Displaying publications 1 - 20 of 36 in total

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  1. Mat Salleh NH, Rahman MFA, Samsusah S, De Silva JR, Ng DC, Ghozali AH, et al.
    Trans R Soc Trop Med Hyg, 2020 Sep 01;114(9):700-703.
    PMID: 32511702 DOI: 10.1093/trstmh/traa042
    Five children in Pos Lenjang, Pahang, Malaysia were PCR-positive for vivax malaria and were admitted to the hospital from 5 to 26 July 2019. One of the patients experienced three episodes of recurrence of vivax malaria. Microsatellite analysis showed that reinfection is unlikely. Drug resistance analysis indicated that Riamet (artemether-lumefantrine) is effective. Cytochrome P450 2D6 (CYP2D6) testing showed that this patient has defective CYP2D6 function. Primaquine failure to clear the Plasmodium vivax hypnozoites may be the cause of recurring infections in this patient. This report highlights the need for the development of liver-stage curative antimalarials that do not require metabolism by the CYP2D6 enzyme.
    Matched MeSH terms: Cytochrome P-450 CYP2D6/genetics; Cytochrome P-450 CYP2D6/therapeutic use
  2. Dong AN, Ahemad N, Pan Y, Palanisamy UD, Yiap BC, Ong CE
    Naunyn Schmiedebergs Arch Pharmacol, 2019 08;392(8):1015-1029.
    PMID: 31025144 DOI: 10.1007/s00210-019-01651-0
    One major source of inter-individual variability in drug pharmacokinetics is genetic polymorphism of the cytochrome P450 (CYP) genes. This study aimed to elucidate the enzyme kinetic and molecular basis for altered activity in three major alleles of CYP2D6, namely CYP2D6*2, CYP2D6*10 and CYP2D6*17. The E. coli-expressed allelic variants were examined using substrate (venlafaxine and 3-cyano-7-ethoxycoumarin[CEC]) and inhibitor (quinidine, fluoxetine, paroxetine, terbinafine) probes in enzyme assays as well as molecular docking. The kinetics data indicated that R296C and S486T mutations in CYP2D6*2 have caused enhanced ligand binding (enhanced intrinsic clearance for venlafaxine and reduced IC50 for quinidine, paroxetine and terbinafine), suggesting morphological changes within the active site cavity that favoured ligand docking and binding. Mutations in CYP2D6*10 and CYP2D6*17 tended to cause deleterious effect on catalysis, with reduced clearance for venlafaxine and CEC. Molecular docking indicated that P34S and T107I, the unique mutations in the alleles, have negatively impacted activity by affecting ligand access and binding due to alteration of the substrate access channel and active site morphology. IC50 values however were quite variable for quinidine, fluoxetine and terbinafine, and a general decrease in IC50 was observed for paroxetine, suggesting ligand-specific altered susceptibility to inhibition in the alleles. This study indicates that CYP2D6 allele selectivity for ligands was not solely governed by changes in the active site architecture induced by the mutations, but that the intrinsic properties of the substrates and inhibitors also played vital role.
    Matched MeSH terms: Cytochrome P-450 CYP2D6/genetics*; Cytochrome P-450 CYP2D6/metabolism; Cytochrome P-450 CYP2D6/chemistry; Cytochrome P-450 CYP2D6 Inhibitors/pharmacology*
  3. Zahari Z, Salleh MR, Teh LK, Ismail R
    Malays J Med Sci, 2009 Jul;16(3):12-20.
    PMID: 22589660 MyJurnal
    Our objective was to investigate the association of CYP2D6 polymorphisms with symptoms and side-effects of patients with schizophrenia.
    Matched MeSH terms: Cytochrome P-450 CYP2D6
  4. Teh LK, Bertilsson L
    Drug Metab. Pharmacokinet., 2012;27(1):55-67.
    PMID: 22185816
    CYP2D6 has received intense attention since the beginning of the pharmacogenetic era in the 1970s. This is because of its involvement in the metabolism of more than 25% of the marketed drugs, the large geographical and inter-ethnic differences in the genetic polymorphism and possible drug-induced toxicity. Many interesting reviews have been published on CYP2D6 and this review aims to reinstate the importance of the genetic polymorphism of CYP2D6 in different populations as well as some clinical implications and important drug interactions.
