Graduate Assistant University of Georgia, United States
Disclosure(s):
Sarah Beth Bell: No financial relationships to disclose
Introduction/Rationale:
Introduction: Mycobacterium tuberculosis (Mtb), the primary causative agent of human Tuberculosis (TB), is the leading cause of infectious death worldwide. Mtb is known to cause a type 1 interferon (T1 IFN) response, which is detrimental to macrophage control of Mtb, evident by increased TB severity or reactivation of latent TB upon viral infection. However, the mechanisms underlying this are poorly understood. Mtb invades macrophages, causing the generation of excess reactive oxygen species (ROS), which can lead to programmed cell death. Nuclear factor erythroid 2-related factor 2 (NRF2) is a transcription factor activated to combat the high levels of ROS by inducing the transcription of antioxidants (AOX). We tested the hypothesis that T1 IFNs impair host resistance to Mtb by suppressing NRF2 and the AOX response.
Methods:
Methods: Bone marrow-derived macrophages (BMDMs) from C57BL/6 (WT) and Ifnar1-/- mice were infected with Mtb or stimulated with IFN and/or heat killed (HK) Mtb. RNA was collected at 6, 12, and 24 hours for RT-qPCR, and total protein was collected for immunoblotting. Nuclear and cytosolic cell fractions were also collected at 24 hours for immunoblotting to determine transcription factor localization.
Results:
Results: Immunoblotting for NRF2 revealed no significant change in protein levels with IFN treatment. Despite this, NRF2-induced AOX genes showed lower mRNA and protein expression when stimulated with IFN in WT BMDMs, which was recapitulated in protein expression at 24 hours. In response to Mtb infection, AOX protein levels were significantly elevated in Ifnar1-/- BMDMs compared to WT BMDMs. Furthermore, IFN stimulation significantly decreased nuclear localization of NRF2.
Conclusion:
Conclusion: These data indicate that T1 IFN signaling suppresses NRF2 nuclear localization and NRF2-induced AOX responses. These results imply that regulation of T1 IFNs or cellular redox status could be viable options for decreasing TB severity.
