Recombinant human interleukin-1 beta primes human polymorphonuclear leukocytes for stimulus-induced myeloperoxidase release

Negative-pressure wound therapy enhances local inflammatory responses in acute infected soft-tissue wound

Clinical studies found that negative-pressure wound therapy (NPWT) displayed significant clinical benefits in the healing of infected wounds. However, the effect of NPWT on local inflammatory responses in acute infected soft-tissue wound has not been investigated thoroughly. The purpose of this study was to test the impact of NPWT on local expression of proinflammatory cytokines, amount of neutrophils, and bacterial bioburden in wound from acute infected soft-tissue wounds. Full-thickness wounds were created on the back of rabbits, and were inoculated with Staphylococcus aureus strain ATCC29213. The wounds were treated with sterile saline-moistened gauze dressings and NPWT with continuous negative pressure (-125 mmHg). Wound samples were harvested on days 0 (6 h after bacterial inoculation), 2, 4, 6, and 8 at the center of wound beds before irrigation for real-time PCR analysis of gene expression of IL-1β, IL-8, and TNF-α. Wound biopsies were examined histologically for neutrophil quantification in different layers of tissue. Quantitative bacterial cultures at the same time point were analyzed for bacterial clearance. Application of NPWT to acute infected wounds in rabbits was compared with treatment with sterile saline-moistened gauze, over an 8-day period. NPWT-treated wounds exhibited earlier and greater peaking of IL-1β and IL-8 expression and decrease in TNF-α expression over the early 4 days (P < 0.05). Furthermore, histologic examination revealed that significantly increased neutrophil count was observed in the shallow layer in wound biopsies of NPWT treatment at day 2 (P < 0.001). In addition, there was a statistically significant decrease of bacteria load from baseline (day 0) at days 2 and 8 in NPWT group (P < 0.05). In conclusion, this study demonstrates that NPWT of acute infected soft-tissue wounds leads to increased local IL-1β and IL-8 expression in early phase of inflammation, which may trigger accumulation of neutrophils and thus accelerate bacterial clearance. Meanwhile, the success of NPWT in the treatment of acute wounds can attenuate the expression of TNF-α, and the result may partly explain how NPWT can avoid significantly impairing wound healing.

Deficient cytokine expression and neutrophil oxidative burst contribute to impaired cutaneous wound healing in diabetic, biofilm-containing chronic wounds

Diabetic patients exhibit dysregulated inflammatory and immune responses that predispose them to chronic wound infections and the threat of limb loss. The molecular underpinnings responsible for this have not been well elucidated, particularly in the setting of wound biofilms. This study evaluates host responses in biofilm-impaired wounds using the TallyHo mouse, a clinically relevant polygenic model of type 2 diabetes. No differences in cytokine or Toll-like receptor (TLR) expression were noted in unwounded skin or noninoculated wounds of diabetic and wild-type mice. However, diabetic biofilm-containing wounds had significantly less TLR 2, TLR 4, interleukin-1β, and tumor necrosis factor-α expression than wild-type wounds with biofilm (all p < 0.001). Both groups had similar bacterial burden and neutrophil infiltration after development of biofilms at 3 days postwounding, but diabetic wounds had significantly less neutrophil oxidative burst activity. This translated into a log-fold greater bacterial burden and significant delay of wound epithelization for biofilm-impaired diabetic wounds at 10 days postwounding. These results suggest that impaired recognition of bacterial infection via the TLR pathway leading to inadequate cytokine stimulation of antimicrobial host responses may represent a potential mechanism underlying diabetic susceptibility to wound infection and ulceration.

Cytokines induced neutrophil extracellular traps formation: implication for the inflammatory disease condition

