In Vitro Interactions between 17β-Estradiol and DNA Result in Formation of the Hormone-DNA Complexes

Abstract

Beyond the role of 17β-estradiol (E2) in reproduction and during the menstrual cycle, it has been shown to modulate numerous physiological processes such as cell proliferation, apoptosis, inflammation and ion transport in many tissues. The pathways in which estrogens affect an organism have been partially described, although many questions still exist regarding estrogens’ interaction with biomacromolecules. Hence, the present study showed the interaction of four oligonucleotides (17, 20, 24 and/or 38-mer) with E2. The strength of these interactions was evaluated using optical methods, showing that the interaction is influenced by three major factors, namely: oligonucleotide length, E2 concentration and interaction time. In addition, the denaturation phenomenon of DNA revealed that the binding of E2 leads to destabilization of hydrogen bonds between the nitrogenous bases of DNA strands resulting in a decrease of their melting temperatures (Tm). To obtain a more detailed insight into these interactions, MALDI-TOF mass spectrometry was employed. This study revealed that E2 with DNA forms non-covalent physical complexes, observed as the mass shifts for app. 270 Da (Mr of E2) to higher molecular masses. Taken together, our results indicate that E2 can affect biomacromolecules, as circulating oligonucleotides, which can trigger mutations, leading to various unwanted effects.

Molecular Mechanism of Binding between 17β-Estradiol and DNA

“…3C, E2 is inserted into the erDNA strand at the centre of the palindromic half site. In agreement with the mass spectrometry results of Heger et al [9], we find evidence for the plausibility of non-covalent bonding that is dominated by van der Waals interactions. As shown in Fig.…”

“…These structural changes affect the biological functions of DNA including the inhibition of transcription, replication, and DNA repair processes, thereby making intercalators potent mutagens and potential antitumor drugs [43]. Destabilization can trigger mutations leading to unwanted side effects [9].…”

“…Estrogen signalling drives cell proliferation in 60–70% of breast cancers that express the estrogen receptor [8], and anti-estrogen therapy is prescribed to the majority of these patients to prevent breast cancer recurrence. Estrogen exposure is now widely accepted as a risk factor in breast cancer development, but the mechanisms through which estrogens induce breast carcinogenesis have not been fully elucidated [9]. Typically, research has demonstrated that endocrine disrupting molecules, such as bisphenol-A inhibit the hormone binding pocket on the estrogen receptor [10], [11], [12].…”

“…Caldon [8] state that high levels of estrogen are a major risk for breast cancer, and that one mechanism by which estrogen could contribute to breast cancer is via the induction of DNA damage. Using mass spectrometry, Heger et al [9] found that E2 binds to DNA and leads to destabilization of hydrogen bonds between nitrogenous bases of DNA strands resulting in a decrease of their melting temperature. Their results revealed that E2 forms non-covalent physical complexes with DNA, and they suggest that these interactions could trigger mutations leading to unwanted side effects [9].…”

“…Using mass spectrometry, Heger et al [9] found that E2 binds to DNA and leads to destabilization of hydrogen bonds between nitrogenous bases of DNA strands resulting in a decrease of their melting temperature. Their results revealed that E2 forms non-covalent physical complexes with DNA, and they suggest that these interactions could trigger mutations leading to unwanted side effects [9]. DNA damage as a result of exposure to E2 has also been demonstrated in barnacle larvae [13] and rodents [14], for example.…”