Cooperative and redundant signaling of leukotriene B4 and leukotriene D4 in human monocytes

BACKGROUND

Leukotriene B(4) (LTB(4)) and cysteinyl leukotrienes (cysLTs) are important immune mediators, often found concomitantly at sites of inflammation. Although some of the leukotriene-mediated actions are distinctive (e.g., bronchial constriction for cysLTs), many activities such as leukocyte recruitment to tissues and amplification of inflammatory responses are shared by both classes of leukotrienes.

OBJECTIVE

We used human monocytes to characterize leukotriene-specific signaling, gene expression signatures, and functions and to identify interactions between LTB(4)- and cysLTs-induced pathways.

METHODS

Responsiveness to leukotrienes was assessed using oligonucleotide microarrays, real-time PCR, calcium mobilization, kinase activation, and chemotaxis assays.

RESULTS

Human monocytes were found to express mRNA for high- and low-affinity LTB(4) receptors, BLT(1) and BLT(2), but signal predominantly through BLT(1) in response to LTB(4) stimulation as shown using selective agonists, inhibitors, and gene knock down experiments. LTB(4) acting through BLT(1) coupled to G-protein α inhibitory subunit activated calcium signaling, p44/42 mitogen-activated protein kinase, gene expression, and chemotaxis. Twenty-seven genes, including immediate early genes (IEG), transcription factors, cytokines, and membrane receptors were significantly up-regulated by LTB(4). LTB(4) and LTD(4) had similar effects on signaling, gene expression, and chemotaxis indicating redundant cell activation pathways but costimulation with both lipid mediators was additive for many monocyte functions.

CONCLUSION

Leukotriene B(4) and LTD(4) display both redundant and cooperative effects on intracellular signaling, gene expression, and chemotaxis in human monocytes. These findings suggest that therapies targeting either leukotriene alone may be less effective than approaches directed at both.

85-kDa cytosolic phospholipase A2 group IValpha gene promoter polymorphisms in patients with severe asthma: a gene expression and case-control study

Cytosolic phospholipase A(2) (cPLA(2)) group IValpha is a critical enzyme involved in the liberation of arachidonic acid from cellular membranes. cPLA(2)(-/-) mice have reduced allergen-induced bronchoconstriction and bronchial hyperresponsiveness. The goal of this study was to investigate polymorphisms of the (CA)(n) and (T)(n) microsatellites and surrounding regions in the cPLA(2)alpha gene promoter. We analysed the cPLA(2) promoter regions containing (CA)(n) and (T)(n) repeats in 87 patients with severe asthma and in 48 control subjects by bidirectional sequencing. Functional studies were performed utilizing reporter genes derived from subjects with varying numbers of these repeats, and on constructs with a series of deletions. We found that the (CA)(n) and (T)(n) regions are polymorphic and that constructs with CA or T repeats or CA and T repeats deleted revealed, respectively, a 41.8 +/- 7%, 22.3 +/- 5% and 100 +/- 20% increase in reporter gene activity. A lower number of CA or T repeats caused higher cPLA(2) promoter luciferase activity. The group of shorter alleles of the (CA)(n) microsatellite region (n = 12-18) (P(cor) = 0.00006), and the group of shorter alleles of (T)(n) repeats region (n = 17-38) (P(cor) = 0.0039) occurred significantly more often in patients with severe asthma. We also found novel SNPs in positions -292 C > G, -185 A > C, -180 T > C and -165 A > C. Two of them were associated with the severe asthma phenotype: -180T allele (P(cor) = 0.03996) and -185 A allele (P(cor) = 0.03966). These results demonstrate that (CA)(n) and (T)(n) repeats may have an influence on cPLA(2) transcription which might play a role in severe asthma pathogenesis.

p11 expression in human bronchial epithelial cells is increased by nitric oxide in a cGMP-dependent pathway involving protein kinase G activation

The effect of nitric oxide on p11 expression was studied in an immortalized human bronchial epithelial cell line (BEAS-2B cells). Three nitric oxide donors were used: spermine NONOate (SP), (+/-)-S-nitroso-N-acetylpenicillamine (SNAP), and S-nitrosoglutathione (SNOG). All three nitric oxide donors had similar effects resulting in dose-dependent and time-dependent accumulation of p11 protein and an increase of steady-state p11 mRNA. Studies using a reporter gene containing the region from -1499 to +89 of the p11 promoter demonstrated an increase in transcriptional activity after stimulation with NO donors for 4 h. These effects were abolished at the promoter and protein level using protein kinase G inhibitors (KT5823 and R(p)-8-pCPT-cGMPS). Incubation of transfected cells with a cell permeable cGMP analogue (8-Br-cGMP) resulted in a dose-related increase of promoter activity. An electrophoretic mobility shift assay of nuclear proteins extracted from BEAS-2B cells identified an AP-1 site located at -82 to -77 of the p11 promoter region as an NO- and cGMP- dependent response element. These data were confirmed using a c-jun dominant negative mutant vector and a c-jun expression plasmid. Therefore, we conclude that nitric oxide-induced p11 expression in human bronchial epithelial cells is mediated at least in part through increased binding of activator protein one to the p11 promoter.

Effects of inhaled nitric oxide on regional blood flow are consistent with intravascular nitric oxide delivery

Nitric oxide (NO) may be stabilized by binding to hemoglobin, by nitrosating thiol-containing plasma molecules, or by conversion to nitrite, all reactions potentially preserving its bioactivity in blood. Here we examined the contribution of blood-transported NO to regional vascular tone in humans before and during NO inhalation. While breathing room air and then room air with NO at 80 parts per million, forearm blood flow was measured in 16 subjects at rest and after blockade of forearm NO synthesis with N(G)-monomethyl-L-arginine (L-NMMA) followed by forearm exercise stress. L-NMMA reduced blood flow by 25% and increased resistance by 50%, an effect that was blocked by NO inhalation. With NO inhalation, resistance was significantly lower during L-NMMA infusion, both at rest and during repetitive hand-grip exercise. S-nitrosohemoglobin and plasma S-nitrosothiols did not change with NO inhalation. Arterial nitrite levels increased by 11% and arterial nitrosyl(heme)hemoglobin levels increased tenfold to the micromolar range, and both measures were consistently higher in the arterial than in venous blood. S-nitrosohemoglobin levels were in the nanomolar range, with no significant artery-to-vein gradients. These results indicate that inhaled NO during blockade of regional NO synthesis can supply intravascular NO to maintain normal vascular function. This effect may have application for the treatment of diseases characterized by endothelial dysfunction.

Nitric oxide transport on sickle cell hemoglobin: where does it bind?

We have recently reported that nitric oxide inhalation in individuals with sickle cell anemia increases the level of NO bound to hemoglobin, with the development of an arterial-venous gradient, suggesting delivery to the tissues. A recent model suggests that nitric oxide, in addition to its well-known reaction with heme groups, reacts with the beta-globin chain cysteine 93 to form S-nitrosohemoglobin (SNO-Hb) and that SNO-Hb would preferentially release nitric oxide in the tissues and thus modulate blood flow. However, we have also recently determined that the primary NO hemoglobin adduct formed during NO breathing in normal (hemoglobin A) individuals is nitrosyl (heme)hemoglobin (HbFeIINO), with only a small amount of SNO-Hb formation. To determine whether the NO is transported as HbFeIINO or SNO-Hb in sickle cell individuals, which would have very different effects on sickle hemoglobin polymerization, we measured these two hemoglobin species in three sickle cell volunteers before and during a dose escalation of inhaled NO (40, 60, and 80 ppm). Similar to our previous observations in normal individuals, the predominant species formed was HbFeIINO, with a significant arterial-venous gradient. Minimal SNO-Hb was formed during NO breathing, a finding inconsistent with significant transport of NO using this pathway, but suggesting that this pathway exists. These results suggest that NO binding to heme groups is physiologically a rapidly reversible process, supporting a revised model of hemoglobin delivery of NO in the peripheral circulation and consistent with the possibility that NO delivery by hemoglobin may be therapeutically useful in sickle cell disease.

