Ventilator-induced lung injury is alleviated by inhibiting NLRP3 inflammasome activation

Role of STIM1 in stretch-induced signaling in human airway smooth muscle

Alteration in the normal mechanical forces of breathing can contribute to changes in contractility and remodeling characteristic of airway diseases, but the mechanisms that mediate these effects in airway cells are still under investigation. Airway smooth muscle (ASM) cells contribute to both contractility and extracellular matrix (ECM) remodeling. In this study, we explored ASM mechanisms activated by mechanical stretch, focusing on mechanosensitive piezo channels and the key Ca2+ regulatory protein stromal interaction molecule 1 (STIM1). Expression of Ca2+ regulatory proteins, including STIM1, Orai1, and caveolin-1, mechanosensitive ion channels Piezo-1 and Piezo-2, and NLRP3 inflammasomes were upregulated by 10% static stretch superimposed on 5% cyclic stretch. These effects were blunted by STIM1 siRNA. Histamine-induced [Ca2+]i responses and inflammasome activation were similarly blunted by STIM1 knockdown. These data show that the effects of mechanical stretch in human ASM cells are mediated through STIM1, which activates multiple pathways, including Piezo channels and the inflammasome, leading to potential downstream changes in contractility and ECM remodeling.NEW & NOTEWORTHY Mechanical forces on the airway can contribute to altered contractility and remodeling in airway diseases, but the mechanisms are not clearly understood. Using human airway smooth muscle cells exposed to cyclic forces with static stretch to mimic breathing and static pressure, we found that the effects of stretch are mediated through STIM1, resulting in the activation of multiple pathways, including Piezo channels and the inflammasome, with potential downstream influences on contractility and remodeling.

Electroacupuncture Attenuates Ventilator-Induced Lung Injury by Modulating the Nrf2/HO-1 Pathway

INTRODUCTION

Ventilator-induced lung injury (VILI) is the most common complication associated with mechanical ventilation. Electroacupuncture (EA) has shown potent anti-inflammatory effects. This study aimed to investigate the effects of EA on VILI and explore the underlying mechanisms.

METHODS

Male C57BL/6 mice were subjected to high tidal volume ventilation to induce VILI. Prior to mechanical ventilation, mice received treatment with EA, nonacupoint EA, or EA combined with zinc protoporphyrin.

RESULTS

EA treatment significantly improved oxygenation, as indicated by increased PaO2 levels in VILI mice. Moreover, EA reduced lung injury score, lung wet/dry weight ratio, and protein concentration in bronchoalveolar lavage fluid. EA also decreased the expression of pro-inflammatory cytokines including interleukin (IL)-1β, IL-6, tumor necrosis factor-α, IL-18, chemokine keratinocyte chemoattractant, macrophage inflammatory protein 2, and malondialdehyde. Furthermore, EA increased the activities of antioxidant enzymes superoxide dismutase, catalase, and glutathione peroxidase in VILI mice. At the molecular level, EA upregulated the expression of Nrf2 (nucleus) and heme oxygenase -1, while down-regulating the expression of p-NF-κB p65, NLR Family Pyrin Domain Containing 3, Cleaved Caspase-1, and ASC in VILI mice. Notably, the effects of EA were reversed by zinc protoporphyrin treatment, nonacupoint EA did not affect the aforementioned indicators of VILI.

CONCLUSIONS

EA alleviates VILI by inhibiting the NLR Family Pyrin Domain Containing three inflammasome through activation of the Nrf2/HO-1 pathway.

4-octyl itaconate ameliorates ventilator-induced lung injury

Ventilator-induced lung injury (VILI) disturbs the disordered immune system and causes persistent inflammatory damage. 4-octyl itaconate (OI) is a synthetic cell-permeable itaconate derivative with antioxidant and anti-inflammatory effects. In this study, we assessed whether OI protects against VILI. OI was intraperitoneally injected for three days before mechanical ventilation (MV; 20 ml/kg at 70 breaths/min) for 2 h. Mouse lung vascular endothelial cells (MLVECs) were pretreated with OI (62.5, 125, and 250 μM) prior to cyclic stretch for 4 h. We found that OI attenuated VILI and inflammatory response. OI also increased superoxide dismutase, nuclear factor E2-related factor 2, and heme oxygenase-1 levels, and decreased reactive oxygen species and malondialdehyde levels. Furthermore, OI inhibited the expression of NLR family pyrin domain-containing 3 (NLRP3), caspase-1 p20, apoptosis-associated speck-like protein containing a CARD, and N-terminal fragment of gasdermin D. Therefore, OI attenuates VILI, potentially by suppressing oxidative stress and NLRP3 activation.

