Protection against lethal bacterial infection in mice by monocyte-chemotactic and -activating factor

Polysaccharide immunomodulators as therapeutic agents: structural aspects and biologic function

Polysaccharide immunomodulators were first discovered over 40 years ago. Although very few have been rigorously studied, recent reports have revealed the mechanism of action and structure-function attributes of some of these molecules. Certain polysaccharide immunomodulators have been identified that have profound effects in the regulation of immune responses during the progression of infectious diseases, and studies have begun to define structural aspects of these molecules that govern their function and interaction with cells of the host immune system. These polymers can influence innate and cell-mediated immunity through interactions with T cells, monocytes, macrophages, and polymorphonuclear lymphocytes. The ability to modulate the immune response in an appropriate way can enhance the host's immune response to certain infections. In addition, this strategy can be utilized to augment current treatment regimens such as antimicrobial therapy that are becoming less efficacious with the advent of antibiotic resistance. This review focuses on recent studies that illustrate the structural and biologic activities of specific polysaccharide immunomodulators and outlines their potential for clinical use.

Chemokine C10 promotes disease resolution and survival in an experimental model of bacterial sepsis

Previous studies have suggested that the C-C chemokine C10 is involved in the chronic stages of host defense reactions. The present study addressed the role of C10 in a murine model of septic peritonitis, induced by cecal ligation and puncture (CLP). Unlike other C-C chemokines, C10 levels in the peritoneal wash were increased approximately 30-fold above baseline levels at 48 h after CLP surgery. Immunoneutralization of peritoneal C10 levels with polyclonal anti-C10 antiserum during CLP-induced peritonitis negatively impacted mouse survival over 4 days. In contrast, when 500 ng of recombinant murine C10 was administered immediately after CLP surgery, the 4-day survival rate increased from 20% to over 60%. The C10 therapy appeared to facilitate a rapid and significant enhancement of the levels of tumor necrosis factor alpha (TNF-alpha) and monocyte chemoattractant protein-1 (MCP-1) and a later increase in interleukin-13 (IL-13) levels in the peritoneal cavity. In vitro studies showed that the combination of IL-1beta and C10 markedly augmented TNF-alpha synthesis by peritoneal macrophages and that C10 synthesis was induced in these cells following their exposure to IL-13. At 24 h after CLP surgery, only 25% of C10-treated mice were bacteremic versus 85% of the control group that exhibited dissemination of bacteria into the circulation. The lack of bacteremia in C10-treated mice appeared to be related, in part, to in vitro evidence that C10 significantly enhanced the bacterial phagocytic activity of peritoneal macrophages. In addition, in vivo evidence suggested that C10 therapy significantly reduced the amount of material that leaked from the damaged gut. Taken together, the results of this study demonstrate that the C10 chemokine rapidly promotes disease resolution in the CLP model through its direct effects on the cellular events critically involved in host defense during septic peritonitis.

Novel protective effects of stem cell factor in a murine model of acute septic peritonitis. Dependence on MCP-1

Mast cells participate in the host response during sepsis and have been shown to have a protective effect in a murine model of acute septic peritonitis and multi-organ failure initiated by cecal ligation and puncture (CLP). Stem cell factor (SCF) is a hematopoietic cytokine important in mast cell proliferation and activation. In the present study, we examined the protective effects of a single intraperitoneal injection of SCF given 2 hours before CLP surgery in mice. Four days after the CLP surgery, SCF pretreatment significantly improved mouse survival from 29 to 56% and mast cells were absolutely required for this effect. Immunoneutralization studies revealed that the SCF-stimulated release of monocyte chemoattractant protein-1 (MCP-1) into the septic peritoneal cavity contributed to the protective effect of SCF in this model. One potential cellular source of MCP-1 was the SCF-activated mast cell. In addition, SCF pretreatment significantly augmented circulating levels of SCF and the immunomodulatory cytokine interleukin-10 in septic mice, in part because the SCF pretreatment seemed to promote the release of both mediators from the liver. Additional hepatic effects of SCF treatment included an accelerated expression of hepatic levels of signal transducer and activator of transcription-3 (STAT-3) in CLP mice pretreated with SCF. Taken together, the findings from the present study demonstrate that the intraperitoneal delivery of SCF has a major protective effect in a murine model of CLP.

Polysaccharide immunomodulators as therapeutic agents: structural aspects and biologic function

Polysaccharide immunomodulators were first discovered over 40 years ago. Although very few have been rigorously studied, recent reports have revealed the mechanism of action and structure-function attributes of some of these molecules. Certain polysaccharide immunomodulators have been identified that have profound effects in the regulation of immune responses during the progression of infectious diseases, and studies have begun to define structural aspects of these molecules that govern their function and interaction with cells of the host immune system. These polymers can influence innate and cell-mediated immunity through interactions with T cells, monocytes, macrophages, and polymorphonuclear lymphocytes. The ability to modulate the immune response in an appropriate way can enhance the host's immune response to certain infections. In addition, this strategy can be utilized to augment current treatment regimens such as antimicrobial therapy that are becoming less efficacious with the advent of antibiotic resistance. This review focuses on recent studies that illustrate the structural and biologic activities of specific polysaccharide immunomodulators and outlines their potential for clinical use.

