Chitra Mandal

Publications of Chitra Mandal

• Functions and Biosynthesis of O-Acetylated Sialic Acids.

  Authors: Chitra Mandal, Reinhard Schwartz-Albiez, Reinhard Vlasak

  Topics in current chemistry. 02/2012;

  Sialic acids have a pivotal functional impact in many biological interactions such as virus attachment, cellular adhesion, regulation of proliferation, and apoptosis. A common modification of sialicSialic acids have a pivotal functional impact in many biological interactions such as virus attachment, cellular adhesion, regulation of proliferation, and apoptosis. A common modification of sialic acids is O-acetylation. O-Acetylated sialic acids occur in bacteria and parasites and are also receptor determinants for a number of viruses. Moreover, they have important functions in embryogenesis, development, and immunological processes. O-Acetylated sialic acids represent cancer markers, as shown for acute lymphoblastic leukemia, and they are known to play significant roles in the regulation of ganglioside-mediated apoptosis. Expression of O-acetylated sialoglycans is regulated by sialic acid-specific O-acetyltransferases and O-acetylesterases. Recent developments in the identification of the enigmatic sialic acid-specific O-acetyltransferase are discussed.

• Sialoglycoproteins adsorbed by Pseudomonas aeruginosa facilitate their survival by impeding neutrophil extracellular trap through siglec-9.

  Authors: Biswajit Khatua, Kaushik Bhattacharya, Chitra Mandal

  Journal of leukocyte biology. 01/2012;

  PA is an opportunistic pathogen that is commonly associated with severe infection in immunocompromised hosts. Siglec-9 binds with Sias by cis interaction on the neutrophil surface, thereby reducingPA is an opportunistic pathogen that is commonly associated with severe infection in immunocompromised hosts. Siglec-9 binds with Sias by cis interaction on the neutrophil surface, thereby reducing immunological activity. However, neutrophils bind with pathogens through trans interactions of siglec-9 with Sias. Neutrophils kill invading pathogens by NETs, along with extracellular phagocytosis. Here, we report the mode of the adsorption of Sias by PA from host serum, the interaction of PA(+Sias) with human neutrophils, and the resulting neutrophil immunological activity. The α2-3-linked sialoglycoproteins adsorbed by PA exhibited potent binding with the soluble siglec-9-Fc chimeras, CHO-siglec-9 and siglec-9 on neutrophils. The binding between PA(+Sias) and neutrophils was blocked by the synthetic sialoglycan Neu5Acα2-3Galβ1-4GlcNAc, confirming the linkage-specific, Sias-siglec-9 interaction. The PA(+Sias) and siglec-9 interaction on neutrophils reduced the level of ROS and the release of elastase, resulting in a reduction of NETs formation, demonstrating the role of the sialoglycoproteins adsorbed by PA in the weakening of neutrophil activity. The resistance of PA(+Sias) to NETs was made evident by the increased survival of PA(+Sias). Moreover, the decrease in PA(-Sias) survival demonstrated the involvement of NETs formation in the absence of the Sias-Nsiglec-9 interaction. N-actylcysteine or sivelestat-pretreated neutrophils enhanced the survival of PA(-Sias). DNAse-pretreated neutrophils did not exhibit any NETs formation, resulting in the enhanced escape of PA(-Sias). Taken together, one of the survival mechanisms of PA(+Sias) is the diminution of innate immunity via its adsorption of sialoglycoproteins by its engagement of the inhibitory molecule siglec-9. This is possibly a general mechanism for pathogens that cannot synthesize Sias to subvert immunity.

• Bak Compensated for Bax in p53-null Cells to Release Cytochrome c for the Initiation of Mitochondrial Signaling during Withanolide D-Induced Apoptosis.

  Authors: Susmita Mondal, Kaushik Bhattacharya, Asish Mallick, Rajender Sangwan, Chitra Mandal

  PloS one. 01/2012; 7(3):e34277.

