Lack of TdT and Immunoglobulin and T-Cell Receptor Gene Rearrangements in Hodgkin's Disease

To study the pathogenesis of Hodgkin's disease (HD), which today remains obscure, we have undertaken a combined experimental approach: determination of TdT and molecular analysis of rearrangements of immunoglobulin heavy chain (IgH), T-cell receptor (TCR) beta chain and the T-cell rearranging gamma (TRG) genes. TdT determination indicate would the presence of immature cells that are not detected in the normal lymphnode; molecular analysis of the rearrangements of these genes would reveal the presence of even a small monoclonal population of both T and B lineages in the lymphnodes. We believe that the combination of these two types of analysis can indicate whether an expanding lymphoid clone is responsible for this disease. TdT determination was negative in all 41 cases tested. Gene rearrangements were studied in 10 cases for IgH and TCR beta genes and in 5 cases for the TRG gene. No abnormal band beside the germ-line ones was detected in any of our cases, ruling out the presence of a minor neoplastic population. We can explain these results in at least three ways: first, the neoplastic population could represent less than 1% of the total, thus escaping detection by current techniques; second, the neoplastic population is not lymphoid in nature or is composed of mature cells that do not rearrange Ig and TCR genes and therefore belongs to a true non-B, non-T lineage; third, the pathogenesis of HD is completely different from that of non-Hodgkin's lymphomas (NHL) and does not involve the clonal expansion of a cell frozen at a particular maturative stage as is thought to happen in most NHL.

Constitutive and Induced Synthesis of Heat Shock Proteins in Transplantable Hepatomas

The synthesis of heat shock proteins (HSP) was studied in rat liver and in a series of transplantable Morris hepatomas with different growth rates, subjected to heat shock in vivo and in vitro. Different from the liver, hepatomas synthesized HSP constitutively, i.e., also before exposure to heat. This constitutive synthesis was low and limited to one HSP in the slowest-growing tumor, more marked and involving other HSP in the intermediate- and fast-growing hepatomas. In tumor that synthesized HSP constitutively, the induction of HSP in response to heat was proportionately reduced. These patterns of reaction were essentially similar in vivo ad in vitro. The amount of HSP 68 was well correlated to the levels of its mRNA in liver and in all hepatomas, whereas the increase in HSP 89 was accompanied by a corresponding increase in the related mRNA in liver and in slow-growing hepatoma, not in the other tumors, thus suggesting a different mechanism of control of HSP 89 synthesis in the more malignant hepatomas.

Interaction of Heat with Chemotherapy in Vitro: Effect on Cell Viability and Protein Synthesis in Human and Murine Cell Lines

Cell survival in response to doxorubicin (Dx) and cis-diammine-dichloroplatinum (cis-Pt) administration, either alone or combined with hyperthermic treatment, was analyzed in human osteosarcoma (U-2-OS), murine melanoma (B16V) and murine leukemia (P388) cell lines and in Dx-resistant sublines derived from B16V and P388. In all cell lines tested there was an enhancement of drug toxicity by hyperthermia. In U-2-OS, the increase was more pronounced for cis-Pt than for Dx. In B16V and in P388, the increase in Dx toxicity was of the same degree in Dx-senstitive and Dx-resistant sublines, whereas heat-induced sensitization to cis-Pt was higher in Dx-resistant sublines than in their Dx-sensitive counterpart. Analysis of the protein pattern in the various cell lines showed that the synthesis of heat-shock proteins induced by heat was not influenced by the combined use of drugs and heat. Moreover, in spite of some differences in the overall protein pattern, no significant differences in the basal levels of heat-shock protein synthesis or in the extent of its induction after heat shock were observed between murine cell lines relatively sensitive to Dx and their corresponding selected resistant cells.

Abstract P4-13-15: Dose intensity and efficacy of the combination of everolimus and exemestane (EVE/EXE) in a real world population of hormone receptor positive advanced breast cancer: A multicenter Italian experience

BACKGROUND: Everolimus, an mTOR inhibitor, in combination with exemestane is approved for hormone receptor (HR) positive advanced breast cancer (ABC), after failure of treatment with non-steroidal aromatase inhibitor (NSAI). We assessed the toxicity of the combination and the correlation between dose intensity and response to therapy, in a real world population of ABC from 11 Italian centers. Moreover, we evaluated OS of the whole population, RR and PFS according to line of treatment (from 1rd to 3th and from 4th on).

METHODS: 154 pts were treated with combination of everolimus 10 mg and exemestane 25 mg daily from 05/2011 today. Median age was 62 (47-82). Median time to metastatic disease was 49 months (0-269). Median number of metastatic sites was 2 (55.2% of pts visceral versus 44.8% non visceral disease). N=117 (75.9%) pretreated with HT as adjuvant; N=126 pts (81.8%) treated with HT for advanced disease prior to EVE/EXE, with a median of one line (0-5). N=102 pts (66.2%) treated with chemotherapy for metastatic disease, with a median of one line (0-6) before everolimus treatment.

RESULTS: Sixteen pts received EVE/EXE as 1st line (10.4%), 39 as 2nd (25.3%), 37 as 3rd (24%), 62 as 4th or more (40,3%). Response was evaluable in 127 out of 154 pts; CR/PR/SD respectively 5/27/56 pts. RR according to line (from 1st to 3rd vs ≥ 4th) was respectively 22.8% vs 26.4% (p=0,864). The median PFS for all population (150 pts) was 38 weeks (95% CI: 33-42). The PFS according to line (1st- 3rd vs ≥ 4th) was 38 wks in both subgroups, p=0.73. OS (126/154 pts) was 28 mths (95% CI: 31-38). The most frequent adverse events were collected in the table.

Adverse eventsOverall %Grade 3-4 %Stomatitis55.810.4Hypercholesterolemia47.40.0Asthenia42.95.2Hyperglycemia36.45.8Hypertriglyceridemia29.20.6Anemia28.63.9Peripheral edema24.71.3Rash23.40.6Increased ALT/AST/GGT21.46.5Thrombocytopenia19.53.9Diarrhea18.81.9Weight loss18.21.3Dysgeusia17.50.6Pneumonitis15.61.9Cutaneous toxicity14.90.6Infection14.33.2Neutropenia11.71.9Nausea11.70.0Anorexia (without stomatitis)10.41.3Electrolyte alterations9.71.3Urea/creatinine increase6.51.3Vomiting6.50.0Uric acid increase4.50.0

Median duration of treatment with everolimus 10 mg and 5 mg was respectively 180 (9-854) and 129 days (3-738). Fifty-eight pts (37,6%) never stopped treatment with everolimus 10 mg; 16 pts (10,4%) definitively stopped everolimus for toxicity; 80 pts (52,0%) temporarily interrupted the treatment, resuming at dose level 10 mg (31 pts) or reducing at 5 mg (49 pts). Main reason for discontinuation/interruption was stomatitis G2-G3. RR and PFS evaluated according to dose intensity, 10 mg vs 5 mg, were respectively 25.9% vs 30% p=0.779, 38 wks (27-44) vs 40 wks (31-48) P=0.614

CONCLUSIONS: efficacy in terms of RR and PFS of the combination EVE/EXE is not related to dose intensity (10 mg vs 5 mg), the discontinuation of the treatment is high with the starting dose of 10 mg, the toxicity is consistent with previous phase II-III studies although we collected some different toxicities.

Citation Format: Forcignanò R, Petrucelli L, Cazzaniga ME, Lupo LI, Chiuri VE, Cairo G, De Matteis E, Febbraro A, Giordano G, Campidoglio S, Fabi A, Giampaglia M, Bilancia D, La Verde N, Maiello E, Morritti M, Giotta F, Lorusso V, Scavelli C, Romito S, Cusmai A, Palmiotti G, Tornesello A, Ciccarese M. Dose intensity and efficacy of the combination of everolimus and exemestane (EVE/EXE) in a real world population of hormone receptor positive advanced breast cancer: A multicenter Italian experience. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P4-13-15.

