Overexpression of Lias Gene Alleviates Cadmium-Induced Kidney Injury in Mice Involving Multiple Effects: Metabolism, Oxidative Stress, and Inflammation.

Oxidative stress is an important mechanism underlying toxicity induced by cadmium (Cd) exposure. However, there are significant differences of the antioxidant baseline in different populations. This means that different human has different intensity of oxidative stress in vivo after exposure to toxicants. LiasH/H mouse is a specific model which is created by genetically modifying the Lias 3'-untranslated region (3'-UTR). LiasH/H mice express high levels of LA and have high endogenous antioxidant capacity which is approximately 150% higher than wild-type C57BL/6 J mice (WT, Lias+/+). But more importantly, they have dual roles of metal chelator and antioxidant. Here, we applied this mouse model to evaluate the effect of endogenous antioxidant levels in the body on alleviating Cd-induced renal injury including Cd metabolism, oxidative stress, and inflammation. In the experiment, mice drank water containing Cd (50 mg/L), for 12 weeks. Many biomarkers of Cd metabolism, oxidative stress, inflammation, and major pathological changes in the kidney were examined. The results showed overexpression of the Lias gene decreased Cd burden in the body of mice, mitigated oxidative stress, attenuated the inflammatory response, and subsequent alleviated cadmium-induced kidney injury in mice.

Lias overexpression alleviates pulmonary injury induced by fine particulate matter in mice.

Oxidative stress and inflammation are mechanisms underlying toxicity induced by fine particulate matter (PM2.5). The antioxidant baseline of the human body modulates the intensity of oxidative stress in vivo. This present study aimed to evaluate the role of endogenous antioxidants in alleviating PM2.5-induced pulmonary injury using a novel mouse model (LiasH/H) with an endogenous antioxidant capacity of approximately 150% of its wild-type counterpart (Lias+/+). LiasH/H and wild-type (Lias+/+) mice were randomly divided into control and PM2.5 exposure groups (n = 10), respectively. Mice in the PM2.5 group and the control group were intratracheally instilled with PM2.5 suspension and saline, respectively, once a day for 7 consecutive days. The metal content, major pathological changes in the lung, and levels of oxidative stress and inflammation biomarkers were examined. The results showed that PM2.5 exposure induced oxidative stress in mice. Overexpression of the Lias gene significantly increased the antioxidant levels and decreased inflammatory responses induced by PM2.5. Further study found that LiasH/H mice exerted their antioxidant function by activating the ROS-p38MAPK-Nrf2 pathway. Therefore, the novel mouse model is useful for the elucidation of the mechanisms of pulmonary injury induced by PM2.5.

Functional Characterization and Structural Insights Into Stereoselectivity of Pulegone Reductase in Menthol Biosynthesis.

Monoterpenoids are the main components of plant essential oils and the active components of some traditional Chinese medicinal herbs like Mentha haplocalyx Briq., Nepeta tenuifolia Briq., Perilla frutescens (L.) Britt and Pogostemin cablin (Blanco) Benth. Pulegone reductase is the key enzyme in the biosynthesis of menthol and is required for the stereoselective reduction of the Δ2,8 double bond of pulegone to produce the major intermediate menthone, thus determining the stereochemistry of menthol. However, the structural basis and mechanism underlying the stereoselectivity of pulegone reductase remain poorly understood. In this study, we characterized a novel (-)-pulegone reductase from Nepeta tenuifolia (NtPR), which can catalyze (-)-pulegone to (+)-menthone and (-)-isomenthone through our RNA-seq, bioinformatic analysis in combination with in vitro enzyme activity assay, and determined the structure of (+)-pulegone reductase from M. piperita (MpPR) by using X-ray crystallography, molecular modeling and docking, site-directed mutagenesis, molecular dynamics simulations, and biochemical analysis. We identified and validated the critical residues in the crystal structure of MpPR involved in the binding of the substrate pulegone. We also further identified that residues Leu56, Val282, and Val284 determine the stereoselectivity of the substrate pulegone, and mainly contributes to the product stereoselectivity. This work not only provides a starting point for the understanding of stereoselectivity of pulegone reductases, but also offers a basis for the engineering of menthone/menthol biosynthetic enzymes to achieve high-titer, industrial-scale production of enantiomerically pure products.

Overexpression of lipoic acid synthase gene alleviates diabetic nephropathy of Leprdb/db mice.

