Induction of macrophage inflammatory protein 2 gene expression by interleukin 1 beta in rat lung

The protective effect of CXC chemokine receptor 2 antagonist on experimental bronchopulmonary dysplasia induced by postnatal systemic inflammation

BACKGROUND

Animal studies have shown that a leukocyte influx precedes the development of bronchopulmonary dysplasia (BPD) in premature sheep. The CXC chemokine receptor 2 (CXCR2) pathway has been implicated in the pathogenesis of BPD because of the predominance of CXCR2 ligands in tracheal aspirates of preterm infants who later developed BPD.

PURPOSE

To test the effect of CXCR2 antagonist on postnatal systemic and pulmonary inflammation and alveolarization in a newborn Sprague-Dawley rat model of BPD.

METHODS

Lipopolysaccharide (LPS) was injected intraperitoneally (i.p.) into the newborn rats on postnatal day 1 (P1), P3, and P5 to induce systemic inflammation and inhibit alveolarization. In the same time with LPS administration, CXCR2 antagonist (SB-265610) or vehicle was injected i.p. to investigate whether CXCR2 antagonist can alleviate the detrimental effect of LPS on alveolarization by attenuating inflammation. On P7 and P14, bronchoalveolar lavage fluid (BALF) and peripheral blood (PB) were collected from the pups. To assess alveolarization, mean cord length and alveolar surface area were measured on 4 random nonoverlapping fields per animal in 2 distal lung sections at ×100 magnification.

RESULTS

Early postnatal LPS administration significantly increased neutrophil counts in BALF and PB and inhibited alveolarization, which was indicated by a greater mean cord length and lesser alveolar surface area. CXCR2 antagonist significantly attenuated the increase of neutrophil counts in BALF and PB and restored alveolarization as indicated by a decreased mean cord length and increased alveolar surface area in rat pups exposed to early postnatal systemic LPS.

CONCLUSION

CXCR2 antagonist preserved alveolarization by alleviating pulmonary and systemic inflammation induced by early postnatal systemic LPS administration. These results suggest that CXCR2 antagonist can be considered a potential therapeutic agent for BPD that results from disrupted alveolarization induced by inflammation.

Relation between Respiratory Mechanics, Inflammation, and Survival in Experimental Mechanical Ventilation

Low-tidal volume (Vt) ventilation might protect healthy lungs from volutrauma but lead to inflammation resulting from other mechanisms, namely alveolar derecruitment and the ensuing alveolar collapse and tidal reexpansion. We hypothesized that the different mechanisms of low- and high-volume injury would be reflected in different mechanical properties being associated with development of pulmonary inflammation and mortality: an increase of hysteresis, reflecting progressive alveolar derecruitment, at low Vt; an increase of elastance, as a result of overdistension, at higher Vt. Mice were allocated to "protective" (6 ml/kg) or "injurious" (15-20 ml/kg) Vt groups and ventilated for 16 hours or until death. We measured elastance and hysteresis; pulmonary IL-6, IL-1β, and MIP-2 (macrophage inflammatory protein 2); wet-to-dry ratio; and blood gases. Survival was greater in the protective group (60%) than in the injurious group (25%). Nonsurvivors showed increased pulmonary cytokines, particularly in the injurious group, with the increase of elastance reflecting IL-6 concentration. Survivors instead showed only modest increases of cytokines, independent of Vt and unrelated to the increase of elastance. No single lung strain threshold could discriminate survivors from nonsurvivors. Hysteresis increased faster in the protective group, but, contrary to our hypothesis, its change was inversely related to the concentration of cytokines. In this model, significant mortality associated with pulmonary inflammation occurred even for strain values as low as about 0.8. Low Vt improved survival. The accompanying increase of hysteresis was not associated with greater inflammation.

