Expression and localization of heat shock proteins in rat basophilic leukemia cells: differential modulation by degranulation, thermal or oxidative stress

BACKGROUND

Rat basophilic leukemia (RBL-2H3) cells are well characterized in terms of morphological and biochemical changes upon activation, and have been extensively used as a model system for studying the mechanisms of the immediate hypersensitivity reaction. To investigate whether overexpression of heat shock/stress proteins (HSP) is involved in the mast cell-dependent reactivity, we examined the adaptive responses of RBL-2H3 cells to classical stress conditions such as heat shock or oxidative injury produced by an aqueous extract of tobacco smoke.

METHODS

HSP were determined by flow cytometry and immunocytochemistry. Degranulation was confirmed as the release of beta-hexosaminidase, determined spectrophotometrically, and by electron microscopy experiments.

RESULTS

We found that RBL-2H3 cells respond to heat shock or oxidative injury by the synthesis of both the inducible 72 kDa HSP (Hsp70), and the oxidation-specific 32 kDa heme oxygenase (HO)-1. Heat shock induced mainly Hsp70 in a cell growth-dependent manner, whereas oxidative stress induced mainly HO-1 in a cell growth-independent manner. However, heat shock or oxidative stress had no significant effects on degranulation.

CONCLUSION

Stress-mediated synthesis of HSP was not associated with RBL-2H3 degranulation and likewise, degranulation did not induce HSP.

Effects of exogenous surfactant and recombinant human copper-zinc superoxide dismutase on oxygen-dependent antimicrobial defenses

The use of human recombinant CuZn superoxide dismutase (rhSOD) in addition to exogenous surfactant has been studied as a therapeutic strategy to prevent acute and chronic lung injury in premature infants with blood monocytes (MO). However, scavenging of superoxide by rhSOD may compromise bacterial killing by phagocytes. In the present study, we investigated the interaction of exogenous surfactant and rhSOD with the antibacterial activity of human blood MO. MO were preincubated in the presence or absence of: (1) modified natural surfactant (Curosurf); 1 mg/ml); (2) rhSOD (2,500 U/ml) and (3) bovine catalase (25,000 U/ml). Bacteria (Legionella pneumophila or Escherichia coli) were then added and incubated for 6 h. Viable bacteria were determined by counting colony-forming units. The ability of the MO to generate superoxide anions (O2-) in response to bacterial infection was also investigated. The antibacterial capacity of MO was not impaired by the presence of rhSOD either alone or combined with Curosurf. In some instances, bactericidal activity was even potentiated by the addition of rhSOD. Exposure of MO to catalase interfered with the increased bacterial killing of MO and rhSOD, suggesting that hydrogen peroxide (H2O2) production was critically important in the process of bacterial killing. Both bacterial species were also found to induce the generation of intra- and extracellular O2- by MO. Data indicate that rhSOD potentiates the killing of bacteria by human MO. The mechanism of action appears to be related to the ability of bacteria to induce the generation of O2-, which in turn is converted to H2O2 in the presence of rhSOD. This has important implications in the development of therapeutic intervention strategies using antioxidant therapy in premature infants with respiratory distress syndrome.

Geranylgeranylacetone protects human monocytes from mitochondrial membrane depolarization independently of Hsp70 expression

The anti-ulcer drug geranylgeranylacetone (GGA) has been shown to induce the expression of heat shock proteins (HSPs), in particular of Hsp70, in gastric and small intestine cells. In this study, we investigated whether GGA was able to induce Hsp70 in another cell type, human monocytes, which represent a well-established model of Hsp70 expression under oxidative stress. In these cells, GGA had no significant effect either on basal or tobacco smoke-induced Hsp70 expression. We further investigated the effects of GGA on mitochondria, a key organelle of oxidant-mediated cell injury and a putative target for GGA-mediated protection. GGA significantly increased basal mitochondrial membrane polarization and inhibited the decrease in mitochondrial membrane potential of human monocytes exposed to distinct sources of clinically relevant oxidants such as tobacco smoke and y-irradiation. Our results indicate that mitochondria are targets for GGA-mediated protection against oxidative stress in human monocytes, independently of Hsp70.

Mitochondrial membrane potential and apoptosis peripheral blood monocytes in severe human sepsis

Reduced mitochondrial membrane potential (Delta(Psi)m), which is considered as an initial and irreversible step towards apoptosis, as well as cell death regulating proteins, such as Fas, Hsp70, or Bcl-2, may play an important role in sepsis. We studied the relationship between sepsis severity and peripheral blood monocyte Delta(Psi)m, cell death (necrosis and apoptosis), soluble Fas ligand, Hsp70, and Bcl-2 expression over time in 18 patients with sepsis, and compared these data with those of a group of 17 healthy control subjects. All measurements were performed within 3 d of the onset of severe sepsis (T1), then 7 to 10 d later (T2), and finally at hospital discharge (T3). Delta(Psi)m was expressed as the percent monocytes with altered Delta(Psi)m (%Delta(Psi)m). Patients with sepsis had greater %Delta(Psi)m at T1 and T2 but not at T3 (14.6 +/- 2.6% and 15.9 +/- 2%, respectively, versus control 6.6 +/- 0.2%, p < 0.01). Septic patients exhibited greater cell death in their monocytes and had greater Hsp70 expression only at T1. Bcl-2 levels were similar in septic and control subjects. Comparing survivors with non-survivors of sepsis, nonsurvivors had a greater %Delta(Psi)m at T1 (26.4 +/- 5.3% versus 10.1 +/- 2.7%, p < 0.01) and a significant decrease in Bcl-2 expression, whereas no difference was found in Hsp70 levels. These results indicate that mitochondrial dysfunction and subsequent cell death occur in severe sepsis and suggest that %Delta(Psi)m is a marker of severity in human sepsis.

KEYWORDS

mitochondria; apoptosis; sepsis; heat-shock protein 70; proto-oncogene protein c-Bcl-2

Laser assisted skin closure (LASC) by using a 815-nm diode-laser system accelerates and improves wound healing

BACKGROUND AND OBJECTIVE

This study aimed to evaluate a 815-nm diode-laser system to assist wound closure to accelerate and improve healing process.

