Retinoic acid and tracheal occlusion for diaphragmatic hernia treatment in rabbit fetuses.

INTRODUCTION: Lung hypoplasia and pulmonary arterial hypertension in congenital diaphragmatic hernia lead to a high perinatal mortality. Although sustained fetoscopic tracheal occlusion (TO) improves lung development, a major side effect is abnormal pneumocyte differentiation. This study evaluated the potential ability of intratracheal retinoic acid (RA) administration to reduce adverse effects of sustained TO in a rabbit model of diaphragmatic hernia. METHODS: A left diaphragmatic defect was created on day 23 in time-dated pregnant rabbits. On day 28, the same rabbits underwent sham surgery or TO, with an injection of empty or RA-loaded liposomes. On day 30, the fetuses were harvested, and the lungs were processed for histology, immunohistochemistry, and gene expression quantification. RESULTS: A tracheal RA injection at the time of TO had no effect on the lung-to-body-weight ratio, radial alveolar count or lung connective tissue composition. Retinoic acid plus TO had synergic effects on vascular measurements, proportional medial thickness, and endothelin-1 receptor type-A gene expression. The most noticeable effect was recovery of normal pneumocyte differentiation. CONCLUSION: Retinoic acid plus TO prevented abnormal pneumocyte differentiation and seemed to have a beneficial effect on pulmonary vascularization.

Sevoflurane for Sedation in Acute Respiratory Distress Syndrome. A Randomized Controlled Pilot Study.

RATIONALE: Sevoflurane improves gas exchange, and reduces alveolar edema and inflammation in preclinical studies of lung injury, but its therapeutic effects have never been investigated in acute respiratory distress syndrome (ARDS). OBJECTIVES: To assess whether sevoflurane would improve gas exchange and inflammation in ARDS. METHODS: We did a parallel, open-label single-center randomized controlled trial at three intensive care units from a French university hospital between April 2014 and February 2016. Adult patients were randomized within 24 hours of moderate-to-severe ARDS onset to receive either intravenous midazolam or inhaled sevoflurane for 48 hours. The primary outcome was the PaO2/FiO2 ratio on Day 2. Secondary endpoints included alveolar and plasma levels of cytokines and soluble form of the receptor for advanced glycation end-products, and safety. Investigators who did the analyses were masked to group allocation. Analysis was by intention to treat. MEASUREMENTS AND MAIN RESULTS: Twenty-five patients were assigned to the sevoflurane group and 25 to the midazolam group. On Day 2, PaO2/FiO2 ratio was higher in the sevoflurane group than in the midazolam group (mean ± SD, 205 ± 56 vs. 166 ± 59, respectively; P = 0.04). There was a significant reduction over time in cytokines and soluble form of the receptor for advanced glycation end-products levels in the sevoflurane group, compared with the midazolam group, and no serious adverse event was observed with sevoflurane. CONCLUSIONS: In patients with ARDS, use of inhaled sevoflurane improved oxygenation and decreased levels of a marker of epithelial injury and of some inflammatory markers, compared with midazolam. Clinical trial registered with www.clinicaltrials.gov (NCT 02166853).

Myocilin expression is regulated by retinoic acid in the trabecular meshwork-derived cellular environment.

Glaucoma is the leading cause of irreversible blindness and is usually classified as angle closure and open angle glaucoma (OAG). Primary open angle glaucoma represents the most frequent clinical presentation leading to ganglion cell death and optic nerve degeneration as a main consequence of an intraocular pressure' (IOP) increase. The mechanisms of this IOP increase in such pathology remain unclear but one protein called Myocilin could be a part of the puzzle in the trabecular meshwork (TM). Previously described to be transcriptionally regulated by glucocorticoids, the comprehension of the trabecular regulation of Myocilin' expression has only weakly progressed since 15 years. Due to the essential molecular and cellular implications of retinoids' pathway in eye development and physiology, we investigate the potential role of the retinoic acid in such regulation and expression. This study demonstrates that the global retinoids signaling machinery is present in immortalized TM cells and that Myocilin (MYOC) expression is upregulated by retinoic acid alone or combined with a glucocorticoid co-treatment. This regulation by retinoic acid acts through the MYOC promoter which contains a critical cluster of four retinoic acid responsive elements (RAREs), with the RARE-DR2 presenting the strongest effect and binding the RARα/RXRα heterodimer. All together, these results open up new perspectives for the molecular understanding glaucoma pathophysiology and provide further actionable clues on Myocilin gene regulation.