Effects of inhaled nitric oxide on regional blood flow are consistent with intravascular nitric oxide delivery

Nitric oxide (NO) may be stabilized by binding to hemoglobin, by nitrosating thiol-containing plasma molecules, or by conversion to nitrite, all reactions potentially preserving its bioactivity in blood. Here we examined the contribution of blood-transported NO to regional vascular tone in humans before and during NO inhalation. While breathing room air and then room air with NO at 80 parts per million, forearm blood flow was measured in 16 subjects at rest and after blockade of forearm NO synthesis with N(G)-monomethyl-L-arginine (L-NMMA) followed by forearm exercise stress. L-NMMA reduced blood flow by 25% and increased resistance by 50%, an effect that was blocked by NO inhalation. With NO inhalation, resistance was significantly lower during L-NMMA infusion, both at rest and during repetitive hand-grip exercise. S-nitrosohemoglobin and plasma S-nitrosothiols did not change with NO inhalation. Arterial nitrite levels increased by 11% and arterial nitrosyl(heme)hemoglobin levels increased tenfold to the micromolar range, and both measures were consistently higher in the arterial than in venous blood. S-nitrosohemoglobin levels were in the nanomolar range, with no significant artery-to-vein gradients. These results indicate that inhaled NO during blockade of regional NO synthesis can supply intravascular NO to maintain normal vascular function. This effect may have application for the treatment of diseases characterized by endothelial dysfunction.

Tumor necrosis factor alpha stimulation of human Clara cell secretory protein production by human airway epithelial cells

Clara cell secretory protein (CCSP) or uteroglobin/CC10 is a product of epithelial cells in a variety of organs including the lung. CCSP has anti-inflammatory properties and may act as an inhibitor of secretory phospholipase A2's. Tumor necrosis factor alpha (TNF-alpha) is capable of inducing the expression of gene products including a variety of cytokines and chemokines in the airway epithelium that may upregulate the airway inflammatory response. Therefore, it was of interest to determine whether this proinflammatory cytokine might also induce the production of a counterregulatory protein such as CCSP, which might modulate the inflammatory response in the airway. Normal human tracheobronchial epithelial cells in primary culture and a human bronchial epithelial cell line (BEAS-2B) were studied. CCSP mRNA levels in BEAS-2B cells were detected by ribonuclease protection assay. CCSP mRNA levels increased in response to TNF-alpha (20 ng/mL) stimulation after 8-36 h, with the peak increase at 18 h. Immunoblotting of CCSP released from BEAS-2B cells into the culture media demonstrated that TNF-alpha induced the synthesis and secretion of CCSP over 8 to 18 h. Similarly, TNF stimulated the release of CCSP from human tracheobronchial epithelial cells in primary culture at 8 and 18 h. The CCSP reporter gene including 801 bases 5' of the transcription start site did not increase transcriptional activity in response to TNF-alpha stimulation. A CCSP mRNA half-life assay indicated that TNF-alpha induced increases in CCSP mRNA at least in part at a posttranscriptional level. Therefore, TNF-alpha induces airway epithelial cell expression of human CCSP and may modulate airway inflammatory responses in this manner.

Disorders of ciliary motility

Clearance of mucus and other debris from the airways is achieved by 3 main mechanisms: mucociliary activity, coughing, and alveolar clearance. Disorders of ciliary structure or function results in impaired clearance, and result in chronic sinopulmonary disease manifested as chronic sinusitis, otitis media, nasal polyposis, and ultimately bronchiectasis. In addition, situs inversus, dextrocardia, and infertility can be associated with dysfunctional ciliary activity. The term primary ciliary dyskinesia has been proposed for the spectrum of these diseases. The term Kartagener syndrome applies to this syndrome when accompanied by infertility and dextrocardia or situs inversus. The more common types of ciliary dysmotility syndromes are characterized by missing dynein arms, central microtubule pairs, inner sheath, radial spokes, or nexin links. In addition to structural defects within the cilia, disordered ciliary beating and disordered ciliary arrays on epithelial cell surfaces have been described in this syndrome. Treatment includes rigorous lung physiotherapy, prophylactic and organism-specific antibiotics, and immunization against common pulmonary pathogens. Late stages of the disease may require surgical intervention for bronchiectasis or lung transplant for end-stage lung disease.

Prostaglandin E(2)-induced interleukin-6 release by a human airway epithelial cell line

Human airway epithelial cell release of interleukin (IL)-6 in response to lipid mediators was studied in an airway cell line (BEAS-2B). Prostaglandin (PG) E(2) (10(-7) M) treatment caused an increase in IL-6 release at 2, 4, 8, and 24 h. IL-6 release into the culture medium at 24 h was 3,396 +/- 306 vs. 1,051 +/- 154 pg/ml (PGE(2)-treated cells vs. control cells). PGE(2) (10(-7) to 10(-10) M) induced a dose-related increase in IL-6 release at 24 h. PGF(2 alpha) (10(-6) M) treatment caused a similar effect to that of PGE(2) (10(-7) M). PGE(2) analogs with relative selectivity for PGE(2) receptor subtypes were studied. Sulprostone, a selective agonist for the EP-3 receptor subtype had no effect on IL-6 release. 11-Deoxy-16,16-dimethyl-PGE(2), an EP-2/4 agonist, and 17-phenyl trinor PGE(2), an agonist selective for the EP-1 > EP-3 receptor subtype (10(-6) to 10(-8) M), caused dose-dependent increases in IL-6 release. 8-Bromo-cAMP treatment resulted in dose-related increases in IL-6 release. RT-PCR of BEAS-2B cell mRNA demonstrated mRNA for EP-1, EP-2, and EP-4 receptors. After PGE(2) treatment, increases in IL-6 mRNA were noted at 4 and 18 h. Therefore, PGE(2) increases airway epithelial cell IL-6 production and release.

Retinoic acid reduces p11 protein levels in bronchial epithelial cells by a posttranslational mechanism

p11 is a member of the S100 family of proteins, is the cellular ligand of annexin II, and interacts with the carboxyl region of 85-kDa cytosolic phospholipase A(2) (cPLA(2)), inhibiting cPLA(2) activity and arachidonic acid (AA) release. We studied the effect of retinoic acid (RA) on PLA(2) activity in human bronchial epithelial cells and whether p11 contributes to these effects. The addition of 10(-6) M RA resulted in reduced p11 protein levels at 4 days, with the greatest effect observed on days 6 and 7. This effect was dose related (10(-6) to 10(-9) M). RA treatment (10(-6) M) had no effect on cPLA(2) protein levels. p11 mRNA levels were unchanged at 6 and 8 days of treatment (correlating with maximum p11 protein reduction). Treatment with RA reduced p11 levels in control cells and in cells transfected with a p11 expression vector, suggesting a posttranslational mechanism. Lactacystin (10(-6) M), an inhibitor of the human 26S proteasome, blocked the decrease in p11 observed with RA treatment. Compared with control cells (n = 3), RA-treated cells (n = 3) had significantly increased AA release after treatment with the calcium ionophore A-23187 (P = 0.006). Therefore, RA reduces p11 protein expression and increases PLA(2) activity and AA release.

Role of circulating nitrite and S-nitrosohemoglobin in the regulation of regional blood flow in humans

To determine the relative contributions of endothelial-derived nitric oxide (NO) vs. intravascular nitrogen oxide species in the regulation of human blood flow, we simultaneously measured forearm blood flow and arterial and venous levels of plasma nitrite, LMW-SNOs and HMW-SNOs, and red cell S-nitrosohemoglobin (SNO-Hb). Measurements were made at rest and during regional inhibition of NO synthesis, followed by forearm exercise. Surprisingly, we found significant circulating arterial-venous plasma nitrite gradients, providing a novel delivery source for intravascular NO. Further supporting the notion that circulating nitrite is bioactive, the consumption of nitrite increased significantly with exercise during the inhibition of regional endothelial synthesis of NO. The role of circulating S-nitrosothiols and SNO-Hb in the regulation of basal vascular tone is less certain. We found that low-molecular-weight S-nitrosothiols were undetectable and S-nitroso-albumin levels were two logs lower than previously reported. In fact, S-nitroso-albumin primarily formed in the venous circulation, even during NO synthase inhibition. Whereas SNO-Hb was measurable in the human circulation (brachial artery levels of 170 nM in whole blood), arterial-venous gradients were not significant, and delivery of NO from SNO-Hb was minimal. In conclusion, we present data that suggest (i) circulating nitrite is bioactive and provides a delivery gradient of intravascular NO, (ii) S-nitroso-albumin does not deliver NO from the lungs to the tissue but forms in the peripheral circulation, and (iii) SNO-Hb and S-nitrosothiols play a minimal role in the regulation of basal vascular tone, even during exercise stress.

