In vitro inhibition by defibrotide of monocyte superoxide anion generation: a possible mechanism for the antithrombotic effect of a polydeoxyribonucleotide-derived drug.
In an attempt to elucidate the antithrombotic potential of defibrotide (D) we have evaluated several functions of monocytes from 7 healthy subjects before and after in vitro incubation of the cells with increasing concentrations of this drug. At concentrations as high as 40 micrograms/ml, D hardly affected the expression of both the procoagulant activity of monocytes and the formation of superoxide anion in response to 1 mg/ml zymosan (STZ). In contrast, at concentrations that may be achieved in vivo following the administration of the drug (5-20 micrograms/ml), D impaired in a dose-dependent manner (p less than 0.05) the generation of O-2 in response to N-formyl-L-methionyl-L-leucyl-L-phenylalanine (FMLP, 1 microM) or calcium ionophore A23187 (10 microM). Regardless of the agonist employed, at concentrations between 1 and 5 mM, extracellular Ca2+ had little effect on the impairment of superoxide anion generation by D. In contrast, the inhibitory effect was time-dependent, the maximum impairment (greater than 30%) being observed when the cells were preincubated with the drug for 20 h. These data support the concept that the antithrombotic potential of D involves the ability of the drug to affect the generation of free radicals by leukocytes and suggest that future in vivo studies for the evaluation of the activity of D should take into account the role of monocytes in hemostasis and thrombosis.
Cirillo
F
F
Cattedra di Medicina Interna, Università degli Studi, Napoli, Italia.
Margaglione
M
M
Vecchione
G
G
Ames
P R
PR
Coppola
A
A
Grandone
E
E
Cerbone
A M
AM
Marelli
C
C
Di Minno
G
G
D000328:Adult; D005343:Fibrinolytic Agents / Q000494:pharmacology*; D005609:Free Radicals; D006801:Humans; D066298:In Vitro Techniques; D008875:Middle Aged; D009000:Monocytes / Q000187:drug effects* / Q000378:metabolism; D011089:Polydeoxyribonucleotides / Q000494:pharmacology*; D013481:Superoxides / Q000378:metabolism*
D005343:Fibrinolytic Agents; D005609:Free Radicals; D011089:Polydeoxyribonucleotides; D013481:Superoxides; C036901:defibrotide