Liver endocytosis and Kupffer cells

Liver sinusoidal cells eliminate blood-borne phage K1F

Phage treatment has regained attention due to an increase in multiresistant bacteria. For phage therapy to be successful, phages must reach their target bacteria in sufficiently high numbers. Blood-borne phages are believed to be captured by macrophages in the liver and spleen. Since liver sinusoids also consist of specialized scavenger liver sinusoidal endothelial cells (LSECs) and Kupffer cells (KCs), this study investigated the contribution of both cell types in the elimination of Escherichia coli phage K1Fg10b::gfp (K1Fgfp) in mice. Circulatory half-life, organ, and hepatocellular distribution of K1Fgfp were determined following intravenous administration. Internalization of K1Fgfp and effects of phage opsonization on uptake were explored using primary mouse and human LSEC and KC cultures. When inoculated with 107 virions, >95% of the total K1Fgfp load was eliminated from the blood within 20 min, and 94% of the total retrieved K1Fgfp was localized to the liver. Higher doses resulted in slower elimination, possibly reflecting temporary saturation of liver scavenging capacity. Phage DNA was detected in both cell types, with a KC:LSEC ratio of 12:1 per population following cell isolation. Opsonization with plasma proteins increased time-dependent cellular uptake in both LSECs and KCs in vitro. Internalized phages were rapidly transported along the endocytic pathway to lysosomal compartments. Reduced viability of intracellular K1Fgfp corroborated inactivation following endocytosis. This study is the first to identify phage distribution in the liver at the hepatocellular level, confirming clearance of K1Fgfp performed mostly by KCs with a significant uptake also in LSECs.IMPORTANCEFaced with the increasing amounts of bacteria with multidrug antimicrobial resistance, phage therapy has regained attention as a possible treatment option. The phage field has recently experienced an emergence in commercial interest as research has identified new and more efficient ways of identifying and matching phages against resistant superbugs. Currently, phages are unapproved drugs in most parts of the world. For phages to reach broad clinical use, they must be shown to be clinically safe and useful. The results presented herein contribute to increased knowledge about the pharmacokinetics of the T7-like phage K1F in the mammalian system. The cell types of the liver that are responsible for rapid phage blood clearance are identified. Our results highlight the need for more research about appropriate dose regimens when phage therapy is delivered intravenously and advise essential knowledge about cell systems that should be investigated further for detailed phage pharmacodynamics.

Crosstalk between liver macrophages and gut microbiota: An important component of inflammation-associated liver diseases

Hepatic macrophages have been recognized as primary sensors and responders in liver inflammation. By processing host or exogenous biochemical signals, including microbial components and metabolites, through the gut-liver axis, hepatic macrophages can both trigger or regulate inflammatory responses. Crosstalk between hepatic macrophages and gut microbiota is an important component of liver inflammation and related liver diseases, such as acute liver injury (ALI), alcoholic liver disease (ALD), and nonalcoholic fatty liver disease (NAFLD). This review summarizes recent advances in knowledge related to the crosstalk between hepatic macrophages and gut microbiota, including the therapeutic potential of targeting hepatic macrophages as a component of gut microecology in inflammation-associated liver diseases.

Crosstalk between Tumor-Associated Macrophages and MicroRNAs: A Key Role in Tumor Microenvironment

As an in-depth understanding of immunotherapy continues to grow, current anticancer therapy research is increasingly focused on the tumor microenvironment (TME). MicroRNAs (miRNAs) play crucial roles in the regulation of genetic information and expression and mediate interactions between tumor cells and components in the TME, such as tumor-associated macrophages (macrophages). Macrophages are abundant in the TME, and their different polarization directions can promote or inhibit tumor growth and progression. By regulating biological behaviors, such as macrophage recruitment, infiltration, and polarization, miRNAs can affect various molecular pathways to regulate tumor progression and treatment response. In this review, we discuss in detail the effects of macrophages on tumors and the multifaceted effects of miRNAs on macrophages. We also discuss the potential clinical applications and prospects of targeted therapy based on miRNAs, novel clinical biomarkers, and drug delivery systems.

Structural and Morphological Changes in the Liver Due to Intestinal Endotoxins

BACKGROUND

Under normal physiological conditions, endotoxin (ET) released during self-renewal of the colibacillus pool is an obligate stimulus for the formation of the immune system and homeostasis of the body. Violation of the barrier function of the intestinal wall and the mechanisms of neutralization of endotoxin lead to systemic endotoxemia of intestinal origin. Its development is facilitated by stress, intoxication, a decrease in nonspecific resistance of the body, as well as damage to the intestinal mucosa and dysbiosis, where the mucous membrane is more vulnerable and permeable to endotoxin.

PURPOSE OF THE RESEARCH

The aim of this study is to compare and assess the severity and nature of hepatocyte damage from endotoxin exposure and the degree of manifestation of stress due to oxidation, to determine the characteristics of structural changes in hepatocytes and to assess the oxidation stress during endotoxin intoxication in the experiment with biochemical markers.

MATERIALS AND METHODS

The experiments were conducted on 40 non-linear rats, divided into two groups of 20 animals. Group 1 animals received intraperitoneal injections of ET of Escherichia coli drug (Sigma USA K-235) for seven days at a rate of 0.1 mg/kg of the body weight. Animals of the second group served as the control group. Character and stage of liver damage were studied using morphological methods, including electron and light microscopy. In studying oxidizing stress, biochemical methods were used to define the changes, such as conjugated dienes and dienketones, spontaneous oxidizing modification of proteins.

RESULTS AND CONCLUSION

1. The severity and depth of morphological changes in the liver during endotoxin intoxication were correlated with the dynamics of the content of lipid oxidation products (CD and DK, MDA) and proteins. There was a tendency for a more significant increase in the oxidative modification of proteins in serum. This confirms the data on the primary damage of proteins by free radicals. 2. When exposed to intestinal microflora endotoxin, pronounced dyscirculatory changes, fatty and hydropic degeneration of hepatocytes with signs of toxic damage to their nuclei were determined, but at the same time, the increased hyperplastic activity of sinusoidal cells remained associated with the effects of endotoxin. These changes are associated with both the direct toxic effect of endotoxin, and the effects of oxidative stress, in which endotoxin is a potent inducer.

Macrophage ablation significantly reduces uptake of imaging probe into organs of the reticuloendothelial system

BACKGROUND

Macrophages engulf particulate contrast media, which is pivotal for biomedical imaging.

PURPOSE

To introduce a macrophage ablation animal model by showing its power to manipulate the kinetics of imaging probes.

MATERIAL AND METHODS

The kinetics of a particulate computed tomography (CT) contrast media was compared in macrophage ablative mice and normal mice. Liposomes (size 220 µg), loaded with clodronate, were injected into the peritoneum of three C57BL/6 mice. On the third day, 200 µL of the particulate agent ExiTron nano 6000 were injected into three macrophage-ablative mice and three control mice. CT scans were acquired before and 3 min, 1 h, 6 h, and 24 h after the ExiTron application. The animals were sacrificed, and their spleens and livers removed. Relative CT values (CTV) were measured and analyzed.

RESULTS

Liver and spleen enhancement of treated mice and controls were increasing over time. The median peak values were different with 225 CTV for treated mice and 582 CTV for controls in the liver (P = 0.032) and 431 CTV for treated and 974 CTV in controls in the spleen (P = 0.016).

CONCLUSION

Macrophage ablation leads to a decrease of enhancement in organs containing high numbers of macrophages, but only marginal changes in macrophage-poor organs. Macrophage ablation can influence the phagocytic activity and thus opens new potentials to investigate and manipulate the uptake of imaging probes.

