Browsing by Author "Rajan Singh"

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Adjuvantation of whole-killed Leishmania vaccine with anti-CD200 and anti-CD300a antibodies potentiates its efficacy and provides protection against wild-type parasites
(Elsevier Ltd, 2023) Rajan Singh; Anshul Anand; Baishakhi Mahapatra; Shashi Saini; Abhishek Singh; Samer Singh; Vinod Kumar; Pradeep Das; Sangram Singh; Rakesh K. Singh
One of the major reasons behind the limited success of vaccine candidates against all forms of leishmaniasis is the inability of parasitic antigens to induce robust cell-mediated immunity and immunological memory. Here we find, for the first time, that the adjuvantation of whole-killed Leishmania vaccine (Leishvacc) with anti-CD200 and anti-CD300a antibodies enhances CD4+ T cells mediated immunity in vaccinated mice and provides protection against wild-type parasites. The antibody adjuvantation, either alone or with a TLR4 agonist monophosphoryl A (MPL-A), induced the production of pro-inflammatory cytokines viz., IFN-γ, TNF-α, and IL-2 by antigen experienced CD4+ T cells, and also enhanced their rate of conversion into their memory phenotypes against Leishvacc antigens. The antibody adjuvanted vaccine also promoted the generation of IgG2a-mediated protective humoral immunity in vaccinated mice. Further, the mice vaccinated with antibodies adjuvanted vaccine showed strong resilience against metacyclic forms of L. donovani parasites as we observed reduced clinical features such as splenomegaly, hepatomegaly, granulomatous tissues in the liver, and parasitic load in their spleen. The findings of this study demonstrate that the anti-CD200 and anti-CD300a antibodies have potential to increase the protective efficacy of the whole-killed Leishmania vaccine, and opens up a new gateway to diversify the roles of immune checkpoints in vaccine development against leishmaniasis. © 2023 Elsevier Ltd
Anti-inflammatory Activity of Ursolic Acid in MPTP-Induced Parkinsonian Mouse Model
(Springer New York LLC, 2019) Sachchida Nand Rai; Walia Zahra; Saumitra Sen Singh; Hareram Birla; Chetan Keswani; Hagera Dilnashin; Aaina Singh Rathore; Rajan Singh; Rakesh K. Singh; Surya Pratap Singh
Neuroinflammation plays an important role in the progression of Parkinson’s disease (PD) and hence may represent a target for treatment. The drugs used currently for PD only provide symptomatic relief and have adverse effects in addition to their inability in preventing degeneration of neurons. Flavonoids show potent antioxidant and anti-inflammatory activities which is very valuable for the health of human beings. Thus, in the present study, we have tried to explore the anti-inflammatory activity of orally given ursolic acid (UA) (25 mg/kg bwt), a pentacyclic triterpenoid in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-intoxicated mouse model. Significant severe oxidative stress and biochemical alterations have been seen in Parkinsonian mice after MPTP intoxication. Whereas, UA administration has significantly rescued the harmful consequence of MPTP intoxication. Ionized calcium-binding adaptor molecule 1 (Iba1), tumor necrosis factor-alpha (TNF-α), and nuclear transcription factor-κB (NF-κB) were seen to be altered in the substantia nigra pars compacta (SNpc) of MPTP-intoxicated mice through immunohistochemical studies. The changes in the expression level of these parameters primarily suggest increased inflammatory responses in MPTP-intoxicated mice as compared with the control. However, UA have significantly reduced these inflammatory parameters (Iba1 and TNF-α) along with transcription factor NF-κB, which regulates these inflammatory parameters and thus have inhibited MPTP-induced neuroinflammation. The immunoreactivity of tyrosine hydroxylase (TH) was considerably increased by UA treatment in the SNpc of Parkinsonian mice. The neuroinflammation and neurodegeneration along with impairments in biochemical and behavioral parameters were found to be reversed on treatment with UA. Thus, UA has shown potent anti-inflammatory activity by preventing the degeneration of dopaminergic neurons from MPTP-induced Parkinsonian mice. © 2019, Springer Science+Business Media, LLC, part of Springer Nature.
