Preparation of antibacterial degummed silk fiber/nano-hydroxyapatite/polylactic acid composite scaffold by degummed silk fiber loaded silver nanoparticles.

In this study, an antibacterial degummed silk fiber (ADSF)/nano-hydroxyapatite/polylactic acid (ADSF/nHA/PLA) porous scaffold with antibacterial properties was prepared by using degummed silk fiber (DSF) loaded with silver nano-particles (Ag NPs) as a reinforcing material. In the experiment, ADSF and nHA were used as the main variables to investigate the effect of the change of the composition ratio on the performance of the composite scaffold, and a composite scaffold with excellent performance was obtained. Firstly, the DSFs were treated with dopamine (DA) and the silver ions were reduced to Ag NPs using the strong reducibility of polydopamine (PDA) to prepare ADSF loaded with Ag NPs. Finally, ADSF/nHA/PLA composite scaffolds with antibacterial properties were prepared using ADSF as a reinforcing material. In addition, samples were found to have good mineralization capacity in in vitro mineralization experiments. At the same time, in cell culture and antibacterial experiments, ADSF/nHA/PLA scaffolds were found to have good bioactivity, biocompatibility and antibacterial properties. All the results showed that the Ag NPs loaded DSF improved the performance of the nHA/PLA composite scaffold, while the ADSF/nHA/PLA had good bioactivity and antibacterial properties, making the antibacterial ADSF/nHA/PLA composite scaffold has a great potential for bone tissue engineering.

High Phosphate-Induced Calcification of Vascular Smooth Muscle Cells is Associated with the TLR4/NF-κb Signaling Pathway.

BACKGROUND/AIMS: Hyperphosphatemia is one of the most notable features of chronic kidney disease (CKD). Numerous epidemiological and clinical studies have found that high serum phosphate concentrations are associated with calcification in the coronary arteries. However, the mechanisms underlying the vascular calcification induced by high phosphate have not been understood fully. METHODS: Vascular smooth muscle cells (VSMCs) were cultured in high-phosphate media to induce vascular calcification, which was detected by Alizarin red S staining. Gene expression and protein levels of differentiation markers were determined by real-time RT-PCR and western blotting, respectively. Protein levels of phosphorylated NF-κB and TLR4 were detected by western blotting, and the role of NF-κB/TLR4 was further confirmed by using an NF-κB inhibitor or TLR4 siRNA. RESULTS: Our results showed that high-phosphate media induced obvious calcification of VSMCs. Simultaneously, VSMC differentiation was confirmed by the increased expression of bone morphogenetic protein-2 and Runt-related transcription factor 2 and decreased expression of the VSMC-specific marker SM22α, which was accompanied by the increased expression of inflammatory cytokines. Moreover, a significant upregulation of TLR4 and phosphorylated NF-κB was also detected in VSMCs with high-phosphate media. In contrast, VSMC calcification and the increased expression of inflammatory cytokines were markedly attenuated by pretreatment with TLR4 siRNA and pyrrolidine dithiocarbamic acid, an NF-κB inhibitor. CONCLUSION: These data suggest that high-phosphate conditions directly induce vascular calcification via the activation of TLR4/NF-κB signaling in VSMCs. Moreover, inhibition of the TLR4/NF-κB signaling pathway might be a key intervention to prevent vascular calcification in patients with CKD.

miR-320a suppresses colorectal cancer progression by targeting Rac1.

MicroRNAs (miRNAs) have emerged as critical epigenetic regulators involved in cancer progression. miR-320a has been identified to be a novel tumour suppressive miRNA in colorectal cancer (CRC). However, the detailed molecular mechanisms are not fully understood. Here, we reported that miR-320a inversely associated with CRC aggressiveness in both cell lines and clinical specimens. Functional studies demonstrated that miR-320a significantly decreased the capability of cell migration/invasion and induced G0/G1 growth arrest in vitro and in vivo. Furthermore, Rac1 was identified as one of the direct downstream targets of miR-320a and miR-320a specifically binds to the conserved 8-mer at position 1140-1147 of Rac1 3'-untranslated region to regulate Rac1 protein expression. Over-expression of miR-320a in SW620 cells inhibited Rac1 expression, whereas reduction of miR-320a by anti-miR-320a in SW480 cells enhanced Rac1 expression. Re-expression of Rac1 in the SW620/miR-320a cells restored the cell migration/invasion inhibited by miR-320a, whereas knockdown of Rac1 in the SW480/anti-miR-320a cells repressed these cellular functions elevated by anti-miR-320a. Conclusively, our results demonstrate that miR-320a functions as a tumour-suppressive miRNA through targeting Rac1 in CRC.

