Proteolytic inactivation of alpha-1-antitrypsin by human neutrophils: involvement of multiple and interlinked cell responses to phagocytosable targets

Acute-phase protein α1-anti-trypsin: diverting injurious innate and adaptive immune responses from non-authentic threats

One would assume that the anti-inflammatory activity of α1-anti-trypsin (AAT) is the result of inhibiting neutrophil enzymes. However, AAT exhibits tolerogenic activities that are difficult to explain by serine-protease inhibition or by reduced inflammatory parameters. Targets outside the serine-protease family have been identified, supporting the notion that elastase inhibition, the only functional factory release criteria for clinical-grade AAT, is over-emphasized. Non-obvious developments in the understanding of AAT biology disqualify it from being a straightforward anti-inflammatory agent: AAT does not block dendritic cell activities, nor does it promote viral and tumour susceptibilities, stunt B lymphocyte responses or render treated patients susceptible to infections; accordingly, outcomes of elevated AAT do not overlap those attained by immunosuppression. Aside from the acute-phase response, AAT rises during the third trimester of pregnancy and also in advanced age. At the molecular level, AAT docks onto cholesterol-rich lipid-rafts and circulating lipid particles, directly binds interleukin (IL)-8, ADAM metallopeptidase domain 17 (ADAM17) and danger-associated molecular pattern (DAMP) molecules, and its activity is lost to smoke, high glucose levels and bacterial proteases, introducing a novel entity - 'relative AAT deficiency'. Unlike immunosuppression, AAT appears to help the immune system to distinguish between desired responses against authentic threats, and unwanted responses fuelled by a positive feedback loop perpetuated by, and at the expense of, inflamed injured innocent bystander cells. With a remarkable clinical safety record, AAT treatment is currently tested in clinical trials for its potential benefit in a variety of categorically distinct pathologies that share at least one common driving force: cell injury.

Carotenoid derived aldehydes-induced oxidative stress causes apoptotic cell death in human retinal pigment epithelial cells

Carotenoids have been advocated as potential therapeutic agents in treating age-related macular degeneration (AMD). In ocular tissues carotenoids may undergo oxidation and form carotenoid-derived aldehydes (CDA), which would be toxic to tissues. We have investigated the cytotoxic effects of CDA from beta-carotene, Lutein and Zeaxanthin on human retinal pigment epithelial cells (ARPE-19). The serum-starved ARPE-19 cells were treated with CDA without or with antioxidant, N-acetylcysteine (NAC) and cell viability, apoptosis, reactive oxygen species (ROS) levels, nuclear chromatin condensation as well as fragmentation, change in mitochondrial membrane potential (MMP) and activation of transcription factors NF-kappaB and AP-1 were determined. We observed a dose and time-dependent decline in cell viability upon incubation of ARPE-19 cells with CDA. The CDA treatment also led to elevation in ROS levels in a dose-dependent manner. Upon CDA treatment a significant number of apoptotic cells were observed. Also early apoptotic changes in ARPE-19 cells induced by CDA were associated with change in MMP. Increased nuclear chromatin condensation and fragmentation were also observed in cells treated with CDA. The cytotoxicity of CDA in ARPE-19 cells was significantly ameliorated by the antioxidant, NAC. Furthermore, CDA induced the activation of NF-kappaB and AP-1 which was significantly inhibited by NAC. Thus our results demonstrate that CDA could increase the oxidative stress in ARPE-19 cells by elevating ROS levels that would cause imbalance in cellular redox status, which could lead to cell death. This would suggest that high carotenoid supplementation for treatment of AMD should be used cautiously.

Pathogenetic mechanisms in usual interstitial pneumonia/idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive, usually fatal, form of interstitial lung disease characterized by failure of alveolar re-epithelialization, persistence of fibroblasts/myofibroblasts, deposition of extracellular matrix, and distortion of lung architecture which ultimately results in respiratory failure. Clinical IPF is associated with a histopathological pattern of usual interstitial pneumonia (UIP) on surgical lung biopsy. Therapy for this disease with glucocorticoids and other immunomodulatory agents is largely ineffective and recent trials of newer anti-fibrotic agents have been disappointing. While the inciting event(s) leading to the initiation of scar formation in UIP remain unknown, recent advances in our understanding of the mechanisms underlying both normal and aberrant wound healing have shed some light on pathogenetic mechanisms that may play significant roles in this disease. Unlike other fibrotic diseases of the lung, such as those associated with collagen vascular disease, occupational exposure, or chemotherapeutic agents, UIP is not associated with a significant inflammatory response; rather, dysregulated epithelial-mesenchymal interactions predominate. Identification of pathways crucial to fibrogenesis might offer potentially novel therapeutic targets to slow or halt the progression of IPF. This review focuses on evolving concepts of cellular and molecular mechanisms in the pathogenesis of UIP/IPF.

