Oxidative stress in malaria

Vitamin C co-administration with artemether-lumefantrine abrogates chronic stress exacerbated Plasmodium berghei-induced sickness behaviour, inflammatory and oxidative stress responses in mice

This study evaluated the effects of vitamin C and artemether-lumefantrine (AL) on sickness behaviour and oxido-inflammatory response in chronically stressed mice infected with Plasmodium berghei. Sickness behaviour severity was examined with weight and assessment of mice behaviours. Results showed that stress increased parasitaemia in infected mice. Vitamin C co-administration with AL increased parasite clearance over AL alone, and modulated inflammatory cytokines (TNF-α, IL-1β, IL-10, IL-12) and antioxidant parameters in plasma and brain tissue. Conclusively, stress worsens malaria-induced sickness behaviour and up-regulates the inflammatory and oxidative stress response. Co-administration of vitamin C with AL appears to counteract these detrimental effects.

Impact on parasitemia, survival time and pro-inflammatory immune response in mice infected with Plasmodium berghei treated with Eleutherine plicata

In vitro studies with Plasmodium falciparum have demonstrated the antiparasitic activity of E. plicata, attributed to its naphthoquinones. This study reports on pro-inflammatory changes in mice infected with P. berghei and correlates these changes with parasitemia and survival. The ethanol extract of Eleutherine plicata (EEEp) was fractionated under reflux to obtain the dichloromethane fraction (FDMEp) and isolated compounds from E. plicata, relating these to survival time and parasitemia. Antimalarial activity was evaluated using the Peters suppressive test, with mice infected with Plasmodium berghei and treated with E. plicata, assessing parasitemia and survival over 30 days. The pro-inflammatory profile was determined by measuring interleukin-10, interferon-γ (IFN-γ), and nitric oxide levels. EEEp, FDMEp, and eleutherol showed activity on the 5th day of infection, with only FDMEp being active on the 8th day. Treatment with EEEp and FDMEp extended animal survival, reduced IFN-γ and NO levels, and increased IL-10 levels. Eleutherol significantly altered the response, with eleutherol glucuronide seemingly active by binding to lactate dehydrogenase, inhibiting hemozoin metabolism, leading to parasite death. Pro-inflammatory changes did not appear to correlate with survival and reduced parasitemia. In summary, FDMEp and eleutherol reduced parasitemia, extended survival, and modulated the inflammatory response. FDMEp and eleutherol are promising candidates for developing new antimalarial drugs.

In vitro, in vivo and in silico antiplasmodial profiling of the aqueous extract of Hibiscus asper HOOK F. Leaf (Malvaceae)

ETHNOPHARMACOLOGICAL RELEVANCE

Plasmodium resistance to antimalarial drugs raises the urgent need to seek for alternative treatments. Aqueous extract of Hibiscus asper leaves is currently used in malaria management but remains less documented.

AIM OF THE STUDY

The study aims to evaluate antimalarial effects of the aqueous extract of Hibiscus asper. UHPLC/MS, was used to identify some likely compounds present in the plant that were thereafter docked to some malaria parasite proteins.

STUDY DESIGN

In vitro anti-plasmodium and antioxidant, UHPLC/Ms analysis, in vivo antimalarial of the plant extract, and in silico molecular docking prediction of some identified compounds were performed to investigate the pharmacological effects of H. asper.

MATERIAL AND METHODS

The in vitro antiplasmodial activity of the extract was carried out on Plasmodium falciparum strains using SYBR-green dye; then, the curative antimalarial activity was conducted on Plasmodium berghei NK65-infected male Wistar rats. The UHPLC/MS analysis was used to identify plant compounds, followed by interactions (docking affinity) between some compounds and parasitic enzymes such as P. falciparum purine nucleoside phosphorylase (2BSX) and 6-phosphogluconate dehydrogenase (6FQY) to explore potential mechanisms of action at the molecular level.

RESULTS

No hemolysis effect of the extract was observed at concentrations up to 100 mg/mL. In vitro test of the aqueous leaves extract of H. asper showed inhibitory activity against P. falciparum Dd2 and 3D7 strains with IC50 values of 19.75 and 21.97 μg/mL, respectively. The curative antimalarial test of the H. asper extract in infected rats exhibited significant inhibition of the parasite growth (p < 0.001) with inhibition percentage of 95.11%, 97.68% and 95.59% at all the doses (50, 100 and 200 mg/kg) respectively. The extract corrected major physiological alterations such as liver and kidney impairments, oxidative stress and architectural disorganization in liver, spleen and kidneys tissues. The UHPLC/MS analysis identified 7 compounds, namely chlorogenic acid, azulene, quercetin, rhodine, 1-ethyl-2,4-dimethyl benzene and phthalan. Out of seven compounds identified in the extract quercetin and phthalan showed higher in silico inhibitory activity against P. falciparum purine nucleoside phosphorylase and Plasmodium falciparum 6-phosphosgluconate dehydrogenase parasite enzymes.

CONCLUSION

These findings indicate that H. asper could be a promising complementary medicine to manage malaria. Meanwhile, the affinity of annoted compounds with these enzymes should be further confirmed.

Antiplasmodial evidence, host mitochondrial biology and possible mechanisms of action of a composite extract of Azadiractha indica and Curcuma longa in Plasmodium berghei-infected mice

Azadirachta indica A. Juss (Meliaceae) (AI) and Curcuma longa L. (Zingiberaceae) (CL) are used for malaria treatment but their anti-glycolytic and host mitochondrial effects have not been studied. The AI stem-bark and CL rhizomes were extracted with methanol. Methanol extract of CL (Turmeric) was partitioned to yield methanol fraction (MF). Swiss mice infected with Plasmodium berghei (NK 65 strain) were treated with 200 and 400 mg/kg of AI and turmeric for seven days. Turmeric and MF (200 and 400 mg/kg) were combined with 400 mg/kg AI to treat mice infected with Plasmodium berghei (ANKA strain) for four days. Drug and infected controls mice were treated with artemether lumefantrine (10 mg/kg) and distilled water (10 mL/kg), respectively. Serum lactate dehydrogenase (LDH) and aldolase activities were determined. Liver mitochondria were obtained for mitochondrial permeability transition (mPT) pore opening and FoF1 ATPase assays. The curcumin content of turmeric was determined using HPLC while LD50 of Turmeric and AI was also determined. The AI, and its combination with turmeric decreased parasite load and increased chemosuppression in both sensitive and resistant studies while MF and its combinations with AI induced mPT pore opening. In the resistant experiment, AI + Turmeric 400 mg/kg decreased FoF1 ATPase, LDH and aldolase activities against the infected control. The LD50 values of both extracts were above 2000 mg/kg while the MF had the highest curcumin content. Antiplasmodial mechanisms of action of AI, CL and their combinations involve anti-glycolytic effects. Their composite formulations are more potent in malaria treatment.

Role of Nitric oxide synthase II in cognitive impairment due to experimental cerebral malaria

The role of nitric oxide (NO) in the pathogenesis of cerebral malaria and its cognitive sequelae remains controversial. Cerebral malaria is still the worst complication of Plasmodium falciparum infection, which is characterized by high rates of morbidity and mortality. Even after recovery from infection due to antimalarial therapy, the development of cognitive impairment in survivors reinforces the need to seek new therapies that demonstrate efficacy in preventing long-lasting sequelae. During disease pathogenesis, reactive oxygen and nitrogen species (RONS) are produced after the established intense inflammatory response. Increased expression of the enzyme inducible nitric oxide synthase (iNOS) seems to contribute to tissue injury and the onset of neurological damage. Elevated levels of NO developed by iNOS can induce the production of highly harmful nitrogen-reactive intermediates such as peroxynitrite. To address this, we performed biochemical and behavioral studies in C57BL6 mice, aminoguanidine (specific pharmacological inhibitor of the enzyme iNOS) treated and iNOS-/-, infected with Plasmodium berghei ANKA (PbA), with the aim of clarifying the impact of iNOS on the pathogenesis of cerebral malaria. Our findings underscore the effectiveness of both strategies in reducing cerebral malaria and providing protection against the cognitive impairment associated with the disease. Here, the absence or blockade of the iNOS enzyme was effective in reducing the signs of cerebral malaria detected after six days of infection. This was accompanied by a decrease in the production of pro-inflammatory cytokines and reactive oxygen and nitrogen species. In addition, nitrotyrosine (NT-3), a marker of nitrosative stress, was also reduced. Futher, cognitive dysfunction was analyzed fifteen days after infection in animals rescued from infection by chloroquine treatment (25 mg/kg bw). We observed that both interventions on the iNOS enzyme were able to improve memory and learning loss in mice. In summary, our data suggest that the iNOS enzyme has the potential to serve as a therapeutic target to prevent cognitive sequelae of cerebral malaria.

