Biology subjects

Frank, D.

Publications and source records attributed to Frank, D..

At least 19 recordsLinked to original sources

bioRxiv2026

Sphingolipid-Driven Lipotoxicity Promotes Calcific Aortic Valve Disease Through ER-Stress-NF-κB-EndMT Signaling and Is Therapeutically Targetable Through Serine Palmitoyltransferase Inhibition

Background: Calcific aortic valve disease (CAVD) lacks disease-modifying therapy. LDL-cholesterol lowering does not attenuate valvular calcification, suggesting cholesterol-independent drivers. Thus, we tested whether ceramide accumulation drives CAVD and whether inhibiting sphingolipid de novo synthesis is therapeutic. Methods: We integrated lipidomics and proteomics of calcified and non-calcified human aortic valves with matched plasma. Mechanistic effects of ceramides were tested in primary human valvular interstitial cells (VICs). Therapeutic efficacy of serine palmitoyltransferase (SPT) inhibition with Myriocin was evaluated in ApoE-/- mice with PCSK9DY-AAV-driven hyperlipidemia on Western diet using preventive treatment and therapeutic initiation after echocardiographically verified gradient elevation. Myriocin was additionally tested in a normolipidemic wild-type aortic valve wire-injury model. Hemodynamics, valve structure, lipid composition, and cell-state transitions were assessed by echocardiography, histology, lipidomics, and single-cell RNA sequencing. Results: Calcified human valves showed enrichment of long-chain ceramides linked to NF-{kappa}B, endothelial-to-mesenchymal transition (EndMT), and ER-stress/unfolded protein response (UPR) programs, whereas matched plasma sphingolipids were not elevated. In hVICs, long-chain C18 ceramide induced GRP78/BiP, CHOP, and ATF4, activated NF-{kappa}B, and promoted dose-dependent calcification. In vivo, SPT inhibition with Myriocin lowered valvular ceramides, reduced leaflet inflammation and mineralization, and improved cusp separation and transvalvular hemodynamics without lowering plasma LDL-cholesterol. In a therapeutic protocol initiated after gradient elevation, Myriocin halted further hemodynamic progression, providing the first evidence that de novo sphingolipid synthesis can be targeted after established CAVD onset in vivo. Myriocin also attenuated injury-induced stenosis in normolipidemic mice. Single-cell RNA sequencing showed reduced NF-{kappa}B/EndMT and ER-stress signatures and shifted VIC states away from osteogenic phenotypes. Conclusions: Human valve lipidomics and human VIC experiments identify ceramide-driven lipotoxicity as a driver of an ER-stress-NF-{kappa}B-EndMT axis in CAVD. In vivo, de novo sphingolipid synthesis is an actionable, LDL-independent target capable of modifying established hemodynamic disease progression, supporting SPT inhibition as a tractable strategy for medical CAVD therapy.

molecular biology↗

bioRxiv2026

Dual control of plasmid copy number in E. coli by combining temperature shifts and RNAI-based genetic circuits for tunable replication dynamics

Plasmid copy number (PCN) is a central determinant of recombinant gene expression levels and metabolic burden in bacterial cell factories. However, dynamic real-time control of PCN during microbial cultivation remains largely unexplored. In the ColE1/pUC19 replication system, PCN is governed by an antisense RNAI/RNAII circuit, but this native mechanism provides no external handle for process-level intervention. Here, we engineer and characterize a dual-layer control architecture that combines two orthogonal perturbations to direct plasmid replication in Escherichia coli populations i.e., temperature shifts, which modulate the secondary structure of RNAII and, consequently, its binding to RNAI and its inhibitory potency (ex vivo control), and arabinose-inducible overexpression of a supplementary RNAI cassette, integrated either on a secondary low-copy plasmid or directly on the high-copy target plasmid (in vivo control). Using a superfolder GFP validated fluorescent reporter and automated flow cytometry in continuous cultures, we track PCN dynamics at the population level in real time under chemostat conditions. Preliminary screening in microplates high-throughput cultivation device across three strains, two carbon sources, and three temperatures (30, 37, and 42C) reveals that the two control layers act synergistically. Neither temperature alone nor inducible RNAI alone achieves the dynamic range obtained by their combination. This synergistic effect is sustained during continuous cultivation at a fixed dilution rate of 0.1/h, with carbon source and temperature transitions producing predictable and reproducible shifts in population-level PCN. These results establish a scalable, dual-input framework for on-demand PCN tuning in continuous bioprocesses, with direct relevance to biopharmaceutical plasmid production and synthetic biology applications.

