Differential regulation of lung homeostasis and silicosis by the TAM receptors MerTk and Axl.

Introduction: TAM receptor-mediated efferocytosis plays an important function in immune regulation and may contribute to antigen tolerance in the lungs, a site with continuous cellular turnover and generation of apoptotic cells. Some studies have identified failures in efferocytosis as a common driver of inflammation and tissue destruction in lung diseases. Our study is the first to characterize the in vivo function of the TAM receptors, Axl and MerTk, in the innate immune cell compartment, cytokine and chemokine production, as well as the alveolar macrophage (AM) phenotype in different settings in the airways and lung parenchyma. Methods: We employed MerTk and Axl defective mice to induce acute silicosis by a single exposure to crystalline silica particles (20 mg/50 µL). Although both mRNA levels of Axl and MerTk receptors were constitutively expressed by lung cells and isolated AMs, we found that MerTk was critical for maintaining lung homeostasis, whereas Axl played a role in the regulation of silica-induced inflammation. Our findings imply that MerTk and Axl differently modulated inflammatory tone via AM and neutrophil recruitment, phenotype and function by flow cytometry, and TGF-ß and CXCL1 protein levels, respectively. Finally, Axl expression was upregulated in both MerTk-/- and WT AMs, confirming its importance during inflammation. Conclusion: This study provides strong evidence that MerTk and Axl are specialized to orchestrate apoptotic cell clearance across different circumstances and may have important implications for the understanding of pulmonary inflammatory disorders as well as for the development of new approaches to therapy.

L-carnitine reduces acute lung injury via mitochondria modulation and inflammation control in pulmonary macrophages.

Acute lung injury (ALI) or acute respiratory distress syndrome (ARDS) is a critical respiratory syndrome with limited effective interventions. Lung macrophages play a critical role in the pathogenesis of abnormal inflammatory response in the syndrome. Recently, impaired fatty acid oxidation (FAO), one of the key lipid metabolic signalings, was found to participate in the onset and development of various lung diseases, including ALI/ARDS. Lipid/fatty acid contents within mouse lungs were quantified using the Oil Red O staining. The protective effect of FAO activator L-carnitine (Lca, 50, 500, or 5 mg/mL) was evaluated by cell counting kit 8 (CCK-8) assay, real-time quantitative PCR (qPCR), ELISA, immunoblotting, fluorescence imaging, and fluorescence plate reader detection in lipopolysaccharide (LPS) (100 ng/mL)-stimulated THP-1-derived macrophages. The in vivo efficacy of Lca (300 mg/kg) was determined in a 10 mg/kg LPS-induced ALI mouse model. We found for the first time that lipid accumulation in pulmonary macrophages was significantly increased in a classical ALI murine model, which indicated disrupted FAO induced by LPS. Lca showed potent anti-inflammatory and antioxidative effects on THP-1 derived macrophages upon LPS stimulation. Mechanistically, Lca was able to maintain FAO, mitochondrial activity, and ameliorate mitochondrial dynamics. In the LPS-induced ALI mouse model, we further discovered that Lca inhibited neutrophilic inflammation and decreased diffuse damage, which might be due to the preservation of mitochondrial homeostasis. These results broadened our understanding of ALI/ARDS pathogenesis and provided a promising drug candidate for this syndrome.

Absence of CCR2 Promotes Proliferation of Alveolar Macrophages That Control Lung Inflammation in Acute Respiratory Distress Syndrome in Mice.

Acute respiratory distress syndrome (ARDS) consists of uncontrolled inflammation that causes hypoxemia and reduced lung compliance. Since it is a complex process, not all details have been elucidated yet. In a well-controlled experimental murine model of lipopolysaccharide (LPS)-induced ARDS, the activity and viability of macrophages and neutrophils dictate the beginning and end phases of lung inflammation. C-C chemokine receptor type 2 (CCR2) is a critical chemokine receptor that mediates monocyte/macrophage activation and recruitment to the tissues. Here, we used CCR2-deficient mice to explore mechanisms that control lung inflammation in LPS-induced ARDS. CCR2-/- mice presented higher total numbers of pulmonary leukocytes at the peak of inflammation as compared to CCR2+/+ mice, mainly by enhanced influx of neutrophils, whereas we observed two to six-fold lower monocyte or interstitial macrophage numbers in the CCR2-/-. Nevertheless, the time needed to control the inflammation was comparable between CCR2+/+ and CCR2-/-. Interestingly, CCR2-/- mice presented higher numbers and increased proliferative rates of alveolar macrophages from day 3, with a more pronounced M2 profile, associated with transforming growth factor (TGF)-ß and C-C chemokine ligand (CCL)22 production, decreased inducible nitric oxide synthase (Nos2), interleukin (IL)-1ß and IL-12b mRNA expression and increased mannose receptor type 1 (Mrc1) mRNA and CD206 protein expression. Depletion of alveolar macrophages significantly delayed recovery from the inflammatory insult. Thus, our work shows that the lower number of infiltrating monocytes in CCR2-/- is partially compensated by increased proliferation of resident alveolar macrophages during the inflammation control of experimental ARDS.

