Rönkkö Seppo, Rekonen Petri, Kaarniranta Kai, Puustjarvi Tuomo, Teräsvirta Markku, Uusitalo Hannu
Department of Ophthalmology, University of Kuopio, Kuopio, Finland.
Mol Vis. 2007 Mar 26;13:408-17.
Phospholipase A2 (PLA2) is a growing family of lipolytic enzymes that play a key role in various biological processes including general lipid metabolism, membrane homeostasis, and in diseases such as atherosclerosis, arthritis, and acute pancreatitis. Oxidative stress as well as inflammation may be associated with glaucoma pathogenesis. Therefore, our aim was to examine the expression of group IIA secretory PLA2 (sPLA2-IIA), group V secretory PLA2 (sPLA2-V), calcium-independent PLA2 (iPLA2), and cytosolic PLA2 (cPLA2) type in the trabecular meshwork (TM) and the canal of Schlemm in normal eyes and in juxtacanalicular tissue samples from patients with primary open angle glaucoma (POAG) or exfoliation glaucoma (ExG).
TM tissues were isolated from healthy donor eyes for corneal transplantation. Specimens of inner wall of the Schlemm's canal and the juxtacanalicular tissue were collected during deep sclerectomy from the eyes of patients who had POAG or ExG. Antibodies against PLA2s (sPLA2-IIA, sPLA2-V, iPLA2, and cPLA2) and a standard immunohistochemical procedure were used for the analysis. Quantification of immunoreactions was provided using a Photoshop-based image analysis. Double-staining immunofluorescence of macrophages and sPLA2-IIA was performed by using confocal microscopy.
sPLA2-IIA was not present in normal TM. In contrast, sPLA2-IIA levels were significantly higher in glaucoma patients than in controls. Furthermore, sPLA2-IIA expression was much higher in POAG when compared to ExG. iPLA2 was found to predominate in normal human TM, and it demonstrated strong labeling in the uveal and corneoscleral meshwork. The staining of juxtacanalicular meshwork was only moderate in density. In contrast, expression of the enzyme was significantly decreased in glaucoma patients, especially in ExG, when compared to normal controls or to POAG. In addition, strong regional differences were detected in sPLA2-IIA and iPLA2 levels in POAG, whereas immunostaining of these enzymes was much lower and rather uniform throughout ExG sample. In POAG, sPLA2-IIA staining was restricted to certain parts of the trabecular samples where sPLA2-IIA positive macrophages were also present. Immunostaining of sPLA2-V or cPLA2 was low, and no significant changes were found in levels of these enzymes between normal and glaucomatous samples.
sPLA2-IIA, an oxidative stress marker in atherosclerosis, is overexpressed especially in POAG. This result supports the hypothesis that oxidative stress may play a significant role in the pathogenesis of POAG. In ExG, a dramatic decrease in the expression level of iPLA2, a housekeeping enzyme in phospholipid remodeling, may indicate imbalance in phospholipid turnover and also inhibition of normal physiological functions in the TM. These findings may contribute to understanding the pathogenesis of POAG and ExG and may be important for the development of novel therapeutic strategies to different glaucomas.
磷脂酶A2（PLA2）是一个不断发展的脂解酶家族，在包括一般脂质代谢、膜稳态等各种生物过程以及动脉粥样硬化、关节炎和急性胰腺炎等疾病中发挥关键作用。氧化应激以及炎症可能与青光眼的发病机制有关。因此，我们的目的是检测正常眼睛小梁网（TM）和施莱姆管以及原发性开角型青光眼（POAG）或剥脱性青光眼（ExG）患者的邻管组织样本中IIA组分泌型PLA2（sPLA2-IIA）、V组分泌型PLA2（sPLA2-V）、钙非依赖性PLA2（iPLA2）和胞质型PLA2（cPLA2）的表达。
从用于角膜移植的健康供体眼中分离TM组织。在对POAG或ExG患者进行深层巩膜切除术时，收集施莱姆管内壁和邻管组织的标本。使用针对PLA2（sPLA2-IIA、sPLA2-V、iPLA2和cPLA2）的抗体和标准免疫组织化学程序进行分析。使用基于Photoshop的图像分析对免疫反应进行定量。通过共聚焦显微镜对巨噬细胞和sPLA2-IIA进行双重染色免疫荧光分析。
正常TM中不存在sPLA2-IIA。相比之下，青光眼患者的sPLA2-IIA水平显著高于对照组。此外，与ExG相比，POAG中sPLA2-IIA的表达更高。发现iPLA2在正常人TM中占主导地位，并且在葡萄膜和角膜巩膜小梁网中显示出强烈的标记。邻管小梁网的染色密度仅为中等。相比之下，与正常对照组或POAG相比，青光眼患者中该酶的表达显著降低，尤其是在ExG中。此外，在POAG中检测到sPLA2-IIA和iPLA2水平存在强烈的区域差异，而在整个ExG样本中这些酶的免疫染色要低得多且相当均匀。在POAG中，sPLA2-IIA染色仅限于小梁样本的某些部分，这些部分也存在sPLA2-IIA阳性巨噬细胞。sPLA2-V或cPLA2的免疫染色较低，并且在正常和青光眼样本之间这些酶的水平未发现显著变化。
sPLA2-IIA是动脉粥样硬化中的一种氧化应激标志物，尤其在POAG中过度表达。这一结果支持氧化应激可能在POAG发病机制中起重要作用的假说。在ExG中，磷脂重塑中的管家酶iPLA2的表达水平急剧下降，这可能表明磷脂周转失衡以及TM中正常生理功能受到抑制。这些发现可能有助于理解POAG和ExG的发病机制，并且对于开发针对不同青光眼的新型治疗策略可能很重要。
