Cytokine-associated tissue injury and lethality in mice: a comparative study

Augmentation of anti-cytokine immunotherapy by combining neutralizing monoclonal antibodies to interferon-γ and the interferon-γ receptor: protection in endotoxin shock

We have employed neutralizing monoclonal antibodies to mouse interferon-γ (IFNγ) and to the receptor for mouse IFNy in studies designed to assess the protective efficacy of each of these monoclonals, administered either separately or in combination, in endotoxin-induced lethality. While pretreatment with either antibody alone, at doses of 200 μg per mouse, provided limited protection (70-50% lethality) in comparison to non-neutralizing antibody controls (100% lethality), the two monoclonal antibodies administered together provided a substantially greater level of protection (17% lethality). Although administration of 100 μg per mouse of either monoclonal alone was not protective (more than 65% lethality), a combination of both antibodies at this dose provided significant protection (19% lethality). In addition, administration of both antibodies 30 min post-endotoxin challenge also demonstrated significant protection in comparison to single antibody immunotherapy. In vitro studies using mouse peritoneal macrophages stimulated with LPS and IFNy have established confirmatory data for a synergistic effect of neutralizing antibody to IFNy and the IFNγ receptor in inhibiting macrophage activation as assessed by production of nitric oxide. These results provide a strong rationale for dual targeting of ligand and receptor in single cytokine immunotherapy.

Clinical application of cultured epithelial autografts on acellular dermal matrices in the treatment of extended burn injuries

Achieving permanent replacement of skin in extensive full-thickness and deep partial-thickness burn injuries and chronic wounds remains one of the fundamental surgical problems. Presently, split-thickness skin grafts are still considered the best material for surgical repair of an excised burn wound. However, in burns that affect greater than 50% of total body surface area, the patient has insufficient areas of unaffected skin from which split-thickness skin grafts can be harvested. The use of cultured epithelial (or epidermal) autografts (CEAs) has achieved satisfactory results. But the take rate of CEAs is poor in full-thickness bed or in chronically infected area. Providing temporary cover with allograft skin, or a more permanent allodermis, may increase clinical take. This review aims to (1) describe the use of CEAs in the regeneration of the epidermis, (2) introduce the application of the acellular dermal matrices (ADMs) in the clinics, and (3) enhance understanding of the CEAs applied with ADM as an appropriate strategy to treat the extended burn injuries. The current evidence regarding the cultured epithelial cell or keratinocyte autograft and dermal grafts applied in the treatment of burn injuries was investigated with an extensive electronic and manual search (MEDLINE and EMBASE). The included literature (N=136 publications) was critically evaluated focusing on the efficacy and safety of this technique in improving the healing of the deep dermal and full-thickness burn injuries. This review concluded that the use of ADM with CEAs is becoming increasingly routine, particularly as a life-saving tool after acute thermal trauma.

Cytokines, growth factors, and plastic surgery

Numerous inflammatory cytokines and growth factors have been identified and are known to be essential for normal wound healing and host defense, and many have been implicated in disease states treated by plastic surgeons. Cytokines and growth factors are members of a large functional group of polypeptide regulatory molecules secreted by different cell lines. These peptides exert their influence through autocrine and paracrine fashions within sites of injury and repair. Although cytokines and growth factors are crucial in initiating, sustaining, and regulating the postinjury response, these same molecules have been implicated in impaired wound healing, abnormal scarring, and chronic cutaneous diseases. Therapeutic manipulation of inflammatory mediators in normal and impaired wounds has been performed, with mixed clinical results, but evolving strategies such as gene therapy, as well as further characterization of the cellular-mechanism cytokines and growth-factor triggers, will further add to our therapeutic options. This article discusses the current understanding of important cytokines and growth factors involved in the normal injury response and then addresses pathological states associated with an inappropriate expression of these mediators. Finally, a summary of various cytokine and growth factor-directed strategies being used in impaired wound healing states is presented.

