- 學位論文
以綠茶多酚活化雌激素受體路徑探討紫外光與自由基引起角膜及視網膜色素上皮損傷之保護作用
Protective effects of (-)-epigallocatechin gallate on UVB and free radical-induced cornea and retinal pigment epithelium disorders by activating estrogen receptor pathway
摘要
氧化壓力會引起眼部組織的損傷，而眼球組織中雌激素受體的存在以及雌激素受體會影響抗氧化以及抗發炎反應，但是眼球組織中綠茶多酚藉由雌激素受體引起的保護作用還未被廣泛的研究。為了瞭解在眼球組織中綠茶多酚是否藉由雌激素受體引起保護作用，實驗分別利用視網膜色素上皮以及角膜做為一個探討。於視網膜色素上皮，為了瞭解綠茶多酚與雌激素受體之間的關係，人類視網膜色素上皮細胞株(ARPE-19) 給予綠茶多酚處理，利用西方墨點法及免疫細胞化學染色檢測雌激素受體的表現，探討綠茶多酚處理後雌激素受體表現並利用過氧化氫氧化傷害模式產生視網膜色素上皮細胞傷害程度相關性。角膜組織方面，實驗小鼠於腹腔注射綠茶多酚並利用免疫組織化學染色檢測雌激素受體於角膜上皮組織表現，利用紫外線引起角膜傷害模式，探討實驗加藥處理雌激素受體表現改變後與傷害情形的可能關連。角膜表面傷害根據膜表面傷害根據角膜平整度與lissamine green染色程度以及偵測角膜中變形生長因子(transforming growth factor-β, TGF-β)與變形生長因子受體(transforming growth factor-β receptor II, TGFβ-RII)的表現情形做為角膜發炎依據。結果顯示，在視網膜色素上皮，綠茶多酚會誘導雌激素受體α蛋白表現上升，並且會減少由過氧化氫的氧化傷害引起的細胞死亡；在角膜組織，綠茶多酚同樣會誘導角膜上皮細胞雌激素受體α蛋白表現上升，且會減少由紫外線引起的角膜上皮不平整、厚度變薄以及降低TGF-β與TGFβ-RII於角膜組織中的程度。整體來說，綠茶多酚會誘導視網膜色素上皮以及組織雌激素受體α蛋白表現上升，且會經由雌激素受體進行保護作用。
並列摘要
Light-induced cell damage can be caused by a variety of cellular mechanisms that involve oxidative stress. Several epidemiologic observations suggest a potential participation of estrogen receptors in the homeostasis of the eye. Both in vitro and in vivo studies demonstrated that estrogen receptors enhance the viability of ocular cells exposed to a variety of oxidative stress and inflammatory responses. However, the estrogen receptor-mediated effects of EGCG, which is extracted from green tea, have not been extensively examined in the ocular tissues of the eyeball. In order to understand the effects of EGCG regulates the expression of cellular protective proteins, such as estrogen receptors; hence, estrogen receptors modulate the degenerative responses in ocular tissues, we performed oxidative stress-induced and UVB-induced injury in vitro and in vivo models to investigate the beneficial effect and mechanisms of EGCG. Expression of estrogen receptors in cultured human retinal pigment epithelium cells were examined via immunohistochemistry and western blot after EGCG treatment. The cell death of EGCG-treated retinal pigment epithelium cells after oxidative stress-induced damage was also investigated. In addition, mice were pretreated with EGCG and corneal oxidative damage was induced by exposure to UVB radiation. Corneal surface damages were graded according to smoothness and the extent of lissamine green staining. TGF-β and TGF-β receptor Ⅱ, inflammatory factors, in cornea were employed to observe corneal injury. Typical histopathological changes following UVB irradiation were all reversed by pretreat with EGCG, with induction of estrogen receptor and inhibition of inflammatory cytokines expression. The hypothesis of the current study was that EGCG regulates the inflammatory cytokines via ERs modulated pathway cytoprotective effects in ocular tissues.