Type I interferon and pattern recognition receptor signaling following particulate matter inhalation

Hepatotoxicity and ALAD Activity Profile for Prediction of NOAEL of Metal Welding Fumes in Albino Rats

Metal fume pollutants of urban Kano, a city of over 10 million people, and widespread metal works have increased exposure with related health effects. Few data on metal fume toxicity and atmospheric levels have been documented in Nigeria and Kano in particular. Hence, the work was aimed at evaluating the metal fume toxicity to laboratory rat species for setting the permissible limit of exposure in urban Kano. The investigation involved the collection of metal welding fumes and subsequent laboratory analysis. Experimental animals were then exposed intratracheally to varying doses of the fumes which were equivalent to normal metal workers' daily routine of 2, 4, and 8 h for 3, 5, 10, and 20 years. Following euthanization, whole blood samples were collected and functions of liver and delta-aminolevunilic acid dehydratase were evaluated in the serum. Exposure to the fumes has caused significant mortality that was observed to be dose-dependent and statistically different (p < 0.05); moreover, the fumes had synergistically affected the functions of liver. In addition, the fumes had increased (statistically) the activity delta-aminolevinilic acid dehydratase. This has indicated that exposure to metal welding fumes being multi-elemental is toxic and had produced mortality at exposure to higher doses of metal welding fumes. It was therefore established from the study that no-observed-adverse-effect level (NOAEL) for metal welding fumes is 25.73 mg with LD₅₀ of 270 mg which corresponds to the metal worker's 4-h shifts daily for 5 years under existing working conditions. It was recommended that regular monitoring should be put in place to limit exposure and extent of engagement in metal works beyond NOAEL levels.

Endotyping asthma related to three different work exposures

BACKGROUND

Work exposures play a significant role in adult-onset asthma, but mechanisms of work-related asthma are not fully elucidated.

OBJECTIVE

We aimed to reveal the molecular mechanisms of work-related asthma associated with flour (FA), isocyanate (IA) or welding fume (WA) exposures and identify potential biomarkers that distinguish these groups from each other.

METHODS

We used a combination of clinical tests, transcriptomic analysis and associated pathway analyses to investigate underlying disease mechanisms of the blood immune cells and the airway epithelium of 61 men.

RESULTS

Compared to the healthy controls, the WA patients had more differentially expressed genes than the FA and IA patients both in the airway epithelia and in the blood immune cells. In the airway epithelia, active inflammation was detected only in WA patients. In contrast, large number of differentially expressed genes were detected in all asthma groups in blood cells. Disease-related immune functions in blood cells were suppressed in all the asthma groups including leukocyte migration and inflammatory responses and decreased expression of upstream cytokines such as TNF and IFNγ. In transcriptome-phenotype correlations, hyperresponsiveness (R∼|0.6|) had the highest clinical relevance and associated with a set of exposure-group specific genes. Finally, biomarker subsets of only 5 genes specifically distinguished each of the asthma exposure group.

CONCLUSIONS

This study provides novel data on the molecular mechanisms underlying work-related asthma. We identified set of 5 promising biomarkers in asthma related to flour, isocyanate and welding exposure to be tested and clinically validated in future studies.

Inhaled particulate matter affects immune responsiveness of human lung phagocytes to mycobacteria

