ICH3, a selective alpha7 nicotinic acetylcholine receptor agonist, modulates adipocyte inflammation associated with obesity.

PURPOSE: The alpha7 nicotinic acetylcholine receptor (α7nAChR), involved in the modulation of inflammation and insulin sensitivity, is downregulated in white adipose tissue (WAT) of obese patients. This study aims to test the ability of a selective synthetic α7nAChR agonist, the spirocyclic Δ2-isoxazoline derivative (R)-(-)-ICH3 (ICH3), to counteract acute inflammation and obesity-associated modifications in WAT. METHODS: We employed the LPS-septic shock murine model, human primary adipocytes and diet-induced obese (DIO) mice. Inflammatory factor expression was assessed by ELISA and quantitative real-time PCR. Flow cytometry was employed to define WAT inflammatory infiltrate. Insulin signaling was monitored by quantification of AKT phosphorylation. RESULTS: In the septic shock model, ICH3 revealed antipyretic action and reduced the surge of circulating cytokines. In vitro, ICH3 stimulation (10 µM) preserved viability of human adipocytes, decreased IL-6 mRNA (P < 0.05) and blunted LPS-induced peak of TNFα (P < 0.05) and IL-6 (P < 0.01). Chronic administration of ICH3 to DIO mice was associated with lower numbers of CD8+ T cells (P < 0.05) and to changed WAT expression of inflammatory factors (Hp, P < 0.05; CD301/MGL1, P < 0.01; Arg-1, P < 0.05). As compared to untreated, ICH3 DIO mice exhibited improved insulin signaling in the skeletal muscle (P < 0.01) mirrored by an improved response to glucose load (ipGTT: P < 0.05 at 120 min). CONCLUSIONS: We proved that ICH3 is an anti-inflammatory drug, able to reduce inflammatory cytokines in human adipocytes and to blunt the effects of obesity on WAT inflammatory profile, on glucose tolerance and on tissue insulin sensitivity.

Agonists with supraphysiological efficacy at the muscarinic M2 ACh receptor.

BACKGROUND AND PURPOSE: Artificial agonists may have higher efficacy for receptor activation than the physiological agonist. Until now, such 'superagonism' has rarely been reported for GPCRs. Iperoxo is an extremely potent muscarinic receptor agonist. We hypothesized that iperoxo is a 'superagonist'. EXPERIMENTAL APPROACH: Signalling of iperoxo and newly synthesized structural analogues was compared with that of ACh at label-free M2 muscarinic receptors applying whole cell dynamic mass redistribution, measurement of G-protein activation, evaluation of cell surface agonist binding and computation of operational efficacies. KEY RESULTS: In CHO-hM2 cells, iperoxo significantly exceeds ACh in Gi /Gs signalling competence. In the orthosteric loss-of-function mutant M2 -Y104(3.33) A, the maximum effect of iperoxo is hardly compromised in contrast to ACh. 'Superagonism' is preserved in the physiological cellular context of MRC-5 human lung fibroblasts. Structure-signalling relationships including iperoxo derivatives with either modified positively charged head group or altered tail suggest that 'superagonism' of iperoxo is mechanistically based on parallel activation of the receptor protein via two orthosteric interaction points. CONCLUSION AND IMPLICATIONS: Supraphysiological agonist efficacy at muscarinic M2 ACh receptors is demonstrated for the first time. In addition, a possible underlying molecular mechanism of GPCR 'superagonism' is provided. We suggest that iperoxo-like orthosteric GPCR activation is a new avenue towards a novel class of receptor activators.

Pharmacological profile of enantiomerically pure chiral muscarinic agonists: desoxymuscarines.

The enantiomers desoxymuscarine 6 were tested in vitro on guinea pig tissues, and their muscarinic potency was evaluated at M2 (heart force and rate) and M3 (ileum and bladder) receptor subtypes together with the enantiomers of the parent compound muscarine 1. The eutomers (+)-1 and (+)-6 and distomers (-)-1 and (-)-6 were also assayed in vivo on pithed rat. Affinity, relative efficacy and enantio-selectivity were also determined for the compounds under study at M2 (heart force and rate) and M3 (ileum and bladder), in order to investigate muscarinic receptor heterogeneity. The results of this study have been discussed in comparison with the data previously reported for the structurally related fluoromuscarine (+)-4 and difluoromuscarines (+)-5 and (-)-5.

