Nitroreduction of imidacloprid by the actinomycete Gordonia alkanivorans and the stability and acute toxicity of the nitroso metabolite.

The insecticide imidacloprid (IMI), which is used worldwide, pollutes environments and has significant ecotoxicological effects. Microbial metabolism and photolysis are the major pathways of IMI degradation in natural environments. Several studies have reported that the metabolites of IMI nitroreduction are more toxic to some insects and mammals than IMI itself. Thus, environmental degradation of IMI may enhance the ecotoxicity of IMI and have adverse effects on non-target organisms. Here, we report that an actinomycete-Gordonia alkanivorans CGMCC 21704-transforms IMI to a nitroreduction metabolite, nitroso IMI. Resting cells of G. alkanivorans at OD600 nm = 10 transformed 95.7% of 200 mg L-1 IMI to nitroso IMI in 4 d. Nitroso IMI was stable at pH 4-9. However, it rapidly degraded under sunlight via multiple oxidation, dehalogenation, and oxidative cleavage reactions to form 10 derivatives; the half-life of nitroso IMI in photolysis was 0.41 h, compared with 6.19 h for IMI. Acute toxicity studies showed that the half maximal effective concentration (EC50) values of IMI, nitroso IMI, and its photolytic metabolites toward the planktonic crustacean Daphnia magna for immobilization (exposed to the test compounds for 48 h) were 17.70, 9.38, 8.44 mg L-1, respectively. The half-life of nitroso IMI in various soils was also examined. The present study reveals that microbial nitroreduction accelerates IMI degradation and the nitroso IMI is easily decomposed by sunlight and in soil. However, nitroso IMI and its photolytic products have higher toxicity toward D. magna than the parent compound IMI, and therefore increase the ecotoxicity of IMI.

Bioinformatics of a Novel Nitrile Hydratase Gene Cluster of the N2-Fixing Bacterium Microvirga flocculans CGMCC 1.16731 and Characterization of the Enzyme.

Microvirga flocculans CGMCC 1.16731 can degrade many cyano group-containing neonicotinoid insecticides. Here, its genome was sequenced, and a novel nitrile hydratase gene cluster was discovered in a plasmid. The NHase gene cluster (pnhF) has gene structure ß-subunit 1, α-subunit, and ß-subunit 2, which is different from previously reported NHase gene structures. Phylogenetic analysis of α-subunits indicated that NHases containing the three subunit (ß1αß2) structure are independent from NHases containing two subunits (αß). pnhF was successfully expressed in Escherichia coli, and the purified PnhF could convert the nitrile-containing insecticide flonicamid to N-(4-trifluoromethylnicotinoyl)glycinamide. The enzymatic properties of PnhF were investigated using flonicamid as a substrate. Homology models revealed that amino acid residue ß1-Glu56 may strongly affect the catalytic activity of PnhF. This study expands our understanding of the structures and functions of NHases and the enzymatic mechanism of the environmental fate of flonicamid.

Maturation Mechanism of Nitrile Hydratase From Streptomyces canus CGMCC 13662 and Its Structural Character.

Nitrile hydratases have received significant interest both in the large-scale industrial production of acrylamide and nicotinamide, and the remediation of environmental contamination with nitrile-containing pollutants. Almost all known nitrile hydratases include an α-subunit (AnhA) and ß-subunit (AnhB), and a specific activator protein is crucial for their maturation and catalytic activity. Many studies exist on nitrile hydratase characteristics and applications, but few have reported their metal insertion and post-translational maturation mechanism. In this study, we investigated the cobalt insertion and maturation mechanism of nitrile hydratase from Streptomyces canus CGMCC 13662 (ScNHase) bearing three subunits (AnhD, AnhE, and AnhA). ScNHase subunits were purified, and the cobalt content and nitrile hydratase activity of the ScNHase subunits were detected. We discovered that cobalt could insert into the cobalt-free AnhA of ScNHase in the absence of activator protein under reduction agent DL-dithiothreitol (DTT) environment. AnhD not only performed the function of AnhB of NHase, but also acted as a metal ion chaperone and self-subunit swapping chaperone, while AnhE did not act as similar performance. A cobalt direct-insertion under reduction condition coordinated self-subunit swapping mechanism is responsible for ScNHase post-translational maturation. Molecular docking of ScNHase and substrates suggested that the substrate specificity of ScNHase was correlated with its structure. ScNHase had a weak hydrophobic interaction with IAN through protein-ligand interaction analysis and, therefore, had no affinity with indole-3-acetonitrile (IAN). The post-translational maturation mechanism and structure characteristics of ScNHase could help guide research on the environmental remediation of nitrile-containing waste contamination and three-subunit nitrile hydratase.

Effects of dietary supplementation with apple peel powder on the growth, blood and liver parameters, and transcriptome of genetically improved farmed tilapia (GIFT, Oreochromis niloticus).

