Epidural distribution of dye administered via an epidural catheter in a porcine model.

BACKGROUND: Local anaesthetics are commonly delivered to the epidural space by either intermittent bolus or continuous infusion. While these methods have been investigated in terms of analgesia and total dose administered, they have not been compared in terms of their effect on the spread of injectate within the epidural space. This animal study compared the spread of dye delivered to the epidural space in a porcine model by either bolus or infusion. METHODS: After ethical approval, epidural catheters were placed at three vertebral levels in seven anaesthetized pigs. Aqueous dye (1 ml) was injected into the catheter as a bolus, or as an infusion over 30 min. Animals were euthanized at the end of the study and necropsy performed immediately to quantify the extent of dye spread. RESULTS: In seven animals, 20 catheters were successfully placed in the epidural space. The mean (sd) extent of dye spread was 8.9 (2.6) cm in the infusion group compared with 15.2 (2.7) cm in the bolus group (P<0.001). Segmental spread was significantly greater in the bolus group compared with the infusion group (P<0.01). CONCLUSION: In the porcine epidural model, spread of one ml of epidural dye solution is more extensive after a single bolus compared with short term infusion.

Relationship between levels of secreted phospholipase A2 groups IIA and X in the airways and asthma severity.

Background Secreted phospholipase A(2) (sPLA(2) ) may be important mediators of asthma, but the specific sPLA(2) s involved in asthma are not known. Objective To evaluate sPLA(2) group IIA, V, and X proteins (sPLA(2) -IIA, sPLA(2) -V, and sPLA(2) -X) in bronchoalveolar lavage (BAL) fluid, BAL cells, and airway epithelial cells of subjects with and without asthma, and examine the relationship between the levels of specific sPLA(2) enzymes and airway inflammation, asthma severity, and lung function. Methods The expression of sPLA(2) -IIA, sPLA(2) -V, and sPLA(2) -X in BAL cells and epithelial brushings was assessed by qPCR. The levels of these sPLA(2) proteins and sPLA(2) activity with and without group II and group X-specific inhibitors were measured in BAL fluid from 18 controls and 39 asthmatics. Results The airway epithelium expressed sPLA(2) -X at higher levels than either sPLA(2) -IIA or sPLA(2) -V, whereas BAL cells expressed sPLA(2) -IIA and sPLA(2) -X at similar levels. The majority of sPLA(2) activity in BAL fluid was attributed to either sPLA(2) -IIA or sPLA(2) -X. After 10-fold concentration of BAL fluid, the levels of sPLA(2) -X normalized to total protein were increased in asthma and were associated with lung function, the concentration of induced sputum neutrophils, and prostaglandin E(2) . The levels of sPLA(2) -IIA were elevated in asthma when normalized to total protein, but were not related to lung function, markers of airway inflammation or eicosanoid formation. Conclusions and Clinical Relevance These data indicate that sPLA(2) -IIA and sPLA(2) -X are the major sPLA(2) s in human airways, and suggest a link between the levels of sPLA(2) -X in the airways and several features of asthma.

Eosinophil peroxidase-induced mast cell secretion.

Eosinophil peroxidase (EPO) at relatively low levels (4-30 mU), when supplemented with H2O2 and a halide, induced mast cell degranulation. Histamine release occurred without concomitant release of the cytoplasmic marker lactic dehydrogenase (LDH), and this, together with ultrastructural studies, indicated a noncytotoxic effect comparable with that induced by other mast cell secretagogues. At pH 7.4, iodide was effective at concentrations down to 10(-5) M, and although chloride alone was ineffective at 0.1 M, a combination of 0.1 M chloride and 10(-6) iodide could meet the halide requirement. Chloride alone was effective at pH 6.5 and 6.0. EPO could be replaced by myeloperoxidase. When the EPO level was increased to 100 mU, combination with H2O2- and iodide-induced cytotoxic histamine release as indicated by concomitant LDH release and ultrastructural evidence of cell disruption. This cytotoxic response reverted to a secretory one on the addition of albumin. Peroxidase was detected on the surface of extruded granules by diaminobenzidine cytochemistry. The mast cell granule (MCG)/EPO complex when supplemented with H2O2 and iodide was more effective than free EPO in the stimulation of mast cell secretion. The stimulation of mast cell mediator release by the EPO-H2O2-halide system and the formation of MCG/EPO complexes with augmented cytotoxic activity may influence the adjacent inflammatory response.

