Has the opening of high-speed railway in China promoted urban low-carbon transformation along the route: re-estimation based on staggered DID robust estimators.

Considering the opening of high-speed railway (HSR) as a quasi-natural experiment, this paper explores the emission reduction effect of HSR opening and its mechanisms and heterogeneity characteristics based on the panel data of 272 cities in China from 2006 to 2019 by staggered DID model and the mediating effect model. It is found that (1) the opening of HSR significantly reduces the carbon emission level of cities, and the conclusion still holds after controlling the endogeneity issue and a series of robustness tests; (2) Bancon decomposition and negative weight diagnostics both show that the estimated average treatment effect bias is small and the robust estimators are more robust; (3) by reducing production costs and promoting inter-regional industrial division of labor, the opening of HSR promotes intra-industrial structural transformation and inter-industrial structural transformation, respectively, thus reducing urban carbon emissions. At the same time, HSR achieves urban carbon emission reduction by promoting free movement of population and human capital agglomeration; and (4) further study finds that there is regional heterogeneity in the emission reduction effect of HSR opening, and the carbon reduction effect is mainly reflected in large and medium-sized cities, near provincial capitals, non-resource-based cities, and cities with rich educational resources, which indicates that the location of future HSR should be combined with the city's own characteristics and be tailored to the city.

Osteopontin interacts with dendritic cells and macrophages in pulp inflammation: Comprehensive transcriptomic analysis and laboratory investigations.

AIM: To investigate novel diagnostic markers for pulpitis and validate by clinical samples from normal and inflamed pulp. To explore the relationship between diagnostic markers and immune cells or their phenotypes during pulp inflammation. METHODOLOGY: Two microarray datasets, GSE77459 and GSE92681, and identified differential expression genes were integrated. To understand immune features, gene functions, Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), Disease Ontology (DO) and ImmuneSigDB Gene Set Enrichment Analysis (GSEA) were analysed. For predictive purposes, machine learning techniques were applied to detect diagnostic markers. Immune infiltration in inflamed pulp was studied using CIBERSORT. The relationship between diagnostic markers and immune cells was investigated and validated their gene expression in clinical samples from the normal or inflamed pulp by qRT-PCR. Finally, the correlation between one marker, secreted phosphoprotein 1 (SPP1), encoding osteopontin (OPN), and dendritic cells (DCs)/macrophages was identified via HE staining and multiplex immunohistochemistry. An in vitro inflammatory dental pulp microenvironment model of THP-1 macrophages cocultured with dental pulp cells derived conditioned media (DPCs-CM) to investigate OPN production and macrophage phenotypes was established. RESULTS: Analysis revealed unique immunologic features in inflamed pulp. Three diagnostic markers for pulpitis: endothelin-1 (EDN1), SPP1, and purine nucleoside phosphorylase (PNP), and validated them using qRT-PCR were predicted. Multiplex immunohistochemistry demonstrated OPN co-localized with activated DCs and M2 macrophages during pulp inflammation. In vitro experiments showed that THP-1 macrophages produced the highest levels of OPN when stimulated with DPCs-CM derived from the 20 µg/mL LPS pre-conditioned group, suggesting an M2b-like phenotype by increasing surface marker CD86 and expression of IL6, TNFα, IL10, and CCL1 but not CCL17 and MerTK. Levels of CCL1 and IL10 elevated significantly in the macrophages' supernatant from the 20 µg/mL LPS pre-conditioned CM group. OPN was proven co-localizing with CD86 in the inflamed pulp by immunofluorescence. CONCLUSIONS: The current findings suggest that OPN can serve as a promising biomarker for pulpitis, correlated with DCs and macrophages. OPN+ macrophages in the inflamed pulp are associated with M2b-like phenotypes. These insights offer the potential for improved diagnosis and targeted therapy.

QTL epistasis plays a role of homeostasis on heading date in rice.

If there was no gene interaction, the gene aggregation effect would increase infinitely with the increase of gene number. Epistasis avoids the endless accumulation of gene effects, playing a role of homeostasis. To confirm the role, QTL epistases were analyzed by four single-segment substitution lines with heading date QTLs in this paper. We found that QTLs of three positive effects and one negative effect generated 62.5% negative dual QTL epistatic effects and 57.7% positive triple QTL epistatic effects, forming the relationship "positive QTLs-negative one order interactions-positive two order interactions". In this way, the aggregation effect of QTLs was partially neutralized by the opposite epistatic effect sum. There also were two exceptions, QTL OsMADS50 and gene Hd3a-2 were always with consistent effect directions with their epistases, implying they could be employed in pyramiding breeding with different objectives. This study elucidated the mechanism of epistatic interactions among four QTLs and provided valuable genetic resources for improving heading date in rice.

