Hemoglobin Degradation Research Articles

Brain endothelial STING1 activation by Plasmodium-sequestered heme promotes cerebral malaria via type I IFN response

Cerebral malaria (CM) is a life-threatening form of Plasmodium falciparum infection caused by brain inflammation. Brain endothelium dysfunction is a hallmark of CM pathology, which is also associated with the activation of the type I interferon (IFN) inflammatory pathway. The molecular triggers and sensors eliciting brain type I IFN cellular responses during CM remain largely unknown. We herein identified the stimulator of interferon response cGAMP interactor 1 (STING1) as the key innate immune sensor that induces Ifnβ1 transcription in the brain of mice infected with Plasmodium berghei ANKA (Pba). This STING1/IFNβ-mediated response increases brain CXCL10 governing the extent of brain leukocyte infiltration and blood-brain barrier (BBB) breakdown, and determining CM lethality. The critical role of brain endothelial cells (BECs) in fueling type I IFN-driven brain inflammation was demonstrated in brain endothelial-specific IFNβ-reporter and STING1-deficient Pba-infected mice, which were significantly protected from CM lethality. Moreover, extracellular particles (EPs) released from Pba-infected erythrocytes activated the STING1-dependent type I IFN response in BECs, a response requiring intracellular acidification. Fractionation of the EPs enabled us to identify a defined fraction carrying hemoglobin degradation remnants that activates STING1/IFNβ in the brain endothelium, a process correlated with heme content. Notably, stimulation of STING1-deficient BECs with heme, docking experiments, and invitro binding assays unveiled that heme is a putative STING1 ligand. This work shows that heme resultant from the parasite heterotrophic activity operates as an alarmin, triggering brain endothelial inflammatory responses via the STING1/IFNβ/CXCL10 axis crucial to CM pathogenesis and lethality.

Immune activation after intraventricular hemorrhage

ObjectivesIntraventricular hemorrhage (IVH) is a subtype of stroke which has high mortality and morbidity, while comprehensive mechanism investigations and effective therapies are still in great need. Plenty of studies have shown that inflammation after stroke plays a critical role in disease outcomes. However, the inflammation after IVH remains unclear. This study aims to observe the immune response after IVH, thus providing therapeutic targets for IVH treatments. Materials and methodsIVH was induced by autologous blood infusion model in SD rats. Totally 588 rats were assigned either in the sham or IVH group. T2* lesion and hemoglobin quantities, ventricular volume, brain edema, ventricular wall damage, blood-brain-barrier (BBB) continuity and immune response were observed by magnetic resonance image (MRI), hematoxylin-eosin staining (HE), Evans Blue, flow cytometry (FACS), and enzyme-linked immunosorbent assay (ELISA) at baseline, 6 h, 1 d, 3 d, 7 d, 14 d after surgery. ResultsWe found that ventricular volume enlargement occurred hours after IVH and peaked at 3 d after IVH, then mildly reduced till 14 d. Similar changes happened in brain edema, ventricular wall damage and BBB leakage. Immune cells and cytokines in the central nervous system and peripheral blood also increased after IVH and experienced similar trends as ventricular enlargement. T2* lesion and hemoglobin degradation occurred 6 h after IVH and kept decreasing till 14 d after IVH. ConclusionsOur investigation illustrates that immune response exists after IVH, which may have a close relationship with disease outcomes. These results may provide promising immune related clues for mechanism and intervention studies in IVH.

Docosahexaenoic acid is potent against the growth of mature stages of Plasmodium falciparum; inhibition of hematin polymerization a possible target.

