Beulah H. Gray

Proteinase 3. A distinct human polymorphonuclear leukocyte proteinase that produces emphysema in hamsters.

Studies were designed to explore the possibility that human polymorphonuclear leukocyte granule constituents in addition to elastase (HLE) had the potential to cause emphysema. A two-step purification of three serine proteinases was developed. Granule extract proteins were initially separated by dye-ligand affinity chromatography. Fractions eluted were divided into four pools. Hamsters were given a single intratracheal instillation of saline +/- 0.1 mg protein of each pool. While pool 2 contained HLE and cathepsin G, the most dramatic bullous emphysema developed in animals treated with pool 4. The esterase from pool 4, designated proteinase 3 (PR-3) was purified, characterized in vitro, and tested for its ability to cause emphysema. PR-3 is a neutral serine proteinase with isoenzyme forms. Its ability to degrade elastin at pH 6.5 is slightly greater than that of HLE, but it is less active than HLE at pH 7.4 or 8.9. PR-3 has weak activity against azocasein. Its ability to degrade hemoglobin is intermediate to that of HLE and cathepsin G at pH 7.4. PR-3 has no activity against chromogenic substrates specific for HLE or cathepsin G. Its pI is substantially less than HLE or cathepsin G. It is also immunologically distinct from HLE. It induces emphysema in hamsters commensurate with that of HLE. We conclude that PR-3 may be important in the pathogenesis of human emphysema.

Peptide derivatives of three distinct lipopolysaccharide binding proteins inhibit lipopolysaccharide-induced tumor necrosis factor-alpha secretion in vitro

BACKGROUND Bactericidal permeability increasing protein (BPI), Limulus anti-lipopolysaccharide factor (LALF), and lipopolysaccharide binding protein (LBP) are three distinct proteins that bind to lipopolysaccharide (LPS). Intriguingly, binding of BPI and LALF to LPS results in neutralization of LPS activity, whereas the binding of LBP to LPS creates a complex that results in augmentation of LPS activity. Despite their different effector functions, we hypothesized that peptides based on the sequences of the proposed LPS-binding motif from each protein would neutralize LPS in vitro. METHODS Three peptide sequences, each 27 amino acids in length, of the proposed LPS-binding motif of BPI (BG38), LALF (BG42), and LBP (BG43) were synthesized. These peptides were then tested for their: (1) ability to inhibit macrophage secretion of TNF-alpha after stimulation by LPS derived from Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Serratia marcescens; and (2) bactericidal activity against these same four gram-negative bacteria in vitro. RESULTS Synthetic peptides BG38 (BPI-derived), BG42 (LALF-derived), and BG43 (LBP-derived) but not control peptide significantly inhibited LPS-induced tumor necrosis factor-alpha secretion by macrophages and mediated the lysis of gram-negative bacteria in vitro. In addition, preincubation of LPS with peptide BG38 mediated complete protection subsequent to lethal endotoxin challenge. CONCLUSIONS These data demonstrate that small peptides derived from BPI, LALF, and LBP retained significant endotoxin-neutralizing and bactericidal activity against many different gram-negative bacteria in vitro. Identification of this conserved LPS-binding region within each protein may aid in the development of new immunomodulatory reagents for use as adjuvant therapy in the treatment of gram-negative bacterial sepsis.

Designed β-sheet-forming peptide 33mers with potent human bactericidal/permeability increasing protein-like bactericidal and endotoxin neutralizing activities

Novel peptide 33mers have been designed by incorporating beta-conformation stabilizing residues from the beta-sheet domains of alpha-chemokines and functionally important residues from the beta-sheet domain of human neutrophil bactericidal protein (B/PI). B/PI is known for its ability to kill bacteria and to neutralize the action of bacterial endotoxin (lipopolysaccharide, LPS) which can induce septic shock leading to eventual death. Here, the goal was to make short linear peptides which demonstrate good beta-sheet folding and maintain bioactivity as in native B/PI. A library of 24 peptide 33mers (betapep-1 to betapep-24) were synthesized with various amino acid substitutions. CD and NMR data acquired in aqueous solution indicate that betapep peptides form beta-sheet structure to varying degrees and self-associate as dimers and tetramers like the alpha-chemokines. Bactericidal activity toward Gram-negative Pseudomonas aeruginosa was tested, and betapep-19 was found to be only about 5-fold less potent (62% kill at 1.2 x 10(-7) M) than native B/PI (80% kill at 2.9 x 10(-8) M). At LPS neutralization, betapep-2 and -23 were found to be most active (66-78% effective at 1.2 x 10(-6) M), being only about 50-100-fold less active than B/PI (50% at 1.5 x 10(-8) M). In terms of structure-activity relations, beta-sheet structural stability correlates with the capacity to neutralize LPS, but not with bactericidal activity. Although a net positive charge is necessary for activity, it is not sufficient for optimal activity. Hydrophobic residues tend to influence activities indirectly by affecting structural stability. Furthermore, results show that sequentially and spatially related residues from the beta-sheet domain of native B/PI can be designed into short linear peptides which show good beta-sheet folding and retain much of the native activity. This research contributes to the development of solutions to the problem of multiple drug-resistant, opportunistic microorganisms like P. aeruginosa and of agents effective at neutralizing bacterial endotoxin.

