Hemoglobin Degradation Research Articles

Light on abnormal red blood cell subpopulations: Label-free optics-based approach for studying in vitro rigidified blood cells

RBC deformability plays a crucial role in maintaining proper blood flow and oxygen delivery throughout the body. Conventional ektacytometry fails to differentiate between variations in RBC subpopulation deformability as the averaging measurement process obscures these differences. In this study, we introduced an approach that integrates label-free optics-based techniques (flow cytometry, phase-contrast, and two-photon excitation fluorescent microscopy) with ektacytometry to evaluate subpopulations that exhibit decreased RBC deformability upon an in vitro oxidation using 0.5 mM TBHP, as a low-level oxidative agent.We found that flow cytometry can easily detect rigidified and oxidized subpopulations based on FSC/SSC light distribution, as well as RBC fluorescence intensity and peak area likely originating from hemoglobin photo and/or degradation products. Two-photon excitation fluorescence microscopy proved altered morphology and spatial location of fluorescence intensity signal near the membrane of oxidized RBCs, when compared to control RBC, indicating a link with the reduced deformability. The proposed label-free optics-based methodology, which combines established techniques with more sophisticated microscopy, emerges as a promising tool for detecting mechano-biological changes in different RBC subpopulations induced by oxidative stress. The findings suggest potential applications in clinical practice for monitoring pathological conditions influenced by physical or environmental stress and as a quality control measure for stored RBCs.

Case Report: Hemoglobin Hasharon with Concurrent Alpha Thalassemia in a Patient with Maple Syrup Urine Disease

Abstract Hemoglobin Hasharon (Hb Hasharon) is an unstable hemoglobin variant stemming from a mutation in the alpha globin gene. This mutation involves the replacement of aspartic acid with histidine at position 47 of the alpha globin chain. Initially identified in 1967 in Israel, Hb Hasharon has since been sporadically reported in various populations, including in Italy, Greece, Germany, and among Latin Americans of Mediterranean descent. Only three English articles have reported several cases of the combined alpha thalassemia deletion and Hasharon mutation, all between 1978-1980. Notably, there has been no prior report of Hb Hasharon with concurrent alpha thalassemia in patients with maple syrup urine disease (MSUD). We hereby present the first case of Hb Hasharon with alpha thalassemia in a patient diagnosed with MSUD. This patient, a 16-month-old female, received a prenatal diagnosis of MSUD through amniocentesis, confirming homozygosity for a known pathogenic variant in DBT (c.75_76delAT, p.C26wfsX2). Prompt initiation of formula feeding has effectively controlled her MSUD. The patient was referred for further evaluation due to hemoglobin newborn screen showing hemoglobin A, Hb F and “variant hemoglobin”. Her parents denied any family history of hemoglobinopathy. Her complete blood count was predominantly normal except for mild microcytosis, with a mean corpuscular volume of 69.1 fl (normal range 70.0-86.0 fl). The patient didn’t exhibit neonatal jaundice or any other signs or symptoms of hemolysis. The reticulocyte count was also within normal limits. The hemoglobin electrophoresis results revealed a complex pattern, with 28.8% of an unknown hemoglobin between zone 4 and 5 on capillary zone electrophoresis (CZE) as well as a possible A2 variant in zone 1. High-performance liquid chromatography (HPLC) indicated a 29.1% peak at a retention time of 4.72 minutes, along with several smaller peaks, that were indicative of the degradation of the unstable unknown hemoglobin. Although the zones and retention time aligned with Hb Hasharon, the percentage differed from the expected range of 19-20% in CZE and 18-21% in HPLC for this variant, prompting the team to order alpha and beta globin sequencing tests. Beta globin gene complete sequencing yielded negative results, while the sequencing of alpha globin gene revealed that the patient carries one copy of the -alpha3.7 alpha-globin deletion and one copy of the c.142G>C (p.Asp48His) variant in the alpha2-globin (HBA2) gene, resulting in an -alpha/alpha2alpha1 genotype with Hb Hasharon. While Hb Hasharon is generally not clinically significant, its co-occurrence with alpha-thalassemia can lead to hemolytic anemia. In our patient, clinic and chemical parameters were predominantly within normal ranges, except for mild microcytosis. The potential interaction between MSUD and Hb Hasharon with concurrent alpha thalassemia remains unknown. Continued patient monitoring will enable us to evaluate whether these conditions may influence each other’s clinical and biochemical profiles.