Elucidation of the Active Agents in a West African Ground Herbal Medicine Formulation That Elicit Antimalarial Activities in In Vitro and In Vivo Models

Agunmu (ground herbal medicine) is a form of West African traditional medicine consisting of a cocktail of herbs. The goal of this study is to evaluate a formulation of Agunmu made from M. indica, A. repens, E. chlorantha, A. boonei, and B. ferruginea, sold in the open market and commonly used for the treatment of malaria by the locals, for its antimalarial effects and to determine the active principles that may contribute to the antimalarial effect. The ethanolic extract obtained from this formulation (Ag-Iba) was analyzed, using TLC, LC-MS, and Tandem-MS techniques, to determine its phytochemical properties. The extract was tested in vitro against representative bacteria strains, cancer and normal human cell lines, and susceptible (D6) and resistant (W2) Plasmodium falciparum. In subsequent in vivo experiments, graded doses of the extract were used to treat mice infected with chloroquine-susceptible (NK-65) and chloroquine-resistant (ANKA) strains of Plasmodium berghei. Bacteria growth was monitored with a disc diffusion assay, cancer cell viability was determined with MTS assay, and percentage parasitemia and parasite clearance were determined by microscopy. Bound heme content, host mitochondria permeability transition (mPT) pore opening, F0F1-ATPase, and lipid peroxidation were determined via spectrophotometry. Indices of oxidative stress, anti-oxidant activities, toxicity, cell death, and inflammatory responses were obtained using biochemical and ELISA techniques. The histology of the liver and spleen was performed using the standard method. We elucidated the structures of the critical active principles in the extract to be flavonoids: kaempferol, quercetin, myricetin, and their glycosides with little or no detectable levels of the toxic Aristolochic acids that are found in Aristolochia repens, one of the components of the formulation. The extract also showed anti-plasmodial activity in in vitro and in vivo models. Furthermore, the extract dose-dependently decreased mitochondrial dysfunction, cell death, and inflammatory and oxidative damage but increased antioxidant potentials. Presumably, the active principles in the extract work as a combinatorial therapy to elicit potent antimalarial activity. Overall, our study unraveled the active components from a commercial herbal formulation that could be reformulated for antimalarial therapy.

Understanding the significance of oxygen tension on the biology of Plasmodium falciparum blood stages: From the human body to the laboratory

Plasmodium falciparum undergoes sequestration within deep tissues of the human body, spanning multiple organ systems with differing oxygen (O2) concentrations. The parasite is exposed to an even greater range of O2 concentrations as it transitions from the human to the mosquito host, suggesting a high level of plasticity as it navigates these different environments. In this review, we explore factors that may contribute to the parasite's response to different environmental O2 concentrations, recognizing that there are likely multiple pieces to this puzzle. We first review O2-sensing mechanisms, which exist in other apicomplexans such as Toxoplasma gondii and consider whether similar systems could exist in Plasmodium. Next, we review morphological and functional changes in P. falciparum's mitochondrion during the asexual-to-sexual stage transition and discuss how these changes overlap with the parasite's access to O2. We then delve into reactive oxygen species (ROS) as ROS production is influenced by O2 availability and oxidative stress impacts Plasmodium intraerythrocytic development. Lastly, given that the primary role of the red blood cell (RBC) is to deliver O2 throughout the body, we discuss how changes in the oxygenation status of hemoglobin, the RBC's O2-carrying protein and key nutrient for Plasmodium, could also potentially impact the parasite's growth during intraerythrocytic development. This review also highlights studies that have investigated P. falciparum biology under varying O2 concentrations and covers technical aspects related to P. falciparum cultivation in the lab, focusing on sources of technical variation that could alter the amount of dissolved O2 encountered by cells during in vitro experiments. Lastly, we discuss how culture systems can better replicate in vivo heterogeneity with respect to O2 gradients, propose ideas for further research in this area, and consider translational implications related to O2 and malaria.

Beta vulgaris Betalains Mitigate Parasitemia and Brain Oxidative Stress Induced by Plasmodium berghei in Mice

Although many drugs have been discovered to treat malaria infection, many of them face resistance from the host's body with long-term use. Therefore, this study aimed to evaluate the activity of betalains (from Beta vulgaris) and chloroquine (a reference drug) against brain oxidative stress induced by Plasmodium berghei in male mice. Two protocols were applied in this study: the therapeutic and prophylactic protocols. The results of the therapeutic protocol revealed a significant decrease in the level of parasitemia caused by P. berghei. Additionally, the histopathological changes in various brain regions were markedly improved after treatment with betalains. Regarding the prophylactic protocol, betalains were able to protect the brain tissues from oxidative stress, inflammation, and disrupted neurotransmitters expected to occur as a result of infection by P. berghei. This was demonstrated by modulating the activities of brain antioxidants (SOD and GSH), inflammatory cytokines (IL-6, IL-10, IL-12, TNF-α, and INF-γ), and neurotransmitters (serotonin, epinephrine, and norepinephrine). This study has proven that using betalains as a treatment or as a preventive has a vital and effective role in confronting the brain histopathological, oxidative stress, and inflammatory changes induced by P. berghei infection.

Discovery of antiplasmodial pyridine carboxamides and thiocarboxamides

Malaria continues to be a significant burden, particularly in Africa, which accounts for 95% of malaria deaths worldwide. Despite advances in malaria treatments, malaria eradication is hampered by insecticide and antimalarial drug resistance. Consequently, the need to discover new antimalarial lead compounds remains urgent. To help address this need, we evaluated the antiplasmodial activity of twenty-two amides and thioamides with pyridine cores and their non-pyridine analogues. Twelve of these compounds showed in vitro anti-proliferative activity against the intraerythrocytic stage of Plasmodium falciparum, the most virulent species of Plasmodium infecting humans. Thiopicolinamide 13i was found to possess submicromolar activity (IC50 = 142 nM) and was >88-fold less active against a human cell line. The compound was equally effective against chloroquine-sensitive and -resistant parasites and did not inhibit β-hematin formation, pH regulation or PfATP4. Compound 13i may therefore possess a novel mechanism of action.

Total antioxidant status levels in malaria: a systematic review and meta-analysis

BACKGROUND

Malaria, a severe health threat, significantly affects total antioxidant status (TAS) levels, leading to considerable oxidative stress. This systematic review and meta-analysis aimed to delineate differences in TAS levels between malaria patients and healthy controls, and assess correlations between disease severity and parasite density.

METHODS

The systematic review was registered with the International Prospective Register of Systematic Reviews (PROSPERO) under registration number CRD42023448761. A comprehensive literature search was conducted in databases such as Embase, MEDLINE, Journals@Ovid, PubMed, Scopus, ProQuest, and Google Scholar to identify studies reporting data on TAS levels in malaria patients. Data from the included studies were analysed both qualitatively and quantitatively. Differences in TAS levels between malaria patients and controls were pooled using a random effects model, with Hedges' g as the effect size measure.

RESULTS

Of 1796 identified records, 20 studies met the inclusion criteria. The qualitative synthesis of these studies revealed a marked decrease in TAS levels in patients with malaria compared to non-malaria cases. The meta-analysis results showed a significant decrease in TAS levels in patients with malaria compared to non-malaria cases (P < 0.01, Hedges' g: - 2.75, 95% CI - 3.72 to -1.78, I2: 98.16%, 13 studies), suggesting elevated oxidative stress in these patients. Subgroup analyses revealed that TAS level variations were significantly influenced by geographical region, age group, Plasmodium species, and method for measuring TAS. Notably, TAS levels were significantly lower in severe malaria cases and those with high parasite density, indicating a potential relationship between oxidative stress and disease severity.

CONCLUSION

This study highlights the potential utility of TAS as a biomarker for disease risk and severity in malaria. The significant decrease in TAS levels in malaria patients compared to controls implies increased oxidative stress. Further well-designed, large-scale studies are warranted to validate these findings and elucidate the intricate mechanisms linking TAS and malaria.

Evaluation of genotoxic damage, production reactive oxygen and nitrogen species in Plasmodium yoelii yoelii exposed to sodium metavanadate

Malaria represents the greatest global health burden among all parasitic diseases, with drug resistance representing the primary obstacle to control efforts. Sodium metavanadate (NaVO3) exhibits antimalarial activity against the Plasmodium yoelii yoelii (Pyy), yet its precise antimalarial mechanism remains elusive. This study aimed to assess the antimalarial potential of NaVO3, evaluate its genotoxicity, and determine the production of reactive oxygen and nitrogen species (ROS/RNS) in Pyy. CD-1 mice were infected and divided into two groups: one treated orally with NaVO3 (10 mg/kg/day for 4 days) and the other untreated. A 50% decrease in parasitemia was observed in treated mice. All experimental days demonstrated DNA damage in exposed parasites, along with an increase in ROS and RNS on the fifth day, suggesting a possible parasitostatic effect. The results indicate that DNA is a target of NaVO3, but further studies are necessary to fully elucidate the mechanisms underlying its antimalarial activity.

Amino acid supplementation confers protection to red blood cells before Plasmodium falciparum bystander stress

ABSTRACT

Malaria is a highly oxidative parasitic disease in which anemia is the most common clinical symptom. A major contributor to the malarial anemia pathogenesis is the destruction of bystander, uninfected red blood cells (RBCs). Metabolic fluctuations are known to occur in the plasma of individuals with acute malaria, emphasizing the role of metabolic changes in disease progression and severity. Here, we report conditioned medium from Plasmodium falciparum culture induces oxidative stress in uninfected, catalase-depleted RBCs. As cell-permeable precursors to glutathione, we demonstrate the benefit of pre-exposure to exogenous glutamine, cysteine, and glycine amino acids for RBCs. Importantly, this pretreatment intrinsically prepares RBCs to mitigate oxidative stress.

Phytochemical evaluation of Ziziphus mucronata and Xysmalobium undulutum towards the discovery and development of anti-malarial drugs

BACKGROUND

The development of resistance by Plasmodium falciparum is a burdening hazard that continues to undermine the strides made to alleviate malaria. As such, there is an increasing need to find new alternative strategies. This study evaluated and validated 2 medicinal plants used in traditional medicine to treat malaria.

