Ventilator-induced Lung Injury In Mice Research Articles

Rutin targets AKT to inhibit ferroptosis in ventilator-induced lung injury.

Our previous research confirmed that rutin reduced ventilator-induced lung injury (VILI) in mice. Ferroptosis has been reported to participate in the pathogenic process of VILI. We will explore whether rutin inhibits ferroptosis to alleviate VILI. A mouse model of VILI was constructed with or without rutin pretreatment to perform a multiomics analysis. Hematoxylin-eosin (HE) staining and transmission electron microscopy were used to evaluate lung injury in VILI mice. Dihydroethidium (DHE) staining and the malondialdehyde (MDA) and superoxide dismutase (SOD) levels were detected. Molecular docking was performed to determine the binding affinity between rutin and ferroptosis-related proteins. Western blot analysis, real-time PCR (RT-PCR) and immunohistochemical (IHC) staining were conducted to detect the expression levels of GPX4, XCT, ACSL4, FTH1, AKT and p-AKT in lung tissues. Microscale thermophoresis (MST) was used to evaluate the binding between rutin and AKT1. Transcriptomic and proteomic analyses showed that ferroptosis may play a key role in VILI mice. Metabolomic analysis demonstrated that rutin may affect ferroptosis via the AKT pathway. Molecular docking analysis indicated that rutin may regulate the expression of ferroptosis-related proteins. Moreover, rutin upregulated GPX4 expression and downregulated the expression of XCT, ACSL4 and FTH1 in the lung tissues. Rutin also increased the ratio of p-AKT/AKT and p-AKT expression. MST analysis showed that rutin binds to AKT1. Rutin binds to AKT to activate the AKT signaling pathway, contributing to inhibit ferroptosis, thus preventing VILI in mice. Our study elucidated a possible novel strategy of involving the use of rutin for preventing VILI.

Electroacupuncture alleviates ventilator-induced lung injury in mice by inhibiting the TLR4/NF-κB signaling pathway

ObjectiveThis study was aimed to explore the protective effect of electroacupuncture (EA) pretreatment at Zusanli point (ST36) on ventilation-induced lung injury (VILI) and its potential anti-inflammatory mechanism.MethodsHigh tidal volume ventilation was used to induce the VILI in mice, and EA pretreatment at ST36 was given for 7 consecutive days. The wet/dry ratio and pathological injury score of lung tissue, and total protein content of pulmonary alveolar lavage fluid (BALF) were detected after 4 h of mechanical ventilation (MV). Meanwhile, the expressions of TLR4 and NF- κB in lung tissue were evaluated by Western Blot, and the inflammatory factors in lung tissue were detected by ELISA.ResultsAfter four hours of mechanical ventilation, mice with ventilator-induced lung injury showed significant increases in lung wet/dry ratio, tissue damage scores, and protein content in bronchoalveolar lavage fluid. Pro-inflammatory cytokines (IL-6, IL-1β, TNF-α) and TLR4/NF-κB expression levels in the lung were also markedly elevated (P < 0.05). Conversely, ST36 acupuncture point pre-treatment significantly reduced these parameters (P < 0.05).ConclusionEA pretreatment at ST36 could alleviate the inflammatory response for VILI via inhibiting TLR4/NF- κB pathway.

Rutin alleviates ventilator-induced lung injury by inhibiting NLRP3 inflammasome activation

Whether rutin relieves ventilator-induced lung injury (VILI) remains unclear. Here, we used network pharmacology, bioinformatics, and molecular docking to predict the therapeutic targets and potential mechanisms of rutin in the treatment of VILI. Subsequently, a mouse model of VILI was established to confirm the effects of rutin on VILI. HE staining showed that rutin alleviated VILI. TUNEL staining showed that rutin reduced apoptosis in the lung tissue of mice with VILI, and the same change was observed in the ratio of Bax/Bcl2. Furthermore, rutin reduced the expression of NLRP3, ASC, Caspase1, IL1β, and IL18 in the lung tissues of mice with VILI. Mechanistically, rutin suppressed the TLR4/NF-κB-P65 pathway, which promoted the M1 to M2 macrophage transition and alleviated inflammation in mice with VILI. Rutin relieved NLRP3 inflammasome activation by regulating M1/M2 macrophage polarization and inhibiting the activation of the TLR4/NF-κB-P65 pathway, resulting in the amelioration of VILI in mice.

Combined angiotensin-converting enzyme and aminopeptidase inhibition for treatment of experimental ventilator-induced lung injury in mice.

