An improved method for the isolation of hepatocytes from liver slices. Selective removal of Trypan blue-dyeable cells

Zonated iron deposition in the periportal zone of the liver is associated with selectively enhanced lipid synthesis

BACKGROUND AND AIMS

Disorders in liver lipid metabolism have been implicated in a range of metabolic conditions, including fatty liver and liver cancer. Altered lipid distribution within the liver, shifting from the pericentral to the periportal zone under pathological circumstances, has been observed; however, the underlying mechanism remains elusive. Iron, an essential metal, exhibits a zonal distribution in the liver similar to that of lipids. Nevertheless, the precise relationship between iron and lipid distribution, especially in the pericentral and periportal zones, remains poorly understood.

METHODS

We conducted comprehensive in vitro and in vivo experiments, combining with in situ analysis and RNA sequencing, aiming for a detailed exploration of the causal relationship between iron accumulation and lipid metabolism.

RESULTS

Our research suggests that iron overload can disrupt the normal distribution of lipids within the liver, particularly in the periportal zone. Through meticulous gene expression profiling in both the pericentral and periportal zones, we identified pyruvate carboxylase (PC) as a pivotal regulator in iron overload-induced lipid accumulation. Additionally, we revealed that the activation of cyclic adenosine monophosphate response element binding protein (CREB) was indispensable for Pc gene expression when in response to iron overload.

CONCLUSIONS

In summary, our investigation unveils the crucial involvement of iron overload in fostering hepatic lipid accumulation in the periportal zone, at least partly mediated by the modulation of Pc expression. These insights offer new perspectives for understanding the pathogenesis of fatty liver diseases and their progression.

Antidiabetic plants and their active constituents

Diabetes mellitus is a debilitating and often life-threatening disease with increasing incidence in rural populations throughout the world. A scientific investigation of traditional herbal remedies for diabetes may provide valuable leads for the development of alternative drugs and therapeutic strategies. Alternatives are clearly needed because of the inability of current therapies to control all of the pathological aspects of diabetes, and the high cost and poor availability of current therapies for many rural populations, particularly in developing countries. This review provides information on more than 1200 species of plants reported to have been used to treat diabetes and/or investigated for antidiabetic activity, with a detailed review of representative plants and some of great diversity of plant constituents with hypoglycemic activity, their mechanisms of action, methods for the bioassay of hypoglycemic agents, potential toxicity problems, and promising directions for future research on antidiabetic plants. The objective of this work is to provide a starting point for programs leading to the development of indigenous botanical resources as inexpensive sources for standardized crude or purified antidiabetic drugs, and for the discovery of lead compounds for novel hypoglycemic drug development.

Stimulation by D-glucose of the direct conversion of arginine to citrulline in enterocytes isolated from pig jejunum

In enterocytes isolated from pig jejunum, L-arginine is metabolized to L-citrulline either directly or indirectly through the sequence of reactions catalysed by arginase and ornithine transcarbamylase. In the presence of 5 mM D-glucose, the direct conversion of 1mM L-[guanido-14C] arginine to L-citrulline was increased more than 4 times. Isolated enterocytes exhibit a high glycolytic capacity. Furthermore, the decarboxylation of 5mM D-[1-14C] glucose was 3.6 fold higher than the decarboxylation of 5 mM D-[6-14C] glucose which suggests the presence of a pentose phosphate pathway in enterocytes. Since the production of labelled L-citrulline from L-[guanido-14C] arginine in pig enterocyte homogenates was markedly increased in the presence of NADPH, it is proposed that the direct conversion of L-arginine to L-citrulline could be stimulated by the production of NADPH from D-glucose in the pentose phosphate pathway.

Arginine metabolism in rat enterocytes

Rat enterocytes exposed to L-arginine in the absence of any other exogenous substrate were found to actively metabolize this cationic amino acid. L-Arginine was converted to L-citrulline either directly in a NADPH-sensitive manner thought to be coupled with the generation of NO, or indirectly through the sequence of reactions catalyzed by arginase and ornithine transcarbamylase. A large fraction of L-citrulline and L-ornithine generated from exogenous L-arginine was released in the incubation medium. The production of CO2 and (poly)amines from L-arginine occurred at rates 2 to 3 orders of magnitude lower than that characterizing the net uptake of the cationic amino acid, and this despite the fact that enterocytes were equipped to allow the interconversion of L-ornithine and L-glutamate. It is concluded that the oxidative catabolism of L-arginine in enterocytes is quantitatively negligible relative to its conversion to L-citrulline and L-ornithine.

Effects of bile acids on liver cell injury by cultured supernatant of activated liver adherents cells

When heat-killed Propionibacterium acnes (P. acnes) is intravenously injected into mice followed by an intravenous injection of a small amount of lipopolysaccharide (LPS) 7 days later, most of the mice die of massive hepatic cell necrosis within 24 hours of LPS injection. In addition, when the liver adherent cells including Kupffer cells are separated from the mice 7 days after P. acnes injection and incubated in vitro with LPS, remarkable activity of the cytotoxic factor is found in the culture supernatant. This cytotoxic factor is thought to cause liver injury. Using this experimental model, the effects of various bile acids on liver cell injury were studied. As a result, ursodeoxycholic acid and dehydrocholic acid suppressed liver cell injury induced by the cytotoxic factor. However, cholic acid, deoxycholic acid and chenodeoxycholic acid did not have any hepatocytoprotective effects.

