Biology subjects

Furness, J. B.

Publications and source records attributed to Furness, J. B..

8 recordsLinked to original sources

bioRxiv2026

Immune responses to infection modulate peripheral sympathetic neuron functions

The central nervous system interprets inflammatory signals in the body and directs the modulation of inflammatory responses by reflexively engaging peripheral sympathetic neurons1,2. This includes sympathetic neurons that innervate the spleen, which can regulate immune functions3-5 and modulate inflammation6-8. Yet, it is unclear if neuroimmune interactions involve specialised immunoregulatory sympathetic neurons, and if the immune system can reciprocally regulate peripheral sympathetic neurons to control these responses. Using retrograde tracing and single-cell transcriptomics, we find that spleen-innervating neurons are heterogeneous but do not exhibit a distinct transcriptional program indicative of specialisation for immune communication. However, we report that immune responses induced by pathogens can regulate postganglionic sympathetic neuron functions. Cytokines produced by immune cells downregulate expression of the neurotrophin nerve growth factor in spleen mesenchymal cells, leading to organ-specific sympathetic nerve retraction from the spleen. Concurrently, splenic type I interferon signalling induces inflammatory gene expression in neurons and suppresses neuron excitability. Chemogenetic activation of sympathetic neurons demonstrates an impaired anti-inflammatory capacity in the spleen during infection. These results reveal regulation of sympathetic neuronal functions by the immune system, which could support optimal generation of immune responses against pathogens.

immunology↗

bioRxiv2024

Magnetic Resonance Imaging of Gastric Motility in Conscious Rats

IntroductionGastrointestinal (GI) magnetic resonance imaging (MRI) can simultaneously capture gastric peristalsis, emptying, and intestinal filling and transit. Performing GI MRI with animals requires anesthesia, which complicates physiology and confounds interpretation and translation from animals to humans. This study aims to enable MRI in conscious rats, and for the first time, characterize GI motor functions in awake versus anesthetized conditions. MethodsWe acclimated rats to remain awake, still, and minimally stressed during MRI. We scanned 14 Sprague-Dawley rats in both awake and anesthetized conditions after voluntarily consuming a contrast-enhanced test meal. ResultsAwake rats remained physiologically stable during MRI, showed gastric emptying of 23.7{+/-}1.4% after 48 minutes, and exhibited strong peristaltic contractions propagating through the antrum with a velocity of 0.72{+/-}0.04 mm/s, a relative amplitude of 40.7{+/-}2.3%, and a frequency of 5.1{+/-}0.1 cycles per minute. In the anesthetized condition, gastric emptying was about half of that in the awake condition, likely due to the effect of anesthesia in halving the amplitudes of peristaltic contractions rather than their frequency (not significantly changed) or velocity. In awake rats, the intestine filled more quickly and propulsive contractions were more occlusive. ConclusionWe demonstrated the effective acquisition and analysis of GI MRI in awake rats. Awake rats show faster gastric emptying, stronger gastric contraction with a faster propagation speed, and more effective intestinal filling and transit, compared to anesthetized rats. Our protocol is expected to benefit future preclinical studies of GI physiology and pathophysiology.

bioengineering↗

bioRxiv2024

Food entrainment in mice leads to sex- and organ-specific responses in nutrient metabolism

