Improved methods for the detection of heme and protoporphyrin IX adducts and quantification of heme B from cytochrome P450 containing systems

Heme B is a critical prosthetic group for the function of numerous proteins including the cytochrome P450 (CYP) family of enzymes. CYP enzymes are involved in the metabolism of endogenous and xenobiotic molecules that are of central interest in drug development. Formation of reactive metabolites by CYPs can lead to heme modification and destruction of the enzyme. The structure of the adducted heme can provide key information on the mechanism of inactivation, which is of great interest during preclinical drug discovery. Historically, techniques to extract the modified heme or protoporphyrin IX species involved harsh extraction conditions and esterification of propionate groups to aid chromatography. We have developed a simplified extraction method and LC/MS chromatography system that does not require derivatization to quantify heme B and identify modified heme B species from multiple CYP-containing matrices. The method uses mass defect filter triggered data dependent MS2 scans to rapidly identify heme and protoporphyrin IX adducts. These methods may also be useful for the analysis of other heme variants and hemoproteins.

Targeting elevated heme levels to treat a mouse model for Diamond-Blackfan Anemia

Diamond-Blackfan anemia (DBA) is a rare genetic disorder in which patients present a scarcity of erythroid precursors in an otherwise normocellular bone marrow. Most, but not all, patients carry mutations in ribosomal proteins such as RPS19, suggesting that compromised mRNA translation and ribosomal stress are pathogenic mechanisms causing depletion of erythroid precursors. To gain further insight to disease mechanisms in DBA, we performed a custom short hairpin RNA (shRNA) based screen against 750 genes hypothesized to affect DBA pathophysiology. Among the hits were two shRNAs against the erythroid specific heme-regulated eIF2α kinase (HRI), which is a negative regulator of mRNA translation. This study shows that shRNA-mediated HRI silencing or loss of one HRI allele improves expansion of Rps19-deficient erythroid precursors, as well as improves the anemic phenotype in Rps19-deficient animals. We found that Rps19-deficient erythroblasts have elevated levels of unbound intracellular heme, which is normalized by HRI heterozygosity. Additionally, targeting elevated heme levels by treating cells with the heme scavenger alpha-1-microglobulin (A1M), increased proliferation of Rps19-deficient erythroid precursors and decreased heme levels in a disease-specific manner. HRI heterozygosity, but not A1M treatment, also decreased the elevated p53 activity observed in Rps19-deficient cells, indicating that p53 activation is caused by ribosomal stress and aberrant mRNA translation and not heme overload in Rps19-deficiency. Together, these findings suggest that targeting elevated heme levels is a promising new treatment strategy for DBA.

Sedimentary Cobalt Protoporphyrin as a Potential Precursor of Prosthetic Heme Group for Bacteria Inhabiting Fossil Organic Matter-Rich Shale Rock

This study hypothesizes that bacteria inhabiting shale rock affect the content of the sedimentary cobalt protoporphyrin present in it and can use it as a precursor for heme synthesis. To verify this hypothesis, we conducted qualitative and quantitative comparative analyses of cobalt protoporphyrin as well as heme, and heme iron in shale rock that were (i) inhabited by bacteria in the field, (ii) treated with bacteria in the laboratory, and with (iii) bacterial culture on synthetic cobalt protoporphyrin. Additionally, we examined the above-mentioned samples for the presence of enzymes involved in the heme biosynthesis and uptake as well as hemoproteins. We found depletion of cobalt protoporphyrin and a much higher heme concentration in the shale rock inhabited by bacteria in the field as well as the shale rock treated with bacteria in the laboratory. Similarly, we observed the accumulation of protoporphyrin in bacterial cells grown on synthetic cobalt protoporphyrin. We detected numerous hemoproteins in metaproteome of bacteria inhabited shale rock in the field and in proteomes of bacteria inhabited shale rock and synthetic cobalt protoporhyrin in the laboratory, but none of them had all the enzymes involved in the heme biosynthesis. However, proteins responsible for heme uptake, ferrochelatase and sirohydrochlorin cobaltochelatase/sirohydrochlorin cobalt-lyase were detected in all studied samples.

In vivo evaluation of heme and non-heme iron content and neuronal density in human basal ganglia

Non-heme iron is an important element supporting the structure and functioning of biological tissues. Imbalance in non-heme iron can lead to different neurological disorders. Several MRI approaches have been developed for iron quantification relying either on the relaxation properties of MRI signal or measuring tissue magnetic susceptibility. Specific quantification of the non-heme iron can, however, be constrained by the presence of the heme iron in the deoxygenated blood and contribution of cellular composition. The goal of this paper is to introduce theoretical background and experimental MRI method allowing disentangling contributions of heme and non-heme irons simultaneously with evaluation of tissue neuronal density in the iron-rich basal ganglia. Our approach is based on the quantitative Gradient Recalled Echo (qGRE) MRI technique that allows separation of the total R2* metric characterizing decay of GRE signal into tissue-specific (R2t*) and the baseline blood oxygen level-dependent (BOLD) contributions. A combination with the QSM data (also available from the qGRE signal phase) allowed further separation of the tissue-specific R2t* metric in a cell-specific and non-heme-iron-specific contributions. It is shown that the non-heme iron contribution to R2t* relaxation can be described with the previously developed Gaussian Phase Approximation (GPA) approach. qGRE data were obtained from 22 healthy control participants (ages 26-63 years). Results suggest that the ferritin complexes are aggregated in clusters with an average radius about 100nm comprising approximately 2600 individual ferritin units. It is also demonstrated that the concentrations of heme and non-heme iron tend to increase with age. The strongest age effect was seen in the pallidum region, where the highest age-related non-heme iron accumulation was observed.

UPLC-MS/MS Determination of Linezolid and Heme in Plasma of Infected Patients and Correlation Analysis

Linezolid can cause serious haematological toxicity, such as thrombocytopenia and aneamia. Heme, composed of iron and porphyrin, is an important component of hemoglobin. In order to investigate the relationship between the concentration of linezolid and heme in the plasma of infected patients, a UPLC-MS/MS method that can determine the concentrations of linezolid and heme simultaneously was developed and validated. A total of 96 healthy subjects and 81 infected patients, who received blood routine blood tests, were included and determined by the UPLC-MS/MS method. The results showed that the concentration of linezolid was 5.08 ± 3.46 μg/mL in infected patients who were treated with linezolid. The heme in healthy subjects was 7.05 ± 8.68 μg/mL, and it was significantly decreased to 0.88 ± 0.79 μg/mL in infected patients (P < 0.01). Spearman correlation analysis showed that linezolid had a high negative correlation with platelet (PLT) (R = -0.309). Heme had a high positive correlation with hemoglobin (Hb) (R = 0.249) in healthy subjects and infected patients. The ROC analysis showed that heme had diagnostic value to distinguish low Hb (110 g/L). In conclusion, there was a positive correlation between heme and Hb, and this correlation was also observed in infected patients. A high concentration of linezolid was inclined to decrease PLT. Monitoring of heme and linezolid helps in the early diagnose of low Hb and PLT.

Severe homocysteinemia in two givosiran-treated porphyria patients: is free heme deficiency the culprit?

Givosiran is a novel approach to treat patients with acute intermittent porphyrias (AIP) by silencing of ∂-ALA-synthase 1, the first enzyme of heme biosynthesis in the liver. We included two patients in the Envision study who responded clinically well to this treatment. However, in both patients, therapy had to be discontinued because of severe adverse effects: One patient (A) developed local injection reactions which continued to spread all over her body with increasing number of injections and eventually caused a severe systemic allergic reaction. Patient B was hospitalized because of a fulminant pancreatitis. Searching for possible causes, we also measured the patients plasma homocysteine (Hcy) levels in fluoride-containing collection tubes: by LC-MS/MS unexpectedly, plasma Hcy levels were 100 and 200 in patient A and between 100 and 400 μmol/l in patient B. Searching for germline mutations in 10 genes that are relevant for homocysteine metabolism only revealed hetero- and homozygous polymorphisms in the MTHFR gene. Alternatively, an acquired inhibition of cystathionine-beta-synthase which is important for homocysteine metabolism could explain the plasma homocysteine increase. This enzyme is heme-dependent: when we gave heme arginate to our patients, Hcy levels rapidly dropped. Hence, we conclude that inhibition of ∂-ALA-synthase 1 by givosiran causes a drop of free heme in the hepatocyte and therefore the excessive increase of plasma homocysteine. Hyperhomocysteinemia may contribute to the adverse effects seen in givosiran-treated patients which may be due to protein-N-homocysteinylation.