Pivotal role of the CC chemokine, macrophage-derived chemokine, in the innate immune response

Macrophage-derived chemokine (MDC), a recently identified CC chemokine, has been regarded to be involved in chronic inflammation and dendritic cell and lymphocyte homing. In this study, we demonstrate a pivotal role for MDC during experimental sepsis induced by cecal ligation and puncture (CLP). Intraperitoneal administration of MDC (1 microg/mouse) protected mice from CLP-induced lethality. The survival was accompanied by increased number of peritoneal macrophages and decreased recovery of viable bacteria from the peritoneum and peripheral blood. In addition, mice treated with an i.p. injection of MDC cleared bacteria more effectively than those in the control when 3 x 108 CFU live Escherichia coli was i.p. inoculated. Endogenous MDC was detected in the peritoneum after CLP, and neutralization of the MDC with anti-MDC Abs decreased CLP-induced recruitment of peritoneal macrophages and increased the recovery of viable bacteria from the peritoneum and peripheral blood. MDC blockade was deleterious in the survival of mice after CLP. In vitro, MDC enhanced the phagocytic and killing activities of peritoneal macrophages to E. coli and induced both a respiratory burst and the release of lysozomal enzyme from macrophages. Furthermore, MDC dramatically ameliorated CLP-induced systemic tissue inflammation as well as tissue dysfunction, which were associated in part with decreased levels of TNF-alpha, macrophage inflammatory proteins-1alpha and -2, and KC in specific tissues. Collectively, these results indicate novel regulatory activities of MDC in innate immunity during sepsis and suggest that MDC may aid in an adjunct therapy in sepsis.

Chemokine signaling in inflammation

The events that lead to an inflammatory response are characterized by recognition of the site of injury by inflammatory cells, specific recruitment of subpopulations of leukocytes into tissue, removal of the offending agent and "debridement" of the injured cells/tissue, and repair of the site of injury with attempts to reestablish normal parenchymal, stromal, and extracellular matrix relationship. The molecular regulation of this complex physiologic process involves the interaction between cell surface, extracellular matrix, and soluble mediators, such as chemokines. Chemokine activities are mediated through G-protein coupled receptors. This is the largest known family of cell-surface receptors, which mediate transmission of stimuli as diverse as hormones, peptides, glycopeptides, and chemokines. In this review, we will focus on the signaling pathways involved in the production and function of chemokines as they relate to the inflammatory response.

Induction of monocyte chemoattractant protein-1 (MCP-1) production by Pseudomonas nitrite reductase in human pulmonary type II epithelial-like cells

Monocyte chemoattractant protein-1 (MCP-1), a chemoattractant for monocytes, is presumed to play a pivotal role in the recruitment and accumulation of monocytes in various diseases including pulmonary infections. We examined here whether or not Pseudomonas nitrite reductase (PNR), a recently identified IL-8 inducer in various respiratory cells, could stimulate human pulmonary type II epithelial-like cells (A549) to induce MCP-1 production. A time- and dose-dependent induction of MCP-1 protein synthesis associated with an increase of MCP-1 mRNA expression by A549 cells was observed in response to PNR. New protein translation was not required for PNR-mediated MCP-1 mRNA expression in the same cells. When anti-human MCP-1 monoclonal antibody was used for neutralizing of monocyte chemotactic factor (MCF) activities in the culture supernatants of these cells stimulated with PNR, significant reductions of MCF activities (the mean reduction rate; 49-59%, P<0. 05) were observed. These data suggest that PNR may contribute to monocyte migration, through inducing pulmonary epithelial cell-derived MCP-1 production in the airway of patients with pneumonia due to P. aeruginosa.

Endogenous Monocyte Chemoattractant Protein-1 (MCP-1) Protects Mice in a Model of Acute Septic Peritonitis: Cross-Talk Between MCP-1 and Leukotriene B4

We investigated the involvement of monocyte chemoattractant protein (MCP)-1 in a murine model of septic peritonitis induced by cecal ligation and puncture (CLP). Initial studies demonstrated that CLP induced a dramatic increase in MCP-1 production in the peritoneum, followed by an increase in the recruitment of leukocytes. MCP-1 blockade with anti-MCP-1 antiserum significantly decreased the survival rate following CLP, which was accompanied by an enhanced recovery of viable bacteria from the peritoneum. This was likely due to the reduction in the recruitment and activation of both macrophages and neutrophils. To understand the mechanisms whereby MCP-1 may influence neutrophil infiltration, levels of chemokines known to attract neutrophils were monitored, which showed that peritoneal levels of macrophage-inflammatory protein (MIP)-2, KC, and MIP-1α were not altered with anti-MCP-1 Abs. However, anti-MCP-1 Abs reduced the peritoneal levels of leukotriene B4 (LTB4) by 59%. The i.p. injection of MCP-1 into normal mice resulted in elevated levels of LTB4 in the peritoneum. In vitro, MCP-1 stimulated the production of LTB4 from peritoneal macrophages, in a dose-dependent manner. A specific LTB4 receptor antagonist (CP-105,696) inhibited CLP-induced recruitment of both neutrophils and macrophages, which was accompanied by a reduced level of MCP-1 in the peritoneum. Finally, administration of CP-105,696 was extremely detrimental to the survival of mice following CLP. These experiments demonstrate that endogenous MCP-1 serves as an indirect mediator to attract neutrophils via the production of LTB4, and suggest the cross-talk can occur between MCP-1 and the lipid mediator LTB4 during septic peritonitis.

