Biology subjects

Saunders, B.

Publications and source records attributed to Saunders, B..

10 recordsLinked to original sources

bioRxiv2026

CD163 protects against pulmonary injury and inflammation induced by acute O3 exposure

Ozone (O3)-driven pulmonary inflammation is partly regulated by damage associated molecular patterns (DAMPs) binding to scavenging receptors (SRs). However, how SRs and DAMPs regulate O3-induced pulmonary inflammation remains incompletely understood. CD163 is a SR responsible for clearing cell free hemoglobin (CFH), a DAMP which accumulates during acute pulmonary injury and is associated with worsening respiratory outcomes. We hypothesized that increased CD163 is necessary for reducing CFH levels and resolving O3-induced pulmonary injury. To test this hypothesis, we defined CD163 and CFH responses to O3 exposure in C57BL/6N (WT) and CD163 deficient (Cd163-/-) mice, as well as in human bronchoalveolar lavage fluid (BALF). In WT mice, lung Cd163 expression was significantly increased by O3 during peak inflammation and declined 24 hours post exposure. Human exposure studies revealed a diversity of Cd163 expression and a reduction of CFH following O3 exposure, suggesting regulation of this pathway in humans. When compared to WT mice, Cd163-/- mice had augmented O3-induced pulmonary injury, inflammation, and oxidative stress. Further, the antioxidant EUK-134 did not reduce O3-induced pulmonary oxidative stress in Cd163-/- mice, suggesting a role for CD163 in the pulmonary response to oxidative insults. Furthermore, compared to WT controls, Cd163-/- mice receiving an oropharyngeal aspiration of CFH had a significant increase in airspace inflammation. Combined, these findings suggest that CD163 mediated clearance of CFH is involved in resolving O3-induced pulmonary injury, inflammation, and oxidative stress. New & NoteworthyOzone (O3) is known to induce damage associated molecular patterns (DAMPs) which drive lung inflammation. The scavenging receptor, CD163, binds and clears the DAMP cell free hemoglobin (CFH), which accumulates during sterile lung injury. Our findings indicate that O3 exposure alters CD163 expression in the lung and that mice lacking Cd163 expression have more lung inflammation. Our data indicate that CD163 serves a protective role in response to acute O3 exposure perhaps through CFH clearance.

pharmacology and toxicology↗

bioRxiv2026

Engineering a Novel Bacterial Encapsulin for Programmable Surface Functionalization: From Single-Target to Mosaic Nanovaccines

Encapsulins are prokaryotic self-assembling protein nanocages with promise as nanovaccine scaffolds. Their utility as modular platforms require tolerance to surface engineering, high-yield soluble production, formulation stability, and controlled antigen (co-)display. Herein, a previously uncharacterized encapsulin from Alkaliphilus metalliredigens is engineered into a SpyCatcher-decorated nanoscaffold (Am-S) that enables controlled surface display of SpyTagged antigens. Cryo-EM confirms that the native encapsulin forms a T = 1 icosahedral nanocage, and that C-terminal SpyCatcher fusion yields Am-S without compromising nanocage assembly, symmetry, or structural integrity. Notably, Am-S exhibits high-yield soluble production in Escherichia coli, remains monodisperse after freeze-thaw and extended storage, and supports efficient SpyTagged peptide conjugation for single- and multi-antigen display. As a proof-of-concept, Am-S is functionalized with Alzheimers disease-associated amyloid-{beta} and/or hyperphosphorylated tau epitopes to generate single-target nanocages displaying either antigen and dual-target mosaic nanocages co-displaying both. In mice, Am-S antigen display enhances antigen-specific IgG responses relative to free antigens and induces predominantly IgG1-biased humoral immunity. Mosaic nanocages elicit antibodies against both targets, with immune sera selectively recognizing amyloid-{beta}- and phosphorylated tau-associated pathology in ex vivo brain sections from Alzheimers disease mouse models. These findings position Am-S as a manufacturable scaffold for developing multi-targeting nanovaccines against complex diseases.

synthetic biology↗

bioRxiv2024

Operant alcohol self-administration targets GluA2-containing AMPAR expression and synaptic activity in the nucleus accumbens in a manner that drives the reinforcing properties of the drug