Introduction: Ventilator-induced lung injury (VILI) may aggravate critical illness. Although angiotensin-converting enzyme (ACE) inhibition has beneficial effects in ventilator-induced lung injury, its clinical application is impeded by concomitant hypotension. We hypothesized that the aminopeptidase inhibitor ALT-00 may oppose the hypotension induced by an angiotensin-converting enzyme inhibitor, and that this combination would activate the alternative renin-angiotensin system (RAS) axis to counteract ventilator-induced lung injury. Methods: In separate experiments, C57BL/6 mice were mechanically ventilated with low (LVT, 6mL/kg) and high tidal volumes (HVT, 30mL/kg) for 4h or remained unventilated (sham). High tidal volume-ventilated mice were treated with lisinopril (0.15μg/kg/min) ± ALT-00 at 2.7, 10 or 100μg/kg/min. Blood pressure was recorded at baseline and after 4h. Lung histology was evaluated for ventilator-induced lung injury and the angiotensin (Ang) metabolite profile in plasma (equilibrium levels of Ang I, Ang II, Ang III, Ang IV, Ang 1-7, and Ang 1-5) was measured with liquid chromatography tandem mass spectrometry at the end of the experiment. Angiotensin concentration-based markers for renin, angiotensin-converting enzyme and alternative renin-angiotensin system activities were calculated. Results: High tidal volume-ventilated mice treated with lisinopril showed a significant drop in the mean arterial pressure at 4h compared to baseline, which was prevented by adding ALT-00 at 10 and 100μg/kg/min. Ang I, Ang II and Ang 1-7 plasma equilibrium levels were elevated in the high tidal volumes group versus the sham group. Lisinopril reduced Ang II and slightly increased Ang I and Ang 1-7 levels versus the untreated high tidal volumes group. Adding ALT-00 at 10 and 100μg/kg/min increased Ang I and Ang 1-7 levels versus the high tidal volume group, and partly prevented the downregulation of Ang II levels caused by lisinopril. The histological lung injury score was higher in the high tidal volume group versus the sham and low tidal volume groups, and was attenuated by lisinopril ± ALT-00 at all dose levels. Conclusion: Combined angiotensin-converting enzyme plus aminopeptidase inhibition prevented systemic hypotension and maintained the protective effect of lisinopril. In this study, a combination of lisinopril and ALT-00 at 10μg/kg/min appeared to be the optimal approach, which may represent a promising strategy to counteract ventilator-induced lung injury that merits further exploration.

Vitamin D analogues activate vitamin D receptor/glutathione peroxidase 4 pathway to improve ventilator-induced lung injury in mice

To investigate the role of vitamin D analogue paricalcitol in activating vitamin D receptor/glutathione peroxidase 4 (VDR/GPX4) pathway in ventilator-induced lung injury (VILI). Twenty-four male C57BL/6J mice were randomly divided into control group, high tidal volume (HVT) induced VILI model group (HVT group), paricalcitol control group (P group), and paricalcitol pretreatment group (P+HVT group), with 6 mice in each group. The mice were endotracheal intubated and ventilated at 40 mL/kg tidal volume to prepare VILI model, while those in the control group were intubated without ventilation. The mice in the P+HVT group were intraperitoneally injected with paricalcitol 0.2 μg/kg once a day 1 week before modeling, while those in the P group were intraperitoneally injected paricalcitol 0.2 μg/kg once a day for 1 week before the experiment. After ventilation for 4 hours, the mice were sacrificed for lung tissue collection. Lung injury was evaluated by wet/dry (W/D) ratio, hematoxylin-eosin (HE) staining and Masson staining. The expressions of VDR and GPX4 were determined by Western blotting and immunohistochemistry. Malondialdehyde (MDA) and glutathione (GSH) contents were determined by micro method. After HVT for 4 hours, compared with the control group, lung injury score and W/D ratio were significantly higher (lung injury score: 0.430±0.035 vs. 0.097±0.025, lung W/D ratio: 4.860±0.337 vs. 3.653±0.332, both P < 0.05), collagen fiber deposition was significantly increased, the content of MDA in lung tissue was significantly increased (nmol/g: 212.420±8.757 vs. 97.073±5.308, P < 0.05), GSH content and the protein expressions and immunoreactive score (IRS) of VDR and GPX4 were significantly decreased [GSH (μg/g): 44.229±1.690 vs. 70.840±0.781; VDR protein (VDR/GAPDH): 0.518±0.029 vs. 0.762±0.081, GPX4 protein (GPX4/GAPDH): 0.452±0.032 vs. 0.649±0.034; IRS score: VDR was 4.168±0.408 vs. 10.167±0.408, GPX4 was 4.333±1.033 vs. 10.333±0.516; all P < 0.05], which meant that the mice in HVT group showed obvious lung injury. After VDR was activated by paricalcitol, compared with the HVT group, lung injury score and W/D ratio were significantly decreased (lung injury score: 0.220±0.036 vs. 0.430±0.035, lung W/D ratio: 4.015±0.074 vs. 4.860±0.337, both P < 0.05), collagen fiber deposition was reduced, MDA content in lung tissue was decreased (nmol/g: 123.840±8.082 vs. 212.420±8.757, P < 0.05), GSH content and the protein expressions and IRS score of VDR and GPX4 were significantly up-regulated [GSH (μg/g): 63.094±0.992 vs. 44.229±1.690; VDR protein (VDR/GAPDH): 0.713±0.056 vs. 0.518±0.029, GPX4 protein (GPX4/GAPDH): 0.605±0.008 vs. 0.452±0.032; IRS score: VDR was 9.000±0.632 vs. 4.168±0.408, GPX4 was 8.833±0.408 vs. 4.333±1.033; all P < 0.05], which meant that lung injury in P+HVT group was significantly improved. Vitamin D analogue paricalcitol ameliorates pulmonary oxidation-reduction imbalance by activating the VDR/GPX4 pathway, thereby alleviating VILI.

