Comparison of the effects of pyridine and its metabolites on rat liver and kidney

Synthesis and Biological Activity Evaluation of Novel 5-Methyl-7-phenyl-3H-thiazolo[4,5-b]pyridin-2-ones

A series of 5-methyl-7-phenyl-3H-thiazolo[4,5-b]pyridin-2-ones has been designed, synthesized, and characterized by spectral data. Target compounds were screened for their antimicrobial activity against some pathogenic bacteria and fungi, and most of them showed moderate activity, especially compound 3g, which displayed the potent inhibitory effect against Pseudomonas aeruginosa and Escherichia coli with MIC value of 0.21 μM. The active thiazolopyridine derivatives 3c, 3f, and 3g were screened for their cytotoxicity effects on HaCat, Balb/c 3T3 cells using MTT assay, which revealed promising results. In silico assessment for compounds 3c, 3f, and 3g also revealed suitable drug-like parameters and ADME properties. The binding interactions of the most active compound 3g were performed through molecular docking against MurD and DNA gyrase, with binding energies and an inhibitory constant compared to the reference drug ciprofloxacin. The tested thiazolo[4,5-b]pyridines constitute an exciting background for the further development of new synthetic antimicrobial agents.

Tuberculosis: An Overview of the Immunogenic Response, Disease Progression, and Medicinal Chemistry Efforts in the Last Decade toward the Development of Potential Drugs for Extensively Drug-Resistant Tuberculosis Strains

Tuberculosis (TB) is a slow growing, potentially debilitating disease that has plagued humanity for centuries and has claimed numerous lives across the globe. Concerted efforts by researchers have culminated in the development of various strategies to combat this malady. This review aims to raise awareness of the rapidly increasing incidences of multidrug-resistant (MDR) and extensively drug-resistant (XDR) tuberculosis, highlighting the significant modifications that were introduced in the TB treatment regimen over the past decade. A description of the role of pathogen-host immune mechanisms together with strategies for prevention of the disease is discussed. The struggle to develop novel drug therapies has continued in an effort to reduce the treatment duration, improve patient compliance and outcomes, and circumvent TB resistance mechanisms. Herein, we give an overview of the extensive medicinal chemistry efforts made during the past decade toward the discovery of new chemotypes, which are potentially active against TB-resistant strains.

Synthesis of new substituted pyridine derivatives as potent anti-liver cancer agents through apoptosis induction: In vitro, in vivo, and in silico integrated approaches

Liver cancer is the most common type of cancer in many countries. New studies and statistics show rising liver cancer worldwide, so it is essential to seek new agents for this type of cancer. PIM1 has an attractive target in the discovery of cancer medications as it is very much expressed in a variety of malignancies and influences such as tumorigenesis, cell cycle progression, cellular proliferation, apoptosis, and cell migration. Accordingly, a series of pyridones and pyridine-amides were synthesized and tested for anti-liver cancer activity. In the synthetic strategy 4,6-diaryl-3-cyano-2-pyridones 3a-n were synthesized using one-pot four component synthetic method. Structural modifications were done on 4,6-diphenyl-3-cayno-2-pyridone 3a to enhance the activity. Alkylation in the presence of K₂CO₃ afforded the O-alkylated products 4-6. The acetoxy hydrazide 7 was synthesized and cyclized into 1,3,4-oxadiazolethione 8 which alkylated on sulfur to give 10. Azide-coupling method was used to couple the 2-(pyridin-2-yloxy)acetohydrazide 7 to different amines and amino acid esters to furnish the products 12a-e and 13a-b. The synthesized derivatives were subjected to cytotoxic screening against HepG2 and THLE-2 cells, Compounds 10, 12e and 13a have a remarkable cytotoxic activity with IC₅₀ values (10.7-13.9 µM). Compound 7 was found to be more cytotoxic by showing the lowest IC₅₀ value of 7.26 compared to 5-FU (IC₅₀ = 6.98 µM). It inhibited cell growth by 76.76%. Additionally, it significantly stimulated apoptotic liver cancer cell death with 49.78-fold (22.90% compared to 0.46% for the control) arresting cell cycle Pre-G1 with 35.16% of a cell population, compared to 1.57% for the control. Moreover, it validated the intrinsic apoptosis through upregulation of P53, and other related genes, with inhibition of anti-apoptotic genes through PIM-1 inhibition.

Two Multivariate Calibration Models for Assay of Niacin in Complex Mixtures with Its Official Impurities: A Pharmaceutical Application

Background

Niacin (NIA) is a water-soluble vitamin and the primary treatment of pellagra. No analytical method was found to assess NIA in complex mixtures with its official impurities.

