Toxoplasma gondii Infection Promotes Neuroinflammation Through Cytokine Networks and Induced Hyperalgesia in BALB/c Mice

The impact of neuroinflammation on neuronal integrity

Neuroinflammation, characterized by a complex interplay among innate and adaptive immune responses within the central nervous system (CNS), is crucial in responding to infections, injuries, and disease pathologies. However, the dysregulation of the neuroinflammatory response could significantly affect neurons in terms of function and structure, leading to profound health implications. Although tremendous progress has been made in understanding the relationship between neuroinflammatory processes and alterations in neuronal integrity, the specific implications concerning both structure and function have not been extensively covered, with the exception of perspectives on glial activation and neurodegeneration. Thus, this review aims to provide a comprehensive overview of the multifaceted interactions among neurons and key inflammatory players, exploring mechanisms through which inflammation influences neuronal functionality and structural integrity in the CNS. Further, it will discuss how these inflammatory mechanisms lead to impairment in neuronal functions and architecture and highlight the consequences caused by dysregulated neuronal functions, such as cognitive dysfunction and mood disorders. By integrating insights from recent research findings, this review will enhance our understanding of the neuroinflammatory landscape and set the stage for future interventions that could transform current approaches to preserve neuronal integrity and function in CNS-related inflammatory conditions.

Contribution of CNS and extra-CNS infections to neurodegeneration: a narrative review

Central nervous system infections have been suggested as a possible cause for neurodegenerative diseases, particularly sporadic cases. They trigger neuroinflammation which is considered integrally involved in neurodegenerative processes. In this review, we will look at data linking a variety of viral, bacterial, fungal, and protozoan infections to Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, multiple sclerosis and unspecified dementia. This narrative review aims to bring together a broad range of data currently supporting the involvement of central nervous system infections in the development of neurodegenerative diseases. The idea that no single pathogen or pathogen group is responsible for neurodegenerative diseases will be discussed. Instead, we suggest that a wide range of susceptibility factors may make individuals differentially vulnerable to different infectious pathogens and subsequent pathologies.

Activity of isoflavone biochanin A in chronic experimental toxoplasmosis: impact on inflammation

Toxoplasma gondii is a worldwide prevalent parasite. The infection has been linked to variable inflammatory effects including neuroinflammation. Biochanin A (BCA) is an isoflavone, known for its anti-inflammatory and anti-oxidative properties. In this study, we examined the effect of BCA on the brain and liver inflammatory lesions in a murine model with chronic toxoplasmosis. Mice were divided in to six groups: non-infected control, non-infected BCA-treated, and four infected groups with Toxoplasmagondii Me49-type II cystogenic strain: infected control, BCA (50 mg/kg/day)-treated, combined BCA/cotrimoxazole-treated and cotrimoxazole (370 mg/kg/day) alone-treated. Gene expression of tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and inducible nitric oxide synthase (iNOS) was evaluated by quantitative real-time PCR in the brain and liver tissues. In the infected control group, an upregulation of TNF-α and IL-1β mRNA expression levels was found. However, a downregulation of iNOS expression was detected in the brain of infected control mice. In both BCA- and combined-treated groups, the brain and liver tissues showed significantly reduced inflammatory lesions compared to the infected control mice with inhibited TNF-α and IL-1β mRNA levels. The iNOS expression levels in the brain tissues of BCA group were significantly higher than the levels of the infected control group. BCA alone or combined significantly reduced T. gondii cyst count in the brain tissues. In conclusion, the anti-inflammatory activity of BCA was demonstrated in the brain tissues of mice with chronic toxoplasmosis with decreased TNF-α and IL-1β expression levels and increased iNOS expression levels.

Strain-specific pre-existing immunity: A key to understanding the role of chronic Toxoplasma infection in cognition and Alzheimer's diseases?

Toxoplasma exposure can elicit cellular and humoral immune responses. In the case of chronic Toxoplasma infection, these immune responses are long-lasting. Some studies suggest that pre-existing immunity from Toxoplasma infection can shape immune responses and resistance to other pathogens and brain insults later in life. Much evidence has been generated suggesting Toxoplasma infection may contribute to cognitive impairment in the elderly. However, there have also been studies that disagree with the conclusion. Toxoplasma has many strain types, with virulence being the most notable difference. There is also considerable variation in the outcomes following Toxoplasma exposure ranging from resolved to persistent infection. Therefore, the brain microenvironment, particularly cellular constituents, differs based on the infecting strain (virulent versus hypovirulent) and infection stage (resolved versus persistent). Such difference might play a critical role in determining the outcome of the host on subsequent challengings to the brain. The ability of Toxoplasma strains to set up distinct stages for neurodegenerative pathology through varying degrees of virulence provides unique experimental tools for characterizing these pathways.

