Iron-positive Macrophages Research Articles

Effects of environmental exposure to iron powder on healthy and elastase-exposed mice

Prolonged exposure to iron powder and other mineral dusts can threaten the health of individuals, especially those with COPD. The goal of this study was to determine how environmental exposure to metal dust from two different mining centers in Brazil affects lung mechanics, inflammation, remodeling and oxidative stress responses in healthy and elastase-exposed mice. This study divided 72 male C57Bl/6 mice into two groups, the summer group and the winter group. These groups were further divided into six groups: control, nonexposed (SAL); nonexposed, given elastase (ELA); exposed to metal powder at a mining company (SAL-L1 and ELA-L1); and exposed to a location three miles away from the mining company (SAL-L2 and ELA-L2) for four weeks. On the 29th day of the protocol, the researchers assessed lung mechanics, bronchoalveolar lavage fluid (BALF), inflammation, remodeling, oxidative stress, macrophage iron and alveolar wall alterations (mean linear intercept-Lm). The Lm was increased in the ELA, ELA-L1 and ELA-L2 groups compared to the SAL group (p < 0.05). There was an increase in the total number of cells and macrophages in the ELA-L1 and ELA-L2 groups compared to the other groups (p < 0.05). Compared to the ELA and SAL groups, the exposed groups (ELA-L1, ELA-L2, SAL-L1, and SAL-L2) exhibited increased expression of IL-1β, IL-6, IL-10, IL-17, TNF-α, neutrophil elastase, TIMP-1, MMP-9, MMP-12, TGF-β, collagen fibers, MUC5AC, iNOS, Gp91phox, NFkB and iron positive macrophages (p < 0.05). Although we did not find differences in lung mechanics across all groups, there were low to moderate correlations between inflammation remodeling, oxidative stress and NFkB with elastance, resistance of lung tissue and iron positive macrophages (p < 0.05). Environmental exposure to iron, confirmed by evaluation of iron in alveolar macrophages and in air, exacerbated inflammation, initiated remodeling, and induced oxidative stress responses in exposed mice with and without emphysema. Activation of the iNOS, Gp91phox and NFkB pathways play a role in these changes.

Characterization of Urothelial Inclusions in Male Wistar Han Rats Treated Orally With the Novel α2A-Adrenoceptor Agonist Tasipimidine.

Intracellular inclusions were observed in urinary bladder epithelium of male Wistar rats, following oral treatment with high doses of the α2A-adrenoceptor agonist tasipimidine for 28 days. No cell death or inflammation was associated with the brightly eosinophilic inclusions. Electron microscopy (EM) studies showed that the inclusions represented intact or fragmented red blood cells (RBC) resulting from erythrophagocytosis, further supported by the presence of iron in urothelial cells. In addition, scattered iron-positive macrophages were observed in the submucosa and muscle layer, indicating microvascular leakage, as no major hemorrhage was evident. Despite the presence of inclusions, the urothelium showed normal uroplakin III distribution, normal cell turnover, and an absence of α-2u-globulin. It is, therefore, concluded that the inclusions were not associated with urothelial damage or increased renewal of the epithelium. This finding shows also that urothelial cells have the capability to phagocytize and break down RBCs originating from submucosal microvascular leakage. Similar changes were not observed in tasipimidine-treated beagle dogs (28 days), suggesting these findings were rat specific. The leakage of RBCs into the urothelium is suggested to be a consequence of exaggerated pharmacology leading to vasoconstriction of submucosal blood vessels in combination with transient increased bladder distension and pressure.

In Vivo Imaging of Macrophages during the Early-Stages of Abdominal Aortic Aneurysm Using High Resolution MRI in ApoE−/− Mice

BackgroundAngiotensin II (ANG II) promotes vascular inflammation and induces abdominal aortic aneurysm (AAA) in hyperlipidemic apolipoprotein E knock-out (apoE−/−) mice. The aim of the present study was to detect macrophage activities in an ANG II-induced early-stage AAA model using superparamagnetic iron oxide (SPIO) as a marker.Methodology/Principal FindingsTwenty-six male apoE−/− mice received saline or ANG II (1000 or 500 ng/kg/min) infusion for 14 days. All animals underwent MRI scanning following administration of SPIO with the exception of three mice in the 1000 ng ANG II group, which were scanned without SPIO administration. MR imaging was performed using black-blood T2 to proton density -weighted multi-spin multi-echo sequence. In vivo MRI measurement of SPIO uptake and abdominal aortic diameter were obtained. Prussian blue, CD68,α-SMC and MAC3 immunohistological stains were used for the detection of SPIO, macrophages and smooth muscle cells. ANG II infusion with 1000 ng/kg/min induced AAA in all of the apoE−/− mice. ANG II infusion exhibited significantly higher degrees of SPIO uptake, which was detected using MRI as a distinct loss of signal intensity. The contrast-to-noise ratio value decreased in proportion to an increase in the number of iron-laden macrophages in the aneurysm. The aneurysmal vessel wall in both groups of ANG II treated mice contained more iron-positive macrophages than saline-treated mice. However, the presence of cells capable of phagocytosing haemosiderin in mural thrombi also induced low-signal-intensities via MRI imaging.Conclusions/SignificanceSPIO is taken up by macrophages in the shoulder and the outer layer of AAA. This alters the MRI signaling properties and can be used in imaging inflammation associated with AAA. It is important to compare images of the aorta before and after SPIO injection.

