Pristine graphene induces innate immune training

Graphene-based materials are of increasing interest for their potential use in biomedical applications. However, there is a need to gain a deeper understanding of how graphene modulates biological responses before moving towards clinical application. Innate immune training is a recently described phenomenon whereby cells of the innate immune system are capable of being programmed to generate an increased non-specific response upon subsequent challenge. This has been well established in the case of certain microbes and microbial products. However, little is known about the capacity of particulate materials, such as pristine graphene (pGr), to promote innate immune training. Here we report for the first time that while stimulation with pGr alone does not directly induce cytokine secretion by bone-marrow derived macrophages (BMDMs), it programs them for enhanced secretion of proinflammatory cytokines (IL-6, TNF-α) and a concomitant decrease in production of the regulatory cytokine, IL-10 after Toll-like receptor (TLR) ligand stimulation. This capacity of pGr to program cells for enhanced inflammatory responses could be overcome if the nanomaterial is incorporated in a collagen matrix. Our findings thus demonstrate the potential of graphene to modulate innate immunity over long timescales and have implications for the design and biomedical use of pGr-based materials.

Men Have a Stronger Monocyte-Derived Cytokine Production Response upon Stimulation with the Gram-Negative Stimulus Lipopolysaccharide than Women: A Pooled Analysis Including 15 Study Populations

The incidence of bacterial infections and sepsis, as well as the mortality risk from sepsis, is sex specific. These clinical findings have been attributed to sex differences in immune responsiveness. The aim of the present study was to investigate sex differences in monocyte-derived cytokine production response upon stimulation with the gram-negative stimulus lipopolysaccharide (LPS) using cytokine data from 15 study populations. Individual data on ex vivo cytokine production response upon stimulation with LPS in whole blood were available for 4,020 subjects originating from these 15 study populations, either from the general population or from patient populations with specific diseases. Men had a stronger cytokine production response than women to LPS for tumour necrosis factor-α, interleukin (IL)-6, IL-12, IL-1β, IL-1RA, and IL-10, but not for interferon-γ. The granulocyte-macrophage colony-stimulating factor production response was lower in men than in women. These sex differences were independent of chronological age. As men had higher monocyte concentrations, we normalized the cytokine production responses for monocyte concentration. After normalization, the sex differences in cytokine production response to LPS disappeared, except for IL-10, for which the production response was lower in men than in women. A sex-based approach to interpreting immune responsiveness is crucial.

Recovery from an acute systemic and central LPS-inflammation challenge is affected by mouse sex and genetic background

Genetic and sexual factors influence the prevalence and the pathogenesis of many inflammatory disorders. In this study their relevance on the peripheral and central inflammatory status induced by a peripheral injection of lipopolysaccharide (LPS) was evaluated. BALB/c and CD-1 male and female mice were intraperitoneally injected with LPS. Spleens and brains were collected 2 and 72 hours later to study the levels of IL-6, TNF-α and IL-1β. Percentage of microglia and astrocytes was determined in the cortex and hippocampus. Locomotor activity was registered before and during the 72 hours after LPS-treatment. Two hours after LPS-injection, a peripheral increase of the three cytokines was found. In brains, LPS increased TNF-α only in males with higher levels in CD-1 than BALB/c. IL-1β increased only in CD-1 males. IL-6 increased in both strains with lower levels in BALB/c females. Peripheral and central levels of cytokines decline 72 hrs after LPS-treatment whilst a significantly increase of Iba-1 expression was detected. A dramatic drop of the locomotor activity was observed immediately after LPS injection. Our results show that acute systemic administration of LPS leads to peripheral and central increase of pro-inflammatory cytokines and microglia activation, in a strain and sex dependent manner.

Chemokine Receptor Ccr6 Deficiency Alters Hepatic Inflammatory Cell Recruitment and Promotes Liver Inflammation and Fibrosis

Chronic liver diseases are characterized by a sustained inflammatory response in which chemokines and chemokine-receptors orchestrate inflammatory cell recruitment. In this study we investigated the role of the chemokine receptor CCR6 in acute and chronic liver injury. In the absence of liver injury Ccr6-/- mice presented a higher number of hepatic macrophages and increased expression of pro-inflammatory cytokines and M1 markers Tnf-α, Il6 and Mcp1. Inflammation and cell recruitment were increased after carbon tetrachloride-induced acute liver injury in Ccr6-/- mice. Moreover, chronic liver injury by carbon tetrachloride in Ccr6-/- mice was associated with enhanced inflammation and fibrosis, altered macrophage recruitment, enhanced CD4+ cells and a reduction in Th17 (CD4+IL17+) and mature dendritic (MHCII+CD11c+) cells recruitment. Clodronate depletion of macrophages in Ccr6-/- mice resulted in a reduction of hepatic pro-inflammatory and pro-fibrogenic markers in the absence and after liver injury. Finally, increased CCR6 hepatic expression in patients with alcoholic hepatitis was found to correlate with liver expression of CCL20 and severity of liver disease. In conclusion, CCR6 deficiency affects hepatic inflammatory cell recruitment resulting in the promotion of hepatic inflammation and fibrosis.

Vasoactive intestinal peptide (VIP) differentially affects inflammatory immune responses in human monocytes infected with viable Salmonella or stimulated with LPS

We compared the effect of VIP on human blood monocytes infected with Salmonella typhimurium 4/74 or stimulated with LPS. VIP (10(-7)M) increased monocyte viability by 24% and 9% when cultured for 24h with 4/74 or Salmonella LPS (100ng/ml), respectively. Significantly increased (P<0.05) numbers of 4/74 were also recovered from monocytes co-cultured with VIP after 6h post-infection (pi) and this remained high after 24h pi. Both 4/74 and LPS increased (P<0.05) the concentration of TNF-α, IL-1β and IL-6 measured in monocyte supernatants. However, LPS induced this effect more rapidly while, with the exception of IL-6, 4/74 induced higher concentrations (P<0.05). VIP significantly decreased (P<0.05) TNF-α and IL-1β production by 4/74-infected monocytes after 6 pi, but only after 24h in LPS-cultured monocytes. This trend was reversed for IL-6 production. However, TNF-α and IL-1β production by 4/74-infected monocytes, cultured with VIP, still remained higher (P<0.05) than concentrations measured in supernatants cultured only with LPS. VIP also increased (P<0.05) production of anti-inflammatory IL-10 in both 4/74 and LPS cultures after 24h. We also show a differential effect of VIP on the expression of TNFα and IL-6 receptors, since VIP was only able to decreased expression in LPS-stimulated monocytes but not in 4/74-infected monocytes. In conclusion, we show a differential effect of VIP on human monocytes infected with virulent Salmonella or stimulated with LPS. Our study suggests that the use of VIP in bacteraemia and/or sepsis may be limited to an adjunctive therapy to antibiotic treatment.

The effect of toll-like receptor 4 on macrophage cytokines during endotoxin induced uveitis

Toll-like receptor 4 (TLR4) signal activation of macrophages can lead to endotoxin-induced uveitis (EIU). Previously, our research group has demonstrated a higher expression of TLR4 in vivo during EIU than normal. In this study, we analyzed levels of peritoneal macrophage cytokines from C3H/HeN mice with LPS stimulation in vitro to elucidate the effect of TLR4 on cytokines during EIU.

CXC Chemokine Ligand 9/Monokine Induced by IFN-γ Production by Tumor Cells Is Critical for T Cell-Mediated Suppression of Cutaneous Tumors

The role of tumor-produced chemokines in the growth of malignancies remains poorly understood. We retrieved an in vivo growing MCA205 fibrosarcoma and isolated tumor cell clones that produce both CXCL9/monokine induced by IFN-gamma (Mig) and CXCL10/IFN-gamma-inducible protein 10 following stimulation with IFN-gamma and clones that produce IFN-gamma-inducible protein 10 but not Mig. The Mig-deficient variants grew more aggressively as cutaneous tumors in wild-type mice than the Mig-producing tumor cells. The growth of Mig-expressing, but not Mig-deficient, tumor cells was suppressed by NK and T cell activity. Transduction of Mig-negative variants to generate constitutive tumor cell production of Mig resulted in T cell-dependent rejection of the tumors and in induction of protective tumor-specific CD8(+) T cell responses to Mig-deficient tumors. The results indicate a critical role for tumor-derived Mig in T cell-mediated responses to cutaneous fibrosarcomas and suggest the loss of Mig expression as a mechanism used by tumor cells to evade these responses.

