PubMed Health⌕ Search

Biomedical subjects

J J Lemasters

Publications and source records attributed to J J Lemasters.

At least 109 records · Page 6Linked to original sources
PubMed1995

Role of Kupffer cells in reperfusion injury in fat-loaded livers from ethanol-treated rats.

Reperfusion injury was studied in blood-free perfused livers from fat-loaded, ethanol-treated rats. Rats were pair-fed a modified Lieber-DeCarli liquid diet containing 36% calories as ethanol or isocaloric maltose-dextrin for 4 to 5 weeks. Reperfusion injury to the liver, which occurs in previously hypoxic regions upon reintroduction of oxygen, was studied in a low-flow, reflow perfusion model. Lactate dehydrogenase in effluent perfusate increased from basal levels of < 1 to 17 IU/g/h in livers from controls, whereas prior alcohol treatment elevated values to 37 IU/g/h. Pretreatment of rats with gadolinium chloride (GdCl3, 20 mg/kg i.v.), a selective Kupffer cell toxicant, minimized lactate dehydrogenase release during reperfusion to 7 to 8 IU/g/h in livers from both groups. Rates of malondialdehyde production were 144 and 166 nmol/g/h during reperfusion in control and alcohol-treated rats, respectively, but values reached only 54 and 79 nmol/g/h after GdCl3 treatment. Interestingly, a typical PBN/carbon-centered free radical adduct signal was detected in bile of livers from ethanol-treated rats, but not in controls or ethanol-treated rats given GdCl3. Portal pressure increased during the reperfusion period in livers from alcohol-treated rats, although not in controls, and GdCl3 reduced it significantly. Taken together, these data indicate that reperfusion injury is greater in fatty livers from alcohol-treated rats in a blood-free model. Inactivation of Kupffer cells minimized reperfusion injury in both control and alcohol-treated rats, most likely by diminishing lipid peroxidation thereby improving hepatic microcirculation.

Animals↗
PubMed1994

Evidence that activation of Kupffer cells increases oxygen uptake after cold storage.

Fasting for long periods of time has previously been shown to increase survival following liver transplantation. The experiments reported here were designed to study the mechanism of this phenomenon. Livers stored in cold Euro-Collins solution for 16 hr were perfused subsequently for 3 hr. Oxygen uptake increased slowly, reaching maximal values after about 80 min of reperfusion. This increase in oxygen uptake was significantly greater in livers from fed rats (73 mumol/g/hr) than in livers from either 4-day fasted rats (42 mumol/g/hr) or from rats where Kupffer cells were inactivated by gadolinium chloride treatment (30 mumol/g/hr). Thus, it is likely that the increase in oxygen uptake involves activation of Kupffer cells on reperfusion. Therefore, carbon uptake, which is due predominantly to phagocytosis by Kupffer cells, was monitored in the perfused liver. Carbon uptake was increased significantly in livers from fed rats at 80 compared with 20 min of perfusion. Further, carbon uptake was diminished significantly by long-term fasting and gadolinium chloride treatment. These results indicate that oxygen uptake increases in parallel with activation of Kupffer cells in livers from fed rats and support the hypothesis that activated Kupffer cells produce factors that stimulate oxygen uptake after cold storage. In further support of this hypothesis, the observed increase in oxygen uptake was diminished when the flow rate was increased. Because mediators would be diluted as the flow rate was increased, this result is consistent with the hypothesis that oxygen uptake depends on chemical mediators released from Kupffer cells. When livers were perfused with indomethacin, a prostaglandin synthesis inhibitor, the increase in oxygen uptake observed in fed rats was reduced by 34%. Further, in livers perfused under hypoxic conditions using a low-flow model, lactate dehydrogenase release in livers from fed rats (547 U/g/hr) was significantly greater than in livers from 4-day fasted rats (397 U/g/hr), indicating that fasting increased tolerance to hypoxia. In conclusion, livers of fasted rats require less oxygen during reperfusion, most likely because activation of Kupffer cells on reperfusion is minimized. These findings could explain why survival after transplantation is improved by long-term fasting.

