Alveolar air-tissue interface and nuclear magnetic resonance behavior of lung

Inflated lungs are characterized by a short nuclear magnetic resonance (NMR) free induction decay (rapid disappearance of NMR signal), likely due to internal (tissue-induced) magnetic field inhomogeneity produced by the alveolar air-tissue interface. This phenomenon can also be detected using temporally symmetric and asymmetric NMR spin-echo sequences; these sequences generate a pair of NMR images from which a difference signal (delta) is obtained (reflecting the signal from lung water experiencing the air-tissue interface effect). We measured delta in normal excised rat lungs at inflation pressures of 0-30 cmH2O for asymmetry times (a) of 1-6 ms. Delta was low in degassed lungs and increased markedly with alveolar opening when measured at a = 6 ms (delta 6 ms); delta 6 ms varied little during the rest of the inflation-deflation cycle. Delta 1 ms (a = 1 ms) did not vary significantly on inflation and deflation. Measurements of delta at a = 3 and 5 ms generally lay between those of delta 1 ms and delta 6 ms. These findings, which are consistent with theoretical predictions, suggest that measurements of delta at appropriate asymmetry times are particularly sensitive to alveolar opening and may provide a means of distinguishing alveolar recruitment from alveolar distension in the pressure-volume behavior of the lung.     

Magnetic resonance behavior of normal and diseased lungs: spherical shell model simulations.

The alveolar air-tissue interface affects the lung NMR signal, because it results in a susceptibility-induced magnetic field inhomogeneity. The air-tissue interface effect can be detected and quantified by measuring the difference signal (Delta) from a pair of NMR images obtained using temporally symmetric and asymmetric spin-echo sequences. The present study describes a multicompartment alveolar model (consisting of a collection of noninteracting spherical water shells) that simulates the behavior of Delta as a function of the level of lung inflation and can be used to predict the NMR response to various types of lung injury. The model was used to predict Delta as a function of the inflation level (with the assumption of sequential alveolar recruitment, partly parallel to distension) and to simulate pulmonary edema by deriving equations that describe Delta for a collection of spherical shells representing combinations of collapsed, flooded, and inflated alveoli. Our theoretical data were compared with those provided by other models and with experimental data obtained from the literature. Our results suggest that NMR Delta measurements can be used to study the mechanisms underlying the lung pressure-volume behavior, to characterize lung injury, and to assess the contributions of alveolar recruitment and distension to the lung volume changes in response to the application of positive airway pressure (e.g., positive end-expiratory pressure).     

Application of respiratory heat exchange for the measurement of lung water.

A noninvasive method for measuring pulmonary blood flow and lung mass (called airway thermal volume), based on the measurements of lung heat exchange with environment, is described. The lungs function as a steady-state heat exchange system, having an inner heat source (pulmonary blood flow) and an external heat sink (ventilation). Sudden changes in the steady-state condition, such as caused by hyperventilation of dry air, lead to a new steady state after a few minutes. The expired air temperature difference between the initial and final steady states is proportional to pulmonary blood flow, whereas the rate at which the new steady state is achieved is proportional to airway thermal volume. The method was tested in 20 isolated dogs lungs, 9 perfused goat lungs, and 27 anesthetized sheep. The expired air temperature fall during hyperventilation was inversely proportional to the perfusion rate of the isolated lungs, and half-time of the temperature fall was proportional to the lung tissue mass. Experiments in anesthetized sheep showed that the measured airway thermal volume is close to the total mass of the excised lungs, including its residual blood (r = 0.98). Pulmonary edema and fluid instillation into the bronchial tree increased in the measured lung mass.     

