Cytolysins increase intracellular calcium and induce eicosanoids release by pheochromocytoma PC12 cell cultures

Cytolysins are the most commonly occurring toxins among bacteria, plants, and animals. By disturbing cell membrane, they impair ionic permeability, leading to cell death. In an attempt to investigate cytolysin action on catecholaminergic neurons, we have treated pheochromocytoma cell cultures with Strep‐tolysin S, Staphylococcus aureus α and δ, Stoichatus, Parcelsin, and cobra direct lytic factor. To measure neurotoxicity, PC12 cultures were loaded with ⁵¹Cr and exposed for 1 hr at 37°C to different concentrations of cytolysins. Cytotoxic dose‐response curves have been generated resulting in CD₅₀ (cytotoxic dose 50%) in the range of 1–50 μg toxin/culture. Using subcytotoxic concentrations of cytolysins (which are of clinical relevance), changes on intracellular calcium were measured by Fura‐2 fluorescence technique. Addition of either Stoichatus toxin and tetanolysin or streptococcus and staphylococcus cytolysins to PC12 cells caused rapidly or gradually a progressive increase in [Ca²⁺]_i, respectively. Under similar conditions, samples of PC12 culture medium were assayed for ³H‐arachidonic acid released and by radioimmunoassay for the content of PGE₂ (prostaglandin), TXB₂ (stable metabolite of thromboxane), and 5‐HETE (hydroxy acid lipoxygenase product). PLA2 was activated 4.5–6.0‐fold and the levels of all three eicosanoids were increased by 2.5–9‐fold (PGE₂), 4–6‐fold (TXB₂), and over 100‐fold (5‐HETE) by Stoichatus and Parcelsin cytolysins. Upon treatment with Streptolysin S and staphylococcus α toxins PLA₂ (phospholipase A₂) was slightly activated (1.5‐fold) and the levels of PGE₂ and TXB₂ increased 1.3–2.0‐fold and that of 5‐HETE up to 30‐fold. These results indicate that the increased intracellular calcium followed by PLA₂ activation and eicosanoid production and release might be involved in neurotoxic action of cytolysins. © 1992 Wiley‐Liss, Inc.