Toxoplasma gondii alters eicosanoid release by human mononuclear phagocytes: role of leukotrienes in interferon gamma-induced antitoxoplasma activity.

Toxoplasma gondii tachyzoites markedly alter the profile of eicosanoids released by human mononuclear phagocytes. Freshly isolated, 2-h adherent human monocytes release both cyclooxygenase (e.g., thromboxane [TX] B2, prostaglandin [PG] E2) and 5-lipoxygenase (e.g., leukotriene [LT] B4, LTC4) products of arachidonic acid metabolism after stimulation by the calcium ionophore A23187 or ingestion of opsonized zymosan particles or heat-killed T. gondii. However, after incubation with viable T. gondii, normal and chronic granulomatous disease monocytes release only the cyclooxygenase products TXB2 and PGE2 and fail to form LTB4, LTC4, or other 5-lipoxygenase products. Monocytes maintained in culture for 5 d lose this capacity to release TXB2 and PGE2 after incubation with T. gondii. T. gondii significantly inhibit calcium ionophore A23187-induced LTB4 release by monocyte-derived macrophages; heat-killed organisms do not affect this calcium ionophore A23187-induced release of LTB4. T. gondii-induced inhibition of LTB4 release by calcium ionophore A23187-stimulated monocyte-derived macrophage is reversed by interferon (IFN)-gamma treatment of the monolayers. LTB4 induced extensive damage to the cellular membranes and cytoplasmic contents of the organisms as observed by transmission electron microscopy. Exogenous LTB4 (10(-6) M) induced intracellular killing of ingested T. gondii by non-IFN-gamma-treated monocyte-derived macrophages. IFN-gamma-induced antitoxoplasma activity in monocyte-derived macrophages was inhibited by the selective 5-lipoxygenase inhibitor zileuton but not by the cyclooxygenase inhibitor indomethacin. These findings suggest a novel role for 5-lipoxygenase arachidonic acid products in human macrophage IFN-gamma-induced antitoxoplasma activity.

Leukotriene generation by eosinophils.

Horse eosinophils purified to greater than 98% generated slow reacting substance (SRS) when incubated with the calcium ionophore A23187. On a per cell basis, eosinophils generated four to five times the SRS produced by similarly treated horse neutrophils. Eosinophil SRS production was inhibited by 5,8,11,14-eicosatetraynoic acid and augmented by indomethacin and arachidonic acid, suggesting that it was a product(s) of the lipoxygenase pathway of arachidonic acid metabolism. Compounds with SRS activity were purified by high-pressure liquid chromatography (HPLC) and identified by ultraviolet spectra, spectral shift on treatment with lipoxygenase, incorporation of [14C]arachidonic acid, gas chromatography-mass spectrometry, and comparison of retention times on HPLC to authentic standards. The eosinophil products characterized were 5-(S), 12-(R)-dihydroxy-6-cis-8, 10-trans-14-cis-eicosatetraenoic acid (leukotriene B4) and its 5-(S), 12-(R)-6-trans and 5-(S), 12-(S)-6-trans isomers, 5-(S)-hydroxy-6-(R)-S-glutathionyl-7,9-trans-11, 14-cis-eicosatetraenoic acid (leukotriene C4) and its 11-trans isomer, and 5-(S)-hydroxy-6-(R)-S-cysteinylglycine-7,9-trans-11,14-cis-eicosatetraenoic acid (leukotriene D4).

Oxidative degradation of leukotriene C4 by human monocytes and monocyte-derived macrophages.

Freshly isolated 2-h adherent normal human monocytes, when stimulated, degrade added leukotriene C4 (LTC4) by a myeloperoxidase (MPO) and H2O2-dependent mechanism. Among the stimuli effective in this regard are phorbol myristate acetate (PMA), the calcium ionophore A23187, opsonized zymosan, and N-formyl-methionine-leucine-phenylalanine (FMLP) when combined with cytochalasin B. The predominant products formed are the all-trans isomers of LTB4, 5-(S), 12-(R)-6-trans-LTB4 and 5-(S),12-(S)-6-trans-LTB4. Degradation is inhibited by azide and catalase, but not by superoxide dismutase. LTC4 degradation does not occur when MPO-deficient monocytes are used, unless MPO is added. Stimulated monocytes from patients with chronic granulomatous disease also are unable to degrade LTC4 under these conditions. Normal monocytes maintained in culture lose their ability to degrade LTC4. The addition of MPO to monocyte-derived macrophages increases degradation, particularly when the monolayers are pretreated with gamma-interferon. The oxidative degradation of LTC4 is a capacity shared by neutrophils, eosinophils, and mononuclear phagocytes, and may be an important mechanism for the modulation of leukotriene activity in inflammatory lesions.

