Protective role of macrophages in noninflammatory lung injury caused by selective ablation of alveolar epithelial type II Cells

Macrophages have a wide variety of activities and it is largely unknown how the diverse phenotypes of macrophages contribute to pathological conditions in the different types of tissue injury in vivo. In this study we established a novel animal model of acute respiratory distress syndrome caused by the dysfunction of alveolar epithelial type II (AE2) cells and examined the roles of alveolar macrophages in the acute lung injury. The human diphtheria toxin (DT) receptor (DTR), heparin-binding epidermal growth factor-like growth factor (HB-EGF), was expressed under the control of the lysozyme M (LysM) gene promoter in the mice. When DT was administrated to the mice they suffered from acute lung injury and died within 4 days. Immunohistochemical examination revealed that AE2 cells as well as alveolar macrophages were deleted via apoptosis in the mice treated with DT. Consistent with the deletion of AE2 cells, the amount of surfactant proteins in bronchoalveolar lavage fluid was greatly reduced in the DT-treated transgenic mice. When bone marrow from wild-type mice was transplanted into irradiated LysM-DTR mice, the alveolar macrophages became resistant to DT but the mice still suffered from acute lung injury by DT administration. Compared with the mice in which both AE2 cells and macrophages were deleted by DT administration, the DT-treated LysM-DTR mice with DT-resistant macrophages showed less severe lung injury with a reduced amount of hepatocyte growth factor in bronchoalveolar lavage fluid. These results indicate that macrophages play a protective role in noninflammatory lung injury caused by the selective ablation of AE2 cells.     

Cytochrome b5 and cytokeratin 17 are biomarkers in bronchoalveolar fluid signifying onset of acute lung injury

Acute lung injury (ALI) is characterized by pulmonary edema and acute inflammation leading to pulmonary dysfunction and potentially death. Early medical intervention may ameliorate the severity of ALI, but unfortunately, there are no reliable biomarkers for early diagnosis. We screened for biomarkers in a mouse model of ALI. In this model, inhalation of S. aureus enterotoxin A causes increased capillary permeability, cell damage, and increase protein and cytokine concentration in the lungs. We set out to find predictive biomarkers of ALI in bronchoalveolar lavage (BAL) fluid before the onset of clinical manifestations. A cutting edge proteomic approach was used to compare BAL fluid harvested 16 h post S. aureus enterotoxin A inhalation versus BAL fluid from vehicle alone treated mice. The proteomic PF 2D platform permitted comparative analysis of proteomic maps and mass spectrometry identified cytochrome b5 and cytokeratin 17 in BAL fluid of mice challenged with S. aureus enterotoxin A. Validation of cytochrome b5 showed tropic expression in epithelial cells of the bronchioles. Importantly, S. aureus enterotoxin A inhalation significantly decreased cytochrome b5 during the onset of lung injury. Validation of cytokeratin 17 showed ubiquitous expression in lung tissue and increased presence in BAL fluid after S. aureus enterotoxin A inhalation. Therefore, these new biomarkers may be predictive of ALI onset in patients and could provide insight regarding the basis of lung injury and inflammation.     

Microarray analysis reveals the changes of circular RNA expression and molecular mechanism in acute lung injury mouse model

Acute lung injury (ALI) is a severe disease with sudden onset, rapid progression, poor treatment response, and high mortality. An increasing number of studies had found that circular RNAs (circRNAs) has significant functions in various diseases, while the role of circRNAs in ALI is not yet clear. The purpose of this study was to find circRNAs related to ALI and their mechanism of action. Expression profiles of lung circRNAs and messenger RNAs (mRNAs) were analyzed by microarray in the ALI mice models and healthy controlled mice. Differentially expressed RNAs were identified, function and pathways were analyzed by bioinformatics analysis. Moreover, the results of the microarray were verified by real-time PCR. We identified 2262 differentially expressed mRNAs and 581 circRNAs between ALI mice and control. Validation of candidate circRNAs by real-time PCR indicates that the majority of circRNAs identified by microarray are reliable and worthy of further study. ALI induced circRNAs primarily function in the metabolic regulatory process. Moreover, differentially expressed circRNAs were mainly involved in signaling pathways of mitogen-activated protein kinases, focal adhesion, FoxO, neurotrophin, and Wnt. In addition, a competitive endogenous RNA network was constructed to further interpret the molecular mechanism of ALI. This study observed significantly changed circRNAs profiles in LPS-induced mouse model and revealed a potential role of circRNAs in ALI.     

