Browsing by Author "Saurabh Srivastav"

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Biphasic ROS accumulation and programmed cell death in a cyanobacterium exposed to salinity (NaCl and Na2SO4)
(Elsevier B.V., 2017) Prashant Swapnil; Amarish Kumar Yadav; Saurabh Srivastav; Naveen K Sharma; Saripella Srikrishna; Ashwani K Rai
High salinity increases antioxidative activities in plants; however, their significance for overall plant salt tolerance remains to be established. This work provided in vivo evidence of salinity induced biphasic reactive oxygen species (ROS) accumulation evoking oxidative stress in the cyanobacterium Anabaena fertilissima. First, a transient increase in ROS (intense and short-lived) was observed within 5 min of salt exposure, which peaked within 15 min and reached basal level by 2 h. This was followed by a second relatively long-lived and low magnitude ROS accumulation that started at 4 h of salt stress, attained its maximal at 6 h, followed by a gradual decline but did not attain the basal level by the end of experimentation (12 h). Phase I ROS accumulation timing corresponded to the reaction of cyanobacterial cells to the salt stress, while altered photosynthetic and respiratory parameters corresponded with the phase II ROS generation. Relatively lower magnitude of ROS generation during phase II may be attributed to the rapid activation of robust antioxidative systems in cyanobacteria. Consequently, ROS generation lead to the activation of programmed cell death (PCD) undergoing various apoptotic stages such as externalization of phosphatidylserine, DNA laddering and loss of plasma membrane integrity. A. fertilissima exposed to salt in the presence of SO4¯ was relatively better equipped to deal with salt stress. © 2017 Elsevier B.V.
Chiral heterobimetallic complexes targeting human DNA-topoisomerase Iα
(2013) Sartaj Tabassum; Ahmad Asim; Rais Ahmad Khan; Zahid Hussain; Saurabh Srivastav; Saripella Srikrishna; Farukh Arjmand
The chiral monometallic CuII (1) and ZnII (2) and heterobimetallic CuII-SnIV and ZnII-Sn IV complexes with tridentate chiral Schiff base -ONO-ligand in the presence of nitrogen donor heterocyclic ligand imidazole; were prepared and characterized by various physico-chemical and spectroscopic methods. Preliminary complex-DNA interaction studies employing optical methods revealed that 3 displayed a higher propensity towards the drug target DNA double helix and recommended predominantly an electrostatic mode of interaction as well as a groove binding affinity of the complex with CT-DNA. This was quantified by Kb and KSV values of complexes 1-4, which demonstrated a multifold increase in complex 3 binding to CT DNA and clearly demonstrates its potency to act as a chemotherapeutic agent. Furthermore, the gel electrophoretic patterns of supercoiled pBR322 DNA with varying concentrations of complex 3 exhibits the ability to cleave DNA and follow a freely diffusible radical mechanism. The antiproliferative effects of complex 3 on human hepatoma cancer cells (Huh7) was investigated. Human Topo I inhibition assay by complex 3 was performed and results confirmed significantly good activity at lower concentrations than some of the classical Topo I inhibitors. Additionally, complex 3 was investigated for the expression of MMP-2 and TGF-β by real time PCR. The cellular uptake of complex 3 by HeLa cells was studied by confocal microscopy. © 2013 The Royal Society of Chemistry.
Enantiomeric fluoro-substituted benzothiazole Schiff base-valine Cu(II)/Zn(II) complexes as chemotherapeutic agents: DNA binding profile, cleavage activity, MTT assay and cell imaging studies
(Elsevier, 2015) Rahman Alizadeh; Imtiyaz Yousuf; Mohd Afzal; Saurabh Srivastav; Saripella Srikrishna; Farukh Arjmand
To evaluate the biological preference of chiral drugs toward DNA target, new metal-based chemotherapeutic agents of Cu(II) and Zn(II), l-/d-fluorobenzothiazole Schiff base-valine complexes 1 & 2 (a and b), respectively were synthesized and thoroughly characterized. Preliminary in vitro DNA binding studies of ligand L and complexes 1 & 2 (a and b) were carried out in Tris-HCl buffer at pH 7.2 to demonstrate the chiral preference of l-enantiomeric complexes over the d-analogues. The extent of DNA binding propensity was ascertained quantitatively by Kb, K and Ksv values which revealed greater binding propensity by l-enantiomeric Cu(II) complex 1a and its potency to act as a chemotherapeutic agent. The cleavage studies with pBR322 plasmid DNA revealed higher nuclease activity of 1a as compared to 2a via hydrolytic cleavage mechanism. The complexes 1 & 2 (a and b) were also screened for antimicrobial activity which demonstrated significantly good activity for l-enantiomeric complexes. Furthermore, cytotoxicity of the complexes 1a and 1b was evaluated by the MTT assay on human HeLa cancer cell line which implicated that more than 50% cells were viable at 15 μM. These results were further validated by cell imaging studies which demonstrated the nuclear blebbing. © 2015 Published by Elsevier B.V.
