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Glucose-dependent insulinotropic polypeptide receptor signaling alleviates gut inflammation in mice

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Abstract

Glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide 1 (GLP-1) are gut-derived peptide hormones that potentiate glucose-dependent insulin secretion. The clinical development of GIP receptor (GIPR)–GLP-1 receptor (GLP-1R) multi-agonists exemplified by tirzepatide and emerging GIPR antagonist-GLP-1R agonist therapeutics such as maritide is increasing interest in the extra-pancreatic actions of incretin therapies. Both GLP-1 and GIP modulate inflammation, with GLP-1 also acting locally to alleviate gut inflammation in part through anti-inflammatory actions on GLP-1R+ intestinal intraepithelial lymphocytes. In contrast, whether GIP modulates gut inflammation is not known. Here, using gain and loss of function studies, we show that GIP alleviates 5-fluorouracil (5FU)-induced gut inflammation, whereas genetic deletion of Gipr exacerbates the proinflammatory response to 5FU in the murine small bowel (SB). Bone marrow (BM) transplant studies demonstrated that BM-derived Gipr-expressing cells suppress 5FU-induced gut inflammation in the context of global Gipr deficiency. Within the gut, Gipr was localized to non-immune cells, specifically stromal CD146+ cells. Hence, the extra-pancreatic actions of GIPR signaling extend to the attenuation of gut inflammation, findings with potential translational relevance for clinical strategies modulating GIPR action in people with type 2 diabetes or obesity.

Authors

Rola Hammoud, Kiran Deep Kaur, Jacqueline A. Koehler, Laurie L. Baggio, Chi Kin Wong, Katie E. Advani, Bernardo Yusta, Irina Efimova, Fiona M. Gribble, Frank Reimann, Sigal Fishman, Chen Varol, Daniel J. Drucker

Prognostic importance of direct assignment of parent-of-origin via long-read genome and epigenome sequencing in retinoblastoma

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Abstract

BACKGROUND. Current clinical sequencing methods cannot effectively detect DNA methylation and allele-specific variation to provide parent-of-origin information from the proband alone. Parent-of-origin effects can lead to differential disease and the inability to assign this in de novo cases limits prognostication in the majority of affected individuals with retinoblastoma, a hereditary cancer with suspected parent-of-origin effects. METHODS. To directly assign parent-of-origin in retinoblastoma patients, genomic DNA was extracted from blood samples for sequencing using a programmable, targeted single-molecule long-read DNA genomic and epigenomic approach. This allowed germline variant calling and simultaneous haplotype-resolved CpG methylation in subjects with familial (n=7) and de novo (n=9) retinoblastoma. RESULTS. Targeted long-read sequencing allowed phasing genomic variation with a differentially methylated region in intron 2 of the RB1 gene to confirm parent-of-origin in known familial samples. Leveraging this approach allowed us to directly assign parent-of-origin rapidly in simple and complex de novo cases from the proband alone. The ability to assign parent-of-origin in all cases of retinoblastoma showed that harboring disease-causing variants on the paternally inherited allele, whether arising familial or de novo, is associated with more advanced cancer staging at presentation and significantly greater risk of chemotherapy failure (P=0.002). CONCLUSION. This study demonstrates the diagnostic potential of multi-omic long-read profiling to unveil the parent-of-origin effect in hereditary cancer. The approach in this work will be instrumental in assigning parent-of-origin to other genetic diseases using local and distant imprinting signals in the genome. FUNDING. National Eye Institute, NIH (K08EY033789); Gerber Foundation; Research to Prevent Blindness

Authors

Andrew W. Stacey, Kenji Nakamichi, Jennifer Huey, Jeffrey Stevens, Natalie Waligorski, Erin E. Crotty, Russell N. Van Gelder, Debarshi Mustafi

