Ruolo della riparazione del danno al DNA indotto da parte di agenti genotossici
Author(s)
Kobos, Katarzyna Agnieszka
Date Issued
March 8, 2011
Type
Doctoral Thesis
Abstract
In the environment many substances have a genotoxic character as they are able to interact
with genetic material either directly or through metabolic activation. This interaction can
lead to the modification of genetic material through structural alteration of the DNA
molecule and can be expressed as adducts, chemical alteration of nitrogen bases, cross‐links
and break of the single and double strand. Generally, these types of alterations can be
repaired by various cellular repair systems. However, the lesions that are not repaired
correctly can lead to abnormalities of the genetic material such as chromosomal aberrations,
gene mutations and neoplasias.
The aim of the present PhD thesis was to investigate the cellular response to DNA damage
caused by genotoxic agents.
In the first year, the research was focused on the role of repairing the damage induced by a
mutagen agent, acetaldehyde (AA), in the repair deficient Chinese hamster ovary (CHO) cells.
In particular, the aim of this research was to verify the effective induction of cross‐links by
acetaldehyde using the Comet Assay modified for the resolution of the cross‐links and
characterization of the cross‐link type induced by this substance.
In addition, the CHO lines with defect in Nucleotide Excision Repair (NER), Transcription
Coupled Repair (TCR) and in the cross‐links (Fanconi like) repairing were analyzed for the
chromosomal damage: chromosomal aberrations (CAs) and sister chromatid exchanges
(SCEs).
The results show that the induction of the cross‐links by acetaldehyde is a dose‐dependent.
DNA‐protein is the prevalent type of the induced cross‐links. Moreover, the results indicate
that the cross‐link DNA‐protein produces mainly CAs. The relationship between induction of
cross‐links and SCEs depends on the type of cross‐link induced.
The cell lines most sensitive to acetaldehyde are those with defect in cross‐links (Fanconi
like; KO40) repair and defect in NER (UV4).
This work was published in an international journal, Mutation Research: Lorenti Garcia et al.,
2009, "Relationship between DNA lesions, DNA repair and chromosomal damage induced by
acetaldehyde."
The following two‐year research was performed in the frame of the "ENEA International
Fellowship Programme 2008", with the assigned tutor dr. Roberto Amendola (Laboratory of
Biotechnology and Biomedical Sciences, BIOTEC MED, ENEA Casaccia Research Center). We
evaluated the responses to DNA damage caused by low doses of ionizing radiation in repair
deficient CHO cell lines. Thus, a chronic sublethal damage caused by increase of the
oxidative stress through overexpression of the spermine oxidase (SMO) enzyme is induced in
the repair deficient CHO cell lines. The SMO is an enzyme found in all higher organisms, that
can catabolize the spermine (SPM) to spermidine (SPD) producing the hydrogen peroxide.
The overexpression of SMO induced the radiosensitivity at relatively high doses of ionizing
radiation in mouse neuroblastoma (NB) by increasing DNA oxidative stress levels (Amendola
et al., 2005, Bianchi et al., 2007).
In relation to these results, the possible involvement of the overexpression of SMO in
alteration of the genotoxic damage in cell lines defective in repair mechanisms such as
Nucleotide Excision Repair and Base Excision Repair was investigated. The results are not
explicit. From the experimental point of view, no significantly different response to various
doses applied over the time was determined. However, considering the response of the
biological systems to the low doses of the ionizing radiations, the absence of the significant
response suggests the involvement of another kind of the response associated not only to
the DNA damage.
Additional information
Dottorato di ricerca in Evoluzione biologica e biochimica
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