Enhanced immediate inflammatory response to Streptococcus pneumoniae in the lungs of mice with pulmonary emphysema

The role of lung macrophages in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) as a common, preventable and treatable chronic respiratory disease in clinic, gets continuous deterioration and we can't take effective intervention at present. Lung macrophages (LMs) are closely related to the occurrence and development of COPD, but the specific mechanism is not completely clear. In this review we will focus on the role of LMs and potential avenues for therapeutic targeting for LMs in COPD.

Airway Hyperresponsiveness, Inflammation, and Pulmonary Emphysema in Rodent Models Designed to Mimic Exposure to Fuel Oil-Derived Volatile Organic Compounds Encountered during an Experimental Oil Spill

BACKGROUND

Fuel oil-derived volatile organic compounds (VOCs) inhalation is associated with accidental marine spills. After the Prestige petroleum tanker sank off northern Spain in 2002 and the Deepwater Horizon oil rig catastrophe in 2009, subjects involved in environmental decontamination showed signs of ongoing or residual lung disease up to 5 y after the exposure.

OBJECTIVES

We aimed at investigating mechanisms driving persistent respiratory disease by developing an animal model of inhalational exposure to fuel oil-derived VOCs.

METHODS

Female Wistar and Brown Norway (BN) rats and C57BL mice were exposed to VOCs produced from fuel oil mimicking the Prestige spill. Exposed animals inhaled the VOCs 2 h daily, 5 d per week, for 3 wk. Airway responsiveness to methacholine (MCh) was assessed, and bronchoalveolar lavage (BAL) and lung tissues were analyzed after the exposure and following a 2-wk washout.

RESULTS

Consistent with data from human studies, both strains of rats that inhaled fuel oil-derived VOCs developed airway hyperresponsiveness that persisted after the washout period, in the absence of detectable inflammation in any lung compartment. Histopathology and quantitative morphology revealed the development of peripherally distributed pulmonary emphysema, which persisted after the washout period, associated with increased alveolar septal cell apoptosis, microvascular endothelial damage of the lung parenchyma, and inhibited expression of vascular endothelial growth factor (VEGF).

DISCUSSION

In this rat model, fuel oil VOCs inhalation elicited alveolar septal cell apoptosis, likely due to DNA damage. In turn, the development of a peculiar pulmonary emphysema pattern altered lung mechanics and caused persistent noninflammatory airway hyperresponsiveness. Such findings suggest to us that humans might also respond to VOCs through physiopathological pathways different from those chiefly involved in typical cigarette smoke-driven emphysema in chronic obstructive pulmonary disease (COPD). If so, this study could form the basis for a novel disease mechanism for lasting respiratory disease following inhalational exposure to catastrophic fuel oil spills. https://doi.org/10.1289/EHP4178.

Enhanced Anti-inflammatory Activity of Peptide-Gold Nanoparticle Hybrids upon Cigarette Smoke Extract Modification through TLR Inhibition and Autophagy Induction

Overwhelming uncontrolled inflammation is the hallmark of pathophysiological features of many acute and chronic inflammatory diseases, such as sepsis and allergy and autoimmune disorders. It is important to develop potent pharmacological interventions to effectively control such detrimental inflammatory reactions in these diseases. Recently, we have developed a special class of peptide-gold nanoparticle hybrid system that can inhibit Toll-like receptor 4 (TLR4) signal transduction pathways and decrease its downstream inflammatory responses. Herein, we serendipitously discovered that a tiny amount of cigarette smoke extract (CSE, 1%) was able to significantly enhance the inhibitory activity of the hybrids on TLR4-mediated inflammatory responses. Mechanistically, it was found that active components in CSE were able to adsorb onto the hybrids and largely increased their cellular uptake in THP-1 cell-derived macrophages. Such high cellular uptake not only enhanced the inhibition on the endosomal acidification required for TLR4 activation but also contributed to autophagy induction and subsequent antioxidant protein expression. Consequently, this duel action strengthened the anti-inflammatory activity of the hybrids in cells and in an acute lung injury (ALI) mouse model. This work aids our fundamental understanding of nanoparticles regulating the innate immune responses. It also provides a new way to design potent anti-inflammatory nanotherapeutics for inflammatory diseases such as ALI.