Abstract P6-10-01: Evaluation of post-progression survival (PPS) in advanced breast cancer (ABC) according to treatment line: Correlation with PFS and OS in an unselected population

Background: MBC remains an incurable disease with a median survival of 2-3 years despite the use of new drugs. The validation of PPS as surrogate endpoint and its correlation to PFS and OS is matter of debate.

Methods: From 2006-2012 we analyzed retrospectively consecutive 192 pts treated for MBC outside of clinical trials, 103 with at least 3 lines CT, in order to evaluate post-progression survival (PPS) according to treatment line and its relation to PFS and OS. Moreover we evaluated the gain of benefit after CT3 and predictive factors of response to multiple lines of therapy.

Results: Median age at M+ diagnosis was 59 years (30-89), median site of disease was 2 (1-6), 67% visceral, HER-2 + pts 32%, median number of anti-Her-2 treatment was 2 (0-6); median number of treatment was 3 (1-8). Median OS for all pts was 45.6 (95% CI: 36.5-54.7). Median OS for CT > = 3 vs CT < 3 was respectively 52.5 (95% CI: 43.3-61.7) and 32.3 (95% CI: 23.6-41.2) P = 0.007. Multivariate Cox analysis showed that OS is related with ER/Pgr status (positive versus negative p<0.0001) number of lines (>3 vs ≤3) p = 0.001 and number of metastatic sites (>2 vs ≤2) p<0.0001. We evaluated the relation between PFS and OS and between PPS and OS until the 6th line of therapy with a linear regression model.

 Median PFS (95% c.i.)Median PPS (95% c.i.)Median OS from M+ diagnosisCorrelation OS-PPSCorrelation OS-PFS1st line11.0 (9.5-12.5)29.9 (18.2-41.6)Not reachedP<0.0001 OS-PPS1P<0.0001 OS-PFS12nd line7.0 (5.8-8.2)20.9 (11.7-30.0)29.1 (17.5-40.7)P<0.0001 OS-PPS2P<0.0001 OS-PFS23rd line5.6 (4.5-6.7)19.5 (14.9-24.1)41.9 (15.5-68.2)P<0.0001 OS-PPS3P<0.0001 OS-PFS34th line5.7 (4.0-7.4)15.3 (13.4-17.2)50.4 (27.4-73.4)P<0.0001 OS-PPS4P<0.0001 OS-PFS45th line3.9 (3.1-4.7)11.2 (7.8-14.5)65.9 (20.8-112.2)P = 0.004 OS-PPS5P<0.0001 OS-PFS56th line3.3 (2.6-4.0)8.2 (2.2-14.2)56.8 (48.7-64.9)P = 0.36 OS- PPS6P = 0.002 OS-PFS6

Conclusion: These results supported the use of chemotherapy after CT3. PFS and PPS are related to OS until the 6th line of treatment. The utility of PPS as surrogate endpoint of OS is a valid hypothesis that could be evaluated in prospective trials of MBC.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P6-10-01.

A precious metal: Iron, an essential nutrient for all cells

Iron is an important cofactor required for a number of essential cell functions and hence is a vital nutrient. However, iron can also be dangerous as a catalyst of free radical reactions. Accordingly, intracellular iron homeostasis and body iron balance are tightly regulated. In this review, we presented an overview of the remarkable new insights that over the last years have been gained into the multifaceted and sophisticated molecular mechanisms controlling iron acquisition, storage and release. We also reviewed the data about nutrition-related abnormalities of iron metabolism, such as iron overload and deficiency. Finally, we discussed how pathogenic microorganisms and host cells compete for iron, a battle whose outcome has a relevant role in infectious disease.

Role of hypoxia-inducible factors in the dexrazoxane-mediated protection of cardiomyocytes from doxorubicin-induced toxicity

BACKGROUND AND PURPOSE

Iron aggravates the cardiotoxicity of doxorubicin, a widely used anticancer anthracycline, and the iron chelator dexrazoxane is the only agent protecting against doxorubicin cardiotoxicity; however, the mechanisms underlying the role of iron in doxorubicin-mediated cardiotoxicity and the protective role of dexrazoxane remain to be established. As iron is required for the degradation of hypoxia-inducible factors (HIF), which control the expression of antiapoptotic and protective genes, we tested the hypothesis that dexrazoxane-dependent HIF activation may mediate the cardioprotective effect of dexrazoxane.

EXPERIMENTAL APPROACH

Cell death, protein levels (by immunoblotting) and HIF-mediated transcription (using reporter constructs) were evaluated in the rat H9c2 cardiomyocyte cell line exposed to low doses of doxorubicin with or without dexrazoxane pretreatment. HIF levels were genetically manipulated by transfecting dominant-negative mutants or short hairpin RNA.

KEY RESULTS

Treatment with dexrazoxane induced HIF-1α and HIF-2α protein levels and transactivation capacity in H9c2 cells. It also prevented the induction of cell death and apoptosis by exposure of H9c2 cells to clinically relevant concentrations of doxorubicin. Suppression of HIF activity strongly reduced the protective effect of dexrazoxane. Conversely, HIF-1α overexpression protected against doxorubicin-mediated cell death and apoptosis also in cells not exposed to the chelator. Exposure to dexrazoxane increased the expression of the HIF-regulated, antiapoptotic proteins survivin, Mcl1 and haem oxygenase.

CONCLUSIONS AND IMPLICATIONS

Our results showing HIF-dependent prevention of doxorubicin toxicity in dexrazoxane-treated H9c2 cardiomyocytes suggest that HIF activation may be a mechanism contributing to the protective effect of dexrazoxane against anthracycline cardiotoxicity.

Doxorubicin irreversibly inactivates iron regulatory proteins 1 and 2 in cardiomyocytes: evidence for distinct metabolic pathways and implications for iron-mediated cardiotoxicity of antitumor therapy

Changes in iron homeostasis have been implicated in cardiotoxicity induced by the anticancer anthracycline doxorubicin (DOX). Certain products of DOX metabolism, like the secondary alcohol doxorubicinol (DOXol) or reactive oxygen species (ROS), may contribute to cardiotoxicity by inactivating iron regulatory proteins (IRP) that modulate the fate of mRNAs for transferrin receptor and ferritin. It is important to know whether DOXol and ROS act by independent or combined mechanisms. Therefore, we monitored IRP activities in H9c2 rat embryo cardiomyocytes exposed to DOX or to analogues which were selected to achieve a higher formation of secondary alcohol metabolite (daunorubicin), a concomitant increase of alcohol metabolite and decrease of ROS (5-iminodaunorubicin), or a defective conversion to alcohol metabolite (mitoxantrone). On the basis of such multiple comparisons, we characterized that DOXol was able to remove iron from the catalytic Fe-S cluster of cytoplasmic aconitase, making this enzyme switch to the cluster-free IRP-1. ROS were not involved in this step, but they converted the IRP-1 produced by DOXol into a null protein which did not bind to mRNA, nor was it able to switch back to aconitase. DOX was also shown to inactivate IRP-2, which does not assemble or disassemble a Fe-S cluster. Comparisons between DOX and the analogues revealed that IRP-2 was inactivated only by ROS. Thus, DOX can inactivate both IRP through a sequential action of DOXol and ROS on IRP-1 or an independent action of ROS on IRP-2. This information serves guidelines for designing anthracyclines that spare iron homeostasis and induce less severe cardiotoxicity.

