Isolation and Characterization of jararaca GPIb-BP, a Snake Venom Antagonist Specific to Platelet Glycoprotein lb

A platelet glycoprotein lb-binding protein (GPIb-BP) was isolated from the snake venom of Bothrops jararaca. Jararaca GPIb-BP showed a single band with Mr of 30,000, and two distinct bands with Mr. of 17,000/13,000 under non-reducing and reducing conditions, respectively, on SDS-polyacrylamide gel electrophoresis. Jararaca GPIb-BP itself induced neither platelet aggregation nor serotonin release from platelets, but specifically bound to GPIb (40,629 ± 2,521 molecules per normal platelet, with Kd 39.1 ± 2.4 nM at saturation). The purified venom protein completely inhibited ristocetin- or botrocetin-induccd von Willebrand factor (vWF) binding, and blocked the bovine vWF binding to GPIb, with IC50 values ranging from 28 to 42 nM, without affecting the platelet aggregation induced by ADP or α-thrombin. 1251-jararaca GPIb-BP binding to GPIb was not altered by the presence of human α-thrombin. Jararaca GPIb-BP at a final concentration of 104 nM totally abolished vWF-dependent shear- induced platelet aggregation (SIPA) at a high shear stress, but had no effect on SIPA at a low shear stress. Reduced and S-carboxyamidomethylated jararaca GPIb-BP lost its inhibitory activity on SIPA. The NH2-terminal amino acid sequences of the subunits revealed a high degree of homology with those of several Ca2+-dependent lectins, especially to those of two functionally opposite venom proteins, botrocetin (a vWF-modulator) and alboaggregin-B (a GPIb- modulator).

Inhibition of Human Platelet Functions by Verapamil

The effects of verapamil, a coronary vasodilator, on platelet functions were studied.

Platelet aggregation induced by ADP, epinephrine or collagen was inhibited by verapamil in vitro. Calcium ionophore A23187-induced platelet aggregation was also inhibited by verapamil in a concentration dependent manner. In washed platelets, verapamil caused a dose-dependent inhibition of serotonin release induced either by thrombin or A23187 in the absence of extracellular calcium. Addition of 1 mM CaCl2 with A23187 or thrombin partially overcame this inhibition. Addition of 1 mM CaCl2 in the absence of verapamil had no effect on thrombin- or A23187-induced secretion. When verapamil was administered to the healthy volunteers at the dosage commonly used, inhibition of platelet aggregation was observed 2 hrs after the drug ingestion. It is of great interest that verapamil potentiated the anti-aggregating activity of prostacyclin in vitro.

Our results may suggest a potential role for verapamil in the treatment of thrombotic disorders.

Incidence rate and patient characteristics of severe hypoglycemia in treated type 2 diabetes mellitus patients in Japan: Retrospective Diagnosis Procedure Combination database analysis

AIMS/INTRODUCTION

To evaluate the incidence rate of and identify factors associated with severe hypoglycemic episodes in patients with treated type 2 diabetes mellitus.

MATERIALS AND METHODS

Using Diagnosis Procedure Combination hospital-based medical database, we carried out a retrospective cohort study to assess the incidence rate of severe hypoglycemia in treated type 2 diabetes mellitus patients. We evaluated the associations between severe hypoglycemia and age, sex, complications, and current use of insulin or sulfonylurea (SU) in a nested case-control study.

RESULTS

Of 166,806 eligible patients, 1,242 had episodes of severe hypoglycemia during the observational period. The incidence rate of the first hypoglycemic events was 3.70/1,000 patient years. Based on the nested case-control analysis, age was associated with hypoglycemic events with adjusted odds ratios (ORs) of 1.64 or 65-74-year-old patients and 3.79 for ≥75-year-old patients in comparison with 20-64-year-old patients. Comorbidities, such as cognitive impairment, cancer, macrovascular disease and diabetic complications (retinopathy, nephropathy and neuropathy), were associated with severe hypoglycemia, with adjusted ORs ranging from 1.25 to 3.80. Severe hypoglycemic events also increased in patients with current use of both SU and insulin, either SU or insulin, with adjusted ORs of 18.36, 6.31 or 14.07, respectively, compared with patients with other antihyperglycemic agents. In patients with an SU glimepiride, adjusted ORs increased dose-dependently from 3.65 (≤1 mg) to 13.34 (>2 mg).

CONCLUSIONS

The incidence rate of severe hypoglycemia in this cohort was 3.70/1,000 patient years. Age, cognitive impairment, cancer, diabetic complications, current use of insulin + SU and SU dosage were identified as risk factors for severe hypoglycemia.