STUDY DESIGN/MATERIALS AND METHODS

A total of 25 male hairless rats (mutant OFA Sprague-Dawley rats, IFFA-CREDO, L'Arbresle, France) with four dorsal skin incisions were used for the study. For each wound, the good apposition of the edges was obtained with buried absorbable suture. In the laser group, the laser beam was applied spot by spot through a transparent adhesive dressing along two incisions with the following parameters: 1.5 W; 3 seconds; spot diameter, 2 mm; fluence, 145 J/cm(2). Both control wounds were closed with conventional suture techniques. The duration of the closure procedure was noted for each group. Clinical examination, histologic study, and measurement of tensile strength were performed at 3, 7, 15, and 21 days after surgery. Determination of activation of heat shock protein 70 (Hsp70) through immunocytochemistry was performed at days 1 and 7.

RESULTS

LASC was 4 times faster to process than conventional suture: 1 minute 49 +/- 20.6 seconds vs. 7 minutes 26 +/- 62.2 seconds. In the laser group, healing was accelerated resulting in a more indiscernible scar than in the control groups. Histologic aspect was better with earlier continuous epidermis and dermis and a thinner resulting scar. Tensile strength was 30 to 58% greater than in control groups at 7 and 15 days (P < 0.001). Expression of Hsp70 was markedly induced in skin structures examined after laser exposure.

CONCLUSIONS

This study shows the ability of the 815-nm diode-laser system to assist wound closure leading to an acceleration and an improvement of wound healing with indiscernible resulting scar. The mechanisms of this phenomenon are still unclear but further investigations are in progress to attempt to explain them.

Increased eosinophil cationic protein levels in bronchoalveolar lavage from wheezy infants

Although studies examining the serum suggest a role for eosinophils in wheezing episodes in infants and toddlers, the presence of a chronic eosinophilic inflammation within their airways remains to be demonstrated. In this study we investigated whether eosinophil cationic protein (ECP) levels are increased in BAL fluid (BALF) from infants and toddlers with recurrent wheezing episodes, during an asymptomatic period. The levels of ECP in BALF were quantitated by radioimmunoassay in 61 children (36 with severe recurrent episodes of wheezing and 25 who were non-wheezy), aged 6-36 months, in whom flexible bronchoscopy was clinically indicated. BALF eosinophil counts were < or = 1% in all patients and did not differ in wheezers, compared to non-wheezers. In contrast, ECP levels in BALF were > or = 2.2 micrograms/l in 18 of 36 (50%) wheezy infants but in only three of 25 (12%) control infants (p < 0.01). Neutrophil counts were significantly higher in the wheezer group than in the non-wheezer group (8.1 x 10(3) cells/ml vs. 3.0 x 10(3) cells/ml). ECP levels in the BALF were not correlated with the absolute number of eosinophils (r = 0.03; p = 0.8) but were correlated with the absolute number of neutrophils (r = 0.54; p = 0.001). There was no association between high ECP levels in BALF and the atopic status of the wheezers. In conclusion, ECP levels are increased in BALF from young children with recurrent wheezing episodes, even during relatively quiescent periods, suggesting a chronic increased cell activation in the lower airways.

Treatment with 815-nm diode laser induces long-lasting expression of 72-kDa heat shock protein in normal rat skin

BACKGROUND

We previously reported that skin closure is improved by photoirradiation of the wound margins with an 815-nm diode laser system.

OBJECTIVES

To determine whether the beneficial effects of laser treatment involve the overexpression of the inducible 72-kDa heat shock protein, Hsp70.

METHODS

Expression of Hsp70 was investigated by immunocytochemistry in normal hairless rat dorsal skin and compared with its expression after laser photoirradiation.

RESULTS

Constitutive expression of Hsp70 was mainly confined to the upper epidermal layer. Laser irradiation further increased epidermal expression of Hsp70 while inducing de novo synthesis of the protein in dermal structures, particularly around blood vessels, hair follicles and sebaceous glands. Laser-induced expression of Hsp70 was still present 7 days after photoirradiation.

CONCLUSIONS

Laser-induced expression of Hsp70 might contribute to improved tissue regeneration and wound healing.

Contrasting effects of NO and peroxynitrites on HSP70 expression and apoptosis in human monocytes

The free radicals nitric oxide (.NO) and superoxide (O(2)(-).) react to form peroxynitrite (ONOO(-)), a highly toxic oxidant species. In this study we investigated the respective effects of NO and ONOO(-) in monocytes from healthy human donors. Purified monocytes were incubated for 6 or 16 h with a pure NO donor (S-nitroso-N-acetyl-DL-penicillamine, 0-2 mM), an.NO/ONOO(-) donor (3-morpholinosydnonimine chlorhydrate, 0-2 mM) with and without superoxide dismutase (200 IU/ml), or pure ONOO(-). We provide evidence that 3-morpholinosydnonimine chlorhydrate alone represents a strong stress to human monocytes leading to a dose-dependent increase in heat shock protein-70 (HSP70) expression, mitochondrial membrane depolarization, and cell death by apoptosis and necrosis. These phenomena were abolished by superoxide dismutase, suggesting that ONOO(-), but not.NO, was responsible for the observed effects. This observation was further strengthened by the absence of a stress response in cells exposed to S-nitroso-N-acetyl-DL-penicillamine. Conversely, exposure of cells to ONOO(-) alone also induced mitochondrial membrane depolarization and cell death by apoptosis and necrosis. Thus ONOO(-) formation may well explain the toxic effect generally attributed to.NO.

Differential basal synthesis of Hsp70/Hsc70 contributes to interindividual variation in Hsp70/Hsc70 inducibility

The source of intraspecies variation in the expression of heat shock proteins (HSPs) remains unresolved but could shed light on differential stress tolerance and disease susceptibility. This study investigated the influence of variable basal HSP synthesis on differential inducibility of HSP synthesis. Basal and heat-induced synthesis of the major HSP families in peripheral blood monocytes from healthy donors (n = 42) were analysed using biometabolic labelling and densitometry. Basal Hsp70/Hsc70 synthesis and percentage induction of Hsp70/Hsc70 synthesis were significantly correlated (r = -0.57, p < 0.0001), and described most accurately by an exponential decay equation (R = 0.68, R2 = 0.46). This regression equation suggests that increasing levels of basal Hsp70/Hsc70 synthesis are accompanied by an exponential decrease in the percentage induction of Hsp70/Hsc70 synthesis. The model fits data from European and non-European population groups independently, although both coefficients in the regression equation were larger for non-Europeans. This implies population group as an additional factor influencing differential HSP expression. The differential inducibility of Hsp70/Hsc70 due to variable basal synthesis of Hsp70/Hsc70 and based upon population group may contribute to differential stress tolerance or disease susceptibility.

