25-Hydroxycholesterol
25-Hydroxycholesterol (25-HC), oxysterol product of cholesterol 25-hydroxylase
Written by Aaron CuhaReviewed Sep 2026
Also known as: 25-HC, 25HC
A cholesterol metabolite the body makes itself, reported in 2025 to reduce aortic stiffness in old mice as effectively as genetic clearance of senescent cells. Other work in mice points the opposite way in the brain, where the same molecule drives neuroinflammation.
Overview
25-Hydroxycholesterol is an oxysterol produced from cholesterol by the enzyme cholesterol 25-hydroxylase, which immune cells switch on during inflammatory activation. It is a signalling molecule, not a drug: it regulates sterol synthesis, interferon responses and inflammatory signalling.
The senolytic claim is recent and narrow. In 2025 a study in old p16-3MR mice, a strain that allows senescent cells to be killed genetically with ganciclovir, compared 25-hydroxycholesterol against that genetic clearance. Five days of 25-hydroxycholesterol reduced aortic pulse wave velocity, a measure of arterial stiffness, to a similar extent as the genetic clearance, and aortic rings from ganciclovir-treated mice showed no further reduction in stiffness on exposure to it, which the authors read as evidence that it works through senescent cell suppression. Collagen-1 fell and alpha-elastin rose.
The same molecule points the other way elsewhere. In mice expressing mutant human tau, deleting the gene that makes 25-hydroxycholesterol markedly reduced age-dependent neurodegeneration and neuroinflammation, and single-nucleus sequencing showed suppressed proinflammatory microglial signalling. In mouse atherosclerosis models, macrophage-derived 25-hydroxycholesterol promoted vascular inflammation and lesion remodelling. A molecule that is beneficial in the aorta of one mouse strain and harmful in the brain and artery wall of others is not a candidate for supplementation on the strength of one paper.
Human data are measurements, not interventions. 25-Hydroxycholesterol has been quantified in human plasma and cerebrospinal fluid, for instance in multiple sclerosis and other neurological disease, but no one has administered it to a person in a published study. No senolytic has improved a clinical outcome in a randomised trial in humans, and 25-hydroxycholesterol has not been given to a human at all.
Mechanism of action
Established in mice and cells: 25-hydroxycholesterol is made by cholesterol 25-hydroxylase, suppresses SREBP-driven cholesterol synthesis, and modulates interferon and inflammatory signalling. In the aortic study, the senolytic reading rests on the absence of any additional stiffness reduction in aortas from mice whose senescent cells had already been cleared genetically, plus suppression of its putative target CRYAB. In tau and atherosclerosis models the same molecule amplifies proinflammatory signalling. Nothing about these effects has been characterised in a person given the compound.
Human evidence
None as an intervention. 25-Hydroxycholesterol has been measured in human plasma, cerebrospinal fluid and atherosclerotic tissue, but no published study has administered it to a person, and no trial is registered.
- Human sterol measurement studies quantify circulating and cerebrospinal fluid 25-hydroxycholesterol in neurological disease and in atherosclerosis. These are observational analyte measurements.
- No pharmacokinetic study, no dose-finding study, and no registered interventional trial of 25-hydroxycholesterol in humans was located.
What this does not tell you: Measuring an endogenous metabolite in patients tells you it varies with disease state. It does not tell you the direction of causation, and it certainly does not tell you what giving more of it would do. The mouse literature runs in both directions depending on the tissue, which is the strongest available reason not to extrapolate.
Reading the research record
This is a single-paper senolytic claim in a molecule with a large and contradictory inflammation literature. The 2025 aortic stiffness result is careful work: it compares the compound against genetic clearance of senescent cells in the same strain, which is a more demanding control than most senolytic papers use. It is also five days of treatment in old mice, with no replication.
