Lymphocyte senescence in COPD is associated with loss of glucocorticoid receptor expression by pro-inflammatory/cytotoxic lymphocytes

Greg Hodge, Hubertus Jersmann, Hai B Tran, Mark Holmes, Paul N Reynolds, Sandra Hodge

BackgroundGlucocorticoid (GC) resistance is a major barrier in COPD treatment. We have shown increased expression of the drug efflux pump, Pgp1 in cytotoxic/pro-inflammatory lymphocytes in COPD. Loss of lymphocyte co-stimulatory molecule CD28 (lymphocyte senescence) was associated with a further increase in their pro-inflammatory/cytotoxic potential and resistance to GC. We hypothesized that lymphocyte senescence and increased Pgp1 are also associated with down-regulation of the GC receptor (GCR).MethodsBlood was collected from 10 COPD and 10 healthy aged-matched controls. Flow cytometry was applied to assess intracellular pro-inflammatory cytokines, CD28, Pgp1, GCR, steroid binding and relative cytoplasm/nuclear GCR by CD28+ and CD28null T, NKT-like cells. GCR localization was confirmed by fluorescent microscopy.ResultsCOPD was associated with increased numbers of CD28nullCD8+ T and NKT-like cells. Loss of CD28 was associated with an increased percentage of T and NKT-like cells producing IFN¿ or TNF¿ and associated with a loss of GCR and Dex-Fluor staining but unchanged Pgp1. There was a significant loss of GCR in CD8¿+¿CD28null compared with CD8¿+¿CD28+ T and NKT-like cells from both COPD and controls (eg, mean ± SEM 8¿±¿3% GCR + CD8¿+¿CD28null T-cells vs 49¿±¿5% GCR¿+¿CD8¿+¿CD28+ T-cells in COPD). There was a significant negative correlation between GCR expression and IFN¿ and TNF¿ production by T and NKT-like cells(eg, COPD: T-cell IFN¿ R¿=¿¿.615; ) and with FEV1 in COPD (R¿=¿¿.777).ConclusionsCOPD is associated with loss of GCR in senescent CD28null and NKT-like cells suggesting alternative treatment options to GC are required to inhibit these pro-inflammatory/cytotoxic cells.