Molecular and functional alterations in a mouse cardiac model of Friedreich ataxia: activation of the integrated stress response, eIF2α phosphorylation, and the induction of downstream targets.

Friedreich ataxia (FA) is a neurodegenerative and cardiodegenerative disease resulting from marked frataxin deficiency. The condition is characterized by ataxia with fatal cardiomyopathy, but the pathogenic mechanisms are unclear. We investigated the association between gene expression and progressive histopathological and functional changes using the muscle creatine kinase conditional frataxin knockout (KO) mouse; this mouse develops a severe cardiac phenotype that resembles that of FA patients. We examined KO mice from 3 weeks of age, when they are asymptomatic, to 10 weeks of age, when they die of the disease. Positive iron staining was identified in KO mice from 5 weeks of age, with markedly reduced cardiac function from 6 weeks. We identified an early and marked up-regulation of a gene cohort responsible for stress-induced amino acid biosynthesis and observed markedly increased phosphorylation of eukaryotic translation initiation factor 2α (p-eIF2α), an activator of the integrated stress response, in KO mice at 3 weeks of age, relative to wild-type mice. Importantly, the eIF2α-mediated integrated stress response has been previously implicated in heart failure via downstream processes such as autophagy and apoptosis. Indeed, expression of a panel of autophagy and apoptosis markers was enhanced in KO mice. Thus, the pathogenesis of cardiomyopathy in FA correlates with the early and persistent eIF2α phosphorylation, which precedes activation of autophagy and apoptosis.

Targeting the metastasis suppressor, NDRG1, using novel iron chelators: regulation of stress fiber-mediated tumor cell migration via modulation of the ROCK1/pMLC2 signaling pathway.

The iron-regulated metastasis suppressor, N-myc downstream-regulated gene 1 (NDRG1), is up-regulated by cellular iron depletion mediated by iron chelators and can inhibit cancer cell migration. However, the mechanism of how NDRG1 achieves this effect remains unclear. In this study, we implemented established and newly constructed NDRG1 overexpression and knockdown models using the DU145, HT29, and HCT116 cancer cell lines to investigate the molecular basis by which NDRG1 exerts its inhibitory effect on cell migration. Using these models, we demonstrated that NDRG1 overexpression inhibits cell migration by preventing actin-filament polymerization, stress fiber assembly and formation. In contrast, NDRG1 knockdown had the opposite effect. Moreover, we identified that NDRG1 inhibited an important regulatory pathway mediated by the Rho-associated, coiled-coil containing protein kinase 1 (ROCK1)/phosphorylated myosin light chain 2 (pMLC2) pathway that modulates stress fiber assembly. The phosphorylation of MLC2 is a key process in inducing stress fiber contraction, and this was shown to be markedly decreased or increased by NDRG1 overexpression or knockdown, respectively. The mechanism involved in the inhibition of MLC2 phosphorylation by NDRG1 was mediated by a significant (P < 0.001) decrease in ROCK1 expression that is a key kinase involved in MLC2 phosphorylation. Considering that NDRG1 is up-regulated after cellular iron depletion, novel thiosemicarbazone iron chelators (e.g., di-2-pyridylketone 4,4-dimethyl-3-thiosemicarbazone) were demonstrated to inhibit ROCK1/pMLC2-modulated actin-filament polymerization, stress fiber assembly, and formation via a mechanism involving NDRG1. These results highlight the role of the ROCK1/pMLC2 pathway in the NDRG1-mediated antimetastatic signaling network and the therapeutic potential of iron chelators at inhibiting metastasis.

