David J. Mangelsdorf

The hormone fibroblast growth factor 21 (FGF21) is induced in murine liver in response to both bacterial and viral infection. In this report, we show that FGF21 is induced by infection with influenza virus in both humans and mice. Mice lacking FGF21 had decreased food intake, body weight, and body temperature compared to wild-type mice following influenza virus inoculation, indicating reduced tolerance to the infection. Conversely, pharmacologic administration of FGF21 after viral infection protected mice against these pathologic changes. Pair feeding studies showed that neither the induction of FGF21 nor the hypothermia was secondary to decreased food intake. Notably, mice selectively lacking FGF21’s coreceptor protein, βKlotho, in noradrenergic neurons were also more susceptible to influenza virus infection, including hypothermia. We show that FGF21 acting on noradrenergic neurons, including those in the locus coeruleus region, stimulates energy expenditure and thermogenic gene expression in brown adipose tissue. Our findings reveal an FGF21-regulated neuronal pathway that protects mice against influenza infection and suggest the potential utility of using FGF21 pharmacologically to improve outcomes after influenza infection.

Ethanol rapidly stimulates the liver to synthesize the hormone fibroblast growth factor 21 (FGF21), which then acts on the brain to elicit a multifaceted protective response. We show that in mice, this induction of FGF21 occurs at the level of gene transcription and is regulated by two byproducts of ethanol metabolism, glycerol-3-phosphate (G3P) and acetyl-CoA. Using cell-based reporter and thermal shift binding assays, we show that G3P binds to a conserved domain and activates the transcription factor carbohydrate-responsive element-binding protein (ChREBP), which regulates the Fgf21 gene promoter. The stimulation of Fgf21 gene transcription by ethanol also requires its metabolism to acetyl-CoA and correlates with histone acetylation. Accordingly, a p300/CBP histone acetyltransferase inhibitor blocks histone acetylation, ChREBP recruitment, and transcriptional activation at the Fgf21 promoter. Together, these findings reveal a dual regulatory mechanism driven by both G3P and acetyl-CoA that explains ethanol’s robust stimulatory effect on Fgf21 and possibly other ChREBP target genes in the liver.

SUMMARY: Animals that consume fermenting fruit or nectar are exposed to ethanol, thus increasing their risk of injury or predation. This risk is heightened in humans, who have actively imbibed alcohol for thousands of years. In this report, we show that the hormone FGF21, which is strongly induced by ethanol in murine and human liver, exerts sobering or “amethystic” effects on both arousal and motor coordination without changing ethanol catabolism. Mice lacking FGF21 take longer than wild-type littermates to recover their righting reflex and balance following ethanol exposure. Conversely, pharmacologic FGF21 administration reduces the time needed for mice to recover from ethanol-induced unconsciousness and ataxia. FGF21 mediates it amethystic effects by directly activating the noradrenergic nervous system, which regulates arousal and alertness. These results indicate that this FGF21 liver-brain pathway evolved to protect against ethanolinduced intoxication and that it might be targeted pharmaceutically for treating acute alcohol poisoning.

Schistosomes infect over 200 million of the world’s poorest people, but unfortunately treatment relies on a single drug. Nuclear hormone receptors are ligand-activated transcription factors that regulate diverse processes in metazoans, yet few have been functionally characterized in schistosomes. During a systematic analysis of nuclear receptor function, we found that an FTZ-F1-like receptor was essential for parasite survival. Using a combination of transcriptional profiling and chromatin immunoprecipitation (ChIP), we discovered that the micro-exon gene meg-8.3 is a transcriptional target of SmFTZ-F1. We found that both Smftz-f1 and meg-8.3 are required for esophageal gland maintenance as well as integrity of the worm’s head. Together, these studies define a new role for micro-exon gene function in the parasite and suggest that factors associated with the esophageal gland could represent viable therapeutic targets.

