Agnes E. Coutinho

The anti-inflammatory and immunosuppressive effects of glucocorticoids, recent developments and mechanistic insights

Since the discovery of glucocorticoids in the 1940s and the recognition of their anti-inflammatory effects, they have been amongst the most widely used and effective treatments to control inflammatory and autoimmune diseases. However, their clinical efficacy is compromised by the metabolic effects of long-term treatment, which include osteoporosis, hypertension, dyslipidaemia and insulin resistance/type 2 diabetes mellitus. In recent years, a great deal of effort has been invested in identifying compounds that separate the beneficial anti-inflammatory effects from the adverse metabolic effects of glucocorticoids, with limited effect. It is clear that for these efforts to be effective, a greater understanding is required of the mechanisms by which glucocorticoids exert their anti-inflammatory and immunosuppressive actions. Recent research is shedding new light on some of these mechanisms and has produced some surprising new findings. Some of these recent developments are reviewed here.

Local amplification of glucocorticoids by 11 beta-hydroxysteroid dehydrogenase type 1 promotes macrophage phagocytosis of apoptotic leukocytes.

Glucocorticoids promote macrophage phagocytosis of leukocytes undergoing apoptosis. Prereceptor metabolism of glucocorticoids by 11β-hydroxysteroid dehydrogenases (11β-HSDs) modulates cellular steroid action. 11β-HSD type 1 amplifies intracellular levels of active glucocorticoids in mice by reactivating corticosterone from inert 11-dehydrocorticosterone in cells expressing the enzyme. In this study we describe the rapid (within 3 h) induction of 11β-HSD activity in cells elicited in the peritoneum by a single thioglycolate injection in mice. Levels remained high in peritoneal cells until resolution. In vitro experiments on mouse macrophages demonstrated that treatment with inert 11-dehydrocorticosterone for 24 h increased phagocytosis of apoptotic neutrophils to the same extent as corticosterone. This effect was dependent upon 11β-HSD1, as 11β-HSD1 mRNA, but not 11β-HSD2 mRNA, was expressed in these cells; 11-dehydrocorticosterone was ineffective in promoting phagocytosis by Hsd11b1−/− macrophages, and carbenoxolone, an 11β-HSD inhibitor, prevented the increase in phagocytosis elicited in wild-type macrophages by 11-dehydrocorticosterone. Importantly, as experimental peritonitis progressed, clearance of apoptotic neutrophils was delayed in Hsd11b1−/− mice. These data point to an early role for 11β-HSD1 in promoting the rapid clearance of apoptotic cells during the resolution of inflammation and indicate a novel target for therapy.

The role and regulation of 11β-hydroxysteroid dehydrogenase type 1 in the inflammatory response

Cortisone, a glucocorticoid hormone, was first used to treat rheumatoid arthritis in humans in the late 1940s, for which Hench, Reichstein and Kendall were awarded a Nobel Prize in 1950 and which led to the discovery of the anti-inflammatory effects of glucocorticoids. To be effective, the intrinsically inert cortisone must be converted to the active glucocorticoid, cortisol, by the intracellular action of 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1). Whilst orally administered cortisone is rapidly converted to the active hormone, cortisol, by first pass metabolism in the liver, recent work has highlighted an anti-inflammatory role for 11beta-HSD1 within specific tissues, including in leukocytes. Here, we review recent evidence pertaining to the anti-inflammatory role of 11beta-HSD1 and describe how inhibition of 11beta-HSD1, as widely proposed for treatment of metabolic disease, may impact upon inflammation. Finally, the mechanisms that regulate 11beta-HSD1 transcription will be discussed.

11β-Hydroxysteroid Dehydrogenase Type 1, But Not Type 2, Deficiency Worsens Acute Inflammation and Experimental Arthritis in Mice

Glucocorticoids profoundly influence immune responses, and synthetic glucocorticoids are widely used clinically for their potent antiinflammatory effects. Endogenous glucocorticoid action is modulated by the two isozymes of 11β-hydroxysteroid dehydrogenase (11β-HSD). In vivo, 11β-HSD1 catalyzes the reduction of inactive cortisone or 11-dehydrocorticosterone into active cortisol or corticosterone, respectively, thereby increasing intracellular glucocorticoid levels. 11β-HSD2 catalyzes the reverse reaction, inactivating intracellular glucocorticoids. Both enzymes have been postulated to modulate inflammatory responses. In the K/BxN serum transfer model of arthritis, 11β-HSD1-deficient mice showed earlier onset and slower resolution of inflammation than wild-type controls, with greater exostoses in periarticular bone and, uniquely, ganglion cysts, consistent with greater inflammation. In contrast, K/BxN serum arthritis was unaffected by 11β-HSD2 deficiency. In a distinct model of inflammation, thioglycollate-induced sterile peritonitis, 11β-HSD1-deficient mice had more inflammatory cells in the peritoneum, but again 11β-HSD2-deficient mice did not differ from controls. Additionally, compared with control mice, 11β-HSD1-deficient mice showed greater numbers of inflammatory cells in pleural lavages in carrageenan-induced pleurisy with lung pathology consistent with slower resolution. These data suggest that 11β-HSD1 limits acute inflammation. In contrast, 11β-HSD2 plays no role in acute inflammatory responses in mice. Regulation of local 11β-HSD1 expression and/or delivery of substrate may afford a novel approach for antiinflammatory therapy.

