Isolation and characterization of murine Kupffer cells and splenic macrophages

Macrophage In Vitro and In Vivo Tracking via Anchored Microcapsules

A new promising trend in personalized medicine is the use of autologous cells (macrophages or stem cells) for cell-based therapy and also as a "Trojan horse" for targeted delivery of a drug carrier. The natural ability of macrophages for chemotaxis allows them to deliver cargo to the damaged area, significantly reducing side effects on healthy organ tissues. Therefore, it is important to develop tools to track their behavior in the organism. While labeled containers can serve as anchored tags for imaging macrophages in vivo, they can affect the properties and functions of macrophages. This work demonstrates that 3 μm sized capsules based on biocompatible polyelectrolytes and fluorescently labeled with both Cy7 and RITC dyes do not affect cell functionalization in vitro, such as viability, proliferation, and movement of transformed monocyte/macrophage-like cells (RAW 264.7) and primary bone marrow derived macrophages (BMDM) at maximal loading of five capsules per cell. In addition, capsules allowed fluorescent detection of ex vivo loaded cells 24 h after the tail vein injection in vivo and visualization of microcapsule-laden macrophages ex vivo using confocal microscopy. We have delivered about 62.5% of injected BMDM containing 12.5 million capsules with 3.75 μg of high-molecular-weight cargo (0.3 pg/capsule) to the liver. Our results demonstrate that 3 μm polyelectrolyte fluorescently labeled microcapsules can be used for safe macrophage loading, allowing cell tracking and drug delivery, which will facilitate development of macrophage-based cell therapy protocols.

Critical Role of Macrophage FcγR Signaling and Reactive Oxygen Species in Alloantibody-Mediated Hepatocyte Rejection

Humoral alloimmunity negatively impacts both short- and long-term cell and solid organ transplant survival. We previously reported that alloantibody-mediated rejection of transplanted hepatocytes is critically dependent on host macrophages. However, the effector mechanism(s) of macrophage-mediated injury to allogeneic liver parenchymal cells is not known. We hypothesized that macrophage-mediated destruction of allogeneic hepatocytes occurs by cell-cell interactions requiring FcγRs. To examine this, alloantibody-dependent hepatocyte rejection in CD8-depleted wild-type (WT) and Fcγ-chain knockout (KO; lacking all functional FcγR) transplant recipients was evaluated. Alloantibody-mediated hepatocellular allograft rejection was abrogated in recipients lacking FcγR compared with WT recipients. We also investigated anti-FcγRI mAb, anti-FcγRIII mAb, and inhibitors of intracellular signaling (to block phagocytosis, cytokines, and reactive oxygen species [ROS]) in an in vitro alloantibody-dependent, macrophage-mediated hepatocytoxicity assay. Results showed that in vitro alloantibody-dependent, macrophage-mediated hepatocytotoxicity was critically dependent on FcγRs and ROS. The adoptive transfer of WT macrophages into CD8-depleted FcγR-deficient recipients was sufficient to induce alloantibody-mediated rejection, whereas adoptive transfer of macrophages from Fcγ-chain KO mice or ROS-deficient (p47 KO) macrophages was not. These results provide the first evidence, to our knowledge, that alloantibody-dependent hepatocellular allograft rejection is mediated by host macrophages through FcγR signaling and ROS cytotoxic effector mechanisms. These results support the investigation of novel immunotherapeutic strategies targeting macrophages, FcγRs, and/or downstream molecules, including ROS, to inhibit humoral immune damage of transplanted hepatocytes and perhaps other cell and solid organ transplants.

A physiologically based pharmacokinetic model to predict the superparamagnetic iron oxide nanoparticles (SPIONs) accumulation in vivo

Superparamagnetic iron oxide nanoparticles (SPIONs) have been identified as a promising material for biomedical applications. These include as contrast agents for medical imaging, drug delivery and/or cancer cell treatment. The nanotoxicological profile of SPIONs has been investigated in different studies and the distribution of SPIONs in the human body has not been fully characterized. The aim of this study was to develop a physiologically-based pharmacokinetic (PBPK) model to predict the pharmacokinetics of SPIONs. The distribution and accumulation of SPIONs in organs were simulated taking into consideration their penetration through capillary walls and their active uptake by specialized macrophages in the liver, spleen and lungs. To estimate the kinetics of SPION uptake, a novel experimental approach using primary macrophages was developed. The murine PBPK model was validated against in vivo pharmacokinetic data, and accurately described accumulation in liver, spleen and lungs. After validation of the murine model, a similar PBPK approach was developed to simulate the distribution of SPIONs in humans. These data demonstrate the utility of PBPK modeling for estimating biodistribution of inorganic nanoparticles and represents an initial platform to provide computational prediction of nanoparticle pharmacokinetics.

Acquiring Kupffer cells in mice using a MACS-based method

OBJECTIVE

This study sought to establish a new method to isolate Kupffer cells (KCs) by magnetic activated cell sorting (MACS).

METHODS

Nonparenchymal cells were acquired from C57BL/6 mice livers by a perfusion system in vivo and then stained with F4/80(+) fluorescein isothiocyanate and CD11c(-) phycoerythrin antibodies. After incubating with immunomagnetic beads, F4/80(+)CD11c(-) KCs were obtained by MACS selection. The purity was evaluated by flow cytometry, and the morphological features and vitality were analyzed in in vitro cultures.

RESULTS

Compared with traditional methods, acquiring KCs by MACS was characterized by economy, efficiency, and high purity. The F4/80(+)CD11c(-) KCs cultured in vitro also showed the typical adherent shape and excellent phagocytic ability.

CONCLUSIONS

With the 2-step method using immunomagnetic beads, we provide a new method by which KCs can be obtained from mouse liver with high purity and distinct phenotype of F4/80(+) CD.

