Correlation between allergic rhinitis and asthma

Abstract

The concept of the „unified respiratory disease” emphasizes the close connection between the upper and lower respiratory pathways in allergic diseases. The structure and function of the upper and lower respiratory pathways are closely interconnected, forming a single morphofunctional entity. Studies show that allergic rhinitis and asthma share the same inflammatory cells and Th2-type cytokines in nasal and bronchial biopsy samples. Additionally, bronchial challenges can induce inflammation in the nasal area and vice versa, suggesting a close link between the two conditions. The epithelial barrier, through its junctions and constituent proteins, plays an essential role in maintaining homeostasis and protection against external factors, and the complex interactions between these two segments of the respiratory pathways are an important research topic. Tight junctions, adhesion junctions, gap junctions, as well as desmosomes contribute to maintaining epithelial integrity and regulating inflammation. The constituent proteins of these junctions and their interactions play crucial roles in the proper functioning of the epithelial barrier. Respiratory allergens such as dust mites, pollen, pets, and fungi are risk factors for both conditions. Recent studies have highlighted numerous environmental factors capable of compromising epithelial integrity and disrupting its barrier function, including allergens with protease activity. Allergenic proteases from various sources, such as dust mites, pollen, fungi, and kitchen cockroaches, have been identified and characterized. Studies have shown the significant role these allergens play in compromising the integrity of the respiratory epithelium and triggering allergic responses. They can activate specific receptors, inducing inflammation and disrupting the epithelium’s barrier function. For example, proteases from dust mites cleave junctional proteins, promoting allergen transport and triggering the release of proinflammatory cytokines. The same effect is observed with pollen, fungi, and kitchen cockroaches. The proteolytic activity of allergens contributes to sensitization and the progression of allergic diseases. Understanding these mechanisms can guide the development of effective therapeutic strategies for preventing and treating these conditions.