Human retinal pigment epithelial cells are protected against hypoxia by BNIP3

Jingyang Feng; Wei Tan; Tong Li; Quan Yan; Hong Zhu; Xiaodong Sun

doi:10.21037/atm-20-7145

Human retinal pigment epithelial cells are protected against hypoxia by BNIP3

Ann Transl Med. 2020 Nov;8(22):1502. doi: 10.21037/atm-20-7145.

Authors

Jingyang Feng^{1

2}, Wei Tan³, Tong Li^{1

2}, Quan Yan^{1

2}, Hong Zhu^{1

2

4}, Xiaodong Sun^{1

2

4}

Affiliations

¹ Department of Ophthalmology, Shanghai General Hospital (Shanghai First People's Hospital), Shanghai Jiao Tong University, School of Medicine, Shanghai, China.
² Shanghai Engineering Center for Visual Science and Photomedicine, Shanghai, China.
³ Department of Ophthalmology, Zunyi First People's Hospital, The Third Affiliated Hospital of Zunyi Medical University, Zunyi, China.
⁴ Shanghai Key Laboratory of Fundus Diseases, Shanghai, China.

Abstract

Background: Hypoxia has been implicated in the process of retinal pigment epithelium (RPE) dysfunction. However, recent studies suggest that hypoxia contributes to survival rather than cell death through induction of Bcl-2/adenovirus E1B 19-kDa interacting protein 3 (BNIP3)-dependent autophagy. In contrast, persistent oxidative stress was found to result in autophagy dysregulation in RPE cells. These seemingly contradictory findings led us to investigate the potential role of BNIP3, a crucial mediator of hypoxia-induced autophagy, in the context of hypoxic RPE cells.

Methods: Human RPE D407 cells were treated with low-oxygen conditions, and cell growth, apoptosis, and autophagy was assessed by Cell Counting Kit-8 assay, flow cytometry analysis and immunofluorescence staining, respectively.

Results: Hypoxic conditions simultaneously triggered a large amount of apoptosis and inhibited autophagy. Moreover, hypoxia led to severe impairments, including the stimulation of reactive oxygen species, and reduction of mitochondrial membrane potential, and adenosine triphosphate production. The stimulation of autophagy by rapamycin inhibited hypoxia-induced severe impairments to a great extent. Interestingly, similar results were observed for BNIP3 overexpression, which can be largely blocked by 3-MA, a well-defined inhibitor of autophagy. Moreover, BNIP3 knockdown further aggravated hypoxia-induced impairments in D407 cells, which can be reversed by rapamycin.

Conclusions: Collectively, these results indicated that BNIP3 can protect human retinal pigmented epithelial cells under hypoxic conditions by inducing autophagy.

Keywords: Bcl-2/adenovirus E1B 19-kDa interacting protein 3 (BNIP3); Retinal pigment epithelium (RPE); apoptosis; autophagy; hypoxia.