The influence of smoke-derived or air pollution-derived cytoplasmic particulate matter (PM) can be detrimental and can lead to failed lung immunity. We investigated mycobacterial uptake, intracellular replication, and soluble immune-mediator responses of human bronchoalveolar lavage cells (BALCs) loaded with/without PM, to infection with mycobacterial strains. We observed that only BALCs containing PM display an ex vivo phenotypic profile dominated by spontaneous interleukin (IL)-10 production. PM-loaded BALCs retained the ability to phagocytose both Mycobacterium bovis Bacille Calmette Guérin (BCG) and Mycobacterium tuberculosis (M.tb) ΔleuDΔpanCD at equal efficacy as clear non-PM-loaded BALCs. However, immune responsiveness, such as the production of IL-6 (P = 0.015) and tumor necrosis factor-α (TNF)-α (P = 0.0172) immediately post M. bovis BCG infection, were dramatically lower in black BALCs loaded with PM versus clear non-PM-loaded BALCs. By 24 h post infection, differential immune responses to M. bovis BCG between black versus clear BALC waned, and instead, production of IL-6 (P = 0.03) and IL-1α (P = 0.04) by black BALCs was lower versus clear BALCs following M.tb ΔleuDΔpanCD infection. Considering that TNF-α and IL-6 are characterized as critical to host protection against mycobacteria, our findings suggest that BALCs loaded with inhaled PM, display lower levels of antimycobacterial mediators and that the response magnitude differs according to infective mycobacterial strain. Even though this did not translate into altered mycobacterial killing at early time points post infection, the long-term impact of such changes remains to be established.

Association of occupational exposures with ex vivo functional immune response in workers handling carbon nanotubes and nanofibers

The objective of this study was to evaluate the association between carbon nanotube and nanofiber (CNT/F) exposure and ex vivo responses of whole blood challenged with secondary stimulants, adjusting for potential confounders, in a cross-sectional study of 102 workers. Multi-day exposure was measured by CNT/F structure count (SC) and elemental carbon (EC) air concentrations. Demographic, lifestyle and other occupational covariate data were obtained via questionnaire. Whole blood collected from each participant was incubated for 18 hours with and without two microbial stimulants (lipopolysaccharide/LPS and staphylococcal enterotoxin type B/SEB) using TruCulture technology to evaluate immune cell activity. Following incubation, supernatants were preserved and analyzed for protein concentrations. The stimulant:null response ratio for each individual protein was analyzed using multiple linear regression, followed by principal component (PC) analysis to determine whether patterns of protein response were related to CNT/F exposure. Adjusting for confounders, CNT/F metrics (most strongly, the SC-based) were significantly (p < 0.05) inversely associated with stimulant:null ratios of several individual biomarkers: GM-CSF, IFN-γ, interleukin (IL)-2, IL-4, IL-5, IL-10, IL-17, and IL-23. CNT/F metrics were significantly inversely associated with PC1 (a weighted mean of most biomarkers, explaining 25% of the variance in the protein ratios) and PC2 (a biomarker contrast, explaining 14%). Among other occupational exposures, only solvent exposure was significant (inversely related to PC2). CNT/F exposure metrics were uniquely related to stimulant responses in challenged whole blood, illustrating reduced responsiveness to a secondary stimulus. This approach, if replicated in other exposed populations, may present a relatively sensitive method to evaluate human response to CNT/F or other occupational exposures.

Comprehensive gene and pathway analysis of cervical cancer progression

Cervical Cancer is one of the leading causes of cancer-associated mortality in women. The present study aimed to identify key genes and pathways involved in cervical cancer (CC) progression, via a comprehensive bioinformatics analysis. The GSE63514 dataset from the Gene Expression Omnibus database was analyzed for hub genes and cancer progression was divided into four phases (phases I-IV). Pathway enrichment, protein-protein interaction (PPI) and pathway crosstalk analyses were performed, to identify key genes and pathways using a criterion nodal degree ≥5. Gene pathway analysis was determined by mapping the key genes into the key pathways. Co-expression between key genes and their effect on overall survival (OS) time was assessed using The Cancer Genome Atlas database. A total of 3,446 differentially expressed genes with 107 hub genes were identified within the four phases. A total of 14 key genes with 11 key pathways were obtained, following extraction of ≥5 degree nodes from the PPI and pathway crosstalk networks. Gene pathway analysis revealed that CDK1 and CCNB1 regulated the cell cycle and were activated in phase I. Notably, the following terms, 'pathways in cancer', 'focal adhesion' and the 'PI3K-Akt signaling pathway' ranked the highest in phases II-IV. Furthermore, FN1, ITGB1 and MMP9 may be associated with metastasis of tumor cells. STAT1 was indicated to predominantly function at the phase IV via cancer-associated signaling pathways, including 'pathways in cancer' and 'Toll-like receptor signaling pathway'. Survival analysis revealed that high ITGB1 and FN1 expression levels resulted in significantly worse OS. CDK1 and CCNB1 were revealed to regulate proliferation and differentiation through the cell cycle and viral tumorigenesis, while FN1 and ITGB1, which may be developed as novel prognostic factors, were co-expressed to induce metastasis via cancer-associated signaling pathways, including PI3K-Art signaling pathway, and focal adhesion in CC; however, the underlying molecular mechanisms require further research.