Characterization of the apicoplast-localized enzyme TgUroD in Toxoplasma gondii reveals a key role of the apicoplast in heme biosynthesis

Apicomplexan parasites such as Toxoplasma gondii possess an unusual heme biosynthesis pathway whose enzymes localize to the mitochondrion, cytosol, or apicoplast, a nonphotosynthetic plastid present in most apicomplexans. To characterize the involvement of the apicoplast in the T. gondii heme biosynthesis pathway, we investigated the role of the apicoplast-localized enzyme uroporphyrinogen III decarboxylase (TgUroD). We found that TgUroD knockdown impaired parasite proliferation, decreased free heme levels in the parasite, and decreased the abundance of heme-containing c-type cytochrome proteins in the parasite mitochondrion. We validated the effects of heme loss on mitochondrial cytochromes by knocking down cytochrome c/c1 heme lyase 1 (TgCCHL1), a mitochondrial enzyme that catalyzes the covalent attachment of heme to c-type cytochromes. TgCCHL1 depletion reduced parasite proliferation and decreased the abundance of c-type cytochromes. We further sought to characterize the overall importance of TgUroD and TgCCHL1 for both mitochondrial and general parasite metabolism. TgUroD depletion decreased cellular ATP levels, mitochondrial oxygen consumption, and extracellular acidification rates. By contrast, depletion of TgCCHL1 neither diminished ATP levels in the parasite nor impaired extracellular acidification rate, but resulted in specific defects in mitochondrial oxygen consumption. Together, our results indicate that the apicoplast has a key role in heme biology in T. gondii and is important for both mitochondrial and general parasite metabolism. Our study highlights the importance of heme and its synthesis in these parasites.

Label-free quantitation of glycated hemoglobin in single red blood cells by transient absorption microscopy and phasor analysis

As a stable and accurate biomarker, glycated hemoglobin (HbA1c) is clinically used to diagnose diabetes with a threshold of 6.5% among total hemoglobin (Hb). Current methods such as boronate affinity chromatography involve complex processing of large-volume blood samples. Moreover, these methods cannot measure HbA1c fraction at single-red blood cell (RBC) level, thus unable to separate the contribution from other factors such as RBC lifetime. Here, we demonstrate a spectroscopic transient absorption imaging approach that is able to differentiate HbA1c from Hb on the basis of their distinct excited-state dynamics. HbA1c fraction inside a single RBC is derived quantitatively through phasor analysis. HbA1c fraction distribution of diabetic blood is apparently different from that of healthy blood. A mathematical model is developed to derive the long-term blood glucose concentration. Our technology provides a unique way to study heme modification and to derive clinically important information void of bloodstream glucose fluctuation.

Development of a peptide-based fluorescent probe for biological heme monitoring

Heme plays a vital role in cell biology and dysregulation of heme levels is implicated in a wide range of diseases. However, monitoring heme levels in biological systems is currently not straightforward. A short synthetic peptide probe containing 7-azatryptophan is shown to bind hemin in vitro with quenching of the azatryptophan fluorescence. This chemical tool can be used to detect the change in free heme induced in human skin cells upon exposure to UVA irradiation.

Visualization of 57Fe-Labeled Heme Isotopic Fine Structure and Localization of Regions of Erythroblast Maturation in Mouse Spleen by MALDI FTICR-MS Imaging

Epoetin beta pegol (continuous erythropoiesis receptor activator; C.E.R.A.), or methoxy-polyethylene glycol-modified epoetin beta, is a long-acting erythropoiesis stimulating agent (ESA) that effectively maintains hemoglobin levels. It promotes proliferation of erythroid progenitor cells in hematopoietic organs and leads to increased reticulocyte and hemoglobin levels. However, the detailed erythropoietic effects of various ESAs on their target organs have yet to be clarified, and new approaches are needed to analyze tissue iron localization with structural information. Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry imaging (MSI) techniques are widely used in basic pharmaceutical research. High-resolution Fourier transform ion cyclotron resonance (FTICR) mass spectrometry (MS) imaging enables the spatial mapping and identification of biomolecules. In this study, mice administered with C.E.R.A. were fed a diet containing the stable iron isotope ⁵⁷Fe. The ⁵⁷Fe-heme⁺ isotopic fine structure peak (m/z 617.1772) was separated from the non-labeled heme⁺ isotopic peak (Δ0.0029) by FTICR-MS with a resolving power of more than 500,000. We optimized the platform to analyze the distribution of ⁵⁷Fe-heme in the spleen using MALDI FTICR-MS imaging. The combination of the ultrahigh resolution power of FTICR-MS and a stable isotope labeling technique has the potential to be very effective in basic pharmaceutical research. Graphical Abstract ᅟ.

Calculation of Haem Iron Intake and Its Role in the Development of Iron Deficiency in Young Women from the Australian Longitudinal Study on Women's Health

Total iron intake is not strongly associated with iron stores, but haem iron intake may be more predictive. Haem iron is not available in most nutrient databases, so experimentally determined haem contents were applied to an Australian Food Frequency Questionnaire (FFQ) to estimate haem iron intake in a representative sample of young women (25–30 years). The association between dietary haem iron intakes and incident self-reported diagnosed iron deficiency over six years of follow-up was examined. Haem iron contents for Australian red meats, fish, and poultry were applied to haem-containing foods in the Dietary Questionnaire for Epidemiological Studies V2 (DQESv2) FFQ. Haem iron intakes were calculated for 9076 women from the Australian Longitudinal Study on Women’s Health (ALSWH) using the DQESv2 dietary data from 2003. Logistic regression was used to examine the association between haem iron intake (2003) and the incidence of iron deficiency in 2006 and 2009. Multiple logistic regression showed baseline haem iron intake was a statistically significant predictor of iron deficiency in 2006 (Odds Ratio (OR): 0.91; 95% Confidence Interval (CI): 0.84–0.99; p-value: 0.020) and 2009 (OR: 0.89; 95% CI: 0.82–0.99; p-value: 0.007). Using the energy-adjusted haem intake made little difference to the associations. Higher haem iron intake is associated with reduced odds of iron deficiency developing in young adult Australian women.

Effects of dietary beef, pork, chicken and salmon on intestinal carcinogenesis in A/J Min/+ mice

The International Agency for Research on Cancer has classified red meat as “probably carcinogenic to humans” (Group 2A). In mechanistic studies exploring the link between intake of red meat and CRC, heme iron, the pigment of red meat, is proposed to play a central role as a catalyzer of luminal lipid peroxidation and cytotoxicity. In the present work, the novel A/J Min/+ mouse was used to investigate the effects of dietary beef, pork, chicken, or salmon (40% muscle food (dry weight) and 60% powder diet) on Apc-driven intestinal carcinogenesis, from week 3–13 of age. Muscle food diets did not differentially affect carcinogenesis in the colon (flat ACF and tumors). In the small intestine, salmon intake resulted in a lower tumor size and load than did meat from terrestrial animals (beef, pork or chicken), while no differences were observed between the effects of white meat (chicken) and red meat (pork and beef). Additional results indicated that intestinal carcinogenesis was not related to dietary n-6 polyunsaturated fatty acids, intestinal formation of lipid peroxidation products (thiobarbituric acid reactive substances, TBARS), or cytotoxic effects of fecal water on Apc^-/+ cells. Notably, the amount of heme reaching the colon appeared to be relatively low in this study. The greatest tumor load was induced by the reference diet RM1, underlining the importance of the basic diets in experimental CRC. The present study in A/J Min/+ mice does not support the hypothesis of a role of red meat in intestinal carcinogenesis.

