Targeting prolyl endopeptidase with valproic acid as a potential modulator of neutrophilic inflammation.

A novel neutrophil chemoattractant derived from collagen, proline-glycine-proline (PGP), has been recently characterized in chronic obstructive pulmonary disease (COPD). This peptide is derived via the proteolytic activity of matrix metalloproteases (MMP's)-8/9 and PE, enzymes produced by neutrophils and present in COPD serum and sputum. Valproic acid (VPA) is an inhibitor of PE and could possibly have an effect on the severity of chronic inflammation. Here the interaction site of VPA to PE and the resulting effect on the secondary structure of PE is investigated. Also, the potential inhibition of PGP-generation by VPA was examined in vitro and in vivo to improve our understanding of the biological role of VPA. UV-visible, fluorescence spectroscopy, CD and NMR were used to determine kinetic information and structural interactions between VPA and PE. In vitro, PGP generation was significantly inhibited by VPA. In vivo, VPA significantly reduced cigarette-smoke induced neutrophil influx. Investigating the molecular interaction between VPA and PE showed that VPA modified the secondary structure of PE, making substrate binding at the catalytic side of PE impossible. Revealing the molecular interaction VPA to PE may lead to a better understanding of the involvement of PE and PGP in inflammatory conditions. In addition, the model of VPA interaction with PE suggests that PE inhibitors have a great potential to serve as therapeutics in inflammatory disorders.

Cigarette smoke enhances chemotaxis via acetylation of proline-glycine-proline.

Several chronic lung diseases have been linked to cigarette smoking (Chronic Obstructive Pulmonary Disease (COPD), and cancer are associated with increased tobacco use). We recently described a collagen fragment, proline-glycine-proline (PGP), chemotactic for neutrophils, that appears to play a role in COPD, cystic fibrosis, and bronchiolitis obliterans syndrome. PGP can exist in either its native or acetylated form (NAcPGP), although the mechanism of N-terminal-acetylation remains unknown. This work investigates the possibility that cigarette smoke (CS) and its components acetylate PGP, describing a possible mechanism for some of the chronic inflammation seen in tobacco-associated disease. CSE and CSC (3.56 and 12.38 ng/ml NAcPGP respectively, p less than 0.01) and its components (acrolein, acetaldehyde, and methyl glyoxal) acetylated PGP (0.51, 1.03, and 0.23 ng/ml NAcPGP, p less than 0.01). Both N-acetyl-cysteine and carbocysteine (scavengers of reactive aldehydes) blocked chemical acetylation of PGP by CS (100 percent and 97 percent inhibition, respectively, p less than 0.01). NAcPGP is more chemoattractive to neutrophils, and less susceptible to degradation by Leukotriene-A4-Hydrolase (detected in the lung). These experiments propose a mechanism for the increased neutrophil recruitment seen in smoking-associated lung diseases.

Proline-glycine-proline as a potential biomarker in chronic obstructive pulmonary disease and cystic fibrosis.

The present review discusses the role of tri-peptide Proline -Glycine -Proline (PGP) as a potential player, biomarker and therapeutic target in this process.

Molecular recognition theory and sense-antisense interaction: therapeutic applications in autoimmunity.

Perhaps behind only the understanding of the genetic code in importance is the comprehension of protein sequence and structure in its effect on modern scientific investigation. How proteins are structured and interact dictates a considerable amount of the body's processes in maintaining homeostasis. Unfortunately, in diseases of autoimmunity, these processes are directed against the body itself and most of the current clinical responses are severely lacking. This review addresses current therapeutics involved in the treatment of various autoimmune diseases and details potential future therapeutics designed with a more targeted approach. Detailed in this manuscript is the concept of utilizing peptides possessing an inverse hydropathy to the immunogenic region of proteins to generate anti-idiotypic (anti-Id) and anti-clonotypic T cell receptor (TCR) antibodies (Abs). Theoretically, the anti-Id Abs cross react with Id Abs and negate the powerful machinery of the adaptive immune response with little to no side effects. A series of studies by a number of groups have shown this to be an exciting and intriguing concept that will likely play a role in the future treatment of autoimmune diseases.