Development of a cytokine-producing immortalized murine Kupffer cell line

Kupffer cells (KC) play a critical role in both liver physiology and the pathogenesis of various liver diseases. Isolated primary KC have a limited lifespan in culture, and due to the relatively low number obtained, limit their study in vitro. Here, a cytokine-producing immortalized KC (ImKC) line was established from transgenic mice that express the thermolabile mutant tsA58 of the Simian virus 40 large T antigen under the control of the H-2k(b) promoter. Primary KC were obtained using a three step procedure: liver perfusion, centrifugal elutriation, and sorting for F4/80⁺ cells. ImKC were identified within the small-intermediate population of KC that maintained stable expression of F4/80, and the surface antigens CD11b, CD14 and TLR4. ImKC grow at IFNγ-independent manner at 37°C and exhibited a doubling time of ∼24 h when cultured in RPMI 1640 with 5% FBS. Our observations indicate that both activation of telomerase and expression of P53 are markedly increased, suggesting that enhanced telomerase activity and P53 expression may contribute to the immortalization of this cell population. ImKC cells maintained a high capacity to phagocytose FITC-latex beads, and bind/phagocytose erythrocytes. In addition, similar to primary KC, ImKC responded to stimulation with lipopolysaccharide (LPS: 0.1-1μg/ml) by upregulating mRNA levels of TNFα (23-fold), IL-6 (28-fold), and IL-1β (1459-fold), as measured by qRT-PCR. Protein levels of TNFα and IL-6 were also increased, 10-fold and 12-fold, respectively. Reactive oxygen species (ROS) and nitric oxide (NO) production were significantly enhanced in ImKC following an LPS challenge. Furthermore, LPS elicited a marked increase in mitogen activated protein kinase (MAPK) phospho-(ERK1/2, JNK) and NF-κB p50 with decreased IκBα in ImKC, as assessed by Western blot. Collectively, these results demonstrate that the ImKC line retains critical characteristics of primary KC, and thus provides a useful tool to assess the role of KC in liver injury and chronic diseases.

Characterization of the liver-macrophages isolated from a mixed primary culture of neonatal swine hepatocytes

We recently developed a novel procedure to obtain liver-macrophages in sufficient number and purity using a mixed primary culture of rat and bovine hepatocytes. In this study, we aim to apply this method to the neonatal swine liver. Swine parenchymal hepatocytes were isolated by a two-step collagenase perfusion method and cultured in T75 culture flasks. Similar to the rat and bovine cells, the swine hepatocytes retained an epithelial cell morphology for only a few days and progressively changed into fibroblastic cells. After 5–13 days of culture, macrophage-like cells actively proliferated on the mixed fibroblastic cell sheet. Gentle shaking of the culture flask followed by the transfer and brief incubation of the culture supernatant resulted in a quick and selective adhesion of macrophage-like cells to a plastic dish surface. After rinsing dishes with saline, the attached macrophage-like cells were collected at a yield of 10⁶ cells per T75 culture flask at 2–3 day intervals for more than 3 weeks. The isolated cells displayed a typical macrophage morphology and were strongly positive for macrophage markers, such as CD172a, Iba-1 and KT022, but negative for cytokeratin, desmin and a-smooth muscle actin, indicating a highly purified macrophage population. The isolated cells exhibited phagocytosis of polystyrene microbeads and a release of inflammatory cytokines upon lipopolysaccharide stimulation. This shaking and attachment method is applicable to the swine liver and provides a sufficient number of macrophages without any need of complex laboratory equipments.

An efficient method to isolate and culture mouse Kupffer cells

Kupffer cells (KCs) play an essential role in the physiological and pathological functions of the liver. Although the isolation methods of KCs have been well-described, most of them are sophisticated and time-consuming. In addition, these methods are mainly used for isolating the KCs of the human and rat. In this study, a three-step procedure was applied to isolate KCs in sufficient number and purity from mouse liver, including the techniques of enzymatic tissue treatment, gradient centrifugation, and selective adherence. F4/80 immunofluorescence and flow cytometry were used for cell identification. The combination method resulted in a satisfactorily high yield of 5-6×10(6) KCs per liver, over 92.0% positive for F4/80 and 98.5% viable cells. After 24h of culturing, the KCs showed typical macrophage morphologic features such as irregular shape, transparent cytoplasm and kidney-like nucleus. The phagocytic assay showed that the isolated cells exhibited strong phagocytosis activity. The KCs we isolated were functionally intact and exhibited a concentration dependent TNF-α production induced by LPS. The method we described is an effective method to isolate mouse KCs in high purity and yield, which consuming fewer collagenase and time without altering the functional capacity of the KCs.

Preparation of Kupffer cell enriched non-parenchymal liver cells with high yield and reduced damage of surface markers by a modified method for flow cytometry

The aim of this study was to optimise a collagenase perfusion protocol for the isolation of a liver non-parenchymal cell (NPC) suspension enriched for Kupffer cells that reduced damage to F4/80 antigen cell surface expression to allow analysis by flow cytometry. Kupffer cell-enriched liver NPCs were isolated from C57BL/6 mice using different protocols. Flow cytometry was used to examine the effect of collagenase digestion on F4/80 expression on Kupffer cells, and results were represented by the percentage of F4/80 positive cells and by the F4/80 mean fluorescence intensity (MFI). The perfusion temperature, concentration of collagenase solution and total dosage of collagenase for liver perfusion influenced the effect of collagenase perfusion on the expression of F4/80 antigen on Kupffer cells. Collagenase perfusion at 28°C resulted in an increased percentage of F4/80 positive cells (P = 0.001) and MFI (P = 0.005) compared with 37°C. Perfusion with a total dose of 1.0 g/kg BW collagenase (using a 0.75 mg/mL solution) resulted in the highest percentage of F4/80 positive cells (P = 0.001) compared with 0.8 g/kg BW and 1.2 g/kg BW collagenase. Isolation of cells using the modified protocol resulted in a higher percentage of Kupffer cells (P < 0.001) and a higher MFI of F4/80 antigen (P < 0.001) compared with the common protocol.

