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Manabu Hirasawa, Motoyo Endo, Seiji Miyake, Toshio Narimatsu, Shunsuke Kubota, Misa Suzuki, Susumu Ishida, Kazuo Tsubota, Yuichi Oike, Yoko Ozawa; Association of Angiopoietin-like Protein 2 with Inflammatory Signals in the Human Retinal Pigment Epithelium. Invest. Ophthalmol. Vis. Sci. 2012;53(14):1655.
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Angiopoietin-like proteins (Angptls) possess a coiled-coil domain at the N-terminus for oligomerization and a fibrinogen-like domain at the C-terminus similarly to angiopoietin. They promote chronic tissue inflammation in adipose tissue as well as carcinogenesis. However, little is known about the role of Angptl2 in the ocular tissue. The final goal is to explore the association of Angptl2 with the inflammatory signals in the human retinal pigment epithelium (RPE).
Cyrosections of postmortem human ocular tissue were prepared and analyzed the expression of Angptl2, immunohistochemically. The human retinal pigment epithelium (RPE) cell line, ARPE-19, was cultured in the in Dulbecco’s modified Eagle’s medium (DMEM) supplemented with 10% fetal bovine serum (FBS). Cells were applied and stimulated by pro-inflammatory cytokines, such as Tumor Necrosis Factor (TNF)-alpha, Transforming growth factor (TGF)-beta, connective tissue growth factor (CTGF), and Vascular Endothelial Growth Factor (VEGF). Cells were collected 24 hours after the stimulation, and mRNA and protein levels of Angplt2 were analyzed using real-time PCR and ELISA.
Immunostaining for Angptl2 was observed in the cytosol of human RPE, and its expression in RPE was confirmed in vivo. In the ARPE19, changes in mRNA expression were observed after stimulation of either TNF-alpha or TGF-beta. Interestingly, the levels were significantly dropped(P<0.01)in a dose-dependent manner. The level of Angptl2 protein was also decreased after TNF-alpha stimulation.
Angptl2 has been known as a pro-inflammatory signal in some tissue, however, in ARPE19, its expression was suppressed by stimulation with a pro-inflammatory cytokine, TNF-alpha. Multiple roles might be involved in Angptl2 in a context dependent manner. Further investigation is required to reveal the role of Angptl2 in inflammation.
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