Free heme toxicity and its detoxification systems in human

Glutathione and the intracellular labile heme pool

One candidate for the cytosolic labile iron pool is iron(II)glutathione. There is also a widely held opinion that an equivalent cytosolic labile heme pool exists and that this pool is important for the intracellular transfer of heme. Here we describe a study designed to characterise conjugates that form between heme and glutathione. In contrast to hydrated iron(II), heme reacts with glutathione, under aerobic conditions, to form the stable hematin-glutathione complex, which contains iron(III). Thus, glutathione is clearly not the cytosolic ligand for heme, indeed we demonstrate that the rate of heme degradation is enhanced in the presence of glutathione. We suggest that the concentration of heme in the cytosol is extremely low and that intracellular heme transfer occurs via intracellular membrane structures. Should any heme inadvertently escape into the cytosol, it would be rapidly conjugated to glutathione thereby protecting the cell from the toxic effects of heme.

Multi-Omics Analysis Provides Novel Insight into Immuno-Physiological Pathways and Development of Thermal Resistance in Rainbow Trout Exposed to Acute Thermal Stress

In recent years, poikilothermic animals such as fish have increasingly been exposed to stressful high-temperature environments due to global warming. However, systemic changes in fish under thermal stress are not fully understood yet at both the transcriptome and proteome level. Therefore, the objective of this study was to investigate the immuno-physiological responses of fish under extreme thermal stress through integrated multi-omics analysis. Trout were exposed to acute thermal stress by raising water temperature from 15 to 25 °C within 30 min. Head-kidney and plasma samples were collected and used for RNA sequencing and two-dimensional gel electrophoresis. Gene enrichment analysis was performed: differentially expressed genes (DEGs) and differentially expressed proteins (DEPs) were identified to interpret the multi-omics results and identify the relevant biological processes through pathway analysis. Thousands of DEGs and 49 DEPs were identified in fish exposed to thermal stress. Most of these genes and proteins were highly linked to DNA replication, protein processing in the endoplasmic reticulum, cell signaling and structure, glycolysis activation, complement-associated hemolysis, processing of released free hemoglobin, and thrombosis and hypertension/vasoconstriction. Notably, we found that immune disorders mediated by the complement system may trigger hemolysis in thermally stressed fish, which could have serious consequences such as ferroptosis and thrombosis. However, antagonistic activities that decrease cell-free hemoglobin, heme, and iron might be involved in alleviating the side effects of thermally induced immuno-physiological disorders. These factors may represent the major thermal resistance traits that allow fish to overcome extreme thermal stress. Our findings, based on integration of multi-omics data from transcriptomics and proteomics analyses, provide novel insight into the pathogenesis of acute thermal stress and temperature-linked epizootics.

Heme Oxygenase-1 in Gastrointestinal Tract Health and Disease

Heme oxygenase 1 (HO-1) is the rate-limiting enzyme of heme oxidative degradation, generating carbon monoxide (CO), free iron, and biliverdin. HO-1, a stress inducible enzyme, is considered as an anti-oxidative and cytoprotective agent. As many studies suggest, HO-1 is highly expressed in the gastrointestinal tract where it is involved in the response to inflammatory processes, which may lead to several diseases such as pancreatitis, diabetes, fatty liver disease, inflammatory bowel disease, and cancer. In this review, we highlight the pivotal role of HO-1 and its downstream effectors in the development of disorders and their beneficial effects on the maintenance of the gastrointestinal tract health. We also examine clinical trials involving the therapeutic targets derived from HO-1 system for the most common diseases of the digestive system.

Isolation and identification of O- and N-linked glycoproteins in milk from different mammalian species and their roles in biological pathways which support infant growth

Milk serves as the sole nutrition for newborns, as well as a medium for the transfer of immunological components from the mother to the baby. This study reveals different glycoprotein profiles obtained from human, bovine, and caprine milk and their potential roles in supporting infant growth. Proteins from these three milk samples are separated and analyzed using two-dimensional gel electrophoresis (2-DE). Glycosylated proteins from all samples are enriched by affinity chromatography using lectins from the seeds of Artocarpus integer before analysis using LC/MS-QTOF. The glycoproteome profiling demonstrates that glycosylated proteins are higher in caprine milk compared to other samples. Analysis using LC/MS-QTOF identified 42 O-glycosylated and 56 N-glycosylated proteins, respectively. Among those identified, human milk has 17 glycoproteins, which are both O- and N-glycosylated, whereas caprine and bovine have 10 and 1, respectively. Only glycoproteins from human milk have shown positive matching to important human biological pathways, such as vesicle-mediated transport, immune system and hemostasis pathways. Human milk remains unique for human babies with the presence of antibodies in the form of immunoglobulins that are lacking in ruminant milk proteomes.

Heme-Induced Oxidation of Cysteine Groups of Myofilament Proteins Leads to Contractile Dysfunction of Permeabilized Human Skeletal Muscle Fibres

Heme released from red blood cells targets a number of cell components including the cytoskeleton. The purpose of the present study was to determine the impact of free heme (20–300 µM) on human skeletal muscle fibres made available during orthopedic surgery. Isometric force production and oxidative protein modifications were monitored in permeabilized skeletal muscle fibre segments. A single heme exposure (20 µM) to muscle fibres decreased Ca²⁺-activated maximal (active) force (F_o) by about 50% and evoked an approximately 3-fold increase in Ca²⁺-independent (passive) force (F_passive). Oxidation of sulfhydryl (SH) groups was detected in structural proteins (e.g., nebulin, α-actinin, meromyosin 2) and in contractile proteins (e.g., myosin heavy chain and myosin-binding protein C) as well as in titin in the presence of 300 µM heme. This SH oxidation was not reversed by dithiothreitol (50 mM). Sulfenic acid (SOH) formation was also detected in the structural proteins (nebulin, α-actinin, meromyosin). Heme effects on SH oxidation and SOH formation were prevented by hemopexin (Hpx) and α1-microglobulin (A1M). These data suggest that free heme has a significant impact on human skeletal muscle fibres, whereby oxidative alterations in structural and contractile proteins limit contractile function. This may explain and or contribute to the weakness and increase of skeletal muscle stiffness in chronic heart failure, rhabdomyolysis, and other hemolytic diseases. Therefore, therapeutic use of Hpx and A1M supplementation might be effective in preventing heme-induced skeletal muscle alterations.

Interaction between Hemin and Prion Peptides: Binding, Oxidative Reactivity and Aggregation

We investigate the interaction of hemin with four fragments of prion protein (PrP) containing from one to four histidines (PrP_106-114, PrP_95-114, PrP_84-114, PrP_76-114) for its potential relevance to prion diseases and possibly traumatic brain injury. The binding properties of hemin-PrP complexes have been evaluated by UV-visible spectrophotometric titration. PrP peptides form a 1:1 adduct with hemin with affinity that increases with the number of histidines and length of the peptide; the following log K₁ binding constants have been calculated: 6.48 for PrP_76-114, 6.1 for PrP_84-114, 4.80 for PrP_95-114, whereas for PrP_106-114, the interaction is too weak to allow a reliable binding constant calculation. These constants are similar to that of amyloid-β (Aβ) for hemin, and similarly to hemin-Aβ, PrP peptides tend to form a six-coordinated low-spin complex. However, the concomitant aggregation of PrP induced by hemin prevents calculation of the K₂ binding constant. The turbidimetry analysis of [hemin-PrP_76-114] shows that, once aggregated, this complex is scarcely soluble and undergoes precipitation. Finally, a detailed study of the peroxidase-like activity of [hemin-(PrP)] shows a moderate increase of the reactivity with respect to free hemin, but considering the activity over long time, as for neurodegenerative pathologies, it might contribute to neuronal oxidative stress.

