http://informahealthcare.com/dct ISSN: 0148-0545 (print), 1525-6014 (electronic) Drug Chem Toxicol, 2014; 37(3): 276–280 ! 2014 Informa Healthcare USA, Inc. DOI: 10.3109/01480545.2013.851686 RESEARCH ARTICLE Evaluation of vitamin B12 effects on DNA damage induced by paclitaxel Karem Alzoubi 1 , Omar Khabour 2 , Manal Khader 1 , Nizar Mhaidat 1 , and Sayer Al-Azzam 1 1 Department of Clinical Pharmacy, Faculty of Pharmacy and 2 Department of Medical Laboratory Sciences, Faculty of Applied Medical Sciences, Jordan University of Science and Technology, Irbid, Jordan Abstract Paclitaxel (PAC) is an anticancer drug that has been shown to generate free radicals leading to irreversible cell injury. Vitamin B12 has antioxidative properties and can protect DNA from free radicals. In this study, we examined the possible genotoxic effect of PAC on DNA as well as the possible protective effect of vitamin B12 on DNA damage induced by paclitaxel. Sister chromatid exchanges (SCEs), chromosomal aberrations (CAs) and 8-hydroxy-2’-deoxyguanosine (8-OHdG) levels were measured in cultured human blood lymphocytes treated with PAC (10 mM) and/or vitamin B12 (2.7 mg/mL). Our results showed that PAC significantly increased the frequencies of SCEs (p50.001) and CAs (p50.001) in human blood lymphocytes, as compared to controls. These DNA damages, caused by PAC drug, were prevented by pretreatment of cells with vitamin B12. In addition, we showed that PAC induced an increase in 8-OHdG, a marker of oxidative DNA damage, and that this increase was prevented by vitamin B12. Vitamin B12 seems to protect against genotoxicity induced by PAC in human blood lymphocytes. Keywords 8-OH-dG, chromosomal aberrations, human blood lymphocyte, paclitaxel, sister chromatid exchanges, vitamin B12 History Received 26 December 2012 Revised 22 June 2013 Accepted 28 July 2013 Published online 11 November 2013 Introduction Paclitaxel (PAC) is an antineoplastic agent that was first isolated from the bark of the pacific yew, Taxus brevifolia, in 1971 (Rodriguez-Antona, 2010). Paclitaxel is clinically effective in treating breast, ovarian, non-small-cell lung and head and neck cancers (Chirgwin & Chua, 2011; Galic et al., 2011; Green, 2008; Huang & Campbell, 2012). The mech- anism of antitumor action of PAC involves inhibition of mitosis and cell proliferation by stabilization of microtubules, as well as blocking cell-cycle progression in late G 2 /M phase (Galletti et al., 2007; Yusuf et al., 2003). In addition, using in vitro systems, PAC has been shown to affect tumor cells by induction of apoptosis (Mhaidat et al., 2009) and increasing intracellular reactive species, including superoxide (O 2 -), H 2 O 2 (Conklin, 2004) and nitric oxide (Kong et al., 2000). Several studies have reported on the genotoxic effect of PAC in vitro using healthy human cells. One study reported that PAC was a strong aneugenic drug in cultured human cells at therapeutic doses (Digue et al., 1999). Another study used the in vitro micronucleus assay, in combination with fluor- escent in situ hybridization of nonspecific centromeric probes, and showed that PAC significantly increased micro- nucleated rates in a concentration-dependent manner (Digue et al., 2002). Lee and colleagues showed that PAC induced chromosomal DNA damage in mouse lymphoma cells by using comet and apoptotic assays (Lee et al., 2003). Finally, PAC has been reported to induce oxidative DNA damage (Branham et al., 2004; Digue et al., 1999; Ollikainen et al., 2000) by generating reactive oxygen (ROS) and nitrogen species (RNS) (Ramanathan et al., 2005). Recent studies revealed that vitamin B12 may modulate oxidative stress responses through enhancing methionine synthase activity that is linked to glutathione synthesis—a major intracellular antioxidant (Al-Maskari et al., 2012; McCaddon & Hudson, 2007). In addition, vitamin B12 (at 1 mmol/mL) might act directly as a scavenger of ROS as has been shown using cultured cells (Richard et al., 2009). Therefore, given the protective effect of vitamin B12 against oxidative damage of other agents, such as pioglitazone (Alzoubi et al., 2012), we aimed to study the potential protective effect of vitamin B12 against the genotoxic effect and oxidative DNA damage induced by PAC. This was achieved by using sister chromatid exchanges (SCEs), chromosomal aberrations (CAs) and 8-hydroxy-2 0 -deoxygua- nosine (8-OHdG) assays and cultured human blood lympho- cytes. Results of this study could provide the basis for further clinical studies of vitamin B12 as a potential protective agent against genotoxicity associated with PAC. Methods Subjects Five healthy nonsmoker males (age range: 22–37 years) were the blood donors. Exclusion criteria were alcohol, cigarette smoking, medications and vitamins use. A sample Address for correspondence: Karem H. Alzoubi, Department of Clinical Pharmacy, Faculty of Pharmacy, Jordan University of Science and Technology, Irbid 22110, Jordan. Fax: +96227201075. E-mail: khalzoubi@just.edu.jo Drug and Chemical Toxicology Downloaded from informahealthcare.com by University of Georgia on 06/03/14 For personal use only.