Macrophage migration inhibitory factor triggers vascular smooth muscle cell dedifferentiation by a p68-serum response factor axis

AIMS: Macrophage migration inhibitory factor (MIF) is an important proinflammatory mediator linked to arterial diseases. Although its inflammatory property such as macrophage recruitment is known for contributing to vascular pathogenesis, the direct effects of MIF on homeostasis and biological function of vascular smooth muscle cell (VSMC) that are crucial for development of arterial abnormalities, are poorly understood. METHODS AND RESULTS: We show that MIF is able to directly induce VSMC dedifferentiation, a pathophysiological process fundamental for progression of various arterial diseases. Mechanistically, MIF suppresses p68 protein, a crucial regulator of cell growth and organ differentiation, via activation of JNK and p38 MAPKs. siRNA targeting of p68 facilitated dedifferentiation state in VSMCs, whereas p68 overexpression blocked MIF-elicited transition. In addition, MIF decreased the expression of serum response factor (SRF) that governs VSMC differentiation marker genes transcription, through repression of p68 protein. Furthermore, we showed a previously uncharacterized molecular interaction between p68 and SRF by co-immunoprecipitation assay. p68 attenuated MIF-elicited suppression of SRF recruitment to VSMC-specific promoter. Finally, anti-MIF treatment could reverse VSMC dedifferentiation, preserve vascular function, and inhibit remodelling due to vascular injury. CONCLUSIONS: Our results demonstrate a novel mechanism for the regulation of VSMC differentiation by MIF involving p68 and SRF. Strategy for targeting of MIF could inhibit aberrant transition of VSMC in cardiovascular pathogenesis, and may be of therapeutic benefit in phenotype-related arterial remodelling.