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Guangpu Shi, Osato Ogbeifun, Lindsey Nugent, Ignacio Rodriguez, Igal Gery; 7-Ketocholesterol Induces Interleukin(IL)-1 beta and IL-18 Production in RPE Cells via Activation of the Inflammasome. Invest. Ophthalmol. Vis. Sci. 2013;54(15):150.
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7-Ketocholesterol is a form of oxidized cholesterol. It has been found to be associated with lipoprotein deposits in Bruch’s membrane, choriocapillaris, and RPE cells in the primate retina as well as a component of drusen in human eyes affected by AMD. The purpose of this study was to assess whether 7-Ketocholesterol could activate inflammasomes in RPE cells to induce IL-1 beta and IL-18 production.
Primary cultured RPE cells from an eighty-year-old human donor, or ARPE-19 cells, were primed using LPS plus IL-1 alpha for 6 hours, followed by incubation with 7-Ketocholesterol for 16 hours. The production of IL-1 beta and IL-18 was assessed in cell culture supernatant using enzyme linked immunosorbant assay. Total protein extracted from treated ARPE-19 cells was subjected to western blot assay to detect cleaved caspase-1 p20, using ATP treatment as a positive control. Glyburide, an inflammasome inhibitor, was added into cell culture together with 7-Ketocholesterol to confirm signaling pathway involvement.
RPE cells from an eighty-year-old human donor incubated with 10 µM 7-Ketocholesterol produced a considerable amount of IL-1 beta, but a lower amount of IL-18. Treatment with glyburide reduced the release of the IL-1 beta by about 60%, but had no effect on IL-18 production. Incubation of 7-Ketocholesterol with ARPE19 cells produced similar amounts of IL-1 beta and IL-18. Western blot of 7-Ketocholesterol-treated APRE-19 cells showed elevated caspase-1 p20 production to levels similar to those stimulated by ATP-treatment.
7-Ketocholesterol induces IL-1 beta and IL-18 production from RPE cells. Accumulation of 7-Ketocholesterol in drusen of AMD patients may therefore have a pathogenic role in the disease process through the release of the proinflammatory cytokine IL-1 beta and IL-18.
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