Anti-leishmanial study of discrete tetrahedral zinc(ii) β-oxodithioester complexes
(Royal Society of Chemistry, 2024) Chote Lal Yadav; None Anamika; Rajan Singh; Akhilesh Kumar; Rakesh K. Singh; Michael G. B. Drew; Krishna K. Manar; Nanhai Singh
We have synthesized four new oxygen/sulfur(O^S) chelate complexes, [Zn(L)2], where L represents different ligands: methyl-3-hydroxy-3-(furyl)-2-propenedithioate (L1, 1), methyl-3-hydroxy-3-(p-fluorophenyl)-2-propenedithioate (L2, 2), methyl-3-hydroxy-3-(p-chlorophenyl)-2-propenedithioate (L3, 3), and methyl-3-hydroxy-3-(p-bromophenyl)-2-propenedithioate (L4, 4). These complexes have been characterized by using IR, multinuclear NMR (1H, 13C{1H}, and 19F{1H}), and UV-vis spectroscopy. The structural characterization of complexes 1, 2, and 4 was further achieved by single crystal X-ray diffraction (SCXRD). The supramolecular structures of these complexes are stabilized by non-covalent C-H⋯π (ZnOSC3, chelate), C-S⋯π (ZnOSC3, chelate), π⋯π (ZnOSC3,), C-H⋯O, C-H⋯F-C and C-H⋯H-C interactions. The luminescence properties of Zn(ii) complexes 1-4 were studied at room temperature in the solid phase. The antileishmanial activity was evaluated for all complexes. Complexes 1 and 4 exhibited significant anti-promastigote and anti-amastigote activities, with IC50 values of 2.0 and 1.33 μg mL−1, and 2.79 and 2.02 μg mL−1, respectively. Additionally, cytotoxicity assays demonstrated that these Zn(ii) β-oxodithioester complexes were toxic to promastigotes, but showed reduced toxicity towards RAW 264.7 cell lines at varying concentrations. Furthermore, the optical band gap energies of complexes 1-4 were measured and found to exhibit semiconducting behavior. © 2025 The Royal Society of Chemistry.
Bio-based synthesis of silver nanoparticles using leaf extract of Uraria picta (Jacq.) Desv. ex DC.: Characterization and evaluation of its activity against Leishmania donovani
(Springer Science and Business Media Deutschland GmbH, 2024) Jyoti Dixit; Pradeep Kumar; Rajan Singh; Pooja Verma; Kavindra Nath Tiwari; Rakesh Kumar Singh; Sunil Kumar Mishra; Jasmeet Singh
Uraria picta is used as a folk medicine to cure various ailments. Regardless of ethnobotanical application, a therapeutic study of the plant parts has yet to be reported. Aqueous leaf extract was enriched with secondary metabolites like phenols, alkaloids, and terpenoids. Total phenol (60.97 mgG−1 GAE), total flavonoid (52.36 mgG−1 RE), and antioxidant activity (IC50 2666.95 µgmL−1) of the extract were measured. Bio-based silver nanoparticles (LEUP-AgNPs) were fabricated using a secondary metabolite-enriched leaf extract of U. picta (LEUP), and characterization of LEUP-AgNPs was done. The LEUP-AgNPs were crystalline, circular (13.04 ± 5.97 nm), monodisperse (pdi 0.205), and stable (-17.8 mV). The LEUP-AgNPs surface was composed of carbon, nitrogen, oxygen, and silver. A comparative study was performed to evaluate the potential of LEUP and LEUP-AgNPs against promastigotes and intra-RAW264.7 macrophage amastigotes of Leishmania donovani. A high dose of LEUP and LEUP-AgNPs significantly inhibited the growth of promastigotes up to 53% and 68%, with an IC50 value of 47.90 µgmL−1 and 6.79 µgmL−1, respectively. LEUP and LEUP-AgNPs higher doses also inhibited intracellular amastigotes up to 53% and 80% with an IC50 value of 6.72 µgmL−1 and 1.16 µgmL−1, respectively. The microscopic examination revealed that LEUP-AgNPs lead to size reduction and aggregations of promastigotes. The LEUP-AgNPs efficiently declined the number of amastigotes per RAW 264.7 macrophages compared to LEUP. LEUP-AgNPs had no cytotoxic effects on RAW 264.7 macrophages based on the CC50 value. Findings showed LEUP-AgNPs were more efficient than LEUP in controlling L. donovani, which induces visceral leishmaniasis. © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2024.
