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Endothelial mitochondria determine rapid barrier failure in chemical lung injury
Rebecca F. Hough, … , Shonit Das, Jahar Bhattacharya
Rebecca F. Hough, … , Shonit Das, Jahar Bhattacharya
Published February 7, 2019
Citation Information: JCI Insight. 2019;4(3):e124329. https://doi.org/10.1172/jci.insight.124329.
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Categories: Research Article Pulmonology Vascular biology

Endothelial mitochondria determine rapid barrier failure in chemical lung injury

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Abstract

Acid aspiration, which can result from several etiologies, including postoperative complications, leads to direct contact of concentrated hydrochloric acid (HCl) with the alveolar epithelium. As a result, rapid endothelial activation induces alveolar inflammation, leading to life-threatening pulmonary edema. Because mechanisms underlying the rapid endothelial activation are not understood, here we determined responses in real time through optical imaging of alveoli of live mouse lungs. By alveolar micropuncture, we microinfused concentrated HCl in the alveolar lumen. As expected, acid contact with the epithelium caused rapid, but transient, apical injury. However, there was no concomitant membrane injury to the endothelium. Nevertheless, H2O2-mediated epithelial-endothelial paracrine signaling induced endothelial barrier failure, as detected by microvascular dextran leakage and lung water quantification. Remarkably, endothelial mitochondria regulated the barrier failure by activating uncoupling protein 2 (UCP2), thereby inducing transient mitochondrial depolarization that led to cofilin-induced actin depolymerization. Knockdown, or endothelium-targeted deletion of UCP2 expression, blocked these responses, including pulmonary edema. To our knowledge, these findings are the first to mechanistically implicate endothelial mitochondria in acid-induced barrier deterioration and pulmonary edema. We suggest endothelial UCP2 may be a therapeutic target for acid-induced acute lung injury.

Authors

Rebecca F. Hough, Mohammad N. Islam, Galina A. Gusarova, Guangchun Jin, Shonit Das, Jahar Bhattacharya

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Figure 2

Effects of alveolar HCl–induced endothelial UCP2 activation.

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Effects of alveolar HCl–induced endothelial UCP2 activation.
(A) Confoca...
(A) Confocal image shows endothelial immunofluorescence in lung capillaries (cap) at low magnification. The other image shows the region of interest marked by the rectangle at high magnification. Capillaries were microinfused with 4% paraformaldehyde and 0.2% Triton X-100 (45 minutes), followed by Alexa Fluor 633–labeled anti–UCP2 goat polyclonal antibody (120 ng/ml, 30 minutes). Capillaries were buffer washed (5 minutes). n = 4 lungs. Scale bar: 20 μm. (B–E) Data are for analyses carried out 48 hours after tail vein injection of indicated siRNA. (B) Gel and bars show immunoblotting (IB) and densitometry of mitochondria isolated from lung homogenates. The antibodies were UCP2 mouse monoclonal antibody and voltage-dependent anion channel (VDAC) rabbit polyclonal antibody. Lanes were run on the same gel. Vertical line indicates the lanes are not contiguous. Results were identical for IB using UCP2 goat polyclonal antibody (data not shown). SI, siUCP2; SC, scRNA. *P < 0.05 versus scRNA. (C) Bars show effects of indicated treatments following alveolar HCl or microvascular H2O2 injections. KO, endothelial cell–specific UCP2-KO; LM, littermate control. For each pair, *P < 0.05 versus left bar. (D) Confocal images show dextran distribution at indicated locations. The endothelial cytosol was loaded with CR. FITC-D70 was infused in vessels at baseline and then again after injection of alveolar HCl. Scale bar: 20 μm. (E) Bars quantify FITC-D70–filled alveoli (edematous alveoli) following the indicated alveolar injections. Equal numbers of alveoli were injected in each group. Alveoli with greater than 50% luminal area filled with FITC-D70 were defined as edematous. UN, untreated. *P < 0.05 versus PBS. Data are shown as mean ± SEM for the number of injections indicated by dots. n, number of lungs. One-way ANOVA with post hoc Bonferroni’s test was used to determine statistical differences between groups.
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