A prevalent feature of Strongyloides stercoralis is a life-long and potentially lethal infection that is due to the nematode parasite’s ability to autoinfect and, thereby, self-replicate within its host. Here, we investigated the role of the parasite’s nuclear receptor, Ss-DAF-12, in governing infection. We identified Δ7-DA as the endogenous Ss-DAF-12 ligand and elucidated the hormone’s biosynthetic pathway. Genetic loss of function of the ligand’s rate-limiting enzyme demonstrated that Δ7-DA synthesis is necessary for parasite reproduction, whereas its absence is required for the development of infectious larvae. Availability of the ligand permits Ss-DAF-12 to function as an on/off switch governing autoinfection, making it vulnerable to therapeutic intervention. In a preclinical model of hyperinfection, pharmacologic activation of DAF-12 suppressed autoinfection and markedly reduced lethality. Moreover, when Δ7-DA was administered with ivermectin, the current but limited drug of choice for treating strongyloidiasis, the combinatorial effects of the two drugs resulted in a near cure of the disease.

A prevalent feature of Strongyloides stercoralis is a life-long and potentially lethal infection that is due to the nematode parasite’s ability to autoinfect and, thereby, self-replicate within its host. Here, we investigated the role of the parasite’s nuclear receptor, Ss- DAF-12, in governing infection. We identified Δ7-DA as the endogenous Ss- DAF-12 ligand and elucidated the hormone’s biosynthetic pathway. Genetic loss of function of the ligand’s rate-limiting enzyme demonstrated that Δ7-DA synthesis is necessary for parasite reproduction, whereas its absence is required for development of infectious larvae. Availability of the ligand permits Ss- DAF-12 to function as an on/off switch governing autoinfection, making it vulnerable to therapeutic intervention. In a preclinical model of hyperinfection, pharmacologic activation of DAF-12 suppressed autoinfection and markedly reduced lethality. Moreover, when Δ7-DA was administered with ivermectin, the current but limited drug of choice for treating strongyloidiasis, the combinatorial effects of the two drugs resulted in a near cure of the disease.

Significance: Understanding the molecular mechanisms controlling nematode parasite infection is important to developing new therapeutic strategies. The DAF-12 nuclear receptor signaling pathway in free-living nematodes regulates a process known as the dauer diapause. In nematode parasites, this signaling pathway is believed to govern the infectious stage. To investigate this hypothesis, we characterized the orthologous components of DAF-12 and a parasite-specific transcriptional coactivator in the potentially lethal parasite Strongyloides stercoralis . Using a CRISPR method developed specifically for S. stercoralis , we demonstrate that DAF-12 and its coactivator are required for both the entry into and exit from the infectious stage. These studies further highlight the potential of therapeutically targeting this pathway in S. stercoralis and other nematode parasites.

Background: While immune responses to the murine hookwormNippostrongylus brasiliensishave been investigated, signaling pathways regulating development of infectious larvae (iL3) are not well understood. We hypothesized thatN. brasiliensiswould use pathways similar to those controlling dauer development in the free-living nematodeCaenorhabditis elegans, which is formally known as the “dauer hypothesis.”Methods: To investigate whether dafachronic acid activates theN. brasiliensisDAF-12 homolog, we utilized anin vitroreporter assay. We then utilized RNA-Seq and subsequent bioinformatic analyses to identifyN. brasiliensisdauer pathway homologs and examine regulation of these genes during iL3 activation.Results: In this study, we demonstrated that dafachronic acid activates theN. brasiliensisDAF-12 homolog. We then identifiedN. brasiliensishomologs for members in each of the four canonical dauer pathways and examined their regulation during iL3 activation by either temperature or dafachronic acid. Similar toC. elegans, we found that transcripts encoding antagonistic insulin-like peptides were significantly downregulated during iL3 activation, and that a transcript encoding a phylogenetic homolog of DAF-9 increased during iL3 activation, suggesting that both increased insulin-like and DAF-12 nuclear hormone receptor signaling accompanies iL3 activation. In contrast toC. elegans, we observed a significant decrease in transcripts encoding the dauer transforming growth factor beta ligand DAF-7 during iL3 activation, suggesting a different role for this pathway in parasitic nematode development.Conclusions: Our data suggest that canonical dauer pathways indeed regulate iL3 activation in the hookwormN. brasiliensisand that DAF-12 may be a therapeutic target in hookworm infections.