Nortriptyline enhances corticosteroid sensitivity of blood T cells from patients with chronic obstructive pulmonary disease.

Steroid unresponsiveness is a significant problem in the management of chronic obstructive pulmonary disease (COPD). The tricyclic antidepressant nortriptyline has been reported to reverse corticosteroid resistance induced by oxidative stress. This study examined the potential synergistic anti-inflammatory effects of nortriptyline and corticosteroids in T lymphocytes from patients with COPD and the molecular mechanisms underlying their action. Peripheral blood mononuclear cells (PBMCs) or whole blood cells from COPD patients were incubated with budesonide, nortriptyline, or their combinations and stimulated with phytohaemagglutinin (PHA) or phorbol myristate acetate (PMA) plus ionomycin. The release of interleukin 4 (IL-4), IL-5, IL-8 and other mediators from PBMCs was measured by ELISA. Intracellular pro-inflammatory cytokines, glucocorticoid receptor (GR) and its isoform GRβ, histone deacetylase 2 (HDAC2), phosphorylated p38 mitogen-activated protein kinase (p38 MAPK) and p65 nuclear factor-κ (p65 NF-κB) were determined in CD4+ and CD8+ T cells using flow cytometry. Nortriptyline 10 μM decreased PHA-induced release of cytokines: IL-4, IL-5, IL-13, IL-17A, IL-33, macrophage migration inhibitory factor and thymic stromal lymphopoietin (TSLP). This drug alone also reduced the percentage of IL-4, IL-8, interferon gamma (IFNγ) positive CD4+ T cells and IL-4, IL-8 expressing CD8+ T cells stimulated with PMA/ionomycin, whereas nortriptyline 1 μM had less pronounced effect. The combination of budesonide 10 nM with nortriptyline 10 μM was more potent at suppressing IL-4, IL-5, IL-8, IL-13, IL-17A, TSLP secretion from PBMCs, as well as IL-4, IL-8, IFNγ, GRβ expression by CD4+ and CD8+ T cells when compared with single budesonide treatment. The association of budesonide 10 nM and Nt (1 μM to 10 μM) effectively decreased p38 MAPK and p65 NF-κB phosphorylation and increased HDAC2 expression in both CD4+ and CD8+ T cells. In conclusion, nortriptyline alone demonstrates anti-inflammatory effects on blood T lymphocytes from COPD patients. Nortriptyline may also potentiate the effects of glucocorticoids and overcome corticosteroid insensitivity.