The present study investigates the potential effect of externally added unsaturated fatty acids on P. falciparum growth. Our results indicate that polyunsaturated fatty acids (PUFAs) inhibit the growth of Plasmodium in proportional to their degree of unsaturation. At higher concentration the PUFA Docosahexaenoic acid (DHA) induces pyknotic nuclei in infected erythrocytes. When Plasmodium stages were treated transiently with DHA, the ring stage culture recovered from the drug effect and parasitemia was increased post DHA removal with delayed growth of 12h, compared to untreated control. Schizont stage treated culture displayed a 36h delay in growth to infect fresh erythrocytes signifying its recovery is less than the ring stage. However the trophozoite stage failed to recover and showed a decrease in parasitemia, similar to that of continuous treated culture. PUFAs inhibited β- hematin polymerization by binding to free heme derived from hemoglobin degradation. Digestive vacuole neutral lipid bodies, which are pivotal for β- hematin polymerization, decreased and subsequently abrogated with increasing concentration of DHA in trophozoite stage treated culture. Our study concludes that DHA interacts with heme monomers and inhibits the β- hematin polymerization and growth of mature stages i.e., trophozoite and schizont stages of plasmodium.

Elevated cerebrospinal fluid iron and ferritin associated with early severe ventriculomegaly in preterm posthemorrhagic hydrocephalus.

Posthemorrhagic hydrocephalus (PHH) following preterm intraventricular hemorrhage (IVH) is among the most severe sequelae of extreme prematurity and a significant contributor to preterm morbidity and mortality. The authors have previously shown hemoglobin and ferritin to be elevated in the lumbar puncture cerebrospinal fluid (CSF) of neonates with PHH. Herein, they evaluated CSF from serial ventricular taps to determine whether neonates with PHH following severe initial ventriculomegaly had higher initial levels and prolonged clearance of CSF hemoglobin and hemoglobin degradation products compared to those in neonates with PHH following moderate initial ventriculomegaly. In this observational cohort study, CSF samples were obtained from serial ventricular taps in premature neonates with severe IVH and subsequent PHH. CSF hemoglobin, ferritin, total iron, total bilirubin, and total protein were quantified using ELISA. Ventriculomegaly on cranial imaging was assessed using the frontal occipital horn ratio (FOHR) and was categorized as severe (FOHR > 0.6) or moderate (FOHR ≤ 0.6). Ventricular tap CSF hemoglobin (mean) and ferritin (initial and mean) were higher in neonates with severe versus moderate initial ventriculomegaly. CSF hemoglobin, ferritin, total iron, total bilirubin, and total protein decreased in a nonlinear fashion over the weeks following severe IVH. Significantly higher levels of CSF ferritin and total iron were observed in the early weeks following IVH in neonates with severe initial ventriculomegaly than in those with initial moderate ventriculomegaly. Among preterm neonates with PHH following severe IVH, elevated CSF hemoglobin, ferritin, and iron were associated with more severe early ventricular enlargement (FOHR > 0.6 vs ≤ 0.6 at first ventricular tap).

Keystone Malaria Symposium 2022: a vibrant discussion of progress made and challenges ahead from drug discovery to treatment

Keystone Malaria Symposium 2022: a vibrant discussion of progress made and challenges ahead from drug discovery to treatment

The Knock-Down of the Chloroquine Resistance Transporter PfCRT Is Linked to Oligopeptide Handling in Plasmodium falciparum.

ABSTRACTThe chloroquine resistance transporter, PfCRT, is an essential factor during intraerythrocytic development of the human malaria parasite Plasmodium falciparum. PfCRT resides at the digestive vacuole of the parasite, where hemoglobin taken up by the parasite from its host cell is degraded. PfCRT can acquire several mutations that render PfCRT a drug transporting system expelling compounds targeting hemoglobin degradation from the digestive vacuole. The non-drug related function of PfCRT is less clear, although a recent study has suggested a role in oligopeptide transport based on studies conducted in a heterologous expression system. The uncertainty about the natural function of PfCRT is partly due to a lack of a null mutant and a dearth of functional assays in the parasite. Here, we report on the generation of a conditional PfCRT knock-down mutant in P. falciparum. The mutant accumulated oligopeptides 2 to at least 8 residues in length under knock-down conditions, as shown by comparative global metabolomics. The accumulated oligopeptides were structurally diverse, had an isoelectric point between 4.0 and 5.4 and were electrically neutral or carried a single charge at the digestive vacuolar pH of 5.2. Fluorescently labeled dipeptides and live cell imaging identified the digestive vacuole as the compartment where oligopeptides accumulated. Our findings suggest a function of PfCRT in oligopeptide transport across the digestive vacuolar membrane in P. falciparum and associated with it a role in nutrient acquisition and the maintenance of the colloid osmotic balance.IMPORTANCE The chloroquine resistance transporter, PfCRT, is important for the survival of the human malaria parasite Plasmodium falciparum. It increases the tolerance to many antimalarial drugs, and it is essential for the development of the parasite within red blood cells. While we understand the role of PfCRT in drug resistance in ever increasing detail, the non-drug resistance functions are still debated. Identifying the natural substrate of PfCRT has been hampered by a paucity of functional assays to test putative substrates in the parasite system and the absence of a parasite mutant deficient for the PfCRT encoding gene. By generating a conditional PfCRT knock-down mutant, together with comparative metabolomics and uptake studies using fluorescently labeled oligopeptides, we could show that PfCRT is an oligopeptide transporter. The oligopeptides were structurally diverse and were electrically neutral or carried a single charge. Our data support a function of PfCRT in oligopeptide transport.