METHODS

Inspired by their ethnobotanical reputation of being effective against malaria, Ziziphus mucronata and Xysmalobium undulutum were collected and sequentially extracted using hexane (HEX), ethyl acetate (ETA), Dichloromethane (DCM) and methanol (MTL). The resulting crude extracts were screened for their anti-malarial and cytotoxic potential using the parasite lactate dehydrogenase (pLDH) and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, respectively. This was followed by isolating the active compounds from the DCM extract of Z. mucronata using silica gel chromatography and structural elucidation using spectroscopic techniques (NMR: 1H, 12C, and DEPT). The active compounds were then targeted against P. falciparum heat shock protein 70-1 (PfHsp70-1) using Autodock Vina, followed by in vitro validation assays using ultraviolet-visible (UV-VIS) spectroscopy and the malate dehydrogenase (MDH) chaperone activity assay.

RESULTS

The extracts except those of methanol displayed anti-malarial potential with varying IC50 values, Z. mucronata HEX (11.69 ± 3.84 µg/mL), ETA (7.25 ± 1.41 µg/mL), DCM (5.49 ± 0.03 µg/mL), and X. undulutum HEX (4.9 ± 0.037 µg/mL), ETA (17.46 ± 0.024 µg/mL) and DCM (19.27 ± 0.492 µg/mL). The extracts exhibited minimal cytotoxicity except for the ETA and DCM of Z. mucronata with CC50 values of 10.96 and 10.01 µg/mL, respectively. Isolation and structural characterization of the active compounds from the DCM extracts revealed that betulinic acid (19.95 ± 1.53 µg/mL) and lupeol (7.56 ± 2.03 µg/mL) were responsible for the anti-malarial activity and had no considerable cytotoxicity (CC50 > µg/mL). Molecular docking suggested strong binding between PfHsp70-1, betulinic acid (- 6.8 kcal/mol), and lupeol (- 6.9 kcal/mol). Meanwhile, the in vitro validation assays revealed the disruption of the protein structural elements and chaperone function.

CONCLUSION

This study proves that X undulutum and Z. mucronata have anti-malarial potential and that betulinic acid and lupeol are responsible for the activity seen on Z. mucronata. They also make a case for guided purification of new phytochemicals in the other extracts and support the notion of considering medicinal plants to discover new anti-malarials.

Host-parasite interaction in severe and uncomplicated malaria infection in ghanaian children

PURPOSE

During malarial infection, both parasites and host red blood cells (RBCs) come under severe oxidative stress due to the production of free radicals. The host system responds in protecting the RBCs against the oxidative damage caused by these free radicals by producing antioxidants. In this study, we investigated the antioxidant enzyme; superoxide dismutase (SOD) activity and cytokine interactions with parasitaemia in Ghanaian children with severe and uncomplicated malaria.

METHODOLOGY

One hundred and fifty participants aged 0-12 years were administered with structured questionnaires. Active case finding approach was used in participating hospitals to identify and interview cases before treatment was applied. Blood samples were taken from each participant and used to quantify malaria parasitaemia, measure haematological parameters and SOD activity. Cytokine levels were measured by commercial ELISA kits. DNA comet assay was used to evaluate the extent of parasite DNA damage due to oxidative stress.

RESULTS

Seventy - Nine (79) and Twenty- Six (26) participants who were positive with malaria parasites were categorized as severe (56.75 × 103 ± 57.69 parasites/µl) and uncomplicated malaria (5.87 × 103 ± 2.87 parasites/µl) respectively, showing significant difference in parasitaemia (p < 0.0001). Significant negative correlation was found between parasitaemia and SOD activity levels among severe malaria study participants (p = 0.0428). Difference in cytokine levels (IL-10) amongst the control, uncomplicated and severe malaria groups was significant (p < 0.0001). The IFN-γ/IL-10 /TNF-α/IL-10 ratio differed significantly between the malaria infected and non- malaria infected study participants. DNA comet assay revealed damage to Plasmodium parasite DNA.

CONCLUSION

Critical roles played by SOD activity and cytokines as anti-parasitic defense during P. falciparum malaria infection in children were established.

Mefloquine-curcumin combinations improve host mitochondrial respiration and decrease mitotoxic effects of mefloquine in Plasmodium berghei-infected mice

Plasmodium infection is a health challenge. Although, antiplasmodial drugs kill the parasites, information on the effects of infection and drugs on the expression of some genes is limited. Malaria was induced in two different studies using NK65 (chloroquine-susceptible, study 1), and ANKA (chloroquine-resistant, study 2) strains of Plasmodium berghei in 30 male Swiss mice (n = 5) in each study. Mice orally received 10 mL/kg distilled water, (infected control), Mefloquine (MF) (10 mg/kg), MF and Curcumin (CM) (25 mg/kg), MF and CM (50 mg/kg), CM (25 mg/kg) and CM (50 mg/kg). Five mice (un-infected) were used as the control. After treatment, total Ribonucleic acid (RNA) was isolated from liver and erythrocytes while Deoxyribonucleic acid (DNA)-free RNA were converted to cDNA. Polymerase Chain Reaction (PCR) amplification was performed and relative expressions of FIKK12, AQP3, P38 MAPK, NADH oxidoreductase, and cytochrome oxidase expressions were determined. Markers of glycolysis, toxicity and antioxidants were determined using ELISA assays. While the expression of FIKK12 was blunted by MF in the susceptible study, co-treatment with curcumin (25 mg/kg) yielded the same results in the chloroquine-resistant study. Similar results were obtained on AQP3 in both studies. Curcumin decreased P38 MAPK in both studies. Plasmodium infection decreased NADH oxidoreductase and cytochrome oxidase but mefloquine-curcumin restored the expression of these genes. While glycolysis and toxicity were inhibited, antioxidant systems improved in the treated groups. Curcumin is needed for effective therapeutic efficacy and prevention of toxicity. Plasmodium infection and treatment modulate the expressions of some genes in the host. Curcumin combination with mefloquine modulates the expression of some genes in the host.

Pharmacokinetics and Pharmacodynamics of a Nanostructured Lipid Carrier Co-Encapsulating Artemether and miRNA for Mitigating Cerebral Malaria

Cerebral malaria (CM), a severe neurological pathology caused by Plasmodium falciparum infection, poses a significant global health threat and has a high mortality rate. Conventional therapeutics cannot cross the blood-brain barrier (BBB) efficiently. Therefore, finding effective treatments remains challenging. The novelty of the treatment proposed in this study lies in the feasibility of intranasal (IN) delivery of the nanostructured lipid carrier system (NLC) combining microRNA (miRNA) and artemether (ARM) to enhance bioavailability and brain targeting. The rational use of NLCs and RNA-targeted therapeutics could revolutionize the treatment strategies for CM management. This study can potentially address the challenges in treating CM, allowing drugs to pass through the BBB. The NLC formulation was developed by a hot-melt homogenization process utilizing 3% (w/w) precirol and 1.5% (w/v) labrasol, resulting in particles with a size of 94.39 nm. This indicates an effective delivery to the brain via IN administration. The results further suggest the effective intracellular delivery of encapsulated miRNAs in the NLCs. Investigations with an experimental cerebral malaria mouse model showed a reduction in parasitaemia, preservation of BBB integrity, and reduced cerebral haemorrhages with the ARM+ miRNA-NLC treatment. Additionally, molecular discoveries revealed that nicotinamide adenine dinucleotide phosphate oxidase 2 (NOX2) and Interleukin-6 (IL-6) levels were reduced in the treated groups in comparison to the CM group. These results support the use of nanocarriers for IN administration, offering a viable method for mitigating CM through the increased bioavailability of therapeutics. Our findings have far-reaching implications for future research and personalized therapy.

Hungry for control: metabolite signaling to chromatin in Plasmodium falciparum

The human malaria parasite Plasmodium falciparum undergoes a complex life cycle in two hosts, mammalian and mosquito, where it is constantly subjected to environmental changes in nutrients. Epigenetic mechanisms govern transcriptional switches and are essential for parasite persistence and proliferation. Parasites infecting red blood cells are auxotrophic for several nutrients, and mounting evidence suggests that various metabolites act as direct substrates for epigenetic modifications, with their abundance directly relating to changes in parasite gene expression. Here, we review the latest understanding of metabolic changes that alter the histone code resulting in changes to transcriptional programmes in malaria parasites.

Phytochemical screening, antioxidant analyses, and in vitro and in vivo antimalarial activities of herbal medicinal plant - Rotheca serrata (L.) Steane & Mabb

ETHNOPHARMACOLOGICAL RELEVANCE

Malaria is a major global health concern that is presently challenged by the emergence of Plasmodium falciparum (Pf) resistance to mainstay artemisinin-based combination therapies (ACTs). Hence, the discovery of novel and effective antimalarial drugs is pivotal to treating and controlling malaria. For many years, traditional plant-based herbal medicines have been employed in the treatment of various illnesses. Rotheca serrata (L.) Steane & Mabb. belongs to the Lamiaceae family that has been traditionally used to treat, cure, and prevent numerous diseases including malaria.

AIM

The present investigation sought to assess the phytoconstituents, antioxidant, cytotoxicity, antimalarial activities of Rotheca serrata extract and its fractions. The in vitro antiplasmodial activity was assessed in chloroquine-sensitive Pf3D7 and artemisinin-resistant PfCam3.IR539T cultures, and the in vivo antimalarial activity was analyzed in Plasmodium berghei (Pb) ANKA strain-infected BALB/c mouse model.

