THE ROLE OF SOCIALIZATION AGAINST THE RISK OF SOCIAL ISOLATION ON PROGRESSION OF ALZHEIMER'S DISEASE IN RATS

Abstract

Alzheimer's disease (AD) is a neurodegenerative progressive disease that leads to impairment of memory and cognitive ability. It characterized by progressive degeneration of the hippocampus and cortical neurons. Progression of AD is time dependent and just starts spread spontaneously. There is a lack of data in understanding its progression especially in the presence of modifiable risk factors. Social isolation (SI) represents a major risk factor; it can exacerbate memory deficits and increase the severity of brain neuronal degenerations associated with AD. Rats were divided into 3 main groups (4 subgroups/each). Each of them included 2 socialized and 2 SI groups; rats were examined after 3, 4 or 5 weeks to evaluate the influence of SI and socialization during different stages of AD progression. One of each socialized and SI groups served as control and received saline, while the other served as AD model and received 70mg/kg, IP daily for either 3, 4 or 5 weeks of the experiment. Isolated rats were housed individually in cages covered with black plastic. For all groups, behavioral tests (Swimming and Y-maze), Biochemical brain measurements as AChE, Aβ, Tau, monoamins, inflammatory mediators, oxidative parameters, brain derived neurotrophic factor (BDNF) and DNA fragmentation were measured as well as histopathological changes in different brain regions. Brain neurological damage characterizing AD and/or SI was more severe by time especially in SI-associated AD group; pyknosis and atrophy spread in the hippocampus at 4 week rather than 5 weeks in AD socialized group. These results confirmed by the significant increase in AChE, Aβ, Tau, MDA, TNF-α, IL-1β and DNA fragmentation together with the decrease in SOD, TAC, monoamins and BDNF. Moreover, deficits of learning ability and spatial memory also appear at four week in SI-associated AD group. Social Isolation enhanced the progression of AD in rats as indicated by behavioral, biochemical and histopatholgical alterations. Socialization provided protection against the impact of time dependent neuronal degenerations induced by AD associated with SI condition. Consequently, socialization is a must especially for older people where the incidence and progression of AD increases with isolation.