Mechanisms involved in the pathogenesis of sepsis are not necessarily reflected by in vitro cell activation studies

It is thought that lipopolysaccharide (LPS) from gram-negative bacteria contributes significantly to the pathogenesis of septic shock. In vitro studies to address the mechanisms involved in this process have often investigated human monocytes or mouse macrophages, since these cells produce many of the mediators found in septic patients. Targeting of these mediators, especially tumor necrosis factor alpha (TNF-alpha), has been pursued as a means of reducing mortality in sepsis. Two experimental approaches were designed to test the assumption that in vitro studies with macrophages accurately predict in vivo mechanisms of LPS pathogenesis. In the first approach, advantage was taken of the fact that on consecutive days after injection of thioglycolate into mice, increased numbers of macrophages could be harvested from the peritoneum. These cells manifested markedly enhanced levels of in vitro TNF-alpha, interleukin 6 (IL-6), and nitric oxide production in response to LPS. In D-galactosamine-sensitized mice, however, thioglycolate treatment significantly decreased mortality due to LPS, as well as levels of circulating TNF-alpha and IL-6. Anti-TNF-alpha treatment confirmed this cytokine's role in the observed lethality. In a second experimental approach, we compared the mouse macrophage-stimulating potencies of different LPS preparations with their lethalities to mice. In these studies, the in vitro macrophage-stimulating profiles presented by rough-LPS and smooth-LPS preparations were the reverse of their relative lethal potencies in vivo. In conclusion, peritoneal macrophages appear not to be the major cells responsible for the overall host response during endotoxic shock. These findings underscore the importance of verifying the correlation of in vivo systems with in vitro systems when attributing specific functions to a cell type.

Monokine production following in vitro stimulation of the THP-1 human monocytic cell line with pertussis vaccine components

Whole-cell pertussis found in diphtheria-tetanus-pertussis (DTP) vaccine can produce symptoms reminiscent of biological responses to circulating proinflammatory monokines such as IL-6, IL-1beta, and TNFalpha. Therefore the ability of pertussis-containing vaccines and several heat-killed Bordetella pertussis preparations to stimulate cytokine production in a human monocytic cell line, THP-1, were examined. The whole-cell pertussis vaccine induced significantly more IL-6, IL-1beta, and TNFalpha production than did the acellular pertussis or diphtheria-tetanus-only vaccine. Polymyxin B was able to inhibit most of the IL-6 induced by pertussis endotoxin and a heat-killed preparation of B. pertussis containing a null mutation in bvgAS, a regulatory locus required for expression of all known protein virulence factors synthesized by this organism. However, it only partially inhibited IL-6 production induced by other pertussis-containing preparations, including DTP vaccine. These results indicate that in vitro whole-cell vaccine is a potent stimulator of IL-6, IL-1beta, and TNFalpha. They also suggest that although endotoxin is a major inducer of IL-6, other components of B. pertussis also contribute to IL-6 production by monocytes.

Differential antigen burden modulates the gamma interferon but not the immunoglobulin response in mice that vary in susceptibility to Sendai virus pneumonia

Sendai virus, a paramyxovirus which causes murine pneumonia, grew to approximately 10-fold higher titers and was cleared less rapidly from the lungs of 129/J (129) than H-2b-compatible C57BL/6J (B6) mice. The more susceptible 129 mice also made higher titers of gamma interferon (IFN-gamma) and immunoglobulin G2a (IgG2a) virus-specific antibody. Analysis with acutely irradiated (950 rads) mice and immunologically reconstituted bone marrow (BM) radiation chimeras indicated that the enhanced virus growth was a function of the radiation-resistant respiratory epithelium. Prolonged exposure to more virus in turn influenced the magnitude of IFN-gamma production, most of which was made by CD4+ T lymphocytes. Somewhat surprisingly, however, the 129 pattern of a higher virus-specific serum Ig response skewed towards IgG2a mapped to the reconstituting BM. Thus, the characteristics of the humoral response are at least partly dissociated from both the antigen load, resulting from viral replication, and the level of IFN-gamma production. Further analysis of double chimeras (B6+129 BM-->B6 recipients) confirmed that the divergent humoral immune response to Sendai virus in B6 and 129 mice is largely determined by the inherent characteristics of the lymphoid cells.

