Identifying a reference list of respiratory sensitizers for the evaluation of novel approaches to study respiratory sensitization.

The induction of immunological responses that trigger bio-physiological symptoms in the respiratory tract following repeated exposure to a substance, is known as respiratory sensitization. The inducing compound is known as a respiratory sensitizer. While respiratory sensitization by high molecular weight (HMW) materials is recognized and extensively studied, much less information is available regarding low molecular weight (LMW) materials as respiratory sensitizers. Variability of symptoms presented in humans from such exposures, limited availability of (and access to) documented reports, and the absence of standardized and validated test models, hinders the identification of true respiratory sensitizers. This review aims to sort suspected LMW respiratory sensitizers based on available compelling, reasonable, inadequate, or questionable evidence in humans from occupational exposures and use this information to compose a reference list of reported chemical respiratory sensitizers for scientific research purposes. A list of 97 reported respiratory sensitizers was generated from six sources, and 52 LMW organic chemicals were identified, reviewed, and assigned to the four evidence categories. Less than 10 chemicals were confirmed with compelling evidence for induction of respiratory sensitization in humans from occupational exposures. Here, we propose the reference list for developing novel research on respiratory sensitization.

LPS-induced lung inflammation in marmoset monkeys - an acute model for anti-inflammatory drug testing.

Increasing incidence and substantial morbidity and mortality of respiratory diseases requires the development of new human-specific anti-inflammatory and disease-modifying therapeutics. Therefore, new predictive animal models that closely reflect human lung pathology are needed. In the current study, a tiered acute lipopolysaccharide (LPS)-induced inflammation model was established in marmoset monkeys (Callithrix jacchus) to reflect crucial features of inflammatory lung diseases. Firstly, in an ex vivo approach marmoset and, for the purposes of comparison, human precision-cut lung slices (PCLS) were stimulated with LPS in the presence or absence of the phosphodiesterase-4 (PDE4) inhibitor roflumilast. Pro-inflammatory cytokines including tumor necrosis factor-alpha (TNF-α) and macrophage inflammatory protein-1 beta (MIP-1ß) were measured. The corticosteroid dexamethasone was used as treatment control. Secondly, in an in vivo approach marmosets were pre-treated with roflumilast or dexamethasone and unilaterally challenged with LPS. Ipsilateral bronchoalveolar lavage (BAL) was conducted 18 hours after LPS challenge. BAL fluid was processed and analyzed for neutrophils, TNF-α, and MIP-1ß. TNF-α release in marmoset PCLS correlated significantly with human PCLS. Roflumilast treatment significantly reduced TNF-α secretion ex vivo in both species, with comparable half maximal inhibitory concentration (IC(50)). LPS instillation into marmoset lungs caused a profound inflammation as shown by neutrophilic influx and increased TNF-α and MIP-1ß levels in BAL fluid. This inflammatory response was significantly suppressed by roflumilast and dexamethasone. The close similarity of marmoset and human lungs regarding LPS-induced inflammation and the significant anti-inflammatory effect of approved pharmaceuticals assess the suitability of marmoset monkeys to serve as a promising model for studying anti-inflammatory drugs.

Low cytotoxicity of solid lipid nanoparticles in in vitro and ex vivo lung models.

The aim of this study was to investigate the potential cytotoxicity of solid lipid nanoparticles (SLN) for human lung as a suitable drug delivery system (DDS). Therefore we used a human alveolar epithelial cell line (A549) and murine precision-cut lung slices (PCLS) to estimate the tolerable doses of these particles for lung cells. A549 cells (in vitro) and precision-cut lung slices (ex vivo) were incubated with SLN20 (20% phospholipids in the lipid matrix of the particles) and SLN50 (50% phospholipids in the lipid matrix of the particles) in increasing concentrations. The cytotoxic effects of SLN were evaluated in vitro by lactate dehydrogenase (LDH) and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Vitality of lung slices was controlled by staining with calcein AM/ethidium homodimer 1 using confocal laser scanning microscopy and followed by quantitative image analysis with IMARIS software. A549 cell line revealed a middle effective concentration (EC(50)) for MTT assay for SLN20 of 4080 microg/ml and for SLN50 of 1520 microg/ml. The cytotoxicity in terms of LDH release showed comparable EC(50) values of 3431 microg/ml and 1253 microg/ml for SLN20 and SLN50, respectively. However, in PCLS we determined only SLN50 cytotoxic values with a concentration of 1500 microg/ml. The lung slices seem to be a more sensitive test system. SLN20 showed lower toxic values in all test systems. Therefore we conclude that SLN20 could be used as a suitable DDS for the lung, from a toxicological point of view.