Neutrophils (PMNs) and cytokines have a critical role to play in host defense and systemic inflammatory response syndrome (SIRS). Neutrophil extracellular traps (NETs) have been shown to extracellularly kill pathogens, and inflammatory potential of NETs has been shown. Microbial killing inside the phagosomes or by NETs is mediated by reactive oxygen and nitrogen species (ROS/RNS). The present study was undertaken to assess circulating NETs contents and frequency of NETs generation by isolated PMNs from SIRS patients. These patients displayed significant augmentation in the circulating myeloperoxidase (MPO) activity and DNA content, while PMA stimulated PMNs from these patients, generated more free radicals and NETs. Plasma obtained from SIRS patients, if added to the PMNs isolated from healthy subjects, enhanced NETs release and free radical formation. Expressions of inflammatory cytokines (IL-1β, TNFα and IL-8) in the PMNs as well as their circulating levels were significantly augmented in SIRS subjects. Treatment of neutrophils from healthy subjects with TNFα, IL-1β, or IL-8 enhanced free radicals generation and NETs formation, which was mediated through the activation of NADPH oxidase and MPO. Pre-incubation of plasma from SIRS with TNFα, IL-1β, or IL-8 antibodies reduced the NETs release. Role of IL-1β, TNFα and IL-8 thus seems to be involved in the enhanced release of NETs in SIRS subjects.

The interleukin-1 receptor antagonist influences interleukin-1 effects in rat and mouse

In this work we have focused on the ability of interleukin-1 to induce an acute phase protein response and a degranulation of polymorphonuclear leukocytes in vivo. The capacity of the interleukin-1 receptor antagonist to influence these events was also investigated. It was shown that interleukin-1 induced an acute phase protein response in rats and mice. In rats alpha(2)-macroglubolin levels were increased in plasma after an interleukin-1 injection whereas alpha(1)-inhibitor-3 decreased in plasma. In the mice plasma amyloid P was increased. The interleukin-1 receptor antagonist blocked the increase of alpha(2)-macroglobulin and plasma amyloid P in a dose dependent way while the effect on the alpha(1)-inhibitor-3 decrease was less pronounced. Interleukin-1 led to polymorphonuclear leukocyte degranulation in vivo as measured by increased cathepsin G plasma levels. The interleukin-1 receptor antagonist could influence the early phase of this degranulation.

Neutrophils in a mouse model of autoantibody-mediated arthritis: critical producers of Fc receptor gamma, the receptor for C5a, and lymphocyte function-associated antigen 1

OBJECTIVE

Neutrophils represent a prominent component of inflammatory joint effusions and are required for synovial inflammation in mouse models, but the mechanisms are poorly understood. In this study, we developed a system with which to test the importance of the production of specific factors by neutrophils in a mouse model of arthritis.

METHODS

Neutrophil-deficient Gfi-1(-/-) mice were administered sublethal doses of radiation and were then engrafted with donor bone marrow cells (BMCs), which resulted in the production of mature neutrophils within 2 weeks. By reconstituting with BMCs from mice lacking selected proinflammatory factors, we generated mice that specifically lacked these factors on their neutrophils. Arthritis was initiated by transfer of K/BxN serum to identify the role of defined neutrophil factors on the incidence and severity of arthritis.

RESULTS

Neutrophils lacking the signaling chain of stimulatory Fc receptors (FcRgamma(-/-)) were unable to elicit arthritis, but neutrophils lacking FcgammaRIII still did so. Neutrophils lacking the chemotactic or adhesion receptor C5a receptor (C5aR) or CD11a/lymphocyte function-associated antigen 1 (LFA-1) also failed to initiate arthritis but could enter joints in which inflammation had been initiated by wild-type neutrophils. Neutrophils unable to produce interleukin-1alpha (IL-1alpha) and IL-1beta (IL-1alpha/beta(-/-)) or leukotrienes (5-lipoxygenase [5-LOX(-/-)]) produced arthritis of intermediate severity. The inability of neutrophils to make tumor necrosis factor or to express receptors for tumor necrosis factor or IL-1 had no effect on arthritis.

CONCLUSION

A novel transfer system was developed to identify neutrophil production of FcRgamma, C5aR, and CD11a/LFA-1 as critical components of autoantibody-mediated arthritis. Neutrophil production of IL-1 and leukotriene B(4) likely contributes to inflammation but is not essential. Molecular requirements for neutrophil influx into joints become more permissive after inflammation is initiated.

