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  1. Zyoud SH, Waring WS, Al-Jabi SW, Sweileh WM, Rahhal B, Awang R
    Basic Clin. Pharmacol. Toxicol., 2016 Nov;119(5):512-519.
    PMID: 27098056 DOI: 10.1111/bcpt.12609
    In recent years, there has been increasing interest in the role of intravenous lipid formulations as potential antidotes in patients with severe cardiotoxicity caused by drug toxicity. The aim of this study was to conduct a comprehensive bibliometric analysis of all human and animal studies featuring lipid emulsion as an antidote for the treatment of acute poisoning. The Scopus database search was performed on 5 February 2016 to analyse the research output related to intravenous lipid emulsion as an antidote for the treatment of acute poisoning. Research indicators used for analysis included total number of articles, date (year) of publication, total citations, value of the h-index, document types, countries of publication, journal names, collaboration patterns and institutions. A total of 594 articles were retrieved from Scopus database for the period of 1955-2015. The percentage share of global intravenous lipid emulsion research output showed that research output was 85.86% in 2006-2015 with yearly average growth in this field of 51 articles per year. The USA, United Kingdom (UK), France, Canada, New Zealand, Germany, Australia, China, Turkey and Japan accounted for 449 (75.6%) of all the publications. The total number of citations for all documents was 9,333, with an average of 15.7 citations per document. The h-index of the retrieved documents for lipid emulsion research as antidote for the treatment of acute poisoning was 49. The USA and the UK achieved the highest h-indices, 34 and 14, respectively. New Zealand produced the greatest number of documents with international collaboration (51.9%) followed by Australia (50%) and Canada (41.4%) out of the total number of publications for each country. In summary, we found an increase in the number of publications in the field of lipid emulsion after 2006. The results of this study demonstrate that the majority of publications in the field of lipid emulsion were published by high-income countries. Researchers from institutions in the USA led scientific production on lipid emulsion research. There is an obvious need to promote a deeper engagement through international collaborative research projects and funding mechanisms.
  2. Lee CY
    Basic Clin. Pharmacol. Toxicol., 2016 Mar;118(3):173-80.
    PMID: 26551045 DOI: 10.1111/bcpt.12524
    Type 2 diabetes mellitus is a chronic metabolic disorder that has become the fourth leading cause of death in the developed countries. The disorder is characterized by pancreatic β-cells dysfunction, which causes hyperglycaemia leading to several other complications. Treatment by far, which focuses on insulin administration and glycaemic control, has not been satisfactory. Glucagon-like peptide-1 (GLP1) is an endogenous peptide that stimulates post-prandial insulin secretion. Despite being able to mimic the effect of insulin, GLP1 has not been the target drug in diabetes treatment due to the peptide's metabolic instability. After a decade-long effort to improve the pharmacokinetics of GLP1, a number of GLP1 analogues are currently available on the market. The current Minireview does not discuss these drugs but presents strategies that were undertaken to address the weaknesses of the native GLP1, particularly drug delivery techniques used in developing GLP1 nanoparticles and modified GLP1 molecule. The article highlights how each of the selected preparations has improved the efficacy of GLP1, and more importantly, through an overview of these studies, it will provide an insight into strategies that may be adopted in the future in the development of a more effective oral GLP1 formulation.
  3. Mohamed IN, Helms PJ, McLay JS
    Basic Clin. Pharmacol. Toxicol., 2012 Dec;111(6):396-401.