Objective

Two validated, accurate, and selective chemometric models were developed to assay NIA in the presence of its four official impurities, including pyridine, a nephrotoxic and hepatotoxic substance. Additionally, the two selective chemometric models were compared by processing UV spectra in the range 220–305 nm and applying partial least squares regression (PLSR) and support vector regression (SVR) models.

Method

A five levels five factors experimental design was chosen to exhibit a training set of 25 mixtures that had numerous variable percentages of tested substances. A test set consisting of 10 mixtures was designed to confirm the predictive power of the suggested models.

Results

The presented results substantiate the strength of the developed multivariate calibration models to assay NIA specifically with high selectivity and accuracy (100.02 ± 1.312 and 100.04 ± 1.272 for PLSR and SVR models, respectively). The root mean square error of prediction for the validation set mixtures was applied as a main comparison tool and it was found to be 0.2016 and 0.1890 for PLSR and SVR models, respectively.

Conclusions

The results of the developed models and the reported HPLC method were statistically compared, where F-values and Student's t-tests did not show significant difference in regards to accuracy and precision. The SVR model proved to be more accurate than the PLSR model, producing a high generalization capacity, while PLSR was easy to implement and fast.

Highlights

Synthesis and biological evaluation of 2,4,5-trisubstituted thiazoles as antituberculosis agents effective against drug-resistant tuberculosis

The dormant and resistant form of Mycobacterium tuberculosis presents a challenge in developing new anti-tubercular drugs. Herein, we report the synthesis and evaluation of trisubstituted thiazoles as antituberculosis agents. The SAR study has identified a requirement of hydrophobic substituent at C2, ester functionality at C4, and various groups with hydrogen bond acceptor character at C5 of thiazole scaffold. This has led to the identification of 13h and 13p as lead compounds. These compounds inhibited the dormant Mycobacterium tuberculosis H37Ra strain and M. tuberculosis H37Rv selectively. Importantly, 13h and 13p were non-toxic to CHO cells. The 13p showed activity against multidrug-resistant tuberculosis isolates.

Novel 1,3,4-oxadiazoles as antitubercular agents with limited activity against drug-resistant tuberculosis

AIM

In recent times, heterocyclic chemotypes are being explored for the development of new antimycobacterials that target the drug-resistant tuberculosis. Here, we are disclosing the 5-substitued 2-mercapto-1,3,4-oxadiazoles as potent antitubercular agents.

METHODOLOGY

A small library of 2-mercapto-1,3,4-oxadiazoles was synthesized using various acids. The compounds were evaluated for antituberculosis activity against M. tuberculosis H37Rv.

RESULTS

Compound 8j was identified as antitubercular lead with MIC of 0.6 μg/ml against M. tuberculosis H37Rv. This compound was nontoxic to CHO-K1 cells and showed selectivity index of 39. Of note, 8j showed antitubercular activity against pre-extensively drug-resistant clinical isolate of Mycobacterium with MIC of 2 μg/ml.

CONCLUSION

This study provides potent antitubercular agent which can be further optimized to discover novel antibiotics.

Volatile and bioactive compounds in opercula from Muricidae molluscs supports their use in ceremonial incense and traditional medicines

Muricidae molluscs are the source of a valuable purple dye that was traded as a luxury item in the Mediterranean region and by the late Byzantine was reserved for royalty and priests. Less well known is the use of muricid opercula in sacred incense and traditional medicines, although they are still used as rare ingredients today. This study provides the first chemical assessment of opercula from Muricidae, based on several traditional preparation procedures. Chemical analysis of opercula smoke revealed aromatic phenols, which act as fragrance stabilisers and produce a "medicinal" odour. Analysis of lipid extracts revealed pharmaceutically active compounds, including brominated indoles, choline esters and adenosine, consistent with their traditional medical applications. Depending on the preparation procedures, toxic pyridine was also detected. ICP-MS analysis of muricid opercula shows the presence of essential macro and microelements, as well as metals, some of which exceed the recommended safe levels for human use. Nevertheless, these findings support the Muricidae as an historically important marine resource, providing Biblical dyes, medicines and perfume. The opercula contains biologically active compounds and produces smoke containing volatile scent compounds, consistent with their identification as the most likely source of onycha, a controversial ingredient in sacred incense.

