Secretion of interferon gamma from human immune cells is altered by exposure to tributyltin and dibutyltin

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 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 immune 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 stimulates synthesis of interferon gamma and tumor necrosis factor alpha in human lymphocytes

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

Tributyltin exposure alters cytokine levels in mouse serum

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, keratinocyte chemoattractant (KC), macrophage inflammatory protein 1β (MIP), MIP2 and regulated on activation normal T-cell-expressed and secreted (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 the serum of mice exposed to TBT for less than 24 h. Levels of IL1β, IL-12 βp40, IL-5 and IL-15 were also modulated in mouse serum, depending on the specific experiment and exposure level. 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

Endophytic Colonization of Flowering Dogwood (Cornus florida L.) and their Potential Applications

The existence of endophytic microorganisms (endophytes) has been known for over a century. Endophytes are generally defined as fungal and bacterial species existing within plants; their presence is not easily observed because host tissue colonization is internal and the infested tissues may remain asymptomatic. Many endophytes are known to produce bioactive metabolites which protect their plant hosts from various pests and pathogens. These bioactive metabolites also function in various agricultural and pharmaceutical applications ranging from biological control agents to chemotherapy treatments. The objectives of this study were to assess endophytic colonization in flowering dogwood (Cornus florida L.) plants by fungal and bacterial organisms, and determine their function as phytopathogens, biological control agents and assess their cytotoxicity based on their production of volatile compounds. Fungi and bacteria were isolated from various sections of the stems of flowering dogwood plants and cultured in nutrient media. Identification of the endophytes was based on morphological features and DNA analysis. Results from this study suggested that endophytes are not localized within the vascular tissue but are found at different sections of the stems. Some endophytes existed as latent pathogens and some were free living, producing secondary metabolites that may have medical or pharmaceutical applications. Gas Chromatography-Mass Spectrometry was used to assess the production of secondary metabolites by these endophytes. Some volatile compounds produced by these endophytes were effective in inhibiting tumor proliferation. The inhibition of tumor proliferation did not appear to be conserved across different cell lines; one endophyte, isolated was more effective on one cell line than on others

Assessment of the Effects of Butyltin Environmental Contaminants on Human and Mouse Cytokine Production and Secretion from Immune Cells

The extensive utilization of butyltins (BTs) has led to global contamination and their bioaccumulation in aquatic organisms and terrestrial mammals. In this study, the dysregulation of IFNγ and TNFα levels in human immune cells by BTs is examined. Increasingly reconstituted immune cell populations were exposed to concentrations of BTs at varied lengths of exposures. In addition, the role of TACE, p38, p44/42, JNK MAPKs and NFκB activation in TBT-induced alterations of IFNγ and TNFα levels were investigated. MD-PBMCs were exposed to appropriate pathway inhibitors and western blot and ELISA assay used to determine TBT-induced cytokine production after 24 h. The serum of TBT-exposed mice was analyzed for changes in the levels of cytokine secretion and production using a MagPix assay and western blot; the effects of TBT-exposure was assessed using a time curve of 6 h, 12 h, 24 h, 48 h and control. When human NK cells, MD-PBMCs and PBMCs were exposed to 0-200 nM TBT and 0-5 μM DBT, results showed a significant TBT-induced stimulation in all cell types. However, the effective concentration of the compound needed to cause increases varied among donors. Studies examining the time course of TBT-induced stimulation of IFNγ and TNFα production, indicate that substantial changes in the levels of these cytokines require an incubation of 24 h. TBT heavily relies on activation of the p38 signaling pathway to cause increases in IFNγ and TNFα, as diminished cytokine levels were seen in all donors after inhibition of this pathway. TBT-induced alterations were observed in IFNγ, TNFα, IL1β, IL-2, IL5, IL12βp40, and IL-15 after mice were exposed to biologically relevant concentrations of TBT. Increases in IFNγ, TNFα and IL-12βp40 were seen in the serum of mice exposed to TBT for less than 24 h. IL-5 and IL-15 were both increased and decreased in mouse serum depending on the specific experiment and the exposure concentration. IL-1β and IL-2 were consistently decreased in mouse serum when animals were exposed to TBT. These data suggest that BT exposures can dysregulate cytokine signaling, thus promoting an inflammatory environment, which could predispose the host to various immunopathologies