Dopamine-induced programmed cell death is associated with cytochrome c release and caspase-3 activation in snail salivary gland cells.
BACKGROUND
PCD (programmed cell death) is a common mechanism to remove unwanted and excessive cells from organisms. In several exocrine cell types, PCD mode of release of secretory products has been reported. The molecular mechanism of the release, however, is largely unknown. Our aim was to study the molecular mechanism of saliva release from cystic cells, the specific cell type of snail SGs (salivary glands).


RESULTS
SG cells in active feeding animals revealed multiple morphological changes characteristic of PCD. Nerve stimulation and DA (dopamine) increased the number of TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling)-positive cells both in inactive and feeding animals. The DA-induced PCD was prevented by TEA (tetraethylammonium chloride) and eticlopride, emphasizing the role of K channels and D2 receptors in the PCD of cystic cells. DA enhanced cyto-c (cytochrome c) translocation into the cytosol and methyl-beta-cyclodextrin prevented it, suggesting apoptosome formation and ceramide involvement in the PCD linking of the surface DA receptor to mitochondria. Western blot analysis revealed that the release of cyto-c was under the control of Bcl-2 and Bad. DA also increased the active caspase-3 in gland cells while D2 receptor antagonists and TEA attenuated it.


CONCLUSIONS
Our results provide evidence for a type of transmitter-mediated pathway that regulates the PCD of secretory cells in a mitochondrial-caspase-dependent manner. The activation of specific molecules, such as K channels, DA receptors, cyto-c, ceramide, Bcl-2 proteins and caspase-3, but not caspase-8, was demonstrated in cells involved in the DA-induced PCD, suggesting that PCD is a physiological method for the release of saliva from SG cells.
Pirger
Zsolt
Z
Department of Experimental Zoology, Balaton Limnological Research Institute, Hungarian Academy of Sciences, Tihany, Hungary.
Rácz
Boglárka
B
Kiss
Tibor
T
D000818:Animals; D017209:Apoptosis; D001692:Biological Transport; D053148:Caspase 3 / Q000378:metabolism*; D045304:Cytochromes c / Q000378:metabolism*; D004298:Dopamine / Q000378:metabolism*; D004789:Enzyme Activation; D053078:Membrane Potential, Mitochondrial; D012469:Salivary Glands / Q000166:cytology / Q000201:enzymology / Q000378:metabolism; D015398:Signal Transduction; D012908:Snails / Q000166:cytology / Q000201:enzymology / Q000378:metabolism*
D045304:Cytochromes c; D053148:Caspase 3; D004298:Dopamine