Asthma trigger
[1] An asthma attack is characterized by an obstruction of the airway, hypersecretion of mucus and bronchoconstriction due to the contraction of smooth muscles around the respiratory tract.
[4] Other studies have also classified asthma triggers into psychological factors, air pollutants, physical activity, allergens and infection.
As an allergen binds to the IgE antibodies on the mast cell surface, clustering and cross-link formation of FceRI takes place.
The Ca2+ level surge results in cytoskeletal rearrangement, allowing exocytosis and degranulation of intracellular granules, thus releasing vasoactive amines and proteases.
[15] Moreover, the elevated Ca2+ level also leads to arachidonic acid enzymatic pathway activation, contributing to the release of lipid mediators.
[16] These lipid mediators, particularly prostaglandins and leukotrienes elicit vasodilation, increased vascular permeability and smooth muscle contraction.
Examples of such triggers of asthma include naturally occurring aeroallergens like house dust mites, animal feces and pollen.
[22] When an asthma patient inhales or come into contact withsuch allergen, mast cells in the airway tract releases vasoactive amines and proteases.
In addition, it may react with macromolecules such as albumin which can induce the production of igE antibodies which can bind to mast cells and lead to hyperresponsiveness of the respiratory tract.
[29] Although the mechanism for such a phenomenon is still unclear, researchers have proposed that as the body gasps for more oxygen during exercise, more cold and dry air is inhaled.
The passage of this cold and dry air causes a loss of moisture from the mucosal membrane of the respiratory tract.
[30][31] Cooling of the respiratory tract may also activate cholinergic receptors, which can induce bronchoconstriction and mucus secretion, further narrowing the airway.
[34] Beta-blocker, or beta-adrenergic antagonists, may also induce bronchial constriction and block the action of other beta-receptor targeted asthmatic drugs, leading to a worsening asthma condition.
[5][43] One of the clinical asthmatic symptoms is shortness of breath due to narrowing of the respiratory tract, caused by mucus plug formation and bronchoconstriction as smooth muscles contract.
[46] In severe complications, as ventilation is impaired, acute respiratory failure may occur due to the inadequate amount of oxygen in the circulatory system.
[7] Another type of treatment for acute asthma attack is immunosuppressive drugs like corticosteroids, which can also alleviate an asthmatic response.
Long term use of certain types of corticosteroids, such as fluticasone propionate may be administered through the pulmonary route to reduce the risk of an asthma attack.
[51][52] Moreover, another option is the use of cromolyn sodium, which can prevent an asthma attack by halting Ca2+ influx, thus preventing mast cell degranulation and subsequent asthmatic complications [53] Other than drugs, an alternative treatment method is de-sensitization, which involves exposure to a well-controlled, small and increasing amounts of specific allergen over a long duration of time.
[54] The rationale is to trigger antigen competition by the development of allergen-specific IgG antibodies, which can reduce to risk of an allergic response.
