Phagocytic properties of hepatic endothelial cells and splenic macrophages compensating for a decreased phagocytic function of Kupffer cells in the chronically ethanol-fed rats

The balance of phagocytic function among Kupffer cells, hepatic endothelial cells and splenic macrophages in the chronically ethanol-fed rats has been investigated. Clearance of latex particles in the blood was measured to estimate the function of the reticuloendothelial system. Phagocytosis of latex particles by Kupffer cells, hepatic endothelial cells or splenic macrophages in vivo was measured by counting the number of ingested particles in a cell after isolation of hepatic nonparenchymal cells or spleen cells following injection of different amounts of latex particles. Latex particle clearance was suppressed in the ethanol-fed rats, demonstrating a decreased phagocytic capacity of the reticuloendothelial system. Markedly decreased phagocytic function was found in 40% of Kupffer cells of the chronically ethanol-fed rats. In contrast, the number of latex particles in hepatic endothelial cells and in splenic macrophages was increased after injection of a triggering dose of latex particles. From these results it may be concluded that an increased phagocytosis of hepatic endothelial cells and splenic macrophages could compensate for the decreased phagocytic function of Kupffer cells.     

Pulmonary intravascular macrophages in domestic animal species: review of structural and functional properties

In dogs, laboratory animals, and man, the clearance of bacteria and particulates from blood occurs predominantly in hepatic Kupffer cells and splenic macrophages. In contrast, removal of blood-borne particulates in calves, sheep, goats, cats, and pigs occurs predominantly in pulmonary intravascular macrophages (PIMs). Review of recent studies indicates that PIMs are a resident cell population, junctionally adherent to the capillary endothelium of lungs and morphologically similar to hepatic Kupffer cells. PIMs are a pulmonary constituent of the mononuclear phagocyte system with respect to secretory, endocytic, and functional properties. Differentiated PIMs are rare in newborn pigs, and the majority of cells closely apposed to capillary endothelium consists of monocytes, which are occasionally in mitosis. In 7-day-old and older pigs, most cells apposed to capillary endothelium have characteristics of differentiated PIMs. This suggests a monocytic origin of PIMs in pigs. Perinatal colonization of lung capillaries by monocytes and their subsequent differentiation into PIMs represent a component of postnatal lung development. Estimates of relative PIM numbers in ovine and porcine lung parenchyma suggest cell densities similar to that of rat hepatic Kupffer cells. Apart from phagocytic properties, PIMs participate in the removal and disintegration of aged and impaired blood cells. After phagocytic stimulation, isolated PIMs secrete oxygen radicals, which are essential for microbicidal function. Similarly, by secreting bioactive lipids, stimulated PIMs may contribute to regulation of pulmonary hemodynamics. After receiving minute amounts of bacterial endotoxin, pulmonary injury is pronounced in sheep, calves, pigs, and cats, but not in laboratory animals and dogs. This presumably is related to the secretion of bioactive lipids by PIMs.     

Chemiluminescence response of phagocytes in E. coli induced experimental ascending pyelonephritis.

The mechanism of tissue injury at the cellular level by following the chemiluminescence response of various phagocytes in E. coli induced experimental pyelonephritis in mice was investigated. There was a marked increase in the capacity of various phagocytic cells viz; renal neutrophils and macrophages peritoneal macrophages, blood monocytes and neutrophils to produce reactive oxygens species through the respiratory burst activity as monitored by the chemiluminescence response. The chemiluminescence response was observed to be increased significantly (p less than 0.001) with increasing days post infection in all phagocytic cells. However, the quantity of total reactive oxygen species produced per million cells was much more in the renal and peritoneal macrophages as compared to blood monocytes and neutrophils. The peak chemiluminescence response time was observed to be decreased from 4 to 2 minutes with the progression of the diseases. The implications of these findings have been discussed.     

