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Autoimmune hepatitis (AIH) is a chronic inflammatory liver disease treated by steroids and immunomodulator thiopurine drugs such as azathioprine (AZA). AZA is metabolized in the human body into bioactive forms such as 6-thioguanine (6-TG) and 6-methyl-mercaptopurine (6-MMP). Monitoring the levels of bioactive AZA metabolites is very important for proper treatment of patients. In this study, our aim was to develop and validate a fast and sensitive ultra-high performance liquid chromatography–mass spectrometry (UHPLC–MS) method for the analysis of 6-TG and 6-MMP from blood samples of patients with AIH to monitor the level of these bioactive metabolites. The detection and quantification of the analytes was carried out by Selected Reaction Monitoring (SRM)-based targeted mass spectrometry. The method was validated according to the EMA guidelines. Blood samples from patients with AIH treated with AZA were analysed with the developed method. The method was successfully validated with appropriate accuracy and precision for the target biomolecules and their concentration in the samples from patients with AIH was determined. The developed and validated UHPLC–MS method enables the fast and precise analysis of AZA metabolites. [ABSTRACT FROM AUTHOR]

6-thioguanine (6-TG) is an antimetabolite drug of purine structure, approved by the FDA for the treatment of acute myeloid lesukemia, and it is of interest in treating other diseases. The interaction of drugs with matrices is of interest to achieving a delayed, sustained, and local release. The interaction of 6-TG with an aluminum metal–organic framework (Al-MOF) DUT-4 is studied using a novel experimental approach, namely, mechano-chemistry by liquid-assisted grinding (LAG). The bonding of 6-TG to the DUT-4 matrix in the composite (6-TG)(DUT-4) was studied using ATR-FTIR spectroscopy and XRD. This interaction involves amino groups and C and N atoms of the heterocyclic ring of 6-TG, as well as the carboxylate COO− and (Al)O-H groups of the matrix, indicating the formation of the complex. Next, an in vitro delayed release of 6-TG was studied from composite powder versus pure 6-TG in phosphate buffered saline (PBS) at 37 °C. Herein, an automated drug dissolution apparatus with an autosampler was utilized, and the molar concentration of the released 6-TG was determined using an HPLC–UV analysis. Pure 6-TG shows a quick (<300 min) dissolution, while the composite gives the dissolution of non-bonded 6-TG, followed by a significantly (factor 6) slower release of the bonded drug. Each step of the release follows the kinetic pseudo-first-order rate law with distinct rate constants. Then, a pharmaceutical shaped body was prepared from the composite, and it yields a significantly delayed release of 6-TG for up to 10 days; a sustained release is observed with the 6-TG concentration being within the therapeutically relevant window. Finally, the composite shows a time-dependent (up to 9 days) stronger inhibition of leukemia MV-4-11 cell colonies than 6-TG. [ABSTRACT FROM AUTHOR]

In this work, a novel Fe, Ni bimetallic porous coordination polymers (PCPs) was synthesized, featuring a ligand composed of N, S-rich 6-thioguanine. Through bimetallic synergistic catalysis and self-sulfurization, this bimetallic PCPs transforms into N, S co-doped carbon (NSC)-coated (Fe,Ni) 9 S 8 /Ni 3 S 2 bridged nanowires. Due to N, S co-doped (Fe,Ni) 9 S 8 /Ni 3 S 2 @NSC bridged nanowires, additional electrocatalytic active sites are provided, while the interconnected nanowires simultaneously enhance the overall conductivity of the catalyst. The as-obtained (Fe,Ni) 9 S 8 /Ni 3 S 2 @NSC exhibits excellent OER performance, with an overpotential as low as 252 mV at a current density of 10 mA cm−2. [Display omitted] • In this work, a novel Fe, Ni bimetallic porous coordination polymers (PCPs) was synthesized, featuring a ligand composed of N, S-rich 6-thioguanine. • Through bimetallic synergistic catalysis and self-sulfurization, the bimetallic PCPs transforms into N, S co-doped carbon (NSC)-coated (Fe,Ni) 9 S 8 /Ni 3 S 2 bridged nanowires. • This work indicates that metal sulfides bridged nanowires are an effective method for improving the overall conductivity of electrocatalysts and enhancing electrocatalytic performance. Improving the conductivity of the electrocatalyst itself is essential for enhancing its performance. In this work, N, S-rich 6-thioguanine (TG) is selected as the ligand to synthesize a Fe, Ni bimetallic porous coordination polymer (PCP), which is then derived to fabricate N,S codoped carbon (NSC)-coated (Fe,Ni) 9 S 8 /Ni 3 S 2 bridged nanowires. The (Fe,Ni) 9 S 8 /Ni 3 S 2 @NSC bridged nanowires obtained through bimetallic synergistic catalysis and self-sulfurization processes not only introduced additional electrocatalytic active sites but also significantly enhance the overall conductivity of the catalyst due to the interconnected nanowire structure. The resulting (Fe,Ni) 9 S 8 /Ni 3 S 2 @NSC demonstrates remarkable oxygen evolution reaction (OER) performance, exhibiting an overpotential as low as 252 mV at a current density of 10 mA cm−2. This work proposes a novel strategy for enhancing the overall conductivity of catalysts by growing bridged nanowires, providing valuable insights and inspiration for the design and preparation of advanced transition metal sulfide electrocatalysts. [ABSTRACT FROM AUTHOR]

Organic heterocyclic corrosion inhibitors play a crucial role in the non-destructive protection of excavated bronze relics exposed to the atmosphere. However, the current selection of corrosion inhibitors, additives, and dosage requires further investigation. This study involves a comprehensive preparation simulation of electrode materials and atmospheric corrosion electrolytes. The corrosion inhibition performance of 6-thioguanine (6-Tg) and traditional benzotriazole (BTA) inhibitors at pH = 7.5 is explored. Analytical techniques such as potentiodynamic polarization, EIS, XRD, XPS, and SEM-EDS were employed to analyze the characteristics of the research electrode materials. Surface analysis reveals that 6-Tg forms a protective corrosion inhibition film on the surface of the covered patina electrode, influencing the transition of Cu2(OH)3Cl to the more stable Cu2(OH)2CO3 crystal. Electrochemical results demonstrate that, after 600 h in the corrosion solution containing 0.1 g/L of 6-Tg, the corrosion potential and corrosion current reach 0.244 V and 4.9 μA cm−2, respectively. Upon adding 1.2 g/L of NaH2PO4, the polarization resistance and inhibiting efficiencies reach 15.6 kΩ cm2 and 99%, resulting in a synergistic corrosion inhibition effect and passivation potential shift from −0.6 V to 0.2 V region.

Introduction: The purine analog 6-thioguanine (6TG), an old drug approved in the 60s to treat acute myeloid leukemia (AML), was tested in the diabetic retinopathy (DR) experimental in vivo setting along with a molecular modeling approach. Methods: A computational analysis was performed to investigate the interaction of 6TG with MC1R and MC5R. This was confirmed in human umbilical vein endothelial cells (HUVECs) exposed to high glucose (25 mM) for 24 h. Cell viability in HUVECs exposed to high glucose and treated with 6TG (0.05-0.5-5 µM) was performed. To assess tube formation, HUVECs were treated for 24 h with 6TG 5 µM and AGRP (0.5-1-5 µM) or PG20N (0.5-1-5-10 µM), which are MC1R and MC5R antagonists, respectively. For the in vivo DR setting, diabetes was induced in C57BL/6J mice through a single streptozotocin (STZ) injection. After 2, 6, and 10 weeks, diabetic and control mice received 6TG intravitreally (0.5-1-2.5 mg/kg) alone or in combination with AGRP or PG20N. Fluorescein angiography (FA) was performed after 4 and 14 weeks after the onset of diabetes. After 14 weeks, mice were euthanized, and immunohistochemical analysis was performed to assess retinal levels of CD34, a marker of endothelial progenitor cell formation during neo-angiogenesis. Results: The computational analysis evidenced a more stable binding of 6TG binding at MC5R than MC1R. This was confirmed by the tube formation assay in HUVECs exposed to high glucose. Indeed, the anti-angiogenic activity of 6TG was eradicated by a higher dose of the MC5R antagonist PG20N (10 µM) compared to the MC1R antagonist AGRP (5 µM). The retinal anti-angiogenic effect of 6TG was evident also in diabetic mice, showing a reduction in retinal vascular alterations by FA analysis. This effect was not observed in diabetic mice receiving 6TG in combination with AGRP or PG20N. Accordingly, retinal CD34 staining was reduced in diabetic mice treated with 6TG. Conversely, it was not decreased in diabetic mice receiving 6TG combined with AGRP or PG20N. Conclusion: 6TG evidenced a marked anti-angiogenic activity in HUVECs exposed to high glucose and in mice with DR. This seems to be mediated by MC1R and MC5R retinal receptors. [ABSTRACT FROM AUTHOR]

