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The role of interleukin-6 in lipopolysaccharide-induced weight loss, hypoglycemia and fibrinogen production, in vivo.

It was recently shown that interleukin (IL)-6 is an important mediator involved in the Colon (C)-26 model of experimental cancer cachexia. In this study, we wished to determine whether IL-6 is also involved in several metabolic changes associated with lipopolysaccharide (LPS) challenge. Administration of a relatively high amount of LPS to mice induced a transient weight loss, hypoglycemia, hypertriglyceridemia and an increase in the hepatic acute phase reactant, fibrinogen. Pretreatment of mice with the rat anti-murine IL-6 antibody (20F3), but not with a control antibody, resulted in a significant improvement of LPS-induced hypoglycemia and weight loss as well as a significant decrease of plasma fibrinogen. Anti-IL-6 antibody had no effect on LPS-induced hypertriglyceridemia. On the other hand, the pretreatment of mice with anti-murine TNF (TN3.19) antibody was able to completely inhibit elevation of triglycerides and modestly improve LPS-induced weight loss although it had no effect on hypoglycemia and fibrinogen production. Taken together, these results suggest that IL-6 plays a role in some of the metabolic changes associated with both an acute (i.e. LPS challenge) and chronic (C-26 cachexia) inflammatory conditions.

Enhanced Hematopoietic Recovery in Irradiated Mice Pretreated with Interleukin-1 (IL-1)

Data in this report compare the number of colony-forming cells (CFC) in bone marrow from irradiated and pre-irradiated C57Bl/6J mice injected with saline or recombinant interleukin-1-alpha (rIL-1). Eight to 12 days after sublethal or lethal irradiation, there were more CFU-E (colony-forming units-erythroid), BFU-E (burst-forming units erythroid), GM-CFC (granulocyte-macrophage colony-forming cells), and day 8 CFU-S (colony-forming units-spleen) in bone marrow from rIL-1 injected mice than from saline injected mice. Prior to irradiation, there was no increase in number of CFC in bone marrow from rIL-1 injected mice. However, as determined by sensitivity to hydroxyurea, rIL-1 injection stimulated GM-CFC into cell cycle. These results demonstrate that rIL-1 injection increases the number of CFC that survive in irradiated mice and may be a consequence of the stimulation of CFC into cell cycle prior to irradiation.

Relationship between interleukin 1 (IL1), tumor necrosis factor (TNF) and a neutrophil attracting peptide (NAP-1)

ConclusionAlthough IL 1 and TNF are biochemically distinct and bind to different cell membrane receptors, they each exhibit only a few distinct biological properties, and have a great number of activities in common. Thus, IL 1 and TNF are radioprotective, have cytocidal effects for some tumor cells, remodel bone and cartilage, induce fever, inflammation, fibroplasia, and angiogenesis. The overlapping effects of IL 1 and TNF are in part due to the induction of the same spectrum of cytokines and their receptors. Both IL 1 and TNF induce IL 2-receptors, IL 6, colony stimulating factors and acute phase proteins which may contribute to their immunoenhancing, inflammatory and radioprotective effects. IL 1 and TNF frequently also are coordinately released by cells and have cooperative effects. For example, IL 1 together with TNF has synergisticin vivo radioprotective effects andin vitro terminal differentiative effects on tumor cell lines. Overall, these data point to the existence of common as well as distinct post-receptor signal transduction pathways for IL 1 and TNF. IL 1 and TNF each can induce a number of cell types to produce IL 6, which appears to act as another “broad spectrum” cytokine. In addition, both IL 1 and TNF induce NAP-1 production by human monocytes and fibroblasts. This novel cytokine which has been purified, sequenced, cloned, expressed and synthesized, may account for some of thein vivo acute inflammatory effects of these cytokines.

Why Should Internists Be Interested in Interleukin-1?

Excerpt Interleukin-1 is a hormone-like polypeptide produced in response to infection, injury, physiologic stress, or antigenic challenge. Originally named for its ability to act as an intercellula...

Evaluation of immunologic assays to determine the effects of differential housing on immune reactivity

The mechanism is being investigated to determine specifically how an environmental variation such as differential housing can influence the multiple components of the host defense mechanism. Male C3H/HeJ mice were housed either one or five per cage. Cells and sera from these mice were analyzed and compared by several immunologic techniques to determine in which cells or tissues the effect of differential housing was most pronounced. The individually housed mice (a) had a greater capacity to phagocytose dead cells of Candida albicans. (b) had spleens that produced more macrophage colony stimulating factor (M-CSF). (c) were more responsive to M-CSF, (d) had peritoneal macrophages that released greater quantities of interleukin-1 in vitro into the surrounding medium and that had a greater capacity to migrate toward a chemotactic stimulus, and (e) had higher titers of IgM hemagglutination antibody to sheep erythrocytes. Differential housing of mice may therefore be a highly important modulator and indicator of the nature and extent of an animals immunologic response to an environmental stimulus.