bioengineering↗

bioRxiv2026

Tricuspid valve regurgitation accelerates heart failure via a cardio-intestinal innate immune circuit

Activation of the immune system impacts the progression of heart failure (HF), but the underlying mechanisms remain incompletely understood. Here, we identify a cardio-intestinal innate immune axis that links systemic venous congestion to myocardial inflammation, fibrosis, and functional decline. Using single-cell and single-nucleus transcriptomic profiling in patients and mice with tricuspid regurgitation (TR), we demonstrate that TR disrupts intestinal barrier integrity and elicits expansion of circulating monocytes which in turn orchestrate pathological crosstalk between the right and left heart. Monocyte-derived Interleukin-6 (IL-6) emerged as a key mediator of TR-driven myocardial fibrosis and dysfunction. Blockade of IL-6 attenuated cardiac fibrosis and improved cardiac function. In patients, catheter-based repair of TR resulted in reduced IL-6 levels. Together, these findings establish cardio-intestinal innate immunity as a mechanism linking altered hemodynamics to left ventricular remodeling and nominate TR patients as a selective target population for IL-6-directed therapy in HF. One Sentence SummaryThis work mechanistically resolves the heart-gut axis in tricuspid valve regurgitation, and its impact on heart failure progression as mediated by Interleukin-6.

immunology↗

bioRxiv2026

Cellular responsiveness as a predictive indicator for population collapse and autonomous control in continuous cultures of Pseudomonas putida

How microbial populations respond to repeated environmental transitions determines both their ecological fitness and their utility in biotechnological applications. Using Pseudomonas putida KT2440 equipped with fluorescent biosensors and monitored by automated flow cytometry in the Segregostat platform, we show that exposure to benzoate, a plastic-derived aromatic feedstock, progressively reduces cellular responsiveness, defined as the fraction of cells that successfully activate a gene circuit following an environmental transition. Unlike classical switching costs, which promote phenotypic diversification, benzoate suppresses responsiveness without increasing population entropy, in a concentration-dependent and circuit-independent manner tightly correlated with fitness loss. A resource allocation model incorporating the competing demands of benzoate assimilation, toxicity, and tolerance reveals that this impairment emerges from a three-way competition for limited cellular resources. Above a critical benzoate load, insufficient resources remain available to sustain the adaptive reallocation required for circuit activation. In continuous culture, a non-responsive subpopulation accumulates as a leading indicator of population collapse. Exploiting this signal, we implement a two-stage connected bioreactor system in which benzoate feeding is autonomously regulated based on real-time population structure, enabling complete substrate consumption and stable operation at otherwise destabilizing concentrations. These results establish cellular responsiveness as a quantitative population variable and demonstrate that structure-aware feedback control, acting on population composition rather than bulk physiology, provides a principled route toward autonomous bioprocesses on challenging substrates.

Systems Biology↗

bioRxiv2026

Altered Tonsillar Microbiome in Children with Down Syndrome and Obstructive Sleep Apnea

Background and ObjectivesChildren with Down syndrome (DS) have a high prevalence of obstructive sleep apnea (OSA) due to anatomic, neuromuscular, immunological and metabolic factors, yet the contribution of the tonsillar microbiome to airway obstruction in this population remains unexplored. We hypothesized that DS-associated OSA would be associated with a distinct tonsillar microbiome compared to non-DS OSA. MethodsTonsillar tissue from 22 DS and 18 NDS participants were analyzed by 16S rRNA sequencing. Alpha and beta diversity were assessed using Faiths phylogenetic diversity and UniFrac distances, respectively, and significantly different taxa were identified with ANCOM-BC and Mann-Whitney testing. ResultsAlthough overall microbial richness and community structure were similar between groups, overweight DS participants demonstrated increased phylogenetic diversity compared to normal-weight DS peers. Taxonomic profiling of the entire patient cohort revealed that in DS tonsils there were selective alterations in key genera with selective depletion of Haemophilus and enrichment of Staphylococcus, Rothia, and Lactobacillales. Haemophilus abundance correlated positively with tonsil weight in both cohorts. ConclusionsThese findings suggest that while global diversity is preserved, specific microbial shifts distinguish the DS tonsillar niche, potentially reflecting altered immune and metabolic environments associated with trisomy 21. Understanding these microbial differences may reveal mechanisms underlying the higher incidence and persistence of OSA in DS and inform targeted therapeutic strategies.

