Toxoplasma gondii: Effects on Serum Serotonin Concentration and Indoleamine 2, 3-Dioxygenase Expression

Background Toxoplasma gondii is an obligate intracellular protozoan that infects approximately one-third of the global population. Research has increasingly suggested a connection between toxoplasmosis and alterations in behavior. This study aims to investigate the effects of T. gondii infection on serum serotonin levels and the expression of the indoleamine 2, 3-dioxygenase (IDO) gene in the brain cells of Balb/c mice. Methods A total of 72 female Balb/c mice were utilized in this study, with 36 assigned to the experimental group and 36 to the control group. The mice were further divided into six subgroups, each containing six mice. Serum serotonin levels were quantified using the ELISA method, while the expression of the IDO1 gene was assessed through quantitative real-time PCR. Results It is observed that the serotonin serum concentration in the infected Balb/c mice was substantially higher than the non-infected groups on the day 10th (371.17 ± 53.391 vs. 233.50 ± 1.225, p < 0.0001), 20th (283.33 ± 41.707 vs. 233.33 ± 1.033, p < 0.05 ), 30th (269.17 ± 36.766 vs. 233.67 ± 0.516, p < 0.05) and 40th (291.50 ± 62.956 vs. 233.67 ± 1.033, p < 0.05) post-infection, while the serotonin serum was dramatically diminished in the infected groups rather than the control mice on day 60th (197.50 ± 23.998 vs. 233.17 ± 1.472, p < 0.01). Notably, the expression of the IDO1 gene in brain cells increased by 5.65-fold on day 10 post-infection, followed by downward trends by day 40th (1.91-fold) was observed. Moreover, sharp fluctuations also took place on the 50th and 60th . Conclusion It is conclusively revealed that the serum level of serotonin and IDO1 mRNA expression were significantly higher in T.gondii infected Balb/c mice than normal control group. However, future investigations could explore therapeutic interventions targeting IDO1 or serotonin pathways to mitigate neurological impacts in chronic T.gondii infections.