Unexpected response of terrestrial carbon sink to rural depopulation in China.

China is experiencing large-scale rural-urban migration and rapid urbanization, which have had significant impact on terrestrial carbon sink. However, the impact of rural-urban migration and its accompanying urban expansion on the carbon sink is unclear. Based on multisource remote sensing product data for 2000-2020, the soil microbial respiration equation, relative contribution rate, and threshold analysis, we explored the impact of rural depopulation on the carbon sink and its threshold. The results revealed that the proportion of the rural population in China decreased from 63.91 % in 2000 to 36.11 % in 2020. Human pressure decreased by 1.82% in rural depopulation areas, which promoted vegetation restoration in rural areas (+8.45 %) and increased the carbon sink capacity. The net primary productivity (NPP) and net ecosystem productivity (NEP) of the vegetation in the rural areas increased at rates of 2.95 g C m-2 yr-1 and 2.44 g C m-2 yr-1. Strong rural depopulation enhanced the carbon sequestration potential, and the NEP was 1.5 times higher in areas with sharp rural depopulation than in areas with mild rural depopulation. In addition, the rural depopulation was accompanied by urban expansion, and there was a positive correlation between the comprehensive urbanization level (CUL) and NEP in 75.29 % of urban areas. In the urban areas, the vegetation index increased by 88.42 %, and the urban green space partially compensated for the loss of carbon sink caused by urban expansion, with a growth rate of 4.96 g C m-2 yr-1. Changes in rural population have a nonlinear impact on the NEP. When the rural population exceeds 545.686 people/km2, an increase in the rural population will have a positive impact on the NEP. Our research shows that rural depopulation offers a potential opportunity to restore natural ecosystems and thus increase the carbon sequestration capacity.

A carbon-neutrality-capactiy index for evaluating carbon sink contributions.

The accurate determination of the carbon-neutrality capacity (CNC) of a region is crucial for developing policies related to emissions and climate change. However, a systematic diagnostic method for determining the CNC that considers the rock chemical weathering carbon sink (RCS) is lacking. Moreover, it is challenging but indispensable to establish a fast and practical index model to determine the CNC. Here, we selected Guizhou as the study area, used the methods for different types of carbon sinks, and constructed a CNC index (CNCI) model. We found that: (1) the carbonate rock chemical weathering carbon sink flux was 30.3 t CO2 km-2 yr-1. Guizhou accounted for 1.8% of the land area and contributed 5.4% of the carbonate chemical weathering carbon sink; (2) the silicate rock chemical weathering carbon sink and its flux were 1.44 × 103 t CO2 and 2.43 t CO2 km-2 yr-1, respectively; (3) the vegetation-soil ecosystem carbon sink and its flux were 1.37 × 108 t CO2 and 831.70 t CO2 km-2 yr-1, respectively; (4) the carbon emissions (CEs) were 280 Tg CO2, about 2.8% of the total for China; and (5) the total carbon sinks in Guizhou were 160 Tg CO2, with a CNCI of 57%, which is 4.8 times of China and 2.1 times of the world. In summary, we conducted a systematic diagnosis of the CNC considering the RCS and established a CNCI model. The results of this study have a strong implication and significance for national and global CNC determination and gap analysis.

The Prognostic Role of Plasma Epstein-Barr Virus DNA Levels in the Middle of Intensity Modulated Radiation Therapy to Guide Cisplatin Dose Recommendation in Concurrent Chemoradiation Therapy in Patients With Locally Advanced Nasopharyngeal Carcinoma: A Large Cohort Study.

