Presence Of Cyclooxygenase Inhibitor Research Articles

Short-term acetaminophen consumption enhances the exercise-induced increase in Achilles peritendinous IL-6 in humans

Through an unknown mechanism, the cyclooxygenase inhibitor and antipyretic acetaminophen (APAP) alters tendon mechanical properties in humans when consumed during exercise. Interleukin-6 (IL-6) is produced by tendon during exercise and is a potent stimulator of collagen synthesis. In nontendon tissue, IL-6 is upregulated in the presence of cyclooxygenase inhibitors and may contribute to alterations in extracellular matrix turnover, possibly due to inhibition of prostaglandin E2 (PGE2). We evaluated the effects of APAP on IL-6 and PGE2 in human Achilles peritendinous tissue after 1 h of treadmill exercise. Subjects were randomly assigned to a placebo (n = 8, 26 ± 1 yr) or APAP (n = 8, 25 ± 1 yr) group. Each subject completed a nonexercise and exercise experiment consisting of 6 h of microdialysis. Drug (APAP, 1,000 mg) or placebo was administered in a double-blind manner during both experiments. PGE2 and IL-6 were determined via enzyme immunoassay and APAP via high-performance liquid chromatography. In subjects given APAP, peritendinous APAP levels increased to 4.08 ± 0.65 μg/ml (P < 0.05). PGE2 did not increase with exercise in either group (P > 0.05), nor was PGE2 significantly reduced in the APAP group. IL-6 levels increased with exercise in both groups (P < 0.05), but this increase was greater in the APAP group (P < 0.05). Our findings suggest that APAP enhances tendon IL-6 production after exercise. Peak levels of APAP obtained in the peritendinous space were twofold lower than values reported in plasma or skeletal muscle. These findings provide insight into the effects of APAP on tendon and provide novel information on the kinetics of APAP in tendon tissue after oral APAP consumption.

Pregnancy regulates thromboxane A2‐induced contractions via endothelium‐derived factors and large‐conductance calcium‐activated potassium channels in rat uterine artery

Endothelium‐derived factors and calcium‐activated potassium channels modulate vascular smooth muscle cell depolarization. We hypothesized that thromboxane A2 (TxA2)‐induced contractions are negatively mediated by endothelium‐derived factors and calcium‐activated potassium channels, and these effects are pregnancy dependent. Uterine arteries (UA) were isolated from pregnant (P) and virgin (NP) rats. Force production in response to a TxA2 mimetic (U46619, 3 μM) was measured in a wire myograph in the absence or presence of inhibitors for: nitric oxide synthase (NOS), cyclooxygenase (COX), large (BKCa), small (SKCa) and intermediate (IKCa) conductance calcium–activated potassium channels. In UA from NP rats, TxA2‐induced contractions (18.2±2.5 mN) were increased in the presence of BKCa inhibition (31.7±1.5 mN) but did not change in the presence of NOS (23.6±2.2 mN) or COX (16.8±1.8 mN) inhibition. In UA from P rats, TxA2‐induced contractions (22.5±1.3 mN) were increased in the presence of BKCa (34.1±2.4 mN) and NOS (30.3±1.5 mN) inhibition and were reduced in the presence of COX inhibition (12.1±3.4 mN). Inhibition of SKCa and IKCa had no effect in any group (p&lt;0.05). Our data suggest that pregnancy regulates UA contractile responses to TxA2 via both endothelium‐derived factors and activation of large‐conductance calcium‐activated potassium channels.Support: NIH, SWHR

Cyclooxygenase and thromboxane/prostaglandin receptor contribute to aortic endothelium-dependent dysfunction in aging female spontaneously hypertensive rats

