Factor VII-activating protease deficiency promotes neointima formation by enhancing leukocyte accumulation

Essentials Factor VII-activating protease (FSAP) is a plasma protease involved in vascular processes. Neointima formation was investigated after vascular injury in FSAP-/- mice. The neointimal lesion size and the accumulation of macrophages were increased in FSAP-/- mice. This was due to an increased activity of the chemokine (C-C motif) ligand 2 (CCL2).

SUMMARY

Background Factor VII-activating protease (FSAP) is a multifunctional circulating plasma serine protease involved in thrombosis and vascular remodeling processes. The Marburg I single-nucleotide polymorphism (MI-SNP) in the FSAP-coding gene is characterized by low proteolytic activity, and is associated with increased rates of stroke and carotid stenosis in humans. Objectives To determine whether neointima formation after vascular injury is increased in FSAP-/- mice. Methods and Results The neointimal lesion size and the proliferation of vascular smooth muscle cells (VSMCs) were significantly enhanced in FSAP-/- mice as compared with C57BL/6 control mice after wire-induced injury of the femoral artery. Accumulation of leukocytes and macrophages was increased within the lesions of FSAP-/- mice at day 3 and day 14. Quantitative zymography demonstrated enhanced activity of gelatinases/matrix metalloproteinase (MMP)-2 and MMP-9 within the neointimal lesions of FSAP-/- mice, and immunohistochemistry showed particular costaining of MMP-9 with accumulating leukocytes. Using intravital microscopy, we observed that FSAP deficiency promoted the intravascular adherence and the subsequent transmigration of leukocytes in vivo in response to chemokine ligand 2 (CCL2). CCL2 expression was increased in FSAP-/- monocytes but not in the vessel wall. There was no difference in the expression of platelet-derived growth factor (PDGF-BB). Conclusions FSAP deficiency causes an increase in CCL2 expression and CCL2-mediated infiltration of leukocytes into the injured vessel, thereby promoting SMC proliferation and migration by the activation of leukocyte-derived gelatinases. These results provide a possible explanation for the observed association of the loss-of-function MI-SNP with vascular proliferative diseases.

Quantum dots modulate leukocyte adhesion and transmigration depending on their surface modification

Although different nanosized materials, including quantum dots (QDs), are intended to be used for biomedical applications, their interactions with microvessels and their inflammatory potential are largely unknown. In this in vivo study we report that leukocyte recruitment is modulated in the presence of quantum dots. We found that the surface chemistry of QDs strongly affects their localization in postcapillary venules, their uptake by perivascular macrophages, and their potential to modify steps of leukocyte recruitment.

Platelet adhesion and fibrinogen deposition in murine microvessels upon inhalation of nanosized carbon particles

SUMMARY BACKGROUND

The translocation of nanoparticles in the lung toward effector organs via the circulation is considered an important direct pathway for systemic effects of nanoparticles after inhalation. Recently, we have reported that a moderate dose of systemically administered nanosized carbon black particles exerted thrombogenic effects in hepatic microvessels of healthy mice.

OBJECTIVES

This study addresses the questions of whether similar thrombogenic effects are also evoked upon inhalation of nanosized carbon particles (NCP) and whether NCP-induced hepatic platelet accumulation is associated with pulmonary or systemic inflammation.

METHODS

Two and 8 h after a 24-h exposure to either filtered air or to NCP, intravital fluorescence microscopy of the hepatic microcirculation was performed in C57Bl/6 mice. Parameters of pulmonary or systemic inflammatory response were determined in bronchoalveolar lavage and blood/plasma samples.

RESULTS

Inhalative exposure to NCP caused platelet accumulation in the hepatic microvasculature, whereas leukocyte recruitment and sinusoidal perfusion did not differ from controls. Fibrinogen deposition was detected by immunohistochemistry in both hepatic and cardiac microvessels from NCP-exposed mice. In contrast, inhalation of NCP affected neither the plasma levels of proinflammatory cytokines nor blood cell counts. Moreover, the bronchoalveolar lavage data indicate that no significant inflammatory response occurred in the lung.

CONCLUSIONS

Thus, exposure to NCP exerts thrombogenic effects in the microcirculation of healthy mice independent of the route of administration (i.e. inhalation or systemic intra-arterial administration). The NCP-induced thrombogenic effects are not liver specific, are associated with neither a local nor a systemic inflammatory response, and seem to be independent of pulmonary inflammation.

Lung injury following thoracic aortic occlusion: comparison of sevoflurane and propofol anaesthesia

BACKGROUND

Halogenated anaesthetics have been shown to reduce ischaemia-reperfusion injuries in various organs due to pre- and post-conditioning mechanisms. We compared volatile and total intravenous anaesthesia with regard to their effect on remote pulmonary injury after thoracic aortic occlusion and reperfusion.

METHODS

Eighteen pigs were randomized after sternotomy and laparotomy (fentanyl-midazolam anaesthesia) to receive either sevoflurane or propofol in an investigator-blinded fashion. Ninety minutes of thoracic aortic occlusion was induced by a balloon catheter. During reperfusion, a goal-directed resuscitation protocol was performed. After 120 min of reperfusion, the anaesthetic regimen was changed to fentanyl-midazolam again for another 180 min. The oxygenation index and intra-pulmonary shunt fractions were calculated. After 5 h of reperfusion, a bronchoalveolar lavage was performed. The total protein content and lactate dehydrogenase activity were measured in epithelial lining fluid (ELF). Alveolar macrophage oxidative burst was analysed. The wet to dry ratio was calculated and tissue injury was graded using a semi-quantitative score. Ten animals (n=5 for each anaesthetic) without aortic occlusion served as time controls.

RESULTS

The oxygenation index decreased and the intra-pulmonary shunt fraction increased significantly in both occlusion groups. There were no significant differences between sevoflurane and propofol with respect to the oxygenation index, ELF composition, morphologic lung damage, wet to dry ratio and alveolar macrophage burst activity. Differences were, however, seen in terms of systemic haemodynamic stability, where catecholamine requirements were less pronounced with sevoflurane.

CONCLUSION

We conclude that the severity of remote lung injury was not different between sevoflurane and propofol anaesthesia in this porcine model of severe lower-body ischaemia and reperfusion injury.

Quantitative Assessment of Angiogenesis in Murine Antigen-Induced Arthritis by Intravital Fluorescence Microscopy

Inhibition of angiogenesis might be a therapeutic approach to prevent joint destruction caused by the overgrowing synovial tissue during chronic joint inflammation. The aim of this study was to investigate angiogenesis in the knee joint of mice with antigen-induced arthritis (AIA) by means of intravital microscopy. In 14 mice (C57BL6/129Sv) intravital microscopic assessment was performed on day 8 after AIA induction in two groups (controls, AIA). Synovial tissue was investigated by intravital fluorescence microscopy using FITC-dextran (150 kD). Quantitative assessment of vessel density was performed according to the following categories: functional capillary density (FCD, vessels <10 microm in diameter), functional vessel density (FVD, vessels >10 microm) and FVD of vessels with angiogenic criteria (convoluted vessels, abrupt changes of diameter, vessels which are generated by sprouting and progressively pruned and remodelled). Microvessel count was performed using immunohistochemistry. There was no significant difference in FCD between the control group (337 +/- 9 cm/cm2; mean +/- SEM) and the AIA group (359 +/- 13 cm/cm2). The density of vessels larger than 10 microm diameter was significantly increased in animals with AIA (135 +/- 10 vs. 61 +/- 5 cm/cm2 in control). The density of blood vessels with angiogenic criteria was enhanced in arthritic animals (79 +/- 17 vs. 12 +/- 2 cm/cm2 in control). There was a significant increase in the microvessel count in arthritic animals (297 +/- 25 vs. 133 +/- 16 mm(-2) in control). These findings demonstrate that angiogenesis in murine AIA can be assessed quantitatively using intravital microscopy. Further studies will address antiangiogenic strategies in AIA.

