Prevalence and features of delirium in older patients admitted to rehabilitation facilities: a multicenter study

BACKGROUND

Delirium is thought to be common across various settings of care; however, still little research has been conducted in rehabilitation.

AIM

We investigated the prevalence of delirium, its features and motor subtypes in older patients admitted to rehabilitation facilities during the three editions of the "Delirium Day project".

METHODS

We conducted a cross-sectional study in which 1237 older patients (age ≥ 65 years old) admitted to 50 Italian rehabilitation wards during the three editions of the "Delirium Day project" (2015 to 2017) were included. Delirium was evaluated through the 4AT and its motor subtype with the Delirium Motor Subtype Scale.

RESULTS

Delirium was detected in 226 patients (18%), and the most recurrent motor subtype was mixed (37%), followed by hypoactive (26%), hyperactive (21%) and non-motor one (16%). In a multivariate Poisson regression model with robust variance, factors associated with delirium were: disability in basic (PR 1.48, 95%CI: 1.17-1.9, p value 0.001) and instrumental activities of daily living (PR 1.58, 95%CI: 1.08-2.32, p value 0.018), dementia (PR 2.10, 95%CI: 1.62-2.73, p value < 0.0001), typical antipsychotics (PR 1.47, 95%CI: 1.10-1.95, p value 0.008), antidepressants other than selective serotonin reuptake inhibitors (PR 1.3, 95%CI: 1.02-1.66, p value 0.035), and physical restraints (PR 2.37, 95%CI: 1.68-3.36, p value < 0.0001).

CONCLUSION

This multicenter study reports that 2 out 10 patients admitted to rehabilitations had delirium on the index day. Mixed delirium was the most prevalent subtype. Delirium was associated with unmodifiable (dementia, disability) and modifiable (physical restraints, medications) factors. Identification of these factors should prompt specific interventions aimed to prevent or mitigate delirium.

The association between low skeletal muscle mass and delirium: results from the nationwide multi-centre Italian Delirium Day 2017

Introduction

Delirium and sarcopenia are common, although underdiagnosed, geriatric syndromes. Several pathological mechanisms can link delirium and low skeletal muscle mass, but few studies have investigated their association. We aimed to investigate (1) the association between delirium and low skeletal muscle mass and (2) the possible role of calf circumference mass in finding cases with delirium.

Methods

The analyses were conducted employing the cross-sectional “Delirium Day” initiative, on patient 65 years and older admitted to acute hospital medical wards, emergency departments, rehabilitation wards, nursing homes and hospices in Italy in 2017. Delirium was diagnosed as a 4 + score at the 4-AT scale. Low skeletal muscle mass was operationally defined as calf circumference ≤ 34 cm in males and ≤ 33 cm in females. Logistic regression models were used to investigate the association between low skeletal muscle mass and delirium. The discriminative ability of calf circumference was evaluated using non-parametric ROC analyses.

Results

A sample of 1675 patients was analyzed. In total, 73.6% of participants had low skeletal muscle mass and 24.1% exhibited delirium. Low skeletal muscle mass and delirium showed an independent association (OR: 1.50; 95% CI 1.09–2.08). In the subsample of patients without a diagnosis of dementia, the inclusion of calf circumference in a model based on age and sex significantly improved its discriminative accuracy [area under the curve (AUC) 0.69 vs 0.57, p < 0.001].

Discussion and conclusion

Low muscle mass is independently associated with delirium. In patients without a previous diagnosis of dementia, calf circumference may help to better identify those who develop delirium.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40520-021-01950-8.

Effect of Spin Clustering on Basic and Relaxometric Properties of Magnetic Nanoparticles

An increasing awareness about novel medical applications of smaller, inorganic-based nanoparticles, possessing unique properties at the nanoscale, has led to a burst of research activities in the development of "nanoprobes" for diagnostic medicine and agents for novel, externally activated therapies. In this research field magnetic nanoparticles are prominent due to fundamental peculiar properties particularly appealing for their use in materials and biomedical applications. Aiming to study the relationship between the topology of the magnetic nanoparticles and their efficacy as MRI contrast agents (relaxometric properties), we prepared three different stable colloidal suspension (ferrofluid) of magnetic nanobeads (MNBs) constituted by a discrete number of maghemite nanoparticles, arranged in disordered clusters or ordered in a polymeric matrix. An accurate morpho-dimensional and magnetic characterization displays the close correlation between the magnetic fundamental properties and the topology of our spin systems. The NMR relaxometry profiles confirmed the nature of the physical mechanisms inducing the increase of nuclear relaxation rates at low (magnetic anisotropy) and high (Curie relaxation) magnetic fields. Moreover the transverse relaxivity (r₂) values for all the MNBs are higher than those of common contrast agents and the differences between the three MNBs are suggested to be due to the spin topology effect.

