Strain-specific differences in perivascular inflammation in lungs in two murine models of allergic airway inflammation

Treatment of allergic eosinophilic asthma through engineered IL-5-anchored chimeric antigen receptor T cells

Severe eosinophilic asthma (SEA) is a therapy-resistant respiratory condition with poor clinical control. Treatment efficacy and patient compliance of current therapies remain unsatisfactory. Here, inspired by the remarkable success of chimeric antigen receptor-based cellular adoptive immunotherapies demonstrated for the treatment of a variety of malignant tumors, we engineered a cytokine-anchored chimeric antigen receptor T (CCAR-T) cell system using a chimeric IL-5-CD28-CD3ζ receptor to trigger T-cell-mediated killing of eosinophils that are elevated during severe asthma attacks. IL-5-anchored CCAR-T cells exhibited selective and effective killing capacity in vitro and restricted eosinophil differentiation with apparent protection against allergic airway inflammation in two mouse models of asthma. Notably, a single dose of IL-5-anchored CCAR-T cells resulted in persistent protection against asthma-related conditions over three months, significantly exceeding the typical therapeutic window of current mAb-based treatments in the clinics. This study presents a cell-based treatment strategy for SEA and could set the stage for a new era of precision therapies against a variety of intractable allergic diseases in the future.

Lung inflammation from repeated exposure to LPS and glyphosate

Agricultural workplaces consist of multiple airborne contaminants and inhalation exposures induce respiratory effects in workers. Endotoxin (LPS) and glyphosate are two common airborne contaminants in agricultural environments. We have previously shown that exposure to a combination of LPS and glyphosate synergistically modulates immune reactions as compared to individual exposures. The immunopathogenesis of acute and chronic exposure to complex agricultural exposures including LPS and glyphosate is not known; therefore, we further investigated the lung cellular inflammatory differences in mice exposed to either a combination, or individual, LPS, and glyphosate for 1 day, 5 days, and 10 days. Exposure to a combination of LPS and glyphosate resulted in greater cellular inflammatory effects in lungs as compared to individual exposures to LPS or glyphosate. Repeated exposures to the combination of LPS and glyphosate resulted in robust infiltration of inflammatory cells in the perivascular, peribronchiolar, and alveolar regions, and increases of alveolar septal thicknesses and perivascular spaces in the lungs with intense intercellular adhesion molecule (ICAM) - 1 staining in the perivascular region, but minimal staining in the pulmonary artery endothelium.

A Synthetic Curcuminoid Analogue, 2,6-Bis-4-(Hydroxyl-3-Methoxybenzylidine)-Cyclohexanone (BHMC) Ameliorates Acute Airway Inflammation of Allergic Asthma in Ovalbumin-Sensitized Mice

2,6-Bis-(4-hydroxyl-3-methoxybenzylidine) cyclohexanone (BHMC), a synthetic curcuminoid analogue, has been shown to exhibit anti-inflammatory properties in cellular models of inflammation and improve the survival of mice from lethal sepsis. We further evaluated the therapeutic effect of BHMC on acute airway inflammation in a mouse model of allergic asthma. Mice were sensitized and challenged with ovalbumin (OVA), followed by intraperitoneal administration of 0.1, 1, and 10 mg/kg of BHMC. Bronchoalveolar lavage fluid, blood, and lung samples were collected, and the respiratory function was measured. OVA sensitization and challenge increased airway hyperresponsiveness (AHR) and pulmonary inflammation. All three doses of BHMC (0.1-10 mg/kg) significantly reduced the number of eosinophils, lymphocytes, macrophages, and neutrophils, as well as the levels of Th2 cytokines (IL-4, IL-5 and IL-13) in bronchoalveolar lavage fluid (BALF) as compared to OVA-challenged mice. However, serum level of IgE was not affected. All three doses of BHMC (0.1-10 mg/kg) were effective in suppressing the infiltration of inflammatory cells at the peribronchial and perivascular regions, with the greatest effect observed at 1 mg/kg which was comparable to dexamethasone. Goblet cell hyperplasia was inhibited by 1 and 10 mg/kg of BHMC, while the lowest dose (0.1 mg/kg) had no significant inhibitory effect. These findings demonstrate that BHMC, a synthetic nonsteroidal small molecule, ameliorates acute airway inflammation associated with allergic asthma, primarily by suppressing the release of inflammatory mediators and goblet cell hyperplasia to a lesser extent in acute airway inflammation of allergic asthma.

Lesions in the lungs of fatal corona virus disease Covid-19

The corona virus outbreak in Wuhan, China, at the end of 2019 has rapidly evolved into a pandemic which is still virulent in many countries. An infection with SARS-CoV-2 can lead to corona virus disease (Covid-19). This paper presents an overview of the knowledge gained so far with regard to histopathological lung lesions in fatal courses of Covid-19. The main findings were diffuse alveolar damage and micro-angiopathies. These included the development of hyaline membranes, thrombi, endothelial inflammation, haemorrhages and angiogenesis. Overall, the vessel lesions seemed to be more lethal than the diffuse alveolar damage. There was obvious hyperreactivity and hyperinflammation of the cellular immune system. An expanded T-cell memory may explain the increased risk of a severe course in the elderly.

Bcl6 and Blimp1 reciprocally regulate ST2+ Treg-cell development in the context of allergic airway inflammation

BACKGROUND

Bcl6 is required for the development of T follicular helper cells and T follicular regulatory (Tfr) cells that regulate germinal center responses. Bcl6 also affects the function of regulatory T (Treg) cells.

OBJECTIVE

The goal of this study was to define the functions of Bcl6 in Treg cells, including Tfr cells, in the context of allergic airway inflammation.

METHODS

We used a model of house dust mite sensitization to challenge wild-type, Bcl6^fl/fl Foxp3-Cre, and Prdm1 (Blimp1)^fl/fl Foxp3-Cre mice to study the reciprocal roles of Bcl6 and Blimp1 in allergic airway inflammation.

RESULTS

In the house dust mite model, Tfr cells repress the production of IgE and Bcl6⁺ Treg cells suppress the generation of type 2 cytokine-producing cells in the lungs. In mice with Bcl6-deficient Treg cells, twice as many ST2⁺ (IL-33R⁺) Treg cells develop as are observed in wild-type mice. ST2⁺ Treg cells in the context of allergic airway inflammation are Blimp1 dependent, express type 2 cytokines, and share features of visceral adipose tissue Treg cells. Bcl6-deficient Treg cells are more susceptible, and Blimp1-deficient Treg cells are resistant, to acquiring the ST2⁺ Treg-cell phenotype in vitro and in vivo in response to IL-33. Bcl6-deficient ST2⁺ Treg cells, but not Bcl6-deficient ST2⁺ conventional T cells, strongly promote allergic airway inflammation when transferred into recipient mice. Lastly, ST2 is required for the exacerbated allergic airway inflammation in Bcl6^fl/fl Foxp3-Cre mice.