Rationale: The positive reinforcing effects of alcohol (ethanol) drive its repetitive use and contribute to alcohol use disorder (AUD). Ethanol alters the expression of glutamate AMPA receptor (AMPAR) subunits in reward-related brain regions, but the extent to which this effect regulates ethanols reinforcing properties is unclear. Objective: This study investigates whether ethanol self-administration changes AMPAR subunit expression and synaptic activity in the nucleus accumbens core (AcbC) to regulate ethanols reinforcing effects in male C57BL/6J mice. Results: Sucrose-sweetened ethanol self-administration (0.81 g/kg/day) increased AMPAR GluA2 protein expression in the AcbC, without effect on GluA1, compared to sucrose-only controls. Infusion of myristoylated Pep2m in the AcbC, which blocks GluA2 binding to N-ethylmaleimide-sensitive fusion protein (NSF) and reduces GluA2-containing AMPAR activity, reduced ethanol-reinforced responding without affecting sucrose-only self-administration or motor activity. Antagonizing GluA2-lacking AMPARs, through AcbC infusion of NASPM, had no effect on ethanol self-administration. AcbC neurons receiving projections from the basolateral amygdala (BLA) showed increased sEPSC area under the curve (a measurement of charge transfer) and slower decay kinetics in ethanol self-administering mice as compared to sucrose. Optogenetic activation of these neurons revealed an ethanol-enhanced AMPA/NMDA ratio and significantly reduced paired-pulse ratio, suggesting elevated GluA2 contributions specifically within the BLA[->]AcbC pathway. Conclusions: Ethanol use upregulates GluA2 protein expression in the AcbC and AMPAR synaptic activity in AcbC neurons receiving BLA projections and enhances synaptic plasticity directly within the BLA[->]AcbC circuit. GluA2-containing AMPAR activity in the AcbC regulates the positive reinforcing effects of ethanol through an NSF-dependent mechanism, highlighting a potential therapeutic target in AUD.

neuroscience↗

bioRxiv2022

The role of bacterial size, shape and surface in macrophage engulfment of uropathogenic E. coli cells

Uropathogenic Escherichia coli (UPEC) can undergo extensive filamentation in the host during acute urinary tract infections (UTIs). It has been hypothesised that this morphological plasticity allows bacteria to avoid host immune responses such as macrophage engulfment. However, it is still unclear what properties of filaments are important in macrophage-bacteria interactions. The aim of this work was to investigate the contribution of bacterial biophysical parameters, such as cell size and shape, and physiological parameters, such as cell surface and the environment, to macrophage engulfment efficiency. Viable, reversible filaments of known lengths and volumes were produced in the UPEC strain UTI89 using a variety of methods, including exposure to cell-wall targeting antibiotics, genetic manipulation and isolation from an in vitro human bladder cell model. Quantification of the engulfment ability of macrophages using gentamicin-protection assays and fluorescence microscopy demonstrated that the ability of filaments to avoid macrophage engulfment is dependent on a combination of size (length and volume), shape, surface and external environmental factors. UTI89 filamentation was also found to occur independently of the SOS-inducible filamentation genes, sulA and ymfM, demonstrating the non-essential requirement of these genes for UTI89 filamentation and their ability to avoid macrophage engulfment. With several strains of UPEC now resistant to current antibiotics, our work identifies the importance of bacterial morphology during infection and may provide new ways to prevent or treat these infections via immune modulation or antimicrobials. Author SummaryUrinary tract infections (UTIs) are one of the most common bacterial infections worldwide with 50% of women suffering from a UTI during their lifetime. Escherichia coli is the primary bacteria responsible for UTIs and is usually found in short rod forms. However, during UTIs E. coli can elongate into extremely long thin shapes called filaments. Filaments are thought to be advantageous during infections because they are too long to be engulfed and killed by immune cells called macrophages. Due to increasing antibiotic resistance in bacteria there is a strong need for the discovery of new ways to treat infections and this is only possible once we thoroughly understand the mechanisms bacteria employ to overcome our immune response. Therefore, we investigated the effect of E. coli filamentation on macrophage engulfment along with other aspects of bacteria reported to influence engulfment. We found that the ability of filaments to avoid macrophage engulfment is dependent on a combination of size (length and volume), shape, surface and external environmental factors. Our research has highlighted the importance of bacterial shape changes during infections and provided a foundational understanding of macrophage engulfment of filaments. Eventually, this knowledge may reveal new targets for treatment of infections.

microbiology↗

bioRxiv2021

Skeletal Muscle Histidine Containing Dipeptide Contents are Increased in Freshwater Turtles (Chrysemys picta bellii) with Cold-Acclimation