    PMID: 22734606 DOI: 10.1111/j.1742-7843.2012.00917.x
    Drug switching is a common medical practice. It indicates continuation of treatment regardless of the reason why the original therapy was stopped and switched. Therefore, the aims of this study were to develop a novel method for determining drug switching from routinely acquired NHS health data and to explore the aspect of continuation of care for patients. Patients who were first prescribed ramipril, simvastatin and an angiotensin receptor blocker (ARB) between 1 March 2004 and 28 February 2007 and discontinued their medication within 6 months of the index prescription were identified from the PTI database. The identified patients were then categorized into three groups: i) patients who were switched to a different drug for the same medical condition, ii) patients who were being prescribed with other types of antihypertensive/lipid-regulating drug prior to the initiation of study; and iii) patients who were without any continuation of care or therapy. Twenty percent (808), 29%(1429) and 14%(455) of the identified patients discontinued ramipril, simvastatin and ARB, respectively, within 6 months of an index prescription. Among the ramipril discontinuation group, 36.4% of the patients were switched to another antihypertensive, while another 31.6% of them were without continuation of care. In patients discontinuing ARB, 30.6% were switched, while another 30.1% were without continuation of treatment. In patients discontinuing simvastatin, 28.8% were switched to another lipid-regulating medicine, while another 63.1% of them were without continuation of care. The results of this study confirm that primary care prescribing databases can be used to determine drug-switching information and continuation of care/therapy.
  4. Ming-Tatt L, Khalivulla SI, Akhtar MN, Mohamad AS, Perimal EK, Khalid MH, et al.
    Basic Clin. Pharmacol. Toxicol., 2012 Mar;110(3):275-82.
    PMID: 21967232 DOI: 10.1111/j.1742-7843.2011.00804.x
    This study investigated the potential antinociceptive efficacy of a novel synthetic curcuminoid analogue, 2,6-bis-(4-hydroxy-3-methoxybenzylidene)cyclohexanone (BHMC), using chemical- and thermal-induced nociception test models in mice. BHMC (0.03, 0.1, 0.3 and 1.0 mg/kg) administered via intraperitoneal route (i.p.) produced significant dose-related inhibition in the acetic acid-induced abdominal constriction test in mice with an ID(50) of 0.15 (0.13-0.18) mg/kg. It was also demonstrated that BHMC produced significant inhibition in both neurogenic (first phase) and inflammatory phases (second phase) of the formalin-induced paw licking test with an ID(50) of 0.35 (0.27-0.46) mg/kg and 0.07 (0.06-0.08) mg/kg, respectively. Similarly, BHMC also exerted significant increase in the response latency period in the hot-plate test. Moreover, the antinociceptive effect of the BHMC in the formalin-induced paw licking test and the hot-plate test was antagonized by pre-treatment with the non-selective opioid receptor antagonist, naloxone. Together, these results indicate that the compound acts both centrally and peripherally. In addition, administration of BHMC exhibited significant inhibition of the neurogenic nociception induced by intraplantar injections of glutamate and capsaicin with ID(50) of 0.66 (0.41-1.07) mg/kg and 0.42 (0.38-0.51) mg/kg, respectively. Finally, it was also shown that BHMC-induced antinociception was devoid of toxic effects and its antinociceptive effect was associated with neither muscle relaxant nor sedative action. In conclusion, BHMC at all doses investigated did not cause any toxic and sedative effects and produced pronounced central and peripheral antinociceptive activities. The central antinociceptive activity of BHMC was possibly mediated through activation of the opioid system as well as inhibition of the glutamatergic system and TRPV1 receptors, while the peripheral antinociceptive activity was perhaps mediated through inhibition of various inflammatory mediators.
  5. Hassan Y, Al-Jabi SW, Aziz NA, Looi I, Zyoud SH
    Basic Clin. Pharmacol. Toxicol., 2012 Apr;110(4):370-7.