Heme Detoxification Protein (PfHDP) is essential for the hemoglobin uptake and metabolism in Plasmodium falciparum.

Hemoglobin degradation is crucial for the growth and survival of Plasmodium falciparum in human erythrocytes. Although the process of Hb degradation has been studied in detail, the mechanisms of Hb uptake remain ambiguous to date. Here, we characterized Heme Detoxification Protein (PfHDP); a protein localized in the parasitophorus vacuole, parasite food vacuole, and infected erythrocyte cytosol for its role in Hb uptake. Immunoprecipitation of PfHDP‐GFP fusion protein from a transgenic line using GFP trap beads showed the association of PfHDP with Hb as well as with the members of PTEX translocon complex. Association of PfHDP with Hb or Pfexp‐2, a component of translocon complex was confirmed by protein–protein interaction and immunolocalization tools. Based on these associations, we studied the role of PfHDP in Hb uptake using the PfHDP‐HA‐GlmS transgenic parasites line. PfHDP knockdown significantly reduced the Hb uptake in these transgenic parasites in comparison to the wild‐type parasites. Morphological analysis of PfHDP‐HA‐GlmS transgenic parasites in the presence of GlcN showed food vacuole abnormalities and parasite stress, thereby causing a growth defect in the development of these parasites. Transient knockdown of a member of translocon complex, PfHSP101 in HSP101‐DDDHA parasites also showed a decreased uptake of Hb inside the parasite. Together, these results advocate an interaction between PfHDP and the translocon complex at the parasitophorus vacuole membrane and also suggest a role for PfHDP in the uptake of Hb and parasite development. The study thus reveals new insights into the function of PfHDP, making it an extremely important target for developing new antimalarials.

Predictive Factors for Recovery Time in Conceived Women Suffering From Moderate to Severe Ovarian Hyperstimulation Syndrome.

ObjectiveThis study aimed to evaluate potential predictors for recovery time in pregnant patients with moderate to severe ovarian hyperstimulation syndrome (OHSS).MethodsA total of 424 pregnant patients with moderate to severe OHSS who underwent in vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI) were retrospectively identified. The clinical features and laboratory findings within 24 h after admission were collected. Treatment for OHSS was carried out according to standard procedures, including fluid replacement therapy, human albumin, aspirin, low-molecular-weight heparin, and paracentesis, when necessary. Patients were discharged from the hospital when the tmorning hematocrit was <40% and no obvious clinically relevant symptoms existed, such as abdominal distension, abdominal pain, and shortness of breath. Meanwhile, ultrasound indicating little pleural or abdominal effusion and biochemical abnormalities returning to normal were required. Spearman’s correlation analysis was used to assess the association between the blood-related parameters and recovery time. Multiple linear regression models were used to assess the relationship between the clinical or laboratory parameters and recovery time.ResultsThe median recovery time of these patients was 11 days. In Spearman’s correlation test, leukocytes, hemoglobin, platelets, hematocrit, creatinine, prothrombin time (PT), fibrinogen (Fib), D-dimer, and fibrinogen degradation products (FDPs) were positively correlated with recovery time. On the other hand, albumin and thrombin time (TT) were negatively correlated with recovery time. Multiple linear regression analysis showed that polycystic ovary syndrome (PCOS), hemoglobin, platelets, albumin, and Fib were significantly associated with the recovery time of patients with OHSS (p = 0.023, p < 0.001, p = 0.007, p < 0.001, and p = 0.019, respectively).ConclusionsIn pregnant patients with OHSS, PCOS and hypoalbuminemia were associated with a significantly longer recovery time. Meanwhile, the recovery time was longer when patients have high levels of hemoglobin, platelets, and Fib.