6-thioguanine (6-TG) is an antimetabolite drug of purine structure, approved by the FDA for the treatment of acute myeloid lesukemia, and it is of interest in treating other diseases. The interaction of drugs with matrices is of interest to achieving a delayed, sustained, and local release. The interaction of 6-TG with an aluminum metal–organic framework (Al-MOF) DUT-4 is studied using a novel experimental approach, namely, mechano-chemistry by liquid-assisted grinding (LAG). The bonding of 6-TG to the DUT-4 matrix in the composite (6-TG)(DUT-4) was studied using ATR-FTIR spectroscopy and XRD. This interaction involves amino groups and C and N atoms of the heterocyclic ring of 6-TG, as well as the carboxylate COO− and (Al)O-H groups of the matrix, indicating the formation of the complex. Next, an in vitro delayed release of 6-TG was studied from composite powder versus pure 6-TG in phosphate buffered saline (PBS) at 37 °C. Herein, an automated drug dissolution apparatus with an autosampler was utilized, and the molar concentration of the released 6-TG was determined using an HPLC–UV analysis. Pure 6-TG shows a quick (

Introduction:The purine analog 6-thioguanine (6TG), an old drug approved in the 60s to treat acute myeloid leukemia (AML), was tested in the diabetic retinopathy (DR) experimental in vivo setting along with a molecular modeling approach.Methods:A computational analysis was performed to investigate the interaction of 6TG with MC1R and MC5R. This was confirmed in human umbilical vein endothelial cells (HUVECs) exposed to high glucose (25 mM) for 24 h. Cell viability in HUVECs exposed to high glucose and treated with 6TG (0.05–0.5–5 µM) was performed. To assess tube formation, HUVECs were treated for 24 h with 6TG 5 µM and AGRP (0.5–1–5 µM) or PG20N (0.5–1–5–10 µM), which are MC1R and MC5R antagonists, respectively. For the in vivo DR setting, diabetes was induced in C57BL/6J mice through a single streptozotocin (STZ) injection. After 2, 6, and 10 weeks, diabetic and control mice received 6TG intravitreally (0.5–1–2.5 mg/kg) alone or in combination with AGRP or PG20N. Fluorescein angiography (FA) was performed after 4 and 14 weeks after the onset of diabetes. After 14 weeks, mice were euthanized, and immunohistochemical analysis was performed to assess retinal levels of CD34, a marker of endothelial progenitor cell formation during neo-angiogenesis.Results:The computational analysis evidenced a more stable binding of 6TG binding at MC5R than MC1R. This was confirmed by the tube formation assay in HUVECs exposed to high glucose. Indeed, the anti-angiogenic activity of 6TG was eradicated by a higher dose of the MC5R antagonist PG20N (10 µM) compared to the MC1R antagonist AGRP (5 µM). The retinal anti-angiogenic effect of 6TG was evident also in diabetic mice, showing a reduction in retinal vascular alterations by FA analysis. This effect was not observed in diabetic mice receiving 6TG in combination with AGRP or PG20N. Accordingly, retinal CD34 staining was reduced in diabetic mice treated with 6TG. Conversely, it was not decreased in diabetic mice receiving 6TG combined with AGRP or PG20N.Conclusion:6TG evidenced a marked anti-angiogenic activity in HUVECs exposed to high glucose and in mice with DR. This seems to be mediated by MC1R and MC5R retinal receptors.

The mechanisms for the deamination reactions of 6-thioguanine (6-TG) with H2O, OH−, and OH−/H2O and for protonated 6-thioguanine (6-TGH+) with H2O have been studied by theoretical calculations. Six pathways, paths A–F, have been explored and relative energies, enthalpies, and Gibbs energies were calculated for each reaction path. Compared with the deamination reaction of 6-TG with H2O or 6-TGH+ with H2O, the deamination reaction of 6-TG with OH− shows a lower overall Gibbs energy of activation, indicating that the 6-TG deamination reaction is favorably to occur for the deprotonated form 6-TG− with H2O. With the assistance of an additional water molecule, the deamination reaction of 6-TG with OH−/H2O (path F) is found to be the most feasible pathway in gas phase and also in aqueous solution. The overall Gibbs energy of activation for path F in gas phase and in aqueous solution is 169.8 and 140.6 kJ mol−1 (SMD model), respectively, at the B3LYP/6–311++G(d,p) level of theory. [ABSTRACT FROM AUTHOR]

Nanoparticle‐based polymeric carriers are highly desirable for efficient delivery of hydrophobic drugs. The development of nanocarriers with high encapsulation efficiency synthesized by a simple emulsification technique has become a challenging task with their controlled and sustained release ability at disease sites. Here, we have synthesized a series of hydrophobically modified hyaluronic–dodecylamide (HD) conjugates by coupling dodecylamine onto hyaluronic acid in varying amounts and characterized them using physicochemical techniques. The synthesized HD conjugates, in an aqueous medium, self‐assembled into nanoparticles of size in the range of ca 189–355 nm with hydrophilic surface and hydrophobic core. 6‐Thioguanine (TG) was used as a model drug for encapsulation into the hydrophobic core of the conjugate (HD‐2) by the standard emulsification technique with high encapsulation efficiency. Spectrophotometric analysis revealed that the drug‐loaded nanoconjugate showed a sustained release of drug over a period of time and also showed enzymatic responsiveness towards hyaluronidase. In vitro experiments were performed with HEK293, HeLa and HepG2 cells and it was observed that drug‐loaded nanoparticles were more toxic towards cancerous cells as compared with free TG. These results advocate that the reported system, being biocompatible, could be used as promising anticancer drug delivery system. © 2022 Society of Industrial Chemistry. [ABSTRACT FROM AUTHOR]

Abstract Background A critical challenge in current acute lymphoblastic leukemia (ALL) therapy is treatment intensification in order to reduce the relapse rate in the subset of patients at the highest risk of relapse. The year-long maintenance phase is essential in relapse prevention. The Thiopurine Enhanced ALL Maintenance (TEAM) trial investigates a novel strategy for ALL maintenance. Methods TEAM is a randomized phase 3 sub-protocol to the ALLTogether1 trial, which includes patients 0–45 years of age with newly diagnosed B-cell precursor or T-cell ALL, and stratified to the intermediate risk-high (IR-high) group, in 13 European countries. In the TEAM trial, the traditional methotrexate (MTX)/6-mercaptopurine (6MP) maintenance backbone (control arm) is supplemented with low dose (2.5–12.5 mg/m2/day) oral 6-thioguanine (6TG) (experimental arm), while the starting dose of 6MP is reduced from 75 to 50 mg/m2/day. A total of 778 patients will be included in TEAM during ~ 5 years. The study will close when the last included patient has been followed for 5 years from the end of induction therapy. The primary objective of the study is to significantly improve the disease-free survival (DFS) of IR-high ALL patients by adding 6TG to 6MP/MTX-based maintenance therapy. TEAM has 80% power to detect a 7% increase in 5-year DFS through a 50% reduction in relapse rate. DFS will be evaluated by intention-to-treat analysis. In addition to reducing relapse, TEAM may also reduce hepatotoxicity and hypoglycemia caused by high levels of methylated 6MP metabolites. Methotrexate/6MP metabolites will be monitored and low levels will be reported back to clinicians to identify potentially non-adherent patients. Discussion TEAM provides a novel strategy for maintenance therapy in ALL with the potential of improving DFS through reducing relapse rate. Potential risk factors that have been considered include hepatic sinusoidal obstruction syndrome/nodular regenerative hyperplasia, second cancer, infection, and osteonecrosis. Metabolite monitoring can potentially increase treatment adherence in both treatment arms. Trial registration EudraCT, 2018–001795-38. Registered 2020-05-15, Clinicaltrials.gov , NCT04307576 . Registered 2020-03-13, https://clinicaltrials.gov/ct2/show/NCT04307576

