Ventilator-induced Lung Injury In Rats Research Articles

Effect of antibody-mediated connective tissue growth factor neutralization on lung edema in ventilator-induced lung injury in rats.

Acute respiratory distress syndrome (ARDS) is characterized by alveolar edema that can progress to septal fibrosis. Mechanical ventilation can augment lung injury, termed ventilator-induced lung injury (VILI). Connective tissue growth factor (CTGF), a mediator of fibrosis, is increased in ARDS patients. Blocking CTGF inhibits fibrosis and possibly vascular leakage. This study investigated whether neutralizing CTGF reduces pulmonary edema in VILI. Following LPS administration, rats were mechanically ventilated for 6h with low (6mL/kg; low VT) or moderate (10mL/kg; mod VT) tidal volume and treated with a neutralizing CTGF antibody (FG-3154) or placebo lgG (vehicle). Control rats without LPS were ventilated for 6h with low VT. Lung wet-to-dry weight ratio, FITC-labeled dextran permeability, histopathology, and soluble RAGE were determined. VILI was characterized by reduced PaO2/FiO2 ratio (low VT: 540 [381-661] vs. control: 693 [620-754], p < 0.05), increased wet-to-dry weight ratio (low VT: 4.8 [4.6-4.9] vs. control: 4.5 [4.4-4.6], p < 0.05), pneumonia (low VT: 30 [0-58] vs. control: 0 [0-0]%, p < 0.05) and interstitial inflammation (low VT: 2 [1-3] vs. control: 1 [0-1], p < 0.05). FG-3154 did not affect wet-to-dry weight ratio (mod VT + FG-3154: 4.8 [4.7-5.0] vs. mod VT + vehicle: 4.8 [4.8-5.0], p > 0.99), extravasated dextrans (mod VT + FG-3154: 0.06 [0.04-0.09] vs. mod VT + vehicle: 0.04 [0.03-0.09] µg/mg tissue, p > 0.99), sRAGE (mod VT + FG-3154: 1865 [1628-2252] vs. mod VT + vehicle: 1885 [1695-2159] pg/mL, p > 0.99) or histopathology. 'Double hit' VILI was characterized by inflammation, impaired oxygenation, pulmonary edema and histopathological lung injury. Blocking CTGF does not improve oxygenation nor reduce pulmonary edema in rats with VILI.

Vascular endothelial glycocalyx shedding in ventilator-induced lung injury in rats

Endothelial permeability deterioration is involved in ventilator-induced lung injury (VILI). The integrality of vascular endothelial glycocalyx (EG) is closely associated with endothelial permeability. The hypothesis was that vascular EG shedding participates in VILI through promoting endothelial permeability. In the present study, male Sprague-Dawley (SD) rats were ventilated with high tidal volume (VT =40 ml/kg) or low tidal volume (VT =8 ml/kg) to investigate the effects of different tidal volume and ventilation durations on EG in vivo. We report disruption of EG during the period of high tidal volume ventilation characterized by increased glycocalyx structural components (such as syndecan-1, heparan sulfate, hyaluronan) in the plasma and decreased the expression of syndecan-1 in the lung tissues. Mechanistically, the disruption of EG was associated with increased proinflammatory cytokines and matrix metalloproteinase in the lung tissues. Collectively, these results demonstrate that the degradation of EG is involved in the occurrence and development of VILI in rats, and the inflammatory mechanism mediated by activation of the NF-κB signaling pathway may be partly responsible for the degradation of EG in VILI in rats. This study enhances our understanding of the pathophysiological processes underlying VILI, shedding light on potential therapeutic targets to mitigate VILI.

MiR-9a-5p alleviates ventilator-induced lung injury in rats by inhibiting the activation of the MAPK signaling pathway via CXCR4 expression downregulation

BackgroundGlobally, Mechanical ventilation is the most commonly used short-term life support technology. Ventilator-induced lung injury (VILI) is an inflammatory injury caused by mechanical ventilation. MicroRNAs (miRNAs) are considered as new gene regulators that play an important role in lung injury and inflammation. However, the role and mechanism of action of miR-9a-5p in VILI remain unclear. MethodsHerein, a rat model of VILI was established. To determine the expression levels of miR-9a-5p and CXCR4 mRNA, real-time quantitative polymerase chain reactions (qRT-PCR) were conducted. As well as western blot (WB) and immunofluorescence analyses, we determined the expression of CXCR4, SDF-1 and MAPK signaling pathway-related kinases. Hematoxylin and eosin (H&E) staining and the wet-dry ratio of the lung tissue were used to evaluate organ injury. An enzyme-linked immunosorbent assay (Elisa) and myeloperoxidase (MPO) activity measurements were performed to evaluate the inflammatory response. In addition, double luciferase reporter assays were used to verify the association between miR-9a-5p and CXCR4. ResultsThe expression of miR-9a-5p was low, whereas that of CXCR4 was high in the lung tissues of VILI rats. The overexpression of miR-9a-5p alleviated the degree of pathological injury in the lung tissues of rats with VILI, downregulating inflammatory cytokine expression and MPO activity. In the VILI rat model, miR-9a-5p targeted the negative regulation of CXCR4, and CXCR4 overexpression to reverse the lung-protective and anti-inflammatory effects of miR-9a-5p overexpression in VILI rats. miR-9a-5p also inhibited the phosphorylation of extracellular signal receptor-activated kinase (ERK), a protein related to the MAPK signaling pathway, by downregulating CXCR4 expression. ConclusionmiR-9a-5p can hinder the activation of the MAPK/ERK signaling pathway and reduce inflammatory reactions and lung injury in VILI rats through the targeted regulation of CXCR4 expression. Therefore, miR-9a-5p could serve as an intervention target to supply a new strategy for the care of VILI.

