The role of cyclooxygenase products in lung injury induced by tumor necrosis factor in sheep

Cervical spinal cord injury leads to injury and altered metabolism in the lungs

High-cervical spinal cord injury often disrupts respiratory motor pathways and disables breathing in the affected population. Moreover, cervically injured individuals are at risk for developing acute lung injury, which predicts substantial mortality rates. While the correlation between acute lung injury and spinal cord injury has been found in the clinical setting, the field lacks an animal model to interrogate the fundamental biology of this relationship. To begin to address this gap in knowledge, we performed an experimental cervical spinal cord injury (N = 18) alongside sham injury (N = 3) and naïve animals (N = 15) to assess lung injury in adult rats. We demonstrate that animals display some early signs of lung injury two weeks post-spinal cord injury. While no obvious histological signs of injury were observed, the spinal cord injured cohort displayed significant signs of metabolic dysregulation in multiple pathways that include amino acid metabolism, lipid metabolism, and N-linked glycosylation. Collectively, we establish for the first time a model of lung injury after spinal cord injury at an acute time point that can be used to monitor the progression of lung damage, as well as identify potential targets to ameliorate acute lung injury.

Inhalationally Administered Semifluorinated Alkanes (SFAs) as Drug Carriers in an Experimental Model of Acute Respiratory Distress Syndrome

Aerosol therapy in patients suffering from acute respiratory distress syndrome (ARDS) has so far failed in improving patients' outcomes. This might be because dependent lung areas cannot be reached by conventional aerosols. Due to their physicochemical properties, semifluorinated alkanes (SFAs) could address this problem. After induction of ARDS, 26 pigs were randomized into three groups: (1) control (Sham), (2) perfluorohexyloctane (F6H8), and (3) F6H8-ibuprofen. Using a nebulization catheter, (2) received 1 mL/kg F6H8 while (3) received 1 mL/kg F6H8 with 6 mg/mL ibuprofen. Ibuprofen plasma and lung tissue concentration, bronchoalveolar lavage (BAL) fluid concentration of TNF-α, IL-8, and IL-6, and lung mechanics were measured. The ibuprofen concentration was equally distributed to the dependent parts of the right lungs. Pharmacokinetic data demonstrated systemic absorption of ibuprofen proofing a transport across the alveolo-capillary membrane. A significantly lower TNF-α concentration was observed in (2) and (3) when compared to the control group (1). There were no significant differences in IL-8 and IL-6 concentrations and lung mechanics. F6H8 aerosol seemed to be a suitable carrier for pulmonary drug delivery to dependent ARDS lung regions without having negative effects on lung mechanics.

Understanding cellular mechanisms underlying airway epithelial repair: selecting the most appropriate animal models

Understanding the mechanisms underlying the process of regeneration and repair of airway epithelial structures demands close characterization of the associated cellular and molecular events. The choice of an animal model system to study these processes and the role of lung stem cells is debatable since ideally the chosen animal model should offer a valid comparison with the human lung. Species differences may include the complex three-dimensional lung structures, cellular composition of the lung airway as well as transcriptional control of the molecular events in response to airway epithelium regeneration, and repair following injury. In this paper, we discuss issues related to the study of the lung repair and regeneration including the role of putative stem cells in small- and large-animal models. At the end of this paper, the author discuss the potential for using sheep as a model which can help bridge the gap between small-animal model systems and humans.

Essential role of IFNbeta and CD38 in TNFalpha-induced airway smooth muscle hyper-responsiveness

We recently identified autocrine interferon (IFN)beta as a novel mechanism mediating tumor necrosis factor (TNF)alpha-induced expression of inflammatory genes in airway smooth muscle (ASM) cells, including CD38, known to regulate calcium signaling. Here, we investigated the putative involvement of IFNbeta in regulating TNFalpha-induced airway hyper-responsiveness (AHR), a defining feature of asthma. Using our pharmacodynamic model to assess ex vivo AHR isolated murine tracheal rings, we found that TNFalpha-induced enhanced contractile responses to carbachol and bradykinin was abrogated by neutralizing anti-IFNbeta antibody or in tracheal rings deficient in CD38. In cultured human ASM cells, where CD38 has been involved in TNFalpha-induced enhanced calcium signals to carbachol and bradykinin, we found that neutralizing anti-IFNbeta prevented TNFalpha enhancing action only on carbachol responses but not to that induced by bradykinin. In a well-characterized model of allergic asthma (mice sensitized and challenged with Aspergillus fumigatus (Af)), we found heightened expression of both IFNbeta and CD38 in the airways. Furthermore, allergen-associated AHR to methacholine, assessed by lung resistance and dynamic compliance, was completely suppressed in CD38-deficient mice, despite the preservation of airway inflammation. These data provide the first evidence that ASM-derived IFNbeta and CD38 may play a significant role in the development of TNFalpha-associated AHR.

