Effects of faba beans with different concentrations of vicine and convicine on egg production, egg quality and red blood cells in laying hens

The faba bean (Vicia faba L.) is a potential source of proteins for poultry, mainly for laying hens whose protein requirements are lower than those of other birds such as growing broilers and turkeys. However, this feedstuff contains anti-nutritional factors, that is, vicine (V) and convicine (C) that are already known to reduce laying hen performance. The aim of the experiment reported here was to evaluate the effects of a wide range of dietary V and C concentrations in laying hens. Two trials were performed with laying hens fed diets including 20% or 25% of faba bean genotypes highly contrasting in V+C content. In Trial 1, faba beans from two tannin-containing cultivars, but with high or low V+C content were dehulled in order to eliminate the tannin effect. In addition to the contrasting levels of V+C in the two cultivars, two intermediate levels of V+C were obtained by mixing the two cultivars (70/30 and 30/70). In Trial 2, two isogenic zero-tannin faba bean genotypes with high or low V+C content were used. In both trials, a classical corn-soybean diet was also offered to control hens. Each experimental diet was given to 48 laying hens for 140 (Trial 1) or 89 (Trial 2) days. Laying performance and egg quality were measured. The redox sensitivity of red blood cells (RBCs) was assessed by measuring hemolysis and reduced glutathione (GSH) concentration in these cells. Egg weight was significantly reduced by the diets containing the highest concentrations of V+C (P<0.0001) in Trial 1 and slightly reduced (P<0.10) in Trial 2, but only weak linear relationships between egg weight and dietary V+C concentration were established. No negative effect of V+C level was observed for egg quality parameters. In contrast, certain parameters (i.e. Haugh units, yolk color) were improved by feeding low V+C diets (P<0.05). Hemolysis of RBCs was higher in hens fed high V+C diets. A decrease in GSH concentration in RBCs of hens fed the highest levels of V+C was observed. Faba bean genotypes with low concentrations of V+C can therefore be used in laying hen diets up to 25% without any detrimental effects on performance levels or egg characteristics, without any risk of hemolysis of RBCs.

Preferential binding of 4-hydroxynonenal to lysine residues in specific parasite proteins in plakortin-treated Plasmodium falciparum-parasitized red blood cells

The data show the frequencies by which the amino acid residues lysine, histidine and cysteine of six proteins of the malaria parasite Plasmodium falciparum are post-translationally modified by the lipoperoxydation endproduct 4-hydroxynonenal after challenging the parasitized red blood cell with plakortin. Plakortin is an antimalarial endoperoxide whose molecular anti-parasitic effect is described in Skorokhod et al. (2015) [1]. Plakortin did not elicit hemoglobin leakage from host red blood cells and did not oxidize reduced glutathione.

Oxidative stress-mediated antimalarial activity of plakortin, a natural endoperoxide from the tropical sponge Plakortis simplex

Plakortin, a polyketide endoperoxide from the sponge Plakortis simplex has antiparasitic activity against P. falciparum. Similar to artemisinin, its activity depends on the peroxide functionality. Plakortin induced stage-, dose- and time-dependent morphologic anomalies, early maturation delay, ROS generation and lipid peroxidation in the parasite. Ring damage by 1 and 10 µM plakortin led to parasite death before schizogony at 20 and 95%, respectively. Treatment of late schizonts with 1, 2, 5 and 10 µM plakortin resulted in decreased reinfection rates by 30, 50, 61 and 65%, respectively. In both rings and trophozoites, plakortin induced a dose- and time-dependent ROS production as well as a significant lipid peroxidation and up to 4-fold increase of the lipoperoxide breakdown product 4-hydroxynonenal (4-HNE). Antioxidants and the free radical scavengers trolox and N-acetylcysteine significantly attenuated the parasite damage. Plakortin generated 4-HNE conjugates with the P. falciparum proteins: heat shock protein Hsp70-1, endoplasmatic reticulum-standing Hsp70-2 (BiP analogue), V-type proton ATPase catalytic subunit A, enolase, the putative vacuolar protein sorting-associated protein 11, and the dynein heavy chain-like protein, whose specific binding sites were identified by mass spectrometry. These proteins are crucially involved in protein trafficking, transmembrane and vesicular transport and parasite survival. We hypothesize that binding of 4-HNE to functionally relevant parasite proteins may explain the observed plakortin-induced morphologic aberrations and parasite death. The identification of 4-HNE-protein conjugates may generate a novel paradigm to explain the mechanism of action of pro-oxidant, peroxide-based antimalarials such as plakortin, artemisinins and synthetic endoperoxides.

Antimalarial NADPH-Consuming Redox-Cyclers As Superior Glucose-6-Phosphate Dehydrogenase Deficiency Copycats

AIMS

Early phagocytosis of glucose-6-phosphate dehydrogenase (G6PD)-deficient erythrocytes parasitized by Plasmodium falciparum were shown to protect G6PD-deficient populations from severe malaria. Here, we investigated the mechanism of a novel antimalarial series, namely 3-[substituted-benzyl]-menadiones, to understand whether these NADPH-consuming redox-cyclers, which induce oxidative stress, mimic the natural protection of G6PD deficiency.

RESULTS

We demonstrated that the key benzoylmenadione metabolite of the lead compound acts as an efficient redox-cycler in NADPH-dependent methaemoglobin reduction, leading to the continuous formation of reactive oxygen species, ferrylhaemoglobin, and subsequent haemichrome precipitation. Structure-activity relationships evidenced that both drug metabolites and haemoglobin catabolites contribute to potentiate drug effects and inhibit parasite development. Disruption of redox homeostasis by the lead benzylmenadione was specifically induced in Plasmodium falciparum parasitized erythrocytes and not in non-infected cells, and was visualized via changes in the glutathione redox potential of living parasite cytosols. Furthermore, the redox-cycler shows additive and synergistic effects in combination with compounds affecting the NADPH flux in vivo.

INNOVATION

The lead benzylmenadione 1c is the first example of a novel redox-active agent that mimics the behavior of a falciparum parasite developing inside a G6PD-deficient red blood cell (RBC) giving rise to malaria protection, and it exerts specific additive effects that are inhibitory to parasite development, without harm for non-infected G6PD-sufficient or -deficient RBCs.

CONCLUSION

This strategy offers an innovative perspective for the development of future antimalarial drugs for G6PD-sufficient and -deficient populations.

Replication of Plasmodium in reticulocytes can occur without hemozoin formation, resulting in chloroquine resistance

Lin et al. generate Plasmodium berghei mutants lacking enzymes critical to hemoglobin digestion. A double gene deletion mutant lacking enzymes involved in the initial steps of hemoglobin proteolysis is able to replicate inside reticulocytes of infected mice with limited hemoglobin degradation and no hemozoin formation, and moreover, is resistant to the antimalarial drug chloroquine.

Most studies on malaria-parasite digestion of hemoglobin (Hb) have been performed using P. falciparum maintained in mature erythrocytes, in vitro. In this study, we examine Plasmodium Hb degradation in vivo in mice, using the parasite P. berghei, and show that it is possible to create mutant parasites lacking enzymes involved in the initial steps of Hb proteolysis. These mutants only complete development in reticulocytes and mature into both schizonts and gametocytes. Hb degradation is severely impaired and large amounts of undigested Hb remains in the reticulocyte cytoplasm and in vesicles in the parasite. The mutants produce little or no hemozoin (Hz), the detoxification by-product of Hb degradation. Further, they are resistant to chloroquine, an antimalarial drug that interferes with Hz formation, but their sensitivity to artesunate, also thought to be dependent on Hb degradation, is retained. Survival in reticulocytes with reduced or absent Hb digestion may imply a novel mechanism of drug resistance. These findings have implications for drug development against human-malaria parasites, such as P. vivax and P. ovale, which develop inside reticulocytes.

