Disruption of proteostasis causes IRE1 mediated reprogramming of alveolar epithelial cells.

Disruption of alveolar type 2 cell (AEC2) protein quality control has been implicated in chronic lung diseases, including pulmonary fibrosis (PF). We previously reported the in vivo modeling of a clinical surfactant protein C (SP-C) mutation that led to AEC2 endoplasmic reticulum (ER) stress and spontaneous lung fibrosis, providing proof of concept for disruption to proteostasis as a proximal driver of PF. Using two clinical SP-C mutation models, we have now discovered that AEC2s experiencing significant ER stress lose quintessential AEC2 features and develop a reprogrammed cell state that heretofore has been seen only as a response to lung injury. Using single-cell RNA sequencing in vivo and organoid-based modeling, we show that this state arises de novo from intrinsic AEC2 dysfunction. The cell-autonomous AEC2 reprogramming can be attenuated through inhibition of inositol-requiring enzyme 1 (IRE1α) signaling as the use of an IRE1α inhibitor reduced the development of the reprogrammed cell state and also diminished AEC2-driven recruitment of granulocytes, alveolitis, and lung injury. These findings identify AEC2 proteostasis, and specifically IRE1α signaling through its major product XBP-1, as a driver of a key AEC2 phenotypic change that has been identified in lung fibrosis.

Characterization of fluorocarbon-in-water emulsions with added triglyceride.

Fluorocarbon-in-water emulsions are being explored clinically as synthetic oxygen carriers in general surgery. Stabilizing fluorocarbon emulsions against coarsening is critical in maintaining the biocompatibility of the formulation following intravenous administration. It has been purported that the addition of a small percentage of long-chain triglyceride results in stabilization of fluorocarbon emulsions via formation of a three-phase emulsion. In a three-phase emulsion, the triglyceride forms a layer around the dispersed fluorocarbon, thereby improving the adhesion of the phospholipid surfactant to the dispersed phase. In the present study, we examined the effect of triglyceride addition on the physicochemical characteristics of the resulting complex dispersion. In particular, we examined the particle composition and stability of the dispersed particles using a method which first fractionates (classifies) the different particles prior to sizing (i.e., sedimentation field-flow fractionation). It was determined that the addition of a long-chain triglyceride (soybean oil) results in oil demixing and two distinct populations of emulsion droplets. The presence of the two types of emulsion droplets is not observed via light scattering techniques, since the triglyceride droplets dominate the scattering due to a large difference in the refractive index between the particles and the medium as compared to fluorocarbon droplets. The growth of the fractionated fluorocarbon emulsion droplets was followed over time, and it was found that there was no difference in growth rates with and without added triglyceride. In contrast, addition of medium-chain-triglyceride (MCT) oils results in a single population of emulsion droplets (i.e., a three-phase emulsion). These emulsions are not stable to droplet coalescence, however, as significant penetration of MCT into the phospholipid lipid interfacial layer results in a negative increment in the monolayer spontaneous curvature, thereby favoring water-in-oil emulsions and resulting in destabilization of the emulsion to the effects of terminal heat sterilization or mechanical stress.

Reduction of cerebral infarction using the third circulation.

OBJECTIVE: To ascertain whether ventriculosubarachnoid perfusion of the brain with an oxygen-carrying nutrient emulsion affects the volume of infarction in animals with permanent middle cerebral artery occlusion. DESIGN: Prospective, randomized, controlled trial. SETTING: An animal laboratory in a university setting. SUBJECTS: Twenty-eight closed colony adult cats weighing between 3.5 and 4.5 kg. INTERVENTIONS: Cats were assigned randomly into one of three groups: untreated surgical controls, artificial cerebrospinal fluid (ACSF) perfused, or oxygenated fluorochemical (t-bis perfluorobutylethylene; F44E) nutrient emulsion (OFNE) perfused. The formulation used in this study was developed for clinical use and is currently being used in a phase 1 clinical trial in patients with severe ischemic stroke. Focal cerebral ischemia was induced by permanently clipping the middle cerebral artery via the retro-orbital approach. Treatment was initiated 90 mins postocclusion and continued for 18 hrs. Animals were killed 1 hr after the termination of perfusion, the brains were sectioned and stained with 2,3,5-triphenyltetrazolium chloride, and the infarct area was determined with a computer digitizer. MEASUREMENTS AND MAIN RESULTS: There was a significant difference in cerebral infarct volume in the OFNE-perfused animals compared with the other groups ( p