Activation of reactive oxygen species-mediated mitogen-activated protein kinases pathway regulates both extrinsic and intrinsic apoptosis induced by arctigenin in Hep G2.

OBJECTIVES: Arctigenin (ARG) has been proved to inhibit the viability of hepatocellular carcinoma (HCC) via inducing apoptosis. However, the precise mechanism remains unknown. The present study was aimed to further investigate the mechanism of ARG against HCC in vitro and in vivo. METHODS: Arctigenin was applied in vitro and in vivo. Western blotting, immunohistochemistry, etc., were used to investigate the mechanisms. KEY FINDINGS: The time-dependent enhancement of Bax/Bcl-2 ratio, cytochrome c release, Fas and FasL levels, caspase cascade activation and the loss in the mitochondrial out membrane potential indicated that both intrinsic and extrinsic apoptotic pathways were triggered by ARG. Moreover, Jun NH2-terminal kinase (JNK) and p38 phosphorylated time-dependently. And inhibition of the phosphorylation of either p38 or JNK led to a significant reduction in HepG2 apoptosis, owing to the crucial roles of p38 and JNK played in regulating the apoptosis pathways. In addition, ARG increased the generation of reactive oxygen species (ROS) in HepG2 cells, while the antioxidant N-acetyl cysteine almost reversed ARG-induced JNK and p38 activation, and dramatically decreased cell apoptosis. In vivo, ARG increased the cell apoptosis in tumour tissues, and p-p38, p-JNK and Bax were significantly upregulated. CONCLUSIONS: Our findings demonstrated that ARG induced apoptosis in HCC via ROS-mediated mitogen-activated protein kinases apoptosis pathway.

Isolation, Diversity, and Antimicrobial and Immunomodulatory Activities of Endophytic Actinobacteria From Tea Cultivars Zijuan and Yunkang-10 (Camellia sinensis var. assamica).

Endophytic actinobacteria exist widely in plant tissues and are considered as a potential bioresource library of natural products. Tea plants play important roles in human health and in the lifestyles of Asians, especially the Chinese. However, little is known about the endophytic actinobacteria of tea plants. In this study, 16 actinobacteria of 7 different genera and 28 actinobacteria of 8 genera were isolated and analyzed by 16S rRNA gene sequencing from tea cultivars of Zijuan and Yunkang-10 (Camellia sinensis var. assamica), respectively. The diversity of actinobacteria species from Zijuan were higher in July than December (6 vs. 3 genera), but the diversity of species from Yunkang-10 were higher in December than July (7 vs. 3 genera). No actinobacteria isolates were obtained from any tea cultivar in September. Ten isolates from Yunkang-10 exhibited antimicrobial activity against at least one human pathogenic microorganism (Staphylococcus epidermidis, Shigella flexneri, and Escherichia coli), but none of the isolates from Zijuan exhibited antimicrobial activities. Fourteen strains were further exammined the genes of polyketide synthetase (PKS)-I and PKS-II and non-ribosomal peptide synthetase (NRPS). Brevibacterium sp. YXT131 from Yunkang-10 showed strong inhibitory activity against S. epidermidis, Sh. flexneri, and E. coli, and PKS-I and PKS-II and NRPS genes were obtained from the strain. In in vitro assays, extracts from 14 actinobacteria that were tested for antibiotic biosynthetic genes showed no inhibition of concanavalin A (ConA)-induced murine splenocyte proliferation. In in vivo assays, the crude extract of YXT131 modulated the immune response by decreasing the proinflammatory cytokines interleukin (IL)-12/IL-23 p40 and tumor necrosis factor (TNF)-α in the serum of mice. These results confirm that endophytic actinobacteria from tea plants might be an undeveloped bioresource library for active compounds.

Deletion of HAPS_2096 Increases Sensitivity to Cecropin B in Haemophilus parasuis.

Cecropin B (CB) is a very effective natural antimicrobial peptide that has shown great potential for future antimicrobial drug development. HAPS_2096 is a Haemophilus parasuis gene that encodes the periplasmic substrate-binding protein of an ATP-binding cassette-type amino acid transporter. In this research, we constructed and verified an HAPS_2096 deletion mutant and a complementary HAPS_2096 mutant of H. parasuis JS0135. A bactericidal assay revealed that the HAPS_2096 deletion mutant was significantly more sensitive than the wild-type strain to 0.25-0.5 µg/ml CB. However, the gene complementation alleviated the CB sensitivity of the mutant. Immunoelectron microscopy observation following a 30-min treatment with a sublethal concentration of CB (0.25 µg/ml) revealed more extensive morphological damage in the mutant strain than in the wild-type strain. Hence, our results suggest that the HAPS_2096 gene contributes to H. parasuis resistance to CB.