https://cyberleninka.org/article/n/148766.pdf

Cytochrome P450 enzymes in drug metabolism: Regulation of gene expression, enzyme activities, and impact of genetic variation

Animal models are commonly used in the preclinical development of new drugs to predict the metabolic behaviour of new compounds in humans. It is, however, important to realise that humans differ from animals with regards to isoform composition, expression and catalytic activities of drug-metabolising enzymes. In this review the authors describe similarities and differences in this respect among the different species, including man. This may be helpful for drug researchers to choose the most relevant animal species in which the metabolism of a compound can be studied for extrapolating the results to humans. The authors focus on CYPs, which are the main enzymes involved in numerous oxidative reactions and often play a critical role in the metabolism and pharmacokinetics of xenobiotics. In addition, induction and inhibition of CYPs are compared among species. The authors conclude that CYP2E1 shows no large differences between species, and extrapolation between species appears to hold quite well. In contrast, the species-specific isoforms of CYP1A, -2C, -2D and -3A show appreciable interspecies differences in terms of catalytic activity and some caution should be applied when extrapolating metabolism data from animal models to humans.

Species differences between mouse, rat, dog, monkey and human CYP-mediated drug metabolism, inhibition and induction.

Electrochemiluminescence (ECL) is chemiluminescence triggered by electrochemical techniques. More than 150 ECL assays with remarkably high sensitivity and extremely wide dynamic range are currently available, and accounts for hundreds of millions of dollars in sales per year. The recent development of ECL is particularly rapid. After a brief introduction to ECL, this critical review presents the active and/or emerging areas of ECL research as well as new applications and phenomena of ECL, such as light-emitting electrochemical cell, wireless electrochemical microarray using ECL as photonic reporter, high throughput analysis, aptasensors, immunoassays and DNA analysis, ECL of nanoclusters and carbon nanomaterials, ECL imaging techniques, scanning ECL microscopy, colorimetric ECL sensor, surface plasmon-coupled ECL, electrostatic chemiluminescence, soliton-like ECL waves, ECL investigation of molecular interaction, and single molecule detection. Finally, some perspectives on this rapidly developing field are discussed (322 references).

Applications and trends in electrochemiluminescence.

In recent years, tools for the development of new drugs have been dramatically improved. These include genomic and proteomic research, numerous biophysical methods, combinatorial chemistry and screening technologies. In addition, early ADMET studies are employed in order to significantly reduce the failure rate in the development of drug candidates. As a consequence, the lead finding, lead optimization and development process has gained marked enhancement in speed and efficiency. In parallel to this development, major pharma companies are increasingly outsourcing many components of drug discovery research to biotech companies. All these measures are designed to address the need for a faster time to market. New screening methodologies have contributed significantly to the efficiency of the drug discovery process. The conventional screening of single compounds or compound libraries has been dramatically accelerated by high throughput screening methods. In addition, in silico screening methods allow the evaluation of virtual compounds. A wide range of new lead finding and lead optimization opportunities result from novel screening methods by NMR, which are the topic of this review article.

Drug Discovery Today

In this review we give an overview of the physiological functions of a group of ATP binding cassette (ABC) transporter proteins, which were discovered, and still referred to, as multidrug resistanc...

Human Multidrug Resistance ABCB and ABCG Transporters: Participation in a Chemoimmunity Defense System

Expression patterns of mouse and human CYP orthologs (families 1-4) during development and in different adult tissues.

Comparative expression profiling of 40 mouse cytochrome P450 genes in embryonic and adult tissues.

