Binding of Pb-Melatonin and Pb-(Melatonin-metabolites) complexes with DMT1 and ZIP8: implications for lead detoxification

We have applied the docking methodology to characterize the binding modes of the divalent metal transporter 1 (DMT1) and the zinc transporter 8 (ZIP8) protein channels with: melatonin, some melatonin metabolites, and a few lead complexes of melatonin and its metabolites, in three different coordination modes (mono-coordinated, bi-coordinated and tri-coordinated). Our results show that bi-coordinated and tri-coordinated lead complexes prefer to bind inside the central region of ZIP8. Moreover, the interaction strength is larger compared with that of the free melatonin and melatonin metabolites. On the other hand, the binding modes with DMT1 of such complexes display lower binding energies, compared with the free melatonin and melatonin metabolites. Our results suggest that ZIP8 plays a major role in the translocation of Pb, bi or tri coordinated, when melatonin metabolites are present. Finally, we have characterized the binding modes responsible for the ZIP8 large affinities, found in bi-coordinated and tri-coordinated lead complexes. Our results show that such interactions are greater, because of an increase of the number of hydrogen bonds, the number and intensity of electrostatic interactions, and the interaction overlay degree in each binding mode. Our results give insight into the importance of the ZIP8 channel on lead transport and a possible elimination mechanism in lead detoxification processes. Graphical abstract .

In silico, Synthesis and Biological Investigations of Pyrrolo[3,4-C]Pyrrole Hydroxamic Acid Derivatives as Potential Anticancer Agents

Based in a general structural pharmacophore model of suberoylanilide hydroxamic acid (commercially known as Vorinostat©), we synthesized a series of new pyrrolo[3,4-c]pyrrole hydroxamic acid derivatives, <strong>9a-c</strong>, to be tested as candidates for anti-cancer drugs. The evaluation of their possible biological activity was assessed in two ways: a) computational characterization from molecular calculations and quantum reactivity descriptors and b) biological assays. Molecular docking and density functional theory calculations were performed to assess the binding properties of our newly synthesized pyrrolo[3,4-c] pyrrole hydroxamic acid derivatives, employing as the biological target the histone deacetylase isoforms available in the protein data bank. Furthermore, to characterize the effect of changing the functional groups that we varied while designing our drug model, and to improve the assessment of the binding energy, conceptual density functional theory reactivity descriptors were calculated to rationalize the capability of the new drugs to interact with the histones active site. Our findings show that the newly synthesized derivative, <strong>9c</strong>, display the best energetic coupling with the biological target and the more favorable values of the density functional theory descriptors to interact with the active site. The biological assay of the anti-cancer drug candidates was done using three different techniques: i) anti-proliferative activity on two breast cancer cell lines; ii) Histone H3 acetylation; and iii) DNA damage. Docking studies were performed on histone deacetylase enzymes. The biological function of these enzymes is the deacetylation of histones. We analyze the level of histone acetylation in two cell lines. The computational findings are in good agreement with the biological evaluation. Our main contribution is that one of our newly synthesized derivatives, <strong>9c</strong>, performs better than the commercial reference suberoylanilide hydroxamic acid.