Mechanosensitive cation channel Piezo1 contributes to ventilator-induced lung injury by activating RhoA/ROCK1 in rats

Background Mechanical ventilation can induce or aggravate lung injury, which is termed ventilator-induced lung injury (VILI). Piezo1 is a key element of the mechanotransduction process and can transduce mechanical signals into biological signals by mediating Ca2+ influx, which in turn regulates cytoskeletal remodeling and stress alterations. We hypothesized that it plays an important role in the occurrence of VILI, and investigated the underlying mechanisms. Methods High tidal volume mechanical ventilation and high magnitude cyclic stretch were performed on Sprague–Dawley rats, and A549 and human pulmonary microvascular endothelial cells, respectively, to establish VILI models. Immunohistochemical staining, flow cytometry, histological examination, enzyme-linked immunosorbent assay, western blotting, quantitative real-time polymerase chain reaction and survival curves were used to assess the effect of Piezo1 on induction of lung injury, as well as the signaling pathways involved. Results We observed that Piezo1 expression increased in the lungs after high tidal volume mechanical ventilation and in cyclic stretch-treated cells. Mechanistically, we observed the enhanced expression of RhoA/ROCK1 in both cyclic stretch and Yoda1-treated cells, while the deficiency or inhibition of Piezo1 dramatically antagonized RhoA/ROCK1 expression. Furthermore, blockade of RhoA/ROCK1 signaling using an inhibitor did not affect Piezo1 expression. GSMTx4 was used to inhibit Piezo1, which alleviated VILI-induced pathologic changes, water content and protein leakage in the lungs, and the induction of systemic inflammatory mediators, and improved the 7-day mortality rate in the model rats. Conclusions These findings indicate that Piezo1 affects the development and progression of VILI through promotion of RhoA/ROCK1 signaling.

The Elk1/MMP-9 axis regulates E-cadherin and occludin in ventilator-induced lung injury

Background Ventilator-induced lung injury (VILI) is a common complication in the treatment of respiratory diseases with high morbidity and mortality. ETS-domain containing protein (Elk1) and Matrix metalloproteinase (MMP) 9 are involved in VILI, but the roles have not been fully elucidated. This study examined the mechanisms of the activation of MMP-9 and Elk1 regulating barrier function in VILI in vitro and in vivo. Methods For the in vitro study, Mouse lung epithelial cells (MLE-12) were pre-treated with Elk1 siRNA or MMP-9 siRNA for 48 h prior to cyclic stretch at 20% for 4 h. For the in vivo study, C57BL/6 mice were pre-treated with Elk1 siRNA or MMP-9 siRNA for 72 h prior to 4 h of mechanical ventilation. The expressions of Elk1, MMP-9, Tissue inhibitor of metalloproteinase 1 (TIMP-1), E-cadherin, and occludin were measured by Western blotting. The intracellular distribution of E-cadherin and occludin was shown by immunofluorescence. The degree of pulmonary edema and lung injury were evaluated by Hematoxylin–eosin (HE) staining, lung injury scores, Wet/Dry (W/D) weight ratio, total cell counts, and Evans blue dye. Results 20% cyclic stretch and high tidal volume increases the expressions of Elk1, MMP-9, and TIMP-1, increases the ratio of MMP-9/TIMP-1, decreases the E-cadherin and occludin level. Elk1 siRNA or MMP-9 siRNA reverses the degradations of E-cadherin, occludin, and the ratio of MMP-9/TIMP-1 caused by cyclic stretch. Elk1 siRNA decreases the MMP-9 level with or not 20% cyclic stretch and high tidal volume. Conclusions The results demonstrate mechanical stretch damages the tight junctions and aggravates the permeability in VILI, Elk1 plays an important role in affecting the tight junctions and permeability by regulating the balance of MMP-9 and TIMP-1, thus indicating the therapeutic potential of Elk1 to treat VILI.

