[Killing effect of anti-MSLN-iCAR-NK cells derived from induced pluripotent stem cells on ovarian epithelial cancer cells]

Objective: To investigate the cytotoxic effects of induced pluripotent stem (iPS) cells of anti-mesothelin (MSLN)-chimeric antigen receptor natural killer (CAR-NK) cells (anti-MSLN-iCAR-NK cells) on ovarian epithelial cancer cells. Methods: Twenty cases of ovarian cancer patients who underwent surgical treatment at Henan Provincial People's Hospital from September 2020 to September 2021 were collected, and 20 cases of normal ovarian tissues resected during the same period due to other benign diseases were also collected. (1) Immunohistochemistry and immunofluorescence were used to verify the expression of MSLN protein in ovarian cancer tissues. (2) Fresh ovarian cancer tissues were extracted and cultured to obtain primary ovarian cancer cells. Recombinant lentiviral vectors targeting anti-MSLN-CAR-CD244 were constructed and co-cultured with iPS cells to obtain anti-MSLN-iCAR cells. These cells were differentiated into anti-MSLN-iCAR-NK cells using cytokine-induced differentiation method. The cell experiments were divided into three groups: anti-MSLN-iCAR-NK cell group, natural killer (NK) cell group, and control group. (3) Flow cytometry and live cell staining experiment were used to detect the apoptosis of ovarian cancer cells in the three groups. (4) Enzyme-linked immunosorbent assay (ELISA) was used to measure the expression levels of interferon-γ (IFN-γ), tumor necrosis factor-α (TNF-α), granzyme B (GZMB), perforin 1 (PRF1), interleukin (IL)-6, and IL-10 in the three groups of ovarian cancer cells. Results: (1) Immunohistochemistry analysis showed that a positive expression rate of MSLN protein in ovarian cancer tissues of 65% (13/20), while normal ovarian tissues had a positive rate of 30% (6/20). The comparison between the two groups was statistically significant (χ2=4.912, P=0.027). Immunofluorescence analysis revealed that the positive expression rate of MSLN protein in ovarian cancer tissues was 70% (14/20), while normal ovarian tissues had a positive rate of 30% (6/20). The comparison between the two groups was statistically significant (χ2=6.400, P=0.011). (2) Flow cytometry analysis showed that the apoptotic rate of ovarian cancer cells in the anti-MSLN-iCAR-NK cell group was (29.27±0.85)%, while in the NK cell group and control group were (8.44±0.34)% and (6.83±0.26)% respectively. There were statistically significant differences in the comparisons between the three groups (all P<0.01). Live cell staining experiment showed that the ratio of dead cells to live cells in the anti-MSLN-iCAR-NK cell group was (36.3±8.3)%, while in the NK cell group and control group were (5.4±1.4)% and (2.0±1.3)% respectively. There were statistically significant differences in the comparisons between the three groups (all P<0.001). (3) ELISA analysis revealed that the expression levels of IFN-γ, TNF-α, GZMB, PRF1, IL-6, and IL-10 in ovarian cancer cells of the anti-MSLN-iCAR-NK cell group were significantly higher than those in the NK cell group and the control group (all P<0.05). Conclusion: The anti-MSLN-iCAR-NK cells exhibit a strong killing ability against ovarian cancer cells, indicating their potential as a novel immunotherapy approach for ovarian cancer.

HER2 and HLA-A*02 dual CAR-T cells utilize LOH in a NOT logic gate to address on-target off-tumor toxicity

BACKGROUND

One of the major challenges in chimeric antigen receptor (CAR)-T cell therapy for solid tumors is the potential for on-target off-tumor toxicity due to the expression of CAR tumor antigens in essential tissues and organs. Here, we describe a dual CAR NOT gate incorporating an inhibitory CAR (iCAR) recognizing HLA-A*02 ("A2") that enables effective treatment with a potent HER2 activating CAR (aCAR) in the context of A2 loss of heterozygosity (LOH).

METHODS

A CAR-T cell screen was conducted to identify inhibitory domains derived from natural immune receptors (iDomains) to be used in a NOT gate, to kill A2- HER2+ lung cancer cell lines but spare A2+ HER2+ lung cancer cell-lines with high specificity. The extensive analysis of lead candidates included T-cell activation and killing, assays of reversibility and durability in sequential challenges, target cell specificity in mixed 3D spheroids and 2D cultures, and the characterization of CAR expression level and cell-trafficking.

RESULTS

A leukocyte immunoglobulin-like receptor B1 (LIR1) iDomain iCAR was identified as most effective in regulating the cytotoxicity of a second generation HER2 aCAR. Target transfer experiments demonstrated that the 'on' and 'off' cell state of the LIR1 NOT gate CAR-T cell is both durable and reversible. Protection required iCAR signaling and was associated with reduced aCAR and iCAR surface expression. iCAR regulation was sufficient to generate high target specificity in a 3D adjacent spheroid assay designed to model the interface between clonal A2 LOH foci and normal tissue. However, we observed significant bystander killing of A2+ cells in admix culture through aCAR dependent and independent mechanisms. LIR1 NOT gate CAR-T cells conferred protection against H1703-A2+ tumors and high efficacy against H1703-A2- tumors in-vivo. We observed that the iCAR is inactive in A2+ donors due to cis-binding, but Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) knockout of HLA-A fully restored iCAR activity.

CONCLUSIONS

We have preclinically validated an iCAR NOT gate technology broadly applicable for targeting HER2 expression in the context of A2 LOH. This approach is designed to prevent off tumor toxicity while allowing highly potent antitumor activity.

Iron therapy mitigates chronic kidney disease progression by regulating intracellular iron status of kidney macrophages

Systemic iron metabolism is disrupted in chronic kidney disease (CKD). However, little is known about local kidney iron homeostasis and its role in kidney fibrosis. Kidney-specific effects of iron therapy in CKD also remain elusive. Here, we elucidate the role of macrophage iron status in kidney fibrosis and demonstrate that it is a potential therapeutic target. In CKD, kidney macrophages exhibited depletion of labile iron pool (LIP) and induction of transferrin receptor 1, indicating intracellular iron deficiency. Low LIP in kidney macrophages was associated with their defective antioxidant response and proinflammatory polarization. Repletion of LIP in kidney macrophages through knockout of ferritin heavy chain (Fth1) reduced oxidative stress and mitigated fibrosis. Similar to Fth1 knockout, iron dextran therapy, through replenishing macrophage LIP, reduced oxidative stress, decreased the production of proinflammatory cytokines, and alleviated kidney fibrosis. Interestingly, iron markedly decreased TGF-β expression and suppressed TGF-β-driven fibrotic response of macrophages. Iron dextran therapy and FtH suppression had an additive protective effect against fibrosis. Adoptive transfer of iron-loaded macrophages alleviated kidney fibrosis, validating the protective effect of iron-replete macrophages in CKD. Thus, targeting intracellular iron deficiency of kidney macrophages in CKD can serve as a therapeutic opportunity to mitigate disease progression.