Insights Into Bloodstain Degradation and Time Since Deposition Estimation Using Electrochemistry

Blood is an important type of forensic evidence because it can be used for source identification, toxicological analyses, and bloodstain pattern interpretation. Determining the time that bloodshed occurred, often described as the bloodstain’s time since deposition (TSD), has important implications for crime scene investigation. In this work, we focus on using electrochemical methods to monitor the gradual oxidative changes and electron-transfer reactions of hemoglobin (Hb) occurring in degrading bloodstains using differential pulse and hydrodynamic voltammetry. Bloodstains were monitored across a two-week time series in five different temperature conditions. Linear mixed models generated from the differential pulse voltammograms (DPV) suggested that 7 of 27 variables related to the redox reactions associated with the blood film were significantly correlated with time (p&amp;lt; 0.033). Of these correlated variables, all were related to the reduction of bound oxygen to hemoglobin or the oxidation of hemoglobin degradation products within the film. Hydrodynamic voltammetry demonstrated that hemoglobin retains its catalytic activity for oxygen reduction when aged on an electrode surface with a shift to greater peroxide formation the longer it is aged. The time series models are improved when the biological replicate is considered as a random effect, and as well as when peak area ratios are included in the model. Interestingly, using linear mixed models we observed a significant change in redox response at the 96-h time point (p&amp;lt; 0.043) regardless of temperature condition. Overall, we demonstrate preliminary support for DPV as a technique for TSD estimation of bloodstains.

Pro-oxidative activity of trout and bovine hemoglobin during digestion using a static in vitro gastrointestinal model

The degradation of trout and bovine hemoglobin (Hb) and their pro-oxidant activities in washed cod muscle mince (WCM) were studied using simple pH-shifts to simulate gastrointestinal (GI) conditions (pH 7 → 6 → 3 → 7), as well as full static in vitro GI digestion. Following gastric acidification to pH 6, metHb formation increased, especially for trout Hb. Subsequent acidification to pH 3 promoted Hb unfolding and partial or complete heme group-loss. During full GI digestion, polypeptide/peptide analyses revealed more extensive Hb-degradation in the gastric than duodenal phase, without any species-differences. When digesting WCM +/-Hb, both Hbs strongly promoted malondialdehyde (MDA), 4-hydroxy-2-hexenal (HHE), and 4-hydroxy-2-nonenal (HNE) formation, peaking at the end of the gastric phase. Trout-Hb stimulated MDA and HHE more than bovine Hb in the first gastric phase. Altogether, partially degraded Hb, and/or free hemin -both mammal and fish-derived- stimulated oxidation of PUFA-rich lipids under GI-conditions, especially gastric ones.

Myelinated axons are the primary target of hemin-mediated oxidative damage in a model of the central nervous system

