Alveolar Capillary Endothelial Cells Research Articles

Expression of genes involved in vascular development and angiogenesis in endothelial cells of adult lung.

Profiling gene expression in endothelial cells advances the understanding of normal vascular physiology and disease processes involving angiogenesis. However, endothelial cell purification has been challenging because of the difficulty of isolating cells and their low abundance. Here we examine gene expression in endothelial cells freshly isolated from lung capillaries after in vivo labeling with fluorescent cationic liposomes and purification by fluorescence-activated cell sorting (FACS). Of the 39,000 genes and expressed sequence tags evaluated on custom oligonucleotide arrays, 555 were enriched in endothelial cell fraction. These included familiar endothelial cell-associated genes such as VEGF, VEGF receptor (VEGFR)-1, VEGFR-2, angiopoietin-2, Tie1, Tie2, Edg1 receptor, VE-cadherin, claudin 5, connexin37, CD31, and CD34. Also enriched were genes in semaphorin/neuropilin (Sema3c and Nrp1), ephrin/Eph (ephrin A1, B1, B2, and EphB4), delta/notch (Hey1, Jagged 2, Notch 1, Notch 4, Numb, and Siah1b), and Wingless (Frizzled-4 and Tle1) signaling pathways involved in vascular development and angiogenesis. Expression of representative genes in alveolar capillary endothelial cells was verified by immunohistochemistry. Such expression reflects features that endothelial cells of normal lung capillaries have in common with embryonic and growing blood vessels. About half of the enriched genes, including exostosin 2, lipocalin 7, phospholipid scramblase 2, pleckstrin 2, protocadherin 1, Ryk, scube 1, serpinh1, SNF-related kinase, and several tetraspanins, had little or no previous association with endothelial cells. This approach can readily be used to profile genes expressed in blood vessels in tumors, chronic inflammation, and other sites in which endothelial cells avidly take up cationic liposomes.

Protease-activated receptor (PAR)-1 and PAR-2 participate in the cell growth of alveolar capillary endothelium in primary lung adenocarcinomas.

Cell growth can be induced via elicitation of protease-activated receptors (PAR) with serine proteases such as thrombin and trypsin. To understand whether PAR are involved in tumor vessel formation in the neoplastic cell-bearing alveolar walls, immunohistochemical and reverse transcriptase-polymerase chain reaction analyses were performed using the lung tissues from 16 patients with primary lung adenocarcinomas. In microdissected tumor alveolar walls, the expressions of PAR-1 and PAR-2 mRNA were increased by 10-fold (P < 0.05) and 16-fold (P < 0.01), respectively, as compared with normal alveolar walls. Confocal microscopy revealed that tumor capillary endothelial cells in alveolar walls lost thrombomodulin expression. Instead, the expression of PAR-2 often became obvious at the normal border. Both PAR-1 and PAR-2 were expressed in the microvessel endothelial cells in tumors. Trypsin mRNA was expressed in 7 of the 16 cancer cell-bearing tissue specimens in contrast to 1 of the 14 normal alveolar walls. Immunohistochemically, trypsin was positive in the neoplastic cells from 10 patients and in lung adenocarcinoma cell lines (A549, HLC-1, LC-2, and PC-14). An in vitro assay showed a significant increase in idoxuridine (IdU) or bromodeoxyuridine uptake in human pulmonary artery endothelial cells and human umbilical cord vein endothelial cells after treatments with alpha-thrombin or activating peptides; SFLLRN for PAR-1 and SLIGKV for PAR-2, respectively. Thus, proliferation of alveolar capillary endothelial cells is initialized in part by PAR activation with serum thrombin and neoplastic cell-released trypsin. These results suggest a synergistic effect of PAR with vascular endothelial growth factor in alveolar angiogenesis.