Interleukin 1 bioactivity in the lungs of rats with monocrotaline-induced pulmonary hypertension

A single subcutaneous injection of monocrotaline in rats provokes lung injury, inflammation, and progressive pulmonary hypertension. The specific mediators of the lung injury and inflammation and the relation of these events to the ensuing hypertensive pulmonary vascular disease are not understood. Since the monokine interleukin 1 (IL-1) has been implicated in acute inflammatory reactions, the present study tested the hypotheses that monocrotaline promotes the appearance of IL-1 in the bronchoalveolar spaces of treated rats and that accumulation of the monokine coincides temporally with development of lung injury, inflammation, and/or pulmonary hypertension. As expected, monocrotaline administration was associated with an early phase of pulmonary edema, manifest at Day 7 post-treatment as an increase in the lung wet-to-dry weight ratio, followed at Day 14 post-treatment by development of pulmonary hypertension as evidenced by progressive right ventricular hypertrophy. Lung inflammation also was present at Days 14 and 21 after monocrotaline as indicated by the accumulation of leukocytes in the bronchoalveolar lavage fluid and by an increase in the lung tissue activity of the granulocyte-specific enzyme myeloperoxidase. Interleukin 1, bioassayed in bronchoalveolar lavage fluid using the standard D10 T-cell assay system, was increased slightly at Day 4 postmonocrotaline, returned to baseline at Day 7, and was markedly elevated at Days 14 and 21 after monocrotaline treatment. These observations indicate that increases in the bronchoalveolar lavage fluid content of IL-1 bioactivity are temporally related to the evolution of monocrotaline-induced lung injury, inflammation, and pulmonary hypertension and suggest that the monokine may play a pathogenetic role in these events.     

Modulation of endoperoxide product levels and cyclophosphamide-induced injury by glutathione repletion

Glutathione is a tripeptide important in a number of diverse cellular functions including enzymatic reactions involved in prostaglandin endoperoxide metabolism. We have previously reported that cyclophosphamide administration to rats results in acute lung injury manifested by increased bronchoalveolar lavage albumin concentrations. In the current study we examine whether cyclophosphamide treatment affects pulmonary glutathione stores or bronchoalveolar endoperoxide metabolic product levels and whether these effects may be related to acute lung injury caused by the drug. We show that cyclophosphamide treatment causes a dose-dependent reduction in pulmonary glutathione stores 4 h after drug administration. In addition, acute lung injury as the result of cyclophosphamide can be abrogated by coadministration of oxothiazolidine carboxylate, an intracellular cysteine delivery system that also reverses pulmonary glutathione depletion induced by cyclophosphamide in our study. Finally, cyclophosphamide treatment reduces prostaglandin E2 concentrations in bronchoalveolar lavage and alveolar macrophage culture supernatant in a dose-dependent fashion and increases bronchoalveolar thromboxane concentrations in low dose-treated animals. These effects are reversed to a variable degree by coadministration of oxothiazolidine carboxylate. Our study suggests in vivo pulmonary arachidonic acid metabolism and cyclophosphamide-induced acute lung injury are modulated by cellular glutathione stores. These findings may have important implications for the treatment of acute lung injury.     

Natural killer cells are involved in acute lung immune injury caused by respiratory syncytial virus infection

It is known that respiratory syncytial virus (RSV) is the main cause of bronchiolitis and pneumonia in young children. RSV infection often leads to severe acute lung immunopathology, but the underlying immune mechanisms are not yet fully elucidated. Here, we found that RSV infection induced severe acute lung immune injury and promoted the accumulation and activation of lung natural killer (NK) cells at the early stage of infection in BALB/c mice. Activated lung NK cells highly expressed activating receptors NKG2D and CD27 and became functional NK cells by producing a large amount of gamma interferon (IFN-γ), which was responsible for acute lung immune injury. NK cell depletion significantly attenuated lung immune injury and reduced infiltration of total inflammatory cells and production of IFN-γ in bronchoalveolar lavage fluid (BALF). These data show that NK cells are involved in exacerbating the lung immune injury at the early stage of RSV infection via IFN-γ secretion.     