CONCLUSIONS

During allergic airway inflammation, Bcl6 and Blimp1 play dual roles in regulating Tfr-cell activity in the germinal center and in the development of ST2⁺ Treg cells that promote type 2 cytokine responses.

Lung-Infiltrating Foxp3+ Regulatory T Cells Are Quantitatively and Qualitatively Different during Eosinophilic and Neutrophilic Allergic Airway Inflammation but Essential To Control the Inflammation

Understanding functions of Foxp3⁺ regulatory T cells (Tregs) during allergic airway inflammation remains incomplete. In this study, we report that, during cockroach Ag-induced allergic airway inflammation, Foxp3⁺ Tregs are rapidly mobilized into the inflamed lung tissues. However, the level of Treg accumulation in the lung was different depending on the type of inflammation. During eosinophilic airway inflammation, ∼30% of lung-infiltrating CD4 T cells express Foxp3, indicative of Tregs. On the contrary, only ∼10% of infiltrating CD4 T cells express Foxp3 during neutrophilic airway inflammation. Despite the different accumulation, the lung inflammation and inflammatory T cell responses were aggravated following Treg depletion, regardless of the type of inflammation, suggesting regulatory roles for Tregs. Interestingly, however, the extent to which inflammatory responses are aggravated by Treg depletion was significantly greater during eosinophilic airway inflammation. Indeed, lung-infiltrating Tregs exhibit phenotypic and functional features associated with potent suppression. Our results demonstrate that Tregs are essential regulators of inflammation, regardless of the type of inflammation, although the mechanisms used by Tregs to control inflammation may be shaped by environmental cues available to them.

The interleukin-33 receptor ST2 is important for the development of peripheral airway hyperresponsiveness and inflammation in a house dust mite mouse model of asthma

BACKGROUND

Several clinical and experimental studies have implicated IL-33 and its receptor ST2 in the development of asthma. However, the effect of IL-33/ST2 signalling on airway responses and inflammation in allergic asthma is not well established.

OBJECTIVE

To investigate the role of IL-33/ST2 signalling in promoting allergen-induced airway hyperresponsiveness (AHR), airway inflammation, antigen-specific IgE production and mast cell activity in a mouse model of asthma.

METHODS

ST2-deficient (ST2(-/-)) mice and control BALB/c mice were given house dust mite (HDM) extract over a 6-week period. Forty-eight hours after the final HDM administration, lung function and airway inflammation were evaluated. Airway responsiveness was determined in the central airways and peripheral lung. Cellular infiltration and mast cell protease mMCP-1 levels were quantified in bronchoalveolar lavage fluid (BALF). Recruitment of inflammatory cells and inflammatory cytokine profiles were assessed in pulmonary tissue, and HDM-specific IgE was measured in serum.

RESULTS

ST2 deficiency diminished HDM-induced AHR in the peripheral lung, while AHR in the central airways was unaffected. Inflammatory responses to HDM were also reduced in ST2(-/-) mice as reflected by the lower induction of HDM-specific serum IgE, inhibition of HDM-induced eosinophilia and reduced macrophage count in BALF, and a diminished influx of inflammatory cells and reduced goblet cell hyperplasia around the peripheral airways. Furthermore, the levels of the inflammatory cytokines IL-1β, IL-5, IL-13, IL-33, GM-CSF, thymic stromal lymphopoietin and mast cell protease mMCP-1 were reduced in HDM-treated ST2(-/-) mice compared with wild-type controls.

CONCLUSIONS

In addition to promoting Th2 inflammation, we now suggest a role for the IL-33/ST2 pathway for the induction of peripheral inflammation and mucus production that causes AHR in the peripheral lung. This mechanism for inducing AHR at distal parts of the lung may be of specific importance as asthma is considered as a small airway disease.

Imidacloprid induced histomorphological changes and expression of TLR-4 and TNFα in lung

The imidacloprid is used worldwide as a pesticide and has been linked with endocrine disturbances and reduced pulmonary function. However, effects of imidacloprid alone or in combination with microbial molecules on lungs are not fully understood. Because the pulmonary effects of interactions of endotoxins with imidacloprid are unknown, we designed a study to investigate that in a mouse model. Mice (N=14) were given imidacloprid orally @ 1/20(th) of LD50 dissolved in corn oil for 30days. After the treatments, six animals from each group were challenged with E. coli lipopolysaccharide (LPS) @ 80μg/animal via intranasal route and remaining animals were challenged with normal saline solution @ 80μl/animal via same route. Imidacloprid in combination with LPS led to significant increase in total cell and neutrophil counts in BAL and peripheral blood. Semi-quantitative histopathology revealed lung injury in imidacloprid treatment group and injury was more marked in animal receiving both imidacloprid and LPS. There was no change (p<0.05) in the expression of TLR-4 and TNF-α both at mRNA and protein levels following exposure to imidacloprid alone or in combination with LPS. The data show that imidacloprid alone or in combination with LPS resulted changes in lung morphology without altering the expression of TLR-4 and TNF-α. Furthermore, pre-treatment with imidacloprid didn't affect response to LPS.

Vascular adhesion protein-1: Role in human pathology and application as a biomarker

Vascular adhesion protein-1 (VAP-1) is a member of the copper-containing amine oxidase/semicarbazide-sensitive amine oxidase (AOC/SSAO) enzyme family. SSAO enzymes catalyze oxidative deamination of primary amines, which results in the production of the corresponding aldehyde, hydrogen peroxide and ammonium. VAP-1 is continuously expressed as a transmembrane glycoprotein in the vascular wall during development and facilitates the accumulation of inflammatory cells into the inflamed environment in concert with other leukocyte adhesion molecules. The soluble form of VAP-1 is released into the circulation mainly from vascular endothelial cells. Over- and under-expression of sVAP-1 result in alterations of the reported reaction product levels, which are involved in the pathogenesis of multiple human diseases. The combination of enzymatic and adhesion capacities as well as its strong association with inflammatory pathologies makes VAP-1 an interesting therapeutic target for drug discovery. In this article, we will review the general characteristics and biological functions of VAP-1, focusing on its important role as a prognostic biomarker in human pathologies. In addition, the potential therapeutic application of VAP-1 inhibitors will be discussed.