Aerogenous spread of primary lung adenocarcinoma induces ultrastructural remodeling of the alveolar capillary endothelium

To determine whether pulmonary alveolar capillaries manifest ultrastructural remodeling at areas of neoplastic invasion of primary lung adenocarcinomas, we examined 17 well-differentiated adenocarcinomas of lung (2 bronchioloalveolar and 15 papillary adenocarcinomas) by electron microscopy. The expression of vascular endothelial growth factor (VEGF) and proliferating cell nuclear antigen (PCNA) was demonstrated by immunohistochemical stainings. VEGF messenger RNA (mRNA) isoforms were detected by reverse-transcription polymerase chain reaction (RT-PCR) in alveolar walls microdissected from normal and tumor-associated tissues. Cytoplasm of neoplastic cells expressed VEGF protein in all patients. Endothelial cell nuclei of alveolar capillaries showed positive reaction for PCNA. Alveolar capillary lumina were distended like venules, and some intercellular junctions remained open. The cytoplasm of the capillary endothelial cells was enlarged and developed numerous organelles such as Weibel-Palade bodies and vesiculovacuolar organelles, in contrast to marked attenuation in their normal counterpart. Capillary sprouting occurred from proper alveolar capillaries in 2 patients. Cytoplasmic segments became extremely attenuated and developed diaphragm-like fenestrae in 65% of the patients. A relatively higher expression of diffusable isoforms of VEGF mRNA was seen in the tumor-bearing alveolar walls than in normal walls. Expression of KDR (one of the VEGF receptors) mRNA in tumor exceeded that in normal tissues. These results suggest that diffusable isoforms of VEGF mRNA released from the neoplastic cells are deeply involved in the induction of growth activity of alveolar capillary endothelial cells as much as in the characterization of tumor-associated microvessels in primary lung adenocarcinomas. HUM PATHOL 32:1050-1058. Copyright © 2001 by W.B. Saunders Company

In situ characterization of human cytomegalovirus infection of bronchiolar cells in human transplanted lung.

Distal airway cell infection by human cytomegalovirus (HCMV) in transplanted lung has been occasionally reported but not systematically investigated. The present study aimed at testing the prevalence of HCMV bronchiolar infection in human transplanted lung. We identified and immunophenotyped, with double labeling, infected lung cells in 31 transbronchial biopsies with HCMV infection, containing distal airways (7 HCMV pneumonias, 7 HCMV infection without inflammation, and 17 morphologically occult, non-cytopathic HCMV infection). HCMV-infected cells in pneumonias, localizations, and occult infections were alveolar epithelia (32.8%, 42.8%, and 53.5%, respectively), endothelia (22.9%, 24.7%, and 26.4%, respectively), macrophages (0.006%, none, and none, respectively), airway epithelia (0.01%, 8.9%, and none, respectively), and bronchiolar smooth muscle cells (0.011%, 14.6%, and 16.1%, respectively). Ciliated and bronchiolar smooth muscle cells in transplanted lung only occasionally harbored viral infection and never showed viral cytopathy. On the basis of our morphological observations, HCMV infection of bronchiolar wall cells is rare, while alveolar epithelia and capillary endothelial cells are the major targets of lung infection.

PULMONARY PATHOLOGY OF ACUTE RESPIRATORY DISTRESS SYNDROME

Lung morphology in ARDS reflects the rapid evolution from interstitial and alveolar edema to end-stage fibrosis consequent to injury of the alveolocapillary unit. This morphologic progression, termed diffuse alveolar damage, has been subdivided into sequentially occurring exudative, proliferative, and fibrotic phases. Pulmonary lesions correlate with the phase of alveolar damage rather than its specific cause. The pathologic features are consistent with the effects of a host of injurious stimuli and the complex interaction of inflammatory mediators on alveolar epithelial and capillary endothelial cells. Although ARDS frequently culminates in "interstitial" fibrosis, the organization of intraluminal exudate dominates the histologic picture in the proliferative phase and establishes the framework for subsequent fibrous remodeling of the lung. Involvement of the pulmonary vasculature is an important aspect of ARDS, from the initial phase of edema to the terminal stage of intractable pulmonary hypertension. Vascular lesions include thrombotic, fibroproliferative, and obliterative changes that, like the parenchymal lesions, correlate with the temporal phase of DAD. Although ARDS is characterized by extensive bilateral lung involvement, alveolar damage can also affect the lung in a localized fashion. RAD is associated with the same clinical risk factors as DAD, suggesting that there is a spectrum in the extent of lung involvement and disease severity in patients at risk for ARDS. The factors that govern which patients will develop the fulminant syndrome are poorly understood. It must be re-emphasized that the lung is stereotyped in its response to injury and, consequently, descriptive, or even quantitative, studies of lung morphology can only provide clues regarding the initiating factors and pathogenetic mechanisms of ARDS. Progress in understanding the pathogenesis of ARDS and development of rational approaches to therapy will ultimately depend on careful clinical and experimental studies and the application of immunohistochemical and molecular biology techniques to unravel basic mechanisms of cellular injury and response.