Endothelial Response to Blood-Brain Barrier Disruption in the Human Brain

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Abstract

Cerebral endothelial cell (EC) injury and blood-brain barrier (BBB) permeability contribute to neuronal injury in acute neurological disease states. Preclinical experiments have used animal models to study this phenomenon, yet the response of human cerebral ECs to BBB disruption remains unclear. In our Phase 1 clinical trial (NCT04528680), we used low-intensity pulsed ultrasound with microbubbles (LIPU/MB) to induce transient BBB disruption of peri-tumoral brain in patients with recurrent glioblastoma. We found radiographic evidence that BBB integrity was mostly restored within 1-hour of this procedure. Using single-cell RNA sequencing and transmission electron microscopy, we analyzed the acute response of human brain ECs to ultrasound-mediated BBB disruption. Our analysis revealed distinct EC gene expression changes after LIPU/MB, particularly in genes related to neurovascular barrier function and structure, including changes to genes involved in the basement membrane, EC cytoskeleton, and junction complexes, as well as caveolar transcytosis and various solute transporters. Ultrastructural analysis showed that LIPU/MB led to a decrease in luminal caveolae, the emergence of cytoplasmic vacuoles, and the disruption of the basement membrane and tight junctions, among other things. These findings suggested that acute BBB disruption by LIPU/MB led to specific transcriptional and ultrastructural changes and could represent a conserved mechanism of BBB repair after neurovascular injury in humans.

Authors

Andrew Gould, Yu Luan, Ye Hou, Farida V. Korobova, Li Chen, Victor A. Arrieta, Christina Amidei, Rachel Ward, Cristal Gomez, Brandyn Castro, Karl Habashy, Daniel Zhang, Mark Youngblood, Crismita Dmello, John Bebawy, Guillaume Bouchoux, Roger Stupp, Michael Canney, Feng Yue, M. Luisa Iruela-Arispe, Adam M. Sonabend

TRPC1 links calcium signaling to cellular senescence in the protection against post-traumatic osteoarthritis

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Abstract

Transient receptor potential channel 1 (TRPC1) is a widely expressed mechanosensitive ion channel located within the endoplasmic reticulum membrane, crucial for refilling depleted internal calcium stores during activation of calcium-dependent signaling pathways. Here, we demonstrate that TRPC1 activity is protective within cartilage homeostasis in the prevention of cellular senescence associated cartilage breakdown during mechanical and inflammatory challenge. We reveal that TRPC1 loss is associated with early stages of osteoarthritis (OA) and plays a non-redundant role in calcium signaling in chondrocytes. Trpc1-/- mice subjected to destabilization of the medial meniscus induced OA developed a more severe OA phenotype than wild type controls. During early OA development, Trpc1-/- mice displayed an increased chondrocyte survival rate, however remaining cells displayed features of senescence including p16INK4a expression and decreased Sox9. RNA sequencing identified differentially expressed genes related to cell number, apoptosis and extracellular matrix organization. Trpc1-/-chondrocytes exhibited accelerated dedifferentiation, while demonstrating an increased susceptibility to cellular senescence. Targeting the mechanism of Trpc1 activation may be a promising therapeutic strategy in osteoarthritis prevention.

Authors

Meike Sambale, Starlee Lively, Osvaldo Espin-Garcia, Pratibha Potla, Chiara Pastrello, Sarah Bödecker, Linda Wessendorf, Simon Kleimann, Peter Paruzel, Rojiar Asgarian, Alexandra Tosun, Johanna Intemann, Jessica Bertrand, Francesco Dell'Accio, Mohit Kapoor, Thomas Pap, Joanna Sherwood

Obesity modulates NK-cell activity via LDL & DUSP1 signaling for Populations with Adverse Social Determinants