Volutrauma Increases Exhaled Pentanal in Rats: A Potential Breath Biomarker for Ventilator-Induced Lung Injury.

Mechanical ventilation injures lungs, but there are currently no reliable methods for detecting early injury. We therefore evaluated whether exhaled pentanal, a lipid peroxidation product, might be a useful breath biomarker for stretch-induced lung injury in rats. A total of 150 male Sprague-Dawley rats were investigated in 2 substudies. The first randomly assigned 75 rats to 7 hours of mechanical ventilation at tidal volumes of 6, 8, 12, 16, and 20 mL·kg-1. The second included 75 rats. A reference group was ventilated at a tidal volume of 6 mL·kg-1 for 10 hours 4 interventional groups were ventilated at a tidal volume of 6 mL·kg-1 for 1 hour, and then for 0.5, 1, 2, or 3 hours at a tidal volume of 16 mL.kg-1 before returning to a tidal volume of 6 mL·kg-1 for additional 6 hours. Exhaled pentanal was monitored by multicapillary column-ion mobility spectrometry. The first substudy included cytokine and leukocyte measurements in blood and bronchoalveolar fluid, histological assessment of the proportion of alveolar space, and measurements of myeloperoxidase activity in lung tissue. The second substudy included measurements of pentanal in arterial blood plasma, cytokine and leukocyte concentrations in bronchoalveolar fluid, and cleaved caspase 3 in lung tissue. Exhaled pentanal concentrations increased by only 0.5 ppb·h-1 (95% confidence interval [CI], 0.3-0.6) when rats were ventilated at 6 mL·kg-1. In contrast, exhaled pentanal concentrations increased substantially and roughly linearly at higher tidal volumes, up to 3.1 ppb·h-1 (95% CI, 2.3-3.8) at tidal volumes of 20 mL·kg-1. Exhaled pentanal increased at average rates between 1.0 ppb·h-1 (95% CI, 0.3-1.7) and 2.5 ppb·h-1 (95% CI, 1.4-3.6) after the onset of 16 mL·kg-1 tidal volumes and decreased rapidly by a median of 2 ppb (interquartile range [IQR], 0.9-3.2), corresponding to a 38% (IQR, 31-43) reduction when tidal volume returned to 6 mL·kg-1. Tidal volume, inspiratory pressure, and mechanical power were positively associated with pentanal exhalation. Exhaled and plasma pentanal were uncorrelated. Alveolar space decreased and inflammatory markers in bronchoalveolar lavage fluid increased in animals ventilated at high tidal volumes. Short, intermittent ventilation at high tidal volumes for up to 3 hours increased neither inflammatory markers in bronchoalveolar fluid nor the proportion of cleaved caspase 3 in lung tissue. Exhaled pentanal is a potential biomarker for early detection of ventilator-induced lung injury in rats.

Leptin reduces ventilator-induced lung injury in rats by regulating NLRP3, NLRC4 and NLRC3.

Leptin has been linked to acute lung injury (ALI) through its regulation of immune responses. We aimed to scrutinize the effects of leptin on nucleotide oligomerization domain-like receptors containing pyrin domain 3 (NLRP3), nucleotide oligomerization domain-like receptors with caspase activation and recruitment domain 4 (NLRC4), and nucleotide oligomerization domain-like receptors with caspase activation and recruitment domain 3 (NLRC3), as an essential part of the immune system, in ventilator-induced lung injury (VILI) of rats. In the present study, pathogen-free adult male SD rats were given saline or leptin, followed by ventilation. Lung tissue samples, bronchoalveolar lavage fluids (BALF), and blood were collected four hours after installation. Notable acute lung inflammation induced by mechanical ventilation is well-characterized by a massive increase in lung injury score and wet/dry weight (W/D) ratio. We also observed VILI was associated with interleukin (IL-1β and IL-18). Rats that received ventilation showed a decrease in the levels of NLRP3 and NLRC4, and an increased level of NLRC3. Pre-treatment with leptin could abolish all of these effects induced by VILI. It has been suggested that the regulation of NLRP3, NLRC4, and NLRC3 may underlie the protection observed during VILI by exogenous leptin.