Interplay between mucus mobility and alveolar macrophage targeting of surface-modified liposomes.

Alveolar macrophages play a crucial role in the initiation and resolution of the immune response in the lungs. Pro-inflammatory M1 alveolar macrophages are an interesting target for treating inflammatory and infectious pulmonary diseases. One commune targeting strategy is to use nanoparticles conjugated with hyaluronic acid, which interact with CD44 overexpressed on the membrane of those cells. Unfortunately, this coating strategy may be countered by the presence on the surface of the nanoparticles of a poly(ethylene glycol) corona employed to improve nanoparticles' diffusion in the lung mucus. This study aims to measure this phenomenon by comparing the behavior in a murine lung inflammation model of three liposomal platforms designed to represent different poly(ethylene glycol) and hyaluronic acid densities (Liposome-PEG, Liposome-PEG-HA and Liposome-HA). In this work, the liposomes were obtained by a one-step ethanol injection method. Their interaction with mucin and targeting ability toward pro-inflammatory macrophages were then investigated in vitro and in vivo in a LPS model of lung inflammation. In vitro, poly(ethylene glycol) free HA-liposomes display a superior targeting efficiency toward M1 macrophages, while the addition of poly(ethylene glycol) induces better mucus mobility. Interestingly in vivo studies revealed that the three liposomes showed distinct cell specificity with alveolar macrophages demonstrating an avidity for poly(ethylene glycol) free HA-liposomes, while neutrophils favored PEGylated liposomes exempt of HA. Those results could be explained by the presence of two forces exercising a balance between mucus penetration and receptor targeting. This study corroborates the importance of considering the site of action and the targeted cells when designing nanoparticles to treat lung diseases.

Effect of mycobacterial proteins that target mitochondria on the alveolar macrophages activation during Mycobacterium tuberculosis infection.

Purpose of the study: During the early and progressive (late) stages of murine experimental pulmonary tuberculosis, the differential activation of macrophages contributes to disease development by controlling bacterial growth and immune regulation. Mycobacterial proteins P27 and PE_PGRS33 can target the mitochondria of macrophages. This study aims to evaluate the effect of both proteins on macrophage activation during mycobacterial infection. Materials and methods: We assess both proteins for mitochondrial oxygen consumption, and morphological changes, as well as bactericide activity, production of metabolites, cytokines, and activation markers in infected MQs. The cell line MH-S was used for all the experiments. Results: We show that P27 and PE_PGRS33 proteins modified mitochondrial dynamics, oxygen consumption, bacilli growth, cytokine production, and some genes that contribute to macrophage alternative activation and mycobacterial intracellular survival. Conclusions: Our findings showed that these bacterial proteins partially contribute to promoting M2 differentiation by altering mitochondrial metabolic activity.

PCV2 infection aggravates OTA-induced immunotoxicity in vivo and in vitro.

