Regulatory Volume Decrease in isolated nematocytes is affected by crude venom from the jellyfish Pelagia noctiluca

Crude venom from nematocysts of the Scyphozoan Pelagia noctiluca possesses hemolytic and cytotoxic power on cultured cells and elicits local and systemic inflammation reactions in vivo. The ability of regulate their volume after exposure to an anisosmotic solution is a fundamental feature common to cells from vertebrates and invertebrates, including Cnidarians. The aim of the present work is to assay whether crude venom from Pelagia noctiluca may affect the Regulatory Volume Decrease (RVD) of nematocytes isolated from the Anthozoan Aiptasia mutabilis, here employed as a cell model. For this purpose, nematocytes were isolated by 605 mM NaSCN plus 0.01 mM Ca2+ application on acontia of Aiptasia mutabilis, while crude venom was obtained by sonication of a population of, respectively, 10, 25 and 50 nematocysts/µl (n/l). Isolated nematocytes were pre-treated for 30 min with crude venom, submitted to hypotonic stress and their osmotic response and RVD were measured optically. Our results show that, after exposure to crude venom, nematocytes were morphologically intact, as shown by the Trypan blue exclusion test, but did not exhibit RVD. This effect was dose-dependent and reversed by the ionophore gramicidin. The last observation suggests an inhibitory effect of venom on cell membrane ion transport mechanisms involved in RVD. Further studies are needed to verify this hypothesis and ascertain if a similar effect could be observed in human cells.