Performance, Correlation and Kinetic Profile of Circulating Serum Fungal Biomarkers of Invasive Aspergillosis in High-Risk Patients with Hematologic Malignancies

As conventional microbiological documentation of invasive aspergillosis (IA) is difficult to obtain, serum fungal biomarkers are important adjunctive diagnostic tools. Positivity rates and the kinetic profiles of galactomannan (GM), 1,3-β-D-glucan (BDG) and Aspergillus DNA (PCR) were studied in high-risk patients with hematologic malignancies. GM, BDG and PCR data from serial serum specimens (n = 240) from 93 adult hematology patients with probable (n = 8), possible (n = 25) and no (n = 60) IA were retrospectively analyzed. Positivity rates and sensitivity/specificity/positive/negative predictive values (NPV) of each fungal biomarker alone and in combination were estimated. The three markers were compared head-to-head and correlated with various biochemical, demographic and patient characteristics. The positivity rates for patients with probable/possible/no IA were 88%/8%/0% for GM (X² = 55, p < 0.001), 62%/46%/35% for BDG (X² = 2.5, p = 0.29), 62%/33%/27% for PCR (X² = 3.9, p = 0.15), 50%/4%/0% for GM + BDG and GM + PCR (X² = 31, p < 0.001), 50%/8%/22% for BDG + PCR (X² = 6.5, p = 0.038) and 38%/4%/0% for GM + BDG + PCR (X² = 21, p < 0.001). Higher agreement (76%) and negative correlation (r_s = −0.47, p = 0.0017) was found between GM index and PCR Ct values. The sensitivity and NPV was 45–55% and 90–92% when biomarkers assessed alone and increased to 75–90% and 93–97%, respectively when combined. Weak significant correlations were found between GM, PCR and BDG results with renal/liver function markers (r = 0.11–0.57) with most GM+ and PCR+ samples found in the first and second week of clinical assessment, respectively and BDG later on. Different positivity rates, time profiles and performances were found for the three biomarkers advocating the combination of GM with PCR for the early diagnosis of IA, whereas the high NPV of combined biomarkerscould help excluding IA.

Role of Liver-Mediated Tolerance in Nanoparticle-Based Tumor Therapy

In the last decades, the use of nanocarriers for immunotherapeutic purposes has gained a lot of attention, especially in the field of tumor therapy. However, most types of nanocarriers accumulate strongly in the liver after systemic application. Due to the default tolerance-promoting role of liver non-parenchymal cells (NPCs), Kupffer cells (KCs), liver sinusoidal endothelial cells (LSECs), and hepatic stellate cells (HSCs), their potential role on the immunological outcome of systemic nano-vaccination approaches for therapy of tumors in the liver and in other organs needs to be considered. Concerning immunological functions, KCs have been the focus until now, but recent studies have elucidated an important role of LSECs and HSCs as well. Therefore, this review aims to summarize current knowledge on the employment of nanocarriers for immunotherapeutic therapy of liver diseases and the overall role of liver NPCs in the context of nano-vaccination approaches. With regard to the latter, we discuss strategies on how to address liver NPCs, aiming to exploit and modulate their immunological properties, and alternatively how to avoid unwanted engagement of nano-vaccines by liver NPCs for tumor therapy.

Lipid nanoparticle technology for therapeutic gene regulation in the liver

Hereditary genetic disorders, cancer, and infectious diseases of the liver affect millions of people around the globe and are a major public health burden. Most contemporary treatments offer limited relief as they generally aim to alleviate disease symptoms. Targeting the root cause of diseases originating in the liver by regulating malfunctioning genes with nucleic acid-based drugs holds great promise as a therapeutic approach. However, employing nucleic acid therapeutics in vivo is challenging due to their unfavorable characteristics. Lipid nanoparticle (LNP) delivery technology is a revolutionary development that has enabled clinical translation of gene therapies. LNPs can deliver siRNA, mRNA, DNA, or gene-editing complexes, providing opportunities to treat hepatic diseases by silencing pathogenic genes, expressing therapeutic proteins, or correcting genetic defects. Here we discuss the state-of-the-art LNP technology for hepatic gene therapy including formulation design parameters, production methods, preclinical development and clinical translation.

The Potential of the FSP1cre-Pparb/d-/- Mouse Model for Studying Juvenile NAFLD

Non-alcoholic fatty liver disease (NAFLD) can progress from steatosis to non-alcoholic steatohepatitis (NASH) characterized by liver inflammation, possibly leading to cirrhosis and hepatocellular carcinoma (HCC). Mice with impaired macrophage activation, when fed a high-fat diet, develop severe NASH. Evidence is mounting that Kupffer cells are implicated. However, it is unknown whether the resident CD68⁺ or bone marrow-derived CD11b⁺ Kupffer cells are involved. Characterization of the FSP1cre-Pparb/d^-/- mouse liver revealed that FSP1 is expressed in CD11b⁺ Kupffer cells. Although these cells only constitute a minute fraction of the liver cell population, Pparb/d deletion in these cells led to remarkable hepatic phenotypic changes. We report that a higher lipid content was present in postnatal day 2 (P2) FSP1cre-Pparb/d^-/- livers, which diminished after weaning. Quantification of total lipids and triglycerides revealed that P2 and week 4 of age FSP1cre-Pparb/d^-/- livers have higher levels of both. qPCR analysis also showed upregulation of genes involved in fatty acid β-oxidation, and fatty acid and triglyceride synthesis pathways. This result is further supported by western blot analysis of proteins in these pathways. Hence, we propose that FSP1cre-Pparb/d^-/- mice, which accumulate lipids in their liver in early life, may represent a useful animal model to study juvenile NAFLD.

Phase Ib study of the combination of pexidartinib (PLX3397), a CSF-1R inhibitor, and paclitaxel in patients with advanced solid tumors

Purpose:

To evaluate the safety, recommended phase II dose (RP2D) and efficacy of pexidartinib, a colony stimulating factor receptor 1 (CSF-1R) inhibitor, in combination with weekly paclitaxel in patients with advanced solid tumors.

Patients and Methods:

In part 1 of this phase Ib study, 24 patients with advanced solid tumors received escalating doses of pexidartinib with weekly paclitaxel (80 mg/m²). Pexidartinib was administered at 600 mg/day in cohort 1. For subsequent cohorts, the dose was increased by ⩽50% using a standard 3+3 design. In part 2, 30 patients with metastatic solid tumors were enrolled to examine safety, tolerability and efficacy of the RP2D. Pharmacokinetics and biomarkers were also assessed.

Results:

A total of 51 patients reported ≥1 adverse event(s) (AEs) that were at least possibly related to either study drug. Grade 3–4 AEs, including anemia (26%), neutropenia (22%), lymphopenia (19%), fatigue (15%), and hypertension (11%), were recorded in 38 patients (70%). In part 1, no maximum tolerated dose was achieved and 1600 mg/day was determined to be the RP2D. Of 38 patients evaluable for efficacy, 1 (3%) had complete response, 5 (13%) partial response, 13 (34%) stable disease, and 17 (45%) progressive disease. No drug–drug interactions were found. Plasma CSF-1 levels increased 1.6- to 53-fold, and CD14dim/CD16+ monocyte levels decreased by 57–100%.

Conclusions:

The combination of pexidartinib and paclitaxel was generally well tolerated. RP2D for pexidartinib was 1600 mg/day. Pexidartinib blocked CSF-1R signaling, indicating potential for mitigating macrophage tumor infiltration.

Balance of pro- and anti-inflammatory cytokines in livers of high fat diet rats exposed to fractionated gamma irradiation

Objective

In this work, the effects of irradiation and high fat diet (HFD) intake have been examined in Wistar rat livers. HFD Wistar rats were exposed three times per week for 2 months to three different doses (0.5, 1, and 2 Gy) of a fractionated whole body gamma irradiation (FWBGI). Hepatic mRNA of these rats was evaluated for five cytokines, TNFα, IL1β, IL6, CRP and IL10. In addition, some critical protein levels were evaluated.

Results

Results demonstrated that FWBGI was able to omit the inflammatory state already induced by the HFD through the depression of all pro-inflammatory genes. In addition, TNFα/IL10 IL1β/IL10, IL6/IL10 and CRP/IL10 ratios were less than 1 at all studied irradiation doses. IL6/IL10 ratio (mRNA and protein) was the best that represented an anti-inflammatory state with all used doses. Results could be of great importance in liver radiotherapy in HFD animal models and may give indicators about the inflammatory state improvement during FWBGI.

