Cells Of Mononuclear Phagocyte System Research Articles

Role of the Ferroportin Iron-Responsive Element in Iron and Nitric Oxide Dependent Gene Regulation

ABSTRACT The newly described iron transporter, ferroportin (MTP1, IREG1), is expressed in a variety of tissues including the duodenum and cells of the mononuclear phagocyte system (MPS). In the MPS, ferroportin is hypothesized to be a major exporter of iron scavenged from senescent erythrocytes. Changes in iron metabolism, including the sequestration of iron in the MPS, are characteristic of both acute and chronic inflammation and these conditions induce changes in ferroportin expression. In a mouse model of acute inflammation, LPS administration is associated with reduced MPS ferroportin protein and mRNA expression. In addition, the ferroportin 5′ UTR also has an iron-responsive element that binds to the iron-response proteins, but whether there is a role for this IRE in inflammation induced regulation of ferroportin has been unclear. A luciferase reporter gene under the control of the mouse ferroportin promoter and 5′ UTR was used to determine if this 5′ UTR conferred IRE-dependent regulation on this reporter gene. Stimulation of reporter gene transfected RAW 264.7 cells (a mouse macrophage cell line) with LPS resulted in IRE-dependent inhibition of luciferase production. Inhibitors of nitric oxide synthase abrogated the IRE-dependent effect of LPS. In addition, direct treatment of RAW 264.7 and with NO donor S-nitroso- N-acetylpenicillamine resulted in IRE-dependent down-regulation of luciferase expression. The effect of NO was consistent with IRP1/IRE mediated translation block. There are most likely both inflammation-mediated transcriptional and post-transcriptional (IRE-dependent) mechanisms for inhibiting ferroportin expression in MPS cells.

Changes in macrophages in spleen and lymph nodes during acute African swine fever: expression of cytokines

To gain further insight into the pathogenesis of African swine fever (ASF), the cytokine expression by macrophages in spleen and lymph nodes were examined. Twenty-one piglets were inoculated with the highly virulent isolate Spain-70 of ASF virus and killed in groups at 1–7 post-inoculation days (pid). An increase in the immunohistochemical detection of proinflammatory monokines in spleen and renal and gastrohepatic lymph nodes is reported, along with an increase in the serum levels of TNF-α and IL-1β. The expression of these cytokines is detected simultaneously in time and space with the viral protein 73 (vp73) of the ASF virus detection. Our results demonstrate that mononuclear phagocyte system cell activation results in the release of several cytokines that could induce apoptosis of lymphocytes and haemodynamic changes.

Induction of Functional Defects in Macrophages by a Poult Enteritis and Mortality Syndrome-Associated Turkey Astrovirus

The interaction of a poult enteritis and mortality syndrome (PEMS)-turkey astrovirus-Ohio State University (TAst-OSU) with the mononuclear phagocytic system cells, namely macrophages, was examined after in vitro and in vivo exposure. In vitro exposures were performed by incubating adherent turkey macrophages with various volumes of 10(6) 50% embryo infective dose (EID50)/ml TAst-OSU stock, whereas for in vivo challenge, poults were given a 200 microl inoculum of 10(6) EID50/ml TAst-OSU stock at 7 days of age. Results show that TAst-OSU in vitro exposure reduced macrophage viability relative to controls (P < 0.05) and decreased phagocytosis (P < 0.05) and intracytoplasmic killing of Escherichia coli (P < 0.05) after a 42-48-hr exposure. Poults challenged with TAst-OSU in vivo recruited almost 50% fewer Sephadex-elicited inflammatory cells in the abdominal cavity (P < 0.05) as compared with the sham controls. Similar to in vitro exposure, macrophages isolated from in vivo TAst-OSU-challenged poults exhibited reduced percentage of phagocytic macrophages (P < 0.05) as well as fewer intracytoplasmic E. coli per phagocytic macrophage (P < 0.05). TAst-OSU-challenged poults had a greater number of viable E. coli in their spleens (P < 0.05) after an intravenous E. coli challenge as compared with the non-TAst-OSU-challenged control poults. Macrophage-mediated cytokines and metabolites were also examined during this study. Both in vitro and in vivo TAst-OSU challenge resulted in reduced interleukin (IL)-1 and IL-6 activity. On the contrary, nitrite levels in macrophage culture supernatant fraction of TAst-OSU-challenged macrophages were significantly higher (P < or = 0.05). The findings of these studies indicated that TAst-OSU challenge induced defects in macrophage effector functions, implying that PEMS-turkey astrovirus can potentially impair the immune response of turkeys, thereby leading to enhanced susceptibility of turkeys to secondary, perhaps even fatal, bacterial infections.

