What specific autophagy pathways are defective in radiation-induced pericyte senescence?

Hypothesis 1: Radiation-induced pericyte senescence is driven by a late-stage autophagy defect at the lysosome acidification and TFEB-recovery step, not by loss of autophagosome formation. Damaged lysosomes would trap LC3-positive cargo, amplify ROS, and sustain SASP signaling. Test: lysosomal pH, cathepsin maturation, TFEB nuclear translocation, and tandem LC3 reporters after irradiation.

Hypothesis 2: The dominant lesion is defective mitophagy through the PINK1-PRKN axis, causing persistence of damaged mitochondria that lock pericytes into a senescent, inflammatory state. Test: mitochondrial membrane potential, Parkin recruitment, mito-QC reporters, and rescue with mitophagy activators.

Hypothesis 3: DNA damage chronically activates mTORC1 and suppresses ULK1-dependent autophagy initiation, with SASP cytokines reinforcing the block. In this version the defect is early and signaling-centered rather than lysosome-centered. Test: ULK1 phosphorylation, mTORC1 readouts, rapalog rescue, and time-resolved flux mapping.

Hypothesis 1 fits many senescence phenotypes, but accumulation of LC3 or SQSTM1 alone cannot distinguish lysosome failure from overproduction of autophagosomes. Without flux measurements and direct pH or cathepsin assays, this interpretation is too coarse.

Hypothesis 2 is compelling because mitochondria are plausible radiation-sensitive organelles, yet mitophagy collapse may be downstream of a broader lysosomal problem rather than the initiating lesion. The falsification test is whether general lysosome rescue normalizes mitochondrial quality control more effectively than PINK1-pathway manipulation.

Hypothesis 3 risks treating mTORC1 as a universal stress answer. If mTORC1 is transiently activated early but the durable defect sits downstream, mTOR inhibition could look partially beneficial while missing the real bottleneck. Time-resolved sampling matters more than endpoint western blots.

The best development plan is a temporal map of autophagy after irradiation in primary human brain pericytes: 6 h, 24 h, 72 h, and senescence endpoints. That can separate initiation defects from clearance defects and reveal whether mitophagy failure is a primary driver or a secondary consequence.

Lysosome and mitophagy programs both offer tractable intervention hooks. If acidification failure dominates, TFEB activators or lysosome-repair strategies become attractive; if mitophagy dominates, mitochondrial QC enhancers are the cleaner path. For translational relevance, the most important bridge is whether the same autophagy lesion correlates with BBB dysfunction markers and inflammatory secretome changes, not simply with senescence staining.