Malarial pigment hemozoin impairs chemotactic motility and transendothelial migration of monocytes via 4-hydroxynonenal

Natural hemozoin, nHZ, is avidly phagocytosed in vivo and in vitro by human monocytes. The persistence of the undigested β-hematin core of nHZ in the phagocyte lysosome for long periods of time modifies several cellular immune functions. Here we show that nHZ phagocytosis by human primary monocytes severely impaired their chemotactic motility toward MCP-1, TNF, and FMLP, by approximately 80% each, and their diapedesis across a confluent human umbilical vein endothelial cell layer toward MCP-1 by 45±5%. No inhibition was observed with latex-fed or unfed monocytes. Microscopic inspection revealed polarization defects in nHZ-fed monocytes due to irregular actin polymerization. Phagocytosed nHZ catalyzes the peroxidation of polyunsaturated fatty acids and generation of the highly reactive derivative 4-hydroxynonenal (4-HNE). Similar to nHZ phagocytosis, the exposure of monocytes to in vivo-compatible 4-HNE concentrations inhibited cell motility in both the presence and the absence of chemotactic stimuli, suggesting severe impairment of cytoskeleton dynamics. Consequently, 4-HNE conjugates with the cytoskeleton proteins β-actin and coronin-1A were immunochemically identified in nHZ-fed monocytes and mass spectrometrically localized in domains of protein-protein interactions involved in cytoskeleton reorganization and cell motility. The molecular and functional modifications of actin and coronin by nHZ/4-HNE may also explain impaired phagocytosis, another motility-dependent process previously described in nHZ-fed monocytes. Further studies will show whether impaired monocyte motility may contribute to the immunodepression and the frequent occurrence of secondary infections observed in malaria patients.

Blood oxidative stress markers and Plasmodium falciparum malaria in non-immune African children

Converging in vitro evidence and clinical data indicate that oxidative stress may play important roles in Plasmodium falciparum malaria, notably in the pathogenesis of severe anaemia. However, oxidative modifications of the red blood cell (RBC)-membrane by 4-hydroxynonenal (4-HNE) and haemoglobin-binding, previously hypothesized to contribute mechanistically to the pathogenesis of clinical malaria, have not yet been tested for clinical significance. In 349 non-immune Mozambican newborns recruited in a double-blind placebo-controlled chemoprophylaxis trial, oxidative markers including 4-HNE-conjugates and membrane-bound haemoglobin were longitudinally assessed from 2·5 to 24 months of age, at first acute malaria episode and in convalescence. During acute malaria, 4-HNE-conjugates were shown to increase significantly in parasitized and non-parasitized RBCs. In parallel, advanced oxidation protein products (AOPP) rose in plasma. 4-HNE-conjugates correlated with AOPP and established plasma but not with RBC oxidative markers. High individual levels of 4-HNE-conjugates were predictive for increased malaria incidence rates in children until 2 years of life and elevated 4-HNE-conjugates in convalescence accompanied sustained anaemia after a malaria episode, indicating 4-HNE-conjugates as a novel patho-mechanistic factor in malaria. A second oxidative marker, haemoglobin binding to RBC-membranes, hypothesized to induce clearing of RBCs from circulation, was predictive for lower malaria incidence rates. Further studies will show whether or not higher membrane-haemoglobin values at the first malaria episode may provide protection against malaria.

Immunopathological effects of malaria pigment or hemozoin and other crystals

Blood-stage malaria parasites produce insoluble hemozoin (Hz) crystals that are released in the blood circulation upon schizont rupture. In general, endogenous crystal formation or inhalation of crystalline materials is often associated with pathology. As the immune system responds differently to crystalline particles than to soluble molecules, in this review, the properties, immunological recognition, and pathogenic responses of Hz are discussed, and compared with two other major pathogenic crystals, monosodium urate (MSU) and asbestos. Because of the size and shape of MSU crystals and asbestos fibers, phagolysosomal formation is inefficient and often results in leakage of lysosomal content in the cell cytoplasm and/or in the extracellular environment with subsequent cell damage and cell death. Phagolysosomal formation after Hz ingestion is normal, but Hz remains stored inside these cells for months or even longer without any detectable degradation. Nonetheless, the different types of crystals are recognized by similar immune receptors, involving Toll-like receptors, the inflammasome, antibodies, and/or complement factors, and through similar signaling cascades, they activate both proinflammatory and anti-inflammatory immune responses that contribute to inflammation-associated pathology.

The Haldane malaria hypothesis: facts, artifacts, and a prophecy

Heterozygous thalassemia and sickle cell disease produce mild hematological symptoms but provide protection against malaria mortality and severe malaria symptoms. Two explanations for resistance are considered in the literature - impaired growth of the parasite or enhanced removal by the host immune cells. A critical overview of studies that connect malaria resistance with impaired intra-erythrocytic growth is presented. All studies are fraught with two kinds of bias. The first one resides in the impossibility of reproducing the in vivo situation in the simplified model in vitro. The second stems from the generalized use of RPMI 1640 culture medium. RPMI 1640 has critically low levels of several amino acids; is devoid of hypoxanthine (essential for parasite growth) and adenine; and is low in reduced glutathione. Analysis of representative studies indicates that impaired parasite growth in heterozygous red blood cells (RBCs) may derive from nutrient limitations and, therefore, possibly be of artefactual origin. This conclusion seems plausible because studies were performed with RPMI 1640 medium at relatively high hematocrit and for prolonged periods of time. Mutations considered are particularly sensitive to nutrient deprivation because they have higher metabolic demands due to permanent oxidant stress related to unpaired globin chains, sickle hemoglobin and high levels of membrane-free iron. In addition, non-parasitized AS- and thalassemic-RBCs are dehydrated and microcytic. Thus, the number of metabolically active elements per unit of blood volume is remarkably larger in mutant RBCs compared to normocytes. The latter point may represent a confirmation of Haldane's prophetic statement: 'The corpuscles of the anaemic heterozygotes are smaller than normal, and more resistant to hypotonic solutions. It is at least conceivable that they are also more resistant to attacks by the sporozoa which cause malaria.'

Simultaneous determination of phagocytosis of Plasmodium falciparum-parasitized and non-parasitized red blood cells by flow cytometry

Background

Severe falciparum malaria anaemia (SMA) is a frequent cause of mortality in children and pregnant women. The most important determinant of SMA appears to be the loss of non-parasitized red blood cells (np-RBCs) in excess of loss of parasitized (p-) RBCs at schizogony. Based on data from acute SMA where excretion of haemoglobin in urine and increased plasma haemoglobin represented respectively less than 1% and 0.5% of total Hb loss, phagocytosis appears to be the predominant mechanism of removal of np- and p-RBC.

Estimates indicate that np-RBCs are cleared in approximately 10-fold excess compared to p-RBCs. An even larger removal of np-RBCs has been described in vivax malaria anaemia. Estimates were based on two single studies both performed on neurosyphilitic patients who underwent malaria therapy. As the share of np-RBC removal is likely to vary between wide limits, it is important to assess the contribution of both np- and p-RBC populations to overall RBC loss, and disclose the mechanism of such variability. As available methods do not discriminate between the removal of np- vs p-RBCs, the purpose of this study was to set up a system allowing the simultaneous determination of phagocytosis of p- and np-RBC in the same sample.

Methods and Results

Phagocytosis of p- and np-RBCs was quantified in the same sample using double-labelled target cells and the human phagocytic cell-line THP-1, pre-activated by TNF and IFNγ to enhance their phagocytic activity. Target RBCs were double-labelled with fluorescent carboxyfluorescein-succinimidyl ester (CF-SE) and the DNA label ethidium bromide (EB). EB, a DNA label, allowed to discriminate p-RBCs that contain parasitic DNA from the np-RBCs devoid of DNA. FACS analysis of THP-1 cells fed with double-labelled RBCs showed that p- and np-RBCs were phagocytosed in different proportions in relation to parasitaemia.

