Mechanisms contributing to the enhanced respiratory burst of neutrophils observed in periodontitis

The aim of this thesis is to investigate possible mechanisms that may contribute to neutrophil hyperactivity and hyper-reactivity. One possibility is the presence of a neutrophil priming factors within the peripheral circulation of periodontitis patients. To examine this possibility differentiated HL-60 cells and primary neutrophils were studied in the presence and absence of plasma from periodontitis patients. In independent experiments, plasma was depleted of IL-8, GM-CSF, interferon-a, immunoglobulins and albumin. This work demonstrated that plasma factors such as IL-8, GM-CSF, and interferon-a present during periodontitis may contribute towards the reported hyperactive neutrophil phenotype. Furthermore, this work demonstrated that products from Pg may regulate neutrophil accumulation at infected periodontal sites by promoting gingipain-dependent modification of IL-8-77 into a more biologically active chemokine. To elucidate whether the oxidatively stressed environment that neutrophils are exposed to in periodontitis could influence hyperactivity and hyper-reactivity, neutrophils were depleted of glutathione. This work showed that during oxidative stress, where cellular redox-levels have been altered, neutrophils exhibit an increased respiratory burst. In conclusion, this work highlights the multiple mechanisms that may contribute to neutrophil hyperactivity and hyperreactivity including gingipain-modulated activity of IL-8 variants, the effect of host factors such as IL-8, GM-CSF, interferon-a on neutrophils priming and activation, and the shift of neutrophil GSH:GSSG ratio in favour of a more oxidised environment as observed in periodontitis.

Activation of the neutrophil respiratory burst by plasma from periodontitis patients is mediated by pro-inflammatory cytokines

Aim: To determine the effect of periodontitis patients' plasma on the neutrophil oxidative burst and the role of albumin, immunoglobulins (Igs) and cytokines. Materials and Methods: Plasma was collected from chronic periodontitis patients (n=11) and periodontally healthy controls (n=11) and used with/without depletion of albumin and Ig or antibody neutralization of IL-8, GM-CSF or IFN-a to prime/stimulate peripheral blood neutrophils, isolated from healthy volunteers. The respiratory burst was measured by lucigenin-dependent chemiluminescence. Plasma cytokine levels were determined by ELISA. Results: Plasmas from patients were significantly more effective in both directly stimulating neutrophil superoxide production and priming for subsequent formyl-met-leu-phe (fMLP)-stimulated superoxide production than plasmas from healthy controls (p<0.05). This difference was maintained after depletion of albumin and Ig. Plasma from patients contained higher mean levels of IL-8, GM-CSF and IFN-a. Individual neutralizing antibodies against IL-8, GM-CSF or IFN-a inhibited the direct stimulatory effect of patients' plasma, whereas the ability to prime for fMLP-stimulated superoxide production was only inhibited by neutralization of IFN-a. The stimulating and priming effects of control plasma were unaffected by antibody neutralization. Conclusions: This study demonstrates that plasma cytokines may have a role in inducing the hyperactive (IL-8, GM-CSF, IFN-a) and hyper-reactive (IFN-a) neutrophil phenotype seen in periodontitis patients.

Thioredoxin is involved in endothelial cell extracellular transglutaminase 2 activation mediated by celiac disease patient IgA

Purpose: To investigate the role of thioredoxin (TRX), a novel regulator of extracellular transglutaminase 2 (TG2), in celiac patients IgA (CD IgA) mediated TG2 enzymatic activation. Methods: TG2 enzymatic activity was evaluated in endothelial cells (HUVECs) under different experimental conditions by ELISA and Western blotting. Extracellular TG2 expression was studied by ELISA and immunofluorescence. TRX was analysed by Western blotting and ELISA. Serum immunoglobulins class A from healthy subjects (H IgA) were used as controls. Extracellular TG2 enzymatic activity was inhibited by R281. PX12, a TRX inhibitor, was also employed in the present study. Results: We have found that in HUVECs CD IgA is able to induce the activation of extracellular TG2 in a dose-dependent manner. Particularly, we noted that the extracellular modulation of TG2 activity mediated by CD IgA occurred only under reducing conditions, also needed to maintain antibody binding. Furthermore, CD IgA-treated HUVECs were characterized by a slightly augmented TG2 surface expression which was independent from extracellular TG2 activation. We also observed that HUVECs cultured in the presence of CD IgA evinced decreased TRX surface expression, coupled with increased secretion of the protein into the culture medium. Intriguingly, inhibition of TRX after CD IgA treatment was able to overcome most of the CD IgA-mediated effects including the TG2 extracellular transamidase activity. Conclusions: Altogether our findings suggest that in endothelial cells CD IgA mediate the constitutive activation of extracellular TG2 by a mechanism involving the redox sensor protein TRX. © 2013 Nadalutti et al.