BMSCs mediates endothelial cell autophagy by upregulating miR-155-5p to alleviate ventilator-induced lung injury.

In this study, we explored to detect the effects and mechanism of bone-marrow-derived mesenchymal stem cells (BMSCs) on ventilator-induced lung injury (VILI). We transplanted BMSCsin mice and then induced VILI using mechanical ventilation (MV) treatment. The pathological changes, the content of PaO2 and PaCO2 , wet/dry weight ratio (W/D) of the lung, levels of tumor necrosis factor-α and interleukin-6 in bronchoalveolar lavage fluid, and apoptosis were detected. The autophagy-associated factor p62, LC3, and Beclin-1 expression were analyzed by western blot. The quantitativepolymerase chain reaction was applied to detect abnormally expressed microRNAs, including miR-155-5p. Subsequently, we overexpressed miR-155-5p in VILI mice to detect the effects of miR-155-5p on MV-induced lung injury. Then, we carried out bioinformatics analysis to verify the BMSCs-regulated miR-155-5p that target messenger RNA. It was observed that BMSCs transplantation mitigated the severity of VILI in mice. BMSCs transplantation reduced lung inflammation, strengthened the arterial oxygen partial pressure, and reduced apoptosis and the W/D of the lung. BMSCs promoted autophagy of pulmonary endothelial cells accompanied by decreased p62 and increased LC3 II/I and Beclin-1. BMSCs increased the levels of miR-155-5p in VILI mice. Overexpression of miR-155-5p alleviated lung injury in VILI mice following reduced apoptosis and increased autophagy. Finally, TAB2 was identified as a downstream target of miR-155-5p and regulated by miR-155-5p. BMSCs may protect lung tissues from MV-induced injury, inhibit lung inflammation, promote autophagy through upregulating of miR-155-5p.

Silencing ROCK1 ameliorates ventilator-induced lung injury in mice by inhibiting macrophages’ NLRP3 signaling

Rho kinase, including two subtypes, ROCK1 and ROCK2, controls a variety of biological processes helping coordinate the tissues response to stress and injury. Some authors believe that alveolar macrophages (AMs) play a key role in the early phase of ventilator-induced lung injury (VILI), which is closely related to the activation of NLRP3 inflammasome and NF-κB signaling. However, there is currently little known about the relationship between ROCK signaling and NLRP3 inflammasome. Accordingly, we focused on exploring the effect of ROCK for NLRP3 inflammasome, the results showed that VILI in C57BL/6 mice significantly increased NF-κB, NLRP3, ASC, caspase1 expression, and the secretion of cytokines, which was reversed by applying the ROCK Inhibitor-Y27632. Moreover, the use of AMs and mechanical stretching suggested that ROCK regulated transcriptional level of NF-κB and NLRP3 inflammasome in AMs. Specifically, we silenced the ROCK1 and ROCK2 respectively, and found that the inflammation of MH-S cells after LPS and ATP priming could be regulated by ROCK1 and ROCK2, while the NLRP3 was only dependent upon ROCK1. Meantime, the related genes of NLRP3 signal are also regulated by ROCK1. Collectively, our data suggest that silencing ROCK1 ameliorates VILI in mice in part by inhibiting AMs’ NLRP3 signaling pathway

Tert-butylhydroquinone augments Nrf2-dependent resilience against oxidative stress and improves survival of ventilator-induced lung injury in mice.

