Читать книгу Alzheimer's Disease - Michelle Deetken - Страница 12

The natural mechanism of the immune system is activated when a cell is in distress or when foreign invaders are detected. This activation may be beneficial to the cell because either the distress is brought under control and any damage is repaired, or the foreign invaders are captured and eliminated. If the damage is too great, however, the immune system goes into overdrive trying to salvage the cell or group of cells. The term “positive feedback loop” means that over the years, depending on the damage or “oxidative stress,” the immune system grows out of control as it tries to repair the cells. This effort produces even more damage, which causes the immune system to send in more immune molecules, and the cycle repeats over and over again. Numerous hypotheses regard chronic oxidative stress suffered over a lifetime to be a contributing factor in Alzheimer's disease (Sultana, Perluigi, and Butterfield, 2006).

What is oxidation and oxidative stress? An oxidant is a molecule that accepts, or in the case of “free radicals,” steals an electron from another molecule. Oxygen is an oxidant that we see in action all the time. When an apple slice turns brown or butter turns rancid, it is because oxygen has interacted with their cells. When copper gets that green patina or metal turns to rust, you can thank oxygen for those changes. Oxygen is nature's way of breaking things down so that they can decompose—as in the case of rotting fruit. Yet oxygen is vital to the body and brain. The oxygen that we inhale goes from our lungs to the blood stream where it combines with glucose (or other fuels) to produce energy for the whole body, and especially the brain. Most of the time, oxygen metabolizes very efficiently within each of our cells, resulting in a balanced exchange of electrons. These interactions are termed “oxidation” (accepting electrons) and “reduction” (the loss of electrons). The interactions actually happen simultaneously and are a natural process that is necessary to keep the body healthy.