Influenza-induced Lung Injury Research Articles

An integrative pharmacology-based study on the efficacy and mechanism of essential oil of Chaihu Guizhi Decoction on influenza A virus induced pneumonia in mice

Ethnopharmacological relevanceChaihu Guizhi Decoction (CGD) has a long history of use in China for the treatment of influenza, which involves the use of a variety of aromatic herbs. Our previous studies have found that the contents of aromatic constituents in CGD affected the efficacy of treatment of influenza-infected mice, suggesting a clue that essential oil from CGD may play a relatively important role in ameliorating influenza induced pneumonia. Aim of the studyTo evaluate the anti-influenza potential of essential oil derived from Chaihu Guizhi Decoction (CGD-EO), to characterize and predict the key active components in CGD-EO, and to explore the mechanism of action of CGD-EO. Materials and methodsCGD-EO was obtained by steam distillation, and the components of the essential oil were characterized by gas chromatography-mass spectrometry (GC-MS) in conjunction with the retention index. The constituents absorbed into the blood of mice treated with CGD-EO were analyzed by headspace solid phase microextraction gas chromatography/mass spectrometry (HS-SPME-GC/MS). The potential anti-influenza active constituents and their possible action pathway were predicted by simulation using a network pharmacology approach. The protective effect of CGD-EO and its major components on H1N1/PR8-infected cells was determined using the CCK8 assay kit. Mice infected with influenza A virus H1N1/PR8 were administered different doses of CGD-EO orally and the body weights and lung weights were recorded. Mice with varying degrees of H1N1/PR8 infection were administered CGD-EO orally, and their daily weight, water consumption, and clinical indicators were recorded. Necropsies were conducted on days 3 and 5, during which lung weights were measured and lung tissues were preserved. Furthermore, the mRNA expression of the H1N1/PR8 virus and inflammatory factors in lung tissue was analyzed using RT-qPCR. Results(E)-cinnamaldehyde was the most abundant compound in the CGD-EO. The results of serum medicinal chemistry combined with network pharmacological analysis indicated that (E)-cinnamaldehyde and 3-phenyl-2-propenal may be potential active components of the CGD-EO anti-influenza, and may be involved in the NF-κB signalling pathway. In vitro studies have demonstrated that both CGD-EO and cinnamaldehyde exert a protective effect on MDCK cells infected with H1N1/PR8. In a 0.5 TCID50 H1N1/PR8-induced influenza model, mice treated with CGD-EO at a dose of 63.50 μg/kg exhibited a reduction in lung index, pathological lung lesions, and H1N1/PR8 viral gene levels. In addition, CGD-EO treatment was found to regulate the levels of inflammatory cytokines, including IL-6, TNF-α, and IFN-γ. Moreover, following three days of administration, an upregulation of NF-κB mRNA levels in mouse lung tissue was observed in response to CGD-EO treatment. ConclusionsThe findings of our study indicate CGD-EO exerts a protective effect against H1N1-induced cytopathic lesions in vitro and is capable of alleviating H1N1-induced pneumonitis in mice. Moreover, it appears to be more efficacious in the treatment of mild symptoms of H1N1 infection. Studies have demonstrated that CGD-EO has antiviral potential to attenuate influenza-induced lung injury by modulating inflammatory cytokines and NF-κB signalling pathways during the early stages of influenza infection. It is possible that (E)-cinnamaldehyde is a potential active ingredient in the anti-influenza efficacy of CGD-EO.

Vagal-α7 nicotinic acetylcholine receptor signaling exacerbates influenza severity by promoting lung epithelial cell infection.

