Biology subjects

Latz, E.

Publications and source records attributed to Latz, E..

At least 19 recordsLinked to original sources

bioRxiv2026

TLR-mediated activation of synovial fibroblasts from osteoarthritis patients promotes chondrocyte dysfunction

Objective: Toll like receptor (TLR) activation by cartilage derived damage-associated molecular patterns contributes to osteoarthritis (OA) pathogenesis, but the role of synovial fibroblasts in this process remains incompletely understood. We investigated the TLR responsiveness of human OA synovial fibroblasts and determined how TLR activation influences fibroblast-mediated regulation of chondrocyte function. Design: Primary synovial fibroblasts isolated from OA patients were characterized for TLR expression and stimulated with agonists targeting TLR1/2 to TLR9. Inflammatory mediator production, matrix metalloproteinase expression, mitochondrial respiration, and transcriptomic responses were assessed. Functional effects on cartilage homeostasis were evaluated using autologous chondrocyte spheroid co-cultures. Results: Approximately 50% of cells within OA synovial membranes were fibroblasts (CD45-CD31-PDPN+). Synovial fibroblasts expressed multiple TLRs at both the transcript and protein levels. Activation of TLR1/2, TLR4, TLR5, and TLR2/6 induced robust expression of IL-6, IL-8, G-CSF, MMP3, and MMP10, with minimal effects on mitochondrial respiratory function. Transcriptomic analysis revealed activation of inflammatory pathways together with enrichment of antigen presentation and protein translation programs. In autologous co-culture, TLR1/2-activated synovial fibroblasts promoted inflammatory and catabolic gene expression, suppressed anabolic gene expression, and impaired chondrocyte spheroid growth. Conclusions: Human OA synovial fibroblasts are highly responsive to TLR activation and acquire a pro-inflammatory, cartilage-degrading phenotype that directly impairs chondrocyte homeostasis. These findings identify synovial fibroblasts as key effectors of innate immune signalling within the OA joint and support targeting shared TLR-mediated pathways in joint-resident cells as a potential disease-modifying therapeutic strategy.

immunology↗

bioRxiv2026

NLRP3 activators disrupt the endocytic AP2 complex and plasma membrane signaling

Organellar perturbations are linked to NLRP3 inflammasome activation, however, it remains unclear whether unrelated agonists converge on a common upstream pathway. Here, we traced intracellular organelle and protein movements by differential ultracentrifugation combined with mass spectrometry-based proteomics. We show that NLRP3 activators uniformly disrupt the endocytic Adaptor Protein 2 (AP2) complex, whereas other subcellular rearrangements are stimulus-specific. We discovered Dynasore as a K-efflux-independent NLRP3 activator that engages this signaling node irrespective of endocytosis inhibition. Pharmacological and genetic perturbation of AP2 renders cells unresponsive to extracellular cues, blunting GPCR signaling, cAMP production, and chemotaxis, thereby enforcing a frozen signaling state that propagates NLRP3 inflammasome activation. Collectively, our study reveals a common surveillance checkpoint linking impaired plasma membrane signaling to the execution of inflammation and cell death. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=200 SRC="FIGDIR/small/707400v1_ufig1.gif" ALT="Figure 1"> View larger version (44K): org.highwire.dtl.DTLVardef@178eb1dorg.highwire.dtl.DTLVardef@193cb02org.highwire.dtl.DTLVardef@1f50080org.highwire.dtl.DTLVardef@1f3e3e4_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗

bioRxiv2026

Local albumin excess exacerbates Candida albicans-induced inflammasome activation underlying the immunopathology of vulvovaginal candidiasis.

