Bryostatin-1 improves function in arteries with suppressed endothelial cell autophagy

We have previously reported that when autophagy is suppressed in endothelial cells (ECs), a glycolytic defect limits shear-stress -induced ATP production to an extent that purinergic 2Y1 receptor (P2Y1R)-mediated activation of EC nitric oxide (NO) synthase (eNOS) is compromised. Subsequently we demonstrated the functional relevance of this finding in arteries from mice with genetic, pharmacological, and age-associated EC autophagy impairment. Using gain and loss of function approaches in vitro, we further revealed that p-PKCδ^T505 serves as a signaling link between P2Y1R activation and NO generation. Here we sought to discern the functional relevance of this observation. First, shear-stress- induced activating phosphorylation of eNOS (p-eNOS^S1177) that is otherwise prevented by knockdown of autophagy-related gene 3 (Atg3) in ECs was restored by the PKC agonist bryostatin-1. Next, in murine models of genetic and age-associated EC autophagy compromise, depressed vasodilation displayed by femoral and cerebral arteries was reversed by bryostatin-1 in a manner that could be prevented by concurrent NO synthase inhibition. Finally, the bryostatin-1-mediated normalization of intraluminal flow-induced vasodilation observed in femoral arteries from both models of EC autophagy disruption was mitigated by inhibiting downstream targets of p-PKCδ^T505 i.e., p-PKD^S744/S748 and p-PKD^S916. These findings provide evidence that stimulating PKC/PKD has strategic potential to restore compromised endothelial function in pathologies associated with suppressed EC autophagy e.g., aging.