CD300a Receptor Blocking Enhances Early Clearance of Leishmania donovani From Its Mammalian Host Through Modulation of Effector Functions of Phagocytic and Antigen Experienced T Cells
(Frontiers Media S.A., 2022) Rajan Singh; Anshul Anand; Arun K. Rawat; Shashi Saini; Baishakhi Mahapatra; Naveen K. Singh; Alok K. Mishra; Samer Singh; Nisha Singh; Dhiraj Kishore; Vinod Kumar; Pradeep Das; Rakesh K. Singh
The parasites of the genus Leishmania survive and proliferate in the host phagocytic cells by taking control over their microbicidal functions. The parasite also promotes differentiation of antigen-specific anti-inflammatory cytokines producing effector T cells, which eventually results in disease pathogenesis. The mechanisms that parasites employ to dominate host adaptive immunity are largely unknown. For the first time, we report that L. donovani, which causes visceral leishmaniasis in the Indian subcontinent, upregulates the expression of an immune inhibitory receptor i.e., CD300a on antigen presenting and phagocytic cells to dampen their effector functions. The blocking of CD300a signals in leishmania antigens activated macrophages and dendritic cells enhanced the production of nitric oxide, pro-inflammatory cytokines along with MHCI/II genes expression, and reduced parasitic uptake. Further, the abrogation of CD300a signals in Leishmania infected mice benefited antigen-experienced, i.e., CD4+CD44+ and CD8+CD44+ T cells to acquire more pro-inflammatory cytokines producing phenotypes and helped in the early clearance of parasites from their visceral organs. The CD300a receptor blocking also enhanced the conversion of CD4+ T effectors cells to their memory phenotypes i.e., CCR7high CD62Lhigh up to 1.6 and 1.9 fold after 14 and 21 days post-infection, respectively. These findings implicate that CD300a is an important determinant of host phagocytic cells functions and T cells differentiation against Leishmania antigens. Copyright © 2022 Singh, Anand, Rawat, Saini, Mahapatra, Singh, Mishra, Singh, Singh, Kishore, Kumar, Das and Singh.
Classification of clinical isolates of klebsiella pneumoniae based on their in vitro biofilm forming capabilities and elucidation of the biofilm matrix chemistry with special reference to the protein content
(Frontiers Media S.A., 2019) Ashish Kumar Singh; Shivangi Yadav; Brijesh Singh Chauhan; Nabarun Nandy; Rajan Singh; Kaushik Neogi; Jagat Kumar Roy; Saripella Srikrishna; Rakesh Kumar Singh; Pradyot Prakash
Klebsiella pneumoniae is a human pathogen, capable of forming biofilms on abiotic and biotic surfaces. The limitations of the therapeutic options against Klebsiella pneumoniae is actually due to its innate capabilities to form biofilm and harboring determinants of multidrug resistance. We utilized a newer approach for classification of biofilm producing Klebsiella pneumoniae isolates and subsequently we evaluated the chemistry of its slime, more accurately its biofilm. We extracted and determined the amount of polysaccharides and proteins from representative bacterial biofilms. The spatial distribution of sugars and proteins were then investigated in the biofilm matrix using confocal laser scanning microscopy (CLSM). Thereafter, the extracted matrix components were subjected to sophisticated analysis incorporating Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, one-dimensional gel-based electrophoresis (SDS-PAGE), high performance liquid chromatography (HPLC), and MALDI MS/MS analysis. Besides, the quantification of its total proteins, total sugars, uronates, total acetyl content was also done. Results suggest sugars are not the only/major constituent of its biofilms. The proteins