Inflammatory bowel disease (IBD), once considered a disease of the Western hemisphere, has emerged as a global disease. As the disease prevalence is on a steady rise, management of IBD has come under the spotlight. 5-Aminosalicylates, corticosteroids, immunosuppressive agents and biologics are the backbone of treatment of IBD. With the advent of biologics and small molecules, the need for surgery and hospitalization has decreased. However, economic viability and acceptability is an important determinant of local prescription patterns. Nearly one-third of the patients in West receive biologics as the first/initial therapy. The scenario is different in developing countries where biologics are used only in a small proportion of patients with IBD. Increased risk of reactivation of tuberculosis and high cost of the therapy are limitations to their use. Thiopurines hence become critical for optimal management of patients with IBD in these regions. However, approximately one-third of patients are intolerant or develop adverse effects with their use. This has led to suboptimal use of thiopurines in clinical practice. This review article discusses the clinical aspects of thiopurine use in patients with IBD with the aim of optimizing their use to full therapeutic potential.

A facile, low-cost, and reliable visual method, based on 6-thioguanine (6-TG) functionalized gold nanoparticles (AuNPs), is introduced for highly sensitive and selective determination of dopamine. In this method, the hydrogen-bonding identification between 6-TG and dopamine can induce the collection of the functionalized AuNPs, causing the color of AuNPs to change from wine red to blue. Therefore, the presence of dopamine can be identified with bare eyes. Moreover, the concentration of dopamine can be quantitatively detected by a UV–vis spectrophotometer. Experiments reveal that in the range from 0.01 to 4 μM, the ratio of the peak at 650 and 520 nm (A650/A520) is linearly proportional to the dopamine concentration, with a lower limit of detection (LOD) of 4.6 nM (S/N = 3). In addition, the selective experiment reveals that the developed method shows high specificity. Meanwhile, this method can be used for the determination of trace levels of dopamine in practical samples, and it reveals a satisfied result. In conclusion, the proposed method is simple and convenient without any tedious treatment processes and sophisticated instruments. Furthermore, the designed method would provide a detection pathway for other organic interring species and make a valuable contribution to improve the visual method. [ABSTRACT FROM AUTHOR]

Background: A critical challenge in current acute lymphoblastic leukemia (ALL) therapy is treatment intensification in order to reduce the relapse rate in the subset of patients at the highest risk of relapse. The year-long maintenance phase is essential in relapse prevention. The Thiopurine Enhanced ALL Maintenance (TEAM) trial investigates a novel strategy for ALL maintenance.Methods: TEAM is a randomized phase 3 sub-protocol to the ALLTogether1 trial, which includes patients 0-45 years of age with newly diagnosed B-cell precursor or T-cell ALL, and stratified to the intermediate risk-high (IR-high) group, in 13 European countries. In the TEAM trial, the traditional methotrexate (MTX)/6-mercaptopurine (6MP) maintenance backbone (control arm) is supplemented with low dose (2.5-12.5 mg/m2/day) oral 6-thioguanine (6TG) (experimental arm), while the starting dose of 6MP is reduced from 75 to 50 mg/m2/day. A total of 778 patients will be included in TEAM during ~ 5 years. The study will close when the last included patient has been followed for 5 years from the end of induction therapy. The primary objective of the study is to significantly improve the disease-free survival (DFS) of IR-high ALL patients by adding 6TG to 6MP/MTX-based maintenance therapy. TEAM has 80% power to detect a 7% increase in 5-year DFS through a 50% reduction in relapse rate. DFS will be evaluated by intention-to-treat analysis. In addition to reducing relapse, TEAM may also reduce hepatotoxicity and hypoglycemia caused by high levels of methylated 6MP metabolites. Methotrexate/6MP metabolites will be monitored and low levels will be reported back to clinicians to identify potentially non-adherent patients.Discussion: TEAM provides a novel strategy for maintenance therapy in ALL with the potential of improving DFS through reducing relapse rate. Potential risk factors that have been considered include hepatic sinusoidal obstruction syndrome/nodular regenerative hyperplasia, second cancer, infection, and osteonecrosis. Metabolite monitoring can potentially increase treatment adherence in both treatment arms.Trial Registration: EudraCT, 2018-001795-38. Registered 2020-05-15, Clinicaltrials.gov , NCT04307576 . Registered 2020-03-13, https://clinicaltrials.gov/ct2/show/NCT04307576. [ABSTRACT FROM AUTHOR]

Monitoring concentrations of thiopurine metabolites is used clinically to prevent adverse effects in patients on thiopurine drug therapy. We developed a LC–MS/MS method for the quantification of 6-thioguanine (6-TG) and 6-methylmercaptopurine (6-MMP) in red blood cells (RBCs). This method utilizes an automated cell washer for RBC separation from whole blood samples and washing of the separated RBCs. The lower limit of quantification of the method was 0.2 μmol/L for 6-TG (∼50 pmol/8 × 108 RBC) and 4 μmol/L for 6-MMP (∼1,000 pmol/8 × 108 RBC). The total imprecision of the assay was <3.0%. The upper limit of linearity for 6-TG and 6-MMP was 7.5 μmol/L and 150 μmol/L, respectively. The stability of the thiopurine metabolites under pre- and post-analytically relevant conditions was also evaluated. A good agreement was observed between this method and validated LC–MS/MS methods from three laboratories, except for ∼40% low bias for 6-MMP observed in one of the methods. The assessment of the association between 6-TG and 6-MMP concentrations with thiopurine S-methyltransferase (TPMT) phenotype and genotype demonstrated a statistically significant difference in the thiopurine metabolite concentrations between the TPMT groups with normal and intermediate activity of 6-MMP (p < 0.0001), while the difference in 6-TG concentrations was statistically not significant (p = 0.096). Among the samples with normal TPMT activity, higher concentrations of 6-MMP (p = 0.015) were observed in pediatric samples than in the samples of adults. No statistically significant differences were observed in the distributions of 6-TG and 6-MMP concentrations among the evaluated genotypes. [ABSTRACT FROM AUTHOR]

The adverse reactions caused by 6-thioguanine (6-TG) in anti-cancer treatment are closely related to the dose, leading to the urgent need for clinical monitoring of its concentration. In this work, a highly reproducible free-standing liquid membrane (FLM) surface-enhanced Raman spectroscopy (SERS) substrate was developed to detect 6-TG in human urine and serum quantitatively. Briefly, a prepared sample was adjusted to pH 2 and mixed with concentrated core–shell bimetallic nanoparticle (AgcoreAushell NP) suspension. The Au/Ag ratio of the AgcoreAushell NPs was optimized. Then the mixture was formed into an FLM using a custom mold. The relative standard deviation (RSD) of the experimental results can be stabilized below 10% (n ≥ 10). The R2 of the calibration curve in the range of 10 ~ 100 μg kg−1 was 0.988. In addition, the limit of detection (LOD) (3σ/k) of 6-TG was 5 μg kg−1. The FLM SERS platform has been successfully applied to the rapid and reliable analysis of 6-TG spiked in body fluids. [ABSTRACT FROM AUTHOR]

Analysis of anticancer drugs is very important and necessary for the correct administration of them in the human body. Electrochemical behavior of 6-thioguanine (6-TG) has been studied using a carbon paste electrode modified by 1-ethyl-3-methylimidazolium tetrafluoroborate (ionic liquid) (1E3MIBF4) and CuO nanoparticles (CuO/1E3MIBF4/CPE). Using square wave voltammetry showed the linear relation between net anodic current and concentration of 6-TG in the range of 70 nmol L-1 to 520 mmol L-1 6-TG with the detection limit of 20 nmol L-1 6-TG. The proposed modified electrode had excellent repeatability (RSD = 1.31%, n = 5) and long term stability (2.9% deviation in 25 days). The diffusion coefficient of 6-TG on the CuO/1E3MIBF4/CPE was found to be 1.54 × 10-5 cm2s−1 .The CuO/1E3MIBF4/CPE was successfully applied for the determination of 6-TG in real samples. In addition, the anodic peaks of 6-TG and fluorouracil (5-FU) in their mixture can be well separated using CuO/1E3MIBF4/CPE and simultaneous determination of them was studied.

