Ramelteon protects against human pulmonary microvascular endothelial cell injury induced by lipopolysaccharide (LPS) via activating nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) pathway.

Acute lung injury (ALI) is classified as a moderate or mild acute respiratory distress syndrome and is a prominent cause of morbidity and mortality among the critically ill population. Ramelteon is a melatonin receptor agonist with anti-inflammatory and antioxidant effects. The current study investigated the role of ramelteon in lipopolysaccharide (LPS)-induced human pulmonary microvascular endothelial cells (HPMECs) and its potential regulatory mechanisms. A CCK-8 assay was used to examine the effect of ramelteon on the viability of LPS-induced HPMECs, HPMECs treated with ML385 [a Nrf2 inhibitor] and HPMECs treated with SnPP [a HO-1 inhibitor]. The Nrf2/HO-1 signaling pathway was additionally assessed by performing Western blotting. The levels of oxidative stress and inflammatory cytokines in HPMECs were detected using kits and reverse transcription-quantitative PCR. Cell apoptosis was evaluated via TUNEL staining. Furthermore, cell permeability was assessed using a FITC-dextran fluorescent probe, ZO-1 and occludin expression was determined via Western blotting. The results demonstrated that ramelteon elevated HPMEC viability after LPS stimulation. Additionally, ramelteon markedly reduced LPS-induced oxidative stress, inflammation and apoptosis. Moreover, cell permeability was notably decreased in ramelteon-treated groups and was accompanied by upregulated ZO-1 and occludin expression. Ramelteon treatment also activated the Nrf2/HO-1 signaling pathway in LPS-induced HPMECs. Furthermore, the addition of ML385 or SnPP reversed the protective effects of ramelteon on LPS-induced oxidative stress, inflammation, apoptosis and cell dysfunction in HPMECs. Collectively, the results suggested that ramelteon alleviated LPS-induced HPMEC damage by activating the Nrf2/HO-1 signaling pathway, making it an effective treatment for ALI.

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.

Effects of intraoperative lung-protective ventilation on clinical outcomes in patients with traumatic brain injury: a randomized controlled trial.

BACKGROUND: Secondary lung injury is the most common non-neurological complication after traumatic brain injury (TBI). Lung-protective ventilation (LPV) has been proven to improve perioperative oxygenation and lung compliance in some critical patients. This study aimed to investigate whether intraoperative LPV could improve respiratory function and prevent postoperative complications in emergency TBI patients. METHODS: Ninety TBI patients were randomly allocated to three groups (1:1:1): Group A, conventional mechanical ventilation [tidal volume (VT) 10 mL/kg only]; Group B, small VT (8 mL/kg) + positive end-expiratory pressure (PEEP) (5 cmH2O); and Group C, small VT (8 mL/kg) + PEEP (5 cmH2O) + recruitment maneuvers (RMs). The primary outcome was the incidence of total postoperative pulmonary complications; Secondary outcomes were intraoperative respiratory mechanics parameters and serum levels of brain injury markers, and the incidence of each postoperative pulmonary and neurological complication. RESULTS: Seventy-nine patients completed the final analysis. The intraoperative PaO2 and dynamic pulmonary compliance of Groups B and C were higher than those of Group A (P = 0.028; P = 0.005), while their airway peak pressure and plateau pressure were lower than those of group A (P = 0.004; P = 0.005). Compared to Group A, Groups B and C had decreased 30-day postoperative incidences of total pulmonary complications, hypoxemia, pulmonary infection, and atelectasis (84.0 % vs. 57.1 % vs. 53.8 %, P = 0.047; 52.0 % vs. 14.3 % vs. 19.2 %, P = 0.005; 84.0 % vs. 50.0 % vs. 42.3 %, P = 0.006; 24.0 % vs. 3.6 % vs. 0.0 %, P = 0.004). Moreover, intraoperative hypotension was more frequent in Group C than in Groups A and B (P = 0.007). At the end of surgery, the serum levels of glial fibrillary acidic protein and ubiquitin carboxyl-terminal hydrolase isozyme L1 in Group B were lower than those in Groups A and C (P = 0.002; P < 0.001). The postoperative incidences of neurological complications among the three groups were comparable. CONCLUSIONS: Continuous intraoperative administration of small VT + PEEP is beneficial to TBI patients. Additional RMs can be performed with caution to prevent disturbances in the stability of cerebral hemodynamics. TRIAL REGISTRATION: Chinese Clinical Trial Registry (ChiCTR2000038314), retrospectively registered on September 17, 2020.

Mechanosensitive Piezo1 channel activation promotes ventilator-induced lung injury via disruption of endothelial junctions in ARDS rats.

OBJECTIVE: This study aimed to investigate the role of endothelial Piezo1 in mediating ventilator-induced lung injury secondary to acute respiratory distress syndrome (ARDS). METHODS: Rats and lung endothelial cells (ECs) were transfected with Piezo1 shRNA (shPiezo1) and Piezo1 siRNA, respectively, to knock down Piezo1. Intratracheal instillation or incubation with lipopolysaccharide (LPS) was used to establish an ARDS model, and high tidal volume (HVT) ventilation or 20% cyclic stretch (CS) was administered to simulate a two-hit injury. Lung injury, alterations in lung endothelial barrier, disruption of adherens junctions (AJs), and Ca2+ influx were assessed. RESULTS: Lung vascular hyperpermeability was further increased in ARDS rats following HVT ventilation, which was abrogated in shPiezo1-treated rats. 20% CS led to severer rupture of AJs following LPS stimulation as indicated by immunofluorescence staining. The internalization and degradation of VE-cadherin were blocked by knockdown of Piezo1. Additionally, 20% CS induced Piezo1 activation, manifesting as elevated intracellular Ca2+ concentration in LPS-treated ECs, and subsequently increased calcium-dependent calpain activity. Pharmacological inhibition of calpain or Piezo1 knockdown prevented the loss of VE-cadherin, p120-catenin, and ß-catenin in ARDS rats undergoing HVT ventilation and LPS-treated ECs exposed to 20% CS. CONCLUSION: Excessive mechanical stretch during ARDS induces the activation of Piezo1 channel and its downstream target, calpain, via Ca2+ influx. This results in the disassembly of endothelial AJs and further facilitates lung endothelial barrier breakdown and vascular hyperpermeability.