Why Freshwater Hydra Does Not Get Alzheimer’s Disease

The history of research into the fundamental mechanisms of the pathogenesis of Alzheimer’s disease (AD) is briefly reviewed. Concepts in which a decisive role in the development of this disease was attributed to aluminum or free radicals are analyzed. The lack of reliable data to date to support these concepts is highlighted. The author’s point of view is stated, according to which almost all the results indicating the advisability of using antioxidants (as well as other potential drugs for AD) for the prevention and treatment of AD were obtained in model animals with certain pathologies (for example, with severe oxidative stress), which contribute to the formation of symptoms similar to those of AD in humans. In this regard, parallels with experimental gerontological work aimed at studying the effect of calorie-restricted nutrition on aging and life span are drawn. It is noted that these studies also used animals that were either not completely normal or were in unfavorable conditions. According to the author, the lack of serious success in the development of effective geroprotectors or drugs for the prevention/treatment of AD is due to the ignorance by most specialists of the principles of classical gerontology, in particular, the definitions of aging and age-related diseases, as well as correct approaches to the selection of control objects for their studies. It is emphasized that humans, unfortunately, cannot use the freshwater hydra method to combat aging and age-related diseases. Under certain conditions, it continuously renews all cells (including nerve cells) of its body and thereby ensures its “immortality.” In humans, replacing “old” neurons can lead to loss of personality/individuality, and “repairing” these cells seems impossible today. In this regard, the author considers it advisable to conduct studies of the aging of postmitotic cells in experiments on stationary cell cultures, which can accelerate, in particular, elucidation of the mechanisms of accumulation of beta-amyloid and senile pigments, such as lipofuscin, in neurons. The need to conduct clinical studies of AD as complementary to experimental work is noted, although the former are much more expensive and time-consuming. Only confirmation in human studies of the effectiveness of drugs developed in experiments on model animals will allow them to be recommended for clinical use.