The murine model of cerebral malaria (ECM) caused by Plasmodium berghei ANKA (PbA) infection in susceptible mice has been extensively used for studies of pathogenesis and identification of potential targets for human CM therapeutics. However, the model has been seldom explored to evaluate adjunctive therapies for this malaria complication. A first step toward this goal is to define a treatment protocol with an effective antimalarial drug able to rescue mice presenting late-stage ECM. We evaluated the efficacy of artemisinin, artemether, artesunate, and quinine given intraperitoneally once a day, and combinations with mefloquine, in suppressing PbA infection in mice with moderate parasitemia. Artemether, artesunate, and quinine were then evaluated for efficacy in rescuing PbA-infected mice with ECM, strictly defined by using objective criteria based on the presentation of clinical signs of neurological involvement, degree of hypothermia, and performance in a set of six motor behavior tests. Artemether at 25 mg/kg presented the fastest parasite killing ability in 24 h and fully avoided recrudescence in a 5-day treatment protocol. Artemether and artesunate were equally effective in rescuing mice with late-stage ECM (46 and 43% survival, respectively), whereas quinine had a poor performance (12.5% survival). Artemether caused a marked decrease in brain leukocyte accumulation 24 h after the first dose. In conclusion, artemether and artesunate are effective in rescuing mice with late-stage ECM and decrease brain inflammation. In addition, the described protocols for more strict clinical evaluation and for rescue treatment provide a framework for studies of CM adjunctive therapies using this mouse model.

Sleep disturbances and chronic pain are prevalent and interrelated conditions that have significant impact on individuals’ quality of life. Understanding the intricate dynamics between sleep and pain is crucial for developing effective treatments that enhance the well-being of affected individuals and reduce the economic burden of these debilitating conditions. This narrative review examines the complex relationship between sleep disturbances and chronic pain. We describe the prevalence and types of sleep disturbances and sleep disorders in chronic pain patients. Posteriorly, we critically review the clinical and experimental evidence, investigating the relationship between sleep disturbances and chronic pain, aiming to clarify the impact of chronic pain on sleep and, conversely, the impact of sleep disturbances on pain perception. In conclusion, the literature largely agrees on the existence of a bidirectional relationship between chronic pain and sleep disturbances, though the strength of each direction in this association remains uncertain. Current evidence suggests that sleep impairment more strongly predicts pain than pain does sleep impairment. Additionally, addressing sleep disturbances in chronic pain patients is crucial, as poor sleep has been linked to higher levels of disability, depression, and pain-related catastrophizing.

Cerebrovascular dysfunction plays a key role in the pathogenesis of cerebral malaria. In experimental cerebral malaria (ECM) induced by Plasmodium berghei ANKA, cerebrovascular dysfunction characterized by vascular constriction, occlusion and damage results in impaired perfusion and reduced cerebral blood flow and oxygenation, and has been linked to low nitric oxide (NO) bioavailability. Here, we directly assessed cerebrovascular function in ECM using a novel cranial window method for intravital microscopy of the pial microcirculation and probed the role of NOS isoforms and phosphorylation patterns in the impaired vascular responses. We show that pial arteriolar responses to endothelial NOS (eNOS) and neuronal NOS (nNOS) agonists (Acetylcholine (ACh) and N-Methyl-D-Aspartate (NMDA)) were blunted in mice with ECM, and could be partially recovered by exogenous supplementation of tetrahydrobiopterin (BH4). Pial arterioles in non-ECM mice infected by Plasmodium berghei NK65 remained relatively responsive to the agonists and were not significantly affected by BH4 treatment. These findings, together with the observed blunting of NO production upon stimulation by the agonists, decrease in total NOS activity, augmentation of lipid peroxidation levels, upregulation of eNOS protein expression, and increase in eNOS and nNOS monomerization in the brain during ECM development strongly indicate a state of eNOS/nNOS uncoupling likely mediated by oxidative stress. Furthermore, the downregulation of Serine 1176 (S1176) phosphorylation of eNOS, which correlated with a decrease in cerebrovascular wall shear stress, implicates hemorheological disturbances in eNOS dysfunction in ECM. Finally, pial arterioles responded to superfusion with the NO donor, S-Nitroso-L-glutathione (GSNO), but with decreased intensity, indicating that not only NO production but also signaling is perturbed during ECM. Therefore, the pathological impairment of eNOS and nNOS functions contribute importantly to cerebrovascular dysfunction in ECM and the recovery of intrinsic functionality of NOS to increase NO bioavailability and restore vascular health represents a target for ECM treatment. Cerebrovascular dysfunction plays a key role in the pathogenesis of murine cerebral malaria (CM). Low nitric oxide (NO) bioavailability has been attributed as a cause of the dysfunction. However, it is unclear if the NO deficit could be inflicted by decreased NO production from its enzymatic sources (NO synthases (NOS)) in the brain. Here, we applied a novel cranial window method to elucidate the role of NOS in cerebrovascular dysfunction in murine CM. We found a state of endothelial NOS (eNOS) and neuronal NOS (nNOS) dysfunctions that are detrimental to cerebroarteriolar reactivity. Supplementation of tetrahydrobiopterin (BH4), a cofactor for NOS activation, ameliorates this effect. Supported by experimental findings on the downregulation of total NOS activity as well as the enhancement of oxidative stress, eNOS protein expression and conformational eNOS and nNOS inactivation in brains of mice with CM, we identified eNOS/nNOS uncoupling as a potential mechanism responsible for the NOS dysfunction. In addition, we discovered a downregulation of eNOS phosphorylation at its Serine residue (S1176) that can possibly decrease eNOS activity and exacerbate eNOS dysfunction. Our study provides new insights on the involvement of NOS in cerebrovascular dysfunction during CM and suggests NOS as a therapeutic target for CM.

Cerebral malaria (CM) is a life-threatening complication of Plasmodium falciparum malaria that continues to be a major global health problem. Brain vascular dysfunction is a main factor underlying the pathogenesis of CM and can be a target for the development of adjuvant therapies for the disease. Vascular occlusion by parasitised red blood cells and vasoconstriction/vascular dysfunction results in impaired cerebral blood flow, ischaemia, hypoxia, acidosis and death. In this review, we discuss the mechanisms of vascular dysfunction in CM and the roles of low nitric oxide bioavailability, high levels of endothelin-1 and dysfunction of the angiopoietin-Tie2 axis. We also discuss the usefulness and relevance of the murine experimental model of CM by Plasmodium berghei ANKA to identify mechanisms of disease and to screen potential therapeutic interventions.