Complement Stimulates Retinal Pigment Epithelial Cells to Undergo Pro-Inflammatory Changes

Abstract

Background/Aims: We examined the effect of human complement sera (HCS) on retinal pigment epithelial (RPE) cells with respect to pro-inflammatory mediators relevant in early age-related macular degeneration (AMD). Methods: RPE cells were treated with complement-containing HCS or with heat-inactivated (HI) HCS or C7-deficient HCS as controls. Cells were analysed for C5b-9 using immunocytochemistry and flow cytometry. Interleukin (IL)-6, IL-8, and monocyte chemoattractant protein-1 (MCP-1) were quantified by ELISA and RT-PCR. Tumour necrosis factor-a (TNF-a), intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1), were analysed by Western blotting. The intracellular distribution of nuclear factor (NF)-κB was investigated by immunofluorescence. Results: A concentration-dependent increased staining for C5b-9 but no influence on cell viability was observed after HCS treatment. ELISA and RT-PCR analysis revealed elevated secretion and expression of IL-6, IL-8, and MCP-1. Western blot analysis showed a concentration-dependent increase in ICAM-1, VCAM-1, and TNF-a in response to HCS, and immunofluorescence staining revealed nuclear translocation of NF-κB. Conclusion: This study suggests that complement stimulates NF-κB activation in RPE cells that might further create a pro-inflammatory environment. All these factors together may support early AMD development.

Activation of the ERK1/2-MAPK Signaling Pathway by Complement Serum in UV-POS-Pretreated ARPE-19 Cells

“…HCS stimulation augmented cytokine secretion in both UV-POS-pretreated and non-pretreated ARPE-19 cells, suggesting a general activation of the cells in response to HCS. This is in line with our previous studies, which demonstrated elevated production of the drusen constituent vitronectin by ARPE-19 cells [23], proinflammatory and proangiogenic functional changes of ARPE-19 cells consistent with pathological features of AMD [24], and translocation and thus acti­vation of the proinflammatory key transcription factor NF-κB [32] in response to HCS.…”

“…Among others, ERK1/2 has also been shown to be an upstream activator of the inflammation-associated transcription factor NF-κB [31]. Indeed, we have previously observed NF-κB translocation from the cytosol to the nucleus in RPE cells stimulated with complement serum [32]. Therefore, ERK1/2 may play an important role in regenerative and degenerative processes as well as in the proinflammatory and proangiogenic properties of RPE cells.…”

The complement system in age-related macular degeneration

“…Classical immune cells aside, complement activation can also stimulate the nearby RPE cells into secreting a range of inflammatory cytokines, such as interleukin 6 (IL-6), interleukin 8 (IL-8) and Monocyte Chemotactic Protein 1 (CCL2) [ 107 ] (Fig. 3 ).…”

Complement Inhibitors in Age-Related Macular Degeneration: A Potential Therapeutic Option

“…The most notable consequence of complement activation is that it can mediate the recruitment and activation of immune cells, such as microglia, monocytes/macrophages, lymphocytes, and mast cells, through the release of complement components C3a and C5a [92,93]. In addition to this, complement activation stimulates surrounding RPE cells to secrete a range of inflammatory factors, for instance, monocyte chemotactic protein 1, interleukin 6, and interleukin 8 [94]. Chronic inflammation is a typical ocular change in AMD.…”