Steroid resistance in COPD is associated with impaired molecular chaperone HSP90 expression by pro-inflammatory lymphocytes

Abstract

Corticosteroid resistance is a major barrier to effective treatment of COPD and is associated with steroid resistant CD28nullCD8+ pro-inflammatory lymphocytes. These senescent lymphocytes express decreased glucocorticoid receptor (GCR) levels. GCR must be bound to molecular chaperones heat shock proteins (HSP)70 and HSP90 to acquire a high-affinity steroid binding conformation and traffic to the nucleus. We hypothesized a loss of HSP70/90 from these lymphocytes that contribute to steroid resistance in COPD. Blood was collected from 10 COPD and 10 aged-matched controls. Cytotoxic mediators (perforin and granzyme B), intracellular pro-inflammatory cytokines (IFNγ and TNFα) and expression of CD28, GCR, HSP70 and HSP90 were determined T and NKT-like cells in the presence of ± 10µM prednisolone and 2.5ng/ml cyclosporine A (binds to GCR-HSP70/90 complex) using flow cytometry, western blot and fluorescence microscopy. Loss of HSP90 and GCR from CD28null CD8+ T and NKT-like cells in COPD was noted (HSP70 unchanged). Loss of HSP90 correlated with the percentage of CD28null CD8+ T and NKT-like cells producing IFNγ or TNFα in all subjects (eg, COPD: R= -.763, p=0.007 for T-cell IFNγ). Up-regulation of HSP90 and associated decrease in pro-inflammatory cytokine production was found in CD28nullCD8+ T and NKT-like cells in the presence of 10 -6 M prednisolone and 2.5 ng/mL cyclosporine A. Loss of HSP90 from cytotoxic/pro-inflammatory CD28nullCD8+ T and NKT-like cells could contribute to steroid resistance in COPD. Combined prednisolone with low-dose cyclosporine A, that up-regulate HSP90 and inhibit these pro-inflammatory cells, may reduce systemic inflammation in COPD.