Measurement of Ferritin-Bearing Lymphocytes in Man. Preliminary Studies on the Use of Monoclonal Antibodies Specific for the L and H Subunits of Ferritin

We used the monoclonal antibodies LFO3 (specific for the L subunit of ferritin) and 2A4 (specific for the H subunit) in an indirect immunofluorescence test for enumerating ferritin-bearing lymphocytes (FBL). In 13 normal subjects, the geometric mean value of FBL was 4 % (range 0–13 %) with the monoclonal antibody LFO3, and 3 % (range 0–8 %) with the monoclonal antibody 2A4. Values in 5 subjects with transfusional iron overload and increased plasma L-type ferritin concentration were 5 % (4–7 %) and 3 % (2–4 %), respectively, which is similar to those in normal subjects. Thirteen patients with malignant disease had normal to increased values for plasma ferritin; the circulating protein was largely of L-type with undetectable or very low concentrations of H-type ferritin. In the same patients, the percentage of FBL was greater with the monoclonal antibody 2A4 (geometric mean value 8 %; range 3–12 %) than with the monoclonal antibody LFO3 (geometric mean value 3 %; range, 1–7 %). It is concluded that acidic and basic isoferritins can be differently expressed on the surface of peripheral blood lymphocytes, and that the monoclonal 2A4 could be particularly useful in the measurement of FBL in patients with malignancy.

Immunological Reactivity of Serum Ferritin in Patients with Malignancy

Serum ferritin has been suggested as a tumor marker in the diagnosis of certain malignancies and for following the activity or dissemination of the malignant process. Since neoplastic tissues generally contain more acidic isoferritins than their normal tissue counterparts, it has also been suggested that the specific assay of such isoferritins in serum may be of particular value in the diagnosis of malignancy. In this work, we have evaluated ferritin concentration in the serum of normal subjects and patients with acute nonlymphocytic leukemia, Hodgkin's disease, breast cancer and lung cancer by simultaneously using three different immunoassays: an immunoradiometric assay based on polyclonal antibodies against human liver (basic, L-subunit rich) ferritin, a radioimmunoassay based on polyclonad antibodies against HeLa cell (acidic, H-subunit rich) ferritin, and an immunoradiometric assay based on the monoclonal antibody 2A4 raised against human heart (acidic, H-subunit rich) ferritin. Most of the patients studied had increased values for liver-type ferritin in the absence of increased iron stores. Binding of serum ferritin to concanavalin A did not prove to be useful in distinguishing a tumor-specific basic isoferritin. The HeLa ferritin assay was found to be less specific than the heart ferritin assay in the detection of acidic isoferritins, and did not provide any advantage over the liver assay in detecting the increased levels of serum ferritin associated with malignant disease. Heart-type ferritin was found in one-fifth of normal sera and 64% of sera from patients with malignancy. Values were very low compared with those for basic ferritin, ranging from less than 0.1 to 17% of total serum ferritin (geometric mean value 1.3%) in patients with malignancy. These findings indicate that at present there is little application for serum ferritin immunoassays based on antibodies to HeLa cell or heart ferritin in the diagnosis or monitoring of malignant disease. This seems to be due to the presence in human serum of biding factors which are responsible for the rapid clearance of acidic isoferritins from the circulation. The serum concentration of basic ferritin, however, can be useful in the diagnosis and management of some malignancies, and it is possible that studies on cell isoferritins can be important in biologic monitoring of neoplastic disorders. It should also be noted that the increased levels of serum ferritin found in patients with malignancy can exert adverse effects on the host immune response and perhaps an inhibitory effect on hematopoiesis.

Characterization of magnetic nanoparticles from Magnetospirillum Gryphiswaldense as potential theranostics tools

We investigated the theranostic properties of magnetosomes (MNs) extracted from magnetotactic bacteria, promising for nanomedicine applications. Besides a physico-chemical characterization, their potentiality as mediators for magnetic fluid hyperthermia and contrast agents for magnetic resonance imaging, both in vitro and in vivo, are here singled out. The MNs, constituted by magnetite nanocrystals arranged in chains, show a superparamagnetic behaviour and a clear evidence of Verwey transition, as signature of magnetite presence. The phospholipid membrane provides a good protection against oxidation and the MNs oxidation state is stable over months. Using an alternate magnetic field, the specific absorption rate was measured, resulting among the highest reported in literature. The MRI contrast efficiency was evaluated by means of the acquisition of complete NMRD profiles. The transverse relaxivity resulted as high as the one of a former commercial contrast agent. The MNs were inoculated into an animal model of tumour and their presence was detected by magnetic resonance images two weeks after the injection in the tumour mass.

A possible novel objective intraoperative measurement of maxillary bone density

AIM

Implant survival and success rates are strictly related to the density of the bone they are placed in. Bone density, in fact, affects both implant primary stability and implant micromovements after implant positioning. Current bone density classifications rely on subjective, scarcely reproducible evaluations. A novel implant micro motor featuring a bone density measurement probe has been recently introduced. The objective of this study was to test such bone density measurement system for its capability of distinguishing different bone density areas in the upper and in the lower jaw.

METHODS

1254 implant placement sites had their bone density measured during standard implant placement at a single clinical facility. After data collection bone density distribution was statistically analyzed in order to test the hypothesis of a non-homogeneous distribution in four different predefined anatomical maxillary zones, namely pre-antral (between teeth from 14 to 24) and sub-antral (more distally) in the upper maxilla and interforaminal (between and including teeth from 34 to 44) and retroforaminal (more distally) zone.

RESULTS

Measured bone density values, organized according the named four anatomical zones, produced a statistically significant inhomogeneous pattern (P<0.001). Density distribution was consistent with data from literature, but not always corresponding with the one achieved by applying the well known Misch classification.