Ginsenoside ameliorated ventilator-induced lung injury in rats

BackgroundGinsenosides have antioxidant and anti-inflammatory features. This study aimed to evaluate the biologic effects of ginsenoside Rb2 pretreatment on ventilator-induced lung injury (VILI) in rats.MethodsRats were divided into four groups with 12 rats per group: control; low tidal volume (TV), TV of 6 mL/kg, VILI, TV of 20 mL/kg, positive end-expiratory pressure of 5 cm H2O, and respiratory rate of 60 breaths per minute for 3 h at an inspiratory oxygen fraction of 0.21; and ginsenosides, treated the same as the VILI group but with 20 mg/kg intraperitoneal ginsenoside pretreatment. Morphology was observed with a microscope to confirm the VILI model. Wet-to-dry weight ratios, protein concentrations, and pro-inflammatory cytokines in the bronchoalveolar lavage fluid were measured. RNA sequencing of the lung tissues was conducted to analyze gene expression.ResultsHigh TV histologically induced VILI with alveolar edema and infiltration of inflammatory cells. Ginsenosides pretreatment significantly reduced the histologic lung injury score compared to the VILI group. Wet-to-dry weight ratios, malondialdehyde, and TNF-α in bronchoalveolar lavage fluid were significantly higher in the VILI group and ginsenoside pretreatment mitigated these effects. In the immunohistochemistry assay, ginsenoside pretreatment attenuated the TNF-α upregulation induced by VILI. We identified 823 genes differentially presented in the VILI group compared to the control group. Of the 823 genes, only 13 genes (Arrdc2, Cygb, Exnef, Lcn2, Mroh7, Nsf, Rexo2, Srp9, Tead3, Ephb6, Mvd, Sytl4, and Ube2l6) recovered to control levels in the ginsenoside group.ConclusionsGinsenosides inhibited the inflammatory and oxidative stress response in VILI. Further studies are required on the 13 genes, including LCN2.

Lipoxin A4 Reduces Ventilator-Induced Lung Injury in Rats with Large-Volume Mechanical Ventilation.

Ventilator-induced lung injury (VILI) is a severe and inevitable complication in patients who require mechanical ventilation (MV) for respiratory support. Lipoxin A4 is an endogenous anti-inflammatory and antioxidant mediator. The present study determined the effects of lipoxin A4 on VILI. Twenty-four rats were randomized to the sham, VILI, and lipoxin A4 (LX4) groups. The rats in the VILI and LX4 groups received large-volume MV for 4 hours to simulate VILI. Capillary permeability was evaluated using the PaO2/FiO2 ratio, lung wet/dry weight ratio, and protein level in the lung. VILI-induced inflammation was assessed by measuring cytokines in serum and lung tissue, the expression and activity of NF-κB, and phosphorylated myosin light chain. The oxidative stress response, lung tissue injury, and apoptosis in lung tissue were also estimated, and the expression of apoptotic proteins was examined. MV worsened all of the indices compared to the sham group. Compared to the VILI group, the LX4 group showed significantly improved alveolar-capillary permeability (increased PaO2/FiO2 and decreased wet/dry weight ratios and protein levels), ameliorated histological injury, and reduced local and systemic inflammation (downregulated proinflammatory factors and NF-κB expression and activity). Lipoxin A4 notably inhibited the oxidative stress response and apoptosis and balanced apoptotic protein levels in lung tissue. Lipoxin A4 protects against VILI via anti-inflammatory, antioxidant, and antiapoptotic effects.

Dexmedetomidine attenuates ventilator-induced lung injury in rats by up-regulating NLRC3.

Mechanical ventilation is a dispensable work in clinical treatment and rescue, and always caused of ventilator-induced lung injury (VILI). Dexmedetomidine is a clinical drug to prevent lung injury, but its mechanism still unclear. Thirty-six SD rats were randomly divided into three groups: self-breathing control group (Group C), high tidal volume (VT 20 mL/kg) group (Group H) and high VT + dexmedetomidine group (Group DEX). Serum, lung tissue, bronchoalveolar lavage fluid (BALF) were collected after rats were sacrificed by anesthetic drug of pentobarbital sodium. The pathological changes of lung tissue were observed by hematoxylin and eosin stain (HE staining), and the lung injury score and wet/dry (W/D) ratio were tested to assess lung injury. The total protein level in BALF and contents of the interleukin-1β (IL-1β), IL-18 in serum and BALF were detected by enzyme-linked immunosorbent assay (ELISA), the mRNA and protein expression level of NLR Family CARD Domain Containing 3 (NLRC3), NLR Family Pyrin Domain Containing 3 (NLRP3), Apoptosis associated speck-like protein containing a CARD domain (ASC) and caspase-1 were measured by qRT-PCR and Western Blotting respectively. Compared with Group C, VILI mode of Group H were success established because of lung injury score and W/D value increased. when compared with Group H, which were decreased significantly in Group DEX (P<0.05), and the total protein level in BALF and the contents of IL-1β, IL-18 in serum and BALF of Group DEX were reduced markedly (P<0.05), Besides the mRNA and protein expression of NLRP3, ASC and caspase-1 in lung tissue of Group DEX were lowered dramatically (P<0.05). However, mRNA and protein expression of NLRC3 in lung tissue of Group DEX were up-regulated observably (P<0.05). This study demonstrates that NLRC3 is involved in the VILI of rats, and dexmedetomidine can attenuate the VILI in rats by up-regulating the expression level of NLRC3.