Interaction between Ferastral and plasma factors

Ferastral, iron-poly (sorbitol-gluconic acid) complex, in aqueous solution is completely adsorbed by magnesium carbonate; Ferastral in serum solution is only partially adsorbed by magnesium carbonate. Adsorption by magnesium carbonate removes the fraction of Ferastral in serum solution which donates iron more readily to transferrin. It is suggested that this fraction comprises the smaller molecular species of the Ferastral complex and that these species have a faster rate of absorption from an intramuscular injection site than the larger molecular species of the iron complex preparation. These findings shed some light on the patterns of serum transferrin bound iron compared with serum Ferastral concentrations which occur with time after intramuscular Ferastral injection.

Transfer of iron from Ferastral and other organic complexes to transferrin as measured by reticulocyte uptake

The transfer of iron from the iron carbohydrate complexes, Ferastral, Imferon, and Jectofer, and from ferric chloride has been studied by the effect of such transfer in reducing reticulocyte uptake of 59Fe from labelled transferrin. There are plasma factors which augment the transfer of iron from complex to transferrin. The pattern of transfer from Ferastral and from Imferon are similar: at concentration of 5000 microgram/100 ml and 1250 microgram/100 ml in plasma these complexes transfer about 0.8% and 1.7%, respectively. Jectofer transfers about four times these amounts under similar conditions. In the case of Ferastral there is evidence of an equilibrium between transferrin-bound and Ferastral-bound iron. The characteristics of Ferastral assessed in this way suggest that it may prove suitable for therapeutic use as a total dose infusion.

Acute injury with intravenous iron and concerns regarding long-term safety

Intravenous iron is widely used to maintain adequate iron stores and prevent iron deficiency anemia in patients with chronic kidney disease, yet concerns remain about its long-term safety with respect to oxidative stress, kidney injury, and accelerated atherosclerosis, which are the subjects of this review. Three parenteral iron formulations are available for use in the United States: Iron dextran, iron gluconate, and iron sucrose. Iron dextran, especially the high molecular form, has been linked with anaphylactoid and anaphylactic reactions, and its use has been declining. A portion of intravenous iron preparations is redox-active, labile iron available for direct donation to transferrin. In vitro tests show that commonly available intravenous iron formulations have differing capacities to saturate transferrin directly: Iron gluconate > iron sucrose > iron dextran. Intravenous iron treatment produces oxidative stress, as demonstrated by increases in plasma levels of lipid peroxidation products (malondialdehyde), at a point that is much earlier than the time to peak concentration of catalytically active iron, suggesting a direct effect of iron sucrose on oxidative stress. Furthermore, iron sucrose infusion produces endothelial dysfunction that seems to peak earlier than the serum level of free iron. Intravenous iron sucrose infusion also has been shown to produce acute renal injury and inflammation as demonstrated by increased urinary albumin, enzyme (N-acetyl-beta-glucosaminidase), and cytokine (chemokine monocyte chemoattractant protein-1) excretions. Although the long-term dangers of intravenous iron are unproved, these data call for examination of effects of intravenous iron on the potential for long-term harm in patients with chronic kidney disease.

Peripheral iron dextran induced degeneration of dopaminergic neurons in rat substantia nigra

Iron accumulation is considered to be involved in the pathogenesis of Parkinson's disease. To demonstrate the relationship between peripheral iron overload and dopaminergic neuron loss in rat substantia nigra (SN), in the present study we used fast cyclic voltammetry, tyrosine hydroxylase (TH) immunohistochemistry, Perls' iron staining, and high performance liquid chromatography-electrochemical detection to study the degeneration of dopaminergic neurons and increased iron content in the SN of iron dextran overloaded animals. The findings showed that peripheral iron dextran overload increased the iron staining positive cells and reduced the number of TH-immunoreactive neurons in the SN. As a result, dopamine release and content, as well as its metabolites contents were decreased in caudate putamen. Even more dramatic changes were found in chronic overload group. These results suggest that peripheral iron dextran can increase the iron level in the SN, where excessive iron causes the degeneration of dopaminergic neurons. The chronic iron overload may be more destructive to dopaminergic neurons than the acute iron overload.

Bioinorganic transformations of liver iron deposits observed by tissue magnetic characterisation in a rat model

The magnetic properties and the ultrastructure, with special emphasis on the nanometric range, of liver tissues in an iron overload rat model have been investigated. The tissues of the animals, sacrificed at different times after a single iron dextran injection, have been characterised by magnetic AC susceptibility measurements together with transmission electron microscopy (TEM) and selected area electron diffraction (SAED) as helping techniques. It has been observed that few days after the iron administration the liver contains at least two iron species: (i) akaganéite nanoparticles, coming from iron dextran and (ii) ferrihydrite nanoparticles corresponding to ferritin. The magnetic susceptibility of the tissues depends not only on the elemental iron content but also on its distribution among chemical species, and varies in a remarkable regular manner as a function of the elapsed time since the iron administration. The results are of relevance with respect to non-invasive techniques for liver iron determination, directly or indirectly based on the magnetic susceptibility of the tissues, as biomagnetic liver susceptometry (BLS) and magnetic resonance (MRI) image treatment.

Iron Uptake and Release by Macrophages is Sensitive to Propranolol

In this study we have tested the effects of d-propranolol (D-Pro) on the iron uptake, iron release and oxidative response of iron-loaded cells in a cellular model of iron-overload using isolated rat peritoneal macrophages incubated with iron-dextran (Fe-D). Pretreatment of macrophages with D-Pro (5-200 microM) prior to Fe-D exposure decreased the cellular iron content and partially prevented iron release from latex-activated macrophages. Release of reactive oxygen species from activated cells was detected by dichlorodihydrofluorescein (DCDHF, 5 microM) oxidation. We found that loading cells with Fe-D increased their response to latex, which was prevented by the lysosomotropic antioxidant agent D-Pro (10 microM).