    Matched MeSH terms: Cytochrome P-450 CYP2D6/genetics*; Cytochrome P-450 CYP2D6/metabolism*
  5. Teh LK, Zilfalil BA, Marina I, Rosemi BS, Ismail R
    J Clin Pharm Ther, 2004 Dec;29(6):559-64.
    PMID: 15584944 DOI: 10.1111/j.1365-2710.2004.00600.x
    BACKGROUND: Cardiovascular diseases are complex diseases that are influenced by both environmental and genetic factors. CYP2D6 found in the brain and the heart is involved in the metabolism of many environmental and some endogenous substances and neurotransmitters responsible for maintaining homeostasis. This raises an interesting hypothesis that it may have a role in the development of or protection against cardiovascular diseases.
    OBJECTIVE: To study the distribution of genotypes of CYP2D6 among patients with cardiovascular diseases in Malaysia.
    METHOD:We obtained DNA from 128 patients who were followed up for cardiovascular diseases. Polymerase chain reaction-based methods were used to determine common CYP2D6 alleles.
    RESULTS: One hundred and twenty-eight patients were enrolled. Most of the patients also had concurrent illnesses. Eleven genotypes were identified in the patients and 41% carried CYP2D6*1/*10. The second most common genotype was homozygous for the wild type gene, followed by homozygous CYP2D6*10/*10 at 14.48 %. A small percentage of the patients were heterozygous CYP2D6*1/*4. One patient was genotyped homozygous CYP2D6*4/*4 predicting a poor metabolizer prevalence of 0.78% (95% CI +/- 1.52%). Analysis using Hardy-Weinberg equilibrium showed that all of the gnotypes were consistent with equilibrium except for CYP2D6*1/*10 (chi(2); P < 0.05).
    CONCLUSION: Our study suggests a possible involvement of CYP2D6 genotypes in cardiovascular system diseases, which need to be validated by further studies.
    Matched MeSH terms: Cytochrome P-450 CYP2D6/genetics*; Cytochrome P-450 CYP2D6/metabolism*
  6. Ismail R, Teh LK
    Eur J Clin Pharmacol, 2001 Oct;57(8):617-8.
    PMID: 11758642
    Matched MeSH terms: Cytochrome P-450 CYP2D6/genetics*; Cytochrome P-450 CYP2D6/metabolism
  7. Pan Y, Abd-Rashid BA, Ismail Z, Ismail R, Mak JW, Ong CE
    Protein J, 2011 Dec;30(8):581-91.
    PMID: 22001938 DOI: 10.1007/s10930-011-9365-6
    This study aimed to express two major drug-metabolizing human hepatic cytochromes P450 (CYPs), CYP2D6 and CYP3A4, together with NADPH-cytochrome P450 oxidoreductase (OxR) in Escherichia coli and to evaluate their catalytic activities. Full length cDNA clones of both isoforms in which the N-terminus was modified to incorporate bovine CYP17α sequence were inserted into a pCWori(+) vector. The modified CYP cDNAs were subsequently expressed individually, each together with OxR by means of separate, compatible plasmids with different antibiotic selection markers. The expressed proteins were evaluated by immunoblotting and reduced CO difference spectral scanning. Enzyme activities were examined using high performance liquid chromatography (HPLC) assays with probe substrates dextromethorphan and testosterone for CYP2D6 and CYP3A4, respectively. Results from immunoblotting demonstrated the presence of both CYP proteins in bacterial membranes and reduced CO difference spectra of the cell preparations exhibited the characteristic absorbance peak at 450 nm. Co-expressed OxR also demonstrated an activity level comparable to literature values. Kinetic parameters, K(m) and V(max) values determined from the HPLC assays also agreed well with literature values. As a conclusion, the procedures described in this study provide a relatively convenient and reliable means of producing catalytically active CYP isoforms suitable for drug metabolism and interaction studies.
    Matched MeSH terms: Cytochrome P-450 CYP2D6/genetics; Cytochrome P-450 CYP2D6/isolation & purification*; Cytochrome P-450 CYP2D6/metabolism; Cytochrome P-450 CYP2D6/chemistry*
  8. Zahari Z, Ismail R
    Drug Metab. Pharmacokinet., 2014;29(1):29-43.
    PMID: 23759977
