Amyloid-β-induced matrix metalloproteinase-9 secretion is associated with retinal pigment epithelial barrier disruption

Abstract

Local and chronic inflammation induced by amyloid-β (Aβ) plays a central role in the development of age-related macular degeneration. The retina is an immune-privileged site due to local tissue barrier. Yet, the manner by which immune cells pass through this barrier and accumulate in the retina remains unclear. Matrix metalloproteinases (MMPs) induce barrier disruption via proteolysis of epithelial tight junction (TJ) proteins. We hypothesized that Aβ-induced MMP secretion causes disruption of epithelial barrier integrity. To test this hypothesis, human adult retinal pigment epithelial (haRPE) cells were exposed to Aβ, and the expression of MMP-2 and MMP-9 was detected using gelatin zymography. To demonstrate the key role of MMPs in modulating epithelial barrier structure, the MMP agonist 4-aminophenylmercuric acetate (APMA), an MMP inhibitor (GM6001) and siRNA against MMP-9 were employed for comparison. We found that MMP-9, secreted by Aβ- or APMA-stimulated cells, mediated low transepithelial electrical resistance (TER) and high transepithelial permeability by disrupting TJ proteins. However, these alterations were reduced by the MMP inhibitor GM6001 or by silencing of the MMP-9 gene. Our findings suggest that the degradation of TJ proteins such as zonula occludens-1, occludin and F-actin by MMP-9 secreted by Aβ-stimulated cells constitutes an important mechanism in the breakdown of the barrier which contributes to chronic inflammation in the retina of age-related macular degeneration.

SIRT1 negatively regulates amyloid-beta-induced inflammation via the NF-κB pathway

“…Oligomerized Aβ (OAβ) was synthesized as previously described (11). Briefly, lyophilized Aβ 1-42 peptide (Sigma-Aldrich, USA) was dissolved in 1.5 M hexafluoroisopropanol (HFIP) on ice and aliquoted at -20°C.…”

“…The donors were between 30 and 40 years of age and none had a history of eye disease. Human RPE cells were harvested as described previously (11). In brief, whole eyes were cleaned in 0.9% NaCl solution, immersed in 5% polyvinylpyrrolidone iodine, and rinsed again in NaCl solution.…”

“…Microarray analysis of gene expression in ARPE-19 revealed that Aβ stimulation significantly upregulated interleukin (IL)-8 gene expression (14). Our previous study found that Aβ stimulation increased IL-6, IL-8, and MMP-9 expression in human adult RPE cells (11). Increased intraocular concentrations of IL-6, IL-8, and MMP-9 have also been found in AMD patients, and the levels were significantly associated with the severity of the disease (15).…”

“…The antioxidant resveratrol has been shown to protect ARPE-19, a spontaneously transformed RPE cell line, from Aβ-induced barrier dysfunction (10). Our previous study found that matrix metalloproteinase-9 (MMP-9) mediated Aβ-induced barrier disruption, suggesting that MMP-9 contributes to chronic inflammation in AMD (11). Breakdown of the epithelial barrier would thus be both a stimulus for inflammation in tissue injury and a component of normal inflammatory processes that permit leukocyte influx into areas of tissue damage.…”

Therapeutic Effect of Bone Marrow Mesenchymal Stem Cells on Laser-Induced Retinal Injury in Mice

“…However, under pathological conditions, the expression level of MMP-2 is raised by stimulating factors, such as tissue injury and inflammation [38,39]. Disruption of the ECM caused by an imbalance of MMP-2 and its inhibitors leads to a further series of histopathological changes, including inflammatory infiltration and retinal cell apoptosis [40,41,42]. Previous studies of experimental autoimmune uveitis have demonstrated that MSCs display their immunomodulatory and therapeutic properties in a paracrine fashion [43,44].…”