Ouabain Suppresses IL-6/STAT3 Signaling and Promotes Cytokine Secretion in Cultured Skeletal Muscle Cells
Open Access
- 25 September 2020
- journal article
- research article
- Published by Frontiers Media SA in Frontiers in Physiology
Abstract
The cardiotonic steroids (CTS), such as ouabain and marinobufagenin, are thought to be adrenocortical hormones secreted during exercise and the stress response. The catalytic α-subunit of Na,K-ATPase (NKA) is a CTS receptor, whose largest pool is located in skeletal muscles, indicating that muscles are a major target for CTS. Skeletal muscles contribute to adaptations to exercise by secreting interleukin-6 (IL-6) and plethora of other cytokines, which exert paracrine and endocrine effects in muscles and non-muscle tissues. Here, we determined whether ouabain, a prototypical CTS, modulates IL-6 signaling and secretion in the cultured human skeletal muscle cells. Ouabain (2.5–50 nM) suppressed the abundance of STAT3, a key transcription factor downstream of the IL-6 receptor, as well as its basal and IL-6-stimulated phosphorylation. Conversely, ouabain (50 nM) increased the phosphorylation of ERK1/2, Akt, p70S6K, and S6 ribosomal protein, indicating activation of the ERK1/2 and the Akt-mTOR pathways. Proteasome inhibitor MG-132 blocked the ouabain-induced suppression of the total STAT3, but did not prevent the dephosphorylation of STAT3. Ouabain (50 nM) suppressed hypoxia-inducible factor-1α (HIF-1α), a modulator of STAT3 signaling, but gene silencing of HIF-1α and/or its partner protein HIF-1β did not mimic effects of ouabain on the phosphorylation of STAT3. Ouabain (50 nM) failed to suppress the phosphorylation of STAT3 and HIF-1α in rat L6 skeletal muscle cells, which express the ouabain-resistant α1-subunit of NKA. We also found that ouabain (100 nM) promoted the secretion of IL-6, IL-8, GM-CSF, and TNF-α from the skeletal muscle cells of healthy subjects, and the secretion of GM-CSF from cells of subjects with the type 2 diabetes. Marinobufagenin (10 nM), another important CTS, did not alter the secretion of these cytokines. In conclusion, our study shows that ouabain suppresses the IL-6 signaling via STAT3, but promotes the secretion of IL-6 and other cytokines, which might represent a negative feedback in the IL-6/STAT3 pathway. Collectively, our results implicate a role for CTS and NKA in regulation of the IL-6 signaling and secretion in skeletal muscle.Keywords
This publication has 150 references indexed in Scilit:
- Control of mTORC1 signaling by the Opitz syndrome protein MID1Proceedings of the National Academy of Sciences of the United States of America, 2011
- Crystal structure of the sodium-potassium pump (Na + ,K + -ATPase) with bound potassium and ouabainProceedings of the National Academy of Sciences of the United States of America, 2009
- Amplification efficiency: linking baseline and bias in the analysis of quantitative PCR dataNucleic Acids Research, 2009
- Endogenous Cardiotonic Steroids: Physiology, Pharmacology, and Novel Therapeutic TargetsPharmacological Reviews, 2009
- The cardiac glycoside binding site on the Na,K-ATPase α2 isoform plays a role in the dynamic regulation of active transport in skeletal muscleProceedings of the National Academy of Sciences of the United States of America, 2009
- Digoxin and other cardiac glycosides inhibit HIF-1α synthesis and block tumor growthProceedings of the National Academy of Sciences of the United States of America, 2008
- Functional roles of Na,K-ATPase subunitsCurrent Opinion in Nephrology and Hypertension, 2008
- Effect of interleukin-6 receptor inhibition with tocilizumab in patients with rheumatoid arthritis (OPTION study): a double-blind, placebo-controlled, randomised trialThe Lancet, 2008
- The wolf in sheep's clothing: the role of interleukin-6 in immunity, inflammation and cancerTrends in Molecular Medicine, 2008
- Evolution of Na,K-ATPase βm-subunit into a coregulator of transcription in placental mammalsProceedings of the National Academy of Sciences of the United States of America, 2007