Macrophage fumarate hydratase restrains mtRNA-mediated interferon production

Metabolic rewiring underlies macrophage effector functions, but the
mechanisms involved remain incompletely defined. Here, using unbiased
metabolomics and stable isotope-assisted tracing, we show induction of an
inflammatory aspartate-argininosuccinate shunt following LPS stimulation.
The shunt, supported by increased ASS1 expression, also leads to increased
cytosolic fumarate levels and fumarate-mediated protein succination.
Pharmacologic inhibition and genetic ablation of the TCA cycle enzyme FH
further elevates intracellular fumarate levels, suppresses mitochondrial
respiration, and increases mitochondrial membrane potential. RNA
sequencing and proteomic analysis demonstrate profound inflammatory
effects resulting from FH inhibition. Of note, acute FH inhibition
suppresses IL-10 expression leading to increased TNF-α secretion, an
effect recapitulated by fumarate esters. Unexpectedly, FH inhibition, but
not fumarate esters, also increases IFN-β production through mechanisms
that are driven by mitochondrial RNA (mtRNA) release and activation of the
RNA sensors TLR7 and RIG-I/MDA5. This effect is recapitulated endogenously
when FH is suppressed following prolonged LPS stimulation. Furthermore,
cells from SLE patients also exhibit FH suppression, indicating a
potential pathogenic role for this process in human disease. We therefore
identify a protective role for FH in maintaining appropriate macrophage
cytokine and interferon responses. Data from this study that is included
in this Dryad submission is as follows: 1. RNA sequencing of
non-stimulated (with vehicle DMSO) or lipopolysaccaharide-stimulated (4 h)
murine bone marrow-derived macrophages (BMDMs) pre-treated with vehicle
(DMSO), 20 micromolar fumarate hydratase inhibitor 1 (FHIN1) or 25
micromolar dimethylfumarate (DMF) for 3 h. Three biological replicates per
condition. 2. Label-free proteomics of lipopolysaccaharide-stimulated (4
h) murine bone marrow-derived macrophages (BMDMs) pre-treated with vehicle
(DMSO), 20 micromolar fumarate hydratase inhibitor 1 (FHIN1) or 25
micromolar dimethylfumarate (DMF) for 3 h. Five biological replicates per
condition.  3. Metabolomics source data used for the study.