Human platelet-mediated cytotoxicity against Toxoplasma gondii: role of thromboxane.

Human platelets, in the absence of antibody, are cytotoxic to tachyzoites of Toxoplasma gondii as determined by vital staining, transmission electron microscopy, and the failure of Toxoplasma to survive and replicate in mice after in vitro interaction of the organisms with platelets. Platelet to T. gondii ratios as low as 1:3 were toxic to the organisms with direct cell-cell contact essential for platelet-mediated cytotoxicity. Adherence of platelets to T. gondii and disruption of surface membranes and cytoplasmic contents of the organisms were observed ultrastructurally. Reactive oxygen species were not implicated in the platelet-mediated toxicity. The interaction of T. gondii with platelets resulted in a marked increase in thromboxane B2 (TXB2) production compared with that by unstimulated platelets. The cyclooxygenase inhibitors acetylsalicylic acid and indomethacin inhibited platelet-mediated cytolytic activity as did the selective TXA2 synthetase inhibitor dazmegrel, indicating a role for thromboxane in the platelet-induced cytotoxicity. Further, toxoplasmacidal activity was retained in the TXA2 synthetase-containing microsomal fractions of platelets disrupted by freezing and thawing; cytolytic activity was absent in microsome-depleted platelet supernatant fractions. Both the TXA2-generating platelet microsome system and a stable TXA2 analogue induced damage to the cellular membranes of the Toxoplasma as noted by transmission electron microscopy. These findings suggest that platelets may play a role in the host defense against Toxoplasma and that release of thromboxane may be important in this cytolytic process.

Mast cell-mediated tumor-cell cytotoxicity. Role of the peroxidase system.

Mast cells, when supplemented with H2O2 and iodide, are cytotoxic to mammalian tumor cells as determined by 51Cr release, and transmission and scanning electron microscopy. H2O2 at the concentration employed (10(-4) M) initiates mast cell degranulation, and mast cell granules (MCG), which contain a small amount of endogenous peroxidase activity, are toxic to tumor cells when combined with H2O2 and iodide. This toxicity is greatly increased by binding eosinophil peroxidase (EPO) to the MCG surface. Each component of the mast cell, MCG, or MCG-EPO system was required and toxicity was inhibited by the addition of the hemeprotein inhibitors azide or aminotriazole, which is compatible with a requirement for peroxidase in the cytotoxic reaction. A sequence of reactions is proposed in which mast cells, stimulated to release their granules by H2O2 generated by adjacent phagocytes, react with H2O2 and a halide to damage tumor cells. EPO release from eosinophils may contribute to this sequence of reactions, both by stimulation of H2O2-induced mast cell secretion and by combination with MCG to form a complex with augmented tumoricidal activity. These rections may play a role in the host defense against neoplasms.

The importance of leukotrienes in airway inflammation in a mouse model of asthma.

Inhalation of antigen in immunized mice induces an infiltration of eosinophils into the airways and increased bronchial hyperreactivity as are observed in human asthma. We employed a model of late-phase allergic pulmonary inflammation in mice to address the role of leukotrienes (LT) in mediating airway eosinophilia and hyperreactivity to methacholine. Allergen intranasal challenge in OVA-sensitized mice induced LTB4 and LTC4 release into the airspace, widespread mucus occlusion of the airways, leukocytic infiltration of the airway tissue and broncho-alveolar lavage fluid that was predominantly eosinophils, and bronchial hyperreactivity to methacholine. Specific inhibitors of 5-lipoxygenase and 5-lipoxygenase-activating protein (FLAP) blocked airway mucus release and infiltration by eosinophils indicating a key role for leukotrienes in these features of allergic pulmonary inflammation. The role of leukotrienes or eosinophils in mediating airway hyperresponsiveness to aeroallergen could not be established, however, in this murine model.

RNA metabolism in tracheal epithelium: alteration in hamsters deficient in vitamin A.

The electrophoretic pattern of RNA molecules that are synthesized in vitro in tracheal epithelium from hamsters deficient in vitamin A differs from that of RNA synthesized in normal, pair-fed control hamsters. There is less RNA of low electrophoretic mobility in the epithelial cells deficient in vitamin A. This alteration is reversed after the deficient animals have been treated with vitamin A.