Purpose: Our purpose was to investigate the prognostic role of plasma Epstein-Barr virus (EBV) DNA levels in the middle of intensity modulated radiation therapy (IMRT). Methods and Materials: In total, 1881 patients with stage III-IVa tumors were included. The overall survival (OS) and progression-free survival (PFS) were calculated using the Kaplan-Meier method, and the differences were compared using the log-rank test. Receiver operating characteristic curve analysis was performed to analyze the diagnostic value of EBV DNA levels for tumor progression or death. Multivariate analyses using the Cox model were used to evaluate potential prognostic factors. Results: The positive predict value and negative predict value of plasma EBV DNA > 0 copies/mL in the middle of IMRT in predicting nasopharyngeal carcinoma progression was 37.4% and 85.5%, respectively. In patients with plasma EBV DNA level = 0 copies/mL, no significant differences in OS were observed between patients treated with 200 mg/m² cisplatin and those treated with >200 mg/m² cisplatin (5-year OS, 94.9% vs 94.4%; PFS, 81.5% vs 87.6%). However, those treated with >200 mg/m² cisplatin had higher PFS. In patients with plasma EBV DNA level > 0 copies/mL, patients treated with >200 mg/m² cisplatin displayed a favorable 5-year OS (84.6% vs 73.9%) and PFS (72.3% vs 54.8%) compared with those treated with 200 mg/m² cisplatin. Additionally, higher incidences of grade 3 and 4 adverse events were recorded in patients treated with >200 mg/m² cisplatin than in those treated with 200 mg/m² cisplatin. Conclusions: Plasma EBV DNA > 0 copies/mL in the middle of IMRT suggests that higher doses of chemotherapy should be used. For concurrent chemoradiation therapy, >200 mg/m² cisplatin is recommended for patients with plasma EBV DNA level > 0 copies/mL in the middle of IMRT but not for patients with plasma EBV DNA level = 0 copies/mL considering the similar OS rates.

Determining the suitability of definitive radiation therapy in patients with metastatic nasopharyngeal carcinoma based on PET/CT: a large cohort study.

OBJECTIVES: To determine patients with de novo metastatic nasopharyngeal carcinoma (mNPC) who would benefit from receiving definitive radiation therapy (DRT) along with their pre-existing palliative chemotherapy (PCT) by evaluating their post-PCT Deauville scores and EBV DNA. METHODS: A total of 570 mNPC patients, treated with PCT or PCT+DRT, were studied. EBV DNA levels, along with post-PCT Deauville scores, were used to stratify risk based on the recursive partitioning analysis (RPA). RESULTS: Significant differences were observed in the survival rates of patients with Deauville scores of 1-3 and 4-5 (2-year progression-free survival (PFS): 23.4% versus 8.5%, p < 0.001; 2-year overall survival (OS): 56.8% versus 18.8%, p < 0.001). RPA yielded three distinct groups in the increasing order of risk (Deauville scores of all RPA I-II were within the range of 1-3): (1) RPA I: EBV DNA levels at a pretreatment concentration ≤ 4000 copies/mL and undetectable post-PCT; (2) RPA II: EBV DNA levels either at a pretreatment concentration > 4000 copies/mL or at a pretreatment concentration ≤ 4000 copies/mL and detectable post-PCT; (3) RPA III: Deauville scores 4-5. While patients in RPA I and RPA II had significantly PFS rates when treated with PCT+DRT than when treated with PCT alone (RPA I: 72.7% versus 13.4%, RPA II: 37.8% versus 6.3%), those in RPA III did not experience such PFS benefits (6.5% versus 9.7%). CONCLUSION: PCT+DRT might improve the survival rates in mNPC patients in the low- and mid-risk strata but not those of patients in the high-risk strata. KEY POINTS: We use the Deauville scores and the concentrations of the Epstein-Barr virus (EBV) DNA to determine those patients with de novo metastatic NPC who would benefit from radiation therapy.

High-resolution mapping of the global silicate weathering carbon sink and its long-term changes.

Climatic and non-climatic factors affect the chemical weathering of silicate rocks, which in turn affects the CO2 concentration in the atmosphere on a long-term scale. However, the coupling effects of these factors prevent us from clearly understanding of the global weathering carbon sink of silicate rocks. Here, using the improved first-order model with correlated factors and non-parametric methods, we produced spatiotemporal data sets (0.25° × 0.25°) of the global silicate weathering carbon-sink flux (SCSFα ) under different scenarios (SSPs) in present (1950-2014) and future (2015-2100) periods based on the Global River Chemistry Database and CMIP6 data sets. Then, we analyzed and identified the key regions in space where climatic and non-climatic factors affect the SCSFα . We found that the total SCSFα was 155.80 ± 90 Tg C yr-1 in present period, which was expected to increase by 18.90 ± 11 Tg C yr-1 (12.13%) by the end of this century. Although the SCSFα in more than half of the world was showing an upward trend, about 43% of the regions were still showing a clear downward trend, especially under the SSP2-4.5 scenario. Among the main factors related to this, the relative contribution rate of runoff to the global SCSFα was close to 1/3 (32.11%), and the main control regions of runoff and precipitation factors in space accounted for about 49% of the area. There was a significant negative partial correlation between leaf area index and silicate weathering carbon sink flux due to the difference between the vegetation types. We have emphasized quantitative analysis the sensitivity of SCSFα to critical factors on a spatial grid scale, which is valuable for understanding the role of silicate chemical weathering in the global carbon cycle.