INTRODUCTION: Diabetic nephropathy (DN) develops in about 40% of patients with type 2 diabetes and remains the leading cause of end-stage renal disease. The mechanisms of DN remain to be elucidated. Oxidative stress is thought to be involved in the development of DN but antioxidant therapy has produced conflicting results. Therefore, we sought to define the role of antioxidant in retarding the development of DN in this study. RESEARCH DESIGN AND METHODS: We generated a new antioxidant/diabetes mouse model, LiasH/HLeprdb/db mice, by crossing db/db mice with LiasH/H mice, which have overexpressed Lias gene (~160%) compared with wild type, and also correspondingly increased endogenous antioxidant capacity. The new model was used to investigate whether predisposed increased endogenous antioxidant capacity was able to retard the development of DN. We systemically and dynamically examined main pathological alterations of DN and antioxidant biomarkers in blood and kidney mitochondria. RESULTS: LiasH/HLeprdb/db mice alleviated major pathological alterations in the early stage of DN, accompanied with significantly enhanced antioxidant defense. The model targets the main pathogenic factors by exerting multiple effects such as hypoglycemic, anti-inflammation, and antioxidant, especially protection of mitochondria. CONCLUSION: The antioxidant animal model is not only very useful for elucidating the underlying mechanisms of DN but also brings insight into a new therapeutic strategy for clinical applications.

Corrigendum: Functional Characterization and Structural Insights Into Stereoselectivity of Pulegone Reductase in Menthol Biosynthesis.

[This corrects the article DOI: 10.3389/fpls.2021.780970.].

Recent Advances on Feasible Strategies for Monoterpenoid Production in Saccharomyces cerevisiae.

Terpenoids are a large diverse group of natural products which play important roles in plant metabolic activities. Monoterpenoids are the main components of plant essential oils and the active components of some traditional Chinese medicinal herbs. Some monoterpenoids are widely used in medicine, cosmetics and other industries, and they are mainly obtained by plant biomass extraction methods. These plant extraction methods have some problems, such as low efficiency, unstable quality, and high cost. Moreover, the monoterpenoid production from plant cannot satisfy the growing monoterpenoids demand. The development of metabolic engineering, protein engineering and synthetic biology provides an opportunity to produce large amounts of monoterpenoids eco-friendly using microbial cell factories. This mini-review covers current monoterpenoids production using Saccharomyces cerevisiae. The monoterpenoids biosynthetic pathways, engineering of key monoterpenoids biosynthetic enzymes, and current monoterpenoids production using S. cerevisiae were summarized. In the future, metabolically engineered S. cerevisiae may provide one possible green and sustainable strategy for monoterpenoids supply.

Investigations into the Antibacterial Mechanism of Action of Viridicatumtoxins.

Viridicatumtoxins are a rare class of tetracycline-like antibiotics that strongly inhibit drug-resistant Gram-positive bacteria. Although reported to exhibit in vitro inhibition activity to undecaprenyl pyrophosphate synthase (UPPS), an essential enzyme in bacterial cell wall synthesis, the biological targets and mechanism of action of viridicatumtoxins, especially the drug-target interactions, remain largely unknown. In this study, the structure of Enterococcus faecalis UPPS (EfaUPPS) was first determined, uncovering that EfaUPPS can form not only a typical functional dimer but also an unexpected atypical dimer. We then observed that viridicatumtoxins A (VirA) and B (VirB) are able to bind to UPPSs of E. faecalis, S. aureus, and E. coli in a direct and high-affinity manner as evidenced by in vitro enzyme inhibition assay, surface plasmon resonance (SPR) binding analysis, and in vivo growth inhibition assay, demonstrating that viridicatumtoxins exert antibacterial effects through UPPS binding. The key amino acid residues involved in the interactions with VirA and VirB in EfaUPPS binding pocket were revealed by molecular docking studies, and further validated by site-directed mutagenesis. A single mutation of EfaUPPS at D29A, N31A, and R42A can obviously increase their affinities to VirA, while a single mutation at W228A conferred significant resistance to VirA. Moreover, translation inhibition assay showed that VirA and VirB can weakly inhibit E. coli 70S ribosome. The weak inhibition of ribosome was proposed to be attributed to steric hindrance between viridicatumtoxin ring F and 70S ribosome helix 34 by molecular docking study. Our structural, biochemical, and computational investigations on the interactions of viridicatumtoxins with UPPS and 70S ribosome not only disclosed the potential biological targets of viridicatumtoxins, but also provided a theoretical basis for structural optimization to make new viridicatumtoxin derivatives with improved antimicrobial activities.