Relative role of heme nitrosylation and beta-cysteine 93 nitrosation in the transport and metabolism of nitric oxide by hemoglobin in the human circulation

To quantify the reactions of nitric oxide (NO) with hemoglobin under physiological conditions and to test models of NO transport on hemoglobin, we have developed an assay to measure NO-hemoglobin reaction products in normal volunteers, under basal conditions and during NO inhalation. NO inhalation markedly raised total nitrosylated hemoglobin levels, with a significant arterial-venous gradient, supporting a role for hemoglobin in the transport and delivery of NO. The predominant species accounting for this arterial-venous gradient is nitrosyl(heme)hemoglobin. NO breathing increases S-nitrosation of hemoglobin beta-chain cysteine 93, however only to a fraction of the level of nitrosyl(heme)hemoglobin and without a detectable arterial-venous gradient. A strong correlation between methemoglobin and plasma nitrate formation was observed, suggesting that NO metabolism is a primary physiological cause of hemoglobin oxidation. Our results demonstrate that NO-heme reaction pathways predominate in vivo, NO binding to heme groups is a rapidly reversible process, and S-nitrosohemoglobin formation is probably not a primary transport mechanism for NO but may facilitate NO release from heme.

Inhaled nitric oxide augments nitric oxide transport on sickle cell hemoglobin without affecting oxygen affinity

Nitric oxide (NO) inhalation has been reported to increase the oxygen affinity of sickle cell erythrocytes. Also, proposed allosteric mechanisms for hemoglobin, based on S-nitrosation of beta-chain cysteine 93, raise the possibility of altering the pathophysiology of sickle cell disease by inhibiting polymerization or by increasing NO delivery to the tissue. We studied the effects of a 2-hour treatment, using varying concentrations of inhaled NO. Oxygen affinity, as measured by P(50), did not respond to inhaled NO, either in controls or in individuals with sickle cell disease. At baseline, the arterial and venous levels of nitrosylated hemoglobin were not significantly different, but NO inhalation led to a dose-dependent increase in mean nitrosylated hemoglobin, and at the highest dosage, a significant arterial-venous difference emerged. The levels of nitrosylated hemoglobin are too low to affect overall hemoglobin oxygen affinity, but augmented NO transport to the microvasculature seems a promising strategy for improving microvascular perfusion.

Pneumocystis carinii major surface glycoprotein induces interleukin-8 and monocyte chemoattractant protein-1 release from a human alveolar epithelial cell line

BACKGROUND

The major surface glycoprotein (MSG) is an abundant, immunogenic glycoprotein located on the surface of Pneumocystis carinii. Little is known about the proinflammatory effects of MSG.

DESIGN

We have investigated the effect of human MSG on the secretion of the chemokines interleukin 8 (IL-8) and monocyte chemoattractant protein-1 (MCP-1) from an alveolar epithelial cell line (A549).

RESULTS

Incubation of A549 cells with MSG in concentrations from 0.4 to 10 microg mL-1 for 24 h caused dose-dependent increases in IL-8 release (3.4-fold above control, P < 0.01). Time course experiments showed increases in IL-8 release at 4 h, 8 h and 24 h compared with control cultures (all P < 0.01). There was a minor (13%) dose- and time-related increase in MCP-1 release at 24 h (P = 0.02). Co-incubation of MSG with mannan or beta-glucan decreased IL-8 release by 48% and 42% respectively, suggesting that MSG stimulates A549 cells in part through carbohydrate moieties. Dexamethasone significantly inhibited MSG-induced IL-8 release in concentrations of 10-6-10-8 mol L-1 compared with control experiments (P < 0.01). Ribonuclease protection assays for steady-state IL-8 mRNA showed that increases in response to MSG stimulation occurred by 4 h and persisted throughout 8 h of stimulation.

CONCLUSION

These findings suggest that MSG can alter alveolar epithelial cytokine release and may be capable of modulating the local inflammatory response in this manner.

Dexamethasone alters arachidonate release from human epithelial cells by induction of p11 protein synthesis and inhibition of phospholipase A2 activity

The effect of the glucocorticosteroid, dexamethasone, on arachidonic acid (AA) release and on protein levels of p11 and cytosolic phospholipase A2 (cPLA2) was studied in two epithelial cell lines, HeLa cells and BEAS-2B cells. Dexamethasone treatment of HeLa cells and BEAS-2B cells increased cellular p11 protein and mRNA levels in a time- and dose-dependent manner. It had little effect on levels of cPLA2 protein. In order to determine if increased p11 protein expression resulted in increased interaction between p11 and cPLA2, anti-cPLA2 antibodies were used to immunoprecipitate p11.cPLA2 complexes and Western blots of the immunoprecipitate were used to detect p11. In cells treated with dexamethasone, more p11 was detected in the anti-cPLA2 immunoprecipitate compared with control cells. Dexamethasone treatment of HeLa cells prelabeled with [3H]AA decreased the release of [3H]AA under basal conditions and after stimulation with the calcium ionophore A23187 (10(-6) M). In order to determine if altering the p11 protein levels in HeLa cells independent of glucocorticosteroid treatment could also produce an effect on [3H]AA release, cells were stably transfected with plasmids expressing either p11 antisense mRNA or p11 mRNA. Cloned HeLa cells expressing p11 antisense mRNA exhibited less cellular p11 protein compared with control cells and greater [3H]AA release compared with cells transfected with a control vector. Cloned HeLa cells stably transfected with a p11 expression vector exhibited increased p11 cellular protein and diminished [3H]AA release under basal conditions and in response to A23187. Therefore, dexamethasone alteration of epithelial cell AA release may be due in part to induction of p11 protein expression.

Tumor necrosis factor-alpha stimulates human Clara cell secretory protein production by human airway epithelial cells

Clara cell secretory protein (CCSP), or CC10, is an inhibitor of secretory phospholipase A2 which may be produced by phagocytic cells and by a variety of other cells in the airway. Tumor necrosis factor-alpha (TNF-alpha) is capable of activating phospholipases and inducing the expression of a variety of genes in the airway epithelium which may modulate the airway inflammatory response. Therefore, it was of interest to determine whether this proinflammatory cytokine could induce the production of a counterregulatory protein such as CCSP which might modulate the production of eicosanoid mediators in the airway. Using a human bronchial epithelial cell line (BEAS-2B), CCSP messenger RNA (mRNA) levels were detected by ribonuclease protection assay. TNF treatment of these cells increased CCSP mRNA levels in a time- and dose-dependent manner. The CCSP mRNA level increased in response to TNF-alpha (20 ng/ml) stimulation after 8 to 36 h with the peak increase at 18 h. Immunoblotting of CCSP protein released into the culture media demonstrated that TNF-alpha induced the synthesis and secretion of CCSP protein in a time-dependent manner over 8 to 18 h. The results of a CCSP reporter gene activity assay, nuclear run-on assay, and CCSP mRNA half-life assay indicated that the TNF-alpha-induced increases in CCSP gene expression are regulated at the post-transcriptional level. We conclude that TNF-alpha induces airway epithelial cell expression of human CCSP protein and may modulate airway inflammatory responses in this manner.

Polypoid lesions of airways: early experience with computer-assisted detection by using virtual bronchoscopy and surface curvature

PURPOSE

To test the application of a technique developed by the authors for the computer-assisted diagnosis of polypoid airway lesions from surface rendered virtual bronchoscopic reconstructions.

MATERIALS AND METHODS

A computer algorithm was developed to detect polypoid airway lesions by means of segmentation of the bronchial surface with curvature classification. This method was tested with a bronchial phantom, five cadaveric lung specimens, and virtual bronchoscopic studies in 16 patients.

RESULTS

For the patient studies, the sensitivity and specificity of the method were 47%-88% and 58%-89%, respectively, depending on the value of an adjustable parameter (the mean curvature threshold). The sensitivity increased (by 20% to 34%) when only lesions larger than 5 mm in diameter were considered.