Conclusions

The assay allowed the analysis of phagocytosis rapidly and with low subjective error, and the differentiation between phagocytosed p- and np-RBCs in the same sample. The presented method may help to analyse the factors or conditions that modulate the share of np-RBC removal in vitro and in vivo and lead to a better understanding of the pathogenesis of SMA.

Life and Death of Glucose-6-Phosphate Dehydrogenase (G6PD) Deficient Erythrocytes - Role of Redox Stress and Band 3 Modifications

SUMMARY

G6PD catalyzes the first, pace-making reaction of pentosephosphate cycle (PPC) which produces NADPH. NADPH maintains glutathione and thiol groups of proteins and enzymes in the reduced state which is essential for protection against oxidative stress. Individuals affected by G6PD deficiency are unable to regenerate reduced glutathione (GSH) and are undefended against oxidative stress. G6PD deficiency accelerates normal senescence and enhances the precocious removal of chronologically young, yet biologically old cells. The term hemolytic anemia is misleading because RBCs do not lyse but are removed by phagocytosis. Acute hemolysis by fava bean ingestion in G6PD deficient individuals (favism) is described being the best-studied natural model of oxidant damage. It bears strong analogies to hemolysis by oxidant drugs or chemicals. Membrane alterations observed in vivo during favism are superimposable to changes in senescent RBCs. In summary, RBC membranes isolated from favic patients contained elevated amounts of complexes between IgG and the complement fragment C3b/C3c and were prone to vesiculation. Anti-band 3 IgG reacted to aggregated band 3-complement complexes. In favism extensive clustering of band 3 and membrane deposition of hemichromes were also observed. Severely damaged RBCs isolated from early crises had extensive membrane cross-bonding and very low GSH levels and were phagocytosed 10-fold more intensely compared to normal RBCs.

Transfer of 4-hydroxynonenal from parasitized to non-parasitized erythrocytes in rosettes. Proposed role in severe malaria anemia

Severe anaemia is a life-threatening complication of falciparum malaria associated with loss of predominantly non-parasitized red blood cells (npRBCs). This poorly elucidated process might be influenced by (i) rosettes, i.e. npRBCs cytoadherent to haemozoin-containing parasitized RBCs (pRBCs) and (ii) generation in pRBCs of 4-hydroxynonenal (4-HNE) through haemozoin-catalysed lipid peroxidation. We explored whether close proximity in rosettes may facilitate 4-HNE transfer to npRBCs, which is likely to enhance their phagocytosis and contribute to malaria anaemia. Fluorescence microscopy and flow cytometry data indicated 4-HNE transfer to npRBCs in rosettes. Rosettes were formed by 64·8 ± 1·8% varO-expressing pRBCs, and 8·7 ± 1·1% npRBCs were positive for 4-HNE-protein-conjugates, while low-rosetting parasites generated only 2·4 ± 1·1% 4-HNE-conjugate-positive npRBCs. 4-HNE transfer decreased after blocking rosetting by monoclonal antibodies. A positive linear relationship between rosette frequency and 4-HNE-conjugates in npRBCs was found in 40 malaria patients, a first indication for a role of rosetting in npRBCs modifications in vivo. Children with severe malaria anaemia had significantly higher percentages of 4-HNE-conjugate-positive npRBCs compared to children with uncomplicated malaria. In conclusion, 4-HNE transfer from pRBCs to npRBCs in rosettes is suggested to play a role in the phagocytic removal of large numbers of npRBCs, the hallmark of severe malaria anaemia.

Natural haemozoin modulates matrix metalloproteinases and induces morphological changes in human microvascular endothelium

Severe malaria, including cerebral malaria (CM), is characterized by the sequestration of parasitized erythrocytes in the microvessels after cytoadherence to endothelial cells. Products of parasite origin, such as haemozoin (HZ), contribute to the pathogenesis of severe malaria by interfering with host inflammatory response. In human monocytes, HZ enhanced the levels of matrix metalloproteinase-9 (MMP-9), a protease involved in neuroinflammation. Here the effects of HZ on the regulation of MMPs by the human microvascular endothelial cell line HMEC-1 were investigated. Cells treated with natural (n)HZ appeared elongated instead of polygonal, and formed microtubule-like vessels on synthetic basement membrane. nHZ enhanced total gelatinolytic activity by inducing proMMP-9 and MMP-9 without affecting basal MMP-2. The level of the endogenous tissue inhibitor of MMP-9 (TIMP-1) was not altered by nHZ, while TIMP-2, the MMP-2 inhibitor, was enhanced. Additionally, nHZ induced MMP-1 and MMP-3, two enzymes sequentially involved in collagenolysis and proMMP-9 proteolytic activation. Lipid-free HZ did not reproduce nHZ effects. Present data suggest that the lipid moiety of HZ alters the MMP/TIMP balances and promotes the proteolytic activation of proMMP-9 in HMEC-1, thereby enhancing total gelatinolytic activity, cell activation and inflammation. These findings might help understanding the mechanisms of blood brain barrier damage during CM.

Role of the NF-κB transcription pathway in the haemozoin- and 15-HETE-mediated activation of matrix metalloproteinase-9 in human adherent monocytes

Haemozoin (HZ, malarial pigment) is a crystalline ferriprotoporphyrin IX polymer derived from undigested host haemoglobin haem, present in late stages of Plasmodium falciparum-parasitized RBCs and in residual bodies shed after schizogony. It was shown previously that phagocytosed HZ or HZ-containing trophozoites increased monocyte matrix metalloproteinase-9 (MMP-9) activity and enhanced production of MMP-9-related cytokines TNF and IL-1beta. Here we show that in human monocytes the HZ/trophozoite phagocytosis effects and their recapitulation by 15(S,R)-hydroxy-6,8,11,13-eicosatetraenoic acid (15-HETE), a potent lipoperoxidation derivative generated by HZ from arachidonic acid via haem catalysis, were mediated via activation of NF-κB transcription pathway. After phagocytosis of HZ/trophozoites or treatment with 15-HETE, the NF-κB complex migrated to the nuclear fraction while the inhibitory cytosolic IκBalpha protein was phosphorylated and degraded. All HZ/trophozoite/15-HETE effects on MMP-9 activity and TNF/IL-1beta production were abrogated by quercetin, artemisinin and parthenolide, inhibitors of IκBalpha phosphorylation and subsequent degradation, NF-κB nuclear translocation, and NF-κB-p65 binding to DNA respectively. In conclusion, enhanced activation of MMP-9, and release of pro-inflammatory cytokines TNF and IL-1beta, a triad of effects involved in malaria pathogenesis, elicited in human monocytes by trophozoite and HZ phagocytosis and recapitulated by 15-HETE, appear to be causally connected to persisting activation of the NF-κB system.

Synthesis and antiplasmodial activity of new indolone N-oxide derivatives

A series of 66 new indolone-N-oxide derivatives was synthesized with three different methods. Compounds were evaluated for in vitro activity against CQ-sensitive (3D7), CQ-resistant (FcB1), and CQ and pyrimethamine cross-resistant (K1) strains of Plasmodium falciparum (P.f.), as well as for cytotoxic concentration (CC(50)) on MCF7 and KB human tumor cell lines. Compound 26 (5-methoxy-indolone-N-oxide analogue) had the most potent antiplasmodial activity in vitro (<3 nM on FcB1 and = 1.7 nM on 3D7) with a very satisfactory selectivity index (CC(50) MCF7/IC(50) FcB1: 14623; CC(50) KB/IC(50) 3D7: 198823). In in vivo experiments, compound 1 (dioxymethylene derivatives of the indolone-N-oxide) showed the best antiplasmodial activity against Plasmodium berghei, 62% inhibition of the parasitaemia at 30 mg/kg/day.

