Biology subjects

Kay, M.

Publications and source records attributed to Kay, M..

6 recordsLinked to original sources

bioRxiv2026

Oxytocin treats respiratory depression and reduces mortality from fentanyl and the combination of xylazine-fentanyl

Opioid addiction and misuse are a serious national crisis that affects public health, as well as social and economic welfare. Mortality due to opioid misuse is further exasperated by the combination of opioids with non-opioid respiratory depressants such as xylazine that are resistant to mu opioid receptor antagonists such as naloxone. This study tested the hypothesis that oxytocin can mitigate the severe opioid induced respiratory depression (OIRD) and mortality induced by high doses of fentanyl or the combination of fentanyl with xylazine. Our results show OXT can improve survival and respiratory function in both male and female rats with opioid induced respiratory depression caused by fentanyl, as well as a combination of fentanyl and xylazine. The improvement in respiratory function by OXT post fentanyl-xylazine was significantly greater than the recovery using only naloxone. Chemogenetic activation of OXT receptor positive neurons in the ventral respiratory group (VRG) provided similar benefits to that of OXT administration in reversing OIRD. These results indicate OXT is a promising therapeutic target for reversing OIRD and the respiratory depression that occurs with the combination of opioids and xylazine, a situation where naloxone is only partially effective. Additional translational benefits of OXT include it can be repurposed as it is already a FDA approved drug for other uses, has a high safety profile, and is unlikely to induce the withdrawal or reversal of analgesia that occurs with naloxone. Key PointsO_LIOxytocin (OXT) improves survival and respiratory function in both male and female rats with opioid induced respiratory depression (OIRD) caused by fentanyl C_LIO_LIOXT also reverses OIRD induced by the combination of fentanyl and xylazine C_LIO_LIThe improvement in respiratory function by OXT post fentanyl-xylazine was significantly greater than the recovery using only naloxone C_LIO_LIChemogenetic activation of OXT receptor positive neurons in the ventral respiratory group (VRG) provided similar benefits to that of OXT administration in reversing OIRD C_LIO_LIThese results indicate OXT is a promising therapeutic target for reversing OIRD and the respiratory depression that occurs with the combination of opioids and xylazine C_LI

pharmacology and toxicology↗

bioRxiv2025

Modeling the Interplay of Sex Hormones in Cardiac Hypertrophic Signaling

Biological sex plays a crucial role in the outcomes of cardiac health and therapies. Sex hormones are known to strongly influence cardiac remodeling through intracellular signaling pathways, yet their underlying mechanisms remain unclear. To address this need, we developed and validated a logic-based systems biology model of cardiomyocyte hypertrophy that, for the first time, incorporates the effects of both estradiol (E2) and testosterone (T) alongside well-established hypertrophic stimuli (Strain, angiotensin II (AngII), and endothelin-1 (ET-1)). We qualitatively validated the model to literature data with 84% agreement. Quantitative validation was done by simulating the impact of the inputs (E2, T, Strain, AngII, and ET-1) on cardiac hypertrophy, captured as change in CellArea. We perturbed the validated model to examine the differential response to hypertrophy and identify changes in influential and sensitive downstream nodes for a male, pre-menopausal female, and post-menopausal female condition. Our results suggest that T has a greater impact on hypertrophy than E2. This model increases our understanding of the mechanisms through which sex hormones influence cardiac hypertrophy and can aid with developing more effective cardiac therapies for all patients. Author summaryDifferences between female and male hearts extend far beyond size and structure. Sex hormones estradiol and testosterone play key roles in sex-specific cardiac remodeling via intracellular pathways. Understanding how these sex hormones impact cardiac remodeling is critical for developing more effective, sex-specific approaches to cardiovascular care. Logic-based systems biology models have proven useful in quantifying and analyzing complex and intricate intracellular signaling network dynamics in various cell types. We leverage this method to develop a model of cardiomyocyte hypertrophy, which, for the first time, includes the effect of both estradiol and testosterone. Considering the combined influence of these hormones is important because both women and men have varying concentrations of these hormones throughout their lives. The model was developed and validated based on previously published studies. We then investigated differences in cardiomyocyte hypertrophy in pre- and post-menopausal women and men.

systems biology↗

bioRxiv2024

A Structural Mechanism for Noncanonical GPCRSignal Transduction in the Hedgehog Pathway

SUMMARY PARAGRAPHThe Hedgehog (Hh) signaling pathway is fundamental to embryogenesis, tissue homeostasis, and cancer. Hh signals are transduced via an unusual mechanism: upon agonist-induced phosphorylation, the noncanonical G protein-coupled receptor SMOOTHENED (SMO) binds the catalytic subunit of protein kinase A (PKA-C) and physically blocks its enzymatic activity. By combining computational structural approaches with biochemical and functional studies, we show that SMO mimics strategies prevalent in canonical GPCR and PKA signaling complexes, despite little sequence or secondary structural homology. An intrinsically disordered region of SMO binds the PKA-C active site, resembling the PKA regulatory subunit (PKA-R) / PKA-C holoenzyme, while the SMO transmembrane domain binds a conserved PKA-C interaction hub, similar to other GPCR-effector complexes. In contrast with prevailing GPCR signal transduction models, phosphorylation of SMO promotes intramolecular electrostatic interactions that stabilize key structural elements within the SMO cytoplasmic domain, thereby remodeling it into a PKA-inhibiting conformation. Our work provides a structural mechanism for a central step in the Hh cascade and defines a paradigm for disordered GPCR domains to transmit signals intracellularly.

