Neuroimmunology of Common Parasitic Infections in Africa

Plasma Neutrophil Gelatinase-Associated Lipocalin as a Biomarker of Kidney Injury and Potential Predictor of Hypoxic Brain Injury in Severe Plasmodium falciparum Malaria: Insights From India

Severe malaria is associated with kidney and brain injury, yet potential mechanisms linking both complications remain understudied. We investigated the associations between kidney and brain injuries in a cohort of Indian adults and children with severe Plasmodium falciparum malaria. We found that acute kidney injury was prevalent in both adults (64.4%) and children (71.4%). We also found that plasma levels of the structural kidney injury biomarker neutrophil gelatinase-associated lipocalin (NGAL) were strongly associated with acute kidney injury severity (P < .0001) and negatively correlated with whole brain magnetic resonance imaging apparent diffusion coefficient values in cerebral malaria (r = -0.6, 95% confidence interval, -0.8 to -0.3). Low apparent diffusion coefficient values indicate cytotoxic edema, a form of hypoxic brain injury mediated by parasite sequestration and inflammation. Severe cytotoxic edema has been shown to be associated with increased mortality in severe malaria. In our cohort, there was a 5.5-fold greater risk of this form of brain injury (prevalence risk ratio, 5.5, 95% confidence interval, 2.3-13.2) in patients with high NGAL levels (>300 ng/mL). These results suggest that plasma NGAL may play a critical role in structural kidney injury and could serve as a predictive marker for hypoxic brain injury in the context of severe malaria.

Hydrazinated geraniol derivatives as potential broad-spectrum antiprotozoal agents

Geraniol, a primary component of several essential oils, has been associated with broad-spectrum antiprotozoal activities, although moderate to weak. This study primarily concentrated on the synthesis of hydrazinated geraniol derivatives as potential antiprotozoal agents. The synthesised compounds were tested in vitro against different parasitic protozoans of clinical relevance, including Trypanosoma brucei brucei, Trypanosoma brucei rhodesiense, Trypanosoma cruzi and Leishmania infantum. Compounds 6, 8, 13, 14 and 15 demonstrated low micromolar activity against the different parasites. Compounds 8, 13, 14 and 15 had the highest efficacy against Trypanosoma brucei rhodesiense, as indicated by their respective IC50 values of 0.74, 0.56, 1.26 and 1.00 µM. Compounds 6, 14 and 15 displayed the best activity against Trypanosoma brucei brucei, with IC50 values of 1.49, 1.48 and 1.85 µM, respectively. The activity of compounds 6, 14 and 15 also extended to intracellular Trypanosoma cruzi, with IC50 values of 5.14, 6.30 and 4.90 µM, respectively. Compound 6, with an IC50 value of 11.73 µM, and compound 14, with an IC50 value of 8.14 µM, demonstrated some modest antileishmanial activity.

Unveiling potential repurposed drug candidates for Plasmodium falciparum through in silico evaluation: A synergy of structure-based approaches, structure prediction, and molecular dynamics simulations

The rise of drug resistance in Plasmodium falciparum, rendering current treatments ineffective, has hindered efforts to eliminate malaria. To address this issue, the study employed a combination of Systems Biology approach and a structure-based pharmacophore method to identify a target against P. falciparum. Through text mining, 448 genes were extracted, and it was discovered that plasmepsins, found in the Plasmodium genus, play a crucial role in the parasite's survival. The metabolic pathways of these proteins were determined using the PlasmoDB genomic database and recreated using CellDesigner 4.4.2. To identify a potent target, Plasmepsin V (PF13_0133) was selected and examined for protein-protein interactions (PPIs) using the STRING Database. Topological analysis and global-based methods identified PF13_0133 as having the highest centrality. Moreover, the static protein knockout PPIs demonstrated the essentiality of PF13_0133 in the modeled network. Due to the unavailability of the protein's crystal structure, it was modeled and subjected to a molecular dynamics simulation study. The structure-based pharmacophore modeling utilized the modeled PF13_0133 (PfPMV), generating 10 pharmacophore hypotheses with a library of active and inactive compounds against PfPMV. Through virtual screening, two potential candidates, hesperidin and rutin, were identified as potential drugs which may be repurposed as potential anti-malarial agents.

Tractable Quinolone Hydrazides Exhibiting Sub-Micromolar and Broad Spectrum Antitrypanosomal Activities

Nagana and Human African Trypanosomiasis (HAT), caused by (sub)species of Trypanosoma, are diseases that impede human and animal health, and economic growth in Africa. The few drugs available have drawbacks including suboptimal efficacy, adverse effects, drug resistance, and difficult routes of administration. New drugs are needed. A series of 20 novel quinolone compounds with affordable synthetic routes was made and evaluated in vitro against Trypanosoma brucei and HEK293 cells. Of the 20 compounds, 12 had sub-micromolar potencies against the parasite (EC50 values=0.051-0.57 μM), and most were non-toxic to HEK293 cells (CC50 values>5 μM). Two of the most potent compounds presented sub-micromolar activities against other trypanosome (sub)species (T. cruzi and T. b. rhodesiense). Although aqueous solubility is poor, both compounds possess good logD values (2-3), and either robust or poor microsomal stability profiles. These varying attributes will be addressed in future reports.

A metabolite attenuates neuroinflammation, synaptic loss and cognitive deficits induced by chronic infection of Toxoplasma gondii

Background

Neurodegenerative diseases including AD is currently one of intractable problems globally due to the insufficiency of intervention strategies. Long-term infection of Toxoplasma gondii (T. gondii) can induce cognitive impairment in hosts, which is closely implicated in the pathogenesis of neurodegenerative diseases. Aconitate decarboxylase 1 (Acod1) and its produced metabolite itaconate (termed Acod1/itaconate axis), have recently attracted extensive interests due to its anti-inflammatory role in macrophages. However, whether the axis can influence cognitive function remains unknown.

Methods

A chronic T. gondii-infected mice (C57BL/6J) model was established via administration of cysts by gavage. Novel location (NL), novel object recognition (NOR), Y-maze spatial memory and nest building tests were used to evaluate the behavior performance. Transmission electron microscopy, immunofluorescence, RT-PCR, western-blotting and RNA sequencing were utilized to determine the pathological changes, neuroinflammation and transcription profile in hippocampus tissues post infection, respectively. Moreover, the protective effect of Acod1/itaconate axis in T. gondii-induced cognitive deficits was evaluated.

Results

We found that the latent infection of the parasite impaired the cognitive function, which was assessed behaviorally by novel location (NL), novel object recognition (NOR), Y-maze spatial memory and nest building tests. RNA sequencing of hippocampus showed that the infection downregulated the expression of genes related to synaptic plasticity, transmission and cognitive behavior. To our attention, the infection robustly upregulated the expression of genes associated with pro-inflammatory responses, which was characterized by microglia activation and disorder of Acod1/itaconate axis. Interestingly, administration of dimethyl itaconate (DI, an itaconate derivative with cell membrane permeability) could significantly ameliorate the cognitive deficits induced by T. gondii, which was proved by improvement of behavior performance and synaptic ultrastructure impairment, and lower accumulation of pro-inflammatory microglia. Notably, DI administration had a potential therapeutic effect on the cognitive deficits and synaptic impairment induced by the parasitic infection.

Conclusions

Overall, these findings provide a novel insight for the pathogenesis of T. gondii-related cognitive deficits in hosts, and also provide a novel clue for the potential therapeutic strategies.