Adrenomedullin ameliorates lipopolysaccharide-induced acute lung injury in rats

Adrenomedullin (AM), an endogenous peptide, has been shown to have a variety of protective effects on the cardiovascular system. However, the effect of AM on acute lung injury remains unknown. Accordingly, we investigated whether AM infusion ameliorates lipopolysaccharide (LPS)-induced acute lung injury in rats. Rats were randomized to receive continuous intravenous infusion of AM (0.1 microg x kg(-1) x min(-1)) or vehicle through a microosmotic pump. The animals were intratracheally injected with either LPS (1 mg/kg) or saline. At 6 and 18 h after intratracheal instillation, we performed histological examination and bronchoalveolar lavage and assessed the lung wet/dry weight ratio as an index of acute lung injury. Then we measured the numbers of total cells and neutrophils and the levels of tumor necrosis factor (TNF)-alpha and cytokine-induced neutrophil chemoattractant (CINC) in bronchoalveolar lavage fluid (BALF). In addition, we evaluated BALF total protein and albumin levels as indexes of lung permeability. LPS instillation caused severe acute lung injury, as indicated by the histological findings and the lung wet/dry weight ratio. However, AM infusion attenuated these LPS-induced abnormalities. AM decreased the numbers of total cells and neutrophils and the levels of TNF-alpha and CINC in BALF. AM also reduced BALF total protein and albumin levels. In addition, AM significantly suppressed apoptosis of alveolar wall cells as indicated by cleaved caspase-3 staining. In conclusion, continuous infusion of AM ameliorated LPS-induced acute lung injury in rats. This beneficial effect of AM on acute lung injury may be mediated by inhibition of inflammation, hyperpermeability, and alveolar wall cell apoptosis.     

辛伐他汀对烟雾吸入性肺损伤大鼠炎性因子及氧化应激反应的影响

目的:研究辛伐他汀对烟雾吸入性肺损伤大鼠炎性因子及氧化应激反应的影响。方法:选取60只清洁级SD大鼠,将其按照随机抽签法分成正常组、盐水组以及辛伐他汀组,每组各20只。盐水组与辛伐他汀组大鼠均制备发烟罐烟雾吸入性肺损伤模型,建模成功后30 min,辛伐他汀组大鼠予以50 mg/kg剂量的辛伐他汀灌胃,盐水组则予以等量的生理盐水灌胃,正常大鼠予以正常饲养处理。采用酶联免疫法检测血清、肺泡灌洗液中炎症因子[包括白细胞介素-6(IL-6)、肿瘤坏死因子-α(TNF-α)]及氧化应激反应指标[包括超氧化物歧化酶(SOD)、丙二醛(MDA)]水平。结果:盐水组、辛伐他汀组大鼠血清、肺泡灌洗液中IL-6、TNF-α水平均高于正常组,且辛伐他汀组大鼠上述各项指标低于盐水组(均P<0.05)。盐水组、辛伐他汀组大鼠血清、肺泡灌洗液中SOD水平低于正常组,辛伐他汀组明显高于盐水组(均P<0.05),盐水组、辛伐他汀组大鼠血清、肺泡灌洗液中MDA水平高于正常组,辛伐他汀组明显低于盐水组(均P<0.05)。结论:辛伐他汀对烟雾吸入性肺损伤大鼠的炎性因子具有明显的改善作用,且有利于减轻大鼠的氧化应激反应程度。     

Effect of adenosine A2A receptor activation in murine models of respiratory disorders

Activation of the adenosine A(2A) receptor has been postulated as a possible treatment for lung inflammatory diseases such as asthma and chronic obstructive pulmonary disease (COPD). In this report, we have studied the anti-inflammatory properties of the reference A(2A) agonist CGS-21680, given intranasally at doses of 10 and 100 microg/kg, in a variety of murine models of asthma and COPD. After an acute ovalbumin challenge of sensitized mice, prophylactic administration of CGS-21680 inhibited the bronchoalveolar lavage fluid inflammatory cell influx but not the airway hyperreactivity to aerosolized methacholine. After repeated ovalbumin challenges, CGS-21680 given therapeutically inhibited the bronchoalveolar lavage fluid inflammatory cell influx but had no effect on the allergen-induced bronchoconstriction, the airway hyperreactivity, or the bronchoalveolar lavage fluid mucin levels. As a comparator, budesonide given intranasally at doses of 0.1-1 mg/kg fully inhibited all the parameters measured in the latter model. In a lipopolysaccharide-driven model, CGS-21680 had no effect on the bronchoalveolar lavage fluid inflammatory cell influx or TNF-alpha, keratinocyte chemoattractant, and macrophage inflammatory protein-2 levels, but potently inhibited neutrophil activation, as measured by bronchoalveolar lavage fluid elastase levels. With the use of a cigarette smoke model of lung inflammation, CGS-21680 did not significantly inhibit bronchoalveolar lavage fluid neutrophil infiltration but reversed the cigarette smoke-induced decrease in macrophage number. Together, these results suggest that activation of the A(2A) receptor would have a beneficial effect by inhibiting inflammatory cell influx and downregulating inflammatory cell activation in asthma and COPD, respectively.     

