Frogs have emerged as an unlikely ally in the fight against human diseases. Substances secreted by their skin are a rich source of chemicals that can be used for a range of purposes from lowering blood pressure to providing an alternative to conventional antibiotics.
The School of Biomedical Sciences at the University of Ulster, Coleraine, is involved in an analysis of frog venom in an effort to find novel substances to stop blood clotting, help tackle cancer tumours and make crops resistant to insect attack.
There are "hundreds if not thousands of new molecules waiting to be discovered" in frog venom, according to Prof Chris Shaw, head of Coleraine's pharmaceutical biotechnology research group.
Prof Shaw will lead an expedition to China on Monday. The team will join experts from the University of Fuzhou in a three-week search for rare varieties of tree and water frogs.
The researchers want to sample the skin secretions released by the frogs. It is "non-invasive and non-destructive research," he said. "This is done in a way that doesn't harm the frogs at all." Only tiny samples are taken before the frogs are released but these are enough to allow the researchers to learn about the proteins released in frog skin and to establish the chemical structure.
Frogs are members of a very ancient family line that includes the amphibians, the water creatures that first ventured on to dry land. They had no fangs or claws to protect them from predators and had soft, easily damaged skins. They had to evolve ways to protect themselves from bacteria, viruses and land animals that saw them as a quick snack.
"They really had to develop a system of protection against predators. It is something that is very ancient and the modern amphibians have retained this," says Prof Shaw. "Biological warfare has been going on in the rain forest for millions of years as each organism living there has fought for its survival. I believe that we can put that biological weaponry to use for the good of humankind in the ultimate defeat of those diseases which have thus far remained intractable," he adds.
He is particularly interested in the peptides found in frog venom, strings of amino acids that provide a wide range of services for the frogs. "Frog skins are a very rich source of peptides." Many of the peptides have powerful biological activity. Some kill off bacteria. Others ward off insect attack. The Coleraine team uses "bioassays" to look for interesting peptides so they can be studied and possibly used against human diseases.
The researchers have already identified a number of peptides that have potential human application. One obtained from the Giant Mexican Leaf Frog, Pachymedusa dacnicolor, has been found to reduce blood pressure by 50 per cent when administered in very low doses in the lab. The same frog also produces a peptide that stops blood from clotting.
These peptides might be useful in drugs designed to reduce blood pressure or to provide a treatment for deep vein thrombosis, the so-called "economy class syndrome".
The African Running Frog produces a venom which paralyses giant insects which prey on it. This might be genetically engineered into food crops to reduce insect attack without the need for pesticides.
A peptide found in a tree frog from Australia is a powerful bactericide that might be useful in killing antibiotic-resistant bacteria. The bacteria "have no resistance to this because the peptide kills them by disrupting the bacterial membrane," said Prof Shaw. The Ulster researchers break down the peptides of interest to establish their active parts. These components can then be synthesised and tested in new treatments. The advance of technology means that the structural analysis of large numbers of peptides that might have taken 12 months can now be done in an afternoon. "You get vast, vast information about the structure of these molecules."
These peptides could have a huge impact on human health, Prof Shaw believes. "We can use the biological weaponry evolved in the frog's venom to fight against cancer, heart disease and neuro-degenerative diseases. I believe the cure for these exist in the rain forest in the molecules that have evolved over millions of years."