Vulvovaginal candidiasis (VVC) is a mucosal yeast infection where symptoms are driven by inflammatory responses. The onset of VVC is instigated by the yeast Candida albicans, but the underlying causes of disease-driving hyperinflammation remains incompletely resolved. We found that vaginal albumin concentrations are higher in women with recurrent VVC and during VVC in mice. These albumin levels correlated with inflammatory cytokines in vaginal lavages. While the abundance of this serum protein in the vagina can represent a hallmark of inflammation-induced vascular permeability, we reveal molecular mechanisms by which albumin also drives inflammation. It increased NLRP3 inflammasome activation in human macrophages elicited by C. albicans. Albumin induced fungal adaptations that increased resistance to macrophage-mediated clearance. Further it increased the expression of fungal secreted aspartic protease 1, which we identified as the effector driving inflammasome activation. Moreover, neutrophils show impaired effectivity in clearing C. albicans in presence of albumin. Collectively, vaginal albumin may not only be a consequence of inflammation of the vaginal mucosa, but also can drive hyperinflammatory responses that underlie immunopathology in VVC. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=187 SRC="FIGDIR/small/700771v1_ufig1.gif" ALT="Figure 1"> View larger version (48K): org.highwire.dtl.DTLVardef@f13fd5org.highwire.dtl.DTLVardef@95e58aorg.highwire.dtl.DTLVardef@11104dforg.highwire.dtl.DTLVardef@56e9be_HPS_FORMAT_FIGEXP M_FIG C_FIG

microbiology↗

bioRxiv2025

NLRP3 inhibition maintains microglia architecture and enhances behavioral recovery after traumatic brain injury

NLRP3 plays an essential role in secondary neuroinflammatory damage following traumatic brain injury (TBI). However, the specific mechanisms mediating NLRP3s effects in TBI remain poorly understood, and it is unknown whether its pharmacological inhibition with oral compounds during initial phases confers long-term protection. In this study, we investigated the role of the NLRP3 inflammasome pathway in TBI-induced neuroinflammation and long-term neurobehavioral impairment, as well as the impact of its pharmacological inhibition. Following controlled cortical impact (CCI), most NLRP3 inflammasome-related proteins and key inflammatory markers were elevated during the first week post-injury. Genetic Nlrp3 deletion and treatment with oral NLRP3-specific inhibitors preserved microglial homeostatic architecture, reduced ASC aggregation, and enhanced neurological and cognitive recovery after CCI. Repeated intravital imaging confirmed that NLRP3 inhibition prevents microglial activation post-TBI. These findings suggest NLRP3 inflammasome targeting represents a viable translational strategy for clinical trials and may mitigate long-term neurocognitive decline following TBI.

neuroscience↗

bioRxiv2025

ASC contributes to sustained glial reactivity and mild cognitive impairment after closed-head injury

Mild brain traumatic brain injury (mTBI) from closed-head injuries (CHI) can lead to prevalent neuropsychiatric disorders, including an increased risk for neurodegenerative diseases and dementia. Inflammasomes are molecular complexes crucial for neuroinflammation and secondary damage after trauma, however their role in mild CHI is poorly understood. In this study, we investigate the cellular expression of inflammasome-related genes and their functional significance in CHI models. Single-cell RNA sequencing of cortical tissue revealed selective expression of Pycard (PYD and CARD domain containing), also known as Asc (apoptosis-associated speck-like protein containing a caspase recruitment domain), which encodes the inflammasome adaptor ASC, predominantly in microglial clusters. Sustained upregulation of inflammasome-related proteins persisted up to 21 days in a model for mTBI, with this pattern significantly reduced in Asc-/- mice. Importantly, mild cognitive impairment induced after mild CHI was largely abrogated in Asc-/- mice. These findings suggest that ASC, as the primary inflammasome adaptor, plays a critical role in sustaining neuroinflammation and contributes to cognitive deficits after mild CHI. This study provides insights into the molecular neuroinflammatory mechanisms underlying CHI, potentially informing future therapeutic strategies.

neuroscience↗

bioRxiv2024

Cytosolic sodium accumulation is a cellular danger signal triggering endocytic dysfunction and NLRP3 inflammasome activation

Detecting and responding to noxious molecules internalized within the endolysosomal system, including bacterial toxins and particulate matter, is essential to prevent cellular intoxication and damage. Here, we demonstrate that the NLRP3 inflammasome detects perturbations of the endolysosomal system by large clostridial toxins, including toxin B from Clostridioides difficile, as well as monosodium urate and silica crystals in human macrophages. These molecules cause sodium efflux from the endolysosomal system into the cytosol, driving cytosolic sodium accumulation. The rapid increase in cytosolic sodium subsequently triggers cell swelling and inhibits endocytic trafficking to activate the NLRP3 inflammasome. Furthermore, we demonstrate that cytosolic sodium accumulation is a common trigger for NLRP3 activation by non-particulate stimuli, including nigericin and inhibition of the Na+/K+ ATPase. Our findings reveal that accumulation of cytosolic sodium is the common denominator underlying activation of the NLRP3 inflammasome upon exposure to different danger signals.

