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IFNγ sensitizes macrophages to pathogen ligand killing via a unique caspase-8 and mitochondrial cell death pathway licensed by nitric oxide

ABSTRACT: Caspase-8 modulates TLR-induced gene transcription, which is only partially dependent on caspase-8 catalytic activity. Moreover, The slow kinetics of IFNγ and LPS-induced BMDM killing offers the possibility that transcriptional responses may contribute to cell death activation. We performed 3' mRNA-sequencing to examine whether caspase-8 might contribute, at least in part, to IFNγ and LPS-triggered macrophage death via its transcriptional role. We found that caspase-8-mediated transcriptional re-programming of BMDMs. Importantly, caspase-8 modulates expression of Bcl-2 family members and inducible nitric oxide synthase (iNOS) to promote activation of the mitochondrial apoptotic effectors, BAX and BAK.

ORGANISM(S): Mus musculus

PROVIDER: GSE161179 | GEO | 2021/12/15

REPOSITORIES: GEO

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Project description:RNA sequencing of wild-type or Interferon Alpha receptor 1 Knockout MEF cells treated with DMSO or the Broad-spectrum Caspase Inhibitor Q-VD-OPh The mechanism by which cells undergo death determines whether dying cells trigger inflammatory responses or remain immunologically silent. Mitochondria play a central role in the induction of cell death, as well as in immune signaling pathways. Here, we identify of a mechanism by which mitochondria and downstream pro-apoptotic caspases regulate the activation of antiviral immunity. In the absence of active caspases, mitochondrial outer membrane permeabilization by Bax and Bak results in the expression of type I interferons (IFNs). This induction is mediated by mitochondrial DNA-dependent activation of the cGAS/STING pathway and results in the establishment of a potent state of viral resistance. Our results show that mitochondria have the capacity to simultaneously expose a cell-intrinsic inducer of the IFN response, and to inactivate this response in a caspase-dependent manner. This mechanism provides a dual control, which determines whether mitochondria initiate an immunologically silent or a pro-inflammatory type of cell death. To determine whether the pharmacological inhibition of caspases could recapitulate the phenotype caused by genetic deficiencies, we treated WT MEFs with broad-spectrum inhibitors of caspases (Q-VD-OPH). The inhibitor induced an increased expression of ISGs, similar to the effect of caspase or Apaf-1 deficiency. Next, we compared the transcriptional changes induced by caspase inhibition in WT and IFNAR1 KO cells, which lack a critical subunit of the receptor for IFNα/β (Muller et al., 1994). We observed that the absence of the IFNAR receptor abrogated the transcriptional response of the cells to caspase inhibition by Q-VD-OPH, demonstrating the role of type I IFNs in this response. RNA was extracted from duplicate samples and libraries generated for sequencing using the directional RNA-Seq library prep at the Yale Center for Genome Analysis. Libraries were sequenced using a Hiseq2500 sequencer to generate 76bp single-end reads. Duplicate samples were analyzed for each condition.

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IFNγ sensitizes macrophages to pathogen ligand killing via a unique caspase-8 and mitochondrial cell death pathway licensed by nitric oxide

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