NONISCHEMIC LUNG INJURY BY MEDIATORS FROM UNILATERAL ISCHEMIC REPERFUSED LUNG

Superoxide Dismutase Administration: A Review of Proposed Human Uses

Superoxide dismutases (SODs) are metalloenzymes that play a major role in antioxidant defense against oxidative stress in the body. SOD supplementation may therefore trigger the endogenous antioxidant machinery for the neutralization of free-radical excess and be used in a variety of pathological settings. This paper aimed to provide an extensive review of the possible uses of SODs in a range of pathological settings, as well as describe the current pitfalls and the delivery strategies that are in development to solve bioavailability issues. We carried out a PubMed query, using the keywords "SOD", "SOD mimetics", "SOD supplementation", which included papers published in the English language, between 2012 and 2020, on the potential therapeutic applications of SODs, including detoxification strategies. As highlighted in this paper, it can be argued that the generic antioxidant effects of SODs are beneficial under all tested conditions, from ocular and cardiovascular diseases to neurodegenerative disorders and metabolic diseases, including diabetes and its complications and obesity. However, it must be underlined that clinical evidence for its efficacy is limited and consequently, this efficacy is currently far from being demonstrated.

RNAi therapeutic strategies for acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS), replacing the clinical term acute lung injury, involves serious pathophysiological lung changes that arise from a variety of pulmonary and nonpulmonary injuries and currently has no pharmacological therapeutics. RNA interference (RNAi) has the potential to generate therapeutic effects that would increase patient survival rates from this condition. It is the purpose of this review to discuss potential targets in treating ARDS with RNAi strategies, as well as to outline the challenges of oligonucleotide delivery to the lung and tactics to circumvent these delivery barriers.

Does methylene blue attenuate inflammation in nonischemic lungs after lung transplantation?

Objective:

To evaluate whether methylene blue (MB) could minimize the effects of ischemia-reperfusion injury in the nonischemic lung on a lung transplantation rodent model.

Methods:

Forty female Sprague-Dawley rats were divided into 20 donors and 20 recipients. The 20 recipient rats were divided into two groups (n = 10) according to the treatment (0.9% saline vs. 1% MB solutions). All animals underwent unilateral lung transplantation. Recipients received 2 mL of saline or MB intraperitoneally prior to transplantation. After 2 h of reperfusion, the animals were euthanized and histopathological and immunohistochemical analyses were performed in the nonischemic lung.

Results:

There was a significant decrease in inflammation-neutrophil count and intercellular adhesion molecule-1 (ICAM-1) expression in lung parenchyma were higher in the saline group in comparison with the MB group-and in apoptosis-caspase-3 expression was higher in the saline group and Bcl-2 expression was higher in MB group.

Conclusions:

MB is an effective drug for the protection of nonischemic lungs against inflammation and apoptosis following unilateral lung transplantation in rats.

Inhibition of NKCC1 Modulates Alveolar Fluid Clearance and Inflammation in Ischemia-Reperfusion Lung Injury via TRAF6-Mediated Pathways

Background: The expression of Na-K-2Cl cotransporter 1 (NKCC1) in the alveolar epithelium is responsible for fluid homeostasis in acute lung injury (ALI). Increasing evidence suggests that NKCC1 is associated with inflammation in ALI. We hypothesized that inhibiting NKCC1 would attenuate ALI after ischemia-reperfusion (IR) by modulating pathways that are mediated by tumor necrosis-associated factor 6 (TRAF6).

Methods: IR-ALI was induced by producing 30 min of ischemia followed by 90 min of reperfusion in situ in an isolated and perfused rat lung model. The rats were randomly allotted into four groups comprising two control groups and two IR groups with and without bumetanide. Alveolar fluid clearance (AFC) was measured for each group. Mouse alveolar MLE-12 cells were cultured in control and hypoxia-reoxygenation (HR) conditions with or without bumetanide. Flow cytometry and transwell monolayer permeability assay were carried out for each group.