Milano summer particulate matter (PM10) triggers lung inflammation and extra pulmonary adverse events in mice

Recent studies have suggested a link between particulate matter (PM) exposure and increased mortality and morbidity associated with pulmonary and cardiovascular diseases; accumulating evidences point to a new role for air pollution in CNS diseases. The purpose of our study is to investigate PM10sum effects on lungs and extra pulmonary tissues. Milano PM10sum has been intratracheally instilled into BALB/c mice. Broncho Alveolar Lavage fluid, lung parenchyma, heart and brain were screened for markers of inflammation (cell counts, cytokines, ET-1, HO-1, MPO, iNOS), cytotoxicity (LDH, ALP, Hsp70, Caspase8-p18, Caspase3-p17) for a putative pro-carcinogenic marker (Cyp1B1) and for TLR4 pathway activation. Brain was also investigated for CD68, TNF-α, GFAP. In blood, cell counts were performed while plasma was screened for endothelial activation (sP-selectin, ET-1) and for inflammation markers (TNF-α, MIP-2, IL-1β, MPO). Genes up-regulation (HMOX1, Cyp1B1, IL-1β, MIP-2, MPO) and miR-21 have been investigated in lungs and blood. Inflammation in the respiratory tract of PM10sum-treated mice has been confirmed in BALf and lung parenchyma by increased PMNs percentage, increased ET-1, MPO and cytokines levels. A systemic spreading of lung inflammation in PM10sum-treated mice has been related to the increased blood total cell count and neutrophils percentage, as well as to increased blood MPO. The blood-endothelium interface activation has been confirmed by significant increases of plasma ET-1 and sP-selectin. Furthermore PM10sum induced heart endothelial activation and PAHs metabolism, proved by increased ET-1 and Cyp1B1 levels. Moreover, PM10sum causes an increase in brain HO-1 and ET-1. These results state the translocation of inflammation mediators, ultrafine particles, LPS, metals associated to PM10sum, from lungs to bloodstream, thus triggering a systemic reaction, mainly involving heart and brain. Our results provided additional insight into the toxicity of PM10sum and could facilitate shedding light on mechanisms underlying the development of urban air pollution related diseases.

Death by a thousand cuts in Alzheimer's disease: hypoxia--the prodrome

A wide range of clinical consequences may be associated with obstructive sleep apnea (OSA) including systemic hypertension, cardiovascular disease, pulmonary hypertension, congestive heart failure, cerebrovascular disease, glucose intolerance, impotence, gastroesophageal reflux, and obesity, to name a few. Despite this, 82 % of men and 93 % of women with OSA remain undiagnosed. OSA affects many body systems, and induces major alterations in metabolic, autonomic, and cerebral functions. Typically, OSA is characterized by recurrent chronic intermittent hypoxia (CIH), hypercapnia, hypoventilation, sleep fragmentation, peripheral and central inflammation, cerebral hypoperfusion, and cerebral glucose hypometabolism. Upregulation of oxidative stress in OSA plays an important pathogenic role in the milieu of hypoxia-induced cerebral and cardiovascular dysfunctions. Strong evidence underscores that cerebral amyloidogenesis and tau phosphorylation--two cardinal features of Alzheimer's disease (AD), are triggered by hypoxia. Mice subjected to hypoxic conditions unambiguously demonstrated upregulation in cerebral amyloid plaque formation and tau phosphorylation, as well as memory deficit. Hypoxia triggers neuronal degeneration and axonal dysfunction in both cortex and brainstem. Consequently, neurocognitive impairment in apneic/hypoxic patients is attributable to a complex interplay between CIH and stimulation of several pathological trajectories. The framework presented here helps delineate the emergence and progression of cognitive decline, and may yield insight into AD neuropathogenesis. The global impact of CIH should provide a strong rationale for treating OSA and snoring clinically, in order to ameliorate neurocognitive impairment in aged/AD patients.

Effects of in vitro exposure to autologous blood and serum on expression of interleukin-8, interleukin-1β, and chemokine (C-X-C motif) ligand 2 in equine primary bronchial epithelial cell cultures

OBJECTIVE

To examine the effects of in vitro exposure to solutions of autologous horse blood (AHB) and autologous horse serum (AHS) on expressions of selected cytokine genes in equine primary bronchial epithelial cell (BEC) cultures and to contrast these responses to those induced in BEC cultures by endotoxin and hay dust.

SAMPLE

BEC cultures established from bronchi of 6 healthy horses.

PROCEDURES

5-day-old BEC cultures were treated with PBS solution, AHB (2 concentrations), AHS, hay dust solution, and lipopolysaccharide solution for 24 hours. Gene expressions of interleukin (IL)-8, IL-1β, chemokine (C-X-C motif) ligand 2 (CXCL2), and glyceralde-hyde-3-phosphate dehydrogenase were subsequently measured with a kinetic PCR assay.