immunology↗

bioRxiv2024

Butyrate and propionate are microbial danger signals that activate the NLRP3-inflammasome in human macrophages in the presence of TLR stimulation

Short chain fatty acids (SCFAs) are immunomodulatory compounds produced by the microbiome through fermentation of dietary fibre. Although they are generally considered beneficial for gut health, patients suffering from inflammatory bowel disease (IBD) have shown poor tolerance to fibre-rich diets, suggesting that SCFAs may have contrary effects under inflammatory conditions. To investigate this, we examined the effect of SCFAs on human macrophages in the presence of toll-like receptor agonists. In contrast to their anti-inflammatory effects under steady state conditions, we observed that the SCFAs butyrate and propionate triggered the activation of the NLRP3 inflammasome when added in conjunction with TLR agonists. Mechanistically, butyrate and propionate activated NLRP3 by inhibiting HDACs 1-3 and 10, leading to an uneven distribution of histone hyperacetylation that resulted in alterations in the transcriptome. Specifically, there was a lack of hyperacetylation at the loci of the CFLAR and IL10 genes, two important inhibitors of NLRP3 inflammasome activation. The concurrent loss of transcription and protein expression of cFLIP and IL-10 enabled caspase-8-dependent NLRP3-inflammasome activation. SCFA-driven NLRP3 activation did not require potassium efflux and did not result in cell death but rather triggered hyperactivation and IL-1{beta} release. Our findings demonstrate that butyrate and propionate are bacterially-derived, viability-dependent danger signals (vita-PAMPs) that regulate NLRP3 inflammasome activation through epigenetic modulation of the inflammatory response. SummaryUnder inflammatory conditions, SCFAs are bacterially-derived, viability-dependent danger signals that, through HDAC inhibition and epigenetic modification, prevent expression of the anti-cell death gene cFLIP to trigger activation of the NLRP3 inflammasome.

immunology↗

bioRxiv2024

NLRP3-induced systemic inflammation controls the development of JAK2V617F mutant myeloproliferative neoplasms

The development of Philadelphia chromosome-negative classical myeloproliferative neoplasms (MPN) involves an inflammatory process that facilitates outgrowth of the malignant clone and correlates with clinical outcome measures. This raises the question to which extent inflammatory circuits in MPN depend on activation of innate immune sensors. Here, we investigated whether NLRP3, which precipitates inflammasome assembly upon detection of cellular stress, drives murine JAK2V617F mutant MPN. Deletion of Nlrp3 within the hematopoietic compartment completely prevented increased IL-1{beta} and IL-18 release in MPN. NLRP3 in JAK2V617F hematopoietic cells, but not in JAK2 wild type radioresistant cells, promoted excessive platelet production via stimulation of the direct thrombopoiesis differentiation pathway, as well as granulocytosis. It also promoted expansion of the hematopoietic stem and progenitor cell compartment despite inducing pyroptosis at the same time. Importantly, NLRP3 inflammasome activation enhanced bone marrow fibrosis and splenomegaly. Pharmacological blockade of NLRP3 in fully established disease led to regression of thrombocytosis and splenomegaly. These findings suggest that NLRP3 is critical for MPN development and its inhibition represents a new therapeutic intervention for MPN patients. Key pointsO_LIThe increased IL-1{beta} and IL-18 release in JAK2V617F mutant MPN depends on NLRP3 inflammasome activation C_LIO_LINLRP3 in MPN promotes excess platelet production, granulocytosis, HSPC compartment expansion, splenomegaly and bone marrow fibrosis C_LI

cancer biology↗

bioRxiv2024

From Planning Stage To FAIR Data: A Practical Metadatasheet For Biomedical Scientists

Datasets consist of measurement data and metadata. Metadata provides context, essential for understanding and (re-)using data. Various metadata standards exist for different methods, systems and contexts. However, relevant information resides at differing stages across the data-lifecycle. Often, this information is defined and standardized only at publication stage, which can lead to data loss and workload increase. In this study, we developed Metadatasheet, a metadata standard based on interviews with members of two biomedical consortia and systematic screening of data repositories. It aligns with the data-lifecycle allowing synchronous metadata recording within Microsoft Excel, a widespread data recording software. Additionally, we provide an implementation, the Metadata Workbook, that offers user-friendly features like automation, dynamic adaption, metadata integrity checks, and export options for various metadata standards. By design and due to its extensive documentation, the proposed metadata standard simplifies recording and structuring of metadata for biomedical scientists, promoting practicality and convenience in data management. This framework can accelerate scientific progress by enhancing collaboration and knowledge transfer throughout the intermediate steps of data creation.