Early effects of lipopolysaccharide on cytokine release, hemodynamic and renal function in newborn piglets

BACKGROUND

Gram-negative sepsis in newborns is associated with high mortality and morbidity. Lipopolysaccharide (LPS) and cytokines released upon exposure to gram-negative sepsis are well known to be involved in the pathophysiology.

OBJECTIVE

In this report we investigate cytokine release, hemodynamic, and renal function induced by LPS in a newborn animal model with the intention to further examine early changes in gram-negative sepsis.

METHODS

Five 7- to 10-day-old domestic piglets were anesthetized and catheters placed in the jugular veins, left ventricle, and femoral artery. Urine output was monitored via suprapubic cystostomy. Mean arterial pressure, heart rate, and arterial blood gases were continuously monitored. Thirty minutes after line placement and obtaining baseline values, 0.06 mug/kg LPS were administered intravenously. One, 2, and 3 h later samples were taken to monitor tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta, endothelin, and nitric oxide (NO)/nitrate via ELISA. In addition, blood flow was assessed by the microsphere method.

RESULTS

Our data show an initial surge of TNF-alpha and IL-1beta at 1 h after exposure to LPS. NO/nitrate, endothelin, and hemodynamic as well as metabolic changes became apparent mostly 3 h after exposure, by which time TNF-alpha and IL-1beta fell back to baseline.

CONCLUSIONS

Our sepsis model suggests a brief initial TNF-alpha and IL-1beta surge following LPS challenge; however, their effects become apparent by the time the levels are already subsiding. The emergence of vasoactive substances, NO and endothelin, precedes the first substantial clinical symptoms.

Etanercept reduces late endotoxin-induced pulmonary hypertension in the pig

To evaluate whether etanercept, a tumor necrosis factor (TNF)-blocking agent, may counteract hemodynamic deterioration in endotoxemic shock, we designed a prospective, randomized placebo-controlled trial with parallel groups, consisting of 13 pigs aged 10-14 weeks receiving general anesthesia. Five pigs were given 25 mg of etanercept, 1 h before the start of a 4-h continuous infusion of endotoxin. Another 5 pigs were given the corresponding volume of saline, 1 h before the start of a 4-h continuous infusion of endotoxin. Three pigs were given 25 mg of etanercept, 1 hr before the start of a 4-h continuous infusion of saline. At 1 h of endotoxemia, mean pulmonary arterial pressure (MPAP) and pulmonary vascular resistance index (PVRI) increased identically in both groups of pigs receiving endotoxin. Thereafter, two distinct different patterns in hemodynamics were observed. TNF-blocked pigs showed significantly lower MPAP and PVRI compared to controls. In the etanercept-treated endotoxemic pigs, Doppler analysis of the diastolic mitral inflow demonstrated a significantly increased E/A-ratio (early mitral wave inflow was divided by the atrial wave) at 2 h. The TNFblocking agent etanercept normalized two hemodynamic features of endotoxin-induced septic shock in pigs: (1) the sustained pulmonary hypertension and (2) diastolic dysfunction.

TNF-[alpha] modulates murine tracheal rings responsiveness to G-protein-coupled receptor agonists and KCl