Reduced serum ceruloplasmin levels in hereditary haemochromatosis

As ceruloplasmin (Cp) seems to be involved in iron mobilization, serum Cp levels were measured in 35 patients with hereditary haemochromatosis (HH), 12 with acquired iron overload (AIO) and 36 healthy subjects. Cp was lower in HH patients than in controls (P < 0.001); no difference was found between untreated HH patients and those on a phlebotomy programme (P = 0.07) and between the HH patients carrying the normal and the mutated alleles of the HFE gene (P = 0.8). Cp levels in AIO subjects were significantly higher than in HH patients (P < 0.004) and similar to those of controls (P = 0.2). No differences in albumin, alpha1 acid glycoprotein and copper serum levels were observed in the three groups.

Macrophage preconditioning with synthetic malaria pigment reduces cytokine production via heme iron-dependent oxidative stress

Hemozoin (malaria pigment), a polymer of hematin (ferri-protoporphyrin IX) derived from hemoglobin ingested by intraerythrocytic plasmodia, modulates cytokine production by phagocytes. Mouse peritoneal macrophages (PM) fed with synthetic beta-hematin (BH), structurally identical to native hemozoin, no longer produce tumor necrosis factor alpha (TNFalpha) and nitric oxide (NO) in response to lipopolysaccharide (LPS). Impairment of NO synthesis is due to inhibition of inducible nitric oxide synthase (iNOS) production. BH-mediated inhibition of PM functions cannot be ascribed to iron release from BH because neither prevention by iron chelators nor down-regulation of iron-regulatory protein activity was detected. Inhibition appears to be related to pigment-induced oxidative stress because (a) thiol compounds partially restored PM functions, (b) heme oxygenase (HO-1) and catalase mRNA levels were up-regulated, and (c) free radicals production increased in BH-treated cells. The antioxidant defenses of the cells determine the response to BH: microglia cells, which show a lower extent of induction of HO-1 and catalase mRNAs and lower accumulation of oxygen radicals, are less sensitive to the inhibitory effect of BH on cytokine production. Results indicate that BH is resistant to degradation by HO-1 and that heme-iron mediated oxidative stress may contribute to malaria-induced immunosuppression. This study may help correlate the different clinical manifestations of malaria, ranging from uncomplicated to severe disease, with dysregulation of phagocyte functions and promote better therapeutic strategies to counteract the effects of hemozoin accumulation.

Iron regulatory proteins in pathobiology

The capacity of readily exchanging electrons makes iron not only essential for fundamental cell functions, but also a potential catalyst for chemical reactions involving free-radical formation and subsequent oxidative stress and cell damage. Cellular iron levels are therefore carefully regulated in order to maintain an adequate substrate while also minimizing the pool of potentially toxic 'free iron'. Iron homoeostasis is controlled through several genes, an increasing number of which have been found to contain non-coding sequences [i.e. the iron-responsive elements (IREs)] which are recognized at the mRNA level by two cytoplasmic iron-regulatory proteins (IRP-1 and IRP-2). The IRPs belong to the aconitase superfamily. By means of an Fe-S-cluster-dependent switch, IRP-1 can function as an mRNA-binding protein or as an enzyme that converts citrate into isocitrate. Although structurally and functionally similar to IRP-1, IRP-2 does not seem to assemble a cluster nor to possess aconitase activity; moreover, it has a distinct pattern of tissue expression and is modulated by means of proteasome-mediated degradation. In response to fluctuations in the level of the 'labile iron pool', IRPs act as key regulators of cellular iron homoeostasis as a result of the translational control of the expression of a number of iron metabolism-related genes. Conversely, various agents and conditions may affect IRP activity, thereby modulating iron and oxygen radical levels in different pathobiological settings. As the number of mRNAs regulated through IRE-IRP interactions keeps growing, the definition of IRPs as iron-regulatory proteins may in the near future become limiting as their role expands to other essential metabolic pathways.

HIF-1-mediated activation of transferrin receptor gene transcription by iron chelation

Treatment with iron chelators mimics hypoxic induction of the hypoxia inducible factor (HIF-1) which activates transcription by binding to hypoxia responsive elements (HRE). We investigated whether HIF-1 is involved in transcriptional activation of the transferrin receptor (TfR), a membrane protein which mediates cellular iron uptake, in response to iron deprivation. The transcription rate of the TfR gene in isolated nuclei was up-regulated by treatment of Hep3B human hepatoma cells with the iron chelator desferrioxamine (DFO). The role of HIF-1 in the activation of TfR was indicated by the following observations: (i) DFO-dependent activation of a luciferase reporter gene in transfected Hep3B cells was mediated by a fragment of the human TfR promoter containing a putative HRE sequence; (ii) mutation of this sequence prevented stimulation of luciferase activity; (iii) binding to this sequence of HIF-1alpha, identified by competition experiments and supershift assays, was induced by DFO. Furthermore, in mouse hepatoma cells unable to assemble functional HIF-1, inducibility of TfR transcription by DFO was lost and TfR mRNA up-regulation was reduced. These results, which show the role of HIF-1 in the control of TfR gene expression in conditions of iron depletion, give insights into the mechanisms of transcriptional regulation which concur with the well-characterized post-transcriptional control of TfR expression to expand the extent of response to iron deficiency.

Transferrin receptor induction by hypoxia. HIF-1-mediated transcriptional activation and cell-specific post-transcriptional regulation

The tight relationship between oxygen and iron prompted us to investigate whether the expression of transferrin receptor (TfR), which mediates cellular iron uptake, is regulated by hypoxia. In Hep3B human hepatoma cells incubated in 1% O(2) or treated with CoCl(2), which mimics hypoxia, we detected a 3-fold increase of TfR mRNA despite a decrease of iron regulatory proteins activity. Increased expression resulted from a 4-fold stimulation of the nuclear transcription rate of the TfR gene by both hypoxia and CoCl(2). A role for hypoxia-inducible factor (HIF-1), which activates transcription by binding to hypoxia-responsive elements in the activation of TfR, stems from the following observations. (a) Hypoxia and CoCl(2)-dependent expression of luciferase reporter gene in transiently transfected Hep3B cells was mediated by a fragment of the human TfR promoter containing a putative hypoxia-responsive element sequence, (b) mutation of this sequence prevented hypoxic stimulation of luciferase activity, (c) binding to this sequence of HIF-1alpha, identified by competition experiments and supershift assays, was induced in Hep3B cells by hypoxia and CoCl(2). In erythroid K562 cells, the same treatments did not affect iron regulatory proteins activity, thus resulting in a stimulation of TfR gene expression higher than in hepatoma cells.

Role of iron in anthracycline cardiotoxicity: new tunes for an old song?

The clinical use of anticancer anthracyclines is limited by the development of a distinctive and life-threatening form of cardiomyopathy upon chronic treatment. Commonly accepted mechanistic hypotheses have assigned a pivotal role to iron, which would act as a catalyst for free radical reactions and oxidative stress. Although perhaps involved in acute aspects of anthracycline cardiotoxicity, the role of free radical-based mechanisms in long-term effects has been challenged on both experimental and clinical grounds, and alternative hypotheses independent of iron and free radicals have flourished. More recently, studies of the role of C-13 hydroxy metabolites of anthracyclines have provided new perspectives on the role of iron in the cardiotoxicity of these drugs, showing that such metabolites can impair intracellular iron handling and homeostasis. The present review applies a multisided approach to the critical evaluation of various hypotheses proposed over the last decade for the role of iron in anthracycline-induced cardiotoxicity. The main goal of the authors is to build a unifying pattern that would both account for hitherto unexplained experimental observations and help design novel and more rational strategies toward a much-needed improvement in the therapeutic index of anthracyclines.