Non-Heme Iron Loading Capacities of Anchovy (Engraulis japonicus) Meat Fractions under Simulated Gastrointestinal Digestion

A ferric oxyhydroxide nanoparticle (FeONP)-mediated mechanism has been suggested recently for anchovy (Engraulis japonicus) meat (AM) enhancement of non-heme iron absorption. The current paper fractionates AM biomass into protein (70.67%), lipid (20.98%), and carbohydrate (i.e., glycogen and mucopolysaccharide, 1.07%) and evaluates their capacities in templating the formation of FeONPs under simulated gastrointestinal digestion. Results show that their iron-loading capacities (mg/g) follow the ascending order glycogen (2.43 ± 0.65), protein (20.16 ± 0.56), AM (28.19 ± 0.86), lipid (33.60 ± 1.12), and mucopolysaccharide (541.33 ± 32.33). Protein and lipid act in synergy to contribute the overwhelming majority (about 90%) of AM's iron-loading capacity. l-α-Phosphatidylcholine and l-α-lysophosphatidylcholine are the predominant iron-loading fractions in the lipid digest. Dynamic light scattering and transmission electron microscopy exhibit coating of inorganic cores of the formed FeONPs with peptides or phospholipid-based mixed micelles. Overall, protein and phospholipid are key players in the nanoparticle-mediated "meat factor" mechanism.

Haem Biosynthesis and Antioxidant Enzymes in Circulating Cells of Acute Intermittent Porphyria Patients

The aims of the present study were to explore the expression pattern of haem biosynthesis enzymes in circulating cells of patients affected by two types of porphyria (acute intermittent, AIP, and variegate porphyria, VP), together with the antioxidant enzyme pattern in AIP in order to identify a possible situation of oxidative stress. Sixteen and twelve patients affected by AIP and VP, respectively, were analysed with the same numbers of healthy matched controls. Erythrocytes, neutrophils and peripheral blood mononuclear cells (PBMCs) were purified from blood, and RNA and proteins were extracted for quantitative real time PCR (qRT-PCR) and Western-blot analysis, respectively. Porhobilinogen deaminase (PBGD) and protoporphyrinogen oxidase (PPOX) gene and protein expression was analysed. Antioxidant enzyme activity and gene expression were additionally determined in blood cells, together with protein carbonyl content in plasma. PBMCs isolated from AIP patients presented low mRNA levels of PBGD when compared to controls, while PBMCs isolated from VP patients presented a decrease in PPOX mRNA. PPOX protein content was higher in AIP patients and lower in VP patients, compared to healthy controls. Regarding antioxidant enzymes, PBMCs and erythrocyte superoxide dismutase (SOD) presented statistically significant higher activity in AIP patients compared to controls, while catalase activity tended to be lower in these patients. No differences were observed regarding antioxidant gene expression in white blood cells. Circulating cells in AIP and VP patients present altered expression of haem biosynthetic enzymes, which could be useful for the differential diagnosis of these two types of porphyria in certain difficult cases. AIP patients present a condition of potential oxidative stress similar to VP patients, evidenced by the post-transcriptional activation of SOD and possible catalase impairment.

Heme Iron Release from Alginate Beads at In Vitro Simulated Gastrointestinal Conditions

Heme iron (Fe) release from alginate beads at in vitro simulated gastrointestinal conditions for potential use as oral heme Fe supplement was studied. Five beads at different ratios of sodium alginate (SA)-to-spray-dried bovine blood cells (SDBC) with weight ratios of 1:1.25, 1:2.5, 1:5, 1:10, and 1:15 (w/w) were prepared. Release characteristics of these beads were investigated at in vitro simulated gastrointestinal conditions. Release media pH strongly influenced the controlled Fe release from the beads. The heme Fe-beads in simulated gastric fluid (pH 2) remained in a shrinkage state and Fe release was low: 25.8, 21.1, 11.6, 12.1, and 12.0 % for 1:1.25, 1:2.5, 1:5, 1:10, and 1:15 ratios, respectively. Proportion and amount of Fe released by 1:1.25 and 1:2.5 ratios was higher than the other ratios. The heme Fe-beads swelled and dissociated in simulated intestinal fluid (pH 6), releasing three-fourths of the Fe in 200 min. The morphology studies showed that Fe release followed formation of pores in the alginate matrix, generating erosion of the beads and complete disintegration after 75 and 200 min of gastric and intestinal incubation, respectively. These results indicate that heme Fe-beads may be useful for oral delivery of heme Fe supplement.

A Biochemical Approach to Understand the Pathogenesis of Advanced Pulmonary Arterial Hypertension: Metabolomic Profiles of Arginine, Sphingosine-1-Phosphate, and Heme of Human Lung

Pulmonary arterial hypertension (PAH) is a vascular disease characterized by persistent precapillary pulmonary hypertension (PH), leading to progressive right heart failure and premature death. The pathological mechanisms underlying this condition remain elusive. Analysis of global metabolomics from lung tissue of patients with PAH (n = 8) and control lung tissue (n = 8) leads to a better understanding of disease progression. Using a combination of high-throughput liquid-and-gas-chromatography-based mass spectrometry, we showed unbiased metabolomic profiles of disrupted arginine pathways with increased Nitric oxide (NO) and decreased arginine. Our results also showed specific metabolic pathways and genetic profiles with increased Sphingosine-1-phosphate (S1P) metabolites as well as increased Heme metabolites with altered oxidative pathways in the advanced stage of the human PAH lung. The results suggest that PAH has specific metabolic pathways contributing to the vascular remodeling in severe pulmonary hypertension. Profiling metabolomic alterations of the PAH lung has provided a new understanding of the pathogenic mechanisms of PAH, which benefits therapeutic targeting to specific metabolic pathways involved in the progression of PAH.

Sire breed effect on beef longissimus mineral concentrations and their relationships with carcass and palatability traits

The objective of this study was to evaluate sire breed effect on mineral concentration in beef longissimus thoracis (LT) and investigate the correlations between beef mineral concentrations and carcass and palatability traits. Steer progeny (N=246) from the Germplasm Evaluation project-Cycle VIII were used in this study. In addition to carcass traits, LT was evaluated for mineral concentrations, Warner-Bratzler shear force, and palatability traits. A mixed linear model estimated breed effects on mineral concentrations. No significant sire breed (P≥0.43) or dam breed (P≥0.20) effects were identified for mineral concentrations. Pearson correlation coefficients were calculated among mineral concentrations, carcass, and sensory traits. Zinc concentration was positively correlated (P≤0.05) with total iron (r=0.14), heme iron (r=0.13), and magnesium (r=0.19). Significant (P<0.05) correlations were identified between non-heme or heme iron and most traits in this study. Magnesium concentration was correlated with all carcass and palatability traits.

Characterization of calmodulin-free murine inducible nitric-oxide synthase

Nitric-Oxide Synthase (NOS), that produces the biological signal molecule Nitric-Oxide (NO), exists in three different isoforms called, neuronal (nNOS), endothelial (eNOS) and inducible (iNOS). All NOS isoforms require post-translational interaction with the calcium-binding protein, calmodulin (CaM) for manifesting their catalytic activity. However, CaM has been suggested to control the translational assembly of the enzyme as well, particularly in helping its inducible isoform, iNOS assume a stable, heme-replete, dimeric and active form. Expression of recombinant murine iNOS in E.coli in the absence of CaM has been previously shown to give extremely poor yield of the enzyme which was claimed to be absolutely heme-free, devoid of flavins, completely monomeric and catalytically inactive when compared to the heme-replete, active, dimeric iNOS, generated through co-expression with CaM. In contrast, we found that although iNOS expressed without CaM does produce significantly low amounts of the CaM-free enzyme, the iNOS thus produced, is not completely devoid of heme and is neither entirely monomeric nor absolutely bereft of catalytic activity as reported before. In fact, iNOS synthesized in the absence of CaM undergoes compromised heme incorporation resulting in extremely poor dimerization and activity compared to its counterpart co-expressed with CaM. Moreover, such CaM-free iNOS has similar flavin content and reductase activity as iNOS co-expressed with CaM, suggesting that CaM may not be as much required for the functional assembly of the iNOS reductase domain as its oxygenase domain. LC-MS/MS-based peptide mapping of the CaM-free iNOS confirmed that it had the same full-length sequence as the CaM-replete iNOS. Isothermal calorimetric measurements also revealed high affinity for CaM binding in the CaM-free iNOS and thus the possible presence of a CaM-binding domain. Thus CaM is essential but not indispensible for the assembly of iNOS and such CaM-free iNOS may help in elucidating the role of CaM on iNOS catalysis.

