Pathophysiology of Asthma

Abstract

Asthma is a complex disorder causing the narrowing of the lung airways and affects people of all ages but is most prevalent during childhood. The main symptoms involved are wheezing, chest tightness, coughing and shortness of breath. Many cells which include eosinophils, lymphocytes, and mast cells are involved in the pathogenesis of asthma. The present drugs that are used to alleviate asthma symptoms are steroidal that has many side effects. In order to develop most effective and nonsteroidal drugs the path physiology need to be explored at biochemical level. The lipoxygenases and their metabolites could be a potential target for the development of new drugs for the treatment of asthma. In this review, we highlight the various path physiological pathways involved in asthma, which could pave for the discovery of novel drugs. Keywords: Asthma, Lung airways, Wheezing, Lymphocytes, Lipoxygenases. I.INTRODUCTION Asthma is a complex disorder that causes the narrowing of the lung airways leading to wheezing, chest tightness, and shortness of breath and coughing. Asthma affects people of all ages but most often in childhood. Asthma is classified into two types: a) Extrinsic (allergic or atopic asthma) is most common in childhood and accounts for about 75% of asthma cases. It is caused by immune response to inhaled allergens such as pollens, dander's and dust mite particles, b) Intrinsic asthma (non-allergic) predominantly affects people of 30 years of age and accounts for about 10% of all cases. It is triggered by cigarette smoke exposure, aspirin intake, laughter, stress, cold air, food preservatives, exercise and myriad of other factors. Genetic makeup of an individual is one of very common predisposing factors for the development of atopic or extrinsic asthma persons. Atopic asthma is considered as a syndrome due to its various phenotypic characteristics such as airway hyper responsiveness, increased IgE production, goblet cell metaplasia, sub epithelial fibrosis, and airway remodeling. The inhaled steroids are the current most effective therapy for asthma though it is not beneficial to all asthmatic patients and on the other hand treatment itself leads to various intolerable side effects. Asthma is a multi cellular process involving many eosinophils, lymphocytes, and mast cells however eosinophilic infiltration is the striking dominant feature. Among lymphocytes both B and T lymphocytes are having crucial roles by generating IgE mediated humoral and Th2 mediated cellular responses respectively. Imbalance between TH-1 and TH-2 immune response with elevation of TH-2 cytokines such as IL-4, IL-13, IL-5, and IL-9 and decrease in Th1 cytokines such as IL-12 and IFN-gamma is the dominant feature in asthma pathogenesis.Th2 cytokines and macrophages also leads to increase the levels chemokines which are responsible for recruiting and activation of various inflammatory cells such as eosinophils in the airway and those inflammatory cells secrete different proinflammatory mediators such as histamine, leukotrienes to...