2011;50:211C221. necrosis in human peripheral blood lymphocytes and Jurkat cells, and could also induce late apoptosis, especially in the tumor cell line. These results shed light on fluoxetine-induced cell death and its potential use Rabbit Polyclonal to FOXO1/3/4-pan (phospho-Thr24/32) in cancer treatment. [3C11] and to prevent the growth of tumors [5, 12C14]. Fluoxetine reduces cell viability in various models of cancer. Moreover, fluoxetine does not decrease the viability of non-cancer cell lines such as HSF  or primary cells such as peripheral blood mononuclear cells and B lymphocytes , suggesting that fluoxetine selectively kills tumor cells. Several types of cell death seem to be involved, with various publications reporting not only apoptosis [7C10], but also autophagy . However, the precise mechanisms involved in fluoxetine-induced cell death remain largely unresolved at this time. Fluoxetine and SSRIs also have reported effects on cytosolic calcium concentration ([Ca2+]cyt) and on ion channels, which can be either activated or inhibited. For example, numerous experiments have shown that fluoxetine induces an increase in [Ca2+]cyt in immune cells [9, 10, 15C17] and central nervous system cells [18, 19]. This effect is found both in healthy and cancer cell models. Reports that fluoxetine induces Ca2+ release from the Endoplasmic Reticulum (ER) and mimics B-cell receptor (BCR) ligation [9, 20] suggest that the pathway could involve PhosphoLipase C (PLC) activation, leading to Zaltidine the production of Inositol 1,4,5-trisPhosphate (IP3) and to the activation of the IP3 Receptors (IP3R) located within the ER membrane. However, other authors have shown that IP3 is on the contrary not involved in fluoxetine-induced increase in [Ca2+]cyt [16, 17, 20]. Nevertheless, whether IP3R is involved or not, Ca2+ is released from an intracellular compartment after a fluoxetine treatment . It appears that the increase in [Ca2+]cyt induced by fluoxetine is due to a Ca2+ entry [10, 15C17, 20]. Ca2+ is a second messenger, which is of utmost importance for numerous cellular processes including cell death. Hence, Ca2+ homeostasis is crucial, and it is well known Zaltidine that Ca2+ overload or an alteration in Ca2+ levels within different cellular compartments can be cytotoxic and may lead to cell death by necrosis, apoptosis or autophagy [21, 22]. Notably, mitochondria are a central compartment regarding Ca2+-induced cell death, and fluoxetine is found mainly accumulated in this organelle . Overall, further insight is needed in order to elucidate the pathways involved in the increase in [Ca2+]cyt triggered by fluoxetine. The purpose of this study was thus to determine the signaling pathway triggered by fluoxetine, leading to a [Ca2+]cyt increase in both cancer and healthy immune cells. For cancer cells, both adherent and non-adherent cell models were used. Additionally, we studied the relationship Zaltidine between the Ca2+ pathway and the cell death pathway. We confirmed that fluoxetine induces an ER-dependent cytosolic Ca2+ increase in adherent and non-adherent cell models. However, our data shows that this cytosolic Ca2+ increase is due to a thapsigargin-like effect, where Ca2+ leaves the ER via the translocon and triggers Store-Operated Ca2+ Entry (SOCE). The initial calcium leak is produced by a direct or indirect inhibition of SERCA activity, since fluoxetine impairs ATP production by inhibiting the respiratory chain. The rise in [Ca2+]cyt resulted in a mitochondrial Ca2+ overload leading to cell death, mainly by necrosis. RESULTS Fluoxetine induces an increase in the cytosolic Ca2+ concentration resulting from Ca2+ release as well as Ca2+ entry In Jurkat.