Biology subjects

Worthmann, A.

Publications and source records attributed to Worthmann, A..

7 recordsLinked to original sources

bioRxiv2026

CD73-derived adenosine at the blood-brain barrier confers protection in a mouse model of ischemic stroke

Ischemic stroke remains a leading cause of death and disability, and current reperfusion therapies do not address the secondary neuroinflammatory response following blood-brain barrier (BBB) disruption. Purinergic signaling critically regulates this process: extracellular ATP promotes inflammation, whereas its enzymatic conversion into adenosine exerts tissue-protective effects. Notably, the ectonucleotidase CD73 (NT5E), which catalyzes AMP-to-adenosine conversion, is highly expressed by human but not murine brain endothelial cells (BECs). Here, we investigated the role of endothelial CD73 in ischemic stroke using an AAV vector engineered for selective transduction of murine BECs to induce BBB-specific CD73 expression. Endothelial CD73 enhanced extracellular ATP degradation toward adenosine generation and established a purine metabolism profile resembling that of human BECs. In the transient middle cerebral artery occlusion (tMCAO) mouse model, BBB-targeted CD73 expression reduced infarct volume by 40% and prevented early mortality within 48 h after reperfusion. Transcriptomic and flow cytometric analyses revealed altered leukocyte responses, including increased recruitment of monocytes/macrophages whose gene expression signatures were consistent with inflammation-resolving programs. These findings identify endothelial CD73 as an important regulator of post-ischemic neuroinflammation and highlight species-specific differences in BBB purine metabolism with implications for translational stroke research.

neuroscience↗

bioRxiv2025

Sympathetic signaling directs macrophage efferocytosis in thermogenic adipose tissue

Brown adipose tissue (BAT) undergoes significant remodeling upon thermogenic activation. During this process, brown adipocytes and immune cells, such as macrophages, contribute to thermogenesis and energy expenditure. Among the various functions exerted by macrophages, the clearance of dying cells, known as efferocytosis, is a key regulator of tissue remodeling across multiple organs in both physiological and pathological contexts. However, whether macrophages contribute to BAT remodeling and thermogenic adaptation through efferocytosis, and what drives efferocytosis in BAT, remain unknown. Here, we identify norepinephrine (NE), which is highly released in BAT upon cold challenge, as a tissue-specific trigger of macrophage efferocytosis. Transcriptomic and lipidomic analyses of BAT after cold exposure revealed a population of lipid-handling macrophages enriched in efferocytosis-related transcripts. Consistently, cold exposure enhanced the efferocytic capacity of BAT macrophages. These effects were recapitulated by stimulation of macrophages with NE and were dependent on {beta}2-adrenergic signaling and the efferocytic receptors AXL and MERTK. Mice lacking Axl and Mertk in macrophages exhibited impaired lipolysis, reduced thermogenic gene expression, and increased adipose tissue inflammation. Together, our findings identify a so far neglected role for NE in adipose tissue, linking sympathetic activation to macrophage efferocytosis and thereby promoting tissue remodeling and metabolic adaptation. Uncovering the role of NE in one of the core functions of macrophages, efferocytosis, not only expands our understanding of the multifaceted effects of NE on the immune system but also highlights therapeutic potential for targeting impaired efferocytosis in metabolic disorders. One sentence summaryNorepinephrine is a novel trigger of macrophage efferocytosis in brown adipose tissue, linking sympathetic signaling to metabolic adaptation and macrophage tissue remodeling responses through {beta}2-adrenergic and Axl/Mertk pathways.

immunology↗

bioRxiv2025

Infrared Laser Sampling of Low Volumes Reveals Marker Lipids in Palatine Tonsil Carcinoma via Shotgun Lipidomics

Complete surgical resection is essential for oropharyngeal squamous cell carcinoma (OPSCC) therapy, underscoring the need for improved intraoperative margin assessment. To advance in-vivo diagnostics of OPSCC, Nanosecond infrared laser (NIRL) tissue sampling combined with shotgun lipidomic analysis reveals lipidome differences between OPSCC tissue and adjacent healthy tissue. Ablations were performed on tonsil squamous cell carcinoma on n=28 samples from 11 patients with an established chamber setup and a subset of n=6 samples from three patients with a custom-made handheld applicator. Welchs t-test results (p=0.05, two-fold change) revealed a similar OPSCC lipid profile in 7 of 11 patients. Potential tumor lipid markers were identified as consistently significantly increased, despite biological heterogeneity of the samples, underscoring their potential diagnostic value. Tissue ablation with a custom-made handheld applicator coupled to a laser fiber was successful and the lipidomic analysis was consistent to the chamber setup. Although our setup is currently limited by an ablation time exceeding one minute, this study demonstrates the potential of the handheld applicator for future applications such as endoscopy or intraoperative diagnostics.

cancer biology↗

bioRxiv2025

Shiny-Calorie: A context-aware application for indirect calorimetry data analysis and visualization using R

Indirect calorimetry is a cornerstone technique for metabolic phenotyping of animal models in preclinical research, with well-established experimental protocols and platforms. However, a flexible, extensible, and user-friendly software suite that enables standardized integration of data and metadata from diverse metabolic phenotyping platforms--followed by unified statistical analysis and visualization--remains absent. We present Shiny-Calorie, an open-source interactive web application for transparent data and metadata integration, comprehensive statistical data analysis, and visualization of indirect calorimetry datasets. Shiny-Calorie is compatible with data formats from widely used commercial metabolic phenotyping platforms, such as TSE and Sable Systems, and includes functionality for exporting processed data in these formats. Built using GNU R and a Shiny-based reactive interface, Shiny-Calorie enables intuitive exploration of complex, multi-modal longitudinal datasets comprising categorical, continuous, ordinal, and count variables. The platform incorporates state-of-the-art statistical methods for robust hypothesis testing, thereby facilitating biologically meaningful interpretation of energy metabolism phenotypes, including resting metabolic rate and energy expenditure. Overall, Shiny-Calorie streamlines routine analysis workflows and enhances reproducibility and transparency in metabolic phenotyping studies.

