Biology subjects

McLaughlin, E.

Publications and source records attributed to McLaughlin, E..

7 recordsLinked to original sources

bioRxiv2025

COX2-independent and COX2-dependent effects of naproxen on bone quality, osteocytes, and fatigue fracture healing in male and female mice

Regular non-steroidal anti-inflammatory drug (NSAID) use increases stress fracture risk, but the mechanisms remain unclear. Here, we used Ptgs2-Y385F mice, which lack cyclooxygenase 2 (COX2) enzyme activity, to test the hypothesis that naproxen decreases strain adaptive bone remodeling in a COX2-dependent manner and decreases bone toughness and fracture resistance through COX2-independent effects. MicroCT and mechanical testing showed minimal baseline differences between Ptgs2-Y385F and wild-type (WT) mice. Following non-damaging forelimb compression, naproxen decreased load-induced bone formation in WT, but not Ptgs2-Y385F mice, consistent with a COX2-dependent effect. In contrast, naproxen reduced bone toughness and post-yield deformation across genotypes and doses, supporting a COX2-independent mechanism. Histologically, naproxen increased empty osteocyte lacunae in both genotypes, while osteoblast number, total lacunae, and perilacunar labeling were increased only in WT mice. Naproxen pre-treatment before fatigue fracture produced mild, sex-specific effects on fracture initiation and healing. Analysis of osteocyte dendritic networks in uninjured femurs revealed sexually dimorphic changes in dendrite number and density in naproxen-treated mice as compared to vehicle. In total, naproxen influences bone through both COX2-dependent and COX2-independent mechanisms, with some sexual dimorphism. These findings confirm that regular NSAID usage compromises skeletal health and underscore the need for new pain management strategies.

bioengineering↗

bioRxiv2025

Osteoblast-derived Nerve Growth Factor is Required for Skeletal Adaptation to Mechanical Load and the Osteoanabolic Effect of Gambogic Amide in Mice

In adult mice, new bone accrual following mechanical load is mediated by the neurotrophin nerve growth factor (NGF) that is expressed by osteoblasts on the bone surface. NGF can bind to its high affinity receptor, neurotrophic tyrosine kinase receptor type 1 (TrkA), on peripheral sensory nerves resident in bone and support new bone formation. However, the osteoanabolic therapeutic potential of NGF-TrkA signaling to repair bone is limited due to the long-lasting thermal and mechanical hyperalgesia induced by administration of NGF in mice and humans. Here, we investigated whether 1) mature osteoblasts are the primary source of NGF required for bone accrual following loading, and 2) a small molecule TrkA receptor agonist - gambogic amide - can harness the downstream osteoanabolic potential of NGF-TrkA signaling in the absence of endogenous NGF. Loss of Ngf transcription in mature osteoblasts did not appear to affect bone structure or bone mass in adulthood. However, Ngf knockout mice significantly reduced periosteal bone accrual and osteogenic Wnt transcription in response to loading compared to wildtype mice. Intraperitoneal injection of gambogic amide prior to loading was unable to produce its osteoanabolic effects in Ngf knockout mice, suggesting that gambogic amide primarily functions in collaboration with endogenous NGF in bone. In total, our study reveals an important role for osteoblastic NGF in the skeletal adaptation of bone to mechanical forces.

bioengineering↗

bioRxiv2024

Longitudinal analysis of glioblastoma response to oncolytic HSV1 guides PLX3397 combination for enhanced viral permissiveness

Clinical trial data underscores the need to improve oncolytic virus (OV) distribution within tumors, a challenge compounded by the lack of predictive biomarkers and limited opportunities for post-treatment analysis. To decipher the factors influencing treatment outcomes, we employed multimodal bioluminescence imaging (MM-BLI) in conjunction with magnetic resonance imaging (MRI) to monitor OV infection, replication, and tumor viability in orthotopic brain glioma mouse models. This approach revealed two distinct therapeutic responses: "Responders" with tumor regression and "Non-Responders" with tumor progression. In-depth analysis of individual brains from both groups uncovered dynamic interactions between the OV and the tumor microenvironment, highlighting the involvement of Iba-1+ microglia and tumor necrosis in hindering OV distribution within the tumor. To address this, we incorporated a CSF-1 receptor inhibitor (PLX3397), which improved tumor control by enhancing OVs direct cytopathic effects and reducing microglial interference. Our findings highlight microglia as a significant barrier to effective OV therapy, suggesting that targeting brain-resident immune cells could enhance the therapeutic efficacy of OVs in resistant brain tumors.

bioengineering↗

bioRxiv2024

Evaluation of a Deep Learning Based Approach to Computational Label Free Cell Viability Quantification

