Oxytocin, the ‘love hormone’, could be used to treat Alzheimer’s disease

Oxytocin is known to facilitate certain cellular chemical activities that are important in strengthening neuronal signalling potential and formation of memories, such as the influx of calcium ions.

Alzheimer’s disease is a progressive disorder in which the nerve cells (neurons) in a person’s brain and the connections among them degenerate slowly. (Representational Image) (Unsplash)

In recent research, scientists looked at oxytocin, a hormone that is conventionally known for its role in the female reproductive system and in inducing the feelings of love and well-being--as a possible element to treat cognitive disorders like Alzheimer’s.

Alzheimer’s disease is a progressive disorder in which the nerve cells (neurons) in a person’s brain and the connections among them degenerate slowly, causing severe memory loss, intellectual deficiencies, and deterioration in motor skills and communication.

One of the main causes of Alzheimer’s is the accumulation of a protein called amyloid b (Ab) in clusters around neurons in the brain, which hampers their activity and triggers their degeneration.

Studies in animal models have found that increasing the aggregation of Ab in the hippocampus--the brain’s main learning and memory centre--causes a decline in the signal transmission potential of the neurons therein.

This degeneration affects a specific trait of the neurons, called “synaptic plasticity,” which is the ability of synapses (the site of signal exchange between neurons) to adapt to an increase or decrease in signalling activity over time.

Synaptic plasticity is crucial to the development of learning and cognitive functions in the hippocampus. Thus, Ab and its role in causing cognitive memory and deficits have been the focus of most research aimed at finding treatments for Alzheimer’s.

Now, advancing this research effort, a team of scientists from Japan, led by Professor Akiyoshi Saitoh from the Tokyo University of Science, has looked at oxytocin.

“Oxytocin was recently found to be involved in regulating learning and memory performance, but so far, no previous study deals with the effect of oxytocin on Ab-induced cognitive impairment,” Prof Saitoh says.

Realising this, Prof Saitoh’s group set out to connect the dots. Their findings are published in Biochemical and Biophysical Research Communication.

Prof Saitoh and team-first perfused slices of the mouse hippocampus with Ab to confirm that Ab causes the signalling abilities of neurons in the slices to decline or--in other words--impairs their synaptic plasticity. Upon additional perfusion with oxytocin, however, the signalling abilities increased, suggesting that oxytocin can reverse the impairment of synaptic plasticity that Ab causes.

To find out how oxytocin achieves this, they conducted a further series of experiments. In a normal brain, oxytocin acts by binding with special structures in the membranes of brain cells, called oxytocin receptors.

The scientists artificially “blocked” these receptors in the mouse hippocampus slices to see if oxytocin could reverse Ab-induced impairment of synaptic plasticity without binding to these receptors.

Expectedly, when the receptors were blocked, oxytocin could not reverse the effect of Ab, which shows that these receptors are essential for oxytocin to act.

Oxytocin is known to facilitate certain cellular chemical activities that are important in strengthening neuronal signalling potential and formation of memories, such as the influx of calcium ions. Previous studies have suspected that Ab suppresses some of these chemical activities.

When the scientists artificially blocked these chemical activities, they found that the addition of oxytocin addition to the hippocampal slices did not reverse the damage to synaptic plasticity caused by Ab.

Additionally, they found that oxytocin itself does not have any effect on synaptic plasticity in the hippocampus, but it is somehow able to reverse the ill-effects of Ab.

Prof Saitoh said, “This is the first study in the world that has shown that oxytocin can reverse Ab-induced impairments in the mouse hippocampus.”

This is only a first step and further research remains to be conducted in vivo in animal models and then humans before sufficient knowledge can be gathered to reposition oxytocin into a drug for Alzheimer’s. But, Prof Saitoh remains hopeful.

Jul 21, 2020 

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