Elevated anti-parasitic activity in peripheral blood monocytes and neutrophils of cattle infected with Babesia bovis

The innate immune response to bovine Babesia bovis infection in vivo has not previously been established. We used assays measuring phagocytosis and oxidative burst to investigate the immune response because they are indicative of the innate antimicrobial capacity of monocytes and neutrophils. Monocyte and neutrophil phagocytosis is thought to be non-specific in nature and so the phagocytosis of either opsonised Zymosan or Escherichia coli was used to indicate the non-specific phagocytic capacity of monocytes and neutrophils ex vivo. The kinetics of both phagocytic and oxidative burst activity in monocytes and neutrophils were followed twice weekly from pre-inoculation (day 0) through to 31 days after inoculation. Peripheral blood monocytes were found to display a pronounced oxidative burst, but a suppressed capacity to phagocytose during a primary infection. On the other hand, neutrophils exhibited an increased phagocytic capacity and reduced oxidative activity during a primary infection. These findings identified considerable antimicrobial activity evident in peripheral blood monocytes and neutrophils from cattle exposed to B. bovis as a primary exposure. This elevated antimicrobial activity was coincident with the time that parasite numbers peaked in the circulation and occurred prior to parasite clearance. These results suggest that peripheral blood monocytes and neutrophils are active mediators in the innate immune response to a primary B. bovis.     

Functional rearrangements in macrophages following intensive physical exercise

The effect of intensive physical exercise (swimming for 3 hours with a load of 4% body weight) on the function of hepatic, pulmonary and peritoneal macrophages has been studied in rats and mice. NBT values in alveolar and peritoneal macrophages of the experimental animals proved to be 1.5 and 1.6 times higher than in the controls. The activity of cathepsin D in the liver, lung and Kupffer cells was greater than the control values. The data obtained indicate that intensive physical exercise caused depression in phagocytic activity of Kupffer cells, the major compartment of the reticuloendothelial system, whereas a similar function in lung macrophages was even greater than in the controls and in peritoneal macrophages changed but insignificantly.     

Vitamin A supplementation improves macrophage function and bacterial clearance during experimental salmonella infection

The effects of additional but nontoxic amounts of vitamin A on susceptibility to salmonella infection was studied by comparing rates of bacterial clearance and phagocytosis. Forty-eight male Lewis rats were divided into a treatment group receiving a total of 6000 units of vitamin A palmitate weekly for 5 weeks and a control group was given an equal volume of saline. After completion of the treatment regimen, one-half from each group were infected intraperitoneally with 10(5) Salmonella typhimurium; the other half received intraperitoneal injection of saline. At this time no differences in weight gain were noted and all animals were sacrificed within 2 weeks. At 72 hr after bacterial challenge, all saline-treated control animals displayed bacteremia. Cultures of liver and splenic homogenates were positive in 89 and 100% of infected control animals vs 0 and 44% for treated animals during the first week of infection. Kupffer cell, peritoneal, and splenic macrophages of the vitamin A-treated group had greater phagocytic activity than controls as assessed by the percentage of cells ingesting yeast particles and by the number of particles ingested (phagocytic index). These results suggest that vitamin A in moderate amounts may benefit the host's response to infection by enhancing phagocytic cell function.     

Effect of the EM Bokashi® Multimicrobial Probiotic Preparation on the Non-specific Immune Response in Pigs

The aim of the study was to determine the effect of EM Bokashi® on the phagocytic activity of monocytes and granulocytes, oxidative burst, SWC3, and CD11b + CD18+ expression on monocytes and granulocytes, and the serum concentration of cytokine and lysozyme in pig. 60 Sixty female piglets were divided into two groups: I – control and II – experimental. For the experimental group, a probiotic in the form of the preparation EM Bokashi® was added to the basal feed. Flow cytometry was used to determine selected non-specific immune response parameters, intracellular production of hydrogen peroxide by peripheral granulocytes and monocytes, and surface particles in peripheral blood. The EM Bokashi® preparation used in the study was found to increase phagocytic activity mainly in monocytes, with an increased percentage of phagocytic cells in the experimental group. The highest serum lysozyme concentration in the piglets in the experimental group (2.89 mg/dl), was noted on day 42 of the study. In the group of pigs receiving EM Bokashi®, the percentage of phagocytic cells with SWC3 (monocyte/granulocyte) expression was statistically significantly higher than in the control. The increase in the number of cells with SWC3 (monocyte/granulocyte) expression in the peripheral circulation in combination with the greater capacity of the cells for phagocytosis and respiratory burst confirms that the non-specific immune response was modulated in the pigs supplemented with EM Bokashi®.