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Abstract

African American (AA) women are disproportionally affected by obesity and hyperlipidemia, particularly in the setting of adverse social determinants of health (aSDoH) contributing to health disparities. Obesity, hyperlipidemia, and aSDoH appear to impair Natural Killer cells (NKs). As potential common underlying mechanisms are largely unknown, we sought to investigate common signaling pathways involved in NK dysfunction related to obesity and hyperlipidemia in AA women from under-resourced neighborhoods. We determined in freshly isolated NKs that obesity and measures of aSDoH are associated with a shift in NK subsets away from CD56dim/CD16+ cytotoxic NKs. Using ex vivo data, we identified LDL as a marker related to NK cell function in an AA population from under-resourced neighborhoods. Additionally, NK cells from AA women with obesity and LDL-treated NK cells displayed a loss in NK cell function. Comparative unbiased RNA sequencing analysis revealed DUSP1 as a common factor. Subsequently, chemical inhibition of DUSP1 and DUSP1 overexpression in NK cells highlighted its significance in NK cell function and lysosome biogenesis in a mTOR/TFEB-related fashion. Our data demonstrate a pathway by which obesity and hyperlipidemia in the setting of aSDoH may relate to NK dysfunction, making DUSP1 an important target for further investigation of health disparities.

Authors

Yvonne Baumer, Komudi Singh, Abhinav Saurabh, Andrew S. Baez, Cristhian A. Gutierrez-Huerta, Long Chen, Muna Igboko, Briana S. Turner, Josette A. Yeboah, Robert N. Reger, Lola R. Ortiz-Whittingham, Sahil Joshi, Marcus R. Andrews, Elizabeth M. Aquino Peterson, Christopher K.E. Bleck, Laurel G. Mendelsohn, Valerie M. Mitchell, Billy S. Collins, Neelam R. Redekar, Skyler A. Kuhn, Christian A. Combs, Mehdi Pirooznia, Pradeep K. Dagur, David S.J. Allan, Daniella Muallem-Schwartz, Richard W. Childs, Tiffany M. Powell-Wiley

Age-related TFEB downregulation in proximal tubules causes systemic metabolic disorders and occasional apolipoprotein A4-related amyloidosis

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Abstract

With the aging of society, the incidence of chronic kidney disease (CKD), a common cause of death, has been increasing. Transcription factor EB (TFEB), the master transcriptional regulator of the autophagy–lysosomal pathway, is regarded as a promising candidate for preventing various age-related diseases. However, whether TFEB in the proximal tubules plays a significant role in elderly CKD patients remains unknown. First, we found that nuclear TFEB localization in proximal tubular epithelial cells (PTECs) declined with age in both mice and humans. Next, we generated PTEC-specific Tfeb-deficient mice and bred them for up to 24 months. We found that TFEB deficiency in the proximal tubules caused metabolic disorders and occasionally led to apolipoprotein A4 (APOA4) amyloidosis. Supporting this result, we identified markedly decreased nuclear TFEB localization in the proximal tubules of elderly patients with APOA4 amyloidosis. The metabolic disturbances were accompanied with mitochondrial dysfunction due to transcriptional changes involved in fatty acid oxidation and oxidative phosphorylation pathways, as well as decreased mitochondrial clearance reflected by the accumulation of mitochondria–lysosome-related organelles, which depends on lysosomal function. These results shed light on the presumptive mechanisms of APOA4 amyloidosis pathogenesis and provide a therapeutic strategy for CKD-related metabolic disorders and APOA4 amyloidosis.

Authors

Jun Nakamura, Takeshi Yamamoto, Yoshitsugu Takabatake, Tomoko Namba-Hamano, Atsushi Takahashi, Jun Matsuda, Satoshi Minami, Shinsuke Sakai, Hiroaki Yonishi, Shihomi Maeda, Sho Matsui, Hideaki Kawai, Isao Matsui, Tadashi Yamamuro, Ryuya Edahiro, Seiji Takashima, Akira Takasawa, Yukinori Okada, Tamotsu Yoshimori, Andrea Ballabio, Yoshitaka Isaka

MUC17 is an essential small intestinal glycocalyx component that is disrupted in Crohn’s disease

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Abstract

Crohn's disease (CD) is the chronic inflammation of the terminal ileum and colon triggered by a dysregulated immune response to bacteria, but insights into specific molecular perturbations at the critical bacteria-epithelium interface are limited. Here we report that the membrane mucin MUC17 protected small intestinal enterocytes against commensal and pathogenic bacteria. In non-inflamed CD ileum, reduced MUC17 levels and a compromised glycocalyx barrier allowed recurrent bacterial contact with enterocytes. Muc17 deletion in mice rendered the small intestine particularly prone to atypical bacterial infection while maintaining resistance to colitis. The loss of Muc17 resulted in spontaneous deterioration of epithelial homeostasis and in the extra-intestinal translocation of bacteria. Finally, Muc17-deficient mice harbored specific small intestinal bacterial taxa observed in CD patients. Our findings highlight MUC17 as an essential regiospecific line of defense in the small intestine with relevance for early epithelial defects in CD.

