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  • Title: Pro-inflammatory role of microrna-200 in vascular smooth muscle cells from diabetic mice.
    Author: Reddy MA, Jin W, Villeneuve L, Wang M, Lanting L, Todorov I, Kato M, Natarajan R.
    Journal: Arterioscler Thromb Vasc Biol; 2012 Mar; 32(3):721-9. PubMed ID: 22247255.
    Abstract:
    OBJECTIVE: Vascular smooth muscle cells (VSMC) from type 2 diabetic db/db mice exhibit enhanced proinflammatory responses implicated in accelerated vascular complications. We examined the role of microRNA(miR)-200 family members and their target Zeb1, an E-box binding transcriptional repressor, in these events. METHODS AND RESULTS: The expression levels of miR-200b, miR-200c, and miR-429 were increased, although protein levels of Zeb1 were decreased in VSMC and aortas from db/db mice relative to control db/+ mice. Transfection of miR-200 mimics into VSMC downregulated Zeb1 by targeting its 3'-UTR, upregulated the inflammatory genes cyclooxygenase-2 and monocyte chemoattractant protein-1, and promoted monocyte binding in db/+VSMC. In contrast, miR-200 inhibitors reversed the enhanced monocyte binding of db/dbVSMC. Zeb1 gene silencing with siRNAs also increased these proinflammatory responses in db/+VSMC confirming negative regulatory role of Zeb1. Both miR-200 mimics and Zeb1 siRNAs increased cyclooxygenase-2 promoter transcriptional activity. Chromatin immunoprecipitation showed that Zeb1 occupancy at inflammatory gene promoters was reduced in VSMC from type 2 diabetic db/db mice. Furthermore, Zeb1 knockdown increased miR-200 levels demonstrating a feedback regulatory loop. CONCLUSION: Disruption of the reciprocal negative regulatory loop between miR-200 and Zeb1 under diabetic conditions enhances proinflammatory responses of VSMC implicated in vascular complications.
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