Alterations in the proteome of pulmonary alveolar type II cells in the rat after hepatic ischemia-reperfusion

Alleviation of remote lung injury following liver ischemia/reperfusion: Possible protective role of vildagliptin

Lung injury is a serious condition encountered following hepatic ischemia/reperfusion (IR). This study aimed to explore whether a dipeptidyl peptidase-4 inhibitor agent vildagliptin (V) could alleviate the lung injury caused by hepatic IR in a rat model and if so elucidate its molecular protective mechanism. Three groups of rats were used. Sham group: received normal saline and exposed to a sham operation, IR group: received normal saline and subjected to the operation of hepatic I (45 min)/ R (180 min), V+IR group: received for 10 days intraperitoneal injection of V (10 mg/kg/day). After reperfusion, liver and lung were collected for biochemical and histological evaluation. Hepatic IR exhibited significant elevation in serum alanine aminotransferase (ALT), alkaline phosphatase (ALP), and lactate dehydrogenase (LDH) enzyme levels, serum and lung malondialdehyde (MDA) and tumor necrosis factor-alpha (TNF-α) in addition to lung nitric oxide (NO) levels, hypoxia-inducible factor 1-alpha (HIF-1α) mRNA and protein levels, hepatocyte growth factor (HGF) mRNA expression, and inducible nitric oxide synthase (iNOS) mRNA and protein expressions in lung tissue along with a marked reduction in the serum and lung content of catalase in comparison to the sham group. Moreover, liver and lung injury in the IR group was detected by histopathological examination. Vildagliptin ameliorated markedly the biochemical changes as well as liver and lung architecture in comparison to the IR group. Vildagliptin mitigated the induced lung injury by hepatic IR via suppression of oxidative stress markers, pro-inflammatory cytokine TNF-α as well as the HIF1-α/iNOS/HGF expressions in lung tissue.

Treatment with Bioartificial Liver Improves Lung Injury in a Swine Model of Partial Hepatectomy and Ischemia/Reperfusion

Purpose

Hepatic ischemia/reperfusion injury can lead to remote lung injury by inducing oxidative stress and inflammation. this study aims to investigate whether support of liver function with a bioartificial liver can attenuate remote lung injury after extended hepatectomy.

Methods

Fourteen domestic pigs were subjected to liver ischemia for 150 minutes and 70–75% hepatectomy. Six hours after initiation of hepatic reperfusion the animals were randomly allocated to a 6-hour treatment with a bioartificial liver (group B, n=7) or observation (group C, n=7). Hemodynamic and metabolic parameters were monitored for 24 hours following reperfusion. Lung biopsies were used for histological, nitrotyrosine and mrNA analysis.

Results

Oxygenation gradually deteriorated in group C, but was not significantly impaired in group B. Histological evaluation revealed improvements in alveolar collapse, necrotized pneumonocytes and lymphocyte infiltration in group B. Nitrotyrosine content of the lung was lower in group B compared to group C (55±12 vs. 132±22 nM/mg protein, p<0.01). Lung mRNA expression of interleukin-6, Stat-3 and E-selectin also decreased in group B. Expression of transforming growth factor-α mRNA did not differ between groups.

Conclusions

Application of a bioartificial liver was associated with improvement in several parameters of post-hepatectomy lung injury. the mechanisms appear to involve reduced nitrosative stress and attenuation of the native inflammatory process in the lung.

Ischemia/Reperfusion

Ischemic disorders, such as myocardial infarction, stroke, and peripheral vascular disease, are the most common causes of debilitating disease and death in westernized cultures. The extent of tissue injury relates directly to the extent of blood flow reduction and to the length of the ischemic period, which influence the levels to which cellular ATP and intracellular pH are reduced. By impairing ATPase-dependent ion transport, ischemia causes intracellular and mitochondrial calcium levels to increase (calcium overload). Cell volume regulatory mechanisms are also disrupted by the lack of ATP, which can induce lysis of organelle and plasma membranes. Reperfusion, although required to salvage oxygen-starved tissues, produces paradoxical tissue responses that fuel the production of reactive oxygen species (oxygen paradox), sequestration of proinflammatory immunocytes in ischemic tissues, endoplasmic reticulum stress, and development of postischemic capillary no-reflow, which amplify tissue injury. These pathologic events culminate in opening of mitochondrial permeability transition pores as a common end-effector of ischemia/reperfusion (I/R)-induced cell lysis and death. Emerging concepts include the influence of the intestinal microbiome, fetal programming, epigenetic changes, and microparticles in the pathogenesis of I/R. The overall goal of this review is to describe these and other mechanisms that contribute to I/R injury. Because so many different deleterious events participate in I/R, it is clear that therapeutic approaches will be effective only when multiple pathologic processes are targeted. In addition, the translational significance of I/R research will be enhanced by much wider use of animal models that incorporate the complicating effects of risk factors for cardiovascular disease. © 2017 American Physiological Society. Compr Physiol 7:113-170, 2017.