Assessing the Oxidative Stress Reducing Potential of Spilanthes filicaulis (Schumach & Thonn) Ethyl-Acetate Sub-fractions on Plasmodium berghei Infected Female Mice.

Infections by Plasmodium parasite actuate oxidative stress. As malaria parasite actions overwhelm host antioxidant defense by producing excessive reactive species during haemoglobin degradation. This study aimed to evaluate the oxidative status by considering the antioxidant level of ethyl-acetate sub-fractions of Spilanthes filicaulis (ESSF) extract on Plasmodium berghei NK-65 parasitized mice. Sixty female mice weighing 20.0 ± 3.0g were inoculated intraperitoneally with 0.2mL of parasitized erythrocytes randomly selected into five groups of 12 mice, Groups I and II were orally administered with normal saline (10mL/kg) and chloroquine (10mg/kg) while, Groups III, IV and V were administered 250,500 and 750mg/kg per day respectively of ESSF. Mice in each group were sacrificed on days 4 and 8 post treatment, thereafter blood and liver samples were collected and prepared using standard methods to obtain erythrocytes and liver homogenates. Malondialdehyde (MDA), a measure of lipid peroxidation, superoxide dismutase (SOD) and catalase (CAT) level was assessed in the erythrocyte and liver. Administration of ESSF produced a significant (p < 0.05) decrease in the MDA concentration of the parasitized treated group when compared to parasitized untreated group on day 4. Concomitantly, a significant (p < 0.05) increase in SOD and CAT activity in the treated groups with a corresponding decrease in the untreated group on day 4. However, effects of this action were more pronounced on day 8 in both tissues. These findings suggest that ESSF might contribute to the protection of malaria infected mice against oxidative disruptions by improving antioxidant status.

An 8-week Aerobic Exercise Intervention Mitigates Iron Overload And Reduces Ferroptosis In Cerebral Cortex Resulting From Hemoglobin Degradation By Activating Lipid Antioxidant Pathway

An 8-week Aerobic Exercise Intervention Mitigates Iron Overload And Reduces Ferroptosis In Cerebral Cortex Resulting From Hemoglobin Degradation By Activating Lipid Antioxidant Pathway

Inhibition of falcilysin from Plasmodium falciparum by interference with its closed-to-open dynamic transition

In the absence of an efficacious vaccine, chemotherapy remains crucial to prevent and treat malaria. Given its key role in haemoglobin degradation, falcilysin constitutes an attractive target. Here, we reveal the mechanism of enzymatic inhibition of falcilysin by MK-4815, an investigational new drug with potent antimalarial activity. Using X-ray crystallography, we determine two binary complexes of falcilysin in a closed state, bound with peptide substrates from the haemoglobin α and β chains respectively. An antiparallel β-sheet is formed between the substrate and enzyme, accounting for sequence-independent recognition at positions P2 and P1. In contrast, numerous contacts favor tyrosine and phenylalanine at the P1’ position of the substrate. Cryo-EM studies reveal a majority of unbound falcilysin molecules adopting an open conformation. Addition of MK-4815 shifts about two-thirds of falcilysin molecules to a closed state. These structures give atomic level pictures of the proteolytic cycle, in which falcilysin interconverts between a closed state conducive to proteolysis, and an open conformation amenable to substrate diffusion and products release. MK-4815 and quinolines bind to an allosteric pocket next to a hinge region of falcilysin and hinders this dynamic transition. These data should inform the design of potent inhibitors of falcilysin to combat malaria.

Therapeutic Targeting and Role of Cysteine Proteases in the Life Cycle of Malaria Parasite.

