Lack of effect of repeated administration of milnacipran, a double noradrenaline and serotonin reuptake inhibitor, on the beta-adrenoceptor-linked adenylate cyclase system in the rat cerebral cortex.

The effects of subacute administration of the double noradrenaline and serotonin uptake inhibitor antidepressant, milnacipran, and the tricyclic antidepressant, imipramine, on radioligand binding to beta-adrenergic receptors and on beta-adrenergic agonist-stimulated adenylate cyclase activity, in the rat cerebral cortex, have been determined. Rats were injected intraperitoneally for 21 days with milnacipran (3, 10 or 30 mg/kg/day) or imipramine (10 mg/kg/day). The treatment with milnacipran up to 30 mg/kg/day did not modify either the maximum number of [3H]CGP-12177 binding sites (Bmax) or the equilibrium dissociation constant (Kd). On the other hand, treatment of the rats with 10 mg/kg/day imipramine induced a decrease (27%) in Bmax [3H]CGP-12177 binding sites without affecting the Kd value. Furthermore, milnacipran did not affect the stimulation of cAMP production induced by either 30 microM isoprenaline, 10 microM GTP gamma S or 10 microM forskolin. Under similar conditions, treatment with imipramine reduced by 70% the isoprenaline-induced stimulation of cAMP production without affecting that induced by either GTP gamma S or forskolin. These results demonstrate that, unlike imipramine, subacute administration of milnacipran does not produce any change in beta-adrenoceptor sensitivity in the rat brain cortex.

From hit to lead. Combining two complementary methods for focused library design. Application to mu opiate ligands.

Compound 1 obtained by random screening and displaying a micromolar activity on the mu opiate receptor was chosen as a starting point for optimization. Two complementary concepts of similarity were used for the design of analogues and compared. These are based, respectively, on a computer-aided comparison of pharmacophoric patterns and on topological similarity. The structure-activity relationships are discussed in light of both similarity concepts. Compound 40, an N-methyl-3-(4-oxo-1-phenyl-1,3,8-triazaspiro[4.5]decyl)acetamide derivative, designed by combining the structure-activity relationships enlightened by each method, has a subnanomolar affinity for mu (h) receptor (IC(50) = 0.9 nM). It is a promising lead, allowing the design of a new series of analogues substituted at the N-3 of the spirocycle moiety.

From hit to lead. Analyzing structure-profile relationships.

Two compounds, obtained by random screening, and displaying micromolar activities on the mu opiate receptor were used as starting points for optimization. In that work, the traditional concept of the activity of a compound (related to one or a few targets) was extended to the comprehensive pharmacological profile of that compound on more than 70 receptors, transporters, and channels relevant to a CNS-oriented project. Using the two complementary design strategies based on two similarity concepts described in the previous paper, we have obtained analogues with IC(50) values ranging between 0.9 nM and a few micromolar on the mu receptor and displaying qualitatively different profiles. We discuss here, both on a case-by-case basis and from a statistical standpoint, the pharmacological profiles in light of the two similarity concepts.

Up-regulation of [3H]-des-Arg10-kallidin binding to the bradykinin B1 receptor by interleukin-1 beta in isolated smooth muscle cells: correlation with B1 agonist-induced PGI2 production.

1. Binding of the specific bradykinin B1 receptor agonist, [3H]-des-Arg10-kallidin (-KD) was investigated in smooth muscle cells (SMC) isolated from rabbit mesenteric arteries (RMA). 2. [3H]-des-Arg10-KD specifically bound to interleukin-1 (IL-1)-treated RMA-SMC in a saturable fashion with an equilibrium dissociation constant (KD) of 0.3-0.5 nM. The number of binding sites per cell was 20,000-35,000. Kinins inhibited [3H]-des-Arg10-KD binding to RMA-SMC with an order of potency very similar to that observed in typical B1 specific bioassays: des-Arg9-bradykinin (BK) approximately KD >> BK. Furthermore, the B1 receptor antagonist [Leu8]des-Arg9-BK inhibited [3H]-des-Arg10-KD binding with an IC50 of 43 nM as expected for its effect at B1 receptors. The B2 receptor antagonists, NPC 567 and Hoe 140 only affected [3H]-des-Arg10-KD binding at very high concentrations (IC50 = 0.8 microM and IC50 > 10 microM, respectively). 3. Des-Arg9-BK (B1 agonist) and [Hyp3]Tyr(Me)8-BK (B2 agonist) did not induce prostacyclin (PGI2) production by RMA-SMC. Lipopolysaccharide (LPS) treatment of the cells did not affect the B1 agonist response whereas IL-1 beta treatment produced a 7 fold increase in des-Arg9-BK-stimulated PGI2 production. IL-1 beta also stimulated the response to B2 agonists. 4. Des-Arg9-BK-induced PGI2 secretion in IL-1-primed RMA-SMC was mediated by B1 receptors since it was inhibited by [Leu8]des-Arg9-BK (IC50 = 56-73 nM) but not by Hoe 140. High concentrations of NPC 567 (IC5o = 2.4 micro M) were required to inhibit PGI2 production induced by B1 agonists.5. IL- 1-treated RMA-SMC displayed a 5 fold increase in the number of B1 receptors without modification of the affinity constant, thus establishing a possible relationship between the receptor density and the IL-i-primed B1 response.6. LPS treatment of the cells induced a 4 fold increase in B1 receptor number without modifying PGI2 secretion. This observation suggests that IL-1 but not LPS, in addition to increase in the number of receptors, signals the cell to permit the coupling of B1 receptors to the PLA2/cyclo-oxygenase pathway.