Propofol attenuated liver transplantation-induced acute lung injury via connexin43 gap junction inhibition

BACKGROUND

Postoperative acute lung injury (ALI) is a severe complication after liver transplantation, which influences patient survival rate obviously. However, its mechanisms are unclear and effective therapies are still lacking. The current study focused on effects of propofol on liver transplantation-induced ALI and whether its underlying mechanism was relative with connexin43 (Cx43) alternation. The authors postulated that endotoxin induced enhancement of Cx43 gap junction (GJ) plays a critical role in mediating post liver transplantation ALI and that pretreatment with the anesthetic propofol, known to inhibit gap junction, can confer effective protection.

METHODS

Male Sprague-Dawley rats underwent autologous orthotopic liver transplantation (AOLT) in the absence or presence of treatments with the selective Cx43 inhibitor, enanthol (0.1 mg/kg) and propofol (50 mg/kg), a commonly used anesthetic in clinical anesthesia. In vitro study, BEAS-2B cells, a kind of lung epithelial cell line expressing Cx43, exposed to lipopolysaccharide (LPS), which mainly contributed to ALI. Function of Cx43 GJ was regulated by Cx43 specific inhibitors, gap26 (300 μM) or enhancer, retinoic acid (10 μM) and two specific siRNAs.

RESULTS

Compared with the sham group, AOLT results in ALI obviously with plasma endotoxin increase. Cx43 inhibition decreased ALI through inflammatory reaction reduction. In vitro studies, LPS-induced BEAS-2B cells damage was attenuated by Cx43 function inhibition, but amplified by enhancement. Another important finding was propofol reduced Cx43 function and protected against LPS-mediated BEAS-2B cells damage or AOLT-induced ALI, mechanisms of which were also associated with inflammatory reaction decrease.

CONCLUSION

Cx43 plays a vital role in liver transplantation-induced ALI. Propofol decreased Cx43 function and protected against ALI in vivo and in vitro. This finding provide a new basis for targeted intervention of organ protection in liver transplantation, even in other kinds of operations.

TLR4 as receptor for HMGB1-mediated acute lung injury after liver ischemia/reperfusion injury

Acute lung injury (ALI) frequently occurs after liver transplantation and major liver surgery. Proinflammatory mediators released by damaged liver after liver ischemia/reperfusion (I/R) injury might contribute to this form of ALI, but the underlying mechanisms have not been well characterized. High-mobility group box protein 1 (HMGB1), a recently identified proinflammatory cytokine, was found to be significantly higher in the serum after liver I/R injury. This study investigated whether HMGB1 was involved as a stimulating factor, and whether its downstream Toll-like receptor 4 (TLR4), p38 mitogen-activated protein kinase (p38MAPK), and activator protein-1 (AP-1) signaling pathways act as mediators in the development of liver I/R injury-induced ALI. Extensive ALI and lung inflammation was induced in a rat model of liver I/R injury. Serum HMGB1 was significantly higher after liver I/R injury, and more importantly, expression of HMGB1 mRNA and protein in the lung tissue was also significantly increased. We further found that liver I/R injury enhanced the expression of TLR4 mRNA and protein, and the activity of p38MAPK and AP-1 in the lung tissue. Inhibition of TLR4 expression in the lung tissue by infection with pGCSIL-GFP-lentivirus-expressing small hairpin RNAs targeting the TLR4 gene (TLR4-shRNA lentivirus) significantly attenuated ALI, lung inflammation, and activity of p38MAPK and AP-1 in the lung tissue. These findings indicate that HMGB1 might contribute to the underlying mechanism for liver I/R injury-induced ALI and that its downstream TLR4, p38MAPK, and AP-1 signaling pathways are potentially important mediators in the development of ALI.