were harvested and subjected to SDS-PAGE which revealed various common and unique protein bands. The common band was excised and analyzed by HPLC. MALDI MS/MS results of this common protein band indicated the presence of different proteins within the biofilm. The 55 different proteins were identified including both cytosolic and membrane proteins. About 22 proteins were related to protein synthesis and processing while 15 proteins were identified related to virulence. Similarly, proteins related to energy and metabolism were 8 and those related to capsule and cell wall synthesis were 4. These results will improve our understanding of Klebsiella biofilm composition and will further help us design better strategies for controlling its biofilm such as techniques focused on weakening/targeting certain portions of the slime which is the most common building block of the biofilm matrix. Copyright © 2019 Singh, Yadav, Chauhan, Nandy, Singh, Neogi, Roy, Srikrishna, Singh and Prakash. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
Click inspired synthesis of piperazine-triazolyl sugar-conjugates as potent anti-Hela activity
(Elsevier Ltd, 2023) Priyanka Bose; Anand K. Agrahari; Rajan Singh; Mala Singh; Sunil Kumar; Rakesh K. Singh; Vinod K. Tiwari
To imbibe the aim of synthesizing water-soluble and biocompatible motif, a click-inspired piperazine glycoconjugate has been devised up. In this report, we present a focused approach to design and synthesis of versatile sugar-appended triazoles through ‘Click Chemistry’ along with their pharmacological studies on cyclin-dependent kinases (CDKs) and cell cytotoxicity on cancer cells using in silico and in vitro approaches, respectively. The study has inclusively recognized the galactose- and mannose-derived piperazine conjugates as the promising motifs. The findings suggested that the galactosyl bis-triazolyl piperazine analogue 10b is the most CDK interactive derivative and also possess significant anticancer activity. © 2023 Elsevier Ltd
Design, Synthesis and Pharmacological Evaluation of Noscapine Glycoconjugates
(Wiley-Blackwell, 2019) Kunj B Mishra; Neeraj Tiwari; Priyanka Bose; Rajan Singh; Arun K Rawat; Sumit K. Singh; Ram C. Mishra; Rakesh K Singh; Vinod K. Tiwari
The present work is directed to design a series of molecules which are hybrids of two non-toxic biocompatible chemical architectures, noscapine and carbohydrates. Fourteen, 7-O-noscapine analogues have been synthesized out of which one of the analogue is 7-O-propargylated derivative and others are in its glycoconjugate form with triazole bridging achieved via Click reaction, where dinuclear copper(I) thiodiacetate complex [(PPh 3 ) 2 Cu(μ-tda)Cu(PPh 3 ) 2 ].6H 2 O has been emerged as an excellent catalyst for the noscapine-glyco Click-coupling. All the developed noscapine glycoconjugates have been investigated for anticancer activity using HeLa cell line and anti-leishmanial activity against Leishmania donovani. Result indicates that five of the developed noscapine glycoconjugates (5 a, 5 b, 5 c, 5 e and 5 l) showed significant anti-proliferative activity. On the other hand, four of them (5 b, 5 c, 5 e, and 5 l) showed significant anti-leishmanial activity. © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Green Synthesis, Characterization, and Application of Ascophyllum Nodosum Silver Nanoparticles
(Springer Science and Business Media Deutschland GmbH, 2023) Sunil Kumar Mishra; Saket Sinha; Amit Kumar Singh; Prabhat Upadhyay; Diya Kalra; Pradeep Kumar; Kavindra Nath Tiwari; Rajan Singh; Rakesh Kumar Singh; Arvind Kumar; Alok Tripathi; Brijesh Singh Chauhan; S. Srikrishna
