Ontogeny of rat CYP2E1 and CYP1A2 : a characterization and a pharmacokinetic model

Infantile exposure to xenobiotics, e.g. from breastfeeding, poses a serious toxicity risk. Since the toxicokinetic mechanisms that principally determine exposure outcomes undergo a significant developmental maturation, infants may respond to exposures in a different way than adults. Hence, suitable model systems are required to provide risk relevant information in pediatric populations. This dissertation’s primary goal was to provide a critical evaluation of two such model systems; first, a pharmacokinetic model that may predict an infant’s capacity to eliminate toxicants by cytochrome P-450 (CYP) mechanisms and second, the developing rat as a model of human CYP2E1 and CYP1A2 ontogeny.The first objective was to evaluate underlying assumptions of a pharmacokinetic model that describes the ontogeny of hepatic CYP activity using the rat. The study recognized some discrepancies with the stated assumptions. The impact of these discrepancies on the potential applicability of the model is discussed. As proof-of-concept, the observed data were fit to a model describing rat CYP2E1 and CYP1A2 ontogeny. A reasonable correlation (r = 0.75) was observed between observed and predicted oral clearance values of a CYP2E1 substrate indicating the potential applicability of such a model in risk assessment. The second objective was to conduct an extensive characterization of rat hepatic CYP2E1 and CYP1A2 ontogeny at mRNA, protein, activity and intrahepatic expression levels. The results were compared to available human data to determine the appropriateness of the rat for assessment of toxicokinetic mechanisms underlying age-dependent differences in susceptibility to toxicity. Similarities in age-dependent changes in mRNA, activity and zonal hepatic expression patterns were noted between the rat and human prior to weaning. Unlike human data, rats show good correlation between changes in CYP2E1 and CYP1A2 activity and transcript levels, but not with the immunoquantifiable protein. Recognizing such similarities and differences between rats and human regarding onset, rate and pattern of CYP ontogeny will improve the accuracy of rat-to-human extrapolation of developmental toxicokinetic data. Overall, the dissertation research provides mounting and supportive evidence for the use of such model systems in providing risk-relevant information in pediatric populations and to identify toxicokinetic mechanisms underlying age-dependent differences in susceptibility to toxicity

Attenuated Combined Action of Cyclosporine A and Hyperlipidemia on Atherogenesis in Rabbits by Thymoquinone

This descriptive study investigates in a rabbit model of atherosclerosis (i) the extent of atherogenesis induced by cyclosporine A (CsA) or hyperlipidemia alone or in combination and (ii) whether thymoquinone (TQ), a known herbal antioxidant, offers protection against these effects. New Zealand White female rabbits were assigned to five groups of six animals each: Group I, control; Group II, CsA [25 mg kg−1 day−1 orally (PO)]; Group III, 1% cholesterol; Group IV, 1% cholesterol + CsA (25 mg kg−1 day−1 PO); and Group V, 1% cholesterol + CsA (25 mg kg−1 day−1 PO) + TQ (10 mg kg−1 day−1 PO). Lipids and oxidative stress parameters [Malondialdehyde (MDA) and protein carbonyl] and aortic atherosclerosis were compared. CsA alone did not show a significant effect on either serum lipids and did not induce atherosclerosis. High-cholesterol diet induced atherosclerosis (45 ± 11% of the intimal surface of aorta was covered with atherosclerotic plaques). CsA and high-cholesterol diet increased atherosclerosis severity as measured from intimal and media lesions, but did not affect the extent of atherosclerosis. TQ decreased aortic MDA by 83%. It was also associated with reduced aortic atherosclerosis extend by 52% compared with Group IV. We concluded that (i) CsA aggravates hyperlipidemia-induced atherosclerosis and (ii) TQ attenuates the oxidative stress and atherogenesis induced by the combined effect of CsA and hyperlipidemia