    PMID: 22023326 DOI: 10.1111/j.1742-7843.2011.00825.x
    There has been recent interest in combining antiplatelets, angiotensin-converting enzyme inhibitors (ACEIs) and statins in primary and secondary ischaemic stroke prevention. This observational study was performed to evaluate the impact of adding ACEIs and/or statins to antiplatelets on post-stroke in-hospital mortality. Ischaemic stroke patients attending a hospital in Malaysia over an 18-month period were evaluated. Patients were categorized according to their vital status at discharge. Data included demographic information, risk factors, clinical characteristics and previous medications with particular attention on antiplatelets, ACEIs and statins. In-hospital mortality was compared among patients who were not taking antiplatelets, ACEIs or statins before stroke onset versus those who were taking antiplatelets alone or in combination with either ACEIs, statins or both. Data analysis was performed using SPSS version 15. Overall, 637 patients met the study inclusion criteria. After controlling for the effects of confounders, adding ACEIs or statins to antiplatelets significantly decreased the incidence of death after stroke attack by 68% (p = 0.036) and 81% (p = 0.010), respectively, compared to patients on antiplatelets alone or none of these medications. Additionally, the addition of both ACEIs and statins to antiplatelet medication resulted in the highest reduction (by 94%) of the occurrence of death after stroke attack (p < 0.001). Our results suggest that adding ACEIs and/or statins to antiplatelets for patients at risk of developing stroke, either as a primary or as a secondary preventive regimen, was associated with a significant reduction in the incidence of mortality after ischaemic stroke than antiplatelets alone. These results might help reduce the rate of ischaemic stroke morbidity and mortality by enhancing the application of specific therapeutic and management strategies for patients at a high risk of acute stroke.
  6. Perimal EK, Akhtar MN, Mohamad AS, Khalid MH, Ming OH, Khalid S, et al.
    Basic Clin. Pharmacol. Toxicol., 2011 Mar;108(3):155-62.
    PMID: 20955360 DOI: 10.1111/j.1742-7843.2010.00635.x
    This study investigated the antinociceptive effects of zerumbone in chemical behavioural models of nociception in mice. Zerumbone given through intraperitoneal route (i.p.) produced dose-related antinociception when assessed on acetic acid-induced abdominal writhing test in mice. In addition, the i.p. administration of zerumbone exhibited significant inhibition of the neurogenic pain induced by intraplantar (i.pl.) injection of capsaicin and bradykinin. Likewise, zerumbone given by i.p. route reduced the nociception produced by i.pl. injection of glutamate and phorbol myristate acetate (PMA). The antinociception caused by zerumbone in the acetic acid test was significantly attenuated by i.p. pre-treatment of mice with l-arginine (nitric oxide precursor) and glibenclamide (ATP-sensitive K(+) channel inhibitor). However, the antinociception of zerumbone was enhanced by methylene blue (non-specific gyanylyl cyclase inhibitor). Together, these results indicate that zerumbone produces pronounced antinociception against chemical models of nociception in mice. It also strongly suggests that the l-arginine-nitric oxide-cGMP-PKC-K(+) ATP channel pathways, the TRPV1 and kinin B2 receptors play an important role in the zerumbone-induced antinociception.
  7. Mohamad AS, Akhtar MN, Khalivulla SI, Perimal EK, Khalid MH, Ong HM, et al.
    Basic Clin. Pharmacol. Toxicol., 2011 Jun;108(6):400-5.
    PMID: 21214864 DOI: 10.1111/j.1742-7843.2010.00670.x
    The possible mechanisms of action in the antinociceptive activity induced by systemic administration (intraperitoneal, i.p.) of flavokawin B (FKB) were analysed using chemical models of nociception in mice. It was demonstrated that i.p. administration of FKB to the mice at 0.3, 1.0, 3.0 and 10 mg/kg produced significant dose-related reduction in the number of abdominal constrictions. The antinociception induced by FKB in the acetic acid test was significantly attenuated by i.p. pre-treatment of mice with L-arginine, the substrate for nitric oxide synthase or glibenclamide, the ATP-sensitive K(+) channel inhibitor, but was enhanced by methylene blue, the non-specific guanylyl cyclase inhibitor. FKB also produced dose-dependent inhibition of licking response caused by intraplantar injection of phorbol 12-myristate 13-acetate, a protein kinase C activator (PKC). Together, these data indicate that the NO/cyclic guanosine monophosphate/PKC/ATP-sensitive K(+) channel pathway possibly participated in the antinociceptive action induced by FKB.
  8. Zyoud SH, Awang R, Sulaiman SA, Al-Jabi SW
    Basic Clin. Pharmacol. Toxicol., 2010 Nov;107(5):887-92.
