Silica-induced NLRP3 inflammasome activation in vitro and in rat lungs

Abstract

RationaleMineral particles in the lung cause inflammation and silicosis. In myeloid and bronchial epithelial cells the inflammasome plays a role in responses to crystalline silica. Thioredoxin (TRX) and its inhibitory protein TRX-interacting protein link oxidative stress with inflammasome activation. We investigated inflammasome activation by crystalline silica polymorphs and modulation by TRX in vitro, as well as its localization and the importance of silica surface reactivity in rats.MethodsWe exposed bronchial epithelial cells and differentiated macrophages to silica polymorphs quartz and cristobalite and measured caspase-1 activity as well as the release of IL-1β, bFGF and HMGB1; including after TRX overexpression or treatment with recombinant TRX. Rats were intratracheally instilled with vehicle control, Dörentruper quartz (DQ12) or DQ12 coated with polyvinylpyridine N-oxide. At days 3, 7, 28, 90, 180 and 360 five animals per treatment group were sacrificed. Hallmarks of silicosis were assessed with Haematoxylin-eosin and Sirius Red stainings. Caspase-1 activity in the bronchoalveolar lavage and caspase-1 and IL-1β localization in lung tissue were determined using Western blot and immunohistochemistry (IHC).ResultsSilica polymorphs triggered secretion of IL-1β, bFGF and HMGB1 in a surface reactivity dependent manner. Inflammasome readouts linked with caspase-1 enzymatic activity were attenuated by TRX overexpression or treatment. At day 3 and 7 increased caspase-1 activity was detected in BALF of the DQ12 group and increased levels of caspase-1 and IL-1β were observed with IHC in the DQ12 group compared to controls. DQ12 exposure revealed silicotic nodules at 180 and 360 days. Particle surface modification markedly attenuated the grade of inflammation and lymphocyte influx and attenuated the level of inflammasome activation, indicating that the development of silicosis and inflammasome activation is determined by crystalline silica surface reactivity.ConclusionOur novel data indicate the pivotal role of surface reactivity of crystalline silica to activate the inflammasome in cultures of both epithelial cells and macrophages. Inhibitory capacity of the antioxidant TRX to inflammasome activation was evidenced. DQ12 quartz exposure induced acute and chronic functional activation of the inflammasome in the heterogeneous cell populations of the lung in associated with its crystalline surface reactivity.Electronic supplementary materialThe online version of this article (doi:10.1186/s12989-014-0058-0) contains supplementary material, which is available to authorized users.

Clofazimine Biocrystal Accumulation in Macrophages Upregulates Interleukin 1 Receptor Antagonist Production To Induce a Systemic Anti-Inflammatory State

“…Intracellular crystals, such as those formed by cholesterol or uric acid, have been implicated in the activation of the NLRP3-Casp 1 inflammasome, which plays a major role in the pathogenesis of chronic inflammatory disorders (14,33,34). The uptake of other nano-and microparticles has also been reported to cause inflammasome activation in macrophages (35)(36)(37). Therefore, to assess whether the bioaccumulation of CFZ crystals leads to activation of the inflammasome, we measured and compared cleaved Casp 1 and IL-1␤ in organs that bioaccumulate CFZ-i.e., the liver, spleen, and lungs-and kidneys, that do not accumulate CFZ, after 2 and 8 weeks of either CFZ or control treatment.…”

“…Of noteworthy significance, the formation and accumulation of cholesterol monohydrate and monosodium urate crystals have been implicated in the pathogenesis of chronic inflammatory diseases, such as atherosclerosis, nonalcoholic steatohepatitis (NASH) (34), and gout (43). Moreover, other artificial nano-and microparticles, such as silica crystals (37), aluminum salt crystals (44), silver nanoparticles (35), poly(lactide-co-glycolide) (PLG), and polystyrene microparticles (36), have also been reported to cause inflammasome activation in macrophages. At the cellular level, the aforementioned particles or crystals are known to augment Toll-like receptor signaling and activate the NLRP3 inflammasome via lysosomal destabilization, which leads to Casp 1 activation and the production of cleaved IL-1␤ (13,14).…”

Phagolysosome acidification is required for silica and engineered nanoparticle-induced lysosome membrane permeabilization and resultant NLRP3 inflammasome activity

“…Therefore, after the protein corona is removed, this would support the notion that specific physiochemical characteristics of the particle would define its LMP-inducing potential. This notion is supported by the fact that altering surface properties of silica and of multiple types of nanoparticles can have profound impacts on their relative toxicity (Morishige et al , 2010; Sohaebuddin et al , 2010; Hamilton et al , 2013; Hamilton et al , 2014; Pavan et al , 2014; Peeters et al , 2014). Alternatively, some studies have directly implicated cathepsin B in LMP (Werneburg et al , 2002; Taha et al , 2005; Jacobson et al , 2013; Brojatsch et al , 2014).…”

Amelioration of particulate matter-induced oxidative damage by vitamin c and quercetin in human bronchial epithelial cells

“…The filters loading samples were cut and surged in Milli-Q water with sonication. To obtain PM 2.5 suspensions, the above suspensions were freeze-dried in vacuum, weighed, and stored at À20 C. The 5 mg PM 2.5 particle supplemented with 1 mL 0.9% physiological saline was blended, treated with ultrasonic oscillation for 20 min, and UV-irradiated over night to inactivate possible contaminating endotoxin, as indicated in the paper of Peeters et al (Peeters et al, 2014). Then 5 mg mL À1 PM 2.5 was stored at 4 C. Prior to use, PM 2.5 suspensions were diluted with sterilized 0.9% physiological saline, surged for 10 min and mixed fully.…”