Dracocephalum palmatum Stephan extract induces caspase­ and mitochondria­dependent apoptosis via Myc inhibition in diffuse large B cell lymphoma.

Dracocephalum palmatum Stephan (DPS), a medicinal plant used by Russian nomads, has been known to exhibit antioxidant properties. However, to the best of our knowledge, its anticancer effect has not been elucidated. The present study aimed to evaluate the tumor­suppressive effect of DPS extract (DPSE) in diffuse large B cell lymphoma (DLBCL) and the underlying mechanism. MTS assays and Annexin V staining were performed to assess the anti­proliferative and apoptotic effects of DPSE, respectively. To reveal the underlying mechanisms, the levels of pro­ and anti­apoptotic Bcl­2 members were analyzed by western blotting. Rescue experiments were performed to investigate the potential involvement of Myc in DPSE­induced tumor­inhibitory effects. Additionally, high­performance liquid chromatography analysis was performed to analyze the components with anticancer effects. Exposure of multiple DLBCL cell lines to DPSE significantly decreased cell viability and increased apoptosis, whereas it had no effect on the survival of normal cells in vitro and in vivo. This indicates that its cytotoxic effect may be specific to cancer cells. Mechanistically, cell death induced by DPSE was dependent on the activation of caspase­3/7 and the disruption of mitochondrial membrane potential. Treatment with the extract ameliorated the expression of anti­apoptotic Bcl­2 members Bcl­xL and Mcl­1, and upregulated that of pro­apoptotic Bcl­2 members Bax and Bak. These modulations led to the disruption of mitochondrial membrane potential, which culminated in the activation of executioner caspases­3 and ­7. Notably, overexpression of Myc inhibited DPSE­induced cell killing, indicating the involvement of Myc in this process. Given that dysregulation of Myc is strongly associated with the pathobiology of DLBCL, the present study highlights the potential therapeutic efficacy of DPSE in patients with DLBCL with aberrant Myc expression. Furthermore, fractionation of DPSE by thin layer chromatography and liquid chromatography/mass spectrometry­based investigation of the fraction with bioactive compounds demonstrated that flavonoids may be responsible for most, if not all, of the anti­lymphoma effect. Efforts to identify the bioactive flavonoids is currently underway.

Diurnal changes of the ascorbate-glutathione cycle components in wheat genotypes exposed to drought.

The ascorbate-glutathione (AsA-GSH) cycle is a major pathway of H2O2 scavenging in plants. The effect of diurnal variations in hydrogen peroxide (H2O2) content, the intensity of lipid peroxidation (malondialdehyde, MDA), photosynthesis, antioxidants and antioxidative enzyme activities involved in AsA-GSH metabolism has been studied comparatively in leaves of durum (Triticum durum Desf.) and bread (Triticum aestivum L.) wheat genotypes exposed to soil drought. Drought stress caused an increase in the content of H2O2, MDA, alterations in the activities of AsA-GSH cycle enzymes and quantitative changes in AsA and GSH content during the day. PSII efficiency was significantly lower in the control and drought exposed leaves at the highest temperature in the afternoon. The ascorbate peroxidase activity was found to increase and ascorbic acid amount decreased with increasing temperature during the day. Further, the glutathione amount and glutathione reductase activity increased at the expense of the regeneration of the oxidised form of glutathione. Our results revealed that wheat can tolerate drought stress by enhancing the antioxidant enzyme activities and alteration of the concentration of ascorbate and glutathione.

Angelica gigas Nakai and Decursin Downregulate Myc Expression to Promote Cell Death in B-cell Lymphoma.

Angelica gigas Nakai (AGN) is an oriental traditional medicine to treat anemia, dysmenorrhea, and migraine. However, its anti-lymphoma effect is yet to be tested. Here, we demonstrated that AGN and its major component decursin target Myc to suppress lymphomagenesis in vitro and in vivo. AGN inhibited cell viability in multiple B lymphoma cells, while sparing normal splenocytes and bone marrow cells. Increased cleaved PARP level and caspase 3/7 activity and the repression of survival-promoting AKT/mTOR and MAPK pathways downstream of BCR, were responsible for the pro-apoptotic effects of AGN. We found that Myc, a prominent downstream target of these signaling pathways, contributes to AGN-induced cell death. Moreover, co-treatment with AGN and a Myc inhibitor, JQ1 or 10058-F4 yielded synergistic cytotoxic activities against cancer cells with markedly reduced Myc expression. AGN downregulated Myc expression and suppressed tumorigenesis in Eµ-myc transgenic mice. The proapoptotic activities of AGN were recapitulated by decursin, indicating that the anti-tumor effect of AGN was mainly caused by decursin. These findings suggest that AGN and decursin possess potent anti-lymphoma activity, and combination therapies with AGN/decursin and a Myc inhibitor to target Myc more efficiently could be a valuable avenue to explore in the treatment of B-cell lymphoma.

ZEBRA-NECROSIS, a thylakoid-bound protein, is critical for the photoprotection of developing chloroplasts during early leaf development.

The zebra-necrosis (zn) mutant of rice (Oryza sativa) produces transversely green/yellow-striped leaves. The mutant phenotype is formed by unequal impairment of chloroplast biogenesis before emergence from the leaf sheath under alternate light/dark or high/low temperatures (restrictive), but not under constant light and temperature (permissive) conditions. Map-based cloning revealed that ZN encodes a thylakoid-bound protein of unknown function. Virus-induced gene silencing of a ZN homolog in Nicotiana benthamiana causes leaf variegation with sporadic green/yellow sectors, indicating that ZN is essential for chloroplast biogenesis during early leaf development. Necrotic lesions often occur in the yellow sectors as a result of an excessive accumulation of reactive oxygen species (ROS). The phenotypic severity (leaf variegation and necrosis) and ROS levels are positively correlated with an increase in light intensity under restrictive conditions. In the mutant leaves, chlorophyll (Chl) metabolism, ROS scavenging activities, maximum quantum yield of photosystem II (PSII), and structures and functions of the photosynthetic complexes are normal in the Chl-containing cells, suggesting that ROS are mainly generated from the defective plastids of the Chl-free cells. The PSII activity of normal chloroplasts is hypersensitive to photoinhibition because the recovery rates of PSII are much slower. In the PSII repair, the degradation of damaged D1 is not impaired, suggesting a reduced activity of new D1 synthesis, possibly because of higher levels of ROS generated from the Chl-free cells by excess light. Together, we propose that ZN is required for protecting developing chloroplasts, especially during the assembly of thylakoid protein complexes, from incidental light after darkness.

Loss of peripheral polypeptides in the stromal side of photosystem I by light-chilling in cucumber leaves.

Photosystem I (PSI) is severely damaged by chilling at 4 degrees C in low light, especially in the chilling sensitive plant cucumber. To investigate the early events in PSI photoinhibition, we examined structural changes in the level of pigment-protein complexes in cucumber leaves in comparison with pea leaves. The complexes were separated on a native green gel and an increase in the intensity of a band was observed only in light-chilled cucumber leaves. The 77 K fluorescence emission spectrum of this green band indicated that the band was mainly composed of PSI with light-harvesting complex I. Each lane was cut from the green gel and separated on a fully denaturing SDS-PAGE in the second dimension. The new green gel band observed after light-chilling in cucumber leaves lacked 19, 18, and 16.5 kDa polypeptides. These results suggest that light-chilling facilitates the release of three peripheral polypeptides as an early event of chilling stress in vivo, which results in the inactivation of PSI in intact cucumber leaves.