MALDI-mass spectrometry imaging as a new technique for detecting non-heme iron in peripheral tissues via caudal vein injection of deferoxamine

As one of the most common iron-chelating agents, deferoxamine (DFO) rapidly chelates iron in the body. Moreover, it does not compete for the iron characteristic of hemoglobin in the blood cells, which is common in the clinical treatment of iron poisoning. Iron is a trace element necessary to maintain organism normal life activities. Iron deficiency can lead to anemia, whereas iron overload can cause elevated levels of cellular oxidative stress and cell damage. As a consequence, detection of the iron content in tissues and blood is of great significance. The traditional techniques for detecting the iron content include inductively coupled plasma-mass spectrometry and atomic absorption spectrometry, which cannot be used for imaging purposes. Laser ablation-ICP-MS and synchrotron radiation micro-X-ray fluorescence can map the concentration and distribution of iron in tissues. However, these methods can only be used to measure the total iron levels in blood or tissues. In recent years, due to the deepening understanding of iron metabolism, diseases related to iron overload have attracted increasing attention. Therefore, we took advantage of the properties of DFO in terms of chelating iron and investigated different sampling times following DFO injection in the tail vein of mice. We used mass spectrometry imaging (MSI) technology to detect the DFO and ferrioxamine content in the blood and different tissues to indirectly characterize the non-heme iron content.

Preparation of a Zirconium-89 Labeled Clickable DOTA Complex and Its Antibody Conjugate

Desferrioxamine B (DFO) is the clinical standard chelator for preparing zirconium-89 labeled antibodies. In the current study, the stabilities of a zirconium-89 labeled panitumumab (PAN; Vectibix®) with three different chelators (DFO, DFO*, and DOTA) were compared. PAN is an anti-HER1/EGFR monoclonal antibody approved by the FDA for the treatment of HER1-expressing colorectal cancers and was used as the model antibody for this study. DFO/DFO* conjugates of PAN were directly radiolabeled with zirconium-89 at room temperature to produce [89Zr]Zr-DFO/DFO*-PAN conjugates following a well-established procedure. A zirconium-89 labeled DOTA-PAN conjugate was prepared by an indirect radiolabeling method. A cyclooctyne-linked DOTA chelator (BCN-DOTA-GA) was first radiolabeled with zirconium-89 at 90 °C under a two-step basic pH adjustment method followed by conjugation with PAN-tetrazene at 37 °C to produce a labeled conjugate, BCN-[89Zr]Zr-DOTA-GA-PAN. High reproducibility of the radiolabeling was observed via this two-step basic pH adjustment. The overall radiochemical yield was 40-50% (n = 12, decay uncorrected) with a radiochemical purity of >95% in 2 h synthesis time. All three conjugates were stable in whole human serum for up to 7 days at 37 °C. The kinetic inertness of the conjugates was assessed against the EDTA challenge. BCN-[89Zr]Zr-DOTA-GA-PAN exhibited excellent inertness followed by [89Zr]Zr-DFO*-PAN. [89Zr]Zr-DFO-PAN displayed the lowest level of inertness.

Chelating Effect of Siderophore Desferrioxamine-B on Uranyl Biomineralization Mediated by Shewanella putrefaciens

In contaminated water and soil, little is known about the role and mechanism of the biometabolic molecule siderophore desferrioxamine-B (DFO) in the biogeochemical cycle of uranium due to complicated coordination and reaction networks. Here, a joint experimental and quantum chemical investigation is carried out to probe the biomineralization of uranyl (UO22+, referred to as U(VI) hereafter) induced by Shewanella putrefaciens (abbreviated as S. putrefaciens) in the presence of DFO and Fe3+ ion. The results show that the production of mineralized solids {hydrogen-uranium mica [H2(UO2)2(PO4)2·8H2O]} via S. putrefaciens binding with UO22+ is inhibited by DFO, which can both chelate preferentially UO22+ to form a U(VI)-DFO complex in solution and seize it from U(VI)-biominerals upon solvation. However, with Fe3+ ion introduced, the strong specificity of DFO binding with Fe3+ causes re-emergence of biomineralization of UO22+ {bassetite [Fe(UO2)2(PO4)2·8(H2O)]} by S. putrefaciens, owing to competitive complexation between Fe3+ and UO22+ for DFO. As DFO possesses three hydroxamic functional groups, it forms hexadentate coordination with Fe3+ and UO22+ ions via these functional groups. The stability of the Fe3+-DFO complex is much higher than that of U(VI)-DFO, resulting in some DFO-released UO22+ to be remobilized by S. putrefaciens. Our finding not only adds to the understanding of the fate of toxic U(VI)-containing substances in the environment and biogeochemical cycles in the future but also suggests the promising potential of utilizing functionalized DFO ligands for uranium processing.

Developing Iron Nanochelating Agents: Preliminary Investigation of Effectiveness and Safety for Central Nervous System Applications

Excessive iron levels are believed to contribute to the development of neurodegenerative disorders by promoting oxidative stress and harmful protein clustering. Novel chelation treatments that can effectively remove excess iron while minimizing negative effects on the nervous system are being explored. This study focuses on the creation and evaluation of innovative nanobubble (NB) formulations, shelled with various polymers such as glycol-chitosan (GC) and glycol-chitosan conjugated with deferoxamine (DFO), to enhance their ability to bind iron. Various methods were used to evaluate their physical and chemical properties, chelation capacity in diverse iron solutions and impact on reactive oxygen species (ROS). Notably, the GC-DFO NBs demonstrated the ability to decrease amyloid-β protein misfolding caused by iron. To assess potential toxicity, in vitro cytotoxicity testing was conducted using organotypic brain cultures from the substantia nigra, revealing no adverse effects at appropriate concentrations. Additionally, the impact of NBs on spontaneous electrical signaling in hippocampal neurons was examined. Our findings suggest a novel nanochelation approach utilizing DFO-conjugated NBs for the removal of excess iron in cerebral regions, potentially preventing neurotoxic effects.

Evaluation of Chelator-to-Antibody Ratio on Development of 89Zr-iPET Tracer for Imaging of PD-L1 Expression on Tumor

89Zr-iPET has been widely used for preclinical and clinical immunotherapy studies to predict patient stratification or evaluate therapeutic efficacy. In this study, we prepared and evaluated 89Zr-DFO-anti-PD-L1-mAb tracers with varying chelator-to-antibody ratios (CARs), including 89Zr-DFO-anti-PD-L1-mAb_3X (tracer_3X), 89Zr-DFO-anti-PD-L1-mAb_10X (tracer_10X), and 89Zr-DFO-anti-PD-L1-mAb_20X (tracer_20X). The DFO-anti-PD-L1-mAb conjugates with varying CARs were prepared using a random conjugation method and then subjected to quality control. The conjugates were radiolabeled with 89Zr and evaluated in a PD-L1-expressing CT26 tumor-bearing mouse model. Next, iPET imaging, biodistribution, pharmacokinetics, and ex vivo pathological and immunohistochemical examinations were conducted. LC-MS analysis revealed that DFO-anti-PD-L1-mAb conjugates were prepared with CARs ranging from 0.4 to 2.0. Radiochemical purity for all tracer groups was >99% after purification. The specific activity levels of tracer_3X, tracer_10X, and tracer_20X were 2.2 ± 0.6, 8.2 ± 0.6, and 10.5 ± 1.6 μCi/μg, respectively. 89Zr-iPET imaging showed evident tumor uptake in all tracer groups and reached the maximum uptake value at 24 h postinjection (p.i.). Biodistribution data at 168 h p.i. revealed that the tumor-to-liver, tumor-to-muscle, and tumor-to-blood uptake ratios for tracer_3X, tracer_10X, and tracer_20X were 0.46 ± 0.14, 0.58 ± 0.33, and 1.54 ± 0.51; 4.7 ± 1.3, 7.1 ± 3.9, and 14.7 ± 1.1; and 13.1 ± 5.8, 19.4 ± 13.8, and 41.3 ± 10.6, respectively. Significant differences were observed between tracer_3X and tracer_20X in the aforementioned uptake ratios at 168 h p.i. The mean residence time and elimination half-life for tracer_3X, tracer_10X, and tracer_20X were 25.4 ± 4.9, 24.2 ± 6.1, and 25.8 ± 3.3 h and 11.8 ± 0.5, 11.1 ± 0.7, and 11.7 ± 0.6 h, respectively. No statistical differences were found between-tracer in the aforementioned pharmacokinetic parameters. In conclusion, 89Zr-DFO-anti-PD-L1-mAb tracers with a CAR of 1.4-2.0 may be better at imaging PD-L1 expression in tumors than are traditional low-CAR 89Zr-iPET tracers.

Distal femoral osteotomy for the valgus knee: indications, complications, clinical and radiological outcome

INTRODUCTION

The aim of this study was to describe the indications and technical aspects of medial closing and lateral opening distal femoral osteotomy (MCDFO and LODFO) for patients with a valgus knee and to report clinical and radiological outcomes and complications.

METHODS

Over 6 years, 28 DFOs (22 MCDFO, 6 LODFO) were performed in 22 Patients. In this cohort study, we retrospectively analyzed clinical and radiological outcome measures as well as complications.

RESULTS

The median (range) age was 47 (17-63) years, height 1.68 (1.56-1.98) m, body mass 80 (49-105) kg, and body mass index (BMI) 27.4 (18.6-37.0) kg/m2. The clinical follow-up was 21 (7-81) months, the need for total or unicompartmental knee arthroplasty (TKA/UKA) and hardware removal was followed up for 59 (7-108) months postoperatively. Preoperatively, hip-knee-ankle angle (HKA, negative values denote varus) was 7.0 (2.0-13.0)°, mechanical lateral distal femoral angle (mLDFA) was 83.7 (79.9-88.2)°, and mechanical proximal tibial angle (MPTA) was 89.0 (86.6-94.5)°. Postoperatively, HKA was -1.3 (-9.0-1.2)° and mLDFA was 90.8 (87.3-97.3)°. The incidence of minor and major complications was 25% and 14%, the incidence of delayed and nonunion was 18% and 4%, respectively. At the last follow-up, 18% of the patients had pain at rest, 25% during activities of daily living, and 39% during physical activity, and 71% were satisfied with the outcome. 7% of the cases received a TKA/UKA, 71% received a hardware removal.

