Uptake of ferritin and iron bound to ferritin by rat hepatocytes: modulation by apotransferrin, iron chelators and chloroquine

Harnessing macrophage-drug conjugates for allogeneic cell-based therapy of solid tumors via the TRAIN mechanism

Treatment of solid tumors remains challenging and therapeutic strategies require continuous development. Tumor-infiltrating macrophages play a pivotal role in tumor dynamics. Here, we present a Macrophage-Drug Conjugate (MDC) platform technology that enables loading macrophages with ferritin-drug complexes. We first show that macrophages actively take up human heavy chain ferritin (HFt) in vitro via macrophage scavenger receptor 1 (MSR1). We further manifest that drug-loaded macrophages transfer ferritin to adjacent cancer cells through a process termed 'TRAnsfer of Iron-binding protein' (TRAIN). The TRAIN process requires direct cell-to-cell contact and an immune synapse-like structure. At last, MDCs with various anti-cancer drugs are formulated with their safety and anti-tumor efficacy validated in multiple syngeneic mice and orthotopic human tumor models via different routes of administration. Importantly, MDCs can be prepared in advance and used as thawed products, supporting their clinical applicability. This MDC approach thus represents a promising advancement in the therapeutic landscape for solid tumors.

Chloroquine inhibits Rhodococcus equi replication in murine and foal alveolar macrophages by iron-starvation

Rhodococcus equi preferentially infects macrophages causing pyogranulomatous pneumonia in young foals. Both the vapA and rhbC genes are up-regulated in an iron (Fe)-deprived environment, such as that found within macrophages. Chloroquine (CQ) is a drug widely used against malaria that suppresses the intracellular availability of Fe in eukaryotic cells. The main objective of this study was to evaluate the ability of CQ to inhibit replication of virulent R. equi within murine (J774A.1) and foal alveolar macrophages (AMs) and to verify whether the mechanism of inhibition could be Fe-deprivation-dependent. CQ effect on R. equi extracellular survival and toxicity to J774A.1 were evaluated. R. equi survival within J774A.1 and foal AMs was evaluated under CQ (10 and 20μM), bovine saturated transferrin (bHTF), and bovine unsaturated transferrin (bATF) exposure. To explore the action mechanism of CQ, the superoxide anion production, the lysozyme activity, as well as the relative mRNA expression of vapA and rhbC were examined. CQ at≤20μM had no effect on R. equi extracellular multiplication and J774A.1 viability. Exposure to CQ significantly and markedly reduced survival of R. equi within J774A.1 and foal AMs. Treatment with bHTF did not reverse CQ effect on R. equi. Exposure to CQ did not affected superoxide anion production or lysozyme activity, however vapA and rhbC expression was significantly increased. Our results reinforce the hypothesis that intracellular availability of Fe is required for R. equi survival, and our initial hypothesis that CQ can limit replication of R. equi in J774A.1 and foal AMs, most likely by Fe starvation.

Oxidative stress and the homeodynamics of iron metabolism

Iron and oxygen share a delicate partnership since both are indispensable for survival, but if the partnership becomes inadequate, this may rapidly terminate life. Virtually all cell components are directly or indirectly affected by cellular iron metabolism, which represents a complex, redox-based machinery that is controlled by, and essential to, metabolic requirements. Under conditions of increased oxidative stress—i.e., enhanced formation of reactive oxygen species (ROS)—however, this machinery may turn into a potential threat, the continued requirement for iron promoting adverse reactions such as the iron/H2O2-based formation of hydroxyl radicals, which exacerbate the initial pro-oxidant condition. This review will discuss the multifaceted homeodynamics of cellular iron management under normal conditions as well as in the context of oxidative stress.

