Biology subjects

Walters, M. S.

Publications and source records attributed to Walters, M. S..

4 recordsLinked to original sources

bioRxiv2025

3-Mercaptopyruvate Sulfurtransferase (MPST) Regulates Mitochondrial Metabolism and Epithelial Differentiation in Neonatal Patient-derived Airway Cells

Early-life airway epithelial development relies on tightly coordinated mitochondrial metabolic programs, yet the pathways that govern normal epithelial maturation during this vulnerable developmental window remain poorly defined. Hyperoxia disrupts airway epithelial maturation, contributing to lung injury and airway remodeling in infants with bronchopulmonary dysplasia (BPD), underscoring the need to identify mitochondrial pathways that regulate early epithelial differentiation. 3-Mercaptopyruvate sulfurtransferase (MPST), a mitochondrial sulfur metabolism enzyme, supports mitochondrial metabolic and bioenergetic function, but its role in human airway epithelial development is unknown. In this study, we used neonatal patient-derived tracheal airway epithelial cells (nTAECs) in a three-dimensional air-liquid interface (ALI) model to show that hyperoxia reduces MPST protein abundance. To determine how MPST loss alters early epithelial differentiation and metabolic homeostasis we used RNAi to knock down MPST during ALI differentiation. MPST loss in nTAECs induced early (ALI day 3) transcriptomic shifts involving mitochondrial metabolic pathways, epithelial differentiation programs, and stress-response signature corresponding with decreased ciliated cell numbers during mid-differentiation phase (ALI day 7). Metabolic flux analysis revealed significantly reduced mitochondrial respiration without compensatory increase in glycolysis, indicative of disrupted metabolic flexibility. Together, these data show that MPST is essential for maintaining mitochondrial metabolic integrity necessary for normal airway epithelial development. Loss of MPST creates a developmental vulnerability that may contribute to hyperoxia-induced airway injury in neonates. Targeting MPST-dependent pathways could represent a new strategy to preserve airway health in infants at risk for BPD airway remodeling. NEW & NOTEWORTHYThis study identifies MPST as a previously unrecognized regulator of neonatal airway epithelial development. In our neonatal patient-derived three-dimensional organotypic model, hyperoxia reduces MPST, and MPST loss alters mitochondrial metabolism and epithelial differentiation programs. These findings indicate that MPST deficiency contributes to mitochondrial dysfunction under hyperoxic conditions and highlight MPST-linked pathways as potential therapeutic targets to mitigate early-life airway injury and remodeling relevant to infants with bronchopulmonary dysplasia.

developmental biology↗

bioRxiv2025

Quantitative Proteomics Links Mitochondrial Dysfunction to Metabolic Changes and Epithelial Differentiation Defects in Hyperoxia-Exposed Neonatal Airway Cells

Premature infants often require supplemental oxygen therapy, however, exposure to supraphysiological oxygen (hyperoxia) can disrupt normal lung development and contribute to bronchopulmonary dysplasia (BPD). Mitochondrial dysfunction is increasingly recognized as a contributor to hyperoxia-induced BPD. However, the effects of hyperoxia on mitochondrial function and mucociliary differentiation in the developing upper airway epithelium remain poorly understood. This study tested the hypothesis that hyperoxia impairs neonatal airway mucociliary differentiation by disrupting mitochondrial bioenergetic function. Neonatal tracheal airway epithelial cells (nTAECs) from term infants (n=5) were cultured in a 3D air-liquid interface (ALI) model and exposed to 60% O2 during the mid-phase of differentiation (ALI day 7-14). Cellular phenotype was assessed using immunofluorescence staining and gene expression analyses. Mitochondrial function was evaluated through Seahorse metabolic flux analysis, and global protein changes were characterized by quantitative proteomics. Hyperoxia exposure significantly impaired terminal epithelial differentiation, characterized by reductions in ciliated and goblet cells. Seahorse assay revealed a decrease in baseline oxygen consumption and mitochondrial ATP production, accompanied by a compensatory increase in glycolytic ATP production. Quantitative proteomics identified disruption of mitochondrial Complex I as a central feature of the hyperoxic response. Downstream proteomic pathway analyses further confirmed the metabolic shift from mitochondrial to glycolytic ATP production and demonstrated altered epithelial differentiation pathways, including NOTCH and TGF-{beta} signaling. These findings reveal that moderate hyperoxia impairs mitochondrial bioenergetics and alters metabolic programming, leading to disrupted mucociliary differentiation. Future in vivo studies should evaluate mitochondrial oxidative fitness as a therapeutic target in neonatal lung disease. NEW & NOTEWORTHYWe report that moderate hyperoxia during a critical window of mucociliary differentiation disrupts terminal maturation in neonatal airway epithelial cells cultured in a 3D model. Hyperoxia induced mitochondrial bioenergetic dysfunction and metabolic reprogramming, with proteomic analysis identifying Complex I disruption as a key driver of impaired differentiation. Overall, these findings reveal a previously underrecognized link between mitochondrial bioenergetics and airway epithelial development, positioning metabolic dysfunction as an early trigger of hyperoxia-induced neonatal airway injury.

developmental biology↗

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↗

bioRxiv2021

The NOTCH3 Downstream Target HEYL Regulates Human Airway Epithelial Club Cell Differentiation

Basal cells (BC) are the resident stem/progenitor cells of the adult pseudostratified airway epithelium, whose differentiation program is orchestrated by the NOTCH signaling pathway. NOTCH3 receptor mediated signaling regulates BC to club cell differentiation; however, the downstream responses that regulate this process are largely unknown. In the present study we used an in vitro air-liquid interface model of the human pseudostratified airway epithelium to identify the NOTCH3-dependent downstream genes/pathways that regulate human BC to club cell differentiation. Activation of NOTCH3 signaling in BC via lentivirus-mediated over-expression of the active NOTCH3 intracellular domain (NICD3) promoted club cell differentiation. Bulk RNA-seq analysis of control vs NICD3-transduced cells, identified 692 NICD3 responsive genes enriched for pathways linked to airway epithelial biology and differentiation including Wnt/{beta}-catenin Signaling. Expression of the classical NOTCH target HEYL increased in response to NOTCH3 activation and positively correlated with expression of the club cell marker SCGB1A1. Further, using single-cell RNA-seq, we report that HEYL+ cells primarily clustered with SCGB1A1+ and NOTCH3+ cells. Moreover, HEYL protein co-localized with SCGB1A1 in ALI cultures in vitro and in the human and mouse airway epithelium in vivo. siRNA-mediated knockdown of HEYL in BC led to changes in epithelial structure including altered morphology and significant reductions in transepithelial electrical resistance and expression of tight junction related genes. Finally, HEYL knockdown significantly reduced the number of SCGB1A1+ club cells, along with a corresponding increase in KRT8+ BC-intermediate cells. Overall, our data identifies NOTCH3-HEYL signaling as a key regulator of BC to club cell differentiation.

cell biology↗