الفهرس | Only 14 pages are availabe for public view |
Abstract Asthma is a chronic, heterogeneous disease with symptoms that include wheeze, cough (particularly at night and during exertion), dyspnea, chest tightness, variable airways obstruction and bronchial hyper-responsiveness (BHR). Exercise-induced bronchoconstriction (EIB) is defined as transient narrowing of the airways that follow vigorous exercise. EIB is a common manifestation of asthma in children and adolescents, occurring in up to 90% of asthmatic children. It`s prevelance in general pediatric population is between 6% and 20%. It has been suggested that exercise causes airway narrowing by the loss of water through evaporation, resulting in thermal and osmotic effects of dehydration in the airways. However, the precise mechanism by which increased osmolarity leads to airflow limitation is unknown. It has been proposed that mediators, such as histamine, leukotrienes, and prostanoids, released from the mast cells and epithelial cells in response to a hyperosmolar stimulus may be responsible for the bronchospasm. Lipoxins were the first agents to be identified as antiinflammatory endogenous lipid mediators involved in the resolution of inflammation. They inhibit granulocyte recruitment and activation, cytokine and chemokine production, and biosynthesis of pro-inflammatory lipid mediators, stimulate the clearance of apoptotic leukocytes, and block edema formation. |