Strand-specific RNA-seq analysis of the Acidithiobacillus ferrooxidans transcriptome in response to magnesium stress.

Bioleaching is a promising process for 350 million tons Jinchuan low-grade pentlandite. But, Jinchuan pentlandite has lots of magnesium and high concentration of Mg2+ is harmful to bioleaching microorganisms. Thus, finding a way to improve the adaption of microorganisms to Mg2+ is a key for bioleaching. In the study, we found that oxidizing activity, bioleaching ability and biofilm formation of A.f were inhibited by Mg2+ stress. In addition, we analyzed mRNA and small RNA (sRNA) of Acidithiobacillus ferrooxidans (A.f) under Mg2+ stress by strand-specific RNA-sequencing (ssRNA-seq). After the bioinformatics process, 2475 coding genes were obtained, and there were 33 differential expression genes (DEGs) in 0.1 M-VS-Con, including 28 down-regulated and 5 up-regulated, whereas 52 DEGs were obtained in 0.5 M-VS-Con, including 28 down-regulated and 24 up-regulated. Gene ontology analysis showed most of DEGs were involved in catalytic activity, metabolic process and single-organism process. Furthermore, we identified 636 sRNA and some differential expression sRNA that may respond to Mg2+ stress. Further analysis of DEGs suggested that Mg2+ stress reduced biofilm formation perhaps through inhibiting Type IV Pili-related gene expression and inhibited bacterial activity perhaps through affecting carbon fixation. The study provided the foundation to understand the mechanisms of Mg2+ resistance in A.f and may be helpful to improve bioleaching ability for pentlandit.

Mg2+ reduces biofilm quantity in Acidithiobacillus ferrooxidans through inhibiting Type IV pili formation.

Bioleaching is a promising process for 350 million tons of Jinchuan low-grade pentlandite. But high concentration of Mg2+ is harmful to bioleaching microorganisms. Interestingly, biofilm formation can improve leaching rate. Thus, it is actually necessary to investigate the effect of Mg2+ stress on Acidithiobacillus ferrooxidans biofilms formation. In this study, we found that 0.1 and 0.5 M Mg2+ stress significantly reduced the total biomass of biofilm in a dose-dependent manner. The observation results of extracellular polymeric substances and bacteria using confocal laser scanning microscopy showed that the biofilm became thinner and looser under Mg2+ stress. Whereas 0.1 and 0.5 M Mg2+ stress had no remarkable effect on the bacterial viability, the attachment rate of Acidithiobacillus ferrooxidans to pentlandite was reduced by Mg2+ stress. Furthermore, sliding motility, twitching motility and the gene expression level of pilV and pilW were inhibited under Mg2+ stress. These results suggested that Mg2+ reduced biofilm formation through inhibiting pilV and pilW gene expression, decreasing Type IV pili formation and then attenuating the ability of attachment, subduing the active expansion of biofilms mediated by twitching motility. This study provided more information about the effect of Mg2+ stress on biofilm formation and may be useful for increasing the leaching rate in low-grade pentlandit.

Bio-adsorption and Bio-transformation of Arsenic by Acidithiobacillus ferrooxidans BY3.

Arsenic, a toxic element in the environment, has seriously threatened the health of hundreds of millions of people in the world. Meanwhile, microorganisms play an important role in the adsorption and bio-transformation of arsenic. Here, we compared the biological characteristics of Acidithiobacillus ferrooxidans BY3 in different media systems, such as arsenic bio-adsorption and bio-transformation capacities. We show that arsenic stress significantly affected the pH and Eh of the culture systems, as well as the oxidation rates of Fe2+ and bacteria numbers. Furthermore, arsenic influenced bacterial structure and composition of the cell membrane, caused volume decreased and changed the vibration conditions of characteristic peaks of surface groups (-CH2, -NH, and -OH) on cell membranes. In addition, At.f-BY3 shows high bio-adsorption abilities and certain bio-transformation abilities for iAsIII. Bio-adsorption and conversion efficiency was also shown to be significantly affected by Fe2+ concentrations in the reaction systems. Statistic analysis revealed 10.07-fold increase of the transformation ability of iAsIII into iAsV in the 9 K growth media containing 1600 mg/L NaAsO2 compared with that in the 1 K growth media. Our findings contribute to understand the applications and microbiological mechanisms of Acidithiobacillus ferrooxidans in arsenic pollution. Graphical Abstract Bio-adsorption and bio-transformation are used as a biological method of heavy metals pollution, such as Cu2+, Ni2+, Pb2+, Cr2+, Zn2+, Cd2+, As3+ and As5+ in acid mine water. The aim of this investigation was to assess the performance of arsenite (iAsIII) to adsorption and transformation by Acidithiobacillus ferrooxidans BY3, and application of Acidithiobacillus ferrooxidans BY3 on the aspect of arsenic pollution has great potential of exploration.