Tuftsin-bearing liposomes in treatment of macrophage-based infections

The use of liposomes as drug carriers in treatment of various diseases has been explored extensively for more than 20 years. ‘Conventional’ liposomes, when administered in vivo by a variety of routes, rapidly accumulate in the mononuclear phagocyte system (MPS). The inherent tendency of the liposomes to concentrate in MPS can be exploited in enhancing the non-specific host defence against infections by entrapping in them the macrophage modulators, and as carriers of antibiotics in treatment of intracellular infections that reside in MPS. This must further be enhanced by grafting on the liposome surface the ligands, e.g. tuftsin, that not only binds specifically to the MPS cells but also enhances their natural killer activity. Keeping this in view, we designed and developed tuftsin-bearing liposomes as drug carriers for the treatment of macrophage-based infections and outline these studies in this overview.

The role of the bone marrow in bovine trypanotolerance II. Macrophage function inTrypanosoma congolense-infected cattle

Sequential biopsies of sternal bone marrow (BM) of three trypanosusceptible Boran and three trypanotolerant N'Dama cattle were examined by light and transmission electron microscopy before and up to 112 days postinfection (DPI) withTrypanosoma congolense. Before infection, the percentage of cells of the mononuclear phagocyte system (MPS) including the macrophage (Mϕ) and the calculated index of Mϕ volume in the BM were similar in both breeds, whereas the mean Mϕ surface area was significantly higher (p<0.0001) in the Boran than in the N'Dama. DuringT. congolense infection, the MPS cell counts, the Mϕ surface area and the calculated Mϕ volume index increased significantly in both breeds particularly in the N'Dama.

Ex vivo interleukin (IL)-1 beta, IL-6, IL-12 and tumor necrosis factor-alpha responsiveness with monocytes from patients with head and neck carcinoma.

Seventy newly diagnosed Caucasian male patients with head and neck squamous cell carcinomas (HNSCC) were included in the study. All patients were less than 80 years of age, with no cachexia or auto-immune disease, and they were not taking immuno-active medications. Monocytes from these patients were cultured in vitro and supplemented with autologous serum under ex vivo conditions or cultured with serum-free medium. Comparison was made to monocytes from 59 patients with benign HN diseases. Similar physical activity levels prior to testing as well as a minimum stress load were ensured in both groups. Increased monocyte supernatant levels were determined under ex vivo conditions of interleukin-1 beta (IL-1 beta), interleukin-6 (IL-6) and tumor necrosis factor (TNF)-alpha, but not of interleukin-12 (IL-12) with endotoxin stimulated monocytes of HNSCC patients compared to control conditions. Increased monokine levels were not present with mononuclear cell cultures stimulated with a T-cell general stimulatory agent or with purified monocytes not specifically stimulated. With endotoxin-stimulated monocytes under in vitro conditions, an increased supernatant was shown for TNF-alpha, but not IL-6. With serum from the different patients cultured with monocytes employed from a healthy control, no difference between the groups was shown in the IL-6 and TNF-alpha response to endotoxin stimulation. The differences in IL-1 beta and TNF-alpha, but not IL-6 levels were differentiated statistically from the smoking and alcohol histories of the patients. These findings suggest that the function of monocytes in general, and thus possibly all mononuclear phagocyte system cells in HNSCC patients, are altered.

MPEO-PLA nanoparticles: effect of MPEO content on some of their surface properties.