Recombinant alpha 1-proteinase inhibitor blocks antigen- and mediator-induced airway responses in sheep

Alpha(1)-proteinase inhibitor (alpha(1)-PI) is a natural serine protease inhibitor. Although mainly thought to protect the airways from neutrophil elastase, alpha(1)-PI may also regulate the development of airway hyperresponsiveness (AHR), as indicated by our previous findings of an inverse relationship between lung alpha(1)-PI activity and the severity of antigen-induced AHR. Because allergic stimulation of the airways causes release of elastase, tissue kallikrein, and reactive oxygen species (ROS), all of which can reduce alpha(1)-PI activity and contribute to AHR, we hypothesized that administration of exogenous alpha(1)-PI should protect against pathophysiological airway responses caused by these agents. In untreated allergic sheep, airway challenge with elastase, xanthine/xanthine oxidase (which generates ROS), high-molecular-weight kininogen, the substrate for tissue kallikrein, and antigen resulted in bronchoconstriction. ROS and antigen also induced AHR to inhaled carbachol. Treatment with 10 mg of recombinant alpha(1)-PI (ralpha(1)-PI) blocked the bronchoconstriction caused by elastase, high-molecular-weight kininogen, and ROS, and the AHR induced by ROS and antigen. One milligram of ralpha(1)-PI was ineffective. These are the first in vivo data demonstrating the effects of ralpha(1)-PI. Our results are consistent with and extend findings obtained with human plasma-derived alpha(1)-PI and suggest that alpha(1)-PI may be important in the regulation of airway responsiveness.

Ambroxol inhibits peroxynitrite-induced damage of alpha1-antiproteinase and free radical production in activated phagocytic cells

The present study examined the effect of ambroxol on toxic action of peroxynitrite and the respiratory burst in activated phagocytic cells. Ambroxol decreased the inactivation or destruction of alpha1-antiproteinase induced by peroxynitrite (ONOO-) or hypochlorous acid (HOCl), which was similar to penicillamine and glutathione and was greater than diclofenac sodium and naproxen sodium. Ambroxol significantly decreased ONOO--mediated tyrosine nitration and iron plus EDTA-mediated degradation of 2-deoxy-D-ribose. Ambroxol significantly attenuated the production of superoxide, hydrogen peroxide, HOCl, and nitric oxide in fMLP- or IL-1-activated phagocytic cells, while the inhibitory effects of antiinflammatory and thiol compounds were only observed in HOCl production. Ambroxol and antiinflammatory drugs did not show a cytotoxic effect on macrophages. The results suggest that ambroxol protects tissue components against oxidative damage by an action different from antiinflammatory drugs. Ambroxol may interfere with oxidative damage of alpha1-antiproteinase through a scavenging action on ONOO- and HOCl and inhibition of the respiratory burst of phagocytic cells.

The profibrinolytic enzyme subtilisin NAT purified from Bacillus subtilis Cleaves and inactivates plasminogen activator inhibitor type 1

In this report, we demonstrate an interaction between subtilisin NAT (formerly designated BSP, or nattokinase), a profibrinolytic serine proteinase from Bacillus subtilis, and plasminogen activator inhibitor 1 (PAI-1). Subtilisin NAT was purified to homogeneity (molecular mass, 27.7 kDa) from a saline extract of B. subtilis (natto). Subtilisin NAT appeared to cleave active recombinant prokaryotic PAI-1 (rpPAI-1) into low molecular weight fragments. Matrix-assisted laser desorption/ionization in combination with time-of-flight mass spectroscopy and peptide sequence analysis revealed that rpPAI-1 was cleaved at its reactive site (P1-P1': Arg(346)-Met(347)). rpPAI-1 lost its specific activity after subtilisin NAT treatment in a dose-dependent manner (0.02-1.0 nm; half-maximal effect at approximately 0.1 nm). Subtilisin NAT dose dependently (0.06-1 nm) enhanced tissue-type plasminogen activator-induced fibrin clot lysis both in the absence of rpPAI-1 (48 +/- 1.4% at 1 nm) and especially in the presence of rpPAI-1 (78 +/- 2.0% at 1 nm). The enhancement observed in the absence of PAI-1 seems to be induced through direct fibrin dissolution by subtilisin NAT. The stronger enhancement by subtilisin NAT of rpPAI-1-enriched fibrin clot lysis seems to involve the cleavage and inactivation of active rpPAI-1. This mechanism is suggested to be important for subtilisin NAT to potentiate fibrinolysis.