Cyclooxygenase (COX)-derived vasoconstrictory prostanoids contribute to impaired endothelium-dependent vasorelaxation in aging male (m) spontaneously hypertensive rats (SHR); however, vasomotor responses in aging female (f) SHR and sex differences in aging SHR are unknown. Examining mechanisms governing dysfunction in aging fSHR will contribute to understanding sex-dependent vascular complications in advanced hypertension. Aortic endothelium-dependent relaxation dose responses (ACh) of 16- and 30-wk-old mSHR and fSHR and normotensive Wistar-Kyoto rats were examined in the absence (no drug control) and presence of COX inhibition [indomethacin (Indo)] and thromboxane/prostaglandin receptor inhibition (SQ-29548). No drug control-treated 16-wk mSHR exhibited considerable blunting of the peak relaxation response to ACh (e.g., 77 +/- 4% relaxation to 10(-5) mol/l) vs. Wistar-Kyoto controls (89 +/- 6%), and greater dysfunction occurred in 30-wk mSHR (63 +/- 2%). Interestingly, ACh relaxations of fSHR were unimpaired at 16 wk (101 +/- 2% to 10(-5) mol/l), but blunted in 30 wk (76 +/- 4%). Indo and SQ-29548 restored robust ACh vasorelaxation in all groups (e.g., 113 +/- 3 and 112 +/- 3%, respectively, in Indo- and SQ-29548-treated 30-wk fSHR). Aortic COX-1 protein expression was elevated by 75% in 30-wk vs. 16-wk fSHR, whereas group-averaged ACh-stimulated aortic PGI(2) release (assessed as 6- keto-PGF(1alpha)) was 30% greater in 30-wk vs. 16-wk fSHR (9,926 +/- 890 vs. 7,621 +/- 690 pg.ml(-1).mg dry wt(-1)), although this did not reach significance (P = 0.0758). Dramatic deterioration of endothelium-dependent vasomotor function in fSHR across this age range involves COX and thromboxane/prostaglandin receptor, supporting a mechanism of impairment similar to that which occurs in aging mSHR.

Effects of propofol on responses of rat isolated renal arteriole to vasoactive agents

Rat renal arterial rings were suspended in organ chambers for isometric tension recording. The effects of propofol on the resting tone, KCl-, norepinephrine (NE)-, serotonin- and thromboxane A 2 analog U46619-induced contractions were observed. The relaxation responses to propofol on KCl-, NE- and U46619-induced contractions were assessed in the absence or presence of cyclooxygenase inhibitor, nitric oxide synthetase inhibitor or specific K + channel inhibitors. Propofol did not significantly affect the resting tone, but inhibited the contractions induced by KCl-, NE-, serotonin- and U46619. Propofol (1–100 µM) concentration-dependently relaxed 60 mM KCl-, 10 µM NE-, and 1 µM U46619-induced contractions with the values of RC 50 (concentration to decline the precontraction by 50%) being 18.9 µM, 70.6 µM and 12.7 µM, respectively. Propofol-induced relaxation was attenuated by indomethacin, but not by either N G nitro- l-arginine methyl ester (L-NAME) or any K + channel specific inhibitors used. The vasorelaxations induced by acetylcholine, sodium nitroprusside and amrinone were not affected by the presence of propofol. The present results indicate that propofol antagonizes provoked contractions of the arteriole and suggest that inhibition of extracellular Ca 2+ influx and synthesis of vasodilator prostanoid may be involved in propofol-induced relaxation of the arteriole.

RAW264.7 cells lack prostaglandin-dependent autoregulation of tumor necrosis factor-α secretion

