A rapid microtiter plate method for the detection of lysozyme release from human neutrophils

Expression of functional recombinant human lysozyme in transgenic rice cell culture

Using particle bombardment-mediated transformation, a codon-optimized synthetic gene for human lysozyme was introduced into the calli of rice (Oryza sativa) cultivar Taipei 309. The expression levels of recombinant human lysozyme in the transformed rice suspension cell culture approached approximately 4% of total soluble protein. Recombinant human lysozyme was purified to greater than 95% homogeneity using a two-step chromatography process. Amino acid sequencing verified that the N-terminus of the mature recombinant human lysozyme was identical to native human lysozyme. This indicates that the rice RAmy3D signal peptide was correctly cleaved off from the human lysozyme preprotein by endogenous rice signal peptidase. Recombinant human lysozyme was found to have the same molecular mass, isoelectric point and specific activity as native human lysozyme. The bactericidal activity of recombinant human lysozyme was determined by turbidimetric assay using Micrococcus lysodeikticus in 96-well microtiter plates. The bactericidal activity of lysozyme on gram-negative bacteria was examined by adding purified lysozyme to mid-log phase cultures of E. coli strain JM109. In this study, significant bactericidal activity was observed after E. coli cells were exposed to recombinant human lysozyme for 60 min. Both native and recombinant human lysozyme displayed the same thermostability and resistance to degradation by low pH. The potential for using rice-derived lysozyme as an antimicrobial food supplement, particularly for infant formula and baby foods, is discussed.

Methods for quantitation of human neutrophil proteins, a survey

Neutrophils contain a variety of proteins that endow the cell with its capacity to migrate towards and eliminate microbial pathogens. Many of these proteins are largely or exclusively localized to neutrophils. It is therefore of interest to quantitate these proteins in a variety of clinical settings as well as in basic research. The aim of this survey is to give an introduction to some of the more commonly used methods for quantitation of neutrophil proteins and to discuss advantages and problems of the different methods and the relevance of quantitating neutrophil proteins in different biological settings.

Novel C5a Receptor Antagonists Regulate Neutrophil Functions In Vitro and In Vivo

Novel recombinant human C5a receptor antagonists were discovered through modification of the C terminus of C5a. The C5a1–71T1M,C27S,Q71C monomer, (C5aRAM; CGS 27913), was a pure and potent functional antagonist. The importance of a C-terminal cysteine at position 71 to antagonist properties of C5aRAM was confirmed by studying C5a1–71 derivatives with replacements of Q71, C5a derivatives of various lengths (70–74) with C-terminal cysteines, and C5a derivatives of various lengths (71–74) with Q71C replacements. The majority of C5a1–71Q71 derivatives were agonists (C5a-like) in the human neutrophil C5a-induced intracellular calcium mobilization assay. The C5a1–71Q71C derivative was an antagonist. C5a derivatives of lengths 73 and 74 with C-terminal cysteines were agonists, while lengths 70 to 72 were antagonists. C5a derivatives of lengths 72, 73, and 74 with Q71C replacements were agonists, while, again, C5a1–71Q71C was an antagonist. C5aRAM and its adducts, including its dimer, C5aRAD (CGS 32359), were pure antagonists. Additionally, C5aRAM and C5aRAD inhibited binding of 125I-labeled recombinant human C5a to neutrophil membranes (Ki = 79 and 2 pM, respectively), C5a-stimulated neutrophil intracellular calcium mobilization (8 and 13 nM), CD11b integrin up-regulation (10 and 1 nM), superoxide generation (182 and 282 nM), lysozyme release (1 and 2 μM), and chemotaxis (11 and 7 μM). In vivo, intradermal injection of C5aRAM inhibited C5a-induced dermal edema in rabbits. Furthermore, a 5-mg/kg i.v. bolus of C5aRAD significantly inhibited C5a-induced neutropenia in micropigs when challenged with C5a 30 min after C5aRAD administration. C5aRAM and C5aRAD are novel, potent C5a receptor antagonists devoid of agonist or proinflammatory activity with demonstrated efficacy in vitro and in vivo.

Lysozyme substrates

The natural substrate of lysozyme is the rigid layer of bacterial cell walls, the murein (peptidoglycan), which is a gigantic polymer of (GlcNAc-MurNAc)n polysaccharide strands crosslinked through short peptide bridges at the lactyl groups of the muramic acid residues. Thus, lysozyme lyses bacteria by degrading their protective exoskeleton, the murein sacculus. The high molecular weight murein is thereby hydrolysed to low molecular weight muropeptides, a process that can be followed quantitatively by different methods. However, due to the insolubility of the murein sacculus, the enzyme kinetics are rather complex. Therefore, a variety of different low molecular weight substrates have been prepared, both murein degradation products and synthetic compounds. These substrates allow a better characterization of the binding and catalytic mechanism of lysozyme. In addition, they are used in various photometric, isotopic and immunological lysozyme assays.