Higher plasma levels of complement C3a, C4a and C5a increase the risk of subretinal fibrosis in neovascular age-related macular degeneration.

Background: The aim of this study was to investigate the plasma levels of complement C3a, C4a, and C5a in different types of neovascular age-related macular degeneration (nAMD) and whether the levels were related to patients’ responsiveness to anti-VEGF therapy.

Results: Ninety-six nAMD patients (including 61 with choroidal neovascularisation (CNV), 17 with retinal angiomatous proliferation (RAP), 14 with polypoidal choroidal vasculopathy (PCV) and 4 unclassified patients) and 43 controls were recruited to this case–control study. Subretinal fibrosis was observed in 45 nAMD patients and was absent in 51 nAMD patients. In addition, the responsiveness to anti-VEGF (Lucentis) therapy was also evaluated in nAMD patients. Forty-four patients were complete responders, 48 were partially responders, and only 4 patients did not respond to the therapy. The plasma levels of C3a, C4a and C5a were significantly higher in nAMD patients compared to
controls. Further analysis of nAMD subgroups showed that the levels of C3a, C4a and C5a were significantly increased in patients with CNV but not RAP and PCV. Significantly increased levels of C3a, C4a and C5a were also observed in nAMD patients with subretinal fibrosis but not in those without subretinal fibrosis. Higher levels of C3a were observed in nAMD patients who responded partially to anti-VEGF therapy.

Conclusions: Our results suggest increased systemic complement activation in nAMD patients with CNV but not RAP and PCV. Our results also suggest that higher levels of systemic complement activation may increase the risk of subretinal fibrosis in nAMD patients

Expression of C5a receptor in mouse brain: Role in signal transduction and neurodegeneration

In this study we explored the potential role of the complement derived anaphylatoxin C5a and the expression of its receptor in mouse brain. Using in situ hybridization, we found that C5a receptor messenger RNA is expressed in mouse brain. In response to intraventricular kainic acid injection, there was marked increase in the C5a receptor messenger RNA expression, particularly in hippocampal formation and cerebral cortex. C5a ligand-binding autoradiography confirmed the functional expression and elevation of the C5a receptor post-lesioning. The expression of Cia receptor messenger RNA in brain was confirmed by northern blot hybridization of total RNA from neuronal and glial cells in vitiro. Based on these findings we explored the role of C5a in mechanisms of signal transduction in brain cells. Treatment of primary cultures of mouse astrocytes with human recombinant C5a resulted in the activation of mitogen-activated extracellular signal-regulated protein kinase. This response appeared to be mediated by the C5a receptor since astrocyte cultures derived from C5a receptor knockout mice were not responsive to the treatment. Understanding the regulation of C5a receptor in brain and mechanisms by which pro-inflammatory C5a modulates specific signal transduction pathways in brain cells is crucial to studies of inflammatory mechanisms in neurodegeneration. (C) 1998 IBRO. Published by Elsevier Science Ltd.

Toxicity of non-abeta component of Alzheimer's disease amyloid, and N-terminal fragments thereof, correlates to formation of beta-sheet structure and fibrils.

Synucleins are small proteins that are highly expressed in brain tissue and are localised at presynaptic terminals in neurons. alpha-Synuclein has been identified as a component of intracellular fibrillar protein deposits in several neurodegenerative diseases, and two mutant forms of alpha-synuclein have been associated with autosomal-dominant Parkinson's Disease. A fragment of alpha-synuclein has also been identified as the non-Abeta component of Alzheimer's Disease amyloid. In this review we describe some structural properties of alpha-synuclein and the two mutant forms, as well as alpha-synuclein fragments, with particular emphasis on their ability to form beta-sheet on ageing and aggregate to form amyloid-like fibrils. Differences in the rates of aggregation and morphologies of the fibrils formed by alpha-synuclein and the two mutant proteins are highlighted. Interactions between alpha-synuclein and other proteins, especially those that are components of amyloid or Lewy bodies, are considered. The toxicity of alpha-synuclein and related peptides towards neurons is also discussing in relation to the aetiology of neurodegenerative diseases.