In vivo cell reprogramming towards pluripotency by virus-free overexpression of defined factors

The ability to induce the reprogramming of somatic mammalian cells to a pluripotent state by the forced expression of specific transcription factors has helped redefine the rules of cell fate and plasticity, as well as open possibilities for disease modeling, drug screening and regenerative medicine. Here, we hypothesized that the non-viral forced expression of the four originally discovered defined factors (OKSM) in adult mice could result in in vivo reprogramming of cells in the transfected tissue in situ. We show that a single hydrodynamic tail-vein (HTV) injection of two plasmids encoding for Oct3/4, Sox2, Klf4 and c-Myc respectively, are highly expressed in the liver tissue of Balb/C adult mice. Hallmark pluripotency markers were upregulated within 24–48 h after injection, followed by down-regulation of all major hepatocellular markers. Generation of transcriptionally reprogrammed cells in vivo was further confirmed by positive staining of liver tissue sections for all major pluripotency markers in Balb/C mice and the Nanog-GFP reporter transgenic strain (TNG-A) with concomitant upregulation of GFP expression in situ. No signs of physiological or anatomical abnormalities or teratoma formation were observed in the liver examined up to 120 days. These findings indicate that virus-free expression of OKSM factors in vivo can transcriptionally reprogram cells in situ rapidly, efficiently and transiently, absent of host tissue damage or teratoma formation.

The effect of artificial lipid envelopment of Adenovirus 5 (Ad5) on liver de-targeting and hepatotoxicity

Human Adenovirus type 5 (Ad5) has been extensively explored in clinical gene therapy, but its immunogenicity dramatically affects the kinetics and toxicity profile of the vector. We previously designed a variety of artificial lipid bilayer envelopes around the viral capsid to develop safer hybrid vectors. Here, we studied the interaction of enveloped Ad in cationic (DOTAP:Chol) or anionic (DOPE:CHEMS) lipid bilayers with different blood components. When Ad was enveloped by cationic lipids, significantly high levels of viral uptake in HepG2 cultured cells were achieved, independent of blood coagulation factors present. In vitro experiments also showed that artificial envelopment of Ad completely altered the affinity towards both human and murine red blood cells. After intravenous administration in BALB/c mice, real-time PCR and transgene expression studies indicated that cationic lipid envelopes significantly reduced hepatocyte transduction significantly increasing virus lung accumulation compared to DOPE:CHEMS enveloped or naked Ad. ALT/AST serum levels and liver histology showed that envelopment also improved hepatotoxicity profiles compared to naked Ad. This study suggests that artificial envelopes for Ad significantly alter the interactions with blood components and can divert viral particles from their natural liver tropism resulting in reduced hepatotoxicity.

The effect of targeted delivery of anti-TNF-α oligonucleotide into CD169+ macrophages on disease progression in lupus-prone MRL/lpr mice

Systemic blockade of TNF-α via monoclonal antibodies and soluble receptors has shown considerable effects against several typical autoimmune disorders, but remains unconvincing for the treatment of lupus. Based on our previous study, a CD169(+) macrophage-specific therapy using TNF-α antisense oligonucleotides (ASO) was tested for its efficacy in MRL/lpr lupus-prone mice. ASO-containing cationic agarose hydrogel were injected into mice subcutaneously. Tissue distribution and cellular localization of ASO were determined. The therapeutic effects and possible mechanism were further studied in MRL/lpr lupus-prone mice. The results showed that specifically accumulation of the anti-TNF-α ASO in CD169(+) macrophages could significantly reduce TNF-α expression in CD169(+) macrophages and inhibit lymphocytes over-proliferation, finally resulted in the relief of the lupus-like symptoms of the animals. The nucleic acid drug based on CD169(+) macrophage-specific TNF-α regulation represents a potential therapeutic approach that may be valuable for lupus therapy.

A genome-wide expression profile of adrenocortical cells in knockout mice lacking steroidogenic acute regulatory protein

Steroidogenic acute regulatory protein (StAR) facilitates cholesterol transfer into the inner mitochondrial membrane in the acute phase of steroidogenesis. Mice lacking StAR (Star(-/-)) share phenotypes with human individuals having congenital lipoid adrenal hyperplasia including compromised production of steroid hormones and florid accumulation of cholesterol esters in adrenal glands and gonads. To define a specific pattern of molecular changes with StAR deficiency, we performed transcriptome analysis of adrenal cells selectively isolated by fluorescent-activated cell sorting at embryonic d 17.5 or 18.5 in seven wild-type (Star(+/+)) or four Star(-/-) mice having the transgene targeting the enhanced green fluorescent protein to cell lineages that express StAR. A gene expression profile was obtained by whole-mouse genome microarray and confirmed by quantitative real-time PCR, identifying 1206 and 767 significantly up-regulated and down-regulated genes, respectively, in Star(-/-) mice compared with Star(+/+) mice (fold difference ≥ 2 and P value < 0.05 with false discovery rate < 0.2). In Star(-/-) mice, expression levels of genes involved in cholesterol efflux and the inflammatory response were significantly up-regulated, whereas those related to steroid hormone biosynthesis or cholesterol biosynthesis and influx were not significantly changed. Immunoreactive Iba1 or F4/80 (macrophage marker) in adrenal glands of Star(-/-) mice was detected not only in an increased number of resident macrophages but also in most adrenocortical cells. These findings expand our understanding of the pathophysiology of adrenal glands with the disruption of StAR and propose a reciprocal interaction between adrenocortical cells and resident macrophages inside adrenal glands of Star(-/-) mice.

Interferon regulatory factor-1 regulates the autophagic response in LPS-stimulated macrophages through nitric oxide

The pathogenesis of sepsis is complex and, unfortunately, poorly understood. The cellular process of autophagy is believed to play a protective role in sepsis; however, the mechanisms responsible for its regulation in this setting are ill defined. In the present study, interferon regulatory factor 1 (IRF-1) was found to regulate the autophagic response in lipopolysaccharide (LPS)-stimulated macrophages. In vivo, tissue macrophages obtained from LPS-stimulated IRF-1 knockout (KO) mice demonstrated increased autophagy and decreased apoptosis compared to those isolated from IRF-1 wild-type (WT) mice. In vitro, LPS-stimulated peritoneal macrophages obtained from IRF-1 KO mice experienced increased autophagy and decreased apoptosis. IRF-1 mediates the inhibition of autophagy by modulating the activation of the mammalian target of rapamycin (mTOR). LPS induced the activation of mTOR in WT peritoneal macrophages, but not in IRF-1 KO macrophages. In contrast, overexpression of IRF-1 alone increased the activation of mTOR and consequently decreased autophagic flux. Furthermore, the inhibitory effects of IRF-1 mTOR activity were mediated by nitric oxide (NO). Therefore, we propose a novel role for IRF-1 and NO in the regulation of macrophage autophagy during LPS stimulation in which IRF-1/NO inhibits autophagy through mTOR activation.