Ochratoxin A (OTA), frequently existing in the food and feeds, could induce immunotoxicity. Porcine circovirus type 2 (PCV2), as a primary causative agent of porcine circovirus-associated disease, also could induce immunosuppression. However, it is still unknown whether PCV2 infection impacts OTA-induced immunotoxicity. The pigs and porcine alveolar macrophages (PAMs) were used as the model in the present experiment. The results in vivo indicated that PCV2 infection exacerbated OTA-induced immunotoxicity, NF-κB p65 phosphorylation, and TLR4 and MyD88 mRNA and protein expression in spleen. The results in vitro showed that OTA at 7.0 and 9.0 µM decreased cell viability and increased LDH release of PAMs without PCV2 infection. However, with PCV2 infection, OTA at 5.0, 7.0 and 9.0 µM significantly decreased cell viability and increased LDH release compared with absence of PCV2 infection. In addition, OTA at 5.0 and 7.0 µM significantly increased Annexin V/PI-positive rate, apoptosis of nuclear, γ-H2AX foci, IL-1α and TNF-α expression in PAMs with PCV2 infection compared with absence of PCV2 infection. In addition, PCV2 infection enhanced OTA-induced TLR4 and MyD88 mRNA and protein expression and NF-κB p65 phosphorylation. Knockdown of TLR4 alleviated the exacerbating effects of PCV2 infection on OTA-induced cytotoxicity, apoptosis and DNA damage in PAMs. These results indicated that PCV2 infection aggravated OTA-induced immunotoxicity and reduced the dose of OTA-induced immunotoxicity via TLR4/NF-κB p65 signaling pathway, which could provide basis for establishing limits for OTA.

Comparative effects of dexmedetomidine and propofol on brain and lung damage in experimental acute ischemic stroke.

Acute ischemic stroke is associated with pulmonary complications, and often dexmedetomidine and propofol are used to decrease cerebral metabolic rate. However, it is unknown the immunomodulatory actions of dexmedetomidine and propofol on brain and lungs during acute ischemic stroke. The effects of dexmedetomidine and propofol were compared on perilesional brain tissue and lung damage after acute ischemic stroke in rats. Further, the mean amount of both sedatives was directly evaluated on alveolar macrophages and lung endothelial cells primarily extracted 24-h after acute ischemic stroke. In twenty-five Wistar rats, ischemic stroke was induced and after 24-h treated with sodium thiopental (STROKE), dexmedetomidine and propofol. Dexmedetomidine, compared to STROKE, reduced diffuse alveolar damage score [median(interquartile range); 12(7.8-15.3) vs. 19.5(18-24), p = 0.007)], bronchoconstriction index [2.28(2.08-2.36) vs. 2.64(2.53-2.77), p = 0.006], and TNF-α expression (p = 0.0003), while propofol increased VCAM-1 expression compared to STROKE (p = 0.0004). In perilesional brain tissue, dexmedetomidine, compared to STROKE, decreased TNF-α (p = 0.010), while propofol increased VCAM-1 compared to STROKE (p = 0.024). In alveolar macrophages and endothelial cells, dexmedetomidine decreased IL-6 and IL-1ß compared to STROKE (p = 0.002, and p = 0.040, respectively), and reduced IL-1ß compared to propofol (p = 0.014). Dexmedetomidine, but not propofol, induced brain and lung protection in experimental acute ischemic stroke.

Effects of propofol and its formulation components on macrophages and neutrophils in obese and lean animals.

We hypothesized whether propofol or active propofol component (2,6-diisopropylphenol [DIPPH] and lipid excipient [LIP-EXC]) separately may alter inflammatory mediators expressed by macrophages and neutrophils in lean and obese rats. Male Wistar rats (n = 10) were randomly assigned to receive a standard (lean) or obesity-inducing diet (obese) for 12 weeks. Animals were euthanized, and alveolar macrophages and neutrophils from lean and obese animals were exposed to propofol (50 µM), active propofol component (50 µM, 2,6-DIPPH), and lipid excipient (soybean oil, purified egg phospholipid, and glycerol) for 1 h. The primary outcome was IL-6 expression after propofol and its components exposure by alveolar macrophages extracted from bronchoalveolar lavage fluid. The secondary outcomes were the production of mediators released by macrophages from adipose tissue, and neutrophils from lung and adipose tissues, and neutrophil migration. IL-6 increased after the exposure to both propofol (median [interquartile range] 4.14[1.95-5.20]; p = .04) and its active component (2,6-DIPPH) (4.09[1.67-5.91]; p = .04) in alveolar macrophages from obese animals. However, only 2,6-DIPPH increased IL-10 expression (7.59[6.28-12.95]; p = .001) in adipose tissue-derived macrophages. Additionally, 2,6-DIPPH increased C-X-C chemokine receptor 2 and 4 (CXCR2 and CXCR4, respectively) in lung (10.08[8.23-29.01]; p = .02; 1.55[1.49-3.43]; p = .02) and adipose tissues (8.78[4.15-11.57]; p = .03; 2.86[2.17-3.71]; p = .01), as well as improved lung-derived neutrophil migration (28.00[-3.42 to 45.07]; p = .001). In obesity, the active component of propofol affected both the M1 and M2 markers as well as neutrophils in both alveolar and adipose tissue cells, suggesting that lipid excipient may hinder the effects of active propofol.

