Angiotensinogen gene G-6A polymorphism influences idiopathic pulmonary fibrosis disease progression.

Angiotensin II is a growth factor that plays a key role in the physiopathology of idiopathic pulmonary fibrosis (IPF). A nucleotide substitution of an adenine instead of a guanine (G-6A) in the proximal promoter region of angiotensinogen (AGT), the precursor of angiotensin II, has been associated with an increased gene transcription rate. In order to investigate whether the G-6A polymorphism of the AGT gene is associated with IPF development, severity and progression, the present study utilised a case-control study design and genotyped G-6A in 219 patients with IPF and 224 control subjects. The distribution of G-6A genotypes and alleles did not significantly differ between cases and controls. The G-6A polymorphism of the AGT gene was not associated with disease severity at diagnosis. The presence of the A allele was strongly associated with increased alveolar arterial oxygen tension difference during follow-up, after controlling for the confounding factors. Higher alveolar arterial oxygen tension changes over time were observed in patients with the AA genotype (0.37+/-0.7 mmHg (0.049+/-0.093 kPa) per month) compared to GA genotype (0.12+/-1 mmHg (0.016+/-0.133 kPa) per month) and GG genotype (0.2+/-0.6 mmHg (0.027+/-0.080 kPa) per month). G-6A polymorphism of the angiotensinogen gene is associated with idiopathic pulmonary fibrosis progression but not with disease predisposition. This polymorphism could have a predictive significance in idiopathic pulmonary fibrosis patients.

Pulmonary response to airway instillation of autologous blood in horses.

REASONS FOR PERFORMING STUDY: Exercise-induced pulmonary haemorrhage (EIPH) occurs in the majority of horses performing strenuous exercise. Associated pulmonary lesions include alveolar and airway wall fibrosis, which may enhance the severity of EIPH. Further work is required to understand the pulmonary response to blood in the equine airways. OBJECTIVES: To confirm that a single instillation of autologous blood into horse airways is associated with alveolar wall fibrosis, and to determine if blood in the airways is also associated with peribronchiolar fibrosis. METHODS: Paired regions of each lung were inoculated with blood or saline at 14 and 7 days, and 48, 24 and 6 h before euthanasia. Resulting lesions were described histologically and alveolar and airway wall collagen was quantified. RESULTS: The main lesion observed on histology was hypertrophy and hyperplasia of type II pneumocytes at 7 days after blood instillation. This lesion was no longer present at 14 days. There were no significant effects of lung region, treatment (saline or autologous blood instillation), nor significant treatment-time interactions in the amount of collagen in the interstitium or in the peribronchial regions. CONCLUSION: A single instillation of autologous blood in lung regions is not associated with pulmonary fibrosis. POTENTIAL RELEVANCE: Pulmonary fibrosis and lung remodelling, characteristic of EIPH, are important because these lesions may enhance the severity of bleeding during exercise. A single instillation of autologous blood in the airspaces of the lung is not associated with pulmonary fibrosis. Therefore the pulmonary fibrosis described in EIPH must have other causes, such as repetitive bleeds, or the presence of blood in the pulmonary interstitium in addition to the airspaces. Prevention of pulmonary fibrosis through therapeutic intervention requires a better understanding of these mechanisms.

Protection of Meconium-Induced Lung Epithelial Injury by Protease Inhibitors.

Earlier work form this laboratory showed that exposure of alveolar epithelial cells (AECs) to meconium caused significant cell detachment and that meconium-induced detachment of cells was prevented by a protease inhibitor cocktail. Therefore, it was hypothesized that protease inhibitors might protect AEC monolayers against meconium-induced collapse of epithelial barrier function both in vitro and in vivo. To investigate this theory in vitro, albumin flux was measured across cultured, confluent monolayers of human type II derived cell line A549 on microporous filter inserts. Human meconium was collected from seven healthy full-term neonates and the samples were pooled and diluted prior to analysis. Exposure of AECs to 5% human meconium increased albumin flux across the cultured AEC monolayers, but the increase was significantly blocked by protease inhibitors (P<0.001). In C57/BL6 mice, intratracheal instillation of 5% human meconium increased the passage of Evans Blue Dye (EBD) from the vascular compartment into the alveolar spaces, measured in bronchoalveolar lavage (BAL) fluid after intravenous injection of EBD. Moreover, intratrachial coinstillation of protease inhibitors prevented the meconium-induced increase in EBD passage into BAL fluid (P<0.01). The data presented herein clearly demonstrate that protease inhibitors protect AEC barrier function against meconium-induced injury, and suggest the future possibility of using protease inhibitors in the treatment of meconium aspiration syndrome.

