Since miR-214 has potential utility as a CTGF inhibitor and may be of therapeutic value, we investigated the molecular mechanisms that account for high miR-214 levels in quiescent HSC. Methods: Immunohistochemistry for Twist-1 or desmin was performed on livers of normal mice. Primary cultured HSC from normal mice were analyzed for expression
of CTGF, miR-214, or Twist-1 either after exposure to 0-25mM ethanol or after transfection with Twist-1 siRNA or Twist-1 overexpressing plasmids. Functional targeting of the miR-214 promoter by Twist-1 was assessed by HSC luciferase production after transfection of the cells with a pGL4.11 luciferase reporter containing either wild type miR-214 promoter or a mutant miR214 promoter lacking the E-box site. Nano-size exosomes were isolated from HSC conditioned Selleckchem JQ1 medium and analyzed by RTPCR for Twist-1 mRNA. Co-culture experiments were used to establish intercellular transfer of Twist-1 mRNA. Results: Twist-1 was localized by IHC to presumptive quiescent (desmin-positive) HSC in normal mouse liver. In primary mouse HSC, miR214 and Twist-1 were co-expressed and dose-dependently inhibited by ethanol in a manner reciprocal to that of CTGF.
Transfection of freshly isolated D10 HSC (high endogenous Twist-1 levels) with Twist-1 siRNA reduced expression of miR214, but increased CTGF production. An opposite effect was shown by transfecting P6 HSC (low endogenous Twist-1 levels) with Twist-1 plasmids. Twist-1 www.selleckchem.com/products/dabrafenib-gsk2118436.html stimulated luciferase activity in HSC transfected with a wild-type miR-214 promoter but not with a mutant miR-214 promoter lacking the E-box site. Twist-1 mRNA was present in exosomes released
by HSC, an effect that was inhibited by the exosomal inhibitor GW4869.Exosomal Twist-1 released from D10 donor HSC regulated activity of wild-type, but not mutant, miR-214 promoter in recipient HSC. Conclusions: MiR-214 production in HSC is dependent on Twist-1, which drives miR-214 promoter activity via Rutecarpine an E-box element. Nano-sized exosomes produced by HSC serve as a conduit for export and delivery of Twist-1 to neighboring cells to modulate miR-214 expression. These data support a role for cellular or exosomal Twist-1 in regulating miR-214 expression in CTGF-dependent fiborgenic pathways. Disclosures: The following people have nothing to disclose: Li Chen, Alyssa Charrier, David Brigstock NADPH oxidase 4 (NO X4) is a relevant source of hydrogen peroxide in activated HSC and hepatocytes. In HSC we have shown that NOX4 activation is directly linked to their transdifferentiation however; its role in hepatocyte injury has not been defined. We hypothesize that during NASH progression hepatocyte NOX4 plays a role in the induction of the doublestranded RNA-activated protein kinase (PKR)-mediated stress pathways; culminating in the activation of eir2α and JNK1 leading to cell death and increased fibrogenesis.
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