Against it sit two well-powered mouse papers in which 25-hydroxycholesterol or the enzyme that makes it drives harm: neurodegeneration in a tauopathy model, and atherogenesis and lesion remodelling in vascular disease. A molecule the immune system produces to amplify inflammatory signalling is an awkward candidate for chronic supplementation, and no one has given it to a person to find out.
The evidence, charted
Fig. 1 · evidence composition
1of 4 citations (25%) are in people
Counted from the citation list on this page. The Human count is the same number shown in the badge at the top. Both understate any literature larger than the sources we cite.
Fig. 2 · evidence over time
Evidence spans 4 distinct years, 2017 to 2025, counted from the citation list on this page.
Fig. 3 · legal status at a glance
US
Not approved
UK
Approved
AU
Not approved
CA
Not approved
Approved in 1 of 4, prescription route in 0, not approved in 3. A jurisdiction's classification is a regulatory fact, not a verdict on the science; see Legal status below for the full text and any notes.
Fig. 4 · dose response
No human dose response curve exists
We draw this figure where the data supports it. For this compound in humans it does not, so the panel stays empty rather than borrowing an animal curve and implying it transfers.
Key studies & citations
- Animal2025
Late Life Supplementation of 25-Hydroxycholesterol Reduces Aortic Stiffness and Cellular Senescence in Mice
Old p16-3MR mice aged 22 to 26 months. Five days of 25-hydroxycholesterol reduced aortic pulse wave velocity (P = 0.002), similar to genetic clearance of p16-positive cells with ganciclovir, with lower collagen-1 and higher alpha-elastin. Aortic rings from ganciclovir-treated mice showed no further reduction in elastic modulus, which the authors read as senescence-mediated action.
Aging Cell - Animal2024
Cholesterol 25-hydroxylase mediates neuroinflammation and neurodegeneration in a mouse model of tauopathy
Mouse, and it points the opposite way. In PS19 mice expressing mutant human tau, deleting Ch25h and reducing 25-hydroxycholesterol markedly reduced age-dependent neurodegeneration and neuroinflammation, with suppressed proinflammatory microglial signalling on single-nucleus sequencing.
Journal of Experimental Medicine - Animal2023
Macrophage-Derived 25-Hydroxycholesterol Promotes Vascular Inflammation, Atherogenesis, and Lesion Remodeling
Mouse atherosclerosis models, with 25-hydroxycholesterol and CH25H expression also measured in human lesions. Macrophage-derived 25-hydroxycholesterol promoted vascular inflammation and lesion remodelling, a harm direction in the same organ system as the aortic stiffness study.
Circulation - Human2017
Reduced Plasma Levels of 25-Hydroxycholesterol and Increased Cerebrospinal Fluid Levels of Bile Acid Precursors in Multiple Sclerosis Patients
Human measurement study. More than 20 non-esterified sterols were quantified by mass spectrometry in plasma and cerebrospinal fluid from patients with multiple sclerosis, other inflammatory and neurodegenerative disease, and controls. 25-Hydroxycholesterol was elevated in cerebrospinal fluid in suspected autoimmune inflammatory disease. Nobody was given the compound.
Molecular Neurobiology
Frequently asked questions
Has anyone taken 25-hydroxycholesterol as a supplement in a study?
No published study has administered it to a person, for ageing or anything else, and no trial is registered. Human data consist of measurements of the naturally occurring molecule in blood, cerebrospinal fluid and tissue.
What did the 2025 mouse study show?
In old p16-3MR mice, five days of 25-hydroxycholesterol reduced aortic pulse wave velocity about as much as genetically killing p16-positive senescent cells, with favourable changes in collagen and elastin. It is one study, five days long, in mice.
Is 25-hydroxycholesterol anti-inflammatory or pro-inflammatory?
Both, depending on the tissue and the model. Deleting the enzyme that produces it reduced neurodegeneration and neuroinflammation in a mouse tauopathy model, and macrophage-derived 25-hydroxycholesterol promoted vascular inflammation and atherogenesis in mouse models. The senolytic vascular result sits alongside these, not above them.