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Published on: May 31, 2018
Cardiotrophin-1 induces interleukin-6 synthesis in human monocytes
Michael Fritzenwanger1, Katharina Meusel, Martin Foerster
1Department of Internal Medicine I, Division of Cardiology, Friedrich-Schiller-University Jena, Erlanger Allee 101, 07740 Jena, Germany. Michael.Fritzenwanger@med.uni-jena.de
Insights
Cardiotrophin-1 (CT-1) significantly increases interleukin-6 (IL-6) in human monocytes, mediated by JAK2/STAT3, p38, and NFkappaB pathways. This finding offers potential therapeutic targets for congestive heart failure (CHF).
Area of Science:
- Immunology
- Cardiology
- Molecular Biology
Background:
- Congestive heart failure (CHF) is associated with elevated cytokine levels, including interleukin-6 (IL-6) and cardiotrophin-1 (CT-1).
- Monocyte function is altered in patients with CHF.
Purpose of the Study:
- To investigate whether CT-1 induces IL-6 production in human monocytes.
- To elucidate the signaling pathway involved in CT-1-mediated IL-6 induction.
Main Methods:
- Human peripheral blood monocytes were cultured with varying concentrations and durations of CT-1.
- IL-6 mRNA and protein levels were quantified using RT-PCR and ELISA, respectively.
- Signal transducer and activation of transcription (STAT) 3 phosphorylation was assessed via western blot and FACS analysis, with pathway inhibitors used to identify signaling molecules.
Main Results:
- CT-1 dose- and time-dependently increased IL-6 mRNA and protein expression in monocytes.
- Maximal IL-6 induction occurred at 100 ng/ml CT-1 after 6 hours (mRNA) and 48 hours (protein).
- The JAK2/STAT3, p38, and NFkappaB pathways were identified as crucial for CT-1-induced IL-6 expression, as confirmed by inhibitor studies and STAT3 phosphorylation analysis.
Conclusions:
- CT-1 stimulates IL-6 mRNA and protein expression in human monocytes through a pathway involving JAK2/STAT3, p38, and NFkappaB.
- These findings provide a molecular basis for increased IL-6 in CHF and suggest that targeting the CT-1 pathway could be a therapeutic strategy for CHF.
Background:
Patients with congestive heart failure (CHF) show increased serum concentrations of cytokines like interleukin-6 (IL-6) and cardiotrophin-1 (CT-1). Additionally, monocyte function is modulated in CHF. The aim of this study was to examine if CT-1 is able to induce IL-6 in human monocytes and to investigate the underlying pathway.
Methods:
Separated peripheral blood monocytes of healthy volunteers were cultured with increasing concentrations of CT-1 for different periods. IL-6 mRNA was determined by RT-PCR or real-time PCR and IL-6 protein concentration in the supernatant by ELISA. Phosphorylation of signal transducer and activation of transcription (STAT) 3 was analyzed by western blot or by FACS analysis. To clarify the signalling pathway of CT-1 induced IL-6 expression various inhibitors of possible signal transducing molecules were used.
Results:
CT-1 induced IL-6 mRNA in monocytes in a time- and concentration-dependent manner. Maximal mRNA induction was detectable after 6h with 100 ng/ml CT-1. IL-6 protein also increased in a time- and concentration-dependent manner with a maximum after 48 h with 100 ng/ml CT-1. AG490 as well as SB 203580 and parthenolide blocked CT-1 induced IL-6 expression completely. AG 490 was able to inhibit STAT3 phosphorylation in western blot analysis completely. This indicates that JAK2/STAT3, p38 and nuclear factor kappaB (NFkappaB) are involved in this pathway. To exclude a possible influence of plastic adherence of monocytes on CT-1 induced IL-6 expression, we determined intracellular STAT3 phosphorylation in whole blood samples by FACS analysis and observed independently of culture conditions a CT-1 concentration-dependent STAT3 phosphorylation.
Conclusion:
CT-1 induces IL-6 mRNA and protein expression in a time- and concentration-dependent manner. The underlying pathway is Janus kinase (JAK)2/STAT3, p38 and NFkappaB dependent. These data may explain increased IL-6 serum concentrations and altered monocyte function found in patients with CHF. Modulation of the CT-1 pathway might be a interesting strategy in the treatment of CHF.
