Skepinone-L

Skepinone-L is a selective inhibitor of p38 mitogen-activated protein kinase (MAPK) with IC50 value of 5 nM[1].

P38 MAPKs are a class of MAPK which are responsive for stress stimuli, such as heat shock and osmotic shock. They are involved in cell differentiation and apoptosis [1].

Skepinone-L is a ATP-competitive inhibitor of p38 MAPK [1]. For in vitro test, the phosphory¬lation of heat shock protein 27 (HSP27) of the p38 MAPK pathway can be used as a marker to assess the activity of p38 MAPK. When HeLa cells were treated with anisomycin, skepinone-L showed dose-dependent inhibition of HSP27 phosphorylation with a cellular IC50 ~25 nM, which confirmed the inhibition of p38 MAPK. Additionally, in peripheral blood mononuclear cells (hPBMCs), treatment of skepinone-L resulted in the reduction of p38 MAPK downstream effectors including TNF-α, IL-1β and IL-10 [1].

In mouse model, oral administration of skepinone-L resulted in very high level of skepinone-L which was 240 nM and higher than the human whole-blood IC50 value of skepinone. Therefore, it resulted in the inhibition of TNF-α by 77% via the inhibition of upstream p38 MAPK. Thus, it demonstrated the pre¬eminent pharmacodynamic properties of skepinone-L [1].

Reference:
[1].  Koeberle, S C et al., Skepinone-L is a selective p38 mitogen-activated protein kinase inhibitor. Nature Chemical Biology, 2012, 8(2), 141-143.

Skepinone-L, a novel potent and highly selective inhibitor of p38 MAP kinase, effectively impairs platelet activation and thrombus formation.[Pubmed:23817201]

Cell Physiol Biochem. 2013;31(6):914-24.

BACKGROUND/AIMS: Platelets are critically important for primary haemostasis and the major players in thrombotic vascular occlusion. Platelets are activated by agonists, such as thrombin and collagen-related peptide as well as second-wave mediators including thromboxane A2 via different intracellular signaling pathways resulting in degranulation, aggregation and thrombus formation. Platelet activation is paralleled by phosphorylation and activation of p38 MAPK. The limited specificity of hitherto known p38 MAPK inhibitors precluded safe conclusions on the precise role of p38 MAPK in the regulation of platelet function. The present study examined the impact of Skepinone-L, a novel and highly selective inhibitor of p38 mitogen-activated protein kinase (p38 MAPK), on platelet activation and thrombus formation. METHODS: Experiments were performed in freshly isolated human platelets. Protein phosphorylation was quantified by Western blotting, thromboxane B2 synthesis by enzyme immunoassay, ATP release by ChronoLume luciferin assay, cytosolic Ca(2+) concentration by Fura-2 fluorescence-measurements, platelet aggregation by a light transmissions measurement and in vitro thrombus formation by a flow chamber. RESULTS: Skepinone-L (1 muM) virtually abrogated the phosphorylation of platelet p38 MAPK substrate Hsp27 following stimulation with CRP (1 mug/ml), thrombin (5 mU/ml) or thromboxane A2 analogue U-46619 (1 muM). Furthermore, Skepinone-L significantly blunted activation-dependent platelet secretion and aggregation following threshold concentrations of CRP, thrombin and thromboxane A2 analogue U-46619. Skepinone-L did not impair platelet Ca(2+) signaling but prevented agonist-induced thromboxane A2 synthesis through abrogation of p38 MAPK-dependent phosphorylation of platelet cytosolic phospholipase A2 (cPLA2). Skepinone-L further markedly blunted thrombus formation under low (500-s) and high (1700-s) arterial shear rates. CONCLUSIONS: The present study discloses a powerful inhibiting effect of p38 MAPK-blocker Skepinone-L on platelet activation and thrombus formation.

Skepinone-L is a selective p38 mitogen-activated protein kinase inhibitor.[Pubmed:22198732]

Nat Chem Biol. 2011 Dec 25;8(2):141-3.

Until now, a lack of inhibitors with high potency and selectivity in vivo has hampered investigation of the p38 mitogen-activated protein kinase (MAPK) signaling pathway. We describe the design of Skepinone-L, which is, to our knowledge, the first ATP-competitive p38 MAPK inhibitor with excellent in vivo efficacy and selectivity. Therefore, Skepinone-L is a valuable probe for chemical biology research, and it may foster the development of a unique class of kinase inhibitors.