Freshwater turtles found in higher latitudes can experience extreme challenges to acid-base homeostasis while overwintering, due to a combination of cold temperatures along with the potential for environmental hypoxia. Histidine containing dipeptides (HCDs; carnosine, anserine and balenine) may facilitate pH regulation in response to these challenges, through their role as pH buffers. We measured the HCDs content of three tissues (liver, cardiac muscle and skeletal muscle) from the anoxia-tolerant painted turtle (Chrysemys picta bellii) acclimated to either 3 or 20{degrees}C. HCDs were detected in all tissues, with the highest content shown in the skeletal muscle. Turtles acclimated to 3{degrees}C had more HCD in their skeletal muscle than those acclimated to 20{degrees}C (carnosine = 20.8{+/-}4.5 vs 12.5{+/-}5.9 mmol{middle dot}kg DM-1; ES = 1.59 (95%CI: 0.16 - 3.00), P = 0.013). The higher HCD content observed in the skeletal muscle of the cold-acclimated turtles suggests a role in acid-base regulation in response to physiological challenges associated with living in the cold, with the increase possibly related to the temperature sensitivity of carnosines dissociation constant and buffering power of the skeletal muscle during anoxic submergence. HighlightsO_LIpH regulation is a major challenge for overwintering freshwater turtles. C_LIO_LIHistidine containing dipeptides are important intracellular buffers. C_LIO_LITurtles acclimated to 3{degrees}C had higher HCD content than those at 20{degrees}C. C_LIO_LIHCDs may be important pH regulators in cold-acclimated turtles. C_LI

physiology↗

bioRxiv2021

Calcium-Permeable AMPA Receptor Activity and GluA1 Trafficking in the Basolateral Amygdala Regulate the Positive Reinforcing Effects of Alcohol

Addiction is viewed as maladaptive glutamate-mediated neuroplasticity that is regulated, in part, by calcium-permeable AMPA receptor (CP-AMPAR) activity. However, the contribution of CP-AMPARs to alcohol-seeking behavior remains to be elucidated. We evaluated CP-AMPAR activity in the basolateral amygdala (BLA) as a potential target of alcohol that also regulates alcohol self-administration in C57BL/6J mice. Operant self-administration of sweetened alcohol increased spontaneous EPSC frequency in BLA neurons that project to the nucleus accumbens as compared to behavior-matched sucrose controls indicating an alcohol-specific upregulation of synaptic activity. Bath application of the CP-AMPAR antagonist NASPM decreased evoked EPSC amplitude only in alcohol self-administering mice indicating alcohol-induced synaptic insertion of CP-AMPARs in BLA projection neurons. Moreover, NASPM infusion in the BLA dose-dependently decreased the rate of operant alcohol self-administration providing direct evidence for CP-AMPAR regulation of alcohol reinforcement. Since most CP-AMPARs are GluA1-containing, we asked if alcohol alters the activation state of GluA1-containing AMPARs. Immunocytochemistry results showed elevated GluA1-S831 phosphorylation in the BLA of alcohol as compared to sucrose mice. To investigate mechanistic regulation of alcohol self-administration by GluA1-containing AMPARs, we evaluated the necessity of GluA1 trafficking using a TET-ON AAV encoding a dominant-negative GluA1 c-terminus (GluA1ct) that blocks activity-dependent synaptic delivery of native GluA1-containing AMPARs. GluA1ct expression in the BLA reduced alcohol self-administration with no effect on sucrose controls. These results show that CP-AMPAR activity and GluA1 trafficking in the BLA mechanistically regulate the reinforcing effects of sweetened alcohol. Pharmacotherapeutic targeting these mechanisms of maladaptive neuroplasticity may aid medical management of alcohol use disorder.

neuroscience↗

bioRxiv2019

Human Skeletal Muscle has Large Capacity to Increase Carnosine Content in Response to Beta-Alanine Supplementation. A Systematic Review with Bayesian Individual and Aggregate Data E-Max Model and Meta-Analysis

Beta-alanine (BA) supplementation increases muscle carnosine content (MCarn), and is ergogenic in many situations. Currently, many questions on the nature of the Mcarn response to supplementation are open, and the response to these has considerable potential to enhance the efficacy and applications of this supplementation strategy. ObjectiveTo conduct a Bayesian analysis of available data on the Mcarn response to BA supplementation. MethodsA systematic review with meta-analysis of individual and published aggregate data using a dose response (Emax) model was conducted. The protocol was designed according to PRISMA guidelines. A three-step screening strategy was undertaken to identify studies that measured the Mcarn response to BA supplementation. In addition, individual data from 5 separate studies conducted in the authors laboratory were analysed. Data were extracted from all controlled and uncontrolled supplementation studies conducted on healthy humans. Meta-regression was used to consider the influence of potential moderators (including dose, sex, age, baseline Mcarn and analysis method used) on the primary outcome. Results and ConclusionThe Emax model indicated that human skeletal muscle has large capacity for non-linear Mcarn accumulation, and that commonly used BA supplementation protocols may not come close to saturating muscle carnosine content. Neither baseline values, nor sex, appear to influence subsequent response to supplementation. Analysis of individual data indicated that Mcarn is relatively stable in the absence of intervention, and effectually all participants respond to BA supplementation (99.3% response [95%CrI: 96.2 - 100]).