The malaria parasite Plasmodium expresses four related papain-family cysteine proteases. Targeting these different cysteine proteases can elucidate their roles and potential as therapeutic targets, thereby expanding the pool of antimalarial targets. During gametogenesis, cysteine proteases like SERA-5, SERA-3, DPAP-1, DPAP-2, DPAP- 3, and Falcipain-1 are required for parasitophorous vacuole membrane (PVM) rupture. In the liver stage, cysteine proteases such as Falcipain-1 and SERA-3, SERA-4, SERA-5, and SERA-6 are essential. Additionally, cysteine proteases like DPAP-3, Falcipain- 1, Falcipain-2, Falcipain-3, and SERA-5, SERA-6 play crucial roles in merozoite invasion into red blood cells (RBCs), hemoglobin degradation, and merozoite release from RBCs. This review summarizes the available literature describing the key roles of various cysteine proteases in the life cycle of the malaria parasite and their potential as targets for antimalarial therapy. Understanding these proteases could aid in developing novel antimalarial treatments and overcoming drug resistance.

2,8-Disubstituted-1,5-naphthyridines as Dual Inhibitors of Plasmodium falciparum Phosphatidylinositol-4-kinase and Hemozoin Formation with In Vivo Efficacy.

Structure-activity relationship studies of 2,8-disubstituted-1,5-naphthyridines, previously reported as potent inhibitors of Plasmodium falciparum (Pf) phosphatidylinositol-4-kinase β (PI4K), identified 1,5-naphthyridines with basic groups at 8-position, which retained Plasmodium PI4K inhibitory activity but switched primary mode of action to the host hemoglobin degradation pathway through inhibition of hemozoin formation. These compounds showed minimal off-target inhibitory activity against the human phosphoinositide kinases and MINK1 and MAP4K kinases, which were associated with the teratogenicity and testicular toxicity observed in rats for the PfPI4K inhibitor clinical candidate MMV390048. A representative compound from the series retained activity against field isolates and lab-raised drug-resistant strains of Pf. It was efficacious in the humanized NSG mouse malaria infection model at a single oral dose of 32 mg/kg. This compound was nonteratogenic in the zebrafish embryo model of teratogenicity and has a low predicted human dose, indicating that this series has the potential to deliver a preclinical candidate for malaria.

MiR-214 aggravates oxidative stress in thalassemic erythroid cells by targeting ATF4.

Oxidative damage to erythroid cells plays a key role in the pathogenesis of thalassemia. The oxidative stress in thalassemia is potentiated by heme, nonheme iron, and free iron produced by the Fenton reaction, due to degradation of the unstable hemoglobin and iron overload. In addition, the levels of antioxidant enzymes and molecules are significantly decreased in erythrocytes in α- and β-thalassemia. The control of oxidative stress in red blood cells (RBCs) is known to be mediated by microRNAs (miRNAs). In erythroid cells, microR-214 (miR-214) has been reported to respond to external oxidative stress. However, the molecular mechanisms underlying this phenomenon remain unclear, especially during thalassemic erythropoiesis. In the present study, to further understand how miR-214 aggravates oxidative stress in thalassemia erythroid cells, we investigated the molecular mechanism of miR-214 and its regulation of the oxidative status in thalassemia erythrocytes. We have reported a biphasic expression of miR-214 in β- and α-thalassemia. In the present study the effect of miR-214 expression was investigated by using miR -inhibitor and -mimic transfection in erythroid cell lines induced by hemin. Our study showed a biphasic expression of miR-214 in β- and α-thalassemia. Subsequently, we examined the effect of miR-214 on erythroid differentiation in thalassemia. Our study reveals the loss-of-function of miR-214 during translational activation of activating transcription factor 4 mRNA, leading to decreased reactive oxygen species levels and increased glutathione levels in thalassemia erythroid cell. Our results suggest that the expression of activating transcription factor 4 regulated by miR-214 is important for oxidative stress modulation in thalassemic erythroid cells. Our findings can help to better understand the molecular mechanism of miRNA and transcription factors in regulation of oxidative status in erythroid cells, particularly in thalassemia, and could be useful for managing and relieving severe anemia symptoms in patients in the future.

Hematin- and Hemin-Induced Spherization and Hemolysis of Human Erythrocytes Are Independent of Extracellular Calcium Concentration.