Regulatory mechanisms of SNAT2, an amino acid transporter, in L6 rat skeletal muscle cells by insulin, osmotic shock and amino acid deprivation

Several studies have demonstrated that the activity of system A is upregulated by insulin, osmotic shock and amino acid deprivation. However, the mechanisms are not clear. We carried out studies using L6 rat skeletal muscle cells to clarify the mechanisms of upregulation of system A activity by insulin, osmotic shock and amino acid deprivation. The upregulation was found to be due to an increase in Vmax, not Km. Chloroquine and wortmannin inhibited the upregulation induced by insulin stimulation and amino acid deprivation but not that induced by osmotic shock. On the other hand, cycloheximide and actinomycin D inhibited the upregulation by each stimulation. Moreover, PD98059 and SP600125 inhibited only amino acid deprivation-induced upregulation and SB202190 inhibited only insulin-induced upregulation. Our findings indicate that the mechanisms of upregulation of system A activity by insulin, osmotic shock and amino acid deprivation are different in L6 cells. Western blot and RT-PCR analysis showed an increase in system A at the protein and mRNA levels with each stimulation.

Chloroquine is therapeutic in murine experimental model of paracoccidioidomycosis

Chloroquine, due to its basic properties, has been shown to prevent the release of iron from holotransferrin, thereby interfering with normal iron metabolism in a variety of cell types. We have studied the effects of chloroquine on the evolution of experimental paracoccidioidomycosis by evaluating the viable fungal recovery from lung, liver and spleen from infected mice and H(2)O(2), NO production, tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-6, IL-10 levels and transferrin receptor (TfR) expression from uninfected and infected peritoneal macrophages. Chloroquine caused a significant decrease in the viable fungal recovery from all organs tested, during all periods of evaluation. Peritoneal macrophages from chloroquine-treated infected mice showed higher H(2)O(2) production and TfR expression, and decreased levels of NO, endogenous and stimulated-TNF-alpha, IL-6 and IL-10 during the three evaluated periods. However, despite its suppressor effects on the macrophage function, the chloroquine therapeutic effect upon murine paracoccidioidomycosis was probably due to its effect on iron metabolism, blocking iron uptake by cells, and consequently restricting iron to fungus growth and survival.

Chloroquine inhibits Paracoccidioides brasiliensis survival within human monocytes by limiting the availability of intracellular iron

The mechanisms used by Paracoccidioides brasiliensis(Pb 18) to survive into monocytes are not clear. Cellular iron metabolism is of critical importance to the growth of several intracellular pathogens, including P. brasiliensis, whose capacity to multiply in mononuclear phagocytes is dependent on the availability of intracellular iron. Chloroquine, by virtue of its basic properties, has been shown to prevent release of iron from holotransferrin by raising endocytic and lysosomal pH, and thereby interfering with normal iron metabolism. Then, in view of this, we have studied the effects of CHLOR on P. brasiliensis multiplication in human monocytes and its effect on the murine paracoccidioidomycosis. CHLOR induced human monocytes to kill P. brasiliensis. The effect of CHLOR was reversed by FeNTA, an iron compound that is soluble at neutral to alkaline pH, but not by holotransferrin, which releases iron only in an acidic environment. CHLOR treatment of Pb 18-infected BALB/c mice significantly reduced the viable fungi recovery from lungs, during three different periods of evaluation, in a dose-dependent manner. This study demonstrates that iron is of critical importance to the survival of P. brasiliensis yeasts within human monocytes and the CHLOR treatment in vitro induces Pb 18 yeast-killing by monocytes by restricting the availability of intracellular iron. Besides, the CHLOR treatment in vivo significantly reduces the number of organisms in the lungs of Pb-infected mice protecting them from several infections. Thus, CHLOR was effective in the treatment of murine paracoccidioidomycosis, suggesting the potential use of this drug in patients' treatment.

