Malarial pigment haemozoin, IFN-gamma, TNF-alpha, IL-1beta and LPS do not stimulate expression of inducible nitric oxide synthase and production of nitric oxide in immuno-purified human monocytes

Abstract

Background: Enhanced production of nitric oxide (NO) following upmodulation of the inducible isoform of NO synthase (iNOS) by haemozoin (HZ), inflammatory cytokines and LPS may provide protection against Plasmodium falciparum malaria by killing hepatic and blood forms of parasites and inhibiting the cytoadherence of parasitized erythrocytes (RBC) to endothelial cells. Monocytes and macrophages are considered to contribute importantly to protective upregulation of iNOS and production of NO. Data obtained with murine phagocytes fed with human HZ and synthetic HZ (sHZ) indicate that supplemental treatment of those cells with IFN-gamma elicited significant increases in protein and mRNA expression of iNOS and NO production, providing a potential mechanism linking HZ phagocytosis and increased production of NO. Purpose of this study was to analyse the effect of P. falciparum HZ and sHZ supplemental to treatment with IFN-gamma and/or a stimulatory cytokine-LPS mix on iNOS protein and mRNA expression in immuno-purified human monocytes.

Hemozoin Regulates iNOS Expression by Modulating the Transcription Factor NF-kB in Macrophages

“…This result shows that the phagocytosis of the Hz by macrophages alters the immune-modulatory effects, which affects the iNOS production. A similar observation, indicating enhanced iNOS expression when macrophages (RAW 264.7 cells) were fed with Hz and treated with IFNγ has been reported [14]. We further checked, if the pretreatment with Hz and subsequent challenge with IFNγ or LPS or IL4 had any morphological effects on macrophages.…”

“…Hemozoin had no effect on expression of iNOS, compared to LPS alone, which was used as positive control (Supplementary Figure 1). Other researchers have used Hz isolated from parasitized RBCs and synthetic Hz and observed differing results [8,14,20,21]. The stimulation with different sources of Hz have reported to induce differential gene expression in macrophages [8,14,20,22].…”

“…Hemozoin is reported to modulate the immune functions of immune cells such as macrophages and dendritic cells. Some reports suggest Hz as an inert, bystander; other suggests contradictory findings as immune-activating or suppressive effects [11–14]. Macrophages are also one of important components of the immune system being involved in both the innate and adaptive immune responses.…”

Malarial hemozoin: From target to tool

“…Crude hemozoin, loaded in vitro to murine macrophages, and to macrophages isolated from malaria infected murine livers, is not capable of generating radicals by itself but it can do so in the presence of a lipid component, specifically unsaturated fatty acids; lipid removal totally abolishes radical production [73]. A lack of activation of nitric oxidase synthase (NOS) in human monocytes when challenged with HZ, in contrast with the upregulation found in murine macrophages, has been reported [93]. This observation was contrary to findings suggesting that inducible NOS (iNOS) upregulation does take place in humans and could even confer protection against malaria [94, 95].…”

Tissular model/sensor seamless system for qualified analysis and its characterization

“…The blots were incubated with the first antibody (eNOS, mAChR, vWF, -Actin and GAPDH antibody) at a dilution of 1:250 for 1 h at room temperature, extensively washed, and incubated with the second antibody (horseradish peroxidase-conjugated antimouse immunoglobulin antibody) at a dilution of 1:500 for one more hour. The proteins were visualized on a Duo Lux (Pierce) [21][22][23].…”