DEVELOPMENT OF BRONCHUS-ASSOCIATED LYMPHOID TISSUE HYPERPLASIA FOLLOWING LIPOPOLYSACCHARIDE-INDUCED LUNG INFLAMMATION IN RATS

Protective effects of propolis extract against nicotine-evoked pulmonary and hepatic damage

There is increasing interest in the use of natural products to treat many diseases, considering the minimal toxicity, availability, and low cost. Propolis, a natural resinous product produced by honeybees, has been proven for its antioxidant and anti-inflammatory properties. Therefore, this study was designed to investigate the protective potential of propolis extract against nicotine-induced pulmonary and hepatic damage in rats. Sprague Dawley rats were divided into six groups: control, propolis (200 and 300 mg/kg, p.o.), nicotine (10 mg/kg, i.p), and nicotine plus propolis-treated groups. Nicotine and propolis were given every day for 8 weeks. Then, blood and bronchoalveolar lavage fluid (BALF) were collected for assessing liver and lung functions. Liver and lung tissues were also harvested to assess oxidative stress and inflammatory biomarkers in addition to histopathological and immunohistochemical analysis. Both doses of propolis significantly decreased AST, ALT, ALP, and total and differential cell counts in a dose-dependent manner. Propolis extract significantly attenuated oxidative stress in both lung and liver tissues. The restoration of antioxidant status (GSH level, SOD activities) and reduction of nitric oxide and MDA content was more so in propolis 300-treated than propolis 200-treated group. This was parallel to the improvement seen in histopathological examination. Propolis 200 and 300 significantly decreased Nrf2 expression and increased HO-1 expression in a dose-dependent manner. Moreover, immunohistochemical examination revealed that propolis 200 and 300 decreased the expression of iNOS in lung and liver tissues while decreased TNF-α expression in lung tissues only. Propolis extract could have a protective potential against nicotine-induced pulmonary and hepatic damage via activating Nrf2/HO-1 signaling.

Diacetyl Vapor Inhalation Induces Mixed, Granulocytic Lung Inflammation with Increased CD4+CD25+ T Cells in the Rat

Diacetyl (DA) is a highly reactive alpha diketone associated with flavoring-related lung disease. In rodents, acute DA vapor exposure can initiate an airway-centric, inflammatory response. However, this immune response has yet to be fully characterized in the context of flavoring-related lung disease progression. The following studies were designed to characterize the different T cell populations within the lung following repetitive DA vapor exposures. Sprague-Dawley rats were exposed to 200 parts-per-million DA vapor for 5 consecutive days × 6 h/day. Lung tissue and bronchoalveolar lavage fluid (BALF) were analyzed for changes in histology by H&E and Trichrome stain, T cell markers by flow cytometry, total BALF cell counts and differentials, BALF IL17a and total protein immediately, 1 and 2 weeks post-exposure. Lung histology and BALF cell composition demonstrated mixed, granulocytic lung inflammation with bronchial lymphoid aggregates at all time points in DA-exposed lungs compared to air controls. While no significant change was seen in percent lung CD3+, CD4+, or CD8+ T cells, a significant increase in lung CD4+CD25+ T cells developed at 1 week that persisted at 2 weeks post-exposure. Further characterization of this CD4+CD25+ T cell population identified Foxp3+ T cells at 1 week that failed to persist at 2 weeks. Conversely, BALF IL-17a increased significantly at 2 weeks in DA-exposed rats compared to air controls. Lung CD4+CD25+ T cells and BALF IL17a correlated directly with BALF total protein and inversely with rat oxygen saturations. Repetitive DA vapor exposure at occupationally relevant concentrations induced mixed, granulocytic lung inflammation with increased CD4+CD25+ T cells in the rat lung.