Meta-analysis of transcriptomic responses as a means to identify pulmonary disease outcomes for engineered nanomaterials

Background

The increasing use of engineered nanomaterials (ENMs) of varying physical and chemical characteristics poses a great challenge for screening and assessing the potential pathology induced by these materials, necessitating novel toxicological approaches. Toxicogenomics measures changes in mRNA levels in cells and tissues following exposure to toxic substances. The resulting information on altered gene expression profiles, associated pathways, and the doses at which these changes occur, are used to identify the underlying mechanisms of toxicity and to predict disease outcomes. We evaluated the applicability of toxicogenomics data in identifying potential lung-specific (genomic datasets are currently available from experiments where mice have been exposed to various ENMs through this common route of exposure) disease outcomes following exposure to ENMs.

Methods

Seven toxicogenomics studies describing mouse pulmonary responses over time following intra-tracheal exposure to increasing doses of carbon nanotubes (CNTs), carbon black, and titanium dioxide (TiO₂) nanoparticles of varying properties were examined to understand underlying mechanisms of toxicity. mRNA profiles from these studies were compared to the publicly available datasets of 15 other mouse models of lung injury/diseases induced by various agents including bleomycin, ovalbumin, TNFα, lipopolysaccharide, bacterial infection, and welding fumes to delineate the implications of ENM-perturbed biological processes to disease pathogenesis in lungs.

Results

The meta-analysis revealed two distinct clusters—one driven by TiO₂ and the other by CNTs. Unsupervised clustering of the genes showing significant expression changes revealed that CNT response clustered with bleomycin injury and bacterial infection models, both of which are known to induce lung fibrosis, in a post-exposure-time dependent manner, irrespective of the CNT’s physical-chemical properties. TiO₂ samples clustered separately from CNTs and disease models.

Conclusions

These results indicate that in the absence of apical toxicity data, a tiered strategy beginning with short term, in vivo tissue transcriptomics profiling can effectively and efficiently screen new ENMs that have a higher probability of inducing pulmonary pathogenesis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12989-016-0137-5) contains supplementary material, which is available to authorized users.

Transcriptional profiling identifies physicochemical properties of nanomaterials that are determinants of the in vivo pulmonary response

We applied transcriptional profiling to elucidate the mechanisms associated with pulmonary responses to titanium dioxide (TiO2 ) nanoparticles (NPs) of different sizes and surface coatings, and to determine if these responses are modified by NP size, surface area, surface modification, and embedding in paint matrices. Adult C57BL/6 mice were exposed via single intratracheal instillations to free forms of TiO2 NPs (10, 20.6, or 38 nm in diameter) with different surface coatings, or TiO2 NPs embedded in paint matrices. Controls were exposed to dispersion medium devoid of NPs. TiO2 NPs were characterized for size, surface area, chemical impurities, and agglomeration state in the exposure medium. Pulmonary transcriptional profiles were generated using microarrays from tissues collected one and 28 d postexposure. Property-specific pathway effects were identified. Pulmonary protein levels of specific inflammatory cytokines and chemokines were confirmed by ELISA. The data were collapsed to 659 differentially expressed genes (P ≤ 0.05; fold change ≥ 1.5). Unsupervised hierarchical clustering of these genes revealed that TiO2 NPs clustered mainly by postexposure timepoint followed by particle type. A pathway-based meta-analysis showed that the combination of smaller size, large deposited surface area, and surface amidation contributes to TiO2 NP gene expression response. Embedding of TiO2 NP in paint dampens the overall transcriptional effects. The magnitude of the expression changes associated with pulmonary inflammation differed across all particles; however, the underlying pathway perturbations leading to inflammation were similar, suggesting a generalized mechanism-of-action for all TiO2 NPs. Thus, transcriptional profiling is an effective tool to determine the property-specific biological/toxicity responses induced by nanomaterials.

