Increases in Cytosolic Calcium Ion Levels in Human Natural Killer Cells in Response to Butyltin Exposure

Abstract

This study investigated whether exposures to butyltins (BTs), tributylin (TBT) and dibutyltin (DBT) were able to alter cytosolic calcium levels in human natural killer (NK) cells. Additionally, the effects of cytosolic calcium ion increases on the activation state of mitogen activated protein kinases (MAPKs) in NK cells were also investigated. NK cells are an intital immune defense against the development of tumors or viral infections. TBT and DBT are widespread environmental contaminants, due to their various industrial applications. Both TBT and DBT have been shown to decrease the ability of NK cells to lyse tumor cells (lytic function). TBT has also been shown to activate MAPKs in NK cells. The results of this study indicated that TBT increased cytosolic calcium levels by as much as 100% after a 60 min exposure to 500 nM TBT while DBT increased cytosolic calcium levels to a much smaller extent (and required higher concentrations). The results also indicated that increases in cytosolic calcium could activate MAPKs but only for a short period of time (5 min), while previous studies showed that activation of MAPKs by TBT last for at least 6 hours. Thus, it appears that TBT stimulated increases in cytosolic calcium may contribute to, but are not fully responsible for, TBT-induced activation of MAPKs.

Assessment of the usefulness of the murine cytotoxic T cell line CTLL-2 for immunotoxicity screening by transcriptomics

“…ER stress also induces leakage of calcium from the ER leading to activation of NFB, calcineurin and NFAT that induces oxidative stress and T cell activation in primary thymocytes and Jurkat cells and ultimately leads to apoptosis as well (Katika et al, 2012b;van Kol et al, 2011). There are strong indications that TBTO acts directly on the endoplasmic reticulum inducing a raise of intracellular Ca 2+ release from the ER leading to the same calcium induced responses as mentioned above for DON (Aw et al, 1990;Bissonnette et al, 2010;Chow et al, 1992;Grundler et al, 2001;Kass and Orrenius, 1999;Katika et al, 2012b;Lane et al, 2009).…”

Activation of p44/42 MAPK plays a role in the TBT-induced loss of human natural killer (NK) cell function

“…Thus, the decreases in granzyme B and perforin expression seen with exposures to TBT (Thomas et al, 2004; and Thomas et al, 2005) cannot be explained by TBT-induced activation of p44/42, in contrast to the TBT-induced effects on lytic function. This indicates that other TBT-induced changes, such as p38 activation (Aluoch and Whalen, 2005; Aluoch et al,2006) or increases in cytosolic calcium ion (Lane et al, 2009), may be responsible for the decreases seen in these proteins.…”

“…We have also shown that the activation of p44/42 is not solely responsible for the loss of NK cell function as specific inhibitors of p44/42 activation cannot block the negative effects of TBT (Abraha and Whalen, 2009). This is likely due to the fact that TBT causes additional changes in NK cells, such increases in cytosolic calcium ion concentrations (Lane et al, 2009). However, in order to understand the mechanism(s) by which TBT interferes with NK cell function, it is important to define the role played by p44/42 activation as it is an important consequence of TBT exposure in NK cells.…”

Evaluation of in vitro immunotoxicity tests using transcriptomics

“…ER stress also induces leakage of calcium from the ER leading to activation of NFκB, calcineurin and NFAT that induces oxidative stress and T cell activation in primary thymocytes and Jurkat cells and ultimately leads to apoptosis as well . There are strong indications that TBTO acts directly on the endoplasmic reticulum inducing a raise of intracellular Ca2+ release from the ER leading to the same calcium induced responses as mentioned above for DON (Aw et al, 1990;Bissonnette et al, 2010;Chow et al, 1992;Kass and Orrenius, 1999;Lane et al, 2009). Biological interpretation of the present mRNA expression data was conducted using three methods: 1) Metacore analysis on groups of genes significantly affected according to limma, 2) Metacore analysis on clusters after hierarchical clustering, and 3) GSEA analysis on the entire microarray dataset followed by Molecular Concepts analysis.…”