Local production of chemokines during experimental vaginal candidiasis

Recurrent vulvovaginal candidiasis, caused by Candida albicans, is a significant problem in women of childbearing age. Although cell-mediated immunity (CMI) due to T cells and cytokines is the predominant host defense mechanism against C. albicans at mucosal tissue sites, host defense mechanisms against C. albicans at the vaginal mucosa are poorly understood. Based on an estrogen-dependent murine model of vaginal candidiasis, our data suggest that systemic CMI is ineffective against C. albicans vaginal infections. Thus, we have postulated that local immune mechanisms are critical for protection against infection. In the present study, the kinetic production of chemokines normally associated with the chemotaxis of T cells, macrophages (RANTES, MIP-1alpha, MCP-1), and polymorphonuclear neutrophils (MIP-2) was examined following intravaginal inoculation of C. albicans in estrogen-treated or untreated mice. Results showed significant increases in MCP-1 protein and mRNA in vaginal tissue of infected mice as early as 2 and 4 days postinoculation, respectively, that continued through a 21-day observation period, irrespective of estrogen status. No significant changes were observed with RANTES, MIP-1alpha, or MIP-2, although relatively high constitutive levels of RANTES mRNA and MIP-2 protein were observed. Furthermore, intravaginal immunoneutralization of MCP-1 with anti-MCP-1 antibodies resulted in a significant increase in vaginal fungal burden early during infection, suggesting that MCP-1 plays some role in reducing the fungal burden during vaginal infection. However, the lack of changes in leukocyte profiles in vaginal lavage fluids collected from infected versus uninfected mice suggests that MCP-1 functions to control vaginal C. albicans titers in a manner independent of cellular chemotactic activity.

New Frontiers in Cytokine Involvement during Experimental Sepsis

Despite significant advances in the antibiotic arsenal and in intensive care unit technology, including mechanical ventilation, sepsis-related morbidity and mortality remain unacceptably high. Ultimately, 25 to 50% of all septic episodes end in death. However, various subsets of septic patients, including those who experience septic peritonitis, and various secondary sequelae like the acute respiratory distress syndrome or nosocomial infections, demonstrate much higher mortality rates ranging from 60 to 95%. Although a number of strategies have been utilized to curb the progression of systemic inflammatory response syndrome with immune or inflammatory modulating therapies, none of these interventions has resulted in significant improvement in survival, and some have proven deleterious. The inability to utilize immune-modulating strategies effectively to treat septic patients likely reflects the inherent conflict that is illustrated by the two diagnostic criteria for the syndrome. The very immune/inflammatory response that has evolved to eliminate infection results in severe and life-threatening damage to host tissues. This review outlines the inflammatory pathways utilized by the host during a septic response. The basis of early immune-modulating therapies and possible reasons these approaches have failed in the treatment of sepsis are discussed. A picture of the ideal therapeutic approach for acute inflammatory diseases like sepsis is also created, and the reason therapies targeting chemokine pathways may more closely approximate the ideal therapy is proposed.

Monocyte chemoattractant protein-1 gene modification of multidrug-resistant human lung cancer enhances antimetastatic effect of therapy with anti-P-glycoprotein antibody in SCID mice

Distant metastases and multidrug resistance are critical problems in the therapy of human small cell lung cancer (SCLC). In this study, we investigated whether transduction of the monocyte chemoattractant protein-1 (MCP-1) gene into multidrug-resistant (MDR) human lung cancer cells affected the formation of metastases or their inhibition by the anti-P-glycoprotein (P-gp) monoclonal antibody (MAb) MRK16. MDR human SCLC (H69/VP) cells were transduced with the human MCP-1 gene inserted into the expression vector BCMGSNeo. MCP-1 gene transduction had no effect on drug sensitivity, the expression of surface antigens or the in vitro proliferation of H69/VP cells. Using the metastatic model of NK cell-depleted SCID mice, H69/VP cells transduced with the MCP-1 gene were inoculated intravenously (i.v.) and formed metastatic colonies in the liver, kidneys and lymph nodes, similar to those formed by parent or mock-transduced cells. However, systemic treatment of the mice with MRK16 reduced the metastases of H69/VP cells in the liver, kidneys and lymph nodes, and was significantly more effective in inhibiting the metastases of MCP-1 producing H69/VP than those of mock-transduced cells. MCP-1 gene transduction significantly prolonged the survival of tumor-bearing mice treated with MRK16. Our findings suggest that local production of MCP-1 in the tumor site increases the anti-P-gp antibody-dependent cell-mediated cytotoxicity, and the MCP-1 gene-induced modification of MDR human SCLC cells thereby enhances the antimetastatic effect of therapy with anti-P-gp antibody. Thus, the accumulation of effector cells in the tumor site is a very important factor in the therapy using the anti-P-gp antibody.