Does place-based green policy improve air pollution? Evidence from China's National Eco-Industrial Demonstration Park Policy.

Air pollution is one of the serious environmental problems facing the world. This paper systematically investigates the impact and transmission mechanism of the construction of national eco-industrial parks (NEDPs) on urban air pollution based on Chinese city-level panel data from 2003 to 2021 using a staggered difference-in-differences (staggered DID) model. It is found that the construction of NEDP significantly reduces urban air pollution, a conclusion supported by the negative weight diagnostic test and two types of robust DID estimators. Mechanism analyses indicate that NEDP construction reduces urban air pollution mainly by improving regional environmental regulation, promoting green technology innovation and improving energy structure. In addition, the mitigation effect of NEDP construction on urban air pollution is heterogeneous by policy intensity, city resource endowment, city size and administrative status. Further tests show that the institutional environment enhances the air pollution mitigation effect of NEDP construction and that the better the degree of marketization, property rights system, legal system and market development in the place where the policy is implemented, the more conducive it is to amplify the air pollution suppression effect brought about by NEDP construction. Developing economies should take complete account of the characteristics of different regions when implementing place-based green policies to achieve synergistic development of the environment and the economy.

Synthesis, structure anatomy, and catalytic properties of Ag14Cu2 nanoclusters co-protected by alkynyl and phosphine ligands.

We report the synthesis, structure anatomy, and catalytic properties of Ag14Cu2(CCArF)14(PPh3)4 (CCArF: 3,5-bis(trifluoromethyl)phenylacetylene) nanoclusters, denoted as Ag14Cu2. Ag14Cu2 has a robust electronic structure with two free valence electrons, and it has a distinctive absorbance feature. Single-crystal X-ray diffraction (SC-XRD) disclosed that Ag14Cu2 possesses an octahedral Ag6 metal kernel capped by two Ag4Cu1(CCArF)7(PPh3)2 metal-ligand units. Remarkably, it exhibits excellent bifunctional catalytic performance for 4-nitrophenol reduction and the electrochemical CO2 reduction reaction (eCO2RR). In 4-nitrophenol reduction, it adopts first-order reaction kinetics with a rate constant of 0.137 min-1, while in the eCO2RR, it shows a CO faradaic efficiency (FECO) of 83.71% and a high current density of 92.65 mA cm-2 at -1.6 V vs. RHE. Moreover, Ag14Cu2 showed robust long-term stability with no significant decay in current density and FECO over 10 h of continuous operation in the eCO2RR. This study not only enriches the potpourri of alkynyl-protected bimetallic AgCu nanoclusters, but also demonstrates the great potential of employing metal nanoclusters for bifunctional catalytic applications.

Alkynyl-protected Ag20 Rh2 Nanocluster with Atomic Precision: Structure Analysis and Tri-functionality Catalytic Application.

We report the overall structure and trifunctionality catalytic application of an atomically precise alloy nanocluster of Ag20 Rh2 (C≡C-t Bu)16 (CF3 CO2 )6 (H2 O)2 (abbreviated as Ag20 Rh2 hereafter). Ag20 Rh2 has a twisted rod-like structure, where a Ag4 @Rh2 kernel is connected by two twisted Ag8 cubes on two sides. Ag20 Rh2 is a superatomic cluster with four free valence electrons, and it has characteristic absorbance feature. Interestingly, Ag20 Rh2 exhibited superior catalytic performance than the larger AgRh nanoparticle counterparts in electrochemical hydrogen evolution reaction (HER), reduction of 4-nitrophenol, and the methyl orange degradation reaction. Such intriguing catalytic properties are attributed to the more exposed active sites from the ultrasmall nanoclusters than relatively large nanoparticles. This study not only enriches the family member of alkynyl-protected AgRh nanoclusters with atomic precision, but also highlights the great advantages of employing nanoclusters as efficient catalysts for multiple functionalities.

Bioactive Aspergteroids G-J from Soft-Coral-Associated Symbiotic and Epiphytic Fungus Aspergillus terreus EGF7-0-1.