Authors

Elena Layunta, Sofia Jäverfelt, Fleur C. van de Koolwijk, Molly Sivertsson, Brendan Dolan, Liisa Arike, Sara I.M. Thulin, Bruce A. Vallance, Thaher Pelaseyed

Dysregulated alveolar epithelial cell progenitor function and identity in Hermansky-Pudlak syndrome

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Abstract

Hermansky-Pudlak syndrome (HPS) is a genetic disorder of endosomal protein trafficking associated with pulmonary fibrosis in specific subtypes, including HPS-1 and HPS-2. Single mutant HPS1 and HPS2 mice display increased fibrotic sensitivity while double mutant HPS1/2 mice exhibit spontaneous fibrosis with aging, which has been attributed to HPS mutations in alveolar epithelial type II (AT2) cells. We utilized HPS mouse models and human lung tissue to investigate mechanisms of AT2 cell dysfunction driving fibrotic remodeling in HPS. Starting at 8 weeks of age, HPS mice exhibited progressive loss of AT2 cell numbers. HPS AT2 cell function was impaired ex vivo and in vivo. Incorporating AT2 cell lineage tracing in HPS mice, we observed aberrant differentiation with increased AT2-derived alveolar epithelial type I cells. Transcriptomic analysis of HPS AT2 cells revealed elevated expression of genes associated with aberrant differentiation and p53 activation. Lineage tracing and organoid modeling studies demonstrated that HPS AT2 cells were primed to persist in a Krt8+ reprogrammed transitional state, mediated by p53 activity. Intrinsic AT2 progenitor cell dysfunction and p53 pathway dysregulation are novel mechanisms of disease in HPS-related pulmonary fibrosis, with the potential for early targeted intervention before the onset of fibrotic lung disease.

Authors

Joanna Y. Wang, Sylvia N. Michki, Sneha Sitaraman, Brandon J. Banaschewski, Reshma Jamal, Jason J. Gokey, Susan M. Lin, Jeremy B. Katzen, Maria C. Basil, Edward Cantu, Jonathan A. Kropski, Jarod A. Zepp, David B. Frank, Lisa R. Young

Orthotopic gastric cancer mouse model identifies trajectory of lymphatic metastasis

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Abstract

Authors

Huafeng Fu, Qinbo Cai, Zhijun Zhou, Yulong He, Min Li, DongJie Yang

Airway-resident memory CD4 T-cell activation accelerates antigen presentation and T-cell priming in draining lymph nodes

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Abstract

Specialized memory CD4 T cells that reside long-term within tissues are critical components of immunity at portals of pathogen entry. In the lung, such tissue-resident memory (TRM) cells are activated rapidly after infection and promote local inflammation to control pathogen levels before circulating T cells can respond. However, optimal clearance of Influenza A virus can require TRM and responses by other virus-specific T cells that reach the lung only several days after their activation in secondary lymphoid organs. Whether local CD4 TRM sentinel activity can impact the efficiency of T cell activation in secondary lymphoid organs is not clear. Here, we found that recognition of antigen by influenza -primed TRM in the airways promotes more rapid migration of highly activated antigen-bearing dendritic cells to the draining lymph nodes. This in turn accelerated the priming of naive T cells recognizing the same antigen, resulting in newly activated effector T cells reaching the lungs earlier than in mice not harboring TRM. Our findings thus reveal a circuit linking local and regional immunity whereby antigen recognition by TRM improves effector T cell recruitment to the site of infection though enhancing the efficiency of antigen presentation in the draining lymph node.

