Interleukin-17 governs hypoxic adaptation of injured epithelium
Mammalian cells autonomously activate hypoxia-inducible transcription factors (HIFs) to ensure survival in low-oxygen environments. We report here that injury-induced hypoxia is insufficient to trigger HIF1Î± in damaged epithelium. Instead, multimodal single-cell and spatial transcriptomics analyses and functional studies reveal that retinoic acid-related orphan receptor Î³t+ (RORÎ³t+) Î³Î´ T cell-derived interleukin-17A (IL-17A) is necessary and sufficient to activate HIF1Î±. Protein kinase B (AKT) and extracellular signal-regulated kinase 1/2 (ERK1/2) signaling proximal of IL-17 receptor C (IL-17RC) activates mammalian target of rapamycin (mTOR) and consequently HIF1Î±. The IL-17A-HIF1Î± axis drives glycolysis in wound front epithelia. Epithelial-specific loss of IL-17RC, HIF1Î±, or blockade of glycolysis derails repair. Our findings underscore the coupling of inflammatory, metabolic, and migratory programs to expedite epithelial healing and illuminate the immune cell-derived inputs in cellular adaptation to hypoxic stress during repair.
Metabolic reprogramming of tumor-associated macrophages by collagen turnover promotes fibrosis in pancreatic cancer
SignificanceThe highly desmoplastic and immunosuppressive microenvironment of pancreatic tumors is a major determinant of the aggressive nature and therapeutic resistance of pancreatic cancer. Therefore, improving our understanding of the mechanisms that regulate the composition and function of the pancreatic tumor microenvironment is critical for the design of intervention strategies for this devastating malignancy. This study identifies a modality for the reprogramming of tumor-associated macrophages involving collagen scavenging followed by a metabolic switch toward a profibrotic paracrine phenotype. These findings establish a molecular framework for the elucidation of regulatory processes that could be harnessed to mitigate the stroma-dependent protumorigenic effects in pancreatic cancer.
chinmo-mutant spermatogonial stem cells cause mitotic drive by evicting non-mutant neighbors from the niche
Niches maintain a finite pool of stem cells via restricted space and short-range signals. Stem cells compete for limited niche resources, but the mechanisms regulating competition are poorly understood. Using the Drosophila testis model, we show that germline stem cells (GSCs) lacking the transcription factor Chinmo gain a competitive advantage for niche access. Surprisingly, chinmo-/- GSCs rely on a new mechanism of competition in which they secrete the extracellular matrix protein Perlecan to selectively evict non-mutant GSCs and then upregulate Perlecan-binding proteins to remain in the altered niche. Over time, the GSC pool can be entirely replaced with chinmo-/- cells. As a consequence, the mutant chinmo allele acts as a gene drive element; the majority of offspring inherit the allele despite the heterozygous genotype of the parent. Our results suggest that the influence of GSC competition may extend beyond individual stem cell niche dynamics to population-level allelic drift and evolution.
Monocyte-derived S1P in the lymph node regulates immune responses
The lipid chemoattractant sphingosine 1-phosphate (S1P) guides cells out of tissues, where the concentration of S1P is relatively low, into circulatory fluids, where the concentration of S1P is high1. For example, S1P directs the exit of T cells from lymph nodes, where T cells are initially activated, into lymph, from which T cells reach the blood and ultimately inflamed tissues1. T cells follow S1P gradients primarily using S1P receptor 1 (ref. 1). Recent studies have described how S1P gradients are established at steady state, but little is known about the distribution of S1P in disease or about how changing levels of S1P may affect immune responses. Here we show that the concentration of S1P increases in lymph nodes during an immune response. We found that haematopoietic cells, including inflammatory monocytes, were an important source of this S1P, which was an unexpected finding as endothelial cells provide S1P to lymph1. Inflammatory monocytes required the early activation marker CD69 to supply this S1P, in part because the expression of CD69 was associated with reduced levels of S1pr5 (which encodes S1P receptor 5). CD69 acted as a 'stand-your-ground' signal, keeping immune cells at a site of inflammation by regulating both the receptors and the gradients of S1P. Finally, increased levels of S1P prolonged the residence time of T cells in the lymph nodes and exacerbated the severity of experimental autoimmune encephalomyelitis in mice. This finding suggests that residence time in the lymph nodes might regulate the differentiation of T cells, and points to new uses of drugs that target S1P signalling.
