The critical role of the cellular thiol homeostasis in cadmium perturbation of the lung extracellular matrix

ArticleinToxicology 267(1-3):60-9 · October 2009with19 Reads
DOI: 10.1016/j.tox.2009.10.021 · Source: PubMed
Cadmium (Cd) inhalation can result in emphysema. Cd exposure of rat lung fibroblasts (RFL6) enhanced levels of metal scavenging thiols, e.g., metallothionein (MT) and glutathione (GSH), and the heavy chain of gamma-glutamylcysteine synthetase (gamma-GCS), a key enzyme for GSH biosynthesis, concomitant with downregulation of lysyl oxidase (LO), a copper-dependent enzyme for crosslinking collagen and elastin in the extracellular matrix (ECM). Cd downregulation of LO in treated cells was closely accompanied by suppression of synthesis of collagen, a major structure component of the lung ECM. Using rats intratracheally instilled with cadmium chloride (30 microg, once a week) as an animal model, we further demonstrated that although 2-week Cd instillation induced a non-significant change in the lung LO activity and collagen synthesis, 4- and 6-week Cd instillation resulted in a steady decrease in the lung LO and collagen expression. The lung MT and total GSH levels were both upregulated upon the long-term Cd exposure. Emphysematous lesions were generated in lungs of 6-week Cd-dosed rats. Increases of cellular thiols by transfection of cells with MT-II expression vectors or treatment of cells with GSH monoethyl ester, a GSH delivery system, markedly inhibited LO mRNA levels and catalytic activities in the cell model. Thus, Cd upregulation of cellular thiols may be a critical cellular event facilitating downregulation of LO, a potential mechanism for Cd-induced emphysema.
    • "For example, in a study with two different lung cell lines, A29 and H441, exposed to Cd, the authors observed highly variable modulations of GSH levels (either no effects or considerable increases ) depending on the cell line investigated [27]. A study with rats instilled intratracheally with cadmium chloride for 6 weeks showed a linear increase in GSH in lung [28]. The listed studies with chemical forms of Cd (as well as some others, e.g., [3, 29]) showed a similar increase in GSH as recorded in the present study with CdO nanoparticles.Fig. "
    [Show abstract] [Hide abstract] ABSTRACT: The paper presents the development of an advanced extraction and fast analytical LC MS/MS method for simultaneous analyses of reduced and oxidized glutathione (GSH and GSSG, respectively) in different animal tissues. The simultaneous determination of GSH and GSSG is crucial because the amount and ratio of both GSH and GSSG may be altered in response to oxidative stress, an important mechanism of toxicity. The method uses the derivatization of free thiol groups in GSH. Its performance was demonstrated for less explored tissues (lung, brain, and liver) in mouse. The combined extraction and analytical method has very low variability and good reproducibility, maximum coefficients of variance for within-run and between-run analyses under 8 %, and low limits of quantification; for GSH and GSSG, these were 0.2 nM (0.06 ng/mL) and 10 nM (6 ng/mL), respectively. The performance of the method was further demonstrated in a model experiment addressing changes in GSH and GSSG concentrations in lung of mice exposed to CdO nanoparticles during acute 72 h and chronic 13-week exposures. Inhalation exposure led to increased GSH concentrations in lung. GSSG levels were in general not affected; nonsignificant suppression occurred only after the longer 13-week period of exposure. The developed method for the sensitive detection of both GSH and GSSG in very low tissue mass enables these parameters to be studied in cases where only a little sample is available, i.e. in small organisms or in small amounts of tissue.
    Full-text · Article · Jul 2014
    • "Our previous studies indicated that Cd exposure induced downregulation of LO and its substrates (collagen and elastin) in Cd-pulsed cells and in CdR cells (Zhao et al., 2006). Furthermore, such relationship of Cd exposure with downregulation of LO, collagen, and elastin was also confirmed in emphysematous lungs of the rat animal model (Zhao et al., 2010). Cd is a ROS inducer (Cuypers et al., 2010), whereas HIF-1α is a hypoxia sensor transcription factor (Kaluz et al., 2008). "
    [Show abstract] [Hide abstract] ABSTRACT: Lysyl oxidase (LO) catalyzes crosslink of collagen, elastin and histone H1 stabilizing the extracellular matrix and cell nucleus. This enzyme displays dual functions for tumorigenesis, i.e., as a tumor suppressor inactivating the ras oncogene as well as a tumor promoter enhancing malignant cell metastasis. To elucidate LO transcriptional regulation, we have cloned the 804 base pair region upstream of the translation start site (ATG) of the rat LO gene with the maximal promoter activity. Computer analysis indicated that at least 4 hypoxia-response element (HRE) consensuses (5'-ACGTG-3') exist in the cloned LO promoter. Treatment of rat lung fibroblasts (RFL6) with CoCl(2) (Co, 10-100 μM), a chemical hypoxia reagent, enhanced LO mRNA expression and promoter activities. Overexpression of LO was associated with upregulation of hypoxia inducible factor (HIF)-1α at mRNA levels in Co-treated cells. Thus, LO is a hypoxia-responsive gene. Dominant negative (DN)-HIF-1α, inhibited LO promoter activities stimulated by Co. Electrophoretic mobility shift, oligonucleotide competition and in vitro translated HIF-1α binding assays indicated that only one HRE mapped at -387/-383 relative to ATG was functionally active among 4 consensuses. Site-directed mutation of this HRE significantly diminished the Co-induced and LO promoter-directed expression of the reporter gene. Cadmium (Cd), an inducer of reactive oxygen species (ROS), inhibited HIF-1α mRNA expression and HIF-1α binding to the LO gene in Co-treated cells as revealed by RT-PCR and ChIP assays, respectively. Thus, modulation of the HRE activity by Co and Cd plays a critical role in LO gene transactivation.
    Article · Nov 2012
    • "It has long been known that cigarette smoke blocks cross-linking of elastin in vitro [112]. Our recent studies using CSC/NNK and Cd treated cells and Cd intratracheally instilled rats as in vitro and in vivo models have demonstrated downregulation of LO at multiple levels accompanied by inhibition of collagen and elastin expression in cell models and emphysema pathology in the lung of the animal model [40,76,88]. Modulation of the ECM gene expression by LO is supported by the observation that addition of BAPN, an inhibitor of LO, reduced mRNA levels of elastin in VSMC [113] and that overexpression of LO in COS-7 cells enhanced the promoter activity of the collagen type III gene [114]. "
    [Show abstract] [Hide abstract] ABSTRACT: Cigarette smoke (CS), a complex chemical mixture, contains more than 4,800 different compounds, including oxidants, heavy metals, and carcinogens, that individually or in combination initiate or promote pathogenesis in the lung accounting for 82% of chronic obstructive pulmonary disease (COPD) deaths and 87% of lung cancer deaths. Lysyl oxidase (LO), a Cu-dependent enzyme, oxidizes peptidyl lysine residues in collagen, elastin and histone H1, essential for stabilization of the extracellular matrix and cell nucleus. Considerable evidences have shown that LO is a tumor suppressor as exemplified by inhibiting transforming activity of ras, a proto oncogene. CS condensate (CSC), 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and cadmium (Cd), major components of CS, down-regulate LO expression at such multiple levels as mRNA, protein and catalytic activity in lung cells in vitro and in vivo indicating LO as a critical intra- and extracellular target for CS pathogenesis in the lung. In view of multiple biological functions and regulation characteristics of the LO gene, molecular mechanisms for CS damage to lung LO and its role in emphysema and cancer pathogenesis are discussed in this review.
    Full-text · Article · Dec 2011
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