Oxidative stress in retinal pigment epithelial cells increased endogenous complement-dependent inflammatory and angiogenic responses - independent from exogenous complement sources
Oxidative stress-induced damage of the retinal pigment epithelium (RPE) together with chronic inflammation has been suggested as major contributors to retinal diseases. Here, we examine the effects of oxidative stress and endogenous complement components on the RPE and its pro-inflammatory and -angiogenic responses.\n\nThe RPE cell line, ARPE-19, treated with H2O2 reduced cell-cell contacts, increased marker for epithelial-mesenchymal transition but showed less cell death. Stressed ARPE-19 cells increased the expression of complement receptors CR3 and C5aR1. CR3 was co-localized with cell-derived complement protein C3, which was observed in its activated form in ARPE-19 cells. C3 as well as its regulators CFH and properdin accumulated in ARPE-19 cells after oxidative stress independent from external complement sources. This cell-associated complement accumulation promoted nlrp3 and foxp3 expression and subsequent increased secretion of pro-inflammatory and pro-angiogenic factors. The complement-associated ARPE-19 reaction to oxidative stress, independent from external complement source, was increased by the PARP-inhibitor olaparib.\n\nOur results indicated that RPE cell-derived complement proteins and receptors are involved in RPE cell homeostasis following oxidative stress and should be considered as targets for treatment developments for retinal degeneration.\n\nO_FIG O_LINKSMALLFIG WIDTH=160 HEIGHT=200 SRC=\"FIGDIR/small/722470v1_ufig1.gif\" ALT=\"Figure 1\">\nView larger version (79K):\norg.highwire.dtl.DTLVardef@9b5cddorg.highwire.dtl.DTLVardef@1edd562org.highwire.dtl.DTLVardef@15415eborg.highwire.dtl.DTLVardef@16b0a72_HPS_FORMAT_FIGEXP M_FIG GRAPHICAL ABSTRACT C_FIG We show a functional link between oxidative stress, complement receptors, endogenous complement proteins, pro-angiogenic and -inflammatory responses in ARPE-19 cells. These effects are independent from extracellularly added complement proteins or receptor ligands. We suggest an oxidative stress-associated autocrine mechanism of complement receptor regulation in ARPE-19 cells in connection with upregulated intracellular proteases.\n\nHIGHLIGHTSO_LIOxidative stress accumulates complement proteins and receptors in RPE cells\nC_LIO_LIOxidative stress activates the RPE inflammasome without external complement proteins\nC_LIO_LIOxidative stress increases foxp3 expression and IL-8/VEGF secretion in RPE cells\nC_LIO_LIOlaparib enhances pro-inflammatory response of RPE\nC_LI