The integrated stress response mediates type I interferon driven necrosis in Mycobacterium tuberculosis granulomas

Abstract

Necrosis in the tuberculous granuloma is a hallmark of tuberculosis that enables pathogen survival and transmission. Susceptibility to tuberculosis and several other intracellular bacteria is controlled by a mouse genetic locus, sst1, and mice carrying the sst1-suscepible (sst1S) genotype develop necrotic inflammatory lung lesions, similar to human TB granulomas. Our previous work established that increased disease severity in sst1S mice reflects dysfunctional macrophage effector or tolerance mechanisms, but the molecular mechanisms have remained unclear. Here we demonstrate that sst1S macrophages develop aberrant, biphasic responses to TNF characterized by super-induction of stress and type I interferon pathways after prolonged TNF stimulation with this late-stage response being initiated by oxidative stress and Myc activation and driven via a JNK -IFNb -PKR circuit. This circuit leads to induction of the integrated stress response (ISR) mediated by eIF2a phosphorylation and the subsequent hyper-induction of ATF3 and ISR-target genes Chac1, Trib3, Ddit4. The administration of ISRIB, a small molecule inhibitor of the ISR, blocked the development of necrosis in lung granulomas of M. tuberculosis-infected sst1S mice and concomitantly reduced the bacterial burden revealing that induction of the ISR and the locked-in state of escalating stress driven by type I IFN pathway in sst1S macrophages plays a causal role in the development of necrosis. Our data support a generalizable paradigm in intracellular pathogen-host interactions wherein host susceptibility emerges within inflammatory tissue due to imbalanced macrophage responses to growth, differentiation, activation and stress stimuli. Successful pathogens such as M. tuberculosis may exploit this aberrant response in susceptible hosts to induce necrotic lesions that favor long-term pathogen survival and transmission. Interruption of the aberrant stress response with inhibitors such as ISRIB may offer novel therapeutic strategies.

Type I interferon-driven susceptibility to Mycobacterium tuberculosis is mediated by IL-1Ra

“…B6.Sst1 S mice exhibit marked susceptibility to aerosol Mtb infection 12,13 , though how the Sst1 S locus confers susceptibility remains incompletely understood. Recent work has established that bone-marrow macrophages (BMMs) from B6.Sst1 S mice exhibit an enhanced type I IFN response 29,30 , as we confirm (Extended Data 1). In addition, we found that infected B6.Sst1 S lungs exhibited higher levels of Ifnb transcripts as compared to B6 (Fig.…”

Maladaptive oxidative stress cascade drives type I interferon hyperactivity in TNF activated macrophages promoting necrosis in murine tuberculosis granulomas

“…We have previously demonstrated that the B6.Sst1S macrophages develop an aberrant response to TNF in vitro within 12 -18 h of TNF stimulation. This is characterized by upregulation of stress markers, but no cell death (16). To determine whether prolonged TNF stimulation (as likely present in the face of persistent mycobacterial infection) would be sufficient to induce death of the sst1-susceptible macrophages, we stimulated bone marrow-derived macrophages (BMDMs) isolated from the B6.WT and B6.Sst1S mice with increasing concentrations of TNF for 24 -48 h. We observed that 50 or 100 ng/mL TNF induces a moderate increase in cell death in B6.Sst1S, while B6.WT macrophages remain resilient (Fig.1F).…”

“…To determine the mechanisms of chronic, TNF-induced cell dysfunction in Sst1S macrophages, we initially focused on the IFN-I pathway, which is upregulated in Sst1S BMDMs and instrumental in escalation of the integrated stress response at early time points after TNF stimulation (16). We sought to determine whether the Sst1S macrophages were more sensitive than WT to chronic TNF stimulation in terms of the type I IFN pathway upregulation.…”

“…After prolonged stimulation with TNF, the Sst1S macrophages expressed higher levels of IFNb and interferon-stimulated genes (ISGs) and upregulated markers of the integrated stress response (ISR) in an IFN-I -dependent manner. In parallel, they displayed evidence of protein aggregation and proteotoxic stress that could be inhibited by ROS scavengers and inhibitors of protein translation, but not by the type I IFN receptor blockade (16). Thus, the…”

“…To study mechanisms of necrosis controlled by the sst1 locus at cellular, tissue and whole organism levels, we made a congenic mouse strain B6J.C3-Sst1 C3HeB/Fej Krmn (B6.Sst1S) that carries the C3HeB/FeJ-derived susceptibility allele of the sst1 locus on the resistant B6 genetic background (15). (16,17). Hyperactivity of IFN-I pathway have also been found in humans with active TB (18), and an excess of IFNβ production in TB infection is known to be maladaptive on the part of the host macrophage (19).…”