Human chymase expression in a mice induces mild hypertension with left ventricular hypertrophy

A number of in vitro studies have suggested potential pathophysiological roles of human (h-) chymase. However, the lack of an appropriate animal model has left the in vivo roles of chymase unclear. To approach this problem, a transgenic mouse (TGM) model carrying the h-chymase gene was established. The h-chymase cDNA transgene was constructed with the chicken beta actin promoter and cytomegalovirus immediate early gene enhancer, and injected into mouse oocytes. Homozygous mice with a high copy number of the h-chymase gene suffered from intrauterine death. In three heterozygous TGM lines, h-chymase transgene expression was detected in entire organs, including the heart, vessels, skin, liver, lung, and brain. The h-chymase immunoreactivity was localized in the extracellular matrices of each organ, especially on the basement membranes of vessels. Aortic and hepatic chymase-dependent angiotensin II formations were significantly higher than those in the wild-type littermates. Three independent TGM lines showed the same phenotypic changes: elevation of blood pressure, left ventricular hypertrophy, emaciation with reduction in the lipid tissue, leukocytosis, and oligotrichia. The angiotensin II subtype 1 (AT1) receptor antagonist valsartan suppressed the elevated blood pressure completely and left ventricular hypertrophy incompletely, but did not affect the other phenotypes. These data suggested that in vivo expression of h-chymase caused mild hypertension (AT1 receptor-dependent) with left ventricular hypertrophy (partially AT1 receptor-dependent), and also chronic inflammatory changes (AT1 receptor-independent).

The acute phase protein serum amyloid A primes neutrophils

We studied here the effect of the acute phase protein serum amyloid A (SAA) on the oxidative burst of neutrophils. Incubation of neutrophils with SAA increased the rate of oxygen uptake and the production of reactive oxygen species of neutrophils activated with opsonized zymosan (OZ). The increment in the neutrophil oxidative burst was dependent on SAA concentration in the range of 3-33 microg protein ml(-1) and was observed only in the presence of a relatively low amount of OZ (1 x 10(6) particles ml(-1)). SAA did not affect oxygen consumption and reactive oxygen production triggered by other stimuli, such as f-Met-Leu-Phe, phorbol myristate acetate or non-opsonized zymosan. Our finding points to a priming effect of SAA probably associated with mobilization of receptors for opsonized particles and strengthens the role of SAA as an effector of neutrophil functions in inflammation.

Selective activation of p38 mitogen-activated protein kinase cascade in human neutrophils stimulated by IL-1beta

We investigated activation of mitogen-activated protein kinase (MAPK) subtype cascades in human neutrophils stimulated by IL-1beta. IL-1beta induced phosphorylation and activation of p38 MAPK and phosphorylation of MAPK kinase-3/6 (MKK3/6). Maximal activation of p38 MAPK was obtained by stimulation of cells with 300 U/ml IL-1beta for 10 min. Extracellular signal-regulated kinase (ERK) was faintly phosphorylated and c-Jun N-terminal kinase (JNK) was not phosphorylated by IL-1beta. IL-1beta primed neutrophils for enhanced release of superoxide (O(2)(-)) stimulated by FMLP in parallel with increased phosphorylation of p38 MAPK. IL-1beta also induced O(2)(-) release and up-regulation of CD11b and CD15, and both responses were inhibited by SB203580 (p38 MAPK inhibitor), suggesting that p38 MAPK activation mediates IL-1beta-induced O(2)(-) release and up-regulation of CD11b and CD15. Combined stimulation of neutrophils with IL-1beta and G-CSF, a selective activator of the ERK cascade, resulted in the additive effects when the priming effect and phosphorylation of p38 MAPK and ERK were assessed. IL-1beta induced phosphorylation of ERK and JNK as well as p38 MAPK in human endothelial cells. These findings suggest that 1) in human neutrophils the MKK3/6-p38 MAPK cascade is selectively activated by IL-1beta and activation of this cascade mediates IL-1beta-induced O(2)(-) release and up-regulation of CD11b and CD15, and 2) the IL-1R-p38 MAPK pathway and the G-CSF receptor-ERK pathway work independently for activation of neutrophils.

Dynamics of tissue neutrophil sequestration after cutaneous burns in rats

BACKGROUND

Neutrophil recruitment in organs after burns may cause local vascular damage, which can be reduced by agents blocking neutrophil adhesion to the vascular wall. Because these agents may increase susceptibility to infection, it is important to characterize the dynamics of neutrophil sequestration in order to optimize an eventual anti-adhesion therapy.

MATERIALS AND METHODS

Rats were scald burned over 20 or 40% of their total body surface area (TBSA) and saline resuscitated. Sham controls were used. Myeloperoxidase (MPO) activity was measured in lungs, liver, kidney, gut, and burned skin up to 1 week postburn. Extravascular accumulation of (125)I-labeled bovine serum albumin ((125)I-BSA) was measured at 12 h postburn.

