As people live longer, age-related changes in memory and thinking are becoming a larger health challenge. Conditions such as Alzheimer’s disease, Parkinson’s disease, and vascular dementia are also becoming more common, yet treatments often focus on symptoms rather than the biological changes that develop as the brain ages.
A review by Timur Saliev and Prim B. Singh of the School of Medicine at Nazarbayev University examines one of those changes: the buildup of damaged cells that enter a state called cellular senescence. These cells can remain alive and active, but their behavior changes in ways that may contribute to long-lasting inflammation and declining brain function.
Why aging cells matter
Cellular senescence normally has useful roles, including stopping damaged cells from continuing to divide. Trouble can arise when senescent cells accumulate and begin releasing a mixture of inflammatory and tissue-damaging substances into their surroundings.
This mixture is known as the senescence-associated secretory phenotype, or SASP. In simple terms, senescent cells can send out chemical signals that irritate nearby tissue, interfere with normal cell activity, and sometimes push neighboring cells toward the same dysfunctional state.
The brain contains several cell types that can develop senescent-like features with age. These include neurons, which carry information, as well as astrocytes and microglia, support cells that help maintain the brain and manage immune activity.
The review describes senescent cells in brain regions involved in memory, planning, and movement. Their inflammatory signals have been linked with weaker connections between nerve cells, reduced production of new nerve cells, and damage to the blood-brain barrier, the protective boundary that controls what can move from the bloodstream into brain tissue.
Two treatment strategies emerge
The proposed treatments are called senotherapeutics, meaning therapies aimed at senescent cells or the harmful signals they release. They fall into two broad groups that take different approaches to the same problem.
Senolytics are drugs or compounds designed to remove senescent cells by triggering their built-in cell-death process. Among the most widely examined examples are dasatinib, a drug approved for certain leukemias, and quercetin, a plant compound found in foods including onions, apples, and berries.
Animal work reviewed by the authors suggests that the combination of dasatinib and quercetin can reduce signs of senescent cells and inflammation. In aged rodents, treatment has also been associated with better performance on memory and learning tasks, along with changes in the brain connections that support learning.
Senomorphics take a different route. Instead of killing senescent cells, compounds such as rapamycin and metformin are being examined for their ability to reduce the harmful substances those cells release, which may be important in the brain because removing certain nerve or support cells could disrupt useful functions.
Animal findings remain strongest
Much of the encouraging evidence still comes from animals rather than people. In aged mice and rats, targeting senescent cells has been linked with lower brain inflammation, improved communication between nerve cells, and better performance on tests of memory and thinking.
Some animal models of Alzheimer’s disease have also shown reductions in amyloid-beta and tau, proteins that can build up abnormally in the brain. These findings raise the possibility that senescent cells are connected not only with inflammation but also with processes involved in neurodegeneration.
Work in nonhuman primates offers another step toward human testing. In one six-month experiment summarized in the review, middle-aged primates received monthly dasatinib and quercetin, and the treatment reduced some signs of senescence and inflammation outside the brain.
Human evidence is much more limited. Early clinical trials are examining whether senolytic treatments are safe and practical in people with mild cognitive problems or early Alzheimer’s disease, while also measuring biological signs of inflammation, nerve injury, and senescence.
Important limits remain
The evidence does not show that senotherapeutics can prevent dementia, reverse brain aging, or restore lost cognitive abilities in people. The review brings together results from earlier work rather than reporting a new experiment, and many of the strongest effects come from laboratory animals.
Results have also been inconsistent across biological settings. Dasatinib and quercetin did not improve memory in one experiment involving aging female rats, and the same combination did not improve immune responses to influenza in aged mice.
In a mouse model of acute kidney injury, dasatinib and quercetin made tissue damage worse rather than better. Those findings are outside the brain, but they show why removing senescent cells cannot be assumed to help every organ, every condition, or every individual.
Senescent cells can have useful jobs in wound healing, tissue repair, and immune regulation. A treatment that removes them too broadly could interfere with those functions, making dose, timing, target tissue, age, sex, and health status important questions for future human trials.
Getting drugs into brain
Another major obstacle is the blood-brain barrier. This protective system helps shield the brain from harmful substances in the circulation, but it can also prevent potentially useful drugs from reaching their intended targets in sufficient amounts.
Researchers are investigating carriers such as nanoparticles and modified drug forms that may improve delivery into the brain. Even with better delivery, however, doctors would still need reliable ways to identify which cells are senescent and to track whether a treatment is actually changing them.
Current markers of senescence are not yet fully validated for routine brain care. The review points to possible future tools based on blood, cerebrospinal fluid, brain imaging, genetic information, and other measures that could help match treatments to the people most likely to benefit.
A cautious path forward
The central idea is attractive because it aims at a biological process connected with aging rather than a single symptom. Yet the evidence also makes clear that senescent cells are diverse, their effects depend on context, and treatments that help in one setting may do little or cause harm in another.
For now, senotherapeutics are best viewed as an experimental direction rather than an established way to protect memory or treat neurodegenerative disease. Better brain delivery, stronger markers, careful safety testing, and larger human trials will be needed before their real value for healthy brain aging can be known.
The research was published in MDPI.
