were screened as the GSTs inhibitors, and C7 was helpful for enhancing the sensitivity of cisplatin in cancer cells. Overall, the designed natural drug screening strategy based on bi-functional fluorescence probe demonstrated its hopeful application to drug rapid discovery.

Spectrophotometric Screening for Potential Inhibitors of Cytosolic Glutathione S-Transferases.

Glutathione S-transferases (GSTs) are metabolic enzymes responsible for the elimination of endogenous or exogenous electrophilic compounds by glutathione (GSH) conjugation. In addition, GSTs are regulators of mitogen-activated protein kinases (MAPKs) involved in apoptotic pathways. Overexpression of GSTs is correlated with decreased therapeutic efficacy among patients undergoing chemotherapy with electrophilic alkylating agents. Using GST inhibitors may be a potential solution to reverse this tendency and augment treatment potency. Achieving this goal requires the discovery of such compounds, with an accurate, quick, and easy enzyme assay. A spectrophotometric protocol using 1-chloro-2,4-dinitrobenzene (CDNB) as the substrate is the most employed method in the literature. However, already described GST inhibition experiments do not provide a protocol detailing each stage of an optimal inhibition assay, such as the measurement of the Michaelis-Menten constant (Km) for CDNB or indication of the employed enzyme concentration, crucial parameters to assess the inhibition potency of a tested compound. Hence, with this protocol, we describe each step of an optimized spectrophotometric GST enzyme assay, to screen libraries of potential inhibitors. We explain the calculation of both the half-maximal inhibitory concentration (IC50) and the constant of inhibition (Ki)-two characteristics used to measure the potency of an enzyme inhibitor. The method described can be implemented using a pool of GSTs extracted from cells or pure recombinant human GSTs, namely GST alpha 1 (GSTA1), GST mu 1 (GSTM1) or GST pi 1 (GSTP1). However, this protocol cannot be applied to GST theta 1 (GSTT1), as CDNB is not a substrate for this isoform. This method was used to test the inhibition potency of curcumin using GSTs from equine liver. Curcumin is a molecule exhibiting anti-cancer properties and showed affinity towards GST isoforms after in silico docking predictions. We demonstrated that curcumin is a potent competitive GST inhibitor, with an IC50 of 31.6 ± 3.6 µM and a Ki of 23.2 ± 3.2 µM. Curcumin has potential to be combined with electrophilic chemotherapy medication to improve its efficacy.

Spectrophotometric Screening for Potential Inhibitors of Cytosolic Glutathione S-Transferases

Spectrophotometric Screening for Potential Inhibitors of Cytosolic Glutathione S-Transferases

Ameliorative Role of Plectranthus esculentus on 4-Vinylcyclohexene Monoepoxide-Induced Oxidative Stress in Drosophila melanogaster

Plectranthus esculentus is a plant used to relieve pain and digestive disorders. 4-Vinylcyclohexene 1,2-monoepoxide (VCM) is a toxic metabolite of 4-vinylcyclohexene. The lifespan effects of leaf varieties of P. esculentus fractions (vat-bebot, MV1) and 2 (vat-riyon, MV2) and their ameliorative effects on VCM-induced oxidative stress were evaluated in D. melanogaster. Flies were treated with vehicle (ethanol), Gallic Acid (0.1 mM), MV1 (100 mg/10 diet), MV2 (200 mg/10 diet), VCM (100 M), (VCM+Gallic Acid), (VCM+MV1) and (VCM+MV2) in the diets for 5 days. The results indicated that MV1 and MV2 reduced the lifespan of flies without affecting the survival of flies after 7 days of treatment. P. esculentus restored VCM-induced depletion of total thiol and inhibition of glutathione S-transferase, acetylcholinesterase, and catalase activities (p < 0.05). Our results demonstrated that short term consumption of P. esculentus is beneficial and that MV1 offered better ameliorative effects than MV2.