Tryptophan metabolism in D-galactosamine-induced liver injury

We have reported that in rats with D-galactosamine-induced liver injury, the serum level of indoleacetic acid (IAA), a metabolite of tryptophan (TRP), increases before the increase in serum transaminase activity. To determine whether this IAA is derived from hepatocytes, isolated hepatocytes were treated with D-galactosamine and loaded with TRP, and the changes in TRP and IAA levels in the culture supernatant of the isolated hepatocytes were measured at various time intervals. As a result, IAA level in the culture supernatant of hepatocytes treated with D-galactosamine and loaded with TRP significantly increased in a time-dependent manner. This indicates that in D-galactosamine-induced liver injury, a metabolic pathway which produces IAA from TRP through tryptamine is present in hepatocytes.

A rapid method of preparing hepatic parenchymal cells for studying drug metabolism

Parenchymal cells were prepared from the livers of male Sprague-Dawley rats by collagenase perfusion and purified by a self-generating Percoll gradient. The method consisted of mixing 31% Percoll and 5 x 10(6) cells/ml, followed by centrifugation at 10,000 x g for 10 min. A self-generated gradient provided a rapid and efficient recovery of highly viable parenchymal cells. The parenchymal cells were determined to be very stable during incubation at 37 degrees C for at least 2 h. Cell integrity was evaluated by trypan blue dye exclusion, lactate dehydrogenase leakage, and membrane peroxidation. In addition, drug metabolism and conjugation were evaluated as markers of intracellular integrity. With increasing p-nitroanisole (pNA) concentration, the formation of p-nitrophenol (pNP) increased. The rate of sulfation was maximal at a pNA concentration of 0.25 mM and decreased greatly above 1.0 mM. Glucuronidation increased from 0.25 mM to a maximum rate of 2.0 mM pNA. Above 1.0 mM pNA, nonconjugated pNP increased proportionately to the decrease in sulfation. These results indicate that the cell integrity was maintained, and that these cells can be used as a model for studying drug metabolism.

The protective effect of cyclosporin A on experimentally-induced acute hepatic injury in mice

When heat-killed Propionibacterium acnes (P. acnes) and a small amount of endotoxin lipopolysaccharide (LPS) were intravenously injected into mice at a week's interval, most of them died of massive hepatic cell necrosis. This experimentally-induced acute liver injury was significantly inhibited by cyclosporin A (CsA), resulting in a remarkable improvement of the survival rate. This protective effect of CsA on acute liver injury was also histopathologically confirmed. To study the mechanism by which CsA protected the mice from fatal hepatic injury, adherent cells prepared from the murine liver 7 days after P. acnes injection were incubated with LPS in the presence of CsA, and the effect of CsA on the production of the cytotoxic factor from the adherent cells was estimated. As a result, CsA inhibited the activation of liver adherent cells and suppressed the release of the cytotoxic factor.

The protective effects of prostaglandin E1 in an experimental massive hepatic cell necrosis model

When a small amount of Gram-negative lipopolysaccharide was intravenously injected into mice which had been injected with heat-killed Propionibacterium acnes 7 days before, massive hepatic cell necrosis was induced and most of the mice died 24 hr later. However, when prostaglandin E1 was administered with lipopolysaccharide, remarkable improvements in the survival rate and in the histological changes of the liver were observed. In order to find out how prostaglandin E1 suppressed the induction of massive hepatic cell necrosis in this experimental model, we studied the effects of prostaglandin E1 on the activation of liver adherent cells, from which the cytotoxic factor is released, and on the protection of hepatocytes from the cytotoxic factor. As a result, prostaglandin E1 not only inhibited the activation of liver adherent cells and suppressed the release of the cytotoxic factor, but it also directly affected the hepatocytes and protected them from the cytotoxic factor.

Protection of liver cells against experimental damage by extract of cultured Lentinus edodes mycelia (LEM)

Liver cell damage can be induced when isolated liver cells coated with specific antibodies against the liver cell membrane are cultured with peripheral blood mononuclear cells. Although this antibody-dependent cell-mediated cytotoxicity (ADCC) is dependent on the close contact of effector cells with target cells via specific antibodies, a cytotoxic factor or factors causing the inhibition of protein synthesis in liver cells has been detected in the culture supernatant from the ADCC reaction. Similarly, peritoneal exudate macrophages activated by endotoxin lipopolysaccharide also exert cytotoxic effects on isolated liver cells by production of a cytotoxic substance or substances. The liver cell damage caused by either the ADCC or activated macrophage culture supernatants were significantly reduced by pretreating the isolated liver cells with the extract of cultured Lentinus edodes mycelia (LEM). These results suggest that LEM may protect liver cells from immunological damage.