Magnetic characterisation of rat muscle tissues after subcutaneous iron dextran injection

Ex vivo freeze-dried rat muscle tissues, collected at different times t after a single dose of subcutaneously injected iron dextran, have been magnetically characterised. The AC susceptibility of the tissues shows an overall superparamagnetic behaviour and the dependence on t of, especially, the out-of-phase component is remarkably systematic despite the fact that each tissue originates in a different rat individual. The experiments show that the akaganéite (beta-FeOOH) nanoparticles contained in the injected drug are progressively degraded in the living tissue and, at times of the order of 1 month and for all the analysed rat individuals, converge to a magnetically well-defined species with much narrower magnetic activation energy distribution than iron dextran. Thorough transmission electron microscopy experiments of the same tissues indicate the presence of oxyhydroxide particles, whose size decreases for increasing t in agreement with the interpretation of the magnetic susceptibility. The conclusions drawn from the magnetic study do well correspond to the properties of the whole tissue since no biochemical extraction work has been done. The AC susceptibility appears to be a valuable and complementary tool in pharmacological studies of iron-containing drugs.

Labile iron in parenteral iron formulations: a quantitative and comparative study

BACKGROUND

Evidence of iron-mediated oxidative stress, neutrophil dysfunction and enhanced bacterial growth after intravenous (IV) iron administration has been ascribed to a labile or bioactive iron fraction present in all IV iron agents.

METHODS

To quantify and compare the size of the labile fraction in several classes of IV iron agents, we examined iron donation to transferrin (Tf) in vitro. We added dilutions of ferric gluconate, iron sucrose and each of two iron dextran preparations to serum in vitro, passed the resulting samples through alumina columns to remove iron agent and free organic iron, and measured Tf-bound iron in the resulting eluates. Comparing results to serum samples without added iron, we calculated delta Tf-bound iron for each agent at each concentration. Finally, we compared delta Tf-bound iron to the concentration of added agent and calculated the percent iron donation to Tf.

RESULTS

We found that Tf-bound iron increased with added iron concentration for each agent: delta Tf-bound iron was directly related to the concentration and type of iron agent (P<0.001). Mean percent iron donation to Tf ranged from 2.5 to 5.8% with the following progression: iron dextran-Dexferrum<iron dextran-INFeD<iron sucrose<ferric gluconate. Pairwise differences between agents for percent iron donation were statistically significant (P<0.05) only between ferric gluconate and both iron dextran agents, and between iron sucrose and iron dextran-Dexferrum.

CONCLUSIONS

Approximately 2-6% of total iron in commonly used IV iron compounds is available for in vitro iron donation to Tf. This fraction may contribute to evidence of bioactive iron in patients after IV iron administration.

Parenteral iron formulations: a comparative toxicologic analysis and mechanisms of cell injury

BACKGROUND

Multiple parenteral iron (Fe) formulations exist for administration to patients with end-stage renal disease. Although there are concerns regarding their potential toxicities, no direct in vitro comparisons of these agents exist. Thus, the present study contrasted pro-oxidant and cytotoxic potentials of four available Fe preparations: Fe dextran (Fe dext), Fe sucrose (Fe sucr), Fe gluconate (Fe gluc), and Fe oligosaccharide (Fe OS).

METHODS

Differing dosages (0.06 to 1 mg/mL) of each compound were added to either (1) isolated mouse proximal tubule segments, (2) renal cortical homogenates, or (3) cultured human proximal tubule (HK-2) cells (0.5- to 72-hour incubations). Oxidant injury (malondialdehyde generation) and lethal cell injury (percentage of lactate dehydrogenase release; tetrazolium dye uptake) were assessed. Effects of selected antioxidants (glutathione [GSH], catalase, dimethylthiourea (DMTU), and sodium benzoate also were assessed.

RESULTS

Each test agent induced massive and similar degrees of lipid peroxidation. Nevertheless, marked differences in cell death resulted (Fe sucr >> Fe gluc > Fe dext approximately Fe OS). This relative toxicity profile also was observed in cultured aortic endothelial cells. Catalase, DMTU, and sodium benzoate conferred no protection. However, GSH and its constituent amino acid glycine blocked Fe sucr-mediated cell death. The latter was mediated by mitochondrial blockade, causing free radical generation and a severe adenosine triphosphate depletion state.

CONCLUSIONS

(1) parenteral Fes are highly potent pro-oxidants and capable of inducing tubular and endothelial cell death, (2) markedly different toxicity profiles exist among these agents, and (3) GSH can exert protective effects. However, the latter stems from GSH's glycine content, rather than from a direct antioxidant effect.

Iron-induced oxidant stress leads to irreversible mitochondrial dysfunctions and fibrosis in the liver of chronic iron-dosed gerbils. The effect of silybin

Hepatic iron toxicity because of iron overload seems to be mediated by lipid peroxidation of biological membranes and the associated organelle dysfunctions. However, the basic mechanisms underlying this process in vivo are still little understood. Gerbils were dosed with weekly injections of iron-dextran alone or in combination with sylibin, a well-known antioxidant, by gavage for 8 weeks. A strict correlation was found between lipid peroxidation and the level of desferrioxamine chelatable iron pool. A consequent derangement in the mitochondrial energy-transducing capability, resulting from a reduction in the respiratory chain enzyme activities, occurred. These irreversible oxidative anomalies brought about a dramatic drop in tissue ATP level. The mitochondrial oxidative derangement was associated with the development of fibrosis in the hepatic tissue. Silybin administration significantly reduced both functional anomalies and the fibrotic process by chelating desferrioxamine chelatable iron.