Although the mechanisms that underlie airway hyperresponsiveness in asthma are complex and involve a variety of factors, evidence now suggests that intrinsic abnormalities in airway smooth muscle (ASM) may play an important role. We previously reported that TNF-alpha, a cytokine involved in asthma, augments G-protein-coupled receptor (GPCR) agonist-evoked calcium responses in cultured ASM cells. Here we have extended our previous studies by investigating whether TNF-alpha also modulates the contractile and relaxant responses to GPCR activation using cultured murine tracheal rings. We found that in tracheal rings treated with 50 ng/ml TNF-alpha, carbachol-induced isometric force was significantly increased by 30% compared with those treated with diluent alone (P < 0.05). TNF-alpha also augmented KCl-induced force generation by 70% compared with rings treated with diluent alone (P < 0.01). The enhancing effect of TNF-alpha on carbachol-induced isometric force generation was completely abrogated in the tracheal rings obtained from TNF-alpha receptor (TNFR)1-deficient mice and in control rings treated with a TNF-alpha mutant that solely activates TNFR2. TNF-alpha also attenuated relaxation responsiveness to isoproterenol but not to PGE2 or forskolin. TNF-alpha modulatory effects on GPCR-induced ASM responsiveness were completely abrogated by pertussis toxin, an inhibitor of Gialpha proteins. Taken together, these data suggest that TNF-alpha may participate in the development of airway hyperresponsiveness in asthma via the modulation of ASM responsiveness to both contractile and beta-adrenoceptor GPCR agonists.

Modulation of calcium homeostasis as a mechanism for altering smooth muscle responsiveness in asthma

Airway hyperresponsiveness remains a defining characteristic of asthma. Traditional views assert that airway smooth muscle is an important structural effector cell in the bronchi that modulates bronchomotor tone induced by contractile agonists. New evidence, however, suggests that abnormalities in airway smooth muscle functions, induced by variety of extracellular stimuli, may play an important role in the development of airway hyperresponsiveness. Studies using isolated bronchial preparations or cultured cells show that inflammatory mediators and cytokines may alter calcium homeostasis in airway smooth muscle and render the cells nonspecifically hyperreactive to agonists.

Ibuprofen attenuates early lung injury in endotoxemic, neutropenic rats

The objective of our study was to determine the role of ibuprofen in protecting neutropenic rats from cardiopulmonary injury due to endotoxemia. We hypothesized that ibuprofen would offer pulmonary protection by altering cytokine production. Neutropenic rats received E. coli lipopolysaccharide (LPS) alone or ibuprofen and LPS. After 4 h, arterial blood gases, heart rate and blood pressure were measured. Blood and bronchoalveolar lavage fluid (BALF) were collected for TNF- alpha and MIP-2 concentrations. Lung tissue for iNOS mRNA and myeloperoxidase were obtained. The ibuprofen group had decreased heart rate and better oxygenation. Ibuprofen suppressed TNF- alpha and MIP-2 production in blood and MIP-2 concentrations in BALF. Lung mRNA for iNOS was higher in the ibuprofen group. Neutrophil infiltration in the lung was similar in both groups. Ibuprofen attenuated cardiopulmonary dysfunction by decreasing the early cytokine response. The balance of vasodilator to vasoconstrictor production in the lung may favor vasodilation as shown by increased iNOS mRNA and suppression of thromboxane.

Changes in airway resistance by simultaneous exposure to TNF-alpha and IL-1beta in perfused rat lungs

Tumor necrosis factor (TNF)-alpha and interleukin (IL)-1beta are formed simultaneously under inflammatory conditions such as asthma and acute respiratory distress syndrome. Here we investigated the effects of TNF-alpha (10 ng/ml) and/or IL-1beta (10 ng/ml) in isolated blood-free perfused rat lungs. In lungs precontracted with methacholine, IL-1beta alone and IL-1beta/TNF-alpha decreased airway resistance 10 min after administration, whereas TNF-alpha alone had no effect. In untreated lungs, airway resistance was unaltered by either cytokine alone but started to increase 40 min after treatment with both cytokines together, indicating bronchoconstriction. The bronchoconstriction was accompanied by a steroid-sensitive increase in cyclooxygenase (COX)-2 mRNA expression and thromboxane formation. The cytokine-induced bronchoconstriction was blocked by the thromboxane receptor antagonist SQ-29548, indomethacin, the selective COX-2 inhibitor NS-398, and the steroid dexamethasone. We conclude that IL-1beta has an early bronchodilatory effect (after 10 min) that is unchanged by TNF-alpha. However, at later time points (after 40 min), IL-1beta and TNF-alpha in concert cause a COX-2- and thromboxane-dependent bronchoconstriction. Our findings show that TNF-alpha and IL-1beta exert complex and time-dependent effects on lung functions that cannot be predicted by studying each cytokine alone.

