Inhibition of Na-K-Cl cotransporter isoform 1 reduces lung injury induced by ischemia-reperfusion

Aqueous extract of Descuraniae Semen attenuates lipopolysaccharide-induced inflammation by inhibiting ER stress and WNK4-SPAK-NKCC1 pathway

Sepsis causes systemic inflammatory responses and acute lung injury (ALI). Despite modern treatments, sepsis-related ALI mortality remains high. Aqueous extract of Descuraniae Semen (AEDS) exerts anti-endoplasmic reticulum (ER) stress, antioxidant and anti-inflammatory effects. AEDS alleviates inflammation and oedema in ALI. Sodium-potassium-chloride co-transporter isoform 1 (NKCC1) is essential for regulating alveolar fluid and is important in ALI. The NKCC1 activity is regulated by upstream with-no-lysine kinase-4 (WNK4) and STE20/SPS1-related proline/alanine-rich kinase (SPAK). This study aimed to investigate the effects of AEDS on lipopolysaccharide (LPS)-induced ALI model in A549 cells, considering the regulation of ER stress, WNK4-SPAK-NKCC1 cascades, inflammation and apoptosis. Cell viability was investigated by the CCK-8 assay. The expressions of the proteins were assessed by immunoblotting analysis assays. The levels of pro-inflammatory cytokines were determined by ELISA. The expression of cytoplasmic Ca2+ in A549 cells was determined using Fluo-4 AM. AEDS attenuates LPS-induced inflammation, which is associated with increased pro-inflammatory cytokine expression and activation of the WNK4-SPAK-NKCC1 pathway. AEDS inhibits the WNK4-SPAK-NKCC1 pathway by regulating of Bcl-2, IP3R and intracellular Ca2+. WNK4 expression levels are significantly higher in the WNK4-overexpressed transfected A549 cells and significantly decrease after AEDS treatment. AEDS attenuates LPS-induced inflammation by inhibiting the WNK4-SPAK-NKCC1 cascade. Therefore, AEDS is regarded as a potential therapeutic agent for ALI.

Single-cell analysis reveals the immune heterogeneity and interactions in lungs undergoing hepatic ischemia-reperfusion

Hepatic ischemia-reperfusion IR (HIR) is an unavoidable pathophysiological process during liver transplantation, resulting in systematic sterile inflammation and remote organ injury. Acute lung injury (ALI) is a serious complication after liver transplantation with high postoperative morbidity and mortality. However, the underlying mechanism is still unclear. To assess the phenotype and plasticity of various cell types in the lung tissue microenvironment after HIR at the single-cell level, single-cell RNA sequencing (scRNA-seq) was performed using the lungs from HIR-induced mice. In our results, we identified 23 cell types in the lungs after HIR and found that this highly complex ecosystem was formed by subpopulations of bone marrow-derived cells that signaled each other and mediated inflammatory responses in different states and different intervals. We described the unique transcriptional profiles of lung cell clusters and discovered two novel cell subtypes (Tspo+Endothelial cells and Vcan+ monocytes), as well as the endothelial cell-immune cell and immune cell-T cell clusters interactome. In addition, we found that S100 calcium binding protein (S100a8/a9), specifically and highly expressed in immune cell clusters of lung tissues and exhibited detrimental effects. Finally, the cellular landscape of the lung tissues after HIR was established, highlighting the heterogeneity and cellular interactions between major immune cells in HIR-induced lungs. Our findings provided new insights into the mechanisms of HIR-induced ALI and offered potential therapeutic target to prevent ALI after liver transplantation.

Primary Graft Dysfunction in Lung Transplantation: A Review of Mechanisms and Future Applications

Lung allograft recipients have worse survival than all other solid organ transplant recipients, largely because of primary graft dysfunction (PGD), a major form of acute lung injury affecting a third of lung recipients within the first 72 h after transplant. PGD is the clinical manifestation of ischemia-reperfusion injury and represents the predominate cause of early morbidity and mortality. Despite PGD's impact on lung transplant outcomes, no targeted therapies are currently available; hence, care remains supportive and largely ineffective. This review focuses on molecular and innate immune mechanisms of ischemia-reperfusion injury leading to PGD. We also discuss novel research aimed at discovering biomarkers that could better predict PGD and potential targeted interventions that may improve outcomes in lung transplantation.