Cytokines in radioprotection and therapy of radiation injury

Industrial and medical applications of ionizing radiation make it necessary to develop means of protection and therapy from damaging, and often lethal, effects of accidental radiation exposure. Although chemical radioprotectors, .primarily thiol compounds, have been studied extensively [1], their clinical application is limited as these agents are extremely toxic and are effective only if administered within minutes prior to irradiation. Transplantation of bone marrow cells to animals or patients protects them from a lethal dose of irradiation (in a dose range below that inducing the gastrointestinal syndrome). Therefore, despite radiation-induced damage, a supply of undamaged hematopoietic and lymphoid cells protects an animal or patient from death. Similar protection from death with hematopoietic syndrome could be achieved with the use of immunomodulatory agents (LPS, BCG or MDP) that stimulate the reticuloendothelial system [2]. The patterns of hematopoietic recovery in endotoxin-treated animals closely resembles the hematopoietic recovery in animals receiving syngeneic bone marrow transplants [3]. Consequently, the accelerated restoration of functional immunocytes and hematopoietic cells is believed to be a major factor in the survival of lethally irradiated mice. The proliferation and differentiation of cells of the hematopoietic and lymphoid system depends directly on growth and differentiation factors which are produced endogenously by the host [4]. These agents belong to a group of factors referred to as cytokines, hormone-like proteins, synthesized and released primarily by the cells of the immune system, namely macrophages and lymphocytes. Their release can be stimulated by inflammatory agents or by immunomodulators, in the course of infections, or following traumatic injuries. The multiplicity of important functions induced by cytokines indicates that these agents play an essential role in defense against infections, in immune surveillance, in recovery from injury, and as will be reviewed, in mediating the radioprotective effects of immunomodulators. High doses of immunomodulators can be hazardous and have toxic effects. Pharmacological doses of cytokines may be more easily tolerated and more efficacious than the exogenous immunomodulators. Studies with cytokines can establish whether the toxic effects of immunomodulators result from the direct action of these drugs or are mediated via induction of mixtures of cytokines, some of which may be detrimental rather than beneficial to the host. Because of the above considerations, we initiated studies to evaluate the radioprotective and therapeutic effects of a number of purified recombinant cytokines.

Radioprotection with interleukin-1 comparison with other cytokines

Murine IL-1α and human IL-1α and IL-1β protect mice from lethal effects of radiation-induced hematopoietic syndrome. A single 100 ng dose of human IL-1α conferred protection, provided it was administered to C57BL/6 and DBA/1 mice 20 hr before irradiation with an LD100/30 dose, with a DRF of 1.25 and 1.2, respectively. Studies of possible mechanisms of radioprotection by IL-1 showed that radioprotection of LD100/30 irradiated mice could not be induced with IL-2, IFN-γ, or GM-CSF. Radioprotection with IL-1 did not depend on the release of prostaglandins, since indomethacin did not diminish survival of IL-1-treated mice. Unlike C57BL/6 and DBA/1 mice, C3H/HeJ mice were not protected from lethal irradiation by IL-1. Nevertheless, both high-responder C57BL/6 and low-responder C3H/HeJ strains, treated with IL-1, develop similarly enhanced levels of acute phase proteins: metallothionein and ceruloplasmin, with known radioprotective abilities. Therefore, the observed differences in radioprotection with IL-1 in murine strains probably cannot be attributed to differences in levels of these scavenging metalloproteins. In contrast, striking differences were observed in the recovery of bone marrow cells after lethal and midlethal irradiation, in that the recovery of total nucleated bone marrow cells and specifically CFU-Es was much greater in C57BL/6 than in C3H/HeJ mice 9 to 12 days following irradiation. However, the radioprotective effect of IL-1 was similar following sublethal irradiation of the two strains when recovery of endogenous hematopoietic splenic colonies was compared. Consequently, IL-1 can protect C3H/HeJ mice against sublethal but not lethal doses of irradiation. Although much remains to be learned about the mechanism by which IL-1 exerts its radioprotective effect, IL-1 treatment, as is the case for many radioprotective agents, induces recovery of erythropoiesis.