In vivo and ex vivo MR imaging of slowly cycling melanoma cells

Slowly cycling cells are believed to play a critical role in tumor progression and metastatic dissemination. The goal of this study was to develop a method for in vivo detection of slowly cycling cells. To distinguish these cells from more rapidly proliferating cells that constitute the vast majority of cells in tumors, we used the well-known effect of label dilution due to division of cells with normal cycle and retention of contrast agent in slowly dividing cells. To detect slowly cycling cells, melanoma cells were labeled with iron oxide particles. After labeling, we observed dilution of contrast agent in parallel with cell proliferation in the vast majority of normally cycling cells. A small and distinct subpopulation of iron-retaining cells was detected by flow cytometry after 20 days of in vitro proliferation. These iron-retaining cells exhibited high expression of a biological marker of slowly cycling cells, JARID1B. After implantation of labeled cells as xenografts into immunocompromised mice, iron-retaining cells were detected in vivo and ex vivo by magnetic resonance imaging that was confirmed by Prussian Blue staining. Magnetic resonance imaging detects not only iron retaining melanoma cells but also iron positive macrophages. Proposed method opens up opportunities to image subpopulation of melanoma cells, which is critical for continuous tumor growth.

Bronchoalveolar Lavage in Other Interstitial Lung Diseases

This article reviews the changes in bronchoalveolar lavage (BAL) cytology and cell differentials in some of the rarer interstitial lung diseases. In a few of these diseases BAL has a diagnostic value and can replace lung biopsy. In pulmonary Langerhans cell histiocytosis the characteristic diagnostic finding is an increase in CD1 + Langerhans cells greater than 4% of total cells. The sensitivity of this cutoff value is low because only approximately 50% of patients show this elevation. In pulmonary alveolar proteinosis, the sensitivity of a diagnostic BAL is almost 100%, and the characteristic finding of milky and turbid fluid on gross examination and the characteristic findings with acellular globules that stain pink with PAS (periodic-acid-Schiff), along with abnormal foamy macrophages and a characteristic dirty background obviates the need for lung biopsy. In diffuse alveolar hemorrhage, BAL is the method of choice to diagnose the alveolar bleeding by showing free red blood cells and hemosiderin-laden, iron-positive macrophages. The underlying disorder has to be identified by history and clinical and laboratory tests. In eosinophilic lung disease, the diagnosis can be made if the BAL cell differentials show 25% or more eosinophils. In collagen vascular disease-associated lung fibrosis, the precise role of BAL in assessment and monitoring disease remains unclear. In drug-induced interstitial lung disease BAL may support a certain clinical/pathological pattern of lung involvement and is helpful for exclusion of other diseases, such as malignancies with pulmonary metastasis, heart disease with pulmonary congestion, or infections. The same is true for radiation-induced lung injury.

MRI detection of macrophage activity after experimental stroke in rats: New indicators for late appearance of vascular degradation?

Focal cerebral ischemia was induced in rats and followed with high-resolution MRI methods for a chronic period of 10 weeks. Two weeks after stroke induction and at the end of the observation period, conventional histological analysis was combined with immunohistochemical staining for macrophages and with Prussian blue staining for the detection of ferric iron. In the late chronic phase, a patchy hypointensity was observed in the ischemic caudoputamen exclusively on T2*-weighted (T2*W) images, with no change in quantitative T(1) and T(2) relaxation time maps. This characteristic MRI pattern is different from hemorrhagic transformations (HTs) at earlier time points (2 weeks post stroke induction), which became apparent on images of all three imaging sequences. The exclusive T2*-sensitive hypointensity colocalized with iron-positive macrophages in the lesion territory at this time. These iron-containing macrophages were found predominantly around blood vessels in the ischemic tissue, and interpreted as the result of a phagocytotic incorporation of red blood cells leaking from slowly degrading vessels. The present investigation demonstrates the sensitivity of heavily T2*W 3D MRI for observing the inflammatory response in the chronic phase after stroke, without prior systemic labeling of the blood-borne macrophages by iron oxide nanoparticles.