CONCLUSION

With this method, polypoid airway lesions can be detected automatically, although false-positive diagnoses present an important limitation.

Interferon-gamma stimulates human Clara cell secretory protein production by human airway epithelial cells

Clara cell secretory protein (CCSP) is an inhibitor of secretory phospholipase A2. It is produced by airway epithelial cells and is present in airway secretions. Because interferon (IFN)-gamma can induce gene expression in airway epithelial cells and may modulate the inflammatory response in the airway, it was of interest to study the effect of this cytokine on epithelial cell CCSP mRNA expression and CCSP protein synthesis. A human bronchial epithelial cell line (BEAS-2B) was used for this study. CCSP mRNA was detected by ribonuclease protection assay. IFN-gamma was found to increase CCSP mRNA expression in a time- and dose-dependent manner. The CCSP mRNA level increased after IFN-gamma (300 U/ml) treatment for 8-36 h, with the peak increase at 18 h. Immunobloting of CCSP protein also demonstrated that IFN-gamma induced the synthesis and secretion of CCSP protein in a time-dependent manner. Nuclear run-on, CCSP reporter gene activity assay, and CCSP mRNA half-life assay demonstrated that IFN-gamma-induced increases in CCSP gene expression were mediated, at least in part, at the posttranscriptional level. The present study demonstrates that IFN-gamma can induce increases in steady-state mRNA levels and protein synthesis of human CCSP protein in airway epithelial cells and may modulate airway inflammatory responses in this manner.

The major surface glycoprotein of Pneumocystis carinii induces release and gene expression of interleukin-8 and tumor necrosis factor alpha in monocytes

Recent studies suggest that interleukin-8 (IL-8) and tumor necrosis factor alpha (TNF-alpha) may play a central role in host defense and pathogenesis during Pneumocystis carinii pneumonia. In order to investigate whether the major surface antigen (MSG) of human P. carinii is capable of eliciting the release of IL-8 and TNF-alpha, human monocytes were cultured in the presence of purified MSG. MSG-stimulated cells released significant amounts of IL-8 within 4 h, and at 20 h, cells stimulated with MSG released 45.5 +/- 9.3 ng of IL-8/ml versus 3.7 +/- 1.1 ng/ml for control cultures (P = 0.01). In a similar fashion, MSG elicited release of TNF-alpha. Initial increases were also seen at 4 h, and at 20 h, TNF-alpha levels reached 6.4 +/- 1.1 ng/ml, compared to 0.08 +/- 0.01 ng/ml for control cultures (P < 0.01). A concentration-dependent increase in IL-8 and TNF-alpha secretion was observed at 20 h with 0.2 to 5 microg of MSG/ml (P < 0.01). Secretion of IL-8 and TNF-alpha from MSG-stimulated monocytes at 20 h was inhibited by 60 and 86%, respectively, after coincubation with soluble yeast mannan (P = 0.01). With an RNase protection assay, increases in steady-state mRNA levels for IL-8 and TNF-alpha were detectable at 4 h. These data show that recognition of MSG by monocytes involves a mannose-mediated mechanism and results in the release of the proinflammatory cytokines IL-8 and TNF-alpha.

Antisense inhibition of 85-kDa cPLA2 blocks arachidonic acid release from airway epithelial cells

Inflammatory cytokines play a critical role in the initiation and perpetuation of inflammation. Several cytokines are known to increase the production of arachidonic acid (AA) metabolites, which may mediate cytokine-induced acute and chronic inflammation. Although cytokines upregulate phospholipase A2 (PLA2) in several target cells, the contribution of individual PLA2 to cytokine-induced AA release and eicosanoid production remains unclear because of the existence of various forms of cellular PLA2. To examine the role of 85-kDa cytosolic PLA2 (cPLA2) in cytokine-induced AA release, a system was developed to inhibit the expression of cPLA2 in a human bronchial epithelial cell line (BEAS-2B cells) by antisense RNA. Cells stably expressing antisense cPLA2 exhibited decreased cPLA2 protein levels as well as decreased cPLA2 activity assayed in vitro. The effects of cytokines interferon-gamma (IFN-gamma), tumor necrosis factor-alpha (TNF-alpha), and interleukin-1 alpha (IL-1 alpha) on the release of prelabeled [3H]AA were then tested in cells stably transfected with vector alone as well as cells transfected with cPLA2 antisense plasmid. IFN-gamma (300 U/ml), TNF-alpha (20 ng/ml), and IL-1 alpha (20 ng/ml) all induced a significantly increased release of prelabeled [3H]AA after 15 min to 2 h of treatment in control cells, and their effects were significantly reduced in cells transfected with cPLA2 antisense vector. These results demonstrate a critical role of cPLA2 in inflammatory cytokine-induced AA metabolism.

P11, a unique member of the S100 family of calcium-binding proteins, interacts with and inhibits the activity of the 85-kDa cytosolic phospholipase A2

Using a two hybrid system screen of a human cDNA library, we have found that p11, a unique member of the S100 family of calcium-binding proteins, interacts with the carboxyl region of the 85-kDa cytosolic phospholipase A2 (cPLA2). p11 synthesized in a cell-free system interacts with cPLA2 in vitro. The p11-cPLA2 complex is detectable from a human bronchial epithelial cell line (BEAS 2B). Furthermore, p11 inhibits cPLA2 activity in vitro. Selective inhibition of p11 expression in the BEAS 2B cells by antisense RNA results in an increased PLA2 activity as well as an increased release of prelabeled arachidonic acid. This study demonstrates a novel mechanism for the regulation of cPLA2 by an S100 protein.

Acute respiratory failure in the HIV-seropositive patient

Since approximately 40% to 65% of patients with AIDS will develop pulmonary disease, HIV-seropositive patients represent a large cohort of immunosuppressed individuals with the potential to progress to respiratory failure requiring mechanical ventilation and admission to the intensive care unit. This article reviews the cause, pathophysiology, diagnostic approach, and management of acute respiratory failure requiring mechanical ventilation in HIV-seropositive patients. Prognostic factors and survival rates for episodes of respiratory failure are also discussed. In addition, an overview of acute respiratory failure in pediatric AIDS patients is presented.

Extracellular release of the type I intracellular IL-1 receptor antagonist from human airway epithelial cells: differential effects of IL-4, IL-13, IFN-gamma, and corticosteroids

Three IL-1R antagonists (IL-1Ra) exist: secreted IL-1Ra and intracellular IL-1Ra (icIL-1Ra) types I and II. We have previously reported that human airway epithelial cells (HAEC) express icIL-1Ra type I, which can be up-regulated by corticosteroids. This study assessed whether cytokines and corticosteroids differentially effect icIL-1Ra type I protein release from HAEC to the extracellular compartment. We report that icIL-1Ra type I mRNA and intracellular protein are up-regulated in NCI-H292 cells, a human pulmonary mucoepidermoid carcinoma cell line, in response to IL-4, IL-13, IFN-gamma, and dexamethasone. The icIL-1Ra type I protein was detected in concentrated cell culture supernatants from NCI-H292 cells and normal human bronchial epithelial cells. The release of biologically relevant concentrations of active IL-1Ra from normal human bronchial epithelial cells was demonstrated by the ability of a neutralizing anti-IL-1Ra Ab to augment IL-1beta-mediated IL-8 secretion. IL-4, IL-13, and IFN-gamma induced immunoreactive IL-1Ra release into supernatants from NCI-H292 cells. Dexamethasone inhibited constitutive and cytokine-induced release of immunoreactive IL-1Ra. The release of icIL-1Ra type I protein was not related to cytotoxicity, as measured by lactate dehydrogenase. We propose that icIL-1Ra type I release from HAEC represents a novel mechanism by which IL-1 bioactivity in the airway microenvironment may be modulated. Cytokine-mediated icIL-1Ra type I synthesis may increase both intracellular protein and release to the extracellular space, where cell surface IL-1R can be antagonized. In contrast, corticosteroid-induced increases in icIL-1Ra type I synthesis and inhibition of extracellular protein release promote accumulation of icIL-1Ra type I protein within the intracellular compartment.

