calcimycin and Dermatitis--Contact

There is a major clinical need for new therapies for the treatment of chronic itch. Many of the molecular components involved in itch neurotransmission are known, including the neuropeptide NPPB, a transmitter required for normal itch responses to multiple pruritogens in mice. Here, we investigated the potential for a novel strategy for the treatment of itch that involves the inhibition of the NPPB receptor NPR1 (natriuretic peptide receptor 1). Because there are no available effective human NPR1 (hNPR1) antagonists, we performed a high-throughput cell-based screen and identified 15 small-molecule hNPR1 inhibitors. Using in vitro assays, we demonstrated that these compounds specifically inhibit hNPR1 and murine NPR1 (mNPR1). In vivo, NPR1 antagonism attenuated behavioral responses to both acute itch- and chronic itch-challenged mice. Together, our results suggest that inhibiting NPR1 might be an effective strategy for treating acute and chronic itch.

Topics: Animals; Behavior, Animal; Cell-Free System; Dermatitis, Contact; Disease Models, Animal; Ganglia, Spinal; Humans; Mice, Inbred C57BL; Mice, Knockout; Neurons; Pruritus; Receptors, Atrial Natriuretic Factor; Reproducibility of Results; Signal Transduction; Small Molecule Libraries

Lipoxin A(4) (LXA(4)) is a structurally and functionally distinct natural product called an eicosanoid, which displays immunomodulatory and anti-inflammatory activity but is rapidly metabolized to inactive catabolites in vivo. A previously described analogue of LXA(4), methyl (5R,6R,7E,9E,11Z,13E,15S)-16-(4-fluorophenoxy)-5,6,15-trihydroxy-7,9,11,13-hexadecatetraenoate (2, ATLa), was shown to have a poor pharmacokinetic profile after both oral and intravenous administration, as well as sensitivity to acid and light. The chemical stability of the corresponding E,E,E-trien-11-yne analogue, 3, was improved over 2 without loss of efficacy in the mouse air pouch model of inflammation. Careful analysis of the plasma samples from the pharmacokinetic assays for both 2 and 3 identified a previously undetected metabolite, which is consistent with metabolism by beta-oxidation. The formation of the oxidative metabolites was eliminated with the corresponding 3-oxatetraene, 4, and the 3-oxatrien-11-yne, 5, analogues of 2. Evaluation of 3-oxa analogues 4 and 5 in calcium ionophore-induced acute skin inflammation model demonstrated similar topical potency and efficacy compared to 2. The 3-oxatrien-11-yne analogue, 5, is equipotent to 2 in an animal model of inflammation but has enhanced metabolic and chemical stability and a greatly improved pharmacokinetic profile.

Topics: Acute Disease; Animals; Anti-Inflammatory Agents, Non-Steroidal; Calcimycin; Dermatitis, Contact; Drug Stability; Ionophores; Lipoxins; Male; Mice; Mice, Inbred BALB C; Oxidation-Reduction; Phenyl Ethers; Stereoisomerism; Structure-Activity Relationship

In early phases of cutaneous inflammation, connective tissue mast cell degranulation is associated with apparent secretion and externalization of immunoreactive chymotryptic serine proteinase. To determine whether this event is associated with structural evidence of granule externalization, we studied the sequential evolution of IgE-mediated hypersensitivity in vivo, as well as mast cell degranulation provoked by a variety of stimuli in cultured explants of human skin. By 1 min after intradermal antigen challenge with ragweed extract, mast cell degranulation was associated with apparent extrusion of intragranule constituents into the pericellular connective tissue. Similar features typified cultured skin explants exposed for 45 min to anti-IgE and other mast cell secretagogues (morphine sulfate, calcium ionophore A23187, compound 48/80, and substance P). Once externalized, granule constituents could be identified within the dermal matrix by their rounded contour and structural similarity to solubilized granule matrices remaining within actively secreting cells. These data indicate that externalization of connective tissue mast cell granule contents occurs early after secretagogue exposure, potentially accounting for infrequent documentation of this event in naturally occurring dermatoses. The ability to recognize externalized granule products at a morphologic level should facilitate the understanding of interactions between mast cell-derived mediators and target structures of the dermal microvasculature.

