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Polarization of alveolar macrophages (AMs) into the M1 phenotype contributes to inflammatory responses and tissue damage that occur during lung ischemia–reperfusion injury (LIRI). Programmed cell death factor-1 (PD-1) regulates polarization of macrophages, but its role in LIRI is unknown. We examined the role of PD-1 in AM polarization in models of LIRI in vivo and in vitro. Adult Sprague–Dawley rats were subjected to ischemia–reperfusion with or without pretreatment with a PD-1 inhibitor, SHP1/2 inhibitor, or Akt activator. Lung tissue damage and infiltration by M1-type AMs were assessed. As an in vitro complement to the animal studies, rat alveolar macrophages in culture were subjected to oxygen/glucose deprivation and reoxygenation. Levels of SHP1/2 and Akt proteins were evaluated using Western blots, while levels of pro-inflammatory cytokines were measured using enzyme-linked immunosorbent assays. Injury upregulated PD-1 both in vivo and in vitro. Inhibiting PD-1 reduced the number of M1-type AMs, expression of SHP1 and SHP2, and levels of inflammatory cytokines. At the same time, it partially restored Akt activation. Similar results were observed after inhibition of SHP1/2 or activation of the PI3K/Akt pathway. PD-1 promotes polarization of AMs to the M1 phenotype and inflammatory responses through the SHP1/2-PI3K/Akt axis. Inhibiting PD-1 may be an effective therapeutic strategy to limit LIRI. [ABSTRACT FROM AUTHOR]

The most prominent host response to viral infection is the production of type 1 interferons (T1 IFNs). One host regulator of the T1 IFNs is the serine-threonine kinase, tumor progression locus 2 (TPL2). We have previously demonstrated that Tpl2−/− mice succumb to infection with a low-pathogenicity influenza A strain (x31), in association with with increased pulmonary levels of interferon-β (IFN-β), chemokine CCL2, and excessive monocyte and neutrophil pulmonary infiltration. TPL2-dependent overexpression of IFN-β has been implicated in enhanced susceptibility to Mycobacterium tuberculosis; therefore, we examined the role of T1 IFNs in susceptibility of Tpl2−/− mice to influenza. CCL2 overexpression and monocyte recruitment were normalized in Ifnar1−/−Tpl2−/− mice, confirming that TPL2 constrains inflammatory monocyte recruitment via inhibition of the T1 IFN/CCL2 axis. Unexpectedly, excessive neutrophil recruitment in Ifnar1−/− strains was further exacerbated by simultaneous TPL2 genetic ablation in Ifnar1−/−Tpl2−/− by 7 dpi, accompanied by overexpression of neutrophil-regulating cytokines, CXCL1 and IFN-λ. Collectively, our data suggest that TPL2 and T1 IFNs synergize to inhibit neutrophil recruitment. However, treatment with the neutrophil-depleting anti-Ly6G antibody showed only a modest improvement in disease. Analysis of sorted innate immune populations revealed redundant expression of inflammatory mediators among neutrophils, inflammatory monocytes and alveolar macrophages. These findings suggest that targeting a single cell type or mediator may be inadequate to control severe disease characterized by a mixed inflammatory exudate. Future studies will consider TPL2-regulated pathways as potential predictors of severe influenza progression as well as investigate novel methods to modulate TPL2 function during viral infection. [ABSTRACT FROM AUTHOR]

Acute lung injury (ALI) usually causes acute respiratory distress syndrome (ARDS), or even death in critical ill patients. Immune cell infiltration in inflamed lungs is an important hallmark of ARDS. Macrophages are a type of immune cell that participate in the entire pathogenic trajectory of ARDS and most prominently via their interactions with lung alveolar epithelial cells (AECs). In the early stage of ARDS, classically activated macrophages secrete pro-inflammatory cytokines to clearance of the pathogens which may damage alveolar AECs cell structure and result in cell death. Paradoxically, in late stage of ARDS, anti-inflammatory cytokines secreted by alternatively activated macrophages dampen the inflammation response and promote epithelial regeneration and alveolar structure remodeling. In this review, we discuss the important role of macrophages and AECs in the progression of ARDS. [ABSTRACT FROM AUTHOR]

