Interaction of alveolar macrophages with inhaled mineral particulates

Molecular insights to in vitro biocompatibility of endodontic Pulpotec with macrophages determined by oxidative stress and apoptosis

Pulp therapy has been emerged as a one of the efficient therapies in the field of endodontics. Among different types of new endodontic materials, pulpotec has been materialized as a recognized material for vital pulp therapy. However, its efficacy has been challenged due to lack of information about its cellular biocompatibility. This study evaluates the mechanistic biocompatibility of pulpotec cement with macrophage cells (RAW 264.7) at cellular and molecular level. The biocompatibility was evaluated using experimental and computational techniques like MTT assay, oxidative stress analysis and apoptosis analysis through flow cytometry and fluorescent microscopy. The results showed concentration-dependent cytotoxicity of pulpotec cement extract to RAW 264.7 cells with an LC 50 of X/10-X/20. The computational analysis depicted the molecular interaction of pulpotec cement extract components with metabolic proteins like Sod1 and p53. The study revealed the effects of Pulpotec cement's extract, showing a concentration-dependent induction of oxidative stress and apoptosis. These effects were due to influential structural and functional abnormalities in the Sod1 and p53 proteins, caused by their molecular interaction with internalized components of Pulpotec cement. The study provided a detailed view on the utility of Pulpotec in endodontic applications, highlighting its biomedical aspects.

Molecular insight to size and dose-dependent cellular toxicity exhibited by a green synthesized bioceramic nanohybrid with macrophages for dental applications

Improvising bioceramics for enhancing their biocompatibility and physical properties has been a focus area for the dental industry. To further explore this area, this study reports a novel green synthesis and molecular in vitro biocompatibility of calcium aluminosilicate-chitosan nanohybrid (CAS-CH). The nanohybrids were synthesized by using a high energy ball milling (HEBM) technique and then characterized for their physiochemical properties using standard techniques including scanning electron microscopy (SEM) and dynamic light scattering (DLS). In vitro cytotoxicity evaluation of a synthesized nanohybrid was made with a RAW264.7 cell line using cell viability assays, such as, MTT, cellular morphology analysis, induction of oxidative stress, and apoptosis. CAS-CH nanohybrids were synthesized at three milling time points: 1H, 2H, and 3H. With increasing milling time, we found a reduction in sizes of particles and increased zeta potential. Viability of cells was found to be decreased with an increase in concentration. Moreover, toxic effects like ROS generation and apoptosis were reduced with increasing milling time. Computational and experimental analysis elucidated the mechanism of toxicity as a consequence of influential functionality of Sod1 and p53 proteins due to interaction and internalization of the nanohybrids with amino acid residues via hydrogen bonds and hydrophobic interactions. The detailed study depicted a novel way of synthesizing biocompatible bioceramic nanohybrids with a mechanistic insight of its cytotoxicity profile.

Proteomic and bioinformatics profile of paired human alveolar macrophages and peripheral blood monocytes

Little is known about proteomic differences between pluripotent human peripheral blood monocytes (MN) and their terminally-differentiated pulmonary counterparts, alveolar macrophages (AM). To better characterize these cell populations, we performed a label-free shotgun proteomics assessment of matched AM and MN preparations from eight healthy volunteers. With an FDR of less than 0.45%, we identified 1754 proteins within AM and 1445 from MN. Comparison of the two proteomes revealed that 1239 of the proteins found in AM were shared with MN, whereas 206 proteins were uniquely identified in MN and 515 were unique to AM. Molecular and cellular functions, protein classes, development associations, and membership in physiological systems and canonical pathways were identified among the detected proteins. Analysis of biologic processes represented by these proteomes indicated that MN were most prominently enriched for proteins involved in cellular movement and immune cell trafficking. In contrast, AM were enriched for proteins involved in protein trafficking, molecular transport, and cellular assembly and organization. These findings provide a baseline proteomic resource for further studies aimed at better understanding of the functional differences between MN and AM in both health and disease.

