Oral administration of EP4-selective agonist KAG-308 suppresses mouse knee osteoarthritis development through reduction of chondrocyte hypertrophy and TNF secretion.

Osteoarthritis (OA) is one of the world's most common degenerative diseases, but there is no disease-modifying treatment available. Previous studies have shown that prostaglandin E2 (PGE2) and PGE2 receptor 4 (EP4) are involved in OA pathogenesis; however, their roles are not fully understood. Here, we examined the efficacy of oral administration of KAG-308, an EP4-selective agonist, in surgically induced mouse knee OA. Cartilage degeneration and synovitis were significantly inhibited by the KAG-308 treatment. Chondrocyte hypertrophy and expression of tumor necrosis factor alpha (TNF) and matrix metalloproteinase 13 (Mmp13) in the synovium were suppressed in the KAG-308-treated mice. In cultured chondrocytes, hypertrophic differentiation was inhibited by KAG-308 and intranuclear translocation of histone deacetylase 4 (Hdac4) was enhanced. In cultured synoviocytes, lipopolysaccharide (LPS)-induced expression of TNF and Mmp13 was also suppressed by KAG-308. KAG-308 was detected in the synovium and cartilage of orally treated mice. TNF secretion from the synovia of KAG-308-treated mice was significantly lower than control mice. Thus, we conclude that oral administration of KAG-308 suppresses OA development through suppression of chondrocyte hypertrophy and synovitis. KAG-308 may be a potent candidate for OA drug development.

KAG-308, a newly-identified EP4-selective agonist shows efficacy for treating ulcerative colitis and can bring about lower risk of colorectal carcinogenesis by oral administration.

Agonists for EP4 receptor, a prostaglandin E2 receptor subtype, appear to be a promising therapeutic strategy for ulcerative colitis (UC) due to their anti-inflammatory and epithelial regeneration activities. However, the clinical development of orally-available EP4 agonists for mild to moderate UC has not yet been reported. Furthermore, the possibility of an increased risk of colitis-associated cancer (CAC) through direct proliferative effects on epithelial cells via EP4 signaling has not been ruled out. Recently, we identified KAG-308 as an orally-available EP4-selective agonist. Here, we investigated the pharmacological and pharmacokinetic profiles of KAG-308. Then, we compared KAG-308 and sulfasalazine (SASP) for their abilities to prevent colitis and promote mucosal healing in a mouse model of dextran sulfate sodium (DSS)-induced colitis. Finally, the effect of KAG-308 treatment on CAC was evaluated in an azoxymethane (AOM)/DSS-induced CAC mouse model. KAG-308 selectively activated EP4 and potently inhibited tumor necrosis factor-α production in peripheral whole blood and T cells. Oral administration of KAG-308, which showed relatively high bioavailability, suppressed the onset of DSS-induced colitis and promoted histological mucosal healing, while SASP did not. KAG-308 also prevented colorectal carcinogenesis by inhibiting colitis development and consequently decreasing mortality in a CAC model, whereas SASP had marginal effects. In contrast, MF-482, an EP4 antagonist, increased mortality. These results indicated that orally-administered KAG-308 suppressed colitis development and promoted mucosal healing. Moreover, it exhibited preventive effects on colorectal carcinogenesis, and thus may be a new therapeutic strategy for the management of UC that confers a reduced risk of colorectal carcinogenesis.

The motility of hepatic Ito cells can be acquired by their myofibroblastic transformation.

We investigated the relationship between the motility of hepatic Ito cells and their myofibroblastic transformation in cultures. Ito cells were freshly isolated from rat liver and cultured in a 10% FBS-supplemented medium. On day 2 after beginning the culture, transmission electron microscopy and oil red O staining showed that Ito cells possessed numerous lipid droplets but not actin filaments in the cytoplasm. On day 8, actin filaments were abundantly found in the cytoplasm, whereas lipid droplets dramatically decreased in number. Western blot analysis also demonstrated that protein levels of alpha-smooth muscle actin in the cell markedly increased with time, but no obvious change was detected in those of desmin and tubulin beta. In Boyden's chamber assay, the migration of Ito cells, which was induced by platelet-derived growth factor-BB (PDGF-BB), was activated in a time-dependent manner. This migration of transformed Ito cells was independent of the degree of their adhesion to various substances of the extracellular matrix. Among these molecules, laminin showed the highest effect upon the migratory activity. The migration of transformed Ito cells on laminin was completely inhibited by cytochalasin D, colchicine, or taxol. Furthermore, their adhesion to the matrix was also decreased by cytochalasin D or colchicine, but not by taxol. These findings indicate that the motility of Ito cells is acquired in conjunction with their myofibroblastic transformation, which is accompanied by morphological changes with a new organization of actin filaments. The results also suggest that microtubules as well as the extracellular matrix are deeply associated with the motility of Ito cells.