Toxoplasma against Alzheimer's disease
Toxoplasma (Toxoplasma gondii) is a protozoan parasite infecting humans and animals. People usually become infected with toxoplasma by ingesting oocysts released as part of cat excrement or by eating unroasted meat containing tissue cysts.
At the first stage of infection, the parasite affects intestinal cells, after which it moves through the blood or lymph to various organs and causes the development of acute or chronic inflammatory reactions. In some cases, infection can lead to severe organ damage, however, as a rule, with the normal functioning of the immune system, the pathogen remains latent in the brain tissue and causes the formation of lifelong immunity.
Earlier experiments on rodents have shown that toxoplasma can have an immunosuppressive effect. Researchers from Seoul National University, working under the leadership of Eun-Hee Shin, analyzed the effect of toxoplasma-induced immunosuppression on the pathogenesis and course of Alzheimer's disease on a mouse model of this disease.
The animals were infected with a cyst-forming strain of the parasite, after which the levels of inflammatory mediators (interferon-gamma and nitric oxide) and pro-inflammatory cytokines (interleukin-10 and transforming growth factor-beta), the degree of damage to neurons and the accumulation of beta-amyloid plaques in their brain tissue and/or in microglial cells were assessed. In addition, infected animals and mice of the control group were subjected to behavioral tests. The analysis of the obtained data showed that, despite the stability of the level of interferon-gamma, the concentrations of anti-inflammatory cytokines in the brain tissue of infected animals were significantly lower than the corresponding indicators in animals of the control group. Moreover, there were significantly fewer beta-amyloid plaques in the cortex and hippocampus of the brain of infected animals, and the results of testing their cognitive function were significantly better than the results obtained by uninfected mice. These observations indicate a positive effect of toxoplasma-induced immunosuppression on the pathogenesis and course of Alzheimer's disease in a mouse model.
Unlike previous studies, in which the immunosuppressive effect of toxoplasma was evaluated at the early stages of infection (within 2 months after infection), the authors demonstrated the effects of chronic latent infection at least 6 months after infection.
The authors note that they used a strain of the pathogen with genotype II to infect the animals. Similar strains are registered in almost all cases of human infection, so the data obtained will help specialists understand the relationship between the infectious process caused by toxoplasma and Alzheimer's disease.
Evgeniya Ryabtseva
Portal "Eternal youth" http://vechnayamolodost.ru based on the article by Bong-Kwang Jung et al. Toxoplasma gondii Infection in the Brain Inhibits Neuronal Degeneration and Learning and Memory Impediments in a Murine Model of Alzheimer's Disease, published in the journal PLoS ONE.
23.03.2012