P-Selectin expression, platelet aggregates, and platelet-derived microparticle formation are increased in peripheral arterial disease

Platelet volume has been reported to be increased in vascular disease. Therefore, we studied the relationship of mean platelet volume and platelet count as well as flow cytometrically measured platelet size and platelet function in 50 patients with peripheral arterial disease and 50 healthy volunteers. Platelet activation was measured by P-selectin expression analysis on resting and on stimulated platelets, and the determination of platelet aggregates and platelet-derived microparticles using flow cytometry. P-Selectin expression on platelets was significantly elevated in patients suffering from peripheral arterial disease (all P<0.0001). Platelet aggregates (P<0.0001) and platelet-derived microparticles (P<0.0001) were significantly higher in the patient group compared with controls, whereas mean platelet volume and platelet count showed no significant differences. Platelet count was inversely related to mean platelet volume in patients and controls (r = -0.43, P<0.001). The present study supports the hypothesis of platelet hyperreactivity and circulating activated platelets in peripheral arterial disease. Mean platelet volume, and platelet count cannot be used as predictive markers for platelet activation in peripheral arterial disease patients.

The inhibitory effect of ambroxol on hypochlorous acid-induced tissue damage and respiratory burst of phagocytic cells

Ambroxol (100 microM and 1 mM) and the thiols (all 1 mM), glutathione, tiopronin and cysteine, significantly attenuated the myeloperoxidase, H(2)O(2) and Cl(-) system-caused destruction of alpha(1)-antiproteinase and the HOCl-induced destruction of collagen, whereas they did not affect the elastase-induced destruction of collagen. Glutathione, tiopronin and cysteine almost completely decomposed both HOCl and H(2)O(2), while ambroxol up to 1 mM did not show a scavenging action on H(2)O(2). Ambroxol (1 to 100 microM) and 1 mM thiol compounds markedly inhibited the HOCl-induced alteration of elastase activity. Thiol compounds significantly attenuated the HOCl production caused by degraded immunoglobulin G-activated neutrophils. Ambroxol depressed superoxide and H(2)O(2) production induced by degraded immunoglobulin G-activated neutrophils and by lipopolysaccharide-activated alveolar macrophages in a dose-dependent manner. The results show that ambroxol may interfere with oxidative tissue damage and decrease proteolytic tissue destruction by attenuation of oxidative stress-induced inactivation of alpha(1)-antiproteinase through both decomposition of HOCl and inhibition of the respiratory burst in phagocytic cells.

Neutrophil dysfunction and increased susceptibility to infection

A critical evaluation of 3 years' experience using laboratory screening to detect neutrophil dysfunction is described. Neutrophil dysfunctions in patients with recurrent bacterial infections were investigated by using the following screening tests: (1) neutrophil chemotaxis towards N-formylmethionyl peptides (FMLP) and the complement fragment C5a; (2) neutrophil production of superoxide anions (O2-) in response to phorbol myristate acetate and opsonized zymosan particles; and (3) examination of May-Grünwald and myeloperoxidase cytochemical staining of peripheral blood smears. These tests were carried out in 100 patients suffering from infections and suspected of having altered neutrophil functional competence. A minority of patients was found to have well defined neutrophil dysfunction syndromes: chronic granulomatous disease (four cases), Chediak-Higashi disease (one case) and myeloperoxidase deficiency (one case). Of the remaining 94 patients, in whom infections localized to airways and/or skin predominated, 53 cases were found to have impaired chemotaxis (41 cases) or partial defects of the O2- production. Defects of chemotaxis toward FMLP and those towards both FLMP and C5a were the most frequent abnormalities. No defect was found in the other 41 patients. Moreover, impaired neutrophil chemotaxis was found in some patients with selective IgA deficiency (five cases) or immotile cilia syndrome (seven cases). The results suggest that (a) additional screening tests are required to ameliorate the efficiency of the diagnostic work-up of the patients suspected to have neutrophil dysfunction; and (b) further evaluation, also at the molecular level, should be considered at least in selected cases of non-classified neutrophil dysfunction in order to clarify diagnosis and plan rational therapeutic strategies.