microbiology↗

bioRxiv2026

IgA Targeting in the Infant Gut Is Modulated by Diet and Increasingly Directed Towards Persistent Species

BackgroundIgA is the dominant antibody in the human gut and a key regulator of host-microbe interactions. Infants begin to produce IgA at around 6 months old and receive large quantities of IgA via human milk, but technical limitations have prevented species-level characterization of IgA binding in early life. This has left basic knowledge gaps about which species are targeted by IgA in infancy, and how modifiable lifestyle factors like breastfeeding and complementary feeding impact IgA targeting. ResultsHere we adapt Metagenomic Immunoglobulin Sequencing (MIg-Seq) for low-biomass infant fecal samples and apply this optimized protocol to 32 longitudinal samples from 16 infants enrolled in the MINT trial, a four-arm randomized controlled trial comparing meat-based, dairy-based, plant-based, and reference complementary feeding patterns, with fecal sampling at 6 and 12 months (pre and post intervention). Infant IgA targeting mirrors adults at the phylum level, with both age groups showing significantly higher IgA targeting of Pseudomonadota and lower targeting of Bacteroidota relative to other phyla. During the substantial microbiome compositional shifts noted between 6 and 12 months, IgA targeting is significantly more stable than the microbiome itself. Among persistent colonizers, IgA targeting strengthens significantly from 6 to 12 months, with the most pronounced effect observed for Bifidobacterium, a finding robust across all dietary arms and feeding modes. The feeding arm to which infants were enrolled was not significantly associated with IgA binding, but several nutrient-specific associations were discovered. Animal-derived nutrients, particularly cholesterol, are strongly positively correlated with IgA targeting of Bifidobacterium longum, while plant-derived carotenoids are positively associated with IgA targeting of Flavonifractor plautii and Ruminococcus gnavus. ConclusionsThis study introduces an experimental and computational framework for species-level IgA profiling in the infant gut. The progressive strengthening of IgA targeting of Bifidobacterium and other beneficial persistent colonizers suggests a role for IgA in reinforcing beneficial microbes during infancy. The nutrient-specific dietary effects on IgA targeting reveal the immunological consequences of the complementary feeding period, and highlight a contrast between animal-versus plant-based diets. Together, these findings point to early nutritional interventions and IgA-based therapeutics as promising tools for promoting healthy immune-microbiome development.

microbiology↗

bioRxiv2026

Hippocampal and Midbrain Function in Superagers Relates to Memory for Novelty and Expectation Violation

Memory performance typically declines with age, but the underlying neurobiological mechanisms remain unclear. Superagers, people over 80 years of age with episodic memory performance comparable to individuals 30 years younger, appear to resist this decline. Novelty and expectation violations are known to engage the hippocampus-midbrain system to enhance memory formation. Here, we examined whether superagers superior memory performance is supported by preserved hippocampal-midbrain function during novelty and expectation processing. We manipulated item and contextual novelty (i.e., expectation violations) during encoding to test whether superagers show greater mnemonic benefits than their age-matched peers, whether these benefits reflect enhanced hippocampal and midbrain functioning as measured by fMRI, and whether they are associated with preserved dopaminergic integrity measured with neuromelanin-sensitive MRI. Our results show that, although superagers demonstrated overall superior memory performance, both groups exhibited superior recognition of contextually unexpected items. Nevertheless, differences emerged in the processing of expectation during encoding. Superagers exhibited stronger hippocampal responses to expectation violations and habituation to expected events, irrespective of item novelty. Conversely, typical older adults exhibited reduced midbrain response when expected novelty was absent. Neuromelanin accumulation did not account for group differences in midbrain activity or memory performance. Taken together, these findings suggest superagers benefit from adaptive responses to expectation and its violation, which is therefore a candidate mechanism distinguishing exceptional from typical cognitive ageing. SIGNIFICANCE STATEMENTAlthough memory typically declines with age, superagers are individuals aged over 80 who maintain memory performance comparable to people 30 years younger. We examined whether preserved hippocampal-midbrain function during novelty and expectation processing could underlie their superior memory. Superagers exhibited adaptive hippocampal responses to expectation and its violation, with higher activation for unexpected events and habituation to expected events. In contrast, typical older adults showed hippocampal and midbrain responses oriented towards anticipated novel content, despite not showing differences in neuromelanin accumulation. These findings underscore the critical role of hippocampal function in supporting memory preservation in late life and advance our understanding of the neural mechanisms underlying healthy cognitive ageing.

neuroscience↗

bioRxiv2025

Synthetic niches enable co-culture bioprocessing but are prone to mutational escape