Two new disubstituted maleimides, aspergteroids G-H (1-2), and two trisubstituted butenolides aspergteroids I-J (3-4), along with four known analogs, were isolated and structurally identified from the fermentation extract of soft-coral-associated symbiotic and epiphytic fungus Aspergillus terreus EGF7-0-1. The structures of the new compounds were established mainly via spectroscopic data analyses, and their absolute configurations were determined via X-ray diffraction analysis and comparison of the calculated and experimental electronic circular dichroism. Myocardial protection assays showed that compounds 1, 2, 5, and 6 possess protective effects against tert-butyl hydroperoxide (TBHP)-induced H9c2 (rat myocardial cells) apoptosis at low concentrations. Based on the analyses of the protein-protein interaction (PPI) network and Western blotting, compound 1 may inhibit the apoptosis and inflammatory response of cardiomyocytes after TBHP induction and improve the antioxidant capacity of cardiomyocytes. We speculate that the anti-inflammatory response of compound 1 is suppressed by the glycogen synthase kinase-3 beta (GSK-3ß), downregulated by the NOD-like receptor thermal protein domain associated protein 3 (NLRP3) inflammasome activation, and suppressed by the expression of cysteinyl aspartate specific proteinase-3 (caspase-3) and B-cell lymphoma-2 associated X protein (Bax).

Structure, optical properties, and catalytic applications of alkynyl-protected M4Rh2 (M = Ag/Au) nanoclusters with atomic precision: a comparative study.

We report two atomically precise alloy nanoclusters of Ag4Rh2(CCArF)8(PPh3)2 and Au4Rh2(CCArF)8(PPh3)2 (Ar = 3,5-(CF3)2C6H3, abbreviated as Ag4Rh2 and Au4Rh2, respectively) co-protected by alkynyl and phosphine ligands. Both clusters have identical octahedral metal core configurations and can be termed superatoms with two free electrons. However, they possess different optical features, manifested by totally different absorbance peaks, and drastically different emission peaks, and also, Ag4Rh2 has a much higher fluorescence quantum yield (18.43%) than Au4Rh2 (4.98%). Moreover, Au4Rh2 exhibited markedly superior catalytic performance in the electrochemical hydrogen evolution reaction (HER), manifested by a much lower overpotential at 10 mA cm-2 and better stability. Density functional theory (DFT) calculations revealed that the free energy change of Au4Rh2 for the adsorption of two H* (0.64 eV) is lower than that of Ag4Rh2 for the adsorption of one H* (-0.90 eV) after stripping a single alkynyl ligand from the cluster. In contrast, Ag4Rh2 demonstrated much stronger catalytic capability for catalyzing 4-nitrophenol reduction. The present study provides an exquisite example to understand the structure-property relationship of atomically precise alloy nanoclusters, and emphasizes the importance of fine-tuning of the physicochemical properties and catalytic performance of the metal nanoclusters through modulating the metal core and beyond.

New Indole Diketopiperazine Alkaloids from Soft Coral-Associated Epiphytic Fungus Aspergillus versicolor CGF 9-1-2.

Two new indole diketopiperazine alkaloids (IDAs), (+)19-epi-sclerotiamide (1) and (-)19-epi-sclerotiamide (2), along with 13 known analogs (3-15), were isolated from a soft coral-associated epiphytic fungus Aspergillus versicolor CGF 9-1-2. The structures of two new compounds were established based on the combination of HR-ESI-MS, 1D and 2D NMR spectroscopy, optical rotation measurements and quantum chemical 13 C-NMR, the absolute configurations were determined by experimental and electronic circular dichroism (ECD) calculations. The results of molecular docking showed that all the compounds had a good binding with TDP1, TDP2, TOP1, TOP2, Ache, NLRP3, EGFR, EGFR L858R, EGFR T790M and EGFR T790/L858. Biological evaluation of compounds 3, 6, 8, 11 showed that 3 exerted a strong inhibitory effect on TDP2 with a rate of 81.72 %.

Quantity or quality? The impact of financial geo-density on firms' green innovation.

