Active oxygen species (AOS) play key roles in many important catalytic reactions relevant to clean energy and environment. However, it remains challenging to characterize the active sites for ...producing AOS and to image the surface properties of AOS, especially on multicomponent metallic catalyst surfaces. Herein, we utilize tip-enhanced Raman spectroscopy (TERS) to probe the local generation and diffusion of OH radicals on a Pd/Au(111) bimetallic catalyst surface. The reactive OH radicals can be catalytically generated from hydrogen peroxide (H2O2) at the metal surface, which then oxidizes the surface adsorbed thiolate, a reactant that is used as the TERS probe. By TERS imaging of the spatial distribution of unreacted thiolate molecules, we demonstrate that the Pd surface is active for generation of OH radicals and the Pd step edge shows much higher activity than the Pd terrace, whereas the Au surface is inactive. Furthermore, we find that the locally generated OH radicals at the Pd step edge could diffuse to both the Au and the Pd surface sites to induce oxidative reactions, with a diffusion length estimated to be about 5.4 nm. Our TERS imaging with few-nanometer spatial resolution not only unravels the active sites but also characterizes in real space the diffusion behavior of OH radicals. The results are highly valuable to understand AOS-triggered catalytic reactions. The strategy of using reactants with large Raman cross sections as TERS probes may broaden the application of TERS for studying catalysis with reactive small molecules.
Visible‐light copper photocatalysis has recently emerged as a viable technology for building sustainable synthetic processes. To broaden the applications of phosphine‐ligated copper(I) complexes, we ...describe herein an effective metal‐organic framework (MOF)‐supported copper(I) photocatalyst for multiple iminyl radical‐mediated reactions. Due to site isolation, the heterogenized copper photosensitizer has a significantly higher catalytic activity than its homogeneous counterpart. Using a hydroxamic acid linker to immobilize copper species on MOF supports affords the heterogeneous catalysts with high recyclability. The post‐synthetic modification sequence on MOF surfaces allows for the preparation of previously unavailable monomeric copper species. Our findings highlight the potential of using MOF‐based heterogeneous catalytic systems to address fundamental challenges in the development of synthetic methodologies and mechanistic investigations of transition‐metal photoredox catalysis.
A binap‐ligated copper dimer has been heterogenized on a pillar‐layered MOF surface for the first time using a hydroxamic acid linker. This MOF‐supported dimeric copper photocatalyst demonstrates much higher activity and recyclability than its homogeneous counterparts in intra‐ and intermolecular radical reactions of N‐acyloxy imidates and O‐acyl oximes.
The role of Fat Mass and Obesity-associated protein （FTO） and its substrate N6-methyladenosine （m6A） in mRNA processing and adipogenesis remains largely unknown. We show that FTO expression and m6A ...levels are inversely correlated during adipogenesis. FTO depletion blocks differentiation and only catalytically active FTO restores adi- pogenesis. Transcriptome analyses in combination with m6A-seq revealed that gene expression and mRNA splicing of grouped genes are regulated by FTO. M6A is enriched in exonic regions flanking 5＇- and 3＇-splice sites, spatially over- lapping with mRNA splicing regulatory serine/arginine-rich （SR） protein exonic splicing enhancer binding regions. Enhanced levels of m6A in response to FTO depletion promotes the RNA binding ability of SRSF2 protein, leading to increased inclusion of target exons. FTO controls exonic splicing of adipogenie regulatory factor RUNX1T1 by regulating m6A levels around splice sites and thereby modulates differentiation. These findings provide compelling evidence that FTO-dependent m6A demethylation functions as a novel regulatory mechanism of RNA processing and plays a critical role in the regulation of adipogenesis.
Perfluorooctane sulfonate (PFOS) is among the most abundant organic pollutants and is widely distributed in the environment, wildlife, and humans. Its toxic effects and biological hazards are ...associated with its long elimination half-life in humans. However, how it affects renal tubular cells (RTCs) remains unclear. In this study, PFOS was observed to mediate the increase in reactive oxygen species (ROS) generation, followed by the activation of the extracellular-signal-regulated kinase 1/2 (ERK1/2) pathway, which induced autophagy in RTCs. Although PFOS treatment induced autophagy after 6 h, prolonged treatment (24 h) reduced the autophagic flux by increasing lysosomal membrane permeability (LMP), leading to increased p62 protein accumulation and subsequent apoptosis. The increase in LMP was visualized through increased green fluorescence with acridine orange staining, and this was attenuated by 3-methyladenine, an autophagy inhibitor. N-acetyl cysteine and an inhibitor of the mitogen-activated protein kinase kinases (U0126) attenuated autophagy and apoptosis. Taken together, these results indicate that ROS activation and ROS-mediated phosphorylated ERK1/2 activation are essential to activate autophagy, resulting in the apoptosis of PFOS-treated RTCs. Our findings provide insight into the mechanism of PFOS-mediated renal toxicity.
