2058 research outputs found
Sort by
The curative effect of fucoidan on visceral leishmaniasis is mediated by activation of MAP kinases through specific protein kinase C isoforms
No full textFucoidan can cure both antimony-sensitive and antimony-resistant visceral leishmaniasis through immune activation.
However, the signaling events underlying this cellular response remain uncharacterized. The present study reveals that fucoidan induces activation of p38 and ERK1/2 and NF-kB DNA binding in both normal and Leishmania donovani-infected macrophages, as revealed by western blotting and electrophoretic mobility shift assay (EMSA), respectively. Pharmacological inhibition of p38, ERK1/2 or the NF-kB pathway markedly attenuated fucoidan-induced pro-inflammatory cytokine synthesis and inducible nitric oxide synthase (iNOS) gene transcription, resulting in a
reduction of parasite clearance. To decipher the underlying mechanism of fucoidan-mediated parasite suppression, the
expression and functionality of various protein kinase C (PKC) isoforms were evaluated by immunoblotting and enzyme
activity assay. Fucoidan elicited an increase in expression and activity of PKC-a, -bI and -bII isoforms in infected
macrophages. Functional knockdown of PKC-a and -b resulted in downregulation of p38 and ERK1/2, along with a
marked reduction of IL-12 and TNF-a production in fucoidan-treated infected macrophages. Collectively, these results
suggest that the curative effect of fucoidan is mediated by PKC-dependent activation of the mitogen-activated protein
kinase (MAPK)/NF-kB pathway, which ultimately results in the production of nitric oxide (NO) and disease-resolving
pro-inflammatory cytokines
Rational Construction of Triazole/Urea Based Peptidomimetic Macrocycles as Pseudocyclo-β-peptides and Studies on Their Chirality Controlled Self-Assembly
No full textA tandem macro-dimerization reaction via a Cu(I)
catalyzed azide/alkyne cycloaddition reaction has been employed to construct triazole/urea based peptidomimetic macrocycles considered as pseudocyclo-β-peptides. Introduction of one particular chirality in the peptide backbone can alter the conformation as well as nature of
self-assembly from cyclic D-,L-,α-peptide to cyclo-β-peptide. One of them (16a) forms antiparallel dimers while the other (16b) undergoes higher order aggregation to form a nanorod structure
Manipulation Of Redox Status Of Chronic Myeloid Leukemic Cells That Favours Apoptosis
No full textRedox status refers to the balance between pro-oxidant and anti-oxidant level in cells. Cancer cells exhibit multiple genetic alterations and high oxidative stress. Therefore, it might be possible to preferentially eliminate these cells by pharmacological ROS insults. However, the
up regulation of antioxidant capacity in adaptation to intrinsic oxidative stress in cancer cells can confer drug resistance. Modulation of the redox mechanisms of cancer cells might be an effective strategy to eliminate these cells. Hydroxychavicol (HCH), a constituent of Piper
betel leaves, has potent anti-chronic myeloid leukemia (CML) activity. HCH causes apoptosis of CML cells by induction of reactive oxygen species (ROS). Here we manipulated the threshold of intracellular ROS by depleting intracellular glutathione, a key antioxidant in cells, using combined treatment with buthionine sulfoximine (BSO), an inhibitor of gammaglutamylcysteine
synthetase, a rate limiting enzyme in glutathione biosynthesis, and nonapoptotic doses of HCH. BSO significantly potentiated apoptosis-inducing activity of HCH in leukemic cells by caspase-dependent as well as caspase-independent but apoptosis inducing
factor (AIF)-dependent manner. Enhanced depletion of intracellular GSH induced by combined treatment correlated with induction of ROS. Activation of ROS- dependent JNK
played a crucial role in ERK1/2 activation which subsequently induced the expression of inducible nitric oxide synthase (iNOS). iNOS-mediated production of nitric oxide (NO) was identified as an effector molecule causing apoptosis of CML cells. Treatment with BSO plus
HCH significantly induced G2/M phase arrest through down regulation of cyclin B1, inhibitory phosphorylations of cdc2 and cdc25C. We also found increased phosphorylation of
ATM and Chk2 time dependently without any effect on Chk1. Furthermore, treatment with ATM inhibitor caffeine and Chk2 inhibitor attenuated G2/M arrest and their downstream
signaling molecules. Restoration of intracellular GSH pool correlated with ATM dephosphorylation. Our results showed that ATM- and Chk2-mediated inhibitory phosphorylation of cdc25C plays a major role in G2/M arrest. We also observed that BSO plus HCH- induced cell cycle arrest was not restricted to p53 status in human leukemia cells.