  The goal of cancer chemotherapy to induce multi-directional apoptosis as targeting a single pathway is unable to decrease all the downstream effect arises from crosstalk. Present study reports thatThe goal of cancer chemotherapy to induce multi-directional apoptosis as targeting a single pathway is unable to decrease all the downstream effect arises from crosstalk. Present study reports that Withanolide D (WithaD), a steroidal lactone isolated from Withania somnifera, induced cellular apoptosis in which mitochondria and p53 were intricately involved. In MOLT-3 and HCT116p53+/+ cells, WithaD induced crosstalk between intrinsic and extrinsic signaling through Bid, whereas in K562 and HCT116p53-/- cells, only intrinsic pathway was activated where Bid remain unaltered. WithaD showed pronounced activation of p53 in cancer cells. Moreover, lowered apoptogenic effect of HCT116p53-/- over HCT116p53+/+ established a strong correlation between WithaD-mediated apoptosis and p53. WithaD induced Bax and Bak upregulation in HCT116p53+/+, whereas increase only Bak expression in HCT116p53-/- cells, which was coordinated with augmented p53 expression. p53 inhibition substantially reduced Bax level and failed to inhibit Bak upregulation in HCT116p53+/+ cells confirming p53-dependent Bax and p53-independent Bak activation. Additionally, in HCT116p53+/+ cells, combined loss of Bax and Bak (HCT116Bax-Bak-) reduced WithaD-induced apoptosis and completely blocked cytochrome c release whereas single loss of Bax or Bak (HCT116Bax-Bak+/HCT116Bax+Bak-) was only marginally effective after WithaD treatment. In HCT116p53-/- cells, though Bax translocation to mitochondria was abrogated, Bak oligomerization helped the cells to release cytochrome c even before the disruption of mitochondrial membrane potential. WithaD also showed in vitro growth-inhibitory activity against an array of p53 wild type and null cancer cells and K562 xenograft in vivo. Taken together, WithaD elicited apoptosis in malignant cells through Bax/Bak dependent pathway in p53-wild type cells, whereas Bak compensated against loss of Bax in p53-null cells.

• Chemotypical variations in Withania somnifera lead to differentially modulated immune response in BALB/c mice.

  Authors: Susheela Kushwaha, Saptarshi Roy, Rita Maity, Asish Mallick, Vishal K Soni, Prashant K Singh, Narayan D Chaurasiya, Rajender S Sangwan, Shailja Misra-Bhattacharya, Chitra Mandal

  Vaccine. 12/2011; 30(6):1083-93.

  Withania somnifera (Ashwagandha) is a plant with known ethnomedicinal properties and its use in Ayurvedic medicine in India is well documented. The present investigation reports on immunomodulatoryWithania somnifera (Ashwagandha) is a plant with known ethnomedicinal properties and its use in Ayurvedic medicine in India is well documented. The present investigation reports on immunomodulatory efficacy of aqueous-ethanol extracts of roots of three selected Withania somnifera chemotypes designated as NMITLI 101R, NMITLI 118R and NMITLI 128R. Each chemotype was administered 10-100 mg/kg orally to BALB/c mice once daily for 14 days. The immunomodulatory consequences were recorded by determining the humoral immune response with the help of hemagglutination, plaque forming cell assay and cellular response by measuring delayed type hypersensitivity reaction. Additionally, other immune parameters such as proliferation of T and B cells, intracellular and secreted Th1 and Th2 cytokines along with modulation in ROS production by peritoneal macrophages were monitored after feeding with lower doses (3-30 mg/kg/day) of these three chemotypes individually. NMITLI 101R incited both humoral and cellular immune response in terms of higher number of antibody producing cells and enhanced foot pad swelling at the 10mg dose as also dose dependent B and T cell proliferations. Levels of intracellular and secreted cytokines post-NMITLI 101R treatment illustrated generation of mixed Th1/Th2 response that remained more polarized towards Th1. This chemotype also generated maximum reactive oxygen species. NMITLI 118R provoked comparatively reduced immune response in all humoral and cellular parameters at lower doses but induced highly polarized Th1 cytokine response. In contrast, NMITLI 128R led to enhanced antibody production with minimal cellular response demonstrating marginally Th2 dominance at a lower dose. Taken together, it may therefore be concluded that there were distinct modulation in the immune response exhibited by the three chemotypes of Withania somnifera and NMITLI 101R appeared to possess a better immunostimulatory activity than the other chemotypes at lower doses.

• Mobilization of lymphoblasts from bone marrow to peripheral blood in childhood acute lymphoblastic leukaemia: role of 9-O-acetylated sialoglycoproteins.

  Authors: Suchandra Chowdhury, Chandan Mandal, Sayantani Sarkar, Arup Kumar Bag, Reinhard Vlasak, Sarmila Chandra, Chitra Mandal

  Leukemia research. 11/2011; 36(2):146-55.

