Discovery of Hsp70-Mediated Lysosomal Repair as a Highly Specific Target for Senolysis

Senescent cells (SnCs) play a central role in aging and various age-related diseases, making their selective elimination a promising therapeutic strategy for extending lifespan and mitigating these conditions. However, the development of selective senolytic agents that exclusively target SnCs remains a challenge due to the absence of mechanisms that distinctly differentiate them from non-senescent cells (non-SnCs). In this study, we report a serendipitous discovery that Pifithrin-µ (PES), through its inhibition of Hsp70, exhibits highly selective senolytic activity. Mechanistic investigations revealed that SnCs harbor dysfunctional lysosomes with compromised membrane integrity—a vulnerability typically counteracted by the upregulation and lysosomal recruitment of Hsp70, which facilitates lysosomal repair by enhancing ceramide production. Inhibition of Hsp70 by PES selectively disrupts this repair mechanism, inducing catastrophic lysosomal membrane permeability (LMP) and triggering lysosome-dependent cell death (LDCD) specifically in SnCs. Moreover, PES treatment improved aging-related phenotypes and reversed lung fibrosis in mouse models of irradiation-induced accelerated aging and pulmonary fibrosis, respectively. These findings establish Hsp70 as a novel and transformative senolytic target and suggest that targeting the senescence-specific lysosomal repair pathway could provide a safer, more selective, and efficacious alternative to current senolytic strategies, which primarily target non-specific anti-apoptotic pathways.