Identification of metabolites of importance in the pathogenesis of pulmonary cryptococcoma using nuclear magnetic resonance spectroscopy

Primary lung infection with Cryptococcus neoformans is characterised by circumscribed lesions (cryptococcomas). To identify cryptococcal and/or host products of importance in pathogenesis, we applied proton nuclear magnetic resonance (NMR) spectroscopy, which identifies mobile compounds present in complex mixtures, to experimental pulmonary cryptococcomas from rats. Magnetic resonance experiments were performed on cryptococcomas (n = 10) and healthy lungs (n = 8). Signal assignment to key metabolites was confirmed by homo-nuclear and hetero-nuclear NMR correlation spectroscopy. Cryptococcal metabolites, dominating spectra from cryptococcomas included the stress protectants, trehalose and mannitol, acetate, and in some animals, ethanol. Glycerophosphorylcholine was also abundant in cryptococcomas, consistent with hydrolysis of phospholipids in vivo by the cryptococcal enzyme, phospholipase B (PLB). PLB has been identified by molecular studies as a cryptococcal virulence determinant. We propose that PLB secreted by cryptococci promotes tissue invasion by hydrolysing host phospholipids, such as dipalmitoyl phosphatidyl choline, which is abundant in pulmonary surfactant, and lung cell membrane phospholipids. Our results confirm the utility of NMR spectroscopy in studies of microbial pathogenesis.     

A new nuclear magnetic resonance property of lung

Inflated lung has a nuclear magnetic resonance (NMR) free-induction decay (FID) which is short compared with that of collapsed lung and those of other body tissues. An almost identically short FID is obtained from a slurry of 5-micron alumina particles in water. Interfaces between air and water in lung and between alumina and water in the slurry appear to be the source of spatial internal magnetic inhomogeneities which produce NMR line broadening and the short FID. Paired images that included lung, taken with paired symmetric and asymmetric NMR spin-echo sequences, permit the generation of an image, by subtraction, of the lung isolated from surrounding tissue. These new lung images are neither proton density, T1 (spin-lattice relaxation time), nor T2 (spin-spin relaxation time) images. They complement current NMR images and provide information about regional lung inflation. This previously unrecognized NMR property of lung tissue has potential application in NMR imaging, in quantitative determination of lung water and its distribution, and in the quantitation of regional lung inflation.     

PAF potentiates protamine-induced lung edema: role of pulmonary venoconstriction

We studied the synergistic interaction between platelet-activating factor (PAF) and protamine sulfate, a cationic protein that causes pulmonary endothelial injury, in isolated rat lungs perfused with a physiological salt solution. A low dose of protamine (50 micrograms/ml) increased pulmonary artery perfusion pressure (Ppa) but did not increase wet lung-to-body weight ratio after 20 min. Pretreatment of the lungs with a noninjurious dose of PAF (1.6 nM) 10 min before protamine markedly potentiated protamine-induced pulmonary vasoconstriction and resulted in severe lung edema and increased lung tissue content of 6-keto-prostaglandin F1 alpha, thromboxane B2, and leukotriene C4. Pulmonary microvascular pressure (Pmv), measured by double occlusion, was markedly increased in lungs given PAF and protamine. These potentiating effects of PAF were blocked by WEB 2086 (10(-5) M), a specific PAF receptor antagonist. Pretreatment of the lungs with a high dose of histamine (10(-4) M) failed to enhance the effect of protamine on Ppa, Pmv, or wet lung-to-body weight ratio. Furthermore, PAF pretreatment enhanced elastase-, but not H2O2-, induced lung edema. To assess the role of hydrostatic pressure in edema formation, we compared lung permeability-surface area products (PS) in papaverine-treated lungs given either protamine alone or PAF + protamine and tested the effect of mechanical elevation of Pmv on protamine-induced lung edema. In the absence of vasoconstriction, PAF did not potentiate protamine-induced increase in lung PS. On the other hand, mechanically raising Pmv in protamine-treated lungs to a level similar to that measured in lungs given PAF + protamine did not result in a comparable degree of lung edema. We conclude that PAF potentiates protamine-induced lung edema predominantly by enhanced pulmonary venoconstriction. However, a pressure-independent effect of PAF on lung vasculature cannot be entirely excluded.     