Extracellular release of the type I intracellular IL-1 receptor antagonist from human airway epithelial cells: differential effects of IL-4, IL-13, IFN-gamma, and corticosteroids

Three IL-1R antagonists (IL-1Ra) exist: secreted IL-1Ra and intracellular IL-1Ra (icIL-1Ra) types I and II. We have previously reported that human airway epithelial cells (HAEC) express icIL-1Ra type I, which can be up-regulated by corticosteroids. This study assessed whether cytokines and corticosteroids differentially effect icIL-1Ra type I protein release from HAEC to the extracellular compartment. We report that icIL-1Ra type I mRNA and intracellular protein are up-regulated in NCI-H292 cells, a human pulmonary mucoepidermoid carcinoma cell line, in response to IL-4, IL-13, IFN-gamma, and dexamethasone. The icIL-1Ra type I protein was detected in concentrated cell culture supernatants from NCI-H292 cells and normal human bronchial epithelial cells. The release of biologically relevant concentrations of active IL-1Ra from normal human bronchial epithelial cells was demonstrated by the ability of a neutralizing anti-IL-1Ra Ab to augment IL-1beta-mediated IL-8 secretion. IL-4, IL-13, and IFN-gamma induced immunoreactive IL-1Ra release into supernatants from NCI-H292 cells. Dexamethasone inhibited constitutive and cytokine-induced release of immunoreactive IL-1Ra. The release of icIL-1Ra type I protein was not related to cytotoxicity, as measured by lactate dehydrogenase. We propose that icIL-1Ra type I release from HAEC represents a novel mechanism by which IL-1 bioactivity in the airway microenvironment may be modulated. Cytokine-mediated icIL-1Ra type I synthesis may increase both intracellular protein and release to the extracellular space, where cell surface IL-1R can be antagonized. In contrast, corticosteroid-induced increases in icIL-1Ra type I synthesis and inhibition of extracellular protein release promote accumulation of icIL-1Ra type I protein within the intracellular compartment.

Lack of clinical utility of bronchoalveolar lavage cultures for cytomegalovirus in HIV infection

This study assessed the presence of cytomegalovirus (CMV) in bronchoalveolar lavage (BAL) in three subpopulations of HIV-infected patients and correlated its presence with clinical status during 3 mo of follow-up. Nineteen asymptomatic volunteers, six patients with CMV retinitis, and 46 patients with acute pulmonary symptoms underwent BAL and were assessed for CMV by cytopathology, conventional shell vial cultures, and antigen detection. Transbronchial biopsies were also obtained when possible and evaluated for histopathologic changes of CMV. All patients were followed for approximately 3 mo. Cytomegalovirus was detected in BAL in nine of 19 (47%) asymptomatic volunteers, in all six patients with CMV retinitis, and in 33 of 46 (72%) patients with pulmonary symptoms. Only one symptomatic patient with a positive CMV BAL culture developed clinically significant CMV pulmonary disease; this patient developed disseminated CMV and died. The only other death occurred in a patient with CMV retinitis who developed staphylococcal bacteremia. None of the asymptomatic volunteers or patients with CMV retinitis developed evidence of CMV pneumonia or any other organ disease with CMV. Cytomegalovirus is frequently detected in BAL from HIV-infected patients regardless of their pulmonary symptoms and its presence does not clinically predict significant pulmonary morbidity or mortality in 3 mo of follow-up.

Vasoactive intestinal peptide (VIP) induces IL-6 and IL-8, but not G-CSF and GM-CSF release from a human bronchial epithelial cell line

Vasoactive intestinal polypeptide (VIP) is a 28-amino acid neuropeptide with vasodilator, bronchodilator, and anti-inflammatory effects. Little is known about pro-inflammatory effects of VIP. We investigated the effect of VIP on the secretion of IL-6, IL-8, GM-CSF, and G-CSF from a bronchial epithelial cell line (BEAS 2B). The incubation of BEAS-2B cells with VIP in concentrations of 10(-13) to 10(-7) M for 4 h, caused dose-related increases of IL-6 (98% increase above control, P < 0.001) and IL-8 (35% increase above control, P < 0.01). After 4 h of incubation, 10(-7) M PHI also increased IL-6 release by 74% (P < 0.01). After 8 h of incubation, VIP increased IL-6 release by 59% (P < 0.01), causing no effect on IL-8 release. After 24 h of incubation, VIP increased the release of IL-6 by 48% (P < 0.05) and IL-8 by 45% (P < 0.05). Ribonuclease protection assays for steady-state IL-6 mRNA revealed that increases in response to VIP stimulation occurred by 1 h and persisted through 16 h of stimulation. VIP had no significant effect on the release of G-CSF and GM-CSF. VIP did not induce cell proliferation at 24 and 48 h. These findings suggest that VIP can alter epithelial cell cytokine release and might be capable of modulating the airway inflammatory response in this manner.

Leukemia inhibitory factor induces the 85-kDa cytosolic phospholipase A2 gene expression in cultured human bronchial epithelial cells

Leukemia inhibitory factor (LIF) has become increasingly recognized as an important regulator of inflammation. This study is designed to determine whether LIF has an effect on arachidonate metabolism in human airway epithelial cells. LIF (100 ng/ml) induced a significantly increased release of prelabeled [3H] arachidonic acid (AA) from the human bronchial epithelial cell line (BEAS 2B cell) as well as from the primary cultures of human bronchial epithelial cells. Exposure of the LIF stimulated BEAS 2B cells to calcium ionophore A23187 (10(-5) M, 15 min) caused a further increase of [3H]AA release. To identify the role of cytosolic phospholipase A2 (cPLA2) in this upregulation of AA release, further experiments were performed to determine the expression of cPLA2 in the BEAS 2B cells. Immunoblot analysis indicated that LIF increased cPLA2 protein expression. Ribonuclease protection assay showed that LIF induced an increase of cPLA2 mRNA levels following 3 h to 24 h treatment. Nuclear run-on experiments suggested that LIF upregulated cPLA2 gene expression through post-translational regulation. These results demonstrate that LIF induces cPLA2 gene expression and modulates arachidonate metabolism in airway epithelial cells.

Endothelin-1 induces GM-CSF, IL-6 and IL-8 but not G-CSF release from a human bronchial epithelial cell line (BEAS-2B)

Endothelin (ET) is a powerful vasoconstrictor and bronchoconstrictor peptide that may be involved in the pathogenesis of bronchial asthma. We have investigated the effect of ET on the secretion of IL-6, IL-8, GM-CSF and G-CSF in a bronchial epithelial cell line (BEAS-2B). Incubation of BEAS-2B cells with ET-1 (10(-13) to 10(-7) M) for 4 h caused dose-related increases in the release of IL-8 (68% increase above control, P < 0.001) and IL-6 (43% increase above control, P < 0.001), compared to untreated control cells. After 48 h incubation, ET-1 also increased the release of IL-8 by 35% (P < 0.001) and GM-CSF by 38% (P < 0.01). ET-1 had no significant effect on G-CSF release. ET-1 did not induce cell proliferation at 24 or 48 h. Since ET-immunoreactive materials are expressed in epithelial cells in asthma, it is possible that ET-1 of epithelial origin may act in a paracrine or autocrine fashion on airway epithelial ET receptors to stimulate IL-8, IL-N6 and GM-CSF release. Thus, ET-1 may play a role in the regulation of the cytokine responses involved in inflammation of the airway mucosa.

Virtual bronchoscopy: segmentation method for real-time display

Computed tomography (CT) data sets obtained in 14 patients were used in a segmentation method for virtual bronchoscopy (VB). The method constrained the distance of propagation of a region-growing algorithm. The resulting three-dimensional bronchial model was a faithful representation of the source CT data and could be manipulated in real time at frame rates of one to two frames per second. Preliminary data showed that 90% of bronchi (up to third order) measureable on multiplanar CT reformations were also measurable at VB. The bronchial diameters measured at VB were within 1 mm of those measured on multi-planar reconstructions of the CT data.

