A plant commonly found in Indian gardens could hold molecules to treat Alzheimer's, a brain disease that severely affects behaviour and memory, said researchers in Bengaluru.
Alzheimer's is typically caused by the corruption of a natural process. In the normal human brain, neurons synthesise a protein called amyloid beta, which begins its life as a solitary molecule. However, within people suffering from Alzheimer’s, these proteins undergo a process called aggregation, where they bunch up and turn into plaques.
In its aggregated form, amyloid beta can bind strongly to a receptor on nerve cells, setting into motion an intra-cellular process that erodes synapses with other nerve cells. The end result is cognitive impairment and often dementia.
In the study, researchers found that proteins from the common butterfly pea plant (clitoria ternatea) protected neurons against this aggregate formation. There was already substantial anecdotal information about the plant’s memory-enhancing properties.
“Plants have hundreds of compounds that could be repurposed for the benefit of society but the first step is to find which ones have the potential for medicinal purposes,” said Neha V Kalmankar, a PhD student at the National Centre for Biological Sciences (NCBS) and lead author of the study.
Researchers extracted and isolated a set of ultra-stable cyclic proteins (or “cyclotides”) from the plant, following which they tested these peptides on tiny free-living soil worms called Caenorhabditis elegans.
The experiments showed that the cyclotides from the plant protected the neurons against the amyloid aggregate formation. The worms which fed on the cyclotides showed significantly less paralysis than the ones that did not.
The researchers said that they chose to use C. elegans for the experiments because neurodegenerative disease studies are challenging to do in mice and difficult to study in humans due to the complexity of biochemical change and limited nature of studies that can be performed on living patients’ brains.
“Using a soil-dwelling nematode like C. elegans as a model is valuable as these worms have conserved gene function, short life cycle and are experimentally tractable,” said Dr Radhika Venkatesan, corresponding author of the study.
Different experiments showed strong evidence for the beneficial value of cyclotides, given that oxidative stress is a commonly related process in Alzheimer’s progression.
The study was published in the Journal of Medicinal Chemistry.