     

Critical role of Kupffer cells in the management of diet-induced diabetes and obesity

The aim of this study was to investigate the role of Kupffer cell in glucose metabolism and hepatic insulin sensitivity in mice. Both phagocytic activity and secretory capacity of Kupffer cells were blunted 24 h after GdCl₃ administration. Glucose tolerance - evaluated following an oral glucose tolerance test (OGTT) - was higher in GdCl₃-treated mice whereas fasting insulinemia and HOMA-IR index decreased. The improvement of glucose tolerance and hepatic insulin signalling pathway after inhibition of Kupffer cells was supported by a lower hepatic gluconeogenic enzyme expression and a higher phosphorylation of Akt upon insulin challenge. Moreover, fasting hyperglycemia, insulin resistance and impaired glucose tolerance - induced by high fat (HF) diet - were improved through chronic administration of GdCl₃. Interestingly, the inhibition of Kupffer cell exerted antiobesity effects in HF-fed mice, and lowered hepatic steatosis. Therefore, strategies targeting Kupffer cell functions could be a promising approach to counteract obesity and related metabolic disorders.     

Th2-associated alternative Kupffer cell activation promotes liver fibrosis without inducing local inflammation

Cirrhosis is the final outcome of liver fibrosis. Kupffer cell-mediated hepatic inflammation is considered to aggravate liver injury and fibrosis. Alternatively-activated macrophages are able to control chronic inflammatory events and trigger wound healing processes. Nevertheless, the role of alternative Kupffer cell activation in liver harm is largely unclear. Thus, we evaluated the participation of alternatively-activated Kupffer cells during liver inflammation and fibrosis in the murine model of carbon tetrachloride-induced hepatic damage. To stimulate alternative activation in Kupffer cells, 20 Taenia crassiceps (Tc) larvae were inoculated into BALBc/AnN female mice. Six weeks post-inoculation, carbon tetrachloride or olive oil were orally administered to Tc-inoculated and non-inoculated mice twice per week during other six weeks. The initial exposure of animals to T. crassiceps resulted in high serum concentrations of IL-4 accompanied by a significant increase in the hepatic mRNA levels of Ym-1, with no alteration in iNOS expression. In response to carbon tetrachloride, recruitment of inflammatory cell populations into the hepatic parenchyma was 5-fold higher in non-inoculated animals than Tc-inoculated mice. In contrast, carbon tetrachloride-induced liver fibrosis was significantly less in non-inoculated animals than in the Tc-inoculated group. The latter showed elevated IL-4 serum levels and low IFN-γ concentrations during the whole experiment, associated with hepatic expression of IL-4, TGF-β, desmin and α-sma, as well as increased mRNA levels of Arg-1, Ym-1, FIZZ-1 and MMR in Kupffer cells. These results suggest that alternative Kupffer cell activation is favored in a Th2 microenvironment, whereby such liver resident macrophages could exhibit a dichotomic role during chronic hepatic damage, being involved in attenuation of the inflammatory response but at the same time exacerbation of liver fibrosis.     

Listeria monocytogenes meningitis and decreased phagocytosis associated with iron overload.