Cytokine-induced bronchoconstriction in precision-cut lung slices is dependent upon cyclooxygenase-2 and thromboxane receptor activation

Cytokines play an essential role in the regulation of inflammatory responses. The effects of cytokines on lung functions are less well known and their study in vivo is complicated by the attraction of leukocytes to the inflamed sites. Recently the model of precision-cut lung slices was developed, where viable lung slices with an intact microanatomy are taken into culture and where bronchoconstriction can be followed by observing single airways under the microscope. We used this model to study the direct effects of cytokines on airway tonus in the absence of blood-derived leukocytes. Incubation of precision-cut lung slices with a mixture of tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta, and interferon (IFN)-gamma resulted in contraction of airways, which was accompanied by expression of cyclooxygenase (Cox)-2 and thromboxane release into the supernatant. The thromboxane receptor antagonist SQ29548 completely prevented the cytokine-induced bronchoconstriction, whereas the 5-lipoxygenase inhibitor AA681 had no effect on cytokine-induced bronchoconstriction. Preventing the expression of Cox-2 by dexamethasone or blocking Cox-2 activity with the selective Cox-2 inhibitor NS398 attenuated both thromboxane formation and bronchoconstriction. Incubation of lung slices with each of the cytokines alone caused no bronchoconstriction; in fact, IL-1 alone rather dilated the airways. However, simultaneous incubation with TNF and IL-1beta caused a bronchoconstriction that was not further enhanced by IFN-gamma. We conclude that TNF-alpha and IL-1beta synergistically cause bronchoconstriction by induction of Cox-2 and subsequent activation of the thromboxane receptor. Our study raises the possibility that TNF and IL-1 may contribute to bronchospasm during inflammatory lung diseases.

Acute respiratory distress syndrome. Potential pharmacologic interventions

Remarkable progress has been made in the past 10 years with regard to understanding the interplay of potent physiologic mediators in patients with acute lung injury. Because there are so many mediators and the interaction of these agents is complex, true insight into the process has been slow in coming. Clinical studies in ARDS, as well as sepsis, the leading cause of ARDS, have increased in number, size, and quality over this same period. Although none of these studies has produced an accepted new therapy for ARDS, each has laid the groundwork for more efficient and more elegant studies of the problem. The stage is now set for the real advances to be brought forward and put to rigorous, efficient clinical testing.

Cyclooxygenase inhibitors attenuate bradykinin-induced vasoconstriction in septic isolated rat lungs

Cyclooxygenase (COX) products play an important role in modulating sepsis and subsequent endothelial injury. We hypothesized that COX inhibitors may attenuate endothelial dysfunction during sepsis, as measured by receptor-mediated bradykinin (BK)-induced vasoconstriction and/or receptor-independent hypoxic pulmonary vasoconstriction (HPV). Rats were administered intraperitoneally a nonselective COX inhibitor (indomethacin, 5 or 10 mg/kg) or a selective COX-2 inhibitor (NS-398, 4 or 8 mg/kg) 1 h before lipopolysaccharide (LPS, 15 mg/kg), or saline (control). Three hours later, the rats were anesthetized, the lungs were isolated, and pulmonary vasoreactivity was assessed with BK (0.3, 1.0, and 3.0 microg) and HPV (3% O(2)). Perfusion pressure was monitored as an index of vasoconstriction. To investigate what receptor-subtype is mediating BK responses, the BK(1)-receptor antagonist des-Arg(9)-[Leu(8)]-BK, the BK(2)-receptor antagonist HOE-140, or the thromboxane A(2)-receptor antagonist SQ 29548 (all at 1 microM) were added to the perfusate. BK-induced vasoconstriction was significantly increased in LPS lungs (1.4-5.2 mm Hg) compared with control (0.1-1.1 mm Hg). In LPS lungs, indomethacin 10 mg/kg significantly decreased BK vasoconstriction by 78% +/- 9%, whereas 5 mg/kg did not. NS-398, 4 mg/kg, significantly attenuated BK vasoconstriction at 0.3 microg (71% +/- 7%) and 1.0 microg (56% +/- 12%), whereas 8 mg/kg attenuated 0.3 microg BK (57% +/- 14%), compared with LPS lungs. HPV was increased in LPS lungs (21.5 +/- 2 mm Hg) compared with control lungs (9.8 +/- 0.6 mm Hg). Indomethacin 5 mg/kg increased HPV in LPS lungs; otherwise, HPV was not altered by COX inhibition. BK-induced vasoconstriction was prevented by BK(2), but not BK(1) or thromboxane A(2)-receptor antagonism. This study suggests that nonselective COX inhibition, and possibly inhibition of the inducible isoform COX-2, may attenuate sepsis-induced, receptor-mediated vasoconstriction in rats.