RESULTS

MPO activity in lungs, liver, and kidney was increased within 3 h postburn and returned to normal within 24-48 h. Peak MPO levels occurred at 6-12 h postburn and were similar for both burn sizes. No MPO increase was observed in gut. MPO levels in burned skin did not increase before 6 h, peaked at 24 h, decreased at 48 h, but remained elevated for up to 7 days. Neutrophil recruitment in lungs and liver was confirmed histochemically. No neutrophils were found in kidneys. Extravascular (125)I-BSA was increased in lungs, liver, kidneys, and gut, in the 40% TBSA group only.

CONCLUSIONS

Neutrophil sequestration in remote organs is a transient phenomenon while neutrophil homing into the wound site is sustained. Neutrophil accumulation dynamics are independent of burn size, although a minimum size is required to trigger vascular damage. Temporary early anti-adhesion therapy to reduce lung and liver neutrophil sequestration with little impact on neutrophil homing into the burn wound may be possible.

Increased elastase and myeloperoxidase activity associated with neutrophil recruitment by IL-17 in airways in vivo

BACKGROUND

A recent study demonstrated that intratracheal administration of the T-lymphocyte cytokine IL-17 recruits neutrophils into airways in vivo by C-X-C chemokine release. It is not known whether IL-17 may also activate airway neutrophils.

OBJECTIVE

Our purpose was to evaluate whether IL-17 activates neutrophils in airways in vivo and, if so, whether the proinflammatory cytokine IL-1beta modulates this action of IL-17.

METHODS

Intratracheal administration of human (h) IL-17 or rat (r) IL-1beta or hIL-17 plus rIL-1beta in anesthetized, spontaneously breathing rats was followed by bronchoalveolar lavage (BAL) 6 hours later. The BAL fluid was characterized in terms of neutrophil count, of the activity for myeloperoxidase (MPO), and in some cases of the activity for elastase (ELA). Isolated rat neutrophils were stimulated with hIL-17 in vitro, followed by characterization of MPO activity in the cell medium.

RESULTS

hIL-17 (1 microg) increased the ELA and the MPO activity, as well as the neutrophil count in BAL fluid, whereas the proinflammatory cytokine rIL-1beta (2.5 ng) did not. Pretreatment with rIL-1beta enhanced IL-17induced ELA and MPO activity, without increasing the neutrophil count. The BAL ELA activity was inhibited by a specific inhibitor of neutrophil serine proteases. Stimulation with hIL-17 in vitro did not increase MPO activity in isolated neutrophils.

CONCLUSION

IL-17 can activate neutrophils in association with their recruitment into the airways in vivo and this effect is probably achieved through induced release of mediators from other airway cells.

Human mast cell chymase induces the accumulation of neutrophils, eosinophils and other inflammatory cells in vivo

The roles of chymase in acute allergic responses are not clear, despite the relative abundance of this serine proteinase in the secretory granules of human mast cells. We have isolated chymase to high purity from human skin tissue by heparin-agarose affinity chromatography and Sephacryl S-200 gel filtration procedures, and have investigated the ability of human mast cell chymase to stimulate cell accumulation following injection into laboratory animals. Injection of chymase provoked marked neutrophilia and eosinophilia in the skin of Dunkin Hartley guinea-pigs. Compared with saline injected control animals, there were some 60 fold more neutrophils and 12 fold more eosinophils present at the injection site. Following injection of chymase into the peritoneum of BALB/c mice, there were up to 700 fold more neutrophils. 21 fold more eosinophils, 19 fold more lymphocytes and 7 fold more macrophages recovered than from saline injected controls at 16 h. Doses of chymase as low as 5 ng (1.7 x 10(-13) mole) stimulated an inflammatory infiltrate, and significant neutrophilia was elicited within 3 h. The chymase induced cell accumulation in both the guinea-pig and mouse models was dependent on an intact catalytic site, being reduced by co-injection of proteinase inhibitors or heat inactivation of the enzyme. Co-injection of histamine or heparin significantly reduced the chymase induced neutrophil accumulation, whereas neither histamine nor heparin by themselves had any effect on the accumulation of nucleated cells. No synergistic or antagonist interactions between chymase and tryptase were observed when these two major mast cell proteinases were co-injected into the mouse peritoneum. Our findings suggest that chymase may provide an potent stimulus for inflammatory cell recruitment following mast cell activation.

