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).