bioinformatics↗

bioRxiv2024

Cell Type-Agnostic Optical Perturbation Screening Using Nuclear In-Situ Sequencing (NIS-Seq)

Genome-scale perturbation screening is widely used to identify disease-relevant cellular proteins serving as potential drug targets. However, most biological processes are not compatible with commonly employed perturbation screening methods, which rely on FACS- or growth-based enrichment of cells. Optical pooled screening instead uses fluorescence microscopy to determine the phenotype in single cells, and subsequently to identify individual perturbagens in the same cells. Published methods rely on cytosolic detection of endogenously expressed barcoded transcripts, which limits application to large, transcriptionally active cell types, and often relies on local clusters of clonal cells for unequivocal barcode assignment, thus precluding genome-scale screening for many biological processes. Nuclear In-Situ Sequencing (NIS-Seq) solves these shortcomings by creating bright sequencing signals directly from nuclear genomic DNA, enabling screening any nucleus-containing cell type at high density and high library complexity. We benchmark NIS-Seq by performing three genome-scale optical screens in live cells, identifying key players of inflammation-related cellular pathways.

genomics↗

bioRxiv2024

Retention of ES cell-derived 129S genome drives NLRP1 hypersensitivity and transcriptional deregulation in Nlrp3-/- mice

Immune response genes are highly polymorphic in humans and mice, with heterogeneity amongst loci driving strain-specific host defense responses. The inadvertent retention of polymorphic loci can introduce confounding phenotypes, leading to erroneous conclusions, and impeding scientific advancement. In this study, we employ a combination of RNAseq and variant calling analyses and identify a substantial region of 129S genome, including the highly polymorphic Nlrp1 locus proximal to Nlrp3, in one of the most commonly used mouse models of NLRP3 deficiency. We show that increased expression of 129S NLRP1b sensitizes Nlrp3-/- macrophages to NLRP1 inflammasome activation. Furthermore, the presence of 129S genome leads to altered gene and protein regulation across multiple cell-types, including of the key tissue-resident macrophage marker, TIM4. To address the challenge of resolving NLRP3-dependent phenotypes, we introduce and validate a conditional Nlrp3 allele, enabling precise temporal and cell-type-specific control over Nlrp3 deletion. Our study establishes a generic framework to identify functionally relevant SNPs and assess genomic contamination in transgenic mice. This allows for unambiguous attribution of phenotypes to the target gene and advances the precision and reliability of research in the field of host defense responses.

immunology↗

bioRxiv2023

Microbiome ssRNA as an environmental cue to activate TLR13-dependent tissue-protective programs in CD5Lhi hepatic macrophages

Hepatic macrophages maintain liver homeostasis, but little is known about the signals that activate the hepatoprotective programs within macrophages. Here, we show that toll-like receptor 13 (TLR13), a sensor of bacterial 23S ribosomal RNA (rRNA), senses microbiome RNAs to drive tissue-protective responses in CD5Lhi hepatic macrophages. Splenomegaly and hepatomegaly developed in the absence of the endosomal RNase, RNaseT2, via TLR13-dependent macrophage proliferation. Furthermore, TLR13 in hepatic Ly6Clo macrophages activated the transcription factors LXR and MafB, leading to expression of tissue-clearance molecules, such as CD5L, C1qb, and Axl. Consequently, Rnaset2-/- mice developed resistance to acute liver injury caused by challenges with acetaminophen and lipopolysaccharide + D-galactosamine. TLR13 responses in Rnaset2-/- mice were impaired by antibiotics, suggesting that TLR13 were activated by microbiome rRNAs, which was detected in the sera and hepatic macrophages. Repeated administration of wild-type mice with the TLR13 ligand, rather than other TLR ligands, selectively increased the number of Kupffer cells, which expressed immunoregulatory and tissue-clearance genes as hepatic macrophages in Rnaset2-/- mice did. Our results suggest that microbiome ssRNA serves as an environmental cue for initiating tissue-protective TLR13 responses in hepatic macrophages. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=192 SRC="FIGDIR/small/540294v1_ufig1.gif" ALT="Figure 1"> View larger version (51K): org.highwire.dtl.DTLVardef@69614eorg.highwire.dtl.DTLVardef@737c69org.highwire.dtl.DTLVardef@1ecd9eforg.highwire.dtl.DTLVardef@d7e10d_HPS_FORMAT_FIGEXP M_FIG In the absence of an endosomal RNase, RNase T2, microbiome RNAs circulating in the vasculature activate TLR13 in hepatic macrophages to drive hepatoprotective responses through expression of immunoregulatory and tissue-clearance molecules. Consequently, mice lacking RNase T2 are resistant against acute liver injuries caused by acetaminophen and LPS + D-galactosamine. C_FIG