Glycerol as a substrate for phospholipid biosynthesis in type II pneumocytes isolated from streptozotocin-diabetic rats.

Glycerol and glucose utilization for phospholipid biosynthesis was examined in type II pneumocytes isolated from normal and streptozotocin-diabetic rats. In cells from diabetic rats, incorporation of [1,3-14C]glycerol into total phosphatidylcholine (PC), disaturated phosphatidylcholine (DSPC), phosphatidylglycerol (PG) and phosphatidylethanolamine (PE) occurred to a greater degree by the glycerol 3-phosphate pathway as opposed to the dihydroxyacetone phosphate pathway. Total incorporation of glycerol into each of the major cellular phospholipids was increased up to 6-fold in cells from diabetic rats, while the total incorporation of glucose into the same lipids was decreased 2-fold. While the percentage of both glucose and glycerol carbons incorporated into the backbone of DSPC was increased in cells from diabetic rats, the percentage of carbons from both substrates incorporated into the fatty acid moieties was decreased. As a measure of DSPC synthesis, choline incorporation into DSPC was significantly decreased in type II cells from diabetic animals if the cells were incubated in the presence of glucose, palmitate and choline but not glycerol. Addition of 0.1 or 0.3 mM glycerol to the incubation medium restored choline incorporation to the control value in cells from diabetic rats, but did not affect the rate of choline incorporation into DSPC in cells from normal rats. These results suggest that exogenous glycerol can compensate for reduced glucose metabolism in type II cells of diabetic animals to maintain a constant rate of DSPC synthesis.

Glycerol metabolism in type II pneumocytes isolated from streptozotocin-diabetic rats.

Glycerol utilization for phospholipid biosynthesis was examined in type II pneumocytes isolated from normal and streptozocinin-diabetic rats. With glucose in the incubation medium, incorporation of exogenous [1,3-14C]glycerol into disaturated phosphatidylcholine, total phosphatidylcholine (PC), phosphatidylglycerol (PG) and phosphatidylethanolamine (PE) was increased 4-fold in cells from diabetic rats. In the absence of glucose, glycerol incorporation was 5-fold greater than in its presence in cells from normal animals, but was further increased 2.2-fold in cells from diabetic rats. Insulin treatment of diabetic rats returned all incorporation rates to control values. The increased glycerol incorporation rates were not due to differences in either phospholipid turnover or the size of the glycerol 3-phosphate precursor pool. Kinetic analysis of glycerol entry into the acid-soluble cell fraction indicated that glycerol transport occurred largely by simple diffusion, and was not rate limiting for its entry into lipids. Glycerol entry into the total lipid fraction was saturable, reaching a Vmax of 48 pmol/micrograms DNA per h in normal cells and 120 pmol/micrograms DNA per h in cells from diabetic rats, with no change in the Km (0.31 mM). While glycerol oxidation was reduced 23% in cells from diabetic rats in the presence of glucose and by 44% in the absence of glucose, glycerol kinase activity in sonicates of cells from diabetic animals was increased 210% and was reversed by in vivo insulin treatment. These results suggest that glycerol utilization in type II pneumocytes is a hormonally regulated function of both glycerol oxidation and glycerol phosphorylation.

Altered phospholipid biosynthesis in type II pneumocytes isolated from streptozotocin-diabetic rats.

To determine whether type II pneumocytes isolated from diabetic animals could serve as a useful model for the study of surfactant phospholipid biosynthesis and its regulation, type II pneumocytes were isolated from adult streptozotocin-diabetic rats and placed in short-term primary culture. On a DNA basis, total cellular disaturated phosphatidylcholine (disaturated PC) and phosphatidylglycerol (PG) were decreased 36 and 66%, respectively, in type II cells from diabetic animals. 7 days of insulin treatment of diabetic rats returned the cellular disaturated PC and PG content to control values and increased the total cellular phosphatidylethanolamine (PE) content by 51%. The rates of glucose and acetate incorporation into disaturated PC per unit DNA were reduced 32 and 38%, respectively, in cells isolated from diabetic rats, while glycerol incorporation was increased by 143%. Insulin treatment of diabetic rats returned the glucose and glycerol incorporation rates to control values and increased acetate incorporation into disaturated PC by 66%. These data suggest that the biosynthesis of surfactant is altered by both diabetes mellitus and in vivo insulin treatment.