Assessment of temporal changes in pulmonary edema with NMR imaging

Nuclear magnetic resonance imaging (NMRI) parameters [longitudinal relaxation time (T1), transverse relaxation time (T2), and signal intensity] acquired at a magnetic field of 2.35 T were validated with a study of nine different phantom gel solutions. This technique was then applied to study 13 anesthetized supine cats, among which 10 had lung edema induced by oleic acid (0.075 ml/kg); the result was compared with postmortem analyses of lung water. Three animals (series A) were imaged until the edema was first visualized in NMRI, usually 15-20 min after oleic acid infusion. Another seven animals (series B) were imaged over 4-5 h. As lung water increased, so did the signal intensity. When edema first appeared, T1, T2, and the volume of the edematous region within the slice in the upper lobes showed no gravity-dependent differences; this was confirmed by postmortem measurements (series A) of lung water. With time, gravity-dependent regions displayed greater volumes of edematous regions and greater T1 values (P less than 0.01), suggesting a continued accumulation of lung water. In comparison, nondependent regions displayed constant volumes of edematous region and lesser T1 values (P less than 0.01), suggesting an increased protein concentration but no change in lung water. This study suggests the potential applicability of NMRI parameters in the assessment of pulmonary edema.     

Lung water measurements with the mean transit time approach

The potential usefulness and limitations of the double-indicator mean transit time approach for measuring lung water are evaluated from both theoretical and empirical points of view. It is concluded that poor tissue perfusion is the most serious factor that can compromise the reliability of this approach. Replacement of the conventional water isotopes with a thermal signal enhances indicator delivery to ischemic areas but the diffusion of heat is not sufficiently rapid to permit measurements of water in macroscopic collections of fluid which remain unperfused. The frequency of pulmonary vascular obstruction in patients with pulmonary edema related to lung injury suggests that interpretation of transit time data will be complicated by uncertainties concerning perfusion. Thermal-dye measurements of lung water may prove more helpful in situations where pulmonary blood flow remains relatively uniform.     

Utility of magnetic resonance imaging and nuclear magnetic resonance-based metabolomics for quantification of inflammatory lung injury

Magnetic resonance imaging (MRI) and metabolic nuclear magnetic resonance (NMR) spectroscopy are clinically available but have had little application in the quantification of experimental lung injury. There is a growing and unfulfilled need for predictive animal models that can improve our understanding of disease pathogenesis and therapeutic intervention. Integration of MRI and NMR could extend the application of experimental data into the clinical setting. This study investigated the ability of MRI and metabolic NMR to detect and quantify inflammation-mediated lung injury. Pulmonary inflammation was induced in male B6C3F1 mice by intratracheal administration of IL-1beta and TNF-alpha under isoflurane anesthesia. Mice underwent MRI at 2, 4, 6, and 24 h after dosing. At 6 and 24 h lungs were harvested for metabolic NMR analysis. Data acquired from IL-1beta+TNF-alpha-treated animals were compared with saline-treated control mice. The hyperintense-to-total lung volume (HTLV) ratio derived from MRI was higher in IL-1beta+TNF-alpha-treated mice compared with control at 2, 4, and 6 h but returned to control levels by 24 h. The ability of MRI to detect pulmonary inflammation was confirmed by the association between HTLV ratio and histological and pathological end points. Principal component analysis of NMR-detectable metabolites also showed a temporal pattern for which energy metabolism-based biomarkers were identified. These data demonstrate that both MRI and metabolic NMR have utility in the detection and quantification of inflammation-mediated lung injury. Integration of these clinically available techniques into experimental models of lung injury could improve the translation of basic science knowledge and information to the clinic.     