Authors

Caroline M. Finn, Kunal Dhume, Eugene Baffoe, Lauren A. Kimball, Tara M. Strutt, K. Kai McKinstry

Negative feedback between PTH1R and IGF1 through the Hedgehog pathway in mediating craniofacial bone remodeling

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Abstract

Regeneration of orofacial bone defects caused by inflammatory-related diseases or trauma remains an unmet challenge. Parathyroid hormone 1 receptor (PTH1R) signaling is a key mediator of bone remodeling whereas the regulatory mechanisms of PTH1R signaling in oral bone under homeostatic or inflammatory conditions have not been demonstrated by direct genetic evidence. Here we observed that deletion of PTH1R in Gli1+-progenitors led to increased osteogenesis and osteoclastogenesis. Single-cell and bulk RNA-seq analysis revealed that PTH1R suppresses the osteogenic potential of Gli1+-progenitors during inflammation. Moreover, we identified upregulated IGF1 expression upon PTH1R deletion. Dual deletion of IGF1 and PTH1R ameliorated the bone remodeling phenotypes in PTH1R-defienct mice. Furthermore, in vivo evidence revealed an inverse relationship between PTH1R and Hedgehog signaling, which was responsible for the upregulated IGF1 production. Our work underscored the negative feedback between PTH1R and IGF1 in craniofacial bone turnover, and revealed mechanisms modulating orofacial bone remodeling.

Authors

Yi Fan, Ping Lyu, Jiahe Wang, Yali Wei, Zucen Li, Shiwen Zhang, Takehito Ouchi, Junjun Jing, Quan Yuan, Clifford J. Rosen, Chenchen Zhou

Angiotensin receptor blockers modulate the lupus CD4+ T cell epigenome characterized by TNF family-linked signaling

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Abstract

In systemic lupus erythematosus (lupus), environmental effects acting within a permissive genetic background lead to autoimmune dysregulation. Dysfunction of CD4+ T cells contributes to pathology by providing help to autoreactive B and T cells, and CD4+ T cell dysfunction coincides with altered DNA methylation and histone modifications of select gene loci. However, chromatin accessibility states of distinct T cell subsets and mechanisms driving heterogeneous chromatin states across patients remain poorly understood. We defined the transcriptome and epigenome of multiple CD4+ T cell populations from lupus patients and healthy individuals. Most lupus patients, regardless of disease activity, had enhanced chromatin accessibility bearing hallmarks of inflammatory cytokine signals. Single cell approaches revealed that chromatin changes extended to naive CD4+ T cells; uniformly affecting naive subpopulations. Transcriptional data and cellular and protein analyses suggested that the TNF family members, TNFɑ, LIGHT, and TWEAK, were linked to observed molecular changes and the altered lupus chromatin state. However, we identified a patient subgroup prescribed angiotensin receptor blockers (ARBs) which lacked TNF-linked lupus chromatin accessibility features. These data raise questions about the role of lupus-associated chromatin changes in naive CD4+ T cell activation and differentiation and implicate ARBs in the regulation of disease-driven epigenetic states.

Authors

Andrew P. Hart, Jonathan J. Kotzin, Steffan W. Schulz, Jonathan S. Dunham, Alison L. Keenan, Joshua F. Baker, Andrew D. Wells, Daniel P. Beiting, Terri M. Laufer

Noise induces Ca2+ signaling waves and Chop/S-Xbp1 expression in the hearing cochlea

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Abstract

Exposure to loud noise is a common cause of acquired hearing loss. Disruption of subcellular calcium homeostasis and downstream stress pathways in the endoplasmic reticulum and mitochondria, including the unfolded protein response, have been implicated in the pathophysiology of noise-induced hearing loss. However, studies on the association between calcium homeostasis and stress pathways have been limited due to limited ability to measure calcium dynamics in mature-hearing, noise-exposed mice. We used a genetically encoded calcium indicator mouse model in which GCaMP is expressed specifically in hair cells or supporting cells under control of Myo15Cre or Sox2Cre, respectively. We performed live calcium imaging and UPR gene expression analysis in 8-week-old mice exposed to levels of noise that cause cochlear synaptopathy (98 db SPL) or permanent hearing loss (106 dB SPL). UPR activation occurred immediately after noise exposure and was noise dose-dependent, with the pro-apoptotic pathway upregulated only after 106 dB noise exposure. Spontaneous calcium transients in hair cells and intercellular calcium waves in supporting cells, which are present in neonatal cochleae, were quiescent in mature-hearing cochleae, but re-activated upon noise exposure. 106 dB noise exposure was associated with more persistent and expansive intercellular Ca2+ signaling wave activity. These findings demonstrated a strong and dose-dependent association between noise exposure, UPR activation, and changes in calcium homeostasis in hair cells and supporting cells, suggesting that targeting these pathways may be effective to develop treatments for noise-induced hearing loss.

