Analysis of the Expression of Regulator Genes in Kupffer Cells and Monocytes.

Differences in the gene expression profiles in resident macrophages (in particular, Kupffer cells) and monocytes were revealed. However, these differences in gene expression profiles do not allow considering resident liver macrophages as purely M2 macrophages and monocytes as purely M1 macrophages. At the same time, a significant number of the genes upregulated in Kupffer cells are associated with normal regulation of liver functions (Arg 1, Flt, iNOs, and Kng). In monocytes, the expression of genes Alox15, Alox12, Tlr2, Tlr4, Tlr7, and Tlr8 (typical functional genes of macrophages) was also upregulated in comparison with Kupffer cells.

Phenotypical and Functional Polymorphism of Liver Resident Macrophages.

Liver diseases are one of the main causes of mortality. In this regard, the development of new ways of reparative processes stimulation is relevant. Macrophages play a leading role in the regulation of liver homeostasis in physiological conditions and in pathology. In this regard, the development of new liver treatment methods is impossible without taking into account this cell population. Resident macrophages of the liver, Kupffer cells, represent a unique cell population, first of all, due to their development. Most of the liver macrophages belong to the self-sustaining macrophage cell population, whose origin is not bone marrow. In addition, Kupffer cells are involved in such processes as regulation of hepatocyte proliferation and apoptosis, remodeling of the intercellular matrix, lipid metabolism, protective function, etc. Such a broad spectrum of liver macrophage functions indicates their high functional plasticity. The review summarizes recent data on the development, phenotypic and functional plasticity, and participation in the reparative processes of liver macrophages: resident macrophages (Kupffer cells) and bone marrow-derived macrophages.

Non-alcoholic steatohepatitis induces transient changes within the liver macrophage pool.

Kupffer cells (KCs) and monocyte-derived macrophages are implicated in non-alcoholic steatohepatitis (NASH) pathogenesis but their functions remain unclear due to the lack of specific markers to distinguish between the different cell types. Additionally, it is unclear if multiple subsets of KCs are present during NASH. Here, we characterized the liver macrophage subsets during methionine/choline deficient (MCD) diet-induced NASH and recovery. We observed a significant reduced contribution of Ly6CloClec4F+Tim4+KCs to the hepatic macrophage pool in MCD fed mice, which normalized during recovery. Ly6CloClec4F-Tim4- monocyte-derived macrophages increased during MCD feeding and returned to baseline during recovery. Ly6CloClec4F+Tim4- monocyte-derived KCs developed during initial recovery but did not self-renew as their numbers were reduced after full recovery. Initial recovery from MCD diet feeding was further characterized by increased proportions of Ki-67+ proliferating KCs. In conclusion, the hepatic macrophage pool undergoes substantial albeit transient changes during NASH and recovery, with the KC pool being maintained by proliferation and differentiation of short-lived monocyte-derived KCs.

Bisphenol A promotes hepatic lipid deposition involving Kupffer cells M1 polarization in male mice.

Bisphenol A (BPA), one of the most common environmental endocrine disruptors, is considered to promote hepatic lipid deposition. However, the mechanism has not been fully elucidated. The polarization of Kupffer cells (KCs) plays an important role in hepatic inflammation by promoting pro-inflammatory M1 phenotype (M1KCs), which contributes to dysregulated lipid metabolism. The purpose of this study is to investigate the role of KC polarization in BPA-induced hepatosteatosis in male mice. In this study, we examined hepatic lipid contents and quantified M1KC in BPA-treated CD1 mice, and further explored the interaction between KCs and hepatocytes using conditional HepG2 cell culture. BPA treatment significantly increased hepatic fat contents in CD1 mice, accompanied by increased number of pro-inflammatory M1KCs and enhanced secretion of inflammatory cytokines. Increased lipid contents were also observed in HepG2 cells treated with BPA. Interestingly, higher TG contents were observed in HepaG2 cells treated with conditional media from BPA-treated KCs, compared with those treated with BPA directly. Incubation of KCs with BPA promoted the polarization of KCs to pro-inflammatory M1 dominant subtypes, which was blocked by estrogen antagonist ICI182780. Taken together, our results revealed that M1KCs polarization is involved in BPA-induced hepatic fat deposition, which is possibly associated with the estrogen receptor signaling pathway.

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.

Characterization of two F4/80-positive Kupffer cell subsets by their function and phenotype in mice.