The cytochrome P450 family 1 (CYP1) is considered to be one of the xenobiotic-metabolizing enzyme families and is responsible for oxidative metabolism of polycyclic aromatic hydrocarbons. For example, mouse Cyp1b1 was originally identified as the enzyme responsible for oxidative metabolism of 7,12-dimethylbenz(alpha)anthracene (DMBA). A comparison of the kinetics of this metabolism by mouse and human CYP1B1 orthologs revealed the mouse enzyme to have a more favorable metabolism of DMBA, with a catalytic efficiency ratio (CER) of 0.23. However, CYP1 enzymes are also capable of metabolism of endobiotics, and in the present study, the metabolism of retinoids and lipid endobiotics by human CYP1B1 and mouse Cyp1b1 orthologs was compared. Both hemoproteins oxidized retinol to retinal and retinal to retinoate, but did not oxidize retinoate. The CYP1B1 to Cyp1b1 CERs were 13 and 26 for the two steps, respectively; the Cyp1b1 K(m(app)) values for retinoids were 20-fold higher. Human family 1 cytochromes P450 had unique regional specificities for arachidonate oxidation: the major metabolites of CYP1A1, CYP1A2, and CYP1B1 were 75% terminal hydroxyeicosatetraenoic fatty acids (HETEs), 52% epoxyeicosatrienoic fatty acids (EETs), and 54% mid-chain HETEs, respectively. CYP1A1 and CYP1B1 K(m(app)) values for arachidonate were about 30 microM, whereas CYP1A2 K(m(app)) was 95 microM. The major metabolites of arachidonic acid by Cyp1b1 were EETs (50%) and midchain HETEs (37%). The mouse ortholog had a CER for metabolite production of 64 due to a K(m(app)) of 0.5 mM for arachidonate.

Metabolism of retinoids and arachidonic acid by human and mouse cytochrome p450 1b1

Piper betle leaves are used in folk medicine for the treatment of various disorders and is commonly chewed among Asians. The present study investigates the protective efficacy of P. betle leaf extract. The presence of the extract inhibited the radiation induced lipid peroxidation process effectively. This could be attributed to its ability to scavenge free radicals involved in initiation and propagation steps. Oral supplementation with extract (1, 5 and 10 mg/kg) was administered daily for 2 weeks to Swiss albino mice and the hepatic antioxidant status was analysed. The GSH content was enhanced and no appreciable change was found in the levels of oxidative damage in terms of lipid peroxidation. Also, the specific activity of SOD increased in a dose dependent manner. These factors indicate the elevation of antioxidant status in the animals. The effect on the glyoxalase system which is considered to be activated under stress conditions was also investigated. Our findings did not observe any significant change in gly I and gly II activities, implying a non-stress condition after oral treatment of the extract. The present study indicates the antioxidant activity of P. betle leaf extract and its potential to elevate the antioxidant status.

Antioxidant and non-toxic properties of Piper betle leaf extract: in vitro and in vivo studies

Advanced bladder cancer (BCa) remains a major source of mortality, with poor treatment options. Cisplatin based chemotherapy is the standard treatment, however many patients are or become resistant. One potential cause of chemoresistance is the Warburg Effect, a metabolic switch to aerobic glycolysis that occurs in many cancers. Upregulation of the pyruvate dehydrogenase kinase family (PDK1-4) is associated with aerobic glycolysis and chemoresistance through inhibition of the pyruvate dehydrogenase complex (PDH). We have previously observed upregulation of PDK4 in high grade compared to low grade bladder cancers. We initiated this study to determine if inhibition of PDK4 could reduce tumor growth rates or sensitize BCa cells to cisplatin. Upregulation of PDK4 in malignant BCa cell lines as compared to benign transformed urothelial cells was confirmed using qPCR. Inhibition of PDK4 with dichloroacetate (DCA) resulted in increased PDH activity, reduced cell growth, and G0/G1 phase arrest in BCa cells. Similarly, siRNA knockdown of PDK4 inhibited BCa cell proliferation. Co-treatment of BCa cells with cisplatin and DCA did not increase caspase-3 activity but did enhance overall cell death in vitro. While daily treatment with 200mg/kg DCA alone did not reduce tumor volumes in a xenograft model, combination treatment with cisplatin resulted in dramatically reduced tumor volumes as compared to either DCA or cisplatin alone. This was attributed to substantial intra-tumoral necrosis. These findings indicate inhibition of PDK4 may potentiate cisplatin induced cell death and warrant further studies investigating the mechanism through which this occurs.

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Dharamainder Choudhary

Papers

Expression patterns of mouse and human CYP orthologs (families 1-4) during development and in different adult tissues.

Comparative expression profiling of 40 mouse cytochrome P450 genes in embryonic and adult tissues.

Metabolism of retinoids and arachidonic acid by human and mouse cytochrome p450 1b1

Antioxidant and non-toxic properties of Piper betle leaf extract: in vitro and in vivo studies

The Role of Pyruvate Dehydrogenase Kinase-4 (PDK4) in Bladder Cancer and Chemoresistance