Playing “telephone”: bioactive lipids as mediators of intercompartmental communication in the alveolus

Playing “telephone”: bioactive lipids as mediators of intercompartmental communication in the alveolus

Heterogeneous distribution of thrombomodulin and von Willebrand factor in endothelial cells in the human pulmonary microvessels.

Laser scanning confocal fluorescence microscopy techniques were used to study the localization of von Willebrand factor (vWf; Factor VIII-related antigen) and thrombomodulin (transmembrane receptor for thrombin) in the microvascular endothelial cells in the normal human lung. Tissues were obtained from lobectomy specimens resected for solitary nodules (7 adenocarcinomas and 4 hamartomas) from 11 patients. The plasma membranes of the capillary endothelial cells in the alveolar zones (A-zones) showed red linear fluorescence for thrombomodulin. However, their cytoplasm was mostly unreactive for vWf. The microvessels which were located in the connective tissue (C-zones), including peribronchial, and subpleural areas and large vascular walls, consistently demonstrated band-like green fluorescence for vWf in their cytoplasm, and their plasma membranes usually lacked reactivity for thrombomodulin. Only a limited number of peribronchial capillaries measuring <10 microm in diameter showed a mosaic-like appearance, in which red fluorescence along the plasma membranes was found together with green fluorescence in the subjacent cytoplasm. In the juxtaalveolar (J-zones) microvessels located along the borders between A- and C-zones, and measuring up to 40 microm in diameter, the endothelial cells showed a mosaic-like pattern of distribution of the two antigens. However, the localization of thrombomodulin in the J-zone microvessels was separate and independent from that of vWf. The thrombomodulin-reactive cells were directly connected to the alveolar capillary endothelial cells. Heterogeneous patterns of distribution of thrombomodulin and vWf suggest that topographic differences of endothelial function occur to maintain a balance of coagulation and anticoagulation in the normal human lung.

In vitro evidence of neutrophil-mediated lung injury after intestinal reperfusion.

This study examines the hypothesis that neutrophils isolated from animals sustaining intestinal reperfusion (IIR) induce pulmonary microvascular dysfunction. Lungs were isolated from normal Sprague-Dawley rats and perfused with a physiologic buffer in vitro. Neutrophils (2 x 10(6)) isolated from animals sustaining IIR (n = 5) or sham operation (SHAM; n = 6) were infused into the isolated lung model. A third group of lungs underwent in vitro perfusion without exposure to neutrophils (n = 5). Lung injury was assessed by measuring wet to dry weight ratios and pulmonary artery pressure (PAP). Pulmonary ultrastructure was assessed by electron microscopy. The wet:dry ratio of lungs from animals sustaining IIR was greater than that of lungs exposed to SHAM neutrophils (p = .03) or perfusate alone (p = .02). The PAP of lungs exposed to IIR neutrophils was nearly 10 times greater than that of lungs exposed to SHAM neutrophils (p = .003) or buffer alone (p = .006). Ultrastructural examination of lungs exposed to IIR neutrophils demonstrated interstitial edema with occasional focal disruptions in the alveolar capillary endothelial cell membrane whereas lungs exposed to SHAM neutrophils were normal. These experiments provide important in vitro correlation of prior in vivo studies suggesting that neutrophils are important pathogenic mediators of IIR-induced lung injury.

