Spatial-temporal variations of carbon storage and carbon sequestration rate in China's national forest parks.

Forests play an important role in regulating climate change and maintaining carbon balance. To explore the carbon storage and carbon sequestration rate of national forest parks is of great significance for carbon sequestration capacity assessment and sustainable forest management. A process-based ecosystem model (CEVSA2 model) was used to simulate the spatial distribution of carbon density, carbon storage and carbon sequestration rate of 881 national forest parks in China during 1982-2017. The results showed that the average carbon density of national forest parks was 255.18 t C·hm-2, being higher than the average carbon density of forest ecosystem in China. In 2017, the total carbon storage of national forest parks increased to 3.56 Pg C, accounting for 11.0%-12.2% of the total carbon storage in national forest ecosystems. During 1982-2017, the average carbon sequestration rate of national forest parks reached 0.45 t C·hm-2·a-1, and the carbon sequestration rate of all national forest parks was above 0.30 t C·hm-2·a-1. National forest parks in the northeast and southwest of China had the highest total carbon storage. The national forest parks in northeast of China had the highest soil organic carbon sequestration rate, while those in eastern China and central southern China had the highest biomass carbon sequestration rate. The area of national forest parks accounted for 5.8% of the total forest area of China, playing an important role in forest carbon sink management of China. Accurate assessment of the growth status, carbon sequestration potential and carbon absorption characteristics of national forest parks could provide reference for the comprehensive assessment of ecosystem service of forest parks in China.

Nrf2 mediates the protective effects of homocysteine by increasing the levels of GSH content in HepG2 cells.

Homocysteine (Hcy) and glutathione (GSH) are crucial reduction­oxidation mediators. The underlying mechanisms governing the effects of Hcy on GSH generation in the progression of alcoholic liver disease has so far received little attention. The present study hypothesized that the antioxidant transcriptional factor nuclear factor (erythroid­derived 2)­like 2 (Nrf2) may participate in Hcy­mediated regulation of GSH production in HepG2 human liver cancer cells. MTT assay was used to study the cytotoxicity of homocysteine, western blot analysis and immunofluorescence staining were used to determine the effect of Hcy on Nrf2 expression. Our data demonstrated that HepG2 cells exposed to exogenous levels of Hcy (0­100 µM) exhibited elevated GSH levels in a concentration­dependent manner. Furthermore, 4­hydroxynonenal (4­HNE)­induced cell injury was attenuated by Hcy; however, this protective effect was blocked by the GSH­production inhibitor buthionine sulfoximine. Hcy treatment was able to induce Nrf2 protein expression in HepG2 cells. Treatment with the Nrf2 activator tert­butylhydroquinone (0­100 µM) increased GSH expression in a concentration­dependent manner; however, Nrf2­siRNA abolished the Hcy­induced increase in GSH expression and cellular protection in 4­HNE­stressed HepG2 cells. In conclusion, the antioxidant transcriptional factor Nrf2 was demonstrated to mediate the Hcy­induced increase in GSH expression levels and cellular protection in HepG2 cells.

[The role of phospholipase D in cellular signaling].

Phospholipase D (PLD) hydrolyzes structural phospholipids of biological membrane to produce phosphatidic acid (PA) and a free-head group. Both of these compounds can participate in signal transduction. Since the activation of PLD involved in many cellular signaling cascades was identified in recent years, knowledge of and interest in PLD have grown greatly, and significant progress has been made toward understanding PLD. This paper reviewed the research progress on gene structure, regulation and cellular function of PLD. PLDs are encoded by a multiple heterogenous gene family. The overall domain structures of plant PLDs are similar, but important differences occur in some of the motifs. The small structural variations underlie distinct regulatory and catalytic properties and cellular function in signaling. PA and other messengers produced by other phospholipase pathways can be interconverted with the action of lipid kinase and phosphatase. PLD is thought to function as an integral part of a network involving other lipid-signaling enzymes and messengers. Some research evidence demonstrated the specificity of PLDs in signal transduction with plant species, cell types, stimuli and cellular processes. Some important questions about PLD study were also raised.