Dopamine facilitates toxoplasma tachyzoite replication by stimulating D1-like dopamine receptors

Toxoplasma gondii is an obligate intracellular parasite. T. gondii leads to increased production of dopamine in the host's brain. It is possible that dopamine plays a role in the proliferation of T. gondii. In this study, the effect of dopamine on the proliferation of Toxoplasma tachyzoites in HFF-1 cells was investigated.

HFF-1 cells were cultured and treated with 500 nM dopamine. 4 × 105 tachyzoites were added to the cell wells. To investigate the role of receptors, first the confluensed cells were treated with dopamine. Dopamine D1 and D2 receptor antagonists (SCH-23390 and sulpiride, respectively), alone and in combination, were added to the culture medium at a concentration of 10 nM. The treated cells were infected with Tachyzoite. The amounts of tachyzoites were evaluated by microscopic counting and by RT-qPCR method.

Dopamine significantly (p < 0.05) increases proliferation of tachyzoites in HFF-1 cells. SCH-23390 significantly neutralized the effect of dopamine in treated cells (p < 0.05), while sulpiride could not avert the effect of dopamine. Moreover, combination of two antagonists, SCH-23390 and sulpiride, significantly reduced the proliferation of tachyzoites in HFF-1 cells (p < 0.05).

Our study showed that dopamine stimulates proliferation of tachyzoites in HFF-1 cell line. In addition, dopamine exerts its effect on parasite proliferation through D1 receptors. These results can help to design and develop effective drugs against Toxoplasma.