Acute lung injury (ALI) is characterized by damage to the alveoli and an overabundance of inflammation. Representing a serious inflammatory condition, ALI lacks a precise treatment approach. Despite the recognized benefit impacts of Fibroblast growth factor-10 (FGF10) on ALI, the underlying mechanisms remain unelucidated. To study the role of FGF10 in ALI, C57BL/6 J mice were intratracheally injected with 5 mg/kg Lipopolysaccharide (LPS) with FGF10 (5 mg/kg) or an equal volume of PBS. Inflammatory factors were quantified in bronchoalveolar lavage fluid (BALF) and plasma using ELISA. RNA sequencing of F4/80+Ly6G− macrophages in BALF explored changes in macrophage phenotype and potential mechanisms. Macrophage polarization in BALF was assessed using qRT-PCR, flow cytometry, and Western blot analysis. In vitro, a Transwell co-culture of mouse lung epithelial cells (MLE12) and bone marrow macrophages (BMDM) validated the role of FGF10 in modulating LPS-induced macrophage phenotypic changes. FGF10 ameliorated LPS-induced ALI by diminishing pro-inflammatory factors (IL-1β, TNF-α, and IL-6) and the neutrophil accumulation in BALF. FGF10 also increased the levels of anti-inflammatory factor IL-10. The FGF10 intervention group exhibited enhanced gene expression of macrophage arginine biosynthesis marker (ARG1), and expression of M2-type marker CD206 in monocytes and macrophages. In addition, phosphorylated STAT3 expression increased in isolated monocyte-derived macrophages. Experiments in vitro confirmed that FGF10 could elevate macrophage M2 marker ARG1 expression through the JAK2/STAT3 pathway. FGF10 ameliorates acute LPS-induced lung injury by modulating the polarization of monocyte-derived macrophages recruited in the alveolar space to the M2 type. [ABSTRACT FROM AUTHOR]

Propofol (Pro) is well known to regulate the asleep-awake-asleep technique. Increasing indication recommends that Pro also has promising properties such as anti-oxidant and anti-inflammation belongings in several disease models. It has been described that Pro has beneficial properties against renal ischemia/reperfusion (rI/R)-mediated acute lung injury (ALI). Nevertheless, pathogenesis underlying the beneficial action of Pro on the remote ALI mediated by rI/R remains unwell unstated. In this research, we displayed that Pro administration remarkably inhibits rI/R-mediated pro-inflammatory cytokines production. Increased levels of oxidative stress were mainly decreased by Pro. Pro administration ameliorated apoptosis-related caspase-3 activation. Furthermore, the levels of crucial necroptosis-associated protein were reduced by Pro. Sirtuin 1 (SIRT1) inhibitor attenuated the aforementioned changes of Pro. In conclusion, these results propose that Pro attenuates rI/R-induced inflammation, oxidative stress, apoptosis, and necroptosis by up-regulation of SIRT1 in rats. Our findings disclose an original pathogenesis underlying the beneficial effect of Pro against rI/R-mediated ALI and reinforce the knowledge that Pro might be a hopeful beneficial agent for the rI/R-mediated ALI. [ABSTRACT FROM AUTHOR]

Mesenchymal stem cells (MSCs) have been demonstrated to attenuate acute lung injury (ALI). We also found that they can suppress the activation of alveolar macrophages (AMs), which can partly account for their therapeutic effects. MSCs do not inherently own immunosuppressive effects, when co-cultured with inflammatory immune cells, MSCs can be activated by inflammatory cytokines and meanwhile exert immunosuppressive effects. In order to further research, RNA sequencing (RNA-seq) of MSCs cultured before and after co-culturing with activated macrophages was performed. The data suggested a total of 5268 differentially expressed genes (DEGs) along the process. We used the data of 2754 upregulated DEGs to develop a signaling network of genes and the transcription factors targeting them in order to predict the altered functions of MSCs after exposure to inflammatory stimuli. This constructed network revealed some critical target genes and potential roles of MSCs under inflammatory conditions. According to the network, Ptgs2 was assumed to be an important gene participating in the immunosuppressive effects of MSCs. We also identified significant increases in the expression of COX2 protein and the secretion of PGE2 from MSCs. The use of the COX2 inhibitor NS-398 restrained the secretion of PGE2 and reversed the suppression of macrophage activation by MSCs in vitro. In addition, a selective antagonist of PGE2 binding receptor (EP4 receptor), GW627368X, also reversed the inhibitory effects of MSCs on AMs and the protective effects in ALI mouse. In summary, the therapeutic effects of MSCs on ALI partly occur through suppressing AM activation via PGE2 binding to EP4 receptor. [ABSTRACT FROM AUTHOR]

