Presenting Author University of Vermont Larner College of Medicine
Exercise has been previously proposed as an adjuvant for traditional vaccines through mechanisms of lymph movement and skeletal muscle damage. However, the novel mRNA technology being used in COVID-19 and other novel vaccines fundamentally changes how we should consider muscle’s active role in protein production and subsequent protective immunity. Following exercise, mammalian target of rapamycin (mTOR) activation drives total protein translation increases in skeletal muscle. We hypothesize that this 4-24 hour window of opportunity can be exploited to augment exogenous mRNA translation. To evaluate the feasibility of this approach, we first interrogated mTOR using fully differentiated C2C12 mouse skeletal muscle myotubes that were transfected with mRNA encoding for enhanced green fluorescent protein (eGFP) or FLAG-tagged Comirnaty SARS-CoV-2 Spike sequence in mTOR modulating conditions. Myotube transfection in the presence of rapamycin (Figure 1A) and resveratrol (Figure 1B) showed significant decreases in protein translation as measured by eGFP fluorescence, indicating that exogenous mRNA translation can be decreased pharmacologically by inhibiting the mTOR pathway. To simulate exercise enhanced protein synthesis, we treated myotubes with insulin-like growth-factor 1 (IGF-1), as this protein is not only upregulated following exercise but also signals through an overlapping pathway with mechanoreceptors. Transfections with mRNA encoding for either eGFP or Comirnaty-FLAG during IGF-1 treatment showed a dose dependent increase in eGFP fluorescence (Figure 1C) and a significant increase in Comirnaty-FLAG translation as measured by ELISA (Figure 1D). Current studies are investigating the use of electrical stimulation induced contraction on C2C12 myotubes prior to transfection as well as in vivo models of exercise and intramuscular mRNA injections. The implications of these results may impact future mRNA therapies to utilize exercise, or modulation of intracellular signaling pathways affected by exercise, as a method to improve vaccine-induced exogenous protein production.
Funding: Larner College of Medicine and the Vermont Lung Center T32HL076122
Figure 1: mTOR modulation affects exogenous mRNA translation in C2C12 myotubes. A-B) Treatment of myotubes with rapamycin and resveratrol decreases eGFP translation. Two Way ANOVA, n=4-8/group, unpaired t test, n=4/group. C-D) Treatment with IGF-1 increases both eGFP fluorescence and Comirnaty-FLAG translation. One way ANOVA, n=4-8/group, unpaired t test n=4/group. *p < 0.05, ** p<0.01, ***p < 0.001, ****p < 0.0001.
