Abstract 563: The Novel Cytokine Interleukin-17A depresses cardiomyocyte contractility via p38 MAPK-NF-κB-iNOS-mediated NO generation
IL-17 and its receptor are members of an emerging family of unique cytokines and receptors that play a role in a variety of inflammatory disorders. Our pilot studies revealed that cardiomyocytes (CM) express IL-17RA. Since IL-17A induces expression of known negative inotropes, IL-1β, TNFα, and iNOS, we hypothesized that IL-17A depresses cardiomyocyte contractility.
Methods: Adult mouse CM (C57BL/6, male) were treated with rmIL-17A (10 ng/ml) for various periods of time. IL-1β and TNFα expression were analyzed by RT-qPCR, Western blotting, and ELISA; iNOS expression by RT-qPCR and Western blotting, and its enzyme activity by the extent of L-[3H] arginine conversion to L-[3H] citrulline in the presence of Ca2+ chelators; NOx levels in culture supernatants by colorimetry; total and phospho-p38 MAPK levels by enzyme immunometric assay; NF-κB levels by ELISA and reporter assays; and CM contractility by fractional shortening of unloaded cells.
Results: IL-17A depressed CM fractional shortening at 4 h (28%, n=8, p<0.01), an effect blunted by anti-IL-17A neutralizing antibodies or IL-17R/Fc chimera. Contractile depression occurred together with induction of iNOS expression (3 h; 2.31-fold, p<0.01) and increased NO generation (5.3-fold, p<0;01). Pre-treatment with the iNOS antagonists L-NIL or 1400W blocked IL-17A-mediated NO generation and contractile depression. IL-17A induced p38 MAPK phosphorylation (an effect blocked by SB203580) and NF-κB activation (p50 and p65), an effect attenuated by PDTC, MG-132, and Ad-dnIκBβ. Inhibition of p38 MAPK blocked IL-17A-mediated NF-κB activation, iNOS expression, and NO generation. More importantly, inhibition of p38 MAPK, NF-κB, and iNOS ameliorated IL-17A-mediated CM contractile depression. In contrast, whereas IL-17A also induced IL-1β and TNFα expression, treatment with respective neutralizing antibodies failed to block IL-17A-mediated iNOS expression and contractile depression.
Conclusions: Our novel results show that IL-17A depresses cardiomyocyte contractility in a p38 MAPK-NF-κB-iNOS-dependent, but IL-1β and TNFα-independent manner, and suggest that IL-17A may play a similar role in contractile depression of cardiac pathologies involving inflammation and injury.