Insulin promotes the cell surface recruitment of the SAT2/ATA2 system A amino acid transporter from an endosomal compartment in skeletal muscle cells

SAT1-3 comprise members of the recently cloned family of System A transporters that mediate the sodium-coupled uptake of short chain neutral amino acids, and their activity is regulated extensively by stimuli such as insulin, growth factors, and amino acid availability. In skeletal muscle, insulin stimulates System A activity rapidly by a presently ill-defined mechanism. Here we demonstrate that insulin induces an increase in the plasma membrane abundance of SAT2 in a phosphatidylinositol 3-kinase-dependent manner and that this increase is derived from an endosomal compartment that is required for the hormonal activation of System A. Chloroquine, an acidotropic weak base that impairs endosomal recycling of membrane proteins, induced a complete inhibition in the insulin-mediated stimulation of System A, which was associated with a loss in SAT2 recruitment to the plasma membrane. The failure to stimulate System A and recruit SAT2 to the cell surface could not be attributed to a block in insulin signaling, as chloroquine had no effect on the insulin-mediated phosphorylation of protein kinase B or glycogen synthase kinase 3 or upon insulin-stimulated GLUT4 translocation and glucose transport. Our data indicate strongly that insulin increases System A transport in L6 cells by stimulating the exocytosis of SAT2 carriers from a chloroquine-sensitive endosomal compartment.

Cryptococcus neoformans resides in an acidic phagolysosome of human macrophages

Recently, we demonstrated that human monocyte-derived macrophages (MDM) treated with chloroquine or ammonium chloride had markedly increased antifungal activity against the AIDS-related pathogen Cryptococcus neoformans. Both of these agents raise the lysosomal pH, which suggested that the increased antifungal activity was a function of alkalinizing the phagolysosome. Moreover, there was an inverse correlation between growth of C. neoformans in cell-free media and pH. These data suggested that C. neoformans was well adapted to survive within acidic compartments. To test this hypothesis, we performed studies to determine the pH of human MDM and neutrophil phagosomes containing C. neoformans. Fungi were labeled with the isothiocyanate derivatives of two pH-sensitive probes: fluorescein and 2',7'-difluorofluorescein (Oregon Green). These probes have pKas of 6.4 and 4.7, respectively, allowing sensitive pH detection over a broad range. The phagosomal pH averaged approximately 5 after ingestion of either live or heat-killed fungi and remained relatively constant over time, which suggested that C. neoformans does not actively regulate the pH of its phagosome. The addition of 10 and 100 microM chloroquine resulted in increases in the phagosomal pH from a baseline of 5.1 up to 6.5 and 7.3, respectively. Finally, by immunofluorescence, colocalization of C. neoformans and the MDM lysosomal membrane protein LAMP-1 was demonstrated, establishing that fusion of C. neoformans-laden phagosomes with lysosomal compartments takes place. Thus, unlike many other intracellular pathogens, C. neoformans does not avoid fusion with macrophage lysosomal compartments but rather resides and survives in an acidic phagolysosome.

Lysosomotropic agents ameliorate macrophage dysfunction following the phagocytosis of IgG-coated erythrocytes: a role for lipid peroxidation

Phagocytosis of IgG-coated erythrocytes (EIgG) can depress several macrophage functions. Our previous studies have suggested that this macrophage dysfunction may be due to an oxidative stress caused by the interaction of hemoglobin-derived iron with superoxide and/or hydrogen peroxide. Since lysosomotropic agents are capable of altering iron handling by macrophages, the present study evaluated the ability of these agents to prevent the macrophage dysfunction and lipid peroxidation caused by a phagocytic challenge with EIgG. Elicited rat peritoneal macrophages showed a depression of PMA-stimulated hydrogen peroxide production, calcium ionophore-stimulated arachidonate release and Fc receptor-mediated phagocytosis. The lysosomotropic agents; chloroquine, quinacrine, ammonium chloride and methylamine all prevented the depression of hydrogen peroxide production and arachidonate release but did not alter the depression of phagocytic function. These agents also prevented the increase in lipid peroxidation products caused by a phagocytic challenge with EIgG. These results suggest that the ability of lysosomotropic agents to prevent some aspects of macrophage dysfunction after a phagocytic challenge may be due to their ability to block the oxidative stress caused by the challenge.

