AMPK-upregulated microRNA-708 plays as a suppressor of cellular senescence and aging via downregulating disabled-2 and mTORC1 activation.

Senescence-associated microRNAs (SA-miRNAs) are important molecules for aging regulation. While many aging-promoting SA-miRNAs have been identified, confirmed aging-suppressive SA-miRNAs are rare, that impeded our full understanding on aging regulation. In this study, we verified that miR-708 expression is decreased in senescent cells and aged tissues and revealed that miR-708 overexpression can alleviate cellular senescence and aging performance. About the molecular cascade carrying the aging suppressive action of miR-708, we unraveled that miR-708 directly targets the 3'UTR of the disabled 2 (Dab2) gene and inhibits the expression of DAB2. Interestingly, miR-708-caused DAB2 downregulation blocks the aberrant mammalian target of rapamycin complex 1 (mTORC1) activation, a driving metabolic event for senescence progression, and restores the impaired autophagy, a downstream event of aberrant mTORC1 activation. We also found that AMP-activated protein kinase (AMPK) activation can upregulate miR-708 via the elevation of DICER expression, and miR-708 inhibitor is able to blunt the antiaging effect of AMPK. In summary, this study characterized miR-708 as an aging-suppressive SA-miRNA for the first time and uncovered a new signaling cascade, in which miR-708 links the DAB2/mTOR axis and AMPK/DICER axis together. These findings not only demonstrate the potential role of miR-708 in aging regulation, but also expand the signaling network connecting AMPK and mTORC1.

New insight into the functional group mechanism and structure-activity relationship of the complexation between DOM and Cr(III) in landfill leachate.

Widespread landfills represent a significant source of groundwater contamination. Due to the unique and diverse nature of dissolved organic matter (DOM) in landfill leachate, the interaction between DOM and heavy metals, along with its quantitative evaluation, remains unknown. Consequently, we collected ten samples from various landfill types to serve as representatives for a comprehensive investigation of the mechanism involving functional groups and Cr(III) through the establishment of a quantitative structure-activity relationship (QSAR). We employed ESI FT-ICR MS, (MW) 2D-COS, and DFT calculations for this purpose. Our findings indicate that DOM from landfill leachate contains a higher proportion of CHON molecules on intensity compared to those from natural sources. The maximum complexation capacity was determined by the proportion of proteins (69%), normalized carbon average oxidation state (16%), double bond equivalence (8%), and the number of oxygen atoms (7%) in landfill leachate DOM. Besides, N-containing groups such as N = O and C-N in landfill leachate DOM with lower humification, can exhibit stronger affinities than COOH, ArOH, CO, and polysaccharide C-O groups, which are typically identified as dominant sites in natural DOM. A QSAR model incorporating four parameters demonstrated an impressive accuracy rate of 98.8%, underscoring its reliability in predicting the complexation potential of different landfill leachate DOM with Cr(III).

A small-scale silica gel column chromatography method for separating carbazole compounds from highly mature crude oil.

The concentration of carbazoles in highly mature crude oil is quite low, making it challenging to separate carbazole compounds for the gas chromatography-mass spectrometry (GC-MS) detection. This study presents a small-scale column chromatography method for separating carbazoles from highly mature crude oil using silica gel as a solid phase adsorbent and a Pasteur pipette as a separation device. The carbazole-rich crude oil from the Pearl River Mouth Basin was selected to explore the impact of reagent polarity and injection mode on the separation of carbazoles. The oil sample was eluted with solvents mixed with different volume proportions of n-hexane and dichloromethane and each eluted fraction was collected for GC-MS testing. The results indicated that increasing the reagent polarity caused the aromatic hydrocarbons and carbazole compounds in crude oil to be eluted sequentially. Most aromatic compounds in the crude oil could be selectively eluted using a reagent polarity ratio of 9:1 (Vn-hexane: Vdichloromethane), with no carbazole compounds. A significant amount of carbazole compounds were eluted in the polar segments of 8:2-6:4, with the eluted carbazoles concentration accounting for more than 98 % of the total concentration. Moreover, the concentration and recovery of carbazoles eluted by direct injection mode were about 10 % higher than those after adsorption by silica gel. The standard deviation of the parameter ratio for the separated carbazole compounds in the three groups of repeatable parallel experiments was less than 0.2 %. Our method is superior to traditional two-step method and C18 column method in separation efficiency and damage to human body. This method can be applied to both highly mature crude oil and other kinds of oils including biodegradable oil. It could be a versatile method for the carbazoles separation and provide technical support in unveiling the geochemical implications of these compounds in complex areas.