STAT3 Inhibitor OPB-51602 Is Cytotoxic to Tumor Cells Through Inhibition of Complex I and ROS Induction
STAT3 is a transcription factor involved in several cellular activities including inflammation, proliferation, and survival, but it also plays a non-transcriptional role in modulating mitochondrial metabolism. Given its diverse functions in human cancers, it is an emerging therapeutic target. Here we show that OPB-51602, a small molecule inhibitor of STAT3, is highly toxic in a STAT3-dependent manner. Specifically, drug toxicity depends on mitochondrial STAT3 as tumor cells expressing only a mitochondrially restricted form of STAT3 are sensitive to the compound, whereas STAT3-null cells are protected. OPB-51602 inhibited complex I activity and led to increased ROS production, which in turn induced mitophagy, actin rearrangements, and cell death. Cells undergoing reduced oxidative phosphorylation or expressing NDI1 NADH dehydrogenase from Saccharomyces cerevisiae, which bypasses mammalian complex I, were resistant to OPB-51602 toxicity. These results show that targeting mitochondrial STAT3 function causes synthetic lethality through complex I inhibition that could be exploited for cancer chemotherapy.
Respiratory Supercomplexes Promote Mitochondrial Efficiency and Growth in Severely Hypoxic Pancreatic Cancer
Pancreatic ductal adenocarcinoma (PDAC) is characterized by extensive fibrosis and hypovascularization, resulting in significant intratumoral hypoxia (low oxygen) that contributes to its aggressiveness, therapeutic resistance, and high mortality. Despite oxygen being a fundamental requirement for many cellular and metabolic processes, and the severity of hypoxia in PDAC, the impact of oxygen deprivation on PDAC biology is poorly understood. Investigating how PDAC cells survive in the near absence of oxygen, we find that PDAC cell lines grow robustly in oxygen tensions down to 0.1%, maintaining mitochondrial morphology, membrane potential, and the oxidative metabolic activity required for the synthesis of key metabolites for proliferation. Disrupting electron transfer efficiency by targeting mitochondrial respiratory supercomplex assembly specifically affects hypoxic PDAC proliferation, metabolism, and inÂ vivo tumor growth. Collectively, our results identify a mechanism that enables PDAC cells to thrive in severe, oxygen-limited microenvironments.
3-Dimensional organization and dynamics of the microsporidian polar tube invasion machinery
Microsporidia, a divergent group of single-celled eukaryotic parasites, harness a specialized harpoon-like invasion apparatus called the polar tube (PT) to gain entry into host cells. The PT is tightly coiled within the transmissible extracellular spore, and is about 20 times the length of the spore. Once triggered, the PT is rapidly ejected and is thought to penetrate the host cell, acting as a conduit for the transfer of infectious cargo into the host. The organization of this specialized infection apparatus in the spore, how it is deployed, and how the nucleus and other large cargo are transported through the narrow PT are not well understood. Here we use serial block-face scanning electron microscopy to reveal the 3-dimensional architecture of the PT and its relative spatial orientation to other organelles within the spore. Using high-speed optical microscopy, we also capture and quantify the entire PT germination process of three human-infecting microsporidia species in vitro: Anncaliia algerae, Encephalitozoon hellem and E. intestinalis. Our results show that the emerging PT experiences very high accelerating forces to reach velocities exceeding 300 Î¼mâ‹…s-1, and that firing kinetics differ markedly between species. Live-cell imaging reveals that the nucleus, which is at least 7 times larger than the diameter of the PT, undergoes extreme deformation to fit through the narrow tube, and moves at speeds comparable to PT extension. Our study sheds new light on the 3-dimensional organization, dynamics, and mechanism of PT extrusion, and shows how infectious cargo moves through the tube to initiate infection.