Results: Bumetanide attenuated the activation of p-NKCC1 and lung edema after IR. In the HR model, bumetanide decreased the cellular volume and increased the transwell permeability. In contrast, bumetanide increased the expression of epithelial sodium channel (ENaC) via p38 mitogen-activated protein kinase (p38 MAPK), which attenuated the reduction of AFC after IR. Bumetanide also modulated lung inflammation via nuclear factor-κB (NF-κB). TRAF6, which is upstream of p38 MAPK and NF-κB, was attenuated by bumetanide after IR and HR.

Conclusions: Inhibition of NKCC1 by bumetanide reciprocally modulated epithelial p38 MAPK and NF-κB via TRAF6 in IR-ALI. This interaction attenuated the reduction of AFC via upregulating ENaC expression and reduced lung inflammation.

Intravenous superoxide dismutase administration reduces contralateral lung injury induced by unilateral lung ischemia and reperfusion in rats through suppression of activity and protein expression of matrix metalloproteases

BACKGROUND

Ischemia and reperfusion (I/R) of the lungs induces massive superoxide radical production. On the other hand, matrix metalloproteases (MMPs) were shown to play an essential role in I/R-associated lung injury. We aimed to investigate the lung-protective efficacy of intravenous superoxide dismutase (SOD) administration and its relation with MMPs activity in the lungs subsequent to I/R injury.

METHODS

Twenty-two male Sprague-Dawley rats were divided into a sham group (n = 6), a unilateral lung I/R group (n = 8), and a SOD-treated lung I/R group (n = 8). Unilateral lung ischemia was conducted by occluding the left lung hilum for 90 min, followed by 5 hours of reperfusion through release of the occlusion. In the SOD-treated group, SOD was administered intravenously during the first hour of reperfusion. We assessed the protein contents in the broncho-alveolar lavage fluid (PCBAL) as a marker for protein permeability and lung wet-to-dry weight ratio (W/D) for lung water content. We also measured levels of lipid peroxidation and MMP activity in the lungs, by tissue malonedealdehyde (MDA) level with the use of enzyme-linked immunoassay, and the gelatin zymography technique, respectively.

RESULTS

Forty-eight hours of left-lung I/R significantly increased PCBAL (P < .001), W/D (P < .05), tissue MDA level (P < .05), and MMP-9 and MMP-2 activity. SOD treatment attenuated I/R-induced contralateral lung injury, reducing pulmonary permeability, lipid peroxidation, and MMP activities.

CONCLUSIONS

I/R injury of the left lung induced increases in W/D, PCBAL, MDA level, and MMP-9 activity in the right lung. SOD treatment during the first hour of a 5-hour reperfusion protected the lung through suppressing MMP-9 activity and reducing tissue lipid peroxidation.

Ulinastatin prevents acute lung injury led by liver transplantation

BACKGROUND

Little is known regarding the effect of ulinastatin (UTI) on acute lung injury (ALI) induced by orthotopic liver transplantation. This study aims to investigate the protective effect of UTI on ALI induced by orthotopic autologous liver transplantation (OALT) in a rat model and to explore the potential underlying mechanism.

MATERIALS AND METHODS

Rats were randomly allocated into the following four groups (n = 8 each): (i) sham control group (group sham); (ii) model group (underwent OALT) (group model); (iii) low-dose UTI-treated group (group u1), with UTI (50 U/g) administered intravenously both before the portal vein was occluded and after liver reperfusion started; and (iv) high-dose UTI-treated group (group uh), with UTI (100 U/g) given in the same way as group ul. The lung pathologic parameters, lung water content, and levels of tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6, malondialdehyde (MDA), superoxide dismutase (SOD) activity, RanBP-type and C3HC4-type zinc finger-containing protein 1 (RBCK1), and peroxiredoxin-2 (Prx-2) were assessed 8 h after OALT was performed.

RESULTS

According to histology, there was severe damage in the lung of group model accompanied by increases in the TNF-α, IL-1β, IL-6, and MDA levels and decreases in SOD activity and the expression of RBCK1 and Prx-2. UTI treatment significantly reduced the pathologic scores, lung water content, and TNF-α, IL-1β, IL-6, and MDA levels while restoring the SOD activity and expression of RBCK1 and Prx-2. Furthermore, compared with group u1, treatment with a high dose of UTI resulted in a better protective effect on the lung when assessed by the TNF-α, IL-1β, IL-6, and MDA levels and SOD activity.