TACI-Ig prevents the development of airway hyperresponsiveness in a murine model of asthma.

BACKGROUND: Increased levels of serum IgE are associated with greater asthma prevalence and disease severity. IgE depletion using an anti-IgE monoclonal antibody has met with success in the treatment of moderate-to-severe and severe persistent allergic asthma. OBJECTIVE: To test whether B cell-targeted therapy is a more effective treatment for airway hyperresponsiveness (AHR) in a murine model compared with IgE-depletion. METHODS: We delivered soluble mTACI-Ig, a receptor for the B cell survival factors BLyS (B Lymphocyte Stimulator) and APRIL (A PRoliferation-Inducing Ligand), or anti-IgE to allergen-sensitized mice before airway challenge with allergen. RESULTS: mTACI-Ig treatment reduced circulating mature B cell levels in the blood, while anti-IgE treatment had no effect on B cell counts. Both mTACI-Ig and anti-IgE decreased the levels of total and allergen-specific IgE in the serum. Histopathologic analysis of lungs showed a reduction in disease severity scores for both treatment groups, but results were more pronounced in mTACI-Ig-treated mice. Neutrophil and eosinophil numbers in the bronchoalveolar lavage (BAL) were significantly reduced following mTACI-Ig treatment, but not after anti-IgE delivery. BLyS and APRIL blockade also resulted in a significant decrease in IL-4 and eotaxin mRNA and IL-4 and KC protein levels in total lung homogenates and BAL fluid, respectively. Finally, mTACI-Ig treatment was more effective than anti-IgE treatment in reducing AHR to inhaled antigen. CONCLUSIONS: Our data demonstrate that delivery of mTACI-Ig is a more effective treatment than anti-IgE mAb in a murine model of AHR.

Exercise-induced hypersensitivity syndromes in recreational and competitive athletes: a PRACTALL consensus report (what the general practitioner should know about sports and allergy).

Exercise-induced (EI) hypersensitivity disorders are significant problems for both recreational and competitive athletes. These include EI-asthma, EI-bronchoconstriction, EI-rhinitis, EI-anaphylaxis and EI-urticaria. A group of experts from the European Academy of Allergology and Clinical Immunology and the American Academy of Allergy Asthma and Immunology met to discuss the pathogenesis of these disorders and how to diagnose and treat them, and then to develop a consensus report. Key words (exercise with asthma, bronchoconstriction, rhinitis, urticaria or anaphylaxis) were used to search Medline, the Cochrane database and related websites through February 2008 to obtain pertinent information which, along with personal reference databases and institutional experience with these disorders, were used to develop this report. The goal is to provide physicians with guidance in the diagnosis, understanding and management of EI-hypersensitivity disorders to enable their patients to safely return to exercise-related activities.

Immunologic and nonimmunologic generation of superoxide from mast cells and basophils.

Mediator release from rat peritoneal and human lung mast cells as well as human leukemic basophils was examined to determine whether super-oxide (O(-) (2)) was concomitantly generated. Immunologic or nonimmunologic stimulation of each preparation induced parallel release of histamine and O(-) (2) within 2 min. O(-) (2) production was quantitated by superoxide dismutase (SOD)-inhibitable chemiluminescence and cytochrome c reduction. SOD was detected in basophil and mast cell lysates and was also released by rat mast cells stimulated by anti-IgE. Secretory granules isolated from purified rat mast cells released histamine, O(-) (2), and SOD upon exposure to cations. Thus, both superoxide radicals and SOD may play a role in host defenses involved in immediate hypersensitivity reactions.

Relative contribution of leukotriene B4 to the neutrophil chemotactic activity produced by the resident human alveolar macrophage.

