Larry L. Froelich

Phosphatidylinositol 3-kinase activation is required for insulin-stimulated sodium transport in A6 cells

Insulin stimulates amiloride-sensitive sodium transport in models of the distal nephron. Here we demonstrate that, in the A6 cell line, this action is mediated by the insulin receptor tyrosine kinase and that activation of phosphatidylinositol 3-kinase (PI 3-kinase) lies downstream of the receptor tyrosine kinase. Functionally, a specific inhibitor of PI 3-kinase, LY-294002, blocks basal as well as insulin-stimulated sodium transport in a dose-dependent manner (IC50 ≈ 6 μM). Biochemically, PI 3-kinase is present in A6 cells and is inhibited both in vivo and in vitro by LY-294002. Furthermore, a subsequent potential downstream signaling element, pp70 S6 kinase, is activated in response to insulin but does not appear to be part of the pathway involved in insulin-stimulated sodium transport. Together with previous reports, these results suggest that insulin may induce the exocytotic insertion of sodium channels into the apical membrane of A6 cells in a PI 3-kinase-mediated manner.

Blockade of human neutrophil activation by 2-[2-propyl-3-[3-[2-ethyl-4-(4-fluorophenyl)-5-hydroxyphenoxy]propoxy]phenoxy]benzoic acid (LY293111), a novel leukotriene B4 receptor antagonist

Leukotriene B4 (LTB4), a naturally occurring pro-inflammatory product of arachidonic acid metabolism, has been associated with human inflammatory disease. This study compares the abilities of two LTB4 receptor antagonists, 2-[2-propyl-3-[3-[2-ethyl-4-(4-fluorophenyl)-5-hydroxyphenoxy]- propoxy]phenoxy]benzoic acid (LY293111) and 7-[3-(4-acetyl-3-methoxy-2-propylphenoxy)-propoxy]- 3,4-dihydro-8-propyl-2H-1-benzopyran-2-carboxylic acid (SC-41930), to displace LTB4 binding and their functional blockade of human neutrophil activation. LY293111 inhibited the binding of [3H]LTB4 with a Ki of 25 nM; SC-41930 displayed a similar potency (Ki = 17 nM). In contrast, LY293111 prevented LTB4-induced calcium mobilization with an IC50 = 20 nM, or 40 times more effectively than SC-41930 (IC50 = 808 nM). LY293111 was 300 times more potent than SC-41930 in blocking LTB4-induced CD11b up-regulation on isolated neutrophils. LY293111 also arrested LTB4-induced up-regulation of CD11b on neutrophils in whole human blood. LY293111 was not effective in blocking human neutrophil activation responses induced by N-formyl-methionyl-leucyl-phenylalanine (fMLP), platelet-activating factor (PAF), human recombinant endothelial interleukin-8 (IL-8) or human recombinant complement component 5a (C5a).

-alkoxyphenol leukotriene B4 receptor antagonists: effect of a chroman carboxylic acid.

Abstract Several ortho -alkoxyphenols containing a chroman carboxylic acid sidechain have been prepared as antagonists of leukotriene B4 receptors. These antagonists were compared to their parent alkoxyphenols containing the tetrazole acid sidechain. These chroman containing antagonists retained their binding potency for human neutrophil receptors; however, showed enhanced potency against guinea pig receptors in both in vitro and in vivo systems.

alkoxyphenol leukotriene B4 receptor antagonists

Abstract A series of ortho -alkoxyphenols containing a tetrazole acid sidechain have been prepared as antagonists of leukotriene B4 receptors. These compounds were tested as receptor antagonists of human neutrophil and guinea pig lung membrane leukotriene B4 receptors. Compounds in this series were found to be up to 18-fold more potent than LY255283. These results indicate that the acyl group of the 1,2,4,5 substituted hydroxyacetophenone class of LTB4 antagonists is not critical to antagonist potency.

QUINOLINE-SUBSTITUTED DIHYDROINDOLES AS CYSLT1 (LTD4 RECEPTOR) ANTAGONISTS

Abstract A series of quinoline-substituted dihydroindoles has been synthesized and evaluated as antagonists of the cysLT 1 receptor. This series, exemplified by 2 (LY302905; pKi = 8.3 for inhibition of binding of 3 H-LTD 4 to guinea pig lung membranes), represents reduced analogues of the corresponding indoles that were previously shown to be potent, orally active cysLT 1 receptor antagonists. These dihydroindole compounds generally displayed increased in vitro and in vivo (oral) activity.

Structural analogues of LY292728, a highly potent xanthone dicarboxylic acid leukotriene B4 receptor antagonist: spatial positioning of the secondary acid group

Abstract We report the preparation and pharmacologic activity of three spatial analogues of LY292728, a highly potent xanthone dicarboxylic LTB4 receptor antagonist. Molecular modeling of these compounds has helped to further elucidate the nature of the secondary acid binding site of the LTB4 receptor.

2-alkyl-4-ethyl-5-[6-methyl-6-(2H-tetrazol-5-yl)heptyloxy]phenol leukotriene B4 receptor antagonists

A series of 2-n-alkyl-4-ethyl-5-[6-methyl-6-(2H-tetrazol-5-yl)heptyloxy]phenols were prepared and shown to be potent leukotriene B4 (LTB4) receptor antagonists. They bound to the human neutrophil and guinea pig lung LTB4 receptors with high affinity. Each compound was also shown to be effective at antagonizing the effects of LTB4-induced integrin up-regulation on human neutrophils and on LTB4-mediated contraction of guinea pig lung parenchyma.

Synthesis and pharmacologic activity of hydroxyacetophenone-substituted benzophenone/xanthone leukotriene B4 receptor antagonists

Abstract The preparation and pharmacologic activity of two new hybrid LTB4 receptor antagonists, 1 and 2 (LY282210), are reported. These compounds are among the most potent in vitro LTB4 receptor antagonists yet described, and add new insight into the critical pharmacophores of the LTB4 receptor.

Aerosolized LTB4 produces delayed onset increases in pulmonary gas trapping

Airway obstruction, as measured by increases in postmortem pulmonary gas trapping, and lung inflammatory changes were examined in guinea pigs exposed for up to 4 h to aerosols of leukotriene B4 (LTB4) or its non-chemotactic isomer, 6-trans-12-epi-LTB4. Airway obstruction and cytological responses in isomer-exposed animals were similar to those of unexposed control animals. LTB4-exposed animals had minimal inflammatory changes at 0.5 h but became dyspneic by 2 h and had increased airway obstruction, bronchoalveolar lavage neutrophils and eosinophils, and pulmonary tissue granulocyte scores. The LTB4-induced effects at 4 h were similar to those 2 h, except for further increase in BAL neutrophils and eosinophils. LTB4-induced airway obstructive and inflammatory changes were prevented by pretreatment with the LTB4 receptor antagonist SC-41930, but were unaffected by indomethacin. Thus, prolonged LTB4 inhalation can produce delayed onset airway obstruction that is stereospecific, cyclooxygenase-independent, and temporally associated with the influx of granulocytes into lung airways.

Diaryl ether/carboxylic acid derivatives of LY255283: receptor antagonists of leukotriene B4

Abstract The preparation and activity of a series of hydroxyacetophenone/diaryl ether LTB 4 receptor antagonists are described. The key acid-substituted diaryl ether moiety is discussed in relation to the spatial and functional group requirements of the LTB 4 receptor.