Nitric oxide reduces nontransferrin-bound iron transport in HepG2 cells

Nitric oxide (NO) donors S-nitroso-N-acetylpenicillamine (SNAP) and sodium nitroprusside (SNP) modulate iron regulatory protein (IRP) activity and may, therefore, affect iron uptake through transferrin receptor expression. However, iron also enters the cell as nontransferrin-bound iron (NTBI), and the aim of this study was to evaluate the effects of NO donors on NTBI transport in HepG2 cells, a model of liver physiology. Incubation with SNP and SNAP led to a time- and concentration-dependent reduction in Fe3+ and Fe2+ uptake, thus indicating an effect on the transporter rather than on the reductase. In terms of Fe2+ uptake, no variations in the Michaelis-Menten constant (Km) and a reduction in maximum uptake (Vmax) (50, 33, and 16.6 fmol/microgram protein/min in control, SNP-, and SNAP-treated cells, respectively) were detected, which suggested a decrease in the number of putative NTBI transport protein(s). Gel shift assays showed that IRP activity was reduced by SNP and slightly increased by SNAP. Northern blot analysis of transferrin receptor messenger RNA (mRNA) levels showed variations similar to those observed for IRPs, but both NO donors increased L-ferritin mRNA levels and had no effect on the stimulator of Fe transport (SFT) mRNA. In conclusion, NO donors significantly reduce NTBI transport in HepG2 cells, an effect that seems to be IRP and SFT independent. Moreover, the reduction in NTBI uptake after NO treatment suggests that this form of iron may play a minor role in the increased hepatic iron stores observed in inflammation or that other liver cells are more involved in this pathological condition.

Preferential activation of iron regulatory protein-2 in cell lines as a result of higher sensitivity to iron

Iron regulatory proteins (IRP)-1 and 2 are cytoplasmic mRNA-binding proteins that control intracellular iron homeostasis by regulating the translation of ferritin mRNA and stability of transferrin receptor mRNA in an iron-dependent fashion. Although structurally and functionally similar, the two IRP are different in their mode of regulation, pattern of tissue expression and modulation by multiple factors, such as bioradicals. In the present study RNA bandshift assays demonstrated that IRP-2, but not IRP-1, activity was higher in cultured cells than in tissues. Increased expression of IRP-2 in cell lines was not related to immortalization and differentiation but seemed associated to cell proliferation, although not closely dependent on cell growth rate. As a growing cell consumes more iron than its quiescent counterpart, we assessed the iron status of cell lines and found that ferritin content was lower than in tissues. Analysis of IRP activity in cell lines supplemented with heme or non-heme iron and in livers of iron-loaded and iron-deficient rats indicated that IRP-2 responds more promptly than IRP-1 to modulations of iron content. We propose that enhanced IRP-2 activity in cultured cells could be due to a proliferation-dependent, relative iron deficiency that is sensed first by IRP-2.

Diacerhein blocks iron regulatory protein activation in inflamed human monocytes

Iron Regulatory Proteins (IRPs), by modulating expression of ferritin, which stores excess iron in a non toxic form, and transferrin receptor, which controls iron uptake, are the main controller of cellular iron metabolism. During inflammation, modification of IRP activity may affect iron availability, free radical generation and cytokine gene response in inflammatory cells. In the present study we tested the effect of inflammatory stimuli on IRP function in a human monocytic-macrophagic cell line and the possibility of interfering with these pathways by using an antiinflammatory compound, diacerhein (DAR). IRP activity was enhanced by interferon gamma/lipopolysaccarhide (IFN/LPS), and this effect was consistently counteracted by increasing concentrations of DAR. No direct effect of DAR on IRP activity was found in vitro. However, in vivo, similar IRP activation was achieved by exposing cells to nitric oxide (NO) donors and the LPS/IFN-induced activation of IRP was reversed by NO inhibitors. Interestingly, NO-induced IRP activation was efficiently blocked by DAR. These data show for the first time that a clinically useful antiinflammatory compound, DAR, interferes with IRP activation by NO in inflammed human cells.

Lack of coordinate control of ferritin and transferrin receptor expression during rat liver regeneration

Transferrin receptor (TfR) and ferritin, key proteins of cellular iron metabolism, are coordinately and divergently controlled by cytoplasmic proteins (iron regulatory proteins, IRP-1 and IRP-2) that bind to conserved mRNA motifs called iron-responsive elements (IRE). IRP, in response to specific stimuli (low iron levels, growth and stress signals) are activated and prevent TfR mRNA degradation and ferritin mRNA translation by hindering ferritin mRNA binding to polysomes. We previously found that, in regenerating liver, IRP activation was accompanied by increased TfR mRNA levels, but not by reduced ferritin expression. The basis for this unexpected behavior was investigated in the present study. Liver regeneration triggered by carbon tetrachloride (CCl4) stimulated by four- to fivefold the synthesis of both L and H ferritin chains. This increase was accompanied with a transcriptionally regulated twofold rise in the amount of ferritin mRNAs. Moreover, polysome-associated ferritin transcripts were fourfold higher in CCl4-treated animals than in control animals. Because RNA bandshift assays showed a fourfold increase in IRP-2 binding activity after CCl4 administration, activated IRP in regenerating liver seemed unable to prevent ferritin mRNAs binding to polysomes. This was confirmed by direct demonstration in the wheat germ translation system that the efficiency of IRP as a translational repressor of a mRNA bearing an IRE motif in front of a reporter transcript is impaired in CCl4-treated rats in spite of an enhanced IRE-binding capacity. In conclusion, we show for the first time that the paradigm of coordinate and opposite control of ferritin and TfR by IRP is contradicted in liver regeneration. Under these circumstances, growth-dependent signals may activate ferritin gene transcription and at the same time hamper the ability of activated IRP-2 to repress translation of ferritin mRNAs, thus preserving for growing liver cells an essential iron-storage compartment.

Effect of reactive oxygen species on iron regulatory protein activity

Iron may be important in catalyzing excessive production of reactive oxygen species (ROS). Cellular iron homeostasis is regulated by iron regulatory proteins (IRPs), which bind to iron-responsive elements (IRE) of mRNAs for ferritin and transferrin receptor (TfR) modulating iron uptake and sequestration, respectively. Although iron is the main regulator of IRP activity, IRP is also influenced by other factors, including the redox state. Therefore, IRP might be sensitive to pathophysiological alterations of redox state caused by ROS. However, previous studies have produced diverging evidence on the effect of oxidative injury on IRP. Results obtained in an animal model close to a pathophysiological condition, such as ischemia reperfusion of the liver as well as in a cell-free system involving an enzymatic source of O2 and H2O2, indicate that IRP is downregulated by oxidative stress. In fact, IRP activity is inhibited at early times of post-ischemic reperfusion. Moreover, the concerted action of O2 and H2O2 produced by xanthine oxidase in a cell-free system caused a remarkable inhibition of IRP activity. IRP seems a direct target of ROS; in fact, in vivo inhibition can be prevented by the antioxidant N-acetylcysteine and by interleukin-1 receptor antagonist. In addition, modulation of iron levels of the cell-free assay did not affect the downregulation imposed by xanthine oxidase. Conceivably, downregulation of IRP activity by O2 and H2O2 may facilitate iron sequestration into ferritin, thus limiting the pro-oxidant challenge of iron.

