Effects of interleukins 2 and 12 on the levels of granzyme B and perforin and their mRNAs in tributyltin-exposed human natural killer cells

Effect of tributyltin (TBT) in the metabolic activity of TBT-resistant and sensitive estuarine bacteria

The effect of tributyltin (TBT) on growth and metabolic activity of three estuarine bacteria with different TBT resistance profiles was investigated in an organic-rich culture medium (TSB) and in phosphate buffered saline (PBS) buffer. Exposure to TBT was assessed by determining its effect on growth (OD(600 nm) measurement), bacterial productivity (leucine incorporation), viability (CFU counts), aggregation and cell size (from Live/Dead analysis), ATP and NADH concentrations. TBT exposure resulted in decrease of bacterial density, cell size, and metabolic activity. In addition, cell aggregates were observed in the TBT-treated cultures. TBT strongly affected bacterial cell metabolism and seemed to exert an effect on its equilibrium, interfering with cell activity. Also, TBT toxicity was lower when cells were grown in TSB than in PBS, suggesting that a nutrient-rich growth medium can protect cells from TBT toxicity. This study contributes to our understanding of the TBT-resistant cell behavior reflected in its physiology and metabolic activity. This information is of utmost importance for further studies of TBT bioremediation.

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

Natural killer (NK) cells destroy (lyse) tumor cells, virally infected cells, and antibody-coated cells. Previous studies indicated that exposure to the environmental contaminant tributyltin (TBT) decreases the lytic function of NK cells and activates mitogen-activated protein kinases (MAPK), including p44/42 (Aluoch and Whalen Toxicology 209:263-277, 2005). If activation of p44/42 is required for TBT-induced decreases of lytic function, then activation of p44/42 to similar extents by pharmacological agents such as phorbol 12-myristate 13-acetate (PMA) should mimic to some extent changes induced in NK cells with TBT exposures. NK cells were exposed to PMA concentrations between 0.25 and 10 nM for 10 min, 1 h, and 6 h before determining the lytic function ((51)Cr release assay) and phosphorylation state of MAPKs (Western blot). A 1-h exposure of NK cells to 5 nM PMA resulted in a loss of lytic function of 47%. Western blot analysis showed that a 1-h exposure to 5 nM PMA caused a sixfold increase in phospho-p44/42 levels. Previous studies showed a fivefold increase in phospho-p44/42 in response to a 1-h exposure to 300 nM TBT. Exposure to 300 nM TBT caused about a 40% decrease in lytic function. This study supports the hypothesis that p44/42 activation (as seen with TBT exposures) can cause a loss of NK-cell lytic function.

Proteomic exploitation on prothymosin α-induced mononuclear cell activation

Prothymosin alpha (ProTalpha) is an acidic polypeptide associated both with cell proliferation and immune regulation. Although ProTalpha's immunomodulating activity is well established at cellular level, limited information is available regarding the signaling pathways triggered by ProTalpha. Using 2-DE proteomic technology, we investigated changes in protein expression of ProTalpha-stimulated peripheral blood mononuclear cells (PBMC) in the course of a 3-day incubation. Using healthy donor- and cancer patient-derived PBMC, 12 gels were studied, identifying 53 differing protein spots via PMF comparison analysis. Among others, we identified interleukin-1 receptor-associated kinase 4, heat-shock protein 90, lipocalin 2, ribophorin 1, eukaryotic elongation factor 2, 14-3-3 protein, L-plastin, and MX2 protein, all of which were found to be overexpressed upon ProTalpha activation. Based on the physiological role of upregulated proteins, we propose the following model for ProTalpha's immunological mode of action: on day 1, ProTalpha triggers monocyte activation, possibly via toll-like receptor signaling, and enhances antigen presentation, consequently promoting and stabilizing monocyte-T-cell immune synapse; on day 2, activated monocytes produce interleukin (IL)-1, while T-cell receptor triggering promotes T-cell proliferation and IL-2 production; finally, on day 3, ProTalpha-activated PBMC express proteins related to adhesion and cytotoxic effector functions, both contributing to the increase of their lytic activity.

Effect of dibutyltin on ATP levels in human natural killer cells

This study investigates the role that decreased ATP levels may play in dibutyltin (DBT)-induced decreases in the tumor-cell-lysing (lytic) function of natural killer (NK) cells. NK cells are a subset of lymphocytes capable of killing tumor cells, virally infected cells, and antibody coated cells. DBT is used as stabilizer in PVC plastics and has also been used as a deworming product in poultry. NK cells were exposed to various concentrations of DBT for 1 h, 24 h, 48 h, and 6 days before determining ATP levels and lytic function. ATP levels and lytic function were also determined in NK cells that were exposed to DBT for 1 h followed by 24 h, 48 h, and 6 days in DBT-free media. The results indicated that exposure of NK cells to 10 muM DBT for 1 h did not cause any significant decrease in NK cell ATP levels but did cause a very significant loss in lytic function. NK cells exposed to 500 nM DBT for 24 h showed significant loss of lytic function but showed no decrease in ATP levels. However, 48 h and 6 days exposures to those concentrations of DBT that caused decreases in tumor lysing function also caused significant decreases in ATP levels. Exposures of NK cells to varying DBT concentrations for 1 h followed by 24 h, 48 h, and 6 days in DBT free media produced effects on lytic function and ATP levels that were similar to those seen with continuous DBT exposures. The results indicate that DBT exposures decrease ATP levels in NK cells but that tumor lysing function can be reduced independent of any decreases in ATP levels. Additionally the results show that the effects of a range of DBT concentrations on ATP levels and tumor lysing function are irreversible.