The interaction of asbestos and iron in lung tissue revealed by synchrotron-based scanning X-ray microscopy

Asbestos is a potent carcinogen associated with malignant mesothelioma and lung cancer but its carcinogenic mechanisms are still poorly understood. Asbestos toxicity is ascribed to its particular physico-chemical characteristics, and one of them is the presence of and ability to adsorb iron, which may cause an alteration of iron homeostasis in the tissue. This observational study reports a combination of advanced synchrotron-based X-ray imaging and micro-spectroscopic methods that provide correlative morphological and chemical information for shedding light on iron mobilization features during asbestos permanence in lung tissue. The results show that the processes responsible for the unusual distribution of iron at different stages of interaction with the fibres also involve calcium, phosphorus and magnesium. It has been confirmed that the dominant iron form present in asbestos bodies is ferritin, while the concurrent presence of haematite suggests alteration of iron chemistry during asbestos body permanence.

Inhaled therapies for tuberculosis and the relevance of activation of lung macrophages by particulate drug-delivery systems

Pathogenic strains of Mycobacterium tuberculosis (Mtb) induce ‘alternative activation’ of lung macrophages that they colonize, in order to create conditions that promote the establishment and progression of infection. There is some evidence to indicate that such macrophages may be rescued from alternative activation by inhalable microparticles containing a variety of drugs. This review summarizes the experience of various groups of researchers, relating to observations of induction of a number of classical macrophage activation pathways. Restoration of a ‘respiratory burst’ and upregulation of reactive oxygen species and nitrogen intermediates through the phagocyte oxidase and nitric oxide synthetase enzyme systems; induction of proinflammatory macrophage cytokines; and finally induction of apoptosis rather than necrosis of the infected macrophage are discussed. It is suggested that there is scope to co-opt host responses in the management of tuberculosis, through the route of pulmonary drug delivery.

Evaluation of early macrophage activation and NF-kappaB activity in pulmonary injury caused by deep hypothermia circulatory arrest: an experimental study

This study aimed to analyze changes in nuclear factor-kappa B (NF-kappaB), inflammation factors, and macrophages in pulmonary tissue under deep hypothermia circulatory arrest (DHCA) at different time points, which can be used to infer the role of early macrophage activation and NF-kappaB activity in pulmonary injury. The possible pathogenic mechanisms of DHCA-induced pulmonary injury were investigated in this study to provide an experimental basis for clinical lung protective strategies. Piglets (n = 12) were randomly divided into 2 groups, with 6 piglets in each group. The control group had ambient temperature cardiopulmonary bypass (CPB), and the experimental group had DHCA. Both groups had conventional CPB with 30 min of parallel circulation. Changes in NF-kappaB and inflammatory factors were examined in each group at 6 different time points. At 0.5 h after ischemia-reperfusion, NF-kappaB expression in the nucleus of pulmonary tissue reached its peak, and brown-stained nuclei were mainly polymorphonuclear antibodies. At 1 h after ischemia-reperfusion, plasma tumor-necrosis factor (TNF)-alpha in the experimental group was significantly increased compared with that before reperfusion (P < 0.05). The plasma levels of interleukin (IL)-8 and IL-6 in the experimental group were significantly increased at 1.5 h after ischemia-reperfusion compared with the levels before reperfusion (P < 0.05). Early activation of NF-kappaB under DHCA might play an important role in DHCA-induced pulmonary injury.

Exposure of the murine RAW 264.7 macrophage cell line to hydroxyapatite dispersions of various composition and morphology: assessment of cytotoxicity, activation and stress response

Cellular stress responses leading to the release of cytotoxic mediators are discussed as indicators of the hazard presented by particles, and in particular ultrafine particles or nanomaterials. The present study was designed to investigate effects of the following materials on RAW 264.7 macrophages: three hydroxyapatite materials of various morphologies, i.e., nano-sized with rod-like (HA-NR), plate-like (HA-NP) or needle-shaped (HA-NN) morphology, and an irregularly shaped composite of hydroxyapatite and protein (HPC) in the low micrometer range. Concentrations of 50, 100, 500, 1000 and 5000 microg/ml were applied and cells were analyzed for viability (XTT-test), cytokine production (TNF-alpha) and induction of nitric oxide (NO) after 18 and 42 h. DQ12 quartz and lipopolysaccharide (LPS) served as positive controls. Up to concentrations of 500 microg/ml, cell viability was not considerably impaired by the test samples at both timepoints. Overall, viability was about one order of magnitude higher than with comparable concentrations of quartz. TNF-alpha release was induced in all samples after 18 h, with HA-NR showing the most pronounced induction at 100 microg/ml, still clearly below the LPS signal. No or little induction was observed after 42 h. NO production was low after 18 and 42 h. The results support the conclusion that the tested materials exhibit good biocompatibility and are safe to use.

