Heavy metal-induced glutathione accumulation and its role in heavy metal detoxification in Phanerochaete chrysosporium

Phanerochaete chrysosporium are known to be vital hyperaccumulation species for heavy metal removal with admirable intracellular bioaccumulation capacity. This study analyzes the heavy metal-induced glutathione (GSH) accumulation and the regulation at the intracellular heavy metal level in P. chrysosporium. P. chrysosporium accumulated high levels of GSH, accompanied with high intracellular concentrations of Pb and Cd. Pb bioaccumulation lead to a narrow range of fluctuation in GSH accumulation (0.72–0.84 μmol), while GSH plummeted under Cd exposure at the maximum value of 0.37 μmol. Good correlations between time-course GSH depletion and Cd bioaccumulation were determined (R ²?>?0.87), while no significant correlations have been found between GSH variation and Pb bioaccumulation (R ²?<?0.38). Significantly, concentration-dependent molar ratios of Pb/GSH ranging from 0.10 to 0.18 were observed, while molar ratios of Cd/GSH were at the scope of 1.53–3.32, confirming the dominant role of GSH in Cd chelation. The study also demonstrated that P. chrysosporium showed considerable hypertolerance to Pb ions, accompanied with demand-driven stimulation in GSH synthesis and unconspicuous generation of reactive oxygen stress. GSH plummeted dramatically response to Cd exposure, due to the strong affinity of GSH to Cd and the involvement of GSH in Cd detoxification mechanism mainly as Cd chelators. Investigations into GSH metabolism and its role in ameliorating metal toxicity can offer important information on the application of the microorganism for wastewater treatment.     

Melanocortin 4 receptors interact with antimicrobial frog peptide analogues

We have developed fluorescence polarization (FP) assays of human melanocortin 4 receptor (MC4R) in 384-well microtiter plates using TAMRA-NDP-MSH as a tracer. The rank order of potency of agonists and antagonists agrees well relative to the published assays: SHU9119>MTII>NDP alphaMSH>alphaMSH. We have screened libraries of Korean plant extracts and frog peptide analogues in search of MC4R ligands using FP assays and cell-based CRE luciferase reporter assays. We report that FLGFLFKVASK, FLGWLFKVASK, FLGALFKWASK, and FLGWLFKWASK are the peptide analogues, which bind to human MC4R receptor with good affinity in vitro. FLGWLFKVASK and FLGWLFKWASK stimulated CRE-driven reporter gene via MC4R. In luciferase reporter assays, they possess the pharmacological and functional profiles of full agonists. We demonstrate the interaction of MC4R with 11-residue antimicrobial peptides derived from the Korean frog, Rana rugosa. The results suggest that MC4R interacts promiscuously with bioactive analogues of antimicrobial peptide, gaegurin-5.     

Soil respiration under climate warming: differential response of heterotrophic and autotrophic respiration

Despite decades of research, how climate warming alters the global flux of soil respiration is still poorly characterized. Here, we use meta‐analysis to synthesize 202 soil respiration datasets from 50 ecosystem warming experiments across multiple terrestrial ecosystems. We found that, on average, warming by 2 °C increased soil respiration by 12% during the early warming years, but warming‐induced drought partially offset this effect. More significantly, the two components of soil respiration, heterotrophic respiration and autotrophic respiration showed distinct responses. The warming effect on autotrophic respiration was not statistically detectable during the early warming years, but nonetheless decreased with treatment duration. In contrast, warming by 2 °C increased heterotrophic respiration by an average of 21%, and this stimulation remained stable over the warming duration. This result challenged the assumption that microbial activity would acclimate to the rising temperature. Together, our findings demonstrate that distinguishing heterotrophic respiration and autotrophic respiration would allow us better understand and predict the long‐term response of soil respiration to warming. The dependence of soil respiration on soil moisture condition also underscores the importance of incorporating warming‐induced soil hydrological changes when modeling soil respiration under climate change.     