The secondary alcohol metabolite of doxorubicin irreversibly inactivates aconitase/iron regulatory protein-1 in cytosolic fractions from human myocardium

Anticancer therapy with doxorubicin (DOX) is limited by severe cardiotoxicity, presumably reflecting the intramyocardial formation of drug metabolites that alter cell constituents and functions. In a previous study, we showed that NADPH-supplemented cytosolic fractions from human myocardial samples can enzymatically reduce a carbonyl group in the side chain of DOX, yielding a secondary alcohol metabolite called doxorubicinol (DOXol). Here we demonstrate that DOXol delocalizes low molecular weight Fe(II) from the [4Fe-4S] cluster of cytoplasmic aconitase. Iron delocalization proceeds through the reoxidation of DOXol to DOX and liberates DOX-Fe(II) complexes as ultimate by-products. Under physiologic conditions, cluster disassembly abolishes aconitase activity and forms an apoprotein that binds to mRNAs, coordinately increasing the synthesis of transferrin receptor but decreasing that of ferritin. Aconitase is thus converted into an iron regulatory protein-1 (IRP-1) that causes iron uptake to prevail over sequestration, forming a pool of free iron that is used for metabolic functions. Conversely, cluster reassembly converts IRP-1 back to aconitase, providing a regulatory mechanism to decrease free iron when it exceeds metabolic requirements. In contrast to these physiologic mechanisms, DOXol-dependent iron release and cluster disassembly not only abolish aconitase activity, but also affect irreversibly the ability of the apoprotein to function as IRP-1 or to reincorporate iron within new Fe-S motifs. This damage is mediated by DOX-Fe(II) complexes and reflects oxidative modifications of -SH residues having the dual role to coordinate cluster assembly and facilitate interactions of IRP-1 with mRNAs. Collectively, these findings describe a novel mechanism of cardiotoxicity, suggesting that intramyocardial formation of DOXol may perturb the homeostatic processes associated with cluster assembly or disassembly and the reversible switch between aconitase and IRP-1. These results may also provide a guideline to design new drugs that mitigate the cardiotoxicity of DOX.

Response of monocyte iron regulatory protein activity to inflammation: abnormal behavior in genetic hemochromatosis

In genetic hemochromatosis (GH), iron overload affects mainly parenchymal cells, whereas little iron is found in reticuloendothelial (RE) cells. We previously found that RE cells from GH patients had an inappropriately high activity of iron regulatory protein (IRP), the key regulator of intracellular iron homeostasis. Elevated IRP should reflect a reduction of the iron pool, possibly because of a failure to retain iron. A defect in iron handling by RE cells that results in a lack of feedback regulation of intestinal absorption might be the basic abnormality in GH. To further investigate the capacity of iron retention in RE cells of GH patients, we used inflammation as a model system as it is characterized by a block of iron release from macrophages. We analyzed the iron status of RE cells by assaying IRP activity and ferritin content after 4, 8, and 24 hours of incubation with lipopolysaccharide (LPS) and interferon-gamma (IFN-gamma). RNA-bandshift assays showed that in monocytes and macrophages from 16 control subjects, IRP activity was transiently elevated 4 hours after treatment with LPS and IFN-gamma but remarkably downregulated thereafter. Treatment with NO donors produced the same effects whereas an inducible Nitric Oxide Synthase (iNOS) inhibitor prevented them, which suggests that the NO pathway was involved. Decreased IRP activity was also found in monocytes from eight patients with inflammation. Interestingly, no late decrease of IRP activity was detected in cytokine-treated RE cells from 12 GH patients. Ferritin content was increased 24 hours after treatment in monocytes from normal subjects but not in monocytes from GH patients. The lack of downregulation of IRP activity under inflammatory conditions seems to confirm that the control of iron release from RE cells is defective in GH.

Nitric oxide-mediated induction of ferritin synthesis in J774 macrophages by inflammatory cytokines: role of selective iron regulatory protein-2 downregulation

Cytokine-treated macrophages represent a useful model to unravel the molecular basis of reticuloendothelial (RE) iron retention in inflammatory conditions. In the present study, we showed that stimulation of murine macrophage J774 cells with interferon (IFN)-gamma/lipopolysaccharide (LPS) resulted in a nitric oxide-dependent modulation of the activity of iron regulatory proteins (IRP)-1 and 2, cytoplasmic proteins which, binding to RNA motifs called iron responsive elements (IRE), control ferritin translation. Stimulation with cytokines caused a small increase of IRP-1 activity and a strong reduction of IRP-2 activity accompanied by increased ferritin synthesis and accumulation. Cytokines induced only a minor increase of H chain ferritin mRNA, thus indicating that IRP-2-mediated posttranscriptional regulation plays a major role in the control of ferritin expression. This was confirmed by direct demonstration that the translational repression function of IRP was impaired in stimulated cells. In fact, translation in cell-free extracts of a reporter transcript under the control of an IRE sequence was repressed less efficiently by IRP-containing lysates from cytokine-treated cells than by lysates from control cells. Our findings throw light on the role of IRP-2 showing that: (1) this protein responds to a stimulus in opposite fashion to IRP-1; (2) when abundantly expressed, as in J774 cells, IRP-2 is sufficient to regulate intracellular iron metabolism in living cells; and (3) by allowing increased ferritin synthesis, IRP-2 may play a role in the regulation of iron homeostasis in RE cells during inflammation.

Mitochondrial respiratory chain deficiency leads to overexpression of antioxidant enzymes

U937 cell growth in the presence of either chloramphenicol or ethidium bromide rapidly leads to respiratory deficiency. The novel finding of this report is that this response is paralleled by a specific increase in Se-dependent and independent glutathione peroxidase activities as well as of glutathione peroxidase and heme oxygenase mRNAs. Under the same experimental conditions, catalase activity and catalase mRNA do not show appreciable changes. These results can be explained by an increased formation of H2O2 at the early times of development of respiratory deficiency followed by induction of antioxidant enzymes.

Haemodynamic alteration in patients undergoing chronic haemodialysis

Fifteen elderly patients, 13 of them undergoing chronic haemodialysis, 1 acute and 1 coming from Continuous Ambulatory Peritoneal Dialysis (CAPD) either with no significant cardiovascular alteration or presenting various cardiovascular pathologies were studied to investigate the possibility of onset of hypotensive episodes during dialytic treatment depending on cardiac or vascular alteration in the patients. Monitoring of the arterial pressure on the contralateral arm and on the lower limbs by using the Takeda System, made it possible to compute the Windsor Index (WI). The figures obtained were correlated to the Ejection Fraction Index (EFI) to investigate the relation between WI alteration and haemodynamic variations in the patient. The results show that cardiothoracic recirculation is much more present in those patients with pathologies that affect EFI which worsens during dialysis due to the loss of fluid. Moreover the results obtained from the two patients with temporary access and no evident cardiovascular pathology show the constancy of the haemodynamic parameters throughout the dialytic treatment.

Haemodynamic Alteration in Patients Undergoing Chronic Haemodialysis

Fifteen elderly patients, 13 of them undergoing chronic haemodialysis, 1 acute and 1 coming from Continuous Ambulatory Peritoneal Dialysis (CAPD) either with no significant cardiovascular alteration or presenting various cardiovascular pathologies were studied to investigate the possibility of onset of hypotensive episodes during dialytic treatment depending on cardiac or vascular alteration in the patients. Monitoring of the arterial pressure on the contralateral arm and on the lower limbs by using the Takeda System, made it possible to compute the Windsor Index (WI). The figures obtained were correlated to the Ejection Fraction Index (EFI) to investigate the relation between WI alteration and haemodynamic variations in the patient. The results show that cardiothoracic recirculation is much more present in those patients with pathologies that affect EFI which worsens during dialysis due to the loss of fluid. Moreover the results obtained from the two patients with temporary access and no evident cardiovascular pathology show the constancy of the haemodynamic parameters throughout the dialytic treatment.