Molecular phenotyping of oxidative stress in diabetes mellitus with point-of-care NMR system

Diabetes mellitus is one of the fastest-growing health burdens globally. Oxidative stress, which has been implicated in the pathogenesis of diabetes complication (e.g., cardiovascular event), remains poorly understood. We report a new approach to rapidly manipulate and evaluate the redox states of blood using a point-of-care NMR system. Various redox states of the hemoglobin were mapped out using the newly proposed (pseudo) two-dimensional map known as T1-T2 magnetic state diagram. We exploit the fact that oxidative stress changes the subtle molecular motion of water proton in the blood, and thus inducing a measurable shift in magnetic resonance relaxation properties. We demonstrated the clinical utilities of this technique to rapidly stratify diabetes subjects based on their oxidative status in conjunction to the traditional glycemic level to improve the patient stratification and thus the overall outcome of clinical diabetes care and management.

The Role of α1-Microglobulin (A1M) in Erythropoiesis and Erythrocyte Homeostasis-Therapeutic Opportunities in Hemolytic Conditions

α₁-microglobulin (A1M) is a small protein present in vertebrates including humans. It has several physiologically relevant properties, including binding of heme and radicals as well as enzymatic reduction, that are used in the protection of cells and tissue. Research has revealed that A1M can ameliorate heme and ROS-induced injuries in cell cultures, organs, explants and animal models. Recently, it was shown that A1M could reduce hemolysis in vitro, observed with several different types of insults and sources of RBCs. In addition, in a recently published study, it was observed that mice lacking A1M (A1M-KO) developed a macrocytic anemia phenotype. Altogether, this suggests that A1M may have a role in RBC development, stability and turnover. This opens up the possibility of utilizing A1M for therapeutic purposes in pathological conditions involving erythropoietic and hemolytic abnormalities. Here, we provide an overview of A1M and its potential therapeutic effect in the context of the following erythropoietic and hemolytic conditions: Diamond-Blackfan anemia (DBA), 5q-minus myelodysplastic syndrome (5q-MDS), blood transfusions (including storage), intraventricular hemorrhage (IVH), preeclampsia (PE) and atherosclerosis.

Multiplicity spin, structure, and charge of iron-verdohemeoxygenase complex: A comparison study by the DFT method

Recently the three-dimensional structure of verdoheme heme oxygenase complex was revealed. However, many parameters of verdoheme heme oxygenase’s complex structure and their role and function on Heme degradation were unknown. In this work the structure of iron verdoheme in complex with heme oxygenase was compared by the density functional theory (DFT)-based B3LYP method using the 6-31G basis set. Many parameters such as charge of verdoheme and iron as central metal, electron distribution, spin multiplicity of the molecule and proximal substituents effects on verdoheme ring stabilization and their arrangement are discussed and compared for twelve different conformations of the molecules to find the most energetically stable states.

Labeling of Peroxide-Induced Oxidative Stress Hotspots by Hemin-Catalyzed Tyrosine Click

Tyrosyl radical generation is one of the major factors for hemin/peroxide-induced oxidative stress. A method for trapping tyrosyl radical directly was developed using N-methyl luminol derivative, a tyrosine labeling reagent. N-Methyl luminol derivative selectively forms a covalent bond with a tyrosine residue under the single-electron oxidation condition. This reaction labels oxidative stress hotspots not only at the protein level but also at the level of tyrosine residues undergoing oxidation. Human serum albumin complexed with hemin was labeled at Tyr138, the tyrosine residue closest to the hemin binding site and most strongly subjected to oxidative stress caused by hemin/H₂O₂. Oxidatively damaged proteins were visualized in protein mixtures.

Genetic screens reveal CCDC115 as a modulator of erythroid iron and heme trafficking

Transferrin-bound iron (TBI), the physiological circulating iron form, is acquired by cells through the transferrin receptor (TfR1) by endocytosis. In erythroid cells, most of the acquired iron is incorporated into heme in the mitochondria. Cellular trafficking of heme is indispensable for erythropoiesis and many other essential biological processes. Comprehensive elucidation of molecular pathways governing and regulating cellular iron acquisition and heme trafficking is required to better understand physiological and pathological processes affecting erythropoiesis. Here, we report the first genome-wide clustered regularly interspaced short palindromic repeats (CRISPR) screens in human erythroid cells to identify determinants of iron and heme uptake, as well as heme-mediated erythroid differentiation. We identified several candidate modulators of TBI acquisition including TfR1, indicating that our approach effectively revealed players mechanistically relevant to the process. Interestingly, components of the endocytic pathway were also revealed as potential determinants of transferrin acquisition. We deciphered a role for the vacuolar-type H+ - ATPase (V- ATPase) assembly factor coiled-coil domain containing 115 (CCDC115) in TBI uptake and validated this role in CCDC115 deficient K562 cells. Our screen in hemin-treated cells revealed perturbations leading to cellular adaptation to heme, including those corresponding to trafficking mechanisms and transcription factors potentiating erythroid differentiation. Pathway analysis indicated that endocytosis and vesicle acidification are key processes for heme trafficking in erythroid precursors. Furthermore, we provided evidence that CCDC115, which we identified as required for TBI uptake, is also involved in cellular heme distribution. This work demonstrates a previously unappreciated common intersection in trafficking of transferrin iron and heme in the endocytic pathway of erythroid cells.

TLR4 Signaling by Heme and the Role of Heme-Binding Blood Proteins

Toll-like receptors (TLRs), also known as pattern recognition receptors, respond to exogenous pathogens and to intrinsic danger signals released from damaged cells and tissues. The tetrapyrrole heme has been suggested to be an agonist for TLR4, the receptor for the pro-inflammatory bacterial component lipopolysaccharide (LPS), synonymous with endotoxin. Heme is a double-edged sword with contradictory functions. On the one hand, it has vital cellular functions as the prosthetic group of hemoproteins including hemoglobin, myoglobin, and cytochromes. On the other hand, if released from destabilized hemoproteins, non-protein bound or “free” heme can have pro-oxidant and pro-inflammatory effects, the mechanisms of which are not fully understood. In this review, the complex interactions between heme and TLR4 are discussed with a particular focus on the role of heme-binding serum proteins in handling extracellular heme and its impact on TLR4 signaling. Moreover, the role of heme as a direct and indirect trigger of TLR4 activation and species-specific differences in the regulation of heme-dependent TLR4 signaling are highlighted.