Synergistic antitumor interaction of human monocyte chemotactant protein-1 gene transfer and modulator for tumor-infiltrating macrophages

PURPOSE

In order to evaluate the possibility of synergistic antitumor gene therapy by the gene delivery of monocyte chemotactant protein-1 (MCP-1/MCAF/IE), the effect of a biological response modulater for macrophages on tumor progression of gene transfected tumor cells was studied.

METHODS

Cachexia-inducing adenocarcinoma cells (cell line colon 26, clone 20) were transfected with either a control plasmid or MCP-1 cDNA.

RESULTS

The production of MCP-1 reached 70-80 ng/ml in vitro when transfectant cells were cultured at a cell density of 1 x 10(5) cells/ml for 3 days. Transfection of MCP-1 cDNA did not affect the growth rate in vitro. Also, MCP-1-transfectants formed tumors after intra-footpad inoculation similar in size to the parental cells. The number of infiltrating macrophages in the primary tumor of the transfectant rapidly increased from the 3rd to 5th day after inoculation as revealed by immunohistochemical staining using an antibody against mouse macrophages. An earlier, greater, but no longer-lasting increase in tumor-infiltrating macrophages was induced in tumors by MCP-1 transfection was compared to that induced by the parent cells. On the 10th day after the inoculation, the tumor-infiltrating macrophages in mice inoculated MCP-1 transfectants were decreased to a level similar to that of the parent cells. Groups of mice were treated intraperitoneally with LPS at different times after the inoculation. Tumor cells producing high levels of MCP-1 were significantly lysed by macrophages treated with LPS, whereas parental or control transfected cells were not. Conclusions. Combination immunotherapy can provide a rationale for the application of MCP-1 treatment to increase immunological responses to cancer.

Chemotaxis of alveolar macrophages in response to signals derived from alveolar epithelial cells

We have postulated that alveolar epithelial cells (AEC) play a critical role in local regulation of alveolar macrophage (AM) recruitment and activation for host defense in the lung. The present study explores the effects of conditioned medium from AEC (AEC-CM) on the migration of AM, using a Boyden chamber assay. AEC-CM was chemotactic for AM, with peak activity observed with a 1:10 dilution. We previously showed that rat AEC express the chemokines RANTES (regulated on activation, normal T expressed and secreted) and monocyte chemoattractant protein 1 (MCP-1) as well as granulocyte-macrophage colony-stimulating factor (GM-CSF). Neutralizing antibodies to RANTES and to MCP-1 and immunoprecipitation of GM-CSF decreased the chemotactic activity of AEC-CM by 58%, 29%, and 47%, respectively. Similar levels of chemotaxis were found in response to recombinant RANTES, MCP-1, and GM-CSF. In each instance the optimal dose was very low (0.01 to 0.1 ng/ml), with diminished chemotaxis at higher doses. Peritoneal macrophages (PM) also migrated in response to AEC-CM and each of the recombinant cytokines; however, AM were much more sensitive to AEC-CM, RANTES, and GM-CSF than were PM. AM migrated preferentially from medium conditioned by unstimulated AEC toward supernatants from interleukin 1alpha-stimulated AEC. Therefore, AEC may control the distribution of AM through the creation of local chemotactic gradients and are likely to play a critical role in the host response to low-level antigen entry into the peripheral lung.

Natural pathogens of laboratory mice, rats, and rabbits and their effects on research

Laboratory mice, rats, and rabbits may harbor a variety of viral, bacterial, parasitic, and fungal agents. Frequently, these organisms cause no overt signs of disease. However, many of the natural pathogens of these laboratory animals may alter host physiology, rendering the host unsuitable for many experimental uses. While the number and prevalence of these pathogens have declined considerably, many still turn up in laboratory animals and represent unwanted variables in research. Investigators using mice, rats, and rabbits in biomedical experimentation should be aware of the profound effects that many of these agents can have on research.

Interleukin-8 (IL-8) and monocyte chemotactic and activating factor (MCAF/MCP-1), chemokines essentially involved in inflammatory and immune reactions

Leukocyte infiltration is a hallmark of inflammation. Knowledge on molecular mechanisms of leukocyte infiltration has advanced rapidly due to the recent elucidation of structures and functions of adhesion molecules and chemokines. Since the discovery of interleukin-8 (IL-8), a prototype of CXC chemokines, in 1987 and monocyte chemotactic and activating factor/monocyte chemoattractant protein-1 (MCAF/MCP-1), a prototype of chemotactic cytokines (CC) chemokines, in 1989, more than 30 members of chemokines have been identified so far. Evidence is accumulating that these chemokines exert overlapping but distinct actions on specific types of leukocytes in vitro through interacting with their specific G-protein-coupled receptors with seven transmembrane domains. However, redundancy at receptor levels has frequently hindered the clarification on the precise physiological or pathophysiological roles of chemokines. Here, we describe the pathophysiological roles of IL-8 and MCAF/MCP-1 in several animal models of neutrophil- and macrophage-mediated inflammation, respectively, by focusing on our recent work using neutralizing antibodies to these chemokines. We discuss further potential roles of these chemokines in T-lymphocyte-mediated immune responses.