Synthesis and pharmacological characterization of new chiral derivatives of muscarine and allo-muscarine.

Novel derivatives of natural muscarine and allo-muscarine, i.e. the benzyl ethers (-)-10 and (-)-12 and the benzoate (-)-13, were synthesized in very high enantiomeric excess. Target compounds were tested in vitro on guinea pig tissues, and their muscarinic potency was evaluated at M2 (heart force and rate) and M3 (ileum and bladder) receptor subtypes. The derivatives under study were also assayed in vivo on pithed rat. In addition, muscarinic receptor heterogeneity was investigated by determining the affinity and the relative efficacy of compounds (-)-10, (-)-12 and (-)-13 at M2 (heart force and rate) and M3 (ileum and bladder) receptor subtypes.

New analogues of oxotremorine and oxotremorine-M: estimation of their in vitro affinity and efficacy at muscarinic receptor subtypes.

Two subsets of tertiary amines (1a-6a) and methiodides (1b-6b) with a structural resemblance to oxotremorine and oxotremorine-M were tested at rabbit vas deferens (M1), guinea pig left atrium (M2), guinea pig ileum and urinary bladder (M3) muscarinic receptor subtypes. The pharmacological profile of the derivatives under study has been discussed by evaluating their potency, affinity and efficacy as well as the regional differences in muscarinic receptor occupancy.

Synthesis and functional characterization of novel derivatives related to oxotremorine and oxotremorine-M.

Two subseries of nonquaternized (5a-10a) and quaternized derivatives (5b-10b) related to oxotremorine and oxotremorine-M were synthesized and tested. The agonist potency at the muscarinic receptor subtypes of the new compounds was estimated in three classical in vitro functional assays: M1 rabbit vas deferens, M2 guinea pig left atrium and M3 guinea pig ileum. In addition, the occurrence of central muscarinic effects was evaluated as tremorigenic activity after intraperitoneal administration in mice. In in vitro tests a nonselective muscarinic activity was exhibited by all the derivatives with potencies values that, in some instances, surpassed those of the reference compounds (i.e. 8b). Functional selectivity was evidenced only for the oxotremorine-like derivative 9a, which behaved as a mixed M3-agonist/M1-antagonist (pD2 = 5.85; pA2 = 4.76, respectively). In in vivo tests non-quaternary compounds were able to evoke central muscarinic effects, with a potency order parallel to that observed in vitro.

Synthesis of new delta 2-isoxazoline derivatives and their pharmacological characterization as beta-adrenergic receptor antagonists.

A series of delta 2-isoxazoline derivatives structurally related to Broxaterol 1 and Falintolol 3 has been prepared and evaluated for their binding affinity to beta 1- and beta 2-adrenergic receptors. Among the tested compounds only the 3-isopropenyl anti derivative 4d is as active as the reference compounds. An electron-releasing group, probably operating through a pi-pi interaction, in the 3-position of the isoxazoline nucleus greatly enhances the affinity of the compounds. Conversely, the closest analogs of Broxaterol (3-bromo delta 2-isoxazolines 4a and 5a) are at least one order of magnitude less active than the model compound 1. Throughout the series of derivatives the anti stereoisomers are invariably more active than their syn counterparts.

Semisynthetic derivatives of purpuromycin as potential topical agents for vaginal infections.

Purpuromycin (1) is an antibiotic with a broad spectrum of antimicrobial activity, encompassing bacteria, fungi, and protozoa, particularly those involved in vaginal infections. With the aim of enhancing the solubility and reducing the serum binding, a chemical program of modifications was undertaken on the natural compound, and a new interesting series of derivatives at the naphthoquinone system was synthesized and evaluated as potential topical agents for vaginal infections. In particular three semisynthetic derivatives, 7'-amino (8a), 7'-methylamino (8b), 7'-ethylamino (8c), of 7'-demethoxypurpuromycin seemed to be the most promising. They were tested for in vitro activity against three of the most important vaginal pathogens and showed activity similar to that of purpuromycin against Candida isolates while they were significantly more active against Trichomonas vaginalis and Gardnerella vaginalis, which are cultured in media containing blood or serum. This is probably due to the fact that the activity of the derivatives is less antagonized by these supplements than that of purpuromycin.