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

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

Regulation of cell proliferation and transdifferentiation compensates for ventilator-induced lung injury mediated by NLRP3 inflammasome activation

BACKGROUND

Mechanical ventilation is an important means of respiratory support and treatment for various diseases. However, its use can lead to serious complications, especially ventilator-induced lung injury (VILI). The mechanisms underlying this disease are complex, but activation of inflammatory signalling pathways results in activation of cytokines and inflammatory mediators, which play key roles in VILI. Recent studies have demonstrated that nod-like receptor protein 3 (NLRP3) inflammasome activation mediates VILI and also accompanied by cell proliferation and transdifferentiation to compensate for alveolar membrane damage. Type I alveolar epithelial cells (AECs I), which are involved in the formation of the blood-air barrier, are vulnerable to damage but cannot proliferate by themselves; thus, replacing AECs I relies on type II alveolar epithelial cells (AECs II).

OBJECTIVE

The review aims to introduce the mechanisms of NLRP3 inflammasome activation and its inhibitors, as well as the mechanisms that regulate cell proliferation and transdifferentiation.

METHODS

A large number of relevant literature was searched, then the key content was summarized and figures were also made.

RESULTS

The mechanism of NLRP3 inflammasome activation has been further explored, including but not limited to pathogenic and aseptic inflammatory signals, such as, pathogenic molecular patterns and host-derived danger-associated molecular patterns activate toll-like receptor 4/nuclear factor-kappaB pathway or reactive oxygen species, cyclic stretch, adenosine triphosphate induce K+ efflux through P2X7, Ca2+ inflow, mitochondrial damage, etc, eventually induce NIMA-related kinase 7/NLRP3 binding and NLRP3 inflammasome activation. Not only that, the review also described in detail the inhibitors of NLRP3 inflammasome. And the mechanisms regulating cell proliferation and transdifferentiation are complex and unclear, including the Wnt/β-catenin, Yap/Taz, BMP/Smad and Notch signalling pathways.

CONCLUSIONS

NLRP3 inflammasome activation mediated VILI, and VILI is alleviated after interfering with its activation, and inflammation and repair exist simultaneously in VILI. Clarifying these mechanisms is expected to provide theoretical guidance for alleviating VILI by inhibiting the inflammatory response and accelerating alveolar epithelial cell regeneration in the early stage.

Aerobic exercise alleviates ventilator-induced lung injury by inhibiting NLRP3 inflammasome activation

BACKGROUND

Ventilator-induced lung injury (VILI) is caused by stretch stimulation and other factors related to mechanical ventilation (MV). NOD-like receptor protein 3 (NLRP3), an important innate immune component, is strongly associated with VILI. This study aimed to investigate the effect and mechanisms of aerobic exercise (EX) on VILI.

METHODS

To test the effects of the PKC inhibitor bisindolylmaleimide I on PKC and NLRP3, male C57BL/6 mice (7 weeks old, 19 ~ 23 g) were randomly divided into four groups: control group(C), bisindolylmaleimide I-pretreated group(B), MV group, and bisindolylmaleimide I-pretreated + MV (B + MV) group. The mice were pretreated with bisindolylmaleimide I through intraperitoneal injection (0.02 mg/kg) 1 h before MV. MV was performed at a high tidal volume (30 ml/kg). To explore the ameliorative effect of EX on VILI, the mice were randomly divided into C group, MV group, EX group and EX + MV group and subjected to either MV or 5 weeks of EX training. After ventilation, haematoxylin-eosin (HE) staining and wet/dry weight ratio was used to assess lung pathophysiological changes. PKCɑ, P-PKCɑ, ASC, procaspase-1, caspase-1, pro-IL-1β, IL-1β, NLRP3 and occludin (tight junction protein) expression in lung tissues was determined by Western blotting. The level of IL-6 in alveolar lavage fluid was determined by ELISA.

RESULTS

NLRP3, P-PKCɑ, and PKCɑ levels were inceased in MV group, but bisindolylmaleimide I treatment reversed these changes. Inhibition of PKC production prevented NLRP3 activation. Moreover, MV increased ASC, procaspase-1, caspase-1, pro-IL-1β, and IL1β levels and decreased occludin levels, but EX alleviated these changes. HE staining and lung injury scoring confirmed an absence of obvious lung injury in C group and EX group. Lung injury was most severe in MV group but was improved in EX + MV group. Overall, these findings suggest that MV activates the NLRP3 inflammasome by activating PKCɑ and inducing occludin degradation, while Exercise attenuates NLRP3 inflammasome and PKCɑ activation. Besides, exercise improves cyclic stretch-induced degradation of occludin.

CONCLUSION

PKC activation can increase the level of NLRP3, which can lead to lung injury. Exercise can reduce lung injury by inhibiting PKCɑ and NLRP3 activation. Exercise maybe a potential measure for clinical prevention of VILI.

Ethanol extracts of Rhaponticum uniflorum (L.) DC inflorescence ameliorate LPS-mediated acute lung injury by alleviating inflammatory responses via the Nrf2/HO-1 signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Rhaponticum uniflorum (L.) DC is a member of the Compositae family. Loulu flowers (LLF) is the inflorescence of this plant, which is a commonly used Mongolian medicine for the treatment of inflammatory diseases due to its heat-clearing and detoxifying properties. It is used caused by. However, its anti-inflammatory mechanisms are not clear.

