tert-Butyl Nitrite-Induced Radical Nitrile Oxidation Cycloaddition: Synthesis of Isoxazole/Isoxazoline-Fused Benzo 6/7/8-membered Oxacyclic Ketones.

A practical metal-free and additive-free approach for the synthesis of 6/7/8-membered oxacyclic ketone-fused isoxazoles/isoxazolines tetracyclic or tricyclic structures is reported through Csp3-H bond radical nitrile oxidation and the intramolecular cycloaddition of alkenyl/alkynyl-substituted aryl methyl ketones. This convenient approach enables the simultaneous formation of isoxazole/isoxazoline and 6/7/8-membered oxacyclic ketones to form polycyclic architectures by using tert-butyl nitrite (TBN) as a non-metallic radical initiator and N-O fragment donor.

Transforming Growth Factor Alpha Taq I Polymorphisms and Nonsyndromic Cleft Lip and/or Palate Risk: A Meta-Analysis.

BACKGROUND: A series of epidemiological studies were conducted to investigate the association between transforming growth factor alpha ( TGFA) polymorphism and nonsyndromic cleft lip and/or palate (CL/P) risk, but the findings remain conflicting. The present meta-analysis summarizes the association between the TGFA Taq I polymorphisms and nonsyndromic CL/P risk. METHODS: We searched PubMed, EMBASE, Web of Science, and Chinese Biomedical Literature databases from their inception to May 1, 2015. Fixed-effects or random-effects models were used to calculate the pooled odds ratio for two genetic comparisons (heterozygous mutation versus wild type, homozygous mutation versus wild type). All of the statistical tests were conducted by STATA 10.0 (StataCorp, College Station, TX). RESULTS: A total of 26 case-control studies were identified for this meta-analysis. There was evidence of a significant association between the TGFA Taq I polymorphism and nonsyndromic CL/P risk in the overall population. The TGFA polymorphism was associated with nonsyndromic CL/P susceptibility in Asian populations under any of genetic models. However, in subgroup analysis, we did not find a significant association of TGFA gene polymorphisms with a reduced cancer risk in White and other populations and (recessive model, odds ratio = 2.37, 95% confidence intervals = 0.92-6.07; odds ratio = 3.45, 95% confidence intervals = 1.07-11.09, respectively). CONCLUSION: Our study indicates that the TGFA gene polymorphism might be associated with nonsyndromic CL/P susceptibility. However, these findings still need to be confirmed by single, large, well-designed prospective studies.

Cutting Edge: mechanical forces acting on T cells immobilized via the TCR complex can trigger TCR signaling.

Engagement of the TCR by antigenic peptides presented by the MHC activates specific T cells to control infections. Recent theoretical considerations have suggested that mechanical forces acting on the TCR may be important for receptor triggering. In this study, we directly tested the hypothesis that physical forces acting on the TCR can initiate signaling in T cells by micromanipulation of individual T cells bound to artificial APCs expressing engineered TCR ligands. We find that mechanical forces acting on T cells bound to APCs via the TCR complex but not other surface receptors can initiate signaling in T cells in an Src kinase-dependent fashion. Our data indicate that T cells are mechanically sensitive when coupled to APCs by the TCR and indicates that the TCR may act as a mechanosensor. Our data provide new insight into TCR function.

Human cytochrome P450 3A-mediated two-step oxidation metabolism of dimethomorph: Implications in the mechanism-based enzyme inactivation.

Dimethomorph (DMM), an effective and broad-spectrum fungicide applied in agriculture, is toxic to environments and living organisms due to the hazardous nature of its toxic residues. This study aims to investigate the human cytochrome P450 enzyme (CYP)-mediated oxidative metabolism of DMM by combining experimental and computational approaches. Dimethomorph was metabolized predominantly through a two-step oxidation process mediated by CYPs, and CYP3A was identified as the major contributor to DMM sequential oxidative metabolism. Meanwhile, DMM elicited the mechanism-based inactivation (MBI) of CYP3A in a suicide manner, and the iminium ion and epoxide reactive intermediates generated in DMM metabolism were identified as the culprits of MBI. Furthermore, three common pesticides, prochloraz (PCZ), difenoconazole (DFZ) and chlorothalonil (CTL), could significantly inhibit CYP3A-mediated DMM metabolism, and consequently trigger elevated exposure to DMM in vivo. Computational studies elucidated that the differentiation effects in charge distribution and the interaction pattern played crucial roles in DMM-induced MBI of CYP3A4 during sequential oxidative metabolism. Collectively, this study provided a global view of the two-step metabolic activation process of DMM mediated by CYP3A, which was beneficial for elucidating the environmental fate and toxicological mechanism of DMM in humans from a new perspective.

Regioselective hydroxylation of carbendazim by mammalian cytochrome P450: A combined experimental and computational study.

Carbendazim (CBZ), a broad-spectrum pesticide frequently detected in fruits and vegetables, could trigger potential toxic risks to mammals. To facilitate the assessment of health risks, this study aimed to characterize the cytochrome P450 (CYPs)-mediated metabolism profiles of CBZ by a combined experimental and computational study. Our results demonstrated that CYPs-mediated region-selective hydroxylation was a major metabolism pathway for CBZ in liver microsomes from various species including rat, mouse, minipig, dog, rabbit, guinea pig, monkey, cow and human, and the metabolite was biosynthesized and well-characterized as 6-OH-CBZ. CYP1A displayed a predominant role in the region-selective hydroxylation of CBZ that could attenuate its toxicity through converting it into a less toxic metabolite. Meanwhile, five other common pesticides including chlorpyrifos-methyl, prochloraz, chlorfenapyr, chlorpyrifos, and chlorothalonil could significantly inhibit the region-selective hydroxylation of CBZ, and consequently remarkably increased CBZ exposure in vivo. Furthermore, computational study clarified the important contribution of the key amino acid residues Ser122, and Asp313 in CYP1A1, as well as Asp320 in CYP1A2 to the hydroxylation of CBZ through hydrogen bonds. These results would provide some useful information for the metabolic profiles of CBZ by mammalian CYPs, and shed new insights into CYP1A-mediated metabolic detoxification of CBZ and its health risk assessment.