Influence of interleukin 1alpha on superoxide anion, platelet activating factor release and phospholipase A2 activity of naive and sensitized guinea-pig alveolar macrophages

1. We studied the effect exerted by hr-interleukin-1alpha (IL-1alpha) on responsiveness of alveolar macrophages (AM) from naive and sensitized guinea-pigs, through O2.- production (by ferricytochrome C reduction), platelet-activating factor (PAF) release (by platelet aggregation), prostaglandin E2 (PGE2) release (by a radioimmunoassay), and cytosolic phospholipase A2 (cPLA2) activity (by hydrolysis of radioactive substrate). 2. In naive guinea-pig AM, 0.06 nM hr-IL-1alpha pretreatment decreased by 65% O2.- release stimulated with 10 nM fMLP. In contrast, O2.- production was not affected in sensitized guinea-pig AM. 3. O2.- release elicited by fMLP stimulation in both cell groups was affected by PLA2 inhibitors (10 microM bromophenacyl bromide, BPB or 10 microM methylprednisolone, MP). In contrast, 10 microM arachidonyl trifluoromethyl ketone (AACOCF3), a cPLA2 inhibitor, was ineffective. 4. In naive AM, PAF release was elicited by hr-IL-1alpha pretreatment and by separate fMLP-stimulation, but when the stimulus was added to hr-IL-1alpha-pretreated cells inhibition of PAF release was observed. In sensitized AM, PAF release was lower than that found in naive guinea-pig AM in both hr-IL-1alpha-pretreated and fMLP-stimulated cells. 5. PGE2 release was unaffected by hr-IL-1alpha pretreatment and it was decreased by fMLP in both naive and sensitized AMs. The latter released less PGE2 than naive cells in basal conditions and after fMLP treatment. 6. Sensitized AM showed a greater cPLA2 activity in all experimental conditions in comparison to naive cells. cPLA2 activity assayed in the cytosolic fraction was found to be enhanced by hr-IL-1alpha pretreatment and by fMLP stimulation in naive but not in sensitized AM. However, when the stimulus was added to hr-IL-1alpha-pretreated cells we observed a decrease in cPLA2 activity in the cytosol and an increase in the membranes, thus suggesting a translocation of enzymatic activity. 7. In conclusion, hr-IL-1alpha can modulate the responsiveness of AM from naive and sensitized guinea-pigs, as suggested by changes found in the release of PAF and O2.- and in cPLA2 activity; therefore, sensitization itself may affect cellular responsiveness.

Alveolar macrophages are required for protective pulmonary defenses in murine Klebsiella pneumonia: elimination of alveolar macrophages increases neutrophil recruitment but decreases bacterial clearance and survival

To study the in vivo role of alveolar macrophages (AM) in gram-negative bacterial pneumonia in mice, AM were eliminated by the intratracheal (i.t.) administration of dichloromethylene diphosphonate encapsulated liposomes. Subsequently, the AM-depleted mice were infected i.t. with 100 CFU of Klebsiella pneumoniae, and the effects of AM depletion on survival, bacterial clearance, and neutrophil (polymorphonuclear leukocyte [PMN]) recruitment were assessed. It was shown that depletion of AM decreases survival dramatically, with 100% lethality at day 3 postinfection, versus 100% long-term survival in the control group. This increased mortality was accompanied by 20- to 27- and 3- to 10-fold increases in the number of K. pneumoniae CFU in lung and plasma, respectively, compared to those in nondepleted animals. This decreased bacterial clearance was not due to an impaired PMN recruitment; on the contrary, the K. pneumoniae-induced PMN recruitment in AM-depleted lungs was sevenfold greater 48 h postinfection than that in control infected lungs. Together with an increased PMN infiltration, 3- and 10-fold increases in lung homogenate tumor necrosis factor alpha (TNF-alpha) and macrophage inflammatory protein 2 (MIP-2) levels, respectively, were measured. Neutralization of TNF-alpha or MIP-2, 2 h before infection, reduced the numbers of infiltrating PMN by 41.6 and 64.2%, respectively, indicating that these cytokines mediate PMN influx in infected lungs, rather then just being produced by the recruited PMN themselves. Our studies demonstrate, for the first time, the relative importance of the AM in the containment and clearance of bacteria in the setting of Klebsiella pneumonia.

