SAN FRANCISCO -- Finding out how the nervous and immune systems interact to cause inflammation and joint damage may lead to new treatments for arthritis to replace the current crop of broad-acting drugs that often are ineffective and toxic, researchers said Tuesday.
'We are finding inflammation can be beneficial or destructive,' Dr. Jon Levine, a rheumatologist at the University of California, San Francisco, said at the annual meeting of the American Association for the Advancement of Science.
'In arthritis, more precisely targeted drugs may promote beneficial aspects of inflammation -- swelling, for example -- and dampen detrimental aspects, such as pain,' he said.
Arthritis causes the body to eat away at its own cartilage and bone until joints no longer function. One of the most severe forms of the autoimmune disorder is rheumatoid arthritis, which affects more than 2 million Americans, most of them women.
While the nervous system probably does not cause the disease, it alters the environment of pain-regulating chemicals in joints, affecting the severity and perhaps, the persistence of the disease.
Levine and his team found evidence that swelling, which is an inflammatory response, helps prevent joint damage in people with arthritis.
They discovered that not only sensory nerves but also nerves of the sympathetic nervous system -- best known for the adrenaline-rush response of increased heartbeat, blood pressure and respiration -- are important in the disease.
Drugs that block the hormone adrenaline from acting in the joints increase swelling and reduce pain in humans, as well as decreasing tissue injury in rats, the researchers found.
'Pain is one of the best predictors of how a patient with arthritis will do,' said Levine, who is searching for drugs that may reduce the impact of specific pain-causing chemicals involved in arthritis.
Aspirin and similar drugs are not always effective, and other therapies -- such as cortisone -- may have serious side effects, he said.