biochemistry↗

bioRxiv2024

GENCODE: massively expanding the lncRNA catalog through capture long-read RNA sequencing

Accurate and complete gene annotations are indispensable for understanding how genome sequences encode biological functions. For more than twenty years, the GENCODE consortium has developed reference annotations for the human and mouse genomes, becoming a foundation for biomedical and genomics communities worldwide. Nevertheless, collections of important yet poorly-understood gene classes like long non-coding RNAs (lncRNAs) remain incomplete and scattered across multiple, uncoordinated catalogs. To address this, GENCODE has undertaken the most comprehensive lncRNA annotation effort to date. This is founded on the manually supervised computational annotation of full-length targeted long-read sequencing, on matched embryonic and adult tissues, of orthologous regions in human and mouse. Altogether 17,931 human genes (140,268 transcripts) and 22,784 mouse genes (136,169 transcripts) have been added to the GENCODE catalog representing a 2-fold and 6-fold growth in transcripts, respectively - the greatest increase in the number of annotated human genes since the sequencing of the human genome. Our targeted design assigned human-mouse orthologs at a rate beyond previous studies, tripling the number of human disease-associated lncRNAs that have mouse orthologs. Novel lncRNA genes consistently exhibit biological signals of functionality, and they greatly enhance the functional interpretability of the human genome. While poorly expressed in bulk RNA-Seq samples, many of them are highly expressed in specific cell populations, maybe even contributing to cell-type determination. The expanded GENCODE lncRNA annotations mark a critical step toward deciphering the human and mouse genomes.

genomics↗

bioRxiv2022

Capsid-mediated chromatin state of the AAV vector genome controls host species range

Recombinant adeno-associated viral vectors (rAAVs) are among the most commonly used vehicles for in vivo based gene therapies. However, it is hard to predict which AAV capsid will provide the most robust expression in human subjects due to the observed discordance in vector-mediated transduction between species. We used a primate specific capsid, AAV-LK03, and demonstrated that the limitation of this capsid towards transduction of mouse cells was unrelated to cell entry and nuclear transport but rather due to depleted histone H3 chemical modifications related to active transcription, namely H3K4me3 and H3K27ac, on the vector DNA itself. A single-amino acid insertion into the AAV-LK03 capsid enabled efficient transduction and the accumulation of active histone marks on the vector chromatin in mouse without compromising transduction efficiency in human cells. Our study suggests that the capsid protein itself is involved in determining the chromatin status of the vector genome, most likely during the process of uncoating. Programming viral chromatin states by capsid design may enable facile DNA transduction between vector and host species.

molecular biology↗

bioRxiv2018

Sudden heart rate reduction upon optogenetic release of acetylcholine from cardiac parasympathetic neurons in perfused hearts

The balance of sympathetic and parasympathetic tone provides exquisite control of heart rate and contractility and has also been shown to modulate coronary flow and inflammation. Understanding how autonomic balance is altered by cardiac disease is an active area of research and developing new ways to control this balance is providing insights into disease therapies. However, achieving acute neuron-specific stimulation of autonomic neurons can be difficult in experiments that measure the acute effects of nerve stimulation on the heart. Conventional electrical and pharmacological approaches can be spatially and temporally non-selective. Cell-specific expression of light-activated channels (channelrhodopsin, ChR2) is a powerful approach that enables control of the timing and distribution of cellular stimulation using light. We present such an optogenetic approach where parasympathetic cardiac neurons are selectively photoactivated at high temporal precision to initiate cholinergic-mediated slowing of heart rate.\n\nMice were crossbred to express ChR2 in peripheral cholinergic neurons using Cre-Lox recombination driven by a choline acetyltransferase (ChAT) promoter. Hearts from adult mice were excised, perfused, and the epicardium was illuminated (peak 460-465nm) to photoactivate ChR2. In one set of studies, hearts were illuminated using a large-field LED light source. In other studies, a micro LED was placed on the right atrium to selectively illuminate the junction of the superior vena cava and right atrium. The ECG was acquired before, during, and after tissue illumination to measure changes in heart rate. Upon illumination, hearts exhibited sudden and dramatic reductions in heart rate with restoration of normal heart rate after cessation of illumination. Delays in atrioventricular conduction were also observed. Heart rate reductions at the highest irradiance levels were similar to heart rate reductions caused by application of bethanechol (10{micro}M) or acetylcholine (800{micro}M). Atropine (50nM) completely blocked the effect of ChR2 photoactivation, confirming cholinergic mediation.\n\nOptogenetic activation of intrinsic parasympathetic neurons reduced heart rate in an immediate, dose-dependent fashion, resembling the slowing of sinus rate in response to acetylcholine. Our results demonstrate a new approach for controlling parasympathetic modulation of cardiac function by selectively activating the endogenous release of acetylcholine from intrinsic cardiac cholinergic neurons.\n\nKey MessageOptogenetic photoactivation of intrinsic cardiac neurons provides immediate, tissuespecific stimulation with minimal cross-reactivity. Our results demonstrate that selective expression of channelrhodopsin within cardiac cholinergic neurons enables photoactivated release of acetylcholine, thereby instantaneously slowing sinus rate and altering atrioventricular conduction. This provides for indepth examination of the endogenous interplay between cardiac autonomic neurons and the functional outcomes of downstream post-synaptic receptor activation.

physiology↗