The regulation of aspartokinase inBacillus licheniformis

Abstract The specific activity of aspartokinase (ATP: l -aspartate 4-phosphotransferase, EC 2.7.2.4) decreases rapidly to a 10 to 20-fold lower level at the end of the growth phase in Bacillus licheniformis grown on a minimal glucose-salts medium. Concurrent with this decrease in specific activity is a loss of sensitivity to feedback inhibition by l -lysine and a slower decrease in the concerted inhibition caused by l -lysine and l -threonine. Growth of the cells in the minimal medium plus l -lysine and l -threonine caused the production of aspartokinase with characteristics similar to those of enzyme from cells harvested 4 h after the end of growth. Growth in the presence of either l -lysine or l -threonine did not affect the specific activity of the enzyme but did alter its inhibition sensitivity. The addition of l -lysine to the medium during growth on the minimal medium caused a rapid loss of sensitivity to lysine inhibition, 50% desensitization occurring in 15 min. These latter conditions did not produce an alteration in the specific activity of the enzyme or in the concerted inhibition by lysine and threonine. Despite the marked alteration in feedback-inhibition properties, changes in physical or kinetic properties of purified aspartokinase were not observed. Throughout the purification steps there was no evidence that more than one aspartokinase was present in B. licheniformis cells. It is concluded that this enzyme is unusually plastic and assumes alternate forms depending on the physiology of the cell.

Design of a potent novel endotoxin antagonist

BACKGROUND Bactericidal permeability increasing protein (BPI) binds to and neutralizes lipopolysaccharide (LPS, endotoxin). Small synthetic peptides based on the amino acid sequence of the LPS binding domain of BPI neutralize LPS, albeit inefficiently. Although the LPS binding domain of native BPI possesses a beta-turn secondary structure, this structure is not present in small derivative peptides. The purpose of this study was to determine whether the addition of a beta-turn to a BPI-derived peptide is associated with more potent endotoxin antagonism. METHODS We generated a hybrid peptide (BU3) on the basis of (1) a portion of the LPS binding domain from BPI and (2) amino acids known to initiate a beta-turn. BU3 folds with a beta-turn, and we tested its effects on LPS neutralization and LPS-induced tumor necrosis factor-alpha secretion, comparing it with BPI-derived peptide BG22 that lacks a beta-turn and to an irrelevant peptide (BG16). RESULTS Compared with BG22, BU3 demonstrated enhanced LPS neutralization and inhibition of LPS-induced tumor necrosis factor-alpha secretion in vitro and a similar diminution of endotoxemia and tumor necrosis factor-alpha secretion in a murine model of endotoxemia. CONCLUSIONS These data demonstrate the potential for enhancing the biologic activity of a BPI-derived peptide endotoxin antagonist via manipulation of its conformational structure.

Proteinase-free myeloperoxidase increases airway epithelial permeability in a whole trachea model.

In cystic fibrosis the bronchiectatic conducting airways have large numbers of neutrophils in their walls and in their luminal contents. The neutrophils primary granule enzyme activities of elastase and peroxidase are increased in the sputum of these patients. It has been postulated that these enzymes—together or individually—act to damage the airway epithelium. However, only peroxidase activity has consistently correlated with the degree of structural and functional airway disease in these patients with leakage of plasma protein into the airway lumen (Regelmann et al., Pediatr Pulmonol. 1995; 19: 1–9). The present study was designed to test whether human neutrophil‐derived myeloperoxidase can independently produce bronchial epithelial damage without the presence of proteases, as measured by increased permeability of the airway epithelium. Human peripheral blood neutrophils were purified, their primary granules isolated, and their peroxidase purified using affinity and ion exchange column chromatography. Activity of the proteinase‐free peroxidase was measured using a chromogenic substrate. The effect of this peroxidase on the permeability of excised rat tracheas was measured using radioactive and fluorescent‐labeled non‐ionic molecules of varying molecular weight.

Preparation and Characterization of a Monoclonal Antibody That Inhibits Human Neutrophil Elastase Activity

Neutrophil proteases are believed to play a role in the pathogenesis of a variety of human diseases. While many studies of proteases in models of disease have focused on elastase, neutrophils contain several proteases some of which share a high degree of homology. This report describes the production and characterization of an lgG1 murine monoclonal antibody (AHN‐10) that reacts with human neutrophil elastase but not with the other major neutrophil neutral proteases: cathepsin G, proteinase 3, collagenase, or the newly purified neutral protease, esterase N. AHN‐10 inhibited the elastinolytic activity of purified human neutrophil elastase and could detect elastase in alcohol‐fixed cytospin preparations. The epitope recognized by AHN‐10 was resistant to treatment with NaIO4, suggesting that the epitope is not a carbohydrate. AHN‐10 should be useful for the immunolocalization of neutrophil elastase in tissue specimens and as a stable source of characterized antibody for quantitative identification of neutrophil elastase.