Intraventricular Hemorrhage and White Matter Injury in Preclinical and Clinical Studies

Germinal matrix-intraventricular hemorrhage (IVH) occurs in nearly half of infants born at less than 26 weeks' gestation. Up to 50% of survivors with IVH develop cerebral palsy, cognitive deficits, behavioral disorders, posthemorrhagic ventricular dilatation, or a combination of these sequelae. After the initial bleeding and the primary brain injury, inflammation and secondary brain injury might lead to periventricular leukomalacia or diffuse white matter injury. Potential factors that are involved include microglia and astrocyte activation, degradation of blood components with release of "toxic" products, infiltration of the brain by systemic immune cells, death of neuronal and glial cells, and arrest of preoligodendrocyte maturation. In addition, impairment of the blood-brain barrier may play a major role in the pathophysiology. A wide range of animal models has been used to explore causes and mechanisms leading to IVH-induced brain injury. Preclinical studies have identified potential targets for enhancing brain repair. However, little has been elucidated about the effectiveness of potential interventions in clinical studies. A systematic review of available preclinical and clinical studies might help identify research gaps and which types of interventions may be prioritized. Future trials should report clinically robust and long-term outcomes after IVH.

Therapeutic Efficacy of Antioxidants in Ameliorating Obesity Phenotype and Associated Comorbidities

Obesity has been a worldwide epidemic for decades. Despite the abundant increase in knowledge regarding the etiology and pathogenesis of obesity, the prevalence continues to rise with estimates predicting considerably higher numbers by the year 2030. Obesity is characterized by an abnormal lipid accumulation, however, the physiological consequences of obesity are far more concerning. The development of the obesity phenotype constitutes dramatic alterations in adipocytes, along with several other cellular mechanisms which causes substantial increase in systemic oxidative stress mediated by reactive oxygen species (ROS). These alterations promote a chronic state of inflammation in the body caused by the redox imbalance. Together, the systemic oxidative stress and chronic inflammation plays a vital role in maintaining the obese state and exacerbating onset of cardiovascular complications, Type II diabetes mellitus, dyslipidemia, non-alcoholic steatohepatitis, and other conditions where obesity has been linked as a significant risk factor. Because of the apparent role of oxidative stress in the pathogenesis of obesity, there has been a growing interest in attenuating the pro-oxidant state in obesity. Hence, this review aims to highlight the therapeutic role of antioxidants, agents that negate pro-oxidant state of cells, in ameliorating obesity and associated comorbidities. More specifically, this review will explore how various antioxidants target unique and diverse pathways to exhibit an antioxidant defense mechanism.

A new model for Trypanosoma cruzi heme homeostasis depends on modulation of TcHTE protein expression

Heme is an essential cofactor for many biological processes in aerobic organisms, which can synthesize it de novo through a conserved pathway. Trypanosoma cruzi, the etiological agent of Chagas disease, as well as other trypanosomatids relevant to human health, are heme auxotrophs, meaning they must import it from their mammalian hosts or insect vectors. However, how these species import and regulate heme levels is not fully defined yet. It is known that the membrane protein TcHTE is involved in T. cruzi heme transport, although its specific role remains unclear. In the present work, we studied endogenous TcHTE in the different life cycle stages of the parasite to gain insight into its function in heme transport and homeostasis. We have confirmed that TcHTE is predominantly detected in replicative stages (epimastigote and amastigote), in which heme transport activity was previously validated. We also showed that in epimastigotes, TcHTE protein and mRNA levels decrease in response to increments in heme concentration, confirming it as a member of the heme response gene family. Finally, we demonstrated that T. cruzi epimastigotes can sense intracellular heme by an unknown mechanism and regulate heme transport to adapt to changing conditions. Based on these results, we propose a model in which T. cruzi senses intracellular heme and regulates heme transport activity by adjusting the expression of TcHTE. The elucidation and characterization of heme transport and homeostasis will contribute to a better understanding of a critical pathway for T. cruzi biology allowing the identification of novel and essential proteins.

Reactive Metamizole Metabolites Enhance the Toxicity of Hemin on the ATP Pool in HL60 Cells by Inhibition of Glycolysis

Metamizole is an analgesic, whose pharmacological and toxicological properties are attributed to N-methyl-aminoantipyrine (MAA), its major metabolite. In the presence of heme iron, MAA forms reactive metabolites, which are toxic for granulocyte precursors. Since decreased cellular ATP is characteristic for MAA-associated toxicity, we studied the effect of MAA with and without hemin on energy metabolism of HL60 cells, a granulocyte precursor cell line. The combination MAA/hemin depleted the cellular ATP stronger than hemin alone, whereas MAA alone was not toxic. This decrease in cellular ATP was observed before plasma membrane integrity impairment. MAA/hemin and hemin did not affect the proton leak but increased the maximal oxygen consumption by HL60 cells. This effect was reversed by addition of the radical scavenger N-acetylcysteine. The mitochondrial copy number was not affected by MAA/hemin or hemin. Hemin increased mitochondrial superoxide generation, which was not accentuated by MAA. MAA decreased cellular ROS accumulation in the presence of hemin. In cells cultured in galactose (favoring mitochondrial ATP generation), MAA/hemin had less effect on the cellular ATP and plasma membrane integrity than in glucose. MAA/hemin impaired glycolysis more than hemin or MAA alone, and N-acetylcysteine blunted this effect of MAA/hemin. MAA/hemin decreased protein expression of pyruvate kinase more than hemin or MAA alone. In conclusion, cellular ATP depletion appears to be an important mechanism of MAA/hemin toxicity on HL60 cells. MAA itself is not toxic on HL60 cells up to 100 µM but boosts the inhibitory effect of hemin on glycolysis through the formation of reactive metabolites.

A lipocalin mediates unidirectional heme biomineralization in malaria parasites

During blood-stage development, malaria parasites are challenged with the detoxification of enormous amounts of heme released during the proteolytic catabolism of erythrocytic hemoglobin. They tackle this problem by sequestering heme into bioinert crystals known as hemozoin. The mechanisms underlying this biomineralization process remain enigmatic. Here, we demonstrate that both rodent and human malaria parasite species secrete and internalize a lipocalin-like protein, PV5, to control heme crystallization. Transcriptional deregulation of PV5 in the rodent parasite Plasmodium berghei results in inordinate elongation of hemozoin crystals, while conditional PV5 inactivation in the human malaria agent Plasmodium falciparum causes excessive multidirectional crystal branching. Although hemoglobin processing remains unaffected, PV5-deficient parasites generate less hemozoin. Electron diffraction analysis indicates that despite the distinct changes in crystal morphology, neither the crystalline order nor unit cell of hemozoin are affected by impaired PV5 function. Deregulation of PV5 expression renders P. berghei hypersensitive to the antimalarial drugs artesunate, chloroquine, and atovaquone, resulting in accelerated parasite clearance following drug treatment in vivo. Together, our findings demonstrate the Plasmodium-tailored role of a lipocalin family member in hemozoin formation and underscore the heme biomineralization pathway as an attractive target for therapeutic exploitation.

Classical complement activation on human erythrocytes in subjects with systemic lupus erythematosus and a history of autoimmune hemolytic anemia

INTRODUCTION

Autoimmune hemolytic anemia (AIHA) is a serious manifestation of systemic lupus erythematosus (SLE) associated with significant morbidity and mortality. In order to more fully understand the causative pathways, we utilized sera from subjects with SLE and active AIHA, or a history of AIHA, to evaluate the classical complement pathway, anti-erythrocyte antibodies, and immune complexes.