Inhibition of the cGAS-STING Pathway Attenuates Lung Ischemia/Reperfusion Injury via Regulating Endoplasmic Reticulum Stress in Alveolar Epithelial Type II Cells of Rats

Purpose

Endoplasmic reticulum stress (ERS) plays an important role in the pathogenesis of lung ischemia/reperfusion (I/R) injury. Cyclic GMP-AMP synthase (cGAS) is a cytosol dsDNA sensor, coupling with downstream stimulator of interferon genes (STING) located in the ER, which involves innate immune responses. The aim of our present study was to investigate the effects of cGAS on lung I/R injury via regulating ERS.

Methods

We used Sprague-Dawley rats to make the lung I/R model by performing left hilum occlusion-reperfusion surgery. cGAS-specific inhibitor RU.521, STING agonist SR-717, and 4-phenylbutyric acid (4-PBA), the ERS inhibitor, were intraperitoneally administered in rats. Double immunofluorescent staining was applied to detect the colocalization of cGAS or BiP, an ERS protein, with alveolar epithelial type II cells (AECIIs) marker. We used transmission electron microscopy to examine the ultrastructure of ER and mitochondria. Apoptosis and oxidative stress in the lungs were assessed, respectively. The profiles of pulmonary edema and lung tissue injury were evaluated. And the pulmonary ventilation function was measured using a spirometer system.

Results

In lung I/R rats, the cGAS-STING pathway was upregulated, which implied they were activated. After cGAS-STING pathway was inhibited or activated in lung I/R rats, the ERS was alleviated after cGAS was inhibited, while when STING was activated after lung I/R, ERS was aggravated in the AECIIs, these results suggested that cGAS-STING pathway might trigger ERS responses. Furthermore, activation of cGAS-STING pathway induced increased apoptosis, inflammation, and oxidative stress via regulating ERS and therefore resulted in pulmonary edema and pathological injury in the lungs of I/R rats. Inhibition of cGAS-STING pathway attenuated ERS, therefore attenuated lung injury and promoted pulmonary ventilation function in I/R rats.

Conclusion

Inhibition of the cGAS-STING pathway attenuates lung ischemia/reperfusion injury via alleviating endoplasmic reticulum stress in alveolar epithelial type II cells of rats.

NF-κB Signaling-Mediated Activation of WNK-SPAK-NKCC1 Cascade in Worsened Stroke Outcomes of Ang II-Hypertensive Mice

BACKGROUND

Worsened stroke outcomes with hypertension comorbidity are insensitive to blood pressure-lowering therapies. In an experimental stroke model with comorbid hypertension, we investigated causal roles of ang II (angiotensin II)-mediated stimulation of the brain WNK (with no lysine [K] kinases)-SPAK (STE20/SPS1-related proline/alanine-rich kinase)-NKCC1 (Na-K-Cl cotransporter) complex in worsened outcomes.

METHODS

Saline- or ang II-infused C57BL/6J male mice underwent stroke induced by permanent occlusion of the distal branches of the middle cerebral artery. Mice were randomly assigned to receive either vehicle dimethyl sulfoxide/PBS (2 mL/kg body weight/day, IP), a novel SPAK inhibitor, 5-chloro-N-(5-chloro-4-((4-chlorophenyl)(cyano)methyl)-2-methylphenyl)-2-hydroxybenzamide (ZT-1a' 5 mg/kg per day, IP) or a NF-κB (nuclear factor-κB) inhibitor TAT-NBD (transactivator of transcription-NEMO-binding domain' 20 mg/kg per day, IP). Activation of brain NF-κB and WNK-SPAK-NKCC1 cascade as well as ischemic stroke outcomes were examined.

RESULTS

Stroke triggered a 2- to 5-fold increase of WNK (isoforms 1, 2, 4), SPAK/OSR1 (oxidative stress-responsive kinase 1), and NKCC1 protein in the ang II-infused hypertensive mouse brains at 24 hours after stroke, which was associated with increased nuclear translocation of phospho-NF-κB protein in the cortical neurons (a Pearson correlation r of 0.77, P<0.005). The upregulation of WNK-SPAK-NKCC1 cascade proteins resulted from increased NF-κB recruitment on Wnk1, Wnk2, Wnk4, Spak, and Nkcc1 gene promoters and was attenuated by NF-κB inhibitor TAT-NBD. Poststroke administration of SPAK inhibitor ZT-1a significantly reduced WNK-SPAK-NKCC1 complex activation, brain lesion size, and neurological function deficits in the ang II-hypertensive mice without affecting blood pressure and cerebral blood flow.