We previously reported that perfluorooctanesulfonate (PFOS) causes autophagy-induced apoptosis in renal tubular cells (RTCs) through a mechanism dependent on reactive oxygen species ...(ROS)/extracellular signal-regulated kinase. This study extended our findings and determined the therapeutic potency of L-Carnitine in PFOS-treated RTCs. L-Carnitine (10 mM) reversed the effects of PFOS (100 µM) on autophagy induction and impaired autophagy flux. Furthermore, it downregulated the protein level of p47Phox, which is partly related to PFOS-induced increased cytosolic ROS in RTCs. Moreover, L-Carnitine reduced ROS production in mitochondria and restored PFOS-impeded mitochondrial function, leading to sustained normal adenosine triphosphate synthesis and oxygen consumption and reduced proton leakage in a Seahorse XF stress test. The increased inositol-requiring enzyme 1α expression by PFOS, which indicated endoplasmic reticulum (ER) stress activation, was associated with PFOS-mediated autophagy activation that could be attenuated through 4-phenylbutyrate (5 mM, an ER stress inhibitor) and L-Carnitine pretreatment. Therefore, by reducing the level of IRE1α, L-Carnitine reduced the levels of Beclin and LC3BII, consequently reducing the level of apoptotic biomarkers including Bax and cleaving PARP and caspase 3. Collectively, these results indicate that through the elimination of oxidative stress, extracellular signal-regulated kinase activation, and ER stress, L-Carnitine reduced cell autophagy/apoptosis and concomitantly increased cell viability in RTCs. This study clarified the potential mechanism of PFOS-mediated RTC apoptosis and provided a new strategy for using L-Carnitine to prevent and treat PFOS-induced RTC apoptosis.
Perfluorinated chemicals (PFCs) are ubiquitously distributed in the environments including stainless pan-coating, raincoat, fire extinguisher, and semiconductor products. The PPAR family has been ...shown to contribute to the toxic effects of PFCs in thymus, immune and excretory systems. Herein, we demonstrated that perfluorooctanesulfonate (PFOS) caused cell apoptosis through increasing ratio of Bcl-xS/xL, cytosolic cytochrome C, and caspase 3 activation in renal tubular cells (RTCs). In addition, PFOS increased transcription of inflammatory cytokines (i.e., TNFα, ICAM1, and MCP1) by NFκB activation. Conversely, PFOS reduced the mRNA levels of antioxidative enzymes, such as glutathione peroxidase, catalase, and superoxide dismutase, as a result of reduced PPARγ transactivational activity by using reporter and chromatin immuoprecipitation (ChIP) assays. PFOS reduced the protein interaction between PPARγ and PPARγ coactivator-1 alpha (PGC1α) by PPARγ deacetylation through Sirt1 upregulation, of which the binding of PPARγ and PGC1α to a peroxisome proliferator response element (PPRE) in the promoter regions of these antioxidative enzymes was alleviated in the ChIP assay. Furthermore, Sirt1 also deacetylated p53 and then increased the binding of p53 to Bax, resulting in increased cytosolic cytochrome C. The effect of PPARγ inactivation by PFOS was validated using the PPARγ antagonist GW9662, whereas the adverse effects of PFOS were prevented by PPARγ overexpression and activators, rosiglitozone and L-carnitine, in RTCs. The in vitro finding of protective effect of L-carnitine was substantiated in vivo using Balb/c mice model subjected to PFOS challenge. Altogether, we provide in vivo and in vitro evidence for the protective mechanism of L-carnitine in eliminating PFOS-mediated renal injury, at least partially, through PPARγ activation.
Among kidney cancers, clear cell renal cell carcinoma (ccRCC) has the highest incidence rate in adults. The survival rate of patients diagnosed as having metastatic ccRCC drastically declines even ...with intensive treatment. We examined the efficacy of simvastatin, a lipid-lowering drug with reduced mevalonate synthesis, in ccRCC treatment. Simvastatin was found to reduce cell viability and increase autophagy induction and apoptosis. In addition, it reduced cell metastasis and lipid accumulation, the target proteins of which can be reversed through mevalonate supplementation. Moreover, simvastatin suppressed cholesterol synthesis and protein prenylation that is essential for RhoA activation. Simvastatin might also reduce cancer metastasis by suppressing the RhoA pathway. A gene set enrichment analysis (GSEA) of the human ccRCC GSE53757 data set revealed that the RhoA and lipogenesis pathways are activated. In simvastatin-treated ccRCC cells, although RhoA was upregulated, it was mainly restrained in the cytosolic fraction and concomitantly reduced Rho-associated protein kinase activity. RhoA upregulation might be a negative feedback effect owing to the loss of RhoA activity caused by simvastatin, which can be restored by mevalonate. RhoA inactivation by simvastatin was correlated with decreased cell metastasis in the transwell assay, which was mimicked in dominantly negative RhoA-overexpressing cells. Thus, owing to the increased RhoA activation and cell metastasis in the human ccRCC dataset analysis, simvastatin-mediated Rho inactivation might serve as a therapeutic target for ccRCC patients. Altogether, simvastatin suppressed the cell viability and metastasis of ccRCC cells; thus, it is a potentially effective ccRCC adjunct therapy after clinical validation for ccRCC treatment.