Animal Models of Pneumococcal pneumonia

Streptococcus pneumoniae remains the most common bacterial pathogen causing lower respiratory tract infections and is a leading cause of morbidity and mortality worldwide, especially in children and the elderly. Another important aspect related to pneumococcal infections is the persistent rate of penicillin and macrolide resistance. Therefore, animal models have been developed to better understand the pathogenesis of pneumococcal disease and test new therapeutic agents and vaccines. This narrative review will focus on the characteristics of the different animal pneumococcal pneumonia models. The assessment of the different animal models will include considerations regarding pneumococcal strains, microbiology properties, procedures used for bacterial inoculation, pathogenesis, clinical characteristics, diagnosis, treatment, and preventive approaches.

Acute Lung Injury in Response to Intratracheal Instillation of Lipopolysaccharide in an Animal Model of Emphysema Induced by Elastase

The response of lungs with emphysema to an acute lung injury (ALI) remains unclear. This study compared the lung response to intratracheal instillation of lipopolysaccharide (LPS) in rats with and without emphysema. Twenty-four Wistar rats were randomized to four groups: control group (C-G), ALI group (ALI-G), emphysema group (E-G), emphysema and ALI group (E-ALI-G). Euthanasia and the following analysis were performed 24 h after ALI induction: lung histology, bronchoalveolar lavage (BAL), mRNA expression of inflammatory mediators, and blood gas measures. The histological analysis showed that animals of ALI-G (0.55 ± 0.15) and E-ALI-G (0.69 ± 0.08) had a higher ALI score compared to C-G (0.12 ± 0.04) and E-G (0.16 ± 0.04) (p < 0.05). The analysis of each component of the score demonstrated that ALI-G and E-ALI-G had greater alveolar and interstitial neutrophil infiltration, as well as greater amount of alveolar proteinaceous debris. Comparing the two groups that received LPS, there was a trend of higher ALI in the E-ALI-G, specially due to a higher neutrophil infiltration in the alveolar spaces and a higher septal thickening. Total cell count (E-G = 3.09 ± 0.83; ALI-G = 4.45 ± 1.9; E-ALI-G = 5.9 ± 2.1; C-G = 0.73 ± 0.37 × 10⁵) and neutrophil count (E-G = 0.69 ± 0.35; ALI-G = 2.53 ± 1.09; E-ALI-G = 3.86 ± 1.4; C-G = 0.09 ± 0.07 × 10⁵) in the BAL were higher in the groups E-G, ALI-G, and E-ALI-G when compared to C-G (p < 0.05). The IL-6, TNF-α, and CXCL2 mRNA expressions were higher in the animals that received LPS (ALI-G and E-ALI-G) compared to the C-G and E-G (p < 0.05). No statistically significant difference was observed in the BAL cellularity and in the expression of inflammatory mediators between the ALI-G and the E-ALI-G. The severity of ALI in response to intratracheal instillation of LPS did not show difference in rats with and without intratracheal-induced emphysema.

Inhibition of Toll-Like Receptor Signaling as a Promising Therapy for Inflammatory Diseases: A Journey from Molecular to Nano Therapeutics

The recognition of invading pathogens and endogenous molecules from damaged tissues by toll-like receptors (TLRs) triggers protective self-defense mechanisms. However, excessive TLR activation disrupts the immune homeostasis by sustained pro-inflammatory cytokines and chemokines production and consequently contributes to the development of many inflammatory and autoimmune diseases, such as systemic lupus erythematosus (SLE), infection-associated sepsis, atherosclerosis, and asthma. Therefore, inhibitors/antagonists targeting TLR signals may be beneficial to treat these disorders. In this article, we first briefly summarize the pathophysiological role of TLRs in the inflammatory diseases. We then focus on reviewing the current knowledge in both preclinical and clinical studies of various TLR antagonists/inhibitors for the prevention and treatment of inflammatory diseases. These compounds range from conventional small molecules to therapeutic biologics and nanodevices. In particular, nanodevices are emerging as a new class of potent TLR inhibitors for their unique properties in desired bio-distribution, sustained circulation, and preferred pharmacodynamic and pharmacokinetic profiles. More interestingly, the inhibitory activity of these nanodevices can be regulated through precise nano-functionalization, making them the next generation therapeutics or “nano-drugs.” Although, significant efforts have been made in developing different kinds of new TLR inhibitors/antagonists, only limited numbers of them have undergone clinical trials, and none have been approved for clinical uses to date. Nevertheless, these findings and continuous studies of TLR inhibition highlight the pharmacological regulation of TLR signaling, especially on multiple TLR pathways, as future promising therapeutic strategy for various inflammatory and autoimmune diseases.