Intracellular glutathione and bronchoalveolar cells in fibrosing alveolitis: effects of N-acetylcysteine

Extracellular glutathione deficiency and exaggerated oxidative stress may contribute to the pathogenesis of fibrosing alveolitis (FA). High-dose N-acetylcysteine (NAC) supplementation partially reverses extracellular glutathione depletion and oxidative damage, but effects on intracellular glutathione are unknown. Intracellular total glutathione (GSHt) and activation of bronchoalveolar lavage cells (BAC) obtained from 18 FA patients (9 males, aged 52+/-2 yrs), before and after 12 weeks of oral NAC (600 mg t.i.d.), were assessed. Eight healthy nonsmokers (2 males, aged 36+/-6 yrs) served as a control group. Intracellular GSHt was decreased in FA (1.57+/-0.20 nmol 1x10(6) BAC(-1) versus 2.78+/-0.43 nmol x 10(6) BAC(-1)). After NAC treatment, the intracellular GSHt content increased (1.57+/-0.20 versus 1.87+/-0.19 nmol x 1 x 10(6) BAC(-1)). The spontaneous oxidative activity of BAC decreased after NAC treatment (2.7+/-0.8 versus 1.0+/-0.2 nmol x 1 x 10(6) BAC(-1) x h(-1)). Interleukin-8 concentration (82.1+/-31.5 versus 80.0+/-22.6 pg x mL bronchoalveolar fluid (BALF), nonsignificant (NS)) and myeloperoxidase activity (1.93+/-0.64 versus 1.55+/-0.47 mU x mL(-1) BALF, NS) did not change significantly, but were found to be inversely correlated to intracellular GSHt. In conclusion, high-dose N-acetylcysteine supplementation increases intracellular glutathione levels slightly. This increase is associated with a mild reduction of oxidative activity but not with a reduction of bronchoalveolar cell activation in these patients.

Differential function of nitric oxide in murine antigen-induced arthritis

BACKGROUND

The aim of our study was to investigate the role of inducible nitric oxide synthase (iNOS)-derived nitric oxide (NO) production in different stages of murine antigen-induced arthritis (AiA).

METHODS

Clinical, histological and microcirculatory parameters (measured by intravital fluorescence microscopy) were assessed in the knee joint during acute and chronic AiA after inhibition of iNOS with L-N(6)-(1-iminoethyl)lysine (L-NIL). Plasma concentrations of and were evaluated by the Griess reaction and the expression of iNOS, P- and E-selectin, intercellular adhesion molecule 1 (ICAM-1) and vascular cell adhesion molecule 1 (VCAM-1) by immunohistochemistry.

RESULTS

In both stages of the disease, plasma concentrations of and were increased and iNOS was expressed. In the acute phase, swelling, leucocyte adhesion, leucocyte infiltration and expression of adhesion molecules were increased in arthritic animals treated with L-NIL in comparison with untreated arthritic animals. In the chronic phase, no change in the disease parameters could be detected after L-NIL treatment.

CONCLUSION

Increased NO production induced by iNOS during the acute phase of AiA can be regarded as a protective response in the prevention of further leucocytic infiltration and joint destruction, whereas it seems to play a subordinate role in chronic AiA.

The influence of organ temperature on hepatic ischemia-reperfusion injury: a systematic analysis

BACKGROUND

Although hepatic ischemia-reperfusion (I/R) injury can be reduced by cooling of the ischemic organ, a systematic in vivo analysis of the influence of organ temperature in I/R injury is missing. The aim of this study was to systematically investigate the impact of defined temperatures of the ischemic liver tissue on microvascular I/R injury.

METHODS

Ischemia of the left liver lobe was induced in C57BL/6 mice for 90 min. The ischemic lobe was placed in a polyethylene well and the temperature was adjusted to 37 degrees C, 26 degrees C, 15 degrees C, and 4 degrees C by superfusion with cooled/warmed saline solution. The ischemia groups (n=7 each) were compared with a sham-operated group (n=7). The sinusoidal perfusion index and the number of leukocytes firmly adherent to the endothelium of postsinusoidal venules were assessed using intravital fluorescence microscopy at 30 min, 120 min, and 240 min of reperfusion, respectively. At the end of the experiment, serum activities of the liver enzymes aspartate aminotransferase/alanine aminotransferase were determined, and tissue specimens were examined by electron microscopy.

RESULTS

Core body temperature did not differ significantly between the groups. In the 37 degrees C group, the sinusoidal perfusion index was significantly reduced and the number of adherent leukocytes was significantly increased compared with the sham group. In all hypothermia groups, however, the microcirculatory parameters did not differ from the sham group. Serum activities of aspartate aminotransferase/alanine aminotransferase were significantly increased and hepatocellular integrity was severely affected in the 37 degrees C group as compared with all other groups.

CONCLUSIONS

These findings demonstrate that in the mouse liver the known protective effect of hypothermia is already encountered at 26 degrees C. Further reduction of temperature did not generate additional protection from I/R injury.

Exacerbation of antigen-induced arthritis in inducible nitric oxide synthase-deficient mice

OBJECTIVE

Inhibition of nitric oxide (NO) produced by inducible NO synthase (iNOS) is suggested to be beneficial in experimental arthritis. Although NO is important for the integrity of the microcirculation, the effects of inhibition of iNOS on the synovial microcirculation are not currently known. This study investigated the synovial microcirculation and leukocyte-endothelial cell interactions in iNOS-deficient mice with antigen-induced arthritis (AIA) and compared these findings with disease severity.

METHODS

Fourteen homozygous iNOS-/- and 14 iNOS+/+ mice were used. The severity of AIA was assessed by measuring knee joint swelling and by histologic scoring. The number of rolling and adherent leukocytes was quantitatively analyzed in synovial microvessels using intravital microscopy of intraarticular synovial tissue. Nitrite/nitrate concentrations were measured, and the expression of iNOS, E- and P-selectin, intercellular adhesion molecule 1, and vascular cell adhesion molecule 1 (VCAM-1) was assessed by immunohistochemistry.

RESULTS

In iNOS+/+ animals with AIA, the plasma concentration of nitrite/nitrate was increased 3-fold and iNOS expression was detected in cells of the joint. Swelling of the knee joint as well as leukocyte infiltration were enhanced in the iNOS-/- arthritic animals compared with iNOS+/+ mice with AIA. AIA-associated leukocyte-endothelial cell interaction in synovial postcapillary venules was more pronounced in iNOS-/-, compared with iNOS+/+, arthritic mice. A strong expression of P-selectin and VCAM-1 was observed in the iNOS-/- arthritic mice only.

CONCLUSION

These data suggest that NO production by iNOS in vivo has antiinflammatory effects in experimental arthritis, by mediating a reduction in leukocyte adhesion and infiltration.

Interaction of alveolar macrophages with inhaled mineral particulates

Pulmonary disorders triggered by inhalation of occupational and environmental mineral particulates can be endpoints of a chronic inflammatory process in which alveolar macrophages (AMs), as a first line of defense, play a crucial role. The biological processes involved in particulate-induced activation of AMs include indirect or direct interactions of particulates with the cell membrane, subsequent stimulation of signal transduction pathways, and activation of gene transcription. Depending on the nature of particulate involved, particulate-induced activation of AMs has been shown to result in the release of potent mediators, such as reactive oxygen and nitrogen species, cytokines, eicosanoids, and growth factors. The prolonged and enhanced production of such effector molecules may result in a complex cascade of events that can contribute to the development of pulmonary disorders. This paper will give a short review of the present knowledge of AM interaction with inhaled mineral particulates and of the possible implications these interactions may have in the development of pulmonary disorders.