The vagus nerve circuit, operating through the alpha-7 nicotinic acetylcholine receptor (α7 nAChR), regulates the inflammatory response by influencing immune cells. However, the role of vagal-α7 nAChR signaling in influenza virus infection is unclear. In particular, does vagal-α7 nAChR signaling impact the infection of alveolar epithelial cells (AECs), the primary target cells of influenza virus? Here, we demonstrated a distinct role of α7 nAChR in type II AECs compared to its role in immune cells during influenza infection. We found that deletion of Chrna7 (encoding gene of α7 nAChR) in type II AECs or disruption of vagal circuits reduced lung influenza infection and protected mice from influenza-induced lung injury. We further unveiled that activation of α7 nAChR enhanced influenza infection through PTP1B-NEDD4L-ASK1-p38MAPK pathway. Mechanistically, activation of α7 nAChR signaling decreased p38MAPK phosphorylation during infection, facilitating the nuclear export of influenza viral ribonucleoproteins and thereby promoting infection. Taken together, our findings reveal a mechanism mediated by vagal-α7 nAChR signaling that promotes influenza viral infection and exacerbates disease severity. Targeting vagal-α7 nAChR signaling may offer novel strategies for combating influenza virus infections.

Vascular endothelial-derived SPARCL1 exacerbates viral pneumonia through pro-inflammatory macrophage activation

Inflammation induced by lung infection is a double-edged sword, moderating both anti-viral and immune pathogenesis effects; the mechanism of the latter is not fully understood. Previous studies suggest the vasculature is involved in tissue injury. Here, we report that expression of Sparcl1, a secreted matricellular protein, is upregulated in pulmonary capillary endothelial cells (EC) during influenza-induced lung injury. Endothelial overexpression of SPARCL1 promotes detrimental lung inflammation, with SPARCL1 inducing ‘M1-like’ macrophages and related pro-inflammatory cytokines, while SPARCL1 deletion alleviates these effects. Mechanistically, SPARCL1 functions through TLR4 on macrophages in vitro, while TLR4 inhibition in vivo ameliorates excessive inflammation caused by endothelial Sparcl1 overexpression. Finally, SPARCL1 expression is increased in lung ECs from COVID-19 patients when compared with healthy donors, while fatal COVID-19 correlates with higher circulating SPARCL1 protein levels in the plasma. Our results thus implicate SPARCL1 as a potential prognosis biomarker for deadly COVID-19 pneumonia and as a therapeutic target for taming hyperinflammation in pneumonia.

Preventing occludin tight-junction disruption via inhibition of microRNA-193b-5p attenuates viral load and influenza-induced lung injury

Virus-induced lung injury is associated with loss of pulmonary epithelial-endothelial tight junction integrity. While the alveolar-capillary membrane may be an indirect target of injury, viruses may interact directly and/or indirectly with miRs to augment their replication potential and evade the host antiviral defense system. Here, we expose how the influenza virus (H1N1) capitalizes on host-derived interferon-induced, microRNA (miR)-193b-5p to target occludin and compromise antiviral defenses. Lung biopsies from patients infected with H1N1 revealed increased miR-193b-5p levels, marked reduction in occludin protein, and disruption of the alveolar-capillary barrier. In C57BL/6 mice, the expression of miR-193b-5p increased, and occludin decreased, 5-6days post-infection with influenza (PR8). Inhibition of miR-193b-5p in primary human bronchial, pulmonary microvascular, and nasal epithelial cells enhanced antiviral responses. miR-193b-deficient mice were resistant to PR8. Knockdown of occludin, both invitro and invivo, and overexpression of miR-193b-5p reconstituted susceptibility to viral infection. miR-193b-5p inhibitor mitigated loss of occludin, improved viral clearance, reduced lung edema, and augmented survival in infected mice. Our results elucidate how the innate immune system may be exploited by the influenza virus and how strategies that prevent loss of occludin and preserve tight junction function may limit susceptibility to virus-induced lung injury.