Human alveolar macrophages release chemotactic activity for neutrophils, providing a role for alveolar macrophages in regulating inflammation in the lung. As alveolar macrophages produce large amounts of leukotriene B4 (LTB4), a chemotactically active lipoxygenase product of arachidonic acid, we investigated the contribution of LTB4 to the total neutrophil chemotactic activity produced by these cells. Normal human alveolar macrophages were recovered by bronchoalveolar lavage from healthy volunteers and incubated either with the calcium ionophore A23187 for 1 h, or with opsonized zymosan particles or latex beads for 3 h. Nordihydroguaretic acid (NDGA), a relatively specific lipoxygenase inhibitor, blocked the release of neutrophil chemotactic activity after all three stimuli in a dose-dependent manner. This correlated with blockade of LTB4 production as measured by high performance liquid chromatography using freshly isolated alveolar macrophages, as well as blockade of [3H]LTB4 production by macrophages prelabeled with [3H]arachidonate. Molecular sieve chromatography using Sephadex G-50 confirmed that essentially all of the chemotactic activity in the stimulated macrophage supernatants co-eluted with authentic [3H]LTB4, and that NDGA completely blocked the chemotactic activity in the eluting fractions. Readdition of authentic LTB4 (1 X 10(-7) M) to the NDGA-blocked macrophage supernatants restored the chemotactic activity in the supernatants. The macrophage supernatants did not contain platelet-activating factor-like activity, as measured by the stimulation of [3H]serotonin release from rabbit platelets, and by high performance liquid chromatography. NDGA did not change the protein-secretion profiles of fresh alveolar macrophages, or of macrophages prelabeled with [35S]methionine. The complement (C) components C5adesarg were not detected in any of the supernatants by radioimmunoassay. Concentration of the supernatants by positive pressure filtration (5,000-D membrane) did not augment chemotactic activity in the stimulated supernatants or uncover chemotactic activity in the NDGA-blocked supernatants. As with the 3-h studies, when alveolar macrophages were incubated overnight with opsonized zymosan, all of the increase in chemotactic activity could also be blocked by NDGA. These data indicate that LTB4 is the predominant neutrophil chemotactic factor secreted by the normal resident human alveolar macrophage in response to two major types of stimuli, calcium fluxes across the cell membrane and the phagocytosis of opsonized particulates.

Stimulation of neutrophil oxygen-dependent metabolism by human leukocytic pyrogen.

The ability of highly purified human leukocytic pyrogen (LP) to stimulate neutrophil oxygen-dependent metabolism was studied. Human peripheral blood neutrophils exposed to leukocytic pyrogen in vitro demonstrated an increase in the percentage of neutrophils reducing nitroblue tetrazolium (NBT) dye and a marked stimulation of superoxide dismutase inhibitable reduction of ferricytochrome c. LP stimulation of neutrophil oxygen-dependent metabolism was dose and time dependent. Procedures that destroyed the pyrogenicity of LP also abolished the effects on neutrophil metabolism. Neutrophil hexose monophosphate shunt activity was also stimulated by LP. In a rabbit model, the effect of in vivo LP on neutrophil superoxide generation was also studied. There was a consistent increase in the percent and absolute number of NBT positive neutrophils. Peak stimulation of neutrophil metabolism occurred after defervescence suggesting several possible mechanisms. The observations reported here may, in part, explain the nonspecificity of the NBT test in febrile, noninfected patients and provide further understanding of neutrophil physiology during acute inflammation.

Blockade of CD49d (alpha4 integrin) on intrapulmonary but not circulating leukocytes inhibits airway inflammation and hyperresponsiveness in a mouse model of asthma.

Immunized mice after inhalation of specific antigen have the following characteristic features of human asthma: airway eosinophilia, mucus and Th2 cytokine release, and hyperresponsiveness to methacholine. A model of late-phase allergic pulmonary inflammation in ovalbumin-sensitized mice was used to address the role of the alpha4 integrin (CD49d) in mediating the airway inflammation and hyperresponsiveness. Local, intrapulmonary blockade of CD49d by intranasal administration of CD49d mAb inhibited all signs of lung inflammation, IL-4 and IL-5 release, and hyperresponsiveness to methacholine. In contrast, CD49d blockade on circulating leukocytes by intraperitoneal CD49d mAb treatment only prevented the airway eosinophilia. In this asthma model, a CD49d-positive intrapulmonary leukocyte distinct from the eosinophil is the key effector cell of allergen-induced pulmonary inflammation and hyperresponsiveness.

Structure-activity relationships of retinoids in hamster tracheal organ culture.

