背景:流行病学研究表明,沙漠沙尘事件与增加呼吸道发病率和死亡率有关。虽然撒哈拉沙漠是沙漠灰尘的最大来源,在毒理学研究中几乎没有检查过撒哈拉尘埃(SD)。这里,我们旨在评估在先进的气-液界面(ALI)共培养模型中,SD与结晶二氧化硅(DQ12石英)相比,NLRP3炎性小体-caspase-1途径依赖性促炎效能.因此,我们使用体外细胞云系统将肺泡上皮A549细胞和巨噬细胞样分化的THP-1细胞的ALI共培养物暴露于10、21和31µg/cm²SD和DQ12中24小时。此外,我们将含有caspase(CASP)1-/-和NLRP3-/-THP-1细胞的ALI共培养物暴露于SD。
结果:雾化的DQ12和SD的表征显示超过90%的两种粉尘的附聚物小于2.5μm。ALI共培养模型的表征表明,它产生了表面活性蛋白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表面受体分化簇14(CD14),toll样受体2(TLR2),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而不是DQ12上调白细胞介素1β(IL1B)的基因表达,IL6和IL8以及IL-1β的释放,IL-6、IL-8和肿瘤坏死因子α(TNFα)。暴露野生型,CASP1-/-,和NLRP3-/-共培养至SD在所有共培养物中诱导IL1B基因表达,而IL-1β释放仅在野生型共培养物中诱导。在CASP1-/-和NLRP3-/-共培养中,IL-6、IL-8和TNFα释放也减少。
结论:由于表面活性剂可以降低难溶性颗粒的毒性,在这种产生表面活性剂的ALI模型中,SD比DQ12更高的效力强调了易溶SD成分如微生物化合物的重要性。SD比DQ12更高的效力也使SD成为解决急性炎症作用的研究的潜在替代颗粒阳性对照。取决于NLRP3,CASP-1和IL-1β的高促炎效能表明SD引起急性肺损伤,这可能解释了与沙漠粉尘事件相关的呼吸道发病率和死亡率增加。
BACKGROUND: 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.
RESULTS: 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.
CONCLUSIONS: 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.