Monitoring concentrations of thiopurine metabolites is used clinically to prevent adverse effects in patients on thiopurine drug therapy. We developed a LC–MS/MS method for the quantification of 6-thioguanine (6-TG) and 6-methylmercaptopurine (6-MMP) in red blood cells (RBCs). This method utilizes an automated cell washer for RBC separation from whole blood samples and washing of the separated RBCs. The lower limit of quantification of the method was 0.2 μmol/L for 6-TG (∼50 pmol/8 × 108 RBC) and 4 μmol/L for 6-MMP (∼1,000 pmol/8 × 108 RBC). The total imprecision of the assay was

Inflammatory bowel disease (IBD), once considered a disease of the Western hemisphere, has emerged as a global disease. As the disease prevalence is on a steady rise, management of IBD has come under the spotlight. 5-Aminosalicylates, corticosteroids, immunosuppressive agents and biologics are the backbone of treatment of IBD. With the advent of biologics and small molecules, the need for surgery and hospitalization has decreased. However, economic viability and acceptability is an important determinant of local prescription patterns. Nearly one-third of the patients in West receive biologics as the first/initial therapy. The scenario is different in developing countries where biologics are used only in a small proportion of patients with IBD. Increased risk of reactivation of tuberculosis and high cost of the therapy are limitations to their use. Thiopurines hence become critical for optimal management of patients with IBD in these regions. However, approximately one-third of patients are intolerant or develop adverse effects with their use. This has led to suboptimal use of thiopurines in clinical practice. This review article discusses the clinical aspects of thiopurine use in patients with IBD with the aim of optimizing their use to full therapeutic potential. [ABSTRACT FROM AUTHOR]

ABSTRACT Herpes simplex virus 1 (HSV-1) infects eye corneal tissues leading to herpetic stromal keratitis (HSK), which is one of the leading causes of blindness. Here in our study, we found that 6-thioguanine (6-TG), a once clinically approved medication for child acute myelogenous leukemia, inhibited multiple strains of HSV-1 infection in vitro and in vivo. 6-TG is more potent than acyclovir (ACV) and ganciclovir (GCV), with the 50% inhibitory concentration (IC50) of 6-TG at 0.104 μM with high stimulation index (SI) (SI = 6,475.48) compared to the IC50 of ACV at 1.253 μM and the IC50 of GCV at 1.257 μM. In addition, 6-TG at 500 μM topically applied to the eyes with HSV-1 infection significantly inhibits HSV-1 replication, alleviates virus-induced HSK pathogenesis, and improves eye conditions. More importantly, 6-TG is effective against ACV-resistant HSV-1 strains, including HSV-1/153 and HSV-1/blue. Knockdown of Rac1 with small interfering RNA (siRNA) negatively affected HSV-1 replication, suggesting that Rac1 facilitated HSV-1 replication. Following HSV-1 infection of human corneal epithelial cells (HCECs), endogenous Rac1 activity was upregulated by glutathione S-transferase (GST) pulldown assay. We further found that Rac1 was highly expressed in the corneal tissue of HSK patients compared to normal individuals. Mechanistic study showed that 6-TG inhibited HSV-1 replication by targeting Rac1 activity in HSV-1 infected cells, and the Rac1 is critical in the pathogenesis of HSK. Our results indicated that 6-TG is a promising therapeutic molecule for the treatment of HSK. IMPORTANCE We reported the discovery of 6-TG inhibition of HSV-1 infection and its inhibitory roles in HSK both in vitro and in vivo. 6-TG was shown to possess at least 10× more potent inhibitory activity against HSV-1 than ACV and GCV and, more importantly, inhibit ACV/GCV-resistant mutant viruses. Animal model studies showed that gel-formulated 6-TG topically applied to eyes locally infected with HSV-1 could significantly inhibit HSV-1 replication, alleviate virus-induced HSK pathogenesis, and improve eye conditions. Further study showed that HSV-1 infection upregulated Rac1 expression, and knockdown of Rac1 using siRNA markedly restricted HSV-1 replication, suggesting that Rac1 is required for HSV-1 replication. In addition, we also documented that Rac1 is highly expressed in corneal tissues from HSK patients, indicating that Rac1 is associated with HSK pathogenesis. In view of the high potency of 6-TG, low cytotoxicity, targeting a distinct therapeutic target, we suggest that 6-TG is a potential candidate for development as a therapeutic agent for HSK therapy.

The severe fever with thrombocytopenia syndrome virus (SFTSV) is a novel phlebovirus , recently being officially renamed as Dabie bandavirus, and a causative agent for an emerging infectious disease associated with high fatality. Effective therapeutics and vaccines are lacking and disease pathogenesis is yet to be fully elucidated. In our effort to identify new SFTSV inhibitory molecules, 6-Thioguanine (6-TG) was found to potently inhibit SFTSV infection. 6-TG has been widely used as therapeutic agent since the approval of the Food and Drug Administration in the 1960s. In the current study, we showed that 6-TG was a potent inhibitor of SFTSV infection with 50% effective concentrations (EC 50) of 3.465 μM in VeroE6 cells, and 1.848 μM in HUVEC cells. The selectivity index (SI) was >57 in VeroE6 cells and >108 in HUVEC cells, respectively. The SFTSV RNA transcription, protein synthesis, and progeny virions were reduced in a dose dependent manner by the presence of 6-TG in the in vitro infection assay. Further study on the mechanism of the anti-SFTSV activity showed that 6-TG downregulated the production of early growth response gene-1 (EGR1). Using gene silencing and overexpression, we further confirmed that EGR1 was a host restriction factor against SFTSV. Meanwhile, treatment of infected experimental animals with 6-TG inhibited SFTSV infection and alleviated multi-organ dysfunction. In conclusion, we have identified 6-TG as an effective inhibitor of SFTSV replication via the inhibition of EGR1 expression. Further studies are needed to evaluate of 6-TG as a potential therapeutic for treating SFTS. • 6-TG could significantly inhibit SFTSV infection. • EGR1 was a key regulator of 6-TG for its antiviral effect. • EGR1 was required for SFTSV infection. [ABSTRACT FROM AUTHOR]

Aim: Erwinia amylovora is the causal agent of fire blight, a devastating disease of apples and pears. This study determines whether the E. amylovora guanine–hypoxanthine transporter (EaGhxP) is required for virulence and if it can import the E. amylovora produced toxic analogue 6‐thioguanine (6TG) into cells. Methods and Results: Characterization of EaGhxP in guanine transport deficient Escherichia coli reveals that it can transport guanine, hypoxanthine and the toxic analogues 8‐azaguanine (8AG) and 6TG. Similarly, EaGhxP transports 8AG and 6TG into E. amylovora cells. EaGhxP has a high affinity for 6TG with a Ki of 3·7 µmol l−1. An E. amylovora⊿ghxP::Camr strain shows resistance to growth on 8AG and 6TG. Although EaGhxP is expressed during active disease propagation, it is not necessary for virulence as determined on immature apple and pear assays. Conclusions: EaGhxP is not required for virulence, but it does import 6TG into E. amylovora cells. Significance and impact of the Study: As part of the disease establishment process, E. amylovora synthesizes and exports a toxic guanine derivative 6TG. Our results are counter intuitive and show that EaGhxP, an influx transporter, can move 6TG into cells raising questions regarding the role of 6TG in disease establishment. [ABSTRACT FROM AUTHOR]