The role of cellular oxidases and catalytic iron in the pathogenesis of ethanol-induced liver injury

Free radical generation and catalytic iron have been implicated in the pathogenesis of alcohol-induced liver injury but the source of free radicals is a subject of controversy. The mechanism of ethanol-induced liver injury was investigated in isolated hepatocytes from a rodent model of iron loading in which free radical generation was measured by the determination of alkane production (ethane and pentane). Iron loading (125 mg/kg i.p.) increased hepatic non-heme iron 3-fold, increased the prooxidant activity of cytosolic ultrafiltrates 2-fold and doubled ethanol-induced alkane production. The addition of desferrioxamine (20 microM), a tight chelator of iron, completely abolished alkane production indicating the importance of catalytic iron. The role of cellular oxidases as a source of ethanol induced free radicals was studied through the use of selective inhibitors. In both the presence and absence of iron loading, selective inhibition of xanthine oxidase with oxipurinol(20 microM) diminished ethanol-induced alkane production 0-40%, inhibition of aldehyde oxidase with menadione (20 microM) diminished alkane production 36-75%, while the inhibition of aldehyde and xanthine oxidase by feeding tungstate (100 mg/kg/day) virtually abolished alkane production. Addition of acetaldehyde(50 microM) to hepatocytes generated alkanes at rates comparable to those achieved with ethanol indicating the importance of acetaldehyde metabolism in free radical generation. The cellular oxidases (aldehyde and xanthine oxidase) along with catalytic iron play a fundamental role in the pathogenesis of free radical injury due to ethanol.

Dextran magnetite as a liver contrast agent

The superparamagnetic particle dextran magnetite was studied as a liver tumor contrast agent for magnetic resonance imaging (MRI). The effects of dextran magnetite on the longitudinal (T1) and transverse (T2) relaxation times in liver, spleen, and an implanted rat liver tumor were measured at 0.47 T (IBM/Bruker PC-20 relaxometer) over the dose range of 23 to 69 mumol Fe/kg. Dextran magnetite substantially reduced the T2 of the liver and spleen, but not of the tumor, thereby providing a basis for improved tumor imaging. The T1 of the tumor was not affected following injection of dextran magnetite in the dose range studied, while the spleen T1 was reduced substantially more than the T1 of the liver. Histological studies using the iron reaction for Prussian blue clearly showed dextran magnetite in the liver and spleen, but not in the tumor. While dextran magnetite was sequestered in macrophages in both liver and spleen, the distribution in the liver was more diffuse (70 microns average particle separation) than that in the spleen (25 microns separation). The lack of a T1 effect in the liver is consistent with the fact that a majority of the water in the tissue cannot diffuse to the relaxational centers on the time scale of the liver's intrinsic T1 (280 ms). In the spleen, however, the dextran magnetite is more densely packed in the red pulp allowing a significant fraction of the water to be relaxed by a T1 mechanism. Spin-echo images of the implanted tumor (mammary adenocarcinoma. R3230AC) in the livers of Fischer 344 rats were obtained at 0.50 T (Siemens Magnetom). The tumor-to-liver contrast was improved for both T1 and T2-weighted spin-echo images after intravenous injection of the dextran magnetite contrast agent. The contrast determined from these images agreed with that predicted by the measured T1 and the T2 (Hahn spin-echo) values. In addition, gradient-echo T2-weighted images with good contrast were obtained in a much shorter imaging time than was needed for T2-weighted spin-echo images. These results demonstrate that the MRI contrast enhancement observed with dextran magnetite is based on its selective uptake and distribution in the macrophages in the liver and spleen and that this agent has substantial potential as a superparamagnetic MR contrast agent.

Wheat germ agglutinin is selectively transported to multivesicular bodies

Colloidal iron dextran particles bearing wheat germ agglutinin (WGA/FeDex) were bound by glycoconjugates expressed at the surface of HepG2 cells. Bound WGA/FeDex was internalized when cells were incubated at 37 degrees C and accumulated in intracellular structures which have the same buoyant density as the plasma membrane when examined on Percoll density gradients. The intracellular structures containing WGA/FeDex were identified as multivesicular bodies (MVB) by transmission electron microscopy. WGA/FeDex was not transported to lysosomes nor did it interfere with uptake and transport of GalBSA to lysosomes by the asialoglycoprotein receptor. WGA/FeDex was seen predominantly in non-coated invaginations at the cell surface, suggesting it may enter cells at a different site than GalBSA/FeDex. Highly enriched plasma membranes and MVBs containing superparamagnetic [125I]WGA/FeDex particles were prepared by high gradient magnetic affinity chromatography (HIMAC). Plasma membranes prepared by HIMAC were enriched 30-fold for [125I]WGA/FeDex, 15-fold for alkaline phosphodiesterase I, and 9-fold for galactosyltransferase relative to the crude post-nuclear homogenate and consisted entirely of plasmalemmal sheets. Intracellular structures containing WGA/FeDex were enriched 35-fold for [125I]WGA/FeDex, 10-fold for alkaline phosphodiesterase I, and 10-fold for galactosyltransferase but did not contain lysosomal beta-galactosidase. WGA/FeDex has a different ultimate destination in HepG2 cells than ligands internalized by the asialoglycoprotein receptor and can be used to obtain highly enriched plasma membranes and MVBs from cultured cells.

Analysis of iron-containing compounds in different compartments of the rat liver after iron loading

The livers of iron-loaded rats were fractionated and a cytosolic fraction, a lysosomal fraction, a siderosomal fraction and haemosiderin were obtained. All iron-containing compounds from these fractions were isolated and their morphology, Fe/P ratios, iron core diameter and peptide content were compared. The cytosolic fraction contained ferritin (CF) and a slower sedimenting, light ferritin (CLF). The lysosomal fraction also contained ferritin (LF) and a slower sedimenting light ferritin (LLF). The siderosomal fraction contained ferritin (SF), a faster sedimenting non-ferritin iron compound (SIC) and haemosiderin (HS). SIC and HS did not resemble ferritin as much as the other products did, but were found to be water-insoluble aggregates. The Fe/P ratios of CF and CLF were lower than the Fe/P ratios of LF and LLF and these in turn had lower Fe/P ratios than SF, SIC and HS. The iron core diameter of the cytosolic ferritin was increased after lysosomal uptake. The iron core diameters of the siderosomal products were smaller. CLF, CF, LF, LLF and SF contained one kind of subunit of approximately 20.5 kDa. SIC and HS contained other peptides in addition to the 20.5-kDa subunit. The results indicate that storage of ferritin molecules is not limited to the cytosolic compartment, but is also the case in the lysosomes. Extensive degradation of the ferritin molecule seems to be confined to the siderosomes.