Macrophage inflammatory response to self-assembling rosette nanotubes

Rosette nanotubes (RNTs) are a new class of nanomaterials with significant therapeutic potential. However, societal concerns related to the potential adverse health effects of engineered nanomaterials drew attention towards the investigation of their interaction with the human U937 macrophage cell line. The cells are treated with medium only (control), lysine (50 microg mL(-1)), lysine-functionalized RNTs (RNT-K; 1, 5, and 50 microg mL(-1)), Min-U-Sil quartz microparticles (80 microg mL(-1)), or lipopolysaccharide (1 microg mL(-1)). The supernatant and cells are assayed for cell viability, cytokine protein, and mRNA expression at 1, 6, and 24 h post-treatment. The results indicate that RNT-K activate transcription of proinflammatory genes (interleukin-8 and tumor necrosis factor-alpha (TNF-alpha)) within 1 h, but this effect is not accompanied by protein secretion into the supernatant. The effect of the length of RNTs on human U937 macrophage viability is also investigated. Although both short and long RNT-K exhibit time-dependent effects on TNF-alpha transcription, only the short RNT-K (5 microg mL(-1)) increase TNF-alpha concentration at 6 h relative to the long RNT-K. Moreover, RNT-K (1 and 5 microg mL(-1)) have no effect on cell viability by 24 h. These data indicate that RNT-K do not induce a robust inflammatory response or cytotoxicity in the U937 human macrophage cell line, and therefore could be used for biomedical applications.

Hepcidin expression and iron transport in alveolar macrophages

Alveolar macrophages express many proteins important in iron homeostasis, including the iron importer divalent metal transport 1 (DMT1) and the iron exporter ferroportin 1 (FPN1) that likely participate in lung defense. We found the iron regulatory hormone hepcidin (HAMP) is also produced by alveolar macrophages. In mouse alveolar macrophages, HAMP mRNA was detected at a low level when not stimulated but at a high level when exposed to lipopolysaccharide (LPS). LPS also affected the mRNA levels of the iron transporters, with DMT1 being upregulated and FPN1 downregulated. However, iron had no effect on HAMP expression but was able to upregulate both DMT1 and FPN1 in alveolar macrophages. IL-1 and IL-6, which are important in HAMP augmentation in hepatocytes, also did not affect HAMP expression in alveolar macrophages. In fact, the LPS-induced alterations in the expression of HAMP as well as DMT1 and FPN1 were preserved in the alveolar macrophages isolated from IL-1 receptor or IL-6-deficient mice. When alveolar macrophages were loaded with transferrin-bound (55)Fe, the subsequent release of (55)Fe was inhibited significantly by LPS. In addition, treatment of these cells with either LPS or HAMP caused the diminishment of the surface FPN1. These findings are consistent with the current model that HAMP production leads to a decreased iron efflux. Our studies suggest that iron mobilization by alveolar macrophages can be affected by iron and LPS via several pathways, including HAMP-mediated degradation of FPN1, and that these cells may use unique regulatory mechanisms to cope with iron imbalance in the lung.

Depletion of alveolar macrophages by clodronate-liposomes aggravates ischemia-reperfusion injury of the lung

BACKGROUND

Macrophages play an important role in ischemia-reperfusion injury of various organs. Liposome-encapsulated dichloromethylene diphosphonate (clodronate-liposome) depletes local macrophages in vivo. However, the effect of this approach on alveolar macrophages in pulmonary ischemia-reperfusion injury has not yet been evaluated.

METHODS

Clodronate-liposomes in Hanks' balanced salt solution (HBSS) or HBSS alone were given intratracheally to anesthetized male Lewis rats in the clodronate or the control group (n = 6/each group). After 3 days, we subjected the lungs to ischemia (37 degrees C, 60 minutes) and reperfusion (60 minutes) in an isolated blood-perfused rat lung model. Analysis during reperfusion included gas exchange, hemodynamics, and airway mechanics. At the end of reperfusion, we determined leukocyte recruitment and macrophage inflammatory protein-2 (MIP-2) in bronchoalveolar lavage fluid.

