Effect of Ethanol on the Binding of Warfarin Enantiomers to Human Serum Albumin

Label-free biosensing of lignans for therapeutics using engineered model surfaces

The label-free interaction analysis of macromolecules and small molecules has increasing importance nowadays, both in diagnostics and therapeutics. In the blood vascular system, human serum albumin (HSA) is a vital globular transport protein with potential multiple ligand binding sites. Characterizing the binding affinity of compounds to HSA is essential in pharmaceutics and in developing new compounds for clinical application. Aryltetralin lignans from the roots of Anthriscus sylvestris are potential antitumor therapeutic candidates, but their molecular scale interactions with specific biomolecules are unrevealed. Here, we applied the label-free grating-coupled interferometry (GCI) biosensing method with a polycarboxylate-based hydrogel layer with immobilized HSA on top of it. With this engineered model surface, we could determine the binding parameters of two novel aryltetralin lignans, deoxypodophyllotoxin (DPT), and angeloyl podophyllotoxin (APT) to HSA. Exploiting the multi-channel referencing ability, the unique surface sensitivity, and the throughput of GCI, we first revealed the specific biomolecular interactions. Traditional label-free kinetic measurements were also compared with a novel, fast way of measuring affinity kinetics using less sample material (repeated analyte pulses of increasing duration (RAPID)). Experiments with well-characterized molecular interactions (furosemide to carbonic-anhydrase (CAII) and warfarin, norfloxacin to HSA) were performed to prove the reliability of the RAPID method. In all investigated cases, the RAPID and traditional measurement gave similar affinity values. In the case of DPT, the measurements and relevant modeling suggested two binding sites on HSA, with dissociation constant values of K_d1 = 1.8 ± 0.01 μM, K_d2 = 3 ± 0.02 μM. In the case of APT, the experiments resulted in K_d1 = 9 ± 1.7 μM, K_d2 = 28 ± 0.3 μM. The obtained binding values might suggest the potential medical application of DPT and APT without further optimization of their binding affinity to HSA. These results could be also adapted to other biomolecules and applications where sample consumption and the rapidity of the measurements are critical.

[Assessment of individual risk of food interactions while taking warfarin]

AIM

To develop a questionnaire to assess the individual risk of food interactions in a patient taking warfarin.

MATERIALS AND METHODS

Based on the review of 159 literature sources, a test version of the questionnaire was formed. 196 respondents took part in the pilot part of the study to assess the multiplicity and volume of food consumption. For the initial assessment of the risk limit of the diet, complications of warfarin therapy were registered no earlier than 24 weeks later.

RESULTS

The final version of the questionnaire included 25 products that are most frequently consumed and significant in relation to the risk of alimentary interactions. The questionnaire contains 2 groups of products: increasing and decreasing the activity of warfarin. The volume and frequency of use of each product is evaluated in points that are calculated as the simple product of weights of frequency and volume, with a minimum value of 0 and maximum of 12. The number of points for each product is calculated separately. The points obtained are summed for a group of products that increase the activity of warfarin, and for a group of products that reduce it, and the overall risk score is calculated. The average number of points for the use of products that affect the activity of warfarin in patients with AF with complications of therapy was 75.7831.97 b. The calculation of the design validity of the questionnaire (Cronbachs a=0.864) showed a good level for confirmation purposes.

CONCLUSION

A specialized questionnaire was developed, implemented as a computer program, to assess the significance of food preferences in ensuring the safety and effectiveness of warfarin therapy. Further research is required to determine the risk limit of alimentary interactions of warfarin, but now this questionnaire can be used to monitor the uniformity of consumption of products that affect its activity. The authors suggested using a questionnaire for assessing the risk of food interactions as one of the factors influencing the decision to prescribe warfarin to patients with insufficient adherence to lifestyle modification.

Decrease in Efficacy of Warfarin as a Result of Drug-Drug Interaction (Case Report)

The one of the main aims in modern clinical pharmacology is to provide safe and effective therapy considering a frequent administration of several drugs having different drug-drug interactions. Warfarin belongs to the number of popular anticoagulants which along with its efficiency not infrequently alters anticoagulant characteristics when administered with other drugs and food products. A case of a decrease in the efficacy of warfarin in a patient with mitral stenosis while taking a combined choleretic drug is presented in the article. The components of this choleretic drug (dry animal bile, dry garlic extract, dry nettle extract, activated charcoal) could impair the absorption of warfarin, increase intestinal absorption of vitamin K, and have a negative effect on the anticoagulant effect of warfarin. Management of patients receiving anticoagulants should be performed in accordance with clinical recommendations. Prescription of drugs, including multicomponent ones, without proven efficacy, for such patients should be considering the potential drug interaction.

Clinically significant food preferences of patients with atrial fibrillation: a nosological and regional peculiarities

The aim of the investigation was to study the peculiarities of food consumption in patients with atrial fibrillation, capable of influencing the anticoagulant therapy with warfarin, in comparison with healthy volunteers and taking into account geographical specifics. Materials and methods. In an open cohort study, 196 respondents (88 men, 108 women) evaluated food preferences using a questionnaire survey. The quantitative evaluation of adherence to lifestyle modification was studied by QAA-25. Statistical data processing was performed by parametric (Student's t-test) and nonparametric (Wald-Wolfowitz, Kolmogorov-Smirnov, Pearson) analysis methods. Results. There were no statistically significant differences in food rations between the studied categories of respondents, both increasing [37.0±19.5 points versus 37.3±17.98 points; Wald-Wolfowitz (Z), p=0.16] and reducing the activity of warfarin [62.2±26.3 points versus 63.4±23.8 points; Wald-Wolfowitz (Z), p=0.95]. The absence of differences remained in the evaluation, taking into account regional characteristics of nutrition. The respondents were taking warfarin, there is no relationship between the level of commitment to the modification of lifestyle and diet modification. Conclusion: it is shown that medical recommendations aimed at correcting the eating behavior of respondents taking warfarin are not effective, which can be an independent risk factor for complications of both warfarin therapy and the underlying disease.

Chiral toxicology: it's the same thing...only different

Chiral substances possess a unique architecture such that, despite sharing identical molecular formulas, atom-to-atom linkages, and bonding distances, they cannot be superimposed. Thus, in the environment of living systems, where specific structure-activity relationships may be required for effect (e.g., enzymes, receptors, transporters, and DNA), the physiochemical and biochemical properties of racemic mixtures and individual stereoisomers can differ significantly. In drug development, enantiomeric selection to maximize clinical effects or mitigate drug toxicity has yielded both success and failure. Further complicating genetic polymorphisms in drug disposition, stereoselective metabolism of chiral compounds can additionally influence pharmacokinetics, pharmacodynamics, and toxicity. Optically pure pharmaceuticals may undergo racemization in vivo, negating single enantiomer benefits or inducing unexpected effects. Appropriate chiral antidotes must be selected for therapeutic benefit and to minimize adverse events. Enantiomers may possess different carcinogenicity and teratogenicity. Environmental toxicology provides several examples in which compound bioaccumulation, persistence, and toxicity show chiral dependence. In forensic toxicology, chiral analysis has been applied to illicit drug preparations and biological specimens, with the potential to assist in determination of cause of death and aid in the correct interpretation of substance abuse and "doping" screens. Adrenergic agonists and antagonist, nonsteroidal anti-inflammatory agents, SSRIs, opioids, warfarin, valproate, thalidomide, retinoic acid, N-acetylcysteine, carnitine, penicillamine, leucovorin, glucarpidase, pesticides, polychlorinated biphenyls, phenylethylamines, and additional compounds will be discussed to illustrate important concepts in "chiral toxicology."