Chloroquine induces human mononuclear phagocytes to inhibit and kill Cryptococcus neoformans by a mechanism independent of iron deprivation

Infections due to Cryptococcus neoformans are common in AIDS patients. We investigated the effect of chloroquine, which raises the pH of phagolysosomes, on the anticryptococcal activity of mononuclear phagocytes. C. neoformans multiplied within monocyte-derived macrophages (MDM) in the absence of chloroquine but were killed with the addition of chloroquine. Ammonium chloride was also beneficial, suggesting that effects were mediated by alkalinizing the phagolysosome. Chloroquine inhibits growth of other intracellular pathogens by limiting iron availability. However, chloroquine-induced augmentation of MDM anticryptococcal activity was unaffected by iron nitriloacetate, demonstrating that chloroquine worked by a mechanism independent of iron deprivation. There was an inverse correlation between growth of C. neoformans in cell-free media and pH, suggesting that some of the effect of chloroquine on the anticryptococcal activity of MDM could be explained by relatively poor growth at higher pH. Chloroquine enhanced MDM anticryptococcal activity against all tested cryptococcal strains except for one large-capsule strain which was not phagocytosed. Positive effects of chloroquine were also seen in monocytes from both HIV-infected and -uninfected donors. Finally, chloroquine was therapeutic in experimental cryptococcosis in outbred and severe combined immunodeficient mice. Thus, chloroquine enhances the activity of mononuclear phagocytes against C. neoformans by iron-independent, pH-dependent mechanisms and is therapeutic in murine models of cryptococcosis. Chloroquine might have clinical utility for the prophylaxis and treatment of human cryptococcosis.

Iron-loading of cultured adult rat hepatocytes reversibly enhances lactoferrin binding and endocytosis

Isolated rat hepatocytes bind and internalize bovine lactoferrin (Lf) protein and Lf-bound Fe3+ via Ca2+-dependent recycling Lf binding sites (McAbee, 1995, Biochem. J., 311:603-609). In this study, we determined if iron loading of primary cultures of adult rat hepatocytes altered their ability to bind and internalize Lf. Rat hepatocytes were cultured 16-24 h with or without ferric ammonium citrate (FAC) and then assayed for Ca2+-dependent 125I-Lf binding at 4 degrees C or 125I-Lf endocytosis at 37 degrees C. Cells pretreated with FAC (5 microg/mL) internalized two- to sixfold more 125I-Lf than did control cells. The FAC-induced increase in 125I-Lf endocytosis required 4-8 h of culture at 37 degrees C and was fully reversible if cells were incubated an additional 24 h without FAC either in the presence or absence of the Fe3+ chelator desferrioxamine. Maximal endocytic rates for untreated and FAC-treated cells were 370 and 2,300 molecules 125I-Lf cell(-1) sec(-1), respectively. Both 125I-Lf binding at 4 degrees C and endocytosis at 37 degrees C increased up to sixfold between 0.3 10 microg/mL FAC, indicating that iron-induced enhancement of 125I-Lf uptake was due to an increase in the number of Lf receptors present on the cells. 125I-Lf bound to untreated and FAC-treated cells at 4 degrees C with similar affinities (K(d) approximately 1.5 microM). Cycloheximide but not actinomycin D blocked the FAC-induced increase in 125I-Lf binding, indicating that the increase in the number of Lf binding sites required translation but not transcription. Notably, iron loading blocked endocytosis of asialoorosomucoid by hepatocytes by up to 80%, reducing the number of active intracellular asialoglycoprotein receptors >65% without altering the number of active cell surface receptors. We conclude from these studies that Lf receptor activity on hepatocytes is regulated posttranscriptionally by the iron status of the cells.