Adaptive responses of human monocytes infected by bordetella pertussis: the role of adenylate cyclase hemolysin

The activation/adaptive responses of human monocytes exposed to Bordetella pertussis parental or mutant strains were evaluated and correlated to the expression of two bacterial toxins: adenylate cyclase-hemolysin and pertussis toxin. The marked rise in intracellular cyclic adenosine monophosphate (cAMP) observed in monocytes infected by B. pertussis parental strain, inversely correlated with (1) the production of tumor necrosis factor alpha; (2) the release of superoxide anion; and (3) the expression of the 72-kDa heat shock/stress protein, Hsp70. Experiments performed with mutants deficient in adenylate cyclase-hemolysin or with purified bacterial toxins confirmed the key role of adenylate cyclase-hemolysin in the control of monocytes' response to infection by B. pertussis. This bacterial strategy primarily involves evasion from antimicrobial defenses and, eventually, the sacrifice of the host cell.

Inducibility of the 70 kD heat shock protein in peripheral blood monocytes is decreased in human acute respiratory distress syndrome and recovers over time

The heat shock/stress proteins (HSP), and, in particular, the inducible, cytosolic Hsp70, represent an extremely conserved response to many different cellular injuries, including reactive oxygen species (ROS). Hsp70 has been shown to confer to cells and tissues protection against the deleterious effects of ROS or cytokines, both in vitro and in animal models of acute respiratory distress syndrome (ARDS). We hypothesized that Hsp70 expression levels in peripheral blood monocytes (PBM) of patients with ARDS, would correlate with disease severity. We prospectively included 13 patients with previous ARDS (50 +/- 17 yr; range, 20 to 76 yr), nine ventilated patients with non-ARDS/ALI disease (45 +/- 20 yr; range, 19 to 76 yr), and 14 healthy volunteers (45 +/- 20 yr; range, 22 to 77 yr). PBM activation state was evaluated according to their membrane expression of CD16, and oxidative status according to plasma lipid peroxidation products. Both baseline expression and Hsp70 inducibility (after in vitro heat shock) were examined in PBM, using flow cytometric analysis. We found that basal expression of Hsp70 in PBM was similar for patients and control subjects, whereas Hsp70 inducibility- a reflection of the ability to mount a stress response-was significantly reduced in the patients with ARDS (p = 0. 02). Among all correlation analyses we considered between Hsp70 inducibility on the one hand, clinical and laboratory biomarkers for disease severity and outcome in the patients with ARDS on the other, only the duration of ventilatory support was significant (p < 0.003). As an approach to distinguish between disease and ventilation, we also analyzed a group of, ventilated patients without ARDS. Our results indicate that in patients with ARDS, Hsp70 inducibility in PBM is decreased, but it recovers over time with duration of ventilatory support.

Curosurf modulates cAMP accumulation in human monocytes through a membrane-controlled mechanism

The cellular mechanisms by which pulmonary surfactant exerts its effects, including anti-inflammatory or proinflammatory effects, have remained elusive. To address the issue of whether plasma membrane modifications represent a target for these mechanisms, we designed an experimental protocol involving the determination of changes in cAMP levels under membrane-dependent or -independent stimulatory pathways. The effects of a modified natural porcine surfactant, Curosurf, and the major surfactant protein A were evaluated on resting and stimulated cAMP levels of human monocytes. We found that agents that elevate intracellular cAMP exhibit different susceptibilities toward a preexposure to Curosurf. The rise in cAMP induced by membrane-active agents such as cholera toxin or the diterpene forskolin was significantly inhibited by monocyte preexposure to Curosurf. In contrast, the rise in cAMP induced by the membrane-permeant phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine or by the Bordetella pertussis toxin adenylate cyclase-hemolysin was unaffected by Curosurf. Surfactant protein A did not affect either cAMP levels or the inhibitory capacity of Curosurf. We suggest that a plasma membrane-associated event affecting the mechanism underlying the effects of cholera toxin or forskolin is involved in the inhibition of cAMP accumulation caused by Curosurf.

Modified natural porcine surfactant modulates tobacco smoke-induced stress response in human monocytes

Tobacco smoke (TS) is a potent source of oxidants and oxidative stress is an important mechanism by which TS exerts its toxicity in the lung. We have shown that TS induces heat shock (HS)/stress protein (HSP) synthesis in human monocytes. Pulmonary surfactant (PS) whose major physiological function is to confer mechanical stability to alveoli, also modulates oxidative metabolism and other pro-inflammatory functions of monocytes-macrophages. In order to determine whether PS alters the stress response induced by TS, we incubated human peripheral blood monocytes overnight with modified natural porcine surfactant (Curosurf) (1 mg/ml) before exposure to TS. Curosurf decreased TS-induced, but not HS-induced, expression of the major cytosolic, inducible 72 kD HSP (Hsp70). Furthermore, TS-generated superoxide anions production was significantly decreased by Curosurf in an acellular system, suggesting a direct scavenging effect of PS. We also examined the effects of TS and PS on monocytes ultrastructure. Monocytes incubated with Curosurf presented smoother cell membranes than control monocytes, while TS-induced monocyte vacuolization was, at least in part, prevented by Curosurf. Taken together, our data suggest that PS plays a protective role against oxygen radical-mediated, TS-induced cellular stress responses.