Inherited glutathione reductase deficiency and Plasmodium falciparum malaria--a case study

In Plasmodium falciparum-infected red blood cells (RBCs), the flavoenzyme glutathione reductase (GR) regenerates reduced glutathione, which is essential for antioxidant defense. GR utilizes NADPH produced in the pentose phosphate shunt by glucose-6-phosphate dehydrogenase (G6PD). Thus, conditions affecting host G6PD or GR induce increased sensitivity to oxidants. Hereditary G6PD deficiency is frequent in malaria endemic areas and provides protection against severe malaria. Furthermore, GR deficiency resulting from insufficient saturation of the enzyme with its prosthetic group FAD is common. Based on these naturally occurring phenomena, GR of malaria parasites and their host cells represent attractive antimalarial drug targets. Recently we were given the opportunity to examine invasion, growth, and drug sensitivity of three P. falciparum strains (3D7, K1, and Palo Alto) in the RBCs from three homozygous individuals with total GR deficiency resulting from mutations in the apoprotein. Invasion or growth in the GR-deficient RBCs was not impaired for any of the parasite strains tested. Drug sensitivity to chloroquine, artemisinin, and methylene blue was comparable to parasites grown in GR-sufficient RBCs and sensitivity towards paraquat and sodium nitroprusside was only slightly enhanced. In contrast, membrane deposition of hemichromes as well as the opsonizing complement C3b fragments and phagocytosis were strongly increased in ring-infected RBCs of the GR-deficient individuals compared to ring-infected normal RBCs. Also, in one of the individuals, membrane-bound autologous IgGs were significantly enhanced. Thus, based on our in vitro data, GR deficiency and drug-induced GR inhibition may protect from malaria by inducing enhanced ring stage phagocytosis rather than by impairing parasite growth directly.

Co-ordinated stage-dependent enhancement of Plasmodium falciparum antioxidant enzymes and heat shock protein expression in parasites growing in oxidatively stressed or G6PD-deficient red blood cells

Background

Plasmodium falciparum-parasitized red blood cells (RBCs) are equipped with protective antioxidant enzymes and heat shock proteins (HSPs). The latter are only considered to protect against thermal stress. Important issues are poorly explored: first, it is insufficiently known how both systems are expressed in relation to the parasite developmental stage; secondly, it is unknown whether P. falciparum HSPs are redox-responsive, in view of redox sensitivity of HSP in eukaryotic cells; thirdly, it is poorly known how the antioxidant defense machinery would respond to increased oxidative stress or inhibited antioxidant defense. Those issues are interesting as several antimalarials increase the oxidative stress or block antioxidant defense in the parasitized RBC. In addition, numerous inhibitors of HSPs are currently developed for cancer therapy and might be tested as anti-malarials. Thus, the joint disruption of the parasite antioxidant enzymes/HSP system would interfere with parasite growth and open new perspectives for anti-malaria therapy.

Methods

Stage-dependent mRNA expression of ten representative P. falciparum antioxidant enzymes and hsp60/70–2/70–3/75/90 was studied by quantitative real-time RT-PCR in parasites growing in normal RBCs, in RBCs oxidatively-stressed by moderate H2O2 generation and in G6PD-deficient RBCs. Protein expression of antioxidant enzymes was assayed by Western blotting. The pentosephosphate-pathway flux was measured in isolated parasites after Sendai-virus lysis of RBC membrane.

Results

In parasites growing in normal RBCs, mRNA expression of antioxidant enzymes and HSPs displayed co-ordinated stage-dependent modulation, being low at ring, highest at early trophozoite and again very low at schizont stage. Additional exogenous oxidative stress or growth in antioxidant blunted G6PD-deficient RBCs indicated remarkable flexibility of both systems, manifested by enhanced, co-ordinated mRNA expression of antioxidant enzymes and HSPs. Protein expression of antioxidant enzymes was also increased in oxidatively-stressed trophozoites.

Conclusion

Results indicated that mRNA expression of parasite antioxidant enzymes and HSPs was co-ordinated and stage-dependent. Secondly, both systems were redox-responsive and showed remarkably increased and co-ordinated expression in oxidatively-stressed parasites and in parasites growing in antioxidant blunted G6PD-deficient RBCs. Lastly, as important anti-malarials either increase oxidant stress or impair antioxidant defense, results may encourage the inclusion of anti-HSP molecules in anti-malarial combined drugs.

Phagocytosis of haemozoin (malarial pigment) enhances metalloproteinase-9 activity in human adherent monocytes: role of IL-1beta and 15-HETE

BACKGROUND

It has been shown previously that human monocytes fed with haemozoin (HZ) or trophozoite-parasitized RBCs displayed increased matrix metalloproteinase-9 (MMP-9) enzyme activity and protein/mRNA expression and increased TNF production, and showed higher matrix invasion ability. The present study utilized the same experimental model to analyse the effect of phagocytosis of: HZ, delipidized HZ, beta-haematin (lipid-free synthetic HZ) and trophozoites on production of IL-1beta and MMP-9 activity and expression. The second aim was to find out which component of HZ was responsible for the effects.

METHODS

Native HZ freshly isolated from Plasmodium falciparum (Palo Alto strain, Mycoplasma-free), delipidized HZ, beta-haematin (lipid-free synthetic HZ), trophozoites and control meals such as opsonized non-parasitized RBCs and inert latex particles, were fed to human monocytes. The production of IL-1beta by differently fed monocytes, in presence or absence of specific MMP-9 inhibitor or anti-hIL-1beta antibodies, was quantified in supernatants by ELISA. Expression of IL-1beta was analysed by quantitative real-time RT-PCR. MMP-9 activity and protein expression were quantified by gelatin zymography and Western blotting.

RESULTS

Monocytes fed with HZ or trophozoite-parasitized RBCs generated increased amounts of IL-1beta and enhanced enzyme activity (in cell supernatants) and protein/mRNA expression (in cell lysates) of monocyte MMP-9. The latter appears to be causally related to enhanced IL-1beta production, as enhancement of both expression and enzyme activity were abrogated by anti-hIL-1beta Abs. Upregulation of IL-1beta and MMP-9 were absent in monocytes fed with beta-haematin or delipidized HZ, indicating a role for HZ-attached or HZ-generated lipid components. 15-HETE (15(S,R)-hydroxy-6,8,11,13-eicosatetraenoic acid) a potent lipoperoxidation derivative generated by HZ from arachidonic acid via haem-catalysis was identified as one mediator possibly responsible for increase of both IL-1beta production and MMP-9 activity.

CONCLUSION

Results indicate that specific lipoperoxide derivatives generated by HZ may play a role in modulating production of IL-1beta and MMP-9 expression and activity in HZ/trophozoite-fed human monocytes. Results may clarify aspects of cerebral malaria pathogenesis, since MMP-9, a metalloproteinase able to disrupt the basal lamina is possibly involved in generation of hallmarks of cerebral malaria, such as blood-brain barrier endothelium dysfunction, localized haemorrhages and extravasation of phagocytic cells and parasitized RBCs into brain tissues.

Hemozoin and the human monocyte--a brief review of their interactions

In vitro, human monocytes avidly ingest hemozoin (HZ) that modifies a number of monocyte functions. Inhibitory effects: inhibition of: PMA-elicited respiratory burst, ability to killing and repeat phagocytosis, activity of NADPH-oxidase and PKC, expression of ICAM-1, integrin-CD11c, MHC-class-II (IFN-gamma-mediated), differentiation to functional, antigen-presenting dendritic cells. Stimulatory effects: increase in phagocytosis-related respiratory burst and accumulation of lipoperoxidation products; induction of metalloproteinase-9 and pro-inflammatory cytokines and chemokines. Mechanism of action: HZ generates by nonenzymatic catalysis large amounts of lipoperoxidation products, such as monohydroxy derivatives of arachidonic (HETE) and linoleic (HODE) acid, and 4-hydroxynonenal (HNE). Several HZ effects were reproduced by supplementation with plausible concentrations of HETE or HNE, the first most likely via interaction with PPAR-receptors, the second via adduct or crosslinks formation with critical targets.

