Mitochondrial aldehyde dehydrogenase-2 activation prevents β-amyloid-induced endothelial cell dysfunction and restores angiogenesis

Amyloid beta peptides (A beta(1-40) and A beta(1-42)) cause cerebral degeneration by impairing the activity of angiogenic factors and inducing apoptosis and senescence in the endothelium. Amyloid peptides are known to induce oxidative stress. Impairment of mitochondrial aldehyde dehydrogenase 2 (ALDH2) following oxidative stress, results in accumulation of toxic aldehydes, particularly 4-hydroxynoneal (4-HNE). We sought to determine the role of mitochondrial ALDH2 in A beta-related impairment of angiogenesis. We hypothesized that by increasing the detoxification activity of ALDH2 we would reduce A beta-driven endothelial injuries and restore angiogenesis. We used a selective ALDH2 activator, Alda-1, assessing its ability to repair mitochondrial dysfunction in the endothelium. Treatment of human endothelial cells with A beta(1-40) (5-50 mu M) induced loss of mitochondrial membrane potential, increased cytochrome c release and ROS accumulation. These events were associated with 4-HNE accumulation and decrease in ALDH2 activity (40%), and resulted in disassembly of endothelial junctions, as evidenced by beta-catenin phosphorylation, disorganization of adherens and tight junctions, and by disruption of pseudocapillary formation. Alda-1 (10-40 mu M) abolished A beta-induced 4-HNE accumulation, apoptosis and vascular leakiness, fully restoring the pro-angiogenic endothelial phenotype and responses to FGF-2. Our data document that mitochondrial ALDH2 in the endothelium is a target for the vascular effect of A beta, including loss of barrier function and angiogenesis. ALDH2 activation, by restoring mitochondrial functions in the endothelium, prevents A beta-induced dysfunction and anti-angiogenic effects. Thus, agents activating ALDH2 may reduce endothelial injuries including those occurring in cerebral amyloid angiopathy, preserving the angiogenic potential of the endothelium.