Tobacco smoke induces coordinate activation of HSF and inhibition of NFkappaB in human monocytes: effects on TNFalpha release

Tobacco smoke (TS) exposure is a major risk factor for human disease, and macrophages of healthy smokers have a depressed capacity to release cytokines, including tumor necrosis factor (TNF)alpha. TS induces the synthesis of heat shock (HS)/stress proteins (HSP), and, in particular, of Hsp70. We determined whether Hsp70 induction by TS was mediated by the activation of the HS transcription factor, HSF. HSF activation has been shown to inhibit NFkappaB. Thus, we also determined the effects of TS on NFkappaB. U937 cells and human peripheral blood monocytes were exposed to TS, binding activities of the respective transcription factors were analyzed, and Hsp70 expression and TNFalpha release were determined in parallel. TS activated HSF, which was associated with Hsp70 overexpression and inhibition of NFkappaB binding activity and TNFalpha release. The altered cytokine profile observed in smokers may relate to an HSF/Hsp70-mediated inhibition of NFkappaB activity.

Flow cytometry is a rapid and reliable method for evaluating heat shock protein 70 expression in human monocytes

The increasing interest in stress/heat shock proteins (Hsps) as markers of exposure to environmental stress or disease requires an easily applicable method for Hsp determination in peripheral blood cells. Of these cells, monocytes preferentially express Hsps upon stress. An appropriate fixation/permeabilization procedure was developed, combined with immunofluorescence staining and flow cytometry for the detection of the inducible, cytosolic, 72 kDa Hsp (Hsp70) in human monocytes. Higher relative fluorescence intensity was observed in cells exposed to heat shock (HS), reflecting a higher expression of Hsp70 in these cells as compared with cells kept at 37 degrees C. The heat-inducible increased Hsp70 expression was temperature- and time-dependent. Expression of Hsp70 was not uniform within the monocyte population, indicating the presence of subpopulations expressing variable levels of Hsp70 in response to HS. Simultaneous measurements of intracellular Hsp70 and membrane CD14 expression revealed that the higher Hsp70 inducibility coincided with the higher CD14 expression. Comparisons performed with biometabolic labelling, Western blotting, immunofluorescence and immunoperoxidase microscopic analysis, showed a high concordance between these different methods; however, cytometry was more sensitive for Hsp70 detection than Western blotting. Flow cytometric detection of intracellular Hsp70 is a rapid, easy and quantitative method, particularly suited for the determination of protein levels in individual cells from an heterogeneous population such as peripheral mononuclear blood cells, and applicable to cohort studies.

Increased spontaneous release of tumour necrosis factor-alpha by alveolar macrophages from wheezy infants

We determined if alveolar macrophages (AMs) from infants with severe recurrent wheezing episodes release increased amounts of tumour necrosis factor-alpha (TNF-alpha), as described in adults with asthma. We compared TNF-alpha release by unstimulated and lipopolysaccharide-stimulated AMs obtained by bronchoalveolar lavage in 13 wheezy and seven nonwheezy infants (aged 6-36 months) and analysed its regulation by dexamethasone. Metabolites in cell supernatants were quantified by enzyme-linked immunosorbent assay (ELISA) (TNF-alpha) or radioimmunoassay (thromboxane B2 and prostaglandin E2). Comparison of results was performed by the Mann-Whitney U-test and values were expressed as median (interquartile range) in ng x 10(6) cells(-1). Resting AMs from wheezy infants released larger amounts of TNF-alpha and thromboxane B2 as compared to controls: 2.67 (0.89-8.33) vs 0.48 (0.25-1.08) and 75.63 (38.07-158.91) vs 10.03 (7.36-76.08), respectively (p<0.05). When stimulated overnight with bacterial lipopolysaccharide, AMs from both groups released similar amounts of metabolites. Dexamethasone induced a consistent inhibition of the lipopolysaccharide-stimulated release of all the mediators. Our results show that alveolar macrophages from wheezy infants are activated to release increased amounts of tumour necrosis factor-alpha, as in asthma, and suggest that infants with recurrent wheezing may eventually benefit from treatment with glucocorticoids.

5-Lipoxygenase and endotoxin-induced microvascular albumin exchanges and leucocyte recruitment in guinea-pig lungs

The interference of the 5-lipoxygenase inhibitor, BW B70C ((E)-N-(3-[3-(4-fluorophenoxy)phenyl]-1(R,S)-methyl prop-2-enyl)-N-hydroxyurea), with Escherichia coli lipopolysaccharide (endotoxin)-induced lung leucocyte sequestration and microvascular albumin exchanges was evaluated in the anaesthetised guinea-pig using radioactive tracers, in parallel to the effects on cell counts in the broncho-alveolar lavage fluid, blood tumour necrosis factor (TNF-alpha) content, secretion of phospholipase A2 and synthesis of leukotriene C4 by alveolar macrophages. Intravenous injections of 0.1 or 1 mg/kg endotoxin induced lung leucocyte sequestration but only the higher dose induced an increase in albumin microvascular exchanges and the infiltration of leucocytes towards the airway lumen. Leukotriene B4, a potential mediator of the 5-lipoxygenase-dependent endotoxin effects, induced a rapid and transient lung leucocyte sequestration and leucopenia associated with a more progressive increase in microvascular exchanges. The 5-lipoxygenase inhibitor, BW B70C, injected i.p. (30 mg/kg) prevented leukotriene C4 synthesis by alveolar macrophages and reduced leucocyte migration to the airways lumen as well as albumin microvascular leakage but did not affect the endotoxin-induced increase in the blood level of TNF-alpha and of secreted phospholipase A2. However, BW B70C failed to modify vascular leucocyte margination induced by 1 mg/kg endotoxin, suggesting that, apart from a role of 5-lipoxygenase, alternative pathways operate in response to endotoxin in guinea-pig.

Modified natural porcine surfactant inhibits superoxide anions and proinflammatory mediators released by resting and stimulated human monocytes

Pulmonary surfactant has a potential role in modulating inflammation in normal and injured lungs. In lung injury, monocytes become activated and participate in lung inflammation. We therefore, investigated the proinflammatory functions of stimulated human blood monocytes after an overnight preincubation period with modified natural porcine surfactant (Curosurf) (500-1000 micrograms/mL). Monocytes were stimulated either with phorbol myristate acetate (PMA), bacterial extract OM-85, lipopolysaccharide (LPS), or Ca2+ ionophore A23187. The present study shows that Curosurf significantly inhibits: 1) the production of superoxide anions stimulated with OM-85 (1 mg/mL, 30 min), but not with PMA (100 ng/mL, 30 min); 2) the release of cyclooxygenase metabolites prostaglandin E2 and thromboxane B2 stimulated with OM-85 (1 mg/mL, overnight); 3) the release of lipoxygenase metabolite leukotriene C4 stimulated with A23187 (10 microM, 10 min); 4) the release of the cytokine TNF-alpha stimulated overnight with either OM-85 (1 mg/mL) or LPS (10 micrograms/mL)) in a dose-dependent fashion. In addition, Curosurf decreases the spontaneous adherence of monocytes to plastic culture wells in a dose-dependent fashion. Experiments performed with staurosporine, an inhibitor of protein kinase C (PKC) indicate that, in contrast with PMA, the production of superoxide anions stimulated by OM-85 is not related to PKC activation. Consequently, we propose that the mechanism involved in the suppressive effects of Curosurf is PKC-independent. In summary, the present study provides experimental evidence that favors the anti-inflammatory role of modified natural porcine surfactant (Curosurf) in human monocytes in vitro.