MATERIALS AND METHODS

The fresh leaves of Rotheca serrata were extracted in methanol (RsMeOH crude leaf extract). A portion of the extract was used to prepare successive solvent fractions using ethyl acetate (RsEA) and hexane (RsHex). The in vitro antiplasmodial activity was evaluated using [3H]-hypoxanthine incorporation assays against Pf3D7 and PfCam3.IR539T cultures. In vitro cytotoxicity study on HeLa, HEK-293T, and MCF-7 cell lines was carried out using MTT assay. The human red blood cells (RBCs) were used to perform the hemolysis assays. In vitro antioxidant studies and detailed phytochemical analysis were performed using GC-MS and FTIR. The four-day Rane's test was performed to evaluate the in vivo antimalarial activity against Pb ANKA strain-infected mice.

RESULTS

Phytochemical quantification of Rotheca serrata extract (RsMeOH) and its fractions (RsEA and RsHex) revealed that RsMeOH crude extract and RsEA fraction had higher contents of total phenol and flavonoid than RsHex fraction. The RsEA fraction showed potent in vitro antiplasmodial activity against Pf3D7 and PfCam3.IR539T with IC50 values of 9.24 ± 0.52 μg/mL and 17.41 ± 0.43 μg/mL, respectively. The RsMeOH crude extract exhibited moderate antiplasmodial activity while the RsHex fraction showed the least antiplasmodial activity. The GC-MS and FTIR analysis of RsMeOH and RsEA revealed the presence of triterpenes, phenols, and hydrocarbons as major constituents. The RsMeOH crude extract was non-hemolytic and non-cytotoxic to HeLa, HEK-293T, and MCF-7 cell lines. The in vivo studies showed that a 1200 mg/kg dose of RsMeOH crude extract could significantly suppress parasitemia by ∼63% and prolong the survival of treated mice by ∼10 days. The in vivo antiplasmodial activity of RsMeOH was better than the RsEA fraction.

CONCLUSION

The findings of this study demonstrated that traditionally used herbal medicinal plants like R. serrata provide a platform for the identification and isolation of potent bioactive phytochemicals that in turn can promote the antimalarial drug research. RsMeOH crude extract and RsEA fraction showed antiplasmodial, antimalarial and antioxidant activities. Chemical fingerprinting analysis suggested the presence of bioactive phytocompounds that are known for their antimalarial effects. Further detailed investigations on RsMeOH crude extract and RsEA fraction would be needed for the identification of the entire repertoire of the active antimalarial components with potent pharmaceutical and therapeutic values.

Status of Blood Levels of Superoxide Dismutase in Patients with Malaria: A Systematic Review and Meta-Analysis

Aims: The evidence of superoxide dismutase (SOD) in the pathogenesis of malaria is inconsistent. This study aimed to synthesize the evidence of blood levels of SOD in patients with malaria and determine the association of blood levels of SOD with the severity of malaria. Results: A total of 1874 articles were retrieved from database searches and 28 studies were included in the review. The blood levels of SOD were lower in individuals with malaria compared with those without malaria infection (p < 0.01, Cohen's d: -2.06, 95% CI: -2.99 to -1.14), I2: 98.96%, 2181 malaria cases/1186 uninfected cases). There were no differences in blood levels of SOD between severe and nonsevere malaria patients (p = 0.09, Cohen's d: -1.57, 95% CI: -3.39 to 0.26), I2: 96.02%, 69 severe malaria cases/256 nonsevere malaria cases). Innovation and Conclusion: The blood levels of SOD were lower in malaria patients compared with those without malaria infection. Further studies will be required to determine the extent to which SOD might prevent Plasmodium infections during pregnancy. Antioxid. Redox Signal. 40, 222-235.

Drug Repurposing in the Chemotherapy of Infectious Diseases

Repurposing is a universal mechanism for innovation, from the evolution of feathers to the invention of Velcro tape. Repurposing is particularly attractive for drug development, given that it costs more than a billion dollars and takes longer than ten years to make a new drug from scratch. The COVID-19 pandemic has triggered a large number of drug repurposing activities. At the same time, it has highlighted potential pitfalls, in particular when concessions are made to the target product profile. Here, we discuss the pros and cons of drug repurposing for infectious diseases and analyze different ways of repurposing. We distinguish between opportunistic and rational approaches, i.e., just saving time and money by screening compounds that are already approved versus repurposing based on a particular target that is common to different pathogens. The latter can be further distinguished into divergent and convergent: points of attack that are divergent share common ancestry (e.g., prokaryotic targets in the apicoplast of malaria parasites), whereas those that are convergent arise from a shared lifestyle (e.g., the susceptibility of bacteria, parasites, and tumor cells to antifolates due to their high rate of DNA synthesis). We illustrate how such different scenarios can be capitalized on by using examples of drugs that have been repurposed to, from, or within the field of anti-infective chemotherapy.

DHA-rich fish oil plays a protective role against experimental cerebral malaria by controlling inflammatory and mechanical events from infection

Every year, thousands of children, particularly those under 5 years old, die because of cerebral malaria (CM). Following conventional treatment, approximately 25% of surviving individuals have lifelong severe neurocognitive sequelae. Therefore, improved conventional therapies or effective alternative therapies that prevent the severe infection are crucial. Omega-3 (Ω-3) polyunsaturated fatty acids (PUFAs) are known to have antioxidative and anti-inflammatory effects and protect against diverse neurological disorders, including Alzheimer's and Parkinson's diseases. However, little is known regarding the effects of Ω-3 PUFAs against parasitic infections. In this study, C57BL/6 mice received supplemental treatment of a fish oil rich in the Ω-3 PUFA, docosahexaenoic acid (DHA), which was started 15 days prior to infection with Plasmodium berghei ANKA and was maintained until the end of the study. Animals treated with the highest doses of DHA, 3.0 and 6.0 g/kg body weight, had 60 and 80% chance of survival, respectively, while all nontreated mice died by the 7th day postinfection due to CM. Furthermore, the parasite load during the critical period for CM development (5th to 11th day postinfection) was controlled in treated mice. However, after this period all animals developed high levels of parasitemia until the 20th day of infection. DHA treatment also effectively reduced blood-brain barrier (BBB) damage and brain edema and completely prevented brain hemorrhage and vascular occlusion. A strong anti-inflammatory profile was observed in the brains of DHA-treated mice, as well as, an increased number of neutrophil and reduced number of CD8+ T leukocytes in the spleen. Thus, this is the first study to demonstrate that the prophylactic use of DHA-rich fish oil exerts protective effects against experimental CM, reducing the mechanical and immunological events caused by the P. berghei ANKA infection.

Metacaspase (Pf MCA-1) as antimalarial drug target: An in silico approach and their biological validation

AIMS

Acquired drug resistance of Plasmodium is a global issue for the treatment of malaria. There are various proteases in the genome of Plasmodium falciparum (P. falciparum) including metacaspase-1 (PfMCA-1) that are essential and are being considered as an attractive drug target. It is aimed to identify novel therapeutics against malaria and their action on PfMCA-1 along with other apoptotic pathway events.

MAIN METHODS

High throughput virtual screening of 55,000 compounds derived from Maybridge library was performed against PfMCA-1. Based on the docking score, sixteen compounds were selected for in vitro antimalarial screening against drug sensitive and resistant strains of P. falciparum using SYBR green-based assay. Subsequently, three lead molecules were selected and subjected to the evaluation of cytotoxicity, caspase like protease activity, mitochondrial membrane potential, ROS generation and DNA fragmentation via TUNEL assay.

KEY FINDINGS

The in silico and in vitro approaches have brought forward some Maybridge library compounds with antiplasmodial activity most likely by enhancing the metacaspase activity. The compound CD11095 has shown better antimalarial efficacy, and KM06591 depicted higher caspase mediated killing, elevated TUNEL positive cells and moderate ROS generation. Mitochondrial membrane depolarization was augmented by RJC0069. Exposure of P. falciparum to CD11095, KM06591 and RJC0069 has ended up in parasite growth arrest via multiple mechanisms.

SIGNIFICANCE

It is proposed that the Maybridge molecules CD11095, KM06591 and RJC0069 have antimalarial activity. Their mechanism of action was found to be by enhancing the metacaspases-like protease activity, mitochondrial depolarization and DNA fragmentation which stipulates significant insights towards promising candidates for drug development.

Ethanol extract of aloe vera ameliorates Artemether-Lumefantrine-induced reproductive toxicity in adult male Albino rats (Wistar Strain)

Artemether-Lumefantrine (AL) is one of the alternative drugs used in treating malaria - an endemic scourge in Africa. AL has been reported to generate free radicals with long term use implicated in testicular pathologies. The antioxidative properties of Aloe vera (AV) has been well documented. This study investigated the ameliorative effect of ethanol extract of Aloe Vera on Artemether-Lumefantrine induced testicular toxicity. Thirty adult male albino rats were randomly divided into 5 groups (Control, AL-dosed, AV-dosed, AL+AV concurrently administered and AV-pretreated). Spermiogram, serum testosterone, testicular histopathology and inducible nitric oxide synthase (iNOS) immunohistochemistry were carried out. AL-dosed rats had poor spermiogram indices which were greatly improved in AV-dosed and AV-pretreated rats. These also corresponded with the testicular histopathology observations and were further buttressed by oxidative stress marker (iNOS) as AL-dosed rats had higher signal intensity compared to the control and AV-pretreated rats. Authors posit that concurrent administration of AV and AL protected testicular architecture while pretreating with AV prior AL administration improved the spermiogram. AL induces testicular pathology, thus should be used with care in male subjects. AV can confer a level of protection against these defects if used prior to administration of the drug.