Naturally occurring anti-band 3 antibodies and red blood cell removal under physiological and pathological conditions

Naturally occurring antibodies (NAbs) directed to band 3 protein (major erythrocyte membrane protein) are involved in the clearance of red blood cell (RBC) at the end of their lifespan as well as in the removal of RBC in different hereditary haemolytic disorders and in malaria. In all cited situations RBC undergoes oxidative stress and hemichromes (haemoglobin degradation products) are formed. Hemichromes possess a strong affinity for band 3 cytoplasmic domain and, following their binding, lead to band 3 oxidation and clusterisation. Those band 3 clusters show increased affinity for NAbs which activate complement and finally trigger the phagocytosis of altered RBC. During intra-erythrocytic malaria parasite growth, NAbs begin to bind to RBC surface at early parasite development stages increasing their abundance in parallel with parasite development. Interestingly, a number of hereditary haemolytic disorders, known to exert a protective effect on malaria, tend to exacerbate this phenomenon leading to a more precocious and effective opsonization of diseased RBC infected by malaria parasites. The exact definition of band 3 neo-antigens and the mechanism of their surface exposure are still unclear. Also band 3 clusterisation is only superficially understood, new insights about band 3 phosphorylation by Src kinases suggest the presence of a complex regulatory pathway.

HNE produced by the malaria parasite Plasmodium falciparum generates HNE-protein adducts and decreases erythrocyte deformability

In Plasmodium falciparum-parasitized erythrocytes, hemozoin (HZ) formation was accompanied by enhanced formation of 4-hydroxynonenal (HNE)-protein adducts on the cell surface, reaching in the HZ-rich schizont forms the 16.8-fold amount of control non-parasitized cells. The addition of 1-100 microM exogenous HNE to control non-parasitized cells generated HNE-adducts on surface proteins in amounts similar to those found in schizonts. Parasitized as well as HNE-treated non-parasitized erythrocytes showed decreased cell deformability (measured as decreased filterability through cylindrical-pore filters) related to the amount of HNE adducts. In vivo, the HZ-containing trophozoites and schizonts are phagocytic targets for monocytes/macrophages. The reduced deformability of circulating erythrocytes carrying HNE-adducts may increase their phagocytic elimination. Uncontrolled HNE production by parasitized erythrocytes may additionally modify non-parasitized bystander erythrocytes, induce their phagocytosis, and contribute to malarial anemia, which is predominantly due to the removal of large numbers of indirectly damaged non-parasitized erythrocytes.

Band 3/complement-mediated recognition and removal of normally senescent and pathological human erythrocytes

Band 3 modifications that normally occur during physiological red blood cell (RBC) senescence in humans, and occasionally in pathological conditions are described in the context of their role in enhancing RBC recognition and phagocytic removal. Band 3 modifications are mostly due to oxidative insults that gradually accumulate during the RBC lifespan or impact massively in a shorter time period in pathological conditions. The oxidative insults that impact on the RBC, the protective mechanisms that counteract those damages and the phenotypic modifications that accumulate during the RBC lifespan are described. It is shown how specific oxidative as well as non-oxidative band 3 modifications enhance RBC membrane affinity for normally circulating anti-band 3 antibodies, and how membrane-bound anti-band 3 antibodies bring about a limited complement activation and membrane deposition of complement C3 fragments. The partially covalent complexes between anti-band 3 antibodies and complement C3 fragments are very powerful opsonins readily recognized by the CR1 complement receptor on the phagocyte. Band 3 modifications typically encountered in old RBCs have crystallized to a number of band 3-centered models of RBC senescence. One of those band 3-centered models, the so-called 'band 3/complement RBC removal model' first put up by Lutz et al. is discussed in more detail. Finally, it is shown how the genetic deficiency of glucose-6-phosphate dehydrogenase (G6PD) plus fava bean consumption, and a widespread RBC parasitic disease, P. falciparum malaria, may lead to massive and rapid destruction of RBCs by a mechanism comparable to a dramatic, time-compressed enhancement of normal RBC senescence.

Phagocytosis of hemozoin enhances matrix metalloproteinase-9 activity and TNF-alpha production in human monocytes: role of matrix metalloproteinases in the pathogenesis of falciparum malaria

Matrix metalloproteinase-9 (MMP-9), secreted by activated monocytes, degrades matrix proteins, disrupts basal lamina, and activates TNF-alpha from its precursors. In turn, TNF-alpha enhances synthesis of MMP-9 in monocytes. We show here that trophozoite-parasitized RBCs/hemozoin-fed adherent human monocytes displayed increased MMP-9 activity and protein/mRNA expression, produced TNF-alpha time-dependently, and showed higher matrix invasion ability. MMP-9 activation was specific for trophozoite/hemozoin-fed monocytes, was dependent on TNF-alpha production, and abrogated by anti-TNF-alpha Ab and by a specific inhibitor of MMP-9/MMP-13 activity. Hemozoin-induced enhancement of MMP-9 and TNF-alpha production would have a 2-fold effect: to start and feed a cyclic reinforcement loop in which hemozoin enhances production of TNF-alpha, which in turn induces both activation of MMP-9 and shedding of TNF-alpha into the extracellular compartment; and, second, to disrupt the basal lamina of endothelia. Excess production of TNF-alpha and disruption of the basal lamina with extravasation of blood cells into perivascular tissues are hallmarks of severe malaria. Pharmacological inhibition of MMP-9 may offer a new chance to control pathogenic mechanisms in malaria.

Detection of Circulating Prostate Cancer Cells Using Real Time Rt – Pcr: Our Experience

PCR (Polymerase Chain Reaction) has revolutionized molecular genetics and continues to be applied to many fields of medicine and biology. We used nested real time RT – PCR to detect circulating prostate cells in patients affected by prostate cancer, in order to evaluate a possible clinical role of this technique. We present our initial experience.

Role of 4-hydroxynonenal in the hemozoin-mediated inhibition of differentiation of human monocytes to dendritic cells induced by GM-CSF/IL-4

In falciparum malaria, rupture of parasitized RBC liberates hemozoin (HZ), polymerized heme that contains and generates lipoperoxidation products. In HZ and HZ-loaded monocytes 4-HNE attained approx. 50 and 15 microM, respectively. In malaria, HZ-loaded monocytes are precursors of dendritic cells (DC). Here, the role of 4-HNE as inhibitor of DC differentiation was examined. 4-HNE in HZ was quantified after derivatization by HPLC. DC were differentiated in vitro from human monocytes supplemented with GM-CSF/IL-4 and analyzed for surface antigens and 4-HNE-adducts by FACScan after labelling with specific antibodies. HZ-loading, or treatment with 4-HNE induced large numbers of 4-HNE-protein-adducts on the monocyte membrane. As low as 10 nM 4-HNE inhibited up-regulation of functionally important DC differentiation markers. 1 microM 4-HNE elicited inhibition of up-regulation of DC differentiation markers as follows: MHC-class I and II, -29% and -40%; CD1a, -16%; CD40, -25%; CD54, -27%; and CD83 (the most important DC differentiation marker), -45%, with no signs of apoptosis. The sequence of additions was important, as the inhibitory effect was reduced when 4-HNE was added after GM-CSF/IL-4, indicating that GM-CSF/IL-4 receptors could be modified by 4-HNE. In conclusion, inhibition of DC differentiation by 4-HNE may play a role in malaria immunodepression.