Therapeutic effects of nitric oxide inhibition during experimental fecal peritonitis: role of interleukin-10 and monocyte chemoattractant protein 1

This study demonstrates that the therapeutic effect of a nitric oxide inhibitor in a murine model of fecal peritonitis is mediated in part by increased levels of interleukin-10 (IL-10) and monocyte chemoattractant protein 1 (MCP-1). Female CD1 mice were subjected to cecal ligation and puncture (CLP) with a 21-gauge needle and, immediately following surgery, were injected intraperitoneally with saline, N(G)-nitro-L-arginine methyl ester (L-NAME; 8 mg/kg), or N(G)-nitro-D-arginine methyl ester (D-NAME; 8 mg/kg). At 96 h after surgery and drug treatment, 20% of mice that received D-NAME had survived whereas 60% of mice that received L-NAME were alive. To elucidate the effect of L-NAME treatment on chemokine and cytokine production during fecal peritonitis, the levels of macrophage inflammatory protein 2 (MIP-2), IL-10, and MCP-1 were measured in peritoneal washings from additional groups of mice 24 h after the CLP surgery. Peritoneal fluids from L-NAME-treated mice contained significantly higher levels of IL-10 and MCP-1 than did those from D-NAME-treated mice. To elucidate the effect of nitric oxide inhibition on potential cellular sources of IL-10 and MCP-1 in the CLP model, cultured alveolar and peritoneal macrophages were activated with bacterial lipopolysaccharide in the presence of L-NAME; these macrophages produced significantly more MCP-1 than did similarly activated macrophages in the presence of D-NAME. In the CLP surgery model, immunoneutralization of IL-10 alone or IL-10 and MCP-1 together with polyclonal antibodies prior to surgery significantly reduced the survival rates in L-NAME-treated groups compared with L-NAME-treated groups that received preimmune serum. Taken together, these data demonstrate that the inhibition of nitric oxide following experimental CLP fecal peritonitis is therapeutic, in part through the modulatory effect of this treatment on the synthesis of IL-10 and MCP-1.

Analysis of the immune response in sheep efferent lymph during Salmonella abortusovis infection

The efferent lymph duct of the ovine prescapular lymph node was cannulated, and Salmonella abortusovis (SAO), a specific pathogen for sheep inducing abortion and mortality of newborn lambs, was inoculated by the subcutaneous route in this lymph node drained area. While the prescapular lymph node draining the inoculation site represented an efficient barrier for the vaccinal SAO Rv6 strain spreading, SAO 15/5 virulent bacteria were steadily detected in efferent lymph of infected sheep. The inoculation of the virulent strain of SAO induced a greater increase of the cell output than did the attenuated vaccinal strain, but proportions of blast cells appearing in the efferent lymph were similar in both cases. Flow cytometry analysis showed that B and T cell outputs were both increased during SAO infections, but while T cell subset proportions slightly decreased, B cell percentages significantly rose, and, at the peak response, almost all of the lymphoblast cells were activated B cells. Typical antibody profiles characteristic of a primary immune response were observed, and antibody titres were greater in the efferent lymph of animals inoculated with the virulent strain of SAO. Many of the cytokine mRNAs we investigated were steadily detected by RT-PCR in efferent lymph cells of control sheep, but frequencies of detection of IL-2, IFN gamma, IL-1 beta and TNF alpha mRNAs were augmented in efferent lymph cells following inoculation of both SAO virulent or vaccinal strains. IL-10 and IL-8 mRNAs could only be detected after a SAO inoculation, while detection of IL-4 mRNAs was increased only in efferent lymph cells from SAO virulent strain-infected sheep. The efferent lymph cannulation technique thus appeared a very powerful way to study the in vivo development of the immune response to SAO, in its natural host, the sheep.

MCP-1 protects mice in lethal endotoxemia

The overzealous production of proinflammatory cytokines in sepsis can result in shock, multiorgan dysfunction, and even death. In this study, we assessed the role of monocyte chemoattractant protein-1 (MCP-1) as a mediator of sepsis in endotoxin-challenged mice. Intraperitoneal administration of LPS to CD-1 mice induced a substantial time-dependent increase in MCP-1 in plasma, lung, and liver. The passive immunization of mice with rabbit antimurine MCP-1 antiserum 2 h before endotoxin administration resulted in a striking increase in LPS-induced mortality from 10% in control animals to 65% in anti-MCP-1-treated animals. Importantly, the administration of anti-MCP-1 antibodies to endotoxin-challenged mice resulted in increases in peak TNF-alpha and IL-12 levels, and also in a trend toward decreased serum levels of IL-10. Conversely, the administration of recombinant murine MCP-1 intraperitoneally significantly protected mice from endotoxin-induced lethality, and resulted in an increase in IL-10 levels, a decrease in IL-12 levels, and a trend toward decreased levels of TNF. In conclusion, our findings indicate that MCP-1 is a protective cytokine expressed in murine endotoxemia, and does so by shifting the balance in favor of antiinflammatory cytokine expression in endotoxin-challenged animals.

