Endocrine Abstracts

In chronic inflammatory disease, an increased proportion of M1 polarised macrophages have been shown to contribute to inflammation and tissue damage through the production of pro-inflammatory cytokines such as TNFα. Previously, we have identified expression of the enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1), which converts inactive glucocorticoids (GCs) to their active counterparts, in M1 polarised macrophages in vivo. We hypothesised that 11β-HSD1 plays an important role in regulating M1 macrophage polarisation and function. Primary human monocytes were isolated from blood using CD14 positive-selection, and their purity assessed by FACS. Monocytes were differentiated into M1- or M2-polarised macrophages using GM-CSF or M-CSF respectively (both 50 ng/ml) before being stimulated with IFNγ (50 ng/ml) and LPS (10 ng/ml) for activated M1 or IL-4 (20 ng/ml) for activated M2. Macrophage polarisation and inflammatory gene expression were assessed by RT-PCR and steroid metabolism determined by thin layer scanning chromatography. TNFα secretion was assessed using ELISA. The macrophage marker CD68 was highly expressed in all macrophage cultures, whilst the M1 marker FcγRIB was greatly increased in M1 polarised macrophages following stimulation with IFNγ and LPS. Significant levels of GC activation by 11β-HSD1 were detected in M1 polarised cultures but were significantly lower in M2 counterparts (M1 polarised: 5.73±2.6 pmol/mg per hr vs M2 polarised: 1.35±0.75 pmol/mg per hr, P≤0.01). Pro-inflammatory gene expression of IL-6 and TNFα were greatly increased in M1 polarised macrophages, where they were potently suppressed following incubation with the endogenous glucocorticoid cortisol (100 nmol/l). Similar suppression of TNFα was observed using ELISA in M1 macrophages (M1 stimulated; 337.6±190.5 pg/ml vs M1 stimulated/cortisol; 88.6±123.01 pg/ml, P≤0.01). These findings emphasise differences in 11β-HSD1 expression between different macrophage subtypes and highlight a possible role for this enzyme in regulating inflammatory macrophage polarisation and function in chronic inflammatory disease.