Cost-Effectiveness analysis of combining plasma Epstein-Barr virus DNA testing and different surveillance imaging modalities for nasopharyngeal carcinoma patients in first remission.

BACKGROUND: To evaluate the cost-effectiveness of stage-based post-radiotherapy (PRT) nasopharyngeal carcinoma (NPC) surveillance strategies. METHODS: Four post-radiotherapy surveillance strategies were established by a Markov model based on data from 1664 patients: 1) clinical follow-up (CFP) with biannual Epstein-Barr virus (EBV) DNA (EBV DNA strategy); 2) CFP with biannual EBV DNA, annual head and neck magnetic resonance imaging (HNMRI), chest X-ray, abdominal ultrasonography, bone scan (only for the first two years) for five years (MCWU strategy); 3) CFP with biannual EBV DNA, annual HNMRI, chest, abdomen, pelvic computerized tomography (CT) and bone scan for the first two years, followed by annual MCWU strategy (without bone scans) for the last three years (CT strategy); 4) CFP with biannual EBV DNA, annual whole-body positron emission/computerized tomography (PET/CT) for the first two years and biannual EBV DNA for the last three years (PET/CT strategy). RESULTS: Compared with the EBV DNA strategy, the MCWU, CT, and PET/CT strategies gained 0.017, 0.047, and 0.082 quality-adjusted life years (QALY) for stage I-II patients. For stage III and IVa patients, the PET/CT strategy had a favorable incremental effectiveness (ICERs) of 0.277 and 0.385 QALY, respectively. The ICERs for the MCWU, CT, and PET/CT strategies were $74,037, $34,882, and $34,696 for stage III and $62,364, $27,981, and $28,340 for stage IVa, respectively. CONCLUSION: EBV DNA strategy was cost-effective for the long-term surveillance of stage I-II NPC patients with CR. PET/CT strategy was recommeded for patients having IVa NPC. As for stage III NPC, PET/CT strategy was still acceptable with the development of economy in China.

EBV infection-induced GPX4 promotes chemoresistance and tumor progression in nasopharyngeal carcinoma.

Epstein-Barr virus (EBV) was the first oncogenic virus identified in humans. It is primarily associated with multiple lymphoid and epithelial cancers, including nasopharyngeal carcinoma (NPC). However, its association with ferroptosis and its role in cancer therapy resistance have not been fully elucidated. Here, we show that EBV infection reduces the sensitivity of NPC cells to ferroptosis by activating the p62-Keap1-NRF2 signaling pathway in conjunction with upregulation of SLC7A11 and GPX4 expression. Knockdown of endogenous GPX4 or blockade of GPX4 using a specific inhibitor enhanced the chemosensitivity of EBV-infected NPC cells. Functional studies revealed that GPX4 knockdown suppresses the proliferation and colony formation of NPC cells. Mechanistically, GPX4 interacts with the TAK1-TAB1/TAB3 complex, regulates TAK1 kinase activity, and further activates downstream MAPK-JNK and NFκB pathways. High GPX4 expression is correlated with poor clinical outcomes in patients with NPC and other cancer types. Taken together, our findings suggest that EBV infection has important effects on redox homeostasis, revealing a previously unappreciated role for GPX4 in tumor progression. This novel mechanism provides a potential new target for the treatment of EBV-related tumors.

Management of first-line palliative chemotherapy for post-treatment metastasis after gemcitabine plus cisplatin induction chemotherapy: Gemcitabine plus cisplatin and non-gemcitabine plus cisplatin chemotherapy.