Imaging of Macrophages in Soft-Tissue Infection in Rats: Relationship between Ultrasmall Superparamagnetic Iron Oxide Dose and MR Signal Characteristics

To describe dose-dependent signal intensity (SI) characteristics of experimentally induced soft-tissue abscesses on 1.5-T T1- and T2*-weighted magnetic resonance (MR) images obtained 24 hours after administration of ultrasmall superparamagnetic iron oxide (USPIO) and to describe the relationship between SI and amount of USPIO uptake and macrophage iron content. Local institutional review committee on animal care approved the experiments, which were performed according to the guidelines of the National Institutes of Health and the committee on animal research at our institution. Unilateral calf muscle abscesses were induced in 21 rats with an injection of a Staphylococcus aureus suspension. The rats were divided into three groups of seven animals each: low USPIO dose (50 micromol of iron per kilogram of body weight), high USPIO dose (150 micromol Fe/kg), and control (saline solution). All rats were imaged before and 24 hours after USPIO administration at 1.5 T (transverse T1-weighted spin-echo, T2*-weighted fast gradient-echo, and short inversion time inversion-recovery sequences). Images were analyzed quantitatively and qualitatively with regard to SI and signal pattern. Temporal variation of calculated contrast-to-noise ratios was analyzed with the Wilcoxon signed rank test. MR findings were correlated with histopathologic findings, including those of electron microscopy. Twenty-four hours after USPIO administration in the high-dose group, susceptibility effects were present in abscess periphery on postcontrast T2*-weighted images (P=.04), and SI enhancement was noted on postcontrast T1-weighted images within both abscess wall and abscess center (P=.04 for both). In the low-dose group, SI enhancement was noted in entire abscess on T1-weighted postcontrast images (P=.03). Neither significant SI loss (P=.09) nor susceptibility effects were detected in periphery or center of any abscess on postcontrast T2*-weighted images. There was no obvious difference in total amount of macrophages among the groups, but there was a clear difference with regard to individual iron content of iron-positive macrophages between the USPIO dose groups. At 1.5 T, SI characteristics of abscesses on T1- and T2*-weighted images obtained 24 hours after USPIO injection strongly depend on administered dose of the contrast agent. At low doses, T1 effects were stronger than T2* effects.

Bone marrow transplantation prolongs life span and ameliorates neurologic manifestations in Sandhoff disease mice.

The GM2 gangliosidoses are a group of severe, neurodegenerative conditions that include Tay-Sachs disease, Sandhoff disease, and the GM2 activator deficiency. Bone marrow transplantation (BMT) was examined as a potential treatment for these disorders using a Sandhoff disease mouse model. BMT extended the life span of these mice from approximately 4.5 mo to up to 8 mo and slowed their neurologic deterioration. BMT also corrected biochemical deficiencies in somatic tissues as indicated by decreased excretion of urinary oligosaccharides, and lower glycolipid storage and increased levels of beta-hexosaminidase activity in visceral organs. Even with neurologic improvement, neither clear reduction of brain glycolipid storage nor improvement in neuronal pathology could be detected, suggesting a complex pathogenic mechanism. Histological analysis revealed beta-hexosaminidase-positive cells in the central nervous system and visceral organs with a concomitant reduction of colloidal iron-positive macrophages. These results may be important for the design of treatment approaches for the GM2 gangliosidoses.

Pulmonary response of hamsters to fibrous glass. — Clearance and morphology after a single intratracheal instillation

In a one-year serial sacrifice study 10 mg glass fibres (length, 95% alpha 20 microns, 89% alpha 12 microns, 58% alpha 5 microns and 25% alpha 2 microns; diameter, 88% alpha 1.0 micron, 60% alpha 0.5 micron and 31% alpha 0.25 micron) suspended in 0.2 ml saline solution were administered to Syrian golden hamsters by a single intratracheal instillation to determine the clearance of the glass fibres from the lungs and to examine their effects on the lungs using light and electron microscopy. The clearance was rather efficient with a half-time of about 3 months. Coating and corrosion of glass fibres were sporadic findings. A violent focal acute pneumonitis was evoked by the glass fibres and was followed by excessive accumulations of alveolar macrophages often loaded with glass fibres. Thereafter, "silicotic granulomas" developed which were seen as clusters of tightly packed iron-positive macrophages containing glass fibres. These granulomas were surrounded by a layer of alveolar epithelium, and were by the end of the study the predominant lesion in otherwise normal lungs.

Pulmonary response of hamsters to fibrous glass: chronic effects of repeated intratracheal instillation with or without benzo[a]pyrene.

Syrian golden hamsters were given intratracheal instillations of glass fibres with or without benzo[a]pyrene suspended in saline, once a fortnight for 52 weeks. The experiment was terminated at week 85. 'Silicotic granulomas' consisting of tightly packed, iron-positive macrophages filled with glass fibres and surrounded by a layer of alveolar epithelial cells were the predominant pulmonary lesion. No mesotheliomas or other tumours of the respiratory tract were observed in hamsters treated with glass fibres alone. There was no indication that glass fibres enhanced the development of respiratory tract tumours induced by benzo[a]pyrene. In hamsters similarly exposed to crocidolite fibres with or without benzo[a]pyrene no mesotheliomas or other respiratory tract tumours were observed either. An explanation for the absence of pulmonary tumours might be that repeated administration of fibres over a period of 52 weeks entails an acute pulmonary reaction after each administration with the implication that the fibres cannot settle down well enough to be able to induce tumours. Another possible explanation is the relatively short duration of the experimental period.