Discovery of novel S1P2 antagonists. Part 1: discovery of 1,3-bis(aryloxy)benzene derivatives.

The structure-activity relationships of a novel series of sphingosine-1-phosphate receptor antagonists have been examined in detail. The initial hit compound 1 was modified through synthesis to improve its S1P2 activity. The synthesis of a series of analogs revealed that 1,3-bis(aryloxy)benzene derivatives, as represented by 22, are potent and selective S1P2 antagonists.

Prostaglandin E2 receptor type 2-selective agonist prevents the degeneration of articular cartilage in rabbit knees with traumatic instability.

INTRODUCTION: Osteoarthritis (OA) is a common cause of disability in older adults. We have previously reported that an agonist for subtypes EP2 of the prostaglandin E2 receptor (an EP2 agonist) promotes the regeneration of chondral and osteochondral defects. The purpose of the current study is to analyze the effect of this agonist on articular cartilage in a model of traumatic degeneration. METHODS: The model of traumatic degeneration was established through transection of the anterior cruciate ligament and partial resection of the medial meniscus of the rabbits. Rabbits were divided into 5 groups; G-S (sham operation), G-C (no further treatment), G-0, G-80, and G-400 (single intra-articular administration of gelatin hydrogel containing 0, 80, and 400 µg of the specific EP2 agonist, ONO-8815Ly, respectively). Degeneration of the articular cartilage was evaluated at 2 or 12 weeks after the operation. RESULTS: ONO-8815Ly prevented cartilage degeneration at 2 weeks, which was associated with the inhibition of matrix metalloproteinase-13 (MMP-13) expression. The effect of ONO-8815Ly failed to last, and no effects were observed at 12 weeks after the operation. CONCLUSIONS: Stimulation of prostaglandin E2 (PGE2) via EP2 prevents degeneration of the articular cartilage during the early stages. With a system to deliver it long term, the EP2 agonist could be a new therapeutic tool for OA.

Endogenous prostaglandin E2 inhibits aberrant overgrowth of rheumatoid synovial tissue and the development of osteoclast activity through EP4 receptor.

OBJECTIVE: We recently developed an ex vivo cellular model of pannus, the aberrant overgrowth of human synovial tissue. This study was undertaken to use that model to investigate the role of prostaglandin E2 (PGE2) and its receptor subtypes in the development of pannus growth and osteoclast activity in rheumatoid arthritis (RA). METHODS: Inflammatory cells that infiltrated pannus from patients with RA were collected without enzyme digestion and designated synovial tissue-derived inflammatory cells. Their single-cell suspensions were cultured in medium alone to observe an aberrant overgrowth of inflammatory tissue in vitro. Levels of cytokines produced in culture supernatants were measured using enzyme-linked immunosorbent assay kits. Osteoclast activity was assessed by the development of resorption pits in calcium phosphate-coated slides. RESULTS: Primary culture of the synovial tissue-derived inflammatory cells resulted in spontaneous reconstruction of inflammatory tissue in vitro within 4 weeks, during which tumor necrosis factor α, PGE2, macrophage colony-stimulating factor, and matrix metalloproteinase 9 were produced in the supernatant. This aberrant overgrowth was inhibited by antirheumatic drugs including methotrexate and infliximab. On calcium phosphate-coated slides, synovial tissue-derived inflammatory cells showed numerous resorption pits. In the presence of inhibitors of endogenous prostanoid production such as indomethacin and NS398, exogenous PGE1 and EP4-specific agonists significantly inhibited all these activities of synovial tissue-derived inflammatory cells in a dose-dependent manner. Addition of indomethacin, NS398, or EP4-specific antagonist resulted in the enhancement of these cells' activities. EP2-specific agonist had a partial effect, while EP1- and EP3-specific agonists had no significant effects. CONCLUSION: These results suggest that endogenous PGE2 produced in rheumatoid synovium negatively regulates aberrant synovial overgrowth and the development of osteoclast activity via EP4.

Identification of EP4 as a potential target for the treatment of castration-resistant prostate cancer using a novel xenograft model.

More effective therapeutic approaches for castration-resistant prostate cancer (CRPC) are urgently needed, thus reinforcing the need to understand how prostate tumors progress to castration resistance. We have established a novel mouse xenograft model of prostate cancer, KUCaP-2, which expresses the wild-type androgen receptor (AR) and which produces the prostate-specific antigen (PSA). In this model, tumors regress soon after castration, but then reproducibly restore their ability to proliferate after 1 to 2 months without AR mutation, mimicking the clinical behavior of CRPC. In the present study, we used this model to identify novel therapeutic targets for CRPC. Evaluating tumor tissues at various stages by gene expression profiling, we discovered that the prostaglandin E receptor EP4 subtype (EP4) was significantly upregulated during progression to castration resistance. Immunohistochemical results of human prostate cancer tissues confirmed that EP4 expression was higher in CRPC compared with hormone-naïve prostate cancer. Ectopic overexpression of EP4 in LNCaP cells (LNCaP-EP4 cells) drove proliferation and PSA production in the absence of androgen supplementation in vitro and in vivo. Androgen-independent proliferation of LNCaP-EP4 cells was suppressed when AR expression was attenuated by RNA interference. Treatment of LNCaP-EP4 cells with a specific EP4 antagonist, ONO-AE3-208, decreased intracellular cyclic AMP levels, suppressed PSA production in vitro, and inhibited castration-resistant growth of LNCaP-EP4 or KUCaP-2 tumors in vivo. Our findings reveal that EP4 overexpression, via AR activation, supports an important mechanism for castration-resistant progression of prostate cancer. Furthermore, they prompt further evaluation of EP4 antagonists as a novel therapeutic modality to treat CRPC.

Local sustained release of prostaglandin E1 induces neovascularization in murine hindlimb ischemia.

BACKGROUND: Although intravenous administration of prostaglandin E(1) (PGE(1)) is commonly used in the treatment of peripheral arterial disease, it rapidly becomes inactivated in the lung. Whether local administration of sustained-release (SR) PGE(1) enhances neovascularization in murine hindlimb ischemia was investigated. METHODS AND RESULTS: Poly lactide-co-glycolide (PLGA) microspheres were the 4-week SR carrier of PGE(1). C57BL/6 mice with unilateral hindlimb ischemia were randomly treated as follows: no treatment (Group N); single administration of 100 microg/kg PGE(1) solution (Group L) into the ischemic muscles; daily systemic administration of PGE(1) for 2 weeks at a total dose 100 microg/kg (Group S); and single administration of PGE(1)-100 microg/kg-loaded PLGA (Group P100) into the ischemic muscles. The blood perfusion in Group P100 was higher than in Groups N, L and S (ischemic/nonischemic blood perfusion ratio 88 +/-11% vs 73 +/-11% (P<0.01), 77 +/-9% (P<0.05), 79 +/-11% (P<0.05), respectively). Vascular density and alphaSMA-positive-vessel density in Group P100 were higher than in Groups N, L and S (vascular density (vessels/m(2)): 241 +/-39 vs 169 +/-49 (P<0.01), 169 +/-54 (P<0.01), 201 +/-42 (P<0.05), respectively; alphaSMA-positive-vessel density (vessels/m(2)): 34 +/-10 vs 18 +/-6 (P<0.01), 21 +/-11 (P<0.01), 22 +/-10 (P<0.01), respectively) CONCLUSIONS: Local administration of a single dose of SR PGE(1) enhances neovascularization in mice hindlimb ischemia more efficiently than daily systemic administration.