Asthma is a chronic inflammatory disorder of the airways. Schisandrin B (SB) is the main effective component. This study investigated the effects of SB on airway inflammation and airway remodeling in asthma. The rat model of asthma was established. The rats were treated with SB to evaluate the effects of SB on airway inflammation, airway remodeling, NLRP3 inflammasome activation, and pyroptosis. Alveolar macrophages of rats were isolated, and the macrophage inflammatory model was established by lipopolysaccharide (LPS) induction. The LPS-induced macrophages were treated with SB. The binding relationship between miR-135a-5p and TPRC1 was analyzed. LPS + SB-treated macrophages were transfected with miR-135a-5p inhibitor. The expressions of key factors of the STAT3/NF-κB pathway were detected. SB reduced airway inflammation and airway remodeling in asthmatic rats. SB inhibited NLRP3 inflammasome activation and reduced pyroptosis in asthmatic rats and LPS-induced macrophages. SB reversely regulated the miR-135a-5p/TRPC1 axis. Downregulation of miR-135a-5p attenuated the inhibitory effect of SB on NLRP3 inflammasome activation. SB inhibited the STAT3/NF-κB pathway via the miR-135a-5p/TRPC1 axis. In conclusion, SB inhibited NLRP3 inflammasome activation and reduced pyroptosis via the miR-135a-5p/TRPC1/STAT3/NF-κB axis, thus alleviating airway inflammation and airway remodeling in asthma. This study may confer novel insights for the management of asthma. [ABSTRACT FROM AUTHOR]

Pseudoginsenoside-F11 (PF11), an ocotillol-type saponin, has been reported to have anti-inflammatory properties, but the effects of PF11 on acute lung inflammation were unknown. The present study aimed to investigate the protective effects and potential mechanisms of PF11 on lipopolysaccharide (LPS)-induced acute lung injury (ALI) in male BALB/c mice. After being treated with PF11 (3, 10, and 30 mg/kg, intravenous) once a day for 3 consecutive days, the mice were challenged by intratracheal instillation of LPS, and then their lung tissues and bronchoalveolar lavage fluid (BALF) were collected for further analysis. The results showed that PF11 attenuated LPS-induced ALI, with alleviated histopathological damage, decreased lung wet/dry weight ratio, and reduced protein concentration and inflammatory cells number in BALF. Moreover, PF11 reversed the LPS-induced increases of mRNA expression and protein levels of interleukin-6, tumor necrosis factor-α, and interleukin-1β. Meanwhile, PF11 decreased LPS-induced myeloperoxidase activity and neutrophil infiltration in lung tissue by reducing the expression of macrophage inflammatory protein-2 and intercellular adhesion molecule-1, as well as enhanced neutrophil clearance by accelerating neutrophils apoptosis and their phagocytosis by alveolar macrophages. In conclusion, these results indicated that PF11 significantly attenuated LPS-induced ALI through suppressing neutrophil infiltration and accelerating neutrophil clearance, suggesting its potential in the treatment of ALI. [ABSTRACT FROM AUTHOR]

Protein phosphatase 2A (PP2A) is one main serine/threonine phosphatase in eukaryotes, and its activation changes have been linked to modulation of numerous pathological processes, such as cancer, inflammation, fibrosis, and neurodegenerative diseases. Acute respiratory distress syndrome (ARDS), the major cause of respiratory failure, remains with limited therapies available up to now. Alveolar macrophages (AMs) are essential to innate immunity and host defense, participating in the pathogenesis of ARDS. As a result, AMs are considered as a potential therapeutic target for ARDS. In our study, we firstly found that PP2A activity was significantly decreased in the lipopolysaccharide (LPS)-stimulated AMs. Furthermore, adoptive transfer of AMs with enhanced PP2A enzyme activity that was improved by C2-ceramide prior to LPS exposure alleviated acute lung inflammation. Conversely, AM-specific ablation of PP2ACα exacerbated inflammatory responses to LPS. Mechanistically, PP2ACα negatively regulates LPS-induced cytokine secretion of AMs by NF-κB and MAPK pathways. Together, these findings provide the evidence to guide the development of novel therapeutic options targeting PP2ACα for ARDS/acute lung injury. [ABSTRACT FROM AUTHOR]