Iron released from oligodendrocytes during demyelination or derived from haemoglobin breakdown products is believed to amplify oxidative tissue injury in multiple sclerosis (MS). However, the pathophysiological significance of iron-containing haemoglobin breakdown products themselves is rarely considered in the context of MS and their cellular specificity and mode of action remain unclear. Using myelinating cell cultures, we now report the cytotoxic potential of hemin (ferriprotoporphyrin IX chloride), a major degradation product of haemoglobin, is 25-fold greater than equimolar concentrations of free iron in myelinating cultures; a model that reproduces the complex multicellular environment of the CNS. At low micro molar concentrations (3.3 - 10 μM) we observed hemin preferentially binds to myelin and axons to initiate a complex detrimental response that results in targeted demyelination and axonal loss but spares neuronal cell bodies, astrocytes and the majority of oligodendroglia. Demyelination and axonal loss in this context are executed by a combination of mechanisms that include iron-dependent peroxidation by reactive oxygen species (ROS) and ferroptosis. These effects are microglial-independent, do not require any initiating inflammatory insult and represent a direct effect that compromises the structural integrity of myelinated axons in the CNS. Our data identify hemin-mediated demyelination and axonal loss as a novel mechanism by which intracerebral degradation of haemoglobin may contribute to lesion development in MS.

The Antagonizing Role of Heme in the Antimalarial Function of Artemisinin: Elevating Intracellular Free Heme Negatively Impacts Artemisinin Activity in Plasmodium falciparum.

The rich source of heme within malarial parasites has been considered to underly the action specificity of artemisinin. We reasoned that increasing intraparasitic free heme levels might further sensitize the parasites to artemisinin. Various means, such as modulating heme synthesis, degradation, polymerization, or hemoglobin digestion, were tried to boost intracellular heme levels, and under several scenarios, free heme levels were significantly augmented. Interestingly, all results arrived at the same conclusion, i.e., elevating heme acted in a strongly negative way, impacting the antimalarial action of artemisinin, but exerted no effect on several other antimalarial drugs. Suppression of the elevated free heme level by introducing heme oxygenase expression effectively restored artemisinin potency. Consistently, zinc protoporphyrin IX/zinc mesoporphyrin, as analogues of heme, drastically increased free heme levels and, concomitantly, the EC50 values of artemisinin. We were unable to effectively mitigate free heme levels, possibly due to an unknown compensating heme uptake pathway, as evidenced by our observation of efficient uptake of a fluorescent heme homologue by the parasite. Our results thus indicate the existence of an effective and mutually compensating heme homeostasis network in the parasites, including an uncharacterized heme uptake pathway, to maintain a certain level of free heme and that augmentation of the free heme level negatively impacts the antimalarial action of artemisinin. Importance: It is commonly believed that heme is critical in activating the antimalarial action of artemisinins. In this work, we show that elevating free heme levels in the malarial parasites surprisingly negatively impacts the action of artemisinin. We tried to boost free heme levels with various means, such as by modulating heme synthesis, heme polymerization, hemoglobin degradation and using heme analogues. Whenever we saw elevation of free heme levels, reduction in artemisinin potency was also observed. The homeostasis of heme appears to be complex, as there exists an unidentified heme uptake pathway in the parasites, nullifying our attempts to effectively reduce intraparasitic free heme levels. Our results thus indicate that too much heme is not good for the antimalarial action of artemisinins. This research can help us better understand the biological properties of this mysterious drug.

Divergent roles of haptoglobin and hemopexin deficiency for disease progression of Shiga-toxin–induced hemolytic-uremic syndrome in mice

Thrombotic microangiopathy, hemolysis and acute kidney injury are typical clinical characteristics of hemolytic-uremic syndrome (HUS), which is predominantly caused by Shiga-toxin-producing Escherichia coli. Free heme aggravates organ damage in life-threatening infections, even with a low degree of systemic hemolysis. Therefore, we hypothesized that the presence of the hemoglobin- and the heme-scavenging proteins, haptoglobin and hemopexin, respectively impacts outcome and kidney pathology in HUS. Here, we investigated the effect of haptoglobin and hemopexin deficiency (haptoglobin-/-, hemopexin-/-) and haptoglobin treatment in a murine model of HUS-like disease. Seven-day survival was decreased in haptoglobin-/- (25%) compared to wild type mice (71.4%), whereas all hemopexin-/- mice survived. Shiga-toxin-challenged hemopexin-/- mice showed decreased kidney inflammation and attenuated thrombotic microangiopathy, indicated by reduced neutrophil recruitment and platelet deposition. These observations were associated with supranormal haptoglobin plasma levels in hemopexin-/- mice. Low dose haptoglobin administration to Shiga-toxin-challenged wild type mice attenuated kidney platelet deposition and neutrophil recruitment, suggesting that haptoglobin at least partially contributes to the beneficial effects. Surrogate parameters of hemolysis were elevated in Shiga-toxin-challenged wild type and haptoglobin-/- mice, while signs for hepatic hemoglobin degradation like heme oxygenase-1, ferritin and CD163 expression were only increased in Shiga-toxin-challenged wild type mice. In line with this observation, haptoglobin-/- mice displayed tubular iron deposition as an indicator for kidney hemoglobin degradation. Thus, haptoglobin and hemopexin deficiency plays divergent roles in Shiga-toxin-mediated HUS, suggesting haptoglobin is involved and hemopexin is redundant for the resolution of HUS pathology.