Induction of ferritin synthesis in ischemic-reperfused rat liver: analysis of the molecular mechanisms

BACKGROUND & AIMS

Iron may catalyze the production of reactive oxygen species (ROS) during postischemic reoxygenation. Ferritin, a cellular iron storage protein, can either represent a source of iron or perform a cytoprotective action against ROS. The aim of this study was to address the role of ferritin in postischemic reperfusion.

METHODS

Transcriptional and posttranscriptional mechanisms controlling ferritin gene expression were studied in reperfused rat livers.

RESULTS

Proteolysis reduced ferritin levels 2 hours after reperfusion, but a concomitant increase of synthesis, accompanied by enhanced transcription and accumulation of H and L ferritin subunit messenger RNAs (mRNAs), almost re-established normal ferritin content at 4 hours. Pretreatment with interleukin 1 receptor antagonist (IL-1RA) did not prevent the rise of ferritin mRNAs. RNA bandshift assays showed that the activity of the iron regulatory proteins (IRPs), which control ferritin mRNA translation, declined early after reperfusion and recovered progressively thereafter. Pretreatment with either the antioxidant N-acetyl cysteine or IL-1RA was sufficient to prevent almost completely down-regulation of IRP activity.

CONCLUSIONS

Postischemic reperfusion causes degradation of ferritin, possibly increasing iron levels. However, induction of ferritin gene transcription, possibly mediated by ferritin-derived iron and ROS-mediated inactivation of IRP, which allows translation of ferritin mRNAs, counteracts this effect and concurs to reestablish the amount of ferritin, which may thus act to limit reperfusion damage.

Hereditary hyperferritinemia-cataract syndrome: relationship between phenotypes and specific mutations in the iron-responsive element of ferritin light-chain mRNA

Recent reports have described families in whom a combination of elevated serum ferritin not related to iron overload and congenital nuclear cataract is transmitted as an autosomal dominant trait. We have studied the molecular pathogenesis of hyperferritinemia in two families showing different phenotypic expression of this new genetic disorder. Serum ferritin levels ranged from 950 to 1,890 microg/L in affected individuals from family 1, and from 366 to 635 microg/L in those from family 2. Cataract was clinically manifested in family 1 and asymptomatic in family 2. By using monoclonal antibodies specific for the H and L ferritin subunits, serum ferritin was found to be essentially L type in both normal and affected individuals. The latter also showed normal amounts of H-type ferritin in circulating mononuclear cells; on the contrary, L-type ferritin contents were 13 times normal in family 1 and five times normal in family 2 on average. Serum ferritin was glycosylated in both normal and affected individuals. There was a close relationship between mononuclear cell L-type ferritin content and serum ferritin concentration (r = 0.95, P < .00001), suggesting that the excess production of ferritin in cells was directly responsible for the hyperferritinemia. The dysregulated L-subunit synthesis was found to result from different point mutations in a noncoding sequence of genomic L-subunit DNA, which behaves as an mRNA cis-acting element known as iron regulatory element (IRE). Affected individuals from family 1 were heterozygous for a point mutation (a single G to A change) in the highly conserved, three-nucleotide motif forming the IRE bulge. Affected members from family 2 were heterozygous for a double point mutation in the IRE lower stem. Using a gel retardation assay, the observed molecular lesions were shown to variably reduce the IRE affinity for an iron regulatory protein (IRP), which inhibits ferritin mRNA translation. The direct relationship between the degree of hyperferritinemia and severity of cataract suggests that this latter is the consequence of excessive ferritin production within the lens fibers. These findings provide strong evidence that serum ferritin is a byproduct of intracellular ferritin synthesis and that the L-subunit gene on chromosome 19 is the source of glycosylated serum ferritin. From a practical standpoint, this new genetic disorder should be taken into account by clinicians when facing a high serum ferritin in an apparently healthy person.

Inappropriately high iron regulatory protein activity in monocytes of patients with genetic hemochromatosis

In genetic hemochromatosis (GH), excess iron is deposited in parenchymal cells, whereas little iron is found in reticuloendothelial (RE) cells until the later stages of the disease. As iron absorption is inversely related to RE cells stores, a failure of RE to retain iron has been proposed as the basic defect in GH. In RE cells of GH subjects, we examined the activity of iron regulatory protein (IRP), a reliable indicator of the elusive regulatory labile iron pool, which modulates cellular iron homeostasis through control of ferritin (Ft) and transferrin receptor gene expression. RNA-bandshift assays showed a significant increase in IRP activity in monocytes from 16 patients with untreated GH compared with 28 control subjects (1.5-fold) and five patients with secondary hemochromatosis (SH) with similar iron burden (fourfold). In 17 phlebotomy-treated GH patients, IRP activity did not differ from that of control subjects. In both GH and SH monocyte-macrophages, Ft content increased by twofold and the L subunit-rich isoferritin profile was unchanged as compared with controls. IRP activity was still upregulated in vitro in monocyte-derived macrophages of GH subjects but, following manipulations of iron levels, was modulated normally. Therefore, the sustained activity of monocyte IRP found in vivo in monocytes of GH patients is not due to an inherent defect of its control, but is rather the expression of a critical abnormality of iron metabolism, eg, a paradoxical contraction of the regulatory iron pool. By preventing Ft mRNA translation, high IRP activity in monocytes may represent a molecular mechanism contributing to the inadequate Ft accumulation and insufficient RE iron storage in GH.

Superoxide and hydrogen peroxide-dependent inhibition of iron regulatory protein activity: a protective stratagem against oxidative injury

Cellular iron homeostasis is regulated by the cytoplasmic iron regulatory protein (IRP), which binds to iron-responsive elements (IRE) of mRNAs, modulating iron uptake and sequestration, respectively. When iron is scarce, IRP binds to IRE and coordinately increases the synthesis of transferrin receptor and decreases that of ferritin, thus providing the cell with readily available free iron. When iron is in excess, IRP does not bind and iron sequestration prevails over iron uptake. We have found that incubation of rat liver lysates with xanthine oxidase (XO), which generates superoxide (O2-.) and hydrogen peroxide (H2O2), caused a remarkable but reversible inhibition of IRP activity, as the formation of IRE-IRP decreased by 70-80% but returned to baseline values upon exposure to a reducing agent like 2-mercaptoethanol. IRP inhibition was prevented by separate or simultaneous addition of superoxide dismutase and catalase, showing that both O2-. and H2O2 were involved. By contrast, iron chelators and hydroxyl radical scavengers did not impede the inhibition of IRP, suggesting that O2-. and H2O2 acted independently of free iron sources. Ferritin enhanced IRP inhibition, but this process involved tightly bound iron centers that shunted reducing equivalents from XO and returned them to oxygen, thus increasing the formation of O2-. In agreement with the exclusive role of O2-. and H2O2, XO also inhibited recombinant human IRP in the absence of iron. These results demonstrate that O2-. and H2O2 can directly but reversibly down-regulate the RNA-binding activity of IRP, causing transient decrease of free iron that otherwise would convert them into more potent oxidants such as hydroxyl radicals or equally aggressive iron-peroxo complexes. This establishes a novel protective stratagem against oxidative injury under pathophysiologic conditions characterized by the excessive generation of O2-. and H2O2.