Changes in expression of caspase recruitment domain protein 3 during ventilator-induced lung injury in rats

Objective To evaluate the changes in the expression of caspase recruitment domain protein 3 (NLRC3) during ventilator-induced lung injury (VILI) in rats. Methods Twenty-four clean-grade healthy adult male Sprague-Dawley rats, aged 8 weeks, weighing 180-220 g, were divided into 2 groups (n=12 each) according to the random number table method: control group (group C) and group VILI.Both groups underwent tracheotomy and intubation, group C kept spontaneous breathing, and the animals were mechanically ventilated, with tidal volume 20 ml/kg, respiratory rate 80 breaths/min, inspiratory/expiratory ratio 1∶1, fraction of inspired oxygen 21%, and positive end-expiratory pressure 0 in group VILI.The rats were sacrificed 4 h later, bronchoalveolar lavage fluid (BALF) was collected for determination of concentrations of interleukin-1beta (IL-1β)and IL-18 in BALF (by enzyme-linked immunosorbent assay), and lung tissues were obtained for examination of the pathological changes which were scored and for determination of wet to dry weight ratio (W/D ratio) and expression of nucleotide binding oligomerization domain-like receptor family caspase recruitment domain containing 3 (NLRC3), NOD-like receptor pyrin domain containing 3 (NLRP3), ASC and caspase-1 protein and mRNA (by Western blot and real-time polymerase chain reaction). Results Compared with group C, the score of pathological damage to lung tissues, W/D ratio, and concentrations of IL-1β and IL-18 in BALF were significantly increased, the expression of NLRP3, ASC and caspase-1 protein and mRNA in lung tissues was up-regulated, and the expression of NLRC3 protein and mRNA in lung tissues was down-regulated in group VILI (P<0.05). Conclusion The mechanism of VILI may be related to down-regulating NLRC3 expression and activating NLRP3 inflammasomes in rats. Key words: Ventilator-induced lung injury; NLR family, pyrin domain-containing 3 protein

Role of H1 receptor in inflammatory response during ventilator-induced lung injury in rats

Objective To evaluate the role of H1 receptor in inflammatory responses during ventilator-induced lung injury (VILI) in rats. Methods Thirty clean-grade healthy male Sprague-Dawley rats, aged 9-10 weeks, weighing 250-300 g, were divided into 3 groups (n=10 each) using a random number table method: control group (group C), VILI group (group V) and H1 receptor antagonist clemastine group (group Cle). The animals were anesthetized and tracheostomized, and the rats in group C kept spontaneous breathing.The rats were mechanically ventilated for 4 h with the tidal volume of 40 ml/kg, respiratory rate 40 breaths/min, inspiratory/expiratory ratio 1∶1, and inspired oxygen fraction ratio 21% in group V. In group Cle, clemastine 0.9 mg/kg was intramuscularly injected at 30 min before anesthesia, the animals were tracheostomized after being anesthetized, and then the rats were mechanically ventilated with the same ventilator settings as group V. The animals were sacrificed at 4 h of ventilation, bronchoalveolar lavage fluid (BALF) was collected for determination of concentrations of total protein, interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α), and the lung specimens were obtained for microscopic examination of pathologic changes and for determination of wet/dry weight ratio (W/D ratio). Results Compared with group C, the concentrations of total protein, IL-6 and TNF-α in BALF and W/D ratio were significantly increased in group V (P<0.05). Compared with group V, the concentrations of total protein, IL-6 and TNF-α in BALF and W/D ratio were significantly decreased in group Cle (P<0.05). The pathologic changes of lung tissues were significantly attenuated in group Cle as compared with group V. Conclusion H1 receptor is involved in the process of inflammatory responses during VILI in rats. Key words: Receptors, histamine H1; Ventilator-induced lung injury; Inflammation

BML-111 accelerates the resolution of inflammation by modulating the Nrf2/HO-1 and NF-κB pathways in rats with ventilator-induced lung injury