Emphysema induced by elastase enhances acute inflammatory pulmonary response to intraperitoneal LPS in rats

Abnormalities in lungs caused by emphysema might alter their response to sepsis and the occurrence of acute lung injury (ALI). This study compared the extension of ALI in response to intraperitoneal lipopolysaccharide (LPS) injection in Wistar rats with and without emphysema induced by elastase. Adult male Wistar rats were randomized into four groups: control, emphysema without sepsis, normal lung with sepsis and emphysema with sepsis. Sepsis was induced, and 24 h later the rats were euthanised. The following analysis was performed: blood gas measurements, bronchoalveolar lavage (BAL), lung permeability and histology. Animals that received LPS showed significant increase in a lung injury scoring system, inflammatory cells in bronchoalveolar lavage (BAL) and IL-6, TNF-α and CXCL2 mRNA expression in lung tissue. Animals with emphysema and sepsis showed increased alveolocapillary membrane permeability, demonstrated by higher BAL/serum albumin ratio. In conclusion, the presence of emphysema induced by elastase increases the inflammatory response in the lungs to a systemic stimulus, represented in this model by the intraperitoneal injection of LPS.

Role of chemokine C-C motif ligand-1 in acute and chronic pulmonary inflammations

Background

Chemokine C-C motif ligand 1 (CCL1) accumulates C-C motif chemokine receptor 8 positive leukocytes to the inflammatory sites. Single-nucleotide polymorphisms in the chemokine CCL1 gene are associated with exacerbation of chronic obstructive lung disease. However, it is unclear whether CCL1 has immunomodulatory functions during pulmonary inflammation. This study aimed to elucidate this issue using newly generated transgenic mice that express CCL1 in the lungs (SPC-CCL1 mice).

Methods

To evaluate the phenotypes of these mice, lung section and bronchoalveolar lavage (BAL) fluid analyses were performed. We intratracheally administered lipopolysaccharide (LPS) or Mycobacterium bovis as a model of acute or chronic lung inflammation, respectively.

Results

No histological differences were observed between lung tissue from SPC-CCL1 Tg and wild-type mice in the resting condition and after LPS administration. In the resting condition, the total BAL cell concentration was lower in SPC-CCL1 Tg mice than in wild-type mice (P = 0.0097). Flow cytometric analyses showed that SPC-CCL1 Tg mice had fewer F4/80-positive cells than wild-type mice (P = 0.0278). After intratracheal LPS administration, CCL1 overexpression changed neither the total numbers nor population of BAL cells. After mycobacterial administration, pulmonary granuloma formation was significantly enhanced. The degree of Immunostaining for endoplasmic reticulum to nucleus signaling 1, a molecule associated with granuloma formation and endoplasmic reticulum stress, was significantly enhanced in the granuloma regions of SPC-CCL1 mice treated with Mycobacterium, compared to those of wild-type mice.

Conclusions

CCL1 overexpression in the lungs did not change the acute inflammatory response induced by LPS, but enhanced granuloma formation after mycobacterial treatment, possibly through enhancing endoplasmic reticulum stress.

