Alzheimer's Disease. Michelle Deetken
Conversely, a very small percentage of oxygen interactions may create an unstable reactive molecule. That instability occurs when a molecule is left with an unpaired electron—known as a “free radical”—during the electron exchange with oxygen. These unstable free radicals steal electrons from the body's healthy molecules in order to balance their electrons and stabilize themselves. These interactions are also called oxidation, but this kind of oxidation is not a balanced, simultaneous exchange of electrons that creates a stable molecule. Instead, the unstable free radical may start a chain reaction, because the molecule from which it stole the electron becomes a new free radical. That new free radical steals an electron from another molecule, and so the chain reaction proceeds. Unfortunately, during the time the molecules are free radicals searching for an electron with which to pair, they cause a great deal of damage to different parts of one or many cells.
Especially hard hit are the cell's lipid membranes. This damage is dangerous because the cell's membrane is its barrier to the extracellular environment. If the oxidation happens inside the cell, its DNA, RNA, lipids, and proteins may also be damaged, having enormous implications for the everyday functioning of the cell. The body does have a defense against these free radicals, and they are antioxidants. Antioxidants give the free radicals the electrons they need in order to stop the radical oxidants from causing more damage and generating more free radicals. “Oxidative stress” is defined as the unbalance between free radical oxidants and antioxidants, favoring the oxidant to the point that exceeds the body's ability to defend itself against such damage. Oxidative stress promotes a host of chronic diseases. Nutrition has a major role to play in oxidative stress, as well.
Oxidants and Antioxidants
A healthy immune system keeps up with normal, reactive oxygen species interactions. It also handles the variety of other reactions that generate free radicals formed normally in cells as they continuously use carbohydrates, fats, and proteins for energy and other normal metabolic functions. Oxygen is not the only molecule that causes oxidation; a number of other factors contribute to the generation of free radicals that come from external sources. The major contributors are environmental contaminants, our modern diet, and the stress of our lifestyles. These external sources may overwhelm the body's natural antioxidant defense system leading to oxidative stress. Even our healthy immune system generates free radicals to combat what it perceives as foreign invaders.
One of many tools the immune system uses is a tactic called “oxidative burst” produced by specialized cells called phagocytes. To kill a bacteria or virus, a phagocyte blasts the invader with many free radicals—called hydroxyl radicals—that are derived from hydrogen peroxide. This blast kills the invader and also sends out hydroxyl radicals that miss the invader. The hydroxyl radicals continue to actively search for an electron with which to pair. These free radicals have the potential to damage healthy cells and tissues if not stopped right away. Fortunately, a healthy immune system can handle these attacks. When we have a cold or flu virus, the symptoms we experience are the result of the immune system fighting back and repairing the damage so that the body can recover.
The brain, however, is different from the rest of the body in that it is highly vulnerable to oxidative damage. This difference is due to the brain's immense energy needs. The brain has a high oxygen consumption as well as a high lipid content and retains relatively few natural antioxidants compared to other organs in the body. Unless ample supplies of antioxidants are continually made available through our diet, the external sources of free radicals can easily overwhelm the brain's defense system, causing unwanted oxidative stress.
In the twenty-first century, we need to consume more antioxidants than we did a hundred years ago because of the many toxic free radical generators that we encounter each day. Cigarette smoke and air pollution are huge free radical generators; pesticides, additives, and preservatives in our food and water supplies also harbor many sources of free radicals. And now we are learning that hazardous chemicals used in the production of food products do not have to be recorded on the ingredient list because they are considered to be “components in a production procedure” by the US Department of Agriculture (USDA). Prime examples are the ammonia in “pink slime” beef and arsenic in fruit juices. It has also been revealed that hazardous chemicals employed in the manufacturing of products that we use are everywhere in our environment—even inside our tissues and cells. Examples are the chemicals bisphenol A (BPA) found in plastics and in the lining of food containers and fire retardants used in clothing, curtains, and upholstered furniture. Cumulative oxidative damage in the brain over a lengthy period of time might activate pathways that lead to cell death (called apoptosis). This process may cause the brain to shrink, which leads to dementia. If oxidative damage does begin in one's twenties, this factor might account for the slow progression of the disease and the later life onset of AD that is not related to genetic factors.
Inflammation—Friend and Foe
The last major player in Alzheimer's disease is the captain of the team: inflammation. Inflammation is an active part of the immune system where the response may vary greatly, depending on the playing field. This team captain is playing to win at any cost because every cell in the whole body depends on the captain for protection. Inflammation is the body's best defense against an enemy, whether it is an injury, an infection, or an invading pathogen. Antioxidants cruising throughout the body are the first line of this defense. They give up their electrons to stop free radicals as part of their job, with new recruits taking over as the used up ones retire. When the system is overwhelmed due to oxidative stress and there are no new antioxidant recruits, damage to the cells occurs. A distress signal is sent out to the immune system. Localized tissue hormones called prostaglandins, which are important to the whole immune system, send out the distress signals. While the remaining antioxidants are working hard to minimize the damage, inflammation is preparing its team by calling on the immune response to examine the damage, help isolate the area, and mobilize immune molecules to the site of the damage. Pro-inflammatory genes are also activated, leading to the release of immune molecules called cytokines, chemokines, and adhesion molecules. Counter regulatory or anti-inflammatory pathways are simultaneously activated to keep the inflammatory response under control. This activation allows repair and healing to take place after the attack. When the inflammatory response is acute, the inflammation will last only a few days, similar to getting a cut or contracting the flu. But low-grade, chronic inflammation may last for several weeks, months, or even years. Chronic inflammation renders the counter anti-inflammatory pathways inadequate in order to control the immune system's response, and repair is never fully completed because of the positive feedback loop. This chronic inflammation may lead to excessive damage to cell membranes, proteins, lipids, DNA, and RNA. The damage may be so severe that it compromises tissue and organ functions as in the cases of arteriosclerosis, arthritis, tumor development, and dementia.
The Amazing Body
To summarize the predicament: oxidation that generates a free radical under normal cell metabolism is controlled naturally by antioxidants and a healthy immune system. External causes of oxidation that have increased over the last hundred years of civilization have taxed the natural antioxidants to the point where oxidative stress has occurred more frequently, damaging neurons in the process. The immune response is activated, inflammation is initiated to repair the injury, and the Aβ protein is increased to assist the damaged neurons to generate new growth. As we age and the AD risk factors causing the immune system and brain metabolism to decline increase, the Aβ peptides are not adequately cleared from the brain and thus cause toxic aggregates. This process causes more damage, more inflammation, and an endless destructive cycle of damage and partial repair. That cycle, among other problems, causes tau to become inoperable, and the cytoskeleton falls apart, resulting in the death of neurons.
Do not despair or believe that there is nothing anyone can do about the damage that might have started in our twenties. The body is amazing. When given the correct tools, it can repair itself and function optimally in a relatively short amount of time. Edgar Cayce's readings indicated that every cell in the body will have been rebuilt over a seven-year period, so you will have a new body every