Citrate modulates lipopolysaccharide-induced monocyte inflammatory responses

Citrate, a central component of cellular metabolism, is a widely used anti-coagulant due to its ability to chelate calcium. Adenosine triphosphate (ATP)-citrate lyase, which metabolizes citrate, has been shown to be essential for inflammation, but the ability of exogenous citrate to impact inflammatory signalling cascades remains largely unknown. We hypothesized that citrate would modulate inflammatory responses as both a cellular metabolite and calcium chelator, and tested this hypothesis by determining how clinically relevant levels of citrate modulate monocyte proinflammatory responses to lipopolysaccharide (LPS) in a human acute monocytic leukaemia cell line (THP-1). In normal medium (0.4 mM calcium), citrate inhibited LPS-induced tumour necrosis factor (TNF)-α and interleukin (IL)-8 transcripts, whereas in medium supplemented with calcium (1.4 mM), TNF-α and IL-8 levels increased and appeared independent of calcium chelation. Using an IL-8-luciferase plasmid construct, the same increased response was observed in the activation of the IL-8 promoter region, suggesting transcriptional regulation. Tricarballylic acid, an inhibitor of ATP-citrate lyase, blocked the ability of citrate to augment TNF-α, linking citrate's augmentation effect with its metabolism by ATP-citrate lyase. In the presence of citrate, increased histone acetylation was observed in the TNF-α and IL-8 promoter regions of THP-1 cells. We observed that citrate can both augment and inhibit proinflammatory cytokine production via modulation of inflammatory gene transactivation. These findings suggest that citrate anti-coagulation may alter immune function through complex interactions with the inflammatory response.

Dual role of interleukin-10 in the regulation of respiratory syncitial virus (RSV)-induced lung inflammation

RSV lower respiratory tract infections (LRTI) are among the most common diseases necessitating hospital admission in children. In addition to causing acute respiratory failure, RSV infections are associated with sequelae such as secondary bacterial infections and reactive airway disease. One characteristic host response observed in severe RSV-induced LRTI and/or subsequent development of asthma is increased expression of interleukin (IL)-10. However, contradictory results have been reported regarding whether IL-10 inhibits asthmatic responses or intensifies the disease. We aimed to reconcile these discordant observations by elucidating the role of IL-10 in regulating the host response to RSV LRTI. In this study, we used a lung-specific, inducible IL-10 over-expression (OE) transgenic mouse model to address this question. Our results showed that the presence of IL-10 at the time of RSV infection not only attenuated acute inflammatory process (i.e. 24 h post-infection), but also late inflammatory changes [characterized by T helper type 2 (Th2) cytokine and chemokine expression]. While this result appears contradictory to some clinical observations where elevated IL-10 levels are observed in asthmatic patients, we also found that delaying IL-10 OE until the late immune response to RSV infection, additive effects rather than inhibitory effects were observed. Importantly, in non-infected, IL-10 OE mice, IL-10 OE alone induced up-regulation of Th2 cytokine (IL-13 and IL-5) and Th2-related chemokine [monocyte chemoattractant protein 1 (MCP-1), chemokine (C-C motif) ligand 3 (CCL3) and regulated upon activation normal T cell expressed and secreted (RANTES)] expression. We identified a subset of CD11b(+)CD11c(+)CD49b(+)F4/80(-)Gr-1(-) myeloid cells as a prinicipal source of IL-10-induced IL-13 production. Therefore, the augmented pathological responses observed in our 'delayed' IL-10 over-expression model could be attributed to IL-10 OE alone. Taken together, our study indicated dual roles of IL-10 on RSV-induced lung inflammation which appear to depend upon the timing of when elevated IL-10 is expressed in the lung.

The use of extracorporeal membrane oxygenation in pediatric patients with sickle cell disease

Previous reports have described the use of extracorporeal membrane oxygenation (ECMO) for acute chest syndrome of sickle cell disease (SCD). However, there have been no reports of venoarterial (VA) ECMO for cardiac dysfunction in patients with SCD. We describe a patient with SCD and life-threatening cardiogenic shock who was successfully treated with VA ECMO. Furthermore, SCD patients have unique comorbidities that warrant particular consideration when utilizing ECMO. We discuss these considerations and review the documented experience with ECMO for pediatric SCD patients from the Extracorporeal Life Support Organization (ELSO) registry. From 1990 until 2012, 52% of the 65 pediatric patients with SCD placed on ECMO survived, with 85% of those receiving venovenous (VV) ECMO surviving and 43% of those receiving VA ECMO surviving. However, significant complications, such as bleeding, neurological injury and kidney injury, also occurred with both VV and VA ECMO. Ten percent of SCD patients receiving VA ECMO experienced either a cerebral infarct or hemorrhage; our patient suffered a cerebrovascular accident while on ECMO, though she survived with good neurologic outcome. To our knowledge, this is the first report of a pediatric patient with SCD and cardiogenic shock successfully managed with VA ECMO. In conjunction with the ELSO registry review, this case report suggests that, while VA ECMO can be successfully used in patients with SCD and severe cardiovascular dysfunction, clinicians should also be aware of the potential for serious complications in this high-risk population.

Geldanamycin inhibits NF-kappaB activation and interleukin-8 gene expression in cultured human respiratory epithelium

Geldanamycin is a benzoquinone ansamycin with multiple pharmacologic properties. Recent data demonstrated that geldanamycin conferred protection in an animal model of inflammation-associated acute lung injury. In the current study, we investigated the effects of geldanamycin on interleukin (IL)-8 gene expression and nuclear factor (NF)-kappaB activation. Geldanamycin inhibited tumor necrosis factor (TNF)-alpha-mediated IL-8 gene expression in A549 human respiratory epithelial cells as measured by enzyme-linked immunosorbent assay and Northern blot analyses. In cells transiently transfected with an IL-8 promoter-luciferase reporter plasmid, geldanamycin inhibited TNF-alpha-mediated luciferase activity. Geldanamycin inhibited TNF-alpha-mediated NF-kappaB activation as measured by electromobility shift assays and transient transfections with a NF-kappaB-dependent luciferase reporter plasmid. In contrast, geldanamycin did not affect TNF-alpha-mediated degradation of the NF-kappaB inhibitory protein IkappaBalpha and did not block nuclear translocation of the NF-kappaB p65 subunit as measured by Western blot analyses. Geldanamycin added directly to nuclear extracts of TNF-alpha-treated cells reduced the formation of the NF-kappaB/DNA complex. These results demonstrate that geldanamycin inhibits TNF-alpha-mediated IL-8 gene expression in A549 cells by inhibiting activation of the IL-8 promoter. The mechanism of inhibition involves inhibition of NF-kappaB activation, which is independent of IkappaBalpha degradation or p65 nuclear translocation. Geldanamycin appears to directly inhibit the ability of NF-kappaB to bind DNA. The observed in vitro effects could account, in part, for the anti-inflammatory properties of geldanamycin observed in vivo.