IMPLICATIONS

This study demonstrated that, in an isolated rat lung model, nonselective inhibition of the cyclooxygenase pathway, and possibly selective inhibition of the inducible cyclooxygenase-2 isoform, may attenuate sepsis-induced endothelial dysfunction.

Early alterations of lung injury following acute smoke exposure and 21-aminosteroid treatment

In a simulated fire-related smoke exposure protocol, New Zealand white rabbits were utilized to investigate the potential effects of the 21-aminosteroid (lazaroid) analog U75412E on the early events of acute lung injury. Inhalation of a total of 1.6 mg/kg U75412E aerosolized at a rate of 1.53 mg/min at 0.5 hr after smoke exposure significantly attenuated the extent of lung injury at 1 hr, as evidenced by decreased bronchoalveolar lavage (BAL) concentration of total protein, 6-keto-prostaglandin F1-alpha, and blood gas defect. Histopathologic examination demonstrated that the lazaroid significantly attenuated smoke-induced lung injury as evidenced by a decrease in wet lung/body weight ratio, necrosis, and sloughing of airway epithelial cells. Electron microscopy showed that the lazaroid decreased smoke-induced interstitial edema and the vacuolization of alveolar type II epithelium (21.6 +/- 9.7 vs 8.5 +/- 3.6 vacuoled blebs/cell, smoke only vs smoke + lazaroid). However, U75412E did not attenuate smoke-induced changes in BAL concentration of tumor necrosis factor-alpha, total cell count, and granulocyte percentage. These observations suggest that U75412E may exert its action through cooperative mechanisms, such as the modulation of arachidonic acid metabolism, in addition to its characterized antioxidative effects.

Arachidonic acid is preferentially metabolized by cyclooxygenase-2 to prostacyclin and prostaglandin E2

The two cyclooxygenase isoforms, cyclooxygenase-1 and cyclooxygenase-2, both metabolize arachidonic acid to prostaglandin H2, which is subsequently processed by downstream enzymes to the various prostanoids. In the present study, we asked if the two isoforms differ in the profile of prostanoids that ultimately arise from their action on arachidonic acid. Resident peritoneal macrophages contained only cyclooxygenase-1 and synthesized (from either endogenous or exogenous arachidonic acid) a balance of four major prostanoids: prostacyclin, thromboxane A2, prostaglandin D2, and 12-hydroxyheptadecatrienoic acid. Prostaglandin E2 was a minor fifth product, although these cells efficiently converted exogenous prostaglandin H2 to prostaglandin E2. By contrast, induction of cyclooxygenase-2 with lipopol- ysaccharide resulted in the preferential production of prostacyclin and prostaglandin E2. This shift in product profile was accentuated if cyclooxygenase-1 was permanently inactivated with aspirin before cyclooxygenase-2 induction. The conversion of exogenous prostaglandin H2 to prostaglandin E2 was only modestly increased by lipopolysaccharide treatment. Thus, cyclooxygenase-2 induction leads to a shift in arachidonic acid metabolism from the production of several prostanoids with diverse effects as mediated by cyclooxygenase-1 to the preferential synthesis of two prostanoids, prostacyclin and prostaglandin E2, which evoke common effects at the cellular level.

The effects of bovine respiratory syncytial on normal ovine lymphocyte responses to mitogens or antigens in vitro

In the present study peripheral blod mononuclear cells (MNC) obtained from normal uninfected lambs were used to study the possible effects of bovine respiratory syncytial virus (BRSV) on lymphocyte responses to the mitogens, phytohaemagglutinin (PHA), concanavalin A (Con A) and pokeweed mitogen (PWM) in vitro. Live BRSV had a depressive effect on the proliferative responses of normal MNC to PHA, Con A and PWM. Inactivated BRSV and a commercial preparation of prostaglandin E2 were also found to depress the proliferative responses of normal ovine MNC to PHA but recombinant tumour necrosis factor-alpha (TNF-alpha) had no such effect. Serum samples obtained from BRSV-infected lambs contained substances inhibitory to PHA-driven lymphocyte blastogenesis. Memory blastogenic responses to border disease virus (BDV) of lymyphocytes obtained from lambs previously primed with BDV were significantly reduced when lymphocytes were exposed to infectious BRSV.

