Figure 2. “Senolytic” drug screening strategy. Here, normal fibroblasts (MRC-5 and BJ), originally derived from human lung and skin tissues, were subjected to prolonged culture (8-days) in the presence of BrdU (100 μM) to induce controlled DNA-damage and senescence. Then, isogenically-matched cultures of normal and senescent fibroblasts were employed for drug screening to identify the potential senolytic activity of clinically-approved drugs, such as antibiotics (Erythromycin, Azithromycin and Roxithromycin, among others). Senolytic activity was detected using the SRB assay, which measures the amount of protein remaining attached to the tissue-culture dishes, which is a surrogate marker for cell viability.