Fenspiride: an anti-inflammatory drug with potential benefits in the treatment of endotoxemia

Using a model of endotoxemia triggered by the intravenous injection of bacterial lipopolysaccharide (0.1 and 1 mg/kg) to guinea-pigs, we investigated the interference of fenspiride, an anti-inflammatory drug recommended for the treatment of inflammatory diseases of the upper respiratory tract. Administered orally at 60 mg/kg, fenspiride reduced the lipopolysaccharide-induced early rise of tumor necrosis factor concentrations in serum (4.2 +/- 0.9 vs. 2.3 +/- 0.5 ng/ml, P < 0.05) and in the bronchoalveolar lavage fluid (55.7 +/- 20 vs. 19.7 +/- 7.5 ng/ml, P < 0.05). The lipopolysaccharide-induced primed stimulation of alveolar macrophages, defined as their enhanced release of arachidonic acid metabolites as compared to cells from untreated controls upon stimulation with N-formyl-methionyl-phenylalanine was also reduced by fenspiride (1551.5 +/- 183.7 vs. 771.5 +/- 237.5 pg/mu g protein, P < 0.05 for thromboxane B2 and 12.6 +/- 4.9 vs. 3.6 +/- 0.9 pg/ mu g protein, P < 0.05 for leukotriene C4). Finally, fenspiride reduced the increased serum concentrations of extracellular type II phospholipase A2 (3.9 +/- 1.2 vs. 1.2 +/- 0.1 nmol/ml per min, P < 0.01), the intensity of the neutrophilic alveolar invasion and the lethality due to the lipopolysaccharide. The protective effect of fenspiride may result from the inhibition of the formation of tumor necrosis factor, a major mediator of the effects of lipopolysaccharide.

Interference of dexamethasone with leukocyte blood volume and albumin movements in lungs from endotoxemic guinea-pigs

Using radioactive tracers, we measured blood volume, albumin exchanges and blood leukocyte sequestration within lungs, following an intravenous injection of lipopolysaccharide (0.1-1 mg/kg). Neutrophil infiltration into the airways was followed in parallel experiments. Dexamethasone pretreatment (20 mg/kg, subcutaneous) failed to prevent early pulmonary changes induced by lipopolysaccharide as decreased blood volume, leukocyte sequestration, leukopenia or the increased trans-endothelial albumin exchanges. However, dexamethasone provided a significant protection against the later albumin leakage through the endothelial/epithelial barrier and the neutrophil accumulation in the airways observed in lipopolysaccharide-treated guinea-pigs. Our results indicate that the protective effect of dexamethasone in lipopolysaccharide-induced lung injury might derive from an initial reduction of leukocyte adhesion and a later decrease in alveolo-capillary permeability.

Enhanced arachidonic acid metabolism in alveolar macrophages from wheezy infants. Modulation by dexamethasone

To test the hypothesis that alveolar macrophages (AM) from wheezy infants release increased amounts of eicosanoids, as do AM from adults with asthma, we compared eicosanoid release by unstimulated- and ionophore-A23187-stimulated AM from 13 wheezy and six nonwheezy infants and analyzed its regulation by dexamethasone in vitro. Alveolar macrophages from wheezy infants released greater amounts of thromboxane A2 (TxA2) and leukotriene B4 (LTB4) under resting conditions and of TxA2 upon stimulation than did those from control subjects. Dexamethasone induced a dose-dependent inhibition of the spontaneous and A23187-stimulated release of TxA2, but not of the A23187-stimulated release of lipoxygenase products. The inhibition of TxA2 formation was maintained when free arachidonic acid was added during A23187 stimulation, demonstrating that dexamethasone acted mainly at a postphospholipase A2 site. AM exposed to acetylsalicylate and then incubated overnight exhibited de novo cyclooxygenase synthesis, suggesting the presence of the inducible cyclooxygenase as a target for inhibition by dexamethasone. In conclusion, our findings suggest that AM from wheezy infants are activated in vivo to release eicosanoids, as are AM from asthmatic adults, and they support the therapeutic indications of glucocorticoids in severe recurrent wheezing of infancy.

Modulation by dexamethasone of phospholipase A2 activities in endotoxemic guinea pigs

One hour after lipopolysaccharide (LPS) administration (intravenous) in guinea pigs, alveolar macrophages are primed for an ex vivo increased secretion of arachidonic acid metabolites from the cyclooxygenase and the lipoxygenase pathways, with challenge by a second stimulus. At the same time, maximal levels of tumor necrosis factor-alpha (TNF-alpha) are observed in the circulation and in the bronchoalveolar lavage fluid. An extracellular form of phospholipase A2, corresponding probably to the low-molecular-mass type II enzyme, known to accumulate in inflammatory exudates, appears later in the serum of guinea pigs, to reach maximal levels 6 h after the LPS. Unlike the intracellular enzyme, extracellular phospholipase A2 is not increased by LPS in alveolar macrophages or in bronchoalveolar lavage fluids. After 24 h, at the time when neither TNF-alpha nor extracellular phospholipase A2 is present and priming of macrophages is over, maximal neutrophil infiltration is observed in the alveolar space of LPS-treated guinea pigs. Dexamethasone administered repeatedly during 3 days (subcutaneous) before the LPS challenge prevented both early events such as the macrophage priming and the TNF-alpha appearance and later events such as extracellular phospholipase A2 release and neutrophil recruitment.

