STUDYING THE REGULATION OF 11β-HSD1 EXPRESSION AND ACTIVITY IN PERIPHERAL BLOOD MONOCYTES

The peripheral control of inflammation involves the conversion of inactive cortisone to cortisol by 11β-hydroxysteroid dehydrogenases (11β-HSDs). Glucocorticoids such as cortisone or prednisone may work therapeutically only if they are converted to active glucocorticoids (cortisol and prednisolone) by the intracellular 11β-HSD enzymes. The 11β-HSD1 enzyme is bidirectional, but primarily activates glucocorticoids, whereas the 11β-HSD2 enzyme is unidirectional and a powerful glucocorticoid inactivator. The levels of 11β-HSD1 are highly dependent upon the cellular differentiation status and modulated by the cytokine environment. Hence, studying the influence of cytokines on 11β-HSD1 activity and expression could provide valuable insights to improve the therapeutic options involved in reducing inflammation. Several studies have reported the role of the pro-inflammatory cytokine IL-17 in glucocorticoid (GC) insensitivity but the mechanism underlying this is still unclear. In order to understand this better we tested the effect of IL-17 in the two main classes of monocytes, CD14++ CD16- (CD14) and CD14+ CD16+ (CD16). The anti-inflammatory actions of IL-4 are well established through earlier findings. However, the exact mechanism it uses to downregulate the pro- inflammatory cytokine production through monocytes and macrophages is poorly understood. In this study, we examined the effect of IL-4 in the induction of 11β- HSD1 in the two main classes of monocytes, CD14++ CD16- (CD14) and CD14+ CD16+ (CD16). It is well-known that M2 macrophages express 11β-HSD1 but it is not known if M2 is a prerequisite for 11β-HSD1 gene expression. Hence, after IL- 4 stimulation of CD14 and CD16 monocytes we analyzed the monocyte subpopulation phenotypes according to the expression of M1 and M2 markers by flow cytometry. In addition, the molecular mechanisms underlying the induction of 11β-HSD1 by IL-4 are still to be unravelled. Therefore, we studied various regions of the 11β-HSD1 promoter to understand how IL-4 regulates its expression and activity in peripheral blood monocytes.