Vascular to alveolar leak of iron dextran (120 kD) in the immature ventilated rabbit lung

Rabbit fetuses were delivered by hysterotomy on day 27 or 28 of gestation. Immediately after birth, the animals were tracheotomized and received by intravenous injection 0.2 mu Ci radiolabeled albumin and 11 mg iron dextran in 0.2 ml saline. The newborn rabbits then were ventilated artificially with a tidal vol of 12 ml/kg for 5-20 min. One group of nonventilated animals served as controls. At the end of the experiment, one lung was lavaged via the airways and the other was fixed for histologic examination. The recovery of labeled albumin and iron dextran in the lavage fluid was quantified. Iron dextran complexes were easily identified in the lung sections by staining with Prussian blue. Iron dextran accumulated in the airspaces of animals delivered on day 27 (about 4% of the injected dose during 10-20 min of ventilation). The albumin leakage was slightly higher than that of the dextran, a result consistent with different mol wt of the markers. The vol density of leaking alveoli in histologic sections increased with time, from 0 at birth to a mean value of 0.36 after 20 min of ventilation. The leakage starts as a focal event, gradually involving more and more terminal airspaces. In the histologic sections, there was no indication of a significant leakage at the bronchiolar level, although the epithelium of terminal and preterminal airways was clearly injured in all ventilated animals.

Accumulation and metabolism of iron-dextran by hepatocytes, Kupffer cells and endothelial cells in the neonatal pig liver

Treatment of newborn pigs with supplemental iron is a common procedure utilized to prevent neonatal anemia. The aim of this study was to investigate the hepatic distribution and intracellular metabolism of iron-dextran, a widely used colloidal-iron-carbohydrate preparation. Piglets were injected intramuscularly with iron-dextran (50 mg Fe/kg body wt) at 1 d of age. Hepatocytes and sinusoidal cells (Kupffer cells and endothelial cells) were isolated from iron-treated and control (uninjected) piglets at 2, 6 and 11 d of age. The concentrations of iron, copper and zinc in isolated cells were determined by atomic-absorption spectroscopy. In addition, the quantities of ferritin-protein and ferritin-iron were measured by immunoelectrophoresis and ion-exchange chromatography, respectively. At 2 d of age, the concentration (microgram/mg cell protein) of iron was 5-, 62- and 54-fold higher in hepatocytes, Kupffer cells and endothelial cells, respectively, isolated from iron-treated piglets than from control piglets. Hepatocytes, Kupffer cells and endothelial cells accumulated ferritin in response to iron-dextran treatment. Higher concentrations of ferritin-protein and ferritin-iron were present in Kupffer cells and endothelial cells than in hepatocytes at all times after treatment with iron-dextran. The percentage of cellular iron that was associated with ferritin, however, was greater in hepatocytes than in sinusoidal cells. Iron accumulated by all three liver cell types was mobilized to extrahepatic sites. Slight alterations in zinc and copper status of liver cells were evident at 11 d of age as a result of iron treatment.

Structural variations in soluble iron complexes of models for ferritin: an x-ray absorption and Mössbauer spectroscopy comparison of horse spleen ferritin to Blutal (iron-chondroitin sulfate) and Imferon (iron-dextran)

Variations in the turnover of storage iron have been attributed to differences in apoferritin and in the cytoplasm but rarely to differences in the structure of the iron core (except size). To explore the idea that the iron environment in soluble iron complexes could vary, we compared horse spleen ferritin to pharmaceutically important model complexes of hydrous ferric oxide formed from FeCl3 and dextran (Imferon) or chondroitin sulfate (Blutal), using x-ray absorption (EXAFS) and Mössbauer spectroscopy. The results show that the iron in the chondroitin sulfate complex was more ordered than in either horse spleen ferritin or the dextran complex (EXAFS), with two magnetic environments (Mössbauer), one (80%-85%) like Fe2O3 X nH2O (ferritinlike) and one (15%-20%) like Fe2O3 (hematite); since sulfate promotes the formation of inorganic hematite, the sulfate in the chondroitin sulfate most likely nucleated Fe2O3 and hydroxyl/carboxyls, which are ligands common to chondroitin sulfate, ferritin and dextran most likely nucleated Fe2O3 X nH2O. Differences in the structure of the iron complexed with chondroitin sulfate or dextran coincide with altered rates of iron release in vivo and in vitro and provide the first example relating function to local iron structure. Differences might also occur among ferritins in vivo, depending on the apoferritin (variations in anion-binding sites) or the cytoplasm (anion concentration).

Interaction of intravenously injected liposomes with mouse liver mitochondria. A fluorescence and electron microscopy study

Megamitochondria, resulting from cuprizone feeding of Swiss ICR mice, were fluorescent in hepatocytes after the intravenous injection to mice of a liposome-encapsulated acridine orange-DNA complex (AO-DNA). Flow cytofluorimetric analysis of isolated megamitochondria showed that the proportion of liposome-encapsulated AO-DNA which localized in megamitochondria increased from 0.02% of the dose injected per liver cell at 3 min after injection to an average of 0.34% at 1 h after injection. Megamitochondria showed negligible fluorescence by fluorescence activated cell sorting (FACS) analysis when free AO-DNA was intravenously injected. Transmission electron micrographs of mouse liver tissue after intravenous injection of liposomes encapsulating iron dextran showed an association of the liposomes with megamitochondria which appeared identical to liposome association with normal mitochondria. These results support and extend our earlier observation that a fraction of the liposomes injected intravenously into mice associate with mitochondria in the liver, and possibly deliver their aqueous contents there.

Studies of glomerular mesangial uptake and processing of macromolecules. I. Effect of polyvinyl alcohol-induced macrophages on uptake of iron dextran

The influence of prior glomerular mesangial uptake of a macromolecule that induces the infiltration of macrophages (M phi) into the mesangium on the uptake of a second macromolecule by the mesangium was studied in inbred Lewis rats. Renal transplantation of kidneys from rats previously injected with polyvinyl alcohol (PVA) was performed to avoid the potential influences of ongoing uptake of PVA and altered host milieu on the glomerular uptake of iron dextran (ID), a macromolecule that localizes primarily in the intrinsic mesangial cells of unmodified rats. In contrast to that in the recipient's native kidney, the uptake of ID was markedly increased in the glomeruli in kidneys previously exposed to PVA. This enhanced uptake was the consequence of the phagocytic activity of mesangial M phi elicited by and containing PVA since the site of increased ID content was shown by ultrastructural studies to be within mesangial M phi. Isogeneic renal transplantation per se did not influence mesangial function since the glomerular uptake of ID in donor and recipient kidneys was the same when donors were normal rats. In addition to the enhanced uptake of ID into lysosomes by mesangial M phi these cells were also much more active in the further processing of ID to ferritin particles within the cytoplasm than were intrinsic mesangial cells. These studies demonstrate that M phi attracted to the mesangium by a stimulus such as PVA may have important effects on the consequences of additional challenges to the mesangium.

