Abstract
Tributyltin (TBT) has been used as a biocide in industrial applications such as wood preservation, antifouling paint and antifungal agents. Owing to its many uses, it contaminates the environment and has been found in human blood samples. Interleukin-1 beta (IL-1β) is a pro-inflammatory cytokine that promotes cell growth, tissue repair and immune response regulation. Produced predominately by both monocytes and macrophages, IL-1β appears to increase the invasiveness of certain tumors. This study shows that TBT modifies the secretion of IL-1β from increasingly reconstituted preparations of human immune cells. IL-1β secretion was examined after 24-, 48-h or 6-day exposures to TBT in highly enriched human natural killer (NK) cells, monocyte-depleted peripheral blood mononuclear cells (MD-PBMCs), PBMCs, granulocytes and a preparation combining both PBMCs and granulocytes (PBMCs+granulocytes). TBT altered IL-1β secretion from all of the cell preparations. The 200 nM concentration of TBT normally blocked the secretion of IL-1β, whereas lower concentrations (usually 5-50 nM) elevated secretion of IL-1β. Examination of the signaling pathway(s) responsible for the elevated secretion of IL-1β was carried out in MD-PBMCs. Pathways examined were IL-1β processing (Caspase-1), mitogen-activated protein kinases (MAPKs) and nuclear factor kappa B (NFκB). Results indicated that MAPK pathways (p44/42 and p38) appear to be the targets of TBT that lead to increased IL-1β secretion from immune cells. These results from human immune cells show IL-1β dysregulation by TBT is occurring ex vivo. Thus, the potential for in vivo effects on pro-inflammatory cytokine levels may possibly be a consequence of TBT exposures.