Inhibition of mammalian mtDNA transcription acts paradoxically to reverse diet-induced hepatosteatosis and obesity.

The oxidative phosphorylation system1 in mammalian mitochondria plays a key role in transducing energy from ingested nutrients2. Mitochondrial metabolism is dynamic and can be reprogrammed to support both catabolic and anabolic reactions, depending on physiological demands or disease states. Rewiring of mitochondrial metabolism is intricately linked to metabolic diseases and promotes tumour growth3-5. Here, we demonstrate that oral treatment with an inhibitor of mitochondrial transcription (IMT)6 shifts whole-animal metabolism towards fatty acid oxidation, which, in turn, leads to rapid normalization of body weight, reversal of hepatosteatosis and restoration of normal glucose tolerance in male mice on a high-fat diet. Paradoxically, the IMT treatment causes a severe reduction of oxidative phosphorylation capacity concomitant with marked upregulation of fatty acid oxidation in the liver, as determined by proteomics and metabolomics analyses. The IMT treatment leads to a marked reduction of complex I, the main dehydrogenase feeding electrons into the ubiquinone (Q) pool, whereas the levels of electron transfer flavoprotein dehydrogenase and other dehydrogenases connected to the Q pool are increased. This rewiring of metabolism caused by reduced mtDNA expression in the liver provides a principle for drug treatment of obesity and obesity-related pathology.

Small-molecule inhibitors of human mitochondrial DNA transcription.

Altered expression of mitochondrial DNA (mtDNA) occurs in ageing and a range of human pathologies (for example, inborn errors of metabolism, neurodegeneration and cancer). Here we describe first-in-class specific inhibitors of mitochondrial transcription (IMTs) that target the human mitochondrial RNA polymerase (POLRMT), which is essential for biogenesis of the oxidative phosphorylation (OXPHOS) system1-6. The IMTs efficiently impair mtDNA transcription in a reconstituted recombinant system and cause a dose-dependent inhibition of mtDNA expression and OXPHOS in cell lines. To verify the cellular target, we performed exome sequencing of mutagenized cells and identified a cluster of amino acid substitutions in POLRMT that cause resistance to IMTs. We obtained a cryo-electron microscopy (cryo-EM) structure of POLRMT bound to an IMT, which further defined the allosteric binding site near the active centre cleft of POLRMT. The growth of cancer cells and the persistence of therapy-resistant cancer stem cells has previously been reported to depend on OXPHOS7-17, and we therefore investigated whether IMTs have anti-tumour effects. Four weeks of oral treatment with an IMT is well-tolerated in mice and does not cause OXPHOS dysfunction or toxicity in normal tissues, despite inducing a strong anti-tumour response in xenografts of human cancer cells. In summary, IMTs provide a potent and specific chemical biology tool to study the role of mtDNA expression in physiology and disease.

Gasdermin D plays a vital role in the generation of neutrophil extracellular traps.

The death of a cell is an inevitable part of its biology. During homeostasis, most cells die through apoptosis. If homeostasis is disturbed, cell death can switch to proinflammatory forms of death, such as necroptosis, pyroptosis, or NETosis. We demonstrate that the formation of neutrophil extracellular traps (NETs), a special form of neutrophil cell death that releases chromatin structures to the extracellular space, is dependent on gasdermin D (GSDMD). GSDMD is a pore-forming protein and an executor of pyroptosis. We screened a chemical library and found a small molecule based on the pyrazolo-oxazepine scaffold that efficiently blocks NET formation and GSDMD-mediated pyroptotic cell death in human cells. During NETosis, GSDMD is proteolytically activated by neutrophil proteases and, in turn, affects protease activation and nuclear expansion in a feed-forward loop. In addition to the central role of GSDMD in pyroptosis, we propose that GSDMD also plays an essential function in NETosis.

Potent agonists of the Hedgehog signaling pathway.

A family of biaryl substituted 1,4-diaminocyclohexanamides of 3-chlorobenzothiophene-2-carboxylic acid is reported as picomolar modulators of Hedgehog protein function. SAR for the 1,4-diaminocyclohexane group is shown to be exquisitely sensitive to substitution on the 4-amino group, and SAR for the 3-chlorobenzothiophene group is highly specific. Preliminary SAR studies of the biaryl substituent led to a picomolar compound with in vivo activity.