Sayantani Das

Withaferin A Induces ROS-Mediated Paraptosis in Human Breast Cancer Cell-Lines MCF-7 and MDA-MB-231.

Advancement in cancer therapy requires a better understanding of the detailed mechanisms that induce death in cancer cells. Besides apoptosis, themode of other types of cell death has been increasingly recognized in response to therapy. Paraptosis is a non-apoptotic alternative form of programmed cell death, morphologically) distinct from apoptosis and autophagy. In the present study, Withaferin-A (WA) induced hyperpolarization of mitochondrial membrane potential and formation of many cytoplasmic vesicles. This was due to progressive swelling and fusion of mitochondria and dilation of endoplasmic reticulum (ER), forming large vacuolar structures that eventually filled the cytoplasm in human breast cancer cell-lines MCF-7 and MDA-MB-231. The level of indigenous paraptosis inhibitor, Alix/AIP-1 (Actin Interacting Protein-1) was down-regulated by WA treatment. Additionally, prevention of WA-induced cell death and vacuolation on co-treatment with protein-synthesis inhibitor indicated requirement of de-novo protein synthesis. Co-treatment with apoptosis inhibitor resulted in significant augmentation of WA-induced death in MCF-7 cells, while partial inhibition in MDA-MB-231 cells; implyingthat apoptosis was not solely responsible for the process.WA-mediated cytoplasmic vacuolationcould not be prevented by autophagy inhibitor wortmanninas well, claiming this process to be a non-autophagic one. Early induction of ROS (Reactive Oxygen Species)by WA in both the cell-lines was observed. ROS inhibitorabrogated the effect of WA on: cell-death, expression of proliferation-associated factor andER-stress related proteins,splicing of XBP-1 (X Box Binding Protein-1) mRNA and formation of paraptotic vacuoles.All these results conclusively indicate thatWA induces deathin bothMCF-7 and MDA-MB-231 cell lines byROS-mediated paraptosis.

Withaferin A induced impaired autophagy and unfolded protein response in human breast cancer cell-lines MCF-7 and MDA-MB-231

The autophagy-lysosome pathway and the ubiquitin-proteasome systems are the two major routes for eukaryotic intracellular protein clearance. Cancerous cells often display elevated protein synthesis and byproduct disposal, thus, inhibition of the protein degradation pathways became an emerging approach for cancer therapy. The present study revealed that withaferin-A (WA), the biologically active withanolide derived from Withania somnifera, initially induced formation of autophagosomes in human breast cancer cell-lines, MCF-7 and MDA-MB-231. WA treatment elevated the levels of autophagic substrate p62/SQSTM1 (p62) and both LC3-II and LC3-I (microtubule-associated protein 2 light chain 3) and simultaneously reduced the upstream autophagy markers like beclin-1 and ATG5-ATG12 complex, which indicate accumulation of autophagosomes in the cells. WA induced disruption of microtubular network through inhibition of tubulin polymerization and its hyper-acetylation, thus prevent the formation of autolysosome (by merging of autophagosomes with lysosomes) and its recycling process, leading to incomplete autophagy. Further, WA caused ER (Endoplasmic Reticulum) stress, which is evident from the activation of ER-related caspase-4 and increased levels of ER stress marker proteins. Thus, these findings altogether indicate that WA mediated inhibition of proteasomal degradation system and perturbation of autophagy, i.e. suppression of both the intracellular degradation systems caused accumulation of ubiquitinated proteins, which in turn led to unfolded protein response and ER stress mediated proteotoxicity in human breast cancer cell-lines, MCF-7 and MDA-MB-231.

Investigation of dielectric properties of La0.33NbO3 ceramics

La0.33NbO3 ceramics was prepared via conventional solid-state reaction method. Structural analysis show the existence of single phase of La0.33NbO3 has been synthesized with an average particle size of 2 µm – 4 µm estimated from FESEM image. Detailed investigation on the dielectric properties and AC conductivity of the La0.33NbO3 ceramics in a wide range of frequency (800 Hz – 5 MHz) and temperatures (30 °C – 300 °C) revealed that these properties are strongly temperature and frequency dependent.

Magnetic study of Co-doped CdSe nanoparticles

Cobalt (2 %, 5 % and 10 %) doped cadmium selenide (CdSe) nanoparticles have been synthesized by soft chemical route. The XRD pattern shows the cubic structure of the sample. Crystallization temperature of the samples is calculated using differential scanning calorimeter. The average particle size of all the samples is found to be ∼ 25 nm. Field dependent (M-H) and temperature dependent (M-T) magnetization explains the presence of ferromagnetic components in the samples at room temperature and low temperature. In order to estimate the antiferromagnetic coupling among the doped TM atoms, an M-T measurement at 500 Oe has been carried out under zero field cooled (ZFC) and field cooled (FC) conditions and Curie-Weiss temperature θ of the samples has been estimated from 1/χ vs T plots.

Dielectric relaxation and study of electrical conduction mechanism in BaZr0.1Ti0.9O3 ceramics by correlated barrier hopping model

Abstract This work aims to study the electrical conduction mechanism in the dielectric material BaZr0.1Ti0.9O3 (BZT) ceramics by applying AC signal in the frequency range of 102 Hz to 106 Hz. The phase purity and microstructure of the sample have been studied by X-ray diffraction refinement and field-emission scanning electron microscope (FE-SEM) analysis. The appearance of resonance peaks in the loss tangent at high temperature is due to inherent dielectric relaxation processes of this oxide. The temperature dependent Cole-Cole plot has been studied in details to determine both the grain and grain boundary contribution to the conductivity. Electrical modulus analysis reveals that the hopping of charge carriers is the most probable conduction mechanism in BZT ceramics. The obtained data of AC conductivity obey the universal double power law and have been discussed in terms of microstructural network characteristics. The behavior of frequency exponent n of AC conductivity as a function of temperature verify the applicability of the correlated barrier hopping (CBH) model. The AC conductivity data are used to estimate the minimum hopping length, density of states at Fermi level, thermal conductivity and apparent activation energy. The value of activation energy confirms that the oxygen vacancies play a vital role in the conduction mechanism.