Hyperoxia upregulates the NO pathway in alveolar macrophages in vitro: role of AP-1 and NF-kappaB

The inducible nitric oxide (NO) synthase gene in alveolar macrophages (AMs) is a stress response gene that may contribute to tissue injury in the lung after respiration with high O(2) concentrations through extensive production of NO. In this study, we investigated the influence of hyperoxia on the NO pathway in rat AMs in vitro, its regulation by the transcription factors nuclear factor (NF)-kappaB and activator protein (AP)-1, and the role of reactive oxygen species (ROS). AMs were treated with lipopolysaccharide (LPS) and/or interferon (IFN)-gamma and incubated under 21 or 85% O(2). Stimulation with LPS and IFN-gamma led to induction of the NO pathway that was further upregulated by hyperoxia. The binding activity of NF-kappaB, in contrast to that of AP-1, was activated on stimulation with LPS and IFN-gamma, and both were further increased under hyperoxia. The antioxidants pyrrolidine dithiocarbamate and N-acetyl-L-cysteine inhibited intracellular ROS production and the NO pathway under both normoxic and hyperoxic conditions but had diverse effects on the transcription factors. The results presented here indicate that hyperoxia can upregulate the NO pathway in stimulated AMs through increased production of intracellular ROS and activation of NF-kappaB and AP-1.

Differential responses of rat alveolar and peritoneal macrophages to man-made vitreous fibers in vitro

Different approaches, including inhalation and intraperitoneal injection assays, have been used to assess the potential health effects of man-made vitreous fibers (MMVF). The purpose of this study was to compare the phagocytic activity and the formation of reactive oxygen species by rat alveolar macrophages (AM) and peritoneal macrophages (PM) upon exposure to MMVF10 glass wool and MMVF21 rock wool fibers. Macrophage (Mphi) phagocytosis of mineral fibers was assessed by optical videomicroscopy and computer-aided image analysis. Mphi were classified as cells not associated with fibers, cells with attached fibers, cells with incompletely phagocytized fibers (an appearance known as "frustrated phagocytosis"), and cells with completely phagocytized fibers. The production of superoxide anions by AM and PM upon incubation with MMVF10 and MMVF21 fibers was determined by the superoxide dismutase-inhibitable reduction of ferricytochrome C. PM were found to have a lower phagocytic activity than AM. A significantly higher percentage of AM than of PM underwent frustrated phagocytosis of MMVF10 and MMVF21 fibers. In line with these findings, AM generated higher levels of oxygen radicals than PM upon exposure to MMVF21 fibers. In contrast, MMVF10 fibers failed to induce the generation of reactive oxygen species by both AM and PM. Our in vitro results show that the phagocytic activity, in particular the frustrated phagocytosis of mineral fibers, was significantly lower in PM than in AM. The data support the idea that the durability and biopersistence of mineral fibers are higher in the peritoneal cavity than in the lung.

Phenotypic and functional differences between rat alveolar, pleural, and peritoneal macrophages

Tissue macrophages (M phi) play a central and essential role in modulating the initiation and perpetuation of the inflammatory response. Phenotypical and functional differences among alveolar M phi (AM) and peritoneal M phi (PM) have been reported, but less is known about pleural M phi (PLM) and their ability and capacity to release biologically active substances. Therefore, the aim of this study was to determine the production of superoxide anion, nitric oxide (NO), and tumor necrosis factor alpha (TNF-alpha) by PLM in comparison to AM and PM in vitro. M phi from rats were isolated by lavage of the respective body compartment and characterized by evaluating the expression of the surface antigens MHC class II molecules, CD11b, and ED2-like antigen. Upon activation, AM produced significantly higher amounts of superoxide anion, NO, and TNF-alpha compared to PM and PLM. Taken together, the findings of this study demonstrate that rat PLM resemble PM more than AM in terms of production of key inflammatory mediators.

Ischemia at 4 degrees C: a novel mouse model to investigate the effect of hypothermia on postischemic hepatic microcirculatory injury

Hypothermia of the ischemic organ at 4 degrees C protects hepatic microcirculation from ischemia-reperfusion (IR) injury. The effect of hypothermia during ischemia was investigated in animal models using liver transplantation and storage of the harvested organ in cold preservation solutions. No investigation of the isolated influence of hypothermia at 4 degrees C of the ischemic organ on hepatic IR injury exists, due to the lack of an appropriate animal model. Therefore, the aim of our present study was to develop such a model using intravital video fluorescence microscopy (IVM). In C57BL/6 mice, a reversible isolated ischemia of the left liver lobe was induced for 90 min, followed by 240 min of reperfusion. The temperature of the ischemic organ was adjusted to either 4 degrees C or 37 degrees C by superfusion with 0.9% NaCl. Sham-operated animals without IR served as controls. The hepatic microcirculation was analyzed using IVM at 30 min and 240 min after reperfusion by quantifying sinusoidal perfusion and leukocyte-endothelial cell interaction in postsinusoidal venules. At the end of the experiment, blood and tissue samples were taken for measurement of liver enzyme activities and light and electron microscopy. Mean arterial pressure and body temperature were kept constant throughout the experiment, while the temperature of the ischemic liver lobe was adjusted to predefined levels. After normothermic ischemia, hepatic microvascular perfusion was significantly impaired compared with sham-operated animals. Perfusion failure was significantly reduced in hypothermic livers and did not differ from livers of the sham-group. Liver enzyme activities in the normotherimic group were significantly higher than in the sham and hypothermic groups. Light and electron microscopy revealed severe histological alterations at 37 degrees C ischemia, whereas at 4 degrees C ischemia only minimal lesions were encountered. Our novel model allows for isolated adjustment of ischemic liver lobe temperature without changing body temperature and systemic macrohemodynamic parameters. Hypothermia at 4 degrees C largely attenuates postischemic microvascular perfusion injury of the liver.

Comparison of the phagocytic response of rat and hamster alveolar macrophages to man-made vitreous fibers in vitro

Rats and hamsters are well known for their disparate response to inhaled mineral fibers/particles. Alveolar macrophages (AM) play an important role in the pulmonary clearance and retention of mineral fibers/particles mainly through the process of phagocytosis. The aim of this study was to investigate whether there exist differences in the phagocytic response and release of reactive oxygen species (ROS) between rat and hamster AM upon exposure to man-made vitreous fibers (MMVF) in vitro. AM were obtained by bronchoalveolar lavage and macrophage-enriched cultures were exposed to MMVF10 and MMVF21 fibers for 20 h. The phagocytic response of macrophages was determined by computer-assisted video-microscopy and the superoxide anion production was evaluated by cytochrome c reduction. A significantly higher percentage of rat AM underwent frustrated phagocytosis of both types of MMVF compared to hamster AM. This was associated with a higher ROS release by rat AM compared to hamster AM. These data may help to explain the cellular mechanisms underlying the disparate pulmonary response of rat and hamster to inhaled particulate matter.

Pulmonary glutathione levels in acute episodes of Farmer's lung

Acute episodes of farmer's lung (FL) are associated with activation and migration of neutrophils into the lungs, causing oxidative stress. We conducted a study to evaluate the effect of episodes of FL on antioxidant defense of the lung by glutathione (GSH). A total of 15 patients with symptomatic FL (one female and 14 males, age 42 +/- 1 yr [mean +/- SEM]) underwent a standardized hay exposure test for 1 h and were then monitored through lung function measurements for 6 h, after which bronchoalveolar lavage (BAL) was performed. As a control, 10 asymptomatic farmers (AF) (two males and eight females, age 43 +/- 1 yr) underwent the same diagnostic procedures. At 3 to 6 h after antigen exposure, the lung function of FL patients was significantly impaired (VC: -31 +/- 4%; single-breath diffusing capacity of carbon monoxide [DL(CO)]: -17 +/- 3%; and Pa(O(2)): -14 +/- 2%, all versus baseline, whereas in AF, only minor changes occurred VC: -4 +/- 5%; DL(CO): -9 +/- 3%, and Pa(O(2)): -5 +/- 2%, all versus baseline). The number of neutrophils in bronchoalveolar lavage fluid was increased in FL patients as compared with AF (29 +/- 7 x 10(4)/ml versus 10 +/- 7 x 10(4)/ml, p < 0.05). The concentrations of total and reduced glutathione (GSH(T) and GSH, respectively) in epithelial lining fluid were decreased in FL patients and increased in AF (GSH(T): 292.5 +/- 27.5 microM versus 1, 185.0 +/- 189.9 microM, respectively, p < 0.001; GSH: 256.8 +/- 22.1 microM versus 1,054.5 +/- 172.9 microM, respectively, p < 0.001). These findings suggest that the individual ability to upregulate GSH in the alveolar space in response to an inflammatory stimulus may have implications for the development of symptomatic FL. We conclude that intrapulmonary GSH levels are distinctly different in patients with FL and AF, and that the regulation of GSH may play an important role in the pathogenesis of FL.