Alveolar basement membrane breaks down in diffuse alveolar damage: An immunohistochemical study

Sequential structural changes of the alveoli in diffuse alveolar damage (DAD) were examined by immunohistochemical methods. Lung specimens obtained at autopsy from 52 patients with DAD were stained with antibodies to laminin, 7S collagen (7S) and type IV collagen (type IV) for alveolar basement membrane, to von Willebrand factor, CD-31 and thrombomodulin (TM) for the alveolar capillary endothelial cell, and to epithelial membrane antigen and surfactant apo-protein (PE-10) for the alveolar epithelium. Forty-two of the patients had the exudative form of DAD; 10 of the patients had the proliferative form of DAD. The results were summarized as follows: (i) laminin was most easily impaired both in the epithelial and capillary basement membrane in the early exudative stage; (ii) following laminin, 7S and type IV in the capillary basement membrane were also injured in the early exudative stage, and recovered in the proliferative stage; (iii) subsequently, 7S and type IV in the epithelial basement membrane were also impaired in the late exudative stage, and remained impaired even in the proliferative stage; and (iv) alveolar epithelium regenerated almost completely in the late exudative stage, but staining for TM in the alveolar capillary recovered in the proliferative stage. Because the alveolar basement membrane must govern the homeostasis of alveolar tissue architecture, it was concluded that its preservation is necessary to avoid the abnormal remodeling of the alveoli in the reparative stage of DAD, if the patient survives the acute episodes of the disease.

Establishment of an animal model for pulmonary fibrosis in mice using monocrotaline.

A preliminary attempt at experimental induction of pulmonary fibrosis in which male ICR mice received 15 weekly sc injections of 200 or 100 mg/kg monocrotaline (MC) revealed that most animals treated with the larger dose died of severe interstitial pneumonia, whereas those given 100 mg/kg exhibited only relatively slight lung injury. Based on these results, male mice were administered sc injections of 200 and 100 mg/kg MC once a week for 9 and 18 times, respectively, and then maintained without any further treatment until week 28 after the start. Mice treated with 200 mg/kg MC showed severe pulmonary damage and died by week 25. Mortalities also occurred in the 100-mg group from week 16, with 11 of 40 animals surviving at the termination of the experiment. Histologically, both dose groups demonstrated severe interstitial pneumonia and/or pulmonary fibrosis. Ultrastructurally, inflammatory edema possibly attributable to injuries of alveolar capillary endothelial cells was observed in the high-dose group at week 8, and there was a remarkable increase in collagen fibers in alveolar septa in this group thereafter. The present study results suggest that lung injuries induced by MC treatment progress to irreversible lung fibrosis and that this animal model may have advantage for studying the pathogenesis of lung cancers in patients with pulmonary fibrosis.

Immunolocalization of cytokeratin 19 in bovine and human pulmonary microvascular endothelial cells in situ

1. 1. Immunocytochemical analysis of bovine and human lung sections revealed the presence of the 41 kD intermediate filament protein cytokeratin 19 in microvessel and subpleural lymphatic endothelial cells as well as the mesothelial cell layer of the lung visceral pleura. 2. 2. Cytokeratin 19 was expressed by human and bovine pulmonary microvessels with diameters ranging from 5 to 50 μm. 3. 3. Cytokeratin 19 was also found in microvessels of the rete mirabile, an oxygen exchange organ of the eel. 4. 4. Immunoperoxidase electron microscopy demonstrated cytokeratin 19 associated with the lateral membranes of adjacent bovine alveolar capillary endothelial cells.

Experimental study in a rabbit model of ischemia-reperfusion lung injury during cardiopulmonary bypass

Adult white rabbits were subjected to 2 hours of partial cardiopulmonary bypass (flow rate 90 ml/min/kg) at 32 degrees C, and unilateral pulmonary artery occlusion was used to simulate total cardiopulmonary bypass in the lung subjected to arterial occlusion, with the other side used as the control lung. The lung subjected to arterial occlusion was reperfused by one of the following methods: (1) by whole blood (WB group), (2) by leukocyte-depleted blood (LD group), and (3) by whole blood with protease inhibitor (nafamostat mesilate, FUT group), expecting its anticomplement action. In the fourth group, the lung was inflated with oxygen during pulmonary artery occlusion followed by whole blood reperfusion (OXY group). As a result, lungs subjected to pulmonary artery occlusion showed significant decreases in tissue concentrations of adenosine triphosphate and regional tissue blood flow during cardiopulmonary bypass. Furthermore, recovery of adenosine triphosphate was depressed in the WB group and recovery of regional tissue blood flow in the WB and OXY groups. Ultrastructural findings in alveolar epithelial cells and capillary endothelial cells showed worsening at reperfusion in only the WB group. Transpulmonary gradients of C5a and leukocyte showed significant increases at reperfusion in the WB and OXY groups. Alveolar-arterial oxygen difference was significantly higher in the WB group than in the others. Results indicate that complete cessation of pulmonary artery flow in normothermic cardiopulmonary bypass may cause ischemia of the lung followed by reperfusion injuries with the no-reflow phenomenon, with possible involvement of activation of leukocytes and complement.