Metastasis suppressor, NDRG1, mediates its activity through signaling pathways and molecular motors.

The metastasis suppressor, N-myc downstream regulated gene 1 (NDRG1), is negatively correlated with tumor progression in multiple neoplasms, being a promising new target for cancer treatment. However, the precise molecular effects of NDRG1 remain unclear. Herein, we summarize recent advances in understanding the impact of NDRG1 on cancer metastasis with emphasis on its interactions with the key oncogenic nuclear factor-kappaB, phosphatidylinositol-3 kinase/phosphorylated AKT/mammalian target of rapamycin and Ras/Raf/mitogen-activated protein kinase kinase/extracellular signal-regulated kinase signaling pathways. Recent studies demonstrating the inhibitory effects of NDRG1 on the epithelial-mesenchymal transition, a key initial step in metastasis, TGF-ß pathway and the Wnt/ß-catenin pathway are also described. Furthermore, NDRG1 was also demonstrated to regulate molecular motors in cancer cells, leading to inhibition of F-actin polymerization, stress fiber formation and subsequent reduction of cancer cell migration. Collectively, this review summarizes the underlying molecular mechanisms of the antimetastatic effects of NDRG1 in cancer cells.

The iron chelators Dp44mT and DFO inhibit TGF-ß-induced epithelial-mesenchymal transition via up-regulation of N-Myc downstream-regulated gene 1 (NDRG1).

The epithelial-mesenchymal transition (EMT) is a key step for cancer cell migration, invasion, and metastasis. Transforming growth factor-ß (TGF-ß) regulates the EMT and the metastasis suppressor gene, N-myc downstream-regulated gene-1 (NDRG1), could play a role in regulating the TGF-ß pathway. NDRG1 expression is markedly increased after chelator-mediated iron depletion via hypoxia-inducible factor 1α-dependent and independent pathways (Le, N. T. and Richardson, D. R. (2004) Blood 104, 2967-2975). Moreover, novel iron chelators show marked and selective anti-tumor activity and are a potential new class of anti-metabolites. Considering this, the current study investigated the relationship between NDRG1 and the EMT to examine if iron chelators can inhibit the EMT via NDRG1 up-regulation. We demonstrated that TGF-ß induces the EMT in HT29 and DU145 cells. Further, the chelators, desferrioxamine (DFO) and di-2-pyridylketone-4,4-dimethyl-3-thiosemicarbazone (Dp44mT), inhibited the TGF-ß-induced EMT by maintaining E-cadherin and ß-catenin, at the cell membrane. We then established stable clones with NDRG1 overexpression and knock-down in HT29 and DU145 cells. These data showed that NDRG1 overexpression maintained membrane E-cadherin and ß-catenin and inhibited TGF-ß-stimulated cell migration and invasion. Conversely, NDRG1 knock-down caused morphological changes from an epithelial- to fibroblastic-like phenotype and also increased migration and invasion, demonstrating NDRG1 knockdown induced the EMT and enhanced TGF-ß effects. We also investigated the mechanisms involved and showed the TGF-ß/SMAD and Wnt pathways were implicated in NDRG1 regulation of E-cadherin and ß-catenin expression and translocation. This study demonstrates that chelators inhibit the TGF-ß-induced EMT via a process consistent with NDRG1 up-regulation and elucidates the mechanism of their activity.

How does digital transformation improve new product development performance from the perspective of resource orchestration?-Analysis based on configuration.