Inhibitory effect of TJN-101 ((+)-(6S,7S,R-biar)-5,6,7,8-tetrahydro-1,2,3,12-tetramethoxy -6,7-dimethyl-10,11- methylenedioxy-6-dibenzo[a,c]cyclooctenol) on immunologically induced liver injuries

TJN-101, which is a lignan component isolated from schisandra fruits, inhibits hepatotoxic chemicals-induced liver injuries. In this study, effects of TJN-101 on immunologically induced liver injuries were investigated in vivo and in vitro. When a small dose of lipopolysaccharide was injected into mice previously injected with heat-killed Propionibacterium acnes, most of the animals died with acute hepatic failure which was produced by cytotoxic factors from activated adherent cells, and liver cells were injured by antibody-dependent cell-mediated cytotoxic (ADCC) reaction or activated macrophages in vitro. TJN-101 reduced the mortality of the mice with acute hepatic failure dose-dependently. Histologically, necrosis was suppressed by the treatment of TJN-101, but infiltration of non-specific inflammatory cells was not. TJN-101 inhibited the isolated liver cell injuries induced by ADCC reaction or activated macrophages in vitro. These results suggest that TJN-101 can be markedly protective against immunological liver injuries.

Cytological and quantitative cytochemical changes in the hepatocyte population of newborn rats following hydrocortisone administration

Changes have been assessed in cytological and quantitative cytochemical parameters of the hepatocyte population of newborn rats under glucocorticoid stimulation. Administration of hydrocortisone-acetate at the dose of 25 micrograms/g b.w./d during the 2nd week of postnatal life, caused: 1. an increase of the liver weight and of average dry mass, protein content, and volume of the hepatocytes; 2. a decrease of the number of hepatocytes per mg of liver tissue; 3. a reduction of the mitotic activity in liver parenchyma; 4. a gain in number of hepatocytes per liver lower than under normal conditions; 5. an increase of frequency of binuclear cells; 6. an increase of DNA-Feulgen per hepatocyte nucleus; 7. an increase per cell, greater than the mean protein increase per cell, in activity of arylhydrocarbonmonooxygenase and 7-ethoxycoumarin 0-deethylase, 2 enzymes dependent on cytochrome P-450. Induction of arylhydrocarbonmonooxygenase activity was prevalent in centrolobule. All the examined parameters, except that of DNA-Feulgen per nucleus and that of mitotic activity, changed strictly correlated with the duration of hormonal treatment. The values of a number of hepatocyte parameters (particularly: mean cell dry mass and volume, frequency of binuclear cells, enzymic activity) detected in the 12 d old rats after a 5 d long hormonal pretreatment, were in the range of those of animals 1 to 2 weeks older.

Changes in methionine metabolism induced by D-galactosamine in isolated rat hepatocytes

We studied several steps of methionine metabolism in isolated rat hepatocytes both with and without the presence of a hepatotoxic agent (D-galactosamine). By use of selective labelling either on methyl or on carboxyl groups, we showed that intracellular methionine is used preferentially for the methylation of phospholipids (42%) and nucleic acids (31%) via S-adenosylmethionine. In the presence of D-galactosamine, the incorporation of L-(14CH3) methionine into macromolecules is significantly inhibited (greater than 50%). This inhibition is associated with a decrease of S-adenosylmethionine and an increase of methionine in the injured cells. These results suggest that hepatotoxicity of galactosamine may be due in part to an inhibition of the methylation of nucleic acids and phospholipids. Consequently, we hypothesize that hypermethioninemia associated with human liver disease could be due, at least partly, to a defect in synthesis and/or utilization of S-adenosylmethionine by hepatocytes.

Protection of liver cells from experimentally induced liver cell injuries by tritoqualine

Liver cell damages were inducible, when isolated liver cells coated with specific antibody against the liver cell membrane were cultured with peripheral blood mononuclear cells. Although this antibody-dependent cell-mediated cytotoxicity (ADCC) was induced by the closed contact of effector cells to targets via the specific antibody, a cytotoxic factor or factors causing the inhibition of protein synthesis in the liver cells was detected in the culture supernatant of the ADCC reaction. Similarly, peritoneal exudate macrophages activated by endotoxin lipopolysaccharide also exerted cytotoxic effects on the isolated liver cells by producing a cytotoxic substance or substances. These liver cell injuries induced by either the ADCC or activated macrophage culture supernatant were significantly reduced, when the isolated liver cells were pretreated with tritoqualine before adding the cytotoxic culture supernatants. These results suggest that tritoqualine may protect liver cells from immunological injuries.

The distribution of cytochrome P-450-mediated drug oxidation and glutathione in periportal and perivenous rat hepatocytes after phenobarbital treatment

The effect of phenobarbital pretreatment on acinar distribution of microsomal drug metabolizing enzymes was investigated by analysis of periportal (pp) and perivenous (pv) enriched rat hepatocytes isolated by collagenase gradient perfusion. In untreated animals the activities of cytochrome P-450, NADPH-cytochrome c reductase and microsomal ethanol oxidation were significantly higher in pv cells. Phenobarbital produced a 45% increase of the yielded microsomes related to the hepatocytic protein but did not change their relative distribution. The content of reduced glutathione (GSH) was lower in hepatocytes from the pv area. The GSH content was more than 20% increased after phenobarbital treatment in both subclasses of cells, but the distribution pattern remained unchanged. The higher activity of drug metabolizing enzymes in the pv area of untreated animals may account for the higher cytotoxicity of numerous drugs to the perivenous hepatocytes. A 3-day treatment with phenobarbital equalized the pp-pv difference by producing more induction of the periportal cytochrome P-450-mediated drug and ethanol oxidation capacities in microsomes derived from periportally enriched hepatocytes.

