Biology subjects

Leben, R.

Publications and source records attributed to Leben, R..

4 recordsLinked to original sources

bioRxiv2024

Two-Photon NAD(P)H-FLIM reveals unperturbed energy metabolism of Ascaris suum larvae, in contrast to host macrophages upon artemisinin derivatives exposure

Soil-transmitted helminths (STH) are widespread, with Ascaris lumbricoides infecting millions globally. Malaria and STH co-infections are common in co-endemic regions. Artemisinin derivatives (ARTs)--artesunate, artemether, and dihydroartemisinin--are standard malaria treatments and are also known to influence the energy metabolism of parasites, tumors, and immune cells. Herein, we explore the potential of ARTs to influence ascariasis either by directly affecting larvae or indirectly by modifying macrophage responses. Ascaris suum third-stage larvae and porcine IL-4 polarised (M2-like) macrophages were exposed to ARTs in vitro, and their metabolism was evaluated using two-photon NAD(P)H-FLIM. Both larvae and M2-like macrophages exhibited a steady-state bioenergetic profile of high oxidative phosphorylation and low anaerobic glycolysis. In A. suum larvae, two metabolically distinct regions were identified, with particularly high DUOX activity in the pharynx compared to the midgut. The metabolic profile of both larval regions were, however, unperturbed by ARTs exposure. In contrast, exposure of M2-like macrophages to ARTs induced a metabolic shift towards high anaerobic glycolysis and reduced metabolic activity, suggesting a possible indirect effect of ARTs on the helminth infection. Overall, two-photon NAD(P)H-FLIM proved to be a powerful tool for studying specific metabolic pathways in Ascaris larvae and host macrophages, offering valuable insights into the metabolic mechanisms of drug action on both parasite and host.

biophysics↗

bioRxiv2024

Anomalous diffusion analysis reveals cooperative locomotion of adult parasitic nematodes in sex-mixed groups.

Parasitic worms are widespread throughout the world and causing agents of chronic infections in humans and animals. The majority of these pathogens parasitize the gut of the infected hosts, however very little is known about the locomotion of the worms dwelling the gut. We studied the movement of Heligmosomoides bakeri (previously Heligmosomoides polygyrus), a natural infection of mice and usually used as animal model to study the roundworm infections. We investigated the locomotion of H. bakeri in simplified environments mimicking key physical features of the intestinal lumen, i.e. various medium viscosities, and a periodical intestinal villi topography. The non-periodical nematode motion in these settings could be described by anomalous diffusion theory. Fascinatingly, an oriented, super-diffusive locomotion of nematodes in sex-mixed groups were detected, in the sense of a cooperative, but not collective (swarm-like) migration stimulated by mating and reproduction, while individual nematodes moved randomly, following a diffusive motion regime. High mucus-like medium viscosity and villi topography, representing physical constraints of nematode locomotion, slowed down but did not prevent this cooperative migration. Additionally, the mean displacement rate of nematodes in sex-mixed groups of 6{middle dot}10-4 mm/s in viscous mucus-like medium are in good agreement with estimates of nematode migration velocities between 10-4 to 10-3 mm/s in the gut. Thus, our data indicate the intestinal nematodes motion to be non-periodic and random but triggered to be oriented by kin of the different sex.

biophysics↗

bioRxiv2023

In vivo optimized three-photon imaging of intact mouse tibia links plasma cell motility to functional states in the bone marrow.

Intravital multi-photon imaging of the bone marrow is crucial to the study of cellular dynamics, communication with the microenvironment and functions, however, imaging of deep tissue areas is challenging and minimally invasive methods for deep-marrow imaging in intact long bones are needed. We developed a high pulse energy 1650 nm laser prototype, which permits to surpass >100 {micro}m thick cortical bone and to perform three-photon microscopy (3PM) in more than 400 {micro}m depth in the marrow cavity of intact mouse tibia in vivo. Its unique 3 and 4 MHz laser repetition rates allowed us to analyze motility patterns of rare cells over large fields of view deep within the unperturbed marrow. In this way, we found a bi-modal migratory behavior of marrow plasma cells. Besides, the analysis of third harmonics generation (THG) in the tibia identified this signal to be a label-free indicator of the abundance of cellular organelles, in particular the endoplasmic reticulum, reflecting protein biosynthesis capacity. We found that only one third of the plasma cells in the tibia marrow of adult mice have a strong THG signal and, thus, a high protein synthesis capacity, while the other two thirds of plasma cells display a low THG signal. Finally, we identified an inverse link between migratory behavior and THG signal strength in marrow plasma cells. As in these cells, the protein biosynthesis capacity indicated by a strong THG signal is mainly associated with antibody secretion, we could relate motility to functional states of plasma cells in vivo. Our 3PM method retains the ability to connect cellular dynamics to protein biosynthesis capacity in various marrow cell types beyond plasma cells, as THG is a ubiquitous signal, opening new perspectives on understanding how tissue microenvironment impacts on cellular functions in the bone marrow.

biophysics↗

bioRxiv2019

Intravital quantification of absolute cytoplasmic B cell calcium reveals dynamic signaling across B cell differentiation stages

Development, function and maintenance of lymphocytes largely depend upon the cellular mobilization and storage of Ca2+ ions. In B lymphocytes, the absolute amount of calcium mobilized and retained after cell signaling remains unknown, athough it is a crucial part of their selection within germinal centers and differentiation into plasma cells. Here, we introduce the novel reporter mouse strain YellowCaB that expresses the genetically encoded calcium indicator TN-XXL in CD19+ lymphocytes. The construct consists of the electrondonor fluorophore eCFP and the acceptor citrine, linked by a calcium sensitive domain. Its conformation and therefore donor quenching is directly linked to cytosolic calcium concentrations. By combining intravital two-photon fluorescence lifetime microscopy with our numerical approach for phasor-based analysis, we are able to extract absolute cytoplasmic calcium concentrations in activated B cells for the first time in vivo. We show that calcium concentrations in B cells are highly dynamic and fluctuations persist in extrafollicular B cells with functional relevance.

immunology↗