Animals↗
PubMed1994

Activation of Kupffer cells in vivo following femur fracture.

OBJECTIVE: To test the hypothesis that Kupffer cells are activated after blunt femur fracture leading to altered hepatic oxygen (O2) consumption. DESIGN: Prospective randomized experimental trials. SETTING: Laboratory. MATERIALS AND METHODS: Male Sprague-Dawley rats underwent closed femur fracture with associated soft-tissue injury. Control animals received only anesthesia. After 30 minutes and 2 hours, livers were perfused and fixed. Tissue was processed for scanning and transmission electron microscopy. In separate experiments, hepatic O2 consumption was measured in isolated perfused livers 2 and 48 hours after femur fracture using a Clark-type electrode. Oxygen consumption was calculated from the influent-effluent concentration difference, flow rate, and liver weight. RESULTS: In femur-fractured animals, scanning electron microscopy revealed alterations in Kupffer cell surface characteristics, including increases in cell volume and complex foldings and extensions of the plasma membrane. Transmission electron microscopy showed internal vacuolization and dark-staining granule formation. The changes were more pronounced 2 hours after femur fracture. Hepatic O2 consumption increased significantly at both 2 and 48 hours after femur fracture. Morphologic and functional activation of Kupffer cells were not seen in control animals. CONCLUSION: In vivo ultrastructural evidence shows Kupffer cell activation after closed femur fracture. This activation is associated with increased hepatic O2 consumption, which is present at 2 hours and persists 48 hours following injury. The results suggest that Kupffer cell activation may be related to the acute-phase response following trauma.

Animals↗
PubMed1994

A cytotoxicity assay for tumor necrosis factor employing a multiwell fluorescence scanner.

Tumor necrosis factor (TNF) is an important mediator of many biological processes. This study sought to develop a sensitive bioassay allowing quantitative determination of TNF. The assay is based on uptake of the membrane impermeant dye, propidium iodide, by L929 cells when their viability is lost. L929 cells were plated on 96-well plates and cultured overnight in Eagle's minimum essential medium containing 10% horse serum. Propidium iodide (30 microM) was added, and fluorescence was monitored with a multiwell fluorescence scanner using 560-nm excitation and 645-nm emission filters. Human recombinant TNF caused a dose- and time-dependent increase in fluorescence, indicating onset of cell death. Cycloheximide (50 micrograms/ml) and actinomycin D (5 micrograms/ml) sensitized L929 cells to TNF-induced killing. By measuring cell killing early (12 h) and late (30 h), responses proportional to TNF concentration were obtained over a dynamic range of 1 to 5000 pg/ml. These findings serve as the basis for a simple TNF assay that is easy to perform and sensitive over a very broad range of TNF concentrations.

Animals↗
PubMed1994

Distribution of electrical potential, pH, free Ca2+, and volume inside cultured adult rabbit cardiac myocytes during chemical hypoxia: a multiparameter digitized confocal microscopic study.

Exploiting the optical sectioning capabilities of laser scanning confocal microscopy and using parameter-specific fluorescent probes, we determined the distribution of pH, free Ca2+, electrical potential, and volume inside cultured adult rabbit cardiac myocytes during ATP depletion and reductive stress with cyanide and 2-deoxyglucose ("chemical hypoxia"). During normoxic incubations, myocytes exhibited a cytosolic pH of 7.1 and a mitochondrial pH of 8.0 (delta pH = 0.9 units). Sarcolemmal membrane potential (delta psi) was -80 mV, and mitochondrial delta psi was as high as -100 mV, yielding a mitochondrial protonmotive force (delta p) of -155 mV (delta P = delta psi - 60 delta pH). After 30 min of chemical hypoxia, mitochondrial delta pH decreased to 0.5 pH units, but mitochondrial delta psi remained essentially unchanged. By 40 min, delta pH was collapsed, and mitochondrial and cytosolic free Ca2+ began to increase. Mitochondrial and sarcolemmal delta psi remained high. as Ca2+ rose, myocytes shortened, hypercontracted, and blebbed with a 30% decrease of cell volume. After hypercontraction, extensive mitochondrial Ca2+ loading occurred. After another few minutes, mitochondrial depolarized completely and released their load of Ca2+. After many more minutes, the sarcolemmal permeability barrier broke down, and viability was lost. These studies demonstrate a sequence of subcellular ionic and electrical changes that may underlie the progression to irreversible hypoxic injury.