AIM OF THIS STUDY

We investigated whether ethanol extracts of LLF can alleviate LPS-induced acute lung injury and explored the mechanism involved.

MATERIAL AND METHODS

BALB/C mice were intragastrically administered with sodium carboxymethyl cellulose (0.5%, 1 mL/100 g) or ethanol extracts of LLF at a dose of 100, 200, and 400 mg/kg, once daily, for 3 days. Subsequently, mice models of acute lung injury were established by LPS and used for the determination of anti-inflammatory effects of LLF. After 6 h of treatment, mice were sacrificed to collect lung tissues and bronchoalveolar lavage fluid (BALF). H&E staining assay was performed on the tissues for pathological analysis. The ELISA test was conducted to measure NO, IL-6, TNF-α, MPO, SOD, CAT, MDA and GSH-PX levels. The expression level of proteins associated with the Nrf2/HO-1 and MAPK/NF-κB signaling pathways were determined using Western blot analysis. Levels of F4/80 and Nrf2 in lungs were quantified using immunohistochemistry.

RESULTS

Oral administration of LLF extracts alleviated LPS-induced pathological alterations, reduced lung W/D weight ratio, decreased levels of TP, pro-inflammatory factors (TNF-α and IL-6), and NO in BALF. Pretreatment with LLF extract downregulated F4/80 expression in lung tissue and suppressed LPS-induced elevations in BALF and lung tissue levels of MPO. Moreover, treatment with LLF extract reduced the expression level of proteins associated with the MAPK signaling pathway (p-p38, p-JNK, p-ERK) and TLR4/NF-κB signaling pathways (TLR4, Myd88, p-IκB, p-p65). Moreover, LLF extract upregulated Nrf2, HO-1 and NQO1 protein levels, downregulated Keap1 protein level. Immunohistochemical analysis revealed that LLF reduced the LPS-induced increase in Nfr2 expression in lung tissues.

CONCLUSION

Ethanol extracts of LLF ameliorated LPS-induced acute lung injury by suppressing inflammatory response and enhancing antioxidation capacity, which correlated with the MAPK/NF-κB and Nfr2/HO-1 signaling pathways.

Low tidal volume ventilation alleviates ventilator-induced lung injury by regulating the NLRP3 inflammasome

PURPOSE

Low tidal volume ventilation (LTVV) is a well-known ventilation mode which can improve ventilator-induced lung injury (VILI). However, the mechanism of LTVV ameliorating VILI has not yet been elucidated. In this study, we aimed to reveal LTVV protected against VILI by inhibiting the activation of the NLRP3 inflammasome in bronchoalveolar lavage fluid (BALF) from humans and lungs from mice.

MATERIALS AND METHODS

Twenty-eight patients scheduled for video-assisted thoracoscopic esophagectomy were randomized to receive high-tidal-volume ventilation [V_t = 10 mL/kg without positive end-expiratory pressure (PEEP)] or LTVV (V_t = 5 mL/kg along with 5 cm of H₂O PEEP) during one-lung ventilation. BALF was collected before and at the end of surgery. Male C57BL/6 mice received high-tidal-volume ventilation, LTVV or MCC950 (an inhibitor of NLRP3). The activation of the formation of NLRP3 inflammasome in BALF from patients and in lungs from mice were analyzed.

RESULTS

LTTV decreased the peak airway pressure (P_peak), plateau airway pressure (P_plat) and driving pressure (ΔP) during one-lung ventilation. Additionally, LTVV not only inhibited pulmonary infiltration and inflammation caused by mechanical ventilation, but also suppressed the NLRP3 inflammasome activation in BALF from humans. In mice, ventilator-induced inflammatory response and pulmonary edema were suppressed by LTVV with an efficacy comparable to that of MCC950 treatment. Furthermore, LTVV, similar to MCC950, clearly decreased ventilator-induced NLRP3 inflammasome activation.

CONCLUSION

Our study showed that LTVV played a protective role in ventilator-induced lung injury by suppressing the activation of the NLRP3 inflammasome.

TRIAL REGISTRATION

This study was registered in The Chinese Clinical Trial Registry, ChiCTR1900026190 on 25 September 2019.

The Role of Circadian Clock Genes in Critical Illness: The Potential Role of Translational Clock Gene Therapies for Targeting Inflammation, Mitochondrial Function, and Muscle Mass in Intensive Care

The Earth's 24-h planetary rotation, with predictable light and heat cycles, has driven profound evolutionary adaptation, with prominent impacts on physiological mechanisms important for surviving critical illness. Pathways of interest include inflammation, mitochondrial function, energy metabolism, hypoxic signaling, apoptosis, and defenses against reactive oxygen species. Regulation of these by the cellular circadian clock (BMAL-1 and its network) has an important influence on pulmonary inflammation; ventilator-associated lung injury; septic shock; brain injury, including vasospasm; and overall mortality in both animals and humans. Whether it is cytokines, the inflammasome, or mitochondrial biogenesis, circadian medicine represents exciting opportunities for translational therapy in intensive care, which is currently lacking. Circadian medicine also represents a link to metabolic determinants of outcome, such as diabetes and cardiovascular disease. More than ever, we are appreciating the problem of circadian desynchrony in intensive care. This review explores the rationale and evidence for the importance of the circadian clock in surviving critical illness.