    PMID: 20456332 DOI: 10.1111/j.1742-7843.2010.00594.x
    Identifying indices of poor prognosis at first presentation after acetaminophen poisoning is the key to both improving clinical care and determining targets for intervention. This study intended to document the prevalence, clinical characteristics and predictors of vomiting and to investigate the relationship between episodes of vomiting at first hospital presentation and outcome in acetaminophen poisoning. This retrospective cohort study included patients who attended the emergency department and were admitted within 24 hr of acetaminophen ingestion. The study was conducted over a period of 5 years from 1 January 2004 to 31 December 2008. Parametric and non-parametric tests were used to test differences between groups depending on the normality of the data. SPSS 15 was used for data analysis. Data from 291 patients were included. Vomiting was present in 65.3% of patients with acetaminophen poisoning at the time of first presentation. Multiple logistic regression showed that significant risk factors for vomiting were present among patients who reported an ingested dose of acetaminophen ≥10 g (p < 0.001) and a latency time of more than 8 hr (p = 0.030). Overall, an increasing trend in prothrombin time (p = 0.03), serum bilirubin (p < 0.001), serum creatinine (p = 0.005), serum potassium (p < 0.001), length of hospital stay (p < 0.001) and the prevalence of patients who had a serum acetaminophen level above a 'possible toxicity' treatment line (p = 0.001) were associated with an increased number of episodes of vomiting. In conclusion, vomiting was common among patients with acetaminophen poisoning. This study suggests that an increase in episodes of vomiting at first presentation appears to be an important risk marker of subsequent nephrotoxicity and hepatotoxicity.
  9. Zyoud SH, Awang R, Sulaiman SA, Khan HR, Sawalha AF, Sweileh WM, et al.
    Basic Clin. Pharmacol. Toxicol., 2010 Sep;107(3):718-23.
    PMID: 20374238 DOI: 10.1111/j.1742-7843.2010.00567.x
    Intravenous N-acetylcysteine is usually regarded as a safe antidote. However, during the infusion of the loading dose, different types of adverse drug reactions (ADR) may occur. The objective of this study was to investigate the relation between the incidence of different types of ADR and serum acetaminophen concentration in patients presenting to the hospital with acetaminophen overdose. This is a retrospective study of patients admitted to the hospital for acute acetaminophen overdose over a period of 5 years (1 January 2004 to 31 December 2008). Parametric and non-parametric tests were used to test differences between groups depending on the normality of the data. SPSS 15 was used for data analysis. Of 305 patients with acetaminophen overdose, 146 (47.9%) were treated with intravenous N-acetylcysteine and 139 (45.6%) were included in this study. Different types of ADR were observed in 94 (67.6%) patients. Low serum acetaminophen concentrations were significantly associated with cutaneous anaphylactoid reactions but not other types of ADR. Low serum acetaminophen concentration was significantly associated with flushing (p < 0.001), rash (p < 0.001) and pruritus (p < 0.001). However, there were no significant differences in serum acetaminophen concentrations between patients with and without the following ADR: gastrointestinal reactions (p = 0.77), respiratory reactions (p = 0.96), central nervous reactions (p = 0.82) and cardiovascular reactions (p = 0.37). In conclusion, low serum acetaminophen concentrations were associated with higher cutaneous anaphylactoid reactions. Such high serum acetaminophen concentrations may be protective against N-acetylcysteine-induced cutaneous ADR.
  10. Maniam S, Mohamed N, Shuid AN, Soelaiman IN
    Basic Clin. Pharmacol. Toxicol., 2008 Jul;103(1):55-60.