Glucocorticoid-Augmented Efferocytosis Inhibits Pulmonary Pneumococcal Clearance in Mice by Reducing Alveolar Macrophage Bactericidal Function

Inhaled corticosteroids (ICS) increase community-acquired pneumonia (CAP) incidence in patients with chronic obstructive pulmonary disease (COPD) by unknown mechanisms. Apoptosis is increased in the lungs of COPD patients. Uptake of apoptotic cells (ACs) ("efferocytosis") by alveolar macrophages (AMøs) reduces their ability to combat microbes, including Streptococcus pneumoniae, the most common cause of CAP in COPD patients. Having shown that ICS significantly increase AMø efferocytosis, we hypothesized that this process, termed glucocorticoid-augmented efferocytosis, might explain the association of CAP with ICS therapy in COPD. To test this hypothesis, we studied the effects of fluticasone, AC, or both on AMøs of C57BL/6 mice in vitro and in an established model of pneumococcal pneumonia. Fluticasone plus AC significantly reduced TLR4-stimulated AMø IL-12 production, relative to either treatment alone, and decreased TNF-α, CCL3, CCL5, and keratinocyte-derived chemoattractant/CXCL1, relative to AC. Mice treated with fluticasone plus AC before infection with viable pneumococci developed significantly more lung CFUs at 48 h. However, none of the pretreatments altered inflammatory cell recruitment to the lungs at 48 h postinfection, and fluticasone plus AC less markedly reduced in vitro mediator production to heat-killed pneumococci. Fluticasone plus AC significantly reduced in vitro AMø killing of pneumococci, relative to other conditions, in part by delaying phagolysosome acidification without affecting production of reactive oxygen or nitrogen species. These results support glucocorticoid-augmented efferocytosis as a potential explanation for the epidemiological association of ICS therapy of COPD patients with increased risk for CAP, and establish murine experimental models to dissect underlying molecular mechanisms.

Inhibition of elastase-pulmonary emphysema in dominant-negative MafB transgenic mice

Alveolar macrophages (AMs) play important roles in the pathogenesis of chronic obstructive pulmonary disease (COPD). We previously demonstrated upregulation of the transcription factor MafB in AMs of mice exposed to cigarette smoke. The aim of this study was to elucidate the roles of MafB in the development of pulmonary emphysema. Porcine pancreatic elastase was administered to wild-type (WT) and dominant-negative (DN)-MafB transgenic (Tg) mice in which MafB activity was suppressed only in macrophages. We measured the mean linear intercept and conducted cell differential analysis of bronchoalveolar lavage (BAL) cells, surface marker analysis using flow cytometry, and immunohistochemical staining using antibodies to matrix metalloproteinase (MMP)-9 and MMP-12. Airspace enlargement of the lungs was suppressed significantly in elastase-treated DN-MafB Tg mice compared with treated WT mice. AMs with projected pseudopods were decreased in DN-MafB Tg mice. The number of cells intermediately positive for F4/80 and weakly or intermediately positive for CD11b, which are considered cell subsets of matured AMs, decreased in the BAL of DN-MafB Tg mice. Furthermore, MMP-9 and -12 were significantly downregulated in BAL cells of DN-MafB Tg mice. Because MMPs exacerbate emphysema, MafB may be involved in pulmonary emphysema development through altered maturation of macrophages and MMP expression.

Dual role of Toll-like receptors in asthma and chronic obstructive pulmonary disease

During the last decade, significant research has been focused on Toll-like receptors (TLRs) in the pathogenesis of airway diseases. TLRs are pattern recognition receptors that play pivotal roles in the detection of and response to pathogens. Because of the involvement of TLRs in innate and adaptive immunity, these receptors are currently being exploited as possible targets for drug development. Asthma and chronic obstructive pulmonary disease (COPD) are chronic inflammatory airway diseases in which innate and adaptive immunity play an important role. To date, asthma is the most common chronic disease in children aged 5 years and older. COPD is prevalent amongst the elderly and is currently the fifth-leading cause of death worldwide with still-growing prevalence. Both of these inflammatory diseases result in shortness of breath, which is treated, often ineffectively, with bronchodilators and glucocorticosteroids. Symptomatic treatment approaches are similar for both diseases; however, the underlying immunological mechanisms differ greatly. There is a clear need for improved treatment specific for asthma and for COPD. This review provides an update on the role of TLRs in asthma and in COPD and discusses the merits and difficulties of targeting these proteins as novel treatment strategies for airway diseases. TLR agonist, TLR adjuvant, and TLR antagonist therapies could all be argued to be effective in airway disease management. Because of a possible dual role of TLRs in airway diseases with shared symptoms and risk factors but different immunological mechanisms, caution should be taken while designing pulmonary TLR-based therapies.