Contribution of neutrophils to lipopolysaccharide-induced tumor necrosis factor production and mortality in a carrageenan-pretreated mouse model

Carrageenan (CAR) pretreatment primes mice for lipopolysaccharide (LPS)-induced tumor necrosis factor (TNF)-alpha production in sera and increases their mortality rate. To study the contribution of neutrophils in this model, blood neutrophil count was regulated with cyclophosphamide. After LPS challenge, both serum TNF-alpha activity and mortality risk ratio were significantly higher in neutrophilic mice, but significantly lower in neutropenic mice. In vitro, CAR treatment primed for TNF-alpha production of blood neutrophils, but conversely, that of monocytes was suppressed. We suggest that neutrophils are the major cells to produce TNF-alpha and to determine mouse mortality after LPS challenge in the mouse CAR model.

Differential priming effects of proinflammatory cytokines on human neutrophil oxidative burst in response to bacterial N-formyl peptides

Cytokines such as tumor necrosis factor alpha (TNF-alpha), granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin 8 (IL-8), IL-6, IL-1 alpha, and IL-1 beta produced during the immune and inflammatory responses to bacterial stimuli have been reported to interact with polymorphonuclear neutrophil (PMN) activities. However, contradictory findings on their direct and priming effects on the PMN oxidative burst, which is essential for bacterial killing, have been reported. We have used a flow cytometry method to study the effects of these cytokines on the oxidative burst of PMN in whole blood to avoid PMN activation related to isolation procedures. None of the cytokines tested directly activated the PMN oxidative burst, but they did have differential priming effects on the oxidative burst in response to bacterial N-formyl peptides. TNF, GM-CSF, and IL-8 strongly primed a subpopulation of PMN to produce H2O2 in response to N-formyl-methionyl-leucyl-phenylalanine (FMLP), while IL-1 alpha, IL-1 beta, and IL-6 failed to do so. Furthermore, the addition of TNF, GM-CSF, or IL-8 to whole blood increased the capacity of a subpopulation of PMN to bind N-formyl peptides, a phenomenon that could account, at least in part, for the strong H2O2 production in response to FMLP after priming by the cytokines. The size of the primed hyperresponsive subpopulation was greater after priming with TNF or GM-CSF than after priming with IL-8. However, GM-CSF, TNF, and IL-8 at suboptimal concentrations cooperated in the induction of a subpopulation hyperresponsive to FMLP. These results show that, of the various proinflammatory cytokines tested, TNF, GM-CSF, and IL-8 strongly prime the PMN oxidative burst in response to bacterial peptides in whole blood and suggest that these cytokines may play a critical role in bacterial killing in vivo.

Effects of supernatant from tonsillar cell culture on neutrophil functions

The palatine tonsil is the most important element of Waldeyer's ring as a defense mechanism against various microorganisms. The neutrophils are the initial active participants in bacterial infection and inflammation, but their interaction with other cellular participants is poorly understood. To clarify this point, the effects of culture supernatant from human tonsillar cells on the peripheral neutrophil function were investigated. Supernatants from tonsillar cells were incubated in the presence or absence of streptococcal preparation (OK-432) enhanced chemiluminescence, adherence, phagocytosis, chemotaxis, and superoxide production of human peripheral neutrophils. The results suggest that tonsils play an important role in the regulation of neutrophil function.

Activated pulmonary vascular neutrophils as early mediators of endotoxin-induced lung inflammation