Antioxidant-Based Therapy Reduces Early-Stage Intestinal Ischemia-Reperfusion Injury in Rats

Intestinal ischemia-reperfusion injury (i-IRI) is a rare disorder with a high mortality rate, resulting from the loss of blood flow to an intestinal segment. Most of the damage is triggered by the restoration of flow and the arrival of cytokines and reactive oxygen species (ROS), among others. Inactivation of these molecules before tissue reperfusion could reduce intestinal damage. The aim of this work was to analyze the preventive effect of allopurinol and nitroindazole on intestinal mucosal damage after i-IRI. Wag/RijHsd rats were subjected to i-IRI by clamping the superior mesenteric artery (for 1 or 2 h) followed by a 30 min period of reperfusion. Histopathological intestinal damage (HID) was assessed by microscopic examination of histological sections obtained from injured intestine. HID was increased by almost 20% by doubling the ischemia time (from 1 to 2 h). Nitroindazole reduced HID in both the 1 and 2 h period of ischemia by approximately 30% and 60%, respectively (p < 0.001). Our preliminary results demonstrate that nitroindazole has a preventive/protective effect against tissue damage in the early stages of i-IRI. However, to better understand the molecular mechanisms underlying this phenomenon, further studies are needed.

Organized lymphatic tissue (BALT) in lungs of rhesus monkeys after air pollutant exposure

The presence of bronchus-associated lymphoid tissue (BALT) and its size in humans largely depends upon age. It is detected in 35% of children less than 2 years of age, but absent in the healthy adult lung. Environmental gases or allergens may have an effect on the number of BALT. Lungs of rhesus macaque monkeys were screened by histology for the presence, size, and location of BALT after exposure to filtered air for 2, 6, 12, or 36 months or 12 and 36 months to ozone or 2, 12, or 36 months of house dust mite or a combination of ozone and house dust mite for 12 months. In the lungs of monkeys housed in filtered air for 2 months, no BALT was identified. After 6, 12, or 36 months, the number of BALT showed a significantly increased correlation with age in monkeys housed in filtered air. After 2 months of episodic house dust mite (HDM) exposure, no BALT was found. Monkeys exposed to HDM or HDM + ozone did not show a significant increase in BALT compared to monkeys housed in filtered air. However, monkeys exposed to ozone alone did show significant increases in BALT compared to all other groups. In particular, there were frequent accumulations of lymphocytes in the periarterial space of ozone exposed animals. In conclusion, BALT in rhesus monkeys housed under filtered air conditions is age-dependent. BALT significantly increased in monkeys exposed to ozone in comparison with monkeys exposed to HDM.

Tiron protects against nicotine-induced lung and liver injury through antioxidant and anti-inflammatory actions in rats in vivo

AIMS

Tobacco smoking is a major health problem associated with lung and liver damage. Lung and liver damage secondary to tobacco smoking is mediated through nicotine-induced oxidative stress. Therefore, we hypothesized that antioxidant treatment with tiron may improve nicotine-induced lung and liver damage.

MATERIALS AND METHODS

Rats were divided into six groups, a control, nicotine (10 mg/kg/day, i.p.; for 8 weeks) and tiron (100 or 200 mg/kg/day, i.p.; for 8 weeks) with or without nicotine administration.

KEY FINDINGS

Tiron improved survival rate and attenuated lung and liver damage as reflected by decreased total and differential cell counts, lactate dehydrogenase (LDH) activity in bronchoalveolar lavage fluid (BALF) and decreased alanine aminotransferase (ALT), aspartate aminotransferase (AST) and alkaline phosphatase (ALP) in serum; also histopathological examination confirmed the protective effect of tiron in lung and liver tissues of nicotine treated rats. Tiron attenuated dyslipidemia, which is associated with nicotine. These ameliorative effects of tiron may be mainly due to its antioxidant effect as proved by a significant decrease in malondialdehyde (MDA) content, reactive oxygen species (ROS) and total nitrite/nitrate (NOx) levels, and increase in reduced glutathione (GSH) level, catalase (CAT) and superoxide dismutase (SOD) activities. This is likely related to suppression of protein levels of NADPH oxidase enzyme (NOX1), inducible nitric oxide synthase (iNOS), nuclear factor kappa B (NF-κB) and tumor necrosis factor alpha (TNF-α); and up-regulation of protein levels of nuclear factor erythroid-2 (Nrf2).

SIGNIFICANCE

This makes tiron (synthetic analogue of vitamin E) good candidate for future use to minimize nicotine's hazards among smokers.

The influence of allopurinol and post-conditioning on lung injuries induced by lower-limb ischemia and reperfusion in Wistar rats

PURPOSE

To analyze the effects of allopurinol and of post-conditioning on lung injuries induced by lower-limb ischemia and reperfusion.