A patient with Listeria monocytogenes meningitis was found to have idiopathic haemochromatosis and monocytes with reduced phagocytic capacity. The phagocytic function recovered completely after a series of therapeutic phlebotomies. In-vitro iron had a deleterious effect on the phagocytic capacity of monocytes and granulocytes. These findings show that iron overload in the host can increase susceptibility to L monocytogenes infection not only by increasing the virulence of the organism but also by reducing the phagocytic capacity of the monocytes.     

Kuppfer Cells Trigger Nonalcoholic Steatohepatitis Development in Diet-induced Mouse Model through Tumor Necrosis Factor-α Production

Nonalcoholic steatohepatitis (NASH), characterized by lipid deposits within hepatocytes (steatosis), is associated with hepatic injury and inflammation and leads to the development of fibrosis, cirrhosis, and hepatocarcinoma. However, the pathogenic mechanism of NASH is not well understood. To determine the role of distinct innate myeloid subsets in the development of NASH, we examined the contribution of liver resident macrophages (i.e. Kupffer cells) and blood-derived monocytes in triggering liver inflammation and hepatic damage. Employing a murine model of NASH, we discovered a previously unappreciated role for TNFα and Kupffer cells in the initiation and progression of NASH. Sequential depletion of Kupffer cells reduced the incidence of liver injury, steatosis, and proinflammatory monocyte infiltration. Furthermore, our data show a differential contribution of Kupffer cells and blood monocytes during the development of NASH; Kupffer cells increased their production of TNFα, followed by infiltration of CD11b^intLy6C^hi monocytes, 2 and 10 days, respectively, after starting the methionine/choline-deficient (MCD) diet. Importantly, targeted knockdown of TNFα expression in myeloid cells decreased the incidence of NASH development by decreasing steatosis, liver damage, monocyte infiltration, and the production of inflammatory chemokines. Our findings suggest that the increase of TNFα-producing Kupffer cells in the liver is crucial for the early phase of NASH development by promoting blood monocyte infiltration through the production of IP-10 and MCP-1.     

Inhibition of caspase activity prevents CD95-mediated hepatic microvascular perfusion failure and restores Kupffer cell clearance capacity.

Using a murine model, we studied the effect of agonistic anti-CD95 antibodies (aCD95) on sinusoidal lining cells and a potential protection by caspase inhibition. C3H/HeN mice were intravenously administered aCD95 (10 microgram/mouse) or unspecific IgG (control) in the presence or absence of the caspase inhibitor z-VAD-fmk. Analysis of hepatic microcirculation using intravital fluorescence microscopy revealed severe (P<0.01) sinusoidal perfusion failure and reduced (P<0.05) phagocytic activity of Kupffer cells (KC) within 2 h. Transmission electron micrographs demonstrated loss of integrity of sinusoidal endothelial cells as early as 1 h after aCD95 application, whereas histological manifestation of hepatocellular apoptosis and hemorrhagic necrosis was most pronounced at 6 h. Blocking of caspase activity attenuated (P<0.01) both hepatic microvascular perfusion failure and KC dysfunction. Accordingly, full protection of the liver from apoptotic damage and intact microarchitecture was observed in histological sections after z-VAD-fmk treatment. Mortality rate was 40% 6 h after aCD95 administration, whereas all animals survived in the z-VAD-fmk group (P<0.05). The activation of caspases through CD95 may primarily lead to damage of sinusoidal endothelial cells and hepatic microvascular perfusion failure. Moreover, reduced phagocytic capacity of KC may contribute to accumulation of toxic metabolites released by dying cells at the local site of inflammation, further aggravating liver injury.     