CONCLUSION

The measuring system we tested allowed to distinguish different and clinically significant anatomical zones according to their different bone density, and can represent a fundamental diagnostic tool to plan the proper implant placement steps.

NMR-D study of the local spin dynamics and magnetic anisotropy in different nearly monodispersed ferrite nanoparticles

We present a systematic experimental comparison of the superparamagnetic relaxation time constants obtained by means of dynamic magnetic measurements and (1)H-NMR relaxometry, on ferrite-based nanosystems with different composition, various core sizes and dispersed in different solvents. The application of a heuristic model for the relaxivity allowed a comparison between the reversal time of magnetization as seen by NMR and the results from the AC susceptibility experiments, and an estimation of fundamental microscopic properties. A good agreement between the NMR and AC results was found when fitting the AC data to a Vogel-Fulcher law. Key parameters obtained from the model have been exploited to evaluate the impact of the contribution from magnetic anisotropy to the relaxivity curves and estimate the minimum approach distance of the bulk solvent.

Multifunctional nanoparticles for dual imaging

For imaging with different modalities, labels, which provide contrast for all modalities, are required. Colloidal nanoparticles composed out of an inorganic core and a polymer shell offer progress in this direction. Both, the core and the polymer shell, can be synthesized to be fluorescent, magnetic, or radioactive. When different cores are combined with different polymer shells, different types of particles for dual imaging can be obtained, as for example, fluorescent cores with radioactive polymer shells. Properties and perspectives of such nanoparticles for multimodal imaging are discussed.

Flow cytometry evaluation of erythroid dysplasia in patients with myelodysplastic syndrome

Erythroid dysplasia is the pathologic hallmark of myelodysplastic syndromes (MDS). To develop a quantitative flow-cytometry approach to its evaluation, we analyzed the expression of CD71, CD105, cytosolic H-ferritin (HF), cytosolic L-ferritin (LF) and mitochondrial ferritin (MtF) in erythroblasts from 104 MDS patients, 69 pathologic control patients and 19 healthy subjects. Six-parameter, 4-color flow cytometry was employed, and data were expressed as mean fluorescence intensity. Compared with pathologic and healthy controls, MDS patients had higher expression of HF (P < 0.001) and CD105 (P < 0.001), and lower expression of CD71 (P < 0.001). MtF was specifically detected in MDS with ringed sideroblasts, and there was a close relationship between its expression and Prussian blue staining (r = 0.89, P < 0.001). In vitro cultures of myelodysplastic hematopoietic progenitors showed that both HF and MtF were expressed at a very early stage of erythroid differentiation, and that MtF expression is specifically related to mitochondrial iron loading. A classification function based on expression levels of HF, CD71 and CD105 allowed us to correctly classify > 95% of MDS patients. This flow-cytometry approach provides an accurate quantitative evaluation of erythroid dysplasia and allows a reliable diagnosis of sideroblastic anemia, and may therefore be a useful tool in the work-up of patients with MDS.

Biochemical and genetic defects underlying human congenital hypotransferrinemia

INTRODUCTION

Human congenital hypotransferrinemia is a rare disorder characterized by the virtual absence of transferrin in the serum. No information on the causes of the disease is known.

MATERIALS AND METHODS

Here we describe the identification of a new case, its treatment and the biochemical and genetic defects underlying the disorder.

RESULTS

At diagnosis the patient had serum Tf levels equal to about 1% of the normal values. The treatment with plasma infusions each month allowed a good erythropoiesis and the prevention of iron overload with no need of red blood cell transfusions or iron chelators. In order to define the genetic basis of the disease, we performed a haplotype analysis of the Tf gene region in the 26 individuals forming the proband's family, and demonstrated that the genetic defect is located in the Tf gene and that it is inherited as a recessive trait. Protein analyses indicate that the proband serum contains two transferrin forms: one of 80 kD analogous to the normal one, and a smaller one of 50 kD, which may arise from a specific degradation or be the gene product of a modified allele.

CONCLUSION

These data suggest the presence of two Tf alleles carrying genetic defects that cause two distinct abnormalities. One allele causes low expression of an apparently normal protein that probably allowed the survival of the patient in the first years of age. The other allele produces a modified Tf with different biochemical characteristics compared to the normal one.

Denatured H-ferritin subunit is a major constituent of haemosiderin in the liver of patients with iron overload

BACKGROUND AND AIMS

Iron is stored in hepatocytes in the form of ferritin and haemosiderin. There is a marked increase in iron rich haemosiderin in iron overloaded livers, and ferric iron in amounts exceeding the ferritin and haemosiderin binding capacity may promote free radical generation, causing cellular damage. The aim of this study was to characterise hepatic haemosiderin using four antibodies specific for either native or denatured H/L-ferritin subunits.

METHODS

Ferritin and haemosiderin were prepared from the livers of three patients with post-transfusional iron overload. The assembled ferritin molecules were analysed by non-denaturing polyacrylamide gel electrophoresis (PAGE)-immunoblotting. Ferritin subunits in the haemosiderin fraction were assessed by denaturing sodium dodecyl sulphate (SDS)-PAGE-immunoblotting. Distribution of native and denatured ferritin subunits in hepatocytes was examined by immunogold electron microscopy.