Oxidative stress caused by mechanical ventilation contributes to the pathophysiology of ventilator-induced lung injury (VILI). A key mechanism maintaining redox balance is the upregulation of nuclear factor-erythroid-2-related factor 2 (Nrf2)-dependent antioxidant gene expression. We tested whether pretreatment with an Nrf2-antioxidant response element (ARE) pathway activator tert-butylhydroquinone (tBHQ) protects against VILI. Male C57BL/6J mice were pretreated with an intraperitoneal injection of tBHQ (n = 10), an equivalent volume of 3% ethanol (EtOH3%, vehicle, n = 13), or phosphate-buffered saline (controls, n = 10) and were then subjected to high tidal volume (HVT) ventilation for a maximum of 4 h. HVT ventilation severely impaired arterial oxygenation ([Formula: see text] = 49 ± 7 mmHg, means ± SD) and respiratory system compliance, resulting in a 100% mortality among controls. Compared with controls, tBHQ improved arterial oxygenation ([Formula: see text] = 90 ± 41 mmHg) and respiratory system compliance after HVT ventilation. In addition, tBHQ attenuated the HVT ventilation-induced development of lung edema and proinflammatory response, evidenced by lower concentrations of protein and proinflammatory cytokines (IL-1β and TNF-α) in the bronchoalveolar lavage fluid, respectively. Moreover, tBHQ enhanced the pulmonary redox capacity, indicated by enhanced Nrf2-depentent gene expression at baseline and by the highest total glutathione concentration after HVT ventilation among all groups. Overall, tBHQ pretreatment resulted in 60% survival (P < 0.001 vs. controls). Interestingly, compared with controls, EtOH3% reduced the proinflammatory response to HVT ventilation in the lung, resulting in 38.5% survival (P = 0.0054 vs. controls). In this murine model of VILI, tBHQ increases the pulmonary redox capacity by activating the Nrf2-ARE pathway and protects against VILI. These findings support the efficacy of pharmacological Nrf2-ARE pathway activation to increase resilience against oxidative stress during injurious mechanical ventilation.

Death-associated Protein Kinase 1 Mediates Ventilator-induced Lung Injury in Mice by Promoting Alveolar Epithelial Cell Apoptosis

Alveolar epithelial cell apoptosis is implicated in the onset of ventilator-induced lung injury. Death-associated protein kinase 1 (DAPK1) is associated with cell apoptosis. The hypothesis was that DAPK1 participates in ventilator-induced lung injury through promoting alveolar epithelial cell apoptosis. Apoptosis of mouse alveolar epithelial cell was induced by cyclic stretch. DAPK1 expression was altered (knockdown or overexpressed) in vitro by using a small interfering RNA or a plasmid, respectively. C57/BL6 male mice (n = 6) received high tidal volume ventilation to establish a lung injury model. Adeno-associated virus transfection of short hairpin RNA and DAPK1 inhibitor repressed DAPK1 expression and activation in lungs, respectively. The primary outcomes were alveolar epithelial cell apoptosis and lung injury. Compared with the control group, the 24-h cyclic stretch group showed significantly higher alveolar epithelial cell apoptotic percentage (45 ± 4% fold vs. 6 ± 1% fold; P < 0.0001) and relative DAPK1 expression, and this group also demonstrated a reduced apoptotic percentage after DAPK1 knockdown (27 ± 5% fold vs. 53 ± 8% fold; P < 0.0001). A promoted apoptotic percentage in DAPK1 overexpression was observed without stretching (49 ± 6% fold vs. 14 ± 3% fold; P < 0.0001). Alterations in B-cell lymphoma 2 and B-cell lymphoma 2-associated X are associated with DAPK1 expression. The mice subjected to high tidal volume had higher DAPK1 expression and alveolar epithelial cell apoptotic percentage in lungs compared with the low tidal volume group (43 ± 6% fold vs. 4 ± 2% fold; P < 0.0001). Inhibition of DAPK1 through adeno-associated virus infection or DAPK1 inhibitor treatment appeared to be protective against lung injury with reduced lung injury score, resolved pulmonary inflammation, and repressed alveolar epithelial cell apoptotic percentage (47 ± 4% fold and 48 ± 6% fold; 35 ± 5% fold and 34 ± 4% fold; P < 0.0001, respectively). DAPK1 promotes the onset of ventilator-induced lung injury by triggering alveolar epithelial cell apoptosis through intrinsic apoptosis pathway in mice.

