Monica Amati

Università Politecnica delle Marche, Ancona, The Marches, Italy

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Publications (35)76.63 Total impact

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    ABSTRACT: Aim: MiR126 was found to be frequently lost in many types of cancer including malignant mesothelioma (MM), which represents one of the most challenging neoplastic diseases. In this study, we investigated the potential tumor suppressor function of MiR126 in MM cells. The effect of MiR126 was examined in response to oxidative stress, aberrant mitochondrial function induced by inhibition of complex I, mtDNA depletion and hypoxia. Results: MiR126 was upregulated by oxidative stress in non-malignant mesothelial (Met5A) and MM (H28) cell lines. In Met5A cells, rotenone inhibited MiR126 expression but mtDNA depletion and hypoxia up-regulated MiR126. However, these various stimuli all suppressed the levels of MiR126 in H28 cells. MiR126 affected mitochondrial energy metabolism, reduced mitochondrial respiration and promoted glycolysis in H28 cells. This metabolic shift, associated with IRS1-modulated ATP-citrate lyase deregulation, resulted in higher ATP and citrate production. These changes were linked to down-regulation of IRS1 by ectopic MiR126, reducing Akt signaling and inhibiting cytosolic sequestration of FoxO1, which promoted the expression of genes involved in gluconeogenesis and oxidative stress defense. These metabolic changes induced HIF-1 stabilization. Consequently, MiR126 suppressed the malignancy of MM cells in vitro, a notion corroborated by the failure of H28MiR126 cells to form tumors in nude mice. Innovation and conclusion: MiR126 affects mitochondrial energy metabolism resulting in MM tumor suppression. Since MM is a fatal neoplastic disease with few therapeutic options, this finding is of potential translational importance.
    Antioxidants & Redox Signaling 01/2014; · 8.20 Impact Factor
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    ABSTRACT: The circadian clock can regulate the metabolic process of xenobiotics, but little is known as to circadian rhythms can be perturbed by xenobiotics. Styrene is a organic chemical widely used in occupational settings. The effects of styrene on the circadian genes of HuDE cells were evaluated after serum-shocking synchronization. A subtoxic dose of 100 µM of styrene altered the expression of clock genes BMAL1, PER2, PER3, CRY1, CRY2, and REV-ERB-α.
    Bioscience Biotechnology and Biochemistry 06/2013; · 1.27 Impact Factor
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    ABSTRACT: The aim of this study was to evaluate the expression of a panel of genes involved in toxicology in response to styrene exposure at levels below the occupational standard setting. Workers in a fiber glass boat industry were evaluated for a panel of stress- and toxicity-related genes and associated with biochemical parameters related to hepatic injury. Urinary styrene metabolites (MA+PGA) of subjects and environmental sampling data collected for air at workplace were used to estimate styrene exposure. Expression array analysis revealed massive upregulation of genes encoding stress-responsive proteins (HSPA1L, EGR1, IL-6, IL-1β, TNSF10 and TNFα) in the styrene-exposed group; the levels of cytokines released were further confirmed in serum. The exposed workers were then stratified by styrene exposure levels. EGR1 gene upregulation paralleled the expression and transcriptional protein levels of IL-6, TNSF10 and TNFα in styrene exposed workers, even at low level. The activation of the EGR1 pathway observed at low-styrene exposure was associated with a slight increase of hepatic markers found in highly exposed subjects, even though they were within normal range. The ALT and AST levels were not affected by alcohol consumption, and positively correlated with urinary styrene metabolites as evaluated by multiple regression analysis. The pro-inflammatory cytokines IL-6 and TNFα are the primary mediators of processes involved in the hepatic injury response and regeneration. Here, we show that styrene induced stress responsive genes involved in cytoprotection and cytotoxicity at low-exposure, that proceed to a mild subclinical hepatic toxicity at high-styrene exposure.
