Causal Role for Neutrophil Elastase in Thoracic Aortic Dissection in Mice.

BACKGROUND: Thoracic aortic dissection (TAD) is a life-threatening aortic disease without effective medical treatment. Increasing evidence has suggested a role for NE (neutrophil elastase) in vascular diseases. In this study, we aimed at investigating a causal role for NE in TAD and exploring the molecular mechanisms involved. METHODS: ß-aminopropionitrile monofumarate was administrated in mice to induce TAD. NE deficiency mice, pharmacological inhibitor GW311616A, and adeno-associated virus-2-mediated in vivo gene transfer were applied to explore a causal role for NE and associated target gene in TAD formation. Multiple functional assays and biochemical analyses were conducted to unravel the underlying cellular and molecular mechanisms of NE in TAD. RESULTS: NE aortic gene expression and plasma activity was significantly increased during ß-aminopropionitrile monofumarate-induced TAD and in patients with acute TAD. NE deficiency prevents ß-aminopropionitrile monofumarate-induced TAD onset/development, and GW311616A administration ameliorated TAD formation/progression. Decreased levels of neutrophil extracellular traps, inflammatory cells, and MMP (matrix metalloproteinase)-2/9 were observed in NE-deficient mice. TBL1x (F-box-like/WD repeat-containing protein TBL1x) has been identified as a novel substrate and functional downstream target of NE in TAD. Loss-of-function studies revealed that NE mediated inflammatory cell transendothelial migration by modulating TBL1x-LTA4H (leukotriene A4 hydrolase) signaling and that NE regulated smooth muscle cell phenotype modulation under TAD pathological condition by regulating TBL1x-MECP2 (methyl CpG-binding protein 2) signal axis. Further mechanistic studies showed that TBL1x inhibition decreased the binding of TBL1x and HDAC3 (histone deacetylase 3) to MECP2 and LTA4H gene promoters, respectively. Finally, adeno-associated virus-2-mediated Tbl1x gene knockdown in aortic smooth muscle cells confirmed a regulatory role for TBL1x in NE-mediated TAD formation. CONCLUSIONS: We unravel a critical role of NE and its target TBL1x in regulating inflammatory cell migration and smooth muscle cell phenotype modulation in the context of TAD. Our findings suggest that the NE-TBL1x signal axis represents a valuable therapeutic for treating high-risk TAD patients.

Inhibition of host- and bacteria-derived proteinases by natural anthocyanins.

BACKGROUND AND OBJECTIVES: Host- and bacteria-derived proteinases are considered to play critical roles in periodontitis progression. This study investigated the ability of a blackcurrant extract and its major anthocyanins (cyanidin-3-O-glucoside, cyanidin-3-O-rutinoside and delphinidin-3-O-rutinoside) to inhibit the activity of matrix metalloproteinases (MMPs), neutrophil elastase and periodontopathogen (Porphyromonas gingivalis, Tannerella forsythia and Treponema denticola) proteinases. MATERIAL AND METHODS: Enzyme inhibition was detected using fluorometric and colorimetric assays after incubating blackcurrant extract and its major anthocyanins (at concentrations of 6.25, 12.5, 25 and 50 µg/mL) with MMPs, elastase or bacterial proteinases, along with their specific substrates. Substrate degradation was recorded every hour for up to 4 h. RESULTS: The blackcurrant extract (50 µg/mL) inhibited all proteinases tested. MMP-1 and MMP-9 were significantly inhibited by pure anthocyanins at concentrations ranging from 6.25 to 50 µg/mL. Elastase activity was inhibited by cyanidin-3-O-glucoside and cyanidin-3-O-rutinoside in the range of 6.25-50 µg/mL and by delphinidin-3-O-rutinoside at 50 µg/mL. P. gingivalis, T. forsythia and T. denticola proteinases were also significantly inhibited by pure anthocyanins. In all cases, enzyme inhibition was time-dependent. CONCLUSION: Our study showed that a blackcurrant extract and its major anthocyanins were able to inhibit the activity of host- and bacteria-derived proteinases. This suggests that such natural compounds may represent promising agents for use in adjunctive treatments for periodontitis.

Inhibition of proteasome by bortezomib causes intracellular aggregation of hepatic serpins and increases the latent circulating form of antithrombin.

