[Mechanism of action of nasal glucocorticosteroids in the treatment of allergic rhinitis. Part 1: Pathophysiology, molecular basis].

Allergic rhinitis (AR) is a common airway disease characterized by mucosal swelling leading to congestion, mucosal hyperreactivity and increased secretions. Inflammatory processes in the mucosa are responsible for most symptoms and are characterized by mucosal remodeling after longer time periods. The early phase response, which is characterized by sneezing, rhinorrhea and nasal congestion, is the response of the sensory nerve terminals and blood vessels in the nasal mucosa to chemical mediators such as histamine, prostaglandins and leukotrienes. Nasal exposure to allergens leads to infiltration of inflammatory cells, such as activated eosinophils and T helper type 2 (TH2) cells, into the nasal mucosa by chemoattractant factors such as cytokines including interleukin 5 (IL-5), chemical mediators including cysLTs and chemokines including eotaxin. Edema of the nasal mucosa develops as a secondary reaction with inflammatory cells. This inflammation, referred to as the late-phase response, develops 6-10 h after allergen challenge and causes prolonged nasal congestion. In addition, a neurogenic mechanism is activated after liberation of substance P and others. Therefore, allergic rhinitis is a complex immunogenic disease that also activates mechanisms of the immune system in general. Antiallergic and antiinflammatory medications such as nasal glucocorticosteroids (nGCS) are thought to be the most effective treatment for controlling the symptoms and inflammatory mechanisms of AR. The antiinflammatory action of nGCS depends on at least two different mechanisms: transactivation and transrepression. Moreover, they regulate immune functions by inducing regulatory cytokines and forkhead box P3 (Foxp3). Foxp3 is of upmost importance as a transcription factor of regulatory t-cells, allowing the inhibition of effector function and proliferation of other CD4+ cells.