Unripe Black Raspberry (Rubus coreanus Miquel) Extract and Its Constitute, Ellagic Acid Induces T Cell Activation and Antitumor Immunity by Blocking PD-1/PD-L1 Interaction

Rubus coreanus Miquel (R. coreanus) is a unripen fruit of black raspberry native to eastern Asia. It is used as traditional oriental medicine and supplementary foods for centuries. Previous studies have shown that the R. coreanus extract (RCE) and its main constitute ellagic acid possess diverse biological activities. However, the effects of RCE on antitumor immunity and T cell function were not fully understood. The present study describes the anti-tumor effect of RCE in humanized PD-1 mice by blocking PD-1/PD-L1 interaction. Competitive enzyme-linked immunosorbent assay (ELISA) and pull down assay were performed to elucidate the binding properties of RCE in vitro. Cellular PD-1/PD-L1 blockade activities were measured by T cell receptor (TCR)-induced nuclear factor of activated T cells-luciferase activity in co-cultured cell models with PD-1/NFAT Jurkat and PD-L1/aAPC CHO-K1 cells. The in vivo efficacy of RCE was confirmed in humanized PD-1 mice bearing MC38 colorectal tumor. RCE and ellagic acid dose-dependently block the binding of PD-1 to PD-L1. Moreover, oral administration of RCE showed the potent anti-tumor activity similar to anti-PD-1 antibody. The present study suggests that RCE possesses potent anti-tumor effect via PD-1/PD-L1 blockade, and ellagic acid is the main compound in RCE. Thus, we provide new aspects of RCE as an immunotherapeutic agent.

Black Raspberry (Rubus coreanus Miquel) Promotes Browning of Preadipocytes and Inguinal White Adipose Tissue in Cold-Induced Mice

The alteration of white adipose tissue (WAT) “browning”, a change of white into beige fat, has been considered as a new therapeutic strategy to treat obesity. In this study, we investigated the browning effect of black raspberry (Rubus coreanus Miquel) using in vitro and in vivo models. Black raspberry water extract (BRWE) treatment inhibited lipid accumulation in human mesenchymal stem cells (hMSCs) and zebrafish. To evaluate the thermogenic activity, BRWE was orally administered for 2 weeks, and then, the mice were placed in a 4 °C environment. As a result, BRWE treatment increased rectal temperature and inguinal WAT (iWAT) thermogenesis by inducing the expression of beige fat specific markers such as PR domain zinc-finger protein 16 (PRDM16), uncoupling protein 1 (UCP1), peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α), and t-box protein 1 (TBX1) in cold-exposed mice. Furthermore, ellagic acid (EA), a constituent of BRWE, markedly promoted beige specific markers: UCP1, PGC1α, TBX1, and nuclear respiratory factor 1 in beige differentiation media (DM)-induced 3T3-L1 adipocytes. Our findings indicate that BRWE can promote beige differentiation/activation, and EA is the active compound responsible for such effect. Thus, we suggest the nature-derived agents BRWE and EA as potential agents for obesity treatment.