Summary of Epithelial Barrier Dysfunction in Allergic Diseases
Epithelial Barrier Dysfunction in Allergic Diseases | Study Guide
Introduction
This study material summarizes how several common environmental pollutants (particulate matter, nanoparticles, ozone, tobacco and e-cigarettes, allergen-derived enzymes, detergents, and bacteria/viruses) affect human tissues and cellular processes. The focus is on mechanisms, examples, and real-world implications, avoiding detailed coverage of epithelial barrier dysfunction, allergic diseases, microbiome, and microplastics (these are covered elsewhere).
Definition: Environmental pollutant — any physical, chemical, or biological agent present in air, water, soil, or products that can adversely affect human health or ecosystems.
1. Particulate Matter (PM)
What is PM?
- Particulate matter consists of tiny solid or liquid particles suspended in air. Categories often used are PM10, PM2.5, and PM0.1 (ultrafine).
Definition: PM2.5 — particulate matter with aerodynamic diameter less than $2.5\ \mu m$ that penetrates deep into lungs and can enter circulation.
Key mechanisms of harm
- Chemical interactions: Aromatic compounds can adhere to metal oxide-containing PM at lower combustion temperatures, forming surface-stable environmentally persistent free radicals (EPFRs).
- Oxidative stress: EPFR redox cycles generate reactive oxygen species (ROS), triggering antioxidant and inflammatory responses.
- Cellular damage: ROS and PM exposure can cause DNA damage, protein carbonylation, lipid peroxidation, and other molecular injury.
- Immune signaling changes: Exposure can alter cytokine levels (e.g., increased IFN-γ, IL-2, IL-4, IL-6, IL-10) in animal models.
- Lysosomal effects: PM2.5 and PM0.1 can increase lysosomal membrane permeability, promoting oxidative stress and cell death at high doses.
Practical examples and implications
- Urban air with high PM2.5 from traffic and combustion increases respiratory and cardiovascular risks.
- Industrial emissions with incomplete combustion yield EPFR-rich PM; reducing combustion temperature and emissions controls reduces EPFR formation.
2. Nanoparticles (NPs)
What are nanoparticles?
- Particles with sizes from $1$ to $100\ \text{nm}$ used in many products (e.g., TiO2, SiO2) as additives in food, cosmetics, paints, and catalysts.
Definition: Nanoparticle — engineered or incidental particle with dimensions in the nanometer scale, often exhibiting unique surface and biological interactions.
Mechanisms of interaction and harm
- Membrane interactions: High affinity for lipids leads to encapsulation and disruption of phospholipid membranes (pulmonary surfactant and cell membranes).
- Lysosomal destabilization: NPs can compromise lysosomal membrane stability and trigger cell death pathways.
- Inflammatory signaling: Certain NPs (e.g., needle-like TiO2) stimulate release of pro-inflammatory cytokines such as IL-1α, IL-1β, IL-6, TNF-α, IL-8.
- Neurotrophic pathway effects: TiO2-NP can dysregulate immature neurotrophic factors via $p75NTR$ signaling, promoting apoptosis in epithelial cells.
- Gastrointestinal uptake: NPs accumulate on intestinal epithelial surfaces and M cells; endocytosis can increase paracellular permeability and lead to leakage.
Real-world applications and risks
- Sunscreens and cosmetics commonly contain TiO2 nanoparticles; inhalation exposure (e.g., powders or spray forms) carries greater risk than topical use when formulated safely.
- Food and drug formulations using nanoparticle carriers must evaluate uptake, lysosomal effects, and inflammatory potential.
3. Ozone (O3)
What is ozone in this context?
- Ozone is a triatomic oxygen molecule with strong oxidizing properties. Ground-level ozon
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Environmental Pollutants Overview
Klíčová slova: Epithelial barrier dysfunction in allergic diseases, Epithelial barrier dysfunction in respiratory and allergic diseases, Allergic diseases, Microbiome, Environment, Microplastics
Klíčové pojmy: Particulate matter forms EPFRs that generate ROS and cause DNA, protein, and lipid damage., Nanoparticles disrupt lipid membranes, destabilize lysosomes, and provoke pro-inflammatory cytokine release., Ozone generates ROS, induces IL-1α and IL-33, and causes acute respiratory injury and remodeling., Cigarette smoke and e-cigarette aerosols increase tissue permeability and alter gene/protein expression., Allergen-derived proteases cleave host proteins and activate protease-activated receptors, triggering immune signals., Detergents can damage membranes, raise transepidermal water loss, and disrupt surface interactions., Bacterial toxins and viral products target adhesion proteins and cytoskeletal elements, increasing permeability., Mitigation strategies: reduce exposure, use filtration and PPE, choose low-emission products, and implement occupational controls.