Acute lung injury (ALI), developing as a component of the systemic inflammatory response syndrome (SIRS), leads to significant morbidity and mortality. Reactive oxygen species (ROS), produced in part by the neutrophil NADPH oxidase 2 (Nox2), have been implicated in the pathogenesis of ALI. Previous studies in our laboratory demonstrated the development of pulmonary inflammation in Nox2-deficient (gp91phox-/y) mice that was absent in WT mice in a murine model of SIRS. Given this finding, we hypothesized that Nox2 in a resident cell in the lung, specifically the alveolar macrophage, has an essential anti-inflammatory role. Using a murine model of SIRS, we examined whole-lung digests and bronchoalveolar lavage fluid (BALf) from WT and gp91phox-/y mice. Both genotypes demonstrated neutrophil sequestration in the lung during SIRS, but neutrophil migration into the alveolar space was only present in the gp91phox-/y mice. Macrophage inflammatory protein (MIP)-1α gene expression and protein secretion were higher in whole-lung digest from uninjected gp91phox-/y mice compared to the WT mice. Gene expression of MIP-1α, MCP-1, and MIP-2 was upregulated in alveolar macrophages obtained from gp91phox-/y mice at baseline compared with WT mice. Further, ex vivo analysis of alveolar macrophages, but not bone marrow-derived macrophages or peritoneal macrophages, demonstrated higher gene expression of MIP-1α and MIP-2. Moreover, isolated lung polymorphonuclear neutrophils migrate to BALf obtained from gp91phox-/y mice, further providing evidence of a cell-specific anti-inflammatory role for Nox2 in alveolar macrophages. We speculate that Nox2 represses the development of inflammatory lung injury by modulating chemokine expression by the alveolar macrophage. [ABSTRACT FROM AUTHOR]

Smoke inhalation leads to acute lung injury (ALI), a devastating clinical problem associated with high mortality rates. Suppressor of cytokine signaling-1 (SOCS-1) is a negative regulator of proinflammatory cytokine signaling. We have found that adenoviral gene transfer of SOCS-1 ameliorates smoke inhalation-induced lung injury in C57BL/6 mice. We also found that the release of adenosine triphosphate (ATP) was increased post smoke exposure, while oxidized ATP, an inhibitor of purinergic P2X7 receptor, suppressed smoke-induced NALP3 inflammasome assembly, caspase-1 activation, and K+ efflux. Similar to oxidized ATP, high protein level of SOCS-1 dampened the formation of NALP3 inflammasome and the activation of caspase-1 and IL-1β induced by smoke exposure in mouse alveolar macrophages. In conclusion, SOCS-1 relieves smoke inhalation-induced pulmonary inflammation and injury by inhibiting NALP3 inflammasome formation. [ABSTRACT FROM AUTHOR]

The molecular mechanisms of acute lung injury (ALI) are closely associated with nucleotide-binding domains and leucine-rich repeat (NLR) pyrin domains containing 3 (NLRP3) inflammasome, in which alveolar macrophages (AMs) exert an essential function. Our study has been proved that artesunate (AS) inhibits ALI. Nevertheless, the inhibition actions of AS on activation of NLRP3 in renal ischemia-reperfusion (RIR)-mediated ALI remain to be further discussed. Male Sprague-Dawley rats were randomly assigned into four groups: sham + NS, sham + AS, RIR + NS, and RIR + AS. RIR-mediated ALI was performed through bilateral renal pedicle occlusion for 60 min followed by reperfusion for 24 h. AS (15 mg/kg) or NS was injected intraperitoneal to rat 1 h before RIR treatment. AMs were rendered hypoxic (0.5%) for 2 h and reoxygenated for 24 h. Lung injury index and histology, and inflammatory cells and cytokine release in the BALF and AMs were examined. The protein and mRNA levels of NLRP3, ASC, and caspase-1 in the lung and AMs were evaluated via Western blot and real-time RCR. In this research, we indicated that AS preconditioning inhibited RIR-mediated lung damage, vascular permeability, and edema in rats. AS reduced RIR-mediated ALI, as characterized by abatement in the count of inflammatory cells, and the production of inflammatory cytokines in the BALF. AS administration inhibited the number of F4/80-positive cells, the activity of myeloperoxidase, and the fiery cytokines mRNA expression in lung samples of RIR-stimulated rats. Furthermore, AS alleviated the activity of caspase-1 and activation of NLRP3 through depending on reactive oxygen species (ROS). An in vitro finding that AS mitigated hypoxia/reoxygenation-mediated activation of AMs partially supported in vivo study. In a word, these findings demonstrate that AS pretreatment attenuated RIR-mediated ALI potentially through reducing ROS-induced activation of the NLRP3 inflammasome. [ABSTRACT FROM AUTHOR]

