- FRIDAY, Aug. 22 (HealthDay News) — New details about how
rheumatoid arthritis destroys bone have been uncovered by University of
Rochester Medical Center researchers, who said their findings are already
helping efforts to create new drugs to reverse the process.

Rheumatoid arthritis, an autoimmune disease that affects about two
million Americans, causes swelling, pain and deformity in joints and also
thins bone.

Overproduction of the immune system chemical tumor necrosis factor
alpha (TNF alpha) leads to the destruction of cartilage and bone in
rheumatoid arthritis patients. Along with controlling immune cells, TNF
alpha also influences bone mass. It's known that TNF alpha decreases the
number of bone-building cells called osteoblasts, but how it does this
hasn't been clear.

In experiments with mice, the University of Rochester team found that
TNF alpha affects osteoblasts through an enzyme called Smad Ubiquitin
Regulatory Factor 1 (Smurf1) which, in turn, turns off two proteins that
drive bone-building.

“The significance of our study is that it identifies Smurf1 as the
signaling partner through which TNF does its damage in RA-related bone
loss,” Lianping Xing, assistant professor of pathology and laboratory
medicine, said in a university news release.

Xing said the finding “enables us to begin designing small molecule
drugs to shut down the action of Smurf1 and its relatives. Furthermore,
since mice engineered to have less Smurf1 develop thicker bones, future
drugs that shut down Smurf1 may be also useful against more common forms
of osteoporosis simply by changing the dose. Of course, this is early
stage work with many obstacles ahead, but is exciting nonetheless.”

The study was published in the Aug. 22 issue of The Journal of
Biological Chemistry.

More information

The Arthritis Foundation has more about rheumatoid arthritis.