Effect and distribution of intravenously injected 125I-endothelin-1 in rat kidney and lung examined by electron microscopic radioautography

The morphological effect of endothelin-1 (ET-1) and the distribution of endothelin-binding sites on the kidney and lung was investigated ultrastructually by intravenous injection of [125I]-ET-1 into rats. About 10% decrease of the diameter of glomeruli was observed at 10 min after the injections of ET-1 or [125I]-ET-1 (1.3-2.4 nmole/kg). When localization of [125I]-ET-1 in the kidney was examined by light and electron microscopic radioautography, silver grains were preferably localized on the fenestrated endothelial cells of glomeruli and peritubular capillary endothelial cells. Some grains were also localized on the interdigitating processes of urinary tubules. Quantitative analysis of silver grains in the glomeruli showed that 83% of grains were located on the fenestrated endothelial cells, 12% on the podocytes of visceral cells, and 5% on mesangial cells at 10 min. After 60 min, 50% of silver grains were incorporated into the cytoplasm of fenestrated endothelial cells. In contrast to glomeruli, silver grains were rare on the arteries and large arterioles. However, a few silver grains were often observed on the smooth muscle cells of small arterioles (8-20 microns in diameter). In the lung, 70% of silver grains were located on the alveolar capillary endothelial cells. These results indicate the abundance of ET receptors on the glomerular fenestrated endothelium, peritubular fenestrated endothelium and alveolar capillary endothelium.

Localization of [125I]Endothelin-1 in Rat Tissues Observed by Electron-Microscopic Radioautography

[125I]Endothelin-1 (ET-1) was administered intravenously into rats, and binding sites in various tissues were examined by electron-microscopic radioautography. Labeling was observed predominantly on the glomerular fenestrated endothelial cells of kidney, alveolar capillary endothelial cells of lung, fat-storing cells in the sinusoids of liver, and subepithelial myofibroblasts of the small intestine. At first, silver grains were observed mostly on the plasmalemma of these cells and with time translocated into the cytoplasm of these cells. Myofibroblasts of the small intestine were cultured to study the cellular effects of ET. By fura-2 fluorescence method, transient increase and oscillation of intracellular Ca2+ level were observed in the cultured myofibroblasts following the application of ET-1 or endothelin-3 (ET-3). These results suggest that ET induces diverse physiological reactions in specific cells of various tissues.

Pulmonary Pathology of the Adult Respiratory Distress Syndrome

Lung morphology in ARDS reflects the rapid evolution from interstitial and alveolar edema to end-stage fibrosis consequent to injury of the alveolocapillary unit. This morphologic progression, termed diffuse alveolar damage, has been subdivided into sequentially occurring exudative, proliferative, and fibrotic phases. Pulmonary lesions correlate with the phase of alveolar damage rather than with its specific cause. As suggested by experimental models of acute lung injury, the pathologic features seen in humans are consistent with the effects of a host of injurious stimuli and the complex interaction of inflammatory mediators on alveolar epithelial and capillary endothelial cells. Although ARDS frequently culminates in "interstitial" fibrosis, the organization of intraluminal exudate dominates the histologic picture in the proliferative phase and establishes the framework for subsequent fibrous remodeling of the lung. Involvement of the pulmonary vasculature is an important aspect of ARDS, from the initial phase of edema to the terminal stage of intractable pulmonary hypertension. Vascular lesions include thrombotic, fibroproliferative, and obliterative changes, which, like the parenchymal lesions, correlate with the temporal phase of diffuse alveolar damage. Although ARDS is characterized by extensive bilateral lung involvement, alveolar damage can affect the lung in a localized fashion. "Regional alveolar damage" is associated with the same clinical risk factors as diffuse damage, suggesting that there is a spectrum in the extent of lung involvement and disease severity in patients at risk for ARDS. The factors that govern which patients will develop the fulminant syndrome are poorly understood. It must be re-emphasized that the lung is stereotyped in its response to injury, and, consequently, descriptive, or even quantitative, studies of lung morphology can only provide clues regarding the initiating factors and pathogenetic mechanisms of ARDS. Progress in understanding the pathogenesis of ARDS and the devising of rational approaches to therapy will ultimately depend on careful clinical and experimental studies that unravel basic mechanisms of cellular injury and response. The course of these investigations must be guided by and constantly correlated with the pathologic features that occur in humans.

