Induction of EMT-like phenotypes by an active metabolite of leflunomide and its contribution to pulmonary fibrosis

Abstract

Drug-induced interstitial lung disease (ILD), particularly pulmonary fibrosis, is a serious clinical concern and myofibroblasts have been suggested to have a major role, with it recently being revealed that some of these myofibroblasts are derived from lung epithelial cells through epithelial-mesenchymal transition (EMT). In this study, we examined the EMT-inducing abilities of drugs known to induce ILD clinically. EMT-like phenotypes were induced by A771726, an active metabolite of leflunomide having an inhibitory effect on dihydroorotate dehydrogenase (DHODH). Smad-interacting protein 1 (a transcription factor regulating EMT) and the Notch-signaling pathway but not transforming growth factor-b was shown to be involved in A771726-induced EMT-like phenotypes. When the cultures were supplemented with exogenous uridine, the A771726-induced EMT-like phenotypes and activation of the Notch-signaling pathway disappeared. Similarly, an A771726 analog without inhibitory activity on DHODH produced no induction, suggesting that this process is mediated through the inhibition of DHODH. In vivo, administration of leflunomide stimulated bleomycin-induced EMT-like phenomenon in pulmonary tissue, and exacerbated bleomycin-induced pulmonary fibrosis, both of which were suppressed by coadministration of uridine. Taken together, these findings suggest that leflunomide-dependent exacerbation of bleomycin-induced pulmonary fibrosis is mediated by stimulation of EMT of lung epithelial cells, providing the first evidence that drug-induced pulmonary fibrosis involves EMT of these cells.

Involvement of epithelial-mesenchymal transition in methotrexate-induced pulmonary fibrosis

“…Based on previous data, we next examined whether MAECs and A549 cells exhibit an EMT-like phenotype. Some studies have reported bleomycin-induced histopathologic features consistent with pulmonary fibrosis, including inflammation, disruption of normal alveolar architecture, increased collagen, and myofibroblasts in the alveolar air spaces (Namba et al, 2010;Schneider et al, 2012). TGF-β1 significantly decreased the expression of E-cadherin and increased α-SMA, vimentin and FN, which was consistent with previous studies.…”

Rheumatoid arthritis-associated lung disease

“…It has been associated with the development and/or exacerbation of ILD, potentially secondary to an active metabolite that may induce transition of lung epithelial cells to myofibroblasts, a process known as the epithelial-mesenchymal transition [99]. However, in an animal model, administration of leflunomide alone did not result in this phenomenon.…”

“…define the disease. In an Australian cohort of rheumatoid arthritis patients with a disease duration <2 years, 58% of these patients had changes consistent with ILD on either chest radiograph, high-resolution computed tomography (HRCT), pulmonary function testing (PFT), bronchoalveolar lavage (BAL) and/or 99 Tc-DTPA (technetium-99 m-labelled diethylenetriamine pentaacetate) scan. Of these patients, 76% had clinically silent disease [5].…”

“…However, in an animal model, administration of leflunomide alone did not result in this phenomenon. Rather, the process was enhanced when leflunomide was administered in the setting of bleomycin, a known profibrotic agent [99]. This suggests that leflunomide could provoke the development of ILD in predisposed populations.…”

Interstitial lung involvement in rheumatoid arthritis

“…Основным механизмом ЛЕФ-индуциро-ванного пневмонита является реакция гиперчувствительно-сти, аналогичная таковой при «метотрексатном» пневмоните [70]. Развитие ИПЛ, возможно, связано с повышением плаз-менной концентрации активного метаболита ЛЕФ А771726, что может вызвать трансформацию эпителиальных клеток ле-гочной ткани в фиброзную ткань [71] -процесс, известный как «эпителиально-мезенхимальная трансформация» (ЭМТ) [72].…”