RESULTS

In the clodronate group, 4 experiments had to be terminated within 10 minutes of reperfusion because of severe lung injury, whereas all lungs of the controls could be studied during the 60-minute reperfusion period (p < 0.05). Clodronate significantly decreased dynamic airway compliance (p < 0.05) and increased airway resistance. Besides a tendency toward greater pulmonary vascular resistance, this was associated with recruitment of polymorphonuclear neutrophils (p < 0.05) and increased MIP-2 concentrations in the bronchoalveolar lavage fluid (p < 0.05).

CONCLUSIONS

Intratracheal administration of liposome-encapsulated clodronate does not benefit, but aggravates, warm ischemia-reperfusion injury of the lung, increasing MIP-2-associated alveolar neutrophil recruitment and airway mechanical dysfunction.

Prostanoids Secreted by Alveolar Macrophages Enhance Ionic Currents in Swine Tracheal Submucosal Gland Cells

We examined the effect of substances released by swine alveolar macrophages (AMs) on ionic currents in airway submucosal gland cells (SGCs). AMs obtained by lavage were activated by 24-h zymosan exposure (0.1 mg/ml). Supernatant was collected and used to stimulate short-circuit current changes (DeltaI(SC)) in SGC monolayers in Ussing chambers. Dexamethasone (1 microM) or indomethacin (5 muM) during zymosan exposure of AMs reduced or abolished the supernatant-induced DeltaI(SC). Zymosan exposure induced a 5-fold increase in cyclooxygenase (COX)-2 but not COX-1 protein levels in AMs. Prostaglandin E(2) (PGE(2)) concentration in the supernatant from zymosan-activated AMs was 550 +/- 10 nM (n = 3) compared with 28 +/- 3 nM for unstimulated AMs (n = 3). PGE(2), applied serosally, induced DeltaI(SC) with an EC(50) of 15.5 +/- 1.3 nM (n = 4) and 3.6 +/- 1.8 microM (n = 3) when applied apically. Four types of endoprostanoid receptors (EP(1-4)) were detected in SGCs using Western blot. PGE(2)-induced DeltaI(SC) were inhibited by AH6809 (6-isopropoxy-9-oxoxanthene-2-carboxylic acid) but not by SC19220 (8-chloro-dibenzo[b,f][1,4]oxazepine-10(11H)-carboxylic acid, 2-acetylhydrazide), suggesting that endoprostanoid (EP)(2) but not EP(1) receptors were activated by PGE(2). Pretreatment of SGCs with supernatant from zymosan-activated AMs, PGE(2), or forskolin enhanced the sensitivity to acetylcholine (ACh)-induced DeltaI(SC). PGE(2)-induced DeltaI(SC) were blocked by charybdotoxin (ChTX), chromanol 293B, or glibenclamide. ACh-induced DeltaI(SC) were only blocked by ChTX or glibenclamide. None of these blockers altered PGE(2) pretreatment-induced sensitization of ACh-induced DeltaI(SC). These results demonstrate that prostanoids released from activated AMs directly increase cystic fibrosis transmembrane conductance regulator and K(+) channel activity. ACh-induced DeltaI(SC) are also enhanced due to enhanced activation of Ca(2+)-activated K(+) channels (K(Ca)).

Effects of various man-made mineral fibers on cell apoptosis and viability

Evaluating the pathogenic potentials of man-made mineral fibers (MMMF) is an important task performed by the European Community. Noting that it has been proposed that the use of laboratory animals for scientific tests should be reduced or phased out, macrophages then become the cells of choice for conducting in vitro studies. We have evaluated the in vitro toxicity of six commercial stonewool fibers (A, B1, B2, C, D, and E) on U-937 cells. The physical interaction between U-937 cells and MMMF was observed using scanning electron microscopy, and the cytotoxicity was evaluated by studying cell viability using MTT assay and cell apoptosis with an ELISA detection kit. Scanning electron microscopy (SEM) analysis has shown that long fibers can be covered by several macrophages, and that a small fiber can be completely engulfed by one cell. With 50 microg/mL of MMMF, a decrease in cell viability appeared after seven days of incubation, whereas 200 microg/mL induced loss of viability and apoptosis after one day. Fiber D, comprising a high proportion of fibers >20 microm in length and a high concentration of MgO, induced the highest loss in viability and the highest rate of apoptosis compared to the other five fibers. Whether this toxic effect is related to either the physical characteristics of the fibers (such as length), or to the high concentration of magnesium is still to be determined. Because the results can be rapidly obtained, the proposed model is suitable for studying the toxicities of mineral components, even if the tested concentrations are far from the ones reached in the lung.