Mechanistic insight into Cr(VI) retention by Si-containing ferrihydrite.

Hexavalent chromium [Cr(VI)] causes serious harm to the environment due to its high toxicity, solubility, and mobility. Ferrihydrites (Fh) are the main adsorbent and trapping agent of Cr(VI) in soils and aquifers, and they usually coexist with silicate (Si), forming Si-containing ferrihydrite (Si-Fh) mixtures. However, the mechanism of Cr(VI) retention by Si-Fh mixtures is poorly understood. In this study, the behaviors and mechanisms of Cr(VI) adsorption onto Si-Fh with different Si/Fe molar ratios was investigated. Transmission electron microscope, Fourier transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and other techniques were used to characterize Si-Fh and Cr(VI)-loading of Si-Fh. The results show that specific surface area of Si-Fh increases gradually with increasing Si/Fe ratios, but Cr(VI) adsorption on Si-Fh decreases with increasing Si/Fe ratios. This is because with an increase in Si/Fe molar ratio, the point of zero charge of Si-Fh gradually decreases and electrostatic repulsion between Si-Fh and Cr(VI) increases. However, the complexation of Cr(VI) is enhanced due to the increase in adsorbed hydroxyl (A-OH-) on Si-Fh with increasing Si/Fe molar ratio, which partly counteracts the effect of the electrostatic repulsion. Overall, the increase in the electrostatic repulsion has a greater impact on adsorption than the additional complexation with Si-Fh. Density functional theory calculation further supports this observation, showing the increases in electron variation of bonding atoms and reaction energies of inner spherical complexes with the increase in Si/Fe ratio.

APPL1 Is a Prognostic Biomarker and Correlated with Treg Cell Infiltration via Oxygen-Consuming Metabolism in Renal Clear Cell Carcinoma.

Kidney renal clear cell carcinoma (KIRC) is one of the most hazardous tumors in the urinary system. The regulation of oxygen consumption in renal clear cell carcinoma is a consequence of adaptive reprogramming of oxidative metabolism in tumor cells. APPL1 is a signaling adaptor involved in cell survival, oxidative stress, inflammation, and energy metabolism. However, the correlation of APPL1 with regulatory T cell (Treg) infiltration and prognostic value in KIRC remain unclear. In this study, we comprehensively predicted the potential function and prognostic value of APPL1 in KIRC. For KIRC patients, relatively low expression of APPL1 was associated with high degree of metastasis, pathological stage, and shorter overall time or poor prognosis. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses suggested that low expression of APPL1 may be adapted to the malignant progression of tumors via affecting oxygen-consuming metabolism. In addition, the expression level of APPL1 was negatively correlated with Treg cell infiltration and chemotherapy sensitivity, which indicated that APPL1 may regulate the tumor immune infiltration and chemotherapy resistance by decrease oxygen-consuming metabolic process in KIRC. Therefore, APPL1 may become one of the important prognostic factors, and it may serve as a candidate prognostic biomarker in KIRC.

Glutamine Availability Regulates the Development of Aging Mediated by mTOR Signaling and Autophagy.

Glutamine is a conditionally essential amino acid involved in energy production and redox homeostasis. Aging is commonly characterized by energy generation reduction and redox homeostasis dysfunction. Various aging-related diseases have been reported to be accompanied by glutamine exhaustion. Glutamine supplementation has been used as a nutritional therapy for patients and the elderly, although the mechanism by which glutamine availability affects aging remains elusive. Here, we show that chronic glutamine deprivation induces senescence in fibroblasts and aging in Drosophila melanogaster, while glutamine supplementation protects against oxidative stress-induced cellular senescence and rescues the D-galactose-prompted progeria phenotype in mice. Intriguingly, we found that long-term glutamine deprivation activates the Akt-mTOR pathway, together with the suppression of autolysosome function. However, the inhibition of the Akt-mTOR pathway effectively rescued the autophagy impairment and cellular senescence caused by glutamine deprivation. Collectively, our study demonstrates a novel interplay between glutamine availability and the aging process. Mechanistically, long-term glutamine deprivation could evoke mammalian target of rapamycin (mTOR) pathway activation and autophagy impairment. These findings provide new insights into the connection between glutamine availability and the aging process.