Studies of the response of RAW264.7 cells (RAW) to lipopolysaccharide (LPS) were carried out to determine why these cells do not demonstrate the prostaglandin (PG)-dependent autocrine regulation of tumor necrosis factor-alpha (TNF-alpha) secretion observed in primary resident peritoneal macrophages (RPMs). The major cyclooxygenase (COX) product of LPS-stimulated RAW was PGD2, with lesser amounts of PGE2. LPS-treated RAW produced PGs more slowly and reached their maximal PG synthetic rate later than did LPS-treated RPMs, as a result of lower constitutive COX-1 expression and a slower rate of COX-2 induction. Cytosolic phospholipase A2 and levels of free arachidonic acid were similar in RAW and RPMs. In contrast to RPMs, LPS-treated RAW produced high quantities of TNF-alpha, which were not altered in the presence of COX inhibitors. This failure of endogenous PGs to suppress TNF-alpha secretion was explained by the absence of the prostaglandin D2 receptor and the low levels of PGE2 produced during the first 2 h of the LPS response. These studies demonstrate that autocrine regulation of TNF-alpha secretion in response to LPS is greatly facilitated by a COX-1-mediated rapid accumulation of PGs as well by a correspondence between the PGs produced and the receptors expressed by the cells.

Role of shear stress in nitric oxide-dependent modulation of renal angiotensin II vasoconstriction.

1. Renal vasoconstriction in response to angiotensin II (ANGII) is known to be modulated by nitric oxide (NO). Since shear stress stimulates the release of a variety of vasoactive compounds from endothelial cells, we studied the impact of shear stress on the haemodynamic effect of ANGII in isolated perfused kidneys of rats under control conditions and during NO synthase inhibition with L-NAME (100 microM). 2. Kidneys were perfused in the presence of cyclo-oxygenase inhibitor (10 microM indomethacin) with Tyrode's solution of relative viscosity zeta=1 (low viscosity perfusate, LVP) or, in order to augment shear stress, with Tyrode's solution containing 7% Ficoll 70 of relative viscosity zeta=2 (high viscosity perfusate, HVP). 3. Vascular conductance was 3.5+/-0.4 fold larger in HVP as compared with LVP kidneys, associated with an augmentation of overall wall shear stress by 37+/-5%. During NO inhibition, vascular conductance was only 2.5+/-0.2 fold elevated in HVP vs LVP kidneys, demonstrating shear stress-induced vasodilatation by NO and non-NO/non-prostanoid compound(s). 4. ANGII (10 - 100 pM) constricted the vasculature in LVP kidneys, but was without effect in HVP kidneys. During NO inhibition, in contrast, ANGII vasoconstriction was potentiated in HVP as compared with LVP kidneys. 5. The potentiation of ANGII vasoconstriction during NO inhibition has been shown to be mediated by endothelium-derived P450 metabolites and to be sensitive to AT2 receptor blockade in our earlier studies. Accordingly, in HVP kidneys, increasing concentrations of the AT2 receptor antagonist PD123319 (5 and 500 nM) gradually abolished the potentiation of ANGII vasoconstriction during NO inhibition, but did not affect vasoconstriction in response to ANGII in LVP kidneys. 6. Our results demonstrate, that augmentation of shear stress by increasing perfusate viscosity induces vasodilatation in the rat kidney, which is partially mediated by NO. Elevated levels of shear stress attenuate renal ANGII vasoconstriction through enhanced NO production and are required for AT2 sensitive potentiation during NO inhibition.

Regulation of macrophage eicosanoid generation is dependent on nuclear factor kappaB.

Prostaglandin E2 (PGE2) is a major contributor to the production and maintenance of immunosuppression after overwhelming injury, leading to increased infectious morbidity and mortality in trauma patients. Elucidation of the cellular pathways involved in PGE2 production could lead to potential therapeutic interventions. The purpose of this study was to determine the role of cyclooxygenase II (COX-2) in PGE2 production by Mphi and to investigate the cellular mechanism of COX-2 gene activation. Mouse macrophages (Mphi), RAW 264.7, were exposed to Escherichia coli lipopolysaccharide (LPS) in the presence of cyclooxygenase inhibitors (ibuprofen or NS398). COX-1 and COX-2 mRNA expression and PGE2 production were measured by Northern blot assay and enzyme-linked immunosorbent assay, respectively. Nuclear factor kappaB (NFkappaB) activity was measured by electrophoretic mobility shift assay. To elucidate the role of NFkappaB in LPS-induced COX-2 gene activation, Mphi were exposed to LPS in the presence of an NFkappaB inhibitor, TPCK. LPS increased Mphi COX-2 mRNA expression but had no effect on COX-1 mRNA expression. Both ibuprofen and NS398 inhibited COX-2 mRNA as well as PGE2 production by LPS-stimulated Mphi. In addition, LPS-induced NFkappaB activity was attenuated by these agents. Inhibition of NFkappaB with TPCK reduced COX-2 but not COX-1 gene expression and decreased PGE2 production by LPS-stimulated Mphi. Our data indicate that COX-2 gene expression by LPS-stimulated Mphi is dependent on NFkappaB. Cyclooxygenase inhibitors reduced PGE2 production by inhibiting both COX-2 mRNA expression and preventing NFkappaB activation.