METHODS

Thirty rats were used. They were divided in 5 groups: (1) group A: abdominal aortic dissection only, (2) group B: ischemia and reperfusion, (3) group C: administered allopurinol (100mg/Kg) a few hours before procedure, (4) group D: post-conditioned and (5) group E: administered allopurinol and post-conditioned. With the exception of group A, all groups were submitted to infrarenal aortic ischemia for 2 hours, and reperfusion for 72 hours. After euthanasia, lungs were removed for histological analysis. They were graded under two scores: pulmonary injury (neutrophil infiltration, interstitial edema, vascular congestion, and destruction of lung architecture) and lymphocytic score (neutrophil infiltration, lymphoid aggregate and secondary follicle).

RESULTS

On the pulmonary injury score, the degree of injury was smaller than in groups D and E, when compared to group B, p<0.05. Group C did not obtain the same result (p>0,05). On the lymphocytic score, there was no statistic difference among groups, p>0.05.

CONCLUSION

Both post-conditioning and the combination of allopurinol and post-conditioning were effective in remote lung protection induced by lower-limbs I/R. When used in isolation, allopurinol showed no protective effect.

Bronchus-associated lymphoid tissue in pulmonary hypertension produces pathologic autoantibodies

RATIONALE

Autoimmunity has long been associated with pulmonary hypertension. Bronchus-associated lymphoid tissue plays important roles in antigen sampling and self-tolerance during infection and inflammation.

OBJECTIVES

We reasoned that activated bronchus-associated lymphoid tissue would be evident in rats with pulmonary hypertension, and that loss of self-tolerance would result in production of pathologic autoantibodies that drive vascular remodeling.

METHODS

We used animal models, histology, and gene expression assays to evaluate the role of bronchus-associated lymphoid tissue in pulmonary hypertension.

MEASUREMENTS AND MAIN RESULTS

Bronchus-associated lymphoid tissue was more numerous, larger, and more active in pulmonary hypertension compared with control animals. We found dendritic cells in and around lymphoid tissue, which were composed of CD3(+) T cells over a core of CD45RA(+) B cells. Antirat IgG and plasma from rats with pulmonary hypertension decorated B cells in lymphoid tissue, resistance vessels, and adventitia of large vessels. Lymphoid tissue in diseased rats was vascularized by aquaporin-1(+) high endothelial venules and vascular cell adhesion molecule-positive vessels. Autoantibodies are produced in bronchus-associated lymphoid tissue and, when bound to pulmonary adventitial fibroblasts, change their phenotype to one that may promote inflammation. Passive transfer of autoantibodies into rats caused pulmonary vascular remodeling and pulmonary hypertension. Diminution of lymphoid tissue reversed pulmonary hypertension, whereas immunologic blockade of CCR7 worsened pulmonary hypertension and hastened its onset.

CONCLUSIONS

Bronchus-associated lymphoid tissue expands in pulmonary hypertension and is autoimmunologically active. Loss of self-tolerance contributes to pulmonary vascular remodeling and pulmonary hypertension. Lymphoid tissue-directed therapies may be beneficial in treating pulmonary hypertension.

Pulmonary expression of oncostatin M (OSM) promotes inducible BALT formation independently of IL-6, despite a role for IL-6 in OSM-driven pulmonary inflammation

Inducible BALT (iBALT) is associated with immune responses to respiratory infections as well as with local pathology derived from chronic inflammatory lung diseases. In this study, we assessed the role of oncostatin M (OSM) in B cell activation and iBALT formation in mouse lungs. We found that C57BL/6 mice responded to an endotracheally administered adenovirus vector expressing mouse OSM, with marked iBALT formation, increased cytokine (IL-4, IL-5, IL-6, IL-10, TNF-α, and IL-12), and chemokine (CXCL13, CCL20, CCL21, eotaxin-2, KC, and MCP-1) production as well as inflammatory cell accumulation in the airways. B cells, T cells, and dendritic cells were also recruited to the lung, where many displayed an activated phenotype. Mice treated with control adenovirus vector (Addl70) were not affected. Interestingly, IL-6 was required for inflammatory responses in the airways and for the expression of most cytokines and chemokines. However, iBALT formation and lymphocyte recruitment to the lung tissue occurred independently of IL-6 and STAT6 as assessed in gene-deficient mice. Collectively, these results support the ability of OSM to induce B cell activation and iBALT formation independently of IL-6 and highlight a role for IL-6 downstream of OSM in the induction of pulmonary inflammation.