The serine/threonine phosphatase, PP2A: endogenous regulator of inflammatory cell signaling

We have investigated the regulation of kinases and phosphatases in early gene activation in monocytes because these cells are implicated in the pathogenesis of acute inflammatory states, such as sepsis and acute lung injury. One early gene up-regulated by endotoxin is c-Jun, a member of the activating protein (AP) family. C-Jun is phosphorylated by c-Jun N-terminal kinase (JNK) and associates with c-Fos to form the AP-1 transcriptional activation complex that can drive cytokine expression. Inhibition of the serine/threonine phosphatase, PP2-A, with okadaic acid resulted in a significant increase in JNK activity. This finding was associated with increased phosphorylation of c-Jun, AP-1 transcriptional activity, and IL-1beta expression. Activation of PP2A inhibited JNK activity and JNK coprecipitated with the regulatory subunit, PP2A-Aalpha, supporting the conclusion that PP2A is a key regulator of JNK in the context of an inflammatory stimulus.

Role of RANTES in experimental cardiac allograft rejection

The host response to alloantigen results in upregulation of Class II MHC antigens and associated cytokine production (especially IL-2 and interferon-gamma (IFN-gamma)) as well as lymphocytic infiltration and cellular activation which leads to graft damage/destruction. RANTES (Regulated upon Activation, Normal T-cell Expressed and presumably Secreted) is a member of the beta subfamily (CC) of chemokines and has been shown to function as a lymphocyte chemoattractant. We now describe the requirement for RANTES in cardiac heterotopic allograft (brown Norway into Lewis rats) rejection in rats. By Northern blot analysis, mRNA could be detected in allografts at 6 and 8 days post-transplantation but not in isogenic (Lewis) grafts. RANTES protein could be demonstrated by Western blot analysis in homogenates from allografts at day 8 but not at day 0 and could not be identified in isogenic cardiac transplants. By immunostaining, RANTES protein was present in mononuclear cells of allografts at day 6 but was absent in the isogenic transplants. When rats were treated with anti-RANTES serum, there was a significant delay in rejection time (cessation of beating) of the allografts. These data demonstrate that expression of RANTES in rat cardiac allografts is linked to the rejection phenomenon.

Heat shock inhibits phosphorylation of I-kappaBalpha

Previous studies demonstrated that induction of the heat shock response is associated with inhibition of the proinflammatory transcription factor NF-kappaB by a mechanism involving inhibition of I-kappaBalpha degradation. To provide further insight regarding the interactions of these fundamental cellular responses, the present experiments were designed to elucidate the mechanism(s) by which heat shock inhibits degradation of I-kappaBalpha. In an in vitro model of inflammatory cell signaling, treatment of RAW 264.7 murine macrophages with LPS (100 ng/mL) caused rapid degradation of I-kappaBalpha. Heat shock, 1 h before treatment with LPS, completely inhibited LPS-mediated degradation of I-kappaBalpha. Immunoprecipitation studies demonstrated that heat shock inhibited LPS-mediated ubiquitination of I-kappaBalpha. Western-blot analyses using a phosphorylated I-kappaBalpha-specific antibody demonstrated that heat shock inhibited LPS-mediated phosphorylation of I-kappaBalpha. In contrast, heat shock induced phosphorylation of c-jun. In murine fibroblasts having genetic ablation of the heat shock factor-1 gene, heat shock inhibited tumor necrosis factor-alpha mediated degradation of I-kappaBalpha. We conclude that the mechanism by which heat shock inhibits LPS-mediated degradation of I-kappaBalpha involves specific inhibition of I-kappaBalpha phosphorylation and subsequent I-kappaBalpha ubiquitination. In addition, this mechanism does not involve activation of heat shock factor-1 or the heat shock proteins regulated by heat shock factor-1.

Role of macrophage inflammatory protein-2 in aspiration-induced lung injury

OBJECTIVE

To determine the role of the chemokine, macrophage inflammatory protein (MIP)-2, in the pathogenesis of aspiration-induced lung injury in the rat.

DESIGN

Prospective, randomized, controlled animal study.

SETTING

University research laboratories.

SUBJECTS

Adult, male Long-Evans rats.

INTERVENTIONS

Anesthetized rats underwent induction of lung injury by well-described models of aspiration triggered by intra-tracheal delivery of acid alone, gastric particles alone, or the combination. After injury, induction of MIP-2 messenger RNA in whole lungs and immunoreactive MIP-2 in bronchoalveolar lavage (BAL) fluids was determined. The contribution of MIP-2 to BAL fluid chemotactic activity was defined by using an in vitro chemotaxis assay. The in vivo effect of blocking MIP-2 on pulmonary vascular leak, BAL fluid neutrophils, PaO2/FIO2 ratio, and alveolar-arterial oxygen tension gradient in acid-induced lung injury was determined.

MEASUREMENTS AND MAIN RESULTS

Induction of MIP-2 messenger RNA and protein over time was observed in response to all three stimuli. A significant portion (25% to 41%) of the chemotactic activity in BAL fluids from injured rats was inhibited by anti-MIP-2 antibody. After acid injury, blocking of MIP-2 was associated with a 53% decrease in BAL fluid neutrophils and a 33% decrease in pulmonary vascular leak. Although acid injury both impaired oxygenation and increased venous admixture, in vivo blocking of MIP-2 was associated with improved oxygenation as well as decreased venous admixture.

CONCLUSIONS

MIP-2 was up-regulated during the development of aspiration-induced lung injury in rats. MIP-2 contributed to lung accumulation of neutrophils via a chemotactic mechanism. Although oxygenation and venous admixture are worsened by acid-induced lung injury in vivo, blocking of MIP-2 at the onset of injury improved these physiologic alterations. Because the aspiration event often is witnessed, chemokines may be valid therapeutic targets for inhibiting the subsequent inflammatory response.

Regulation of chemokine expression by IL-10 in lung inflammation

We have been interested in understanding the mechanisms regulating the inflammatory process underlying acute lung injury. The current studies have employed a model of acute lung inflammation in mice triggered by bacterial lipopolysaccharide. The development of this injury was associated with increased expression of the chemokines, MIP-1alpha and MIP-2, that coordinate recruitment of neutrophils to the lung. IL-10 is a potent, endogenous anti-inflammatory molecule that has been shown to decrease lung inflammation partly on the basis of TNF-alpha and IL-1beta inhibition. In these studies we tested the hypothesis that endogenous IL-10 modulates chemokine expression using the IL-10 knock-out mouse, and then explored the molecular mechanisms by which IL-10 might do so. The results demonstrate that significant elevations in both chemokines were observed in the absence of IL-10 and that these findings were associated with significant increases in lung neutrophil accumulation. In vitro studies defined two, gene-specific, mechanisms by which IL-10 regulated chemokine expression: mRNA destabilization and NF-kappaB inhibition. These results suggested that IL-10 is an important, endogenous regulator of chemokine expression in acute lung inflammation.

