Exposure of mice to cigarette smoke and/or light causes DNA alterations in heart and aorta

https://doi.org/10.1016/j.mrfmmm.2008.06.012Get rights and content

Abstract

Cigarette smoke (CS) is a major risk factor for cardiovascular diseases, cancer, and other chronic degenerative diseases. UV-containing light is the most ubiquitous DNA-damaging agent existing in nature, but its possible role in cardiovascular diseases had never been suspected before, although it is known that mortality for cardiovascular diseases is increased during periods with high temperature and solar irradiation. We evaluated whether exposure of Swiss CD-1 mice to environmental CS (ECS) and UV-C-covered halogen quartz lamps, either individually or in combination, can cause DNA damage in heart and aorta cells. Nucleotide alterations were evaluated by 32P postlabeling methods and by HPLC-electrochemical detection. The whole-body exposure of mice to ECS considerably increased the levels of 8-oxo-7,8-dihydro-2′-deoxyguanosine (8-oxodGuo) and of bulky DNA adducts in both heart and aorta. Surprisingly, even exposure to a light that simulated solar irradiation induced oxidatively generated damage in both tissues. The genotoxic effects of UV light in internal organs is tentatively amenable to formation of unidentified long-lived mutagenic products in the skin of irradiated mice. Nucleotide alterations were even more pronounced when the mice were exposed to smoke and/or light during the first 5 weeks of life rather than during adulthood for an equivalent period of time. Although the pathogenetic meaning is uncertain, DNA damage in heart and aorta may tentatively be related to cardiomyopathies and to the atherogenesis process, respectively.

Introduction

Cigarette smoke (CS) is one of the major risk factors for atherosclerosis, which accounts for nearly 50% of deaths in western societies [1]. Environmental CS (ECS), which is a form of indoor air pollution resulting from the mixture of sidestream CS (SCS) and that portion of mainstream CS (MCS) which is released into ambient air by actively smoking individuals, contains many free radicals and redox-active compounds [2]. The involuntary exposure to ECS in never smokers is associated with a significant excess of coronary heart disease [3], [4]. A short-term exposure of mice to ECS resulted in oxidative stress in the lung, heart, and liver, as shown by alterations of antioxidant enzymes in these tissues [5], while in the long-term ECS created a state of permanent inflammation and an imbalance in the profile of lipid peroxidation products [6].

In spite of its essential role in life, solar irradiation is the most ubiquitous DNA-damaging agent existing in nature. Especially in susceptible individuals, an excessive exposure to sunlight can cause degenerative diseases of the skin, also including the 10% of all human cancers [7]. We previously showed that certain widespread artificial light sources, and above all traditional halogen quartz bulbs, emit UV-A, UV-B, and even UV-C wavelengths [8]. Their light is mutagenic in vitro [8] and induces a potent carcinogenic response in the skin of hairless mice [9], [10]. Furthermore, exposure of hairless mice to either ECS or UV-C-covered halogen quartz bulbs, simulating solar irradiation, produced extensive biochemical, molecular, and cytogenetic alterations not only in the expected target organs but even at a systemic level [11], [12]. However, a possible involvement of exposure to UV-containing light in cardiovascular diseases has never been investigated.

The goal of the present study was to evaluate whether exposure of Swiss CD-1 albino mice to ECS and UV-C-covered halogen light, either individually or in combination, can cause DNA damage in heart and aorta cells. Bulky DNA adducts and 8-oxo-7,8-dihydro-2′-deoxyguanosine (8-oxodGuo) were measured. Bulky DNA adducts are premutagenic lesions that have been involved in the initiation of cancer and other chronic degenerative diseases [13], while 8-oxodGuo is one of the mutagenic adducts formed upon oxidation of the nucleoside 2′-deoxyguanosine by reactive oxygen species [14]. A further goal of the present study was to investigate the influence of age on DNA damage and repair in mouse heart and aorta, by comparing adult mice with mice exposed to ECS and/or light starting at birth until weaning. In fact, the analysis of respiratory tissues from the same animals has shown that both ECS and light induce a greater oxidative DNA damage early in life than in adults [15].

Section snippets

Treatment of mice

Twenty-five pregnant Swiss CD-1 albino mice (Harlan, Italy, San Pietro al Natisone, Udine, Italy) generated a total of 250 pups. Within 12 h after birth, the neonatal mice and their dams were divided into four groups, including (a) sham-exposed mice, kept in filtered air; (b) ECS-exposed mice; (c) light-exposed mice; and (d) mice exposed to both ECS and light. All treatments were in accordance with NIH and our national and institutional guidelines.

Exposure to ECS and/or light

A whole-body exposure of mice to ECS was

Bulky DNA adducts

A weak radioactive signal was detected in TLCs of heart and aorta samples from both sham-exposed and light-exposed mice. In contrast, an evident diagonal radioactive zone (DRZ) and an individual spot in the upper end of the DRZ were detected in both heart and aorta samples from ECS-exposed mice, irrespective of co-exposure to light (chromatograms not shown). As reported in Table 1, the baseline levels of bulky DNA adducts detected in sham-exposed mice were significantly higher in both heart

Discussion

The results obtained in the present study provide evidence that exposure of mice to ECS resulted in a considerable stimulation of 8-oxodGuo and bulky DNA adduct formation in both aorta and heart. In addition, the simple exposure to light containing UV-A and UV-B significantly increased 8-oxodGuo levels in both tissues. This conclusion was drawn by using two different methodologies. HPLC-ECD requires relatively high amounts of DNA but is quantitative and specific [18]. In contrast, 32P

Conflicts of interest

None.

