Up-regulation of brain ceruloplasmin in thrombin preconditioning

Pretreatment with low-dose thrombin attenuates brain edema induced by iron or intracerebral hemorrhage (ICH). Ceruloplasmin is involved in iron metabolism by oxidizing ferrous iron to ferric iron. The present study examines whether thrombin modulates brain ceruloplasmin levels and whether exogenous ceruloplasmin reduces brain edema induced by ferrous iron in vivo. In the first set of experiments, rats received intracerebral infusion of saline or 1 U thrombin into the right basal ganglia. Rats were killed 1, 3, or 7 days later for Western blot analysis and RT-PCR analysis. In the second set of experiments, rats received either ferric iron, ferrous iron, or ferrous iron plus ceruloplasmin, then were killed 24 hours later for brain edema measurement. We found that ceruloplasmin protein levels in the ipsilateral basal ganglia increased on the first day after thrombin stimulation and peaked at day 3. Brain ceruloplasmin levels were higher after thrombin infusion than after saline injection. RT-PCR showed that brain ceruloplasmin mRNA levels were also up-regulated after thrombin injection (p < 0.05). We also found ipsilateral brain edema after intracerebral infusion of ferrous iron but not ferric iron at 24 hours. Co-injection of ferrous iron with ceruloplasmin reduced ferrous iron-induced brain edema (p < 0.05). Our results demonstrate that thrombin increases brain ceruloplasmin levels and exogenous ceruloplasmin reduces ferrous iron-induced brain edema, suggesting that ceruloplasmin up-regulation may contribute to thrombin-induced brain tolerance to ICH by limiting the injury caused by ferrous iron released from the hematoma.