The timely resolution of pulmonary inflammation coordinated by endogenous pro-resolving mediators helps limit lung tissue injury, but few endogenous pro-resolving mediators that are normally operative during acute inflammation. The protective effects of BML-111 (5(S)-6(R)-7-trihydroxyheptanoic acid methyl ester), a potent commercially available anti-inflammatory and pro-resolving mediator, on ventilation-induced lung injury (VILI) have been extensively studied, but its characteristics as a pro-resolving mediator have not. Here, anesthetized Sprague-Dawley rats were ventilated with a high tidal volume (20 mL/kg, HVT) for 1 h and randomly allocated to recover for 6, 12, 24, 48, 72, 96 or 168 h; BML-111 was administered at the peak of inflammation to evaluate its pro-resolving effect on VILI. The one-hour HVT induced a maximal pulmonary inflammatory response at 12 h that was largely resolved by 72 h. BML-111 largely resolved the maximal inflammatory response at 48 h; the resolution interval (Ri) was shortened by 26 h. Similarly, HVT elicited a time course of changes in histopathology and pulmonary edema, and BML-111 alleviates these changes. Mechanistically, neutrophil apoptosis was significantly increased in BML-111-treated rats subjected to HVT. The apoptosis inhibitor z-VAD-fmk partially reversed the proapoptotic actions of BML-111 on neutrophil and the resolving effects of BML-111 on VILI but had no effect alone. Importantly, the HVT treatment activated the nuclear factor E2-related factor 2(Nrf2)/heme oxygenase-1(HO-1) and NF-κB signaling pathways in the lung tissue, and BML-111 further induced Nrf2 and HO-1 expression but inhibited the NF-κB pathway. Intriguingly, when we inhibited the Nrf2/HO-1 pathway with the HO-1 inhibitor zinc protoporphyrin IX (ZnPPIX), Nrf2 expression was further increased, but the inhibitory effects of BML-111 on the NF-κB pathway and on the subsequent inflammatory response, and the proapoptotic actions on neutrophil were reversed. The results suggest that BML-111 promotes the resolution of HVT-induced inflammation to mitigate VILI in rats, perhaps by modulating the Nrf2/HO-1 and NF-κB pathways and subsequently increasing neutrophil apoptosis.

Effects of Human Interleukin-10 on Ventilator-Associated Lung Injury in Rats.

Ventilator-induced lung injury (VILI) is one of the most serious complications of mechanical ventilation (MV) and can increase the mortality of patients with acute respiratory distress syndrome (ARDS). This work aimed to test the hypothesis that the anti-inflammatory properties of human interleukin-10 (hIL-10) can reduce VILI. Thirty-six healthy male Sprague-Dawley rats were randomly assigned into three groups (n = 12) as follows: a control group, a VILI group, and a hIL-10 group. Lung function was evaluated by oxygenation index and pulmonary edema, and morphological changes associated with lung injury were assessed by HE staining and quantitative histological lung injury score. Malondialdehyde (MDA) and Superoxide dismutase (SOD) were measured, and the levels of various inflammatory cytokines were assessed in BALF and plasma. The oxygenation index in the VILI group decreased significantly relative to the control group and improved substantially in the hIL-10 group (P < 0.01). Compared to the control group, MDA production was stimulated (P < 0.01), and SOD activity rapidly declined (P < 0.01) in the VILI group. After hIL-10, MDA content was lower than that seen in the VILI group (P < 0.01), and SOD activity was enhanced (P < 0.01). The VILI group had the highest cytokine levels, compared to either the hIL-10 group or the control group (P < 0.05). High tidal volume MV can induce VILI. hIL-10 may regulate the inflammatory response in the lung tissue, improve lung tissue oxygenation, and inhibit oxidative stress, therefore reducing VILI in rats. These experiments reveal a potential new treatment option for VILI.

Syndecan-2-positive, Bone Marrow-derived Human Mesenchymal Stromal Cells Attenuate Bacterial-induced Acute Lung Injury and Enhance Resolution of Ventilator-induced Lung Injury in Rats.

WHAT THIS ARTICLE TELLS US THAT IS NEW: BACKGROUND:: Human mesenchymal stromal cells demonstrate promise for acute respiratory distress syndrome, but current studies use highly heterogenous cell populations. We hypothesized that a syndecan 2 (CD362)-expressing human mesenchymal stromal cell subpopulation would attenuate Escherichia coli-induced lung injury and enhance resolution after ventilator-induced lung injury. In vitro studies determined whether CD362 human mesenchymal stromal cells could modulate pulmonary epithelial inflammation, wound healing, and macrophage phagocytosis. Two in vivo rodent studies determined whether CD362 human mesenchymal stromal cells attenuated Escherichia coli-induced lung injury (n = 10/group) and enhanced resolution of ventilation-induced injury (n = 10/group). CD362 human mesenchymal stromal cells attenuated cytokine-induced epithelial nuclear factor kappa B activation, increased epithelial wound closure, and increased macrophage phagocytosis in vitro. CD362 human mesenchymal stromal cells attenuated Escherichia coli-induced injury in rodents, improving arterial oxygenation (mean ± SD, 83 ± 9 vs. 60 ± 8 mmHg, P < 0.05), improving lung compliance (mean ± SD: 0.66 ± 0.08 vs. 0.53 ± 0.09 ml · cm H2O, P < 0.05), reducing bacterial load (median [interquartile range], 1,895 [100-3,300] vs. 8,195 [4,260-8,690] colony-forming units, P < 0.05), and decreasing structural injury compared with vehicle. CD362 human mesenchymal stromal cells were more effective than CD362 human mesenchymal stromal cells and comparable to heterogenous human mesenchymal stromal cells. CD362 human mesenchymal stromal cells enhanced resolution after ventilator-induced lung injury in rodents, restoring arterial oxygenation (mean ± SD: 113 ± 11 vs. 89 ± 11 mmHg, P < 0.05) and lung static compliance (mean ± SD: 0.74 ± 0.07 vs. 0.45 ± 0.07 ml · cm H2O, P < 0.05), resolving lung inflammation, and restoring histologic structure compared with vehicle. CD362 human mesenchymal stromal cells efficacy was at least comparable to heterogenous human mesenchymal stromal cells. A CD362 human mesenchymal stromal cell population decreased Escherichia coli-induced pneumonia severity and enhanced recovery after ventilator-induced lung injury.