Green innovation is an essential support for environmentally sustainable development. However, little attention has been given to the impact of financial expansion on green innovation in the existing literature, and there is a lack of studies based on the perspective of the financial geographical supply structure. This study uses latitude and longitude information to construct firm-level financial geo-density data in China. It examines the impact of financial geo-density on a firm's green innovation and mechanisms. The results reveal that as financial geo-density increases, green innovation quantity increases, but green innovation quality decreases. The findings of the mechanism test indicate that an increase in financial geo-density decreases the cost of financing and boosts bank competition in the vicinity of the firm, hence resulting in a rise in the firms' green innovation quantity. Nevertheless, the degree of bank competition increased by financial geo-density increase negatively affects firms' green innovation quality. Heterogeneity analysis shows that financial geo-density has a more significant positive impact on a firm's green innovation quantity in high environmental regulation areas and high-pollution industries. Firms with low innovation capabilities are the main group responsible for the decline in green innovation quality. For firms located in low environmental regulation areas and medium- to light-pollution industries, financial geo-density has a more significant inhibition effect on green innovation quality. Further tests have shown that the extent to which financial geo-density enhances a firm's green innovation quantity diminishes as market segmentation increases. A new concept of financial development policies based on green development and innovation is presented in this paper for developing economies.

Metacarpophalangeal Joint Pathology and Bone Mineral Density Increase with Exercise but Not with Incidence of Proximal Sesamoid Bone Fracture in Thoroughbred Racehorses.

Proximal sesamoid bone (PSB) fracture is the leading cause of fatal musculoskeletal injury in Thoroughbred racehorses in Hong Kong and the US. Efforts are underway to investigate diagnostic modalities that could help identify racehorses at increased risk of fracture; however, features associated with PSB fracture risk are still poorly understood. The objectives of this study were to (1) investigate third metacarpal (MC3) and PSB density and mineral content using dual-energy X-ray absorptiometry (DXA), computed tomography (CT), Raman spectroscopy, and ash fraction measurements, and (2) investigate PSB quality and metacarpophalangeal joint (MCPJ) pathology using Raman spectroscopy and CT. Forelimbs were collected from 29 Thoroughbred racehorse cadavers (n = 14 PSB fracture, n = 15 control) for DXA and CT imaging, and PSBs were sectioned for Raman spectroscopy and ash fraction measurements. Bone mineral density (BMD) was greater in MC3 condyles and PSBs of horses with more high-speed furlongs. MCPJ pathology, including palmar osteochondral disease (POD), MC3 condylar sclerosis, and MC3 subchondral lysis were greater in horses with more high-speed furlongs. There were no differences in BMD or Raman parameters between fracture and control groups; however, Raman spectroscopy and ash fraction measurements revealed regional differences in PSB BMD and tissue composition. Many parameters, including MC3 and PSB bone mineral density, were strongly correlated with total high-speed furlongs.

Photobiomodulation activates undifferentiated macrophages and promotes M1/M2 macrophage polarization via PI3K/AKT/mTOR signaling pathway.

Macrophages are the main mediators of the inflammatory response and play a major role in the onset and maintenance of periodontitis. Studies revealed that photobiomodulation (PBM) can change the polarization state of macrophages and inflammation reduction, although the cellular mechanisms are not fully elucidated. Here, the present study explored the effect of PBM (980 nm) on undifferentiated and M1-type macrophages and the underlying mechanism. RAW264.7 cells were exposed to laser irradiation under different laser parameters (0.5, 5.0, and 10.0 J/cm2) with or without LY294002 (an inhibitor of PI3K pathway). Then, confocal laser microscopy was used to observe cell differentiation; qPCR was performed to examine the gene expression and western blotting was used to detect the protein in the PI3K/AKT/mTOR pathway and activated macrophage markers. The obtained results revealed that 980 nm PBM increased the mRNA expression of iNOS, Il-10, Arg1, and Il-12 along with the inflammatory cytokines Tnfα, IL-1ß, and Il-6 in M0-type macrophages in dose-dependent manner. More interestingly, PBM at 5 J/cm2 decreased the mRNA expression of iNOS, Il-12, Tnfα, IL-1ß, and Il-6 and increased the expression of Arg1 and Il-10 by M1-type macrophages, along with the elevated expression of phosphorylation of AKT and mTOR. Moreover, PBM-induced M1-type macrophage polarization was significantly attenuated via LY294002 treatment. These suggest that 980 nm PBM could activate M0-type macrophages and increase M2/M1 ratio via the PI3K/AKT/mTOR pathway.

Sema3A Drives Alternative Macrophage Activation in the Resolution of Periodontitis via PI3K/AKT/mTOR Signaling.