    CYP2D6 polymorphisms show large geographical and interethnic differences. Variations in CYP2D6 activity may impact upon a patient's pain level and may contribute to interindividual variations in the response to opioids. This paper reviews the evidence on how CYP2D6 polymorphisms might influence pain sensitivity and clinical response to codeine and tramadol. For example, it is shown that (1) CYP2D6 poor metabolizers (PMs) may be less efficient at synthesizing endogenous morphine compared with other metabolizers. In contrast, ultra-rapid metabolizers (UMs) may be more efficient than other metabolizers at synthesizing endogenous morphine, thus strengthening endogenous pain modulation. Additionally, for codeine and tramadol that are bioactivated by CYP2D6, PMs may undergo no metabolite formation, leading to inadequate analgesia. Conversely, UMs may experience quicker analgesic effects but be prone to higher mu-opioid-related toxicity. The literature suggested the potential usefulness of the determination of CYP2D6 polymorphisms in elucidating serious adverse events and in preventing subsequent inappropriate selection or doses of codeine and tramadol. Notably, even though many studies investigated a possible role of the CYP2D6 polymorphisms on pain sensitivity, pharmacokinetics and pharmacodynamics of these drugs, the results of analgesia and adverse effects are conflicting. More studies are required to demonstrate genetically determined unresponsiveness and risk of developing serious adverse events for patients with pain and these should involve larger numbers of patients in different population types.
    Matched MeSH terms: Cytochrome P-450 CYP2D6/genetics*; Cytochrome P-450 CYP2D6/metabolism
  9. Pan Y, Abd-Rashid BA, Ismail Z, Ismail R, Mak JW, Pook PC, et al.
    Chem Biol Interact, 2011 Mar 15;190(1):1-8.
    PMID: 21276781 DOI: 10.1016/j.cbi.2011.01.022
    Orthosiphon stamineus (OS) has been traditionally used to treat diabetes, kidney and urinary disorders, high blood pressure and bone or muscular pain. To assess the possibility of drug-herb interaction via interference of metabolism, effects of four OS extracts of different polarity and three active constituents (sinensetin, eupatorin and rosmarinic acid) on major human cDNA-expressed cytochrome P450 (CYP) enzymes were investigated. Three substrate-probe based high-performance liquid chromatography (HPLC) assays were established to serve as activity markers for CYP2C9, CYP2D6 and CYP3A4. Our results indicate that OS extracts and constituents exhibited differential modulatory effects on different CYPs. While none of the OS components showed significant inhibition on CYP2C9, eupatorin strongly and uncompetitively inhibited CYP2D6 activity with a K(i) value of 10.2μM. CYP3A4 appeared to be the most susceptible enzyme to OS inhibitory effects. It was moderately inhibited by OS dichloromethane and petroleum ether extract with mixed-type and noncompetitive inhibitions (K(i)=93.7 and 44.9μg/mL), respectively. Correlation study indicated that the inhibition was accounted for by the presence of eupatorin in the extracts. When IC(50) values of these extracts were expressed in volume per dose unit to reflect inhibitory effect at recommended human doses from commercially available products, moderate inhibition was also observed. In addition, CYP3A4 was strongly and noncompetitively inhibited by eupatorin alone, with a K(i) value of 9.3μM. These findings suggest that co-administration of OS products, especially those with high eupatorin content, with conventional drugs may have the potential to cause drug-herb interactions involving inhibition of major CYP enzymes.
    Matched MeSH terms: Cytochrome P-450 CYP2D6/metabolism; Cytochrome P-450 CYP2D6 Inhibitors*
  10. Yu CY, Ang GY, Subramaniam V, Johari James R, Ahmad A, Abdul Rahman T, et al.
    Genet Test Mol Biomarkers, 2017 Jul;21(7):409-415.
    PMID: 28525288 DOI: 10.1089/gtmb.2016.0235
    AIMS: CYP2D6 is one of the major enzymes in the cytochrome P450 monooxygenase system. It metabolizes ∼25% of prescribed drugs and hence, the genetic diversity of a CYP2D6 gene has continued to be of great interest to the medical and pharmaceutical industries. This study was designed to perform a systematic analysis of the CYP2D6 gene in six subtribes of the Malaysian Orang Asli.