BACKGROUND: To evaluate whether patients with post-treatment metastasis are suitable for GP first-line palliative chemotherapy (PCT) after undergoing GP IC. METHODS: Seven hundred and forty-six patients with post-treatment metastasis after undergoing GP IC were eligible. Survival outcomes were compared. RESULTS: Significant differences in survival rates were observed between patients treated with GP and non-GP chemotherapy (2-year progression-free survival [PFS]: 0.7% vs. 9.7%). We investigated survival outcomes of patients treated with GP PCT within 2 years after undergoing GP IC, treated with GP PCT 2 years after undergoing GP IC, and those of non-GP PCT patients (2-year PFS: 0.0%, 2.3%, 9.7%). However, there was no difference in the 2-year PFS between the patients that received GP PCT 2 years after undergoing GP IC and the non-GP PCT treated patients. CONCLUSIONS: GP is not recommended for patients that have received GP IC within 2 years. Two years after undergoing GP IC, GP can be considered.

Conserved Conformational Changes in the Regulation of Mycobacterium tuberculosis MazEF-mt1.

Toxin-antitoxin (TA) systems, which regulate many important cellular processes, are abundantly present in prokaryotic organisms. MazEF is a common type of TA system implicated in the formation of "persisters cells" of the pathogen Mycobacterium tuberculosis, which contains 10 such systems. However, the exact function and inhibition mode of each MazF protein are not quite understood. Here, we report four high-resolution crystal structures of MazF-mt1 in various forms, including one in complex with MazE-mt1. The toxin displayed two unique interlocked loops that allow the formation of a tight dimer. These loops would open upon interacting with the MazE-mt1 antitoxin mediated by the last two helices of MazE-mt1. With our structure-based design, a mutant that could bind to the antitoxin with an enhanced affinity was produced. Combined crystallographic and biochemical studies further revealed that the binding affinity of MazE-mt1 to MazF-mt1 was mainly attributed to its α3 helical region, while the terminal helix η1 contributes very little or even negatively to the association of the pair, in stark contrast to the MazEF-mt9 system. This study provides structural insight into the binding mode and the inhibition mechanism of the MazE/F-mt1 TA pair, which may reflect the functional differences between different TA systems.

Characteristics and Assessment of Toxic Metal Contamination in Surface Water and Sediments Near a Uranium Mining Area.

Concentrations of potentially toxic metals including Cd, Cu, Pb, Cr, U, Th in surface water and sediment samples collected from a river were analyzed to assess the contaminations, distribution characteristics, and sources of these metals. The contents of the metals were lower than the standard levels set by World Health Organization (WHO) for drinking water. However, U and Th contents were far beyond the background values of surface water. The concentrations of Cd, Cr, and U in sediments were higher than the background values and the Probable Effect Level (PEL) of sediment quality guidelines (SQGs) which may result in high potential harmful biological effects to aquatic ecosystems. Based on the contamination factor (CF), geo-accumulation index (Igeo), and potential ecological risk index (RI), Cd, Cr, and U were considered to be the metals that mainly contribute to the contamination of sediments. The calculation results also indicated that the sites adjacent to the uranium ore field were highly polluted. Results of cluster analysis, principal component analysis, and correlation analysis revealed that Cr, Pb, U, and Th were highly correlated with each other. These metals mainly originated from both anthropogenic sources and natural processes, especially emissions from uranium mining and quarrying, whereas Cd mostly came from anthropogenic sources (agricultural activities) of the upper reaches of the river.

Structural and Biochemical Characterization of the Cognate and Heterologous Interactions of the MazEF-mt9 TA System.

Toxin-antitoxin (TA) modules widely exist in bacteria, and their activities are associated with the persister phenotype of the pathogen Mycobacterium tuberculosis (M. tb). M. tb causes tuberculosis, a contagious and severe airborne disease. There are 10 MazEF TA systems in M. tb that play important roles in stress adaptation. How the antitoxins antagonize toxins in M. tb or how the 10 TA systems crosstalk to each other are of interest, but the detailed molecular mechanisms are largely unclear. MazEF-mt9 is a unique member among the MazEF family due to its tRNase activity, which is usually carried out by the VapC toxins. Here, we present the cocrystal structure of the MazEF-mt9 complex at 2.7 Å. By characterizing the association mode between the TA pairs through various techniques, we found that MazF-mt9 bound not only its cognate antitoxin but also the noncognate antitoxin MazE-mt1, a phenomenon that could be also observed in vivo. Based on our structural and biochemical work, we propose that the cognate and heterologous interactions among different TA systems work together in vivo to relieve the toxicity of MazF-mt9 toward M. tb cells.

