Myogenin Regulates DUSP13 to Inhibit Apoptosis Induced by Reactive Oxygen Species.

BACKGROUND: Myogenin is well known as a crucial transcription factor in skeletal muscle development, yet its other biological functions remain unexplored. Previous research showed that myogenin suppresses apoptosis induced by angiotensin II in human induced pluripotent stem cell-derived cardiomyocytes, and offered a new perspective on myogenin's role in cardioprotection. However, the detailed mechanism of this cardioprotection, especially under oxidative stress, is still unclear. METHODS: In this study, hydrogen peroxide (H2O2) was used to generate reactive oxygen species in myogenin-overexpressing cardiomyocytes. The apoptosis was examined by flow cytometry. Transcriptome sequencing (RNA-seq) was performed to identify genes regulated by myogenin. Western blotting was used to detect the protein level of DUSP13 and the phosphorylation level of p38 mitogen-activated protein kinase (MAPK). The dual-luciferase reporter assay and ChIP assay were used to confirm the binding of myogenin to the promoter region of DUSP13. DUSP13 overexpression and knockdown assays were performed to study its anti-apoptotic role. RESULTS: Flow cytometry analysis of apoptosis showed that overexpressing myogenin for 24 and 48 hours decreased the apoptotic ratio by 47.9% and 63.5%, respectively, compared with untreated controls. Transcriptome sequencing performed on cardiomyocytes that expressed myogenin for different amounts of time (6, 12, 24, and 48 hours) identified DUSP13 as being up-regulated by myogenin. Western blotting showed that overexpression of myogenin increased the expression of DUSP13 and decreased the phosphorylation level of p38 MAPK. A dual-luciferase reporter assay proved that myogenin bound directly to the promoter region of DUSP13 and led to strong relative luciferase activity. Direct expression of DUSP13A and DUSP13B significantly reduced the rates of apoptosis and necrosis in cells treated with H2O2. Knockdown of DUSP13B significantly increased the rate of apoptosis in cells treated with H2O2. CONCLUSIONS: The present findings suggest that myogenin might attenuate apoptosis induced by reactive oxygen species by up-regulating DUSP13 and inactivating the p38 MAPK pathway.

[Phenylpropanoids from Saussureae hieracioides].

OBJECTIVE: To isolate and identify the phenylpropanoids from Saussurea hieracioides. METHODS: The compounds were isolated by chromatographic and their structures were elucidated on the basis of spectra data. RESULTS: Seven compounds were isolated and identified as umbelliferone (1), scopoletin(2), caffeic acid (3), esculetin (4), skimmin (5), scopolin (6) and chlorogenic acid (7), respectively. CONCLUSION: Compounds 3, 4 and 7 are isolated from this plant for the first time.

[Stud on quality standard for Aconiti Tatsienensis Radix].

OBJECTIVE: To establish the quality standard for Aconiti Tatsiehensis Radix. METHODS: TLC was used to detect yunaconi- tine and talasamine in Aconiti Tatsiensis Radix. HPLC was adopted to determine the content of yunaconitine. Moisture,ash,acid insolu- ble ash and ethanol soluble extractive were determined according the procedures recorded in the Appendix of Chinese Pharmacopoeia (2010 edition). The microscopic identification was also carried out. RESULTS: Aconiti Tatsienensis Radix had obvious microscopic char- acteristics,and its TLC identification had a good resolution with clear spots. An average content of moisture was 11. 48%, ash was 4. 83% ,acid insoluble was 1. 81%, ethanol soluble extractive was 20. 46% and yunaconitine was 0. 23%. CONCLUSION: The established standard is acceptable for quality evaluation of Aconiti Tatsienensis Radix.

[Population characteristics and ecological suitability of Saussureae hieracioides].

