Biology subjects

Pfabe, J.

Publications and source records attributed to Pfabe, J..

7 recordsLinked to original sources

bioRxiv2026

PFKFB3 inhibition restores β-cell responsiveness to acetylcholine in a 3xTg-AD pancreatic tissue-slice mode

The glycolytic regulator PFKFB3 supports dysfunctional {beta}-cell states, but its role in pancreatic Ca2+ signaling remains unclear. We examined responses to PFKFB3 inhibitors (AZ67, AZ26) in pancreatic tissue slices from aged 3xTg-AD mice, a model of Alzheimer's disease that develops impaired glucose tolerance and diabetes as comorbidity. Compared to wild-type controls, {beta}-cells showed weaker glucose-stimulated and acetylcholine-potentiated Ca2+ activity, accompanied by increased nuclear PFKFB3 positivity in insulin-defined islet-cell populations, used here as a PFKFB3-associated stress-state marker. During glucose and acetylcholine stimulation, AZ67 increased {beta}-cell Ca2+ event frequency while maintaining short events. In neighboring acinar cells, PFKFB3 inhibitor exposure was followed by renewed oscillations after acetylcholine-evoked activity had waned. {beta}-cell recruitment was preserved during adrenergic inhibition, and enhanced activity persisted after inhibitor withdrawal, although these recordings were exploratory and residual tissue drug exposure could not be excluded. An effect that survives both drug removal and adrenergic opposition identifies a Ca2+ signaling phenotype in 3xTg-AD {beta}-cells that is acutely inducible yet not transient, and establishes PFKFB3 as a regulator of muscarinic responsiveness in the stressed {beta}-cell.

physiology↗

bioRxiv2026

Spatial and functional mapping of the human pancreas reveals endocrine and exocrine cell states in health and metabolic disease

The human pancreas contains diverse endocrine and exocrine cell populations whose spatial organization is essential for tissue physiology. While single-cell and spatial transcriptomics revealed molecular heterogeneity across pancreatic cell types, linking these states to physiological activity in situ has remained challenging. Here, we combined single-nucleus RNA sequencing, spatial transcriptomics, and functional calcium imaging across pancreatic samples in health and metabolic disease. We identified heterogeneous endocrine and exocrine cell states associated with obesity and diabetes, including inflammatory remodeling of acinar and ductal populations. To directly couple tissue physiology with molecular state, we developed Slice-seq, which integrates calcium imaging with spatial transcriptomics in acute pancreatic slices. Slice-seq linked local endocrine composition and transcriptional programs with {beta} cell activity and identified extra-islet {beta} cells with reduced glucose responsiveness and mitochondrial oxidative metabolism. Together, our study provides a framework for linking pancreatic cell states to tissue organization and physiological activity in health and disease.

genomics↗

bioRxiv2025

Presenilin-1 controls glucose metabolism and identity of pancreatic beta cells

AbstractPresenilin 1 is an endoplasmic reticulum protein, most known for its role in pathogenesis of familial Alzheimers Disease (AD). Presenilin 1 has been attributed roles in intracellular calcium homeostasis in the brain, as well as in the pancreatic beta cells, where it has been shown to be fundamental for glucose-induced insulin secretion. Functional similarity of presenilin 1 in regulation of intracellular calcium homeostasis in the brain and pancreas prompted us to investigate a prevalent assumption that associates AD and diabetes mellitus. By examining pancreatic islets from AD model mice, we have found deficits in initial phase of glucose-induced calcium signaling and insulin secretion. Furthermore, these transgenic mice showed a tendency towards reduced expression of mature beta cell markers, which was even more pronounced in islets and beta cell lines with a transient knock down of presenilin 1. We demonstrate here that presenilin 1 controls beta cell glycolysis by regulating sub-cellular calcium homeostasis and, in doing so, contributes to preservation of beta cell identity.

cell biology↗

bioRxiv2025

Calorie Restriction modulates beta cell IP3R activity to regulate Ca2+ homeostasis and cell network connectivity