[Protective effect of low-power laser radiation in acute toxic stress]

The effect of preliminary short-term irradiation with He-Ne laser light (632.8 nm, 0.2 mW/cm2) of the thymus zone projection of male NMRI mice subjected to acute toxic stress on the responses of immune cells was studied. Stress was modeled by lipopolysaccharide injection, 250 mg/100 g of body weight, which induced a significant increase in the production of several macrophage cytokines, IL-1alpha, IL-1beta, IL-6, IL-10 and TNF-alpha. A single irradiation with laser light did not provoke considerable variations in NO production in cells but induced an enhancement in the production of heat shock proteins Hsp25, Hsp70, and Hsp90. Nevertheless, when irradiation with red laser light was applied prior to toxic stress, considerable normalization of production of nearly all cytokines studied and nitric oxide was observed. Moreover, the normalization of production of heat shock proteins has been shown in these conditions. Thus, preliminary exposure of a small area of animal skin surface provoked a significant lowering in the toxic effect of lipopolysaccharide.

Spondyloarthropathy: disease at the crossroads of immunity

Up until recently, the prevailing paradigm relating to spondyloarthropathy (SpA) pathogenesis was that they were human leukocyte antigen (HLA)-associated, T-cell-driven autoimmune diseases. This view is now being questioned. Careful studies of well-characterised cohorts of patients with SpA, including detailed analysis of involved tissue, together with clinical trials of targeted treatments, in particular anti-tumour necrosis factor (TNF) therapies, have contributed enormously to both interest in and understanding of disease pathogenesis. In this chapter, our current knowledge and understanding of the relative contributions of the components of the innate and adaptive arms of the immune response to SpA pathogenesis is reviewed. It is clear that both arms of the immune response are involved and inter-dependent in SpA. With continued emphasis on discovery research, including detailed analysis of novel therapeutic interventions, significant additional breakthroughs in SpA are likely to be forthcoming.

Tumour necrosis factor alpha mediated apoptosis in murine macrophages by Salmonella enterica serovar Typhi under oxidative stress

Invasive Salmonella has been reported to induce apoptosis of macrophages as part of its infection process, which may allow it to avoid detection by the innate immune system. However, the induction of apoptosis under the different host environments remains to be examined, including the oxidative stress experienced by pathogens in the macrophage milieu. To simulate in vivo oxidative conditions, Salmonella enterica serovar Typhi was grown in the presence of hydrogen peroxide and its ability to induce apoptosis of murine macrophages was assessed. Analysis of data revealed that oxidative stressed S. Typhi caused apoptotic cell death in 51% of macrophages, whereas S. Typhi grown under normal conditions accounted for apoptotic cell death in only 32% of macrophages. A significant increase in the levels of oxidants and decrease in the antioxidant was also observed which correlated with the increased generation of tumour necrosis factor alpha, interleukin-1alpha and interleukin-6. These results suggest that tumour necrosis factor alpha in conjunction with other cytokines may induce apoptotic cell death through the up-regulation of lipid peroxidation and down-regulation of superoxide dismutase. This finding may help us to understand better the host-pathogen interactions and may be of clinical importance in the development of preventive intervention against infection.

A suppressive role of nitric oxide in MIP-2 production by macrophages upon coculturing with apoptotic cells

Macrophages phagocytose apoptotic cells without causing neutrophil infiltration in vivo under physiological conditions. Our recent study, however, showed that macrophages produce IL-8 or MIP-2, a murine IL-8 homologue, upon coculturing with apoptotic cells, indicating that there must be unknown mechanisms for preventing IL-8 or MIP-2 production. As activated macrophages produce NO to regulate inflammation, we examined the NO production by macrophages upon coculturing with apoptotic or necrotic cells and explored the role of NO in MIP-2 production. NO was produced on coculturing with early apoptotic cells much more significantly than with late apoptotic or necrotic cells. On the contrary, MIP-2 was produced on coculturing with late apoptotic or necrotic cells much more significantly than with early apoptotic cells. N(G)-Nitro-L-arginine methyl ester, an inhibitor of NO synthase, or 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, a scavenger of NO, augmented MIP-2 production on coculturing with early apoptotic cells. The addition of N-ethylethanamine:1,1-diethyl-2-hydroxy-2-nitrosohydrazine [1:1], a donor of NO, conversely, caused suppression of MIP-2 production on coculturing with late apoptotic cells. These results suggest an important role of NO for preventing MIP-2 production by macrophages upon coculturing with early apoptotic cells.

Glycogen synthase kinase-3beta inhibition attenuates the degree of arthritis caused by type II collagen in the mouse

Recently, glycogen synthase kinase-3 (GSK-3) has being identified as an ubiquitous serine-threonine protein kinase that participates in a multitude of cellular processes and plays an important role in the pathophysiology of a number of diseases. The aim of this study was to investigate the effects of GSK-3beta inhibition on the degree of arthritis caused by type II collagen (CII) in the mouse (collagen-induced arthritis; CIA). Mice developed erosive hind paw arthritis when immunized with CII in an emulsion in complete Freund's adjuvant (CFA). The incidence of CIA was 100% by day 28 in the CII-challenged mice and the severity of CIA progressed over a 35-day period with radiographic evaluation revealing focal resorption of bone. The histopathology of CIA included erosion of the cartilage at the joint margins. Treatment of mice with the GSK-3beta inhibitor TDZD-8 (1 mg/kg/day i.p.) starting at the onset of arthritis (day 25) ameliorated the clinical signs at days 26-35 and improved histological status in the joint and paw. Immunohistochemical analysis for nitrotyrosine, poly(ADP-ribose) (PAR), inducible nitric oxide synthase (iNOS), and cyclooxygenase-2 (COX-2) revealed a positive staining in inflamed joints from mice subjected to CIA. The degree of staining for nitrotyrosine, PAR, iNOS, and COX-2 was significantly reduced in CII-challenged mice treated with the GSK-3beta inhibitor. Plasma levels of tumor necrosis factor (TNF)-alpha and the joint tissue levels of macrophage inflammatory protein (MIP)-1alpha and MIP-2 were also significantly reduced by GSK-3beta inhibition. These data demonstrate that GSK-3beta inhibition exerts an anti-inflammatory effect during chronic inflammation and is able to ameliorate the tissue damage associated with CIA.

Theiler's virus induces the MIP-2 chemokine (CXCL2) in astrocytes from genetically susceptible but not from resistant mouse strains

The murine encephalomyelitis virus of Theiler (TMEV) induces demyelination in susceptible strains of mice by a CD4(+) Th1 T cell mediated immunopathologic process. We focused on the production of one chemokine, the macrophage inflammatory protein-2 (MIP-2 or CXCL2), by cultured mouse astrocytes infected with the BeAn strain of TMEV. Analysis of a murine genome DNA hybridized with cRNA from mock- and TMEV-infected astrocytes, revealed up-regulation of three sequences encoding MIP-2. Northern blot analysis indicated increased MIP-2 mRNA expression. Levels of MIP-2 in the supernatants of infected cells as detected by ELISA, varied directly with the multiplicity of infection used. This secreted CXCL2 was biologically active inducing chemoattraction of neutrophils but not of lymphocytes. CXCL2 was specifically induced by TMEV infection, since induction was inhibited by anti TMEV antibodies. The inflammatory cytokines, IL-1alpha and TNF-alpha, which are also induced in astrocytes by TMEV, were very potent inducers of CXCL2. Nevertheless, both mechanisms of induction follows different pathways as antibodies to both cytokines fails to inhibit TMEV-induced CXCL2 up-regulation. Sera from TMEV-infected SJL/J mice with chronic demyelination, but not from BALB/c TMEV-resistant mice, revealed CXCL2 at the peak of clinical disease. Our main novel finding is the strain-dependent differences in CXCL2 expression both in vitro and in vivo. This suggest an role for this chemokine in attracting immune cells within the CNS, which in turn, might trigger demyelination in this experimental model of MS.

Effect of boldine, secoboldine, and boldine methine on angiotensin II-induced neurtrophil recruitment in vivo

Angiotensin-II (Ang-II) has inflammatory activity and is involved in different diseases associated with the cardiovascular system. This study has evaluated the effect of boldine (B), and two phenanthrene alkaloids semisynthesized by us, secoboldine (SB) and boldine methine (BM), on Ang-II-induced neutrophil recruitment. Intraperitoneal administration of 1 nM Ang-II induced significant neutrophil accumulation, which was maximal at 4-8 h. BM inhibited neutrophil infiltration into the peritoneal cavity at 4 h and 8 h by 73% and 77%, respectively, SB at 8 h by 55%, and B had no effect on this response. Although BM inhibited the release of cytokine-inducible neutrophil chemoattractant/keratinocyte-derived chemokine, macrophage inflammatory protein-2 (MIP-2), and platelet-activating factor (PAF) elicited by Ang-II, SB only reduced the release of MIP-2 after 4 h of its administration. Sixty-minute superfusion of the rat mesentery with 1 nM Ang-II induced a significant increase in the leukocyte-endothelial cell interactions and P-selectin up-regulation, which were inhibited by 1 microM BM and SB. The generation of reactive oxygen species (ROS) in endothelial cells stimulated with Ang-II was inhibited significantly by the three alkaloids tested. BM also diminished Ang-II-induced interleukin-8 release from endothelial cells and blocked the PAF receptor on human neutrophils (concentration of the compound needed to produce 50% inhibition value: 28.2 microM). Therefore, BM is a potent inhibitor of Ang-II-induced neutrophil accumulation in vivo. This effect appears to be mediated through inhibition of CXC chemokine and PAF release, ROS scavenging activity, and blockade of the PAF receptor. Thus, it may have potential therapeutic interest for the control of neutrophil recruitment that occurs in inflammation associated with elevated levels of Ang-II.