Redox regulation of protein damage in plasma

The presence and concentrations of modified proteins circulating in plasma depend on rates of protein synthesis, modification and clearance. In early studies, the proteins most frequently analysed for damage were those which were more abundant in plasma (e.g. albumin and immunoglobulins) which exist at up to 10 orders of magnitude higher concentrations than other plasma proteins e.g. cytokines. However, advances in analytical techniques using mass spectrometry and immuno-affinity purification methods, have facilitated analysis of less abundant, modified proteins and the nature of modifications at specific sites is now being characterised. The damaging reactive species that cause protein modifications in plasma principally arise from reactive oxygen species (ROS) produced by NADPH oxidases (NOX), nitric oxide synthases (NOS) and oxygenase activities; reactive nitrogen species (RNS) from myeloperoxidase (MPO) and NOS activities; and hypochlorous acid from MPO. Secondary damage to proteins may be caused by oxidized lipids and glucose autooxidation.In this review, we focus on redox regulatory control of those enzymes and processes which control protein maturation during synthesis, produce reactive species, repair and remove damaged plasma proteins. We have highlighted the potential for alterations in the extracellular redox compartment to regulate intracellular redox state and, conversely, for intracellular oxidative stress to alter the cellular secretome and composition of extracellular vesicles. Through secreted, redox-active regulatory molecules, changes in redox state may be transmitted to distant sites. © 2014 The Authors.

Antenatal corticosteroids impact the inflammatory rather than the antiangiogenic profile of women with preeclampsia

Circulating antiangiogenic factors and proinflammatory cytokines are implicated in the pathogenesis of preeclampsia. This study was performed to test the hypothesis that steroids modify the balance of inflammatory and proangiogenic and antiangiogenic factors that potentially contribute to the patient’s evolving clinical state. Seventy singleton women, admitted for antenatal corticosteroid treatment, were enrolled prospectively. The study group consisted of 45 hypertensive women: chronic hypertension (n=6), severe preeclampsia (n=32), and superimposed preeclampsia (n=7). Normotensive women with shortened cervix (<2.5 cm) served as controls (n=25). Maternal blood samples of preeclampsia cases were obtained before steroids and then serially up until delivery. A clinical severity score was designed to clinically monitor disease progression. Serum levels of angiogenic factors (soluble fms-like tyrosine kinase-1 [sFlt-1], placental growth factor [PlGF], soluble endoglin [sEng]), endothelin-1 (ET-1), and proinflammatory markers (IL-6, C-reactive protein [CRP]) were assessed before and after steroids. Soluble IL-2 receptor (sIL-2R) and total immunoglobulins (IgG) were measured as markers of T- and B-cell activation, respectively. Steroid treatment coincided with a transient improvement in clinical manifestations of preeclampsia. A significant decrease in IL-6 and CRP was observed although levels of sIL-2R and IgG remained unchanged. Antenatal corticosteroids did not influence the levels of angiogenic factors but ET-1 levels registered a short-lived increase poststeroids. Although a reduction in specific inflammatory mediators in response to antenatal steroids may account for the transient improvement in clinical signs of preeclampsia, inflammation is unlikely to be the major contributor to severe preeclampsia or useful for therapeutic targeting.

Antenatal corticosteroids impact the inflammatory rather than the antiangiogenic profile of women with preeclampsia

Circulating antiangiogenic factors and proinflammatory cytokines are implicated in the pathogenesis of preeclampsia. This study was performed to test the hypothesis that steroids modify the balance of inflammatory and proangiogenic and antiangiogenic factors that potentially contribute to the patient's evolving clinical state. Seventy singleton women, admitted for antenatal corticosteroid treatment, were enrolled prospectively. The study group consisted of 45 hypertensive women: chronic hypertension (n=6), severe preeclampsia (n=32), and superimposed preeclampsia (n=7). Normotensive women with shortened cervix (<2.5 cm) served as controls (n=25). Maternal blood samples of preeclampsia cases were obtained before steroids and then serially up until delivery. A clinical severity score was designed to clinically monitor disease progression. Serum levels of angiogenic factors (soluble fms-like tyrosine kinase-1 [sFlt-1], placental growth factor [PlGF], soluble endoglin [sEng]), endothelin-1 (ET-1), and proinflammatory markers (IL-6, C-reactive protein [CRP]) were assessed before and after steroids. Soluble IL-2 receptor (sIL-2R) and total immunoglobulins (IgG) were measured as markers of T- and B-cell activation, respectively. Steroid treatment coincided with a transient improvement in clinical manifestations of preeclampsia. A significant decrease in IL-6 and CRP was observed although levels of sIL-2R and IgG remained unchanged. Antenatal corticosteroids did not influence the levels of angiogenic factors but ET-1 levels registered a short-lived increase poststeroids. Although a reduction in specific inflammatory mediators in response to antenatal steroids may account for the transient improvement in clinical signs of preeclampsia, inflammation is unlikely to be the major contributor to severe preeclampsia or useful for therapeutic targeting. © 2014 American Heart Association, Inc.