Endoplasmic reticulum stress is involved in ventilator-induced lung injury in mice via the IRE1α-TRAF2-NF-κB pathway

Inflammation plays a criticalrole in the development of ventilator-induced lung injury (VILI). Endoplasmic reticulum (ER) stress is associated with a variety of diseases through the modulation of inflammatory responses. However, little is known about how ER stress is implicated in VILI. In this study, murine mechanical ventilation models were constructed. Total protein and inflammatory cytokines were measured in bronchoalveolar lavage fluid (BALF),and lung tissue injurywasassessedby histology. Our data revealed that mice subjected to high tidal ventilation (TV) for 4 h showed more severe pulmonary edema and inflammation than those of mice with spontaneous breathing and low TV-treatment. In addition, the high TV-treated animals upregulated the ER stress markers GRP78, CHOP, p-IRE1α, TRAF2, and p-NF-κB expression at both the mRNA and protein levels in lung tissue. Administration of thapsigargin exacerbated the histological changes, inflammation and expression of GRP78 and CHOP after high TV, but treatment with ER stress and IRE1α kinase inhibitors attenuated the pathological damage and downregulated the high expression of GRP78, CHOP, p-IRE1α, TRAF2, and p-NF-κB, suggesting that ER stress is involved in VILI though the IRE1α/TRAF2/NF-κB signaling pathway in mice.

Role of microRNA-125b in ventilator-induced lung injury in mice

Objective To evaluate the role of microRNA-125b (miR-125b) on ventilator-induced lung injury (VILI) in mice. Methods Forty healthy male C57BL/6 male mice, weighing 25-30 g, aged 2-3 months, were divided into 4 groups (n=10 each) using a random number table method: sham operation group (group Sham), group VILI, VILI plus miR-125b negative control group (group VILI+ NC), and VILI plus miR-125b overexpression group (group VILI+ miR-125b agomir). In VILI+ NC and VILI+ miR-125b agomir groups, miR-125b negative control and miR-125b agomir transfection complex 50 μl were intratracheally instilled, respectively, and 48 h later VILI model was established.The animals were mechanically ventilated for 4 h with high tidal volume (40 ml/kg) to induce VILI.Blood samples were obtained from the femoral artery at 4 h of mechanical ventilation for detection of PaO2, then animals were sacrificed, lungs were removed for determination of wet to dry weight ratio (W/D ratio) and for examination of pathological changes (with a light microscope), and lung injury was scored.In VILI+ NC and VILI+ miR-125b agomir groups, bronchoalveolar lavage fluid (BALF) was collected to measure the concentrations of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) by enzyme-linked immunosorbent assay.The cell apoptosis of lung tissues was measured using TUNEL, apoptosis index was calculated, the caspase-3 expression was detected by Western blot, and the miR-125b expression was detected by real-time polymerase chain reaction. Results Compared with Sham group, PaO2 was significantly decreased, and W/D ratio and lung injury score were increased in VILI, VILI+ NC and VILI+ miR-125b agomir groups, and the expression of miR-125b was down-regulated in VILI and VILI+ NC groups (P<0.05). Compared with VILI group, PaO2 was significantly increased, W/D ratio and lung injury score were decreased, the expression of miR-125b was up-regulated (P<0.05), the pathological changes of lung tissues were significantly attenuated in group VILI+ miR-125b agomir, and no significant change was found in the parameters mentioned above in group VILI+ NC (P<0.05). Compared with group VILI+ NC, the concentrations of TNF-α and IL-6 in BALF and apoptotic index were significantly decreased, and the expression of caspase-3 was down regulated in group VILI+ miR-125b agomir (P<0.05). Conclusion MiR-125b is involved in the endogenous protective mechanism of VILI in mice. Key words: MicroRNAs; Ventilator-induced lung injury

Role and mechanism of Ly6Chigh monocyte in ventilator-induced lung injury in mice