Folic Acid Supplementation Ameliorates Oxidative Stress, Metabolic Functions and Developmental Anomalies in a Novel Fly Model of Parkinson’s Disease
(Springer New York LLC, 2015) Saurabh Srivastav; Sandeep Kumar Singh; Amarish Kumar Yadav; Saripella Srikrishna
Mutations in parkin cause early-onset Parkinson’s disease. Studies involving Drosophila model have emphasised mitochondrial dysfunction as a critical event in disease pathogenesis. In this context, we employed a novel recessive allele of parkin, parkc00062, for the current study. The piggyBac insertion at 3rd intron of parkin in parkc00062 was confirmed by PCR. Homozygous parkc00062 has diminished levels of truncated parkin transcript with no detectable protein as confirmed by qRT-PCR and western blot analysis, respectively. The homozygous parkc00062 displayed severe developmental anomalies involving reduced body size, ~45 % pupal lethality, high mortality with locomotory defect, elevated oxidative stress, low metabolic active cell status with low mitochondrial respiration as reflected from reduced ATP levels. Further, folic acid therapeutic potential was analysed in parkc00062. Here we show that dietary folic acid provided protection against disparities involving pupal lethality, high mortality, locomotory defect, elevated oxidative stress and low metabolic active cell status associated with parkc00062. Further mitochondrial respiration was enhanced as reflected from improved ATP levels in folate supplemented parkc00062. To corroborate mitochondrial functioning further our analysis regarding transcript status of p53 and spargel by qRT-PCR, revealed down regulation of p53 and up regulation of spargel in folate supplemented parkc00062, which was originally vice a versa. Our data thus support the potential of FA in alleviating the disparities associated with parkin loss of function in fly model. Further, FA role in alleviating mitochondrial dysfunction is encouraging to further explore FA mechanistic role to be utilized as potential therapeutics for parkin mediated neurodegenerative diseases. © 2015, Springer Science+Business Media New York.
Folic acid supplementation rescues anomalies associated with knockdown of parkin in dopaminergic and serotonergic neurons in Drosophila model of Parkinson's disease
(Academic Press Inc., 2015) Saurabh Srivastav; Sandeep Kumar Singh; Amarish Kumar Yadav; Saripella Srikrishna
parkin loss associated early-onset of Parkinson's disease, involves mitochondrial dysfunction and oxidative stress as the plausible decisive molecular mechanisms in disease pathogenesis. Mitochondrial dysfunction involves several up/down regulation of gene products, one of which being p53 is found to be elevated. Elevated p53 is involved in mitochondrial mediated apoptosis of neuronal cells in Parkinson's patients who are folate deficient as well. The present study therefore attempts to examine the effect of Folic acid (FA) supplementation in alleviation of anomalies associated with parkin knockdown using RNAi approach, specific to Dopaminergic (DA) neurons in Drosophila model system. Here we show that FA supplementation provide protection against parkin RNAi associated discrepancies, thereby improves locomotor ability, reduces mortality and oxidative stress, and partially improves Zn levels. Further, metabolic active cell status and ATP levels were also found to be improved thereby indicating improved mitochondrial function. To corroborate FA supplementation in mitochondrial functioning further, status of p53 and spargel was checked by qRT-PCR. Here we show that folic acid supplementation enrich mitochondrial functioning as depicted from improved spargel level and lowered p53 level, which was originally vice versa in parkin knockdown flies cultured in standard media. Our data thus support the potential of folic acid in alleviating the behavioural defects, oxidative stress, augmentation of zinc and ATP levels in parkin knock down flies. Further, folic acid role in repressing mitochondrial dysfunction is encouraging to further explore its possible mechanistic role to be utilized as potential therapeutics for Parkinson's disease. © 2015 Elsevier Inc. All rights reserved.
Highly sensitive cell imaging Off-On fluorescent probe for mitochondria and ATP
(Elsevier Ltd, 2015) Priyanka Srivastava; Syed S. Razi; Rashid Ali; Saurabh Srivastav; Satyakam Patnaik; Saripella Srikrishna; Arvind Misra
A smart Off-On molecular scaffold/fluorescent probe 1 has been designed and synthesized. The probe has shown considerable photostability, cell permeability, organelle specificity and selectivity for ATP. The multicolor live cell imaging experiments in HeLa cells showed high selectivity of probe 1 for mitochondria with fluorescence turn-on response. As a proof of concept and promising prospects for application in biological sciences probe 1 has been utilized to detect ATP sensitively in a partial aqueous medium and intracellularly in HeLa cells. The favorable interaction between triphosphate unit of ATP and piperazine N atoms of probe 1 is attributed to synergistic effects of H-bonding and electrostatic interactions that encouraged the CH-π and π→π stacking between anthracene and purine rings. Consequently, the observed enhanced turn-on emission and a naked-eye sensitive blue-green color in the medium is attributable to arrest in photoinduced electron transfer (PET) process. © 2015 Elsevier B.V.