Physiological and biochemical markers of alveolar epithelial barrier dysfunction in perfused human lungs

To study air space fluid clearance (AFC) under conditions that resemble the clinical setting of pulmonary edema in patients, we developed a new perfused human lung preparation. We measured AFC in 20 human lungs rejected for transplantation and determined the contribution of AFC to lung fluid balance. AFC was then compared with air space and perfusate levels of a biological marker of epithelial injury. The majority of human lungs rejected for transplant had intact basal (75%) and beta(2)-adrenergic agonist-stimulated (70%) AFC. For lungs with both basal and stimulated AFC, the basal AFC rate was 19 +/- 10%/h, and the beta(2)-adrenergic-stimulated AFC rate was 43 +/- 13%/h. Higher rates of AFC were associated with less lung weight gain (Pearson coefficient -0.90, P < 0.0001). Air space and perfusate levels of the type I pneumocyte marker receptor for advanced glycation end products (RAGE) were threefold and sixfold higher, respectively, in lungs without basal AFC compared with lungs with AFC (P < 0.05). These data show that preserved AFC is a critical determinant of favorable lung fluid balance in the perfused human lung, raising the possibility that beta(2)-agonist therapy to increase edema fluid clearance may be of value for patients with acute lung injury and pulmonary edema. Also, although additional studies are needed, a biological marker of alveolar epithelial injury may be useful clinically in predicting preserved AFC.     

1H NMR studies of drugs with achiral and chiral lanthanide shift reagents: Applications to the anticonvulsant pheneturide

The anticonvulsant pheneturide, PNT, has been studied by 300 MHz ¹H NMR in CDCl₃ at ambient temperatures with the achiral lanthanide shift reagent (LSR) Eu(FOD)₃, and with the chiral LSR, Eu(HFC)₃. Both LSRs produced spectral simplification of the aryl proton signal region, and substantial lanthanide‐induced shifts (LIS). With added Eu(HFC)₃, enantiomeric shift differences (ΔΔδ) were induced for most nuclei of PNT, indicating substantial potential for direct determination of enantiomeric excess. Valley heights between corresponding signals in the PNT enantiomers as low as 3.6% were achieved for the meta resonance. Least squares line‐fitting was applied to the variation of chemical shift vs. [LSR]/[PNT] molar ratios for both LSRs. Tentative assignments were made for the NH absorptions based on two‐dimensional NMR (COSY45), as well as their relative magnitudes of LIS, ΔΔδ, and lanthanide‐induced line broadening. The PNT conformation reported in the crystal is believed to be retained in solution with added LSR. The relative senses of magnetic nonequivalence were found to be the same among the three sets of aryl protons, and among the three kinds of protons in the ethyl moiety, with high levels of added chiral LSR, using 2D NMR. Chirality 11:529–535, 1999. © 1999 Wiley‐Liss, Inc.     

Simple Resolution of Enantiomeric NMR Signals of α‐Amino Acids by Using Samarium(III) Nitrate With L‐Tartarate

Readily available L‐tartaric acid, which is a bidentate ligand with two chiral centers forming a seven‐membered chelate ring, was applied to the chiral ligand for the chiral nuclear magnetic resonance (NMR) shift reagent of samarium(III) formed in situ. This simple method does not cause serious signal broadening in the high magnetic field. Enantiomeric ¹³C and ¹H NMR signals and enantiotopic ¹H NMR signals of α‐amino acids were successfully resolved at pH 8.0 and the 1:3 molar ratio of Sm(NO₃)₃:L‐tartaric acid. It is elucidated that the enantiomeric signal resolution is attributed to the anisotropic magnetic environment for the enantiomers induced by the chiral L‐tartarato samarium(III) complex rather than differences in stability of the diastereomeric substrate adducts. The present ¹³C NMR signal resolution was also effective for the practical simultaneous analysis of plural kinds of DL‐amino acids. Chirality 27:353–357, 2015.© 2015 Wiley Periodicals, Inc.     

Synthesis and odor of chiral partial structures of β‐vetivone,Part 2

Several stereoisomeric, monocyclic analogs of (−)‐β‐vetivone (1), one of the main constituents of vetiver oil, were studied to examine if the olfactory properties of (−)‐β‐vetivone (1) could be reproduced from these structurally simpler, synthetically accessible compounds. The effects of diastereomeric and enantiomeric structural differences on the odor of the partial vetivone structure were studied. A chiral phenyl sulfoximine was used for separation of the racemic mixtures. Detailed nuclear magnetic resonance (NMR)‐spectroscopic studies (¹H, ¹³C) were used to determine relative configurations whereas absolute configurations were determined by circular dichroism (CD) methods. Chirality 11:133–138, 1999. © 1999 Wiley‐Liss, Inc.     