Macrophages actively participate in immunomodulatory processes throughout periodontal inflammation. Regulation of M1/M2 polarization affects macrophage chemokine and cytokine secretion, resulting in a distinct immunological status that influences prognosis. Semaphorin 3A (Sema3A), a neurite growth factor, exerts anti-inflammatory effects. In this study, we investigated the immunomodulation of Sema3A on macrophage-related immune responses in vivo and in vitro. Topical medications of Sema3A in mice with periodontitis alleviated inflammatory cell infiltration into gingival tissue and reduced areas with positive IL-6 and TNFα expression. We observed that the positive area with the M2 macrophage marker CD206 increased and that of the M1 macrophage marker iNOS decreased in Sema3A-treated mice. It has been postulated that Sema3A alleviates periodontitis by regulating alternative macrophage activation. To understand the mechanism underlying Sema3A modulation of macrophage polarization, an in vitro macrophage research model was established with RAW264.7 cells, and we demonstrated that Sema3A promotes LPS/IFNγ-induced M1 macrophages to polarize into M2 macrophages and activates the PI3K/AKT/mTOR signaling pathways. Inhibition of the PI3K signaling pathway activation might reduce anti-inflammatory activity and boost the expression of the inflammatory cytokines, iNOS, IL-12, TNFα, and IL-6. This study indicated that Sema3A might be a feasible drug to regulate alternative macrophage activation in the inflammatory response and thus alleviate periodontitis.

980 nm Photobiomodulation Promotes Osteo/Odontogenic Differentiation of the Stem Cells from Human Exfoliated Deciduous Teeth Via the Cross talk Between BMP/Smad and Wnt/ß-Catenin Signaling Pathways.

Increasing evidence suggests stem cells from human exfoliated deciduous teeth (SHEDs) serve as desirable sources of dentin regeneration. Photobiomodulation (PBM) has shown great potential in enhancing the proliferation and osteogenesis of human bone marrow mesenchymal stem cells (hBMMSCs). However, the specific role of PBM in odontogenic differentiation of SHEDs is little know, and we further investigated potential mechanism of PBM osteo/odontogenisis. A 980 nm diode laser with different energy densities of (0.5, 5, 10 J cm-2 ) in a 100-mW continuous wave was used for irradiation every 24 h. Osteo/odontogenic differentiation of SHEDs was achieved by performing alkaline phosphatase (ALP) and alizarin red staining (ARS) and osteo/odontogenic markers were also evaluated by qRT-PCR and western blotting. Additionally, western blot and immunohistochemical staining were performed to evaluate the levels of BMP/Smad and Wnt/ß-catenin signaling-related proteins. We found that PBM at 5 J cm-1 increased mineral deposition and upregulated the expression of related osteo/odontogenic markers along with the elevated expression of ß-catenin and phosphorylation level of Smad1/5/9. Furthermore, Wnt signaling inhibition using DKK1 and BMP signaling inhibition using noggin inhibited PBM-induced osteo/odontogenic marker expression when used individually or jointly. In conclusion, PBM induces the osteo/odontogenic differentiation of SHEDs through cross talk between BMP/Smad and Wnt/ß-catenin signaling pathways.

Corrigendum: The effects of empathy by caregivers on healthcare service satisfaction.

[This corrects the article DOI: 10.3389/fpsyg.2022.912076.].

The effects of empathy by caregivers on healthcare service satisfaction.

Healthcare service satisfaction focuses not only on the patients but also on the caregivers' perspectives. This study explored how caregivers' empathy toward patients affects their satisfaction with healthcare services through an electroencephalography (EEG) experiment. EEG mu rhythm was used as the neural indicator to reflect empathy. The results showed that empathy reduces caregivers' evaluation of healthcare service satisfaction because they share suffering with the patients. However, implementing physician-patient communication through a process-based informed consent (IC), compared to an event-based IC, can effectively alleviate such adverse effects.

Trehalose Attenuates Oxidative Stress and Endoplasmic Reticulum Stress-Mediated Apoptosis in IPEC-J2 Cells Subjected to Heat Stress.

