host behavior

No evidence of association between Toxoplasma gondii infection and financial risk taking in females

January 4, 2015
Lanchava, L., Carlson, K., Sebankova, B., Flegr, J., Nave, G.
Plos One 2015; 10: ARTN e0136716 10.1371/journal.pone.0136716

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Background Past research linked Toxoplasma gondii (TG) infection in humans with neurological and mental disorders (e.g., schizophrenia, Alzheimer's disease and attention disorders), irregularities of the dopaminergic and testosterone system, and increased likelihood of being involved in traffic accidents. Methodology/Principal Findings We test for an association between TG infection and financial decision-making (DM) using a case-control design in a sample of female Czech students (n = 79). We estimate each subject's risk attitude and loss aversion using an experimental economic task involving real monetary incentives. We find no significant evidence that either measure of decision-making is associated with TG infection. Conclusion We were unable to find evidence of an association between TG infection and financial decision- making in females.

Tagged: decision-making, host behavior, latent toxoplasmosis, loss aversion, parasite manipulation, preferences, prospect-theory, rhd molecule, testosterone change, traffic accidents

Behavior

MicroRNA-132 dysregulation in Toxoplasma gondii infection has implications for dopamine signaling pathway

October 29, 2014
Xiao, J., Li, Y., Prandovszky, E., Karuppagounder, S. S., Talbot, C. C., Dawson, V. L., Dawson, T. M., Yolken, R. H.
Neuroscience 2014; 268: 128-138

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Congenital toxoplasmosis and toxoplasmic encephalitis can be associated with severe neuropsychiatric symptoms. However, which host cell processes are regulated and how Toxoplasma gondii affects these changes remain unclear. MicroRNAs (miRNAs) are small noncoding RNA sequences critical to neurodevelopment and adult neuronal processes by coordinating the activity of multiple genes within biological networks. We examined the expression of over 1000 miRNAs in human neuroepithelioma cells in response to infection with Toxoplasma. MiR-132, a cyclic AMP-responsive element binding (CREB)-regulated miRNA, was the only miRNA that was substantially upregulated by all three prototype Toxoplasma strains. The increased expression of miR-132 was also documented in mice following infection with Toxoplasma. To identify cellular pathways regulated by miR-132, we performed target prediction followed by pathway enrichment analysis in the transcriptome of Toxoplasma-infected mice. This led us to identify 20 genes and dopamine receptor signaling was their strongest associated pathway. We then examined myriad aspects of the dopamine pathway in the striatum of Toxoplasma-infected mice 5 days after infection. Here we report decreased expression of D1-like dopamine receptors (DRD1, DRD5), metabolizing enzyme (MAOA) and intracellular proteins associated with the transduction of dopamine-mediated signaling (DARPP-32 phosphorylation at Thr34 and Ser97). Increased concentrations of dopamine and its metabolites, serotonin (5-HT) and 5-hydroxyindoleacetic acid were documented by HPLC analysis; however, the metabolism of dopamine was decreased and 5-HT metabolism was unchanged. Our data show that miR-132 is upregulated following infection with Toxoplasma and is associated with changes in dopamine receptor signaling. Our findings provide a possible mechanism for how the parasite contributes to the neuropathology of infection

Tagged: alteration in expression, darpp-32, dopamine receptor pathway, expression, host behavior, messenger-rnas, mice, microRNA-132, mouse striatum, neurons, neurotransmitter, phosphatase, Schizophrenia, strains, Toxoplasma gondii

Mental health

Toxoplasma gondii infection and behaviour – location, location, location?

March 26, 2013
McConkey, G. A., Martin, H. L., Bristow, G. C., Webster, J. P.
Journal of Experimental Biology 2013; 216: 113-119

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Parasite location has been proposed as an important factor in the behavioural changes observed in rodents infected with the protozoan Toxoplasma gondii. During the chronic stages of infection, encysted parasites are found in the brain but it remains unclear whether the parasite has tropism for specific brain regions. Parasite tissue cysts are found in all brain areas with some, but not all, prior studies reporting higher numbers located in the amygdala and frontal cortex. A stochastic process of parasite location does not, however, seem to explain the distinct and often subtle changes observed in rodent behaviour. One factor that could contribute to the specific changes is increased dopamine production by T. gondii. Recently, it was found that cells encysted with parasites in the brains of experimentally infected rodents have high levels of dopamine and that the parasite encodes a tyrosine hydroxylase, the rate-limiting enzyme in the synthesis of this neurotransmitter. A mechanism is proposed that could explain the behaviour changes due to parasite regulation of dopamine. This could have important implications for T. gondii infections in humans

Tagged: brain, Dopamine, dopamine hypothesis, host behavior, manipulation., mice, mood disorders, neurotransmitter, obsessive-compulsive disorder, Parasite, parkinsonian symptoms, psychiatric patients, rattus-norvegicus, Schizophrenia, wild brown-rats

Behavior Mental health

The relationship between Toxoplasma gondii infection and mood disorders in the third national health and nutrition survey

October 12, 2012
Pearce, B.D., Kruszon-Moran, D., Jones, J.L.
Biological Psychiatry 2012; 72: 290-295

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Background: Toxoplasma gondii (T. gondii) is a neurotropic protozoan parasite that causes persistent infection in humans. A substantial literature suggests that schizophrenia is associated with increased seroprevalence of T. gondii, but a possible link of the parasite with mood disorders has not been as thoroughly investigated. Methods: We examined the association of Toxoplasma-specific immunoglobulin G results with mood disorder outcomes in 7440 respondents from the third National Health and Nutrition Survey, which is a nationally representative sample of the United States noninstitutionalized civilian population. Regression models were adjusted for numerous potential confounders, including tobacco smoking and C-reactive protein levels. Results: No statistically significant associations were found between T. gondii seroprevalence and a history of major depression (n = 574; adjusted odds ratio [OR]:.8; 95% confidence interval [CI]:.5-1.2), severe major depression (n = 515; adjusted OR:.8; 95% CI:.6-1.2), dysthymia (n = 548; adjusted OR: 1.1; 95% CI:.7-1.8), or dysthymia with comorbid major depression (n = 242, adjusted OR: 1.2; 95% CI:.6-2.4), all p values were > .05, including analysis stratified by gender. However, there was a significant relationship between T. gondii seroprevalence and bipolar disorder type I for respondents in which both manic and major depression symptoms were reported (n = 41; adjusted OR: 2.4; 95% CI: 1.2-4.8; p < .05). Conclusions: In a population-based sample, T. gondii seroprevalence is not elevated in unipolar mood disorders but is higher in a subset of respondents with a history of bipolar disorder type 1.