藍光暴露時間和強度對小鼠視網膜之光毒性效應
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2022
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根據DIGITAL 2022–Global Overview報告顯示，全球每人每日有將近7小時使用智慧型手機、平板以及電腦等電子設備連接網路的時間，此意昧著扣除睡眠，人眼有超過40%的清醒時間暴露於藍光 (blue light, BL)的環境中。BL因波長短能量高能穿透眼球直達視網膜，藉由刺激活性氧物質 (reactive oxygen species, ROS)生成，造成視網膜組織之光化學毒性 (photochemical toxicity)與相關眼病變。本研究之目的在於探討BL之照射強度與暴露時間對生物體之視網膜損傷效應，實驗選用9週齡雄性ICR小鼠，分別探討短期高強度BL (short-term high-intensity BL)與長期低強度BL (long-term low-intensity BL)照射模式對於視網膜之影響。以hematoxylin and eosin (H&E) staining分析視網膜組織型態之病理變化；以免疫組織化學染色 (immunohistochemistry, IHC)分析視紫質 (rhodopsin)、8-羥基去氧鳥苷 (8-OHdG)、介白素1β (interleukin-1β, IL-1β)、cleaved caspase-3及膠質纖維酸性蛋白 (glial fibrillary acidic protein, GFAP)表現；以視網膜電位圖 (electroretinogram, ERG)評估感光細胞功能。結果顯示，實驗小鼠每日經BL LED (465 ± 10 nm, 5000 lux)照射6小時連續5日，其視網膜外核層 (outer nuclear layer, ONL)、感光細胞內外節 (inner segment/ outer segment, IS/OS)及內核層 (inner nuclear layer, INL)之組織型態與未照射BL組比較無顯著差異 (p < 0.05)；眼底鏡 (fundus photography)與眼底螢光血管攝影 (fluorescein angiography)亦無出現血管滲漏、血管增生與黃斑部病變之現象。我們另模擬日常環境BL照度，將實驗小鼠暴露於108 lux (44.8 µW/cm2)之BL LED，進行為期4–28週，每日6小時之長期低強度模式照射。實驗小鼠經低照度BL照射4週可導致ONL細胞核數減少30%；照射至第8週造成ONL平均厚度變薄，且伴隨rhodopsin表現下降30%與8-OHdG表現增加4.7倍，此顯示暴露於低照度BL環境中4–8週，視網膜感光細胞可因BL誘發之氧化壓力開始產生損傷效應。連續照射12週之小鼠其IS/OS層厚度開始減少，同時可見氧化壓力指標8-OHdG相較於之前時間點，其表現大幅提升約2.5倍；同時cleaved caspase-3與GFAP表現上升，顯示感光與神經細胞凋亡以及Müller細胞活化的現象。上述各項分析指標均隨BL暴露時間呈漸進式上升的現象，在藍光連續照射20及28週時達到最顯著之損傷效應。然而促發炎細胞激素IL-1β之表現與未照射BL組比較，於各個時間點並無顯著差異 (p> 0.05)。綜合上述，相較於短期高強度之BL照射，持續性的暴露於低強度BL更可能是導致視網膜損傷的危險因子。本研究模擬生活環境之低照度BL照射條件，嘗試建立更接近生活環境之藍光動物試驗平台，期望能作為日後開發抗藍光護眼保健食品之參考。
According to the DIGITAL 2022: Global Overview Report, people worldwide spend nearly 7 h a day using electronic devices such as smartphones, tablets, and computers to connect to the Internet. The human eye, thus, is exposed to blue light (BL) for more than 40% of the waking time. Because of its short wavelength and high energy, BL can easily reach the retina and induce the generation of reactive oxygen species (ROS), causing photochemical retinal toxicity and related eye diseases. In this study, we investigated the effects of BL irradiation intensity and exposure time on retinal damage in vivo. Nine-week-old male ICR mice were selected for the experiment, and the effects of short-term high-intensity BL and long-term low-intensity BL on the retina were investigated. Hematoxylin and eosin staining was used to analyze the pathological changes in retinal histology; immunohistochemistry was used to analyze the expression of rhodopsin, 8-hydroxydeoxyguanosine (8-OHdG), interleukin-1β (IL-1β), cleaved caspase-3, and glial fibrillary acidic protein (GFAP) in the retina; and an electroretinogram (ERG) was used to evaluate the function of photoreceptor cells. The results showed that the outer nuclear layer (ONL), inner segment/outer segment (IS/OS), and inner nuclear layer of experimental mice irradiated for 6 h/day with BL LED (465 ± 10 nm, 5000 lux) for 5 consecutive days showed no significant difference compared to those of mice in the unirradiated group (p< 0.05). Fundus photography and fluorescein angiography showed no vascular leakage, vascular hyperplasia, or macular degeneration. We further simulated daily environment BL illumination by exposing ICR mice to 6 h/day of 108 lux (44.8 µW/cm2) long-term low-intensity BL LED irradiation for 4–28 weeks. The results showed that ONL nuclei decreased by 30% in wk4 irradiation. The average ONL thickness significantly decreased in wk8 irradiation, accompanied by a decrease in rhodopsin expression and an increase 8-OHdG expression. This indicates that after 4–8-week low-light BL exposure, the photoreceptor cells of the retina begin to show damage effects due to BL-induced oxidative stress. The thickness of the IS/OS layer began to decrease by wk12 irradiation, and the levels of the oxidative stress marker 8-OHdG significantly increased by approximately 2.5 times as compared with the unirradiated group. The above biochemical parameters all showed a gradual increase with BL exposure time, and the most significant damage effect was observed at wk20 and wk28 of continuous BL irradiation. However, the expression