A murine model of smoke inhalation

The United States has one of the world's largest per capita fire death rates. House fires alone kill >9,000 Americans annually, and smoke inhalation is the leading cause of mortality from structural fires. Animal models are needed to develop therapies to combat this problem. We have developed a murine model of smoke inhalation through the design, construction, and use of a controlled-environment smoke chamber. There is a direct relationship between the quantity of wood combusted and mortality in mice. As with human victims, the primary cause of death from smoke inhalation is an elevated blood carboxyhemoglobin level. Lethal (78%) and sublethal (50%) carboxyhemoglobin levels were obtained in mice subjected to varying amounts of smoke. Mice exposed to wood smoke demonstrated more dramatic pathology than mice exposed to cotton or polyurethane smoke. A CD-1 model of wood smoke exposure was developed, demonstrating type II cell hypertrophy, cytoplasmic blebbing, cytoplasmic vacuolization, sloughing, hemorrhage, edema, macrophage infiltration, and lymphocyte infiltration. The bronchoalveolar lavage fluid of smoke-exposed mice demonstrated a significant increase in total cell counts compared with those in control mice. These findings are comparable to the lung tissue response observed in human victims of smoke inhalation.     

Lipopolysaccharide-Induced Lung Injury Is Independent of Serum Vitamin D Concentration

Vitamin D deficiency is increasing in incidence around the world. Vitamin D, a fat-soluble vitamin, has documented effects on the innate and adaptive immune system, including macrophage and T regulatory (Treg) cell function. Since Treg cells are important in acute lung injury resolution, we hypothesized that vitamin D deficiency increases the severity of injury and delays injury resolution in lipopolysaccharide (LPS) induced acute lung injury. Vitamin D deficient mice were generated, using C57BL/6 mice, through diet modification and limited exposure to ultraviolet light. At 8 weeks of age, vitamin D deficient and sufficient mice received 2.5 g/kg of LPS or saline intratracheal. At 1 day, 3 days and 10 days, mice were anesthetized and lung elastance measured. Mice were euthanized and bronchoalveolar lavage fluid, lungs and serum were collected. Ex vivo neutrophil chemotaxis was evaluated, using neutrophils from vitamin D sufficient and deficient mice exposed to the chemoattractants, KC/CXCL1 and C5a, and to bronchoalveolar lavage fluid from LPS-exposed mice. We found no difference in the degree of lung injury. Leukocytes were mildly decreased in the bronchoalveolar fluid of vitamin D deficient mice at 1 day. Ex-vivo, neutrophils from vitamin D deficient mice showed impaired chemotaxis to KC but not to C5a. Vitamin D deficiency modestly impairs neutrophil chemotaxis; however, it does not affect lung injury or its resolution in an LPS model of acute lung injury.     

Role of CD13/aminopeptidase N in rat lymphocytic alveolitis caused by thoracic irradiation

CD13/aminopeptidase N is a cell surface glycoprotein that is widely distributed in a variety of mammalian cells. It was recently shown to have chemotactic activity for T lymphocytes. This study examined the role of CD13/aminopeptidase N in lymphocytic alveolitis in radiation-induced lung injury caused by a single-dose thoracic irradiation (15 Gy) in rats. Significantly increased aminopeptidase activity was detected in bronchoalveolar lavage fluid obtained from irradiated rats at 4 weeks after irradiation compared to the activity in unirradiated rats. Significantly higher aminopeptidase activity was detected on alveolar macrophages from irradiated rats at 2 and 4 weeks than on those from unirradiated rats. Western blot analysis showed an increased expression of CD13/aminopeptidase N protein in alveolar macrophages from irradiated rats at 4 weeks. Chemotactic activity for normal rat lymphocytes was detected in bronchoalveolar lavage fluid from irradiated rats at 4 weeks, and approximately 60% of the activity was inhibited by pretreatment of bronchoalveolar lavage fluid with bestatin, a specific aminopeptidase inhibitor. This study suggests that CD13/aminopeptidase N may play an important role as a lymphocyte chemoattractant in lymphocyte-mediated alveolitis in experimental radiation-induced lung injury.     