Pathologies such as malaria, hemorrhagic stroke, sickle cell disease, and thalassemia are characterized by the release of hemoglobin degradation products from damaged RBCs. Hematin (liganded with OH-) and hemin (liganded with Cl-)-are the oxidized forms of heme with toxic properties due to their hydrophobicity and the presence of redox-active Fe3. In the present study, using the original LaSca-TM laser particle analyzer, flow cytometry, and confocal microscopy, we showed that both hematin and hemin induce dose-dependent RBC spherization and hemolysis with ghost formation. Hematin and hemin at nanomolar concentrations increased [Ca2+]i in RBC; however, spherization and hemolysis occurred in the presence and absence of calcium, indicating that both processes are independent of [Ca2+]i. Both compounds triggered acute phosphatidylserine exposure on the membrane surface, reversible after 60 min of incubation. A comparison of hematin and hemin effects on RBCs revealed that hematin is a more reactive toxic metabolite than hemin towards human RBCs. The toxic effects of heme derivatives were reduced and even reversed in the presence of albumin, indicating the presence in RBCs of the own recovery system against the toxic effects of heme derivatives.

The Digestive Vacuole of the Malaria Parasite: A Specialized Lysosome.

The malaria parasite resides within erythrocytes during one stage of its life cycle. During this intraerythrocytic period, the parasite ingests the erythrocyte cytoplasm and digests approximately two-thirds of the host cell hemoglobin. This digestion occurs within a lysosome-like organelle called the digestive vacuole. Several proteases are localized to the digestive vacuole and these proteases sequentially breakdown hemoglobin into small peptides, dipeptides, and amino acids. The peptides are exported into the host cytoplasm via the chloroquine-resistance transporter and an amino acid transporter has also been identified on the digestive vacuole membrane. The environment of the digestive vacuole also provides appropriate conditions for the biocrystallization of toxic heme into non-toxic hemozoin by a poorly understood process. Hemozoin formation is an attribute of Plasmodium and Haemoproteus and is not exhibited by other intraerythrocytic protozoan parasites. The efficient degradation of hemoglobin and detoxification of heme likely plays a major role in the high level of replication exhibited by malaria parasites within erythrocytes. Unique features of the digestive vacuole and the critical importance of nutrient acquisition provide therapeutic targets for the treatment of malaria.

Mitochondrial ferritin upregulation reduced oxidative stress and blood-brain-barrier disruption by maintaining cellular iron homeostasis in a neonatal rat model of germinal matrix hemorrhage

Germinal matrix hemorrhage (GMH) is a devasting neurological disease in premature newborns. After GMH, brain iron overload associated with hemoglobin degradation contributed to oxidative stress, causing disruption of the already vulnerable blood-brain barrier (BBB). Mitochondrial ferritin (FTMT), a novel mitochondrial outer membrane protein, is crucial in maintaining cellular iron homeostasis. We aimed to investigate the effect of FTMT upregulation on oxidative stress and BBB disruption associated with brain iron overload in rats. A total of 222 Sprague-Dawley neonatal rat pups (7 days old) were used to establish a collagenase-induced GMH model and an iron-overload model of intracerebral FeCl2 injection. Deferiprone was administered via gastric lavage 1 h after GMH and given daily until euthanasia. FTMT CRISPR Knockout and adenovirus (Ad)-FTMT were administered intracerebroventricularly 48 h before GMH and FeCl2 injection, respectively. Neurobehavioral tests, immunofluorescence, Western blot, Malondialdehyde measurement, and brain water content were performed to evaluate neurobehavior deficits, oxidative stress, and BBB disruption, respectively. The results demonstrated that brain expressions of iron exporter Ferroportin (FPN) and antioxidant glutathione peroxidase 4 (GPX4) as well as BBB tight junction proteins including Claudin-5 and Zona Occulta (ZO)-1 were found to be decreased at 72 h after GMH. FTMT agonist Deferiprone attenuated oxidative stress and preserved BBB tight junction proteins after GMH. These effects were partially reversed by FTMT CRISPR Knockout. Iron overload by FeCl2 injection resulted in oxidative stress and BBB disruption, which were improved by Ad-FTMT mediated FTMT overexpression. Collectively, FTMT upregulation is neuroprotective against brain injury associated with iron overload. Deferiprone reduced oxidative stress and BBB disruption by maintaining cellular iron homeostasis partially by the upregulating of FTMT after GMH. Deferiprone may be an effective treatment for patients with GMH.

