Background Aromatases increase estrogen synthesis in inflammatory tissues whereas vitamin D (calcitriol, 1,25-dihydroxyvitamin D3, 1,25(OH)2D3) seems to decrease the aromatase expression at least in human cancer cells (BCa cells) (1). Interestingly, the aromatase activity is increased together with the estrogen synthesis in the synovial tissue of rheumatoid arthritis (RA) patients, especially at the level of macrophages (2-4).
Objectives To evaluate in cultures of human activated macrophages the influence exerted by calcitriol on aromatase expression, as a new target for 1,25(OH)2D3cell modulation of proinflammatory cytokine production (5).
Methods Cultures of human monocytic THP-1 were activated to macrophages and treated for 24 hours with 1,25(OH)2D3 (10-8M), alone or in combination with 17b-estradiol (E2, 10-8M), in order to evaluate the effects on the intracrine estrogen metabolism (aromatase-driven) and cytokine synthesis. Untreated human macrophages were used as controls (basal condition). P450-aromatase synthesis was evaluated by immunocytochemistry (ICC) and western blot analysis (WB). The expression of P450-aromatase gene (CYP19A1) was investigated by real-time PCR (RT-PCR). Macrophage proinflammatory cytokines IL1-β, IL-6 and TNF-α were evaluated by ELISA and WB.
Results Interestingly, 1,25(OH)2D3 downregulated P450-aromatase synthesis, CYP19A1-gene expression, and proinflammatory cytokine production (IL1-β, IL-6 and TNF-α) in basal conditions when compared to 1,25(OH)2D3-untreated macrophages. However and interestingly, the treatment with 1,25(OH)2D3significantly reduced the increase in P450-aromatase (p<0.001), CYP19A1 gene expression (p<0.001) as well as IL-1bβ, IL-6, TNF-α production (p<0.001) induced by estrogen treatment vs. estrogen-treated (but 1,25(OH)2D3-untreated) macrophages.
Conclusions Our data suggest that 1,25(OH)2D3 may downregulate the proinflammatory cytokine production in human activated macrophages by significantly decreasing the aromatase activity, especially in presence of an enhancing estrogenic milieu. Interestingly, this latter hormonal metabolic condition is observed in the synovial tissue and fluid of RA patients of both sexes (2,3).
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Disclosure of Interest None Declared
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