Stabilizing microbial co-cultures is a central challenge for bioproduction. While division of labor between strains can enhance efficiency, it often results in population instability over time. Classical strategies, including cross-feeding, quorum sensing, and toxin-antitoxin modules, often rely on complex ecological interactions that are difficult to predict or maintain under bioprocess conditions. Here, we introduce synthetic niches as an alternative framework, using genetic toggle switches that couple growth to defined phenotypic states. We engineered two auxotrophic strains, TOGGLE_green and TOGGLE_yellow, in which growth is linked to either GFP- or YFP-expressing states and assessed their behavior in continuous bioreactor cultures using automated flow cytometry. Unexpectedly, the introduction of auxotrophic pressure reshaped circuit function i.e., instead of maintaining bistability, toggle strains behaved as unidirectional inducible systems that reverted upon inducer withdrawal. This feature enabled simplified control with a single input but also revealed a vulnerability to mutational escape under intensified cultivation. A simple repression-based ODE model recapitulated the reversible dynamics, but deviations under prolonged operation highlighted the rapid evolutionary erosion of control. Our findings demonstrate both the potential and the limitations of synthetic niches for co-culture engineering and emphasize the need to integrate evolutionary robustness into the design of next-generation bioprocess control strategies.

synthetic biology↗

bioRxiv2025

Overriding bioprocess perturbations with a cell machine interface for reliable microbial stress-response control

Controlling cell population dynamics and phenotypic diversification is a key objective in systems and synthetic biology, particularly for ensuring uniform responses from engineered gene circuits. While cell-machine interfaces have been employed to modulate host-gene circuit interactions, environmental perturbations typical of industrial bioreactor conditions remain underexplored. In this study, we investigate the impact of such perturbations on the general stress response in Escherichia coli and Saccharomyces cerevisiae. Using scale-down bioreactor experiments, we evaluate the performance of the Segregostat, a real-time control system that leverages automated flow cytometry to induce dynamic nutrient shifts. The Segregostat achieves robust stress response control, even under severe perturbations such as extended residence times in a two-compartment reactor. We hypothesize that this robustness arises from the systems ability to amplify host-compatible fluctuations beyond bioreactor-induced perturbations. Our findings highlight the importance of integrating environmental factors into control strategies for reliable gene circuit behavior in industrial bioprocessing environments.

bioengineering↗

bioRxiv2025

Regulation of YAP activity by nuclear G-actin binding

O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=81 SRC="FIGDIR/small/667612v1_ufig1.gif" ALT="Figure 1"> View larger version (21K): org.highwire.dtl.DTLVardef@1d109c2org.highwire.dtl.DTLVardef@d7d6daorg.highwire.dtl.DTLVardef@5ab7fcorg.highwire.dtl.DTLVardef@1e51b37_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOGraphical Abstract:C_FLOATNO YAP functions as a G-actin binding protein. Three high affinity actin binding sites, L65, L68 and W199 are identified in YAP that when mutated into YAPDDY attenuate YAP/actin interaction as well as YAP activity. Thus, nuclear actin binding to YAP is necessary for its transcriptional activity as a co-activator of TEAD. Incorporation of G-actin into the YAP/TEAD complex is predicted to induce TEAD conformational change involving a 4 interface. Therefore, the formation of a dynamic TEAD/YAP/actin ternary complex necessary for transcription is proposed. C_FIG The Yes-associated protein YAP belongs to the TEAD (TEA/ATTS domain) transcriptional co-activators that shuttle between cytoplasm and nuclear compartment. YAP and its paralog TAZ (transcriptional co-activator with PDZ-binding motif) play essential roles in the Hippo pathway to control tissue and organ size. In addition, YAP is critically involved in numerous cellular processes such as differentiation, proliferation, cell migration and cancer metastasis as well as mechanotransduction and cytoskeletal dynamics. The actin cytoskeleton controls YAP activity in multiple ways via tensile forces, cell density and cell-cell adhesion as well as shear stress or other biomechanical cues. Here we discover YAP as a novel G-actin binding protein. We identify three high affinity YAP actin binding sites involving critical residues within the N-terminus of YAP. Moreover, actin binding to YAP is necessary for its transcriptional activity and function such as during cell density control. Mutation of the three actin binding residues results in a loss of nuclear YAP co-activator function towards TEAD while actin binding to YAP is required for TEAD target gene regulation. Our data point towards the formation of a dynamic TEAD/YAP/actin ternary complex necessary for transcription.