RESULTS

With the exception of AHS, all treatments of the BECs resulted in upregulation of each target gene expression relative to its expression in cultures exposed to PBS solution. Treatment with AHB induced a dose-dependent increase of each target gene, with IL-1β expression increasing the most (> 1,200-fold increase). Lipopolysaccharide and hay dust solution treatments each resulted in 20-fold increases in IL-8 and IL-1β gene expressions. Lipopolysaccharide and hay dust solution treatments also resulted in a 7- and 8-fold increase in CXCL2 gene expression, respectively. The increases in IL-8 and CXCL2 gene expressions following treatment with the higher concentration of blood were equivalent to those associated with hay dust solution or lipopolysaccharide.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggested that chemokine expression by cultured equine BECs following exposure to pulmonary hemorrhage conditions may contribute to the development of inflammatory airway disease in horses.

Effect of IL-1β and TNF-α vs IL-13 on bronchial hyperresponsiveness, β2-adrenergic responses and cellularity of bronchial alveolar lavage fluid

1 Levels of IL-13, IL-1β and TNF-α are increased in bronchial lavage fluid of asthmatics and induce certain significant features of bronchial asthma including airway hyper-responsiveness (AHR). In this study, we have investigated the effect of these cytokines in naïve mice and those sensitized to ovalbumin (OVA) on bronchoconstrictions to methacholine (MCh) and the functional antagonism induced by β2 -adrenoceptor agonism. 2 Naïve or OVA-sensitized mice were treated for 3 days with IL-1β (250 U), TNF-α (150 ng), IL-13 (5 μg) or combinations of IL-1β with TNF-α or IL-1β with IL-13. MCh-induced bronchoconstriction and its sensitivity to albuterol, a β2-adrenoceptor agonist, was assessed 24 h after the last cytokine administration. 3 In naïve mice, responsiveness to MCh was significantly increased by the combination of IL-1β and TNF-α, IL-13 alone or in combination with IL-1β, but not by treatment with IL-1β or TNF-α alone. Similar results were obtained in OVA-sensitized mice except that treatment with IL-13 alone did not increase sensitivity to MCh. 4 In naïve mice, albuterol sensitivity was only significantly attenuated by treatment with IL-1β and TNF-α in combination. In mice sensitized to OVA, albuterol sensitivity was significantly attenuated by treatment with TNF-α, IL-13 or IL-13 in combination with IL-1β. 5 Inflammatory cell influx was increased by all cytokines and combinations except IL-13 in OVA-sensitized mice. 6 Our data do not support a link between inflammatory cell influx and AHR. In addition, the mechanism of IL-13-induced AHR might involve decreased β2-adrenoceptor responsiveness.

Effects of in vitro exposure to hay dust on the gene expression of chemokines and cell-surface receptors in primary bronchial epithelial cell cultures established from horses with chronic recurrent airway obstruction

OBJECTIVE

To examine effects of in vitro exposure to solutions of hay dust, lipopolysaccharide (LPS), or beta-glucan on chemokine and cell-surface receptor (CSR) gene expression in primary bronchial epithelial cell cultures (BECCs) established from healthy horses and horses with recurrent airway obstruction (RAO).

SAMPLE POPULATION

BECCs established from bronchial biopsy specimens of 6 RAO-affected horses and 6 healthy horses.

PROCEDURES

5-day-old BECCs were treated with PBS solution, hay dust solutions, LPS, or beta-glucan for 6 or 24 hours. Gene expression of interleukin (IL)-8, chemokine (C-X-C motif) ligand 2 (CXCL2), IL-1beta, toll-like receptor 2, toll-like receptor 4, IL-1 receptor 1, and glyceraldehyde 3-phosphate dehydrogenase was measured with a kinetic PCR assay.

RESULTS

Treatment with PBS solution for 6 or 24 hours was not associated with a significant difference in chemokine or CSR expression between BECCs from either group of horses. In all BECCs, treatment with hay dust or LPS for 6 hours increased IL-8, CXCL2, and IL-1beta gene expression > 3-fold; at 24 hours, only IL-1beta expression was upregulated by > 3-fold. In all BECCs, CSR gene expression was not increased following any treatment. With the exception of a 3.7-fold upregulation of CXCL2 in BECCs from RAO-affected horses (following 6-hour hay dust treatment), no differences in chemokine or CSR gene expression were detected between the 2 groups. At 24 hours, CXCL2 gene expression in all BECCs was downregulated.

