Biology subjects

Oliver, E.

Publications and source records attributed to Oliver, E..

10 recordsLinked to original sources

bioRxiv2026

Endothelial β3-Adrenergic Receptor activation prevents pulmonary hypertension

BackgroundPulmonary hypertension (PH) is a progressive vascular disease characterized by endothelial dysfunction, vascular remodeling and increased pulmonary vascular resistance. The {beta}3-adrenergic receptor ({beta}3-AR) has been implicated in cardiovascular regulation and cardioprotective mechanisms; however, its role in pulmonary vascular disease remains poorly understood. We investigated whether activation of {beta}3-AR protects pulmonary endothelial function and prevents the development of pre-capillary PH. Methods{beta}3-AR expression was evaluated in pulmonary endothelium from patients with Chronic Obstructive Pulmonary Disease (COPD) and in murine models of hypoxia-induced PH. Genetic mouse models including {beta}3-AR knockout (KO) and conditional {beta}3-AR overexpression in endothelial cells (EC) or in smooth muscle cells (SMC), were used to determine cell-specific roles. Pharmacological activation of {beta}3-AR was achieved using the selective {beta}3-agonist mirabegron in hypoxia-induced PH mice and monocrotaline-induced PH rats. Pulmonary vascular reactivity and vasodilatory responses to {beta}3-AR stimulation were evaluated by wire myography in isolated pulmonary arteries. Mechanistic studies were performed in human pulmonary artery endothelial cells (HPAEC) under hypoxic conditions, in human pulmonary arterial smooth muscle cells (HPASMC) and in endothelial nitric oxide synthase (NOS3) KO mice. Results{beta}3-AR was upregulated in pulmonary endothelium of COPD patients and mice exposed to chronic hypoxia. Genetic deletion of {beta}3-AR aggravated PH, whereas endothelial-specific overexpression attenuated the disease phenotype, reducing right ventricular systolic pressure (RVSP), vascular remodeling and right ventricular (RV) hypertrophy. Activation of {beta}3-AR with mirabegron improved pulmonary hemodynamics, reduced vascular remodeling and preserved RV function. {beta}3-AR activation promoted endothelial nitric oxide synthase (eNOS)-dependent NO production, indirectly inhibiting SMC proliferation. Additionally, {beta}3-AR activation improved mitochondrial fitness in endothelial cells by increasing uncoupling protein 2 (UCP2) expression, reducing reactive oxygen species (ROS) generation and preventing mitochondrial fragmentation. ConclusionsThese findings identify endothelial {beta}3-AR as a previously unrecognized regulator of pulmonary vascular homeostasis and provide a strong translational rationale for targeting the {beta}3-adrenergic pathway in PH. Given that mirabegron is already approved for clinical use, our results support its repurposing as a therapeutic strategy for pre-capillary forms of PH.

pharmacology and toxicology↗

bioRxiv2026

Somatic CRISPR editing of Msh3 mitigates Huntington's disease pathology in mice

Huntingtons disease (HD) is a fatal, dominantly inherited neurodegenerative disorder caused by a CAG repeat expansion in Huntingtin (HTT) exon 1. Further progressive CAG repeat expansion occurs in somatic cells, particularly in neurons, and drives the timing of clinical onset. Therefore, therapeutic strategies to slow somatic expansion are predicted to be disease-modifying. Somatic CAG expansion is driven by mismatch repair protein MSH3, a leading therapeutic target supported by human genetic data. To gain insight into the impact of targeting MSH3 at different stages of the disease process we used somatic CRISPR-Cas9 editing to knock out Msh3 in HttQ111 mice at ages of 6, 16, 24 weeks exhibiting progressively increasing somatic expansion. Intervention at all three ages slowed striatal CAG expansion, reduced nuclear huntingtin pathology and suppressed transcriptional dysregulation, with earlier intervention having greater impact. Msh3 knockout also suppressed the production of the exon 1 Htt1a transcript. The results of our study provide important preclinical information relevant to an MSH3 therapeutic in humans that would be expected to impact a subset of cells in the brain, provide insight into the influence of timing of intervention on therapeutic effectiveness and deepen our understanding of how targeting MSH3 could alter the trajectory of HD.