Toward functional proteomics of alveolar macrophages

Alveolar macrophages (AM) belong to a phenotype of macrophages with distinct biological functions and important pathophysiological roles in lung health and disease. The molecular details determining AM differentiation from blood monocytes and AM roles in lung homeostasis are largely unknown. With the use of different technological platforms, advances in the field of proteomics have made it possible to search for differences in protein expression between AM and their precursor monocytes. Proteome features of each cell type provide new clues into understanding mononuclear phagocyte biology. In-depth analyses using subproteomics and subcellular proteomics offer additional information by providing greater protein resolution and detection sensitivity. With the use of proteomic techniques, large-scale mapping of phosphorylation differences between the cell types have become possible. Furthermore, two-dimensional gel proteomics can detect germline protein variants and evaluate the impact of protein polymorphisms on an individual's susceptibility to disease. Finally, surface-enhanced laser desorption and ionization (SELDI) time-of-flight mass spectrometry offers an alternative method to recognizing differences in protein patterns between AM and monocytes or between AM under different pathological conditions. This review details the current status of this field and outlines future directions in functional proteomic analyses of AM and monocytes. Furthermore, this review presents viewpoints of integrating proteomics with translational topics in lung diseases to define the mechanisms of disease and to uncover new diagnostic and therapeutic targets.

ROS-mediated TNF-alpha and MIP-2 gene expression in alveolar macrophages exposed to pine dust

BACKGROUND: Respiratory symptoms, impaired lung function, and asthma have been reported in workers exposed to wood dust in a number of epidemiological studies. The underlying pathomechanisms, however, are not well understood. Here, we studied the effects of dust from pine (PD) and heat-treated pine (HPD) on the release of reactive oxygen species (ROS) and inflammatory mediators in rat alveolar macrophages. METHODS: Tumour necrosis factor-alpha (TNF-alpha) and macrophage inflammatory protein-2 (MIP-2) protein release, TNF-alpha and MIP-2 mRNA expression, and generation of ROS were studied as end points after treatment of rat alveolar macrophages with PD or HPD. In a separate series of experiments, the antioxidants glutathione and N-acetyl-L-cysteine were included in combination with wood dust. To determine the endogenous oxidative and antioxidant capacity of wood dusts, electron spin resonance (ESR) spectroscopy was used. RESULTS: After 4 h incubation, both PD and HPD elicited a significantly (p < 0.05) increased mRNA expression of TNF-alpha and MIP-2 as well as a concentration-dependent release of TNF-alpha and MIP-2 protein. Interestingly, PD induced a significantly higher TNF-alpha and MIP-2 production than HPD. Moreover, a significantly increased ROS production was observed in alveolar macrophages exposed to both PD and HPD. In the presence of the antioxidants glutathione and N-acetyl-L-cysteine, the PD- and HPD-induced release of ROS, TNF-alpha, and MIP-2 was significantly reduced. Finally, electron spin resonance analyses demonstrated a higher endogenous antioxidant capacity of HPD compared to PD. Endotoxin was not present in either dust sample. CONCLUSION: These results indicate that pine dust is able to induce expression of TNF-alpha and MIP-2 in rat alveolar macrophages by a mechanism that is, at least in part, mediated by ROS.

In vitro and in vivo evaluation of the effects of PLA microparticle crystallinity on cellular response

Previous research suggests that crystallinity of poly(L-lactide) P(L)LA microparticles can influence surface free energy, which in turn might influence biocompatibility. This work studies the cellular response to P(L)LA microparticles of different crystallinity both in vitro and in vivo. Following incubation with P(L)LA microparticles, the in vitro production of reactive oxygen intermediates (ROI) was measured as a marker of cellular response. In both fluorescence and chemiluminescence experiments to measure ROI, a small effect of microparticle crystallinity on NR8383 AM response was observed. Microparticles of higher crystallinity elicited a smaller inflammatory response compared to lower crystallinity particles. Compared to the elevated inflammatory response induced by zymosan, the response to all P(L)LA microparticles tested was practically negligible. Results from in vivo experiments further supported conclusions that P(L)LA microparticles elicit minimal inflammatory response. Following acute exposure to P(L)LA microparticles in guinea-pig lungs, the inflammatory response was not significantly different from the response observed when sterile saline was administered. In contrast to the in vitro experiments, there were not apparent differences in cellular responses to microparticles of different crystallinity.