Authors: Milo E Light, Sohom Mookherjee, J. David Symons, Megan Tandar, Nathan Hill
Mentors: John David Symons
Insitution: University of Utah
Acute ischemic stroke (AIS) deprives cerebral artery endothelial cells (ECs) of nutrients which decreases mTORC1 activity to initiate autophagic flux. We hypothesized that depletion of EC autophagy worsens outcomes of AIS. Methods and results. First, adult male C57Bl6 mice consumed a standard diet (control) or chow supplemented with the mTORC1 inhibitor rapamycin. After 3-weeks, phosphorylated ribosomal S6 / total S6 was greater (p<0.05) in liver segments of rapamycin vs. control-fed mice, indicating mTORC1 repression. Transient middle cerebral artery occlusion (tMCAO, 60-min;) followed by reperfusion (R, 23 h) increased infarct volume, neurobehavioral deficits, and motor dysfunction, to a greater extent (p<0.05) in control vs. rapamycin-supplemented mice. Second, adult male C57Bl6 mice with intact EC autophagy-related protein 3 (Atg3WT) or inducible depletion of EC ATG3 (Atg3EC-/-) completed tMCAO+R. ATG3 colocalization with VE-Cdh5 increased (p<0.05) after tMCAO+R in ipsilesional vs. contralesional hemispheres of Atg3WT but not Atg3EC-/- mice. Neutrophil infiltration, cell death, microglia and astrocyte activation, and neurodegeneration, were greater (p<0.05) in ipsilesional hemispheres of Atg3EC-/- vs. Atg3WT mice. Further, infarct volume was greater (p<0.05), and motor and neurobehavioral performance were worse (p<0.05), in Atg3EC-/- vs. Atg3WT mice. Third, tMCAO+R evoked infarct volume was less severe after rapamycin feeding in Atg3WT but not Atg3EC-/- mice, underscoring the importance of EC autophagy. Conclusions. Intact EC autophagy is protective concerning AIS, potentially via enabling: (i) recycling of damaged proteins; (ii) nutrient generation from degraded substrates; and / or (iii) arterial vasodilation for nutrient delivery.