Isolation of a nitric oxide synthase from the protozoan parasite, Leishmania donovani

A soluble nitric oxide synthase (NOS) activity was purified 2800-fold from Leishmania donovani, the causative parasite of visceral leishmaniasis, by two-step affinity and anion-exchange chromatography. The purified enzyme ran as a prominent band of 110 kDa on SDS-PAGE whereas gel filtration experiments estimated the native molecular mass to be 230±20 kDa indicating that the native enzyme exists as a dimer. The enzyme activity required NADPH and was blocked by EGTA. The enzyme kinetics, cofactor requirements, inhibition studies and Western blot analysis with brain anti-NOS antibody suggest its similarity with mammalian NOS isoform I

HUMAN UDP-GLUCURONOSYLTRANSFERASES SHOW ATYPICAL METABOLISM OF MYCOPHENOLIC ACID AND INHIBITION BY CURCUMIN

ABSTRACT: Although the promising immunosuppressant, mycophenolic acid (MPA), has many desirable properties and is widely prescribed for organ transplant recipients, its high oral dosage requirement is not understood. Whereas previous Northern blot analysis by Basu and colleagues (2004) located the mRNAs encoding MPA primary metabolizers, UDP-glucuronosyltransferases (UGTs) 1A7, 1A8, 1A9, and 1A10, in human gastrointestinal (GI) tissues, in situ hybridization analysis of mRNAs found that the isozymes were restricted to the mucosal layer of various GI organs. Concomitantly, MPA was glucuronidated by microsomes isolated from normal adjoining specimens. Microsomal studies showed the highest relative rates of metabolism in esophagus, ileum, duodenum, colon, and stomach at pH 6.4; only esophagus showed high pH 7.6 activity. Properties of the recombinant UGTs indicate that MPA is metabolized with pH 6.4 or 7.6 optimum. Activity for 1A7 and 1A9 increased with increasing concentrations up to 2.4 mM, with parallel production of both ether-and acylglucuronides; similarly, 1A8 and 1A10 reached plateaus at 1.6 mM, producing both glucuronides. K m values were 250 to 550 M. Between 400 and 1600 M MPA, isozymes generated between 15 and 42% of the acylglucuronides. In effect, high K m values (MPA) are associated with high concentrations to achieve saturation kinetics. Finally, transient inhibition of UGTs in human LS180 colon cells and mouse duodenum by the dietary agent, curcumin, has implications for in vivo pretreatment to reduce MPA glucuronidation to increase the therapeutic index

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

Active targeting of doxorubicin to macrophages was studied by incorporating it in mannosecoated 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)–g was evaluated to act synergistically with mannosylated liposomal doxorubicin therapy. Combination chemotherapy with a suboptimal dose of IFNg 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-g, 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

Purification and characterization of an organ specific haemorrhagic toxin from <i>Vipera russelli russelli </i>(Russell's viper) venom

114-120A haemorrhagic toxin (VRR-12) from Vipera russelli russelli (Russell's viper) venom has been purified by ionexchange chromatography on CM-Sephadex C-50 followed by size-exclusion HPLC to electrophoretically homogeneous state. It is a 12 kDa single polypeptide having 1 mole of  Zn+2 ion. This toxin induces intense intestinal haemorrhage and to a lesser extent skeletal muscle haemorrhage in mice. It does not show detectable proteolytic and esterolytic activity with selected substrates under specified conditions, haemolytic and phospholipase activity. When VRR-12, preincubated with bivalent anti serum against Saw-scaled and Russell's viper venom or EDTA was injected, haemorrhagic activity was not reduced, on the otherhand preincubation with phenylmethyl sulphonyl fluoride reduced the activity markedly. Biodistribution studies with 1251 VRR- 12 show that haemorrhagic manifestation by this toxin is not a direct function of the fraction of the totally administered toxin distributed to that tissue

A Crystalline Compound (BM-ANF1) from the Indian Toad (Bufo melanostictus, Schneider) Skin Extract, Induced Antiproliferation and Apoptosis in Leukemic and Hepatoma Cell Line Involving Cell Cycle Proteins.