Increased expression of the tetraspanins CD53 and CD63 on apoptotic human neutrophils

The recently discovered tetraspanin superfamily comprises a group of cell-surface proteins that are suggested to be involved in cell activation and signal transduction as well as in cell adhesion, motility, and metastasis. In this study, we have assessed the expression of two tetraspanins, CD53 and CD63, and two principal leukocyte adhesion molecules, CD11b and CD62L, on human apoptotic neutrophils. After aging of human neutrophils for 20 and 40 h in vitro, apoptosis was analyzed by light microscopy and flow cytometry. The binding of monoclonal antibodies directed against CD11b, CD62L, CD53, and CD63 on apoptotic and nonapoptotic cells was determined by dual-color flow cytometry. Aging of neutrophils in vitro resulted in a significant (P < 0.05) down-regulation of expression of the selectin CD62L, and a significantly increased expression of the two tetraspanins CD53 and CD63. The selective analysis of apoptotic versus nonapoptotic cells proved that both the increased expression of the tetraspanins and the loss of CD62L were restricted to the apoptotic subpopulation. An identical pattern of surface molecule expression was detected at 12 h after induction of apoptosis by an agonistic anti-Fas IgM monoclonal antibody. Further studies are required to clarify whether tetraspanins participate in the recognition of apoptotic circulating or extravasated neutrophils by macrophages.

Implementation of the microdialysis method in the hamster dorsal skinfold chamber

The aim of this study was to implement the microdialysis method, a well-established technique for measuring the local concentration of neurotransmitters and metabolites in the brain, in the dorsal skinfold chamber of the awake hamster. First, the effects of implanted, nonperfused microdialysis probes on the microcirculation were examined. Skinfold chambers were prepared with and without probes. Two and 3 days later, the following parameters were assessed: diameter, red blood cell (RBC) velocity, macromolecular leakage, leukocyte rolling fraction, and adherent leukocytes in venules, diameter and macromolecular leakage in arterioles, and functional capillary density (FCD). No significant differences between the animals of the two groups were observed in any of the parameters on either day. Second, the interstitial lactate concentration was measured at two perfusion rates in groups with and without a 4-h tourniquet ischemia. The induction of ischemia resulted in a significant increase in lactate concentration over the control values in the tissue within 1 h to 8000 +/- 860 microM, where it remained until the reperfusion, at which point the concentration returned to control values within 1 h. The microdialysis method provides the opportunity to measure the concentration of metabolites in the extravascular space of the hamster dorsal skinfold chamber.

In vivo assessment of synovial microcirculation and leukocyte-endothelial cell interaction in mouse antigen-induced arthritis

OBJECTIVE

The microcirculation and leukocyte-endothelial cell interaction in synovial tissue of an inflamed joint are known to play a crucial role in the pathogenesis of rheumatoid arthritis. The aim of this study was to characterize the in vivo changes in the microvasculature and in leukocyte-endothelial cell interactions in the mouse synovial tissue using intravital fluorescence microscopy in three stages of antigen-induced arthritis. The expression of E- and P-selectin and ICAM-1 were also studied using immunohistochemistry.

METHODS

Antigen-induced arthritis (AiA) was produced in Balb/c mice. The severity of arthritis at three different phases was quantified using a clinical and histological score. For the intravital fluorescence microscopy measurements, the patella tendon was partially resected for visualization of the intraarticular synovial tissue of the knee joint. The number of rolling and adherent leukocytes, functional capillary density (FCD) and RBC velocity were quantitatively measured in synovial microvessels. Expression of ICAM-1, E- and P-selectin was assessed by immunohistochemistry.

RESULTS

There was a significant increase in the leukocyte rolling fraction in postcapillary venules in the acute phase of AiA (from 0.26 +/- 0.05 in controls to 0.45 +/- 0.04 8 d after AiA induction). The number of leukocytes adherent to the endothelium was significantly elevated in all phases of arthritis (from 121 +/- 27 in controls to 376 +/- 62 mm2 63 d after AiA-induction). Functional capillary density was significantly enhanced in the acute (332 +/- 15 cm/cm2) and intermediate phases (320 +/- 15 cm/cm2) compared to control values (227 +/- 15 cm/cm2). Arthritis resulted in a distinct increase in the expression of ICAM-1 on the synovial endothelium in all phases of AiA. E- and P-selectin expression were detected only in the acute phase.

CONCLUSION

Our model provides new insights into the microcirculatory changes which occur in the synovial tissue of an arthritic joint.

Fibrinogen deposition at the postischemic vessel wall promotes platelet adhesion during ischemia-reperfusion in vivo

Following ischemia-reperfusion (I/R), platelet adhesion is thought to represent the initial event leading to remodeling and reocclusion of the vasculature. The mechanisms underlying platelet adhesion to the endothelium have not been completely established. Endothelial cells rendered ischemic acquire a procoagulant phenotype, characterized by fibrinogen accumulation. Therefore, we evaluated whether fibrinogen deposition during I/R mediates platelet adhesion. Using fluorescence microscopy, fibrinogen deposition and the accumulation of platelets were assessed in vivo in a model of intestinal I/R (1.5 hours/60 minutes). Fibrinogen accumulated in arterioles and venules early after the onset of reperfusion. The deposition of fibrinogen colocalized with large numbers of adherent platelets (520 +/- 65 and 347 +/- 81 platelets/mm(2) in arterioles and venules). Pretreatment with an antifibrinogen antibody attenuated platelet adhesion. Intracellular adhesion molecule (ICAM)-1 served as a major receptor for fibrinogen, since fibrinogen deposition and platelet adhesion to the endothelial cell surface were markedly decreased in ICAM-1-deficient mice. The platelet alpha(IIb)/beta(3) integrin plays a key role in fibrinogen-dependent platelet accumulation, because (1) platelet adhesion involved RGD-recognition sequences, and (2) platelets isolated from a patient with Glanzmann's disease showed decreased interaction with the postischemic endothelium. Since platelets are demonstrated here to induce tyrosine phosphorylation in endothelial cells, platelet recruitment might contribute to the development of an inflammatory reaction during I/R.

Effects of NO synthase inhibitors on the synovial microcirculation in the mouse knee joint

Production of nitric oxide by the inducible NO synthase (iNOS) is known to be enhanced in chronic joint inflammation and osteoarthritis as well as aseptic loosening of joint prostheses. Initial studies yielded promising results after inhibition of the nitric oxide synthase (NOS). However, the effect of NOS inhibition has not been studied at the site of the primary function of NO, the microcirculation of the synovium in vivo. Using our recently developed model for the in vivo study of synovial microcirculation in the mouse knee joint, the effects of selective versus nonselective inhibition of iNOS were investigated by means of intravital fluorescence microscopy. After resection of the patella tendon, the synovial fatty tissue was exposed for intravital microscopy. Diameter of arterioles, functional capillary density (FCD), diameter of venules, venular red blood cell velocity and leukocyte-endothelial cell interaction were quantitatively analyzed before, and 10 and 60 min after intravenous injection of NOS inhibitors [selective iNOS inhibitor N-iminoethyl-L-lysine (L-NIL), and nonselective NOS inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME)]. Our results demonstrate that L-NAME causes a significant decrease in the arteriolar diameter and FCD associated with an increase in the leukocyte accumulation in the synovium in vivo. In contrast, L-NIL neither altered the microhemodynamics nor the leukocyte-endothelial cell interaction in the synovium, indicating its potential use for selective inhibition of iNOS in joint inflammation. Using our method, further studies will provide new insights into the unknown effect of NOS inhibition on the synovial microvasculature in inflammatory joint disease in vivo.