Benzylisoquinoline alkaloids from the tubers of Corydalis ternata and their cytotoxicity

Chemical investigation of the tubers of Corydalis ternata resulted in the isolation and characterization of four new benzylisoquinoline alkaloids, epi-coryximine (1) and coryternatines A–C (2–4), along with 10 known alkaloids (5–14). Their structures were established on the basis of extensive spectroscopic data analyses and comparison with spectroscopic data reported. In addition, the cytotoxicities of the alkaloids (1–14) were evaluated by determining their inhibitory effects on several human tumor cell lines (A549, SK-OV-3, SK-MEL-2, and HCT-15) using the SRB assay. Compound 8 showed significant cytotoxicity against A549, SK-OV-3, SK-MEL-2, and HCT-15 cell lines (IC₅₀ = 8.34, 5.14, 7.87, and 2.86 μM, respectively). The four new compounds (1–4) exhibited selective cytotoxicity against the HCT-15 cell line.     

Effects of soybean agglutinin on body composition and organ weights in rats

An experiment was conducted to assess the effect of soybean agglutinin dosage level on growth, body composition, plasma lipids, glucose, urea nitrogen content and aminotransferase activities in rats. Male and female rats (n=60) weaned at 19 d were given a dose of 0, 3.5, 7.0, 10.5, or 14.0 mg soybean agglutinin by gastric infusion once daily for 10 days. With increasing doses of soybean agglutinin, body weight, lipid content of carcass, spleen and kidneys relative dry weights decreased, while small intestine and pancreatic weight, the contents of urea nitrogen and triglyceride, and the activities of aspartate aminotransferase linearly increased in plasma. Though soybean agglutinin decreased plasma insulin content, changes in plasma glucose content due to soybean agglutinin were not detected. It is suggested that dietary soybean agglutinin may affect the secretion of other hormones besides insulin, which modulate blood glucose reserves. In conclusion, consumption of soybean agglutinin resulted in a depletion of lipid and an overgrowth of small intestine and pancreas in rats. Meanwhile, poor growth of spleen and kidneys was observed in the soybean agglutinin-fed rats.     

Activity-dependent shedding of heparin-binding EGF-like growth factor in brain neurons

Heparin-binding epidermal growth factor-like growth factor (HB-EGF) is initially produced as a membrane-anchored precursor (pro-HB-EGF) and subsequently liberated from the cell membrane through ectodomain shedding. Here, we characterized the molecular regulation of pro-HB-EGF shedding in the central nervous system. Cultured neocortical or hippocampal neurons were transfected with the alkaline-phosphatase-tagged pro-HB-EGF gene and stimulated with various neurotransmitters. Both kainate and N-methyl-D-aspartate, but not agonists for metabotropic glutamate receptors, promoted pro-HB-EGF shedding and HB-EGF release, which were attenuated by an exocytosis blocker and metalloproteinase inhibitors. In the brain of transgenic mice over-expressing human pro-HB-EGF, kainate-induced seizure activity decreased content of pro-HB-EGF-like immunoreactivity and conversely increased levels of soluble HB-EGF. There was concomitant phosphorylation of EGF receptors (ErbB1) following seizures, suggesting that seizure activities liberated HB-EGF and activated neighboring ErbB1 receptors. Therefore, we propose that glutamatergic neurotransmission in the central nervous system plays a crucial role in regulating ectodomain shedding of pro-HB-EGF.     

Tetramethylpyrazine Protects Against Oxygen-Glucose Deprivation-Induced Brain Microvascular Endothelial Cells Injury via Rho/Rho-kinase Signaling Pathway