Androctonus australis hector (Aah) scorpion venom is well known to induce a systemic inflammatory response associated with cell infiltration in lung and edema formation. The present study investigate (i) in vivo the evolution of lung and systemic inflammation triggered by Aah venom and (ii) analyze in vitro the signaling cascade, upstream of inflammatory cytokine expression after Aah venom-stimulated mouse alveolar macrophage (MH-S), the main resident immune cells in the lung. The inflammation induced by Aah venom was assessed in mice through inflammatory cell count, nitric oxide metabolite, and lactate dehydrogenase (LDH) activity in blood, concordantly with neutrophil sequestration in tissue and lung histology. In the in vitro study, MH-S cells are stimulated with Aah venom in the presence of signaling pathway inhibitors, NG25 an inhibitor of transforming growth factor β-activated kinase (TAK1), PD184352 MAP kinase (MKK)1/2 inhibitor, BI605906 an inhibitor of IKκ-β (inhibitor of nuclear factor kappa B), and BIRB0796 an inhibitor of p38 MAPK. Obtained results showed that leukocyte transmigration is important in some area of the lung and is closely associated with systemic increase of nitric oxide and LDH. The in vitro study showed that Aah venom induce significantly an increase of the expression of TNF-α, IL-1β, and MIP-2 in MH-S cells. The pretreatment with inhibitors showed that cytokine increase involves TAK1, IKκ-β, and ERK1/2 pathways, similarly to Toll-like receptor activation. These findings highlight the contribution of alveolar macrophage and their secretory products to tissue damage and made of TAK1 and ERK1/2, an interesting target in scorpion envenomation. [ABSTRACT FROM AUTHOR]

In the lungs, endothelial nitric oxide synthase (eNOS) is usually expressed in endothelial cells and inducible nitric oxide synthase (iNOS) is mainly expressed in alveolar macrophages and epithelial cells. Both eNOS and iNOS are involved in lung inflammation. While they play several roles in lung inflammation formation and resolution, their expression and activity are also regulated by inflammatory factors. Their expression relationship in virus infection-induced lung injury is not well addressed. In this report, we analyzed expression of both eNOS and iNOS, the production of nitric oxide (NO) and reactive oxygen species (ROS), and expression of their associated regulatory proteins, heat shock protein 90 (HSP90) and caveolin-1 (Cav-1), in a swine lung injury model induced by porcine reproductive and respiratory syndrome virus (PRRSV) infection. The combination of upregulation of iNOS and downregulation of eNOS was observed in both natural and experimental PRRSV-infected lungs, while the combination is much enhanced in natural infected lungs. While NO production is much reduced in both infections, ROS was enhanced only in natural infected lungs. Moreover, HSP90 is increased in both natural and experimental infection and less Cav-1 expressed was observed only in the natural PRRSV-infected lungs. Therefore, the increased ROS generation is likely due to the increased iNOS and its unbalanced regulation by HSP90 and Cav-1, and it also likely causes higher endothelial dysfunction in clinical PRRSV-infected lungs. [ABSTRACT FROM AUTHOR]

