Therapeutic Effect of a Low Molecular Weight Dermatan Sulphate (Desmin 370) in Rat Venous Thrombosis - Evidence for an Anticoagulant-Independent Mechanism

We evaluated the capacity of a low molecular weight dermatan sulphate (D370) to prevent thrombus formation and to induce a reduction of a stabilized thrombus in a rat venous thrombosis model. Injection of D370, 10 min before induction of venous stasis (prevention model), prevented thrombus formation in a dose-dependent way (ED50: 2.3 mg/kg). When given to rats 6 h after induction of venous stasis (therapeutic model), D370 caused a time- and dose-dependent reduction in thrombus size (60% to 70% reduction 2 h after injection of 10 mg/kg). At comparable antithrombotic dosages (i.e. minimum dose giving complete inhibition of thrombus formation), heparin (0.5 mg/kg) only caused 40% reduction of a preformed thrombus while hirudin (1 mg/kg) was virtually ineffective (less than 10% reduction in weight). All three compounds inhibited 125I-fibrin(ogen) deposition on 6-h aged thrombi by more than 85%, suggesting that D370 and, to a lesser extent, heparin reduce thrombus size via mechanisms other than inhibition of thrombus accretion. The involvement of a fibrinolysis-mediated mechanism in the D370-induced effect is suggested by the following. EACA (1 g/kg), when given to thrombus-bearing control animals, did not influence thrombus weight. However, when administered before D370 treatment, it prevented the expected reduction in thrombus weight by more than 80%, without influencing the effect of D370 on 125I-fibrin(ogen) accumulation onto preexisting thrombi. D370 injection caused neither an enhancement of fibrinolytic activity nor a reduction of PAI in plasma. In vitro, D370 (200 μg/ml) was unable to potentiate the spontaneous or PA-induced lysis of 125I-fibrinogen labelled blood, plasma, or purified fibrin clots. It is suggested that prevention of thrombus formation by D370 is related mainly to inhibition of blood coagulation, whereas reduction of the weight of aged thrombi is primarily due to an anticoagulant-independent mechanism, most probably involving local enhancement of the fibrinolytic process. D370 may represent an alternative pharmacologic agent both in the prevention and in the therapy of venous thrombosis.

Zinc causes acute impairment of glutathione metabolism followed by coordinated antioxidant defenses amplification in gills of brown mussels Perna perna

Zinc demonstrates protective and antioxidant properties at physiological levels, although these characteristics are not attributed at moderate or high concentrations. Zinc toxicity has been related to a number of factors, including interference with antioxidant defenses. In particular, the inhibition of glutathione reductase (GR) has been suggested as a possible mechanism for acute zinc toxicity in bivalves. The present work investigates the biochemical effects of a non-lethal zinc concentration on antioxidant-related parameters in gills of brown mussels Perna perna exposed for 21 days to 2.6 μM zinc chloride. After 2 days of exposure, zinc caused impairment of the antioxidant system, decreasing GR activity and glutathione levels. An increase in antioxidant defenses became evident at 7 and 21 days of exposure, as an increase in superoxide dismutase and glutathione peroxidase activity along with restoration of glutathione levels and GR activity. After 7 and 21 days, an increase in cellular peroxides and lipid peroxidation end products were also detected, which are indicative of oxidative damage. Changes in GR activity contrasts with protein immunoblotting data, suggesting that zinc produces a long lasting inhibition of GR. Contrary to the general trend in antioxidants, levels of peroxiredoxin 6 decreased after 21 days of exposure. The data presented here support the hypothesis that zinc can impair thiol homeostasis, causes an increase in lipid peroxidation and inhibits GR, imposing a pro-oxidant status, which seems to trigger homeostatic mechanisms leading to a subsequent increase on antioxidant-related defenses.

Optimisation and application of the voltammetric technique for speciation of chromium in the Patos Lagoon Estuary--Brazil

The chemical speciation analysis of chromium in one of the most important South American Estuary was performed for the first time. Samples were collected in Patos Lagoon Estuary (Brazil) and were analysed by adsorptive cathodic stripping voltammetry, with the following analytical figures of merit: limit of detection, 0.1 nmol L(-1); precision RSD = 3%, n = 7; linearity, from limit of quantitation up to 20 nmol L(-1); and accuracy of 99.8%, expressed as recovery. No labile chromium forms were identified in samples, beside industries and a city were near the study area. It is pointed out a reverse correlation between total and non-active chromium and salinity, which could be explained by biogeochemical processes.

