Vincenzo Costantini

The role of fibrin in tumor metastasis

SummaryA volume of data that has accumulated for over a century has suggested that fibrin may facilitate the persistence and progression of malignancy. Techniques that have been developed recently have shown that fibrin is indeed a component of the connective tissue stroma in human malignancy but in only a few tumor types. However, therapeutic intervention studies with drugs that limit thrombin activity or enhance fibrinolysis have shown favorable clinical effects in at least one such tumor type. These favorable findings affirm the concept that cause-and-effect relationships do, in fact, exist between thrombin generation with fibrin formation and tumor progression, and suggest that a rational basis exists for the design of future drug intervention trials that target reactions relevant to specific tumor types. These findings also provide a basis for the design of experiments capable of defining further the role of fibrin in the integrity of these tumor types. Because fibrinogen is found much more commonly than fibrin in the connective tissue of a variety of human malignancies, attention might reassumably be directed to determining the possible contribution of this molecule as well as of fibrin to tumor progression.

Treatment of acute occlusion of peripheral arteries

Acute lower-extremity peripheral arterial occlusion is responsible for a wide variety of complications culminating in limb loss or death. The real incidence of acute limb ischemia (ALI) in the general population is not well known even though recent epidemiological data estimated that it occurs in 14 out of a population of 100,000 and that it accounts for 10-16% of the vascular workload. The two main causes of acute occlusion of peripheral arteries are: (i) embolism and (ii) thrombosis, which usually occurs in cases of severe atherosclerotic stenoses. Arterial flow can be restored through operative revascularization or pharmacological dissolution of thrombus. Immediate surgical revascularization is indicated in the profoundly ischemic limb. Catheter embolectomy is also usually preferred for emboli to a non-atherosclerotic limb. Catheter-directed thrombolysis has become a commonly employed technique in the treatment of ALI. It may offer definitive treatment without the need of major surgery in a significant subset of patients with acute occlusion of a native leg artery or a bypass graft. A number or reports from individual centers and three large prospective studies, which compared intra-arterial thrombolysis to surgical intervention, suggest that thrombolytic therapy may be an appropriate initial treatment of ALI, provided that the limb is not immediately or irreversibly threatened. Using this approach, the underlying lesions can be further defined by angiography, and the percutaneous or surgical revascularization procedure can be performed. However, severe bleeding is still a non-rare complication of intra-arterial thrombolysis and the risk of intracranial hemorrhage is 1-2%.

Salicylates Inhibit T Cell Adhesion on Endothelium Under Nonstatic Conditions: Induction of L-Selectin Shedding by a Tyrosine Kinase-Dependent Mechanism

Salicylates inhibit T cell adhesion to and transmigration through endothelium by preventing integrin activation induced by contact with endothelial cells. In the present study the effects of aspirin and sodium salicylate on the first steps of T cell adhesion have been analyzed in a nonstatic in vitro system. Salicylates partially reduced adhesion to activated endothelium and, in parallel, L-selectin expression on resting T cells by inducing shedding of the molecule without affecting its mRNA transcript. The role of L-selectin down-regulation in reducing T cell adhesion in this system was supported by the fact that aspirin inhibited T cell adhesion also on plastic-immobilized L-selectin ligand or when α4 integrin-mediated adhesion to endothelium was blocked by specific mAbs. In addition, preincubation of T cells with inhibitors of L-selectin shedding prevented both functional and phenotypic inhibitory effects of salicylates. The decrease in T cell adhesion and L-selectin expression seems to be dependent on intracellular calcium increase and tyrosine kinase activation, because these effects could be reversed by preincubating salicylate-treated T cells with EGTA, genistein, or tyrphostin. Finally, the infusion of aspirin into healthy volunteers induced down-regulation of L-selectin on circulating T cells. These results suggest that salicylates interfere not only with integrin activation, but also with the L-selectin-mediated first steps of T cell binding to endothelium.