CONCLUSIONS AND CLINICAL RELEVANCE

Epithelial CXCL2 upregulation in response to hay dust particulates may incite early airway neutrophilia in horses with RAO.

Comparison of the systemic and pulmonary inflammatory response to endotoxin of neutropenic and non-neutropenic rats

Background

Neutrophil infiltration commonly occurs in acute lung injury and may be partly responsible for the inflammatory response. However, acute lung injury still occurs in the neutropenic host. The objectives of this study are to determine if inflammation and acute lung injury are worse in neutropenic versus the normal host after endotoxemia.

Methods

Rats were divided into four groups: 1) control, 2) neutropenic, 3) endotoxemic and 4) endotoxemic and neutropenic. Tumor necrosis factor (TNF)-α and macrophage inflammatory protein (MIP-2) were measured in the blood, lung lavage and for mRNA in the lung. Arterial blood gases were measured to determine the alveolar-arterial oxygen gradient which reflects on lung injury.

Results

In endotoxemia, the neutropenic rats had lower plasma TNF-α (116 ± 73 vs. 202 ± 31 pg/ml) and higher plasma MIP-2 (26.8 + 11.9 vs. 15.6 + 6.9 ng/ml) when compared to non-neutropenic rats. The endotoxemic, neutropenic rats had worse lung injury than the endotoxemic, non-neutropenic rats as shown by increase in the alveolar-arterial oxygen gradient (24 ± 5 vs. 12 ± 9 torr). However, lavage concentrations of TNF-α and MIP-2 were similar in both groups.

Conclusion

Neutrophils may regulate TNF-α and MIP-2 production in endotoxemia. The elevation in plasma MIP-2 in the endotoxemic, neutropenic rat may be secondary to the lack of a neutrophil response to inhibit production or release of MIP-2. In endotoxemia, the severe lung injury observed in neutropenic rats does not depend on TNF-α or MIP-2 produced in the lung.

Central and systemic endotoxin challenges exacerbate the local inflammatory response and increase neuronal death during chronic neurodegeneration

The contribution of inflammation to the progression of neurodegenerative diseases such as Alzheimer's, Parkinson's, and prion diseases is poorly understood. Brain inflammation in animal models of these diseases is dominated by chronic microglial activation with minimal proinflammatory cytokine expression. However, these inflammatory cells are "primed" to produce exaggerated inflammatory responses to subsequent lipopolysaccharide (LPS) challenges. We show that, using the ME7 model of prion disease, intracerebral challenge with LPS results in dramatic interleukin-1beta (IL-1beta) expression, neutrophil infiltration, and inducible nitric oxide synthase expression in the brain parenchyma of prion-diseased mice compared with the same challenge in normal mice. Systemic inflammation evoked by LPS also produced greater increases in proinflammatory cytokines, pentraxin 3, and inducible nitric oxide synthase transcription in prion-diseased mice than in control mice and induced microglial expression of IL-1beta. These systemic challenges also increased neuronal apoptosis in the brains of ME7 animals. Thus, both central and peripheral inflammation can exacerbate local brain inflammation and neuronal death. The finding that a single acute systemic inflammatory event can induce neuronal death in the CNS has implications for therapy in neurodegenerative diseases.

Airway hyperresponsiveness: a story of mice and men and cytokines

Bronchial hyperresponsiveness (BHR) is an essential part of the definition of asthma. Although our understanding of the allergic inflammatory and immunologic mechanisms of asthma have markedly increased, the mechanism of BHR remains to be elucidated. Increased BHR is associated temporally with exposure to allergens, certain respiratory viruses, pollutants such as ozone, and certain occupational chemicals. An important research use of determining the degree of BHR to direct and indirect challenge is to determine the efficacy of pharmacologic and immunodulatory agents. Beta-adrenergic agents inhibit BHR and certain genetic polymorphisms of the beta-adrenergic receptor are associated with increased BHR. When beta-adrenergic receptors are blocked, sensitivity to allergens is markedly increased in patients with asthma and animal models of asthma. Allergen challenge and clinical asthma are associated with synthesis and release of pro-inflammatory cytokines such as IL-1 and TNF-alpha which have been shown to decrease the response to beta-agonists and increased the reactivity to methacholine and the airways neutrophils and alveolar macrophages. The Th2 cytokine IL-13 is increased in the airways of asthmatics and increases BHR in normal unsensitized animals. The mechanisms of this effect of IL-13 are being intensively investigated. Our group has shown that IL-13 induced BHR persisted for at least 7 days and the soluble receptor IL-13R2alpha protected against their BHR. Other investigators have demonstrated that IL-13 is necessary and sufficient for the induction of BHR and that eosinophilic airway inflammation in the absence of IL-13 fails to induce BHR. These studies indicate that treatment of human asthma with antagonists of IL-13 may be very effective.