Human Neutrophil Defensins Disrupt Liver Interendothelial Junctions and Aggravate Sepsis

Human neutrophil peptides 1-3 (HNP1-3), also known as human α-defensins, are the most abundant neutrophil granule proteins. The genes that encode HNP1-3, DEFA1/DEFA3, exhibit extensive copy number variations, which correlate well with their protein levels. Human and mouse studies have shown that increased copy numbers of DEFA1/DEFA3 worsen sepsis outcomes. Additionally, high concentrations of HNP1-3 in body fluids have been reported in patients with sepsis. However, direct evidence for the pathogenic role of HNP1-3 proteins during sepsis progression is lacking. In current study, sepsis was induced by means of cecal puncture and ligation. Various doses of HNP-1 (low dose with 0.5 mg/kg body weight and high dose with 10 mg/kg body weight) or phosphate buffer saline were intraperitoneally administered to mice at six hours after sepsis onset. Survival rate was monitored, and vascular permeability, endothelial cell pyroptosis, and immunofluorescence of endothelial adherens junction protein vascular endothelial-cadherin were evaluated. The administration of a high dose of HNP-1 after sepsis onset led to increased mortality, more severe liver injury, and increased vascular permeability in the liver and mesentery. The injection of high dose of HNP-1 did not directly induce liver endothelial cell death but destroyed interendothelial junctions in the liver. Moreover, genetic deficiency of nucleotide-binding oligomerization domain-like receptor protein-3 or caspase-1 abrogated the high mortality and disrupted liver interendothelial junctions caused by high dose of HNP-1 during sepsis. This study directly demonstrates that neutrophil defensins play a key role in regulating endothelial stability during sepsis development.

Roxadustat Attenuates the Disruption of Epithelial Tight Junction in Caco2 Cells and a Rat Model of CKD Through MicroRNA-223

Introduction

Increasing evidence supports the idea that the disruption of epithelial tight junction proteins (TJPs) caused by accumulation of uremia toxins, such as homocysteine (Hcy), is one of the most important mechanisms underlying the damage of intestinal barrier function (IBF) in chronic kidney disease (CKD). Since the decrease of hypoxia inducible factor-1α (HIF-1α) is reported to be involved in Hcy-induced cell injury, and the upregulation of microRNA-223 (miR-223) plays a vital protective role in the impairment of IBF in the experimental colitis, we investigated the effect of HIF-1α stabilizer roxadustat on the disruption of TJPs induced by Hcy and CKD and the underlying mechanism.

Methods

Chronic kidney disease was induced in rats via 5/6 nephrectomy. In a series of experiments, the rats were treated orally with roxadustat of different doses. The expression of tight junction proteins, HIF-1α, and miR-223 was analyzed in different groups by western blotting analysis, RT-qPCR techniques and immunofluorescence. A series of experiments with cultured Caco2 cells was performed.

Results

The results showed that the expression of TJPs (occludin, claudin-1, and ZO-1) decreased significantly, accompanied by the reduction of HIF-1α and miR-223 in Hcy-treated Caco2 cells and colonic mucosa of uremic rats. The reduction of HIF-1α and miR-223 was reversed by roxadustat and the decrease of TJPs expression was attenuated in both Caco2 cells induced by Hcy and colon tissue of CKD rats. Furthermore, transfection with miR-223 mimics increased the expression of TJPs, while transfection with miR-223 inhibitor decreased their expression in Caco2 cells. MiR-223 inhibitor applied before roxadustat treatment partly diminished the effect of roxadustat on TJPs expression in Caco2 cells.

Conclusion

These results indicated that roxadustat attenuated the disruption of epithelial TJPs induced by Hcy in Caco2 cells and the damage of colonic epithelium in CKD rats through the upregulation of miR-223 induced by HIF-1α. A novel insight into the IBF dysfunction in CKD was provided, and it suggests a potential therapeutic use of roxadustat for the IBF dysfunction besides anemia in CKD.

