Toxoplasma gondii induces metabolic disturbances in the hippocampus of BALB/c mice

Investigation of the effects of Toxoplasma gondii on behavioral and molecular mechanism in bradyzoite stage

Toxoplasma gondii is a single-celled parasite that causes a disease called toxoplasmosis. It can reach the central nervous system, but the mechanism of T. gondii disrupting the functioning of these brain regions occurs in bradyzoite stage of parasite, causing brain damage by forming tissue cysts in brain. In our study, the effects of T. gondii on locomotor activity, anxiety, learning and memory, and norepinephrine (NE), levodopa (L-DOPA), dopamine (DA) and 3,4-D-dihydroxyphenylacetic acid (DOPAC) catecholamines in amygdala, striatum, prefrontal cortex and hippocampus regions of the brain were investigated in bradyzoite stage. Twenty male Albino mice Mus musculus, 4-5 weeks old, weighing 20-25 g, were used. T. gondii inoculated to mice intraperitonealy with 48-50-hour passages of T. gondii RH Ankara strain. For intraperitoneal inoculation of mice 5x104 tachyzoites per mouse. No inoculation was made in control group (n: 20). Locomotor activity behavior in open field test (OFT), anxious behavior in elevated plus maze (EPM), and learning behavior in novel object recognition (NOR) tests were evaluated. NE, L-DOPA, DA and DOPAC were measured by HPLC in brain tissues of amygdala, striatum, prefrontal cortex and hippocampus. A decrease was observed in the locomotor activity, anxiety and learning values of the T. gondii group compared to the control group (p < 0.05). The heighten in NE and L-DOPA levels in amygdala tissue of T. gondii group compared to control group, an elevation in NE, L-DOPA, DA and DOPAC levels in striatum tissue, and an increase in levels of NE in prefrontal cortex tissue were detected in monoamine results. In hippocampus tissue, an increase was observed in DA levels, while a decrease was observed in NE, L-DOPA and DOPAC levels. In our study, it has been shown that T. gondii in bradyzoite stage reduces locomotor activity, causes learning and memory impairment, and has anxiogenic effects.

Expression profiles of host miRNAs and circRNAs and ceRNA network during Toxoplasma gondii lytic cycle

Toxoplasma gondii is an opportunistic protozoan parasite that is highly prevalent in the human population and can lead to adverse health consequences in immunocompromised patients and pregnant women. Noncoding RNAs, such as microRNAs (miRNAs) and circular RNAs (circRNAs), play important regulatory roles in the pathogenesis of many infections. However, the differentially expressed (DE) miRNAs and circRNAs implicated in the host cell response during the lytic cycle of T. gondii are unknown. In this study, we profiled the expression of miRNAs and circRNAs in human foreskin fibroblasts (HFFs) at different time points after T. gondii infection using RNA sequencing (RNA-seq). We identified a total of 7, 7, 27, 45, 70, 148, 203, and 217 DEmiRNAs and 276, 355, 782, 1863, 1738, 6336, 1229, and 1680 DEcircRNAs at 1.5, 3, 6, 9, 12, 24, 36, and 48 h post infection (hpi), respectively. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses revealed that the DE transcripts were enriched in immune response, apoptosis, signal transduction, and metabolism-related pathways. These findings provide new insight into the involvement of miRNAs and circRNAs in the host response to T. gondii infection.

Alterations in the jejunal microbiota and fecal metabolite profiles of rabbits infected with Eimeria intestinalis

Background

Rabbit coccidiosis is a major disease caused by various Eimeria species and causes enormous economic losses to the rabbit industry. Coccidia infection has a wide impact on the gut microbiota and intestinal biochemical equilibrium. In the present study, we established a model of Eimeria intestinalis infection in rabbits to evaluate the jejunal microbiota and fecal metabolite profiles.

Methods

Rabbits in the infected group were orally inoculated with 3 × 10³E. intestinalis oocysts. On the eighth day of infection, jejunal contents and feces were collected for 16S rRNA gene sequencing and liquid chromatography–tandem mass spectrometry (LC–MS/MS) analysis, respectively. Jejunum tissues were harvested for hematoxylin and eosin (H&E), periodic acid-Schiff (PAS), and immunohistochemistry (IHC) staining.

Results

Histopathological analysis showed that the whole jejunum was parasitized by E. intestinalis in a range of life cycle stages, and PAS staining showed that E. intestinalis infection caused extensive loss of goblet cells. IHC staining revealed that TNF-α expression was higher in the E. intestinalis infection group. Moreover, both the jejunal microbiota and metabolites significantly altered after E. intestinalis infection. At the genus level, the abundances of Escherichia and Enterococcus significantly increased in the infected group compared with the control group, while those of Oscillospira, Ruminococcus, Bacteroides, Akkermansia, Coprococcus, and Sarcina significantly decreased. In addition, 20 metabolites and two metabolic pathways were altered after E. intestinalis infection, and the major disrupted metabolic pathway was lipid metabolism.

Conclusions

Eimeria intestinalis infection induced intestinal inflammation and destroyed the intestinal homeostasis at the parasitized sites, leading to significant changes in the gut microbiota and subsequent corresponding changes in metabolites.

Graphical Abstract

Behavioral and Neuropathological Changes After Toxoplasma gondii Ocular Conjunctival Infection in BALB/c Mice

Ocular infection with Toxoplasma gondii causes toxoplasmosis in mice. However, following ocular infection with tachyzoites, the cause of the accompanying progressive changes in hippocampal-dependent tasks, and their relationship with the morphology and number of microglia, is less well understood. Here, in 6-month-old, female BALB/c mice, 5 μl of a suspension containing 48.5 × 10⁶ tachyzoites/ml was introduced into the conjunctival sac; control received an equal volume of saline. Before and after instillation, all mice were subject to an olfactory discrimination (OD) test, using predator (cat) feces, and to an open-field (OF) task. After the behavioral tests, the animals were culled at either 22 or 44 days post-instillation (dpi), and the brains and retinas were dissected and processed for immunohistochemistry. The total number of Iba-1-immunolabeled microglia in the molecular layer of the dentate gyrus was estimated, and three-dimensional reconstructions of the cells were evaluated. Immobility was increased in the infected group at 12, 22, and 43 dpi, but the greatest immobility was observed at 22 dpi and was associated with reduced line crossing in the OF and distance traveled. In the OD test, infected animals spent more time in the compartment with feline fecal material at 14 and at 43 dpi. No OD changes were observed in the control group. The number of microglia was increased at 22 dpi but returned to control levels by 44 dpi. These changes were associated with the differentiation of T. gondii tachyzoites into bradyzoite-enclosed cysts within the brain and retina. Thus, infection of mice with T. gondii alters exploratory behavior, gives rise to a loss in predator’s odor avoidance from 2 weeks after infection, increased microglia number, and altered their morphology in the molecular layer of the dentate gyrus.