Dissolved oxygen and ammonia affect ammonia production via GDH/AMPK signaling pathway and alter flesh quality in Chinese perch (Siniperca chuatsi).

The dissolved oxygen (DO) and ammonia are crucial to the growth of Chinese perch (Siniperca chuatsi). Information on the effects of DO and total ammonia nitrogen (TAN) in regulating ammonia nitrogen excretion and flesh quality in Chinese perch is scanty. This study aimed to evaluate the effects of dissolved DO at oxygen levels of 3 mg/L and 9 mg/L, as well as the TAN concentrations of 0.3 mg/L and 0.9 mg/L on ammonia excretion and flesh quality. Results showed that the ammonia contents in plasma, muscle, and liver of the 9 mg/L DO group were significantly higher than those of the 3 mg/L DO group (P < 0.05). However, the expression of AMPK-related signaling pathway genes (gdh, lkb1, and ampd) and flesh quality indicators (gumminess, chewiness, hardness) in the 9 mg/L DO group were significantly lower than those in the 3 mg/L DO group. Under long-term exposure to 0.9 mg/L TAN, the ammonia contents in plasma and gill filaments, as well as muscle flesh quality (resilience, gumminess, chewiness, cohesiveness), were significantly lower than those in the 0.3 mg/L TAN group (P < 0.05). However, the activities of GDH and AMPD enzymes in the 0.9 mg/L TAN group were significantly higher than those in the 0.3 mg/L TAN group. In summary, when fish are exposed to 3 mg/L DO and 0.9 mg/L TAN in the environment for a long time, their amino acids are used for transamination and deamination, resulting in insufficient energy supply for Chinese perch, whereas 9 mg/L DO and 0.9 mg/L TAN caused deterioration of the flesh quality.

Visualization and bibliometric analysis of cAMP signaling system research trends and hotspots in cancer.

Cyclic adenosine monophosphate (cAMP) is an essential second messenger that widely distributed among prokaryotic and eukaryotic organisms. cAMP can regulate various biological processes, including cell proliferation, differentiation, apoptosis and immune functions. Any dysregulation or alteration of cAMP signaling may cause cell metabolic disorder, immune dysfunction and lead to disease or cancer. This study aimed to conduct a scientometric analysis of cAMP signaling system in cancer field, and explored the research trend, hotspots and frontiers from the past decade. Relevant literatures published from 2009 to 2019 were collected in the Web of Science Core Collection database. EndNote X9 was used to remove duplicate articles, and irrelevant articles were manually filtered. Bibliometric analyses were completed by CiteSpace V. A total of 4306 articles were included in this study. The number of related literatures published each year is gradually increasing. Most of them belong to "Biochemistry & Molecular Biology", "Oncology", "Cell Biology", "Pharmacology & Pharmacy" and "Endocrinology & Metabolism" areas. In the past decade, USA, China, and Japan contributed the most to the research of cAMP signaling system in cancer. The frontiers and hotspots of cAMP signaling pathway system related to cancer fields mainly focused on cancer cell apoptosis, metastasis, and multiple tumors occurrence in patients with Carney complex. Intervention of the cAMP metabolic pathway may be a potential and promising therapeutic strategy for controlling clinical cancer and tumor diseases.

Low dose lead exposure at the onset of puberty disrupts spermatogenesis-related gene expression and causes abnormal spermatogenesis in mouse.