Catalpol protects rat pheochromocytoma cells against oxygen and glucose deprivation-induced injury.

OBJECTIVES: Catalpol has been identified to have neuroprotective effect on gerbils subjected to transient global cerebral ischemia. However, the mechanism that catalpol prevents ischemia is still unclear. In the present study, PC12 cells, exposed to oxygen and glucose deprivation (OGD) followed by reperfusion, were used as an in vitro model of ischemia. The protective effects of catalpol were investigated in ischemic-induced apoptosis in PC12 cells. METHODS: After OGD for 3 hours and reoxygenation for 18 hours, cell survival was quantified by the reduction of 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT). The activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-PX) were determined using commercially available kits. Caspase-3 assay was performed using caspase-3 assay kit. Microplate reader was used to detect the intensities of rhodamine123 (Rh123) and reactive oxygen species (ROS). The level of Bcl-2 protein was measured by flow cytometry. RESULTS: Catalpol attenuated ischemia-induced apoptotic death via preventing the decrease in the level of Bcl-2 protein and the activities of SOD and GSH-PX, inhibiting the reduction of mitochondrial membrane potential and suppressing activation of caspase-3. DISCUSSION: The results suggest that the catalpol has the potential to prevent ischemic-induced apoptosis.

Electrically Pumped III-N Microcavity Light Emitters Incorporating an Oxide Confinement Aperture.

In this work, we report on electrically pumped III-N microcavity (MC) light emitters incorporating oxide confinement apertures. The utilized SiO2 aperture can provide a planar ITO design with a higher index contrast (~1) over other previously reported approaches. The fabricated MC light emitter with a 15-µm-aperture shows a turn-on voltage of 3.3 V, which is comparable to conventional light emitting diodes (LEDs), showing a good electrical property of the proposed structure. A uniform light output profile within the emission aperture suggesting the good capability of current spreading and current confinement of ITO and SiO2 aperture, respectively. Although the quality factor (Q) of fabricated MC is not high enough to achieve lasing action (~500), a superlinear emission can still be reached under a high current injection density (2.83 kA/cm2) at 77 K through the exciton-exciton scattering, indicating the high potential of this structure for realizing excitonic vertical-cavity surface-emitting laser (VCSEL) action or even polariton laser after fabrication optimization.

The Affinity of Elongated Membrane-Tethered Ligands Determines Potency of T Cell Receptor Triggering.

T lymphocytes are important mediators of adoptive immunity but the mechanism of T cell receptor (TCR) triggering remains uncertain. The interspatial distance between engaged T cells and antigen-presenting cells (APCs) is believed to be important for topological rearrangement of membrane tyrosine phosphatases and initiation of TCR signaling. We investigated the relationship between ligand topology and affinity by generating a series of artificial APCs that express membrane-tethered anti-CD3 scFv with different affinities (OKT3, BC3, and 2C11) in addition to recombinant class I and II pMHC molecules. The dimensions of membrane-tethered anti-CD3 and pMHC molecules were progressively increased by insertion of different extracellular domains. In agreement with previous studies, elongation of pMHC molecules or low-affinity anti-CD3 scFv caused progressive loss of T cell activation. However, elongation of high-affinity ligands (BC3 and OKT3 scFv) did not abolish TCR phosphorylation and T cell activation. Mutation of key amino acids in OKT3 to reduce binding affinity to CD3 resulted in restoration of topological dependence on T cell activation. Our results show that high-affinity TCR ligands can effectively induce TCR triggering even at large interspatial distances between T cells and APCs.

Identification of Escherichia coli β-glucuronidase inhibitors from Polygonum cuspidatum Siebold & Zucc

Abstract Gut bacterial β-glucuronidase (GUS) can reactivate xenobiotics that exert enterohepatic circulation- triggered gastrointestinal tract toxicity. GUS inhibitors can alleviate drug-induced enteropathy and improve treatment outcomes. We evaluated the inhibitory effect of Polygonum cuspidatum Siebold & Zucc. and its major constituents against Escherichia coli GUS (EcGUS), and characterized the inhibitory mechanism of each of the components. Trans-resveratrol 4'-O-β-D-glucopyranoside (HZ-1) and (-)-epicatechin gallate (HZ-2) isolated from P. cuspidatum were identified as the key components and potent inhibitors. These two components displayed strong to moderate inhibitory effects on EcGUS, with Ki values of 9.95 and 1.95 μM, respectively. Results from molecular docking indicated that HZ-1 and HZ-2 could interact with the key residues Asp163, Ser360, Ile 363, Glu413, Glu504, and Lys 568 of EcGUS via hydrogen bonding. Our findings demonstrate the inhibitory effect of P. cuspidatum and its two components on EcGUS, which supported the further evaluation and development of P. cuspidatum and its two active components as novel candidates for alleviating drug-induced damage in the mammalian gut.