INVESTIGATION OF THE BLOOD-BRAIN BARRIER BREAKDOWN MECHANISMS CAUSED BY Phoneutria nigriventer SPIDER VENOM

Le Sueur, L.P., Collares-Buzato, C.B., Cruz-Höfling, M.A. 

Departamento de Histologia e Embriologia, UNICAMP, Campinas, SP, Brasil,

Objective: We have recently demonstrated that intravenous injection of Phoneutria nigriventer venom (PNV) induces blood-brain barrier (BBB) breakdown in adult rats. The increased permeability was observed in hippocampus by ultrastructural method using the extracellular tracer lanthanum nitrate. The tracer was detected in clefts between two endothelial cells and into pinocytotic vesicles, indicating that changes in BBB permeability may occur by para- and transcellular route. In this work, we investigated the effect of PNV on the expression of some proteins associated to intercellular junctional complex, responsible for the paracellular barrier properties.

Methods and Results: The rats were injected with an i.v. single dose of 850 mg/kg PNV or saline and 5 h, 1, 5, and 9 days (n=5/each) post-injection (p.i.) they were anaesthetized and the hippocampus isolated. Biochemical analyses were done by Western Blot for occludinand b-catenin, proteins associated to the tight and adherens junctions, respectively. Both junctional proteins were localized specifically at the cell-to-cell contact region of brain vessel cells, as revealed by immunocytochemistry. In our findings no statistical differences in occludin and b-catenin proteins expression was observed when compared control and PNV-treated groups. Only a tendency to increase in occludin expression was observed at 5 h and 1 d of PNV p.i., probably indicating an enhancement of the paracellular tightness as a compensatory mechanism for the BBB breakdown occurring by transcellular route.

Conclusion: The BBB breakdown seen in rats injected with PNV may not occur through the paracellular transport, and the presence of the tracer in interendothelial clefts is probably due to discharge of lanthanum-filled pinocytotic vesicles at the lateral cell surface.

Financial support: FAPESP, CAPES, CNPq, FAEP.

CORRESPONDENCE TO:

Luciana LeSueur Maluf, Rua Hércules Florence, 170 Apto 52, Campinas, SP, CEP: 13020-170, Brasil, Email: lumaluf@hotmail.com