Magazine article Science News

Origins of Ache: Immune Proteins May Yield Chronic-Pain Clues

Magazine article Science News

Origins of Ache: Immune Proteins May Yield Chronic-Pain Clues

Article excerpt

In people with chronic pain that has no obvious cause, chemical messengers that rev up or slow down inflammation are often out of balance, a new study finds. These proteins, called cytokines, are made predominantly by immune cells.

Millions of people have chronic pain without any known injury or disease, a condition sometimes called fibromyalgia syndrome. Diagnostic tests are unreliable and treatments are often unsatisfactory, says Claudia Sommer, a neurologist at the University of Wurzburg in Germany. To assess whether cytokines influence such chronic pain, she and her colleagues identified 40 people who had endured unexplained chronic pain for an average of 14 years. Most had symptoms that fit the description of fibromyalgia.

The scientists compared blood samples from these patients with samples from 40 people without pain who matched them in age and gender. All the people--with or without chronic pain--had similar complements of three inflammation-causing cytokines, says Sommer.

However, the team found that compared with the others, the people with chronic pain were low on two anti-inflammatory cytokines: interleukin-4 and interleukin-10. The scientists next enlisted 15 more people with chronic pain who were taking pain medications different from those taken by the first 40 patients. The new group showed the same shortages of interleukin-4 and interleukin-10 that the original group of pain patients showed. The findings appear in the August Arthritis & Rheumatism.

Chronic pain can be impervious to treatment with many analgesics, including narcotics. Some research has suggested that interleukin-4 regulates cells' capacity to display receptors for morphine, codeine, or other opioids.

"It is possible that the patients we examined ... have a lack of opioid response through [this] mechanism," Sommer says. …

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