Silica Triggers Inflammation and Ectopic Lymphoid Neogenesis in the Lungs in Parallel with Accelerated Onset of Systemic Autoimmunity and Glomerulonephritis in the Lupus-Prone NZBWF1 Mouse

Genetic predisposition and environmental factors influence the development of human autoimmune disease. Occupational exposure to crystalline silica (cSiO₂) has been etiologically linked to increased incidence of autoimmunity, including systemic lupus erythematosus (SLE), but the underlying mechanisms are poorly understood. The purpose of this study was to test the hypothesis that early repeated short-term cSiO₂ exposure will modulate both latency and severity of autoimmunity in the lupus-prone female NZBWF1 mouse. Weekly intranasal exposure to cSiO₂ (0.25 and 1.0 mg) for 4 wk beginning at 9 wk of age both reduced latency and increased intensity of glomerulonephritis. cSiO₂ elicited robust inflammatory responses in the lungs as evidenced by extensive perivascular and peribronchial lymphoplasmacytic infiltration consisting of IgG-producing plasma cells, and CD45R+ and CD3+ lymphocytes that were highly suggestive of ectopic lymphoid tissue (ELT). In addition, there were elevated concentrations of immunoglobulins and the cytokines MCP-1, TNF-α and IL-6 in bronchoalveolar lavage fluid. cSiO₂-associated kidney and lung effects paralleled dose-dependent elevations of autoantibodies and proinflammatory cytokines in plasma. Taken together, cSiO₂-induced pulmonary inflammation and ectopic lymphoid neogenesis in the NZBWF1 mouse corresponded closely to systemic inflammatory and autoimmune responses as well as the early initiation of pathological outcomes in the kidney. These findings suggest that following airway exposure to crystalline silica, in mice genetically prone to SLE, the lung serves as a platform for triggering systemic autoimmunity and glomerulonephritis.

Angiotensin-(1-7) attenuates airway remodelling and hyperresponsiveness in a model of chronic allergic lung inflammation

BACKGROUND AND PURPOSE

A long-term imbalance between pro- and anti-inflammatory mediators leads to airway remodelling, which is strongly correlated to most of the symptoms, severity and progression of chronic lung inflammation. The Angiotensin-(1-7) [Ang-(1-7)]/Mas receptor axis of the renin-angiotensin system is associated with attenuation of acute and chronic inflammatory processes. In this study, we investigated the effects of Ang-(1-7) treatment in a model of chronic allergic lung inflammation.

EXPERIMENTAL APPROACH

Mice were sensitized to ovalbumin (OVA; 4 injections over 42 days, 14 days apart) and were challenged three times per week (days 21-46). These mice received Ang-(1-7) (1 μg·h(-1) , s.c.) by osmotic mini-pumps, for the last 28 days. Histology and morphometric analysis were performed in left lung and right ventricle. Airway responsiveness to methacholine, analysis of Ang-(1-7) levels (RIA), collagen I and III (qRT-PCR), ERK1/2 and JNK (Western blotting), IgE (elisa), cytokines and chemokines (elisa multiplex), and immunohistochemistry for Mas receptors were performed.

KEY RESULTS

Infusion of Ang-(1-7) in OVA-sensitized and challenged mice decreased inflammatory cell infiltration and collagen deposition in the airways and lung parenchyma, and prevented bronchial hyperresponsiveness. These effects were accompanied by decreased IgE and ERK1/2 phosphorylation, and decreased pro-inflammatory cytokines. Mas receptors were detected in the epithelium and bronchial smooth muscle, suggesting a site in the lung for the beneficial actions of Ang-(1-7).

CONCLUSIONS AND IMPLICATIONS

Ang-(1-7) exerted beneficial attenuation of three major features of chronic asthma: lung inflammation, airway remodelling and hyperresponsiveness. Our results support an important protective role of Ang-(1-7) in lung inflammation.

Low-dose carvedilol protects against acute septic renal injury in rats during the early and late phases

Recent findings from septic acute renal injury studies have implicated the mitochondrion as an important factor in kidney injury, and that increased sympathetic nerve activity may contribute to the induction of organ failure. This study investigated the impact of a nondepressor dose of carvedilol, which is a beta-adrenoreceptor antagonist with antioxidant activity, on septic renal injury induced in rats with cecal ligation and puncture (CLP). Three groups of rats were studied. The first group was the sham-operated control. The other 2 groups of rats underwent CLP, and were administered either the vehicle or carvedilol (2.0 mg/kg body mass, by intraperitoneal (i.p.) injection, daily for 2 days as well as 30 min prior to CLP). Kidney function, inflammatory parameters, mitochondrial function, and renal perfusion pressure (RPP) were investigated at 6 and 18 h after CLP. Carvedilol did not significantly induce hypotension, and it significantly improved RPP and renal dysfunction induced with CLP, together with significant reductions in serum levels of interleukin 6 and tumor necrosis factor-alpha. Septic kidney injury mediated increased levels of malondialdehyde and protein carbonyls. Carvedilol also attenuated the decrease in kidney mitochondrial glutathione and nicotinamide adenine dinucleotide phosphate dehydrogenase. Further, intracellular renal edema and inflammation induced with CLP were reduced with carvedilol. These findings suggest renoprotective effects of carvedilol in sepsis.

Glucagon-like peptide-1 (GLP-1) reduces mortality and improves lung function in a model of experimental obstructive lung disease in female mice

The incretin hormone glucagon-like peptide-1 (GLP-1) is an important insulin secretagogue and GLP-1 analogs are used for the treatment of type 2 diabetes. GLP-1 displays antiinflammatory and surfactant-releasing effects. Thus, we hypothesize that treatment with GLP-1 analogs will improve pulmonary function in a mouse model of obstructive lung disease. Female mice were sensitized with injected ovalbumin and treated with GLP-1 receptor (GLP-1R) agonists. Exacerbation was induced with inhalations of ovalbumin and lipopolysaccharide. Lung function was evaluated with a measurement of enhanced pause in a whole-body plethysmograph. mRNA levels of GLP-1R, surfactants (SFTPs), and a number of inflammatory markers were measured. GLP-1R was highly expressed in lung tissue. Mice treated with GLP-1R agonists had a noticeably better clinical appearance than the control group. Enhanced pause increased dramatically at day 17 in all control mice, but the increase was significantly less in the groups of GLP-1R agonist-treated mice (P < .001). Survival proportions were significantly increased in GLP-1R agonist-treated mice (P < .01). SFTPB and SFTPA were down-regulated and the expression of inflammatory cytokines were increased in mice with obstructive lung disease, but levels were largely unaffected by GLP-1R agonist treatment. These results show that GLP-1R agonists have potential therapeutic potential in the treatment of obstructive pulmonary diseases, such as chronic obstructive pulmonary disease, by decreasing the severity of acute exacerbations. The mechanism of action does not seem to be the modulation of inflammation and SFTP expression.

