Celastrol Activates SIRT1/PGC-1α/Nrf2 Axis to Inhibit Oxidative Damage for Subconjunctival Fibrosis Alleviation

Purpose: Subconjunctival fibrosis can lead to symblepharon and recurrent pterygium, seriously threatening vision. Our previous research found that celastrol could inhibit subconjunctival fibrosis. The purpose of this study was to investigate the underlying mechanisms of celastrol-nanomicelles (Cel) in inhibiting subconjunctival fibrosis. Methods: We established rat subconjunctival injury model in vivo and TGF-β1-activated human pterygium fibroblasts systems in vitro to study fibrotic pathogenesis. RNA-seq analysis was used to identify the targets of Cel. Immunofluorescence and Western blot analyses were performed to determine whether Cel modulates the SIRT1/PGC-1α/Nrf2 axis, thereby alleviating oxidative damage and subconjunctival fibrosis in vitro. The critical involvement of the SIRT1/PGC-1α/Nrf2 axis was definitively established through pharmacological inhibition using EX527, a selective SIRT1 antagonist. Moreover, the effects of Cel on subconjunctival fibrosis in vivo were further explored through histopathological assessments, Masson's trichrome staining, and immunofluorescence. Results: In vivo evaluation with a rat subconjunctival injury model showed that Cel effectively attenuated oxidative damage and subconjunctival fibrosis. The RNA-seq analysis indicated that SIRT1 signal and oxidative stress regulation as candidate targets of Cel for subconjunctival fibrosis. The results of immunofluorescence and Western blot showed that Cel inhibited subconjunctival fibrosis by activating SIRT1/PGC-1α/Nrf2 axis and suppressing TGF-β1/Smad2/3 pathway, while the SIRT1 inhibitor eliminated the effects of Cel. Conclusions: This work demonstrated that Cel effectively alleviated subconjunctival fibrosis by inhibiting oxidative damage via activating SIRT1/PGC-1α/Nrf2 signaling pathway, providing a new potential mechanism to clarify Cel as a potential therapeutic drug to inhibit subconjunctival fibrosis.