Limited role for interleukin-18 in the host protection response to pulmonary infection with Pseudomonas aeruginosa in mice

We report that clearance of Pseudomonas aeruginosa, accumulation of neutrophils, and synthesis of tumor necrosis factor alpha and macrophage inflammatory protein 2 in the infected lung were not largely different in interleukin-18 (IL-18) knockout or transgenic mice compared with control mice. Our results suggest a limited role for IL-18 in the host defense against P. aeruginosa.

Role of endogenous macrophage inflammatory protein-2 in regulating fever induced by bacterial endotoxin in normal and immunosuppressed rats

During myelosuppressive chemotherapy, Gram-negative bacterial infection with consequent exposure to lipopolysaccharide (LPS) is one of the most important causes of persistent fever. The classical model of the pathogenesis of fever suggests that pro-inflammatory cytokines, produced by leucocytes in the bloodstream in response to exogenous pyrogens such as bacterial LPS, represent the distal mediators of the febrile response. Neutrophils are the first effectors cells and the most prominent leucocyte population involved in acute bacterial infection. Macrophage inflammatory protein (MIP)-2 plays a crucial role in influencing early cell trafficking and neutrophil activation during pathophysiological processes and serves the same chemotactic function as human interleukin-8. In the present study, we investigated the role of MIP-2 in the development of a febrile response induced by LPS in immunocompetent and leukopenic rats. Intraperitoneal injection of LPS in leukopenic rats elicited a biphasic febrile response of rapid onset, the magnitude and duration of which were significantly greater than in immunocompetent animals. The febrile responses to LPS were accompanied by a pronounced induction of serum MIP-2 levels at 1, 2 and 4 h compared with their respective controls. In both normal and leukopenic rats, neutralization of endogenous MIP-2 bioactivity by systemic administration of antirat MIP-2 antibody caused a significant attenuation of the early phase of LPS fever. However, in contrast with normal rats, the second phase of fever was unimpaired by anti-MIP-2 in leukopenic rats. These findings suggest that circulating MIP-2 is involved in the generation of the early phase of LPS fever that contributes to the maintenance of the later phase of fever in immunocompetent, but not leukopenic, rats. Our data support a regulatory role for endogenous MIP-2 in initiating the fever responses to LPS. Furthermore, these results provide evidence that different cellular and humoral mechanisms are implicated in the development of a febrile response triggered by Gram-negative bacterial infections in leukopenic hosts.

Effects of albumin and Ringer's lactate on production of lung cytokines and hydrogen peroxide after resuscitated hemorrhage and endotoxemia in rats

RATIONALE AND HYPOTHESIS

Acute lung injury is a frequent complication of severe sepsis or blood loss and is often associated with an excessive inflammatory response requiring mechanical ventilation. We tested the hypothesis that the types of fluids used during early resuscitation have an important effect on the evolution of lung injury.

METHODS

Rats were subjected to either hemorrhage or endotoxemia for 1 hr, followed by resuscitation to a controlled mean blood pressure with Ringer's lactate, 5% albumin, or 25% albumin for 1 hr. After resuscitation, blood cytokine levels were measured. The lung was then excised and ventilated with a tidal volume of 30 mL/kg for 2 hrs.

RESULTS

The volume of fluids required was significantly smaller in the albumin-treated groups than in the Ringer's lactate groups. In the hemorrhagic shock model, plasma concentrations of tumor necrosis factor-alpha, interleukin-6, and macrophage inflammatory protein-2 were significantly lower and interleukin-10 was significantly higher in the albumin-treated groups compared with the Ringer's lactate-treated group. The levels of tumor necrosis factor-alpha and macrophage inflammatory protein-2 in bronchoalveolar lavage fluid were lower and interleukin-10 was higher in the albumin-treated groups than in the Ringer's lactate group. The decreased cytokine production was associated with a reduction of hydrogen peroxide formation with albumin resuscitation. The lung wet/dry ratio was lower in the 5% albumin (0.54 +/- 0.01) and 25% albumin (0.55 +/- 0.02) groups than in the Ringer's lactate group (0.62 +/- 0.02; both p <.05). These effects of albumin seen in the hemorrhagic shock model were not observed in the endotoxic shock model.

CONCLUSIONS

We conclude that resuscitation with albumin may have utility in reducing ventilator-induced lung injury after hemorrhagic shock, but not after endotoxic shock. These findings suggest that the mechanisms leading to ventilator-induced lung injury after hemorrhage differ from those after endotoxemia.

Interactions of lung stretch, hyperoxia, and MIP-2 production in ventilator-induced lung injury

The use of positive pressure mechanical ventilation can cause ventilator-induced lung injury (VILI). We hypothesized that hyperoxia in combination with large tidal volumes (VT) would accentuate noncardiogenic edema and neutrophil infiltration in VILI and be dependent on stretch-induced macrophage inflammatory protein-2 (MIP-2) production. In rats ventilated with VT 20 ml/kg, there was pulmonary edema formation that was significantly increased by hyperoxia. Total lung neutrophil infiltration and MIP-2 in bronchoalveolar lavage (BAL) fluid were significantly elevated, in animals exposed to high VT both on room air (RA) and with hyperoxia. Hyperoxia markedly augmented the migration of neutrophils into the alveoli. Anti-MIP-2 antibody blocked migration of neutrophils into the alveoli in RA by 51% and with hyperoxia by 65%. We concluded that neutrophil migration into the alveoli was dependent on stretch-induced MIP-2 production. Hyperoxia significantly increased edema formation and neutrophil migration into the alveoli with VT 20 ml/kg, although BAL MIP-2 levels were nearly identical to VT 20 ml/kg with RA, suggesting that other mechanisms may be involved in hyperoxia-augmented neutrophil alveolar content in VILI.

Macrophage inflammatory protein-2 and vascular endothelial growth factor regulate corneal neovascularization induced by infection with Pseudomonas aeruginosa in mice

Pseudomonas aeruginosa ocular infection causes extensive corneal neovascularization. The purpose of the present study was to investigate the role of the angiogenic factors macrophage inflammatory protein-2 (MIP-2) and vascular endothelial growth factor (VEGF) in the regulation of corneal neovascularization during P. aeruginosa ocular infection. After administering anti-MIP-2 antibody or control antibody, mouse corneas were challenged with P. aeruginosa. The expression of MIP-2 and VEGF was detected using an ELISA from ocular homogenates. Corneal neovascularization was examined by histology. The cellular sources of MIP-2 and VEGF were identified by immunohistochemistry. In addition, protein expression of MIP-2 and VEGF in isolated corneas was measured to determine the ability of the cornea to produce these two mediators. Results showed that the expression of MIP-2 and VEGF was significantly (P < 0.05) elevated after bacterial infection, and high levels of these two mediators paralleled the extensive corneal neovascularization seen at later stages of the infection. Anti-MIP-2 antibody treatment resulted in a significant (P < 0.05) reduction in VEGF expression and in corneal neovascularization. Both corneal resident cells and infiltrating neutrophils had the ability to produce MIP-2 and VEGF after stimulation. The present study demonstrates that both MIP-2 and VEGF are important mediators in the regulation of corneal neovascularization caused by P. aeruginosa infection, and that MIP-2 regulates the production of VEGF.

Pathogenic mechanisms of P. aeruginosa keratitis: a review of the role of T cells, Langerhans cells, PMN, and cytokines

The aim of this article is to review our current understanding of the role of cytokines, chemokines, T cells, Langerhans cells, and neutrophils (PMN) and their interactions in vivo in the host response to Pseudomonas aeruginosa ocular challenge. The cellular/cytokine network in vivo has begun to be unraveled, and the data discussed provide substantive evidence for a regulatory role of CD4(+) T cells (Th1 type) contributing directly to persistence of PMN in the cornea of susceptible C57BL/6 (cornea perforates) versus resistant BALB/c (cornea heals) mice. Additionally, in the susceptible mouse model, CD4(+) T cells interact with Langerhans cells and B7/CD28 ligation appears critical for antigen presentation and the susceptibility response. Various cytokines and chemokines (e.g., MIP-1alpha, IL-1beta, MIP-2, IL-12, and IFN-gamma) and their pattern of sustained upregulation after infection in susceptible versus resistant mice also will be discussed in light of an in vivo cytokine network. T-cell-mediated pathogenic mechanisms are of importance in development of the susceptible response to P. aeruginosa ocular infection. In the absence of T-cell infiltration into the cornea, PMN do not persist in the stroma, and cytokines and chemokines are better balanced, resulting in decreased stromal destruction and the resistance response.

