Background: Ethylene is a widely distributed alkene product which is formed enzymatically (e.g., in plants) or by photochemical reactions (e.g., in the upper oceanic layers from dissolved organic carbon). This gaseous compound was recently found to induce in cells from the marine sponge Suberites domuncula, an increase in intracellular Ca2+ level ([Ca2+]i) and an upregulation of the expression of two genes, the potential ethylene-responsive gene, SDERR, and a Ca2+/calmodulin-dependent protein kinase.
Results: Here we describe for the first time, that besides sponge cells, mammalian cell lines (mouse NIH-3T3 and human HeLa and SaOS-2 cells) respond to ethylene, generated by ethephon, with an immediate and strong, transient increase in [Ca2+]i level, as demonstrated using Fura-2 imaging method. A rise of [Ca2+]i level was also found following exposure to ethylene gas of cells kept under pressure (SaOS-2 cells). The upregulation of [Ca2+]i was associated with an increase in the level of the cell cycle-associated Ki-67 antigen. In addition, we show that the effect of ethephon addition to S. domuncula cells depends on the presence of calcium in the extracellular milieu.
Conclusion: The results presented in this paper indicate that ethylene, previously known to act as a mediator (hormone) in plants only, deserves also attention as a potential signaling molecule in higher vertebrates. Further studies are necessary to clarify the specificity and physiological significance of the effects induced by ethylene in mammalian cells.