Pan-mTOR inhibitors sensitize the senolytic activity of navitoclax via mTORC2 inhibition-mediated apoptotic signaling.

Compounds with senolysis activity are discovered in recent years, featuring by their capacity to specifically eliminate senescent cells in vitro or in vivo. These compounds, referring to as Senolytics, provide a new method for aging counteraction and probably for geriatric disease amelioration. However, their clinical application is unpractical still, mainly because of the safety issue. In fact, the effective dose range even of the most potent senolytic cannot guarantee the safety requirements application for human being. Here, we report a study which investigated the combinational application of one potential senolytic molecule navitoclax, a Bcl-2 inhibitor with several mTOR inhibitors, to assess the influence of this combination on the senolytic outcome. Our results reveal that pan-mTOR inhibitors can reduce the dosage or timespan of navitoclax necessary for reaching IC50 and LT50 in senescent cells, also extend the lifespan of premature-aged Drosophila and mitigate the aging-related phenotype. Our results also confirmed that mTOR inhibitor sensitized senolytic cell death is apoptotic and pan-mTOR inhibitors PP242 and AZD8055 works more effectively than mTORC1 inhibitor Rapamycin. Mechanically, we verified the crucial role of mTORC2 inhibition contributes sensitization by increasing the expression of the pro-apoptotic protein Bim. In summary, this study firstly exposes the sensitization effect of pan-mTOR inhibitors on navitoclax-induced senolytic apoptosis, therefore providing novel evidence to show the advantage of drug combination on setting senotherapy. It also provides an intriguing clue to demonstrate the value of mTORC2 inhibition for apoptotic death of senescent cells.

miR-146a impedes the anti-aging effect of AMPK via NAMPT suppression and NAD+/SIRT inactivation.

Nicotinamide adenine dinucleotide (NAD+) is indispensable for the anti-aging activity of the sirtuin (SIRT) family enzymes. AMP-activated protein kinase (AMPK) upregulates NAD+ synthesis and SIRT activity in a nicotinamide phosphoribosyltransferase (NAMPT)-dependent manner. However, the molecular mechanisms that affect AMPK-driven NAMPT expression and NAD+/SIRT activation remain unclear. In this study, we tried to identify senescence-associated microRNAs (miRNAs) that negatively regulate the cascade linking AMPK and NAMPT expression. miRNA-screening experiments showed that the expression of miR-146a increased in senescent cells but decreased following AMPK activation. Additionally, miR-146a overexpression weakened the metformin-mediated upregulation of NAMPT expression, NAD+ synthesis, SIRT activity, and senescence protection, whereas treatment with the miR-146a inhibitor reversed this effect. Importantly, these findings were observed both in vitro and in vivo. Mechanistically, miR-146a directly targeted the 3'-UTR of Nampt mRNA to reduce the expression of NAMPT. AMPK activators metformin and 5-aminoimidazole-4-carboxamide (AICAR) hindered miR-146a expression at the transcriptional level by promoting IκB kinase (IKK) phosphorylation to attenuate nuclear factor-kappaB (NF-κB) activity. These findings identified a novel cascade that negatively regulates the NAD+/SIRT pathway by suppressing miR-146a-mediated NAMPT downregulation. Furthermore, our results showed that miR-146a impedes the anti-aging effect of AMPK. This mutual inhibitory relationship between miR-146a and AMPK enriches our understanding of the molecular connections between AMPK and SIRT and provides new insight into miRNA-mediated NAD+/SIRT regulation and an intervention point for the prevention of aging and age-related diseases.

Novel efficient capture of Cr(VI) from soil driven by capillarity and evaporation coupling.