An Intestinal Organoid-Based Platform That Recreates Susceptibility to T Cell-Mediated Tissue Injury
A goal in precision medicine is to use patient-derived material to predict disease course and intervention outcomes. Here, we use mechanistic observations in a preclinical animal model to design an ex vivo platform that recreates genetic susceptibility to T cell-mediated damage. Intestinal graft-versus-host disease (GVHD) is a life-threatening complication of allogeneic hematopoietic cell transplantation (allo-HCT). We found that intestinal GVHD in mice deficient in Atg16L1, an autophagy gene that is polymorphic in humans, is reversed by inhibiting necroptosis. We further show that co-cultured allogeneic T cells kill Atg16L1 mutant intestinal organoids from mice, which was associated with an aberrant epithelial interferon signature. Using this information, we demonstrate that pharmacologically inhibiting necroptosis or interferon signaling protects human organoids derived from individuals harboring a common ATG16L1 variant from allogeneic T cell attack. Our study provides a roadmap for applying findings in animal models to individualized therapy that targets affected tissues.
Amyloid-like substance in mice and human oocytes and embryos
PURPOSE/OBJECTIVE:To identify and characterize amyloid-like substance (ALS) in human and mouse oocytes and preimplantation embryos. METHODS:An experimental prospective pilot study. A total of 252 mouse oocytes and preimplantation embryos and 50 immature and in vitro matured human oocytes and parthenogenetic human embryos, from 11 consenting fertility patients, ages 18-45. Fluorescence intensity from immunofluorescent staining and data from confocal microscopy were quantified. Data were compared by one-way analysis of variance, with the least square-MEANS post-test, Pearson correlation coefficients (r), and bivariate analyses (t tests). ALS morphology was verified using transmission electron microscopy. RESULTS:Immunostaining for ALS appears throughout the zona pellucida, as well as in the cytoplasm and nucleus of mouse and human oocytes, polar bodies, and parthenogenetic embryos, and mouse preimplantation embryos. In mouse, 2-cell embryos exhibited the highest level of ALS (69000187.4â€‰Â±â€‰6733098.07). Electron microscopy confirmed the presence of ALS. In humans, fresh germinal vesicle stage oocytes exhibited the highest level of ALS (4164.74088â€‰Â±â€‰1573.46) followed by metaphase I and II stages (pâ€‰=â€‰0.008). There was a significant negative association between levels of ALS and patient body mass index, number of days of ovarian stimulation, dose of gonadotropin used, time between retrieval and fixation, and time after the hCG trigger. Significantly higher levels of ALS were found in patients with AMH between 1 and 3Â ng/ml compared to <â€‰1Â ng/ml. CONCLUSION/CONCLUSIONS:We demonstrate for the first time the presence, distribution, and change in ALS throughout some stages of mouse and human oocyte maturation and embryonic development. We also determine associations between ALS in human oocytes with clinical characteristics.
Regulation of BACE1 expression after injury is linked to the p75 neurotrophin receptor
BACE1 is a transmembrane aspartic protease that cleaves various substrates and it is required for normal brain function. BACE1 expression is high during early development, but it is reduced in adulthood. Under conditions of stress and injury, BACE1 levels are increased; however, the underlying mechanisms that drive BACE1 elevation are not well understood. One mechanism associated with brain injury is the activation of injurious p75 neurotrophin receptor (p75), which can trigger pathological signals. Here we report that within 72â€¯h after controlled cortical impact (CCI) or laser injury, BACE1 and p75 are increased and tightly co-expressed in cortical neurons of mouse brain. Additionally, BACE1 is not up-regulated in p75 null mice in response to focal cortical injury, while p75 over-expression results in BACE1 augmentation in HEK-293 and SY5Y cell lines. A luciferase assay conducted in SY5Y cell line revealed that BACE1 expression is regulated at the transcriptional level in response to p75 transfection. Interestingly, this effect does not appear to be dependent upon p75 ligands including mature and pro-neurotrophins. In addition, BACE1 activity on amyloid precursor protein (APP) is enhanced in SY5Y-APP cells transfected with a p75 construct. Lastly, we found that the activation of c-jun n-terminal kinase (JNK) by p75 contributes to BACE1 up-regulation. This study explores how two injury-induced molecules are intimately connected and suggests a potential link between p75 signaling and the expression of BACE1 after brain injury.