Food intake is one of the main zeitgebers in the digestive system; however, little is known about organ- and sex-specific differences in food-driven regulation. We placed male and female C57Bl/6 mice on time-restricted feeding (TRF), limiting the food intake period to 8 hours. Food was added either at dark (ZT12) or light (ZT0) onset for 14 days. Afterwards, an additional 4-hour delay in the feeding period was introduced for half of the mice, and the TRF regime continued for another 14 days. TRF from ZT12 to ZT20 led to the highest weight gain in females but the lowest in males while improving intestinal transepithelial resistance (TEER) in both sexes. However, it also led to the disappearance of food-anticipatory response in several hepatic genes. Delaying the start of TRF until ZT16 led to an increase in weight gain and a decrease in fasting plasma glucose levels in male mice, as well as to strong entrainment of metabolism-related hepatic and duodenal genes in both sexes. The alignment of food intake with the early lights-on phase (ZT0-ZT8) caused only minor changes in physiological responses. However, it did lead to an overall downregulation of hepatic and an upregulation of duodenal and gastric genes, with additional loss of food-anticipatory gene expression in both sexes. Delaying the start of food intake until ZT4 was highly detrimental, causing an increase in fasting blood glucose levels, a decrease in TEER, and further disruptions in gene expression patterns in the stomach and liver. In contrast, the duodenum was able to restore its food-driven gene expression. These results demonstrate that the adjustment to food intake time in mice is highly sex- and organ-specific. Our chosen TRF regimes were not able to synchronize food-anticipatory responses between the liver and gut. Instead, we observed that organs entrain to food intake at different rates.

molecular biology↗

bioRxiv2023

Re-coding of G protein-coupled receptor signaling enables emergent cellular behavior.

All cells face the challenge of integrating multiple extracellular signals to produce relevant physiological responses. Different combinations of G protein-coupled receptors, when co-expressed, can lead to distinct cellular outputs, yet the molecular basis for this co-operativity is controversial. One such interaction is the reversal, from inhibition to excitation, at the dopamine D2 receptor in the ghrelin receptors presence, relevant for defecation control. Here we demonstrate that this reversal of dopamine D2 activity, to excitatory, occurs through a dominant switch in downstream signaling. This dominant switch, mediated by downstream signaling, enables fidelity in cellular responses not possible under alternative models, and provides an explanation for previously unresolved observations. Importantly, the switch in D2 signaling does not require ghrelin receptor agonism, rather its constitutive activity, thus accounting for the importance of central nervous system-ghrelin receptor in the absence of endogenous ligands. This re-coding has important implications for our understanding of how atypical receptor pharmacology can occur as well as how sequential signaling at individual neurons may be encoded to produce new outputs.

cell biology↗

bioRxiv2023

Stratification of enterochromaffin cells by single-cell expression analysis

Dynamic interactions between gut mucosal cells and the external environment are essential to maintain gut homeostasis. Enterochromaffin (EC) cells transduce both chemical and mechanical signals and produce 5-hydroxytryptamine (5-HT) to mediate disparate physiological responses. However, the molecular and cellular basis for functional diversity of ECs remains to be adequately defined. Here, we integrated single-cell transcriptomics with spatial image analysis to identify fourteen EC clusters that are topographically organized along the gut. Subtypes predicted to be sensitive to the chemical environment and mechanical forces were identified that express distinct transcription factors and hormones. A Piezo2+ population in the distal colon was endowed with a distinctive neuronal signature. Using a combination of genetic, chemogenetic and pharmacological approaches, we demonstrated Piezo2+ ECs are required for normal colon motility. Our study constructs a molecular map for ECs and offers a framework for deconvoluting EC cells with pleiotropic functions.

cell biology↗

bioRxiv2023

Mapping the Organization and Morphology of Calcitonin Gene-Related Peptide (CGRP)-IR Axons in the Whole Mouse Stomach