Pulmonary macrophages and their different roles in health and disease.

Macrophages are a heterogeneous population of myeloid cells with phenotype and function modulated according to the microenvironment in which they are found. The lung resident macrophages known as Alveolar Macrophages (AM) and Interstitial Macrophages (IM) are localized in two different compartments. During lung homeostasis, macrophages can remove inhaled particulates, cellular debris and contribute to some metabolic processes. Macrophages may assume a pro-inflammatory phenotype after being classically activated (M1) or anti-inflammatory when being alternatively activated (M2). M1 and M2 have different transcription profiles and act by eliminating bacteria, viruses and fungi from the host or repairing the damage triggered by inflammation, respectively. Nevertheless, macrophages also may contribute to lung damage during persistent inflammation or continuous exposure to antigens. In this review, we discuss the origin and function of pulmonary macrophages in the context of homeostasis, infectious and non-infectious lung diseases.

Alveolar Macrophages Inherently Express Programmed Death-1 Ligand 1 for Optimal Protective Immunity and Tolerance.

Macrophages play a central role in lung physiology and pathology. In this study, we show in mice that alveolar macrophages (AMs), unlike other macrophage types (interstitial, peritoneal, and splenic macrophages), constitutively express programmed death-1 ligand 1 (PD-L1), thereby possessing a superior phagocytic ability and the capacity to repress CTLs by cis- and trans-interacting with CD80 and programmed death-1 (PD-1), respectively. This extraordinary ability of AMs assures optimal protective immunity and tolerance within the lung. These findings uncover a unique characteristic of AMs and an innate immune function of PD-L1 and CD80 and therefore help in the understanding of lung physiology, diseases, and PD-L1/PD-1-based immunotherapy.

Exploring the Toxicity, Lung Distribution, and Cellular Uptake of Rifampicin and Ascorbic Acid-Loaded Alginate Nanoparticles as Therapeutic Treatment of Lung Intracellular Infections.

Nanotechnology is a very promising technological tool to combat health problems associated with the loss of effectiveness of currently used antibiotics. Previously, we developed a formulation consisting of a chitosan and tween 80-decorated alginate nanocarrier that encapsulates rifampicin and the antioxidant ascorbic acid (RIF/ASC), intended for the treatment of respiratory intracellular infections. Here, we investigated the effects of RIF/ASC-loaded NPs on the respiratory mucus and the pulmonary surfactant. In addition, we evaluated their cytotoxicity for lung cells in vitro, and their biodistribution on rat lungs in vivo after their intratracheal administration. Findings herein demonstrated that RIF/ASC-loaded NPs display a favorable lung biocompatibility profile and a uniform distribution throughout lung lobules. RIF/ASC-loaded NPs were mainly uptaken by lung macrophages, their primary target. In summary, findings show that our novel designed RIF/ASC NPs could be a suitable system for antibiotic lung administration with promising perspectives for the treatment of pulmonary intracellular infections.

TNF-mediated alveolar macrophage necroptosis drives disease pathogenesis during respiratory syncytial virus infection.

Respiratory syncytial virus (RSV) is the major cause of acute bronchiolitis in infants under 2 years old. Necroptosis has been implicated in the outcomes of respiratory virus infections. We report that RSV infection triggers necroptosis in primary mouse macrophages and human monocytes in a RIPK1-, RIPK3- and MLKL-dependent manner. Moreover, necroptosis pathways are harmful to RSV clearance from alveolar macrophages. Additionally, Ripk3-/- mice were protected from RSV-induced weight loss and presented with reduced viral loads in the lungs.Alveolar macrophage depletion also protected mice from weight loss and decreased lung RSV virus load. Importantly, alveolar macrophage depletion abolished the upregulation of Ripk3 and Mlkl gene expression induced by RSV infection in the lung tissue.Autocrine tumor necrosis factor (TNF)-mediated RSV-triggered macrophage necroptosis and necroptosis pathways were also involved in TNF secretion even when macrophages were committed to cell death, which can worsen lung injury during RSV infection. In line, Tnfr1-/- mice had a marked decrease in Ripk3 and Mlkl gene expression and a sharp reduction in the numbers of necrotic alveolar macrophages in the lungs. Finally, we provide evidence that elevated nasal levels of TNF are associated with disease severity in infants with RSV bronchiolitis.We propose that targeting TNF and/or the necroptotic machinery may be valuable therapeutic approaches to reduce the respiratory morbidity caused by RSV infection in young children.

