Deficient Kupffer cell phagocytosis and lysosomal enzymes in the endotoxin-low-responsive C3H/HeJ mouse.

Various substances, including lysosomal enzymes, are produced by Kupffer cells and other macrophages; their release has been implicated in the toxic response to endotoxins. C3H/HeJ mice exhibit little or no response to doses of endotoxin that are lethal in syngeneic C3HeB/FeJ mice. To explore the nature of this deficient response, the Kupffer cells of these mice were studied using in vivo microscopic as well as histochemical and electron microscopical methods. In vivo, the rate of phagocytosis of single 0.8 micron latex particles was measured in individual Kupffer cells as was the number of phagocytic cells per microscopic field. Frozen sections of livers were stained for a variety of lysosomal enzymes and liver specimens also were processed for electron microscopy. In comparison to the endotoxin-sensitive C3HeB/FeJ mice, the livers of the C3H/HeJ mice contained 60% fewer Kupffer cells that phagocytosed latex. However, the rate of phagocytosis by these cells was not statistically different and ranged from 19-26 sec. The volume density of acid-phosphatase-positive Kupffer cells was 40% less in the C3H/HeJ mice. Similar differences were observed with other lysosomal enzymes including cathepsins B and H and dipeptidyl peptidases I and II. However, light and electron microscopy revealed a relatively normal number of Kupffer cells in livers stained for peroxidase, a nonlysosomal enzyme. The results suggest that the insensitivity of C3H/HeJ mice to endotoxin may be related in part to a lysosomal enzyme deficiency and a paucity of phagocytic Kupffer cells in these animals.

The microcirculation during endotoxemia.

The initial responses to endotoxemia are detectable in the microcirculation as a microvascular inflammatory response characterized by activation of the endothelium stimulating these cells from their normal anticoagulant state to a procoagulant state with increased adhesiveness for leukocytes and platelets. Concomitantly, arteriolar tone is lost and reactivity to a variety of agonists is modified. Tissue damage subsequently results not only from reduced perfusion of the exchange vessels, but also from injurious substances released from activated, sequestered leukocytes as well as activated endothelial cells, macrophages, and platelets. This is the result of endotoxins inducing activation and interaction of a number of effector cells, cascades, and acute-phase responses, such as the complement, coagulation, bradykinin/kinin, and hematopoietic systems accompanied by the release of a myriad of mediators. These include eicosanoids, cytokines, chemokines, adhesion molecules, reactive free radicals, platelet-activating factor, and nitric oxide. This paper briefly reviews the microvascular responses to endotoxemia and discusses some of the mechanisms involved.

Ethanol exacerbates hepatic microvascular dysfunction, endotoxemia, and lethality in septic mice.

The effect of acute ethanol administration on the hepatic microvascular responses to sepsis was studied. Polymicrobial sepsis was induced 30 min after mice had received ethanol (1 g/kg b.w.) or isocaloric maltose-dextrin by gastric gavage. Lethality within 24 h was 91.7% in the ethanol-treated animals and 40.0% in septic controls. Endotoxin levels in ethanol treated animals were 107 pg/ml at 6 hr and 1205 pg/ml at 12 h, compared with 32 pg/ml and 104 pg/ml, respectively in the controls. In vivo microscopy revealed that at 3 h in the ethanol treated septic animals, Kupffer cell phagocytic activity was increased by 41%, whereas the number of sinusoids containing blood flow were reduced by 34% concomitant with a 144% increase in the adherence of leukocytes to the sinusoidal walls when compared with the septic controls. By 6 h, however, Kupffer cell phagocytic activity was reduced by 48% in the ethanol treated animals; this was accompanied by a further deterioration in sinusoidal blood flow. Thus, a small, acute dose of ethanol causes significant impairment of the hepatic microcirculation followed by suppression of Kupffer cell activity. This results in exacerbation of endotoxemia and lethality during polymicrobial sepsis.

Effect of immunoglobulin G on the hepatic microvascular inflammatory response during sepsis.

