Cytotoxic enterotoxin of Aeromonas hydrophila induces cytoskeletal changes and perturbation mitochondrial on intestinal epithelial cells

Falcón, R.(1,2), Martins, L.M.(1), Pimentel, S.(3), Carvalho, H.F.(3), Gatti, M.S.V.(1), Yano T.(1)

(1)Pedro Kouri Institute, Havana, Cuba and Departments of (2)Microbiology and Immunology, and (3)Cell Biology, Institute of Biology, University (UNICAMP), Campinas, SP, Brasil.

Introduction: The cytotoxic enterotoxin secreted by Aeromonas hydrophila  (Ent-ctx) possesses the ability to evoke a fluid secretory response in a ligated intestinal loop model, amongst other biological activities. The purpose of the current study was to evaluate the alterations induced by Ent-ctx on intestinal epithelial cells and its association with the pathogenesis of the gastrointestinal infections.

Methods: The enterotoxic toxin purified was assayed in the rat intestinal loop test. Intestinal epithelial cells treated with Entx-ctx were included in historesinBJ₄ and stained with blue toluidine for microscopic analyses. The structural organization of epithelial cells was analyzed by fluorescence actin staining. The morphological and intracellular changes were accompanied by scanning and transmission electron microscopy.

Results and discussion: Gross morphology showed a dilation and collapse of the intestinal villi, apparently provoked by edema. Ultrastructural analyses showed intracellular alterations such as mitochondrial swelling with obliterated cristae and membrane accumulation as mielin-bodies. The prominent features of the epithelial cells were a disruption of the basal lamina and disalignment the microvilli leading to cytoskeletal disorganization.

Conclusions: Ent-ctx acts on the intestinal epithelial cell cytoskeleton to alter actin microfilaments. The cytopathogenic response of this enterotoxin was irreversible and progressive, causing perturbation of the mitochondrial structure and function. These alterations induced by the cytotoxic enterotoxin of A. hydrophila can be correlated with the capacity of this toxin to induce cell death by apoptosis in HT29 (Falcón et al. Biochem Cell Biol. 79: 525, 2001).

CORRESPONDENCE TO:

RosabelFalcón Márquez, Rua 14 de Dezembro, No. 80, Apto, 78,  Campinas,  SP, CEP: 13015-130, Brasil, Email: rosabell@unicamp.br