PI3-Kinase Inhibition Promotes Tolerogenic CD8+ T Cell Function in Lung Transplant Recipients with a History of Cigarette Smoke Exposure

Abstract

Purpose Lung transplant (LTx) recipients with significant cigarette smoke (CS) exposure histories continue to have poorer long-term outcomes. We utilized a systems biology approach to analyze a novel murine model of allogeneic LTx into CS exposed recipients. Through in silico modeling, we sought to identify therapeutic targets that could modulate post-Tx outcomes in the CS exposed patient population. Methods C57Bl/6 mice were either chronically exposed to CS or room air (NS) prior to receiving an orthotopic left LTx from non-smoke Balb/c age matched controls. Lungs were harvested at 7 days post-LTx, after which histological, nanostring mRNA immune profiling, and high dimensional mass cytometry (CyTOF) assays were performed. Results We demonstrate that acute rejection is exacerbated in CS recipients as compared to NS controls. Principle component analysis of nanostring data revealed significant differences IL17A, CTLA4, IL6, and IL4 pathways in CS vs NS. In silico predictive modeling suggested this phenotype could be reversed by the PI3K pathway inhibitor LY294002 (LY). Therapy of CS exposed mice with LY restored the CS recipient to a rejection profile in keeping with that seen in NS recipients. CyTOF and flow cytometry revealed significant alterations in splenic CD8+ central memory (CM) versus effector memory (EM) ratios, with EM predominating in CS mice pre-LTx, as compared to NS. Treatment with LY differentially restored the CM:EM ratio, in vitro and in vivo, in CS samples, and was associated with reversing the rejection phenotype in LY-treated CS recipients to that seen in NS controls. Finally, reconstitution of ex vivo-treated and -untreated CD8+ cells into CD8 KO mice prior to LTx replicated our observed rejection patterns, further implicating the CD8+ population as a key regulator of CS related alloimmunity. Conclusion Pre-transplant CS exposure, particularly in COPD and IPF patients, predisposes to poorer post-LTx outcomes. Using a clinically relevant LTx system and in silico modeling we have identified PI3K inhibition as a novel therapeutic approach predicted to be efficacious in CS exposed LTx recipients.