  Childhood acute lymphoblastic leukaemia is characterized by aberrant proliferation and accumulation of malignant lymphoblasts in bone marrow (BM), followed by their migration into circulation. AnChildhood acute lymphoblastic leukaemia is characterized by aberrant proliferation and accumulation of malignant lymphoblasts in bone marrow (BM), followed by their migration into circulation. An enhanced cell-surface expression of ALL-associated 9-O-acetylated sialoglycoproteins (Neu5,9Ac(2)-GPs) was demonstrated. Present investigation reports a positive correlation between the increased density of Neu5,9Ac(2)-GPs on lymphoblasts and their mobilization from BM involving enhanced Neu5,9Ac(2) on CD45 demonstrating modulation of FAK and ERK molecules. In contrast, a small population of cells, identified as haematopoietic precursors, with comparatively lesser Neu5,9Ac(2)-GPs showed increased binding towards BM stroma. Thus, Neu5,9Ac(2)-GPs is a developmentally regulated oncofoetal antigen, whose up-regulation is imperative in the interaction between lymphoblasts and BM stroma, governing their mobilization into circulation.

• Regulation of O-acetylation of sialic acids by sialate-O-acetyltransferase and sialate-O-acetylesterase activities in childhood acute lymphoblastic leukemia.

  Authors: Chandan Mandal, Chhabinath Mandal, Sarmila Chandra, Roland Schauer, Chitra Mandal

  Glycobiology. 08/2011; 22(1):70-83.

  Enhanced expression of 9-O-acetylated sialoglycoproteins (Neu5,9Ac(2)-GPs) and 9-O-acetylated disialoganglioside (9-OAcGD3) was observed on lymphoblasts of childhood acute lymphoblastic leukemiaEnhanced expression of 9-O-acetylated sialoglycoproteins (Neu5,9Ac(2)-GPs) and 9-O-acetylated disialoganglioside (9-OAcGD3) was observed on lymphoblasts of childhood acute lymphoblastic leukemia (ALL). Sialate-O-acetyltransferase (SOAT) and sialate-O-acetylesterase (SIAE) are the two main enzymes responsible for the quantity of the O-acetyl ester groups on sialic acids (Sias). We have earlier shown an enhanced level of SOAT activity, capable of transferring acetyl groups to Sias of glycoconjugates in the microsomes of lymphoblasts of these children. We further observed a decreased SIAE activity in both lysosomal and cytosolic fractions of ALL cell lines and primary cells from bone marrow of patients compared with peripheral blood mononuclear cells from healthy donors, which preferentially hydrolyze O-acetyl groups at C-9 of Sia. The level of O-acetylated Sias in the cytosolic and the lysosomal fractions showed a good correlation with SIAE activity in the corresponding fractions. The apparent K(M) values for SIAE in the lysosomal and the cytosolic fractions from lymphoblasts of ALL patients are 0.38 and 0.39 mM, respectively. These studies demonstrate that both SIAE and SOAT activities seem to be responsible for the enhanced level of Neu5,9Ac(2) in lymphoblasts, which is a hallmark in ALL. This was subsequently confirmed by using an enzyme-linked immunosorbent assay that also demonstrated a steady decline in SOAT activities even in cell lysates of lymphoblasts during successful chemotherapy, like radioactive methods have shown earlier.

• Natural products: promising resources for cancer drug discovery.

  Authors: Susmita Mondal, Santu Bandyopadhyay, Mrinal K Ghosh, Sibabrata Mukhopadhyay, Siddhartha Roy, Chitra Mandal

  Anti-cancer agents in medicinal chemistry. 06/2011; 12(1):49-75.

  Natural products are important sources of anti-cancer lead molecules. Many successful anti-cancer drugs are natural products or their analogues. Many more are under clinical trials. The presentNatural products are important sources of anti-cancer lead molecules. Many successful anti-cancer drugs are natural products or their analogues. Many more are under clinical trials. The present review focuses on chemopreventive and anti-cancer activities of polar and non-polar extracts, semi purified fractions and pure molecules from terrestrial plants of India reported between 2005 and 2010 emphasizing possible mechanisms of action of pure molecules.

• 9-O-Acetyl GD3 in lymphoid and erythroid cells.

  Authors: Kankana Mukherjee, Suchandra Chowdhury, Susmita Mondal, Chandan Mandal, Sarmila Chandra, Chitra Mandal

  Advances in experimental medicine and biology. 01/2011; 705:317-34.

• A perspective on the emergence of sialic acids as potent determinants affecting leishmania biology.

  Authors: Angana Ghoshal, Chitra Mandal

  Molecular biology international. 01/2011; 2011:532106.

  Leishmaniasis caused by Leishmania sp. has a wide range of manifestations from cutaneous to the deadly visceral form. They shuttle between the invertebrate and vertebrate hosts as promastigotes andLeishmaniasis caused by Leishmania sp. has a wide range of manifestations from cutaneous to the deadly visceral form. They shuttle between the invertebrate and vertebrate hosts as promastigotes and amastigotes having adaptations for subverting host immune responses. Parasite-specific glycoconjugates have served as important determinants influencing parasite recognition, internalization, differentiation, multiplication, and virulence. Despite the steady progress in the field of parasite glycobiology, sialobiology has been a less traversed domain of research in leishmaniasis. The present paper focuses on identification, characterization, and differential distribution of sialoglycotope having the linkage-specific 9-O-acetylated sialic acid in promastigotes of different Leishmania sp. causing different clinical ramifications emphasizing possible role of these sialoglycotopes in infectivity, virulence, nitric oxide resistance, and host modulation in Leishmania spp. asserting them to be important molecules influencing parasite biology.

