Downloaded from www.microbiologyresearch.org by IP: 54.237.57.119 On: Fri, 15 Apr 2016 02:39:03 HOST RESPONSE TO INFECTION NADH-oxidase, NADPH-oxidase and myeloperoxidase activity of visceral leishmaniasis patients PROMOD KUMAR, KALPANA PAI  , HAUSHILA P. PANDEY and SHYAM SUNDAR  Department of Biochemistry, Faculty of Science, Banaras Hindu University and  Department of Medicine, Institute of Medical Sciences, Institute of Medical Sciences, Banaras Hindu University, Varanasi- 221005, India It is believed that the enhanced capability of activated macrophages to resist infection is related to the remarkable increase in the production of oxygen metabolites in response to phagocytosis. Both the production of H 2 O 2 and the oxidation of NAD(P)H are directly dependent upon NAD(P)H-oxidase. It has been established that the respiratory burst is due to activation of NAD(P)H-oxidase localised in the plasmalemma. Myeloperoxidase is believed to be involved in augmenting the cytotoxic activity of H 2 O 2 . Low NADH- oxidase, NADPH-oxidase and myeloperoxidase activity were observed in monocytes of patients with active visceral leishmaniasis as compared with healthy controls. These results suggest that low NADH-oxidase, NADPH-oxidase and myeloperoxidase activities may account for persistence of Leishmania parasites in visceral leishmaniasis. Introduction Visceral leishmaniasis (VL) or kala-azar is caused by Leishmania donovani, an obligate intracellular proto- zoan that parasitises tissue macrophages. Intramacroph- age infection by L. donovani results in potentially fatal visceral infections in man and the elimination of Leishmania parasites by the macrophage depends upon the mounting of an effective cell-mediated immune response by the mammalian host [1]. The diseases caused by all species of the Leishmania genus are determined by the fact that these parasites multiply and survive in the microbicidal environment of mononuclear phagocytes [2]. This survival has to be seen in the context that promastigotes of Leishmania are destroyed in vitro by the metabolites of the oxidative burst, hydrogen peroxide (H 2 O 2 ) and super- oxide anion (O 2  ) [3] with H 2 O 2 being more effective than O 2  . The respiratory burst is due to increased activation of NAD(P)H-oxidase localised in the plas- malemma [4]. The generation of reactive oxidative species (ROIs) is associated with production of certain oxygen metabolites, which is linked to induction of cellular damage, microbicidal activity and the regula- tion of the activity of natural killer cells, polymorpho- nuclear leucocytes (PMNLs) and monocytes [5]. The conversion of oxygen to microbicidal product is mediated by a plasma membrane-associated enzymes or enzyme system. Myeloperoxidase (MPO; H 2 O 2 oxidoreductase) is an enzyme found in the azurophilic granules of mammal- ian neutrophils and also identified in human mono- cytes. PMNLs employ a system comprised of MPO, H 2 O 2 and oxidisable halide co-factor to kill a variety of micro-organisms [6]. MPO is believed to be involved in augmenting the cytotoxic activity of H 2 O 2 and O 2  . Klebenoff [6] has demonstrated that, during endocy- tosis, MPO is released into the phagosomes as a result of fusion of the phagosome membrane with the azurophil granules. Extracellular release of granule components occurs upon contact of the PMNLs with a large membrane or membrane-like surface. Therefore, NADH-oxidase, NADPH-oxidase and MPO activity were examined in monocytes from patients with active VL. Materials and methods Reagents All reagents were prepared in quartz distilled water. Ficoll-Hypaque (Lymphoprep) was obtained from Nycomed Pharma, Norway. RPMI 1640, Hanks’s Received 6 Feb. 2001; revised version accepted 23 May 2002. Corresponding author: Professor S. Sundar (e-mail: shyam_vns@satyam.net.in). J. Med. Microbiol. — Vol. 51 (2002), 832–836 # 2002 Society for General Microbiology ISSN 0022-2615