Hemozoin (malarial pigment) inhibits differentiation and maturation of human monocyte-derived dendritic cells: a peroxisome proliferator-activated receptor-gamma-mediated effect

Acute and chronic Plasmodium falciparum malaria are accompanied by severe immunodepression possibly related to subversion of dendritic cells (DC) functionality. Phagocytosed hemozoin (malarial pigment) was shown to inhibit monocyte functions related to immunity. Hemozoin-loaded monocytes, frequently found in circulation and adherent to endothelia in malaria, may interfere with DC development and play a role in immunodepression. Hemozoin-loaded and unloaded human monocytes were differentiated in vitro to immature DC (iDC) by treatment with GM-CSF and IL-4, and to mature DC (mDC) by LPS challenge. In a second setting, hemozoin was fed to iDC further cultured to give mDC. In both settings, cells ingested large amounts of hemozoin undegraded during DC maturation. Hemozoin-fed monocytes did not apoptose but their differentiation and maturation to DC was severely impaired as shown by blunted expression of MHC class II and costimulatory molecules CD83, CD80, CD54, CD40, CD1a, and lower levels of CD83-specific mRNA in hemozoin-loaded iDC and mDC compared with unfed or latex-loaded DC. Further studies indicated activation of peroxisome proliferator-activated receptor-gamma (PPAR-gamma) in hemozoin-loaded iDC and mDC, associated with increased expression of PPAR-gamma mRNA, without apparent involvement of NF-kappaB. Moreover, expression of PPAR-gamma was induced and up-regulation of CD83 was inhibited by supplementing iDC and mDC with plausible concentrations of 15(S)-hydroxyeicosatetraenoic acid, a PPAR-gamma ligand abundantly produced by hemozoin via heme-catalyzed lipoperoxidation.

Enhanced phagocytosis of ring-parasitized mutant erythrocytes: a common mechanism that may explain protection against falciparum malaria in sickle trait and beta-thalassemia trait

High frequency of erythrocyte (red blood cell [RBC]) genetic disorders such as sickle cell trait, thalassemia trait, homozygous hemoglobin C (Hb-C), and glucose-6-phosphate dehydrogenase (G6PD) deficiency in regions with high incidence of Plasmodium falciparum malaria and case-control studies support the protective role of those conditions. Protection has been attributed to defective parasite growth or to enhanced removal of the parasitized RBCs. We suggested enhanced phagocytosis of rings, the early intraerythrocytic form of the parasite, as an alternative explanation for protection in G6PD deficiency. We show here that P falciparum developed similarly in normal RBCs and in sickle trait, beta- and alpha-thalassemia trait, and HbH RBCs. We also show that membrane-bound hemichromes, autologous immunoglobulin G (IgG) and complement C3c fragments, aggregated band 3, and phagocytosis by human monocytes were remarkably higher in rings developing in all mutant RBCs considered except alpha-thalassemia trait. Phagocytosis of ring-parasitized mutant RBCs was predominantly complement mediated and very similar to phagocytosis of senescent or damaged normal RBCs. Trophozoite-parasitized normal and mutant RBCs were phagocytosed similarly in all conditions examined. Enhanced phagocytosis of ring-parasitized mutant RBCs may represent the common mechanism for malaria protection in nonimmune individuals affected by widespread RBC mutations, while individuals with alpha-thalassemia trait are likely protected by a different mechanism.

Mechanisms of band 3 oxidation and clustering in the phagocytosis of Plasmodium falciparum-infected erythrocytes

Erythrocytes (RBCs) opsonized by IgG and complement are prevalently recognized and phagocytosed by complement receptor CR1. This mechanism, effective in senescent and damaged RBCs seems to be operative in ring-parasitized RBCs, since infection by Plasmodium falciparum induces stage-dependent binding of auto-antibodies and activated C3 to the RBC membrane. Later, parasite forms are also recognized by non-opsonic receptors, such as scavenger receptor CD36. Malaria parasites induce the oxidative formation of hemichromes which are the trigger for the auto-antigen development. Band 3 protein is the most plausible candidate of the RBC auto-antigen, induced by hemichromes. Auto-antigens isolated from trophozoites were found only in a high-molecular-weight protein aggregates not present in the normal RBC. The immunocomplex was purified by protein-A affinity chromatography, purified proteins digested by trypsin and analyzed by MALDI-TOF. Peptide mapping showed that the main antigen consisted of band 3 protein aggregates that also contained hemichromes, IgGs, complement factor 3 (C3), and traces of spectrin and glycophorin but no parasite proteins. Two cysteines located in the band 3 cytoplasmic domain were found to be particularly reactive to oxidants and mediated band 3 covalent dimerization via disulfide bonds. Thus, parasites promote oxidative alterations in the membrane of the host which lead to exposure of antigenic sites recognized by anti-band 3 auto-antibodies. Formation of band 3 clusters appears to be mediated by cytoplasmic binding of hemichromes and also by direct band 3 oxidation, whereby clustered, oxidized and antigenic band 3 was underglycosylated.

Hemozoin- and 4-hydroxynonenal-mediated inhibition of erythropoiesis. Possible role in malarial dyserythropoiesis and anemia

Malarial anemia involves destruction of parasitized and non-parasitized red blood cells and dyserythropoiesis. Malarial pigment, hemozoin (HZ), is possibly implicated in dyserythropoiesis. We show that supernatants of HZ and HZ-fed-monocytes, and 4-hydroxynonenal generated by them, inhibited progenitor growth.

Malaria-parasitized erythrocytes and hemozoin nonenzymatically generate large amounts of hydroxy fatty acids that inhibit monocyte functions

Plasmodium falciparum digests up to 75% of erythrocyte (red blood cell [RBC]) hemoglobin and forms hemozoin. Phagocytosed hemozoin and trophozoites inhibit important monocyte functions. Delipidized trophozoites and hemozoin were remarkably less toxic to monocytes. Parasitized RBCs and hemozoin contained large amounts of mostly esterified monohydroxy derivatives (OH-PUFAs), the stable end products of peroxidation of polyenoic fatty acids. The concentrations of OH-PUFA were 1.8 micromoles per liter RBCs in nonparasitized RBCs, 11.1 micromoles per liter RBCs in rings, 35 micromoles per liter RBCs in trophozoites; and approximately 90 micromoles per liter RBC equivalents in hemozoin. In parasitized RBCs and hemozoin a complex mixture of monohydroxy derivatives of arachidonic (HETEs) and linoleic (HODEs) acid was determined. Respectively, 13- and 9-HODE and 9- and 12-HETE were predominant in hemozoin and parasitized RBCs. The estimated concentrations of all HETE isomers were 33 and 39 micromoles per liter RBCs or RBC equivalents in trophozoites and hemozoin, respectively. No evidence of lipoxygenase activity was found, whereas the large number of positional and optical isomers, the racemic structure, and their generation by incubation of arachidonic acid with hemozoin indicated nonenzymatic origin via heme-catalysis. Sub/low micromolar concentrations of 12- and 15-HETE were toxic to monocytes, whereas HODE isomers were ineffective. Low micromolar concentrations of HETE isomers were estimated to be similarly present in monocytes after phagocytosis of trophozoites or hemozoin. Thus, specific products of heme-catalyzed lipid peroxidation appear to contribute to hemozoin toxicity to phagocytes and may thus play a role in increased cytoadherence, vascular permeability, and chemotaxis, as well as in immunodepression in malaria.

