Glucocorticoid receptor hypersensitivity enhances inflammatory signaling and inhibits cell cycle progression in porcine PBMCs

Dexamethasone has profound influence on the energy metabolism of porcine blood leukocytes and prevents the LPS-induced glycolytic switch

In farm animals, little is known about the relationship between energy metabolism of immune cells and their activation state. Moreover, there has recently been evidence that dexamethasone, a powerful glucocorticoid-based drug, can exert its anti-inflammatory effects by interfering with the energy metabolism of immune cells, but the mechanisms are not yet fully understood. To address these knowledge gaps, we explored the connection between the energy metabolism of porcine peripheral blood mononuclear cells (PBMCs) and their response to pro- and anti-inflammatory stimulation with lipopolysaccharide (LPS) and dexamethasone (DEX) in vitro. Interventions in the metabolism of PBMCs with the glycolysis inhibitor 2-deoxy-D-glucose or the HIF-1α inhibitor KC7F2 reduced the LPS-induced TNF-α production, but the mitochondrial ATP synthesis inhibitor oligomycin showed no significant effect. The anti-inflammatory action of DEX was not affected by any of the inhibitors. To investigate the metabolic actions of LPS and DEX in PBMCs, we evaluated glycolysis and mitochondrial respiration following 24 hours stimulation using the Seahorse XFe96 flux analyzer. Our results revealed significantly higher glycolysis in LPS-treated PBMCs, but provided no evidence for a change in mitochondrial respiration. In contrast, DEX reduced LPS-induced glycolysis and, especially when administered alone, significantly lowered mitochondrial respiration. Pretreatment with KC7F2 counteracted the effects of LPS and DEX on glycolysis, and reduced mitochondrial respiration regardless of the inflammatory state of the PBMCs. Gene expression analysis identified the glucose transporter SLC2A3, and the tricarboxylic acid cycle genes IDH1 and SDHB as the main switches for the antagonistic metabolic actions of LPS and DEX, which are closely associated with the inflammatory state of PBMCs.

Heat-Induced Secretion of Heat Shock Proteins 70 and 90 Does not Affect the Expression of the Glucocorticoid Receptor in Primary Airway Cells in COPD

PURPOSE

The response to glucocorticoids is hampered in many COPD patients by a yet unknown mechanism. Earlier we reported that short-term heat exposure of primary human bronchial epithelial cells (BEC) and airway smooth muscle cells (ASMC) of asthma patients increased the expression and secretion of extracellular heat shock proteins (eHSPs) resulting in increased expression of glucocorticoid receptor (GR) in BEC and inhibition of ASMC remodeling. The aim of the present study was to assess if the same mechanism is also present in primary airway wall cells of COPD patients.

METHODS

Primary BEC and ASMC were established from endobronchial biopsies obtained from COPD patients (n = 73), who participated in the HISTORIC study, an investigator-initiated and driven clinical trial. Secretion and protein expression of HSPs was assessed by ELISA and Western blotting. Expression of total GR, its isoforms GRα and GRβ and toll-like receptor 4 (TLR4) was determined by Western-blotting.

RESULTS

Short heat exposure (65 °C, 10 s) of BEC resulted in a significant increase of the secretion of eHSP70 and eHSP90, while the intracellular protein was not altered. Heat treatment or exposure to eHSP70 or eHSP90 had no effect on the expression of GR and GR-isoforms. However, eHSP70 and eHSP90 significantly reduced the expression of TLR4.

CONCLUSIONS

The results of this study indicate that primary airway cells from COPD patients respond differently to heat exposure and extracellular HSP70 or HSP90 than cells from asthma patients regarding the expression of GR and this may explain the reduced response to glucocorticoids in patients with COPD.

TRIAL REGISTRATION

ISRCTN11017699.