Realgar transforming solution displays anticancer potential against human hepatocellular carcinoma HepG2 cells by inducing ROS.

Realgar (As4S4), as a mineral drug containing arsenic compound, has been employed in clinical therapy of cancer for its good therapeutic reputation in Chinese traditional medicine. However, large dose of realgar and long period of treatment are necessary for achieving the effective blood medicine concentration due to its low bioavailability resulted from poor solubility. In this study, we obtained realgar transforming solution (RTS) using intrinsic biotransformation in microorganism, and investigated underlying mechanisms of RTS for HepG2 cells. Our results demonstrated that an effective biotransformation of realgar method by A. ferrooxidans was established, in which realgar was biologically converted into an aqueous solution, and RTS had a strong activity inducing apoptosis and interrupting G2/M progression in HepG2 cells via upregulation of cellular ROS. Importantly, RTS inhibited the cellular antioxidant defense system leading to abundant ROS accumulation, and activated cell cycle arrest and mitochondrial pathway of apoptosis mediated by activating p53 due to cellular uncontrolled ROS. Collectively, our findings suggest that RTS is a potential candidate for therapy of human hepatocellular carcinoma.

Paenibacillus ripae sp. nov., isolated from bank side soil.

A Gram-stain-variable, rod-shaped, non-motile and endospore-forming bacterium, designated strain HZ1T, was isolated from a sample of bank side soil from Hangzhou city, Zhejiang province, PR China. On the basis of 16S rRNA gene sequence analysis, strain HZ1T was closely related to members of the genus Paenibacillus, sharing the highest levels of sequence similarity with Paenibacillus agarexedens DSM 1327T (94.4 %), Paenibacillus sputi KIT00200-70066-1T (94.4 %). Growth occurred at 15-42 °C (optimum 30-37 °C), pH 5.0-9.5 (optimum pH 7.0-8.0) and NaCl concentrations of up to 6.0 % (w/v) were tolerated (optimum 0.5 %). The dominant respiratory quinone was MK-7 and the DNA G+C content was 40.1 mol%. The major fatty acids were anteiso-C15 : 0 and iso-C16 : 0. The major polar lipids of strain HZ1T were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine and several unknown lipids. The diagnostic diamino acid found in the cell-wall peptidoglycan was meso-diaminopimelic acid. Based on its phenotypic and chemotaxonomic characteristics and phylogenetic data, strain HZ1T represents a novel species of the genus Paenibacillus, for which the name Paenibacillus ripae sp. nov. (type strain HZ1T = CCTCC AB 2014276T = LMG 28639T) is proposed.

[Cloning and expression of the alpha-amylase gene from a Bacillus sp. WS06, and characterization of the enzyme].

A Bacillus sp. WS06, which produces an extracellular alpha-amylase, was isolated from the cecum in a piglet. An amyF gene from this Bacillus strain was cloned and its nucleotide sequence was determined. An open reading frame composed of 1581 bases, which encodes 526 amino acid residues was found. The amyF gene shows high sequence homologies with other microbial amylase genes, such as Bacillus megaterium and Bacillus polymyxa (93% and 53% identity). The deduced amino acid sequence revealed that four highly conserved regions of the alpha-amylase family. The amyF gene was overepressed using the pET21a vector and Escherichia coli BL21 (DE3). The recombinant enzyme was purified 22.2 fold to electrophoretic homogeneity and had a molecular mass of 57kD (by SDS-PAGE). The enzyme was optimally active at pH 7 and 55 approximately 60 degrees C and showed stability at the temperature below 55 degrees C. This enzyme efficiently hydrolyzed various types of starch to yield a series of malto-oligosaccharides by endo-cleavage mode.