Identification, Biochemical Characterization, and In Vivo Detection of a Zn-Metalloprotease with Collagenase Activity from Mannheimia haemolytica A2.

Respiratory diseases in ruminants are a main cause of economic losses to farmers worldwide. Approximately 25% of ruminants experience at least one episode of respiratory disease during the first year of life. Mannheimia haemolytica is the main etiological bacterial agent in the ruminant respiratory disease complex. M. haemolytica can secrete several virulence factors, such as leukotoxin, lipopolysaccharide, and proteases, that can be targeted to treat infections. At present, little information has been reported on the secretion of M. haemolytica A2 proteases and their host protein targets. Here, we obtained evidence that M. haemolytica A2 proteases promote the degradation of hemoglobin, holo-lactoferrin, albumin, and fibrinogen. Additionally, we performed biochemical characterization for a specific 110 kDa Zn-dependent metalloprotease (110-Mh metalloprotease). This metalloprotease was purified through ion exchange chromatography and characterized using denaturing and chaotropic agents and through zymography assays. Furthermore, mass spectrometry identification and 3D modeling were performed. Then, antibodies against the 110 kDa-Mh metalloprotease were produced, which achieved great inhibition of proteolytic activity. Finally, the antibodies were used to perform immunohistochemical tests on postmortem lung samples from sheep with suggestive histology data of pneumonic mannheimiosis. Taken together, our results strongly suggest that the 110-Mh metalloprotease participates as a virulence mechanism that promotes damage to host tissues.

Hemin competitively inhibits HSPA8 ATPase activity mitigating its foldase function

Hemolysis in red blood cells followed by hemoglobin degradation results in high hemin levels in the systemic circulation. Such a level of hemin is disastrous for cells and tissues and is considerably responsible for the pathologies of diseases like severe malaria. Hemin's hydrophobic chemical nature and structure allow it to bind several proteins leading to their functional modification. Such modifications in physiologically relevant proteins can have a high impact on various cellular processes. HSPA8 is a chaperone that has a protective role in oxidative stress by aiding protein refolding. Through ATPase activity assays we found that hemin can competitively inhibit ATP hydrolysis by the chaperone HSPA8. Hemin as such does not affect the structural integrity of the protein which is inferred from CD spectroscopy and Gel filtration but it hinders the ATP-dependent foldase function of the chaperone. HSPA8 was not able to cause the refolding of the model protein lysozyme in the presence of hemin. The loss in HSPA8 function was due to competition between hemin and ATP as the chaperone was able to regain the foldase function when the concentration of ATP was gradually increased with hemin present at the inhibitory concentration. In-silico studies to establish the competition for the specific binding site revealed that ATP was unable to replace hemin from the ATP binding pocket of HSPA8 and was forced to form a non-specific and unstable complex. In-vitro isothermal calorimetry revealed that the affinity of ATP for binding to HSPA8 was reduced 22 folds in the presence of hemin. The prevention of HSPA8's cytoprotective function by hemin can be a major factor contributing to the overall cellular damage during hemin accumulation in the case of severe malaria and other hemolytic diseases.

Endocytosis in malaria parasites: An ultrastructural perspective of membrane interplay in a unique infection model.

Malaria remains a major global threat, representing a severe public health problem worldwide. Annually, it is responsible for a high rate of morbidity and mortality in many tropical developing countries where the disease is endemic. The causative agent of malaria, Plasmodium spp., exhibits a complex life cycle, alternating between an invertebrate vector, which transmits the disease, and the vertebrate host. The disease pathology observed in the vertebrate host is attributed to the asexual development of Plasmodium spp. inside the erythrocyte. Once inside the red blood cell, malaria parasites cause extensive changes in the host cell, increasing membrane rigidity and altering its normal discoid shape. Additionally, during their intraerythrocytic development, malaria parasites incorporate and degrade up to 70% of host cell hemoglobin. This mechanism is essential for parasite development and represents an important drug target. Blocking the steps related to hemoglobin endocytosis or degradation impairs parasite development and can lead to its death. The ultrastructural analysis of hemoglobin endocytosis on Plasmodium spp. has been broadly explored along the years. However, it is only recently that the proteins involved in this process have started to emerge. Here, we will review the most important features related to hemoglobin endocytosis and catabolism on malaria parasites. A special focus will be given to the recent analysis obtained through 3D visualization approaches and to the molecules involved in these mechanisms.