This combined treatment merits further testing in pre-clinical settings
In-Silico studies on opioid receptors and ligands : Understanding the structural basis of protein-ligand interactions and designing ligands with improved therapeutic profile
No full textThe present thesis entitled “In-silico studies on opioid receptors and ligands: Understanding the structural basis of protein-ligand interactions and designing ligands with improved therapeutic profile”, is based on application of computational approaches for getting insights into the structural requirements of ligands for binding to opioid receptors and identification of agonists acting at opioid receptors. Designing new agonists for opioid receptors is an active area of research due to the side-effect profile associated with the present opioid drugs as analgesics. The thesis covers five chapters. Chapter 1 consists of two parts. The first part provides an overview of opioid receptors and ligands, which includes uses of opioids, side effects of using opioids as therapeutics and the need for new opioids with better therapeutic profile. The second part of this chapter gives a broad overview of molecular modeling methods and in-silico tools, used in computer aided drug designing. Chapter 1 ends with the objective and relevance of the present study. Chapter 2 deals with generating homology models of three opioid receptors (mu,kappa and delta) based on single and multiple templates. Multiple templates are supposed to increase the sequence similarity of the query sequence with the target sequences and consequently may result in better homology models. To investigate the advantage of using multiple templates, a comparative study was performed for assessing the structural quality of the homology models based on single and multiple templates. Structural qualities of the homology models were checked with standard tools used for validating homology models. The results obtained from this study shows that the use of multiple templates not always helps in generating structurally better 3D models. Chapter 3 deals with identifying the interactions leading to binding of kappa opioid agonists into the binding site of kappa opioid receptor. In this study, two nitrogen containing non-peptidic kappa opioid agonists, one non-protonated and the other protonated, were docked using induced fit docking. From this study, differences between interactions of protonated and non-protonated kappa opioid agonists have been visualised. In Chapter 4, the 2D-QSAR studies, performed on a series of aminomorphinan ligands having dual agonistic activities towards mu and kappa opioid receptors, have been described. The QSAR models were developed individually for activities towards both the receptors using a set of descriptors. GFA and G/PLS were used as regression techniques. A common feature pharmacophore was generated and used for aligning the compounds for CoMFA based 3D-QSAR studies. All the QSAR models were validated using important statistical metrices and checked for applicability domains. Bioactive conformation of the compound having high and comparable activity for both the receptors was used for ROCS based virtual screening of ZINC database. The obtained hits were enriched using various in silico methods and the activities of the hits were predicted using the QSAR models having best external predictability. As an outcome of this study, a novel in silico protocol was developed for identifying hits which may be considered as prospective dual agonists for mu and kappa opioid receptors.Chapter 5 summarizes the entire research component of the thesis
Role of different aberrant cell signalling pathways prevalent in acute lymphoblastic leukemia
No full textAcute lymphoblastic leukemia (ALL) is one of the major forms of leukemia that affects mostly adolescent
individuals. The main cause of the development of ALL is not known though several important signal transduction pathways have been reported with functional abnormality in all the cases. Crucial signalling pathways reported in ALL include PI3K/Akt, Notch, Wnt, mTOR, JaK/Stat, etc. Over the past several decades important progress has been made in the
management of ALL, however, relapses and post therapy survival ratio has not improved much. This brings the need for understanding the biology and mechanism involved in ALL occurrences and find new molecular targets for better treatment options and risk-adapted therapies to improve the outcome of ALL patient
Targeted immunology for prevention and cure of VL
No full textLeishmaniasis is a neglected tropical disease caused by a group of
protozoan parasites of the genus Leishmania. Clinical presentation
of leishmaniasis can range from cutaneous, mucocutaneous,
or visceral forms depending on the parasite species. Visceral leishmaniasis
(VL) caused by L. donovani and L. infantum is the severest
and one of the deadliest parasitic diseases of the tropics second
only to malaria (1). Nearly, 20,000–40,000 annual deaths are estimated
due to this disease (2). Except for the Indian subcontinent
andWest Africa, VL is frequent in dogs, which serve as the major
reservoir for zoonosis (3)
Ring-Closing Metathesis and Glycosylation Reactions: Synthesis and Biophysical Studies of Polyether-Linked Carbohydrate-Based Macrocyclic Nucleosides
No full textBis-, tris-, and tetrakisuracil-substituted 12-, 13-,
17-, and 21-membered macrocyclic nucleoside analogues with
polyether linkages, including C2-symmetric molecules, have
been synthesized through coupling of two appropriately
allylated sugar derivatives, derived from D-glucose, followed
by a sequential ring-closing metathesis reaction using Grubbs
catalysts, double-bond reduction, and nucleoside base insertion
under Vorbrüggen reaction conditions. Spectroscopic studies
on the interaction of these nucleoside analogues with small
molecules, such as the alkaloids berberine and palmatine and
the DNA intercalator ethidium bromide, revealed a change in
the absorbance and fluorescence of the small molecules suggesting the potential use of these nucleoside molecules as a carrier of
small molecules in biological systems. Circular dichroism studies indicated that the complexes of the nucleosides with small
molecules undergo aggregation/self-organization. This has been further evidenced by a SEM experiment showing the binding of
berberine with one of the nucleoside derivatives, which confirms the occurrence of secondary structure reorganization
Targeting Double-Stranded RNA with Spermine, 1‑Naphthylacetyl Spermine and Spermidine: A Comparative Biophysical Investigation
No full textRNA targeting is an evolving new approach to
anticancer therapeutics that requires identification of small molecules to selectively target specific RNA structures. In this report, the interaction of biogenic polyamines spermine, spermidine and the synthetic analogue 1-naphthylacetyl spermine with three double-stranded RNA polynucleotidespoly(I)·poly(C), poly(C)·poly(G), and poly(A)·poly(U)has been described to understand the structural and thermodynamic basis of the binding and the comparative
efficacy of the analogue over the natural polyamines. Circular dichroism spectroscopy, thermal melting experiments, and ethidium bromide displacement assay were used to characterize the interaction. Microcalorimetry studies were performed to deduce the energetics of the interaction and atomic force microscopy experiments done to gain insight into the interaction at the molecular level. The experiments demonstrated structural perturbations in the polynucleotides on binding of the polyamines.