IFN-gamma inhibits internalization of soluble aminated beta-1,3-D-glucan by macrophages and thereby down-regulates the glucan induced release of TNF-alpha and IL-1 beta

We have previously shown that soluble animated beta-1,3-D-glucan (AG) and glucan-derivatized microbeads (GDM) bind to the specific beta-glucan receptor on mouse peritoneal macrophages. Phagocytosis of GDM by macrophages is mediated through the beta-glucan receptor. IFN-gamma which increases macrophage phagocytic capacity, also increased the phagocytosis of GDM. In the present study we show that IFN-gamma inhibits internalization of AG in macrophages in a dose- and time-dependent manner. The inhibitory effect of IFN-gamma was neutralized by treatment of the macrophages with cycloheximide. These results were confirmed by confocal laser scanning microscopy which showed that IFN-gamma treated cells incorporated less fluorescein-labelled AG than did untreated cells. IFN-gamma did not change the macrophage-binding capacity for AG showing that the inhibitory effect of IFN-gamma is not caused by decreased number of beta-glucan receptors on the cells. The stimulatory effect of AG on IL-1 beta and TNF-alpha release from macrophages was reduced by pretreatment of the cells with IFN-gamma. We conclude that the uptake of AG and GDM in macrophages, both mediated through the beta-glucan receptor, are differently regulated by IFN-gamma. The reduced internalization of AG after IFN-gamma treatment of macrophages, is probably responsible for the down-regulation of IL-1 and TNF-alpha secretion.

IL-6 induces hepatic inflammation and collagen synthesis in vivo

IL-6 regulates the synthesis of a broad spectrum of acute phase proteins in the liver. Also, it is involved in the pathogenesis of many fibrogenic diseases. To study the inflammatory effects of IL-6 on the liver in vivo, human rIL-6, produced in Escherichia coli, was injected intraperitoneally into rats (25 micrograms/100 g body weight). The major fraction of injected IL-6 was accumulated in the liver within 40 min, and the number of platelets was increased during 72 h after injection. After 5 weeks of injection, the levels of serum glutamine pyruvic transaminase (GPT) and glutamic oxaloacetic transaminase (GOT) were not changed, but they were significantly elevated at 13 weeks of treatment. Meanwhile, serum albumin levels were slightly decreased compared with those of controls. The same phenomena were observed in carbon tetrachloride-treated rats. Collagen synthesis was increased in the liver tissues and in the culture supernatants of hepatic lipocytes isolated from the rats treated with IL-6 for 13 weeks. Histological analysis correlated well with biochemical analysis. At 5 weeks of treatment, only mild pathological changes were observed, but severe hepatocyte necrosis and the accumulation of fibres in necrotic area were developed in the liver of IL-6-treated rats after 13 weeks of treatment, confirming that hepatic inflammation and fibrosis were developed. IL-6 activities in the sera and in the culture supernatants of lipocytes from IL-6-treated rats were elevated compared with those in controls. These biochemical and pathological data indicate that IL-6 can induce hepatic inflammation, and it has important roles in the pathogenesis of fibrosis and diseases of the liver in vivo. In addition, these results will provide useful information for the clinical trials of IL-6.

IL-6 induces hepatic inflammation and collagen synthesis in vivo

IL-6 regulates the synthesis of a broad spectrum of acute phase proteins in the liver. Also, it is involved in the pathogenesis of many fibrogenic diseases. To study the inflammatory effects of IL-6 on the liver in vivo, human rIL-6, produced in Escherichia coli, was injected intraperitoneally into rats (25 micrograms/100 g body weight). The major fraction of injected IL-6 was accumulated in the liver within 40 min, and the number of platelets was increased during 72 h after injection. After 5 weeks of injection, the levels of serum glutamine pyruvic transaminase (GPT) and glutamic oxaloacetic transaminase (GOT) were not changed, but they were significantly elevated at 13 weeks of treatment. Meanwhile, serum albumin levels were slightly decreased compared with those of controls. The same phenomena were observed in carbon tetrachloride-treated rats. Collagen synthesis was increased in the liver tissues and in the culture supernatants of hepatic lipocytes isolated from the rats treated with IL-6 for 13 weeks. Histological analysis correlated well with biochemical analysis. At 5 weeks of treatment, only mild pathological changes were observed, but severe hepatocyte necrosis and the accumulation of fibres in necrotic area were developed in the liver of IL-6-treated rats after 13 weeks of treatment, confirming that hepatic inflammation and fibrosis were developed. IL-6 activities in the sera and in the culture supernatants of lipocytes from IL-6-treated rats were elevated compared with those in controls. These biochemical and pathological data indicate that IL-6 can induce hepatic inflammation, and it has important roles in the pathogenesis of fibrosis and diseases of the liver in vivo. In addition, these results will provide useful information for the clinical trials of IL-6.

