Seamon Vanessa, Vellala Kavyasri, Zylberberg Claudia, Ponamareva Olga, Azzarolo Ana Maria
Department of Clinical Science and Medical Education, Florida Atlantic University, Charles E. Schmidt College of Biomedical Science, Boca Raton, FL 33431-0991, USA.
Exp Eye Res. 2008 Sep;87(3):184-90. doi: 10.1016/j.exer.2008.05.012. Epub 2008 Jul 23.
Tear lipocalin (TL) (approximately 18 kDa), a member of the lipocalin superfamily, has been identified as one of the major proteins present in rabbit lacrimal fluid. The concentration of TL has been found to be decreased in the tears of patients with dry eye disease. Lacrimal gland insufficiency, one of the major causes of dry eye disease, is known to affect mainly postmenopausal women, where there is a significant decrease in the production of androgen and estrogen. These observations suggest that sex hormones might influence dry eye indirectly by regulating the expression of TL. The purpose of this study was to determine: (1) the effect of sexual maturation on the expression of TL; and (2) if the expression of TL is regulated by the estrogen, 17beta-estradiol, and/or the androgen, dihydrotestosterone, in sexually mature female rabbits. Lacrimal fluid (LF) and lacrimal gland soluble fraction (Si) was collected from juvenile (2 kg) and sexually mature (4 kg) male and female New Zealand white (NZW) rabbits. In addition, LF and Si were collected from 4 kg rabbits, 7 days after being either sham operated (control), ovariectomized (OVX), ovariectomized treated with estrogen (OVX+E) or ovariectomized treated with dihydrotestosterone (OVX+DHT). Samples were analyzed for protein levels of TL by SDS-PAGE and Western blotting using a polyclonal rat anti-rabbit TL antibody. Densitometry analysis showed that TL protein levels in both LF and Si increased with age in male and female rabbits. In addition, TL protein levels were significantly higher in the sexually mature 4 kg male compared with the 4 kg female, while no significant difference in TL protein levels were seen among the juvenile male and female rabbits. Furthermore, ovariectomy decreased the protein levels of TL in LF and Si fraction by 50% and 20% respectively, compared with control values. Estrogen treatment increased TL protein levels by 30% and 50% in the LF and Si fraction respectively, compared with the sham operated group. DHT treatment also increased TL protein levels by approximately 150% in both LF and Si fraction compared with control values. These results support the hypothesis that sex hormones influence TL protein levels in rabbit lacrimal glands. The possibility of a role of TL in dry eye needs to be further investigated.
泪液视黄醇结合蛋白（TL）（约18 kDa）是视黄醇结合蛋白超家族的成员之一，已被确定为兔泪液中的主要蛋白质之一。研究发现，干眼症患者泪液中TL的浓度会降低。泪腺功能不全是干眼症的主要病因之一，已知主要影响绝经后女性，此时雄激素和雌激素的分泌会显著减少。这些观察结果表明，性激素可能通过调节TL的表达间接影响干眼症。本研究的目的是确定：（1）性成熟对TL表达的影响；（2）在性成熟的雌性兔中，TL的表达是否受雌激素17β-雌二醇和/或雄激素双氢睾酮的调节。从幼年（2 kg）和性成熟（4 kg）的雄性和雌性新西兰白兔（NZW）收集泪液（LF）和泪腺可溶性部分（Si）。此外，在假手术（对照）、卵巢切除（OVX）、雌激素治疗的卵巢切除（OVX+E）或双氢睾酮治疗的卵巢切除（OVX+DHT）7天后，从4 kg的兔子收集LF和Si。使用多克隆大鼠抗兔TL抗体，通过SDS-PAGE和蛋白质印迹法分析样品中TL的蛋白质水平。密度测定分析表明，雄性和雌性兔的LF和Si中TL蛋白质水平均随年龄增加。此外，4 kg性成熟雄性兔的TL蛋白质水平显著高于4 kg雌性兔，而幼年雄性和雌性兔的TL蛋白质水平无显著差异。此外，与对照值相比，卵巢切除分别使LF和Si部分中TL的蛋白质水平降低了50%和20%。与假手术组相比，雌激素治疗使LF和Si部分中TL的蛋白质水平分别增加了30%和50%。与对照值相比，DHT治疗也使LF和Si部分中TL的蛋白质水平增加了约150%。这些结果支持性激素影响兔泪腺中TL蛋白质水平的假说。TL在干眼症中的作用可能性需要进一步研究。