CONCLUSION

DFO is a reasonable treatment for lateral osteoarthritis in younger patients to avoid disease progression and the need for an UKA/TKA. However, there is a long rehabilitation time, a considerable risk for complications, and a high need for hardware removal. While many patients experienced symptoms at the long-term follow-up, most were satisfied with the outcome. Appropriate patient information is essential. Level of evidence Level IV, Case Series. Trial registration number NCT04382118, clinicaltrials.gov, May 11, 2020.

Iron Chelator Deferoxamine Alleviates Progression of Diabetic Nephropathy by Relieving Inflammation and Fibrosis in Rats

Diabetic nephropathy (DN) is one of the most devastating diabetic microvascular complications. It has previously been observed that iron metabolism levels are abnormal in diabetic patients. However, the mechanism by which iron metabolism levels affect DN is poorly understood. This study was designed to evaluate the role of iron-chelator deferoxamine (DFO) in the improvement of DN. Here, we established a DN rat model induced by diets high in carbohydrates and fat and streptozotocin (STZ) injection. Our data demonstrated that DFO treatment for three weeks greatly attenuated renal dysfunction as evidenced by decreased levels of urinary albumin, blood urea nitrogen, and serum creatinine, which were elevated in DN rats. Histopathological observations showed that DFO treatment improved the renal structures of DN rats and preserved podocyte integrity by preventing the decrease of transcripts of nephrin and podocin. In addition, DFO treatment reduced the overexpression of fibronectin 1, collagen I, IL-1β, NF-κB, and MCP-1 in DN rats, as well as inflammatory cell infiltrates and collagenous fibrosis. Taken together, our findings unveiled that iron chelation via DFO injection had a protective impact on DN by alleviating inflammation and fibrosis, and that it could be a potential therapeutic strategy for DN.

The use of tranexamic acid reduces blood loss in osteotomy at knee level: a systematic review

PURPOSE

Aim of this systematic review was to evaluate the literature regarding the effect of tranexamic acid (TXA) on the outcome after knee osteotomy.

METHODS

A systematic literature search was carried out in various databases on studies on the use of tranexamic acid in osteotomies around the knee. Primary outcome criterion was the hemoglobin (drop). Secondary outcome criteria were total blood loss, drainage volume, adverse effects such as thromboembolic events, blood transfusions, wound complications and clinical scores. A meta-analysis was performed for quantitative measures. The present study was registered prospectively ( www.crd.york.ac.uk/PROSPERO ; no.: CRD42021229624).

RESULTS

Seven studies with 584 patients (TXA group: 282 patients, non TXA group: 302 patients) Hemoglobin decrease (1.54 g/dl vs. 2.28 g/dl), blood loss (394.49 ml vs. 595.54 ml) and drainage volume (266.5 ml vs. 359.05 ml) were significantly less in the TXA group compared to the non TXA group. No thromboembolic event was noted in any study. In the non TXA group four blood transfusions were given. Eleven wound complications occurred in the non TXA group in comparison to two wound complications in the TXA group.

CONCLUSIONS

The results of the present study show that the application of TXA reduces hemoglobin drop, blood loss and drainage volume. These effects could be responsible for the lesser rate of side effects after administration of TXA during knee osteotomy.

Consistent indications, targets and techniques for double-level osteotomy of the knee: a systematic review

PURPOSE

To systematically review and critically appraise the literature on double-level osteotomy (DLO) of the knee, and determine the indications, contraindications, targets and outcomes.

MATERIALS AND METHODS

A systematic literature search was performed on PubMed, Embase®, and Cochrane for studies that reported on DLO by any technique or approach, including indications, contraindications, and targets for DLO, as well as patient-reported outcome measures (pROMS) and radiographic angles.

RESULTS

Twelve eligible studies were found: 9 case series and 3 studies that compared DLO to high-tibial osteotomy (HTO). In all studies, DLO was performed by medial opening-wedge tibial osteotomy and lateral closing-wedge femoral osteotomy. Seven specified that DLO was performed if simple HTO would exceed thresholds of postoperative medial proximal tibial angle (MPTA), lateral distal femoral angle (LDFA), and/or predicted wedge size. The targets were 88°-95° for MPTA, 84°-89° for LDFA, and 0°-4° for hip-knee-ankle (HKA) angle. The 3 comparative studies reported lower MPTA after DLO (89.6°-92.5°) than after HTO (91.5°-98.3°). All 3 reported similar postoperative HKA after DLO (0.2°-4.4°) as HTO (0.4°-4.8°); only 2 compared postoperative LDFA, which was lower after DLO (85.4° and 84.9°) than HTO (88.7° and 88.8°). Two comparative studies reported postoperative overall KOOS which was slightly lower after DLO (351-403) than HTO (368-410); only 1 study reported separate items of the KOOS.

CONCLUSION

There was relative consistency between studies on the indications, targets and techniques for DLO. Furthermore, while the comparative studies reported similar preoperative MPTA, LDFA and HKA, the postoperative MPTA and LDFA were lower after DLO than after HTO, though both treatments achieved equivalent postoperative HKA.

LEVEL OF EVIDENCE

IV, systematic review.

Toward Optimized 89Zr-Immuno-PET: Side-by-Side Comparison of [89Zr]Zr-DFO-, [89Zr]Zr-3,4,3-(LI-1,2-HOPO)- and [89Zr]Zr-DFO*-Cetuximab for Tumor Imaging: Which Chelator Is the Most Suitable?

89Zr represents a highly favorable positron emitter for application in immuno-PET (Positron Emission Tomography) imaging. Clinically, the 89Zr4+ ion is introduced into antibodies by complexation with desferrioxamine B. However, producing complexes of limited kinetic inertness. Therefore, several new chelators for 89Zr introduction have been developed over the last years. Of these, the direct comparison of the most relevant ones for clinical translation, DFO* and 3,4,3-(LI-1,2-HOPO), is still missing. Thus, we directly compared DFO with DFO* and 3,4,3-(LI-1,2-HOPO) immunoconjugates to identify the most suitable agent stable 89Zr-complexation. The chelators were introduced into cetuximab, and an optical analysis method was developed, enabling the efficient quantification of derivatization sites per protein. The cetuximab conjugates were efficiently obtained and radiolabeled with 89Zr at 37 °C within 30 min, giving the [89Zr]Zr-cetuximab derivatives in high radiochemical yields and purities of >99% as well as specific activities of 50 MBq/mg. The immunoreactive fraction of all 89Zr-labeled cetuximab derivatives was determined to be in the range of 86.5−88.1%. In vivo PET imaging and ex vivo biodistribution studies in tumor-bearing animals revealed a comparable and significantly higher kinetic inertness for both [89Zr]Zr-3,4,3-(LI-1,2-HOPO)-cetuximab and [89Zr]Zr-DFO*-cetuximab, compared to [89Zr]Zr-DFO-cetuximab. Of these, [89Zr]Zr-DFO*-cetuximab showed a considerably more favorable pharmacokinetic profile with significantly lower liver and spleen retention than [89Zr]Zr-3,4,3-(LI-1,2-HOPO)-cetuximab. Since [89Zr]Zr-DFO* demonstrates a very high kinetic inertness, paired with a highly favorable pharmacokinetic profile of the resulting antibody conjugate, DFO* currently represents the most suitable chelator candidate for stable 89Zr-radiolabeling of antibodies and clinical translation.

Practical syntheses of DOTAGA-DBCO and DFO-DBCO, strained alkyne pre-cursors to radioimmunoconjugates for targeted alpha therapy

We describe practical methods to prepare DOTAGA-DBCO and DFO-DBCO from commercially available starting materials. DOTAGA-DBCO is available in five steps from cyclen with a 33 % overall yield at gram scale. Our synthesis of DFO-DBCO also proceeds in five steps from commercially available starting materials. These bifunctional molecules possess chelating functionality for the binding of medically important radiometals and a strained alkyne suitable for Huisgen cyclization with an azide. These syntheses represent an important step toward improved radioimmunoconjugates for imaging and therapeutic applications.

Spectroscopic evidence of fluorescence by 1,8-diazafluoren-9-one aggregates-A prospective new ultrasensitive method for fingerprint trace detection

Friction ridge analysis would not have been one of the most recognized branches of forensics without molecular spectroscopy. The phenomenon of fluorescence is used on daily basis to develop latent fingerprints and to enhance those that are visible. The idea behind the research was to discover selected spectroscopic properties of 1,8-diazafluoren-9-one (DFO) in various environments. This fluorescent compound has been routinely used for decades to develop latent fingerprints due to its numerous advantages, but to this day, it has not been well-understood. Analysis of absorption, fluorescence, and excitation spectra of DFO in ethanol at high dye concentration allowed identification of aggregates in the excited state. A significant influence of the dye concentration on the fluorescence spectra and on the fluorescence excitation spectra was found. In particular, dye-host aggregation was found to be much stronger in a polar solvent. DFO aggregates are strongly fluorescent in ethanol, as can be seen from the steady-state emission spectra. The impact of excitation wavelength on the effect of fingerprint detection is presented. A new reaction medium has been proposed, ethanol, which is nontoxic in relation to the currently used one, methanol. The existence in this medium of DFO aggregates in the excited state, which significantly influences the identification of amino acids present in fingerprint traces, was observed, emitting in a wide spectral range (green light).

Work intensity and quality of life can be restored following double-level osteotomy in varus knee osteoarthritis

PURPOSE

The purpose of this study was to assess changes in health-related quality of life (HRQL) and work intensity following double-level knee osteotomy (DLO). It was hypothesized that postoperative HRQL would be comparable to that of the general population and that work intensity can be restored in the short term.

METHODS

Twenty-four patients (28 varus knees; mechanical tibiofemoral angle: -11.0 ± 3.0° (-6.0 to -17.0), age: 49.1 ± 9.5 (31-65) years) who underwent DLO were included. The duration the patients were unable to work was evaluated. HRQL was measured with the SF-36 questionnaire, which consists of a physical (PCS) and mental component summary score (MCS). The pre- to postoperative changes in the PCS and MCS were analysed. The PCS and MCS were also compared to those of the general population, who has a reference score value of 50 points. The work intensity measured with the REFA classification and the Tegner activity scale were assessed preoperatively and at the final postoperative follow-up examination (18.0 ± 10.0 (5-43) months).

