Grouping of carbonaceous nanomaterials based on association of patterns of inflammatory markers in BAL fluid with adverse outcomes in lungs.

Carbonaceous nanomaterials (CNMs) are universally being used to make commodities, as they present unique opportunities for development and innovation in the fields of engineering, biotechnology, etc. As technology advances to incorporate CNMs in industry, the potential exposures associated with these particles also increase. CNMs have been found to be associated with substantial pulmonary toxicity, including inflammation, fibrosis, and/or granuloma formation in animal models. This study attempts to categorize the toxicity profiles of various carbon allotropes, in particular, carbon black, different multi-walled carbon nanotubes, graphene-based materials, and their derivatives. Statistical and machine learning-based approaches were used to identify groups of CNMs with similar pulmonary toxicity responses from a panel of proteins measured in bronchoalveolar lavage (BAL) fluid samples and with similar pathological outcomes in the lungs. Thus, grouped particles, based on their pulmonary toxicity profiles, were used to select a small set of proteins that could potentially identify and discriminate between the toxicity profiles associated within each group. Specifically, MDC/CCL22 and MIP-3ß/CCL19 were identified as common protein markers associated with both toxicologically distinct groups of CNMs. In addition, the persistent expression of other selected protein markers in BAL fluid from each group suggested their ability to predict toxicity in the lungs, i.e. fibrosis and microgranuloma formation. The advantages of such approaches can have positive implications for further research in toxicity profiling.

Acute in vitro and in vivo toxicity of a commercial grade boron nitride nanotube mixture.

Boron nitride nanotubes (BNNTs) are an emerging engineered nanomaterial attracting significant attention due to superior electrical, chemical and thermal properties. Currently, the toxicity profile of this material is largely unknown. Commercial grade BNNTs are composed of a mixture (BNNT-M) of ∼50-60% BNNTs, and ∼40-50% impurities of boron and hexagonal boron nitride. We performed acute in vitro and in vivo studies with commercial grade BNNT-M, dispersed by sonication in vehicle, in comparison to the extensively studied multiwalled carbon nanotube-7 (MWCNT-7). THP-1 wild-type and NLRP3-deficient human monocytic cells were exposed to 0-100 µg/ml and C57BL/6 J male mice were treated with 40 µg of BNNT-M for in vitro and in vivo studies, respectively. In vitro, BNNT-M induced a dose-dependent increase in cytotoxicity and oxidative stress. This was confirmed in vivo following acute exposure increase in bronchoalveolar lavage levels of lactate dehydrogenase, pulmonary polymorphonuclear cell influx, loss in mitochondrial membrane potential and augmented levels of 4-hydroxynonenal. Uptake of this material caused lysosomal destabilization, pyroptosis and inflammasome activation, corroborated by an increase in cathepsin B, caspase 1, increased protein levels of IL-1ß and IL-18 both in vitro and in vivo. Attenuation of these effects in NLRP3-deficient THP-1 cells confirmed NLRP3-dependent inflammasome activation by BNNT-M. BNNT-M induced a similar profile of inflammatory pulmonary protein production when compared to MWCNT-7. Functionally, pretreatment with BNNT-M caused suppression in bacterial uptake by THP-1 cells, an effect that was mirrored in challenged alveolar macrophages collected from exposed mice and attenuated with NLRP3 deficiency. Analysis of cytokines secreted by LPS-challenged alveolar macrophages collected after in vivo exposure to dispersions of BNNT-M showed a differential macrophage response. The observed results demonstrated acute inflammation and toxicity in vitro and in vivo following exposure to sonicated BNNT-M was in part due to NLRP3 inflammasome activation.

Performance evaluation of cytometric bead assays for the measurement of lung cytokines in two rodent models.

There is a growing demand for a cost-effective, efficient, and high-throughput method for measuring cytokines. Currently, many studies are using flow cytometric bead-based multiplex assays in the measurement of cytokines. However, limited data are available regarding the performance of these cytometric bead assays versus enzyme-linked immunosorbent assay (ELISA) or correlation with mRNA expression using real time reverse transcriptase-polymerase chain reaction (RT-PCR). In one of our studies, cytometric bead array (CBA) was used to measure inflammatory cytokine protein levels in bronchoalveolar lavage (BAL) samples from mice exposed to welding fume, an inflammatory particulate. The results were then compared to whole lung mRNA levels of the same cytokines measured by real time RT-PCR in the same mouse model. It was found that the trends in cytokine profiles measured via CBA agreed with the whole lung mRNA results. In a separate experiment, we used a rat zymosan infectivity model to induce a pulmonary immunomodulatory response and determined cytokine concentrations in recovered BAL fluid by ELISA and two different types of cytometric bead-based assays, CBA and FlowCytomix (FC). The sample-to-sample correlation was good between ELISA and CBA with correlation coefficient R values of 0.76, 0.66, and 0.92 for rat IFN-gamma, TNF-alpha, and IL-6, respectively. ELISA only correlated significantly with the FC assay for TNF-alpha with R=0.43. Patterns of cytokine response in our rat model also differed among the assays but overall, the ELISA and CBA yielded similar results. For a method-to-method comparison, we assayed supplied cytokine standards from ELISA kits using both ELISA and CBA to determine the R values and found it to be greater than 0.90 for all the cytokines tested. It was found that the ELISA was more sensitive in the low range of the standard curve while the bead assays were capable of detecting higher protein concentrations, which would allow for direct measurement of concentrated samples. There was a lack of agreement between the absolute protein values for the ELISA and flow cytometric bead-based assays; in most cases, the latter method tended to give higher protein concentrations than ELISA. In conclusion, direct comparisons between absolute protein values did not agree among the assays tested in this study, but patterns of cytokine response generally agreed between ELISA and CBA. In the case of the mouse CBA, a companion measurement is recommended if samples with low concentrations of an analyte are reported and extrapolated below sensitivity or zero.