PKCε-CREB-Nrf2 signalling induces HO-1 in the vascular endothelium and enhances resistance to inflammation and apoptosis.

Aims Vascular injury leading to endothelial dysfunction is a characteristic feature of chronic renal disease, diabetes mellitus, and systemic inflammatory conditions, and predisposes to apoptosis and atherogenesis. Thus, endothelial dysfunction represents a potential therapeutic target for atherosclerosis prevention. The observation that activity of either protein kinase C epsilon (PKCe) or haem oxygenase-1 (HO-1) enhances endothelial cell (EC) resistance to inflammation and apoptosis led us to test the hypothesis that HO-1 is a downstream target of PKCe. Methods and results Expression of constitutively active PKCe in human EC significantly increased HO-1 mRNA and protein, whereas conversely aortas or cardiac EC from PKCe-deficient mice exhibited reduced HO-1 when compared with wild-type littermates. Angiotensin II activated PKCe and induced HO-1 via a PKCe-dependent pathway. PKCe activation significantly attenuated TNFα-induced intercellular adhesion molecule-1, and increased resistance to serum starvation-induced apoptosis. These responses were reversed by the HO antagonist zinc protoporphyrin IX. Phosphokinase antibody array analysis identified CREB1(Ser133) phosphorylation as a PKCe signalling intermediary, and cAMP response element-binding protein 1 (CREB1) siRNA abrogated PKCe-induced HO-1 up-regulation. Likewise, nuclear factor (erythroid-derived 2)-like 2 (Nrf2) was identified as a PKCe target using nuclear translocation and DNA-binding assays, and Nrf2 siRNA prevented PKCe-mediated HO-1 induction. Moreover, depletion of CREB1 inhibited PKCe-induced Nrf2 DNA binding, suggestive of transcriptional co-operation between CREB1 and Nrf2. Conclusions PKCe activity in the vascular endothelium regulates HO-1 via a pathway requiring CREB1 and Nrf2. Given the potent protective actions of HO-1, we propose that this mechanism is an important contributor to the emerging role of PKCe in the maintenance of endothelial homeostasis and resistance to injury.