Chemokines are differentially expressed by astrocytes, microglia and inflammatory leukocytes in Toxoplasma encephalitis and critically regulated by interferon-gamma

The intracerebral formation of inflammatory infiltrates is a complex process, which may be regulated by chemokines. This study defines the kinetics and cellular sources of T cell- and macrophage-attracting chemokines in murine Toxoplasma encephalitis (TE) by ribonuclease protection assay, reverse transcription-PCR, in situ hybridization, and immunohistochemistry. Whereas astrocytes were the major source of interferon (IFN)-gamma-inducible protein-10 (CRG-2/IP-10) and monocyte chemoattractant protein (MCP)-1, microglia expressed RANTES, monokine induced by IFN-gamma (MuMIG) and occasionally CRG-2/IP-10 RNA. Despite being ubiquitously activated, only astrocytes and microglia confined to inflammatory infiltrates expressed chemokine genes. Intracerebral leukocytes transcribed RANTES, MuMIG, and occasionally CRG-2/IP-10 and MCP-1. IFN-gamma-deficient mice failed to produce CRG-2/IP-10, MuMIG, RANTES and expressed macrophage inflammatory protein (MIP-1)alpha, MIP-1 beta, and MCP-1 mRNA at reduced levels, functionally resulting in a strongly reduced recruitment of leukocytes across the blood-brain barrier and prevented their further invasion of the brain parenchyma. Since T cells are the single source of IFN-gamma in TE, these findings indicate that T cells pave the way of leukocytes to parenchymatous parasites via IFN-gamma.

Blocking chemokine responsive to gamma-2/interferon (IFN)-gamma inducible protein and monokine induced by IFN-gamma activity in vivo reduces the pathogenetic but not the antiviral potential of hepatitis B virus-specific cytotoxic T lymphocytes

Using transgenic mice that replicate hepatitis B virus (HBV) at high levels in the liver as recipients of HBV-specific cytotoxic T lymphocytes (CTLs), we showed that the chemokines responsive to gamma-2/IFN-gamma inducible protein ([Crg2]IP-10) and monokine induced by interferon-gamma (Mig) are rapidly and strongly induced in the liver after CTL transfer. The transferred CTLs produce neither chemokine; rather, they activate (via the secretion of IFN-gamma) hepatocytes and nonparenchymal cells of the liver to produce (Crg2)IP-10 and Mig. Importantly, blocking these chemokines in vivo reduces the recruitment of host-derived lymphomononuclear cells into the liver and the severity of the liver disease without affecting the IFN-gamma-dependent antiviral potential of the CTLs. The finding that neutralization of these chemokines is associated with maintenance of antiviral effects but diminished tissue damage may be significant for the development of immunotherapeutic approaches for the treatment of chronic HBV infection.

Detection of monokines in paraffin-embedded tissues of pigs using polyclonal antibodies

Monokines are glycoproteins, synthesised by macrophages, which exert various effects on the organism. The most important monokines are interleukin (IL)-1alpha, IL-1beta, tumor necrosis factor (TNF)-alpha and IL-6. This paper reports on immunohistochemical techniques developed for the detection of IL-alpha, IL-1beta, IL-6 and TNF-alpha in fixed and paraffin-embedded pig tissues (spleen, lymph nodes, thymus, liver and kidney). Different fixatives (buffered formalin, acetic formalin, paraformadehyde-lysine-periodate and Bouin solution), and antigen unmasking techniques (permeabilisation with Tween 20, pronase enzymatic digestion and microwave-citrate buffer) were used. We describe different protocols for detection of monokines using polyclonal antibodies against the studied monokines. No signal was obtained with monoclonal antibodies against pig-TNF-alpha and human IL-1alpha. Bouin solution was shown to be the best fixative for immunohistochemical detection of IL-1alpha, TNF-alpha, and IL-6, using permeabilisation with Tween 20 as an unmasking antigen method. Acetic formalin was shown to be the best fixative for IL-1beta detection, not needing antigen retrieval techniques. Macrophages were identified as the main cytokine-producing cells, although other types of cells also stained positively to some cytokines. These techniques represent valuable tools for studies of the pathogenesis of viral and bacterial diseases, and of the immune system of the pigs.

Non-redundant roles for interleukin-1 alpha and interleukin-1 beta in regulating human IgG2

BACKGROUND

Serum concentrations of immunoglobulin G2 (IgG2) are elevated in localized aggressive periodontitis (LAgP) patients, and secretory products of monocytes from LAgP patients enhance IgG2 responses of lymphocytes from healthy subjects. Furthermore, genes regulating production of interleukin (IL)-1 influence the risk for both aggressive periodontitis (AgP) and chronic periodontitis. These observations, and the fact that IgG2 dominates responses to carbohydrates from Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis, prompted the hypothesis that IL-1 alpha, IL-1 beta, and IL-RA may help regulate human IgG2 responses.

METHODS

Human peripheral blood leukocytes (PBL) were stimulated in culture with pokeweed mitogen (PWM); the levels of available IL-1 gene products were manipulated; and the effect on IgG2 production was monitored. Manipulations of IL-1 were accomplished by adding specific neutralizing monoclonal antibodies or recombinant IL-1RA, IL-1 alpha, or IL-1 beta.

RESULTS

Blocking the IL-1 receptor with IL-1RA or neutralizing IL-1 alpha or IL-1 beta with specific antibody dramatically suppressed IgG2 production (50% to 70%). Additionally IL-1 alpha did not compensate for neutralized IL-1 beta, and additional IL-1 beta did not compensate for neutralized IL-1 alpha, suggesting the 2 monokines have separate roles in promoting IgG2. Furthermore, combinations of anti-IL-1 alpha and anti-IL-1 beta were more inhibitory than either antibody alone, and IL-1 alpha and IL-1 beta in combination appeared to work additively in promoting IgG2. Moreover, PBL cultures from a group of LAgP patients with high IgG2 levels had elevated levels of IL-1 beta.

CONCLUSION

IL-1 alpha and IL-1 beta appear to have critical and non-redundant roles in the generation and regulation of potent IgG2 responses, which appear to be important in human responses to carbohydrate-bearing bacteria.

Developmental expression of two CXC chemokines, MIP-2 and KC, and their receptors

CXC chemokines, macrophage inflammatory protein-2 (MIP-2) and KC, (a cloning designation based on ordinate and abscissa position) as well as the CXC chemokine receptor, CXCR2, are expressed in a variety of cells and tissues in adult mice. Targeted deletion of the gene encoding murine CXCR2 does not result in obvious changes in the development of the organ system of the mouse, though the CXCR2-/- mouse is compromised with regard to its ability to resist infection, heal wounds, and maintain homeostasis when challenged with microbes and/or chemicals. In an attempt to develop insight into additional possible subtle roles of CXCR2 and its ligands in the development of the mouse, we examined the expression of MIP-2, KC, CXCR2, as well as the Duffy antigen binding protein for chemokines during embryonic (p.c.) days 11.5 through 14.5 in the mouse. We observed strong correlation between the expression of MIP-2 and CXCR2 in the developing brain, cardiovascular system and condensing mesenchyme between 11.5 and 13.5 days. Moreover, the expression of KC was parallel to the expression of the Duffy antigen binding protein for chemokines with regard to temporal pattern and tissue localization. MIP-2 and CXCR2 are highly expressed in the brain, first in the cerebellum and in the head mesenchyme, the meninges and the floor plate, and by 14.5 days are also present in the telencephalon, thalamus and hypothalamus. In the developing brain KC and Duffy were prominently expressed in the neuronal tracts, the forebrain, sympathetic ganglia, and along the periphery of the neural tube. However, KC and Duffy were less prevalent in the developing cardiovascular system, lung and other organs, muscle and bone, than are CXCR2 and MIP-2. These data suggest that the roles for these chemokines and their receptors during development may be more significant than was initially thought based upon the phenotype of the mice with targeted deletion of CXCR2 and Duffy.

Expression of interleukin-18 and its monokine-directed function in rheumatoid arthritis

OBJECTIVES

To investigate the expression of and monokine induction by interleukin 18 (IL-18; also called interferon-gamma inducing factor, IGIF), in peripheral blood mononuclear cells (PBMC) and cultured synoviocytes from rheumatoid arthritis (RA) patients.