Disrupting the characteristic twist motion; tailored in silico approach towards the design of plasmepsin inhibitors

The effort to eradicate malaria has not yet been achieved, and the parasitic infection remains a global challenge. The burden stems from the worldwide dissemination of parasites resistant to commonly used chemotherapeutics and the scarcity of the malaria vaccine, Mosquirix. In the quest to augment malaria treatment, current focus has been geared towards plasmepsin (P). These classes of aspartic acid proteases are expressed at multiple stages of the parasite's life cycle and are implicated in host haemoglobin degradation and parasite dissemination in vivo; elaborating their essentiality as therapeutic targets. Our earlier research examined the structural dynamics of WM382, a novel antimalarial compound, in relation to its enzyme inhibitory mechanism on plasmepsin IX (PMIX) and plasmepsin X (PMX). WM382 inflicts structural compactness on both proteases. The pharmacophoric moieties of WM382 were used in the present study to search the Zinc database for WM382 derivatives. The leads, ZINC06868602, ZINC09431717 and ZINC13367223 formed strong intermolecular bonds with the catalytic dyad Asp32 and Asp281. The flap regions generally move away from the binding pocket, divulging the active site to the inhibitor and keeping it near to the catalytic dyad. However, upon binding of the leads, the flap residues wrapped inward to surround the inhibitors, further restricting the characteristic twist motion of these proteases for enzyme activity. Likewise, for the experimental drug candidate WM382, the identified leads displayed high affinity for PMIX, with total binding free energies of leads estimated to be −33.45 kcal/mol, −30.33 kcal/mol and −29.67 kcal/mol, respectively. Evaluation of per residue energy composition indicated the catalytic dyad contributes immensely towards ligand binding. Results from our study suggest these compounds have better inhibitory prowess against PMIX. The potency of these chemicals should further be tested in the experimental laboratory to evaluate their usefulness.

Hemolysis contributes to anemia during long-duration space flight

Anemia in astronauts has been noted since the first space missions, but the mechanisms contributing to anemia in space flight have remained unclear. Here, we show that space flight is associated with persistently increased levels of products of hemoglobin degradation, carbon monoxide in alveolar air and iron in serum, in 14 astronauts throughout their 6-month missions onboard the International Space Station. One year after landing, erythrocytic effects persisted, including increased levels of hemolysis, reticulocytosis and hemoglobin. These findings suggest that the destruction of red blood cells, termed hemolysis, is a primary effect of microgravity in space flight and support the hypothesis that the anemia associated with space flight is a hemolytic condition that should be considered in the screening and monitoring of both astronauts and space tourists.

Ultrastructural Aspects of The Intestinal Cells Surface of Angiostrongylus Cantonensis By Using of Transmission Electron Microscopy.

SummaryThe rat lungworm Angiostrongylus cantonensis is a zoonotic parasite and the main cause of eosinophilic meningitis in the world. Its main source of nutrients originates from the degradation of host hemoglobin in blood-feeding helminths, such as A. cantonensis. The purpose of this study was to analyze the ultrastructure of the intestinal cells by using of transmission electron microscopy (TEM). A. cantonensis worms obtained from Rattus norvegicus (norway rats) from endemic area were used for TEM. The ultrastructural analysis was performed using fragments cut from the middle part of the worms, and the TEM study revealed the cells with microvilli and nuclei containing areas of loose and condensed chromatin and the presence of macrovesicles and microvesicles of digestion and it was observed in this study that intestinal epithelium is look like a syncytium. The ultrastructural aspects of the intestinal cells surface of A. Cantonensis the indicate that the intestinal epithelium is a multinucleate mosaic or syncytium.

