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Search Results: 1 - 10 of 191279 matches for " Chakravortty D "
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Intracellular delivery of doxorubicin encapsulated in novel pH-responsive chitosan/heparin nanocapsules
Thomas MB, Radhakrishnan K, Gnanadhas DP, Chakravortty D, Raichur AM
International Journal of Nanomedicine , 2013, DOI: http://dx.doi.org/10.2147/IJN.S37737
Abstract: tracellular delivery of doxorubicin encapsulated in novel pH-responsive chitosan/heparin nanocapsules Original Research (1212) Total Article Views Authors: Thomas MB, Radhakrishnan K, Gnanadhas DP, Chakravortty D, Raichur AM Published Date January 2013 Volume 2013:8 Pages 267 - 273 DOI: http://dx.doi.org/10.2147/IJN.S37737 Received: 05 September 2012 Accepted: 22 October 2012 Published: 11 January 2013 Midhun B Thomas,1,* Krishna Radhakrishnan,1,* Divya P Gnanadhas,2,* Dipshikha Chakravortty,2 Ashok M Raichur1,3 1Department of Materials Engineering, 2Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore, India; 3Department of Applied Chemistry, University of Johannesburg, Doornfontein, South Africa *These authors contributed equally to this work Abstract: A novel polyelectrolyte nanocapsule system composed of biopolymers, chitosan and heparin has been fabricated by the layer-by-layer technique on silica nanoparticles followed by dissolution of the silica core. The nanocapsules were of the size range 200 ± 20 nm and loaded with the positively charged anticancer drug doxorubicin with an efficiency of 89%. The loading of the drug into the capsule happens by virtue of the pH-responsive property of the capsule wall, which is determined by the pKa of the polyelectrolytes. As the pH is varied, about 64% of the drug is released in acidic pH while 77% is released in neutral pH. The biocompatibility, efficiency of drug loading, and enhanced bioavailability of the capsule system was confirmed by MTT assay and in vivo biodistribution studies.
Intracellular delivery of doxorubicin encapsulated in novel pH-responsive chitosan/heparin nanocapsules
Thomas MB,Radhakrishnan K,Gnanadhas DP,Chakravortty D
International Journal of Nanomedicine , 2013,
Abstract: Midhun B Thomas,1,* Krishna Radhakrishnan,1,* Divya P Gnanadhas,2,* Dipshikha Chakravortty,2 Ashok M Raichur1,31Department of Materials Engineering, 2Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore, India; 3Department of Applied Chemistry, University of Johannesburg, Doornfontein, South Africa*These authors contributed equally to this workAbstract: A novel polyelectrolyte nanocapsule system composed of biopolymers, chitosan and heparin has been fabricated by the layer-by-layer technique on silica nanoparticles followed by dissolution of the silica core. The nanocapsules were of the size range 200 ± 20 nm and loaded with the positively charged anticancer drug doxorubicin with an efficiency of 89%. The loading of the drug into the capsule happens by virtue of the pH-responsive property of the capsule wall, which is determined by the pKa of the polyelectrolytes. As the pH is varied, about 64% of the drug is released in acidic pH while 77% is released in neutral pH. The biocompatibility, efficiency of drug loading, and enhanced bioavailability of the capsule system was confirmed by MTT assay and in vivo biodistribution studies.Keywords: drug delivery, layer-by-layer, electrostatic interaction, biocompatible
Curcumin Increases the Pathogenicity of Salmonella enterica Serovar Typhimurium in Murine Model
Sandhya A. Marathe,Seemun Ray,Dipshikha Chakravortty
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0011511
Abstract: Curcumin has gained immense importance for its vast therapeutic and prophylactic applications. Contrary to this, our study reveals that it regulates the defense pathways of Salmonella enterica serovar Typhimurium (S. Typhimurium) to enhance its pathogenicity. In a murine model of typhoid fever, we observed higher bacterial load in Peyer's patches, mesenteric lymph node, spleen and liver, when infected with curcumin-treated Salmonella. Curcumin increased the resistance of S. Typhimurium against antimicrobial agents like antimicrobial peptides, reactive oxygen and nitrogen species. This increased tolerance might be attributed to the up-regulation of genes involved in resistance against antimicrobial peptides - pmrD and pmrHFIJKLM and genes with antioxidant function - mntH, sodA and sitA. We implicate that iron chelation property of curcumin have a role in regulating mntH and sitA. Interestingly, we see that the curcumin-mediated modulation of pmr genes is through the PhoPQ regulatory system. Curcumin downregulates SPI1 genes, required for entry into epithelial cells and upregulates SPI2 genes required to intracellular survival. Since it is known that the SPI1 and SPI2 system can be regulated by the PhoPQ system, this common regulator could explain curcumin's mode of action. This data urges us to rethink the indiscriminate use of curcumin especially during Salmonella outbreaks.
