New breakthrough links collagen and copper poisoning

3 November 2010

Collagen (stained blue) was much thicker in copper-exposed zoanthids compared to control zoanthids. Photo credit: Dr Adrienne Grant.
Collagen (stained blue) was much thicker in copper-exposed zoanthids compared to control zoanthids. Photo credit: Dr Adrienne Grant.

Research by Dr Adrienne Grant and advanced biology students Lisa Nivison-Smith, David Seung and Haley Bowcock has shown that too much copper can poison marine animals by damaging the collagen in their body wall. The study, published in Comparative Biochemistry and Physiology, is the first ever to identify the exact site of copper-induced damage in a marine animal and to reveal the presence of elastin in invertebrates.

Copper is a common marine pollutant as it is used in antifoulant paints for boats and is also washed into the sea in stormwater. Although, trace amounts of copper are essential for the synthesis of several body proteins, in excess copper is harmful because it causes oxidative damage.

In the marine environment, pollution damage to animals is often assessed by determining the concentration of pollutant that results in 50 % mortality. However, this method does not indicate where the damage has occurred or if is reversible.

Using the zoanthid, Zoanthus robustus, which is a cnidarian with long, flexible tubular bodies, Dr Grant and colleagues were able to pinpoint the exact tissue-type that is damaged by copper.

"We found that when zoanthids were exposed to copper, the body wall became thicker and the outer skin layer became stiff, which meant the zoanthid bodies could no longer stretch and contract," said Dr Grant, lead author on the study.

After examining the zoanthid body tissues using histological techniques, the authors discovered that copper had damaged the collagen in the extracellular matrix (ECM). This damage resulted in contraction of the body wall, which in turn reduced the size of the gastrovascular cavity, causing less water and food to flow into the zoanthid.

"We were also delighted that our study confirmed the presence of elastin in invertebrates for the first time," said Dr Grant. "Along with collagen, the protein elastin contributes to the strength and flexibility of zoanthid bodies."

The link between copper and damage to elastin and collagen, which are common proteins found in many animals, may also shed new light on copper poisoning in humans.

"Another point of interest is that the changes we observed to zoanthid collagen following copper exposure, are similar to those observed in submucosal fibrosis in humans who chew Areca nuts that contain copper. The changes are also similar to the occlusion of human blood vessels observed in atherosclerosis and diabetes," said Dr Grant.

"Zoanthids will provide a useful model for determining the effects of pollutants on other marine invertebrates particularly those that are rich in collagen, for example sponges. As collagen and elastin are proteins that have a slow rate of turnover the damage could be permanent. We plan to monitor the zoanthids to find out if they recover once the copper has been removed.

"And, as cnidarians contain collagens that have been highly conserved throughout multi-cellular animals, they may also provide a practical model for the study of oxidative damage to ECM protein in mammals."

Contact: Carla Avolio

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