• Glycosylation of erythrocyte spectrin and its modification in visceral leishmaniasis.

  Authors: Sajal Samanta, Devawati Dutta, Angana Ghoshal, Sumi Mukhopadhyay, Bibhuti Saha, Shyam Sundar, Saulius Jarmalavicius, Michael Forgber, Chhabinath Mandal, Peter Walden, Chitra Mandal

  PloS one. 01/2011; 6(12):e28169.

  Using a lectin, Achatinin-H, having preferential specificity for glycoproteins with terminal 9-O-acetyl sialic acid derivatives linked in α2-6 linkages to subterminal N-acetylgalactosamine, eightUsing a lectin, Achatinin-H, having preferential specificity for glycoproteins with terminal 9-O-acetyl sialic acid derivatives linked in α2-6 linkages to subterminal N-acetylgalactosamine, eight distinct disease-associated 9-O-acetylated sialoglycoproteins was purified from erythrocytes of visceral leishmaniaisis (VL) patients (RBC(VL)). Analyses of tryptic fragments by mass spectrometry led to the identification of two high-molecular weight 9-O-acetylated sialoglycoproteins as human erythrocytic α- and β-spectrin. Total spectrin purified from erythrocytes of VL patients (spectrin(VL)) was reactive with Achatinin-H. Interestingly, along with two high molecular weight bands corresponding to α- and β-spectrin another low molecular weight 60 kDa band was observed. Total spectrin was also purified from normal human erythrocytes (spectrin(N)) and insignificant binding with Achatinin-H was demonstrated. Additionally, this 60 kDa fragment was totally absent in spectrin(N). Although the presence of both N- and O-glycosylations was found both in spectrin(N) and spectrin(VL), enhanced sialylation was predominantly induced in spectrin(VL). Sialic acids accounted for approximately 1.25 kDa mass of the 60 kDa polypeptide. The demonstration of a few identified sialylated tryptic fragments of α- and β-spectrin(VL) confirmed the presence of terminal sialic acids. Molecular modelling studies of spectrin suggest that a sugar moiety can fit into the potential glycosylation sites. Interestingly, highly sialylated spectrin(VL) showed decreased binding with spectrin-depleted inside-out membrane vesicles of normal erythrocytes compared to spectrin(N) suggesting functional abnormality. Taken together this is the first report of glycosylated eythrocytic spectrin in normal erythrocytes and its enhanced sialylation in RBC(VL). The enhanced sialylation of this cytoskeleton protein is possibly related to the fragmentation of spectrin(VL) as evidenced by the presence of an additional 60 kDa fragment, absent in spectrin(N) which possibly affects the biology of RBC(VL) linked to both severe distortion of erythrocyte development and impairment of erythrocyte membrane integrity and may provide an explanation for their sensitivity to hemolysis and anemia in VL patients.

• Arsenic-induced cell proliferation is associated with enhanced ROS generation, Erk signaling and CyclinA expression.

  Authors: Rajdeep Chowdhury, Raghunath Chatterjee, Ashok K Giri, Chitra Mandal, Keya Chaudhuri

  Toxicology letters. 10/2010; 198(2):263-71.

  Arsenic is a well-established human carcinogen; however molecular mechanisms to arsenic-induced carcinogenesis are complex and elusive. The present study identifies a potential biomarker of arsenicArsenic is a well-established human carcinogen; however molecular mechanisms to arsenic-induced carcinogenesis are complex and elusive. The present study identifies a potential biomarker of arsenic exposure, and redefines arsenic-induced signaling in stimulation of cell proliferation. The effect of arsenic exposure on gene expression was evaluated in PBMC of arsenic-exposed individuals selected from a severely affected district of West Bengal, India. A novel, un-documented biomarker of arsenic exposure, CyclinA was identified by microarray analysis from the study. Non-transformed cell lines HaCat and Int407 when exposed to clinically achievable arsenic concentration showed significant increase of CyclinA substantiating the clinical data. An associated increase in S phase population of cells in cell cycle, indicative of enhanced proliferation was also noticed. On further investigation of the pathway to arsenic-induced proliferation, we observed that arsenic resulted: ROS generation; activated Erk signaling; stimulated AP-1 activity, including immediate early genes, c-Jun and c-Fos. N-Acetyl-l-cysteine, a ROS quencher, blocked the arsenic-induced effects. Our study underlines a previously undefined mechanism by which arsenic imparts its toxicity and results in uncontrolled cell proliferation.

