Three-dimensional quantitative structure–activity relationship (3D-QSAR) analysis and molecular docking-based combined in silico rational approach to design potent and novel TRPV1 antagonists

The discovery of clinically relevant antagonists of TRPV1 for neuropathy pain therapy has proven to be a challenging task. For better understanding of the molecular interactions of antagonists with TRPV1 receptor, a series of chroman and tetrahydroquinoline ureas were analyzed by k-nearest neighbor molecular field analysis (kNN-MFA) and molecular docking. To elucidate the structural properties required for activity as TRPV1 antagonists, we report here kNN-MFA-based 3D-QSAR model for chroman and tetrahydroquinoline ureas as potent TRPV1 antagonists. Sphere exclusion method was used for dividing the compounds into training (26 compounds) and test (5 compounds) set. Overall model classification accuracy was 81.35 % (q ² = 0.8135, representing internal validation) in training set and 81.44 % (pred_r ² = 0.8144, representing external validation) in test set using stepwise forward as a method of variable selection. The stereo view of molecular rectangular grid field of 3D-QSAR using this approach showed that steric and hydrophobic effects dominantly determine binding affinities. Furthermore, the crystal structure of TRPV1 was obtained from protein data bank (PDB code 2NYJ, resolution 3.20 Å), and docking of 31 TRPV1 antagonists into putative binding sites of the TRPV1 were studies. Molecular docking was employed to explore the binding mode between these compounds and the receptor, as well as help understanding the structure–activity relationship revealed by kNN-MFA. Our QSAR model and molecular docking results corroborate with each other and propose directions for the design of new antagonists with better activity toward TRPV1.     

Sera from patients with heparin-induced thrombocytopenia generate platelet-derived microparticles with procoagulant activity: an explanation for the thrombotic complications of heparin-induced thrombocytopenia

Heparin-induced thrombocytopenia is characterized by moderate thrombocytopenia and thrombotic complications, whereas quinine/quinidine-induced thrombocytopenia usually presents with severe thrombocytopenia and bleeding. Using flow cytometry and assays of procoagulant activity, we investigated whether sera from patients with these immune drug reactions could stimulate normal platelets to generate platelet-derived microparticles with procoagulant activity. Sera or purified IgG from patients with heparin-induced thrombocytopenia stimulated the formation of platelet-derived microparticles in a heparin-dependent fashion. Further studies showed that heparin-induced thrombocytopenia sera also produced a marked increase in procoagulant activity. In contrast, sera from patients with quinine- or quinidine-induced thrombocytopenia did not generate platelet-derived microparticles nor generate increased procoagulant activity. However, quinine/quinidine-induced thrombocytopenia sera produced a significant increase in the binding of IgG to platelets in a drug-dependent fashion, whereas sera from patients with heparin-induced thrombocytopenia demonstrated no drug-dependent binding of IgG to platelets. We also observed increased levels of circulating microparticles in patients with acute heparin-induced thrombocytopenia compared with control patients. Our observations indicate that the generation of procoagulant platelet-derived microparticles in vivo is a plausible explanation for the thrombotic complications observed in some patients with heparin-induced thrombocytopenia.     

Rates of hospitalization among patients with deep vein thrombosis before and after the introduction of rivaroxaban

Background. Compared to warfarin, the non-vitamin K antagonist oral anticoagulant rivaroxaban may have advantages in treating patients with venous thromboembolism, because injectable bridging therapy and routine laboratory monitoring are not required. The objective of this study was to compare the rate of hospitalization in patients treated with rivaroxaban after its introduction with what it would have been before the introduction of rivaroxaban. Methods. A retrospective claims analysis was conducted using the MarketScan Hospital Drug Database from January 2011 to December 2013. Adult patients with a primary diagnosis of deep vein thrombosis (DVT) treated with rivaroxaban or low-molecular-weight heparin (LMWH) bridged to warfarin during the first day of an evaluation at a hospital were identified. Based on propensity-score methods, historical LMWH/warfarin patients (i.e., patients who received LMWH/warfarin before the approval of rivaroxaban) were matched 4:1 to rivaroxaban patients, and the rates of hospitalization were compared. Results. All rivaroxaban-treated patients (n = 134) in the database were well matched with four historical LMWH/warfarin-treated patients (n = 536). Among the rivaroxaban cohort, 60% of the patients were admitted to the hospital, compared to 82% of the historical patients treated with LMWH/warfarin in the matched cohort. The difference was statistically significant and corresponded to a 27% reduction in hospital admissions (rate ratio [95% confidence interval]: 0.73 [0.62–0.84]). Hospital admission rates adjusted for time-trend analyses also led to similar results. Conclusion. The availability of rivaroxaban significantly reduced the hospitalization rate in patients with DVT treated with rivaroxaban compared to what it would have been if only LMWH/warfarin were available.     