bioinformatics↗

bioRxiv2025

Single-nucleus mRNA-sequencing reveals dynamics of lipogenic and thermogenic adipocyte populations in murine brown adipose tissue in response to cold exposure

Brown adipose tissue (BAT) comprises a heterogeneous population of adipocytes and non-adipocyte cell types. To characterize these cellular subpopulations and their adaptation to cold, we performed single-nucleus mRNA-sequencing (snRNA-seq) on interscapular BAT from mice maintained at room temperature or exposed to acute (24h) or chronic (10 days) cold (6{degrees}C). To investigate the role of the de novo lipogenesis (DNL)-regulating transcription factor carbohydrate response element-binding protein (ChREBP), we analyzed control and brown adipocyte-specific ChREBP knockout mice. We identified different cell populations, including seven brown adipocyte subtypes with distinct metabolic profiles. One of them highly expressed ChREBP and DNL enzymes. Notably, these lipogenic adipocytes were highly sensitive to acute cold exposure, showing a marked depletion in BAT of control mice that was compensated by other brown adipocyte subtypes maintaining DNL. Chronic cold exposure resulted in an expansion of basal brown adipocytes and adipocytes putatively derived from stromal and endothelial precursors. In ChREBP-deficient mice, lipogenic adipocytes were almost absent under all conditions, identifying the transcription factor as a key determinant of this adipocyte subtype. Pathway and cell-cell interaction analyses implicated a Wnt-ChREBP axis in the maintenance of lipogenic adipocytes, with Wnt ligands from stromal and muscle cells providing instructive cues. Our findings provide a comprehensive atlas of BAT cellular heterogeneity and reveal a critical role for ChREBP in lipogenic adipocyte identity, with implications for BAT plasticity and metabolic function.

cell biology↗

bioRxiv2024

Control of cholesterol-induced adipocyte inflammation by the Nfe2l1-Atf3 pathway

While adipocytes are critical pillars of energy metabolism, their dysfunction is linked to adipose tissue (AT) inflammation, insulin resistance, and ectopic lipotoxicity in cardiometabolic diseases. However, the mechanisms causing adipocyte inflammation and insulin resistance remain unclear. Here, we show that excess cholesterol induces adipocyte dysfunction, which is suppressed by the transcription factor Nfe2l1 (nuclear factor erythroid derived-2, like-1). Nfe2l1 is required to sustain proteasome function in adipocytes and proteotoxic stress induces adipocyte inflammation via the activation of Atf3. In humans, the Nfe2l1-proteasome pathway is inversely correlated to body mass index (BMI) in an adipose-depot specific manner. In mice, loss of adipocyte Nfe2l1 caused AT inflammation with a pronounced infiltration of macrophages and T cells. Mice lacking adipocyte Nfe2l1 displayed severe adipocyte dysfunction during diet-induced obesity (DIO), characterized by lower adipokine levels, steatosis, glucose intolerance and insulin resistance. Nfe2l1{Delta}AT mice on an Apoe-deficient (Apoe-/-) background fed a cholesterol-rich Western Diet (WD), developed a lipoatrophy-like syndrome, dyslipidemia, and enhanced atherosclerosis. Our results reveal an important role for proteasome-mediated proteostasis in adipocytes and indicate that Nfe2l1 is linked to metabolic health in humans and preclinical mouse models. Promoting proteostasis in adipocytes may thus alleviate inflammation in obesity, potentially averting adverse cardiometabolic outcomes. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=191 SRC="FIGDIR/small/604614v1_ufig1.gif" ALT="Figure 1"> View larger version (61K): org.highwire.dtl.DTLVardef@145e32borg.highwire.dtl.DTLVardef@1454df1org.highwire.dtl.DTLVardef@1002383org.highwire.dtl.DTLVardef@1b7319_HPS_FORMAT_FIGEXP M_FIG C_FIG

physiology↗

bioRxiv2021

Susceptibility to diet induced obesity at thermoneutral conditions is independent of UCP1

ObjectiveActivation of uncoupling protein 1 (UCP1) in brown adipose tissue (BAT) upon cold stimulation leads to substantial increase in energy expenditure to defend body temperature. Increases in energy expenditure after a high caloric food intake, termed diet-induced thermogenesis, are also attributed to BAT. These properties render BAT a potential target to combat diet-induced obesity. However, studies investigating the role of UCP1 to protect against diet-induced obesity are controversial and rely on the phenotyping of a single constitutive UCP1-knockout model. To address this issue, we generated a novel UCP1-knockout model by Cre-mediated deletion of Exon 2 in the UCP1 gene. We studied the effect of constitutive UCP1 knockout on metabolism and the development of diet-induced obesity. MethodsUCP1 knockout and wildtype mice were housed at 30{degrees}C and fed a control diet for 4-weeks followed by 8-weeks of high-fat diet. Body weight and food intake were monitored continuously over the course of the study and indirect calorimetry was used to determine energy expenditure during both feeding periods. ResultsBased on Western blot analysis, thermal imaging and noradrenaline test, we confirmed the lack of functional UCP1 in knockout mice. However, body weight gain, food intake and energy expenditure were not affected by deletion of UCP1 gene function during both feeding periods. ConclusionConclusively, we show that UCP1 does not protect against diet-induced obesity at thermoneutrality. Further we introduce a novel UCP1-KO mouse enabling the generation of conditional UCP1-knockout mice to scrutinize the contribution of UCP1 to energy metabolism in different cell types or life stages.

physiology↗