Endotoxin Primes Perfused Rabbit Lungs for Enhanced Vasoconstrictor Response to Staphylococcal α-Toxin

The major pore-forming exotoxin of Staphylococcus aureus, staphylococcal alpha-toxin, causes thromboxane-mediated pulmonary hypertension and prostanoid-independent protracted vascular leakage in perfused rabbit lungs. We asked whether lung responsiveness to the staphylococcal agent would be altered by a preceding period of endotoxin priming. Isolated rabbit lungs were perfused with Krebs-Henseleit buffer in the presence or absence of 100 ng/ml Salmonella abortus equii endotoxin for up to 5 h. The lipopolysaccharide exposure evoked the release of large quantities of tumor necrosis factor into the vascular and alveolar spaces but did not significantly alter pulmonary artery pressure, organ weight, or the repeatedly assessed capillary filtration coefficient (Kfc). Two and 4 h after endotoxin administration, alpha-toxin (10 to 30 ng/ml) was bolus-injected into the pulmonary artery. Toxin-evoked prostanoid generation (TxB2, 6-keto-PGF1 alpha) and pressor responses were markedly accelerated and enhanced in endotoxin-primed lungs, both for the 2 h and the 4 h priming period. No significant influence of endotoxin was noted when applied simultaneously with alpha-toxin. Cyclooxygenase inhibition suppressed the alpha-toxin-evoked pressure rise in both endotoxin-primed and nonprimed lungs. Endotoxin priming did not influence the alpha-toxin-induced protracted increase in Kfc values, assessed in the presence of cyclooxygenase inhibition. We conclude that endotoxin primes rabbit lungs for enhanced prostanoid generation and pulmonary hypertension in response to S. aureus alpha-toxin. Such cooperativity of endotoxin priming and exotoxin triggering may be relevant in critically ill patients suffering from both endotoxemia and gram-positive sepsis.

Neuronal M2Muscarinic Receptor Function in Guinea-Pig Lungs Is Inhibited by Indomethacin

The function of M2 muscarinic autoreceptors on pulmonary parasympathetic nerves was investigated in the absence and presence of cyclooxygenase inhibitors in vivo. Guinea pigs were anesthetized, paralyzed, and artificially ventilated. Pulmonary inflation pressure, heart rate, and blood pressure were recorded. Electrical stimulation of vagus nerves produced bronchoconstriction (measured as an increase in pulmonary inflation pressure) and bradycardia. In control guinea pigs, pilocarpine (1 to 100 micrograms/kg) given intravenously stimulated inhibitory M2 muscarinic receptors on pulmonary parasympathetic nerves, thus attenuating vagally induced bronchoconstriction. Conversely, blockade of these autoreceptors by the selective M2 antagonist gallamine (0.1 to 10 mg/kg given intravenously) potentiated vagally induced bronchoconstriction. Separate groups of animals were given either indomethacin or naproxen. These cyclooxygenase inhibitors potentiated vagally induced bronchoconstriction. Furthermore, in those animals pretreated with either indomethacin or [+] naproxen, pilocarpine did not inhibit and gallamine did not potentiate vagally induced bronchoconstriction. In the heart, the effects of pilocarpine and gallamine on M2 muscarinic receptors were not altered by either cyclooxygenase inhibitor. Neither intravenously administered indomethacin (1 mg/kg) nor [+] naproxen (5 mg/kg) altered baseline pulmonary inflation pressure or baseline heart rate in the treated guinea pigs. These studies demonstrate that inhibitory M2 muscarinic receptors on pulmonary parasympathetic nerves do not function in the presence of cyclooxygenase inhibitors. Loss of M2 receptor function may contribute to aspirin-induced airway hyperresponsiveness.