In vitro assessment of virulence in Yersinia enterocolitica and related species

We have examined 136 isolates of Yersinia species, comprising 112 strains of Yersinia enterocolitica, 12 of Y. frederiksenii, 8 of Y. intermedia, and 5 of Y. kristensenii, for the presence of 40- to 50-megadalton virulence-associated plasmids and expression of the following plasmid-associated characteristics: Congo red pigmentation (CR), calcium dependence, autoagglutination, hydrophobicity, resistance to normal human serum, and pathogenicity in mice. All 136 strains yielded both pigmented (CR+) and nonpigmented (CR-) variants. Only CR+ variants, however, were virulent for iron-overloaded, desferrioxamine B-treated mice (R. M. Robins-Browne and J. K. Prpic, Infect. Immun. 47:744-779, 1985). Although the in vitro virulence-associated characteristics generally occurred together, each one could be expressed independently. Strains of Y. frederiksenii, Y. intermedia, and Y. kristensenii also expressed individual virulence-associated properties. Of 53 Y. enterocolitica strains which were virulent for iron-overloaded, desferrioxamine-treated mice, all but one expressed every virulence-associated characteristic. Several strains which were avirulent for mice, however, demonstrated these characteristics in various combinations. Because many Yersinia strains, particularly environmental isolates, carried plasmids of 40 to 50 megadaltons, detection of plasmids provided little information about bacterial pathogenicity unless virulence-associated properties were also sought. The best in vitro predictor of virulence was autoagglutination, followed by calcium dependence. Because only CR+ variants expressed virulence-associated determinants, Congo red pigmentation is useful for selecting potentially virulent strains.

Persistence of inert macromolecules (Imposil) in the rat mesangium and glomerular functional disturbance

Imposil iron-dextran is an inert tracer that has been used to study mesangial uptake and clearance of macromolecular material from the glomerular circulation. Such a tracer may be a useful marker of altered mesangial function in animals with some forms of glomerulonephritis. We have studied mesangial handling of intravenously injected Imposil (50 mg/100 g body weight) in normal rats by light, immunofluorescence and electron microscopy for up to 3 months. Mesangial cell uptake was maximal at 48-54 h. Extrusion and drainage of tracer to the vascular pole and distal tubule was evident at 3 days but iron was still present in mesangial cells at 3 months. Possible functional renal impairment resulting from persistent mesangially sequestered tracer was examined by measuring daily urine protein and iron excretion. A possible relationship between failure of mesangial cells to eliminate inert tracer and increasing glomerular permeability is demonstrated, suggesting that Imposil and similar inert macromolecules cannot be used for long-term studies of mesangial function.

Electron microscopic study of the peritoneal kinetics of iron dextran during peritoneal dialysis in the rabbit

Iron dextran, an electron-dense tracer, was given intravenously (100 mg of iron/100 g of body weight) to 8 normal rabbits to study its movement from the plasma to the peritoneal cavity during peritoneal dialysis. The dialysate infused at 75 ml/kg contained 1.5 g/dl of glucose in 4 animals and 4.25 g/dl in the remainder. Peritoneal dialysis was discontinued and the peritoneum was fixed in vivo at various times (20-120 min) after the injection of the iron dextran. Large amounts of tracer were detected in the effluent after draining the peritoneal cavity. Electron microscopic examination of the mesentery showed particles of iron dextran in the endothelial cells of small vessels (capillaries and venules) the interstitium and the mesothelial cells adjacent to vessels irrespective of the dialysate concentration or duration of dialysis. Tracer was not clearly demonstrated in the interendothelial or intermesothelial spaces. In the mesothelial cells, the particles were found exclusively in (small, elongated or large) vesicles, while in the endothelial cells they were both in vesicles and free in the cytoplasm. Our findings suggest that during the 20- to 120-min period after intravenous administration, the intracellular transport of iron dextran, depends on either moving vesicles or the presence of pre-existing tunnels in the mesothelial cells of rabbit mesentery.

The permeability of the basal lamina at the neuromuscular junction. An ultrastructural study of rat skeletal muscle using particulate tracers

Various macromolecular substances, such as toxins and antibodies, may interfere with neuromuscular transmission. The neuromuscular junction is also known to be a site for the uptake of macromolecular substances into the axon for subsequent transport to the central nervous system. The synaptic cleft of the neuromuscular junction is separated from the rest of the extracellular compartment of muscle by the basal lamina, the permeability properties of which are not known. The penetration of macromolecular substances of varying size into the synaptic cleft of the neuromuscular junction has been studied in rats. Four different tracers: Imferon (an iron-dextran measuring 11 X 7 X 7 nm), ferritin (a spherical iron-protein 12 nm in diameter), Imposil (an iron-dextran measuring 21 X 12 X 12 nm) and colloidal gold-protein (20-25 nm in diameter) were injected into the palmaris longus muscle. Fifteen and 120 min after injection, the distribution of these particulate tracers was studied by electron microscopy. Imferon and ferritin penetrated rapidly through the basal lamina along the muscle fibres and also into the synaptic cleft of the neuromuscular junction. The larger Imposil and colloidal gold particles were restricted from penetrating the basal lamina even after 2 h, and these particles were traced only occasionally within the synaptic cleft. The results indicate that the basal lamina of muscle acts as a diffusion barrier to large macromolecules, preventing them from entering the synaptic cleft.

Increased transfer of iron to the fetus after total dose infusion of iron dextran during pregnancy

After total dose infusion of iron dextran to 14 pregnant women the saturation of transferrin and the concentration of ferritin were increased in the cord blood at birth, compared with untreated cases. These changes suggest that the fetal iron stores may be increased by such treatment.

