α-Aminoadipic acid protects against retinal disruption through attenuating Müller cell gliosis in a rat model of acute ocular hypertension

Xiaolei Wang1 Department of Ophthalmology, Beijing Friendship Hospital;2 Department of Neurobiology, Beijing Institute for Brain Disorders, Capital Medical University, Beijing

Jier Su2 Department of Neurobiology, Beijing Institute for Brain Disorders, Capital Medical University, Beijing;3 Ningbo College of Health Sciences, Ningbo

Jingwen Ding4 Department of Ophthalmology, Beijing Tongren Hospital, Capital Medical University, Beijing

Song Han2 Department of Neurobiology, Beijing Institute for Brain Disorders, Capital Medical University, Beijing

Wei Ma2 Department of Neurobiology, Beijing Institute for Brain Disorders, Capital Medical University, Beijing;5 Beijing Stomatological Hospital, Capital Medical University, Beijing, People’s Republic of China

Hong Luo2 Department of Neurobiology, Beijing Institute for Brain Disorders, Capital Medical University, Beijing

Guy Hughes6 University of California, Irvine School of Medicine, Irvine, CA, USA

Zhaoyang Meng1 Department of Ophthalmology, Beijing Friendship Hospital

Yi Yin1 Department of Ophthalmology, Beijing Friendship Hospital

Yanling Wang1 Department of Ophthalmology, Beijing Friendship HospitalCorrespondence[email protected]

Junfa Li2 Department of Neurobiology, Beijing Institute for Brain Disorders, Capital Medical University, BeijingCorrespondence[email protected]

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Abstract

Objective

Ocular hypertension is an important risk factor for glaucoma. The purpose of this study was to investigate the gliotoxic effects of α-aminoadipic acid (AAA) in a rat model of AOH and its underlying mechanisms.

Materials and methods

In the rat model of acute ocular hypertension (AOH), intraocular pressure was increased to 110 mmHg for 60 minutes. Animals were divided into four groups: sham operation (Ctrl), AOH, AOH + phosphate-buffered saline (PBS), and AOH + AAA. Cell apoptosis in the ganglion cell layer was detected with the terminal deoxynucleotidyl transferase-mediated uridine 5′-triphosphate-biotin nick end labeling (TUNEL) assay, and retinal ganglion cells (RGCs) immunostained with Thy-1 were counted. Müller cell activation was detected using immunostaining with glutamine synthetase and glial fibrillary acidic protein. Tumor necrosis factor-α (TNF-α) was examined using Western blot.

Results

In the rat model of AOH, cell apoptosis was induced in the ganglion cell layer and the number of RGCs was decreased. Müller cell gliosis in the retinas of rats was induced, and retinal protein levels of TNF-α were increased. Intravitreal treatment of AAA versus PBS control attenuated these retinal abnormalities to show protective effects in the rat model of AOH.

Conclusion

In the retinas of the rat model of AOH, AAA treatment attenuated retinal apoptosis in the ganglion cell layer and preserved the number of RGCs, likely through the attenuation of Müller cell gliosis and suppression of TNF-α induction. Our observations suggest that AAA might be a potential therapeutic target in glaucoma.

Keywords:

Supplementary materials

Figure S1 (A) Reprehensive results of Hoechst staining in rat retina after 1 d, 3 d, and 5 d of AOH; (B) Quantitative analysis of the retinal thickness.

Notes: The results showed that the thickness of IPL and INL layers decreased significantly following the reperfusion time after AOH treatment (scale bar =50 μm). *P<0.05 compared with the control group (n=4 per group).
Abbreviations: AOH, acute ocular hypertension; IPL, inner plexiform layer; INL, inner nuclear layer; Ctrl, control; d, day; GCL, ganglion cell layer; ONL, outer nuclear layer.

Figure S2 Immunohistochemistry costained with antibodies against GS (green) and GFAP (red).

Note: Strong expression of GFAP was shown in the GS-positive Müller cell after 5 d of AOH compared with the control group (scale bar =50 μm).
Abbreviations: GS, glutamine synthetase; GFAP, glial fibrillary acidic protein; AOH, acute ocular hypertension; Ctrl, control; GCL, ganglion cell layer; IPL, inner plexiform layer; INL, inner nuclear layer; ONL, outer nuclear layer; d, days.

Figure S3 Increased GFAP immunoreactivity after AOH induction in rat retinas.

Notes: (A) Immunofluorescent staining showed that AOH increased GFAP immunoreactivity in the Müller cell processes across IPL. Scale bar =50 μm. (B). Quantitative analysis of fluorescence intensity of GFAP (n=4 per group). *P<0.05 compared with the control group.
Abbreviations: GFAP, glial fibrillary acidic protein; AOH, acute ocular hypertension; IPL, inner plexiform layer; d, day; PBS, phosphate-buffered saline; AAA, α-aminoadipic acid.

Acknowledgments

This study was funded by Beijing Municipal Administration of Hospitals Clinical Medicine Development of Special Funding Support (No XM201305) and Clinical-Basic Cooperation Program from Capital Medical University (Nos 14JL32 and 2015YKSJ02).

Disclosure

The authors report no conflicts of interest in this work.