Effects of nutraceuticals on inflammation and muscle recovery in a co-culture model of laceration and exercise-induced muscle damage
Authors: Sargent Ava , Leedberg Jordan , Straight Chad , Gaines Peter 
Published: May 2023

Intensive and eccentric exercise causes subclinical muscle damage and the recruitment of innate immune cells, which can stimulate muscle repair processes while also exasperating exercise-induced muscle damage (EIMD) by causing oxidative stress. This leads to further tissue damage in a feedback loop that can lead to clinical damage unless sufficient healing is provided. We developed a murine in vitro co-culture model that recapitulates the in vivo interactions between damaged C2C12 muscle and bone marrow derived neutrophils or macrophages to better understand the mechanisms of EIMD or muscle laceration with these immune cells. The model utilizes either the FlexCell system that mimics EIMD using mature myofibers grown on flexible rubber membranes that are repeatedly stretched at regular time intervals for 18 hours, or the scratch assay that mimics skeletal muscle laceration (muscle scratched with a pipet tip in 3 parallel lines). The goal of this study was to determine if supplementation with nutraceuticals such as tart cherry extract (TCE) or Perceptiv® (a nutraceutical used to treat inflammation associated with Alzheimer’s disease) to attenuate the oxidative damage caused by these immune cells. Neutrophils and macrophages release reactive oxygen species (ROS) when stimulated, a measure of oxidative stress, which is expected to be suppressed by treatment with either TCE or Perceptiv®. Extracellular lactate dehydrogenase (LDH), a marker of skeletal muscle damage, is expected to increase post-damage, and ameliorated by the addition of TCE (8 μg/mL) and increasing Perceptiv® concentrations (0.1X- 1X). The rate and extent of wound closure in the scratch assay is also expected to be improved with nutraceutical intervention. TCE and Perceptiv® sequestered ROS from innate immune cells in a dose dependent manner, for which the IC50 concentrations were calculated to be 3.695 μg/mL TCE on neutrophils, 1.531 μg/mL TCE on macrophages, 0.344X Perceptiv® on neutrophils, and 0.729X Perceptiv® on macrophages. Significant reductions in ROS production were seen at 4 μg/mL TCE on both cell types, 0.5X Perceptiv® on neutrophils, and 1X Perceptiv® on macrophages ( P < 0.05). LDH levels were significantly elevated in the damaged muscle at 24 hours post-damage ( P < 0.05) as compared to non-damaged muscle (two-fold increase in flexed muscle, four-fold increase in scratched muscle), suggesting the magnitude of LDH release is dependent on the type of muscle damage. TCE decreased LDH levels across all conditions as compared to the control, indicating that TCE may aid in preventing further damage from occurring by reducing oxidative stress in both damaged and non-damaged muscle. Perceptiv® caused further damage to the cells, increasing LDH levels across all conditions at concentrations as low as 0.1X Perceptiv®. Neither nutraceutical increased the rate or extent of wound closure in the scratch assay, suggesting that their effects occur over a longer period of supplementation. Funding was provided by a research collaborative agreement between the University of Massachusetts Lowell and the US Army Combat Capabilities Development Command Soldier Center This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.