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.
|Publication status||Published - 2021 Mar|
Bibliographical noteFunding Information:
This research was supported by the Creative Materials Discovery Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science and ICT (2018M3D1A1058826 to JHK), the National Research Foundation of Korea (NRF) Grants (2015M3A7B6027946 to JHK), the Development of Platform Technology for Innovative Medical Measurements funded by Korea Research Institute of Standards and Science (KRISS–2020–GP2020‐0004 to JHK), and the Medical Research Center Program funded by the Ministry of Science and ICT (2017R1A5A2015369 to K.‐S.P).
© 2021 Federation of American Societies for Experimental Biology
All Science Journal Classification (ASJC) codes
- Molecular Biology