• Identification and quantification of the active component quercetin 3-O-rutinoside from Barringtonia racemosa, targets mitochondrial apoptotic pathway in acute lymphoblastic leukemia.

  Authors: Suman Kumar Samanta, Kaushik Bhattacharya, Chitra Mandal, Bikas Chandra Pal

  Journal of Asian natural products research. 08/2010; 12(8):639-48.

  Barringtonia racemosa has been used as a traditional medicine for the treatment of various diseases. The antitumor property of the seed extract of this plant in mice model promotes us to search forBarringtonia racemosa has been used as a traditional medicine for the treatment of various diseases. The antitumor property of the seed extract of this plant in mice model promotes us to search for the active component present in the fruit extract. Quercetin 3-O-rutinoside (QOR) has been isolated from the fruits of this plant for the first time and quantified by HPLC method. The compound was identified by IR, mass, and NMR (1D, 2D) spectral data analysis. QOR showed dose- and time-dependent anti-proliferative activity in several leukemic cell lines with negligible effect on normal human peripheral blood mononuclear cell (PBMC). A representative T-lineage acute lymphoblastic leukemia cell line (MOLT-3) showed phosphatidyl serine externalization and DNA fragmentation, indicating QOR-induced programmed cell death. We established that QOR-induced apoptosis occurred preferentially on accumulation of cells in the sub-G(0) phase and genomic DNA fragmentation through the activation of mitochondria-dependent caspase cascade for the first time in T-lineage ALL cell line.

• Sialic acids in different Leishmania sp., its correlation with nitric oxide resistance and host responses.

  Authors: Angana Ghoshal, Gerrit J Gerwig, Johannis P Kamerling, Chitra Mandal

  Glycobiology. 05/2010; 20(5):553-66.

  The presence of different derivatives of sialic acids (SA) on Leishmania donovani instigated us to investigate their status on different strains of Leishmania sp. causing different forms of theThe presence of different derivatives of sialic acids (SA) on Leishmania donovani instigated us to investigate their status on different strains of Leishmania sp. causing different forms of the disease. Leishmania tropica (K27), Leishmania major (JISH118) and Leishmania mexicana (LV4) responsible for cutaneous, Leishmania braziliensis (L280) and Leishmania amazonensis (LV81) causing diffuse and Leishmania infantum (MON29) responsible for visceral leishmaniasis were included in this study. The strains showed a differential distribution of SA in spite of their close resemblance in pathogenesis. K27, JISH118, L280 and MON29 were categorized as high SA-containing strains having enhanced 9-O-acetyl sialic acid (9-O-AcSA(high)) whereas LV4 and LV81 evidenced considerably reduced SA. Interestingly, 9-O-AcSA(high) promastigotes showed significant viability as compared to their de-O-acetylated forms after exposure to NaNO(2) suggesting the involvement of 9-O-AcSA in conferring nitric oxide (NO) resistance. Enhanced intracellular survivability was demonstrated following infection of human macrophages with 9-O-AcSA(high) promastigotes in contrast to their de-O-acetylated forms indicating their contribution in bestowing a survival benefit. Additionally, reduced accumulation of NO, interleukin-12 and interferon-gamma in the supernatant of macrophages infected with 9-O-AcSA(high) promastigotes indicated suppression of leishmanicidal host responses. However, LV4 and LV81 with least 9-O-AcSA, before and after de-O-acetylation, showed unaltered NO resistance, multiplicity and host responses signifying the probable involvement of other determinants which may be a function of their inherent parasitic attribute. Hence, enhanced levels of 9-O-AcSA serve as one of the potential determinants responsible for increased NO resistance and survivability of parasites by inhibition of host responses.

• Withanolide D induces apoptosis in leukemia by targeting the activation of neutral sphingomyelinase-ceramide cascade mediated by synergistic activation of c-Jun N-terminal kinase and p38 mitogen-activated protein kinase.

  Authors: Susmita Mondal, Chandan Mandal, Rajender Sangwan, Sarmila Chandra, Chitra Mandal

  Molecular cancer. 01/2010; 9:239.