RESULTS

Non-denaturing PAGE-immunoblot analyses showed that the assembled liver ferritins were recognised by the antibodies for native ferritins and not by those for the denatured subunits. Both SDS-PAGE-immunoblot and immunogold electron microscopic analyses disclosed that haemosiderin of iron overloaded liver reacted predominantly to the monoclonal antibody for the denatured H-ferritin subunit, to a lesser degree to that for denatured L-ferritin, and very weakly, if any, with antibodies for native H-ferritin or L-ferritin.

CONCLUSIONS

These results suggest that in iron overloaded liver, haemosiderin consists predominantly of denatured H-ferritin subunits.

Structure of mouse L-chain ferritin at 1.6 A resolution

Cubic F432 crystals of recombinant mouse L-chain apoferritin were obtained by the hanging-drop technique with ammonium sulfate and cadmium sulfate as precipitants. The structure was refined to 2.1 and 1.6 A resolution from data obtained at room temperature and under cryogenic conditions, respectively. The structure of an eight-amino-acid loop insertion in the mouse sequence is found to be highly disordered both at room temperature and at low temperature.

Is hydrogen peroxide produced during iron(II) oxidation in mammalian apoferritins?

The ferritins are a class of iron storage and detoxification proteins that play a central role in the biological management of iron. These proteins have a catalytic site, "the ferroxidase site", located on the H-type subunit that facilitates the oxidation of Fe(II) to Fe(III) by O(2). Measurements during the past 10 years on a number of vertebrate ferritins have provided evidence that H(2)O(2) is produced at this diiron ferroxidase site. Recently reported experiments using three different analytical methods with horse spleen ferritin (HoSF) have failed to detect H(2)O(2) production in this protein [Lindsay, S., Brosnahan, D., and Watt, G. D. (2001) Biochemistry 40, 3340-3347]. These findings contrast with earlier results reporting H(2)O(2) production in HoSF [Xu, B., and Chasteen, N. D. (1991) J. Biol. Chem. 266, 19965-19970]. Here a sensitive fluorescence assay and an assay based on O(2) evolution in the presence of catalase were used to demonstrate that H(2)O(2) is produced in HoSF as previously reported. However, because of the relatively few H-chain ferroxidase sites in HoSF and the reaction of H(2)O(2) with the protein, H(2)O(2) is more difficult to detect in this ferritin than in recombinant human H-chain ferritin (HuHF). The proper sequence of addition of reagents is important for measurement of the total amount of H(2)O(2) produced during the ferroxidation reaction.

A human mitochondrial ferritin encoded by an intronless gene

Ferritin is a ubiquitous protein that plays a critical role in regulating intracellular iron homoeostasis by storing iron inside its multimeric shell. It also plays an important role in detoxifying potentially harmful free ferrous iron to the less soluble ferric iron by virtue of the ferroxidase activity of the H subunit. Although excess iron is stored primarily in cytoplasm, most of the metabolically active iron in cells is processed in mitochondria. Little is yet known of how these organelles regulate iron homeostasis and toxicity. Here we report an unusual intronless gene on chromosome 5q23.1 that encodes a 242-amino acid precursor of a ferritin H-like protein. This 30-kDa protein is targeted to mitochondria and processed to a 22-kDa subunit that assembles into typical ferritin shells and has ferroxidase activity. Immunohistochemical analysis showed that it accumulates in high amounts in iron-loaded mitochondria of erythroblasts of subjects with impaired heme synthesis. This new ferritin may play an important role in the regulation of mitochondrial iron homeostasis and heme synthesis.

Immunosuppressive effects of melanoma-derived heavy-chain ferritin are dependent on stimulation of IL-10 production

Cultured melanoma cells release soluble factors that influence immune responses. Screening of a cDNA library with anti-sera from a melanoma patient identified an immunoreactive plaque, which encoded heavy-chain ferritin (H-ferritin). Previous studies have drawn attention to the immunosuppressive effects of this molecule and prompted further studies on its biochemical and functional properties in human melanoma. These studies demonstrated, firstly, that H-ferritin appeared to be secreted by melanoma cells, as shown by immunoprecipitation of a 21.5 kDa band from supernatants. It was also detected in extracts of melanoma cells by Western blotting as 43 and 64 kDa dimers and trimers of the 21.5 kDa fraction. Secondly, flow-cytometric analysis of H- and light-chain ferritin (L-ferritin) expression on melanoma showed a wide variation in L-ferritin expression and consequently of the ratio of H- to L-ferritin expression. Suppression of mitogenic responses of lymphocytes to anti-CD3 showed a correlation with the ratio of H- to L-ferritin in the supernatants and was specific for H-ferritin, as shown by inhibition studies with a monoclonal antibody (MAb) against H-ferritin. Similar results were obtained with H- and L-ferritin from other sources. Suppression of mitogenic responses of lymphocytes to anti-CD3 by H-ferritin was inhibited using a MAb against IL-10, which suggested that the immunosuppressive effect of H-ferritin was mediated by IL-10. Assays of cytokine production from anti-CD3-stimulated lymphocytes showed that H-ferritin markedly increased production of IL-10 and IFN-gamma and had only slight effects on IL-2 and IL-4 production. Our results suggest that melanoma cells may be a major source of H-ferritin and that production of the latter may account for some of the immunosuppressive effects of melanoma.