Redox modulating small molecules having antimalarial efficacy

The search for effective antimalarial agents remains a critical priority because malaria is widely spread and drug-resistant strains are becoming more prevalent. In this review, a variety of small molecules capable of modulating redox processes were showcased for their potential as antimalarial agents. The compounds were designed to target the redox balance of Plasmodium parasites, which has a pivotal function in their ability to survive and multiply within the host organism. A thorough screening method was utilized to assess the effectiveness of these compounds against both drug-sensitive and drug-resistant strains of Plasmodium falciparum, the malaria-causing parasite. The results revealed that several of the tested compounds exhibited significant effectiveness against malaria, displaying IC50 values at a low micromolar range. Furthermore, these compounds displayed promising selectivity for the parasite, as they exhibited low cytotoxicity towards mammalian cells. Thorough mechanistic studies were undertaken to clarify how the active compounds exert their mode of action. The findings revealed that these compounds disrupted the parasites' redox balance, causing oxidative stress and interfering with essential cellular functions. Additionally, the compounds showed synergistic effects when combined with existing antimalarial drugs, suggesting their potential for combination therapies to combat drug resistance. Overall, this study highlights the potential of redox-modulating small molecules as effective antimalarial agents. The identified compounds demonstrate promising antimalarial activity, and their mechanism of action offers insights into targeting the redox balance of Plasmodium parasites. Further optimization and preclinical studies are warranted to determine their efficacy, safety, and potential for clinical development as novel antimalarial therapeutics.

Chemo-proteomics in antimalarial target identification and engagement

Humans have lived in tenuous battle with malaria over millennia. Today, while much of the world is free of the disease, areas of South America, Asia, and Africa still wage this war with substantial impacts on their social and economic development. The threat of widespread resistance to all currently available antimalarial therapies continues to raise concern. Therefore, it is imperative that novel antimalarial chemotypes be developed to populate the pipeline going forward. Phenotypic screening has been responsible for the majority of the new chemotypes emerging in the past few decades. However, this can result in limited information on the molecular target of these compounds which may serve as an unknown variable complicating their progression into clinical development. Target identification and validation is a process that incorporates techniques from a range of different disciplines. Chemical biology and more specifically chemo-proteomics have been heavily utilized for this purpose. This review provides an in-depth summary of the application of chemo-proteomics in antimalarial development. Here we focus particularly on the methodology, practicalities, merits, and limitations of designing these experiments. Together this provides learnings on the future use of chemo-proteomics in antimalarial development.

Unravelling the Influence of Host Genetic Factors on Malaria Susceptibility in Asian Populations

Malaria is a deadly blood-borne disease caused by a Plasmodium parasite. Infection results in various forms of malaria, including an asymptomatic state, uncomplicated disease, or severe disease. Severe malaria (SM) is particularly prevalent among young children and is a significant cause of mortality. SM is associated with the sequestration of parasitized erythrocytes in the microvasculature of vital host organs, disrupting the normal functioning of the immune system. Although the exact mechanisms of malaria pathogenesis are yet to be fully understood, researchers have been investigating the role of host genetics in determining the severity of the disease and the outcome of infection. The objective of this study is to identify specific host genes that have been examined for their association with malaria in Asian populations and pinpoint those most likely to influence susceptibility. Through an extensive screening process, a total of 982 articles were initially identified, and after careful review, 40 articles discussing 68 genes were included in this review. By constructing a network of protein-protein interactions (PPIs), we identified six key proteins (TNF, IL6, TLR4, IL1β, IL10, and IL8) that exhibited substantial interactions (more than 30 edges), suggesting their potential as significant targets for influencing malaria susceptibility. Notably, these six proteins have been previously identified as crucial components of the immune response, associated with malaria susceptibility, and capable of affecting different clinical forms of the disease. Identifying genes that contribute to malaria susceptibility or resistance holds the promise of enhancing the diagnosis and treatment of this debilitating illness. Such knowledge has the potential to pave the way for more targeted and effective strategies in combating malaria, particularly in Asian populations where controlling Plasmodium vivax is challenging, and India contributes the highest number of cases. By understanding the genetic factors underlying malaria vulnerability, we can develop interventions that are tailored to the specific needs of Asian populations, ultimately leading to better outcomes in the fight against this disease.

Association of reduced glutathione levels with Plasmodium falciparum and Plasmodium vivax malaria: a systematic review and meta-analysis

Reduced glutathione (GSH) is a crucial antioxidant with recognized roles in malaria pathogenesis and host response. Despite its importance, reports on the association of GSH with malaria are inconsistent. Therefore, this systematic review and meta-analysis investigated the differences in GSH levels in relation to Plasmodium infection. A comprehensive literature search of six electronic databases (Embase, MEDLINE, Ovid, PubMed, Scopus, and ProQuest) was conducted. Of the 2158 initially identified records, 18 met the eligibility criteria. The majority of studies reported a significant decrease in GSH levels in malaria patients compared with uninfected controls, and this was confirmed by meta-analysis (P < 0.01, Hedges g: - 1.47, 95% confidence interval [CI] - 2.48 to - 0.46, I2: 99.12%, 17 studies). Additionally, there was no significant difference in GSH levels between Plasmodium falciparum malaria and P. vivax malaria (P = 0.80, Hedges g:  0.11, 95% CI - 0.76 to 0.98, I2: 93.23%, three studies). Similarly, no significant variation was observed between symptomatic and asymptomatic malaria cases (P = 0.78, Hedges g: 0.06, 95% CI - 0.34 to 0.46, I2: 48.07%, two studies). In conclusion, although GSH levels appear to be generally lower in malaria patients, further detailed studies are necessary to fully elucidate this complex relationship.

Differences in catalase levels between malaria-infected individuals and uninfected controls: a systematic review and meta-analysis

Inconsistent catalase (CAT) research necessitates a comprehensive review of CAT levels among patients with malaria to achieve better therapeutic strategies. This study aimed to systematically review and meta-analyze available literature on CAT levels in nonpregnant and pregnant individuals with malaria compared with those in uninfected controls, with the goal of providing a robust evidence base for future research and potential interventions. Following PRISMA guidelines, a systematic literature search across six databases was conducted to examine CAT levels in patients with malaria. Data was extracted independently by two reviewers, and study quality was assessed using the Joanna Briggs Institute (JBI) critical appraisal checklist. The standardized mean difference of CAT levels was calculated with heterogeneity assessment. Subgroup and sensitivity analyses were conducted to explore heterogeneity and assess the robustness of the findings. Publication bias was visually and statistically assessed and corrected, if necessary. Statistical analyses were performed using Stata software, with a significance level set at P < 0.05. Nineteen studies were included in the review. These studies, published from before 2000 to 2023, primarily from Africa and Asia, focused on different Plasmodium species and age groups. Results of qualitative synthesis among nonpregnant individuals consistently showed lower CAT levels in malaria-infected individuals, although some studies reported higher levels. No significant differences in CAT levels were found between malaria-infected and uninfected individuals, as demonstrated by a meta-analysis overall (P = 0.05, Hedges' g: - 0.78, 95% confidence interval (CI): (- 1.56)-0.01, I2: 98.47, 15 studies), but subgroup analyses showed significant differences in CAT levels in studies conducted in Africa (P = 0.02, Hedges' g: - 0.57, 95% CI: - 1.02-(0.11), I2: 91.81, 7 studies), and in studies that specifically focused on children (P = 0.03, Hedges' g: - 0.57, 95% CI: - 1.07-(- 0.07), I2: 87.52, 4 studies). Pregnant women showed variations in CAT levels across trimesters. This study provides valuable insights into the association between malaria infection and CAT enzyme levels, particularly in nonpregnant individuals. Furthermore, well-designed studies are essential to decoding the intricacies of this relationship, which could have significant implications for understanding disease processes and improving patient care.

In vitro and in vivo antimalarial activity of green synthesized silver nanoparticles using Sargassum tenerrimum - a marine seaweed

Green nanotechnology has recently attracted a lot of attention as a potential technique for drug development. In the present study, silver nanoparticles were synthesised by using Sargassum tenerrimum, a marine seaweed crude extract (Ag-ST), and evaluated for antimalarial activity in both in vitro and in vivo models. The results showed that Ag-ST nanoparticles exhibited good antiplasmodial activity with IC50 values 7.71±0.39 µg/ml and 23.93±2.27 µg/ml against P. falciparum and P. berghei respectively. These nanoparticles also showed less haemolysis activity suggesting their possible use in therapeutics. Further, P. berghei infected C57BL/6 mice were used for the four-day suppressive, curative and prophylactic assays where it was noticed that the Ag-ST nanoparticles significantly reduced the parasitaemia and there were no toxic effects observed in the biochemical and haematological parameters. Further to understand its possible toxic effects, both in vitro and in vivo genotoxicological studies were performed which revealed that these nanoparticles are non-genotoxic in nature. The possible antimalarial activity of Ag-ST may be due to the presence of bioactive phytochemicals and silver ions. Moreover, the phytochemicals prevent the nonspecific release of ions responsible for low genotoxicity. Together, the bio-efficacy and toxicology outcomes demonstrated that the green synthesized silver nanoparticles (Ag-ST) could be a cutting-edge alternative for therapeutic applications.