    PMID: 18598299 DOI: 10.1111/j.1742-7843.2008.00241.x
    The aim of this study was to investigate the effects of vitamin E on the levels of lipid peroxidation and antioxidant enzymes in rat bones. Fifty-six normal male Sprague-Dawley rats, aged 3 months, were randomly divided into seven groups with eight rats in each group. The age-matched control group was given the vehicle olive oil, by oral gavage daily. Six of the treatment groups received either palm tocotrienol or pure alpha-tocopherol at the dose of 30, 60 or 100 mg/kg body weight, by oral gavage daily, 6 days a week for 4 months. Thiobarbituric acid-reactive substance (TBARS) that is an index to measure the level of lipid peroxidation and the antioxidant enzymes, glutathione peroxidase and superoxide dismutase levels were measured in the femur at the end of the study. Palm tocotrienol at the dose of 100 mg/kg body weight significantly reduced the TBARS level in the femur with a significant increase in glutathione peroxidase activity compared to the age-matched control group. These were not observed in the alpha-tocopherol groups. Palm tocotrienol was more effective than pure alpha-tocopherol acetate in suppressing lipid peroxidation in bone. Palm tocotrienol showed better protective effect against free radical damage in the femur compared to alpha-tocopherol. This study suggests that palm tocotrienol plays an important role in preventing imbalance in bone metabolism due to free radicals.
  11. Yap MK, Tan NH, Sim SM, Fung SY, Tan CH
    Basic Clin. Pharmacol. Toxicol., 2015 Oct;117(4):274-9.
    PMID: 25819552 DOI: 10.1111/bcpt.12398
    The treatment protocol of antivenom in snake envenomation remains largely empirical, partly due to the insufficient knowledge of the pharmacokinetics of snake venoms and the effects of antivenoms on the blood venom levels in victims. In this study, we investigated the effect of a polyvalent antivenom on the serum venom antigen levels of Naja sputatrix (Javan spitting cobra) venom in experimentally envenomed rabbits. Intravenous infusion of 4 ml of Neuro Polyvalent Snake Antivenom [NPAV, F(ab')2 ] at 1 hr after envenomation caused a sharp decline of the serum venom antigen levels, followed by transient resurgence an hour later. The venom antigen resurgence was unlikely to be due to the mismatch of pharmacokinetics between the F(ab')2 and venom antigens, as the terminal half-life and volume of distribution of the F(ab')2 in serum were comparable to that of venom antigens (p > 0.05). Infusion of an additional 2 ml of NPAV was able to prevent resurgence of the serum venom antigen level, resulting in a substantial decrease (67.1%) of the total amount of circulating venom antigens over time course of envenomation. Our results showed that the neutralization potency of NPAV determined by neutralization assay in mice may not be an adequate indicator of its capability to modulate venom kinetics in relation to its in vivo efficacy to neutralize venom toxicity. The findings also support the recommendation of giving high initial dose of NPAV in cobra envenomation, with repeated doses as clinically indicated in the presence of rebound antigenemia and symptom recurrence.
  12. Li Lee M, Chung I, Yee Fung S, Kanthimathi MS, Hong Tan N
    Basic Clin. Pharmacol. Toxicol., 2014 Apr;114(4):336-43.
    PMID: 24118879 DOI: 10.1111/bcpt.12155
    King cobra (Ophiophagus hannah) venom L-amino acid oxidase (LAAO), a heat-stable enzyme, is an extremely potent antiproliferative agent against cancer cells when compared with LAAO isolated from other snake venoms. King cobra venom LAAO was shown to exhibit very strong antiproliferative activities against MCF-7 (human breast adenocarcinoma) and A549 (human lung adenocarcinoma) cells, with an IC50 value of 0.04±0.00 and 0.05±0.00 μg/mL, respectively, after 72-hr treatment. In comparison, its cytotoxicity was about 3-4 times lower when tested against human non-tumourigenic breast (184B5) and lung (NL 20) cells, suggesting selective antitumour activity. Furthermore, its potency in MCF-7 and A549 cell lines was greater than the effects of doxorubicin, a clinically established cancer chemotherapeutic agent, which showed an IC50 value of 0.18±0.03 and 0.63±0.21 μg/mL, respectively, against the two cell lines. The selective cytotoxic action of the LAAO was confirmed by phycoerythrin (PE) annexin V/7-amino-actinomycin (AAD) apoptotic assay, in which a significant increase in apoptotic cells was observed in LAAO-treated tumour cells than in their non-tumourigenic counterparts. The ability of LAAO to induce apoptosis in tumour cells was further demonstrated using caspase-3/7 and DNA fragmentation assays. We also determined that this enzyme may target oxidative stress in its killing of tumour cells, as its cytotoxicity was significantly reduced in the presence of catalase (a H2O2 scavenger). In view of its heat stability and selective and potent cytotoxic action on cancer cells, king cobra venom LAAO can be potentially developed for treating solid tumours.