Double-gradient denaturing gradient gel electrophoresis assay for identification of L-ferritin iron-responsive element mutations responsible for hereditary hyperferritinemia-cataract syndrome: identification of the new mutation C14G

BACKGROUND

Hereditary hyperferritinemia-cataract syndrome is an autosomic dominant disorder caused by heterogeneous mutations on the iron-responsive element (IRE) of ferritin L-chain mRNA. The mutations described to date were identified by direct sequencing of DNA from probands with hyperferritinemia often associated to bilateral cataracts. A direct genetic approach on a large population is useful to recognize polymorphisms in the DNA region and the prevalence of mutations associated with minor increases in serum ferritin and subclinical cataracts. We developed a rapid DNA scanning technique to detect mutations in a single electrophoretic analysis.

METHODS

The double-gradient denaturing gradient gel electrophoresis (DG-DGGE) method consisted of PCR amplification of the target genomic DNA with GC-clamped oligonucleotides. The sequence encoded the 5' untranslated flanking region of ferritin L-chain mRNA, which includes an IRE stem-loop structure. The product was subjected to DG-DGGE (8.5-15% polyacrylamide and 50-95% denaturant) to separate the homo- and heteroduplexes.

RESULTS

The method clearly identified all eight accessible mutations, including C-G transversions, which are the most difficult to detect. The method was applied to scan DNA samples from 50 healthy subjects and from 230 subjects with serum ferritin >400 microg/L. The new mutation G14C was identified.

CONCLUSIONS

The DG-DGGE method detects all the mutations in the L-ferritin IRE sequence, is rapid and economical, and can be applied to scan large populations. The first population study indicated that the mutations are rare and may involve regions of the IRE structure not yet characterized.

Relationship between TNF-alpha and iron metabolism in differentiating human monocytic THP-1 cells

The human monocytic cell line THP-1 differentiates along the macrophage line after phorbol-12-myristate-13-acetate (PMA) supplementation and can be stimulated to secrete tumour necrosis factor alpha (TNF-alpha) by interferon gamma (IFN-gamma) addition. We found that, in the early stage of differentiation (1-48 h), PMA induction elicited an upregulation of intracellular H ferritin and H ferritin binding sites and a downregulation of transferrin receptor. In addition, we found that iron administration to PMA-differentiating cells induced the expression of TNF-alpha mRNA and TNF-alpha secretion to levels even higher than those induced by IFN-gamma alone. The iron chelator desferrioxamine showed the opposite effect and reduced TNF-alpha release. In contrast, preincubation of the cells with iron before PMA induction resulted in a decrease of the TNF-alpha secretion induced by IFN-gamma, whereas the opposite was true after preincubation with desferrioxamine. The data support a co-ordinate interaction between iron and TNF-alpha in monocyte macrophages, with an iron-mediated upregulation of TNF-alpha in the early phase of differentiation and an iron-mediated inhibition at later stages. This complex relationship has to be considered in evaluating the effects of iron on inflammation.

Expression, refolding, and ferritin-binding activity of the isolated VL-domain of monoclonal antibody F11

Expression of the VL-domain of mouse monoclonal antibody F11 to human spleen ferritin in Escherichia coli cells is associated with the formation of insoluble protein aggregates (inclusion bodies). The aggregates were solubilized in the presence of guanidine hydrochloride and the recombinant VL-domain was purified by immobilized metal affinity chromatography (IMAC). Subsequent renaturation results in approximately 99% pure preparation with high yield. The VL-domain forms dimers at concentrations from 1 to 10 mg/ml. Monomeric form is detected only at protein concentrations below 0.5 mg/ml. Functional activity of the VL-domain was verified by two variants of ELISA. The affinity of the VL-domain ((0.2-1.2). 108 M(-1)) is similar to the affinity of the full-length parental antibody F11 because when the immobilized VL-domain was used, the binding constant of ferritin to the VL-domain was only 4-6-fold lower than that in the case of F11 antibody. In another ELISA system with immobilized ferritin, affinity was decreased 30-fold. The VL-domain of antibody F11 is the first example of the recombinant variable domain of the immunoglobulin light chain that preserves the antigen-binding activity in the absence of the partner VH-domain. The data indicate that the recombinant VL-domain can be used in construction of chimeric immunotoxins and other antigen-binding proteins in immunotherapy and in studies of correlations between folding, stability, and activity of immunoglobulins.

Overexpression of wild type and mutated human ferritin H-chain in HeLa cells: in vivo role of ferritin ferroxidase activity

Transfectant HeLa cells were generated that expressed human ferritin H-chain wild type and an H-chain mutant with inactivated ferroxidase activity under the control of the tetracycline-responsive promoter (Tet-off). The clones accumulated exogenous ferritins up to levels 14-16-fold over background, half of which were as H-chain homopolymers. This had no evident effect in the mutant ferritin clone, whereas it induced an iron-deficient phenotype in the H-ferritin wild type clone, manifested by approximately 5-fold increase of IRPs activity, approximately 2.5-fold increase of transferrin receptor, approximately 1.8-fold increase in iron-transferrin iron uptake, and approximately 50% reduction of labile iron pool. Overexpression of the H-ferritin, but not of the mutant ferritin, strongly reduced cell growth and increased resistance to H(2)O(2) toxicity, effects that were reverted by prolonged incubation in iron-supplemented medium. The results show that in HeLa cells H-ferritin regulates the metabolic iron pool with a mechanism dependent on the functionality of the ferroxidase centers, and this affects, in opposite directions, cellular growth and resistance to oxidative damage. This, and the finding that also in vivo H-chain homopolymers are much less efficient than the H/L heteropolymers in taking up iron, indicate that functional activity of H-ferritin in HeLa cells is that predicted from the in vitro data.