Cholera toxin stimulates type II pneumocyte proliferation by a cyclic AMP-independent mechanism.

Cholera toxin (CT) stimulated DNA synthesis by low-density primary cultures of adult rat type II pneumocytes (T2P) in a dose-dependent manner, either in the presence or the absence of serum. In the presence of 1% rat serum, 1 microgram/ml CT also stimulated a 50% increase in cell number over 8 days of incubation (P<0.01); this was in addition to a 2-fold increase in cell number induced by the serum alone (P<0.05). The same dose of CT also elevated intracellular cAMP and the total activity of protein kinase A (both P<0.01), suggesting toxin stimulation of T2P proliferation by a cAMP-dependent mechanism. However, the effect of CT on DNA synthesis could not be mimicked by 8-bromoadenosine 3':5'-cyclic monophosphate (8-bromo-cAMP), nor by N6,2'-O-dibutyryladenosine 3':5'-cyclic monophosphate (dibutyryl-cAMP), each tested over a wide range of concentrations. l-Isoproterenol stimulated surfactant secretion by over 5-fold (P<0. 01), but neither the beta-agonist, forskolin nor 3-isobutyl-1-methylxanthine had any significant effect on DNA synthesis. The purified B-subunit of CT stimulated DNA synthesis to the same degree as did the holotoxin, either in the presence or the absence of rat serum. In contrast, the purified A-subunit had no significant effect. These data suggest that cholera toxin stimulates type II pneumocyte proliferation through a mechanism that is independent of cAMP, protein kinase A and toxin-catalyzed ADP-ribosylation.

Upregulation of gelatinases A and B, collagenases 1 and 2, and increased parenchymal cell death in COPD.

BACKGROUND: A central feature in the pathogenesis of COPD is the inflammation coexisting with an abnormal protease/antiprotease balance. However, the possible role of different serine and metalloproteinases remains controversial. PATIENTS AND MEASUREMENTS: We examined the expression of gelatinases A and B (matrix metalloproteinase [MMP]-2 and MMP-9); collagenases 1, 2, and 3 (MMP-1, MMP-8, and MMP-13); as well as the presence of apoptosis in lung tissues of 10 COPD patients and 5 control subjects. In addition, gelatinase-A and gelatinase-B activities were assessed in BAL obtained from eight COPD patients, and from six healthy nonsmokers and six healthy smoker control subjects. SETTING: Tertiary referral center and university laboratories of biochemistry, and lung cell kinetics. RESULTS: Immunohistochemical analysis of COPD lungs showed a markedly increased expression of collagenases 1 and 2, and gelatinases A and B, while collagenase 3 was not found. Neutrophils exhibited a positive signal for collagenase 2 and gelatinase B, whereas collagenase 1 and gelatinase A were revealed mainly in macrophages and epithelial cells. BAL gelatin zymography showed a moderate increase of progelatinase-A activity and intense bands corresponding to progelatinase B. In situ end labeling of fragmented DNA displayed foci of positive endothelial cells, although some alveolar epithelial, interstitial, and inflammatory cells also revealed intranuclear staining. CONCLUSION: These findings suggest that there is an upregulation of collagenase 1 and 2 and gelatinases A and B, and an increase in endothelial and epithelial cell death, which may contribute to the pathogenesis of COPD through the remodeling of airways and alveolar structures.

Regulation of apoptosis by angiotensin II in the heart and lungs (Review).

Cell death by apoptosis is now known to be an important mechanism of cell population control in organ development and in normal tissue homeostasis. Inappropriate apoptosis also contributes to the pathogenesis of a number of diseases involving the heart and lungs. Knowledge of the regulation of apoptosis in these organs is therefore of fundamental importance. A growing body of evidence suggests that the renin-angiotensin system (RAS), traditionally viewed as an endocrine system in the regulation of blood pressure, also functions as a regulator of apoptosis in a variety of cell types through both paracrine and autocrine mechanisms that are likely independent of the endocrine RAS. Much of the evidence in support of this premise comes from investigations of cardiac myocytes, endothelial cells and epithelial cells of the lung, both in culture and in situ within human pathological specimens and animal models of heart, vascular and pulmonary disease. Evidence from each of these areas is reviewed and discussed in relation to diseases of the heart, vascular system and lungs.