CONCLUSIONS

The ang II-induced stimulation of NF-κB transcriptional activity upregulates brain WNK-SPAK-NKCC1 cascade and contributes to worsened ischemic stroke outcomes, illustrating the brain WNK-SPAK-NKCC1 complex as a therapeutic target for stroke with comorbid hypertension.

The roles of sodium-potassium-chloride cotransporter isoform-1 in acute lung injury

Acute lung injury (ALI) is often characterized by severe lung inflammation and pulmonary edema with poor gas exchange and hypoxemia. Alveolar inflammation and water flooding are, in fact, notable features of ALI pathogenesis. The sodium-potassium-chloride co-transporter isoform 1 (NKCC1), localized at the basolateral surface of the lung epithelium, drives water transport via back transport of Na⁺ and Cl⁻ to the alveolar air space. NKCC1, therefore, is crucial in regulating alveolar fluid. Increased expression of NKCC1 results in increased alveolar fluid secretion and impaired alveolar fluid clearance. During ALI, the with no lysine kinase (WNK), oxidative stress responsive kinase 1 (OSR1), and STE20/SPS1-related proline/alanine-rich kinase (SPAK) pathways are activated, which upregulates NKCC1 expression. Proinflammatory cytokines also enhance the expression of NKCC1 via c-Jun N-terminal kinase-and p38-dependent pathways. NKCC1 activation also increases the expression of proinflammatory cytokines via cell rupture and activation of macrophages. Increased proinflammatory cytokines, in turn, recruit inflammatory cells to the site of injury and cause further lung damage. Animals with high expression of NKCC1 show more severe lung injury with presentations of more severe pulmonary edema and microvascular permeability, higher expression of proinflammatory cytokines, and greater neutrophilic infiltration. In contrast, animals with low expression of NKCC1 or those treated with NKCC1 inhibitors show less severe lung injury with milder levels of presentations of ALI. These reports collectively highlight a novel role of NKCC1 in ALI pathogenesis. Manipulation of NKCC1 expression levels could, therefore, represent novel modalities for effective ALI treatment.

Erythropoietin alleviates acute lung injury induced by ischemia-reperfusion through blocking p38 MAPK signaling

Erythropoietin (EPO) has antiapoptotic, antioxidative, and anti-inflammatory effects on ischemia tissues and protects against acute lung injury (ALI) induced by ischemia-reperfusion (I/R). p38 mitogen-activated protein kinases (p38 MAPK) signaling is involved in the processes of I/R-induced ALI. However, the interaction of EPO with p38 MAPK signaling in I/R-induced ALI has not been reported. To explore this issue, we constructed an I/R-induced ALI model in vivo and in vitro using Sprague Dawley rats and BEAS-2B cells. Some I/R rats and hypoxia-reoxygenation (H/R)-induced cells were treated with EPO, and the others were used as control groups. The injuries of lung tissues and cells were respectively assessed by inflammatory cytokine, morphologic changes, cell viability, apoptosis, and oxidative damage-related factors. Western blot determined key proteins in the p38 MAPK signaling. Results indicated that I/R induced the increase of inflammatory factors, lung weight, filtration coefficient, bronchoalveolar lavage fluid protein content, apoptosis, neutrophil, and lung peroxidation, and H/R caused cell growth inhibition, apoptosis, and oxidative damage-related factors' release. EPO attenuated I/R-induced injury in vivo and in vitro. Furthermore, the increase of p-p38, p-JNK, and p-ERK1/2 in lung tissues and cells induced by I/R was downregulated by EPO. Moreover, both EPO and an inhibitor of p38 MAPK (SB203580) alleviated H/R-induced cell injury. Erythropoietin along with SB203580 had more obvious protection effects than EPO alone. Collectively, EPO alleviated I/R-induced ALI by blocking p38 MAPK signaling. The interaction mechanism of EPO with p38 MAPK signaling contributes to understanding the processes of I/R-induced ALI and provides new insights for the disease treatment.

