Alzheimer's disease is characterized by the pathognomonic presence of intracellular neuroibrillary tangles containing hyperphosphorylated tau protein and extracellular senile plaques primarily formed by -amyloid. Both the neuroibrillary tangles and the plaques formed by -amyloid 1-42 are the inal result of a chain of events that progressed along with the disease for a long time. Oxidative stress plays a fundamental role among those events as proven by the experiments carried out using animal models. This can be demonstrated since there are studies indicating that, although the formation ofamyloid is inhibited through diferent mechanisms using drugs or speciic antibodies), cognitive deicit is not prevented. In this chapter, we will focus on reviewing the role the chronic state of oxidative stress plays in the development of Alzheimer's disease and how the loss of redox balance induces a vicious cycle that may change normal signaling. As a consequence, there are alterations in multiple metabolic pathways that end up in the formation of hyperphosphorylated tau and insoluble -amyloid, leading to the advance of a progressive neurodegeneration process. This is characterized by neuronal dead, astrocytic changes, microglia activation, and the loss of brain repair.Keywords: oxidative stress, Alzheimer's disease, -amyloid 1-42, ozone, neurodegeneration © 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
. IntroductionDespite a great deal of studies and the eforts of researchers in the ield, the physiopathology of Alzheimer's disease AD) is not yet clear. There is neither an accurate early diagnosis nor an efective treatment that allows the patients to have beter life expectancies [1]. Perhaps one of the most important problems to solve is understand that when the diagnosis is made, the symptoms and the signs of Alzheimer's disease are the result of a long chain of events that took place during an extended period of time and that such symptoms and signs change with time [2].One can assume that intracellular signaling and metabolic changes found during the early stages of the disease are not the same as the ones found at more advanced stages. For this reason, recent postmortem studies fail to completely clarify the physiopathology of this disease.
. Changes at cellular level caused by chronic oxidative stressAcute oxidative stress is reversible and it is present in a number of physiological and pathological mechanisms that are reversible as well. These mechanisms play a defensive role ...