Airway epithelial barrier dysfunction is increasingly recognized as a key feature of asthma and other lung diseases. Respiratory viruses are responsible for a large fraction of asthma exacerbations, and are particularly potent at disrupting epithelial barrier function through pattern recognition receptor engagement leading to tight junction dysfunction. Although different mechanisms of barrier dysfunction have been described, relatively little is known about whether barrier integrity can be promoted to limit disease. Here, we tested three classes of drugs commonly prescribed to treat asthma for their ability to promote barrier function using a cell culture model of virus-induced airway epithelial barrier disruption. Specifically, we studied the corticosteroid budesonide, the long acting beta-agonist formoterol, and the leukotriene receptor antagonist montelukast for their ability to promote barrier integrity of a monolayer of human bronchial epithelial cells (16HBE) before exposure to the viral mimetic double-stranded RNA. Of the three, only budesonide treatment limited transepithelial electrical resistance and small molecule permeability (4 kDa FITC-dextran flux). Next, we used a mouse model of acute dsRNA challenge that induces transient epithelial barrier disruption in vivo, and studied the effects budesonide when administered prophylactically or therapeutically. We found that budesonide similarly protected against dsRNA-induced airway barrier disruption in the lung, independently of its effects on airway inflammation. Taken together, these data suggest that an under-appreciated effect of inhaled budesonide is to maintain or promote airway epithelial barrier integrity during respiratory viral infections.
Dopamine neurons use autoregulation for appropriate modulation of goal-directed behaviors, and yet the mechanisms for D2 receptor (D2R)-mediated autoregulation are not fully understood. Electrophysiology suggests close proximity between dopamine release and receipt, but actual dendro-dendritic synapses are rare. This ultrastructural study used transgenic mice with a knockin of superecliptic green fluorescent protein (SEP) on the D2R (SEP-D2R) to determine how often autoreceptors are localized at directly apposed dendrites in the substantia nigra pars compacta (SNc). Silver-enhanced immunogold labeling for SEP-D2R was observed within dendrites, axon varicosities, astrocytes, and soma. Although most gold particles were intracellular, 28% of SEP-D2R gold was irregularly distributed along the plasma membrane. Structures immediately adjacent to dendritic membrane gold particles were axons (40%), astrocytes (19%), and other dendrites (7%), with the remaining structures unidentified in single sections. Known limitations in antibody penetration suggest the actual incidence of D2R localization at apposed dendrites is probably greater than 7%. Nevertheless, these results indicate that intercellular dopamine communication in the SNc is primarily extrasynaptic. The thin astrocytic processes often seen separating adjacent dendrites may provide channels along which transmitter diffuses to access dendritic D2Rs. Expression of D2Rs by the astrocytes themselves suggests they may participate in dopamine autoregulation. A novel finding of SEP-D2R on the axon initial segments (AISs) of SNc neurons was confirmed by immunofluorescence to involve dopamine cells. While some of this may represent axonal trafficking, membrane D2Rs might serve an autoregulatory function at the AIS yet to be physiologically characterized for dopamine neurons.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.