16alpha-bromoepiandrosterone, an antimalarial analogue of the hormone dehydroepiandrosterone, enhances phagocytosis of ring stage parasitized erythrocytes: a novel mechanism for antimalarial activity

Dehydroepiandrosterone (DHEA) and DHEA-sulfate (DHEA-S), which are the most abundant hormones secreted by the adrenal cortex and are present in plasma at approximately 6 micro M, as well as their analogue, 16alpha-bromoepiandrosterone (EPI), exerted antimalarial activities against two chloroquine-sensitive Plasmodium falciparum strains (Palo Alto, 50% inhibitory concentration [IC(50)] of EPI, 4.8 +/- 0.68 micro M; T996/86, IC(50) of EPI, 7.5 +/- 0.91 micro M, and IC(50) of DHEA-S, 19 +/- 2.6 micro M) and one mildly chloroquine-resistant strain (FCR-3, IC(50) of EPI, 6.5 +/- 1.01 micro M). Both EPI and DHEA/DHEA-S are potent inhibitors of glucose-6-phosphate dehydrogenase (G6PD), and G6PD deficiency is known to exert antimalaria protection via enhanced opsonization and phagocytosis of rings, the early forms of the parasite. Plasma-compatible antimalarial EPI concentrations did not inhibit G6PD activity and did not induce ring opsonization by immunoglobulin G and complement fragments, as observed in G6PD deficiency, but nevertheless remarkably stimulated ring phagocytosis. Plasma-compatible, low-micromolar concentrations of EPI induced exposure on the ring surface of phosphatidylserine, a signal for phagocytic removal independent of opsonization. We propose that enhanced ring phagocytosis due to exposure of negatively charged membrane phospholipids may explain the antimalarial activity of EPI.

Cytoadherence of Plasmodium falciparum-infected erythrocytes is mediated by a redox-dependent conformational fraction of CD36

The adherence of Plasmodium falciparum-infected RBC (IRBC) to postcapillary venular endothelium is an important determinant of the pathogenesis of severe malaria complications. Cytoadherence of IRBC to endothelial cells involves specific receptor/ligand interactions. The glycoprotein CD36 expressed on endothelial cells is the major receptor involved in this interaction. Treatment of CD36-expressing cells with reducing agents, such as DTT and N-acetylcysteine, was followed by CD36 conformational change monitorable by the appearance of the Mo91 mAb epitope. Only a fraction of the surface expressed CD36 molecules became Mo91 positive, suggesting the presence of two subpopulations of molecules with different sensitivities to reduction. The Mo91 epitope has been localized on a peptide (residues 260-279) of the C-terminal, cysteine-rich region of CD36. Treatment with reducing agents inhibited the CD36-dependent cytoadherence of IRBC to CD36-expressing cells and dissolved pre-existent CD36-mediated IRBC/CD36-expressing cell aggregates. CD36 reduction did not impair the functionality of CD36, since the reactivity of other anti-CD36 mAbs as well as the binding of oxidized low density lipoprotein, a CD36 ligand, were maintained. The modifications induced by reduction were reversible. After 14 h CD36 was reoxidized, the cells did not express the Mo91 epitope, and cytoadherence to IRBC was restored. The results indicate that IRBCs bind only to a redox-modulated fraction of CD36 molecules expressed on the cell surface. The present data indicate the therapeutic potential of reducing agents, such as the nontoxic drug N-acetylcysteine, to prevent or treat malaria complications due to IRBC cytoadhesion.

Acute haemolysis in childhood falciparum malaria

Acute haemolysis associated with clinical episodes of high-level Plasmodium falciparum parasitaemia was studied in 20 children from an holoendemic area (coastal Tanzania). The change in blood haemoglobin (Hb) concentration ranged from -46 to g/L during the 72-h observation period and was linearly related to maximum parasitaemia. Balance studies between loss of blood Hb, increase in plasma Hb and appearance of Hb in the urine indicated that extravascular clearance of red cells was the predominant mode of erythrocyte clearance. Most subjects, however, showed minor signs of intravascular haemolysis. The plasma Hb was << 1% of blood Hb and haemoglobinuria was detected in 14/20 children but the excretion of Hb in urine was < 0.5% of total Hb loss. Haemoglobinuria was, however, a marker of severe haemolysis, since the maximum blood Hb loss in children without haemoglobinuria was 10 g/L. Erythrocyte-bound opsonins known to induce erythrophagocytosis, i.e., complement C3c fragments and autologous IgG, were increased in all patients. In the patients with major haemolysis, the changes correlated to the haemolysis over time. Hence, a similar mechanism for predominantly extravascular erythrocyte clearance may be operative in acute malarial anaemia, normal erythrocyte senescence and other forms of acute haemolysis.

Independent factors predict supranormal CA 15-3 serum levels in advanced breast cancer patients at first disease relapse

Data currently available are insufficient to demonstrate a real utility for CA 15-3 in the diagnosis, staging or surveillance of breast cancer patients following primary treatment. The aim of this study was to determine if there was a correlation between supranormal CA 15-3 serum levels and clinical and biological variables in breast cancer patients at first disease relapse. From October 1988 to March 1998, 430 consecutive patients entered the study. Overall CA 15-3 sensitivity was 60.7%. Elevated CA 15-3 levels were found more frequently in patients with liver metastases (74.6%) and in those with pleural effusion (75.7%). CA 15-3 sensitivity was 70.4% in patients with estrogen-receptor-positive (ER+) primary tumors and 45.9% in those with estrogen-receptor-negative (ER-) tumors (p < 0.0001). In patients with a limited extent of disease, marker sensitivity was 57.7% in ER+ tumors and 25.7% in ER- tumors (p < 0.0001). Logistic regression analysis showed ER status, disease extent and pleural effusion as independent variables associated with CA 15-3 positivity. The multivariate Cox analysis showed ER and disease extent as independent variables predicting overall survival, whereas CA 15-3 failed to be statistically significant. CA 15-3 was an independent variable only when the disease extent variable was removed. This study suggests that CA 15-3 in advanced breast cancer patients is a marker of both disease extent and ER status. The direct relationship with ER status indicates that CA 15-3 diagnostic sensitivity in the early detection of disease recurrence could be greater in ER+ patients than in ER- ones. Furthermore, this suggests that patients with elevated CA 15-3 levels could have disease that is more sensitive to hormone manipulation than those with normal CA 15-3 values.

Phagocytosis of malarial pigment haemozoin by human monocytes: a confocal microscopy study

Haem from host erythrocyte (RBC) haemoglobin is polymerized in the digestive organelle of Plasmodium falciparum to haemozoin (HZ), a crystaLline, insoluble substance. Human monocytes avidly ingest HZ that persists undigested for long periods of time, and generates potent bioactive lipid peroxide derivatives. Protein kinase C, an effector of signal transduction, phagolysosome formation and acidification, is inhibited in HZ-fed monocytes. Inability to digest HZ might derive from impairment in phagolysosome formation or acidification. Time-course and extent of HZ phagocytosis and acidification of phagolysosomes were studied by quantitative confocal microscopy. From 180 min until 72 h after the start of phagocytosis approximately 75-79% of the monocytes contained massive amounts of HZ. Coincidence between red (HZ) and green (acidic organelles) fluorescent compartments was very high. Confocal images showed that at 30-60 min after the start of phagocytosis, HZ was preferentially present as separated particles, with full co-localization of red and green fluorescence. Later on HZ-laden phagolysosomes tended to fuse together. In conclusion, phagolysosome formation and acidification were normal in HZ-fed monocytes during the 72-h observation time. The presence of HZ in the phagolysosome, the site of antigen processing, may offer a physical link with immunodepression in malaria.

