Biology subjects

Upchurch, C.

Publications and source records attributed to Upchurch, C..

4 recordsLinked to original sources

bioRxiv2026

ST2 Signaling Regulates Innate Immune Responses in Kidney Injury

IntroductionInnate immune cells are critical in inflammation, repair, and fibrosis post-kidney injury. Nuclear-cytokine interleukin (IL)-33, which is released upon tissue damage, signals through IL-1-receptor-like-1 (IL1RL1 or ST2), expressed on many immune cells, including macrophages. However, macrophage regulation by IL-33/ST2 is incompletely understood. We hypothesized that ST2 plays a vital role in activating and/or mobilizing myeloid cells and macrophages to sites of injury. MethodsWe performed acute and chronic ischemia-reperfusion injury (IRI) in mice with myeloid cell-specific deletion of ST2 (ST2fl/fl.LysMCre) to examine the role of myeloid cells ST2 expression in renal injury. The structure and function of the kidney were probed using flow cytometry, histology, immunohistochemistry, quantitative gene expression, and biochemical analysis. The invitro efferocytosis assay, RNA Seq, and Seahorse assay were carried out using bone-marrow-derived macrophages ResultsInterestingly, ST2 deletion resulted in attenuated renal pathology in the acute renal IRI model, whereas in chronic IRI, the loss of ST2 exacerbated kidney injury, suggesting a role of ST2 in the resolution of chronic injury. RNA sequencing (RNASeq) analysis of bone-marrow-derived ST2 sufficient and deficient macrophages showed that loss of ST2 downregulated genes involved in oxidative phosphorylation and clearance of dead cells (efferocytosis). Indeed, the ST2-deficient macrophages had reduced phagocytosis activity. Further, Seahorse analysis revealed that ST2-deficient macrophages had compromised mitochondrial metabolism. ConclusionsWe conclude that the IL-33/ST2 axis is essential for regulating macrophage function and contributes to regulating tissue homeostasis following renal injury.

immunology↗

bioRxiv2025

7-ketocholesterol contributes to microglia-driven increases in astrocyte reactive oxygen species in Alzheimer's disease

Oxidative stress is a prominent feature of Alzheimers disease. Within this context, cholesterol undergoes oxidation, producing the pro-inflammatory product 7-ketocholesterol (7-KC). In this study, we observe elevated levels of 7-KC in the brains of the 3xTg mouse model of AD. To further understand the contribution of 7-KC on the oxidative environment, we developed a method to express a genetically encoded fluorescent hydrogen peroxide (H2O2) sensor in astrocytes, the primary source of cholesterol in the brain. With this sensor, we discovered that 7-KC increases H2O2 levels in astrocytes in vivo, but not when directly applied to astrocytes in vitro. Interestingly, when 7-KC was applied to a microglia cell line alone or mixed astrocyte and microglia cultures, it resulted in microglia activation and increased oxidative stress in astrocytes. Depletion of microglia from 3xTg mice resulted in reduced 7-KC in the brains of these mice. Taken together, these findings suggest that 7-KC, acting through microglia, contributes to increased astrocyte oxidative stress in AD. This study sheds light on the complex interplay between cholesterol oxidation, microglia activation, and astrocyte oxidative stress in the pathogenesis of AD.

neuroscience↗

bioRxiv2023

Pannexin 1 Channels Control Cardiomyocyte Metabolism and Neutrophil Recruitment During Non-Ischemic Heart Failure

Pannexin 1 (PANX1), a ubiquitously expressed ATP release membrane channel, has been shown to play a role in inflammation, blood pressure regulation, and myocardial infarction. However, a possible role of PANX1 in cardiomyocytes in the progression of heart failure has not yet been investigated. We generated a novel mouse line with constitutive deletion of PANX1 in cardiomyocytes (Panx1MyHC6). PANX1 deletion in cardiomyocytes had no effect on unstressed heart function but increased the glycolytic metabolism both in vivo and in vitro. In vitro, treatment of H9c2 cardiomyocytes with isoproterenol led to PANX1-dependent release of ATP and Yo-Pro-1 uptake, as assessed by pharmacological blockade with spironolactone and siRNA-mediated knock-down of PANX1. To investigate non-ischemic heart failure and the preceding cardiac hypertrophy we administered isoproterenol, and we demonstrate that Panx1MyHC6 mice were protected from systolic and diastolic left ventricle volume increases and cardiomyocyte hypertrophy. Moreover, we found that Panx1MyHC6 mice showed decreased isoproterenol-induced recruitment of immune cells (CD45+), particularly neutrophils (CD11b+, Ly6g+), to the myocardium. Together these data demonstrate that PANX1 deficiency in cardiomyocytes impacts glycolytic metabolism and protects against cardiac hypertrophy in non-ischemic heart failure at least in part by reducing immune cell recruitment. Our study implies PANX1 channel inhibition as a therapeutic approach to ameliorate cardiac dysfunction in heart failure patients.

physiology↗

bioRxiv2021

Long-Term Inactivation of Sodium Channels as a Mechanism of Adaptation in CA1 Pyramidal Neurons

Many hippocampal CA1 pyramidal cells function as place cells, increasing their firing rate when a specific place field is traversed. The dependence of CA1 place cell firing on position within the place field is asymmetric. We investigated the source of this asymmetry by injecting triangular depolarizing current ramps to approximate the spatially-tuned, temporally-diffuse depolarizing synaptic input received by these neurons while traversing a place field. Ramps were applied to CA1 pyramidal neurons from male rats in vitro (slice electrophysiology) and in silico (multi-compartmental NEURON model). Under control conditions, CA1 neurons fired more action potentials at higher frequencies on the up-ramp versus the down-ramp. This effect was more pronounced for dendritic compared to somatic ramps. We incorporated a four-state Markov scheme for NaV1.6 channels into our model and calibrated the spatial dependence of long-term inactivation according to the literature; this spatial dependence was sufficient to explain the difference in dendritic versus somatic ramps. Long-term inactivation reduced the firing frequency by decreasing open-state occupancy, and reduced spike amplitude during trains by decreasing occupancy in closed states, which comprise the available pool. PKC activator phorbol-dibutyrate, known to reduce NaV long-term inactivation, removed spike amplitude attenuation in vitro more visibly in dendrites and greatly reduced adaptation, consistent with our hypothesized mechanism. Intracellular application of a peptide inducing long-term NaV inactivation elicited spike amplitude attenuation during spike trains in the soma and greatly enhanced adaptation. Our synergistic experimental/computational approach shows that long-term inactivation of NaV1.6 is a key mechanism of adaptation in CA1 pyramidal cells. Significance statementThe hippocampus plays an important role in certain types of memory, in part through context-specific firing of "place cells"; these cells were first identified in rodents as being particularly active when an animal is in a specific location in an environment, called the place field of that neuron. In this in vitro/in silico study, we found that long-term inactivation of sodium channels causes adaptation in the firing rate that could potentially skew the firing of CA1 hippocampal pyramidal neurons earlier within a place field. A computational model of the sodium channel revealed differential regulation of spike frequency and amplitude by long-term inactivation, which may be a general mechanism for spike frequency adaptation in the central nervous system.

neuroscience↗