Morphological and Metabolic Features of Brain Aging in Mammals

Brain aging in mammals is characterized by morphological and functional changes of neural cells. Macroscopically, this process leading to progressive cerebral volume loss and functional decline, includes memory and motor neuron defiance and behavioral disorders as well. Morphologically, brain aging is associated with aged neurons and astrocytes, appearing enlarged and flattened, and expressing an enhanced pH-dependent β-galactosidase activity. Multiple mechanisms are considered hallmarks of cellular senescence in vitro. Among them, cell cycle arrest, increased lysosomal activity, telo-mere shortening, oxidative stress and DNA damage. The most common markers for senescence identification were identified in: i) proteins implicated in cell cycle arrest, such as p16, p21, p53 ii) increased lysosomal mass iii) increased reactive oxygen species (ROS) and senescence associated secretory phenotype (SASP) expression. Finally, dys-functional autophagy, a process occurring during aging, contributes to alter brain homeostasis. The aim of this review is to summarize and update the most recent knowledge about brain aging with a comparative approach, where similarities and differences in some mammalian species are considered.