High-density aquaculture and nutritional imbalances may promote fatty liver in genetically improved farmed tilapia (GIFT, Oreochromis niloticus), thus reducing the gains achieved by breeding. In this study, apple peel powder (APP) was used as a feed additive for GIFT. A control group (fed on a diet without APP) and five groups fed on diets supplemented with APP (at 0.05%, 0.1%, 0.2%, 0.4%, or 0.8% of the diet, by weight) were established to investigate the effects of APP on GIFT growth performance and physiological parameters, and on gene expression as determined by transcriptomic analysis. Dietary supplementation with APP at 0.2% promoted GIFT growth, reduced total cholesterol and triacylglycerol levels in the serum and liver, and decreased alanine aminotransferase and aspartate aminotransferase activities in the serum. Gene expression profiles in the liver were compared among the control, 0.2% APP, and 0.8% APP groups, and differentially expressed genes among these groups were identified. Annotation analyses using tools at the Gene Ontology and Kyoto Encyclopedia of Genes and Genomes databases showed that the differentially expressed genes were mainly involved in the regulation of immunity and fat metabolism. The results showed that excessive supplementation with APP in the diet significantly inhibited the expression of insulin-like growth factor 2 and liver-type fatty acid-binding protein, and stimulated the expression of fatty acid desaturase 2, heat shock protein 90 beta family member 1, and nuclear factor kappa B. This resulted in disordered lipid metabolism and increased pro-inflammatory reactions, which in turn caused liver damage. Therefore, APP has good potential as an environmentally friendly feed additive for GIFT at levels of 0.1%-0.2% in the diet, but excessive amounts can have adverse effects.

Effects of propofol and etomidate on inflammation and oxidative stress in septic mice / 临床麻醉学杂志

Objective To observe the effects of propofol and etomidate on inflammation and ox-idative stress in septic mice.Methods Sixty-four male adult BALB/c mice were randomly divided into four groups:normal control group (N),sepsis group (S),propofol treatment group (P)and etomid-ate treatment group (E).The septic mice model was established by lipopolysaccharide (LPS,20 mg/kg)intraperitoneal injection,and propofol (60 mg/kg)or etomidate (10 mg/kg)was injected in the abdominal cavity at 0.5 h after LPS injection.Serum interleukin-6 (IL-6)concentrations and in-terleukin-10 (IL-10)concentrations were measured at 2 h and 6 h after LPS injection;malondialde-hyde (MDA)content of lung,liver and kidney tissue was measured at 6 h after LPS injection. Results Compared with group N,serum IL-6 concentrations increased significantly (P <0.05),and IL-10 concentrations decreased significantly (P <0.05)at 2 h and 6 h after LPS injection in group S;MDA content of lung,liver,kidney increased significantly (P <0.05 )at 6 h after LPS injection in group S;Compared with group S,serum IL-6 concentrations decreased significantly (P <0.05),and IL-10 concentrations increased significantly (P < 0.05 )at 2 h and 6 h after LPS injection in both group P and E;MDA content of lung,liver,kidney decreased significantly (P <0.05 )at 6 h after LPS injection in group E,but only MDA content of lung decreased significantly (P <0.05)at 6 h af-ter LPS injection in group P;Compared with group P,serum IL-6 concentrations was significantly lower (P <0.05),and IL-10 concentrations was significantly higher (P <0.05)at 2 h and 6 h after LPS injection in group E;MDA content of lung,liver,kidney was significantly lower (P <0.05)at 6 h after LPS injection in group E.Conclusion Both propofol and etomidate injected in the abdominal cavity can reduce injury of inflammatory and oxidative stress in septic mice induced by LPS,and the effect of etomidate is more significant.

Dexmedetomidine protects against LPS-induced ALI in septic mice / 军事医学

Objective To observe the effect of dexmedetomidine on inflammation, oxidative stress and lung injury in lipopolysaccharide( LPS)-induced septic mice.Methods Forty eight male adult BALB/c mice were randomly divided into three groups (n=16): normal control group (Ctrl), sepsis group (Sep), and Dex group.Ae septic mice model was established by LPS 20 mg/kg,and Dex 30μg/kg injected intraperitoneally at 0.5 h after LPS injection.The concentrations of serum IL-6 and IL-10 were detected at 2 h and 6 h after LPS injection while myeloperoxidase ( MPO ) activity and malondialdehyde( MDA) content of lungs were detected and weight dry ratio ( W/D) of lungs was calculated at 6 h after LPS injection.Pathological changes were observed in left lung HE stained with optical microscopy at 6 h after LPS injection. Results Compared with Sep group, the concentrations of serum IL-6 decreased significantly(P <0.05), while the concentrations of IL-10 increased significantly(P<0.05) at 2 h and 6 h after LPS injection in Dex group.MPO activity, MDA content and W/D of lungs decreased significantly(P<0.05) at 6 h after LPS injection in Dex group.The injury to the lung was lightened significantly under optical microscopy in Dex group.Conclusion Dex protects against LPS-induced ALI in septic mice by inhibiting systemic inflammatory response, reducing lung tissue inflammatory infiltration and oxidative stress.