Can Toxoplasma gondii Pave the Road for Dementia?

Area of Science:

• Neuroimmunology
• Infectious Diseases
• Neuropathology

Background:

• Dementia is a significant neurological disorder with complex pathogenesis.
• A potential link exists between *Toxoplasma gondii* (*T. gondii*) infection and dementia.
• The impact of chronic *T. gondii* infection on neuronal receptors like IGF-1R is not fully understood.

Purpose of the Study:

• To investigate the effect of the anti-*Toxoplasma* immune response on Insulin-like Growth Factor-1 Receptor (IGF-1R) expression in chronic cerebral toxoplasmosis.
• To explore the correlation between *T. gondii* cyst distribution, TNF-α levels, NF-κβ expression, and IGF-1R abundance in infected mice.

Main Methods:

• Utilized a mouse model infected with the low virulent ME-49 *T. gondii* strain.
• Assessed *T. gondii* cyst distribution, serum levels of Tumor Necrosis Factor-alpha (TNF-α), in situ expression of Nuclear Factor-kappa B (NF-κβ), and IGF-1R.
• Performed correlational analyses between measured parameters.

Main Results:

• Elevated serum TNF-α levels (p ≤ 0.004) and increased NF-κβ expression were observed in infected mice compared to controls.
• IGF-1R expression was significantly lower (p < 0.05) in infected mice.
• Strong positive correlation between TNF-α and NF-κβ (r ≈ 0.943, p ≈ 0.005); strong negative correlations between TNF-α and IGF-1R (r = -0.584 to -0.725).

Conclusions:

• The activated TNF-α/NF-κβ pathway in chronic cerebral toxoplasmosis controls *T. gondii* but at the expense of IGF-1R expression.
• Reduced IGF-1R may impair neuronal function by limiting the effects of IGF-1, potentially contributing to dementia pathogenesis.
• The immunopathological reaction to *T. gondii* could be a contributing factor in the development of dementia.