    PLoS ONE 01/2013; 8(9):e75401. · 3.73 Impact Factor
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    ABSTRACT: Aim of this study was to evaluate the accuracy and precision of the detection of individual miRNA as clinical biomarkers in the serum. miRNA-126 was quantified in serum using endogenous and exogenous controls for normalization and the accuracy and precision of the method evaluated. The diagnostic value of serum miRNA-126 was evaluated in malignant mesothelioma (MM) and non-small-cell lung cancer (NSCLC) patients using both relative and absolute qRT-PCR methods. The use of endogenous invariant and exogenous synthetic controls as well sample dilution markedly improves the accuracy and precision of the assay. The inter- and intra-assay analyses revealed that relative qRT-PCR is a more reliable method. Circulating miR-126 detected in the serum by relative qRT-PCRs was found low-expressed in both malignancies, significantly differentiated MM patients from healthy controls and NSCLC from MM, but do not discriminate NSCLC patients from control subjects. Kaplan-Meier analysis revealed that low level of circulating miR-126 in MM patients was strongly associated with worse prognosis. We propose that this approach can be adopted for accurate analysis of other suitable circulating miRNA markers of different types of cancer.
    Clinical biochemistry 02/2012; 45(7-8):575-81. · 2.02 Impact Factor
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    ABSTRACT: Due to the toxic effect of asbestos, other materials with similar chemical-physical characteristics have been introduced to substitute it. We evaluate the angiogenic effect of certain asbestos substitute fibres such as glass fibres (GFs), ceramic fibres (CFs) and wollastonite fibres (WFs) and then compare angiogenic responses to those induced by crocidolite asbestos fibres (AFs). An in vitro model using human endothelial cells in small islands within a culture matrix of fibroblasts (Angio-Kit) was used to evaluate vessel formation. The release of IL-6, sIL-R6, IL-8, VEGF-A and their soluble receptors, sVEGFR-1, sVEGFR-2, was determined in the conditioning medium of Angio-Kit system after fibre treatment. ROS formation and cell viability were evaluated in cultured endothelial cells (HUVEC). To evaluate the involvement of intracellular mechanisms, EGFR signalling, ROS formation and nuclear factor-κB (NFκB) pathway were then inhibited by incubating HUVEC cells with AG1478, NAC and PDTC respectively, and the cytokine and growth factor release was analyzed in the culture medium after 7 days of fibre incubation. Among the mineral fibres tested, WFs markedly induced blood vessel formation which was associated with release of IL-6 and IL-8, VEGF-A and their soluble receptors. ROS production was observed in HUVEC after WFs treatment which was associated with cell cytotoxicity. The EGFR-induced ERK phosphorylation and ROS-mediated NFκB activation were involved in the cytokine and angiogenic factor release. However, only the EGFR activation was able to induce angiogenesis. The WFs are potential angiogenic agents that can induce regenerative cytokine and angiogenic factor production resulting in the formation of new blood vessels.
    Toxicology 10/2011; 288(1-3):34-42. · 4.02 Impact Factor
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    ABSTRACT: Shift-work, particularly night-work, interferes with the physiological circadian rhythm and has the potential to induce psycho-physiological disturbances. A nurse population was investigated to establish whether shift-work can induce changes in a number of immune variables. Lymphocyte immunophenotype and proliferative response, NK cytotoxicity, cytokines and cortisol were determined in 68 shift-working and 28 daytime nurses at baseline and at 12 months. None of the variables studied differed significantly between shift and daytime workers, either at baseline or at 12 months, except IL-1β and TNF-α, which were significantly higher among daytime nurses at baseline, but not at follow-up. No effect of shift-work on immune variable and cortisol levels was seen at 12 months after adjustment for baseline values and job seniority. The specific work schedule as well as job type likely influenced our results, suggesting that rotational shift-work does not necessarily affect the immune system adversely. The immune changes reported by other studies in shift-workers should not be generalized.
