Azithromycin and Roxithromycin Define a New Family of “Senolytic” Drugs That Target Senescent Human Fibroblasts

Abstract

This study employed a senolytic assay system to identify and repurpose FDA-approved antibiotics for targeting senescent human fibroblasts. Using MRC-5 and BJ cell lines induced into senescence via BrdU treatment, the researchers discovered that Azithromycin and Roxithromycin selectively eliminated senescent cells without affecting normal cells. Notably, Erythromycin, a closely related compound, lacked this activity. Azithromycin also induced autophagy and aerobic glycolysis, with bi-phasic effects on mitochondrial oxygen consumption rates, suggesting these metabolic changes underpin its senolytic activity.

Key Findings

• Selective Senolytic Activity: Azithromycin and Roxithromycin effectively targeted senescent MRC-5 and BJ fibroblasts, sparing normal cells. Erythromycin showed no senolytic activity.
• Metabolic Effects: Azithromycin induced autophagy and increased glycolysis in fibroblasts. Its impact on mitochondrial respiration was dose-dependent, inhibiting at 50 μM and stimulating at 100 μM.
• Validation: The xCELLigence real-time assay confirmed Azithromycin's selectivity, removing approximately 97% of senescent cells.
• Clinical Implications: The findings suggest potential for repurposing Azithromycin and Roxithromycin as senolytic agents in anti-aging therapies.

Methodology

Senescence was induced in MRC-5 and BJ human fibroblast cell lines using 100 μM BrdU over 8 days. Post-treatment, cells were exposed to Azithromycin, Roxithromycin, or Erythromycin. Cell viability was assessed using the SRB assay. Metabolic changes were evaluated via autophagy markers and mitochondrial respiration measurements. The xCELLigence system provided real-time analysis of cell viability and senolytic activity.

Conclusion

Azithromycin and Roxithromycin demonstrate potent, selective senolytic activity against human fibroblasts, with distinct metabolic effects contributing to their efficacy. These findings support the potential repurposing of these antibiotics as senolytic agents in therapeutic strategies targeting aging and age-related diseases.