METHODS

We carried out IL-18 Western blotting and semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) of cytokines in PBMC [IL-18, IL-1beta and tumour necrosis factor alpha (TNF-alpha)] and long-term cultured fibroblast-like synoviocytes (FLS) [IL-18, IL-1beta, TNF-alpha, IL-6, interferon gamma (INF-gamma) and [granulocyte-macrophage colony stimulating factor (GM-CSF)] from RA patients and controls. FLS were isolated from RA synovial membranes (FLS(SM)) and RA synovial fluids (FLS(SF)), osteoarthritis (OA) FLS(SM) and FLS(SF) from spondyloarthropathy patients. FLS were characterized by fluorescence-activated cell sorting of the FLS. PBMC and FLS from RA patients and control subjects were stimulated with recombinant human IL-18 and IL-1beta (rHuIL-18/rHuIL-1beta), and TNF-alpha, IL-1beta and MMP-1 were measured by ELISA in supernatants.

RESULTS

Constitutive expression of IL-18 mRNA was significantly reduced whereas that of TNF-alpha was enhanced in RA PBMC. Persistent low expression of IL-18, TNF-alpha, GM-CSF and IL-1beta was observed in RA and OA FLS(SM) as well as spondyloarthropathy FLS(SF). In contrast, high constitutive expression of IL-18 in FLS (CD90/Thy-1- and CD54-positive, CD14- and CD86-negative), accompanied by persistent high levels of TNF-alpha, GM-CSF and IL-1beta expression, was restricted to synovial fluid-derived FLS obtained from RA patients. IFN-gamma was not detectable in any culture, but IL-6 mRNA was equally expressed in all FLS cultures. rHuIL-18 was effective in stimulating TNF-alpha and IL-1beta secretion in PBMC from healthy controls, but failed to stimulate TNF-alpha and IL-1beta secretion from PBMC in 11 of 12 RA patients, and all FLS cultures. rHu-IL-1beta, but not rHu-IL-18, induced interstitial collagenase (MMP-1) in FLS.

CONCLUSIONS

Persistent high production of proinflammatory cytokines in RA-FLS(SF) may be relevant for chronic progression in RA synovitis. Levels of TNF-alpha and IL-1beta expression are increased in RA-FLS(SF), but are independent of IL-18. The pathological function of enhanced IL-18 expression in RA-FLS(SF) remains to be further elucidated.

Ratio of local to systemic chemokine concentrations regulates neutrophil recruitment

CXC chemokines are important regulators of local neutrophil recruitment. In this study, we examined the role of the ratio of local to systemic chemokine concentrations as a significant factor determining local neutrophil recruitment. Thioglycollate was injected intraperitoneally into BALB/c mice resulting in a dose-dependent increase in neutrophil recruitment and local inflammation, as measured by peritoneal levels of interleukin 6. At the high dose of 3% thioglycollate, antibody inhibition of the murine chemokines KC and macrophage inflammatory protein-2 caused a reduction in peritoneal neutrophil recruitment by as much as 93%. A paradoxical effect was observed with a 0.3% thioglycollate intraperitoneal challenge. In this situation, inhibition of KC resulted in a significant increase in peritoneal neutrophils, and inhibition of macrophage inflammatory protein-2 also resulted in increased peritoneal neutrophils. These results were consistent with a reverse chemotactic gradient as described by the ratio of peritoneal to plasma KC levels. A higher ratio (ie, increased peritoneal chemokines compared to plasma) resulted in increased neutrophil recruitment after either the 3% or 0.3% thioglycollate challenge. Our results demonstrate that whereas sufficient local concentrations of chemokines are necessary, a critical factor dictating local neutrophil recruitment is the ratio of the local to the systemic chemokine concentrations.

Aging and PMN response to P. aeruginosa infection

PURPOSE

Alterations in immune system function associated with aging may contribute to increased morbidity in this population of individuals. The current studies were performed to determine aging-related changes in polymorphonuclear neutrophil (PMN) function after corneal infection with Pseudomonas aeruginosa.

METHODS

Total PMN number, macrophage inflammatory protein (MIP)-2 mRNA and protein expression, and ocular bacterial load were determined in 8-week- and 12-month-old inbred BALB/c mice at various times after infection with P. aeruginosa. In addition, 12-month-old mice were treated systemically with the MIP-2 polyclonal antibody (pAb) to determine the effects of MIP-2 neutralization on ocular disease and PMN recruitment.

RESULTS

Histologically, PMN infiltration into the cornea of 12-month-old mice was delayed initially and was associated with an inability to reduce bacterial load at later postinfection (PI) times. In addition, a significantly greater number of PMNs were found in the cornea of 12-month-old mice at later PI times. The increase in PMN number in 12-month-old mice correlated with a persistence of MIP-2 expression in cornea at these later times. Systemic treatment of 12-month-old mice with neutralizing MIP-2 pAb versus normal rabbit serum (NRS) resulted in reduced corneal PMN number and ocular disease.

CONCLUSIONS

These data provide evidence that persistence of PMN in the cornea of 12-month-old mice contributes to corneal tissue destruction after P. aeruginosa challenge. Further evidence also is provided that the chemoattractant MIP-2 contributes to the altered PMN response in these animals.

Transient infiltration of neutrophils into the thymus in association with apoptosis induced by whole-body X-irradiation

Generally, the process of apoptosis does not cause leakage of noxious cytosolic contents and is therefore non-inflammatory. However, as previously shown, macrophages ingesting apoptotic CTLL-2 cells produced pro-inflammatory cytokines, particularly interleukin-8 (IL-8) and macrophage inflammatory protein-2 (MIP-2), a murine IL-8 homolog. This predicted that rapid and massive apoptosis may induce neutrophil accumulation in vivo. In this study, we tested this prediction by inducing apoptosis by whole-body X-irradiation in mice. After exposure to 4 Gy X-ray irradiation, mice exhibited considerable apoptosis of thymic cells, which was associated with transient infiltration of neutrophils as well as MIP-2 mRNA expression. In contrast, in p53-deficient mice in which irradiation-induced apoptosis was suppressed, as has been reported, infiltration of neutrophils into the thymus was less than that found in p53+/+ mice. Taken together, these results suggest that massive and rapid apoptosis can result in infiltration of neutrophils.

Immunopathology of a two-hit murine model of acid aspiration lung injury

In a two-hit model of acid aspiration lung injury, mice were subjected to nonlethal cecal ligation and puncture (CLP). After 48 h, intratracheal (IT) acid was administered, and mice were killed at several time points. Recruitment of neutrophils in response to acid was documented by myeloperoxidase assay and neutrophil counts in bronchoalveolar lavage (BAL) fluid and peaked at 8 h post-IT injection. Albumin in BAL fluid, an indicator of lung injury, also peaked at 8 h. When the contributions of the two hits were compared, neutrophil recruitment and lung injury occurred in response to acid but were not greatly influenced by addition of another hit. Neutrophil sequestration was preceded by elevations in KC and macrophage inflammatory protein-2alpha in plasma and BAL fluid. KC levels in BAL fluid were higher and peaked earlier than macrophage inflammatory protein-2alpha levels. When KC was blocked with specific antiserum, neutrophil recruitment was significantly reduced, whereas albumin in BAL fluid was not affected. In conclusion, murine KC mediated neutrophil recruitment but not lung injury in a two-hit model of aspiration lung injury.

Therapeutic effect of anti-macrophage inflammatory protein 2 antibody on influenza virus-induced pneumonia in mice

We investigated the effect of anti-macrophage inflammatory protein 2 immunoglobulin G (aMIP-2 IgG) on the progression of influenza virus-induced pneumonia in mice. When mice were infected with a mouse lung-adapted strain of influenza A/PR/8/34 virus by intranasal inoculation, neutrophil counts in the bronchoalveolar lavage fluid (BALF) increased in parallel with the kinetics of MIP-2 production, which peaked 2 days after infection. After intracutaneous injection of a dose of 10 or 100 microg of aMIP-2 IgG once a day on days 0 and 1, neutrophil counts in BALF on day 2 were reduced to 49 or 37%, respectively, of the value in the control infected mice administered anti-protein A IgG. The antibody administration also improved lung pathology without affecting virus replication. Furthermore, by prolonged administration with a higher or lower dose for up to 5 days, body weight loss became slower and finally 40% of mice in both treatment groups survived potentially lethal pneumonia. These findings suggest that MIP-2-mediated neutrophil infiltration during the early phase of infection might play an important role in lung pathology. Thus, MIP-2 was considered to be a novel target for intervention therapy in potentially lethal influenza virus pneumonia in mice.