[Placental deposition and transfer of iron dextran to fetuses in mice at near term]

Deposition of iron dextran particles in the fetoplacental system was investigated by light and electron microscopy after intravenous injection into pregnant mice on days 18-19 of gestation. Thirty minutes after injection, the labyrinth trophoblast cells were strongly positive for iron whereas the fetal capillary endothelium was weakly stained. Electron microscopy revealed the transfer of iron dextran particles to the intercellular space between the first and second layers of trophoblasts, as well as within the vacuoles of the second layer trophoblasts. Transport through the second layer trophoblasts, however, was not evidenced, suggesting that the trophoblast layer may constitute a significant barrier. Three hours after injection, heavy iron reaction was observed in Reichert's membrane, trophoblast cells lined with this membrane, and visceral yolk sac. Electron microscopic examination of parietal yolk sac revealed the aggregation of iron dextran particles in the trophoblast cells with little penetration into the Reichert's membrane and parietal endoderm, suggesting that the Reichert's membrane and adhering trophoblast cells may be a significant barrier for selective transport of particulate materials in the yolk sac placenta.

The glomerular mesangium: a comparative study of mesangial handling of iron dextran complex and endogenous IgG in mice and rats

The function and channel system of the glomerular mesangium in mice and rats was investigated by studying the uptake and transport of intravenously injected iron-dextran particles, and the localization of endogenous IgG. Animals were killed at 30 min, 8 h, 1 and 3 days and 1 and 2 weeks after intravenous injection of iron dextran complex. It was found that the tracer was present maximally in the mesangium of the mouse at one day after injection whereas a maximum was not reached until the third day in the rat. Maximal levels of tracer particles in the extra-glomerular lacis area were found at three days in the mouse and at 2 weeks in the rat. Disappearance of the tracer from the blood as indicated by the measured serum iron levels did not seem to differ significantly in the two species. Using an ultrastructural immunoperoxidase technique, considerable amount of endogenous IgG were localized in the mesangial channel system in the stalk region and in the extraglomerular lacis area of mice, whereas in rats only very scanty endogenous IgG was present in these locations. It is suggested that the difference in mesangial handling of macromolecular material in mice and rats is more likely to be due to a different rate of transport through the mesangial channel system than to primary differences in mesangial phagocytotic activity.

Malabsorption and defective utilization of iron in three siblings

Three siblings had iron deficiency anemia without evidence of reduced iron intake or gastrointestinal blood loss. They failed to respond to oral iron therapy, and malabsorption of oral medicinal iron was demonstrated in two of the children. All three had a partial but incomplete hematologic response to intramuscular iron dextran treatment. There was no evidence for other well-defined causes of hypochromic microcytic anemia or for a generalized disorder of intestinal absorption. These three patients appear to have a familial disorder characterized by impaired iron absorption and utilization, similar to that observed in the mk/mk mouse.

Neuronal uptake of iron: somatopetal axonal transport and fate of cationized and native ferritin, and iron-dextran after intramuscular injections

Mice were injected into the muscles of the vibrissae with native ferritin (NF), cationized ferritin (CF) and iron-dextran. CF adsorbed on to the surface of the axon terminal at the neuromuscular junction, while NF did not. Both CF and NF were incorporated into vesicles and vacuoles at the synapse, but CF uptake was detected after injections at much lower concentrations than NF. In contrast to NF, CF was also found histochemically in cell bodies of facial neurones after a single i.m. injection, showing that the electrical charge of a molecule is one factor of importance for its potential to be incorporated in axons and transported somatopetally. Repeated i.m. injection of iron-dextran into suckling mice resulted in a marked iron load of Schwann cells and nerve cell bodies. This produced no signs of toxicity and the nerve fibre developed normally. Iron had disappeared from the nerve cell bodies after 25 days, while in Schwann cells it still persisted after 223 days.

[Evolution of the storage site of iron-dextran after retrograde axonal transport in the rat central nervous system (author's transl)]

The uptake, transport, and storage of an iron-dextran complex (used as a neuroanatomical tracer in the nigrostriatal pathway of rat) by neurons of the CNS is described. The complex is taken up by endocytosis and transported by lysosomes. Some iron-containing mitochondria are observed within the nigral cell bodies. The neuronal labelling remains for 10 days. Thereafter, the iron labelling of neurons decreases. No important neuronal degeneration is observed as a result of iron toxicity. The iron lost by neurons is taken up by glial cells. It is converted into ferritin and increases the intracerebral endogenous iron content.

Elimination pattern and tissue distribution of intravenous iron-poly (sorbitol-gluconic acid) complex in the rat

The elimination pattern and tissue distribution in rats of intravenous [14C-gluconic acid]-poly(sorbitol-gluconic acid) and 59Fe-iron-poly(sorbitol-gluconic acid) complex, glusoferron (Ferastral) have been examined. Twenty-four hours after injection of 20 or 200 mg/kg of [14C-gluconic acid]-poly(sorbitol-gluconic acid), 5%-6% of the injected dose of radiolabel was eliminated as 14CO2 and about 85% in the urine and faeces. Administration of 59Fe-iron-poly(sorbitol-gluconic acid) complex (10 and 100 mg of iron/kg) resulted in a urinary and faecal excretion of about 18% and 40% of the given dose, respectively, during the first 4 days. Biliary excretion was low. The mean molecular weight of the biliary product after the iron complex was lower than that of the parent compound. Radiocarbon in tissues after 24 hours was negligible. Liver and bones accounted for most of the retained radioiron following 100 mg of iron/kg bodyweight of the 59Fe-iron complex with maximum levels of 27% and 12% of the injected dose, respectively, 4 days after dosing. Red cell incorporation of 59Fe attained a level of 16% at the end of 28 days.

Relative contribution of parenchymal and non-parenchymal cells to the hepatic distribution and metabolism of iron-poly(sorbitol-gluconic acid) complex in the rat

The hepatic cellular distribution in rats of radioiron and radiocarbon after [14C-gluconic acid]-and 59Fe-labelled iron-poly(sorbitol-gluconic acid) complex, glusoferron (Ferastral), has been investigated. Following administration of the 59Fe-iron complex at a dose level corresponding to 10 mg of iron per kg bodyweight, the ratio of radioactivity per 10(8) cells in parenchymal (P) and non-parenchemal (NP) cell fractions, the P/NP ratio, was 3.0 after 24 hours and rose to 10.4 at day 14. After 100 mg/kg the ratio was 0.9, 10.5 and 5.7 at day 1, 4 and 14, respectively. Radiocarbon content in the different cell compartments fell steadily throughout. Radioiron from 59Fe-iron-poly(sorbitol-gluconic acid) complex was shown to be incorporated into whole liver 59Fe-ferritin. In vitro uptake studies with the different liver cells were also performed. Parenchymal cells were found to be more active than non-parenchymal cells with regard to cellular uptake of radiolabel from both iron complex and polymeric ligand without iron.

