The inflammatory process and asthma

Townsend Letter for Doctors and Patients,  May, 2004  by Jason Barker,  Chris Meletis

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Asthma, considered an inflammatory disease process, has demonstrated increasing prevalence in many industrial nations (particularly the United States) in the last 20 years. Among the trends in asthma prevalence are increasing mortality, racial and regional disparities, emergency department visits, and hospitalizations. (1) The 1998 National Health Interview Survey names asthma as one of the most widespread chronic diseases in the United States, with approximately 26 million Americans having been diagnosed with asthma at some point in their respective lifetimes; the survey went on to report an increased mortality of 55.6% while all cause mortality rates decreased by 18%. (2) Undoubtedly, there are numerous causative factors for asthma, ranging from genetic susceptibility to air pollution. Regardless of cause, our understanding of asthma has shifted as well in the last 20 years, namely that asthma is considered a chronic inflammatory condition, rather than a disease that manifests symptoms acutely. Accordingly, the treatment focus for asthma has shifted from treating asthma reactively to preventatively, and chronic long-term use of inhaled corticosteroids comprises the therapeutic mainstay. Despite this change in approach and treatment, increasingly negative statistics continue to manifest.

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Fortunately, the perspectives of "complementary" and "alternative" medicine allow physicians numerous avenues in which to prevent, treat, and cure asthma and its symptoms. A condition with so many different causative factors (heredity, allergic, environmental, nutritional, to name a few) and varied symptomatology between individuals with the condition, must be addressed on an individual basis. Physicians treating asthma today must be aware of the multiple avenues of therapy, and develop a greater focus on addressing causation. Mainstream asthma treatment can be credited with numerous positive aspects, however this method has not yet addressed the increasingly morbid statistics surrounding this condition. True, many of asthma's causative factors are out of the realm of physician management, and greater societal change is needed to force larger issues such as environmental pollution to the forefront of social medical issues. In the meantime, natural medicine-based therapies and the many yields in clinical research of these therapies provide the physician with several tools that often result in a decrease or removal of asthma symptoms.

Pathophysiology

Asthma is defined as a chronic inflammatory disorder of the airways in which several different cells and cellular components take part; among these are mast cells, eosinophils, T-lymphocytes, neutrophils, macrophages, and epithelial cells. Activation of these cells, leading to asthma, results in symptoms of wheezing, shortness of breath, coughing, and chest tightness. Generally, asthma symptoms tend to occur more at night and in the early morning hours. Interestingly, the Traditional Chinese Medicine (TCM) perspective defines 12 'organs' of the body, each having peak hours of activity during which symptoms may arise if an imbalance exists. The lungs are assigned the hours of 3:00 am to 5:00 am in the TCM system. We also know from a Western medicine perspective that peak flow values for the lungs are typically lowest at 4:00 am, and this is also a time when various hormonal patterns begin their shift in advance of the coming day. Exacerbation of asthma occurring in the early morning hours is therefore delineated by both historical/traditional and modern Western medical science and perspectives.

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Bronchial hyperreactivity, that is, the tendency for the smaller airways of the lungs to react by constricting, can be precipitated by a number of factors. Some of the most common examples of this are cold air, air pollution, and typically benign environmental allergens such as dust mite feces and animal dander proteins. On a cellular level, most asthma symptoms are the result of IgE antibodies produced as a result of the immune system's encounter with the aforementioned factors. IgE then binds to specific lymphocytes known as mast cells. Once the foreign antigen makes contact with the IgE-sensitized mast cells, pro-inflammatory cytokines such as histamine and various leukotrienes are released, stimulating bronchial smooth muscle constriction, most often within one hour of exposure to the antigen. In addition to mast cells, eosinophils take part in the asthmatic process by releasing destructive elements such as major basic protein that can directly damage airway epithelial cells, contributing to increased bronchial responsiveness and further mast cell and basophil degranulation. Eosinophils release additional leukotrienes, contributing further to airway constriction, increased vascular permeability (allowing for greater influx of pro-inflammatory immune cells) and further recruitment of additional eosinophils. Presumptively, this scenario was designed to protect the body from foreign proteins that are perceived to be dangerous to the organism. However, in the asthmatic condition, this is an immunologic/inflammatory response that is out of sync with the true protective nature of the immune system. This process can be maintained at various levels on a continuous basis in the lungs of a person with asthma, leading to chronic degenerative changes in the lungs as the tissue is constantly exposed to the destructive nature of the inflammatory immune response. Keeping in mind that this reaction, although well intentioned in view of the immune system's protective role, is in response to harmless substances such as animal dander, pollen, or household dust. Therapy must be directed at two areas; the first being identification and removal or avoidance of the offending substance(s) and secondly, working with the body to quell the idiosyncratic inflammatory response in the lungs. As a side note, asthma is often seen in conjunction with other manifestations of inflammation in the body. Most typically, asthma symptoms are accompanied by allergies and eczema; however the appearance of each is not dependent on the other and may occur in conjunction or separately, depending on the individual state of affairs.