OBJECTIVE: To analyze the population characteristics and the appropriate producing area of Saussureae hieracioides in China. METHODS: Chuanxibei plateau, one of the main producing areas of Saussureae hieracioides, was selected as the analytical basal place. Ecological methods were used to investigate the density and biomass of Saussureae hieracioides. Traditional Chinese Medicine Geographic Information System (TCMGIS-II) was used to analyze the appropriate producing area of Saussureae hieracioides. RESULTS: Saussureae hieracioides could form the dominant species in its distribution area. The proper region (with similarity of 90% - 100%) of Saussureae hieracioides accounted for 338 776.89 km2, including 5 provinces/municipalities and 226 counties/cities. The largest area among them was Tibet Autonomous Region with area of 148 175.55 km2, followed by Sichuan Province (110 216.46 km2), Qinghai Province (62 947.61 km2), Gansu Province (16 233.09 km2) and Yunnan Province (1 177.18 km2). CONCLUSION: TCMGIS is much valuable to the recognition of formation of producing area, the division of adaptive area, introduction and acclimatization of medicinal materials, it also provides a scientific reference for the introduction and cultivation of Saussureae hieracioides.

[Determination of skimmin, scopolin and umbelliferone in Tibetan medicine Saussurea hieracioides by HPLC].

This study is aimed to establish a high-performance liquid chromatography (HPLC) method for simultaneous determination of skimmin, scopolin and umbelliferone in Saussurea hieracioides. Samples were analyzed on a Wondasil C18-WR column (4.6 mm x 250 mm, 5 microm) with methanol (A) and water containing 0.1% phosphate (B) as mobile phases for gradient elution at a flow rate of 1.0 mL x min(-1). The detection wavelength and column temperature were set at 325 nm and 35 degrees C, respectively, and the sample size was 10 microL. The results showed that skimmin, scopolin and umbelliferone were simultaneously achieved within 40 min under the above conditions. A good linearity was observed in the range of 0.18-5.6 microg (r = 1.000 0), 0.060-1.8 microg (r = 0.999 9), 0.032-0.97 microg (r = 0.999 8) for skimmin, scopolin and umbelliferone, respectively, with the average recoveries of 99.16% (RSD = 0.41%), 100.3% (RSD = 0.79%), 102.2% (RSD = 0.87%). The method is simple, accurate and reproducible and can be used for the quality control of S. hieracioides.

Ribosomal protein-Mdm2-p53 pathway coordinates nutrient stress with lipid metabolism by regulating MCD and promoting fatty acid oxidation.

The tumor suppressor p53 has recently been shown to regulate energy metabolism through multiple mechanisms. However, the in vivo signaling pathways related to p53-mediated metabolic regulation remain largely uncharacterized. By using mice bearing a single amino acid substitution at cysteine residue 305 of mouse double minute 2 (Mdm2(C305F)), which renders Mdm2 deficient in binding ribosomal proteins (RPs) RPL11 and RPL5, we show that the RP-Mdm2-p53 signaling pathway is critical for sensing nutrient deprivation and maintaining liver lipid homeostasis. Although the Mdm2(C305F) mutation does not significantly affect growth and development in mice, this mutation promotes fat accumulation under normal feeding conditions and hepatosteatosis under acute fasting conditions. We show that nutrient deprivation inhibits rRNA biosynthesis, increases RP-Mdm2 interaction, and induces p53-mediated transactivation of malonyl-CoA decarboxylase (MCD), which catalyzes the degradation of malonyl-CoA to acetyl-CoA, thus modulating lipid partitioning. Fasted Mdm2(C305F) mice demonstrate attenuated MCD induction and enhanced malonyl-CoA accumulation in addition to decreased oxidative respiration and increased fatty acid accumulation in the liver. Thus, the RP-Mdm2-p53 pathway appears to function as an endogenous sensor responsible for stimulating fatty acid oxidation in response to nutrient depletion.

Arbuscular mycorrhizal fungi increase organic carbon decomposition under elevated CO2.

The extent to which terrestrial ecosystems can sequester carbon to mitigate climate change is a matter of debate. The stimulation of arbuscular mycorrhizal fungi (AMF) by elevated atmospheric carbon dioxide (CO(2)) has been assumed to be a major mechanism facilitating soil carbon sequestration by increasing carbon inputs to soil and by protecting organic carbon from decomposition via aggregation. We present evidence from four independent microcosm and field experiments demonstrating that CO(2) enhancement of AMF results in considerable soil carbon losses. Our findings challenge the assumption that AMF protect against degradation of organic carbon in soil and raise questions about the current prediction of terrestrial ecosystem carbon balance under future climate-change scenarios.