Punicalagin suppresses inflammation in ventilator-induced lung injury through protease-activated receptor-2 inhibition-induced inhibition of NLR family pyrin domain containing-3 inflammasome activation

Punicalagin is recorded to be a potent anti-inflammatory drug, while its effect on inflammation existing in ventilator-induced lung injury (VILI) requires further verification. Rats were pretreated with punicalagin, followed by VILI modeling. Lung histopathological examination was performed with hematoxylin-eosin staining accompanied by the lung injury score. The lung wet/dry (W/D) weight ratio and total bronchoalveolar lavage fluid (BALF) protein level were measured. After transfection with protease-activated receptor-2 (PAR2) overexpression plasmids, mouse alveolar epithelial MLE-12 cells were treated with punicalagin and then subjected to cyclic stretching. Punicalagin's cytotoxicity to MLE-12 cells were measured by MTT assay. The levels of inflammatory cytokines (tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6), PAR2, NLR family pyrin domain containing-3 (NLRP3), and apoptosis-associated speck-like protein containing a CARD (ASC) in the BALF, lung tissues or cells were analyzed by enzyme-linked immune-sorbent assay (ELISA), qRT-PCR or/and western blot. Punicalagin treatment attenuated VILI-induced lung histopathological changes and counteracted VILI-induced increases in the lung injury score, W/D weight ratio and total protein level in BALF. Also, punicalagin treatment counteracted in vivo VILI/cyclic stretching-induced increases in the levels of PAR2, inflammatory cytokines, NLRP3, and ASC. PAR2 overexpression potentiated the cyclic stretching-induced effects, while punicalagin treatment revoked this PAR2 overexpression-induced potentiation effect. In turn, PAR2 overexpression partly resisted the punicalagin treatment-induced counteractive effects on the cyclic stretching-induced effects. Punicalagin suppresses inflammation in VILI through PAR2 inhibition-induced inhibition of NLRP3 inflammasome activation.

Mediators of neutrophil lymphocyte ratio in the relationship between ondansetron pre-treatment and the mortality of ICU patients on mechanical ventilation: causal mediation analysis from the MIMIC-IV database

AIMS

The mortality of critically ill patients undergoing mechanical ventilation (MV) is high and few strategies are available. We explored the relationship between ondansetron pre-treatment, the neutrophil:lymphocyte ratio (NLR), and platelet:lymphocyte ratio (PLR), and mortality of ventilated patients in the intensive care unit.

METHODS

We developed a retrospective cohort study that involved patients undergoing MV in the Multiparameter Intelligent Monitoring in Intensive Care IV (MIMIC-IV) database. Causal mediation analysis was conducted to assess the relationship of ondansetron use and mortality and explore the potential causal pathway mediated by the NLR or PLR. The primary outcome was 28-day mortality.

RESULTS

A total of 17,927 eligible patients was obtained (5665 had taken ondansetron before MV initiation and 12,262 patients had not). The OR for 28-day mortality for ondansetron use uncorrelated with the mediator (NLR, PLR) was 0.72 (95%CI=0.64-0.81, P <0.001). Ondansetron was also associated with a reduction in 28-day mortality after controlling for the mediator of NLR (OR = 0.98, 95%CI = 0.97-0.99, P < 0.01). For the indirect effect, the NLR could explain 13.47% (95%CI = 8.59-20.54%, P < 0.01) of the impact of ondansetron use on 28-day mortality. The proportion mediated increased to 21.50% (95%CI = 12.36-47.44%, P < 0.01) for 90-day mortality. Adjusted mediation analysis revealed no suggestion of a causal mediation pathway for this effect by the PLR (P = 0.12).

CONCLUSIONS

NLR may play substantial roles in the relationship between ondansetron pre-treatment before initiation of mechanical ventilation and the reduction of death risk in ventilated patients.

The Elk1/MMP-9 axis regulates E-cadherin and occludin in ventilator-induced lung injury

Background

Ventilator-induced lung injury (VILI) is a common complication in the treatment of respiratory diseases with high morbidity and mortality. ETS-domain containing protein (Elk1) and Matrix metalloproteinase (MMP) 9 are involved in VILI, but the roles have not been fully elucidated. This study examined the mechanisms of the activation of MMP-9 and Elk1 regulating barrier function in VILI in vitro and in vivo.

Methods

For the in vitro study, Mouse lung epithelial cells (MLE-12) were pre-treated with Elk1 siRNA or MMP-9 siRNA for 48 h prior to cyclic stretch at 20% for 4 h. For the in vivo study, C57BL/6 mice were pre-treated with Elk1 siRNA or MMP-9 siRNA for 72 h prior to 4 h of mechanical ventilation. The expressions of Elk1, MMP-9, Tissue inhibitor of metalloproteinase 1 (TIMP-1), E-cadherin, and occludin were measured by Western blotting. The intracellular distribution of E-cadherin and occludin was shown by immunofluorescence. The degree of pulmonary edema and lung injury were evaluated by Hematoxylin–eosin (HE) staining, lung injury scores, Wet/Dry (W/D) weight ratio, total cell counts, and Evans blue dye.

Results

20% cyclic stretch and high tidal volume increases the expressions of Elk1, MMP-9, and TIMP-1, increases the ratio of MMP-9/TIMP-1, decreases the E-cadherin and occludin level. Elk1 siRNA or MMP-9 siRNA reverses the degradations of E-cadherin, occludin, and the ratio of MMP-9/TIMP-1 caused by cyclic stretch. Elk1 siRNA decreases the MMP-9 level with or not 20% cyclic stretch and high tidal volume.