Immunomodulatory spectrum of lipids associated with Mycobacterium avium serovar 8

Lipid fractions obtained from Mycobacterium avium serovar 8 were assessed for the ability to affect various immune functions of human peripheral blood mononuclear cells (PBM). Lipids included a total lipid fraction and fractions eluted from silicic acid column separation of that total lipid fraction, using chloroform and chloroform-methanol combinations. Lipid fractions were assayed for total carbohydrate and total 6-deoxyhexose content and were assessed for the ability to influence human macrophage function and the capacity to induce secretion of prostaglandin E2 (PGE2) and tumor necrosis factor alpha in PBM. The total lipid and serovar-specific glycopeptidolipid (GPL) fractions both induced significant levels of tumor necrosis factor alpha, as well as PGE2, in PBM exposed to a sublethal concentration of 100 micrograms lipid per 2 x 10(6) cells. In addition, the same concentrations of the 5 to 7% and GPL fractions induced significant levels of leukotriene B4 in PBM. Comparison of carbohydrate and 6-deoxyhexose contents of each fraction suggested a relationship to carbohydrate content and ability of fractions to induce immune modulator secretion. Analysis of GPL fractions from M. avium serovars 4 and 20 revealed that those GPL lacked the ability to induce PGE2. These results are explained by considering the difference in the carbohydrate residues of the oligosaccharide moieties.

Selective Mycobacterium avium-induced production of nitric oxide by human monocyte-derived macrophages

Infection with a virulent strain of Mycobacterium avium, but not with virulent Mycobacterium tuberculosis or avirulent Mycobacterium smegmatis, induced the formation of nitric oxide by human monocyte-derived macrophages. This process was not affected by lipopolysaccharide or cytokines such as interferon-gamma or tumor necrosis factor alpha. M. avium-induced nitric oxide production was significantly decreased by NG-monomethyl-L-arginine, a potent inhibitor of nitric oxide synthase activity, without any significant enhancement of intramacrophagic mycobacterial growth. Infection with all the three mycobacterial species induced a significant activation of phospholipase A2 activity of macrophages as evidenced by the increased release of thromboxane A2. Finally, nitric oxide production by human monocyte-derived macrophages required infection with live M. avium, as neither gamma-irradiated M. avium nor the subcellular fractions of this microorganism (cell wall, cytosol) were able to trigger nitric oxide synthesis.

Nonspecific refractoriness to adenylyl cyclase stimulation in alveolar macrophages from infants with recurrent bronchiolitis

Epidemiologic studies suggest an association between recurrent bronchiolitis in children younger than 3 years of age and diagnosis of asthma later in life. Bronchoalveolar lavages from 20 infants with recurrent wheezing and 18 nonwheezy control subjects were analyzed to determine whether alveolar macrophages of wheezy infants present abnormalities similar to those described in adults with asthma. Alveolar macrophages from both groups responded in vitro, in a concentration-dependent manner, to prostaglandin E2, salbutamol, and forskolin, drugs that increase cyclic adenosine monophosphate levels. However, alveolar macrophages from infants with recurrent wheezing accumulated less cyclic adenosine monophosphate than those from control subjects in response to all three stimulations. These results are in agreement with the reduced cyclic adenosine monophosphate response to different agonists demonstrated in leukocytes from patients with asthma, and suggest that this refractoriness could be one of the precipitating events in the development of asthma observed in a large proportion of infants who have had bronchiolitis.

Studies on the mechanism of spasmolytic activity of (O-methyl-)-N-(2,6-dihydroxybenzoyl)tyramine, a constituent of Aniba riparia (Nees) Mez. (Lauraceae), in rat uterus, rabbit aorta and guinea-pig alveolar leucocytes

The mechanism of action of a nonspecific smooth muscle relaxant, (O-methyl-)-N-(2,6-dihydroxybenzoyl)tyramine (riparin), a constituent of Aniba riparia (Nees) Mez. (Lauraceae) was studied in relation to Ca2+ metabolism in smooth muscle tissues and in guinea-pig alveolar leucocytes. In rat depolarized uterus, riparin inhibited in a reversible and noncompetitive manner CaCl2-induced contraction, a response mediated through voltage-dependent Ca2+ channels. The pD2 value (mean +/- s.e.m.) for riparin was 4.98 +/- 0.06. When compared with sodium nitroprusside (IC50 2.5 microM), an antagonist of receptor-operated Ca2+ channels, riparin was ineffective in suppressing noradrenaline-induced sustained contractions of rabbit aortic strips. However, in the aorta, the compound inhibited intracellular calcium-dependent transient contractions of noradrenaline and riparin (IC50 10.1 microM) was approximately two and a half times more potent than procaine (IC50 25.5 microM) a known inhibitor. In guinea-pig alveolar leucocytes, riparin (IC50 3.2 microM) inhibited intracellular Ca2+ accumulation induced by the calcium ionophore A23187. The results suggest that the inhibition of Ca2+ influx and of Ca2+ release from intracellular stores contribute to the spasmolytic effects of riparin, which may not involve cyclic AMP generation as the levels of this nucleotide were not increased in alveolar macrophages treated with riparin (10-100 microM).

Immunomodulation of human peripheral blood mononuclear cell functions by defined lipid fractions of Mycobacterium avium

Mycobacterial fractions, some of which are associated with the cell envelope of Mycobacterium avium serovar 4, were assessed for their ability to affect various immunological functions of human peripheral blood mononuclear cells (PBM). Treatment of PBM with a total lipid fraction derived from M. avium serovar 4 resulted in a significant suppression of lymphoproliferative responsiveness to phytohemagglutinin stimulation at concentrations not affecting cell viability. Although a similar suppression was not observed when PBM were treated with purified serovar 4-specific glycopeptidolipids (GPL), treatment with the beta-lipid fragment derived from the GPL did result in a significant suppression of phytohemagglutinin responsiveness. Further studies revealed that the total lipid fraction and the beta-lipid fragment were effective at significantly reducing the ability of human macrophages to restrict the intracellular growth of mycobacteria and at stimulating PBM to secrete prostaglandin E2. These same effects were not observed when purified GPL or the reduced oligosaccharide fragment of the GPL was used. Other studies revealed that the total lipid and purified GPL fractions were effective at stimulating tumor necrosis factor alpha release from human PBM, whereas the beta-lipid fragment was not. These results indicate that mycobacterial lipids have various immunomodulatory capabilities, depending upon their chemical nature and ability to interact with certain host cells.

