Thrombin preconditioning attenuates iron-induced neuronal death.

Pretreatment with a low dose of thrombin attenuated brain injury after intracerebral hemorrhage (ICH) or cerebral ischemia. This phenomenon has been called thrombin preconditioning (TPC). The current study investigated whether or not TPC reduces neuronal death induced by iron in cultured neurons. The roles of protease-activated receptors (PARs) and the p44/42 mitogen-activated protein kinase (p44/42MAPK)/70-kDa ribosomal protein S6 kinase (p70S6K) signal transduction pathway in TPC were also examined. This study had three parts: (1) primary cultured neurons were pretreated with vehicle, thrombin or PAR agonists. Cell death was induced by ferrous iron (500 μM) 24 h later. After 48 h, culture medium was collected for lactate dehydrogenase measurement; (2) neurons were treated with vehicle, thrombin or thrombin plus PPACK (D-Phe-Pro-Arg chloromethylketone) thrombin and were collected for Western blotting; (3) the effect PD098059 on TPC was examined. Cells were treated with 20 μM PD098059 or vehicle 1 h before TPC. Neuron viability was measured 24 h following exposure to ferrous iron. Preconditioning with thrombin or PAR agonists reduced iron-induced neuronal death (p<0.05). Thrombin, but not PPACK thrombin, upregulated the protein levels of activated p44/42 MAPK and p70 S6K (p<0.05) in neurons. PD098059 also abolished the TPC-induced neuronal protection against iron (p<0.05). In conclusion, the protective effect of thrombin preconditioning is partially achieved through activating PARs and the p44/42 MAPK/p70S6K signal transduction pathway.