Asthma - Chronic Inflammation And Free Radicals

In addition to increased airway reactivity, the lungs of an asthmatic are usually chronically inflamed. Even when we microscopically examine an asthmatic's lungs between attacks, we find inflammatory cells surrounding the airways. An inflammatory cell works with the immune system to fight infection and tissue injury. There are various types of inflammatory cells, including eosinophils, lymphocytes, mast cells, macrophages, and neutrophils. They release chemicals such as histamine, prostaglandins, bradykinin, interferon, and endothelin-1 that work together to kill fungi, bacteria, and viruses. Perhaps the most important cells in asthma are the T cells (T lymphocytes), especially the CD4+ Th2 subset, which researchers say plays a pivotal role in the immune system abnormalities seen in asthma. Researchers believe that a shift in the balance from Thl to Th2 is a leading cellular mechanism in asthma, because increased Th2 levels result in elevated levels of leukotrienes, prostaglandin E2, and certain inter-leukins—chemical mediators known to initiate and perpetuate inflammation and asthma.

 

Most of these chemicals, besides killing germs, are known to be potent instigators of bronchoconstriction. For reasons that remain poorly understood, asthmatic lungs are chronically on the defensive, always ready to fight and release these inflammatory mediators at the slightest provocation. Ironically, the same cells that are intended to protect us can actually cause harm in the asthmatic.

 

This is how the immune response works: A bacterium enters the lungs and is recognized by the immune system. The immune system sounds the alarm for the inflammatory cells to come rushing in to release chemicals and free radicals that kill the invading bacteria. Free radicals are highly reactive oxygen molecules that cause such profound damage to the germ that it dies. Free radicals are used by our immune system to kill invading organisms.

 

The only problem is that when these free radicals are released, they kill not only the invading organism but also some surrounding normal tissue, a kind of shotgun approach to healing. Usually, this is not a problem since only a tiny amount of healthy tissue is damaged and the body can repair itself. Then, after the bug is killed, the inflammatory cells calm down and the immune system returns to normal. Sure, a few inflammatory cells will remain to watch the fort, but after the battle is over most of the cells depart.

 

In asthmatics, these inflammatory cells never calm down and stay in the lung. Even worse, they continue as if the fight isn't over, spewing out toxic chemicals and free radicals that damage the lungs. Like toxic chemicals, free radicals are potent bronchoconstrictors and there is evidence that the free radicals produced by asthmatics are more reactive than normal. One French study concluded, "there was a significant correlation between the overall severity of asthma and the amount of reactive species of oxygen generated." So what you have in the asthmatic is a state of chronic inflammation that promotes bronchoconstriction.

 

Chronic inflammation and tissue damage makes water enter the lungs. This is called pulmonary edema. The more water in the lungs, the more narrow the airways become and the greater the airway obstruction. Add to this the fact that inflammatory cells tend to recruit more inflammatory cells and you have a self-perpetuating cycle of airway inflammation, tissue damage, and edema. Making matters worse, these chemicals cause the lungs to make more mucus that, in turn, further obstructs the airway.

 

These chemicals and free radicals also gang up on the cells that line the airways, the epithelial cells. The epithelium is designed to protect the lungs; however, in asthma, the epithelium gets tricked by the inflammatory cells into thinking the lung is under attack and releases its own chemicals that help perpetuate this vicious cycle. This further damages the airway epithelium, which ultimately falls off, leaving behind raw lung tissue that can no longer defend itself. Doctors suspect that once this protective epithelium is removed, nerve endings are exposed causing the nerves to send panic signals to the rest of the lung, resulting in widespread bronchoconstriction, inflammation, and edema—otherwise known as an asthmatic attack.

 

So, in asthma, there are too many inflammatory cells that, instead of protecting the lungs, actually harm them by constantly generating toxic chemicals and free radicals. These chemicals and free radicals injure the lung's epithelial lining, resulting in both increased airway reactivity and bronchospasm.

 

While all this sounds pretty grim, the good news is that many natural therapies are designed to reduce the state of chronic inflammation. What this means for you is better control of your symptoms. And there's more good news. Free radicals cause lung damage by a mechanism called "oxidative stress." Under normal circumstances, our bodies are able to neutralize this oxidative stress with natural antioxidants like vitamins C and E. In asthma, our natural antioxidant defenses become overwhelmed, ultimately resulting in bronchoconstriction. However, we can boost our antioxidant defenses naturally through diet and supplements, breaking this cycle.