The robustness of ANAMMOX process under the transient oxytetracycline (OTC) shock

The effect of transient oxytetracycline (OTC) shock on the stability of anaerobic ammonium oxidation (ANAMMOX) process was evaluated in the present study. The shock test was implemented with 155-1731mgL(-1) OTC, lasting for 1 to 3-fold hydraulic retention times, under the nitrogen loading rate (NLR) of 6.72 and 13.4kgm(-3)d(-1). The response of the process was divided into shock and recovery stage and the performance under the stress was indicated by stability index and granule characteristic. In the shock period, nitrogen removal rate (NRR) was ranged from 12.1 to 12.1-4.04kgm(-3)d(-1). The specific ANAMMOX activity (SAA) and heme c content, were respectively reduced by 1.4% and 17.6-29.4%. Foremost, the OTC shock was restorable and the recovery lasted for 4-353h. The robustness of ANAMMOX process was dependent on OTC level, duration of shock and NLR applied.

Mass spectrometry for malaria diagnosis

A physical method currently being developed for malaria parasite detection and diagnosis in blood is reviewed in this article. The method - direct laser desorption mass spectrometry - is based on the detection of heme (iron protoporphyrin) as a unique qualitative and quantitative molecular biomarker for malaria. In infected erythrocytes, the parasite sequesters heme in a molecular crystal (hemozoin) - a volume of highly concentrated and purified biomarker molecules. Laser desorption mass spectrometry detects only heme from hemozoin in parasite-infected blood, and not heme that is bound to hemoglobin or other proteins in uninfected blood samples. The method requires only a drop of blood with minimal sample preparation. Laser desorption mass spectrometry may become a rapid and high-throughput tool for specific and sensitive pan-malaria detection at levels below 10 parasites/mul of blood.

Performance of the ANAMMOX process using multi- and single-fed upflow anaerobic sludge blanket reactors

The performance of the ANAMMOX process was investigated in two identical laboratory-scale multi- and single-fed upflow anaerobic sludge blanket (UASB) reactors (denoted R1 and R0) at different hydraulic residence times (HRTs) varying from 2.06 to 1.52 h and NH4(+)-N inf concentrations ranging from 70 to 266 mg L(-1). The substrate removal efficiencies of both reactors decreased as HRT decreased and NH4(+)-N inf increased. The kinetics of these reactions were analyzed, and the Stover-Kincannon model was appropriate to describe the process kinetics of the reactors. In addition, an empirical model incorporating the influent substrate concentration and HRT adequately described R1. Shock experiments were conducted in which the reactors were subjected to transient shock loads. The results showed that the operation of R1 was more stable than that of R0, especially in response to the substrate shocks. Subsequently, the properties of the ANAMMOX granules and the effects of the feeding protocol on those properties were investigated.

Vascular peroxidase 1 catalyzes the formation of hypohalous acids: characterization of its substrate specificity and enzymatic properties

The heme-containing peroxidase family comprises eight members in humans. The physiological and pathophysiological roles of heme-containing peroxidases are not well understood. Phagocyte-derived myeloperoxidase (MPO) utilizes chloride and bromide, in the presence of hydrogen peroxide (H(2)O(2)), to generate hypochlorous acid and hypobromous acid, potent oxidizing species that are known to kill invading pathogens. Vascular peroxidase 1 (VPO1) is a new member of the heme-containing peroxidase family; VPO1 is highly expressed in the cardiovascular system, lung, liver, pancreas, and spleen. However, functional roles of VPO1 have not been defined. In this report, we demonstrate the capacity for VPO1 to catalyze the formation of hypohalous acids, and characterize its enzymatic properties. VPO1, like MPO but unlike lactoperoxidase, is able to generate hypochlorous acid, hypobromous acid, and hypothiocyanous acid in the presence of H(2)O(2). Under physiological pH and concentrations of halides (100μM KBr, 100μM KSCN, and 100mM NaCl), VPO1 utilizes approximately 45% of H(2)O(2) for the generation of hypobromous acid, 35% for hypothiocyanous acid, and 18% for hypochlorous acid. The specific activity of VPO1 is ∼10- to 70-fold lower than that of MPO, depending on the specific substrate. These studies demonstrate that the enzymatic properties and substrate specificity of VPO1 are similar to MPO; however, significantly lower catalytic rate constants of VPO1 relative to MPO suggest the possibility of other physiologic roles for this novel heme-containing peroxidase.

[Effect of stress actions on some hematologic and biochemical parameters of rat blood and on energetic intermolecular interactions in lipid extract under effect of light radiation]

Comparative study has been carried of effect of the three-day long starvation, running, and their combination on morphological parameters of rat blood, lipid metabolism, and activity of blood Na,K-ATPase. Different effect has been shown of these stress factors on the blood erythrocyte composition. Starvation is accompanied by the most pronounced release of stored erythrocyte into blood, which results in a significant decrease both of the total amount of reticulocytes and the complete absence of reticulocytes of the I stage of maturity (the youngest). The running on treadmill led to a significant increase of the total amount of blood reticulocytes and to multiple increase of immature reticulocytes (RC-I and RC-II), which can indicate some stress of the bone marrow erythroid stem line. The curve of acid resistance of blood reticulocytes has shown the animal to experience the greatest stress at a combination of starvation and running. Starvation and running produced different effects on blood lipid characteristics. The content of triacylglycerides (TAG) in blood rose by 40% at starvation and decreased by 30% at running, a similar tendency being found for index of atherogeneity. The fatty acid composition of blood phospholipids at running and its combination with starvation practically did not differ from control. A change of Na,K-ATPase, which is so characteristic of reaction to various kinds of stress, sharply fell at starvation (by 22%), but increased at running (by 13%) and decreased markedly at combination of these actions. Absorption spectra of lipid extracts of the whole blood of the rats submitted to various stress actions showed that extracted from blood (at different amount depending on the kind of action) is an organic substance with coupled bonds, which absorbs light in the diapason of 360-620 nm. The absorption of light in the diapason of 400-410 nm has been found to belong to the Soret band of ferroheme and ferriheme. The shift of the Soret band indicates electron transitions in the iron cation. By the change and disappearance of the Soret band, it is possible to judge about the processes occurring in the lipid extract. The disappearance of the Soret band in the lipid extract indicates formation in it of steady radicals as a result of the ferriheme disintegration due to accumulation of energy in porphyrin, which does not seem to occur in the blood cell membranes. The iron atom in the ferriheme molecule is known to accept electron and yields a part of energy probably to porphyrin. Then ferriheme yields electron and becomes ferriheme with excess of energy in porphyrin. Hence, at admission of the next electron to the iron atom the porphyrin molecule is to get rid of the energy obtained earlier to prevent its disintegration. The heme is possible to be an accumulator and distributor of energy in tissue.

Femtosecond stimulated Raman spectrometer in the 320-520nm range

Multi-µJ narrow-bandwidth (≈ 10 cm(-1)) picosecond pulses, broadly tunable in the visible-UV range (320-520 nm), are generated by spectral compression of femtosecond pulses emitted by an amplified Ti:sapphire system. Such pulses provide the ideal Raman pump for broadband femtosecond stimulated Raman spectroscopy, as here demonstrated on a heme protein.

Methods for analysis of photosynthetic pigments and steady-state levels of intermediates of tetrapyrrole biosynthesis

Tetrapyrroles and carotenoids are required for many indispensable functions in photosynthesis. Tetrapyrroles are essential metabolites for photosynthesis, redox reaction, and detoxification of reactive oxygen species and xenobiotics, while carotenoids function as accessory pigments, in photoprotection and in attraction to animals. Their branched metabolic pathways of synthesis and degradation are tightly controlled to provide adequate amounts of each metabolite (carotenoids/tetrapyrroles) and to prevent accumulation of photoreactive intermediates (tetrapyrroles). Many Arabidopsis mutants and transgenic plants have been reported to show variations in steady-state levels of tetrapyrrole intermediates and contents of different carotenoid species. It is a challenging task to determine the minute amounts of these metabolites to assess the metabolic flow and the activities of both pigment-synthesising and degrading pathways, to unravel limiting enzymatic steps of these biosynthetic pathways, and to characterise mutants with accumulating intermediates. In this chapter, we present a series of methods to qualify and quantify anabolic and catabolic intermediates of Arabidopsis tetrapyrrole metabolism, and describe a common method for quantification of different plant carotenoid species. Additionally, we introduce two methods for quantification of non-covalently bound haem. The approach of analysing steady-state levels of tetrapyrrole intermediates in plants, when applied in combination with analyses of transcripts, proteins, and enzyme activities, enables the biochemical and genetic elucidation of the tetrapyrrole pathway in wild-type plants, varieties, and mutants. Steady-state levels of tetrapyrrole intermediates are only up to 1/1,000 of the amounts of the accumulating end-products, chlorophyll, and haem. Although present in very low amounts, the accumulation and availability of tetrapyrrole intermediates have major consequences on the physiology and activity of chloroplasts due to their additional photoreactive and possible signalling functions. Although adjusted for Arabidopsis tetrapyrrole metabolites, the presented methods can also be applied for analysis of cyanobacterial and other plant tetrapyrroles.