In our earlier communication, it was reported that Indian toad (Bufo melanostictus) skin extract (TSE) possesses antiproliferative and apoptogenic activity in U937 and K562 cells [Giri et al., 2006. Antiproliferative, cytotoxic and apoptogenic activity of Indian toad (Bufo melanostictus, Schneider) skin extract in U937 and K562 cells. Toxicon 48 (4), 388–400]. In the present study, a compound (BM-ANF1) has been isolated from the TSE by alumina gel column chromatography, crystallized and evaluated for its antiproliferative and apoptogenic activity in U937, K562 and HepG2 cells. BM-ANF1 produced dose-dependent inhibition of U937, K562 and HepG2 cell growth. The antiproliferative activity was reflected by the MTT assay and demonstrated by the reduced expression of proliferative cell nuclear antigen (PCNA). Flow-cytometric analysis showed that BM-ANF1 arrested the cell cycle at G1 phase and enhanced annexin-V binding in U937 and K562 cells. Scanning electron microscopic and fluorescent microscopic analysis of U937 and K562 cells revealed the apoptogenic nature of the compound. Alkaline comet assay showed that BM-ANF1 produced DNA fragmentation. The dose-dependent expression of caspase 3 indicated that the apoptogenic properties of BM-ANF1 were mediated through the activation of downstream effector nucleases in the cancer cells. The increased expression of p53 and moderate expression of p21Cip1/p27Kip1 due to BM-ANF1 treatment in HepG2 cells supported that the apoptogenic activity of BM-ANF1 was mediated through p53 tumor-suppressor gene expression followed by the expression of p21Cip1 and p2

Targeting of Parasite-Specific Immunoliposome-Encapsulated Doxorubicin in the Treatmentof Experimental Visceral Leishmaniasis

A parasite-specific 51-kDa protein has been isolated from the membrane of macrophages infected with Leishmania donovani, the causative agent of visceral leishmaniasis. Active targeting of doxorubicin to infected macrophages was studied by incorporating it in immunoliposomes prepared by grafting F(ab)�2 of anti–51-kDa antibody onto the liposomal surface. In a 45-day mouse model of visceral leishmaniasis, complete elimination of spleen parasite burden was achieved by doxorubicin incorporated in immunoliposome (immunodoxosome) at a dose of 250 mg/kg/day that was given for 4 consecutive days. A similar dose of free and liposomal drug (doxosome) had 45% and 84% parasite suppressive effects, respectively. Immunodoxosome and doxosome were generally less toxic than the free drug, as determined by several clinical parameters of cardiotoxicity and liver toxicity. These results not only indicate the potential of doxorubicin as an effective chemotherapeutic agent but also establish the use of immunoliposomes as drug carrier in the therapy of leishmaniasis

Targeting of Parasite-Specific Immunoliposome- Encapsulated Doxorubicin in the Treatment of Experimental Visceral Leishmaniasis

A parasite-specific 51-kDa protein has been isolated from the membrane of macrophages infected with Leishmania donovani, the causative agent of visceral leishmaniasis. Active targeting of doxorubicin to infected macrophages was studied by incorporating it in immunoliposomes prepared by grafting F(ab)�2 of anti–51- kDa antibody onto the liposomal surface. In a 45-day mouse model of visceral leishmaniasis, complete elimination of spleen parasite burden was achieved by doxorubicin incorporated in immunoliposome (immunodoxosome) at a dose of 250 mg/kg/day that was given for 4 consecutive days. A similar dose of free and liposomal drug (doxosome) had 45% and 84% parasite suppressive effects, respectively. Immunodoxosome and doxosome were generally less toxic than the free drug, as determined by several clinical parameters of cardiotoxicity and liver toxicity. These results not only indicate the potential of doxorubicin as an effective chemotherapeutic agent but also establish the use of immunoliposomes as drug carrier in the therapy of leishmaniasis