RESULTS

The duration that the patients were unable to work was 12.2 ± 4.4 (6-20) weeks. The PCS improved from 32.1 ± 11.3 (14.5-53.3) preoperatively to 54.6 ± 8.5 (25.2-63.7) (p < 0.001) at the final follow-up, and the MCS improved from 53.9 ± 11.1 (17.1-67.7) to 57.2 ± 3.1 (47.3-61.7) (n.s). The preoperative PCS was significantly lower than the reference score of the general population (p < 0.001), whereas the preoperative MCS was similar between the two groups (n.s.). At follow-up, no significant differences were observed between the PCS and the MCS of the patient group and those of the general population. Five patients who were unable to work prior to surgery due to knee symptoms returned to work with moderate (four patients) or even very heavy (one patient) workloads. The Tegner activity scale increased significantly from a median of 2.0 (0.0-5.0) to 4.0 (2.0-7.0) (p < 0.001).

CONCLUSION

Our results demonstrate an improvement in quality of life and return to working activity following DLO in the short term. The HRQL can be improved by DLO in patients with varus knee osteoarthritis to the level of the general population. These results can assist surgeons in discussing realistic expectations when considering patients for DLO.

LEVEL OF EVIDENCE

Study type: therapeutic, IV.

Side-by-Side Comparison of Five Chelators for 89Zr-Labeling of Biomolecules: Investigation of Chemical/Radiochemical Properties and Complex Stability

In this work, five different chelating agents, namely DFO, CTH-36, DFO*, 3,4,3-(LI-1,2-HOPO) and DOTA-GA, were compared with regard to the relative kinetic inertness of their corresponding ⁸⁹Zr complexes to evaluate their potential for in vivo application and stable ⁸⁹Zr complexation. The chelators were identically functionalized with tetrazines, enabling a fully comparable, efficient, chemoselective and biorthogonal conjugation chemistry for the modification of any complementarily derivatized biomolecules of interest. A small model peptide of clinical relevance (TCO-c(RGDfK)) was derivatized via iEDDA click reaction with the developed chelating agents (TCO = trans-cyclooctene and iEDDA = inverse electron demand Diels-Alder). The bioconjugates were labeled with ⁸⁹Zr⁴⁺, and their radiochemical properties (labeling conditions and efficiency), logD_(7.4), as well as the relative kinetic inertness of the formed complexes, were compared. Furthermore, density functional theory (DFT) calculations were conducted to identify potential influences of chelator modification on complex formation and geometry. The results of the DFT studies showed-apart from the DOTA-GA derivative-no significant influence of chelator backbone functionalization or the conjugation of the chelator tetrazines by iEDDA. All tetrazines could be efficiently introduced into c(RGDfK), demonstrating the high suitability of the agents for efficient and chemoselective bioconjugation. The DFO-, CTH-36- and DFO*-modified c(RGDfK) peptides showed a high radiolabeling efficiency under mild reaction conditions and complete ⁸⁹Zr incorporation within 1 h, yielding the ⁸⁹Zr-labeled analogs as homogenous products. In contrast, 3,4,3-(LI-1,2-HOPO)-c(RGDfK) required considerably prolonged reaction times of 5 h for complete radiometal incorporation and yielded several different ⁸⁹Zr-labeled species. The labeling of the DOTA-GA-modified peptide was not successful at all. Compared to [⁸⁹Zr]Zr-DFO-, [⁸⁹Zr]Zr-CTH-36- and [⁸⁹Zr]Zr-DFO*-c(RGDfK), the corresponding [⁸⁹Zr]Zr-3,4,3-(LI-1,2-HOPO) peptide showed a strongly increased lipophilicity. Finally, the relative stability of the ⁸⁹Zr complexes against the EDTA challenge was investigated. The [⁸⁹Zr]Zr-DFO complex showed-as expected-a low kinetic inertness. Unexpectedly, also, the [⁸⁹Zr]Zr-CTH-36 complex demonstrated a high susceptibility against the challenge, limiting the usefulness of CTH-36 for stable ⁸⁹Zr complexation. Only the [⁸⁹Zr]Zr-DFO* and the [⁸⁹Zr]Zr-3,4,3-(LI-1,2-HOPO) complexes demonstrated a high inertness, qualifying them for further comparative in vivo investigation to determine the most appropriate alternative to DFO for clinical application.

The Race for Hydroxamate-Based Zirconium-89 Chelators

Simple Summary

Chelators are small molecules that can form a complex with a metal ion by coordinating electron rich atoms from the chelator to the electron-poor cation. Bifunctionalization of the chelator allows for the coupling of the chelator to a vector, such as a biomolecule. Using this approach, radiolabeling of biomolecules with metallic radionuclides can be performed, enabling nuclear imaging studies for diagnosis and radiotherapy of diseases. In the case of positron emission tomography (PET) of radiolabeled antibodies, this approach is called immunoPET. In this review we focus on chelators using hydroxamate groups to coordinate the radionuclide zirconium-89 ([⁸⁹Zr]Zr⁴⁺, denoted as ⁸⁹Zr in the following). The most common chelator used in this context is desferrioxamine (DFO). However, preclinical studies indicate that the ⁸⁹Zr-DFO complex is not stable enough in vivo, in particular when combined with biomolecules with slow pharmacokinetics (e.g., antibodies). Subsequently, new chelators with improved properties have been developed, of which some show promising potential. The progress is summarized in this review.

Abstract

Metallic radionuclides conjugated to biological vectors via an appropriate chelator are employed in nuclear medicine for the diagnosis (imaging) and radiotherapy of diseases. For the application of radiolabeled antibodies using positron emission tomography (immunoPET), zirconium-89 has gained increasing interest over the last decades as its physical properties (t_1/2 = 78.4 h, 22.6% β⁺ decay) match well with the slow pharmacokinetics of antibodies (t_biol. = days to weeks) allowing for late time point imaging. The most commonly used chelator for ⁸⁹Zr in this context is desferrioxamine (DFO). However, it has been shown in preclinical studies that the hexadentate DFO ligand does not provide ⁸⁹Zr-complexes of sufficient stability in vivo and unspecific uptake of the osteophilic radiometal in bones is observed. For clinical applications, this might be of concern not only because of an unnecessary dose to the patient but also an increased background signal. As a consequence, next generation chelators based on hydroxamate scaffolds for more stable coordination of ⁸⁹Zr have been developed by different research groups. In this review, we describe the progress in this research field until end of 2020, including promising examples of new candidates of chelators currently in advanced stages for clinical translation that outrun the performance of the current gold standard DFO.

Role of hepcidin in oxidative stress and cell death of cultured mouse renal collecting duct cells: protection against iron and sensitization to cadmium

The liver hormone hepcidin regulates systemic iron homeostasis. Hepcidin is also expressed by the kidney, but exclusively in distal nephron segments. Several studies suggest hepcidin protects against kidney damage involving Fe2+ overload. The nephrotoxic non-essential metal ion Cd2+ can displace Fe2+ from cellular biomolecules, causing oxidative stress and cell death. The role of hepcidin in Fe2+ and Cd2+ toxicity was assessed in mouse renal cortical [mCCD(cl.1)] and inner medullary [mIMCD3] collecting duct cell lines. Cells were exposed to equipotent Cd2+ (0.5-5 μmol/l) and/or Fe2+ (50-100 μmol/l) for 4-24 h. Hepcidin (Hamp1) was transiently silenced by RNAi or overexpressed by plasmid transfection. Hepcidin or catalase expression were evaluated by RT-PCR, qPCR, immunoblotting or immunofluorescence microscopy, and cell fate by MTT, apoptosis and necrosis assays. Reactive oxygen species (ROS) were detected using CellROX™ Green and catalase activity by fluorometry. Hepcidin upregulation protected against Fe2+-induced mIMCD3 cell death by increasing catalase activity and reducing ROS, but exacerbated Cd2+-induced catalase dysfunction, increasing ROS and cell death. Opposite effects were observed with Hamp1 siRNA. Similar to Hamp1 silencing, increased intracellular Fe2+ prevented Cd2+ damage, ROS formation and catalase disruption whereas chelation of intracellular Fe2+ with desferrioxamine augmented Cd2+ damage, corresponding to hepcidin upregulation. Comparable effects were observed in mCCD(cl.1) cells, indicating equivalent functions of renal hepcidin in different collecting duct segments. In conclusion, hepcidin likely binds Fe2+, but not Cd2+. Because Fe2+ and Cd2+ compete for functional binding sites in proteins, hepcidin affects their free metal ion pools and differentially impacts downstream processes and cell fate.

Exploration and Exploitation Zones in a Minimalist Swarm Optimiser

The trade off between exploration and exploitation is one of the key challenges in evolutionary and swarm optimisers which are led by guided and stochastic search. This work investigates the exploration and exploitation balance in a minimalist swarm optimiser in order to offer insights into the population’s behaviour. The minimalist and vector-stripped nature of the algorithm—dispersive flies optimisation or DFO—reduces the challenges of understanding particles’ oscillation around constantly changing centres, their influence on one another, and their trajectory. The aim is to examine the population’s dimensional behaviour in each iteration and each defined exploration-exploitation zone, and to subsequently offer improvements to the working of the optimiser. The derived variants, titled unified DFO or uDFO, are successfully applied to an extensive set of test functions, as well as high-dimensional tomographic reconstruction, which is an important inverse problem in medical and industrial imaging.

In Vitro and In Vivo Comparison of 3,2-HOPO Versus Deferoxamine-Based Chelation of Zirconium-89 to the Antimesothelin Antibody Anetumab

Introduction: [²²⁷Th]Th-3,2-HOPO-MSLN-mAb, a mesothelin (MSLN)-targeted thorium-227 therapeutic conjugate, is currently in phase I clinical trial; however, direct PET imaging using this conjugate is technically challenging. Thus, using the same MSLN antibody, we synthesized 3,2-HOPO and deferoxamine (DFO)-based zirconium-89 antibody conjugates, [⁸⁹Zr]Zr-3,2-HOPO-MSLN-mAb and [⁸⁹Zr]Zr-DFO-MSLN-mAb, respectively, and compared them in vitro and in vivo.

Methods: [⁸⁹Zr]Zr-3,2-HOPO-MSLN-mAb and [⁸⁹Zr]Zr-DFO-MSLN-mAb were evaluated in vitro to determine binding affinity and immunoreactivity in HT29-MSLN and PDX (NCI-Meso16, NCI-Meso21) cells. For both the zirconium-89 conjugates, in vivo studies (biodistribution/imaging) were performed at days 1, 3, and 6, from which tissue uptake was determined.