Pregnancy loss and maternal methemoglobin levels: an indirect explanation of the association of environmental toxics and their adverse effects on the mother and the fetus

The aim of this epidemiologic study was to point out a relationship between the exposure to products of coal combustion, and complications in pregnancy where one third of causes of stillbirth are still unknown. In the town of Labin (Croatia) a coal-powered thermoelectric power plant is the single major air polluter. We compared the records of miscarriages, premature births and stillbirths in two periods: the control and the exposure period. Data on reproductive loss was based on the records of pregnant women visiting for regular monthly pregnancy checkups. At the time of the epidemiological prospective study, 260 women (n = 138 in the clean period and n = 122 in the dirty period) were considered representative. The data were processed using Chi square and correlation tests. The frequencies of miscarriages and stillbirths were significantly lower in the control than in the exposure period (p < 0.05). Methemoglobinemia and stillbirths recorded over the "exposure" period are significantly higher than in the "control" period (p = 0.0205). The level of methemoglobin in the bloodstream is an worthy biomarker, predictor and precursor of environmental toxics' adverse effects on the mother and fetus, and can indirectly explain the unrecognized level of fetal methemoglobin. Methemoglobin and heme, having prooxidant properties, also cause the early and late endothelial dysfunction of vital organs. Despite our retrospective epidemiological study findings, we emphasize that the rate of reproductive loss represents a hypothetical risk, which needs to be confirmed with further fetal clinical and anatomopatholgical researches about the effects of methemoglobin catabolism products on the fetal CNS.

Zinc intake and the risk of hyperglycemia among Chinese adults: the prospective Jiangsu Nutrition Study (JIN)

OBJECTIVE

To prospectively examine the associations between zinc intake, the zinc to heme iron ratio and the incidence of hyperglycemia in Chinese.

METHODS

We followed 1056 healthy adults aged 20 and older from 2002 to 2007. Dietary data were collected using 3-day food record and food frequency questionnaire. Hyperglycemia was defined as fasting plasma glucose > 5.6 mmol/l.

RESULTS

During the 5 years of follow-up, we documented 125 incident cases of hyperglycemia. Zinc intake alone was not associated with the risk of hyperglycemia. The zinc to heme iron ratio was inversely associated with the risk of hyperglycemia: odds ratios (OR, 95% CI) across increasing quartiles of the zinc to heme iron ratio were 1.00, 0.78(0.44-1.37), 0.40(0.19-0.83), and 0.21(0.08-0.54)(p for trend= 0.001). Adjustment for lifestyle covariates did not significantly change the associations.

CONCLUSIONS

This cohort study suggests that the zinc to heme iron intake ratio was significantly associated with a decreased risk of hyperglycemia in Chinese adults.

Total iron and heme iron content and their distribution in beef meat and viscera

To determine the content of total iron (TFe) and heme iron (HeFe) in major cuts of meat and principal viscera of bovine origin. 55Fe (30 mCi) was injected into two 4-month-old calves. Triplicate samples of the 12 basic American cuts of meat and major viscera were obtained from each specimen. Samples were acid digested and their iron content was read by atomic absorption spectrophotometry. Duplicate samples of the basic cuts of meat and major viscera were analyzed to determine the concentration of 55Fe using a double isotopic technique. The mean and standard deviation of TFe for all cuts was 1.4 ± 0.3 mg/100 g of meat. The mean TFe for organs was (per mg/100 g): 0.9 ± 0.1 brain, 3.0 ± 0.05 kidney, 3.2 ± 0.04 heart, 5.7 ± 0.2 lung, 6.0 ± 0.1 liver, and 31.2 ± 0.4 spleen. HeFe was 64% of TFe in meat and 72.8% in spleen, 53.8% in lung, 35.7% in brain, 35.0% in kidney, 27.3% in heart, and only 13.6% in liver. Blood contained 85.5% of the radioisotope and only 1.4% was found in muscle and 1.6% was found in viscera. Results suggest that bovine cuts of meat have a low variation in TFe and that HeFe comprises more than 60% of TFe.

Meat and meat-related compounds and risk of prostate cancer in a large prospective cohort study in the United States

The authors examined associations between meat consumption (type, cooking method, and related mutagens), heme iron, nitrite/nitrate, and prostate cancer in a cohort of 175,343 US men aged 50-71 years. During 9 years of follow-up (1995-2003), they ascertained 10,313 prostate cancer cases (1,102 advanced) and 419 fatal cases. Hazard ratios comparing the fifth intake quintile with the first revealed elevated risks associated with red and processed meat for total (red meat: hazard ratio (HR) = 1.12, 95% confidence interval (CI): 1.04, 1.21; processed meat: HR = 1.07, 95% CI: 1.00, 1.14) and advanced (red meat: HR = 1.31, 95% CI: 1.05, 1.65; processed meat: HR = 1.32, 95% CI: 1.08, 1.61) prostate cancer. Heme iron, barbecued/grilled meat, and benzo[a]pyrene were all positively associated with total (HR = 1.09 (95% CI: 1.02, 1.17), HR = 1.11 (95% CI: 1.03, 1.19), and HR = 1.09 (95% CI: 1.00, 1.18), respectively) and advanced (HR = 1.28 (95% CI: 1.03, 1.58), HR = 1.36 (95% CI: 1.10, 1.69), and HR = 1.28 (95% CI: 1.00, 1.65), respectively) disease. Nitrite (HR = 1.24, 95% CI: 1.02, 1.51) and nitrate (HR = 1.31, 95% CI: 1.07, 1.61) intakes were associated with advanced prostate cancer. There were no clear associations for fatal prostate cancer. Red and processed meat may be positively associated with prostate cancer via mechanisms involving heme iron, nitrite/nitrate, grilling/barbecuing, and benzo[a]pyrene.

Inactivation of cystathionine beta-synthase with peroxynitrite

Cystathionine beta-synthase (CBS) is a homocysteine metabolizing enzyme that contains pyridoxal phosphate (PLP) and a six-coordinate heme cofactor of unknown function. CBS was inactivated by peroxynitrite, the product of nitric oxide and superoxide radicals. The IC(50) was approximately 150microM for 5microM ferric CBS. Stopped-flow kinetics and competition experiments showed a direct reaction with a second-order rate constant of (2.4-5.0)x10(4)M(-1)s(-1) (pH 7.4, 37 degrees C). The radicals derived from peroxynitrite, nitrogen dioxide and carbonate radical, also inactivated CBS. Exposure to peroxynitrite did not modify bound PLP but led to nitration of Trp208, Trp43 and Tyr223 and alterations in the heme environment including loss of thiolate coordination, conversion to high-spin and bleaching, with no detectable formation of oxo-ferryl compounds nor promotion of one-electron processes. This study demonstrates the susceptibility of CBS to reactive oxygen/nitrogen species, with potential relevance to hyperhomocysteinemia, a risk factor for cardiovascular diseases.

Longitudinal study of a mouse model of familial porphyria cutanea tarda

Most rodent models of porphyria cutanea tarda (PCT) share in common the administration of iron and agents that induce transcription of cytochrome P450s. Dissection of changes related to porphyrin accumulation required generation of a genetic model free from exogenous precipitants. Mice heterozygous for a null Urod mutation and homozygous for null Hfe alleles spontaneously develop major increases in hepatic and urinary porphyrins several months after weaning but the high % uroporphyrin signature of PCT is established earlier, before total hepatic and urinary porphyrins rise. Total porphyrin levels eventually plateau at higher levels in females than in males. Porphyrinogens were the dominant tetrapyrroles accumulating in hepatocytes. Hepatic Urod activity is markedly reduced but total hepatic heme content does not diminish. Microsomal heme, however, is reduced and in vitro metabolism of prototype substrates showed that some but not all cytochrome P450 activities are reduced. High hepatic levels of uroporphyrinogen are also associated with increased glutathione S-transferase activity and elevated mRNA of 2 transporters, Abcc1 and Abcc4. This murine model of familial PCT affords the opportunity to study changes in porphyrinogen and porphyrin accumulation and transport in the absence of exogenous factors that alter P450 activity and transmembrane transporters.