A Safe Vaccine (DV-STM-07) against Salmonella Infection Prevents Abortion and Confers Protective Immunity to the Pregnant and New Born Mice
Vidya Devi Negi,Arvindhan G. Nagarajan,Dipshikha Chakravortty
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0009139
Abstract: Pregnancy is a transient immuno-compromised condition which has evolved to avoid the immune rejection of the fetus by the maternal immune system. The altered immune response of the pregnant female leads to increased susceptibility to invading pathogens, resulting in abortion and congenital defects of the fetus and a subnormal response to vaccination. Active vaccination during pregnancy may lead to abortion induced by heightened cell mediated immune response. In this study, we have administered the highly attenuated vaccine strain ΔpmrG-HM-D (DV-STM-07) in female mice before the onset of pregnancy and followed the immune reaction against challenge with virulent S. Typhimurium in pregnant mice. Here we demonstrate that DV-STM-07 vaccine gives protection against Salmonella in pregnant mice and also prevents Salmonella induced abortion. This protection is conferred by directing the immune response towards Th2 activation and Th1 suppression. The low Th1 response prevents abortion. The use of live attenuated vaccine just before pregnancy carries the risk of transmission to the fetus. We have shown that this vaccine is safe as the vaccine strain is quickly eliminated from the mother and is not transmitted to the fetus. This vaccine also confers immunity to the new born mice of vaccinated mothers. Since there is no evidence of the vaccine candidate reaching the new born mice, we hypothesize that it may be due to trans-colostral transfer of protective anti-Salmonella antibodies. These results suggest that our vaccine DV-STM-07 can be very useful in preventing abortion in the pregnant individuals and confer immunity to the new born. Since there are no such vaccine candidates which can be given to the new born and to the pregnant women, this vaccine holds a very bright future to combat Salmonella induced pregnancy loss.
lac Repressor Is an Antivirulence Factor of Salmonella enterica: Its Role in the Evolution of Virulence in Salmonella
Sandeepa M. Eswarappa, Guruswamy Karnam, Arvindhan G. Nagarajan, Sangeeta Chakraborty, Dipshikha Chakravortty
PLOS ONE , 2009, DOI: 10.1371/journal.pone.0005789
Abstract: The genus Salmonella includes many pathogens of great medical and veterinary importance. Bacteria belonging to this genus are very closely related to those belonging to the genus Escherichia. lacZYA operon and lacI are present in Escherichia coli, but not in Salmonella enterica. It has been proposed that Salmonella has lost lacZYA operon and lacI during evolution. In this study, we have investigated the physiological and evolutionary significance of the absence of lacI in Salmonella enterica. Using murine model of typhoid fever, we show that the expression of LacI causes a remarkable reduction in the virulence of Salmonella enterica. LacI also suppresses the ability of Salmonella enterica to proliferate inside murine macrophages. Microarray analysis revealed that LacI interferes with the expression of virulence genes of Salmonella pathogenicity island 2. This effect was confirmed by RT-PCR and Western blot analysis. Interestingly, we found that SBG0326 of Salmonella bongori is homologous to lacI of Escherichia coli. Salmonella bongori is the only other species of the genus Salmonella and it lacks the virulence genes of Salmonella pathogenicity island 2. Overall, our results demonstrate that LacI is an antivirulence factor of Salmonella enterica and suggest that absence of lacI has facilitated the acquisition of virulence genes of Salmonella pathogenicity island 2 in Salmonella enterica making it a successful systemic pathogen.