Alveolar Macrophages Are Key Players in the Modulation of the Respiratory Antiviral Immunity Induced by Orally Administered Lacticaseibacillus rhamnosus CRL1505.

The oral administration of Lacticaseibacillus rhamnosus CRL1505 differentially modulates the respiratory innate antiviral immune response triggered by Toll-like receptor 3 (TLR3) activation in infant mice, improving the resistance to Respiratory Syncytial Virus (RSV) infection. In this work, by using macrophages depletion experiments and a detailed study of their production of cytokines and antiviral factors we clearly demonstrated the key role of this immune cell population in the improvement of both viral elimination and the protection against lung tissue damage induced by the CRL1505 strain. Orally administered L. rhamnosus CRL1505 activated alveolar macrophages and enhanced their ability to produce type I interferons (IFNs) and IFN-γ in response to RSV infection. Moreover, an increased expression of IFNAR1, Mx2, OAS1, OAS2, RNAseL, and IFITM3 was observed in alveolar macrophages after the oral treatment with L. rhamnosus CRL1505, which was consistent with the enhanced RSV clearance. The depletion of alveolar macrophages by the time of L. rhamnosus CRL1505 administration abolished the ability of infant mice to produce increased levels of IL-10 in response to RSV infection. However, no improvement in IL-10 production was observed when primary cultures of alveolar macrophages obtained from CRL1505-treated mice were analyzed. Of note, alveolar macrophages from the CRL1505 group had an increased production of IL-6 and IL-27 suggesting that these cells may play an important role in limiting inflammation and protecting lung function during RSV infection, by increasing the maturation and activation of Treg cells and their subsequent production of IL-10. In addition, we provided evidence of the important role of CD4+ cells and IFN-γ in the activation of alveolar macrophages highlighting a putative pathway through which the intestinal and respiratory mucosa are communicated under the influence of L. rhamnosus CRL1505.

Role of Mitochondria in the Redox Signaling Network and Its Outcomes in High Impact Inflammatory Syndromes.

Inflammation is associated with the release of soluble mediators that drive cellular activation and migration of inflammatory leukocytes to the site of injury, together with endothelial expression of adhesion molecules, and increased vascular permeability. It is a stepwise tightly regulated process that has been evolved to cope with a wide range of different inflammatory stimuli. However, under certain physiopathological conditions, the inflammatory response overwhelms local regulatory mechanisms and leads to systemic inflammation that, in turn, might affect metabolism in distant tissues and organs. In this sense, as mitochondria are able to perceive signals of inflammation is one of the first organelles to be affected by a dysregulation in the systemic inflammatory response, it has been associated with the progression of the physiopathological mechanisms. Mitochondria are also an important source of ROS (reactive oxygen species) within most mammalian cells and are therefore highly involved in oxidative stress. ROS production might contribute to mitochondrial damage in a range of pathologies and is also important in a complex redox signaling network from the organelle to the rest of the cell. Therefore, a role for ROS generated by mitochondria in regulating inflammatory signaling was postulated and mitochondria have been implicated in multiple aspects of the inflammatory response. An inflammatory condition that affects mitochondrial function in different organs is the exposure to air particulate matter (PM). Both after acute and chronic pollutants exposure, PM uptake by alveolar macrophages have been described to induce local cell activation and recruitment, cytokine release, and pulmonary inflammation. Afterwards, inflammatory mediators have been shown to be able to reach the bloodstream and induce a systemic response that affects metabolism in distant organs different from the lung. In this proinflammatory environment, impaired mitochondrial function that leads to bioenergetic dysfunction and enhanced production of oxidants have been shown to affect tissue homeostasis and organ function. In the present review, we aim to discuss the latest insights into the cellular and molecular mechanisms that link systemic inflammation and mitochondrial dysfunction in different organs, taking the exposure to air pollutants as a case model.

