Allergic asthma to Bacillus subtilis enzyme: a model for the effects of inhalable proteins

Laundry detergents and detergent residue after rinsing directly disrupt tight junction barrier integrity in human bronchial epithelial cells

BACKGROUND

Defects in the epithelial barrier have recently been associated with asthma and other allergies. The influence of laundry detergents on human bronchial epithelial cells (HBECs) and their barrier function remain unknown.

OBJECTIVE

We investigated the effects of laundry detergents on cytotoxicity, barrier function, the transcriptome, and the epigenome in HBECs.

METHODS

Air-liquid interface cultures of primary HBECs from healthy control subjects, patients with asthma, and patients with chronic obstructive pulmonary disease were exposed to laundry detergents and detergent residue after rinsing. Cytotoxicity and epithelial barrier function were evaluated. RNA sequencing, Assay for Transposase Accessible Chromatin with high-throughput sequencing, and DNA methylation arrays were used for checking the transcriptome and epigenome.

RESULTS

Laundry detergents and rinse residue showed dose-dependent toxic effects on HBECs, with irregular cell shape and leakage of lactate dehydrogenase after 24 hours of exposure. A disrupted epithelial barrier function was found with decreased transepithelial electrical resistance, increased paracellular flux, and stratified tight junction (TJ) immunostaining in HBECs exposed to laundry detergent at 1:25,000 dilutions or rinse residue at further 1:10 dilutions. RNA sequencing analysis showed that lipid metabolism, apoptosis progress, and epithelially derived alarmin-related gene expression were upregulated, whereas cell adhesion-related gene expression was downregulated by laundry detergent at 1:50,000 dilutions after 24 hours of exposure without substantially affecting chromatin accessibility and DNA methylation.

CONCLUSION

Our data demonstrate that laundry detergents, even at a very high dilution, and rinse residue show significant cell-toxic and directly disruptive effects on the TJ barrier integrity of HBECs without affecting the epigenome and TJ gene expression.

Experiences from occupational exposure limits set on aerosols containing allergenic proteins

Occupational exposure limits (OELs) together with determined airborne exposures are used in risk assessment based managements of occupational exposures to prevent occupational diseases. In most countries, OELs have only been set for few protein-containing aerosols causing IgE-mediated allergies. They comprise aerosols of flour dust, grain dust, wood dust, natural rubber latex, and the subtilisins, which are proteolytic enzymes. These aerosols show dose-dependent effects and levels have been established, where nearly all workers may be exposed without adverse health effects, which are required for setting OELs. Our aim is to analyse prerequisites for setting OELs for the allergenic protein-containing aerosols. Opposite to the key effect of toxicological reactions, two thresholds, one for the sensitization phase and one for elicitation of IgE-mediated symptoms in sensitized individuals, are used in the OEL settings. For example, this was the case for flour dust, where OELs were based on dust levels due to linearity between flour dust and its allergen levels. The critical effects for flour and grain dust OELs were different, which indicates that conclusion by analogy (read-across) must be scientifically well founded. Except for subtilisins, no OEL have been set for other industrial enzymes, where many of which are high volume chemicals. For several of these, OELs have been proposed in the scientific literature during the last two decades. It is apparent that the scientific methodology is available for setting OELs for proteins and protein-containing aerosols where the critical effect is IgE sensitization and IgE-mediated airway diseases.

Allergy risk in an enzyme producing plant: a retrospective follow up study

OBJECTIVE

To investigate the risk of enzyme sensitisation and clinical allergy in workers exposed to enzymes at Novo Nordisk A/S.

METHODS

The study was a retrospective follow up study based on medical history and test data originally collected at routine screenings for enzyme allergy by the Occupational Health Service (OHS) of Novo Nordisk A/S during the period 1970-92. Workers were exposed to proteases, lipases, cellulases, and carboxyhydrases. Medical records of 3815 subjects were registered in the OHS database. According to criteria including possible enzyme exposure, allergy tests at the time of engagement, and participation in the allergy screening programme 1064 were selected for the present study. Outcomes were allergy symptoms, specific IgE test (radioallergosorbent test (RAST)) to enzymes, skin test reactions to common allergens and enzymes, forced expiratory volume in one second (FEV1), and forced vital capacity (FVC). Potential risk factors were smoking habits, workplace, type of job, age, and sex.

RESULTS

Sensitisation occurred to all types of enzymes handled in the plant, most often in production areas and laboratories; 8.8% developed clinical enzyme allergy during the first three years of employment. The risk declined during the period. The frequency of enzyme sensitisation, expressed as RAST values > 0.5 SU, was 36%, and the frequency of significant RAST values > or = 2 SU was 8%. Ranking diagnoses of enzyme allergy by severity, the frequency of asthma was 5.3%, rhinitis 3.0%, and urticaria 0.6%. Half of the cases occurred within the first 15 months of exposure. Smoking was an independent risk factor for clinical enzyme allergy (odds ratio (OR) = 2.3 (95% exact confidence interval (95% CI) 1.4 to 3.9), measurable RAST > or = 0.5 SU (OR = 1.5 (95% CI 1.1 to 2.1)), and RAST > or = 2 SU (OR = 4.5 (95% CI 2.2 to 8.4)). Atopic predisposition at the time of engagement was not a significant risk factor for enzyme allergy. This could be due to various selection mechanisms.