The new product development (NPD) activities of enterprises serve as a critical source of competitiveness. To effectively harness the opportunities presented by digital transformation and enhance the performance of NPD in organizations amidst the digital revolution is an area of concern that warrants attention. In this context, we conducted research using data from the annual reports of 35 listed mainboard enterprises in 2021. This research used the resource arrangement theory and the resource-structure-capability research framework. In addition, we utilized the quantitative comparative analysis (QCA) method to investigate how digital transformation capability, R&D investment capability, and heterogeneity synergies impact the performance of NPD. The findings indicate that: (1) Four distinct paths (i.e., digital innovation-driven, large-scale multi-talent, mature and robust, and digital start-up) drive improvements in NPD performance. Notably, there exists an asymmetric causal relationship between these four paths and the performance; (2) Digital transformation capability, firm R&D investment, and firm heterogeneity all contribute to enhancing NPD performance. However, they do not individually guarantee high performance. A synergistic effect of at least two factors is required to yield notable NPD performance; (3) Enterprise heterogeneity plays a pivotal role. Companies with different characteristics must opt for distinct digital transformation paths to improve their NPD performance; (4) In the initial stage of digital transformation, enterprises can enhance NPD performance by augmenting their investment in R&D personnel.

Editorial: New Advances in Nanomaterials.

In the past few years, people have been committed to a variety of properties and functional materials, among which are nanomaterials, which have been gradually developed in-depth [...].

Flame retardant properties and mechanism of PLA/P-PPD -Ph /ECE conjugated flame retardant composites.

In this article, 4, 4'-{1'',4''-phenylene-bis[amido-(10'' ''-oxo-10'''-hydro-9'''-oxa-10'''λ5-phosphafi-10'''-yl)-methyl]}-diphenol (P-PPD-Ph) was synthesized by a two-step synthesis, followed by the addition of various levels of epoxy chain extender (ECE) with 5 wt% of P-PPD-Ph The PLA/P-PPD-Ph/ECE conjugated flame retardant composites were produced by co-extrusion into poly(lactic acid) (PLA). The chemical structure of P-PPD-Ph was characterized by FTIR, 1H NMR and 31P NMR tests, demonstrating the successful synthesis of the phosphorus heterophilic flame retardant P-PPD-Ph. The structural, thermal, flame retardant and mechanical properties of the PLA/P-PPD-Ph/ECE conjugated flame retardant composites were characterised using FTIR, thermogravimetric analysis (TG), vertical combustion testing (UL-94), limiting oxygen index (LOI), cone calorimetry, scanning electron microscopy (SEM), elemental energy spectroscopy (EDS) and mechanical properties testing. The structural, thermal, flame retardant and mechanical properties of PLA/P-PPD-Ph/ECE conjugated flame retardant composites were characterised. The results showed that with the increase of ECE content, the residual carbon rate of the composites increased from 1.6% to 3.3%, and the LOI value increased from 29.8% to 32.6%. The cross-linking reaction between P-PPD-Ph and PLA and the increase of reaction sites led to the generation of more phosphorus-containing radicals on the PLA molecular chain, which strengthened the cohesive phase flame retardant effect of PLA flame retardant composites, and The bending strength, tensile strength and impact strength were all improved.

ERp29 induces breast cancer cell growth arrest and survival through modulation of activation of p38 and upregulation of ER stress protein p58IPK.

Endoplasmic reticulum protein 29 (ERp29) is an ER luminal protein that has a role in protein unfolding and secretion, but its role in cancer is unclear. Recently, we reported that overexpression of ERp29 significantly inhibited cell proliferation and prevented tumorigenesis in highly proliferative MDA-MB-231 breast cancer cells. Here, we show that ERp29-induced cancer cell growth arrest is modulated by the interplay between the concomitant phosphorylation of p38 and upregulation of the inhibitor of the interferon-induced, double-stranded RNA-activated protein kinase, p58(IPK). In this cell model, ERp29 overexpression significantly downregulates modulators of cell proliferation, namely urokinase plasminogen activator receptor, ß(1)-integrin and epidermal growth factor receptor. Furthermore, ERp29 significantly (P<0.001) increases phosphorylation of p38 (p-p38) and reduces matrix metalloproteinase-9 secretion. The role of ERp29 in upregulating cyclin-dependent kinase inhibitors (p15 and p21) and in downregulating cyclin D(2) is demonstrated in slowly proliferating ERp29-overexpressing MDA-MB-231 cells, whereas the opposite response was observed in ERp29-knockdown MCF-7 cells. Pharmacological inhibition of p-p38 downregulates p15 and p21 and inhibits eIF2α phosphorylation, indicating a role for p-p38 in this process. Furthermore, p58(IPK) expression was increased in ERp29-overexpressing MDA-MB-231 cells and highly decreased in ERp29-knockdown MCF-7 cells. This upregulation of p58(IPK) by ERp29 suppresses the activation of p-p38/p-PERK/p-eIF2α by repressing eIF2α phosphorylation. In fact, reduction of p58(IPK) expression by RNA interference stimulated eIF2α phosphorylation. The repression of eIF2α phosphorylation by p58(IPK) prevents ERp29-transfected cells from undergoing ER-dependent apoptosis driven by the activation of ATF4/CHOP/caspase-3. Hence, the interplay between p38 phosphorylation and p58(IPK) upregulation has key roles in modulating ERp29-induced cell-growth arrest and survival.

