High susceptibility of neonatal mice to molecular, biochemical and cytogenetic alterations induced by environmental cigarette smoke and light

Department of Health Sciences, University of Genoa, Via A. Pastore 1, I-16132 Genoa, Italy.
Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis (Impact Factor: 3.68). 12/2007; 659(1-2):137-46. DOI: 10.1016/j.mrrev.2007.11.004
Source: PubMed


Our recent studies have shown that both cigarette smoke and UV-containing light, which are the most widespread and ubiquitous mutagens and carcinogens in the world, cause systemic genotoxic damage in hairless mice. Further studies were designed with the aim of evaluating the induction of genotoxic and carcinogenic effects in Swiss albino mice exposed to smoke and/or light since birth. We observed that a 4-month whole-body exposure of mice to mainstream cigarette smoke, starting at birth, caused an early and potent carcinogenic response in the lung and other organs. Our further experiments showed that exposure of mice to environmental cigarette smoke, during the first 5 weeks of life, resulted in a variety of significant alterations of intermediate biomarkers, including cytogenetic damage in bone marrow and peripheral blood, formation of lipid peroxidation products, increase of bulky DNA adduct levels, induction of oxidative DNA damage, and overexpression of OGG1 gene in lung, stimulation of apoptosis, hyperproliferation and loss of Fhit protein in pulmonary alveolar macrophages and/or bronchial epithelial cells, and early histopathological alterations in the respiratory tract. Moreover, exposure of mice to UV-containing light, mimicking solar irradiation, significantly enhanced oxidative DNA damage and bulky DNA adduct levels in lung, and synergized with smoke in inducing molecular alterations in the respiratory tract. The baseline OGG1 expression in lung was particularly high at birth and decreased in post-weanling mice. Oxidative DNA damage and other investigated end-points exhibited differential patterns in post-weanling mice and adult mice. The findings of these studies provide a mechanistic clue to the general concept that the neonatal period and early stages of life are critical in affecting susceptibility to carcinogens.

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Available from: Silvio De Flora, Dec 15, 2015
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    • "It is known that children are especially sensitive to the respiratory effects of CS exposure (California Environmental Protection Agency, 2005). Due to a variety of composite mechanisms, mice exposed during the first 5 weeks of life are more susceptible than their dams, exposed under identical conditions, to molecular , biochemical and cytogenetic alterations induced by CS in the respiratory tract (De Flora et al., 2008). As shown in mice exposed to CS, oxidative stress and the resulting DNA damage provide a major contribution to the high susceptibility of mice exposed early in life (Micale et al., 2013). "
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    ABSTRACT: Although the adverse effects of active smoking on sperm quality and fertilization ability are well established, little is known about possible effects of involuntary exposures to cigarette smoke (CS). We designed an experimental study aimed at evaluating the induction of possible noxious effects on testicular morphology and functions in A/J mice exposed whole-body to CS during the first 70 days of life, from birth to early adulthood. Twenty-five sham-exposed neonatal mice and 23 CS-exposed neonatal mice were used. Exposure to CS caused a variety of interconnected alterations in male gonads, including loss of weight and histomorphological alterations of testis, accompanied by a significant increase in abnormalities affecting epidydimal spermatozoa. Induction of oxidative stress was demonstrated by significantly increased concentrations of both reactive oxygen species and lipid peroxidation products in sperm cells. Occurrence of DNA damage in the same cells was documented by using the single cell gel electrophoresis (comet) assay, which showed a remarkable increase in DNA single- and double-strand breaks in CS-exposed mice, as compared with sham-exposed mice. Since biochemical and molecular alterations of sperm cells are known to be associated with impaired sperm quality, our findings suggest that involuntary smoking is potentially able to impair fertility in subjects exposed early in life.
    Full-text · Article · Sep 2014 · International Journal of Hygiene and Environmental Health
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    • "Other downregulated miRNAs, like let-7a, miR-30b, miR-30c, miR-124a, miR-219, and miR-376, increase cell proliferation. Cell proliferation, known to increase in the lungs upon exposure to smoke, replenishes the smoke damaged lung tissue [38, 39]. "
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    ABSTRACT: Dysregulation of microRNAs (miRNAs), particularly their downregulation, has been widely shown to be associated with the development of lung cancer. Downregulation of miRNAs leads to the overactivation of their oncogene targets, while upregulation of some miRNAs leads to inhibition of important tumor suppressors. Research has implicated cigarette smoke in miRNA dysregulation, leading to carcinogenesis. Cigarette smoke may lead to genetic or epigenetic damage to miRNAs, many of which map to fragile sites and some of which contain single nucleotide polymorphisms. Cigarette smoke may also cause dysregulation by affecting regulatory mechanisms controlling miRNA expression. Researchers have shown a correlation between smoke-exposure-induced dysregulation of miRNAs and age. Furthermore, dysregulation seems to be associated with intensity and duration of smoke exposure and duration of cessation. Longer exposure at a threshold level is needed for irreversibility of changes in expression. Better understanding of miRNA dysregulation may allow for improved biomonitoring and treatment regimens for lung cancer.
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    • "We have recently shown that pulmonary alveolar macrophages and lung cells from the same CS-exposed mice used in the present study exhibit dose-dependent cytogenetic alterations (Balansky, D'Agostini, Micale, La Maestra, Steele, and De Flora, in preparation) as well as increased bulky DNA adducts, 8-oxo-dGuo lesions, and dysregulated microRNA expression (Izzotti et al., 2010). While DNA damage in mitotic tissues activates cellular processes that may lead to tumorigenesis, DNA damage in postmitotic tissues might activate similar cellular processes that disrupt normal development or lead to degenerative diseases (Behrens et al., 2009; De Flora et al., 1996; Staropoli, 2008). This hypothesis is consistent with the observed CS-induced alterations of tau, a cytoskeletal protein with an important role in both brain development and function. "
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    ABSTRACT: The prenatal and perinatal periods of brain development are especially vulnerable to insults by environmental agents. Early life exposure to cigarette smoke (CS), which contains both genotoxicants and oxidants, is considered an important risk factor for both neurodevelopmental and neurodegenerative disorders. Yet, little is known regarding the underlying pathogenetic mechanisms. In the present study, neonatal Swiss ICR (CD-1) albino mice were exposed to various concentrations of CS for 4 weeks and the brain examined for lipid peroxides, DNA damage, base-excision repair (BER) enzymes, apoptosis, and levels of the microtubule protein tau. CS induced a dose-dependent increase in both malondialdehyde and various types of DNA damage, including single-strand breaks, double-strand breaks, and DNA-protein cross-links. However, the CS-induced DNA damage in the brain returned to basal levels 1 week after smoking cessation. CS also modulated the activity and distribution of the BER enzymes 8-oxoguanine-DNA-glycosylase (OGG1) and apyrimidinic/apurinic endonuclease (APE1) in several brain regions. Normal tau (i.e., three-repeat tau, 3R tau) and various pathological forms of tau were also measured in the brain of CS-exposed neonatal mice, but only 3R tau and tau phosphorylated at serine 199 were significantly elevated. The oxidative stress, genomic dysregulation, and alterations in tau metabolism caused by CS during a critical period of brain development could explain why CS is an important risk factor for both neurodevelopmental and neurodegenerative disorders appearing in later life.
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