Toxoplasma gondii activates NLRP12 inflammasome pathway in the BALB/c murine model

The host resistance against Toxoplasma gondii (T. gondii) infection is related to the initiation of the immune response. The study aimed to investigate the role of the leucine-rich repeat family, pyrin domain -containing protein 12 (NLRP12), and cytoplasmic nucleotide-binding domain in the inflammasome-mediated cell death during murine toxoplasmosis. Groups of BALB/c mice (n = 10) were inoculated intraperitoneally with live tachyzoites, excretory-secretory antigens (ESAs) of T. gondii RH strain, and RPMI. The gene expression levels of NLRP12, caspase-3, caspase-1, IL-1β, IL-18, ASC, and Bcl-2 were measured in the peritoneal cells using quantitative real-time PCR, while the determination of NLRP12 protein level was measured by Western blot. Also, the intracellular reactive oxygen species (ROS) production was investigated. Quantitative and comparative analyses showed that injection of tachyzoites significantly increased NLRP12, caspase-3, caspase-1, IL-1β, IL-18, and ASC genes mRNA expression levels (p<0.01). Contrary to the acute infection, the Bcl-2 gene was significantly expressed in the ESAs group (p<0.0001). The level of NLRP12 protein was significantly higher in the mice that received tachyzoites and ESAs in comparison to the control group (p<0.0001). These findings provide an inside into the host-T. gondii interaction and NLRP12 regulation, which is important for the modulation of the immunological response.

The High Potency of Green Synthesized Copper Nanoparticles to Prevent the Toxoplasma gondii Infection in Mice

PURPOSE

Nowadays, due to the lack of an effective vaccine to prevent the toxoplasmosis, chemotherapy with the combination of pyrimethamine and sulfadiazine is considered as the "gold standard" treatment for toxoplasmosis. Recent reports have exhibited that these synthesized chemical drugs are associated with some serious side effects. The present study aims to evaluate the prophylactic effects of copper nanoparticles (CuNPs) green synthesized by Capparis spinosa fruit methanolic extract alone and combined with atovaquone against chronic toxoplasmosis induced by the Tehran strain of Toxoplasma gondii in mice METHODS: Mice were then orally administrated with CuNPs at the doses of 2 and 4 mg/kg/day and in combined with atovaquone 50 mg/kg for 14 days. Male BALB/c mice were divided into two seven groups include C1 (non-treated non-infected); C2 (treated with normal saline); C3 (Infected mice treated with atovaquone 100 mg/kg/day); Ex1 (treated with CuNPs 2 mg/kg/day); Ex2 (treated with CuNPs 4 mg/kg/day); Ex3 (treated with CuNPs 2 mg/kg/day + atovaquone 50 mg/kg/day); Ex3 (treated with CuNPs 4 mg/kg/day + atovaquone 50 mg/kg/day). On the 15th day, the mice were infected with the intraperitoneal inoculation of 20-25 tissue cysts from the Tehran strain of T. gondii. The mean numbers of brain tissue cysts and the mRNA levels of IL-12, IFN-γ, and inducible nitric oxide synthase (iNOS) in mice of each tested group were measured.

RESULTS

CuNPs were green synthesized by C. spinosa methanolic extract. Scanning electron microscopy showed that the particle size of CuNPs was 17 and 41 nm with maximum peak at the wavelength of 414 nm. The mean number of T. gondii tissue cysts in mice of tested groups of Ex1, Ex2, Ex3, and Ex4, significantly decreased as a dose-dependent response compared with control group. Moreover, in similar to the control group C3, no T. gondii tissue cysts was observed in mice of experimental group Ex3 and Ex4. The mRNA levels of IFN-γ, IL-12, and iNO was measured in mice of all tested groups. The mRNA levels of IFN-γ, IL-12, and iNO was increased in all mice of experimental groups in comparison with the control group C2; however, a significant enhancement was detected in mRNA level of IFN-γ, IL-12, and iNO in the tested groups of Ex3 and Ex4 when compared with control group C3.

CONCLUSION

The obtained results revealed the high potency of CuNPs alone and combined with atovaquone to prevent toxoplasmosis in mice. Although, the prophylactic effects of CuNPs and other properties, such as improved cellular immunity and low toxicity, are positive topics; however, more studies are required to approve these findings especially in clinical settings.

Green synthesis of zinc nanoparticles using Lavandula angustifolia Vera. Extract by microwave method and its prophylactic effects on Toxoplasma gondii infection

Background

Today, a suitable vaccine has not yet been discovered to prevent Toxoplasma gondii infection. Therefore, prophylaxis can be suggested as the preferred approach to prevent toxoplasmosis. This study aims to evaluate the prophylactic effects of synthesized zinc nanoparticles (ZnNPs) using Lavandula angustifolia Vera., by microwave method on chronic toxoplasmosis in mice.

Methods

BALB/c Mice orally administrated with ZnNPs the doses of 32.5, 75, 150 mg/kg/day for two weeks. On the 15th day, the mice were intraperitoneally infected with the Tehran strain of T. gondii (25 tissue cysts). The mean diameter and the numbers of brain tissue cysts, as well as the mRNA levels of inducible nitric oxide synthesize (iNOs), and interferon-gamma (IFN-γ) in mice of each experimental group were evaluated.

Results

The synthesized ZnNPs represent a spherical form with a size ranging from 30 to 80 nm. The results revealed that oral administration of Zn NPs at the doses of 32.5 (p < 0.001) and 75 mg/kg/day (p < 0.001) for 14 days significantly reduced the mean number and diameter of the brain tissue cysts in tested mice. No T. gondii tissue cyst was observed after oral administration of Zn NPs at the doses of 150 mg/kg. Based on the results of Real-time PCR analysis, the expression level of IFN-γ and iNOs was significantly increased (p < 0.001) in mice treated with 32.5, 75, 150 mg/kg/day for two weeks.

