Abstract
Catecholamines stimulate interleukin-6 (IL-6) secretion in skeletal muscles. However, whether other cytokines are secreted is currently unknown. Skeletal muscle ex vivo preparations commonly used to study cytokine secretion have dealt with limitations including auto-oxidation of catecholamines. The use of metal chelators could be an alternative to avoid auto-oxidation and allow catecholamines to be used at physiological doses. We exposed isolated soleus muscles to 1 or 100 ng/mL epinephrine (EPI) and collected bath samples at 1 and 2 h for multiplex cytokine analysis. Keratinocyte chemoattractant (CXCL1), IL-6, and IL-1α were significantly elevated by 100 ng/mL exposure, but not by 1 ng/mL (median [CXCL1] (2 h) = 83 pg/mL; [IL-6] = 19 pg/mL; IL-1α = 7.5 pg/mL). CXCL1 and IL-6 were highly correlated in each sample (P = 0.0001). A second experiment combined the metal chelator, deferoxamine mesylate (DFO), to prevent EPI autoxidation, with 2 ng/mL EPI and 10.5 ng/mL norepinephrine (NOREPI) to mimic peak exercise. Unexpectedly, DFO alone stimulated both IL-6 and CXCL1 secretion, but together with EPI and NOREPI had no additional effects. Stimulation of cytokine secretory responses from skeletal muscle cells in response to DFO thus precludes its use as a chelating agent in ex vivo models. In conclusion, 100 ng/mL EPI stimulates a robust secretory CXCL1 response, which together with IL-6 and IL-1α, may constitute an adrenal-muscle endocrine response system.