Novel small-molecule positive allosteric modulator 1 with blood-brain barrier penetration activity exerts anti-cellular senescence effects via the PAC1-R/YY1/SIRT6 pathway

Aging is the primary risk factor for neurodegeneration. SIRT6, a key longevity regulator, is downregulated in aged brain tissue and linked to neurodegeneration. Thus, activating SIRT6 may delay brain aging. Based on this, the present study reveals the molecular mechanism by which the novel small-molecule positive allosteric modulator (SPAM1) antagonizes neuronal senescence through the PAC1-R/YY1/SIRT6 signaling axis, along with its highly efficient brain-targeting properties. In a naturally aging model of long-term cultured retinal ganglion cells (RGC-5), sustained administration of SPAM1 (1 μM) significantly ameliorates aging phenotypes, including upregulation of SIRT6 and Lamin B1 expressions and suppression of p16 accumulation. Dual luciferase reporter assays confirm that SPAM1 activates the SIRT6 promoter. Mechanistically, SPAM1 induces nuclear translocation of PAC1-R and releases its 24-kDa C-terminal fragment, which forms a complex with the transcription factor YY1 within the nucleus. ChIP-qPCR confirms that SPAM1 enhances YY1 enrichment on the SIRT6 promoter, while YY1 knockdown inhibits SPAM1-mediated SIRT6 activation, establishing YY1's pivotal role. Pharmacokinetics and in vivo imaging demonstrate that SPAM1 possesses rapid and persistent brain targeting capabilities: the drug is detectable in the brain within 10 min after intraperitoneal injection; following tail vein administration, brain fluorescence signals appear within 10 min, peak at 1 h, and persist for over 12 h. This study elucidates SPAM1's anti-neurogerontogenic mechanism through a complete signaling cascade: inducing PAC1-R nuclear translocation, recruiting YY1, and activating SIRT6 transcription. Its well-defined mechanism and unique brain targeting establish a pharmacological foundation for developing innovative drugs to intervene in age-related central nervous system decline. .