Cost-effectiveness and safety of the molecular targeted drugs afatinib, gefitinib and erlotinib as first-line treatments for patients with advanced EGFR mutation-positive non-small-cell lung cancer

Epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs), including gefitinib, erlotinib and afatinib are standard first-line treatments for EGFR gene mutation-positive non-small cell lung cancer. The present study aimed to compare the cost-effectiveness of using erlotinib, afatinib or gefitinib. The safety of EGFR-TKIs was also investigated. Expected costs were calculated based on data from patients with advanced EGFR mutation-positive non-small-cell lung cancer who were treated with gefitinib, erlotinib or afatinib. Literature was collected to obtain the necessary clinical information for calculating the probability and the validity of each chemotherapy. Median survival time (MST) was used to evaluate the therapeutic effect of the regimens. The cost-effectiveness ratio was calculated using expected costs and MSTs for the three regimens. The cost-effectiveness ratio per month was JPY 386,859.4/MST for afatinib, JPY 264,788.7/MST for gefitinib and JPY 397,039.9/MST for erlotinib. Significant differences were observed between the three groups (p<0.001). The incremental cost-effectiveness ratio (ICER) of gefitinib compared with afatinib per month was JPY 122,070.7/MST. The ICER of gefitinib compared with erlotinib was JPY -69,605.9/MST. Adverse effects of Grade 3 and higher, including diarrhoea (28.6%) and paronychia (14.3%) were observed in the afatinib treatment group. Paronychia (23.1%) was observed in the erlotinib treatment group, while none were observed in the gefitinib treatment group. These findings demonstrate that gefitinib is more cost effective in comparison with the afatinib and erlotinib regimens, although the afatinib and erlotinib regimens were well-tolerated and produce sufficient effects.

Risk factors contributing to the development of neutropenia in patients receiving oral trifluridine-tipiracil (TAS-102) chemotherapy for advanced/recurrent colorectal cancer

Elucidating the factors influencing severe neutropenia could aid in earlier management of neutropenia during oral trifluridine-tipiracil (TAS-102) chemotherapy in advanced and recurrent colorectal cancer (CRC). This study was conducted to assess the risk of TAS-102-induced grade 3 or more neutropenia. Between August 2014 and July 2017, 60 patients underwent oral TAS-102 monotherapy at Ogaki Municipal Hospital, Japan. The patients were divided into two groups based on the development of grade 3 or more neutropenia (9 patients) or not (51 patients). Risk factors for grade 3 or more neutropenia were examined by univariate and multivariate analyses. Creatinine clearance rate (CrCl) before TAS-102 administration significantly correlated with the incidence of Grade 3 or more neutropenia after TAS-102 administration (odds ratio 6.5, 95% confidence interval 1.14-30.00; p = 0.02). Multivariate analysis revealed that a CrCl of lower than 57.1 mL/min before TAS-102 administration (odds ratio 54.06, 95% confidence interval 2.14-1364.2; p = 0.02) was an independent risk factor significantly contributing to the development of grade 3 or more neutropenia, induced by TAS-102. CrCl < 57.1 mL/min in patients with advanced and recurrent CRC who underwent TAS-102 chemotherapy was associated with grade 3 or more neutropenia.

Structural basis of the redox switches in the NAD+-reducing soluble [NiFe]-hydrogenase

NAD⁺ (oxidized form of NAD:nicotinamide adenine dinucleotide)-reducing soluble [NiFe]-hydrogenase (SH) is phylogenetically related to NADH (reduced form of NAD⁺):quinone oxidoreductase (complex I), but the geometrical arrangements of the subunits and Fe-S clusters are unclear. Here, we describe the crystal structures of SH in the oxidized and reduced states. The cluster arrangement is similar to that of complex I, but the subunits orientation is not, which supports the hypothesis that subunits evolved as prebuilt modules. The oxidized active site includes a six-coordinate Ni, which is unprecedented for hydrogenases, whose coordination geometry would prevent O₂ from approaching. In the reduced state showing the normal active site structure without a physiological electron acceptor, the flavin mononucleotide cofactor is dissociated, which may be caused by the oxidation state change of nearby Fe-S clusters and may suppress production of reactive oxygen species.

A Heparin-coated Circuit Maintains Platelet Aggregability in Response to Shear Stress in an In Vitro Model of Cardiopulmonary Bypass

Alterations in platelet aggregability may play a role in the pathogenesis of qualitative platelet defects associated with cardiopulmonary bypass (CPB). We circulated fresh heparinized whole blood through tubing sets coated with heparin (C group, n = 10) and through non-coated sets (N group, n = 10) as a simulated CPB circuit. Shear stress (108 dyne/cm2)-induced platelet aggregation (hSIPA), plasma von Willebrand factor (vWF) activity and platelet glycoprotein (GP) Ib expression were measured, before, during, and after this in vitro set up of circulation. In the two groups, the extent of hSIPA significantly decreased during circulation and was partially restored after circulation. Decreases in the extent of hSIPA were significantly less with use of heparin-coated circuits. There was an equivalent reduction in plasma vWF activity, in the two groups. Expression of platelet surface GP Ib decreased significantly during circulation and recovered after circulation. Reduction of surface GP Ib expression during circulation was significantly less in the C group than that in the N group. Decrease in surface GP Ib expression correlated (r = 0.88 in either group) with the magnitude of hSIPA, in the two groups. The progressive removal of surface GP Ib was mainly attributed to redistribution of GP Ib from the membrane skeleton into the cytoskeleton. Our observations suggest that use of heparin-coated circuits partly blocks the reduction of hSIPA, as a result of a lesser degree of redistribution of GP Ib.