Cytokines induce airway smooth muscle cell hyperresponsiveness to contractile agonists

The important pathophysiological features of the airways in asthma include exaggerated narrowing to bronchoconstrictor agonists and attenuated relaxation to beta adrenoceptor stimulation. These physiological perturbations are associated with inflammation and remodelling of the airways, the latter including an increase in airway smooth muscle cell mass, disruption of the airway epithelium, and changes in the airway tissue extracellular matrix. Recent evidence suggests that cytokines, important molecules modulating airway inflammation, also directly decrease airway smooth muscle responsiveness to beta adrenergic agents, stimulate cytokine secretion, inhibit or promote airway smooth muscle proliferation, and "prime" airway smooth muscle to become hyperresponsive to bronchoconstrictors. Characterisation of the cellular and biochemical events that are involved in activation of airway smooth muscle is likely to be the major consideration in the design of future therapies for asthma. Because calcium is an essential regulatory element for cell growth and cell contraction, it is likely that alterations in calcium mobilisation may, in part, play a role in creating an airway smooth muscle phenotype that is hyperresponsive to contractile agonists. Further studies will be required to determine the precise mechanisms involved in cytokine modulation of calcium homeostasis in airway smooth muscle.

Mechanisms underlying TNF-alpha effects on agonist-mediated calcium homeostasis in human airway smooth muscle cells

We have previously shown that tumor necrosis factor (TNF)-alpha, a cytokine involved in asthma, enhances Ca2+ responsiveness to bronchoconstrictor agents in cultured human airway smooth muscle (ASM) cells. In the present study, we investigated the potential mechanism(s) by which TNF-alpha modulates ASM cell responsiveness to such agents. In human ASM cells loaded with fura 2, TNF-alpha and interleukin (IL)-1 beta significantly enhanced thrombin- and bradykinin-evoked elevations of intracellular Ca2+. In TNF-alpha-treated cells. Ca2+ responses to thrombin and bradykinin were 350 +/- 14 and 573 +/- 93 nM vs. 130 +/- 17 and 247 +/- 48 nM in nontreated cells, respectively (P < 0.0001). In IL-1 beta-treated cells, the Ca2+ response to bradykinin was 350 +/- 21 vs. 127 +/- 12 nM in nontreated cells (P < 0.0001). The time course for TNF-alpha potentiation of agonist-induced Ca2+ responses requires a minimum of 6 h and was maximum after 12 h of incubation. In addition, cycloheximide, a protein synthesis inhibitor, completely blocked the potentiating effect of TNF-alpha on Ca2+ signals. We also found that TNF-alpha significantly enhanced increases in phosphoinositide (PI) accumulation induced by bradykinin. The percentage of change in PI accumulation over control was 115 +/- 8 to 210 +/- 15% in control cells vs. 128 +/- 10 to 437 +/- 92% in TNF-alpha-treated cells for 3 x 10(-9) to 3 x 10(-6) M bradykinin. The PI turnover to 10 mM NaF, a direct activator of G proteins, was also found to be enhanced by TNF-alpha. The percentage of change in PI accumulation over control increased from 280 +/- 35% in control cells to 437 +/- 92% in TNF-alpha-treated cells. Taken together, these results show that TNF-alpha can potently regulate G protein-mediated signal transduction in ASM cells by activating pathways dependent on protein synthesis. Our study demonstrates one potential mechanism underlying the enhanced Ca2+ response to bronchoconstrictor agents induced by cytokines in human ASM cells.