Combined therapy of multidrug-resistant human lung cancer with anti-P-glycoprotein antibody and monocyte chemoattractant protein-1 gene transduction: the possibility of immunological overcoming of multidrug resistance

We determined whether transduction of the monocyte chemoattractant protein-1 (MCP-1) gene into MDR human lung cancer cells affected their tumorigenicity and sensitivity to antibody-dependent cellular cytotoxicity (ADCC) reaction mediated by the anti-P-glycoprotein (P-gp) monoclonal antibody MRK16. The human MCP-1 gene inserted into an expression vector (BCMGSNeo) was transfected into MDR human small-cell lung cancer (H69/VP) cells. Monocyte chemotactic activity was found in culture supernatants collected from MCP-1-transfected H69/VP cells, but not in supernatants of parent and mock-transfected cells. In an in vitro experiment, recombinant MCP-1 did not affect monocyte-mediated ADCC against H69/VP cells when added to the monocyte culture in either the activation or the effector phase at sufficient concentrations to attract and activate monocytes. Tumorigenicity and growth rates of MCP-1-producing H69/VP cells in nude mice were similar to those of parental cells and mock-transfected cells. However, systemic treatment with MRK16 was more effective in inhibiting the formation of tumors by MCP-1-gene-transfected cells than by mock-transfected cells. Systemic treatment with MRK16 also inhibited the growth of a mixture (1:1) of MCP-1-producing cells and mock-transfected cells. These results suggest that combination therapy with MRK16 and MCP-1 gene transduction may be a useful immunological strategy to inhibit the growth of human MDR cancer cells expressing P-gp.

Construction of a recombinant human GM-CSF/MCAF fusion protein and study on itsin vitro andin vivo antitumor effects

A novel cytokine fusion protein was constructed by fusing granulocyte macrophage colony stimulating factor (GM-CSF) with monocyte chemotactic activating factor (MCAF), which acts as a factor directing effector cells (monocytes) to a target site. The recombinant human GM-CSF/MCAF fusion protein could sustain the growth of GMCSF-dependent cell line TF1 and was chemotactic for monocytes. Thein vitro antitumor effect showed that rhGM-CSF/MCAF could activate monocytes to inhibit the growth of several human tumor cell lines, including a promyelocyte leukemia cell line HL-60, a lung adenocarcinoma cell line A549, a hepatoma cell line SMMC-7721 and a melanoma cell line Bowes. Furthermore, the cytotoxicity of monocytes activated by rhGM-CSF/MCAF against HL-60 and A549 was greater than that activated by GM-CSF or MCAF alone, even greater than that activated by a combination of GM-CSF and MCAF, suggesting that the fusion protein has synergistic or enhanced effects. Thein vivo antitumor effect indicated that rhGM-CSF/MCAF had marked antitumor effect against A549 tumor in nude mice and even completely suppressed tumor formation. rhGM-CSF/MCAF was significantly more effective in inhibiting tumor growth than rhGM-CSF. Histological analysis showed that tumor site injected with rhGM-CSF/MCAF was infiltrated by a large number of monocytes while a sparse infiltration of monocytes was observed at the tumor site injected with rhGM-CSF or normal saline, suggesting that the antitumor effect of rhGM-CSF/MCAF was mediated by the recruitment of a large number of monocytes to the tumor site.

Activation of human monocytes for enhanced production of interleukin 8 during transendothelial migration in vitro

Interleukin-8 (IL-8) is a chemokine for polymorphonuclear leukocytes (PMNs) and lymphocytes, which promotes the extravasation of these inflammatory cells. In this study, we investigated IL-8 synthesis induced by the adhesive interaction between monocytes and endothelial cells during transmigration and the capacity of transmigrated monocytes to produce IL-8. Cocultured human monocytes and human umbilical vein endothelial cell (HUVEC) monolayers induced the synergistic production of IL-8, compared with cultures of either monocytes or HUVEC monolayers alone. Coculture-induced IL-8 production almost doubled after HUVECs were stimulated with IL-1 beta. The induced IL-8 mRNA expression was consistent with the protein data, indicating the de novo synthesis of IL-8 by the coculture. Monoclonal antibodies (mAbs) against IL-8 inhibited the transendothelial chemotactic activity of the supernatants for PMNs by 55%. Immunohistochemistry revealed that both adherent and transmigrated monocytes and unstimulated HUVECs expressed IL-8 protein, whereas nonadherent monocytes did little. Transmigrated monocytes spontaneously secreted a 3.8-fold greater amount of IL-8 than the initial monocytes. Coculture-induced IL-8 production was inhibited about 30% by polyclonal Abs against IL-alpha, IL-1 beta, or tumor necrosis factor alpha, while it was not affected by mAbs against intercellular adhesion molecule 1 or vascular cell adhesion molecule 1. The results suggested that adhesive interaction during the transmigration of monocytes through HUVEC monolayers activates both cell types to produce IL-8 and that transmigrated monocytes are capable of producing ample IL-8.

