Distinct transcriptomic profiles of early-onset atopic dermatitis in blood and skin of pediatric patients.

BACKGROUND: Atopic dermatitis (AD) predominantly affects young children, but our understanding of AD pathogenesis is based on skin and blood samples from long-standing adult AD. Genomic biopsy profiling from early pediatric AD showed significant Th2 and Th17/Th22-skewing, without the characteristic adult Th1 up-regulation. Because obtaining pediatric biopsies is difficult, blood gene expression profiling may provide a surrogate for the pediatric skin signature. OBJECTIVE: To define the blood profile and associated biomarkers of early moderate-to-severe pediatric AD. METHODS: We compared microarrays and reverse transcription polymerase chain reaction (RT-PCR) of blood cells from 28 AD children (<5 years and within 6 months of disease onset) to healthy control blood cells. Differentially expressed genes (DEGs) in blood (fold change [FCH] > 1.2 and false discovery rate [FDR] < 0.05) were then compared with skin DEGs. RESULTS: Eosinophil and Th2 markers (IL5RA, IL1RL1/ST2, HRH4, CCR3, SIGLEC8, PRSS33, CLC from gene arrays; IL13/IL4/CCL22 from RT-PCR) were up-regulated in early pediatric AD blood, whereas IFNG/Th1 was decreased. Th1 markers were negatively correlated with clinical severity (EASI, pruritus, transepidermal water loss [TEWL]), whereas Th2/Th17-induced interleukin (IL)-19 was positively correlated with SCORAD. Although a few RT-PCR-defined immune markers (IL-13/CCL22) were increased in blood, as previously also reported for skin, minimal overlap based on gene array DEGs was seen. CONCLUSION: The whole blood signature of early moderate-to-severe pediatric AD blood cells show predominantly a Th2/eosinophil profile; however, markers largely differ from the skin profile. Given their complementarity, pooling of biomarkers from blood and skin may improve profiling and predictions, providing insight regarding disease course, allergic comorbidity development, and response to systemic medications.

Phosphodiesterase 4 inhibitors.

Historically, drugs available for treating atopic dermatitis (AD) have been limited to topical corticosteroids and topical calcineurin inhibitors, with systemic immunosuppressants and phototherapy reserved for severe AD. Despite their efficacy and infrequent adverse events, phobia about the use of topical steroids and calcineurin inhibitors has limited their use. More targeted options with fewer systemic and cutaneous side effects are needed for treating AD. Phosphodiesterase 4 (PDE4) is involved in the regulation of proinflammatory cytokines via the degradation of cyclic adenosine monophosphate. PDE4 activity is increased in the inflammatory cells of patients with AD, leading to increased production of proinflammatory cytokines and chemokines. Targeting PDE4 reduces the production of these proinflammatory mediators in AD. Both topical and oral PDE4 inhibitors have a favorable safety profile. Crisaborole 2% ointment, a topical PDE4, is now US Food and Drug Administration-approved for children older than 2 years and adults in the treatment of AD. Crisaborole 2% ointment shows early and sustained improvement in disease severity and pruritus and other AD symptoms, with burning and/or stinging upon application as the only related adverse event. Other PDE4 inhibitors are currently in trials with promising efficacy and safety.

Internalization of carbon black and maghemite iron oxide nanoparticle mixtures leads to oxidant production.

