Essential role of Smad3 in the inhibition of inflammation‐induced PPARβ/δ expression

NS Tan, L Michalik, N Di‐Poï, CY Ng, N Mermod… - The EMBO …, 2004 - embopress.org
NS Tan, L Michalik, N Di‐Poï, CY Ng, N Mermod, AB Roberts, B Desvergne, W Wahli
The EMBO journal, 2004embopress.org
Wound healing proceeds by the concerted action of a variety of signals that have been well
identified. However, the mechanisms integrating them and coordinating their effects are
poorly known. Herein, we reveal how PPARβ/δ (PPAR: peroxisome proliferator‐activated
receptor) follows a balanced pattern of expression controlled by a crosstalk between
inflammatory cytokines and TGF‐β1. Whereas conditions that mimic the initial inflammatory
events stimulate PPARβ/δ expression, TGF‐β1/Smad3 suppresses this inflammation …
Wound healing proceeds by the concerted action of a variety of signals that have been well identified. However, the mechanisms integrating them and coordinating their effects are poorly known. Herein, we reveal how PPARβ/δ (PPAR: peroxisome proliferator‐activated receptor) follows a balanced pattern of expression controlled by a crosstalk between inflammatory cytokines and TGF‐β1. Whereas conditions that mimic the initial inflammatory events stimulate PPARβ/δ expression, TGF‐β1/Smad3 suppresses this inflammation‐induced PPARβ/δ transcription, as seen in the late re‐epithelialization/remodeling events. This TGF‐β1/Smad3 action involves an inhibitory effect on AP‐1 activity and DNA binding that results in an inhibition of the AP‐1‐driven induction of the PPARβ/δ promoter. As expected from these observations, wound biopsies from Smad3‐null mice showed sustained PPARβ expression as compared to those of their wild‐type littermates. Together, these findings suggest a mechanism for setting the necessary balance between inflammatory signals, which trigger PPARβ/δ expression, and TGF‐β1/Smad3 that governs the timely decrease of this expression as wound healing proceeds to completion.
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