Mediators involved in inflammation: effects of Daflon 500 mg on their release.

Each step of an inflammatory reaction is triggered by one or several chemical or biological mediators such as arachidonic acid derivatives (prostaglandins [PG], leukotrienes [LT], or thromboxanes [TX]), vasoactive amines (histamine or serotonin), and oxygen free radicals (superoxide ion, O2-, or hydrogen peroxide, H2O2). In perivenous inflammation, these mediators play a prominent role in favoring vasodilatation (histamine), increasing membrane permeability (PGE2, histamine, free radicals) and providing a chemotactic signal for specialized cells, ie, neutrophil polynuclears, macrophages, lymphocytes (LTB4, free radicals). The antiinflammatory effects of Daflon 500 mg,* a micronized purified flavonoid fraction (90% diosmin, 10% hesperidin), were studied in different in vivo and in vitro models. In a model of inflammatory granuloma in the rat, Daflon 500 mg (100 mg/kg, orally) reduced edema formation and inhibited the synthesis for PGE2 (78.5%), PGF2 alpha (45.2%) and TXB2 (59.5%) (Damon et al, Arzneim-Forsch/Drug Res 37:1149-1153, 1987). Intravenous injection of Daflon 500 mg (25 and 50 mg/kg) reduced the hyperglycemia induced by injection of alloxan in rat. This effect of Daflon 500 mg was linked to its ability to scavenge active oxygen radicals, demonstrated in vitro using human neutrophils (Lonchampt et al, Arzneim-forsch/Drug Res 39:882-885, 1989) or mouse peritoneal macrophages (Bodinier et al, manuscript in preparation) stimulated by zymosan. The free radical scavenger effect of Daflon 500 mg is observed at concentrations ranging from 10(-7) M to 10(-4) M, with half-maximal effect between 10(-6) M and 10(-5) M. Thus, Daflon 500 mg behaves as a potent protective agent against inflammatory disorders. These properties may explain, at least in part, the clinical activity of Daflon 500 mg and justify its therapeutic use.

Membrane isoforms of human immunoglobulins of the A1 and A2 isotypes: structural and functional study.

As for IgM, human IgA occurs either as soluble molecules in plasma and various other body fluids, or as membrane-bound molecules on differentiated B cells, where they are part of the B-cell receptor for antigen (BCR). We studied the structure of transcripts encoding the membrane-anchored alpha-chain of the human BCR alpha, which may be present in two different forms resulting from alternate splicing of the alpha-chain mRNA (type I or type II). The ratio of type I versus type II did not vary upon stimulation of a B-cell line with various cytokines. Rather, it differed strikingly in cells expressing either the IgA1 or IgA2 isotype of the BCR alpha, with virtually no type II alpha-chain in the latter. Co-modulation experiments also yielded different results for both isotypes, since they demonstrated a physical association of both membrane (m)IgA1 and mIgA2 with CD79b, the beta component of the BCR Ig alpha/Ig beta heterodimer, but only of mIgA1 with CD19. Whatever the isotype, the BCR of the IgA class was able to carry out signal transduction upon cross-linking by specific monoclonal antibodies but, in contrast to mIgM, it relied mainly on the entry of extracellular Ca2+ rather than on the release of intracellular stocks.