Visit our Expo - Redox and Inflammation signaling 2012

Session X : Cell death in cancer Poster X, 48
Ceramide–modulation of antigen-triggered Ca2+-signals and cell fate: a diversity in the
responses by different lymphoid and myeloid cells.
Endre Kiss, Gabriella Sármay and János Matkó
Eötvös Lorand University, Institute of Biology, Department of Immunology, Budapest,
Hungary
Release of ceramide (Cer) from plasma membrane sphingomyelin upon cell death, stress and
inflammation stimuli is a signal mediating the mitochondrial cell death pathway in various
cell types. We have shown recently that Cer-accumulation differentially affects T-cell fate
(apoptosis vs. survival) depending on its strength and duration [Detre et al, Cellular Signalling
2006. 18:294-306]. Moderate, non-apoptotic Cer stimuli suppressed the early and late events
of both antigen-specific or polyclonal T-cell activation signalling. K+ channels (Kv1.3, KCa)
as regulators and Ca2+ channels (CRAC, VDCC) as executors of the calcium influx were
proposed so far as potential targets of Cer-mediated inhibition. The molecular background of
the ceramides’ modulatory effect, however, still remained unresolved. Here we analyzed how
general is this modulation among further antigen-dependent cells of the immune system, with
attention to their maturation or differentiation stage, as well. The antigen-dependent calcium
signals of murine (IP12-7) and human (Jurkat) T cells, as well as of mast cells (RBL-2H3)
were remarkably inhibited by short (10 min) C2-Cer stimuli, in a concentration dependent
manner. Similar, but much less inhibition was observed in murine B splenocytes and
immature or mature B cell lines, 38C13 and A20, respectively. In contrast, in two human
Burkitt’s lymphoma B cell lines (BL41 and ST486) or the X16C murine B cell line of
marginal zone origin the magnitude of the antigen-BCR mediated calcium response was
uneffected or enhanced by Cer compared to the untreated cells. Interestingly, the sensitivity of
the above cells to Cer-mediated apoptosis (long duration C2-Cer), monitored through
mitochodrial depolarization and DNA-fragmentation, showed a similar diversity. The
Burkitt’s lymphoma cells were highly resistant, in contrast to the high and Cer dosedependent
apoptotic rate of T cells. The murine immature and mature B cells did not display
any apoptotic marker either, but became PI-positive (necrotic), depending on the ceramide
dose. Our data together suggest that the antigen-dependent immune cells have differential
sensitivity to ceramide-generating death or stress signals. Understanding the mechanisms
underlying these differences needs further investigations, particularly on Cer-induced
reorganization of the plasma membrane and identification of further molecular targets for
ceramide action involved in modulation of antigen-induced activation signals.
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