Implications of lead (Pb) exposure in dysregulated spermatogenesis in sexually active individuals during adulthood is well established; however, the effect of Pb exposure on spermatogenesis in the early stages of puberty is not clear yet. Moreover, the mechanism of Pb mediated dysregulation of spermatogenesis in adults is also poorly understood. Exposure to environmental toxicants during puberty may cause serious consequences in adulthood causing developmental retardations, especially in the reproductive system. Here we investigated the effects of lead exposure on spermatogenesis at the onset of puberty and the underlying mechanisms of these effects. Male ICR mice were exposed to low (50 mg/L) and high (200 mg/L) doses of Pb through the drinking water for 90 days. At the end of this period, the blood Pb level of the low-dose and high-dose exposure groups were found 6.14 ± 0.34 µg/dL and 11.92 ± 2.92 µg/dL respectively which were in agreement with the US CDC-recommended (5 µg/dL) and Chinese CDC-recommended (10 µg/dL) reference blood Pb level for the children. Although no visible toxicity was observed in either group, Pb exposure caused considerable histopathological changes in testis and epididymis; increased sperm DNA fragmentation indices as well as disrupted sperm heads and head-neck conjunctions. Moreover, both low and high-dose Pb exposures caused aberrant expressions of several important spermatogenesis-related genes in epididymis and testis. These results suggest that although the blood Pb levels are close to the recommended-reference values, low dose Pb exposure at the onset of puberty can disrupt spermatogenesis-related gene expression and cause abnormal mouse spermatogenesis.

Research Trends and Hotspots Analysis Related to Monocarboxylate Transporter 1: A Study Based on Bibliometric Analysis.

Background: Monocarboxylate transport protein 1 (MCT1) has been defined as a critical regulator in tumor energy metabolism, but bibliometric analysis of MCT1 research is rare. This study aimed to comprehensively analyze the global scientific output of MCT1 research and explore the hotspots and frontiers from the past decade. Methods: Publications and their literature information from 2008 to 2018 were retrieved from the Web of Science Core Collection database. We used Microsoft Excel 2016 to detect the trend of annual numbers of publications, and used Citespace V software as the bibliometric method to analyze the research areas, countries, institutions, authors, journals, research hotspots, and research frontiers. Results: A total of 851 publications were identified with an increasing trend. Relevant literature mainly focused on the field of oncology. The most prolific country and institution were the USA and University of Minho, respectively. Baltazar was the most productive author while Halestrap had the highest co-citations. The hottest topics in MCT1 were hypoxia, gene expression, and CD147 over the last decade. The three research frontier topics were proliferation, tumor cell, and resistance. The special role of MCT1 in human tumor cells has become the focus for scholars recently. Conclusion: The development prospects of MCT1 research could be expected and researchers should pay attention to the clinical significance of MCT1 inhibitors as anti-cancer or immunosuppressive drugs and the possibility of drug-resistance formation.

Overcoming biomass recalcitrance by synergistic pretreatment of mechanical activation and metal salt for enhancing enzymatic conversion of lignocellulose.

BACKGROUND: Due to biomass recalcitrance, including complexity of lignocellulosic matrix, crystallinity of cellulose, and inhibition of lignin, the bioconversion of lignocellulosic biomass is difficult and inefficient. The aim of this study is to investigate an effective and green pretreatment method for overcoming biomass recalcitrance of lignocellulose. RESULTS: An effective mechanical activation (MA) + metal salt (MAMS) technology was applied to pretreat sugarcane bagasse (SCB), a typical kind of lignocellulosic biomass, in a stirring ball mill. Chlorides and nitrates of Al and Fe showed better synergistic effect with MA, especially AlCl3, ascribing to the interaction between metal salt and oxygen-containing groups induced by MA. Comparative studies showed that MAMS pretreatment effectively changed the recalcitrant structural characteristics of lignocellulosic matrix and reduced the inhibitory action of lignin on enzymatic conversion of SCB. The increase in hydroxyl and carboxyl groups of lignin induced by MAMS pretreatment led to the increase of its hydrophilicity, which could weaken the binding force between cellulase and lignin and reduce the nonproductive binding of cellulase enzymes to lignin. CONCLUSIONS: MAMS pretreatment significantly enhanced the enzymatic digestibility of polysaccharides substrate by overcoming biomass recalcitrance without the removal of lignin from enzymatic hydrolysis system.

Exposure to Pb and Cd alters MCT4/CD147 expression and MCT4/CD147-dependent lactate transport in mice Sertoli cells cultured in vitro.