Body fat measurement in Indian men: comparison of three methods based on a two-compartment model

Obesity is a major risk factor for diabetes and related disorders. The current classification of obesity is based on body mass index (BMI, kg/m(2)), which is a surrogate for the total body fat. Since the relationship between BMI and body fat varies in different populations, an independent validation of the BMI-body fat relationship in the population of interest is desirable. OBJECTIVES: (1) To study the validity of field methods of measuring body fat (multiple skinfolds and bioimpedance) against a criterion method (deuterium dilution) and (2) To compare the prevalence of obesity (WHO 2000 criteria for BMI) with adiposity (body fat >25%) in middle-aged Indian men in rural and urban Pune. DESIGN: Community-based multistage stratified random sampling of middle-aged men from rural and urban Pune for study of body composition and cardiovascular risk. A third of these men, selected to represent wide BMI distribution, were studied for body fat measurements by specific methods. SUBJECTS: A total of 141 healthy men, approximately similar number from rural, urban slums and middle class from Pune. They were 39.3 (+/-6.2) y old and had a BMI of 21.9 (+/-3.7) kg/m(2). MEASUREMENTS: Anthropometry (height, weight and multiple skinfold thicknesses) by trained observers using standardised technique to calculate body fat by Durnin and Womersley's equation. Total body water and body fat by bioelectrical impedance analysis (BIA) and deuterium oxide dilution (D(2)O). RESULTS: Mean total body fat was 14.3 kg (23.0%) by anthropometry, 16.5 kg (26.0%) by BIA and 15.3 kg (24.6%) by D(2)O method. Although there was a good correlation between fat estimation by three methods (r= approximately 0.9, P<0.001 all), compared to D(2)O method anthropometry underestimated body fat by 1.0 kg and BIA overestimated fat by 1.2 kg (P<0.001 both). Using the standard cut-point of 25% body fat for 'adiposity' 29.5% rural, 46.0% slum and 75.0% middle class men were adipose. These proportions were considerably higher than the number of men who were 'preobese' (BMI> or =25-29.9 kg/m(2), 9.0% rural, 22.0% urban slums and 27.0% urban middle class) and 'obese' (BMI >30 kg/m(2), 4.0% urban slums, none in rural and urban middle class). CONCLUSION: We recommend that future studies assessing risk for chronic diseases in Indians should measure adiposity by anthropometry (multiple skinfolds) or BIA (calibrated for Indians) rather than relying only on BMI cut-points.     

Role of kidney in the catabolic clearance of human platelet antiheparin proteins from rat circulation

Stimulated platelets release at least two antiheparin proteins: platelet factor 4 (PF4) and low affinity platelet factor 4 (LA-PF4) from which beta-thromboglobulin (beta TG) is derived. We have found previously marked elevation of LA-PF4/beta TG antigen in platelet poor plasma of patients with chronic renal failure, whereas levels of PF4 remained normal. Therefore, we examined the role of the kidneys in the metabolic clearance of LA-PF4/beta TG and PF4. The supernates of aggregates of thrombin-stimulated human platelets were injected into sham operated control rats, nephrectomized rats, and into rats with acute ureteral ligation. The disappearance of human LA-PF4/beta TG antigen and PF4 in rat plasma determined by specific radioimmunoassays followed biphasic exponential curves. The half-lives (t1/2) for the fast and slow components of LA-PF4 in control rats were 6.4 and 68.4 min. Nephrectomy significantly increased these times to 9.7 and 144 min, while ureteral ligation resulted in no significant change. Comparison of the level of LA-PF4/beta TG antigen and of creatinine in aorta and in renal vein showed 25%-30% extraction of these compounds by the kidney. Less than 0.1% of the total LA-PF4 antigen injected was recovered in the urine of control rats. In contrast to these results, the clearance of PF4 was not affected by nephrectomy. In conclusion: (1) functional renal tissue is necessary for normal clearance of LA- PF4/beta TG, but renal excretion does not play a major role in its elimination suggesting that the protein is catabolized by the kidney; and (2) catabolic clearance of PF4 does not depend on functioning kidney tissue.