Antiferritin single-chain Fv fragment is a functional protein with properties of a partially structured state: comparison with the completely folded V(L) domain

Differential scanning calorimetry and spectroscopic probes were applied to study folding and stability of the single-chain Fv fragment (scFv) of the anti-human ferritin antibody F11 and its isolated variable light-chain (V(L)) domain. The scFv fragment followed variable heavy-chain domain (V(H))-linker-V(L) orientation and contained (Gly(4)Ser)(3) linker peptide. The two proteins were produced in Escherichia coli and refolded from denaturant-solubilized inclusion bodies. The isolated V(L) domain demonstrated a typical immunoglobulin fold with well-defined secondary and tertiary structure and was capable of binding human ferritin with K(a) = 1.8 x 10(7) M(-)(1), approximately (1)/(30) of the affinity of the parent F11 antibody. Involvement of this V(L) domain into the two-domain scFv fragment yielded a distorted secondary and significantly destabilized tertiary structure in which neither of the two constituent domains attained complete folding. The thermal unfolding enthalpy of scFv F11 at pH 7.0 was as low as 5. 0 J.g(-)(1) versus 16.3 J.g(-)(1) obtained for the V(L) domain and 24.7 J.g(-)(1) for the parent F11 antibody (mouse IgG2a subclass). Intrinsic fluorescence and near-ultraviolet circular dichroic (CD) spectra, and binding of the hydrophobic probe 8-anilino-1-naphthalene sulfonate, confirmed partial loss of tertiary interactions in scFv. The spectroscopic and calorimetric properties of scFv F11 under physiological conditions are consistent with a model of a partially structured state with a distorted beta-sheet as a secondary structure and partial loss of tertiary interactions, which closely resembles the alternatively folded A-state adopted by an immunoglobulin at pH 2-3 [Buchner, J., Renner, M., Lilie, H., Hinz, H.-J., Jaenicke, R., Kiefhaber, T., and Rudolph, R. (1991) Biochemistry 30, 6922-6929]. However, scFv F11 demonstrated only an approximately 4-fold decrease in the antigen-binding affinity (K(a) = 1.3 x 10(8) M(-)(1)) versus the parent F11 antibody. The scFv fragment F11 provides the first description of a functional protein trapped under physiological conditions in a partially structured state. This state is either close to the native one in the antigen-binding affinity or, alternatively, initial weak binding of the antigenic epitope induces folding of scFv F11 into a more structured conformation that generates relatively high affinity.

Deficient ferritin immunoreactivity in tissues from niemann-pick type C patients: extension of findings to fetal tissues, H and L ferritin isoforms, but also one case of the rare Niemann-Pick C2 complementation group

Previous studies employing rabbit polyclonal anti-human liver ferritin have shown an absence of L ferritin immunoreactivity in liver and spleen tissue from patients with Niemann-Pick disease type C1 (NPC1). The great majority of NPC cases is caused by defects of the NPC1 gene, and a minority by those of another (NPC2). In this study using polyclonal and monoclonal antibodies we show the deficiency of H and L ferritin isoforms in various NPC tissues, including fetal NPC1, not previously described. In particular, evidence is provided for deficiency in H and L ferritins in tissues, except lung, from a patient with Niemann-Pick disease type C2 (NPC2). The present findings indicate that H and L ferritins are deficient in both NPC types characterized by accumulation of unesterified cholesterol and additional metabolites in the endosomal/lysosomal system. We hypothesize that the lesions in NPC1 and NPC2 block the intracellular utilization not only of cholesterol, but also that of iron for the synthesis of cytosolic ferritin.

Functional and immunological analysis of recombinant mouse H- and L-ferritins from Escherichia coli

The production and characterization of recombinant mouse H- and L-ferritin chains from Escherichia coli are described. The proteins were efficiently expressed and purified with yields of 7-40 mg per liter of cell culture. They had the expected molecular mass and showed a physical stability analogous to that of the corresponding human ferritins. Mouse H- and L-ferritins had a very similar mobility on denaturing SDS-PAGE, but could be readily separated on nondenaturing PAGE because of the distinct slow mobility of mouse L-ferritin. Direct comparative experiments showed that mouse and human H-ferritins had the same iron incorporation activity, whereas mouse L-ferritin incorporated iron less efficiently than human L-ferritin. The difference was attributed to the substitution of a residue exposed on the cavity surface (Glu140 --> Lys) in mouse L-ferritin, a hypothesis confirmed by the finding that the mouse L-ferritin mutant Lys140-Glu incorporated iron as efficiently as human L-ferritin. Rabbit antisera elicited by the recombinant mouse ferritins were specific for the H- and L-chains and did not cross-react with the human ferritins. The antibodies and the derived specific ELISA assays allow the determination of H- and L-ferritins in mouse tissues.