Conclusion

The obtained findings of the current investigation exhibit the significant prophylactic effects of ZnNPs against chronic toxoplasmosis in mice; so that oral administration of ZnNPs the doses 32.5, 75, 150 mg/kg reduced the parasite load and even completely controlled the infection in mice. The results show that the ZnNPs had strengthened the innate immune system which could be the reason for its strong prophylactic effects. However, further in vivo and clinical investigations are required to confirm these results as well as other possible mechanisms that can trigger these pharmacological properties.

Histopathological and ultrastructural assessment of atovaquone-proguanil hydrochloride combination in chronic murine toxoplasmosis

Over one billion people worldwide are expected to have Toxoplasma gondii infection with anonymous health problems. Available therapies are ineffective for persistent chronic toxoplasmosis. So, there is an imperative need for effective therapies to eliminate chronic tissue stage. In this study, we aimed to assess the effect of a drug combination of atovaquone and proguanil hydrochloride in the treatment of experimental chronic toxoplasmosis. Fifty Swiss Webster mice were used in the study. Forty mice were infected with Me49 type II cystogenic Toxoplasma gondii strain and allocated into four groups: infected untreated (vehicle-administered), infected and treated with cotrimoxazole (CTX) 370 mg/kg/day, infected and treated with atovaquone (ATV) 100 mg/kg/day, and infected and treated with atovaquone/proguanil (ATV/PROG) 50 mg/kg/day. An additional group of uninfected mice was used as an uninfected control group. Drug treatment was initiated 8 weeks post-infection and continued for two weeks. All mice were sacrificed 12 weeks post-infection. Parasitological and histopathological parameters were assessed. Toxoplasma gondii cysts recovered from brain tissue homogenates of both infected untreated and ATV/PROG-treated groups were examined by scanning electron microscopy. Combined ATV/PROG treatment demonstrated a significant reduction of Toxoplasma gondii cyst count in brain tissue (a reduction rate of 84.87%) compared to untreated group (P < .001). Brain tissues obtained from ATV/PROG treated group showed reduction of inflammatory infiltrate and marked attenuation and deformation of recovered Toxoplasma gondii cysts. We conclude that ATV/PROG drug combination could offer a potential drug therapy for Toxoplasma gondii chronic cystic stage.

New role of sertraline against Toxoplasma gondii-induced depression-like behaviours in mice

Toxoplasma gondii (T. gondii) is a neurotropic protozoan parasite, which can cause mental and behavioural disorders. The present study aimed to elucidate the effects and underlying molecular mechanisms of sertraline (SERT) on T. gondii-induced depression-like behaviours. In the present study, a mouse model and a microglial cell line (BV2 cells) model were established by infecting with the T. gondii RH strain. In in vivo and in vitro experiments, the underlying molecular mechanisms of SERT in inhibiting depression-like behaviours and cellular perturbations caused by T. gondii infection were investigated in the mouse brain and BV2 cells. The administration of SERT significantly ameliorated depression-like behaviours in T. gondii-infected mice. Furthermore, SERT inhibited T. gondii proliferation. Treatment with SERT significantly inhibited the activation of microglia and decreased levels of pro-inflammatory cytokines such as tumour necrosis factor-alpha, and interferon-gamma, by down-regulating tumour necrosis factor receptor 1/nuclear factor-kappa B signalling pathway, thereby ameliorating the depression-like behaviours induced by T. gondii infection. Our study provides insight into the underlying molecular mechanisms of the newly discovered role of SERT against T. gondii-induced depression-like behaviours.

Morphological and biochemical repercussions of Toxoplasma gondii infection in a 3D human brain neurospheres model

Background

Toxoplasmosis is caused by the parasite Toxoplasma gondii that can infect the central nervous system (CNS), promoting neuroinflammation, neuronal loss, neurotransmitter imbalance and behavioral alterations. T. gondii infection is also related to neuropsychiatric disorders such as schizophrenia. The pathogenicity and inflammatory response in rodents are different to the case of humans, compromising the correlation between the behavioral alterations and physiological modifications observed in the disease. In the present work we used BrainSpheres, a 3D CNS model derived from human pluripotent stem cells (iPSC), to investigate the morphological and biochemical repercussions of T. gondii infection in human neural cells.

Methods

We evaluated T. gondii ME49 strain proliferation and cyst formation in both 2D cultured human neural cells and BrainSpheres. Aspects of cell morphology, ultrastructure, viability, gene expression of neural phenotype markers, as well as secretion of inflammatory mediators were evaluated for 2 and 4 weeks post infection in BrainSpheres.

Results

T. gondii can infect BrainSpheres, proliferating and inducing cysts formation, neural cell death, alteration in neural gene expression and triggering the release of several inflammatory mediators.

