Activation of Endothelial Cells to Release Hsp90, an Activator of the Prekallikrein-High Molecular Weight Kininogen (HK) Complex

We have previously demonstrated that Hsp90 release by activated endothelial cells leads to conversion of prekallikrein to kallikrein if prekallikrein is bound to HK. Kallikrein formation is therefore stoichiometric and occurs in the absence of factor XII. Since kallikrein activates factor XII, we theorized that endothelial cell activation might first generate kallikrein which then recruits factor XII. We now demonstrate that estrogen, interleukin 1, and to a lesser degree TNFa can activate endothelial cells to release Hsp90. The dose range tested for each in ng/ml was 0, 0.5, 1.0, 5.0, and 10.0. A dose-response for estrogen or IL-1 was maximal at the 10 ng/ml dose while TNFa was best between 0.1 and 5 ng/ml. A time course for each up to 4 hrs incubation revealed maximal Hsp90 secretion between 30 and 60 min with a significant increase noted by 15 min for each. Our observations are particularly relevant for types I and II HAE (C1 inhibitor deficiency) where estrogen and inflammation are known triggers of angioedema events and for HAE with normal C1 inhibitor (HAE-N) where estrogen exposure is a key precipitant. For the latter, studies of endothelial cell release of urokinase and tissue plasminogen activator are in progress given recent observations regarding inhibitors of fibrinolysis.