Figure 5. Azithromycin shows senolytic activity in senescent MRC-5 human lung fibroblasts. MRC-5 cells were pre-treated with BrdU for 8 days (to induce senescence), before they were exposed to Azithromycin for another 5 days. After that, the SRB assay was performed to determine the effects of the drug on cell viability. Azithromyin had a potent and selective effect on MRC-5, as it eliminated ~50% of senescent cells without affecting control cells after 5 days, at a concentration of 100 µM. However, Azithromycin had no effect at 50 µM. These experiments were repeated at least 3 times independently, with very similar results. Note that the scale bar represents 20 µm in the images. ** p < 0.01.