Sertoli cells (SCs) provide lactate as an energy substrate to develop germ cells during spermatogenesis. Lead (Pb) and cadmium (Cd) can induce SC toxicity. However, the mechanisms remain unclear. This study aimed to investigate the molecular mechanisms by which Pb and Cd alter lactate transport and production by SCs. Mouse SC line (15P-1 cells) were cultured in the absence and presence of lead acetate (PbAc, 1, 10, 20 and 30 µM) or cadmium chloride (CdCl2, 0.5, 5, 10 and 15 µM) for 24 h. The results showed that PbAc exposure significantly decreased lactate dehydrogenase (LDH) activity and mRNA level, intracellular and extracellular lactate, and MCT4 and CD147 protein levels but increased MCT4 and CD147 mRNA levels. However, PbAc did not alter the glucose uptake, glucose transporters 1 (GLUT1) and 3 (GLUT3) mRNA expression of SCs. Thus, PbAc mainly decreased lactate production by inhibiting LDH activity. In CdCl2-treated SCs, intracellular lactate content increased but extracellular lactate content decreased significantly, P < .05. The glucose uptake, LDH activity, and mRNA expression of GLUT1, GLUT3 and LDH, all significantly increased. But the mRNA and protein levels of MCT4 and CD147 significantly decreased. Moreover, the fluorescence intensity of co-localizations of the MCT4-CD147 complex dose-dependently decreased in the cell membrane. Thus, CdCl2 may reduce lactate export by suppressing MCT4 and CD147 expression. These results suggest that PbAc and CdCl2 disrupt lactate production and transport in mouse SCs by disturbing glycolysis or inhibiting MCT4-CD147 transporter expression and co-localizations.

Dietary Intakes of Calcium, Iron, Magnesium, and Potassium Elements and the Risk of Colorectal Cancer: a Meta-Analysis.

The purpose of this study was to analyze the existing studies and to investigate the relationship between the risk of colorectal cancer (CRC) and intakes of four individual dietary elements calcium (Ca), iron (Fe), magnesium (Mg), and potassium (K). All relevant articles in both Chinese and English were searched and collected from PubMed, Web of Science, and Chinese National Knowledge Infrastructure databases up to December 17, 2017. There were 29 eligible literatures selected for further meta-analysis, including 14 cohort studies and 15 case-control studies. The meta-analysis of cohort studies indicated that the high intakes of dietary Ca and Mg were negatively associated with the risk of CRC, as the hazard ratios (HR) were 0.76 (95% confidence interval (CI) 0.72, 0.80) and 0.80 (95% CI 0.73, 0.87), respectively. Nevertheless, high intake of dietary heme Fe was positively correlated to the incidence of colon cancer (HR = 1.01, 95% CI 0.82, 1.19) and rectal cancer (HR = 1.04, 95% CI 0.67, 1.42). A meta-analysis of case-control studies indicated that high intakes of dietary Ca, Mg, and K were negatively related with the occurrence of CRC, because the odds ratios (OR) were 0.36 (95% CI 0.32, 0.40), 0.80 (95% CI 0.63, 0.98) and 0.97 (95% CI 0.74, 1.21), respectively. However, high Fe intake from diet was positively correlated with the rising increasing of CRC (OR = 1.04, 95% CI 0.91, 1.18). More research is needed to indicate the risk relationship between element intake and CRC.

Cyclic dinucleotide (c-di-GMP, c-di-AMP, and cGAMP) signalings have come of age to be inhibited by small molecules.

Bacteria utilize nucleotide-based second messengers to regulate a myriad of physiological processes. Cyclic dinucleotides have emerged as central regulators of bacterial physiology, controlling processes ranging from cell wall homeostasis to virulence production, and so far over thousands of manuscripts have provided biological insights into c-di-NMP signaling. The development of small molecule inhibitors of c-di-NMP signaling has significantly lagged behind. Recent developments in assays that allow for high-throughput screening of inhibitors suggest that the time is right for a concerted effort to identify inhibitors of these fascinating second messengers. Herein, we review c-di-NMP signaling and small molecules that have been developed to inhibit cyclic dinucleotide-related enzymes.