Changing glucocorticoid action: 11β-Hydroxysteroid dehydrogenase type 1 in acute and chronic inflammation

Highlights ► 11β-HSD1 converts inert glucocorticoids into active forms, amplifying glucocorticoid action. ► 11β-HSD1 is markedly induced by pro-inflammatory cytokines. ► 11β-HSD1 deficiency/inhibition worsens acute inflammation. ► 11β-HSD1 inhibition reduces inflammation in obesity or atherosclerosis. ► An increased angiogenic response may underlie some of the benefits.

Local Amplification of Glucocorticoids by 11β‐Hydroxysteroid Dehydrogenase Type 1 and Its Role in the Inflammatory Response

Abstract:  Glucocorticoids are widely used to treat chronic inflammatory conditions including rheumatoid arthritis. They promote mechanisms important for normal resolution of inflammation, notably macrophage phagocytosis of leukocytes undergoing apoptosis. Prereceptor metabolism of glucocorticoids by 11β‐hydroxysteroid dehydrogenase type 1 (11β‐HSD1) amplifies intracellular levels of glucocorticoids by oxoreduction of intrinsically inert cortisone (in humans, 11‐dehydrocorticosterone in mice) into active cortisol (corticosterone in mice) within cells expressing the enzyme. Recently, we have shown in a mouse model of acute inflammation, high expression of 11β‐HSD oxoreductase but not dehydrogenase activity in cells elicited rapidly in the peritoneum by a single thioglycollate injection. 11β‐HSD oxoreductase activity remained high in peritoneal cells until the inflammation resolved. In vitro, the 11β‐HSD1 substrate, 11‐dehydrocorticosterone, increased macrophage phagocytosis of apoptotic neutrophils to the same extent as corticosterone. This effect was dependent upon 11β‐HSD1: these cells solely expressed the type 1 11β‐HSD isozyme (not 11β‐HSD2), and carbenoxolone, an 11β‐HSD inhibitor, prevented the increase in phagocytosis elicited by 11‐dehydrocorticosterone. Macrophages from 11β‐HSD1‐deficient mice failed to respond to 11‐dehydrocorticosterone. In vivo, 11β‐HSD1‐deficient mice showed a delay in acquisition of macrophage phagocytic competence and had an increased number of free apoptotic neutrophils during sterile peritonitis. Importantly, in preliminary experiments, 11β‐HSD1‐deficient mice exhibited delayed resolution of inflammation in experimental arthritis. These findings suggest 11β‐HSD1 may be a component of mechanisms engaged early during the inflammatory response that promote its subsequent resolution.

11β-hydroxysteroid dehydrogenase type 1 deficiency in bone marrow-derived cells reduces atherosclerosis

11β‐Hydroxysteroid dehydrogenase type‐1 (11β‐HSD1) converts inert cortisone into active cortisol, amplifying intracellular glucocorticoid action. 11β‐HSD1 deficiency improves cardiovascular risk factors in obesity but exacerbates acute inflammation. To determine the effects of 11β‐HSD1 deficiency on atherosclerosis and its inflammation, atherosclerosis‐prone apolipoprotein E‐knockout (ApoE‐KO) mice were treated with a selective 11β‐HSD1 inhibitor or crossed with 11β‐HSD1‐KO mice to generate double knockouts (DKOs) and challenged with an atherogenic Western diet. 11β‐HSD1 inhibition or deficiency attenuated atherosclerosis (74–76%) without deleterious effects on plaque structure. This occurred without affecting plasma lipids or glucose, suggesting independence from classical metabolic risk factors. KO plaques were not more inflamed and indeed had 36% less T‐cell infiltration, associated with 38% reduced circulating monocyte chemoattractant protein‐1 (MCP‐1) and 36% lower lesional vascular cell adhesion molecule‐1 (VCAM‐1). Bone marrow (BM) cells are key to the atheroprotection, since transplantation of DKO BM to irradiated ApoE‐KO mice reduced atherosclerosis by 51%. 11β‐HSD1‐null macrophages show 76% enhanced cholesterol ester export. Thus, 11β‐HSD1 deficiency reduces atherosclerosis without exaggerated lesional inflammation independent of metabolic risk factors. Selective 11β‐HSD1 inhibitors promise novel antiatherosclerosis effects over and above their benefits for metabolic risk factors via effects on BM cells, plausibly macrophages.—Kipari, T., Hadoke, P. W. F., Iqbal, J., Man, T. Y., Miller, E., Coutinho, A. E., Zhang, Z., Sullivan, K. M., Mitic, T., Livingstone, D. E. W., Schrecker, C., Samuel, K., White, C. I., Bouhlel, M. A., Chinetti‐Gbaguidi, G., Staels, B., Andrew, R., Walker, B. R., Savill, J. S., Chapman, K. E., Seckl, J. R. 11β‐hydroxysteroid dehydrogenase type 1 deficiency in bone marrow‐derived cells reduces atherosclerosis. FASEB J. 27, 1519–1531 (2013). www.fasebj.org