NADPH oxidase and mitochondria are relevant sources of superoxide anion in the oxinflammatory response of macrophages exposed to airborne particulate matter.

Exposure to ambient air particulate matter (PM) is associated with increased cardiorespiratory morbidity and mortality. In this context, alveolar macrophages exhibit proinflammatory and oxidative responses as a result of the clearance of particles, thus contributing to lung injury. However, the mechanisms linking these pathways are not completely clarified. Therefore, the oxinflammation phenomenon was studied in RAW 264.7 macrophages exposed to Residual Oil Fly Ash (ROFA), a PM surrogate rich in transition metals. While cell viability was not compromised under the experimental conditions, a proinflammatory phenotype was observed in cells incubated with ROFA 100 µg/mL, characterized by increased levels of TNF-α and NO production, together with PM uptake. This inflammatory response seems to precede alterations in redox metabolism, characterized by augmented levels of H2O2, diminished GSH/GSSG ratio, and increased SOD activity. This scenario resulted in increased oxidative damage to phospholipids. Moreover, alterations in mitochondrial respiration were observed following ROFA incubation, such as diminished coupling efficiency and spare respiratory capacity, together with augmented proton leak. These findings were accompanied by a decrease in mitochondrial membrane potential. Finally, NADPH oxidase (NOX) and mitochondria were identified as the main sources of superoxide anion () in our model. These results indicate that PM exposure induces direct activation of macrophages, leading to inflammation and increased reactive oxygen species production through NOX and mitochondria, which impairs antioxidant defense and may cause mitochondrial dysfunction.

Interplay between alveolar epithelial and dendritic cells and Mycobacterium tuberculosis.

The innate response plays a crucial role in the protection against tuberculosis development. Moreover, the initial steps that drive the host-pathogen interaction following Mycobacterium tuberculosis infection are critical for the development of adaptive immune response. As alveolar Mϕs, airway epithelial cells, and dendritic cells can sense the presence of M. tuberculosis and are the first infected cells. These cells secrete mediators, which generate inflammatory signals that drive the differentiation and activation of the T lymphocytes necessary to clear the infection. Throughout this review article, we addressed the interaction between epithelial cells and M. tuberculosis, as well as the interaction between dendritic cells and M. tuberculosis. The understanding of the mechanisms that modulate those interactions is critical to have a complete view of the onset of an infection and may be useful for the development of dendritic cell-based vaccine or immunotherapies.

The Role of Alveolar Macrophages in the Improved Protection against Respiratory Syncytial Virus and Pneumococcal Superinfection Induced by the Peptidoglycan of Lactobacillus rhamnosus CRL1505.

The nasal priming with nonviable Lactobacillus rhamnosus CRL1505 (NV1505) or its purified peptidoglycan (PG1505) differentially modulates the respiratory innate immune response in infant mice, improving their resistance to primary respiratory syncytial virus (RSV) infection and secondary pneumococcal pneumonia. In association with the protection against RSV-pneumococcal superinfection, it was found that NV1505 or PG1505 significantly enhance the numbers of CD11c+SiglecF+ alveolar macrophages (AMs) producing interferon (IFN)-ß. In this work, we aimed to further advance in the characterization of the beneficial effects of NV1505 and PG1505 in the context of a respiratory superinfection by evaluating whether their immunomodulatory properties are dependent on AM functions. Macrophage depletion experiments and a detailed study of their production of cytokines and antiviral factors clearly demonstrated the key role of this immune cell population in the improvement of both the reduction of pathogens loads and the protection against lung tissue damage induced by the immunobiotic CRL1505 strain. Studies at basal conditions during primary RSV or S. pneumoniae infections, as well as during secondary pneumococcal pneumonia, brought the following five notable findings regarding the immunomodulatory effects of NV1505 and PG1505: (a) AMs play a key role in the beneficial modulation of the respiratory innate immune response and protection against RSV infection, (b) AMs are necessary for improved protection against primary and secondary pneumococcal pneumonia, (c) the generation of activated/trained AMs would be essential for the enhanced protection against respiratory pathogens, (d) other immune and nonimmune cell populations in the respiratory tract may contribute to the protection against bacterial and viral infections, and (e) the immunomodulatory properties of NV1505 and PG1505 are strain-specific. These findings significantly improve our knowledge about the immunological mechanisms involved in the modulation of respiratory immunity induced by beneficial microbes.