Animals↗
PubMed1994

Novel mechanisms in chemically induced hepatotoxicity.

This review focuses on cellular events that modulate hepatotoxicity subsequent to initial liver insult. Cellular events that determine the nature and extent of hepatotoxic injury and the ultimate outcome of that injury are also discussed. The roles of cell types other than hepatocytes, hepatocyte organelle-specific processes, and regeneration in progression or recovery from liver injury are emphasized. Leukocyte activities are key events in two distinct hepatotoxicities. Neutrophil-mediated, periportal inflammation appears to play a primary role in progression of alpha-naphthylisothiocyanate-induced cholangiolitic hepatitis. However, a humorally mediated autoimmune response to protein adducts that occurs after anesthesia is critical in onset of halothane-induced hepatitis. New insights into specific events at the hepatocyte level are also emerging. Although reducing gap junctional communication between hepatocytes can protect against progression of liver injury, down-regulation of the subunit proteins (connexins) can isolate neoplastic cells from growth regulation. Acidic intracellular pH characteristic of hypoxia is protective against both hypoxic and toxicant-induced cell injury. In oxidative injury, a pH-mediated mitochondrial permeability transition causes mitochondrial uncoupling and ATP loss and leads to cell death. The ultimate outcome of hepatotoxic injury depends on the extent of tissue repair. Stimulation of tissue repair after a sublethal dose of CCl4 appears to be the central mechanism in protection against death from a subsequent large dose. Taken together, these examples illustrate the importance of events subsequent to initial liver injury as determinants of extent of liver damage.

1-Naphthylisothiocyanate↗
PubMed1994

SPC-100270, a protein kinase C inhibitor, reduced hypoxic injury due to reperfusion following orthotopic liver transplantation in the rat.

Recently, we reported that SPC-100270, a sphingosine derivative and inhibitor of protein kinase C (50-90 microM) in mixed micelle assays, reduced reperfusion injury resulting from hypoxia in a low-flow, reflow model of liver perfusion. Here we report that SPC-100270 has similar beneficial effects following liver transplantation in vivo. Rat liver transplantation was performed using nonarterial and rearterial techniques. Livers from syngenic rats were harvested surgically, prepared with vascular cuffs and a splint, and stored for 24 or 48 h in University of Wisconsin (UW) cold storage solution. Just prior to completion of vascular reconstruction, the organ was rinsed with 3 or 10 ml of Ringer's solution, vehicle, or a solution containing SPC-100270 (up to 500 microM). Following implantation surgery, low doses of SPC-100270 were ineffective at reducing both parenchymal and nonparenchymal cell death, yet significant (P < 0.05) reductions were observed with 500 microM. Further, nonparechnymal cell viability was improved nearly four fold by the drug. SPC-100270 (500 microM) tended to increase survival following 48 h cold storage in UW solution, but the improvement was not statistically significant. SPC-100270 also did not diminish carbon-centered free radical formation in transplanted livers from alcohol-treated rats. Collectively, these data support the hypothesis that pretreatment of donor livers with an inhibitor of protein kinase C is effective in vivo at reducing reperfusion injury, particularly to nonparenchymal cells, following orthotopic liver transplantation in the rat.

Adenosine↗
PubMed1994

Kupffer cells participate in rejection following liver transplantation in the rat.