CONCLUSIONS

UTI dose-dependently attenuates ALI that is induced by OALT in this rat model, which is mainly due to the suppression of the inflammatory response and oxidant stress, which may, in turn, be mediated by the upregulation of RBCK1 and Prx-2 expression.

Knockdown of myeloid differentiation protein-2 reduces acute lung injury following orthotopic autologous liver transplantation in a rat model

BACKGROUND

Acute lung injury (ALI) is a serious complication that commonly occurs during orthotopic liver transplantation (OLT). Toll-like receptor 2/4 (TLR2/4) are the main membrane receptors that respond to inflammatory stimuli and mediate NF-kappa B (NF-κB) signal pathway. We previously showed that TLR2/4 expression on monocytes and serum cytokine levels were increased in patients with ALI induced by OLT. Myeloid differentiation protein-2 (MD-2) expresses the functional domains that combines TLRs and play a key regulatory role in TLRs activation. Therefore, we hypothesized that blocking MD-2 would inhibit the TLR2/4-mediated inflammatory response and lessen ALI induced by liver transplantation.

METHOD

Thirty-two Sprague Dawley (SD) rats were randomly divided into four groups. One group received a sham operation (Group S), and the other three groups underwent orthotopic autologous liver transplantation (OALT) 48 h after intratracheal administration of saline (Model group; Group M), non-targeting siRNA (negative siRNA control group; Group NC) or siRNA against MD-2 (intervention group; Group RNAi). Lung pathology, lung water content, PaO2, and expression levels of MD-2, TLR2/4, NF-κB, TNF-α, IL-1β and IL-6 were assessed 8 h after OALT.

RESULTS

In Groups M and NC, OALT produced marked lung pathology with decreased PaO2 levels and increased MD-2, TLR2/4 gene and protein expression levels. Furthermore, the nuclear translocation of the NF-κB P65 subunit, was increased, as were lung concentrations of TNF-α, IL-1β and IL-6. The pathology of ALI and the severity of the above biochemical changes induced by OALT were significantly reduced in the group treated with MD-2 siRNA.

CONCLUSION

MD-2 gene knock-down attenuated the increase in TLR2/4 activation and reduced ALI after OALT.

The role and source of tumor necrosis factor-α in hemorrhage-induced priming for septic lung injury

Tumor necrosis factor α (TNF-α) has been reported to be a key component of the functional priming, of both myeloid and nonmyeloid cells, that is thought to contribute to the lung's increased susceptibility to injury following shock. Not surprisingly, we found that mice deficient in TNF-α exhibited reduced acute lung injury (ALI) resultant from the combined insults of hemorrhagic shock and sepsis. However, we found that when we adoptively transferred neutrophils from mice expressing TNF-α to neutrophil-depleted mice that lacked TNF-α, they were not able to serve as priming stimulus for the development of ALI. Based on these findings, we proposed that resident lung tissue cells mediate TNF-α priming. To begin to unravel the complex signaling pathway of various resident lung tissue cells in TNF-α-induced priming, we compared the effect of local (intratracheal [i.t.]) versus systemic [intravenous (i.v.)] delivery of TNF-α small interference (siRNA). We hypothesized that alternately suppressing expression of TNF-α in lung endothelial (i.v.) or epithelial (i.t.) cells would produce a differential effect in shock-induced ALI. We found that when in vivo siRNA i.t. or i.v. against TNF-α was administered to C57/BL6 mice at 2 h after hemorrhage, 24 h before septic challenge, that systemic/i.v., but not i.t., delivery of TNF-α siRNA following hemorrhage priming significantly reduces expression of indices of ALI compared with controls. These findings suggest that an absence of local lung tissue TNF-α significantly reduces lung tissue injury following hemorrhage priming for ALI and that pulmonary endothelial and/or other possible vascular resident cells, not epithelial cells, play a greater role in mediating the TNF-α priming response in a mouse model of hemorrhage/sepsis-induced ALI.

