Biology subjects

Bruns, O. T.

Publications and source records attributed to Bruns, O. T..

6 recordsLinked to original sources

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↗

bioRxiv2024

Macroscopic label-free biomedical imaging withshortwave infrared Raman scattering

Shortwave infrared (SWIR) imaging provides enhanced tissue penetration and reduced autofluorescence in clinical and pre-clinical applications. However, existing applications often lack the ability to probe chemical composition and molecular specificity without the need for contrast agents. Here, we present a SWIR imaging approach that visualizes spontaneous Raman scattering with remarkable chemical contrast deep within tissue across large fields of view. Our results demonstrate that Raman scattering overcomes autofluorescence as the predominant source of endogenous tissue background at illumination wavelengths as short as 892 nm. We highlight the versatility of SWIR Raman imaging through in vivo monitoring of whole-body tissue composition dynamics and non-invasive detection of fatty liver disease in mice, and identification of calcification and lipids in unfixed human atherosclerotic plaques. Moreover, our approach facilitates the visualization of nerves embedded in fatty tissue, a major advancement for surgical applications. With a simple wide-field setup orthogonal to fluorescence, SWIR Raman imaging holds promise for rapid adoption by clinicians and biologists. This technique opens new possibilities for contrast agent-free visualization of pathophysiology in whole animals and intraoperative imaging in humans. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=89 SRC="FIGDIR/small/597863v1_ufig1.gif" ALT="Figure 1"> View larger version (20K): org.highwire.dtl.DTLVardef@394289org.highwire.dtl.DTLVardef@13f3289org.highwire.dtl.DTLVardef@ee6f7org.highwire.dtl.DTLVardef@5d7399_HPS_FORMAT_FIGEXP M_FIG C_FIG

bioengineering↗

bioRxiv2023

Shortwave infrared (SWIR) fluorescence imaging of peripheral organs in awake and freely moving mice

Extracting biological information from awake and unrestrained mice is imperative to in vivo basic and pre-clinical research. Accordingly, imaging methods which preclude invasiveness, anesthesia, and/or physical restraint enable more physiologically relevant biological data extraction by eliminating these extrinsic confounders. In this article we discuss the recent development of shortwave infrared (SWIR) fluorescent imaging to visualize peripheral organs in freely-behaving mice, as well as propose potential applications of this imaging modality in the neurosciences.

bioengineering↗

bioRxiv2022

Development of a shortwave infrared (SWIR) sinuscope for the detection of cerebrospinal fluid (CSF) leaks

SignificanceCSF rhinorrhea (leakage of brain fluid from the nose) can be difficult to identify and currently requires invasive procedures such as intrathecal fluorescein which requires a lumbar drain placement. Fluorescein is also known to have rare but significant side effects including seizures and death. As the number of endonasal skull base cases increase, the number of CSF leaks have also increased for which an alternative diagnostic method would be highly advantageous to patients. AimTo develop an instrument to identify CSF leaks based on water absorption in the SWIR without the need of intrathecal contrast agents. This device needed to be adapted to the anatomy of the human nasal cavity while maintaining low weight and ergonomic characteristics of current surgical instruments. ApproachAbsorption spectra of CSF and artificial CSF were obtained to characterize the absorption peaks that could be targeted with SWIR light. Different illumination systems were tested and refined prior to adapting them into a portable endoscope for testing in 3D printed models and cadavers for feasibility. ResultsWe identified CSF to have an identical absorption profile as water. In our testing, a narrow band laser source at 1480nm proved superior to using a broad 1450 nm LED. Using a SWIR enabling endoscope set up, we tested the ability to detect artificial CSF in a cadaver model. ConclusionsAn endoscopic system based on SWIR narrow band imaging can provide an alternative in the future to invasive methods of CSF leak detection.

bioengineering↗

bioRxiv2022

Shortwave-Infrared Line-Scan Confocal Microscope for Deep Tissue Imaging in Intact Organs

Imaging at wavelengths beyond the visible spectrum enables imaging depths of hundreds of microns in intact tissue, making this attractive for volumetric imaging applications. The development of fluorophores with photoemission beyond 1000nm provide the opportunity to develop novel fluorescence microscopes sensitive to those wavelengths. Here, we present a shortwave-infrared line-scan confocal microscope that is capable of deep imaging of biological specimens, as demonstrated by visualization of labelled glomeruli in a fixed uncleared kidney at depths beyond 400 m. We also show imaging of brain vasculature labelled with the near-infrared organic dye indocyanine green, the shortwave-infrared organic dye Chrom7, and rare earth-doped nanoparticles, thus encompassing the entire spectrum detectable by a typical shortwave-infrared sensitive InGaAs detector.

bioengineering↗

bioRxiv2017

Shortwave Infrared Fluorescence Imaging with the Clinically Approved Near-Infrared Dye Indocyanine Green

Fluorescence imaging is a method of real-time molecular tracking in vivo that has enabled many clinical technologies. Imaging in the shortwave infrared region (SWIR, 1-2 m) promises higher contrast, sensitivity, and penetration depths compared to conventional visible and near-infrared (NIR) fluorescence imaging. However, adoption of SWIR imaging in clinical settings has been limited, due in part to the absence of FDA-approved fluorophores with peak emission in the SWIR. Here, we show that commercially available NIR dyes, including the FDA-approved contrast agent indocyanine green (ICG), exhibit optical properties suitable for in vivo SWIR fluorescence imaging. Despite the fact that their emission reaches a maximum in the NIR, these dyes can be imaged non-invasively in vivo in the SWIR spectral region, even beyond 1500 nm. We demonstrate real-time fluorescence angiography at wavelengths beyond 1300 nm using ICG at clinically relevant doses. Furthermore, we show tumortargeted SWIR imaging with trastuzumab labeled with IRDye 800CW, a NIR dye currently being tested in multiple phase II clinical trials. Our findings suggest that high-contrast SWIR fluorescence imaging can be implemented alongside existing imaging modalities by switching the detection of conventional NIR fluorescence systems from silicon-based NIR cameras to emerging indium gallium arsenide (InGaAs) SWIR cameras. Using ICG in particular opens the possibility of translating SWIR fluorescence imaging to human clinical applications.

bioengineering↗