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BackgroundPatients with systemic sclerosis (SSc) are known to have higher incidence of atherosclerosis (AS). Mitochondrial injuries in SSc can cause endothelial dysfunction, leading to AS; thus, mitochondria appear to be hubs linking SSc to AS. This study aimed to identify the mitochondria-related biomarkers of SSc and AS.MethodsWe identified common differentially expressed genes (DEGs) in the SSc (GSE58095) and AS (GSE100927) datasets of the Gene Expression Omnibus (GEO) database. Considering the intersection between genes with identical expression trends and mitochondrial genes, we used the least absolute shrinkage and selection operator (LASSO) as well as random forest (RF) algorithms to identify four mitochondria-related hub genes. Diagnostic nomograms were then constructed to predict the likelihood of SSc and AS. Next, we used the CIBERSORT algorithm to evaluate immune infiltration in both disorders, predicted the transcription factors for the hub genes, and validated these genes for the two datasets.ResultsA total of 112 genes and 13 mitochondria-related genes were identified; these genes were then significantly enriched for macrophage differentiation, collagen-containing extracellular matrix, collagen binding, antigen processing and presentation, leukocyte transendothelial migration, and apoptosis. Four mitochondria-related hub DEGs (IFI6, FSCN1, GAL, and SGCA) were also identified. The nomograms showed good diagnostic values for GSE58095 (area under the curve (AUC) = 0.903) and GSE100927 (AUC = 0.904). Further, memory B cells, γδT cells, M0 macrophages, and activated mast cells were significantly higher in AS, while the resting memory CD4+ T cells were lower and M1 macrophages were higher in SSc; all of these were closely linked to multiple immune cells. Gene set enrichment analysis (GSEA) showed that IFI6 and FSCN1 were involved in immune-related pathways in both AS and SSc; GAL and SGCA are related to mitochondrial metabolism pathways in both SSc and AS. Twenty transcription factors (TFs) were predicted, where two TFs, namely BRCA1 and PPARγ, were highly expressed in both SSc and AS.ConclusionFour mitochondria-related biomarkers were identified in both SSc and AS, which have high diagnostic value and are associated with immune cell infiltration in both disorders. Hence, this study provides new insights into the pathological mechanisms underlying SSc and AS. The specific roles and action mechanisms of these genes require further clinical validation in SSc patients with AS.

The interactions between organic particulate matter and water vapour affect climate predictions, yet the mechanisms of these interactions remain unresolved. Here, the authors propose a phase separation mechanism that reconciles the observed hygroscopicity and cloud condensation nuclei activity.

Light-absorbing organic carbon (or brown carbon, BrC) in atmospheric particles has received much attention for its potential role in global radiative forcing. While a number of field measurement campaigns have differentiated light absorption by black carbon (BC) and BrC, the chemical characteristics of BrC are not well understood. In this study, we present co-located real-time light absorption and chemical composition measurements of atmospheric particles to explore the relationship between the chemical and optical characteristics of BrC at a suburban site downwind of Guangzhou, China from November to December 2014. BrC and BC contributions to light absorption were estimated using measurements from a seven-wavelength aethalometer, while the chemical composition of non-refractory PM1 was measured with a high resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS). Using the Absorption Angstrom Exponent (AAE) method, we estimated that BrC contributed 23.6% to the total aerosol absorption at 370nm, 18.1% at 470nm, 10.7% at 520nm, 10.7% at 590nm, and 10.5% at 660nm. Biomass burning organic aerosol (BBOA) has the highest mass absorption coefficient among sources of organic aerosols. Its contribution to total brown carbon absorption coefficient decreased but that of low-volatility oxygenated organic aerosol (LVOOA) increased with increasing wavelength, suggesting the need for wavelength-dependent light absorption analysis for BrC in association with its chemical makeup. Clear correlations of N-containing ion fragments with absorption coefficient were observed. These correlations also depended on their degrees of unsaturation/cyclization and oxygenation. While the current study relates light absorption by BrC to ion fragments, more detailed chemical characterization is warranted to constrain this relationship. [ABSTRACT FROM AUTHOR]

