Androgen Conversion in Osteoarthritis and Rheumatoid Arthritis
Androgen Conversion in Osteoarthritis and Rheumatoid Arthritis
In synovial cells of patients with osteoarthritis (OA) and rheumatoid arthritis (RA), conversion products of major antiinflammatory androgens are as yet unknown but may be proinflammatory. Therefore, therapy with androgens in RA could be a problem. This study was carried out in order to compare conversion products of androgens in RA and OA synoviocytes. In 26 OA and 24 RA patients, androgen conversion in synovial cells was investigated using radiolabeled substrates and analysis by thin-layer chromatography and HPLC. Aromatase expression was studied by immunohistochemistry. Dehydroepiandrosterone (DHEA) was converted into androstenediol, androstenedione (ASD), 16αOH-DHEA, 7αOH-DHEA, testosterone, estrone (E1), estradiol (E2), estriol (E3), and 16αOH-testosterone (similar in OA and RA). Surprisingly, levels of E2, E3, and 16α-hydroxylated steroids were as high as levels of testosterone. In RA and OA, 5α-dihydrotestosterone increased conversion of DHEA into testosterone but not into estrogens. The second androgen, ASD, was converted into 5α-dihydro-ASD, testosterone, and negligible amounts of E1, E2, E3, or 16αOH-testosterone. 5α-dihydro-ASD levels were higher in RA than OA. The third androgen, testosterone, was converted into ASD, 5α-dihydro- ASD, 5α-dihydrotestosterone, and negligible quantities of E1 and E2. 5α-dihydrotestosterone was higher in RA than OA. ASD and testosterone nearly completely blocked aromatization of androgens. In addition, density of aromatase-positive cells and concentration of released E2, E3, and free testosterone from superfused synovial tissue was similar in RA and OA but estrogens were markedly higher than free testosterone. In conclusion, ASD and testosterone might be favorable antiinflammatory compounds because they decrease aromatization and increase anti-inflammatory 5α-reduced androgens. In contrast, DHEA did not block aromatization but yielded high levels of estrogens and proproliferative 16α-hydroxylated steroids. Androgens were differentially converted to pro- and anti-inflammatory steroid hormones via diverse pathways.
Adrenal and gonadal androgens such as dehydroepiandrosterone (DHEA), androstenedione (ASD), and testosterone have anti-inflammatory properties mediated by blocking the secretion of interleukin (IL)-1β, IL-6, tumor necrosis factor (TNF), and other proinflammatory mediators. The more potent, pure androgen 5α-dihydrotestosterone has been found to repress the NFκB-mediated activation of the human IL-6 gene promoter in human fibroblasts, and it also inhibits T cell proliferation. An open, double-blind therapy study with testosterone demonstrated remarkable benefits in patients with RA. As a prerequisite for further therapeutic administration of androgens to patients with RA, it is important to know how androgens can be converted into downstream hormones in affected synovial tissue.
Apart from gonadal cells, different peripheral cells are able to convert androgens into downstream steroid hormone products such as estrogens. Figure 1 demonstrates the complexity of intracellular steroid hormone conversion (intracrinology). In a recent preliminary study in mixed synovial cells of three patients with rheumatoid arthritis (RA) and osteoarthritis (OA), we demonstrated that DHEA can be converted to testosterone, estrone (E1), and 17β-estradiol (E2). In collagen type II arthritic animals, others have demonstrated that DHEA can be converted into the proinflammatory steroid hormone 7αOH-DHEA, due to increased expression of the P450 enzyme CYP7B. This has been confirmed in RA synovial fibroblasts (J Dulos, personal communication). However, unlike in the case of DHEA, it is presently unknown how ASD and testosterone can be converted into downstream hormones in mixed synovial cells of patients with RA, and whether this conversion is different in OA patients. This is important to know because the delta 4 androgens ASD and testosterone are more potent and, thus, may be used in clinical trials in patients with RA. If ASD and testosterone are also converted into more proinflammatory downstream steroid hormones their therapeutic administration may be a problem.
(Enlarge Image)
Complexity of androgen conversion in peripheral Complexity of androgen conversion in peripheral cells. DHEAS, DHEA, and ASD are the major androgen precursors, which are released from the adrenal gland (particularly relevant in postmenopausal women). These androgens enter the peripheral cell to be converted to downstream metabolites using diverse enzyme pathways. 3β-HSD, 3β-hydroxysteroid dehydrogenase (converts delta 5 androgens into delta 4 androgens); 5α-DH, 5α-dihydro; 5-α-R, 5α-reductase; 17β-HSD, 17β-hydroxysteroid dehydrogenase; ADIOL, androstenediol; ASD, androstenedione; AROM, aromatase; DHEA, dehydroepiandrosterone; DHEAS, DHEA sulfate; DST, DHEA sulfotransferase; E1, estrone; E2, 17β-estradiol; E3, 16α-hydroxylated E2 (also known as estriol); OH, hydroxyl group at the indicated position; ST, sulfatase; T, testosterone.
This study was initiated in order to investigate conversion of DHEA, ASD, and testosterone in synovial tissue of patients with RA and OA. We functionally tested hormone conversion in mixed synovial cells of RA and OA patients and tried to find the factors that influence these particular enzyme steps in primary synovial cells. We used mixed primary synovial cells in order to give an in vivo figure of steroid conversion. Furthermore, we studied aromatase expression in synovial tissues of patients with RA and OA.
