The plant alkaloid chelerythrine binds to chromatin, alters H3K9Ac and modulates global gene expression.

Chelerythrine (CHL), a plant alkaloid, possesses antimicrobial, anti-inflammatory, and antitumor properties. Although CHL influences several key signal transduction pathways, its ability to interact directly with nucleoprotein complex chromatin, in eukaryotic cells has so far not been looked into. Here we have demonstrated its association with hierarchically assembled chromatin components, viz. long chromatin, chromatosome, nucleosome, chromosomal DNA, and histone H3 and the consequent effect on chromatin structure. CHL was found to repress acetylation at H3K9. It is more target-specific in terms of gene expression alteration and less cytotoxic compared to its structural analog sanguinarine.

A novel nanohybrid for cancer theranostics: folate sensitized Fe2O3 nanoparticles for colorectal cancer diagnosis and photodynamic therapy.

Organic-inorganic nanohybrids are becoming popular for their potential biological applications, including diagnosis and treatment of cancerous cells. The motive of this study is to synthesise a nanohybrid for the diagnosis and therapy of colorectal cancer. Here we have developed a facile and cost-effective synthesis of folic acid (FA) templated Fe2O3 nanoparticles with excellent colloidal stability in water using a hydrothermal method for the theranostics applications. The attachment of FA to Fe2O3 was confirmed using various spectroscopic techniques including FTIR and picosecond resolved fluorescence studies. The nanohybrid (FA-Fe2O3) is a combination of two nontoxic ingredients FA and Fe2O3, showing remarkable photodynamic therapeutic (PDT) activity in human colorectal carcinoma cell lines (HCT 116) via generation of intracellular ROS. The light induced enhanced ROS activity of the nanohybrid causes significant nuclear DNA damage, as confirmed from the comet assay. Assessment of p53, Bax, Bcl2, cytochrome c (cyt c) protein expression and caspase 9/3 activity provides vivid evidence for cell death via an apoptotic pathway. In vitro magnetic resonance imaging (MRI) experiments in folate receptor (FR) overexpressed cancer cells (HCT 116) and FR deficient human embryonic kidney cells (HEK 293) reveal the target specificity of the nanohybrid towards cancer cells, and are thus pronounced MRI contrasting agents for the diagnosis of colorectal cancer.

Photoinduced Dynamics and Toxicity of a Cancer Drug in Proximity of Inorganic Nanoparticles under Visible Light.

Drug sensitization with various inorganic nanoparticles (NPs) has proved to be a promising and an emergent concept in the field of nanomedicine. Rose bengal (RB), a notable photosensitizer, triggers the formation of reactive oxygen species under green-light irradiation, and consequently, it induces cytotoxicity and cell death. In the present study, the effect of photoinduced dynamics of RB upon complexation with semiconductor zinc oxide NPs is explored. To accomplish this, we successfully synthesized nanohybrids of RB with ZnO NPs with a particle size of 24 nm and optically characterized them. The uniform size and integrity of the particles were confirmed by high-resolution transmission electron microscopy. UV/Vis absorption and steady-state fluorescence studies reveal the formation of the nanohybrids. ultrafast picosecond-resolved fluorescence studies of RB-ZnO nanohybrids demonstrate an efficient electron transfer from the photoexcited drug to the semiconductor NPs. Picosecond-resolved Förster resonance energy transfer from ZnO NPs to RB unravel the proximity of the drug to the semiconductor at the molecular level. The photoinduced ROS formation was monitored using a dichlorofluorescin oxidation assay, which is a conventional oxidative stress indicator. It is observed that the ROS generation under green light illumination is greater at low concentrations of RB-ZnO nanohybrids compared with free RB. Substantial photodynamic activity of the nanohybrids in bacterial and fungal cell lines validated the in vitro toxicity results. Furthermore, the cytotoxic effect of the nanohybrids in HeLa cells, which was monitored by MTT assay, is also noteworthy.

Association of antitumor antibiotic Mithramycin with Mn2+ and the potential cellular targets of Mithramycin after association with Mn2+.

Mithramycin (MTR), an aureolic acid group of antitumor antibiotic is used for the treatment of several types of tumors. We have reported here the association of MTR with an essential micronutrient, manganese (Mn(2+)). Spectroscopic methods have been used to characterize and understand the kinetics and mechanism of complex formation between them. MTR forms a single type of complex with Mn(2+) in the mole ratio of 2:1 [MTR: Mn(2+)] via a two step kinetic process. Circular dichroism (CD) spectroscopic study indicates that the complex [(MTR)2 Mn(2+)] has a right-handed twist conformation similar in structure with the complexes reported for Mg(2+) and Zn(2+). This conformation allows binding via minor groove of DNA with (G, C) base preference during the interaction with double-stranded B-DNA. Using absorbance, fluorescence, and CD spectroscopy we have shown that [(MTR)2 Mn(2+)] complex binds to double-stranded DNA with an apparent dissociation constant of 32 µM and binding site size of 0.2 (drug/nucleotide). It binds to chicken liver chromatin with apparent dissociation constant value 298 µM. Presence of histone proteins in chromatin inhibits the accessibility of the complex for chromosomal DNA. We have also shown that MTR binds to Mn(2+) containing metalloenzyme manganese superoxide dismutase from Escherichia coli.