AICAR suppresses TNF-\u03b1-induced complement factor B in RPE cells

Eun Jee Chung,Lucy H Young,Joan W Miller,Daniel E Maidana,Nikolaos E Efstathiou,Demetrios G Vavvas,Eleni K Konstantinou

doi:10.1038/s41598-017-17744-w

Abstract

Age related macular degeneration is the leading cause of blindness in the developed world. Although its precise cause remains elusive, dysfunction of the retinal pigment epithelium (RPE) and dysregulation of complement have been implicated in its pathogenesis. The goal of this study was to evaluate the role of an AMP-dependent kinase (AMPK) activator, 5-aminoimidazole-4-carboxamide riboside (AICAR), on tumor necrosis factor alpha (TNF-α) induction of complement factor B (CFB) in RPE cells. We found that AICAR inhibited TNF-α-induced CFB expression in ARPE-19 and human primary RPE cells in a dose-dependent fashion. Treatment of cells with dipyridamole, which blocks AICAR cellular uptake abolished these effects. In contrast, the adenosine kinase inhibitor, 5-iodotubericidin, which inhibits the conversion of AICAR to the direct activator of AMPK, ZMP, did not reverse the effects on TNF-α-induced CFB expression, suggesting AMPK-independent effects. Indeed, knockout of AMPK in RPE cells using Clustered Regularly Interspaced Palindromic Repeats (CRISPR)/Cas9 did not abolish the inhibitory effects of AICAR on RPE CFB expression. Collectively, our results suggest that AICAR can suppress TNF-α-induced CFB expression in RPE cells in an AMPK-independent mechanism, and could be used as a therapeutic target in certain complement over-activation scenarios.

Highlights

Age-related macular degeneration (AMD) is the leading cause of irreversible vision loss in individuals over 55 years[1]
Since chronic inflammation and complement dysregulation are known factors associated with AMD development, in the present study we examined the role of Adenosine monophosphate (AMP)-dependent kinase (AMPK) in the regulation of complement factor B (CFB) expression induced by a pro-inflammatory cytokine, TNF-α, in retinal pigment epithelium (RPE) cells
The current study shows the ability of Aminoimidazole-4-carboxamide ribonucleotide (AICAR) to inhibit TNF-α-induced CFB expression in human RPE cells

Summary

Introduction

Age-related macular degeneration (AMD) is the leading cause of irreversible vision loss in individuals over 55 years[1]. Several studies have demonstrated that human RPE cells can synthesize C3, C5, CFH, CFB, factor I, and factor H-related protein (FHL)[10,11] At these local sites of inflammation, inflammatory cytokines, IFN-γ and TNF-α, regulate CFB expression[12,13,14,15]. It has been shown that decreased membrane complement regulators in RPE contributed to RPE damage in AMD and local production of the CFB by the RPE is sufficient to promote laser-induced CNV17,18. Since chronic inflammation and complement dysregulation are known factors associated with AMD development, in the present study we examined the role of AMPK in the regulation of CFB expression induced by a pro-inflammatory cytokine, TNF-α, in RPE cells

Objectives

Methods

Results

Conclusion