High Tidal Volume Induces Mitochondria Damage and Releases Mitochondrial DNA to Aggravate the Ventilator-Induced Lung Injury.

This study aimed to determine whether high tidal volume (HTV) induce mitochondria damage and mitophagy, contributing to the release of mitochondrial DNA (mtDNA). Another aim of the present study was to investigate the role and mechanism of mtDNA in ventilator-induced lung injury (VILI) in rats. Rats were tracheotomized and allowed to breathe spontaneously or mechanically ventilated for 4 h. After that, lung injury was assessed. Inhibition of toll-like receptor 9 (TLR9), named ODN2088, was used to determine the involvement of TLR9/myeloid differentiation factor 88 (MyD88)/nuclear factor-κB (NF-κB) signaling pathway in VILI. The mitochondrial damage and release of mtDNA were assessed. Pharmacological inhibition of mtDNA (chloroquine) was used to determine whether mtDNA trigger inflammation via TLR9 in VILI. EDU-labeled mtDNA deriving from mitophagy was assessed by immunofluorescence. The role of mitophagy in VILI was shown by administration of antimycin A and cyclosporine A. Rats subjected to HTV showed more severe pulmonary edema and inflammation than the other rats. The decreased expression of TLR9, MyD88, and NF-κB were observed following the use of ODN2088. Mechanical ventilation (MV) with HTV damaged mitochondria which resulted in dysfunctional ATP synthesis, accumulation of reactive oxygen species, and loss of mitochondrial membrane potential. Moreover, the results of distribution of fluorescence in rats upon HTV stimulation indicated that mtDNA cleavage was associated with mitophagy. The expression levels of mitophagy related genes (LC3B-II/LC3B-I, PINK1, Parkin, and mitofusin 1) in animals ventilated with HTV were significantly upregulated. Administration of antimycin A aggregated the histological changes and inflammation after MV, but these effects were attenuated when administered in the presence of cyclosporine A. MV with HTV induces mitochondrial damage and mitophagy, contributing to the release of mtDNA, which may be induced VILI in rat via TLR9/MyD88/NF-κB signaling pathway.

Impact of Different Tidal Volume Levels at Low Mechanical Power on Ventilator-Induced Lung Injury in Rats.

Tidal volume (VT) has been considered the main determinant of ventilator-induced lung injury (VILI). Recently, experimental studies have suggested that mechanical power transferred from the ventilator to the lungs is the promoter of VILI. We hypothesized that, as long as mechanical power is kept below a safe threshold, high VT should not be injurious. The present study aimed to investigate the impact of different VT levels and respiratory rates (RR) on lung function, diffuse alveolar damage (DAD), alveolar ultrastructure, and expression of genes related to inflammation [interleukin (IL)-6], alveolar stretch (amphiregulin), epithelial [club cell secretory protein (CC)16] and endothelial [intercellular adhesion molecule (ICAM)-1] cell injury, and extracellular matrix damage [syndecan-1, decorin, and metalloproteinase (MMP)-9] in experimental acute respiratory distress syndrome (ARDS) under low-power mechanical ventilation. Twenty-eight Wistar rats received Escherichia coli lipopolysaccharide intratracheally. After 24 h, 21 animals were randomly assigned to ventilation (2 h) with low mechanical power at three different VT levels (n = 7/group): (1) VT = 6 mL/kg and RR adjusted to normocapnia; (2) VT = 13 mL/kg; and 3) VT = 22 mL/kg. In the second and third groups, RR was adjusted to yield low mechanical power comparable to that of the first group. Mechanical power was calculated as [(Δ/Est,L)/2]× RR (ΔP,L = transpulmonary driving pressure, Est,L = static lung elastance). Seven rats were not mechanically ventilated (NV) and were used for molecular biology analysis. Mechanical power was comparable among groups, while VT gradually increased. ΔP,L and mechanical energy were higher in VT = 22 mL/kg than VT = 6 mL/kg and VT = 13 mL/kg (p < 0.001 for both). Accordingly, DAD score increased in VT = 22 mL/kg compared to VT = 6 mL/kg and VT = 13 mL/kg [23(18.5–24.75) vs. 16(12–17.75) and 16(13.25–18), p < 0.05, respectively]. VT = 22 mL/kg was associated with higher IL-6, amphiregulin, CC16, MMP-9, and syndecan-1 mRNA expression and lower decorin expression than VT = 6 mL/kg. Multiple linear regression analyses indicated that VT was able to predict changes in IL-6 and CC16, whereas ΔP,L predicted pHa, oxygenation, amphiregulin, and syndecan-1 expression. In the model of ARDS used herein, even at low mechanical power, high VT resulted in VILI. VT control seems to be more important than RR control to mitigate VILI.