Assessment of heavy metal contamination and human health risk with oxidative stress in fish (Cyprinus carpio) from Shahpur Dam, Fateh Jang, Pakistan

The study was conducted to analyze the water quality of Shahpur Dam, Pakistan, health of native fish Cyprinus carpio, and health risks associated to humans as consumers. Metal (Pb, Cu, Cr, Fe, Ni) concentrations in water and its bioaccumulation in fish tissues (liver, gills, muscles, kidneys, and brain) were determined by using an atomic absorption spectrophotometer. Pb was abundantly found in water (8.15 mg L−1) and fish organs compared with other metals, beyond the permissible referred guidelines. Metal pollution index (MPI) was found high in fish liver followed by gill, muscle, kidney, and brain. Toxicity potential of water pollution was determined in the form of oxidative stress by analyzing catalase (CAT), glutathione S-transferase (GST), and reduced glutathione (GSH) activities in liver and gill of Cyprinus carpio, using UV spectrophotometer. The CAT activity was found higher with inhibition of 41.1% and 2.1% in liver and gill of exposed fish. Inhibition of GST in liver and gill was recorded as 29.4% and 28.1%, respectively, whereas that of the GSH was observed 12.8% and 13.9%, respectively, showing significant oxidative stress in exposed fish of the dam compared with farm fish. Consequently, people consuming the contaminated fish are prone to health impacts, which was estimated by target hazard quotient (THQ), hazard index (HI), and cancer risk (CR). No metal was found to pose potential noncarcinogenic health risk individually or collectively at present but people consuming contaminated fish regularly were expected to be at target cancer risk in 70 years or more of their lifetime.

Benoxacor is enantioselectively metabolized by rat liver subcellular fractions

This study investigated the enantioselective metabolism of benoxacor, an ingredient of herbicide formulations, in microsomes or cytosol prepared from female or male rat livers. Benoxacor was incubated for ≤30 min with microsomes or cytosol, and its enantioselective depletion was measured using gas chromatographic methods. Benoxacor was depleted in incubations with active microsomes in the presence and absence of NADPH, suggesting its metabolism by hepatic cytochrome P450 enzymes (CYPs) and microsomal carboxylesterases (CESs). Benoxacor was depleted in cytosolic incubations in the presence of glutathione, consistent with its metabolism by glutathione S-transferases (GSTs). The depletion of benoxacor was faster in incubations with cytosol from male than female rats, whereas no statistically significant sex differences were observed in microsomal incubations. The consumption of benoxacor was inhibited by the CYP inhibitor 1-aminobenzotriazole, the CES inhibitor benzil, and the GST inhibitor ethacrynic acid. Estimates of the intrinsic clearance of benoxacor suggest that CYPs are the primary metabolic enzyme responsible for benoxacor metabolism in rats. Microsomal incubations showed an enrichment of the first eluting benoxacor enantiomer (E1-benoxacor). A greater enrichment occurred in incubations with microsomes from female (EF = 0.67 ± 0.01) than male rats (EF = 0.60 ± 0.01). Cytosolic incubations from female rats resulted in enrichment of E1-benoxacor (EF = 0.54 ± 0.01), while cytosolic incubations from male rats displayed enrichment of the second eluting enantiomer (E2-benoxacor; EF = 0.43 ± 0.01). Sex-dependent differences in the metabolism of benoxacor in rats could significantly impact ecological risks and mammalian toxicity. Moreover, changes in the enantiomeric enrichment of benoxacor may be a powerful tool for environmental fate and transport studies.