Soil contaminated by hexavalent chromium (Cr(VI)) poses a severe environmental threat owing to the carcinogenic and genotoxic characteristics of Cr(VI). Currently, field application of remediation technologies for Cr(VI) removal or detoxification fails to achieve optimum results owing to various limitations, such as high energy consumption, high chemical cost, secondary pollution, and long treatment duration. Herein, a novel strategy, namely, the capillary-evaporation membrane (CEM) method, which is based on the ubiquitous phenomena of capillarity and evaporation in natural soil environment without external forces, was applied to remove Cr(VI) from contaminated soil. The CEM method enables Cr(VI) dissolved in the soil solution to move upwards through soil pores and inter-particle spaces and get attached to the surface of adsorption membrane under the coupling action of capillarity and evaporation to achieve Cr(VI) removal. The CEM method showed high Cr(VI) removal capacity during 22 days of treatment of bulk soil (47.26%), sandy fraction (34.60%), and silt-clay fraction (52.50%), respectively. Further research on optimization of the CEM process conditions could remarkably improve Cr(VI) remediation performance. For example, the Cr(VI) removal rate increased to 89.04% in bulk soil through prolongation of the remediation period to 61 days. This study demonstrated a new environment-friendly remediation method driven by natural phenomena for Cr(VI)-contaminated soils.

New insight into the adsorption mechanism of PCP by humic substances with different degrees of humification in the presence of Cr(VI).

Humic substances (HSs) have great retention effects on pentachlorophenol (PCP) migration in subsurface environment, but the adsorption mechanism of PCP by HSs with various aromatic/aliphatic moieties and acidic functional groups in the presence of Cr(VI) is still unclear. In this study, the adsorption mechanism of PCP by undissolved humic acid (HA) and humin (HM) extracted from peat, black soil, lignite and coal was investigated under the presence of Cr(VI). According to the results, HA samples had much lower adsorption capacity for hydrophobic PCP than HM samples due to their higher contents of hydrophilic polar oxygen-containing functional groups. In respect to PCP adsorption mechanism, the molecular unsaturation of HSs associated with humification degree was found to be the determinant instead of polarity. Notably, after reacting with Cr(VI), significant decreasing of PCP adsorption quantities occurred on HSs extracted from lignite and coal with higher degrees of unsaturation (H/C < 0.64), while HSs extracted from peat and black soil with lower degrees of unsaturation (H/C > 0.83) kept almost unchanged, which can be attributed to the much higher reactivity of aromatic domains of HSs for Cr(VI) reduction compared with aliphatic moieties. This indicated that the adsorption mechanism of PCP by HSs with higher and lower degrees of unsaturation might be respectively driven by π-π interaction and hydrophobic interaction. This study highlighted the diverse adsorption mechanisms of PCP on HSs with different degrees of humification, and emphasized the coexisting Cr(VI) only have significant effect on PCP adsorption by HSs with higher humification degrees instead of the lower ones.

Natural attenuation mechanism of hexavalent chromium in a wetland: Zoning characteristics of abiotic and biotic effects.

Natural wetland has great retention effect on Cr(VI) migration due to its abiotic and biotic reduction abilities, however, the zoning characteristics of dominating reduction mechanism along Cr(VI) pollution plume in wetland is still unclear. In this study, a Cr(VI) contaminated natural wetland was explored to investigate the distributions of Cr and Fe in groundwater and sediment, and their relationship with microorganisms according to metagenomics, aiming to reveal the natural attenuation mechanism of Cr(VI) from the perspective of zoning characteristics of abiotic and biotic effects. The wetland was divided into contaminated zone, transition zone and uncontaminated zone according to the contamination states of groundwater and sediment. At the upstream of contaminated zone, Cr(VI) concentration in groundwater was as high as 26.7 mg L-1, which has significant inhibition effect on microbial growth, and thus chemical reduction of Cr(VI) by natural organic matters (NOMs) dominated in this area, leading to the increasing of H/C and O/C ratios of NOMs because of the oxidation of aromatic moieties. At the downstream of contaminated zone, Cr(VI) concentration in groundwater decreased to less than 4.46 mg L-1 resulting from dilution and attenuation, but the microbial community was altered substantially, chromate resistant bacteria with ChrA, ChrR, NemA and AzoR genes were enriched, such as Sphingomonas, Mesorhizobium and Comamonadaceae, and thus the direct microbial reduction of Cr(VI) dominated in this area. While at the transition zone, which is located at the front edge of the pollution plume, Cr(VI) could only reached in this area intermittently, and the microbial community remained similar to that of the uncontaminated zone, dominated by Chloroflexi and Acidobateria phylum with dissimilatory ferric iron reduction capacity, and thus Cr(VI) was indirectly reduced by Fe2+ intermediately in this area.

