CYP7B expression and activity in fibroblast-like synoviocytes from patients with rheumatoid arthritis: regulation by proinflammatory cytokines.
OBJECTIVE
The cytochrome P450 enzyme CYP7B catalyzes the conversion of dehydroepiandrosterone (DHEA) into 7alpha-hydroxy-DHEA (7alpha-OH-DHEA). This metabolite can stimulate the immune response. We previously reported that the severity of murine collagen-induced arthritis is correlated with CYP7B messenger RNA (mRNA) expression and activity in the arthritic joint. The purpose of this study was to investigate the presence of 7alpha-OH-DHEA in synovial samples and the cytokine regulation of CYP7B activity in fibroblast-like synoviocytes (FLS) from patients with rheumatoid arthritis (RA).


METHODS
The presence of 7alpha-OH-DHEA was examined in synovial biopsy tissues, synovial fluid, and serum by radioimmunoassay. The effect of cytokines on CYP7B mRNA expression and CYP7B activity in FLS was examined by determining the formation of the CYP7B enzyme product 7alpha-OH-DHEA with the use of high-performance liquid chromatography.


RESULTS
The CYP7B enzyme product 7alpha-OH-DHEA was found in synovial biopsy tissues, synovial fluid, and serum from RA patients. The proinflammatory cytokines tumor necrosis factor alpha (TNFalpha), interleukin-1alpha (IL-1alpha), IL-1beta, and IL-17 up-regulated CYP7B activity in an FLS cell line 2-10-fold. Enhanced CYP7B activity was correlated with an increase in CYP7B mRNA. The cytokine transforming growth factor beta inhibited CYP7B activity. Moreover, CYP7B activity was detected in 10 of 13 unstimulated synovial fibroblast cell lines. Stimulation with TNFalpha increased CYP7B activity in all cell lines tested.


CONCLUSIONS
Exposure to the proinflammatory cytokines TNFalpha, IL-1alpha, IL-1beta, and IL-17 increases CYP7B activity in synovial tissue. Increased CYP7B activity leads to higher levels of the DHEA metabolite 7alpha-OH-DHEA in synovial fluid, which may contribute to the maintenance of the chronic inflammation observed in RA patients.
Dulos
John
J
University Medical Center Utrecht, The Netherlands. John.Dulos@Organon.com <John.Dulos@Organon.com>
van der Vleuten
Monique A J
MA
Kavelaars
Annemieke
A
Heijnen
Cobi J
CJ
Boots
Annemieke M
AM
D001172:Arthritis, Rheumatoid / Q000276:immunology*; D002460:Cell Line; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis* / Q000276:immunology; D000072474:Cytochrome P450 Family 7; D016207:Cytokines / Q000276:immunology / Q000502:physiology; D003687:Dehydroepiandrosterone / Q000031:analogs & derivatives* / Q000276:immunology* / Q000378:metabolism; D015536:Down-Regulation; D006801:Humans; D007375:Interleukin-1 / Q000502:physiology; D016753:Interleukin-10 / Q000502:physiology; D013250:Steroid Hydroxylases / Q000096:biosynthesis* / Q000276:immunology; D013582:Synovial Fluid / Q000378:metabolism; D013583:Synovial Membrane / Q000166:cytology / Q000276:immunology*; D016212:Transforming Growth Factor beta / Q000502:physiology; D014409:Tumor Necrosis Factor-alpha / Q000502:physiology; D015854:Up-Regulation
D016207:Cytokines; D007375:Interleukin-1; D016212:Transforming Growth Factor beta; D014409:Tumor Necrosis Factor-alpha; D016753:Interleukin-10; D003687:Dehydroepiandrosterone; C003587:7-hydroxydehydroepiandrosterone; D003577:Cytochrome P-450 Enzyme System; D013250:Steroid Hydroxylases; C115867:oxysterol 7-alpha-hydroxylase; D000072474:Cytochrome P450 Family 7; C499571:CYP7B1 protein, human