Role of CC chemokines (macrophage inflammatory protein-1 beta, monocyte chemoattractant protein-1, RANTES) in acute lung injury in rats

The role of the CC chemokines, macrophage inflammatory protein-1 beta (MIP-1 beta), monocyte chemotactic peptide-1 (MCP-1), and RANTES, in acute lung inflammatory injury induced by intrapulmonary deposition of IgG immune complexes injury in rats was determined. Rat MIP-1 beta, MCP-1, and RANTES were cloned, the proteins were expressed, and neutralizing Abs were developed. mRNA and protein expression for MIP-1 beta and MCP-1 were up-regulated during the inflammatory response, while mRNA and protein expression for RANTES were constitutive and unchanged during the inflammatory response. Treatment of rats with anti-MIP-1 beta Ab significantly decreased vascular permeability by 37% (p = 0.012), reduced neutrophil recruitment into lung by 65% (p = 0.047), and suppressed levels of TNF-alpha in bronchoalveolar lavage fluids by 61% (p = 0.008). Treatment of rats with anti-rat MCP-1 or anti-rat RANTES had no effect on the development of lung injury. In animals pretreated intratracheally with blocking Abs to MCP-1, RANTES, or MIP-1 beta, significant reductions in the bronchoalveolar lavage content of these chemokines occurred, suggesting that these Abs had reached their targets. Conversely, exogenously MIP-1 beta, but not RANTES or MCP-1, caused enhancement of the lung vascular leak. These data indicate that MIP-1 beta, but not MCP-1 or RANTES, plays an important role in intrapulmonary recruitment of neutrophils and development of lung injury in the model employed. The findings suggest that in chemokine-dependent inflammatory responses in lung CC chemokines do not necessarily demonstrate redundant function.

The role of tumor necrosis factor-alpha in the pathogenesis of aspiration pneumonitis in rats

BACKGROUND

Aspiration pneumonitis is characterized by proteinaceous pulmonary edema and acute infiltration of neutrophils into the alveolar space. This study examined the role of the proinflammatory cytokine, tumor necrosis factor-alpha (TNF-alpha), on the pathogenesis of the injury produced by the different components that may be present in the aspirate, acid, or gastric particles.

METHODS

Rats were injured by intratracheal instillation of a vehicle containing acid or gastric particles. TNF-alpha concentration of bronchoalveolar lavage fluid was determined using a bioassay. upregulation of lung TNF-alpha mRNA was also measured. The effect of intratracheal anti-rat TNF-alpha treatment was assessed by lung protein permeability, blood gases, and lung myeloperoxidase activity.

RESULTS

Injury vehicle alone and acid injury resulted in a small TNF-alpha peak 1-2 h after injury in the lavage fluid. Both particulate and acidic particulate groups produced a much more robust TNF-alpha signal that reached a plateau at 2-4 h after injury and declined at 8 h. Upregulation of TNF-alpha mRNA was only detected in the particulate-containing groups. Acidic particulate exposure yielded a synergistic increase in protein permeability and decrease in blood oxygenation. Anti-TNF-alpha treatment reduced protein permeability and myeloperoxidase activity and increased blood oxygenation in the groups exposed to only acid. Such treatment had no effect on either of the particulate containing injuries.

CONCLUSIONS

TNF-alpha is differentially manifested according to the components that make up the aspirate but the levels of TNF-alpha expression do not correlate with the severity of the resultant injury. However, the reduction in acid-induced lung injury by anti-TNF-alpha treatment indicates that TNF-alpha plays a role in the pathogenesis of aspiration pneumonitis.

Role of matrix metalloproteinases in models of macrophage-dependent acute lung injury. Evidence for alveolar macrophage as source of proteinases

Matrix metalloproteinases (MMPs) have been implicated in the tissue injury seen in neutrophil-dependent models of acute lung injury. However, the role of MMPs in macrophage-dependent models of lung injury is unknown. To address this issue, the macrophage-dependent immunoglobulin A immune complex-induced lung injury model and the macrophage-dependent portion of the lipopolysaccharide-induced acute lung injury model in the rat were assessed for MMP involvement and for the source of these activities. In both models, injury was inhibited by the recombinant human tissue inhibitor of metalloproteinases-2. Bronchoalveolar lavage fluids (BALFs) from injured animals in both models showed increased levels of MMPs. Characterization of MMP production by isolated lung fibroblasts, endothelial cells, type II epithelial cells, and alveolar macrophages revealed that only the macrophage had the same spectrum of MMP activity as seen in the BALF. Further, isolated alveolar macrophages from injured lungs showed evidence of in vivo activation with the release of the same spectrum of MMP activities. Together these studies show that MMPs are produced during macrophage-dependent lung injury, that these MMPs play a role in the development of the lung injury, and that the alveolar macrophage is the likely source of these MMPs.

Regulatory effects of endogenous protease inhibitors in acute lung inflammatory injury

Inflammatory lung injury is probably regulated by the balance between proteases and protease inhibitors together with oxidants and antioxidants, and proinflammatory and anti-inflammatory cytokines. Rat tissue inhibitor of metalloprotease-2 (TIMP-2) and secreted leukoprotease inhibitor (SLPI) were cloned, expressed, and shown to be up-regulated at the levels of mRNA and protein during lung inflammation in rats induced by deposition of IgG immune complexes. Using immunoaffinity techniques, endogenous TIMP-2 in the inflamed lung was shown to exist as a complex with 72- and 92-kDa metalloproteinases (MMP-2 and MMP-9). In inflamed lung both TIMP-2 and SLPI appeared to exist as enzyme inhibitor complexes. Lung expression of both TIMP-2 and SLPI appeared to involve endothelial and epithelial cells as well as macrophages. To assess how these endogenous inhibitors might affect the lung inflammatory response, animals were treated with polyclonal rabbit Abs to rat TIMP-2 or SLPI. This intervention resulted in significant intensification of lung injury (as revealed by extravascular leak of albumin) and substantially increased neutrophil accumulation, as determined by cell content in bronchoalveolar lavage (BAL) fluids. These events were correlated with increased levels of C5a-related chemotactic activity in BAL fluids, while BAL levels of TNF-alpha and chemokines were not affected by treatment with anti-TIMP-2 or anti-SLPI. The data suggest that endogenous TIMP-2 and SLPI dynamically regulate the intensity of lung inflammatory injury, doing so at least in part by affecting the generation of the inflammatory mediator, C5a.