  13. Yap MKK, Misuan N
    PMID: 30417596 DOI: 10.1111/bcpt.13169
    Type II diabetes mellitus (T2DM) is a chronic non-communicable disease due to abnormal insulin actions causing uncontrolled hyperglycaemia. The treatment for T2DM, for instance, metformin and incretin mimetic, mainly focuses on the restoration of insulin sensitivity and secretion. Exendin-4 is a short incretin-mimetic peptide consisting of 39 amino acids. It is discovered in the venom of Heloderma suspectum as a full agonist for the glucagon-like peptide 1 (GLP-1) receptor and produces insulinotropic effects. It is more resistant to enzymatic degradation by dipeptidyl-peptidase-4 and has a longer half-life than the endogenous GLP-1; thus, it is further developed as an incretin hormone analogue used to treat T2DM. The helical region of the peptide first interacts with the extracellular N-terminal domain (NTD) of GLP-1 receptor while the C-terminal extension containing the tryptophan cage further enhances its binding affinity. After binding to the NTD of the receptor, it may cause the receptor to switch from its auto-inhibited state of the receptor to its auto-activated state. Exendin-4 enhances the physiological functions of β-cells and the up-regulation of GLP-1 receptors, thus reducing the plasma glucose levels. Moreover, exendin-4 has also been found to ameliorate neuropathy, nephropathy and ventricular remodelling. The therapeutic effects of exendin-4 have also been extrapolated into several clinical trials. Although exendin-4 has a reasonable subcutaneous bioavailability, its half-life is rather short. Therefore, several modifications have been undertaken to improve its pharmacokinetics and insulinotropic potency. This review focuses on the pharmacology of exendin-4 and the structure-function relationships of exendin-4 with GLP-1 receptor. The review also highlights some challenges and future directions in the improvement of exendin-4 as an anti-diabetic drug.
  14. Bjørklund G, Dadar M, Martins N, Chirumbolo S, Goh BH, Smetanina K, et al.
    Basic Clin. Pharmacol. Toxicol., 2018 Jun;122(6):539-558.
    PMID: 29369521 DOI: 10.1111/bcpt.12972
    Several studies have reported that nature-derived antioxidants may prevent free radicals over-production and therefore control the onset and prevent the exacerbation of different kinds of diseases caused by oxidative stress and redox-derived stressors, including ageing, fundamentally by suppressing the oxidative by-products-mediated degradation. Naturally derived antioxidants exert their anti-ageing action via a panoply of signalling systems, many of which engaging reactive oxygen and nitrogen species scavenging, with the Nrf2/Keap1-ARE system and improving the many survival genes and functions (such as the pathway mTOR/Foxo/SIRT1) able to slow cellular senescence. Most of the research in this field has evaluated the regulative effects and even pathways of herbal extracts with antioxidant property in the ageing process, and various age-related disorders such as cardiovascular disease, ischaemia-reperfusion injury, coronary and myocardial circulatory perfusion, peripheral vascular resistance, and even neurodegenerative disorders are prevented plant phytochemicals often via their antioxidant potential. A much more complex ability to interact with survival functions makes these compounds successfully active in preventing ageing-related disorders. This report aimed to discuss in more detail some selected medicinal plants including Allium sativum, Aloe vera, Crataegus spp., Cynara scolymus, Eleutherococcus senticosus, Ginkgo biloba, Hippophae rhamnoides, Panax ginseng, Rosmarinus officinalis, Schizandra chinensis, Vitis vinifera and seaweeds in the prevention of ageing-related pathologies. A systematic overview of the relevant information in the antioxidant function of the many herbal products reviewed here for the control of the ageing process is proposed, to provide a new horizon on the design of anti-ageing herbal medicines.