Growth of Plasmodium falciparum induces stage-dependent haemichrome formation, oxidative aggregation of band 3, membrane deposition of complement and antibodies, and phagocytosis of parasitized erythrocytes

Plasmodium falciparum-parasitized erythrocytes (RBCs) are progressively transformed into non-self cells, phagocytosed by human monocytes. Haemichromes, aggregated band 3 (Bd3) and membrane-bound complement fragment C3c and IgG were assayed in serum-opsonized stage-separated parasitized RBCs. All parameters progressed from control to rings to trophozoites to schizonts: haemichromes, nil; 0.64 +/- 0.12; 5.6 +/- 1.91; 8.4 +/- 2.8 (nmol/ml membrane); Bd3, 1 +/- 0.1; 4.3 +/- 1.5; 23 +/- 5; 25 +/- 6 (percentage aggregated); C3c, 31 +/- 11; 223 +/- 86; 446 +/- 157; 620 +/- 120 (mOD405/min/ml membrane); IgG, 35 +/- 12; 65 +/- 23; 436 +/- 127; 590 +/- 196 (mOD405/min/ml membrane). All increments in rings versus controls and in trophozoites versus rings were highly significant. Parasite development in the presence of 100 micromol/l beta-mercaptoethanol largely reverted haemichrome formation, Bd3 aggregation, C3c and IgG deposition and phagocytosis. Membrane proteins extracted by detergent C12E8 were separated on Sepharose CL-6B. Haemichromes, C3c and IgG were present exclusively in the high-molecular-weight fractions together with approximately 30% of Bd3, indicating the oxidative formation of immunogenic Bd3 aggregates. Immunoblots of separated membrane proteins with anti-Bd3 antibodies confirmed Bd3 aggregates that, in part, did not enter the gel. Immunoprecipitated antibodies eluted from trophozoites reacted preferentially with aggregated Bd3. Changes in parasitized RBC membranes and induction of phagocytosis were similar to oxidatively damaged, senescent or thalassaemic RBC, indicating that parasite-induced oxidative modifications of Bd3 were per se sufficient to induce and enhance phagocytosis of malaria-parasitized RBC.

Severe steroid-unresponsive ulcerative colitis: outcomes of restorative proctocolectomy in patients undergoing cyclosporin treatment

PURPOSE

The recent introduction of the immune suppressor cyclosporin for treatment of steroid-refractory ulcerative colitis has required surgeons to perform a colectomy in those patients who eventually fail this rescue treatment, thus raising questions as to the safety of surgery as performed in patients with a heavily manipulated immune system. To assess the rates of mortality and morbidity in this setting, we studied a cohort of consecutive patients who had surgery after failing cyclosporin for refractory ulcerative colitis at our center.

METHODS

Between January 1991 and December 1996, 25 patients with ulcerative colitis underwent restorative proctocolectomy performed in three steps (21 patients) and in two steps (4 patients). Seventeen of the 25 patients (68 percent) were initial nonresponders to a dose of 2 mg/kg/day of intravenous cyclosporin and underwent surgery immediately, the remaining 8 (32 percent) relapsed as outpatients on oral cyclosporin and were readmitted for surgery.

RESULTS

There was no operative mortality. Nine patients of the 25 developed postoperative (early) complications (36 percent). The three-step operation subset had a 28 percent complication rate, the two-step 75 percent. Three patients needed reoperation. A total of 11 patients (44 percent) reported with late complications: two patients required surgical treatment, one for obstruction and one for pouch-perianal fistula. Three cases of pouchitis were recorded. No patient required pouch removal.

CONCLUSION

Given the absence of postoperative mortality and a low overall complication rate, restorative proctocolectomy can safely be performed in patients who fail rescue treatment with a dose of 2 mg/kg of cyclosporin for steroid-refractory ulcerative colitis. Corollary evidence in this article hints but does not prove that the three-step procedure is safer than the two-step operation.

[Chemoresistance in ovarian cancer. State of the art and future prospects]

Aim of this study was to provide a review of the basic mechanisms of drug resistance in ovarian cancer and novel strategies to modulate drug resistance. Relevant articles published through August 1999 were identified using the Medline data base. Publications identified by the search were reviewed and evaluated critically for their relevance to drug resistance in ovarian cancer. Ovarian cancer patients have high response rates to initial chemotherapy after cytoreductive surgery. However, most will develop resistance to chemotherapy during the course of their treatment. There are multiple mechanisms resulting in drug resistance. Strategies to modulate drug resistance include dose intensity, various pharmacologic agents, and gene therapy.

15(S)-hydroxyeicosatetraenoic acid (15-HETE), a product of arachidonic acid peroxidation, is an active component of hemozoin toxicity to monocytes

Several studies have shown that human and murine hemozoin-fed phagocytes are functionally impaired. Unpurified hemozoin contains unspecifically attached unsaturated fatty acids such as arachidonic and linolenic acids. The presence in unpurified hemozoin of large quantities of ferric heme with small amounts of free iron makes hemozoin a generator of oxidative radicals capable of forming lipoperoxides or other breakdown products from polyunsaturated fatty acids. Here we show that delipidized hemozoin had reduced toxicity to monocytes. Phorbol myristate acetate (PMA)-elicited burst was poorly affected by delipidized hemozoin (ca. 17% and 21% burst inhibition by delipidized hemozoin vs ca. 75% and 65% burst inhibition by native hemozoin at 20 min or 17 h post-phagocytosis, respectively). Analysis of the lipid fraction isolated from native hemozoin by HPLC and chiral-phase HPLC showed equimolar amounts of 15(R)- and 15(S)-HETE (HETE, 15-hydroxy-6,8,11,13-eicosatetraenoic acid), most likely by-products of non-enzymatic peroxidation of arachidonic acid. The biologically active isomer, 15(S)-HETE, the product of 15-lipoxygenase, is a powerful mediator of inflammation and the effector of a large number of bioactions. 15(R,S)-HETE was found in native hemozoin (0.24 millimole/mole hemozoin heme), in supernatants of hemozoin-fed monocytes (87 nMol) and in hemozoin-fed monocytes (9.6 microMol). Approximately 84% of 15-HETE attached to hemozoin was in the esterified form. A large preponderance of esterified over free 15-HETE was also noted in supernatants of hemozoin-fed monocytes and in hemozoin-fed monocytes. In the latter cells, remarkable levels of the substance were attained. A dose-dependent curve of inhibition of PMA-elicited oxidative burst was observed. Assuming homogenuous distribution of 15-HETE in hemozoin-fed monocytes, 15(S)-HETE concentrations measured in hemozoin-fed monocytes (8 muMol) would bring about ca. 85% inhibition of PMA-elicited burst. In conclusion, derivatives of lipoperoxidation of unsaturated fatty acids such as 4-hydroxynonenal, 15-HETE and others now under study, appear to be relevant causes of hemozoin toxicity.

Hemozoin stability and dormant induction of heme oxygenase in hemozoin-fed human monocytes

Human monocytes avidly ingest malarial pigment, hemozoin. Phagocytosed hemozoin persists in the monocyte for a long time and modifies important monocyte functions. Stability of phagocytosed hemozoin may depend on modifications of the hemozoin heme moiety or reduced ability to express heme-inducible heme oxygenase. We show here that the spectral characteristics of alkali-solubilized hemozoin were identical to those of authentic heme, although hemozoin was solubilized by alkali much more slowly than authentic heme. Alkali-solubilized hemozoin was a substrate of microsomal rat heme oxygenase and bilirubin reductase, with bilirubin as the main final product. Hemozoin feeding to human monocytes did not induce heme oxygenase, but authentic heme and alkali-solubilized hemozoin supplemented to hemozoin-fed monocytes induced heme oxygenase and were degraded normally. Lysosomes isolated from hemozoin-fed monocytes released only traces of heme while lysosomes from erythrocyte-fed monocytes liberated considerable quantities of heme. Lack of heme release from hemozoin did not depend on proteolysis-resistant, heme-binding proteins, since lysosomal proteases fully degraded hemozoin-associated proteins but did not solubilize hemozoin. In conclusion, our data indicate that lack of induction of HO1 is due to the intrinsic structural characteristics of hemozoin and not to hemozoin-mediated impairment of the mechanism of HO1 induction.