Nitric-oxide-mediated activation of iron-regulatory protein controls hepatic iron metabolism during acute inflammation

The molecular regulation of intracellular iron metabolism has been studied in the livers of rats undergoing an acute inflammatory reaction following turpentine injection. Treatment induced an increase in the steady-state level of the transferrin receptor (TfR) mRNA, peaking 18 h after treatment and returning to control levels 24 h after treatment, with no change in TfR gene transcription. RNA band-shift assays documented an activation of the cytoplasmic RNA-binding protein called the iron-regulatory protein (IRP), in parallel with a rise in the amount of TfR transcripts. A 2-3-fold increase in the amount of H and L ferritin subunit mRNAs was found 12-18 h after turpentine treatment. Surprisingly, higher accumulation of ferritin mRNAs did not result in appreciable differences in the liver ferritin content. This might be due to the concomitant rise of IRP activity, which is known to prevent ferritin mRNA translation. The absence of significant changes in the total iron and ferritin contents prompted us to investigate the role of nitric oxide (NO), an inflammatory mediator which is also known to modulate the activity of IRP. Northern-blot analysis showed a marked enhancement in the expression of the inducible form of nitric oxide synthase mRNA in turpentine-treated rats. Furthermore, the activation of IRP and the increase of the TfR mRNA content that occur in turpentine-treated rats were abolished by treatment with N5-nitro-L-arginine, a specific nitric oxide synthase inhibitor. The present data suggest that NO-mediated activation of IRP regulates alterations of hepatic iron homeostasis that occur in acute inflammation.

Induction of ferritin synthesis by oxidative stress. Transcriptional and post-transcriptional regulation by expansion of the "free" iron pool

Ferritin, by regulating the "free" intracellular iron pool, controls iron-catalyzed generation of reactive oxygen species, but its role in oxidative damage is still unclear. We show that ferritin synthesis is significantly stimulated in the liver of rats subjected to oxidative stress by treatment with phorone, a glutathione-depleting drug. RNA-bandshift assays document reduced activity of iron regulatory factor, in particular of IRFB, the cytoplasmic protein that post-transcriptionally controls ferritin mRNA translation. Furthermore, Northern blot analysis shows increased accumulation of H and L subunit mRNAs, and nuclear run-on experiments provide evidence of transcriptional activation. Direct measurements of intracellular free iron levels by EPR indicate that the increased ferritin synthesis can be mediated by an expansion of the free iron pool. An early drop of ferritin content after phorone treatment indicates that part of the iron that fuels the free pool might derive from ferritin degradation. Present data seem to suggest that, under conditions of oxidative stress, liver ferritin can represent either a pro- or an anti-oxidant in a time-dependent manner. In fact, its early degradation contributes to expand the intracellular free iron pool that, later on, activates multiple molecular mechanisms to reconstitute ferritin content, thus limiting the pro-oxidant challenge of iron.

Duodenal ferritin synthesis in genetic hemochromatosis

BACKGROUND/AIMS

The molecular defect of genetic hemochromatosis (GH) is unknown. It is believed that low expression of duodenal ferritin in GH is caused by tissue or cell specific defect of ferritin synthesis. Our study was designed to ascertain whether the control of duodenal ferritin synthesis in GH was defective.

METHODS

Expression at the single cell level of H and L ferritin messenger RNAs and protein and activity of the iron regulatory factor, which controls the translation of ferritin messenger RNA, were assessed in 43 duodenal biopsy specimens from individuals with GH, secondary hemochromatosis (SH), anemia, or normal iron balance.

RESULTS

Signal for ferritin H and L subunit messenger RNAs was detected in both absorptive and nonabsorptive cells by in situ hybridization, but in 10 of 14 patients with untreated GH, the signal was lower than in patients with SH or normal subjects. However, immunostaining for ferritin protein documented a diffuse/cytoplasmic pattern, whereas a supranuclear/granular staining was found in normal subjects or patients with SH. The spontaneous activity of duodenal iron regulatory factor was consistently higher in patients with GH than in normal subjects or subjects with anemia or SH.

CONCLUSIONS

In patients with GH, ferritin gene transcription is preserved in both absorptive and nonabsorptive intestinal cells. Low accumulation of ferritin is not caused by a defective control of ferritin synthesis but by low expression of ferritin messenger RNA and sustained activity of iron regulatory factor.

Transferrin receptor gene expression during rat liver regeneration. Evidence for post-transcriptional regulation by iron regulatory factorB, a second iron-responsive element-binding protein

Transferrin receptor (TfR) expression is regulated by iron at the level of mRNA stability through a factor (IRF/IRE-BP) which binds to specific iron-responsive elements (IRE). On the other hand, growth-dependent regulation of TfR expression is generally believed to be transcriptionally controlled. We analyzed the molecular mechanisms that control TfR gene expression at the onset of cell proliferation in vivo during liver regeneration after partial hepatectomy. The amount of TfR mRNA increased considerably after partial hepatectomy while run-on assays did not show significant changes in TfR gene transcription. RNA band-shift assays documented a significant activation of IRF/IRE-BP specific for the faster migrating IRE-protein complex (IRFB). These changes occurred in the absence of modifications of total liver iron concentration but together with a significant decrease of ferritin content. Moreover, when extreme variations of liver iron content were achieved by either chronic iron overload or severe iron deficiency, liver regeneration was unable to influence IRE-binding activity. We conclude that IRF/IRE-BP-mediated post-transcriptional control can fully account for TfR mRNA induction during liver cell proliferation in vivo. IRF/IRE-BP activation in the absence of changes in total tissue iron content might depend either on a drop of iron levels into the regulatory pool or on a relatively iron-independent mechanism specific for the faster migrating complex.

Expression of a growth arrest specific gene (gas-6) during liver regeneration: molecular mechanisms and signalling pathways

A set of growth arrest-specific (gas) genes negatively regulated by serum has been identified. To define the role of gas genes in a model of cell proliferation in vivo we analyzed the expression of one of these genes (gas-6) during liver regeneration after partial hepatectomy (PH). We found that gas-6 mRNA was down-regulated 4 hours after PH, within the G0 to G1 transition. Later on, gas-6 mRNA increased over the level found in normal liver with a peak at 16 hours, before the onset of DNA synthesis. This surge was probably triggered by an inflammatory response caused by the surgical trauma, because an increase of similar extent occurring with the same time course was present in livers of sham-operated and turpentine-treated rats. Comparison of mRNA steady state levels with nuclear transcription rates indicated that gas-6 expression is post-transcriptionally regulated. As we found that down-regulation of gas-6 expression was prevented by treatment with Actinomycin D, a labile protein might be involved in the determination of gas-6 mRNA stability. To investigate the mitogenic signals controlling gas-6 expression during liver regeneration we treated hepatectomized rats with a specific alpha-1-adrenoceptor blocker (prazosin) as well as with drugs which modify intracellular calcium levels. The decrease of gas-6 mRNA 4 hours after PH was prevented by prazosin and by neomycin, an inhibitor of calcium release from endogenous stores. These findings suggest that down-regulation of gas-6 expression during hepatic regeneration is triggered by catecholamines interaction with alpha-1-adrenergic receptors and by subsequent calcium release. In addition we found that the rise of gas-6 gene expression occurring at 16 hours after PH was not affected by prazosin but was inhibited by trifluoperazine. Therefore, we suggest that up-regulation of gas-6 gene expression is mediated by the interaction of calcium with calmodulin, independently of catecholamines.

Course and prognosis of 132 patients with diabetic non ketotic hyperosmolar state

One hundred and thirty two episodes of diabetic non ketotic hyperosmolar states were studied after a prospective schedule of treatment was designed. The admission data, the prognostic factors and their outcome were analyzed. Initial high osmolarity, urea and sodium plasma levels and low plasma pH were related to the admission level of consciousness (p < 0.01). High glucose, osmolarity, urea and sodium plasma levels at entry were related to the admission level of dehydration (p < 0.01). In multivariate regression analysis, osmolarity was the most influential variable in both the level of consciousness and the admission level of dehydration (p < 0.0001). Twenty two patients died (16.9%). Septic shock was the most frequent cause of death (31%) and mortality was higher in patients with cardiovascular disease (acute myocardial infarction or stroke) as the precipitating factor for diabetic hyperosmolar state (p < 0.002). Older age, low blood pressure, low sodium, pH and bicarbonate plasma levels, and high urea plasma levels were related to mortality (p < 0.01). In multiple regression analysis, urea was the most influential mortality risk factor (p < 0.0118). Non survivors received higher doses of insulin than survivors (p < 0.01). All these data suggest that it is not the hyperosmolarity itself, but the hemodynamical state of the patients, which is the most influential factor on the prognosis of a diabetic hyperosmolar state.