  Ceramide is an important second messenger that has diverse cellular and biological effect. It is a specific and potent inducer of apoptosis and suppressor of cell growth. In leukemia, chemoresistanceCeramide is an important second messenger that has diverse cellular and biological effect. It is a specific and potent inducer of apoptosis and suppressor of cell growth. In leukemia, chemoresistance generally developed due to deregulated ceramide metabolism. In combinatorial treatment strategies of leukemia, few components have the capability to increases ceramide production. Manipulation in ceramide production by physiological and pharmacological modulators therefore will give additive effect in leukemia chemotherapy. Here, we show that Withanolide D (C4β-C5β,C6β-epoxy-1-oxo-,20β, dihydroxy-20S,22R-witha-2,24-dienolide; WithaD), a pure herbal compound isolated from Withania somnifera could effectively induces apoptosis in a dose and time dependant manner both in myeloid (K562) and lymphoid (MOLT-4) cells being nontoxic to normal lymphocytes and control proliferative cells. WithaD potentially augment ceramide production in these cells. Downstream of ceramide, WithaD acted on MKK group of proteins and significantly increased JNK and p38MAPK phosphorylation. Pharmacological inhibition of p38MAPK and JNK proves their cooperative action on WithaD-induced cell death. Dissecting the cause of ceramide production, we found activation of neutral sphingomyelinase and showed neutral-sphingomyelinase 2 (N-SMase 2) is a critical mediator of WithaD-induced apoptosis. Knockdown of N-SMase 2 by siRNA and inhibitor of N-SMase (GW4869) significantly reduced WithaD-induced ceramide generation and phosphorylation of MKK4 and MKK3/6, whereas phosphorylation of MKK7 was moderately regulated in leukemic cells. Also, both by silencing of N-SMase 2 and/or blocking by GW4869 protects these cells from WithaD-mediated death and suppressed apoptosis, whereas Fumonisin B1, an inhibitor of ceramide synthase, did not have any effect. Additionally, WithaD effectively induced apoptosis in freshly isolated lymphoblasts from patients and the potent cell killing activity was through JNK and p38MAPK activation. Our results demonstrate that WithaD enhance the ceramide accumulation by activating N-SMase 2, modulate phosphorylation of the JNK and p38MAPK and induced apoptosis in both myeloid and lymphoid cells along with primary cells derived from leukemia patients. Taken together, this pure herbal compound (WithaD) may consider as a potential alternative tool with additive effects in conjunction with traditional chemotherapeutic treatment, thereby accelerate the process of conventional drug development.

• Sialic acids acquired by Pseudomonas aeruginosa are involved in reduced complement deposition and siglec mediated host-cell recognition.

  Authors: Biswajit Khatua, Angana Ghoshal, Kaushik Bhattacharya, Chandan Mandal, Bibhuti Saha, Paul R Crocker, Chitra Mandal

  FEBS letters. 11/2009;

  The opportunism of Pseudomonas aeruginosa (PA) in immunocompromised hosts prompted us to explore the potential role of sialic acids (Sia) in this phenomenon. Culture of PA in the presence ofThe opportunism of Pseudomonas aeruginosa (PA) in immunocompromised hosts prompted us to explore the potential role of sialic acids (Sia) in this phenomenon. Culture of PA in the presence of exogenous Sia resulted in linkage-specific incorporation of Sia which was associated with decreased complement-deposition on the bacteria. Sia acquired by PA mediated enhanced binding of bacteria to recombinant-CHO cells expressing human siglec-7 or siglec-9, as well as to human NK-cells and monocytes naturally expressing these siglecs. Therefore, Sia may be acquired by PA in the host and contribute to bacterial pathogenicity and host cell interactions via reduction of complement-deposition and siglec-dependent recognition.

• Leishmania cell surface prohibitin: role in host-parasite interaction.

  Authors: Rohit Jain, Angana Ghoshal, Chitra Mandal, Chandrima Shaha

  Cellular microbiology. 11/2009;

  Abstract Proteins selectively upregulated in infective parasitic forms could be critical for disease pathogenesis. A mammalian prohibitin orthologue is upregulated in infective metacyclicAbstract Proteins selectively upregulated in infective parasitic forms could be critical for disease pathogenesis. A mammalian prohibitin orthologue is upregulated in infective metacyclic promastigotes of Leishmania donovani, a parasite that causes visceral leishmaniasis. Leishmania donovani prohibitin shares 41% similarity with mammalian prohibitin and 95-100% within the genus. Prohibitin is concentrated at the surface of the flagellar and the aflagellar pole, the aflagellar pole being a region through which host-parasite interactions occur. Prohibitin is attached to the membrane through a GPI anchor. Overexpression of wild-type prohibitin increases protein surface density resulting in parasites with higher infectivity. However, parasites overexpressing a mutant prohibitin with an amino acid substitution at the GPI anchor site to prevent surface expression through GPI-link, shows lesser surface expression and lower infective abilities. Further, the presence of anti-prohibitin antibodies during macrophage-Leishmania interaction in vitro reduces infection. The cognate binding partner for Leishmania prohibitin on the host cell appears to be macrophage surface HSP70, siRNA mediated downregulation of which abrogates the capability of the macrophage to bind to parasites. Leishmania prohibitin is able to generate a strong humoral response in visceral leishmaniasis patients. The above observations suggest that prohibitin plays an important role in events leading to Leishmania-host interaction.