Effect of dietary state on hepatocyte size.

In order to calculate cellular metabolite concentrations, it is necessary to determine accurately the cellular volume. The purpose of the experiments reported here was to determine the effect of dietary state on the volume of hepatocytes isolated from livers of fed, fasted (48 h) or fasted (48 h)-refed (48 h) male Sprague-Dawley rats. Cellular volumes of the essentially spherical hepatocytes were calculated from the diameters of the cells obtained easily and rapidly by using an optical micrometer. Fasting resulted in approximately a two-fold reduction in hepatocyte volume, and refeeding resulted in a return to 83% of the control value. The protein content/1000 cells also dropped two-fold upon fasting but returned to 70% of the control value upon refeeding. This rapid, simple method for determining hepatocyte volumes agrees well with data obtained by more laborious means.

Mechanisms of liquid flux across pulmonary alveolar epithelial cell monolayers.

Active transport of sodium by pulmonary alveolar epithelial cells (AEC) is believed to be an important component of edema clearance in the normal and injured lung. Data supporting this premise have come from measurements of sodium movement across AEC monolayers or from perfused lung model systems. However, direct measurement of fluid flux across AEC monolayers has not been reported. In the present work, AEC were studied with an experimental system for the measurement of fluid flux (Jv) across functionally intact cell monolayers. Primary adult rat type II alveolar epithelial cells were cultured on 0.8 micron nuleopore filters previously coated with gelatin and fibronectin. Intact monolayers were verified by high electrical resistance (> 1000 omega) at 4-5 d of primary culture. At the same time interval, transmission electron microscopy revealed cells with type I cell-like morphology throughout the monolayer. These were characterized by both adherens and tight junctional attachments. Fluid flux across the monolayers was measured volumetrically over a period of 2 h in the presence of HEPES-buffered DMEM containing 3% fatty acid-free bovine serum albumin. Flux (Jv) was inhibited 39% by 1 X 10(-4) M ouabain (P < 0.01) and 27% by 5 X 10(-4) M amiloride (P < 0.05). These data support the concept that AEC Na+/K(+)-ATPase and Na+ transport systems are important determinants of AEC transepithelial fluid movement in vitro.

Angiotensin II in apoptotic lung injury: potential role in meconium aspiration syndrome.

Meconium aspiration injures a number of cell types in the lung, most notably airway and alveolar epithelial lining cells. Recent data show that at least some of the cell death induced by meconium occurs by apoptosis, and therefore has the potential for pharmacologic inhibition through the use of apoptosis blockers or other strategies. Related work in adult animal models of lung injury has shown that apoptosis of lung epithelial cells induces a local (that is, entirely lung tissue specific) renin-angiotensin system (RAS(L)). Furthermore, this inducible RAS(L) is required for the apoptotic response and affects other adjacent cell types through the release of angiotensin II and related peptides. This manuscript reviews the published data supporting this viewpoint as well as more recent works that suggest the involvement of a RAS(L) in the perinatal lung damage associated with meconium aspiration syndrome (MAS). The implications of these findings regarding their potential for the clinical management of MAS are also discussed.

Equine multinodular pulmonary fibrosis: a newly recognized herpesvirus-associated fibrotic lung disease.

