Hormetic preconditioning suppresses endothelial inflammatory markers but fails to reverse cytoskeletal‑driven ICAM‑1 immobilization and eNOS uncoupling

Hormetic stresses such as intermittent hypoxia, mild heat shock, or low‑dose superoxide induce a transient antioxidant response that lowers ICAM‑1 transcription and monocyte adhesion in senescent endothelial cells. However, the same stimuli do not restore the structural defects that underlie sustained inflammation: impaired alpha‑actinin tyrosine phosphorylation, loss of cortical actin anchoring, and persistent eNOS uncoupling. We hypothesize that hormesis activates Nrf2‑dependent detox pathways without engaging the focal adhesion kinase (FAK)–Src circuit required to re‑phosphorylate alpha‑actinin and re‑couple eNOS. Consequently, ICAM‑1 remains immobilized in the membrane, its mobility stays low, and the endothelial barrier remains leaky despite reduced cytokine secretion.

To test this, we will expose late‑passage HUVECs (passage 15‑18) to a hormetic protocol—three cycles of 10 min 10 % O₂ followed by 20 min normoxia—then assess: (1) eNOS coupling ratio via biotin‑switch assay and superoxide production with DHE fluorescence; (2) ICAM‑1 lateral mobility using FRAP (fluorescence recovery after photobleaching) and the diffusion coefficient; (3) tyrosine phosphorylation of alpha‑actinin by immunoprecipitation and western blot; (4) monolayer permeability to FITC‑dextran and monocyte adhesion under flow. Parallel cultures will receive N‑acetylcysteine (NAC) as a positive control for redox recoupling. If hormesis reduces ICAM‑1 mRNA and monocyte adhesion but does not increase alpha‑actinin phosphorylation, does not improve ICAM‑1 diffusion, and fails to shift the eNOS coupling ratio toward NO production, the hypothesis is supported. Conversely, if hormetic pretreatment restores all three parameters to levels comparable with NAC‑treated cells, the hypothesis is falsified.

This work distinguishes superficial anti‑inflammatory adaptation from genuine structural repair, clarifying why hormetic regimens improve functional readouts in aging models without necessarily reversing endothelial senescence at the mechanistic level.