Results: Both the conjugates demonstrated a low nanomolar binding affinity for MSLN and >95% immunoreactivity. In all the three tumor types, biodistribution of [⁸⁹Zr]Zr-DFO-MSLN-mAb resulted in higher tumor uptake(15.88-28-33%ID/g) at all time points compared with [⁸⁹Zr]Zr-3,2-HOPO-MSLN-mAb(7–13.07%ID/g). [⁸⁹Zr]Zr-3,2-HOPO-MSLN-mAb femur uptake was always higher than [⁸⁹Zr]Zr-DFO-MSLN-mAb, and imaging results concurred with the biodistribution studies.

Conclusions: Even though the conjugates exhibited a high binding affinity for MSLN, [⁸⁹Zr]Zr-DFO-MSLN-mAb showed a higher tumor and lower femur uptake than [⁸⁹Zr]Zr-3,2-HOPO-MSLN-mAb. Nevertheless, [⁸⁹Zr]Zr-3,2-HOPO-MSLN-mAb could be used to study organ distribution and lesion uptake with the caveat of detecting MSLN-positive bone lesions. Clinical trial (NCT03507452).

Endothelial Iron Homeostasis Regulates Blood-Brain Barrier Integrity via the HIF2α-Ve-Cadherin Pathway

The objective of this study was to investigate the molecular response to damage at the blood-brain barrier (BBB) and to elucidate critical pathways that might lead to effective treatment in central nervous system (CNS) pathologies in which the BBB is compromised. We have used a human, stem-cell derived in-vitro BBB injury model to gain a better understanding of the mechanisms controlling BBB integrity. Chemical injury induced by exposure to an organophosphate resulted in rapid lipid peroxidation, initiating a ferroptosis-like process. Additionally, mitochondrial ROS formation (MRF) and increase in mitochondrial membrane permeability were induced, leading to apoptotic cell death. Yet, these processes did not directly result in damage to barrier functionality, since blocking them did not reverse the increased permeability. We found that the iron chelator, Desferal© significantly decreased MRF and apoptosis subsequent to barrier insult, while also rescuing barrier integrity by inhibiting the labile iron pool increase, inducing HIF2α expression and preventing the degradation of Ve-cadherin specifically on the endothelial cell surface. Moreover, the novel nitroxide JP4-039 significantly rescued both injury-induced endothelium cell toxicity and barrier functionality. Elucidating a regulatory pathway that maintains BBB integrity illuminates a potential therapeutic approach to protect the BBB degradation that is evident in many neurological diseases.

Head-to-head comparison of DFO* and DFO chelators: selection of the best candidate for clinical 89Zr-immuno-PET

Purpose

Almost all radiolabellings of antibodies with ⁸⁹Zr currently employ the hexadentate chelator desferrioxamine (DFO). However, DFO can lead to unwanted uptake of ⁸⁹Zr in bones due to instability of the resulting metal complex. DFO*-NCS and the squaramide ester of DFO, DFOSq, are novel analogues that gave more stable ⁸⁹Zr complexes than DFO in pilot experiments. Here, we directly compare these linker-chelator systems to identify optimal immuno-PET reagents.

Methods

Cetuximab, trastuzumab and B12 (non-binding control antibody) were labelled with ⁸⁹Zr via DFO*-NCS, DFOSq, DFO-NCS or DFO*Sq. Stability in vitro was compared at 37 °C in serum (7 days), in formulation solution (24 h ± chelator challenges) and in vivo with N87 and A431 tumour-bearing mice. Finally, to demonstrate the practical benefit of more stable complexation for the accurate detection of bone metastases, [⁸⁹Zr]Zr-DFO*-NCS and [⁸⁹Zr]Zr-DFO-NCS-labelled trastuzumab and B12 were evaluated in a bone metastasis mouse model where BT-474 breast cancer cells were injected intratibially.

Results

[⁸⁹Zr]Zr-DFO*-NCS-trastuzumab and [⁸⁹Zr]Zr-DFO*Sq-trastuzumab showed excellent stability in vitro, superior to their [⁸⁹Zr]Zr-DFO counterparts under all conditions. While tumour uptake was similar for all conjugates, bone uptake was lower for DFO* conjugates. Lower bone uptake for DFO* conjugates was confirmed using a second xenograft model: A431 combined with cetuximab. Finally, in the intratibial BT-474 bone metastasis model, the DFO* conjugates provided superior detection of tumour-specific signal over the DFO conjugates.

Conclusion

DFO*-mAb conjugates provide lower bone uptake than their DFO analogues; thus, DFO* is a superior candidate for preclinical and clinical ⁸⁹Zr-immuno-PET.

Electronic supplementary material

The online version of this article (10.1007/s00259-020-05002-7) contains supplementary material, which is available to authorized users.

UVA irradiation increases ferrous iron release from human skin fibroblast and endothelial cell ferritin: Consequences for cell senescence and aging

UVA irradiation of human dermal fibroblasts and endothelial cells induces an immediate transient increase in cytosolic Fe(II), as monitored by the fluorescence Fe(II) reporters, FeRhonox1 in cytosol and MitoFerroGreen in mitochondria. Both superoxide dismutase (SOD) inhibition by tetrathiomolybdate (ATM) and catalase inhibition by 3-amino-1, 2, 4-triazole (ATZ) increase and prolong the cytosolic Fe(II) signal after UVA irradiation. SOD inhibition with ATM also increases mitochondrial Fe(II). Thus, mitochondria do not source the UV-dependent increase in cytosolic Fe(II), but instead reflect and amplify raised cytosolic labile Fe(II) concentration. Hence control of cytosolic ferritin iron release is key to preventing UVA-induced inflammation. UVA irradiation also increases dermal endothelial cell H₂O₂, as monitored by the adenovirus vector Hyper-DAAO-NES(HyPer). These UVA-dependent changes in intracellular Fe(II) and H₂O₂ are mirrored by increases in cell superoxide, monitored with the luminescence probe L-012. UV-dependent increases in cytosolic Fe(II), H₂O₂ and L-012 chemiluminescence are prevented by ZnCl₂ (10 μM), an effective inhibitor of Fe(II) transport via ferritin's 3-fold channels. Quercetin (10 μM), a potent membrane permeable Fe(II) chelator, abolishes the cytosolic UVA-dependent FeRhonox1, Fe(II) and HyPer, H₂O₂ and increase in MitoFerroGreen Fe(II) signals. The time course of the quercetin-dependent decrease in endothelial H₂O₂ correlates with the decrease in FeRhox1 signal and both signals are fully suppressed by preloading cells with ZnCl₂. These results confirm that antioxidant enzyme activity is the key factor in controlling intracellular iron levels, and hence maintenance of cell antioxidant capacity is vitally important in prevention of skin aging and inflammation initiated by labile iron and UVA.

The Luminescence of 1,8-Diazafluoren-9-One/Titanium Dioxide Composite Thin Films for Optical Application

The investigation of innovative label-free α-amino acids detection methods represents a crucial step for the early diagnosis of several diseases. While 1,8-diazafluoren-9-one (DFO) is known in forensic application because of the fluorescent products by reacting with the amino acids present in the papillary exudate, its application for diagnostic purposes has not been fully investigated. The stabilization of DFO over a transparent substrate allows its complexation with biomolecules for the detection of α-amino acids. In this study, DFO was immobilized into a titanium dioxide (TiO₂) matrix for the fluorescence detection of glycine, as a target α-amino acid (a potential marker of the urogenital tract cancers). The DFO/TiO₂ composite was characterized by atomic force microscopy, spectroscopic ellipsometry, fluorescence spectroscopy and fluorescence microscopy. The performed fluorescent studies indicate spectacular formation of aggregates at higher concentration. The measurements performed using various fluorescence and microscopic techniques together with the suitable analysis show that the aggregates are able to emit short-lived fluorescence.

Tibial and femoral osteotomies in varus deformities - radiological and clinical outcome

BACKGROUND

Varus deformities of the knee are frequently corrected by osteotomies, which should be performed at the level of origin. But in contrast to high tibial osteotomies (HTO), little data exists for distal femoral osteotomies (DFO). This study evaluates radiological and clinical outcomes after valgisation osteotomies in the proximal tibia and distal femur.

METHODS

We used an observational cohort study design and prospectively performed preoperative long standing radiographs (LSR), lateral x-rays and clinical questionnaires (SF-36, Lysholm score, VAS). Postoperative LSR and lateral x-rays were obtained on average 18 months postoperative and postoperative clinical questionnaires at final visit (mean follow up 46 months). A subgroup analysis of the different surgical techniques (oHTO vs. cDFO) was performed, with regards to radiological and clinical outcomes.

RESULTS

Finally 28 osteotomies with medial tibial opening (oHTO) or lateral femoral closing (cDFO) wedge osteotomies in 25 consecutive patients (mean age 40 years) were identified. There were 17 tibal and 11 femoral procedures. All osteotomies were performed at the origin of deformity, which was of different etiology. The average deviation of the final HKA compared to the preoperative planning was 2.4° ± 0.4°. Overall, there was a significant improvement in all clinical scores (SF-36: 61.8 to 79.4, p < 0.001; Lysholm-score: 72.7 to 90.4, p < 0.001; VAS: 3 to 1, p < 0.001). There was no significant correlation between surgical accuracy and outcome scores.

CONCLUSION

Valgisation osteotomies lead to a significant improvement in all clinical scores with the demonstrated treatment protocol. An appreciable proportion of varus deformities are of femoral origin. Since cDFO provides comparable radiological and clinical results as oHTO, this is an important treatment option for varus deformities of femoral origin.

An evidence based narrative review on treatment of diabetic foot osteomyelitis

OBJECTIVE

The diagnosis of diabetic food infection is usually clinical, and its severity is related to location and depth of the lesion, and the presence of necrosis or gangrene. Osteomyelitis of the foot and ankle can be extremely debilitating, and, in the preantibiotic era acute staphylococcal osteomyelitis carried a mortality rate of 50%. The microbiology of diabetic foot osteomyelitis (DFO) is usually polymicrobial. Indeed, gram-negative and gram-positive bacilli can be identified using molecular techniques applied to bone biopsies compared to conventional techniques. The aim of the present study is to report a complete overview regarding medical and surgical management of diabetic foot osteomyelitis (DFO) in combination or alone.

MATERIALS AND METHODS

We performed a search in PubMed and Scopus electronic databases (up to January 2019) of articles assessing the epidemiology, diagnostic strategy and pharmacological treatment of diabetic foot infection. In the search strategy, we used various combinations of the following key terms: infection, orthopaedic, diabetic foot, management, DFO.