Peripheral 5-HT7 receptors as a new target for prevention of lung injury and mortality in septic rats

Sepsis is a complex pathophysiological event involving metabolic acidosis, systemic inflammatory response syndrome, tissue damage and multiple organ dysfunction syndrome. Although many new mechanisms are being investigated to enlighten the pathophysiology of sepsis, there is no effective treatment protocol yet. Presence of 5-HT7 receptors in immune tissues prompted us to hypothesize that these receptors have roles in inflammation and sepsis. We investigated the effects of 5-HT7 receptor agonists and antagonists on serum cytokine levels, lung oxidative stress, lung histopathology, nuclear factor κB (NF-κB) positivity and lung 5-HT7 receptor density in cecal ligation and puncture (CLP) induced sepsis model of rats. Agonist administration to septic rats increased survival time; decreased serum cytokine response against CLP; decreased oxidative stress and increased antioxidant system in lungs; decreased the tissue NF-κB immunopositivity, which is high in septic rats; and decreased the sepsis-induced lung injury. In septic rats, as a result of high inflammatory response, 5-HT7 receptor expression in lungs increased significantly and agonist administration, which decreased inflammatory response and related mortality, decreased the 5-HT7 receptor expression. In conclusion, all these data suggest that stimulation of 5-HT7 receptors may be a new therapeutic target for prevention of impaired inflammatory response related lung injury and mortality.

Inflammatory priming predisposes mice to age-related retinal degeneration

Disruption of cellular processes affected by multiple genes and accumulation of numerous insults throughout life dictate the progression of age-related disorders, but their complex etiology is poorly understood. Postmitotic neurons, such as photoreceptor cells in the retina and epithelial cells in the adjacent retinal pigmented epithelium, are especially susceptible to cellular senescence, which contributes to age-related retinal degeneration (ARD). The multigenic and complex etiology of ARD in humans is reflected by the relative paucity of effective compounds for its early prevention and treatment. To understand the genetic differences that drive ARD pathogenesis, we studied A/J mice, which develop ARD more pronounced than that in other inbred mouse models. Although our investigation of consomic strains failed to identify a chromosome associated with the observed retinal deterioration, pathway analysis of RNA-Seq data from young mice prior to retinal pathological changes revealed that increased vulnerability to ARD in A/J mice was due to initially high levels of inflammatory factors and low levels of homeostatic neuroprotective factors. The genetic signatures of an uncompensated preinflammatory state and ARD progression identified here aid in understanding the susceptible genetic loci that underlie pathogenic mechanisms of age-associated disorders, including several human blinding diseases.

Suppression of bronchiolitis obliterans in allogeneic rat lung transplantation--effectiveness of everolimus

BACKGROUND

Chronic rejection (CR) after lung transplantation (LTX) manifests pathologically by fibrotic airway remodelling and bronchiolitis obliterans (BO). The role of the mammalian target of rapamycin inhibitor everolimus in preventing this process is poorly understood.

METHODS

A rat model of left lung allo-transplantation (Fisher 344 to Wistar Kyoto) was used to analyze the effect of everolimus (2.5 mg/kg/day) on the development of CR. Drug therapy began on postoperative day (POD) 0, 7 and 14 characterizing different grade of acute rejection (AR) of the allograft before drug treatment.

RESULTS

Non-treated recipients developed severe acute rejection (AR) and first signs of CR on POD 20 and a pronounced CR on POD 60. On POD 20, only application of everolimus from POD 0 to 60 significantly reduced acute inflammatory infiltration (p<0.001). Independent of treatment scheme, everolimus suppressed the development of early signs of chronic alterations (POD 20). However, neither early (POD 7-60) nor late (POD 14-60) application of everolimus affected the progression of CR (POD 60). Only its initial treatment (POD 0-60) inhibited the development of BO and vasculopathy (p<0.001). An additional finding was a decrease in body weight after drug application.

CONCLUSION

The effectiveness of everolimus after rat LTX depended on the grade of inflammation of the allograft before initiation of drug treatment. Only allografts with no or low grade AR benefit from long-term treatment with everolilmus in the prevention of BO after LTX. It could be speculated that conversion to an everolimus-based immunosuppression after LTX might only be successful in patients free of BO.

Sildenafil treatment attenuates lung and kidney injury due to overproduction of oxidant activity in a rat model of sepsis: a biochemical and histopathological study

Sepsis is a systemic inflammatory response to infection and a major cause of morbidity and mortality. Sildenafil (SLD) is a selective and potent inhibitor of cyclic guanosine monophosphate (cGMP)-specific phosphodiesterase PDE5. We aimed to investigate the protective effects of sildenafil on caecal ligation and puncture (CLP)-induced sepsis in rats. Four groups of rats were used, each composed of 10 rats: (i) 10 mg/kg SLD-treated CLP group; (ii) 20 mg/kg SLD-treated CLP group; (iii) CLP group; and (iv) sham-operated control group. A CLP polymicrobial sepsis model was applied to the rats. All groups were killed 16 h later, and lung, kidney and blood samples were analysed histopathologically and biochemically. Sildenafil increased glutathione (GSH) and decreased the activation of myeloperoxidase (MPO) and of lipid peroxidase (LPO) and levels of superoxide dismutase (SOD) in the septic rats. We observed a significant decrease in LPO and MPO and a decrease in SOD activity in the sildenafil-treated CLP rats compared with the sham group. In addition, 20 mg/kg sildenafil treatment in the sham-operated rats improved the biochemical status of lungs and kidneys. Histopathological analysis revealed significant differences in inflammation scores between the sepsis group and the other groups, except the CLP + sildenafil 10 mg/kg group. The CLP + sildenafil 20 mg/kg group had the lowest inflammation score. Sildenafil treatment decreased the serum tumour necrosis factor (TNF)-α level when compared to the CLP group. Our results indicate that sildenafil is a highly protective agent in preventing lung and kidney damage caused by CLP-induced sepsis via maintenance of the oxidant-anti-oxidant status and decrease in the level of TNF-α.