Conclusions

BrainSpheres reproduce many aspects of T. gondii infection in human CNS, constituting a useful model to study the neurotoxicity and neuroinflammation mediated by the parasite. In addition, these data could be important for future studies aiming at better understanding possible correlations between psychiatric disorders and human CNS infection with T. gondii.

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T. gondii infects, proliferates and induce cysts formation in neurospheres.

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T. gondii infection induces neural cell death in neurospheres.

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T. gondii infection promotes alteration in neural gene expression in neurospheres.

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T. gondii infection promotes release of inflammatory mediators in neurospheres.

Myrtus communis Essential Oil; Anti-Parasitic Effects and Induction of the Innate Immune System in Mice with Toxoplasma gondii Infection

Background: Myrtus communis (M. communis) is a wild aromatic plant used for traditional herbal medicine that can be demonstrated in insecticidal, antioxidant, anti-inflammatory, and antimicrobial activity of its essential oils (MCEO). Aim: The present study aimed to evaluate the prophylactic effects of M. communis essential oil (MCEO) against chronic toxoplasmosis induced by the Tehran strain of Toxoplasma gondii in mice. Methods: Gas chromatography/mass spectrometry (GC/MS) analysis was performed to determine the chemical composition of MCEO. Mice were then orally administrated with MCEO at the doses of 100, 200, and 300 mg/kg/day and also atovaquone 100 mg/kg for 21 days. On the 15th day, the mice were infected with the intraperitoneal inoculation of 20–25 tissue cysts from the Tehran strain of T. gondii. The mean numbers of brain tissue cysts and the mRNA levels of IL-12 and IFN-γ in mice of each tested group were measured. Results: By GC/MS, the major constituents were α-pinene (24.7%), 1,8-cineole (19.6%), and linalool (12.6%), respectively. The results demonstrated that the mean number of T. gondii tissue cysts in experimental groups Ex1 (p < 0.05), Ex2 (p < 0.001) and Ex3 (p < 0.001) was meaningfully reduced in a dose-dependent manner compared with the control group (C2). The mean diameter of tissue cyst was significantly reduced in mice of the experimental groups Ex2 (p < 0.01) and Ex3 (p < 0.001). The results demonstrated that although the mRNA levels of IFN-γ and IL-12 were elevated in all mice of experimental groups, a significant increase (p < 0.001) was observed in tested groups of Ex2 and Ex3 when compared with control groups. Conclusion: The findings of the present study demonstrated the potent prophylactic effects of MCEO especially in the doses 200 and 300 mg/kg in mice infected with T. gondii. Although the exceptional anti-Toxoplasma effects of MCEO and other possessions, such as improved innate immunity and low toxicity are positive topics, there is, however, a need for more proof from investigations in this field.

Effect of chitosan on Toxoplasma gondii infection: A systematic review

Background

The preferred treatment for management of toxoplasmosis is the combined use of pyrimethamine and sulfadiazine. However, there are a wide number of adverse side effects with these medications. Recent research has focused on the use of chitosan for the treatment of Toxoplasma gondii infections. This review was performed to obtain a better understanding of the in vivo and in vitro effects of chitosan on T. gondii strains.

Methods

The current study was carried out according to the PRISMA guideline and registered in the CAMARADES-NC3Rs Preclinical Systematic Review and Meta-analysis Facility (SyRF) database. The search was performed in five scientific databases, including Scopus, PubMed, Web of Science, EMBASE, and Google Scholar, with date limits of 1992 to December 2019. The search was restricted to articles published in the English language. The words and terms searched were "Toxoplasma gondii", "Chitosan", "nanoparticles" and "anti-toxoplasmosis" with AND or OR.

Results

Of 2500 manuscripts, 9 met the eligibility criteria for review. All studies used the RH strain of T. gondii, with Me49 and PRU each included in one study. Five studies (56%) were performed in vivo, one study in vitro and 3 studies included in vivo and in vitro tests.

Conclusion

Considering the low toxicity and the high inhibitory potency of chitosan against T. gondii, chitosan nanoparticles show potential as an alternative treatment for T. gondii infections.

Catastrophic consequences: can the feline parasite Toxoplasma gondii prompt the purrfect neuroinflammatory storm following traumatic brain injury?

Traumatic brain injury (TBI) is one of the leading causes of morbidity and mortality worldwide; however, treatment development is hindered by the heterogenous nature of TBI presentation and pathophysiology. In particular, the degree of neuroinflammation after TBI varies between individuals and may be modified by other factors such as infection. Toxoplasma gondii, a parasite that infects approximately one-third of the world’s population, has a tropism for brain tissue and can persist as a life-long infection. Importantly, there is notable overlap in the pathophysiology between TBI and T. gondii infection, including neuroinflammation. This paper will review current understandings of the clinical problems, pathophysiological mechanisms, and functional outcomes of TBI and T. gondii, before considering the potential synergy between the two conditions. In particular, the discussion will focus on neuroinflammatory processes such as microglial activation, inflammatory cytokines, and peripheral immune cell recruitment that occur during T. gondii infection and after TBI. We will present the notion that these overlapping pathologies in TBI individuals with a chronic T. gondii infection have the strong potential to exacerbate neuroinflammation and related brain damage, leading to amplified functional deficits. The impact of chronic T. gondii infection on TBI should therefore be investigated in both preclinical and clinical studies as the possible interplay could influence treatment strategies.