Cell biology of ischemia/reperfusion injury

Disorders characterized by ischemia/reperfusion (I/R), such as myocardial infarction, stroke, and peripheral vascular disease, continue to be among the most frequent causes of debilitating disease and death. Tissue injury and/or death occur as a result of the initial ischemic insult, which is determined primarily by the magnitude and duration of the interruption in the blood supply, and then subsequent damage induced by reperfusion. During prolonged ischemia, ATP levels and intracellular pH decrease as a result of anaerobic metabolism and lactate accumulation. As a consequence, ATPase-dependent ion transport mechanisms become dysfunctional, contributing to increased intracellular and mitochondrial calcium levels (calcium overload), cell swelling and rupture, and cell death by necrotic, necroptotic, apoptotic, and autophagic mechanisms. Although oxygen levels are restored upon reperfusion, a surge in the generation of reactive oxygen species occurs and proinflammatory neutrophils infiltrate ischemic tissues to exacerbate ischemic injury. The pathologic events induced by I/R orchestrate the opening of the mitochondrial permeability transition pore, which appears to represent a common end-effector of the pathologic events initiated by I/R. The aim of this treatise is to provide a comprehensive review of the mechanisms underlying the development of I/R injury, from which it should be apparent that a combination of molecular and cellular approaches targeting multiple pathologic processes to limit the extent of I/R injury must be adopted to enhance resistance to cell death and increase regenerative capacity in order to effect long-lasting repair of ischemic tissues.

Balance of life and death in alveolar epithelial type II cells: proliferation, apoptosis, and the effects of cyclic stretch on wound healing

After acute lung injury, repair of the alveolar epithelium occurs on a substrate undergoing cyclic mechanical deformation. While previous studies showed that mechanical stretch increased alveolar epithelial cell necrosis and apoptosis, the impact of cell death during repair was not determined. We examined epithelial repair during cyclic stretch (CS) in a scratch-wound model of primary rat alveolar type II (ATII) cells and found that CS altered the balance between proliferation and cell death. We measured cell migration, size, and density; intercellular gap formation; cell number, proliferation, and apoptosis; cytoskeletal organization; and focal adhesions in response to scratch wounding followed by CS for up to 24 h. Under static conditions, wounds were closed by 24 h, but repair was inhibited by CS. Wounding stimulated cell motility and proliferation, actin and vinculin redistribution, and focal adhesion formation at the wound edge, while CS impeded cell spreading, initiated apoptosis, stimulated cytoskeletal reorganization, and attenuated focal adhesion formation. CS also caused significant intercellular gap formation compared with static cells. Our results suggest that CS alters several mechanisms of epithelial repair and that an imbalance occurs between cell death and proliferation that must be overcome to restore the epithelial barrier.

Iron chelation prevents lung injury after major hepatectomy

AIM

Oxidative stress has been implicated in lung injury following ischemia/reperfusion and resection of the liver. We tested whether alleviating oxidative stress with iron chelation could improve lung injury after extended hepatectomy.

METHODS

Twelve adult female pigs subjected to liver ischemia for 150 min, 65-70% hepatectomy and reperfusion of the remnant liver for 24 h were randomized to a desferrioxamine (DF) group (n = 6) which received i.v. desferrioxamine to a total dose of 100 mg/kg during both ischemia and reperfusion, and a control (C) group (n = 6). We recorded hemodynamic and respiratory parameters, plasma interleukin-6 and malondialdehyde levels, as well as liver malondialdehyde and protein carbonyls content. Total non-heme iron was measured in lung and liver. Pulmonary tissue was evaluated histologically for its nitrotyrosine and protein carbonyls content and for superoxide dismutase (SOD) and platelet-activating factor acetylhydrolase (PAF-AcH) activities.

RESULTS

Reperfusion of the remnant liver resulted in gradual deterioration of gas-exchange and pulmonary vascular abnormalities. Iron chelation significantly decreased the oxidative markers in plasma, liver and the lung and lowered activities of pulmonary SOD and PAF-AcH. The improved liver function was followed by improved arterial oxygenation and pulmonary vascular resistance. DF also improved alveolar collapse and inflammatory cell infiltration, while serum interleukin-6 increased.

CONCLUSION

In an experimental pig model that combines liver resection with prolonged ischemia, iron chelation during reperfusion of the remnant liver is associated with improvement of several parameters of oxidative stress, lung injury and arterial oxygenation.