The haem-accessibility in leghaemoglobin of Lupinus luteus as observed by proton magnetic relaxation

Using the solvent-protons' longitudinal magnetic relaxation rates (p.m.r.) for Lupinus luteus leghaemoglobin derivatives the accessibility of the haem has been evaluated by our "stereo-chemical p.m.r. titration" method with nonexchangeable protons of aliphatic lower alcohols in otherwise deuterated solutions. The haem in leghaemoglobin is more accessible and its protein environment more flexible compared with vertebrate haemoglobins. The correlation time in aquometleghaemglobin aqueous solution has been determined by measuring the frequency dispersion of the p.m.r. rates between 6.1 and 93 MHZ. Taking into account the measured value of tauc = (7.7 +/- 0.5 x 10(-10) s the iron-to-proton inter-spin distances have been calculated. The significance of these distances as well as the electronic g-factor anisotrophy for elucidation of fine structural details of the haem-environment are discussed.

[Phenotypic properties of Sulfobacillus thermotolerans: comparative aspects]

The phenotypic characteristics of the species Sulfobacillus thermotolerans Kr1(T), as dependent on the cultivation conditions, are described in detail. High growth rates (0.22-0.30 h(-1)) and high oxidative activity were recorded under optimum mixotrophic conditions at 40 degrees C on medium with inorganic (Fe(II), S(0), or pyrite-arsenopyrite concentrate) and organic (glucose and/or yeast extract) substrates. In cells grown under optimum conditions on medium with iron, hemes a, b, and, most probably, c were present, indicating the presence of the corresponding cytochromes. Peculiar extended structures in the form of cylindrical cords, never observed previously, were revealed; a mucous matrix, likely of polysaccharide nature, occurred around the cells. In the cells of sulfobacilli grown litho-, organo-, and mixotrophically at 40 degrees C, the enzymes of the three main pathways of carbon utilization and some enzymes of the TCA cycle were revealed. The enzyme activity was maximum under mixotrophic growth conditions. The growth rate in the regions of limiting temperatures (55 degrees C and 12-14 degrees C) decreased two- and tenfold, respectively; no activity of 6-phosphogluconate dehydrogenase, one of the key enzymes of the oxidative pentose phosphate pathway, could be revealed; and a decrease in the activity of almost all enzymes of glucose metabolism and of the TCA cycle was observed. The rate of 14CO2 fixation by cells under auto-, mixo-, and heterotrophic conditions constituted 31.8, 23.3, and 10.3 nmol/(h mg protein), respectively. The activities of RuBP carboxylase (it peaked during lithotrophic growth) and of carboxylases of heterotrophic carbon dioxide fixation were recorded. The physiological and biochemical peculiarities of the thermotolerant sulfobacillus are compared versus moderately thermophilic sulfobacilli.

Relation of iron and red meat intake to blood pressure: cross sectional epidemiological study

OBJECTIVE

To investigate associations of dietary iron (total, haem, and non-haem), supplemental iron, and red meat with blood pressure.

DESIGN

Cross sectional epidemiological study.

SETTING

17 population samples from Japan, China, the United Kingdom, and the United States participating in the international collaborative study on macro-/micronutrients and blood pressure (INTERMAP).

PARTICIPANTS

4680 adults aged 40-59.

MAIN OUTCOME MEASURE

Average of eight blood pressure readings.

RESULTS

In multiple linear regression analyses dietary total iron and non-haem iron were consistently inversely associated with blood pressure. With adjustment for potential non-dietary and dietary confounders, dietary total iron intake higher by 4.20 mg/4.2 MJ (2 SD) was associated with -1.39 mm Hg (P<0.01) lower systolic blood pressure. Dietary non-haem iron intake higher by 4.13 mg/4.2 MJ (2 SD) was associated with -1.45 mm Hg (P<0.001) lower systolic blood pressure. Differences were smaller for diastolic blood pressure. In most models haem iron intake from food was positively, non-significantly associated with blood pressure. Iron intake from combined diet and supplements yielded smaller associations than dietary iron alone. Red meat intake was directly associated with blood pressure; 102.6 g/24 h (2 SD) higher intake was associated with 1.25 mm Hg higher systolic blood pressure. Associations between red meat and blood pressure persisted after adjustment for multiple confounders.

CONCLUSION

Non-haem iron has a possible role in the prevention and control of adverse blood pressure levels. An unfavourable effect of red meat on blood pressure was observed. These results need confirmation including in prospective studies, clinical trials, and from experimental evidence on possible mechanisms.

Characterization of DESI-FTICR mass spectrometry - from ECD to accurate mass tissue analysis

Implementation of desorption electrospray ionization (DESI) technique on a 9.4 T Fourier transform ion cyclotron resonance (FTICR) mass spectrometer is described. Desorption electrospray technique is capable of the direct investigation of natural samples without any need for sample preparation or chromatographic separation. Since the DESI mass spectra of natural samples are very complex owing to the lack of preseparation or cleanup, the ideal mass spectrometric analyzer for these applications is a high-resolution instrument such as FTICR mass spectrometer. DESI was implemented by constructing an electronically controlled source framework comprising six linear moving stages and one rotating stage. A three-dimensional linear stage was used to accommodate samples, while another 3D linear stage equipped with rotating stage was used as a spray mount. A modified electrosonic sprayer was used as a primary electrospray device. DESI-FTICR setup was characterized with regard to geometrical, electrical and flow conditions using deposited peptide samples in range of 1-100 pmol gross deposited amount on glass and polymer surfaces. Optimized conditions enabled the routine acquisition of DESI-MS spectra on the instrument at 130 000 resolution in the broadband mode and with comparable sensitivity to data reported in the literature. Since the main significance of DESI-FTICR MS is the combination of intact tissue analysis, the capabilities of the technique were demonstrated by analyzing murine liver samples. Presence of lysophospholipids in the liver tissue was tentatively associated with the lipid metabolism taking place in liver. DESI-FTICR is also a promising technique in the field of peptide analysis due to capability of top-down sequencing using electron capture dissociation. As a proof-of-principle experiment, a small synthetic polypeptide containing 36 amino acids was ionized using DESI and was sequenced in the FTICR by means of ECD (electron capture dissociation) fragmentation. Spectra gave almost full sequence information in agreement with the known amino acid sequence of the species.

Mitochondrial resuscitation with exogenous cytochrome c in the septic heart

OBJECTIVE

Mitochondrial dysfunction may play a role in the pathogenesis of sepsis-induced organ dysfunction. Respiratory-chain deficiencies that occur in sepsis, however, have never been shown to cause organ failure or to be reversible. Cytochrome oxidase uses electrons donated by its substrate, cytochrome c, to reduce oxygen to H2O. In the septic heart, cytochrome oxidase is competitively inhibited. We hypothesized that cytochrome oxidase inhibition coupled with reduced substrate availability is a reversible cause of sepsis-associated myocardial depression.

DESIGN

Prospective observational study aimed to overcome myocardial cytochrome oxidase inhibition with excess cytochrome c and improve cardiac function.

SETTING

University hospital-based laboratory.

SUBJECTS

Seventy-five C57Bl6 male mice.

INTERVENTIONS

Mice underwent cecal ligation and double puncture, sham operation, or no operation. Exogenous cytochrome c or an equal volume of saline was intravenously injected at the 24-hr time point. All animals were evaluated 30 mins after injection.

MEASUREMENTS AND MAIN RESULTS

Exogenous cytochrome c readily repleted cardiac mitochondria with supranormal levels of substrate (>1.6 times baseline), restored heme c content, and increased cytochrome oxidase kinetic activity. This increased left ventricular pressure and increased pressure development during isovolumic contraction (dP/dtmax) and relaxation (dP/dtmin) by >45% compared with saline injection.