Dioscin alleviates lung ischemia/reperfusion injury by regulating FXR-mediated oxidative stress, apoptosis, and inflammation

Dioscin showed various pharmacological effects in our previous studies; however, the effects and mechanisms against lung ischemia/reperfusion injury (LI/RI) have not been reported. Hypoxia/reoxygenation (H/R) models were established using A549 and primary AEC-II cells, while LI/RI models were established in rats and mice. The effects of dioscin on oxidative stress, inflammation and apoptosis in vivo and in vitro were investigated. The mechanisms were investigated focus on dioscin regulating FXR/LKB1 signaling pathway. Dioscin improved cell viability and mitochondrial membrane potential, reduced reactive oxygen species level, and inhibited H/R-mediated cell apoptosis. It also significantly decreased the lung wet/dry weight ratio, ameliorated levels of oxidative stress indicators, and enhanced the mitochondrial membrane potential and inhibited cell apoptosis in vivo. The results of mechanism research showed that dioscin activated FXR/LKB1 signals by increasing the expression of p-LKB1 and p-AMPKα, promoting the nuclear translocation of Nrf2, up-regulating the levels of HO-1, NQO1 and GCLC, expressed against oxidative stress. Furthermore, dioscin reduced Cyt C released, decreased the expression levels of Caspase-9 and Caspase-3 during apoptosis. Dioscin suppressed inflammation by inhibiting NF-κB translocation, reducing the expression levels of NF-κB, HMGB1, COX-2, IL-1β, IL-6 and TNF-α. The transfection of FXR or LKB1 siRNA further confirmed that the protective effect of dioscin against LI/RI was attributable to the regulation of FXR/LKB1 signaling pathway. Our research showed that dioscin exhibited potent activity against LI/RI, by adjusting the levels of FXR/LKB1-mediated oxidative stress, apoptosis, and inflammation, and should be considered as a new candidate for treating LI/RI.

Obesity Attenuates Ventilator-Induced Lung Injury by Modulating the STAT3-SOCS3 Pathway

Background

Ventilator-induced lung injury (VILI) is characterized by vascular barrier dysfunction and suppression of alveolar fluid clearance (AFC). Obesity itself leads to chronic inflammation, which may initiate an injurious cascade to the lungs and simultaneously induce a protective feedback. In this study, we investigated the protective mechanism of obesity on VILI in a mouse model.

Methods

The VILI model was set up via 6-h mechanical ventilation with a high tidal volume. Parameters including lung injury score, STAT3/NFκB pathway, and AFC were assessed. Mice with diet-induced obesity were obtained by allowing free access to a high-fat diet since the age of 3 weeks. After a 9-week diet intervention, these mice were sacrificed at the age of 12 weeks. The manipulation of SOCS3 protein was achieved by siRNA knockdown and pharmaceutical stimulation using hesperetin. WNK4 knockin and knockout obese mice were used to clarify the pathway of AFC modulation.

Results

Obesity itself attenuated VILI. Knockdown of SOCS3 in obese mice offset the protection against VILI afforded by obesity. Hesperetin stimulated SOCS3 upregulation in nonobese mice and provided protection against VILI. In obese mice, the WNK4 axis was upregulated at the baseline, but was significantly attenuated after VILI compared with nonobese mice. At the baseline, the manipulation of SOCS3 by siRNA and hesperetin also led to the corresponding alteration of WNK4, albeit to a lesser extent. After VILI, WNK4 expression correlated with STAT3/NFκB activation, regardless of SOCS3 status. Obese mice carrying WNK4 knockout had VILI with a severity similar to that of wild-type obese mice. The severity of VILI in WNK4-knockin obese mice was counteracted by obesity, similar to that of wild-type nonobese mice only.

Conclusions

Obesity protects lungs from VILI by upregulating SOCS3, thus suppressing the STAT3/NFκB inflammatory pathway and enhancing WNK4-related AFC. However, WNK4 activation is mainly from direct NFκB downstreaming, and less from SOCS3 upregulation. Moreover, JAK2-STAT3/NFκB signaling predominates the pathogenesis of VILI. Nevertheless, the interaction between SOCS3 and WNK4 in modulating VILI in obesity warrants further investigation.

MicroRNA-486-5p Promotes Acute Lung Injury via Inducing Inflammation and Apoptosis by Targeting OTUD7B

The aim of this article is to study the effect of miR-486-5p in acute lung injury (ALI). MiR-486-5p expression in peripheral blood was determined in ALI patients and healthy volunteers by qRT-PCR. ALI mouse model were reproduced by LPS treatment, and miR-486-5p NC and miRNA-486 inhibitors were injected through trachea. ALI patients' peripheral blood and LPS-induced acute lung injury in mice had significantly higher miR-486-5p levels than control subjects. Inhibition of miR-486-5p by injection with antagomiR-486-5p markedly reduced LPS-induced lung inflammation. Moreover, knockdown of miR-486-5p can reduce protects A549 cell against LPS-induced injury and its corresponding inflammatory response. In addition, Mechanistic analysis indicated that miR-486-5p on the occurrence of ALI is related to the inhibition of OTUD7B activity, which induces the downregulation of inflammatory in ALI. Our results identified miR-486-5p independently associated with ALI. miR-486-5p can mediate the formation of ALI by promoting inflammation.