Induction of transforming growth factor-beta and prostaglandin E2 production by ethanol in human monocytes

To test our hypothesis that monocytes (M phi) and their mediators are major contributors to ethanol-related immunodepression, the modulating capacity of acute ethanol treatment was assessed on the production of transforming growth factor-beta (TGF beta) and prostaglandin E2 (PGE2) by human peripheral blood M phi. We demonstrate that acute in vitro treatment of adherent M phi with either 50 or 150 mM ethanol induced a significant increase in the production of TGF beta (P < 0.045 and P < 0.001, respectively). Furthermore, M phi pretreatment with both 50 and 150 mM ethanol augmented TGF beta production in response to subsequent stimulation with the synthetic bacterial analog, muramyl dipeptide (MDP) (P < 0.05 and P < 0.001, respectively). Ethanol also increased TGF beta production in interferon gamma (IFN gamma-activated M phi in response to MDP stimulus (P < 0.05). M phi TGF beta levels, however, were always lower in IFN gamma-activated than in non-IFN gamma-activated M phi after the same stimulation with ethanol plus MDP, suggesting that M phi preactivation by IFN gamma can partially counteract the TGF beta inducing potential of ethanol. Similar to its TGF beta-inducing potential, ethanol (150 mM) had the capacity to induce PGE2 production in adherent human M phi (P < 0.045). However, ethanol failed to augment M phi PGE2 production induced by the PGE2 secretagogue, MDP. TGF beta induction by ethanol was unaffected by the presence of cyclooxygenase inhibitor, suggesting that ethanol-induced M phi TGF beta production does not require M phi PGE2 production. These results indicate that ethanol is a potent inducer for inhibitory M phi mediators, TGF beta and PGE2, and also has the capacity to augment M phi TGF beta production in response to subsequent stimulation. Thus, ethanol-induced elevation of M phi TGF beta and PGE2 production might contribute to decreased T cell proliferation and abnormal M phi functions after alcohol exposure, resulting in a depressed immune response.

Leukotriene and hydroxyeicosatetraenoic acid generation elicited by low doses of Escherichia coli hemolysin in rabbit lungs

Low doses of Escherichia coli hemolysin cause thromboxane-mediated hypertension and vascular leakage in blood-free perfused rabbit lungs (W. Seeger, H. Walter, N. Suttorp, M. Muhly, and S. Bhakdi, J. Clin. Invest. 84:220-227, 1989). The recirculating buffer medium and bronchoalveolar lavage fluid from lungs exposed to hemolysin (2.5 hemolytic units per ml) in the presence of cyclooxygenase inhibitor were analyzed for leukotrienes (LTs) and hydroxyeicosatetraenoic acids (HETEs) by reverse-phase and straight-phase high-pressure liquid chromatographic techniques combined with UV spectrum analysis and post-high-pressure liquid chromatography radioimmunoassay. A rapid release of large amounts of cysteinyl-LTs and leukotriene B4 (LTB4) into the intravascular space was noted (total sum, approximately 4 to 5 micrograms). Similar quantities have hitherto been elicited only by high concentrations of the artificial calcium ionophore A 23187. Moreover, a marked liberation of 5-HETE and 12-hydroxyheptadecatrienoic acid into the buffer medium occurred, whereas LTB4 represented the predominant compound in the lavage fluid. The hemolysin-induced burst of LT and HETE generation preceded the onset of vascular leakage. The outstanding capacity of E. coli hemolysin to produce the liberation of potent lipid mediators is probably relevant to the pathways of vascular injury and amplification of inflammatory events during severe infection with hemolytic E. coli strains.