The availability of different sources of cholesterol for bile acid synthesis by cultured chick embryo hepatocytes

The availability of different sources of cholesterol for bile acid synthesis by cultured chick embryo hepatocytes was studied. Mevalonolactone was taken up by the cells and converted to cholesterol, cholesterol ester and tauroconjugates of bile acids. The addition of mevalonolactone had little effect on the conversion of endogenous cholesterol to taurocholic acid; however, taurochenodeoxycholic acid synthesis was stimulated. 25-30% of the cholesterol synthesized from mevalonolactone was converted to taurochenodeoxycholic, taurocholic and two so-far unidentified bile acids. All bile acids were secreted into the incubation medium. When cholesterol was added as mixed liposomes with phosphatidylcholine, it was taken up by the cells and converted to bile acids. At low concentrations of liposomes, the greater part of the cholesterol which was taken up by the cells was converted to bile acids. At higher concentrations, considerable amounts of cholesterol and cholesterol ester accumulated inside the cells. When mevalonolactone and cholesterol liposomes was added together, both substrates were used simultaneously for bile acids synthesis. HDL cholesterol was the best substrate tested, yielding large amounts of two, so-far, unidentified bile acids (possibly allo-bile acids) and smaller amounts of taurocholic and taurochenodeoxycholic acid. Addition of HDL suppressed the conversion of endogenous cholesterol to taurocholic acid; taurochenodeoxycholic acid synthesis, however, was stimulated.

Mechanically isolated hepatocytes are unsuitable to detect antibodies directed against plasma membrane determinants

The ultrastructural morphology of mechanically and enzymatically isolated hepatocytes was compared. Plasma membrane integrity was evaluated by electron microscopy, both in the absence and in the presence of ruthenium red, which stains cell coat glycoproteins and makes it possible to identify even partially permeable cells, and by indirect immunofluorescence using experimental antibodies directed against epithelial submembranous components (prekeratin, actin). In order to evaluate the antigenic integrity of the hepatocellular plasma membrane after the isolation procedures, an immuno-electronmicroscopical technique (Staph. pA-colloidal gold) was applied using the IgG fraction from two liver-kidney microsomal antibody (LKM) positive sera, known to react with both plasma membranes and smooth endoplasmic reticulum (SER). Enzymatic procedure made it possible to isolate hepatocytes with a good preservation of both plasma membranes and subcellular organelles. Ruthenium red staining was confined to plasma membranes, thus indicating the preservation of both cell-coat glycoproteins and plasma membrane. Most cells were negative after exposure to experimental antibodies. After exposure to LKM positive sera colloidal gold was strictly confined to the plasma membrane. On the other hand, mechanically isolated hepatocytes showed wide interruptions of the plasma membrane and gross alterations of subcellular organelles. Most cells were stained by ruthenium red, thus confirming the plasma membrane permeability. In addition, a linear peripheral positivity was found in the vast majority of the cells tested with anti-prekeratin and anti-actin antibodies. LKM-colloidal gold complexes were found at the level of both residual plasma membrane and SER.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of ethanol metabolism in isolated periportal or perivenous hepatocytes: effects of chronic ethanol treatment

Ethanol metabolism in rat hepatocytes isolated either from the periportal (pp) or the perivenous (pv) area by collagenase gradient perfusion was compared to reveal metabolic factors that could be associated with the development of perivenous alcoholic liver damage. Cells were also isolated from rats given ethanol (E) chronically by addition to the drinking fluid. One group (EM) received in addition the alcohol dehydrogenase inhibitor 4-methylpyrazole, which potentiated the ethanol treatment by causing sustained elevated diurnal blood ethanol levels. Fatty degeneration ensued in only one-third of the E rats but in all of the EM rats. The periportal/perivenous activity distributions of alanine aminotransferase (ALAT) and glutamate dehydrogenase (GLDH) were 2.2 and 0.75, respectively. Both ethanol treatments significantly decreased the ALAT and increased the GLDH activities, but did not change their pp/pv distributions. Ethanol treatment also increased ethanol and acetaldehyde oxidation, but to the same extent in pp and pv cells. The increase was more marked in cells from EM rats despite their more severe liver fatty degeneration. Ethanol incubation also increased the lactate/pyruvate ratio to the same extent in pp and pv cells both from control or ethanol-treated rats. Our results indicate that periportal and perivenous hepatocytes convert ethanol via acetaldehyde to acetate equally well and with similar effects even after chronic ethanol treatment. Consequently, preferential damage of the perivenous area after chronic ethanol intake is not caused by inherent or acquired differences in ethanol metabolism between perivenous and periportal hepatocytes. Rather, sinusoidal gradients only established in the intact liver may exaggerate the metabolic imbalance by ethanol in the perivenous area, thus explaining its greater vulnerability to damage by alcohol abuse.