Endothelial Colony-forming Cells Attenuate Ventilator-induced Lung Injury in Rats with Acute Respiratory Distress Syndrome

Mechanical ventilation (MV) can cause ventilator-induced lung injury (VILI). This study investigated whether endothelial colony-forming cells (ECFC) could inhibit VILI in a rat model of acute respiratory distress syndrome (ARDS). Male Wistar rats received the femoral artery and venous cannulation (sham group) or were injected intravenously with 500μg/kg lipopolysaccharide to induce ARDS. The ARDS rats were subjected to MV. Immediately after the MV, the rats were randomized and injected intravenously with vehicle (ARDS group) or ECFC (ECFC group, n=8 per group). The oxygen index, lung wet-to-dry weight (W/D) ratios, cytokine protein levels in serum or bronchoalveolar lavage fluid (BALF), neutrophil counts, neutrophil elastase and total protein levels in BALF, histology and cell apoptosis in the lung were detected. The protein levels of endothelin-1, inducible nitric oxide synthase (iNOS), endothelial NOS, matrix metalloproteinase (MMP)-9, Bax, Bcl-2, gelsolin, cleaved caspase-3, phosphorylated NF-κBp65 and myosin light chain (MLC) in the lung were analyzed. Compared with the ARDS group, treatment with ECFC significantly increased the oxygen index, and decreased the lung W/D ratios and injury, and the numbers of apoptotic cells in the lungs, neutrophils counts, total protein and elastase concentrations in BALF of rats. ECFC treatment significantly minimized the protein levels of pro-inflammatory cytokines in BALF and serum, but increased interleukin 10 in rats. Furthermore, ECFC treatment significantly reduced the protein levels of endothelin-1, iNOS, Bax, Gelsolin, MMP-9, cleaved caspase-3, phosphorylated NF-κBp65 and MLC, but enhanced eNOS and Bcl-2 in the lungs of rats. Therefore, ECFC attenuated inflammation, cell apoptosis and VILI in ARDS rats.

Curcumin ameliorated ventilator-induced lung injury in rats

BackgroundCurcumin (CUR) is a Chinese medicine monomer with antioxidant and anti-inflammatory properties. The aim of this study was to investigate the effects and mechanisms of CUR treatment on ventilator-induced lung injury (VILI) in rats. MethodsTotal 50 SD rats were divided into five groups: sham, VILI, VILI+CUR-50 (CUR 50 mg/kg pretreated intraperitoneal), VILI+CUR-200 (CUR 200 mg/kg pretreated intraperitoneal) and VILI + DXM (5 mg/kg pretreated intraperitoneal). The morphology and ultrastructure were observed by microscope and transmission electron microscope. The wet to dry ratio, protein concentration in bronchoalveolar lavage fluid (BALF), evans blue dye (EBD) content, nuclear factor kappa B (NF-κB) activity, myeloperoxidase (MPO), malondialdehyde (MDA), xanthine oxidase (XO) and total antioxidative capacity (TAOC) levels were measured. ResultsHistological studies revealed that inflammatory cells infiltration and alveolar edema were significantly severe in VILI as compared to other groups. CUR-200 and DXM treatment reversed lung injury significantly. The wet to dry ratio, protein concentration in BALF, EBD content, MPO activity, tumor necrosis factor (TNF)-α level and NF-κB activity were significantly increased in VILI group as compared to other groups. CUR-200 and DXM treatment significantly suppressed permeability and inflammation induced by ventilation. Furthermore, the significantly higher MDA content in VILI could be markedly decreased by CUR-200 and DXM treatment while the levels of XO and TAOC were markedly recovered only by CUR (200 mg/kg) treatment after VILI. ConclusionCUR could inhibit the inflammatory response and oxidative stress during VILI, which is partly through NF-κB pathway.

Desflurane Attenuates Ventilator-Induced Lung Injury in Rats with Acute Respiratory Distress Syndrome.

