Abnormalities of neurotransmitter and neuropeptide systems in human neuroepithelioma cells infected by three Toxoplasma strains

Since Toxoplasma gondii can establish a persistent infection in the central nervous system in humans, we studied its effects on a host's neurotransmitter and neuropeptide systems (NNS). Using microarray technology, we have screened the expression of genes coding for NNS in human neuroepithelioma cells in response to representative strains of Toxoplasma to identify potential target genes. Transcripts that displayed expression levels distinct from uninfected controls were examined by RT-PCR and Western blot. Our results indicate the presence of disturbed NNS upon Toxoplasma infection and the extent of this disturbance varies considerably among the three strains. In cells infected by type I strain, three neurotransmitter systems (dopamine, glutamate and serotonin) and two neuropeptides (PROK2 and TAC1) displayed abnormalities relative to controls. Type III infection led to the change of a critical enzyme, TDO2, in the kynurenine pathway. No significant effects of type II infection were found in the NNS. These data may have implications for understanding the pathogenesis and heterogeneity of neurologic disturbances in toxoplasmosis.