An ex vivo RT-qPCR-based assay for human peripheral leukocyte responsiveness to glucocorticoids in surgically induced inflammation

Abstract

Introduction: An assay to determine glucocorticoid (GC) responsiveness in humans could be used to monitor GC non-responsiveness in states of GC insufficiency and could provide a tool to adapt GC treatment to individual patients. We propose an ex vivo assay to test GC responsiveness in peripheral leukocytes. The assay was evaluated in a human experimental model of surgery-induced inflammation.

Patients and methods: Changes in expression of the GC-regulated genes GILZ, IL1R2, FKBP5, and HLA-DR and glucocorticoid receptor alpha (GRα) were determined by reverse transcriptase quantitative polymerase chain reaction (RT-qPCR) in peripheral leukocytes from surgical patients and healthy blood donors (total n=60) in response to low (1 nM) and high (1 µM) dexamethasone (DEX). The final selection of a suitable endogenous control gene was based on the studies of stability during DEX treatment and inflammation. Correlations between pre- and postoperative GC-induced gene expression, the postoperative systemic inflammatory and metabolic response (CRP, IL-6, white blood cell count, cytokines, resistin, free fatty acids, glucose, insulin, and adiponectin), and the clinical outcome were analyzed. The length of stay in the intensive care unit (ICU-LOS), the length of stay in the hospital, and postoperative complications were used to measure clinical outcome.

Results: When the blood donors were compared to the patients, there were no significant differences in the regulation of the genes in response to DEX, except for GRα. Preoperative, but not postoperative, gene regulation of GILZ and GRα was negatively correlated to ICU-LOS (P<0.05 and P<0.01, respectively). Preoperative GILZ and FKBP5 gene regulation was negatively correlated to postoperative systemic TNFα and MIP-1α levels.

Conclusion: We suggest that this assay could be used to determine GC responsiveness. An alteration in preoperative GC responsiveness may be related to a patient's ability to recover from surgically induced inflammatory stress.

Keywords: GILZ; GRα; clinical outcome; cytokines; gene regulation; glucocorticoid responsiveness.

Figure 1

Gene expression of GC-regulated genes in peripheral leukocytes in response to 1 µM dexamethasone (DEX) in healthy blood donors (BD1, n=21, A) and in surgical patients (PAT1, n=9, B) using the endogenous control G6PD. Notes: *P<0.05, **P<0.01, and ***P<0.0001, vs unstimulated sample. Data are presented as box plots showing median and IQR with whiskers at quartiles ±1.5 IQR. Abbreviations: FKBP5, FK506 binding protein 5; G6PD, glucose-6-phosphate dehydrogenase; GILZ, glucocorticoid-induced leucine zipper; GRα, glucocorticoid receptor alpha; HLA-DR, human leukocyte antigen DR; IL1R2, interleukin 1 receptor II; IQR, interquartile range.

Figure 2

Correlation between preoperative gene expression of GILZ (P<0.05, A) and GRα (P<0.05, B) in response to 10 nM DEX in peripheral leukocytes from the patient cohort 2 (PAT2) (surgical patients, n=21) and length of stay (days) intensive care unit (ICU). Note: Scatterplot with fitted regression lines with 95% confidence interval of predicted means. Abbreviations: GILZ, glucocorticoid-induced leucine zipper; GRα, glucocorticoid receptor alpha.