Influenza A viruses (IAVs) utilize host shutoff mechanisms to limit antiviral gene expression and redirect translation machinery to the synthesis of viral proteins. Previously, we showed that IAV replication is sensitive to protein synthesis inhibitors that block translation initiation and induce the formation of cytoplasmic condensates of untranslated messenger ribonucleoprotein complexes called stress granules (SGs). In this study, using an image-based high-content screen, we identified two thiopurines, 6-thioguanine (6-TG) and 6-thioguanosine (6-TGo), that triggered SG formation in IAV-infected cells and blocked IAV replication in a dose-dependent manner without eliciting SG formation in uninfected cells. 6-TG and 6-TGo selectively disrupted the synthesis and maturation of the IAV glycoproteins hemagglutinin (HA) and neuraminidase (NA) without affecting the levels of the viral RNAs that encode them. By contrast, these thiopurines had a minimal effect on other IAV proteins or global host protein synthesis. Disruption of IAV glycoprotein accumulation by 6-TG and 6-TGo correlated with the activation of the unfolded protein response (UPR) sensors activating transcription factor 6 (ATF6), inositol-requiring enzyme 1 (IRE1), and double-stranded RNA-activated protein kinase (PKR)-like endoplasmic reticulum (ER) kinase (PERK), leading to downstream UPR gene expression. Treatment of infected cells with the chemical chaperone 4-phenylbutyric acid diminished thiopurine-induced UPR activation and partially restored the processing and accumulation of HA and NA. By contrast, chemical inhibition of the integrated stress response downstream of PERK restored the accumulation of NA monomers but did not restore the processing of viral glycoproteins. Genetic deletion of PERK enhanced the antiviral effect of 6-TG without causing overt cytotoxicity, suggesting that while UPR activation correlates with diminished viral glycoprotein accumulation, PERK could limit the antiviral effects of drug-induced ER stress. Taken together, these data indicate that 6-TG and 6-TGo are effective host-targeted antivirals that trigger the UPR and selectively disrupt the accumulation of viral glycoproteins. [ABSTRACT FROM AUTHOR]

Disulfiram is a promising repurposed drug that, combining with radiation and chemotherapy, exhibits effective anticancer activities in several preclinical models. The cellular metabolites of disulfiram have been established, however, the intracellular targets of disulfiram remain largely unexplored. We have previously reported that disulfiram suppresses the coronaviral papain-like proteases through attacking their zinc-finger domains, suggesting an inhibitory function potentially on other proteases with similar catalytic structures. Ubiquitin-specific proteases (USPs) share a highly-conserved zinc-finger subdomain that structurally similar to the papain-like proteases and are attractive anticancer targets as upregulated USPs levels are found in a variety of tumors. Here, we report that disulfiram functions as a competitive inhibitor for both USP2 and USP21, two tumor-related deubiquitinases. In addition, we also observed a synergistic inhibition of USP2 and USP21 by disulfiram and 6-Thioguanine (6TG), a clinical drug for acute myeloid leukemia. Kinetic analyses revealed that both drugs exhibited a slow-binding mechanism, moderate inhibitory parameters, and a synergistically inhibitory effect on USP2 and USP21, suggesting the potential combinatory use of these two drugs for USPs-related tumors. Taken together, our study provides biochemical evidence for repurposing disulfiram and 6TG as a combinatory treatment in clinical applications. [ABSTRACT FROM AUTHOR]

In this study we suggested a new strategy for drug delivery of 6-thioguanine (6-TG) as a cancer drug by loading of this thiolic drug at a surface of Au nanoparticles. For this goal, we synthesized Au nanoparticle (Au/NPs) by reduction of tetrachloroauric (III) acid solutions by sodium borohydride and characterized Au/NPs by X-ray powder diffraction (XRD), dynamic light scattering (DLS), Ultraviolet–visible spectroscopy (UV-Vis) and transmission electron microscopy (TEM) methods. Results showed good distribution of synthesized Au nanoparticle with diameter ~ 5 nm. In the second step, we loaded 6-thioguanine with strong Au-S bond by addition of this drug to Au nanoparticle suspension and characterized it by UV-Vis method. Furthermore, Au nanoparticle loaded with 6-thioguanine was utilized as a new system against breast cancer cell line (MCF7). IC50 for free 6-thioguanine, unloaded Au nanoparticle and 6-thioguanine loaded Au nanoparticle (6-TG/Au/NPs) were >15.0, 80.0 and 3.5 μg/ml, respectively. The results obtained revealed high cytotoxicity effect of 6-TG/Au/NPs on breast cancer cell line.

Objective(s): This study aimed to investigate the effect of Shogaol on dextran sodium sulfate (DSS)- induced ulcerative colitis (UC) in mice compared to an immune-suppressant chemotherapeutic medicine, known as 6-thioguanine (6-TG). Materials and Methods: Thirty-six adult BALB/c mice were divided into six groups: group 1 (positive control): no DSS exposure and no treatment; group 2 (negative control): DSS exposure without treatment; group 3 (vehicle control): DSS exposure and olive oil treatment; group 4: DSS exposure and 0.3 mg/kg 6-TG treatment; group 5: DSS exposure and 20 mg/kg Shogaol treatment; and group 6: DSS exposure and 40 mg/kg Shogaol treatment. At day 16, the mice were euthanized and UC was evaluated according to colon length, histologically index score and expression scores of the epidermal growth factor receptor (EGFR).Results: The disease activity index (DAI) and histological index scores of mice treated with 40 mg/kg body weight (BW) Shogaol were approximately lower than the corresponding scores of mice treated with 6-TG. In addition, the rate of healing in the former mice was approximately 3 folds higher than that of the latter ones as indicated by the lack of EGFR expression in colonic glands and macrophages. Conclusion: These findings showed that the therapeutic effect of 40 mg/kg BW Shogaol could be better than 6-TG in the treatment of UC, and it may draw the attention regarding the priority of using this cheap plant-derived substance for treatment of the inflammatory bowel diseases because treatment with 6-TG is usually associated with adverse side effects.

Pancreatic cancer is one of the most difficult cancers to cure due to the lack of early diagnostic tools and effective therapeutic agents. In this study, we aimed to isolate new bioactive compounds that effectively kill pancreatic ductal adenocarcinoma (PDAC) cells, but not untransformed, human pancreatic ductal epithelial (HPDE) cells. To this end, we established four primary PDAC cell lines and screened 4141 compounds from four bioactive‐compound libraries. Initial screening yielded 113 primary hit compounds that caused over a 50% viability reduction in all tested PDAC cells. Subsequent triplicate, dose‐dependent analysis revealed three compounds with a tumor cell‐specific cytotoxic effect. We found that these three compounds fall into a single category of thiopurine biogenesis. Among them, 6‐thioguanine (6‐TG) showed an IC50 of 0.39–1.13 μm toward PDAC cells but had no effect on HPDE cells. We propose that this cancer selectivity is due to differences in thiopurine methyltransferase (TPMT) expression between normal and cancer cells. This enzyme is responsible for methylation of thiopurine, which reduces its cytotoxicity. We found that TPMT levels were lower in all four PDAC cell lines than in HPDE or Panc1 cells, and that knockdown of TPMT in HPDE or Panc1 cells sensitized them to 6‐TG. Lastly, we used a patient‐derived xenograft model to confirm that 6‐TG has a significant antitumor effect in combination with gemcitabine. Overall, our study presents 6‐TG as a strong candidate for use as a therapeutic agent against PDAC with low levels of TPMT.

