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Chemical Research in Toxicology Jun 2024Chemicals often require metabolic activation to become genotoxic. Established test guidelines recommend the use of the rat liver S9 fraction or microsomes to introduce...
Chemicals often require metabolic activation to become genotoxic. Established test guidelines recommend the use of the rat liver S9 fraction or microsomes to introduce metabolic competence to cell-based bioassays, but the use of animal-derived components in cell culture raises ethical concerns and may lead to quality issues and reproducibility problems. The aim of the present study was to compare the metabolic activation of cyclophosphamide (CPA) and benzo[]pyrene (BaP) by induced rat liver microsomes and an abiotic cytochrome P450 (CYP) enzyme based on a biomimetic porphyrine catalyst. For the detection of genotoxic effects, the chemicals were tested in a reporter gene assay targeting the activation of the cellular tumor protein p53. Both chemicals were metabolized by the abiotic CYP enzyme and the microsomes. CPA showed no activation of p53 and low cytotoxicity without metabolic activation, but strong activation of p53 and increased cytotoxicity upon incubation with liver microsomes or abiotic CYP enzyme. The effect concentration causing a 1.5-fold induction of p53 activation was very similar with both metabolization systems (within a factor of 1.5), indicating that genotoxic metabolites were formed at comparable concentrations. BaP also showed low cytotoxicity and no p53 activation without metabolic activation. The activation of p53 was detected for BaP upon incubation with active and inactive microsomes at similar concentrations, indicating experimental artifacts caused by the microsomes or NADPH. The activation of BaP with the abiotic CYP enzyme increased the cytotoxicity of BaP by a factor of 8, but no activation of p53 was detected. The results indicate that abiotic CYP enzymes may present an alternative to rat liver S9 fraction or microsomes for the metabolic activation of test chemicals, which are completely free of animal-derived components. However, an amendment of existing test guidelines would require testing of more chemicals and genotoxicity end points.
PubMed: 38900731
DOI: 10.1021/acs.chemrestox.4c00101 -
Antimicrobial Agents and Chemotherapy Jun 2024In response to the spread of artemisinin (ART) resistance, ART-based hybrid drugs were developed, and their activity profile was characterized against drug-sensitive and...
In response to the spread of artemisinin (ART) resistance, ART-based hybrid drugs were developed, and their activity profile was characterized against drug-sensitive and drug-resistant parasites. Two hybrids were found to display parasite growth reduction, stage-specificity, speed of activity, additivity of activity in drug combinations, and stability in hepatic microsomes of similar levels to those displayed by dihydroartemisinin (DHA). Conversely, the rate of chemical homolysis of the peroxide bonds is slower in hybrids than in DHA. From a mechanistic perspective, heme plays a central role in the chemical homolysis of peroxide, inhibiting heme detoxification and disrupting parasite heme redox homeostasis. The hybrid exhibiting slow homolysis of peroxide bonds was more potent in reducing the viability of ART-resistant parasites in a ring-stage survival assay than the hybrid exhibiting fast homolysis. However, both hybrids showed limited activity against ART-induced quiescent parasites in the quiescent-stage survival assay. Our findings are consistent with previous results showing that slow homolysis of peroxide-containing drugs may retain activity against proliferating ART-resistant parasites. However, our data suggest that this property does not overcome the limited activity of peroxides in killing non-proliferating parasites in a quiescent state.
PubMed: 38899927
DOI: 10.1128/aac.00143-24 -
Journal of Neurochemistry Jun 20243,4-Methylenedioxymethamphetamine (MDMA, 'ecstasy') is re-emerging in clinical settings as a candidate for the treatment of specific neuropsychiatric disorders (e.g....
3,4-Methylenedioxymethamphetamine (MDMA, 'ecstasy') is re-emerging in clinical settings as a candidate for the treatment of specific neuropsychiatric disorders (e.g. post-traumatic stress disorder) in combination with psychotherapy. MDMA is a psychoactive drug, typically regarded as an empathogen or entactogen, which leads to transporter-mediated monoamine release. Despite its therapeutic potential, MDMA can induce dose-, individual-, and context-dependent untoward effects outside safe settings. In this study, we investigated whether three new methylenedioxy bioisosteres of MDMA improve its off-target profile. In vitro methods included radiotracer assays, transporter electrophysiology, bioluminescence resonance energy transfer and fluorescence-based assays, pooled human liver microsome/S9 fraction incubations, metabolic stability studies, isozyme mapping, and liquid chromatography coupled to high-resolution mass spectrometry. In silico methods included molecular docking. Compared with MDMA, all three MDMA bioisosteres (ODMA, TDMA, and SeDMA) showed similar pharmacological activity at human serotonin, dopamine, and norepinephrine transporters (hSERT, hDAT, and hNET, respectively) but decreased agonist activity at 5-HT receptors. Regarding their hepatic metabolism, they differed from MDMA, with N-demethylation being the only metabolic route shared, and without forming phase II metabolites. In addition, TDMA showed an enhanced intrinsic clearance in comparison to its congeners. Additional screening for their interaction with human organic cation transporters (hOCTs) and plasma membrane monoamine transporter (hPMAT) revealed a weaker interaction of the MDMA analogs with hOCT1, hOCT2, and hPMAT. Our findings suggest that these new MDMA bioisosteres might constitute appealing therapeutic alternatives to MDMA, sparing the primary pharmacological activity at hSERT, hDAT, and hNET, but displaying a reduced activity at 5-HT receptors and alternative hepatic metabolism. Whether these MDMA bioisosteres may pose lower risk alternatives to the clinically re-emerging MDMA warrants further studies.