The coumarin derivative AD6 inhibits the release of arachidonic acid by interfering with phospholipase A2 activity in human platelets stimulated with thrombin

AD6 is a coumarin derivative which is able to inhibit platelet aggregation and release due to various agonists as adrenaline, PAF, Ca++ ionophore and others. It has been demonstrated that this compound reduces the production of free arachidonate and diglyceride from human platelets pulse-labeled with radioactive arachidonic acid thus suggesting a possible interference with the activity of phospholipase A2 and/or phospholipase C. The present report indicates that the drug has no effect on the increase of the labeling of phosphatidic acid which takes place when platelets pulse-labeled with arachidonic acid are stimulated with thrombin. Furthermore, AD6 is not able to cause changes on the metabolism of phosphoinositides monitored using platelets pre-labeled with [3H] inositol. These observations exclude the possibility that AD6 interferes with phospholipase C activity. Experiments with platelets pulse-labeled with arachidonate suggest that AD6 inhibits phospholipase(s) A2 activity or modulate negatively one or more processes involved in its activation.

Effects of Dipyridamole on the Hypoxemic Pulmonary Hypertension of Patients with Chronic Obstructive Pulmonary Disease

Based on the hypothesis that blood platelets contribute to the pathogenesis of hypoxemic pulmonary hypertension in patients with chronic obstructive pulmonary disease (COPD), the effect of a prolonged treatment with dipyridamole, a platelet-inhibiting drug, on hypoxemic pulmonary hypertension was evaluated in a double-blind cross-over study. Eight patients with COPD, pulmonary hypertension [mean systolic pressure 52.2 +/- (SD) 9.7 mm Hg; mean diastolic pressure 25.8 +/- (SD) 6.8 mm Hg] and shortened platelet regeneration time [mean 5.2 +/- (SD) 1.2 days] received, in a cross-over random sequence, the following two 3-month treatments: (a) dipyridamole 100 mg and acetylcysteine 100 mg every 6 h; (b) acetylcysteine, 100 mg every 6 h. Dipyridamole significantly prolonged the platelet regeneration time [mean 6.5 +/- (SD) 1.0 days; p less than 0.05]. There was no significant effect on diastolic pulmonary pressure. However, systolic pressure was significantly (p less than 0.05) lower after dipyridamole [46.8 +/- (SD) 16 mm Hg] than after placebo [56.1 +/- (SD) 14 mm Hg]. These results suggest that dipyridamole can slow the progression of hypoxemic pulmonary hypertension in patients with COPD.

AD6 (8-monochloro-3-beta-diethylamino-ethyl-4-methyl-7-ethoxycarbonyl-methoxy coumarin) inhibits the release of arachidonic acid in human platelets stimulated by thrombin

The coumarin derivative AD6 is known to inhibit platelet aggregation and release and it possesses vasodilatory properties on coronary arteries of laboratory animals. Furthermore, the inhibition of the production of TxB2 from endogenous substrates after stimulation of human platelets with collagen has been demonstrated. The present report demonstrates that AD6 inhibits the production of labeled arachidonic acid and diglycerides from phospholipids of platelets stimulated with thrombin. This effect is dose-dependent and is already evident at a concentration of the drug (25 microM) which is unable to prevent the aggregation. Apparently, AD6 inhibits the release of arachidonic acid from phosphatidylinositol and choline phosphoglycerides which are the main sources of the substrate for the synthesis of prostaglandins and thromboxanes.

Exhausted platelets in chronic obstructive pulmonary disease.

Experimental and clinical evidence has suggested that vasoconstrictor substances released from activated platelets could play a role in mediating the pulmonary hypertension of hypoxemic patients with chronic obstructive pulmonary disease. In order to extend previous knowledge on platelet function in such patients, platelet production of malondialdehyde and plasma levels of beta-thromboglobulin were assayed in 12 patients before and after a short-term treatment with the platelet-inhibiting drug, dipyridamole. The impairment of platelet malondialdehyde generation concomitant with the increase of plasma levels of beta-thromboglobulin suggests that in patients with chronic obstructive pulmonary disease, blood platelets undergo chronic overstimulation and become exhausted. Dipyridamole can antagonize this platelet activation and thus may prove useful in reducing the pulmonary hypertension of these patients.

