The Deepwater Horizon disaster began on April 20, 2010 with an explosion at an oil drilling rig operated by BP in the Gulf of Mexico, killing 11 workers. Almost immediately, oil began to seep into the waters of the Gulf, an environmental disaster that took months to bring under control, but not before it became the largest oil slick in the history of the petroleum industry.
It’s been nearly 10 years since then, and the oil slick faded long ago. However, despite early predictions, the effects of this oil are still being felt in wildlife in the area, research published in Environmental Toxicology and Chemistry It showed that negative health effects resolved not only on dolphins that were alive at the time of the spill, but also in their young who were born years later.
A team of researchers, including a professor of pathology at UConn University and director of the Sea Grant Sylvain De Guise program, Connecticut College, is part of a network that is conducting a long-term study of the health of dolphins that live in Barataria Bay, Louisiana, in the vicinity of the disaster. This group of dolphins includes individuals who lived during a disaster and some of them were born afterwards.
“We were ready and as quickly as possible, and in 2011 we started a comprehensive health assessment where 60 to 80 people in this field worked together to find a multidisciplinary sample, multiple experiences, and study efforts and follow them safely to assess the health of dolphins,” de Guise says.
De Guise explains that after collection, the samples were processed in 60 to 80 different specialized laboratories, and the researchers then regrouped the information to bring the information together. De Guise’s research group specializes in studying the immune system, and from the first set of samples they began to see consistent and abnormal immune responses in Barataria Bay dolphins, compared to a similar control group of dolphins from Sarasota Bay who were not exposed to oil.
For the Barataria Bay dolphins, the researchers observed immune cells called T cells that were overly responsive to stimulation. The body uses T cells to respond to a stimulus, or something known to be foreign. In particular, there have been increasing numbers of cells called regulatory T cells, or Tregs, which De Guise describes as cells that help put the brakes during the immune response to prevent the body from over-responding and doing more harm than good.
Despite the increasing numbers, De Guise says they were surprised to find that the Barataria Bay dolphin appears to be functionally defective of the Tregs dolphin.
In some ways, the immune response can be viewed almost like a relay race, with cells signaling others to respond and join this effort. In the case of T-helper (Th) cells, important signals called cytokines determine which type of T-helper will be next in the sequence, and for Barataria Bay dolphins the signals are not transmitted as expected.
The T helper cells determine the direction in which your immune system will respond. If you have a pathogen that invades cells, such as a virus, you need a T-helper1 (Th1) response that will destroy the infected cells. If you have a pathogen that does not invade cells, like most types of bacteria, you need to produce antibodies to bind to these bacteria and help eliminate them with the Th2 response, ”says De Guise.
In the lab, researchers studied immune cells from the two groups of dolphins by exposing them to proteins called cytokines that elicit predictable responses from T cells. Researchers also exposed T cells from the dolphin control group to the oil to see what would happen. In all oil-exposed T cell samples, Th2 responses were amplified compared to the control group.
“We were able to demonstrate that there was a difference in response between populations, in both real-life and lab tests, that increased the Th2 response in Barataria Bay dolphins,” De Guise says.
The researchers went one step further by conducting a study in mice to see if a similar immune response could be seen in mice exposed to the oil, and they did.
“The effects we found on the mouse immune system were surprisingly similar to what we saw in dolphins,” says De Guise. “We want to show the possibility of a cause-and-effect relationship and add to the weight of evidence that the oil affects the immune system in a reproducible way across species. The changes we found in the Barataria Bay dolphins are specific to oil and have nothing to do with anything else.”
Although researchers are not sure whether the abnormal immune response was caused by the initial exposure or continued exposure to the oil that is still present in the sediments, De Guise says the finding could lead to dolphins being more susceptible to pathogens such as viruses, due to a dysfunction. T-reg cells. Only future studies can shed light, and De Guise now says that photos of oil spills no longer attract attention, and funding is harder to come by.
However, for this study, De Guise notes that it is very rare to obtain such a long-term, detailed follow-up on a group of wild animals, and the researchers were very surprised to see the effects in the second generation who did not survive. … the disaster.
“The result of this work is that we are not sure whether these effects are reversible or not. The longer we look, they still exist. I think this is the first time that we have found such evidence across generations in a group of wildlife, and that’s scary. It raises concerns about the long-term recovery of these dolphins, “says de Guise. “These are long-lived mammals, and in many ways, they are no different from the humans who live in the area and depend on natural resources. It’s an interesting science, but it’s very frightening.”
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