    METHODS: Genomic DNAs were extracted from the blood samples followed by whole-genome sequencing. The reads were aligned to the reference human genome hg19 and variants in the CYP2D6 gene were analyzed. CYP2D6*5 and duplication of CYP2D6 were analyzed using previously established methods.

    RESULTS: A total of 72 single nucleotide polymorphisms were identified. CYP2D6*1, *2, *4, *5, *10,*41, and duplication of the gene were found in the Orang Asli, whereby CYP2D6*2 and *41 alleles are reported for the first time in the Malaysian population.

    CONCLUSION: The findings in this study provide insights into the genetic polymorphisms of CYP2D6 in the Orang Asli of Peninsular Malaysia.

    Matched MeSH terms: Cytochrome P-450 CYP2D6/blood; Cytochrome P-450 CYP2D6/genetics*; Cytochrome P-450 CYP2D6/metabolism
  11. Yan P, Tze UY, Jagadish PAR, Hon LK, Chowdhury LNS, Tao S, et al.
    Drug Metab Bioanal Lett, 2022;15(3):178-191.
    PMID: 36508274 DOI: 10.2174/1872312815666220707114744
    BACKGROUND: Agarwood tea derived from Aquilaria malaccensis Lamk is becoming an increasingly popular herbal drink that is said to have multiple health benefits. Co-administration of this tea and clinical used drugs is possible, but it increases the risk of drug-herb interactions.

    OBJECTIVE: This in vitro study investigated the inhibitory effects of agarwood tea aqueous extract on the eight major human drug-metabolising cytochrome P450 (CYP) enzyme activities.

    METHODS: High-throughput fluorescence-based Vivid® CYP450 screening kits were employed to obtain the enzyme activities before and after incubation with agarwood tea aqueous extract.

    RESULTS: Agarwood aqueous extract potently inhibited CYP2C9, CYP2D6, and CYP3A4 activities with Ki values of 5.1, 34.5, and 20.3μg/ml, respectively. The most likely inhibition mode responsible for these inhibitions was non-competitive inhibition. On the other hand, at 1000μg/ml, agarwood tea aqueous extract negligibly inhibited CYP1A2, CYP2B6, CYP2C19, CYP2E1, and CYP3A5 activities.

    CONCLUSION: These findings can be used to design additional in vitro investigations using clinical relevant drug substrates for CYP2C9, CYP2D6, and CYP3A4. Subsequently, future studies can be conducted to determine potential interactions between agarwood tea aqueous extract and CYP using in vivo models.