In this study, the electrochemical behavior of an Al–air battery is improved by mixing 6‐thioguanine into 4.0 M NaOH electrolyte. The electrochemical performance of the Al electrodes is analyzed using potentiodynamic polarization, potentiostatic oxidation, and electrochemical impedance spectroscopy. The surface morphology of the Al electrodes after discharging for 1,000 s is characterized using scanning electron microscopy coupled with X‐ray elemental mapping for Al, O, C, N, and S. Furthermore, the utilization efficiencies of these samples are also determined. The results show that the corrosion resistance of the Al electrodes initially increases and then decreases with an increase in 6‐thioguanine concentration. The presence of 6‐thioguanine enhances the corrosion resistance to the maximum, with a corrosion current density (Icorr) of 6.170 mA/cm2, and corrosion inhibition efficiency (η) of 36.56%, at 0.5 mM of 6‐thioguanine. [ABSTRACT FROM AUTHOR]

In this study, the reactivity and electronic sensitivity of the Be12O12, Mg12O12, and Zn12O12 nanoclusters were investigated for 6-thioguanine (TG) anticancer drug using density functional theory calculations at the gas phase and aqueous solution. Our results show that the electronic properties of Mg12O12 and Zn12O12 nanoclusters are significantly sensitive to the presence of TG and the nanoclusters may be a promising candidate for adsorption of this drug. The results show that all complexes are energetically favourable, especially in the aqueous phase. Also, our ultraviolet–visible results show that the electronic spectra of TG/(MO)12 complexes exhibit a blue shift toward lower wavelengths (higher energies). In order to go further and gain insight into the binding features of considered (MO)12 nanoclusters with TG drug, the Atoms in Molecules analysis was performed. Consequently, the results demonstrated that the Mg12O12 and Zn12O12 nanoclusters could be used as potential carriers for the delivery of TG drug. The results represented that the Mg12O12 and Zn12O12 nanoclusters could be used as potential carriers for delivery of 6-thioguanine drug in the nanomedicine domain. [ABSTRACT FROM AUTHOR]

Analysis of anticancer drugs is very important and necessary for the correct administration of them in the human body. Electrochemical behavior of 6-thioguanine (6-TG) has been studied using a carbon paste electrode modified by 1-ethyl-3-methylimidazolium tetrafluoroborate (ionic liquid) (1E3MIBF4) and CuO nanoparticles (CuO/1E3MIBF4/CPE). Using square wave voltammetry showed the linear relation between net anodic current and concentration of 6-TG in the range of 70 nmol L-1 to 520 mmol L-1 6-TG with the detection limit of 20 nmol L-1 6-TG. The proposed modified electrode had excellent repeatability (RSD = 1.31%, n = 5) and long term stability (2.9% deviation in 25 days). The diffusion coefficient of 6-TG on the CuO/1E3MIBF4/CPE was found to be 1.54 x 10-5 cm²s-1. The CuO/1E3MIBF4/CPE was successfully applied for the determination of 6-TG in real samples. In addition, the anodic peaks of 6-TG and fluorouracil (5-FU) in their mixture can be well separated using CuO/1E3MIBF4/CPE and simultaneous determination of them was studied. [ABSTRACT FROM AUTHOR]

This article reports a simple, convenient, and very sensitive method for the determination of 6-thio guanine (6-TG). The basic phenomenon in the proposed method is fluorescence resonance energy transfer, where acridine orange (AO) act as a donor and citrate-stabilized silver nanoparticles (AgNPs) as an acceptor. A noncovalent bond between the surfaces of AgNPs and AO was found, and the effect of fluorescence quenching was observed. The fluorescence spectra of AO recovered after further addition of 6-TG are responsible for the aggregation of AgNPs. Under ideal conditions, the linear relationship of 6-TG in the concentration range of 0.005 to 0.04 μM was displayed, and the limit of detection of 6-TG was obtained as 5.3 nM. Under ideal conditions, the linear relationship of 6-TG was displayed in the concentration range of 0.005 to 0.04 μM, and the limit of detection of 6-TG was obtained as 5.3 nM. The proposed method offers a rapid analysis to determine 6-TG in human serum, blood, and urine samples. [ABSTRACT FROM AUTHOR]

Here, we report a density functional theory (DFT) study on the endohedral metalloborospherenes Li@X4B32 (X = C and Si) as high-performance materials for drug delivery applications. Inspired by a new class of borospherenes which were designed by doping four C atoms in the B364– nanocage (C4B32), we suggest the pristine and Li-doped C4B32 and Si4B32 nanoclusters as suitable materials for drug delivery applications. The main objective of the present work is to investigate the interaction of pristine X4B32 and Li@X4B32 nanoclusters with an anticancer drug (6-thioguanine) by DFT. Our ultraviolet–visible calculations reveal that the electronic spectra of the drug/nanocluster complexes show a red shift toward higher wavelengths (lower energies). To gain insight into the binding features of the studied nanoclusters with 6-thioguanine drug, the atoms in molecules analysis was performed. Our results determine the electrostatic nature of the 6-thioguanine/Li@C4B32 bonding. Consequently, our results represented that the Li@C4B32 could be a potential carrier for delivery of 6-thioguanine. [ABSTRACT FROM AUTHOR]

6-Thioguanine encapsulated chitosan nanoparticles (6-TG-CNPs) has formulated by the ionic-gelation method. Morphologically, the 6-TG-CNPs were spherical and showed mean size, PDI, z eta potential, and entrapment efficiency of 261.63 ± 6.01 nm, 0.34 ± 0.10, +15.97 ± 0.46 mV and 44.27%, respectively. The IR spectra confirmed the 6-TG complex with chitosan. The in vitro drug release profile of 6-TG-CNPs revealed an increase in sustained-release (91.40 ± 1.08% at 48 h) at pH 4.8 compared to less sustained-release (73.96 ± 1.12% at 48 h) at pH 7.4. The MTT assay was conducted on MCF-7 and PA-1 cell lines at 48 h incubation to determine % cell viability. The IC 50 values of 6-TG, 6-TG-CNPs, and curcumin for MCF-7 were 23.09, 17.82, and 15.73 μM, respectively. Likewise, IC 50 values of 6-TG, 6-TG-CNPs, and curcumin for PA-1 were 5.81, 3.92, and 12.89 μM, respectively. A combination of 6-TG-CNPs (IC 25) with curcumin (IC 25) on PA-1 and MCF-7 showed % cell viability of 43.67 ± 0.02 and 49.77 ± 0.05, respectively. The in vitro cytotoxicity potential in terms of % cell viability, early apoptosis, G2/M phase arrest, and DNA demethylating activity of 6-TG-CNPs alone and combination with curcumin proved to be more effective than that of 6-TG on PA-1 cells. [ABSTRACT FROM AUTHOR]

• Metal encapsulated improved 6-TG adsorption. • The desorption times of the 6-TG molecule are very short. • Solvent effects increase interaction and solubility in biological medium. • B40 and M@B40 have the potential of delivery of 6-TG anticancer drug. In the recent years all boron fullerene have been noticed as drug delivery system. Due to the fact that so far metal encapsulated fullerenes has not been investigated as a carrier of 6-Thioguanine(6-TG), therefore in this study, adsorption behavior of (TG) on the B 40 and M@ B 40 (M = Mg and K) fullerene was investigated through density functional theory (DFT). We found that the 6-TG interacts with the M@ B 40 fullerene stronger than bare B40 fullerene in the gas and water phases. The calculated adsorption energies are about −14.2, –22.5 and −15.7 kcalmol−1for B40, Mg@B40 and K@ B 40 respectively. Dipole moment of encapsulated complexes enhanced by 50 % and 80 % in the gas and water phase respectively. The calculated energy gap (Eg) and the other reactivity parameters indicates that, reactivity of B40 fullerene was enhanced in presence alkaline and alkaline earth metal. In the result, B 40 , Mg@ B 40 and K@ B 40 fullerenes have the potential of delivery of 6-TG anticancer drug. [ABSTRACT FROM AUTHOR]

Hematopoietic stem/progenitor cell (HSPC)-based anti-HIV-1 gene therapy holds great promise to eradicate HIV-1 or to provide long-term remission through a continuous supply of anti-HIV-1 gene-modified cells without ongoing antiretroviral therapy. However, achieving sufficient engraftment levels of anti-HIV gene-modified HSPC to provide therapeutic efficacy has been a major limitation. Here, we report an in vivo selection strategy for anti-HIV-1 gene-modified HSPC by introducing 6-thioguanine (6TG) chemoresistance through knocking down hypoxanthine-guanine phosphoribosyl transferase (HPRT) expression using RNA interference (RNAi). We developed a lentiviral vector capable of co-expressing short hairpin RNA (shRNA) against HPRT alongside two anti-HIV-1 genes: shRNA targeting HIV-1 co-receptor CCR5 and a membrane-anchored HIV-1 fusion inhibitor, C46, for efficient in vivo selection of anti-HIV-1 gene-modified human HSPC. 6TG-mediated preconditioning and in vivo selection significantly enhanced engraftment of HPRT-knockdown anti-HIV-1 gene-modified cells (>2-fold, p < 0.0001) in humanized bone marrow/liver/thymus (huBLT) mice. Viral load was significantly reduced (>1 log fold, p < 0.001) in 6TG-treated HIV-1-infected huBLT mice compared to 6TG-untreated mice. We demonstrated that 6TG-mediated preconditioning and in vivo selection considerably improved engraftment of HPRT-knockdown anti-HIV-1 gene-modified HSPC and repopulation of anti-HIV-1 gene-modified hematopoietic cells in huBLT mice, allowing for efficient HIV-1 inhibition., Competing Interests: Declaration of interests D.S.A. has a financial interest in CSL Behring. D.S.A. and S.S. hold US and Japanese patents US20210310007A1 and the University of California Board of Regents has licensed that intellectual property to CSL Behring. No funding was provided by these companies to support this work. All of the other authors declare no competing interests., (Copyright © 2023. Published by Elsevier Inc.)

