Brandstetter Carolina, Mohr Lena K M, Latz Eicke, Holz Frank G, Krohne Tim U
Department of Ophthalmology, University of Bonn, Ernst-Abbe-Str. 2, 53127, Bonn, Germany.
J Mol Med (Berl). 2015 Aug;93(8):905-16. doi: 10.1007/s00109-015-1275-1. Epub 2015 Mar 18.
Photooxidative damage and chronic innate immune activation have been implicated in retinal pigment epithelium (RPE) dysfunction, a process that underlies blinding diseases such as age-related macular degeneration (AMD). To identify a potential molecular link between these mechanisms, we investigated whether lipofuscin-mediated phototoxicity activates the NLRP3 inflammasome in RPE cells in vitro. We found that blue light irradiation (dominant wavelength 448 nm, irradiance 0.8 mW/cm(2), duration 6 h) of lipofuscin-loaded primary human RPE cells and ARPE-19 cells induced photooxidative damage, lysosomal membrane permeabilization (79.5 % of cells vs. 3.8 % in nonirradiated controls), and cytosolic leakage of lysosomal enzymes. This resulted in activation of the inflammasome with activation of caspase-1 and secretion of interleukin-1β (14.6 vs. 0.9 pg/ml in nonirradiated controls) and interleukin-18 (87.7 vs. 0.2 pg/ml in nonirradiated controls). Interleukin secretion was dependent on the activity of NLRP3, caspase-1, and lysosomal proteases cathepsin B and L. These results demonstrate that accumulation of lipofuscin-like material in vitro renders RPE cells susceptible to phototoxic destabilization of lysosomes, resulting in NLRP3 inflammasome activation and secretion of inflammatory cytokines. This new mechanism of inflammasome activation links photooxidative damage and innate immune activation in RPE pathology and may provide novel targets for therapeutic intervention in retinal diseases such as AMD.
• Visible light irradiation of lipofuscin-loaded RPE cells activates inflammasome. • Inflammasome activation results from lysosomal permeabilization and enzyme leakage. • Inflammasome activation induces secretion of inflammatory cytokines by RPE cells. • Photooxidative damage by visible light as new mechanism of inflammasome activation. • Novel link between hallmark pathogenetic features of retinal degenerative diseases.
光氧化损伤和慢性先天性免疫激活与视网膜色素上皮（RPE）功能障碍有关，这一过程是年龄相关性黄斑变性（AMD）等致盲疾病的基础。为了确定这些机制之间潜在的分子联系，我们研究了脂褐素介导的光毒性是否在体外激活RPE细胞中的NLRP3炎性小体。我们发现，对装载脂褐素的原代人RPE细胞和ARPE - 19细胞进行蓝光照射（主峰波长448 nm，辐照度0.8 mW/cm²，持续时间6小时）会诱导光氧化损伤、溶酶体膜通透性增加（79.5%的细胞出现，而未照射对照组为3.8%）以及溶酶体酶的胞质泄漏。这导致炎性小体激活，伴有半胱天冬酶 - 1的激活以及白细胞介素 - 1β（未照射对照组为0.9 pg/ml，照射组为14.6 pg/ml）和白细胞介素 - 18（未照射对照组为0.2 pg/ml，照射组为87.7 pg/ml）的分泌。白细胞介素的分泌依赖于NLRP3、半胱天冬酶 - 1以及溶酶体蛋白酶组织蛋白酶B和L的活性。这些结果表明，体外脂褐素样物质的积累使RPE细胞易受溶酶体光毒性破坏，导致NLRP3炎性小体激活和炎性细胞因子的分泌。炎性小体激活的这一新机制将光氧化损伤与RPE病理中的先天性免疫激活联系起来，可能为视网膜疾病如AMD的治疗干预提供新的靶点。
• 对装载脂褐素的RPE细胞进行可见光照射可激活炎性小体。
• 炎性小体激活源于溶酶体通透性增加和酶泄漏。
• 炎性小体激活诱导RPE细胞分泌炎性细胞因子。
• 可见光的光氧化损伤作为炎性小体激活的新机制。
• 视网膜退行性疾病标志性致病特征之间的新联系。
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