An evaluation of normal strial capillary transport using the electron-opaque tracers ferritin and iron dextran

Enzymatic tracer techniques to study normal and pathologic strial capillary transport pose various problems. The use of electron opaque tracers can circumvent many of these problems. Iron dextran (mol. diam 20--70 A) and ferritin (mol. diam 110 A) were injected intravenously and the mice sacrificed at intervals of 1/2, 1, 2, 5, and 24 h. The iron dextran results were unusual in that from 1/2 to 5 h after administration the tracer was present within the cytoplasmic matrix of endothelia, but by 24 h it had been cleared out. No transendothelial exchange was noted. The ferritin results were in conflict and previous results using horse-radish peroxidase. Transport of ferritin was minimal regardless of time sacrificed. No more than a few molecules were scattered about the capillary basal limina. Those molecules transported across capillaries were apparently delivered by means of the micropinocytotic system. The results suggest a blood-strial barrier similar to the blood-thymic and blood-myenteric barriers. Experimental as well as control animals exhibited strial light cells which contained ferritin-like particles within their cytoplasmic matrices. These light cells are probably reticuloendothelial type cells. Ferritin may be useful to gauge strial capillary transport alterations associated with auditory pathologies.

Uptake and retrograde axonal transport of various exogenous macromolecules in normal and crushed hypoglossal nerves

Macromolecular tracers were injected into the tongue or around a crush in mouse hypoglossal nerves. At various times thereafter, the tracers were histochemically localized on the basis of peroxidase activity. The distribution of reaction product was then examined using light microscopy in order to study the influence of molecular charge and size on uptake and retrograde axonal transport from the periphery or from the crushed axon. Of various proteins with peroxidase activity, horseradish peroxidase and cytochrome-c showed the greatest penetration into axons proximal to the crush. Following injection into the tongue, intra-axonal cytochrome-c was detectable in some of the peripheral branches but not any of the other proteins. Retrograde transport to the nerve cell bodies was demonstrated for horseradish peroxidase and cytochrome-c, both from the tongue and from the axonal crush but not for microperoxidase, myoglobin, hemoglobin, lactoperoxidase and catalase. The number of neuronal cell bodies having detectable reaction product was higher for peroxidase-injected than for cytochrome-c-injected animals. Ferritin and iron-dextran (Imferon) also accumulated in hypoglossal neurons, but this could be detected only after repeated injections into the tongue. Uptake and retrograde transport from the tongue or from the crush occurred both for anionic and for cationic horseradish peroxidase. This is interpreted as evidence against absolute specificity in the uptake and transport of macromolecules on the basis of electrical charge.

Uptake and transport of Imposil by the glomerular mesangium in the mouse

The mesangial uptake and transport of particulate material has been studied using an iron-dextran complex, Imposil, as a tracer particle. The tracer was given as a single dose into the tail vein of the mouse, and animals were killed at intervals from 5 minutes to 48 hours. Light and electron microscopy showed that the iron-dextran complex was initially taken into the matrix channels of the mesangium from which it progressed over the course of 8 hours to the matrix of the juxtaglomerular apparatus and intercellular spaces of the macula densa. This delineated a continuous functional pathway from the glomerular capillary lumen to the macula densa cells of the distal tubule for material taken up by the mesangium. It is suggested that the products of inflammatory lesions in the glomerulus could affect the secretory function of the granular cells of the juxtaglomerular apparatus as it would appear that such products must circulate in the immediate environment of these cells.

Cellular distribution of orally and intramuscularly administered iron dextran in newborn piglets

Histochemical studies were performed on tissues from piglets of different ages treated orally with iron dextran soon after birth. The mucosal cells in the distal region of the small intestine were heavily laden with stainable iron granules during the first three days after the iron administration. The absorptive epithelial cells are desquamated within seven to ten days after birth. Consequently, the number of iron granules gradually diminishes during the first seven days after treatment and no iron granules are demonstrated 12 days after the administration of iron. The iron dextran complex is pinocytosed in newborn piglets and then transported via the lymphatic system. Thus the sinusoidal lining cells of the body and mesenteric lymph nodes are already heavily laden with iron granules 24 hours after oral treatment. This iron store is released only slowing during the first weeks of life. Great amounts of iron granules are demonstrated in the liver and spleen macrophages during the first week after the administration of iron. Due to the rapid utilization of iron in growing piglets these iron stores diminish sharply during the weeks following birth. The distribution of stainable iron in the lymph nodes, liver and spleen seven days after intramuscular injection of iron dextran in newborn piglets was comparable to that for oral administration at that stage of the experiment.

Detection of concanavalin A receptors by affinity to peroxidase and iron dextran by scanning and transmission electron microscopy and x-ray microanalysis

A method of cell surface mapping has been developed on spermatozoa. Concanavalin A binding sites have been simultaneously revelaed both by peroxidase DAB reaction and by iron dextran coupling. The areas are examined in scanning and transmission electron microscopes and submitted to electron probe X-ray microanalysis.

Transfer of iron-dextran across the placenta

In pregnant mice. 55Fe-labeled iron-dextran (Imferon) is transferred across the placenta. It was detected in the bone marrow, liver, spleen and peripheral blood of the pregnant animal, as well as in the embryonic liver erythroid precursors and peripheral blood. Uptake by liver and peripheral blood cells of pregnant anemic mice and by liver erythroid precursors of anemic embryos was significantly higher than in normal control animals. Electron-microscopic examination revealed that the iron deposits in the embryonic liver erythroid precursors had the same structure as the injected Imferon.

Properties of a complex of iron and a sorbitol-gluconic acid polymer for treatment of piglet anaemia

The properties of a complex of iron and a sorbitol-gluconic acid polymer useful for intramuscular treatment of piglet anaemia have been studied. In rabbits it is well absorbed from muscle and a small percentage (8 %) of the administered iron is excreted in the urine. A satisfactory utilization of the administered iron for haemoglobin synthesis has been shown in rats. A high degree of tolerance in piglets was observed also for the highest test doses, 600 mg iron per kg body weight. The clinical utilization was compared to that of iron-dextran using a total of 209 piglets and a dose of 200 mg iron for each animal. Five of these piglets were lost, but these deaths cannot be correlated to the treatment. Of the remaining animals 102 were treated with ISGP and 102 with iron-dextran, and the anaemia-preventing effect was similar for these 2 iron complexes.