Hypoxic/hyperoxic oscillating oxygen conditions is shown to induce pro‐inflammatory cytokine release to a lesser extent and later than constant hyperoxia. Evident was severe production of peroxynitri...

Supplemental oxygen is frequently used together with mechanical ventilation to achieve sufficient blood oxygenation. Despite the undoubted benefits, it is vigorously debated whether too much oxygen can also have unpredicted side-effects. Uncertainty is also due to the fact that the molecular mechanisms are still insufficiently understood. The lung endothelium is covered with an exceptionally broad glycocalyx, carrying N- and O-glycans, proteoglycans, glycolipids and glycosaminoglycans. Glycan structures are not genetically determined but depend on the metabolic state and the expression level and activity of biosynthetic and glycan remodeling enzymes, which can be influenced by oxygen and the redox status of the cell. Altered glycan structures can affect cell interactions and signaling. In this study, we investigated the effect of different oxygen conditions on aspects of the glycobiology of the pulmonary endothelium with an emphasis on N-glycans and terminal sialylation using an in vitro cell culture system. We combined a proteomic approach with N-glycan structure analysis by LC-MS, qRT-PCR, sialic acid analysis and lectin binding to show that constant and intermittent hyperoxia induced time dependent changes in global and surface glycosylation. An siRNA approach identified St6gal1 as being primarily responsible for the early transient increase of α2-6 sialylated structures in response to hyperoxia.

Evaluating beneficial effects of potential protective therapies following cardiac arrest in rodent models could be enhanced by exploring behavior and cognitive functions. The Morris Water Maze is a well-known cognitive paradigm to test spatial learning and memory. Behavioral testing with the Morris Water Maze in Sprague–Dawley rats (300 ± 25 g) resuscitated after 8 min of ventricular fibrillation cardiac arrest was carried out 5 and 12 weeks after cardiac arrest (CA) and compared to results of naïve rats (Control). At 5 weeks, within each group latency time to reach the hidden platform (reflecting spatial learning) decreased equally from day 1 to 4 (CA: 105.6 ± 8.2 vs. 8.9 ± 1.2 s, p < 0.001; Control: 75.5 ± 13.2 vs. 17.1 ± 4.5, p < 0.001) with no differences between groups (p = 0.138). In the probe trial 24 h after the last trial, time spent in the target sector (reflecting memory recall) within each group was significantly longer (CA: 25 ± 1.3; Control: 24.7 ± 2.5 s) than in each of the three other sectors (CA: 7.7 ± 0.7, 14.3 ± 2.5, 8.4 ± 0.8 and Control: 7.8 ± 1.2, 11.7 ± 1.5, 10.3 ± 1.6 s) but with no significantly differences between groups. Seven days later (reflecting memory retention), control group animals remained significantly longer in the target sector compared to every other sector, whereas the cardiac arrest group animals did not. Even 12 weeks after cardiac arrest, the single p values showed that the control animals displayed a trend to perform better than the resuscitated animals. Memory recall was impaired early after 8 min of ventricular fibrillation cardiac arrest and might be a more valuable tool for cognitive testing than learning recall after global ischemia due to cardiac arrest.

The lung can experience different oxygen concentrations, low as in hypoxia, high as under supplemental oxygen therapy, or oscillating during intermittent hypoxia as in obstructive sleep apnea or intermittent hypoxia/hyperoxia due to cyclic atelectasis in the ventilated patient. This study aimed to characterize the oxygen-condition-specific protein composition of extracellular vesicles (EVs) released from human pulmonary microvascular endothelial cells in vitro to decipher their potential role in biotrauma using quantitative proteomics with bioinformatic evaluation, transmission electron microscopy, flow cytometry, and non-activated thromboelastometry (NATEM). The release of vesicles enriched in markers CD9/CD63/CD81 was enhanced under intermittent hypoxia, strong hyperoxia and intermittent hypoxia/hyperoxia. Particles with exposed phosphatidylserine were increased under intermittent hypoxia. A small portion of vesicles were tissue factor-positive, which was enhanced under intermittent hypoxia and intermittent hypoxia/hyperoxia. EVs from treatment with intermittent hypoxia induced a significant reduction of Clotting Time in NATEM analysis compared to EVs isolated after normoxic exposure, while after intermittent hypoxia/hyperoxia, tissue factor in EVs seems to be inactive. Gene set enrichment analysis of differentially expressed genes revealed that EVs from individual oxygen conditions potentially induce different biological processes such as an inflammatory response under strong hyperoxia and intermittent hypoxia/hyperoxia and enhancement of tumor invasiveness under intermittent hypoxia.