BACKGROUND & AIMS: Liver Kupffer cells have been suggested to be heterogeneous macrophage lineage cells. We explored this possibility by classifying the mouse Kupffer cells into subpopulations and characterizing them by their phenotype and function. METHODS: Liver mononuclear cells (MNCs) from C57BL/6 mice were isolated and their phenotypes and functions were analyzed. The effects of clodronate liposomes and gadolinium chloride (GdCl(3)) on Kupffer cells were also investigated. RESULTS: Approximately 25% of liver MNCs were F4/80(+) Kupffer cells. Of these, 46% were CD11b(-)CD68(+), 22% were CD11b(+)CD68(-), and 6% were CD11b(+)CD68(+). CD68(+) cells showed potent phagocytic activity and reactive oxygen species (ROS) production capacity after lipopolysaccharide (LPS) stimulation, whereas CD11b(+) cells did not. CD11b(+) cells showed a strong capacity for the production of cytokines (TNF and IL-12), which was much less prominent in CD68(+) cells. At 24h after LPS or Escherichia coli injection into mice, the proportions of CD11b(+)CD68(-) and CD11b(+)CD68(+) cells increased but that of CD11b(-)CD68(+) cells decreased. The increase in CD11b(+)CD68(+) cells appeared to be derived from the CD11b(+)CD68(-) subset. Although the CD11b(+) cells augmented phagocytic activity after LPS injection, they did not increase ROS production, suggesting their weak lytic activity. Injection of clodronate or GdCl(3) into mice depleted the CD68(+) cells but increased CD11b(+) cells proportionally because CD68(+) cells may phagocytose these toxic reagents and undergo apoptosis. GdCl(3)-treated mice also consistently increased serum TNF after LPS challenge. CONCLUSIONS: Two F4/80(+) Kupffer cell subsets may exist, a CD68(+) subset with phagocytic activity and a CD11b(+) subset with cytokine-producing capacity.

Browicz or Kupffer cells?

The paper is concerned to problem of discovery of macrofage cells present in the liver sinusoid, which are recognized in the world medical literature as Kuppffer cells. On the other hand in Poland the name of professor Tadeusz Browicz is firmly connected with the cells resulting in eponymous Browicz cells. The authors are trying to determine who has priority in this respect; Karl Kupffer, a professor of anatomy in Koniggsberg, and then in München, or professor of pathological anatomy at Jagiellonian University, Tadeusz Browicz.

Transmission electron microscopic study of hepatocytes in bioartificial liver.

A bioartificial liver (BAL) was prepared by simple inoculation of hepatocytes into the inner space of hollow fibers of a hemodialyzer and it was maintained in a closed circuit for in vitro culture. Morphology of hepatocytes in the hollow fibers was studied in detail using transmission electron microscopy (TEM). The hepatocytes formed three-dimensional, rod-shaped aggregates of 200 microm in diameter throughout the whole dimension of the hollow fibers after 1 day of culture. Approximately five hepatocyte layers existed from the surface to the center of the aggregate. The hepatocytes in the aggregate displayed mostly polygonal shapes and were surrounded by five to six cells. Abundant bile canaliculi were formed between the hepatocytes and were sealed by tight junctions. The distance between the adjacent hepatocytes except the bile canaliculus domain was approximately 20 nm, and interdigitation was observed between some hepatocytes. These observations indicate that the hepatocytes formed functionally associated aggregates, that is, organoids. Although the cells facing the inner surface of the hollow fiber lost their polygonal shape and became flattened during the following several-day culture, no drastic change was observed in the morphology of the hepatocytes located inside the aggregate. After 14 days of culture, the number of living cells decreased and most of these had a deformed nucleus, few numbers of organelles, and intermittent lipid droplets.

A life stage of particle-laden rat dendritic cells in vivo: their terminal division, active phagocytosis, and translocation from the liver to the draining lymph.

Initiation of an adoptive immune response against pathogenic organisms, such as bacteria and fungi, may involve phagocytic activity of dendritic cells (DC) or their immature precursors as a prelude to antigen processing and presentation. After intravenous injection of rats with particulate matter, particle-laden cells were detected in the peripheral hepatic lymph. Since it has been known there is a constant efflux of DC from nonlymphoid organs into the draining peripheral lymph, we examined whether these particle-laden cells belonged to the DC or macrophage lineage. The majority of particle-laden cells in lymph showed immature monocyte-like cytology, and the amount of ingested particles was small relative to typical macrophages. We identified these particle-laden cells as DC based on a number of established criteria: (a) they had a phenotype characteristic of rat DC, that is, major histocompatibility complex class Ihigh+ and IIhigh+, intercellular adhesion molecule 1+ and 80% positive with the rat DC-specific mAb OX62; (b) they showed strong stimulating capacity in primary allogeneic mixed leukocyte reaction; (c) in vitro, they had little phagocytic activity; and (d) the kinetics of translocation was similar to that of lymph DC in that they migrated to the thymus-dependent area of the regional nodes. Furthermore, bromodeoxyuridine feeding studies revealed that most of the particle-laden DC were recently produced by the terminal division of precursor cells, at least 45% of them being <5.5 d old. The particle-laden DC, defined as OX62+ latex-laden cells, were first found in the sinusoidal area of the liver, in the liver perfusate, and in spleen cell suspensions, suggesting that the site of particle capture was mainly in the blood marginating pool. It is concluded that the particle-laden cells in the hepatic lymph are recently produced immature DC that manifest a temporary phagocytic activity for intravascular particles during or after the terminal division and that the phagocytic activity is downregulated at a migratory stage when they translocate from the sinusoidal area to the hepatic lymph.