title: Entamoeba histolytica depresses chemiluminescence in stimulated human polymorphonuclear leukocytes.
abstract: Effect of Entamoeba histolytica proteinase/toxin (Ehp/t) on the luminol-dependent chemiluminescence (CL) in stimulated human polymorphonuclear leukocytes (PMN) was studied. The role of superoxide (SO) and hydroxyl (OH) anions in the Ehp/t-associated enhancement/inhibition of CL was also studied using specific scavengers and a biological response modifier, muramyldipeptide (MDP). Ehp/t was isolated from axenic trophozoites of the HM-1:IMSS strain of virulent strain of E. histolytica. Proteinase activity was assayed on a synthetic substrate, Z-arg-arg-AFC and cytotoxicity was tested on HeLa cell monolayers. PMN isolated from blood were incubated with Ehp/t prior to stimulation by phorbol myristateacetate (PMA, 2 micrograms/ml), serum-treated zymosan (2.5 mg/ml) and glucan (2 mg/ml). CL was monitored in an LKB (Wallac) Luminometer. Ehp/t was found to depress up to 90% of CL induced by PMA, glucan and zymosan. Such a depression was Ehp/t concentration-dependent. A 150 micrograms/ml concentration of Ehp/t, obtained from a 0.015-1.5 mg/ml concentration range tested at different incubation times and temperatures, was used in most of our experiments. Incubation time and temperature optima were 15 min and 37 degrees C, respectively. Ehp/t partially inhibited the CL associated with SO and OH. MDP, in the presence of Ehp/t, enhanced CL response in human PMN to about 67% with reference to normal CL without inhibitor. PMN were confirmed to play a vital role in amebic tissue invasion mechanisms.
authors.affiliation: Department of Medicine, College of Medicine, King Saud University, Riyadh, Saudi Arabia.
authors.forename: I A
authors.initials: IA
authors.lastname: Al-Mofleh
authors.forename: A S
authors.initials: AS
authors.lastname: Al-Tuwaijri
authors.forename: A A
authors.initials: AA
authors.lastname: Mahmoud
authors.forename: M
authors.initials: M
authors.lastname: Alam
mesh_terms: D000119:Acetylmuramyl-Alanyl-Isoglutamine / Q000494:pharmacology; D000818:Animals; D002374:Catalase / Q000494:pharmacology; D004748:Entamoeba histolytica / Q000201:enzymology / Q000472:pathogenicity*; D005609:Free Radicals; D006801:Humans; D008163:Luminescent Measurements; D008165:Luminol; D009504:Neutrophils / Q000378:metabolism / Q000469:parasitology*; D010100:Oxygen / Q000032:analysis; D010447:Peptide Hydrolases / Q000494:pharmacology*; D013482:Superoxide Dismutase / Q000494:pharmacology; D014118:Toxins, Biological / Q000494:pharmacology*
chemical_list: D005609:Free Radicals; D014118:Toxins, Biological; D000119:Acetylmuramyl-Alanyl-Isoglutamine; D008165:Luminol; D002374:Catalase; D013482:Superoxide Dismutase; D010447:Peptide Hydrolases; D010100:Oxygen