    Industrial Health 08/2011; 49(5):597-604. · 0.87 Impact Factor
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    ABSTRACT: Malignant mesothelioma (MM) is often complicated by thromboembolic episodes, with thrombomodulin (TM) playing a critical role in the anticoagulant process. Heterogeneous expression of TM has been observed in cancer, and low or no TM expression in cancer cells is associated with poor prognosis. In this study, we analyzed TM expression in biopsies of MM patients and compared them with normal mesothelial tissue. The role of DNA methylation-associated gene silencing in TM expression was investigated. To evaluate poly(ADP-ribose) polymerase-1 (PARP1) as responsible for gene promoter epigenetic modifications, nonmalignant mesothelial cells (Met-5A) and MM cells (H28) were silenced for PARP1 and the DNA methylation/acetylation-associated TM expression evaluated. A correlation between low TM expression and high level of TM promoter methylation was found in MM biopsies. Low expression of TM was restored in MM cells by their treatment with 5-aza-2'-deoxycytidine and, to a lesser extent, with trichostatin, whereas the epigenetic agents did not affect TM expression in Met-5A cells. Silencing of PARP1 resulted in a strong down-regulation of TM expression in Met-5A cells, while restoring TM expression in H28 cells. PARP1 silencing induced TM promoter methylation in Met-5A cells and demethylation in MM cells, and this was paralleled by corresponding changes in the DNA methyltransferase activity. We propose that methylation of the TM promoter is responsible for silencing of TM expression in MM tissue, a process that is regulated by PARP1.
    Journal of Biological Chemistry 06/2011; 286(22):19478-88. · 4.65 Impact Factor
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    ABSTRACT: Asbestos is known to induce malignant mesothelioma (MM) and other asbestos-related diseases. It is directly genotoxic by inducing DNA strand breaks and cytotoxic by promoting apoptosis in lung target cells. Poly(ADP-ribose) polymerase-1 (PARP1) is a nuclear zinc-finger protein with a function as a DNA damage sensor. To determine whether PARP1 is involved in asbestos-induced carcinogenesis, PARP1 expression and activity as well as DNA damage and repair were evaluated in circulating cells of asbestos-exposed subjects, MM patients and age-matched controls. PARP1 expression and activity were also evaluated in pleural biopsies of MM patients and compared with normal tissue. Accumulation of the pre-mutagenic 8-hydroxy-2'-deoxyguanosine and elevated PARP1 expression were found both in asbestos-exposed subjects and MM patients. Although PARP1 was highly expressed, its activity was relatively low. Low DNA repair efficiency was observed in lymphocytes from MM patients. High expression of PARP1 associated with low PARP activity was also found in MM biopsies. To mimic PARP1 dysfunction, PARP1 expression and activity were induced in immortalised mesothelial cells by their exposure to asbestos in the presence of a PARP1 inhibitor, which resulted in transformation of the cells. We propose that exposure to asbestos inhibits the PARP1 activity possibly resulting in higher DNA instability, thus causing malignant transformation.
    Mutagenesis 05/2011; 26(5):585-91. · 3.50 Impact Factor
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    ABSTRACT: Improved detection methods for diagnosis of malignant pleural mesothelioma (MPM) are essential for early and reliable detection as well as treatment. Since recent data point to abnormal levels of microRNAs (miRNAs) in tumors, we hypothesized that a profile of deregulated miRNAs may be a marker of MPM and that the levels of specific miRNAs may be used for monitoring its progress. miRNAs isolated from fresh-frozen biopsies of MPM patients were tested for the expression of 88 types of miRNA involved in cancerogenesis. Most of the tested miRNAs were downregulated in the malignant tissues compared with the normal tissues. Of eight significantly downregulated, three miRNAs were assayed in cancerous tissue and adjacent non-cancerous tissue sample pairs collected from 27 formalin-fixed, paraffin-embedded MPM tissues by quantitative RT-PCR. Among the miRNAs tested, only miR-126 significantly remained downregulated in the malignant tissues. Furthermore, the performance of the selected miR-126 as biomarker was evaluated in serum samples of asbestos-exposed subjects and MPM patients and compared with controls. MiR-126 was not affected by asbestos exposure, whereas it was found strongly associated with VEGF serum levels. Levels of miR-126 in serum, and its levels in patients' serum in association with a specific marker of MPM, SMRPs, correlate with subjects at high risk to develop MPM. We propose miR-126, in association with SMRPs, as a marker for early detection of MPM. The identification of tumor biomarkers used alone or, in particular, in combination could greatly facilitate the surveillance procedure for cohorts of subjects exposed to asbestos.