HIF1α-Induced Glycolysis Metabolism Is Essential to the Activation of Inflammatory Macrophages

Hypoxia-inducible factor (HIF) 1α is a metabolic regulator that plays an important role in immunologic responses. Previous studies have demonstrated that HIF1α participates in the M1 polarization of macrophages. To clarify the mechanism of HIF1α-induced polarization of M1 macrophage, myeloid-specific HIF1α overexpression (Lysm HIF1α lsl) mice were employed and the bone marrow-derived and peritoneal macrophages were isolated. RT-PCR results revealed that HIF1α overexpression macrophage had a hyperinflammatory state characterized by the upregulation of M1 markers. Cellular bioenergetics analysis showed lower cellular oxygen consumption rates in the Lysm HIF1α lsl mice. Metabolomics studies showed that HIF1α overexpression led to increased glycolysis and pentose phosphate pathway intermediates. Further results revealed that macrophage M1 polarization, induced by HIF1α overexpression, was via upregulating the mRNA expression of the genes related to the glycolysis metabolism. Our results indicate that HIF1α promoted macrophage glycolysis metabolism, which induced M1 polarization in mice.

Distinct Hepatic Macrophage Populations in Lean and Obese Mice

Obesity is a complex metabolic disorder associated with the development of non-communicable diseases such as cirrhosis, non-alcoholic fatty liver disease, and type 2 diabetes. In humans and rodents, obesity promotes hepatic steatosis and inflammation, which leads to increased production of pro-inflammatory cytokines and acute-phase proteins. Liver macrophages (resident as well as recruited) play a significant role in hepatic inflammation and insulin resistance (IR). Interestingly, depletion of hepatic macrophages protects against the development of high-fat-induced steatosis, inflammation, and IR. Kupffer cells (KCs), liver-resident macrophages, are the first-line defense against invading pathogens, clear toxic or immunogenic molecules, and help to maintain the liver in a tolerogenic immune environment. During high fat diet feeding and steatosis, there is an increased number of recruited hepatic macrophages (RHMs) in the liver and activation of KCs to a more inflammatory or M1 state. In this review, we will focus on the role of liver macrophages (KCs and RHMs) during obesity.

Macrophages: development and tissue specialization

Macrophages are myeloid immune cells that are strategically positioned throughout the body tissues, where they ingest and degrade dead cells, debris, and foreign material and orchestrate inflammatory processes. Here we review two major recent paradigm shifts in our understanding of tissue macrophage biology. The first is the realization that most tissue-resident macrophages are established prenatally and maintained through adulthood by longevity and self-renewal. Their generation and maintenance are thus independent from ongoing hematopoiesis, although the cells can be complemented by adult monocyte-derived macrophages. Second, aside from being immune sentinels, tissue macrophages form integral components of their host tissue. This entails their specialization in response to local environmental cues to contribute to the development and specific function of their tissue of residence. Factors that govern tissue macrophage specialization are emerging. Moreover, tissue specialization is reflected in discrete gene expression profiles of macrophages, as well as epigenetic signatures reporting actual and potential enhancer usage.

Variable uptake feature of focal nodular hyperplasia in Tc-99m phytate hepatic scintigraphy/single-photon emission computed tomography-A parametric analysis

Tc-99m phytate hepatic scintigraphy remains the standard method for evaluating the functional features of Kupffer cells. In this study, we demonstrate the variable uptake feature of focal nodular hyperplasia (FNH) in Tc-99m phytate scintigraphy. We reviewed all patients who underwent Tc-99m phytate hepatic scintigraphy between 2008 and 2012 in Kaohsiung Medical University Hospital, Kaohsiung, Taiwan. Cases with FNH were diagnosed on the basis of pathology or at least one or more prior imaging with a periodic clinical follow-up. All patients received a standard protocol of dynamic flow study and planar and Tc-99m phytate single-photon emission computed tomography (E. CAM; Siemens). The correlation of variable nodular radioactivity with parameters such as tumor size and localization was analyzed. In total, 15 lesions of 14 patients in the clinic were diagnosed as FNH. The tumor size was approximately 2.9-7.4 cm (mean size 4.6 cm). Four lesions were larger than 5 cm. The major anatomic distribution was in the right hepatic lobe (10 lesions), particularly in the superior segments (7 lesions). Tc-99m phytate single-photon emission computed tomography imaging for determining the functional features of Kupffer cells included cool/cold (8 lesions), isoradioactive/warm (6 lesions), and hot (1 lesion) patterns of uptake. We did not observe any statistically significant correlation between variable nodular radioactivity and tumor size (p=0.68) or localization (p=0.04). Herein, we demonstrate the variable uptake feature of FNH in Tc-99m phytate scintigraphy. In small FNH tumors (< 5 cm), increased or equal uptake still provided specificity for the differential diagnosis of hepatic solid tumors.

Soluble CLEC2 Extracellular Domain Improves Glucose and Lipid Homeostasis by Regulating Liver Kupffer Cell Polarization

The polarization of tissue resident macrophages toward the alternatively activated, anti-inflammatory M2 phenotype is believed to positively impact obesity and insulin resistance. Here we show that the soluble form of the extracellular domain (ECD) of C-type lectin-like receptor 2, CLEC2, regulates Kupffer cell polarization in the liver and improves glucose and lipid parameters in diabetic animal models. Over-expression of Fc-CLEC2(ECD) in mice via in vivo gene delivery, or injection of recombinant Fc-CLEC2(ECD) protein, results in a reduction of blood glucose and liver triglyceride levels and improves glucose tolerance. Furthermore, Fc-CLEC2(ECD) treatment improves cytokine profiles and increases both the M2 macrophage population and the genes involved in the oxidation of lipid metabolism in the liver. These data reveal a previously unidentified role for CLEC2 as a regulator of macrophage polarity, and establish CLEC2 as a promising therapeutic target for treatment of diabetes and liver disease.

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CLEC2, a type II C-type lectin-like receptor, is expressed on a variety of cell types including Kupffer cells.

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Overexpression of CLEC2 ECD in mice improves glucose and lipid parameters and induces markers of alternatively activated Kupffer cells.

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CLEC2 is a promising therapeutic target for the treatment of diabetes and liver diseases.

Distinct development and functions of resident and recruited liver Kupffer cells/macrophages

Although mouse liver F4/80(+) Kupffer cells consist of cytokine-producing CD11b(+) cells and phagocytic CD68(+) cells, an undefined CD11b(-) CD68(-) subset (30%) also exists. We herein demonstrate a more fundamental classification by adding CD32 (FcγRII), which covers most liver F4/80(+) cells and the distinct functions of them. Among the F4/80(+) cells, 50%, 40%, and 30% of cells were CD32(+), CD68(+), and CD11b(+), respectively, and one-half of the CD68(+) cells coexpressed CD32. CD68(+) and CD32(+) cells, but not CD11b(+) cells, expressed a phagocytosis-related CRIg. Gy (6) irradiation depleted liver CD11b(+) cells and those in the spleen, bone marrow, and peripheral blood but not liver CD32/CD68(+) cells. Transfer of bone marrow cells into the irradiated mice reconstituted liver CD11b(+) cells. Conversely, clodronate pretreatment depleted only liver CD32/CD68(+) cells but not liver CD11b(+) cells and peripheral blood or spleen CD11b(+) monocytes/macrophages. Moreover, the CD32(+) cells might be precursors of CD68(+) cells, as a large proportion of CD32(+) cells expressed the c-kit (CD117), and CD34 and CD32(+) cells acquired CD68 immediately after bacteria administration. CD32/CD68(+) cells, but not CD11b(+) cells, expressed resident macrophage-specific MerTK and CD64 (FcγRI). Challenge with Staphylococcus aureus or liver metastatic EL-4 tumor cells indicated that the CD68(+) subset is engaged in systemic bactericidal activity, whereas the CD11b(+) subset is pivotal for liver antitumor immunity. Human liver CD14(+) Kupffer cells could also be classified into three similar subsets. These results suggest that liver CD68(+) Kupffer cells and CD11b(+) Kupffer cells/macrophages are developmentally and functionally distinct subsets.