Nociceptive afferent axons innervate the stomach and send signals to the brain and spinal cord. Peripheral nociceptive afferents can be detected with a variety of markers [e.g., substance P (SP) and calcitonin gene-related peptide (CGRP)]. We recently examined the topographical organization and morphology of SP-immunoreactive (SP-IR) axons in the whole mouse stomach muscular layer. However, the distribution and morphological structure of CGRP-IR axons remain unclear. We used immunohistochemistry labeling and applied a combination of imaging techniques, including confocal and Zeiss Imager M2 microscopy, Neurolucida 360 tracing, and integration of axon tracing data into a 3D stomach scaffold to characterize CGRP-IR axons and terminals in the whole mouse stomach muscular layers. We found that: 1) CGRP-IR axons formed extensive terminal networks in both ventral and dorsal stomachs. 2) CGRP-IR axons densely innervated the blood vessels. 3) CGRP-IR axons ran in parallel with the longitudinal and circular muscles. Some axons ran at angles through the muscular layers. 4) They also formed varicose terminal contacts with individual myenteric ganglion neurons. 5) CGRP-IR occurred in DiI-labeled gastric-projecting neurons in the dorsal root and vagal nodose ganglia, indicating CGRP-IR axons were visceral afferent axons. 6) CGRP-IR axons did not colocalize with tyrosine hydroxylase (TH) or vesicular acetylcholine transporter (VAChT) axons in the stomach, indicating CGRP-IR axons were not visceral efferent axons. 7) CGRP-IR axons were traced and integrated into a 3D stomach scaffold. For the first time, we provided a topographical distribution map of CGRP-IR axon innervation of the whole stomach muscular layers at the cellular/axonal/varicosity scale.

neuroscience↗

bioRxiv2022

Surface-based Characterization of Gastric Anatomy and Motility using Magnetic Resonance Imaging and Neural Ordinary Differential Equation

Gastrointestinal magnetic resonance imaging (MRI) provides rich spatiotemporal data about the volume and movement of the food inside the stomach, but does not directly report on the muscular activity of the stomach itself. Here we describe a novel approach to characterize the motility of the stomach wall that drives the volumetric changes of the gastric content. In this approach, a surface template was used as a deformable model of the stomach wall. A neural ordinary differential equation (ODE) was optimized to model a diffeomorphic flow that ascribed the deformation of the stomach wall to a continuous biomedical process. Driven by this diffeomorphic flow, the surface template of the stomach progressively changes its shape over time or between conditions, while preserving its topology and manifoldness. We tested this approach with MRI data collected from 10 Sprague Dawley rats under a lightly anesthetized condition. Our proposed approach allowed us to characterize gastric anatomy and motility with a surface coordinate system common to every individual. Anatomical and motility features could be characterized for each individual, and then compared and summarized across individuals for group-level analysis. As a result, high-resolution functional maps were generated to reveal the spatial, temporal, and spectral characteristics of muscle activity as well as the coordination of motor events across different gastric regions. The relationship between muscle thickness and gastric motility was also evaluated throughout the entire stomach wall. Such a structure-function relationship was used to delineate two distinctive functional regions of the stomach. These results demonstrate the efficacy of using GI-MRI to measure and model gastric anatomy and function. This approach described herein is expected to enable non-invasive and accurate mapping of gastric motility throughout the entire stomach for both preclinical and clinical studies.

physiology↗

bioRxiv2020

Unacylated ghrelin and AZP531 suppress the 3D growth of breast cancers

Breast cancer is the most common type of cancer in women and notwithstanding important therapeutic advances, it remains the second leading cause of cancer-related death in the US. Despite extensive research relating to the hormone ghrelin, responsible for the stimulation of growth hormone release and appetite, little is known of the effects of its unacylated form, especially in cancer. One major area of research relates to its reported effects to increase insulin sensitivity in diabetics, this being the basis for the development of unacylated ghrelin analog, AZP531 or livoletide, now in clinical trials for the treatment of Prader-Willi Syndrome. The mechanism of action of unacylated ghrelin is largely uncharacterized, in any system, because it does not bind to or activate the cognate ghrelin receptor, GHSR1a. The present study aimed to characterize effects of unacylated ghrelin on breast cancer cells, define its mechanism of action, and explore the therapeutic potential of unacylated ghrelin or analog AZP531. We report potent effects of unacylated ghrelin, at picomolar doses, on the growth of breast cancer cells, dependent on 3D culture and activation of Gi. Suppression of MAPK signaling by unacylated ghrelin leads to cell cycle arrest and apoptosis. AZP531 also suppresses the growth of breast cancer cells in vitro and in xenografts, and may be a novel approach for the safe and effective treatment of breast cancer.

cancer biology↗