Ankylosing spondylitis (AS) is a disease with increased bone resorption and formation in areas of chronic inflammation. There is mainly involvement of the sacroiliac joints and of the spine. This present study was done to identify the proteins involved in the synovial membranes of patients with AS, rheumatoid arthritis (RA,) and osteoarthritis (OA,) to compare them. The tissues were obtained from hip joint replacement surgery in 10 patients.
Carbonic anhydrase 1 (CA1) enzyme is involved with normal calcification and bone formation. It is known that CA1 is a catalyst for the production of bicarbonate (HCO3) by combining water (H2O) and carbon dioxide (CO2.) The HCO3 is combined with calcium ion to form a calcium carbonate (CaCO3) precipitate for bone formation. Normal bone is formed from CaCO3 and calcium phosphate.
Increased bone resorption is seen with AS. CA1 is necessary for the bone resorption to occur. CA inhibitors have been known to reduce the increased bone resorption in arthritis in rats.
Peptides were extracted from the synovial tissues taken from patients during hip surgery. Carbonic anhydrase extract was extracted from the peptides for measurements and comparisons between OA, RA, and AS.
The results of the study showed that the synovial membranes of AS patients had significant increases in carbonic anhydrase 1 (CA1) expression. The results were very reproducible. This results in a thickening of the synovial membranes. The ultimate result is fusion of the axial skeleton in AS.
It has been shown that CaCO3 production is reduced by CA1 inhibitors such as EDTA and acetazolamide. These were not evaluated in the present study.
CONCLUSION: Carbonic anhydrase 1 overproduction in the synovial tissues is seen and may be the cause of ankylosing spondylitis. Overexpression of CA1 in the synovial tissues plays a role in abnormal bone resorption and bone formation.
NOTE: Synovial tissues are the soft tissues that line bony joints.
Bone resorption and formation is an ongoing process of normal bone maintenance. The rate of this process is altered in ankylosing spondylitis.
Natural products, resveratrol, catechins, curcumin, and silymarin are good inhibitors of carbonic anhydrase I and II. Acetazolamide (diamox) is a pharmaceutical carbonic anhydrase inhibitor. Read about carbonic anhydrase inhibitors for glaucoma.