Nanoparticles of poly(lactic acid) (PLA) and of blends of PLA and monomethoxypoly(ethylene oxyde) (MPEO-PLA) were prepared by the double emulsion method. Sucrose was added to overcome nanoparticle aggregation with freeze-drying. Whereas PLA nanoparticles rapidly are phagocytosed by the mononuclear phagocyte system cells, the uptake of MPEO-PLA nanoparticles is delayed. Opsonization is one of the steps of phagocytosis, and serum complement is a major component of the opsonin system. The in vitro complement consumption of the prepared nanoparticles was evaluated as a function of time and of their surface area. To avoid the aggregation of MPEO-PLA nanoparticles due to MPEO crystallization, sucrose was necessary, and its concentration was dependent on MPEO proportion in the nanoparticle suspension. As expected, the complement consumption for PLA nanoparticles is faster and more important than for PLA/MPEO-PLA blends. The complement consumption decreases with the increase in MPEO surface density. Complement is less consumed with the lower surface density provided by a higher molecular weight than by the higher surface density provided by a lower molecular weight MPEO. The complement consumption seems to be dependent on the number of nanoparticles in contact with human serum. Finally, the model of steric repulsion of MPEO towards proteins and the importance of the surface density of MPEO were emphasized.

MPEO‐PLA nanoparticles: Effect of MPEO content on some of their surface properties

Nanoparticles of poly(lactic acid) (PLA) and of blends of PLA and monomethoxypoly(ethylene oxyde) (MPEO-PLA) were prepared by the double emulsion method. Sucrose was added to overcome nanoparticle aggregation with freeze-drying. Whereas PLA nanoparticles rapidly are phagocytosed by the mononuclear phagocyte system cells, the uptake of MPEO-PLA nanoparticles is delayed. Opsonization is one of the steps of phagocytosis, and serum complement is a major component of the opsonin system. The in vitro complement consumption of the prepared nanoparticles was evaluated as a function of time and of their surface area. To avoid the aggregation of MPEO-PLA nanoparticles due to MPEO crystallization, sucrose was necessary, and its concentration was dependent on MPEO proportion in the nanoparticle suspension. As expected, the complement consumption for PLA nanoparticles is faster and more important than for PLA/MPEO-PLA blends. The complement consumption decreases with the increase in MPEO surface density. Complement is less consumed with the lower surface density provided by a higher molecular weight than by the higher surface density provided by a lower molecular weight MPEO. The complement consumption seems to be dependent on the number of nanoparticles in contact with human serum. Finally, the model of steric repulsion of MPEO towards proteins and the importance of the surface density of MPEO were emphasized. © 1999 John Wiley & Sons, Inc. J Biomed Mater Res, 44, 109–115, 1999.

Primary structure of rat CD14 and characteristics of rat CD14, cytokine, and NO synthase mRNA expression in mononuclear phagocyte system cells in response to LPS.

Rat CD14 cDNA clones were isolated. The predicted protein sequence exhibits 82, 61.6, and 64% identity with the mouse, rabbit, and human CD14, respectively. The levels of rat CD14 mRNA expression in resident peritoneal macrophages (PM), alveolar macrophages (AM), and peripheral blood monocytes (BM) were constitutively high, whereas that in Kupffer cells (KC) was low. On intravenous injection with lipopolysaccharide (LPS), the expression of rat CD14 mRNA in KC increased markedly, whereas the increases in PM, AM, and BM were mild. Similar features of expression of rat CD14 in these cells were observed after stimulation with LPS in vitro. The level of tumor necrosis factor alpha (TNF-alpha) mRNA expression in KC after stimulation with LPS in vivo was comparable to that in PM, AM, and BM, whereas that of TNF-alpha mRNA expression in KC and PM after stimulation with LPS in vitro was lower than that in AM and BM. Interleukin (IL)-1 beta and iNOS mRNA expressions in KC after stimulation with LPS in vivo and in vitro were low, whereas those in PM, AM, and BM were high. Little or no expression of IL-6 was observed in KC after stimulation with LPS in vivo and in vitro, whereas higher expression was observed in PM, AM, and BM than in KC.