Mechanosensitive Cation Channel Piezo1 Contributes To Ventilator-Induced Lung Injury By Activating RhoA/ROCK1 In Rats

Background: Mechanical ventilation can induce or aggravate lung injury, which is termed ventilator‑induced lung injury. Piezo1 is a key element of the mechanotransduction process and can transduce mechanical signals into biological signals by mediating Ca2+ influx, which in turn regulates cytoskeletal remodeling and stress alterations. We hypothesized that it plays an important role in the occurrence of ventilator‑induced lung injury, and we investigated the underlying mechanisms. Methods: High tidal volume mechanical ventilation and high magnitude cyclic stretch were performed on Sprague Dawley rats, and A549 and human pulmonary microvascular endothelial cells, respectively, to establish ventilator‑induced lung injury models. Immunohistochemical staining, flow cytometry, histological examination, enzyme-linked immunosorbent assay, western blotting, quantitative real-time reverse transcription-PCR and survival curves were used to assess the effect of Piezo1 on induction of lung injury, as well as the signaling pathways involved.Results: We observed that Piezo1 expression increased in the lungs after high tidal volume mechanical ventilation and in cyclic stretch-treated cells. Mechanistically, we observed the enhanced expression of RhoA/ROCK1 in both cyclic stretch and Yoda1-treated cells, while the deficiency or inhibition of Piezo1 dramatically antagonized RhoA/ROCK1 expression. Furthermore, blockade of RhoA/ROCK1 signaling using an inhibitor did not affect Piezo1 expression. GSMTx4 was used to inhibit Piezo1, which alleviated ventilator‑induced lung injury-induced pathologic changes, water content and protein leakage in the lungs, and the induction of systemic inflammatory mediators, and improved the 7-day mortality rate in the model rats. Conclusions: These findings indicate that Piezo1 affects the development and progression of ventilator‑induced lung injury through promotion of RhoA/ROCK1 signaling.

Effects of Feedback and Education on Nurses’ Clinical Competence in Mechanical Ventilation and Accurate Tidal Volume Setting

Background: Patients under mechanical ventilation are at risk of ventilator-associated complications. One of these complications is lung injury due to high tidal volume. Nurses’ competence in mechanical ventilation is critical for preventing ventilator-associated complications. This study assessed the effects of feedback and education on nurses’ clinical competence in mechanical ventilation and accurate tidal volume setting. Methods: This single arm pretest-post-test interventional study was conducted in 2019 at Shariati hospital affiliated to Tehran University of Medical Sciences. Participants were 75 conveniently selected nurses. Initially, nurses’ clinical competence in mechanical ventilation and ventilator parameters of 250 patients were assessed. A mechanical ventilation -based feedback and education intervention was implemented for nurses. Finally, mechanical ventilation clinical competence of nurses and ventilator parameters of 250 new patients were assessed. Moreover, patients’ height was estimated based on their ulna length and then, their predicted body weight was calculated using their estimated height. Accurate tidal volume was determined per predicted body weight. Results: The mean score of nurses’ clinical competence increased from 8.27±3.09 at pretest to 10.07±3.34 at post-test (p<0.001). The mean values of both total tidal volume and tidal volume per kilogram of predicted body weight were significantly reduced respectively from 529.84±69.11 and 9.11±1.73 (ml) at pretest to 476.30±31.01 and 7.79±1.14 (ml) at post-test (p<0.001). Conclusion: The feedback and education intervention is effective in promoting nurses’ clinical competence in mechanical ventilation and reducing tidal volume. Thereby, it can reduce lung injuries associated with high tidal volume and ensure patient safety.

Effect of Recombinant Human Thrombomodulin on Ventilator-Induced Lung Injury in Septic Rats

Background: High tidal ventilation with inflammation causes ventilator-induced lung injury (VILI). We previously found that recombinant thrombomodulin (rTM) has a protective effect regarding non-septic VILI caused by high-tidal-volume (HV) ventilation with high oxygen levels. This study aimed to investigate the preventive effect of rTM on VILI caused by sepsis and HV ventilation. Methods: A total of 46 adult male rats were subcutaneously administered either 3mg/kg of rTM or saline. Twelve hours later, the rats were underwent cecal ligation and puncture (CLP). At 2 h after this procedure, the rats were placed on a ventilator set at either low tidal volume [(LV) 6 ml/kg] or high tidal volume (HV 35 ml/kg) ventilation for another 2 h. Results: After 2 h of mechanical ventilation, the PaO2 was significantly lower and BALF protein was significantly higher in HV rats than in LV rats. The rTM did not improve oxygenation or BALF protein levels. Also in HV rats, lung tissue interleukin-6 and monocyte chemotactic protein-1 mRNA levels were significantly higher in the rTM-treated rats.Conclusion: rTM does not improve oxygenation in a non-DIC, CLP-pretreated, high-tidal-ventilation rat model.