    PLoS ONE 01/2011; 6(4):e18232. · 3.73 Impact Factor
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    ABSTRACT: To examine the relationship between job satisfaction, psychological distress, psychosocial processes and stress-related biological factors, and to evaluate whether over time changes of work satisfaction could affect the immunological-inflammatory status of workers. One hundred and one nurses were enrolled at the Clinic of Occupational Medicine, Polytechnic University of Marche, Ancona, Italy. Perceived job satisfaction, psychological distress, and social support were assessed every 4 mo over a 1-yr period using 4 self-reported questionnaires. T lymphocytes CD3, CD4(+), CD8(+), CD8(+)-CD57(+), B lymphocyte CD19(+), NK cells CD56(+), and NK cell activity were determined. Job satisfaction was associated with reduced psychological distress and was characterized by low cell numbers of CD8(+) suppressor T cells, CD8(+)-CD57(+) activated T cells, CD56(+) NK cells and low IL-6 levels. Over time changes in psychological parameters were related to changes in the immunological-inflammatory variables. Subjects who increased their job satisfaction showed a reduced psychological stress associated with reduced number of CD8(+)-CD57(+) activated T cells and inflammatory cytokines. Job (dis)satisfaction is related with psychological mechanisms in stress affecting cellular immune function.
    Journal of Occupational Health 01/2010; 52(1):31-8. · 1.63 Impact Factor
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    ABSTRACT: Malignant mesothelioma (MM) is an aggressive neoplasm of serosal cavities, which is resistant to conventional therapy, with patient survival from presentation of <12 months. MM remains a universally fatal disease of increasing incidence worldwide. Although the main risk factor is asbestos exposure, other factors, Simian virus 40 infection and inheritance of susceptibility genes, likely play a role. Asbestos-related carcinogenic process is primarily based on the interaction between susceptibility (genetic and acquired) and exposure to carcinogenic environmental agents. Asbestos-induced carcinogenesis includes generation of reactive oxygen species, which induce DNA strand breaks and oxidant-induced base modifications to DNA. Persistent oxidative DNA damage can alter signaling cascades, gene expression, induce or arrest transcription, and increase replication errors and genomic instability. The long promotion phase observed in MM pathogenesis and the absence of early symptoms both contribute to late diagnosis of the disease. This results in delayed therapeutic intervention of patients, making the outcome of the disease very grim. There have been several developments in MM management, principally based on early detection, improved diagnosis, development of more effective therapies, and new insights into the pathobiology of the disease. Several programs have been used to screen asbestos-exposed individuals for lung and pleural disease. These programs involve annual pulmonary function tests, chest radiography and high resolution computer tomography. Blood tests make screening of target populations an attractive strategy. Many current gene and protein expression studies aim to identify clinically useful biomarkers and new therapeutic targets for improved management of MM.
    Current Molecular Pharmacology 06/2009; 2(2):190-206.
  • Toxicology Letters - TOXICOL LETT. 01/2009; 189.
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    ABSTRACT: Hereditary Non-Polyposis Colorectal Cancer (HNPCC) is associated with germline mutations in one of several MisMatch Repair (MMR) genes. An increasing proportion (20-25%) of the reported MSH2 variants consists of single amino-acid substitution with uncertain disease-causing significance. The present study was undertaken to functionally characterize 3 MSH2 nontruncating variants: p.Gly162Arg (c.484G>C), p.Asp167His (c.499G>C) and p.Arg359Ser (c.1077A>T). Missense alterations, were assessed in a human system for expression/stability and for the ability to heterodimerize with MSH6 and correctly localize into the nucleus. Functional assays results were correlated with clinical and genetic features indicative of HNPCC as MicroSatellite-Instability (MSI), abnormalities of MMR gene expression in tumour tissue (IHC) and familial history. p.Gly162Arg and p.Arg359Ser variants showed a clearly decreased expression level of the MutSá complex and were associated with an abnormal subcellular localization pattern, which can be suggestive of an incorrect MSH2/MSH6 heterodimerization. Functional analysis results were supported by MSI and IHC data and by familial cancer history. The subcellular localization assay, performed in a human expression system, classifies as pathogenetic two MSH2 nontruncating alterations providing a useful tool in genetic testing programs.
