PTP1B Inhibition Could Restore Brain Cleanup in Alzheimer’s Disease

Memory loss in Alzheimer’s disease is commonly associated with sticky protein plaques that accumulate in the brain.

Yet scientists are increasingly exploring another possibility: the brain’s own waste-clearance system may be failing.

A new study indicates that this clearance process could potentially be restored by blocking one enzyme that functions as a molecular brake on immune cells.

Researchers at Cold Spring Harbor Laboratory (CSHL) switched off this enzyme in mice with an Alzheimer’s-like condition. The animals’ immune cells in the brain then started removing plaque material again, and their memory performance improved.

These findings are not a cure, and the research has only been carried out in mice so far.

Even so, the results point to a potentially useful approach: enabling the brain to restart processes it previously managed naturally, rather than depending solely on drugs designed to attack plaques directly.

The brain enzyme linked to recovery

In searching for what enabled this recovery, the scientists identified one molecular switch that had been quietly suppressing the brain’s immune reaction.

Known as PTP1B, this switch usually serves as a brake on cell activity, reducing the speed at which cells respond when a problem arises.

In the Alzheimer’s mouse model, removing that brake improved memory performance alongside the revived clearance activity in the brain.

As the same switch affects numerous organs outside the brain, any future treatment would have to combine potential benefits with close control.

Why the brain’s cleanup process slows

After years of disease-related stress, microglia - immune cells that scan the brain for debris - often begin to lose momentum.

Continual exposure to damaged cells and sticky protein accumulation makes these cells work without interruption, progressively depleting the energy required to keep moving.

Once fatigue takes hold, phagocytosis - the process through which harmful material is engulfed and digested - becomes weaker. Debris can then remain for longer, placing greater stress on nearby brain tissue.

The researchers linked this decline to a breakdown in communication within the cells. Signals that would normally instruct microglia to activate and start clearing harmful material had become weaker, leaving the cells in place but less able to respond.

Restoring that signalling increased clearance activity once more. The result suggests that reawakening these internal communication routes might help restore the brain’s natural defence system.

The findings also underline the need to regulate immune activation carefully to prevent unintended side effects.

Plaques and current therapies

Amyloid plaques develop when tiny protein fragments, known as amyloid-beta, bind together in the brain. Healthy brains make amyloid-beta each day, but ageing and disease may shift the balance towards accumulation and clumping.

As these clusters enlarge, they may interfere with neighbouring nerve connections and set off immune responses that increase stress in surrounding tissue.

Removing plaques could reduce one source of harm, but other changes in the brain continue to advance, restricting the effect of any approach aimed at only one target.

Recent therapies have concentrated on removing plaques directly. Leqembi, one recently approved treatment, slows decline in early Alzheimer’s by tagging plaques for removal.

However, the immune response responsible for clearing plaques can also sometimes cause brain swelling or small bleeding events that can be seen on medical scans.

Patients need regular infusions and continuing monitoring, limiting access even among people who are eligible. This limitation increases interest in methods that make the brain’s own clearance systems more effective while lowering the burden of treatment.

The need for new Alzheimer’s therapies

An estimated 57 million people worldwide were living with dementia in 2021. According to the World Health Organization, the global economic cost was about $1.3 trillion in 2019.

“You lose the person piece-by-piece,” said Dr. Nicholas Tonks of Cold Spring Harbor Laboratory, stressing the urgent need for better ways to slow the progression of disease.

Wider health risks also influence dementia outcomes. Raised blood sugar and excess weight increase the risk of dementia, while PTP1B affects the signalling pathways involved in both of these conditions.

This enzyme influences both metabolism and immune activity. Consequently, medicines initially developed to improve insulin signalling could eventually contribute to Alzheimer’s therapy, if researchers can establish safe doses and timing that affect the brain without disturbing other systems.

Next steps for therapy

Drug development is now at the point between laboratory findings and testing in people, with early experiments already using a chemical inhibitor that targets PTP1B.

To benefit patients, these molecules must reach brain tissue at consistent doses without disrupting related enzymes in other parts of the body. Researchers also need to show long-term safety and establish which existing Alzheimer’s medicines are most suitable for combination with this approach.

By encouraging microglia to become active again, PTP1B inhibition provided a way to target plaque while protecting thinking skills in mice - a dual effect that might translate into meaningful clinical benefits.

“The goal is to slow Alzheimer’s progression and improve quality of life of the patients,” said Tonks.

Human trials will eventually show whether this promise is realised and whether combining the method with current treatments can slow cognitive decline in real-world settings.