SPAK-p38 MAPK signal pathway modulates claudin-18 and barrier function of alveolar epithelium after hyperoxic exposure

BACKGROUND

Hyperoxia downregulates the tight junction (TJ) proteins of the alveolar epithelium and leads to barrier dysfunction. Previous study has showed that STE20/SPS1-related proline/alanine-rich kinase (SPAK) interferes with the intestinal barrier function in mice. The aim of the present study is to explore the association between SPAK and barrier function in the alveolar epithelium after hyperoxic exposure.

METHODS

Hyperoxic acute lung injury (HALI) was induced by exposing mice to > 99% oxygen for 64 h. The mice were randomly allotted into four groups comprising two control groups and two hyperoxic groups with and without SPAK knockout. Mouse alveolar MLE-12 cells were cultured in control and hyperoxic conditions with or without SPAK knockdown. Transepithelial electric resistance and transwell monolayer permeability were measured for each group. In-cell western assay was used to screen the possible mechanism of p-SPAK being induced by hyperoxia.

RESULTS

Compared with the control group, SPAK knockout mice had a lower protein level in the bronchoalveolar lavage fluid in HALI, which was correlated with a lower extent of TJ disruption according to transmission electron microscopy. Hyperoxia down-regulated claudin-18 in the alveolar epithelium, which was alleviated in SPAK knockout mice. In MLE-12 cells, hyperoxia up-regulated phosphorylated-SPAK by reactive oxygen species (ROS), which was inhibited by indomethacin. Compared with the control group, SPAK knockdown MLE-12 cells had higher transepithelial electrical resistance and lower transwell monolayer permeability after hyperoxic exposure. The expression of claudin-18 was suppressed by hyperoxia, and down-regulation of SPAK restored the expression of claudin-18. The process of SPAK suppressing the expression of claudin-18 and impairing the barrier function was mediated by p38 mitogen-activated protein kinase (MAPK).

CONCLUSIONS

Hyperoxia up-regulates the SPAK-p38 MAPK signal pathway by ROS, which disrupts the TJ of the alveolar epithelium by suppressing the expression of claudin-18. The down-regulation of SPAK attenuates this process and protects the alveolar epithelium against the barrier dysfunction induced by hyperoxia.

Surfactant Attenuates Air Embolism-Induced Lung Injury by Suppressing NKCC1 Expression and NF-κB Activation

Excessive amounts of air can enter the lungs and cause air embolism (AE)-induced acute lung injury (ALI). Pulmonary AE can occur during diving, aviation, and iatrogenic invasive procedures. AE-induced lung injury presents with severe hypoxia, pulmonary hypertension, microvascular hyper-permeability, and severe inflammatory responses. Pulmonary AE-induced ALI is a serious complication resulting in significant morbidity and mortality. Surfactant is abundant in the lungs and its function is to lower surface tension. Earlier studies have explored the beneficial effects of surfactant in ALI; however, none have investigated the role of surfactant in pulmonary AE-induced ALI. Therefore, we conducted this study to determine the effects of surfactant in pulmonary AE-induced ALI. Isolated-perfused rat lungs were used as a model of pulmonary AE. The animals were divided into four groups (n = 6 per group): sham, air embolism (AE), AE + surfactant (0.5 mg/kg), and AE+ surfactant (1 mg/kg). Surfactant pretreatment was administered before the induction of pulmonary AE. Pulmonary AE was induced by the infusion of 0.7 cc air through a pulmonary artery catheter. After induction of air, pulmonary AE was presented with pulmonary edema, pulmonary microvascular hyper-permeability, and lung inflammation with neutrophilic sequestration. Activation of NF-κB was observed, along with increased expression of pro-inflammatory cytokines, and Na-K-Cl cotransporter isoform 1 (NKCC1). Surfactant suppressed the activation of NF-κB and decreased the expression of pro-inflammatory cytokines and NKCC1, thereby attenuating AE-induced lung injury. Therefore, AE-induced ALI presented with pulmonary edema, microvascular hyper-permeability, and lung inflammation. Surfactant suppressed the expressions of NF-κB, pro-inflammatory cytokines, and NKCC1, thereby attenuating AE-induced lung injury.

