The influence of extracorporeal photopheresis on NFκB signaling and cytokine expression in lung transplant patients

Abstract

Lung transplant patients suffering from chronic lung allograft dysfunction often receive extracorporeal photopheresis (ECP) in addition to calcineurin inhibitor (CNI) based immunosuppression. CNI partly inhibit the NFκB pathway, which induces the transcription of pro-inflammatory cytokines. The mechanisms of the observed ECP-mediated immunosuppression remain unclear. In this study we analyzed, if ECP contributes to immunosuppression by inhibiting NFκB signaling. As NFκB activation is tightly related to its nuclear location, the nuclear translocation rate and intracellular expression levels of IFNγ were analyzed after PMA/Ionomycin stimulation in T cells of 13 lung transplant patients procured before and after ECP (n=33) by Multispectral Imaging Flow Cytometry, which combines flow cytometry and fluorescence microscopy. After ECP the nuclear NFκB translocation rate in stimulated T cells was significantly reduced (mean ± SD [%]) from 51.5 ± 13.8 to 44.7 ± 14.5 (p=0.01). The capability of ECP to impair nuclear NFκB translocation was additionally proven by an in vitro model, in which blood cells of healthy controls (n=4) were treated with methoxypsoralen and UVA. Compared to non-treated cells, nuclear NFκB translocation rate was substantially decreased in ECP-treated T cells from 74.2 ± 11.5 to 48.1 ± 18. Similarly, the intracellular IFNγ expression (mean ± SD mean fluorescence intensity [MFI]) was diminished from 6310 ± 1693 to 3619 ± 1430. In conclusion, these results provide first evidence that ECP impairs NFκB signaling, and consequently decreases NFκB-dependent expression of IFNγ, which may partly explain the well-known immunosuppressive effect of ECP.