PubMed: 38898705
DOI: 10.1111/jnc.16149 -
Biochemical and Biophysical Research... Jun 2024The long-term goal of our research is to develop safe and effective soluble epoxide hydrolase (sEH) inhibitors. The objective of this study is to evaluate the potency...
GOAL
The long-term goal of our research is to develop safe and effective soluble epoxide hydrolase (sEH) inhibitors. The objective of this study is to evaluate the potency and selectivity of six natural isothiocyanates (ITCs) as sEH inhibitors.
METHODS
Molecular docking was used to model likely interactions between the ligands and receptors. The sEH inhibitory activity was tested using a validated fluorescence-based assay and PHOME as a substrate. To evaluate their selectivity as sEH inhibitors, the inhibitory potential of the ITCs was determined on microsomal epoxide hydrolase (mEH) and cytochrome P450 (CYP) enzymes in human liver microsomes. Probe substrates such as styrene oxide (mEH substrate) and established substrates for CYP2A6, CYP2C9, CYP2C19, CYP2D6, CYP2E1, and CYP3A4 were used in this study. The metabolites of these substrates were analyzed using validated LC-MS/MS and HPLC-UV assays.
RESULTS
Molecular Docking revealed significant differences in binding site preference among the ITCs in silico and pointed to important interactions between the ligands and the catalytic residues of the sEH enzyme. In vitro, the ITCs showed varying degrees of sEH inhibition, but sulforaphane (SFN) and phenyl isothiocyanate (PITC) were the most potent inhibitors with IC values of 3.65 and 7.5 μM, respectively. mEH was not significantly inhibited by any of the ITCs. Erucin and iberin were the only ITCs that did not inhibit the activity of any of the tested CYP enzymes.
CONCLUSION
Our results demonstrate that natural ITCs have the potential to offer safe, selective, and potent sEH inhibition.
PubMed: 38897040
DOI: 10.1016/j.bbrc.2024.150261 -
Dalton Transactions (Cambridge, England... Jul 2024The search for new metal-based anticancer drug candidates is a fundamental task in medicinal inorganic chemistry. In this work, we assessed the potential of two new...
The search for new metal-based anticancer drug candidates is a fundamental task in medicinal inorganic chemistry. In this work, we assessed the potential of two new Ru(II)-phosphine-mercapto complexes as potential anticancer agents. The complexes, with the formula [Ru(bipy)(dppen)(Lx)]PF [(1), HL1 = 2-mercapto-pyridine and (2), HL2 = 2-mercapto-pyrimidine, bipy = 2,2'-bipyridine, dppen = -1,2-bis(diphenylphosphino)-ethylene] were synthesized and characterized by nuclear magnetic resonance (NMR) [H, P(H), and C], high resolution mass spectrometry (HR-MS), cyclic voltammetry, infrared and UV-Vis spectroscopies. Complex 2 was obtained as a mixture of two isomers, 2a and 2b, respectively. The composition of these metal complexes was confirmed by elemental analysis and liquid chromatography-mass spectrometry (LC-MS). To obtain insights into their lipophilicity, their distribution coefficients between -octanol/PBS were determined. Both complexes showed affinity mainly for the organic phase, presenting positive log values. Also, their stability was confirmed over 48 h in different media (, DMSO, PBS and cell culture medium) HPLC, UV-Vis and P{H} NMR spectroscopies. Since enzymes from the P-450 system play a crucial role in cellular detoxification and metabolism, the microsomal stability of 1, which was found to be the most interesting compound of this study, was investigated using human microsomes to verify its potential oxidation in the liver. The analyses by LC-MS and ESI-MS reveal three main metabolites, obtained by oxidation in the dppen and bipy moieties. Moreover, 1 was able to interact with human serum albumin (HSA). The cytotoxicity of the metal complexes was tested in different cancerous and non-cancerous cell lines. Complex 1 was found to be more selective than cisplatin against MDA-MB-231 breast cancer cells when compared to MCF-10A non-cancerous cells. In addition, complex 1 affects cell morphology and migration, and inhibits colony formation in MDA-MB-231 cells, making it a promising cytotoxic agent against breast cancer.