Introducing Critical Appraisal to studies of animal models investigating novel therapies in sepsis

OBJECTIVES

To discuss theoretical and practical aspects relating to the design of animal studies investigating the efficacy of novel therapeutic agents for the treatment of sepsis, and to make explicit the process whereby these studies can be evaluated for the purpose of designing clinical trials in humans.

DATA SOURCES

Relevant articles from the pertinent literature were reviewed.

STUDY SELECTION

Studies relevant to an evidence-based assessment of clinical studies on therapeutic efficacy, and studies relevant to the design of animal models of sepsis were selected.

DATA EXTRACTION

Concepts relevant to an evidence-based assessment of the animal literature were extracted.

DATA SYNTHESIS

Articles were reviewed and an evidence-based framework for the assessment of animal studies was developed. In this process, we discuss the steps that are necessary to assess the internal validity of an individual study and review topics relevant to the application of animal data to the design of clinical trials.

CONCLUSIONS

The success of clinical trials of sepsis therapies is predicated on the generation and interpretation of sound preclinical data. In this review, we have attempted to outline an evidence-based approach to the assessment of preclinical animal studies evaluating novel therapeutic interventions in sepsis.

Cytokines and bacterial infections

During the recent 10-15 years a growing amount of knowledge has been accumulated on the role of cytokines in the pathogenesis and resistance to infections caused by nonviral agents, including a wide range of bacteria. Cytokines can be major mediators of the pathogenic effect in some diseases, and represent important defense mechanisms in others. Detailed knowledge on the role of the growing number of recognised cytokines is important, because it may represent means to combat and to prevent diseases caused by such infections.

Induction of macrophage antiprotozoal activity by monocyte chemotactic and activating factor

To determine if monocyte chemotactic and activating factor (MCAF) induces intracellular antimicrobial activity, human monocyte-derived macrophages were treated with MCAF and challenged with Toxoplasma gondii and Leishmania donovani. Pretreatment with MCAF induced macrophages to inhibit protozoal replication by approximately 50%. These findings suggest a potential host defense role for MCAF in the inflammatory response to intracellular pathogens.

Human MCAF gene transfer enhances the metastatic capacity of a mouse cachectic adenocarcinoma cell line in vivo

PURPOSE

To evaluate the effect of monocyte chemotactic and activating factor (MCAF/MCP-1/JE) on tumor progression and metastasis.

METHODS

Cachexia-inducing adenocarcinoma cells (cell line colon 26, clone 20) were transfected with either a control plasmid or MCAF expression vector. Spontaneous lung metastases were determined in mouse.

RESULTS

The production of MCAF reached 0.4 ng/ml in vitro when transfectant cells were cultured at a cell density of 5 x 10(4) cells/ml for 3 days. Transfection of MCAF expression vector did not affect the growth rate in vitro. Also, after MCAF-transfection, the size of tumors after intra-footpad inoculation was similar to that of the parental cells. When the primary tumors were resected on the 10th day after inoculation, the incidence of spontaneous lung metastasis was less than 20% in both cells. The number of endothelial cells in the primary tumor rapidly increased from the 10th to the 14th day after inoculation, as revealed by immunohistochemical staining. In accordance with enhanced angiogenesis, the incidence rates of spontaneous metastasis increased when the primary tumors were resected on the 14th day after inoculation. Moreover, the spontaneous lung metastases were augmented in the animals injected with MCAF-transfectants compared to those injected with parental cells with a concomitant increase of angiogenesis.

CONCLUSIONS

These results suggest that MCAF may augment the metastastic potential by modulating tumor associated angiogenesis.

Airway interleukin-8 in elderly patients with bacterial lower respiratory tract infections

We investigated the interleukin-8 (IL-8) levels and neutrophil numbers in the sputum of 9 elderly patients with lower respiratory tract infections, including Pseudomonas aeruginosa infection, before and after treatment with various antimicrobial agents. The IL-8 levels in sputum supernatants and the neutrophil numbers in sputum smears from 9 patients decreased significantly after the elimination of the causative respiratory pathogens. We also demonstrated that human recombinant IL-8 at a range of 6.25-25 ng/ml significantly enhanced opsonophagocytic killing of P. aeruginosa immunotype-1 strain by human neutrophils in the presence of a serotype-specific anti-lipopolysaccharide monoclonal antibody and fresh normal human serum. These data suggest that the level of IL-8 production in the airways of patients with lower respiratory tract infections is dependent on bacterial densities, and indicate the important role of IL-8 not only in neutrophil migration but also in opsonophagocytic killing of bacteria in the lower respiratory tract.

Chemokines: progress toward identifying molecular targets for therapeutic agents

Leukocyte migration towards injury sites is directed by the interaction of chemokines with their receptors. The stages of migration are closely regulated events that involve chemokine-induced leukocyte adhesion, diapedesis and homing. Current research suggests a pathophysiological role for chemokines in diverse inflammatory states arising from viral, bacterial and parasitic infection, allergic and asthmatic reactions, atherosclerosis and arthritis. A role for chemokines in tumor immunity and angiogenesis has recently been demonstrated. A basis for the rational design of chemokine antagonists is emerging from a knowledge of tertiary structures and mutational analysis of chemokine ligands and receptors. Here, we discuss advances in knowledge about chemokine structure and function, with emphasis on potential therapeutic agents.

