The role of platelets in brain-body communication
In addition to the pivotal role that platelets play in blood coagulation and the process of haemostasis, recent studies have shown that these small fragments of cells in the blood perform other important functions. While the role of platelets in the immune system is well known, how they act in the modulation of neurological interactions is something that is still little investigated.
Do platelets influence behaviour to some extent? This is the question behind the study, coordinated by Cristina Limatola of Sapienza’s Department of Physiology and Pharmacology and recently published in the journal ‘Cell Reports’. The answer seems to be positive: as a matter of fact, the research identifies platelets as a key element in brain-body communication, capable of activating mechanisms that influence memory and behaviour.
This function derives from the fact that platelets store serotonin, a neurotransmitter mainly produced in the nervous system and the gastrointestinal tract. As is well known, serotonin regulates mood, influences certain biological functions such as sleep and appetite, and also has an effect on learning and memorising processes. When one considers that platelets contain the majority of serotonin in the body, it becomes clear that they are involved in the regulation of neuro-immune responses.
The study showed that reducing or altering the number of platelets in mouse models also reduced the amount of serotonin in the brain, affecting fear-related behaviour in mice. Generally, both human and animal brains tend to modulate behaviour based on past experiences. If, for example, an event has been associated with danger in the past, its reappearance will immediately trigger flight or defence responses.
On the contrary, new stimuli that are very different from those perceived as dangerous will not induce fear-driven behaviour. This happens because, depending on the circumstances, inhibitory neurons, i.e. neurons that slow down the memorising process, are activated in the hippocampus - the area of the brain that controls memory.
Researchers identified the reduced presence of serotonin in the brain as a factor capable of blocking the activity of inhibitory neurons, causing impaired memory formation and the onset of fear responses even in the presence of harmless stimuli. The study also showed that the reduction of serotonin in the brain results from a mechanism that is regulated by specific cells, the Natural Killers.
These are the cells that induce the production of serotonin in the gastrointestinal tract and thus determine the load carried by platelets throughout the body.
Experimentally decreasing natural killer cells or platelets reduces the amount of serotonin in the brain and triggers the process that modulates fear behaviour by controlling inhibitory neurotransmission and plasticity in the hippocampus.
‘Our study,’ says Cristina Limatola of Sapienza University, ‘adds a new element to our understanding of the mechanisms by which the brain communicates with and receives information from the body, defining a new communication mechanism between the cells of the immune system, platelets and the gut-brain axis for maintaining brain homeostasis’.
References:
Garofalo S, Mormino A, Mazzarella L, Cocozza G, Rinaldi A, Di Pietro E, Di Castro MA, De Felice E, Maggi L, Chece G, Andolina D, Ventura R, Ielpo D, Piacentini R, Catalano M, Stefanini L, Limatola C. “Platelets tune fear memory in mice”. Cell Rep. 2025 Feb 25;44(2):115261. doi: 10.1016/j.celrep.2025.115261
Further Information
Cristina Limatola
Department of Physiology and Pharmacology “Vittorio Erspamer”