Corticosteroids induce intracellular interleukin-1 receptor antagonist type I expression by a human airway epithelial cell line

Interleukin-1 (IL-1) is an important proinflammatory cytokine which may contribute to the pathogenesis of inflammatory airway disorders, such as asthma and cystic fibrosis. Interleukin-1 receptor antagonist (IL-1ra) is a naturally occurring IL-1 inhibitor which binds to IL-1 receptors without inducing agonist activity. Three IL-1ra isoforms have been identified: secreted IL-1ra (sIL-1ra), which is preferentially expressed by-inflammatory cells; intracellular IL-1ra (iIL-1ra) type I, which lacks a signal peptide and is preferentially expressed by epithelial cells; and iIL-1ra type II, which is identical to iIL-1ra type I except for the insertion of an additional 21 amino acids. The goal of this study was to assess whether airway epithelial cell iIL-1ra type I production can be regulated by corticosteroids. First, using reverse transcription-polymerase chain reaction (RT-PCR) and immunoblotting, we confirm that normal human bronchial epithelial (NHBE) cells and a human pulmonary mucoepidermoid carcinoma cell line (NCI-H292) express intracellular IL-1ra type I messenger RNA (mRNA) and protein. Second, using immunoblotting and ELISA, we report that dexamethasone induces time- and concentration-dependent increases in iIL-1ra type I protein within NCI-H292 cell lysates. Lastly, utilizing a ribonuclease protection assay, we report that dexamethasone induces concentration-dependent increases in iIL-1ra type I mRNA levels in NCI-H292 cells. These data suggest that corticosteroid-mediated induction of iIL-1ra type I mRNA and protein by human bronchial epithelial cells represents a novel mechanism by which IL-1-mediated airway inflammatory events might be regulated.

Pulmonary infiltrates in the cancer patient. New approaches to an old problem

A variety of etiologies may produce pulmonary infiltrates in a patient with cancer. Infectious etiologies, of an ever-increasing number, are always of paramount concern due to their high mortality in this patient population. Patients may be rendered immunosuppressed for prolonged periods of time and therefore are highly susceptible to infection. We present an overview of the many causes of pulmonary infiltrates in the cancer patient and an approach to diagnosis and treatment.

The laboratory evaluation of opportunistic pulmonary infections

The patient population at risk for opportunistic pulmonary infections has increased during the last decade. The spectrum of organisms causing opportunistic infections has also grown. With an ever broader list of potential diagnosis, a specific diagnosis of the cause of pulmonary disease becomes more important. Recent microbiologic advances have helped to facilitate the laboratory diagnosis of some of these agents. Immunoassays are available for the detection of antigen in nasopharyngeal secretions (respiratory syncytial virus, influenza) in serum (Cryptococcus species), and in urine (Legionella or Histoplasma species). Rapid-culture techniques are available for the culture and detection of various viruses, including cytomegalovirus. Molecular probes can now assist in the rapid identification of Mycobacterium tuberculosis and some fungi. In the near future, polymerase chain reaction-based techniques may assist in the detection of Pneumocystis carinii and Legionella, Chlamydia, Mycoplasma, and Mycobacteria species. An expeditious evaluation of pulmonary disease requires an understanding of the differential diagnosis of likely causes of pulmonary disease in specific immunosuppressed patient populations, an understanding of the most appropriate specimens to process for these diagnoses, and an understanding of the limitations (sensitivity and specificity) of these diagnostic tests. An understanding of the most appropriate specimens and tests in a given institution should allow for early, relatively specific treatment of many potentially life-threatening infections.

Protein kinase C, interleukin-1 beta, and corticosteroids regulate shedding of the type I, 55 kDa TNF receptor from human airway epithelial cells

Tumor necrosis factor (TNF) may contribute to the pathogenesis of inflammatory airway disorders via the regulation of inflammatory and cellular immune responses. Shed cell surface TNF receptors can act as soluble TNF binding proteins and modulate TNF biological activity. We report that normal human airway epithelial cells, as well as two human airway epithelial cell lines, shed soluble type I TNF receptors (sTNF-RI) in a concentration-dependent fashion following protein kinase C (PKC) activation by PMA. Interleukin (IL)-1beta also induced concentration-dependent sTNF-RI shedding from NCI-H292 cells, which could be inhibited by the PKC inhibitor calphostin C. Since corticosteroids are commonly utilized as antiinflammatory agents in airway disorders, the effect of dexamethasone on sTNF-RI release was assessed. Dexamethasone inhibited constitutive, as well as PMA- and IL-1beta-mediated sTNF-RI release from NCI-H292 cells in a concentration-dependent fashion. Furthermore, dexamethasone increased while PMA decreased total cellular 55 kDa TNF-RI protein as detected by immunoblotting. These changes in total cellular 55kDa TNF-RI protein did not appear to be mediated at the mRNA level, as assessed by ribonuclease protection assays. This suggests that sTNF-RI shedding represents a mechanism by which airway epithelial cells can actively participate in local cytokine networks and modulate TNF-mediated inflammation. Furthermore, since corticosteroids inhibit sTNF-RI release and are known to downregulate TNF synthesis, this may represent a mechanism by which equilibrium between TNF ligand and soluble binding protein is maintained in the airway microenvironment.

Tumor necrosis factor-alpha induces the 85-kDa cytosolic phospholipase A2 gene expression in human bronchial epithelial cells

Phospholipase A2 (PLA2) activity has been suggested to mediate some of the tumor necrosis factor (TNF) induced cellular responses including cytotoxicity. We evaluated the induction of both the 85-kDa cytosolic phospholipase A2 (cPLA2) and non-pancreatic group II PLA2 gene expression by TNF-alpha in a human bronchial epithelial cell line (BEAS 2B cell). TNF-alpha (20 ng/ml) induced a significantly increased release of prelabeled [3H]arachidonic acid (AA) following 4-24 h incubation. Calcium ionophore A23187 (10(-5) M) further increased the [3H]AA release from the TNF-alpha-treated cells. In vitro activity assay revealed that TNF-alpha increased the dithiothreitol (DTT)-resistant PLA2 activity which was blocked by the cPLA2 inhibitor AACOCF3. Treatment with TNF-alpha for 4-24 h increased the cPLA2 protein and mRNA levels which were blocked by the broad inhibitor of protein kinases staurosporine, the protein kinase C (PKC) inhibitor calphostin C, and to a lesser extent the calcium/calmodulin-dependent protein kinase inhibitor W-7. Reverse transcription and polymerase chain reaction amplification of the group II PLA2 mRNA showed that it is expressed in human lung but not in the bronchial epithelial cell line. TNF-alpha failed to induce the expression of group II PLA2 in the BEAS 2B cells. These results demonstrate that the cPLA2 gene expression is up-regulated by TNF-alpha and this effect may contribute to the TNF-alpha stimulated AA release in airway epithelial cells.

NIH conference. Airway inflammation

Diseases characterized by airway inflammation, excessive airway secretion, and airway obstruction affect a substantial proportion of the population. These diseases include asthma, chronic bronchitis, bronchiectasis, and cystic fibrosis. Asthma and chronic bronchitis may affect 25 million persons in the United States. Much progress has been made in the last decade toward an understanding of the mechanisms underlying chronic airway inflammation; recent work has resulted in several new concepts of the initiation and maintenance of airway inflammation. Airway production of chemokines, cytokines, and growth factors in response to irritants, infectious agents, and inflammatory mediators may play an important role in the modulation of acute and chronic airway inflammation. Lipid mediators may be produced by resident airway cells and by inflammatory cells; production of these mediators may also be altered by inflammatory cytokines. Increased airway obstruction may be related to intercurrent viral respiratory infection and to the induction of airway inflammation and airway hyperreactivity that results from such infection. Furthermore, several models exist to explain the processes by which airway inflammation is perpetuated in diseases such as asthma and chronic bronchitis. These include neurogenic inflammation, the perpetuation of the acute inflammatory response, and cycles of airway epithelial cell-mediated and inflammatory cell-mediated recruitment and activation of inflammatory cells. An understanding of these mechanisms of airway inflammation may provide the clinician with new therapeutic approaches to the treatment of these common and chronic diseases.