The role of IL-1beta in the regulation of IL-8 and IL-6 in human corneal epithelial cells during Pseudomonas aeruginosa colonization

PURPOSE

Recent studies have shown that the levels of interleukin (IL)-1beta, IL-6 and IL-8 are associated with the severity of infectious diseases. The purpose of this study was to investigate whether IL-1beta regulates the expression of IL-6 and IL-8 in human corneal epithelial cells during Pseudomonas aeruginosa colonization.

METHODS

Confluent immortalized human corneal epithelial cells were challenged with P. aeruginosa 6294 in the presence of anti-human IL-1beta antibody or matched control antibody. The cells were also challenged with recombinant IL-1beta protein without bacterial colonization. Expression of IL-1beta, IL-6 and IL-8 mRNA and protein was detected by reverse transcription (RT)-PCR and by enzyme-linked immunosorbent assay (ELISA), respectively. IL-1beta localization was determined by immunohistochemistry.

RESULTS

Human corneal epithelial cells expressed low levels of IL-1beta and high levels of IL-6 and IL-8 during P. aeruginosa colonization. Addition of IL-1beta Ab resulted in a significant decrease (P < 0.05) in IL-8 protein expression at 4 h, 8 h and 12 h. Addition of IL-1beta Ab reduced IL-6 protein expression at 8 h and increased IL-6 protein expression at 12 h. Addition of recombinant IL-1beta protein alone strongly stimulated the expression of IL-8 and IL-6. Immunohistochemical staining showed that IL-1beta protein was present both intracellularly and extracellularly in P. aeruginosa colonized cells.

CONCLUSIONS

IL-1beta is able to modulate expression of both IL-6 and IL-8 at transcriptional and post-transcriptional levels in human corneal epithelial cells.

Prolonged elevation of IL-1 in Pseudomonas aeruginosa ocular infection regulates macrophage-inflammatory protein-2 production, polymorphonuclear neutrophil persistence, and corneal perforation

The kinetics of IL-1 (alpha and beta) production after Pseudomonas aeruginosa corneal infection was examined in susceptible (cornea perforates) C57BL/6J (B6) and resistant (cornea heals) BALB/cByJ (BALB/c) mice. IL-1alpha and -1beta (mRNA and protein) were elevated in both mouse strains, and levels peaked at 1 day postinfection (p.i. ). Significantly greater amounts of IL-1 protein were detected in B6 vs BALB/c mice at 1 and 3 days p.i. At 5 days p.i., IL-1alpha and -1beta (mRNA and protein) remained elevated in B6, but began to decline in BALB/c mice. To test the significance of elevated IL-1 in B6 mice, a polyclonal neutralizing Ab against IL-1beta was used to treat infected B6 mice. A combination of subconjunctival and i.p. administration of IL-1beta polyclonal Ab significantly reduced corneal disease. The reduction in disease severity in infected B6 mice was accompanied by a reduction in corneal polymorphonuclear neutrophil number, bacterial load, and macrophage inflammatory protein-2 mRNA and protein levels. These data provide evidence that IL-1 is an important contributor to P. aeruginosa corneal infection. At least one mechanism by which prolonged and/or elevated IL-1 expression contributes to irreversible corneal tissue destruction appears to be by increasing macrophage inflammatory protein-2 production, resulting in a prolonged stimulation of polymorphonuclear neutrophil influx into cornea. In contrast, a timely down-regulation of IL-1 appears consistent with an inflammatory response that is sufficient to clear the bacterial infection with less corneal damage.

The effect of heat on cytokine production in rat endotoxemia

OBJECTIVE

To determine whether heat stress protects the endotoxemic rat by up-regulation of the counterinflammatory cytokine interleukin (IL)-10, thereby attenuating the inflammatory response.