Exogenous and endogenous catecholamines inhibit the production of macrophage inflammatory protein (MIP) 1 alpha via a beta adrenoceptor mediated mechanism

Noradrenaline (NA) and adrenaline (Ad) are modulators of cytokine production. Here we investigated the role of these neurotransmitters in the regulation of macrophage inflammatory protein (MIP)-1alpha expression. Pretreatment of RAW 264.7 macrophages with NA or Ad decreased, in a concentration-dependent manner (1 nM-100 microM), MIP-1alpha release induced by bacterial lipopolysaccharide (LPS 10 ng ml(-1) LPS). The effect of NA was reversed by the selective beta-adrenoceptor antagonist propranolol (10 microM), but not by the alpha-adrenoceptor antagonist phentolamine (10 microM). In the concentration range of 10 nM-10 microM, isoproterenol, a beta-adrenoceptor agonist, but not phenylephrine (a selective alpha1-adrenoceptor agonist) or UK-14304 (a selective alpha2-adrenoceptor agonist) mimicked the inhibitory effects of catecholamines on MIP-1alpha production. Increases in intracellular cyclic adenosine monophosphate, elicited either by the selective type IV phosphodiesterase inhibitor rolipram (0.1 - 10 microM), or by prostaglandin E2, (10 nM-10 microM) decreased MIP-1alpha release, suggesting that increased cyclic AMP may contribute to the suppression of MIP-1alpha release by beta-adrenoceptor stimulation. Northern blot analysis demonstrated that NA (100 nM-10 microM), Ad, isoproterenol, as well as rolipram (100 nM-10 microM) decreased LPS-induced MIP-1alpha mRNA accumulation. NA and Ad (1-100 microM) also decreased MIP-1alpha production in thioglycollate-elicited murine peritoneal macrophages. Pretreatment of mice with either isoproterenol (10 mg kg(-1), i.p.) or rolipram (25 mg kg(-1), i.p.) decreased LPS-induced plasma levels of MIP-1alpha, while propranolol (10 mg kg(-1), i.p.) augmented the production of this chemokine, confirming the role of a beta-adrenoceptor mediated endogenous catecholamine action in the regulation of MIP-1alpha production in vivo. Thus, based on our data we conclude that catecholamines are important endogenous regulators of MIP-1alpha expression in inflammation.

Induction of the stress response with prostaglandin A1 increases I-kappaBalpha gene expression

I-kappaBalpha is an intracellular protein that functions as a primary inhibitor of the proinflammatory transcription factor NF-kappaB. Induction of the stress response with heat shock was previously demonstrated to induce I-kappaBalpha gene expression. Because the stress response can also be induced by nonthermal stimuli, we determined whether induction of the stress response with prostaglandin A1 (PGA1) would induce I-kappaBalpha gene expression. Treatment of human bronchial epithelium (BEAS-2B cells) with PGA1 induced nuclear translocation of heat shock factor 1, thus confirming that PGA1 induces the stress response in BEAS-2B cells. Induction of the stress response with PGA1 increased I-kappaBalpha mRNA expression in a time-dependent manner and increased I-kappaBalpha peptide expression. Transient transfection assays involving a human I-kappaBalpha promoter-luciferase reporter construct demonstrated that induction of the stress response with PGA1 activated the I-kappaBalpha promoter. Induction of the stress response with PGA1 and concomitant induction of I-kappaBalpha were associated with inhibition of TNF-alpha-mediated secretion of interleukin 8 and with inhibition of TNF-alpha-mediated nuclear translocation and activation of NF-kappaB. These data demonstrate that induction of the stress response, by a nonthermal stimulus, increases I-kappaBalpha gene expression by a mechanism involving activation of the I-kappaBalpha promoter. Coupled with previous data demonstrating heat shock-mediated induction of I-kappaBalpha gene expression, these data suggest that I-kappaBalpha may be considered to be one of the stress proteins. The functional consequences of stress response-mediated I-kappaBalpha gene expression may involve attenuation of cellular proinflammatory responses.

Suppression of macrophage inflammatory protein (MIP)-1alpha production and collagen-induced arthritis by adenosine receptor agonists

1. Ligands of the various adenosine receptor subtypes modulate the production of pro-and anti-inflammatory cytokines. Here we evaluated the effect of adenosine and various ligands of the adenosine receptor subtypes (A1, A2, A3) on the chemokine macrophage inflammatory protein (MIP) 1alpha production in immunostimulated RAW macrophages in vitro. Furthermore, we studied whether a selected A3 adenosine receptor agonist inhibits MIP-1alpha production and affects the course of inflammation in collagen-induced arthritis. 2. In the cultured macrophages, the A3 receptor agonist N6-(3-iodobenzyl)-adenosine-5'-N-methyluronamide (IB-MECA), and, less potently, the A2 receptor agonist 2-p-(2-carboxyethyl) phenethylamino-5'-N-ethyl-carboxamidoadenosine (CGS; 1-200 micro) dose-dependently suppressed the production of MIP-1alpha. The selective A1 receptor agonist 2-chloro-N6-cyclopentyladenosine (CCPA, 1-200 microM) was ineffective, and adenosine was a weak inhibitor. The inhibition of MIP-1alpha production by the A3 and A2 agonist was associated with suppression of its steady-state mRNA levels. 3. Based on the in vitro data, we concluded that activation of A3, and to a lesser extent A2 adenosine receptors suppresses MIP-1alpha expression. Since IB-MECA was the most potent inhibitor of MIP-1alpha expression, we next investigated whether it affects the production of other pro-inflammatory mediators. We observed that IB-MECA (1-300 microM) inhibited, in a dose-dependent manner, the production of IL-12, IL-6, and, to a lesser extent, nitric oxide in the immunostimulated cultured macrophages. 4. Since MIP-alpha is a chemokine which enhances neutrophil recruitment into inflammatory sites, we investigated whether the A3 agonist IB-MECA affects the course of inflammation, MIP-alpha production and the degree of neutrophil recruitment in arthritis. In a model of collagen-induced arthritis in mice, IB-MECA (0.5 mg/kg/day) reduced the severity of joint inflammation. IB-MECA inhibited the formation of MIP-1alpha, IL-12 and nitrotyrosine (an indicator of reactive nitrogen species) in the paws, and suppressed neutrophil infiltration. 5. We conclude that adenosine receptor agonists, most notably the A3 agonist IB-MECA suppress the production of MIP-alpha, and exert anti-inflammatory effects. Therefore, stimulation of adenosine receptor subtypes A3 and A2 may be a strategy worthy of further evaluation for the abrogation of acute or chronic inflammatory disorders.

Cytokine and adhesion molecule requirements for lung injury induced by anti-glomerular basement membrane antibody

Acute hemorrhagic lung injury occurs in humans with anti-GBM antibody (Goodpasture's syndrome), however, the mechanism of this injury is still largely unknown. To date, treatment has been confined to steroids and plasmaphoresis. Infusion of anti-GBM antibody into rats caused lung injury with intra-alveolar hemorrhage and intrapulmonary accumulation of neutrophils. Lung injury was dependent on the presence of neutrophils and complement and required both TNF alpha and IL-1. Experiments employing blocking antibodies to adhesion molecules demonstrated requirements for the beta 1 integrin VLA-4, beta 2 integrins LFA-1 and Mac-1, and L-selection. The endothelial cell adhesion molecules, E-selectin and ICAM-1, were also required for the full development of lung injury. Inhibition of TNF alpha or IL-1 or adhesion molecules reduced both lung injury and tissue neutrophil accumulation. Thus, this study underscores cytokine and adhesion molecule requirements for neutrophil mediated injury in lung and kidney caused by anti-GBM, suggesting potential targets for the treatment of Goodpasture's syndrome in humans.