Design, Synthesis, and Application in OFET of a Quinoxaline-Based D-A Conjugated Polymer.

A novel alternating donor-acceptor polymer PQ1 is designed and synthesized by palladium-catalyzed Stille coupling between quinoxaline as an electron-deficient unit and indacenodithiophene (IDT) as electron-rich groups. Polymer PQ1 presents not only a strong intramolecular charge transfer effect, which is beneficial for the charge transport within single molecules but also a narrow electrochemical band gap and a high highest occupied molecular orbital (HOMO) energy level. In addition, the optical absorption study indicates that the PQ1 film exhibits good aggregation, which is an advantage for the charge transport between neighboring molecules. As a consequence, PQ1 presents p-type semiconductor properties with a high hole mobility of up to 0.12 cm2 V-1 s-1. This study reveals the great potential of quinoxaline-type chromophores in constructing novel organic semiconductors.

Pyrrolopyrrole-Based Aza-BODIPY Small Molecules for Organic Field-Effect Transistors.

Diketopyrrolopyrrole (DPP), due to its good planarity, π-conjugate structure, thermal stability, and structural modifiability, has received much attention from the scientific community as an excellent semiconductor material for its applications in the field of optoelectronics, such as organic solar cells, organic photovoltaics, and organic field effect transistors. In this study, a new small molecule, pyrrolopyrrole aza-BODIPY (PPAB), based on the thiophene-substituted DPP structure was developed using the Schiff-base formation reaction of DPP and heteroaromatic amines. Absorption spectroscopy, electrochemistry, X-ray diffraction, molecular theoretical simulation calculation were performed, and organic field-effect transistor properties based on PPAB were investigated. It was found that PPAB exhibits a broad absorption range in the visible and near-infrared regions, which is attributed to its long-range conjugate structure. In addition, it is worth noting that PPAB has multiple F atoms resulting in the low LUMO level, which is conducive to the injection and transportation of charge carriers between the semiconductor layer and the electrode. Meanwhile, its hole carrier mobility is up to 1.3 × 10-3 cm2 V-1 s-1 due to its large conjugate structure, good intramolecular charge transfer effect, and high degree of coplanarity. In this study, a new chromophore with electron-deficient ability for designing high-performance semiconductors was successfully synthesized.

DPP-based polymers with linear/branch side chain for organic field-effect transistors.

For polymer semiconductors, the packing ability and molecular weight of polymers play a very critical role in their optoelectronic properties and carrier transport properties. In this work, two polymers, named linear and branch, are designed and synthesized with donor-acceptor (D-A) structure, based on diketopyrrolopyrrole as an electron acceptor and carbazole as an electron donor, and applied these two polymers in organic field-effect transistors. Linear and branch have similar conjugated backbones but different molecular weights and alkyl chains. The effects of molecular weight and molecular aggregation ability on the carrier transfer efficiency are investigated. As a result, linear exhibits better aggregation ability, but due to its smaller molecular weight than branch molecule, the hole transfer efficiency of linear (1.1 × 10-2 cm2 V -1 s-1) is slightly lower than that of branch (2.3 × 10-2 cm2 V -1 s-1). This work proves that molecular weight is more important than molecular aggregation ability when designing organic field-effect transistors for polymer semiconductors.

Flame-Retardant Properties and Mechanism of Polylactic Acid-Conjugated Flame-Retardant Composites.