Conclusions

The results demonstrate mechanical stretch damages the tight junctions and aggravates the permeability in VILI, Elk1 plays an important role in affecting the tight junctions and permeability by regulating the balance of MMP-9 and TIMP-1, thus indicating the therapeutic potential of Elk1 to treat VILI.

Attenuation of ventilator-induced lung injury through suppressing the pro-inflammatory signaling pathways: A review on preclinical studies

Mechanical ventilation (MV) is a relatively common medical intervention in ICU patients. The main side effect of MV is the so-called "ventilator-induced lung injury" (VILI). The pathogenesis of VILI is not completely understood; however, it has been reported that MV might be associated with up-regulation of various inflammatory mediators within the lung tissue and that these mediators might act as pathogenic factors in lung tissue injury. One potential mechanism for the generation of inflammatory mediators is through the release of endogenous molecules known as damage associated molecular patterns (DAMPs). These molecules are released from injured tissues and can bind to pattern recognition receptors (PRRs). PRR activation generally leads to the production and release of inflammation-related molecules including innate immune cytokines and chemokines. It has been suggested that blocking DAMP/PRR signaling pathways might diminish the progression of VILI. Herein, we review the latest findings with regard to the effects of DAMP/PRRs and their blockade, as well as the potential therapeutic targets and future research directions in VILI. Results of studies performed on human samples, animal models of disease, as well as relevant in vitro systems will be discussed.

Genetic and epigenetic regulation of the non-muscle myosin light chain kinase isoform by lung inflammatory factors and mechanical stress

RATIONALE

The myosin light chain kinase gene, MYLK, encodes three proteins via unique promoters, including the non-muscle isoform of myosin light chain kinase (nmMLCK), a cytoskeletal protein centrally involved in regulation of vascular integrity. As MYLK coding SNPs are associated with severe inflammatory disorders (asthma, acute respiratory distress syndrome (ARDS)), we explored clinically relevant inflammatory stimuli and promoter SNPs in nmMLCK promoter regulation.

METHODS

Full-length or serially deleted MYLK luciferase reporter promoter activities were measured in human lung endothelial cells (ECs). SNP-containing non-muscle MYLK (nmMYLK) DNA fragments were generated and nmMYLK promoter binding by transcription factors (TFs) detected by protein-DNA electrophoretic mobility shift assay (EMSA). Promoter demethylation was evaluated by 5-aza-2'-deoxycytidine (5-Aza). A preclinical mouse model of lipopolysaccharide (LPS)-induced acute lung injury (ALI) was utilized for nmMLCK validation.

RESULTS

Lung EC levels of nmMLCK were significantly increased in LPS-challenged mice and LPS, tumor necrosis factor-α (TNF-α), 18% cyclic stretch (CS) and 5-Aza each significantly up-regulated EC nmMYLK promoter activities. EC exposure to FG-4592, a prolyl hydroxylase inhibitor that increases hypoxia-inducible factor (HIF) expression, increased nmMYLK promoter activity, confirmed by HIF1α/HIF2α silencing. nmMYLK promoter deletion studies identified distal inhibitory and proximal enhancing promoter regions as well as mechanical stretch-, LPS- and TNFα-inducible regions. Insertion of ARDS-associated SNPs (rs2700408, rs11714297) significantly increased nmMYLK promoter activity via increased transcription binding (glial cells missing homolog 1 (GCM1) and intestine-specific homeobox (ISX), respectively). Finally, the MYLK rs78755744 SNP (-261G/A), residing within a nmMYLK CpG island, significantly attenuated 5-Aza-induced promoter activity.

CONCLUSION

These findings indicate nmMYLK transcriptional regulation by clinically relevant inflammatory factors and ARDS-associated nmMYLK promoter variants are consistent with nmMLCK as a therapeutic target in severe inflammatory disorders.

Loganin alleviates sepsis-induced acute lung injury by regulating macrophage polarization and inhibiting NLRP3 inflammasome activation

Sepsis is a systemic inflammatory response syndrome resulted from severe infection. Excessive inflammation response plays an important role in sepsis-induced acute lung injury (ALI). Loganin is an iridoid glycoside isolated from Corni fructus and exerts an anti-inflammatory effect in multiple inflammatory diseases; however, the role of loganin in sepsis-induced ALI remains unknown. In the current study, the cecal ligation and puncture (CLP)-induced murine sepsis model was constructed to investigate the anti-inflammatory property of loganin in sepsis-induced ALI. Lipopolysaccharide (LPS)-treated Raw 264.7 cells and primary murine peritoneal macrophages were established to further explore underlying mechanism of loganin. Results showed that intragastrical administration of loganin significantly increased murine survival, reduced the alveolar structure damage and inflammatory cell infiltration. Loganin suppressed the release of the M1 macrophage-associated pro-inflammatory cytokines and induced the activation of M2-type anti-inflammatory cytokines. Besides, loganin dramatically inhibited NLRP3 inflammasome-mediated caspase-1 activation and subsequent IL-1β secretion. Further in vitro studies confirmed that loganin efficiently inhibited M1 macrophage polarization and NLRP3 inflammasome activation by blocking the extra-cellular signal-regulated kinase (ERK) and nuclear factor-kappa B (NF-κB) pathways. Taken together, the anti-inflammatory effect of loganin in sepsis-induced ALI was associated with the ERK and NF-κB pathway-mediated macrophage polarization and NLRP3 inflammasome activation. Our study offers a favorable mechanistic basis to support the therapeutic potential of loganin in anti-inflammatory diseases, such as sepsis-induced ALI.

