Studies of Molecular and Cellular Underlying Mechanisms of Ferrous Citrate-Induced Cerebral Vasospasm and Brain Injury

Cerebral vasospasm and brain liquefaction are two major complications in patients suffering from aneurysmal subarachnoid hemorrhage (SAH). Our previous in vivo studies have demonstrated that continuous administration of the male rat with 17 -estradiol (E2) at a physiological level prevents SAH-induced cerebral vasospasm through inhibiting iNOS gene expression (Shih et al., Stroke 2006) and reduces the ferrous citrate (FC)-induced brain injury through thioredoxin (Trx) induction (Chen et al., Stroke 2009). While our in vivo studies suggested that E2 inhibits the SAH-induced an increase of iNOS by increasing the association of p65/ER, which in turn inhibits the binding of p65 to the iNOS DNA, the mechanisms underlying E2-induced Trx induction was not studied. Our data suggest the protection effect of E2 on SAH-induced vasospasm as well as brain injury and the potential applications of E2 in the treatment of SAH patient. These findings together with epidemiological data also suggest the sex difference in the response to SAH. In fact, our preliminary studies have found a significant difference in gene expression patterns of the basilar artery between male and female after SAH and in the induction on survival proteins (i.e., Trx) by intra-cerebral injection with ferrous citrate. Although the pathogenesis of SAH-induced cerebral vasospasm and brain injury is not fully understood, one theory holds that SAH-induced cerebral vasospasm and brain injury are the responses of the vascular wall and neuronal tissues to iron. Accordingly, we will use the FC-treated cerebral endothelial cells and neuronal cells as the cell models to address the issues of molecular mechanisms of hormonal effects on SAH-induced cerebral vasospasm and brain injury. Because our previous study has suggested that E2 protects the SAH-induced vasospasm by decreasing iNOS expression through inhibition of the binding of p65 to iNOS DNA, we have constructed the iNOS promoter and have been studying how FC and E2 affects the iNOS promoter activity in our initial study. We also plan to construct the Trx promoter for studying the regulation of Trx expression by estrogen. In this proposed studies, we will also examine the possible involvement of endothelin-1 and oxidative damage in the FC-induced cerebral vasospasm and brain injury. The outcome of this proposed study will help us getting insight the molecular mechanisms underlying SAH-induced vasospasm and brain injury and the E2-mediated protection against these injuries.