Purpose: Green nanotechnology as a field has emerged and gained popularity amongst biologists due to its cost-effective and environment-friendly advancements. The most preferred is the biological method which involves plants and their extracts. Methods: The silver nanoparticles were synthesized by a sunlight-driven aqueous extract (AE) of whole plant powder of Ascophyllum nodosum. Advanced techniques like high-resolution scanning electron microscopy (HRSEM), energy dispersive X-ray (EDX), high-resolution transmission electron microscopy (HRTEM), and particle size analysis were used to determine the nature of nanoparticles. Antioxidant, anti-fungal, and anti-leishmanial activities were evaluated. Result: The techniques confirmed the formation of spherical particles of the desired range of size. Silver nanoparticles exhibited a much greater DPPH (2,2-diphenyl-1-picryl-hydrazine-hydrate) radical scavenging activity which was almost six to seven folds more than that exhibited by the AE alone. The anti-leishmanial and cytotoxic activities were evaluated on Leishmania donovani promastigote and amastigote. Conclusion: The synthesized AgNPs showed remarkable DPPH radical scavenging ability owing to their antioxidant properties. The anti-leishmanial activity was exceptionally viable in both AE and AgNPs. The findings all together support the tendency of Ascophyllum nodosum to efficiently synthesized AgNPs which could be utilized for its anti-leishmanial properties. Graphical Abstract: [Figure not available: see fulltext.] © 2023, The Author(s), under exclusive licence to The Regenerative Engineering Society.
Impact of substituents on the crystal structures and anti-leishmanial activity of new homoleptic Bi(iii) dithiocarbamates
(Royal Society of Chemistry, 2019) Anamika; Rajan Singh; Krishna K. Manar; Chote Lal Yadav; Akhilesh Kumar; Rakesh K. Singh; Michael. G. B. Drew; Nanhai Singh
Six new functionalised homoleptic Bi(iii) dithiocarbamate complexes, [Bi(L1-L6)3] (L1 = (N-4-nitrobenzyl-N-furfuryl)dithiocarbamate 1, L2 = (N-4-chlorobenzyl-N-3-methylpyridyl)dithiocarbamate 2, L3 = (N-4-bromobenzyl-N-3-methylpyridyl)dithiocarbamate 3, L4 = (N-4-dimethylaminobenzyl-N-3-methylpyridyl)dithiocarbamate 4, L5 = (1-(2-pyridyl)piperazine)dithiocarbamate 5 and L6 = (N-4-methoxybenzyl-N-benzyl)dithiocarbamate 6), have been prepared and characterised by elemental analyses, powder X-ray diffraction (PXRD) and (IR, UV-Vis, 1H and 13C{1H} NMR) spectroscopy. The structures of the six complexes have been revealed in the solid state by X-ray crystallography and assessed by DFT calculations. Complexes 1 and (2, 5 and 6) are similarly dimeric in which the three dithiocarbamate ligands are bound to the seven and eight-coordinate Bi(iii) centre, respectively, in asymmetric S,S-bidentate and μ2,κ2 S,S-chelating/chelating-bridging modes. By contrast, complex 4 is monomeric with a six-co-ordinate metal atom while complex 3 forms a polymeric structure with the metal in a seven-coordinate environment. The specific geometries of all compounds are distorted by the stereochemical lone pair. In these complexes, supramolecular structures have been sustained by non-covalent C-H⋯N, C-H⋯O, C-H⋯Cl, C-H⋯Br, C-H⋯π, C-H⋯π (BiCS2, chelate) and H⋯H interactions. The anti-leishmanial activities of the complexes have been tested; 5 and 6 showed potential anti-promastigote activity with IC50 values of 7.16 and 7.44 μM, and anti-amastigote activity with IC50 values of 8.40 and 9.70 μM, respectively. Cytotoxicity assays for complexes 1-6 showed toxicity on promastigotes but lower toxicity against the RAW 264.7 cell line at different concentrations. © 2019 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.
