Figure 11.

Humanin delays oxidative stress–induced senescence in RPE cells. The RPE cells were treated with 500 μM H₂O₂ or 500 μM H₂O₂ plus 10 μg/mL HN and processed for SA-β-Gal staining or p16^INK4a immunoblot. Oxidative stress significantly increased the number of SA-β-Gal–positive cells and RPE cell senescence was considerably lower with HN cotreatment (A, B) The H₂O₂ treatment induced 75% cell senescence, whereas the HN cotreatment showed less than 30% cell senescence (B). (C) Gene expression of senescence marker gene ApoJ by real-time PCR (forward, 5′-AGAGTGTAAGCCCTG CCTGA-3′; reverse, 5′-CATCCAGAAGTAGAAGGGCG-3′). The expression of ApoJ was significantly higher in H₂O₂-treated cells than in control RPE cells. The increase in expression of ApoJ was significantly suppressed when cells were coincubated with HN. (D, E) Oxidative stress significantly increased expression of p16^INK4a, while HN cotreatment restored p16^INK4a expression to that of control cells. Expression of p16^INK4a was considerably low in normal confluent RPE cells. *P < 0.05, **P < 0.01.