Human MCAF gene transfer enhances the metastatic capacity of a mouse cachectic adenocarcinoma cell line in vivo

PURPOSE

To evaluate the effect of monocyte chemotactic and activating factor (MCAF/MCP-1/JE) on tumor progression and metastasis.

METHODS

Cachexia-inducing adenocarcinoma cells (cell line colon 26, clone 20) were transfected with either a control plasmid or MCAF expression vector. Spontaneous lung metastases were determined in mouse.

RESULTS

The production of MCAF reached 0.4 ng/ml in vitro when transfectant cells were cultured at a cell density of 5 x 10(4) cells/ml for 3 days. Transfection of MCAF expression vector did not affect the growth rate in vitro. Also, after MCAF-transfection, the size of tumors after intra-footpad inoculation was similar to that of the parental cells. When the primary tumors were resected on the 10th day after inoculation, the incidence of spontaneous lung metastasis was less than 20% in both cells. The number of endothelial cells in the primary tumor rapidly increased from the 10th to the 14th day after inoculation, as revealed by immunohistochemical staining. In accordance with enhanced angiogenesis, the incidence rates of spontaneous metastasis increased when the primary tumors were resected on the 14th day after inoculation. Moreover, the spontaneous lung metastases were augmented in the animals injected with MCAF-transfectants compared to those injected with parental cells with a concomitant increase of angiogenesis.

CONCLUSIONS

These results suggest that MCAF may augment the metastastic potential by modulating tumor associated angiogenesis.

Induction of monocyte chemoattractant protein-1 synthesis in human monocytes during transendothelial migration in vitro

Monocyte chemoattractant protein-1 (MCP-1, or monocyte chemotactic and activating factor) plays important roles in the recruitment of monocytes and thus in the development of atherosclerosis. In this study, we determined whether MCP-1 synthesis was induced by the cellular interaction between monocytes and endothelial cells during the process of transendothelial migration. We found that when human peripheral blood monocytes (2.5 x 10(6) cells) and umbilical vein endothelial cells (HUVECs; 5.0 x 10(5) cells) were cocultured for 5 hours, 7.9 ng/mL MCP-1 was secreted into the medium, whereas when the two were cultured separately, MCP-1 levels were 1.0 and 0.9 ng/mL, respectively. Furthermore, the use of interleukin-1 beta (IL-1 beta)-pretreated HUVECs in cocultures induced twice the levels of MCP-1 as in unstimulated HUVEC culture. Conditioned medium had transendothelial chemotactic activity for monocytes, and this activity was completely abolished by addition of anti-MCP-1 antibody. Although MCP-1 mRNA levels were very low or undetectable in HUVECs or monocytes alone, message could be detected after 2 hours of coculture in total mRNA preparations from both monocytes and HUVECs. mRNA levels increased by 4 hours and had declined slightly by 24 hours. The rapid induction of message suggests that cell contact between monocytes and HUVECs induces the de novo synthesis of MCP-1 protein. Anti-interleukin (IL)-1 alpha/beta and anti-tumor necrosis factor-alpha antibodies, or anti-lymphocyte function-associated antigen-1 and very late antigen-4 antibodies, had little or no inhibitory effects on MCP-1 secretion by cocultures.(ABSTRACT TRUNCATED AT 250 WORDS)

Suppressive role of endogenous endothelial monocyte chemoattractant protein-1 on monocyte transendothelial migration in vitro

Monocyte chemoattractant protein-1 (MCP-1, or monocyte chemotactic and activating factor) is thought to play an important role in monocyte infiltration into tissue, but little is known about its effect on monocyte-endothelium interaction. We examined the effect of MCP-1 produced by cytokine-activated endothelial cells (ECs) on monocyte-endothelium adhesion and subsequent transendothelial migration by using a double-chamber vessel model. Unstimulated ECs showed no MCP-1 expression, but exposure to interleukin-1 beta (IL-1 beta, 25 U/mL) induced marked MCP-1 mRNA expression and protein synthesis. When placed in the lower compartment, recombinant human (rh) MCP-1 (100 ng/mL) produced a 1.9-fold and a 2.7-fold increase in adhesion and migration, respectively, compared with a corresponding 51% and 59% decrease when placed in the upper compartment. Migration of monocytes was dependent on a gradient of rh-MCP-1 from the apical to basilar side of the EC layer. Furthermore, a forward gradient of MCP-1 induced adherent cells to increase their subsequent migration, whereas a reverse gradient induced the cells to detach and completely inhibited their subsequent migration. Pretreatment with IL-1 beta for 4 and 24 hours produced a 20% and 63% increase in monocyte migration, respectively. In the presence of anti-MCP-1 antibody, the increase was further enhanced by 52% and 152%, respectively. These results suggest that endogenous endothelial MCP-1, when secreted by IL-1-stimulated ECs, suppresses monocyte migration in the presence of MCP-1 on the basilar side of the EC layer.(ABSTRACT TRUNCATED AT 250 WORDS)