Leishmania donovani induces CD300a expression to dampen effector properties of CD11c+ dendritic and antigen activated CD8+ T cells
(Elsevier B.V., 2023) Anshul Anand; Rajan Singh; Shashi Saini; Baishakhi Mahapatra; Abhishek Singh; Samer Singh; Rakesh K. Singh
CD8+ T cells are an important regiment of adaptive immunity that play a decisive role in elimination of many species of Leishmania parasite from the host. In visceral leishmaniasis, caused by L. donovani, the loss of CD8+ T cells function has been found associated with augmented pathogenesis. The factors determining CD8+ T cells activation and function against Leishmania antigens are largely unknown. In this study, we investigated the role of an immune inhibitory receptor, CD300a, on the effector properties of dendritic cells and CD8+ T cells. We observed that the Leishmania regulates the effectors function of CD8+ T cells by increasing CD300a expression on CD11c+ dendritic cells. The abrogation of CD300a signaling in parasites infected animals induced CD8+ T cell abilities to produce IFN-γ, TNF-α and also helped them to acquire desired multifunctionality. The CD300a receptor blocking also enhanced the number of CD8+ T cells memory phenotypes at the early days of infection, suggesting its potential beneficial role in vaccine induced immunity. We also observed significantly enhanced levels of pro-inflammatory cytokines in the spleen of CD300a blocked infected animals with concomitant reduced spleen parasite load. Additionally, the abrogation of CD300a signals in the infected animals helped in establishing Th1 type protective humoral immunity with significantly elevated levels of IgG2a antibodies. Since CD8+ T cells are an important determinant of vaccine induced immunity against leishmaniasis, the findings corroborate the potential of CD300a in vaccine induced immunity and thus require further attention. © 2023 Elsevier B.V.
Peptide-triggered IL-12 and IFN-γ mediated immune response in CD4+ T-cells against Leishmania donovani infection
(Royal Society of Chemistry, 2024) Swati Sharma; Anshul Anand; Rajan Singh; Rakesh K. Singh; Sandeep Verma
Leishmania donovani are intracellular, human blood parasites that cause visceral leishmaniasis or kala-azar. Cell-penetrating peptides (CPPs) have been shown to modulate intracellular processes and cargo delivery, whereas host defense peptides (HDPs) promote proliferation of both naïve and antigen activated CD4+ T-cells. We report newly designed tripeptides that were able to trigger proinflammatory cytokine (IL-12 and IFN-γ) secretion by CD4+CD44+ T-cells in response to Leishmania donovani infection. These peptides can be used to induce antigen specific TH1 responses to combat obstacles of cytotoxicity and drug resistance associated with current anti-leishmanial drugs. Furthermore, these peptides can also be used as adjuvants to develop an effective immunoprophylactic approach for immunity restoration against visceral leishmaniasis. © 2024 The Royal Society of Chemistry.
Synthesis & characterization of amino acid-based acrylamide derived amphiphilic block copolymer using a new xanthate and its influence on cell cytotoxicity & cell viability
(Elsevier Ltd, 2023) Shere Afgan; Krishtan Pal; Arti Srivastava; Koushik Nandy; Paramjeet Yadav; Sheetal Jaiswal; Rajan Singh; Rakesh K. Singh; Rajesh Kumar
The development of amino acid-based polymers was due to their unique properties and structures like of biocompatible polymers having sensitive effects for numerous medicinal and biological actions like biochemical sensing and controlled release of drugs. To achieve this, poly (N-vinylpyrrolidone) (PNVP) and its block copolymer poly (N-vinylpyrrolidone)-b-poly (N-acryloyl-L-phenylalanine) (PNVP-b-PNALP) were synthesized by using a xanthate i.e., ethyl 2-((isopropoxycarbonothioyl)thio)-2-methylpropanoate (IPX), which exhibits good control RAFT polymerization. The plot between molar mass and conversion yields a linear line which confirms the pseudo-first-order kinetics, and molar mass distribution (Ðm) was found between (1.50–1.24). Both polymers were