of the pro-inflammatory cytokine IL-1β was not significantly different at each time point compared to that in the unirradiated group (p> 0.05). The increased expression of cleaved caspase-3 and GFAP indicated the apoptosis of photoreceptors and Müller cell activation. In summary, compared to short-term high-intensity BL irradiation, continuous exposure to low-intensity BL is more likely to be a risk factor for retinal damage. This study attempts to establish a BL animal experimental platform by simulating the low-illumination BL irradiation conditions of the daily environment, with the aim of serving as a scientific reference for the development of anti-BL eye-protecting health foods in the future.
According to the DIGITAL 2022: Global Overview Report, people worldwide spend nearly 7 h a day using electronic devices such as smartphones, tablets, and computers to connect to the Internet. The human eye, thus, is exposed to blue light (BL) for more than 40% of the waking time. Because of its short wavelength and high energy, BL can easily reach the retina and induce the generation of reactive oxygen species (ROS), causing photochemical retinal toxicity and related eye diseases. In this study, we investigated the effects of BL irradiation intensity and exposure time on retinal damage in vivo. Nine-week-old male ICR mice were selected for the experiment, and the effects of short-term high-intensity BL and long-term low-intensity BL on the retina were investigated. Hematoxylin and eosin staining was used to analyze the pathological changes in retinal histology; immunohistochemistry was used to analyze the expression of rhodopsin, 8-hydroxydeoxyguanosine (8-OHdG), interleukin-1β (IL-1β), cleaved caspase-3, and glial fibrillary acidic protein (GFAP) in the retina; and an electroretinogram (ERG) was used to evaluate the function of photoreceptor cells. The results showed that the outer nuclear layer (ONL), inner segment/outer segment (IS/OS), and inner nuclear layer of experimental mice irradiated for 6 h/day with BL LED (465 ± 10 nm, 5000 lux) for 5 consecutive days showed no significant difference compared to those of mice in the unirradiated group (p< 0.05). Fundus photography and fluorescein angiography showed no vascular leakage, vascular hyperplasia, or macular degeneration. We further simulated daily environment BL illumination by exposing ICR mice to 6 h/day of 108 lux (44.8 µW/cm2) long-term low-intensity BL LED irradiation for 4–28 weeks. The results showed that ONL nuclei decreased by 30% in wk4 irradiation. The average ONL thickness significantly decreased in wk8 irradiation, accompanied by a decrease in rhodopsin expression and an increase 8-OHdG expression. This indicates that after 4–8-week low-light BL exposure, the photoreceptor cells of the retina begin to show damage effects due to BL-induced oxidative stress. The thickness of the IS/OS layer began to decrease by wk12 irradiation, and the levels of the oxidative stress marker 8-OHdG significantly increased by approximately 2.5 times as compared with the unirradiated group. The above biochemical parameters all showed a gradual increase with BL exposure time, and the most significant damage effect was observed at wk20 and wk28 of continuous BL irradiation. However, the expression of the pro-inflammatory cytokine IL-1β was not significantly different at each time point compared to that in the unirradiated group (p> 0.05). The increased expression of cleaved caspase-3 and GFAP indicated the apoptosis of photoreceptors and Müller cell activation. In summary, compared to short-term high-intensity BL irradiation, continuous exposure to low-intensity BL is more likely to be a risk factor for retinal damage. This study attempts to establish a BL animal experimental platform by simulating the low-illumination BL irradiation conditions of the daily environment, with the aim of serving as a scientific reference for the development of anti-BL eye-protecting health foods in the future.
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藍光, 光化學毒性, 氧化壓力, 細胞凋亡, 視網膜損傷, blue light, photochemical toxicity, oxidative stress, apoptosis, retinal damage