    Matched MeSH terms: Cytochrome P-450 CYP2D6
  12. Gan SH, Ismail R, Wan Adnan WA, Zulmi W
    Mol Diagn Ther, 2007;11(3):171-81.
    PMID: 17570739
    Tramadol is metabolized by the highly polymorphic enzyme cytochrome P450 (CYP)2D6. Patients with different CYP2D6 genotypes may respond differently to tramadol in terms of pain relief and adverse events. In this study, we compare the pharmacokinetics and effects of tramadol in Malaysian patients with different genotypes to establish the pharmacokinetic-pharmacodynamic relationship of tramadol.
    Matched MeSH terms: Cytochrome P-450 CYP2D6/genetics*
  13. Ismail R
    J Postgrad Med, 2006 Oct-Dec;52(4):245.
    PMID: 17243206
    Matched MeSH terms: Cytochrome P-450 CYP2D6/genetics*
  14. Ismail R, Hussein A, Teh LK, Nizam Isa M
    J Clin Pharm Ther, 2000 Oct;25(5):379-83.
    PMID: 11123490
    Although they originated from China, Malays have undergone a lot of intermarriages. A study suggested that CYP2D6 poor metabolism (PM) phenotype was more common in Malays compared to Chinese. CYP2D6 is highly polymorphic and is involved in the metabolism of many drugs and has been implicated in some environmentally-induced diseases. It is therefore useful to further study this polymorphism in Malays.
    Matched MeSH terms: Cytochrome P-450 CYP2D6/genetics*
  15. Teh LK, Ismail R, Yusoff R, Hussein A, Isa MN, Rahman AR
    J Clin Pharm Ther, 2001 Jun;26(3):205-11.
    PMID: 11422605
    Although Malays shared an origin with Chinese, their evolution saw substantial divergences. Phenotyping studies suggested that they differed in CYP2D6 polymorphism, with higher PM prevalence but lesser right-shift for debrisoquine MRs.
    Matched MeSH terms: Cytochrome P-450 CYP2D6/genetics*
  16. Ismail R, Teh LK, Amir J, Alwi Z, Lopez CG
    J Clin Pharm Ther, 2003 Aug;28(4):279-84.
    PMID: 12911679
    Although Malaysian Chinese share an origin with the mainland Chinese, their evolution has been influenced by intermarriages. With a gene such as CYP2D6, which is highly polymorphic, it is expected that the Malaysian Chinese would exhibit a polymorphism profile different from those of the Chinese populations in other geographical locations.
    Matched MeSH terms: Cytochrome P-450 CYP2D6/genetics*
  17. Gan SH, Ismail R, Wan Adnan WA, Zulmi W, Kumaraswamy N, Larmie ET
    Br J Clin Pharmacol, 2004 Jun;57(6):785-9.
    PMID: 15151524
    A person with Type A personality is an 'aggressor' compared with the rarely harried Type B. Although debrisoquine hydroxylase (CYP2D6) capacity has been associated with personality, no study has specifically investigated its association with personality Type A and B. Therefore the aim of this research was to study the impact of CYP2D6 on Type A and B personality.
    Matched MeSH terms: Cytochrome P-450 CYP2D6/metabolism*
  18. Gan SH, Ismail R, Wan Adnan WA, Wan Z
    Clin Chim Acta, 2003 Mar;329(1-2):61-8.
    PMID: 12589966 DOI: 10.1016/s0009-8981(03)00019-6
    BACKGROUND: Hair roots provide a useful alternative to blood as a source of DNA for genotyping. Besides simple and non-invasive collections, the DNA extraction step is also easy to perform and is fast. The aim of our study is to determine if hair roots can be used to genotype all of the common CYP2D6 alleles for routine screening purposes.

    METHOD: The study complies with the Declaration of Helsinki. After obtaining informed consents, both blood and hair samples were collected from 92 patients for genotyping of the CYP2D6 gene. PCR was used to detect the following mutations: CYP2D6*1, *3, *4, *5, *9, *10, *17 and duplication gene. The results were compared where hair roots and blood were used as templates for DNA respectively.