Protection of liver cells from experimentally induced liver cell injury by glycyrrhizin

Liver cell damage is induced when isolated liver cells coated with specific antibody against the liver cell membrane are cultured with peripheral blood mononuclear cells. Although this antibody-dependent cell-mediated cytotoxicity (ADCC) was induced by closed contact of effector cells with targets via specific antibody, a cytotoxic factor or factors causing inhibition of protein synthesis in liver cells was detected in the culture supernatant of the ADCC reaction. Similarly, peritoneal exudate macrophages activated by endotoxin lipopolysaccharide (LPS) also had cytotoxic effects on isolated liver cells by producing a cytotoxic substance or substances. These liver cell injuries caused by either ADCC or activated macrophage culture supernatants were significantly reduced by pretreatment of the isolated liver cells with glycyrrhizin before the addition of the cytotoxic culture supernatants. These results suggest that glycyrrhizin may protect liver cells from immunological injuries.

Insulin-responsive cultured foetal-rat hepatocytes. Their preparation and characterization

An improved non-perfusion method for the preparation of cultured foetal-rat hepatocytes is described. Digestion of the liver with collagenase and deoxyribonuclease I gave yields of 40 X 10(6) hepatocytes/g of liver. The plating efficiency of hepatocytes in medium with 10 microM-cortisol was 50%. Cell morphology and metabolism were maintained through 3 days of monolayer culture, with minimal contamination by haematopoietic cells or fibroblasts. The cultured cells bound and degraded 125I-insulin in a time- and dose-dependent manner. The estimated ED50 for competitive binding at 37 degrees C was 1.1 nM. Curvilinear Scatchard plots were observed, with estimates of 16 500 high-affinity sites (Kd = 813 pM) and 53 000 low-affinity sites (Kd = 23 nM) per cell. The cultured cells demonstrated a glycogenic response to insulin, with an estimated ED50 of 120 pM. The degree of glycogenic response to insulin varied with time in culture: 500% above basal on day 1, 200% on day 2, and only 150% on day 3. Cultured foetal cells also exhibited a time-dependent uptake of 2-aminoisobutyric acid, which, in contrast with previous reports with adult cells, was not stimulated by the presence of 10 nM-insulin. Cultured foetal hepatocytes may provide an interesting model with which to study the relationship between insulin-receptor binding and insulin action.

Isolation, culture and characterization of adult human hepatocytes from surgical liver biopsies

A technique is described for isolation and culture of adult human hepatocytes from surgical liver biopsies. The mean cell yield was 1.75 X 10(7) cells per gm liver and viability averaged 80%. Hepatocytes were maintained in primary culture for about 10 days. Cell morphology and histochemical characteristics were similar to hepatocytes in vivo. Bile canaliculi were observed by electron microscopy. Intracellular albumin was demonstrated up to the 7th day of culture; albumin secretion rate was maximal (0.6 +/- 0.33 micrograms per hr per 10(6) cells) 5 days after plating. These studies demonstrate that adult human hepatocytes can be isolated from surgical biopsies with high yield, and differentiated function can be maintained for several days.

The effect of chronic ethanol ingestion on ethanol metabolizing enzymes in isolated periportal and perivenous rat hepatocytes

Periportal (pp) and perivenous (pv) hepatocyte populations were separated using a two-directional closed perfusion technique with selective addition of collagenase either to direct or retrograde perfusions (Väänänen, H. et al., Liver 1983; 3:131). The activity of GPT in hepatocytes from the pp-area was 1.9 times higher than in cells from the pv-area (p less than 0.01). The distribution of glutamate dehydrogenase and pyruvate kinase activities was reversed; pp/pv ratios of 0.7 and 0.5, respectively, were observed (p less than 0.001, p less than 0.05). Chronic ethanol consumption for 12 weeks (mean daily ethanol intake 11.4 gm per body weight corresponding to 29% of total energy intake) did not cause histological changes but decreased GPT activity, increased glutamate dehydrogenase and pyruvate kinase activities and did not alter their pp/pv distribution. Alcohol dehydrogenase and aldehyde dehydrogenase activities were evenly distributed in pp- and pv-hepatocytes. Chronic ethanol treatment slightly decreased alcohol dehydrogenase activity (p less than 0.05) and increased the activity of low Km aldehyde dehydrogenase (p less than 0.001, p less than 0.05). The specific activity of NADPH-dependent microsomal ethanol oxidation was 50% higher in pv-hepatocytes (p less than 0.05). Chronic ethanol treatment did not increase the specific activity of microsomal ethanol oxidation but reduced the pp-pv activity difference. The results indicate that the enzymatic capacity to oxidize ethanol is evenly distributed in the acinus and that, after long-term moderate ethanol treatment, despite lack of parenchymal lesions, changes in the activity of enzymes involved in ethanol metabolism are observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Methionine metabolism and ultrastructural changes with D-galactosamine in isolated rat hepatocytes