RESULTS

This article discusses the definition, epidemiology, microbiological assessment, clinical evaluation, pharmacological and surgical management and a comparison between them, of DFO. After the initial literature search and removal of duplicate records, a total of 756 potentially relevant citations were identified. After a further screening and according to the inclusion criteria, a total of 65 articles were included in the present review.

CONCLUSION

The association of antibiotic and surgical therapy seems to be more effective compared to each one alone. The lack of comparison studies and randomized controlled trials makes it difficult to give information about the efficacy of the different management therapies.

Return to Collegiate Athletics After Distal Femoral Osteotomy: A Report of Three Cases and Review of the Literature

BACKGROUND

The authors present three cases of high-level athletes with successful return to competitive collegiate athletics following distal femoral osteotomy for knee lateral compartment overload.

CONCLUSION

Distal femoral varus osteotomy (DFO) is used to treat valgus knee malalignment and to offload the lateral knee compartment in the setting of symptomatic cartilage or meniscus pathology. DFO can be considered a viable treatment for collegiate athletes, with satisfactory outcomes and ability to return to sport participation at pre-injury functional levels.Level of Evidence: IV.

The iron chelator desferrioxamine synergizes with chemotherapy for cancer treatment

BACKGROUND

Cisplatin (CDDP) resistance remains a major obstacle for treatment of ovarian cancer. Iron contributes to the growth and reproduction of malignant cells, thus iron chalators can inhibit the growth of tumor cells by depleting the intracellular iron pool. The iron chelator, desferrioxamine (DFO), has performed anticancer in previous study. The aim of our study is to determine the correlation between iron-deprivation and tumor chemosensitivity in ovarian cancer.

METHODS

To investigate the prognostic value of ferritin light (FTL), ferroportin (FPN), hepcidin (HAMP) and divalent metal-ion transporter-1 (DMT1) in ovarian cancer, the Kaplan-Meier analysis and the Gene Expression Profiling Interactive Analysis (GEPIA) were used. The ovarian cancer cell lines (SKOV-3 and OVCAR-3) were exposed to a gradient concentration of DFO (10, 20, 50, 100, 200 μM) and CDDP (1, 5, 10, 50,100 μM) for 24 h. The protein expression of FTL was tested. The expression of cancer stem cell (CSC) markers, including Sox2, Nanog and C-myc, were downregulated with treatment of DFO. Also, the mamosphere formation and the plation of CD44^+/high/CD133^+/high and Aldehyde dehydrogenase (ALDH)^+/high SKOV-3 cells were reduced after treatment for 7d. Furthermore, we detected the expression of p53, BCL-2, BAX, and caspase-8.

RESULTS

The survival analysis revealed that high expression of FTL, DMT1, HAMP, showed poor overall survival (OS) in ovarian cancer patients. Our combined data found that DFO could effectively inhibit CSCs, improve the resistance to chemotherapy, and significantly enhanced the efficacy of CDDP therapy in vitro in promoting apoptosis. Besides, targeting molecular targets, including BAX, BCL-2, p53 and caspase-8 could serve as the clinical biomarkers to evaluate the effects of ovarian cancer. It is reasonable to believe that DFO adjuvant therapy in combination with CDDP chemotherapy can promote the improvement of treatment response in ovarian cancer patients.

CONCLUSION

Our research suggests the experimental evidence for DFO and CDDP as a new effective combination therapy to enhance the efficacy of chemical therapy in ovarian cancer.

Patients' expectations of osteotomies around the knee are high regarding activities of daily living

PURPOSE

This study was conducted to investigate patients' expectations on high tibial osteotomies, distal femur osteotomies, and double-level osteotomies in different health-related domains. It was hypothesized that expectations are high in terms of capacity to work, pain relief, and restoring knee function.

METHODS

A total of 264 patients (age 47 years ± 11 years) were enrolled in this study from March 2015 until May 2016 in seven specialized orthopaedic surgery departments. Data were collected via the Knee injury and Osteoarthritis Outcome Score, the Hospital for Special Surgery-Knee Surgery Expectations Survey, and a ten-item (non-validated) questionnaire to specifically ask about expectations of osteotomies around the knee 24-48 h prior to surgery. In addition, self-efficacy was assessed. Parametric tests were used to test the hypothesis.

RESULTS

Knee injury and Osteoarthritis Outcome Score test results showed that all patients suffered because of their knee impairments prior to surgery. All participants had high expectations in all aspects regarding the surgical outcome: on a four-point Likert scale ranging from 1 (very important) to 4 (not important), all mean values were between 1.2 and 1.7. For patients who had a demanding physical work, the ability to keep a stressful working posture was more important than for other patients (i.e. to kneel, to squat). Furthermore, preoperative lower quality of life was associated with higher expectations concerning improving the ability to walk, to achieve improvements in activities of daily living and social well-being.

CONCLUSIONS

Patients' expectations of osteotomies around the knee are high in terms of capacity to work, pain relief, and restoring functions. The natural course of osteoarthritis and the potential need for conversion to TKA were underestimated by a substantial proportion of the study population. However, the expectation regarding survival rate is in line with the reported literature. The results of this study should assist surgeons in discussing realistic expectations when considering and counselling patients regarding osteotomies around the knee. This may help to clarify realistic expectations preoperatively and ultimately improve patients' satisfaction.

LEVEL OF EVIDENCE

Therapeutic study, Level II.

Direct comparison of the in vitro and in vivo stability of DFO, DFO* and DFOcyclo* for 89Zr-immunoPET

Purpose

Currently, the most commonly used chelator for labelling antibodies with ⁸⁹Zr for immunoPET is desferrioxamine B (DFO). However, preclinical studies have shown that the limited in vivo stability of the ⁸⁹Zr-DFO complex results in release of ⁸⁹Zr, which accumulates in mineral bone. Here we report a novel chelator DFOcyclo*, a preorganized extended DFO derivative that enables octacoordination of the ⁸⁹Zr radiometal. The aim was to compare the in vitro and in vivo stability of [⁸⁹Zr]Zr-DFOcyclo*, [⁸⁹Zr]Zr-DFO* and [⁸⁹Zr]Zr-DFO.

Methods

The stability of ⁸⁹Zr-labelled chelators alone and after conjugation to trastuzumab was evaluated in human plasma and PBS, and in the presence of excess EDTA or DFO. The immunoreactive fraction, IC₅₀, and internalization rate of the conjugates were evaluated using HER2-expressing SKOV-3 cells. The in vivo distribution was investigated in mice with subcutaneous HER2⁺ SKOV-3 or HER2⁻ MDA-MB-231 xenografts by PET/CT imaging and quantitative ex vivo tissue analyses 7 days after injection.

Results

⁸⁹Zr-labelled DFO, DFO* and DFOcyclo* were stable in human plasma for up to 7 days. In competition with EDTA, DFO* and DFOcyclo* showed higher stability than DFO. In competition with excess DFO, DFOcyclo*-trastuzumab was significantly more stable than the corresponding DFO and DFO* conjugates (p < 0.001). Cell binding and internalization were similar for the three conjugates. In in vivo studies, HER2⁺ SKOV-3 tumour-bearing mice showed significantly lower bone uptake (p < 0.001) 168 h after injection with [⁸⁹Zr]Zr-DFOcyclo*-trastuzumab (femur 1.5 ± 0.3%ID/g, knee 2.1 ± 0.4%ID/g) or [⁸⁹Zr]Zr-DFO*-trastuzumab (femur 2.0 ± 0.3%ID/g, knee 2.68 ± 0.4%ID/g) than after injection with [⁸⁹Zr]Zr-DFO-trastuzumab (femur 4.5 ± 0.6%ID/g, knee 7.8 ± 0.6%ID/g). Blood levels, tumour uptake and uptake in other organs were not significantly different at 168 h after injection. HER2⁻ MDA-MB-231 tumour-bearing mice showed significantly lower tumour uptake (p < 0.001) after injection with [⁸⁹Zr]Zr-DFOcyclo*-trastuzumab (16.2 ± 10.1%ID/g) and [⁸⁹Zr]Zr-DFO-trastuzumab (19.6 ± 3.2%ID/g) than HER2⁺ SKOV-3 tumour-bearing mice (72.1 ± 14.6%ID/g and 93.1 ± 20.9%ID/g, respectively), while bone uptake was similar.

Conclusion

⁸⁹Zr-labelled DFOcyclo* and DFOcyclo*-trastuzumab showed higher in vitro and in vivo stability than the current commonly used ⁸⁹Zr-DFO-trastuzumab. DFOcyclo* is a promising candidate to become the new clinically used standard chelator for ⁸⁹Zr immunoPET.

Electronic supplementary material

The online version of this article (10.1007/s00259-019-04343-2) contains supplementary material, which is available to authorized users.

Comparison of desferrioxamine and NODAGA for the gallium-68 labeling of exendin-4

INTRODUCTION

Radiolabeled exendin-4 (Ex4) derivatives are used to target the glucagon-like peptide-1 receptor (GLP-1R) for the clinical diagnosis of insulinomas, a rare type of neuroendocrine tumor. Gallium-68 is an ideal diagnostic nuclide for this application and a study evaluating an exendin-4-NODAGA conjugate is currently underway. However, in complexion with the chelator DFO, its in vivo stability has been a matter of dispute. The aim of this work was to directly compare [⁶⁸Ga]Ga-Ex4NOD with [⁶⁸Ga]Ga-Ex4DFO in vitro and in vivo.

METHODS

In our approach, we directly compared N'-[5-(acetyl-hydroxy-amino)pentyl]-N-[5-[3-(5-aminopentyl-hydroxy-carbamoyl)propanoylamino]pentyl]-N-hydroxy-butane diamide (desferriox-amine B, DFO) and 2-(4,7-bis (carboxymethyl)-1,4,7-triazonan-1-yl) pentanedioic acid (NODAGA) conjugated to exendin-4 in vitro and in vivo. We radiolabeled the peptides with gallium-68, followed by HPLC quality control. In vitro characterization was performed in CHL cells overexpressing the GLP-1R and in vivo studies were conducted with CD1 nu/nu mice carrying tumors derived from these cells.

RESULTS

We found that both peptides could be radiolabeled with a molar activity of about 9.33 MBq/nmol without further purification. They internalized equally well into GLP-1R-expressing cells and their IC₅₀ was similar with 15.6 ± 7.8 nM and 18.4 ± 3.0 nM for [^natGa]Ga-Ex4NOD and [^natGa]Ga-Ex4DFO, respectively. In vivo, [⁶⁸Ga]Ga-Ex4NOD accumulated more in all tissue, while [⁶⁸Ga]Ga-Ex4DFO exhibited a more favorable target-to-kidney ratio.