Downregulation of lncRNA-11496 in the Brain Contributes to Microglia Apoptosis via Regulation of Mef2c in Chronic T. gondii Infection Mice

Though it is well known that chronic infections of Toxoplasma gondii (T. gondii) can induce mental and behavioral disorders in the host, little is known about the role of long non-coding RNAs (lncRNAs) in this pathological process. In this study, we employed an advanced lncRNAs and mRNAs integration chip (Affymetrix HTA 2.0) to detect the expression of both lncRNAs and mRNAs in T. gondii Chinese 1 strain infected mouse brain. As a result, for the first time, the downregulation of lncRNA-11496 (NONMMUGO11496) was identified as the responsible factor for this pathological process. We showed that dysregulation of lncRNA-11496 affected proliferation, differentiation and apoptosis of mouse microglia. Furthermore, we proved that Mef2c (Myocyte-specific enhancer factor 2C), a member of the MEF2 subfamily, is the target gene of lncRNA-11496. In a more detailed study, we confirmed that lncRNA-11496 positively regulated the expression of Mef2c by binding to histone deacetylase 2 (HDAC2). Importantly, Mef2c itself could coordinate neuronal differentiation, survival, as well as synapse formation. Thus, our current study provides the first evidence in terms of the modulatory action of lncRNAs in chronic toxoplasmosis in T. gondii infected mouse brain, providing a solid scientific basis for using lncRNA-11496 as a therapeutic target to treat T. gondii induced neurological disorder.

Prophylactic effects of biogenic selenium nanoparticles on acute toxoplasmosis: An in vivo study

Background

In this investigation, the in vivo efficacy and safety of biogenic selenium nanoparticles (SeNPs) are assessed against acute toxoplasmosis caused by Toxoplasma gondii (Sarcocystidae) in the mice.

Methods

Male NMRI mice were orally treated with normal saline (control group) and SeNPs at the doses of 5 and 10 mg/kg once a day for 14 days. On the 15th day, the mice were infected with 10⁴ tachyzoites of T. gondii RH strain by the intraperitoneal route. The mortality rate and parasite load were determined in the infected mice. The mRNA levels of IFN-γ, IL10, IL12, and inducible nitric oxide synthase were also examined in the infected mice by quantitative real-time PCR.

Results

The rate of mortality in the infected mice receiving SeNPs at the doses of 5 and 10 mg/kg compared with the mice in the control group was 100% on the 9 and 10 days after the administration. The mean number of tachyzoites in the infected mice receiving SeNPs was significantly lower than that in the control group. No significant difference (p > 0.05) was found in the biochemical parameters between the mice treated with SeNPs and the mice in the control group. The results revealed that mRNA levels significantly improved in the infected mice treated with SeNPs compared with those in the control group.

Conclusion

Findings of the present investigation showed the considerable efficacy of SeNPs with no important toxicity for curing acute toxoplasmosis in the mice model. However, further studies are needed to clarify the accurate anti-Toxoplasma mechanisms of SeNPs.

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We evaluated the efficacy of Biogenic Selenium Nanoparticles (SeNPs) against acute toxoplasmosis.

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Mice were orally treated with SeNPs at the doses of 5 and 10 mg/kg once a day for 14 days.

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The average number of tachyzoites and mortality rate was significantly lower in treated mice.

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No significant difference (p > 0.05) observed in the biochemical parameters between the mice treated.

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The mRNA levels of meaningfully improved in infected mice treated with SeNPs.

Schizophrenia and bipolar disorders: The Toxoplasma connection

The infectious etiology of psychiatric illnesses has remained an unexplored area till recently. During the past two decades, numerous studies from multiple angles have tried to link chronic toxoplasmosis with schizophrenia and bipolar disorders, among others. Most of the evidence has come from serological studies in the patient population, but other facets have also been explored. This review examines the various areas from which a causal link has been deduced and includes: (a) serological studies, (b) effect of maternal toxoplasmosis on children, (c) neurotransmitter studies, (d) parasite localization in the brain, (e) role of cytokines, and (f) psychotherapy and its effect on Toxoplasma. However, multiple factors may play a role in the etiopathogenesis of psychiatric illnesses, and chronic Toxoplasma infection may be considered an important risk factor for the genesis and symptomatology of schizophrenia and bipolar disorders.