The biochemical and morphological effects of 2, 10 and 100 mM of D-galactosamine (GalN) were studied in isolated rat hepatocytes during 2 h of incubation. Lactate dehydrogenase (LDH), alanine aminotransferase (ALAT) and cell viability did not change, whatever the concentration used. The variations observed, which were dose dependent, included a large drop in ATP levels and inhibition of RNA and protein synthesis. A very high concentration of GalN was necessary, however, to induce a significant decline in methionine adenosyltransferase activity compared to control cells. The use of L-[methyl-14C]methionine during cell incubation with GalN demonstrated a decrease of S-adenosyl-L-methionine (SAMe) and an accumulation of L-methionine content related to the GalN concentration. These results suggested that an hepatotoxic agent such as GalN was able to induce disturbances of methionine metabolism. Some of the ultrastructural changes observed were different from those previously found in vivo, in rats given GalN intraperitoneally, underlining the marked difference between in vivo and in vitro intoxication.

Lipid peroxide formation in isolated hepatocytes by cytotoxic factors produced from lymphokine-activated macrophages

When peripheral blood lymphocytes from patients with chronic active hepatitis were stimulated with liver specific lipoprotein (LSP), considerably higher frequencies of lymphocyte transformation and MIF production were induced. Peritoneal macrophages from guinea pigs were activated by lymphokine-containing lymphocyte culture supernatant and produced a cytotoxic (or cytostatic) factor acting on isolated hepatocytes in culture. The cytotoxic (or cytostatic) factor, which was fractionated by Sephadex G-75 column gel filtration followed by DEAE-cellulose column chromatography, had cytotoxic effect on isolated liver cells and produced a significant amount of lipid peroxide. These results suggested the possibility that the cytotoxic effects may be caused at least partially by the lipid peroxide formation.

Induction of liver cell injury by antibody-dependent monocyte-mediated cytotoxicity in vitro

The isolated liver cells coated with the anti-liver cell membrane antibody were damaged by incubation with the peripheral blood mononuclear cells. This was demonstrated by measuring the reduction of protein synthesis in the target liver cells. Adherent cells from the peripheral blood mononuclear cells were shown to have a sufficient capacity acting on the isolated liver cells as an effector when they were separated from the peripheral blood of normal and patients with acute or chronic active hepatitis. However, those from patients with liver cirrhosis or hepatoma did not show such effector activity in antibody-dependent cell-mediated liver cell damage. These results suggest that possibly antibody-dependent macrophage-mediated cytotoxicity may play some role in the induction of liver cell injury because the anti-hepatocyte membrane antibody is frequently detected in patient's sera, especially in those with chronic active hepatitis.

Metabolic capability of rat hepatocytes isolated by perfusion and tissue slice techniques

The metabolic capability of hepatocytes prepared by the perfusion method (P cells) and the tissue slice method (S cells) has been compared using standardised procedures. Yields of P cells were four times greater than for S cells. Trypan blue exclusion viability and oxygen utilization were similar although the viability of S cells deteriorated faster with time. P cells had a lower endogenous rate of glycogenolysis and showed better glucagon stimulation than S cells. Similarly, P cells performed gluconeogenesis at a higher rate. However, there was no significant differences in the metabolism of the xenobiotic ethoxycoumarin. It is concluded that while S cells are probably satisfactory for studies of drug metabolism their use for work involving surface receptor binding and energy demanding processes should be questioned.

Studies on the mechanism of liver injury by macrophage-mediated cytotoxicity--partial purification of cytotoxic factor detected in the culture supernatant of activated macrophages

The culture supernatant of activated lymphocytes was shown to contain macrophage activating factor (MAF), a kind of lymphokine, which activated the peritoneal macrophages prepared from guinea pigs. When the culture fluid of the MAF-activated macrophages was added to the isolated liver cells, a significant inhibition of their albumin biosynthesis was demonstrated. The active material was recovered in a definitive fraction by gel filtration using a Sephadex G-75 column and this was further fractionated into two fractions by DEAE-cellulose column chromatography, suggesting that at least two kinds of active substances existed. By isoelectric focusing electrophoresis it was shown that these two active principles were substances having different isoelectric points, by isoelectric focusing electrophoresis. These results suggest that some cytotoxic or cytostatic materials are produced from the lymphokine-activated macrophages and they may participate in the occurrence of liver injury at least partially.

Studies on the mechanism of liver injury by antibody-dependent cell-mediated cytotoxicity (ADCC)--partial purification of cytotoxic factor detected in the culture supernatant of ADCC reaction

Liver cell damage is inducible when isolated liver cells coated with the specific antibody against the liver cell membrane are cultured with peripheral blood mononuclear cells. Moreover, a cytotoxic material (or materials) causing an inhibition of protein synthesis in liver cells was detected in culture supernatant of these antibody-dependent cell-mediated cytotoxicity (ADCC) reactions. By gel filtration using a Sephadex C-75 column, the active material (materials) was recovered in a definitive fraction and was further fractionated into two portions by DEAE-cellulose column chromatography. These active principles were shown by isoelectric focusing electrophoresis to be different substances from each other. These results suggest that some cytotoxic or cytostatic materials are produced in consequence of ADCC reaction and these may cause liver injury.