Endothelial cell phagocytosis of senescent neutrophils decreases procoagulant activity

Abundant senescent neutrophils traverse the vascular compartment and may contribute to pathologic conditions. For example, they become procoagulant when undergoing apoptosis and may contribute to thrombosis or inflammation. Our previous studies demonstrated a dominant clearance pathway in which the neutrophils can be phagocytosed by liver macrophages. The aim of this study was to explore an alternate pathway of neutrophil clearance by endothelial cells. Phagocytosis of the neutrophils by endothelial cells was performed using various experimental approaches includingflow cytometry, confocal microscopy and electron microscopy assays in vitro and in vivo. Procoagulant activity of cultured neutrophils was evaluated by coagulation time, factor Xase and prothrombinase assays. Lactadherin functioned as a novel probe for the detection of phosphatidylserine on apoptotic cells, an opsonin (bridge) between apoptotic cell and phagocyte for promoting phagocytosis, and an efficient anticoagulant for inhibition of factor Xase and thrombin formation. When cultured, purified human neutrophils spontaneously entered apoptosis and developed procoagulant activity that was directly related to the degree of phosphatidylserine exposure. Co-culture of aged neutrophils and endothelial cells resulted in phagocytosis of the neutrophils and prolonged coagulation time. Lactadherin diminished the procoagulant activity and increased the rate of neutrophil clearance. In vivo, neutrophils were sequestered by endothelial cells after blockade of Kupffer cells, a process that was dependent upon both phosphatidylserine exposure and P-selectin expression. Thus, the ability of endothelial cells to clear senescent neutrophils may limit the procoagulant and/or inflammatory impact of these cells.

Integrin αXβ₂ is a leukocyte receptor for Candida albicans and is essential for protection against fungal infections

The opportunistic fungus Candida albicans is one of the leading causes of infections in immunocompromised patients, and innate immunity provides a principal mechanism for protection from the pathogen. In the present work, the role of integrin α(X)β₂ in the pathogenesis of fungal infection was assessed. Both purified α(X)β₂ and α(X)β₂-expressing human epithelial kidney 293 cells recognized and bound to the fungal hyphae of SC5314 strain of C. albicans but not to the yeast form or to hyphae of a strain deficient in the fungal mannoprotein, Pra1. The binding of the integrin to the fungus was inhibited by β-glucans but not by mannans, implicating a lectin-like activity in recognition but distinct in specificity from that of α(M)β₂. Mice deficient in α(X)β₂ were more prone to systemic infection with the LD₅₀ fungal inoculum decreasing 3-fold in α(X)β₂-deficient mice compared with wild-type mice. After challenging i.v. with 1.5 × 10⁴ cell/g, 60% of control C57BL/6 mice died within 14 d compared with 100% mortality of α(X)β₂-deficient mice within 9 d. Organs taken from α(X)β₂-deficient mice 16 h postinfection revealed a 10-fold increase in fungal invasion into the brain and a 2-fold increase into the liver. These data indicate that α(X)β₂ is important for protection against systemic C. albicans infections and macrophage subsets in the liver, Kupffer cells, and in the brain, microglial cells use α(X)β₂ to control fungal invasion.

The evolving story of macrophages in acute liver failure

Acute liver failure (ALF) remains a worldwide problem. The innate immune system acts as an important regulator of ALF. Kupffer cells (KCs), the resident macrophages in liver, play a key role in liver innate immune response. Recent researches have shown that macrophages display a remarkable plasticity and can differentiate into functionally diverse subsets. However, the dynamic polarized phenotypes and functional status of macrophages at different stage of ALF are not clear. In this paper, we present a review of evidence that KCs play a significant role in the pathogenesis of ALF, including the phenotype and functions of macrophages, signaling pathways involved in macrophage functional status and cell-crosstalks of KCs with other immune cells. More information on macrophages will promote a better understanding of the cellular molecular mechanisms of ALF and provide new insights for the development of therapeutic targets for ALF.

Increased serum enzyme levels associated with kupffer cell reduction with no signs of hepatic or skeletal muscle injury

Macrophage colony-stimulating factor (M-CSF) is a hematopoietic growth factor that is responsible for the survival and proliferation of monocytes and the differentiation of monocytes into macrophages, including Kupffer cells (KCs) in the liver. KCs play an important role in the clearance of several serum enzymes, including aspartate aminotransferase and creatine kinase, that are typically elevated as a result of liver or skeletal muscle injury. We used three distinct animal models to investigate the hypothesis that increases in the levels of serum enzymes can be the result of decreases in KCs in the apparent absence of hepatic or skeletal muscle injury. Specifically, neutralizing M-CSF activity via a novel human monoclonal antibody reduced the CD14(+)CD16(+) monocyte population, depleted KCs, and increased aspartate aminotransferase and creatine kinase serum enzyme levels in cynomolgus macaques. In addition, the treatment of rats with clodronate liposomes depleted KCs and led to increased serum enzyme levels, again without evidence of tissue injury. Finally, in the osteopetrotic (Csf1(op)/Csf1(op)) mice lacking functional M-CSF and having reduced levels of KCs, the levels of serum enzymes are higher than in wild-type littermates. Together, these findings support a mechanism for increases in serum enzyme levels through M-CSF regulation of tissue macrophage homeostasis without concomitant histopathological changes in either the hepatic or skeletal system.

The role of intestinal endotoxin in liver injury: a long and evolving history

From the mid-1950s, it was observed that liver injury by a variety of toxins greatly sensitized the host to the effects of administered lipopolysaccharide. In the nutritional cirrhosis of choline deficiency, and in acute toxic injury as well, the need for the presence of enteric endotoxin was demonstrated. The universality of this association was striking for almost all agents associated with liver injury. In addition, the presence of endotoxemia in human liver disease was documented in the 1970s, when the hypothesis was first proposed, and correlated with the severity of the disease. Despite imposing evidence of the critical role of enteric endotoxin in liver injury, it did not excite much interest in investigators until the 1980s. With the ability to study effects of alcohol in newer delivery systems, and an increased understanding of the role of Kupffer cells in the process, the original hypothesis has been accepted. This historical review details the progress of this novel concept of disease initiation and suggests future directions to bring potential therapies to the bedside.

Evaluation of hepatotropic targeting properties of allogenic and xenogenic erythrocyte ghosts in normal and liver-injured rats

BACKGROUND/AIMS

Haemoglobin-depleted erythrocyte ghosts have been recommended as vesicle carriers of drugs with hepatotropic properties. However, the influence of liver injury on ghost elimination and targeting has not been reported so far.

METHODS

Human and rat ghosts were prepared and loaded with model substances, and the basic parameters were characterized. Ghosts were injected intravenously into rats with acute, subacute and chronic liver injuries. Elimination from circulation, organ distribution and cellular targeting was measured. The uptake of ghosts by liver macrophages/Kupffer cells was determined in cell culture.

RESULTS

Ghosts are strong hepatotropic carriers with a recovery of 90% in normal liver. Kupffer cells are the almost exclusive target cell type. Hepatotropic properties remain in rats with chronic liver diseases, but are reduced by 60-70% in acute liver damage as a result of decline of phagocytosis of macrophages/Kupffer cells. Although the uptake of ghosts per gram liver tissue in chronic liver injury was also reduced by about 40%, the increase of liver mass and of macrophages/Kupffer cells compensated for the reduced phagocytotic activity. In subacute injury, the uptake per gram liver tissue was only moderately reduced.

CONCLUSION

Drug targeting with ghosts might be feasible in chronic and subacute liver injuries, e.g. fibrogenesis and tumours, because the content of ingested ghosts is released by Kupffer cells into the micro-environment, providing the uptake by and pharmacological effects on adjacent cells.

