Submitted to: Journal of Toxicological Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/19/2012
Publication Date: 1/29/2013
Citation: Rath, N.C., Rasaputra, K., Liyanage, R., Lay, J., Slavik, M. 2013. Effect of thiram on avian growth plate chondrocytes in culture. Journal of Toxicological Sciences. 38(1):93-101. Interpretive Summary: Thiram is a fungicide and general use pesticide. Ingestion of thiram by young poultry induces lameness due to its effect on knee joint cartilage. To understand how thiram affects cartilage, we studied its effects using knee joint cartilage cells grown in culture, and comparing with those that did not receive thiram, and analyzing the proteins from these cells. Our results show that this pesticide produces cellular stress and causes cell death. The presence of dead cells in the joint causes lameness.
Technical Abstract: Thiram (tetramethyl thiuram disulfide) is a general use pesticide. It causes tibial dyschondroplasia, a cartilage defect in poultry leading to growth plate deformation and lameness. The mechanism of its action on chondrocytes is not understood. Since proteins play significant role in development and differentiation of cells, the objective of this study was to find whether thiram induces proteomic changes that may be consequential to the failure of endochondral bone formation. Growth plate chondrocytes from proximal tibia were cultured with sublethal concentrations of thiram for 48h and the cell protein extracts were subjected to 2-D gel electrophoresis. Triplicate gels from each group were compared and statistically evaluated using Melanie software to find differentially changed protein spots. Of total 72 identifiable spots, 5 were down regulated in thiram treated cells. In-gel digestion of these spots followed by the identification of the tryptic peptides in the digests by matrix assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF-MS) revealed the down-regulated proteins as HSP 70, and a GALE protein. Serpin H1 precursor protein involved in collagen metabolism and NMRA-like protein-1 involved in apoptosis were found to be up-regulated. GALE and NMRAL proteins are involved in maintaining energy metabolism. HSP 70 is implicated in cartilage hypertrophy essential for endochondral bone formation. It appears that thiram affects proteins involved in energy metabolism and cellular stress, the compromise of which leads to the loss of cellular integrity and viability leading to cell death. Inefficient removal of dead chondrocytes and their retention in the growth plate appear to be cause tibial dyschondroplasia.