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

Abstract

Tuberculosis remains a critical infectious disease world-wide. The development of novel therapeutic strategies requires greater understanding of host factors that contribute to disease susceptibility. A major unknown in TB pathogenesis is the mechanism of necrosis in TB granulomas that leads to the massive lung tissue damage and cavity formation necessary for the pathogen transmission. In humans, TB progression has been linked to hyperactivity of type I IFN (IFN-I) pathway, the primary cause of which remains elusive.We studied the mechanistic drivers of pulmonary TB progression using a unique model B6J.C3-Sst1C3HeB/Fej Krmn mice that develop human-like necrotic TB granulomas and IFN-I hyperactivity. We established that IFNβ super-induction occurred in the susceptible macrophages in response to continuous TNF stimulation in the context of a dysregulated antioxidant defense. We observed that unresolving oxidative stress amplified the induction of IFNβ through JNK activation and induced the Integrated Stress Response via PKR activation as a compensatory pathway. Subsequently, PKR amplifies IFNβ upregulation, forming a positive feedback loop, maintaining the hyperinflammatory state in susceptible macrophages and leading to mitochondrial dysfunction. Thus, within the inflammatory milieu, a cell-intrinsic mechanism of chronic regulatory dysfunction and unresolved stress gradually weakens the macrophage and ultimately promotes the necrotization of TB granulomas. The aberrant macrophage response to TNF can be prevented by an iron chelator and inhibitor of lipid peroxidation, ferrostatin-1. Moreover, ferrostatin treatment increased macrophage survival and boosted bacterial control in the TNF-stimulated macrophages infected with virulent Mtb. These findings identify targets for host-directed therapeutics to interrupt necrotization in TB granulomas.

Role of the transcriptional regulator SP140 in resistance to bacterial infections via repression of type I interferons

“…In addition to enhanced type I IFN responses to TNFa, we also observed that both B6.Sst1 S and Sp140 -/-BMMs show increased cell death in vitro upon stimulation with polyI:C compared to B6 BMMs, as measured by lactate dehydrogenase (LDH) release (Figure 3 figure supplement 1). This result is analogous to previous findings that B6.Sst1 S BMMs die upon sustained TNF stimulation (Brownhill et al, 2020). The enhanced polyI:C-induced LDH release in both Sp140 -/and B6.Sst1 S BMMs was blunted upon genetic deletion of Ifnar (Figure 3 figure supplement 1), consistent with type I IFNs playing an important role in the cell death phenotype.…”

“…However, much more indirect mechanisms are also possible. Recent studies suggest that hyper type I IFN responses in TNF-stimulated B6.Sst1 S BMMs derive from aberrant oxidative stress that activates the kinase JNK and ultimately results in a non-resolving stress response that promotes necrosis (Bhattacharya et al, 2021;Brownhill et al, 2020). Interestingly, mouse SP140 localizes to nuclear structures called PML bodies.…”

Role of the transcriptional regulator SP140 in resistance to bacterial infections via repression of type I interferons

“…We and others previously reported that TNF induces higher levels of type I IFN-induced genes in Sst1 S BMMs as compared to B6 BMMs (Bhattacharya et al, 2021;Ji et al, 2019). We also observed higher levels of Ifnb transcripts in the lungs of B6.Sst1 S mice infected with M. tuberculosis, as compared to infected B6 mice (Ji et al, 2019 (Brownhill et al, 2020). The enhanced polyI:C-induced LDH release in both Sp140 -/and B6.Sst1 S BMMs was blunted upon genetic deletion of Ifnar (Figure 3  figure supplement 1), consistent with type I IFNs playing an important role in the cell death phenotype.…”

“…We expect that future mechanistic studies will be critical to further confirm this conclusion. stress that activates the kinase JNK and ultimately results in a non-resolving stress response that promotes necrosis (Bhattacharya et al, 2021;Brownhill et al, 2020). Interestingly, mouse SP140 localizes to nuclear structures called PML bodies.…”

Dissemination and progression of pulmonaryMycobacterium aviuminfection in mouse model is associated with type 2 macrophage activation

“…This unique necrotic granuloma phenotype is controlled by a single genetic locus sst1 (supersusceptibility to tuberculosis-1), which has been characterized in our previous studies (27)(28)(29)(30)(31). We have shown that this locus controls macrophage responses to TNF and the sst1 susceptibility allele reduces macrophage stress resilience and increases type I interferon production (32)(33)(34)(35). It has been shown to control host resistance to several taxonomically unrelated intracellular bacterial pathogens (32,36,37).…”