Inhibition of lipopolysaccharide activation of Kupffer cells by transition metals

BACKGROUND

Bacterial endotoxins are the principal agents causing sepsis and septic shock. Cytokine cascades produced by cellular interactions to endotoxins can cause cardiovascular failure followed by multi-organ failure and death. Endotoxin intravenously administered to mice can have fatal consequences. Previous studies have shown that the transition metals Mn2+ and Cr3+ can be protective.

METHODS

The effects of Mn2+, Cr3+, Zn2+, and Cu2+ on lipopolysaccharide (LPS) binding to rat Kupffer cell extracts were analyzed using dot-blots, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and Western transfer. Kupffer cells were isolated from rat livers by collagenase perfusion, differential centrifugation, and adhesion to plastic.

RESULTS

Five millimolar of Mn2+, Zn2+, Cr3+, and Cu2+ completely inhibited LPS binding. Isolated Kupffer cells were also exposed to Mn2+ and to LPS and tumor necrosis factor-alpha release measured. The presence of Mn2+ significantly (P < 0.05) reduced tumor necrosis factor-alpha production by Kupffer cells in response to LPS. Experiments to determine if these effects were mediated by binding to LPS-binding proteins showed this was not the case. More likely a complex occurs between the metal and LPS. We also showed significantly enhanced uptake of LPS into Kupffer cells in the presence of Mn2+.

CONCLUSIONS

The data are consistent with the metals binding to LPS via its two phosphate groups and neutralizing their charge. These data also support the hypothesis that there is enhanced cellular uptake by non-receptor-mediated methods such as absorptive pinocytocis. At the same time receptor binding and activation of the cells is inhibited. This can explain the effects of transition metals on LPS toxicity.

Evaluation of medicinal plant hepatotoxicity in co-cultures of hepatocytes and monocytes

Non-parenchymal cells might play an important role in the modulation of xenobiotic metabolism in liver and its pharmacological and toxicological consequences. Therefore, the role of cell-to-cell interactions in herbal induced liver toxicity was investigated in monocultures of cells from the human hepatocyte cell line (HepG2) and in co-cultures of cells from the HepG2 cell line and cells from the human monocyte cell line (THP1). Cells were treated with various concentrations (1-500 microg ml(-1)) of extracts of Pistacia palaestina, Juglans regia and Quercus ithaburensis for 24 h. Extracts from Cleome droserifolia, a known toxic plant, were taken as positive control. In the co-culture system, toxic effects were observed after exposure to extracts of Pistacia palestina and C. droserifolia. These two extracts significantly reduced by cell viability as measured the MTT test and the LDH assay. Whereas in hepatocyte cultures, only extracts of C. droserifolia were found to affect the cell viability. The production levels of albumin from hepatocytes were not affected by treatment with plant extracts in both culture systems. It seems that the observed reduction in cell viability after exposure to extracts of P. palestina in co-cultures but not in monocultures is a result of monocyte-derived factors. The use of liver cell co-cultures is therefore a useful approach to investigate the influence of intercellular communication on xenobiotic metabolism in liver.

Normal liver regeneration and liver cell apoptosis after partial hepatectomy in tumor necrosis factor-alpha-deficient mice

AIMS/BACKGROUND

Tumor necrosis factor-alpha (TNF-alpha) is known as a proinflammatory cytokine that has been implicated as a contributing factor in a number of disease processes. TNF-alpha also influences liver repair following hepatotoxic damage, and regeneration following partial hepatectomy (PH). The aim of this study was to assess the mechanism by which TNF-alpha influences liver cell apoptosis and regeneration following PH in TNF-alpha-deficient (TNF-alpha(-/-)) mice.

METHODS

PH was performed in wild mice and TNF-alpha(-/-) mice.

RESULTS

In both groups, serum alanine aminotransferase and serum total bilirubin levels comparably peaked at 6 and 48 h after PH, respectively. No differences were observed in hepatocyte proliferation, as determined by mitotic and the proliferating cell nuclear antigen labeling indices, between TNF-alpha(+/+) and TNF-alpha(-/-) mice. Few terminal deoxynucleotidyl transferase nick end-labeling-positive hepatocytes were seen in either type of mice. Nuclear factor-kappa B DNA binding activity in the remaining liver of TNF-alpha(-/-) mice after PH was similar to that of control mice. Ribonuclease protection assay showed that transforming growth factor beta1 mRNA was up-regulated comparably in the livers of the two groups, and that other cytokines were hardly seen in either. Interleukin-6/ signal transducer and activator of transcription-3-dependent pathway was not affected in TNF-alpha(-/-) mice.

CONCLUSIONS

These findings suggest that TNF-alpha has little influence on liver regeneration and liver cell apoptosis after PH in mice.

Regulation of cytokine production in carcinoembryonic antigen stimulated Kupffer cells by beta-2 adrenergic receptors: implications for hepatic metastasis

Elevated Carcinoembryonic antigen (CEA) levels in the serum indicate a poor prognosis for colorectal cancer patients. Induction of proinflammatory cytokines by CEA interaction with Kupffer cells has been proposed as a mechanism for hepatic metastasis formation. Studies show that the cytokine response in circulating and peritoneal macrophages is regulated by beta-adrenergic receptor signals, though little information is available regarding Kupffer cells. We investigated the relationship between beta-adrenergic receptor stimulation and the response of Kupffer cells to CEA. Comparisons between unstimulated and CEA stimulated rat Kupffer cells, using cDNA arrays, showed up-regulation (>4 fold) of the beta2-adrenergic receptor mRNA. Peak up-regulation occurred after 30 min with a decline at 1 h. We examined the effects of the specific beta2-adrenergic receptor agonist terbutaline on cytokine production by CEA stimulated rat Kupffer cells. Pre-treatment of Kupffer cells with terbutaline followed by CEA caused a significant increase in IL-6 and IL-10 production, but a significant reduction in TNF-alpha production (>3 fold). mRNA levels reflected those of the ELISA assays for IL-6 and IL-10 but not for TNF-alpha. For IL-6 and TNF-alpha, these changes were serum independent, while IL-10 was serum dependent. This response is different from LPS treated Kupffer cells where all three cytokines showed serum dependency. Overall, these data suggest that Kupffer cell stimulation by CEA is under beta-adrenergic receptor control and induction of the beta-receptor is an early event following CEA binding to its receptor. Control of TNF-alpha production is negatively affected by terbutaline, while that of IL-6 and IL-10 is positively controlled suggesting that very different beta-adrenergic receptor signaling pathways are involved.

The preferential homing of a platelet derived growth factor receptor-recognizing macromolecule to fibroblast-like cells in fibrotic tissue

Platelet derived growth factor (PDGF) is a key factor in the induction and progression of fibrotic diseases with the activated fibroblast as its target cell. Drug targeting to the PDGF-receptor is explored as a new approach to treat this disease. Therefore, we constructed a macromolecule with affinity for the PDGF-beta receptor by modification of albumin with a small peptide that recognises this PDGF-beta receptor. The binding of the peptide-modified albumin (pPB-HSA) to the PDGF-beta receptor was confirmed in competition studies with PDGF-BB using NIH/3T3-fibroblasts and activated hepatic stellate cells. Furthermore, pPB-HSA was able to reduce PDGF-BB-induced fibroblast proliferation in vitro, and proved to be devoid of proliferation-inducing activity itself. We assessed the distribution of pPB-HSA in vivo in two models of fibrosis and related the distribution of pPB-HSA to PDGF-beta receptor density. In rats with liver fibrosis (bile duct ligation model), pPB-HSA quickly accumulated in the liver in contrast to unmodified HSA (P<0.001). The major part of pPB-HSA in the fibrotic liver was localized in hepatic stellate cells. In rats with renal fibrosis (anti-Thy1.1 model), pPB-HSA also homed to the cells that expressed the PDGF-beta receptor, i.e. the mesangial cells in the glomeruli of the kidney. These results indicate that pPB-HSA may be applied as a macromolecular drug-carrier that accumulates specifically in cells expressing the PDGF-beta receptor, thus allowing a selective delivery of anti-fibrotic agents to these cells.