Thermal melting studies showed enhanced stabilization of RNA−polyamine complexes with increase in the total standard molar enthalpy of transition. The binding affinity was strongest for poly(I)·poly(C) as revealed by microcalorimetry results and varied as poly(I)·poly(C) > poly(C)·poly(G) > poly(A)·poly(U). The order of affinity for the polyamines was spermine >1- naphthylacetyl spermine > spermidine. Total enthalpy−entropy compensation and high standard molar heat capacity values characterized the interactions. The results of the study on the binding of polyamines to dsRNAs presented here have been compared to those reported earlier with dsDNAs. The present findings advance our knowledge on the mechanism of interaction
of polyamines with RNA and may help in the search for analogues that can interfere with biogenic polyamine metabolism and function
Gene-Rich Large Deletions Are Overrepresented in POAG Patients of Indian and Caucasian Origins
No full textLarge copy number variations (CNV) can contribute to increased burden for neurodegenerative diseases. In this study, we analyzed the genome-wide burden of large CNVs
> 100 kb in primary open angle glaucoma (POAG), a neurodegenerative disease of the eye that is the largest cause of irreversible blindness.Genome-wide analysis of CNVs > 100 kb were analyzed in a total of 1720
individuals, including an Indian cohort (347 POAG cases and 345 controls) and a Caucasian cohort (624 cases and 404 controls). All the CNV data were obtained from experiments
performed on Illumina 660W-Quad (infinium) arrays.
We observed that for both the populations CNVs > 1 Mb was significantly enriched for gene-rich regions unique to the POAG cases (P 1
Mb (39 calls) in patients influenced 125 genes while in controls 31 such CNVs influenced only 5 genes with no overlap. In both cohorts we observed 1.9-fold gene enrichment in patients for deletions compared to duplications, while such a bias was not observed in
controls (0.3-fold). Overall duplications > 1 Mb were more than deletions (Del/Dup ¼ 0.82) confirming that the enrichment of gene-rich deletions in patients wasassociated with the disease. Of the 39 CNVs > 1 Mb from Indian patients, 28 (72%) also were implicated in other
neurodegenerative disorders, like autism, schizophrenia, sensorineural hearing loss, and so forth. We found one large duplication encompassing CNTN4 gene in Indian and Caucasian POAG patients that was absent in the controls.
To our knowledge, our study is the first report on large CNV bias for gene-rich regions in glaucomatous neurodegeneration, implicating its impact across populations of contrasting ethnicities. We identified CNTN4 as a novel candidate gene for POAG
Conformational Adaptation in the E. coli Sigma 32 Protein in Response to Heat Shock
No full textE. coli, like other organisms, responds to heat shock by
rapidly up-regulating several proteins, including chaperones. The heatshock sigma factor, sigma 32 (σ32), a transcription factor, plays a pivotal role in this response. The level of σ32 is normally kept low through a DnaK/J mediated degradation. Elevated temperature rapidly
increases the σ32 level and initiates a heat-shock response. A plausible way for the up-regulation of free σ32 levels would be to destabilize the σ32:DnaK:DnaJ complex initiated via a conformational change in σ32 structure at elevated temperatures. In this study, we have modeled the
E. coli σ32 structure by homology modeling and conducted extensive molecular dynamics (MD) simulations at non-heat-shock (30 °C) and heat-shock (42 °C) temperatures. Substantial structural rearrangements at 42 °C were observed around the N-terminus (residues 11− 60, which cover the DnaJ binding region) and the region spanning
residues 190−210 (covering the DnaK binding site, residues 198−201). At 42 °C, a large amount of helix melting and structural destabilization was observed around residues 11−60, while regions 91−101 and 216−221 of σ32 undergo conformational change,leading to formation of a lid-like structure over region 198-VLYL-201 resulting in reduced accessibility of the DnaK binding sites.These temperature induced melting and fluctuations observed around the DnaJ and/or DnaK binding regions suggest reduction of DnaK/DnaJ affinity for σ32 at 42 °C, which is further supported by our molecular docking analysis. Emission maxima of
environment sensitive fluorescence probes inserted at several cysteine mutants of σ32 protein at 30 and 42 °C are also supportive of the structural changes observed in the molecular dynamics study