Colorimetric determination of formaldehyde in air using a hanging drop of chromotropic acid

A simple and sensitive method to determine parts per billion (ppb) of atmospheric formaldehyde in situ, using chromotropic acid, is described. A colorimetric sensor, coupled to a droplet of 15.5 microL chromotropic acid, was constructed and used to sample and quantify formaldehyde. The sensor was set up with two optical fibers, a light emitting diode (LED) and two photodiodes. The reference and transmitted light were measured by a photodetection arrangement that converts the signals into units of absorbance. Air was sampled around the chromotropic acid droplet. A purple product was formed and measured after the sampling terminated (typically 7 min). The response is proportional to the sampling period, analyte concentration and sample flow rate. The detection limit is approximately 2 ppb and can be improved by using longer sampling times and/or a sampling flow rate higher than that used in this work, 200 mL min-1. The present technique affords a simple, inexpensive near real-time measurement with very little reagent consumption. The method is selective and highly sensitive. This sensor could be used either for outdoor or indoor atmospheres.

Bioavailability of Desmin, a low molecular weight dermatan sulfate, after subcutaneous administration to healthy volunteers

The bioavailability of two different s.c. doses of Desmin (a new low molecular weight dermatan sulfate) was evaluated in 12 healthy volunteers (6 men, 6 women aged 22-45 years) who were injected, on 3 separate days and with a wash-out period of at least 21 days between each administration, with 200 and 300 mg of Desmin by the s.c. route and 200 mg by the i.v. route. Immediately before injection and at various times thereafter (after 15 min and 30 min for i.v. only and after 1, 2, 3, 4, 6, 8, 12, and 24 h for both s.c. and i.v. dosing), blood samples were drawn to investigate bioavailability by measuring several coagulation parameters: activated partial thromboplastin time, thrombin time, inhibition of factor Xa, Heptest, and heparin cofactor II. Furthermore the local tolerance of the s.c. and i.v. injections were investigated. The s.c. administration of the two Desmin doses had a negligible effect on the activated partial thromboplastin time and a very small effect on the thrombin time, measured with human thrombin; in contrast, Heptest, heparin cofactor II, and anti-Xa activities increased, with a good drug bioavailability (more than 100%). The plasma effects of Desmin were dose dependent only when measured by Heptest, which also gave a greater response after the s.c. administrations. There were no symptoms of intolerance or pain at the injection site after single i.v. and s.c. Desmin administration.

Pharmacology of desmin (low molecular weight dermatan sulphate) in healthy volunteers following intravenous bolus administration of different dosages (200, 400, 800 mg)

Eight healthy volunteers (6 males, 2 females, mean age 31.6 yrs), were administered--on three separate days--200, 400 and 800 mg of a new low molecular weight Dermatan sulphate (Desmin), given as a single i.v. bolus (2 min.) injection. Before each administration and 10, 20, 30 min., 1, 2, 4, 8, 12, 24 hours after, blood samples were drawn and the following coagulative assays performed: aPTT (activated Partial Thromboplastin Time), TT (Thrombin Time), anti Xa (Xa Factor inhibition), Heptest, Stachrom D.S.. Furthermore, a kinetic analysis was performed on the activity curves calculated on the Heptest and Stachrom data. Plasma peak values and half lives of the parameters checked showed a clear dose-effect relationship. aPTT and TT showed very short-lasting variations and the inhibition of Factor Xa was moderate, but significant. The most evident and specific effects of Desmin were those on Heptest and Stachrom D.S.: both tests were influenced in a clear-cut and dose-dependent way, mainly as a consequence of the action of Desmin on HCII, with partially different kinetic patterns. A series of in vitro experiments proved an anti Xa effect of Desmin, mediated by antithrombin III, well above the possible interference of the small (< 1%) heparin contaminants in Desmin. An even more marked anti Xa activity was seen in the in vivo study, an observation so far unrecognized for this type of drug: some possible interpretations of this fact are discussed.