Pulmonary fibrosis and interstitial lung disease are poorly understood in horses; the causes of such conditions are rarely identified. Equine herpesvirus 5 (EHV-5) is a gamma-herpesvirus of horses that has not been associated with disease in horses. Pathologic and virologic findings from 24 horses with progressive nodular fibrotic lung disease associated with EHV-5 infection are described and compared with 23 age-matched control animals. Gross lesions consisted of multiple nodules of fibrosis throughout the lungs. Histologically, there was marked interstitial fibrosis, often with preservation of an "alveolar-like" architecture, lined by cuboidal epithelial cells. The airways contained primarily neutrophils and macrophages. Rare macrophages contained large eosinophilic intranuclear viral inclusion bodies; similar inclusion bodies were also found cytologically. The inclusions were identified as herpesviral-like particles by transmission electron microscopy in a single horse. In situ hybridization was used to detect EHV-5 nucleic acids within occasional macrophage nuclei. With polymerase chain reaction (PCR), the herpesviral DNA polymerase gene was detected in 19/24 (79.2%) of affected horses and 2/23 (8.7%) of the control horses. Virus genera-specific PCR was used to detect EHV-5 in all of the affected horses and none of the control horses. EHV-2 was detected in 8/24 (33.3%) of affected horses and 1/9 (11.1%) of the control horses. This disease has not been reported before, and the authors propose that based upon the characteristic gross and histologic findings, the disease be known as equine multinodular pulmonary fibrosis. Further, we propose that this newly described disease develops in association with infection by the equine gamma-herpesvirus, EHV-5.

Flow cytometric study of the type II pneumocyte cell cycle in vivo and in vitro.

The type II pneumocyte cell cycle was studied in vivo and in vitro through bivariate flow cytometric analysis of DNA content vs. incorporated 5-bromo-2-deoxyuridine (BrdUrd). The cell cycle phase durations Ts (7.8 h) and TG2/M (1.1 h), measured in vivo, agreed well with earlier estimates obtained by thymidine labeling. Left unilateral pneumonectomy increased the BrdUrd labeling index of type II cells in the remaining lung from an initial value of 1.9 +/- 0.3% to 4.8 +/- 1.0%, but had no effect on Ts or TG2/M in vivo. In both normal and pneumonectomized animals, BrdUrd-positive cells in vivo rapidly completed mitosis but did not enter a second S-phase. These results demonstrate that proliferating type II cells do not form a continuously cycling population in the normal or regenerating adult lung. When cell cycle parameters were measured in vitro immediately after type II cell isolation, Ts increased 2-fold and TG2/M rose up to 10-fold above the value obtained in vivo. After 2 d of primary culture under customary plating conditions, Ts had returned to the same value as that in vivo, but TG2/M remained elevated. Little variability was observed in the duration of S-phase within each treatment group. In contrast, type II cells exhibited considerable heterogeneity in the rate of G2/M-phase traverse, especially in vitro. These data suggest that the inability of adult rat type II pneumocytes to proliferate in primary culture is related to delayed G2/M-phase transit and imply the existence of pneumocyte subpopulations which differ in susceptibility to growth arrest.

Cell cycle kinetics in the alveolar epithelium.

The type II alveolar epithelial cell has important metabolic and biosynthetic functions but also serves as the stem cell of the alveolar epithelium. Much of the evidence underlying this premise was obtained before 1980 and provided the basis for a working model that has not been reconsidered for more than fifteen years. With the exceptions to be discussed below, little evidence has accumulated in the interim to suggest that the model requires significant alteration. Important questions remain unanswered, however, and some components of the model need to be supplemented, particularly in light of recent investigations that have provided insights not possible in earlier work. In particular, in vitro studies have suggested that the relationship between the parent type II cell and its progeny may not be as straightforward as originally thought. In addition, the rate of epithelial cell loss was recognized long ago to be an important factor in the regulation of this system, but its kinetics and mechanisms have received little attention. These and other unresolved issues are critical to our understanding of the homeostasis of the alveolar epithelium under normal and pathological conditions.

Type II pneumocyte hypertrophy without activation of surfactant biosynthesis after partial pneumonectomy.

Hypertrophic and normotrophic type II pneumocytes were isolated from pneumonectomized adult rats by unit gravity (1 g) sedimentation or by fluorescence-activated cell sorting (FACS). In vivo or in vitro, hypertrophic cells incorporated significantly more 5-bromo-2'-deoxyuridine or tritiated thymidine into acid-insoluble material than did normotrophic cells. By FACS analysis of cell subpopulations isolated by 1 g, > 97% of normotrophic cells had G0-phase DNA content. In contrast, the cell cycle distribution of hypertrophic cells was 75% G1, 5% S, and 20% G2/M phases. Rates of incorporation of tritiated choline into total cellular phosphatidylcholine (PC) were identical in type II cells isolated from normal or pneumonectomized rats. The intracellular contents of disaturated phosphatidylcholine (DSPC) and total PC, as well as the ratio of these two lipids, were the same in hypertrophic and normotrophic cells from pneumonectomized rats and in cells isolated from normal rats. No significant difference was observed in the rate at which hypertrophic or normotrophic cells incorporated choline into DSPC. These results demonstrate that type II pneumocyte hypertrophy after pneumonectomy reflects balanced cell growth secondary to cell cycle progression in vivo. The data also indicate that epithelial cell hypertrophy after pneumonectomy, in contrast to that which develops after more acute lung injury, occurs without activation of surfactant biosynthesis or storage.