Effects of lung preservation solutions on PMN activation in vitro

Polymorphonuclear leukocyte (PMN) activation and PMN-endothelial cell interactions may cause graft failure due to ischemia-reperfusion injury after lung transplantation. We investigated the effects of Euro-Collins solution (EC), low-potassium dextran solution (LPD), and EC plus pentoxifylline (EC-PTXF) on adhesion molecule (CD11b/CD18 and L-selectin) expression, chemotaxis, and oxidative burst of PMN. PMN from healthy human volunteers were incubated with EC, LPD, and EC-PTXF, and, in controls, without preservation solution. LPD exerted a suppressive effect on PMN chemotaxis as compared to EC (P < 0.05), but had no attenuating effect on the increase of CD11b/CD18, the shedding of L-selectin, and intracellular oxidant generation. EC-PTXF attenuated the expression of CD11b/CD18 and the oxidative burst as compared to EC alone (P < 0.05). These effects of LPD and PTXF on PMN function may contribute to successful organ preservation in transplantation.

Increased adhesion and aggregation of platelets lacking cyclic guanosine 3',5'-monophosphate kinase I

Atherosclerotic vascular lesions are considered to be a major cause of ischemic diseases, including myocardial infarction and stroke. Platelet adhesion and aggregation during ischemia-reperfusion are thought to be the initial steps leading to remodeling and reocclusion of the postischemic vasculature. Nitric oxide (NO) inhibits platelet aggregation and smooth muscle proliferation. A major downstream target of NO is cyclic guanosine 3', 5'-monophosphate kinase I (cGKI). To test the intravascular significance of the NO/cGKI signaling pathway in vivo, we have studied platelet-endothelial cell and platelet-platelet interactions during ischemia/reperfusion using cGKI-deficient (cGKI-/-) mice. Platelet cGKI but not endothelial or smooth muscle cGKI is essential to prevent intravascular adhesion and aggregation of platelets after ischemia. The defect in platelet cGKI is not compensated by the cAMP/cAMP kinase pathway supporting the essential role of cGKI in prevention of ischemia-induced platelet adhesion and aggregation.

Formation of nitric oxide by rat and hamster alveolar macrophages: an interstrain and interspecies comparison

Nitric oxide (NO) plays an important role in non-specific host defense, which can be recognized by its antimicrobial and cytotoxic activity against pathogens. However, there appear to exist interspecies differences in the ability of macrophages to generate NO. The object of this study was to determine whether there exist intraspecies differences in the production of NO. We compared NO formation by alveolar macrophages (AM) from five different rat strains (Sprague Dawley, Wistar, Lewis, Fisher, and Brown Norway), two different stocks of Syrian Golden hamsters, and one stock of Chinese hamsters. The AM were harvested by bronchoalveolar lavage and stimulated in vitro with various concentrations of LPS and/or IFN-gamma. The oxidation product of NO, nitrite, was measured in the AM supernatant by the Griess reaction. Upon stimulation with LPS and/or IFN-gamma, AM from all five rat strains were able to release NO, but the amount of NO produced differed significantly among the rat strains. However, none of the stimuli was able to induce AM from the two stocks of Syrian Golden hamsters as well as AM from the stock of Chinese hamsters to release measurable amounts of NO. These findings point to distinct regulatory mechanisms of the NO pathway in AM from different species and to variations of this mechanism in the AM from the investigated rat strains.

Platelet-endothelial cell interactions during ischemia/reperfusion: the role of P-selectin

Growing evidence supports a pathophysiological role for platelets during the manifestation of postischemic reperfusion injury; in the current study, we investigated the nature and the molecular determinants of platelet-endothelial cell interactions induced by ischemia/reperfusion (I/R). Platelet-endothelium and leukocyte-endothelium interactions after 1 hour of ischemia were monitored in vivo within mouse small intestine. By intravital fluorescence microscopy, we observed that platelets, like leukocytes, roll along or firmly adhere to postischemic microvascular endothelial cells. In contrast, few leukocyte-endothelial cell interactions were detected in sham-operated controls. Monoclonal antibodies against P-selectin significantly attenuated platelet rolling and adherence in response to I/R. To identify whether platelet or endothelial P-selectin plays the major role in mediating postischemic platelet-endothelial cell interactions, P-selectin-deficient or wild-type platelets were transfused into wild-type or P-selectin-deficient mice, respectively. Whereas platelets lacking P-selectin rolled along or adhered to postischemic wild-type endothelium, interactions between wild-type platelets with mutant endothelium were nearly absent, indicating that I/R-induced platelet-endothelium interactions are dependent on the expression of P-selectin by endothelial cells. Concomitantly, P-selectin expression in the intestinal microvasculature was enhanced in response to I/R, whereas no upregulation of P-selectin was observed on circulating platelets. In summary, we provide first in vivo evidence that platelets accumulate in the postischemic microvasculature early after reperfusion via P-selectin-ligand interactions. Platelet recruitment and subsequent activation might play an important role in the pathogenesis of I/R injury.

Quantitative analysis of small intestinal microcirculation in the mouse

Impairment of intestinal nutritive perfusion and accumulation of inflammatory cells in the intestinal microvasculature are well-known sequelae of mesenteric ischemia/reperfusion, sepsis, and shock. However, the molecular mechanisms underlying these alterations are still not fully understood. The mouse is particularly suitable for the study of these mechanisms since in this species the involvement of, for example, adhesion receptors or pro-/anti-adhesive mediators can be selectively investigated by the use of monoclonal antibodies or gene-targeted strains. The aim of our present study was, therefore, to establish a model to investigate the microcirculation in the mouse small intestine. Under anesthesia by inhalation of isoflurane-N2O, Balb/c mice (n = 16) were laparotomized, and a segment of the jejunum was exteriorized for intrvital fluorescence microscopy. Using FITC-dextran (MW 150,000) as a plasma marker, functional capillary density (FCD) of both the intestinal mucosa and muscle layer was analyzed. Nutritive perfusion was homogeneous in both compartments with values for FCD of 512 +/- 15 cm-1 in mucosa and 226 +/- 21 cm-1 in the muscle layer. No significant changes were observed throughout the observation period of 2 h (FCD values at the end of the observation period: 524 +/- 31 cm-1 and 207 +/- 7 cm-1 in mucosa and muscle, respectively). Besides capillary perfusion, leukocyte-endothelial cell interaction was analyzed in postcapillary venules of the intestinal submucosa using rhodamine-6G as an in vivo leukocyte stain. Under physiological conditions only a few white blood cells were found rolling along or firmly adherent to the microvascular endothelium (number of rolling leukocytes 1 +/- 0.2 cells/mm per second; number of adherent leukocytes: 18 +/- 7 cells/mm2). In a separate group rhodamine-6G-labeled syngeneic platelets were infused to analyze platelet-endothelial cell interactions quantitatively in vivo. Platelets rolled along or attached to the endothelium in a manner similar to leukocytes. However, in contrast to leukocytes the interactions were not restricted to venules, but were also observed in small arterioles. The newly established model allows for the visualization and quantitative assessment of both nutritive perfusion and platelet/leukocytendothelial cell interactions within the distinct layers of the mouse small intestine. Using this model in combination with gene-targeted mice or monoclonal antibodies it is possible to investigate the molecular mechanisms of intestinal inflammation reactions.

