Inflammation: What can deep-diving seals teach us?

As scientists dig deeper into inflammation, its role in health and disease is coming into focus. A new study investigates the lungs of deep-diving seals and provides new insight.

Although inflammation is not inherently bad — it is a way for the body to protect itself from further damage and speed up healing — when it runs off the leash, it can cause more harm than good.

With a role in seemingly unrelated diseases, such as diabetes, schizophrenia, and autoimmune conditions, the race is on for scientists to understand how they might reign in this process.

Although they are slowly unpicking the mechanisms behind inflammation, researchers still have much more work to do.

As part of this search, they are looking in unusual places. For instance, a recent study, published in the Journal of Experimental Biology, takes a long hard look at the lungs of marine mammals.

Studying deep divers

A team of investigators based at a number of institutions across the United States decided to investigate two particular pinnipeds: the elephant and Weddell seals.

Weddell seals can dive to depths of over 600 meters, and elephant seals have been recorded descending well over 2 kilometers. At those depths, the water pressure around the seal is around 240 times greater than air pressure at sea level.

Among the array of physiological challenges that deep diving presents, the lungs take a significant battering. During a dive, to prevent the absorption of nitrogen, the seal's lungs collapse, crushing tissues; then, on their return to the surface, blood rushes back in at incredible speeds.

In most mammals, this type of treatment of sensitive tissues causes widespread damage. However, according to the authors of this intriguing study, "There is no evidence that diving damages pulmonary function in these species."

Led by Allyson Hindle of Harvard Medical School in Boston, MA, and Milton Levin of the University of Connecticut in Storrs, the scientists wanted to understand more about how seals deal with such extreme pulmonary events. Specifically, they wanted to understand whether a reduced inflammatory response might provide protection.

Challenging seal lungs

To test their theory, they applied a lipopolysaccharide — a bacterial toxin — to seal blood samples; this endotoxin produces a reliable, robust immune response in vertebrates. In most animals, such an affront would cause inflammation; in the seal blood, however, there was barely any response. When the same toxin was added to human blood, the reaction was 50–500 times stronger.

Next, they added seal serum to immune cells taken from mice; the serum significantly reduced the inflammatory response to the toxin. The authors write:

"These data suggest that seal serum possesses anti-inflammatory properties, which may protect deep divers from naturally occurring inflammatory challenges, such as dive-induced hypoxia-deoxygenation and lung collapse."

Researchers hope that this line of investigation might lead to medical interventions beyond the protection of divers' lungs. For instance, it might one day be used to extend the lifespan of transplanted organs and help treat acute lung injuries.

Much more work will be needed before we understand which components of the serum carry these miraculous anti-inflammatory powers, but the findings are exciting. In the future, once the active ingredients are identified, another piece of the inflammatory puzzle will be added.