DgcA, a diguanylate cyclase from Xanthomonas oryzae pv. oryzae regulates bacterial pathogenicity on rice.

Xanthomonas oryzae pv. oryzae (Xoo) is the causal agent of rice blight disease as well as a serious phytopathogen worldwide. It is also one of the model organisms for studying bacteria-plant interactions. Current progress in bacterial signal transduction pathways has identified cyclic di-GMP as a major second messenger molecule in controlling Xanthomonas pathogenicity. However, it still remains largely unclear how c-di-GMP regulates the secretion of bacterial virulence factors in Xoo. In this study, we focused on the important roles played by DgcA (XOO3988), one of our previously identified diguanylate cyclases in Xoo, through further investigating the phenotypes of several dgcA-related mutants, namely, the dgcA-knockout mutant ΔdgcA, the dgcA overexpression strain OdgcA, the dgcA complemented strain CdgcA and the wild-type strain. The results showed that dgcA negatively affected virulence, EPS production, bacterial autoaggregation and motility, but positively triggered biofilm formation via modulating the intracellular c-di-GMP levels. RNA-seq data further identified 349 differentially expressed genes controlled by DgcA, providing a foundation for a more solid understanding of the signal transduction pathways in Xoo. Collectively, the present study highlights DgcA as a major regulator of Xoo virulence, and can serve as a potential target for preventing rice blight diseases.

Characterization of a natural triple-tandem c-di-GMP riboswitch and application of the riboswitch-based dual-fluorescence reporter.

c-di-GMP riboswitches are structured RNAs located in the 5'-untranslated regions (5'-UTRs) of mRNAs that regulate expression of downstream genes in response to changing concentrations of the second messenger c-di-GMP. We discovered three complete c-di-GMP riboswitches (Bc3, Bc4 and Bc5 RNA) with similar structures, which are arranged in tandem to constitute a triple-tandem (Bc3-5 RNA) riboswitch in the 5'-UTR of the cspABCDE mRNA in Bacillus thuringiensis subsp. chinensis CT-43. Our results showed that this natural triple-tandem riboswitch controlled the expression of the reporter gene more stringently and digitally than the double-tandem or single riboswitch. A sandwich-like dual-fluorescence reporter was further constructed by fusing the Bc3-5 RNA gene between the two fluorescence protein genes amcyan and turborfp. This reporter strain was found to exhibit detectable fluorescence color changes under bright field in response to intracellular c-di-GMP level altered by induced expression of diguanylate cyclase (DGC) PleD. Using this system, two putative membrane-bound DGCs from B. thuringiensis and Xanthomonas oryzae were verified to be functional by replacing pleD with the corresponding DGC genes. This report represented the first native triple-tandem riboswitch that was applied to serve as a riboswitch-based dual-fluorescence reporter for the efficient and convenient verification of putative DGC activity in vivo.

A green and efficient technology for the degradation of cellulosic materials: structure changes and enhanced enzymatic hydrolysis of natural cellulose pretreated by synergistic interaction of mechanical activation and metal salt.

A new technology for the pretreatment of natural cellulose was developed, which combined mechanical activation (MA) and metal salt treatments in a stirring ball mill. Different valent metal nitrates were used to investigate the changes in degree of polymerization (DP) and crystallinity index (CrI) of cellulose after MA+metal salt (MAMS) pretreatment, and Al(NO3)3 showed better pretreatment effect than NaNO3 and Zn(NO3)2. The destruction of morphological structure of cellulose was mainly resulted from intense ball milling, and the comparative studies on the changes of DP and crystal structure of MA and MA+Al(NO3)3 pretreated cellulose samples showed a synergistic interaction of MA and Al(NO3)3 treatments with more effective changes of structural characteristics of MA+Al(NO3)3 pretreated cellulose and substantial increase of reducing sugar yield in enzymatic hydrolysis of cellulose. In addition, the results indicated that the presence of Al(NO3)3 had significant enhancement for the enzymatic hydrolysis of cellulose.

