Leishmania amazonensis infection induces behavioral alterations and modulates cytokine and neurotrophin production in the murine cerebral cortex

Neurotrophic Factors in Experimental Cerebral Acanthamoebiasis

To date, no studies have addressed the role of neurotrophins (NTs) in Acanthamoeba spp. infections in the brain. Thus, to clarify the role of NTs in the cerebral cortex and hippocampus during experimental acanthamoebiasis in relation to the host immune status, the purpose of this study was to determine whether Acanthamoeba spp. may affect the concentration of brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), neurotrophin-3 (NT-3), and neurotrophin-4 (NT-4) in brain structures. Our results suggest that at the beginning of infection in immunocompetent hosts, BDNF and NT-3 may reflect an endogenous attempt at neuroprotection against Acanthamoeba spp. infection. We also observed a pro-inflammatory effect of NGF during acanthamoebiasis in immunosuppressed hosts. This may provide important information for understanding the development of cerebral acanthamoebiasis related to the immunological status of the host. However, the pathogenesis of brain acanthamoebiasis is still poorly understood and documented and, therefore, requires further research.

Effect of Artesunate on Leishmania Amazonesis Induced Neuroinflammation and Nociceptive Behavior in Male Balb/C Mice

Simple Summary

Leishmaniasis is a multisystemic zoonotic disease with several symptoms, and treating this disease is a great challenge for veterinary medicine. Artemisinin derivatives are currently the most widely used drugs for the treatment of malaria, especially for their excellent safety profile and low cost. Artesunate is a more stable derivative of its precursor, artemisin, and has been shown to be a pluripotent agent with different pharmacological actions. In this study, we evaluated the role of neuroinflammation in leishmaniasis and its correlation with pain and sickness behavior, and the anti-inflammatory and neuroprotective effects of artesunate in a murine model of Leishmania amazonensis infection in BALB/c mice. The results from this study indicate that artesunate is a good candidate for treatment and/or as an adjuvant in anti- leishmaniasis therapy, and for preventing and alleviating leishmaniasis-induced pain and neuroinflammation.

Abstract

Background: Leishmaniasis is a multisystemic zoonotic disease with several symptoms, including neurological disorders. Leishmaniasis is accompanied by an increase in nociceptive behaviors, linked to the presence of a chronic inflammatory state, in both peripheral tissue and the central nervous system. Artesunate is a more stable derivative of its precursor artemisin and has been shown to be a pluripotent agent with different pharmacological actions. Methods: In this study, we investigated the effects of artesunate in Leishmaniaamazonensi- infected BALB/c mice, evaluating its effectiveness in reducing inflammation, neuroinflammation, and nociceptive and sickness behaviors. Results: Our results demonstrate a significant increase in pain sensitivity and sickness behaviors after L. amazonensis infection. Moreover, the infection induced a significant increase in inflammatory response at both the paw and spinal cord level. Treatment with artesunate was able to induce a significant decrease in tissue inflammation and neuroinflammation and thus induce a significant decrease in pain sensitivity and sickness behaviors. Conclusions: The results from this study indicate that artesunate is a good candidate for treatment and/or as an adjuvant in leishmanicidal therapy, and to prevent and alleviate leishmaniasis-induced pain and neuroinflammation and thereby improve the quality of life of leishmaniasis patients.

Microglia in neuropathology caused by protozoan parasites

Involvement of the central nervous system (CNS) is the most severe consequence of some parasitic infections. Protozoal infections comprise a group of diseases that together affect billions of people worldwide and, according to the World Health Organization, are responsible for more than 500000 deaths annually. They include African and American trypanosomiasis, leishmaniasis, malaria, toxoplasmosis, and amoebiasis. Mechanisms underlying invasion of the brain parenchyma by protozoa are not well understood and may depend on parasite nature: a vascular invasion route is most common. Immunosuppression favors parasite invasion into the CNS and therefore the host immune response plays a pivotal role in the development of a neuropathology in these infectious diseases. In the brain, microglia are the resident immune cells active in defense against pathogens that target the CNS. Beside their direct role in innate immunity, they also play a principal role in coordinating the trafficking and recruitment of other immune cells from the periphery to the CNS. Despite their evident involvement in the neuropathology of protozoan infections, little attention has given to microglia-parasite interactions. This review describes the most prominent features of microglial cells and protozoan parasites and summarizes the most recent information regarding the reaction of microglial cells to parasitic infections. We highlight the involvement of the periphery-brain axis and emphasize possible scenarios for microglia-parasite interactions.

The missing link in parasite manipulation of host behaviour

The observation that certain species of parasite my adaptively manipulate its host behaviour is a fascinating phenomenon. As a result, the recently established field of ‘host manipulation’ has seen rapid expansion over the past few decades with public and scientific interest steadily increasing. However, progress appears to falter when researchers ask how parasites manipulate behaviour, rather than why. A vast majority of the published literature investigating the mechanistic basis underlying behavioural manipulation fails to connect the establishment of the parasite with the reported physiological changes in its host. This has left researchers unable to empirically distinguish/identify adaptive physiological changes enforced by the parasites from pathological side effects of infection, resulting in scientists relying on narratives to explain results, rather than empirical evidence. By contrasting correlative mechanistic evidence for host manipulation against rare cases of causative evidence and drawing from the advanced understanding of physiological systems from other disciplines it is clear we are often skipping over a crucial step in host-manipulation: the production, potential storage, and release of molecules (manipulation factors) that must create the observed physiological changes in hosts if they are adaptive. Identifying these manipulation factors, via associating gene expression shifts in the parasite with behavioural changes in the host and following their effects will provide researchers with a bottom-up approach to unraveling the mechanisms of behavioural manipulation and by extension behaviour itself.

Unveiling Cerebral Leishmaniasis: parasites and brain inflammation in Leishmania donovani infected mice

Visceral leishmaniasis (VL) is a systemic disease with multifaceted clinical manifestations, including neurological signs, however, the involvement of the nervous system during VL is underestimated. Accordingly, we investigated both brain infection and inflammation in a mouse model of VL. Using bioluminescent Leishmania donovani and real-time 2D-3D imaging tools, we strikingly detected live parasites in the brain, where we observed a compartmentalized dual-phased inflammation pattern: an early phase during the first two weeks post-infection, with the prompt arrival of neutrophils and Ly6Chigh macrophages in an environment presenting a variety of pro-inflammatory mediators (IFN-γ, IL-1β, CXCL-10/CXCR-3, CCL-7/CCR-2), but with an intense anti-inflammatory response, led by IL-10; and a re-inflammation phase three months later, extremely pro-inflammatory, with novel upregulation of mediators, including IL-1β, TNF-α and MMP-9. These new data give support and corroborate previous studies connecting human and canine VL with neuroinflammation and blood-brain barrier disruption, and conclusively place the brain among the organs affected by this parasite. Altogether, our results provide convincing evidences that Leishmania donovani indeed infects and inflames the brain.