Poster Presentation 28th Annual Lorne Proteomics Symposium 2023

Identification of oxidatively modified proteins to utilise as biomarkers of immune cell activation (#103)

Angelo R Bautista 1 2 , Marisa N Duong 2 , Peter G Arthur 1 , Jessica R Terrill 1
  1. University of Western Australia, Perth, Western Australia, Australia
  2. Proteomics International, Perth, Western Australia, Australia

Inflammation is evident in chronic diseases and condition, and the inflammatory response involves the pathogenic generation of oxidants including hydrogen peroxide and hypochlorous acid. Oxidants can also oxidatively modify the side chains of proteins, and we propose that the measurement of such in biofluids such as blood would be useful as reporters of inflammation and therefore severity of many diseases. One such disease, is the fatal childhood muscle wasting disease Duchenne muscular dystrophy (DMD), which currently has no effective treatment. The exact pathological mechanisms of DMD are not understood, however we and others have proposed that white blood cells, particularly neutrophils, contribute to the pathology. To explore the potential of oxidatively modified proteins to be readouts of disease pathology in biofluids, we used immunoassays and mass spectrometry to identify oxidatively modified proteins in the blood of mice DMD model. A modification of particular interest is the halogenation of protein tyrosines because this modification occurs only when a tyrosine residue encounters hypochlorous acid, which is specifically produced by the enzyme myeloperoxidase, an enzyme produced in neutrophils. We identified a protein in plasma that is 26% more halogenated in dystrophic animals compared to wildtype (n=7-8). We show that the halogenation of this protein (hal-X) correlates strongly with muscle pathology (including inflammation). To further investigate the use of halogenation of this protein as a readout of disease pathology, we measured hal-X in plasma from dystrophic mice treated with taurine, an anti-inflammatory drug we have previously shown to be effective at decreasing inflammation and muscle cell death [1]. We show that in the mouse model, a decrease of 15% in halogenation of this protein occurs after taurine treatment (n=8), which again correlates with other readouts of muscle pathology.  Our results provide evidence that oxidatively modified proteins, particularly halogenation, have the potential to be useful biomarkers of disease pathology in conditions associated with excess inflammation, and these can be readily detected in blood. These biomarkers could be utilized for monitoring putative treatments in DMD, where currently the testing of potential therapies is limited by clinical outcome measures that require 12-18 months to properly determine efficacy. We hypothesize that the measurement of oxidatively modified proteins in biofluids could report the efficacy of prospective treatments within a few weeks, which would significantly reduce the cost and time burden of clinical trials in DMD and numerous other conditions.

  1. Terrill, J.R., et al., Increasing taurine intake and taurine synthesis improves skeletal muscle function in the mdx mouse model for Duchenne muscular dystrophy. The Journal of Physiology, 2016. 594(11): p. 3095-3110.