Vanadyl(IV) binding to mammalian ferritins. An EPR study aided by site-directed mutagenesis

During its metabolism, vanadium is known to become associated with the iron storage protein, ferritin. To elucidate probable vanadium binding sites on the protein, VO2+ binding to mammalian ferritins was studied using site-directed mutagenesis and EPR spectroscopy. VO2+-apoferritin EPR spectra of human H-chain (100% H), L-chain (100% L), horse spleen (84% L, 16% H) and sheep spleen (45% L, 55% H) ferritins revealed the presence of alpha and beta VO2+ species in all the proteins, implying that the ligands for these species are conserved between the H- and L-chains. The alpha species is less stable than the beta species and decreases with increasing pH, demonstrating that the two species are not pH-related, a result contrary to earlier proposals. EPR spectra of site-directed HuHF variants of several residues conserved in H- and L-chain ferritins (Asp-131, Glu-134, His-118 and His-128) suggest that His-118 near the outer opening of the three-fold channel is probably a ligand for VO2+ and is responsible for the beta signals in the EPR spectrum. The data indicate that VO2+ does not bind to the Asp-131 and Glu-134 residues within the three-fold channels nor does it bind at the ferroxidase site residues Glu-62 or His-65 or at the putative nucleation site residues Glu-61,64,67. While the ferroxidase site is not a site for VO2+ binding, mutation of residues Glu-62 and His-65 of this site to Ala affects VO2+ binding at His-118, located some 17 A away. Thus, VO2+ spin probe studies provide a window on structural changes in ferritin not seen in most previous work and indicate that long-range effects caused by point mutations must be carefully considered when drawing conclusions from mutagenesis studies of the protein.

Crystallization and preliminary X-ray diffraction data of mouse L-chain apoferritin crystals

Crystals of recombinant mouse L-chain apoferritin were obtained by the hanging-drop technique using ammonium sulfate as precipitant. Two crystal forms were observed in the same drop. The crystals belong to either the P2 monoclinic or to the P42(1)2 tetragonal space group. The monoclinic crystals diffracted to beyond 2.4 A resolution but were systematically twinned, while the tetragonal crystals diffracted to beyond 2.9 A. These crystallization conditions in the absence of metal salts should facilitate the study of the interaction between L-chain ferritins and heavy metals, particularly the iron core.

Immunohistochemistry of HFE in the duodenum of C282Y homozygotes with antisera for recombinant HFE protein

BACKGROUND AND OBJECTIVE

HFE is a class-I MHC related protein which carries the C282Y mutation in most patients with hereditary hemochromatosis, an iron overload disease. HFE protein is expected to have a relevant role in the regulation of duodenal iron absorption, and HFE protein was immunohistochemically identified in the crypt cells. The aim of the work was to analyze whether the C282Y mutation affects HFE accumulation in the duodenum.

DESIGN AND METHODS

We developed antisera for the extracellular portion of recombinant human HFE protein expressed in E. coli. The antisera were specific for HFE protein and the C282Y mutant in immunoblotting, immunoprecipitation and immunocytochemistry experiments of transfected cells, and they did not cross react with HLA antigens in various analyses. The antisera gave positive results in the staining of paraffin-fixed sections of duodenal slices of subjects with hemochromatosis.

RESULTS

The antisera stained evident supranuclear granules in all enterocytes of 7 C282Y homozygous subjects, and a dark area in the same region in 3 other C282Y homozygotes. Granular bodies were absent from the duodenal sections of 8 C282Y negative subjects, from 2 C282Y heterozygotes and 3 C282Y homozygotes, with or without hemochromatosis.

INTERPRETATION AND CONCLUSIONS

The detection of HFE-protein in granular bodies in the enterocytes of the large majority (77%) of C282Y homozygotes and not in other subjects suggests that the mutation facilitates protein accumulation in the duodenum.

Molecular diffusion into ferritin: pathways, temperature dependence, incubation time, and concentration effects

The detailed kinetics of permeation and effusion of small nitroxide spin probe radicals with the protein shells of horse spleen ferritin (HoSF) and human H-chain ferritin (HuHF) and a 3-fold channel variant D131H+E134H of HuHF were studied by electron paramagnetic resonance spectroscopy and gel permeation chromatography under a variety of experimental conditions. The results confirm that the permeation of molecular species of 7-9-A diameter into ferritin is a charge selective process and that the threefold channels are the likely pathways for entry into the protein. Studies with holoHoSF show that increased temperature increases the rates of penetration and effusion and also increases the concentration of positively charged spin probe accumulated within the protein in excess of that in the external solution. The interior of HoSF is much more accessible to small molecules at physiological temperature of approximately 40 degrees C than at room temperature. The large activation energy of 63-67 kJ/mol measured for the effusion/penetration and the small diffusion coefficient, D approximately 5 x 10(-22) m(2)/s at 20 degrees C, corresponding to a time of approximately 60 min for traversing the protein shell, is consistent with the kinetics of diffusion being largely controlled by the restrictive porosity of the protein itself. An inverse dependence of the first-order rate constant for effusion out of the protein channel on the incubation time used for radical penetration into the protein is attributed to increased binding of the radical within the funnel-shaped channel.