In synovial cells of patients with osteoarthritis (OA) and rheumatoid arthritis (RA), conversion products of major antiinflammatory androgens are as yet unknown but may be proinflammatory. Therefore, therapy with androgens in RA could be a problem. This study was carried out in order to compare conversion products of androgens in RA and OA synoviocytes. In 26 OA and 24 RA patients, androgen conversion in synovial cells was investigated using radiolabeled substrates and analysis by thin-layer chromatography and HPLC. Aromatase expression was studied by immunohistochemistry. Dehydroepiandrosterone (DHEA) was converted into androstenediol, androstenedione (ASD), 16αOH-DHEA, 7αOH-DHEA, testosterone, estrone (E1), estradiol (E2), estriol (E3), and 16αOH-testosterone (similar in OA and RA). Surprisingly, levels of E2, E3, and 16α-hydroxylated steroids were as high as levels of testosterone. In RA and OA, 5α-dihydrotestosterone increased conversion of DHEA into testosterone but not into estrogens. The second androgen, ASD, was converted into 5α-dihydro-ASD, testosterone, and negligible amounts of E1, E2, E3, or 16αOH-testosterone. 5α-dihydro-ASD levels were higher in RA than OA. The third androgen, testosterone, was converted into ASD, 5α-dihydro- ASD, 5α-dihydrotestosterone, and negligible quantities of E1 and E2. 5α-dihydrotestosterone was higher in RA than OA. ASD and testosterone nearly completely blocked aromatization of androgens. In addition, density of aromatase-positive cells and concentration of released E2, E3, and free testosterone from superfused synovial tissue was similar in RA and OA but estrogens were markedly higher than free testosterone. In conclusion, ASD and testosterone might be favorable antiinflammatory compounds because they decrease aromatization and increase anti-inflammatory 5α-reduced androgens. In contrast, DHEA did not block aromatization but yielded high levels of estrogens and proproliferative 16α-hydroxylated steroids. Androgens were differentially converted to pro- and anti-inflammatory steroid hormones via diverse pathways.
Adrenal and gonadal androgens such as dehydroepiandrosterone (DHEA), androstenedione (ASD), and testosterone have anti-inflammatory properties mediated by blocking the secretion of interleukin (IL)-1β, IL-6, tumor necrosis factor (TNF), and other proinflammatory mediators. The more potent, pure androgen 5α-dihydrotestosterone has been found to repress the NFκB-mediated activation of the human IL-6 gene promoter in human fibroblasts, and it also inhibits T cell proliferation. An open, double-blind therapy study with testosterone demonstrated remarkable benefits in patients with RA. As a prerequisite for further therapeutic administration of androgens to patients with RA, it is important to know how androgens can be converted into downstream hormones in affected synovial tissue.
Apart from gonadal cells, different peripheral cells are able to convert androgens into downstream steroid hormone products such as estrogens. Figure 1 demonstrates the complexity of intracellular steroid hormone conversion (intracrinology). In a recent preliminary study in mixed synovial cells of three patients with rheumatoid arthritis (RA) and osteoarthritis (OA), we demonstrated that DHEA can be converted to testosterone, estrone (E1), and 17β-estradiol (E2). In collagen type II arthritic animals, others have demonstrated that DHEA can be converted into the proinflammatory steroid hormone 7αOH-DHEA, due to increased expression of the P450 enzyme CYP7B. This has been confirmed in RA synovial fibroblasts (J Dulos, personal communication). However, unlike in the case of DHEA, it is presently unknown how ASD and testosterone can be converted into downstream hormones in mixed synovial cells of patients with RA, and whether this conversion is different in OA patients. This is important to know because the delta 4 androgens ASD and testosterone are more potent and, thus, may be used in clinical trials in patients with RA. If ASD and testosterone are also converted into more proinflammatory downstream steroid hormones their therapeutic administration may be a problem.
(Enlarge Image)
Complexity of androgen conversion in peripheral Complexity of androgen conversion in peripheral cells. DHEAS, DHEA, and ASD are the major androgen precursors, which are released from the adrenal gland (particularly relevant in postmenopausal women). These androgens enter the peripheral cell to be converted to downstream metabolites using diverse enzyme pathways. 3β-HSD, 3β-hydroxysteroid dehydrogenase (converts delta 5 androgens into delta 4 androgens); 5α-DH, 5α-dihydro; 5-α-R, 5α-reductase; 17β-HSD, 17β-hydroxysteroid dehydrogenase; ADIOL, androstenediol; ASD, androstenedione; AROM, aromatase; DHEA, dehydroepiandrosterone; DHEAS, DHEA sulfate; DST, DHEA sulfotransferase; E1, estrone; E2, 17β-estradiol; E3, 16α-hydroxylated E2 (also known as estriol); OH, hydroxyl group at the indicated position; ST, sulfatase; T, testosterone.
This study was initiated in order to investigate conversion of DHEA, ASD, and testosterone in synovial tissue of patients with RA and OA. We functionally tested hormone conversion in mixed synovial cells of RA and OA patients and tried to find the factors that influence these particular enzyme steps in primary synovial cells. We used mixed primary synovial cells in order to give an in vivo figure of steroid conversion. Furthermore, we studied aromatase expression in synovial tissues of patients with RA and OA.