Blood-stage antimalarial activity, favourable metabolic stability and in vivo toxicity of novel piperazine linked 7-chloroquinoline-triazole conjugates

The persistence of drug resistance poses a significant obstacle to the advancement of efficacious malaria treatments. The remarkable efficacy displayed by 1,2,3-triazole-based compounds against Plasmodium falciparum highlights the potential of triazole conjugates, with diverse pharmacologically active structures, as potential antimalarial agents. We aimed to synthesize 7-dichloroquinoline-triazole conjugates and their structure-activity relationship (SAR) derivatives to investigate their anti-plasmodial activity. Among them, QP11, featuring a m-NO2 substitution, demonstrated efficacy against both chloroquine-sensitive and -resistant parasite strains. QP11 selectively inhibited FP2, a cysteine protease involved in hemoglobin degradation, and showed synergistic effects when combined with chloroquine. Additionally, QP11 hindered hemoglobin degradation and hemozoin formation within the parasite. Metabolic stability studies indicated high stability of QP11, making it a promising antimalarial candidate. In vivo evaluation using a murine malaria model demonstrated QP11's efficacy in eradicating parasite growth without neurotoxicity, presenting it as a promising compound for novel antimalarial development.

Targeting the Schistosoma mansoni nutritional mechanisms to design new antischistosomal compounds

The chemical classes of semicarbazones, thiosemicarbazones, and hydrazones are present in various compounds, each demonstrating diverse biological activities. Extensive studies have revealed their potential as schistosomicidal agents. Thiosemicarbazones, in particular, have shown inhibitory effects on Schistosoma mansoni's cathepsin B1 enzyme (SmCB1), which plays a crucial role in hemoglobin degradation within the worm's gut and its nutrition processes. Consequently, SmCB1 has emerged as a promising target for novel schistosomiasis therapies. Moreover, chloroquinoline exhibits characteristics in its aromatic structure that hold promise for developing SmCB1 inhibitors, along with its interaction with hemoglobin's heme group, potentially synergizing against the parasite's gut. In this context, we report the synthesis of 22 hybrid analogs combining hydrazones and quinolines, evaluated against S. mansoni. Five of these hybrids demonstrated schistosomicidal activity in vitro, with GPQF-8Q10 being the most effective, causing worm mortality within 24 h at a concentration of 25 µM. GPQF-8Q8 proved to be the most promising in vivo, significantly reducing egg presence in feces (by 52.8%) and immature eggs in intestines (by 45.8%). These compounds exhibited low cytotoxicity in Vero cells and an in in vivo animal model (Caenorhabditis elegans), indicating a favorable selectivity index. This suggests their potential for the development of new schistosomiasis therapies. Further studies are needed to uncover specific target mechanisms, but these findings offer a promising starting point.

The efficiency and safety evaluation of hemoglobin hydrolysate as a non-heme iron fortifier

Hemoglobin hydrolysate is derived from the enzymatic degradation of hemoglobin. This work aimed to evaluate whether hemoglobin hydrolysate promotes the absorption of non-heme iron and the safety of absorbed iron in mice by analyzing the iron binding content, iron circulation, and liver homeostasis. We found that hemoglobin hydrolysate promoted the absorption of non-heme iron with high efficiency in duodenum by spontaneously binding non-heme iron during digestion, and increased hepatic iron content by up-regulating divalent metal transporter 1, zinc transporter 14, but hepatic iron content only increased at 3 weeks. Duodenal iron entered the blood through ferroportin without restriction at 3 weeks, and excessive iron entered the liver and then affected the hepatocyte membranes permeability and lipid synthesis through oxidative stress. With the prolongation of dietary intervention, the up-regulated hepcidin acted on the ferroportin to restrict excess iron from entering the blood, and then the hepatic homeostasis recovered. In addition, hemoglobin hydrolysate enhanced the hepatic antioxidant capacity. Taken together, hemoglobin hydrolysate has a strong ability to promote the absorption of non-heme iron in vivo, and the absorbed iron is relatively safe due to the regulation of hepcidin.