CONCLUSION

Impaired oxidative phosphorylation is a cause of sepsis-associated myocardial depression, and mitochondrial resuscitation with exogenous cytochrome c overcomes cytochrome oxidase inhibition and improves cardiac function.

Raman acoustic levitation spectroscopy of red blood cells and Plasmodium falciparum trophozoites

Methods to probe the molecular structure of living cells are of paramount importance in understanding drug interactions and environmental influences in these complex dynamical systems. The coupling of an acoustic levitation device with a micro-Raman spectrometer provides a direct molecular probe of cellular chemistry in a containerless environment minimizing signal attenuation and eliminating the affects of adhesion to walls and interfaces. We show that the Raman acoustic levitation spectroscopic (RALS) approach can be used to monitor the heme dynamics of a levitated 5 microL suspension of red blood cells and to detect hemozoin in malaria infected cells. The spectra obtained have an excellent signal-to-noise ratio and demonstrate for the first time the utility of the technique as a diagnostic and monitoring tool for minute sample volumes of living animal cells.

Heme crystallization in the midgut of triatomine insects

Hemozoin (Hz) is a heme crystal produced by several blood-feeding organisms in order to detoxify free heme released upon hemoglobin (Hb) digestion. Here we show that heme crystallization also occurs in three species of triatomine insects. Ultraviolet-visible and infrared light absorption spectra of insoluble pigments isolated from the midgut of three triatomine species Triatoma infestans, Dipetalogaster maximus and Panstrongylus megistus indicated that all produce Hz. Morphological analysis of T. infestans and D. maximus midguts revealed the close association of Hz crystals to perimicrovillar membranes and also as multicrystalline assemblies, forming nearly spherical structures. Heme crystallization was promoted by isolated perimicrovillar membranes from all three species of triatomine bugs in vitro in heat-sensitive reactions. In conclusion, the data presented here indicate that Hz formation is an ancestral adaptation of Triatominae to a blood-sucking habit and that the presence of perimicrovillar membranes plays a central role in this process.

Induction of heme oxygenase-1 in renovascular hypertension is associated with inhibition of apoptosis

The goal of this study was to characterize the impact of induction or inhibition of the heme-HO system on renal apoptosis in clipped and non-clipped kidneys from 2K1C hypertensive rats. Male Sprague-Dawley rats had a 0.25 mm silver clip placed around the left renal artery. Four groups of rats were studied: sham operated animals, 2K1C control rats, 2K1C rats received weekly injections of CoPP (5 mg/100 g body wt, administered subcutaneously), and 2K1C rats pretreated with SnMP (5 mg/ 100g body wt, administered intraperitoneally three times a week). The animals were sacrificed three weeks after surgery. We measured systolic blood pressure, plasma renin activity, non-clipped and clipped kidney HO-1 and HO-2 protein expression, HO activity, heme content, nitrotyrosine levels, and activation of selected pro- and anti-apoptotic proteins. Systolic blood pressure and plasma renin activity were significantly higher in 2K1C rats compared to sham rats. Compared to kidneys from sham animals, clipped kidneys from 2K1C rats showed a significant increase in HO-1 expression with increases in HO activity (26%), heme content (47%) and nitrotyrosine levels (49%), accompanied by an increase in caspase-3 and caspase-9 activity. In contrast, non-clipped kidneys from 2K1C rats showed no differences in HO-1 expression, HO activity, heme content, nitrotyrosine levels and caspase activity compared to sham rats. In clipped kidneys from 2K1C rats, inhibition of HO activity by SnMP augmented caspase-3 and caspase-9 activity and decreased expression of the anti-apoptotic Bcl-2 protein, while induction of HO-1 with CoPP strongly inhibited the activity of both caspases and increased the induction of Bcl-2 and Bcl-xl proteins. These findings demonstrate that the clipped kidneys responded to decreased renal perfusion pressure and increased oxidative stress by activation of the heme-HO system, which exerts antiapoptotic action via mechanisms involving decreased caspase-3 and caspase-9 activity, and increased expression of antiapoptotic molecules.

Development of a bacterial system for high yield expression of fully functional adrenal cytochrome b561

Adrenal cytochrome b561 (cyt b561) is the prototypical member of an emerging family of proteins that are distributed widely in vertebrate, invertebrate and plant tissues. The adrenal cytochrome is an integral membrane protein with two b-type hemes and six predicted transmembrane helices. Adrenal cyt b561 is involved in catecholamine biosynthesis, shuttling reducing equivalents derived from ascorbate. We have developed an Escherichia coli system for expression, solubilization and purification of the adrenal cytochrome. The spectroscopic and redox properties of the purified recombinant protein expressed in this prokaryotic system confirm that the cytochrome retains a native, fully functional form over a wide pH range. Mass spectral analysis shows that the N-terminal signal peptide is intact. The new bacterial expression system for cyt b561 offers a sixfold improvement in yield and other substantial advantages over existing insect and yeast cell systems for producing the recombinant cytochrome for structure-function studies.

Zinc protoporphyrin/heme in large-for-gestation newborns

BACKGROUND

Zinc protoporphyrin/heme (ZnPP/H) ratios are indicators of incomplete erythrocyte iron delivery. ZnPP/H is more sensitive than measures of iron stores, such as plasma ferritin, in identifying early pre-anemic iron-deficient erythropoiesis. Cord ZnPP/H ratios are elevated in conditions associated with fetal hypoxia, such as diabetes mellitus during pregnancy. In chronic fetal hypoxemia, erythrocyte and hemoglobin syntheses are accelerated and iron is incorporated into erythrocytes. Cord ZnPP/H ratios are correlated with fetal size after diabetic pregnancy. Because fetal size is a surrogate for diabetes control, it is unclear whether glycemic control in diabetes mellitus or fetal size was the major determinant of ZnPP/H ratios and disturbed erythrocyte iron delivery.

OBJECTIVE

Our goal was to examine whether ZnPP/H ratios were elevated or were associated with growth in large-for-gestation newborns born to mothers without the diagnosis of diabetes mellitus.

METHODS

In cord blood samples from large and appropriately grown healthy newborns, we measured ZnPP/H and indices of erythropoiesis and iron status. Analyses included simple linear regression, Fisher's exact, and unpaired t testing.

RESULTS

In the absence of diabetes mellitus, ZnPP/H in 25 large and 24 appropriately grown healthy newborns was similar, and the ratios were within the limits of previously reported normal cord ZnPP/H. Ratios were not correlated with plasma ferritin levels. In large newborns, but not appropriately grown newborns, ZnPP/H ratios were positively correlated with fetal growth (p < 0.03) and estimates of body hemoglobin (p <0.04).

CONCLUSIONS

Despite 33% greater body hemoglobin mass observed in healthy large, compared to appropriately grown newborns, mean ZnPP/H was normal. Iron incorporation into erythrocytes in large newborns appears adequate. Because the association of ZnPP/H with size and estimated body hemoglobin was observed only in large newborns, factors determining ZnPP/H may differ between large and appropriately grown newborns.

Spectroscopic investigations of intermediates in the reaction of cytochrome P450BM3–F87G with surrogate oxygen atom donors☆

Rapid mixing of substrate-free ferric cytochrome P450(BM3)-F87G with m-chloroperoxybenzoic acid (mCPBA) resulted in the sequential formation of two high-valent intermediates. The first was spectrally similar to compound I species reported previously for P450(CAM) and CYP 119 using mCPBA as an oxidant, and it featured a low intensity Soret absorption band characterized by shoulder at 370nm. This is the first direct observation of a P450 compound I intermediate in a type II P450 enzyme. The second intermediate, which was much more stable at pH values below 7.0, was characterized by an intense Soret absorption peak at 406nm, similar to that seen with P450(CAM) [T. Spolitak, J.H. Dawson, D.P. Ballou, J. Biol. Chem. 280 (2005) 20300-20309]. Double mixing experiments in which NADPH was added to the transient 406nm-absorbing intermediate resulted in rapid regeneration of the resting ferric state, with the flavins of the flavoprotein domain in their reduced state. EPR results were consistent with this stable intermediate species being a cytochrome c peroxidase compound ES-like species containing a protein-based radical, likely localized on a nearby Trp or Tyr residue in the active site. Iodosobenzene, peracetic acid, and sodium m-periodate also generated the intermediate at 406nm, but not the 370nm intermediate, indicating a probable kinetic barrier to accumulating compound I in reactions with these oxidants. The P450 ES intermediate has not been previously reported using iodosobenzene or m-periodate as the oxygen donor.