11β-Hydroxysteroid dehydrogenase type 1—A role in inflammation?

Abstract Glucocorticoids are widely used for their potent anti-inflammatory effects. Endogenous glucocorticoids are immunomodulatory and shape both adaptive and innate immune responses. Over the past decade, it has become apparent that an important level of control over endogenous glucocorticoid action is exerted by the 11β-hydroxysteroid dehydrogenase enzymes. The type 1 enzyme, 11β-HSD1, reduces inert glucocorticoids into active forms, thereby increasing intracellular ligand availability to receptors. Although 11β-HSD1 activity has been shown to play an important role in the metabolic actions of glucocorticoids, its role in the immune response has, until recently, remained unclear. Here we review recent evidence pertaining to the role of 11β-HSD1 in the inflammatory response.

11β-Hydroxysteroid Dehydrogenase Type 1 Is Expressed in Neutrophils and Restrains an Inflammatory Response in Male Mice

Endogenous glucocorticoid action within cells is enhanced by prereceptor metabolism by 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1), which converts intrinsically inert cortisone and 11-dehydrocorticosterone into active cortisol and corticosterone, respectively. 11β-HSD1 is highly expressed in immune cells elicited to the mouse peritoneum during thioglycollate-induced peritonitis and is down-regulated as the inflammation resolves. During inflammation, 11β-HSD1-deficient mice show enhanced recruitment of inflammatory cells and delayed acquisition of macrophage phagocytic capacity. However, the key cells in which 11β-HSD1 exerts these effects remain unknown. Here we have identified neutrophils (CD11b+,Ly6G+,7/4+ cells) as the thioglycollate-recruited cells that most highly express 11β-HSD1 and show dynamic regulation of 11β-HSD1 in these cells during an inflammatory response. Flow cytometry showed high expression of 11β-HSD1 in peritoneal neutrophils early during inflammation, declining at later states. In contrast, expression in blood neutrophils continued to increase during inflammation. Ablation of monocytes/macrophages by treatment of CD11b-diphtheria-toxin receptor transgenic mice with diphtheria toxin prior to thioglycollate injection had no significant effect on 11β-HSD1 activity in peritoneal cells, consistent with neutrophils being the predominant 11β-HSD1 expressing cell type at this time. Similar to genetic deficiency in 11β-HSD1, acute inhibition of 11β-HSD1 activity during thioglycollate-induced peritonitis augmented inflammatory cell recruitment to the peritoneum. These data suggest that neutrophil 11β-HSD1 increases during inflammation to contribute to the restraining effect of glucocorticoids upon neutrophil-mediated inflammation. In human neutrophils, lipopolysaccharide activation increased 11β-HSD1 expression, suggesting the antiinflammatory effects of 11β-HSD1 in neutrophils may be conserved in humans.

Mast Cells Express 11β-hydroxysteroid Dehydrogenase Type 1: A Role in Restraining Mast Cell Degranulation

Mast cells are key initiators of allergic, anaphylactic and inflammatory reactions, producing mediators that affect vascular permeability, angiogenesis and fibrosis. Glucocorticoid pharmacotherapy reduces mast cell number, maturation and activation but effects at physiological levels are unknown. Within cells, glucocorticoid concentration is modulated by the 11β-hydroxysteroid dehydrogenases (11β-HSDs). Here we show expression and activity of 11β-HSD1, but not 11β-HSD2, in mouse mast cells with 11β-HSD activity only in the keto-reductase direction, regenerating active glucocorticoids (cortisol, corticosterone) from inert substrates (cortisone, 11-dehydrocorticosterone). Mast cells from 11β-HSD1-deficient mice show ultrastructural evidence of increased activation, including piecemeal degranulation and have a reduced threshold for IgG immune complex-induced mast cell degranulation. Consistent with reduced intracellular glucocorticoid action in mast cells, levels of carboxypeptidase A3 mRNA, a glucocorticoid-inducible mast cell-specific transcript, are lower in peritoneal cells from 11β-HSD1-deficient than control mice. These findings suggest that 11β-HSD1-generated glucocorticoids may tonically restrain mast cell degranulation, potentially influencing allergic, anaphylactic and inflammatory responses.