Authors

Yesai Park, Jiang Li, Noura Ismail Mohamad, Ian R. Matthews, Peu Santra, Elliott H. Sherr, Dylan K Chan

Noncoding variation near UBE2E2 orchestrates cardiometabolic pathophenotypes through polygenic effectors

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Abstract

Mechanisms underpinning signals from genome wide association studies remain poorly understood, particularly for non-coding variation and for complex diseases such as type 2 diabetes mellitus (T2D) where pathogenic mechanisms in multiple different tissues may be disease driving. One approach is to study relevant endophenotypes, a strategy we applied to the UBE2E2 locus where non-coding SNVs are associated with both T2D and visceral adiposity (a pathologic endophenotype). We integrated CRISPR targeting of SNV-containing regions and unbiased CRISPRi screening to establish candidate cis-regulatory regions, complemented by genetic loss of function in murine diet-induced obesity or ex vivo adipogenesis assays. Nomination of a single causal gene was complicated, however, because targeting of multiple genes near UBE2E2 attenuated adipogenesis in vitro, CRISPR excision of SNV-containing non-coding regions and a CRISPRi regulatory screen across the locus suggested concomitant regulation of UBE2E2, the more distant UBE2E1, and other neighborhood genes, and compound heterozygous loss of function of both Ube2e2 and Ube2e1 better replicated pathological adiposity and metabolic phenotypes than homozygous loss of either gene in isolation. This study advances a model whereby regulatory effects of non-coding variation not only extend beyond the nearest gene but may also drive complex diseases through polygenic regulatory effects.

Authors

Yang Zhang, Natalie L. David, Tristan Pesaresi, Rosemary E. Andrews, G.V. Naveen Kumar, Hongyin Chen, Wanning Qiao, Jinzhao Yang, Kareena Patel, Tania Amorim, Ankit X. Sharma, Silvia Liu, Matthew L. Steinhauser

Regulatory T cells promote decidual vascular remodeling and modulate uterine NK cells in pregnant mice

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Abstract

Regulatory T (Treg) cells are essential for maternal immune tolerance of the fetus and placenta. In preeclampsia, aberrant Treg cell tolerance is implicated, but whether and how Treg cells affect the uterine vascular dysfunction thought to precede placental impairment and maternal vasculopathy is unclear. We utilized Foxp3DTR mice to test the hypothesis that Treg cells are essential regulators of decidual spiral artery adaptation to pregnancy. Transient Treg cell depletion during early placental morphogenesis caused impaired remodeling of decidual spiral arteries, altered uterine artery function and led to fewer DBA+ uterine natural killer (uNK) cells, resulting in late gestation fetal loss and fetal growth restriction. Replacing the Treg cells by transfer from wild-type donors mitigated the impact on uNK cells, vascular remodeling, and fetal loss. RNA sequencing of decidua revealed genes associated with NK cell function and placental extravillous trophoblasts were dysregulated after Treg cell depletion, and normalized by Treg cell replacement. These data implicate Treg cells as essential upstream drivers of uterine vascular adaptation to pregnancy, through a mechanism likely involving phenotypic regulation of uNK cells and trophoblast invasion. The findings provide insight into mechanisms linking impaired adaptive immune tolerance and altered spiral artery remodeling, two hallmark features of preeclampsia.