Clinical evidence indicates that patients with severe chronic obstructive pulmonary disease (COPD) are more susceptible to Aspergillus. However, the exact mechanisms underlying this effect are not known. In this study, we used cigarette smoke exposure to generate COPD rat model. colony-forming units (CFU) count assessment and phagocytosis were applied to evaluate the defense function of COPD rats against Aspergillus challenge. ELISA, western blotting, and GST-Rac1 pull-down assays were conducted to determine the expressions of cytokines and TLR2-associated signaling pathway. Our data showed that Aspergillus burdens increased, phagocytosis of Aspergillus as well as the expressions of inflammatory cytokines from alveolar macrophages (AMs) were impaired in COPD rats compared with normal rats. Though TLR2 signaling-related proteins were induced in response to the stimulation of Aspergillus or Pam3csk4 (TLR2 agonist), the activation of TLR2-associated signaling pathway was apparently interfered in rats with COPD, compared to that in normal rats. Taken together, our study demonstrated that COPD caused the deficiency of AMs function and impaired the activation of TLR2/PI3K/Rac 1 signaling pathway, leading to invasion of Aspergillus infection, which also provides a future basis for the infection control in COPD patients. [ABSTRACT FROM AUTHOR]

P38 inhibitors are potent anti-inflammatory agents with distinctive mechanism of action from corticosteroid; the potential combined use of both anti-inflammatory agents could be an effective treatment for inflammatory lung disease; however, the impact of such combination on the homeostasis of immune response was poorly understood. To investigate the combined effect of dexamethasone (DEX) and/or SB203580 on tumor necrosis factor (TNF)-α (pro-inflammatory) and interleukin (IL)-10 (anti-inflammatory) secretion in mouse alveolar macrophage cell line. Secreted TNF-α and IL-10 were measured by ELISA. Phosphorylated STAT3 were investigated using Western blotting and immunocytochemistry. Pre-treatment of DEX or SB203580 inhibited lipopolysaccharide (LPS)-stimulated IL-10, TNF-α secretion, and STAT3 phosphorylation. Combined use of both agents showed stronger inhibitory effect. Combining DEX and SB203580 showed strong inhibition on the LPS-induced IL-10 secretion and STAT3 phosphorylation, which might reflect a very important drawback from the combined use of both anti-inflammatory agents. [ABSTRACT FROM AUTHOR]

The reparative and immunoregulatory properties of mesenchymal stromal cells (MSCs) have made them attractive candidates for cellular therapy. However, the underlying mechanism of the effects of transplanted MSCs on allergic asthma remains elusive. Here, we show that administration of MSCs isolated from human bone marrow provoked a pronounced polarization in alveolar macrophages to M2 subtypes, rather than induced an increase in the total macrophage number, and efficiently inhibited hallmark features of asthma, including airway hyperresponsiveness and eosinophilic accumulation. Moreover, transforming growth factor beta (TGF-β) signaling pathway appeared to mediate the effects of MSCs on macrophage polarization and subsequently the inhibition of hallmark features of asthma. Inhibition of TGF-β signaling was sufficient to inhibit the macrophage polarization in response to MSCs and consequently reserved the inhibitory effects of macrophage polarization on hallmark features of asthma. Collectively, our data demonstrate that human MSCs have immunosuppressive activity on asthma, which is mediated by TGF-β-signaling-dependent alveolar macrophage polarization. [ABSTRACT FROM AUTHOR]

Toll-like receptor 4 (TLR4) and myeloid differentiation protein 2 (MD-2) are the main lipopolysaccharide (LPS) binding receptors that respond to inflammatory stimuli and mediate NF-kappa B (NF-κB) signaling pathway in macrophages. We have previously shown that plasminogen activator inhibitor-1 (PAI-1) deletion increased lung injury induced by intratracheal instillation of LPS through downregulation of TLR4 negative regulators. However, the mechanisms by which PAI-1 regulates lung inflammation are largely unknown. The aim of this study is to assess the relationship between PAI-1 and TLR4 signaling pathways in LPS-induced NR8383 cells inflammatory reaction. The results showed that the levels of PAI-1, TNF-α, and IL-1β protein were increased remarkably in NR8383 cell supernatants after LPS stimulation. PAI-1 gene knockdown reduced TNF-α and IL-1β levels in cell supernatants and inhibited the NF-κB p65 protein expression in NR8383 cells. The upregulated mRNA and protein expressions of TLR4, MD-2, and myeloid differentiation protein (MyD88) induced by LPS were attenuated after PAI-1 gene knockdown. Conversely, overexpression of PAI-1 in NR8383 cells not only resulted in additional mRNA and protein production of PAI-1, TLR4, MD-2, and MyD88, it also aggravated the inflammatory response induced by LPS. In conclusion, PAI-1 contributes to the regulation of LPS-induced inflammatory response in NR8383 cells, likely by affecting the TLR4-MD-2/NF-κB signaling transduction pathway. [ABSTRACT FROM AUTHOR]