Inflammatory Caspases Drive Pyroptosis in Acute Lung Injury

Acute lung injury (ALI), a critical respiratory disorder that causes diffuse alveolar injury leads to high mortality rates with no effective treatment. ALI is characterized by varying degrees of ventilation/perfusion mismatch, severe hypoxemia, and poor pulmonary compliance. The diffuse injury to cells is one of most important pathological characteristics of ALI. Pyroptosis is a form of programmed cell death distinguished from apoptosis induced by inflammatory caspases, which can release inflammatory cytokines to clear cells infected by pathogens and promote monocytes to reassemble at the site of injury. And pyroptosis not only promotes inflammation in certain cell types, but also regulates many downstream pathways to perform different functions. There is increasing evidence that pyroptosis and its related inflammatory caspases play an important role in the development of acute lung injury. The main modes of activation of pyroptosis is not consistent among different types of cells in lung tissue. Meanwhile, inhibition of inflammasome, the key to initiating pyroptosis is currently the main way to treat acute lung injury. The review summarizes the relationship among inflammatory caspases, pyroptosis and acute lung injury and provides general directions and strategies to conduct further research.

The NLRP3 inflammasome: Multiple activation pathways and its role in primary cells during ventricular remodeling

Inflammasomes are a group of multiprotein signaling complexes located in the cytoplasm. Several inflammasomes have been identified, including NLRP1, NLRP2, NLRP3, AIM2, and NLRC4. Among them, NLRP3 was investigated in most detail, and it was reported that it can be activated by many different stimuli. Increased NLRP3 protein expression and inflammasome assembly lead to caspase-1 mediated maturation and release of IL-1β, which triggers inflammation and pyroptosis. The activation of the NLRP3 inflammasome has been widely reported in studies of tumors and neurological diseases, but relatively few studies on the cardiovascular system. Ventricular remodeling (VR) is an important factor contributing to heart failure (HF) after myocardial infarction (MI). Consequently, delaying VR is of great significance for improving heart function. Studies have shown that the NLRP3 inflammasome plays an essential role in the process of VR. Here, we reviewed the latest studies on the activation pathway of the NLRP3 inflammasome, focusing on the effects of the NLRP3 inflammasome in primary cells during VR, and finally discuss future research directions in this field.

Physiological and Pathological Roles of Mammalian NEK7

NEK7 is the smallest NIMA-related kinase (NEK) in mammals. The pathological and physiological roles of NEK7 have been widely reported in many studies. To date, the major function of NEK7 has been well documented in mitosis and NLRP3 inflammasome activation, but the detailed mechanisms of its regulation remain unclear. This review summarizes current advances in NEK7 research involving mitotic regulation, NLRP3 inflammasome activation, related diseases and potential inhibitors, which may provide new insights into the understanding and therapy of the diseases associated with NEK7, as well as the subsequent studies in the future.

Epithelial Dysfunction in Lung Diseases: Effects of Amino Acids and Potential Mechanisms

Lung diseases affect millions of individuals all over the world. Various environmental factors, such as toxins, chemical pollutants, detergents, viruses, bacteria, microbial dysbiosis, and allergens, contribute to the development of respiratory disorders. Exposure to these factors activates stress responses in host cells and disrupt lung homeostasis, therefore leading to dysfunctional epithelial barriers. Despite significant advances in therapeutic treatments for lung diseases in the last two decades, novel interventional targets are imperative, considering the side effects and limited efficacy in patients treated with currently available drugs. Nutrients, such as amino acids (e.g., arginine, glutamine, glycine, proline, taurine, and tryptophan), peptides, and bioactive molecules, have attracted more and more attention due to their abilities to reduce oxidative stress, inhibit apoptosis, and regulate immune responses, thereby improving epithelial barriers. In this review, we summarize recent advances in amino acid metabolism in the lungs, as well as multifaceted functions of amino acids in attenuating inflammatory lung diseases based on data from studies with both human patients and animal models. The underlying mechanisms for the effects of physiological amino acids are likely complex and involve cell signaling, gene expression, and anti-oxidative reactions. The beneficial effects of amino acids are expected to improve the respiratory health and well-being of humans and other animals. Because viruses (e.g., coronavirus) and environmental pollutants (e.g., PM2.5 particles) induce severe damage to the lungs, it is important to determine whether dietary supplementation or intravenous administration of individual functional amino acids (e.g., arginine-HCl, citrulline, N-acetylcysteine, glutamine, glycine, proline and tryptophan) or their combinations to affected subjects may alleviate injury and dysfunction in this vital organ.