This study was carried out to investigate the effects of trehalose (Tre) on antioxidant capacity, endoplasmic reticulum stress (ERS) response and apoptosis of heat-stressed intestinal porcine epithelial cells (IPEC-J2). IPEC-J2 cells were cultured at 37 °C until the end of the experiment (control, CON); exposed to heat stress for 2 h (43 °C, HS); or pretreated with 0.1, 1, 5, 10, and 15 mM trehalose at 37 °C for 4 h prior to heat stress exposure for 2 h. The optimum level of trehalose for protecting against HS-induced cell injuries was determined to be 10 mM, as evidenced by the highest cellular viability and lowest malondialdehyde (MDA) content and lactate dehydrogenase (LDH) activity. Based on these, IPEC-J2 cells were divided into three groups: the first group was cultured at 37 °C until the end of the experiment (control, CON); the second group was exposed to heat stress for 2 h (43 °C, HS); the third group was pretreated with 10 mM trehalose for 4 h at 37 °C prior to heat stress exposure for 2 h (Tre + HS). The reactive oxygen species (ROS) content, superoxide dismutase (SOD) activity, mitochondrial membrane potential (MMP) changes, and expressions of the manganese superoxide dismutase (SOD2), ERS and apoptosis-related proteins were determined. Compared to the CON group, HS significantly increased ROS generation (p < 0.01), decreased SOD activity (p < 0.05), and downregulated protein expression of SOD2 (p < 0.01). Compared to the HS group, Tre supplementation reduced ROS levels and increased SOD activity and SOD2 expression to the levels that were comparable to the control (p < 0.05). The HS-induced ERS response was evidenced by the increased protein expressions of glucose-regulated protein 78 (GRP78) (p < 0.01), eukaryotic translation initiation factor 2α (p-eif2α) (p < 0.01), transcription activator 4 (ATF4) (p < 0.01), and the protein expression of C/EBP homologous protein (CHOP) (p < 0.01), which were the four hallmarks of ERS. The Tre + HS group showed lower expressions of GRP78 (p < 0.01), p-eif2α (p < 0.01), ATF4 (p < 0.01), and CHOP (p < 0.01) than that of the HS group. Tre pretreatment attenuated HS-induced mitochondrial apoptosis in IPEC-J2 cells, demonstrated by the increased MMP and decreased proapoptotic proteins active caspase 3, Bax, and cytochrome c (Cyt c). Taken together, trehalose can protect against HS-induced oxidative damage and endoplasmic reticulum stress-mediated apoptosis in IPEC-J2 cells. These data may provide a nutritional strategy for alleviating heat stress in pig production.

Exploring the association between resource dependence and haze pollution in China: the mediating effect of green technology innovation.

Haze pollution has been addressed in extensive studies over the last few years. However, the relationship between resource dependence and haze pollution has not been fully investigated. This study focuses on addressing this problem while considering the mediating role of green technology innovation. A panel dataset of 263 prefecture-level cities in China from 2005 to 2018 is used for the analysis. The results show the following: (1) the two-way fixed-effect model reveals that resource dependence contributes significantly to haze pollution, and this finding remains robust across a series of robustness tests. (2) A mediation analysis indicates that resource dependence is unfavorable for green technology innovation, indirectly affecting the alleviation of haze pollution. (3) The results of panel threshold regression suggest that green technology innovation promotes haze reduction in the weak and medium resource dependence stages, whereas this optimization effect disappears in the strong resource dependence stage due to rebound effects. (4) The results of regional heterogeneity demonstrate that the positive effects of resource dependence on haze pollution exist in eastern and western China but not in central China. Based on these results, policy implications are given to reduce haze pollution.

Digital economy and urban low-carbon sustainable development: the role of innovation factor mobility in China.

To address climate change, one of the toughest contemporary environmental issues, growing importance is attached to the role of the digital economy in combating environmental degradation. Using panel data from 237 Chinese cities during the period 2011-2018, this paper attempts to provide a more systematic view of the relationship between the digital economy and urban low-carbon sustainable development to make up for the existing empirical inconclusiveness. Based on the fixed-effect model, results show that boosting the digital economy can effectively promote urban low-carbon sustainable development, and the conclusion remains robust across a series of robustness checks. Furthermore, innovation factor mobility is the critical transmission channel through which the digital economy affects urban low-carbon sustainable development. Spatiotemporal heterogeneity analysis reveals that the promoting effect of the digital economy on urban low-carbon sustainable development decreases from the northeast to the southeast of China, whereas the impact of innovation factor mobility on urban low-carbon sustainable development decreases from the southeast to the northeast with the Pearl River Delta as the core. Panel threshold regression analysis shows that the impact of the digital economy on urban low-carbon sustainable development is getting stronger with the increase of economic development level charactered with nighttime lights.