Acute and chronic effects of a new low molecular weight dermatan sulphate (Desmin 370) on blood coagulation and fibrinolysis in healthy subjects

The acute and chronic effects on blood coagulation and fibrinolysis of a new molecular weight dermatan sulphate (Desmin 370) have been investigated in a double blind, placebo-controlled cross over study in 12 healthy volunteers. The compound (100 and 200 mg) was injected IM and the expected heparin cofactor II potentiating effect, reflecting dermatan sulphate activity, peaked after 2 h and was still detectable after 9 h. Surprisingly for this type of compound, a substantial increase in anti-Xa activity also appeared and lasted up to 12 h in the absence of a significant change in aPTT. The bovine-thrombin time was not changed, while human-thrombin times were slightly, albeit non-significantly, prolonged. The activity of t-PA was increased 6h after the higher dose, but the overall pattern of fibrinolytic activities did not suggest any important change after drug treatment in comparison to placebo. No residual or cumulative effect on any of the investigated parameters was detectable 24 h after the injection on the 4th and 8th days during repeated daily administration. Parallel in vitro and in vivo investigations showed that the unexpected anti-Xa effect was not attributable to contamination by traces of low molecular weight heparin. Desmin 370, a low molecular weight dermatan sulphate that potentiates heparin cofactor II and also inhibits Factor Xa, deserves clinical evaluation as an antithrombotic agent.

Human pharmacokinetics of glycosaminoglycans using deuterium-labeled and unlabeled substances: evidence for oral absorption

In the present study, the pharmacokinetics of extractive GAGs used as therapeutic agents have been studied after intravenous and oral administration on volunteers. The use of native or deuterium-labeled compounds, followed by HPLC/MS detection, allowed the quantitation of exogenous heparin and DS as major disaccharide fragments, obtained either by enzymatic or chemical depolymerization. In particular the high level of labeling reached in DS allowed its differentiation from structurally related endogenous species. The estimated plasmatic bioavailability was about 18% for DS. Notwithstanding the impossibility of evaluating the same parameters for heparin species, due to the interferences of endogenous GAGs, the results obtained provided clear evidence of oral availability of heparin and DS through detection and quantitation of structures specifically related to these GAGs. Due to the selectivity of the lyases used, the enzymatic degradation specifically allowed the detection of both DS and heparin species still retaining the original sulfation pattern. Additionally, the chemical degradation could detect the main metabolites of the drugs, consisting of partially to totally desulfated GAGs showing a more or less marked reduction in their molecular weight.

Therapeutic effect of a low molecular weight dermatan sulphate (Desmin 370) in rat venous thrombosis--evidence for an anticoagulant-independent mechanism

We evaluated the capacity of a low molecular weight dermatan sulphate (D370) to prevent thrombus formation and to induce a reduction of a stabilized thrombus in a rat venous thrombosis model. Injection of D370, 10 min before induction of venous stasis (prevention model), prevented thrombus formation in a dose-dependent way (ED50: 2.3 mg/kg). When given to rats 6 h after induction of venous stasis (therapeutic model), D370 caused a time- and dose-dependent reduction in thrombus size (60% to 70% reduction 2 h after injection of 10 mg/kg). At comparable antithrombotic dosages (i.e. minimum dose giving complete inhibition of thrombus formation), heparin (0.5 mg/kg) only caused 40% reduction of a preformed thrombus while hirudin (1 mg/kg) was virtually ineffective (less than 10% reduction in weight). All three compounds inhibited 125I-fibrin(ogen) deposition on 6-h aged thrombi by more than 85%, suggesting that D370 and, to a lesser extent, heparin reduce thrombus size via mechanisms other than inhibition of thrombus accretion. The involvement of a fibrinolysis-mediated mechanism in the D370-induced effect is suggested by the following. EACA (1 g/kg), when given to thrombus-bearing control animals, did not influence thrombus weight. However, when administered before D370 treatment, it prevented the expected reduction in thrombus weight by more than 80%, without influencing the effect of D370 on 125I-fibrin(ogen) accumulation onto preexisting thrombi. D370 injection caused neither an enhancement of fibrinolytic activity nor a reduction of PAI in plasma. In vitro, D370 (200 microns/ml) was unable to potentiate the spontaneous or PA-induced lysis of 125I-fibrinogen labelled blood, plasma, or purified fibrin clots.(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacodynamic effects of single and repeated doses of oral sulodexide in healthy volunteers. A placebo-controlled study with an enteric-coated formulation