Immunoglobulin-G-dependent stimulation of guinea pig lung mast cells and macrophages

Alveolar macrophages and mast cells isolated from guinea pig lung were passively sensitized with IgG1, IgG2, or serum obtained from guinea pigs actively sensitized with ovalbumin. The release of histamine by mast cells and of thromboxane A2 by alveolar macrophages upon ovalbumin challenge indicated that both antibodies and serum were capable of sensitizing these cells with similar effectiveness. Heating the serum at 56 degrees C for 4 h to inactivate IgE did not modify the antigen-dependent response of lung cells. These results suggest a predominant role for IgG in the allergic response of the guinea pig through the activation of different cell types such as lung mast cells and alveolar macrophages.

Intracellular growth of Mycobacterium avium in human macrophages is linked to the increased synthesis of prostaglandin E2 and inhibition of the phagosome-lysosome fusions

A virulent strain of Mycobacterium avium grew actively inside human adherent peripheral blood monocyte-derived macrophages. Bacteria were always confined to the phagosome compartment and were encapsulated. Cytochemical labeling of acid phosphatase using transmission electron microscopy showed a strong inhibition of the phagosome-lysosome fusions (PLF) in macrophages as not more than 25-30% bacteria containing phagosome at any time effectively fused with lysosomes. In case of a positive fusion event, the bacterial capsule prevented the diffusion of the lysosomal contents to the bacterial surface. Moreover, the infection of macrophages both by living and gamma-killed M. avium was linked to an increased synthesis of prostaglandin E2 (PGE2); however the total amount of PGE2 synthesized in the latter case was significantly lower than that observed with viable organisms. Our results suggest that the inability of human macrophages to control M. avium infection is linked to immunosuppressive pathways, e.g. enhanced synthesis of PGE2 and also to an impairment of normal microbicidal functions of the infected macrophages.

Effect of indomethacin on the modulation of Mycobacterium avium growth in human macrophages by interferon gamma, retinoic acid and 1,25(OH)2-vitamin D3

A virulent strain of Mycobacterium avium was grown actively inside human adherent peripheral blood monocyte-derived macrophages with enhanced synthesis of prostaglandin E2 (PGE2). We therefore decided to investigate if the inability of human macrophages to control M. avium infection could be reversed using various immunomodulators, i.e. retinoic acid (RA), 1,25 dihydroxyvitamin D3 (D3) and interferon gamma (IFN gamma) alone or in combination, and whether this reversal was further potentiated by the addition of indomethacin (IND), a potent inhibitor of PGE2 biosynthesis. Among the various immunomodulators employed, only RA alone or in association with D3 or both D3 and IFN gamma were able to induce a clear mycobacteriostatic effect, which was further potentiated by IND. Our data suggest that immunosuppressive pathways induced in macrophages infected by M. avium result partly from an increased synthesis of PGE2 occurring soon after infection.

Azelastine potentiates the prostaglandin-induced increase of cyclic AMP content in human platelets and in guinea-pig alveolar macrophages

The effect of azelastine on intracellular cyclic AMP concentration and on various indexes of cell activation was evaluated in guinea-pig alveolar macrophages and in human platelets. The effect of azelastine was further investigated on adenylate cyclase activity using membranes and homogenates from guinea-pig alveolar macrophages. Pretreatment of alveolar macrophages with azelastine prevented the activation induced by PAF-acether and by the chemotactic peptide fMLP as estimated by the reduced liberation of arachidonic acid metabolites formed by the cyclooxygenase and the lipoxygenase pathways. The effect of azelastine was concentration-dependent (50 to 500 microM) and reversible. Similarly, a short pretreatment with azelastine (100 microM) prevented arachidonic acid-induced platelet aggregation. This effect was also reversible after washing the platelets. In guinea-pig alveolar macrophages, azelastine induced a concentration-dependent (10 to 500 microM) increase in intracellular cyclic AMP and markedly potentiated the increase induced by PGE2. In human platelets, azelastine alone increased intracellular cyclic AMP concentration marginally only but, as in the case of macrophages, synergized with PGI2. Azelastine did not activate significantly adenylate cyclase unless a cytosolic factor was included within the membrane fraction. This effect of azelastine was not due to Ca2+ movements and was not modified by GTP. Our findings show that azelastine interferes with cell activation through a mechanism related to an increase in intracellular cyclic AMP concentration. The increase in cyclic AMP was induced by azelastine in intact cells and in homogenates but not in a crude membrane fraction. Those results indicate that azelastine modifies a cytosolic factor that may be phosphodiesterase. In addition, similarities between the effects of azelastine and those of reference phosphodiesterase inhibitors (theophylline, isobutyl-methyl-xanthine) are shown in this study, suggesting that azelastine might behave as a phosphodiesterase inhibitor.

Reduced responsiveness of adenylate cyclase in alveolar macrophages from patients with asthma

Alveolar macrophages from patients with asthma accumulated less cyclic adenosine monophosphate when these macrophages were exposed to isobutyl methylxanthine, salbutamol, or prostaglandin E2, compared to cells from control subjects without asthma, and the degree of the hyporesponsiveness was related to the severity of asthma. In addition, a significantly lower adenylate cyclase activity was observed in crude membrane fractions of macrophages from the group with asthma in the presence of salbutamol and prostaglandin E2. The refractoriness observed in patients with asthma is thus not accounted for by a specific beta-adrenergic desensitization at the adenylate cyclase receptor level but should rather be explained by a cyclic adenosine monophosphate-dependent postreceptor mechanism.

Antigen-dependent activation of alveolar macrophages from ovalbumin-sensitized guinea-pigs: relevance of the route of administration and the amount of antigen provided

Alveolar macrophages from guinea-pigs sensitized by different amounts of ovalbumin, administered either by subcutaneous injection or aerosol exposure, liberate increased amounts of arachidonic acid and thromboxane B2 when challenged in vitro with ovalbumin. This antigen-dependent activation of macrophages was immunospecific. The comparison between different sensitization procedures showed that the aerosol exposure was the most efficient with respect to the activation of macrophages, as cells from guinea-pigs sensitized subcutaneously were poorly activated by the antigen unless high doses were used for sensitization. The antigen-dependent activation of macrophages was affected by acid and neutral washings, suggesting the involvement of a loosely bound antibody that could not be identified. These observations suggest that, as mast cells and basophils, alveolar macrophages from actively sensitized guinea-pigs contribute to the allergic reaction by an antibody-mediated mechanism.