Bradykinin decreases podocyte permeability through ADAM17-dependent epidermal growth factor receptor activation and zonula occludens-1 rearrangement

Recent data show that increases in bradykinin (BK) concentration contribute to the beneficial effects of angiotensin-converting enzyme inhibitor (ACEI) treatment in chronic kidney disease. However, the possible role of BK in attenuated proteinuria, often seen in ACEI-treated patients, is not well studied. Here, we report that BK decreases mouse podocyte permeability through rearrangement of the tight junction protein zonula occludens-1 (ZO-1) and identify some of the major signaling events leading to permeability change. We show that BK2 receptor (BK2R) stimulation transactivates the epidermal growth factor receptor (EGFR). EGFR transactivation is mediated by a disintegrin and metalloenzyme (ADAM) family members, which are required for both extracellular signal-regulated kinase (ERK) and EGFR activation by BK. Using a gene-silencing approach we observed that both BK-induced ERK activation and BK-induced permeability decrease in podocytes is attenuated by ADAM17 down-regulation, and we identified epiregulin (ER) as the EGFR ligand participating in ADAM-dependent BK2R-EGFR cross-talk. EGFR inhibition attenuated both ZO-1 rearrangement and BK-induced permeability decreases in podocyte. We propose that ZO-1 redistribution is an important element of BK-induced permeability change and the signaling events involved in ZO-1 rearrangement include transactivation of the EGFR via ADAM17 activation and ER shedding. Our data indicate that ADAM17 and the EGFR may be potential novel therapeutic targets in diabetic nephropathy and other chronic kidney diseases.

Lung-lung interaction in isolated perfused unilateral hyperventilated rat lungs

The technique of conducting high tidal volume (TV) ventilation-induced lung inflammation including remote organs is still open to discussion, and our aim is to investigate this issue in isolated ventilated rat lungs perfused with salt solution. Selective right lung (RL) hyperventilation (TV of 15 mL/kg with air containing 5% CO(2) on zero or 2.5 cm H(2)0 end expiratory pressure [ZEEP or PEEP] in addition to left lung (LL) on 2.5 cm H(2)0 continuous positive airway pressure (CPAP) for 60 min, was realized after 30 min both lungs ventilation by occluding the left main bronchus, and it was allocated to the following 5 groups: groups 1 and 2 underwent hyperventilation under ZEEP, groups 3 and 4 underwent hyper ventilation under PEEP with recirculation or nonrecirculation (R-ZEEP or NR-ZEEP and R-PEEP or NR-PEEP), and group 5 served as the control group. Recirculation means the same perfusate recirculates the system throughout the procedure. The wet/dry ratio and protein content of bronchoalveolar lavage fluid (Prot-BALF), cytokine messenger RNAs (mRNAs), localization of tumor necrosis factor-alpha (TNF-alpha) by immunofluorescence double staining, and TNF-alpha concentration in the perfusate and BALF in each lung were measured and compared between groups by Kruskal-Wallis test. Lung injury (increased wet/dry ratio, Prot-BALF, and TNF-alpha on endothelial and epithelial cells) was shown in the hyperventilated RLs with ZEEP compared with their corresponding CPAP LLs. PEEP prevented these injuries. Lung injury was also demonstrated in the recirculated LL compared with the nonrecirculated LL (Prot-BALF, TNF-alpha and interleukin-1beta [IL-1beta] mRNAs: the LL of the R-ZEEP is greater than the LL of NR-ZEEP by P < 0.01). Unilateral hyperventilated lungs with ZEEP induced TNF-alpha, increased permeability, and injured the control lung via perfusion.