Direct leukocyte migration across pulmonary arterioles and venules into the perivascular interstitium of murine lungs during bleomycin injury and repair

During acute lung injury and repair, leukocytes are thought to enter the lung primarily across alveolar capillaries and postcapillary venules. We hypothesized that leukocytes also migrate across pulmonary arterioles and venules, which serve as alternative sites for leukocyte influx into the lung during acute lung injury and repair. Lung sections from C57BL/6J mice up to 14 days after intratracheal bleomycin (3.33 U/kg) or saline instillation were assessed by light, fluorescence, confocal, and transmission electron microscopy for evidence of inflammatory cell sequestration and transmigration at these sites. After bleomycin treatment, large numbers of leukocytes (including neutrophils, eosinophils, and monocytes) were present in the vascular lumina and in perivascular interstitia of pulmonary arterioles and venules, as well as within the vascular walls. Leukocytes were observed within well-defined pathways in arteriolar walls and much less structured pathways in venular walls, apparently in the process of transmigration. Intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) were expressed at sites of leukocyte interaction with the luminal surface, especially in arterioles. Leukocytes appeared to exit from the vessels near collagen fibers into the perivascular interstitium. Results indicate that leukocytes can directly migrate across arteriolar and venular walls into the perivascular interstitium, which may represent an important but under-recognized pathway for leukocyte influx into the lung during injury and repair.

Mast cell progenitor trafficking and maturation

Mast cells are derived from the hematopoietic progenitors found in bone marrow and spleen. Committed mast cell progenitors are rare in bone marrow suggesting they are rapidly released into the blood where they circulate and move out into the peripheral tissues. This migration is controlled in a tissue specific manner. Basal trafficking to the intestine requires expression of α4β7 integrin and the chemokine receptor CXCR2 by the mast cell progenitors and expression of MAdCAM-1 and VCAM-1 in the intestinal endothelium; and is also controlled by dendritic cells expressing the transcriptional regulatory protein T-bet. None of these play a role in basal trafficking to the lung. With the induction of allergic inflammation in the lung, there is marked recruitment of committed mast cell progenitors to lung and these cells must express α4β7 and α4β1 integrins. Within the lung there is a requirement for expression of VCAM-1 on the endothelium that is regulated by CXCR2, also expressed on the endothelium. There is a further requirement for expression of the CCR2/CCL2 pathways for full recruitment of the mast cell progenitors to the antigen-inflamed lung.

Icariin attenuates LPS-induced acute inflammatory responses: involvement of PI3K/Akt and NF-kappaB signaling pathway

This study aimed to investigate the mechanism underlying the attenuation of LPS-induced lung inflammation by icariin in vivo and in vitro. The anti-inflammatory effects of icariin on LPS-induced acute inflammatory and the molecular mechanism were investigated. Pretreatment with icarrin (20mg/kg) could attenuate acute lung inflammation by inhibiting mRNA expressions of tumor necrosis factor alpha (TNF-alpha), interleukin-6 (IL-6), metalloproteinase cycloxygenase-2 (COX-2), and inducible nitric oxide synthase (iNOS) in the lung of LPS-treated mice. In addition, icariin suppressed the secretion of TNF-alpha, prostaglandin E2 (PGE(2)) and nitric oxide (NO) as well as NF-kappaB p65 activation. Furthermore, decreased myeloperoxidase (MPO) activity was observed in the lung tissue and LPS-induced cytotoxicity in the RAW 264.7 macrophages cells was also markedly attenuated by icariin. Western blotting analysis and confocal microscopy showed that icariin pretreatment reduced the nucleus transportation and constant level of NF-kappaB p65 in the RAW 264.7 macrophage cells. However, the protective effects of icariin were reversed by a PI3K/Akt inhibitor (wortmannin). Our in vitro and in vivo results suggested that activation of the PI3K/Akt pathway and the inhibition of NF-kappaB were involved in the protective effects of icariin on LPS-induced acute inflammatory responses.

A simple quantitative method for assessing pulmonary damage after x irradiation

Pulmonary damage after radiotherapy is typically characterized by an initial alveolar inflammation (pneumonitis) followed by chronic fibrosis. In the present study, changes in lung architecture were measured in the pneumonitis phase after whole-body low-dose X irradiation of C57BL/6 mice. Radiation damage was evaluated at 24 h and 1-8 weeks postirradiation. Three distinct scoring systems were used: ( 1 ) manually evaluating alveolar distortion and infiltration of inflammatory cells into the alveolar space using a continuous numerical scale across an entire lung section, ( 2 ) physically measuring the average thickness of the alveolar septa from multiple representative microscope fields, and ( 3 ) a new rapid automated mathematical algorithm based on image segmentation of alveolar space across an entire section. Each scoring method detected significant changes in alveolar architecture at the earliest times compared with sham-treated controls and gave comparable evaluations of injury. The results from the automated mathematical algorithm correlated significantly with both the manual evaluation method (Spearman's correlation coefficient rho = 0.044) and the direct physical measurement of septa thickness (rho = 0.002). These data demonstrate that evaluating alveolar space by segmentation analysis provides a reliable method for scoring early pulmonary radiation damage that is consistent with more established methodologies but is more rapid and is independent of potential operator and selection bias.

Toll-like receptor 4 deficiency increases disease and mortality after mouse hepatitis virus type 1 infection of susceptible C3H mice

Severe acute respiratory syndrome (SARS) is characterized by substantial acute pulmonary inflammation with a high mortality rate. Despite the identification of SARS coronavirus (SARS-CoV) as the etiologic agent of SARS, a thorough understanding of the underlying disease pathogenesis has been hampered by the lack of a suitable animal model that recapitulates the human disease. Intranasal (i.n.) infection of A/J mice with the CoV mouse hepatitis virus strain 1 (MHV-1) induces an acute respiratory disease with a high lethality rate that shares several pathological similarities with SARS-CoV infection in humans. In this study, we examined virus replication and the character of pulmonary inflammation induced by MHV-1 infection in susceptible (A/J, C3H/HeJ, and BALB/c) and resistant (C57BL/6) strains of mice. Virus replication and distribution did not correlate with the relative susceptibilities of A/J, BALB/c, C3H/HeJ, and C57BL/6 mice. In order to further define the role of the host genetic background in influencing susceptibility to MHV-1-induced disease, we examined 14 different inbred mouse strains. BALB.B and BALB/c mice exhibited MHV-1-induced weight loss, whereas all other strains of H-2(b) and H-2(d) mice did not show any signs of disease following MHV-1 infection. H-2(k) mice demonstrated moderate susceptibility, with C3H/HeJ mice exhibiting the most severe disease. C3H/HeJ mice harbor a natural mutation in the gene that encodes Toll-like receptor 4 (TLR4) that disrupts TLR4 signaling. C3H/HeJ mice exhibit enhanced morbidity and mortality following i.n. MHV-1 infection compared to wild-type C3H/HeN mice. Our results indicate that TLR4 plays an important role in respiratory CoV pathogenesis.