Protection by nedocromil sodium of active immunization-induced bronchopulmonary alterations in the guinea pig

The effect of nedocromil sodium on PAF-acether- and antigen-induced bronchoconstriction (BC) and mediator release in lungs from actively sensitized guinea pigs and on the eosinophil content of bronchoalveolar lavage (BAL) was investigated. Guinea pigs were actively sensitized by two subcutaneous injections of 10 micrograms ovalbumin in 1 mg AI(OH)3 at 2-wk intervals. One week after the second (booster) injection, the lungs were removed, perfused in the absence or presence of indomethacin, and challenged at 10-min intervals with PAF-acether (1 and 100 ng) and with ovalbumin (1 micrograms). No inhibition of PAF-acether- and antigen-induced BC or mediator release from sensitized lungs was observed when nedocromil sodium (10 microM) was added directly to the buffer solution. By contrast, when guinea pigs were treated for 1 wk before the experiment with nedocromil sodium (30 mg/kg per day), BC and the release of leukotrienelike material (but not of thromboxane B2) to 1 ng PAF-acether were reduced by around 50% (p less than 0.05) and 62% (p less than 0.05), respectively. No inhibition was observed for 100 ng PAF-acether and 1 micrograms ovalbumin. Furthermore, nedocromil sodium markedly impaired histamine secretion induced by both PAF-acether and antigen administration. Nedocromil sodium did not affect the titers of circulating ovalbumin-specific immunoglobulin G, as detected by an enzyme-linked immunosorbent assay. The 1-wk treatment with nedocromil sodium also reduced markedly the proportion of eosinophils in the BAL of sensitized guinea pigs, whereas it was ineffective when injected once subcutaneously at the dose of 30 mg/kg 2 h before the experiment.(ABSTRACT TRUNCATED AT 250 WORDS)

Phospholipase A2-mediated release of arachidonic acid in stimulated guinea pig alveolar macrophages: interaction with lipid mediators and cyclic AMP

The stimulation of cultured guinea pig alveolar macrophages by the chemotactic peptide N-formyl-L-methionyl-L-leucyl-L-phenylalanine, or by the phospholipid inflammatory mediator platelet activating factor (PAF) induced an increase in arachidonic acid release and its cyclooxygenase products. This release, which was mimicked by the association of threshold concentrations of the calcium ionophore A 23187 and of the protein kinase C activator tetradecanoyl phorbol acetate arose mainly from diacyl- and alkyl-acyl-phosphatidylcholine and phosphatidylinositol. Using [1-14C]arachidonic acid-labeled membranes as an endogenous substrate as well as dioleoyl-phosphatidyl [14C]ethanolamine as an exogenous substrate, we showed that phospholipase A2 activity of stimulated macrophages increases upon stimulation. Treatment of macrophages by prostaglandin E2 decreased the arachidonic acid release elicited by the chemotactic peptide and PAF. Furthermore, prostaglandin E2 increased and PAF decreased the cellular content in cyclic AMP. From these results we suggest that an initial stimulation of alveolar macrophages by a bacterial signal initiates the sequential activation of a phospholipase C and of phospholipase A2, leading to the release of PAF and eicosanoids. These mediators may in turn modulate the cell response by increasing or decreasing cyclic AMP, Ca2+, or diacyglycerol macrophage content.

PAF-acether and experimental anaphylaxis as a model for asthma

Several lines of evidence indicate that platelet-activating factor (PAF-acether) is implicated in hypersensitivity reactions. Indeed, PAF-acether reproduces the features of asthma in vivo and in vitro, since it induces bronchoconstriction, hypotension, and hemoconcentration and activates platelets and leukocytes. Both PAF-acether and antigen evoke eosinophil margination and diapedesis in guinea pig lung parenchyma and bronchial submucosa. Furthermore, intradermal administration of PAF-acether to atopics induces a more intense eosinophil degranulation as compared to normal subjects. PAF-acether also induces bronchopulmonary hyperresponsiveness in various animal models and in humans. We showed that lungs from actively sensitized guinea pigs exhibit an in vitro bronchopulmonary hyperresponsiveness to PAF-acether as compared to nonsensitized animals. This phenomenon is probably due to a lung invasion by inflammatory cells or to a variation of the reactivity of resident lung cells such as alveolar macrophages. In these cells, the cyclic adenosine monophosphate content is much less increased by prostaglandin E2 and salbutamol when they are obtained from actively sensitized animals.

Reduced responsiveness of bronchoalveolar cells from sensitised guinea-pigs to the cyclic AMP--stimulating effect of prostaglandin E2 and beta-adrenoceptor agonists

Prostaglandin E2 and the beta-adrenoceptor agonist salbutamol were less effective in increasing the intracellular cAMP content of bronchoalveolar cells and adherent alveolar macrophages from ovalbumin-sensitised as compared to control guinea-pigs. This refractoriness to the cyclic AMP-stimulating effects of PGE2 and salbutamol induced by the sensitisation procedure may be relevant to the altered bronchopulmonary responsiveness in asthma.

Interaction between PAF-acether and drugs that stimulate cyclic AMP in guinea-pig alveolar macrophages

The PAF-acether (1-alkyl-2-acetyl-sn-glycero-3-phosphocholine)-induced arachidonate release from alveolar macrophages was significantly reduced by prostaglandin E2 (PGE2) and by the beta-adrenoceptor agonist salbutamol. In addition, PAF-acether markedly reduced the increase in intracellular cyclic AMP (cAMP) concentrations induced by PGE2 and salbutamol. Our data indicate an inverse relationship between intracellular cAMP levels and free arachidonate availability in alveolar macrophages treated with PAF-acether. A rise in intracellular cAMP therefore represents an important alternative route for controlling the effects of PAF-acether and the resulting inflammatory alterations in the respiratory system.