Sarah Karin Wideman

Red blood cell development from erythroid progenitors requires profound reshaping of metabolism and gene expression. How these transcriptional and metabolic alterations are coupled is unclear. Nprl3 (an inhibitor of mTORC1) has remained in synteny with the α-globin genes for >500 million years, and harbours most of the a-globin enhancers. However, whether Nprl3 serves an erythroid role is unknown. We found that while haematopoietic progenitors require basal Nprl3 expression, erythroid Nprl3 expression is further boosted by the α-globin enhancers. This lineage-specific upregulation is required for sufficient erythropoiesis. Loss of Nprl3 affects erythroblast metabolism via elevating mTORC1 signalling, suppressing autophagy and disrupting glycolysis. Broadly consistent with these murine findings, human NPRL3-knockout erythroid progenitors produce fewer enucleated cells and demonstrate dysregulated mTORC1 signalling in response to nutrient availability and erythropoietin. Therefore, we propose that the anciently conserved linkage of NprI3, α-globin and their associated enhancers has coupled metabolic and developmental control of erythropoiesis.

Respiratory viral infections caused by rhinoviruses (RVs), influenza A virus (IAV) and endemic corona viruses (HCoV) result in a serious strain on healthcare systems and public health, underscoring an urgent need for inhaled broad-spectrum antiviral therapies. However, their development is challenging, as no standardized in vitro methodologies that can fully replicate the in vivo environment have been established. In this work, we aimed to investigate the antiviral and anti-inflammatory effect of three 2-deoxylated glucose analogues (2-DGA): 2-deoxy-D-glucose, 2-fluoro-2-dexoy-D-glucose and 2-fluoro-2-dexoy-D-mannose (2-FDM), by utilizing advanced in vitro air-liquid interface (ALI) airway models. We demonstrated that commonly used ALI models have variable susceptibility to RV, IAV and HCoV infection. Further, we showed that 2-DGA have an anti-inflammatory effect and suppress respiratory viral replication in models mimicking the upper and lower respiratory airways. Moreover, we confirmed that 2-DGA can be delivered via nebulization in vitro , highlighting their potential to be used as broad-spectrum inhaled antivirals. Finally, our results demonstrate the importance of incorporating complex in vitro methodologies, such as primary cell ALI cultures and aerosol exposure, at an early stage of drug development.

Lipids play a major role in inflammatory diseases by altering inflammatory cell functions, either through their function as energy substrates or as lipid mediators such as oxylipins. Autophagy, a lysosomal degradation pathway that limits inflammation, is known to impact on lipid availability, however, whether this controls inflammation remains unexplored. We found that upon intestinal inflammation visceral adipocytes upregulate autophagy and that adipocyte‐specific loss of the autophagy gene Atg7 exacerbates inflammation. While autophagy decreased lipolytic release of free fatty acids, loss of the major lipolytic enzyme Pnpla2/Atgl in adipocytes did not alter intestinal inflammation, ruling out free fatty acids as anti‐inflammatory energy substrates. Instead, Atg7 ‐deficient adipose tissues exhibited an oxylipin imbalance, driven through an NRF2‐mediated upregulation of Ephx1 . This shift reduced secretion of IL‐10 from adipose tissues, which was dependent on the cytochrome P450‐EPHX pathway, and lowered circulating levels of IL‐10 to exacerbate intestinal inflammation. These results suggest an underappreciated fat‐gut crosstalk through an autophagy‐dependent regulation of anti‐inflammatory oxylipins via the cytochrome P450‐EPHX pathway, indicating a protective effect of adipose tissues for distant inflammation.

Malaria and iron deficiency are major global health problems with extensive epidemiological overlap. Iron deficiency-induced anaemia can protect the host from malaria by limiting parasite growth. On the other hand, iron deficiency can significantly disrupt immune cell function. However, the impact of host cell iron scarcity beyond anaemia remains elusive in malaria. To address this, we employed a transgenic mouse model carrying a mutation in the transferrin receptor ( Tfrc ^Y20H/Y20H ), which limits the ability of cells to internalise iron from plasma. At homeostasis Tfrc ^Y20H/Y20H mice appear healthy and are not anaemic. However, Tfrc ^Y20H/Y20H mice infected with Plasmodium chabaudi chabaudi AS showed significantly higher peak parasitaemia and body weight loss. We found that Tfrc ^Y20H/Y20H mice displayed a similar trajectory of malaria-induced anaemia as wild-type mice, and elevated circulating iron did not increase peak parasitaemia. Instead, P. chabaudi infected Tfrc ^Y20H/Y20H mice had an impaired innate and adaptive immune response, marked by decreased cell proliferation and cytokine production. Moreover, we demonstrated that these immune cell impairments were cell-intrinsic, as ex vivo iron supplementation fully recovered CD4 T cell and B cell function. Despite the inhibited immune response and increased parasitaemia, Tfrc ^Y20H/Y20H mice displayed mitigated liver damage, characterised by decreased parasite sequestration in the liver and an attenuated hepatic immune response. Together, these results show that host cell iron scarcity inhibits the immune response but prevents excessive hepatic tissue damage during malaria infection. These divergent effects shed light on the role of iron in the complex balance between protection and pathology in malaria.