• Four new dinuclear Cu(ii) hydrazone complexes using various organic spacers: syntheses, crystal structures, DNA binding and cleavage studies and selective cell inhibitory effect towards leukemic and normal lymphocytes.

  Authors: Sambuddha Banerjee, Susmita Mondal, Soma Sen, Saurabh Das, David L Hughes, Corrado Rizzoli, Cédric Desplanches, Chitra Mandal, Samiran Mitra

  Dalton transactions (Cambridge, England : 2003). 10/2009;

  Syntheses and crystal structures of four new hydrazone-based Cu(ii) complexes, [{Cu(L(1))(H(2)O)}(2)(mu-pyraz)](ClO(4))(2) (), [{Cu(L(1))(OClO(3))}(2)(mu-4,4'-bipy)] (),Syntheses and crystal structures of four new hydrazone-based Cu(ii) complexes, [{Cu(L(1))(H(2)O)}(2)(mu-pyraz)](ClO(4))(2) (), [{Cu(L(1))(OClO(3))}(2)(mu-4,4'-bipy)] (), [{Cu(L(2)H)}(mu-pyraz){Cu(L(2)H)(OClO(3))}].(ClO(4)) () and [{Cu(L(2))}(2)(mu-bpe)] () [L(1)H = condensation product of benzhydrazide and pyridine-2-carbaldehyde and L(2)H(2) = condensation product of benzoyl acetone and benzhydrazide], bridged by various organic spacers [pyrazine (pyraz), 4,4'-bipyridine (4,4'-bipy) and 1,2-di(4-pyridyl)ethane (bpe)] are reported in this paper. The single-crystal X-ray crystallographic studies reveal that all are dinuclear units where and form strong intermolecular H-bonding to form sheets of interconnected ions, whereas forms sheets of dinuclear chains through pi-pi interactions; in , molecules are linked only through van der Waals interactions. The variable-temperature magnetic moment studies reveal that and show antiferromagnetic coupling between the Cu(ii) centers at lower temperatures. The binding ability of with calf thymus DNA [CT-DNA] is reported using various spectroscopic studies (UV-Vis titration, circular dichroism and fluorescence). The binding constants of with CT-DNA, as calculated by different methodologies, are of the order of 10(5) M(-1). The mode of interaction between and CT-DNA has been predicted using circular dichroic (CD) spectroscopy, where it has been shown that most probably interacts with DNA via intercalation between the base pairs leading to a change in B-DNA conformation. is also able to cleave supercoiled (SC) plasmid DNA pUC19 in a time and dose dependent manner as demonstrated by agarose gel electrophoresis, and also demonstrates its potential to cleave the SC plasmid DNA via both oxidative and hydrolytic mechanisms. Approximately 50% of leukemic cells are found to be dead when two representative leukemic cell lines are exposed to ( approximately 80 muM) even for 24 h as determined by different cell cytotoxicity assays. Preliminary results also showed that, at 20 muM, could selectively induce apoptosis in leukemic cells without affecting normal lymphocytes.

• Elevated mRNA level of hST6Gal I and hST3Gal V positively correlates with the high risk of pediatric acute leukemia.

  Authors: Susmita Mondal, Sarmila Chandra, Chitra Mandal

  Leukemia research. 09/2009;

  Altered sialylation occurs in essentially all types of human and experimental cancers. Although, aberrant sialylation is believed to mainly due to altered sialyltransferase (ST) level, so far,Altered sialylation occurs in essentially all types of human and experimental cancers. Although, aberrant sialylation is believed to mainly due to altered sialyltransferase (ST) level, so far, expression pattern of different STs in acute lymphoblastic leukemia has never been investigated. Accordingly, the aim of our study was to monitor the changes in mRNA expression of ST6Gal I, ST3Gal V and ST8Sia I in patients by real-time PCR, which may provide prognostic information useful in defining appropriate therapeutic options. Our data demonstrated that ST6Gal I and ST3Gal V mRNA were up-regulated in lymphoblasts whereas its presence was negligible in non-malignant donors. In contrast, ST8SiaI was downregulated in patients. The extents of linkage-specific sialylation of glycoconjugates were found to be associated with disease establishment. Additionally, ST6Gal I and ST3Gal V were positively correlated with the high risk of the disease (P=0.0032 and 0.0016). This differential ST level can be used as biomarker with the molecular method of quantitative PCR and may be useful to discriminate normal and cancer patients.