immunology↗

bioRxiv2023

NULISA: a novel proteomic liquid biopsy platform with attomolar sensitivity and high multiplexing

The blood proteome holds great promise for precision medicine but poses substantial challenges due to the low abundance of most plasma proteins and the vast dynamic range across the proteome. We report a novel proteomic technology - NUcleic acid Linked Immuno-Sandwich Assay (NULISA) - that incorporates a dual capture and release mechanism to suppress the assay background and improves the sensitivity of the proximity ligation assay by over 10,000-fold to the attomolar level. It utilizes pairs of antibodies conjugated to DNA oligonucleotides that enable immunocomplex purification and generate reporter DNA containing target- and sample-specific barcodes for a next-generation sequencing-based, highly multiplexed readout. A 200-plex NULISA targeting 124 cytokines and chemokines and 80 other immune response-related proteins demonstrated superior sensitivity for detecting low-abundance proteins and high concordance with other immunoassays. The ultrahigh sensitivity allowed the detection of previously difficult-to-detect, but biologically important, low-abundance biomarkers in patients with autoimmune diseases and COVID-19. Fully automated NULISA addresses longstanding challenges in proteomic analysis of liquid biopsies and makes broad and in-depth proteomic analysis accessible to the general research community and future diagnostic applications.

genomics↗

bioRxiv2023

SKA2 regulated hyperactive secretory autophagy drives neuroinflammation-induced neurodegeneration

High levels of proinflammatory cytokines induce neurotoxicity and catalyze inflammation-driven neurodegeneration, but the specific release mechanisms from microglia remain elusive. We demonstrate that secretory autophagy (SA), a non-lytic modality of autophagy for secretion of vesicular cargo, regulates neuroinflammation-mediated neurodegeneration via SKA2 and FKBP5 signaling. SKA2 inhibits SA-dependent IL-1{beta} release by counteracting FKBP5 function. Hippocampal Ska2 knockdown in mice hyperactivates SA resulting in neuroinflammation, subsequent neurodegeneration and complete hippocampal atrophy within six weeks. The hyperactivation of SA increases IL-1{beta} release, initiating an inflammatory feed-forward vicious cycle including NLRP3-inflammasome activation and Gasdermin D (GSDMD)-mediated neurotoxicity, which ultimately drives neurodegeneration. Results from protein expression and co-immunoprecipitation analyses of postmortem brains demonstrate that SA is hyperactivated in Alzheimers disease. Overall, our findings suggest that SKA2-regulated, hyperactive SA facilitates neuroinflammation and is linked to Alzheimers disease, providing new mechanistic insight into the biology of neuroinflammation.

neuroscience↗

bioRxiv2023

Epigenetic regulation of innate immune genes and enhanced interleukin-10 expression underlie chronic subclinical Plasmodium chabaudi infection

