The pharmacologic activities of leukotrienes C-i and D (LTC-1 and LTD), constituents of slow reacting substance of anaphylaxis (SRS-A), were evaluated in vitro on airway contractile tissues and in vivo on pulmonary mechanical function, mean systemic arterial pressure, and cutaneous microcirculation. In vitro both LTC-Land LTD were potent and selective peripheral airway agonists, being more active than histamine; furthermore, LTD was active on peripheral airways at concentrations 1/100th those of LTC-1. The concentration-effect relationship for LTD and the profile of antagonism by FPL 55712 are consistent with the activity. of this molecule at two separate peripheral airway receptors. Ii vivo, LTC1 and LTD were nearly equally active in their effects on pulmonary mechanics, and the pattern of alterations was consistent with the predominant site of action being in the lung periphery. Furthermore, both agents had a direct systemic arterial hypotensive effect and were vasoactive on the cutaneous microcirculation. Thus, these compounds are likely to be major mediators of the pathologic alterations in immediate type hypersensitivity reactions in which peripheral airway constriction and hypotension are prominent features.Slow reacting substance of anaphylaxis (SRS-A) (1), which is an activity generated during immediate type hypersensitivity reactions (2), has been found to be composed of leukotrienes C-i (LTC-1) and D (LTD) (3). Native SRS-A has a unique profile of contractile activity in vitro in smooth muscle preparations (4). Both partially and highly purified native SRS-A produced by an anaphylactic reaction in the rat peritoneal cavity (SRS-Arat) exhibit a preferential contractile activity for guinea pig pulmonary parenchymal strips compared to musculus trachealis (5), and LTC-1 and LTD exhibit the same differential effect, at concentrations less than 0.1% of those required for histamine to be active (3). Partially purified SRS-Arat augments vascular permeability when injected into guinea pig skin (6). When administered intravenously into the unanesthetized guinea pig, it produces an alteration in pulmonary mechanics consistent with peripheral rather than central airway action (7). We have now demonstrated that intravenous infusion of LTC-1 and LTD alters pulmonary mechanics in unanesthetized and anesthetized guinea pigs in a manner similar to native partially purified SRS-Arat and that, in addition, these newly described products of arachidonate metabolism (8-10) can differ in their actions on the cutaneous microvasculature and on mean systemic arterial pressure.MATERIALS AND METHODS LTC-1 and LTD were prepared as described (3, 10), sealed in ampoules in 10% methanol under argon, and stored frozen until the day of use. Histamine diphosphate was obtained from Sigma. FPL 55712, a specific SRS-A antagonist, was a gift from P. Sheard (Fisons Pharmaceuticals, Ltd., U.K.).Tracheal spirals and parenchymal strips were prepared for recording isometric contractile activity (5) and allowed to relax to baseline tensi...