Tumor necrosis factor alpha in experimental empyema thoracis

PURPOSE

To determine serum and pleural concentrations of tumor necrosis factor alpha (TNF-α) in an experimental model of empyema induced by intrapleural inoculation of Staphylococcus aureus or Streptococcus pneumoniae.

METHODS

Wistar rats were inoculated with S. aureus (SA group, 17 animals) or S. pneumoniae (SP group, 30 animals). The presence of free fluid or pus in the pleural space was investigated. TNF-α levels >150 pg/ml (minimum detection limit) were determined in pleural fluid and blood. Histopathological examination of pleural tissue was performed to determine the severity of infection.

RESULTS

Serum TNF-α was >150 pg/ml in nine SA versus 10 SP rats. In pleural fluid, TNF-α was >150 pg/ml in 11 SA versus 19 SP rats. Pleural and serum TNF-α concentrations were significantly different in the SP group (P = 0.035), but not in the SA group (P = 0.727). Pleural TNF-α was similar in both groups (P = 0.92), but serum TNF-α was significantly higher in SA (P = 0.03). Out of 17 SA animals, 1 (5.8%) did not develop empyema, versus 4 (13.3%) out of 30 SP animals. A mild inflammatory response was predominant in both groups, but the inflammatory process was significantly more severe in SP (P = 0.012). However, TNF-α levels were not associated with severity of the inflammatory response.

CONCLUSIONS

We describe a simple and effective rat model of empyema. TNF-α levels above 150 pg/ml in the pleural fluid are useful to confirm empyema, but cannot predict the severity of the inflammatory response. TNF-α levels below 150 pg/ml are useful to rule out empyema.

Inflammatory mechanisms and treatment of obstructive airway diseases with neutrophilic bronchitis

Obstructive airway diseases such as asthma and chronic obstructive pulmonary disease (COPD) are major global health issues. Although considered as distinct diseases, airway inflammation is a key underlying pathophysiological process in asthma, COPD and bronchiectasis. Persistent neutrophilic airway inflammation (neutrophilic bronchitis) occurs with innate immune activation and is a feature of each of these airway diseases. Little is known about the mechanisms leading to neutrophilic bronchitis and few treatments are effective in reducing neutrophil accumulation in the airways. There is a similar pattern of inflammatory mediator release and toll like receptor 2 expression in asthma, COPD and bronchiectasis. We propose the existence of an active amplification mechanism, an effector arm of the innate immune system, involving toll like receptor 2, operating in persistent neutrophilic bronchitis. Neutrophil persistence in the airways can occur through a number of mechanisms such as impaired apoptosis, efferocytosis and mucus hypersecretion, all of which are impaired in airways disease. Impairment of neutrophil clearance results in a reduced ability to respond to bacterial infection. Persistent activation of airway neutrophils may result in the persistent activation of the innate immune system resulting in further airway insult. Current therapies are limited for the treatment of neutrophilic bronchitis; possible treatments being investigated include theophylline, statins, antagonists of pro-inflammatory cytokines and macrolide antibiotics. Macrolides have shown great promise in their ability to reduce airway inflammation, and can reduce airway neutrophils, levels of CXCL8 and neutrophil proteases in the airways. Studies also show improvements in quality of life and exacerbation rates in airways diseases.

Immune homeostasis in the respiratory tract and its impact on heterologous infection

Innate immunity at mucosal surfaces requires additional restraint to prevent inflammation to innocuous antigens or commensal microorganisms. The threshold above which airway macrophages become activated is raised by site-specific factors including the receptors for transforming growth factor beta, interleukin 10 and CD200; the ligands for which are produced by, or expressed on, respiratory epithelium. We discuss such site-specific regulation and how this is continually altered by prior infections. Resetting of innate reactivity represents a strategy for limiting excessive inflammation, but in some may pre-dispose to secondary bacterial pneumonia.