MNK/eIF4E Ser209 Inhibitor eFT-508 Prevents and Therapeutically Treats Fibrosis in a Murine Model of Restrictive Chronic Lung Allograft Rejection

Abstract

<h3>Purpose</h3> Lung transplant is limited by poor outcomes due to chronic lung allograft dysfunction, CLAD. A fulminant CLAD phenotype, restrictive allograft syndrome (RAS), with limited therapies underscores the need to understand underlying mechanisms. MNK1 kinase is a key translational regulator of cellular functions via eIF4E serine 209 phosphorylation. Here we investigate the role of MNK/eIF4E Ser209 in mesenchymal cell activation and the therapeutic effectiveness of eFT-508 in a murine model of RAS. <h3>Methods</h3> Human lung allograft derived MCs treated with eFT-508 (10uM x 24h) were immunoblotted for collagen I, alpha smooth muscle actin, CD44, autotaxin. A modified boyden chamber assay was utilized for migration. We recently reported a murine RAS model, B6D2F1/J into C57BL6/J. Mice were administered eFT-508 5mg/kg/daily/gavage in a preventive group days 7-28, or therapeutic group days 14-28. <h3>Results</h3> Human allograft derived MCs from CLAD patients demonstrated 4-fold increase in MNK1 (Thr197/202) and eIF4E Ser209 compared to non-fibrotic MCs. Upon eFT-508 treatment, we observed reduced eIF4E Ser209, collagen I, alpha smooth muscle actin and SPARC expression, and migration (n=7; p<0.05). CD44 and autotaxin protein expression was decreased upon eFT-508 treatment, along with secreted autotaxin activity (n=9; p=0.0005). <i>In vivo</i> preventive treatment with eFT-508 decreased airway fibrosis upon histological examination utilizing trichrome staining. Pleural thickness measurements were also reduced compared to vehicle treated controls. A significant reduction in hydroxyproline content, autotaxin secretion, and activity were also noted in eFT-508 treated transplant lung homogenates (n=7; p<0.001). Therapeutic treatment with eFT-508 reduced hydroxyproline content compared to vehicle treated allografts (n=4; p=0.0252). <h3>Conclusion</h3> MNK/eIF4E Ser209 inhibition reduced fibrotic protein expression and migration, demonstrating a role for this pathway in MC activation. <i>In vivo</i> MNK/eIF4E Ser209 inhibition reduced graft fibrosis by preventive and therapeutic treatment regimens in a murine model of RAS. This data highlights a novel therapeutic option for preventing development and progression of RAS.