Effect of the novel senolytic drug, BCL-xL PROTAC, on small airway epithelial cells in COPD

<bold>Background:</bold> COPD is associated with accelerated lung aging and increased cellular senescence. Senescent cells cannot replicate but are metabolically active and secrete proinflammatory factors that may drive disease progression. Senolytic therapies selectively delete senescent cells by inducing their apoptosis. We determined the effect of BCL-xL PROTAC, a senolytic drug that targets the anti-apoptotic molecule BCLXL, on cellular senescence and proliferation of small airway epithelial cells (SAEC) derived from COPD patients. <bold>Methods:</bold> SAEC from COPD patients were cultured for 72h with 0.1μM-3μM of BCL-xL PROTAC. BCLxL and p21CIP1 expression were analysed by Western Blot and PAI1, measured by ELISA. The activation of caspase 3/7 and the proliferative marker Ki67 were analysed by flow cytometry. <bold>Results:</bold> COPD SAEC culture with 3μM BCL-xL PROTAC for 72h downregulated its target BCLXL (40-fold compared to untreated cells, n=6, p<0.05) and led to the activation of caspase 3/7 (n=4, p<0.05). These cells also showed decreased expression of the senescence marker p21CIP1 (5-fold, n=6, p<0.05) and decreased production of PAI1 in cell media (22.3 ± 6.7ng/ml in untreated cells vs 9.1 ± 1.7 ng/ml protac-navitoclax, n=6, p<0.05). Moreover, the proportion of COPD SAEC positive for the proliferation marker Ki-67 increased following culture with 3μM BCL-xL PROTAC (10.5 ± 4.3% untreated 30.2 ± 13.3% protac-navitoclax, n=4, p<0.05). <bold>Conclusion:</bold> These data suggest that the treatment of COPD SAEC with BCL-xL PROTAC leads to the reduction of cellular senescence and lung inflammation and induce cell regeneration. Thus, senolytic therapies may be a new therapeutic approach for COPD.