A negative trial for vasoactive intestinal peptide in COVID-19-associated acute hypoxaemic respiratory failure

A negative trial for vasoactive intestinal peptide in COVID-19-associated acute hypoxaemic respiratory failure

Mechanism of Jinzhen Oral Liquid against influenza-induced lung injury based on metabonomics and gut microbiome

Ethnopharmacological relevanceJinzhen Oral Liquid (JZOL) is a traditional Chinese patent medicine and widely used clinically, which consists of eight herbs including Bovis Calculus Atifactus, Fritillariae Ussuriensis Bulbus (Fritillaria ussuriensis Maxim.), Caprae Hircus Cornu, Rhei Radix et Rhizoma (Rheum palmatum L.), Scutellariae Radix (Scutellaria baicalensis Georgi), Glycyrrhizae Radix et Rhizoma (Glycyrrhiza uralensis Fisch. ex DC.), Chloriti Lapis, and Gypsum Fibrosum (Their ratio is 9.45 : 47.25: 94.5 : 31.5: 15.75 : 31.5: 15.75 : 23.62). A large number of clinical studies have proved that JZOL has a good antiviral effect and can treat lung injury, pneumonia, and bronchitis caused by a variety of viral infections. Aim of the studyInfluenza infection frequently exhibit dysregulation of gut microbiota and host metabolomes, but the mechanism of JZOL is still unclear and needs to be further explored. Here, after influenza virus infection induced lung injury, the regulation roles of JZOL in metabolic and gut microbiota balances are investigated to comprehensively elucidate its therapeutic mechanism. Materials and methodsA mouse model of lung injury was replicated via intranasal instillation of influenza A (H1N1). The efficacy of JZOL was evaluated by pathological sections, lung index, the levels of TNF-α and IFN-γ, and viral load in lung tissue. Its modulation of endogenous metabolites and gut microbiota was assessed using plasma metabolomic technique and 16S rRNA high-throughput sequencing technique. ResultsJZOL not only significantly relieved lung inflammation and edema in influenza mice, but also alleviated the disturbance of endogenous metabolites and the imbalance of gut microbiota mainly by regulating glycerophospholipid and fatty acid metabolism and Lactobacillus. The anti-influenza effects of JZOL were gut microbiota dependent, as demonstrated by antibiotic treatment.The altered metabolites were significantly correlated with Lactobacillus and pharmacodynamic indicators, further confirming the reliability of these results. ConclusionsJZOL attenuates H1N1 influenza infection induced lung injury by regulating lipid metabolism via the modulation of Lactobacillus. The results support the clinical application of JZOL, and are useful to further understand the mechanism of TCM in the treatment of influenza.

Delayed angiopoietin-2 blockade reduces influenza-induced lung injury and improves survival in mice.

Influenza remains a major cause of death and disability with limited treatment options. Studies of acute lung injury have identified angiopoietin‐2 (Ang‐2) as a key prognostic marker and a potential mediator of Acute respiratory distress syndrome. However, the role of Ang‐2 in viral pneumonia remains poorly defined. This study characterized the time course of lung Ang‐2 expression in severe influenza pneumonia and tested the therapeutic potential of Ang‐2 inhibition. We inoculated adult mice with influenza A (PR8 strain) and measured angiopoietin‐1 (Ang‐1), Ang‐2, and Tie2 expressions during the evolution of inflammatory lung injury over the first 7 days post‐infection (dpi). We tested a peptide‐antibody inhibitor of Ang‐2, L1‐7, administered at 2, 4, and 6 dpi and measured arterial oxygen saturation, survival, pulmonary edema, inflammatory cytokines, and viral load. Finally, we infected primary human alveolar type II epithelial (AT2) cells grown in air‐liquid interface culture with influenza and measured Ang‐2 RNA expression. Influenza caused severe lung injury between 5 and 7 dpi in association with increased Ang‐2 lung RNA and a dramatic increase in Ang‐2 protein in bronchoalveolar lavage. Inhibition of Ang‐2 improved oxygenation and survival and reduced pulmonary edema and alveolar‐capillary barrier permeability to protein without major effects on inflammation or viral load. Finally, influenza increased the expression of Ang‐2 RNA in human AT2 cells. The increased Ang‐2 levels in the airspaces during severe influenza pneumonia and the improvement in clinically relevant outcomes after Ang‐2 antagonism suggest that the Ang‐1/Ang‐2 Tie‐2 signaling axis is a promising therapeutic target in influenza and potentially other causes of viral pneumonia.

