Molecular composition of drusen and possible involvement of anti‐retinal autoimmunity in two different forms of macular degeneration in cynomolgus monkey ( Macaca fascicularis )

Abstract

We have previously reported a cynomolgus monkey (Macaca fascicularis) pedigree with early onset macular degeneration that develops drusen at 2 yr after birth. In this study, the molecular composition of drusen in monkeys affected with late onset and early onset macular degeneration was both characterized. Involvement of anti-retinalautoimmunity in the deposition of drusen and the pathogenesis of the disease was also evaluated. Funduscopic and histological examinations were performed on 278 adult monkeys (mean age=16.94 yr) for late onset macular degeneration. The molecular composition of drusen was analyzed by immunohistochemistry and/or direct proteome analysis using liquid chromatography tandem mass spectroscopy (LC-MS/MS). Anti-retinal autoantibodies in sera were screened in 20 affected and 10 age-matched control monkeys by Western blot techniques. Immunogenic molecules were identified by 2D electrophoresis and LC-MS/MS. Relative antibody titer against each antigen was determined by ELISA in sera from 42 affected (late onset) and 41 normal monkeys. Yellowish-white spots in the macular region were observed in 90 (32%) of the late onset monkeys that were examined. Histological examination demonstrated that drusen or degenerative retinal pigment epithelium (RPE) cells were associated with the pigmentary abnormalities. Drusen in both late and early onset monkeys showed immunoreactivities for apolipoprotein E, amyloid P component, complement component C5, the terminal C5b-9 complement complex, vitronectin, and membrane cofactor protein. LC-MS/MS analyses identified 60 proteins as constituents of drusen, including a number of common components in drusen of human age-related macular degeneration (AMD), such as annexins, crystallins, immunoglobulins, and complement components. Half of the affected monkeys had single or multiple autoantibodies against 38, 40, 50, and 60 kDa retinal proteins. The reacting antigens of 38 and 40 kDa were identified as annexin II and mu-crystallin, respectively. Relative antibody titer against annexin II in affected monkeys was significantly higher than control animals (P<0.01). Significant difference was not observed in antibody titer against mu-crystallin; however, several affected monkeys showed considerably elevated titer (360-610%) compared with the mean for unaffected animals. Monkey drusen both in late and early onset forms of macular degeneration had common components with drusen in human AMD patients, indicating that chronic inflammation mediated by complement activation might also be involved in the formation of drusen in these affected monkeys. The high prevalence of anti-retinalautoantibodies in sera from affected monkeys demonstrated an autoimmune aspect of the pathogenesis of the disease. Although further analyses are required to determine whether and how autoantibodies against annexin II or mu-crystallin relate to the pathogenesis of the disease, it could be hypothesized that immune responses directed against these antigens might trigger chronic activation of the complement ...

Classical complement activation and acquired immune response pathways are not essential for retinal degeneration in the rd1 mouse

“…Recent genetic evidence has strongly implicated polymorphisms in the complement control protein factor H (Edwards et al 2005;Hageman et al 2005;Haines et al 2005;Klein et al 2005;Umeda et al 2005) and factor B (Gold et al 2006) as major risk (or, depending on the polymorphism, protective) factors for AMD. Based on these results, it has been proposed that inadequate control of complement-driven immune-response may be an important factor in the pathogenesis of AMD.…”

“…Local inflammation may not only be involved in the formation of drusen, a hallmark of AMD (Hageman et al 2001;Johnson et al 2002) but inflammation triggered by the debris generated by dying RPE cells may also lead to photoreceptor cell death and loss of vision (Johnson et al 2002). Furthermore, mutations in complement factor H and factor B were shown to significantly increase the risk to develop age-related macular degeneration (AMD) (Edwards et al 2005;Hageman et al 2005;Haines et al 2005;Klein et al 2005;Umeda et al 2005;Gold et al 2006). Topographical analysis of retinas affected by AMD revealed that rod cell death precedes cone cell death (Curcio 2001).…”

Age-related Macular Degeneration and the Immune Response: Implications for Therapy

“…68 Several authors have reported the presence of circulating autoantibodies in patients with AMD. 69,70,71 It is not clear whether these antibodies play a role in the pathogenesis of the disease.…”

Microarray Analysis of Differentially Expressed Genes in the Brains of Tubby Mice

“…For example, families with hereditary nonsyndromic deafness carry a mutation of CRYM gene that prevents NADPH-dependent T3 binding to CRYM and causes severe deafness (Abe et al, 2003;Oshima et al, 2006). In addition, based on the critical role of thyroid hormone in retinal development (Roberts et al, 2006) and evidence that CRYM is associated with macular degeneration of the retina (Umeda et al, 2005), the observed down-regulation of CRYM expression in tubby mice suggests that CRYM is involved in the progression of retinal degeneration. Moreover, thyroid hormone is a positive regulator of tubby gene expression (Koritschoner et al, 2001).…”