Joint pain can exist without inflammation.
The autoimmune antibodies of rheumatoid arthritis, which exist in the joints before the onset of joint inflammation, can cause pain by directly activating the neurons of the pain system, regardless of any inflammatory reaction. A new paradigm according to Swedish researchers.
Results that could facilitate the development of new modalities of non-inflammatory pain treatment, focused on the activation of neurons of the pain system during rheumatoid arthritis or other autoimmune diseases.
The researchers found that the antibodies involved in the autoimmune reaction form so-called immune complexes, which activate the pain via direct stimulation of the Fc-gamma receptor, receptors found on the neurons of the system. pain. "We all know that inflammation is painful," says Camilla Svensson, a professor of physiology at the Karolinska Institute. "But pain can appear before any sign of inflammation in the joints and may remain a problem after its healing.Our goal was to find the explanatory factors" of this process.
After injecting antibodies into the cartilage of mice, his team found that the animals became more sensitive to pain even before they could see any sign of inflammation in the joints. "Antibodies to these immune complexes can directly activate pain neurons" without there being joint inflammation, summarizes Camilla Svensson.
Rheumatoid arthritis is a chronic inflammatory disease of joints that develop in relapses. It is an autoimmune disease, but several immunological, genetic, hormonal or environmental factors are needed to trigger it.
Without treatment, the disease gradually reaches new joints and causes deformity or progressive destruction of the affected joints (often those of the hands and feet). In some rarer forms of the disease, extra-articular manifestations appear, affecting other organs. In France, rheumatoid arthritis affects 0.3 to 0.8% of the adult population, about 200 000 people. It is two to three times more common among women than men.