METHODS

To evaluate antibody-mediated complement activation on the surface of erythrocytes, as occurs in AIHA, blood type O erythrocytes were incubated with sera from 19 subjects with SLE and a history of AIHA. Circulating anti-erythrocyte antibodies and immune complexes were measured with ELISA-based assays.

RESULTS

In total, 90% of subjects with SLE and a history of AIHA, but not active clinical hemolysis, had measurable anti-erythrocyte antibodies. Of those with anti-erythrocyte antibody, 53% demonstrated complement opsonization on the erythrocyte surface >twofold above negative control and 29% generated the anaphylatoxin C5a.

CONCLUSIONS

For subjects with SLE and a history of AIHA, the persistence of circulating anti-erythrocyte antibodies and resultant erythrocyte complement opsonization and anaphylatoxin generation suggests the possibility that these complement effectors contribute to chronic morbidity and risk of AIHA relapse.

Mitochondrial-nuclear heme trafficking in budding yeast is regulated by GTPases that control mitochondrial dynamics and ER contact sites

Heme is a cofactor and signaling molecule that is essential for much of aerobic life. All heme-dependent processes in eukaryotes require that heme is trafficked from its site of synthesis in the mitochondria to hemoproteins located throughout the cell. However, the mechanisms governing the mobilization of heme out of the mitochondria, and the spatio-temporal dynamics of these processes, are poorly understood. Here, using genetically encoded fluorescent heme sensors, we developed a live-cell assay to monitor heme distribution dynamics between the mitochondrial inner membrane, where heme is synthesized, and the mitochondrial matrix, cytosol and nucleus. Surprisingly, heme trafficking to the nucleus is ∼25% faster than to the cytosol or mitochondrial matrix, which have nearly identical heme trafficking dynamics, potentially supporting a role for heme as a mitochondrial-nuclear retrograde signal. Moreover, we discovered that the heme synthetic enzyme 5-aminolevulinic acid synthase (ALAS, also known as Hem1 in yeast), and GTPases in control of the mitochondrial dynamics machinery (Mgm1 and Dnm1) and ER contact sites (Gem1), regulate the flow of heme between the mitochondria and nucleus. Overall, our results indicate that there are parallel pathways for the distribution of bioavailable heme.This article has an associated First Person interview with the first author of the paper.

A neuroglobin-based high-affinity ligand trap reverses carbon monoxide-induced mitochondrial poisoning

Carbon monoxide (CO) remains the most common cause of human poisoning. The consequences of CO poisoning include cardiac dysfunction, brain injury, and death. CO causes toxicity by binding to hemoglobin and by inhibiting mitochondrial cytochrome c oxidase (CcO), thereby decreasing oxygen delivery and inhibiting oxidative phosphorylation. We have recently developed a CO antidote based on human neuroglobin (Ngb-H64Q-CCC). This molecule enhances clearance of CO from red blood cells in vitro and in vivo Herein, we tested whether Ngb-H64Q-CCC can also scavenge CO from CcO and attenuate CO-induced inhibition of mitochondrial respiration. Heart tissue from mice exposed to 3% CO exhibited a 42 ± 19% reduction in tissue respiration rate and a 33 ± 38% reduction in CcO activity compared with unexposed mice. Intravenous infusion of Ngb-H64Q-CCC restored respiration rates to that of control mice correlating with higher electron transport chain CcO activity in Ngb-H64Q-CCC-treated compared with PBS-treated, CO-poisoned mice. Further, using a Clark-type oxygen electrode, we measured isolated rat liver mitochondrial respiration in the presence and absence of saturating solutions of CO (160 μm) and nitric oxide (100 μm). Both CO and NO inhibited respiration, and treatment with Ngb-H64Q-CCC (100 and 50 μm, respectively) significantly reversed this inhibition. These results suggest that Ngb-H64Q-CCC mitigates CO toxicity by scavenging CO from carboxyhemoglobin, improving systemic oxygen delivery and reversing the inhibitory effects of CO on mitochondria. We conclude that Ngb-H64Q-CCC or other CO scavengers demonstrate potential as antidotes that reverse the clinical and molecular effects of CO poisoning.

Biosynthesized silver nanoparticles protect against hepatic injury induced by murine blood-stage malaria infection

Biosynthesized nanoparticles proposed to have antiplasmodial activities have attracted increasing attention for malaria that considered being one of the foremost hazardous diseases. In this study, Indigofera oblongifolia leaf extracts were used for the synthesis of silver nanoparticles (AgNPs), which were characterized utilizing transmission electron microscopy. We investigated the antiplasmodial and hepatoprotective effects of AgNPs against Plasmodium chabaudi-induced infection in mice. Treatment of the infected mice with 50 mg/kg AgNPs for seven days caused a significant decrease in parasitemia and reduced the histopatholoical changes in the liver, as indicated by Ishak's histology index. Further, the AgNPs alleviated the oxidative damage in the liver infected with P. chabaudi. This was evidenced by the changed levels of malondialdehyde, nitric oxide, and glutathione, as well as increased catalase activity after treatment with AgNPs. In addition, levels of the liver enzymes alanine aminotransferase, aspartate aminotransferase, and alkaline phosphatase were increased after treatment. Moreover, the findings showed the efficiency of AgNPs in improving the infected mice's erythrocyte counts and hemoglobin content. Generally, our results reported that AgNPs possess antiplasmodial and hepatoprotective properties.

Association of ABO blood group and antituberculosis drug-induced liver injury: A case-control study from a Chinese Han population

WHAT IS KNOWN AND OBJECTIVE

Antituberculosis drug-induced liver injury (ATLI) is a serious adverse drug reaction, and its pathogenic mechanism is still largely unknown. Rifampin (RIF) has been reported to cause haemolysis due to the production of drug-dependent antibodies, and haemolysis results in an increased level of free haem, which affects the function of hepatocytes. Blood group determinants can act as specific receptor sites for drug-antibody complexes, causing erythrocyte destruction in the presence of RIF. RIF-induced immune haemolysis may be a potential mechanism for ATLI. Thus, the study aimed to explore the role of ABO blood group systems in Chinese ATLI patients.

METHODS

A 1:4 matched case-control study was conducted among 146 ATLI cases and 584 controls. Multivariable conditional logistic regression and Cox proportional regression were used to estimate the association between ABO blood group and risk of ATLI by odds ratio (OR), hazards ratio (HR) and 95% confidence intervals (CIs), and liver disease history and taking hepatoprotectant were used as covariates.

RESULTS AND DISCUSSION

Patients in the A, B, AB and non-O blood groups had a significantly higher risk of ATLI than those in the O blood group (OR = 1.832, 95% CI: 1.126-2.983, P = .015; OR = 1.751, 95% CI: 1.044-2.937, P = .034; OR = 2.059, 95% CI: 1.077-3.938, P = .029; OR = 1.822, 95% CI: 1.173-2.831, P = .007, respectively). After considering the time of ALTI occurrence, similar results were found in the A, B, AB and non-O blood groups (HR = 1.676, 95% CI: 1.072-2.620, P = .024; HR = 1.620, 95% CI: 1.016-2.584, P = .043; HR = 2.010, 95% CI: 1.130-3.576, P = .018; HR = 1.701, 95% CI: 1.138-2.542, P = .010, respectively). Furthermore, subgroup analysis also detected a significant association between ABO blood group and ATLI in patients taking RIF (P < .05). However, no significant difference was observed in patients not taking RIF (P > .05).

