Insufficient SIRT1 in macrophages promotes oxidative stress and inflammation during scarring.

Macrophage is a critical regulator in wound healing and scar formation, and SIRT1 is related to macrophage activation and polarization, while the specific mechanism is still unclear. To explore the specific effects of SIRT1 in scarring, we established a skin incision mouse model and LPS-induced inflammation cell model. The expression of SIRT1 in tissue and macrophage was detected, and the level of SIRT1 was changed to observe the downstream effects. LPS-induced macrophages with or without SIRT1 deficiency were used for TMT-based quantitative proteomic analysis. SIRT1 was suppressed in scar while increased in macrophages of scar tissue. And macrophages were proven to be necessary for wound healing. In the early stage of wound healing, knockout of SIRT1 in macrophage could greatly strengthen inflammation and finally promote scarring. NADH-related activities and oxidoreductase activities were differentially expressed in TMT-based quantitative proteomic analysis. We confirmed that ROS production and NOX2 level were elevated after LPS stimulation while the Nrf2 pathway and the downstream proteins, such as Nqo-1 and HO-1, were suppressed. In contrast, the suppression of SIRT1 strengthened this trend. The NF-κB pathway was remarkably activated compared with the control group. Insufficient increase of SIRT1 in macrophage leads to over activated oxidative stress and activates NF-κB pathways, which then promotes inflammation in wound healing and scarring. Further increasing SIRT1 in macrophages could be a promising method to alleviate scarring. KEY MESSAGES: SIRT1 was suppressed in scar while increased in macrophages of scar tissue. Inhibition of SIRT1 in macrophage leads to further activated oxidative stress. SIRT1 is negatively related to oxidative stress in macrophage. The elevation of SIRT1 in macrophage is insufficient during scarring.