Detection of endothelin immunoreactivity and mRNA in pulmonary tumours

Paraffin sections of 66 surgically resected lung tumours were immunostained with antisera to human endothelin-1 and to the C-terminal peptide of big endothelin. With both antisera, strong immunoreactivity was demonstrated in 11 of 15 squamous cell carcinomas and 11 of 16 adenocarcinomas. Focal immunoreactivity was seen in small cell carcinoma (2/12), large cell carcinoma (2/5), and carcinoid tumours (2/11). Four lymphomas and three sarcomas did not show endothelin immunoreactivity. Cryostat sections of 22 of the 66 tumours were hybridized with radiolabelled complementary RNA probes prepared from the 3' non-coding region of endothelin-1 cDNA, and the chromosomal genes encoding endothelin-2 and -3. In situ hybridization demonstrated the presence of endothelin mRNAs in 4 of 7 squamous cell carcinomas and in 5 of 8 adenocarcinomas, in a pattern similar to that shown by immunocytochemistry. No hybridization signals were obtained from the other types of tumours. In lung tissue adjacent to the tumours, endothelin-like immunoreactivity and mRNA were detected in pulmonary endocrine cells and, in some cases, other epithelial cells, and in alveolar capillary endothelial cells. This study demonstrates the expression of endothelin in a number of pulmonary tumours and suggests a possible role for this peptide in the growth and/or differentiation of these tumours.

Ultrastructural Morphogenesis of 4-ipomeanol-induced Bronchiolitis and Interstitial Pneumonia in Calves

The two objectives of this research were 1) to describe the ultrastructural morphogenesis of pulmonary damage and repair induced in calves after treatment with 4-ipomeanol and 2) to characterize infiltrating pulmonary inflammatory cells by bronchoalveolar lavage. Interstitial edema was observed as early as 4 hours after intravenous injection of 4-ipomeanol (5 mg/kg body weight) and progressed to severe alveolar edema by 72 hours. Damage to type I alveolar epithelial cells and terminal bronchiolar nonciliated cells included dilation of endoplasmic reticulum and perinuclear envelopes and was present at 4 hours after treatment. Necrosis and sloughing of these cells from basement membranes occurred at times from 12 to 96 hours after treatment. Alveolar capillary endothelial cells had mild dilation of endoplasmic reticulum at times from 12 to 72 hours after treatment. Necrosis of endothelial cells was not observed. Inflammatory cell infiltrates in bronchioles and alveoli were dominated by macrophages and neutrophils. Significant elevations (P less than 0.05) in numbers of neutrophils and macrophages were recovered by bronchoalveolar lavage at times from 24 to 96 hours after 4-ipomeanol-treatment. Hyperplasia of nonciliated bronchiolar epithelial cells and of type II alveolar epithelial cells were observed at 72 and 96 hours after treatment. The results indicate that type I alveolar epithelial cells and nonciliated bronchiolar epithelial cells are most susceptible to 4-ipomeanol-induced damage and necrosis in calves. 4-ipomeanol-induced pulmonary edema in calves occurs prior to ultrastructurally-demonstrable, mild, alveolar capillary endothelial cell damage.