Radioprotection of Mice with Interleukin-1: Relationship to the Number of Spleen Colony-Forming Units

Compared to saline-injected mice 9 days after 6.5 Gy irradiation, there were twofold more Day 8 spleen colony-forming units (CFU-S) per femur and per spleen from B6D2F1 mice administered a radioprotective dose of human recombinant interleukin-1-alpha (rIL-1) 20 h prior to their irradiation. Studies in the present report compared the numbers of CFU-S in nonirradiated mice 20 h after saline or rIL-1 injection. Prior to irradiation, the number of Day 8 CFU-S was not significantly different in the bone marrow or spleens from saline-injected mice and rIL-1-injected mice. Also, in the bone marrow, the number of Day 12 CFU-S was similar for both groups of mice. Similar seeding efficiencies for CFU-S and percentage of CFU-S in S phase of the cell cycle provided further evidence that rIL-1 injection did not increase the number of CFU-S prior to irradiation. In a marrow repopulation assay, cellularity as well as the number of erythroid colony-forming units, erythroid burst-forming units, and granulocyte-macrophage colony-forming cells per femur of lethally irradiated mice were not increased in recipient mice of donor cells from rIL-1-injected mice. These results demonstrated that a twofold increase in the number of CFU-S at the time of irradiation was not necessary for the earlier recovery of CFU-S observed in mice irradiated with sublethal doses of radiation 20 h after rIL-1 injection.

Contrasting mechanisms of the myeloprotective effects of interleukin-1 against ionizing radiation and cytotoxic 5-fluorouracil

Pretreatment with a single dose of interleukin-1 (IL-1) counteracts the myelosuppressive effects of radiation. In contrast, multiple doses are required to protect against several cytoablative drugs, suggesting different mechanisms. We examined the possibility that myeloprotection is due to IL-1-induced cycling of primitive progenitor cells. First, we evaluated the effect of the time between administration of IL-1 and 5-fluorouracil (5-FU), which kills cycling cells but spares quiescent early progenitors, on their interaction. Pretreatment with a single dose of IL-1 resulted in the death of mice treated with 5-FU provided IL-1 was given 18 h, but not 4 or 48 h, prior to administration of sublethal doses of 5-FU. Second, evaluation of primitive hematopoietic progenitor cells, 13-day spleen colony-forming units (CFU-S) and CFU with high proliferative potential revealed that treatment with 5-FU 18 h after administration of IL-1 results in reduction of CFU-S by 98% and of CFU with high proliferative potential by 65%, but only a 7 and 10% reduction, respectively, at 48 h. Third, in contrast to protection from death by pretreatment with a single dose of IL-1 at 24 h, two injections of IL-1 at 72 and 24 h before irradiation abrogated such protection. Similarly, the toxicity of 5-FU to progenitor cells was reduced when two injections of IL-1 were administered 48 h apart. This correlates with the time of up-regulation in the bone marrow cells of TGF-beta. These findings suggest that, depending on the schedule of treatment, administration of IL-1 may result in cycling of primitive progenitors, to protect against radiation, and may cause inhibition of cycling to protect against chemotherapeutic drugs.

Radioprotection of Mice with Interleukin-1: Relationship to the Number of Erythroid and Granulocyte-Macrophage Colony-Forming Cells

This report presents the results of an investigation of changes in the number of erythroid and granulocyte-macrophage colony-forming cells (GM-CFC) that had occurred in tissues of normal B6D2F1 mice 20 h after administration of a radioprotective dose (150 ng) of human recombinant interleukin-1 (rIL-1). Neutrophilia in the peripheral blood and changes in the tissue distribution of GM-CFC demonstrated that cells were mobilized from the bone marrow in response to rIL-1 injection. For example, 20 h after rIL-1 injection marrow GM-CFC numbers were 80% of the numbers in bone marrow from saline-injected mice. Associated with this decrease there was a twofold increase in the number of peripheral blood and splenic GM-CFC. Also, as determined by hydroxyurea injection, there was an increase in the number of GM-CFC in S phase of the cell cycle in the spleen, but not in the bone marrow. Data in this report suggest that when compared to the spleen, stimulation of granulopoiesis after rIL-1 injection is delayed in the bone marrow. Also, the earlier recovery of GM-CFC in the bone marrow of irradiated mice is not dependent upon an increase in the number of GM-CFC at the time of irradiation.