Secreted phospholipase A2-IIA modulates key regulators of proliferation on astrocytoma cells.
Human group IIA secreted phospholipase A(2) (sPLA(2)-IIA) has been characterized in numerous inflammatory and neoplastic conditions. sPLA(2)-IIA can either promote or inhibit cell growth depending on the cellular type and the specific injury. We have previously demonstrated that exogenous sPLA(2)-IIA, by engagement to a membrane structure, induces proliferation and activation of mitogen-activated protein kinases cascade in human astrocytoma cells. In this study, we used human astrocytoma 1321N1 cells to investigate the key molecules mediating sPLA(2)-IIA-induced cell proliferation. We found that sPLA(2)-IIA promoted reactive oxygen species (ROS) accumulation, which was abrogated in the presence of allopurinol and DPI, but not by rotenone, discarding mitochondria as a ROS source. In addition, sPLA(2)-IIA triggered Ras and Raf-1 activation, with kinetics that paralleled ERK phosphorylation, and co-immunoprecipitation assays indicated an association between Ras, Raf-1 and ERK. Additionally, Akt, p70 ribosomal protein S6 kinase, and S6 ribosomal protein were also phosphorylated upon sPLA(2)-IIA treatment, effect that was abrogated by N-acetylcysteine or LY294002 treatment indicating that ROS and phosphatidylinositol 3 kinase are upstream signaling regulators. As the inhibitors N-acetylcysteine, PD98059, LY294002 or rapamycin blocked sPLA(2)-IIA-induced proliferation without activation of the apoptotic program, we suggest that inhibition of these intracellular signal transduction elements may represent a mechanism of growth arrest. Our results reveal new potential targets for therapeutic intervention in neuroinflammatory disorders and brain cancer in particular.
Martín
Rubén
R
Instituto de Biología y Genética Molecular, CSIC-Universidad de Valladolid, Valladolid, Spain.
Hernández
Marita
M
Ibeas
Elvira
E
Fuentes
Lucia
L
Salicio
Veronica
V
Arnés
Mercedes
M
Nieto
María Luisa
ML
D001254:Astrocytoma / Q000473:pathology*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D045604:Extracellular Fluid / Q000187:drug effects / Q000378:metabolism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000235:genetics / Q000378:metabolism; D054501:Group II Phospholipases A2 / Q000494:pharmacology*; D006801:Humans; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D051058:Oncogene Protein v-akt / Q000235:genetics / Q000378:metabolism; D019908:Proto-Oncogene Proteins c-raf / Q000235:genetics / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013997:Time Factors; D014162:Transfection / Q000379:methods
D004791:Enzyme Inhibitors; D017382:Reactive Oxygen Species; D051058:Oncogene Protein v-akt; D019908:Proto-Oncogene Proteins c-raf; D048049:Extracellular Signal-Regulated MAP Kinases; D054501:Group II Phospholipases A2