Biosimilars: Review of regulatory, manufacturing, analytical aspects and beyond

Biologics have more complex production processes compared to small-molecule drugs. They may even prove labile when drifting from batch-to-batch or in different production locations. The development of new similar biological product was regulated early to face the relevant challenges of this industry. As a result, since 2006 biosimilars were introduced to biotechnology arena with a massive competition in pharmaceutical industry. In this review, the aspects related to similarity testing of biosimilars to the original biological products are discussed involving manufacturing challenges to ensure the quality, safety, and efficacy of these products to the patient health. Immunogenicity studies are highlighted as an important part of the safety assessments. Additionally, several analytical methods that are usually used to evaluate biosimilars in comparison to their reference biologic are summarized and categorized in terms of the intended physicochemical and biological characterization. On the other hand, the international efforts of several regulatory agencies including the European Medicines Agency, World Health Organization and United States Food and Drug Administration for biosimilar development are discussed according to updated revised guidelines

Original Article Attenuated Combined Action of Cyclosporine A and Hyperlipidemia on Atherogenesis in Rabbits by Thymoquinone

Copyright © 2011 Ahmed Ragheb et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. This descriptive study investigates in a rabbit model of atherosclerosis (i) the extent of atherogenesis induced by cyclosporine A (CsA) or hyperlipidemia alone or in combination and (ii) whether thymoquinone (TQ), a known herbal antioxidant, offers protection against these effects. New Zealand White female rabbits were assigned to five groups of six animals each: Group I

The protective effect of thymoquinone, an anti-oxidant and anti--inflammatory agent, against renal injury: A review

Thymoquinone (TQ), 2-Isopropyl-5-methyl-1, 4-benzoquinone, is one of the most active ingredients of <i>Nigella Sativa </i>seeds. TQ has a variety of beneficial properties including anti-oxidative and anti-inflammatory activities. Studies have provided original observations on the role of oxidative stress and inflammation in the development of renal diseases such as glomerulo-nephritis and drug-induced nephrotoxicity. The renoprotective effects of TQ have been demons-trated in animal models. Also, TQ has been used successfully in treating allergic diseases in humans. The aim of this review is to highlight the importance of reactive oxygen species in renal pathophysiology and the intriguing possibility for a role of TQ in the prevention of and/or protection from renal injury in humans

The Antihypertensive Effect of Quercetin in Young Spontaneously Hypertensive Rats; Role of Arachidonic Acid Metabolism

Hypertension affects almost 50% of the adult American population. Metabolites of arachidonic acid (AA) in the kidney play an important role in blood pressure regulation. The present study investigates the blood pressure-lowering potential of quercetin (QR), a naturally occurring polyphenol, and examines its correlation to the modulation of AA metabolism. Spontaneously hypertensive rats (SHR) were randomly divided into four groups. Treatment groups were administered QR in drinking water at concentrations of 10, 30, and 60 mg/L. Blood pressure was monitored at seven-day intervals. After a total of seven weeks of treatment, rats were killed and kidney tissues were collected to examine the activity of the two major enzymes involved in AA metabolism in the kidney, namely cytochrome P450 (CYP)4A and soluble epoxide hydrolase (sEH). Medium- and high-dose QR resisted the rise in blood pressure observed in the untreated SHR and significantly inhibited the activity of the CYP4A enzyme in renal cortical microsomes. The activity of the sEH enzyme in renal cortical cytosols was significantly inhibited only by the high QR dose. Our data not only demonstrate the antihypertensive effect of QR, but also provide a novel mechanism for its underlying cardioprotective properties

Development and Validation of High-Throughput Bioanalytical Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS) Method for the Quantification of Newly Synthesized Antitumor Carbonic Anhydrase Inhibitors in Human Plasma