Association of vascular amyloid beta and cells of the mononuclear phagocyte system in hereditary cerebral hemorrhage with amyloidosis (Dutch) and Alzheimer disease.

Arterial and arteriolar amyloid-beta (A beta) deposition in hereditary cerebral hemorrhage with amyloidosis (Dutch) (HCHWA-D) and Alzheimer disease (AD) cerebral amyloid angiopathy (CAA) were studied as to morphology, extent, and association with mononuclear phagocyte system (MPS) cells using A beta, a-smooth muscle actin, and monocyte/macrophage marker (HLA-DR, CD68, CD11c, CD45) immunohistochemistry. The HCHWA-D/AD arterial/arteriolar media showed compact A beta deposits, first appearing at the media/adventitia junction, and concomitant smooth muscle loss. Only HCHWA-D CAA featured (a) severe involvement of larger arteries and (b) arterioles showing a single or double ring of radial A beta surrounding compact A beta. Radial A beta appeared to develop at the media/adventitia junction. Monocyte/macrophage marker-positive foci/cells co-localized with HCHWA-D arterial A beta. Focal HLA-DR/CD11c positivity was observed at the media/adventitia junction of AD/HCHWA-D arteries in the absence of local A beta, but not in controls. Monocyte/macrophage marker positivity co-localizing with radial A beta appeared continuous with perivascular cells and microglia clustering perivascularly. These results suggest that (a) MPS cells are topographically associated with HCHWA-D arterial A beta and radial arteriolar A beta, and (b) HLA-DR/CD11c immunoreactivity may appear at the media/adventitia junction prior to A beta. The latter finding and the assumed formation of radial A beta at the media/adventitia junction may relate to involvement of the abluminal basement membrane in CAA pathogenesis. The role of MPS cells in this process remains to be established.

Ebola virus infection in guinea pigs: presumable role of granulomatous inflammation in pathogenesis.

An approach combining virology with light and electron microscopy was used to study the organs of guinea pigs during nine serial passages of Ebola virus, strain Zaire. It was observed that the wild type of Ebola virus causes severe granulomatous inflammation in the liver and reproduces in the cells of the mononuclear phagocyte system (MPS). Based on morphological characterization, two types of virus-cell interactions were demonstrated. The obtained data evidenced for heterogeneity of the population of wild type of Ebola virus. The virus accumulated in the liver of the infected animals, and the lesions became more pronounced with passage. Degenerative changes appeared, and their severity was increased with passage in the other organs as well. The set of target cells diversified and, as a result, not only the MPS cells, but also hepatocytes, spongiocytes, endotheliocytes and fibroblasts became involved in the reproduction of Ebola virus. The possible role of granulomatous inflammation in the development of the adaptive mechanism of Ebola virus to guinea pigs is discussed.

Interaction of inflammatory cytokines and erythropoeitin in iron metabolism and erythropoiesis in anaemia of chronic disease.

In chronic inflammatory conditions increased endogenous release of specific cytokines (TNFα, IL-1, IL-6, IFNγ and others) is presumed. It has been shown that those of monocyte lineage play a key role in cytokine expression and synthesis. This may be associated with changes in iron metabolism and impaired erythropoiesis and may lead to development of anaemia in patients with rheumatoid arthritis. Firstly, increased synthesis of acute phase proteins, like ferritin, during chronic inflammation is proposed as the way by which the toxic effect of iron and thereby the synthesis of free oxy-radicals causing the damage on the affected joints, may be reduced. This is associated with a shift of iron towards the mononuclear phagocyte system which may participate in the development of anaemia of chronic disease. Secondly, an inhibitory action of inflammatory cytokines (TNFα, IL-1), on proliferation and differentiation of erythroid progenitors as well as on synthesis of erythropoietin has been shown, thereby also contributing to anaemia. Finally, chronic inflammation causes multiple, complex disturbances in the delicate physiologic equilibrium of interaction between cytokines and cells (erythroid progenitors, cells of mononuclear phagocyte system and erythropoietin producing cells) leading to development of anaemia of chronic disease (Fig. 1).

Experimental African swine fever: apoptosis of lymphocytes and virus replication in other cells.