The ferritins: molecular properties, iron storage function and cellular regulation

The iron storage protein, ferritin, plays a key role in iron metabolism. Its ability to sequester the element gives ferritin the dual functions of iron detoxification and iron reserve. The importance of these functions is emphasised by ferritin's ubiquitous distribution among living species. Ferritin's three-dimensional structure is highly conserved. All ferritins have 24 protein subunits arranged in 432 symmetry to give a hollow shell with an 80 A diameter cavity capable of storing up to 4500 Fe(III) atoms as an inorganic complex. Subunits are folded as 4-helix bundles each having a fifth short helix at roughly 60 degrees to the bundle axis. Structural features of ferritins from humans, horse, bullfrog and bacteria are described: all have essentially the same architecture in spite of large variations in primary structure (amino acid sequence identities can be as low as 14%) and the presence in some bacterial ferritins of haem groups. Ferritin molecules isolated from vertebrates are composed of two types of subunit (H and L), whereas those from plants and bacteria contain only H-type chains, where 'H-type' is associated with the presence of centres catalysing the oxidation of two Fe(II) atoms. The similarity between the dinuclear iron centres of ferritin H-chains and those of ribonucleotide reductase and other proteins suggests a possible wider evolutionary linkage. A great deal of research effort is now concentrated on two aspects of ferritin: its functional mechanisms and its regulation. These form the major part of the review. Steps in iron storage within ferritin molecules consist of Fe(II) oxidation, Fe(III) migration and the nucleation and growth of the iron core mineral. H-chains are important for Fe(II) oxidation and L-chains assist in core formation. Iron mobilisation, relevant to ferritin's role as iron reserve, is also discussed. Translational regulation of mammalian ferritin synthesis in response to iron and the apparent links between iron and citrate metabolism through a single molecule with dual function are described. The molecule, when binding a [4Fe-4S] cluster, is a functioning (cytoplasmic) aconitase. When cellular iron is low, loss of the [4Fe-4S] cluster allows the molecule to bind to the 5'-untranslated region (5'-UTR) of the ferritin m-RNA and thus to repress translation. In this form it is known as the iron regulatory protein (IRP) and the stem-loop RNA structure to which it binds is the iron regulatory element (IRE). IREs are found in the 3'-UTR of the transferrin receptor and in the 5'-UTR of erythroid aminolaevulinic acid synthase, enabling tight co-ordination between cellular iron uptake and the synthesis of ferritin and haem. Degradation of ferritin could potentially lead to an increase in toxicity due to uncontrolled release of iron. Degradation within membrane-encapsulated "secondary lysosomes' may avoid this problem and this seems to be the origin of another form of storage iron known as haemosiderin. However, in certain pathological states, massive deposits of "haemosiderin' are found which do not arise directly from ferritin breakdown. Understanding the numerous inter-relationships between the various intracellular iron complexes presents a major challenge.

Inhibition of growth of Histoplasma capsulatum yeast cells in human macrophages by the iron chelator VUF 8514 and comparison of VUF 8514 with deferoxamine

Histoplasma capsulatum requires intracellular iron to survive and multiply within human and murine macrophages (M phi). Thus, iron chelators may be useful compounds in the treatment of histoplasmosis. In the present study we compared the efficacies of five different iron chelators with deferoxamine (DEF) for their capacity to inhibit the growth of H. capsulatum yeast cells in culture medium and within human M phi. Of the agents tested, only one, VUF 8514, a 2,2'-bipyridyl analog, was found to be effective. VUF 8514 inhibited the growth of yeast cells in tissue culture medium and within M phi in a dose-response fashion. In tissue culture medium, the 50% effective dose (ED50) of VUF 8514 was 30 nM and the ED50 of DEF was 1 mM. In human M phi, the ED50 of VUF 8514 was 520 nM and the ED50 of DEF was 4 mM. Thus, VUF 8514 was effective at a concentration 7.7 x 10(3)-fold lower than DEF in inhibiting the growth of yeast cells in M phi. Inhibition of the intracellular growth of yeast cells by VUF 8514 was reversed by holotransferrin and iron nitriloacetate, an iron compound that is soluble at neutral to alkaline pH. Thus, VUF 8514 inhibits the intracellular growth of yeast cells by acting as an iron chelator rather than through its capacity as a weak base. These data suggest that the hydroxamic acid siderophore of H. capsulatum yeast cells competes successfully for iron against some iron chelators but not others and that VUF 8514 may be a potential therapeutic agent for the treatment of histoplasmosis.