Profiling of how nociceptor neurons detect danger - new and old foes

The host evolves redundant mechanisms to preserve physiological processing and homeostasis. These functions range from sensing internal and external threats, creating a memory of the insult and generating reflexes, which aim to resolve inflammation. Impairment in such functioning leads to chronic inflammatory diseases. By interacting through a common language of ligands and receptors, the immune and sensory nervous systems work in concert to accomplish such protective functions. Whilst this bidirectional communication helps to protect from danger, it can contribute to disease pathophysiology. Thus, the somatosensory nervous system is anatomically positioned within primary and secondary lymphoid tissues and mucosa to modulate immunity directly. Upstream of this interplay, neurons detect danger, which prompts the release of neuropeptides initiating (i) defensive reflexes (ranging from withdrawal response to coughing) and (ii) chemotaxis, adhesion and local infiltration of immune cells. The resulting outcome of such neuro-immune interplay is still ill-defined, but consensual findings start to emerge and support neuropeptides not only as blockers of T_H 1-mediated immunity but also as drivers of T_H 2 immune responses. However, the modalities detected by nociceptors revealed broader than mechanical pressure and temperature sensing and include signals as various as cytokines and pathogens to immunoglobulins and even microRNAs. Along these lines, we aggregated various dorsal root ganglion sensory neuron expression profiling datasets supporting such wide-ranging sensing capabilities to help identifying new danger detection modalities of these cells. Thus, revealing unexpected aspects of nociceptor neuron biology might prompt the identification of novel drivers of immunity, means to resolve inflammation and strategies to safeguard homeostasis.

Dihydroartemisinin regulates the immune system by promotion of CD8+ T lymphocytes and suppression of B cell responses

Artemisia annua is an anti-fever herbal medicine first described in traditional Chinese medicine 1,000 years ago. Artemisinin, the extract of A. annua, and its derivatives (dihydroartemisinin (DHA), artemether, and artesunate) have been used for the treatment of malaria with substantial efficacy. Recently, DHA has also been tested for the treatment of lupus erythematosus, indicating that it may function to balance the immune response in immunocompromised individuals. In the present study, the regulatory effect of artemisinin on the murine immune system was systematically investigated in mice infected with two different protozoan parasites (Toxoplasma gondii and Plasmodium berghei). Our results revealed that the mouse spleen index significantly increased (spleen enlargement) in the healthy mice after DHA administration primarily due to the generation of an extra number of lymphocytes and CD8⁺ T lymphocytes in both the spleen and circulation. DHA could increase the proportion of T helper cells and CD8⁺ T cells, as well as decrease the number of splenic and circulatory B cells. Further, DHA could reduce the production of proinflammatory cytokines. Our study revealed that apart from their anti-parasitic activity, artemisinin and its derivatives can also actively modulate the immune system to directly benefit the host.

Guanabenz Reverses a Key Behavioral Change Caused by Latent Toxoplasmosis in Mice by Reducing Neuroinflammation

Toxoplasma gondii is an intracellular parasite that has infected one-third of humans. The infection is permanent because the replicative form (tachyzoite) converts into a latent tissue cyst form (bradyzoite) that evades host immunity and is impervious to current drugs. The continued presence of these parasitic cysts hinders treatment and leads to chronic infection that has been linked to behavioral changes in rodents and neurological disease in humans. How these behavioral changes occur, and whether they are due to parasite manipulation or the host response to infection, remains an outstanding question. We previously showed that guanabenz possesses antiparasitic activity; here, we show that guanabenz reproducibly lowers brain cyst burden up to 80% in chronically infected male and female BALB/cJ mice when given intraperitoneally but not when administered by gavage or in food. Regardless of the administration route, guanabenz reverses Toxoplasma-induced hyperactivity in latently infected mice. In contrast, guanabenz increases cyst burden when given to chronically infected C57BL/6J mice yet still reverses Toxoplasma-induced hyperactivity. Examination of the brains from chronically infected BALB/cJ and C57BL/6J mice shows that guanabenz decreases inflammation and perivascular cuffing in each strain. Our study establishes a robust model for cyst reduction in BALB/cJ mice and shows for the first time that it is possible to reverse a key behavioral change associated with latent toxoplasmosis. The rescue from parasite-induced hyperactivity correlates with a decrease in neuroinflammation rather than reduced cyst counts, suggesting that some behavioral changes arise from host responses to infection.IMPORTANCE Toxoplasma gondii is a common parasite of animals, including up to one-third of humans. The single-celled parasite persists within hosts for the duration of their life as tissue cysts, giving rise to chronic infection. Latent toxoplasmosis is correlated with neurological dysfunction in humans and results in dramatic behavioral changes in rodents. When infected, mice and rats adapt behaviors that make them more likely to be devoured by cats, the only host that supports the sexual stage of the parasite. In this study, we establish a new mouse model of tissue cyst depletion using a drug called guanabenz and show that it is possible to reverse a key behavior change back to normal in infected animals. We also show that the mechanism appears to have nothing to do with parasite cyst burden but rather the degree of neuroinflammation produced by chronic infection.

Naloxone Ameliorates Spatial Memory Deficits and Hyperthermia Induced by a Neurotoxic Methamphetamine Regimen in Male Rats

BACKGROUND

Methamphetamine (METH) as a synthetic psychostimulant is being increasingly recognized as a worldwide problem, which may induce memory impairment. On the other hand, it is well established that naloxone, an opiate antagonist, has some beneficial effects on learning and memory. The present research aimed at evaluating naloxone effects on spatial learning and memory impairment triggered by a neurotoxic regimen of METH in male rats.

MATERIALS AND METHODS

The animals received the subcutaneous (sc) regimen of METH (4×6 mg/kg at 2-h intervals), intraperitoneal (ip) naloxone (4×1 mg/kg at 2-h intervals), or normal saline at four events. The Nal-METH group of rats received four naloxone injections (1 mg/ kg, ip) 30 min before each METH injection (6 mg/kg, sc) at 2-h intervals. Seven days later, they were evaluated for spatial learning and memory in the Morris Water Maze (MWM) task.