FGFR2 Is Required for AEC2 Homeostasis and Survival after Bleomycin-induced Lung Injury.

Alveolar epithelial cell (AEC) injury is central to the pathogenesis of pulmonary fibrosis. Epithelial FGF (fibroblast growth factor) signaling is essential for recovery from hyperoxia- and influenza-induced lung injury, and treatment with FGFs is protective in experimental lung injury. The cell types involved in the protective effect of FGFs are not known. We hypothesized that FGF signaling in type II AECs (AEC2s) is critical in bleomycin-induced lung injury and fibrosis. To test this hypothesis, we generated mice with tamoxifen-inducible deletion of FGFR1-3 (fibroblast growth factor receptors 1, 2, and 3) in surfactant protein C-positive (SPC+) AEC2s (SPC triple conditional knockout [SPC-TCKO]). In the absence of injury, SPC-TCKO mice had fewer AEC2s, decreased Sftpc (surfactant protein C gene) expression, increased alveolar diameter, and increased collagen deposition. After intratracheal bleomycin administration, SPC-TCKO mice had increased mortality, lung edema, and BAL total protein, and flow cytometry and immunofluorescence revealed a loss of AEC2s. To reduce mortality of SPC-TCKO mice to less than 50%, a 25-fold dose reduction of bleomycin was required. Surviving bleomycin-injured SPC-TCKO mice had increased collagen deposition, fibrosis, and ACTA2 expression and decreased epithelial gene expression. Inducible inactivation of individual Fgfr2 or Fgfr3 revealed that Fgfr2, but not Fgfr3, was responsible for the increased mortality and lung injury after bleomycin administration. In conclusion, AEC2-specific FGFR2 is critical for survival in response to bleomycin-induced lung injury. These data also suggest that a population of SPC+ AEC2s require FGFR2 signaling for maintenance in the adult lung. Preventing epithelial FGFR inhibition and/or activating FGFRs in alveolar epithelium may therefore represent a novel approach to treating lung injury and reducing fibrosis.

Increased expression of microRNA-155-5p by alveolar type II cells contributes to development of lethal ARDS in H1N1 influenza A virus-infected mice

Alveolar type II (ATII) cells are essential to lung function and a primary site of influenza A virus (IAV) replication. Effects of IAV infection on ATII cell microRNA (miR) expression have not been comprehensively investigated. Infection of C57BL/6 mice with 10,000 or 100 pfu/mouse of IAV A/WSN/33 (H1N1) significantly altered expression of 73 out of 1908 mature murine miRs in ATII cells at 2 days post-infection (d.p.i.) and 253 miRs at 6 d.p.i. miR-155-5p (miR-155) showed the greatest increase in expression within ATII cells at both timepoints and the magnitude of this increase correlated with inoculum size and pulmonary edema severity. Influenza-induced lung injury was attenuated in C57BL/6-congenic miR-155-knockout mice without affecting viral replication. Attenuation of lung injury was dependent on deletion of miR-155 from stromal cells and was recapitulated in ATII cell-specific miR-155-knockout mice. These data suggest that ATII cell miR-155 is a potential therapeutic target for IAV-induced ARDS.

Therapeutically Attenuating Neutrophil Recruitment With a CXCR2 Antagonist in Combination With Oseltamivir Ameliorates Influenza-Induced Lung Injury and Disease.

Mice were infected with influenza and treated with a CXCR2 antagonist in combination with antiviral or antiviral alone starting 4 days postinfection. Neutrophil recruitment to the lung was reduced, and improvements in health outcomes and lung consolidation were observed in combination-treated mice with no evidence of worsening outcome.