Chloroquine induces human macrophage killing of Histoplasma capsulatum by limiting the availability of intracellular iron and is therapeutic in a murine model of histoplasmosis

We investigated the role of intracellular iron on the capacity of Histoplasma capsulatum (Hc) yeasts to multiply within human macrophages (Mphi). Coculture of Hc-infected Mphi with the iron chelator deferoxamine suppressed the growth of yeasts in a concentration-dependent manner. The effect of deferoxamine was reversed by iron-saturated transferrin (holotransferrin) but not by iron-free transferrin (apotransferrin). Chloroquine, which prevents release of iron from transferrin by raising endocytic and lysosomal pH, induced human Mphi to kill Hc. The effect of chloroquine was reversed by iron nitriloacetate, an iron compound that is soluble at neutral to alkaline pH, but not by holotransferrin, which releases iron only in an acidic environment. Chloroquine (40-120 mg/kg) given intraperitoneally for 6 d to Hc-infected C57BL/6 mice significantly reduced the growth of Hc in a dose-dependent manner. At 120 mg/kg there was a 17- and 15-fold reduction (P < 0.01) in CFU in spleens and livers, respectively. The therapeutic effect of chloroquine also correlated with the length of treatment. As little as 2 d of chloroquine therapy (120 mg/kg), when started at day 5 after infection, reduced CFU in the spleen by 50%. Treatment with chloroquine for 10 d after a lethal inoculum of Hc protected six of nine mice; all control mice were dead by day 11 (P = 0.009). This study demonstrates that: (a) iron is of critical importance to the survival and multiplication of Hc yeasts in human Mphi; (b) in vitro, chloroquine induces Mphi killing of Hc yeasts by restricting the availability of intracellular iron; and (c) in vivo, chloroquine significantly reduces the number of organisms in the spleens and livers of Hc-infected mice and can protect mice from a lethal inoculum of Hc yeasts. Thus, chloroquine may be effective in the treatment of active histoplasmosis and also may be useful in preventing relapse of histoplasmosis in patients with acquired immunodeficiency syndromes.

Evaluation of iron binding and peroxide-mediated toxicity in rat hepatocytes

A novel assay was developed to determine subnanomolar amounts of Fenton-reactive iron (FRI) in biological tissues. FRI represents that pool of iron that is redox active and capable of participating in a model Fenton reaction. The FRI was used to identify a kinetically-defined cellular iron binding site. This site displays positive cooperativity, with apparent kinetic constants of Kd = 10.6 microM, Bmax = 20.7 nmol/mg protein, and the Hill coefficient = 1.4. After addition of exogenous ferrous ammonium sulfate to hepatocytes, binding occurred within a few seconds and was stable for at least an hour. Free extracellular iron, but not bound iron, stimulated lipid peroxidation in hepatocytes. In contrast, bound but not free iron produced a concentration-dependent increase in tert-butyl hydroperoxide (TBH)-mediated toxicity, suggesting the toxicological relevance of bound, rather than free iron. Furthermore, the hydroxyl radical scavengers mannitol and 2-deoxyribose inhibited Fe2/TBH-mediated lipid peroxidation, but not cell killing, suggesting that hydroxyl radical may not be involved in the critical toxic event. The divalent cations Mn2+ and Co2+ inhibited iron-mediated hepatocyte killing in the presence of TBH, but only if added prior to Fe2+. Mn2+, but not Co2+, inhibited Fe(2+)-mediated lipid peroxidation regardless of the order of addition. These results indicate the existence of a specific, kinetically-defined cellular iron binding site. Such binding is involved in peroxide-mediated toxicity, but independent of lipid peroxidation. The specific nature of this site and involvement with other forms of chemical intoxication or cellular iron homeostasis are unknown.