characterized by 1H NMR, FTIR, DSC, TGA-DTA, GPC, and XRD analysis. TEM and DLS study of the aqueous solution of the block copolymer (PNVP-b-PNALP) exhibited self-assembly (119–160 nm with a few smaller particles of 91 nm). Different concentrations of polymers (200–0.75 μM) were evaluated for their toxicities on macrophages (RAW 264.7) and cancer (MCF7) cell lines. The polymers were found to be nontoxic as we did not observe any significant changes in the rate of proliferation of both cells even at higher concentrations (up to 100 μM). However, the polymers were found to induce apoptosis-like changes in the cancer cells up to 100 μM, albeit not significant. © 2023 Elsevier Ltd
The benzyl ethyl trithiocarbonate mediated control synthesis of a block copolymer containing N-vinyl pyrrolidone by RAFT methodology: Influence of polymer composition on cell cytotoxicity and cell viability
(Elsevier Ltd, 2020) Koushik Nandy; Arti Srivastava; Shere Afgan; Deepak; Rajesh Kumar; Arun Kumar Rawat; Rajan Singh; Rakesh K. Singh
Benzyl ethyl trithiocarbonate (BET) mediated reversible addition–fragmentation chain transfer (RAFT) polymerization was carried out in dry 1,4-dioxane medium at 85 °C to synthesize Poly(n-Butyl Acrylate) (PBA) with pre-determined molecular weight (Mn 7999), narrow polydispersity (PDI 1.13) and precise chain end structure. The end chain functionality of macro chain transfer agent (CTA) was proved by homo-chain and hetero-chain extension polymerization experiment to get the poly (n-Butyl Acrylate) (Mn 17902) and poly (n-Butyl Acrylate)-b-poly(N-Vinyl Pyrrolidone) di-block copolymer (Mn 16029) respectively. Resulting polymers were characterized by 1H NMR, FTIR, GPC, TGA-DTA, DTG, DSC. The kinetic investigations confirmed the pseudo-first-order kinetic of the homopolymerization and linear evolution of the molar mass w.r.t. conversion within the range of polydispersity (PDI) (1.11 –1.20) in dry 1, 4-dioxane medium. The cyto-toxicities of PBA Macro CTA and PBA-b-PNVP polymers were evaluated on RAW264.7 mouse macrophage cells. The cellular viability was found to be 60.31% and 77.83% at 250 μM concentration, respectively for the two polymers. The viability was found more at high concentrations of polymers. The mechanism of cell death associated with these polymers was further evaluated in terms of apoptosis and necrosis on MCF-7 cell lines. Both the polymers induced apoptotic-like changes in MCF-7 cells. © 2019 Elsevier Ltd
The CD200-CD200R cross-talk helps Leishmania donovani to down regulate macrophage and CD4+CD44+ T cells effector functions in an NFκB independent manner
(Elsevier B.V., 2020) Arun Kumar Rawat; Kavita Pal; Rajan Singh; Anshul Anand; Smita Gupta; Dhiraj Kishore; Sangram Singh; Rakesh K. Singh
The lacuna in the knowledge of immunobiology, especially in visceral infections that are fatal if left untreated, are a major hurdle in getting a vaccine candidate for leishmaniasis. Till date, only a few drugs are available to combat human leishmaniasis and a vaccine candidate either prophylactic or preventive is still awaited. Therefore, identification of host and parasitic factors involved in the regulation of specific immune mechanisms are essentially needed. In this study, we observed that CD200-CD200R immune inhibitory axis regulates host macrophages effectors properties and helps antigen experienced T cells (CD4+CD44+ T cells) to acquire anti-inflammatory cytokines (IL-4, IL-10, TGF-β, IL-27) producing abilities in an NFkB independent manner. After CD200 blocking the macrophages effectively inhibited proliferation of Leishmania amastigotes and also induced the production of IL-12, IFN-γ, TNF-α and nitric oxide (NOx). Further, the blocking of CD200 signaling also restored macrophages MHC-II expression and helped CD4+CD44+ T cells to produce pro-inflammatory cytokines like IL-2, IL-12 and IFN-γ. The finding of this study suggested the importance of immune inhibitory mechanisms in controlling Leishmania growth and survival and therefore, requires more studies to understand its role in vaccine induced immunity. © 2020 Elsevier B.V.