Requirements for alpha d in IgG immune complex-induced rat lung injury

Alpha d is a newly cloned adhesion molecule that forms a heterodimer with CD18. The requirement for alpha d in IgG immune complex-induced lung injury in rats has been evaluated by the use of blocking polyclonal and monoclonal antibodies to rat alpha d. Using whole lung extracts, Northern and Western blot analyses have revealed up-regulation of mRNA and alpha d protein in inflamed lungs. Immunostaining has revealed the presence of alpha d in lung tissue and in alveolar macrophages as early as 1 h after initiation of the inflammatory reaction. When polyclonal rabbit Ab to rat alpha d was coinstilled into lung together with Ab to BSA, lung injury (as determined by leakage of [125I]albumin into lung parenchyma) was significantly diminished. In parallel, there was reduced accumulation of neutrophils recoverable in bronchoalveolar lavage (BAL) fluids. These findings were associated with reduced levels of TNF-alpha as well as NO2-/NO3- in BAL fluids. A hamster mAb to rat alpha d was also protective in this lung injury model. Anti-alpha d inhibited in vitro production of NO2-/NO3- by rat alveolar macrophages (stimulated with LPS and IFN-gamma) by approximately 60%. These data suggest that, in the lung inflammatory model employed, alpha d up-regulation occurs in lung macrophages and is necessary for expression of TNF-alpha, recruitment of neutrophils, and full development of lung injury.

Role of Kupffer cells in gut ischemia/reperfusion-induced hepatic microvascular dysfunction in mice

Kupffer cells (KCs) have been implicated in the leukocyte recruitment and microvascular dysfunction associated with liver inflammation. The overall objective of this study was to assess the role of KCs in the leukocyte adhesion and oxidative stress elicited in the liver by gut ischemia/reperfusion (I/R). The accumulation of rhodamine-6G-labeled leukocytes and the number of nonperfused sinusoids (NPS) were monitored (by intravital microscopy) in mouse liver for 1 hour after a 15-minute period of normothermic intestinal ischemia. Autofluorescence of pyridine nucleotide [NAD(P)H] was measured as an index of mitochondrial O2 consumption and redox status. Leukostasis, as well as increases in NPS and NAD(P)H autofluorescence (indicating hypoxia), were observed in the liver at 60 minutes after gut I/R. Pretreatment with gadolinium chloride (GdCl3), which reduces KC function, attenuated the liver leukostasis and NPS elicited by gut I/R. The platelet activating factor (PAF) antagonist, WEB2086, and a tumor necrosis factor (TNF)-alpha-specific antibody were also effective in attenuating the gut I/R-induced leukostasis and NAD(P)H autofluorescence. The findings of this study suggest that KCs play an important role in mediating the leukocyte recruitment, impaired sinusoidal perfusion, and tissue hypoxia elicited in the liver after gut I/R. These KC-mediated responses appear to involve the participation of both PAF and TNF-alpha.

In vivo suppression of NF-kappa B and preservation of I kappa B alpha by interleukin-10 and interleukin-13

IL-10 and IL-13 have powerful antiinflammatory activities in vitro and in vivo. In the IgG immune complex model of lung injury in rats, exogenously administered IL-10 or IL-13 have recently been shown to suppress neutrophil recruitment and ensuing lung injury by greatly depressing pulmonary production of TNF alpha. Transcriptional control of the TNF alpha gene is regulated by the nuclear factor kappa B (NF-kappa B). Activation of NF-kappa B involves the degradation of its cytoplasmic inhibitor I kappa B alpha, allowing the nuclear translocation of NF-kappa B, with ensuing transcriptional activation. In this study, we sought to determine whether the protective effects of IL-10 and IL-13 in IgG immune complex-induced lung injury were mediated by inhibition of NF-kappa B activation. Electrophoretic mobility shift analysis of nuclear extracts from alveolar macrophages and whole lung tissues demonstrated that both IL-10 and IL-13 suppressed nuclear localization of NF-kappa B after in vivo deposition of IgG immune complexes. Western blot analysis indicated that these effects were due to preserved protein expression of I kappa B alpha in both alveolar macrophages and whole lungs. Northern blot analysis of lung mRNA showed that, in the presence of IgG immune complexes, IL-10 and IL-13 augmented I kappa B alpha mRNA expression. These findings suggest that in vivo, IL-10 and IL-13 may operate by suppressing NF-kappa B activation through preservation of I kappa B alpha.

Protective effects of IL-4, IL-10, IL-12, and IL-13 in IgG immune complex-induced lung injury: role of endogenous IL-12

Using the IgG immune complex (BSA-anti-BSA) model of acute lung injury in rats, we have compared four intratracheally administered cytokines for their protective effects on parameters of injury (albumin leak and hemorrhage) and on neutrophil accumulation (lung content of myeloperoxidase). The descending rank order of protective effects was: IL-10 > or = IL-13 > IL-4 > > IL-12. In animals receiving an intratracheal instillation of 1.0 microg murine rIL-4, IL-10, IL-12 or IL-13, the levels of TNF-alpha in bronchoalveolar (BAL) fluids after intrapulmonary deposition of IgG immune complexes were reduced by 98, 98, 34, and 97%, respectively, implying a corresponding reduction in up-regulation of lung vascular intercellular adhesion molecule-1. The unexpected findings with IL-12 were further evaluated. In spite of reduced BAL levels of TNF-alpha in IL-12-treated animals, BAL levels of IFN-gamma were elevated sixfold, indicative of the expected biologic response to IL-12. Alveolar macrophages obtained from the same animals showed a 68% reduction in formation in vitro of NO2-/NO3-. When rats undergoing intrapulmonary deposition of IgG immune complexes were treated either i.v. or intratracheally with blocking Ab to murine IL-12, there were significant increases in lung permeability and myeloperoxidase values, suggesting that in this model intrinsic IL-12 functions in a regulatory manner. In homogenates of injured lungs, this Ab detected heterodimeric complex, consistent with rat IL-12. These data confirm the ability of certain cytokines to suppress in vivo lung inflammatory responses and underscore the unexpected anti-inflammatory activities of IL-12.

Protective effects of IL-4, IL-10, IL-12, and IL-13 in IgG immune complex-induced lung injury: role of endogenous IL-12

Using the IgG immune complex (BSA-anti-BSA) model of acute lung injury in rats, we have compared four intratracheally administered cytokines for their protective effects on parameters of injury (albumin leak and hemorrhage) and on neutrophil accumulation (lung content of myeloperoxidase). The descending rank order of protective effects was: IL-10 > or = IL-13 > IL-4 > > IL-12. In animals receiving an intratracheal instillation of 1.0 microg murine rIL-4, IL-10, IL-12 or IL-13, the levels of TNF-alpha in bronchoalveolar (BAL) fluids after intrapulmonary deposition of IgG immune complexes were reduced by 98, 98, 34, and 97%, respectively, implying a corresponding reduction in up-regulation of lung vascular intercellular adhesion molecule-1. The unexpected findings with IL-12 were further evaluated. In spite of reduced BAL levels of TNF-alpha in IL-12-treated animals, BAL levels of IFN-gamma were elevated sixfold, indicative of the expected biologic response to IL-12. Alveolar macrophages obtained from the same animals showed a 68% reduction in formation in vitro of NO2-/NO3-. When rats undergoing intrapulmonary deposition of IgG immune complexes were treated either i.v. or intratracheally with blocking Ab to murine IL-12, there were significant increases in lung permeability and myeloperoxidase values, suggesting that in this model intrinsic IL-12 functions in a regulatory manner. In homogenates of injured lungs, this Ab detected heterodimeric complex, consistent with rat IL-12. These data confirm the ability of certain cytokines to suppress in vivo lung inflammatory responses and underscore the unexpected anti-inflammatory activities of IL-12.