Low plasma iron (hypoferremia) induced by hepcidin is a conserved inflammatory response that protects against infections but inhibits erythropoiesis. How hypoferremia influences leukocytogenesis is unclear. Using proteomic data, we predicted that neutrophil production would be profoundly more iron-demanding than generation of other white blood cell types. Accordingly in mice, hepcidin-mediated hypoferremia substantially reduced numbers of granulocytes but not monocytes, lymphocytes, or dendritic cells. Neutrophil rebound after anti-Gr-1–induced neutropenia was blunted during hypoferremia but was rescued by supplemental iron. Similarly, hypoferremia markedly inhibited pharmacologically stimulated granulopoiesis mediated by granulocyte colony-stimulating factor and inflammation-induced accumulation of neutrophils in the spleen and peritoneal cavity. Furthermore, hypoferremia specifically altered neutrophil effector functions, suppressing antibacterial mechanisms but enhancing mitochondrial reactive oxygen species–dependent NETosis associated with chronic inflammation. Notably, antagonizing endogenous hepcidin during acute inflammation enhanced production of neutrophils. We propose plasma iron modulates the profile of innate immunity by controlling monocyte-to-neutrophil ratio and neutrophil activity in a therapeutically targetable system.

Lipids play a major role in inflammatory diseases by altering inflammatory cell functions, through their use as energy substrates or as lipid mediators such as oxylipins. Autophagy, a lysosomal degradation pathway that limits inflammation, is known to impact on lipid availability, however whether this controls inflammation remains unexplored. We found that upon intestinal inflammation visceral adipocytes upregulate autophagy and that adipocyte-specific loss of the autophagy gene Atg7 exacerbates inflammation. While autophagy decreased lipolytic release of free fatty acids, loss of the major lipolytic enzyme Pnpla2/Atgl in adipocytes did not alter intestinal inflammation, ruling out free fatty acids as anti- inflammatory energy substrates. Instead, Atg7 -deficient adipose tissues exhibited an altered oxylipin balance, driven through an NRF2-mediated upregulation of Ephx1 . This was accompanied by a shift in adipose tissue macrophage polarization with reduced secretion of IL-10, leading to lower circulating levels of IL-10. These results suggest an underappreciated fat-gut crosstalk through an autophagy- dependent regulation of anti-inflammatory oxylipins, indicating a protective effect of adipose tissues for distant inflammation.

Iron is critical for life but toxic in excess because of iron-catalysed formation of pro-oxidants that cause tissue damage in a range of disorders. The transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) orchestrates cell-intrinsic protective antioxidant responses, while the peptide hormone hepcidin maintains systemic iron homoeostasis, but is pathophysiologically decreased in haemochromatosis and β-thalassaemia. Here, we show that Nrf2 is activated by iron-induced, mitochondria-derived pro-oxidants and drives bone morphogenetic protein 6 (Bmp6) expression in liver sinusoidal endothelial cells, which in turn increases hepcidin synthesis by neighbouring hepatocytes. In Nrf2 knockout mice, the Bmp6–hepcidin response to oral and parenteral iron is impaired, and iron accumulation and hepatic damage are increased. Pharmacological activation of Nrf2 stimulates the Bmp6–hepcidin axis, improving iron homoeostasis in haemochromatosis and counteracting the inhibition of Bmp6 by erythroferrone in β-thalassaemia. We propose that Nrf2 links cellular sensing of excess toxic iron to the control of systemic iron homoeostasis and antioxidant responses, and may be a therapeutic target for iron-associated disorders.

Human herpesvirus 6B (HHV-6B) is a neurotropic betaherpesvirus that achieves latency by integrating its genome into host cell chromosomes. Several viruses can induce epigenetic modifications in their host cells, but no study has investigated the epigenetic modifications induced by HHV-6B. This study analyzed methylation with an Illumina 450K array, comparing HHV-6B-infected and uninfected Molt-3 T cells 3 days postinfection. Bisulfite pyrosequencing was used to validate the Illumina results and to investigate methylation over time in vitro . Expression of genes was investigated using quantitative PCR (qPCR), and virus integration was investigated with PCR. A total of 406 CpG sites showed a significant HHV-6B-induced change in methylation in vitro . Remarkably, 86% (351/406) of these CpGs were located IMPORTANCE The ability to establish latency in the host is a hallmark of herpesviruses, but the mechanisms differ. Human herpesvirus 6B (HHV-6B) is known to establish latency through integration of its genome into the telomeric regions of host cells, with the ability to reactivate. Our study is the first to show that HHV-6B specifically induces hypomethylated regions close to the telomeres and that integrating viruses may use the host methylation machinery to facilitate their integration process. The results from this study contribute to knowledge of HHV-6B biology and virus-host interaction. This in turn will lead to further progress in our understanding of the underlying mechanisms by which HHV-6B contributes to pathological processes and may have important implications in both disease prevention and treatment.