Acknowledgements

This work was supported by the US National Cancer Institute contract N01-CN53301 and by the Bulgarian Ministry of Education and Science.

References (42)

  • M. Neri et al.

    Children's exposure to environmental pollutants and biomarkers of genetic damage. Part II. Results of a comprehensive literature search and meta-analysis

    Mutat. Res.

    (2006)
  • D.F. Church et al.

    Free-radical chemistry of cigarette smoke and its toxicological implications

    Environ. Health Perspect.

    (1985)
  • Z. Chen et al.

    Smoking and cardiovascular disease

    Semin. Vasc. Med.

    (2002)
  • H. Yuan et al.

    The effects of second-hand smoke on biological processes important in atherogenesis

    BMC Cardiovasc. Disord.

    (2007)
  • J. Higginson et al.

    Environmental carcinogenesis: misconceptions and limitations to cancer control

    J. Natl. Cancer Inst.

    (1979)
  • S. De Flora et al.

    Potent genotoxicity of halogen lamps, compared to fluorescent light and sunlight

    Carcinogenesis

    (1990)
  • S. De Flora et al.

    Halogen lamp carcinogenicity

    Nature

    (1992)
  • F. D’Agostini et al.

    Potent carcinogenicity of uncovered halogen lamps

    Cancer Res.

    (1994)
  • R.M. Balansky et al.

    Systemic genotoxic effects produced by light, and synergism with cigarette smoke in the respiratory tract of hairless mice

    Carcinogenesis

    (2003)
  • A. Izzotti et al.

    Alterations of gene expression in skin and lung of mice exposed to light and cigarette smoke

    FASEB J.

    (2004)
  • Y. Kuchino et al.

    Misreading of DNA templates containing 8-hydroxydeoxyguanosine at the modified base and at adjacent residues

    Nature

    (1987)
  • Cited by (27)

    • Aldehydes and Cardiovascular Disease

      2018, Comprehensive Toxicology: Third Edition
    • Environmental carcinogens and mutational pathways in atherosclerosis

      2015, International Journal of Hygiene and Environmental Health
      Citation Excerpt :

      Surprisingly, even exposure to a light that simulated solar irradiation induced oxidatively generated damage in aorta tissues. Indeed UV exposure doubled oxidative DNA damage levels in the aorta of mice exposed to UV-light 6 h per day for 5 weeks (Izzotti et al., 2008). The genotoxic effects of UV light in internal organs is tentatively amenable to formation of unidentified long-lived mutagenic products in the skin of irradiated mice.

    • Micronucleated erythrocytes in newborns of rat dams exposed to ultraviolet-A light during pregnancy; protection by ascorbic acid supplementation

      2015, Mutation Research - Genetic Toxicology and Environmental Mutagenesis
      Citation Excerpt :

      UVA can damage DNA by several mechanisms; however, we suggest that damage to the genome of the neonate rats was due to maternal exposure to UVA forming ROS [13]. We did not analyze the ROS levels generated, but we believe that the UVA-induced damage to erythropoietic cells may result from ROS or secondary products generated by prolonged oxidative stress [61]; these products could circulate and cause damage to cells, membranes, and DNA [14,62,63]. Long-lived protein radicals and protein hydroperoxides are agents [64–68] which might pass through the placenta [64,69] and cause oxidative stress following irradiation [70].

    • Effects of blue light phototherapy on DNA integrity in preterm newborns

      2014, Journal of Photochemistry and Photobiology B: Biology
      Citation Excerpt :

      In the first few hours after birth, PNBs are exposed to different procedures that may underlie an increase in MNE post-birth. Because phototherapy causes damage to genetic material by oxidative stress processes [13,14,16,17,37,38], we assumed that the erythropoietic cell damage due to phototherapy is primarily produced in an indirect manner and possibly induced by the production of reactive oxygen species and secondary products as a result of prolonged oxidative stress [39]; the oxidized products generated as a consequence of these conditions are highly reactive, and they could spread to other places and cause damage to cells, cell membranes and genetic material [40–42]. It is unlikely that the light can reach the erythropoietic organs, although we cannot rule this out because the PNBs have an immature skin that is very thin and very permeable to light.

    • Resveratrol prevents nicotine-induced teratogenesis in cultured mouse embryos

      2012, Reproductive Toxicology
      Citation Excerpt :

      Nicotine, a major toxic component of cigarette smoke, crosses the placental barrier and acts directly and indirectly on fetal systems [4]. Reactive oxygen species (ROS) damage mitochondrial and nuclear DNA, proteins, and lipids, and these have been recognized as one of the most important toxic mechanisms of nicotine [5–7]. Administration of nicotine to rats leads to higher lipid peroxidation and a subsequent decrease in antioxidant enzymes [8].

    View all citing articles on Scopus
    View full text