Inflammation dynamically regulates steroid hormone metabolism and action within macrophages in rheumatoid arthritis.

RATIONALE: In inflammatory diseases such as rheumatoid arthritis (RA), steroid metabolism is a central component mediating the actions of immuno-modulatory glucocorticoids and sex steroids. However, the regulation and function of cellular steroid metabolism within key leukocyte populations such as macrophages remain poorly defined. In this study, the inflammatory regulation of global steroid metabolism was assessed in RA macrophages. METHODS: Bulk RNA-seq data from RA synovial macrophages was used to assess transcripts encoding key enzymes in steroid metabolism and signalling. Changes in metabolism were assessed in synovial fluids, correlated to measures of disease activity and functionally validated in primary macrophage cultures. RESULTS: RNA-seq revealed a unique pattern of differentially expressed genes, including changes in genes encoding the enzymes 11ß-HSD1, SRD5A1, AKR1C2 and AKR1C3. These correlated with disease activity, favouring increased glucocorticoid and androgen levels. Synovial fluid 11ß-HSD1 activity correlated with local inflammatory mediators (TNFα, IL-6, IL-17), whilst 11ß-HSD1, SRD5A1 and AKR1C3 activity correlated with systemic measures of disease and patient pain (ESR, DAS28 ESR, global disease activity). Changes in enzyme activity were evident in inflammatory activated macrophages in vitro and revealed a novel androgen activating role for 11ß-HSD1. Together, increased glucocorticoids and androgens were able to suppress inflammation in macrophages and fibroblast-like-synoviocytes. CONCLUSIONS: This study underscores the significant increase in androgen and glucocorticoid activation within inflammatory polarized macrophages of the synovium, contributing to local suppression of inflammation. The diminished profile of inactive steroid precursors in postmenopausal women may contribute to disturbances in this process, leading to increased disease incidence and severity.

11ß-HSD1 plays a critical role in trabecular bone loss associated with systemic glucocorticoid therapy.

BACKGROUND: Despite their efficacy in the treatment of chronic inflammation, the prolonged application of therapeutic glucocorticoids (GCs) is limited by significant systemic side effects including glucocorticoid-induced osteoporosis (GIOP). 11ß-Hydroxysteroid dehydrogenase type 1 (11ß-HSD1) is a bi-directional enzyme that primarily activates GCs in vivo, regulating tissue-specific exposure to active GC. We aimed to determine the contribution of 11ß-HSD1 to GIOP. METHODS: Wild type (WT) and 11ß-HSD1 knockout (KO) mice were treated with corticosterone (100 µg/ml, 0.66% ethanol) or vehicle (0.66% ethanol) in drinking water over 4 weeks (six animals per group). Bone parameters were assessed by micro-CT, sub-micron absorption tomography and serum markers of bone metabolism. Osteoblast and osteoclast gene expression was assessed by quantitative RT-PCR. RESULTS: Wild type mice receiving corticosterone developed marked trabecular bone loss with reduced bone volume to tissue volume (BV/TV), trabecular thickness (Tb.Th) and trabecular number (Tb.N). Histomorphometric analysis revealed a dramatic reduction in osteoblast numbers. This was matched by a significant reduction in the serum marker of osteoblast bone formation P1NP and gene expression of the osteoblast markers Alp and Bglap. In contrast, 11ß-HSD1 KO mice receiving corticosterone demonstrated almost complete protection from trabecular bone loss, with partial protection from the decrease in osteoblast numbers and markers of bone formation relative to WT counterparts receiving corticosterone. CONCLUSIONS: This study demonstrates that 11ß-HSD1 plays a critical role in GIOP, mediating GC suppression of anabolic bone formation and reduced bone volume secondary to a decrease in osteoblast numbers. This raises the intriguing possibility that therapeutic inhibitors of 11ß-HSD1 may be effective in preventing GIOP in patients receiving therapeutic steroids.

Therapeutic glucocorticoids prevent bone loss but drive muscle wasting when administered in chronic polyarthritis.

BACKGROUND: Patients with rheumatoid arthritis (RA) experience extra-articular manifestations including osteoporosis and muscle wasting, which closely associate with severity of disease. Whilst therapeutic glucocorticoids (GCs) reduce inflammation in RA, their actions on muscle and bone metabolism in the context of chronic inflammation remain unclear. We utilised the TNF-tg model of chronic polyarthritis to ascertain the impact of therapeutic GCs on bone and muscle homeostasis in the context of systemic inflammation. METHODS: TNF-tg and wild-type (WT) animals received either vehicle or the GC corticosterone (100 µg/ml) in drinking water at onset of arthritis. Arthritis severity and clinical parameters were measured, serum collected for ELISA and muscle and bone biopsies collected for µCT, histology and mRNA analysis. In vivo findings were examined in primary cultures of osteoblasts, osteoclasts and myotubes. RESULTS: TNF-tg mice receiving GCs showed protection from inflammatory bone loss, characterised by a reduction in serum markers of bone resorption, osteoclast numbers and osteoclast activity. In contrast, muscle wasting was markedly increased in WT and TNF-tg animals receiving GCs, independently of inflammation. This was characterised by a reduction in muscle weight and fibre size, and an induction in anti-anabolic and catabolic signalling. CONCLUSIONS: This study demonstrates that when given in early onset chronic polyarthritis, oral GCs partially protect against inflammatory bone loss, but induce marked muscle wasting. These results suggest that in patients with inflammatory arthritis receiving GCs, the development of interventions to manage deleterious side effects in muscle should be prioritised.

11 Beta-hydroxysteroid dehydrogenase type 1 regulates synovitis, joint destruction, and systemic bone loss in chronic polyarthritis.

OBJECTIVE: In rheumatoid arthritis, the enzyme 11 beta-hydroxysteroid dehydrogenase type 1 (11ß-HSD1) is highly expressed at sites of inflammation, where it converts inactive glucocorticoids (GC) to their active counterparts. In conditions of GC excess it has been shown to be a critical regulator of muscle wasting and bone loss. Here we examine the contribution of 11ß-HSD1 to the pathology of persistent chronic inflammatory disease. METHODS: To determine the contribution of 11ß-HSD1 to joint inflammation, destruction and systemic bone loss associated with persistent inflammatory arthritis, we generated mice with global and mesenchymal specific 11ß-HSD1 deletions in the TNF-transgenic (TNF-tg) model of chronic polyarthritis. Disease severity was determined by clinical scoring. Histology was assessed in formalin fixed sections and fluorescence-activated cell sorting (FACS) analysis of synovial tissue was performed. Local and systemic bone loss were measured by micro computed tomography (micro-CT). Measures of inflammation and bone metabolism were assessed in serum and in tibia mRNA. RESULTS: Global deletion of 11ß-HSD1 drove an enhanced inflammatory phenotype, characterised by florid synovitis, joint destruction and systemic bone loss. This was associated with increased pannus invasion into subchondral bone, a marked polarisation towards pro-inflammatory M1 macrophages at sites of inflammation and increased osteoclast numbers. Targeted mesenchymal deletion of 11ß-HSD1 failed to recapitulate this phenotype suggesting that 11ß-HSD1 within leukocytes mediate its protective actions in vivo. CONCLUSIONS: We demonstrate a fundamental role for 11ß-HSD1 in the suppression of synovitis, joint destruction, and systemic bone loss. Whilst a role for 11ß-HSD1 inhibitors has been proposed for metabolic complications in inflammatory diseases, our study suggests that this approach would greatly exacerbate disease severity.