Discovery of a new nucleoside template for human A3 adenosine receptor ligands: D-4'-thioadenosine derivatives without 4'-hydroxymethyl group as highly potent and selective antagonists.
ABSTRACT Truncated D-4'-thioadenosine derivatives lacking the 4'-hydroxymethylene moiety were synthesized starting from D-mannose, using cyclization to the 4-thiosugar and one-step conversion of the diol to the acetate as key steps. At the human A3 adenosine receptor (AR), N6-substituted purine analogues bound potently and selectively and acted as antagonists in a cyclic AMP functional assay. An N6-(3-chlorobenzyl)purine analogue 9b displayed a Ki value of 1.66 nM at the human A3 AR. Thus, truncated D-4'-thioadenosine is an excellent template for the design of novel A3 AR antagonists to act at both human and murine species.
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ABSTRACT: Truncated N(6)-substituted-4'-oxo- and 4'-thioadenosine derivatives with C2 or C8 substitution were studied as dual acting A(2A) and A(3) adenosine receptor (AR) ligands. The lithiation-mediated stannyl transfer and palladium-catalyzed cross-coupling reactions were utilized for functionalization of the C2 position of 6-chloropurine nucleosides. An unsubstituted 6-amino group and a hydrophobic C2 substituent were required for high affinity at the hA(2A)AR, but hydrophobic C8 substitution abolished binding at the hA(2A)AR. However, most of synthesized compounds displayed medium to high binding affinity at the hA(3)AR, regardless of C2 or C8 substitution, and low efficacy in a functional cAMP assay. Several compounds tended to be full hA(2A)AR agonists. C2 substitution probed geometrically through hA(2A)AR docking was important for binding in order of hexynyl > hexenyl > hexanyl. Compound 4g was the most potent ligand acting dually as hA(2A)AR agonist and hA(3)AR antagonist, which might be useful for treatment of asthma or other inflammatory diseases.Journal of Medicinal Chemistry 12/2011; 55(1):342-56. · 5.61 Impact Factor
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ABSTRACT: Adenosine is an ubiquitous local modulator that regulates various physiological and pathological functions by stimulating four membrane receptors, namely A(1) , A(2A) , A(2B) , and A(3) . Among these G protein-coupled receptors, the A(3) subtype is found mainly in the lung, liver, heart, eyes, and brain in our body. It has been associated with cerebroprotection and cardioprotection, as well as modulation of cellular growth upon its selective activation. On the other hand, its inhibition by selective antagonists has been reported to be potentially useful in the treatment of pathological conditions including glaucoma, inflammatory diseases, and cancer. In this review, we focused on the pharmacology and the therapeutic implications of the human (h)A(3) adenosine receptor (AR), together with an overview on the progress of hA(3) AR agonists, antagonists, allosteric modulators, and radioligands, as well as on the recent advances pertaining to the computational approaches (e.g., quantitative structure-activity relationships, homology modeling, molecular docking, and molecular dynamics simulations) applied to the modeling of hA(3) AR and drug design. © 2011 Wiley Periodicals, Inc. Med Res Rev.Medicinal Research Reviews 11/2011; · 9.58 Impact Factor
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ABSTRACT: Adenosine is present in the normal kidney and significantly elevated in response to cellular damage. The renal A3 adenosine receptor (A3AR) is up-regulated under stress, but the therapeutic effects of A3AR antagonists on chronic kidney disease are not fully understood. The present study examined the therapeutic effect of LJ-1888 [(2R,3R,4S)-2-[2-chloro-6-(3-iodobenzylamino)-9H-purine-9-yl]-tetrahydrothiophene-3,4-diol], a newly developed potent, selective, species-independent, and orally active A3AR antagonist, on unilateral ureteral obstruction (UUO)-induced renal fibrosis. Pretreatment with LJ-1888 effectively inhibited UUO-induced fibronectin and collagen I up-regulation in a dose-dependent manner. Masson's trichrome staining confirmed that LJ-1888 treatment effectively reduced UUO-induced interstitial collagen accumulation. Furthermore, delayed administration of LJ-1888 showed an equivalent therapeutic effect on tubulointerstitial fibrosis to that of losartan. Small-interfering A3AR transfection effectively inhibited transforming growth factor-β1 (TGF-β1)-induced fibronectin and collagen I up-regulation in murine proximal tubular cells similar to LJ-1888, confirming that the renoprotective effect of LJ-1888 resulted from A3AR blockade. UUO- or TGF-β1-induced c-Jun N-terminal kinase and extracellular signal-regulated kinase phosphorylation decreased significantly after LJ-1888 administration. A3AR blockade reduced UUO- or TGF-β1-induced up-regulation of lysyl oxidase, which induces cross-linking of extracellular matrix, suggesting that LJ-1888 may also regulate extracellular matrix accumulation via post-translational regulation. In conclusion, the present data demonstrate that the A3AR antagonist, LJ-1888, blocked the development of tubulointerstitial fibrosis and attenuated the progression of renal fibrosis, and they suggest that LJ-1888 may become a new therapeutic modality for renal interstitial fibrosis.American Journal Of Pathology 08/2013; · 4.60 Impact Factor