Regulatory effects of interleukin-6 in immunoglobulin G immune-complex-induced lung injury

Interleukin-6 (IL-6) is a cytokine produced in response to a variety of inflammatory stimuli. Although IL-6 is often observed in increased amounts in acute respiratory distress syndrome, its role in the development of lung injury is unclear. The role of IL-6 was studied in the rat model of lung injury induced by the intra-alveolar deposition of IgG immune complexes. IL-6 induction, as determined by Northern blot analysis and bioactivity, was found as a function of time during the course of development of injury. Recombinant IL-6 instilled intratracheally at commencement of injury led to substantial reductions in lung vascular permeability, neutrophil accumulation, and levels of tumor necrosis factor (TNF)-alpha and macrophage inflammatory protein (MIP)-2 in bronchoalveolar lavage fluids. Conversely, blocking of intrinsic IL-6 by a neutralizing antibody resulted in increases in lung vascular permeability, neutrophil content, and TNF-alpha levels in bronchoalveolar lavage fluids. Rat alveolar macrophages stimulated in vitro with lipopolysaccharide in the presence of IL-6 showed a significant reduction in TNF-alpha expression. Together, these findings suggest that IL-6 acts as an intrinsic regulator of lung inflammatory injury after deposition of IgG immune complexes and that the protective effects of exogenously administered IL-6 may be in part linked to suppressed TNF-alpha production.

Sublytic concentrations of the membrane attack complex of complement induce endothelial interleukin-8 and monocyte chemoattractant protein-1 through nuclear factor-kappa B activation

Activation of the complement cascade and subsequent assembly of the membrane attack complex (MAC) occur in a number of pathophysiological settings. When formed on the surface of endothelial cells in sublytic concentrations, the MAC can induce a number of proinflammatory activities, including the secretion of soluble mediators (eg, interleukin (IL)-8 and monocyte chemoattractant protein (MCP)-1) and the up-regulation of cell surface adhesion molecules. Available data indicate that MAC-induced cell activation may occur through several complex signal transduction pathways, but little is known about the intranuclear mechanisms by which complement-derived products promote the up-regulation of inflammatory mediators. Using purified distal complement proteins (C5-9) to assemble functional MAC on early-passage human umbilical vein endothelial cells (HUVECs), we examined mechanisms of MCP-1 and IL-8 induction. Formation of sublytic concentrations of MAC promoted an increase in nuclear factor (NF)-kappa B DNA binding activity within 60 minutes as determined by serial electrophoretic mobility shift assay. Cytosolic to nuclear translocation of NF-kappa B was confirmed by Western immunoblot and immunocytochemical analyses. Formation of the C5b-8 complex also promoted NF-kappa B translocation but to a lesser degree than observed in HUVECs containing complete MAC. No cytosolic to nuclear translocation of the p65 NF-kappa B subunit was observed in unstimulated HUVECs or in cells incubated with the MAC components devoid of C7. Preincubation of HUVECs with pyrrolidine dithiocarbamate prevented MAC-induced increases in IL-8 and MCP-1 mRNA concentrations and protein secretion. A direct cause and effect linkage between MAC assembly and NF-kappa B activation was established through examination of the pharmacological effect of the peptide SN50 on IL-8 and MCP-1 expression. SN50 is a recently engineered 26-amino-acid peptide that contains a lipophilic cell-membrane-permeable motif and a nuclear localization sequence that specifically competes with the nuclear localization sequence of the NF-kappa B p50 subunit. This study provides direct in vitro evidence that the distal complement system (MAC) can promote proinflammatory endothelial cell activation, specifically, increases in IL-8 and MCP-1 mRNA concentrations and protein secretion, and that cytosolic to nuclear translocation of NF-kappa B is necessary for this response.

Requirement for C-X-C chemokines (macrophage inflammatory protein-2 and cytokine-induced neutrophil chemoattractant) in IgG immune complex-induced lung injury

The C-X-C chemokines of the IL-8 family possess potent chemotactic activity for neutrophils, but their in vivo role in inflammatory responses is not well understood. In the IgG immune complex-induced model of acute lung inflammatory injury in the rat we have evaluated the roles of two rat chemokines, macrophage inflammatory protein-2 (MIP-2) and cytokine-induced neutrophil chemoattractant (CINC). Both mRNA and protein for MIP-2 and CINC appeared in a time-dependent manner after initiation of IgG immune complex deposition in lung. There exists a 69% homology between the amino acid sequences for these proteins, and we found cross-reactivity between polyclonal Abs raised to these chemokines. By purifying the blocking Abs using double affinity methods (with Ag-immobilized beads), this cross-reactivity was removed. Individually, anti-MIP-2 and anti-CINC Ab significantly reduced lung injury (as measured by 125I-labeled albumin leakage from the pulmonary vasculature) and reduced neutrophil accumulation in the lung (as determined by myeloperoxidase (MPO content) and neutrophil counts in bronchoalveolar lavage (BAL) fluids); however, no change in TNF-alpha levels in BAL fluids was found. Chemotactic activity in BAL fluids collected 2 h after injury from animals undergoing immune complex deposition could be shown to be chiefly due to the combined contributions of MIP-2 (39%), CINC (28%), and C5a (21%). When either MIP-2 or CINC was blocked in vivo, up-regulation of Mac-1 expression on neutrophils obtained from BAL fluids was significantly reduced. These data suggest that, in the model studied, both MIP-2 and CINC contribute significantly to the influx of neutrophils and their activation.

Requirement for C-X-C chemokines (macrophage inflammatory protein-2 and cytokine-induced neutrophil chemoattractant) in IgG immune complex-induced lung injury

The C-X-C chemokines of the IL-8 family possess potent chemotactic activity for neutrophils, but their in vivo role in inflammatory responses is not well understood. In the IgG immune complex-induced model of acute lung inflammatory injury in the rat we have evaluated the roles of two rat chemokines, macrophage inflammatory protein-2 (MIP-2) and cytokine-induced neutrophil chemoattractant (CINC). Both mRNA and protein for MIP-2 and CINC appeared in a time-dependent manner after initiation of IgG immune complex deposition in lung. There exists a 69% homology between the amino acid sequences for these proteins, and we found cross-reactivity between polyclonal Abs raised to these chemokines. By purifying the blocking Abs using double affinity methods (with Ag-immobilized beads), this cross-reactivity was removed. Individually, anti-MIP-2 and anti-CINC Ab significantly reduced lung injury (as measured by 125I-labeled albumin leakage from the pulmonary vasculature) and reduced neutrophil accumulation in the lung (as determined by myeloperoxidase (MPO content) and neutrophil counts in bronchoalveolar lavage (BAL) fluids); however, no change in TNF-alpha levels in BAL fluids was found. Chemotactic activity in BAL fluids collected 2 h after injury from animals undergoing immune complex deposition could be shown to be chiefly due to the combined contributions of MIP-2 (39%), CINC (28%), and C5a (21%). When either MIP-2 or CINC was blocked in vivo, up-regulation of Mac-1 expression on neutrophils obtained from BAL fluids was significantly reduced. These data suggest that, in the model studied, both MIP-2 and CINC contribute significantly to the influx of neutrophils and their activation.

