Tributyltin (TBT) and dibutyltin (DBT) are widespread environmental contaminants found in food, beverages, and human blood samples. Both of these butyltins (BTs) interfere with the ability of human natural killer (NK) cells to lyse target cells and also alter secretion of the pro-inflammatory cytokine tumor necrosis factor alpha (TNFα) from human immune cells in vitro. The capacity of BTs to interfere with secretion of other pro-inflammatory cytokines has not been examined. Interferon gamma (IFNγ) is a modulator of adaptive and innate immune responses, playing an important role in overall immune competence. This study shows that both TBT and DBT alter secretion of IFNγ from human immune cells. Peripheral blood cell preparations that were increasingly reconstituted were used to determine if exposures to either TBT or DBT affected IFNγ secretion and how the makeup of the cell preparation influenced that effect. IFNγ secretion was examined after 24 h, 48 h and 6 day exposures to TBT (200- 2.5 nM) and DBT (5- 0.05 μM) in highly enriched human NK cells, a monocyte-depleted preparation of PBMCs, and monocyte-containing PBMCs. Both BTs altered IFNγ secretion from NK cells at most of the conditions tested (either increasing or decreasing secretion). However, there was significant variability among donors as to the concentrations and time points that showed changes as well as the baseline secretion of IFNγ. The majority of donors showed an increase in IFNγ secretion in response to at least one concentration of TBT or DBT at a minimum of one length of exposure.

Tributyltin (TBT), a toxic environmental contaminant, has been widely utilized for various industrial, agricultural and household purposes. Its usage has led to a global contamination and its bioaccumulation in aquatic organisms and terrestrial mammals. Previous studies suggest that TBT has debilitating effects on the overall immune function of animals, rendering them more vulnerable to diseases. TBT (at concentrations that have been detected in human blood) alters secretion of inflammatory cytokines from human lymphocytes ex vivo. Thus, it is important to determine if specified levels of TBT can alter levels of cytokines in an in vivo system. Mice were exposed to biologically relevant concentrations of TBT (200, 100 or 25 nM final concentrations). The quantitative determination of interferon (IFN)-γ, tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL2, IL5, IL7, IL12βp40, IL13, IL15, KC, MIP1β, MIP2 and RANTES was performed in mouse sera by MAGPIX analysis and Western blot. Results indicated alterations (both decreases and increases) in several cytokines. The pro-inflammatory cytokines IFNγ, TNFα, IL-1β, IL-2, IL5, IL12βp40, and IL-15 were altered as were the chemokines MIP-1 and RANTES and the anti-inflammatory cytokine IL-13. Increases in IFNγ and TNFα were seen in serum of mice exposed to TBT for less than 24 hr. IL1-β, IL-12βp40, IL-5 and IL-15 were also modulated in mouse serum depending on the specific experiment and the exposure concentration. IL-2 was consistently decreased in mouse serum when animals were exposed to TBT. There were also TBT-induced increases in MIP-1β, RANTES, and IL-13. These results from human and murine samples clearly suggest that TBT exposures modulate the secretion inflammatory cytokines.

Tributyltin (TBT) is found in human blood and other tissues and thus is of considerable concern as to its effects on human health. Previous studies have demonstrated that TBT has detrimental effects on immune function. Recently, we found that exposures to TBT caused increased secretion of two important proinflammatory cytokines, tumor necrosis factor alpha (TNFα) and interferon gamma (IFNγ). Elevation of either of these cytokines has the potential to cause chronic inflammation, which is an important factor in a number of diseases including cancer. The current study examined the mechanism of TBT-induced elevations of TNFα and IFNγ secretion and found that the p38 mitogen-activated protein kinase pathway was essential to the ability of TBT to stimulate secretion. Additionally, this study demonstrated that increased secretion of these cytokines was due to TBT-induced increases in their overall synthesis, rather than simply being due to an increase in the release of already formed proteins. The TBT-induced increases in synthesis were evident within 6 hours of exposure. The p38 mitogen-activated protein kinase pathway is also necessary for the TBT-induced increases in both TNFα and IFNγ synthesis. The role of increased transcription of TNFα and IFNγ mRNA in response to TBT exposures as a possible explanation for the increased synthesis of these cytokines was also examined. It was found that increased mRNA levels did not appear to explain fully the increases in either TNFα or IFNγ synthesis. Thus, TBT is able to increase secretion of two important proinflammatory cytokines by increasing their synthesis.