Magnetic and dielectric study of Fe-doped CdSe nanoparticles

Nanoparticles of cadmium selenide (CdSe) and Fe (5% and 10%) doped CdSe have been synthesized by soft chemical route and found to have cubic structure. The magnetic field dependent magnetization measurement of the doped samples indicates the presence of anti-ferromagnetic order. The temperature dependent magnetization (M-T) measurement under zero field cooled and field cooled conditions has also ruled out the presence of ferromagnetic component in the samples at room temperature as well as low temperature. In order to estimate the anti-ferromagnetic coupling among the doped Fe atoms, an M-T measurement at 500 Oe has been carried out, and the Curie-Weiss temperature θ of the samples has been estimated from the inverse of susceptibility versus temperature plots. The dielectric relaxation peaks are observed in the spectra of imaginary part of dielectric constant. The temperature dependent relaxation time is found to obey the Arrhenius law having activation energy ~ 0.4 eV for Fe doped samples. The frequency dependent conductivity spectra are found to obey the power law.

Establishment of twist-1 and TGFBR2 as direct targets of microRNA-20a in mesenchymal to epithelial transition of breast cancer cell-line MDA-MB-231

Abstract Messenchymal to epithelial transition (MET) is a significant physiological phenomenon involved in embryogenesis and cancer. This study aims at investigating the mechanism of microRNA‐20a (miR‐20a) mediated regulation of mesenchymal to epithelial transition and identification of its direct target genes in breast cancer cell‐line, MDA‐MB‐231. Reduced migratory and invasive property, altered cellular morphology along with reduced capability for attachment to basement membrane was acquired by over‐expression of miR‐20a in invasive MDA‐MB‐231 cell‐line initially expressing low level of this micro‐RNA, indicating direct correlation between abundance of miR‐20a and metastatic property. The switch from mesenchymal to epithelial cells mediated by miR‐20a involved post‐transcriptional down‐regulation of twist1, which in turn controls downstream epithelial markers like E‐cadherin, claudin and mesenchymal markers like N‐cadherin, fibronectin, the crucial players of mesenchymal to epithelial transition (MET). Furthermore, another key component, TGF‐&bgr; and one of its receptors (TGFBR2) were found to be down‐regulated by miR‐20a. Additionally, reporter assay established that post‐transcriptional down‐regulation of TGFBR2 occurred through direct binding of miR‐20a to its 3′UTR, thus abrogating the TGF‐&bgr; signaling pathway resulting in inhibition of MET. Delineating the underlying molecular mechanism of miR‐20a‐mediated MET and defining the target genes will help us to introduce a miRNA‐mediated effective therapeutic strategy against breast cancer. HighlightsMetastatic property and miR‐20a level is directly correlated in MDA‐MB‐231 cell‐line.Over‐expression of miR‐20a down‐regulates expression of twist1.twist1 upregulates crucial epithelial markers and down‐regulates mesenchymal markers.TGF‐&bgr; and its receptor, TGFBR2 were found to be targets of miR‐20a.

Magnetic study of Fe-doped CdSe nanomaterials

Nanoparticles of pure and iron (50 %) doped cadmium selenide (CdSe) have been synthesized by soft chemical route. EDAX analysis supports the inclusion of Fe into CdSe nanoparticles. The average particle size of pure and doped CdSe is found to be ∼50 nm from scanning electron microscopy (SEM). Magnetization of the samples are measured under the field cooled (FC) and zero field cooled (ZFC) modes in the temperature range from 5K to 300K applying a magnetic field of 500Oe. Field dependent magnetization (M-H) measurement indicates presence of room temperature (RT) paramagnetism and low temperature (5K) ferromagnetism of the sample.

Understanding the photoluminescence characteristics of Eu3+-doped double-perovskite by electronic structure calculation

Europium-doped luminescent barium samarium tantalum oxide Ba2SmTaO6 (BST) has been investigated by first-principles calculation, and the crystal structure, electronic structure, and optical properties of pure BST and Eu-doped BST have been examined and compared. Based on the calculated results, the luminescence properties and mechanism of Eu-doped BST has been discussed. In the case of Eu-doped BST, there is an impurity energy band at the Fermi level, which is formed by seven spin up energy levels of Eu and act as the luminescent centre, which is evident from the band structure calculations.

Structural and transport properties of CdSe nanorods

The nanorods of cadmium selenide (CdSe) have been synthesized by soft chemical route. The selected area electron diffraction pattern, high resolution TEM and X-ray diffraction pattern indicate the cubic structure of the sample. The band gap of the sample is obtained using Tauc relation to UV-visible spectrum and found to be 1.92 eV. 1st order and 2nd order Raman bands are followed to investigate the behaviour of the phonon modes of the materials which is considered to be important to predict the potential of the material to microwave applications. Thermal behaviour of the sample is investigated using differential scanning calorimeter. Kissinger equation is used to calculate the activation energy of the sample, which is found to be 1.67 eV.