Nevada desert dust with heavy metals suppresses IgM antibody production

Saharan dust induces NLRP3-dependent inflammatory cytokines in an alveolar air-liquid interface co-culture model

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.

Cigarette waste: Assessment of hazard to the environment and health in Riyadh city

Cigarette waste/litter is considered a major environmental contamination problem worldwide as trillions of cigarettes are smoked worldwide and a large part of that, cigarette waste, is disposed of in the open areas including roads, parks, and streets, etc. cigarette litter is the most commonly found litter. It is mainly cigarette filter, made of cellulose acetate, and unburnt part of the tobacco filler. Filters from smoked cigarettes contain a significant amount of tar trapped in it. The tar contains thousands of chemicals and heavy metals. Both of these organic and inorganic constituents have been reported to be toxic to humans and cause a variety of diseases including inflammatory lung diseases, cardiovascular diseases, and cancers. Cigarette litter is a significant environmental concern as the chemicals and heavy metals can leach into the soil or water sources and pose threat to animals and plants, from there they can enter into the food chain as well. Several reports indicate toxicities to aquatic and terrestrial animals as they consumed cigarette litter. In the present investigation, cigarette litter was collected from 28 randomly selected locations in the Riyadh city to assess the risk to the environment. Cigarette litter, in the form of cigarette butts, was collected, counted, weighed and analyzed for heavy metal content. Data indicate the presence of a significant amount of cigarette litter on roadsides, streets, and parks in the Riyadh city. However, the investigation had its limitations as it did not focus on the absolute amount of cigarette litter vs the time. It also did not consider the amount of cigarette litter percent in the total waste discarded. The investigation presents the results of the screening of the cigarette litter present on the Riyadh city roads, streets, and parks. The findings raise concerns regarding the hazards the cigarette litter poses to the environment and human health. The investigation sheds the light on this unexplored aspect of smoking-associated issues in the Kingdom of Saudi Arabia.