    Human Mutation 09/2008; 29(11):E296-309. · 5.21 Impact Factor
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    ABSTRACT: Improved detection methods for diagnosis of asymptomatic malignant mesothelioma (MM) are essential for an early and reliable detection and treatment of this type of neoplastic disease. Thus, focus has been on finding tumor markers in the blood that can be used for noninvasive detection of MM. Ninety-four asbestos-exposed subjects defined at high risk, 22 patients with MM, and 54 healthy subjects were recruited for evaluation of the clinical significance of 8-hydroxy-2'-deoxyguanosine (8OHdG) in WBCs and plasma concentrations of soluble mesothelin-related peptides (SMRPs), angiogenic factors [platelet-derived growth factor beta, hepatocyte growth factor, basic fibroblast growth factor, and vascular endothelial growth factor beta (VEGFbeta)], and matrix proteases [matrix metalloproteinase (MMP) 2, MMP9, tissue inhibitor of metalloproteinase (TIMP) 1, and TIMP2] for potential early detection of MM. The area under receiver operating characteristic (ROC) curves indicate that 8OHdG levels can discriminate asbestos-exposed subjects from healthy controls but not from MM patients. Significant area under ROC curve values were found for SMRPs, discriminating asbestos-exposed subjects from MM patients but not from healthy controls. Except for platelet-derived growth factor beta, the hepatocyte growth factor, basic fibroblast growth factor, and VEGFbeta can significantly differentiate high-risk individuals from healthy control and cancer groups. No diagnostic value was observed for MMP2, MMP9, TIMP1, and TIMP2. In addition to the diagnostic performance defined by the ROC analysis, the sensitivity and specificity results of markers with clinical significance were calculated at defined cutoffs. The combination of 8OHdG, VEGFbeta, and SMRPs best distinguished the individual groups, suggesting a potential indicator of early and advanced MM cancers. The combination of blood biomarkers and radiographic findings could be used to stratify the risk of mesothelioma in asbestos-exposed populations.
    Cancer Epidemiology Biomarkers &amp Prevention 02/2008; 17(1):163-70. · 4.56 Impact Factor
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    ABSTRACT: Epidemiological studies have shown that mortality from malignant mesothelioma (MM) and lung cancer have increased with increasing cumulative exposure to asbestos. To investigate whether tumour-related biomarkers can contribute towards the evaluation of the carcinogenic risk in populations exposed to asbestos, the DNA adduct 8-hydroxy-2'-deoxyguanosine (80HdG), interleukine-6 (IL-6), platelet-derived growth factor (PDGF-BB), hepatocyte growth factor (HGF), basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGFbeta) and soluble mesothelin-related peptides (SMRPs) were analysed in a cohort of workers differently exposed to asbestos fibres at the workplace. To document biomarker levels in an unexposed population, 54 age-matched subjects were enrolled. A total of 119 subjects with a history of occupational exposure to asbestos underwent clinical examination and were interviewed by trained personnel, responding to a detailed questionnaire related to duration of asbestos exposure, smoking, and occupational task. According to the occupational tasks, asbestos-exposed subjects were analysed for their asbestos cumulative dose and the association with the biomarkers was evaluated. Among the occupational groups, maintenance workers, pipe fitters and electricians were exposed to a higher cumulative dose of asbestos fibres. Exposure to asbestos significantly increased the steady-state content of 80HdG in DNA. Elevated levels of 80HdG and IL-6 best reflected a high level of SMRPs, which is related to cell transformation. Subjects heavily exposed to asbestos [> 60(ff/cm3) x years] showed also a higher level of angiogenic factors. A combination of angiogenic biomarkers with a specific mesothelioma-biomarker such as SMRPs could be used for close surveillance of workers with a history of asbestos exposure.
    Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis 01/2008; 655(1-2):52-8. · 3.90 Impact Factor
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    ABSTRACT: A longitudinal study was carried out to evaluate the effect of psycho-physical and occupational stress on some biochemical and immunological parameters. The study was aimed to the identification of new and reliable method for the identification of subjects at high risk of occupational stress. 101 nurses which were working at several departments were enrolled. A blood sample was collected from all subjects after have filled the questionnaires at the time T0 and at the followed time points of 4 months (T1), 8 months (T2) and 12 months (T3). The self-reported questionnaires were: Rating Scale for Rapid Stress Assessment (VRS), General Health Questionnaire to 12 items (GHQ-12) Multidimensional Scale of Perceived Social Support (MSPSS) and a questionnaire on the occupational satisfaction (SOD). Haemachrome glycaemia, homocysteine, cortisol, lymphocyte numbers and their subtypes (CD4, CD8, CD19, NK CD56, NK CD57), NK activity and inflammatory cytokines were evaluated. A high reliability has been found between the psychometric tests. Correlations between biochemical and immunological variables were performed by Pearson coefficients and multiple regression analysis. Subjects with elevated value of stress evaluated as VRS and GHQ-12 score showed an altered immune response. A reduction of NK CD57 and IL-6 content better characterize the occupational satisfaction.
    Giornale italiano di medicina del lavoro ed ergonomia 01/2007; 29(3 Suppl):356-8.
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    ABSTRACT: A biogenic and a pyrogenic amorphous silica were incubated in normal human plasma and compared on a per unit surface basis for their ability to split C5 molecules and yield small C5a peptides. Since C5a peptides induce selective chemotactic attraction of polymorphonuclear leukocytes (PMN), measurement of PMN-induced chemotaxis was used as an index of C5 activation. Though to a lesser extent than the crystalline forms, amorphous silicas can promote the cleavage of C5 protein and generation of C5a-like fragment. The biogenic silica, which differs from the pyrogenic variety in particle shape, level of contaminants, and degree of surface hydrophilicity, besides specific surface, induced a greater response. Both silicas activated C5 through a process which seems to involve multiple events similar to those induced by crystalline silica. C5 molecules are adsorbed and hydroxyl radicals are generated through Haber Weiss cycles catalyzed by the redox-active iron present at the particle surface either as trace impurities or chelated from plasma by silanol groups. In turn, these radicals convert native C5 to an oxidized C5-like form C5(H2O2). Finally, C5(H2O2) is cleaved by protease enzymatic action of plasma kallikrein activated by the same silica dusts, yielding a product, C5a(H2O2), having the same functional characteristic as C5a.
    Toxicology and Applied Pharmacology 11/2005; 208(1):68-77. · 3.98 Impact Factor
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    ABSTRACT: The effects of the same form of crystalline silica variously modified were compared to investigate the mechanisms by which silica activates C5 molecules. After incubation in human plasma, silica generated C5a-type fragments that stimulated polymorphonuclear leukocyte chemotaxis. This activity was totally abolished when plasma, adsorbed with antiserum against C5a or thermally inactivated, was used. Pretreatment of plasma with deferoxamine, 1,3 dimethyl-2-thiourea, or aprotinin markedly inhibited or totally abolished C5 activation. Finally, a significant increase in kallikrein activity was detected after incubation of silica particles in plasma. The results seem to indicate that the activation of C5 by crystalline silica occurs through a complex mechanism: the redox-active iron possibly present at the silica surface catalyzes, via Haber-Weiss cycles, the production of hydroxyl radicals, which in turn convert native C5 to an oxidized C5-like form. This product is then cleaved by kallikrein, activated by the same silica particles, yielding oxidized C5a with the same functional properties as C5a. The different types of the same form of silica exhibited different reactivity. Two separate properties of the dusts seem to contribute to C5 activation: the potential to release hydroxyl radicals and the extent of C5 adsorption at the surface. The degree of surface hydrophobicity/hydrophilicity appeared sufficient to explain the different responses.