Slow reacting substance(s) of anaphylaxis (SRS-A) was isolated from both human (lung) and rat sources and compared with three synthetic SRS-As of known structureleukotrienes (LTs) C-1, C-2, and D. Reversed-phase liquid chromatography was used both as a final purification step and a means of comparison of biologically derived and synthetic substances. Two major peaks of SRS-A activity of both rat and human origin corresponded chromatographically with LTC-1 and LTD, respectively, and had equivalent specific activities on the guinea pig ileum. With guinea pig ileum, the specific activities (units/pmol) for synthetic leukotrienes and anaphylactic peaks were (mean -SEM): synthetic LTC-1, 1.93 -0.13; SRS-Arat peak I, 1.69 + 0.43; synthetic LTD, 6.10 i 1.15; SRS-Arat peak 11, 7.14 + 0.51; and SRS-AhU peak II, 1.90. Both synthetic LTC-1 and LTD and their SRS-A natural counterparts had a preferential contractile activity on guinea pig peripheral airway compared to central airways and were at least 200 times more active than histamine on peripheral airways on a molar basis. Leukotriene D is the major SRS-A of human lung and accounts for almost all of the biological activity. It likely is formed from leukotriene C-1 in vivo by an enzymic process of the well-known 'y-glutamyltransferase type.Although "slow reacting substance of anaphylaxis" (SRS-A) has been recognized as a putative major mediator of immediate hypersensitivity reactions for 40 years (1), only in the past decade have both proof of potency and evidence of chemical structure emerged. Brocklehurst (2) distinguished SRS-A from histamine in an anaphylactic perfusate by its contractile action on an (H-1) antihistamine-blocked guinea pig ileum wth a slow progression to maximal effect. Subsequent investigations established it to be a polar lipid (3, 4) with strong ultraviolet absorbance and possibly containing sulfur (4, 5). Cysteine was subsequently observed to augment generation of SRS-A (6) and a calcium ionophore was shown to stimulate production of nonanaphylactic slow-reacting substance (SRS) (7, 8) with incorporation of radiolabeled arachidonic acid as the lipid precursor (9, 10). Recently, an ionophore-stimulated SRS from mouse mastocytoma cells designated as leukotriene C-1 (11) (LTC-1) was identified as 5(S)-hydroxy-6(R)-S-glutathionyl-7,9-trans,11,14-cts-icosatetraenoic acid (II in Fig. 1) (12, 13) and was prepared in quantity by total synthesis.This communication reports the use of synthetic leukotrienes C-1 (13) and D (IV) (LTD) to standardize retention times on high-performance liquid chromatography (HPLC) (14,15) and to calculate the specific functional activities of SRS-A produced by an anaphylactic reaction in the rat peritoneal cavity or human lung. Additionally, naturally derived SRS-A components were compared with the synthetic leukotrienes in regard to differential and specific activities on the guinea pig tracheal and lung parenchymal muscle strips in vitro (14, 16), UV absorption, and enzymic oxidation. MATERIALS AND METHODSMaterials. ...

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The synthesis and biological activity of a new series of LpxC inhibitors represented by pyridone methylsulfone hydroxamate 2a is presented. Members of this series have improved solubility and free fraction when compared to compounds in the previously described biphenyl methylsulfone hydroxamate series, and they maintain superior Gram-negative antibacterial activity to comparator agents.

In addition to having desirable inhibitory effects on inflammation, anaphylaxis, and smooth muscle contraction, PDE-IV inhibitors also produce undesirable side effects including nausea and vomiting. In general, compounds that inhibit PDE-IV also potently displace [3H]rolipram from a high-affinity binding site in rat cortex. While this binding site has not been identified, it has been proposed to be an allosteric binding site on the PDE-IV enzyme. Preliminary studies have suggested that the emetic potency of PDE-IV inhibitors is correlated with affinity for the brain rolipram binding site rather than potency at inhibiting PDE-IV enzyme activity. Efforts to eliminate the emetic potential of PDE-IV inhibitors were directed toward developing compounds with decreased [3H]rolipram binding affinity while retaining PDE-IV potency. Thus, a novel series of 4-(3-alkoxy-4-methoxyphenyl)benzoic acids and their corresponding carboxamides were prepared and evaluated for their PDE-IV inhibitory and rolipram binding site properties. Modification of the catechol ether moiety led to phenylbutoxy and phenylpentoxy analogues that provided the desired activity profile. Specifically, 4-[3-(5-phenylpentoxy)-4-methoxyphenyl]-2-methylbenzoic acid, 18, was found to exhibit potent PDE-IV inhibitory activity (IC50 0.41 microM) and possessed 400 times weaker activity than rolipram for the [3H]rolipram binding site. In vivo, compound 18 was efficacious in the guinea pig aerosolized antigen induced airway obstruction assay (ED50 8.8 mg/kg, po) and demonstrated a significant reduction in emetic side effects (ferret, 20% emesis at 30 mg/kg, po).

In this paper, we present the synthesis and SAR as well as selectivity, pharmacokinetic, and infection model data for representative analogues of a novel series of potent antibacterial LpxC inhibitors represented by hydroxamic acid.

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