The risk of potential human exposure to mixed nanomaterials in consumer, occupational, and medicinal settings is increasing as nanomaterials enter both the workplace and the marketplace. In this study, we investigated the toxicity of mixed engineered carbon black (ECB) and maghemite iron oxide (Fe(2)O(3)) nanoparticles in a cellular system to understand the mechanism of toxicity and potential methods of toxicity mitigation. Lung epithelial cells (A549) were exposed to mixed Fe(2)O(3) and ECB nanoparticles, mixed Fe(2)O(3) and ECB nanoparticles with the addition of L-ascorbic acid, and mixed Fe(2)O(3) and surface-oxidized engineered carbon black (ox-ECB) nanoparticles. The nanoparticles were characterized using transmission electron microscopy, nitrogen adsorption surface area measurement (BET), X-ray diffraction, and surface charge measurement. The carbon black nanoparticles were also characterized with a reductive capacity assay and by X-ray photoelectron spectroscopy (XPS). The cellular uptake of nanoparticles was analyzed via transmission electron microscopy and fluorescence microscopy; the cellular uptake of iron was quantified using inductively coupled plasma mass spectrometry (ICP-MS). Both the MTT assay and the ethidium homodimer and calcein AM live/dead assay were used to measure cellular proliferation and cytotoxicity, respectively. The dichlorofluorescein diacetate (DCFH-DA) assay was used to measure the intracellular generation of reactive oxygen species. Results show that both Fe(2)O(3) and ECB (or Fe(2)O(3) and ox-ECB) were co-internalized in intracellular vesicles. Additionally, after exposure to the mixture of nanoparticles, the amount of acidified lysosomes increased over time. The cellular uptake of Fe(2)O(3) nanoparticles was unaffected by mixing with ECB. Significant oxidant production occurred in cells exposed to mixed Fe(2)O(3) and ECB, but not in cells exposed to mixed Fe(2)O(3) and ox-ECB or in cells exposed to Fe(2)O(3) and ECB with the addition of ascorbic acid. Furthermore, exposure to mixed Fe2O3 and ECB nanoparticles yielded a dose-dependent decrease in the level of cellular proliferation (MTT assay) and a decrease in cellular viability (ethidium homodimer and calcein AM live/dead assay) that were not seen in the Fe(2)O(3) and ox-ECB scenario. The results support the hypothesis that exposure to mixed Fe(2)O(3) and ECB nanoparticles produces oxidants that are mediated by the surface reductive capability of ECB when both particle types are colocalized in acidic cellular compartments. This oxidant production mechanism may lead to oxidative stress, but it can be mitigated by an antioxidant such as ascorbic acid or by surface treatment of the ECB to decrease its surface reductive capacity.

Synergistic effect of co-exposure to carbon black and Fe2O3 nanoparticles on oxidative stress in cultured lung epithelial cells.

BACKGROUND: There is a need to better understand synergism in the biological effects of particles composed of multiple substances. The objective of this study was to determine if the oxidative stress in cultured cells caused by co-exposure to carbon black and Fe2O3 nanoparticles was significantly greater than the additive effects of exposure to either type of particles alone; and to determine a possible cause for such synergistic effect if one was found. Cultured A549 human lung epithelial cells were exposed to (1) carbon black nanoparticles alone, (2) Fe2O3 nanoparticles alone, and (3) both types of particles simultaneously. Protein oxidation, lipid peroxidation, and cellular uptake of Fe in these cells were measured after 25 hours of exposure. The reduction of solubilized Fe3+ by the carbon black nanoparticles was measured separately in a cell-free assay, by incubating the carbon black and the Fe2O3 nanoparticles in 0.75 M sulfuric acid at 40 degrees C and measuring the amount of reduced Fe3+ at different time points up to 24 hours. RESULTS: Cells exposed to carbon black particles alone did not show protein oxidation, nor did the cells exposed to Fe2O3 particles alone, relative to the control. However, cells co-exposed to both carbon black and Fe2O3 particles showed up to a two-fold increase in protein oxidation relative to the control. In addition, co-exposure induced significant lipid peroxidation, although exposure to either particle type alone did not. No significant difference in cellular iron uptake was found between single exposure and co-exposure, when the Fe2O3 dosing concentration was the same in each case. In the cell-free assay, significant reduction of Fe3+ ions by carbon black nanoparticle was found within 2 hour, and it progressed up to 24 hours. At 24 hours, the carbon black nanoparticles showed a reductive capacity of 0.009 g/g, defined as the mass ratio of reduced Fe3+ to carbon black. CONCLUSION: Co-exposure to carbon black and Fe2O3 particles causes a synergistic oxidative effect that is significantly greater than the additive effects of exposures to either particle type alone. The intracellular redox reaction between carbon black and Fe3+ is likely responsible for the synergistic oxidative effect. Therefore elemental carbon particles and fibres should be considered as potential reducing agents rather than inert materials in toxicology studies. Acidified cell organelles such as the lysosomes probably play a critical role in the solubilization of Fe2O3. Further research is necessary to better understand the mechanisms.