Isolation and characterization of macrophages from a mixed primary culture of bovine liver cells

Previously, we developed a simple and efficient method to isolate liver macrophages from a mixed primary culture of adult rat liver cells. To extend the applicability of this method, we isolated macrophages from mixed primary cultures of bovine liver cells. Macrophage cells proliferated on the cell sheet of mixed bovine liver cells after 8-16d of culture. These cells were detached by shaking of the culture flasks. Subsequent transfer and brief incubation in plastic dishes resulted in selective adhesion of macrophages. After rinses with PBS, attached macrophages were harvested. More than 10(6) cells could be harvested from the culture flask at intervals of 2-3d for more than three weeks. The isolated cells were strongly positive for bovine macrophage markers, such as CD68, CD172a and Iba-1. These cells exhibited functional properties of macrophages, including active phagocytosis of polystyrene microbeads, proliferative response to recombinant bovine granulocyte-macrophage colony-stimulating factor, upregulation of specific inflammatory cytokine genes upon stimulation with lipopolysaccharide, and formation of multinucleated giant cells. The shaking and attachment method provides a simple and efficient alternative to obtain bovine liver macrophages without requiring complex equipment or specialized technical skills.

Liver regeneration and tumour stimulation: implications of the renin-angiotensin system

Liver resection is the most effective treatment for primary liver tumours and metastasis to the liver, and remains the only potentially long-term curative therapy for patients with colorectal cancer (CRC) liver metastases. Nevertheless, there is a significant incidence of tumour recurrence following liver resection. Cellular and molecular changes resulting from resection and the subsequent liver regeneration process may influence the kinetics of tumour growth, contributing to recurrence. Although commonly associated with the systemic homeostasis of blood pressure, fluid and electrolyte, the renin-angiotensin system (RAS) has recently been shown to play a role in regulating cell proliferation, apoptosis and angiogenesis in local organs as well as in malignancies. An electronic search of the English literature on the role of the RAS in liver regeneration and tumourigenesis was performed using PubMed, with additional relevant articles sourced from reference lists. Studies have shown that the blockade of the RAS pathway stimulates liver regeneration and inhibits tumour progression. An understanding of the role of RAS in liver regeneration and tumourigenesis may enable alternative strategies to improve patient outcome and survival after liver resection. This review will discuss the role of the RAS in liver regeneration and in tumour recurrence post-liver resection. The potential of the RAS as a novel therapeutic target for CRC liver metastases patients undergoing liver resection will be outlined.

A novel isolation method for macrophage-like cells from mixed primary cultures of adult rat liver cells

We report a simple and efficient method to obtain macrophage-like cells from the mixed primary cultures of adult rat liver cells. A parenchymal hepatocyte enriched fraction was prepared from adult rat livers and seeded into culture flasks. After 7 to 10 days of culture, when most hepatocytes were degenerated or transformed into fibroblastic cells, macrophage-like cells vigorously proliferated on the cell sheet. By shaking the flasks, macrophage-like cells were readily detached. Subsequent transfer and incubation in plastic dishes resulted in quick and selective adhesion of macrophage-like cells, while other contaminating cells remained suspended in the medium. After rinsing with saline, attached macrophage-like cells were harvested with 95 to 99% purity, as evaluated by flow cytometry or immunocytochemistry. These cells showed typical macrophage morphology and were strongly positive for markers of rat macrophages, such as ED-1, ED-3, and OX-41, but negative for cytokeratins and alpha-smooth muscle actin. They possessed functional properties of typical macrophages, including active phagocytosis of latex beads, proliferative response to recombinant GM-CSF, secretion of inflammatory and anti-inflammatory cytokines upon stimulation with LPS, and formation of multinucleated giant cells. As more than 10(6) cells can be recovered repeatedly from a T75 culture flask at two to three day intervals for more than two weeks, our procedure might implicate a novel alternative to obtain Kupffer cells in sufficient number and purity without complex equipment and skills.

Adenoviral-mediated endothelial precursor cell delivery of soluble CD115 suppresses human prostate cancer xenograft growth in mice

Prostate cancer tumor growth and neovascularization is promoted by an interplay between migratory tumor stromal cells such as specialized tumor-associated macrophages (TAMs) and circulating endothelial precursor cells (CEPs). As vehicles for tumor therapy, human CEPs are relatively easy to isolate from peripheral blood, are able to proliferate long-term in vitro, are amenable to viral manipulation, and preferentially home to regions of ischemia found in growing tumors. We show here that human peripheral blood CEPs expanded ex vivo migrate to prostate cancer cells in vitro and efficiently home to human prostate tumor xenografts in vivo. Infection of precursors ex vivo with an adenovirus constructed to secrete a soluble form of the colony-stimulating factor-1 receptor CD115 that inhibits macrophage viability and migration in vitro significantly decreases the number of TAMs in xenografts (p < .05), reduces proliferation (p < .01) and vascular density (p < .03), and suppresses the growth of xenografts (p < .03). These data show for the first time that targeting stromal cell processes with cellular therapy has the potential to retard prostate tumor growth.