Topics: Humans; Antineoplastic Agents; Phosphines; Ruthenium; Coordination Complexes; Cell Line, Tumor; Sulfhydryl Compounds; Cell Proliferation; Cell Survival; Drug Screening Assays, Antitumor; Molecular Structure
PubMed: 38895770
DOI: 10.1039/d4dt01191k -
Molecules (Basel, Switzerland) Jun 2024GSK-3β, IKK-β, and ROCK-1 kinases are implicated in the pathomechanism of Alzheimer's disease due to their involvement in the misfolding and accumulation of amyloid β...
Connecting GSK-3β Inhibitory Activity with IKK-β or ROCK-1 Inhibition to Target Tau Aggregation and Neuroinflammation in Alzheimer's Disease-Discovery, In Vitro and In Cellulo Activity of Thiazole-Based Inhibitors.
GSK-3β, IKK-β, and ROCK-1 kinases are implicated in the pathomechanism of Alzheimer's disease due to their involvement in the misfolding and accumulation of amyloid β (Aβ) and tau proteins, as well as inflammatory processes. Among these kinases, GSK-3β plays the most crucial role. In this study, we present compound , a novel, remarkably potent, competitive GSK-3β inhibitor (IC = 8 nM, K = 2 nM) that also exhibits additional ROCK-1 inhibitory activity (IC = 2.3 µM) and demonstrates anti-inflammatory and neuroprotective properties. Compound effectively suppresses the production of nitric oxide (NO) and pro-inflammatory cytokines in the lipopolysaccharide-induced model of inflammation in the microglial BV-2 cell line. Furthermore, it shows neuroprotective effects in an okadaic-acid-induced tau hyperphosphorylation cell model of neurodegeneration. The compound also demonstrates the potential for further development, characterized by its chemical and metabolic stability in mouse microsomes and fair solubility.
Topics: tau Proteins; Glycogen Synthase Kinase 3 beta; Alzheimer Disease; Animals; Thiazoles; Humans; rho-Associated Kinases; Mice; I-kappa B Kinase; Neuroprotective Agents; Protein Kinase Inhibitors; Cell Line; Anti-Inflammatory Agents; Microglia; Nitric Oxide; Lipopolysaccharides; Protein Aggregates; Neuroinflammatory Diseases
PubMed: 38893493
DOI: 10.3390/molecules29112616 -
Comparative Biochemistry and... Jun 2024Tizoxanide (TZX) is an active metabolite of nitazoxanide (NTZ) originally developed as an antiparasitic agent, and is predominantly metabolized into TZX glucuronide. In...
Glucuronidation of tizoxanide, an active metabolite of nitazoxanide, in liver and small intestine: Species differences in humans, monkeys, dogs, rats, and mice and responsible UDP-glucuronosyltransferase isoforms in humans.
Tizoxanide (TZX) is an active metabolite of nitazoxanide (NTZ) originally developed as an antiparasitic agent, and is predominantly metabolized into TZX glucuronide. In the present study, TZX glucuronidation by the liver and intestinal microsomes of humans, monkeys, dogs, rats, and mice, and recombinant human UDP-glucuronosyltransferase (UGT) were examined. The kinetics of TZX glucuronidation by the liver and intestinal microsomes followed the Michaelis-Menten or biphasic model, with species-specific variations in the intrinsic clearance (CL). Rats and mice exhibited the highest CL values for liver microsomes, while mice and rats were the highest for intestinal microsomes. Among human UGTs, UGT1A1 and UGT1A8 demonstrated significant glucuronidation activity. Estradiol and emodin inhibited TZX glucuronidation activities in the human liver and intestinal microsomes in a dose-dependent manner, with emodin showing stronger inhibition in the intestinal microsomes. These results suggest that the roles of UGT enzymes in TZX glucuronidation in the liver and small intestine differ extensively across species and that UGT1A1 and/or UGT1A8 mainly contribute to the metabolism and elimination of TZX in humans. This study presents the relevant and novel-appreciative report on TZX metabolism catalyzed by UGT enzymes, which may aid in the assessment of the antiparasitic, antibacterial, and antiviral activities of NTZ for the treatment of various infections.
PubMed: 38889874
DOI: 10.1016/j.cbpc.2024.109962 -
Biopharmaceutics & Drug Disposition Jun 2024Icaritin is a prenylflavonoid derivative of the genus Epimedium (Berberidaceae) and has a variety of pharmacological actions. Icaritin is approved by the National...