Knockdown of APPL mimics transgenic Aβ induced neurodegenerative phenotypes in Drosophila
(Elsevier Ireland Ltd, 2017) Sandeep Kumar Singh; Saurabh Srivastav; Amarish Kumar Yadav; Saripella Srikrishna
A variety of Drosophila mutant lines have been established as potential disease-models to study various disease mechanisms including human neurodegenerative diseases like Alzheimer's disease (AD), Huntington's disease (HD) and Parkinson's disease (PD). The evolutionary conservation of APP (Amyloid Precursor Protein) and APPL (Amyloid Precursor Protein-Like) and the comparable detrimental effects caused by their metabolic products strongly implies the conservation of their normal physiological functions. In view of this milieu, a comparative analysis on the pattern of neurodegenerative phenotypes between Drosophila APPL-RNAi line and transgenic Drosophila line expressing eye tissue specific human Aβ (Amyloid beta) was undertaken. Our results clearly show that Drosophila APPL-RNAi largely mimics transgenic Aβ in various phenotypes which include eye degeneration, reduced longevity and motor neuron deficit functions, etc. The ultra-structural morphological pattern of eye degeneration was confirmed by scanning electron microscopy. Further, a comparative study on longevity and motor behaviour between Aβ expressing and APPL knockdown lines revealed similar kind of behavioural deficit and longevity phenotypes. Therefore, it is suggested that APPL-knockdown approach can be used as an alternative approach to study neurodegenerative diseases in the fly model. To the best of our knowledge this is the first report showing comparable phenotypes between APPL and Aβ in AD model of Drosophila. © 2017 Elsevier B.V.
Nuclear blebbing of biologically active organoselenium compound towards human cervical cancer cell (HeLa): In vitro DNA/HSA binding, cleavage and cell imaging studies
(Elsevier Masson SAS, 2015) Masood Ahmad Rizvi; Mehvash Zaki; Mohd. Afzal; Manoj Mane; Manjeet Kumar; Bhahwal Ali Shah; Saurabh Srivastav; Saripella Srikrishna; Ghulam Mustafa Peerzada; Sartaj Tabassum
New pharmacophore organoselenium compound (1) was designed, synthesized and characterized by various spectroscopic methods (IR, ESI-MS, 1H, 13C and 77Se NMR) and further confirmed by X-ray crystallography. Compound 1 consists of two 3,5-bis(trifluoromethyl)phenyl units which are connected to the selenium atom via the organometallic C-Se bond. In vitro DNA binding studies of 1 was investigated by absorption and emission titration methods which revealed that 1 recognizes the minor groove of DNA in accordance with molecular docking studies with the DNA duplex. Gel electrophoretic assay demonstrates the ability of 1 to cleave pBR322 DNA through hydrolytic process which was further validated by T4 religation assay. To understand the drug-protein interaction of which ultimate molecular target was DNA, the affinity of 1 towards HSA was also investigated by the spectroscopic and molecular modeling techniques which showed hydrophobic interaction in the subdomain IIA of HSA. Furthermore, the intracellular localization of 1 was evidenced by cell imaging studies using HeLa cells. © 2014 Elsevier Masson SAS.
Overview of Alzheimer's disease and some therapeutic approaches targeting A β by using several synthetic and herbal compounds
(Hindawi Publishing Corporation, 2016) Sandeep Kumar Singh; Saurabh Srivastav; Amarish Kumar Yadav; Saripella Srikrishna; George Perry
Alzheimer's disease (AD) is a complex age-related neurodegenerative disease. In this review, we carefully detail amyloid-β metabolism and its role in AD. We also consider the various genetic animal models used to evaluate therapeutics. Finally, we consider the role of synthetic and plant-based compounds in therapeutics. © 2016 Sandeep Kumar Singh et al.
Synthesis and crystal structure determination of copper(II)-complex: In vitro DNA and HSA binding, pBR322 plasmid cleavage, cell imaging and cytotoxic studies
(Elsevier Masson SAS, 2014) Sartaj Tabassum; Mehvash Zaki; Musheer Ahmad; Mohd Afzal; Saurabh Srivastav; Saripella Srikrishna; Farukh Arjmand
New Cu(II) complex 1 of indole-3-propionic acid and 1,10-phenanthroline was synthesized and characterized by analytical, spectroscopic and single crystal X-ray diffraction. In vitro DNA binding studies of 1 was performed by employing UV-vis and fluorescence spectroscopic techniques. The binding affinity towards human serum albumin (HSA) was also investigated to understand the carrier role in body system, as the time dependent HPLC experiment of 1 revealed that bonded drug with protein releases slowly in presence of DNA. Complex 1 exhibited good anti-tumor activity (GI50 values <10 μg/ml), and to elucidate the mechanism of tumor inhibition, topoisomerase I enzymatic activity was carried out and further validated by cell imaging studies which clearly showed its nuclear localization. © 2014 Elsevier Masson SAS. All rights reserved.