Physalia physalis Poison Depolarizes Beta Cell Membrane and Increases Insulin Secretion

Abstract

Peptide toxins isolated from marine cnidarians are considered as useful tools for studying ionic channels and promising drugs for therapeutics. Hemolytic and cardiotoxic activities have been described in Physalia physalis venom, and two toxins with anticholinergic and antiglutamatergic effects have been isolated in its high molecular weight fraction.In this work, we explored some crude extract of P. physalis and its low molecular weight fractions on ionic currents and insulin secretion of pancreatic rat beta-cells. P. physalis specimens were collected at the north littoral of La Habana, Cuba. Crude extract were purified by a gel filtration (Superdex 200). Mass spectrometry MALDI-TOF and RP-HPLC (C18 column) were performed on each fraction collected from gel filtration. The biological activity on insulin secretion was tested in a reverse hemolytic plaque assay on primary cultures of pancreatic beta cells from male Wistar rats.In basal glucose (5.6 mM), the crude extract (25 protein ug/mL) increased by 77% the average immunoplaque area, which is directly proportional to insulin secreted by isolated cells, without disrupting of beta cells or erythrocytes integrity. Low molecular fractions from gel filtration did not exceed of 20 kDa, and most of them eluted before the 20 % of acetonitrile on RP-HPLC. These fractions increased both, the percentage of insulin-secreting cells and the average immunoplaque area at a basal glucose level, suggesting a direct effect on TRP-type channels that are responsible for beta cell depolarization.Physalia physalis poison contains polar bioactive compounds capable of enhance the secretory behavior of pancreatic beta cells from male Wistar rats by depolarizing the membrane, in non stimulant glucose conditions.Supported by Instituto de Ciencia y Tecnologia del DF, ICYT (PICSD 08-72).