The purpose of the presented work was to modify the surface of core/shell-type CdSexS1–x/ZnS quantum dots (QDs) with an anticancer drug to form bifunctional nanoconjugate for imaging and drug delivery. 6-Thioguanine (6-TG) which is used to treat acute myeloid and lymphoblastic leukemia was applied for this aim. The modification of the nanocrystals was carried out using a biphasic method, based on transferring of QDs from the organic phase to the aqueous one with the simultaneous exchange of hydrophobic ligand to the hydrophilic one. To enable a complex evaluation of 6-TG bioactivity, the surface of quantum dots was also modified using mercaptoacetic acid (MAA). Mercaptoacetic acid was chosen as a biologically neutral ligand; so, it was possible to evaluate the effect of nanocrystals toxicity without the participation of the drug (6-TG ligand versus neutral ligand). Moreover, the effect of 6-TG itself on cells was also studied. The studies were carried out on three cell lines: K562 (human myeloid leukemia), A549 (human lung cancer cells) and MRC-5 (normal human lung cells). Evaluation of the cytotoxicity of nanostructures, at various concentrations, was carried out after 24- and 48-h incubation of the cell culture with nanoparticles/drug solutions. MTT and the Alamar Blue assays were used to determine cell viability. Based on the cytotoxicity measurements, it was found that quantum dots modified with 6-TG are more toxic than the drug itself or QDs modified with 3-mercaptoacetic acid. Images taken using fluorescence and confocal microscopy allowed to define the location of examined QDs inside cells. [ABSTRACT FROM AUTHOR]

Therapeutic drug monitoring of azathioprine metabolites is required for pharmacotherapy individualisation in patients with inflammatory bowel disease. Currently mainly hemolysates are used, requiring long sample preparation and showing limited analytes stability. Therefore, a quantitative LC-MS/MS method for determination of 6-thioguanine (6-TG) and 6-methylmercaptopurine (6-MMP) in dried blood spot samples (DBS) was developed. Analysis involves liquid extraction from 30 μL blood spot, hydrolysis and quantification with LC-MS/MS. Method met the validation criteria in terms of selectivity, linearity, accuracy, and precision in a range from 50 to 5300 pmol/8 × 108 Ery for 6-TG and from 260 to 5300 pmol/8 × 108 Ery for 6-MMP. Range can be increased to 8000 pmol/8 × 108 Ery. No matrix effect was observed and the recovery was >80%. DBS specific validation parameters were confirmed: spot homogeneity, no influence of blood spot volume (>30 μL) on 6 mm DBS disk, and absence of haematocrit effect. DBS samples were stable for at least one month at temperatures from −20 to 40 °C. Clinical validation confirmed that DBS method and routine clinical method with hemolysate samples give comparable results and enable similar clinical decisions. The newly developed DBS method is simple and presents an alternative to conventional methods for therapeutic drug monitoring of azathioprine metabolites. • DBS method for measuring 6-TG and 6-MMP levels in patients with IBD was developed. • Analysis involves liquid extraction, hydrolysis and quantification with LC-MS/MS. • Method meets general and DBS specific validation criteria. • DBS method and routine method using hemolysate enable similar clinical decisions. • New DBS method is simple and presents an alternative to conventional methods. [ABSTRACT FROM AUTHOR]

The presence of mixed 6-thioguanine-nonionic surfactant adsorption layers affects the mechanism and kinetics of the irreversible Bi(III) ion electroreduction process in chlorates(VII). Tween 80 and Triton X-100 change the dynamics of the catalytic effects of 6-thioguanine on Bi(III) ion electroreduction with the tendency of inhibition. The mechanism of catalytic activity of 6-thioguanine is associated with formation of complexes under specific conditions which exist on the electrode surface. The effects of both 6TG and suitable surfactant mixture on the first electron transfer are much greater than those on the transition of other electrons. The Bi-6TG type complex plays the main role in the Bi-6-thioguanine-Tween 80 or Bi-6-thioguanine-Triton X-100 systems, as 6-thioguanine dominates in the formation of adsorption equilibria of the studied mixtures. [ABSTRACT FROM AUTHOR]

Background Azathioprine is widely used for the maintenance of remission in children with inflammatory bowel disease (IBD). Measuring thiopurine metabolites 6-thioguanine (6-TGN) and 6-methyl-mercaptopurine (6-MMP) can aid in optimizing treatment and preventing toxicity. We report a proactive approach combining early metabolite measurements with IBD activity index to achieve optimal azathioprine dosing. Methods The reporting of azathioprine dosing, IBD activity indexes and thiopurine metabolites was evaluated retrospectively in 40 children with IBD. Additional treatments and the effect of azathioprine on blood counts were also examined. Results Forty children (40% female) with IBD (26 Crohn's disease, 12 ulcerative colitis, and 2 unclassified IBD), mean age 12.2±3.4 years, were included in the study. The mean azathioprine dose was 1.3±0.4 mg/kg; mean 6-TGN level was 280±151 pmol/8 × 108 red blood cells (RBC) and mean 6-MMP level 1022±1007 pmol/8 × 108 RBC. Disease activity index (Crohn's and ulcerative colitis, pediatric specific) at the time of metabolite measurement was 6.5±8. Twenty-eight children did not require azathioprine dose adjustment, while it was increased in 12. Data from children with azathioprine monotherapy were analyzed separately and the results were similar. Conclusion Timely measurement of thiopurine metabolites and clinical assessment can provide a powerful tool to optimize azathioprine dosing and reduce serious adverse effects in children with IBD. [ABSTRACT FROM AUTHOR]

The mixed adsorption layers of 6-thioguanine-TritonX-100 and 6-thioguanine-Tween 80 formed at the electrode/chlorate(VII) interface are discussed. The systems were characterized by measurements of differential capacity, zero charge potential, and surface tension at this potential. It was found that 6-thioguanine dominates in the formation of adsorption equilibria of the studied mixture. Competitive adsorption between 6-thioguanine-Triton X-100 and 6-thioguanine-Tween 80, ClO ions or mixed micelles cannot be excluded. [ABSTRACT FROM AUTHOR]

Highlights • SERS repeatability was substantially improved by using the droplet-based SERS method. • High detection speed was achieved with 10 s each assay. • The droplets provided a stable environment for detecting 6-TG in serum. Abstract 6-thioguanine is an anticancer drug with narrow safe dose range and intense toxic reactions, so it is urgently necessary to evaluate its clinical usage. Reproducibility and analysis speed are important factors to take into account when analyzing drug concentration in body fluids. In this work, we fabricated a droplet-based microfluidic chip for detecting 6-thioguanine in human serum by using the surface-enhanced Raman scattering (SERS) technique. The easily-prepared Au nanoparticles were used as SERS substrates, and reagent mixing and signal acquiring happened in droplets one by one. This assay device is endowed with the superiority in improving determination repeatability with coefficient of variation of no more than 5% (n = 25) and high speed of 10 s each assay. The SERS peak at 1295 cm−1 originated from N1-C6 stretching vibration mode of purine ring was selected for quantitating 6-thioguanine. The signals indicated a satisfied linear relationship with the concentrations of 6-thioguanine in the range of 0.010 μM to 10 μM, with a detection limit of 0.032 μM. The droplet-based microfluidic SERS system was successfully applied for credible and rapid analysis of 6-thioguanine in human serum, and is pretty promising for performing the therapeutic drug monitoring. [ABSTRACT FROM AUTHOR]

Granulocytic sarcoma (GS), also called myeloid sarcoma is an extramedullary tumor of the immature granulocytic cells. It is a rare entity and mostly accompanied by acute myeloid leukemia (AML). Very rarely, it is detected before clinical signs of leukemia or other diseases. When the bone marrow biopsy reveals no other hematologic malignancies, the GS is described as aleukemic, primary or isolated. Here, we report two rare cases, one of which presented as aleukemic GS of lymph nodes with aleukemic leukemia cutis, and the other with aleukemic GS of lung. Both cases posed diagnostic dilemma in view of their atypical presentations and site of involvement. Final diagnosis was made by immunohistochemistry (IHC). Both patients were treated with standard induction chemotherapy for AML. One patient had relapsed on treatment and was further treated with only 6-thioguanine leading to complete remission. Our cases emphasize the importance of early suspicion and use of IHC in diagnosis of aleukemic GS and also potential role of oral thioguanine alone in relapsed cases not eligible for hematopoietic stem cell transplant.