Pyruvate cycle increases aminoglycoside efficacy and provides respiratory energy in bacteria.

The emergence and ongoing spread of multidrug-resistant bacteria puts humans and other species at risk for potentially lethal infections. Thus, novel antibiotics or alternative approaches are needed to target drug-resistant bacteria, and metabolic modulation has been documented to improve antibiotic efficacy, but the relevant metabolic mechanisms require more studies. Here, we show that glutamate potentiates aminoglycoside antibiotics, resulting in improved elimination of antibiotic-resistant pathogens. When exploring the metabolic flux of glutamate, it was found that the enzymes that link the phosphoenolpyruvate (PEP)-pyruvate-AcCoA pathway to the TCA cycle were key players in this increased efficacy. Together, the PEP-pyruvate-AcCoA pathway and TCA cycle can be considered the pyruvate cycle (P cycle). Our results show that inhibition or gene depletion of the enzymes in the P cycle shut down the TCA cycle even in the presence of excess carbon sources, and that the P cycle operates routinely as a general mechanism for energy production and regulation in Escherichia coli and Edwardsiella tarda These findings address metabolic mechanisms of metabolite-induced potentiation and fundamental questions about bacterial biochemistry and energy metabolism.

Metabolic Mechanism for l-Leucine-Induced Metabolome To Eliminate Streptococcus iniae.

Crucial metabolites that modulate hosts' metabolome to eliminate bacterial pathogens have been documented, but the metabolic mechanisms are largely unknown. The present study explores the metabolic mechanism for l-leucine-induced metabolome to eliminate Streptococcus iniae in tilapia. GC-MS-based metabolomics was used to investigate the tilapia liver metabolic profile in the presence of exogenous l-leucine. Thirty-seven metabolites of differential abundance were determined, and 11 metabolic pathways were enriched. Pattern recognition analysis identified serine and proline as crucial metabolites, which are the two metabolites identified in survived tilapias during S. iniae infection, suggesting that the two metabolites play crucial roles in l-leucine-induced elimination of the pathogen by the host. Exogenous l-serine reduces the mortality of tilapias infected by S. iniae, providing a robust proof supporting the conclusion. Furthermore, exogenous l-serine elevates expression of genes IL-1ß and IL-8 in tilapia spleen, but not TNFα, CXCR4 and Mx, suggesting that the metabolite promotes a phagocytosis role of macrophages, which is consistent with the finding that l-leucine promotes macrophages to kill both Gram-positive and Gram-negative bacterial pathogens. Therefore, the ability of phagocytosis enhanced by exogenous l-leucine is partly attributed to elevation of l-serine. These results demonstrate a metabolic mechanism by which exogenous l-leucine modulates tilapias' metabolome to enhance innate immunity and eliminate pathogens.

Glucose enhances tilapia against Edwardsiella tarda infection through metabolome reprogramming.

We have recently reported that the survival of tilapia, Oreochromis niloticus, during Edwardsiella tarda infection is tightly associated with their metabolome, where the survived O. niloticus has distinct metabolomic profile to dying O. niloticus. Glucose is the key metabolite to distinguish the survival- and dying-metabolome. More importantly, exogenous administration of glucose to the fish greatly enhances their survival for the infection, indicating the functional roles of glucose in metabolome repurposing, known as reprogramming metabolomics. However, the underlying information for the reprogramming is not yet available. Here, GC/MS based metabolomics is used to understand the mechanisms by which how exogenous glucose elevates O. niloticus, anti-infectious ability to E. tarda. Results showed that exogenous glucose promotes stearic acid and palmitic acid biosynthesis but attenuates TCA cycle to potentiate O. niloticus against bacterial infection, which is confirmed by the fact that exogenous stearic acid increases immune protection in O. niloticus against E. tarda infection in a manner of Mx protein. These results indicate that exogenous glucose reprograms O. niloticus anti-infective metabolome that characterizes elevation of stearic acid and palmitic acid and attenuation of the TCA cycle. Therefore, our results proposed a novel mechanism that glucose promotes unsaturated fatty acid biosynthesis to cope with infection, thereby highlighting a potential way of enhancing fish immunity in aquaculture.