Icaritin is a prenylflavonoid derivative of the genus Epimedium (Berberidaceae) and has a variety of pharmacological actions. Icaritin is approved by the National Medical Products Administration as an anticancer drug that exhibits efficacy and safety advantages in patients with hepatocellular carcinoma cells. This study aimed to evaluate the inhibitory effects of icaritin on UDP-glucuronosyltransferase (UGT) isoforms. 4-Methylumbelliferone (4-MU) was employed as a probe drug for all the tested UGT isoforms using in vitro human liver microsomes (HLM). The inhibition potentials of UGT1A1 and 1A9 in HLM were further tested by employing 17β-estradiol (E2) and propofol (PRO) as probe substrates, respectively. The results showed that icaritin inhibits UGT1A1, 1A3, 1A4, 1A7, 1A8, 1A10, 2B7, and 2B15. Furthermore, icaritin exhibited a mixed inhibition of UGT1A1, 1A3, and 1A9, and the inhibition kinetic parameters (K) were calculated to be 3.538, 2.117, and 0.306 (μM), respectively. The inhibition of human liver microsomal UGT1A1 and 1A9 both followed mixed mechanism, with K values of 2.694 and 1.431 (μM). This study provides supporting information for understanding the drug-drug interaction (DDI) potential of the flavonoid icaritin and other UGT-metabolized drugs in clinical settings. In addition, the findings provide safety evidence for DDI when liver cancer patients receive a combination therapy including icaritin.
Topics: Glucuronosyltransferase; Humans; Flavonoids; Microsomes, Liver; Drug Interactions; Estradiol; Hymecromone; Propofol; Enzyme Inhibitors
PubMed: 38886878
DOI: 10.1002/bdd.2397 -
Bioscience, Biotechnology, and... Jun 2024Dinophysistoxin 1 (DTX1, 1) and okadaic acid (OA, 2), produced by the dinoflagellates Dinophysis spp. and Prorocentrum spp., are primary diarrhetic shellfish toxins...
Dinophysistoxin 1 (DTX1, 1) and okadaic acid (OA, 2), produced by the dinoflagellates Dinophysis spp. and Prorocentrum spp., are primary diarrhetic shellfish toxins (DSTs), which may cause gastric illness in people consuming such as bivalves. Both compounds convert to dinophysistoxin 3 (DTX3, 3; generic name for 1 and 2 with fatty acids conjugated at 7-OH) in bivalves. The enzyme okadaic acid O-acyl transferase (OOAT) is a membrane protein found in the microsomes of the digestive glands of bivalves. In this study, we established an in vitro enzymatic conversion reaction using 4-nitro-2,1,3-benzoxadiazole (NBD)-OA (4), an OA derivative conjugated with (R)-(-)-4-nitro-7-(3-aminopyrrolidin-1-yl)-2,1,3-benzoxadiazole (NBD-APy) on 1-CO2H, as a substrate. We detected the enzymatically produced 3, NBD-7-O-palmitoyl-OA (NBD-Pal-OA), using high-performance liquid chromatography-fluorescence detection. We believe that an OOAT assay using 4 will facilitate the fractionation and isolation of OOAT in the future.
PubMed: 38886126
DOI: 10.1093/bbb/zbae085 -
Chemical Research in Toxicology Jun 2024Chlortoluron (CTU) is an herbicide extensively used in agricultural settings for crop cultivation. Its presence in water has been identified as a pollutant detrimental...
Chlortoluron (CTU) is an herbicide extensively used in agricultural settings for crop cultivation. Its presence in water has been identified as a pollutant detrimental to aquatic species. The objective of the present study was to explore the metabolic activation and hepatotoxicity of CTU. Through human and rat liver microsomal incubations supplemented with CTU, nicotinamide adenine dinucleotide phosphate (NADPH), and either glutathione or -acetyl cysteine, a benzylic alcohol metabolite (M1) was discerned, alongside a phenol metabolite (M2), a glutathione conjugate (M3), and an -acetyl cysteine conjugate (M4). In rats exposed to CTU, biliary M3 and urinary M4 were detected in their bile and urine, respectively. The generation of M1 was detected in the presence of NADPH. The observation of M3 and M4 suggests the formation of an iminoquinone methide intermediate arising from the oxidation of M1. CYP3A4 was found to be the principal enzyme catalyzing the metabolic activation of CTU. Furthermore, CTU exhibited cytotoxic properties in cultured rat primary hepatocytes in a concentration-dependent pattern. Concomitant treatment of hepatocytes with ketoconazole mitigated their susceptibility to the cytotoxic effects of CTU.
PubMed: 38885202
DOI: 10.1021/acs.chemrestox.3c00351