WHAT IS NEW AND CONCLUSION

The present study is the first to evaluate the role of ABO blood group systems in Chinese ATLI cases. Based on the present matched case-control study, the ABO blood group may be associated with susceptibility to ATLI in the Chinese antituberculosis population, especially in patients with blood groups A, B and AB who are taking RIF.

Formation of novel N-acetylcysteine-hemin adducts abrogates hemin-induced cytotoxicity and suppresses the NRF2-driven stress response in human pro-erythroid K562 cells

Heme (iron protoporphyrin IX), as the prosthetic group in hemoproteins, regulates vital cellular functions in human tissues. However, free heme released during hemolysis events promotes severe complications to millions of people worldwide. Over the years, thiols like glutathione (GSH) were known to antagonize heme toxicity. In this study, we have uncovered the underlying molecular mechanism by which N-acetylcysteine (NAC), a well-known thiol prevents hemin-induced cytotoxicity (HIC). Hemin-responsive human pro-erythroid K562 cells were employed to assess hemin intracellular accumulation and cytotoxicity at concentrations ≥50 μΜ, in cultures exposed only to hemin and/or both hemin and NAC. NAC inhibited the intracellular accumulation of hemin and prevented hemin-induced cell growth inhibition, cell death, oxidative stress, and accumulation of ubiquitinated proteins. Meanwhile, the activation of the NF-E2-related factor-2 (NRF2)-driven stress gene activation, a key element involved in HIC, was suppressed by NAC. A refined mechanism of the chemical reaction between NAC and hemin leading to adduct formation via a nucleophilic attack on hemin was uncovered for the first time by tandem mass spectrometry analysis (LC-MS/MS). Such thiol-hemin adducts acted as intermediates to mitigate HIC and to suppress hemin-induced NRF2-driven gene activation. Our findings support the concept that NAC-hemin adduct formation is the major novel molecular mechanism rather than the reactive oxygen species-scavenging capacity of thiols to protect cells from HIC. Our results imply that thiols and their derivatives can be of potential therapeutic value in hemolytic disorders.

Activation of KEAP1/NRF2 stress signaling involved in the molecular basis of hemin-induced cytotoxicity in human pro-erythroid K562 cells

During hemolysis, free heme released from damaged RBCs impairs adjacent cells. As a response, heme induces its metabolic degradation via heme oxygenase-1 (HO-1), activated by NF-E2-related factor 2 (NRF2), the master stress response transcription factor. Heme is well considered a signaling molecule, but how heme does activate NRF2 is not well understood. K562, human pro-erythroid cells responding to hemin (ferric chloride heme), were employed to uncover the major role of Kelch-like ECH-associated protein 1 (KEAP1)/NRF2 stress response signaling, embedded in hemin-induced cytotoxicity (HIC), at ≥50 μM. The intracellular pools of hemin were found to determine the progression from the reversible cell growth inhibition to non-apoptotic cell death. Hemin-induced accumulation of both reactive oxygen species (ROS) and ubiquitinated proteins provoked disturbed cellular proteostasis. Immediate accumulation and nuclear translocation of NRF2 were recorded as defensive adaptation. The NRF2-driven genes encoding glutamate-cysteine ligase (GCLC) and cystine/glutamate antiporter (xCT) were substantially activated. Hemin orchestrated a defensive pathway involving the management of cellular non-protein thiols, via an increase in GSH levels and secretion of cysteine. Mechanistically, hemin stabilized NRF2 protein levels selectively by inhibiting the KEAP1-driven ubiquitination of NRF2, while allowing KEAP1 ubiquitination. High-molecular-weight ubiquitinated KEAP1 variants formed in hemin-treated cells degraded in proteasomes, while a portion of them translocated into the nucleus. The KEAP1/NRF2 system can be revealed as a basic homeostatic mechanism, activated in cells encountering free heme, both in healthy and diseased state. Its activation provides a multi-target cytoprotective platform to develop agents preventing heme toxicity.

From Synthesis to Utilization: The Ins and Outs of Mitochondrial Heme

Heme is a ubiquitous and essential iron containing metallo-organic cofactor required for virtually all aerobic life. Heme synthesis is initiated and completed in mitochondria, followed by certain covalent modifications and/or its delivery to apo-hemoproteins residing throughout the cell. While the biochemical aspects of heme biosynthetic reactions are well understood, the trafficking of newly synthesized heme-a highly reactive and inherently toxic compound-and its subsequent delivery to target proteins remain far from clear. In this review, we summarize current knowledge about heme biosynthesis and trafficking within and outside of the mitochondria.

The Interplay between Molten Globules and Heme Disassociation Defines Human Hemoglobin Disassembly

Hemoglobin functions as a tetrameric oxygen transport protein, with each subunit containing a heme cofactor. Its denaturation, either in vivo or in vitro, involves autoxidation to methemoglobin, followed by cofactor loss and globin unfolding. We have proposed a global disassembly scheme for human methemoglobin, linking hemin (ferric protoporphyrin IX) disassociation and apoprotein unfolding pathways. The model is based on the evaluation of circular dichroism and visible absorbance measurements of guanidine-hydrochloride-induced disassembly of methemoglobin and previous measurements of apohemoglobin unfolding. The populations of holointermediates and equilibrium disassembly parameters were estimated quantitatively for adult and fetal hemoglobins. The key stages are characterized by hexacoordinated hemichrome intermediates, which are important for preventing hemin disassociation from partially unfolded, molten globular species during early disassembly and late-stage assembly events. Both unfolding experiments and independent small angle x-ray scattering measurements demonstrate that heme disassociation leads to the loss of tetrameric structural integrity. Our model predicts that after autoxidation, dimeric and monomeric hemichrome intermediates occur along the disassembly pathway inside red cells, where the hemoglobin concentration is very high. This prediction suggests why misassembled hemoglobins often get trapped as hemichromes that accumulate into insoluble Heinz bodies in the red cells of patients with unstable hemoglobinopathies. These Heinz bodies become deposited on the cell membranes and can lead to hemolysis. Alternatively, when acellular hemoglobin is diluted into blood plasma after red cell lysis, the disassembly pathway appears to be dominated by early hemin disassociation events, which leads to the generation of higher fractions of unfolded apo subunits and free hemin, which are known to damage the integrity of blood vessel walls. Thus, our model provides explanations of the pathophysiology of hemoglobinopathies and other disease states associated with unstable globins and red cell lysis and also insights into the factors governing hemoglobin assembly during erythropoiesis.