Comparisons of effects of intravenous and inhaled methacholine on airway physiology in a murine asthma model

Airway responses to intravenous (i.v.) and inhaled (i.h.) delivery of methacholine (MCh) in BALB/c and C57BL/6 mouse strains have been compared with and without ovalbumin (OVA)-induced airway inflammation. Bronchial reactivity to MCh was assessed in anaesthetised and tracheostomised animals by using an animal ventilator (flexiVent). We partitioned the response of the lungs into airway and parenchymal components in order to compare the contributions of the airways with those of the lung parenchyma to the pulmonary mechanical responses resulting from different routes of MCh administration. Our results indicate disparate physiological responses. Intravenous MCh delivery induced a higher maximum lung resistance than i.h. MCh in OVA-treated BALB/c mice but not in C57BL/6 mice. Inhaled MCh delivery led to a significantly larger fall in lung compliance and a greater impact on peripheral airways than i.v. MCh in both strains. In conclusion, i.v. and i.h. MCh produced disparate effects in different murine strains and variant responses in inflamed airways and healthy controls. The two methods of MCh delivery have important advantages but also certain limitations with regard to measuring airway reactivity in a murine model of allergic asthma.

Mutated glutathione-S-transferase reduced airway inflammation by limiting oxidative stress and Th2 response

Oxidative stress is an important factor in the pathogenesis of asthma. Furthermore, antioxidants like GST are reduced in asthma patients. In the present study, the therapeutic effects of exogenous GST and mGST were evaluated in a mice model. GST mutated at residues 21/27 has reduced IgE binding with similar enzyme activity as that of GST. To evaluate the therapeutic effects of GST, BALB/c mice were immunized and challenged with ovalbumin. Mice were given GST, mGST, and alpha-lipoic acid by inhalation and sacrificed on Day 31 to evaluate inflammation and oxidative stress. Mice treated with mGST showed significantly reduced total cell count (P<0.01) and eosinophils (P<0.01) in BALF compared to GST- or PBS-treated groups. The lung inflammation score was lowest for the mGST-treated group along with reduced IL-4 (P<0.01) and OVA-specific IgE than other groups. Oxidative stress as per the lipid peroxidation level in BALF of mGST-treated mice was reduced significantly in comparison to PBS- or GST-treated mice. In conclusion, inhalation of mGST reduced airway inflammation in mice. Mutated GST with reduced allergenicity has better therapeutic potential and can be explored as an adjunct therapy in asthma.

Aerobic conditioning and allergic pulmonary inflammation in mice. II. Effects on lung vascular and parenchymal inflammation and remodeling

Recent evidence suggests that asthma leads to inflammation and remodeling not only in the airways but also in pulmonary vessels and parenchyma. In addition, some studies demonstrated that aerobic training decreases chronic allergic inflammation in the airways; however, its effects on the pulmonary vessels and parenchyma have not been previously evaluated. Our objective was to test the hypothesis that aerobic conditioning reduces inflammation and remodeling in pulmonary vessels and parenchyma in a model of chronic allergic lung inflammation. Balb/c mice were sensitized at days 0, 14, 28, and 42 and challenged with ovalbumin (OVA) from day 21 to day 50. Aerobic training started on day 21 and continued until day 50. Pulmonary vessel and parenchyma inflammation and remodeling were evaluated by quantitative analysis of eosinophils and mononuclear cells and by collagen and elastin contents and smooth muscle thickness. Immunohistochemistry was performed to quantify the density of positive cells to interleukin (IL)-2, IL-4, IL-5, interferon-gamma, IL-10, monocyte chemotatic protein (MCP)-1, nuclear factor (NF)-kappaB p65, and insulin-like growth factor (IGF)-I. OVA exposure induced pulmonary blood vessels and parenchyma inflammation as well as increased expression of IL-4, IL-5, MCP-1, NF-kappaB p65, and IGF-I by inflammatory cells were reduced by aerobic conditioning. OVA exposure also induced an increase in smooth muscle thickness and elastic and collagen contents in pulmonary vessels, which were reduced by aerobic conditioning. Aerobic conditioning increased the expression of IL-10 in sensitized mice. We conclude that aerobic conditioning decreases pulmonary vascular and parenchymal inflammation and remodeling in this experimental model of chronic allergic lung inflammation in mice.

Lipopolysaccharide induced inflammation in the perivascular space in lungs

Background

Lipopolysaccharide (LPS) contained in tobacco smoke and a variety of environmental and occupational dusts is a toxic agent causing lung inflammation characterized by migration of neutrophils and monocytes into alveoli. Although migration of inflammatory cells into alveoli of LPS-treated rats is well characterized, the dynamics of their accumulation in the perivascular space (PVS) leading to a perivascular inflammation (PVI) of pulmonary arteries is not well described.

Methods

Therefore, we investigated migration of neutrophils and monocytes into PVS in lungs of male Sprague-Dawley rats treated intratracheally with E. coli LPS and euthanized after 1, 6, 12, 24 and 36 hours. Control rats were treated with endotoxin-free saline. H&E stained slides were made and immunohistochemistry was performed using a monocyte marker and the chemokine Monocyte-Chemoattractant-Protein-1 (MCP-1). Computer-assisted microscopy was performed to count infiltrating cells.

Results

Surprisingly, the periarterial infiltration was not a constant finding in each animal although LPS-induced alveolitis was present. A clear tendency was observed that neutrophils were appearing in the PVS first within 6 hours after LPS application and were decreasing at later time points. In contrast, mononuclear cell infiltration was observed after 24 hours. In addition, MCP-1 expression was present in perivascular capillaries, arteries and the epithelium.

Conclusion

PVI might be a certain lung reaction pattern in the defense to infectious attacks.

Impact of boostering for the strength of asthma parameters and dendritic cell numbers in a C57BL/6 model of allergic airway inflammation

BACKGROUND

Murine models assist in elucidating the pathogenesis of allergic asthma and evaluation of new therapeutic strategies. We aimed to assess the requirement of boostering needed in the BL/6 murine asthma model and its influence on DC populations in lungs and bronchial lymph nodes.