Glomerular inflammation induces resistance to tubular injury in the rat. A novel form of acquired, heme oxygenase-dependent resistance to renal injury

Considerable attention is directed to a surprising biologic phenomenon wherein tissues exposed to one insult acquire resistance to another. We identify a novel example of acquired resistance to acute renal failure and a mechanism that contributes to such resistance. Nephrotoxic serum, administered to rats 24 h before the induction of glycerol-induced acute renal failure, reduces functional and structural injury that occurs in this model. Since heme oxygenase, the rate-limiting enzyme in heme degradation, protects against heme protein-induced renal injury, we questioned whether induction of heme oxygenase underlies the protection afforded by nephrotoxic serum. Kidney heme oxygenase (HO-1) mRNA was induced 6 h after nephrotoxic serum and renal tubules were identified as the site of expression of heme oxygenase protein. Induction of heme oxygenase was accompanied by increased renal content of ferritin but not by induction of other antioxidant enzymes. Inhibition of heme oxygenase prevented the protection afforded by nephrotoxic serum. Nephrotoxic serum did not protect against ischemic acute renal failure, a model in which heme oxygenase is not induced. Thus, nephrotoxic serum protects against glycerol-induced acute renal failure by inducing heme oxygenase in tubules. This study provides the first demonstration of resistance to tubular injury acquired from glomerular inflammation, uncovers a mechanism for such resistance, and exposes the dialogue that occurs between glomeruli and tubules.

Role for macrophage inflammatory protein-2 in lipopolysaccharide-induced lung injury in rats

Macrophage inflammatory protein-2 (MIP-2) is a C-X-C chemokine that possesses chemotactic activity for neutrophils. Rat MIP-2 was cloned and expressed as a 7.9-kDa peptide that exhibited dose-dependent neutrophil chemotactic activity at concentrations from 10 to 250 nM. Rabbit polyclonal Ab to the 7.9-kDa peptide showed reactivity by western blot analysis and suppressed its in vitro chemotactic activity. Cross-desensitization chemotaxis experiments suggested that the chemotactic responses elicited by MIP-2 and the related chemokine, cytokine-induced neutrophil chemoattractant, may be mediated through a common receptor. Also, chemotactic responses to human GRO-alpha were blocked by exposure of human neutrophils to either GRO-alpha or rat MIP-2, suggesting conservation of this receptor-mediated response. After LPS instillation into rat lung, mRNA for MIP-2 was up-regulated in a time-dependent manner, peaking at 6 h. MIP-2 protein was detected in bronchoalveolar lavage fluids of these animals and a significant amount of chemotactic activity present in these fluids was attributed to MIP-2. On the basis of intrapulmonary instillation of Ab to MIP-2, neutrophil accumulation in lungs after airway instillation of LPS was found to be MIP-2-dependent. These data indicate that MIP-2 plays a significant role in LPS-induced inflammatory response in rat lungs and is required for the full recruitment of neutrophils.

Role for macrophage inflammatory protein-2 in lipopolysaccharide-induced lung injury in rats

Macrophage inflammatory protein-2 (MIP-2) is a C-X-C chemokine that possesses chemotactic activity for neutrophils. Rat MIP-2 was cloned and expressed as a 7.9-kDa peptide that exhibited dose-dependent neutrophil chemotactic activity at concentrations from 10 to 250 nM. Rabbit polyclonal Ab to the 7.9-kDa peptide showed reactivity by western blot analysis and suppressed its in vitro chemotactic activity. Cross-desensitization chemotaxis experiments suggested that the chemotactic responses elicited by MIP-2 and the related chemokine, cytokine-induced neutrophil chemoattractant, may be mediated through a common receptor. Also, chemotactic responses to human GRO-alpha were blocked by exposure of human neutrophils to either GRO-alpha or rat MIP-2, suggesting conservation of this receptor-mediated response. After LPS instillation into rat lung, mRNA for MIP-2 was up-regulated in a time-dependent manner, peaking at 6 h. MIP-2 protein was detected in bronchoalveolar lavage fluids of these animals and a significant amount of chemotactic activity present in these fluids was attributed to MIP-2. On the basis of intrapulmonary instillation of Ab to MIP-2, neutrophil accumulation in lungs after airway instillation of LPS was found to be MIP-2-dependent. These data indicate that MIP-2 plays a significant role in LPS-induced inflammatory response in rat lungs and is required for the full recruitment of neutrophils.

Streptococcal cysteine protease augments lung injury induced by products of group A streptococci

Streptococcus pyogenes infections in humans may be associated with severe clinical manifestations, including adult respiratory distress syndrome and a toxic shock-like syndrome. These observations have led to the investigation of products of group A streptococci that may contribute to increased virulence. Streptococcal pyrogenic exotoxin B is a highly conserved precursor of an extracellular cysteine protease that is secreted by S. pyogenes. We investigated the ability of this streptococcal cysteine protease (SCP) to act synergistically with either streptococcal cell wall antigen (SCW) or streptolysin-O (SLO) to augment lung injury in rats. Intratracheal administration of either SCW or SLO alone caused lung injury, as measured by pulmonary vascular leak. Bronchoalveolar lavage (BAL) fluid analysis showed that SCW induced neutrophil accumulation and appearance of interleukin-1beta and tumor necrosis factor alpha. In contrast, SLO induced neither neutrophil influx nor significant cytokine elevations in BAL fluids. Intratracheal administration of SCP with either SCW or SLO resulted in synergistic augmentation of lung vascular permeability and accumulation of BAL neutrophils. The synergy was reduced when SCP was either heat inactivated or coinstilled with a peptide inhibitor of the protease. SCP in the presence of SCW resulted in a significant increase in BAL fluid tumor necrosis factor alpha content but not in immunoreactive interleukin-1beta. Moreover, the copresence of SAP with SAW resulted in increased BAL fluid nitrite-nitrate levels, indicative of nitric oxide production. These data demonstrate that SCP acts synergistically with other S. pyogenes products (SCW or SLO) to increase tissue injury and provide additional evidence that SCP may function as an important virulence factor in group A streptococcal infections.

