Tissue inhibitor of metalloproteinase 4 in aqueous humor of patients with primary open angle glaucoma, pseudoexfoliation syndrome and pseudoexfoliative glaucoma and its role in proteolysis imbalance

BMC Ophthalmology, Nov 2013

Background To quantify the levels of tissue inhibitor of metalloproteinase 4 (TIMP4) and its ratios with free metalloproteinases (MMP) in the aqueous humor of patients with primary open angle glaucoma (POAG), pseudoexfoliation syndrome (PXS) and pseudoexfoliative glaucoma (PXG) and to evaluate a possible imbalance between MMPs and TIMPs in these samples. Methods Free MMP2, MMP3, MMP9, TIMP1, TIMP2, TIMP4 concentrations and active levels of MMP2 and MMP3 were determined with immunoassay ELISA and activity assay kits in 168 aqueous samples. Results TIMP4 was elevated in glaucoma patients(POAG: 0.95 ± 0.49 PXG: 1.28 ± 1.38 pg/ml. p < 0.001). POAG, PXS and PXG samples demonstrated higher MMP2, TIMP1 and TIMP2 concentrations (p < 0.001). Samples from the PXS and PXG groups had a lower total/active MMP2 ratio (p < 0.004 and p < 0.008 respectively). Stoichiometric analysis showed an overbalance of TIMPsover MMPs in both POAG & PXG groups,especially of TIMP4. Conclusion TIMP4 elevation is a novel finding in glaucomatous eyes. A disregulation of extracellular matrix homeostasis is suggested in POAG, PXS and PXG.

A PDF file should load here. If you do not see its contents the file may be temporarily unavailable at the journal website or you do not have a PDF plug-in installed and enabled in your browser.

Alternatively, you can download the file locally and open with any standalone PDF reader:

http://www.biomedcentral.com/content/pdf/1471-2415-13-69.pdf

Tissue inhibitor of metalloproteinase 4 in aqueous humor of patients with primary open angle glaucoma, pseudoexfoliation syndrome and pseudoexfoliative glaucoma and its role in proteolysis imbalance

BMC Ophthalmology Tissue inhibitor of metalloproteinase 4 in aqueous humor of patients with primary open angle glaucoma, pseudoexfoliation syndrome and pseudoexfoliative glaucoma and its role in proteolysis imbalance Nikitas Fountoulakis 0 1 Georgios Labiris 0 1 Antonios Aristeidou 0 1 Andreas Katsanos 2 Ioannis Tentes 3 Alexandros Kortsaris 3 Vassilios P Kozobolis 0 1 0 Eye Institute of Thrace , Alexandroupolis , Greece 1 Department of Ophthalmology, Democritus University of Thrace , Alexandroupolis , Greece 2 Department of Ophthalmology, University of Ioannina , Ioannina , Greece 3 Department of Biochemistry, Democritus University of Thrace , Alexandroupolis , Greece Background: To quantify the levels of tissue inhibitor of metalloproteinase 4 (TIMP4) and its ratios with free metalloproteinases (MMP) in the aqueous humor of patients with primary open angle glaucoma (POAG), pseudoexfoliation syndrome (PXS) and pseudoexfoliative glaucoma (PXG) and to evaluate a possible imbalance between MMPs and TIMPs in these samples. Methods: Free MMP2, MMP3, MMP9, TIMP1, TIMP2, TIMP4 concentrations and active levels of MMP2 and MMP3 were determined with immunoassay ELISA and activity assay kits in 168 aqueous samples. Results: TIMP4 was elevated in glaucoma patients(POAG: 0.95 0.49 PXG: 1.28 1.38 pg/ml. p < 0.001). POAG, PXS and PXG samples demonstrated higher MMP2, TIMP1 and TIMP2 concentrations (p < 0.001). Samples from the PXS and PXG groups had a lower total/active MMP2 ratio (p < 0.004 and p < 0.008 respectively). Stoichiometric analysis showed an overbalance of TIMPsover MMPs in both POAG & PXG groups,especially of TIMP4. Conclusion: TIMP4 elevation is a novel finding in glaucomatous eyes. A disregulation of extracellular matrix homeostasis is suggested in POAG, PXS and PXG. Glaucoma; Pseudoexfoliation; Metalloproteinases; TIMP4; TIMP/MMP ratios - Background The most important risk factor for the development and progression of glaucoma is the elevation of the intraocular pressure (IOP) [1]. IOP regulation is directly associated with aqueous humor outflow. Although the exact mechanism has not been thoroughly elucidated, studies have shown that the main resistance to the aqueous humour outflow is located at the trabecular meshwork (TM), especially the juxtacanalicular part directly underneath the inner wall of Schlemms canal [2,3]. The special characteristics of the extracellular matrix and the cell interactions in this region can potentially determine the outflow facility [4]. In glaucoma, the normal architecture and function of the juxtacanalicular TM is altered by the pathological accumulation of connective tissue and the partial loss of endothelial cells [5,6]. Other local factors such as the expression of vasoconstrictive molecules and oxidative stress may also be involved [7,8]. Pseudoexfoliation syndrome (PXS) is an age-related systemic disorder characterized by the abnormal accumulation of extracellular matrix (ECM) material in extraocular and ocular tissues. The pseudoexfoliative material might congest the outflow pathways of the TM contributing to the elevation of the IOP and may be involved in the development of pseudoexfoliative glaucoma (PXG) [9,10]. ECM remodeling is primarily controlled by endogenous enzymes, known as matrix metalloproteinases (MMPs). MMPs are a family of endopeptidases that contain an active Zn2+ site which is responsible for their enzymatic activity [11]. They are synthesized as proenzymes and secreted as inactive molecules which are activated in vivo by disruption of the cystein-Zn link [11,12]. The regulation of the proteolytic activity of MMP is mainly controlled by the presence of tissue inhibitors of MMPs (TIMPs) which bind MMPs in a 1:1 stoichiometry [13]. Four TIMPs have been identified in vertebrates which can inhibit the action of MMPs. All TIMPs except TIMP3 are in soluble form [13,14]. In biological fluids, MMPs are found either as free proforms, activated enzymes or as complexes with TIMPs. It is well documented that MMPs and TIMPs play an important role in many ocular pathological processes, including glaucoma [15]. In vitro and in vivo studies have shown that MMPs in TM directly control outflow resistance [16]. Their presence in aqueous humor has also been established [17,18]. Moreover, the recently identified TIMP4, which is associated with MMP inhibition along with other biological processes such as apoptosis [19], has never been traced or quantified in the aqueous humor. Within this context, the objectives of this study were: a) to trace and estimate the levels of TIMP4 in the aqueous humor, b) to investigate the ratios of TIMP4 to other free MMPs and TIMPs in the aqueous humor, and c) to investigate the potential imbalance of free forms of MMPs and TIMPs in eyes with POAG, PXS and PXG. Methods Setting This was a clinic-based, cross-sectional study. The protocol adhered to the tenets of the Helsinki Declaration and written informed consent was given by (...truncated)


This is a preview of a remote PDF: http://www.biomedcentral.com/content/pdf/1471-2415-13-69.pdf

Nikitas Fountoulakis, Georgios Labiris, Antonios Aristeidou, Andreas Katsanos, Ioannis Tentes, Alexandros Kortsaris, Vassilios P Kozobolis. Tissue inhibitor of metalloproteinase 4 in aqueous humor of patients with primary open angle glaucoma, pseudoexfoliation syndrome and pseudoexfoliative glaucoma and its role in proteolysis imbalance, BMC Ophthalmology, 2013, pp. 69, 13, DOI: 10.1186/1471-2415-13-69