One of the most common techniques found in a cell biology or tissue engineering lab is the cytotoxicity assay. This can be performed using a variety of different dyes and stains and various protocols to result in a clear indication of dead and live cells within a culture to quantify the viability of a culture and monitor for sudden drops or increases in viability by a drug, material, viral vector, etc introduced into the culture. This assay helps cell biologists determine the health of their culture and what toxicity added substances may add to the culture and whether they are appropriate and safe to use with human cells. However, many of the dyes and stains used for this process are eventually toxic to cells, rendering the cells useless after testing and preventing real time monitoring of the same culture over a period of hours or days. Computation biology is moving cell biology towards novel and innovative techniques such as in silico labeling and dye free labeling using deep learning algorithms. In this work, we investigate whether it is feasible to train a Resnet CNN model to detect morphological changes in human cells that indicate cell death in order to classify cells as live or dead without utilizing a stain or dye. This work also aims to train one CNN model to count all cells regardless of viability status to get a total cell count, and then one CNN model that specifically identifies and counts all of the dead cells for an accurate dead and live cell total by utilizing both pieces of data to determine a general viability percentage for the culture. Additionally, this work explores the use of various image enhancements to understand if this process helps or impedes the deep learning models in their detection of total cells and dead cells.

cell biology↗

bioRxiv2024

Mitochondrial Phosphopantetheinylation is Required for Oxidative Function

4-phosphopantetheinyl (4PP) groups are essential co-factors added to target proteins by phosphopantetheinyl transferase (PPTase) enzymes. Although mitochondrial 4PP-modified proteins have been described for decades, a mitochondrially-localized PPTase has never been found in mammals. We discovered that the cytoplasmic PPTase aminoadipate semialdehyde dehydrogenase phosphopantetheinyl transferase (AASDHPPT) is required for mitochondrial respiration and oxidative metabolism. Loss of AASDHPPT results in failed 4PP modification of the mitochondrial acyl carrier protein and blunted activity of the mitochondrial fatty acid synthesis (mtFAS) pathway. We found that in addition to its cytoplasmic localization, AASDHPPT localizes to the mitochondrial matrix via an N-terminal mitochondrial targeting sequence contained within the first 20 amino acids of the protein. Our data show that this novel mitochondrial localization of AASDHPPT is required to support mtFAS activity and oxidative function. We further identify five variants of uncertain significance in AASDHPPT that are likely pathogenic in humans due to loss of mtFAS activity.

molecular biology↗

bioRxiv2022

IL-6 prevents Th2 cell polarization by promoting SOCS3-dependent suppression of IL-2 signaling

Defective interleukin-6 (IL-6) signaling has been associated with Th2 bias and elevated IgE. However, the underlying mechanism by which IL-6 prevents the development of Th2-driven diseases remains unknown. Using a model of house-dust-mite (HDM)-induced Th2 differentiation and allergic airway inflammation, we show that IL-6 signaling in allergen-specific T cells was required to prevent Th2 development and subsequent IgE response and allergic inflammation. Th2 cell lineage commitment required strong sustained IL-2 signaling. Importantly, we found that IL-6 turned off IL-2 signaling during early T cell activation and thus inhibited Th2 priming. Mechanistically, we found that IL-6-driven inhibition of IL-2 signaling in responding T cells was mediated by upregulation of Suppressor Of Cytokine Signaling 3 (SOCS3). This mechanism could be mimicked by pharmacological Janus Kinase-1 (JAK1) inhibition. Collectively, our results identify an unrecognized mechanism that prevents the development of unwanted Th2 cell responses and associated diseases and outline potential preventive interventions.

immunology↗

bioRxiv2021

DNA double strand break position leads to distinct gene expression changes and regulates VSG switching pathway choice.

Antigenic variation is an immune evasion strategy used by Trypanosoma brucei that results in the periodic exchange of the surface protein coat. Underlying this process is the movement of variant surface glycoprotein genes in or out of a specialized locus known as bloodstream form expression site by homologous recombination, facilitated by blocks of repetitive sequence known as the 70-bp repeats, that provide homology for gene conversion events. DNA double strand breaks are potent drivers of antigenic variation, however where these breaks must fall to elicit a switch is not well understood. To understand how the position of a break influences antigenic variation we established a series of cell lines to study the effect of an I-SceI meganuclease break in the active expression site. We found that a DNA break within repetitive regions is not productive for VSG switching, and show that the break position leads to a distinct gene expression profile and DNA repair response which dictates how antigenic variation proceeds in African trypanosomes.

molecular biology↗