Nonionic surfactant attenuates acute lung injury by restoring epithelial integrity and alveolar fluid clearance

Introduction: Acute lung injury (ALI) has a great impact and a high mortality rate in intensive care units (ICUs). Excessive air may enter the lungs, causing pulmonary air embolism (AE)-induced ALI. Some invasive iatrogenic procedures cause pulmonary AE-induced ALI, with the presentation of severe inflammatory reactions, hypoxia, and pulmonary hypertension. Pulmonary surfactants are vital in the lungs to reduce the surface tension and inflammation. Nonionic surfactants (NIS) are a kind of surfactants without electric charge on their hydrophilic parts. Studies on NIS in AE-induced ALI are limited. We aimed to study the protective effects and mechanisms of NIS in AE-induced ALI. Materials and methods: Five different groups (n = 6 in each group) were created: sham, AE, AE + NIS pretreatment (0.5 mg/kg), AE + NIS pretreatment (1 mg/kg), and AE + post-AE NIS (1 mg/kg). AE-induced ALI was introduced by the infusion of air via the pulmonary artery. Aerosolized NIS were administered via tracheostomy. Results: Pulmonary AE-induced ALI showed destruction of the alveolar cell integrity with increased pulmonary microvascular permeability, pulmonary vascular resistance, pulmonary edema, and lung inflammation. The activation of nuclear factor-κB (NF-κB) increased the expression of pro-inflammatory cytokines, and sodium-potassium-chloride co-transporter isoform 1 (NKCC1). The pretreatment with NIS (1 mg/kg) prominently maintained the integrity of the epithelial lining and suppressed the expression of NF-κB, pro-inflammatory cytokines, and NKCC1, subsequently reducing AE-induced ALI. Conclusions: NIS maintained the integrity of the epithelial lining and suppressed the expression of NF-κB, pro-inflammatory cytokines, and NKCC1, thereby reducing hyperpermeability, pulmonary edema, and inflammation in ALI.

High glucose-induced effects on Na+-K+-2Cl- cotransport and Na+/H+ exchange of blood-brain barrier endothelial cells: involvement of SGK1, PKCβII, and SPAK/OSR1

Hyperglycemia exacerbates edema formation and worsens neurological outcome in ischemic stroke. Edema formation in the early hours of stroke involves transport of ions and water across an intact blood-brain barrier (BBB), and swelling of astrocytes. We showed previously that high glucose (HG) exposures of 24 hours to 7 days increase abundance and activity of BBB Na⁺-K⁺-2Cl^- cotransport (NKCC) and Na⁺/H⁺ exchange 1 (NHE1). Further, bumetanide and HOE-642 inhibition of these transporters significantly reduces edema and infarct following middle cerebral artery occlusion in hyperglycemic rats, suggesting that NKCC and NHE1 are effective therapeutic targets for reducing edema in hyperglycemic stroke. The mechanisms underlying hyperglycemia effects on BBB NKCC and NHE1 are not known. In the present study we investigated whether serum-glucocorticoid regulated kinase 1 (SGK1) and protein kinase C beta II (PKCβII) are involved in HG effects on BBB NKCC and NHE1. We found transient increases in phosphorylated SGK1 and PKCβII within the first hour of HG exposure, after 5-60 min for SGK1 and 5 min for PKCβII. However, no changes were observed in cerebral microvascular endothelial cell SGK1 or PKCβII abundance or phosphorylation (activity) after 24 or 48 h HG exposures. Further, we found that HG-induced increases in NKCC and NHE1 abundance were abolished by inhibition of SGK1 but not PKCβII, whereas the increases in NKCC and NHE activity were abolished by inhibition of either kinase. Finally, we found evidence that STE20/SPS1-related proline/alanine-rich kinase and oxidative stress-responsive kinase-1 (SPAK/OSR1) participate in the HG-induced effects on BBB NKCC.