Salvage of nonischemic control lung from injury by unilateral ischemic lung with apocynin, a nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibitor, in isolated perfused rat lung

Ischemia reperfusion (I/R) injury of the lung affects the function of the nonischemic lung. Our objective is to determine how apocynin, which is a nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibitor, protects the nonischemic control right lung (RL) from injury by the unilateral ischemic left lung (LL). In isolated ventilated (by air containing 5% CO(2)) rat lungs, in which differential perfusion of the RL or LL was feasible, the LL was selectively made ischemic (60 min) and reperfused (30 min) in a nonrecirculating or recirculating manner with buffer (Krebs-Henseleit) solution, or in a recirculating manner with buffer that contained apocynin (10 mmol/L) or apocynin + TACEI (tumor necrosis factor)-alpha converting enzyme inhibitor; 10 microg/mL) (each group: n = 12) or with buffer that contained SOD (superoxide dismutase, 3000 U before ischemia and at reperfusion) or SOD + TACEI (each group: n = 5). The permeability of pulmonary endothelium/epithelium (wet/dry ratio and protein content of bronchoalveolar lavage fluid of each lung), perfusion pressure, and cytokine messenger RNA (mRNA) expression was increased not only in the LL (compared with nonischemic control RL, P < 0.01 with paired-samples T) but also in the RL in recirculating groups (compared with RL in the nonrecirculating group). Apocynin + TACEI as well as SOD + TACEI prevented those permeability increases in the RL by the ischemic LL. However, apocynin with or without TACEI as well as SOD with or without TACEI could only partially ameliorate I/R injury in the LL (P < 0.01 by 1-way analysis of variance (ANOVA)). TNF-alpha and possibly reactive oxygen species produced and released from the ischemic lung may synergistically induce control RL (remote organ) damage.

Lung injury after in vivo reperfusion: outcome at 27 hours after reperfusion

BACKGROUND

Although short-term findings after lung reperfusion have been extensively reported, in vivo animal studies have not described outcome beyond the immediate time period. Therefore, the authors evaluated lung injury 27 h after reperfusion. They also investigated whether attenuation of lung injury with the A3 adenosine receptor agonist MRS3558 was sustained beyond the immediate time period.

METHODS

In intact-chest, spontaneously breathing cats in which the left lower lung lobe was isolated and subjected to 2 h of ischemia and 3 h of reperfusion, MRS3558 was administered before reperfusion. Animals were killed 3 or 27 h after reperfusion.

RESULTS

When compared with 3 h of reperfusion, at 27 h the left lower lobe showed reduced apoptosis and no change in inflammation, but increased edema. Increased edema of the nonischemic right lung and hypoxemia were observed at 27 h after left lower lobe reperfusion. Increases in phosphorylated p38 levels were found at 3 h of reperfusion compared with control lung, with further increases at 27 h. The attenuation of injury observed with MRS3558 treatment at 3 h of reperfusion was sustained at 27 h.

CONCLUSIONS

Lung edema may worsen hours after the immediate postreperfusion period, even though lung apoptosis and inflammation are reduced or show no change, respectively. This was associated with further increases in phosphorylated p38 levels. The nonischemic lung may also be affected, suggesting a systemic response to reperfusion. In addition, early attenuation of injury is beneficial beyond the immediate period after reperfusion. Treatment aimed at inhibiting p38 activation, such as A3 receptor activation, should be further studied to explore its potential long-term beneficial effect.

The endothelium in acute lung injury/acute respiratory distress syndrome

PURPOSE OF REVIEW

Since pulmonary edema from increased endothelial permeability is the hallmark of acute lung injury, a frequently encountered entity in critical care medicine, the study of endothelial responses in this setting is crucial to the development of effective endothelial-targeted treatments.

RECENT FINDINGS

From the enormous amount of research in the field of endothelial pathophysiology, we have focused on work delineating endothelial alterations elicited by noxious stimuli implicated in acute lung injury. The bulk of the material covered deals with molecular and cellular aspects of the pathogenesis, reflecting current trends in the published literature. We initially discuss pathways of endothelial dysfunction in acute lung injury and then cover the mechanisms of endothelial protection. Several experimental treatments in animal models are presented, which aid in the understanding of the disease pathogenesis and provide evidence for potentially useful therapies.

SUMMARY

Mechanistic studies have delivered several interventions, which are effective in preventing and treating experimental acute lung injury and have thus provided objectives for translational studies. Some of these modalities may evolve into clinically useful tools in the treatment of this devastating illness.