Triptolide impairs genome integrity by directly blocking the enzymatic activity of DNA-PKcs in human cells.

Triptolide is a multi-functional natural small molecular compound extracted from a traditional Chinese medicinal herb. Triptolide and its derivatives exhibit cytotoxicity through inducing DNA damage, therefore increasing sensitivity to DNA-damage based chemotherapy or radiotherapy in different types of cells. However, the regulatory mechanism of genotoxicity by triptolide, and the loss of genome integrity induced by triptolide are not fully understood. Here, we measured the effects of triptolide on genome integrity in a human fibroblast line HCA2-hTERT using the neutral comet assay. We demonstrated that treating cells with triptolide induced genomic instability in HCA2-hTERT cells. Furthermore, we observed the accumulation of γH2AX foci in triptolide treated cells than control cells at 24 h post ionizing radiation. Further mechanistic studies indicated that triptolide inhibited the enzymatic activity of DNA-PKcs, the critical nonhomologous end joining factor. In vitro kinase activity assays showed that triptolide suppressed the kinase activity of DNA-PKcs and molecular docking also predicted a potential interaction between triptolide and DNA-PKcs. As a consequence, we found that triptolide treatment enhanced the interaction between DNA-PKcs and KU80 and hampered the following recruitment of 53BP1. Altogether, our finding provides a new perspective about the toxicity of triptolide in non-cancer cells and highlights the necessity of taking genome effects of triptolide and its derivatives into consideration in the future clinical and research applications.

Effects of Physical Practice and Imagery Practice on Bilateral Transfer in Learning a Sequential Tapping Task.

Recent research on bilateral transfer suggests that imagery training can facilitate the transfer of motor skill from a trained limb to that of an untrained limb above and beyond that of physical practice. To further explore this effect, the present study examined the influence of practice duration and task difficulty on the extent to which imagery training and physical training influences bilateral transfer of a sequential key pressing task. In experiment 1, participants trained on the key pressing task using their non-dominant arm under one of three conditions (physical practice, imagery practice, and no practice). In a subsequent bilateral transfer test, participants performed the sequential task using their untrained dominant arm in either an original order or mirror-ordered sequence. In experiment 2, the same procedures were followed as in experiment 1 except that participants trained with their dominant arm and performed the bilateral transfer task with their non-dominant arm. Results indicated that with extended practice beyond what has been employed in previous studies, physical practice is more effective at facilitating bilateral transfer compared to training with imagery. Interestingly, significant bilateral transfer was only observed for transfer from the non-dominant to the dominant arm with no differences observed between performing the task in an original or mirror ordered sequence. Overall, these findings suggest that imagery training may benefit bilateral transfer primarily at the initial stages of learning, but with extended training, physical practice leads to larger influences on transfer.

Omega-3 Polyunsaturated Fatty Acids Enhance Cisplatin Efficacy in Gastric Cancer Cells by Inducing Apoptosis via ADORA1.

It has been suggested that administration of the omega-3 polyunsaturated fatty acids (ω-3 PUFAs), including docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), can alter the toxicity and/or activity of several anticancer drugs in in vitro and in vivo studies. Here, we investigated the ability of ω-3 PUFAs to potentiate the antineoplastic activity of cisplatin (CDDP) in gastric cancer cells. The increase in CDDP-induced growth inhibition was measured by the IC50 values obtained when the cells were incubated with CDDP alone or with CDDP plus DHA or EPA. DHA and EPA enhanced the growth-inhibition activity of increasing concentrations of CDDP. The interactions between CDDP and DHA or EPA at the cellular level were assessed through the combination index (CI) method of Chou-Talalay. The results demonstrated synergism between CDDP and DHA or EPA in MKN45 cells. Cell cycle analysis showed that the combination treatment increased G0/G1 phase and S phase arrest, and significantly increased the number of apoptotic cells. According to our previous study, ω -3 PUFAs induce apoptosis of gastric cells via ADORA1, a subtype of adenosine receptor functionally related to cell death. The ADORA1 mRNA and protein expression was higher in the combination treatment than in the individual treatments. Notable, when GC cells were pretreated with DPCPX, a selective ADORA1 antagonist, the combination treatment effect on apoptosis was significantly reduced. Our results suggest that ω-3 PUFAs enhance the antineoplastic effects of CDDP in gastric cancer cells, and the synergistic effect between ω-3 PUFAs and CDDP is partly dependent on activating the ADORA1-mediated apoptosis pathway.

Omega-3 PUFAs induce apoptosis of gastric cancer cells via ADORA1.

Omega-3 polyunsaturated fatty acids (Omega-3 PUFAs), including docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), have been suggested to have anti-cancer effects by epidemiological and clinical studies. However, their underlying anti-cancer mechanisms are still unclear. In this study, we examined the influence of two Omega-3 PUFAs (DHA and EPA) on the proliferation and apoptosis of gastric cancer (GC) cells, and found that DHA and EPA reduced the viability of GC cells and induced apoptosis by activating caspase-3. Moreover, we screened the expression profile of apoptosis-related genes in GC cells upon the treatment of DHA and/or EPA, and discovered that ADORA1, one subtype of adenosine receptor functionally involved in cell death, was up-regulated in response to DHA and EPA. Importantly, when GC cells were treated with a selective ADORA1 antagonist, DPCPX, the DHA/EPA-induced apoptosis was substantially reduced. Taken together, our results suggest that the anti-cancer effect of Omega-3 PUFAs on gastric cancer is at least partly dependent on activating the ADORA1-mediated apoptosis pathway.