Acute Hyperglycemia Aggravates Lung Injury via Activation of the SGK1-NKCC1 Pathway

Acute lung injury (ALI) is characterized by severe hypoxemia and has significantly high mortality rates. Acute hyperglycemia occurs in patients with conditions such as sepsis or trauma, among others, and it results in aggravated inflammation and induces damage in patients with ALI. Regulation of alveolar fluid is essential for the development and resolution of pulmonary edema in lung injury. Pulmonary sodium-potassium-chloride co-transporter 1 (NKCC1) regulates the net influx of ions and water into alveolar cells. The activation of with-no-lysine kinase 4 (WNK4), STE20/SPS1-related proline/alanine rich kinase (SPAK) and the NKCC1 pathway lead to an increase in the expression of NKCC1 and aggravation of ALI. Moreover, hyperglycemia is known to induce NKCC1 expression via the activation of the serum-glucocorticoid kinase 1 (SGK1)-NKCC1 pathway. We aim to evaluate the influence of acute hyperglycemia on the SGK1-NKCC1 pathway in ALI. ALI was induced using a high tidal volume for four hours in a rat model. Acute hyperglycemia was induced by injection with 0.5 mL of 40% glucose solution followed by continuous infusion at 2 mL/h. The animals were divided into sham, sham+ hyperglycemia, ALI, ALI + hyperglycemia, ALI + inhaled bumetanide (NKCC1 inhibitor) pretreatment, ALI + hyperglycemia + inhalational bumetanide pretreatment, and ALI + hyperglycemia + post-ALI inhalational bumetanide groups. Severe lung injury along with pulmonary edema, alveolar protein leakage, and lung inflammation was observed in ALI with hyperglycemia than in ALI without hyperglycemia. This was concurrent with the higher expression of pro-inflammatory cytokines, infiltration of neutrophils and alveolar macrophages (AM) 1, and NKCC1 expression. Inhalational NKCC1 inhibitor significantly inhibited the SGK1-NKCC1, and WNK4-SPAK-NKCC1 pathways. Additionally, it reduced pulmonary edema, inflammation, levels of pro-inflammatory cytokines, neutrophils and AM1 and increased AM2. Therefore, acute hyperglycemia aggravates lung injury via the further activation of the SGK1-NKCC1 pathway. The NKCC1 inhibitor can effectively attenuate lung injury aggravated by acute hyperglycemia.

Is Inhaled Furosemide a Potential Therapeutic for COVID-19?

The potentially lethal infection caused by the novel Severe Acute Respiratory Disease Coronavirus-2 (SARS-CoV-2) has evolved into a global crisis. Following the initial viral infection is the host inflammatory response that frequently results in excessive secretion of inflammatory cytokines (e.g., IL-6 and TNFα), developing into a self-targeting, toxic "cytokine storm" causing critical pulmonary tissue damage. The need for a therapeutic that is available immediately is growing daily but the de novo development of a vaccine may take years. Therefore, repurposing of approved drugs offers a promising approach to address this urgent need. Inhaled furosemide, a small molecule capable of inhibiting IL-6 and TNFα, may be an agent capable of treating the Coronavirus Disease 2019 cytokine storm in both resource-rich and developing countries. Furosemide is a "repurpose-able" small molecule therapeutics, that is safe, easily synthesized, handled, and stored, and is available in reasonable quantities worldwide.

Inflammation in acquired hydrocephalus: pathogenic mechanisms and therapeutic targets

Hydrocephalus is the most common neurosurgical disorder worldwide and is characterized by enlargement of the cerebrospinal fluid (CSF)-filled brain ventricles resulting from failed CSF homeostasis. Since the 1840s, physicians have observed inflammation in the brain and the CSF spaces in both posthaemorrhagic hydrocephalus (PHH) and postinfectious hydrocephalus (PIH). Reparative inflammation is an important protective response that eliminates foreign organisms, damaged cells and physical irritants; however, inappropriately triggered or sustained inflammation can respectively initiate or propagate disease. Recent data have begun to uncover the molecular mechanisms by which inflammation - driven by Toll-like receptor 4-regulated cytokines, immune cells and signalling pathways - contributes to the pathogenesis of hydrocephalus. We propose that therapeutic approaches that target inflammatory mediators in both PHH and PIH could address the multiple drivers of disease, including choroid plexus CSF hypersecretion, ependymal denudation, and damage and scarring of intraventricular and parenchymal (glia-lymphatic) CSF pathways. Here, we review the evidence for a prominent role of inflammation in the pathogenic mechanism of PHH and PIH and highlight promising targets for therapeutic intervention. Focusing research efforts on inflammation could shift our view of hydrocephalus from that of a lifelong neurosurgical disorder to that of a preventable neuroinflammatory condition.

