Discovery and structure-activity relationship of imidazolinylindole derivatives as kallikrein 7 inhibitors

A series of imidazolinylindole derivatives were discovered as novel kallikrein 7 (KLK7, stratum corneum chymotryptic enzyme) inhibitors. Structure-activity relationship (SAR) studies led to the identification of potent human KLK7 inhibitors. By further modification of the benzenesulfonyl moiety to overcome species differences in inhibitory activity, potent inhibitors against both human and mouse KLK7 were identified. Furthermore, the complex structure of 25 with mouse KLK7 could explain the SAR and the cause of the species differences in inhibitory activity.

Discovery and structure-activity relationship study of 1,3,6-trisubstituted 1,4-diazepane-7-ones as novel human kallikrein 7 inhibitors

Compound 1, composed of a 1,3,6-trisubstituted 1,4-diazepane-7-one, was discovered as a novel human kallikrein 7 (KLK7, stratum corneum chymotryptic enzyme, SCCE) inhibitor, and its derivatives were synthesized and evaluated. Structure-activity relationship studies of the amidoxime unit and benzoic acid part of this new scaffold led to the identification of 25 and 34, which were more potent than the hit compound, 1. The X-ray co-crystal structure of compound 25 and human KLK7 revealed the characteristic interactions and enabled explanations of the structure-activity relationship.

Phosphodiesterase 7A inhibitor ASB16165 impairs proliferation of keratinocytes in vitro and in vivo

Excessive proliferation of epidermal keratinocytes is a typical aspect of chronic skin diseases such as psoriasis. In the present study, the effect of phosphodiesterase 7A (PDE7A) inhibitor ASB16165 on proliferation of keratinocytes was investigated to examine the role of PDE7A in keratinocyte proliferation and the possible therapeutic relevance of PDE7A inhibition in psoriasis. Topical application of ASB16165 inhibited the increase of thickness of skin as well as epidermis in a skin inflammation model induced by repeated painting of 12-O-tetradecanoylphorbol-13-acetate (TPA) in a concentration-dependent manner. The ASB16165 treatment also suppressed the increase in the number of Ki67-positive keratinocytes in the model, showing the disturbance of keratinocyte proliferation by the treatment. In addition, both ASB16165 and dibutyryl cAMP significantly decreased the proliferation of human keratinocytes in vitro, suggesting that PDE7A participates in keratinocyte proliferation probably by controlling intracellular cAMP, while the contribution of other mechanism(s) is not completely denied. The findings in the present study indicate that the effect of ASB16165 on skin and epidermal hyperplasia in the TPA-induced skin inflammation is mediated, at least in part, by the inhibition of keratinocyte proliferation. The inhibitors for PDE7A including ASB16165 might be useful for the treatment of psoriasis.

Phosphodiesterase 7A inhibitor ASB16165 suppresses proliferation and cytokine production of NKT cells

A possible involvement of phosphodiesterase 7A (PDE7A) in proliferation and function of NKT cells was examined using ASB16165, a selective inhibitor for PDE7A. Stimulation of isolated murine NKT cells with anti-CD3 antibody plus IL-2 induced not only cell proliferation but production of cytokines including IFN-gamma, TNF-alpha, IL-17 and IL-22. ASB16165 significantly inhibited the CD3/IL-2-stimulated cell proliferation and production of all the cytokines examined. Forskolin (an activator of adenylyl cyclase) and dibutyryl cAMP also exerted inhibitory effects on the cell proliferation and cytokine production of NKT cells. In addition, Rp-8-Br-cAMPS, an inhibitor of protein kinase A (PKA), reversed the suppressive effects of ASB16165 against NKT cells. These results suggest that PKA/cAMP as well as PDE7A is involved in regulation of cell proliferation and cytokine production of NKT cells, and that the inhibitory effects of ASB16165 in NKT cells shown here are mediated by increase in cellular cAMP level. Our findings also raise the possibility that PDE7A inhibitor including ASB16165 may be useful for treatment of the diseases in which NKT cells have pathogenic roles.

β-Replacement reaction of serine-O-carbonate derivatives with thiols catalyzed by a pyridoxal model having an ionophore side-chain

Serine-O-carbonate derivatives, including peptides having a serine-O-carbonate residue at the N-terminal position, are catalytically transformed into S-substituted cysteine derivatives employing the pyridoxal model having an ionophore function in the presence of Li+; this is the first artificial model mimicking cystathionine Beta-synthase.

Discovery of a non-peptide small molecule that selectively mimics the biological actions of calcitonin

Calcitonin (CT), a 32-amino acid peptide hormone secreted mainly from the thyroid gland, plays an important role in maintaining bone homeostasis. To discover non-peptide small molecules with biological actions similar to those of CT, a cell-based screening of an in-house chemical library was performed and a pyridone derivative (SUN B8155) was identified. Like CT, it elevated cyclic AMP (cAMP) levels in T47D and UMR106-06 cells which endogenously express human and rat CT receptor, respectively. SUN B8155 also stimulated cAMP formation in cells expressing recombinant human CT receptor, but not in those expressing human parathyroid hormone/parathyroid hormone-related peptide receptor. Accumulation of cAMP in T47D cells was blocked by a selective antagonist of CT receptor, salmon CT(8-32), whereas SUN B8155 did not displace the specific binding of [(125)I]CT to the receptor. Our results suggested that the compound selectively interacts with the CT receptor by a mechanism similar to but probably different from that of CT itself. In rats, intraperitoneal administration of SUN B8155 significantly lowered serum calcium levels, like CT. Our results demonstrate, for the first time, that the biological activities of the newly identified small molecule can mimic that of CT, acting via the CT receptor.

Identification of a novel inhibitor of LPS-induced TNF-alpha production with antiproliferative activity in monocyte/macrophages

An isoquinoline derivative, 5-methyl-7,8-dimethoxy-1-phenylpyrazolo[5,4-c]isoquinoline (compound 1), was identified as a novel inhibitor of LPS-induced TNF-alpha production by cell-based screening. Compound 1 suppressed LPS-induced TNF-alpha production in RAW264.7 cells and murine peritoneal macrophages in a dose-dependent manner similar to SB203580, known as a specific inhibitor of p38 MAPK. It also inhibited an LPS-induced increase in serum TNF-alpha in a mouse endotoxic shock model with an ED(50) of approximately 10 mg/kg. Compound 1 had little effect on the incorporation of [3H]-leucine into the cells, while it suppressed LPS-induced TNF-alpha mRNA levels in RAW264.7 cells. The results indicate that suppression of TNF-alpha production was not a result of nonspecific inhibition of de novo translation but was based on the decreased TNF-alpha mRNA levels. The in vitro kinase assay revealed that compound 1 did not strongly inhibit p38 MAPK activity, its potency being much lower than that of SB203580, suggesting that the TNF-alpha-suppressive action of compound 1 cannot be attributed to the inhibition of p38 MAPK. Furthermore, in contrast to SB203580, it significantly inhibited the growth of RAW264.7 and THP-1 cells in a cytostatic manner. Compound 1 is likely to have antiinflammatory and antiproliferative effects by acting on some molecule other than p38 MAPK that contributes to both LPS-induced TNF-alpha production and the cell growth of monocyte/macrophages.