Absidia corymbifera necrotizing cellulitis in an immunocompromised patient while on voriconazole treatment

Dear Editor, Here we report on a case of Absidia corymbifera infection in a leukemia patient while on voriconazole prophylaxis for an Aspergillus fumigatus lung infection. A 76-year-old male, a controlled diabetic with acute myelogenous secondary leukemia, was admitted to hospital in June 2007 because of fever, pain, edema, and erythema around a localized area of necrosis on the lateral surface of the first toe of the right foot probably as the consequence of a traumatic injury while gardening. The patient had been previously treated for 4 months with steroids and cyclosporine for myelodysplasia. However, he was not being treated for leukemia. Since February 2007, the patient was taking voriconazole prophylaxis for a possible A. fumigatus lung infection. On admission, abnormal laboratory values were: hemoglobin, 8.6 g/dl; white blood cell count, 14.76×10/l with 9% neutrophils; platelet count, 21×10/l; and creatinine clearance, 45 ml/min. Before admission, the patient was taking linezolid 600 mg twice a day orally for 10 days and cefepime 1 g three times daily was added for the last 2 days. Both of these antimicrobials were reconfirmed on admission. The first swab was negative for bacteria and fungi. Four days after, due to the progression of disease, therapy was changed to teicoplanin 400 mg daily and imipenem 500 mg IV every 6 h while voriconazole was continued. Debridement and excision of the necrotic tissue were performed. Eight days following admission, the first toe was amputated. Unfortunately, overall condition worsened and the second toe and the anterior part of the foot had to be amputated (Fig. 1a). Microscopy of necrotic tissues resulted negative for microorganisms and inflammatory cells. However, aseptate molds were evident on cultures. Thus, zygomycoses was suspected and additional tissue samples were taken. Due to amphotericin B lipid complex intolerance, lyposomal amphotericin (L-AmB) [4] 3 mg/kg was initiated. On the same day, an above-knee leg Ann Hematol (2008) 87:687–689 DOI 10.1007/s00277-008-0468-x

Degradation of Membrane Phosphoglycerides by the Reversal of Phosphotransferase Reactions

Phosphocholine and phosphoethanolamine transferases of different tissues catalyze reversible reactions. The role of the “direct reactions” is well established because they lead to the biosynthesis of choline and ethanol-amine phosphoglycerides (CPG and EPG) from diglycerides and CDPamines. Whether or not “back-reactions” might have metabolic importance is still under discussion. In the past, we have reported that diglycerides, produced from brain microsomal phospholipids by the reversal of phosphotransferase reactions, become available for diglyceride lipase and free fatty acids (FFA) are released (1,2). Thus, we have postulated a CMP-dependent pathway for the degradation of microsomal CPG and EPG. Further studies have indicated that this mechanism might contribute to the release of FFA during an energy deficiency such as brain ischemia (3). Alternatively, diglycerides produced by the “back-reaction” could be utilized for the synthesis of other phospholipid molecules (interconversion). The rate of the formation of diglycerides and their fate depend on the relative concentration of CMP, CDPcholine, and CDPethanolamine (4). Both aspects are summarized in Fig. 1.

Effect of aspirin and dipyridamole treatment on prostacyclin production by human veins

Patients admitted for surgical removal of varicose veins were treated in a blinded manner for 48 hours prior to surgery with either placebo, low-dose aspirin (25 mg twice daily), dipyridamole (150 mg twice daily) or both. Segments of vein excised at surgery were incubated with or without sodium arachidonate and subsequent prostacyclin (PGI2) production was measured without knowledge of treatment given. During the first 5 minute period of incubation in the presence of arachidonate, veins from dipyridamole-treated patients demonstrated increased (by 75%) arachidonate-stimulated PGI2 production compared to placebo-treated patients. By contrast, PGI2 production was reduced by 64% by aspirin treatment and 67% by aspirin plus dipyridamole compared to placebo-treated patients (p = less than 0.05). In unstimulated vein segments incubated in the absence of arachidonate, spontaneous PGI2 production during the first 5 minute incubation period was increased 32% following dipyridamole treatment but was unchanged following aspirin treatment. By contrast, unstimulated (spontaneous) PGI2 production in patients treated with aspirin plus dipyridamole was reduced by 57% (p = less than 0.05), compared to both placebo- and aspirin-treated patients, and by 71% (p = less than 0.05) compared to dipyridamole-treated patients. With repeated change of incubation medium, the ability of vein walls to produce PGI2 declined. This exhaustion was not prevented by drug treatment. However, drug effects between patient treatment groups were consistent over successive incubation periods. These results suggest that certain therapeutic benefits that might be achieved by enhancement of PGI2 production from vascular endothelium following dipyridamole treatment may be reduced by simultaneous aspirin treatment.(ABSTRACT TRUNCATED AT 250 WORDS)