Kupffer cells from Schistosoma mansoni-infected mice participate in the prompt type 2 differentiation of hepatic T cells in response to worm antigens

Infection with Schistosoma mansoni, a portal vein-residing helminth, is well known to generate life cycle-dependent, systemic immune responses in the host, type 1 deviation during the prepatent period, and type 2 polarization after oviposition. Here we investigated local immunological changes in the liver after infection. Unlike splenocytes, hepatic lymphocytes from infected mice during the prepatent period already produced a higher amount of IL-4 and a lesser amount of IFN-gamma than those from uninfected mice. Hepatic lymphocytes, particularly conventional T cells, but not NK1.1+ T cells, promptly produced IL-4 in response to worm products, soluble worm Ag preparation (SWAP), whenever presented by Kupffer cells from infected mice. The hepatic lymphocytes that had been stimulated with SWAP presented by infected mice-derived Kupffer cells produced a huge amount of IL-4, IL-13, and IL-5 as well as little IFN-gamma in response to immobilized anti-CD3 mAb. Kupffer cells from uninfected mice produced IL-6 and IL-10, but not IL-12 or IL-18, in response to SWAP stimulation and gained the potential to additionally produce IL-4 and IL-13 after the infection. These results suggested that prompt type 2 deviation in the liver after the infection might be due to the alteration of Kupffer cells that induces SWAP-mediated type 2-development of hepatic T cells.     

Are Kupffer cells involved in the metabolic adaptation of the liver to dietary carbohydrates given after fasting?

In rats, a high carbohydrate fat-free (HCFF) diet, given after fasting, induces both hepatic lipogenic and glycogenic enzymes. In the present study, we evaluated the involvement of Kupffer cells in the metabolic events occurring in the liver during the fasting-refeeding transition. Male Wistar rats were fasted for 48 h and received an intravenous injection of either NaCl 0.9% (Gd-) or 10 mg/kg GdCl(3) (Gd+), an inhibitor of Kupffer cells, then fed for 12 h with a HCFF diet. The comparison of colloidal carbon uptake was similar in rats fasted and in rats fasted and then refed a HCFF diet, thus indicating that refeeding does not affect per se Kupffer cell phagocytic activity. The inhibition of Kupffer cells by GdCl(3) did not affect fatty acid synthase (FAS) induction, as shown by the analysis of both FAS mRNA and activity; refeeding a HCFF diet increased the hepatic triglyceride and glycogen content to the same extent in Gd+ and Gd- rats. Our results do not support the involvement of Kupffer cells in the metabolic events occurring in the liver tissue by feeding a HCFF diet after fasting. However, the discussion supports the involvement of Kupffer cells in the modulation of the hepatic lipid metabolism by other nutrients than carbohydrates.     

HSP and apoptosis in leukocytes from infected or vaccinated animals by Brucella abortus

The production of hsp and apoptosis of leukocytes in the peripheral blood of animals naturally infected with Brucella spp or treated with the vaccine Brucella abortus 19 have been investigated in this study. Cytokines able to induce phagocytic activity in macrophages of non treated healthy animals were found in the supernatant of bovine leukocytes cultivated in vitro. A long-lasting antibody response against hsp 60 kDa and 27 kDa, which lasts a long time, is induced in naturally infected animals, while in animals vaccinated with B. abortus 19 we detected an antibody response against hsp 60 and 70 kDa which is much shorter, disappearing in two months. During the early phase of infection, lymphocytes and monocytes of naturally infected animals show a delay of apoptosis in vitro compared to the same cells coming from healthy controls and vaccinated animals.     

Superoxide Generation by Kupffer Cells and Priming of Neutrophils During Reperfusion After Hepatic Ischemia

The objective of this study was to identify the cellular source of the vascular oxidant stress in hepatic ischemia-reperfusion injury in male Fischer rats. Nonparenchymal cells (Kupffer cells, endothelial cells) and neutrophils were isolated from postischemic liver lobes by collagenase-pronase digestion followed by centrifugal elutriation. The spontaneous and stimulated generation of superoxide by these cells were subsequently quantified in vitro. Large Kupffer cells from the postischemic lobes spontaneously generated 300% more superoxide than similar cells from control animals. No difference in spontaneous superoxide formation was found when the small Kupffer cells were compared. No other cells isolated from the postischemic lobes or control liver including neutrophils released any detectable superoxide spontaneously. In contrast, small Kupffer cells and neutrophils from the postischemic liver generated significantly more superoxide after stimulation with phorbol ester or opsonized zymosan than the controls. The considerably higher response with zymosan stimulation compared to phorbol ester indicates a particular priming for a receptor-mediated signal transduction pathway during reperfusion. These studies demonstrate that Kupffer cells are the principal source of the oxidant stress during the initial reperfusion phase after hepatic ischcmia. The priming of neutrophils during this time may be an important factor for the later neutrophil-induced injury phase.     