IL10 deficiency promotes alveolar enlargement and lymphoid dysmorphogenesis in the aged murine lung

The connection between aging‐related immune dysfunction and the lung manifestations of aging is poorly understood. A detailed characterization of the aging IL10‐deficient murine lung, a model of accelerated aging and frailty, reconciles features of both immunosenescence and lung aging in a coherent model. Airspace enlargement developed in the middle‐aged (12 months old) and aged (20–22 months old) IL10‐deficient lung punctuated by an expansion of macrophages and alveolar cell apoptosis. Compared to wild‐type (WT) controls, the IL10‐deficient lungs from young (4‐month‐old) mice showed increased oxidative stress which was enhanced in both genotypes by aging. Active caspase 3 staining was increased in the alveolar epithelial cells of aged WT and mutant lungs but was greater in the IL10‐deficient milieu. Lung macrophages were increased in the aged IL10‐deficient lungs with exuberant expression of MMP12. IL10 treatment of naïve and M2‐polarized bone marrow‐derived WT macrophages reduced MMP12 expression. Conditioned media studies demonstrated the secretome of aged mutant macrophages harbors reduced AECII prosurvival factors, specifically keratinocyte growth factor (KGF) and hepatocyte growth factor (HGF), promotes cell death, and reduces survival of primary alveolar epithelial cells. Compared to WT controls, aged IL10‐deficient mice have increased parenchymal lymphoid collections comprised of a reduced number of apoptotic cells and B cells. We establish that IL10 is a key modulator of airspace homeostasis and lymphoid morphogenesis in the aging lung enabling macrophage‐mediated alveolar epithelial cell survival and B‐cell survival within tertiary lymphoid structures.     

Simultaneous measurement of fluid and protein permeability in isolated rabbit lungs during edema.

Fluid conductance and protein permeability have been studied in isolated perfused lung models of pulmonary edema. However, previous studies have not investigated changes of both fluid conductance and protein permeability in the same isolated lung preparation after injury. Arachidonic acid (AA) metabolites are involved in the inflammatory processes that lead to the development of pulmonary edema. The hemodynamic effects of AA have been well established; however, controversy exists concerning the ability of AA to alter the permeability of the pulmonary microvasculature to fluid and protein. The purpose of this study was to simultaneously determine whether transvascular fluid conductance and protein permeability are increased in isolated perfused rabbit lungs with pulmonary edema induced by AA. Indomethacin (80 microM) was added to the perfusate to inhibit the hemodynamic effects of AA and produce a pressure-independent model of pulmonary edema. Fluid conductance was assessed by determination of the capillary filtration coefficient (Kf), and protein permeability was evaluated by measurement of 125I-albumin clearance. The injection of AA (3 mg/200 ml of perfusate) into the pulmonary arterial catheter resulted in an increase in lung weight over the remaining 30-min experimental period. Kf (microliter.s-1 x cmH2O-1 x g dry lung-1) was increased (P < 0.05) in AA-treated lungs at 10 and 30 min post-AA injection when compared with control lungs and baseline values (determined 10 min before AA injection). Albumin clearance was also greater (P < 0.05) in lungs that received AA. 125I-albumin clearance was measured at different rates of fluid flux produced by elevation of venous pressure.(ABSTRACT TRUNCATED AT 250 WORDS)     

大气中粉尘颗粒物对支气管肺泡上皮影响的实验研究

目的探讨大气污染物对呼吸道的病理变化,为预防大气污染对人体健康的损害提供理论依据。方法采用模拟大气污染方法,用大鼠制备大气污染物模型,对大鼠气管、肺进行透射电镜及气管扫描电镜检查。结果大气污染大鼠动物模型的气管、肺与对照组相比,实验组气管及肺泡上皮有渐进性损伤,且随量的蓄积损伤逐渐加重,最终发生肺实变。结论吸入的污染粉尘可造成气管及肺泡上皮的渐进性损伤,形态学变化与吸入粉尘的量呈一致性,并随吸人量的累积而逐渐变得严重,最终变为肺实变,残留肺组织为代偿性气肿。     