A significant association between high blood-based tumor mutational burden (bTMB) and improved progression-free survival (PFS) was observed in advanced non-small cell lung cancer (NSCLC) receiving ...atezolizumab. However, this result was unrepeatable in a recent prospective study. We hypothesized that there might be a non-linear association between bTMB and survival. This study used the clinical and genetic data from POPLAR (n = 105, training set) and OAK (n = 324, validation set) trials. The non-linear association between bTMB and survival was assessed using restricted cubic spline (RCS). The cutoff values for bTMB were calculated via X-tile software. Non-linear relationships were observed between bTMB and PFS and overall survival (OS) in RCS plots (both P
non-linearity
< 0.001). The optimal cutoff values of bTMB for predicting PFS and OS were 7 and 14 mutations/Mb, respectively. The median PFS and OS of patients with low and high bTMB were significantly longer than those of patients with medium bTMB in the training, validation, and combined sets. Low and high bTMB were also associated with longer PFS and OS in high-programmed death-ligand 1 (PD-L1) expression population. In conclusion, there was a positive non-linear association between bTMB and survival in NSCLC patients receiving atezolizumab. Patients with low bTMB could also derive benefit from immunotherapy.
Long noncoding RNAs (lncRNAs) are involved in a variety of cancers, but the role of LncRNA DUBR in lung adenocarcinoma (LUAD), the most prevalent form of lung cancer, remains unclear. In this study ...we investigated the expression of DUBR in LUAD to ascertain its association with the clinical pathology and prognosis of LUAD. Analysis of mRNA expression in The Cancer Genome Atlas (TCGA) LUAD database and in-house LUAD cohort (n = 94) showed that DUBR was significantly downregulated in LUAD, and was associated with poor prognosis. In LUAD cell lines (H1975, A549), overexpression of DUBR significantly suppressed the migration and invasion of the LUAD cells. We demonstrated that c-Myc could bind to the promoter of DUBR, and transcriptionally suppressed its expression. Knockdown of c-Myc almost completely blocked the invasion and migration of LUAD cells, whereas knockdown of DUBR partially rescued c-Myc-knockdown suppressed cell migration and invasion. Furthermore, DUBR overexpression significantly increased the expression of a downstream protein of DUBR, zinc finger, and BTB domain containing 11 (ZBTB11), in H1975 and A549 cells; knockdown of ZBTB11 partially rescued the DUBR-overexpression suppressed cell migration and invasion; knockdown of c-Myc significantly upregulated the expression of ZBTB11 in LUAD cells. Finally, we revealed that DUBR/ZBTB11 axis suppressed oxidative phosphorylation in LUAD cells. In short, we demonstrate that c-Myc/DUBR/ZBTB11 axis suppresses migration and invasion of LUAD by attenuating cell oxidative phosphorylation, which provides new insights into the regulatory mechanism of DUBR.
N6-methyladenosine (m6A) is the most prevalent internal modification of messenger RNA (mRNA) in higher eukaryotes. Here we report ALKBH5 as another mammalian demethylase that oxidatively reverses m6A ...in mRNA in vitro and in vivo. This demethylation activity of ALKBH5 significantly affects mRNA export and RNA metabolism as well as the assembly of mRNA processing factors in nuclear speckles. Alkbh5-deficient male mice have increased m6A in mRNA and are characterized by impaired fertility resulting from apoptosis that affects meiotic metaphase-stage spermatocytes. In accordance with this defect, we have identified in mouse testes 1,551 differentially expressed genes that cover broad functional categories and include spermatogenesis-related mRNAs involved in the p53 functional interaction network. The discovery of this RNA demethylase strongly suggests that the reversible m6A modification has fundamental and broad functions in mammalian cells.
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► ALKBH5 is a mammalian m6A RNA demethylase ► RNA demethylation affects mRNA export and RNA metabolism ► RNA demethylation is important for mouse fertility ► Reversible mammalian messenger RNA methylation affects gene expression
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