Disturbed Flow Induces Autophagy, but Impairs Autophagic Flux to Perturb Mitochondrial Homeostasis.

Temporal and spatial variations in shear stress are intimately linked with vascular metabolic effects. Autophagy is tightly regulated in intracellular bulk degradation/recycling system for maintaining cellular homeostasis. We postulated that disturbed flow modulates autophagy with an implication in mitochondrial superoxide (mtO2(•-)) production. In the disturbed flow or oscillatory shear stress (OSS)-exposed aortic arch, we observed prominent staining of p62, a reverse marker of autophagic flux, whereas in the pulsatile shear stress (PSS)-exposed descending aorta, p62 was attenuated. OSS significantly increased (i) microtubule-associated protein light chain 3 (LC3) II to I ratios in human aortic endothelial cells, (ii) autophagosome formation as quantified by green fluorescent protein (GFP)-LC3 dots per cell, and (iii) p62 protein levels, whereas manganese superoxide dismutase (MnSOD) overexpression by recombinant adenovirus, N-acetyl cysteine treatment, or c-Jun N-terminal kinase (JNK) inhibition reduced OSS-mediated LC3-II/LC3-I ratios and mitochondrial DNA damage. Introducing bafilomycin to Earle's balanced salt solution or to OSS condition incrementally increased both LC3-II/LC3-I ratios and p62 levels, implicating impaired autophagic flux. In the OSS-exposed aortic arch, both anti-phospho-JNK and anti-8-hydroxy-2'-deoxyguanosine (8-OHdG) staining for DNA damage were prominent, whereas in the PSS-exposed descending aorta, the staining was nearly absent. Knockdown of ATG5 with siRNA increased OSS-mediated mtO2(•-), whereas starvation or rapamycin-induced autophagy reduced OSS-mediated mtO2(•-), mitochondrial respiration, and complex II activity. Disturbed flow-mediated oxidative stress and JNK activation induce autophagy. OSS impairs autophagic flux to interfere with mitochondrial homeostasis. Antioxid. Redox Signal. 23, 1207-1219.