To investigate the role and mechanism of Ly6Chigh monocyte in mice with ventilator-induced lung injury (VILI). Forty-eight healthy male SPF C57BL/6 mice were divided into spontaneous breathing group (n = 8), normal tidal volume (VT) group (VT was 8 mL/kg, n = 8), and high VT group (VT was 20 mL/kg, n = 32). The mice in the high VT group were subdivided into 1, 2, 3 and 4 hours subgroups, with 8 mice in each subgroup. All mice underwent direct tracheal intubation, those in the spontaneous breathing group maintained spontaneous breathing, and those in the normal VT group and high VT group were mechanically ventilated with different VT. After ventilation for 4 hours, bronchoalveolar lavage fluid (BALF) was collected to determine total protein, and the levels of inflammatory factors including tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) were determined by enzyme-linked immune sorbent assay (ELISA). The lung tissues were harvested to determine the wet/dry (W/D) ratio, and lung tissue injury was assessed in terms of lung histopathologic examination after hematoxylin-eosin (HE) staining under the light microscope. The protein expressions of monocyte chemotactic protein-1 (MCP-1) and CC-chemokine receptor 2 (CCR2) in lung tissues were determined by Western Blot. Flow cytometry was used to detect the proportion of Ly6Chigh monocyte in lung tissue. The histopathology of lung tissue structures was normal in the spontaneous breathing group and the normal VT group. Inflammatory reaction began to appear at 2 hours of high VT ventilation, and inflammatory reaction was gradually aggravated with the time extension. Compared with the spontaneous breathing group, the total protein, TNF-α, and IL-1β levels in BALF, the lung W/D ratio and MCP-1 expression were increased from 2 hours of high VT ventilation [total protein in BALF (g/L): 1.05±0.13 vs. 0.58±0.11, TNF-α in BALF (ng/L): 116.86±16.14 vs. 38.27±8.00, IL-1β in BALF (ng/L): 178.98±10.41 vs. 117.56±23.40, lung W/D ratio: 5.76±0.27 vs. 4.98±0.39, MCP-1/GAPDH: 0.87±0.19 vs. 0.29±0.12, all P < 0.05], and CCR2 expression and the proportion of Ly6Chigh monocyte was significantly increased from 3 hours of high VT ventilation [CCR2/GAPDH: 0.84±0.19 vs. 0.24±0.11, Ly6Chigh monocyte proportion: (9.01±2.47)% vs. (1.06±0.35)%, both P < 0.05], and they all showed an increased tendency with the time extension. There was no significant difference in the parameters mentioned above among the spontaneous breathing group, normal VT group and high VT ventilation 1-hour group. Ly6Chigh monocytes are involved in VILI, which aggravate VILI by activating the MCP-1/CCR2 axis.

Telocytes promote VEGF expression and alleviate ventilator-induced lung injury in mice.

Mechanical ventilation (MV) is an important procedure for the treatment of patients with acute lung injury or acute respiratory distress syndrome in a clinical setting; however, MV can lead to severe complications, including ventilator-induced lung injury (VILI). Telocytes (TCs) can promote tissue repair following injury in the heart, kidneys, and other organs. The aim of this study was to investigate the role of TCs in VILI in mice and the associated mechanisms. By using in vivo studies in mice and in vitro studies in cells, we demonstrated that an airway injection of TCs can reduce the pulmonary inflammatory response and improve the lung function in mice with VILI and promote the proliferation of pulmonary vascular endothelial cells. We also demonstrated that the impact of TCs on VILI repair might partially due to vascular endothelial growth factor (VEGF) secreted by TCs upon VILI stimulation, and that VEGF could induce the proliferation of hemangioendothelioma endothelial cells (EOMA). Collectively, our results revealed novel functions of TCs in VILA repair and shed light on the complications that are caused by MV.

Effects of peiminine preconditioning on ventilator-induced lung injury in mice

Objective To evaluate the effect of peiminine preconditioning on ventilator-induced lung injury (VILI) in mice. Methods Thirty-two clean healthy male BALB/c mice, aged 9-10 weeks, weighing 20-25 g, were divided into 4 groups (n=8 each) using a random number table: control group (group C), VILI group, dexamethasone group (group D) and peiminine preconditioning group (group P). Normal saline 0.2 ml was administered by intragastric gavage for 7 days in C and VILI groups, dexamethasone 10 mg/kg was administered by intragastric gavage for 7 days in group D, and peiminine 1 mg/kg was administered by intragastric gavage for 7 days in group P. VILI model (respiratory rate 80 breaths/min, tidal volume 40 ml/kg, fraction of inspired oxygen 21%, inspiratory/expiratory ratio 1∶2, for 4 h) was established on the 7th day of intragastric administration.After the end of ventilation, blood samples were collected from hearts for determination of serum interleukin-8 (IL-8) and tumor necrosis factor-α (TNF-α) concentrations (by enzyme-linked immunosorbent assay), and bilateral lung tissues were obtained for examination of the pathological changes after haematoxylin and eosin staining and for determination of contents of aquaporin 1 (AQP-1) and AQP-5 in lung tissues. Results Compared with group C, the concentrations of IL-8 and TNF-α in serum were significantly increased and the contents of AQP-1 and AQP-5 in lung tissues were decreased in group VILI (P 0.05). Compared with group VILI, the concentrations of IL-8 and TNF-α in serum were significantly decreased, the content of AQP-1 in lung tissues was increased (P 0.05), and the pathological changes were significantly attenuated in D and P groups.Compared with group D, no significant change was found in concentrations of IL-8 and TNF-α in serum or contents of AQP-1 and AQP-5 in lung tissues (P>0.05), and the pathological changes were comparable in group P. Conclusion Peiminine preconditioning can reduce VILI in mice. Key words: Fritillaria; Respiration, artificial; Respiratory distress syndrome, adult

Sphingolipids in Ventilator Induced Lung Injury: Role of Sphingosine-1-Phosphate Lyase.

