Oxidative stress, caused by excessive reactive oxygen species (ROS), is evident in many chronic diseases. Protein thiol oxidation is the focus of this research because thiol groups (-SH) on cysteine residues of proteins are particularly sensitive to oxidation. As a consequence, changes in protein function have the potential to cause cellular dysfunction. In preliminary work using gel electrophoresis and mass spectrometry identification, fourteen proteins were observed to undergo thiol oxidation in muscles of a dog model for dystrophy. Ten of these proteins were identified and found to be located in various subcellular compartments including the cytosol, nucleus, mitochondria and also in the extracellular space. Of particular note, lactotransferrin showed a remarkable increase in thiol oxidation of dystrophic muscle. Lactotransferrin is found in the granules of neutrophils, which suggests that neutrophils could be a major source of oxidative stress in the pathogenesis of dystrophy.
These data show that cell and tissue dysfunction could be a collective response to the thiol oxidation of multiple proteins. Expanding the number of proteins that can be identified as being oxidised would improve understanding of how protein thiol oxidation is causing pathogenesis in dystrophy. We propose proteomic methods (high throughput proteomic techniques using gel-free mass spectrometry) to elucidate protein location, involvement in molecular networks and to elucidate molecular pathways that contribute to cellular dysfunction in muscular dystrophy.