Impact of high tidal volume ventilation on surfactant metabolism and lung injury in infant rats

The poorly understood tolerance toward high tidal volume (VT) ventilation observed in critically ill children and age-equivalent animal models may be explained by surfactant homeostasis. The aim of our prospective animal study was to test whether high VT with adequate positive end-expiratory pressure (PEEP) is associated with surfactant de novo synthesis and secretion, leading to improved lung function, and whether extreme mechanical ventilation affects intracellular lamellar body formation and exocytosis. Rats (14 days old) were allocated to five groups: nonventilated controls, PEEP 5 cmH2O with VT of 8, 16, and 24 mL/kg, and PEEP 1 cmH2O with VT 24 mL/kg. Following 6 h of ventilation, lung function, surfactant proteins and phospholipids, and lamellar bodies were assessed by forced oscillation technique, quantitative real-time polymerase chain reaction, mass spectrometry, immunohistochemistry, and transmission electron microscopy. High VT (24 mL/kg) with PEEP of 5 cmH2O improved respiratory system mechanics and was not associated with lung injury, elevated surfactant protein expression, or surfactant phospholipid content. Extreme ventilation with VT 24 mL/kg and PEEP 1 cmH2O produced a mild inflammatory response and correlated with higher surfactant phospholipid concentrations in bronchoalveolar lavage fluid without affecting lamellar body count and morphology. Elevated phospholipid concentrations in the potentially most injurious strategy (VT 24 mL/kg, PEEP 1 cmH2O) need further evaluation and might reflect accumulation of biophysically inactive small aggregates. In conclusion, our data confirm the resilience of infant rats toward high VT-induced lung injury and challenge the relevance of surfactant synthesis, storage, and secretion as protective factors.

Does Iso-mechanical Power Lead to Iso-lung Damage?

Background Excessive tidal volume, respiratory rate, and positive end-expiratory pressure (PEEP) are all potential causes of ventilator-induced lung injury, and all contribute to a single variable: the mechanical power. The authors aimed to determine whether high tidal volume or high respiratory rate or high PEEP at iso-mechanical power produce similar or different ventilator-induced lung injury. Methods Three ventilatory strategies—high tidal volume (twice baseline functional residual capacity), high respiratory rate (40 bpm), and high PEEP (25 cm H2O)—were each applied at two levels of mechanical power (15 and 30 J/min) for 48 h in six groups of seven healthy female piglets (weight: 24.2 ± 2.0 kg, mean ± SD). Results At iso-mechanical power, the high tidal volume groups immediately and sharply increased plateau, driving pressure, stress, and strain, which all further deteriorated with time. In high respiratory rate groups, they changed minimally at the beginning, but steadily increased during the 48 h. In contrast, after a sudden huge increase, they decreased with time in the high PEEP groups. End-experiment specific lung elastance was 6.5 ± 1.7 cm H2O in high tidal volume groups, 10.1 ± 3.9 cm H2O in high respiratory rate groups, and 4.5 ± 0.9 cm H2O in high PEEP groups. Functional residual capacity decreased and extravascular lung water increased similarly in these three categories. Lung weight, wet-to-dry ratio, and histologic scores were similar, regardless of ventilatory strategies and power levels. However, the alveolar edema score was higher in the low power groups. High PEEP had the greatest impact on hemodynamics, leading to increased need for fluids. Adverse events (early mortality and pneumothorax) also occurred more frequently in the high PEEP groups. Conclusions Different ventilatory strategies, delivered at iso-power, led to similar anatomical lung injury. The different systemic consequences of high PEEP underline that ventilator-induced lung injury must be evaluated in the context of the whole body. Editor’s Perspective What We Already Know about This Topic What This Article Tells Us That Is New