Benzenesulfonamide derivatives as potent acetylcholinesterase, α-glycosidase, and glutathione S-transferase inhibitors: biological evaluation and molecular docking studies

Sulfonamide derivatives exhibit a wide biological activity and can function as potential medical molecules in the development of a drug. Studies have reported that the compounds have an effect on many enzymes. In this study, the derivatives of amine sulfonamide (1i-11i) were prepared with reduced imine compounds (1-11) with NaBH4 in methanol. The synthesized compounds were fully characterized by spectral data and analytical. The effect of the synthesized derivatives on acetylcholinesterase (AChE), glutathione S-transferase (GST) and α-glycosidase (α-GLY) enzymes were determined. For the AChE and α-GLY, the most powerful inhibition was observed on 10 and 10i series with K I value in the range 2.26 ± 0.45–3.57 ± 0.97 and 95.73 ± 13.67–102.45 ± 11.72 µM, respectively. K I values of the series for GST were found in the range of 22.76 ± 1.23–49.29 ± 4.49. Finally, the compounds have a stronger inhibitor in lower concentrations by the attachment of functional electronegative groups such as two halogens (-Br and -CI), -OH to the benzene ring and -SO2NH2. The crystal structures of AChE, α-GLY, and GST in complex with selected derivatives 4 and 10 show the importance of the functional moieties in the binding modes within the receptors. Communicated by Ramaswamy H. Sarma

Toxicity of cypermethrin and enzyme inhibitor synergists in red hairy caterpillar Amsacta albistriga (Lepidoptera: Arctiidae)

BackgroundThe frequent usage of broad-spectrum insecticides like cypermethrin in agriculture activities could lead to the development of resistance in insects like Amsacta albistriga.ObjectivesThe present study was conducted to understand the toxicity of cypermethrin with and without a combination of three enzyme inhibitors (PBO, DEM, and TPP) on A. albistriga using a topical bioassay.MethodologyThe in vitro and in vivo studies were conducted to understand the effect of three enzyme inhibitors such as piperonyl butoxide (PBO) and diethyl maleate (DEM) and triphenyl phosphate along with six different concentration of cypermethrin on the activities of acetylcholinesterase (AChE), esterase (EST), glutathione S-transferase (GST), and mixed-function oxidase (MFO) of A. albistriga.ResultsBioassay shows elevated LC50 for cypermethrin (63.32 ppm) whereas in a combination of PBO cypermethrin LC50 values were reduced into 12.039 ppm followed by TPP combination as 13.234 ppm. In vitro and in vivo inhibition analysis shows AChE inhibition by PBO P < 0.01, esterase inhibition by PBO, and TPP were less; GST inhibition by DEM was observed at P < 0.001. Native PAGE results revealed that the in vitro AChE isoenzyme inhibition could be possible by PBO synergism with cypermethrin in A. albistriga.ConclusionsThe overall results conclude that the PBO and TPP enzyme inhibitors could be fine synergist molecules when it mixed with cypermethrin insecticide to control and manage the insecticide-resistant Amsacta albistriga in the field.

Quizalofop-p-ethyl resistance in Polypogon fugax involves glutathione S-transferases.

Asia minor bluegrass (Polypogon fugax) is one of the main weeds invading Chinese canola fields. The P. fugax resistant population SC-R, which survived quizalofop-p-ethyl at the field-recommended rate (67.5 g ha-1 ), was collected from a canola field in Qingsheng County in China. The present study aimed to (1) characterize the SC-R resistance pattern to acetyl-CoA carboxylase (ACCase)-inhibiting herbicides, and (2) investigate the mechanism of quizalofop-p-ethyl resistance in this population. Dose-response studies showed that resistance to quizalofop-p-ethyl and haloxyfop occurred in the SC-R population. Four transcripts/genes encoding the plastidic ACCase carboxyl-transferase domain were isolated from the P. fugax plants. No mutations in the four ACCase genes were detected in the SC-R population compared to the SC-S population. Pre-treatment with the known glutathione S-transferase (GST) inhibitor 4-chloro-7-nitrobenzoxadiazole (NBDCl), reversed resistance to quizalofop-p-ethyl and partially reversed resistance to haloxyfop-R-methyl in the resistant population (SC-R). However, the cytochrome P450 inhibitor malathion did not reverse the resistance. There was no difference in basal GST activity (using CDNB as a substrate), but there was higher inducible GST activity in SC-R relative to SC-S. Two GST genes, GST2c and GSTL3, were constitutively overexpressed in the resistant SC-R population. This study confirmed that resistance to quizalofop-p-ethyl in the resistant P. fugax population is likely nontarget-site based involving GST, and this resistance mechanism also partially confers haloxyfop-R-methyl resistance. © 2020 Society of Chemical Industry.