Eight male and 8 female healthy volunteers, aged on average 32 +/- 6 years, underwent a randomized, crossover study, aimed at comparing the activity on some fibrinolysis and coagulation parameters of 100 and 200 mg/day of oral sulodexide, administered as enteric-coated tablets. After the single and the repeated (for 7 days) administration of the two daily dosages, the Fibrin Plates test, the Heptest, the Plasminogen Activator Inhibitor test (as to both activity and antigen level) and the activated Partial Thromboplastin Time were checked during the first 6 hours after administration. The pro-fibrinolytic and antithrombotic activity of sulodexide was confirmed to be significant with both dosage schemes and potentiated by repeated administrations. On the other hand, the absence of any influence on aPTT confirmed the lack of interference of the drug, after oral administration, on the intrinsic pathway of coagulation. No adverse reactions or events were observed.

Protein C deficiency in insulin-dependent diabetes: a hyperglycemia-related phenomenon

In 30 insulin-dependent diabetic patients protein C (PC) antigen and PC activity were significantly lower than those of matched control healthy subjects. An inverse correlation between fasting plasma glucose and both PC concentration and activity was present in diabetics, while a direct correlation between PC concentration and PC activity was observed. Induced hyperglycemia in diabetic and normal subjects was able to decrease both PC antigen levels and PC activity, and heparin reversed in part this effect. In diabetic patients euglycemia obtained by insulin infusion restored to normal the depressed PC levels. Heparin did not alter both the basal PC concentration and activity in healthy controls. These data stress the major role of hyperglycemia in determining PC decrease in diabetics, and suggest that PC reduction is probably associated to hyperglycemia-enhanced thrombin formation.

Non-enzymatic glycation reduces heparin cofactor II anti-thrombin activity

The effects of non-enzymatic glycation on heparin cofactor II activity, at glucose concentrations which might be expected in physiological or diabetic conditions have been evaluated in this study. Radiolabelled glucose incorporation was associated with a loss of heparin cofactor anti-thrombin activity. The heparin cofactor heparin and dermatan sulfate-dependent inhibition of thrombin was significantly reduced, showing a remarkable decrease of the maximum second order rate constant. This study shows that heparin cofactor can be glycated at glucose concentrations found in the blood, and that this phenomenon produces a loss of heparin cofactor-antithrombin activity. These data suggest, furthermore, a possible link between heparin cofactor glycation and the pathogenesis of thrombosis in diabetes mellitus.

Evidence for a reduced heparin cofactor II biological activity in diabetes

A reduction of heparin cofactor II (HCII) biological activity, despite its normal plasma concentration, is reported in insulin-dependent diabetic patients. A good linear correlation between HCII activity and concentration is present in normal controls but not in diabetics. In these subjects HCII activity correlates inversely with fasting blood glucose and glycated proteins but not with Hb A1. These data demonstrate the presence of a depressed HCII activity in the presence of its normal plasma concentration in insulin-dependent diabetics and suggest a role for short-term metabolic control in conditioning this phenomenon.

Synthesis of 2-hydroxyacetyl-7-acetyl-xanthone, a new xanthone derivative endowed with antianaphylactic, analgesic, and antiinflammatory activities

2-Hydroxyacetyl-7-acetylxanthone (V), a new xanthone derivative, was synthesized in four steps starting from xanthene, by two synthetic approaches. The new compound displayed antianaphylactic activity in the PCA test and in the anaphylaxis shock test in rats. It also displayed analgesic activity in the writhing test in mice, and antiinflammatory activity in the carrageenin edema test in rats. The activity of the new compound has been tentatively interpreted on the basis of its chemical and structural analogy with known drugs.