Microphthalmia-Associated Transcription Factor in Senescence and Age-Related Diseases.

Although microphthalmia-associated transcription factor (MITF) has been known for decades as a key regulator for melanocytic differentiation, recent studies expanded its other roles in multiple biological processes. Among these newfound roles, the relationship between MITF and aging is attractive; however, the underlying mechanism remains elusive. Here, we review the documented cues that highlight the implication of MITF in the aging process and particularly discuss the possible mechanisms underlying the participation of MITF in cellular senescence. First, it summarizes the association of MITF with melanocytic senescence, including the roles of MITF in cell cycle regulation, DNA damage repair, oxidative stress response, and the generation of senescence-associated secretory phenotype. Then, it collects the information involving MITF-related senescent changes in nonmelanocytes, such as retinal pigment epithelium cells, osteoclasts, and cardiomyocytes. This review may deepen the understanding of MITF function and be helpful to develop new strategies for improving geriatric health.

Insights into the kinetic processes of solute migration by unidirectional freezing in porous media with micromodel visualization at the pore-scale.

Field investigations have proved that frozen soil does not act as a completely impermeable barrier for contaminants in cold regions. However, the subsurface behaviors of solutes in freezing and frozen porous media are still unclear. To unveil their nature, the pore-scale behavior of potassium permanganate in saturated porous media subjected to the unidirectional freezing was investigated using micromodel visualizations. An optical microscope was applied to obtain the pore-scale kinetics of solute redistribution in a two-dimensional micromodel using a calibration curve between the color intensity and concentration. We found that (1) the solute migration was not only limited to the ice-water interface but also occurred in the freezing area; (2) the redistribution of solutes had a significant hysteresis effect relative to the freezing front movement during the freezing of the porous media. By combining these results with the theory of sea ice, we suggested that the formation and re-motion of solute-rich inclusions in the mushy layer appear to be vital processes responsible for these phenomena. It was believed that the major mechanism for the re-motion of liquid inclusions was brine diffusion and expulsion in this experiment. The results of this study provide a better understanding of the physics of contaminant migration and their complex kinetics at the pore scale, which has important implications for the assessment and remediation of contaminated soils in seasonal frozen soils and permafrost.

Mechanism and multi-step kinetic modelling of Cr(VI) adsorption, reduction and complexation by humic acid, humin and kerogen from different sources.

Humin (HM) and kerogen (KG) are widespread in soils and sediments, which have strong retention effects on the migration and transformation of Cr(VI) in subsurface environment. Previous studies mainly focused on the interaction between Cr(VI) and soluble organic matter, such as humic acid (HA); however, the adsorption and reduction mechanism for Cr(VI) by insoluble HM and KG are still unclear, the processes of which might be quite different from HA due to their different sources and humification degrees. Consequently, in this study, HA, HM and KG extracted from different sources were used to explore the adsorption, reduction and complexation mechanisms of Cr(VI) in soils and sediments, based on which a multi-step kinetic model of Cr(VI) was carried out. According to the results, the retention of Cr(VI) by humus was found to obey a coupling mechanism of "adsorption-reduction-complexation", where Cr(VI) adsorption was by complexation with carboxylic groups by ligand exchange. The phenolic and hydroxylic groups were determined to be the main electron donor for Cr(VI) reduction. Notably, the Cr(III) produced was found to be adsorbed on the surface of humus by complexation on phenolic and hydroxylic groups, and the excesses were released into the liquid phase after the saturation of complexation sites. Based on the revealed mechanism, a multi-step kinetic model for simultaneously describing Cr(VI) adsorption and reduction and behaviour of Cr(III) was proposed producing a better fitting performance (R2 ≥ 0.984) than the first-order and second-order kinetic models (R2 ≤ 0.84 and 0.87, respectively) and hence could provide more factual understanding of Cr(VI) transformation in soils and sediments enriched in various types of humus.