Tetramethylpyrazine (TMP, also known as Ligustrazine), which is isolated from Chinese Herb Medicine Ligustium wollichii Franchat (Chuan Xiong), has been widely used in China for the treatment of ischemic stroke by Chinese herbalists. Brain microvascular endothelial cells (BMECs) are the integral parts of the blood–brain barrier (BBB), protecting BMECs against oxygen-glucose deprivation (OGD) which is important for the treatment of ischemic stroke. Here, we investigated the protective mechanisms of TMP, focusing on OGD-injured BMECs and the Rho/Rho-kinase (Rho-associated kinases, ROCK) signaling pathway. The model of OGD-injured BMECs was established in this study. BMECs were identified by von Willebrand factor III staining and exposed to fasudil, or TMP at different concentrations (14.3, 28.6, 57.3 µM) for 2 h before 24 h of OGD injury. The effect of each treatment was examined by cell viability assays, measurement of intracellular reactive oxygen species (ROS), and transendothelial electric resistance and western blot analysis (caspase-3, endothelial nitric oxide synthase (eNOS), RhoA, Rac1). Our results show that TMP significantly attenuated apoptosis and the permeability of BMECs induced by OGD. In addition, TMP could notably down-regulate the characteristic proteins in Rho/ROCK signaling pathway such as RhoA and Rac1, which triggered abnormal changes of eNOS and ROS, respectively. Altogether, our results show that TMP has a strong protective effect against OGD-induced BMECs injury and suggest that the mechanism might be related to the inhibition of the Rho/ROCK signaling pathway.     

Synthesis and anti-tumor evaluation of panaxadiol halogen-derivatives

In the current work, 13 novel panaxadiol (PD) derivatives were synthesized by reacting with chloroacetyl chloride and bromoacetyl bromide. Their in vitro antitumor activities were evaluated on three human tumor cell lines (HCT-116, BGC-823, SW-480) and three normal cells (human gastric epithelial cell line-GES-1, hair follicle dermal papilla cell line-HHDPC and rat myocardial cell line-H9C2) by MTT assay. Compared with PD, the results demonstrated that compound 1e, 2d, 2e showed significant anti-tumor activity against three tumor cell lines, the IC50 value of compound 2d against HCT-116 was the lowest (3.836 μM). The anti-tumor activity of open-ring compounds are significantly better than the compounds of C-25 cyclization. Compound 1f, 2f, 2g showed the strong anti-tumor activity. The IC50 value of compound 2g against BGC-823 and SW-480 were the lowest (0.6 μM and 0.1 μM, respectively). Combined with cytotoxicity test, the IC50 value of compound 1e, 2d, 2e are greater than 100. the open-ring compounds (1f, 2f, 2g) showed a strong toxicity. The toxicity of 1f is lower than 2f and 2g. These compounds may be useful for the development of novel antiproliferative agents.     

Effects of different LED sources on the growth and nitrogen metabolism of lettuce

Using a light-emitting diode (LED) as the light source, the effects of eight different light treatments [white light (control, W), purple light (P), blue light (B), red light (R), green light (G), yellow light (Y), red–blue light in a 9:1 ratio (9R/1B), and red–blue light in a 4:1 ratio (4R/1B)] on the growth, quality and nitrogen metabolism of lettuce were studied. The results showed that compared with the white light, the purple light, blue light, red light, and the red-blue light combination could all increase the biomass of the aboveground part of lettuce to various degrees, while green light and yellow light inhibited lettuce growth. Under blue light, the contents of soluble protein and flavonoid in lettuce were the highest; under red light, the soluble sugar content was the highest, while the contents of soluble protein, free amino acids, and vitamin C (VC) were relatively higher under the 4R/1B light condition. Compared with white light, the sources of purple, blue, and red lights as well as the red–blue light combination all significantly reduced nitrate accumulation in lettuce, and the activities of the nitrogen (N) metabolism-related enzymes such as nitrate reductase, nitrite reductase, glutamine synthetase, glutamate synthase, and glutamate dehydrogenase were increased to varying degrees. In contrast, the contents of nitrate and ammonium N were significantly accumulated in lettuce under green light, and the activities of relative enzymes were significantly reduced. Therefore, the purple light, blue light, and red–blue combination light sources could promote N assimilation and improve the aboveground biomass accumulation in lettuce by improving the activity of the N metabolism-related enzymes in lettuce. Particularly under the 4R/1B light source, the biomass, soluble protein, VC, and total amino acid content were rather high in lettuce, which indicated that the 4R/1B light source could better effectively improve the nutritional quality and promote the growth of lettuce, while yellow light and green light are not suitable to serve as direct sources in a plant factory. These results provide a certain theoretical basis for the regulation of the light environment in cultivation facilities.