Visit our Expo - Redox and Inflammation signaling 2012

Session X : Cell death in cancer Poster X, 53
Cyclosporine A induced cytotoxicity, cell cycle arrest and mitochondrial apoptosis in a
human monocytic leukaemia cell line
Molay Kumar Roy*1, Makiko Takenaka1, Masuko Kobori1, Kazuhiko Nakahara2,
Seiichiro Isobe1, Tojiro Tsushida1.
1National Food Research Institute, 2-1-9, Kannondai, Tsukuba, Ibaraki, 305-0051,
Japan.
2Japan International Research Center for Agricultural Sciences (JIRCAS), 1-1 Owashi,
Tsukuba, Ibaraki 305-8686, Japan.
The immunosuppressive drug cyclosporine A (CsA) has been used in organ transplantation
and in the treatment of autoimmune disorders. However, the drug causes adverse effects in
kidney, liver and nervous system characterized by cellular loss in the affected area. Apoptosis
was found to play a role in CsA induced cytotoxicity. Because mitochondrial membrane
permeabilization is a common criterion in the most setting of apoptosis in vertebrate cells, the
aim of this study was to evaluate whether CsA induces mitochondrial function loss in the
pathway leading to cytotoxicity in a cell line. In this study we found that CsA caused a
concentration and time dependent cell viability loss in U937 cell line. CsA treatment of cells
at 10 µM dose resulted in G0/G1 arrest with concurrent decrease of cells in S and G2/M
phases. In mechanistic studies related to its viability lost we found that treatments of cells
with 10 µM CsA for 24 h resulted in DNA fragmentation and in the increase of annexin V
positive cells. CsA also increased the activity of a cysteine protease caspase-3. In other
studies, we observed that CsA treatment decreased mitochondrial membrane potential and
increased cytochrome c release into cytosol. Furthermore, CsA treatment increased the
number of cells in sub-G0/G1 peak, an indicative of reduced DNA, however this effect was
not observed, when cells were pre-treated with a broad caspase inhibitor. In the study, we
also found that a higher dose of CsA induces LDH release when the cells were incubated for a
longer period. The overall result suggests that the mode of cell death is dose and time
dependent. Short-term incubation with lower doses of CsA arrests cell growth, this overlaps
with the occurrence of apoptosis and then necrosis after longer treatment periods with higher
doses.
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