Regulatory effects of endogenous interleukin-1 receptor antagonist protein in immunoglobulin G immune complex-induced lung injury

IL-1 receptor antagonist (IL-1Ra) has regulatory effects on IL-1 activity both in vitro and in vivo. In the IgG immune complex model of lung injury in rats, exogenously administered human IL-1Ra suppressed neutrophil recruitment and ensuing lung injury. In this study, we sought to determine if endogenous rat IL-1Ra might regulate this lung-inflammatory response. By Northern blot analysis of lung mRNA and Western analysis of bronchoalveolar lavage (BAL) fluids, rat IL-1Ra expression was found to increase during development of inflammation in IgG immune complex-mediated alveolitis. By immunostaining, alveolar macrophages and recruited neutrophils were the apparent sources of IL-1Ra. In vivo blocking of endogenous IL-1Ra resulted in a 53% increase in lung vascular permeability and a 180% increase in BAL fluid neutrophils. In companion studies, a significant increase in IL-1beta was found, whereas no significant change in TNF-alpha activity was observed. Whereas the in vivo regulatory effects of IL-1R appear to be limited to IL-1beta, IL-10 regulates both IL-1beta and TNF-alpha in this model, reflected by a 48% increase in BAL IL-1beta in rats treated with anti-IL-10. These findings suggest that IL-1Ra is an intrinsic regulator of inflammatory injury after deposition of IgG immune complexes and that it regulates production of IL-1beta.

Role of macrophage inflammatory protein-1 alpha (MIP-1 alpha) in acute lung injury in rats

The role of macrophage inflammatory protein-1 alpha (MIP-1 alpha) in the pathogenesis of acute lung injury in rats after intrapulmonary deposition of IgG immune complexes or intratracheal administration of LPS has been assessed. Critical to these studies was the cloning and functional expression of rat MIP-1 alpha. The resulting product shared 92% and 90% homology with the known murine sequence at the cDNA level and protein level, respectively. Recombinant rat MIP-1 alpha exhibited dose-dependent chemotactic activity for both rat and human monocytes and neutrophils, which could be blocked by anti-murine MIP-1 alpha Ab. Rat MIP-1 alpha mRNA and protein expression were determined as a function of time in both injury models. A time-dependent increase in MIP-1 alpha mRNA in lung extracts was observed in both models. In the LPS model, MIP-1 alpha protein could also be detected in bronchoalveolar lavage (BAL) fluids by Western blot analysis. Anti-MIP-1 alpha administered at commencement of IgG immune complex- or LPS-induced injury resulted in significant reductions in BAL neutrophils as well as in injury as measured by pulmonary vascular permeability. Under such conditions, in both models TNF-alpha content in BAL fluids was substantially reduced as compared with BAL fluids from positive control animals. These findings suggest that rat MIP-1 alpha plays an important role in the development of lung injury in these neutrophil-dependent models. The role of MIP-1 alpha seems to be related to production of TNF-alpha, which in turn up-regulates vascular adhesion molecules required for neutrophil influx.

Role of macrophage inflammatory protein-1 alpha (MIP-1 alpha) in acute lung injury in rats

The role of macrophage inflammatory protein-1 alpha (MIP-1 alpha) in the pathogenesis of acute lung injury in rats after intrapulmonary deposition of IgG immune complexes or intratracheal administration of LPS has been assessed. Critical to these studies was the cloning and functional expression of rat MIP-1 alpha. The resulting product shared 92% and 90% homology with the known murine sequence at the cDNA level and protein level, respectively. Recombinant rat MIP-1 alpha exhibited dose-dependent chemotactic activity for both rat and human monocytes and neutrophils, which could be blocked by anti-murine MIP-1 alpha Ab. Rat MIP-1 alpha mRNA and protein expression were determined as a function of time in both injury models. A time-dependent increase in MIP-1 alpha mRNA in lung extracts was observed in both models. In the LPS model, MIP-1 alpha protein could also be detected in bronchoalveolar lavage (BAL) fluids by Western blot analysis. Anti-MIP-1 alpha administered at commencement of IgG immune complex- or LPS-induced injury resulted in significant reductions in BAL neutrophils as well as in injury as measured by pulmonary vascular permeability. Under such conditions, in both models TNF-alpha content in BAL fluids was substantially reduced as compared with BAL fluids from positive control animals. These findings suggest that rat MIP-1 alpha plays an important role in the development of lung injury in these neutrophil-dependent models. The role of MIP-1 alpha seems to be related to production of TNF-alpha, which in turn up-regulates vascular adhesion molecules required for neutrophil influx.

Regulatory effects of intrinsic IL-10 in IgG immune complex-induced lung injury

IL-10 has regulatory effects in vitro on cytokine production by activated macrophages. In the IgG immune complex model of lung injury, exogenously administered IL-10 has been shown to suppress in vivo formation of TNF-alpha, up-regulation of vascular ICAM-1, neutrophil recruitment, and ensuing lung injury. In the current study, we sought to determine whether endogenous IL-10 is playing a regulatory role in the lung inflammatory response. On the basis of lung mRNA and ELISA measurements, IL-10 induction was found during development of inflammation in the IgG immune complex model of lung injury. Blocking of IL-10 by Ab resulted in a 52% increase in lung vascular permeability, a 56% increase in TNF-alpha activity in bronchoalveolar lavage fluids, and a 47 to 48% increase in bronchoalveolar lavage neutrophils and lung myeloperoxidase content. These findings suggest that IL-10 is an important natural regulator of lung inflammatory injury after deposition of IgG immune complexes.

Regulatory effects of intrinsic IL-10 in IgG immune complex-induced lung injury

IL-10 has regulatory effects in vitro on cytokine production by activated macrophages. In the IgG immune complex model of lung injury, exogenously administered IL-10 has been shown to suppress in vivo formation of TNF-alpha, up-regulation of vascular ICAM-1, neutrophil recruitment, and ensuing lung injury. In the current study, we sought to determine whether endogenous IL-10 is playing a regulatory role in the lung inflammatory response. On the basis of lung mRNA and ELISA measurements, IL-10 induction was found during development of inflammation in the IgG immune complex model of lung injury. Blocking of IL-10 by Ab resulted in a 52% increase in lung vascular permeability, a 56% increase in TNF-alpha activity in bronchoalveolar lavage fluids, and a 47 to 48% increase in bronchoalveolar lavage neutrophils and lung myeloperoxidase content. These findings suggest that IL-10 is an important natural regulator of lung inflammatory injury after deposition of IgG immune complexes.

The role of cytokines and adhesion molecules in the development of inflammatory injury

Clinicians are constantly challenged by patients who demonstrate the ill effects of an uncontrolled host inflammatory response. Patients with sepsis and adult respiratory distress syndrome (ARDS) are frequently encountered examples of this syndrome. Despite advances in intensive care, mortality from these syndromes remains unchanged over the past two decades. In order to gain a better understanding of this pathophysiological response and to identify more specific therapeutic targets, the techniques of molecular biology have been applied to in vivo inflammatory models. Recent data indicate that the inflammatory response is dependent on the presence of both cytokines and adhesion molecules that mediate neutrophil-endothelial cell adhesive interactions. In this article, we review our experience using a lung model of inflammation that has provided insight into the events leading to injury. Cytokines [particularly, interleukin 1 (IL-1) and tumor necrosis factor alpha (TNF-alpha)], and endothelial, as well as leukocyte, adhesion molecules appear to coordinate a cascade of interactions between leukocytes and endothelial cells, which results in tissue injury.