School of Optometry, University of California, Berkeley, California, United States of America.
PLoS One. 2013 Jun 6;8(6):e65797. doi: 10.1371/journal.pone.0065797. Print 2013.
Dry eye disease can cause ocular surface inflammation that disrupts the corneal epithelial barrier. While dry eye patients are known to have an increased risk of corneal infection, it is not known whether there is a direct causal relationship between these two conditions. Here, we tested the hypothesis that experimentally-induced dry eye (EDE) increases susceptibility to corneal infection using a mouse model. In doing so, we also examined the role of surfactant protein D (SP-D), which we have previously shown is involved in corneal defense against infection. Scopolamine injections and fan-driven air were used to cause EDE in C57BL/6 or Black Swiss mice (wild-type and SP-D gene-knockout). Controls received PBS injections and were housed normally. After 5 or 10 days, otherwise uninjured corneas were inoculated with 10(9) cfu of Pseudomonas aeruginosa strain PAO1. Anesthesia was maintained for 3 h post-inoculation. Viable bacteria were quantified in ocular surface washes and corneal homogenates 6 h post-inoculation. SP-D was measured by Western immunoblot, and corneal pathology assessed from 6 h to 4 days. EDE mice showed reduced tear volumes after 5 and 10 days (each by ∼75%, p<0.001) and showed fluorescein staining (i.e. epithelial disruption). Surprisingly, there was no significant difference in corneal pathology between EDE mice and controls (∼10-14% incidence). Before bacterial inoculation, EDE mice showed elevated SP-D in ocular washes. After inoculation, fewer bacteria were recovered from ocular washes of EDE mice (<2% of controls, p = 0.0004). Furthermore, SP-D knockout mice showed a significant increase in P. aeruginosa corneal colonization under EDE conditions. Taken together, these data suggest that SP-D contributes to corneal defense against P. aeruginosa colonization and infection in EDE despite the loss of barrier function to fluorescein.
干眼症可引起眼表炎症，破坏角膜上皮屏障。已知干眼症患者角膜感染的风险增加，但尚不清楚这两种情况之间是否存在直接因果关系。在这里，我们通过小鼠模型检验了实验性干眼症 (EDE) 是否会增加角膜感染易感性的假设。在这样做的过程中，我们还研究了表面活性剂蛋白 D (SP-D) 的作用，我们之前的研究表明 SP-D 参与了角膜抗感染防御。东莨菪碱注射和风扇驱动空气用于引起 C57BL/6 或黑色瑞士小鼠（野生型和 SP-D 基因敲除）的 EDE。对照接受 PBS 注射并正常饲养。5 或 10 天后，将未受伤的角膜用 10(9)cfu 铜绿假单胞菌 PAO1 接种。接种后 3 小时维持麻醉。接种后 6 小时通过眼部表面冲洗和角膜匀浆定量活细菌。通过 Western 免疫印迹测量 SP-D，并在接种后 6 小时至 4 天评估角膜病理学。EDE 小鼠在第 5 天和第 10 天的泪液体积减少（分别减少约 75%，p<0.001），并出现荧光素染色（即上皮破坏）。令人惊讶的是，EDE 小鼠和对照组之间的角膜病理学没有显著差异（约 10-14%的发生率）。在细菌接种前，EDE 小鼠的眼部冲洗液中 SP-D 水平升高。接种后，EDE 小鼠的眼部冲洗液中回收的细菌较少（对照组的<2%，p=0.0004）。此外，在 EDE 条件下，SP-D 基因敲除小鼠的铜绿假单胞菌角膜定植显著增加。总之，这些数据表明，尽管屏障功能对荧光素的丧失，SP-D 仍有助于 EDE 中对铜绿假单胞菌定植和感染的角膜防御。