Topics: Adult; Calcimycin; Cell Degranulation; Chymases; Connective Tissue; Dermatitis, Contact; Humans; Immunohistochemistry; Male; Mast Cells; Morphine; Organ Culture Techniques; p-Methoxy-N-methylphenethylamine; Serine Endopeptidases; Skin; Substance P

1. This paper describes the pharmacological profile of ICI207968, a novel, orally-active and selective inhibitor of 5-lipoxygenase. 2. Inhibition of leukotriene B4 (LTB4) synthesis by 2-substituted indazolinones was not directly related to redox potential but was critically dependent on the nature of the N2 substituent. 2-(3-Pyridylmethyl)-indazolinone (ICI207968) combined selectivity and oral potency. 3. In several in vitro systems ICI207968 exhibited similar lipoxygenase inhibitory potency (IC50 values from 1.5 microM to 6.0 microM) and was approximately 300 times less potent against cyclo-oxygenase, as measured by inhibition of prostaglandin E2 (PGE2) synthesis. 4. ICI207968 also produced selective lipoxygenase inhibition following oral administration in the rat. ED50 values of 2.5, 10 and 25 mg kg-1 p.o. for inhibition of LTB4 release from A23187-stimulated blood were obtained 1, 3 and 5 h after dosing. The compound did not inhibit PGE2 synthesis at oral doses up to 300 mg kg-1. 5. Co-administration of ICI207968 with arachidonic acid, into rabbit dermis, potently inhibited both plasma extravasation and polymorphonuclear leucocyte (PMNL) infiltration induced by this inflammatory fatty acid. The anti-inflammatory potency of a number of intradermally administered indazolinones, with similar redox potentials, was related to their inhibitory potency against leukotriene generation in blood. Oral administration of ICI207968 (100 mg kg-1) in the rabbit inhibited ex vivo leukotriene generation in blood and arachidonic acid-induced skin inflammation. 6. These data demonstrate that ICI207968 is an orally active and selective inhibitor of 5-lipoxygenase which has anti-inflammatory properties. IC1207968 will be a valuable agent for clarifying the biological roles of leukotrienes and the therapeutic potential of 5-lipoxygenase inhibitors.

Topics: Administration, Oral; Animals; Anti-Inflammatory Agents, Non-Steroidal; Arachidonate Lipoxygenases; Arachidonic Acid; Arachidonic Acids; Biological Availability; Calcimycin; Dermatitis, Contact; Eicosanoids; In Vitro Techniques; Indazoles; Lipoxygenase Inhibitors; Macrophages; Male; Mice; Oxidation-Reduction; Pyrazoles; Rabbits; Rats; Rats, Inbred Strains

Basophil releasability is an important parameter in several pathophysiological conditions. In normal donors, the maximum percent histamine release and cell sensitivity to rabbit anti-Fc epsilon (anti-IgE) is correlated with the age of cell donors. A positive correlation between serum IgE level and anti-IgE-induced histamine release was found in subjects below 20 years old. The response to formyl-Met-Leu-Phe (f-met peptide) was significantly reduced in subjects above 60 years old. In twins, IgE-mediated releasability and serum IgE levels appear to be controlled by two different genetic mechanisms. Basophils of patients with atopic dermatitis were more responsive than those of control subjects of matched ages to anti-IgE.

Topics: Adolescent; Adult; Age Factors; Aged; Antibodies, Anti-Idiotypic; Basophils; Calcimycin; Child; Child, Preschool; Dermatitis, Contact; Deuterium; Histamine Release; Humans; Immunoglobulin E; Infant; Middle Aged; N-Formylmethionine Leucyl-Phenylalanine; Receptors, Fc