Learning from Artemisinin: Bioinspired Design of a Reaction-Based Fluorescent Probe for the Selective Sensing of Labile Heme in Complex Biosystems

Labile heme (LH) is an important signaling molecule in virtually all organisms. However, specifically detecting LH remains an outstanding challenge. Herein, by learning from the bioactivation mechanism of artemisinin, we have developed the first LH-responsive small-molecule fluorescent probe, HNG, based on a 4-amino-1,8-naphthalimide (NG) fluorophore. HNG showed high selectivity for LH without interference from hemin, protein-interacting heme, and zinc protoporphyrin. Using HNG, the changes of LH levels in live cells were imaged, and a positive correlation of LH level with the degree of hemolysis was uncovered in hemolytic mice. Our study not only presents the first molecular probe for specific LH detection but also provides a strategy to construct probes with high specificity through a bioinspired approach.

Comprehensive profiling identifies a novel signature with robust predictive value and reveals the potential drug resistance mechanism in glioma

Background

Gliomas are the most common and malignant brain tumors. The standard therapy is surgery combined with radiotherapy, chemotherapy, and/or other comprehensive methods. However, the emergence of chemoresistance is the main obstacle in treatment and its mechanism is still unclear.

Methods

We firstly developed a multi-gene signature by integrated analysis of cancer stem cell and drug resistance related genes. The Chinese Glioma Genome Atlas (CGGA, 325 samples) and The Cancer Genome Atlas (TCGA, 699 samples) datasets were then employed to verify the efficacy of the risk signature and investigate its significance in glioma prognosis. GraphPad Prism, SPSS and R language were used for statistical analysis and graphical work.

Results

This signature could distinguish the prognosis of patients, and patients with high risk score exhibited short survival time. The Cox regression and Nomogram model indicated the independent prognostic performance and high prognostic accuracy of the signature for survival. Combined with a well-known chemotherapy impact factor-MGMT promoter methylation status, this risk signature could further subdivide patients with distinct survival. Functional analysis of associated genes revealed signature-related biological process of cell proliferation, immune response and cell stemness. These mechanisms were confirmed in patient samples.

Conclusions

The signature was an independent and powerful prognostic biomarker in glioma, which would improve risk stratification and provide a more accurate assessment of personalized treatment.

Pharmacophore Modeling, Synthesis, Scaffold Hopping and Biological β- Hematin Inhibition Interaction Studies for Anti-malaria Compounds

Backgound:

Exploring potent compounds is critical to generating multi-target drug discovery. Hematin crystallization is an important mechanism of malaria.

Methods:

A series of chloroquine analogues were designed using a repositioning approach to develop new anticancer compounds. Protein-ligand interaction fingerprints and ADMET descriptors were used to assess docking performance in virtual screenings to design chloroquine hybrid β-hematin inhibitors. A PLS algorithm was applied to correlate the molecular descriptors to IC50 values. The modeling presented excellent predictive power with correlation coefficients for calibration and cross-validation of r2 = 0.93 and q2 = 0.72. Using the model, a series of 4-aminoquinlin hybrids were synthesized and evaluated for their biological activity as an external test series. These compounds were evaluated for cytotoxic cell lines and β-hematin inhibition.

Results:

The target compounds exhibited high β-hematin inhibition activity and were 3-9 times more active than the positive control. Furthermore, all the compounds exhibited moderate to high cytotoxic activity. The most potent compound in the dataset was docked with hemoglobin and its pharmacophore features were generated. These features were used as input to the Pharmit server for screening of six databases.

Conclusion:

The compound with the best score from ChEMBL was 2016904, previously reported as a VEGFR-2 inhibitor. The 11 compounds selected presented the best Gold scores with drug-like properties and can be used for drug development.

Labile Heme Aggravates Renal Inflammation and Complement Activation After Ischemia Reperfusion Injury

Background: Ischemia reperfusion injury (IRI) plays a major role in solid organ transplantation. The length of warm ischemia time is critical for the extent of tissue damage in renal IRI. In this experimental study we hypothesized that local release of labile heme in renal tissue is triggered by the duration of warm ischemia (15 vs. 45 min IRI) and mediates complement activation, cytokine release, and inflammation. Methods: To induce IRI, renal pedicle clamping was performed in male C57BL/6 mice for short (15 min) or prolonged (45 min) time periods. Two and 24 h after experimental ischemia tissue injury labile heme levels in the kidney were determined with an apo-horseradish peroxidase assay. Moreover, renal injury, cytokines, and C5a and C3a receptor (C5aR, C3aR) expression were determined by histology, immunohistochemistry and qPCR, respectively. In addition, in vitro studies stimulating bone marrow-derived macrophages with LPS and the combination of LPS and heme were performed and cytokine expression was measured. Results: Inflammation and local tissue injury correlated with the duration of warm ischemia time. Labile heme concentrations in renal tissue were significantly higher after prolonged (45 min) as compared to short (15 min) IRI. Notably, expression of the inducible heme-degrading enzyme heme oxygenase-1 (HO-1) was up-regulated in kidneys after prolonged, but not after short IRI. C5aR, the pro-inflammatory cytokines IL-6 and TNF-α as well as pERK were up-regulated after prolonged, but not after short ischemia times. Consecutively, neutrophil infiltration and up-regulation of pro-fibrotic cytokines such as CTGF and PAI were more pronounced in prolonged IRI in comparison to short IRI. In vitro stimulation of macrophages with LPS revealed that IL-6 expression was enhanced in the presence of heme. Finally, administration of the heme scavenger human serum albumin (HSA) reduced the expression of pro-inflammatory cytokines, C3a receptor and improved tubular function indicated by enhanced alpha 1 microglobulin (A1M) absorption after IRI. Conclusions: Our data show that prolonged duration of warm ischemia time increased labile heme levels in the kidney, which correlates with IRI-dependent inflammation and up-regulation of anaphylatoxin receptor expression.

Redox Balance Keepers and Possible Cell Functions Managed by Redox Homeostasis in Trypanosoma cruzi

The toxicity of oxygen and nitrogen reactive species appears to be merely the tip of the iceberg in the world of redox homeostasis. Now, oxidative stress can be seen as a two-sided process; at high concentrations, it causes damage to biomolecules, and thus, trypanosomes have evolved a strong antioxidant defense system to cope with these stressors. At low concentrations, oxidants are essential for cell signaling, and in fact, the oxidants/antioxidants balance may be able to trigger different cell fates. In this comprehensive review, we discuss the current knowledge of the oxidant environment experienced by T. cruzi along the different phases of its life cycle, and the molecular tools exploited by this pathogen to deal with oxidative stress, for better or worse. Further, we discuss the possible redox-regulated processes that could be governed by this oxidative context. Most of the current research has addressed the importance of the trypanosomes' antioxidant network based on its detox activity of harmful species; however, new efforts are necessary to highlight other functions of this network and the mechanisms underlying the fine regulation of the defense machinery, as this represents a master key to hinder crucial pathogen functions. Understanding the relevance of this balance keeper program in parasite biology will give us new perspectives to delineate improved treatment strategies.