Mechanical ventilation (MV) performed in respiratory failure patients to maintain lung function leads to ventilator-induced lung injury (VILI). This study investigates the role of sphingolipids and sphingolipid metabolizing enzymes in VILI using a rodent model of VILI and alveolar epithelial cells subjected to cyclic stretch (CS). MV (0 PEEP (Positive End Expiratory Pressure), 30 mL/kg, 4 h) in mice enhanced sphingosine-1-phosphate lyase (S1PL) expression, and ceramide levels, and decreased S1P levels in lung tissue, thereby leading to lung inflammation, injury and apoptosis. Accumulation of S1P in cells is a balance between its synthesis catalyzed by sphingosine kinase (SphK) 1 and 2 and catabolism mediated by S1P phosphatases and S1PL. Thus, the role of S1PL and SphK1 in VILI was investigated using Sgpl1+/− and Sphk1−/− mice. Partial genetic deletion of Sgpl1 protected mice against VILI, whereas deletion of SphK1 accentuated VILI in mice. Alveolar epithelial MLE-12 cells subjected to pathophysiological 18% cyclic stretch (CS) exhibited increased S1PL protein expression and dysregulation of sphingoid bases levels as compared to physiological 5% CS. Pre-treatment of MLE-12 cells with S1PL inhibitor, 4-deoxypyridoxine, attenuated 18% CS-induced barrier dysfunction, minimized cell apoptosis and cytokine secretion. These results suggest that inhibition of S1PL that increases S1P levels may offer protection against VILI.

Hydrogen Sulfide Confers Lung Protection During Mechanical Ventilation via Cyclooxygenase 2, 15-deoxy Δ12,14-Prostaglandin J2, and Peroxisome Proliferator-Activated Receptor Gamma.

Hydrogen sulfide reduces ventilator-induced lung injury in mice. Here, we have examined the underlying mechanisms of hydrogen sulfide-mediated lung protection and determined the involvement of cyclooxygenase 2, 15-deoxy Δ-prostaglandin J2, and peroxisome proliferator-activated receptor gamma in this response. Randomized, experimental study. University medical center research laboratory. C57BL/6 mice and in vitro cell catheters. The effects of hydrogen sulfide were analyzed in a mouse ventilator-induced lung injury model in vivo as well as in a cell stretch model in vitro in the absence or presence of hydrogen sulfide. The physiologic relevance of our findings was confirmed using pharmacologic inhibitors of cyclooxygenase 2 and peroxisome proliferator-activated receptor gamma. Mechanical ventilation caused significant lung inflammation and injury that was prevented in the presence of hydrogen sulfide. Hydrogen sulfide-mediated protection was associated with induction of cyclooxygenase 2 and increases of its product 15-deoxy Δ-prostaglandin J2 as well as cyclooxygenase 2/15-deoxy Δ-prostaglandin J2-dependent activation of peroxisome proliferator-activated receptor gamma. Hydrogen sulfide-dependent effects were mainly observed in macrophages. Applied mechanical stretch to RAW 264.7 macrophages resulted in increased expression of interleukin receptor 1 messenger RNA and release of macrophage inflammatory protein-2. In contrast, incubation of stretched macrophages with sodium hydrosulfide prevented the inflammatory response dependent on peroxisome proliferator-activated receptor gamma activity. Finally, application of a specific peroxisome proliferator-activated receptor gamma inhibitor abolished hydrogen sulfide-mediated protection in ventilated animals. One hydrogen sulfide-triggered mechanism in the protection against ventilator-induced lung injury involves cyclooxygenase 2/15-deoxy Δ-prostaglandin J2-dependent activation of peroxisome proliferator-activated receptor gamma and macrophage activity.

Disruption of the gut microbiome augments the development of ventilator-induced lung injury in mice

Disruption of the gut microbiome augments the development of ventilator-induced lung injury in mice

Increasing the inspiratory time and I:E ratio during mechanical ventilation aggravates ventilator-induced lung injury in mice.