Estrogen-regulated expression of a growth arrest specific gene (gas-1) in rat uterus

gas-1 belongs to a family of growth arrest specific genes negatively regulated after growth induction of arrested cells. We report the expression of gas-1 in an in vivo system of cell proliferation. gas-1 mRNA accumulates progressively in the uterus of ovariectomized rats with a peak at three weeks after surgery. After estrogen treatment gas-1 mRNA levels decrease within two hours, at a time when c-myc expression is greatly increased, and return to pretreatment levels at 48 hours. Treatment with cycloheximide does not prevent estrogen-induced down-regulation of gas-1 mRNA levels. The present results show that: i) estrogen affects the uterine growth state by regulating the expression of both positively and negatively acting genes, ii) gas-1 expression is controlled by cellular growth state also in vivo.

Molecular basis of reduced albumin gene expression in hepatoma cell lines with different growth rates

To study the relationship between expression of a differentiated function and cellular proliferation we analyzed the molecular mechanisms controlling albumin gene expression in rat liver and in rat hepatoma cell lines of different growth rates: low (MH1C1), intermediate (FAO), and high (3924A), as evaluated by both cell doubling time and histone H3 gene expression. In comparison with the liver, albumin accumulation was reduced in FAO cells and absent in MH1C1 and 3924A cells. Thus, these hepatoma cell lines do not show the inverse relationship between cellular growth rate and expression of a differentiation marker that has been often described in several hepatic and nonhepatic cellular systems. This conclusion is further reinforced by the finding that all cell lines, irrespective of their growth rate, failed to express alpha-fetoprotein mRNA, a dedifferentiation marker, and that two other liver-abundant genes, transferrin and apolipoprotein A-1, are regulated in a way similar to that of albumin. The defect in albumin accumulation was due to decreased or lacking synthesis which, in turn, was accompanied by reduction or absence of albumin mRNA. Run-on transcription assays provided evidence for diminished or absent albumin gene transcription. Southern blot analysis revealed that the structure of the albumin gene is preserved in all the tumor cell lines; however, we found a different methylation state of the albumin gene that correlated well with albumin expression.

Protein synthesis and gene expression in transplanted and postischemic livers

The expression of some genes has been comparatively studied in transplanted rat liver and in liver reperfused after ischemia in situ. Experiments on protein synthesis by tissue slices from cold-stored or transplanted livers show that rat livers that retain a good capacity for protein synthesis during storage undergo a profound impairment in the capacity for protein synthesis during the first hours after transplantation. This recovers in the following hours. There is never any indication of synthesis of stress proteins, and of hsp 70 in particular. The steady-state level of mRNAs for albumin, transferrin, and beta-actin, which are well expressed in reperfused postischemic livers in vivo, are reduced early after transplantation and recover only many hours later. Run-on analysis shows that an early defect in transcription and a partial recovery of this process later on are responsible for these changes. The steady-state levels of the same mRNAs are well maintained in donor livers preserved in University of Wisconsin solution for at least 12 hr, and less satisfactorily in Euro-Collins solution. Results of run-on analysis parallel the data on mRNA levels. The behavior of these mRNAs is, therefore, clearly different in reperfused and transplanted liver. The early stages of liver transplantation seem to be characterized by a depressed capacity of gene expression, without the reactive phenomenon of activation of stress protein genes that occurs in reperfused postischemic livers.

Stress proteins and reperfusion stress in the liver

Blood reperfusion after temporary liver ischemia induces the expression of heat shock genes and the synthesis of heat shock proteins (hsps), in particular hsp 70. Induction requires a certain duration of ischemia, suggesting that cell damage before reperfusion is essential for activation of heat shock genes. The expression of the hsp 70 gene is preceded by activation of the cellular protooncogenes c-fos and c-jun. However, the product of these genes, which is transcription factor AP-1, seems unnecessary for activation of the hsp 70 gene, which does not require the integrity of protein synthesis. Hsp genes seem to behave as "early response genes," enabling the cell to respond to emergency situations.

Ferritin synthesis on polyribosomes attached to the endoplasmic reticulum

The evidence that ferritin is synthesized both on free polyribosomes and on polyribosomes attached to the endoplasmic reticulum is reviewed. Evidence that some ferritin is secreted from cells after synthesis on bound polyribosomes was found to be inconclusive.

Expression of a growth arrest specific gene (gas-1) in transformed cells

A set of growth arrest-specific (gas) genes negatively regulated by serum has been identified. We report the analysis of the expression of one of them (gas-1) in transformed cells. We found a down regulation of gas-1 expression in NIH 3T3 cells transfected in vitro with an activated Ha-ras oncogene. In five chemically-induced mouse tumours grown in vivo the amounts of gas-1 mRNA were largely different but not related to the proliferating activity (evaluated by both H3 histone expression and 3H-thymidine incorporation into DNA). The amount of gas-1 mRNA in the tumours was in general higher than in normal tissues. Expression of c-myc was also evaluated and found to be high in tumours which exhibited low gas-1 expression. Two fibrosarcomas, CA-2 and CB-20, with similar phenotype, similar growth rate, different expression of c-myc and 100-fold difference in gas-1 expression were further investigated and gas-1 expression was found to be correlated with the expression of a differentiated function (as judged from collagen expression). Cell lines derived from CA-2 and CB-20 and maintained under different culture conditions showed that the cell cycle regulation and serum response of gas-1 expression were lost in CA-2. The higher steady state level of gas-1 mRNA in spite of a shorter mRNA half life suggests that in CB-20 cells the gas-1 gene is transcribed faster than in CA-2 cells indicating that transcriptional regulation is the major determinant of gas-1 gene expression in tumour cells. The finding of gas-1 expression in tumour cells suggests that its expression is not sufficient to maintain cells into quiescence, however, as a marker specific for the G0 phase, it could be useful, in conjunction with other growth related genes, to define the cell cycle distribution of a cell population.

Ferritin mRNAs on rat liver membrane-bound polysomes synthesize ferritin that does not translocate across membranes

Ferritin is a typical intracellular protein but small amounts are also present in serum and other biological fluids. The source and physiological significance of serum ferritin are still obscure. The presence of ferritin mRNAs on polysomes bound to endoplasmic reticulum (ER) could be relevant for the secretion of ferritin. By Northern blot analysis we found significant amounts of both L and H subunit mRNAs on rat liver membrane-bound polysomes. Immunoprecipitation of translational products of membrane-bound polysomes with anti-rat liver ferritin antibody showed that ferritin is actually synthesized on ER membranes. Analysis of RNA extracted from salt-washed rat liver microsomes demonstrated that ferritin mRNAs are translated by polysomes tightly bound to ER membranes. Following iron treatment, both the amount of H and L subunit mRNAs and ferritin synthesis increased sharply in both free and bound polysomal fractions. Translation of membrane-bound polysomes in the presence of microsomal membranes indicated that ferritin is not processed by signal sequence cleavage or glycosylation and is not translocated into ER membranes. Ferritin mRNAs found on membrane-bound polysomes are associated with ER in a specific way, however, their products do not seem to follow the classic secretory pathway and therefore the significance of the large amount of ferritin mRNAs in the bound ribosome fraction remains unclear.