Recognition of foreign antigens involves macrophages which release mediators such as immunoactive interleukins, and in the liver, the resident macrophages (Kupffer cells) are activated following transplantation. Therefore, we evaluated the hypothesis that Kupffer cells participate in the rejection reaction following transplantation. Orthotopic liver transplantation was performed between different syngenic rat strains. Livers from Lewis rats were stored in lactated Ringer's solution for 1 h to minimize cold ischemic injury and transplanted into PVG recipients. At 24 h postoperatively, transaminases (AST) were elevated to values around 2000 U/l, total bilirubin was increased to values around 20 micromol/l, and five of six rats died within 3 days. Macroscopic and histological examination showed large areas of necrosis without cellular infiltration, characteristic of rejection. When donor rats were treated with gadolinium chloride (GdCl3, 10 mg/kg i.v. 24 h before storage of the liver) to inactivate the Kupffer cells, AST levels only rose to around 700 U/l, and the total bilirubin level was in the normal range (< 4 micromol/l). Survival was improved significantly by GdCl3, with five of seven rats surviving more than 1 month (P < 0.05) and four of seven rats surviving for at least 100 days without immunosuppressive drug therapy. Rejection was not totally prevented, however, since the surviving rats had elevated AST and bilirubin levels, and cellular infiltration in portal areas along with proliferation of bile canaliculi was observed. These data are consistent with the hypothesis that Kupffer cells participate in mechanisms of early rejection following liver transplantation.

Animals↗
PubMed1994

High concentrations of adenosine are needed in Carolina rinse to prevent activation of Kupffer cells.

Adenosine is a key component of Carolina rinse solution, which was developed to prevent an O2-dependent reperfusion injury following liver transplantation. Kupffer cells are activated following liver transplantation, an effect minimized by adenosine. In this study, the concentration of adenosine was varied in Carolina rinse, Ringer's, and Ringer's containing hydroxyethyl starch. Following 24 h of cold storage in University of Wisconsin cold storage solution, colloidal carbon uptake was measured to assess phagocytosis by Kupffer cells. Carbon uptake was elevated significantly in this model from values of 136 +/- 15 in unstored control livers to 187 +/- 25 mg/g per hour following a rinse with 10 ml of Ringer's solution. Phagocytosis was reduced about 50% when 0.1 mM adenosine was added to the Ringer's solution; however, addition of up to 1 mM adenosine in Carolina Rinse did not prevent elevated phagocytosis. In contrast, values were reduced significantly by addition of 5-10 mM adenosine to Carolina Rinse or Ringer's containing hydroxyethyl starch. Thus, the higher concentrations of adenosine needed to reduce Kupffer cell activation can best be explained by binding of adenosine to hydroxyethyl starch.

Adenosine↗
PubMed1994

ATP depletion rather than mitochondrial depolarization mediates hepatocyte killing after metabolic inhibition.

The importance of ATP depletion and mitochondrial depolarization in the toxicity of cyanide, oligomycin, and carbonyl cyanide m-cholorophenylhydrazone (CCCP), an uncoupler, was evaluated in rat hepatocytes. Oligomycin, an inhibitor of the reversible mitochondrial ATP synthase (F1F0-adenosinetriphosphatase), caused dose-dependent cell killing with 0.1 microgram/ml being the minimum concentration causing the maximum cell killing. Oligomycin also caused rapid ATP depletion without causing mitochondrial depolarization. Fructose (20 mM), a potent glycolytic substrate in liver, protected completely against oligomycin toxicity. CCCP (5 microM) also caused rapid killing of hepatocytes. Fructose retarded cell death caused by CCCP but failed to prevent lethal cell injury. Although oligomycin (1.0 microgram/ml) was lethally toxic by itself, in the presence of fructose it protected completely against CCCP-induced cell killing. Cyanide (2.5 mM), an inhibitor of mitochondrial respiration, caused rapid cell killing that was reversed by fructose. CCCP completely blocked fructose protection against cyanide, causing mitochondrial depolarization and rapid ATP depletion. In the presence of fructose and cyanide, oligomycin protected cells against CCCP-induced ATP depletion and cell death but did not prevent mitochondrial depolarization. In every instance, cell killing was associated with ATP depletion, whereas protection against lethal cell injury was associated with preservation of ATP. In conclusion, protection by fructose against toxicity of cyanide, oligomycin, and CCCP was mediated by glycolytic ATP formation rather than by preservation of the mitochondrial membrane potential. These findings support the hypothesis that inhibition of cellular ATP formation is a crucial event in the progression of irreversible cell injury.