Ferroptosis: a potential therapeutic target for stroke.

Ferroptosis is a form of regulated cell death characterized by massive iron accumulation and iron-dependent lipid peroxidation, differing from apoptosis, necroptosis, and autophagy in several aspects. Ferroptosis is regarded as a critical mechanism of a series of pathophysiological reactions after stroke because of iron overload caused by hemoglobin degradation and iron metabolism imbalance. In this review, we discuss ferroptosis-related metabolisms, important molecules directly or indirectly targeting iron metabolism and lipid peroxidation, and transcriptional regulation of ferroptosis, revealing the role of ferroptosis in the progression of stroke. We present updated progress in the intervention of ferroptosis as therapeutic strategies for stroke in vivo and in vitro and summarize the effects of ferroptosis inhibitors on stroke. Our review facilitates further understanding of ferroptosis pathogenesis in stroke, proposes new targets for the treatment of stroke, and suggests that more efforts should be made to investigate the mechanism of ferroptosis in stroke.

Synthesis, In-Silico, In Vitro and DFT Assessments of Substituted Imidazopyridine Derivatives as Potential Antimalarials Targeting Hemoglobin Degradation Pathway

Malaria is a serious illness transmitted through the bite of an infected mosquito, which is caused by a type of parasite called plasmodium and can be fatal if left untreated. Thus, newer antimalarials with unique mode of actions are encouraged. Fused pyridines have been vastly reported for numerous pharmacological activities including but not limited to analgesics, antitubercular, antifungal, antibacterial and antiapoptotic agents. In a current study, a series of substituted Imidazo[1,2-a]pyridine-3-carboxamides (IMPCs) (SM-IMP-01-13) along with some hydrazides (DA-01-DA-02) were synthesized and characterized by Fourier-transform infrared spectroscopy (FTIR), 1H-/[Formula: see text]C-NMR (proton/carbon nuclear magnetic resonance), elemental analyses and mass spectra. These synthesized analogies were subjected for in vitro biological activities such as Brine Shrimp lethality (BSL), and assay of [Formula: see text]-hematin formation inhibitions. The BSL assay results suggested that compounds, SM-IMP-09, SM-IMP-05 were found to be less toxic and they also had comparable toxicity as of 5-Flurouracil (control) ((e.g., at 10 [Formula: see text]g/ml: 20% deaths of nauplii). Derivatives SM-IMP-02, and DA-05 inhibited [Formula: see text]-hematin formation: IC[Formula: see text]: 1.849 and 0.042 [Formula: see text]M, respectively). Our molecular docking analysis on plasmodial cysteine protease falcipain-2 indicated that compound DA-05 (–9.993 kcal/mol) had highest docking score and it was comparable to standard Chloroquine (–7.673 kcal/mol). The most active molecule, DA-05 was also retained with lower HOMO–LUMO energy gap as 3.36 eV. Further, we have also analyzed MEP, and other global reactivity indexes for all IMPCs using DFT. Finally, our in-silico pharmacokinetic analysis suggested that all compounds were having good% human oral absorption values ([Formula: see text]100%), good Caco-2 cell permeabilities (&gt;1600 nm/s), and non- carcinogenic profiles.

Distinct evolution of type I glutamine synthetase in Plasmodium and its species-specific requirement

Malaria parasite lacks canonical pathways for amino acid biosynthesis and depends primarily on hemoglobin degradation and extracellular resources for amino acids. Interestingly, a putative gene for glutamine synthetase (GS) is retained despite glutamine being an abundant amino acid in human and mosquito hosts. Here we show Plasmodium GS has evolved as a unique type I enzyme with distinct structural and regulatory properties to adapt to the asexual niche. Methionine sulfoximine (MSO) and phosphinothricin (PPT) inhibit parasite GS activity. GS is localized to the parasite cytosol and abundantly expressed in all the life cycle stages. Parasite GS displays species-specific requirement in Plasmodium falciparum (Pf) having asparagine-rich proteome. Targeting PfGS affects asparagine levels and inhibits protein synthesis through eIF2α phosphorylation leading to parasite death. Exposure of artemisinin-resistant Pf parasites to MSO and PPT inhibits the emergence of viable parasites upon artemisinin treatment.