Laurin, J. | Search bioRxiv

bioRxiv2022

Bumetanide increases microglia-interneuron contact following traumatic brain injury

ObjectiveThe Na-K-Cl cotransporter (NKCC1) inhibitor bumetanide has prominent positive effects on the pathophysiology of many neurological disorders. Here we studied whether bumetanide could influence post-traumatic cognitive decline and inflammatory processes by regulating astrocyte and microglia activation. MethodControlled cortical impacted (CCI) animals were treated with bumetanide during the first post-CCI week. Immunochemistry, flow cytometry, immunoassay, and in vivo imaging were used to study astrocytic and microglial morphology and phenotype as well as adult neurogenesis. Telemetric electroencephalograms and cognitive behavioral test were performed at one-month post CCI. ResultsBumetanide prevented CCI-induced decrease in hippocampal neurogenesis and parvalbumin positive interneuron loss. Deletion of NKCC1 in astrocytes neither rescued interneurons nor promote neurogenesis. Interestingly, bumetanide had a strong effect on microglial activation by inducing polarization towards the M1-like phenotype 3 days post-CCI and the M2-like phenotype 7 days post-CCI. Bumetanide increased microglial Brain-derived neurotrophic factor (BDNF) expression and interaction with parvalbumin interneurons. The early treatment with bumetanide resulted in improvements in working and episodic memory, one-month post-CCI, as well as the normalization of theta band oscillations. InterpretationHere, we disclose a novel mechanism for the neuroprotective action of bumetanide mediated by an acceleration of microglial activation dynamics that leads to an increase of parvalbumin interneuron survival following CCI, possibly resulting from increased microglial BDNF expression and contact with interneurons. Salvage of interneurons may normalize ambient gamma-aminobutyric acid (GABA) resulting in the preservation of adult neurogenesis processes as well as contributing to bumetanide-mediated improvement of cognitive performance.

neuroscience↗

bioRxiv2018

Visualizing structure-mediated interactions in supercoiled DNA molecules

We directly visualize the topology-mediated interactions between an unwinding site on a supercoiled DNA plasmid and a specific probe molecule designed to bind to this site, as a function of DNA supercoiling and temperature. The visualization relies on containing the DNA molecules within an enclosed array of glass nanopits using the Convex Lens-induced Confinement (CLiC) imaging method. This method traps molecules within the focal plane while excluding signal from out-of-focus probes. Simultaneously, the molecules can freely diffuse within the nanopits, allowing for accurate measurements of exchange rates, unlike other methods which could introduce an artifactual bias in measurements of binding kinetics. We demonstrate that the plasmids structure influences the binding of the fluorescent probes to the unwinding site through the presence, or lack, of other secondary structures. With this method, we observe an increase in the binding rate of the fluorescent probe to the unwinding site with increasing temperature and negative supercoiling. This increase in binding is consistent with the results of our numerical simulations of the probability of site-unwinding. The temperature dependence of the binding rate has allowed us to distinguish the effects of competing higher order DNA structures, such as Z-DNA, in modulating local site-unwinding, and therefore binding.

biophysics↗