In the present study, a sensitive and fully validated bioanalytical high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) method has been developed for the quantitative determination of three newly synthesized carbonic anhydrases inhibitors (CAIs) with potential antitumor activity in human plasma. The analytes and the internal standard (IS) were extracted using 1.5 mL acetonitrile from only 450 &micro;L aliquots of human plasma to achieve the desired protein precipitation. Chromatographic separations were achieved on Phenomenex Kinetex&reg; C18 column (100 &times; 4.6 mm, 2.6 &micro;m) using a binary gradient elution mode with a run time of less than 6 min. The mobile phase consisted of solvent (A): 0.1% formic acid in 50% methanol and solvent B: 0.1% formic acid in acetonitrile (30:70, v/v), pumped at a flow rate of 0.8 mL/min. Detection was employed using triple quadrupole tandem mass spectrometer (API 3500) equipped with an electrospray ionization (ESI) source in the positive ion mode. Multiple reaction monitoring (MRM) mode was selected for quantitation through monitoring the precursor-to-parent ion transition at m/z 291.9 &rarr; 173.0, m/z 396.9 &rarr; 225.1, m/z 388.9 &rarr; 217.0, and m/z 146.9 &rarr; 91.0 for AW-9a, WES-1, WES-2, and Coumarin (IS), respectively. Linearity was computed using the weighted least-squares linear regression method (1/x2) over a concentration range of 1&ndash;1000, 2.5&ndash;800, and 5&ndash;500 ng/mL for AW-9a, WES-1, and WES-2; respectively. The bioanalytical LC-MS/MS method was fully validated as per U.S. Food and Drug Administration (FDA) guidelines with all respect to linearity, accuracy, precision, carry-over, selectivity, dilution integrity, and stability. The proposed LC-MS/MS method was applied successfully for the determination of all investigated drugs in spiked human plasma with no significant matrix effect, which is a crucial cornerstone in further therapeutic drug monitoring of newly developed therapeutic agents

The effects of genetic polymorphism on toxicity and pharmacokinetics of methotrexate in Egyptian adult patients with leukaemia or lymphoma

Polymorphisms in genes coding folate-metabolising enzymes might alter the pharmacokinetics and sensitivity for methotrexate “MTX”.The aim of the study aimed to investigate the influence of MTHFR C677T, DHFR19 Ins/del, GGH −401 C > T, and MTR A2756G polymorphisms on MTX toxicity and pharmacokinetics in Egyptian patients with Acute lymphoblastic leukaemia (ALL) or Non-Hodgkin lymphoma (NHL).Fifty adult Egyptian patients with ALL and NHL, treated with high dose MTX, were prospectively enrolled in the study. Clinical and biochemical data was collected objectively from medical records after each cycle of MTX. Plasma concentrations of MTX were measured after 72 h of initiation of infusion. Genotyping was done with a PCR-ARMS and PCR-RFLP assays.The MTHFR C677T T variants significantly increased the risk of leukopoenia, whereas the genotype MTHFR 677 C > T TT significantly associated with lymphocytopenia, thrombocytopenia, and anaemia. The genotype GGH-401 TT was significantly correlated with anaemia. Plasma MTX level was significantly higher in patients with MTR A2756G G variants.MTHFR polymorphism played the main role in MTX toxicities. The pharmacokinetics of MTX was affected by MTR polymorphism. GGH mutation was mainly concerned with anaemia. Pharmacogenetic testing are recommended to optimise MTX therapy. Polymorphisms in genes coding folate-metabolising enzymes might alter the pharmacokinetics and sensitivity for methotrexate “MTX”. The aim of the study aimed to investigate the influence of MTHFR C677T, DHFR19 Ins/del, GGH −401 C > T, and MTR A2756G polymorphisms on MTX toxicity and pharmacokinetics in Egyptian patients with Acute lymphoblastic leukaemia (ALL) or Non-Hodgkin lymphoma (NHL). Fifty adult Egyptian patients with ALL and NHL, treated with high dose MTX, were prospectively enrolled in the study. Clinical and biochemical data was collected objectively from medical records after each cycle of MTX. Plasma concentrations of MTX were measured after 72 h of initiation of infusion. Genotyping was done with a PCR-ARMS and PCR-RFLP assays. The MTHFR C677T T variants significantly increased the risk of leukopoenia, whereas the genotype MTHFR 677 C > T TT significantly associated with lymphocytopenia, thrombocytopenia, and anaemia. The genotype GGH-401 TT was significantly correlated with anaemia. Plasma MTX level was significantly higher in patients with MTR A2756G G variants. MTHFR polymorphism played the main role in MTX toxicities. The pharmacokinetics of MTX was affected by MTR polymorphism. GGH mutation was mainly concerned with anaemia. Pharmacogenetic testing are recommended to optimise MTX therapy.</p