ABSTRACT
The tobacco alkaloid nicotine is responsible for addiction to tobacco and supposed to contribute to tobacco carcinogensis, too. Recently, genotoxic effects of nicotine have been reported in human cells from blood and upper aerodigestive tract. Because of nicotine accumulation in saliva, the study of possible in vitro genotoxic effects of nicotine have been extended to human salivary gland cells. Specimens of parotid glands of 10 tumor patients were obtained from tumor-free tissue. Single cells were prepared by enzymatic digestion immediately after surgery and exposed for 1h to 0.125-4.0mM of nicotine. Possible genotoxic effects were determined by the Comet assay using the % DNA in tail (DT) as a reliable indicator of DNA damage. Nicotine induced a significant dose-dependent increase of DNA migration in parotid gland single-cells. The mean DT was 1.12-fold (0.125mM) to 2.24-fold (4.0mM) higher compared to control. The lowest concentration eliciting significant DNA damage within 1h, 0.25mM nicotine, is only 10-fold higher than maximal concentrations of nicotine reported in saliva after unrestricted smoking. Although conclusive evidence for a carcinogenic potential of nicotine is still lacking, the safety of long-term nicotine replacement therapy should be carefully monitored.
Subject(s)
DNA Damage , Nicotine/adverse effects , Nicotinic Agonists/adverse effects , Parotid Gland/drug effects , Smoking/adverse effects , Adult , Aged , Aged, 80 and over , Cells, Cultured , Comet Assay/methods , Female , Humans , In Vitro Techniques , Male , Middle Aged , Mutagenicity TestsABSTRACT
Defects in apoptosis play a decisive role in both tumorigenesis and drug resistance in tumor treatment. The purpose of this study was to investigate the balance between formation of genomic damage and induction of apoptosis upon genotoxic stress. For this, we influenced the apoptotic response and measured the amount of genomic damage expressed as micronucleus formation after treatment with the topoisomerase II inhibitor etoposide. Apoptosis was reduced by the addition of pifithrin (PFT) alpha and enhanced by transient transfection with bcl-2 antisense-oligonucleotide in Bcl-2-overexpressing cells. We used three human lymphoblastoid cell lines with different p53 status (TK6, wild-type p53; WTK1, mutated p53; NH32, p53 double knockout). Under conditions of reduced apoptosis, micronucleus formation was also reduced. When apoptosis was increased, micronucleus formation remained unchanged or was also increased. Overall, we did not find an expected inverse correlation between induction of apoptosis and genomic damage.