• Apoptotic effects of mahanine on human leukemic cells are mediated through crosstalk between Apo-1/Fas signaling and the Bid protein and via mitochondrial pathways.

  Authors: Kaushik Bhattacharya, Suman K Samanta, Rakshamani Tripathi, Asish Mallick, Sarmila Chandra, Bikas C Pal, Chandrima Shaha, Chitra Mandal

  Biochemical pharmacology. 09/2009;

  Apo-1 (Fas/CD95), a cell surface receptor, triggers apoptosis after binding to its physiological ligand, Apo-1L (FasL/CD95L). This study reports that mahanine, purified from the leaves of MurrayaApo-1 (Fas/CD95), a cell surface receptor, triggers apoptosis after binding to its physiological ligand, Apo-1L (FasL/CD95L). This study reports that mahanine, purified from the leaves of Murraya koenigii, has a dose- and time-dependent anti-proliferative activity in acute lymphoid (MOLT-3) and chronic myeloid (K562) leukemic cell lines and in the primary cells of leukemic and myeloid patients, with minimal effect on normal immune cells including CD34(+) cells. Leukemic cells underwent phosphatidylserine externalization and DNA fragmentation, indicating mahanine-induced apoptosis. An increase in reactive oxygen species suggests that the mahanine-induced apoptosis was mediated by oxidative stress. A significant drop in the Bcl2/Bax ratio, the loss of mitochondrial transmembrane potential as well as cytochrome c release from the mitochondria to the cytosol suggested involvement of the mitochondrial pathway of apoptosis. Cytochrome c release was followed by the activation of caspase-9, caspase-3 and caspase-7, and cleavage of PARP in both MOLT-3 and K562 cells. In MOLT-3 cells, formation of the Fas-FasL-FADD-caspase-8 heterotetramer occurred, leading to the cleavage of Bid to its truncated form, which consequently resulted in formation of the mitochondrial transmembrane pore. The incubation of MOLT-3 cells with mahanine in the presence of caspase-8 inhibitor or FasL-neutralizing NOK-2 antibody resulted in the decrease of mahanine-induced cell death. Mahanine was also a potent inhibitor of K562 xenograft growth, which was evident in an athymic nude mice model. In summary, these results provide evidence for involvement of the death receptor-mediated extrinsic pathway of apoptosis in the mahanine-induced anticancer activity in MOLT-3 cells, but not in K562 cells, which are deficient in Fas/FasL.

• An orally effective dihydropyrimidone (DHPM) analogue induces apoptosis-like cell death in clinical isolates of Leishmania donovani overexpressing pteridine reductase 1.

  Authors: Neeloo Singh, Jaspreet Kaur, Pranav Kumar, Swati Gupta, Nasib Singh, Angana Ghosal, Avijit Dutta, Ashutosh Kumar, RamaPati Tripathi, Mohammad Siddiqi, Chitra Mandal, Anuradha Dube

  Parasitology research. 08/2009;

  The protozoan parasite Leishmania donovani is the causative agent of visceral leishmaniasis. The enzyme pteridine reductase 1 (PTR1) of L. donovani acts as a metabolic bypass for drugs targetingThe protozoan parasite Leishmania donovani is the causative agent of visceral leishmaniasis. The enzyme pteridine reductase 1 (PTR1) of L. donovani acts as a metabolic bypass for drugs targeting dihydrofolate reductase (DHFR); therefore, for successful antifolate chemotherapy to be developed against Leishmania, it must target both enzyme activities. Leishmania cells overexpressing PTR1 tagged at the N-terminal with green fluorescent protein were established to screen for proprietary dihydropyrimidone (DHPM) derivatives of DHFR specificity synthesised in our laboratory. A cell-permeable molecule with impressive antileishmanial in vitro and in vivo oral activity was identified. Structure activity relationship based on homology model drawn on our recombinant enzyme established the highly selective inhibition of the enzyme by this analogue. It was seen that the leishmanicidal effect of this analogue is triggered by programmed cell death mediated by the loss of plasma membrane integrity as detected by binding of annexin V and propidium iodide (PI), loss of mitochondrial membrane potential culminating in cell cycle arrest at the sub-G0/G1 phase and oligonucleosomal DNA fragmentation. Hence, this DHPM analogue [(4-fluoro-phenyl)-6-methyl-2-thioxo-1, 2, 3, 4-tetrahydropyrimidine-5-carboxylic acid ethyl ester] is a potent antileishmanial agent that merits further pharmacological investigation.