Cytokines are important regulators of immune responsiveness. Alterations of cytokine secretion from immune cells would have the potential to disrupt both immune destruction of cancer cells and to alter the proliferation and invasiveness of tumor cells due to their capacity to act as growth factors, angiogenic factors, and inducers of epithelial-mesenchymal transition. Tributyltin (TBT) is a widespread environmental contaminant having been used in a variety of industrial applications and is found in human blood at levels ranging as high as 261 nM. Studies in human immune cells have shown that secretion of tumor necrosis factor alpha (TNFα) is altered by exposures to TBT. There have been no in vivo studies of the effects of exposure to TBT on the cytokine communication network. As it is not possible to examine alterations of this network in exposed humans, we examined the effects of TBT exposure in a mouse model using Milliplex mouse cytokine/chemokine magnetic bead premixed 32 plex kit. Serum and spleens of TBT-exposed mice were analyzed for changes in cytokine secretion/levels. TBT increased the levels of IL13 in the serum of non-tumor-bearing mice and increased IL1β, IL6, KC, and M-CSF in tumor-bearing mice. The spleens of both non-tumor-bearing and tumor-bearing mice showed increases in Eotaxin when exposed to TBT. Of significant interest is the fact that the presence of tumor causes increases in Eotaxin, IL12p40, M-CSF, and TNFα and exposure to TBT alone can cause increases in these same cytokines. Tumors are known to increase levels of cytokines that enhance their ability to survive. The results showing that TBT can amplify the levels of several cytokines that are increased by tumor suggest that TBT may have tumor-promoting abilities by modulating tumor growth and/or invasiveness. Experiments are under way to dissect cytokine signaling pathways that are affected by TBT. The findings will allow identification of molecular targets that are necessary to intercept the tumor promoting signaling following TBT exposure. Supported by: NIH grant 5U54CA163066-03 Citation Format: Shanieek Lawrence, Samuel Troy Pellom, Tasia Hurd-Brown, Anil Shanker, Margaret Whalen. Elevation of tumor-promoting cytokines in mice exposed to the environmental contaminant tributyltin. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3191. doi:10.1158/1538-7445.AM2014-3191

Tributyltin (TBT) is an environmental contaminant that has been used for several industrial, agricultural and household purposes. Despite limited bans on the usage of Tributyltin, the stability and toxicity of the compound may prove to have negative effects on immune function in terrestrial mammals. Studies show that there is an increase in the incidences of tumors and decreased immune cell function in TBT-exposed mammals. TBT interferes with the ability of human natural killer (NK) cells to lyse target cells; it also alters the secretion of the pro-inflammatory cytokines Interferon gamma (IFNγ) and Tumor necrosis factor alpha (TNFα) from human immune cells ex vivo. Any dysregulation of the cytokine communication network may have detrimental effects on immune function, as cytokines play a key role in the regulation of immune responsiveness. There have been no in vivo studies on the effects of exposure to TBT on the cytokine communication network. The effects of 24 hour exposure to TBT on the production of IFNγ and TNFα from human immune cells were analyzed in an ex vivo system using western blotting. The serum of TBT-exposed mice was analyzed for changes in the levels of cytokine secretion and production using a Milliplex mouse cytokine/chemokine magnetic bead premixed 32 plex kit and western blotting; the effects of TBT-exposure was assessed using a time curve of 6h, 12h, 24h, 48h and control. TBT increased the levels of the cytokines IFNγ, TNFα, IL1β, IL5, IL7, IL12βp40, IL13, IL15, MIP1β, MIP2 and RANTES in the serum at a minimum of one time point. IFNγ and TNFα secretion and production from human cells also increased, showing striking agreement in the response to TBT between the human and mouse systems. Supported by: NIH grant 5U54CA163066-03 Citation Format: Shanieek T. Lawrence, Margaret Whalen, Samuel Pellom, Anil Shanker. Tributyltin alters the production and secretion of inflammatory cytokines from human and mouse immune cells. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2735. doi:10.1158/1538-7445.AM2015-2735