Patients presenting with insufficient tissue oxygenation and impaired lung function as in acute respiratory distress syndrome (ARDS) frequently require mechanical ventilation with supplemental oxygen. Despite the lung being used to experiencing the highest partial pressure of oxygen during healthy breathing, the organ is susceptible to oxygen-induced injury at supraphysiological concentrations. Hyperoxia-induced lung injury (HALI) has been regarded as a second hit to pre-existing lung injury and ventilator-induced lung injury (VILI) attributed to oxidative stress. The injured lung has a tendency to form atelectasis, a cyclic collapse and reopening of alveoli. The affected lung areas experience oxygen conditions that oscillate between hyperoxia and hypoxia rather than remaining in a constant hyperoxic state. Mechanisms of HALI have been investigated in many animal models previously. These studies provided insights into the effects of hyperoxia on the whole organism. However, cell type-specific responses have not been dissected in detail, but are necessary for a complete mechanistic understanding of ongoing pathological processes. In our study, we investigated the effects of constant and intermittent hyperoxia on the lung endothelium from a mouse by an in vitro proteomic approach. We demonstrate that these oxygen conditions have characteristic effects on the pulmonary endothelial proteome that underlie the physiological (patho)mechanisms.

Background: Patients suffering from severe COVID-19 often develop acute respiratory distress syndrome (ARDS), necessitating intensive care unit (ICU) and extracorporeal membrane oxygenation (ECMO). Survivors frequently experience negative impacts on their health-related quality of life. These individuals may experience a range of symptoms and may require extended hospitalization and rehabilitation. The objective of this prospective cohort study was to assess the long-term health-related quality of life in intensive care survivors of COVID-19-related ARDS who received ECMO therapy, >18 months after their ICU discharge. Methods: The health-related quality of life of COVID-19 survivors who had received extracorporeal membrane oxygenation was evaluated using an augmented version of the Short-Form Health Survey-36, >18 months after their ICU discharge. The outcomes were compared to preexisting data from a meta-analysis analyzing patients with non-COVID-19 ARDS and ECMO therapy. Results: Of the 43 eligible patients (mean age 52 ± 9.5 years), 18 patients (46.2%) responded to the written invitation and were included in this study. The four subscales of the Short-Form Health Survey-36 survey, performed via telephone interview, that showed the most severe limitations (points) were role limitation due to physical problems (37.5), emotional problems (47.9), social functioning (38.1), and general health (49.2). The general health, energy/fatigue (vitality), and physical functioning significantly correlated with higher age (p = 0.004, p = 0.003, and p = 0.05, respectively). A longer duration of extracorporeal membrane oxygenation was positively associated with an improved energy/fatigue ratio (vitality) and emotional well-being (p = 0.04 and p = 0.02, respectively). Compared to survivors of non-COVID-19 ARDS treated with ECMO, the survivors in our cohort scored significantly lower on social functioning, physical functioning, and general health (p < 0.01, p = 0.02, p < 0.01). Conclusions: Patients who have recovered from intensive care treatment for COVID-19-related ARDS and have received ECMO therapy continue to experience more severe impairments in their physical, mental, and cognitive health-related quality of life. A longer ECMO duration may improve outcomes in this selected patient population.