Zonula occludens toxin structure-function analysis. Identification of the fragment biologically active on tight junctions and of the zonulin receptor binding domain.

Zonula occludens toxin (Zot) is an enterotoxin elaborated by Vibrio cholerae that increases intestinal permeability by interacting with a mammalian cell receptor with subsequent activation of intracellular signaling leading to the disassembly of the intercellular tight junctions. Zot localizes in the bacterial outer membrane of V. cholerae with subsequent cleavage and secretion of a carboxyl-terminal fragment in the host intestinal milieu.

The enterotoxic effect of zonula occludens toxin on rabbit small intestine involves the paracellular pathway.

Background & Aims: Zonula occludens toxin is a novel toxin elaborated by Vibrio cholerae that modulates intestinal tight junctions. The aim of this study was to establish whether the permeabilizing effect of the toxin leads to intestinal secretion.

Methods: Rabbit intestine was mounted in Ussing chambers and exposed to increasing concentrations of purified toxin.

Zonula occludens toxin modulates tight junctions through protein kinase C-dependent actin reorganization, in vitro.

The intracellular signaling involved in the mechanism of action of zonula occludens toxin (ZOT) was studied using several in vitro and ex vivo models. ZOT showed a selective effect among various cell lines tested, suggesting that it may interact with a specific receptor, whose surface expression on various cells differs. When tested in IEC6 cell monolayers, ZOT-containing supernatants induced a redistribution of the F-actin cytoskeleton.

Effect of lactation on hypothalamic preproenkephalin gene expression.

Enkephalin appears to modulate several aspects of reproductive function in female rats. The purpose of this study was to determine if lactation influences preproenkephalin gene expression in one or more hypothalamic nuclei known to be involved in maternal or reproductive behavior and prolactin secretion. Lactating rats were killed on day 3 (LAC 3) or day 10 (LAC 10) of lactation.