Biphasic Effects of Ingenol 3,20-Dibenzoate on the Erythropoietin Receptor: Synergism at Low Doses and Antagonism at High Doses

Abstract

Although ingenol 3,20-dibenzoate (IDB) is known as a selective novel protein kinase C (PKC) agonist, its biologic actions and underlying mechanisms remain incompletely understood. In this study, we identified IDB as a proliferative agent for an erythropoietin (EPO)-dependent cell line, UT-7/EPO, through the screening of a natural compound library. To clarify the underlying mechanism of IDB's EPO-like activities, we thoroughly analyzed the mutual relation between EPO and IDB in terms of in vitro and in vivo activities, signaling molecules, and a cellular receptor. IDB substantially induced the proliferation of UT-7/ EPO cells, but not as much as EPO. IDB also lessened the anemia induced by 5-fluorouracil in an in vivo mouse model. Interestingly, IDB showed a synergistic effect on EPO at low concentration, but an antagonistic effect at higher concentration. Physical interaction and activation of PKCs by IDB-and EPO-competitive binding of IDB to EPO receptor (EPOR) explain these synergistic and antagonistic activities, respectively. Importantly, we addressed IDB's mechanism of action by demonstrating the direct binding of IDB to PKCs, and by identifying EPOR as a novel molecular target of IDB. Based on these dual targeting properties, IDB holds promise as a new small molecule modulator of EPO-related pathologic conditions.

The differential short- and long-term effects of HIV-1 latency-reversing agents on T cell function

“…Our study has some limitations. Given the technical challenges associated with measuring PKC modulator pharmacokinetics in vivo 27 , more work is needed to determine in vitro doses of these compounds that reflect efficacious clinically-achievable exposures, particularly as phenotypic and functional outcomes may be highly dose-dependent 36 54 55 . The increased expression of CD25 on T cells after an oral dose of Vorinostat but not following exposure to the drug in vitro suggests that LRAs may have effects on T cell tissue distribution that could not be measured in a static in vitro system.…”

Factor-specific generative pattern from large-scale drug-induced gene expression profile

“…IDB exhibits various biological activities, including anti-inflammatory and anticancer effects 18 , 19 ; therefore, further understanding of the precise mechanism of action of IDB is crucial for its potential therapeutic applications. Despite ongoing research and numerous studies, the precise mechanism of action of IDB is yet to be fully elucidated 20 , 21 . We found that 6.7% (32 out of 480) of the significant genes exhibited IDB-specific effects (Fig.…”