Ameliorative role of diets fortified with Curcumin in a Drosophila melanogaster model of aluminum chloride-induced neurotoxicity

Aluminum is an environmental and industrial neurotoxicant known to induce oxidative damage and inflammation in tissues. Curcumin is a polyphenol with antioxidant and anti-inflammatory properties. Here, we evaluated Curcumin’s protective role in Aluminum Chloride (AlCl3)-induced toxicity in D. melanogaster. A 21-day survival analysis was carried out and subsequently, flies were exposed to AlCl3 (100 and 200 mg/kg diet) and/or Curcumin (0.2 and 0.5 mg/kg diet) for 7 days. Curcumin restored AlCl3-induced inhibition of glutathione S-transferase (GST) and catalase activities, as well as depletion of total thiol and glutathione contents. In addition, Curcumin ameliorated AlCl3-induced increase in acetylcholinesterase activity and accumulation of hydrogen peroxide and nitrite levels in flies. Additionally, AlCl3-induced disruption of climbing activity and emergence rate were ameliorated by curcumin in D. melanogaster (p < 0.05). Overall, Curcumin ameliorated AlCl3-induced toxicity in D. melanogaster. Therefore, it can be regarded as a therapeutic agent against AlCl3-induced toxicity.

Caffeic Acid Phenethyl Ester Assisted by Reversible Electroporation-In Vitro Study on Human Melanoma Cells.

Melanoma is one of the most serious skin cancers. The incidence of this malignant skin lesion is continuing to increase worldwide. Melanoma is resistant to chemotherapeutic drugs and highly metastatic. Surgical resection can only be used to treat melanoma in the early stages, while chemotherapy is limited due to melanoma multi-drug resistance. The overexpression of glutathione S-transferase (GST) may have a critical role in this resistance. Caffeic acid phenethyl ester (CAPE) is a natural phenolic compound, which occurs in many plants. Previous studies demonstrated that CAPE suppresses the growth of melanoma cells and induces reactive oxygen species generation. It is also known that bioactivation of CAPE to its corresponding quinone metabolite by tyrosinase would lead to GST inhibition and selective melanoma cell death. We investigated the biochemical toxicity of CAPE in combination with microsecond electropermeabilization in two human melanoma cell lines. Our results indicate that electroporation of melanoma cells in the presence of CAPE induced high oxidative stress, which correlates with high cytotoxicity. Moreover, it can disrupt the metabolism of cancer cells by inducing apoptotic cell death. Electroporation of melanoma cells may be an efficient CAPE delivery system, enabling the application of this compound, while reducing its dose and exposure time.

Synthesis, Biological Evaluation and Molecular Docking of Novel Thiophene‐Based Indole Derivatives as Potential Antibacterial, GST Inhibitor and Apoptotic Anticancer Agents

AbstractHeteroaromatic indoles play a leading role in the development of pharmaceutical, medical, chemical and agricultural fields due to their structural properties. In this study, it was first time that biological properties of (antioxidant, antimicrobial, cytotoxic and apoptotis‐induced anticancer) 3‐(5‐bromothiophen‐2‐yl)‐1‐ethyl‐2‐phenyl‐1H‐indole 4 and 3‐([2,2′‐bithiophen]‐5‐yl)‐1‐ethyl‐2‐phenyl‐1H‐indole 5 were described. According to the overall results, while 4 did not show any significant cytotoxic, antioxidant and antimicrobial activities, 5 showed high reducing activity and very strong antibacterial activity against Enterococcus faecalis. Furthermore, 5 showed dose‐dependent cytotoxic effect in all tested cell lines. The EC50 values of the 5 were found to be 16 μM for CaCo‐2, 29 μM for LnCaP, 14 μM for MDA‐MB231, 21 μM for HepG2 and 87 μM for HEK293 cells, respectively. 5 also caused induction of apoptosis and promising glutathione S‐transferase (GST) enzyme inhibition in HepG2 cells. Consequently, 5 could be also considered as a promising medical agent in cancer treatment.

