Synthesis, characterization, and evaluation of Cd[L-proline]2, a novel histone deacetylase inhibitor that induces epigenetic modification of histone deacetylase isoforms in A549 cells

Abstract

Histone deacetylases (HDACs) play an important role in the epigenetic regulation of gene expression through their effects on the compact chromatin structure. In clinical studies, several classes of histone deacetylase inhibitors (HDACi) have demonstrated potent anticancer activities with metal complexes. Hence, we synthesized cadmium-proline complexes using both the D- and L-isomers of proline and evaluated their biological activities by observing the efficiency of their inhibition of HDAC activity, ability to reduce the expression of HDAC isoforms in A549 cells and effect on apoptosis. The synthesized compounds were characterized by UV, IR, NMR spectroscopy and elemental analysis. In-vitro cell toxicity was evaluated by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay, and the 50% inhibitory concentration (IC; 2 μM) was obtained at 12 h. The morphological study at nuclear levels was performed by acridine orange/ethidium bromide (AO/EB) and Hoechst staining, and the results showed an association with cell cycle arrest at the G2/M phase. Both cadmium-proline complexes intensely inhibited HDAC activity at 2 μM concentration. Interestingly, Cd[L-proline] was found to be a potent inhibitor for all HDAC isoforms, whereas Cd[D-proline] inhibited only HDAC1 and 2. HDACi are novel chemotherapeutic drugs that induce hyperacetylation of histones H3 and H4, counteracting the aberrant repression of genes, such as insulin-like growth factor-binding protein 3 (IGFBP-3), p53, and p21. ERK/MAPK signaling pathway resulted in the downregulation of the expression of matrix metalloproteinases 2 and 9 (MMP-2 and MMP-9), contributing to the inhibition of metastasis in A549 cells. Apoptosis induction was accompanied by the activation of death receptors and their ligands which recruit initiator caspase 8, decrease in mitochondrial membrane potential (ΔΨm), as well as increased Bax/Bcl ratio, followed by activation of caspases 9 and 3. Our finding suggests that Cd[L-proline] complex accelerates epigenetic rearrangement by HDAC inhibition, which may be the key mechanism for its anticancer activity.

Metabolomic Investigation of Ultraviolet Ray-Inactivated White Spot Syndrome Virus-Induced Trained Immunity in Marsupenaeus japonicus

“…L-proline reportedly increases DNA methylation to regulate the pluripotency of embryonic stem cells ( 24 ). And synthesized cadmium–proline complexes accelerate epigenetic rearrangement by histone deacetylases inhibition ( 25 ). The treatment of cultured hepatocellular carcinoma cells with hydrogen peroxide caused methylation of the E-cadherin promoter ( 26 ).…”

A novel binuclear hydrazone-based Cd(II) complex is a strong pro-apoptotic inducer with significant activity against 2D and 3D pancreatic cancer stem cells

“…Some of the investigated complexes target DNA non-covalently by groove binding [20], intercalation [36,38,54,57,60,64] and combined mode of intercalation and groove binding [45], while in some cases nuclease activity [31,54,57] and covalent binding similar to CDDP were observed [30]. Also, proteasomal chymotrypsin-like [34,35,44], proteasomal deubiquitinase [56], histone deacetylase [43] and telomerase [72] inhibiton properties were revealed as mode of action of several Cd complexes, as well as inhibition of incorporation of 3H-thymidine into DNA and the respiration of tumor cells [18].…”

“…It seems that ligand type used for preparation of Cd complexes may cause their very favorable anti-tumor effects [17]. Ligands used for preparation of Cd complexes can be classified as: thiosemicarbazones [16,[18][19][20][21][22][23][24], selenosemicarbazones [25][26][27], hydrazones [16,[27][28][29][30][31][32][33][34][35][36], hydrazides [38,39], diimines [40], amides [41,42], aminoacids [43,44], heterocycles [44][45][46][47][48][49][50][51][52][53][54][55][56], macrocycles [58][59][60], drugs [61][62][63]…”

“…Comparative studies with Zn(II), Cu(II), Co(II), Ni(II), Ce(IV), Zr(IV), Mn(II), Pb(II), Ca(II), and Sn(II) metal complexes revealed that Cd(II) complexes possess better activities [17,21,23,34,36,41,47,49,53,57,61,71]. Mechanistic studies revealed that Cd(II) complexes kill cancer cells via apoptosis [25,34,35,38,41,43,54,56,59,71]. Some of the investigated complexes target DNA non-covalently by groove binding [20], intercalation [36,38,54,57,60,64] and combined mode of intercalation and groove binding [45], while in some cases nuclease activity [31,54,57] and covalent binding similar to CDDP were observed [30].…”

Exploring novel Cd(ii) complexes with 5-methyl-4-imidazolecarboxaldehyde: synthesis, structure, computational insights, and affinity to DNA through switchSense methodology

“…19 In addition to DNA, they can also be directed at other protein targets. [20][21][22][23] In the case of cancer cells, they inhibit their respiration and also lead to their death through apoptosis. 14,[20][21][22]24 Apart from this, Cd(II) coordination compounds may have stronger antimicrobial activity than some previously used antibiotics.…”