Shi-Liang Huang

Turning off Transcription of the bcl-2 Gene by Stabilizing the bcl-2 Promoter Quadruplex with Quindoline Derivatives

Human bcl-2 gene is an apoptosis-related oncogene containing a GC-rich sequence which is located upstream from P1 promoter and has the potential to form G-quadruplex structures. However, the regulatory role of the quadruplex and the effect of its ligands on bcl-2 have not been clarified. Here, we demonstrated that the G-quadruplex structure was disrupted when partial mutation of G --> A was made, resulting in a 2-fold increase in basal transcriptional activity of bcl-2 promoter. Quindoline derivatives, the highly active G-quadruplex ligands developed by our group, could significantly suppress bcl-2 transcriptional activation but had less effect on mutated bcl-2 transcription. These results provided direct evidence that G-quadruplex structure formed in bcl-2 promoter region could function as a transcriptional repressor element, and G-quadruplex specific ligands could regulate the transcription of bcl-2 through stabilization of quadruplex structure. The results further indicated that quindoline derivatives could induce apoptosis of HL-60 tumor cells.

Isaindigotone Derivatives: A New Class of Highly Selective Ligands for Telomeric G-Quadruplex DNA

Four isaindigotone derivatives (5a,b and 6a,b) designed as telomeric G-quadruplex ligands have been synthesized and characterized. The unfused aromatic rings in these compounds allow a flexible and adaptive conformation in G-quadruplex recognition. The interaction of human telomeric G-quadruplex DNA with these designed ligands was explored by means of FRET melting, fluorescence titration, CD spectroscopy, continuous variation, and molecular modeling studies. Our results showed that the adaptive scaffold might not only allow the ligands to well occupy the G-quartet but also perfectly bind to the grooves of the G-quadruplex. The synergetic effect of the multiple binding modes might be responsible for the improved binding ability and high selectivity of these ligands toward G-quadruplex over duplex DNA. Long-term exposure of HL60 and CA46 cancer cells to compound 5a showed a remarkable decrease in population growth, cellular senescence phenotype, and shortening of the telomere length, which is consistent with the behavior of an effective telomeric G-quadruplex ligand and telomerase inhibitor.

Synthesis, biological evaluation and molecular modeling of oxoisoaporphine and oxoaporphine derivatives as new dual inhibitors of acetylcholinesterase/butyrylcholinesterase.

Aporphine alkaloids, isolated from Chinese medicinal herb, are important natural products. We recently reported that synthetic derivatives of oxoisoaporphine alkaloids exhibited high acetylcholinesterase inhibitory activity and high selectivity for AChE over BuChE (Bioorg. Med. Chem. Lett. 2007, 17, 3765-3768). In this paper, further research results were presented. A series of novel derivatives of oxoaporphine alkaloids (5a-j, 4-carboxylic amide-7-oxo-7H-dibenzo[de,g]quinoline, Ar-CONH(CH(2))(n)NR) and their quaternary methiodide salts (6a-h, Ar-CONH(CH(2))(n)N(+)(CH(3))RI(-)) were designed and synthesized as acetylcholinesterase (AChE) and/or butyrylcholinesterase (BuChE) inhibitors. The AChE inhibition potency of synthetic oxoaporphine derivatives was decreased about 2-3 orders of magnitude as compared with that of oxoisoaporphine derivatives. Non-competitive binding mode was found for both kinds of derivatives. Molecular docking simulations on the oxoisoaporphine derivatives 7 series and oxoaporphine derivatives 6 series with AChE from Torpedo californica have demonstrated that the ligands bound to the dual-site of the enzyme.

Synthesis and evaluation of curcumin analogues as potential thioredoxin reductase inhibitors

Series of curcumin derivatives were synthesized; the inhibitory activities on thioredoxin reductase (TrxR) of all analogues were evaluated by DTNB assay in vitro. It is found that most of the analogues can inhibit TrxR in the low micromolar range; Structure-activity relationship analysis reveals that analogues with furan moiety have excellent inhibitory effect on TrxR in an irreversible manner, indicating that the furan moiety may serve as a possible pharmacophore during the interaction of curcumin analogues with TrxR. The effect of selected curcuminoids on growth of different TrxR overexpressed cancer cell lines was also investigated and discussed.