Allergen-stimulated Release of Thromboxane A2and Leukotriene E4in Humans: Effect of Indomethacin

Allergen-stimulated release of a cyclooxygenase product (thromboxane [TX] A2) and a 5-lipoxygenase product (leukotriene [LT] E4) into the urine was measured in 10 atopic asthmatics undergoing allergen inhalation. Because indomethacin has been reported to increase allergic-stimulated 5-lipoxygenase product formation and to inhibit the late asthmatic response, we determined the effect of indomethacin (50 mg 3 times a day) or placebo on airway and biochemical responses to inhaled allergen in a randomized, blinded study. Urinary levels of the enzymatic metabolite of TXB2, 11-dehydro-TXB2, increased from 585 +/- 330 to 1,500 +/- 250 pg/mg creatinine (mean +/- SEM, p less than 0.05) 2 h after allergen. Urinary LTE4 increased from 190 +/- 37 to 1,100 +/- 400 (p less than 0.05) 2 h after challenge. The urinary levels of these eicosanoids were not elevated during the late response. Indomethacin significantly reduced urinary 11-dehydro-TXB2 levels without affecting the excretion of LTE4 or pulmonary function. Thus, we failed to obtain evidence for enhanced leukotriene formation during allergic stimulation in vivo in the presence of cyclooxygenase inhibition. Furthermore, we conclude that cyclooxygenase products are likely to play only a marginal role in allergic bronchoconstriction.

Cyclooxygenase inhibition potentiates myogenic activity in skeletal muscle arterioles

The proposition that arteriolar constriction to increased intravascular pressure is mediated through either the increased local production of an eicosanoid constrictor factor or decreased production of a dilating factor was examined. The myogenic response of arterioles was studied by enclosing anesthetized rats in an airtight Plexiglas box with the cremaster muscle exteriorized into a tissue bath containing Krebs solution. Microvascular responses were observed by video microscopy. The arteriolar response to a 20-mmHg increase in intravascular pressure was examined in the absence or presence of cyclooxygenase inhibition. In the absence of cyclooxygenase inhibition, second-order arterioles (2As) responded passively to increased pressure by distending to 107 +/- 1% of control diameter. In the presence of the indomethacin, 2As constricted to 79 +/- 5% of control. Third-order arterioles (3As) constricted to 47 +/- 8% of control without indomethacin and similarly to 33 +/- 4% with indomethacin. To test whether inhibitors of endothelium-derived relaxation factor would potentiate the myogenic response of 3As, methylene blue or gossypol was topically applied to the cremaster muscle. Neither inhibitor was found to augment the myogenic vasoconstriction; however, these inhibitors were observed to significantly reduce basal vascular tone. In comparison, the tonic local production of dilating prostaglandins appears to attenuate myogenic activity as demonstrated by the appearance of myogenic activity in the normally passive 2As when exposed to cyclooxygenase inhibitors.

Prostaglandin E 1 modifies porcine cerebral arterial tone through cyclooxygenase related eicosanoid(s) release

The effects of prostaglandin E 1 (PGE 1) on porcine cerebral arteries were studied in the absence and presence of cyclooxygenase inhibitors, 5×10 −6 M indomethacin or 10 −4 M aspirin. In preparations placed at a resting tension, 3×10 −9 to 10 −6 M PGE 1 caused dose-dependent contractions. In prostaglandin F 2α ( PGF 2α )- contracted preparations, low concentrations of 10 −9 and 3 × 10 −9 M PGE 1 did not modify arterial tone and higher concentrations of 10 −8 to 10 −6 M PGE 1 further increased the arterial tone in all preparations tested. In contrast, in the presence of the cyclooxygenase inhibitors, low concentration of 10 −9 and 3×10 −9 M PGE 1 markedly decreased the arterial tone induced by PGF 2α and higher dose of 10 −8 to 10 −6 M PGE 1 increased the arterial tone in 15 of 18 preparations (83%). These findings suggest that PGE 1 modifies porcine cerebral vascular tone at least partly through cyclooxygenase-related eicosanoid(s) production.