The DOPO derivative-conjugated flame retardant 4, 4'-{1'', 4'' - phenylene - bis [amino - (10‴ - oxy -10‴-hydro-9‴-hydrogen-10‴ λ5 -phosphaphenanthrene-10''-yl)-methyl]}-diphenol (P-PPD-Ph) with two hydroxyl groups was synthesized. Polylactic acid conjugated flame-retardant composites with P-PPD-Ph were papered by using a twin-screw extruder. The flame-retardant properties of polylactic acid-conjugated flame-retardant composites were investigated. The flame-retardant properties of PLA-conjugated flame-retardant composites were characterized by the limiting oxygen index (LOI) and the vertical burning test (UL94). The results showed that the PLA-conjugated flame-retardant composites achieved a V-0 rating (UL-94, 3.2 mm) when the conjugated flame retardant was added at 5 wt%, and increase in LOI value from 22.5% to 31.4% relative to composites without added conjugated flame retardant. The flame-retardant mechanism of PLA-conjugated flame-retardant composites were further studied by TG-FTIR, the results showed that the P-PPD-Ph promoted the PLA-conjugated flame-retardant composites to decompose and also released fragments with quenching and dilution, which suggests that P-PPD-Ph for PLA-conjugated flame-retardant composites mainly play a role of the gas-phase flame retardant.

Flame Retardancy Properties and Rheological Behavior of PP/DiDOPO Conjugated Flame Retardant Composites.

A bridged 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide derivative (DiDOPO) with conjugated structure was utilized as a novel conjugated flame retardant, Polypropylene(PP)/DiDOPO conjugated flame retardant composites were papered by being melt-extruding with a twin-screw extruder. The flame retardant efficiency of PP/DiDOPO conjugated flame retardant composites were investigated by cone calorimetry, limiting oxygen index (LOI), vertical burning test (UL-94). Besides, the rheological behavior of PP/DiDOPO conjugated flame retardant composites are measured by ARES rheometer. The results showed that when the content of DiDOPO with conjugated structure was 16 wt%, the LOI values of PP/DiDOPO conjugated flame retardant composites was 24%, and PP/DiDOPO conjugated flame retardant composites reaches V-0 grade. The heat release rate (HRR), total heat release rate (THR) and CO2 of PP/DiDOPO conjugated flame retardant composites decreased, so PP/DiDOPO conjugated flame retardant composites had excellent flame retardant effect. Rheological analysis results indicated that DiDOPO with conjugated structure suppressed the melt dripping of PP/DiDOPO conjugated flame retardant composites by enhancing the melt stability. The results showed that the DiDOPO with conjugated structure can significantly enhance the flame retardancy effect of PP/DiDOPO conjugated flame retardant composites. In addition, the materials PP/DiDOPO might be with low conductivity and charge transport mobility.

Synthesis and Characterization of P-PPD-Ph-Conjugated Flame Retardant.

The conjugated flame retardants have rarely been studied. A conjugate flame-retardant 4, 4'-{1″, 4″-phenylene-bis [amino- (10‴-oxy10‴-hydro-9‴-hydrogen- 10‴λ5-phosphaphenanthrene-10″-yl)-methyl]}-diphenol (P-PPD-Ph) was synthesized and added into the polylactic acid (PLA) matrix. The P-PPD-Ph-conjugated flame-retardant structure was tested by FTIR, 1H, and 31P NMR analysis. The thermal and rheological properties of PLA/P-PPD-PH-conjugated flame-retardant composites were investigated. The results showed that P-PPD-Ph-conjugated flame retardant affects PLA/P-PPD-PH-conjugated flame-retardant composites for promoting the formation of a carbon layer when the P-PPD-Ph-conjugated flame-retardant content was 15% and the residual carbon ratio for PLA/P-PPD-PH-conjugated flame-retardant composites increased by 4.2%.

Flame-retardant properties and mechanism of LGF/PBT/DOPO-HQ-conjugated flame-retardant composites.