Metabolic resistance to S-metolachlor in two waterhemp (Amaranthus tuberculatus) populations from Illinois, USA.

Two waterhemp (Amaranthus tuberculatus) populations from Illinois demonstrating multiple-resistance to acetolactate synthase (ALS)-, 4-hydroxyphenylpyruvate dioxygenase, and photosystem II (PSII)-inhibiting herbicides (designated CHR and SIR) also displayed reduced sensitivity to very-long-chain fatty acid-inhibiting herbicides, including S-metolachlor. We hypothesized that a physiological mechanism, such as enhanced metabolism, could be responsible for the reduced efficacy of S-metolachlor. Metabolism experiments indicated that resistant populations degraded S-metolachlor more rapidly than sensitive populations and equally as rapidly as corn 2-24 h after treatment (HAT). Resistant waterhemp and corn metabolized 90% (DT90 ) of absorbed S-metolachlor in less than 3.2 h whereas DT90 values for sensitive waterhemp exceeded 6 h. The glutathione S-transferase inhibitor 4-chloro-7-nitrobenzofurazon and cytochrome P450-inhibitor malathion decreased the amount of S-metolachlor metabolized in resistant waterhemp at 4 HAT but not in sensitive waterhemp or corn, and altered the abundance of certain metabolites in resistant waterhemp. Results from this research demonstrate that resistance to S-metolachlor in these waterhemp populations is due to enhanced herbicide metabolism relative to sensitive populations. In addition, our results indicate that resistant waterhemp might utilize metabolic pathway(s) more intricate than either sensitive waterhemp or corn based on their metabolite profiles. © 2020 Society of Chemical Industry.

In Vitro Inhibition Effect and Molecular Docking Study of Curcumin, Resveratrol, and Quercetin on Human Erythrocyte Glutathione Transferase

Background:Chemotherapy has shown varying success rates in the treatment of metastatic cancer in the last 50 years. One of the problems in the use of many chemotherapeutic agents is to increase the expression of glutathione transferase enzyme (GST; EC 2.5.1.18). Therefore, the development of GST inhibitors is important to improve the effectiveness of antitumor drugs and to overcome multi-drug resistance.Introduction:Glutathione S-transferases (GSTs) are a major member of enzymes serving in the detoxification of exogenous and endogenous substances. But, it has been reported that GSTs are overexpressed in many tumour cells, and it has been found to be related to developing resistance to anticancer drugs by these cells. The development of GST inhibitors is important to increase the efficacy of antitumor drugs and overcome multi-drug resistance. The aim of our study was to investigate the effect of natural compounds including curcumin, resveratrol, and quercetin on GST enzyme activity. We also aimed to specify inhibition mechanism of the compounds on human erythrocytes GST (hGST) with in silico study.Method:GST was purified from human erythrocytes using affinity chromatography (glutathione agarose). The enzyme purity was checked with SDS-PAGE. After the inhibitory effect of the curcumin, quercetin, resveratrol was investigated. Lastly, inhibition mechanisms of these natural compound were identified with induced-fit docking method.Result:GST was purified with 19.31% yield from human erythrocytes. In inhibition studies, Ki values of curcumin, quercetin, resveratrol were determined as 0.0021 ± 0.0008, 0.0257 ± 0.0011, 663.3301 ± 0.0936 µM respectively. According to our results, all natural products showed the inhibition effect and the order of inhibition is as follows: curcumin ˃ quercetin ˃ resveratrol.Conclusion:According to the results of the in vitro and in silico studies, it can be said that curcumin, quercetin, resveratrol are the inhibitors of human erythrocyte GST. In conclusion, these observations may be of great importance for the potential use of these natural compounds as chemopreventive agents.