A novel model for the study of synovial microcirculation in the mouse knee joint in vivo

A novel model for the investigation of the microcirculation in synovial tissue of the mouse knee joint is presented. The mouse knee joint was exposed on a specially designed plexiglass stage with a slight flexion. After partial resection of the skin, the patella tendon was cut transversally, which allowed for visualization of the "Hoffa's fatty body", an intraarticular fatty tissue containing synovial cells on the interior surface of the joint. An intravital fluorescence microscope was adjusted to observe the microcirculation of this intraarticular synovial tissue without opening of the joint capsula. For staining of the plasma, fluorescein isothiocyanate (FITC)-dextran was used, and for the staining of leukocytes rhodamine 6G was used. The tissue investigated presents with a high-density honeycomb-like capillary network, containing some postcapillary venules and a few arterioles. The following parameters were assessed off-line using a computer-assisted microcirculation analysis system: flow and diameter of arterioles and postcapillary venules, as well as functional capillary density. Moreover, leukocyte-endothelial cell interaction was quantified by counting the number of rolling cells and cells adhering to the endothelium in postcapillary venules. As an indication of endothelial leakage, macromolecular extravasation was also assessed. To validate the model, we investigated these parameters at three time points during an observation period of 60 min. There was no change in functional capillary density, nor in vessel diameter after 60 min of observation. Moreover, there was neither a change in the number of rolling cells, nor in the number of cells adhering to the endothelium nor in extravasation of FITC-dextran, thus indicating the stability of the preparation. The new model allows the quantitative analysis of the intraarticular microcirculation of the synovial fatty tissue in vivo. It provides insight into the dynamics of synovial microcirculation and leukocyte-endothelial cell interaction in acute or chronic joint inflammation.

Recombinant human interleukin-10 attenuates TNFalpha production by porcine monocytes

BACKGROUND

Human recombinant interleukin-10 (rhIL-10) has been found to inhibit endotoxin-induced production of several proinflammatory cytokines including tumor necrosis factor alpha (TNFalpha) from human monocytes. The exogenous therapeutic administration of rhIL-10 in acute and chronic hyperinflammatory conditions has been discussed. For none of the large animal species that have been used to study the role and effects of various mediators during septicemia, crossreactivity of rhIL-10 has been shown so far. Therefore, the aim of the present investigation was to evaluate the crossreactivity of rhIL-10 in a porcine model.

METHODS

To determine the effects of rhIL-10 on endotoxin-challenged porcine monocytes, we incubated porcine peripheral blood monocytes from five donors with three different concentrations of rhIL-10 (500 ng/ml, 1000 ng/ml and 2000 ng/ml, respectively) either simultaneously with, or two hours prior to lipopolysaccharide (LPS) administration.

RESULTS

As compared to incubation with LPS (1 microg/ml) alone, coincubation with LPS and rhIL-10 (500 ng/ml, 1000 ng/ml and 2000 ng/ml) (n = 5) for four hours resulted in a marked and uniform reduction of immunoreactive TNFalpha. For preincubation (n = 5), only the addition of 500 ng/ml rhIL-10 led to a homogeneous decrease of TNFalpha levels in each sample. There was no consistent reduction in TNFalpha after preincubation with 1000 and 2000 ng/ml rhIL-10. Our results indicate crossreactivity of recombinant human interleukin-10 in porcine peripheral blood monocytes. Further investigations on the potential therapeutical role of exogenously administered rhIL-10 are thus possible in porcine models.

Defective smooth muscle regulation in cGMP kinase I-deficient mice

Regulation of smooth muscle contractility is essential for many important biological processes such as tissue perfusion, cardiovascular haemostasis and gastrointestinal motility. While an increase in calcium initiates smooth muscle contraction, relaxation can be induced by cGMP or cAMP. cGMP-dependent protein kinase I (cGKI) has been suggested as a major mediator of the relaxant effects of both nucleotides. To study the biological role of cGKI and its postulated cross-activation by cAMP, we inactivated the gene coding for cGKI in mice. Loss of cGKI abolishes nitric oxide (NO)/cGMP-dependent relaxation of smooth muscle, resulting in severe vascular and intestinal dysfunctions. However, cGKI-deficient smooth muscle responded normally to cAMP, indicating that cAMP and cGMP signal via independent pathways, with cGKI being the specific mediator of the NO/cGMP effects in murine smooth muscle.

[Microcirculation research in experimental surgery]

The microcirculation is the organ that provides the direct link between blood and tissue, and thereby between the whole organism and the single cell. Modern microcirculation research in experimental surgery is characterized by the use of high-resolution video fluorescence microscopy and quantitative computer-assisted image analysis coupled with the techniques of molecular biology and transgenic or knockout gene technology. These advances should improve knowledge about surgically relevant physiologic and pathophysiologic phenomena at the interface between blood and tissues and help us to understand the initial molecular mechanisms leading to organ dysfunction following inflammation, ischemia-reperfusion, and transplantation.

[Influence of selective versus nonselective inhibitors of nitric oxide synthases on synovial microcirculation of the knee joint of the mouse in vivo]

Nitric oxide production by the inducible NO-synthase in the synovium and chondrocytes is known to be enhanced during chronic joint inflammation and aseptic loosening of joint prostheses. Due to the distinct side effects of non-selective NO-inhibitors on the macro- and microhemodynamics, we investigated the in vivo changes after selective (N-iminoethyl-L-lysine (NIL)) versus non-selective NO-synthase inhibition (NG-nitro-L-arginine methyl ester (L-NAME)) in the synovium of the mouse knee joint. Our results show a significant decrease in the functional capillary density and an increase in the leukocyte accumulation after L-NAME injection. In contrast, NIL did not alter the microhemodynamics or the leukocyte-endothelial cell interaction in the synovium, indicating its potential use for therapeutic selective inhibition of iNOS in joint inflammation.

Biochemical and cellular composition of alveolar epithelial lining fluid in anesthetized healthy lambs

Pulmonary toxicity of inhaled materials is often evaluated by (repetitive) assessment of the composition of bronchoalveolar lavage (BAL) fluid or of epithelial lining fluid (ELF) in sheep and lambs. Knowledge of the typical constituents of these fluids obtained from healthy animals is essential for identification of pathologic changes. Few studies have dealt with normal constituents of BAL fluid or ELF in sheep and lamb. The comparability of these studies, however, is limited for reasons concerning the choice of model and BAL technique. The biochemical and cellular composition of alveolar ELF obtained by a standardized BAL procedure was examined in 15 pento-barbital anesthetized 4 months old Merino lambs unexposed to inhaled substances. ELF volume was calculated by using the urea dilution method. We found 20.3 x 10(5) leucocytes per ml ELF, 87.5% of which were alveolar macrophages. Basophils and neutrophils were practically absent while 5% of the counted cells were lymphocytes. 76% of recovered cells were viable. The ELF contained 7 mg/ml total protein; enzyme activities of LDH and AP were 1692 U/l and 145 U/l, respectively.