Ventilator-induced lung injury aggravates the existing lung injury. This study investigated the effect of desflurane on VILI in a rat model of acute respiratory distress syndrome. Forty-eight rats were randomized into a sham (S) group, control (C) group, lipopolysaccharide/ventilation (LV) group, lipopolysaccharide/ventilation/desflurane (LVD) group, or lipopolysaccharide/low ventilation with and without desflurane (LLV and LLVD) groups. Rats in the S group received anesthesia only. Rats in the LV and LVD groups received lipopolysaccharide and were ventilated with a high tidal volume. Rats in LLV and LLVD groups were treated as the LV and LVD groups and ventilated with a low tidal volume. PaO2/FiO2, lung wet-to-dry weight ratios, concentrations of inflammatory factors in serum and BALF, histopathologic analysis of lung tissue, and levels of nuclear factor- (NF-) κB protein in lung tissue were investigated. PaO2/FiO2 was significantly increased by desflurane. Total cell count, macrophages, and neutrophils in BALF and proinflammatory factors in BALF and serum were significantly decreased by desflurane, while IL-10 was increased. The histopathological changes and levels of NF-κB protein in lung tissue were decreased by desflurane. The results indicated that desflurane ameliorated VILI in a rat model of acute respiratory distress syndrome.

Alpha 1-antitrypsin ameliorates ventilator-induced lung injury in rats by inhibiting inflammatory responses and apoptosis.

Mechanical ventilation is extensively used to treat patients with lung injury but may result in ventilator-induced lung injury (VILI). The present study investigated the protective effect of alpha 1-antitrypsin (AAT) on VILI. Adult male rats were subjected to sham, ventilation + saline, or ventilation + AAT treatment and lung injuries were evaluated. Peripheral blood and bronchoalveolar lavage fluid (BALF) were obtained to assess systemic and local inflammatory responses, respectively. Mechanical ventilation resulted in lung injury, as evidenced by histological abnormalities as well as elevations in PaO2/FiO2 ratio, the wet-to-dry weight ratio, and the BALF level of proteins. The intravenous administration of AAT significantly improved these parameters of lung function, suggesting a protective role of AAT in VILI. Mechanistically, ventilator-induced inflammation was effectively reduced by AAT, as evidenced by decreases in BALF neutrophil counts, BALF cytokines, and serum adhesion factors. In contrast, anti-inflammatory interleukin-10 in BALF was increased in response to AAT. AAT treatment also inhibited the expression of nuclear factor-κB, Bax, and cleaved caspase-3 while promoting Bcl-2 expression in ventilator-injured lung tissues. AAT treatment can ameliorate VILI by inhibiting inflammatory mediator production and apoptosis. Impact statement Mechanical ventilation has been commonly used to treat patients with lung injury but may result in ventilator-induced lung injury (VILI). Few effective treatment options are currently available to reduce VILI. Alpha 1-antitrypsin (AAT) is an inhibitor of serine protease with anti-inflammatory and antiapoptotic properties, suggesting a possible role in attenuating lung injury. The present study demonstrates that AAT inhibits the development of VILI by modulating inflammation- and apoptosis-related protein expression. Therefore, AAT may be a novel therapeutic agent for acute respiratory distress syndrome patients undergoing mechanical ventilation.

Relationship between shedding of syndecan-4 in lung tissues and ventilator-induced lung injury in rats

Objective To evaluate the relationship between the shedding of syndecan-4 (SDC-4) in lung tissues and ventilator-induced lung injury in rats. Methods Thirty pathogen-free healthy adult male Wistar rats, weighing 220-250 g, were divided into 3 groups (n=10 each) using a random number table: control group (group C), mechanical ventilation with traditional tidal volume (VT) group (group T-VT) and mechanical ventilation with high VT group (group H-VT). The animals were anesthetized with pentobarbital sodium and tracheostomized.The rats kept spontaneous breathing in group C. The rats were mechanically ventilated for 4 h with the VT set at 6 ml/kg in group T-VT and with the VT set at 40 ml/kg in group H-VT.Blood samples were collected immediately after the end of ventilation for measurement of serum SDC-4 concentrations by enzyme-linked immunosorbent assay.The left lung was lavaged, and broncho-alveolar lavage fluid was collected for determination of interleukin-1beta (IL-1β), IL-18, tumor necrosis factor-alpha and SDC-4 concentrations by enzyme-linked immunosorbent assay.The lungs were removed for determination of the wet to dry weight ratio and expression of SDC-4 protein and mRNA in lung tissues (by Western blot and real-time polymerase chain reaction, respectively) and for examination of the pathological changes.The lung injury scores were recorded. Results Compared with group C, the wet to dry weight ratio, lung injury scores, concentrations of IL-1β, IL-18, tumor necrosis factor-alpha and SDC-4 in broncho-alveolar lavage fluid and concentrations of SDC-4 in serum were significantly increased, the expression of SDC-4 mRNA was up-regulated, and the expression of SDC-4 was down-regulated in group H-VT (P 0.05). Marked pathological changes of lung tissues were found in group H-VT. Conclusion A large shedding of SDC-4 in lung tissues may be involved in the pathophysiological mechanism of ventilatior-induced lung injury in rats. Key words: Syndecan-4; Respiration, artificial; Respiratory distress syndrome, adult