Auranofin-Mediated NRF2 Induction Attenuates Interleukin 1 Beta Expression in Alveolar Macrophages.

Stephanie B Wall,Rui Li,Hubert M Tse,Clyde J Wright,Trent E Tipple,Jennifer L Larson-Casey,Ashley R Burg,A Brent Carter,Lynette K Rogers,Brittany Butler

doi:10.3390/antiox10050632

Abstract

Background: Alveolar macrophages (AMs) are resident inflammatory cells in the lung that serve as early sentinels of infection or injury. We have identified thioredoxin reductase 1 inhibition by gold compounds increases activation of nuclear factor erythroid 2-related factor 2 (NRF2)-dependent pathways to attenuate inflammatory responses. The present studies utilized murine alveolar macrophages (MH-S) to test the hypothesis that the gold compound, auranofin (AFN), decreases interleukin (IL)-1β expression through NRF2-mediated interactions with nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) pathway genes and/or increases in glutathione synthesis. Methods: MH-S cells were treated with AFN and lipopolysaccharide (LPS) and analyzed at 6 and 24 h. The Il1b promoter was analyzed by chromatin immunoprecipitation for direct interaction with NRF2. Results: Expression of IL-1β, p-IκBα, p-p65 NF-kB, and NOD-, LRR-, and pyrin domain-containing protein 3 were elevated by LPS exposure, but only IL-1β expression was suppressed by AFN treatment. Both AFN and LPS treatments increased cellular glutathione levels, but attenuation of glutathione synthesis by buthionine sulfoximine (BSO) did not alter expression of Il-1β. Analysis revealed direct NRF2 binding to the Il1b promoter which was enhanced by AFN and inhibited the transcriptional activity of DNA polymerase II. Conclusions: Our data demonstrate that AFN-induced NRF2 activation directly suppresses IL-1β synthesis independent of NFκB and glutathione-mediated antioxidant mechanisms. NRF2 binding to the promoter region of IL1β directly inhibits transcription of the IL1β gene. Collectively, our research suggests that gold compounds elicit NRF2-dependent pulmonary protection by suppressing macrophage-mediated inflammation.

Highlights

Acute respiratory distress syndrome (ARDS), a serious health disorder affecting both children and adults, involves the activation of inflammatory signaling resulting in lung injury
The reader is directed to a recent publication by Saha and colleagues, which extensively summarizes key relationships between nuclear factor erythroid 2-related factor 2 (NRF2)/antioxidant response elements (AREs), inflammatory mediator expression, canonical and non-canonical NFκB pathway activation, and macrophage metabolism [18]
Our analysis revealed similar findings: NRF2 immunoprecipitated with the Il1b promoter, an effect that was significantly increased in the presence of AFN

Summary

Introduction

Acute respiratory distress syndrome (ARDS), a serious health disorder affecting both children and adults, involves the activation of inflammatory signaling resulting in lung injury. Inflammatory responses are driven, in part, by alveolar macrophages (AMs), resident inflammatory cells in the lung that serve as early sentinels of infection or injury [1]. Previous work by our group identified thioredoxin reductase (Txnrd) 1 inhibition by gold compounds as a means to increase activation of nuclear factor erythroid 2-related factor 2 (NRF2)-dependent pathways to attenuate lung injury [2]. Isakov et al. Alveolar macrophages (AMs) are resident inflammatory cells in the lung that serve as early sentinels of infection or injury. The present studies utilized murine alveolar macrophages (MH-S) to test the hypothesis that the gold compound, auranofin (AFN), decreases interleukin (IL)-1β expression through NRF2-mediated interactions with nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) pathway genes and/or increases in glutathione synthesis.

Methods

Discussion

Conclusion