A new mutation (G51C) in the iron-responsive element (IRE) of L-ferritin associated with hyperferritinaemia-cataract syndrome decreases the binding affinity of the mutated IRE for iron-regulatory proteins

Hereditary hyperferritinaemia-cataract syndrome is an autosomal dominant disorder characterized by a constitutively increased synthesis of L-ferritin in the absence of iron overload. The disorder is associated with point mutations in the iron-responsive element (IRE) of L-ferritin mRNA. We report a new mutation, G51C, identified in two members of a Canadian family, presenting a moderate increase in serum ferritin and a clinically silent bilateral cataract. Gel retardation assays showed that the binding of the mutated IRE to iron-regulatory proteins (IRPs) was reduced compared with the wild type. Structural modelling predicted that the G51C induces a rearrangement of base pairing at the lateral bulge of the IRE structure which is likely to modify IRE conformation.

Early embryonic lethality of H ferritin gene deletion in mice

Ferritin molecules play an important role in the control of intracellular iron distribution and in the constitution of long term iron stores. In vitro studies on recombinant ferritin subunits have shown that the ferroxidase activity associated with the H subunit is necessary for iron uptake by the ferritin molecule, whereas the L subunit facilitates iron core formation inside the protein shell. However, plant and bacterial ferritins have only a single type of subunit which probably fulfills both functions. To assess the biological significance of the ferroxidase activity associated with the H subunit, we disrupted the H ferritin gene (Fth) in mice by homologous recombination. Fth(+/-) mice are healthy, fertile, and do not differ significantly from their control littermates. However, Fth(-/-) embryos die between 3.5 and 9.5 days of development, suggesting that there is no functional redundancy between the two ferritin subunits and that, in the absence of H subunits, L ferritin homopolymers are not able to maintain iron in a bioavailable and nontoxic form. The pattern of expression of the wild type Fth gene in 9.5-day embryos is suggestive of an important function of the H ferritin gene in the heart.

The X-ray three-dimensional structure of avidin

Avidin is a basic, highly stable, homotetrameric protein, isolated from bird egg-white, binding up to four molecules of D-biotin with extremely high affinity (Kd approximately 10(-15) M). The protein has been the object of different crystallographic investigations. In all the crystal structures, the four avidin subunits display almost exact 222 symmetry. Each avidin chain (128 amino acids) is arranged in a eight-stranded antiparallel beta-barrel, whose inner region defines the D-biotin binding site. The molecular bases of D-biotin affinity can be recognised in a fairly rigid binding site, which is sterically complementary to the shape and polarity of the incoming vitamin, and is readily accessible in the apoprotein structure. Avidin displays remarkable structural and functional relationships to the acidic protein sretpavidin, isolated from Streptomyces avidinii.

Overexpression of the hereditary hemochromatosis protein, HFE, in HeLa cells induces and iron-deficient phenotype

A transfectant HeLa cell clone expressing HFE under the control of a tetracycline-repressible promoter was generated. HFE expression was fully repressed by the presence of doxycycline, while it was strongly induced by growth in the absence of doxycycline. HFE accumulation was accompanied by a large (approximately 10-fold) decrease in H- and L-ferritin levels, by a approximately 3-4-fold increase in transferrin receptor, and a approximately 2-fold increase in iron regulatory protein activity. These indices of cellular iron deficiency were reversed by iron supplementation complexes. The overexpressed HFE immunoprecipitated together with transferrin receptor, indicating a physical association which is the likely cause for the observed approximately 30% decrease in 55Fe-transferrin incorporation after 18 h incubation. In the HFE-expressing cells the reduction in transferrin-mediated iron incorporation was partially compensated by a approximately 30% increase in non-transferrin iron incorporation from 55Fe-NTA, evident after prolonged, 18 h, incubations. The findings indicate that HFE binding to transferrin receptor reduces cellular iron availability and regulates the balance between transferrin-mediated and non-transferrin-mediated cellular iron incorporation.

An immunoglobulin-like fold in a major plant allergen: the solution structure of Phl p 2 from timothy grass pollen

BACKGROUND

Grass pollen allergens are the most important and widespread elicitors of pollen allergy. One of the major plant allergens which millions of people worldwide are sensitized to is Phl p 2, a small protein from timothy grass pollen. Phl p 2 is representative of the large family of cross-reacting plant allergens classified as group 2/3. Recombinant Phl p 2 has been demonstrated by immunological cross-reactivity studies to be immunologically equivalent to the natural protein.

RESULTS

We have solved the solution structure of recombinant Phl p 2 by means of nuclear magnetic resonance techniques. The three-dimensional structure of Phl p 2 consists of an all-beta fold with nine antiparallel beta strands that form a beta sandwich. The topology is that of an immunoglobulin-like fold with the addition of a C-terminal strand, as found in the C2 domain superfamily. Lack of functional and sequence similarity with these two families, however, suggests an independent evolution of Phl p 2 and other homologous plant allergens.

CONCLUSIONS

Because of the high homology with other plant allergens of groups 1 and 2/3, the structure of Phl p 2 can be used to rationalize some of the immunological properties of the whole family. On the basis of the structure, we suggest possible sites of interaction with IgE antibodies. Knowledge of the Phl p 2 structure may assist the rational structure-based design of synthetic vaccines against grass pollen allergy.