Contribution of NKT cells to the immune response and pathogenesis triggered by respiratory viruses.

Human respiratory syncytial virus (hRSV) and human metapneumovirus (hMPV) cause acute respiratory tract infections in children worldwide. Natural killer T (NKT) cells are unconventional T lymphocytes, and their TCRs recognize glycolipids bound to the MHC-I-like molecule, CD1d. These cells modulate the inflammatory response in viral infections. Here, we evaluated the contribution of NKT cells in both hRSV and hMPV infections. A significant decrease in the number of neutrophils, eosinophils, and CD103+DCs infiltrating to the lungs, as well as an increased production of IFN-γ, were observed upon hRSV-infection in CD1d-deficient BALB/c mice, as compared to wild-type control mice. However, this effect was not observed in the CD1d-deficient BALB/c group, upon infection with hMPV. Importantly, reduced expression of CD1d in CD11b+ DCs and epithelial cells was found in hRSV -but not hMPV-infected mice. Besides, a reduction in the expression of CD1d in alveolar macrophages of lungs from hRSV- and hMPV-infected mice was found. Such reduction of CD1d expression interfered with NKT cells activation, and consequently IL-2 secretion, as characterized by in vitro experiments for both hRSV and hMPV infections. Furthermore, increased numbers of NKT cells recruited to the lungs in response to hRSV- but not hMPV-infection was detected, resulting in a reduction in the expression of IFN-γ and IL-2 by these cells. In conclusion, both hRSV and hMPV might be differently impairing NKT cells function and contributing to the immune response triggered by these viruses.

Human Alveolar and Splenic Macrophage Populations Display a Distinct Transcriptomic Response to Infection With Mycobacterium tuberculosis.

Mycobacterium tuberculosis (Mtb) infects alveolar macrophages (AMs), causing pulmonary tuberculosis (PTB), the most common form of the disease. Less frequently, Mtb is disseminated to many other organs and tissues, resulting in different extrapulmonary forms of TB. Nevertheless, very few studies have addressed the global mRNA response of human AMs, particularly from humans with the active form of the disease. Strikingly, almost no studies have addressed the response of human extrapulmonary macrophages to Mtb infection. In this pilot study, using microarray technology, we examined the transcriptomic ex vivo response of AMs from PTB patients (AMTBs) and AMs from control subjects (AMCTs) infected with two clinical isolates of Mtb. Furthermore, we also studied the infection response of human splenic macrophages (SMs) to Mtb isolates, as a model for extrapulmonary infection, and compared the transcriptomic response between AMs and SMs. Our results showed a striking difference in global mRNA profiles in response to infection between AMs and SMs, implicating a tissue-specific macrophage response to Mtb.

Immune-pineal axis protects rat lungs exposed to polluted air.

Environmental pollution in the form of particulate matter <2.5 µm (PM2.5 ) is a major risk factor for diseases such as lung cancer, chronic respiratory infections, and major cardiovascular diseases. Our goal was to show that PM2.5 eliciting a proinflammatory response activates the immune-pineal axis, reducing the pineal synthesis and increasing the extrapineal synthesis of melatonin. Herein, we report that the exposure of rats to polluted air for 6 hours reduced nocturnal plasma melatonin levels and increased lung melatonin levels. Melatonin synthesis in the lung reduced lipid peroxidation and increased PM2.5 engulfment and cell viability by activating high-affinity melatonin receptors. Diesel exhaust particles (DEPs) promoted the synthesis of melatonin in a cultured cell line (RAW 264.7 cells) and rat alveolar macrophages via the expression of the gene encoding for AANAT through a mechanism dependent on activation of the NFκB pathway. Expression of the genes encoding AANAT, MT1, and MT2 was negatively correlated with cellular necroptosis, as disclosed by analysis of Gene Expression Omnibus (GEO) microarray data from the human alveolar macrophages of nonsmoking subjects. The enrichment score for antioxidant genes obtained from lung gene expression data (GTEx) was significantly correlated with the levels of AANAT and MT1 but not the MT2 melatonin receptor. Collectively, these data provide a systemic and mechanistic rationale for coordination of the pineal and extrapineal synthesis of melatonin by a standard damage-associated stimulus, which activates the immune-pineal axis and provides a new framework for understanding the effects of air pollution on lung diseases.