Synthesis and biological evaluation of new fragments from kirromycin antibiotic.

New N-acyl derivatives of 1-N-desmethyl goldinamine were obtained from degradation of kirromycin. Periodate-oxidation of these derivatives provided new aldehydic fragments that were further elaborated. Both N-phenyl ureido and N-phthalimido derivatives of 1-N-desmethyl goldinamine are able to inhibit bacterial protein synthesis in cell-free assay and are active against whole microorganisms, although with lower potency than kirromycin. The derivatives from the aldehydic fragments are totally inactive.

Synthesis and antimicrobial activities of 4-purpuromycin derivatives.

Purpuromycin (1) is a natural antibiotic with a broad spectrum of activity encompassing bacteria, fungi and protozoa. A new series of derivatives of 1 was prepared by the modification or replacement of the C-4 hydroxyl group. The physico-chemical characteristics and the in vitro antimicrobial activity of these new semisynthetic purpuromycin derivatives are reported. Attachment of a variety of bulky groups to the C-4 hydroxyl group as well as acylation or mesylation of 1 gave derivatives with significantly reduced antifungal activity, while the antimicrobial activity of these derivatives against Gram-positive and Gram-negative bacteria was only slightly decreased. All compounds were inactive against Escherichia coli. The C-4 epimers showed different in vitro activity as compared with those having the natural configuration, particularly against fungi.

Synthesis and pharmacological investigation of the enantiomers of muscarone and allomuscarone.

A strategy based on the use of (R)- and (S)-lactic ester as starting materials allowed the synthesis of the two enantiomers of muscarone [(-)-1 and (+)-1] and allomuscarone [(-)-5 and (+)-5] in greater than 98% enantiomeric excess. The compounds were examined for their ability to bind to membranes from cerebral cortex (M1), heart (M2), and salivary glands (M3) and to recognize affinity agonist states of the muscarinic receptors. The two pairs of enantiomers were also tested in five functional assays, and their muscarinic potency was determined. In both binding and functional tests, (-)-1 (2S,5S) and (-)-5 (2R,5S) were the eutomers of muscarone and allomuscarone, respectively. The eudismic ratio of muscarone, evaluated in the functional tests, spanned a range of 280-440. These values are substantially different from ones (2.4-10.1) reported in the literature. From a stereochemical point of view, muscarone behaves as muscarine and all other major muscarinic agonists; as a consequence, the hypotheses advanced to account for the anomalies of muscarone no longer have reason to exist.

Synthesis and pharmacological investigation of stereoisomeric muscarines.

The synthesis of the eight stereoisomers of muscarine has been efficiently accomplished by utilizing the two enantiomers of lactic esters as starting material. The synthetic strategy is based on a SnCl4-catalyzed addition of allyltrimethylsilane to O-protected lactic aldehydes followed by an iodocyclization process. All the final derivatives possess an enantiomeric excess higher than 98%. The four pairs of enantiomers bound to M1, M2, and M3 muscarinic receptor subtypes in membranes from cerebral cortex, heart, and salivary glands, respectively, and recognized heterogeneous states of the receptors. Of the eight isomers, only natural muscarine (+)-1 recognized three affinity states of the M2 receptor. The compound was also the only one to show selectivity in the binding study, demonstrating 37- to 44-fold higher affinity for the M2 than for the M1 or M3 receptors. In addition, the compounds were tested in functional assays on isolated guinea pig atria (M2 receptors) and ileum (mixed population of M2 and M3 receptors) and their muscarinic potencies were determined. Among the eight isomers, again only (+)-1 enantiomer was found to be very active on both tissues. Its potency was more than two orders of magnitude higher than that of its enantiomer (-)-1 as well as the other six isomers. The eudismic ratios (E.R.) deduced from the two functional tests were 324 and 331.