RESULTS

METH regimen induced hyperthermia, as well as a poor performance, in the acquisition and retention phases of the task, indicating spatial learning and memory impairment compared to the controls. Naloxone administration (1 mg/kg, ip) before each METH injection led to significant attenuations of both hyperthermia and METH adverse effects on the rat performance in the MWM task.

CONCLUSION

The results revealed that pretreatment with the opiate antagonist naloxone could prevent METH adverse effects on body temperature and memory performance. It seems that the opioidergic system and hyperthermia may, at least partially, be involved in METH effects on spatial memory.

Toxoplasmosis: A pathway to neuropsychiatric disorders

Toxoplasma gondii is an obligate intracellular parasite that resides, in a latent form, in the human central nervous system. Infection with Toxoplasma drastically alters the behaviour of rodents and is associated with the incidence of specific neuropsychiatric conditions in humans. But the question remains: how does this pervasive human pathogen alter behaviour of the mammalian host? This fundamental question is receiving increasing attention as it has far reaching public health implications for a parasite that is very common in human populations. Our current understanding centres on neuronal changes that are elicited directly by this intracellular parasite versus indirect changes that occur due to activation of the immune system within the CNS, or a combination of both. In this review, we explore the interactions between Toxoplasma and its host, the proposed mechanisms and consequences on neuronal function and mental health, and discuss Toxoplasma infection as a public health issue.

From inflammatory reactions to neurotransmitter changes: Implications for understanding the neurobehavioral changes in mice chronically infected with Toxoplasma gondii

Toxoplasma gondii is a protozoan parasite that can cause a latent infection in the central nervous system, leading to neurobehavioral abnormalities in the host. However, the mechanism underlying these changes remains relatively unexplored. In this study, we detected behavioral changes, pathological injury, secretion of neurotransmitters and related signal pathway in mice infected by T. gondii using behavioral test, histopathology, immunofluorescence staining, western blotting, HPLC and real time PCR. Mice showed neurobehavioral disturbances two months after infection with T. gondii. Histopathology revealed the activation of astrocytes and microglia, apoptosis of neurons and decreases in synapses in the brain of infected mice. Excessive secretion of cytokines and chemokines was detected in the brains of mice infected by T. gondii compared to uninfected mice. Furthermore, T. gondii infection led to abnormalities in neurotransmitters and the activation of NF-κB and dopamine (DA) signaling pathways in the infected mice. In conclusion, excessive activation of the inflammation in the brain could induce neuronal apoptosis in mice chronically infected with T. gondii. Dysregulation of the dopaminergic neurotransmitter could provide an explanation of neurobehavioral disorders in infected hosts.

Chronic Toxoplasma infection is associated with distinct alterations in the synaptic protein composition

Background

Chronic infection with the neurotropic parasite Toxoplasma gondii has been implicated in the risk for several neuropsychiatric disorders. The mechanisms, by which the parasite may alter neural function and behavior of the host, are not yet understood completely.

Methods

Here, a novel proteomic approach using mass spectrometry was employed to investigate the alterations in synaptic protein composition in a murine model of chronic toxoplasmosis. In a candidate-based strategy, immunoblot analysis and immunohistochemistry were applied to investigate the expression levels of key synaptic proteins in glutamatergic signaling.

Results

A comparison of the synaptosomal protein composition revealed distinct changes upon infection, with multiple proteins such as EAAT2, Shank3, AMPA receptor, and NMDA receptor subunits being downregulated, whereas inflammation-related proteins showed an upregulation. Treatment with the antiparasitic agent sulfadiazine strongly reduced tachyzoite levels and diminished neuroinflammatory mediators. However, in both conditions, a significant number of latent cysts persisted in the brain. Conversely, infection-related alterations of key synaptic protein levels could be partly reversed by the treatment.

Conclusion

These results provide evidence for profound changes especially in synaptic protein composition in T. gondii-infected mice with a downregulation of pivotal components of glutamatergic neurotransmission. Our results suggest that the detected synaptic alterations are a consequence of the distinct neuroinflammatory milieu caused by the neurotropic parasite.

Electronic supplementary material

The online version of this article (10.1186/s12974-018-1242-1) contains supplementary material, which is available to authorized users.

The association of latent toxoplasmosis and level of serum testosterone in humans

Objectives

Latent toxoplasmosis modifies various hormones and behaviors in infected hosts and possibly involves in etiology of different neurologic and psychiatric disorders. The aim of the current study was to assess possible associations between latent toxoplasmosis and testosterone concentration in Toxoplasma infected and free subjects. Briefly, 18–49 year-old participated in the study. After collected blood samples, sera were analyzed for the detection of anti-Toxoplasma IgG antibody. Totally, 76 positive sera were selected as study group (38 from men and 38 from women) and a same number of negative sera as control group.

