%0 Journal Article %A Nandi, Nilay %A Sen, Abhik %A Banerjee, Rajdeep %A Kumar, Sudeep %A Kumar, Vikash %A Ghosh, Amar Nath %A Das, Pradeep %T Hydrogen peroxide induces apoptosis-like death in Entamoeba histolytica trophozoites %D 2010 %J Microbiology, %V 156 %N 7 %P 1926-1941 %@ 1465-2080 %R https://doi.org/10.1099/mic.0.034066-0 %K MDA, malondialdehyde %K E-64d, (2S,3S)-trans-epoxysuccinyl-l-leucylamido-3-methylbutane ethyl ester %K PI, propidium iodide %K TG, thapsigargin %K H2DCFDA, 2′,7′-dichlorodihydrofluorescein diacetate %K MTT, 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyltetrazolium bromide %K PCD, programmed cell death %K SOD, superoxide dismutase %K BCECF, 2,7-bis(2-carboxyethyl)-5-(and 6)-carboxyfluorescein %K PS, phosphatidylserine %K [Ca2+]i, intracellular calcium %K AMC, 7-amino-4-methylcoumarin, BAPTA/AM, 1,2-bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid tetrakis(acetoxymethyl ester) %K Fe-SOD, iron-containing superoxide dismutase %K eh29, thiol-dependent peroxidase %K ROS, reactive oxygen species %I Microbiology Society, %X Programmed cell death (PCD) is an essential process in the growth and development of multicellular organisms. However, accumulating evidence indicates that unicellular eukaryotes can also undergo PCD with apoptosis-like features. This study demonstrates that after exposure to 0.8 mM H2O2 for 9 h Entamoeba histolytica presents morphological and biochemical evidence of apoptosis-like death. Morphological characteristics of apoptosis-like death including DNA fragmentation, increased vacuolization, nuclear condensation and cell rounding were observed for H2O2-exposed trophozoites with preservation of membrane integrity. Biochemical alteration in ion fluxes is also a key feature in PCD, and H2O2-exposed trophozoites showed overproduction of reactive oxygen species, increased cytosolic Ca2+ and decreased intracellular pH. Phosphatidylserine was also found to be expressed in the outer leaflet of the plasma membrane of the H2O2-treated trophozoites. Pretreatment with the cysteine protease inhibitor E-64d, the extracellular and intracellular Ca2+ chelators EGTA and BAPTA/AM, and the Ca2+ influx inhibitor verapamil prior to H2O2 exposure abolished DNA fragmentation. The oxidatively stressed trophozoites also showed an increased calpain activity, indicating involvement of Ca2+-dependent calpain-like cysteine proteases in PCD of E. histolytica. A homogeneous caspase assay showed no significant caspase activity, and administration of caspase 1 inhibitor also did not prevent the death phenotype for the oxidatively stressed trophozoites, indicating a caspase-independent apoptosis-like death. Our observations clearly demonstrate that there is a distinct calpain-dependent but caspase-independent pathway for apoptosis-like death in oxidatively stressed E. histolytica trophozoites. %U https://www.microbiologyresearch.org/content/journal/micro/10.1099/mic.0.034066-0