Interleukin-8 and eicosanoid production in the lung during moderate to severe Pneumocystis carinii pneumonia in AIDS: a role of interleukin-8 in the pathogenesis of P. carinii pneumonia

Pneumocystis carinii pneumonia (PCP) may cause severe respiratory distress. This is believed to be partly caused by the accumulation of neutrophils in the lung. Interleukin-8 (IL-8) and leukotriene B4 (LTB4) are potent neutrophil chemo-attractants and activators. Eicosanoids [i.e. prostaglandins (PG) and leukotrienes (LT)] are pro-inflammatory mediators released from arachidonic acid by action of phospholipase A2 (PLA2) and have been implicated in the host response to micro-organisms. Bronchoalveolar lavage (BAL) was performed on patients with PCP as part of a randomized study of adjuvant corticosteroids vs. placebo, in addition to standard antimicrobial therapy. Re-bronchoscopy was offered at day 10. BAL fluid was available for 26 patients who had follow-up bronchoscopy performed. At diagnosis, IL-8 levels were elevated in patients with PCP, compared to healthy controls, and correlated with relative BAL neutrophilia and P(A-a)O2. LTB4 was also elevated in PCP, but failed to correlate with either BAL neutrophilia or P(A-a)O2. PLA2 activity in patients correlated with IL-8 levels and BAL neutrophilia, but not with P(A-a)O2. A trend towards a decrease in IL-8 levels in BAL fluid was detected in the corticosteroid-treated patients from days 0-10, whereas no change was detected in the placebo group. No change in levels of LTB4, LTC4, PGE2, PGF2a and PLA2 were detected cover time in either treatment group. This study establishes a correlation between IL-8, BAL neutrophilia and P(A-a)O2, and suggests a role of IL-8 as a mediator in the pathogenesis of PCP, whereas the role of eicosanoids seems less clear.

Pneumocystis carinii pneumonia: a major complication of immunosuppressive therapy in patients with Wegener's granulomatosis

The risk factors and clinical and laboratory parameters in Pneumocystis carinii pneumonia in patients with Wegener's granulomatosis have not been well characterized. We undertook a retrospective chart review of all patients with a diagnosis of Wegener's granulomatosis and P. carinii pneumonia who were followed at the National Institute of Allergy and Infectious Diseases of the National Institutes of Health. The chart review focused on clinical, laboratory, and roentgenologic evidence of P. carinii pneumonia. Eleven cases of P. carinii pneumonia were diagnosed in some 180 patients with Wegener's granulomatosis, for an overall incidence of approximately 6%. All patients developed P. carinii pneumonia either during the initial course of treatment or during therapy for recurrent Wegener's granulomatosis. All patients were receiving daily glucocorticoids and a second immunosuppressive therapy. Lymphocytopenia was noted in all patients, with a mean +/- SEM total lymphocyte count of 303 +/- 69 cells/microL. All patients tested (10 of 11) were seronegative for human immunodeficiency virus (HIV) infection. Eight presented with worsening chest roentgenograms compared with baseline, whereas three presented with normal chest roentgenograms. We conclude that P. carinii is a common opportunistic pathogen in patients with Wegener's granulomatosis receiving immunosuppressive therapy. Therapeutic immunosuppression (daily glucocorticoids and immunosuppressive agents) and the resultant lymphocytopenia, as well as the lymphocyte and monocyte functional abnormalities caused by glucocorticoids, may be the most likely factors predisposing to P. carinii pneumonia in patients with Wegener's granulomatosis. Based on our data, all patients with Wegener's granulomatosis should be given chemoprophylaxis against P. carinii while they are receiving daily glucocorticoids.(ABSTRACT TRUNCATED AT 250 WORDS)

Platelet-activating factor stimulates eicosanoid production in cultured feline tracheal epithelial cells

The effect of platelet-activating factor (PAF) on eicosanoid generation and release in cultured feline tracheal epithelial cells was investigated by measuring a wide range of lipoxygenase and cyclooxygenase pathway products. Subconfluent epithelial cell cultures were stimulated by PAF and eicosanoid production was determined by high performance liquid chromatography (HPLC) of [3H]-labeled arachidonic acid (AA) metabolites and by radioimmunoassay (RIA) following HPLC separation. The HPLC chromatograms revealed that PAF augmented the release of prostaglandin (PG)E2, PGF2 alpha, 12-hydroxyeicosatetraenoic acid (HETE), and AA. Among these eicosanoids, PGE2 predominated under baseline conditions and following PAF exposure. RIAs of the nonradiolabeled HPLC elution corresponding to various eicosanoid standards demonstrated that PAF increased the production of 6-keto-PGF1 alpha, thromboxane B2 (TXB2), PGD2, 5-HETE, and 15-HETE, as well as PGE2, PGF2 alpha, and 12-HETE. The PAF-induced eicosanoid augmentation was dose-dependent and occurred within 1 hour with a prompt decline following termination of PAF exposure. This stimulating effect of PAF on eicosanoid release was blocked by two PAF receptor antagonists, Ro 19-3704 and WEB 2086. The PAF-induced increase in eicosanoid release was similar in magnitude to the increase caused by calcium ionophore (Ca-ionophore) A23187, a potent known stimulus for eicosanoid release. Cells of different culture durations (3 and 6 days) showed similar capacity for eicosanoid production. We conclude that PAF stimulates the production of cyclooxygenase and lipoxygenase pathway products from airway epithelial cells via PAF receptors, and that these epithelium-derived eicosanoids may be responsible for some of the PAF-induced respiratory physiological and pathophysiological effects.

Tumor necrosis factor-alpha induces mucin hypersecretion and MUC-2 gene expression by human airway epithelial cells

Tumor necrosis factor-alpha (TNF-alpha) is a multifunctional, proinflammatory cytokine that is capable of activating a diverse number of target genes within multiple cell types. Little information is known regarding the role of TNF-alpha in the regulation of human airway mucin hypersecretion and MUC-2 gene expression. To assess the effect of TNF-alpha exposure on mucin secretion, human airway organ cultures and primary cultures of human airway epithelial cells were stimulated with 20 ng/ml of recombinant human TNF-alpha and mucin secretion quantitated by an enzyme-linked immunosorbent assay using a specific monoclonal antibody directed against human airway mucin. Significant increases in mucin secretion from human airway organ cultures were initially detected at 1 h, peaked at 8 h, and persisted for 24 h. The TNF-alpha-mediated mucin hypersecretion at 8 h was concentration dependent. Significant increases in mucin secretion from primary cultures of human airway epithelial cells were initially detected at 4 h, peaked at 48 h, and persisted for 72 h after stimulation with 20 ng/ml of recombinant human TNF-alpha. The TNF-alpha-mediated mucin hypersecretion at 48 h from primary cultures of human airway epithelial cells was inhibited by coincubation with soluble 55 kD, type I TNF receptors. Using reverse transcription-polymerase chain reaction and a human pulmonary mucoepidermoid carcinoma cell line (NCI-H292), increases in MUC-2 steady-state mRNA levels were first detectable after 30 min of TNF-alpha stimulation and persisted for 24 h. Cycloheximide did not inhibit TNF-alpha-mediated MUC-2 mRNA expression at 1 h, suggesting that new protein translation was not required.(ABSTRACT TRUNCATED AT 250 WORDS)

Eicosanoid production by human aortic endothelial cells in response to endothelin

Endothelial cells actively regulate their environment by secreting humoral substances, including endothelin-1 and a variety of eicosanoids, that have local actions. To elucidate interactions among these local mediators, we measured release of cyclooxygenase and lipoxygenase pathway products of arachidonate metabolism by human aortic endothelial cells after incubation with endothelin-1. Supernatants were collected, extracted, and fractionated using high-performance liquid chromatography. Radioimmunoassays for eicosanoids were performed on the appropriate fractions. After endothelin stimulation, production of the prostacyclin metabolite 6-ketoprostaglandin F1 alpha (6-keto-PGF1 alpha), the thromboxane (Tx) metabolite TxB2, and prostaglandin E2 (PGE2) were increased (307 +/- 48, 320 +/- 91, and 315 +/- 74% of control, P < 0.05). Leukotriene B4 (LTB4) release was modestly increased (195 +/- 19% of control, P < 0.05). The release of 5-hydroxyeicosatetraenoic acid (5-HETE) was increased (300 +/- 57% of control, P < 0.05); production of 12-HETE and 15-HETE was unchanged. Production of eicosanoids peaked between 30 and 120 min. Preincubation with pertussis toxin prevented increased production of PGE2, LTB4, and 5-HETE after endothelin-1 stimulation; pretreatment with sphingosine had no effect. Interactions between endothelin and eicosanoids may be important components of the complex network that regulates vascular tone, coagulation, and inflammation at the local level.

