Crude venom from the jellyfish Pelagia noctiluca (Cnidaria, Scyphozoa) affects Regulatory Volume Decrease in HEK 293 cells

Cnidarians are a source of biologically active compounds. The lytic effect of crude venom extracted from the stinging cells of the jellyfish Pelagia noctiluca has been demonstrated on erythrocytes and neuronal cell lines. The aim of the present work is to verify if the crude venom from Pelagia n., at doses not leading to cell necrosis, may affect Regulatory Volume Decrease (RVD) in Human Embryonic Kidney (HEK 293) cells. RVD is an homeostatic response essential to many cells, including HEK 293, to counteract the changes in osmolarity of the external medium. To accomplish this aim, the experimental procedure consisted in: i) jellyfish collection from the Strait of Messina (Italy), isolation of stinging organoids (nematocysts) and extraction of crude venom by ultrasound application; ii) cell culture preparation and treatment of cells with 0.025 μg/ml crude venom and iii) measurement of volume changes in different conditions. Crude venom extract (0.025 μg/μl), added to the extracellular hypotonic solution at the beginning or after 5 min of hypotonic stress, dramatically impaired RVD. Pre-incubation of cells in extracellular isotonic solution containing crude venom prevented RVD after hypotonic stress application, leading to a notable cell swelling during the hypotonic challenge, not observed in control condition. Surprisingly, the presence of crude venom in extracellular isotonic solution induced cell swelling in the absence of an osmotic gradient. Our results show that crude venom leads to cell swelling in isotonic conditions and inhibits RVD, hypothetically due to a blockade of channels involved in RVD mechanisms.