Modulation of the Arginase Pathway in the Context of Microbial Pathogenesis: A Metabolic Enzyme Moonlighting as an Immune Modulator
Priyanka Das equal contributor,Amit Lahiri equal contributor,Ayan Lahiri,Dipshikha Chakravortty
PLOS Pathogens , 2010, DOI: 10.1371/journal.ppat.1000899
Abstract: Arginine is a crucial amino acid that serves to modulate the cellular immune response during infection. Arginine is also a common substrate for both inducible nitric oxide synthase (iNOS) and arginase. The generation of nitric oxide from arginine is responsible for efficient immune response and cytotoxicity of host cells to kill the invading pathogens. On the other hand, the conversion of arginine to ornithine and urea via the arginase pathway can support the growth of bacterial and parasitic pathogens. The competition between iNOS and arginase for arginine can thus contribute to the outcome of several parasitic and bacterial infections. There are two isoforms of vertebrate arginase, both of which catalyze the conversion of arginine to ornithine and urea, but they differ with regard to tissue distribution and subcellular localization. In the case of infection with Mycobacterium, Leishmania, Trypanosoma, Helicobacter, Schistosoma, and Salmonella spp., arginase isoforms have been shown to modulate the pathology of infection by various means. Despite the existence of a considerable body of evidence about mammalian arginine metabolism and its role in immunology, the critical choice to divert the host arginine pool by pathogenic organisms as a survival strategy is still a mystery in infection biology.
Salmonella enterica Serovar Typhimurium Lacking hfq Gene Confers Protective Immunity against Murine Typhoid
Uday Shankar Allam,M. Gopala Krishna,Amit Lahiri,Omana Joy,Dipshikha Chakravortty
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0016667
Abstract: Salmonella enterica is an important enteric pathogen and its various serovars are involved in causing both systemic and intestinal diseases in humans and domestic animals. The emergence of multidrug-resistant strains of Salmonella leading to increased morbidity and mortality has further complicated its management. Live attenuated vaccines have been proven superior over killed or subunit vaccines due to their ability to induce protective immunity. Of the various strategies used for the generation of live attenuated vaccine strains, focus has gradually shifted towards manipulation of virulence regulator genes. Hfq is a RNA chaperon which mediates the binding of small RNAs to the mRNA and assists in post-transcriptional gene regulation in bacteria. In this study, we evaluated the efficacy of the Salmonella Typhimurium Δhfq strain as a candidate for live oral vaccine in murine model of typhoid fever. Salmonella hfq deletion mutant is highly attenuated in cell culture and animal model implying a significant role of Hfq in bacterial virulence. Oral immunization with the Salmonella hfq deletion mutant efficiently protects mice against subsequent oral challenge with virulent strain of Salmonella Typhimurium. Moreover, protection was induced upon both multiple as well as single dose of immunizations. The vaccine strain appears to be safe for use in pregnant mice and the protection is mediated by the increase in the number of CD4+ T lymphocytes upon vaccination. The levels of serum IgG and secretory-IgA in intestinal washes specific to lipopolysaccharide and outer membrane protein were significantly increased upon vaccination. Furthermore, hfq deletion mutant showed enhanced antigen presentation by dendritic cells compared to the wild type strain. Taken together, the studies in murine immunization model suggest that the Salmonella hfq deletion mutant can be a novel live oral vaccine candidate.