In order to determine the cause of cellular death of lymphocytes in pigs with acute African swine fever and the relationships between African swine fever virus (ASFV) and interstitial cells, ten pigs were inoculated with a highly virulent strain of ASFV (Malawi '83) and samples taken for ultrastructural study of hepatic and renal interstitial tissues. We demonstrated death by apoptosis of lymphocytes and virus replication in fibroblasts, smooth muscle cells and endothelial cells in the interstitial tissues of pigs inoculated with ASFV. From day 5 onwards, apoptotic lymphocyte and intense virus replication in hepatic interstitial macrophages and fibroblasts were observed. By day 7, apoptotic lymphocytes and virus replication in macrophages, interstitial capillary endothelial cells and fibroblasts in the kidney were observed. Virus replication was also seen in smooth muscle cells of hepatic and renal arterioles and venules. Our results suggest that mononuclear phagocyte system (MPS) cell activation, and the resulting release of cytokines, could induce apoptosis of lymphocytes and virus replication in non-MPS cells.

Mechanism of macrophage-mediated regulation of osteogenesis

Phase changes of the functional activity of cells of the mononuclear phagocyte system are shown on a model of closed fracture of the femur in laboratory rodents. Analogous changes included the dynamics of both number and activity of the bone marrow hemopoietic islets. The parameters studied fall in the early post-traumatic stage and rise during the active phase of osteogenesis. It is concluded that there is an interrelationship between bone tissue and the hemopoietic and macrophage systems during osteogenesis, which is, in particular, realized via changes in hemopoietic islet formation.

Microvascular pathology and vascular basement membrane components in Alzheimer's disease.

Several factors have highlighted the vasculature in Alzheimer's disease (AD): Cerebral amyloid angiopathy (CAA) is common, amyloid fibrils emanate from the vascular basement membrane (VBM), and similar forms of beta-amyloid are found in vascular and parenchymal amyloid accumulations. The present article discusses the presence of microvascular pathology in AD. Microangiopathy, in addition to neurofibrillary tangles, senile plaques, and CAA, is a common pathologic hallmark of AD. VBM components are associated with amyloid plaques, and nonamyloidotic alterations of the VBM occur in brain regions susceptible to AD lesions. Also, intra-VBM perivascular cells (traditionally called pericytes), a subset of which share the immunophenotype of microglia and other mononuclear phagocytic system (MPS) cells, have been implicated in vascular alterations and cerebrovascular amyloid deposition. Perivascular and parenchymal MPS cells have access to several sources of the beta-amyloid protein precursor, including platelets, circulating white cells, and neurons. MPS cells would thus be ideally situated to uptake and process the precursor, and deposit beta-amyloid in a fashion analogous to that seen in other forms of systemic and cerebral amyloidoses.

Pathomorphologic findings of lead poisoning in white-fronted geese (Anser albifrons).

Nineteen lead-poisoned white-fronted geese (Anser albifrons), including nine immature birds, were examined pathologically. Subacute lead poisoning due to ingestion of spent lead shots was diagnosed pathologically and confirmed by demonstrating high lead concentration in the liver. The liver lead concentration ranged from 6.9 to 67.7 mg/kg wet weight. The most suggestive gross lesions were mottled bile-stained liver in eight geese and proventricular impaction and/or the presence of lead pellets in the gizzard. Histologic lesions of the liver consisted of Kupffer cell hemosiderosis, large bile plugs in dilated canaliculi, bile pigmentation in hepatocytes, and bile extravasation and associated hepatic necrosis. Seven geese of the remaining 11 birds also had hepatic necrosis in the liver, the greenish discoloration of which was obscure macroscopically. The liver discoloration was considered a jaundice due to both rapid overproduction of bile from increased breakdown of erythrocytes and intrahepatic impaired excretion of bile. The severity of lesions was not correlated to the liver lead concentrations. All examined geese had hemosiderosis of mononuclear phagocytic system cells in the spleen and hypoplasia or edema of the bone marrow with increased numbers of polychromatic erythroblasts. These prominent changes probably resulted from excess breakdown of erythrocytes, hypercholia followed by intrahepatic cholestasis, and disrupted erythropoiesis in bone marrow caused by lead.