Immunostimulatory properties and enhanced TNF- alpha mediated cellular immunity for tumor therapy by C60(OH)20 nanoparticles

Publications concerning the mechanism of biological activity, especially the immunological mechanism of C(60)(OH)(20) nanoparticles, are relatively limited. However, the structure and characteristics of this carbon allotrope have been widely investigated. In this paper, we have demonstrated that water-soluble C(60)(OH)(20) nanoparticles have an efficient anti-tumor activity in vivo, and show specific immunomodulatory effects to the immune cells, such as T cells and macrophages, both in vivo and in vitro. For example, C(60)(OH)(20) nanoparticles can increase the production of T-helper cell type 1 (Th1) cytokines (IL-2, IFN- gamma and TNF-alpha), and decrease the production of Th2 cytokines (IL-4, IL-5 and IL-6) in serum samples. On the other hand, C(60)(OH)(20) nanoparticles show almost no adverse effect to the viability of immune cells in vitro but stimulate the immune cells to release more cytokines, in particular TNF- alpha, which plays a key role in the cellular immune process to help eliminate abnormal cells. TNF- alpha production increased almost three-fold in treated T lymphocytes and macrophages. Accordingly, we conclude that C(60)(OH)(20) nanoparticles have an efficient anti-tumor activity and this effect is associated with an increased CD(4)(+)/CD(8)(+) lymphocyte ratio and the enhancement of TNF- alpha production. The data suggest that C(60)(OH)(20) nanoparticles can improve the immune response to help to scavenge and kill tumor cells.

Neutrophils sequestered in the liver suppress the proinflammatory response of Kupffer cells to systemic bacterial infection

The liver plays a major role in clearing bacteria from the bloodstream. Rapid clearance is primarily the function of fixed tissue macrophages (Kupffer cells) that line the hepatic sinusoids. Although Kupffer cells play a critical role in blood clearance, the actual elimination of the bulk of bacteria taken up by the liver depends upon the accumulation of bactericidal neutrophils. Subsequent experiments demonstrating neutrophils inside Kupffer cells derived from infected animals prompted our speculation that neutrophils modulate the proinflammatory response of Kupffer cells to bacteria cleared from the bloodstream. Indeed, we report here that neutrophils accumulated in the liver sinusoids suppress cytokine and chemokine mRNA expression and protein production by Kupffer cells. Using listeriosis in mice as an experimental model, we found that IL-1beta, IL-6, IL-10, IL-12, TNF-alpha, MIP-1alpha, keratinocyte-derived chemokine, and MCP-1 mRNA levels were >or=10-fold more in the livers of Listeria-infected, relative to noninfected control, mice at 0.5-2 h after i.v. infection. Most message levels were sharply diminished thereafter, correlating inversely with increased neutrophil sequestration. Relative to intact animals, mice rendered neutrophil deficient exhibited marked increases in cytokine/chemokine mRNA expression and protein production in the liver subsequent to infection. Moreover, purified Kupffer cells derived from infected, neutrophil-depleted mice produced significantly more IL-6, IL-10, IL-12, TNF-alpha, keratinocyte-derived chemokine, and MCP-1 in culture. These findings document the critical role of neutrophils in moderating the proinflammatory response of Kupffer cells to bacteria taken up by the liver.

Inflammation enhances consumption and presentation of transfused RBC antigens by dendritic cells

Factors regulating which patients become alloimmunized to red blood cell (RBC) antigens are poorly understood. Using a murine model of transfusion, we recently reported that viral-like inflammation with polyinosinic polycytidylic acid [poly (I:C)] significantly enhances RBC alloimmunization. Herein, we tested the hypothesis that poly (I:C) exerts this effect, at least in part, at the level of antigen-presenting cells (APCs). Using a novel in vivo method, we report that in the noninflamed state, most transfused RBCs were consumed by splenic macrophages, with only trace consumption by splenic dendritic cells (DCs). To a lesser extent, RBCs were also consumed by APCs in the liver. However, unlike soluble antigens, no RBCs were consumed by APCs in the lymph nodes. Inflammation with poly (I:C) induced significant consumption of transfused RBCs by splenic DCs, with a concomitant increase in costimulatory molecule expression. Moreover, this resulted in increased proliferation of CD4(+) T cells specific for the mHEL RBC alloantigen. Finally, splenectomy abrogated the enhancing effects of poly (I:C) on RBC alloimmunization. Together, these data provide additional insight into the nature of transfused RBCs as an immunogen and provide a mechanism by which viral-like inflammation enhances alloimmunization to transfused RBCs.

Gene expression profiles of hepatic cell-type specific marker genes in progression of liver fibrosis

AIM: To determine the gene expression profile data for the whole liver during development of dimethylni-trosamine (DMN)-induced hepatic fibrosis.

METHODS: Marker genes were identified for different types of hepatic cells, including hepatic stellate cells (HSCs), Kupffer cells (including other inflammatory cells), and hepatocytes, using independent temporal DNA microarray data obtained from isolated hepatic cells.

RESULTS: The cell-type analysis of gene expression gave several key results and led to formation of three hypotheses: (1) changes in the expression of HSC-specific marker genes during fibrosis were similar to gene expression data in in vitro cultured HSCs, suggesting a major role of the self-activating characteristics of HSCs in formation of fibrosis; (2) expression of mast cell-specific marker genes reached a peak during liver fibrosis, suggesting a possible role of mast cells in formation of fibrosis; and (3) abnormal expression of hepatocyte-specific marker genes was found across several metabolic pathways during fibrosis, including sulfur-containing amino acid metabolism, fatty acid metabolism, and drug metabolism, suggesting a mechanistic relationship between these abnormalities and symptoms of liver fibrosis.

CONCLUSION: Analysis of marker genes for specific hepatic cell types can identify the key aspects of fibrogenesis. Sequential activation of inflammatory cells and the self-supporting properties of HSCs play an important role in development of fibrosis.

Generation and functional characterization of a clonal murine periportal Kupffer cell line from H-2Kb -tsA58 mice

Murine Kupffer cells (KCs) are heterogeneous and survive only for a short time in vitro. Here, a clonal, murine KC line was generated from transgenic mice, expressing the thermolabile mutant tsA58 of the Simian virus 40 large T antigen under the control of the H-2K(b) promoter. Thirty-three degrees Celsius and 37 degrees C but not 39 degrees C have been permissive for growth of the clone; it required conditioned media from hepatocytes and endothelial cells for proliferation. In contrast to primary cells, the cells of the clone were uniform, survived detachment, and could therefore be analyzed by cytofluorimetry. The clone, as primary KCs, constitutively expressed nonspecific esterase, peroxidase, MOMA-2, BM8, scavenger receptor A, CD14, and Toll-like receptor 4 (TLR4); the antigen-presenting molecules CD40, CD80, and CD1d; and endocytosed dextran-fluorescein isothiocyanate. It lacked complement, Fc receptors, F4/80 marker, and the phagosomal coat protein tryptophan aspartate-containing coat protein (TACO). The clone exhibited CD14- and TLR4/MD2-independent, plasma-dependent lipopolysaccharide (LPS) binding, Escherichia coli and Streptococcus pneumoniae phagocytosis, and LPS- and interferon-gamma-induced NO production but no tumor necrosis factor alpha, interleukin (IL)-6, or IL-10 release. The large size, surface-marker expression, and capacity to clear gram-negative and -positive bacteria indicate that the clone was derived from the periportal, large KC subpopulation. The clone allows molecular studies of anti-infective and immune functions of KCs.