Soluble Receptor for Advanced Glycation End-Products Predicts Impaired Alveolar Fluid Clearance in Acute Respiratory Distress Syndrome.

RATIONALE: Levels of the soluble form of the receptor for advanced glycation end-products (sRAGE) are elevated during acute respiratory distress syndrome (ARDS) and correlate with severity and prognosis. Alveolar fluid clearance (AFC) is necessary for the resolution of lung edema but is impaired in most patients with ARDS. No reliable marker of this process has been investigated to date. OBJECTIVES: To verify whether sRAGE could predict AFC during ARDS. METHODS: Anesthetized CD-1 mice underwent orotracheal instillation of hydrochloric acid. At specified time points, lung injury was assessed by analysis of blood gases, alveolar permeability, lung histology, AFC, and plasma/bronchoalveolar fluid measurements of proinflammatory cytokines and sRAGE. Plasma sRAGE and AFC rates were also prospectively assessed in 30 patients with ARDS. MEASUREMENTS AND MAIN RESULTS: The rate of AFC was inversely correlated with sRAGE levels in the plasma and the bronchoalveolar fluid of acid-injured mice (Spearman's ρ = -0.73 and -0.69, respectively; P < 10(-3)), and plasma sRAGE correlated with AFC in patients with ARDS (Spearman's ρ = -0.59; P < 10(-3)). Similarly, sRAGE levels were significantly associated with lung injury severity, and decreased over time in mice, whereas AFC was restored and lung injury resolved. CONCLUSIONS: Our results indicate that sRAGE levels could be a reliable predictor of impaired AFC during ARDS, and should stimulate further studies on the pathophysiologic implications of RAGE axis in the mechanisms leading to edema resolution. Clinical trial registered with www.clinicaltrials.gov (NCT 00811629).

RAGE inhibition reduces acute lung injury in mice.

The receptor for advanced glycation end-products (RAGE) is involved in inflammatory response during acute respiratory distress syndrome (ARDS). Growing body of evidence support strategies of RAGE inhibition in experimental lung injury, but its modalities and effects remain underinvestigated. Anesthetised C57BL/6JRj mice were divided in four groups; three of them underwent orotracheal instillation of acid and were treated with anti-RAGE monoclonal antibody (mAb) or recombinant soluble RAGE (sRAGE), acting as a decoy receptor. The fourth group served as a control. Lung injury was assessed by the analysis of blood gases, alveolar permeability, histology, AFC, and cytokines. Lung expression and distribution epithelial channels ENaC, Na,K-ATPase, and aquaporin (AQP)-5 were assessed. Treatment with either anti-RAGE mAb or sRAGE improved lung injury, arterial oxygenation and decreased alveolar inflammation in acid-injured animals. Anti-RAGE therapies were associated with restored AFC and increased lung expression of AQP-5 in alveolar cell. Blocking RAGE had potential therapeutic effects in a translational mouse model of ARDS, possibly through a decrease in alveolar type 1 epithelial cell injury as shown by restored AFC and lung AQP-5 expression. Further mechanistic studies are warranted to describe intracellular pathways that may control such effects of RAGE on lung epithelial injury and repair.

All-trans retinoic acid promotes wound healing of primary amniocytes through the induction of LOXL4, a member of the lysyl oxidase family.

Thirty percent of preterm births directly result from preterm premature rupture of fetal membranes (PPROM). Clinical management currently proposes using a collagen plug to mechanically stop loss of amniotic fluid. Vitamin A and its active metabolite (retinoic acid) have well-known pro-healing properties and could thus make good candidates as a proposable adjuvant to this mechanical approach. Here we investigate the molecular mechanisms involved in the pro-healing properties of all-trans retinoic acid (atRA) in fetal membranes via an approach using an in vitro primary amniocyte wound model and transcriptomics. The results demonstrate that atRA promotes migration in primary amniocytes, improving wound healing in vitro by up to 90%. This effect is mediated by the induction of LOXL4, which plays a crucial role in the dynamics of the extracellular matrix by regulating collagen reticulation. This new insight into how atRA exerts its pro-healing properties prompts us to propose using atRA as a candidate strategy to help prevent future PPROM.