Glutathione peroxidase 3 (GPX3) suppresses the growth of melanoma cells through reactive oxygen species (ROS)-dependent stabilization of hypoxia-inducible factor 1-α and 2-α.

In this study, we aimed to explore the mechanism of glutathione peroxidase 3 (GPX3) in the growth of malignant melanoma (MM) cells by hypoxia-inducible factor-1α (HIF1-α) and HIF2-α regulating the metabolism through reactive oxygen species (ROS). The messenger RNA and protein expression of GPX3, HIF1-α, HIF2-α in tissues, and cell lines were measured by reverse transcription-quantitative PCR and Western blot analysis. A375 cells were transfected with GPX3 overexpression plasmid, small interfering RNA (siRNA) targeting GPX3, or siRNA targeting HIF1-α/HIF2-α to upregulate or downregulate the expression of GPX3 or HIF1-α/HIF2-α. The effects of H2 O2 and N-acetylcysteine (NAC) on the levels of HIF1-α and HIF2-α after overexpression of GPX3 were studied. The cell viability was detected by Cell Counting Kit-8. The levels of ROS, glucose uptake and lactic acid production, oxidative phosphorylation, and glycolysis of cells were measured for assessment of cellular metabolism. The expression of GPX3 decreased, while ROS, HIF1-α, and HIF2-α increased in MM tissues and cells. Overexpression of GPX3 inhibited the viability of MM cells and the growth of melanoma xenografts. The overexpression of GPX3 reduced the glucose uptake, extracellular lactic acid content, and extracellular acidification rate and increased the oxygen consumption rate level. Overexpression of GPX3 could reduce the levels of HIF1-α and HIF2-α, which could regulate metabolic levels. GPX3 reduced ROS level in MM to inhibit HIF1-α and HIF2-α. The addition of H2 O2 increased while NAC reduced the protein levels of HIF1-α and HIF2-α in the cells overexpressing GPX3. Our study demonstrates that GPX3 inhibits the growth of MM cells through its inhibitory effect on cell metabolic disorder by inhibiting HIF1-α via regulating ROS.

[Evaluating the Significance of Odor Gas Released During the Directly Drying Process of Sludge: Based on the Multi-index Integrated Assessment Method].

Co-processing of sewage sludge using the cement kiln can realize sludge harmless treatment, quantity reduction, stabilization and reutilization. The moisture content should be reduced to below 30% to meet the requirement of combustion. Thermal drying is an effective way for sludge desiccation. Odors and volatile organic compounds are generated and released during the sludge drying process, which could lead to odor pollution. The main odor pollutants were selected by the multi-index integrated assessment method. The concentration, olfactory threshold, threshold limit value, smell security level and saturated vapor pressure were considered as indexes based on the related regulations in China and foreign countries. Taking the pollution potential as the evaluation target, and the risk index and odor emission intensity as evaluation indexes, the odor pollution potential rated evaluation model of the pollutants was built according to the Weber-Fechner law. The aim of the present study is to form the rating evaluation method of odor potential pollution capacity suitable for the directly drying process of sludge.

[Treatment of Flue Gas from Sludge Drying Process by A Thermophilic Biofilter].

A thermophilic biofilter was employed to treat the flue gas generated from sludge drying process, and the performance in both the start period and the stationary phase was studied under the gas flow rate of 2 700-3 100 m3 x h(-1) and retention time of 21.88-25.10 s. The results showed that the thermophilic biofilter could effectively treat gases containing sulfur dioxide, ammonia and volatile organic compounds (VOC). The removal efficiencies could reach 100%, 93.61% and 87.01%, respectively. Microbial analysis indicated that most of the population belonged to thermophilic bacteria. Paenibacillus sp., Chelatococcus sp., Bacillus sp., Clostridium thermosuccinogenes, Pseudoxanthomonas sp. and Geobacillus debilis which were abundant in the thermophilic biofilter, had the abilities of denitrification, desulfurization and degradation of volatile organic compounds.

[Characteristics of odors and VOCs from sludge direct drying process].

Co-processing sewage sludge by using the high-temperature feature of cement kiln can realize harmless disposal and energy recycling. In this paper, investigation on characteristics of the flue gas from sludge drying process was carried out in Guangzhou Heidelberg Yuexiu Cement Co., LTD. The composition and the main source of odors and volatile organic compounds (VOCs) emitted during the drying process were analyzed, aimed to provide scientific basis for the treatment of sewage sludge. Results showed that there were a large number of malodorous substances and VOCs in the flue gas. Sulfur dioxide and other sulfur-containing compounds were the main components in the malodorous substances, while benzene derivatives were predominant in VOCs. The compositions of odors and VOCs were influenced by the characteristics of the sludge and the heat medium (kiln tail gas). Total organic compounds in the sludge were significantly decreased after drying. Other organic substances such as volatile fatty acid, protein, and polysaccharide were also obviously reduced. The organic matter in sludge was the main source of VOCs in the flue gas. Part of sulfurous substances, such as sulfur dioxide, carbon disulfide, were from sulfur-containing substances in the sludge, and the rest were from the kiln tail gas itself.