Adenosine Triphosphate↗
PubMed1994

Changes in shape and viability of cultured adult rabbit cardiac myocytes during ischemia/reperfusion injury.

The goal of this work was to define the distinction between irreversible structural changes and actual loss of cell viability during hypoxic/ischemic/reperfusion injury to one-day cultured adult rabbit cardiac myocytes. Myocytes were exposed to 5 mM NaCN and 20 mM 2-deoxyglucose (chemical hypoxia) or anoxia at pH 6.2 to simulate ischemia. Shortening and hypercontraction (cell rounding and blebbing) were monitored by bright field microscopy, and loss of viability was determined by nuclear labeling with propidium iodide. After both treatments, myocytes began to shorten after 30 minutes, and most were hypercontracted after 3 hours. 50% loss of viability did not occur until after 6 hours or more. To simulate reperfusion, myocytes were washed with fresh aerobic buffer at pH 7.4. Loss of viability was accelerated when cells were reperfused with Krebs-Ringer solution. This cell killing was prevented when myocytes were reperfused with nutrient culture medium instead of Krebs-Ringer solution. Both contracted and hypercontracted cells partially relaxed after reperfusion. These results indicate that structural changes (contraction, hypercontraction and blebbing) to adult cardiac myocytes are distinct from outright cell death caused by plasma membrane failure. Persistence of cell viability suggests that rescue of cardiac myocytes from necrotic cell death may be possible even very late in injury.

Animals↗
PubMed1994

Comparison of peptidoglycan-polysaccharide and lipopolysaccharide stimulation of Kupffer cells to produce tumor necrosis factor and interleukin-1.

Endotoxin (lipopolysaccharide) is a cell wall polymer from gram-negative bacteria that stimulates Kupffer cell release of cytokines such as tumor necrosis factor-alpha and interleukin-1. Another bacterial cell wall polymer in both gram-negative and gram-positive organisms is peptidoglycan-polysaccharide. Lipopolysaccharide and peptidoglycan-polysaccharide exist together in the intestinal lumen and can cross the intestinal mucosa, enter the portal vein and activate Kupffer cells. The purpose of this study was to compare the effects of lipopolysaccharide stimulation and peptidoglycan-polysaccharide stimulation of Kupffer cells on release of tumor necrosis factor-alpha and interleukin-1. Both bacterial polymers caused maximum tumor necrosis factor-alpha release from Kupffer cells after incubation for 4 to 8 hr. Maximum tumor necrosis factor-alpha release induced by 400 ng/ml lipopolysaccharide was 704 +/- 258 pg/ml, compared with 329 +/- 91 pg/ml tumor necrosis factor-alpha after 100 micrograms/ml peptidoglycan-polysaccharide (p < 0.001). Polymyxin B blocked lipopolysaccharide stimulation of tumor necrosis factor-alpha by 95% +/- 5% but blocked peptidoglycan-polysaccharide-stimulated tumor necrosis factor-alpha by 30% +/- 14% (p < 0.001). Repeat incubation of Kupffer cells with lipopolysaccharide after prior lipopolysaccharide incubation induced low tumor necrosis factor-alpha release (tolerance). Repeat incubation with peptidoglycan-polysaccharide induced no tolerance to tumor necrosis factor-alpha release. Incubation of lipopolysaccharide plus peptidoglycan-polysaccharide released less tumor necrosis factor-alpha than did each polymer used alone, but this inhibition was prevented by indomethacin. Dibutyryl cyclic AMP, prostaglandin E1, prostaglandin E2 and the adenosine A2-receptor agonist N-ethylcarboxyamideadenosine inhibited lipopolysaccharide-stimulated tumor necrosis factor-alpha release by 83%, 97%, 90% and 94%, respectively, but inhibited peptidoglycan-polysaccharide-stimulated tumor necrosis factor-alpha release by 52%, 60%, 45% and 51%, respectively (p < 0.001 for each). This indicates that intracellular signaling pathways differ for lipopolysaccharide-stimulated and peptidoglycan-polysaccharide-stimulated tumor necrosis factor-alpha release. After incubation for 8 and 24 hr, 100 micrograms/ml peptidoglycan-polysaccharide had induced significantly more interleukin-1 release from cultured Kupffer cells than had 400 ng/ml lipopolysaccharide (p < 0.001). Lipopolysaccharide induced tolerance to interleukin-1 release after repeat incubation, but peptidoglycan-polysaccharide caused no tolerance. These studies show that peptidoglycan-polysaccharide, a ubiquitous bacterial cell wall polymer, shares several proinflammatory properties with lipopolysaccharide but that there are differences that may have pathophysiological significance.