Results

Comparison of testosterone concentrations and control groups showed that testosterone concentration in study group was higher than that in control group with statistically significant difference (P = 0.024 and P = 0.043 for men and women, respectively). Significant differences were found in testosterone concentrations and anti-Toxoplasma IgG antibody levels in study and control groups (P < 0.05). Toxoplasmosis can affect the mean concentration of serum testosterone in human. Alteration of testosterone during latent toxoplasmosis can result in alterations in behavioral, physiologic and immunological parameters in long time.

Neurophysiological Changes Induced by Chronic Toxoplasma gondii Infection

Although the parasite Toxoplasma gondii is one of the most pervasive neurotropic pathogens in the world, the host-parasite interactions during CNS infection and the consequences of neurological infection are just beginning to be unraveled. The chronic stages of infection have been considered dormant, although several studies have found correlations of infection with an array of host behavioral changes. These may facilitate parasite transmission and impact neurological diseases. During infection, in addition to the presence of the parasites within neurons, host-mediated neuroimmune and hormonal responses to infection are also present. T. gondii induces numerous changes to host neurons during infection and globally alters host neurological signaling pathways, as discussed in this review. Understanding the neurophysiological changes in the host brain is imperative to understanding the parasitic mechanisms and to delineate the effects of this single-celled parasite on health and its contribution to neurological disease.

Infectious immunity in the central nervous system and brain function

Inflammation is emerging as a critical mechanism underlying neurological disorders of various etiologies, yet its role in altering brain function as a consequence of neuroinfectious disease remains unclear. Although acute alterations in mental status due to inflammation are a hallmark of central nervous system (CNS) infections with neurotropic pathogens, post-infectious neurologic dysfunction has traditionally been attributed to irreversible damage caused by the pathogens themselves. More recently, studies indicate that pathogen eradication within the CNS may require immune responses that interfere with neural cell function and communication without affecting their survival. In this Review we explore inflammatory processes underlying neurological impairments caused by CNS infection and discuss their potential links to established mechanisms of psychiatric and neurodegenerative diseases.

The possible association between Toxoplasma gondii infection and risk of anxiety and cognitive disorders in BALB/c mice

There are conflicting reports concerning the association of Toxoplasma gondii infection with increased risk of mental disorders. This investigation will provide a good understanding about defining the possible association between T. gondii exposure and risk of anxiety and cognitive alterations. Besides, a secondary objective of this study was to determine the effect of pioglitazone administration on the possible alterations induced by T. gondii exposure. Male BALB/c mice were used for this study. The animal model of Toxoplasma infection was established by the intraperitoneal inoculation of 20-25 tissue cysts from Tehran strain of T. gondii. Pioglitazone (20 mg/kg, i.p.1/day) was administered to the animals for 2 weeks before behavioural tests. Behavioural tests including open-field, elevated plus-maze and passive avoidance learning were evaluated in the groups. Since cytokines were implicated as a contributing factor for mood disorders, the mRNA levels of TNF-α, IL-1β, IL-6 as well as inducible nitric oxide synthase (iNOs) were examined by real-time PCR. Findings demonstrated that T. gondii caused anxiety-like symptoms and impaired cognitive functions of the infected BALB/c mice, whereas pioglitazone, a peroxisome proliferator-activated receptor agonist, showed a promising effect against the cognitive impairments induced by Toxoplasma infection. The results also revealed that the mRNA levels of the aforementioned cytokines were significantly (p < 0.05) increased in the infected mice compared to the uninfected BALB/c ones. Pioglitazone can be offered as a potential neuroprotective agent in the treatment of patients with T. gondii infection that manifests anxiety and cognitive impairments; however, further studies are needed to clarify the exact mechanisms.

Toxoplasma gondii Infection Potentiates Cognitive Impairments of Alzheimer's Disease in the BALB/c Mice

This study tests the hypothesis that in chronic Toxoplasma gondii infection communication among immune cells promotes neuroinflammation through cytokine networks and potentiate cognitive impairments in BALB/c mice with Alzheimer's disease (AD). The animal model of Toxoplasma infection was established by the intraperitoneal inoculation of 20-25 tissue cysts from the Tehran strain of T. gondii . We injected amyloid-beta 1-42 peptide (Aβ_1-42, 1 and 2 μl) into the hippocampus of BALB/c mice to establish an animal model of AD. The behavioral experiments such as spatial learning and memory were performed using the Morris water maze test. The mRNA levels of TNF-α, IL-1β, IFN-γ, and inducible nitric oxide synthase (iNOS) were examined by real-time PCR. We found that T. gondii infection caused AD-like symptoms and impaired learning and memory functions of the infected BALB/c mice. We also found that in Toxoplasma infection + Aβ_1-42 (1 μl) group, T. gondii infection could potentiate AD in infected mice receiving subdoses of Aβ_1-42 (1 μl) and caused considerable impairment in learning and memory functions similar to AD group. Comparison of the results demonstrated that mRNA levels of IL-1β, TNF-α, IFN-γ, and iNOS significantly (P < 0.001) increased in T. gondii + Aβ_1-42 (1 μl) in comparison with the other tested groups. The obtained results showed that chronic T. gondii infection communication among immune cells promotes neuroinflammation through cytokine networks and induces pathological progression of AD in the mice brain, whereas the presence of neuroanatomical Toxoplasma tissue cysts in the brain could also affect the behavioral functions in T. gondii -infected mice.