Pathomorphological study on location and distribution of Kupffer cells in hepatocellular carcinoma

AIM: To clarify the location and distribution of Kupffer cells in hepatocellular carcinoma (HCC), and to investigate their role in hepatocarcinogenesis.

METHODS: Kupffer cells were immunohistochemically stained by streptavadin-peroxidase conjugated method (S-P). The numbers of Kupffer cells in cancerous, para-cancerous and adjacent normal liver tissues of 48 HCCs were comparatively examined.

RESULTS: The mean number of Kupffer cells in cancerous, para-cancerous and adjacent normal liver tissues was 12.7 ± 6.8, 18.1 ± 8.2 and 18.9 ± 7.9 respectively. The number of Kuppfer cells in cancerous tissues was significantly lower than that in para-cancerous tissues (t = 2.423, P < 0.05) and adjacent normal liver tissues (t = 2.521, P < 0.05). As tumor size increased, the number of Kupffer cells in cancerous tissues significantly decreased (F = 4.61, P < 0.05). Moreover, there was also a significant difference in the number of Kupffer cells among well-differentiated, moderately-differentiated and poorly-differentiated cases(F = 4.49, P < 0.05).

CONCLUSION: This study suggests that decrease of Kupffer cells in HCCs may play an important role in the carcinogenesis of HCC, the number of Kupffer cells in HCC is closely related to the size and differentiation grade of the tumor.

Receptors, mediators, and mechanisms involved in bacterial sepsis and septic shock

Bacterial sepsis and septic shock result from the overproduction of inflammatory mediators as a consequence of the interaction of the immune system with bacteria and bacterial wall constituents in the body. Bacterial cell wall constituents such as lipopolysaccharide, peptidoglycans, and lipoteichoic acid are particularly responsible for the deleterious effects of bacteria. These constituents interact in the body with a large number of proteins and receptors, and this interaction determines the eventual inflammatory effect of the compounds. Within the circulation bacterial constituents interact with proteins such as plasma lipoproteins and lipopolysaccharide binding protein. The interaction of the bacterial constituents with receptors on the surface of mononuclear cells is mainly responsible for the induction of proinflammatory mediators by the bacterial constituents. The role of individual receptors such as the toll-like receptors and CD14 in the induction of proinflammatory cytokines and adhesion molecules is discussed in detail. In addition, the roles of a number of other receptors that bind bacterial compounds such as scavenger receptors and their modulating role in inflammation are described. Finally, the therapies for the treatment of bacterial sepsis and septic shock are discussed in relation to the action of the aforementioned receptors and proteins.

Phagocytosis of apoptotic cells by liver: a morphological study

The present review deals with the morphological features of the removal of apoptotic cells by liver. The engulfment of cells undergoing apoptosis can be considered a specialized form of phagocytosis, playing a major role in the general tissue homeostasis in physiological and pathological conditions. In fact, defects of phagocytosis of apoptotic cells might have deleterious consequences for neighboring healthy cells, i.e., pathogenesis of inflammatory disease or dysregulation of the immune system. Phagocytosis of apoptotic cells by liver is a complex phenomenon, involving multiple molecular mechanisms of recognition (i.e., lectin-like receptors and receptors for externalized phosphatydilserine) of both parenchymal (hepatocytes) and nonparenchymal (Kupffer and endothelial cells) liver cells, often operating in cooperation. The data discussed in the present review are drawn from studies of phagocytosis of apoptotic cells in the liver, carried out with in vivo and in situ adhesion experiments as well as in vitro assays. Our results indicate that the three main liver cell types (hepatocytes, Kupffer, and endothelial cells) are able to recognize and internalize apoptotic cells by means of specific receptors (galactose and mannose-specific receptor; receptor for phosphatydilserine) and by cytoskeletal reorganization that favors the engulfment of the apoptotic cells. The "flags" for the identification of apoptotic cells by the liver are modifications of the surface of dead cells, i.e., sugar residues and phosphatydilserine exposition. Vitronectin receptor is not involved in such a recognition. The adhesions between modified cell surfaces of apoptotic cells and phagocytes generate cytoplasmatic signaling pathways that drive apoptotic cells to their final fate within the phagocytes (i.e., lysosomal digestion).

Apoptosis in diseases of the liver

Apoptosis, or programmed cell death, and the elimination of apoptotic cells are crucial factors in the maintenance of liver health Apoptosis allows hepatocytes to die without provoking a potentially harmful inflammatory response In contrast to necrosis, apoptosis is tightly controlled and regulated via several mechanisms, including Fas/Fas ligand interactions, the effects of cytokines such as tumor necrosis factor alpha (TNF-alpha) and transforming growth factor beta (TGF-beta), and the influence of pro- and antiapoptotic mitochondria-associated proteins of the B-cell lymphoma-2 (Bcl-2) family. Efficient elimination of apoptotic cells in the liver relies on Kupffer cells and endothelial cells and is thought to be regulated by the expression of certain cell surface receptors. Liver disease is often associated with enhanced hepatocyte apoptosis, which is the case in viral and autoimmune hepatitis, cholestatic diseases, and metabolic disorders. Disruption of apoptosis is responsible for other diseases, for example, hepatocellular carcinoma. Use and abuse of certain drugs, especially alcohol, chemotherapeutic agents, and acetaminophen, have been associated with increased apoptosis and liver damage. Apoptosis also plays a role in transplantation-associated liver damage, both in ischemia/reperfusion injury and graft rejection. The role of apoptosis in various liver diseases and the mechanisms by which apoptosis occurs in the liver may provide insight into these diseases and suggest possible treatments.

Role of the liver in regulating numbers of circulating neutrophils

Neutrophils (polymorphonuclear leukocytes [PMNs]) carry potent destructive enzymes that can destroy invasive bacteria or damage normal tissue. PMNs have a half-life of only 6 hours in the blood, but the details of this homeostasis are unknown. In a rat model of endotoxemia, P-selectin was selectively up-regulated in hepatic sinusoids and veins where it was necessary for phagocytosis of PMNs by Kupffer cells in the liver, as opposed to the spleen or the lungs. Apoptotic PMNs appeared in the lungs and spleen only after inactivation of Kupffer cells by gadolinium chloride (GdCl(3)). Blocking of Fas protein reduced the number of apoptotic cells in the liver; binding of annexin V to phosphatidylserine (PS) reduced the number of PMNs phagocytosed by Kupffer cells. The results support a clearance pathway in which apoptosis and phagocytosis are effected by Kupffer cells after P-selectin-mediated sequestration. (Blood. 2001;98:1226-1230)

Cytokines in the liver

Cytokines comprise a group of small proteins released from cells in order to influence the function of other cells. By binding to highly specific cell-surface receptors, they trigger a vast array of intracellular signalling cascades. Cytokines have been described as interleukins, growth factors, interferons and chemokines. Unlike hormones, which act in a similar way, cytokines are produced by many different types of cell and act on many other types. Most of them are produced only after certain stimuli. The most intense field of cytokine activity is without doubt host defence. The liver resembles a central organ of cytokine activity due to the fact that it hosts hepatocytes, which are highly susceptible to the activity of cytokines in a variety of physiological and pathophysiological processes. Moreover, the non-parenchymal cells of the liver, in particular Kupffer cells (KCs), the resident tissue macrophages of the liver, are able to synthesize a variety of cytokines that may act systemically on any other organ of the body, or in a paracrine manner on hepatocytes and other non-parenchymal liver cells. A classic example of how cytokines act can be observed during the acute phase reaction discussed in this article. The role of cytokines in liver development, acute liver injury, liver regeneration, liver fibrosis and liver metastasis is also discussed.