Synergistic/antagonistic effects and mechanisms of Cr(VI) adsorption and reduction by Fe(III)-HA coprecipitates.

Widespread Fe(III)-humic acid (HA) coprecipitates (FHCs) have substantial impacts on the adsorption and reduction of Cr(VI) in soils and sediments, but whether this process is equal to the sum of their individual components remains unknown. In this study, ferrihydrite (Fh)- and HA-like FHCs (C/Fe<3 and C/Fe>3, respectively) were synthesized by controlling the initial C/Fe ratios (0.5-18) to explore the potential synergistic/antagonistic effects during the adsorption and reduction of Cr(VI). According to the results, antagonistic effects on Cr(VI) adsorption (5%-80%) were observed on Fh- and HA-like FHCs, where the antagonistic intensity increased with increasing HA proportions, respectively caused by the more serious occupation of adsorption sites and the stronger electrostatic repulsion to Cr(VI). Notably, significant synergistic reduction effects (5%-650%) occurred on Fh-like FHCs were found to be achieved by the activation of low-molecular HA (0.1-0.3 kDa) with primary/secondary hydroxylic groups, which might be induced by the inductive effect of Fh on complexed HA molecules according to density-functional theory (DFT) calculation. While slight antagonistic reduction effects (2%-45%) by HA-like FHCs were attributed to the decreasing accessibility of Cr(VI) to reductive phenolic groups, which might be blocked within FHC particles or complexed with Fe(III) ions through cation bridges.

Synergistic Effects of Micronano Structures on Porosity and the Permeability of Shale Under Varying Effective Stresses and Temperatures: A Case Study of Fresh Outcrops from Lower Silurian Longmaxi Formation Shale in the Southern Sichuan Basin, China.

To study the changes in porosity-permeability and the characteristics of the pore structure of shale under stress and high temperature, the Lower Silurian Longmaxi Formation shale in the southern Sichuan Basin, China, was investigated under conditions of continuous pressurization and heating. In addition, the pore compression coefficients and permeability stress sensitivity coefficients were analyzed and quantified. The mineral composition of these black shales was analyzed using scanning electron microscopy (SEM) and nuclear magnetic resonance (NMR). Our results reveal that the porosity and permeability of the shales exponentially decreases with increasing stress, reflecting that microfracture development during increasing stress causes the pores in these shale samples to enlarge. However, the pore compressibility and stress sensitivity coefficient vary for each sample, and the quantitative results indicate an overall decrease with increasing stress, suggesting that the shale deformation is nonlinear during stress release. Based on the mineral composition analyses and SEM measurements, we conclude that the nonuniform changes during stress release are related to the complexity of the shale mineral compositions and the different intercrystalline/ interlaminar pores of the different minerals, which are affected in different ways by pressure. The NMR measurements reveal that the mesopores are most developed in the shale samples, the pore volumes of the micro- and macropores are small, and the nanoscale pores are mainly from 1-60 nm in diameter. The different types of pore sizes decrease with increasing stress, indicating that the porosities measured experimentally reflect the synergistic effects of the different pore sizes on porosity. As the temperature increases, the permeability of the shale decreases significantly, which is primarily caused by the thermal expansion effect. The high clay mineral content of the shales also causes their permeabilities to be sensitive to temperature.

A CpxR-Regulated zapD Gene Involved in Biofilm Formation of Uropathogenic Proteus mirabilis.