physiology↗

bioRxiv2017

Instantiation of incentive value and movement invigoration by distinct midbrain dopamine circuits

Environmental cues, through Pavlovian learning, become conditioned stimuli that guide animals towards the acquisition of \"rewards\" (i.e., food) that are necessary for survival. Here, we test the fundamental role of midbrain dopamine neurons in conferring predictive or motivational properties to cues, independent of external rewards. We demonstrate that phasic optogenetic excitation of dopamine neurons throughout the midbrain, when presented in temporal association with discrete sensory cues, is sufficient to instantiate those cues as conditioned stimuli that subsequently both evoke dopamine neuron activity on their own, and elicit cue-locked conditioned behaviors. Critically, we identify highly parcellated behavioral functions for dopamine neuron subpopulations projecting to discrete regions of striatum, revealing dissociable mesostriatal systems for the generation of incentive value and movement invigoration. These results show that dopamine neurons orchestrate Pavlovian conditioning via functionally heterogeneous, circuit-specific motivational signals to shape cue-controlled behavior.

neuroscience↗

bioRxiv2017

The conflict negativity: Neural correlate of value conflict and indecision during financial decision making

Individuals struggle when making financial decisions, sometimes preferring to avoid difficult decisions and receive lower future rewards over actively deliberating between options of similar value. Here, we examine how conflict deriving from objective and subjective value characteristics of stocks, as well as the behavioural and phenomenological correlates of decision conflict, are accompanied by variation in a thus far understudied ERP component, the conflict negativity (CN). In a novel EEG paradigm (N = 53), we simulated a financial decision situation in which participants made incentivized choices between different, sometimes conflicting, stock options. Our results indicate that participants become slower, more undecided, and less pleased, when choosing between similar options compared to choices in which one option clearly outweighs the other. This effect even held when participants chose between two objectively good alternatives. We further provide preliminary evidence that the CN, a negative-going ERP recorded over the medial prefrontal cortex, is not only sensitive to decision conflict, but also predicts behavioural indecision. What is more, subjective value characteristics of stocks, impressions based on brand perception of the stock options, modestly influenced affective and behavioural reactions over and above objective stock characteristics. While our results are at odds with assumptions made by classic economic theory, they may serve as one out of several indicators as to why private investors seem to avoid financial decisions.

neuroscience↗

bioRxiv2017

Midfrontal theta and pupil dilation parametrically track subjective conflict (but also surprise) during intertemporal choice

Many everyday choices are based on personal, subjective preferences. When choosing between two options, we often feel conflicted, especially when trading off costs and benefits occurring at different times (e.g., saving for later versus spending now). Although previous work has investigated the neurophysiological basis of conflict during inhibitory control tasks, less is known about subjective conflict resulting from competing subjective preferences. In this pre-registered study, we investigated subjective conflict during intertemporal choice, whereby participants chose between smaller immediate versus larger delayed rewards (e.g., $15 today vs. $22 in 30 days). We used economic modeling to parametrically vary eleven different levels of conflict, and recorded EEG data and pupil dilation. Midfrontal theta power, derived from EEG, correlated with pupil responses, and our results suggest that these signals track different gradations of subjective conflict. Unexpectedly, both signals were also maximally enhanced when decisions were surprisingly easy. Therefore, these signals may track events requiring increased attention and adaptive shifts in behavioral responses, with subjective conflict being only one type of such event. Our results suggest that the neural systems underlying midfrontal theta and pupil responses interact when weighing costs and benefits during intertemporal choice. Thus, understanding these interactions might elucidate how individuals resolve self-control conflicts.\n\nHighlightsO_LIModeled conflict during intertemporal choice and measured EEG and pupil responses.\nC_LIO_LIMidfrontal theta and pupil responses parametrically tracked subjective conflict.\nC_LIO_LIBut theta and pupil responses were also large when decisions were surprisingly easy.\nC_LIO_LIThese signals may implement adaptive control during value-guided choice.\nC_LI

neuroscience↗