The lymphoid liver: considerations on pathways to autoimmune injury

Immunologic injury in the liver involves immigrant T and B lymphocytes and a resident lymphoid population that comprises distinct lymphocytic cells and accessory cells. The forerunner to autoimmunity is breaching of natural self-tolerance and hence the disruption of a fundamental property of the immune system. Such breaching occurs by processes that include inflammatory activation of immunocytes and macrophages, spillage of intracellular constituents, and epitope mimicry by constituents of microorganisms, with these acting on a genetically conditional phenotype; compounding factors include aberrations of apoptosis, whether insufficient or excess. The downstream end requires specifically directed inflammatory leukocyte traffic as an essential component of autoimmune expressions in the liver. The culmination is an orchestrated attack on hepatocytes or biliary epithelial cells by multiple effector pathways. Progress in type 1 autoimmune hepatitis still requires knowledge of a disease-specific autoantigen(s) involved in T-cell reactivity, although such knowledge in type 2 autoimmune hepatitis, in which the known autoantigen is cytochrome P4502D6, has not yet been integrated into a clearly defined scheme of pathogenesis. For PBC there has been a very promising amalgamation of molecular knowledge of the mitochondrial autoantigens. Future insights require deeper analysis of molecular, genetic, macroenvironmental, and microenvironmental elements in predisposition.

Plasma nitrite/nitrate concentrations as a tumor marker for hepatocellular carcinoma

Since plasma concentrations of nitrite/nitrate, the stable end-products of nitric oxide, increase in patients with hepatocellular carcinoma (HCC) correlatively to tumor volume, we examined the ability of plasma nitrite/nitrate to discriminate between those patients with HCC and those without and compared the diagnostic performance of the parameter with that of serum alpha-fetoprotein (AFP) concentrations. Plasma nitrite/nitrate and serum AFP concentrations were measured using a Griess reaction and a solid phase enzyme immunoassay, respectively. Eighty-nine patients with chronic liver diseases (CLD) with (n=39) or without HCC (n=50) and 50 healthy control subjects participated in the study. A receiver operating characteristic (ROC) curve was used to determine the optimal cut-off value and accuracy. The areas under ROC curves for nitrite/nitrate and AFP were calculated to be 0.758 and 0.812, respectively, which were not significantly different. There was no correlation between the concentrations of plasma nitrite/nitrate and serum AFP. The sensitivity, the specificity, and diagnostic efficiency were 79.5, 72.0, and 75.3%, respectively, for nitrite/nitrate, and 74.4, 76.0, and 75.3%, respectively, for AFP. Based on a partial ROC curve, the clinical utility of plasma nitrite/nitrate as a tumor marker approximated that of serum AFP, but exceeded in AFP-negative patients. Indeed, nitrite/nitrate was positive in 70% of AFP-negative HCC patients. The simultaneous determinations of serum AFP and plasma nitrite/nitrate concentrations gave significant improvement in detection of HCC in CLD patients compared with that of serum AFP alone.

Successful targeting to rat hepatic stellate cells using albumin modified with cyclic peptides that recognize the collagen type VI receptor

The key pathogenic event in liver fibrosis is the activation of hepatic stellate cells (HSC). Consequently, new antifibrotic therapies are directed toward an inhibition of HSC activities. The aim of the present study was to develop a drug carrier to HSC, which would allow cell-specific delivery of antifibrotic drugs thus enhancing their effectiveness in vivo. We modified human serum albumin (HSA) with 10 cyclic peptide moieties recognizing collagen type VI receptors (C*GRGDSPC*, in which C* denotes the cyclizing cysteine residues) yielding pCVI-HSA. In vivo experiments showed preferential distribution of pCVI-HSA to both fibrotic and normal rat livers (respectively, 62 +/- 6 and 75 +/- 16% of the dose at 10 min after intravenous injection). Immunohistochemical analysis demonstrated that pCVI-HSA predominantly bound to HSC in fibrotic livers (73 +/- 14%). In contrast, endothelial cells contributed mostly to the total liver accumulation in normal rats. In vitro studies showed that pCVI-HSA specifically bound to rat HSC, in particular to the activated cells, and showed internalization of pCVI-HSA by these cells. In conclusion, pCVI-HSA may be applied as a carrier to deliver antifibrotic agents to HSC, which may strongly enhance the effectiveness and tissue selectivity of these drugs. This approach has the additional benefit that such carriers may block receptors that play a putative role in the pathogenesis of liver fibrosis.

Hepatic fibronectin matrix turnover in rats: involvement of the asialoglycoprotein receptor

Fibronectin (Fn) is a major adhesive protein found in the hepatic extracellular matrix (ECM). In adult rats, the in vivo turnover of plasma Fn (pFn) incorporated into the liver ECM is relatively rapid, i.e., <24 h, but the regulation of its turnover has not been defined. We previously reported that cellular Fn (cFn) and enzymatically desialylated plasma Fn (aFn), both of which have a high density of exposed terminal galactose residues, rapidly interact with hepatic asialoglycoprotein receptors (ASGP-R) in association with their plasma clearance after intravenous infusion. With the use of adult male rats (250-350 g) and measurement of the deoxycholate (DOC)-insoluble (125)I-labeled Fn in the liver, we determined whether the ASGP-R system can also influence the hepatic matrix retention of various forms of Fn. There was a rapid deposition of (125)I-pFn, (125)I-aFn, and (125)I-cFn into the liver ECM after their intravenous injection. Although (125)I-pFn was slowly lost from the liver matrix over 24 h, more than 90% of the incorporated (125)I-aFn and (125)I-cFn was cleared within 4 h (P < 0.01). Intravenous infusion of excess nonlabeled asialofetuin to competitively inhibit the hepatic ASGP-R delayed the rapid turnover of both aFn and cFn already incorporated within the ECM of the liver. ECM retention of both (125)I-aFn and (125)I-cFn was also less than (125)I-pFn (P < 0.01) as determined in vitro using liver slices preloaded in vivo with either tracer form of Fn. The hepatic ASGP-R appears to participate in the turnover of aFn and cFn within the liver ECM, whereas a non-ASGP-R-associated endocytic pathway apparently influences the removal of normal pFn incorporated within the hepatic ECM, unless it becomes locally desialylated.

Involvement of circulating CEA in liver metastases from colorectal cancers re-examined in a new experimental model

Both experimental and clinical data show evidence of a correlation between elevated blood levels of carcinoembryonic antigen (CEA) and the development of liver metastases from colorectal carcinomas. However, a cause-effect relationship between these two observations has not been demonstrated. For this reason, we developed a new experimental model to evaluate the possible role of circulating CEA in the facilitation of liver metastases. A CEA-negative subclone from the human colon carcinoma cell line CO115 was transfected either with CEA-cDNA truncated at its 3' end by the deletion of 78 base pairs leading to the synthesis of a secreted form of CEA or with a full-length CEA-cDNA leading to the synthesis of the entire CEA molecule linked to the cell surface by a GPI anchor. Transfectants were selected either for their high CEA secretion (clone CO115-2C2 secreting up to 13 microg CEA per 10(6) cells within 72 h) or for their high CEA membrane expression (clone CO115-5F12 expressing up to 1 x 10(6) CEA molecules per cell). When grafted subcutaneously, CO115-2C2 cells gave rise to circulating CEA levels that were directly related to the tumour volume (from 100 to 1000 ng ml(-1) for tumours ranging from 100 to 1000 mm3), whereas no circulating CEA was detectable in CO115 and CO115-5F12 tumour-bearing mice. Three series of nude mice bearing a subcutaneous xenograft from either clone CO115-2C2 or the CO115-5F12 transfectant, or an untransfected CO115 xenograft, were further challenged for induction of experimental liver metastases by intrasplenic injection of three different CEA-expressing human colorectal carcinoma cell lines (LoVo, LS174T or CO112). The number and size of the liver metastases were shown to be independent of the circulating CEA levels induced by the subcutaneous CEA secreting clone (CO115-2C2), but they were directly related to the metastatic properties of the intrasplenically injected tumour cells.

Perforin and granzyme B lytic protein expression during chronic viral and autoimmune hepatitis

BACKGROUND

Cytotoxic T lymphocytes and Kupffer cells are essential components of the immune response during liver diseases. Recent studies have highlighted the role of cytotoxic T lymphocytes using Fas and its ligand in induced hepatocyte death during acute and chronic hepatitis.