    Toxicology and Applied Pharmacology 04/2002; 179(3):129-36. · 3.98 Impact Factor
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    ABSTRACT: Chrysotile and crocidolite fibers incubated in normal human plasma (NHP) generated from the C5 component of complement C5a-type fragments that stimulated polymorphonuclear leukocyte (PMN) chemotaxis. Absorption of NHP with antiserum against C5a totally abolished neutrophil chemotactic activity. Asbestos fibers also produced C5a small peptides in the presence of ethylene glycol bis(beta-aminoethyl ether) N,N,N'N'-tetraacetic acid (EGTA) but not ethylene diamine tetraacetic acid (EDTA). Activation of C5 was significantly inhibited when asbestos fibers were pretreated with iron chelators such as sodium dithionite (DTN), deferoxamine (DFX), or ascorbate (AA). Concentration-related inhibition of C5 activation was also observed when asbestos fibers were added concurrently to plasma in the presence of DFX, 1,3-dimethyl-2-thiourea (DMTU), a strong hydroxyl scavenger, or aprotinin (APR), a specific protease inhibitor. Further, chrysotile and crocidolite significantly increased plasma kallikrein activity. Data demonstrate that asbestos-induced C5 activation plays a role in inflammatory reactions characteristic of asbestosis through mechanisms involving iron ions, hydroxyl radicals, and oxidized C5-ike fragments. The ferrous ions present at the asbestos fiber surface trigger this activation and catalyze, via Fenton reaction, the production of hydroxyl radicals, which in turn convert native C5 to an oxidized C5-like form. This product is then cleaved by kallikrein, activated by the same asbestos fibers, yielding an oxidized C5a with the same functional properties as C5a.
    Journal of Toxicology and Environmental Health Part A 05/2000; 59(7):539-52. · 1.73 Impact Factor
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    ABSTRACT: Asbestos bodies (AB) were harvested from human lung tissue digests and isolated from uncoated asbestos fibers. Samples containing 1000 AB were added to a reactive solution to investigate the ability of AB to oxidize deoxy-D-ribose and generate reactive oxygen species (ROS) in the presence of ascorbate and hydrogen peroxide as determined by formation of thiobarbituric acid (TBA)-reactive products. Three types of asbestos fibers were tested for comparison, since they are known to be able to produce ROS. The absorbance values measured with 1000 AB were significantly higher than those observed with 1000 fibers of the three types of asbestos. Since in our reaction system the only source of transition metals was the iron-rich AB, data suggest iron derived from the ferritin coating of AB was involved in oxidant generation. Addition of iron to AB enhanced TBA-reactive product formation, while chelation of Fe with deferoxamine reduced this reaction. Hydroxyl radical scavengers 1,3-dimethyl-2-thiourea (DMTU) and mannitol (MN) also effectively blocked TBA-reactive product generation. Data indicate the importance of Fe in AB-induced oxidant damage. With the addition of polymorphonuclear leukocytes (PMN) to AB, incubation in the reactive solution gave very high amounts of TBA-reactive products, but using a reactive solution devoid of ascorbate, very low amounts of TBA-reactive products were generated. In the latter condition, the superoxide of cell membranes probably reduced and removed iron from AB-coating ferritin, but less effectively than ascorbate. Further after the possible reoxidation of Fe2+, Fe3+ could be coordinated by lactoferrin. Since such availability of reductant is never approached in living systems, the iron in the AB coating is unlikely to function as a catalyst of Fenton-type reactions in vivo.
    Journal of Toxicology and Environmental Health Part A 12/1999; 58(5):279-87. · 1.73 Impact Factor