Inhibiting Bruton's tyrosine kinase rescues mice from lethal influenza-induced acute lung injury.

Infection with seasonal influenza A virus (IAV) leads to lung inflammation and respiratory failure, a main cause of death in influenza-infected patients. Previous experiments in our laboratory indicate that Bruton's tyrosine kinase (Btk) plays a substantial role in regulating inflammation in the respiratory region during acute lung injury in mice; therefore, we sought to determine if blocking Btk activity has a protective effect in the lung during influenza-induced inflammation. The Btk inhibitor ibrutinib (also known as PCI-32765) was administered intranasally to mice starting 72 h after lethal infection with IAV. Our data indicate that treatment with the Btk inhibitor not only reduced weight loss and led to survival, but also had a dramatic effect on morphological changes to the lungs, in IAV-infected mice. Attenuation of lung inflammation indicative of acute lung injury, such as alveolar hemorrhage, interstitial thickening, and the presence of alveolar exudate, together with reduced levels of the inflammatory mediators TNFα, IL-1β, IL-6, KC, and MCP-1, strongly suggests amelioration of the pathological immune response in the lungs to promote resolution of the infection. Finally, we observed that blocking Btk specifically in the alveolar compartment led to significant attenuation of neutrophil extracellular traps released into the lung in vivo and neutrophil extracellular trap formation in vitro. Our innovative findings suggest that Btk may be a new drug target for influenza-induced lung injury, and, in general, that immunomodulatory treatment may be key in treating lung dysfunction driven by excessive inflammation.

AIM2 Inflammasome Is Critical for Influenza-Induced Lung Injury and Mortality.

The absent in melanoma 2 (AIM2) inflammasome plays an important role in many viral and bacterial infections, but very little is known about its role in RNA virus infection, including influenza A virus (IAV). In this study, we have designed in vivo and in vitro studies to determine the role of AIM2 in infections with lethal doses of IAVs A/PR8/34 and A/California/07/09. In wild-type mice, IAV infection enhanced AIM2 expression, induced dsDNA release, and stimulated caspase-1 activation and release of cleaved IL-1β in the lung, which was significantly reduced in AIM2-deficient mice. Interestingly, AIM2 deficiency did not affect the transcription of caspase-1 and IL-1β. In addition, AIM2-deficient mice exhibited attenuated lung injury and significantly improved survival against IAV challenges, but did not alter viral burden in the lung. However, AIM2 deficiency did not seem to affect adaptive immune response against IAV infections. Furthermore, experiments with AIM2-specific small interfering RNA-treated and AIM2-deficient human and mouse lung alveolar macrophages and type II cells indicated a macrophage-specific function of AIM2 in regulation of IAV-stimulated proinflammatory response. Collectively, our results demonstrate that influenza infection activates the AIM2 inflammasome, which plays a critical role in IAV-induced lung injury and mortality. AIM2 might serve as a therapeutic target for combating influenza-associated morbidity and mortality without compromising the host antiviral responses.

IL-6 ameliorates acute lung injury in influenza virus infection

Interleukin 6 (IL-6) is involved in innate and adaptive immune responses to defend against pathogens. It also participates in the process of influenza infection by affecting viral clearance and immune cell responses. However, whether IL-6 impacts lung repair in influenza pathogenesis remains unclear. Here, we studied the role of IL-6 in acute influenza infection in mice. IL-6-deficient mice infected with influenza virus exhibited higher lethality, lost more body weight and had higher fibroblast accumulation and lower extracellular matrix (ECM) turnover in the lung than their wild-type counterparts. Deficiency in IL-6 enhanced proliferation, migration and survival of lung fibroblasts, as well as increased virus-induced apoptosis of lung epithelial cells. IL-6-deficient lung fibroblasts produced elevated levels of TGF-β, which may contribute to their survival. Furthermore, macrophage recruitment to the lung and phagocytic activities of macrophages during influenza infection were reduced in IL-6-deficient mice. Collectively, our results indicate that IL-6 is crucial for lung repair after influenza-induced lung injury through reducing fibroblast accumulation, promoting epithelial cell survival, increasing macrophage recruitment to the lung and enhancing phagocytosis of viruses by macrophages. This study suggests that IL-6 may be exploited for lung repair during influenza infection.