Impact of malaria on glutathione peroxidase levels: a systematic review and meta-analysis

The primary antioxidant, glutathione peroxidase (GPx), is hypothesized to contribute to the pathophysiology of malaria. This current study conducted a meta-analysis to examine variations in GPx blood levels in malaria patients. Seven electronic databases-ProQuest, Scopus, Embase, MEDLINE, PubMed, Ovid, and Google Scholar-were searched for relevant studies with no limitations to publication language or publication date. The Joanna Briggs Institute critical appraisal tools were used to appraise the risk of bias among the included studies critically. The meta-analysis was conducted by pooling the effect estimates and Hedges's g using a random-effects model. Search results returned 1253 articles, of which 16 studies were used for syntheses. Results of the meta-analysis indicated that malaria patients had decreased blood levels of GPx compared to uninfected individuals (P < 0.01, Hedges' g: - 4.06, 95% CI - 5.49-(- 2.63), I2: 99.07%, 1278 malaria patients/627 uninfected individuals, 15 studies). Subgroup analyses indicated that peripheral levels of GPx were significantly diminished in patients with P. falciparum malaria compared to uninfected controls (P < 0.01, Hedges' g: - 3.06, 95% CI - 4.46-(- 1.65), I2: 98.39%, 9 studies) but not in patients with P. vivax malaria (P = 0.15, Hedges' g: - 2.05, 95% CI - 4.83-0.74), I2: 98.64%, 2 studies) Overall, malaria is associated with declined levels of GPx, particularly in patients with P. falciparum malaria. The finding provides valuable insights that prompt the need to investigate the role of GPx depletion in malaria pathogenesis.

Effect of Malaria on Blood Levels of Vitamin E: A Systematic Review and Meta-Analysis

Vitamin E has an antioxidant property and is associated with protection against malaria. The current study used systematic review and meta-analysis approaches examining the variance in blood levels of vitamin E in malaria patients as compared with uninfected individuals. The protocol for the systematic review was registered with PROSPERO (CRD4202341481). Searches for pertinent studies were carried out on Embase, MEDLINE, Ovid, PubMed, Scopus, ProQuest, and Google Scholar. The combined effect estimate (Cohen's d) of the difference in vitamin E levels in malaria patients as compared with uninfected individuals was estimated using the random effects model. The searches yielded 2009 records, and 23 studies were included in the systematic review. The majority of the studies (80%) found that vitamin E levels were significantly lower in malaria patients than those who were not infected. Overall, the results revealed a significant reduction in blood levels of vitamin E in malaria patients when compared with uninfected individuals (p < 0.01, Cohen's d: -2.74, 95% CI: -3.72-(-1.76), I2: 98.69%, 21 studies). There was a significant reduction in blood levels of vitamin E in patients suffering from severe malaria, in comparison with those experiencing less severe forms of the disease (p < 0.01, Cohen's d: -0.56, 95% CI: -0.85-(-0.26), I2: 0%, 2 studies), but no variation in blood levels of vitamin E among patients suffering from either P. falciparum or P. vivax malaria (p = 0.13, Cohen's d: -1.15, 95% CI: -2.62-0.33, I2: 93.22%, 3 studies). In summary, the present study strongly suggests that vitamin E levels are significantly reduced in malaria patients, with a more pronounced decrease observed in cases of severe malaria. However, the type of malaria parasite, specifically P. falciparum or P. vivax, did not appear to influence the levels of vitamin E. This study highlights the potential role of vitamin E in the pathogenesis of malaria and suggests that improved vitamin E status might be beneficial for improving disease outcomes.

Effects of Daily Zinc Alone or in Combination with Other Nutrient Supplements on the Risk of Malaria Parasitaemia: A Systematic Review and Meta-Analysis of Randomised Controlled Trials

Zinc supplementation has been explored as a potential intervention to reduce the risk of malaria parasitaemia in randomised controlled trials (RCTs). However, inconsistent evidence has been obtained regarding the efficacy of zinc supplementation in the context of malaria prevention. This systematic review was implemented to survey the existing literature to determine the effects of the daily oral administration of zinc, either alone or in combination with other nutrient supplements, on the risk of malaria parasitaemia. The systematic review was prospectively registered in the PROSPERO database CRD42023424345 and followed PRISMA protocols. A comprehensive search was conducted across multiple databases, including Embase, MEDLINE, Ovid, PubMed, Scopus, ProQuest, and Google Scholar, from their inception until 6 May 2023. The risk of bias in RCTs was assessed using the Cochrane Risk of Bias Tool 2 (RoB 2). The effect sizes, represented as risk ratios (RRs) with 95% confidence intervals (CIs), were standardised by transforming them into log RRs and then pooling them using a fixed-effects or random-effects model depending on the heterogeneity across studies. Comparisons were made between individuals who received zinc alone or zinc in combination with other micronutrient supplements and those who did not receive zinc. A total of 1339 articles were identified through the database searches, and after the screening and selection process, 10 studies were included in the final synthesis. The meta-analysis revealed that zinc supplementation alone did not significantly affect the risk of malaria parasitaemia compared with placebo (p = 0.30, log RR = 0.05, 95% CI: -0.05-0.15, I² = 0.00%, with 566 malaria cases in the zinc intake group and 521 malaria cases in the placebo group). However, the analysis demonstrated a borderline significant effect of zinc supplementation in combination with other micronutrients on the risk of malaria parasitaemia compared with placebo (p = 0.05, log RR = 1.31, 95% CI: 0.03-2.59, I² = 99.22%, with 8904 malaria cases in the zinc intake group and 522 malaria cases in the placebo group). The findings of this systematic review indicate that zinc supplementation, either alone or combined with the supplementation of other micronutrients such as vitamin A, iron, or multiple nutrients, does not significantly alter the risk of malaria parasitaemia. Further research with larger sample sizes is warranted to explore the potential effects of multi-nutrient supplementation and to identify more specific micronutrients and additional factors associated with the risk of malaria, rather than just zinc alone, among individuals in different malaria-endemic areas.

The antioxidant protein glutaredoxin 1 is essential for oxidative stress response and pathogenicity of Toxoplasma gondii

Glutaredoxins (Grxs) are ubiquitous antioxidant proteins involved in many molecular processes to protect cells against oxidative damage. Here, we study the roles of Grxs in the pathogenicity of Toxoplasma gondii. We show that Grxs are localized in the mitochondria (Grx1), cytoplasm (Grx2), and apicoplast (Grx3, Grx4), while Grx5 had an undetectable level of expression. We generated Δgrx1-5 mutants of T. gondii type I RH and type II Pru strains using CRISPR-Cas9 system. No significant differences in the infectivity were detected between four Δgrx (grx2-grx5) strains and their respective wild-type (WT) strains in vitro or in vivo. Additionally, no differences were detected in the production of reactive oxygen species, total antioxidant capacity, superoxide dismutase activity, and sensitivity to external oxidative stimuli. Interestingly, RHΔgrx1 or PruΔgrx1 exhibited significant differences in all the investigated aspects compared to the other grx2-grx5 mutant and WT strains. Transcriptome analysis suggests that deletion of grx1 altered the expression of genes involved in transport and metabolic pathways, signal transduction, translation, and obsolete oxidation-reduction process. The data support the conclusion that grx1 supports T. gondii resistance to oxidative killing and is essential for the parasite growth in cultured cells and pathogenicity in mice and that the active site CGFS motif was necessary for Grx1 activity.

Amino acid supplementation confers protection to red blood cells prior to Plasmodium falciparum bystander stress

Malaria is a highly oxidative parasitic disease in which anemia is the most common clinical symptom. A major contributor to malarial anemia pathogenesis is the destruction of bystander, uninfected red blood cells. Metabolic fluctuations are known to occur in the plasma of individuals with acute malaria, emphasizing the role of metabolic changes in disease progression and severity. Here, we report that conditioned media from Plasmodium falciparum culture induces oxidative stress in healthy uninfected RBCs. Additionally, we show the benefit of amino acid pre-exposure for RBCs and how this pre-treatment intrinsically prepares RBCs to mitigate oxidative stress.

Key points

Intracellular ROS is acquired in red blood cells incubated with Plasmodium falciparum conditioned media Glutamine, cysteine, and glycine amino acid supplementation increased glutathione biosynthesis and reduced ROS levels in stressed RBCs.

Vanadium compounds as antiparasitic agents: An approach to their mechanisms of action

BACKGROUND

Parasitic infections are a public health problem since they have high morbidity and mortality worldwide. In parasitosis such as malaria, leishmaniasis and trypanosomiasis it is necessary to develop new compounds for their treatment since an increase in drug resistance and toxic effects have been observed. Therefore, the use of different compounds that couple vanadium in their structure and that have a broad spectrum against different parasites have been proposed experimentally.

OBJECTIVE

Report the mechanisms of action exerted by vanadium in different parasites.

CONCLUSION

In this review, some of the targets that vanadium compounds have were identified and it was observed that they have a broad spectrum against different parasites, which represents an advance to continue investigating therapeutic options.