Animals↗
PubMed1994

Suppression of lipopolysaccharide-stimulated release of tumor necrosis factor by adenosine: evidence for A2 receptors on rat Kupffer cells.

In liver grafts that will fail as a result of storage injury, reperfusion activates Kupffer cells. Overproduction of tumor necrosis factor by activated Kupffer cells may cause primary graft nonfunction, multiple organ failure and, eventually, death of graft recipients. Carolina rinse solution, adenosine, nisoldipine, pentoxifylline and prostaglandin E1 reduce graft failure from storage/reperfusion injury. To test the hypothesis that these agents act by suppressing cytokine release by activated Kupffer cells, we assessed the effect of each drug on tumor necrosis factor released from cultured rat Kupffer cells stimulated with lipopolysaccharide. Adenosine, nisoldipine and prostaglandin E1 each suppressed lipopolysaccharide-stimulated tumor necrosis factor release. The adenosine A2 receptor agonists. 5-n-ethylcarboxamidadenosine, 2-chloro-adenosine and R-phenylisopropyl adenosine also blocked tumor necrosis factor release in a potency suggestive of A2 receptor activity. Xanthine amine congener, a specific A1 receptor antagonist, failed to reverse the suppression by adenosine of tumor necrosis factor release, whereas CGS15943A, an A2 receptor antagonist, did reverse suppression by adenosine and 5-n-ethylcarboxamidadenosine. CGS15943A had no effect on suppression of lipopolysaccharide-stimulated tumor necrosis factor release by nisoldipine or prostaglandin E1. Dibutyryl-cyclicAMP also suppressed tumor necrosis factor release. Adenosine, 5-n-ethylcarboxamidadenosine, prostaglandin E1 and pentoxifylline increased cyclicAMP levels in cultured Kupffer cells, but nisoldipine did not.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine↗
PubMed1993

Development of a new method for hepatic rearterialization in rat orthotopic liver transplantation. Reduction of liver injury and improvement of surgical outcome by arterialization.

The purpose of this study was to develop a simple new method for rearterialization to compare rearterialized and nonarterialized models of liver transplantation in the rat in the same laboratory with the same surgeon. Hepatic rearterialization in the rat was completed by connecting the proper hepatic artery with a splint of polyethylene tubing (PE 10). With this technique, no extrahepatic arteries or modification of other organs was required. Further, the recipient's gastroduodenal artery remained intact to minimize bile duct hypoxia, and the anastomosis was completed rapidly (< 3 min). Postoperative arterial thrombosis and bile duct necrosis occurred with low frequencies with this model (< 15%). For comparison, the nonarterialized model of Kamada was used. With the nonarterialized method, survival of livers stored for 24 hr in cold University of Wisconsin solution was approximately 85% (6/7), whereas survival of livers stored for 48 hr was poor (< 10%; 1/16). Rearterialization improved survival following 48 hr of storage in UW solution from less than 10% to 50% (3/6), and reduced early enzyme release (AST) by about 50%. Rearterialization also reduced enzyme release following 24 hr of cold storage by about 50%. We conclude that this new technique is a simple and reliable method for hepatic artery reconstruction that may be particularly useful in studying the mechanism of primary graft non-function. These data are consistent with the hypothesis that hepatic rearterialization minimizes hypoxic injury to parenchymal cells postoperatively, most likely by increasing oxygen delivery.