Inability to Detect β-Amyloid Protein Precursor mRNA in Alzheimer Plaque-Associated Microglia

A close association between Alzheimer senile plaques and microglia (the resident mononuclear phagocytic system cells of the brain) is well documented. To determine whether microglia contain detectable β-amyloid protein precursor (β-APP) mRNA, the present study combined immunocytochemistry (LN3 antibody to label microglia) with in situ hybridization (full-length cRNA probe to detect all forms of β-APP mRNA). We report that immunolabeled microglia, including those clustered around senile plaques, generally lack detectable β-APP mRNA—suggesting that microglia are not synthesizing the plaque-associated amyloid. The possibility that, analogous to the process in other forms of amyloidosis, the resident mononuclear phagocytic cells ingest an amyloidogenic precursor and secrete amyloid was not examined. Recent demonstrations of interactions between immune-related factors and Alzheimer lesions suggest that β-APP and its breakdown products, along with microgila and their secretory products, may work synergistically in an AD pathogenetic cascade.

Immunohistochemical distribution of S-100 α-positive cells in bovine mycobacterial and non-mycobacterial granulomas

By means of immunohistochemistry, the distribution of the alpha-subunit (S-100 alpha) and the beta-subunit (S-100 beta) of S-100 protein was studied in bovine granulomas caused by Actinomyces bovis, Actinobacillus lignieresi, Actinomyces (Corynebacterium) pyogenes, Pseudomonas aeruginosa, Staphylococcus aureus, Mycobacterium bovis and Mycobacterium paratuberculosis. S-100 alpha-positive epithelioid cells or dendritic cells were scattered among the predominantly S-100 alpha-negative cells of the mononuclear phagocyte system (MPS). S-100 beta was not found in the MPS cells of granulomas but was observed in the endothelial cells of blood vessels. A positive reaction to S-100 was also seen in normal cells in the lymphoid and mammary tissues. Mycobacterial granulomas contained more S-100 alpha-positive cells than did non-mycobacterial ones.

Specific features of ultrastructural changes in cells of the rat mononuclear phagocyte system in experimental endotoxemia

Specific features of ultrastructural changes in cells of the rat mononuclear phagocyte system in experimental endotoxemia

MHC class II-positive microglia in human brain: association with Alzheimer lesions.

Cells of the mononuclear phagocytic system (MPS) present foreign antigen on their cell surfaces bound to major histocompatibility complex (MHC) class II molecules. Previous studies of normal human brain samples reported MHC class II expression primarily by perivascular MPS cells and white matter microglial cells. Marked increases in MHC class II-expressing microglia have been shown in many neuropathologic disorders, including Alzheimer's disease (AD). A close morphologic association between these cells and Alzheimer senile plaque beta-amyloid has been demonstrated. The present study used a mixed aldehyde fixative to enhance the localization of MHC class II-expressing MPS cells in non-AD and AD brain. Two antibodies against MHC class II (HLA-DR; LN3), as well as the lectin Ricinus communis agglutinin (which recognizes both ramified and activated microglia) were used for light and electron microscopic analyses. We now report that MHC class II-expressing ramified microglia are distributed in a uniform reticular array throughout the grey, as well as the white matter in non-AD cases. In AD cases, immunolabelled cells had the morphology of activated microglia, with darkly stained plump somata and short, thick processes. Microglia clustered around senile plaque amyloid and neurofibrillary tangles (NFT), rather than forming the uniform array characteristic of control tissue. Finally, we report that perivascular MPS cells are found in a morphologic relationship with vascular amyloid identical to that seen between microglial cells and senile plaque beta-amyloid. These data suggest that MHC class II-expressing cells may be involved in the degradation of NFT-laden neurons and the posttranslational modification of extracellular-NFT epitopes. In addition, both parenchymal and perivascular MPS cells are ideally situated to uptake and process the beta-amyloid protein precursor and deposit beta-amyloid on senile plaques, NFT, and the cerebrovasculature.