Synthesis and antimalarial activity of amide and ester conjugates of siderophores and ozonides

Despite advances in chemotherapeutic interventions for the treatment of malaria, there is a continuing need for the development of new antimalarial agents. Previous studies indicated that co-administration of chloroquine with antioxidants such as the iron chelator deferoxamine (DFO) prevented the development of persistent cognitive damage in surrogate models of cerebral malaria. The work described herein reports the syntheses and antimalarial activities of covalent conjugates of both natural (siderophores) and artificial iron chelators, namely DFO, ferricrocin and ICL-670, with antimalarial 1,2,4-trioxolanes (ozonides). All of the synthesized conjugates had potent antimalarial activities against the in vitro cultures of drug resistant and drug sensitive strains of Plasmodium falciparum. The work described herein provides the basis for future development of covalent combination of iron chelators and antimalarial chemotherapeutic agents for the treatment of cerebral malaria.

Primaquine, an antimalarial drug that controls the growth of cryptococcal cells

INTRODUCTION

The treatment of Cryptococcus neoformans with fluconazole and amphotericin B is, at times, characterised by clinical failure. Therefore, this study sought to re-purpose primaquine (PQ) as an anti-Cryptococcus compound.

METHOD

The susceptibility profile of some cryptococcal strains towards PQ was determined using EUCAST guidelines, and PQ's mode of action was examined. In the end, the ability of PQ to enhance in vitro macrophage phagocytosis was also assessed.

RESULTS

We show that PQ had a significant inhibitory effect on the metabolic activity of all tested cryptococcal strains, with 60 µM, defined as MIC₅₀ in this preliminary study, as it reduced the metabolic activity by more than 50%. Moreover, at this concentration, the drug was able to affect mitochondrial function adversely, as treated cells displayed significant (p < 0.05) loss of mitochondrial membrane potential, cytochrome c (cyt c) leakage and overproduction of reactive oxygen species (ROS) when compared to non-treated cells. It is our reasoned summation that the produced ROS targeted the cell walls and cell membranes, inducing observable ultrastructural changes and a significant (p < 0.05) increase in membrane permeability when compared to non-treated cells. Concerning the PQ effect on macrophages, it was noted that it significantly (p < 0.05) enhanced macrophage phagocytic efficiency compared to non-treated macrophages.

CONCLUSION

This preliminary study highlights the potential of PQ to inhibit the in vitro growth of cryptococcal cells. Moreover, PQ could control the proliferation of cryptococcal cells inside macrophages, which they often manipulate in a Trojan horse-like manner.

Diagnosis of cerebral malaria: Tools to reduce Plasmodium falciparum associated mortality

Cerebral malaria (CM) is a major cause of mortality in Plasmodium falciparum (Pf) infection and is associated with the sequestration of parasitised erythrocytes in the microvasculature of the host's vital organs. Prompt diagnosis and treatment are key to a positive outcome in CM. However, current diagnostic tools remain inadequate to assess the degree of brain dysfunction associated with CM before the window for effective treatment closes. Several host and parasite factor-based biomarkers have been suggested as rapid diagnostic tools with potential for early CM diagnosis, however, no specific biomarker signature has been validated. Here, we provide an updated review on promising CM biomarker candidates and evaluate their applicability as point-of-care tools in malaria-endemic areas.

Luffa cylindrica (Linn. M. J. Roem) Reduces Oxidative Stress In Vivo in Plasmodium berghei-Infected Albino Mice

Background: Malaria is endemic in sub-Saharan Africa, and oxidative stress has been implicated in malaria disease. Luffa cylindrica is an ethnomedicinal plant used to treat various diseases, including malaria. The oxidative stress-reducing potential of L. cylindrica in malaria-disease state of Plasmodium berghei NK-65 parasite-infected mice was carried out in vivo.

Methods: Mice were infected with P. berghei NK-65, and the effect of administration of methanolic leaves extract (100, 200, and 400 mg/kg b.w) of L. cylindrica on percentage parasitemia in blood smear, antioxidant enzymes (catalase CAT, superoxide dismutase SOD, glutathione-s-transferase GST), non-enzymatic antioxidant (reduced glutathione GSH) and malondialdehyde concentration in tissues (plasma, liver, kidneys, and spleen) of mice was investigated and compared to chloroquine and artesunate as reference antimalarial drugs. Phytochemical constituents of the extract were determined by standard methods.

Results: Saponins, tannins, terpenes, phenolics, flavonoids, alkaloids, and glycosides were the phytochemical constituents identified in the extract. The extract at three doses (100, 200, and 400 mg/kg b.w.) investigated caused a significant reduction (p < 0.05) of parasite growth with over 90% reduction in parasitemia level in mice infected with the parasite. The extract also ameliorated oxidative stress in mice by significantly (p < 0.05) increasing the activities of CAT, SOD, and GST in the studied tissues of mice. The level of malondialdehyde, a marker of oxidative stress in mice, was also significantly (p < 0.05) reduced by the extract. The results were comparable with chloroquine- and artesunate-treated groups.

Conclusion: The study concludes that L. cylindrica is an effective therapy for treating malaria and for the management of its oxidative stress-related complications due to its antioxidant properties.

A Postulated Mechanism of the Antimalarial Effect of Free Radicals Generated by Artemisinin on Plasmodium falciparum

Artemisinin and its derivatives, a class of antimalarial drugs, were first isolated from Artemisia annua. Artemisinin can alter the pH of the malaria parasite’s digestive vacuole from acidic to alkaline, leading to parasite death. However, the precise mechanism of artemisinin action in changing the digestive vacuole pH has not yet been confirmed. Previous studies reported that artemisinin and its derivatives could kill the parasites through the generation of oxidative stress by the free radicals they generate. This review aims to provide a better understanding of the possible mechanism of action of artemisinin, focusing on the antimalarial activity caused by the generated free radicals through the induction of mutation in the genes that encode the proton pump of the Plasmodium falciparum digestive vacuole.

Potential Benefits of Lycopene Consumption: Rationale for Using It as an Adjuvant Treatment for Malaria Patients and in Several Diseases

Malaria is a disease that affects thousands of people around the world every year. Its pathogenesis is associated with the production of reactive oxygen and nitrogen species (RONS) and lower levels of micronutrients and antioxidants. Patients under drug treatment have high levels of oxidative stress biomarkers in the body tissues, which limits the use of these drugs. Therefore, several studies have suggested that RONS inhibition may represent an adjuvant therapeutic strategy in the treatment of these patients by increasing the antioxidant capacity of the host. In this sense, supplementation with antioxidant compounds such as zinc, selenium, and vitamins A, C, and E has been suggested as part of the treatment. Among dietary antioxidants, lycopene is the most powerful antioxidant among the main carotenoids. This review aimed to describe the main mechanisms inducing oxidative stress during malaria, highlighting the production of RONS as a defense mechanism against the infection induced by the ischemia-reperfusion syndrome, the metabolism of the parasite, and the metabolism of antimalarial drugs. Furthermore, the effects of lycopene on several diseases in which oxidative stress is implicated as a cause are outlined, providing information about its mechanism of action, and providing an evidence-based justification for its supplementation in malaria.

Nitric oxide in parasitic infections: a friend or foe?

The complex interaction between the host and the parasite remains a puzzling question. Control of parasitic infections requires an efficient immune response that must be balanced against destructive pathological consequences. Nitric oxide is a nitrogenous free radical which has many molecular targets and serves diverse functions. Apart from being a signaling messenger, nitric oxide is critical for controlling numerous infections. There is still controversy surrounding the exact role of nitric oxide in the immune response against different parasitic species. It proved protective against intracellular protozoa, as well as extracellular helminths. At the same time, it plays a pivotal role in stimulating detrimental pathological changes in the infected hosts. Several reports have discussed the anti-parasitic and immunoregulatory functions of nitric oxide, which could directly influence the control of the infection. Nevertheless, there is scarce literature addressing the harmful cytotoxic impacts of this mediator. Thus, this review provides insights into the most updated concepts and controversies regarding the dual nature and opposing sides of nitric oxide during the course of different parasitic infections.

Effect of black seeds (Nigella sativa) on inflammatory and immunomodulatory markers in Plasmodium berghei-infected mice

Nigella sativa, a core dietary supplement and food additive in folklore is one of the most broadly studied seed plants in the global nutraceutical sector. Malaria infection impairs the ability of principal cells of the immune system to trigger an efficient inflammatory and immune response. Ninety-six mice, weighing 20-25 g, were grouped into 12 consisting of 8 animals each. The mice were infected with standard inoculum of the strain NK65 Plasmodium berghei (chloroquine sensitive) and the percentage parasitemia suppression were evaluated. The individual effect of black seed supplemented diet and its combinatory effect with chloroquine (CQ) were investigated on reactive oxygen species (ROS), glutathione peroxidase (GPx), reduced glutathione (GSH), glutathione-S-transferase (GST), serum immunoglobulins (IgG and IgM), and the hematological parameters (hemoglobin, packed cell volume, and red blood cell count) in P. berghei infected mice. The inflammatory cytokines, tumor necrosis factor (TNF-α), interleukin (IL-6 and IL-10), as well as IgG and IgM were assayed in the serum. The mice temperature and behavioral changes were observed. Infected mice treated with the dietary supplementation of black seed with a percentage inclusion (2.5%, 5%, 10%) showed significantly decreased parasitemia and ROS levels (p < 0.05) compared with the untreated mice. The result demonstrated a significant suppression in the pro-inflammatory cytokines (TNF-α, IL-6) levels and a notable elevation in the anti-inflammatory cytokine (IL-10), antioxidant markers as well as the immunoglobulin levels of the P. berghei-infected mice treated with black seed. The study revealed that black seed enhanced host antioxidant status, modulated inflammatory and immune response by regulating some inflammatory cytokines and immunomodulatory mediators. PRACTICAL APPLICATIONS: Black seed (Nigella sativa) has been a dietary supplement and natural remedy for many centuries. Inflammatory and immune diseases are the most notable cause of mortality in the world and more than 50% of deaths have been attributed to it. However, there is paucity of information on the effect of N. sativa on anti-inflammatory and immunomodulatory ability during malaria infection. The result suggests that N. sativa produced antioxidant, anti-inflammatory, and immunomodulatory effect in Plasmodium berghei-infected mice via the participation of glutathione antioxidant system, serum antibodies, and some inflammatory cytokines.