Characterization of the promoter for the human 85 kDa cytosolic phospholipase A2 gene

The 85 kDa cytosolic phospholipase A2 (cPLA2) plays a key role in the production of arachidonic acid and lysophospholipids, the precursors of eicosanoids and platelet-activating factor. Here we report the cloning of the promoter of the human cPLA2 gene. A 5.7 kb EcoRI fragment containing the most 5' region of the cPLA2 cDNA was sequenced. The transcription initiation site was identified by rapid amplification of 5'-cDNA ends (5'-RACE) and primer extension analysis. DNA sequence analysis of the 595 base pairs 5' of the transcription start site reveals a 48 base purine-pyrimidine dinucleotide repeat (CA repeat), five interferon-gamma response elements (gamma-IRE), one interferon-gamma activated sequence (GAS) and two glucocorticoid response elements (GRE). The promoter lacks a TATA box. It contains a possible CAAT box at -111 and two octamer binding motifs. The 595 base fragment located immediately upstream of the transcriptional start site exhibited functional promoter activity in transient transfection assays in a bronchial epithelial cell line (BEAS 2B cells). Deletion analysis revealed that the CA repeat may confer an inhibitory effect on the cPLA2 promoter activity. The characterization of the human cPLA2 promoter sequence will allow further studies defining the molecular events regulating the expression of the cPLA2 enzyme, especially the cytokine mediated cPLA2 gene expression.

Platelet-activating factor induces airway mucin release via activation of protein kinase C: evidence for translocation of protein kinase C to membranes

Platelet-activating factor (PAF), a proinflammatory lipid mediator, is a potent airway mucin secretagogue. This study assessed the role of protein kinase C (PKC) in PAF-induced mucin release from primary cultures of feline tracheal epithelial cells (FTEC). Mucin secretion was quantitated by enzyme-linked immunosorbent assay using a monoclonal antibody raised against airway mucin-type glycoproteins. Coincubation of FTEC with PAF (5 microM) and pharmacologic PKC inhibitors, sphingosine, H7, or calphostin C, inhibited PAF-induced mucin secretion at 30 min. The PKC inhibitors produced a concentration-dependent, noncytotoxic inhibition. Exposure of FTEC with the PKC activator phorbol 12-myristate 13-acetate (PMA), failed to increase the release of mucin. Stimulation of FTEC with PAF caused a transient increase of membrane-bound PKC activity after 5 min of stimulation. PMA also induced the translocation of PKC activity from the cytosol to the membrane fraction, which was still present after 15 min of exposure. Determination of the specific PKC isozyme(s) involved in PAF-induced mucin release was performed by immunoblot analysis of the subcellular fractions using a battery of antibodies against various PKC isozymes (anti-PKC alpha, beta, delta, gamma, epsilon, and zeta). We found that PKC zeta (mol wt approximately 70 kD) was a major identifiable PKC isozyme present in the cytosolic fraction of FTEC. Furthermore, PKC zeta isozyme was also found to translocate to the membrane fraction following PAF exposure. Thus, these results demonstrate the crucial role of PKC in the intracellular events that culminate in mucin release following PAF stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of neutrophil protenase enzymes on the release of mucus from feline and human airway cultures

Neutrophils may be central in the pathogenesis of several airway diseases. The effect of two neutrophil products upon mucus release from feline and human airways was examined in vitro. Neutrophil elastase (HNE) and cathepsin G (HCG) were equipotent in stimulating mucus release from feline trachea. A potential mechanism of the mucus release was studied by exposure to HNE and various inhibitors of serine proteases or eicosanoid metabolism. Coincubation with the serine protease inhibitor, chloromethylketone, completely blocked HNE-stimulated mucus release. The putative selective cyclooxygenase inhibitor, ibuprofen, did not alter HNE-stimulated mucus release. The phospholipase A2 inhibitor, bromophenacyl bromide, and various lipoxygenase inhibitors blocked HNE-stimulated mucus release by 30-40%. The effect of HNE upon mucus release from human upper and lower airways was also examined. HNE stimulated greater mucus release from human bronchi than from nasal mucosa. The cellular source of the mucus was investigated in feline trachea and human upper airway by quantitation of mucus using enzyme assays for a specific mucous cell marker (monoclonal antibody 7F-10). HNE stimulated the release of 7F-10 detectable mucus, and after coincubation with chloromethylketone this stimulation was blocked. These data demonstrate that neutrophil products may alter airway mucus secretion and that altered eicosanoid metabolism may partially mediate these effects. Additionally, the lower airways appear more responsive to HNE than upper airways.

Interferon-gamma induces the synthesis and activation of cytosolic phospholipase A2

Both IFN-alpha/beta and IFN-gamma have recently been demonstrated to induce a rapid but transient activation of phospholipase A2 (PLA2) in BALB/c 3T3 fibroblasts and a human neuroblastoma cell line. We report that IFN-gamma induces the synthesis and prolonged activation of cytosolic phospholipase A2 (cPLA2) in a human bronchial epithelial cell line (BEAS 2B). Treatment of the cells with IFN-gamma (300 U/ml) increased the release of [3H]arachidonic acid (AA) from prelabeled cells with a maximal effect at 12 h after stimulation. The increased [3H]AA release was inhibited by the PLA2 inhibitor p-bromophenacyl bromide (10(-5) M). Calcium ionophore A23187 (10(-5) M) further increased the [3H]AA release from the IFN-gamma-treated cells. Subcellular enzyme activity assay revealed that IFN-gamma increased PLA2 activity in both the cytosol and membrane fractions with a translocation of the cPLA2 to cell membranes in a Ca(2+)-free cell lysing buffer. Treatment with IFN-gamma also induced the release of 15-HETE, an arachidonic acid metabolite. Immunoblot showed that IFN-gamma induced the synthesis of cPLA2 protein. Nuclear run-on assay demonstrated that IFN-gamma initiated cPLA2 gene transcription within 15 min, and this effect was sustained at 4 h and returned to near control level at 12 h. The cPLA2 mRNA level was assayed by reverse transcription and PCR. IFN-gamma was found to increase the cPLA2 mRNA after 2-24 h treatment. Furthermore, the IFN-gamma induced cPLA2 mRNA increase was blocked by inhibitors of protein kinase C and calcium/calmodulin-dependent protein kinases, suggesting the involvement of these protein kinases in IFN-gamma-induced gene expression of cPLA2. This study shows that IFN-gamma induces the synthesis and prolonged activation of cPLA2.

Severe Pneumocystis carinii pneumonia produces a hyperdynamic profile similar to bacterial pneumonia with sepsis

OBJECTIVES

To investigate the effects of Pneumocystis carinii on the cardiovascular system. To compare the hemodynamic data from patients with P. carinii pneumonia with those data from patients with bacterial pneumonia with sepsis.

DESIGN

Retrospective, descriptive study of prospectively gathered hemodynamic and clinical data.

SETTING

Tertiary referral hospital, medical intensive care unit.

PATIENTS

Forty-one consecutive patients with severe P. carinii pneumonia and 31 patients with bacterial pneumonia who had invasive hemodynamic monitoring for management of hypotension and/or hypoxemia.

MEASUREMENTS AND MAIN RESULTS

On initial presentation, both groups had a hyperdynamic hemodynamic profile that included tachycardia, an increased cardiac index, and a low systemic vascular resistance index. The mean heart rate of the P. carinii pneumonia patients (113 +/- 3 beats/min) was significantly lower than that of the patients with bacterial pneumonia (126 +/- 4 beats/min). The cardiac index, systemic vascular resistance index, pulmonary vascular resistance index, and pulmonary artery pressures did not differ significantly between the two groups. The patients with bacterial pneumonia had a significantly lower mean left ventricular stroke volume index and stroke work index than the patients with P. carinii pneumonia.

CONCLUSION

P. carinii can produce a hyperdynamic hemodynamic profile similar to that seen in patients with bacterial pneumonia with sepsis.