A self-propagating matrix metalloprotease-9 (MMP-9) dependent cycle of chronic neutrophilic inflammation.

BACKGROUND: Chronic neutrophilic inflammation is a poorly understood feature in a variety of diseases with notable worldwide morbidity and mortality. We have recently characterized N-acetyl Pro-Gly-Pro (Ac-PGP) as an important neutrophil (PMN) chemoattractant in chronic inflammation generated from the breakdown of collagen by the actions of MMP-9. MMP-9 is present in the granules of PMNs and is differentially released during inflammation but whether Ac-PGP contributes to this ongoing proteolytic activity in chronic neutrophilic inflammation is currently unknown. METHODOLOGY/PRINCIPAL FINDINGS: Utilizing isolated primary blood PMNs from human donors, we found that Ac-PGP induces significant release of MMP-9 and concurrently activates the ERK1/2 MAPK pathway. This MMP-9 release is attenuated by an inhibitor of ERK1/2 MAPK and upstream blockade of CXCR1 and CXCR2 receptors with repertaxin leads to decreased MMP-9 release and ERK 1/2 MAPK activation. Supernatants obtained from PMNs stimulated by Ac-PGP generate more Ac-PGP when incubated with intact collagen ex vivo; this effect is inhibited by an ERK1/2 pathway inhibitor. Finally, clinical samples from individuals with CF demonstrate a notable correlation between Ac-PGP (as measured by liquid chromatography-tandem mass spectrometry) and MMP-9 levels even when accounting for total PMN burden. CONCLUSIONS/SIGNIFICANCE: These data indicate that ECM-derived Ac-PGP could result in a feed-forward cycle by releasing MMP-9 from activated PMNs through the ligation of CXCR1 and CXCR2 and subsequent activation of the ERK1/2 MAPK, highlighting for the first time a matrix-derived chemokine (matrikine) augmenting its generation through a discrete receptor/intracellular signaling pathway. These findings have notable implications to the development unrelenting chronic PMN inflammation in human disease.

Human neutrophil elastase-mediated cleavage sites of MMP-9 and TIMP-1: implications to cystic fibrosis proteolytic dysfunction.

Cystic fibrosis (CF) is a lethal genetic disorder characterized by airway remodeling and inflammation, leading to premature death. Recent evidence suggests the importance of protease activity in CF pathogenesis. One prominent protease, matrix metalloprotease (MMP)-9, demonstrates increased activity in CF individuals undergoing acute pulmonary exacerbation. This is thought to be mediated by both direct MMP-9 activation and the degradation of its natural inhibitor, tissue inhibitor of metalloprotease-1 (TIMP-1). To examine if this relationship exists in nonexacerbating CF individuals, we examined protease activity in sputum from these individuals compared with nondisease controls. We demonstrated increased gelatinolytic activity in CF sputum. These samples had elevated human neutrophil elastase (HNE) levels which correlated with an increased MMP-9/TIMP-1 ratio. To determine if HNE could discretely cleave and activate MMP-9, these enzymes were coincubated and two specific cleavage sites, between Valine(38) and Alanine(39), and between Alanine (39) and glutamic acid(40) were observed. These sites corresponded with appropriate molecular weight for the activated MMP-9 isoform in CF sputum. Using N-terminal sequencing of cleavage fragments obtained with TIMP-1 incubation with HNE, we confirmed the TIMP-1 cleavage site for HNE is at Valine(69)-Cysteine(70). We also show for the first time that human neutrophils were capable of degrading TIMP-1 ex vivo and that a 16 kDa TIMP-1 fragment was identified in CF sputum, consistent with the expected cleavage of TIMP-1 by HNE. These results demonstrate increased MMP-9 activity in stable CF lung disease, and the presence of specific protease products in CF sputum highlights that HNE-mediated activity plays a role in this dysregulation.