Lonomia obliqua caterpillar venom increases permeability of the blood-brain barrier in rats

Human envenoming by caterpillars of the saturniid moth Lonomia obliqua in southern Brazil produces a mild local response (erythema, some edema, and pain) and systemic effects that include incoagulable blood, renal failure and in severe accidents intracerebral hemorrhage. In this work, we used light and electron microscopy to investigate the morphological alterations in the brain and blood-brain barrier of rats injected intravenously with venom from L. obliqua spicules (200 microg/kg). Five semi-purified fractions of venom (200 microg/kg each) were also assayed. Quantitative morphological and ultrastructural analyses were done 6, 18, 24 and 72 h after the i.v. injection of venom and its fractions. Light microscopy showed that 6h after envenoming there was cerebellar edema, which decreased by 72 h. Intracerebral hemorrhage occurred in only one rat 24h after the injection of venom. Blood-brain barrier (BBB) breakdown, assessed by transmission electron microscopy based on the passage of an extracellular tracer (lanthanum nitrate) between brain capillary endothelial cells, was observed in the cerebellum and hippocampus 18 h after venom injection. At this time, the cerebellum was more sensitive to the venom than the hippocampus, as shown by the greater number of leaky vessels. The number of capillaries showing breakdown was lower after 72 h than after 18 h. None of the semi-purified fractions significantly increased the number of leaky vessels. These results indicate that L. obliqua caterpillar venom has a deleterious action on the rat BBB. The lack of effect of the venom fractions when administered alone suggested that a synergistic action of venom components may be responsible for the damage seen in the central nervous system, but this was not confirmed when three combinations of the fractions were tested.