cell biology↗

bioRxiv2025

A genetic model for development, physiology and behavior of zebrafish larvae devoid of catecholamines

Dopamine and noradrenaline have conserved roles in control of physiology and behaviors of vertebrates. However, vertebrate genetic systems completely devoid of catecholamines are not available. We have generated a genetic zebrafish model completely devoid of catecholamines by combining mutations in all three genes involved in L-DOPA synthesis: the tyrosine hydroxylase genes th and th2, and tyrosinase tyr. We found catecholamine-deficient zebrafish larvae to be viable and to develop an anatomically normal nervous system including catecholaminergic neuron somata and projections, albeit with reduced cell numbers detected in some clusters. In contrast, selected physiological functions that depend on catecholamines are impaired, including hatching and heart rate regulation upon temperature challenges. Spontaneous locomotion and optomotor behaviors are also impaired. Despite the changes observed, it is surprising that larvae develop a largely normal behavioral repertoire. Our model will be useful to investigate how physiology and neural circuit function are regulated in catecholamine deficient larvae.

developmental biology↗

bioRxiv2025

A simple, fast and cost-efficient protocol for ultra-sensitive ribosome profiling

Ribosome profiling has become an essential tool for studying mRNA translation in cells with codon-level resolution. However, its widespread application remains hindered by the labour-intensive workflow, low efficiency and high costs associated with sequencing sample preparation. Here, we present a new cost-effective and ultra-sensitive library preparation method that significantly advances the applicability of ribosome profiling. By implementing bead-coupled enzymatic reactions and product purifications, our approach increases both yield and throughput while maintaining high reproducibility. Demonstrating the sensitivity of the protocol we prepared libraries from as little as 12 fmol of RNA, which expands the feasibility of ribosome profiling from minimal input samples, such as derived from small populations, stressed cells, or patient-derived specimens. Additionally, we validate the versatility of the protocol across multiple species and demonstrate its applicability for RNA-seq library preparation. Altogether, this protocol provides a highly accessible and efficient alternative to existing ribosome profiling workflows, facilitating research in previously challenging experimental contexts.

systems biology↗

bioRxiv2025

mRNA-LNP vaccines against Hepatitis B virus induce protective immune responses in preventive and chronic mouse challenge models

Over 300 million people worldwide suffer from chronic hepatitis B virus infections that can cause serious liver damage and hepatocellular carcinoma. Ineffective innate and adaptive immune responses characterize these chronic infections, making the development of a therapeutic vaccine an urgent medical need. While current vaccines can prevent HBV infections, they are ineffective in treating chronic disease. This study investigated lipid nanoparticle (LNP)-formulated nucleoside-modified mRNA vaccines encoding Hepatitis B surface antigen (HBsAg) for prophylactic and therapeutic applications. We found that HBsAg mRNA-LNP vaccines induced robust humoral and cellular immune responses, outperforming the protein-based vaccine approved for human use. The incorporation of an MHC class I signal peptide further enhanced Th1-biased responses preventing HBV infections in a mouse model. Importantly, mRNA-LNP vaccination led to seroconversion, HBsAg clearance, and strong T cell responses in a chronically infected mouse model. These findings highlight the potential of mRNA-LNP as an alternative and effective vaccine modality for HBV prophylaxis and therapeutic use in treating chronic infections.

immunology↗

bioRxiv2024

Biological oscillations without genetic oscillator or external forcing

Oscillators are fundamental to biological systems, underpinning essential processes such as cell division, circadian rhythms, and developmental cycles. While both natural and synthetic genetic oscillators have been extensively studied, oscillatory behaviors in cells can also emerge without dedicated genetic circuits. In earlier work, we uncovered sustained oscillations in phenotypic switching across diverse cellular systems and gene circuits, occurring spontaneously, without external forcing and linked them to the induction of slow-growing phenotypes. In this study, we identify the conditions that give rise to such intrinsic phenotypic instabilities, leading to population-level oscillations. We develop and analytically solve a simplified mathematical model of a stress-induced phenotype, mapping the range of continuous culture conditions that trigger oscillatory gene expression. This instability range, predicted by the model, was experimentally validated in Bacillus subtilis cultures. Our findings reveal that oscillations can arise in the complete absence of genetic oscillators or external perturbations. Although demonstrated here for a stress response in continuous culture, this phenomenon may occur in any long-term cultivation where environmental feedback links an inducer to the cellular system, broadening the landscape of possible oscillatory behaviors in microbiology and synthetic biology.