Catalytic oxidation of manganese(II) by multicopper oxidase CueO and characterization of the biogenic Mn oxide.

Manganese(II) contamination is naturally occurring in many groundwater and surface water sources. Moreover, industrial wastewater is also responsible for much of the Mn(II) contamination. Nowadays, Mn(II) contamination has become a serious environmental problem in some regions of the world. To explore a biological approach for removing excessive amounts of aqueous Mn(II) from water, we found a new biocatalyst multicopper oxidase CueO, which was firstly proved to catalyze the oxidation of Mn(II) both in vitro and in vivo. Subsequently, we established a CueO-mediated catalysis system to prepare biogenic Mn oxide (BioMnOx), which was confirmed to be γ-Mn3O4 by X-ray diffraction. This newly prepared BioMnOx consisted of 53.6% Mn(II), 18.4% Mn(III) and 28.0% Mn(IV) characterized by X-ray photoelectron spectroscopy. It exhibited distinct polyhedral structure with nanoparticles of 150-350 nm diameters observed by transmission electron microscopy. Importantly, CueO could remove 35.7% of Mn(II) after a seven-day reaction, and on the other hand, the cueO-overexpressing Escherichia coli strain (ECueO) could also oxidize 58.1% dissolved Mn(II), and simultaneously remove 97.7% Mn(II). Based on these results, we suggest that ECueO strain and CueO enzyme have potential applications on Mn(II) decontamination in water treatment.

Growth performance, body lipid, brood amount, and rearing environment response to supplemental neutral phytase in zebrafish (Danio rerio) diet.

The present study was to evaluate the effects of neutral phytase supplementation on growth performance, survival ratio (SR), body lipid, brood amount, and rearing environment in zebrafish. The control diet was not supplemented phytase, and three levels of phytase (500, 1000, or 1500 U kg(-1)) was added to the three other diets (named as PP500, PP1000, and PP1500). Triplicate groups (twelve 100-L tanks) of zebrafish (initial mean weight, 0.284±0.012 g) were fed twice daily (08:00 and 16:00 h) to satiation for 12 weeks. The results showed that supplemental phytase in the diet improved weight gain (60.49%, 86.63%, 99.06%, and 111.88% in control, PP500, PP1000, and PP1500) and the specific growth ratio of zebrafish (p<0.05). Dietary phytase addition increased the whole body lipid content of zebrafish. The brood amounts (116, 123, and 124 eggs in PP500, PP1000, and PP1500) of fish fed with phytase-supplemented diets were little higher than the control (mean egg was 112). The ammonia-nitrogen concentration in water of fish fed with phytase-supplemented diet was significantly lower than the control. The nitrite concentration in water was also decreased in water of fish fed with phytase-supplemented diet. The SR was increased with the increasing of dietary phytase despite no significant difference was observed among each group. The present study first suggested that neutral phytase could be applied in the zebrafish diet. Furthermore, phytase addition increased the growth, body lipid, brood amount, and SR of zebrafish, and meanwhile decreased the ammonia-nitrogen and nitrite concentrations in rearing water.

Highly efficient enzymatic preparation of c-di-AMP using the diadenylate cyclase DisA from Bacillus thuringiensis.

Cyclic 3',5'-diadenosine monophosphate (c-di-AMP) is a newly recognized bacterial nucleotide second messenger molecule. In addition, it has been shown to be a potential vaccine adjuvant. Although multiple methods are available for c-di-AMP synthesis, the yields are low and the purification procedures are laborious. Here, we report an enzymatic method for more efficient and economical c-di-AMP synthesis using a diadenylate cyclase DisA from Bacillus thuringiensis BMB 171 (btDisA). After overexpression and purification of btDisA, the enzyme-catalyzed reaction conditions were further investigated. Under the optimum conditions, in which 100mM CHES (pH 9.5) containing 2µM btDisA, 10mM ATP, and 10mM MgCl2 was incubated at 50°C for 4h, a high conversion rate of c-di-AMP was obtained. Coupling this process with HPLC purification and lyophilization yielded 100mg of highly pure c-di-AMP that was harvested in white powder form from a 50mL enzyme-catalyzed reaction system. The protocol is not only directly applicable for preparing abundant amounts of c-di-AMP for extensive biochemical and immunological use, but can also be scaled up to meet the requirements for medical applications.