TLR 9 Activation in Dendritic Cells Enhances Salmonella Killing and Antigen Presentation via Involvement of the Reactive Oxygen Species
Amit Lahiri,Ayan Lahiri,Priyanka Das,Janakiraman Vani,M. S. Shaila,Dipshikha Chakravortty
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0013772
Abstract: Synthetic CpG containing oligodeoxynucleotide Toll like receptor-9 agonist (CpG DNA) activates innate immunity and can stimulate antigen presentation against numerous intracellular pathogens. It was observed that Salmonella Typhimurium growth can be inhibited by the CpG DNA treatment in the murine dendritic cells. This inhibitory effect was mediated by an increased reactive oxygen species production. In addition, it was noted that CpG DNA treatment of dendritic cells during Salmonella infection leads to an increased antigen presentation. Further this increased antigen presentation was dependent on the enhanced reactive oxygen species production elicited by Toll like receptor-9 activation. With the help of an exogenous antigen it was shown that Salmonella antigen could also be cross-presented in a better way by CpG induction. These data collectively indicate that CpG DNA enhance the ability of murine dendritic cells to contain the growth of virulent Salmonella through reactive oxygen species dependent killing.
Differentially Evolved Genes of Salmonella Pathogenicity Islands: Insights into the Mechanism of Host Specificity in Salmonella
Sandeepa M. Eswarappa, Jessin Janice, Arvindhan G. Nagarajan, Sudhagar V. Balasundaram, Guruswamy Karnam, Narendra M. Dixit, Dipshikha Chakravortty
PLOS ONE , 2008, DOI: 10.1371/journal.pone.0003829
Abstract: Background The species Salmonella enterica (S. enterica) includes many serovars that cause disease in avian and mammalian hosts. These serovars differ greatly in their host range and their degree of host adaptation. The host specificity of S. enterica serovars appears to be a complex phenomenon governed by multiple factors acting at different stages of the infection process, which makes identification of the cause/s of host specificity solely by experimental methods difficult. Methodology/Principal Findings In this study, we have employed a molecular evolution and phylogenetics based approach to identify genes that might play important roles in conferring host specificity to different serovars of S. enterica. These genes are ‘differentially evolved’ in different S. enterica serovars. This list of ‘differentially evolved’ genes includes genes that encode translocon proteins (SipD, SseC and SseD) of both Salmonella pathogenicity islands 1 and 2 encoded type three secretion systems, sptP, which encodes an effector protein that inhibits the mitogen-activated protein kinase pathway of the host cell, and genes which encode effector proteins (SseF and SifA) that are important in placing the Salmonella-containing vacuole in a juxtanuclear position. Conclusions/Significance Analysis of known functions of these ‘differentially evolved genes’ indicates that the products of these genes directly interact with the host cell and manipulate its functions and thereby confer host specificity, at least in part, to different serovars of S. enterica that are considered in this study.
Cationic Amino Acid Transporters and Salmonella Typhimurium ArgT Collectively Regulate Arginine Availability towards Intracellular Salmonella Growth
Priyanka Das,Amit Lahiri,Ayan Lahiri,Minakshi Sen,Namrata Iyer,Nisha Kapoor,Kithiganahalli Narayanaswamy Balaji,Dipshikha Chakravortty
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0015466
Abstract: Cationic amino acid transporters (mCAT1 and mCAT2B) regulate the arginine availability in macrophages. How in the infected cell a pathogen can alter the arginine metabolism of the host remains to be understood. We reveal here a novel mechanism by which Salmonella exploit mCAT1 and mCAT2B to acquire host arginine towards its own intracellular growth within antigen presenting cells. We demonstrate that Salmonella infected bone marrow derived macrophages and dendritic cells show enhanced arginine uptake and increased expression of mCAT1 and mCAT2B. We show that the mCAT1 transporter is in close proximity to Salmonella containing vacuole (SCV) specifically by live intracellular Salmonella in order to access the macrophage cytosolic arginine pool. Further, Lysosome associated membrane protein 1, a marker of SCV, also was found to colocalize with mCAT1 in the Salmonella infected cell. The intra vacuolar Salmonella then acquire the host arginine via its own arginine transporter, ArgT for growth. The argT knockout strain was unable to acquire host arginine and was attenuated in growth in both macrophages and in mice model of infection. Together, these data reveal survival strategies by which virulent Salmonella adapt to the harsh conditions prevailing in the infected host cells.
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