Particulate matter (PM) pollution on the peripheries of Chinese megacities can be as serious as in cities themselves. Given the substantial vehicular emissions in inner-city areas, the direct transport of primary PM (e.g., black carbon and primary organics) and effective formation of secondary PM from precursors (e.g., NOx and volatile organic compounds) can contribute to PM pollution in "buffer" zones between cities. To investigate how traffic emissions in inner-city areas impact these adjacent buffer zones, a suite of real-time instruments were deployed in Panyu, downwind from central Guangzhou, from November to December 2014. Nitrate mass fraction was higher on high-PM days, with the average nitrate-to-sulfate ratio increasing from around 0.35 to 1.5 as the PM mass concentration increased from 10 to 160 μgm-3. Particulate nitrate was strongly correlated with excess ammonium (([NH+ 4 ]/[SO2- 4]-1.5)×[SO2- 4]), with higher concentrations in December than in November due to lower temperatures. The organic mass fraction was the highest across all PM1 levels throughout the campaign. While organic aerosols (OA) were dominated by secondary organic aerosols (SOA = semi-volatile oxygenated organic aerosols + low-volatility oxygenated organic aerosols) as a campaign average, freshly emitted hydrocarbon-like organic aerosols (HOA) contributed up to 40% of OA during high- OA periods, which typically occurred at nighttime and contributed 23.8 to 28.4% on average. This was due to daytime traffic restrictions on heavy-duty vehicles in Guangzhou, and HOA almost increased linearly with total OA concentration. SOA increased as odd oxygen (Ox =O3 +NO2) increased during the day due to photochemistry. A combination of nighttime traffic emissions and daytime photochemistry contributed to the buildup of PM in Panyu. The mitigation of PM pollution in inner-city areas by reducing vehicular traffic can potentially improve air quality in peripheral areas. [ABSTRACT FROM AUTHOR]

Particulate matter (PM) pollution on the peripheries of rapidly expanding megacities in China can be as serious as in the cities due to direct emission and transport of primary PM from cities and effective formation of secondary PM. To investigate the emission and formation of PM on the periphery of Guangzhou (a megacity in southern China), a suite of real-time instruments were deployed at Panyu, downwind of Guangzhou, for PM measurements from November to December 2014. Dominated by organics, PM1 (particles with diameter less than 1 μm) concentrations in Panyu were higher (average ~ 55.4 μg/m3) than those in nearby cities such as Hong Kong and Shenzhen. Five sources for organic aerosols (OA) were resolved by positive matrix factorization (PMF) analysis with the multilinear engine (ME-2). These sources are hydrocarbon-like organic aerosol (HOA), cooking organic aerosol (COA), biomass burning related organic aerosol (BBOA), as well as semi-volatile oxygenated organic aerosol (SVOOA) and low-volatile oxygenated organic aerosol (LVOOA). The use of the COA mass spectrum obtained in our earlier study at a urban site in Hong Kong as a constraining factor in ME-2 produced the most interpretable results for the Panyu dataset. Freshly emitted HOA contributed 40 % to the high concentrations of organics at night. The mass concentration of SOA (SVOOA + LVOOA) continuously increased as odd oxygen (Ox = O3 + NO2) increased during daytime, attributable to the secondary production of PM facilitated by photochemistry. The SOA-to-Ox ratio was higher than those reported in previous studies in North America (covering the period from spring to summer), indicating efficient photochemical production of SOA even in late autumn and early winter at this subtropical downwind site. The efficient SOA formation during daytime was likely fueled by the sufficient SOA precursors in the atmosphere. The large input of NOx, which tracked well with HOA from automobile emissions, resulted in the significant formation of nitrate in both daytime and nighttime. Strong correlations between particulate nitrate and excess ammonium ([NH4+]/[SO42-] - 1.5) × [SO42-]) were observed. Higher partitioning of nitrate into the gas phase was found in November than in December, likely due to the lower temperatures in December. Results from this study suggest that there is much room to mitigate the PM pollution in urbanized areas such as Guangzhou, as well as their peripheries, by reductions in traffic-related pollutants. [ABSTRACT FROM AUTHOR]