Dibutyltin alters immune cell production of the pro-inflammatory cytokines interleukin (IL) 1ß and IL-6: role of mitogen-activated protein kinases and changes in mRNA.

Dibutyltin (DBT) is used to stabilize plastics and as a deworming agent in some poultry. It is found in human blood (levels as high as 0.3 µM). Interleukin (IL) 1ß (IL-1ß) and IL-6 are pro-inflammatory cytokines produced by lymphocytes, monocytes, and other cells. Elevated levels of IL-1ß and IL-6 have been associated with pathologies including rheumatoid arthritis and cancers. DBT was shown to decrease IL-1ß and IL-6 secretion from immune cells at higher concentrations while causing increases at lower concentrations. However, it was not clear if these changes were due to DBT's alteration of the secretory process or due its ability to change cellular synthesis/production of these proteins. This study addresses this question, as well as mechanisms for any observed changes in synthesis/production. Monocyte-depleted peripheral blood mononuclear cells (MD-PBMCs) were exposed to DBT at concentrations of 5, 2.5, 1, 0.5, 0.25, 0.1, and 0.05 µM for 1, 6, and 24 h and the production (combination of secreted and intracellular levels from the same cells) of both IL-1ß and IL-6 were measured. Effects of selected DBT exposures on cytokine production were also examined in PBMCs and DBT's effects were similar when monocytes were present. The 24-h exposures to DBT decreased production of both IL-1ß and IL-6 at the two highest concentrations but increased production at lower concentrations. Both decreases and increases in cytokine production appear to be explained by DBT-induced changes in mRNA levels. DBT-induced increases in cellular production of the cytokines appear to require p38 and ERK1/2 MAPK pathways.

The organochlorine pesticides pentachlorophenol and dichlorodiphenyltrichloroethane increase secretion and production of interleukin 6 by human immune cells.

The environmental contaminants pentachlorophenol (PCP) and 4, 4'-dichlorodiphenyltrichloroethane (DDT) are detected in some human blood samples at levels as high as 5 µM (PCP) and 260 nM (DDT). Several cancers are associated with exposures to these contaminants. IL-6 is a pro-inflammatory cytokine that when dysregulated stimulates inflammatory diseases and tumor progression. Immune cells exposed to PCP at 0.05-5 µM and DDT at 0.025-2.5 µM showed increased secretion of IL-6 when the cell preparations contained either T lymphocytes or monocytes. Increased IL-6 secretion was due to PCP and DDT induced cellular production of the cytokine and was dependent on MAP kinase signaling pathways (in the case of PCP). Compound-induced increases in IL-6 production were in part due to increases in either the transcription of and/or stability of its mRNA. Thus, both PCP and DDT have the potential to produce chronic inflammation by stimulating production of IL-6 by immune cells.

Exposures to the environmental contaminants pentachlorophenol and dichlorodiphenyltrichloroethane increase production of the proinflammatory cytokine, interleukin-1ß, in human immune cells.

Pentachlorophenol (PCP) and dichlorodiphenyltrichloroethane (DDT) are organochlorine environmental contaminants found in human blood at very significant levels (as high as 5 µm for PCP and 260 nm for DDT). Cancers of the blood (lymphoma and myeloma) and kidney as well as others have been associated with exposure to these contaminants. Interleukin (IL)-1ß is a proinflammatory cytokine and is involved in stimulating cell proliferation. High levels of IL-1ß are associated with inflammatory diseases and tumor progression. Previous studies showed that PCP and DDT at certain concentrations were able to stimulate secretion of IL-1ß. This study shows that the increased secretion of IL-1ß seen with both contaminants is due to compound-induced increases in the production of this cytokine. Increased production began within 6 hours of exposure to PCP and continued to increase up to 24 hours. DDT-induced stimulation of IL-1ß appeared to be maximal after 6 hours of exposure and then diminished by 24 hours. The increases seen in IL-1ß production stimulated by PCP appear to be at least partially due to compound-induced increases in IL-1ß mRNA. Although DDT caused increased production of IL-1ß, it did not appear to cause consistent increases in its mRNA. PCP- and DDT-induced increases in IL-1ß production were dependent primarily on the p38 mitogen-activated protein kinase pathway. These results indicate that both PCP and DDT are able to increase IL-1ß production in a p38 mitogen-activated protein kinase-dependent manner, which may have the potential to influence chronic inflammation.