genetics↗

bioRxiv2025

Huntington's disease LIG1 modifier variant increases ligase fidelity and suppresses somatic CAG repeat expansion

Huntingtons disease (HD) is a fatal neurodegenerative disorder caused by inheriting an expanded CAG repeat tract in the huntingtin gene (HTT) that further expands in somatic cells over an individuals lifetime. Genome-wide association studies have provided critical insight into factors that modify the course of disease. These include DNA repair genes that alter the rate of somatic expansion and other genes that do not appear to directly influence this process. One modifier gene is DNA ligase 1 (LIG1), in which a variant specifying a lysine to asparagine substitution (K845N) is associated with a profound (7-8 year) delay in the onset of motor signs. Here, we have taken a multifaceted approach to gain insight into the protective nature of this variant in HD. We demonstrate using in vitro ligase assays and enzyme kinetics that K845N enhances discrimination towards mismatched substrates and increases repair fidelity. Consistent with increased ligation fidelity, K845N confers protection against oxidative stress in cell-based assays. Finally, we demonstrate that the mouse LIG1 K843N orthologue suppresses somatic CAG expansion in HD knock-in mice. Overall, our data provide evidence that altered LIG1 function due to the K845N substitution may contribute to HD clinical delay by slowing somatic expansion in the brain and protecting the genome globally against damage. Significantly, our results provide a mechanistic foundation for considering DNA ligase fidelity as a therapeutic target in HD and potentially in other trinucleotide repeat disorders. Significance StatementWe analyzed a missense variant in DNA Ligase 1 (K845N) that is associated with a profound delay in the onset of Huntingtons disease (HD). We find that K845N enhances substrate discrimination towards mismatched substrates, thus increasing repair fidelity, conferring protection against oxidative stress and slows somatic expansion of the HD CAG repeat. Our observations provide insight into underlying mechanisms of disease modification and suggest avenues that can be harnessed for disease-modifying therapeutic intervention. Classification: Biological Sciences, Genetics

genetics↗

bioRxiv2025

Insights into global antimicrobial resistance dynamics through the sequencing of enteric bacteria from U.S. international travelers

Antimicrobial resistance (AMR) is an urgent threat to public health, but gaps in surveillance limit the detection of emergent novel threats and knowledge about the global distribution of AMR genes. International travelers frequently acquire AMR organisms, and thus may provide a window into AMR dynamics in otherwise poorly monitored regions and environments. To assess the utility of travelers as global AMR sentinels, we collected pre- and post-travel stool samples from 608 travelers, which were screened for the presence of extended-spectrum beta-lactamase producing Enterobacterales, carbapenem-resistant Enterobacterales, and mcr-mediated colistin-resistant Enterobacterales. A total of 307 distinct AMR organisms were sequenced in order to determine genotypic patterns and their association with travel region and behavior. Travel-associated AMR organisms were overwhelmingly E. coli, which exhibited considerable phylogenetic diversity regardless of travel region. However, the prevalence of resistance genes varied by region, with blaCTX-M-55 and blaCTX-M-27 significantly more common in travelers returning from South America and South-Eastern Asia, respectively. Hybrid assembly and plasmid reconstruction revealed the genomic neighborhood of blaCTX-M-55 frequently matched a motif previously linked to animal populations. Contact with animals was also associated with virulence factors in acquired AMR organisms, including carriage of the ColV plasmid, a driver of avian pathogenic E. coli. We identified novel variants of the mcr-1 gene in strains acquired from Western Africa, highlighting the potential for traveler surveillance to detect emerging clinical threats. Ongoing efforts to track travel-acquired organisms could complement existing global AMR surveillance frameworks. ImportanceWe collected pre- and post-travel stool samples from 608 U.S. international travelers, which were screened for the presence of three clinically relevant antimicrobial-resistant organisms, with the goal of understanding the utility of travelers as sentinels for emerging AMR and identifying regional resistance patterns. We sequenced 307 organisms and uncovered significant diversity and geographic heterogeneity in AMR organisms. We found significant differences in certain resistance gene alleles of travelers returning from South America and South-Eastern Asia, traveler contact with animals associated with virulence factors, including a plasmid that is a known driver of avian pathogenic E. coli, and novel variants of the colistin resistance mcr-1 gene in strains acquired from Western Africa. This work emphasizes the value of monitoring international travelers as a proxy for understanding AMR patterns globally and could be an important addition to existing global AMR surveillance frameworks.