Pulmonary vascular sequestration of leukocytes has been reported to increase in some models of lung injury, including that induced by gram-negative bacterial lipopolysaccharide (LPS). Neutrophils recruited to the lung likely participate in LPS-induced lung inflammation and associated injury, but the functional activities of these pulmonary vascular neutrophils have not been directly assessed. In the current study, cells were recovered by pulmonary vascular lavage (PVL) of isolated rat lungs, harvested 2 h after intravenous infusion of LPS (3 mg/kg) or saline in intact rats, at which time LPS-induced neutrophil recruitment to the lung could be appreciated histologically but not by airway lavage. Relative concentrations of leukocytes recovered from the pulmonary vasculature by PVL were compared with those present in circulating blood, normalizing for lavage dilution on the basis of erythrocyte counts. Excess neutrophils, lymphocytes, monocytes, and eosinophils were recovered from the pulmonary vasculature of controls, and LPS infusion increased recovery of neutrophils (most prominently), lymphocytes, and monocytes. Compared with cells recovered from controls, PVL neutrophils from LPS-infused animals were primed for increased zymosan-stimulated superoxide generation, determined by ferricytochrome C reduction, and were more adherent to nylon wool columns. Northern blots of extracted RNA demonstrated that LPS infusion also upregulated interleukin-1 beta (IL-1 beta) mRNA expression in PVL leukocyte samples, but not BAL or circulating blood samples. Ficoll-hypaque separation demonstrated that the LPS-induced IL-1 beta signal in PVL leukocytes was derived primarily from polymorphonuclear rather than mononuclear leukocytes. In conclusion, all circulating leukocyte populations are sequestered in rat lungs, and LPS increases pulmonary vascular sequestration of leukocytes, recruiting most prominently an activated pool of neutrophils that are more adherent, primed for increased oxygen radical production, and expressing increased IL-1 beta message. These findings suggest a more prominent role than previously appreciated for sequestered neutrophils in sepsis-induced lung inflammation.

Platelet-activating factor and interleukin 1 are involved in colonic dysmotility in experimental colitis in rats

BACKGROUND

Intracolonic administration of trinitrobenzene sulfonic acid (TNBS) to rats produces chronic colitis associated with an increased release of eicosanoids, platelet-activating factor (PAF), and interleukins.

METHODS

Motor effects of TNBS on proximal colon were evaluated electromyographically in rats. Mediator involvement was investigated using eicosanoids and PAF antagonists.

RESULTS

The colonic myoelectrical activity was 59 +/- 17 spike bursts per hour lasting 6.9 +/- 1.3 seconds. Two to eight days after TNBS treatment, spike-burst duration was significantly (P < 0.05) higher, with a maximal 1.5-4-fold enhancement at day 3. These alterations were significantly (P < 0.05) reduced by daily treatment with MK-886, a 5-lipoxygenase inhibitor (10 mg/kg, orally), whereas indomethacin (1 mg/kg per day, intramuscularly) was ineffective. At day 3, RP55778, a PAF antagonist (45, 60 mg/kg, intraperitoneally), and rIRAP, an interleukin 1 antagonist (0.3 mg/kg, intraperitoneally) but not KT1-32, a thromboxane A2 antagonist (30, 60 mg/kg orally), nor SKF104,353, a leukotriene D4 antagonist (2, 4 mg/kg, orally), significantly (P < 0.05) reduced the TNB-induced motor effects.

CONCLUSION

TNBS-induced colitis in rats involves a delayed long-lasting dysmotility involving PAF, interleukin 1, and some leukotrienes but not leukotriene D4, thromboxane A2, or other cyclo-oxygenase products.

Platelet activating factor amplifies human neutrophil adherence to bovine endothelial cells: evidence for a lipoxygenase dependent mechanism

Platelet activating factor (PAF) is a potent lipid mediator that induces the release of leukotrienes and prostaglandins from various cells and tissues. We examined the capacity of PAF alone and in combination with soluble stimuli to enhance eicosanoid synthesis and adherence of human neutrophils. Neutrophils were preincubated with PAF and washed before exposure to the soluble stimuli F-Met-Leu-Phe (FMLP), calcium ionophore A23187, and phorbol myristate acetate. Preincubation of neutrophils with 1 microM PAF enhanced the release of both LTB4 and LTC4 in response to each of the three agonists, in contrast with the unprimed neutrophils. Priming was specific for PAF since lyso-PAF was inactive. Priming concentrations of PAF also augmented the adherence of neutrophils to endothelium in the presence of the soluble agonists A23187, phorbol myristate acetate, and FMLP. The priming effect of PAF on eicosanoid release and neutrophil adherence was shown to have similar time- and dose-dependent effects. Further, the priming effects of PAF on adherence could be reversed by preincubation of neutrophils with the lipoxygenase inhibitors nordihydroguiaretic acid and 5,8,11,14-ETYA but not by preincubation with the cyclooxygenase inhibitor indomethacin. These data demonstrate that PAF amplifies neutrophil adherence to endothelium through a lipoxygenase dependent mechanism.