Authors

Shanna L. Hosking, Lachlan M. Moldenhauer, Ha M. Tran, Hon Y. Chan, Holly M. Groome, Evangeline A.K. Lovell, Ella S. Green, Stephanie E. O'Hara, Claire T. Roberts, Kerrie L. Foyle, Sandra T. Davidge, Sarah A. Robertson, Alison S. Care

Live Cell Imaging of Human Liver Fibrosis using Hepatic Micro-Organoids

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Abstract

Due to the limitations of available in vitro systems and animal models, we lack a detailed understanding of the pathogenetic mechanisms and have minimal treatment options for liver fibrosis. Therefore, we engineered a live cell imaging system that assesses fibrosis in a human multi-lineage hepatic organoid in a microwell (i.e., microHOs). Transcriptomic analysis revealed that TGFβ1 converted mesenchymal cells in microHOs into myofibroblast-like cells resembling those in fibrotic human liver tissue. When pro-fibrotic intracellular signaling pathways were examined, the anti-fibrotic effect of receptor-specific tyrosine kinase inhibitors was limited to the fibrosis induced by the corresponding growth factor, which indicates their anti-fibrotic efficacy would be limited to fibrotic diseases solely mediated by that growth factor. Based upon transcriptomic and transcription factor activation analyses in microHOs, GSK3β and p38 MAPK inhibitors were identified as potential new broad-spectrum therapies for liver fibrosis. Other new therapies could subsequently be identified using the microHO system.

Authors

Yuan Guan, Zhuoqing Fang, Angelina Hu, Sarah Roberts, Meiyue Wang, Wenlong Ren, Patrik K. Johansson, Sarah C. Heilshorn, Annika Enejder, Gary Peltz

Monocyte uptake of polymeric peptidoglycan is bimodal and governed by complement C3 and C4 opsonins

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Abstract

Peptidoglycans (PGNs) are structural polymers of the bacterial cell wall and a common microbial molecular pattern encountered by our immune system daily. Low levels of PGNs are constitutively present in the systemic circulation in humans and elevate during inflammatory pathologies. Since all known PGN sensors are intracellular, PGN internalization is a prerequisite for the initiation of cellular immune responses. Here we report the mechanisms controlling the recognition and uptake of polymeric PGNs by circulating human mononuclear phagocytes. We found that complement C3 and C4 opsonins govern PGN recognition and internalization, but no single opsonin is indispensable due to multiple uptake redundancies. We observed a bimodal internalization of polymeric PGNs with distinct requirements for complement C4. At low PGN concentrations, C3 mediated PGN recognition by surface receptors while the efficient internalization of PGN polymers critically required C4. Supraphysiologic PGN concentrations triggered a secondary uptake modality that was insensitive to C4 and mediated instead by C3 engagement of complement receptors 1 and 3. To our knowledge this is the first description of non-overlapping C3 and C4 opsonophagocytoses working in parallel. Controlling these uptake mechanisms has the potential to modulate PGN clearance and/or the dysregulated immune responses during bacterial infections.

Authors

Narcis I. Popescu, Jędrzej Kluza, Megan A. Reidy, Elizabeth Duggan, John D. Lambris, Linda F. Thompson, K. Mark Coggeshall

RasGRP4 aggravates ischemia-reperfusion injury in diabetic kidneys by mediating communication between macrophages and T cells

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Abstract

Diabetes mellitus (DM) is acknowledged as an independent risk factor for acute kidney injury. Ras guanine nucleotide-releasing protein-4 (RasGRP4) exerts a notable role in modulating immune-inflammatory responses and kidney disease progression in diabetes. Herein, we delved into the specific role and mechanism of RasGRP4 in diabetic renal ischemia-reperfusion injury. Diabetes was induced by a high-fat diet and STZ injections, followed by creating an ischemia-reperfusion kidney injury via renal pedicle clamping and reperfusion. In vitro, a high glucose and hypoxia-reoxygenation modeled cellular inflammatory injury. We found RasGRP4 knockout (KO) mice, compared to C57BL/6J (WT) mice, showed markedly less renal dysfunction and fibrosis in diabetic ischemia-reperfusion injury. There was a significant decrease in the renal infiltration of M1 macrophages and Th17 cells, along with downregulated IL17 pathway proteins and effectors. In vitro, RasGRP4 deletion restrained M1 macrophage polarization and Th17 cell differentiation, inhibiting the IL17 signaling pathway in HK-2 cells. Hyperglycemia intensified renal inflammation state. Together, RasGRP4, through the regulation of interactions among M1 macrophages, CD4+ T cells and HK-2 cells, formed a cascade that intensified the inflammatory storm activity, ultimately exacerbating the inflammatory injury of diabetic ischemia-reperfusion kidneys. DM intensified this inflammatory injury mechanism, worsening the injury from renal ischemia-reperfusion.