Design, synthesis and evaluation of novel tacrine-multialkoxybenzene hybrids as dual inhibitors for cholinesterases and amyloid beta aggregation

A new series of tacrine-multialkoxybenzene hybrids (9a-9n) were designed, synthesized and evaluated as dual inhibitors of cholinesterases (ChEs) and self-induced β-amyloid (Aβ) aggregation. All the synthesized compounds had high acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) inhibitory activity with IC₅₀ values at the nanomolar range, which were much better than tacrine alone. A Lineweaver-Burk plot and molecular modeling study showed that these hybrids targeted both the catalytic active site (CAS) and the peripheral anionic site (PAS) of AChE. Besides, compounds 9a-9f with methylenedioxybenzene moiety showed higher self-induced Aβ aggregation inhibitory activity than a reference compound, curcumin. These compounds could be selected as multi-potent agents for further investigation to treat AD.

Synthesis and evaluation of 9-O-substituted berberine derivatives containing aza-aromatic terminal group as highly selective telomeric G-quadruplex stabilizing ligands

A series of new 9-O-substituted berberine derivatives (4a-j) as telomeric quadruplex ligands was synthesized and evaluated. The results from biophysical and biochemical assay indicated that introducing of positive charged aza-aromatic terminal group into the side chain of 9-position of berberine significantly improved the binding ability with G-quadruplex, and exhibited the inhibitory effect on the hybridization and on telomerase activity. These derivatives showed excellent selectivity for telomeric G-quadruplex DNA over duplex.

Synthesis and evaluation of heterobivalent tacrine derivatives as potential multi-functional anti-Alzheimer agents

A new series of heterobivalent tacrine derivatives were designed, synthesized and evaluated as potential multi-functional anti-Alzheimer agents for their inhibitory activity on cholinesterases, antioxidant activity and self-induced β-amyloid (Aβ) aggregation. All these synthesized compounds had potent inhibition activity on acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) at nanomolar range. A Lineweaver-Burk plot and molecular modeling study showed that these compounds targeted both the catalytic active site (CAS) and the peripheral anionic site (PAS) of AChE. The compounds containing hydroxyl group showed potent peroxyl radical absorbance activity. In addition, compound 5j exhibited higher self-induced Aβ aggregation inhibitory activity than curcumin, which could become a multi-functional agent for further development for the treatment of AD.

Hybrids of oxoisoaporphine-tacrine congeners: novel acetylcholinesterase and acetylcholinesterase-induced β-amyloid aggregation inhibitors.

A series of dual binding site acetylcholinesterase (AChE) inhibitors have been designed, synthesized, and tested for their ability to inhibit AChE, butyrylcholinesterase (BChE), AChE-induced and self-induced β-amyloid (Aβ) aggregation. The new hybrids consist of a unit of 1-azabenzanthrone and a tacrine or its congener, connected through an oligomethylene linker containing an amine group at variable position. These hybrids exhibit high AChE inhibitory activity with IC(50) values in the nanomolar range in most cases. Moreover, five out of the 12 hybrids of this series, particularly those bearing a tetrahydroacridine moiety, exhibit a significant in vitro inhibitory activity toward the AChE-induced and self-induced Aβ aggregation, which makes them promising anti-Alzheimer drug candidates.

Synthesis and evaluation of novel rutaecarpine derivatives and related alkaloids derivatives as selective acetylcholinesterase inhibitors.

A series of novel rutaecarpine derivatives and related alkaloid derivatives 3-aminoalkanamido-substituted rutaecarpine 4a-f and 7,8-dehydrorutaecarpine 5a-c, and 6-aminoalkanamido-substituted 3-[2-(3-Indolyl)ethyl]-4(3a)-quinazolinones 8a-c, were synthesized and subjected to pharmacological evaluation as acetylcholinesterase (AChE) inhibitors. The synthetic compounds exhibited strong inhibitory activity for AChE and high selectivity for AChE over BuChE. The structure-activity relationships were discussed and their binding conformation and simultaneous interactions mode were further clarified by kinetic characterization and the molecular docking studies.

Quinolino-benzo-[5, 6]-dihydroisoquindolium compounds derived from berberine: a new class of highly selective ligands for G-quadruplex DNA in c-myc oncogene.

A series of quinolino-benzo-[5, 6]-dihydroisoquindolium compounds (3a, 3f, 3g, and 3j) derived from alkaloid berberine were designed and synthesized as novel G-quadruplex ligands. Subsequent biophysical and biochemical evaluation demonstrated that the addition of pyridine ring and amino group into berberine improved the binding ability and selectivity towards G-quadruplex DNA in comparison with the previously reported 9-N-substituted berberine derivatives. Furthermore, qRT-PCR assay showed compound 3j led the down-regulation of c-myc gene transcription in leukemia cell line HL60, while little effect on normal cell line ECV-304, which was consistent with the behavior of an effective G-quadruplex ligand targeting c-myc oncogene.