Calorie restriction (CR) promotes beta cell longevity by regulating cell identity, organelle and protein homeostasis, and metabolism pathways. CR beta cells have higher cAMP levels and mitochondria with an elevated potential to generate ATP. However, CR beta cells have reduced insulin secretion due to increased peripheral insulin sensitivity. How CR impacts beta cell Ca2+ homeostasis to regulate beta cell insulin release remains unknown. We investigated this question using acute pancreatic tissue slices prepared from ad-libitum (AL) or CR mice loaded with a low affinity Ca2+ indicator and recorded cytosolic Ca2+ gradients with fast confocal imaging. We exposed these slices to increasing glucose concentrations and applied our semi-automatic analysis pipeline to detect thousands of individual beta cells followed by identification of individual Ca2+ spiking events. We observed that CR beta cells have fast short-amplitude Ca2+ oscillations that correlate with largely disconnected beta cell networks across the islet. Using acetylcholine stimulation, we found that faster IP3R-driven Ca2+ oscillations linked to higher cytosolic cAMP levels protect beta cells against acute depletion of ER Ca2+ stress. Therefore, this study provides new mechanistic insight into adaptation of beta cell and of beta cell networks to CR interventions. Article highlightsO_LIBeta cells from calorie restricted (CR) mice have decreased insulin release, however the mechanisms underlying this adaptive response remain unknown. C_LIO_LICR beta cells have elevated basal cytosolic cAMP ([cAMP]cyt) compared to beta cells in control ad libitum fed (AL) mice, and they operate with faster and shorter cytosolic Ca2+ oscillations. C_LIO_LIWhile AL beta cells form interconnected activity networks, CR beta cells are largely disconnected and fire more independently of each other. C_LIO_LIIslets of CR mice can sustain prolonged activity during ER stressing conditions due to elevated IP3R activity and improved Ca2+ homeostasis. C_LI Why did we undertake this study?We have previously shown that calorie restriction (CR) promotes beta cell longevity by enhancing beta cell identity and organelle homeostasis mechanisms. This long-lived phenotype correlated with the onset of enhanced peripheral insulin sensitivity and reduced beta cell insulin release in vivo despite higher cAMP levels and increased potential for mitochondrial ATP generation. However, the mechanisms underlying the reduced cell insulin release phenotype of CR beta cells remains unknown. Therefore, we investigated the underlying Ca2+ homeostasis mechanisms regulating insulin release in AL and CR beta cells. What is the specific question(s) we wanted to answer?We were interested in determining what are the cell Ca2+ activity patterns during basal and glucose-stimulated conditions in AL and CR beta cells. In addition, we also investigated how CR beta cells respond to epinephrine inhibition and supra-stimulatory concentrations of acetylcholine (ACh), which drive acute beta cell stress by disrupting normal cAMP and ER Ca2+ signaling, respectively. Finally, we investigate whether CR beta cells formed more interconnected beta cell networks driven by changes in Ca2+ activity patterns. What did we find?We found that CR beta cells are more active with significantly higher rates of Ca2+ oscillation at basal and high glucose concentrations. In fact, CR beta cells have shorter inter-Ca2+ event intervals that are more resistant to depletion of cAMP by epinephrine application. In contrast, stimulation of IP3R activity (to force depletion of ER Ca2+ stores) by supraphysiological ACh concentrations revealed that CR beta cells were able to sustain a prolonged Ca2+ activity versus AL beta cells. Surprisingly, this enhanced beta cell activity profile reduced beta cell activity network connectivity. What are the implications of our findings?Our work demonstrates that CR beta cells have higher baseline and glucose-stimulated Ca2+ activity due to higher cAMP levels. These cells also have dominant IP3R activity that grants improved ER Ca2+ homeostasis and significantly reduces beta cell network connectivity to tone down insulin secretion. These studies provide a mechanistic understanding of how beta cells adapt to CR and to CR-associated enhanced insulin sensitivity.

cell biology↗

bioRxiv2025

Effects of Arginine Vasopressin on Islet Cells in Pancreatic Tissue Slices: Glucose-Dependent Modulation of IP3 Receptor-Specific Responses