CotA, a multicopper oxidase from Bacillus pumilus WH4, exhibits manganese-oxidase activity.

Multicopper oxidases (MCOs) are a family of enzymes that use copper ions as cofactors to oxidize various substrates. Previous research has demonstrated that several MCOs such as MnxG, MofA and MoxA can act as putative Mn(II) oxidases. Meanwhile, the endospore coat protein CotA from Bacillus species has been confirmed as a typical MCO. To study the relationship between CotA and the Mn(II) oxidation, the cotA gene from a highly active Mn(II)-oxidizing strain Bacillus pumilus WH4 was cloned and overexpressed in Escherichia coli strain M15. The purified CotA contained approximately four copper atoms per molecule and showed spectroscopic properties typical of blue copper oxidases. Importantly, apart from the laccase activities, the CotA also displayed substantial Mn(II)-oxidase activities both in liquid culture system and native polyacrylamide gel electrophoresis. The optimum Mn(II) oxidase activity was obtained at 53°C in HEPES buffer (pH 8.0) supplemented with 0.8 mM CuCl2. Besides, the addition of o-phenanthroline and EDTA both led to a complete suppression of Mn(II)-oxidizing activity. The specific activity of purified CotA towards Mn(II) was 0.27 U/mg. The Km, Vmax and kcat values towards Mn(II) were 14.85±1.17 mM, 3.01×10(-6)±0.21 M·min(-1) and 0.32±0.02 s(-1), respectively. Moreover, the Mn(II)-oxidizing activity of the recombinant E. coli strain M15-pQE-cotA was significantly increased when cultured both in Mn-containing K liquid medium and on agar plates. After 7-day liquid cultivation, M15-pQE-cotA resulted in 18.2% removal of Mn(II) from the medium. Furthermore, the biogenic Mn oxides were clearly observed on the cell surfaces of M15-pQE-cotA by scanning electron microscopy. To our knowledge, this is the first report that provides the direct observation of Mn(II) oxidation with the heterologously expressed protein CotA, Therefore, this novel finding not only establishes the foundation for in-depth study of Mn(II) oxidation mechanisms, but also offers a potential biocatalyst for Mn(II) removal.

The metabolic regulation of sporulation and parasporal crystal formation in Bacillus thuringiensis revealed by transcriptomics and proteomics.

Bacillus thuringiensis is a well-known entomopathogenic bacterium used worldwide as an environmentally compatible biopesticide. During sporulation, B. thuringiensis accumulates a large number of parasporal crystals consisting of insecticidal crystal proteins (ICPs) that can account for nearly 20-30% of the cell's dry weight. However, the metabolic regulation mechanisms of ICP synthesis remain to be elucidated. In this study, the combined efforts in transcriptomics and proteomics mainly uncovered the following 6 metabolic regulation mechanisms: (1) proteases and the amino acid metabolism (particularly, the branched-chain amino acids) became more active during sporulation; (2) stored poly-ß-hydroxybutyrate and acetoin, together with some low-quality substances provided considerable carbon and energy sources for sporulation and parasporal crystal formation; (3) the pentose phosphate shunt demonstrated an interesting regulation mechanism involving gluconate when CT-43 cells were grown in GYS medium; (4) the tricarboxylic acid cycle was significantly modified during sporulation; (5) an obvious increase in the quantitative levels of enzymes and cytochromes involved in energy production via the electron transport system was observed; (6) most F0F1-ATPase subunits were remarkably up-regulated during sporulation. This study, for the first time, systematically reveals the metabolic regulation mechanisms involved in the supply of amino acids, carbon substances, and energy for B. thuringiensis spore and parasporal crystal formation at both the transcriptional and translational levels.