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Jian Liu, Kevin Harkin, Chang Luo, Jiansu Chen, Shibo Tang, Mei Chen, Heping Xu; Photoreceptors Constitutively Express A Variety of Complement Components. Invest. Ophthalmol. Vis. Sci. 2018;59(9):5556. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
The complement system is known to be critically involved in retinal pathophysiology. We and other have shown that the retina expresses a variety of components although the cellular source of complement expression is not fully elucidated. This study examined the expression of complement components by photoreceptors and their regulation under pathophysiological conditions.
Quantitative RT-PCR, western blot and immunofluorescence were employed to analyze the expression of complement components in a photoreceptor cell line, 661W cells, under normal, high glucose (25 mM, mannitol as control), 1%O2, or inflammatory conditions (TNF-α: 20 ng/ml; LPS: 200 ng/ml; or IL-4: 20 ng/ml; respectively). A transwell co-culture system was used to study the effects of macrophage on complement expression by 661w cells. The expression of complement components in vivo was examined by immunohistochemistry in normal eyes, and eyes with uveoretinitis or retinal detachment.
Quantitative RT-PCR shows that 661w cells express high levels of C1r, C1s, C3 of the classical pathway (CP), MASP1 of the mannose binding lectin (MBL) pathway and complement factor H (CFH) of the alternative pathway (AP). In addition, complement regulators, including Crry, CD59, C1INH, DAF1 and C4BP were also detected at significant levels in photoreceptors. TNF-α significantly upregulated the expression of C1ra, C1s, CFB, CD59, Crry and C3 genes. Whereas IL-4 treatment increased the expression of C1s, C1r and CFH genes. LPS-induced M1 macrophages increased the expression of C1ra, C1s, C3, and C4 by 661W cell, whereas IL-4 induced M2 macrophages increased CFH and C3 expression by 661W cells. Hypoxia increased the expression of Crry and CD59. High glucose did not significantly affect the expression of the complement genes in photoreceptors.
Photoreceptors constitutively express a variety of complement components predominately CP components and complement regulators. Their expression is regulated by cytokines and activated macrophages. Our results suggest that photoreceptors may play an important role in regulating retinal complement activation in pathophysiological conditions.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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