Oxysterol-induced activation of macrophage NADPH-oxidase enhances cell-mediated oxidation of LDL in the atherosclerotic apolipoprotein E deficient mouse: inhibitory role for vitamin E

In the present study we provide evidence, both direct and circumstantial, that macrophage oxysterols induce translocation of p47phox from the cytosol to the cell's plasma membrane, forming an active NADPH-oxidase complex which produces superoxide anion and facilitates cell-mediated oxidation of LDL. The study was performed on macrophages from atherosclerotic apolipoprotein E deficient (E(0)) mice, which are under oxidative stress. The oxysterol content in peritoneal macrophages (MPM) from E(0) mice was significantly higher (by 50-80%) than that observed in MPM from control (C57BL6) mice. E(0) MPM release 2-fold more superoxide anions and oxidize LDL by 2.5-fold more than control MPM. Furthermore, macrophage protein kinase C (PKC) activity and arachidonic acid (AA) release (which are both involved in NADPH-oxidase activation) were elevated by 60 and 70%, respectively, in E(0) MPM compared with control MPM. Dietary supplementation of vitamin E (40 mg/kg per day for 2 months) to E(0) mice resulted in a reduction in MPM total oxysterols content (-27%) and this effect was associated with a reduction in PKC activity (-36%), AA release (-39%), cytosolic p47phox translocation to the plasma membrane (-30%), superoxide anion release (-25%) and MPM-mediated LDL oxidation (-28%), compared with unsupplemented E(0) mice. Enrichment of MPM from control mice with the major oxysterols found in E(0) MPM (7-ketocholesterol, beta-epoxycholesterol and 7beta-hydroxycholesterol) resulted in a dose-dependent increase (60-80%) in PKC activity, AA release, p47phox translocation, superoxide anion release and cell-mediated oxidation of LDL. These data clearly demonstrate for the first time that under oxidative stress, cellular lipids are oxidized, and that macrophage enrichment with oxysterols (as exists in E(0) mice) activates the NADPH-oxidase system and enhances cell-mediated oxidation of LDL, a key event during early atherogenesis.

Induction of interleukin-1beta and interleukin-6 mRNA by low doses of ionizing radiation in macrophages

We have previously reported the antimetastatic effects and augmentation of immune responses, which would be a mechanism of the antimetastatic effects, of 0.1 to 0.2 Gy total body irradiation. To elucidate the cellular mechanisms of the augmentation of immune response, we investigated the effects of low-dose irradiation on gene expression of interleukin-1beta (IL-1beta) and IL-6 using mouse peritoneal macrophages in vitro. Absolute mRNA quantification was carried out using competitive polymerase chain reaction. Gene expression of IL-1beta and IL-6 was increased 1 to 2 hr after 2.0 Gy irradiation and then decreased to below the basal expression level 4 hr after irradiation. Irradiation with 0.1 Gy increased IL-6 expression 2 hr after irradiation, but it did not affect IL-1beta expression. Downregulation of IL-1beta and IL-6 observed 4 hr after 2.0 Gy irradiation was not observed with 0.1 Gy irradiation. The protein kinase C (PKC) inhibitor H7 and the phosphatidylinositol 3-kinase (PI3-kinase) inhibitor wortmannin inhibited induction of IL-1beta and IL-6 expression, which suggests that radiation-induced IL-1beta and IL-6 expression is achieved by PKC- and PI3-kinase-mediated signaling.

Virally infected hepatocytes are resistant to perforin-dependent CTL effector mechanisms

Cell-mediated cytotoxicity plays an important role in the clearance of noncytopathic viruses from infected tissues. Perforin-dependent cytotoxic mechanisms have been noted to play an important role in the clearance of infections from multiple extrahepatic organs. In contrast, mice with defects in the Fas/Fas ligand (FasL)-mediated cytotoxicity pathway exhibit delayed clearance of adenovirus from the liver without apparent delay in the clearance of viral infections from extrahepatic organs. The present studies examined the role of cytotoxic effector mechanisms in intrahepatic immune responses to a replication-defective, recombinant beta-galactosidase-encoding adenovirus (AdCMV-lacZ). Delayed clearance of AdCMV-lacZ from the livers of FasL-defective B6.gld mice, but not perforin-deficient B6.pfp(-/-) mice, was noted despite no significant differences in initial hepatic CD8(+) T cell IFN-gamma or TNF responses or in activation of intrahepatic cytotoxic lymphocytes cells capable of killing AdCMV-lacZ-infected fibroblast targets. In contrast, AdCMV-lacZ-infected hepatocyte targets were far more sensitive to killing by intrahepatic cytotoxic lymphocytes from B6.pfp(-/-) than from B6.gld mice, and residual levels of virus-specific killing of hepatocyte targets by FasL-defective B6.gld CTL were blocked by TNF inhibition. These results suggest that inherent resistance of hepatocytes to cytotoxicity mediated by perforin-dependent mechanisms leaves Fas/FasL-dependent, cell-mediated cytotoxicity as the major pathway for CTL-mediated killing of virally infected hepatocytes and accounts for the more prominent role of perforin-independent anti-viral mechanisms in immune responses in the liver.