Oxidative stress and reduced responsiveness of challenged circulating leukocytes following pulmonary instillation of metal-rich particulate matter in rats

Welding fume is an exposure that consists of a mixture of metal-rich particulate matter with gases (ozone, carbon monoxide) and/or vapors (VOCs). Data suggests that welders are immune compromised. Given the inability of pulmonary leukocytes to properly respond to a secondary infection in animal models, the question arose whether the dysfunction persisted systemically. Our aim was to evaluate the circulating leukocyte population in terms of cellular activation, presence of oxidative stress, and functionality after a secondary challenge, following welding fume exposure. Rats were intratracheally instilled (ITI) with PBS or 2 mg of welding fume collected from a stainless steel weld. Rats were sacrificed 4 and 24 h post-exposure and whole blood was collected. Whole blood was used for cellular differential counts, RNA isolation with subsequent microarray and Ingenuity Pathway Analysis, and secondary stimulation with LPS utilizing TruCulture technology. In addition, mononuclear cells were isolated 24 h post-exposure to measure oxidative stress by flow cytometry and confocal microscopy. Welding fume exposure had rapid effects on the circulating leukocyte population as identified by relative mRNA expression changes. Instillation of welding fume reduced inflammatory protein production of circulating leukocytes when challenged with the secondary stimulus LPS. The effects were not related to transcription, but were observed in conjunction with oxidative stress. These findings support previous studies of an inadequate pulmonary immune response following a metal-rich exposure and extend those findings showing leukocyte dysfunction occurs systemically.

Transcriptome-wide RNA sequencing analysis of rat skeletal muscle feed arteries. I. Impact of obesity

We employed next-generation RNA sequencing (RNA-Seq) technology to determine the influence of obesity on global gene expression in skeletal muscle feed arteries. Transcriptional profiles of the gastrocnemius and soleus muscle feed arteries (GFA and SFA, respectively) and aortic endothelial cell-enriched samples from obese Otsuka Long-Evans Tokushima Fatty (OLETF) and lean Long-Evans Tokushima Otsuka (LETO) rats were examined. Obesity produced 282 upregulated and 133 downregulated genes in SFA and 163 upregulated and 77 downregulated genes in GFA [false discovery rate (FDR) < 10%] with an overlap of 93 genes between the arteries. In LETO rats, there were 89 upregulated and 114 downregulated genes in the GFA compared with the SFA. There were 244 upregulated and 275 downregulated genes in OLETF rats (FDR < 10%) in the GFA compared with the SFA, with an overlap of 76 differentially expressed genes common to both LETO and OLETF rats in both the GFA and SFA. A total of 396 transcripts were found to be differentially expressed between LETO and OLETF in aortic endothelial cell-enriched samples. Overall, we found 1) the existence of heterogeneity in the transcriptional profile of the SFA and GFA within healthy LETO rats, 2) that this between-vessel heterogeneity was markedly exacerbated in the hyperphagic, obese OLETF rat, and 3) a greater number of genes whose expression was altered by obesity in the SFA compared with the GFA. Also, results indicate that in OLETF rats the GFA takes on a relatively more proatherogenic phenotype compared with the SFA.