genomics↗

bioRxiv2024

Vascular HIF2 signaling prevents cardiomegaly, alveolar congestion and capillary remodeling during chronic hypoxia

Hypoxia is associated with the onset of cardiovascular diseases including cardiac hypertrophy and pulmonary arterial hypertension (PAH). Endothelial HIF2 signaling mediates pulmonary arterial remodeling and subsequent right ventricular systolic pressure (RVSP) elevation during chronic hypoxia, encouraging novel therapeutic opportunities for PAH based on specific HIF2 inhibitors. Nevertheless, HIF2 relevance beyond the pulmonary endothelium or in the cardiac adaptation to hypoxia remains elusive. Wilms tumor 1 lineage contributes to heart and lung vascular compartments including pericytes, endothelial and smooth muscle cells. Here we describe the response to chronic hypoxia of a novel HIF2 mutant mouse model in the Wt1 lineage (Hif2/Wt1 cKO). Hif2/Wt1 cKO is protected against pulmonary remodeling and increased RVSP induced by hypoxia, but displays alveolar congestion, inflammation and hemorrhages associated with microvascular instability. Furthermore, lack of HIF2 in the Wt1 lineage leads to cardiomegaly, capillary remodeling, right and left ventricular hypertrophy, systolic dysfunction and left ventricular dilation, suggesting pulmonary-independent cardiac direct roles of HIF2 in hypoxia. These structural defects are partially restored upon reoxygenation, while functional parameters remain altered. Our results suggest that cardiopulmonary HIF2 signaling prevents excessive vascular proliferation during chronic hypoxia and define novel protective roles of HIF2 to warrant stable microvasculature and organ function.

pathology↗

bioRxiv2024

Re-programming of GM-CSF-dependent alveolar macrophages through GSK3 activity modulation

Monocyte-derived macrophages recruited into inflamed tissues can acquire an array of functional states depending on the extracellular environment. Since the anti-inflammatory/pro-fibrotic macrophage profile is determined by MAFB, whose activity/protein levels are regulated by GSK3, we addressed the macrophage re-programming potential of GSK3 modulation. GM-CSF-dependent (GM-MO) and M-CSF-dependent monocyte-derived macrophages (M-MO) exhibited distinct levels of inactive GSK3, and inhibiting GSK3 in GM-MO led to acquisition of transcriptional, phenotypic and functional properties characteristic of M-MO (enhanced expression of IL-10 and monocyte-recruiting factors, and higher efferocytosis). These re-programming effects were also observed upon GSK3/{beta} knockdown, and through GSK3 inhibition in ex vivo isolated human alveolar macrophages (AMO). Notably, GSK3 downmodulation potentiated the transcriptional signature of Interstitial Macrophages (IMO) while suppressed the AMO-specific gene profile. Indeed, heightened levels of inactive GSK3 and MAFB-dependent proteins were observed in severe COVID-19 patients lung macrophages, highlighting the GSK3-MAFB axis as a therapeutic target for macrophage re-programming.

immunology↗

bioRxiv2024

Identification of genetic modifiers of Huntington's disease somatic CAG repeat instability by in vivo CRISPR-Cas9 genome editing