Animals↗
PubMed1993

Bacterial cell wall polymers (peptidoglycan-polysaccharide) cause reactivation of arthritis.

Intraperitoneal (i.p.) injection of peptidoglycan-polysaccharide derived from group A streptococci (PG-APS) causes chronic arthritis with spontaneous remissions and exacerbations. We hypothesized that, following i.p. injection, PG-APS released from hepatic stores mediated spontaneous recurrences of arthritis. We tested whether transplanted livers with large amounts of PG-APS were able to reactivate quiescent arthritis. Saline-loaded (group 1) or PG-APS-loaded (group 2) livers were transplanted into rats which had been injected intra-articularly 10 days earlier with PG-APS in one joint and saline in the other. A comparison was made with the arthritis that occurred in rats injected i.p. with PG-APS which did not receive transplants (group 3). Arthritis was monitored by serial measurement of joint diameters. Transplantation of saline-loaded livers (group 1) caused no reactivation of arthritis. However, transplantation of PG-APS-loaded livers (group 2) reactivated arthritis (P < 0.0001). Injection of PG-APS i.p. (group 3) induced the most-severe arthritis. PG-APS levels in plasma decreased with time, and PG-APS accumulated in the spleen in groups 2 and 3. Plasma and hepatic levels of PG-APS in rats injected i.p. with PG-APS were greater than levels in rats transplanted with PG-APS-loaded livers, which in turn were greater than levels in rats with saline-loaded livers. Plasma tumor necrosis factor did not correlate with recurrence of arthritis. Transplantation with PG-APS-loaded livers induced reactivation of arthritis in preinjured joints. The extent of arthritis was proportional to hepatic PG-APS content. Reactivation of arthritis may be mediated by slow release of liver-sequestered PG-APS or cytokines (not tumor necrosis factor) released by the liver.

Animals↗
PubMed1993

Mitochondria as a source of reactive oxygen species during reductive stress in rat hepatocytes.

Cell killing, oxygen consumption, and hydroperoxide formation were determined in rat hepatocytes after glycolytic and respiratory inhibition. These conditions model the ATP depletion and reductive stress of anoxia ("chemical hypoxia"). Glycolysis was inhibited with iodoacetate, and mitochondrial electron transfer was blocked with sodium azide, cyanide, or myxothiazol. Cell killing, hydroperoxide formation, and inhibitor-insensitive oxygen consumption were greater after azide than after myxothiazol or cyanide. Desferrioxamine, an inhibitor of iron-catalyzed hydroxyl radical formation, delayed cell killing after each of the respiratory inhibitors. Anoxia also delayed cell killing during chemical hypoxia. However, during anoxic incubations, desferrioxamine did not delay the onset of cell death. These findings indicate that reactive oxygen species participate in lethal cell injury during chemical hypoxia. In isolated mitochondria, previous studies have shown that myxothiazol inhibits Q cycle-mediated ubisemiquinone formation in complex III (ubiquinol-cytochrome c oxidoreductase) and that ubisemiquinone can react with molecular oxygen to form superoxide. Decreased killing of hepatocytes with myxothiazol compared with azide suggests, therefore, that mitochondrial oxygen radical formation by complex III is involved in cell killing during reductive stress. In support of this hypothesis, myxothiazol reduced rates of cell killing and hydroperoxide formation in hepatocytes incubated with azide or cyanide. This mitochondrial mechanism for oxygen radical formation may be important in relative but not absolute hypoxia.

Animals↗