Macrophage inflammatory protein-2 is a mediator of polymorphonuclear neutrophil influx in ocular bacterial infection

Polymorphonuclear neutrophils (PMN) in Pseudomonas aeruginosa-infected cornea are required to clear bacteria from affected tissue, yet their persistence may contribute to irreversible tissue destruction. This study examined the role of C-X-C chemokines in PMN infiltration into P. aeruginosa-infected cornea and the contribution of these mediators to disease pathology. After P. aeruginosa challenge, corneal PMN number and macrophage inflammatory protein-2 (MIP-2) and KC levels were compared in mice that are susceptible (cornea perforates) or resistant (cornea heals) to P. aeruginosa infection. While corneal PMN myeloperoxidase activity (indicator of PMN number) was similar in both groups of mice at 1 and 3 days postinfection, by 5-7 days postinfection corneas of susceptible mice contained a significantly greater number of inflammatory cells. Corneal MIP-2, but not KC, levels correlated with persistence of PMN in the cornea of susceptible mice. To test the biological relevance of these data, resistant mice were treated systemically with rMIP-2. This treatment resulted in increased corneal PMN number and significantly exacerbated corneal disease. Conversely, administration of neutralizing MIP-2 pAb to susceptible mice reduced both PMN infiltration and corneal destruction. Collectively, these findings support an important role for MIP-2 in recruitment of PMN to P. aeruginosa-infected cornea. These data also strongly suggest that a timely down-regulation of the host inflammatory response is critical for resolution of infection.

Attenuation of acute lung injury in transgenic mice expressing human transforming growth factor-alpha

Transforming growth factor-alpha (TGF-alpha) is produced in the lung in experimental and human lung diseases; however, its physiological actions after lung injury are not understood. To determine the influence of TGF-alpha on acute lung injury, transgenic mouse lines expressing differing levels of human TGF-alpha in distal pulmonary epithelial cells under control of the surfactant protein C gene promoter were generated. TGF-alpha transgenic and nontransgenic control mice were exposed to polytetrafluoroethylene (PTFE; Teflon) fumes to induce acute lung injury. Length of survival of four separate TGF-alpha transgenic mouse lines was significantly longer than that of nontransgenic control mice, and survival correlated with the levels of TGF-alpha expression in the lung. The transgenic line expressing the highest level of TGF-alpha (line 28) and nontransgenic control mice were then compared at time intervals of 2, 4, and 6 h of PTFE exposure for differences in pulmonary function, lung histology, bronchoalveolar lavage fluid protein and cell differential, and lung homogenate proinflammatory cytokines. Line 28 TGF-alpha transgenic mice demonstrated reduced histological changes, decreased bronchoalveolar lavage fluid total protein and neutrophils, and delayed alterations in pulmonary function measures of airway obstruction compared with those in nontransgenic control mice. Both line 28 and nontransgenic control mice had similar increases in interleukin-1beta protein levels in lung homogenates. In contrast, interleukin-6 and macrophage inflammatory protein-2 levels were significantly reduced in line 28 transgenic mice compared with those in nontransgenic control mice. In the transgenic mouse model, TGF-alpha protects against PTFE-induced acute lung injury, at least in part, by attenuating the inflammatory response.

Inhibition of murine neutrophil recruitment in vivo by CXC chemokine receptor antagonists

In this study, we have examined the ability of chemokine receptor antagonists to prevent neutrophil extravasation in the mouse. Two murine CXC chemokines, macrophage-inflammatory protein (MIP)-2 and KC, stimulated the accumulation of leukocytes into s.c. air pouches, although MIP-2 was considerably more potent. The leukocyte infiltrate was almost exclusively neutrophilic in nature. A human CXC chemokine antagonist, growth-related oncogene (GRO)-alpha(8-73), inhibited calcium mobilization induced by MIP-2, but not by platelet-activating factor in leukocytes isolated from the bone marrow, indicating that this antagonist inhibits MIP-2 activity toward murine leukocytes. Pretreatment of mice with GROalpha(8-73) inhibited, in a dose-dependent manner, the MIP-2-induced influx of neutrophils to levels that were not significantly different from control values. Moreover, this antagonist was also effective in inhibiting the leukocyte recruitment induced by TNF-alpha, LPS, and IL-1beta. Leukocyte infiltration into the peritoneal cavity in response to MIP-2 was also inhibited by prior treatment of mice with GROalpha(8-73) or the analogue of platelet factor 4, PF4(9-70). The results of this study indicate 1) that the murine receptor for MIP-2 and KC, muCXCR2, plays a major role in neutrophil recruitment to s.c. tissue and the peritoneal cavity in response to proinflammatory agents and 2) that CXCR2 receptor antagonists prevent acute inflammation in vivo.

Dynamics of production of MIP-1alpha, MCP-1 and MIP-2 and potential role of neutralization of these chemokines in the regulation of immune responses during experimental autoimmune neuritis in Lewis rats

Experimental autoimmune neuritis (EAN) is an inflammatory autoimmune demyelinating disease of the peripheral nervous system (PNS) and represents an animal model of Guillain-Barré syndrome (GBS), which is a major inflammatory demyelinating disease of the PNS in humans. In the present study, the dynamics of the expression of the chemokines macrophage inflammatory protein-1alpha (MIP-1alpha), MIP-2 and monocyte chemotactic protein-1 (MCP-1) were determined in the sciatic nerves of EAN rats. Additionally, the effect of neutralizing antibodies against MIP-1alpha, MIP-2 and MCP-1 on the clinical course of EAN and the chemokine expression was investigated. The maximum of MIP-1alpha positive cells in the sciatic nerves was seen on day 14 post immunization (p.i.) correlating with the development of severe clinical signs. Administration of an anti-MIP-1alpha antibody suppressed the clinical signs of EAN and inhibited inflammation and demyelination in the sciatic nerve. Peak numbers of MCP-1 positive cells in the sciatic nerves were detected on day 7 p.i. Administration of an anti-MCP-1 antibody caused a delay of onset of EAN. However, 4 of the 6 EAN rats receiving the anti-MCP-antibody showed the same degree of inflammatory cell infiltration and demyelination in the sciatic nerves as sham-treated EAN rats, whereas only 2 EAN rats had less inflammation and demyelination. The numbers of MIP-2 positive cells reached a maximum on day 21 p.i. Anti-MIP-2 antibody failed to suppress the clinical signs of EAN and the inflammation and demyelination in the sciatic nerves. Only administration of the anti-MIP-1alpha antibody resulted in a significant reduction in the number of chemokine (MIP-1alpha)-positive cells and ED1-positive macrophages in the sciatic nerves. The present results demonstrate that MIP-1alpha and MCP-1 may play a role in the immunopathogenesis of EAN, and that MIP-1alpha induced trafficking of inflammatory cells can be inhibited by immunoneutralization. Further elucidation of the regulation and coordination of MIP-1alpha and MCP-1 production may lead to new therapeutic approaches to GBS in humans.

Role of chemotactic factors in neutrophil activation after thermal injury in rats

Acute thermal trauma is well known to produce evidence of a "systemic inflammatory response" in vivo, as manifested by evidence of complement activation, appearance in plasma of a variety of inflammatory factors, and development of multi-organ injury. The current studies were focused on acute thermal injury of rat skin and factors responsible for accompanying activation of blood neutrophils. Acute thermal injury of rat skin resulted in a time-dependent loss of L-selectin and up-regulation of Mac-1 (CD11b/CD18) on blood neutrophils, with no changes in LFA-1 (CD11a/CD18). The loss of L-selectin was prevented by blockade of C5a but not by blockade of the alpha-chemokine, macrophage inflammatory protein-2 (MIP-2). C5a, the alpha chemokines, MIP-2 and keratinocyte-derived cytokine (KC), and platelet activating factor (PAF) contributed to up-regulation of blood neutrophil Mac-1. Blocking interventions against these mediators also blunted the degree of neutropenia developing after thermal trauma. These data suggest that activation of blood neutrophils after thermal trauma is related to the role of several chemotactic mediators. These studies may provide clues regarding factors responsible for development of the "systemic inflammatory response syndrome" after thermal injury in the experimental model employed.

Neutrophil sequestration in liver and lung is differentially regulated by C-X-C chemokines during experimental peritonitis

C-X-C chemokines play an important role in the migration and activation of neutrophils (PMNs) during an inflammatory event. We measured mRNA and protein expression of the murine C-X-C chemokines macrophage inflammatory protein-2 (MIP-2) and KC in the lungs, liver, blood, and peritoneal cavity of Swiss Webster mice after cecal ligation and puncture (CLP). Neutralizing antibodies to MIP-2 and KC were also used to determine the biological effects of these chemokines on neutrophil sequestration and organ injury in the CLP model. The data showed that early after CLP, MIP-2 mRNA and protein were expressed predominantly by the lung, whereas KC mRNA and protein were expressed by the liver. Inhibition of MIP-2 reduced both lung neutrophil sequestration and peritoneal neutrophil migration. Inhibition of KC had no effect on overall neutrophil sequestration in liver but reduced injury as measured by serum transaminases. An early survival benefit was found with anti-KC treatment, although overall survival was not different. Our study showed a differential expression by organs of C-X-C chemokines during sepsis and suggested that such chemokine effects are tissue-specific.

