New Thinking in Pathophysiology
Overactive Immune Response
Asthma is primarily an immunologic process characterized by an overly responsive immune system creating excess inflammation and damage along the bronchial airways. The physiologic abnormalities associated with asthma are not just limited to the airways themselves though. Important immune mediators such as Th1/Th2 imbalance and leukotrienes have been implicated in the asthma state.
Additionally, the autonomic nervous system plays an important role in the development and maintenance of asthma symptoms. B2 receptors responsive to acetylcholine create hyper-reactive smooth airway muscles and in particular the cGMP/cAMP ratio at the cellular level.
Gastrointestinal System and Asthma
Less well known is the contribution of the gastrointestinal system to asthma. In particular, patients demonstrate lower than normal gastric acid levels (hypochlorhydria), dysbiosis (abnormal types and amounts of intestinal bacteria) and increased intestinal permeability (a state which allows the entrance of allergenic food proteins into the blood stream).
Each of these factors contribute to overall gut function that can worsen the asthma state since 70% of the circulating immune system lines the digestive tract. Food, therefore, can stimulate the immune system to behave in more aggressive ways, creating an increased body burden of inflammation. For asthmatics, this can lead to more frequent and intense wheezing episodes.
Understanding the link between the gastrointestinal system and the immune system is still in its infancy, but has already been implicated in auto-immune diseases, endocrine disorders, neurologic processes and even cardiovascular disease. Therefore, the digestive tract is also a potential site of assessment and intervention beyond pulmonary specific treatments alone.
Endocrine System and Asthma
Finally, endocrine abnormalities have also been implicated in asthma. In particular, adrenal function and low production of endogenous anti-inflammatory hormones such as cortisol and dehydroepiandrosterone (DHEA).
The hypothalamic-pituitary-adrenal axis is the primary system through which the human organizes a physiologic stress response. If this system is compromised, the body cannot produce adequate inflammatory hormones, or control inflammation effectively. It is the reason why stress in all forms - physical, emotional, and even spiritual - can precipitate asthma symptoms.