Investigations of AGEs’ inhibitory and nephroprotective potential of ursolic acid towards reduction of diabetic complications

Journal of Natural Medicines - In diabetes, interactions between AGEs (advanced glycation end products) and RAGEs (receptors of AGEs) are responsible for chronic complications and the current work...     

Dendrimers as a carrier for pulmonary delivery of enoxaparin, a low-molecular weight heparin

This study was designed to test the hypothesis that positively charged dendrimers form a complex with enoxaparin, a low-molecular weight heparin (LMWH), and that the resulting drug-dendrimer complex is effective in preventing deep vein thrombosis after pulmonary administration. Fourier Transform Infrared (FTIR) spectroscopy and the azure A assay were used to evaluate interactions between dendrimers and enoxaparin. The efficacy of polyamidoamine (PAMAM) dendrimers in enhancing pulmonary absorption of enoxaparin was studied by administering enoxaparin-dendrimer formulations into the lungs of anesthetized rats and monitoring drug absorption by measuring plasma anti-factor Xa activity. The optimized formulations were evaluated for their efficacy in preventing deep vein thrombosis in a rodent model. The safety of the formulations was tested by studying their effects on mucociliary transport rate (MTR) in a frog palate model and by measuring injury markers in rat bronchoalveolar fluid. The FTIR data and azure A assay revealed ionic interactions between the amino groups of cationic dendrimers and the carboxylic and sulfate groups of enoxaparin. Positively charged dendrimers increased the relative bioavailability of enoxaparin by 40%, while a negatively charged dendrimer had no effect. Formulations containing 1% G2 or 0.5% G3 PAMAM dendrimer plus enoxaparin were as efficacious in preventing deep vein thrombosis in a rat model as subcutaneously administered enoxaparin. The formulations did not adversely affect the MTR or produce extensive damage to the lungs. Positively charged dendrimers are a suitable carrier for pulmonary delivery of enoxaparin. They enhance pulmonary absorption of LMWH probably by reducing negative surface charge density of the drug molecule.     

Clinical laboratory monitoring of a synthetic antithrombin agent, argatroban, using high performance liquid chromatography and functional methods.

BACKGROUND: Argatroban is a peptidomimetic inhibitor of thrombin which is in clinical trials for thrombotic complications. Clot-based assays measure the cumulative anticoagulant effect of argatroban and its metabolites(s). To monitor the absolute concentrations of argatroban, a specific HPLC method was developed. METHODS: Validation studies included normal volunteers administered with escalating doses of argatroban (ARG 102 Study), patients undergoing coronary interventional procedures (ARG 310), and patients receiving argatroban in conjuction with streptokinase for acute myocardial infarction (ARG 230). Plasma samples were extracted with acetonitrile and reconstituted in a mobile phase. UV detection was made at 333 nm. Calibratrion curves were prepared with known standards of argatroban in normal human plasma. RESULTS: The retention time for argaeroban was 6.0+/-0.5 min and the extraction efficiency was >98% (r2=0.99). In the ARG102 Study, argatroban levels were: 0.84+/-0.23 (day 1), 1.55+/-0.34 (day 2), 2.92+/-0.15 (day 3), and 3.04+/-0.49 (day 4). In the ARG310 trial, the mean argatroban levels were: 0.23+0.09 microg/ml (preinfusion), 5.77+/-0.92 microg/ml (postinfusion/intraprocedure), and 2.23+/-0.29 microg/ml (postprocedure). In the ARG 230 Study, the mean argatroban levels at 2-8 hrs were between 1.5-2.0 microg/ml. Upon completion of the infusion, a time-dependent clearance of argatroban was noted. CONCLUSIONS: Since heparinization, hemodilution and hypofibrinogenemia due to thrombolysis influence the clotting tests, absolute quantitation of argatroban by HPLC in these patients provides a more reliable means of monitoring this anticoagulant and helps in the dosage-optimization of this agent. The current HPLC method is of value in the monitoring of patients who are simultaneously administered with thrombolytic drugs.     

Inhibition of proteolytic enzymes in the in vitro amnion model for basement membrane invasion

The ability of B16-F10 mouse melanoma cells to cross an amnion basement membrane was determined in the presence of strong inhibitors of both serine and cysteine proteases. The concentrations of inhibitors were at orders of magnitude higher than their Ki values to serine and cysteine proteases implicated in metastasis, thus ensuring a complete inhibition for tumor secreted proteases such as cathepsin B-like proteases, plasminogen activators, and plasmin. Under these conditions of high serine and cysteine protease inhibitor concentrations, no significant decrease in B16-F10 melanoma cell invasion through the amnion was observed. Separate experiments showed that the inhibitors were neither toxic to the cells nor degraded. The results show that neither tumor cell secreted cathepsin B-like proteases nor plasminogen activator have a controlling role in basement membrane crossing in this metastatic model. A possible role for tumor cell membrane proteases in basement membrane invasion, in which the substrates of the protease bind to receptor sites near a membrane associated proteolytic activity, is not eliminated.     

The influence of posture on the pharmacokinetics of orally administered nifedipine.

1. Nifedipine (20 mg as capsules) and soluble paracetamol (1 g) were co-administered to eight healthy young volunteers on three separate occasions, following which in random order they stood, lay on their left side or lay on their right side for 4 h. 2. The time to maximum plasma concentration of paracetamol was significantly lower when standing or lying on the right side compared with recumbent left, indicating more rapid gastric emptying. 3. The times to maximum plasma concentrations of nifedipine and its metabolite produced at first pass were reduced when standing or lying on the right side. These postures were associated with significantly higher peak plasma concentrations and AUC values of nifedipine but not of its nitropyridine metabolite. 4. The increase in heart rate following nifedipine administration was significantly greater when lying on the right side compared with the left. 5. The data are consistent with transient saturation of first pass metabolism of nifedipine with postures which favour rapid gastric emptying. The results demonstrate the importance of defining the precise posture in studies in which pharmacokinetic and pharmacodynamic measurements are made on drugs which are absorbed rapidly and are subject to presystemic elimination.