Effects of a membrane modulator derived from 3-hydroxypyridine class on the development of pulmonary edema

The experiment on white rats has revealed that water-soluble antioxidant-emoxipin, having obvious membrane modulating effect, does not influence the rate of watering and congestion of the lungs, the speed of reabsorption of fluid from lung tissue, the permeability of the capillary-alveolar barrier both in the blood-tissue direction and vice versa. Preliminary introduction of emoxipin increased the amount of edema fluid in the lungs when noradrenaline, centrogenic and especially vasopressin pulmonary edema developed, but in did not influence the development of vagotomic pulmonary edema. Stimulation of adenylcyclase or introduction of prostacyclin slowed down the development of centrogenic and vasopressin edema of the lungs. On the basis of these data it can be concluded that the intensification of pulmonary edema after emoxipin introduction is connected with its antioxidant activity.     

Protective effect of alpha-human atrial natriuretic polypeptide (alpha-hANP) on chemical-induced pulmonary edema

It has been established that alpha-hANP, the newly discovered peptide extracted from human cardiac atria, has potent natriuretic and hypotensive actions. Our present investigation is the first to demonstrate that alpha-hANP is capable of protecting against pulmonary edema caused by various chemicals, using isolated perfused guinea pig lung system. Lungs were perfused via pulmonary artery with Krebs-Ringer bicarbonate buffer at 5.0 ml/min, and wet weight of lungs and perfusion pressure of pulmonary artery (Pa) were monitored. Bolus injection of Triton-X or CHAPS into cannulated pulmonary artery produced edema as indicated by a massive increase in wet weight and a slight increase in Pa. Constant infusion of alpha-hANP through pulmonary artery at 200 ng/ml was effective in causing decrease in wet weight of lung. Perfusion of lung with paraquat or PGF2 alpha, and repeated bolus injection of arachidonic acid or PGE2 caused elevation in both wet weight of lung and Pa. The treatment with alpha-hANP similar to that described above also protected against edema caused by paraquat or arachidonic acid. Bolus administration of epinephrine induced a slight increase in wet weight and Pa, and alpha-hANP was effective in decreasing the elevated lung wet weight and Pa of lungs. Infusion or bolus administration of alpha-hANP into control lungs increased cGMP level in outflow perfusate as well as in lung tissue significantly. In lungs with edema which were induced by Triton-X or paraquat, there was a slight increase in cGMP level in Triton-X treated and no increase in paraquat treated lung tissues. In either cases, was there any increase in cGMP level in perfusate. The specific binding study of [125I]alpha-hANP revealed that the lack of increase in cGMP was not due to a loss of receptor in Triton-X or paraquat treated lungs. Thus our study demonstrated that alpha-hANP had a direct anti-edematic action(s) in lung which was not secondary to the systemic natriuretic and/or hypotensive action(s).     

Lipidomic characterization and localization of phospholipids in the human lung

Lipids play a central role in lung physiology and pathology; however, a comprehensive lipidomic characterization of human pulmonary cells relevant to disease has not been performed. The cells involved in lung host defense, including alveolar macrophages (AMs), bronchial epithelial cells (BECs), and alveolar type II cells (ATIIs), were isolated from human subjects and lipidomic analysis by LC-MS and LC-MS/MS was performed. Additionally, pieces of lung tissue from the same donors were analyzed by MALDI imaging MS in order to determine lipid localization in the tissue. The unique distribution of phospholipids in ATIIs, BECs, and AMs from human subjects was accomplished by subjecting the large number of identified phospholipid molecular species to univariant statistical analysis. Specific MALDI images were generated based on the univariant statistical analysis data to reveal the location of specific cell types within the human lung slice. While the complex composition and function of the lipidome in various disease states is currently poorly understood, this method could be useful for the characterization of lipid alterations in pulmonary disease and may aid in a better understanding of disease pathogenesis.