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Blockade of mTORC1‐NOX signaling pathway inhibits TGF‐β1‐mediated senescence‐like structural alterations of the retinal pigment epithelium
Author(s) -
Lee Seok Jae,
Kim SooJin,
Jo Dong Hyun,
Park KyuSang,
Kim Jeong Hun
Publication year - 2021
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fj.202001939rr
Subject(s) - mtorc1 , retinal pigment epithelium , microbiology and biotechnology , blockade , signal transduction , senescence , retinal , epithelium , transforming growth factor , chemistry , biology , receptor , pi3k/akt/mtor pathway , biochemistry , genetics
The retinal pigment epithelium (RPE) undergoes characteristic structural changes and epithelial‐mesenchymal transition (EMT) during normal aging, which are exacerbated in age‐related macular degeneration (AMD). Although the pathogenic mechanisms of aging and AMD remain unclear, transforming growth factor‐β1 (TGF‐β1) is known to induce oxidative stress, morphometric changes, and EMT as a senescence‐promoting factor. In this study, we examined whether intravitreal injection of TGF‐β1 into the mouse eye elicits senescence‐like morphological alterations in the RPE and if this can be prevented by suppressing mammalian target of rapamycin complex 1 (mTORC1) or NADPH oxidase (NOX) signaling. We verified that intravitreal TGF‐β1‐induced stress fiber formation and EMT in RPE cells, along with age‐associated morphometric changes, including increased variation in cell size and reduced cell density. In RPE cells, exogenous TGF‐β1 increased endogenous expression of TGF‐β1 and upregulated Smad3‐ERK1/2‐mTORC1 signaling, increasing reactive oxygen species (ROS) production and EMT. We demonstrated that inhibition of the mTORC1‐NOX4 pathway by pretreatment with 5‐aminoimidazole‐4‐carboxamide ribonucleotide (AICAR), an activator of AMP‐dependent protein kinase, or GKT137831, a NOX1/4 inhibitor, decreased ROS generation, prevented stress fiber formation, attenuated EMT, and improved the regularity of the RPE structure in vitro and in vivo. These results suggest that intravitreal TGF‐β1 injection could be used as a screening model to investigate the aging‐related structural and functional changes to the RPE. Furthermore, the regulation of TGF‐β‐mTORC1‐NOX signaling could be a potential therapeutic target for reducing pathogenic alterations in aged RPE and AMD.