Murine gammaherpesvirus 68 (MHV68) is a natural rodent pathogen that has been used as a model to study the pathogenesis of human gammaherpesviruses. Like other herpesviruses, MHV68 causes acute infection and establishes life-long latency in the host. Recently, it has been shown that mice latently infected with MHV68 have resistance to unrelated pathogens in secondary infection models. We therefore hypothesized that latent MHV68 infection could modulate the host response to influenza A virus. To test this hypothesis, mice were infected intranasally with influenza virus following the establishment of MHV68 latency. Mice latently infected with MHV68 showed significantly higher survival to influenza A virus infection than did PBS mock-infected mice. Latent MHV68 infection led to lower influenza viral loads and decreased inflammatory pathology in the lungs. Alveolar macrophages of mice latently infected with MHV68 showed activated status, and adoptive transfer of those activated macrophages into mice followed the infection with influenza A virus had significantly greater survival rates than control mice, suggesting that activated alveolar macrophages are a key mechanistic component in protection from secondary infections. [ABSTRACT FROM AUTHOR]

Early detection and prevention is an important goal in acute respiratory distress syndrome research. We determined the concentration of the anti-inflammatory 15-deoxy-Δ-prostaglandin-J2 (15d-PGJ2) and other components of the cyclopentenone prostaglandin cascade in relation to lung inflammation in cytokine (IL-1/LPS)-insufflated rats. We found that 15d-PGJ2 levels increase in the bronchoalveolar lavage (BAL) fluid of rats insufflated with cytokines 2 h before. BAL 15d-PGJ2 increases preceded neutrophil recruitment, lung injury, and oxidative stress in the lungs of cytokine-insufflated rats. 15d-PGJ2 was localized in alveolar macrophages that decreased following cytokine insufflation. 15d-PGJ2 may constitute an early biomarker of lung inflammation and may reflect an endogenous attempt to regulate ongoing inflammation in macrophages and elsewhere after cytokine insufflation. [ABSTRACT FROM AUTHOR]

Macrophages play a critical role in mediating inflammatory processes; activated macrophages respond to endotoxin by releasing pro-inflammatory cytokines including tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and IL-6. Ketamine, a widely used anesthetic agent, has unequivocally anti-inflammatory effects in vivo and in vitro. However, the detailed mechanisms for the anti-inflammatory effects of ketamine in microglia have not been elucidated yet. This study aimed to evaluate the effects of ketamine on lipopolysaccharide (LPS)-induced nitric oxide (NO), hydroxyl radical (·OH) production, and intracellular calcium accumulation in macrophages. Macrophages were pretreated with ketamine at the concentrations of 10, 100, and 1,000 μM 1 h before LPS stimulation. The production of NO and ·OH in the culture supernatant of macrophages was assayed by Griess Reagent Kit. LPS enhanced NO and ·OH production and provoked a significant intracellular calcium elevation. With the concentrations higher than 100 μM, ketamine inhibited LPS-induced NO and ·OH accumulation and intracellular calcium elevation. However, a low concentration of ketamine (10 μM) did not exert anti-inflammatory effects. These results suggest that intracellular calcium elevation is, at least, partially involved in the inhibitory effect of ketamine. [ABSTRACT FROM AUTHOR]

Preliminary studies show that intranasal (i.n.) administration of BCG in mice induces M1 activation of alveolar macrophages (M∅) that increase TNF-α production and cyclooxygenase-2 (COX-2) expression but reduce constitutive peroxisome proliferator-activated receptor gamma (PPARγ) expression. However, COX-2 is catalytically inactive for prostaglandin E release, unlike COX-2 that is active in M1 activation in vitro by BCG. In this study, we determined the role of PPARγ for BCG-induced M1 activation in vivo and in vitro. We found that treatment of mice with GW9662, a PPARγ antagonist, prior to i.n. BCG, partially restored PPARγ expression, and decreased TNF-α production and COX-2 expression. But COX-2 was still inactive. The decreased effects on TNF-α and COX-2 were also observed when alveolar M∅ were treated in vitro with GW9662/BCG, but COX-2 was still active. Our results indicate that PPARγ upregulates M1 activation of alveolar M∅, but inactive COX-2 formation is independent of PPARγ in mycobacterial pulmonary inflammation. [ABSTRACT FROM AUTHOR]