Effects of acetylated wood powder on growth performance, hepatic and muscular free amino acid profiles, and inosine 5'-monophosphate concentration of breast meat in broiler chickens

The present study was conducted to determine the effects of acetylated wood powder (AW) as a new feed additive on performance, liver and muscle metabolism of amino acids and fatty acids and nucleotide-related substances of meat in broiler chickens. It was hypothesised that acetic acid desorbed from AW during intestinal digestion affects tissue metabolism. Two-week-old broiler chicks were divided into four groups and fed on diets supplemented with wood powder (30 g/kg) less than 106 µm in diameter, except for controls. The AW was added to diets at 0, 10 and 30 g/kg to replace the non-acetylated wood powder (NAW) for 26 d. Plasma, liver tissue and breast muscle were taken from half of birds at 40 d of age under the fed condition. After the remaining chickens were fasted for 14 h, breast muscle was taken and refrigerated for 24 h. Consumption of wood powder with or without acetyl groups had no effect on growth performance including tissue weights of abdominal fat and breast muscle and plasma metabolites. Feeding AW decreased total free amino acid concentrations in the liver compared to the group only fed on the NAW. This response was dependent mainly on reduced non-essential and glucogenic amino acid concentrations. However, in breast muscle, alterations of free amino acid concentrations were observed only for histidine and tryptophan. In addition, the fatty acid composition of liver and breast muscle was not affected by feeding AW. In breast meat obtained from fasted chickens, the higher level of AW increased the concentration of inosine 5'-monophosphate, a taste-active compound, and in contrast, decreased the subsequent catabolites (inosine and hypoxanthine). However, the concentration of glutamic acid, a taste-active compound, was lowered at this level of AW ingestion. Therefore, this study suggested that feeding AW as a new feed additive regulates ante-mortem amino acid utilisation in the liver and contributes to retard post-mortem degradation of inosine 5'-monophosphate as a taste-active compound in chicken meat.

An overview of the synthetic routes to the best selling drugs containing 6-membered heterocycles

This review which is the second in this series summarises the most common synthetic routes as applied to the preparation of many modern pharmaceutical compounds categorised as containing a six-membered heterocyclic ring. The reported examples are based on the top retailing drug molecules combining synthetic information from both scientific journals and the wider patent literature. It is hoped that this compilation, in combination with the previously published review on five-membered rings, will form a comprehensive foundation and reference source for individuals interested in medicinal, synthetic and preparative chemistry.

An overview of the synthetic routes to the best selling drugs containing 6-membered heterocycles

This review which is the second in this series summarises the most common synthetic routes as applied to the preparation of many modern pharmaceutical compounds categorised as containing a six-membered heterocyclic ring. The reported examples are based on the top retailing drug molecules combining synthetic information from both scientific journals and the wider patent literature. It is hoped that this compilation, in combination with the previously published review on five-membered rings, will form a comprehensive foundation and reference source for individuals interested in medicinal, synthetic and preparative chemistry.

Induction of micronuclei by 2-hydroxypyridine in water and elimination of solution genotoxicity by UVC (254 nm) photolysis

2-Hydroxypyridine (2-HPY) is a major first-stage product formed upon the photolytic destruction of 2-halogenated pyridines. Genotoxicity of 2-HPY in water was studied as a function of concentration. Aqueous solutions of 2-HPY were irradiated by ultraviolet (UV) at 254 nm. 2-HPY concentration, solution total organic carbon (TOC) concentration and solution genotoxicity were measured as a function of treatment time and their profile as a function of time is presented in this work. 2-HPY was found to be genotoxic at all concentrations in the range of 5-400 μg ml(-1). 2-HPY mineralises completely upon prolonged UV irradiation. All untreated and irradiated solution samples, taken at different photo-treatment times, were tested in cultured human lymphocytes applying the cytokinesis block micronucleus (CBMN) assay. The genotoxicity of the solution was reduced near to the control level after prolonged UV irradiation.

Grand rounds: an outbreak of toxic hepatitis among industrial waste disposal workers

CONTEXT

Industrial waste (which is composed of various toxic chemicals), changes to the disposal process, and addition of chemicals should all be monitored and controlled carefully in the industrial waste industry to reduce the health hazard to workers.

CASE PRESENTATION

Five workers in an industrial waste plant developed acute toxic hepatitis, one of whom died after 3 months due to fulminant hepatitis. In the plant, we detected several chemicals with hepatotoxic potential, including pyridine, dimethylformamide, dimethylacetamide, and methylenedianiline. The workers had been working in the high-vapor-generating area of the plant, and the findings of pathologic examination showed typical features of acute toxic hepatitis.

DISCUSSION

Infectious hepatitis and drug-induced hepatitis were excluded by laboratory findings, as well as the clinical course of hepatitis. All cases of toxic hepatitis in this plant developed after the change of the disposal process to thermochemical reaction-type treatment using unslaked lime reacted with industrial wastes. During this chemical reaction, vapor containing several toxic materials was generated. Although we could not confirm the definitive causative chemical, we suspect that these cases of hepatitis were caused by one of the hepatotoxic agents or by a synergistic interaction among several of them.