N-acetylcysteine alleviates post-resuscitation myocardial dysfunction and improves survival outcomes via partly inhibiting NLRP3 inflammasome induced-pyroptosis

Background

NOD-like receptor 3 (NLRP3) inflammasome is necessary to initiate acute sterile inflammation. Increasing evidence indicates the activation of NLRP3 inflammasome induced pyroptosis is closely related to reactive oxygen species (ROS) in the sterile inflammatory response triggered by ischemia/reperfusion (I/R) injury. N-acetylcysteine (NAC) is an antioxidant and plays a protective role in local myocardial I/R injury, while its effect on post-resuscitation myocardial dysfunction, as well as its mechanisms, remain elusive. In this study, we aimed to investigate the effect of NAC on post-resuscitation myocardial dysfunction in a cardiac arrest rat model, and whether its underlying mechanism may be linked to ROS and NLRP3 inflammasome-induced pyroptosis.

Methods

The rats were randomized into three groups: (1) sham group, (2) cardiopulmonary resuscitation (CPR) group, and (3) CPR + NAC group. CPR group and CPR + NAC group went through the induction of ventricular fibrillation (VF) and resuscitation. After return of spontaneous circulation (ROSC), rats in the CPR and CPR + NAC groups were again randomly divided into two subgroups, ROSC 6 h and ROSC 72 h, for further analysis. Hemodynamic measurements and myocardial function were measured by echocardiography, and western blot was used to detect the expression of proteins.

Results

Results showed that after treatment with NAC, there was significantly better myocardial function and survival duration; protein expression levels of NLRP3, adaptor apoptosis-associated speck-like protein (ASC), Cleaved-Caspase-1 and gasdermin D (GSDMD) in myocardial tissues were significantly decreased; and inflammatory cytokines levels were reduced. The marker of oxidative stress malondialdehyde (MDA) decreased and superoxide dismutase (SOD) increased with NAC treatment.

Conclusions

NAC improved myocardial dysfunction and prolonged animal survival duration in a rat model of cardiac arrest. Moreover, possibly by partly inhibiting ROS-mediated NLRP3 inflammasome-induced pryoptosis.

Resveratrol protects human bronchial epithelial cells against nickel-induced toxicity via suppressing p38 MAPK, NF-κB signaling, and NLRP3 inflammasome activation

Nickel is a common environmental pollutant that can impair the lung, but the underlying mechanisms have not yet been fully elucidated. Furthermore, natural products are generally used to inhibit cell damage induced by heavy metal. Resveratrol possesses wide biological activities, including anti-inflammation and antioxidative stress. This study was conducted to explore the toxicity of nickel on human bronchial epithelial (BEAS-2B) cells and evaluate the protective effect of resveratrol. The results showed that nickel could induce cell apoptosis, increase oxidative stress, and promote the expression of pro-inflammatory cytokines, including tumor necrosis factor-α, interleukin (IL)-1β, IL-6, IL-8, C-reaction protein. Western blot analysis showed that nickel activated p38 mitogen-activated protein kinase (MAPK), nuclear factor-kappa B, and nucleotide-binding oligomerization domain-like receptor pyrin-domain-containing protein 3 pathways, while resveratrol could reverse these effects. Our results suggested that resveratrol could protect BEAS-2B cells from nickel-induced cytotoxicity. Therefore, resveratrol is a potential chemopreventive agent against nickel-induced lung disease.

Protective role of p120-catenin on mitochondria by inhibiting NLRP3 in ventilator-induced lung injury

Mitochondria supply energy to maintain the integrity of cell junctions. NLRP3, as the core component of the inflammatory response, is crucial in mechanical stretching. Mechanical stretching could activate NLRP3 and induce mitochondrial dysfunction. The relationship between p120 and mitochondria in ventilator-induced lung injury (VILI) has not been elucidated. MLE-12 cells and wild-type male C57BL/6 mice were pre-treated with MCC950 (specific and highly efficient inhibitor of NLRP3) or a p120 siRNA-liposome complex. Then, the cells were subjected to 20% cyclic stretching, and the mice were subjected to mechanical ventilation at a high tidal volume. Cell lysates and lung tissues were obtained to detect the expression of NLRP3, p120, TLR4 pathway components, IL-6 and IL-1β, to determine the functions and structures of mitochondria, and the wet/dry ratio of the lung, and to perform pathological staining and an Evans blue dye assay. Mechanical stretching could increase the levels of NLRP3, ROS and damaged mitochondria, while these changes could be reversed by MCC950. Moreover, p120 prevented the activation of NLRP3 and regulated NLRP3 by inhibiting the TLR4 pathway and ROS production. Additionally, p120 played a vital role in protecting mitochondrial structures and functions after mechanical stretching. Taken together, these findings suggest that p120 depletion during mechanical stretching aggravates mitochondrial dysfunction by activating NLRP3, which indicates that p120 has a protective role on mitochondria in VILI by inhibiting NLRP3 activation.