Synthesis of the active metabolite of vitamin D, 1,25(OH)2D3, by synovial fluid macrophages in arthritic diseases

Article Abstract:

Vitamin D is broken down to 25-hydroxyvitamin D3 in the liver and, then, to either 24,25-dihydroxy-vitamin D3 or 1,25-dihydroxyvitamin D3 in the kidney. The active form, 1,25-dihydroxyvitamin D3 binds to specific protein sites, or receptors, on the cell membrane and controls calcium metabolism in the intestine, bone, and kidneys. Studies have shown that 1,25-dihydroxyvitamin D3 and its receptors are present in joint cells and fluid of patients with joint disorders. In addition, macrophages, immune cells capable of ingesting foreign particles, were shown to produce 1,25-dihydroxyvitamin D3 when activated by certain factors. Such factors include bacterial substances and diseases, such as peritonitis (inflammation of the membrane lining the abdominal organs). Macrophages were taken the joint fluid of patients with various joint disorders, and the ability of the macrophages to produce 1,25-dihydroxyvitamin D3 was examined. 1,25-dihydroxyvitamin D3 was detected in cells from the joint fluid of 20 patients with various joint diseases including inflammatory rheumatoid disease, reactive and psoriatic arthritis, gout, and sterile decay of the lower joints of the thigh bone. Cells from 18 patients with inflammatory arthritis and 6 patients with osteoarthritis, another type of joint disease, were unable to synthesize 1,25-dihydroxyvitamin D3 from 25-hydroxyvitamin D3. Because of their increased numbers and prevalence in samples containing the vitamin D derivative, it is thought that macrophages are responsible for producing 1,25-dihydroxyvitamin D3. (Consumer Summary produced by Reliance Medical Information, Inc.)

Causes of, Vitamin metabolism, Vitamin D metabolism

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Possible clearance of effete polymorphonuclear leucocytes from synovial fluid by cytophagocytic mononuclear cells: implications for pathogenesis and chronicity in inflammatory arthritis

Article Abstract:

Programmed cell death of polymorphonuclear leukocytes (PMNLs) may play a role in the formation of cytophagocytic mononuclear cells (CPMs) in synovial fluid. The accumulation of PMNLs in synovial fluid is characteristic of all forms of inflammatory arthritis. The enzymes released by PMNLs appear to mediate joint destruction and inflammation. CPMs are phagocytic cells that contain whole or partial PMNLs. Of 187 samples of synovial fluid, 71 contained CPMs and 116 did not. CPMs were detected in 75% of samples from patients with reactive arthritis and in about 60% of samples from patients with septic arthritis, spondyloarthritis, Reiter's syndrome and gout. CPMs were not seen in samples from patients with non-inflammatory arthritis. There was a significant correlation between the number of PMNLs undergoing cell death and the number of CPMs present. Along with previous studies, these findings suggest that PMNLs undergo programmed cell death which triggers engulfment by phagocytic cells and the subsequent formation of CPMs.

Analysis, Cell death, Neutrophils, Synovial fluid

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Autocrine control of vitamin D metabolism in synovial cells from arthritic patients

Article Abstract:

A variation of vitamin D is produced by macrophages in laboratory experiments which duplicate living body conditions in terms of concentration of substances. The D vitamin can increase its own process of breaking down complex compounds into simpler ones by use of the fibroblasts found in the joint spaces. Furthermore, the specific mechanism of mediation seems to have be identified.

Fibroblasts

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