Compensating P. falciparum artemisinin resistance

Amino acid deprivation from reduced hemoglobin degradation in Pfkelch13 artemisinin-resistant parasites reduces fitness. In this issue of Cell Host & Microbe, Mesén-Ramírez etal. decipher the role of nutrient permeable channel activity within the parasitophorous vacuolar membrane to compensate for this fitness cost in asexual blood-stage Plasmodium falciparum parasites.

Oxidative Stress and Pathogenesis in Malaria.

Malaria is a highly inflammatory and oxidative disease. The production of reactive oxygen species by host phagocytes is an essential component of the host response to Plasmodium infection. Moreover, host oxidative enzymes, such as xanthine oxidase, are upregulated in malaria patients. Although increased production of reactive oxygen species contributes to the clearance of the parasite, excessive amounts of these free radicals can mediate inflammation and cause extensive damage to host cells and tissues, probably contributing to severe pathologies. Plasmodium has a variety of antioxidant enzymes that allow it to survive amidst this oxidative onslaught. However, parasitic degradation of hemoglobin within the infected red blood cell generates free heme, which is released at the end of the replication cycle, further aggravating the oxidative burden on the host and possibly contributing to the severity of life-threatening malarial complications. Additionally, the highly inflammatory response to malaria contributes to exacerbate the oxidative response. In this review, we discuss host and parasite-derived sources of oxidative stress that may promote severe disease in P. falciparum infection. Therapeutics that restore and maintain oxidative balance in malaria patients may be useful in preventing lethal complications of this disease.

Macrophages and Iron: A Special Relationship.

Macrophages perform a variety of different biological functions and are known for their essential role in the immune response. In this context, a principal function is phagocytic clearance of pathogens, apoptotic and senescent cells. However, the major targets of homeostatic phagocytosis by macrophages are old/damaged red blood cells. As such, macrophages play a crucial role in iron trafficking, as they recycle the large quantity of iron obtained by hemoglobin degradation. They also seem particularly adapted to handle and store amounts of iron that would be toxic to other cell types. Here, we examine the specific and peculiar iron metabolism of macrophages.

X-ray Structure Determination, Antioxidant Voltammetry Studies of Butein and 2',4'-Dihydroxy-3,4-dimethoxychalcone. Computational Studies of 4 Structurally Related 2',4'-diOH Chalcones to Examine Their Antimalarial Activity by Binding to Falcipain-2.

Malaria is a huge global health burden with resistance to currently available medicines resulting in the search for newer antimalarial compounds from traditional medicinal plants in malaria-endemic regions. Previous studies on two chalcones, homobutein and 5-prenylbutein, present in E. abyssinica, have shown moderate antiplasmodial activity. Here, we describe results from experimental and computational investigations of four structurally related chalcones, butein, 2′,4′-dihydroxy-3,4-dimethoxychalcone (DHDM), homobutein and 5-prenylbutein to elucidate possible molecular mechanisms by which these compounds clear malaria parasites. The crystal structures of butein and DHDM show that butein engages in more hydrogen bonding and consequently, more intermolecular interactions than DHDM. Rotating ring-disk electrode (RRDE) voltammetry results show that butein has a higher antioxidant activity towards the superoxide radical anion compared to DHDM. Computational docking experiments were conducted to examine the inhibitory potential of all four compounds on falcipain-2, a cysteine protease that is involved in the degradation of hemoglobin in plasmodium-infected red blood cells of the host. Overall, this work suggests butein as a better antimalarial compound due to its structural features which allow it to have greater intermolecular interactions, higher antioxidant activity and to create a covalent complex at the active site of falcipain-2.