Combining single molecule counting with bead-based multiplexing to quantify biological inflammation time course following skeletal muscle injury

Abstract Bead-based analysis methods allow for the exploration of a variety of complex biological processes. In particular, these techniques can be applied to better understand how peripheral muscle injury contributes to systemic inflammation. Understanding how these two processes affect one another can give additional insight concerning how changes in inflammation effect readiness to perform in exercise and work environments. The present method sought to combine the strengths of bead-based multiplexing with the precision and low-end detection of single molecule counting (SMC) methods. We used performance of an extreme aerobic exercise session (i.e. half-marathon race) to cause a defined quantity of lower body muscle injury and a systemic inflammatory response lasting up to 24 h. Using a high-sensitivity, multiplex assay (Milliplex; Millipore-Sigma) we were able to identify 9 of 21 cytokines that were significantly elevated at either 4 or 24 h post half-marathon performance. Despite the known role of IL-1β, IL-6, and TNF-α in the pro-inflammatory response, they did not appear to change based on the multiplex analysis. We thus, conducted further analysis using an SMC assay and found increases in IL-1β, IL-6, and TNF-α at 4 h compared to 24 h post exercise. This method approach demonstrates how combining two common, bead-based protein assays can increase the amount of meaningful biological information that can be collected. We anticipate that this approach will be useful in a variety of inflammation-associated disease states.