The effects of intravenous immunoglobulin G (ivIG) on the hepatic microvascular inflammatory response to sepsis were studied in rats by in vivo microscopy. High doses of ivIG (300 mg/kg bw) (Sandoglobulin or rat IgG) significantly improved the 48 h survival of septic rats from 25-66% when ivIG was given before or immediately after cecal ligation and puncture. Circulating endotoxin also was significantly reduced. Eight hours after inducing sepsis, the average number of leukocytes adhering to the sinusoidal endothelium increased 15-fold and the average decrease in the number of perfused sinusoids was 22%. IvIG administration minimized these responses. In both septic and nonseptic animals, ivIG also reduced the phagocytic activity of Kupffer cells. The results suggest that high doses of ivIG not only reduce lethality but also limit hepatic microcirculatory dysfunction during sepsis by minimizing leukocyte-endothelial interactions that may be a result of reducing circulating endotoxin and modifying Kupffer cell function.

No evidence for endotoxin transfer across high flux polysulfone membranes.

Recently, there has been some concern that high-flux membranes may expose dialysis patients to the risk of endotoxin transfer secondary to backfiltration within the dialyzer. To evaluate the safety of high-flux polysulfone dialyzers, we examined in an in vitro recirculation system whether lipopolysaccharides (LPS) and lipid A respectively penetrate from the dialysate to the blood compartment and vice versa using a F-60 hemofilter (Fresenius AG). For the detection of endotoxin, a sensitive, kinetic limulus amebocyte lysate (LAL) microtiter test was used. It can be concluded that LPS and lipid A do not pass from either side through the filter system used when saline was recirculated for more than 10 h on both sides of the membrane.

[Pathophysiological significance of endotoxins]. / Zur pathophysiologischen Bedeutung der Endotoxine

The biological activities of endotoxin are manifold. Besides the drop in platelets and the biphasic change in the number of leukocytes, severe disturbances in the capillary bed are among the first changes observed following the administration of endotoxin. It is well known that endotoxins cause the release of various vasoactive mediators. According to our results endotoxins enhance the activity of histamine and serotonin; these findings may contribute to a better understanding of the action of histamine and serotonin in the early post-endotoxin phase. The histamine-sensitizing effect of endotoxins is not prevented by antihistamines. Endotoxins and biogenic amines cause similar disturbances in the capillary bed. The changes that are observed in the content of the vessels, the vessel wall, and the perivascular region are the following: slowing down of the blood stream, degranulation of perivascular mast cells, granulocytosis, wall adhering granulocytes, plasma skimming, rouleaux-formation of erythrocytes, reduction in plasticity of many erythrocytes, acanthocytes, acanthocytosis, appearance of spherocytes and microcytes, and formation of massive aggregates of platelets and of microthrombi. Also, occasionally cell aggregates dissolve and as microemboli form new thrombi. Swelling of pericytes, endothelial, and periendothelial cells is observed, and dissociation and deformation of the endothelial cells occur. By means of contact of the vessel contents with the collagen, there is an additional activation of the coagulation system by factor XII possible. The changes of the epithelial lining and the wall adhering cells enhance the narrowing of the vessel lumen. Prestasis and occasionally stasis occur. One observes increased swelling of the endothelial and periendothelial cells, increased permeability of the vessel wall, passage of plasma and occasionally blood cells, especially erythrocytes, through the endothelium and massive microbleedings. While stasis is observed in the nutritive capillaries, in regions where arteriolar-venular shunts exist the flow continues. The systemic blood pressure may therefore remain unchanged during this phase, although the severe disturbances described occur in the capillary bed. Metabolic alterations, especially in the carbohydrate metabolism are mentioned.

The inflammatory response to endotoxins.

1. Endotoxins are very potent and widely spread inflammation-inducing substances. 2. In the course of local infections endotoxins represent one of the main principles of the pathogenicity of gram-negative bacteria by inducing acute nonspecific inflammation. 3. The pharmacological activities of endotoxins consist primarily in generating and liberating the classic mediators of acute nonspecific inflammation. 4. Endotoxins are able to enter into the circulation through their capicity to activate pharmacological mediators. 5. The endotoxic mediators which increase the permeability of the microcirculation of the intestinum enable endotoxins as components of the physiological intestinal flora to enter into the circulation; these induce systemic disease or shock depending on their concentration in the circulation. 6. In the course of chronic inflammation recidivism or recrudescence as trasient acute inflammatory outburst can be caused by local effects of endotoxins. 7. According to some recent observations the inflammation inducing capacity of endotoxins may promote the entry of aerobic bacteria into the blood stream which can result in mixed septicemia.

Aspects of beneficial endotoxin-mediated effects.