Modelling heme-mediated brain injury associated with cerebral malaria in human brain cortical organoids

Human cerebral malaria (HCM), a severe encephalopathy associated with Plasmodium falciparum infection, has a 20-30% mortality rate and predominantly affects African children. The mechanisms mediating HCM-associated brain injury are difficult to study in human subjects, highlighting the urgent need for non-invasive ex vivo human models. HCM elevates the systemic levels of free heme, which damages the blood-brain barrier and neurons in distinct regions of the brain. We determined the effects of heme on induced pluripotent stem cells (iPSCs) and a three-dimensional cortical organoid system and assessed apoptosis and differentiation. We evaluated biomarkers associated with heme-induced brain injury, including a pro-inflammatory chemokine, CXCL-10, and its receptor, CXCR3, brain-derived neurotrophic factor (BDNF) and a receptor tyrosine-protein kinase, ERBB4, in the organoids. We then tested the neuroprotective effect of neuregulin-1 (NRG-1) against heme treatment in organoids. Neural stem and mature cells differentially expressed CXCL-10, CXCR3, BDNF and ERBB4 in the developing organoids and in response to heme-induced neuronal injury. The organoids underwent apoptosis and structural changes that were attenuated by NRG-1. Thus, cortical organoids can be used to model heme-induced cortical brain injury associated with HCM pathogenesis as well as for testing agents that reduce brain injury and neurological sequelae.

Heme Oxygenases: Cellular Multifunctional and Protective Molecules against UV-Induced Oxidative Stress

Ultraviolet (UV) irradiation can be considered as a double-edged sword: not only is it a crucial environmental factor that can cause skin-related disorders but it can also be used for phototherapy of skin diseases. Inducible heme oxygenase-1 (HO-1) in response to a variety of stimuli, including UV exposure, is vital to maintain cell homeostasis. Heme oxygenase-2 (HO-2), another member of the heme oxygenase family, is constitutively expressed. In this review, we discuss how heme oxygenase (HO), a vital rate-limiting enzyme, participates in heme catabolism and cytoprotection. Phylogenetic analysis showed that there may exist a functional differentiation between HO-1 and HO-2 during evolution. Furthermore, depending on functions in immunomodulation and antioxidation, HO-1 participates in disease progression, especially in pathogenesis of skin diseases, such as vitiligo and psoriasis. To further investigate the particular role of HO-1 in diseases, we summarized the profile of the HO enzyme system and its related signaling pathways, such as Nrf2 and endoplasmic reticulum crucial signaling, both known to regulate HO-1 expression. Furthermore, we report on a C-terminal truncation of HO-1, which is generally considered as a signal molecule. Also, a newly identified alternative splice isoform of HO-1 not only provides us a novel perspective on comprehensive HO-1 alternative splicing but also offers us a basis to clarify the relationship between HO-1 transcripts and oxidative diseases. To conclude, the HO system is not only involved in heme catabolism but also involved in biological processes related to the pathogenesis of certain diseases, even though the mechanism of disease progression still remains sketchy. Further understanding the role of the HO system and its relationship to UV is helpful for revealing the HO-related signaling networks and the pathogenesis of many diseases.

Acute Exposure to Permethrin Modulates Behavioral Functions, Redox, and Bioenergetics Parameters and Induces DNA Damage and Cell Death in Larval Zebrafish

Permethrin (PM) is a synthetic pyrethroid insecticide widely used as domestic repellent. Damage effects to nontarget organisms have been reported, particularly in the early stages of development. Studies indicate redox unbalance as secondary PM effect. Therefore, our goal was to investigate the acute PM effects on larval zebrafish. Larvae (6 days postfertilization) were exposed to PM (25–600 μg/L) during 24 hours, and 50% lethal concentration was estimated. For subsequent assays, the sublethal PM concentrations of 25 and 50 μg/L were used. PM increased anxiety-like behaviors according to the Novel Tank and Light-Dark tests. At the molecular level, PM induced increased ROS, which may be related to the increased lipid peroxidation, DNA damage, and apoptosis detected in PM-exposed organisms. In parallel, upregulation of the antioxidant system was detected after PM exposure, with increased superoxide dismutase, glutathione S-transferase and glutathione reductase activities, and thiol levels. The increased of Nrf2 target genes and the activation of an electrophile response element-driven reporter Tg(EPRE:LUC-EGFP) suggest that the Nrf2 pathway can mediate a fast response to PM, leading to antioxidant amplification. By using high-resolution respirometry, we found that exposure to PM decreased the oxygen consumption in all respiratory stages, disrupting the oxidative phosphorylation and inhibiting the electron transfer system, leading to decrease in bioenergetics capacity. In addition, PM led to increases of residual oxygen consumption and changes in substrate control ratio. Glucose metabolism seems to be affected by PM, with increased lactate dehydrogenase and decreased citrate synthase activities. Taken together, our results demonstrated the adverse effects of acute sublethal PM concentrations during larval development in zebrafish, causing apparent mitochondrial dysfunction, indicating a potential mechanism to redox unbalance and oxidative stress, which may be linked to the detected cell death and alterations in normal behavior patterns caused by acute PM exposure.

Heme as a target for protection against doxorubicin-induced apoptosis in H9c2 cardiomyocytes

Heme homeostasis is of vital importance to many biological processes associated with cell redox activity. However, the role of heme in the doxorubicin (DOX)-induced cardiotoxicity is still not clear. The aim of the present study was to test the hypothesis that heme is related to the DOX-induced oxidative stress and inhibition of heme expression may protect H9c2 cardiomyocytes against DOX-induced cardiotoxicity. For the evaluation of heme changing under doxorubicin treatment, H9c2 cells were treated with 0.5, 1, 2, and 4 mg/mL doxorubicin respectively. H9c2 cells were divided into 5 groups: Control group (cells were cultured without intervention), DOX group (cells were treated with 2 mg/mL doxorubicin for 6 h), Heme depletion+DOX group (cells were cultured with heme-depleted serum media, 0.5 mM succinylacetone and 2 mg/mL doxorubicin), Heme group (cells were treated with 30 μM heme), and Heme depletion+DOX+Heme group. Apoptotic cells were detected by flow cytometry with Annexin V-FITC/PI. The intracellular oxidant levels were measured by DCFH-DA fluorescence. The levels of heme were detected by ELISA. Doxorubicin significantly increased intracellular heme level from 5013 ± 187 ng/mL to the highest level of 11,720 ± 107 ng/mL, as well as the intracellular oxidants and cell apoptosis rate elevated by the increase of doxorubicin concentration. Heme depletion can significantly suppress the DOX-induced apoptosis from 39.8 ± 0.5% to 20.8 ± 0.5% (p < 0.001). Re-supplemented with exogenous heme partially but significantly restored the DOX-induced apoptosis. Heme plays an important role in doxorubicin toxicity-induced cardiomyocyte injury. By appropriate reduction in the accumulation of free heme in cardiomyocytes, doxorubicin-induced cardiotoxicity may be alleviated.

