Labanyamoy Kole

Synergistic Effect of Interferon-γ and Mannosylated Liposome-Incorporated Doxorubicin in the Therapy of Experimental Visceral Leishmaniasis

Active targeting of doxorubicin to macrophages was studied by incorporating it in mannose-coated liposomes by use of visceral leishmaniasis in BALB/c mice as the model macrophage disease. Mannosylated liposomal doxorubicin was more effective than liposomal doxorubicin or free doxorubicin. Because leishmaniasis is accompanied by immunosuppression, immunostimulation by interferon (IFN)-gamma was evaluated to act synergistically with mannosylated liposomal doxorubicin therapy. Combination chemotherapy with a suboptimal dose of IFN-gamma resulted in possibly complete elimination of spleen parasite burden. Analysis of mRNA levels of infected spleen cells suggested that targeted drug treatment together with IFN-gamma, in addition to greatly reducing parasite numbers, resulted in reduced levels of interleukin (IL)-4 but increased levels of IL-12 and inducible nitric oxide synthase. Such combination chemotherapy may provide a promising alternative for the cure of leishmaniasis, with a plausible conversion of antiparasitic T cell response from a Th2 to Th1 pattern indicative of long-term resistance.

Isolation of a laminin-binding protein from the protozoan parasite Leishmania donovani that may mediate cell adhesion

Extracellular matrix (ECM)-binding proteins on the surface of Leishmania are thought to play a crucial role in the onset of leishmaniasis, as these parasites invade mononuclear phagocytes in various organs after migrating through the ECM. In a previous report, we presented several lines of evidence suggesting that Leishmania has a specific receptor for laminin, a major ECM protein, with a Kd in the nanomolar range. Here we describe the identification, purification and biochemical characterization of the Leishmania laminin receptor. When the outer membrane proteins of L. donovani were blotted on to nitrocellulose paper and probed with laminin, a prominent laminin-binding protein of 67 kDa was identified. The purified protein was isolated by a three-step process involving DEAE-cellulose, Con A (concanavalin A)-Sepharose and laminin-Sepharose affinity chromatography and was used to raise a monospecific antibody. The same protein was obtained when parasite membrane extracts were adsorbed to antibody affinity matrix and eluted with glycine. The affinity-purified protein bound to laminin in a detergent-solubilized form as well as after integration into artificial bilayers, and was subsequently characterized as an integral membrane protein. Metaperiodate oxidation and metabolic inhibition of glycosylation studies indicate the binding protein to be glycoprotein in nature and that N-linked oligosaccharides play a part in the interaction of laminin with the binding protein. Surface-labelled parasites attached to microtitre wells coated with laminin and the 67 kDa protein blocked the adhesion to laminin substrate. We propose that the 67 kDa protein is an adhesin involved in the attachment of Leishmania to host tissues.

Receptor-mediated endocytosis of fucosylated neoglycoprotein by macrophages

The characteristics of the recognition system involved in the receptor mediated endocytosis of the neoglycoprotein, fucose human serum albumin (HSA) were studied. It was found that (i) fucose-HSA showed strong affinity binding and uptake by various macrophages; (ii) binding was specific for L-fucose and D-mannose; (iii) binding was found to be inhibited by oxidant like H2O2 and swainsonine whereas it was elevated by dexamethasone; (iv) clearance of125I-fucose-HSA was rapid and strongly inhibited by unlabelled fucose-HSA. Greater than 70% of fucose-HSA was found in liver and more than 60% of this was found in liver lysosomes; (v) uptake of fucose-HSA was thirty-fold more efficient in liver macrophages (Kupffer cells) than in hepatocytes; (vi) moreover, mannose-HSA and ovalbumin which are potent inhibitors of mannose/N-acetylglucosamine receptors inhibited clearance and uptake of fucose-HSA by liver as well as by isolated Kupffer cells suggesting the involvement of both fucose and mannose receptors or a single type of receptor having greater affinity for fucose-HSA than for mannose-HSA. These results emphasize the important role of fucose-terminated glycoproteins in site-specific drug targeting.

The Major Chemical-detoxifying System of UDP-glucuronosyltransferases Requires Regulated Phosphorylation Supported by Protein Kinase C

Finding rapid, reversible down-regulation of human UDP-glucuronosyltransferases (UGTs) in LS180 cells following curcumin treatment led to the discovery that UGTs require phosphorylation. UGTs, distributed primarily in liver, kidney, and gastrointestinal tract, inactivate aromatic-like metabolites and a vast number of dietary and environmental chemicals, which reduces the risk of toxicities, mutagenesis, and carcinogenesis. Our aim here is to determine relevant kinases and mechanism(s) regulating phosphorylation of constitutive UGTs in LS180 cells and 10 different human UGT cDNA-transfected COS-1 systems. Time- and concentration-dependent inhibition of immunodetectable [33P]orthophosphate in UGTs and protein kinase Cϵ (PKCϵ), following treatment of LS180 cells with curcumin or the PKC inhibitor calphostin-C, suggested UGT phosphorylation is supported by active PKC(s). Immunofluorescent and co-immunoprecipitation studies with UGT-transfected cells showed co-localization of UGT1A7His and PKCϵ and of UGT1A10His and PKCα or PKCδ. Inhibition of UGT activity by PKCϵ-specific antagonist peptide or by PKCϵ-targeted destruction with PKCϵ-specific small interference RNA and activation of curcumin-down-regulated UGTs with typical PKC agonists verified a central PKC role in glucuronidation. Moreover, in vitro phosphorylation of nascent UGT1A7His by PKCϵ confirms it is a bona fide PKC substrate. Finally, catalase or herbimycin-A inhibition of constitutive or hydrogen peroxide-activated-UGTs demonstrated that reactive oxygen species-related oxidants act as second messengers in maintaining constitutive PKC-dependent signaling evidently sustaining UGT phosphorylation and activity. Because cells use signal transduction collectively to detect and respond appropriately to environmental changes, this report, combined with our earlier demonstration that specific phospho-groups in UGT1A7 determined substrate selections, suggests regulated phosphorylation allows adaptations regarding differential phosphate utilization by UGTs to function efficiently.

Expression and characterization of a parasite-specific antigen on macrophages after infection with Leishmania donovani.

A rabbit polyclonal antibody to crude soluble antigen ofLeishmania donovani promastigotes recognized a determinant expressed on the surface membrane of mouse peritoneal macrophages and human monocyte derived macrophages infectedin vitro. The determinant was recognized on infected macrophage surface only when F (ab′)2 fragments of anti-leishmanial antiserum was employed in immunofluorescence. F(ab′)2 fragments of human patient sera also could recognize the determinant. The expression of this antigen was not stage-specific for the parasite. Immunochemical analyses revealed this antigen to be of 51 kDa protein. Specific leaching of membrane proteins by trypsin showed three bands of expressed antigens of 26, 11 and 10 kDa, which in all likelihood might be arising from the 51 kDa antigen. The antigen was not expressed until 12 h of post infection, reached a maximum level at 24 h and thereafter attained a steady state level as studied upto 96 h of post infection. This typc of antigen might have a great potential in immunodiagnostics and site-specific drug targeting.

RESPONSE TO THE LETTER TO THE EDITOR BY DRS. N. PICARD AND P. MARQUET REGARDING A PUBLICATION: BASU ET AL., DRUG METABOLISM AND DISPOSITION (32:768–773, (2004)

What is the value of studying mycophenolic acid (MPA) glucuronidation in the esophagus? Whereas the authors would consider the esophagus not worthy of study viz. MPA bioavailability, our stated aim was to carry out in vitro characterization of the primary metabolizers of mycophenolic acid among