Nowadays, carbon quantum dots (CQDs) with size less than 10 nm have emerged as one of the most exciting areas of chemical research in the class of inorganic nanomaterials. This article presents interesting characteristics of CQDs and their fluorescence turn-on/turn-off quenching for the detection of 6-Thioguanine (6-TG). The CQDs were fabricated by a simple one-step microwave technique and used for the simultaneous reduction of Au3+ to form Au0-CQD core-shell (Au@CQD) nanocomposites. The CQDs formed were spherical in shape having an average size of ~ 7 nm confirmed by high-resolution transmission electron microscopy (HRTEM) and DLS study. The interaction of CQDs with Au leads to its fluorescence turn-off up to 96% analyzed by UV-visible, fluorescence spectroscopy, and fluorescence lifetime measurements. The turn-on fluorescence of CQDs has been witnessed by the formation of complex with 6-TG [Au-(6-TG)n]3− in the presence of thiols. Meanwhile, linear relationship between turn-on fluorescence against the concentration of 6-TG is obtained in the range of 0-100 μM with the correlation coefficient of 0.9944 and limit of detection for 6-TG has been found to be 0.01 μM. The Au@CQDs could also act as biosensor for the detection of various amino acids, enzymes, and pentids drug.ᅟ [ABSTRACT FROM AUTHOR]

Surface-enhanced Raman scattering (SERS) spectroscopy is an ultrasensitive analytical technique with high specificity, making it an ideal candidate for therapeutic drug monitoring. However, SERS measurement of drugs in biological samples is inevitably affected by the proteins adsorbed nonspecifically on metal nanoparticles, so the drugs usually require separation before SERS detection. In this work, semipermeable alginate microparticles containing gold nanoparticles were fabricated via a centrifugal microfluidic chip, and served as a reliable substrate for SERS detection of 6-thioguanine in serum without protein removal. In comparison with the conventional microfluidic methods using oil for droplet generation, this oil-free method can fabricate more clean and versatile microparticles. The microparticles were characterized by size/charge selectivity and pH response, which effectively improved anti-interference ability and SERS sensitivity for 6-thioguanine detection in serum. The microparticles were further endowed with magnetic property and SERS activity simultaneously by forming Janus structures embedded with magnetic nanoparticles and gold nanoparticles separately in independent hemispheres, which was convenient for manipulation in SERS detection. More broadly, the microparticles are potentially applicable for SERS detection of other small molecules in complex real samples. [ABSTRACT FROM AUTHOR]

Abstract Porcine epidemic diarrhea virus (PEDV) is a coronavirus (CoV) discovered in the 1970s that infects the intestinal tract of pigs, resulting in diarrhea and vomiting. It can cause extreme dehydration and death in neonatal piglets. In Asia, modified live attenuated vaccines have been used to control PEDV infection in recent years. However, a new strain of PEDV that belongs to genogroup 2a appeared in the USA in 2013 and then quickly spread to Canada and Mexico as well as Asian and European countries. Due to the less effective protective immunity provided by the vaccines against this new strain, it has caused considerable agricultural and economic loss worldwide. The emergence of this new strain increases the importance of understanding PEDV as well as strategies for inhibiting it. Coronaviral proteases, including main proteases and papain-like proteases, are ideal antiviral targets because of their essential roles in viral maturation. Here we provide a first description of the expression, purification and structural characteristics of recombinant PEDV papain-like protease 2, moreover present our finding that 6-thioguanine, a chemotherapeutic drug, in contrast to its competitive inhibition on SARS- and MERS-CoV papain-like proteases, is a noncompetitive inhibitor of PEDV papain-like protease 2. Highlights • PEDV PL2pro exhibits much higher DUB activity than that of other PLpros in spite of their structural similarities. • In contrast to its competitive inhibition on SARS- and MERS-CoV PLpros, 6-thioguanine inhibits PEDV PL2pro allosterically. • Putative 6-thioguanine binding site is proposed to render the blocking loop less flexible and therefore disfavor catalysis. • 6-thioguanine can be a lead compound for anti-coronaviral drug development. [ABSTRACT FROM AUTHOR]

Objective(s): This study aimed to investigate the effect of Shogaol on dextran sodium sulfate (DSS)- induced ulcerative colitis (UC) in mice compared to an immune-suppressant chemotherapeutic medicine, known as 6-thioguanine (6-TG). Materials and Methods: Thirty-six adult BALB/c mice were divided into six groups: group 1 (positive control): no DSS exposure and no treatment; group 2 (negative control): DSS exposure without treatment; group 3 (vehicle control): DSS exposure and olive oil treatment; group 4: DSS exposure and 0.3 mg/kg 6-TG treatment; group 5: DSS exposure and 20 mg/kg Shogaol treatment; and group 6: DSS exposure and 40 mg/kg Shogaol treatment. At day 16, the mice were euthanized and UC was evaluated according to colon length, histologically index score and expression scores of the epidermal growth factor receptor (EGFR). Results: The disease activity index (DAI) and histological index scores of mice treated with 40 mg/kg body weight (BW) Shogaol were approximately lower than the corresponding scores of mice treated with 6-TG. In addition, the rate of healing in the former mice was approximately 3 folds higher than that of the latter ones as indicated by the lack of EGFR expression in colonic glands and macrophages. Conclusion: These findings showed that the therapeutic effect of 40 mg/kg BW Shogaol could be better than 6-TG in the treatment of UC, and it may draw the attention regarding the priority of using this cheap plant-derived substance for treatment of the inflammatory bowel diseases because treatment with 6-TG is usually associated with adverse side effects. [ABSTRACT FROM AUTHOR]

Pancreatic cancer is one of the most difficult cancers to cure due to the lack of early diagnostic tools and effective therapeutic agents. In this study, we aimed to isolate new bioactive compounds that effectively kill pancreatic ductal adenocarcinoma (PDAC) cells, but not untransformed, human pancreatic ductal epithelial (HPDE) cells. To this end, we established four primary PDAC cell lines and screened 4141 compounds from four bioactive‐compound libraries. Initial screening yielded 113 primary hit compounds that caused over a 50% viability reduction in all tested PDAC cells. Subsequent triplicate, dose‐dependent analysis revealed three compounds with a tumor cell‐specific cytotoxic effect. We found that these three compounds fall into a single category of thiopurine biogenesis. Among them, 6‐thioguanine (6‐TG) showed an IC50 of 0.39–1.13 μ m toward PDAC cells but had no effect on HPDE cells. We propose that this cancer selectivity is due to differences in thiopurine methyltransferase (TPMT) expression between normal and cancer cells. This enzyme is responsible for methylation of thiopurine, which reduces its cytotoxicity. We found that TPMT levels were lower in all four PDAC cell lines than in HPDE or Panc1 cells, and that knockdown of TPMT in HPDE or Panc1 cells sensitized them to 6‐TG. Lastly, we used a patient‐derived xenograft model to confirm that 6‐TG has a significant antitumor effect in combination with gemcitabine. Overall, our study presents 6‐TG as a strong candidate for use as a therapeutic agent against PDAC with low levels of TPMT. [ABSTRACT FROM AUTHOR]