Unresponsiveness of intrahepatic lymphocytes to bacterial superantigen: rapid development of suppressive Mac-1(high) cells in the mouse liver

We previously found that a small dose (2 microg per mouse) of staphylococcal enterotoxin B (SEB) induced early emerging unresponsiveness in intrahepatic-lymphocyte populations (IHLs). The purpose of this study was to reveal the inducing role of accessory cells involved in IHLs in this phenomenon. IHLs prepared at 3 to 24 hours after SEB injection failed to proliferate in response not only to SEB but also to SEA, representing ligand-nonspecific unresponsiveness, whereas spleen cells (SPCs) and mesenteric lymph-node cells showed transient proliferation. Unresponsiveness in IHLs was related to a deficit of their accessory cell function as measured by coculture of irradiated IHLs and antigen-specific, type 1 T-helper (Th1) clone cells. High levels of nitrite were detected in the culture supernatant. Supplement of N(G)-monomethyl-L-arginine lowered nitrite levels and concurrently restored the proliferative response of Th1 cells, indicating the involvement of nitric oxide in suppression. Adherent cells prepared from IHLs well reproduced these results. As shown by flow cytometry, Mac-1(high) Ia(+) cells, which mainly included F4/80(+) cells (macrophages) and a minor population of CD11c(+) cells (dendritic cells), increased in proportion in IHLs but not in SPCs at 6 to 24 hours. Depletion of Mac-1(high) cells from IHLs with antibody-coated magnetic beads recovered the proliferative response. Depleted Mac-1(high) cells had a monocytoid appearance. In immunostained sections, Kupffer cells came to highly express both Mac-1 and Ia at 12 hours. These results indicate that Mac-1(high)Ia(+) adherent cells, largely Kupffer cells activated by SEB, nonspecifically suppress the proliferation of Th1 cells via nitric oxide production before manifestation of ligand-specific unresponsiveness.

Macrophage-released proteoglycans enhance LDL aggregation: studies in aorta from apolipoprotein E-deficient mice

Aggregated low-density lipoprotein (LDL) was shown to be present in the atherosclerotic lesion, but the mechanism responsible for its formation in vivo is not known yet. To find out whether LDL aggregation occurs in the arterial wall during atherogenesis, LDLs were extracted from the aortas of apolipoprotein E-deficient (E(0)) mice during their aging (and the development of atherosclerosis), and were analyzed for their aggregation states, in comparison to LDLs isolated from aortas of control mice. LDL isolated from aortas of E(0) mice was already aggregated at 1 month of age and its aggregation state substantially increased with age, with 3-fold elevation at 6 months of age compared to younger, 1-month-old, mice. Only minimal aggregation could be detected in LDL derived from control mice. Electron microscopy examination revealed that LDL particles from aortas of the E(0) mice were heterogeneous in their size, ranging between 20 and 300 nm. The mouse aortic LDL contained proteoglycans (PGs) and their content increased with the age of the mice, with about 2-fold higher levels than those found in LDLs derived from aortas of control mice. Macrophage-released PGs were previously demonstrated to enhance LDL aggregation in vitro. However, their involvement in LDL aggregation in vivo has not been studied yet. Thus, we next studied the effect of arterial macrophage-released PGs on the susceptibility of plasma LDL to aggregation by Bacillus cereus sphingomyelinase (SMase). Foam cell macrophages were isolated from aortas of the atherosclerotic E(0) mice at 6 months of age and were found to be loaded with cholesterol and to contain oxidized lipids. To analyze the effect of macrophage-released PGs on LDL aggregation, PGs were prelabeled by cell incubation with [35S]sulfate, followed by incubation of macrophage-released PGs with E(0) mouse plasma LDL (200 microg protein/ml) for 1 h at 37 degrees C. [35S]Sulfated PGs were found to be LDL-associated and the susceptibility of PG-associated LDL to aggregation by SMase was increased by up to 45% in comparison to control LDL. Similar results demonstrating the involvement of PGs in LDL aggregation were obtained upon incubation of LDL with increasing concentrations of PGs that were isolated from the entire aorta of E(o) mice (rather than the isolated macrophages). The stimulatory effect of macrophage-released PGs on LDL aggregation was markedly reduced when the PGs were pretreated with the glycosaminoglycan-hydrolyzing enzymes, chondroitinase ABC or chondroitinase AC, and to a much lesser extent with heparinase. We thus conclude that macrophage-released chondroitin sulfate PG can contribute to the formation of atherogenic aggregated LDL in the arterial wall.

Oxidized monocyte-derived macrophages in aortic atherosclerotic lesion from apolipoprotein E-deficient mice and from human carotid artery contain lipid peroxides and oxysterols

Oxidative stress is thought to play an important role in atherogenesis. The present study demonstrated, for the first time, that macrophages (originally derived from blood monocytes) isolated from aortas of the atherosclerotic apolipoprotein E deficient (E degrees ) mice or from human carotid artery, are oxidized as they contain lipid peroxides and oxysterols. The major oxysterol in arterial macrophages was found to be 7-ketocholesterol (51% of total oxysterols). To find out whether lipid peroxidation of monocytes occurs in vivo already in the blood, we analyzed the oxidative state of monocytes derived from E degrees mice in comparison to monocytes from control mice. Cellular lipid peroxides and total oxysterols were four and sevenfold higher respectively, in monocytes derived from E degrees mice in comparison to monocytes from control mice. The results of the present study thus demonstrated the presence of lipid-peroxidized monocytes already in the blood, which are further oxidized in the arterial wall after their conversion into macrophages. The arterial oxidized macrophages could be considered key contributors to foam cell formation, the hallmark of early atherosclerosis.

The effect of adrenaline and Walker-256 tumour-induced cachexia upon Kupffer cell metabolism

Kupffer cells (KC), the liver macrophages, are able to produce PGE(2), which is involved in immune suppression and in the aggravation of cancer cachexia due to interference with lipid metabolism in the liver. Since tumour-bearing (TB) rats present high plasma epinephrine levels, and this hormone is able to affect macrophage metabolism and function, we have assessed the effect of epinephrine (5 nM) upon Kupffer cell PGE(2) production. Epinephrine induced increased production of PGE(2) both by control (3.5-fold) and TB rats (27 per cent) KC, an effect blocked by propranolol. Enhancement of cAMP content in the cells by addition of isoproterenol (0.1 microM) to the incubations, however, failed to induce the same response in the cells. Nevertheless, when phenylephrine (1 microM) was added to the incubation, a similar pattern of PGE(2) production to that observed for epinephrine was found for control and TB rat KC. We propose that the effect of epinephrine upon KC PGE(2) production is mediated by alpha-adrenergic receptors and that Ca(2+) is involved in the response, since increasing concentrations of the ion added to the incubation medium (0.25, 0.5 and 1.0 mM) enhanced the eicosanoid production, while EDTA abolished the response.