DESIGN

A total of 16 rats were assigned to either the heat stress group (n = 8) or the control group (n = 8). The heat stress group was warmed to a temperature of >42 degrees C (107.6 degrees F) rectally for 10-15 mins; 20 hrs later, all rats were intubated, paralyzed, and ventilated. After jugular venous and arterial catheterization, endotoxin was given intravenously. Arterial blood was removed at 0, 2, 4, and 5 hrs for blood gases, tumor necrosis factor (TNF)-alpha, nitric oxide metabolites (NO), IL-10, and macrophage inflammatory protein (MIP)-2. The alveolar macrophages were removed, counted, and then incubated for 24 hrs. The supernatant was analyzed for TNF-alpha, NO, IL-10, and MIP-2.

SETTING

University research laboratory.

SUBJECTS

Male Sprague-Dawley rats (n = 16).

INTERVENTIONS

Administration of heat before endotoxin infusion.

MEASUREMENTS AND MAIN RESULTS

Alveolar-arterial oxygen gradient was lower in the heat stress group at 4 and 5 hrs after endotoxemia. Plasma and alveolar macrophage supernatant concentrations of TNF-alpha, NO, and IL-10 were not affected by heat. Plasma and alveolar macrophage supernatant MIP-2 concentrations were higher in endotoxemic rats receiving heat pretreatment compared with controls.

CONCLUSIONS

Our study demonstrates that heat leads to pulmonary protection of short duration in severe endotoxemia. This protection was not mediated by plasma TNF-alpha, IL-10, or NO. Contrary to our hypothesis, pretreatment with heat increased rather than decreased the plasma MIP-2 concentration and alveolar macrophage production of MIP-2 in endotoxemia. The mechanism of heat-conferred pulmonary protection in endotoxemia remains unclear. Alveolar macrophages do not produce IL-10 in endotoxemia. The increased MIP-2 production by heated alveolar macrophages was not attributable to alterations in production of either TNF-alpha or IL-10. The significance of increased MIP-2 by endotoxin-exposed alveolar macrophages in heated rats is unknown.

A regulatory role for interleukin 4 in differential inflammatory responses in the lung following infection of mice primed with Th1- or Th2-inducing pertussis vaccines

Protection against infectious pathogens at mucosal surfaces is dependent on local antibody responses, production of inflammatory mediators, and recruitment of immune effector cells to the site of infection. Since Th1 and Th2 cells produce cytokines with pro- and anti-inflammatory activities, immunization with vaccines that induce these T-cell subtypes may regulate the subsequent inflammatory response to infection. We have demonstrated that immunization of mice with pertussis whole-cell or acellular vaccines (Pw or Pa) selectively induces Th1 and Th2 cells, respectively. In this study we have used a murine respiratory-infection model to demonstrate that priming with a Th1- or Th2-inducing pertussis vaccine can influence the local inflammatory response and immune effector cells in the lung following aerosol challenge with Bordetella pertussis. Analysis of bronchoalveolar lavage (BAL) fluid taken during the course of B. pertussis infection of naïve mice or mice immunized with Pw revealed an early influx of neutrophils and local production of interleukin 1beta (IL-1beta) in the lungs. In contrast, neutrophil infiltration and IL-1beta production were not observed following challenge of mice immunized with the Th2-inducing Pa. Conversely, during infection local production of IL-6 and IL-1ra was significantly greater in mice immunized with Pa than in those immunized with Pw. Studies of knockout mice revealed neutrophil and lymphocyte infiltration in the lungs following B. pertussis infection of IL-4-defective (IL-4(-/-)) mice but not in wild-type mice immunized with Pa. Furthermore, the levels of IL-1beta, IL-6, and IL-1ra in Pa-immunized IL-4(-/-) mice were comparable to those in mice immunized with Pw. These results demonstrate distinct influences of Th1- and Th2-inducing vaccines on the protective inflammatory responses in the lungs following challenge with B. pertussis and implicate IL-4 as an important regulator of inflammatory-cell recruitment.