METHODS

In the present work, the main purpose was to investigate perforin and granzyme B expression in liver biopsies of patients with chronic hepatitis (10 HBV, 14 HCV and 10 autoimmune hepatitis) using immunohistochemistry. The liver biopsies of two normal individuals were also studied in the same conditions.

RESULTS

Few intrahepatic T lymphocytes expressed perforin and granzyme B, while a large number of Kupffer cells were positive for both proteins in all the patients tested. The co-localization of perforin and granzyme B, and CD3 or CD68 antigens was visualized, respectively, in T cells and Kupffer cells, using confocal microscopy. In situ hybridization assays confirmed that perforin and granzyme B mRNAs were present in the liver during chronic hepatitis. The results were similar among the three groups of patients and whatever the activity of the disease. Perforin and granzyme B expression was lacking in liver samples from normal individuals.

CONCLUSIONS

These data suggest a minor role for the T cell-mediated perforin/granzyme B death pathway, and a putative role for Kuppfer cells via lytic protein release, during chronic hepatitis.

Endothelial cells potentiate oxidant-mediated Kupffer cell phagocytic killing

Phagocytosis and killing of circulating organisms by Kupffer cells (KCs) are discrete, important components of host defense. However, the killing mechanism(s) are not fully understood, and the potential role of adjacent nonparenchymal cells such as hepatic endothelial cells has not been defined. Rat KCs -/+ an hepatic endothelial cell enriched cellular fraction (HECEF) were incubated with Candida parapsilosis and assayed for phagocytosis and phagocytic killing by validated fluorochromatic vital staining. The role of reactive oxygen metabolites in KC phagocytic functions was examined by inhibition with superoxide dismutase and/or catalase. Diphenyleneiodonium and allopurinol were used to examine the potential roles of NADPH oxidase and xanthine oxidase, respectively, in generating these toxic oxidants. Coculture with HECEF increased KC phagocytic activity (from 75% to 88%) and candidacidal activity (from 20% to 31%). Superoxide dismutase, catalase, diphenyleneiodonium, or allopurinol caused inhibition of candidacidal activity, but did not affect phagocytosis, and did not block the potentiation of phagocytosis or of killing caused by coculture with HECEF. Reactive oxygen intermediates generated by both NADPH oxidase and xanthine oxidase-dependent pathways are important in KC killing of Candida parapsilosis. In vitro, KC phagocytosis and killing are potentiated (via a non-oxidant-mediated mechanism) by coculture with a preparation of hepatic non-parenchymal cells composed primarily of endothelial cells.

Transient suppression of macrophage functions by liposome-encapsulated drugs

Macrophages play an important role in host defense reactions, for example, by phagocytosis of particulate materials. This process also results in the rapid removal of targeting devices such as liposomes and adenovirus vectors and of non-autologous grafted cells and materials. Another aspect of macrophage function is their production and secretion of proinflammatory cytokines. Transient and organ-specific suppression of macrophage function by liposome-mediated manipulation has been shown to improve the efficacy of drug and gene targeting and to reduce the symptoms of inflammatory reactions.

Effect of polymeric nanoparticle administration on the clearance activity of the mononuclear phagocyte system in mice

We investigated the consequences of acute and subacute administration of mice with polyisobutylcyanoacrylate (PIBCA), polyisohexylcyanoacrylate (PIHCA), poly(D,L-lactic) acid (PLA), and polystyrene (PS) nanoparticles on the mononuclear phagocyte system phagocytic function. This was done by measuring the clearance rate of colloidal carbon. Single administration of PIBCA and PIHCA (but not PLA and PS) nanoparticles reduced carbon clearance in both a time- and dose-dependent fashion. Since clearance of preopsonized carbon was normal, it was assumed that PIBCA and PIHCA nanoparticles deplete opsonins specific for carbon recognition. A decrease in plasma fibronectin levels resulting from nanoparticle administration suggested its implication in their removal from blood. However, fibronectin does not seem to be responsible for PIBCA and PIHCA blockade. Phagocytic function was preserved after repeated treatment with nanoparticles, probably as a result of increased Kupffer cell phagocytic activity and the contribution of spleen macrophages. Neither toxicity nor effects due to nanoparticle hepatic accumulation were observed.

Biliary decompression promotes Kupffer cell recovery in obstructive jaundice

BACKGROUND

Jaundiced patients undergoing surgical procedures have an increased risk of Gram negative sepsis with potential morbidity and mortality. Depressed Kupffer cell clearance capacity (KCCC) predisposes jaundiced patients to endotoxaemia and its sequelae. Biliary decompression remains the main therapeutic strategy in obstructive jaundice.

AIMS

This study investigates the efficacy of internal (ID) and external biliary drainage (ED) on KCCC in an experimental model of extrahepatic biliary obstruction.

METHODS

Adult male Wistar rats (250-300 g) were assigned to one of six groups: sham operated, where the bile duct was mobilised but not divided; bile duct ligation (BDL) for three weeks, and sham operated or BDL for three weeks followed by a second laparotomy and further 21 days of ID or ED, by way of choledochoduodenostomy or choledochovesical fistula respectively. KCCC was measured using an isolated hepatic perfusion technique with FITC labelled latex particles (0.75 mu) as the test probe. Plasma was assayed for bilirubin, endotoxin, and anticore glycolipid antibody (ACGA) concentrations.

RESULTS

Jaundiced rats had reduced KCCC (p < 0.001), increased concentrations of ACGA (p < 0.001), and endotoxin (p < 0.001) compared with controls. Biliary drainage for three weeks produced a recovery in KCCC and normalisation of endotoxin and ACGA concentrations, however, external drainage was less effective than ID (p < 0.01).

CONCLUSIONS

These data support the hypothesis that endotoxaemia and its mediated effects are integral in the pathophysiology of jaundice. Furthermore, a short period of internal biliary drainage is a useful therapeutic strategy in restoring Kupffer cell function and negating systemic endotoxaemia and consequent complications in biliary obstruction.

Phagocytic function and metabolite production in thioacetamide-induced liver cirrhosis: a comparative study in perfused livers and cultured Kupffer cells

BACKGROUND/AIMS

The aim of the study presented here was to evaluate the basal and stimulated phagocytic activities and the metabolite production of isolated perfused livers, and also the phagocytic capacity of cultured Kupffer cells from rats with macronodular cirrhosis.

METHODS

Rats were made cirrhotic by oral administration of thioacetamide. The phagocytic activity was assessed by the rate of removal of colloidal carbon. The Kupffer cells were prepared by a pronase/collagenase digestion method followed by elutriation.

RESULTS

The phagocytic activity and production of glucose, lactate and pyruvate were reduced in cirrhotic livers when calculated per g liver. Due to hyperplastic-regenerative processes the mass of the cirrhotic livers was markedly augmented so that the colloidal carbon uptake calculated per cirrhotic liver was not significantly different from the controls. Colloidal carbon-induced glucose release increased more markedly in the controls than in cirrhotic livers. Isoproterenol considerably stimulated phagocytosis and glucose production in controls, whereas the response was clearly reduced in cirrhotic livers when calculated either per g liver or per total liver weight. The cyclic AMP analogue elicited a marked glycogenolytic response in the controls, whereas there was only a slight increase in glucose production in cirrhotic livers. Phagocytosis of cirrhotic livers was only moderately stimulated by opsonized zymosan when compared with the controls. Freshly isolated Kupffer cells exhibited a reduced phagocytic activity. Stimulation by zymosan was observed only in cell suspensions of the controls. In contrast, Kupffer cells from cirrhotic livers did not differ from controls with respect to basal or zymosan-stimulated phagocytic activity after 48-h cultivation.

CONCLUSION

The stimulated phagocytic function was disturbed in perfused macronodular-cirrhotic livers as compared to controls. In contrast, 48-h cultured Kupffer cells from cirrhotic livers exhibited the same basal and stimulated phagocytic capacity as controls. The glucose release from perfused livers, initiated by stimulation of Kupffer cells or hepatocytes, was significantly reduced in cirrhotic livers. Therefore, we postulate an impaired intra- and/or intercellular signalling in macronodular-cirrhotic livers.