Structure-activity relationships are summarized for 87 retinoids, using reversal of keratinization in the hamster tracheal organ culture system to measure biological activity. Classes of compounds evaluated include all-trans-retinoic acid and its esters, ring-modified analogs of all-trans-retinoic acid and its esters, side-chain-modified analogs of all-trans-retinoic acid and its esters, analogs in which both ring and side chain have been modified, all-trans-retinol and derivatives, all-trans-retinyl amine derivatives, all-trans-retinal derivatives, all-trans-retinoic acid amides, 13-cis-retinoic acid and derivatives, and 5,6-epoxyretinoids. the activity of many synthetic amide derivatives of all-trans- or 13-cis-retinoic acid approaches that of the parent compounds. No metabolite of all-trans- or 13-cis-retinoic acid has yet been identified which has greater activity than the parent compounds in this assay. New synthetic derivatives with a gem-dimethyl group at position 4 in the cyclohexenyl ring and two aromatic rings in the side chain have activity equal to or greater than that of all-trans- or 13-cis-retinoic acid, with some activity detectable in the 10(-11) M range.

N-(4-Hydroxyphenyl)retinamide, a new retinoid for prevention of breast cancer in the rat.

The synethesis of a new retinoid, N-(4-hydroxyphenyl)-all-trans-retinamide, which has useful biological properties, is described. This retinoid was more potent than retinyl acetate in reversing keratinization caused by retinoid deficiency in tracheal organ culture. It was markedly less toxic than retinyl acetate when fed p.o. to rats over 2-week or 6-month periods. It was an effective agent for inhibition of the development of breast cancer induced in rats by N-nitroso-N-methylurea, although it was not as potent as retinyl acetate in this regard. However, the lesser toxicity of 4-hydroxyphenylretinamide makes it a superior agent for prevention of breast cancer. High-pressure liquid chromatographic analyses of liver and breast extracts from rats treated for 6 months with retinoids show the pharmacokinetic basis for the superiority of 4-hydroxyphenylretinamide; this retinoid and its metabolites were found in high concentrations in breast tissue, without any measurable accumulation in the liver or evident liver toxicity. In contrast, chronic feeding of retinyl acetate caused marked deposition of retinyl esters in the liver and severe hepatotoxicity. Whole mounts of rat mammary glands, made after chronic feeding of 4-hydroxyphenylretinamide, showed that it had a marked antiproliferative effect on mammary epithelium.

Iodination of arachidonic acid mediated by eosinophil peroxidase, myeloperoxidase and lactoperoxidase. Identification and comparison of products.

Arachidonic acid undergoes iodination in the presence of hydrogen peroxide, iodide, and either eosinophil peroxidase, myeloperoxidase or lactoperoxidase. The profile of products generated by each of the three peroxidases is similar as determined by reversed-phase high-performance liquid chromatography. Structural analysis of the products indicate that: 1, each of the four double bonds in arachidonic acid is susceptible to iodination; 2, arachidonic acid can be multiply iodinated; and 3, the carboxylate moiety does not participate in the formation of all products. The isomeric composition of the isolated products indicates that peroxidase-mediated iodination of arachidonate is not stereoselective.

Type 4 phosphodiesterase inhibitors have clinical and in vitro anti-inflammatory effects in atopic dermatitis.

Increased cyclic AMP-phosphodiesterase activity in peripheral blood leukocytes is associated with the immune and inflammatory hyperreactivity that characterizes atopic dermatitis. Atopic phosphodiesterase has high sensitivity to a variety of enzyme inhibitors, suggesting an increased therapeutic advantage. The objective of this study was to use in vitro assays to identify a potent phosphodiesterase inhibitor and then to investigate its effectiveness in treating atopic dermatitis. Leukocyte enzyme activity was measured by radioenzyme assay, whereas prostaglandin E2 and interleukins 10 (IL-10) and 4 (IL-4) were measured in 24-h culture supernatants of mononuclear leukocytes by immunoassays. The effect of a topical phosphodiesterase inhibitor on atopic dermatitis lesional skin was assessed by double-blind, paired comparisons of active drug and placebo ointments applied to symmetrically involved sites over a 28-d period. Using in vitro, assays, we demonstrated the ability of selective high-potency phosphodiesterase inhibitors to reduce prostaglandin E2, IL-10, and IL-4 production in atopic mononuclear leukocyte cultures. We selected the Type 4 phosphodiesterase inhibitor, CP80,633, based on its inhibitory potency, for clinical testing by topical, bilateral paired comparisons in 20 patients with atopic dermatitis and demonstrated significant reductions of all inflammatory parameters. Phosphodiesterase inhibitors modulate several pathways contributing to the exaggerated immune and inflammatory responses, which characterize atopic dermatitis. This in vivo demonstration of anti-inflammatory efficacy may provide a useful alternative to the over-reliance on corticosteroid therapy in atopic disease.