Functional roles of the ferritin receptors of human liver, hepatoma, lymphoid and erythroid cells

Ferritin receptors are present on the membranes of many normal and malignant cells. The binding specificity of these receptors for H and L subunits was examined using recombinant human ferritin homopolymers. At least two different types of ferritin receptors were found, one derived from normal rat, pig, and human liver which shows similar binding of H- and L-ferritin. The second receptor type, specific for the H-chain ferritin, has been identified on membranes of hepatic and other transformed cells, and of normal lymphoblasts and erythroid precursors. These two receptor types may have different metabolic functions: the hepatic receptor acting as a scavenger for circulating ferritin and possibly for iron exchange between hepatocytes and macrophages; the H-ferritin receptor having a regulatory role which is not directly related to iron metabolism. The expression of the H-ferritin receptor is closely related to the activation and proliferation state of the cells. Addition of H-ferritin to the culture medium of cells expressing the H-ferritin receptor resulted in inhibition of cell proliferation and of colony formation.

Increase in glycosylated and nonglycosylated serum ferritin in chronic alcoholism and their evolution during alcohol withdrawal

Increase in serum ferritin, which occurs in 40 to 70% of chronic alcoholics, remains poorly understood. We tested the hypothesis which links hyperferritinemia in chronic alcoholism not only to ferritin release from damaged liver cells, but also to increased ferritin secretion. Fifty-eight chronic alcoholic patients hospitalized for alcohol withdrawal were subdivided into three groups according to liver damage. Their serum levels of ferritin and ferritin bound to concanavalin A (ferritin Con A, which represents glycosylated, i.e., secreted ferritin) were measured serially on days 1, 7, and 11 of withdrawal and compared with a control group. The results were: (1) Total serum ferritin increased in alcoholics. Both free and Con A ferritins increased in equal proportions, the ferritin Con A to total ferritin ratio remaining unchanged. The increase was dependent on liver disease, as both free and Con A ferritins increased significantly with the severity of liver illness. Serum ferritin levels were related to iron status: it correlated with hepatic iron concentration (obtained in 19 patients); however, high ferritin values were not related to the degree of iron overload, which remained low. Finally, there was no correlation between serum ferritin and the average of alcohol consumption. (2) Both free and Con A ferritin decreased by about 40% during alcohol withdrawal. In conclusion, we have demonstrated that (1) total serum ferritin is increased in chronic alcoholism and (2) that this ferritin increase is due in part to an increase in ferritin Con A, proof of the induction of ferritin secretion by alcohol in humans.

Chloroquine inhibits the intracellular multiplication of Legionella pneumophila by limiting the availability of iron. A potential new mechanism for the therapeutic effect of chloroquine against intracellular pathogens

Chloroquine and ammonium chloride, by virtue of their basic properties, have been shown to raise endocytic and lysosomal pH and thereby interfere with normal iron metabolism in a variety of cell types, including mononuclear phagocytes. Cellular iron metabolism is of critical importance to Legionella pneumophila, an intracellular bacterial pathogen whose capacity to multiply in human mononuclear phagocytes is dependent upon the availability of intracellular iron. In view of this, we have studied the effects of chloroquine and ammonium chloride on L. pneumophila intracellular multiplication in human monocytes. Chloroquine, at a concentration of 20 microM, and ammonium chloride, at a concentration of 20 mM, inhibited L. pneumophila intracellular multiplication by 1.4 +/- 0.2 (SEM) logs and 1.5 +/- 0.2 logs, respectively. Chloroquine- and ammonium chloride-induced inhibition of L. pneumophila intracellular multiplication was completely reversed by iron nitrilotriacetate, an iron compound which is soluble in the neutral to alkaline pH range, but not by iron transferrin, which depends upon acidic intracellular conditions to release iron. Chloroquine had no major direct effect on L. pneumophila multiplication in artificial media except at extremely high concentrations (15,000-fold that which inhibited L. pneumophila multiplication in mononuclear phagocytes), and inhibition at such concentrations was not reversed by iron nitrilotriacetate. This study demonstrates that chloroquine and ammonium chloride inhibit the intracellular multiplication of L. pneumophila by limiting the availability of iron to the bacterium. It is possible that such a mechanism of action underlies chloroquine's antimicrobial effect against other intracellular pathogens, such as the agents of malaria and tuberculosis.