Thiram is a dithiocarbamate
pesticide that causes tibial
dyschondroplasia (TD), a growth plate defect, in poultry. Deaths of transitional zone chondrocytes appear to interrupt endochondral bone development leading to the broadening of growth plate. The mechanism of action of
thiram on chondrocytes is not well understood. Since
proteins play major roles in different aspects of cell's metabolism, growth, and survival, the objective of this study was to find whether
thiram produces proteomic changes that could impair the development of chondrocytes. The chondrocytes, isolated from proximal tibial growth plates, were cultured with or without a sub-lethal concentration of
thiram for 48 hr, and the cell
proteins were extracted, and subjected to 2-D gel electrophoresis. The gel images were compared and statistically evaluated using Melanie software to identify differentially expressed
protein spots. Of a total of 72 identifiable spots 3 were down-regulated and 2 up-regulated in
thiram treated chondrocytes. In-gel
trypsin digestion of the
protein spots followed by their characterization by matrix-assisted
laser desorption ionization-time-of- flight (MALDI-TOF) mass spectrometry identified 25 spots comprising of 23
proteins. Two of 3 down-regulated
proteins were identified as a
heat shock protein 70 (HSP 70) and a GALE (UDP-galactose-4 epimerase)
protein isoform I. The up-regulated
proteins were
Serpin H1, a
protein involved in
collagen metabolism and a redox sensor NmrA-like (NMRAL) family domain protein-1. Both GALE and NMRAL
proteins are implicated in energy metabolism and redox regulation whereas the HSP 70 protects cells against stress, and implicated in chondrocyte
hypertrophy, an important event in endochondral bone formation. The failure of chondrocyte protective mechanisms such as associated with protection against cellular stress and energy metabolism appear to be the likely cause for chondrocyte death induced by
thiram.