Isolation and culture of adult hepatocytes from liver biopsies

Hepatocytes were isolated from liver biopsies of rats, guinea pigs, rabbits, dogs, and humans. The procedure is based on cannulation of large veins in the cut face of the biopsy, followed by collagenase perfusion. Yields averaged 19 x 10(6) viable hepatocytes/g liver. Viability averaged 84%, as determined by trypan blue dye exclusion. Cultures were prepared from the isolated hepatocytes and were found to be comparable in morphology and N-demethylase activity to hepatocyte cultures prepared by the in situ perfusion of the liver. The development of this method should facilitate comparative studies of the cytotoxicity, genotoxicity, and metabolism of foreign chemicals in primary hepatocyte cultures.

Amino acid transport and rubidium-ion uptake in monolayer cultures of hepatocytes from neonatal rats

Amino acid and K(+) transport during development has been investigated in hepatocyte monolayer cultures with either alpha-amino[1-(14)C]isobutyrate or (86)Rb(+) used as a tracer for K(+). Parenchymal cells from neo- and post-natal rat livers have been isolated by an improved non-perfusion technique [Bellemann, Gebhardt & Mecke (1977)Anal.Biochem.81, 408-415], and the resulting hepatocyte suspensions purified from non-hepatocytes before inoculation. In the presence of Na(+) (Na(+)-dependent component), the rates of amino acid uptake in neonatal hepatocytes were markedly enhanced compared with cells from 30-day-old rats. When Na(+) was replaced by choline (Na(+)-independent component) the accumulation of alpha-aminoisobutyrate was decreased and it was not affected by the age of the animals. Kinetic analysis of Na(+)-dependent alpha-aminoisobutyrate transport revealed the existence of a high-affinity low-K(m) component (K(m)0.91mm) with a V(max.) of 2.44nmol/mg of protein per 4min, which later declined gradually with progressive development. Rates of Rb(+) transport were concomitantly enhanced in neonatal hepatocytes and thereafter declined with postnatal age. The increased Rb(+) influx was effectively inhibited by ouabain and reflected elevated activity of the electrogenic Na(+)/K(+)-pump during early stages of development. Kinetic evaluation of the enhanced rates of Rb(+) uptake indicates multiple and co-operative binding sites of the enzyme involved in the Rb(+) uptake, and the transport system is positively co-operative (the Hill coefficient h is >1.0). In short, amino acid transport in neonatal rat hepatocytes is increased as a result of an existing low-K(m) component for the Na(+)-dependent alpha-aminoisobutyrate uptake, which endows the hepatocytes with a high capability for concentrating amino acids at low ambient values. The concomitant enhancement of K(+) transport reflects changes in the electrochemical gradient for Na(+) across the hepatocellular membrane and, along with this, presumably alterations in the membrane potential; the latter might be the driving force for the enhanced alpha-aminoisobutyrate transport in the alanine-preferring system during postnatal age.

The possible involvement of Kupffer cell-mediated hepatocytotoxicity in the pathogenesis of liver injuries

The possible involvement of cell-mediated immune response to liver specific lipoprotein (LSP) in the pathogenesis of liver injury was investigated. The subjects were consisted of one patient with acute hepatitis, five cases with chronic active hepatitis and one case with chronic failure inactive hepatitis. When peripheral blood lymphocytes from these patients were cultured in the presence of LSP and lymphocyte transformation was determined by measuring the uptake of [3H]-thymidine into the acid-insoluble materials, positive blastogenesis was seen in three cases with chronic active hepatitis. Furthermore, when peripheral blood lymphocytes from halothane-induced cholestatic hepatitis were cultured with offending drug in the presence of LSP and lymphocyte transformation was determined, a positive blastogenesis was seen. The factor which activated Kupffer cells (KCAF), a kind of lymphokine, was also detectable in the culture medium of activated lymphocytes from four patients who showed positive blastogenesis by estimating [3H]-glucosamine incorporation into Kupffer cells. The macrophage activating factor (MAF) was detectable in culture medium of activated lymphocytes from three patients who showed positive blastogenesis by estimating [3H]-glucosamine incorporation into macrophages. Furthermore, the KCAF-activated Kupffer cells and MAF-activated macrophages were shown to be cytotoxic for the isolated liver cells causing marked inhibition of albumin synthesis. The observations suggest that Kupffer cell-mediated cytotoxicity and macrophage-mediated cytotoxicity play a role in the pathogenesis of liver disease.

Isolation and primary culture of adult human hepatocytes. Ultrastructural and functional studies

Biopsy tissue of adult human liver was gently dissociated with collagenase followed by Dispase. By repeated low g centrifugation, a large number of almost pure, viable hepatocytes was obtained. This is the first report of a successful procedure for obtaining adult human hepatocytes for study in tissue culture. The isolated cells have the typical morphology of liver parenchyma, and these characteristics persist throughout the period of culturing. Evidence of their function is indicated by albumin synthesis. This procedure is now being used to study human hepatocyte functions in vitro and the effects of a variety of agents including carcinogens and viruses.

