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New Findings Show Environmental Influences Can Aggravate Disease

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Aug. 5, 2002 -- Environmental factors have long been thought to help trigger lupus in people who are genetically predisposed to get the disease. Now researchers have identified just such an environmental trigger in mice, and it may help them understand the causes of lupus in humans.

The findings provide some of the best direct evidence yet that environmental influences play a role in the onset and advancement of lupus, an autoimmune disorder that causes the body's immune system to attack healthy tissue, resulting in a wide range of symptoms including kidney disease, arthritis, fatigue, joint pain, and anemia.

In this study, reported by University of Florida researchers in the August issue of the journal Arthritis and Rheumatism, mice predisposed to develop the disease got sick and died much quicker when they were injected with a component of mineral oil known as pristane.

Although there is no evidence that pristane causes lupus in humans, it has been shown to induce inflammatory disease when absorbed through the respiratory or gastrointestinal tract. Researcher Westley H. Reeves, MD, says the latest findings may help unravel the mystery of why some genetically predisposed people get lupus while others do not.

"We are not saying that mineral oil causes lupus in humans," Reeves tells WebMD. "That would be highly speculative. But if we are able to identify the environmental components in humans that act the way pristane does in mice, we may be able to reduce the probability that someone who is prone to lupus will actually get it." Reeves is chief of rheumatology at the University of Florida College of Medicine.

In the study, mice genetically engineered to develop lupus were injected with either pristane or salt water. As anticipated, all of the predisposed mice developed lupus-specific antibodies, but the mice injected with pristane developed more antibodies more quickly. Disease symptoms were also dramatically accelerated in the pristane-injected mice - 75% died within six months of injection, compared to just 9% of mice injected with the saline solution.

The findings suggest that environmental factors play a bigger role in the development of lupus than has generally been believed, says researcher Hideo Yoshida. Isolating those environmental factors and either avoiding them or treating for them may turn out to be a relatively simple way to prevent or manage the autoimmune disorder.

"We know that the genetic components of lupus are pretty complicated, and there is not much that we can do about them right now," Reeves says. "The environmental components, however, are something that we might be able to change."

It is not clear how many Americans have lupus. Estimates ranged from 240,000 to 4 million, but the Lupus Foundation of America puts the figure at 1.4 million. Women are nine times more likely to develop lupus than men. Autoimmune disease expert Charles Helmick, MD, of the CDC says a national registry is needed to get a better handle on just who has lupus and whether more people are getting it than in the past.

In a study published last May, Helmick and colleagues reported that women are five times more likely to die of lupus than men, and that the number of African American women who die from the disease has increased by 70% over the last two decades.

But Helmick tells WebMD that it is unclear whether more women are actually dying or whether the increase is due to better diagnosis.

"We need to develop a better understanding about just how many people have lupus so that we will know what these figures mean," he says. "A population registry would help us figure out what is going on throughout the United States."

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