PET imaging of lung inflammation with [18F]FEDAC, a radioligand for translocator protein (18 kDa)

Purpose

The translocator protein (18 kDa) (TSPO) is highly expressed on the bronchial and bronchiole epithelium, submucosal glands in intrapulmonary bronchi, pneumocytes and alveolar macrophages in human lung. This study aimed to perform positron emission tomography (PET) imaging of lung inflammation with [¹⁸F]FEDAC, a specific TSPO radioligand, and to determine cellular sources enriching TSPO expression in the lung.

Methods

An acute lung injury model was prepared by intratracheal administration of lipopolysaccharide (LPS) to rat. Uptake of radioactivity in the rat lungs was measured with small-animal PET after injection of [¹⁸F]FEDAC. Presence of TSPO was examined in the lung tissue using Western blot and immunohistochemical assays.

Results

The uptake of [¹⁸F]FEDAC increased in the lung with the progress of inflammation by treatment with LPS. Pretreatment with a TSPO-selective ligand PK11195 showed a significant decrease in the lung uptake of [¹⁸F]FEDAC due to competitive binding to TSPO. TSPO expression was elevated in the inflamed lung section and its level responded to the [¹⁸F]FEDAC uptake and severity of inflammation. Increase of TSPO expression was mainly found in the neutrophils and macrophages of inflamed lungs.

Conclusion

From this study we conclude that PET with [¹⁸F]FEDAC may be a useful tool for imaging TSPO expression and evaluating progress of lung inflammation. Study on human lung using [¹⁸F]FEDAC-PET is promising.

The value of the lipopolysaccharide-induced acute lung injury model in respiratory medicine

Acute lung injury/acute respiratory distress syndrome (ALI/ARDS) is a syndrome characterized by pulmonary edema and acute inflammation. Lipopolysaccharide (LPS), a major component in Gram-negative bacteria, has been used to induce ALI/ARDS. LPS-induced animal models highlight ways to explore mechanisms of multiple diseases and provide useful information on the discovery of novel biomarkers and drug targets. However, each model has its own merits and drawbacks. The goal of this article is to summarize and evaluate the results of experimental findings in LPS-induced ALI/ARDS, and the possible mechanisms and treatments elucidated. Advantages and disadvantages of such models in pulmonary research and new directions for future investigations are also discussed.

Bronchus-associated lymphoid tissue (BALT) structure and function

Bronchus-associated lymphoid tissue (BALT) is a constitutive mucosal lymphoid tissue adjacent to major airways in some mammalian species, including rats and rabbits, but not humans or mice. A related tissue, inducible BALT (iBALT), is an ectopic lymphoid tissue that is formed upon inflammation or infection in both mice and humans and can be found throughout the lung. Both BALT and iBALT acquire antigens from the airways and initiate local immune responses and maintain memory cells in the lungs. Here, we discuss the development and function of BALT and iBALT in the context of pulmonary immunity to infectious agents, tumors, and allergens as well as autoimmunity and inflammatory diseases of the lung.

Regulation of inducible BALT formation and contribution to immunity and pathology

Inducible bronchus-associated lymphoid tissue (iBALT) is an organized tertiary lymphoid structure that is not pre-programmed but develops in response to infection or under chronic inflammatory conditions. Emerging research has shown that iBALT provides a niche for T-cell priming and B-cell education to assist in the clearance of infectious agents, highlighting the prospect that iBALT may be engineered and harnessed to enhance protective immunity against respiratory pathogens. Although iBALT formation is associated with several canonical factors of secondary lymphoid organogenesis such as lymphotoxin-α and the homeostatic chemokines, CXCL13, CCL19, and CCL21, these cytokines are not mandatory for its formation, even though they influence its organization and function. Similarly, lymphoid tissue-inducer cells are not a requisite of iBALT formation. In contrast, dendritic cells are emerging as pivotal players required to form and sustain the presence of iBALT. Regulatory T cells appear to be able to attenuate the development of iBALT, although the underlying mechanisms remain ill-defined. In this review, we discuss facets unique to iBALT induction, the cellular subsets, and molecular cues that govern this process, and the contribution of this ectopic structure toward the generation of immune responses in the pulmonary compartment.