Gao J, Schwalb T A, Addeo J V, Ghosn C R, Stern M E
Department of Biological Science, Allergan, Inc., Irvine, California, USA.
Cornea. 1998 Nov;17(6):654-63. doi: 10.1097/00003226-199811000-00014.
The exact etiology of dry eye is unknown but is believed to be multifactorial. Apoptosis has been implicated in the pathogenesis of autoimmune diseases such as Sjögren's syndrome (SS). This study attempted to gain a better understanding of the role of apoptosis and its regulation in the patho-physiology of dry eye. The therapeutic effect of immunomodulatory agents such as cyclosporin A (CsA) in the treatment of dry eye, particularly its impact on the level of apoptosis in the target tissues, is also investigated.
A colony of dogs with spontaneous chronic idiopathic keratoconjunctivitis sicca (KCS) was maintained. Nictitans lacrimal gland (NLG), an accessory lacrimal gland, and conjunctival biopsies of the KCS and normal dogs were obtained before and after 12 weeks of treatment with 0.2% topical CsA ophthalmic emulsion b.i.d. (Allergan, Inc., Irvine, CA, U.S.A.). Tissues were prepared for the terminal deoxynucleotidyl transferase-mediated dUTP-digoxigenin nick end labeling (TUNEL) apoptosis assay and immunohistochemical analysis for various apoptosis mediators.
The TUNEL assay demonstrated that (i) the normal NLG and conjunctival epithelial cells exhibited a limited level of apoptosis; (ii) in KCS dogs, lacrimal acinar and conjunctival epithelial cells underwent an increased apoptosis, whereas the lymphocytes had a significantly lower level of apoptosis compared to those of the normal dogs; (iii) after topical CsA, apoptosis was induced in the lymphocytes and suppressed in the acinar and conjunctival epithelial cells in KCS dogs. Immunohistochemistry revealed that p53, fas, and fasL, but not bcl-2 were highly expressed in the target tissues of KCS dogs. The immunoreactivity of p53 was significantly decreased, whereas the bcl-2 level was increased after CsA administration.
The induction of epithelial cell apoptosis and the suppression of lymphocytic apoptosis in the NLG and ocular-surface tissues, such as conjunctiva of KCS dogs, indicates the important role of this phenomenon in the etiology of dry eye. Topical CsA appears to facilitate lymphocytic apoptosis and suppress epithelial cell apoptosis in the KCS dog. The differential expression of various apoptotic mediators after topical treatment implicates CsA in facilitating the reestablishment of the normal apoptotic balance, suggesting additional mechanisms by which CsA is therapeutic for dry-eye syndrome.
干眼的确切病因尚不清楚，但被认为是多因素的。细胞凋亡与自身免疫性疾病如干燥综合征（SS）的发病机制有关。本研究试图更好地了解细胞凋亡及其调节在干眼病理生理学中的作用。还研究了免疫调节药物如环孢素A（CsA）在干眼治疗中的疗效，特别是其对靶组织中细胞凋亡水平的影响。
维持一群患有自发性慢性特发性角结膜炎（KCS）的犬。在用0.2%局部CsA眼用乳剂每日两次治疗12周之前和之后，获取KCS犬和正常犬的瞬膜泪腺（NLG，一种副泪腺）以及结膜活检组织。（美国加利福尼亚州欧文市艾尔建公司）将组织制备用于末端脱氧核苷酸转移酶介导的dUTP - 地高辛配基缺口末端标记（TUNEL）细胞凋亡检测以及针对各种细胞凋亡介质的免疫组织化学分析。
TUNEL检测表明：（i）正常的NLG和结膜上皮细胞表现出有限水平的细胞凋亡；（ii）在KCS犬中，泪腺腺泡和结膜上皮细胞的凋亡增加，而淋巴细胞的凋亡水平与正常犬相比显著降低；（iii）局部应用CsA后，KCS犬的淋巴细胞中诱导了细胞凋亡，而腺泡和结膜上皮细胞中的细胞凋亡受到抑制。免疫组织化学显示，p53、fas和fasL在KCS犬的靶组织中高表达，但bcl - 2未高表达。应用CsA后，p53的免疫反应性显著降低，而bcl - 2水平升高。
在KCS犬的NLG和眼表组织如结膜中，上皮细胞凋亡的诱导和淋巴细胞凋亡的抑制表明这种现象在干眼病因中起重要作用。局部应用CsA似乎促进KCS犬的淋巴细胞凋亡并抑制上皮细胞凋亡。局部治疗后各种细胞凋亡介质的差异表达表明CsA有助于重新建立正常的细胞凋亡平衡，提示CsA治疗干眼综合征的其他机制。