Cytokine gene expression after inhalation of corn dust

To characterize the time course and localize the production of proinflammatory cytokines after inhalation of corn dust, we exposed mice (C3H/HeBFeJ) by inhalation challenge to sterile corn dust extract (CDE) and contrasted this response to inhalation of Escherichia coli 0111:B4 lipopolysaccharide (LPS) or pyrogen-free saline. After both CDE and LPS exposure, an increase in the concentration of bronchoalveolar lavage neutrophils was detected 1 h postinhalation and persisted for 48 h. Significant increases in the bronchoalveolar lavage concentration of tumor necrosis factor (TNF)-alpha, interleukin (IL)-1alpha, and macrophage inflammatory protein (MIP)-2 resulted after inhalation of either CDE or LPS. Although the time courses of these cytokines were distinct, a similar pattern of release was observed after both CDE and LPS exposure. A single inhalation exposure of either CDE or LPS resulted in enhanced expression of mRNA for TNF-alpha, IL-1alpha, and MIP-2 that was evident and most pronounced within 1 h of the inhalation challenge. Although enhanced expression of mRNA for TNF-alpha was detectable 12 h after completion of the inhalation challenge, IL-1alpha and MIP-2 mRNA expression remained elevated through the 24-h time point. TNF-alpha, IL-1alpha, and MIP-2 expression was localized by in situ hybridization to inflammatory cells in the airways and alveoli from 1 to 24 h in both CDE- and LPS-exposed lungs. Interestingly, there was no convincing evidence that MIP-2 was substantially produced by airway epithelial cells. The pattern, timing, and location of expression of TNF-alpha, IL-1alpha, and MIP-2 mRNA after a single inhalation exposure of CDE in comparison with LPS is similar, supporting a common etiology and mechanism of inflammation in the lower respiratory tract. Moreover, our findings indicate that inhalation of corn dust or LPS results in an acute inflammatory process that is primarily mediated by inflammatory cells and appears to be self-limited.

Generation of a transgenic mouse with lung-specific overexpression of the human interleukin-1 receptor antagonist protein

The purpose of the studies described here was to test the hypothesis that overexpression of the human interleukin-1 receptor antagonist (IL-1ra) in the distal airway epithelia of mice would result in amelioration of the inflammatory effects of IL-1alpha. The coding region of the human IL-1ra gene was placed under transcriptional control of the 5' flanking region of the human SP-C gene. Transgenic mice were generated by pronuclear injection of the transgene and identified by Southern blot analysis of genomic DNA. RNA expression of the transgene was confirmed by Northern blot analysis. In order to determine whether expression of the transgene conferred protection against inflammatory stimuli, control and transgenic mice were treated with IL-1alpha by intratracheal instillation. Six hours after treatment, bronchoalveolar lavage was performed, which revealed a statistically significant decrease in the degree of neutrophilia in the transgenic mice as compared with control mice. Furthermore, there was a significant reduction in the whole-lung myeloperoxidase concentration. Reverse transcription-polymerase chain reaction analysis of whole-lung RNA revealed a significant reduction in the messenger RNA/beta-actin ratio of macrophage inflammatory protein-1alpha (MIP-1alpha) and MIP-2 in the transgenic animals as compared with controls. The results of these studies indicate that distal airway epithelial cell expression of human IL-1ra results in partial protection from IL-1alpha-induced airway inflammation and injury.

Possible participation of macrophage inflammatory protein 2 in neutrophil infiltration in allergic inflammation in rats

Recombinant rat macrophage inflammatory protein 2 (MIP-2) was prepared from E. coli transfected with a glutathione-S-transferase (GST)-MIP-2 fusion protein expression vector. A polyclonal antibody to rat MIP-2 was then obtained from rabbits by immunization with recombinant rat MIP-2. Using the polyclonal antibody which selectively suppressed neutrophil chemotactic activity of MIP-2, the role of MIP-2 in neutrophil infiltration in allergic inflammation in rats was studied. In an air pouch-type allergic inflammation model in rats, neutrophil infiltration into the pouch fluid increased with time after antigen challenge. Neutrophil chemotactic activity in the pouch fluid collected 8 h after antigen challenge was diminished by anti-MIP-2 antibody. In addition, when leukocytes that had infiltrated into the pouch fluid collected 4 h after antigen challenge were incubated, neutrophil chemotactic activity in the conditioned medium increased time-dependently, and the activity was neutralized by anti-MIP-2 antibody. Furthermore, when anti-MIP-2 antibody was injected into the pouch 6 h after antigen challenge, neutrophil infiltration into the pouch fluid during the next 2 h was suppressed. These findings indicate that MIP-2 plays an important role in neutrophil infiltration in rat allergic inflammation.