Osteopontin Exacerbates Pulmonary Damage in Influenza-Induced Lung Injury.

The level of osteopontin (OPN) increases during bacterial lung infection. However, the OPN level in virus-induced lung injury is unclear, and the relationship between the hyer-production of OPN and lung injury remains to be thoroughly understood. Therefore, we sought to determine whether a relationship exists between OPN and pulmonary damage. Particularly, pulmonary edema and the destruction of pulmonary tissue. In this study, we found that the OPN level was significantly elevated in patients with pulmonary damage, and there was a positive correlation between the OPN serum level and disease severity in influenza lung injury. The epithelial sodium channel (ENaC) is the main mechanism of clearance of pulmonary edema fluid, and matrix metalloproteinase 7 (MMP7) can degrade the extracellular matrix. In lung epithelial cells, OPN markedly decreased the mRNA expression of the α-subunit of ENaC through integrin β3 and CD44 (OPN receptors); however, the expression of MMP7 was promoted by OPN interaction with integrin β1 and CD44. In addition, OPN increased the levels of tumor necrosis factor-α and interleukin-6. These findings suggested that OPN might increase influenza virus-induced lung injury by augmenting lung epithelial cell apoptosis and impairing ENaC and extracellular matrix destruction.

Expression of suppressor of cytokine signaling 1 (SOCS1) impairs viral clearance and exacerbates lung injury during influenza infection.

Suppressor of cytokine signaling (SOCS) proteins are inducible feedback inhibitors of cytokine signaling. SOCS1−/− mice die within three weeks postnatally due to IFN-γ-induced hyperinflammation. Since it is well established that IFN-γ is dispensable for protection against influenza infection, we generated SOCS1−/−IFN-γ−/− mice to determine whether SOCS1 regulates antiviral immunity in vivo. Here we show that SOCS1−/−IFN-γ−/− mice exhibited significantly enhanced resistance to influenza infection, as evidenced by improved viral clearance, attenuated acute lung damage, and consequently increased survival rates compared to either IFN-γ−/− or WT animals. Enhanced viral clearance in SOCS1−/−IFN-γ−/− mice coincided with a rapid onset of adaptive immune responses during acute infection, while their reduced lung injury was associated with decreased inflammatory cell infiltration at the resolution phase of infection. We further determined the contribution of SOCS1-deficient T cells to antiviral immunity. Anti-CD4 antibody treatment of SOCS1−/−IFN-γ−/− mice had no significant effect on their enhanced resistance to influenza infection, while CD8+ splenocytes from SOCS1−/−IFN-γ−/− mice were sufficient to rescue RAG1−/− animals from an otherwise lethal infection. Surprisingly, despite their markedly reduced viral burdens, RAG1−/− mice reconstituted with SOCS1−/−IFN-γ−/− adaptive immune cells failed to ameliorate influenza-induced lung injury. In conclusion, in the absence of IFN-γ, the cytoplasmic protein SOCS1 not only inhibits adaptive antiviral immune responses but also exacerbates inflammatory lung damage. Importantly, these detrimental effects of SOCS1 are conveyed through discrete cell populations. Specifically, while SOCS1 expression in adaptive immune cells is sufficient to inhibit antiviral immunity, SOCS1 in innate/stromal cells is responsible for aggravated lung injury.

