25-Hydroxycholesterol reduces aortic cellular senescence and stiffness in old mice
Authors: Mahoney Sophia , Ciotlos Serban , Darrah Mary , Venkatasubramanian Ravinandan , Rossman Matthew , Campisi Judith , Seals Douglas , Melov Simon , Clayton Zachary 
Published: May 2023

Aortic stiffnessincreases with aging and is an independent risk factor for the development of cardiovascular diseases. Cellular senescence, a state of cell cycle arrest that accumulates in arteries with aging, contributes to age-related aortic stiffening. 25-Hydroxycholesterol (25HC) is a novel senolytic — a compound that eliminates senescent cells by modulating senescent cell anti-apoptotic pathways (SCAPs). However, the senolytic effects of 25HC in the vasculature and its influence on age-related aortic stiffness and associated arterial wall structural remodeling are unknown. Hypothesis: 25HC treatment in old mice treated would favorably modulate the vascular SCAP profile, suppress vascular cell senescence, and reduce aortic stiffness relative to old control mice. Methods & Results. Animals. Two groups (n=10-15/group) of old (24-26mo) female p16-3MR mice were used: 1) untreated control; and 2) 25HC (50 mg/kg/day in 22.5% 2-hydroxypropyl-β-cyclodextrin administered intraperitoneally for 5 consecutive days). SCAPs. Aortic abundance of CRYAB, the therapeutic target of 25HC and a SCAP regulator, was 38% lower in 25HC-treated v. control mice (chemiluminescence units [CU]; P<0.05). A composite score of 6 aortic SCAP genes ( Tp53, Casp3, Bax, Parp, Cycs, Xiap; all lower in senescent cells) was higher with 25HC treatment (+54%, P<0.05), suggesting 25HC favorably regulates aortic SCAPs. Cellular senescence. Compared to control animals, 25HC-treated mice had 75% lower aortic abundance of p16INK4A, a protein that confers cell cycle arrest in senescent cells (CU, P<0.05) and 56% lower aortic gene expression of the cellular senescence marker Cdkn1a ( P<0.05), suggesting that 25HC suppresses vascular cell senescence. Aortic stiffness. Aortic pulse wave velocity (an in vivo measure of aortic stiffness) was lower in 25HC-treated v. control mice (358 ± 5 v. 402 ± 5 cm/s, P<0.0001). This was associated with a reduction in aortic elastic modulus (EM; an ex vivo measure of intrinsic mechanical wall stiffness; 1832 ± 83 v. 2406 ± 120 kPa, P<0.05). Ex vivo incubation (48h) of old control aorta rings with 25HC lowered the EM by 30% ( P<0.05) but did not further reduce the EM of aorta rings from 25HC-treated mice. These findings suggest that 25HC likely lowers aortic stiffness by directly reducing the stiffness of the arterial wall. Aortic structural proteins. Relative to control mice, 25HC-treated mice had lower aortic abundance of collagen-1 (a structural protein that confers stiffness; -42% CU, P<0.05) and higher aortic abundance of α-elastin (a structural protein that confers elasticity; +58% CU, P=0.096), suggesting that 25HC favorably alters arterial wall structure to improve aortic stiffness. Conclusion: 25HC is a novel therapy to reduce aortic cellular senescence and stiffness with aging via modulating SCAPs. R01 AG055822, K99 HL159241, F31 HL165885 This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.