肺胞マクロファージの免疫組織学的研究 Ｃｌａｓｓ ＩＩ ＭＨＣ発現様式を中心に

To elucidate the role of alveolar macrophages in inflammatory and fibrosing processes of lung, the paraquat-induced alveolitis in rats was investigated by the immunohistochemical method with especial references to the class II major histocompatibility antigen complex (MHC) expression. Two days after the peritoncal injection of paraquat, the class II MHC expression by type II alveolar epithelial cells was observed prior to obvious histological and immunohistochemical changes except for pulmonary edema. From four days after the injection, alveolar macrophages increased in number, and expressed class II MHC, which was not demonstrated in the normal control. The intensity of the expression was variable, and alveolar macrophages containing abundant dust particles were still absent for class II MHC. On the contrary, the class II MHC expression by alveolar epithelial cells turned obscure. Two weeks after the injection, alveolar fibrosis developed and inflammatory cell infiltration was almost disappeared. A small number of class II MHC negative foamy cells were observed in the alveolar spaces. Alveolar capillary endothelial cells and alveolar septal cells, which expressed class II MHC in the normal control, did not show significant changes in paraquat-induced alveolitis. These results suggest that resident alveolar macrophages with the active phagocytic activity are not the main component in inflammatory reactions in the lung. In contrast, type II alveolar epithelial cells participate invariably in inflammatory process of alveolitis.

Neutrophil-dependent, oxygen-radical mediated lung injury associated with acute pancreatitis.

Cerulein-induced acute pancreatitis in rats is associated with a reversible lung injury that is characterized by alveolar capillary endothelial-cell injury, increased microvascular permeability, interstitial edema formation, and intraalveolar hemorrhage and fibrin deposition. The role of mediators in this injury was analyzed using gravimetric data, microvascular permeability indices, electron microscopy, and a quantitative morphometric analysis. Neutrophil depletion induced by a specific antibody was highly protective against lung injury. Interruption of the complement pathway (using low dose Naja naja cobra venom factor) also protected against lung injury. Catalase and superoxide dismutase were also protective. The iron chelator deferoxamine and the hydroxyl radical scavenger, dimethylsulfoxide, were not protective against acute lung injury. These data suggest that complement, neutrophils, and neutrophil-derived (H2O2-dependent) oxygen products mediate lung injury that occurs secondary to cerulein-induced pancreatitis. In contrast to other models of neutrophil-dependent, oxygen-radical-mediated lung injury, this lung injury does not appear to be an iron-dependent and hydroxyl-radical mediated injury. We postulate that the process of acute pancreatitis leads to complement activation followed by neutrophil recruitment, sequestration, and adherence to alveolar capillary endothelial cells. Ultimately lung injury appears to result from local endothelial-cell injury secondary to neutrophil-generated oxygen products that may be myeloperoxidase dependent.

Bacteremia-induced suppression of alveolar surfactant production

Sepsis is characterized by Adult Respiratory Distress Syndrome (ARDS)-like pulmonary dysfunction largely attributed to alveolar capillary endothelial cell injury which causes increased microvascular permeability and interstitial edema formation. In addition, quantitative and qualitative abnormalities of the pulmonary surfactant system may be important features of some clinical and experimental lung injuries. This study was designed to investigate the relationship of bacteremia and endotoxemia to pulmonary surfactant production in vivo. A technique for estimation of pulmonary surfactant phospholipid synthesis measuring incorporation of a stable isotope precursor ([2- 13C]acetate) into dipalmitoylphosphatidylcholine (DPPC) in alveolar lavage fluid was developed. Male 350 g Sprague-Dawley rats had placement of central venous catheters. After overnight recovery, sublethal bacteremia ( Escherichia coli, 1 × 10 8 organisms, iv) and sublethal endotoxemia (Difco; 10 mg/kg, iv) were induced. Both were associated with lung microvascular permeability increases consistent with capillary endothelial injury. Eight-hour infusions of [2- 13C]acetate were given. After sacrifice, bronchoalveolar washings and lung tissue were obtained and [2- 13C] incorporation into lavage and lung DPPC was measured by gas chromatography mass spectroscopy. Endotoxin-treated animals had a 21.5% reduction in label incorporation into DPPC [1.215 ± 0.145 APE (%) sham versus 0.954 ± 0.144 APE (%) experimental, P > 0.05] and bacteremic animals had a 56.9% diminution of [2- 13C]acetate incorporation [1.215 ± 0.145 APE (%) sham versus 0.524 ± 0.56 APE (%) experimental, P < 0.05]. Bacteremia-induced dysfunction of alveolar type II epithelial cells manifested as diminished alveolar surfactant phospholipid production may be a contributing factor to sepsis-induced respiratory failure.