Mesenchymal stem cells and the stem cell niche: a new chapter

BONE MARROW-DERIVED mesenchymal stem/stromal cells (MSCs) are self-renewing multipotent cells with therapeutic effects in diverse models of tissue injury (27). In the rodent lung, MSCs reduce collagen deposition in the bleomycin model of pulmonary fibrosis (26) and reduce lung injury and improve survival following intrapulmonary delivery of endotoxin or Escherichia coli (10, 11) and following severe gram-negative peritonitis (18). In the hyperoxia model of bronchopulmonary dysplasia, exposure to high concentrations of oxygen during early postnatal life in rats and mice causes simplification of alveolar and lung capillary structure and reduced pulmonary capillary surface area, leading to pulmonary hypertension. Two groups reported simultaneously in 2009 that MSCs given by airway to rats (12) or by blood to mice (2) during prolonged hyperoxia in early postnatal life prevented arrested alveolar growth. However, engraftment of MSCs during hyperoxia and in other models has not accounted for the therapeutic effects, thus prompting a search for other mechanisms. MSCs are potent immunomodulators, suppressing several functions of lymphocytes, natural killer cells, and monocytes (1), and reduce inflammatory cell lung infiltrates and cytokines during sepsis and acute lung injury (11, 23, 25). In addition, MSCs have direct antibacterial effects (19), secrete epithelial growth factors (21), and can rescue epithelial cellular bioenergetics with mitochondrial transfer (14). MSCs and the Stem Cell Niche

CCR2-Antagonist Prophylaxis Reduces Pulmonary Immune Pathology and Markedly Improves Survival during Influenza Infection

Infection with influenza virus induces severe pulmonary immune pathology that leads to substantial human mortality. Although antiviral therapy is effective in preventing infection, no current therapy can prevent or treat influenza-induced lung injury. Previously, we reported that influenza-induced pulmonary immune pathology is mediated by inflammatory monocytes trafficking to virus-infected lungs via CCR2 and that influenza-induced morbidity and mortality are reduced in CCR2-deficient mice. In this study, we evaluated the effect of pharmacologically blocking CCR2 with a small molecule inhibitor (PF-04178903) on the entry of monocytes into lungs and subsequent morbidity and mortality in influenza-infected mice. Subcutaneous injection of mice with PF-04178903 was initiated 1 d prior to infection with influenza strain H1N1A/Puerto Rico/8/34. Compared with vehicle controls, PF-04178903-treated mice demonstrated a marked reduction in mortality (75 versus 0%) and had significant reductions in weight loss and hypothermia during subsequent influenza infection. Drug-treated mice also displayed significant reductions in bronchoalveolar lavage fluid total protein, albumin, and lactose dehydrogenase activity. Administration of PF-04178903 did not alter viral titers, severity of secondary bacteria infections (Streptococcus pneumoniae), or levels of anti-influenza-neutralizing Abs. Drug-treated mice displayed an increase in influenza nucleoprotein-specific cytotoxic T cell activity. Our results suggest that CCR2 antagonists may represent an effective prophylaxis against influenza-induced pulmonary immune pathology.

Prevention of influenza-induced lung injury in mice overexpressing extracellular superoxide dismutase

Reactive oxygen and nitrogen species such as superoxide and nitric oxide are released into the extracellular spaces by inflammatory and airway epithelial cells. These molecules may exacerbate lung injury after influenza virus pneumonia. We hypothesized that enhanced expression of extracellular superoxide dismutase (EC SOD) in mouse airways would attenuate the pathological effects of influenza pneumonia. We compared the pathogenic effects of a nonlethal primary infection with mouse-adapted Hong Kong influenza A/68 virus in transgenic (TG) EC SOD mice versus non-TG (wild-type) littermates. Compared with wild-type mice, EC SOD TG mice showed less lung injury and inflammation as measured by significant blunting of interferon-gamma induction, reduced cell count and total protein in bronchoalveolar lavage fluid, reduced levels of lung nitrite/nitrate nitrotyrosine, and markedly reduced lung pathology. These results demonstrate that enhancing EC SOD in the conducting and distal airways of the lung minimizes influenza-induced lung injury by both ameliorating inflammation and attenuating oxidative stress.