Transient State Kinetics of Plasmodium falciparum Apicoplast DNA Polymerase Suggests the Involvement of Accessory Factors for Efficient and Accurate DNA Synthesis

Plasmodium, the causative agent of malaria, belongs to the phylum Apicomplexa. Most apicomplexans, including Plasmodium, contain an essential nonphotosynthetic plastid called the apicoplast that harbors its own genome that is replicated by a dedicated organellar replisome. This replisome employs a single DNA polymerase (apPol), which is expected to perform both replicative and translesion synthesis. Unlike other replicative polymerases, no processivity factor for apPol has been identified. While preliminary structural and biochemical studies have provided an overall characterization of apPol, the kinetic mechanism of apPol's activity remains unknown. We have used transient state methods to determine the kinetics of replicative and translesion synthesis by apPol and show that apPol has low processivity and efficiency while copying undamaged DNA. Moreover, while apPol can bypass oxidatively damaged lesions, the bypass is error-prone. Taken together, our results raise the following question─how does a polymerase with low processivity, efficiency, and fidelity (for translesion synthesis) faithfully replicate the apicoplast organellar DNA within the hostile environment of the human host? We hypothesize that interactions with putative components of the apicoplast replisome and/or an as-yet-undiscovered processivity factor transform apPol into an efficient and accurate enzyme.

Transepithelial transport and cellular mechanisms of food-derived antioxidant peptides

Considering the involvement of oxidative stress in the etiology of many non-communicable diseases, food-derived antioxidant peptides (FDAPs) are strong candidates for nutraceutical development for disease prevention and management. This paper reviews current evidence on the transepithelial transport and cellular mechanisms of antioxidant activities of FDAPs. Several FDAPs have multiple health benefits such as anti-inflammatory and anti-photoaging activities, in addition to antioxidant properties through which they protect cellular components from oxidative damage. Some FDAPs have been shown to permeate the intestinal epithelium, which could facilitate their bioavailability and physiological bioactivities. Molecular mechanisms of FDAPs include suppression of oxidative stress as evidenced by reduction in intracellular reactive oxygen species production, lipid peroxidation and apoptotic protein activation as well as increase in antioxidant defense mechanisms (enzymatic and non-enzymatic). Since many FDAPs have demonstrated promising antioxidant activity, future investigation should focus on further elucidation of molecular mechanisms and human studies to explore their practical application for the prevention and management of oxidative stress-related diseases.

Implication of asymptomatic and clinical Plasmodium falciparum infections on biomarkers of iron status among school-aged children in Malawi

Background

Iron status is considered as a continuum from an iron deficiency with anaemia, without anaemia, varying amounts of stored iron to iron overload. The burden of Plasmodium falciparum infections is typically high among school-aged children (SAC). Nonetheless, SAC are often less likely to be covered by malaria interventions, making them a group with an untreated reservoir of parasite transmission. This study aimed to assess the effects of asymptomatic and clinical malaria infections on biochemical markers of iron status among SAC in Malawi.

Methods

Data from the 2015–2016 Malawi Micronutrient Survey (MNS) was used and multivariable logistic regression models using a generalized estimating equation to account for the complex cluster survey design were constructed. Blood samples of 684 children aged 5 to 14 years old were evaluated for clinical and asymptomatic malaria infections. Furthermore, blood samples were used to estimate haemoglobin (Hb), serum ferritin (SF) and, soluble transferrin receptors (sTfR) concentrations.

Results

Of the 684 SAC analysed, approximately 42% had asymptomatic malaria, while 41.0% had clinical malaria. Anaemia (low Hb levels), iron deficiency (low SF concentration), and functional iron deficiency (high sTfR levels) were found in 20%, 5%, and 30% of the children, respectively. School-aged children with asymptomatic malaria had increased odds of being anaemic (adjusted odds ratio [aOR]: 3.71, 95% confidence interval [CI]: 2.29–5.99) and increased levels of sTfR (aOR: 3.00, 95% CI 2.01–4.47). Similarly, SAC with clinical malaria had increased odds of being anaemic (aOR: 3.54, 95% CI 2.19–5.72) and increased levels of sTfR (aOR: 3.02, 95% CI 2.02–4.52).

Conclusions

Both asymptomatic and clinical malaria were independent risk factors for anaemia and functional iron deficiency (FID). The notion that asymptomatic and clinical malaria were associated with both anaemia and FID underscores the need for public health programmers to consider adding mass screening and treatment for malaria to existing school-based health programmes.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12936-022-04297-1.

Impact of Oxidative Stress on Risk of Death and Readmission in African Children With Severe Malaria: A Prospective Observational Study

BACKGROUND

We hypothesized that oxidative stress in Ugandan children with severe malaria is associated with mortality.

METHODS

We evaluated biomarkers of oxidative stress in children with cerebral malaria (CM, n = 77) or severe malarial anemia (SMA, n = 79), who were enrolled in a randomized clinical trial of immediate vs delayed iron therapy, compared with community children (CC, n = 83). Associations between admission biomarkers and risk of death during hospitalization or risk of readmission within 6 months were analyzed.

RESULTS

Nine children with CM and none with SMA died during hospitalization. Children with CM or SMA had higher levels of heme oxygenase-1 (HO-1) (P < .001) and lower superoxide dismutase (SOD) activity than CC (P < .02). Children with CM had a higher risk of death with increasing HO-1 concentration (odds ratio [OR], 6.07 [95% confidence interval {CI}, 1.17-31.31]; P = .03) but a lower risk of death with increasing SOD activity (OR, 0.02 [95% CI, .001-.70]; P = .03). There were no associations between oxidative stress biomarkers on admission and risk of readmission within 6 months of enrollment.

CONCLUSIONS

Children with CM or SMA develop oxidative stress in response to severe malaria. Oxidative stress is associated with higher mortality in children with CM but not with SMA.

CLINICAL TRIALS REGISTRATION

NCT01093989.

Neutrophils in malaria: A double-edged sword role

Neutrophils are the most abundant leukocytes in human peripheral blood. They form the first line of defense against invading foreign pathogens and might play a crucial role in malaria. According to World Health Organization (WHO), malaria is a globally significant disease caused by protozoan parasites from the Plasmodium genus, and it's responsible for 627,000 deaths in 2020. Neutrophils participate in the defense response against the malaria parasite via phagocytosis and reactive oxygen species (ROS) production. Neutrophils might also be involved in the pathogenesis of malaria by the release of toxic granules and the release of neutrophil extracellular traps (NETs). Intriguingly, malaria parasites inhibit the anti-microbial function of neutrophils, thus making malaria patients more susceptible to secondary opportunistic Salmonella infections. In this review, we will provide a summary of the role of neutrophils during malaria infection, some contradicting mouse model neutrophil data and neutrophil-related mechanisms involved in malaria patients' susceptibility to bacterial infection.

The Cross-Species Immunity During Acute Babesia Co-Infection in Mice

Babesiosis causes high morbidity and mortality in immunocompromised individuals. An earlier study suggested that lethal Babesia rodhaini infection in murine can be evaded by Babesia microti primary infection via activated macrophage-based immune response during the chronic stage of infection. However, whether the same immune dynamics occur during acute B. microti co-infection is not known. Hence, we used the mouse model to investigate the host immunity during simultaneous acute disease caused by two Babesia species of different pathogenicity. Results showed that B. microti primary infection attenuated parasitemia and conferred immunity in challenge-infected mice as early as day 4 post-primary infection. Likewise, acute Babesia co-infection undermined the splenic immune response, characterized by the significant decrease in splenic B and T cells leading to the reduction in antibody levels and decline in humoral immunity. Interestingly, increased macrophage and natural killer splenic cell populations were observed, depicting their subtle role in the protection. Pro-inflammatory cytokines (i.e. IFN-γ, TNF-α) were downregulated, while the anti-inflammatory cytokine IL-10 was upregulated in mouse sera during the acute phase of Babesia co-infection. Herein, the major cytokines implicated in the lethality caused by B. rodhaini infection were IFN- γ and IL-10. Surprisingly, significant differences in the levels of serum IFN- γ and IL-10 between co-infected survival groups (day 4 and 6 challenge) indicated that even a two-day delay in challenge infection was crucial for the resulting pathology. Additionally, oxidative stress in the form of reactive oxygen species contributed to the severity of pathology during acute babesiosis. Histopathological examination of the spleen showed that the erosion of the marginal zone was more pronounced during B. rodhaini infection, while the loss of cellularity of the marginal zone was less evident during co-infection. Future research warrants investigation of the roles of various immune cell subtypes in the mechanism involved in the protection of Babesia co-infected hosts.