Huntingtons disease (HD), one of >50 inherited repeat expansion disorders (Depienne and Mandel, 2021), is a dominantly-inherited neurodegenerative disease caused by a CAG expansion in HTT (The Huntingtons Disease Collaborative Research Group, 1993). Inherited CAG repeat length is the primary determinant of age of onset, with human genetic studies underscoring that the property driving disease is the CAG length-dependent propensity of the repeat to further expand in brain (Swami et al., 2009; GeM-HD, 2015; Hensman Moss et al., 2017; Ciosi et al., 2019; GeM-HD, 2019; Hong et al., 2021). Routes to slowing somatic CAG expansion therefore hold great promise for disease-modifying therapies. Several DNA repair genes, notably in the mismatch repair (MMR) pathway, modify somatic expansion in HD mouse models (Wheeler and Dion, 2021). To identify novel modifiers of somatic expansion, we have used CRISPR-Cas9 editing in HD knock-in mice to enable in vivo screening of expansion-modifier candidates at scale. This has included testing of HD onset modifier genes emerging from human genome-wide association studies (GWAS), as well as interactions between modifier genes, thereby providing new insight into pathways underlying CAG expansion and potential therapeutic targets.

genetics↗

bioRxiv2024

Antibody responses in Klebsiella pneumoniae bloodstream infection: a cohort study

BackgroundKlebsiella pneumonia (Kpn) is the fourth leading cause of infection-related deaths globally, yet little is known about human antibody responses to invasive Kpn. In this study, we sought to determine whether the O-specific polysaccharide (OPS) antigen, a vaccine candidate, is immunogenic in humans with Kpn bloodstream infection (BSI). We also sought to define the cross-reactivity of human antibody responses among structurally related Kpn OPS subtypes and to assess the impact of capsule production on OPS-targeted antibody binding and function. MethodsWe measured plasma antibody responses to OPS (and MrkA, a fimbrial protein) in a cohort of patients with Kpn BSI and compared these with controls, including a cohort of healthy individuals and a cohort of individuals with Enterococcus BSI. We performed flow cytometry to measure the impact of Kpn capsule production on whole cell antibody binding and complement deposition, utilizing patient isolates with variable levels of capsule production and isogenic capsule-deficient strains derived from these isolates. FindingsWe enrolled 69 patients with Kpn BSI. Common OPS serotypes accounted for 57/69 (83%) of infections. OPS was highly immunogenic in patients with Kpn BSI, and peak OPS-IgG antibody responses in patients were 10 to 30-fold higher than antibody levels detected in healthy controls, depending on the serotype. There was significant cross-reactivity among structurally similar OPS subtypes, including the O1v1/O1v2, O2v1/O2v2 and O3/O3b subtypes. Physiological amounts of capsule produced by both hyperencapsulated and non-hyperencapsulated Kpn significantly inhibited OPS-targeted antibody binding and function. InterpretationOPS was highly immunogenic in patients with Kpn BSI, supporting its potential as a candidate vaccine antigen. The strong cross-reactivity observed between similar OPS subtypes in humans with Kpn BSI suggests that it may not be necessary to include all subtypes in an OPS-based vaccine. However, these observations are tempered by the fact that capsule production, even in non-highly encapsulated strains, has the potential to interfere with OPS antibody binding. This may limit the effectiveness of vaccines that exclusively target OPS. FundingNational Institute of Allergy and Infectious Diseases at the National Institutes of Health. Research in ContextO_ST_ABSEvidence before this studyC_ST_ABSDespite the potential of O-specific polysaccharide (OPS) as a vaccine antigen against Klebsiella pneumoniae (Kpn), the immunogenicity of OPS in humans remains largely unstudied, creating a significant knowledge gap with regard to vaccine development. A search of PubMed for publications up to March 18, 2024, using the terms "Klebsiella pneumoniae" and "O-specific polysaccharide" or "O-antigen" or "lipopolysaccharide" revealed no prior studies addressing OPS antibody responses in humans with Kpn bloodstream infections (BSI). One prior study1 evaluated antibody response to a single lipopolysaccharide (which contains one subtype of OPS) in humans with invasive Kpn infection; however, in this study OPS typing of the infecting strains and target antigen were not described. Added value of this studyOur investigation into OPS immunogenicity in a human cohort marks a significant advance. Analyzing plasma antibody responses in 69 patients with Kpn BSI, we found OPS to be broadly immunogenic across all the types and subtypes examined, and there was significant cross-reactivity among structurally related OPS antigens. We also demonstrated that Kpn capsule production inhibit OPS antibody binding and the activation of complement on the bacterial surface, even in classical Kpn strains expressing lower levels of capsule. Implications of all the available evidenceWhile the immunogenicity and broad cross-reactivity of OPS in humans with Kpn BSI suggests it is a promising vaccine candidate, the obstruction of OPS antibody binding and engagement by physiologic levels of Kpn capsule underscores the potential limitations of an exclusively OPS-antigen based vaccine for Kpn. Our study provides insights for the strategic development of vaccines aimed at combating Kpn infections, an important antimicrobial resistant pathogen.