Glutathione S-Transferases Play a Crucial Role in Mitochondrial Function, Plasma Membrane Stability and Oxidative Regulation of Mammalian Sperm.

Glutathione S-transferases (GSTs) are essential sperm antioxidant enzymes involved in cell protection against oxidative stress and toxic chemicals, preserving sperm function and fertilising ability. Artificial insemination (AI) in pigs is commonly carried out through the use of liquid-stored semen at 17 °C, which not only reduces sperm metabolic activity but also sperm quality and AI-farrowing rates within the 72 h of storage. While one may reasonably suggest that such enzymes are implicated in the physiology and maintenance of mammalian sperm function during liquid-storage, no previous studies conducted on any species have addressed this hypothesis. Therefore, the objective of the present work was to characterise the presence and function of sperm GSTs in mammalian sperm, using the pig as a model. In this regard, inhibition of such enzymes by ethacrynic acid (EA) during semen storage at 17 °C was performed to evaluate the effects of GSTs in liquid-preserved boar sperm by flow cytometry, immunofluorescence, and immunoblotting analysis. The results of this study have shown, for the first time in mammalian species, that the inhibition of GSTs reduces sperm quality and functionality parameters during their storage at 17 °C. These findings highlight the key role of such enzymes, especially preserving mitochondrial function and maintaining plasma membrane stability. In addition, this study has identified and localised GSTM3 in the tail and equatorial subdomain of the head of boar sperm. Finally, this study has set grounds for future investigations testing supplementation of semen extenders with GSTs, as this may improve fertility outcomes of swine AIs.

Acute toxicity assessment of arsenic, chromium and almix 20WP in Euphlyctis cyanophlyctis tadpoles.

Heavy metals and herbicide are gaining serious environmental concern in aquatic toxicology due to its adverse effects on aquatic organisms especially amphibians. Accordingly, present study first time evaluated the acute toxicity of two heavy metals [arsenic (As3+) and chromium (Cr6+)] and a herbicide (Almix) to Indian skittering frog tadpole, Euphlyctis cyanophlyctis. The LC50 values of As, Cr and Almix for 24, 48, 72 and 96h were 73.58, 56.31, 43.58 and 32.58mgL-1; 326.68, 224.31, 171.92 and 141.99mgL-1; and 1297.85, 1148.22, 1033.62 and 955.17mgL-1, respectively. It also revealed the concentration- and time-dependent increased mortality rate under these toxicants. The safety concentrations (SC) of As, Cr and Almix to tadpoles were 3.26, 14.20 and 95.52mgL-1, respectively. The findings disclosed that As is highly toxic to E. cyanophlyctis than Cr and Almix. Alkaline phosphatase (ALP) activity showed varied responses to exposed chemicals. In particularly, ALP activity reduced significantly for Cr treatment. Glutathione S-transferase (GST) activity in E. cyanophlyctis was significantly inhibited by As treatment (p<0.05); however, GST activity was remain unchanged for Cr and Almix (p>0.05). The As toxicity correlates positively with GST inhibition (r=0.779, p<0.01); contrarily, Cr and Almix revealed negative correlation with GST induction (r=-0.461 and -0.19, respectively; p>0.05). This result indicated that GST play a crucial role for regulating the tadpole mortality and intoxication by As, Cr and Almix. Overall, our findings demonstrate the different levels of toxic sensitivity (adverse effects) under different toxicants on E. cyanophlyctis tadpoles. Finally, the present findings could be used as baseline information of toxicosis for metalloid, heavy metal and herbicide exposures in wild frog populations.

Development of Telintra as an Inhibitor of Glutathione S-Transferase P.