Subclinical (asymptomatic) parasitemia is very common amongst Plasmodium-infected individuals. The immunological mechanisms underlying subclinical parasitemia remain elusive. We investigated the immune regulatory mechanisms behind chronic asymptomatic Plasmodium infection using mice lacking humoral immunity ({micro}MT-/- mice). {micro}MT-/- mice became chronically infected, despite lacking outward signs of disease, and exhibited increased macrophage numbers, decreased dendritic and CD4 cells, massive hemozoin accumulation in the spleen and bone marrow, and inadequate hematopoiesis. These changes were accompanied by high circulating levels of interleukin-10 (IL-10), enhanced chromatin accessibility of the STAT3 promoter, and enhanced STAT3 binding to the IL-10 promoter in macrophages. Inhibition of IL-10 signaling, despite promoting parasite clearance, resulted in a proinflammatory response, weight loss, and mortality. These results suggest that epigenetic changes induced by chronic P. chabaudi infection lead to high levels of circulating IL-10, protecting chronically infected mice against an excessive inflammatory response to high levels of blood-stage parasites. Author summaryMalaria is a life-threatening disease with a range of symptoms, and it is induced in humans by infections with different species of Plasmodium. Highly prevalent in endemic regions, asymptomatic Plasmodium infections are related to long-term exposure to the parasite due to multiple infections and have been demonstrated in human and mouse studies to be associated with elevated levels of IL-10. However, how IL-10 levels remain elevated in the circulation in individuals over the long term has not been determined. We used a mouse model of chronic asymptomatic Plasmodium infection to investigate the mechanisms by which IL-10 levels are elevated during chronic asymptomatic infection. Our results show that epigenetic changes in immune genes of myeloid origin could be responsible for the elevated levels of IL-10, and that IL-10 signaling protected chronically infected mice from a severe inflammatory response induced by the infection.

immunology↗

bioRxiv2022

Aortic valve disease augments vesicular microRNA-145-5p to regulate the calcification of valvular interstitial cells via cellular crosstalk

RationaleAortic valve stenosis (AVS) is a major contributor to cardiovascular death in the elderly population worldwide. MicroRNAs (miRNAs) are highly dysregulated in patients with AVS undergoing surgical aortic valve replacement (SAVR). However, miRNA-dependent mechanisms regulating inflammation and calcification or miRNA-mediated cell-cell crossstalk during the pathogenesis of AVS are still poorly understood. Here, we explored the role of extracellular vesicles (EV)-associated miR-145-5p, which we showed to be highly upregulated upon valvular calcification in AVS in mice and humans. MethodsHuman TaqMan miRNA arrays identified dysregulated miRNAs in aortic valve tissue explants from AVS patients compared to non-calcified valvular tissue explants of patients undergoing SAVR. Echocardiographic parameters were measured in association with the quantification of dysregulated miRNAs in a murine AVS model. In vitro calcification experiments were performed to explore the effects of EV-miR-145-5p on calcification and crosstalk in valvular cells. To dissect molecular miRNA signatures and their effect on signaling pathways, integrated OMICS analyses were performed. RNA sequencing (RNA-seq), high-throughput transcription factor (TF) and proteome arrays showed that a number of genes, miRNAs, TFs, and proteins are crucial for calcification and apoptosis, which are involved in the pathogenesis of AVS. ResultsAmong several miRNAs dysregulated in valve explants of AVS patients, miR-145-5p was the most highly gender-independently dysregulated miRNA (AUC, 0.780, p-value, 0.01). MiRNA arrays utilizing patient-derived- and murine aortic-stenosis samples demonstrated that the expression of miR-145-5p is significantly upregulated and correlates positively with cardiac function based on echocardiography. In vitro experiments confirmed that miR-145-5p is encapsulated into EVs and shuttled into valvular interstitial cells. Based on the integrated OMICs results, miR-145-5p interrelates with markers of inflammation, calcification, and apoptosis. In vitro calcification experiments demonstrated that miR-145-5p regulates the ALPL gene, a hallmark of calcification in vascular and valvular cells. EV-mediated shuttling of miR-145-5p suppressed the expression of ZEB2, a negative regulator of the ALPL gene, by binding to its 3 untranslated region to inhibit its translation, thereby diminishing the calcification of target valvular interstitial cells. ConclusionElevated levels of pro-calcific and pro-apoptotic EV-associated miR-145-5p contribute to the progression of AVS via the ZEB2-ALPL axis, which could potentially be therapeutically targeted to minimize the burden of AVS. Clinical SignificanceO_ST_ABSWhat is known?C_ST_ABSO_LIAortic valve stenosis (AVS) is the most prevalent structural heart valve disease requiring surgical or interventional valve replacement. Currently, no medical treatment option is available to slow, halt, or reverse the progression of the disease. C_LIO_LIAVS induces pressure overload on the left ventricle (LV), resulting in concentric hypertrophy and LV dysfunction. C_LIO_LIAVS is not an exclusively degenerative disease that leads to fibrosis and calcification of the valve cusps but rather a chronic inflammatory disease, in which mechanical strain and shear stress lead to endothelial dysfunction and immune cell infiltration, which induces chronic inflammation, apoptosis and differentiation of valvular interstitial cells into osteoblast-like cells. C_LIO_LIIncreasing osteoblastic differentiation and the formation of macrocalcifications are hallmarks of the later stages of AVS. C_LI What is the new information we provide?O_LIDuring aortic valve stenosis, expression pattern of vesicle-associated regulatory miRNAs is altered. C_LIO_LIPatient-derived aortic valve tissue demonstrated an increased expression of miR-145-5p in humans, as well as in aortic valve explants from an experimental murine AVS model. C_LIO_LIMiR145-5p contributes to calcification of the aortic valve through ZEB2, a transcriptional repressor of ALPL, in valvular interstitial cells. C_LIO_LIExtracellular vesicular shuttling of miR-145-5p contributes to valvular cell-cell crosstalk and plays a role in the pathogenesis of AVS. C_LI

