Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.09.08.288316v1?rss=1 Authors: Schiffer, L., Bossey, A., Taylor, A. E., Akerman, I., Scheel-Toellner, D., Storbeck, K.-H., Arlt, W. Abstract: Context: Androgens are important modulators of immune cell function impacting proliferation, differentiation and cytokine production. The local generation of active androgens from circulating androgen precursors is an important mediator of androgen action in peripheral androgen target cells of tissue. Objective: To characterize the activation of classic and 11-oxygenated androgens in human peripheral blood mononuclear cells (PBMCs). Methods: PBMCs and natural killer cells were isolated from healthy male donors and incubated ex vivo with precursors and end products of the classic and 11-oxygenated androgen pathways. Steroid concentrations were quantified by liquid chromatography-tandem mass spectrometry. The expression of genes encoding steroid metabolizing enzymes was assessed by quantitative PCR. Results: The enzyme AKR1C3 is the major reductive 17{beta}-hydroxysteroid dehydrogenase in PBMCs and has higher activity for the generation of the active 11-oxygenated androgen 11-ketotestosterone than for the generation of the classic androgen testosterone from their respective precursors. Natural killer cells are the major site of AKR1C3 expression and activity within the PBMC compartment. Steroid 5-reductase type 1 catalyzes the 5-reduction of classic but not 11-oxygenated androgens in PBMCs. Lag time prior to the separation of cellular components from whole blood sample increases 11KT serum concentrations in a time-dependent fashion, with significant increases detected from two hours after blood collection. Conclusions: 11-oxygenated androgens are the preferred substrates for androgen activation by AKR1C3 in PBMCs, primarily conveyed by natural killer cell AKR1C3 activity, yielding 11KT the major active androgen in PBMCs. Androgen metabolism by PBMCs can affect the levels of 11-oxygenated androgens measured in serum samples, if samples are not separated in a timely fashion. Copy rights belong to original authors. Visit the link for more info