Ochratoxin A mediates MAPK activation, modulates IL-2 and TNF-alpha mRNA expression and induces apoptosis by mitochondria-dependent and mitochondria-independent pathways in human H9 T cells

摘要

Ochratoxin A (OTA) is a natural fungal secondary metabolite that contaminates food and animal feed. Human exposure and involvement of this mycotoxin in several pathologies have been demonstrated worldwide. We investigated OTA immunotoxicity on H9 cells, a human cutaneous CD4+ T lymphoma cell line. Cells were treated with 0, 1, 5, 10, and 20 mu M OTA for up to 24 hr. Western blotting revealed increased phosphorylation of all three major mitogen-activated protein kinases (extracellular signal-regulated kinase, c-Jun amino-terminal kinase, p38). OTA triggered mitochondrial transmembrane potential loss and caspase-3 activation. The 24-hr OTA treatment caused marked changes in cell morphology and DNA fragmentation, suggesting the occurrence of apoptotic events that involved a mitochondria dependent pathway. Moreover, OTA triggered significant modulation of survivin, interleukin 2 (IL-2) and tumor necrosis factor alpha (TNF-alpha): mRNA expression of survivin and IL-2 were decreased, while TNF-alpha was increased. OTA also caused caspase-8 activation in a time-dependent manner, which evokes the death receptor pathway activation; we suspect that this occurred via the autocrine pro-apoptotic effect of TNF-alpha on H9 cells.