Conformational diseases include heterogeneous disorders sharing a similar pathological mechanism, leading to intracellular aggregation of proteins with toxic effects. Serpins are commonly involved in these diseases. These are structurally sensitive molecules that modify their folding under even minor genetic or environmental variations. Indeed, under normal conditions, the rate of misfolding of serpins is high and unfolded serpins must be degraded by the proteasome system. Our aim was to study the effects of bortezomib, a proteasome inhibitor, on conformationally sensitive serpins. The effects of bortezomib were analysed in patients with multiple myeloma, HepG2 cells, and Swiss mice, as well as in vitro. Levels, anti-FXa activity, heparin affinity, and conformational features of antithrombin, a relevant anticoagulant serpin, were analysed. Histological, ultrastructural features and immunohistological distribution of antithrombin and alpha1-antitrypsin (another hepatic serpin) were evaluated. We also studied the intracellular accumulation of conformationally sensitive (fibrinogen) or non-sensitive (prothrombin) hepatic proteins. The inhibition of the proteasome caused intracellular accumulation and aggregation of serpins within the endoplasmic reticulum that was associated with confronting cisternae and Mallory body formation. These effects were accompanied by a heat stress response. Bortezomib also increased the levels of intracellular fibrinogen, but has no significant effect on prothrombin. Finally, bortezomib had only minor effects on the mature circulating antithrombin, with increased amounts of latent antithrombin in plasma. These results suggest that the impairment of proteasomal activities leads to an intracellular accumulation of conformationally sensitive proteins and might facilitate the release of misfolded serpins into circulation where they adopt more stable conformations.

Relationship between neutrophil elastase and acute lung injury in humans.

We conducted clinical trials in patients with acute lung injury (ALI) associated with systemic inflammatory response syndrome using a selective neutrophil elastase inhibitor, sivelestat sodium hydrate (Sivelestat), to investigate the involvement of neutrophil elastase in ALI. In the phase III double-blind study (Study 1) in 230 patients, the efficacy of Sivelestat was evaluated with the pulmonary function improvement (PFI) rating as the primary endpoint, and the weaning rate from mechanical ventilator, the discharge rate from intensive care unit (ICU), and the survival rate as secondary endpoints. Afterwards, an unblinded study (Study 2) in 20 patients was conducted using procedures for weaning from mechanical ventilation to reevaluate its efficacy with ventilator-free days (VFD) value, the primary endpoint, and to compare with that of Study 1 subgroup, which met the selection criteria used in Study 2. Sivelestat increased PFI rating, reduced duration of mechanical ventilation, and shortened stay in ICU in Study 1, although there was no significant efficacy on the survival rate. VFD value in Study 2 was comparable to that in the optimal-dose group of Study 1 subgroup, and increase in VFD value correlated with PFI rating and increase in ICU free days. It was concluded that neutrophil elastase may be involved in the pathogenesis of ALI in humans.

Proteases and lung injury.

OBJECTIVE: Acute respiratory distress syndrome (ARDS) represents an inflammatory process that is initiated by diverse systemic and/or pulmonary insults, resulting in a clinical syndrome of severe respiratory distress and refractory hypoxemia. Neutrophils and their cytotoxic products, including oxidants and proteases, such as elastase, have been implicated as playing a key role in the pathophysiology of ARDS. This article reviews some of the physiologic actions of proteases, specifically elastase, the evidence for neutrophil elastase involvement in ARDS, and the potential therapeutic use of neutrophil elastase inhibitors in lung injury. DATA SOURCE: A review of published literature (original articles and reviews) in English from 1965 to 2002. CONCLUSION: Although the data support a key role for neutrophil elastase in the pathogenesis of ARDS, further study is needed to fully define the actions of neutrophil elastase, and how these actions affect host functions, before we can exploit this knowledge for therapeutic benefit.

The role of neutrophil elastase in acute lung injury.

Beside its physiological function as a powerful host defense, neutrophil elastase is also known as one of the most destructive enzymes in the body. Current notion holds that neutrophil elastase is able to escape from regulation by multiple protease inhibitors at inflammatory sites. Once unregulated, this enzyme disturbs the function of the lung permeability barrier and induces the release of pro-inflammatory cytokines. These actions then cause symptoms that are typical in the pathophysiology of acute lung injury. In this article, we review recent progress in the understanding of the physiological activity of neutrophil elastase and its role in acute lung injury. Evidence in this review that supports the involvement of neutrophil elastase in the pathophysiology of acute lung injury includes: (1) neutrophil elastase levels are increased in both clinical and animal models of acute lung injury; (2) topical or systemic administration of neutrophil elastase produces typical symptoms of acute lung injury both in vitro and in vivo; and (3) inhibition of increased neutrophil elastase activity reduces symptoms of acute lung injury in animal models. A greater understanding of the role of this enzyme in the pathophysiology of acute lung injury will lead to better treatments for this complicated disease.

A novel oral neutrophil elastase inhibitor (ONO-6818) inhibits human neutrophil elastase-induced emphysema in rats.