  15. Zainal Abidin SA, Rajadurai P, Chowdhury MEH, Ahmad Rusmili MR, Othman I, Naidu R
    Basic Clin. Pharmacol. Toxicol., 2018 Nov;123(5):577-588.
    PMID: 29908095 DOI: 10.1111/bcpt.13060
    The aim of this study was to investigate the cytotoxic, antiproliferative activity and the induction of apoptosis by L-amino acid oxidase isolated from Calloselasma rhodostoma crude venom (CR-LAAO) on human colon cancer cells. CR-LAAO was purified using three chromatographic steps: molecular exclusion using G-50 gel filtration resin, ion-exchange by MonoQ column and desalted on a G25 column. The purity and identity of the isolated CR-LAAO was confirmed by SDS-PAGE and LC-MS/MS. CR-LAAO demonstrated time- and dose-dependent cytotoxic activity on SW480 (primary human colon cancer cells) and SW620 (metastatic human colon cancer cells) with an EC50 values of 6 μg/ml and 7 μg/ml at 48 hr, respectively. Quantification of apoptotic cells based on morphological features demonstrated significant increase in apoptotic cell population in both SW480 and SW620 cells which peaked at 48 hr. Significant increase in caspase-3 activity and reduction in Bcl-2 levels were demonstrated following CR-LAAO treatment. These data provide evidence on the potential anticancer activity of CR-LAAO from the venom of C. rhodostoma for therapeutic intervention of human colon cancer.
  16. Abu-Bakar A, Hu H, Lang MA
    Basic Clin. Pharmacol. Toxicol., 2018 Sep;123 Suppl 5:72-80.
    PMID: 29788535 DOI: 10.1111/bcpt.13046
    The murine cytochrome P450 2a5 (Cyp2a5) gene is regulated by complex interactions of various stress-activated transcription factors (TFs). Elevated Cyp2a5 transcription under chemical-induced stress conditions is achieved by interplay between the various TFs - including as aryl hydrocarbon receptor (AhR) and nuclear factor (erythroid-derived 2)-like 2 wild-type (Nrf2) - at the 'stress-responding' cluster of response elements on the Cyp2a5 promoter, as well as through mRNA stabilization mediated by interaction of the stress-activated heterogeneous nuclear ribonucleoprotein A1 (hnRNP A1) with the 3'-UTR of the CYP2A5 mRNA. We designed a unique toxicity pathway-based reporter assay to include regulatory regions from both the 5' and the 3' untranslated regions of Cyp2a5 in a luciferase reporter plasmid to reflect in vivo responses to chemical insult. Human breast cancer MCF-7 cells were stably transfected with pGL4.38-Cyp2a5_Wt3k (wild-type) or mutant - pGL4.38-Cyp2a5_StREMut and pGL4.38-Cyp2a5_XREMut - reporter gene to monitor chemical-induced cellular response mediated by AhR and Nrf2 signalling. The recombinant cells were treated with representative of AhR agonist, polycyclic aromatic hydrocarbons, brominated flame retardant, fluorosurfactant, aromatic organic compound and metal, to determine the sensitivity of the Cyp2a5 promoter-based gene reporter assays to chemical insults by measuring the LC50 and EC50 of the respective chemicals. The three assays are sensitive to sublethal cellular responses of chemicals, which is an ideal feature for toxicity pathway-based bioassay for toxicity prediction. The wild-type reporter responded well to chemicals that activate crosstalk between the AhR and Nrf2, whilst the mutant reporters effectively gauge cellular response driven by either Nrf2/StRE or AhR/XRE signalling. Thus, the three gene reporter assays could be used tandemly to determine the predominant toxicity pathway of a given compound.
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