Acod1/itaconate axis controls anxiety-like behaviors induced by chronic infection of Toxoplasma gondii in mice.

BACKGROUND

Chronic infection of Toxoplasma gondii (T. gondii) induces the anxiety-like behavior in hosts, which is closely linked to neuroinflammatory processes. Cis-aconite decarboxylase 1 (Acod1) is an enzyme that is responsible for itaconate production in Krebs Cycle. Emerging evidence highlights the Acod1/itaconate axis as a key regulatory node in macrophage immune-metabolic reprogramming. However, its role in infection-induced neurobehavioral alterations remains unclear. Here, we investigated the role of Acod1/itaconate axis in the anxiety induced by T. gondii chronic infection in mice.

METHODS

To assess anxiety-like behaviors, we performed open field test and elevated plus maze test. Transcriptomic alterations and neuroinflammatory responses in the mouse amygdala were profiled via RNA sequencing, immunofluorescence staining, quantitative PCR (qPCR), and western blot. The functional role of the Acod1/itaconate axis was further investigated using Acod1-/- mice. Additionally, the therapeutic potential of dimethyl itaconate (DI), a cell-permeable itaconate derivative, was evaluated in chronically T. gondii-infected mice. The levels of indoleamine 2,3-dioxygenase (IDO), and serotonin (5-hydroxytryptamine, 5-HT) in serum were measured by enzyme-linked immunosorbent assay. Finally, DI's anti-inflammatory mechanism was identified in the microglial cell line BV-2 cells.

RESULTS

Chronic T. gondii infection induced anxiety-like behaviors in mice and triggered the activation of Acod1/itaconate axis in the amygdala. Transcriptomic and histological analyses revealed upregulation of neuroinflammation-related genes, along with microglia activation. Genetic knockout of Acod1 induced the anxiety-like phenotypes, which were rescued by DI administration. Notably, DI treatment conferred both prophylactic and therapeutic benefits, effectively mitigating anxiety induced by infection. Mechanistically, DI suppressed T. gondii-induced M1 polarization in microglia to mitigate neuroinflammation via activating Nrf2 signaling. These events further reduced indoleamine IDO expression, leading to increased 5-HT levels and subsequent amelioration of anxiety-like behavior.

CONCLUSIONS

Our findings demonstrate that the Acod1/itaconate axis plays an important role in regulating anxiety-like behavior by modulating neuroinflammation during chronic T. gondii infection. These results reveal a promising immune-metabolic drug target for treating T. gondii-associated neuropsychiatric conditions.