Febrile-range temperature modifies early systemic tumor necrosis factor alpha expression in mice challenged with bacterial endotoxin

Fever improves survival in acute infections, but the effects of increased core temperature on host defenses are poorly understood. Tumor necrosis factor alpha (TNF-alpha) is an early activator of host defenses and a major endogenous pyrogen. TNF-alpha expression is essential for survival in bacterial infections but, if disregulated, can cause tissue injury. In this study, we show that passively increasing core temperature in mice from the basal (36.5 to 37.5 degrees C) to the febrile (39.5 to 40 degrees C) range modifies systemic TNF-alpha expression in response to bacterial endotoxin (lipopolysaccharide). The early TNF-alpha secretion rate is enhanced, but the duration of maximal TNF-alpha production is shortened. We identified Kupffer cells as the predominant source of the excess TNF-alpha production in the warmer animals. The enhanced early TNF-alpha production observed at the higher temperature in vivo could not be demonstrated in isolated Kupffer cells or in precision-cut liver slices in vitro, indicating the participation of indirect pathways. Therefore, expression of the endogenous pyrogen TNF-alpha is regulated by increments in core temperature during fever, generating an enhanced early, self-limited TNF-alpha pulse.

Differential nitric oxide and TNF-alpha production of murine Kupffer cell subfractions upon priming with IFN-gamma and TNF-alpha

AIMS/BACKGROUND

We have previously shown a striking heterogeneity of naive murine Kupffer cells (KC) that depends on cell size.

METHODS

In the present study, we demonstrate a shift in response of KC fractions separated on cell size by countercurrent elutriation upon priming with tumor necrosis factor-alpha (TNF-alpha) or interferon-gamma (IFN-gamma).

RESULTS

Whereas unprimed large KC are most active in the production of TNF-alpha and nitric oxide (NO), after priming of KC with TNF-alpha predominantly small and intermediate sized KC produce TNF-alpha in response to bacteria. Priming with IFN-gamma enhanced NO production in all KC. A strong synergy, with respect to production of NO, was observed when KC subfractions were exposed to a combination of TNF-alpha and IFN-gamma. Concerning TNF-alpha production, priming of KC subfractions seemed to induce a shift of activity from large KC to smaller KC.

CONCLUSIONS

The present data demonstrate a clear heterogeneity among murine KC with respect to immunologic response to stimuli. These results demonstrate that KC have different functions in immunologic reactions that seem to be related to size.

Involvement of T cells in enhanced resistance to Klebsiella pneumoniae septicemia in mice treated with liposome-encapsulated muramyl tripeptide phosphatidylethanolamine or gamma interferon

We have previously shown that prophylactic administration of the liposome-encapsulated immunomodulating agents muramyl tripeptide phosphatidylethanolamine (MTPPE) and gamma interferon (IFN-gamma) results in strongly increased survival of mice from a normally lethal septicemia with Klebsiella pneumoniae. It was anticipated that the treatment acts on macrophages and nonspecifically augments host resistance to various infections. In the present study, we provide evidence for a key role for T cells in host defense potentiation by the liposomal immunomodulators toward K. pneumoniae septicemia. It is shown that both CD4 and CD8 cells are important in immunomodulation, most likely due to production of IFN-gamma. Depletion of circulating IFN-gamma resulted in strong reduction of the antimicrobial host defense activation. Administration of interleukin-10 resulted in decreased antimicrobial host defense activation by liposomal immunomodulators. Moreover, administration of liposomal immunomodulators was shown to induce predominantly T-helper type 1 (Th1) cell populations in the spleen. These findings indicate that immunomodulation with liposomal MTPPE and IFN-gamma favors Th1 and NK cell activation.

Expression pattern of heme oxygenase isoenzymes 1 and 2 in normal and stress-exposed rat liver

Heme oxygenase (HO) catalyzes the oxidative cleavage of the alpha-mesocarbon of Fe-protoporphyrin-IX yielding equimolar amounts of biliverdin-IXa, iron, and carbon monoxide. The HO-system consists of two isoenzymes, namely HO-2 and the inducible isoform HO-1, also referred to as heat shock protein (hsp) 32. Although both parenchymal and non-parenchymal liver cells participate in heme metabolism, the expression pattern of the isoenzymes in normal and stress exposed liver is unknown. To study this, rats underwent either endotoxin (lipopolysaccharide [LPS]) challenge, hemorrhagic hypotension, glutathione (GSH) depletion, or cobalt chloride injection, all known to provoke oxidative stress. HO-2 messenger RNA (mRNA) and protein were constitutively expressed in hepatocytes, Kupffer/endothelial-, and stellate (Ito-) cell enriched fractions. Although both non-parenchymal cell fractions expressed HO-1 transcripts, HO-1 immunoreactive protein was restricted to Kupffer cells in the normal liver. In contrast to HO-2, a significant increase in HO-1 on the whole organ level was noted by hemorrhagic hypotension, GSH depletion, and cobalt chloride injection. However, the distinct stress models led to a strikingly different cell-type specific and sublobular expression pattern of HO-1 gene expression. HO-1 was inducible in sinusoidal lining cells (hemorrhagic hypotension, LPS challenge), in periportal (cobalt chloride), or pericentral (GSH depletion, hemorrhagic hypotension) hepatocytes. The blockade of protein translation before hemorrhage by cycloheximide reduced upregulation of HO-1/hsp32 mRNA significantly (65.4% reduction, P < .05), whereas the inducibility of hsp70 transcript was maintained. In addition to transcriptional regulation, HO-1 seems to be subject to posttranscriptional control in particular in non-parenchymal cells.