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Naja nigricollis CMS‐9 enhances the mitochondria‐mediated death pathway in adaphostin‐treated human leukaemia U937 cells
Author(s) -
Chen YingJung,
Wang JehJeng,
Chang LongSen
Publication year - 2011
Publication title -
clinical and experimental pharmacology and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 103
eISSN - 1440-1681
pISSN - 0305-1870
DOI - 10.1111/j.1440-1681.2011.05585.x
Subject(s) - protein kinase b , mapk/erk pathway , microbiology and biotechnology , p38 mitogen activated protein kinases , viability assay , pi3k/akt/mtor pathway , mitochondrial ros , kinase , protein kinase a , u937 cell , apoptosis , programmed cell death , chemistry , biology , reactive oxygen species , signal transduction , biochemistry
Summary 1. The aim of the present study was to explore the effect of the Naja nigricollis phospholipase A 2 CMS‐9 on adaphostin‐induced death of human leukaemia U937 cells. 2. Leukaemia U937 cells (Bcr/Abl‐negative cells) were treated with adaphostin (0–10 μmol/L) and CMS‐9 (0–1 μmol/L). The effects of CMS‐9, adaphostin and their combination on cell viability, the generation reactive oxygen species (ROS), [Ca 2+ ] i , p38 mitogen‐activated protein kinase (MAPK) activation, Akt and extracellular signal‐regulated kinase (ERK) inactivation, mitochondrial membrane potential (ΔΨ m ) and Bcl‐2 family proteins were analysed. 3. Both adaphostin and CMS‐9 induced U937 cell apoptosis, characterized by dissipation of ΔΨ m and ROS generation. Combined treatment further increased ΔΨ m loss and reduced the viability of adaphostin‐treated cells. Unlike in CMS‐9‐treated cells, in adaphostin‐treated cells ROS‐induced increases in [Ca 2+ ] i were observed. CMS‐9‐induced ROS generation resulted in p38 MAPK activation, whereas adaphostin treatment elicited ROS/Ca 2+ ‐mediated inactivation of Akt and ERK. Moreover, Akt was found to be involved in ERK phosphorylation. Suppression of p38 MAPK activation blocked CMS‐9‐induced ΔΨ m loss and Bcl‐xL downregulation. Overexpression of constitutively active Akt and mitogen‐activated protein kinase kinase (MEK) 1 rescued adaphostin‐induced ΔΨ m loss and Bcl‐2 downregulation. Similarly, CMS‐9 augmented adaphostin toxicity in human leukaemia K562 cells via increased mitochondrial alterations. 4. The results suggest that two distinct pathways mediate adaphostin‐ and CMS‐9‐induced mitochondrial damage (i.e. the ROS–Ca 2+ –Akt–ERK and ROS–p38 MAPK pathways, respectively). These distinct pathway explain the augmentation by CMS‐9 of ΔΨ m loss and apoptosis in adaphostin‐treated U937 cells.