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OBJECTIVE: The aim of the study was to explore the expression of the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (PKB/AKT)/hypoxia-induced factor-1 alpha (HIF-1α) signaling pathway and the apoptosis of nucleus pulposus cells (NPCs) under different oxygen concentrations to clarify the biological characteristics of NPCs and the molecular mechanism of intervertebral disc degeneration (IVDD). MATERIALS AND METHODS: Normal and degenerated human NPCs were collected. Leibovitz's medium with 100 μmol/L CoCl2 was used to establish a hypoxic culture environment, and 100 μmol/L H2O2 was used to establish an oxidative stress culture environment. Third-generation NPCs were divided into 6 groups: normal NPCs + hypoxia, normal NPCs + normoxia, normal NPCs + oxidative stress, degenerated NPCs + hypoxia, degenerated NPCs + normoxia, and degenerated NPCs + oxidative stress. Normal NPCs + hypoxia was used as the experimental control group. Cell viability and proliferation were detected by using the Cell Counting Kit- 8 (CCK-8) method. Cell apoptosis rate was assessed by flow cytometry, and expression levels of PI3K, AKT, and HIF-1α were determined by Real-Time-Polymerase Chain Reaction (RT-PCR) and Western blotting. RESULTS: The cell proliferation rate of both normal and degenerated NPCs decreased with increasing oxygen concentration. Conversely, the apoptosis rate increased as the oxygen concentration increased (p<0.05). Compared with the control group, whether the cells degenerated had a very significant impact on the apoptosis rate (p<0.001), and oxygen concentration also had a highly significant impact on both the cell proliferation rate and apoptosis rate (both p<0.001). The interaction between cell degeneration and oxygen concentration significantly affected both cell proliferation and apoptosis rates (p<0.05). Considering the expression levels of PI3K, AKT, and HIF-1α, normal NPCs had the highest levels under low oxygen concentrations, followed by oxidative stress and normoxia. In degenerated NPCs, the expression levels also decrease as the oxygen concentration increases. CONCLUSIONS: The PI3K/AKT/HIF-1α signaling pathway plays a significant role in inhibiting oxidative stress, antagonizing NPC apoptosis, and consequently delaying IVDD. [ABSTRACT FROM AUTHOR]

A novel method, noted as approximate envelope method (AEM), was developed to estimate the secondary PM2.5 concentrations based on the air quality monitoring data. This approach made it possible to obtain the long‐term characteristics of the secondary PM2.5 using only conventional observations. The secondary PM2.5 concentrations and their variation characteristics under different PM2.5 pollution levels during wintertime of 2015 to 2018 in Chengdu, a major urban area of Sichuan Basin over Southwest China, were analyzed. The results showed that the secondary PM2.5 concentrations ranged from 52.3 to 122.8 μg·m−3 and accounted for 56.3%, 63.6%, and 67.4% of the total PM2.5 in slight, moderate, and heavy pollution status, respectively. Additionally, the concentrations of secondary PM2.5 increased year by year, while the concentrations of primary PM2.5 performed significant decreasing trends from 2015 to 2018. The diurnal variations of primary and secondary PM2.5 presented a significantly unimodal patterns but with maximum at morning and noon, respectively. Specific meteorological conditions such as high (low) relative humidity and temperature (wind speed and air pressure) aggravated the secondary particulate pollution in wintertime of Chengdu, reflecting an influence of regional climate change over the Sichuan Basin of Southwest China on the urban air pollution. Key Points: The PM2.5/CO ratio is a valid tracer for estimating the concentration of primary particlesSecondary particles dominated wintertime PM2.5 in urban area of Chengdu [ABSTRACT FROM AUTHOR]

Changes in the concentrations of trans-resveratrol (Res) and other phenolic compounds in the skin and seeds of red grape (Vitis vinifera x V. amurensis 'Beiquan') during low temperature storage (-1° ± 0.5°C) after post-harvest UV-B and UV-C irradiation and incubation at room temperature (25°C) were evaluated. No obvious changes in Res levels were observed in control and UV-B-irradiated grape skins after 14 d. A higher content of Res was recorded in UV-B- irradiated grape skins for only 7 d in cold storage, but the content was highest in UV-C-irradiated grape skins for the entire period (28 d) in cold storage. Total levels of anthocyanins in grape skins after either UV treatment were significantly higher than in controls during the first 7 d of storage, while only those in UV-B-treated skins were significantly higher than controls during the later period (from 21 -28 d) of storage, due to sharp declines in levels of the five main anthocyanins in UV-C-treated grape skins. Total flavan-3-ol and flavonol contents remained constant in UV-B- and UV-C-treated grape skins during cold storage and did not differ from controls. Levels of Res in grape seeds remained constant and did not differ between UV treatments, or from controls, over 28 d of low temperature storage. However, the total flavan-3-ol and flavonol contents in control and UV-B-treated grape seeds declined from day-2 to day-28 of cold storage, while those of UV-C-treated grape seeds remained constant. Changes in catechin and epicatechin were responsible for the changes observed in total flavan-3-ols and flavonols during cold storage. [ABSTRACT FROM AUTHOR]