We investigated the effects of a novel oral neutrophil elastase inhibitor (ONO-6818) on acute lung injury and pulmonary emphysema induced by human neutrophil elastase (HNE). Young male Wistar rats were divided into four treatment groups: (1) control group (saline); (2) HNE group (HNE 200 U + 0.5% carboxymethyl-cellulose [solution for ONO-6818]); (3) low-dose ONO-6818 group (HNE 200 U + ONO-6818 10 mg/kg); and (4) high-dose ONO-6818 group (HNE 200 U + ONO-6818 100 mg/kg). Saline and HNE were applied via the trachea using a microsprayer. ONO-6818 was administered orally 1 hour before HNE application. Six hours after HNE application, neutrophil counts and hemoglobin concentration in bronchoalveolar lavage fluid and lung tissue myeloperoxidase activity were determined. Eight weeks after the application, FRC, TLC, lung compliance, and mean linear intercept were estimated. ONO-6818 attenuated dose-dependently HNE-induced increases in lung myeloperoxidase activity, hemoglobin, and neutrophil count in bronchoalveolar lavage fluid. Furthermore, it significantly attenuated HNE-induced increases in FRC, TLC, lung compliance, and mean linear intercept. ONO-6818 inhibited acute lung injury induced by HNE by minimizing lung hemorrhage and accumulation of neutrophils in the lung. ONO-6818 also inhibited the development of HNE-induced emphysematous changes including lung hyperinflation, degradation of elastic recoil, and airspace enlargement.

Neutrophil elastase and acute lung injury: prospects for sivelestat and other neutrophil elastase inhibitors as therapeutics.

OBJECTIVES: To review the evidence and rationale that suggest that neutrophil elastase (NE) may contribute to the development of acute lung injury (ALI) and the acute respiratory distress syndrome. To review selected preliminary data regarding the effectiveness of NE inhibition in animals, in in vitro models, and in patients with ALI. DATA SOURCES: The published literature and observations provided by Ono Pharmaceutical and Eli Lilly investigators and their colleagues. DATA SUMMARY: Taken en toto, the data suggest that NE could contribute to ALI and endothelial cell injury that is relevant to ALI. Moreover, the toxic effects of NE are greatly enhanced by increased oxidative stress, which commonly occurs in patients with ALI. In addition to neutrophils, xanthine oxidase, a constituent of endothelial cells, is a potential source of oxidative stress in ALI; xanthine oxidase-derived oxidants enhance NE toxicity in in vivo, isolated lung, and in vitro endothelial cell test systems. Not surprisingly, endogenous nonoxidatively sensitive NE inhibitors (e.g., eglin C) are more effective in combating the detrimental effects of NE than oxidatively sensitive NE inhibitors (e.g., alpha-1-proteinase inhibitor). In addition, a synthetic NE inhibitor, sivelestat (ONO-5046 and LY544349), is effective in reducing measures of inflammation and injury in multiple animal models of ALI. In a trial of ALI patients with systemic inflammatory response syndrome, conducted in Japan by Ono Pharmaceutical scientists, sivelestat treatment improved the investigator assessment of global improvement and the percentages of patients who were removed from ventilators and transferred out of the intensive care unit. CONCLUSIONS: Further study of the role of NE inhibition as a treatment for ALI is warranted. Additional clinical and preclinical studies with sivelestat and various other NE inhibitors should not only clarify the clinical potential of this intervention strategy, but also better define the activities of NE in inflammatory disorders such as ALI and multiple organ failure.

Polymorphonuclear leukocyte elastase in patients with stroke.

INTRODUCTION/OBJECTIVES: Polymorphonuclear leukocytes (PMNL) are involved in the pathogenesis of acute cerebral ischemia and atherosclerosis. Elastase is one of the proteolytic enzymes released by activated PMNL. We evaluated whether plasma levels of elastase-inhibitor complexes (EIC) are related to acute cerebral damage or with extension of carotid atherosclerosis in patients with stroke. METHODS: Plasma levels of EIC were determined in 44 patients during acute and chronic phases of stroke. We recorded in all patients vascular risk factors, clinical severity on admission, infarct volume, and extension of carotid atherosclerosis using B-mode ultrasound exam. RESULTS: EIC levels were not different between acute and chronic phases of stroke. Eleven patients (25%) had increased values of EIC. On multiple regression analysis diabetes, dislipemia, and coronary disease were predictors of abnormal EIC levels. EIC levels were not related to neurological severity on admission, infarct volume, or carotid atherosclerosis. CONCLUSION: EIC levels in stroke patients are associated to the presence of vascular risk factors and may reflect cellular inflammatory aspects of chronic vessel disease. However, whether elastase contributes to the development of carotid atherosclerosis in patients with stroke remains unknown.