DNA distribution analysis of type II pneumocytes by laser flow cytometry: technical considerations.

Optimal conditions were established for determination of cell cycle phase fractions of freshly isolated or cultured adult rat type II pneumocytes (T2P). Propidium iodide staining of ethanol-fixed cells treated with ribonuclease (RNase) consistently yielded histograms with low coefficients of variation. Contaminating cells and cell clumps were eliminated during data acquisition through electronic gating based on anti-vimentin immunofluorescence and peak red fluorescence, respectively. Failure to delete contaminants, clumps or RNA resulted in overestimation of S or G2/M phase fractions by as much as 20-fold. When T2P were cultured on plastic at an initial density of 2.5 x 10(5)/cm2, the S phase fraction did not change over a culture interval in which thymidine incorporation rates increased almost 10-fold. In contrast, a significant increase in the G2/M phase fraction by day 2 of culture occurred with no significant increase in cell number. These results support the hypothesis that adult rat T2P, when subjected to customary conditions of primary culture, undergo cell cycle block in G2/M phases. The data also indicate that under these in vitro conditions, net thymidine incorporation by T2P may vary independently of the S phase fraction. The methods described in this report address basic considerations crucial to future applications of flow cytokinetics to the study of T2P proliferation and differentiation.

Type II pneumocyte proliferation in vitro: problems and future directions.

In adult animals, the type II pneumocyte is progenitor of both the type I and type II alveolar epithelium. In primary culture, however, the fate of this cell is uncertain. Type II cells in culture lose their differentiated properties and eventually resemble type I cells, but a lack of specific markers has complicated the characterization of the phenotype acquired in vitro. Furthermore, limited proliferation of these cells in vitro has precluded definition of the relationship between type II cell proliferation and differentiation. Recent work in this laboratory has involved the correlation of flow cytometric cell cycle analysis with phenotype markers. Initial results indicate that isolation of type II cells induces cell cycle block similar to that sustained by other cell types in response to stress. In addition, preliminary evaluation of phenotype suggests that traditional markers become ambiguous beyond the 1st day of primary culture. These results raise concern related to the interpretation of experiments conducted in vitro. This report discusses the implications of these findings and directions for future work.

Flow cytometric identification and isolation of hypertrophic type II pneumocytes after partial pneumonectomy.

Type II pneumocytes were isolated by either Percoll density gradient centrifugation or by immunoglobulin G (IgG) panning from the lungs of normal rats and the right lung of rats subjected to left pneumonectomy. Cells were studied at 7- (pnx-7) and 15- (pnx-15) days postoperative, times during and after, respectively, rapid compensatory growth of the right lung. Acridine orange staining permitted resolution of type II cells from contaminants on the basis of high red fluorescence (greater than 590 nm). Simultaneous measurement of forward-angle light scatter (FALS) suggested a shift of pnx-7 cells toward greater size, which was reversed in pnx-15 cells. By Percoll gradient isolation, approximately 15% of pnx-7 cells analyzed were above the mean FALS of control cells. In contrast, approximately 30% of the pnx-7 cells isolated by IgG panning were above the mean FALS of corresponding control cells. Biochemical analyses of pnx-7 cells separated by cell sorting into "high FALS" and "low FALS" subgroups revealed that high FALS type II cells contained 50% more protein (P less than 0.05) and 140% more RNA (P less than 0.01) than low FALS cells, with no significant change in cellular DNA content. These data are consistent with previous studies of type II cells isolated from the lungs of pneumonectomized animals and confirm the presence of hypertrophic cells in these preparations. They provide a foundation from which to design further flow cytometric studies of the role of hypertrophic type II pneumocytes in compensatory lung growth.