METHODS AND RESULTS

Two injections of OVA+alum - one sensitization and one booster - followed by two aerosol challenges were sufficient to induce a distinct asthma-like inflammation in BL/6 mice, including significant increased immunoglobulin (IgE) level, influx of eosinophils in the airway lumen, and evident histopathology. Using this protocol, CD11chighMHC-II+ DC counts in lungs and lymph nodes doubled with no changes of CD8+ DC in the lungs but increase in lung-draining lymph nodes.

CONCLUSIONS

Given the site-specific changes of dendritic cell (DC) subpopulations during allergic asthma we propose a distinct regulation of antigen transport and antigen presentation in the murine asthma model.

Airway inflammatory responses to oxidative stress induced by prolonged low-dose diesel exhaust particle exposure from birth differ between mouse BALB/c and C57BL/6 strains

The authors used BALB/c and C57BL/6 mouse strains to search for genetically based differences in response to prolonged (6 months) low-dose (100 microg/m3) diesel exhaust particle (DEP) exposure from birth in terms of airway inflammatory responses. Histopathological assessment showed that inflammatory cells infiltrated the perivascular areas only in C57BL/6 mice. The count of DEP-laden alveolar macrophages in bronchoalveolar lavage (BAL) fluid was significantly greater in BALB/c mice (P < .05) than in C57BL/6 mice. The lymphocyte and eosinophil count in BAL fluid was significantly greater in C57BL/6 mice (P < .05) than in BALB/c mice. Immunoglobulin (Ig) IgG1 and IgG2 levels in serum, and the monocyte chemoattractant protein (MCP)-1 level in BAL fluid were significantly greater in BALB/c mice than in C57BL/6 mice. The interleukin (IL)-12 level in BAL fluid was significantly greater in C57BL/6 mice than in BALB/c mice, but the IL-13 level in BAL fluid was significantly less in BALB/c mice than in C57BL/6 mice. Glutathione S-transferase (GST) mRNA expression and protein production in lung tissues were significantly lower in C57BL/6 mice than in BALB/c mice, and 8-hydroxy-2'-deoxyguanosine (8-OHdG) level in the lung tissues were significantly greater in C57BL/6 mice than in BALB/c mice. In conclusion, prolonged low-dose DEP exposure induces airway inflammatory responses that differ remarkably among mouse strains; these differences are caused by differences in the host defense response to the oxidative stress induced by DEP exposure and may be useful in the development of biomarkers.

Effects of residual oil fly ash (ROFA) in mice with chronic allergic pulmonary inflammation

Exposure to particulate matter (PM) air pollution is associated with increased asthma morbidity. Residual oil flash ash (ROFA) is rich in water-soluble transition metals, which are involved in the pathological effects of PM. The objective of this study was to investigate the effects of intranasal administration of ROFA on pulmonary inflammation, pulmonary responsiveness, and excess mucus production in a mouse model of chronic pulmonary allergic inflammation. BALB/c mice received intraperitoneal injections of ovalbumin (OVA) solution (days 1 and 14). OVA challenges were performed on days 22, 24, 26, and 28. After the challenge, mice were intranasally instilled with ROFA. After forty-eight hours, pulmonary responsiveness was performed. Mice were sacrificed, and lungs were removed for morphometric analysis. OVA-exposed mice presented eosinophilia in the bronchovascular space (p < .001), increased pulmonary responsiveness (p < .001), and epithelial remodeling (p = .003). ROFA instillation increased pulmonary responsiveness (p = .004) and decreased the area of ciliated cells in the airway epithelium (p = .006). The combined ROFA instillation and OVA exposure induced a further increase in values of pulmonary responsiveness (p = .043) and a decrease in the number of ciliated cells in the airway epithelium (p = .017). PM exposure results in pulmonary effects that are more intense in mice with chronic allergic pulmonary inflammation.

Cytotoxicity and gene expression profiles in cell cultures exposed to whole smoke from three types of cigarettes

The purpose of this study was to evaluate and compare the cytotoxicity and gene expression profiles in cell cultures exposed to whole smoke generated from a full flavor cigarette (Test 1), a low tar cigarette (Test 2), and an ultra-low tar cigarette (Test 3). In addition, a reference cigarette 2R4F was evaluated for cytotoxicity. Neutral red (NR) cytotoxicity assay was performed to determine relative cell death at each exposure concentration (n = 6). LC(50) was generated using wet total particular matter (WTPM), cigarette number, or nicotine concentrations. The overall order of cytotoxicity was Test 1 >> 2R4F approximately Test 2 > Test 3. Cell culture samples were collected for RNA extraction at WTPM concentrations of each cigarette that gave similar nicotine concentrations. Affymetrix mouse whole genome 430 2.0 array was used to characterize the gene expression profiles for each cigarette. A total of 598 genes in Test 1, 176 genes in Test 2, and 234 genes in Test 3 samples were differentially expressed compared to the concurrent sham controls. The major biological processes associated with the changed genes in Test 1 samples were down-regulated DNA replication and cell proliferation; the same biological processes were much less affected in Test 2 and Test 3 samples. The common findings in all three cigarettes types were increased glutathione biosynthesis/consumption and inflammatory response, which are known biological effects caused by smoke exposure. The most significantly up-regulated genes were CYP1A1, GSTs, Hmox1, and Procr in smoke-exposed samples, which are either related to well-studied mechanisms of smoke exposure-related diseases or potential new biomarkers for assessing and monitoring biological effects of cigarette smoke exposure in vivo and in smokers. In summary, both the NR cytotoxicity assay and gene expression profiling were able to differentiate the three types of test cigarettes, and the results demonstrated reduced biological effects for the Test 2 and Test 3 cigarettes compared to the Test 1 cigarette in BALB/c-3T3 Cells.

Coagulation factor Xa modulates airway remodeling in a murine model of asthma

RATIONALE

Previous studies have demonstrated that dysregulated coagulation and fibrinolysis contribute to the pathogenesis of asthma.

OBJECTIVE

The role of procoagulant factor X in a murine model of ovalbumin (OVA)-induced asthma was investigated.

METHODS

Biochemical, cellular, and physiologic in vivo and in vitro approaches were used to determine effects of factor X on the asthmatic response in mice.