Diabetes mellitus reduces immunological activity and increases susceptibility to various infections. Hochuekkito (TJ-41) has been reported to improve the weakened physical condition of various chronic diseases. BALB/c mice were divided into three groups; groups A and B were fed a standard diet, and group C, a TJ-41 diet. Two weeks after starting these diets, hyperglycemia was induced in groups B and C by injection with streptozotocin. Two weeks later, bronchoalveolar lavage was performed. Toll-like receptor (TLR) ligands (TLR2: peptidoglycan, PGN; TLR4: lipopolysaccharide, LPS; TLR5: flagellin, FLG) were used to stimulate alveolar macrophages (AMs), and TNF-α production was measured. Under hyperglycemic conditions and PGN or FLG stimulation, TNF-α production from AMs was significantly reduced in group B compared with group A. However, treatment with TJ-41 (group C) significantly improved the impaired production of TNF-α. These results suggest that, under hyperglycemic conditions, TJ-41 can improve the inflammatory responses of AMs with stimulation of TLR ligands. [ABSTRACT FROM AUTHOR]

Alveolar macrophages (AMs) can initiate lung inflammation by producing pro-inflammatory cytokines and chemokines, but they participate actively in the prevention of inflammation during acute lung injury (ALI). Heme oxygenase-1 (HO-1) is mainly expressed in AMs and has anti-inflammatory properties in ALI, but the anti-inflammatory mechanisms of HO-1 are largely unknown. In this study, AMs were treated with saline, LPS (1 μg/ml), hemin (10 μM), zinc protoporphyrin (ZnPP; 10 μM, 1 h prior to LPS and hemin), SB203580 (10 μM, 1 h prior to LPS and hemin), or their combination up to 24 h. The specific HO-1 inhibitor ZnPP and SB203580 were used to inhibit the effects of HO-1 and the phosphorylated p38 mitogen-activated protein kinase (MAPK), respectively. The protein levels of HO-1 and p38 MAPK were analyzed by western blotting; arginase activity was measured in lysates obtained from cultured cells; nitric oxide production in the extracellular medium of AMs cultured for 24 h was monitored by assessing nitrite levels; the phagocytic ability of macrophage was measured by neutral red uptake. IL-10 of culture supernatants in AMs was determined by enzyme-linked immunosorbent assay. The results indicated that HO-1 induced by hemin increased arginase activity and phagocytic ability and decreased iNOS activity via p38 MAPK pathway in primary rat AMs. These changes and p38 MAPK may be the anti-inflammatory mechanism of HO-1 induced by hemin in primary rat AMs. [ABSTRACT FROM AUTHOR]

Alveolar macrophages (AM) are the primary target cell of the lung for inhaled mycobacterial pathogens. We investigated the effect of the synthetic lipopeptide MALP-2 on the interaction between AM from rats and Mycobacterium bovis BCG. AM were infected with M. bovis BCG at a multiplicity of infection (MOI) of 10 and then cultured in medium alone or medium supplemented with either synthetic macrophage activating lipopeptide-2 (MALP-2), or IFN-γ, or both. Mycobacterial CFU were counted on days 3 and 7 and cell-free supernatants were collected for cytokine measurements. Treatment of macrophages with MALP-2 led to reduced bacterial loads by day 3 and 7 post-infection and at the same time enhanced the release of TNF-α, IL-6 und IL-10 compared to non-stimulated, M. bovis BCG-infected AM. Macrophages co-treated with MALP-2 and IFN-γ or IFN-γ in the absence of MALP-2 limited the growth of M. bovis BCG only by day 3, but not day 7 post-stimulation. Our data show that MALP-2 is effective in decreasing bacterial loads in lung sentinel cells. [ABSTRACT FROM AUTHOR]