Antioxidative and clinical effects of high-dose N-acetylcysteine in fibrosing alveolitis. Adjunctive therapy to maintenance immunosuppression

In fibrosing alveolitis (FA), activated phagocytes cause excessive oxidative stress in the lower respiratory tract. Additionally, levels of glutathione, a major antioxidant of the human lung, are markedly reduced. Since N-acetylcysteine (NAC) is a known precursor for glutathione synthesis, we investigated the effect of NAC on redox balance and lung function in FA. Eighteen patients with an established diagnosis of FA were treated with 600 mg NAC three times daily for 12 wk in addition to their latest immunosuppressive therapy. Before and after NAC therapy, pulmonary function tests (PFTs) and bronchoalveolar lavage (BAL) were performed. BAL fluid was analyzed with regard to cell differential, glutathione status, and methionine sulfoxide content of BAL proteins (Met(O)), as an indicator of oxidative stress at the alveolar surface. There was an increase of total glutathione (GSHt = GSH +/- 2 x GSSG: 3.43 +/- 0.30 microM versus 4.20 +/- 0.66 microM, p < 0.05) and of reduced glutathione (GSH: 2.58 +/- 0.24 microM versus 3.42 +/- 0.54 microM, p < 0.005) in native BAL fluid and in the epithelial lining fluid (GSHt: 267.3 +/- 26.0 microM versus 367.1 +/- 36.0 microM, p < 0.005; GSH: 204.5 +/- 20.7 microM versus 302.9 +/- 32.2 microM, p < 0.005). The increase of GSH was accompanied by a decrease of Met(O) (6.83 +/- 0.71% versus 4.60 +/- 0.40%, p < 0.005). PFTs significantly improved during NAC treatment. We conclude that high-dose NAC significantly improved the antioxidant screen of the lungs by elevating GSH levels. Moreover, the decrease of Met(O) levels indicated an antioxidant effect at the alveolar surface. These biochemical changes were accompanied by an improvement of PFTs in patients under maintenance immunosuppression. NAC supplementation should, therefore, be considered as an adjunct therapy for FA.

Effect of linoleic acid, linoleic acid anilide, and arachidonic acid on the expression of adhesion molecules on human neutrophils

The effects of linoleic acid, linoleic acid anilide, and arachidonic acid on the expression of CD11b/ CD18, CD11c/CD18 integrins and L-selectin on human neutrophils were studied by flow cytometry in a whole blood assay. None of these compounds had any effect on the basal expression of CD11b, CD11c, or L-selectin in the concentration range of 20-100 microM. However, linoleic acid at a concentration of 1000 microM slightly up-regulated CD11b and CD11c by a factor of 2.1 and 1.7, respectively. Linoleic acid, linoleic acid anilide, and arachidonic acid did not affect the formyl-methionyl-leucyl-phenylalanine induced up-regulation of CD11b or CD11c. However, linoleic acid and linoleic acid anilide slightly inhibited the phorbol myristate acetate (PMA)-induced expression of CD11b, which was decreased by 27 and 21% at concentrations of 100 and 1000 microM, respectively. Likewise, arachidonic acid at 40 microM inhibited the PMA-induced expression of CD11b by 19%. Our results suggest that linoleic acid, linoleic acid anilide, and arachidonic acid do not dramatically affect the expression of leukocyte adhesion molecules in a whole blood assay.

Expression of inducible nitric oxide synthase and formation of nitric oxide by alveolar macrophages: an interspecies comparison

Nitric oxide (NO) is suggested to play a role in mediating pulmonary injury. However, interspecies differences appear to exist in the ability of alveolar macrophages (AM) to express the inducible nitric oxide synthase (iNOS) and to generate NO. The purpose of this study was to compare iNOS expression and NO production by rat, hamster, monkey, and human AM using the identical experimental conditions in vitro. As AM donors, CD rats, Syrian golden hamsters, cynomolgus monkeys, and nonsmoking, healthy human volunteers were used. The AM were obtained by bronchoalveolar lavage and stimulated in vitro with various concentrations and combinations of lipopolysaccharide (LPS) and interferon-gamma (IFN-gamma). The oxidation product of NO, nitrite, was measured in the AM supernatant by the Griess reaction. The expression of iNOS in AM was detected using immunocytochemistry and immunoblotting. The expression of iNOS mRNA was assessed by reverse transcriptase-polymerase chain reaction (RT-PCR). Rat AM, stimulated with either LPS or IFN-gamma, produced nitrite in a time- and dose-dependent manner. Combination of LPS and IFN-gamma resulted in a significantly enhanced nitrite formation. However, none of the treatments was able to induce hamster, monkey, or human AM to release measurable amounts of nitrite. Whereas expression of iNOS protein was only detected in stimulated rat AM, expression of iNOS mRNA was found in unstimulated and stimulated rat AM, slightly in stimulated hamster AM, but not in monkey and human AM. In conclusion, our findings point to distinct regulatory mechanisms of the NO pathway in AM from these four different species.

Comparative loss of activity of recombinant secretory leukoprotease inhibitor and alpha 1-protease inhibitor caused by different forms of oxidative stress

Secretory leukoprotease inhibitor (SLPI) and alpha 1-protease inhibitor (alpha 1-PI) are powerful antiproteases currently under investigation for their potential to protect the lung from neutrophil elastase (NE). The aim of this study was to determine whether the recombinant form of SLPI (rSLPI) and alpha 1-PI show different grades of loss of inhibitory activity when exposed to reactive oxygen metabolites. We incubated rSLPI and alpha 1-PI with N-chlorosuccinimide (NCS), chloramines, activated polymorphonuclear leucocytes (PMNs) and activated alveolar macrophages (AMs). Under all conditions evaluated, both antiproteases were partially inactivated. The resulting anti-NE activity of rSLPI was not significantly different from that of alpha 1-PI after exposure to NCS (p > 0.5), chloramines (p > 0.6), activated PMNs (p > 0.07) and activated AMs (p > 0.9). In conclusion, recombinant secretory leukoprotease inhibitor and alpha 1-protease inhibitor lose antineutrophil elastase activity to a similar extent when exposed to conditions that may be present in inflammatory lung disorders.

Interspecies comparison of rat and hamster alveolar macrophage antioxidative and oxidative capacity

Generation of oxidants has been implicated in lung injury and disease caused by a variety of inhaled agents such as ozone, particles, and mineral fibers. Antioxidants in the pulmonary system presumably provide the initial defense against such oxidants. We designed the present study to assess the oxidative and antioxidative capacity of alveolar macrophages (AM) from rats and hamsters. These two laboratory animal species commonly used in biomedical research are well known for their disparate response to pulmonary irritants/toxicants. AM from CD rats and Syrian golden hamsters were obtained by bronchoalveolar lavage. We assessed AM antioxidant levels by measuring the catalase and superoxide dismutase (SOD) activity and the intracellular concentrations of total glutathione, ascorbic acid, and alpha-tocopherol. We determined the AM oxidative capacity by assessing the ability of AM to oxidize extracellular glutathione (GSH) and to release superoxide anions. There were no significant differences in the intracellular antioxidant levels, except for catalase activity that was significantly (p < 0.05) higher in hamster AM than in rat AM. However, AM oxidative capacity was markedly different between the two species studied. The amount of spontaneous and phorbol myristate acetate (PMA)-induced GSH oxidation was about 5-fold higher in rat AM than in hamster AM, whereas the PMA-induced superoxide anion release did not differ significantly between the two rodents. In summary, our data suggest that species variation exists between the oxidative capacity of rat and that of hamster AM. Whereas the oxidative capacity of hamster AM appears to be based mainly on the formation of reactive oxygen species, it is suggested that rat AM possess an additional oxidative system.

Cell size of alveolar macrophages: an interspecies comparison

Alveolar macrophages (AM) play a critical role in the removal of inhaled particles or fibers from the lung. Species differences in AM size may affect the number and size range of particles/fibers that can be actually phagocytized and cleared by AM. The purpose of this study was to compare the cell size of rat, hamster, monkey, and human AM by selective flow cytometric analysis of cell volume. Resident AM from CD rats, Syrian golden hamsters, cynomolgus monkeys, and nonsmoking, healthy human volunteers were harvested by standard bronchoalveolar lavage procedures. Morphometric analysis of AM was performed using a flow cytometer that generates volume signals based on the Coulter-type measurement of electrical resistance. We found that hamster and rat AM had diameters of 13.6 +/- 0.4 microns (n = 8) and 13.1 +/- 0.2 microns (n = 12), respectively. Comparatively, the AM from monkeys (15.3 +/- 0.5 microns, n = 7) and human volunteers (21.2 +/- 0.3 microns, n = 10) were larger than those from rats and hamsters. The AM from humans were significantly larger (p < 0.05) than those from all other species studied, corresponding to a 4-fold larger cell volume of human AM (4990 +/- 174 microns 3) compared to hamster (1328 +/- 123 microns 3) and rat (1166 +/- 42 microns 3) AM. In summary, we have found marked species differences in the cell size of AM. We suggest that the number and size range of particles/fibers that can be phagocytized and cleared by AM may differ among species due to inherent or acquired species differences in AM cell size.

