The role of circulatory chemokines in sepsis-induced myopathy in mice

Abstract

BACKGROUND: Sepsis is a condition of life-threatening organ dysfunction caused by a dysregulated host response to infection and carries a high risk of mortality. A rapidly growing number of “sepsis survivors” experience persistent and severe skeletal muscle weakness and atrophy (i.e., sepsis-induced myopathy). The myopathy is triggered by the interaction of circulating pathogens, inflammatory factors (e.g., cytokines and chemokines), and myofibers. Currently, there are no treatments for sepsis-induced myopathy partially due to a lack of therapeutic targets. Chemokines are peptides that possess chemo attractant properties and are released by immune cells during infection insult. Circulating levels of chemokines in septic patients are known to be high. However, the role these chemokines play in context of sepsis-induced myopathy is currently unknown. Our goal in this study was to identify the role of circulating chemokines on sepsis-induced myopathy. METHODS: We induced sepsis via cecal ligation and puncture (CLP) or sham control surgeries in a group of young adults (5 mo) male C57BL6 mice. Seven days after surgery, serum was collected from sham and CLP mice. The serum samples were pooled for cell culture experiments. In a subset of healthy mice, we isolated primary myoblasts. The myoblasts were co-cultured in conditioned media containing pooled serum samples collected from sham and CLP mice. We performed a multiplex assay to identify the levels of chemokines on the pooled serum samples. We measured myoblast proliferation, myotube area, and fusion index. In follow-up experiments, we exposed C2C12 myotubes to a selected group of chemokine peptides previously identified in serum samples. RESULTS: Exposure to septic serum attenuated the proliferative capacity of healthy myoblasts by 46% (p < 0.05). In addition, myoblasts exposed to septic serum did not differentiate into healthy myotubes. Multiplex analyses of pooled sham and septic serum revealed a marked elevation of the following chemokines: CXCL-1 (healthy = 173.4 ± 0.1, septic = 69,630 ± 13,732 pg/ml), CXCL-2 (healthy = 1,078 ± 0.1, septic = 3,907 ± 259 pg/ml), CXCL-10 (healthy = 366 ± 0.1, septic = 3,961 ± 293 pg/ml), CCL-2 (healthy = 276 ± 0.1, septic = 1672 ± 362 pg/ml). Exposure of mature C2C12 myotubes to the chemokine peptides for 24 h increased the mRNA expression of atrophy-related genes ( FOXO1, GABARAP, BNIP3, TRIM63, MAP11A3B, FOXO32, FOXO30). CONCLUSION: Circulating chemokines play a regulatory role in sepsis-induced myopathy via attenuation of the proliferative capacity of myoblasts and by altering myotube morphology and the expression of atrophy related genes. Chemokines are potential therapeutic targets to treat sepsis-induced myopathy. Funded by NIH R21AG072011-03 to OL 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.