MiR-21-mediated suppression of Smad7 induces TGFβ1 and can be inhibited by activation of Nrf2 in alcohol-treated lung fibroblasts.

MiR-21-mediated suppression of Smad7 induces TGFβ1 and can be inhibited by activation of Nrf2 in alcohol-treated lung fibroblasts.

Alcohol Clin Exp Res. 2017 Sep 09;:

Authors: Marts LT, Green DE, Mills ST, Murphy T, Sueblinvong V

Abstract
BACKGROUND: We previously demonstrated that chronic alcohol ingestion augments TGFβ1 expression in the lung fibroblast and increases the risk of fibroproliferative disrepair in a mouse model of acute lung injury. The effect of alcohol on TGFβ1 is mitigated by treatment with sulforaphane, which can activate nuclear factor (erythroid-derived 2)-like 2 (Nrf2). However, the mechanisms by which alcohol amplifies, or SFP attenuates, TGFβ1 expression in the fibroblast are not known. MicroRNA (miR)-21 has been shown to inhibit Smad7, a TGFβ1 signaling inhibitor. In the present study, we hypothesized that alcohol augments TGFβ1 expression through up-regulation of miR-21, which subsequently inhibits Smad7.
METHODS: Primary mouse lung fibroblasts were cultured ± alcohol ± SFP and assessed for gene expression of miR-21, and gene and/or protein expression of Nrf2, Nrf2-regulated anti-oxidant enzymes, Smad7, STAT3, and TGFβ1. NIH 3T3 fibroblasts were transfected with a miR-21 inhibitor and cultured ± alcohol. α-SMA, Smad7, and TGFβ1 protein expression were then assessed. In parallel, NIH 3T3 lung fibroblasts were transfected with Nrf2 silencing RNA (siRNA) and cultured ± alcohol ± SFP. Gene expression of miR-21, Nrf2, Smad7, and TGFβ1 were assessed.
RESULTS: MiR-21 gene expression was increased by 12-fold at 48 hours and Smad7 gene and protein expression were reduced by ~30% in alcohol-treated fibroblasts. In parallel, inhibition of miR-21 attenuated alcohol-mediated decrease in Smad7 and increase in TGFβ1 and alpha-smooth muscle actin protein expression. Treatment with SFP mitigated the effect of alcohol on miR-21, Smad7, and total and phosphorylated STAT3, and restored Nrf2-regulated antioxidant gene expression. Silencing of Nrf2 prevented the effect of SFP on miR-21, Smad7, and TGFβ1 gene expression in alcohol-treated NIH 3T3 fibroblasts.
CONCLUSIONS: Alcohol treatment increases TGFβ1 in fibroblasts, at least in part, through augmentation of miR-21, which then inhibits Smad7 expression. These effects can be attenuated by activation of Nrf2 with SFP. This article is protected by copyright. All rights reserved.

PMID: 28888052 [PubMed - as supplied by publisher]

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