Protracted circulating lifetimes of mannose-terminated glycoproteins and aggregated albumin in mice infected with LDH-elevating virus.

Several macromolecular homeostasis-regulating mechanisms were tested for functional integrities in mice during acute and early chronic phases of infection with lactic dehydrogenase-elevating virus (LDV). Fractional catabolic rates of carbodiimide-aggregated albumin and immunoglobulin G were studied to evaluate glomerular filtration and hepatic Kupffer cell phagocytic activities. Several glycoproteins (fetuin, IgG antibodies, and ovalbumin) were also compared with their deglycosylated counterparts for fractional catabolic rates and organ distributions as a basis for evaluating virus-induced modifications of saccharide-binding "receptor functions" in vivo. Findings were that normal hepatic clearance of aggregated albumin and of ovalbumin is slowed from the onset of viremia. Fractional catabolic rates of amannosyl-ovalbumin and amannosyl-IgG are similar in uninfected animals to those seen with native ovalbumin or with mannose-terminated IgG in LDV-infected animals. Ovalbumin and aggregated albumin were also found to be mutually competitive for hepatic uptake in uninfected animals. It is proposed that LDV, which replicates in cells of the mononuclear phagocyte system (reticuloendothelial system), alters the clearance functional state of fixed tissue macrophage, thereby explaining in part the protracted circulatory longevity of several enzymes, aggregated albumin and mannose-terminated ovalbumin, and IgG in LDV-infected mice.     

Release of an endogenous pyrogen from guinea pig leukocytes: the role of T lymphocytes and correlation with suppression (desensitization) of delayed hypersensitivity

The pathogenesis of fever in delayed hypersensitivity (DH) was studied in guinea pigs immunized with either ovalbumin or bovine gamma-globulin in complete Freund's adjuvant. In vitro incubation of sensitized lymphocytes with the specific antigen used for immunization resulted in the elaboration of a lymphokine-like factor that activated either monocytes or neutrophils to release endogenous pyrogen (EP), the protein that causes fever. Specifically sensitized T cells appeared to be responsible for release of this EP-inducing factor. Desensitization of the dermal DH response to antigen was produced by several large injections of antigen and was associated with a reduced capacity of lymphocytes from such animals to activate phagocytic cells to release EP. This may explain the reduced fever (pyrogenic tolerance) that occurs when repeated injections of antigen are given to sensitized animals. Fever and the dermal response to DH seem to be closely linked reactions that have evolved to defend the host against invading pathogens. In both reactions, phagocytic cells appear to be activated by lymphokines derived from T lymphocytes specifically responding to microbial antigens.     

Pathology of experimental Babesia microti infection in the Syrian hamster

Pathologic changes produced after 4 weeks of infection by Babesia microti in Syrian hamsters are described and compared to babesiosis of humans. Following intraperitoneal inoculation, both intravascular and extravascular hemolysis developed. Up to 70% of red blood cells were parasitized. The principal morphologic abnormalities were an increase in extramedullary hematopoiesis and hyperplasia of the mononuclear phagocytic cells of the red pulp manifested grossly as splenomegaly, marked renal tubular hemosiderosis and hypertrophy of Kupffer cells. The disease was not fatal to any hamsters during the 4 week study. The clinical signs and lesions were less severe than fatal babesiosis of asplenic humans and similar to severe, but nonfatal disease in spleen intact humans. The hamster may serve as an animal model for the studying the pathophysiology of human babesiosis and for studying potential chemotherapeutic agents.