Abstract 1537: IL-18BP-Fc Chimera Blocks IL-18-Mediated AP-1 and NF-KappaB-Dependent Migration Inhibitory Factor Expression and Human Coronary Artery Smooth Muscle Cell Migration
Introduction: The expression of proinflammatory cytokines interleukin (IL)-18 and migration inhibitory factor (MIF) in atherosclerotic lesions correlate positively with increased intimal-medial thickness, suggesting a role for these cytokines in atherogenesis. We have previously shown that IL-18 induces smooth muscle cell migration. However, the molecular mechanisms underlying this phenomenon are incompletely understood. As MIF is an important factor in SMC migration, we tested the hypothesis that IL-18-mediated human coronary artery SMC (HCASMC) migration is MIF dependent.
Methods and Results:
Our results show that IL-18 induces MIF mRNA and protein expression, and stimulated MIF secretion in a time- and dose-dependent manner.
Using gel shift, supershift, and chromatin immunoprecipitation assays, we determined IL-18-dependent AP-1 and NF-κB activation both in vitro and in vivo.
IL-18-stimulated MIF promoter-reporter activity, and deletion or mutation in AP-1 and NF-κB sites attenuated IL-18-mediated MIF transcription.
While ectopic expression of c-Fos and c-Jun stimulated, forced expression of dominant negative (dn) c-Fos and dnc-jun attenuated MIF transcription.
TLC and immunecomplex kinase assays revealed activation of PI3K, Akt and ERK, and inhibition of PI3K, Akt, and ERK attenuated IL-18-mediated MIF transcription. In converse,
MIF stimulated p38MAPK and NF-κB activation, IL-18 promoter-reporter activity, mRNA and protein expression, and secretion.
Most importantly, treatment with IL-18BP-Fc chimera or knockdown of MIF or its receptor CD74 by RNA interference attenuated IL-18-mediated MIF-dependent SMC migration.
Conclusions: Together, these results demonstrate that
IL-18 and MIF regulate each other’s expression,
IL-18-MIF crosstalk involves NF-κB,
IL-18-induced HCASMC migration is partially dependent on MIF, and
the IL-18BP-Fc chimera blocks IL-18-mediated MIF-dependent HCASMC migration. Thus the coexpression and regulation of IL-18 and MIF may amplify the inflammatory cascade in the vessel wall and promote atherosclerosis. The IL-18BP-Fc chimera may have therapeutic potential by blocking IL-18-dependent signaling, including IL-18-MIF crosstalk.