CONCLUSION AND RELEVANCE

DFO is a suitable chelator for the radiolabeling of exendin-4 derivatives with gallium-68 for in vitro and preclinical in vivo studies. DFO performed better in vivo due to its significantly lower kidney accumulation (p < 0.0001). It was also found to be stable in vivo in mice, contrary to earlier reports. Based on our results, the DFO chelating system in combination with exendin-4 would be an interesting option for clinical imaging of insulinomas.

Lateral Opening Wedge Distal Femoral Osteotomy for Lateral Compartment Arthrosis/Overload

Distal femoral osteotomy (DFO) is a valid option for the treatment of young and active patients with lateral compartment osteoarthritis/overload and valgus malalignment. DFOs can be performed with a closing wedge or opening wedge technique. Lateral opening wedge DFO is usually preferred for smaller corrections, whereas medial closing wedge for larger corrections and in patients with high risk of nonunion. This article describes the relevant aspects regarding lateral opening wedge DFO, including patient selection, preoperative planning, surgical technique, results, and complications.

An evaluation of the effect of incorporating metal salts into 1,8 diazafluoren-9-one (DFO) formulations for fingermark enhancement

A study into the modification of 1,8-diazafluoren-9-one (DFO) formulations by the additions of metal salts into the working solution is reported. Similar additions have been found to increase the fluorescence of marks developed using other amino acid reagents including 1,2-indandione and the ninhydrin analogue 5-methylthioninhydrin. It was found that adding zinc chloride to give a 1:1 ratio of zinc ions:DFO molecules gave optimum fluorescence, and improvements in performance over the standard DFO formulation were achieved. Attempts to produce equivalent formulations with iron, nickel and palladium chlorides were unsuccessful. In a comparative trial with a 1,2-indandione-zinc formulation on brown paper and cardboard substrates, 1,2-indandione-zinc gave superior results and it was decided to focus further research on this reagent instead of DFO-zinc.

Preparation of Zirconium-89 Solutions for Radiopharmaceutical Purposes: Interrelation Between Formulation, Radiochemical Purity, Stability and Biodistribution

Zirconium-89 is a promising radionuclide for nuclear medicine. The aim of the present work was to find a suitable method for obtaining zirconium-89 solutions for radiopharmaceutical purposes. For this purpose, the ion exchange behavior of zirconium-89 solutions was studied. Radio-TLC (thin layer chromatography) and biodistribution studies were carried out to understand speciation of zirconium-89 complexes and their role in the development of new radiopharmaceuticals. Three methods of zirconium-89 isolation were studied using ZR (hydroxamate) and Chelex-100 resins. It was found that ZR-resin alone is not enough to obtain stable zirconium-89 formulations. An easy and effective method of reconstitution of [⁸⁹Zr]Zr-oxalate to [⁸⁹Zr]Zr-citrate using Chelex-100 resin was developed. Developed procedures allow obtaining [⁸⁹Zr]Zr-oxalate (in 0.1 M sodium oxalate solution) and [⁸⁹Zr]Zr-citrate (in 0.1–1.0 M sodium citrate solution). These solutions are perfectly suitable and convenient for radiopharmaceutical purposes. Our results prove [⁸⁹Zr]Zr-citrate to be advantageous over [⁸⁹Zr]Zr-oxalate. During evaluation of speciation of zirconium-89 complexes, a new TLC method was developed, since it was proved that there is no comprehensive method for analysis or zirconium-89 preparations. The new method provides valuable insights about the content of “active” ionic form of zirconium-89. The interrelation of the chromatographic behavior of zirconium-89 preparations and their biodistribution was studied.

Development of the double level osteotomy in severe varus osteoarthritis showed good outcome by preventing oblique joint line

INTRODUCTION

The purpose of the study was to describe the development of the surgical technique of double level osteotomy in patients with severe varus malalignment and to investigate the clinical and radiological outcome. It was hypothesized that good clinical results without a higher complication rate can be achieved by double level osteotomy to normalize joint angles and avoid joint line obliquity even in cases of progressed osteoarthritis.

MATERIALS AND METHODS

Between 2011 and 2014, 33 patients (37 knees) undergoing double level osteotomies (open wedge HTO and closed wedge DFO) were included; of these, 24 patients (28 knees) were available in mean of 18 ± 10 months for the follow-up examination. Indication was symptomatic varus malalignment and medial compartment osteoarthritis. Postoperatively, these patients were assigned to 20 kg partial weight-bearing using two crutches for 6 weeks followed by full weight-bearing. No braces or casts were used. Full weight-bearing long leg anteroposterior radiographs were obtained preoperatively, after 6 weeks and at the time of final follow-up. Mechanical tibiofemoral angle (mTFA), mechanical lateral distal femoral angle (mLDFA) and medial proximal tibia angle (MPTA) were measured. Clinical outcome was evaluated using Lequesne-, Lysholm-, Oxford-, and IKDC-score at the time of follow-up.

RESULTS

The preoperative mTFA of - 11 ± 3° increased to 0 ± 2° at final follow-up. The difference between mTFA-planning and final follow-up was - 2 ± 3° (p < 0.0006). At final follow-up, MPTA and mLDFA were 89.2 ± 2° and 87 ± 2°, respectively. The Lysholm, Oxford, Lequesne, and IKDC scores were 88 ± 13, 44 ± 3, 2 ± 2, and 77 ± 12, respectively.

CONCLUSIONS

This study showed that double level osteotomy for the patients with severe varus malalignment and medial compartment osteoarthritis normalises the alignment, joint-angles, avoids joint line obliquity, and leads to good clinical results, despite progressive osteoarthritis.

LEVEL OF EVIDENCE

Case series, Level IV.

Preclinical Evaluation of [68Ga]Ga-DFO-ZEGFR:2377: A Promising Affibody-Based Probe for Noninvasive PET Imaging of EGFR Expression in Tumors

Radionuclide imaging of epidermal growth factor receptor (EGFR) expression in tumors may stratify patients for EGFR-targeting therapies and predict response or resistance to certain treatments. Affibody molecules, which are nonimmunoglobulin scaffold proteins, have a high potential as probes for molecular imaging. In this study, maleimido derivative of desferrioxamine B (DFO) chelator was site-specifically coupled to the C-terminal cysteine of the anti-EGFR affibody molecule ZEGFR:2377, and the DFO-ZEGFR:2377 conjugate was labeled with the generator-produced positron-emitting radionuclide ⁶⁸Ga. Stability, specificity of binding to EGFR-expressing cells, and processing of [⁶⁸Ga]Ga-DFO-ZEGFR:2377 by cancer cells after binding were evaluated in vitro. In vivo studies were performed in nude mice bearing human EGFR-expressing A431 epidermoid cancer xenografts. The biodistribution of [⁶⁸Ga]Ga-DFO-ZEGFR:2377 was directly compared with the biodistribution of [⁸⁹Zr]Zr-DFO-ZEGFR:2377. DFO-ZEGFR:2377 was efficiently (isolated yield of 73 ± 3%) and stably labeled with ⁶⁸Ga. Binding of [⁶⁸Ga]Ga-DFO-ZEGFR:2377 to EGFR-expressing cells in vitro was receptor-specific and proportional to the EGFR expression level. In vivo saturation experiment demonstrated EGFR-specific accumulation of [⁶⁸Ga]Ga-DFO-ZEGFR:2377 in A431 xenografts. Compared to [⁸⁹Zr]Zr-DFO-ZEGFR:2377, [⁶⁸Ga]Ga-DFO-ZEGFR:2377 demonstrated significantly (p < 0.05) higher uptake in tumors and lower uptake in spleen and bones. This resulted in significantly higher tumor-to-organ ratios for [⁶⁸Ga]Ga-DFO-ZEGFR:2377. In conclusion, [⁶⁸Ga]Ga-DFO-ZEGFR:2377 is a promising probe for imaging of EGFR expression.

Enzymatic Formation of an Injectable Hydrogel from a Glycopeptide as a Biomimetic Scaffold for Vascularization

The construction of functional vascular networks in regenerative tissues is a crucial technology in tissue engineering to ensure the sufficient supply of nutrients. Although natural hydrogels are highly prevalent in fabricating three-dimensional scaffolds to induce neovascular growth, their widespread applicability was limited by the potential risk of immunogenicity or pathogen transmission. Therefore, developing hydrogels with good biocompatibility and cell affinity is highly desirable for fabricating alternative matrices for tissue regeneration applications. Herein, we report the generation of a new kind of hydrogel from supramolecular assembling of a synthetic glycopeptide to mimic the glycosylated microenvironment of extracellular matrix. In the presence of a tyrosine phosphate group, this molecule can undergo supramolecular self-assembling and gelation triggered by alkaline phosphatase under physiological conditions. Following supramolecular self-assembling, the glycopeptide gelator tended to form nanofilament structures displaying a high density of glucose moieties on their surface for endothelial cell adhesion and proliferation. On further incorporation with deferoxamine (DFO), the self-assembled hydrogel can serve as a reservoir for sustainably releasing DFO and inducing endothelial cell capillary morphogenesis in vitro. After subcutaneous injection in mice, the glycopeptide hydrogel encapsulating DFO can work as an effective matrix to trigger the generation of new blood capillaries in vivo.