Chemotactic mediator requirements in lung injury following skin burns in rats

Partial-thickness skin burns have been shown to induce neutrophil-dependent microvascular injury both locally (skin) and systemically (lung). In the present study, interventional measures to block inflammatory chemoattractants were employed to define the pathophysiologic role of these mediators in the development of secondary lung injury following thermal injury of skin. Rats were treated with blocking antibodies to either C5a or to the alpha-chemokines, keratinocyte-derived cytokine (KC), or macrophage inflammatory protein-2 (MIP-2). To study the role of platelet activating factor, a receptor antagonist (PAF-Ra) was utilized. The development of lung vascular injury following thermal injury to skin was significantly attenuated by treatment with anti-C5a (84%), anti-KC (67%), and anti-MIP-2 (77%), but treatment with PAF-Ra had no protective effects. Protective interventions were paralleled by significant reductions in the tissue buildup of myeloperoxidase. When bronchoalveolar lavage fluids from thermally injured rats were evaluated, elevations in TNF;ZA and IL-1 were found and were determined to be C5a-dependent (but unaffected by treatment with PAF-Ra). These studies indicate that lung tissue injury after thermal skin burns is dependent on chemotactic mediators. The data also suggest that lung expression of TNFalpha and IL-1 after thermal injury of skin is C5a-dependent.

Neutralization of the CXC chemokine, macrophage inflammatory protein-2, attenuates bleomycin-induced pulmonary fibrosis

Few studies have addressed the importance of vascular remodeling in the lung during the development of bleomycin-induced pulmonary fibrosis. For fibroplasia and deposition of extracellular matrix to occur, there must be a geometric increase in neovascularization. We hypothesized that net angiogenesis during the pathogenesis of fibroplasia and deposition of extracellular matrix during bleomycin-induced pulmonary fibrosis are dependent in part upon an overexpression of the angiogenic CXC chemokine, macrophage inflammatory protein-2 (MIP-2). To test this hypothesis, we measured MIP-2 by specific ELISA in whole lung homogenates in either bleomycin-treated or control CBA/J mice and correlated these levels with lung hydroxyproline. We found that lung tissue from mice treated with bleomycin, compared with that from saline-treated controls, demonstrated a significant increase in the presence of MIP-2 that was correlated to a greater angiogenic response and total lung hydroxyproline content. Neutralizing anti-MIP-2 Abs inhibited the angiogenic activity of day 16 bleomycin-treated lung specimens using an in vivo angiogenesis bioassay. Furthermore, when MIP-2 was depleted in vivo by passive immunization, bleomycin-induced pulmonary fibrosis was significantly reduced without a change in the presence of pulmonary neutrophils, fibroblast proliferation, or collagen gene expression. This was also paralleled by a reduction in angiogenesis. These results demonstrate that the angiogenic CXC chemokine, MIP-2, is an important factor that regulates angiogenesis/fibrosis in pulmonary fibrosis.

Neutralization of macrophage inflammatory protein 2 (MIP-2) and MIP-1alpha attenuates neutrophil recruitment in the central nervous system during experimental bacterial meningitis

Chemokines are low-molecular-weight chemotactic cytokines that have been shown to play a central role in the perivascular transmigration and accumulation of specific subsets of leukocytes at sites of tissue damage. Using in situ hybridization (ISH), we investigated the mRNA induction of macrophage inflammatory protein 2 (MIP-2), MIP-1alpha, monocyte chemoattractant protein 1 (MCP-1), and RANTES. Challenge of infant rats' brains with Haemophilus influenzae type b intraperitoneally resulted in the time-dependent expression of MIP-2, MIP-1alpha, MCP-1, and RANTES, which was maximal 24 to 48 h postinoculation. Immunohistochemistry showed significant increases in neutrophils and macrophages infiltrating the meninges, the ventricular system, and the periventricular area. The kinetics of MIP-2, MIP-1alpha, MCP-1, and RANTES mRNA expression paralleled those of the recruitment of inflammatory cells and disease severity. Administration of anti-MIP-2 or anti-MIP-1alpha antibodies (Abs) resulted in significant reduction of neutrophils. Administration of anti-MCP-1 Abs significantly decreased macrophage infiltration. Combined studies of ISH and immunohistochemistry showed that MIP-2- and MIP-1alpha-positive cells were neutrophils and macrophages. MCP-1-positive cells were neutrophils, macrophages, and astrocytes. Expression of RANTES was localized predominantly to resident astrocytes and microglia. The present study indicates that blocking of MIP-2 or MIP-1alpha bioactivity in vivo results in decreased neutrophil influx. These data are also the first demonstration that the C-C chemokine MIP-1alpha is involved in neutrophil recruitment in vivo.

Immune response of cattle infected with African trypanosomes

Trypanosomosis is the most economically important disease constraint to livestock productivity in sub-Saharan Africa and has significant negative impact in other parts of the world. Livestock are an integral component of farming systems and thus contribute significantly to food and economic security in developing countries. Current methods of control for trypanosomosis are inadequate to prevent the enormous socioeconomic losses resulting from this disease. A vaccine has been viewed as the most desirable control option. However, the complexity of the parasite's antigenic repertoire made development of a vaccine based on the variable surface glycoprotein coat unlikely. As a result, research is now focused on identifying invariant trypanosome components as potential targets for interrupting infection or infection-mediated disease. Immunosuppression appears to be a nearly universal feature of infection with African trypanosomes and thus may represent an essential element of the host-parasite relationship, possibly by reducing the host's ability to mount a protective immune response. Antibody, T cell and macrophage/monocyte responses of infected cattle are depressed in both trypanosusceptible and trypanotolerant breeds of cattle. This review describes the specific T cell and monocyte/macrophage functions that are altered in trypanosome-infected cattle and compares these disorders with those that have been described in the murine model of trypanosomosis. The identification of parasite factors that induce immunosuppression and the mechanisms that mediate depressed immune responses might suggest novel disease intervention strategies.

The interferon-inducible chemokines MuMig and Crg-2 exhibit antiviral activity In vivo

MuMig (murine monokine induced by gamma interferon) and Crg-2 (cytokine responsive gene 2) are two murine chemokines of the CXC family that are induced by the interferons (IFNs): MuMig specifically by IFN-gamma and Crg-2 by IFN-alpha, IFN-beta, and IFN-gamma. To investigate the biological roles of these chemokines, recombinant vaccinia viruses (rVVs) encoding either MuMig or Crg-2 were constructed. In vitro, the chemokine-encoding rVVs replicated to similar levels to the control virus. Athymic nude mice inoculated with 10(5) PFU or less of VV-HA-Mig or VV-HA-Crg-2 resolved the infection successfully whereas mice given a similar dose of the control virus VV-HA-TK died from generalized infection. At higher doses, there was mortality in all groups but death was significantly delayed in mice infected with either chemokine-encoding rVV compared with those infected with the control virus. Virus-encoded MuMig and Crg-2 enhanced the cytolytic activity of NK cells and splenic cellularity by two- to threefold and resulted in significant increases in mononuclear cell infiltration in the livers of mice. Using specific neutralizing or depleting antibodies, we have established that the control of rVV replication in athymic nude mice, as a consequence of virus-expressed MuMig and Crg-2, requires NK cells and IFN-alpha, IFN-beta, and IFN-gamma.

A central role for astrocytes in the inflammatory response to beta-amyloid; chemokines, cytokines and reactive oxygen species are produced

Alzheimer's disease (AD) is the commonest form of adult onset dementia and is characterised neuropathologically by the accumulation of plaques containing beta-amyloid (A beta) fibrils, reactive astrocytes, activated microglia, and leukocytes. A beta plays a role in the pathology of AD by directly causing neuronal cytotoxicity and stimulating microglia to secrete cytokines and reactive oxygen species (ROS) which also damage neurons. Here, we demonstrate that A beta activates astrocytes and oligodendrocytes (the most common cell types in the brain) to produce chemokines, in particular MCP-1 and RANTES, which serve as potent in vitro microglial and macrophage chemoattractants. Furthermore, we have shown that A beta activates astrocytes to upregulate pro-inflammatory cytokine expression and enhances the production of ROS. We propose therefore that A beta-mediated astrocyte activation initiates an inflammatory cascade which could be targeted for therapeutic intervention in AD.