Increase in circulating ACE-positive endothelial microparticles during acute lung injury

Circulating endothelial microparticles (EMPs) are considered to be markers of endothelial injury, and lung microvascular endothelial cells express higher levels of angiotensin-converting enzyme (ACE). The aim of this study is to examine whether the number of ACE⁺ microvascular EMPs could be a prognostic marker for the development of acute respiratory distress syndrome (ARDS) in septic patients.The numbers of EMPs and ACE⁺ EMPs in the culture supernatant from human microvascular endothelial cells, as well as in the blood of mouse lung injury models and septic patients (n=82), were examined using flow cytometry.ACE⁺ EMPs in the culture supernatant from pulmonary microvascular endothelial cells increased after exposure to an inflammatory stimulus. In the mouse lung injury models, the circulating ACE⁺ EMPs and ACE⁺ EMP/EMP ratio were higher than in the controls (p<0.001). The ACE⁺ EMP/EMP ratio was correlated with the wet/dry lung ratio (r_s=0.775, p<0.001). The circulating ACE⁺ EMPs and ACE⁺ EMP/EMP ratio on admission were significantly increased in septic patients who developed ARDS compared with septic patients who did not (p<0.001).Therefore, circulating ACE⁺ EMPs may be a prognostic marker for the development of ARDS in the septic patients.

Phosphodiesterase-4 Inhibitor Roflumilast Attenuates Pulmonary Air Emboli-Induced Lung Injury

BACKGROUND

Pulmonary air embolism (PAE)-induced acute lung injury (ALI) can be caused by massive air entry into the lung circulation. PAE can occur during diving, aviation, and some iatrogenic invasive procedures. PAE-induced ALI presents with severe inflammation, hypoxia, and pulmonary hypertension, and it is a serious complication resulting in significant morbidity and mortality. Phosphodiesterase-4 (PDE4) inhibitors can regulate inflammation and are therefore expected to have a therapeutic effect on ALI. However, the effect of the PDE4 inhibitor roflumilast on PAE-induced ALI is unknown.

METHODS

The PAE model was undertaken in isolated-perfused rat lungs. Four groups (n = 6 in each group) were defined as follows: control, PAE, PAE + roflumilast 2.5 mg/kg, and PAE + roflumilast 5 mg/kg. Induction of PAE-induced ALI was achieved via the infusion of 0.7 cc air through the pulmonary artery. Roflumilast was administered via perfusate. All groups were assessed for pulmonary microvascular permeability, lung histopathology changes, pulmonary edema (lung weight/body weight, lung wet/dry weight ratio), tumor necrosis factor alpha (TNF-α), interleukin-1β (IL-1β), IL-6, IL-17, nuclear factor-kappa B (NF-κB), and inhibitor of NF-κB alpha (IκB-α).

RESULTS

After the induction of air, PAE-induced ALI presented with pulmonary edema, pulmonary microvascular hyperpermeability, and lung inflammation with neutrophilic sequestration. The PAE-induced ALI also presented with increased expressions of IL-1β, IL-6, IL-8, IL-17, TNF-α, and NF-κB and decreased expression of IκB-α. The administration of roflumilast decreased pulmonary edema, inflammation, cytokines, NF-κB, and restored IκB-α level.

CONCLUSIONS

PAE-induced ALI presents with lung inflammation with neutrophilic sequestration, pulmonary edema, hyperpermeability, increased cytokine levels, and activation of the NF-κB pathway. Roflumilast attenuates lung edema and inflammation and downregulates the NF-κB pathway and cytokines.

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.

Bumetanide attenuates acute lung injury by suppressing macrophage activation

Bumetanide is a potent loop diuretic that acts as an inhibitor of sodium-potassium-chloride cotransporter 2 (NKCC2) and its isoform NKCC1. Although the expression of NKCC2 is limited to the kidney, NKCC1 is widely expressed in various cells, where it participates in a variety of physiological functions including ion transport, alveolar fluid secretion, and cell volume regulation. We investigated the role of NKCC1 in modulation of host immunity. Lipopolysaccharide (LPS) stimulated the expression and phosphorylation of NKCC1 in RAW264.7 cells in vitro and activated these cells to produce inflammatory cytokines. Enlarging the cell volume in a low-osmotic microenvironment amplified the LPS-induced inflammatory responses and phagocytosis activity of RAW264.7 cells. Pretreatment with the NKCC1 inhibitor bumetanide attenuated LPS-induced activation of inflammatory cells and cell volume-related function. Mice treated with an intratracheal bumetanide spray showed greater resistance to LPS-induced tissue inflammation and acute lung injury in vivo. Our studies suggest that NKCC1 plays a unique role as an amplifier of LPS-induced macrophage functions and that NKCC1 might be a novel target for treating sepsis-related acute respiratory distress syndrome.