Cyclic versus Noncyclic Chelating Scaffold for 89Zr-Labeled ZEGFR:2377 Affibody Bioconjugates Targeting Epidermal Growth Factor Receptor Overexpression

Zirconium-89 is an emerging radionuclide for positron emission tomography (PET) especially for biomolecules with slow pharmacokinetics as due to its longer half-life, in comparison to fluorine-18 and gallium-68, imaging at late time points is feasible. Desferrioxamine B (DFO), a linear bifunctional chelator (BFC) is mostly used for this radionuclide so far but shows limitations regarding stability. Our group recently reported on fusarinine C (FSC) with similar zirconium-89 complexing properties but potentially higher stability related to its cyclic structure. This study was designed to compare FSC and DFO head-to-head as bifunctional chelators for ⁸⁹Zr-radiolabeled EGFR-targeting ZEGFR:2377 affibody bioconjugates. FSC-ZEGFR:2377 and DFO-ZEGFR:2377 were evaluated regarding radiolabeling, in vitro stability, specificity, cell uptake, receptor affinity, biodistribution, and microPET-CT imaging. Both conjugates were efficiently labeled with zirconium-89 at room temperature but radiochemical yields increased substantially at elevated temperature, 85 °C. Both ⁸⁹Zr-FSC-ZEGFR:2377 and ⁸⁹Zr-DFO-ZEGFR:2377 revealed remarkable specificity, affinity and slow cell-line dependent internalization. Radiolabeling at 85 °C showed comparable results in A431 tumor xenografted mice with minor differences regarding blood clearance, tumor and liver uptake. In comparison ⁸⁹Zr-DFO-ZEGFR:2377, radiolabeled at room temperature, showed a significant difference regarding tumor-to-organ ratios. MicroPET-CT imaging studies of ⁸⁹Zr-FSC-ZEGFR:2377 as well as ⁸⁹Zr-DFO-ZEGFR:2377 confirmed these findings. In summary we were able to show that FSC is a suitable alternative to DFO for radiolabeling of biomolecules with zirconium-89. Furthermore, our findings indicate that ⁸⁹Zr-radiolabeling of DFO conjugates at higher temperature reduces off-chelate binding leading to significantly improved tumor-to-organ ratios and therefore enhancing image contrast.

Inhibitory Activity of Iron Chelators ATA and DFO on MCF-7 Breast Cancer Cells and Phosphatases PTP1B and SHP2

BACKGROUND

Rapidly-dividing cancer cells have higher requirement for iron compared to non-transformed cells, making iron chelating a potential anticancer strategy. In the present study we compared the anticancer activity of uncommon iron chelator aurintricarboxylic acid (ATA) with the known deferoxamine (DFO).

MATERIALS AND METHODS

We investigated the impact of ATA and DFO on the viability and proliferation of MCF-7 cancer cells. Moreover we performed enzymatic activity assays and computational analysis of the ATA and DFO effects on pro-oncogenic phosphatases PTP1B and SHP2.

RESULTS

ATA and DFO decrease the viability and proliferation of breast cancer cells, but only ATA considerably reduces the activity of PTP1B and SHP2 phosphatases. Our studies indicated that ATA strongly inactivates and binds in the PTP1B and SHP2 active site, interacting with arginine residue essential for enzyme activity.

CONCLUSION

We confirmed that iron chelating can be considered as a potential strategy for the adjunctive treatment of breast cancer.

The Iron Chelator, Dp44mT, Effectively Inhibits Human Oral Squamous Cell Carcinoma Cell Growth in Vitro and in Vivo

Oral squamous cell carcinoma (OSCC) is a common malignancy with a growing worldwide incidence and prevalence. The N-myc downstream regulated gene (NDRG) family of NDRG1, 2, 3, and mammary serine protease inhibitor (Maspin) gene are well-known modulators in the neoplasia process. Current research has considered iron chelators as new anti-cancer agents; however, the anticancer activities of iron chelators and their target genes in OSCC have not been well investigated. We showed that iron chelators (Dp44mT, desferrioxamine (DFO), and deferasirox) all significantly inhibit SAS cell growth. Flow cytometry further indicated that Dp44mT inhibition of SAS cells growth was partly due to induction of G1 cell cycle arrest. Iron chelators enhanced expressions of NDRG1 and NDRG3 while repressing cyclin D1 expression in OSCC cells. The in vivo antitumor effect on OSCC and safety of Dp44mT were further confirmed through a xenograft animal model. The Dp44mT treatment also increased Maspin protein levels in SAS and OECM-1 cells. NDRG3 knockdown enhanced the growth of OECM-1 cells in vitro and in vivo. Our results indicated that NDRG3 is a tumor suppressor gene in OSCC cells, and Dp44mT could be a promising therapeutic agent for OSCC treatment.

Comparison of the octadentate bifunctional chelator DFO*-pPhe-NCS and the clinically used hexadentate bifunctional chelator DFO-pPhe-NCS for 89Zr-immuno-PET

PURPOSE

All clinical ⁸⁹Zr-immuno-PET studies are currently performed with the chelator desferrioxamine (DFO). This chelator provides hexadentate coordination to zirconium, leaving two coordination sites available for coordination with, e.g., water molecules, which are relatively labile ligands. The unsaturated coordination of DFO to zirconium has been suggested to result in impaired stability of the complex in vivo and consequently in unwanted bone uptake of ⁸⁹Zr. Aiming at clinical improvements, we report here on a bifunctional isothiocyanate variant of the octadentate chelator DFO* and the in vitro and in vivo comparison of its ⁸⁹Zr-DFO*-mAb complex with ⁸⁹Zr-DFO-mAb.

METHODS

The bifunctional chelator DFO*-pPhe-NCS was prepared from previously reported DFO* and p-phenylenediisothiocyanate. Subsequently, trastuzumab was conjugated with either DFO*-pPhe-NCS or commercial DFO-pPhe-NCS and radiolabeled with Zr-89 according to published procedures. In vitro stability experiments were carried out in saline, a histidine/sucrose buffer, and blood serum. The in vivo performance of the chelators was compared in N87 tumor-bearing mice by biodistribution studies and PET imaging.

RESULTS

In 0.9 % NaCl ⁸⁹Zr-DFO*-trastuzumab was more stable than ⁸⁹Zr-DFO-trastuzumab; after 72 h incubation at 2-8 °C 95 % and 58 % intact tracer were left, respectively, while in a histidine-sucrose buffer no difference was observed, both products were ≥ 92 % intact. In vivo uptake at 144 h post injection (p.i.) in tumors, blood, and most normal organs was similar for both conjugates, except for skin, liver, spleen, ileum, and bone. Tumor uptake was 32.59 ± 11.95 and 29.06 ± 8.66 % ID/g for ⁸⁹Zr-DFO*-trastuzumab and ⁸⁹Zr-DFO-trastuzumab, respectively. The bone uptake was significantly lower for ⁸⁹Zr-DFO*-trastuzumab compared to ⁸⁹Zr-DFO-trastuzumab. At 144 h p.i. for ⁸⁹Zr-DFO*-trastuzumab and ⁸⁹Zr-DFO-trastuzumab, the uptake in sternum was 0.92 ± 0.16 and 3.33 ± 0.32 % ID/g, in femur 0.78 ± 0.11 and 3.85, ± 0.80 and in knee 1.38 ± 0.23 and 8.20 ± 2.94 % ID/g, respectively. The uptake in bone decreased from 24 h to 144 h p.i. about two fold for the DFO* conjugate, while it increased about two fold for the DFO conjugate.

CONCLUSIONS

Zr-DFO*-trastuzumab showed superior in vitro stability and in vivo performance when compared to ⁸⁹Zr-DFO-trastuzumab. This makes the new octadentate DFO* chelator a candidate successor of DFO for future clinical ⁸⁹Zr-immuno-PET.

Differential targeting of the cyclin-dependent kinase inhibitor, p21CIP1/WAF1, by chelators with anti-proliferative activity in a range of tumor cell-types

Chelators such as 2-hydroxy-1-napthylaldehyde isonicotinoyl hydrazone (311) and di-2-pyridylketone-4,4-dimethyl-3-thiosemicarbazone (Dp44mT) target tumor cell iron pools and inhibit proliferation. These agents also modulate multiple targets, one of which is the cyclin-dependent kinase inhibitor, p21. Hence, this investigation examined the mechanism of action of these compounds in targeting p21. All the chelators up-regulated p21 mRNA in the five tumor cell-types assessed. In contrast, examining their effect on total p21 protein levels, these agents induced either: (1) down-regulation in MCF-7 cells; (2) up-regulation in SK-MEL-28 and CFPAC-1 cells; or (3) had no effect in LNCaP and SK-N-MC cells. The nuclear localization of p21 was also differentially affected by the ligands depending upon the cell-type, with it being decreased in MCF-7 cells, but increased in SK-MEL-28 and CFPAC-1 cells. Further studies assessing the mechanisms responsible for these effects demonstrated that p21 expression was not correlated with p53 status, suggesting a p53-independent mechanism. Considering this, we examined proteins that modulate p21 independently of p53, namely NDRG1, MDM2 and ΔNp63. These studies demonstrated that a dominant negative MDM2 isoform (p75(MDM2)) closely resembled p21 expression in response to chelation in three cell lines. These data suggest MDM2 may be involved in the regulation of p21 by chelators.

Deferoxamine-induced increase in the intracellular iron levels in highly aggressive breast cancer cells leads to increased cell migration by enhancing TNF-α-dependent NF-κB signaling and TGF-β signaling

Recent studies have suggested that excess iron accumulation may be a risk factor for breast cancer. However the role of iron in breast cancer metastasis has remained unclear. The major goal of our study is to investigate the roles of iron in breast cancer metastasis. We modulated the intracellular iron levels of human breast cancer cells, including the aggressive MDA-MB-231 cells and non-aggressive MCF-7 cells, by using Deferoxamine (DFO) - a most widely used iron chelator. We found that DFO treatment could deplete intracellular iron in MCF-7 cells. In contrast, DFO treatment led to a significant increase in the intracellular iron level in MDA-MB-231 cells. The MDA-MB-231 cells with the increased intracellular iron level exhibited increases in both mesenchymal markers and cell migration. Furthermore, the DFO-treated MDA-MB-231 cells showed increases in both tumor necrosis factor α (TNF-α)-induced nuclear factor kappa B (NF-κB) signaling and transforming growth factor-β (TGF-β) signaling, which could contribute to the enhanced cell migration. Collectively, our study has provided the first evidence suggesting that increased intracellular iron levels could lead to enhanced migration of aggressive breast cancer cells by increasing TNF-α-dependent NF-κB signaling and TGF-β signaling. Our study has also suggested that caution should be taken when DFO is applied for treating breast cancer cells, since DFO could produce differential effects on the intracellular iron levels for aggressive breast cancer cells and non-aggressive breast cancer cells.

Visualising substrate-fingermark interactions: Solid-state NMR spectroscopy of amino acid reagent development on cellulose substrates

Most spectroscopic studies of the reaction products formed by ninhydrin, 1,2-indanedione-zinc (Ind-Zn) and 1,8-diazafluoren-9-one (DFO) when reacted with amino acids or latent fingermarks on paper substrates are focused on visible absorption or luminescence spectroscopy. In addition, structural elucidation studies are typically limited to solution-based mass spectrometry or liquid nuclear magnetic resonance (NMR) spectroscopy, which does not provide an accurate representation of the fingermark development process on common paper substrates. The research presented in this article demonstrates that solid-state carbon-13 magic angle spinning NMR ((13)C-MAS-NMR) is a technique that can not only be utilised for structural studies of fingermark enhancement reagents, but is a promising technique for characterising the effect of paper chemistry on fingermark deposition and enhancement. The latter opens up a research area that has been under-explored to date but has the potential to improve our understanding of how fingermark secretions and enhancement reagents interact with paper substrates.

