The role of mitogen activated protein kinase, p44/42, in the butyltin-induced alterations of human natural killer cell function
Natural Killer (NK) cells are a subset of lymphocytes that are capable of killing (lysing) 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, 2005). If activation of p44/42 is required for TBT-induced decreases of lytic function, then selective 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, 6 h, 1 h with 24 h in compound-free media, and 24 h before determining the lytic function (51Cr release assay), phosphorylation state of MAPKs (Western blot), cell surface protein expression (flow cytometry), granzyme and perforin expression (Real-time RT-PCR and 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 6 fold increase in phospho-p44/42 levels. The expression of CD11a, CD16, CD18, and CD56 were reduced, perforin mRNA levels were unchanged and granzyme mRNA levels were increased compared to the control by PMA. To verify that activation of p44/42 was responsible for the alterations seen in CD11a, CD16, CD18, and CD56 with PMA, NK cells were treated with the p44/42 pathway inhibitor (PD98059) prior to PMA exposures. In the presence of PD98059, PMA caused no decreases in the expression of the cell surface markers. Results of these studies indicate that the activation of p44/42 may lead to the loss of NK cell cytotoxic function by decreasing the expression of CD11a, CD16, CD18, and CD56. Further, activation of p44/42 appears to be at least in part responsible for the TBT-induced decreases in expression of CD16, CD18, and CD56. ^
Biology, Molecular|Biology, Cell|Health Sciences, Immunology
Fred D Dudimah,
"The role of mitogen activated protein kinase, p44/42, in the butyltin-induced alterations of human natural killer cell function"
ETD Collection for Tennessee State University.