Association of lipid-related genes implicated in conceptus elongation with female fertility traits in dairy cattle

Elongation of the preimplantation conceptus is a requirement for pregnancy success in ruminants, and failures in this process are highly associated with subfertility in dairy cattle. Identifying genetic markers that are related to early conceptus development and survival and utilizing these markers in selective breeding can improve the reproductive efficiency of dairy herds. Here, we evaluated the association of 1,679 SNP markers within or close to 183 candidate genes involved in lipid metabolism of the elongating conceptus with different fertility traits in US Holstein cattle. A total of 27,371 bulls with predicted transmitting ability records for daughter pregnancy rate, cow conception rate, and heifer conception rate were used as the discovery population. The associations found in the discovery population were validated using 2 female populations (1,122 heifers and 2,138 lactating cows) each with 4 fertility traits, including success to first insemination, number of services per conception, age at first conception for heifers, or days open for cows. Marker effects were estimated using a linear mixed model with SNP genotype as a linear covariate and a random polygenic effect. After multiple testing correction, 39 SNP flagging 27 candidate genes were associated with at least one fertility trait in the discovery population. Of these 39 markers, 3 SNP were validated in the heifer population and 4 SNP were validated in the cow population. The 3 SNP validated in heifers are located within or near genes CAT, MYOF, and RBP4, and the 4 SNP validated in lactating cows are located within or close to genes CHKA, GNAI1, and HMOX2. These validated genes seem to be relevant for reducing pregnancy losses, and the SNP within these genes are excellent candidates for inclusion in genomic tests to improve reproductive performance in dairy cattle.

Antimalarial Quinoline Drugs Inhibit β-Hematin and Increase Free Hemin Catalyzing Peroxidative Reactions and Inhibition of Cysteine Proteases

Malaria caused by Plasmodium affects millions people worldwide. Plasmodium consumes hemoglobin during its intraerythrocytic stage leaving toxic heme. Parasite detoxifies free heme through formation of hemozoin (β-hematin) pigment. Proteolysis of hemoglobin and formation of hemozoin are two main targets for antimalarial drugs. Quinoline antimarial drugs and analogs (β-carbolines or nitroindazoles) were studied as inhibitors of β-hematin formation. The most potent inhibitors were quinacrine, chloroquine, and amodiaquine followed by quinidine, mefloquine and quinine whereas 8-hydroxyquinoline and β-carbolines had no effect. Compounds that inhibited β-hematin increased free hemin that promoted peroxidative reactions as determined with TMB and ABTS substrates. Hemin-catalyzed peroxidative reactions were potentiated in presence of proteins (i.e. globin or BSA) while antioxidants and peroxidase inhibitors decreased peroxidation. Free hemin increased by chloroquine action promoted oxidative reactions resulting in inhibition of proteolysis by three cysteine proteases: papain, ficin and cathepsin B. Glutathione reversed inhibition of proteolysis. These results show that active quinolines inhibit hemozoin and increase free hemin which in presence of H2O2 that abounds in parasite digestive vacuole catalyzes peroxidative reactions and inhibition of cysteine proteases. This work suggests a link between the action of quinoline drugs with biochemical processes of peroxidation and inhibition of proteolysis.

Plasmodium-Salmonella Coinfection Induces Intense Inflammatory Response, Oxidative Stress, and Liver Damage: A Mice Model Study for Therapeutic Strategy

Impairment of host immune response in malaria favors bacteremia caused by typhoidal or nontyphoidal serovars of Salmonella enterica. Ofloxacin and Artesunate are the drugs that are clinically proven for treating typhoid and malaria, respectively. The study evaluates the host responses upon treatment with antibiotic (Ofloxacin) and antimalarial (Artesunate) in a standardized mice model harboring coinfection. BALB/c mice (18-22 g) were simultaneously coinfected with Plasmodium yoelii nigeriensis (Pyn) and S. enterica serovar Typhimurium (STm) and then treated with Ofloxacin or/and Artesunate from day 4 to day 7. The bacterial burden, liver function enzymes, oxidative stress, m-RNA expression of Toll-like receptors (TLR-2 and TLR-4), Th1/Th2 cytokines, hemeoxygenase-1, and NFкB were assessed. Ofloxacin treatment failed to counter the bacterial proliferation in Pyn-STm coinfected mice. However, upon controlling parasitemia with antimalarial, the efficacy of Ofloxacin could be regained. Elevated bacterial burden with malaria induces the expression of TLR-2 and TLR-4 triggering intense inflammatory response (NFκB, Th1/Th2 cytokines) in coinfected mice. This results in critical liver damage (ALT, AST, and ALP), oxidative stress (lipid peroxidation, total GSH, catalase, and super oxide dismutase), and hemeoxygenase-1 (HO-1). The study concludes that malaria infection aggravates the secondary infection of Salmonella serovars and the control of septicemia is critical in recovery of the coinfected subject.

CRISPR/Cas9 knockout of leghemoglobin genes in Lotus japonicus uncovers their synergistic roles in symbiotic nitrogen fixation

Legume nodules contain high concentrations of leghemoglobins (Lbs) encoded by several genes. The reason for this multiplicity is unknown. CRISPR/Cas9 technology was used to generate stable mutants of the three Lbs of Lotus japonicus. The phenotypes were characterized at the physiological, biochemical and molecular levels. Nodules of the triple mutants were examined by electron microscopy and subjected to RNA-sequencing (RNA-seq) analysis. Complementation studies revealed that Lbs function synergistically to maintain optimal N₂ fixation. The nodules of the triple mutants overproduced superoxide radicals and hydrogen peroxide, which was probably linked to activation of NADPH oxidases and changes in superoxide dismutase isoforms expression. The mutant nodules showed major ultrastructural alterations, including vacuolization, accumulation of poly-β-hydroxybutyrate and disruption of mitochondria. RNA-seq of c. 20 000 genes revealed significant changes in expression of carbon and nitrogen metabolism genes, transcription factors, and proteinases. Lb-deficient nodules had c. 30-50-fold less heme but similar transcript levels of heme biosynthetic genes, suggesting a post-translational regulatory mechanism of heme synthesis. We conclude that Lbs act additively in nodules and that the lack of Lbs results in early nodule senescence. Our observations also provide insight into the reprogramming of the gene expression network associated with Lb deficiency, probably as a result of uncontrolled intracellular free O₂ concentration.

Heme Oxygenase-2 (HO-2) as a therapeutic target: Activators and inhibitors

Heme oxygenase (HO) enzymes are involved in heme catabolism and several physiological functions. Among the different HO isoforms, HO-2 stands out for its neuroprotective properties and modulatory activity in male reproduction. However, unlike the HO-1 ligands, the potential therapeutic applications of HO-2 inhibitors/activators have not been extensively explored yet. Moreover, the physiological role of HO-2 is still unclear, mostly due to the lack of highly selective HO-2 chemical probes. To boost the interest on this intriguing target, the present review updates the knowledge on the structure-activity relationships of HO-2 inhibitors and activators, as well as their potential therapeutic applications. To the best of our knowledge, among HO-2 inhibitors, clemizole derivatives are the most selective HO-2 inhibitors reported so far (IC₅₀ HO-1 >100 μM, IC₅₀ HO-2 = 3.4 μM), while the HO-2 nonselective inhibitors described herein possess IC₅₀ HO-2 values ≤ 10 μM. Furthermore, the development of HO-2 activators, such as menadione analogues, helped to understand the critical moieties required for HO-2 activation. Recent advances in the potential therapeutic applications of HO-2 inhibitors/activators cover the fields of neurodegenerative, cardiovascular, inflammatory, and reproductive diseases further stimulating the interest towards this target.