Monitoring effects of 11β-hydroxysteroid dehydrogenase-1 deficiency or inhibition on Region-Specific Corticosteroid Regeneration in Brain using Mass Spectrometry Imaging

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: SAT 26-40-Glucocorticoid Actions & Disease
Saturday, June 15, 2013: 1:45 PM-3:45 PM
Expo Halls ABC (Moscone Center)

Poster Board SAT-33
Diego Federico Cobice*1, Logan MacKay2, Andrew McBride1, Pat Langridge Smith2, Scott Webster1, Brian R Walker1 and Ruth Andrew1
1University of Edinburgh, Edinburgh, United Kingdom, 2Scottish Instrumentation and Resource Centre for Advanced Mass Spectrometry, Edinburgh, United Kingdom
Intracellular inter-conversion of steroids has potent local effects on receptor activation, providing therapeutic targets in diseases as diverse as breast cancer (aromatase inhibition), prostate hyperplasia (5α-reductase inhibition), type 2 diabetes (11β-HSD1 inhibition to reduce glucocorticoid regeneration in liver and adipose), and cognitive impairment (11β-HSD1 inhibition in brain). However, the field is hampered by inadequate methods to assess steroids within tumours or tissue sub-regions. Here, we address this challenge using mass spectrometry imaging (MSI) to assess effects of 11β-HSD1 on conversion of inert 11-dehydrocorticosterone (A) to active corticosterone (B) within sub-regions of murine brain.

Four groups of mice (male, 12 weeks) were studied: 11β-HSD-/- mice (KO) and C57Bl/6 (WT) controls (n=6/group); C57Bl/6 mice (n=3/group) 1h after UE2316 (11β-HSD1 inhibitor; 20mg/kg oral) or vehicle. Steroids and UE2316 were imaged following on-tissue derivatisation with Girard T (GirT) in brain sections (10µm) embedded in gelatin to obtain mass spectral images (150-1000amu, positive ion, spatial resolution 200µm) of m/z 460.31698±0.025 (GirT B), m/z 458.30133±0.025 (GirT A), and m/z 390.08377±0.025 (UE2316) following Matrix assisted Laser Desorption Ionisation using a 12T SolariX Fourier transform Ion cyclotron MS (MALDI-FTICR-MS). Confirmatory quantitation in tissue homogenates was by Liquid Chromatography tandem Mass Spectrometry. Data are mean±SEM, *p<0.05.

Non-derivatised neutral steroids were poorly detected by MSI. Signals were boosted (104 fold) by formation of GirT hydrazones. α-Cyano-4-hydroxycinnamic acid, applied by spray coating, was selected as the matrix producing the best signal to noise.

Glucocorticoids were detected in highest abundance in cortex and hippocampus. In 11β-HSD1 deficiency, the B/A ratio was reduced (KO vs WT; cortex 5.1±0.4* vs 10.1±0.6; hippocampus 3.7±0.4* vs 6.9±0.9; amygdala 1.9±0.5* vs 4.4±0.8), with confirmatory LC/MS values (whole brain) of 5.4±0.7* (KO) vs 11.9±1.6 (WT). Likewise agreement between MSI and LC/MS was observed in plasma (B/A: MSI 8.2±0.5 vs 11.0±1.2; LC/MS 7.3±0.8 vs 11.3±1.1). With 11β-HSD1 inhibition, MSI-detected levels of UE2316 peaked in brain 1h post-dose, with similar reduction in B/A ratio (of 32% cortex, 52% hippocampus, and 58% amygdala; (* significant effect of treatment). Lower ratios in KOs were mainly driven by increased amounts of 11-dehydrocorticosterone.

MSI is a powerful new tool to study the regional variation in steroids within tissues with a resolution <200µm. We have demonstrated its utility for pharmacokinetic/pharmacodynamic analysis during development of novel 11β-HSD1 inhibitors for Alzheimer's disease. MSI has great potential to enhance (patho) physiological studies of steroid metabolism in many tissues and for multiple steroids.

Nothing to Disclose: DFC, LM, AM, PL, SW, BRW, RA

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