Eicosanoid interactions in the canine proximal colon

Effects of eicosanoids on the canine proximal colonic mucosa were examined. Both arachidonic acid (AA) and prostaglandin E2 (PGE2) increased short-circuit currents. Tetrodotoxin did not affect these responses, suggesting that functioning nerves are not required. Indomethacin abolished responses to AA, indicating that the cyclooxygenase pathway is the primary metabolic pathway. Indomethacin significantly potentiated responses to PGE2, suggesting that in the presence of cyclooxygenase inhibition either 1) a normally inhibitory cyclooxygenase product is not present or 2) a potentiating lipoxygenase product is being produced in greater amounts. PGE2 is produced in significant quantities, whereas leukotriene B4 (LTB4) is produced in smaller amounts. Cyclooxygenase inhibitors significantly decreased PGE2 production but had no effect on LTB4. This suggests that an inhibitory PG may be opposing the response to PGE2. Therefore, we tested the effects of several cyclooxygenase products on PGE2 responsiveness. PGD2 alone significantly reduced responses to PGE2. In the canine proximal colon the response to AA is apparently the algebraic sum of the opposing responses of PGE2 and PGD2.

Mechanism of action of leukotrienes on the guinea pig bronchus

The pharmacological activity of leukotrienes (LT) A 4, C 4, D 4, E 4, and histamine was investigated on guinea pig upper and lower bronchi. The contractions of the upper bronchi to histamine, LTA 4, C 4 and D 4 were enhanced by cyclooxygenase inhibitors aspirin (1.67 × 10 −5 and 1.67 × 10 −6 M) and indomethacin (2.8 × 10 −6 and 2.8 × 10 −5 M) whereas the responses to LTE 4 were not affected. The myotropic activity of the lower bronchi to all agonists were either very slightly or not at all modified by the presence of cyclooxygenase inhibitors. The thromboxane synthetase inhibitor OKY-046 (1.77 × 10 −5 and 1.77 × 10 −6 M) did not change the responses of higher bronchi to the agonists which suggested that the response of the upper bronchi may be mediated by prostaglandins but not by thromboxanes. The responses of the lower bronchi to leukotrienes A 4, C 4, D 4 and E 4 were inhibited by compound OKY-046. Blockade of thromboxane receptors together with inhibition of lipoxygenases by compound L-655,240 (2.53 × 10 −8 to 2.53 × 10 −5 M) had a slight effect on the stimulation of upper and lower bronchi by leukotrienes and histamine. The compound FPL-55712 (1.92 × 10 −6 and 1.92 × 10 −5 M) strongly reduced the contractions of the upper and lower bronchi to leukotrienes but did not affect the responses to histamine. These results suggest that the contractile effects of leukotrienes on upper bronchi is modulated by bronchorelaxant prostaglandins whereas the responses of the lower bronchi are mediated by thromboxanes. The responses of both upper and lower bronchi to histamine do no appear to be mediated by cyclooxygenase products.

Human alveolar macrophage arachidonic acid metabolism.