Deletion of complement factor H-related genes CFHR1 and CFHR3 is associated with atypical hemolytic uremic syndrome.

Atypical hemolytic uremic syndrome (aHUS) is associated with defective complement regulation. Disease-associated mutations have been described in the genes encoding the complement regulators complement factor H, membrane cofactor protein, factor B, and factor I. In this study, we show in two independent cohorts of aHUS patients that deletion of two closely related genes, complement factor H-related 1 (CFHR1) and complement factor H-related 3 (CFHR3), increases the risk of aHUS. Amplification analysis and sequencing of genomic DNA of three affected individuals revealed a chromosomal deletion of approximately 84 kb in the RCA gene cluster, resulting in loss of the genes coding for CFHR1 and CFHR3, but leaving the genomic structure of factor H intact. The CFHR1 and CFHR3 genes are flanked by long homologous repeats with long interspersed nuclear elements (retrotransposons) and we suggest that nonallelic homologous recombination between these repeats results in the loss of the two genes. Impaired protection of erythrocytes from complement activation is observed in the serum of aHUS patients deficient in CFHR1 and CFHR3, thus suggesting a regulatory role for CFHR1 and CFHR3 in complement activation. The identification of CFHR1/CFHR3 deficiency in aHUS patients may lead to the design of new diagnostic approaches, such as enhanced testing for these genes.

Genetic variants of complement factor H gene are not associated with premature coronary heart disease:A family-based study in the Irish population

Background: The complement factor H (CFH) gene has been recently confirmed to play an essential role in the development of age-related macular degeneration (AMD). There are conflicting reports of its role in coronary heart disease. This study was designed to investigate if, using a family-based approach, there was an association between genetic variants of the CFH gene and risk of early-onset coronary heart disease. Methods: We evaluated 6 SNPs and 5 common haplotypes in the CFH gene amongst 1494 individuals in 580 Irish families with at least one member prematurely affected with coronary heart disease. Genotypes were determined by multiplex SNaPshot technology. Results: Using the TDT/S-TDT test, we did not find an association between any of the individual SNPs or any of the 5 haplotypes and early-onset coronary heart disease. Conclusion: In this family-based study, we found no association between the CFH gene and early-onset coronary heart disease. © 2007 Meng et al; licensee BioMed Central Ltd.

Further assessment of the complement component 2 and factor B region associated with age-related macular degeneration

PURPOSE. Polymorphic variation in genes involved in regulation of the complement system has been implicated as a major cause of genetic risk, in addition to the LOC387715/HTRA1 locus and other environmental influences. Previous studies have identified polymorphisms in the complement component 2 (CC2) and factor B (CFB) genes, as potential functional variants associated with AMD, in particular CFB R32Q and CC2 rs547154, both of which share strong linkage disequilibrium (LD). METHODS. Data derived from the HapMap Project were used to select 18 haplotype-tagging SNPs across the extended CC2/ CFB region for genotyping, to measure the strength of LD in 318 patients with neovascular AMD and 243 age-matched control subjects to identify additional potential functional variants in addition to those originally reported. RESULTS. Strong LD was measured across this region as far as the superkiller viralicidic activity 2-like gene (SKIV2L). Nine SNPs were identified to be significantly associated with the genetic effect observed at this locus. Of these, a nonsynonymous coding variant SKIV2L R151Q (rs438999; OR, 0.48; 95% confidence interval [CI], 0.31- 0.74; P < 0.001), was in strong LD with CFB R32Q, rs641153 (r2 = 0.95) and may exert a functional effect. When assessed within a logistic regression model measuring the effects of genetic variation at the CFH and LOC387715/HTRA1 loci and smoking, the effect remained significant (OR, 0.38; 95% CI, 0.22- 0.65; P < 0.001). Additional variation identified within this region may also confer a weaker but independent effect and implicate additional genes within the pathogenesis of AMD. CONCLUSIONS. Because of the high level of LD within the extended CC2/CFB region, variation within SKIV2L may exert a functional effect in AMD. Copyright © Association for Research in Vision and Ophthalmology.