In this article, long fiber reinforced polybutylene terephthalate (LGF/PBT/DOPO-HQ) flame-retardant composites were prepared using 10-(2,5-dihydroxy phenyl)-10H-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO-HQ) as the conjugated flame-retardant. The effects of different flame-retardant contents on the combustion properties of the composites were investigated. The results showed that after adding 14% of DOPO-HQ, the flame-retardant effect of the composite reached the V-0 level of UL-94 fire rating with an ultimate oxygen index (LOI) of 26.4%. The average heat release rate (Av-HRR), peak heat release rate (PHRR), and total heat release rate (THR) decreased by 45.9, 56.5, and 32.6%, respectively. This shows that LGF/PBT/DOPO-HQ composite has good flame-retardant properties. Meanwhile, the flame-retardant mechanism of cohesive phase and gas-phase synergy during the combustion of flame retardants was analyzed by carbon layer morphology and dynamic thermal decomposition.

Activation of EP4 alleviates AKI-to-CKD transition through inducing CPT2-mediated lipophagy in renal macrophages.

Acute kidney injury (AKI) is a common clinical syndrome with complex pathogenesis, characterized by a rapid decline in kidney function in the short term. Worse still, the incomplete recovery from AKI increases the risk of progression to chronic kidney disease (CKD). However, the pathogenesis and underlying mechanism remain largely unknown. Macrophages play an important role during kidney injury and tissue repair, but its role in AKI-to-CKD transition remains elusive. Herein, single nucleus RNA sequencing (snRNA-Seq) and flow cytometry validations showed that E-type prostaglandin receptor 4 (EP4) was selectively activated in renal macrophages, rather than proximal tubules, in ischemia-reperfusion injury (IRI)-induced AKI-to-CKD transition mouse model. EP4 inhibition aggravated AKI-to-CKD transition, while EP4 activation impeded the progression of AKI to CKD though regulating macrophage polarization. Mechanistically, network pharmacological analysis and subsequent experimental verifications revealed that the activated EP4 inhibited macrophage polarization through inducing Carnitine palmitoyltransferase 2 (CPT2)-mediated lipophagy in macrophages. Further, CPT2 inhibition abrogated the protective effect of EP4 on AKI-to-CKD transition. Taken together, our findings demonstrate that EP4-CPT2 signaling-mediated lipophagy in macrophages plays a pivotal role in the transition of AKI to CKD and targeting EP4-CPT2 axis could serve as a promising therapeutic approach for retarding AKI and its progression to CKD.

The metastasis suppressor, N-myc downstream regulated gene 1 (NDRG1), upregulates p21 via p53-independent mechanisms.

The metastasis suppressor, N-myc downstream regulated gene-1 (NDRG1), has been shown to markedly reduce metastasis of numerous tumors. The current study was focused on further elucidating the molecular mechanisms behind the antitumor function of NDRG1. We have identified for the first time that NDRG1 upregulates the potent cyclin-dependent kinase inhibitor, p21. This effect was observed in three different cancer cell types, including PC3MM and DU145 prostate cancer cells and H1299 lung carcinoma cells, and occurred independently of p53. In addition, reducing NDRG1 expression using short hairpin RNA in PC3MM and DU145 cells resulted in significantly reduced p21 protein levels. Hence, p21 is closely correlated with NDRG1 expression in these latter cell types. Examining the mechanisms behind the effect of NDRG1 on p21 expression, we found that NDRG1 upregulated p21 via transcriptional and posttranscriptional mechanisms in prostate cancer cells, although its effect on H1299 cells was posttranscriptional only. Further studies identified two additional NDRG1 protein targets. The dominant-negative p63 isoform, ΔNp63, which has been found to inhibit p21 transcription, was downregulated by NDRG1. On the other hand, a truncated 50 kDa MDM2 isoform (p50(MDM2)), which may protect p21 from proteasomal degradation, was upregulated by NDRG1. The downregulation of ΔNp63 and upregulation of p50(MDM2) are potential mechanisms by which NDRG1 increases p21 expression in these cells. Additional functional studies identified that NDRG1 inhibits cancer cell migration, suggesting that p21 is a molecular player in its antimetastatic activity.