Mitochondrial products, especially mitochondrial DNA, are pro-inflammatory in human studies, presumably due to their bacterial evolutionary origins. Therefore their release from tissue necrosis may be an important contributor to the inflammatory response in the horse. The aim of this study was to determine the inflammatory response to mitochondrial products in an in vitro equine whole blood assay.
Mitochondria were isolated from liver tissue of a systemically healthy horse by cell lysis and centrifugation. Mitochondria were then fragmented by freeze-thawing and serially diluted from 1:1 to 1:512 in PBS, and added to aliquots of whole blood from 6 healthy horses, mixed 1:1 with RPMI medium, with one aliquot serving as a negative control. Aliquots were incubated rotating at 37°C for 21 hours. The inflammatory response was determined by measuring TNF-α in the supernatant using a murine L929 fibroblast bioassay.
Mitochondrial fragments caused an inflammatory effect in equine whole blood, producing a concentration-dependent increase in TNF-α release into the plasma/supernatant, which fitted to a sigmoidal concentration-response curve. There was a 7.3-fold increase in TNF-α production at the lowest dilutions of mitochondrial fragments (557.5 ± 470.5 pg/mL at 1:2 dilution compared with 76.1 ± 33.9 pg/mL in whole blood incubated with no fragments).
The release of mitochondrial fragments from localized tissue damage, inflammation or necrosis might contribute to the clinical severity of SIRS, and possibly offer a mechanism for the development of SIRS in horses in the absence of obvious gastrointestinal disease or infection. Further work is warranted to investigate the significance of inflammation caused by mitochondrial fragments in horses, including novel anti-inflammatory therapies.
Lecturer in Equine Medicine
University of Melbourne
Jenni graduated from Murdoch University in Perth, Australia and then completed an internship at the Equine Medical Center of Ocala, Florida. This was followed by a residency in large animal medicine at the University of Pennsylvania’s New Bolton Center, after which she became board certified in large animal internal medicine. She returned to Australia to commence her PhD in equine systemic inflammation at the University of Melbourne, and is now a lecturer in equine medicine at the University of Melbourne. She completed a graduate diploma in tertiary and adult education in 2016 and her PhD in 2017.
Friday, June 15
5:30 PM – 5:45 PM
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