The cytoskeleton, a structure that is susceptible to the toxic mechanism activated by palytoxins in human excitable cells.

Palytoxin is a marine toxin responsible for a fatal type of poisoning in humans named clupeotoxism, with symptoms such as neurologic disturbances. It is believed that it binds to the Na(+)/K(+)-ATPase from the extracellular side and modifies cytosolic ions; nevertheless, its effects on internal cell structures, such as the cytoskeleton, which might be affected by these initial events, have not been fully elucidated. Likewise, ostreocin-D, an analog of palytoxin, has been only recently found, and its action on excitable cells is therefore unknown. Therefore, our aim was to investigate the modifications of ion fluxes associated with palytoxin and ostreocin-D activities, and their effects on an essential cytoskeletal component, the actin system. We used human neuroblastoma cells and fluorescent dyes to detect changes in membrane potential, intracellular Ca(2+) concentration, cell detachment, and actin filaments. Fluorescence values were obtained with spectrofluorymetry, laser-scanning cytometry, and confocal microscopy; the last of these was also used for recording images. Palytoxin and ostreocin-D modified membrane permeability as a first step, triggering depolarization and increasing Ca(2+) influx. The substantial loss of filamentous actin, and the morphologic alterations elicited by both toxins, are possibly secondary to their action on ion channels. The decrease in polymerized actin seemed to be Ca(2+)-independent; however, this ion could be related to actin cytoskeletal organization. Palytoxin and ostreocin-D alter the ion fluxes, targeting pathways that involve the cytoskeletal dynamics of human excitable cells.