Immunological studies on the drug-induced allergic hepatitis

The possible involvement of cell-mediated immunity in the pathogenesis of drug-induced allergic hepatitis was investigated in 21 patients; 6 patients with cholestasis, two cases with the hepatitis resembling viral hepatitis and 13 cholestatic hepatitis. The peripheral blood lymphocytes from all these patients showed the positive lymphocyte transformation and MIF production when stimulated by the offending drug in the presence of liver specific lipoprotein. By injection of the culture medium prepared from activated lymphocytes into mesenteric vein of rat, a marked reduction of bile flow and bile acid secretion was observed in 12 cases among 17 patients tested. Active material which caused the reduction of bile flow was fractionated by a gel filtration and was identified to have similar molecular size to MIF. Morphologically, a dilated bile canaliculus with diminution of microvilli and vesicles around the dilated bile canaliculus were observed by an electron microscopy after injection of culture supernatant or their fractionated material into mesenteric vein of rat. No such changes could be seen in rats by administering the supernatant of lymphocytes from normal individuals prepared as above. Macrophage activating factor (MAF), a kind of lymphokines, was also detected in the culture medium of activated lymphocytes from seven patients among eight cases tested. The MAF-activated macrophages were shown to exhibit a cytotoxic effect on the separated liver cells by judging from the inhibition of albumin biosynthesis. Moreover, the antibody-dependent cell-mediated cytotoxic reaction as well as lymphocyte-mediated cytotoxicity were also demonstrated in three cases among nine patients tested. These observations suggest that diverse immune reactions were possible correlated to the pathogenesis of the drug-induced allergic hepatitis although their exact participation or relative significances are remained to be elucidated.

The use of antiserum with specific reactivity toward fat-cell surface antigen(s) to follow the progression of 3T3-L1 preadipocyte differentiation in vitro

Using an indirect, labelled-second-antibody cellular immunoassay technique, an adipocyte-specific antiserum has been investigated. Components of the antiserum were shown to bind to differentiated 3T3-L1 cells; the cellular capacity for binding increased progressively during the induced differentiation of these cells in vitro.

Primary monolayer culture of liver parenchymal cells and kidney cortical tubules as a useful new model for biochemical pharmacology and experimental toxicology. Studies in vitro on hepatic membrane transport, induction of liver enzymes, and adaptive changes in renal cortical enzymes

Freshly isolated liver parenchymal cells were maintained in either short-term monolayer, suspension of long-term monolayer culture. Rapidly occurring processes through hepatocellular membrane, e.g., the enhanced amino acid transport and the concomitantly increased potassium influx following progressive starvation, were kinetically evaluated best in short-term monolayer culture. The inducibility of tyrosine aminotransferase by glucagon, dexamethasone, and a combination of both was compared in suspension and in monolayer culture. The induction of slowly inducible foreign compound-metabolizing enzymes, (e.g., ethoxycoumarin-O-dealkylase, p-nitroanisole-O-demethylase, and UDP-glucuronyltransferase) by phenobarbital, 3-methylcholanthrene, and dexamethasone were studied in long-term monolayer culture. The latter system was also used to maintain isolated kidney cortical tubules for the investigation of renal enzyme adaptation during progressive time in culture.

Immunological studies on drug-induced allergic hepatitis--hepatocellular injury by macrophage-mediated cytotoxicity

When the peripheral blood lymphocytes from patients with drug-induced allergic hepatitis were stimulated with a specific drug in vitro in the presence of a liver cytosol fraction containing liver specific antigen, lymphocyte transformation was seen in eight out of 11 patients. The macrophage activating factor (MAF), a kind of lymphokines, was also detectable in the culture medium of activated lymphocytes from seven out of eight patients who showed positive blastogenesis evaluated the uptake of 3H-glucosamine into macrophages. MAF-activated macrophages exhibited a cytotoxic effect on separated liver cells resulting in a marked inhibition of albumin synthesis. This macrophage-mediated cytotoxicity was also observed in eight out of 11 patients who showed positive lymphocyte transformation. These observations suggest that macrophage-mediated cytotoxicity may play some role in the pathogenesis of drug-induced allergic hepatitis.

Evaluation of hepatocytes isolated by a nonperfusion technique in a prescreen for cytotoxicity

Twenty-three chemicals, differing widely in cytotoxic (hepatotoxic) potency in vivo, were examined to determine their ability to release glutamic-oxaloacetic transaminase (GOT) from hepatocytes isolated by a nonperfusion method from rat liver. The test chemicals were carbon tetrachloride, chloroform, 1,1,2- and 1,1,1-trichloroethane, six bromobenzene analogs, tri-n-butyl tin, chlorpromazine, tetracycline, halothane, phenobarbital, L-ethionine, acetaminophen, thioacetamide, allyl alcohol, ethanol, ascorbic acid, dimethyl sulfoxide, and acetone. In all but two cases--thioacetamide and allyl alcohol--there was a good correspondence between chemicals active in the assay as now performed and those that elevate serum transaminase and cause liver injury on short-term exposure in vivo. These results indicate that with further effort it may be possible to develop an effective, inexpensive, and rapid prescreen to identify drugs and environmental chemicals that are potentially cytotoxic to animals and humans.