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Editors Selection IGR 8-1

Basic research: C1q

Comment by Abbot Clark on:

13386 Complement component 1Q (C1Q) upregulation in retina of murine, primate, and human glaucomatous eyes, Stasi K; Nagel D; Yang X et al., Investigative Ophthalmology and Visual Science, 2006; 47: 1024-1029

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Complement activation has been implicated in the pathogenesis of certain neuropathogenic disorders such as Alzheimer's disease, and Stasi et al. (44) examined the potential role of complement activation in glaucomatous damage to the retina. They looked at the expression of C1q, one of the activating components of the classical complement pathway, in the retinas of glaucomatous mice and monkeys as well as in some human glaucoma eyes. They showed age-associated increases in retinal C1q mRNA and protein in the DBA/2J glaucomatous mouse and increased retinal C1q immunostaining in DBA/2J mice, laser-induced glaucomatous monkeys, and in some eyes of patients with glaucoma. The C1q immunostaining was most prominently seen in Muller cells, but interestingly not in the retinal ganglion cells. What is the function of C1q in the glaucomatous retina, and does it play an important pathogenic role? Autoantibodies to retinal antigens have been reported in glaucoma patients (Wax et al., 2002), and these antibodies may initiate the complement cascade in the glaucomatous retina. However, other members of the complement cascade, including C3 and the membrane attack complex C5-9, to date have not been shown to be present in the glaucomatous retina. In addition to its well-known role in regulating antibody dependent and independent immune functions, C1q also interacts with and potentially modifies the activity of other proteins such as calreticulin, C-reactive protein, amyloid P, and certain proteoglycans. C1q also can stimulate oxidative metabolism, induce the expression of certain cell surface adhesion molecules, and alter cell proliferation in some cells. Given these diverse activities of C1q, it is clear that additional work needs to be done to determine what role, if any, C1q plays in glaucomatous damage to the retina.

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