Arginine vasopressin (AVP) is well known for regulating fluid volume, osmotic balance, and vascular tone. Its role in the regulation of pancreatic and {beta} cell function has been reported, yet its effects are not fully understood, particularly regarding its interaction with plasma glucose levels. The osmotic and volume challenges posed by hyper- and hypoglycaemia in diabetes can be a significant complication of effective hormonal regulation of metabolism. In this study, we primarily investigated the effects of AVP and synthetic peptide receptor agonists and antagonists on and {beta} cells in pancreatic tissue slices using live confocal Ca2+ imaging. Our findings demonstrate that AVP exerts glucose-dependent effects on both cell types. At low glucose concentrations, AVP, in combination with physiologically or pharmacologically increased cAMP levels, selectively activated cells without significantly affecting {beta} cells. In contrast, at higher glucose concentrations and pharmacologically elevated cAMP levels, physiological levels of AVP enhanced {beta} cell activity, leading to increased Ca2+ oscillations and insulin release. In both cell types, AVP displayed a bell-shaped concentration dependence, with lower AVP concentrations stimulating hormone release and higher concentrations leading to diminished responses, consistent with inositol trisphosphate receptor (IP3R) activation and inactivation properties. Furthermore, our results indicate that AVP acts primarily through V1b receptors in {beta} cells, with no involvement of V1a, V2 or oxytocin receptors. These findings provide new insights into the modulation of glucose-dependent release of pancreatic hormones by AVP in the context of changed blood osmolality due to hyper- or hypoglycemia in diabetes. Importantly, our results emphasize the potential of targeting AVP signaling pathways as a therapeutic approach in diabetes research, aiming to improve hormone regulation and nutrient homeostasis. HighlightsO_LIHighly spatio-temporally resolved imaging of islet Ca2+ oscillations on pancreatic tissue slices provides an in situ-like model for physiological and pharmacological approaches. C_LIO_LIPhysiological glucose stimulation triggers non-linear {beta} cell collective responses that must be taken into account when interpreting single concentration pharmacological experiments. C_LIO_LIIn a high cAMP context, AVP acts through V1b receptors on islet and {beta} cells, exhibiting a bell-shaped dependence driven by the activation-inactivation properties of IP receptors. C_LIO_LIAVP modulates glucose-dependent effects on and {beta} cells in a physiological concentration range, in the presence of altered blood osmolality or volume due to hyperglycemia, or to the direct effects of hypoglycemia in diabetes. C_LI

physiology↗

bioRxiv2024

Cytosolic S100A8/A9 promotes Ca2+ supply at LFA-1 adhesion clusters during neutrophil recruitment

S100A8/A9 is an endogenous alarmin secreted by myeloid cells during many acute and chronic inflammatory disorders. Despite increasing evidence of the proinflammatory effects of extracellular S100A8/A9, little is known about its intracellular function. Here, we show that cytosolic S100A8/A9 is indispensable for neutrophil post-arrest modifications during outside-in signaling under flow conditions in vitro and neutrophil recruitment in vivo, independent of its extracellular functions. Mechanistically, genetic deletion of S100A9 in mice (Mrp14-/-, functional S100a8/a9-/-) caused dysregulated Ca2+ signatures in activated neutrophils resulting in reduced Ca2+ availability at the formed LFA-1/F-actin clusters with defective {beta}2 integrin outside-in signaling during post-arrest modifications. Consequently, we observed impaired cytoskeletal rearrangement, cell polarization and spreading, as well as cell protrusion formation in Mrp14-/- compared to WT neutrophils, making Mrp14-/- cells more susceptible to detach under flow, thereby preventing efficient neutrophil recruitment and extravasation into inflamed tissue. One-sentence summaryintracellular S100A8/A9 is indispensable for firm leukocyte adhesion under flow

physiology↗

bioRxiv2021

Intracellular Ca2+ channels initiate physiological glucose signaling in beta cells examined in situ

The release of peptide hormones is predominantly regulated by a transient increase in cytosolic Ca2+ concentration ([Ca2+]c). To trigger exocytosis, Ca2+ ions enter the cytosol from intracellular Ca2+ stores or from the extracellular space. The molecular events of late stages of exocytosis, and their dependence on [Ca2+]c, were extensively described in isolated single cells from various endocrine glands. Notably less work has been done on endocrine cells in situ to address the heterogeneity of [Ca2+]c events contributing to a collective functional response of a gland. For this beta cell collectives in a pancreatic islet are particularly well suited as they are the smallest, experimentally manageable functional unit, where [Ca2+]c dynamics can be simultaneously assessed on both cellular and collective level. Here we measured [Ca2+]c transients across all relevant timescales, from a sub-second to a minute time range, using high-resolution imaging with low-affinity Ca2+ sensor. We quantified the recordings with a novel computational framework for semi-automatic image segmentation and [Ca2+]c event identification. Our results demonstrate that under physiological conditions the duration of [Ca2+]c events is variable, and segregated into 3 reproducible modes, sub-second, second and tens of seconds time range, and are a result of a progressive temporal summation of the shortest events. Using pharmacological tools we show that activation of intracellular Ca2+ receptors is both sufficient and necessary for glucose-dependent [Ca2+]c oscillations in beta cell collectives, and that a subset of [Ca2+]c events could be triggered even in the absence of Ca2+ influx across the plasma membrane. In aggregate, our experimental and analytical platform was able to readily address the involvement of intracellular Ca2+ receptors in shaping the heterogeneity of [Ca2+]c responses in collectives of endocrine cells in situ.

physiology↗