L-Arginine and tetrahydrobiopterin supported nitric oxide production is crucial for the microbicidal activity of neutrophils

Recent report from this lab has shown role of Rac2 in the translocation of inducible nitric oxide synthase (iNOS) to the phagosomal compartment of polymorphonuclear leukocytes (PMNs) following phagocytosis of beads. This study was undertaken to further assess the status and role of tetrahydrobiopterin (BH₄), a redox-sensitive cofactor, L-arginine, and the substrate of nitric oxide synthase (NOS) in sustained nitric oxide (˙NO) production in killing of phagocytosed microbes (Escherichia coli) by human PMNs. Time-dependent study revealed consistent NO and reactive oxygen species (ROS) production in the PMNs following phagocytosis of beads. In addition, levels of L-arginine and BH₄ were maintained or increased simultaneously to support the enzymatic activity of NOS in the bead activated PMNs. Moreover, translocation of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX) subunits along with iNOS was reconfirmed in the isolated phagosomes. We demonstrate that increase in the level of NO was supported by L-arginine and BH₄ to kill E. coli, by using PMNs from NOS2^?/? mice, human PMNs treated with biopterin inhibitor, N-acetyl serotonin (NAS), or by suspending human PMNs in L-arginine deficient medium. Altogether, this study demonstrates that following phagocytosis, sustained. NO production in the PMNs was well-maintained by redox sensitive cofactor, BH₄ and substrate, and L-arginine to enable microbial killing. Further results suggest NO production in the human PMNs, along with ROS and myeloperoxidase (MPO) is important to execute antimicrobial activity.     

Energy transfer process in a rare earth (Ce3+, Dy3+, Sm3+)-doped nanocrystalline phosphate phosphor

This work presents the optimized luminescence spectra for the Ce³⁺,Sm³⁺-doped NaSrPO₄ phosphor that was synthesized using a wet chemical method. Ce³⁺ and Sm³⁺ are activator impurities that show spectral splitting bands that corresponds to the d–f and f–f transitions, respectively. These impurity elements shows the characteristics spectral bands when doped with the NaSrPO₄ host lattice. Spectral splitting in the Ce³⁺ excitation band was monitored in the 240–340 nm range, in which the observed bands were located at 269 nm, 292 nm and 321 nm, and emission bands were observed in the broad spectral range 330–430 nm. However, when Sm³⁺ ion was doped in the same host lattice we obtained a characteristic emission band at 590 and 645 nm in the orange–red region, under sharp excitation bands located at 345, 361, 375, and 403 nm respectively. Also, we carried out energy transfer analysis in the Ce³⁺/Dy³⁺-doped NaSrPO₄ phosphor. Further crystalline phase and the nanophase nature of the phosphor compound were confirmed using X-ray diffraction and transmission electron microscopy analyses.     

Human Semaphorin 3 Variants Link Melanocortin Circuit Development and Energy Balance

1. Download high-res image (164KB)
2. Download full-size image

     

Homology modeling of nematode Caenorhabditis elegans CED3 protein-inhibitor complex

CED3 protein, the product of a gene necessary for programmed cell death in the nematode Caenorhabditis elegans, is related to a highly specific cysteine protease family i.e., caspases. A tertiary-structural model has been constructed of a complex of the CED3 protein with tetrapeptide-aldehyde inhibitor, Ac-DEVD-CHO. The conformation of CED3 protein active site and the general binding features of inhibitor residues are similar to those observed in other caspases. The loop segment (Phe380-Pro387) binds with the P4 Asp in a different fashion compared to caspase-3. The comparative modeling of active sites from caspase-3 and CED3 protein indicated that although these enzymes require Asp at the position P4, variation could occur in the binding of this residue at the S4 subsite. This model allowed the definition of substrate specificity of CED3 protein from the structural standpoint and provided insight in designing of mutants for structure-function studies of this classical caspase homologue.     

Decreased expression of the pancreatic secretory trypsin inhibitor II gene during aging of the rat liver

The genetic constitution and differential gene expression of an organism play important roles in controlling the species-specific rate of aging and the maximum life span potential. We utilized a differential-display polymerase chain reaction technique to identify the age-dependent expression of genes in the rat liver. We demonstrate in this report, for the first time, that expression of the pancreatic secretory trypsin inhibitor II (PSTI-II) gene declines drastically during aging. We confirmed this decrease by Northern blot analysis. Low PSTI-II levels in aged animals might result in a lack of protection from prematurely activated trypsin-like proteases, which would thus enhance inflammation.Supported by funds from the Department of Biotechnology and by Research Fellowships (to H.P. and G.Z.) from the Council of Scientific and Industrial Research (Government of India).