Toxoplasma gondii Infection Potentiates Cognitive Impairments of Alzheimer's Disease in the BALB/c Mice

Hossein Mahmoudvand, Lorestan University of Medical Sciences and Vahid Sheibani, Kerman University of Medical Sciences and Saeideh Shojaee, Tehran University of Medical Sciences and Seyed Reza Mirbadie, Tehran University of Medical Sciences and Hossein Keshavarz†, Tehran University of Medical Sciences and Khadijeh Esmaeelpour, Kerman University of Medical Sciences and Ali Reza Keyhani, Kerman University of Medical Sciences and Naser Ziaali, Kerman University of Medical Sciences (2016) Toxoplasma gondii Infection Potentiates Cognitive Impairments of Alzheimer's Disease in the BALB/c Mice. Journal of Parasitology.

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Abstract

ABSTRACT: This study tests the hypothesis that in chronic Toxoplasma gondii infection communication among immune cells promotes neuroinflammation through cytokine networks and potentiate cognitive impairments in BALB/c mice with Alzheimer’s disease (AD). The animal model of Toxoplasma infection was established by the intraperitoneal inoculation of 20–25 tissue cysts from the Tehran strain of T. gondii. We injected amyloid-beta 1–42 peptide (Ab1–42, 1 and 2 ll) into the hippocampus of BALB/c mice to establish an animal model of AD. The behavioral experiments such as spatial learning and memory were performed using the Morris water maze test. The mRNA levels of TNF-a, IL-1b, IFN-c, and inducible nitric oxide synthase (iNOS) were examined by real-time PCR. We found that T. gondii infection caused AD-like symptoms and impaired learning and memory functions of the infected BALB/ c mice. We also found that in Toxoplasma infection þ Ab1–42 (1 ll) group, T. gondii infection could potentiate AD in infected mice receiving subdoses of Ab1–42 (1 ll) and caused considerable impairment in learning and memory functions similar to AD group. Comparison of the results demonstrated that mRNA levels of IL-1b, TNF-a, IFN-c, and iNOS significantly (P , 0.001) increased in T. gondii þ Ab1–42 (1 ll) in comparison with the other tested groups. The obtained results showed that chronic T. gondii infection communication among immune cells promotes neuroinflammation through cytokine networks and induces pathological progression of AD in the mice brain, whereas the presence of neuroanatomical Toxoplasma tissue cysts in the brain could also affect the behavioral functions in T. gondii–infected mice.

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