IntroductionLung-protective ventilation reduced acute respiratory distress syndrome (ARDS) mortality. To minimize ventilator-induced lung injury (VILI), tidal volume is limited, high plateau pressures are avoided, and positive end-expiratory pressure (PEEP) is applied. However, the impact of specific ventilatory patterns on VILI is not well defined. Increasing inspiratory time and thereby the inspiratory/expiratory ratio (I:E ratio) may improve oxygenation, but may also be harmful as the absolute stress and strain over time increase. We thus hypothesized that increasing inspiratory time and I:E ratio aggravates VILI.MethodsVILI was induced in mice by high tidal-volume ventilation (HVT 34 ml/kg). Low tidal-volume ventilation (LVT 9 ml/kg) was used in control groups. PEEP was set to 2 cm H2O, FiO2 was 0.5 in all groups. HVT and LVT mice were ventilated with either I:E of 1:2 (LVT 1:2, HVT 1:2) or 1:1 (LVT 1:1, HVT 1:1) for 4 hours or until an alternative end point, defined as mean arterial blood pressure below 40 mm Hg. Dynamic hyperinflation due to the increased I:E ratio was excluded in a separate group of animals. Survival, lung compliance, oxygenation, pulmonary permeability, markers of pulmonary and systemic inflammation (leukocyte differentiation in lung and blood, analyses of pulmonary interleukin-6, interleukin-1β, keratinocyte-derived chemokine, monocyte chemoattractant protein-1), and histopathologic pulmonary changes were analyzed.ResultsLVT 1:2 or LVT 1:1 did not result in VILI, and all individuals survived the ventilation period. HVT 1:2 decreased lung compliance, increased pulmonary neutrophils and cytokine expression, and evoked marked histologic signs of lung injury. All animals survived. HVT 1:1 caused further significant worsening of oxygenation, compliance and increased pulmonary proinflammatory cytokine expression, and pulmonary and blood neutrophils. In the HVT 1:1 group, significant mortality during mechanical ventilation was observed.ConclusionAccording to the “baby lung” concept, mechanical ventilation-associated stress and strain in overinflated regions of ARDS lungs was simulated by using high tidal-volume ventilation. Increase of inspiratory time and I:E ratio significantly aggravated VILI in mice, suggesting an impact of a “stress/strain × time product” for the pathogenesis of VILI. Thus increasing the inspiratory time and I:E ratio should be critically considered.Electronic supplementary materialThe online version of this article (doi:10.1186/s13054-015-0759-2) contains supplementary material, which is available to authorized users.

TLR2 Deficiency Aggravates Lung Injury Caused by Mechanical Ventilation

Innate immunity pathways are found to play an important role in ventilator-induced lung injury. We analyzed pulmonary expression of Toll-like receptor 2 (TLR2) in humans and mice and determined the role of TLR2 in the pathogenesis of ventilator-induced lung injury in mice. Toll-like receptor 2 gene expression was analyzed in human bronchoalveolar lavage fluid (BALF) cells and murine lung tissue after 5 h of ventilation. In addition, wild-type (WT) and TLR2 knockout (KO) mice were ventilated with either lower tidal volumes (VT) of 7 mL/kg with positive end-expiratory pressure (PEEP) or higher VT of 15 mL/kg without PEEP for 5 h. Spontaneously breathing mice served as controls. Total protein and immunoglobulin M levels in BALF, neutrophil influx into the alveolar compartment, and interleukin 6 (IL-6), IL-1β, and keratinocyte-derived chemokine concentrations in lung tissue homogenates were measured. We observed enhanced TLR2 gene expression in BALF cells of ventilated patients and in lung tissue of ventilated mice. In WT mice, ventilation with higher VT without PEEP resulted in lung injury and inflammation with higher immunoglobulin M levels, neutrophil influx, and levels of inflammatory mediators compared with controls. In TLR2 KO mice, neutrophil influx and IL-6, IL-1β, and keratinocyte-derived chemokine were enhanced by this ventilation strategy. Ventilation with lower VT with PEEP only increased neutrophil influx and was similar in WT and TLR2 KO mice. In summary, injurious ventilation enhances TLR2 expression in lungs. Toll-like receptor 2 deficiency does not protect lungs from ventilator-induced lung injury. In contrast, ventilation with higher VT without PEEP aggravates inflammation in TLR2 KO mice.

Increasing the inspiratory time and I:E ratio during mechanical ventilation aggravates Ventilator-induced lung injury in mice

Rationale: Lung protective ventilation in order to minimize ventilator-induced lung injury (VILI) reduced ARDS mortality. Besides limiting tidal volumes, avoiding high plateau pressures and applying adequate positive end expiratory pressure (PEEP), adjustment of ventilatory pattern aiming at lung protective ventilation is not defined to date. Increasing the inspiratory time and thereby the inspiratory/expiratory ratio (I:E ratio) may improve oxygenation due to a prolonged gas exchange period, but may also be harmful as the absolute stress over time increases. We thus hypothesized that increasing inspiratory time and I:E ratio aggravates VILI.