Abstract
Purpose Oxidative stress is a common pathological condition for multiple retinal diseases. Hydrogen peroxide (H2O2) has been applied as an oxidative stress inducer for the in vitro studies. Here, we report the in vivo effect of H2O2 exposure to the mouse retina and its underlying mechanism. Methods The H2O2 or saline solution was intravitreally injected into the eyes of female C57BL/6J mice for two consecutive days. The retinal structure was evaluated by in vivo imaging using spectral domain optical coherence tomography (OCT) and validated by histological assessment as well as retinal marker expression. In addition, retinal stress, cell apoptosis, and antioxidant enzyme expression were also determined. Results Retinal and outer nuclear layer thickness thinning was observed at days 7 and 14 by OCT imaging with the treatment of 10 μg H2O2, which was confirmed by the histopathological analysis. The expressions of photoreceptor (Rho, Rora, Rorb, and Rcvrn), bipolar cell (Chat and Calb2), and retinal pigment epithelial (Rpe65) markers were reduced in the H2O2-treated group, whereas the expression of retinal ganglion cell marker (Tubb3) was increased. TUNEL-positive cells were obviously found in the outer nuclear layer and inner nuclear layer of H2O2-treated mice but sparely found in the ganglion cell layer. Coherently, apoptotic gene expressions (Casp3, Casp9, Bax, and Parp8) were significantly increased in the retina with increasing dosages of H2O2, while Bcl2 expression was mildly decreased. In addition, the expressions of Gfap and antioxidant enzyme genes (Txn2, Sod2, and Gpx4) were significantly upregulated in the retina after the H2O2 treatment, compared to the vehicle control group. Conclusions This study revealed that intravitreal injection of H2O2 induces acute retinal damage by increasing oxidative stress and cell apoptosis in the retina. This acute retinal degeneration mouse model could provide a platform for drug screening against oxidative stress and retinal diseases.
Highlights
Retinal diseases, including age-related macular degeneration (AMD), glaucoma, diabetic retinopathy (DR), and retinitis pigmentosa (RP), are the leading cause of irreversible blindness and visual impairment in most developed countries [1, 2], affecting more than 300 million people worldwide
The optical coherence tomography (OCT) images at baseline and day 2 of the H2O2-treated mice showed the typical laminar structure of the retina (Figures 1(b) and 1(c)) without obvious changes in the retina (day 0: 267.99 ± 7.88 μm and day 2: 269.32 ± 3.19 μm; Figure 1(j)) and outer nuclear layer (ONL) thicknesses (day 0: 84.24 ± 1.71 μm and day 2: 96.29 ± 0.76 μm; Figure 1(k)), which were similar to the morphologies (Figures 1(f) and 1(g)) and thicknesses in the saline-treated group (retina: 275.998 ± 7.85 μm at day 0 and 266.66 ± 0.83 μm at day 2, Figure 1(j); ONL: 88.45 ± 3.29 μm at day 0 and 96.30 ± 2.80 μm at day 2, Figure 1(k))
Our results showed that (1) H2O2 exposure induces the thinning of the whole retina, ONL, and photoreceptor inner segment ellipsoid zone; (2) H2O2 exposure induces retinal cell apoptosis and reduces retinal cell density; and (3) H2O2 increases the oxidative stress in the retina
Summary
Retinal diseases, including age-related macular degeneration (AMD), glaucoma, diabetic retinopathy (DR), and retinitis pigmentosa (RP), are the leading cause of irreversible blindness and visual impairment in most developed countries [1, 2], affecting more than 300 million people worldwide. The common pathology in the retinal diseases is the retinal degeneration mediated by cell apoptosis [4, 5]. Reactive oxygen species (ROS) induces oxidative stress through lipid peroxidation, disruption of normal mitochondrial function, and DNA damage, all of which can initiate the caspase-mediated apoptosis pathway [8]. The in vitro cell culture can mimic the oxidative disease mechanisms for initial high-throughput drug screening; yet, the in vivo model would be more suitable for the development of antioxidative treatments before clinical trials [11, 12]. The in vivo effect and mechanism of H2O2 on mammalian retina in experimental models have yet to be determined
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