Glutathione S-transferase P (GSTP) is a component of a complex series of pathways that provide cellular redox homeostasis. It is an abundant protein in certain tumors and is over-expressed in cancer drug resistance. It has diverse cellular functions that include, thiolase activities with small electrophilic agents or susceptible cysteine residues on the protein to mediate S-glutathionylation, and chaperone binding with select protein kinases. Preclinical and clinical testing of a nanomolar inhibitor of GSTP, TLK199 (Telintra; Ezatiostat) has indicated a role for the enzyme in hematopoiesis and utility for the drug in the treatment of patients with myelodysplastic syndrome.

Protective role of resveratrol, a natural polyphenol, in sodium fluoride-induced toxicity in Drosophila melanogaster.

Sodium fluoride (NaF) is used in water fluoridation and dental products such as mouth rinses and toothpastes. Resveratrol is a natural polyphenol with antioxidant and anti-inflammatory properties. The present study was carried out to evaluate the toxicity of NaF and the protective role of resveratrol in Drosophila melanogaster. For longevity assay, Harwich strain of D. melanogaster was treated with NaF (0, 10, 30, 50, 70 and 90 mg/kg diet) throughout the lifespan and daily mortality recorded. Then, flies were again treated with similar doses of NaF for seven days to evaluate survival rate and oxidative stress markers. Thereafter, 60 mg resveratrol/kg diet was selected to determine its ameliorative role in NaF (70 mg/kg)-induced toxicity in flies: Group A (control), Group B (60 mg resveratrol/kg diet), Group C (70 mg NaF/kg diet), and Group D (resveratrol, 60 mg/kg diet) + NaF, 70 mg/kg diet). Thereafter, Glutathione-S-transferase (GST), catalase and acetylcholinesterase (AchE) activities, as well as total thiol (T-SH), nitrites/nitrates and hydrogen peroxide (H2O2) levels were determined. The results showed that resveratrol prevented NaF-induced elevation of H2O2and nitrites/nitrates levels, as well as catalase activity. In addition, resveratrol restored NaF-induced inhibition of GST and AChE activities and depletion of T-SH content ( P &lt; 0.05). Conclusively, resveratrol offered protective benefit against NaF-mediated toxicity in flies due to its antioxidant and anti-inflammatory properties.Impact statementD. melanogaster was used to understand the impact of NaF on lifespan and emergence rate as well as the rescue role of resveratrol. These parameters are difficult to carry out in previously used models such as rodents. This further enforces in part, the suitability of D. melanogaster in studying NaF-induced toxicity and the therapeutic effects of drugs. Additionally, we found that resveratrol rescued D. melanogaster from oxidative stress-induced by sodium fluoride (NaF) administration. This study is of public health significance as it indicated that the consumption of fruits rich in resveratrol such as grapes may offer protective role against inadvertent exposure to NaF and related chemicals.

Identification of ligands from natural products as inhibitors of glutathione S-transferases using enzyme immobilized mesoporous magnetic beads with high-performance liquid chromatography plus quadrupole time-of-flight mass spectrometry and molecular docking.

Multidrug resistance is recognized as one of the main reasons leading to the failure of chemotherapy. Studies have shown that glutathione S-transferase inhibitors could be regarded as multidrug resistance reversal agents. Herein, a method of applying enzyme immobilization, molecular docking, and high-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry was employed to screen glutathione S-transferase inhibitors from natural products. Magnetic mesoporous silica microspheres were synthesized and modified with a poly(dopamine) layer, which has a large quantity of amino, enabling further non-covalent binding with glutathione S-transferase. Moreover, the immobilization conditions, namely, potential of hydrogen, catalase concentration, reaction temperature and reaction time, were optimized. In total, six potential compounds were isolated and identified from Perilla frutescens (L.) Britt leaves and green tea and molecular docking was applied to identify the binding site. Rosmarinic acid, (-)-epigallocatechin-3-O-gallate and (-)-epicatechin-3-gallate showed higher binding affinity than the compounds, and their half maximal inhibitory concentration values were further determined. The results suggested that this proposed method was effective and convenient for identifying glutathione S-transferase inhibitors from natural products.