Inhalation of sphingosine kinase inhibitor attenuates airway inflammation in asthmatic mouse model

Sphingosine 1-phosphate (S1P) produced by sphingosine kinase (SPHK) is implicated in acute immunoresponses, however, mechanisms of SPHK/S1P signaling in the pathogenesis of bronchial asthma are poorly understood. In this study, we hypothesized that SPHK inhibition could ameliorate lung inflammation in ovalbumin (OVA)-challenged mouse lungs. Six- to eight-week-old C57BL/6J mice were sensitized and exposed to OVA for 3 consecutive days. Twenty-four hours later, mice lungs and bronchoalveolar lavage (BAL) fluid were analyzed. For an inhibitory effect, either of the two different SPHK inhibitors, N,N-dimethylsphingosine (DMS) or SPHK inhibitor [SK-I; 2-(p-hydroxyanilino)-4-(p-chlorophenyl) thiazole], was nebulized for 30 min before OVA inhalation. OVA inhalation caused S1P release into BAL fluid and high expression of SPHK1 around bronchial epithelial walls and inflammatory areas. DMS or SK-I inhalation resulted in a decrease in S1P amounts in BAL fluid to basal levels, accompanied by decreased eosinophil infiltration and peroxidase activity. The extent of inhibition caused by DMS inhalation was higher than that caused by SK-I. Like T helper 2 (Th2) cytokine release, OVA inhalation-induced increase in eotaxin expression was significantly suppressed by DMS pretreatment both at protein level in BAL fluid and at mRNA level in lung homogenates. Moreover, bronchial hyperresponsiveness to inhaled methacholine and goblet cell hyperplasia were improved by SPHK inhibitors. These data suggest that the inhibition of SPHK affected acute eosinophilic inflammation induced in antigen-challenged mouse model and that targeting SPHK may provide a novel therapeutic tool to treat bronchial asthma.     

Regulatory effects of eotaxin on acute lung inflammatory injury

Eotaxin, which is a major mediator for eosinophil recruitment into lung, has regulatory effects on neutrophil-dependent acute inflammatory injury triggered by intrapulmonary deposition of IgG immune complexes in rats. In this model, eotaxin mRNA and protein were up-regulated during the inflammatory response, resulting in eotaxin protein expression in alveolar macrophages and in alveolar epithelial cells. Ab-induced blockade of eotaxin in vivo caused enhanced NF-kappaB activation in lung, substantial increases in bronchoalveolar lavage levels of macrophage inflammatory protein (MIP)-2 and cytokine-induced neutrophil chemoattractant (CINC), and increased MIP-2 and CINC mRNA expression in alveolar macrophages. In contrast, TNF-alpha levels were unaffected, and IL-10 levels fell. Under these experimental conditions, lung neutrophil accumulation was significantly increased, and vascular injury, as reflected by extravascular leak of (125)I-albumin, was enhanced. Conversely, when recombinant eotaxin was administered in the same inflammatory model of lung injury, bronchoalveolar lavage levels of MIP-2 were reduced, as was neutrophil accumulation and the intensity of lung injury. In vitro stimulation of rat alveolar macrophages with IgG immune complexes greatly increased expression of mRNA and protein for MIP-2, CINC, MIP-1alpha, MIP-1beta, TNF-alpha, and IL-1beta. In the copresence of eotaxin, the increased levels of MIP-2 and CINC mRNAs were markedly diminished, whereas MIP-1alpha, MIP-1beta, TNF-alpha, and IL-1beta expression of mRNA and protein was not affected. These data suggest that endogenous eotaxin, which is expressed during the acute lung inflammatory response, plays a regulatory role in neutrophil recruitment into lung and the ensuing inflammatory damage.     

