ABSTRACT
Dibromoacetic acid (DBA), a haloacetic acid by-product of disinfection of drinking water, can cause many adverse effects in test animals, including immunotoxicity. However, the underlying molecular mechanism for the immunomodulatory effects remains unclear. The present study was undertaken to help in defining some potential mechanisms for this type of toxicity. Here, Cl.Ly1+2/-9 T-cells were exposed to varying levels of DBA and then several parameters, including cell survival, apoptosis, changes in mitochondrial potentials, and effects on select kinases (i.e., p38, ERK1/2, JNK1/2) were examined. The data showed that DBA significantly decreased Cl.Ly1+2/-9 cell viability in a dose-related manner. DBA also induced apoptosis, a decrease in mitochondrial trans-membrane potential, and up-regulated the protein expression of cleaved caspase-3. Moreover, DBA increased the phosphorylation of all three mitogen-activated protein kinases (MAPKs) evaluated. Pre-treatment with specific p38, ERK1/2, and JNK1/2 inhibitors (SB203580, U0126, SP600125, respectively) attenuated the inducible phosphorylation events. DBA also induced up-regulation of mRNA levels of the MAPKs downstream transcription factors ATF-2 and Elk-1. When taken together, the results suggest that DBA could induce murine Cl.Ly1+2/-9 T-cells apoptosis through mitochondria-dependent way, and activate the MAPKs pathways and downstream transcription factors ATF-2 and Elk-1.
Subject(s)
Acetates/toxicity , Alkylating Agents/toxicity , Apoptosis/drug effects , Immunologic Factors/toxicity , MAP Kinase Signaling System/drug effects , Protein Processing, Post-Translational/drug effects , T-Lymphocytes/drug effects , Activating Transcription Factor 2/agonists , Activating Transcription Factor 2/genetics , Activating Transcription Factor 2/metabolism , Animals , Caspase 3/chemistry , Caspase 3/genetics , Caspase 3/metabolism , Cell Line , Cell Survival/drug effects , Enzyme Activation/drug effects , Gene Expression Regulation/drug effects , Membrane Potential, Mitochondrial/drug effects , Mice , Osmolar Concentration , Phosphorylation/drug effects , Proteolysis/drug effects , T-Lymphocytes/immunology , T-Lymphocytes/metabolism , ets-Domain Protein Elk-1/agonists , ets-Domain Protein Elk-1/genetics , ets-Domain Protein Elk-1/metabolismABSTRACT
Galectin-1 (gal-1), a member of the mammalian ß-galactoside-binding proteins, exerts biological effects by recognition of glycan ligands, including those involved in cell adhesion and growth regulation. In a previous study, we demonstrated that gal-1 induces cell differentiation processes on the membrane of choriocarcinoma cells BeWo, including the receptor tyrosine kinases, REarranged during transfection, janus kinase 2 and vascular endothelial growth factor receptor 3. Within this study, we examined which mitogen-activated protein kinases (MAPK) and serine/threonine kinases were phoshorylated by gal-1. Out of a number of 21 different MAPKs and other serine/threonine kinases, the stimulation of BeWo cells with gal-1 showed a significant alteration of signal intensity in extracellular-regulated kinases 1/2 (ERK1/2), Akt-3, Akt-pan and glycogen synthase kinase-α/ß (GSK-3α/ß). We demonstrated that gal-1 significantly inhibited ERK1/2, Akt-3/pan and GSK-3α/ß phosphorylation in BeWo cells and in addition induced Elk1 transcription factor activation. In contrast to gal-1 effects, MAPK inhibitor U0126 reduced syncytium formation of BeWo cells. The results of our data showed that phosphorylation of MAP kinases are involved in gal-1-induced signal transduction processes in BeWo cells. Additional results obtained with MAPK inhibitor U0126 close the gap between syncytium formation induced by gal-1 and MAPK activation in trophoblast cells. Furthermore, we demonstrated that gal-1 induces the activation of Elk1, a transcription factor that is activated by MAPK pathways.