Proteus mirabilis, a frequent uropathogen, forms extensive biofilms on catheters that are infamously difficult to treat. To explore the mechanisms of biofilm formation by P. mirabilis, we performed in vivo transposon mutagenesis. A mutant with impaired biofilm formation was isolated. The mutant was found to have Tn5 inserted in the zapD gene, encoding an outer membrane protein of the putative type 1 secretion system ZapBCD. zapBCD and its upstream zapA gene, encoding a protease, constitute an operon under the control of CpxR, a two-component regulator. The cpxR mutant and zapA mutant strains also had a biofilm-forming defect. CpxR positively regulates the promoter activities of zapABCD, cpxP, and cpxR An electrophoretic mobility shift assay revealed that CpxR binds zapA promoter DNA. The loss of zapD reduced CpxR-regulated gene expression of cpxR, zapA, cpxP, and mrpA, the mannose-resistant Proteus-like (MR/P) fimbrial major subunit gene. The restoration of biofilm formation in the zapD mutant with a CpxR-expressing plasmid reinforces the idea that CpxR-mediated gene expression contributes to zapD-involved biofilm formation. In trans expression of zapBCD from a zapBCD-expressing plasmid also reestablished the biofilm formation ability of the cpxR mutant to a certain level. The zapD and cpxR mutants had significantly lower protease activity, adhesion, and autoaggregation ability and production of exopolysaccharides and extracellular DNA (eDNA) than did the wild type. Finally, we identified copper as a signal for CpxR to increase biofilm formation. The loss of cpxR or zapD abolished the copper-mediated biofilm upshift. CpxR was required for copper-induced expression of zapA and cpxR Taken together, these data highlight the important role of CpxR-regulated zapD in biofilm formation and the underlying mechanisms in P. mirabilis.

Nrf2-SHP Cascade-Mediated STAT3 Inactivation Contributes to AMPK-Driven Protection Against Endotoxic Inflammation.

Signal transducer and activator of transcription 3 (STAT3) is implicated in inflammation processing, but the mechanism of its regulation mostly remains limited to Janus kinase (JAK)-mediated phosphorylation. Although AMP-activated protein kinase (AMPK)-mediated STAT3 inactivation has got documented, the molecular signaling cascade connecting STAT3 inactivation and the anti-inflammatory role of AMPK is far from established. In the present study, we addressed the interplay between AMPK and STAT3, and revealed the important role of STAT3 inactivation in the anti-inflammatory function of AMPK in lipopolysaccharide-stressed macrophages and mice. Firstly, we found that pharmacological inhibition of STAT3 can improve the anti-inflammatory effect of AMPK in wild-type mice, and the expression of STAT3 in macrophage of mice is a prerequisite for the anti-inflammatory effect of AMPK. As to the molecular signaling cascade linking AMPK to STAT3, we disclosed that AMPK suppressed STAT3 not only by attenuating JAK signaling but also by activating nuclear factor erythroid-2-related factor-2 (Nrf2), a redox-regulating transcription factor, which consequently increased the expression of small heterodimer protein (SHP), thus repressing the transcriptional activity of STAT3. In summary, this study provided a unique set of evidence showing the relationship between AMPK and STAT3 signaling and explored a new mechanism of AMPK-driven STAT3 inactivation that involves Nrf2-SHP signaling cascade. These findings expand our understanding of the interplay between pro- and anti-inflammatory signaling pathways and are beneficial for the therapeutic development of sepsis treatments.

Autolysosomal degradation of cytosolic chromatin fragments antagonizes oxidative stress-induced senescence.

Oxidative stress-induced DNA damage, the senescence-associated secretory phenotype (SASP), and impaired autophagy all are general features of senescent cells. However, the cross-talk among these events and processes is not fully understood. Here, using NIH3T3 cells exposed to hydrogen peroxide stress, we show that stress-induced DNA damage provokes the SASP largely via cytosolic chromatin fragment (CCF) formation, which activates a cascade comprising cGMP-AMP synthase (cGAS), stimulator of interferon genes protein (STING), NF-κB, and SASP, and that autolysosomal function inhibits this cascade. We found that CCFs accumulate in senescent cells with activated cGAS-STING-NF-κB signaling, promoting SASP and cellular senescence. We also present evidence that the persistent accumulation of CCFs in prematurely senescent cells is partially associated with a defect in DNA-degrading activity in autolysosomes and reduced abundance of activated DNase 2α. Intriguingly, we found that metformin- or rapamycin-induced activation of autophagy significantly lessened the size and levels of CCFs and repressed the activation of the cGAS-STING-NF-κB-SASP cascade and cellular senescence. These effects of autophagy activators indicated that autolysosomal function contributes to CCF clearance and SASP suppression, further supported by the fact that the lysosome inhibitor bafilomycin A1 blocked the role of autophagy-mediated CCF clearance and senescence repression.