Modulation of antibody-mediated glomerular injury in vivo by interleukin-6

We have shown previously that pretreatment with small doses of bacterial lipopolysaccharide (LPS), human recombinant interleukin-1 beta (hrIL-1 beta) and human recombinant tumor necrosis factor-alpha (hrTNF) increase injury in the heterologous phase of nephrotoxic nephritis (NTN). All three pretreatments induce synthesis of interleukin-6 (IL-6) which in some systems down-regulates synthesis of IL-1 and TNF. We have now investigated the influence of IL-6 on injury in both heterologous and autologous phases of NTN in rats. Injection of hrIL-6 in doses sufficient to induce hepatic synthesis of acute phase proteins (assessed by plasma alpha 2-macroglobulin concentration) had no effect on glomerular injury in the heterologous phase of NTN (albuminuria in NTAb alone 9 +/- 6; LPS/NTAb 34 +/- 10 and IL-6/NTAb 2 +/- 1 mg/24 hr, P < 0.001, Wilcoxon test). In contrast, IL-6 pretreatment partially abrogated the effect of LPS on albumin excretion (NTAb 4 +/- 2; LPS/NTAb 85 +/- 11 and IL-6/LPS/NTAb 32 +/- 6 mg/24 hr, P < 0.002), percentage of glomerular capillary thrombi (3 +/- 1%; 39 +/- 8%; and 6 +/- 1%, P < 0.001) and glomerular neutrophil infiltrate (29 +/- 3; 58 +/- 5; and 34 +/- 2 neutrophils/50 glomeruli in section, P < 0.001, respectively) at 24 hours. The effect of IL-6 was also evident four hours after induction of nephritis and was associated with a marked reduction in glomerular concentration of mRNA for IL-1 beta and TNF, without change in that of tubulin. Serum TNF concentrations were also significantly reduced at four hours in IL-6 treated rats.(ABSTRACT TRUNCATED AT 250 WORDS)

An effector role for platelets in systemic and local lipopolysaccharide-induced toxicity in mice, mediated by a CD11a- and CD54-dependent interaction with endothelium

The role of platelets was investigated in two models of lipopolysaccharide (LPS)-induced toxicity in mice: the systemic reaction, provoked by intravenous LPS injection in D-galactosamine-sensitized recipients, which results in host death, and the local reaction, elicited in the skin by sequential injections of LPS and tumor necrosis factor alpha at 24-h intervals, which results in hemorrhagic necrosis. In both models, the depletion of platelets with a rabbit polyclonal or a mouse monoclonal antiplatelet immunoglobulin G afforded significant protection. In the local reaction, studies of the distribution of 111In-labelled platelets as well as optical and electron microscopy showed that platelets are localized in the dermal venules before hemorrhage occurs. Anti-CD11a (LFA-1) and anti-CD54 (ICAM-1) monoclonal antibodies prevented both platelet localization and hemorrhagic necrosis, and these determinants were detected on mouse platelets by immunofluorescence. The antiplatelet monoclonal antibody did not reduce the localization of polymorphonuclear leukocytes in the dermal venules, as shown by histological sections. Thus, in the local reaction, the stimulation with LPS and tumor necrosis factor alpha leads to a binding of platelets to the endothelium of venules by their beta 2 integrins, which seems necessary for the development of the hemorrhagic necrosis.

Cytokine mediators of septic infections in the normal and granulocytopenic host

Cytokines presently known to be involved in systemic bacterial infection are tumour-necrosis factor (TNF), interleukin (IL)-1, IL-6, IL-8 and interferon-gamma (IFN-gamma) and the counterregulatory molecules soluble TNF receptor (sTNFR) and IL-1 receptor antagonist (IL-1 Ra). In animal models TNF, IL-1 and IFN-gamma mediate organ damage, low blood pressure and fatality, whereas IL-6 is involved in infection-related manifestations, like the production of acute-phase protein and fever, and IL-8 is chemotactic to granulocytes. TNF and IL-1 increase expression of adhesion molecules on endothelial cells and influence a number of components of the haemostatic system in favour of coagulation. The presence of cytokines in the circulation is characterized by sequential releases of TNF, IL-1 and IL-6/IL-8; however, many variations of this pattern exist during human infection. In experiments as well as in human infection TNF, IL-1, IL-6, IL-8 and IFN-gamma have been detected, and levels of TNF, IL-6 and IL-8 have been found to be associated with the severity of the disease. Collectively, TNF, IL-1 and IFN-gamma emerge as mediators of systemic infection and septic shock whereas IL-6 and IL-8 are related to other manifestations of infection. Counteracting molecules like sTNFR are released after somewhat of a delay following TNF and IL-1Ra is released concomitantly with IL-1. Probably these factors modulate the cytokine effect although their true potency in natural infection has yet to be clarified. In granulocytopenic infections TNF, IL-1, IL-6 and IL-8 can be detected in serum, and levels of TNF and IL-6 are even higher than in the normal situation in experimental animals. Antibodies to TNF inhibit bacteria-induced fatality in granulocytopenic mice. Altogether, few data related to the granulocytopenic situation are available. However, it is reasonable to believe that the altered development of granulocytopenic infections is due to changes in the cellular constitution and not to changes in cytokine production.