Alkannin attenuates lipopolysaccharide‐induced lung injury in mice via Rho/ROCK/NF‐κB pathway

We investigated the effects and associated mechanism of alkannin (AL) on lipopolysaccharide (LPS)‐induced acute lung injury in a mouse model. Pretreatment with AL in vivo significantly reduced the lung wet/dry weight ratio and inhibited lung myeloperoxidase activity and malondialdehyde content, while increasing superoxide dismutase activity. Hematoxylin and eosin staining demonstrated that AL attenuated lung histopathological changes. In addition, AL‐inhibited overproduction of proinflammatory cytokines in bronchoalveolar lavage fluid and lung tissues in LPS‐injured mice and LPS‐exposed A549 cells. Further analysis showed that AL‐inhibited induction of the Rho/ROCK/NF‐κB pathway via LPS‐induced inflammation in mice and A549 cells. Fasudil, a selective ROCK inhibitor, showed similar effects. Overall, the findings indicate that AL suppresses the expression of messenger RNAs and proteins associated with Rho/ROCK/NF‐κB signaling to effectively ameliorate lung injury.     

Metabolic Consequences of Chronic Alcohol Abuse in Non-Smokers: A Pilot Study

An alcohol use disorder (AUD) is associated with an increased susceptibility to respiratory infection and injury and, upon hospitalization, higher mortality rates. Studies in model systems show effects of alcohol on mitochondrial function, lipid metabolism and antioxidant systems. The present study applied high-resolution metabolomics to test for these changes in bronchoalveolar lavage fluid (BALF) of subjects with an AUD. Smokers were excluded to avoid confounding effects and compliance was verified by cotinine measurements. Statistically significant metabolic features, differentially expressed by control and AUD subjects, were identified by statistical and bioinformatic methods. The results show that fatty acid and acylcarnitine concentrations were increased in AUD subjects, consistent with perturbed mitochondrial and lipid metabolism. Decreased concentrations of methyl-donor compounds suggest altered one-carbon metabolism and oxidative stress. An accumulation of peptides suggests proteolytic activity, which could reflect altered epithelial barrier function. Two metabolites of possible microbial origin suggest subclinical bacterial infection. Furthermore, increased diacetylspermine suggests additional metabolic perturbations, which could contribute to dysregulated alveolar macrophage function and vulnerability to infection. Together, the results show an extended metabolic consequence of AUD in the bronchoalveolar space.     

Pathophysiological analysis of combined burn and smoke inhalation injuries in sheep

We investigated the pathophysiological alterations seen with combined burn and smoke inhalation injuries by focusing on pulmonary vascular permeability and cardiopulmonary function compared with those seen with either burn or smoke inhalation injury alone. To estimate the effect of factors other than injury, the experiments were also performed with no injury in the same experimental setting. Lung edema was most severe in the combined injury group. Our study revealed that burn injury does not affect protein leakage from the pulmonary microvasculature, even when burn is associated with smoke inhalation injury. The severity of lung edema seen with the combined injury is mainly due to augmentation of pulmonary microvascular permeability to fluid, not to protein. Cardiac dysfunction after the combined injury consisted of at least two phases. An initial depression was mostly related to hypovolemia due to burn injury. It was improved by a large amount of fluid resuscitation. The later phase, which was indicated to be a myocardial contractile dysfunction independent of the Starling equation, seemed to be correlated with smoke inhalation injury.     

The lysophosphatidic acid receptor LPA1 links pulmonary fibrosis to lung injury by mediating fibroblast recruitment and vascular leak

Aberrant wound-healing responses to injury have been implicated in the development of pulmonary fibrosis, but the mediators directing these pathologic responses have yet to be fully identified. We show that lysophosphatidic acid levels increase in bronchoalveolar lavage fluid following lung injury in the bleomycin model of pulmonary fibrosis, and that mice lacking one of its receptors, LPA1, are markedly protected from fibrosis and mortality in this model. The absence of LPA1 led to reduced fibroblast recruitment and vascular leak, two responses that may be excessive when injury leads to fibrosis rather than to repair, whereas leukocyte recruitment was preserved during the first week after injury. In persons with idiopathic pulmonary fibrosis, lysophosphatidic acid levels in bronchoalveolar lavage fluid were also increased, and inhibition of LPA1 markedly reduced fibroblast responses to the chemotactic activity of this fluid. LPA1 therefore represents a new therapeutic target for diseases in which aberrant responses to injury contribute to fibrosis, such as idiopathic pulmonary fibrosis.