MEASUREMENTS AND MAIN RESULTS

Factor X transcript levels and factor Xa activity were increased in lungs of asthmatic mice challenged with OVA, compared with controls treated with phosphate-buffered saline. Factor X was highly expressed in bronchoalveolar lavage fluid macrophages from asthmatic mice. Treatment of mice with the factor Xa inhibitor fondaparinux during the last 4 wk of OVA challenge resulted in the attenuation of airway hyperresponsiveness but did not alter infiltration of inflammatory cells into the lung. There was a significant decrease in the thickness of the mucosal layer and in lung collagen deposition in fondaparinux-treated mice. In vitro investigations using human mucus-producing NCI-H292 cells indicated that exogenous factor Xa enhanced mucin production in a dose-dependent manner. Levels of amphiregulin, a protein that induces mucin production, were also increased in cells stimulated by factor Xa.

CONCLUSIONS

The results of this study introduce a novel participant in the asthmatic response and indicate that factor Xa functions in airway remodeling in asthma by stimulating mucin production, through regulation of amphiregulin expression and collagen deposition.

Differential in vivo effects of whole cigarette smoke exposure versus cigarette smoke extract on mouse ciliated tracheal epithelium

In this study the authors compared the affect of vapor phase cigarette smoke (CS) versus cigarette smoke extract (CSE) on the lungs and upper airway of C57BL/6 mice. The authors found that CSE treatment significantly increased neutrophil influx (P < .001), baseline ciliary beat frequency (CBF) (P < .05), and protein kinase C activity compared to CS and controls. Isoproterenol increased CBF with CS exposure, but decreased CBF with CSE (P < .01). Isoproterenol increased protein kinase A (PKA) activity in all groups except CSE. CSE exposure induced inflammatory cell bronchiolitis. These data indicate that CSE exposure has differential effects on the lungs and tracheal epithelium compared to CS exposure.

Host genetics of Bordetella pertussis infection in mice: significance of Toll-like receptor 4 in genetic susceptibility and pathobiology

The susceptibility to and the severity of Bordetella pertussis infections in infants and children varies widely, suggesting that genetic differences between individuals influence the course of infection. We have previously identified three novel loci that influence the severity of whooping cough by using recombinant congenic strains of mice: Bordetella pertussis susceptibility loci 1, 2, and 3 (Bps1, -2, and -3). Because these loci could not account for all genetic differences between mice, we extended our search for additional susceptibility loci. We therefore screened 11 inbred strains of mice for susceptibility to a pertussis infection after intranasal infection. Susceptibility was defined by the number of bacteria in the lungs, being indicative of the effect between the clearance and replication of bacteria. The most resistant (A/J) and the most susceptible (C3H/HeJ) strains were selected for further genetic and phenotypic characterization. The link between bacterial clearance and chromosomal location was investigated with 300 F2 mice, generated by crossing A/J and C3H/HeJ mice. We found a link between the delayed clearance of bacteria from the lung and a large part of chromosome 4 in F2 mice with a maximum log of the odds score of 33.6 at 65.4 Mb, which is the location of Tlr4. C3H/HeJ mice carry a functional mutation in the intracellular domain of Tlr4. This locus accounted for all detectable genetic differences between these strains. Compared to A/J mice, C3H/HeJ mice showed a delayed clearance of bacteria from the lung, a higher relative lung weight, and increased body weight loss. Splenocytes from infected C3H/HeJ mice produced almost no interleukin-1beta (IL-1beta) and tumor necrosis factor alpha (TNF-alpha) upon ex vivo restimulation with B. pertussis compared to A/J mice and also showed a delayed gamma interferon (IFN-gamma) production. TNF-alpha expression in the lungs 3 days after infection was increased fivefold compared to uninfected controls in A/J mice and was not affected in C3H/HeJ mice. In conclusion, Tlr4 is a major host factor explaining the differences in the course of infection between these inbred strains of mice. Functional Tlr4 is essential for an efficient IL-1-beta, TNF-alpha, and IFN-gamma response; efficient clearance of bacteria from the lung; and reduced lung pathology.

Leukocyte infiltration of the periarterial space of the lung after allergen provocation in a rat asthma model

The periarterial space has recently been described and its physiological and pathophysiological role during inflammatory and allergic reactions has been reviewed. The present studies used a light-/electron-microscopic approach to characterize the periarterial space in an asthma model in Brown Norway rats. After repeated sensitization with ovalbumin and heat-killed Bordetella pertussis bacilli, airway challenge was carried out after 1 further week. Four or 24 h after challenge, rats were fixed by perfusion or instillation and processed for microscopy. Several periarterial capillaries and connective tissue characterized the tissue between small pulmonary arteries, bronchioles and alveolar septa. Additionally, a partly pronounced interstitial edema was seen independent of the kind of fixation. Not only small arteries but also arterioles and venules were partly surrounded by edematous fluid already visible by light microscopy. Within the connective tissue and within the periarterial fluid, numerous leukocytes, predominantly eosinophils, were found. However, leukocytes were detected only rarely in the vascular lumen. Only sporadically were eosinophils seen in the wall of small arteries or venules. Eosinophils transmigrating the endothelium of capillaries or arterioles were not visible 4 or 24 h after challenge. Thus, granulocytes transmigrate in the periarterial space very rapidly or even earlier than 4 h after challenge. The location of transmigration in the periarterial space needs further investigation.

Alpha-4 integrins and VCAM-1, but not MAdCAM-1, are essential for recruitment of mast cell progenitors to the inflamed lung

Normal mouse lungs lack appreciable numbers of mast cells (MCs) or MC progenitors (MCp's), yet the appearance of mature MCs in the tracheobronchial epithelial surface is a characteristic of allergic, T-cell-dependent pulmonary inflammation. We hypothesized that pulmonary inflammation would recruit MCp's to inflamed lungs and that this recruitment would be regulated by distinct adhesion pathways. Ovalbumin-sensitized and challenged mice had a greater than 28-fold increase in the number of MCp's in the lungs. In mice lacking endothelial vascular cell adhesion molecule 1 (VCAM-1) and in wild-type mice administered blocking monoclonal antibody (mAb) to VCAM-1 but not to mucosal addressin CAM-1 (MadCAM-1), recruitment of MCp's to the inflamed lung was reduced by greater than 75%. Analysis of the integrin receptors for VCAM-1 showed that in beta7 integrin-deficient mice, recruitment was reduced 73% relative to wild-type controls, and in either BALB/c or C57BL/6 mice, mAb blocking of alpha4, beta1, or beta7 integrins inhibited the recruitment of MCp's to the inflamed lung. Thus, VCAM-1 interactions with both alpha4beta1 and alpha4beta7 integrins are essential for the recruitment and expansion of the MCp populations in the lung during antigen-induced pulmonary inflammation. Furthermore, the MCp is currently unique among inflammatory cells in its partial dependence on alpha4beta7 integrins for lung recruitment.