Cytokine-mediated induction of cyclo-oxygenase-2 by activation of tyrosine kinase in bovine endothelial cells stimulated by bacterial lipopolysaccharide

1. The induction of cyclo-oxygenase-2 (COX-2) afforded by bacterial lipopolysaccharide (LPS, endotoxin) in bovine aortic endothelial cells (BAEC) is mediated by tyrosine kinase. LPS also causes the generation of several cytokines including interleukin-1 beta (IL-1 beta), tumour necrosis factor-alpha (TNF-alpha), epidermal growth factor (EGF) and platelet-derived growth factor (PDGF). This study investigates whether endogenous IL-1 beta, TNF-alpha, EGF or PDGF contribute to the induction of COX-2 elicited by LPS in BAEC and if their action is due to activation of tyrosine kinase. Furthermore, we have studied the induction of COX-2 by exogenous cytokines. 2. Accumulation of 6-oxo-prostaglandin (PG) F1 alpha in cultures of BAEC was measured by radioimmunoassay at 24 h after addition of either LPS (1 microgram ml-1) alone or LPS together with a polyclonal antibody to one of the various cytokines. In experiments designed to measure 'COX activity', 6-oxo-PGF1 alpha generated by BAEC activated with recombinant human IL-1 beta, TNF-alpha, EGF or PDGF for 12 h was measured after incubation of washed cells with exogenous arachidonic acid (30 microM for 15 min). Western blot analysis determined the expression of COX-2 protein in BAEC. 3. The accumulation of 6-oxo-PGF1 alpha caused by LPS in BAEC was attenuated by co-incubation with one of the polyclonal antibodies, anti-IL-1 beta, anti-TNF-alpha, anti-EGF, anti-PDGF or with the IL-1 receptor antagonist, in a dose-dependent manner. Exogenous IL-1 beta, TNF-alpha or EGF also caused an increase in COX activity, while PDGF was ineffective. The increase in COX activity elicited by IL-1,beta(10 ng ml-1), TNF-alpha (100 ng ml-1) or EGF (1000 ng ml-1) in BAEC was attenuated by erbstatin (0.005 to 5 microg ml-1), as was the expression of COX-2 protein measured by Western blot analysis.4. PDGF (10 ng ml-1) significantly augmented the rise in COX activity and COX-2 protein caused by shorter incubation of BAEC with LPS (1 microg ml-1 for 3 h). Combination of PDGF (10 ng ml-1) with a low concentration of IL-l beta (1 ng ml-1) for 12 h, also increased 'COX activity', but combination of PDGF and TNF-alpha (10 ng ml-1) did not show any increased activity.5. These results suggest that (i) the induction of COX activity and COX-2 protein elicited by LPS in BAEC is mediated by TNF-alpha with lesser contributions from PDGF, EGF or IL-1 beta; (ii) exogenous IL-1 beta,TNF-alpha or EGF alone induce COX-2 activity and protein in BAEC; (iii) PDGF synergizes with IL-1 beta,but not TNF-alpha, to cause expression of COX-2; and (iv) the induction of COX-2 protein and activity caused by these cytokines involves the activation of tyrosine kinase.

Effect of tumor necrosis factor receptor binding protein on cell infiltration induced by lipopolysaccharide and Sephadex beads in guinea pig lung

In the present study, the effect of a tumor necrosis factor receptor binding protein (TNFbp) on the cell infiltration induced by lipopolysaccharide (LPS) and Sephadex beads in guinea pig lung was examined. The intratracheal injection of LPS (2.5 micrograms) induced a six-fold increase in total cell number recovered in bronchoalveolar lavage (BAL) fluid at 24 hr. This increase in bronchopulmonary inflammation was mainly due to a neutrophil and macrophage infiltration, representing 60% and 35% of the total cells, respectively. The intravenous or intratracheal injection of Sephadex beads to guinea pigs induced a three-fold increase in total cell number recovered in BAL at 24 h and was characterized by a prominent eosinophil, macrophage, and neutrophil infiltration representing 36%, 42%, and 16% of the total cells, respectively. In addition, bronchial tissues isolated from Sephadex-treated guinea pigs showed an increased in vitro reactivity to both histamine and acetylcholine. TNFbp (1-50 micrograms) induced a dose-dependent inhibition of cell infiltration induced by LPS. In contrast TNFbp neither attenuated the bronchopulmonary cell infiltration observed 24 h following intravenous or intratracheal administration of Sephadex beads nor inhibited the increase in bronchial reactivity. These results show that TNF plays an important role in cell infiltration induced by LPS, but not that induced by Sephadex, in the guinea pig lung.