Authors

Li Zhang, Zhanglong Wang, Yunqi Wu, Binshan Zhang, Zhongli Wang, Sisi Chen, Mengxu Ying, Pei Yu, Saijun Zhou

WNT signaling contributes to the extrahepatic bile duct proliferative response to obstruction in mice

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Abstract

Biliary obstruction and cholangiocyte hyperproliferation are important features of cholangiopathies affecting the large extrahepatic bile duct (EHBD). The mechanisms underlying obstruction-induced cholangiocyte proliferation in the EHBD remain poorly understood. Developmental pathways, including WNT signaling, are implicated in regulating injury responses in many tissues, including the liver. To investigate the contribution of WNT signaling to obstruction-induced cholangiocyte proliferation in the EHBD, we used complementary in vivo and in vitro models with pharmacologic interventions and transcriptomic analyses. To model obstruction, we used bile duct ligation (BDL) in mice. Human and mouse biliary organoids and mouse biliary explants were used to investigate the effects of WNT activation and inhibition in vitro. We observed an upregulation of WNT ligand expression associated with increased biliary proliferation following obstruction. Cholangiocytes were identified as both WNT ligand-expressing and WNT responsive cells. Inhibition of WNT signaling decreased cholangiocyte proliferation in vivo and in vitro, while activation increased proliferation. WNT effects on cholangiocyte proliferation were β-catenin-dependent, and we showed a direct effect of WNT7B on cholangiocyte growth. Our studies suggested that cholangiocyte-derived WNT ligands can activate WNT signaling to induce proliferation after obstructive injury. These findings implicated the WNT pathway in injury-induced cholangiocyte proliferation within the EHBD.

Authors

Ashley N. Calder, Mirabelle Q. Peter, John W. Tobias, Nureen H. Mohamad Zaki, Theresa M. Keeley, Timothy L. Frankel, Linda C. Samuelson, Nataliya Razumilava

Variation in HIV-1 Tat activity is a key determinant in the establishment of latent infection

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Abstract

Despite effective treatment, Human immunodeficiency virus (HIV) persists in optimally treated people as a transcriptionally silent provirus. Latently infected cells evade the immune system and the harmful effects of the virus, thereby creating a long-lasting reservoir of HIV. To gain a deeper insight into the molecular mechanisms of HIV latency establishment, we constructed a series of HIV-1 fluorescent reporter viruses that distinguish active versus latent infection. We unexpectedly observed that the proportion of active-to-latent infection depended on a limiting viral factor, which created a bottle neck that could be overcome by superinfection of the cell, T cell activation or overexpression of HIV-1 trans activator of transcription (Tat). In addition, we found that tat and rev expression levels vary amongst HIV molecular clones and that tat levels were an important variable in latency establishment. Lower rev levels limited viral protein expression whereas lower Tat levels or mutation of the Tat binding element promoted latent infection that was resistant to reactivation even in fully activated primary T cells. Nevertheless, we found that combinations of latency reversal agents targeting both cellular activation and histone acetylation pathways overcame deficiencies in the Tat-TAR axis of transcription regulation. These results provide additional insight into the mechanisms of latency establishment and inform Tat-centered approaches to cure HIV.

Authors

Francisco Gomez-Rivera, Valeri H. Terry, Cuie Chen, Mark M. Painter, Maria C. Virgilio, Marianne E. Yaple-Maresh, Kathleen L. Collins