Lonomia obliqua Caterpillar Spicules Trigger Human Blood Coagulation viaActivation of Factor X and Prothrombin
José L. Donato (1), Ronilson A. Moreno (1), Stephen Hyslop (1), Alaor Duarte (2), Edson Antunes (1), Bernard F. Le Bonniec (3), Francine Rendu (3), Gilberto de Nucci (1)
From the (1) Department of Pharmacology, UNICAMP, Campinas, SP, Brazil, (2) Nephrology Clinic, Passo Fundo University, Passo Fundo, RS, Brazil; (3) U428 INSERM, Université de Formation et de Recherches de Pharmacie, Paris V, France
In southern Brazil, envenomation by larvae of the moth Lonomia
obliqua (Walker) may result in blood clotting factor depletion, leading
to disseminated intravascular coagulation with subsequent haemorrhage
and acute renal failure which may prove fatal. We have examined
the effect of a crude extract of spicules from these caterpillars on
in vitro hemostasis. The extract alone did not aggregate platelets and
had no detectable effect on purified fibrinogen, suggesting that extract
induces clot formation by triggering activation of the clotting cascade.
In agreement with the presence of thrombin-mediated activity, hirudin
prevented clot formation. The extract was found to activate both prothrombin
and factor X, suggesting that the depletion of blood clotting
factors results from the steady activation of factor X and prothrombin.
Heating and diisopropylfluorophosphate abolished the procoagulant
activity of the extract, indicating that the active component involved is
a protein that may belong to the serine protease family of enzymes. The
ability of hirudin to inhibit this coagulant activity suggests that this
inhibitor could be beneficial in the treatment of patients envenomed by
L. obliqua caterpillars.