Tumor necrosis factor-alpha-induced inhibition of phosphatidylcholine synthesis by human type II pneumocytes is partially mediated by prostaglandins

TNF alpha seems to play an important role in the pathogenesis of adult respiratory distress syndrome. We studied the effect of TNF alpha on phospholipid synthesis by isolated type II pneumocytes and attempted to characterize the role of arachidonate metabolites and the influence of pentoxifylline on such an effect. Lung tissue obtained from both multiple organ donors (n = 14) and lung cancer patients (n = 11) was used for cell isolation. Surfactant synthesis was measured by the incorporation of D-[U-14C]glucose into phosphatidylcholine (PC). The basal PC synthesis was higher in the donor group than in the malignant group (3.44 +/- 0.19 vs 2.15 +/- 0.15 pmol/microgram protein x 120 min, P < 0.01), and, in the presence of 100 ng/ml of TNF alpha, the incorporation of labeled glucose into PC was reduced significantly in both donor (1.13 +/- 0.11 vs 3.44 +/- 0.19 pmol/microgram protein x 120 min, P < 0.01) and cancer (0.99 +/- 0.11 vs 2.15 +/- 0.15 pmol/microgram protein x 120 min, P < 0.01) groups. Indomethacin was able to completely block the cytokine-induced decrease in PC synthesis by pneumocytes from the malignant group and to attenuate the inhibitory effect of TNF alpha in those from donors, nordihydroguaiaretic acid having a similar effect. The TNF alpha effect can be blocked by pentoxifylline (100 micrograms/ml), a substance which can even succeed in reverting the basal secretory inhibition of cancer patients' pneumocytes to levels similar to those of the donor group. TNF alpha may contribute to the pathophysiology of adult respiratory distress syndrome by inhibiting the synthesis of surfactant. TNF alpha might be produced in lung tumors, resulting in chronic paracrine or systemic exposure of pneumocytes to low concentrations of the cytokine. The TNF alpha effect was not prevented completely by the blockage of the arachidonic acid metabolism, hence other mediators should also be implicated.

Involvement of thromboxane A2 in bronchial hyperresponsiveness but not lung inflammation induced by bacterial lipopolysaccharide in guinea pigs

We examined both a possible association of bronchial hyperresponsiveness with lung inflammatory responses and the role of thromboxane (Tx) A2 in these responses after lipopolysaccharide (LPS) exposure in guinea pigs treated with metyrapone, a cortisol synthesis inhibitor. The increase in bronchial responsiveness to i.v. acetylcholine was transient, with a peak at 2 h after LPS exposure, which was associated with increases in TxB2 and tumor necrosis factor in bronchoalveolar lavage (BAL) fluid. However, the levels of 6-keto-prostaglandin (PG) F1 alpha, interleukin-1 and interleukin-6 in BAL fluid, and the influx of leukocytes in airway and pulmonary edema were not associated with bronchial hyperresponsiveness. Oral administration of S-1452, a selective TxA2 receptor antagonist, markedly suppressed bronchial hyperresponsiveness without affecting cellular responses, pulmonary edema and production of PGs and cytokines. These findings suggest that LPS-induced bronchial hyperresponsiveness is dependent on secondarily generated TxA2, which appears to be independent of lung inflammation.

Staphylococcal alpha toxin: a study with chronically instrumented awake sheep

The in vivo responses to staphylococcal alpha toxin are reported for 15 chronically instrumented awake yearling sheep. The data obtained from a total of 30 experiments are grouped into four categories of response: no response, noted in seven experiments done on 5 sheep; pressor response, obtained seven times in 4 sheep; fluid and solute exchange, noted on six occasions in 3 sheep; and acute heart failure and death, which occurred in 10 of the 15 sheep. "No response" denoted no change in any of the measured outcome variables. The group of sheep labeled as showing "pressor response" responded to alpha toxin infusion with an increase in pulmonary artery pressure, unaccompanied by changes either in lung lymph flow or in lung mechanics. "Changes in lung fluid and solute exchange" involve increases in lung lymph flow. The harbinger of the last category, acute left heart failure leading to death, was a marked elevation in left atrial pressure. The threshold response dose in sheep is approximately 21 micrograms/kg. A very steep dose-response curve is observed, with only a narrow window of doses, 15 to 25 micrograms/kg, between the group showing no response and the group showing death from acute heart failure. The data obtained in these studies indicate that the lethal effects of alpha toxin in sheep include acute heart failure, which may be due to direct toxicity to heart muscle and/or the coronary vasculature endothelium.