Epidemiological studies have related desert dust events to increased respiratory morbidity and mortality. Although the Sahara is the largest source of desert dust, Saharan dust (SD) has been barely examined in toxicological studies. Here, we aimed to assess the NLRP3 inflammasome-caspase-1-pathway-dependent pro-inflammatory potency of SD in comparison to crystalline silica (DQ12 quartz) in an advanced air-liquid interface (ALI) co-culture model. Therefore, we exposed ALI co-cultures of alveolar epithelial A549 cells and macrophage-like differentiated THP-1 cells to 10, 21, and 31 µg/cm² SD and DQ12 for 24 h using a Vitrocell Cloud system. Additionally, we exposed ALI co-cultures containing caspase (CASP)1−/− and NLRP3−/− THP-1 cells to SD. Characterization of nebulized DQ12 and SD revealed that over 90% of agglomerates of both dusts were smaller than 2.5 μm. Characterization of the ALI co-culture model revealed that it produced surfactant protein C and that THP-1 cells remained viable at the ALI. Moreover, wild type, CASP1−/−, and NLRP3−/− THP-1 cells had comparable levels of the surface receptors cluster of differentiation 14 (CD14), toll-like receptor 2 (TLR2), and TLR4. Exposing ALI co-cultures to non-cytotoxic doses of DQ12 and SD did not induce oxidative stress marker gene expression. SD but not DQ12 upregulated gene expressions of interleukin 1 Beta (IL1B), IL6, and IL8 as well as releases of IL-1β, IL-6, IL-8, and tumor necrosis factor α (TNFα). Exposing wild type, CASP1−/−, and NLRP3−/− co-cultures to SD induced IL1B gene expression in all co-cultures whereas IL-1β release was only induced in wild type co-cultures. In CASP1−/− and NLRP3−/− co-cultures, IL-6, IL-8, and TNFα releases were also reduced. Since surfactants can decrease the toxicity of poorly soluble particles, the higher potency of SD than DQ12 in this surfactant-producing ALI model emphasizes the importance of readily soluble SD components such as microbial compounds. The higher potency of SD than DQ12 also renders SD a potential alternative particulate positive control for studies addressing acute inflammatory effects. The high pro-inflammatory potency depending on NLRP3, CASP-1, and IL-1β suggests that SD causes acute lung injury which may explain desert dust event-related increased respiratory morbidity and mortality.

中文翻译：

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撒哈拉尘埃在肺泡气液界面共培养模型中诱导 NLRP3 依赖性炎症细胞因子

流行病学研究表明，沙漠沙尘事件与呼吸道疾病发病率和死亡率增加有关。尽管撒哈拉沙漠是沙漠尘埃的最大来源，但毒理学研究中几乎没有对撒哈拉尘埃（SD）进行检查。在这里，我们的目的是在先进的气液界面 (ALI) 共培养模型中评估 SD 与结晶二氧化硅 (DQ12 石英) 相比的 NLRP3 炎性体 - caspase-1 通路依赖性促炎效力。因此，我们使用 Vitrocell Cloud 系统将肺泡上皮 A549 细胞和巨噬细胞样分化 THP-1 细胞的 ALI 共培养物暴露于 10、21 和 31 µg/cm² SD 和 DQ12 24 小时。此外，我们将含有半胱天冬酶 (CASP)1−/− 和 NLRP3−/− THP-1 细胞的 ALI 共培养物暴露于 SD。雾化 DQ12 和 SD 的表征表明，两种粉尘 90% 以上的团聚物小于 2.5 μm。ALI 共培养模型的表征表明，它产生表面活性蛋白 C，并且 THP-1 细胞在 ALI 中仍然存活。此外，野生型、CASP1−/− 和 NLRP3−/− THP-1 细胞具有相当水平的分化表面受体簇 14 (CD14)、Toll 样受体 2 (TLR2) 和 TLR4。将 ALI 共培养物暴露于非细胞毒性剂量的 DQ12 和 SD 不会诱导氧化应激标记基因表达。SD 但不包括 DQ12 上调白细胞介素 1 Beta (IL1B)、IL6 和 IL8 的基因表达以及 IL-1β、IL-6、IL-8 和肿瘤坏死因子 α (TNFα) 的释放。将野生型、CASP1−/− 和 NLRP3−/− 共培养物暴露于 SD 会诱导所有共培养物中的 IL1B 基因表达，而仅在野生型共培养物中诱导 IL-1β 释放。在 CASP1−/− 和 NLRP3−/− 共培养中，IL-6、IL-8 和 TNFα 的释放也减少。由于表面活性剂可以降低难溶性颗粒的毒性，因此在产生表面活性剂的 ALI 模型中，SD 的效力比 DQ12 更高，这强调了易溶性 SD 成分（例如微生物化合物）的重要性。SD 比 DQ12 更高的效力也使得 SD 成为解决急性炎症效应研究的潜在替代颗粒阳性对照。NLRP3、CASP-1 和 IL-1β 的高促炎效力表明 SD 会导致急性肺损伤，这可能解释沙漠沙尘事件相关的呼吸道发病率和死亡率增加。