Discussion
Although DOX is used for treating a broad range of solid tumours, nevertheless, its use is associated with severe adverse effects such as cardiotoxicity and myelosuppression (2)(3). The reduced efficacy of DOX in treating cancer and the significant genotoxicity was reported to be related to the direct DNA damage caused by such chemotherapeutic drug and its ability to interact with the DNA molecule and interfering with the activity of topoisomerase-II enzyme, thus, interfering with DNA replication and repair; furthermore, DOX may have an indirect effect through the generation of free radicals, and this consequently leads to the depletion of the antioxidants, increasing lipid, protein and nucleic acid peroxidation, DNA double-strand breakage and chromosomal aberration in normal cells (4)(7). Therefore, reducing the DOX induced unwanted effects on normal cells would enable broader use in chemotherapeutic regimens and improve outcomes in cancer patients.
In the current study, the data showed that acute exposure to DOX caused a significant increase in the serum level of MDA, depleted GSH and antioxidant enzymes, induced structural chromosomal aberration and increased micronuclei appearance in addition to stimulated DNA damage compared to those in control (Group I ) as shown in Fig 1A, tables 1 and 2, and figure 2 A&B, respectively. These results are agreeable with previous studies stating that DOX caused oxidative stress, clastogenic changes and DNA damage (25)(26)(27). In addition, DOX has a noticeable inhibitory effect on the cell division and the mitotic index value, which is agreeable with the earlier findings reported in previous studies (15)(28)(29). Furthermore, the results revealed that DMF (15mg/kg/day) alone caused a non-significant difference in TCAs, MN appearance and the % DNA in Tail of the comet; this might indicate that DMF may have no clastogenic or DNA damaging effects on rats’ BM in vivo .
However, DMF (15mg/kg/day) orally administered for 14 days to rats prior to doxorubicin (90mg/kg) exposure (Group IV ) significantly reduced MDA level, restored GSH level and antioxidant enzymes activity compared to Group III which supports its antioxidant role. Moreover, in rats of Group IV , DMF significantly reduced (P <0.05) TCAs, MN appearance and % DNA in Tail compared to those in the control group; thus, it efficiently protected against DOX-induced genotoxic effects in rats’ BM [Fig. 1B-D, Tables 1 and 2 and Fig. 2B].
There are no previous studies regarding the protective effect of DMF against genotoxicity induced by DOX in vivo . Thus, the present study possibly is the first that demonstrates the modulatory effect of DMF pre-treatment on DOX-induced chromosomal and DNA damage effects in rats’ BM in vivo .
The mechanism underlying DMF anticlastogenic effect against DOX could be related to its antioxidant activity, as it might reduce the DOX-mediated free radicals’ generation, inhibited the formation of DNA adduct, and reduced DNA and chromosomal damage since DOX is well-renowned for inducing cellular oxidative stress (OS) and subsequent DNA damage; what’s more, DMF showed to have an anticarcinogenic/antimutagenic activity in animal models by modulating NrF2 axis (30)(31); furthermore, DMF was previously-reported to show a protective activity against myocardial Ischemic/Reperfusion which is related to DMF mediated improved cellular viability, reduced oxidative stress and enhanced the expression of Nrf2‑regulated antioxidative genes; in addition, DMF was reported to prevent apoptosis, increase the survival rate and proliferation of human adipose-derived mesenchymal stem cells (hASCs) against oxidative stress which is mediated by upregulation of HO-1 and NQO-1 expression (32). Similarly, DMF has been shown to induce apoptosis in cancer and damaged cells, which may facilitate the reduction in the appearance of chromosomal damage (33).