Hyperoxia induces upregulation of CD11b and amplifies LPS-induced TNF-alpha release by alveolar macrophages

Exposure to high concentrations of oxygen is known to induce changes in lung function through effects on several pulmonary cell types, including alveolar macrophages (AM). In this study, we studied the in vitro effects of hyperoxia on the release of proinflammatory cytokines and the expression of surface receptors in AM obtained from cynomolgus monkeys by bronchoalveolar lavage under general anesthesia. AM were exposed for 24 h to moderate (50% O(2)) or severe (95% O&sub2) hyperoxia in the absence or presence of LPS, and the release of IL-1beta, IL-6, and TNF-alpha was measured in culture supernatants by ELISA. In addition, the expression of the surface molecules HLA-DR, CD14, and CD11b was assessed by flow cytometry. Exposure to 95% O2 activated resting AM to produce significantly increased amounts of IL-1beta and IL-6. Moreover, hyperoxia amplified the release of TNF-alpha by LPS-stimulated AM in an oxygen tension-dependent manner. Finally, exposure to 95% O2 upregulated the expression of the adhesion molecule CD11b on AM, whereas the expression of HLA-DR and CD14 was not affected. These findings support the view that hyperoxia-induced activation of AM may represent an initial event in the proinflammatory sequence caused by hyperoxia.

Species differences in NO formation by rat and hamster alveolar macrophages in vitro

Nitric oxide (NO) is a cellular mediator and regulator of multiple biologic functions. NO released by alveolar macrophages (AM) is suggested to play a role in mediating pulmonary injury. In murine and rat macrophages, the expression of inducible NO synthase (iNOS) and the release of NO are well established. However, the existence of such a pathway in other species remains controversial. In this study, we examined NO production and iNOS expression by AM from rats and hamsters, two laboratory animal species that are characterized by their disparate pulmonary responses to various inhaled irritants/toxicants. AM were treated with lipopolysaccharide (LPS), interferon-gamma (IFN-gamma), or tumor necrosis factor-alpha (TNF-alpha) in vitro, and nitrite, the stable oxidation product of NO, was assayed by the Griess reaction. Rat AM produced NO in a dose- and time-dependent manner upon stimulation with LPS and/or IFN-gamma, but not with TNF-alpha. Surprisingly, hamster AM did not release detectable levels of NO after the same treatment. Although iNOS expression was demonstrated in rat AM by immunocytochemical and Western blot analyses, no induction of iNOS expression could be found in hamster AM. Using reverse transcriptase-polymerase chain reaction (RT-PCR) analysis, we found that rat and hamster AM could be induced to express iNOS mRNA after treatment with LPS and IFN-gamma. The results presented here indicate that hamster AM, in contrast to rat AM, lack the ability to express iNOS protein and to generate NO in response to LPS, IFN-gamma, or TNF-alpha in vitro. In conclusion, our data suggest striking differences in iNOS regulation and NO production by AM from rats and hamsters, two rodent species that are commonly used in biomedical research and well-known for their disparate responses to pulmonary irritants/toxicants.

Bronchoalveolar lavage for evaluation and management of scleroderma disease of the lung

Fibrosing alveolitis (FA) is a frequent and often fatal complication of systemic sclerosis (SSC). Alveolar inflammation has been recognized as a primary event in the pulmonary manifestation of SSC. To evaluate the significance of the alveolitis in SSC, we performed bronchoalveolar lavage (BAL) and correlated the generated data with changes in lung function over time. Seventy nine SSC patients with pulmonary involvement were followed for 56.8 +/- 3.1 wk (mean +/- SEM) with a repeat lung function test at the end of the follow-up period. During follow-up, 38 patients were treated with a systemic immunosuppressive regimen. For evaluation, patients were assigned to two groups according to whether their BAL cell differential was normal (inactive BAL) or abnormal (active BAL: i.e., polymorphonuclear leukocytes > 5% and/or lymphocytes > 15%). Active BAL was associated with more severe lung function impairment than was inactive BAL, and patients with active BAL deteriorated during follow-up if untreated. In contrast, treated patients with active BAL stabilized or improved. In summary, active alveolitis as characterized by BAL is associated with progressive pulmonary disease in SSC patients, and a significant positive effect of immunosuppressive therapy on the course of pulmonary disease was observed in patients with active BAL.

Inhalation of prostacyclin (PGI2) for 8 hours does not produce signs of acute pulmonary toxicity in healthy lambs

OBJECTIVE

To study the potential side effects and toxicity of inhaling prostacyclin (PGI2) aerosol for 8 h.

DESIGN

In a prospective, randomized study 14 healthy lambs received either PGI2 (n = 7) or 0.9% NaCl (n = 7) as an aerosol for 8 h.

SETTING

Institute for Surgical Research of the Ludwig-Maximilians-University of Munich.

INTERVENTIONS

All animals were studied under general anesthesia in a prone position. They were first intubated endotracheally and later tracheotomized. PGI2 solution (median dose 28 ng/kg per min) or 0.9% NaCl was administered with a jet nebulizer (delivery rate 4-10 ml/h; mass median diameter of aerosol particles 3.1 microns). Bronchoalveolar lavage was performed before and after the inhalation period to collect epithelial lining fluid of alveoli.

MEASUREMENTS AND RESULTS

Hemodynamic and respiratory parameters, systemic resorption (plasma levels of 6-keto-prostaglandin-F 1 alpha), in vitro bleeding time, collagen-induced platelet aggregation and global biochemical and cellular composition of the epithelial lining fluid were examined in order to assess the side effects and signs of acute pulmonary toxicity induced by inhaled PGI2. No statistically significant differences were found between the PGI2 and the control groups for any of the parameters examined.

CONCLUSION

Inhalation of PGI2 (28 ng/kg per min) over a period of 8 h in healthy lambs does not produce major side effects or acute pulmonary toxicity.

Characterization and quantification of alveolar monocyte-like cells in human chronic inflammatory lung disease

This flow cytometric study was designed to identify, characterize and quantify alveolar monocyte-like cells in healthy volunteers and in patients with chronic inflammatory lung disease. Cells were obtained by bronchoalveolar lavage (BAL) from 19 patients with sarcoidosis, 29 with idiopathic pulmonary fibrosis, 10 with extrinsic allergic alveolitis, 19 with collagen vascular disease, and from 10 healthy volunteers. By taking advantage of the distinct electro-optical features of alveolar macrophages (AMs) and monocyte-like cells, the numbers of alveolar monocyte-like cells were counted, the cell dimensions calculated, and the densities of antigens on the surface of alveolar monocyte-like cells and AMs were compared. By using a panel of monoclonal antibodies detecting CD11b, CD14, CD16, and human leucocyte antigen-DR (HLA-DR), the immunophenotypes of these cells were selectively characterized. In the BAL fluid of patients with chronic inflammatory lung disease, significantly increased numbers of alveolar monocyte-like cells were detected that exhibited an immunophenotype intermediate between blood monocytes and mature AMs. Positive correlations were found between numbers of monocyte-like cells and expression of the monocyte-associated surface antigens CD11b and CD14 on total AMs; in contrast, an inverse relationship existed between monocyte numbers and expression of the macrophage-associated surface antigens CD16 and HLA-DR. When the patients were assigned to two groups according to the percentage of BAL monocyte-like cells being lower or higher than 13% (= mean value of the controls +2SD), it could be demonstrated that a high percentage of BAL monocyte-like cells was associated with significantly reduced lung function parameters. In summary, our flow cytometric data strongly support the view that considerable numbers of blood monocytes are recruited to the bronchoalveolar space in patients with chronic inflammatory lung disease.