systems biology↗

bioRxiv2024

The bat Influenza A virus subtype H18N11 induces nanoscale MHCII clustering upon host cell attachment

Prior to the discovery of the bat influenza A virus (IAV) subtypes H17N10 and H18N11, it was believed that all IAVs bind via the viral hemagglutinin (HA) to sialic acid residues to mediate attachment and subsequent viral entry. Both HA subtypes, H17 and H18, however, do not bind to sialic acids but instead engage a proteinaceous receptor: major histocompatibility complex class II (MHCII). The mechanistic details of this hitherto unknown protein-mediated entry are not understood. Since conventional IAVs require attachment to clusters of sialylated glycans to overcome the low affinity of the HA-sialic acid interaction, we hypothesized that bat HA would likewise interact with multiple MHCII molecules. Here, we used photoactivated localization microscopy (PALM) on fixed and live cells expressing MHCII fused to appropriate fluorescent reporters. We show that bat IAV particles attach to pre-existing MHCII clusters present on susceptible cells and that the local HA-MHCII interaction results in an increased cluster size. To measure the impact of viral attachment on the dynamics of MHCII, we utilized an experimental setup designated "inverse infection" where intact viral particles were immobilized on coverslips before live MHCII-expressing cells were seeded on top. Recording the trajectories of single MHCII molecules, this approach revealed that the mobility of MHCII was indeed slowed down in viral proximity leading to a local enrichment of MHCII molecules beneath the viral particle. Taken together, these data suggest that attachment of viral particles leads to clustering of MHCII, a process similar to the MHCII dynamics observed during the formation of an immunological synapse.

microbiology↗

bioRxiv2024

Automated adjustment of metabolic niches enables the control of natural and engineered microbial co-cultures

A lot of attention has been given to the understanding of microbial interactions leading to stable co-cultures, but the resulting technologies have been rarely challenged in dynamic cultivation conditions. In this work, substrate pulsing was performed to promote better control of the metabolic niches corresponding to each species, leading to the continuous co-cultivation of diverse microbial organisms. For this purpose, we used a cell-machine interface relying on automated flow cytometry, allowing to adjust the temporal profile of two metabolic niches according to a rhythm ensuring the successive growth of two species i.e., in our case a yeast and a bacterium. The resulting approach, called Automated Adjustment of Metabolic Niches (AAMN), was successfully employed for stabilizing both cooperative and competitive co-cultures. Additionally, AAMN can be considered as an enabling technology for the deployment of co-cultures in bioprocesses, demonstrated here based on the continuous bioproduction of p-coumaric acid. Taken altogether, the data accumulated suggest that AAMN could be used for a wider range of biological systems, but also to gain fundamental insights about microbial interaction mechanisms.

microbiology↗

bioRxiv2023

Release of extracellular DNA by Pseudomonas species as a major determinant for biofilm switching and an early indicator for cell population control

Withdrawal StatementThe authors have withdrawn this manuscript due to a duplicate posting of manuscript number BIORXIV/2021/430776. Therefore, the authors do not wish this work to be cited as reference for the project. If you have any questions, please contact the corresponding author. The correct preprint can be found at doi: 10.1101/2021.02.11.430776

microbiology↗

bioRxiv2023

Microbiota-dependent indole production is required for the development of collagen-induced arthritis

Altered tryptophan catabolism has been identified in inflammatory diseases like rheumatoid arthritis (RA) and spondyloarthritis (SpA), but the causal mechanisms linking tryptophan metabolites to disease are unknown. Using the collagen-induced arthritis (CIA) model we identify alterations in tryptophan metabolism, and specifically indole, that correlate with disease. We demonstrate that both bacteria and dietary tryptophan are required for disease, and indole supplementation is sufficient to induce disease in their absence. When mice with CIA on a low-tryptophan diet were supplemented with indole, we observed significant increases in serum IL-6, TNF, and IL-1{beta}; splenic ROR{gamma}t+CD4+ T cells and ex vivo collagen-stimulated IL-17 production; and a pattern of anti-collagen antibody isotype switching and glycosylation that corresponded with increased complement fixation. IL-23 neutralization reduced disease severity in indole-induced CIA. Finally, exposure of human colon lymphocytes to indole increased expression of genes involved in IL-17 signaling and plasma cell activation. Altogether, we propose a mechanism by which intestinal dysbiosis during inflammatory arthritis results in altered tryptophan catabolism, leading to indole stimulation of arthritis development. Blockade of indole generation may present a novel therapeutic pathway for RA and SpA.

immunology↗