Deferoxamine mesylate enhances virulence of community-associated methicillin resistant Staphylococcus aureus

Staphylococcus aureus is a leading cause of bacterial infections. Strains of community-associated methicillin-resistant S. aureus (CA-MRSA), such as USA300, display enhanced virulence and fitness. Patients suffering from iron overload diseases often undergo iron chelation therapy with deferoxamine mesylate (DFO). Here, we show that USA300 uses this drug to acquire iron. We further demonstrate that mice administered DFO I.P., versus those not administered DFO, had significantly higher bacterial burden in livers and kidneys after I.V. challenge with USA300, associated with increased abscess formation and tissue destruction. The virulence of USA300 mutants defective for DFO uptake was not affected by DFO treatment.

Desferrioxamine regulates HIF-1 alpha expression in neonatal rat brain after hypoxia-ischemia

Hypoxia-inducible factor 1α (HIF-1α) promotes cell survival after hypoxia-ischemia by regulating its target genes. Desferrioxamine (DFO) has been found to up-regulate HIF-1α expression in ischemia brain injury. However, the signaling pathway to mediate this regulation remains unclear in neonatal hypoxia-ischemia brain damage (HIBD). Since phosphoinositide 3-kinase (PI3K/Akt) pathway and extracellular signal-related protein kinase pathway (Erk1/2 MAPK) have proven to be involved in the regulation of HIF-1α in neonatal rat brain after hypoxia-ischemia (HI), we hypothesized that DFO might regulate HIF-1α by activating PI3K/Akt and Erk1/2 MAPK pathways in developing rat brain after HI. To test this hypothesis, we subjected postnatal day 10 rats to DFO intraperitoneal injection 30 min before HI. Rat brains were collected to detect the expression of HIF-1α and its target gene VEGF, as well as PI3K/Akt and Erk1/2 MAPK using Western blot analysis. We found that the expression of HIF-1α, VEGF, and p-Erk1/2 was significantly upregulated and peaked at 4 h after HI in DFO treated group, with higher level and earlier peak time than control group. However, the expression of p-Akt was unchanged in DFO treated group compared with control group. Our findings suggest that DFO might up-regulate HIF-1α and its target gene VEGF through Erk1/2 MAPK pathway in the developing rat brain after HI.

Noxa couples lysosomal membrane permeabilization and apoptosis during oxidative stress

The exact roles of lysosomal membrane permeabilization (LMP) in oxidative stress-triggered apoptosis are not completely understood. Here, we first studied the temporal relation between LMP and mitochondrial outer membrane permeabilization (MOMP) during the initial stage of apoptosis caused by the oxidative stress inducer H2O2. Despite its essential role in mediating apoptosis, the expression of the BH3-only Bcl-2 protein Noxa was dispensable for LMP. In contrast, MOMP was dependent on Noxa expression and occurred downstream of LMP. When lysosomal membranes were stabilized by the iron-chelating agent desferrioxamine, H2O2-induced increase in DNA damage, Noxa expression, and subsequent apoptosis were abolished by the inhibition of LMP. Importantly, LMP-induced Noxa expression increase was mediated by p53 and seems to be a unique feature of apoptosis caused by oxidative stress. Finally, exogenous iron loading recapitulated the effects of H2O2 on the expression of BH3-only Bcl-2 proteins. Overall, these data reveal a Noxa-mediated signaling pathway that couples LMP with MOMP and ultimate apoptosis during oxidative stress.

Molecular functions of the iron-regulated metastasis suppressor, NDRG1, and its potential as a molecular target for cancer therapy

N-myc down-regulated gene 1 (NDRG1) is a known metastasis suppressor in multiple cancers, being also involved in embryogenesis and development, cell growth and differentiation, lipid biosynthesis and myelination, stress responses and immunity. In addition to its primary role as a metastasis suppressor, NDRG1 can also influence other stages of carcinogenesis, namely angiogenesis and primary tumour growth. NDRG1 is regulated by multiple effectors in normal and neoplastic cells, including N-myc, histone acetylation, hypoxia, cellular iron levels and intracellular calcium. Further, studies have found that NDRG1 is up-regulated in neoplastic cells after treatment with novel iron chelators, which are a promising therapy for effective cancer management. Although the pathways by which NDRG1 exerts its functions in cancers have been documented, the relationship between the molecular structure of this protein and its functions remains unclear. In fact, recent studies suggest that, in certain cancers, NDRG1 is post-translationally modified, possibly by the activity of endogenous trypsins, leading to a subsequent alteration in its metastasis suppressor activity. This review describes the role of this important metastasis suppressor and discusses interesting unresolved issues regarding this protein.

Suppression of immunoglobulin production in human peripheral blood mononuclear cells by monocytes via secretion of heavy-chain ferritin

In vitro antigen stimulation of peripheral blood mononuclear cells (PBMCs) does not induce immunoglobulin (Ig) production. However, pretreatment of PBMCs with l-leucyl-l-leucine methyl ester (LLME) prior to in vitro stimulation removes the suppression of Ig production. In the present study, we attempted to identify the target cells of LLME and determine the mechanisms by which Ig production in PBMCs is suppressed. We found that CD14(+) monocytes are involved in the suppression of Ig production in PBMCs. Furthermore, we confirmed that heavy-chain ferritin derived from CD14(+) monocytes suppresses Ig production in PBMCs, possibly through iron sequestration.

Targeting dysregulation of brain iron homeostasis in Parkinson's disease by iron chelators

Brain iron accumulation has been implicated in a host of chronic neurological diseases, including Parkinson's disease (PD). The elevated iron levels observed in the substantia nigra of PD subjects have been suggested to incite the generation of reactive oxygen species and intracellular α-synuclein aggregation, terminating in the oxidative neuronal destruction of this brain area. Thus, elucidation of the molecular mechanisms involved in iron dysregulation and oxidative stress-induced neurodegeneration is a crucial step in deciphering PD pathology and in developing novel iron-complexing compounds aimed at restoring brain iron homeostasis and attenuating neurodegeneration. This review discusses the involvement of dysregulation of brain iron homeostasis in PD pathology, with an emphasis on the potential effectiveness of naturally occurring compounds and novel iron-chelating/antioxidant therapeutic hybrid molecules, exerting a spectrum of neuroprotective interrelated activities: antioxidant/monoamine oxidase inhibition, activation of the hypoxia-inducible factor (HIF)-1 signaling pathway, induction of HIF-1 target iron-regulatory and antioxidative genes, and inhibition of α-synuclein accumulation and aggregation.

Modulation of Dcytb (Cybrd 1) expression and function by iron, dehydroascorbate and Hif-2α in cultured cells

BACKGROUND

Duodenal cytochrome b (Dcytb) is a mammalian plasma ferric reductase enzyme that catalyses the reduction of ferric to ferrous ion in the process of iron absorption. The current study investigates the relationship between Dcytb, iron, dehydroascorbate (DHA) and Hif-2α in cultured cell lines.

METHODS

Dcytb and Hif-2α protein expression was analysed by Western blot technique while gene regulation was determined by quantitative PCR. Functional analyses were carried out by ferric reductase and (59)Fe uptake assays.

RESULTS

Iron and dehydroascorbic acid treatment of cells inhibited Dcytb mRNA and protein expression. Desferrioxamine also enhanced Dcytb mRNA level after cells were treated overnight. Dcytb knockdown in HuTu cells resulted in reduced mRNA expression and lowered reductase activity. Preloading cells with DHA (to enhance intracellular ascorbate levels) did not stimulate reductase activity fully in Dcytb-silenced cells, implying a Dcytb-dependence of ascorbate-mediated ferrireduction. Moreover, Hif-2α knockdown in HuTu cells led to a reduction in reductase activity and iron uptake.

CONCLUSIONS

Taken together, this study shows the functional regulation of Dcytb reductase activity by DHA and Hif-2α.

GENERAL SIGNIFICANCE

Dcytb is a plasma membrane protein that accepts electrons intracellularly from DHA/ascorbic acid for ferrireduction at the apical surface of cultured cells and enterocytes.

The role of HIF in cobalt-induced ischemic tolerance

Understanding the endogenous survival pathways induced by ischemic tolerance may yield targets for neuroprotection from stroke. One well-studied pathway reported to be evoked by preconditioning stimuli is the transcription factor HIF (hypoxia-inducible factor). However, whether HIF induction by ischemic insults is neuroprotective or toxic is still unclear. We examined the ability of three prolyl-hydroxylase inhibitors, which induce HIF, to protect hippocampal cultures from oxygen-glucose deprivation. Hippocampal cultures were exposed to ischemic preconditioning or various concentrations of cobalt chloride, deferoxamine (DFO) or dimethyloxylalyglycine (DMOG), prior to lethal oxygen-glucose deprivation (OGD). Cell survival of neurons and astrocytes was determined with dual-label immunocytochemistry. The induction of HIF targets was assessed in mixed as well as astrocyte-enriched cultures. Ischemic preconditioning, as well as low concentrations of cobalt and DFO, enhanced the survival of neurons following OGD. However, DMOG exacerbates OGD-induced neuronal death. At low concentrations, all three prolyl-hydroxylase (PHD) inhibitors increased the survival of astrocytes. Neuroprotective concentrations of cobalt induced the transcription of the cytokine erythropoietin (EPO) in astrocyte cultures. In addition, pretreatment with recombinant human erythropoietin (rH-EPO) also protected neurons from OGD. Our data suggest that HIF-induced EPO, released from astrocytes, protects neurons from OGD. However, the three PHD inhibitors each exhibited different neuroprotective profiles at low concentrations, suggesting that not all PHD inhibitors are created equal. The protective effects at low doses is reminiscent of HIF involvement in ischemic tolerance, in which sub-lethal insults induce HIF pathways resulting in neuroprotection, whereas the high-dose toxicity suggests that over-activation of HIF is not always protective. Therefore, the choice of inhibitor and dose may determine the clinical utility of these compounds. Deferoxamine exhibited little toxicity even at higher doses, and therefore appears a promising candidate for clinical use.