Cytokine technology in basic and applied research on the hematopoietic system

Cytokines are polypeptide molecules important for the regulation and maintenance of immunity and hematopoiesis. Their central role in the control of a number of physiological mechanisms makes them an important area of both basic and applied biomedical research. This review presents an overview of basic and applied biology, and introduces the term cytokine technology to denote the use of cytokines as research tools for understanding the cellular and molecular regulation of hematopoiesis. A number of frontier technologies are reviewed, including fusion toxins, fusion proteins, and animal models of cytokine expression and regulation.

Identification of tumor necrosis factor as a transcriptional regulator of the phosphoenolpyruvate carboxykinase gene following endotoxin treatment of mice

The decreased synthesis of hepatic phosphoenolpyruvate carboxykinase (PEPCK), the rate-limiting enzyme of gluconeogenesis, that occurs during endotoxemia was shown previously in rats to occur at the transcriptional level. In the current study, the exogenous administration of human recombinant tumor necrosis factor (TNF), a proximal mediator of endotoxic shock, reduced the PEPCK transcription rate, mRNAPEPCK levels, and PEPCK enzyme activity in a time- and dose-dependent manner in CD-1 mice. Comparable amounts of circulating TNF were measured in mice 2 h after injection of human recombinant TNF (10(5) U) or a 50% lethal dose of Escherichia coli endotoxin (20 mg/kg). Direct action of TNF to decrease the PEPCK transcription rate was confirmed in vitro with H-4-II-E Reuber hepatoma cells, in which a dose-dependent inhibition of PEPCK transcription was observed with 1 to 100 U of TNF per ml. A role for TNF-elicited changes in PEPCK gene expression during endotoxemia was confirmed by the protective effect of rabbit polyclonal antibodies to recombinant murine TNF. C57BL/6 mice passively immunized with anti-TNF 4 h prior to endotoxin challenge exhibited normal PEPCK enzyme activity. Neutralization of circulating TNF with anti-TNF failed, however, to prevent the hypoglycemia commonly observed during endotoxemia, suggesting the participation of other mediators. Anti-TNF treatment reduced circulating interleukins 1 and 6 at 3 and 6 h after endotoxin treatment, respectively. These results suggest that during endotoxemia, the development of hypoglycemia is multifaceted and that several cytokines are most likely involved. The findings from the Reuber hepatoma cell model afford an opportunity in future work to map putative cytokine response elements in the PEPCK promoter responsible for perturbed hormonal regulation of the gene during endotoxemia.

Different role of cytokine mediators in septic shock related to meningococcal disease and surgery/polytrauma

So far, there has been a tendency towards a uniform concept of the role and kinetics of TNF and other cytokines in septic shock. However, our comparison of data from different groups of shock patients clearly demonstrates marked differences. On the one hand, the cytokine pattern in experimental septic shock and meningococcal disease has similarities which include early burst releases of TNF and IL-6. On the other hand, intensive care unit patients which includes patients with polytrauma, surgery, burns and other underlying diseases have a completely different pattern of appearance of TNF and IL-6 in the circulation. We have not been able to detect bioactive TNF in the circulation of these patients, whereas others have measured elevated levels of immunoreactive TNF. Bioactive IL-6 can be detected in serum; however, the levels are often fluctuating and there is no common pattern of appearance. These differences probably reflect differences in the release of endotoxin and the immunological status of the patients. TNF inhibitors and soluble TNF receptors probably play an important role. Experimental models for septic shock most commonly use administration of live bacteria or endotoxin to anesthesized healthy animals. This appears to be a good model for meningococcal disease, but not for intensive care unit patients.