    RESULTS: When blood was used as a source of DNA for genotyping, all of the investigated CYP2D6 alleles were successfully amplified. However, with hair roots, the genes with the larger fragment sizes: CYP2D6*5 and the duplication gene could not be amplified and the bands of other alleles investigated were faint when visualized under UV light.

    CONCLUSIONS: DNA extraction from hair roots and leucocytes yielded similar results but the DNA extracted from hair roots did not allow successful amplification of the longer genes such as the CYP2D6*5 and the duplication gene.
    Matched MeSH terms: Cytochrome P-450 CYP2D6/genetics*
  19. Lim EL, Seah TC, Koe XF, Wahab HA, Adenan MI, Jamil MF, et al.
    Toxicol In Vitro, 2013 Mar;27(2):812-24.
    PMID: 23274770 DOI: 10.1016/j.tiv.2012.12.014
    CYP450 enzymes are key determinants in drug toxicities, reduced pharmacological effect and adverse drug reactions. Mitragynine, an euphoric compound was evaluated for its effects on the expression of mRNAs encoding CYP1A2, CYP2D6 and CYP3A4 and protein expression and resultant enzymatic activity. The mRNA and protein expression of CYP450 isoforms were carried out using an optimized multiplex qRT-PCR assay and Western blot analysis. CYP1A2 and CYP3A4 enzyme activities were evaluated using P450-Glo™ assays. The effects of mitragynine on human CYP3A4 protein expression were determined using an optimized hCYP3A4-HepG2 cell-based assay. An in silico computational method to predict the binding conformation of mitragynine to the active site of the CYP3A4 enzyme was performed and further validated using in vitro CYP3A4 inhibition assays. Mitragynine was found to induce mRNA and protein expression of CYP1A2. For the highest concentration of 25 μM, induction of mRNA was approximately 70% that of the positive control and was consistent with the increased CYP1A2 enzymatic activity. Thus, mitragynine is a significant in vitro CYP1A2 inducer. However, it appeared to be a weak CYP3A4 inducer at the transcriptional level and a weak CYP3A4 enzyme inhibitor. It is therefore, unlikely to have any significant clinical effects on CYP3A4 activity.
    Matched MeSH terms: Cytochrome P-450 CYP2D6/genetics; Cytochrome P-450 CYP2D6/metabolism*
  20. Koe XF, Lim EL, Seah TC, Amanah A, Wahab HA, Adenan MI, et al.
    Food Chem Toxicol, 2013 Oct;60:98-108.
    PMID: 23876819 DOI: 10.1016/j.fct.2013.07.030
    Drug metabolism involving cytochrome P450 (CYP) enzymes is a key determinant of significant drug interactions. Deoxyelephantopin was evaluated for its effects on the expression of mRNAs encoding CYP1A2, CYP2D6 and CYP3A4, and protein expression and resultant enzymatic activity. The mRNA and protein expression of cytochrome isoforms were carried out using an optimized multiplex qRT-PCR assay and Western blot analysis, respectively. Human CYP3A4 protein expression was determined using an optimized hCYP3A4-HepG2 cell-based assay and the enzymatic activity was evaluated using P450-Glo™ CYP3A4 assay. The molecular interaction and possible inhibition of deoxyelephantopin of the CYP3A4 enzyme was determined in silico and further validated using substrate-specific CYP3A4 inhibition assays. Deoxyelephantopin produced no significant effect on the CYP1A2 and CYP2D6 mRNA and protein expression. However, it has a weak induction effect on CYP3A4 at the transcriptional level. In silico docking simulation showed that deoxyelephantopin has a weak interaction with CYP3A4 enzyme and it minimally affects the metabolism of CYP3A4 substrates. Deoxyelephantopin is not an in vitro CYP1A2 and CYP2D6 inducer. It is both a weak in vitro CYP3A4 inducer and inhibitor and is unlikely to elicit a clinically significant effect in human.
    Matched MeSH terms: Cytochrome P-450 CYP2D6/genetics; Cytochrome P-450 CYP2D6/metabolism*
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