cell biology↗

bioRxiv2022

TLR7/8 stress response drives histiocytosis in SLC29A3 disorders

SLC29A3, also known as ENT3, is a lysosomal transmembrane protein that transports nucleosides from the lysosomes to the cytoplasm1. Loss-of-function mutations in SLC29A3 cause lysosomal nucleoside storage and histiocytosis: phagocyte accumulation in multiple organs2,3. However, little is known about the mechanism through which lysosomal nucleoside storage drives histiocytosis. Herein, histiocytosis in Slc29a3-/- mice was demonstrated to depend on TLR7, which senses a combination of nucleosides and oligoribonucleotides4,5. TLR7 responded to lysosomal nucleoside storage and enhanced proliferation of Ly6Chi CX3CR1low immature monocytes and their maturation into Ly6Clow phagocytes in Slc29a3-/- mice. Because accumulated nucleosides primarily originated from cell corpse phagocytosis, TLR7 in immature monocytes recognized nucleoside storage as lysosomal stress and increased phagocyte numbers. This non-inflammatory compensatory response is referred to as the TLR7 stress response where Syk, GSK3{beta}, {beta}-catenin, and mTORC1 serve as downstream signalling molecules. In SLC29A3 disorders, histiocytosis accompanies inflammation6,7. Nucleoside storage failed to induce pro-inflammatory cytokine production in Slc29a3-/- mice, but enhanced ssRNA-dependent pro-inflammatory cytokine production in Ly6Chi classical monocytes and peripheral macrophages, not proliferating immature monocytes. Patient-derived monocytes harbouring G208R SLC29A3 mutation showed higher survival and proliferation in the presence of M-CSF and produced larger amounts of IL-6 upon ssRNA stimulation than did those derived from healthy subjects. A TLR8 antagonist inhibited the survival/proliferation of patient-derived macrophages. These results demonstrated that TLR7/8 responses to lysosomal nucleoside stress drive SLC29A3 disorders.

immunology↗

bioRxiv2022

Suppression of systemic T cell immunity to viral infection during liver injury is prevented by inhibition of interferon and IL-10 signaling

Patients with liver injury such as cirrhosis are at increased risk of intractable viral infections and are hyporesponsive to vaccination. Here, we report that liver injury leads to inhibition of systemic T cell immunity (LIST), which abrogated anti-viral immunity and caused persistent infection in preclinical liver injury models. Enhanced gut microbial-translocation but not dysbiosis induced tonic type-I-interferon (IFN) signaling in hepatic myeloid cells, which was responsible for their excessive production of IL-10 after viral infection. Antibiotic treatment reducing intestinal microbial burden or inhibition of IFN- and IL-10-signaling all restored anti-viral immunity without immune pathology. Importantly, inhibition of IL-10 restored virus-specific immune responses to vaccination in cirrhotic patients. Thus, LIST results from sequential events involving intestinal microbial translocation, hepatic myeloid cell-derived IFN-/IL-10 expression, and finally inhibitory IL-10 receptor-signaling in T cells, of which IL-10R-signaling may serve as target to reconstitute anti-viral T cell immunity in cirrhotic patients.

immunology↗