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Cytokine and Estrogen Stimulation of Endothelial Cells Augments Activation of the Surface-Bound Prekallikrein-High Molecular Weight Kininogen Complex: Implications for Hereditary Angioedema (HAE)
Monday, March 7, 2016
South Exhibit Hall H (Convention Center)
Kusumam Joseph, PhD, Baby G Tholanikunnel, PhD, Allen P. Kaplan, MD FAAAAI
Background: When the prekallikrein-high molecular weight kininogen complex (PK-HK) is bound to endothelial cells, prekallikrein is stoichiometrically converted to kallikrein due to release of heat shock protein-90 (Hsp90).

Rationale: Since attacks of hereditary angioedema can be related to infection or to estrogen we questioned whether estrogen or cytokine stimulation of endothelial cells could augment release of Hsp90 and prekallikrein activation. We also tested release of profibrinolytic enzymes, urokinase (UK) and tissue plasminogen activator (TPA).

Methods: Cells were stimulated with agonists and Hsp90, UK, and TPA were measured in the culture supernatants by ELISA. Activation of the PK-HK complex was measured employing pro-phe-arg-p-nitroanilide reflecting kallikrein formation.

Results: Hsp90 release was stimulated with optimal doses of estradiol, IL-1, and TNFa (10ng/ml) from 15 min to 120 min. TPA release was not augmented by any of the agonists tested but UK was released by IL-1, TNFa and thrombin (positive control) but not estrogen. Augmented activation of PK-HK was seen with each agonist that releases Hsp90. Addition of 0.1 molar factor XII relative to PK-HK leads to rapid formation of kallikrein; factor XII alone does not autoactivate.

Conclusions: Interleukin-1, TNFa, and estrogen stimulate release of Hsp90 and augment activation of the PK-HK complex. IL-1 and TNFa stimulate release of urokinase which can augment fibrinolysis.

Clinical Implication: Attacks of angioedema in patients with HAE may be initiated by use of estrogen or infection. Cytokine or estrogen stimulation of endothelial cells and activation of the PK-HK complex may contribute to this process.