microbiology↗

bioRxiv2022

GDF15 antagonism limits severe heart failure and prevents cardiac cachexia in mice

Heart failure and associated cachexia is an unresolved and important problem. We report a new model of severe heart failure that consistently results in cachexia. Mice lacking the integrated stress response (ISR) induced eIF2 phosphatase, PPP1R15A, exhibit a dilated cardiomyopathy and severe weight loss following irradiation, whilst wildtype mice are unaffected. This is associated with increased expression of Gdf15 in the heart and increased levels of GDF15 in the circulation. We provide evidence that blockade of GDF15 activity prevents cachexia and slows the progression of heart failure. Our data suggests that cardiac stress mediates a GDF15 dependent pathway that drives weight loss and worsens cardiac function. We show relevance of GDF15 to lean mass and protein intake with patients with heart failure. Blockade of GDF15 could constitute a novel therapeutic option to limit cardiac cachexia and improve clinical outcomes in patients with severe systolic heart failure.

pathology↗

bioRxiv2020

Remote Ischemic Preconditioning Ameliorates Anthracycline-induced Cardiotoxicity and Preserves Mitochondrial Integrity

AimsAnthracycline-induced cardiotoxicity (AIC) is a serious adverse effect in a significant proportion of cancer patients. A central mechanism of AIC is irreversible mitochondrial damage. Despite major efforts, there are currently no effective therapies able to prevent AIC. Methods and ResultsForty Large-White pigs were included. In Study 1, 20 pigs were randomized 1:1 to remote ischemic pre-conditioning (RIPC, 3 cycles of 5 min leg ischemia followed by 5 min reperfusion) or no pretreatment. RIPC was performed immediately before each of five intracoronary doxorubicin injections (0.45 mg/kg) given at weeks 0, 2, 4, 6, and 8. A group of 10 pigs with no exposure to doxorubicin served as healthy controls. Pigs underwent serial cardiac magnetic resonance (CMR) exams at baseline and at weeks 6, 8, 12, and 16. After 16-week CMR, pigs were sacrificed and tissue samples collected. In study 2, 10 new pigs received 3 doxorubicin injections (with/out preceding RIPC) and were sacrificed 2 weeks after the third dose. In Study 1, LVEF remained unchanged in doxorubicin-treated pigs until week 6 (time of the fourth doxorubicin injection). From there on, LVEF progressively declined, but LVEF depression was blunted animals receiving RIPC before doxorubicin (RIPC-Doxo), which had a significantly higher LVEF at week 16 than doxorubicin treated pigs that received no pretreatment (Untreated-Doxo) (41.5{+/-}9.1% vs 32.5{+/-}8.7%, p=0.04). Preserved LVEF was mainly due to conserved contractile function, as evidenced by smaller LVESV, and better regional contractile function. In Study 2, transmission electron microscopy (TEM) after 3 doxorubicin doses showed fragmented mitochondria with severe morphological abnormalities in RIPC+Doxo pigs, together with upregulation of fission proteins and autophagy markers on western blot. At the end of the 16-week Study 1 protocol, TEM revealed overt mitochondrial fragmentation with structural fragmentation in Untreated-Doxo pigs, whereas interstitial fibrosis was significantly less severe in the RIPC+Doxo pigs. ConclusionIn a translatable large animal model of AIC, RIPC applied immediately before each doxorubicin injection resulted in preserved cardiac contractility with significantly higher long-term LVEF and less cardiac fibrosis. RIPC prevented mitochondrial fragmentation and dysregulated autophagy from the early stages of AIC. RIPC is a promising intervention for testing in clinical trials in AIC.

molecular biology↗