RELEVANCE TO CLINICAL OR PROFESSIONAL PRACTICE

In the industrial waste treatment process, the danger of developing toxic hepatitis should be kept in mind, because any subtle change of the treatment process can generate various toxic materials and threaten the workers' health. A mixture of hepatotoxic chemicals can induce clinical manifestations that are quite different from those predicted by the toxic property of a single agent.

CYP1A1 induction by pyridine and its metabolites in HepG2 cells

Pyridine and its metabolites have been shown in previous studies to induce cytochrome P4501A1 (CYP1A1) expression in vivo in the rat and in vitro in cultured human lung explants. In this study, we assessed the role of the metabolites in CYP1A1 induction by the parent compound. This was accomplished by comparing pyridine, 2-hydroxypyridine, 3-hydroxypyridine, pyridine N-oxide, and N-methylpyridinium in terms of the induction of CYP1A1 mRNA, CYP1A1 catalytic activity, and a xenobiotic response element-directed chloramphenicol acetyltransferase reporter gene, using HepG2 cells as the experimental system. We also assessed the effect of expression of the pyridine-metabolizing enzyme cytochrome P4502E1 on CYP1A1 induction by the parent pyridine. Only 2-hydroxypyridine significantly induced the CYP1A1 mRNA expression and CYP1A1-preferential activity ethoxyresorufin O-deethylase in wild-type HepG2 cells. Similarly, only 2-hydroxypyridine induced the expression of a xenobiotic response element-directed reporter gene in transfected HepG2 cells. Pyridine elevated CYP1A1 mRNA abundance 4.6-fold in HepG2 cells transfected with a human CYP2E1 expression vector relative to the abundance of the transcript in empty vector-transfected (control) HepG2 cells; the elevation was inhibited by the CYP2E1 inhibitor dimethyl sulfoxide. The results indicate that CYP1A1 induction by pyridine is mediated largely by metabolites, the formation of which may be catalyzed by CYP2E1.

Comparative induction of CYP1A1 expression by pyridine and its metabolites

We compared pyridine and five of its metabolites in terms of (i) in vivo induction of CYP1A1 expression in the lung, kidney, and liver in the rat and (ii) in vitro binding to, and activation of, the aryl hydrocarbon receptor (AhR) in cytosol from rat liver or Hepa1c1c7 cells. Following a single 2.5 mmol/kg ip dose of either pyridine, 2-hydroxpyridine, 3-hydroxypyridine, 4-hydroxypyridine, N-methylpyridinium, or pyridine N-oxide, CYP1A1 activity (ethoxyresorufin O-deethylase), protein level (as determined by Western blotting), and mRNA level (as determined by Northern blotting) were induced by pyridine, N-methylpyridinium, and pyridine N-oxide in the lung, kidney, and liver. The induction by N-methylpyridinium or pyridine N-oxide was comparable to or greater than that by pyridine in some tissues. 2-Hydroxypyridine and 3-hydroxypyridine caused tissue-specific induction or repression of CYP1A1, whereas 4-hydroxypyridine had no effect on the expression of the enzyme. Pyridine and its metabolites elicited weak activation of the aryl hydrocarbon receptor in a gel retardation assay in cytosol from rat liver but not Hepa 1c1c7 cells. However, the receptor activation did not parallel the in vivo CYP1A1 induction by the pyridine compounds, none of which inhibited binding of ¿(3)H2,3,7, 8-tetrachlorodibenzo-p-dioxin to AhR in a competitive assay in rat liver cytosol. The findings are consistent with a role of pyridine metabolites in CYP1A1 induction by pyridine but do not clearly identify the role of aryl hydrocarbon receptor in the induction mechanism.

Coordinate up-regulation of CYP1A1 and heme oxygenase-1 (HO-1) expression and modulation of delta-aminolevulinic acid synthase and tryptophan pyrrolase activities in pyridine-treated rats