Roles for C-X-C chemokines and C5a in lung injury after hindlimb ischemia-reperfusion

We evaluated the roles of the C-X-C chemokines cytokine-induced neutrophil chemoattractant (CINC) and macrophage inflammatory protein-2 (MIP-2) as well as the complement activation product C5a in development of lung injury after hindlimb ischemia-reperfusion in rats. During reperfusion, CD11b and CD18, but not CD11a, were upregulated on neutrophils [bronchoalveolar lavage (BAL) and blood] and lung macrophages. BAL levels of CINC and MIP-2 were increased during the ischemic and reperfusion periods. Treatment with either anti-CINC or anti-MIP-2 IgG significantly reduced lung vascular permeability and decreased lung myeloperoxidase content by 93 and 68%, respectively (P < 0.05). During the same period, there were significant increases in serum C5a-related neutrophil chemotactic activity. Treatment with anti-C5a decreased lung vascular permeability, lung myeloperoxidase, and BAL CINC by 51, 58, and 23%, respectively (P < 0.05). The data suggest that the C-X-C chemokines CINC and MIP-2 as well as the complement activation product C5a are required for lung neutrophil recruitment and full induction of lung injury after hindlimb ischemia-reperfusion in rats.

Maximal T cell IL-13 production requires monocyte or monokine participation

The T cell-secreted lymphokine interleukin 13 (IL-13) exerts pleiotropic effects on monocytes (Mphi) and B cells. Since accessory cells, like Mphi and B cells, also act in antigen-presenting and lymphokine augmentation of T cells, Mphi and B cells may be able to effect T cell IL-13 production. Purified T cells produced slightly less IL-13 than the lower T cell numbers contained in peripheral blood mononuclear cell population, further suggesting accessory cell augmentation. Addition of 10% B cells [either unstimulated or pokeweed mitogen (PWM)-stimulated] to autologous T cells only moderately augmented T cell IL-13 levels. PWM-stimulated B cell culture supernates had even less augmenting effect on T cell IL-13 levels and unstimulated B cell culture supernates did not augment T cell IL-13 production. In contrast to the moderately augmenting effect of B cells or their stimulated culture supernates, addition of 10% Mphi, either unstimulated or muramyl dipeptide (MDP)+IFN-gamma stimulated, to autologous T cells produced a highly significant increase in T cell IL-13 production. Mphi culture supernates were equally effective in augmenting T cell IL-13 levels, suggesting both that cell-to-cell contact is not critical for Mphi augmentation of T cell IL-13 levels, and that Mphi secreted factors are pivotal. CD64(+) Mphi (or their culture supernates), which are known as poor antigen-presenting cells, also effectively augmented T cell IL-13 production, further supporting the involvement of Mphi secreted factors. Finally, experiments with exogenous addition of recombinant monokines, as well as neutralization experiments with different cytokine antibodies, suggested IL-1beta as a primary cytokine involved in the augmentation of T cell IL-13 levels by accessory cells. However, these experiments also indicated other unidentified Mphi factors as playing a significant role in producing maximal T cell IL-13 production.

Proliferative effects of CXC chemokines in rat hepatocytes in vitro and in vivo

The CXC chemokines have well-documented neutrophil chemotactic, angiogenic, and mitogenic properties. The current investigations evaluate the effects of interleukin-8 (IL-8), epithelial neutrophil activating protein (ENA-78), and macrophage inflammatory peptide-2 (MIP-2) on hepatocyte proliferation in vitro and liver regeneration in vivo. Primary rat hepatocytes were isolated by collagenase digestion and exposed to incremental doses of IL-8, ENA-78, or MIP-2, and cellular proliferation was measured via tritiated thymidine incorporation. These experiments demonstrated significant increases in hepatocyte proliferation in response to IL-8, ENA-78, and MIP-2. Next, rats were sacrificed in a time-dependent manner following 70% hepatectomy or sham laparotomy, and hepatic tissue levels of MIP-2 and ENA-78 were measured using an ELISA. ENA-78 and MIP-2 were significantly elevated following 70% hepatectomy as compared with sham-operated control animals. Rats undergoing 70% hepatectomy were then treated with neutralizing anti-ENA-78 serum, anti-MIP-2 serum, or preimmune control serum, and liver regeneration was evaluated. These experiments demonstrated that neutralization of ENA-78 or MIP-2 slowed the rate of liver regeneration. These data suggest that the CXC chemokines may be important agents for the induction of hepatocyte proliferation and may be important molecules in vivo in the setting of liver injury, repair, and regeneration.

Antioxidants attenuate anthralin-induced skin inflammation in BALB/c mice: role of specific proinflammatory cytokines

Anthralin is the most common therapeutic agent among a small number of pro-oxidant, 9-anthrones effective in the topical treatment of psoriasis. However, the usefulness of this drug is diminished by toxic side effects, including skin irritation and inflammation. The activities of anthralin are believed to be mediated by the generation of reactive oxygen intermediates and anthrone radicals produced in the skin. In this study, the dermal inflammatory response to anthralin was determined using a mouse ear swelling test. Maximum ear swelling induced by anthralin coincided with the elevation of cytokine mRNA expression in the skin, including interleukin-6, granulocyte-macrophage colony-stimulating factor, macrophage inflammatory protein-2, and tumor necrosis factor alpha at 24 h post challenge. The role of free radical generation in ear swelling and cytokine modulation were examined by systemic administration of cell permeable and impermeable antioxidants before anthralin challenge. Superoxide dismutase and alpha-tocopherol acetate, but not the glutathione precursor N-acetyl cysteine, were effective inhibitors of anthralin-induced ear swelling and cytokine elevation. Maximum inflammatory cell infiltration occurred 72-96 h post anthralin challenge and was also reduced by antioxidants. These data suggest that oxidative stress, generated at the site of anthralin treatment, alters the expression of dermal chemokines and other cytokines resulting in the recruitment of inflammatory cells. Systemic antioxidant administration may provide opportunities for therapeutic intervention against anthralin-associated toxicities.

Effect of anti-macrophage migration inhibitory factor antibody on lipopolysaccharide-induced pulmonary neutrophil accumulation

Macrophage migration inhibitory factor (MIF) is a recently rediscovered pro-inflammatory cytokine that has the unique potential to override the anti-inflammatory action of glucocorticoids. Since recent reports suggest the pivotal role of MIF in acute lung injury, we examined the protective effect of anti-MIF antibody on lipopolysaccharide (LPS)-induced acute lung injury in rats. Rats were injected with LPS (7 mg/kg) intraperitoneally with or without pretreatment with anti-MIF antibody. The anti-MIF antibody significantly attenuated LPS-induced migration of neutrophils to the lungs at 4 and 24 h as demonstrated by observation of the number of neutrophils per alveolus, the activity of myeloperoxidase of the lung tissue, and cell differentiation of neutrophils in bronchoalveolar lavage (BAL) fluid. The increased level of macrophage inflammatory protein-2, a powerful neutrophil chemokine, in BAL fluid was also significantly attenuated by pretreatment with the anti-MIF antibody as compared with the control group. Additionally, positive immunostaining for MIF was observed in bronchial epithelial cells and alveolar macrophages, and Northern blot analysis of lung tissues demonstrated increased MIF mRNA 24 h after LPS injection. These data suggest that the anti-MIF antibody has therapeutic potential for the treatment of acute lung injury by suppressing the level of neutrophil chemokine in the lungs.

Role of chemokines and cytokines in a reactivation model of arthritis in rats induced by injection with streptococcal cell walls

Intraarticular injection of streptococcal cell wall (SCW) antigen followed by intravenous challenge results in a T cell-mediated monoarticular arthritis ill female Lewis rats. Initial studies showed that this reactivation response to intravenous SCW antigen is dependent on the presence of interleukin-1 (IL-1) and tumor necrosis factor alpha (TNF-alpha) and that the early phase of swelling is neutrophil-dependent. Neutrophil depletion or passive immunization with antibodies to P-selectin or macrophage inflammatory protein-2 reduced the intensity of ankle edema and the influx of neutrophils. After the first few days, however, the arthritic response is mediated primarily by mononuclear cells. Joint tissues showed up-regulation of mRNA for monocyte chemotactic protein-1 (MCP-1), which could be inhibited in part by anti-IL-4; treatment of rats with antibodies to IL-4 or MCP-1 significantly suppressed development of ankle edema and histopathological evidence of inflammation. Antibodies to interferon-gamma or IL-10 had no effect. Treatment with anti-MCP-1 also suppressed influx of (111)In-labeled T cells into the ankle joint. These data suggest that the late, mononuclear-dependent phase of SCW-induced arthritis in female Lewis rats requires cytokines that up-regulate MCP-1, which in turn may facilitate recruitment and extravasation of mononuclear cells into the joint.