The status of hyperreactivity and hyporeactivity following the administration of endotoxin in a susceptible host represents phenomena which are of interest in an attempt to understand the role of endotoxins in pathophysiological events in general. Two experimental approaches designed to examine these events are reported herein; i.v. injection with minute concentrations of endotoxin (10 ng of a BOIVIN endotoxin from E. coli 0111) induces tolerance against lethal doses of endotoxin (0.5 microgram or 5.0 microgram) within 24 h in hyperreactive NMRI mice that were infected 14 days before with BCG. Transfer of post-endotoxin serum from BCG infected mice, which contains a myriad of macrophage mediators and which induces nonspecific resistance to X-irradiation, renders a strain of mice (C3H/HeJ) that is hyporeactive to endotoxins, susceptible to the lethal effect of endotoxin. Studies of the role of the macrophage and its mediators in the experimental models described here may contribute to a further understanding of the mechanisms underlying endotoxin-induced biological activities.

Ability of Post-endotoxin serum from BCG-infected mice to induce nonspecific resistance and stimulation of granulopoiesis.

Serum from BCG-infected mice obtained 2 h after injection with endotoxin induced elevated levels of colony-stimulating factor and an increase in splenic granulocyte-macrophage progenitor cells in C3H/HeJ mice. The capacity of such serum to stimulate granulopoiesis may be related to its ability to increase nonspecific resistance to lethal irradiation.

Tumor necrosis factor and interleukin 1 as mediators of endotoxin-induced beneficial effects.

Bacterial lipopolysaccharides or endotoxins are known to induce tumor necrosis; enhanced nonspecific resistance to bacterial, viral, and parasitic infections and to radiation sickness; and tolerance to lethal doses of endotoxin. These beneficial effects are achieved by pretreatment with minute amounts of endotoxin. Recombinant tumor necrosis factor (TNF) and interleukin 1 (IL-1) are among the mediators capable of invoking radioprotection or resistance to the consequences of cecal ligation and puncture. Both cytokines are potent inducers of serum colony-stimulating factor (CSF) in C3H/HeJ mice (low responders to endotoxin). The number of splenic granulocyte-macrophage precursors was found to increase 5 days after injection of TNF in these mice. Although with IL-1 no increase in the number of granulocyte-macrophage colonies occurred in culture in the presence of serum CSF, a marked stimulation was observed when TNF was added. This stimulation of myelopoiesis observed in vivo and in vitro may be related to the radioprotective effect of TNF. The data presented suggest that TNF and IL-1 released after injection of endotoxin participate in the mediation of endotoxin-induced enhancement of nonspecific resistance and stimulation of hematopoiesis.

[Studies on the antigenicity of synthetic ACTH (beta1-24-corticotropin) in normal subjects (author's transl)]. / Untersuchungen zur Antigenität von synthetischem ACTH (beta1-24-Corticotropin) bei freiwilligen Versuchspersonen

9 healthy volunteers were subjected to a 3-week treatment with synthetic ACTH. Antibody response against beta1-24-corticotropin (Synacthen) was tested by passive transfer in the Prausnitz-Küstner reaction, complement fixation, passive hemagglutination and agar-gel diffusion. Failure of the healthy persons to produce reaginic or non-reaginic antibodies is compared titerature.

Ability of various adsorbents to bind endotoxins in vitro and to prevent orally induced endotoxemia in mice.

The efficacy of various adsorbents for endotoxin was tested in vitro and in vivo using a murine experimental model of gut-derived endotoxemia. A quantitative limulus amebocyte lysate microtiter test and the limulus amebocyte lysate tube test were used to determine intestinal and circulating levels of endotoxin. Kaopectate, kaolin/pectin mixture, kaolin, pectin, bentonite, charcoal particles, and lactulose were tested for their ability to bind endotoxins both in vitro and in vivo. The most effective material in the prevention of endotoxemia provided to be bentonite followed by Kaopectate and charcoal particles. Kaolin least effectively bound endotoxin at similar concentrations, while lactulose and pectin had minimal effects. Good correlation was shown between the ability of these drugs to bind endotoxin in vitro as compared with in vivo action.

Failure of endotoxin to protect C3H/HeJ mice against lethal x-irradiation.

C3H/HeJ mice are more sensitive to lethal X-irradiation and cannot be protected by pretreatment with endotoxin, compared to the C3HeB/FeJ strain. Lack of a granulopoietic response in C3H/HeJ mice is evident.