To determine the changes in heme metabolism associated with induction of cytochrome P450 expression by pyridine, we compared the time course of CYP1A expression with the time course of (i) expression of heme oxygenase-1 (HO-1) (EC 1.14.99.3), (ii) activity of delta-aminolevulinic acid synthetase (ALAS) (EC 2.3.1.37), and (iii) heme saturation of tryptophan pyrrolase (TPO) (EC 1.13.11.11) in tissues of rats administered a single 100 or 150 mg/kg i.p. dose of pyridine. Both mRNA and protein of HO-1 and CYP1A1 were induced in the liver, kidney, and lung, with the induction of HO-1 mRNA preceding and paralleling that of CYP1A1 mRNA in the liver and lung but not kidney. Induction of CYP1A1 mRNA expression peaked within 9-12 hr and returned to control levels by 24 hr in all tissues examined, whereas induction of HO-1 mRNA expression was sustained for 48 hr in the lung and liver. In contrast to the transient up-regulation of CYP1A1 mRNA, increased microsomal CYP1A1 protein was sustained in all three tissues. Similar to the induction of HO-1 expression, lipid peroxidation was stimulated by pyridine treatment in the kidney, lung, and liver, but with the stimulation being more persistent in the liver and lung than in the kidney. Increased hepatic CYP1A1 or CYP1A2 activity was preceded by increased activities of HO-1 and ALAS. Pyridine treatment negatively modulated heme saturation of hepatic TPO. The findings indicate that pyridine stimulates the synthesis, utilization, and degradation of heme in a coordinate manner, and suggest that these alterations in heme metabolism may contribute to CYP1A1 induction by pyridine.

Sample preparation and high-resolution separation of mycotoxins possessing carboxyl groups

The chromatographic analysis of carboxyl-containing mycotoxins, such as fumonisin B1, ochratoxin A, and citrinin, presents a continual challenge. Toxins must first be extracted from foods or tissues and then cleaned up before chromatographic separation and detection. Liquid-liquid extraction efficiencies for some carboxylic mycotoxins are marginal for spiked samples and uncertain for incurred residues. Immunoaffinity columns may be useful for concentrating mycotoxins from samples before chromatography. In almost every case, more than one analytical method must be used to confirm the identification of the mycotoxin. The fumonisins are especially troublesome to analyze because they are relatively insoluble in organic solvents, they are not separated easily by gas chromatography, and they do not respond to the usual absorbance or fluorescence detectors used in liquid chromatography. Fluorescence derivatization and electrospray liquid chromatography-mass spectrometry have now made it possible to detect trace levels of mycotoxins. The purity of mycotoxin standards for toxicological studies can be determined by liquid chromatography with either an evaporative light scattering detector or electrospray mass spectrometer. New developments in capillary electrophoresis, nonporous microsphere liquid chromatography, and detection methods for low-volatility compounds show promise for improving the analysis of mycotoxins in the future.

Induction of cytochromes P450 2B and 2E1 in rat liver by isomeric picoline N-oxides

Pyridine derivatives are widely used solvents and precursors for the synthesis of chemicals of industrial importance. Oxidized metabolites have been implicated in the observed toxicity of pyridines and are known to induce drug-metabolizing enzymes in rat liver. In this study the three isomeric picoline (methylpyridine) N-oxides, as major oxidized metabolites of 2-, 3- and 4-picoline, were evaluated as inducers of cytochrome P450 (CYP) enzymes in rat liver. After a single dose of 100 mg/kg 24 h before sacrifice the 3- and 4-isomers were effective inducers of microsomal substrate oxidations associated with the phenobarbital-inducible CYPs 2B; upregulation of CYP2B protein was confirmed by immunoblotting. In contrast, the 2-isomer did not increase CYP2B protein or activity in rat liver but CYP2E1 protein expression was upregulated by the isomers to 160-200% of control. The three chemicals increased aniline 4-hydroxylation activity in rat liver, which is consistent with induction of CYPs 2B or 2E1 and 4-nitrophenol 2-hydroxylation activity was increased in microsomal fractions from 3- and 4-picoline N-oxide-treated rats. The activities of several other CYPs were also determined and CYP1A-dependent 7-ethylresorufin O-deethylation was increased (to approximately 6- and 2-fold of control) by the 3- and 4-isomer, respectively, whereas the activity of CYP3A-mediated androstenedione 6beta-hydroxylation was decreased by the agents--most notably by the 2-isomer. During NADPH-supported oxidation of CCl4, lipid peroxidation was increased in microsomes from 3- and 4-picoline N-oxide-pretreated rats and was modulated in vitro by the CYP2B inhibitor orphenadrine, but not by the CYP2E1 inhibitor 4-methylpyrazole. These findings establish that particular isomers of picoline N-oxide rapidly upregulate CYP2B or, to a lesser extent, CYP2E1 and implicate CYP2B in the enhanced lipid peroxidation observed in microsomes from rats treated with 3- and 4-picoline N-oxides. Such induction process may contribute to the hepatotoxicity of pyridines by enhancing the capacity for microsomal lipid peroxidation.