Metabolites of arachidonic acid are potent modulators of many biological events, and their release from macrophages appears to play an important role in immune and inflammatory processes. In addition, metabolites of the cyclooxygenase or lipoxygenase pathway exhibit distinct biological effects. We used a method to determine if human alveolar macrophages (HAM) could be selectively activated to release products of cyclooxygenase or lipoxygenase pathway of arachidonic acid. HAM obtained by bronchoalveolar lavage from individuals were [3H]arachidonic acid labeled and then stimulated with lipopolysaccharide (LPS) or Ca ionophore A23187. Essentially no arachidonate metabolites were released by unstimulated cells. LPS caused dose- and time-dependent release of arachidonate and only cyclooxygenase products; no lipoxygenase products were detected, even in presence of cyclooxygenase inhibition. Metabolites released in response to LPS included thromboxane B2, prostaglandins D2, F2a, E2, and hydroxyheptadecatrienoic acid. A23187 caused a rapid release of arachidonate and 5-lipoxygenase products, leukotriene B4 and 5-hydroxyeicosatetraenoic acid; no cyclooxygenase inhibition. This demonstrates that HAM are specifically activated to release metabolites derived from cyclooxygenase or lipoxygenase pathway of arachidonic acid. Additionally, shunting down an alternate pathway is not induced by use of inhibitors of either pathway. This suggests alveolar macrophages may enhance or suppress various inflammatory or immune processes in lung, in part, by selective release of various derivatives of arachidonic acid.

Potential role for interleukin-1 in fibrosis associated with chronic ambulatory peritoneal dialysis.

Cytokines released by inflammatory cells can modify migration, proliferation and matrix protein synthesis by mesenchymal cells. Interleukin-1 (IL-1) produced by monocytes is one cytokine which could play a role in inducing peritoneal fibrosis in patients undergoing chronic peritoneal dialysis. IL-1 increases collagen synthesis associated with increased levels of procollagen mRNAs in fibroblasts. In some fibroblasts, this increase may be masked by the inhibitory effects of prostaglandins and revealed in the presence of cyclooxygenase inhibitors. Other known cytokines act similarly to IL-1 and may be synergistic with IL-1. The lymphokine interferon-gamma inhibits collagen synthesis. These mediators function in a complex network of feedback and amplification loops to regulate collagen deposition in inflammatory conditions.

Prostacyclin stimulates relaxin release from cultured porcine luteal cells.

The release of relaxin from cultured porcine luteal cells (derived from pregnant sows) was detected by a reverse hemolytic plaque assay. In this assay, luteal cells are cocultured in monolayers with protein-A-coupled ovine erythrocytes. In the presence of porcine relaxin antiserum and complement, a zone of hemolysis--a plaque--develops around relaxin-releasing luteal cells. Treatment with a prostacyclin analogue (carba-prostacyclin; 10 and 100 ng/ml) significantly accelerated the rate of plaque formation in a dose-dependent manner. In contrast, the culture of luteal cells in the presence of cyclooxygenase inhibitors (indomethacin, ibuprofen, and diclofenac sodium) resulted in no change in the rate of basal relaxin release. These results add weight to the view that prostacyclin may contribute alone, or perhaps in combination with other prostanoids, to the overall regulation of ovarian endocrine function and relaxin release during pregnancy in the pig. However, the data are inconsistent with the possibility that prostacyclin arises from relaxin-releasing luteal cells themselves.

A possible role of thromboxane A2 in endothelium in maintaining resting tone and producing contractile response to acetylcholine and arachidonic acid in canine cerebral arteries.

Endothelial thromboxane A2 (TXA2) in maintaining the resting tone and producing the contractile response to acetylcholine (ACh) and arachidonic acid was studied in canine cerebral artery. The spontaneous release of TXB2 from cerebral artery was about tenfold higher than that of coronary, mesenteric and saphenous arteries. The resting tone, the release of TXB2 and the contraction produced by arachidonic acid were decreased by the presence of cyclooxygenase inhibitor, TXA2 synthetase inhibitor, TXA2 antagonist and rubbing of the luminal side of preparations. The contraction produced by ACh was inhibited by the presence of the above inhibitors and rubbing of the preparations without decreasing the release of TXB2. These results suggest that the resting tone of canine cerebral artery and the contractile response to arachidonic acid are related to activation of TXA2 synthesis in the endothelium.