Fifth-order contributions to ultrafast spectrally resolved vibrational echoes: heme-CO proteins

The fifth order contributions to the signals of ultrafast infrared spectrally resolved stimulated vibrational echoes at high intensities have been investigated in carbonmonoxy heme proteins. High intensities are often required to obtain good data. Intensity dependent measurements are presented on hemoglobin-CO (Hb-CO) and a mutant of myoglobin, H64V-CO. The spectrally resolved vibrational echoes demonstrate that fifth order effects arise at both the 1-0 and the 2-1 emission frequencies of the stretching mode of the CO chromophore bound at the active site of heme proteins. Unlike one-dimensional experiments, in which the signal is integrated over all emission frequencies, spectrally resolving the signal shows that the fifth order contributions have a much more pronounced influence on the 2-1 transition than on the 1-0 transition. By spectrally isolating the 1-0 transition, the influence of fifth order contributions to vibrational echo data can be substantially reduced. Analysis of fifth order Feynman diagrams that contribute in the vibrational echo phase-matched direction demonstrates the reason for the greater influence of fifth order processes on the 1-2 transition, and that the fifth order contributions are heterodyne amplified by the third order signal. Finally, it is shown that the anharmonic oscillations in vibrational echo data of Hb-CO that previous work had attributed strictly to fifth order effects arise even without fifth order contributions.

Elevated zinc protoporphyrin/heme ratios in umbilical cord blood after diabetic pregnancy

OBJECTIVE

Offspring of diabetes patients may suffer from tissue iron deficiency. Erythrocyte zinc protoporphyrin/heme (ZnPP/H) ratios measure impaired iron status. The aim of the study was to examine whether cord ZnPP/H ratios were associated with pregnancy glycemic control.

METHODS

ZnPP/H was measured in cord blood from 31 pregnancies with insulin-treated diabetes (diabetes group) and compared to population normal values. Maternal glycemic control was assessed by daily glucose log, glycosylated hemoglobin and birth weight.

RESULTS

Median cord ZnPP/H was higher in the diabetes group than the population normal values (106 (65.2 to 146.8) microM/M vs 68.2 (37.6 to 98.8) micro/M, P < 0.0001). Ratios were directly correlated to surrogates of control (glycosylated hemoglobin, P = 0.05, and birth weight, P < 0.04). Cord ZnPP/H ratios from pregnancies with pre-existing and gestational diabetes were similar.

CONCLUSION

Because cord ZnPP/H was higher in large offspring of diabetic pregnancy, it might identify greater iron utilization for fetal erythropoiesis.

Flavor relationships among muscles from the beef chuck and round1

This research compared off-flavor notes and the relationship of pH and heme-iron content to off-flavor for different beef muscles. After grading, knuckles and shoulder clods were removed from 16 USDA Choice and 14 USDA Select beef carcasses, vacuum-packaged, and aged for 7 d. The rectus femoris (REC), vastus medalis (VAM), vastus lateralis (VAL), teres major (TER), infraspinatus (INF), and triceps brachii-long head (TRI) were separated, cut into steaks, and frozen (-16 degrees C). Sensory analysis was conducted using a trained taste panel, with steaks grilled to an internal temperature of 65 degrees C. Heme-iron concentration and pH were determined. The INF had lower (P < 0.05) off-flavor intensity ratings and less frequent sour flavor than the other muscles, and the VAL had the most intense (P < 0.05) off-flavor ratings and among the greatest frequency of sour, charred, and oxidized flavors. The frequencies of liver-like, bloody, and rancid flavors were not affected by muscle type. Heme-iron concentration did not differ among muscles. Three USDA Select carcasses had intense off-flavor in the muscles. Liver-like flavor was highly negatively correlated with off-flavor intensity for each of the muscles tested. Muscles rated a 5 or below (on an 8-point rating scale, where 1 = extremely intense off-flavor and 8 = no off-flavor) in off-flavor intensity and identified as liver-like by 30% or more of the panelists were grouped together and compared to normal muscles. Those in the liver-flavored group were less frequently identified as charred, probably because the liver-like flavor was so intense. There were no differences between the 2 groups for sour, metallic, bloody, oxidized, or fatty off-flavor notes. Regression equations containing the linear and quadratic functions of heme-iron concentration, muscle pH, and their interaction were established for the frequency of off-flavor notes within each muscle. The REC, TER, VAL, and VAM showed a relationship between pH, heme iron, and off-flavor intensity (P < 0.05). Liver-like flavor was explained partially by pH and heme iron in the REC, VAM, and VAL (R2 = 0.45 to 0.55; P < 0.05). Few other significant relationships were found. Heme iron and pH were unrelated to metallic, oxidized, or rancid flavors for any of the muscles tested. These data suggest that liver-like off-flavors are specific to individual animals, and that pH and heme iron are not strongly related to off-flavor notes.

Siro(haem)amide inAllochromatium vinosumand relevance of DsrL and DsrN, a homolog of cobyrinic acida,c-diamide synthase, for sulphur oxidation

In the purple sulphur bacterium Allochromatium vinosum, the prosthetic group of dissimilatory sulphite reductase (DsrAB) was identified as siroamide, an amidated form of the classical sirohaem. The genes dsrAB are the first two of a large cluster of genes necessary for the oxidation of sulphur globules stored intracellularly during growth on sulphide and thiosulphate. DsrN is homologous to cobyrinic acid a,c diamide synthase and may therefore catalyze glutamine-dependent amidation of sirohaem. Indeed, an A. vinosumDeltadsrN in frame deletion mutant showed a significantly reduced sulphur oxidation rate that was fully restored upon complementation with dsrN in trans. Sulphite reductase was still present in the DeltadsrN mutant. DsrL is a homolog of the small subunits of bacterial glutamate synthases and was proposed to deliver glutamine for sirohaem amidation. However, recombinant DsrL does not exhibit glutamate synthase activity nor does the gene complement a glutamate synthase-deficient Escherichia coli strain. Deletion of dsrL showed that the encoded protein is absolutely essential for sulphur oxidation in A. vinosum.

Iron nutrition and physiological responses to iron stress in Nitrosomonas europaea

Nitrosomonas europaea, as an ammonia-oxidizing bacterium, has a high Fe requirement and has 90 genes dedicated to Fe acquisition. Under Fe-limiting conditions (0.2 microM Fe), N. europaea was able to assimilate up to 70% of the available Fe in the medium even though it is unable to produce siderophores. Addition of exogenous siderophores to Fe-limited medium increased growth (final cell mass). Fe-limited cells had lower heme and cellular Fe contents, reduced membrane layers, and lower NH3- and NH2OH-dependent O2 consumption activities than Fe-replete cells. Fe acquisition-related proteins, such as a number of TonB-dependent Fe-siderophore receptors for ferrichrome and enterobactin and diffusion protein OmpC, were expressed to higher levels under Fe limitation, providing biochemical evidence for adaptation of N. europaea to Fe-limited conditions.

Effect of Glycation of Hemoglobin on its Interaction with Trifluoperazine

Trifluoperazine (TFZ), a phenothiazine drug, penetrates into human erythrocytes and releases oxygen by interaction with hemoglobin. TFZ-induced oxygen release from hyperglycemic erythrocytes isolated from diabetic patients is considerably less compared to that from the cells of normoglycemic individuals. In diabetes mellitus, hemoglobin is significantly glycated by glucose. Non-glycated hemoglobin, HbA0 and its major glycated analog, HbA1c have been separated from the blood samples of diabetic patients. TFZ releases considerable amount of oxygen from HbA0, but very little from HbA1c. Spectrofluorimetric studies reveal that TFZ forms excited state complexes with both HbA0 and HbAlc. Titration of HbA0 with TFZ in a spectrophotometric study exhibits two isosbestic points. Similar experiment with HbAlc causes gradual loss of the Soret peak without appearance of any isosbestic point indicating a possibility of heme loss during interaction, which is also supported by gel filtration experiment and SDS-PAGE experiment followed by heme staining. The results suggest that drug action on hemoglobin is influenced by glycation-induced structural modification of the protein.