CFH Y402H polymorphism and the complement activation product C5a: effects on NF-κB activation and inflammasome gene regulation

Background/aims The Y402H polymorphism in the complement factor H (CFH) gene is an important risk factor for age-related macular degeneration (AMD). Complement activation products and proinflammatory cytokines are associated with this polymorphism at the systemic level, but less is known of the associations in the outer retina of the genotyped eye. Here we investigate complement activation products and their role in nuclear factor (NF)-kappa B activation and gene expression of the NLRP3 inflammasome pathway. Methods Postmortem donor eyes were genotyped for the CFH Y402H polymorphism and assessed for complement C3a, C5a, interleukin (IL)-18 and tumour necrosis factor (TNF)-alpha. ARPE19 cells were stimulated basolaterally with C5a or TNF-alpha in polarised cultures. NF-kappa B activation was assessed with a reporter cell line. Gene expression of inflammasome-related (NLRP3, caspase-1, IL-1 beta and IL-18) and classic inflammatory (IL-6 and IL-8) genes was studied. The distribution of inflammasome products, IL-1 beta and IL-18, was studied in postmortem donor eyes with AMD pathologies. Results Eyes with the homozygous at-risk variant demonstrated higher levels of C5a, IL-18 and TNF-alpha in Bruch's membrane and choroid. C5a promoted NF-kappa B activation and upregulation of IL-18 in polarised ARPE19. TNF-alpha promoted NF-kappa B activation and gene expression of caspase-1, IL-1 beta, IL-18, IL-6 and IL-8, but downregulated NLRP3. In eyes with geographic atrophy, strong immunoreactivity was observed for inflammasome products IL-1 beta and IL-18 compared with age-matched controls. Conclusion The at-risk polymorphism of the CFH Y402H may contribute to AMD disease process through increased complement and NF-kappa B activation, and the upregulation of IL-18, a product of inflammasome activation.