Bovine neutrophils recruited by endotoxin to a teat cistern continuously produce oxygen radicals and show increased phagocytosis and extracellular chemiluminescence

Bovine neutrophils were harvested from a teat cistern following endotoxin infusion and were compared with blood neutrophils by measurements of chemiluminescent and phagocytic activity towards C3- and IgG-opsonized and unopsonized yeast particles. Both phagocytosis and luminol-dependent chemiluminescence elicited by all three particles were enhanced in the teat cells. The increase in the luminol-dependent chemiluminescence towards C3- and IgG-opsonized particles was due to an enhanced extracellular release of myeloperoxidase. The observed increase in phagocytosis of unopsonized yeast was shown to reflect the interaction between up-regulated CR3 receptors on the surface of the teat neutrophils and the yeast particles. A high chemiluminescent activity of the teat neutrophils in both the luminol- and lucigenin-dependent systems in the absence of a phagocytic prey indicated that the NADPH oxidase was permanently active and that myeloperoxidase was continuously released by the cells. Treatment of neutrophils with cytochalasin B showed that the chemiluminescence and phagocytosis of teat neutrophils were less sensitive to this drug than that of blood neutrophils. These results indicate that the teat neutrophils have up-regulated their receptors for IgG- and C3-opsonized and unopsonized yeast on the cell surface by the action of actin. The cells also have a permanently active NADPH oxidase dependent on the association with actin and show a higher tendency than blood neutrophils to secrete the content of their primary granules during phagocytosis.

Inhibition of myeloperoxidase by synovial fluid and serum

An inhibitor of myeloperoxidase has been identified in the synovial fluids and sera from patients with rheumatoid arthritis and sera from normal subjects. Initially, these fluids were found to inhibit stimulus induced degranulation of polymorphonuclear leucocytes independently of the stimulating agent. Subsequently, the fluids were shown to inhibit the released enzyme rather than the degranulation response of polymorphonuclear leucocytes. Both rheumatoid and normal serum samples contained high concentrations of the inhibitor but the concentrations were lower in rheumatoid synovial fluids. The inhibitory activity seemed to be specific for peroxidase as the fluids did not inhibit beta-glucuronidase activity. A protein of relative molecular mass (Mr) 150 kd was purified from synovial fluid by affinity chromatography on myeloperoxidase-Sepharose. It is concluded that serum and synovial fluid contain a novel myeloperoxidase inhibitor, which acts by binding to myeloperoxidase and thereby prevents myeloperoxidase releasing oxidative products in serum.

Identification of a myeloperoxidase inhibitor from normal human serum

An inhibitor of myeloperoxidase (MPO) has been identified in normal human serum. Initial experiments confirmed that high levels of MPO inhibitory activity are present in sera and that the inhibitor did not act by interfering with the assay. Purification of the inhibitor activity by salt precipitation followed by ion exchange and affinity chromatography revealed the presence of a protein of 150 kD. The purified inhibitory activity displayed dose and time dependency and was not associated with IgG or IgA. It is considered that human serum contains an inhibitor of extracellular MPO capable of protecting against hypohalous acid release in host tissues and that if inhibitor levels are reduced such protection may fail.

Human cartilage is degraded by rheumatoid arthritis synovial fluid but not by recombinant cytokines in vitro

Rheumatoid arthritis (RA) synovial fluid (SF) stimulated significant loss of glycosaminoglycans (GAG) from normal and pathological human cartilage biopsies over 2 days as compared with normal human serum. By contrast, 15 RA SFs failed to degrade killed normal cartilage, and degraded killed RA cartilage less effectively than living RA cartilage. Four RA SFs were treated with neutralizing anti-cytokine antisera prior to incubation with normal cartilage. The degrading effects of two of the fluids were reversed by anti-interleukin-1 alpha (IL-1 alpha) while degradation by the third and fourth fluids were reversed by anti-interleukin-1 beta (IL-1 beta) and anti-tumour necrosis factor-alpha (TNF-alpha), respectively. However, recombinant human IL-1 alpha, IL-1 beta, TNF alpha or a combination of all three cytokines had no degrading effect in this 2-day culture system. It is concluded that RA SF degrades cartilage by a mechanism involving a synergistic interaction between cytokines and some other component of SF.