Albillos, A. | Search bioRxiv

bioRxiv2020

Full activation of an α7-α3β4 nicotinic receptor complex decreases desensitization receptor in human chromaffin cells

7 nicotinic receptors have been involved in numerous pathologies. A hallmark of these receptors is their extremely fast desensitization, a process not fully understood yet. Here we show that human native 7 and 3{beta}4 nicotinic receptors physically interact in human chromaffin cells of adrenal glands. The full activation of this 7-3{beta}4 receptor complex avoids subtypes receptor desensitization, leading to gradual increase of currents with successive acetylcholine pulses. Instead, full and partial activation with choline of 7 and 3{beta}4 subtypes, respectively, of this linked receptor leads to 7 receptor desensitization. Therefore choline, a product of the acetylcholine hydrolysis, acts as a brake by limiting the increase of currents by acetylcholine. Very importantly, the efficiency of the 7-3{beta}4 interaction diminishes in subjets older than 50 years, accordingly increasing receptor desensitization and decreasing nicotinic currents. These results open a new line of research to achieve improved therapeutic treatments for nicotinic receptors related diseases.

neuroscience↗

bioRxiv2019

FxR-modulates the gut-vascular barrier by regulating the entry sites for bacterial translocation in experimental cirrhosis

Background and aimsPathological bacterial translocation (PBT) in liver cirrhosis (LC) is the hallmark for spontaneous bacterial infections increasing mortality several-fold. Factors known to contribute to PBT in LC are among others an increased intestinal permeability of which however, the mucus layer has not been addressed so far in detail. A clear route of translocation for luminal intestinal bacteria is yet to be defined but we hypothesize that the recently described gut vascular barrier (GVB) is impaired in experimental portal hypertension leading to increased accessibility of the vascular compartment for translocating bacteria.\n\nResultsHealthy and pre-hepatic portal-hypertensive (PPVL) mice lack translocation of FITC-dextran and GFP-Escherichia coli from the small intestine to the liver whereas bile-duct-ligated (BDL) and CCl4-induced cirrhotic mice demonstrate pathological translocation which is not altered by prior thoracic-duct ligation. Mucus layer is reduced in thickness with loss of goblet-cells and Muc2-staining and expression in cirrhotic but not PPVL-mice associated with bacterial overgrowth in inner mucus layer and pathological translocation of GFP-E.coli through the ileal epithelium. GVB is profoundly altered in BDL and CCl4-mice with Ileal extravasation of large-sized 150 kDa-FITC-dextran but only minor in PPVL-mice. This pathological endothelial permeability and accessibility in cirrhotic mice associates with an augmented expression of PV1 in intestinal vessels. OCA but not fexaramine stabilizes the GVB whereas both FXR-agonists ameliorate gut-liver-translocation of GFP-E.coli.\n\nConclusionsLiver cirrhosis but not portal hypertension per se grossly impairs the endothelial and muco-epithelial barriers promoting PBT to the portal-venous circulation. Both barriers appear FXR-modulated with -agonists reducing PBT via the portal-venous route.

physiology↗