Inhibition of Regulatory-Associated Protein of Mechanistic Target of Rapamycin Prevents Hyperoxia-Induced Lung Injury by Enhancing Autophagy and Reducing Apoptosis in Neonatal Mice

The potential therapeutic effect of human umbilical cord mesenchymal stem cell-derived exosomes in bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is a chronic lung disease of preterm infants, with its incidence rising due to improved survival rates of these infants. BPD results from a combination of prenatal and postnatal factors, such as mechanical ventilation, oxygen toxicity, and infections, all of which significantly impact the prognosis and growth of affected infants. Current treatment options for BPD are largely supportive and do not address the underlying pathology. Exosomes are cell-derived bilayer-enclosed membrane structures enclosing proteins, lipids, RNAs, growth factors, cytokines and metabolites. They have become recognized as crucial regulators of intercellular communication in various physiological and pathological processes. Previous studies have revealed the therapeutic potential of human umbilical cord mesenchymal stem cells-derived exosomes (HUCMSCs-Exos) in promoting tissue repair and regeneration. Therefore, HUCMSCs-Exos maybe a promising and effective therapeutic modality for BPD. In this review, we firstly provide a comprehensive overview of BPD, including its etiology and the mechanisms of lung injury. Then we detail the isolation, characterization, and contents of HUCMSCs-Exos, and discuss their potential mechanisms of HUCMSCs-Exos in BPD treatment. Additionally, we summarize current clinical trials and discuss the challenges in translating these findings from bench to bedside. This review aims to lay the groundwork for future clinical applications of HUCMSCs-Exos in treating BPD.

AMPK/MTOR/TP53 Signaling Pathway Regulation by Calcitonin Gene-Related Peptide Reduces Oxygen-Induced Lung Damage in Neonatal Rats through Autophagy Promotion

Our previous studies indicated that calcitonin gene-related peptide (CGRP) alleviates hyperoxia-induced lung injury and suggested the possible involvement of autophagy in this process. Herein, we aimed to further explore the potential involvement of tumor protein p53 (TP53) and autophagy in the mode of action of CGRP against hyperoxia-induced lung injury in vitro and in vivo. The study conducted tests on type II alveolar epithelial cells (AECII) and rats that were subjected to hyperoxia treatment or combined treatment of hyperoxia with CGRP, CGRP inhibitor, rapamycin (an autophagy agonist), 3-methyladenine (3-MA, an autophagy inhibitor), TP53 silencing/inhibitor (pifithrin-α), or expression vector/activator (PRIMA-1 (2,2-bis(hydroxymethyl)-3-quinuclidinone)) and their corresponding controls. We found that oxidative stress, apoptosis, and autophagy were all increased by hyperoxia treatment in vitro. However, treating AECII cells with CGRP reversed hyperoxia-induced oxidative stress and apoptosis but further promoted autophagy. In addition, the combined treatment with rapamycin or TP53 silencing with CGRP promoted the effect of CGRP, while contrary results were obtained with combined therapy with 3-MA or TP53 overexpression. In vivo, the number of hyperoxia-induced autophagosomes was promoted in the lung tissue of neonatal rats. Furthermore, hyperoxia increased the expression levels of AMP-activated protein kinase (AMPK) alpha 1 (also known as protein kinase AMP-activated catalytic subunit alpha 1 (PRKAA1)) but inhibited TP53 and mechanistic target of rapamycin (MTOR); these expression trends were regulated by CGRP treatment. In conclusion, we showed that CGRP can attenuate hyperoxia-induced lung injury in neonatal rats by enhancing autophagy and regulating the TP53/AMPK/MTOR crosstalk axis.

FAM134B deletion exacerbates apoptosis and epithelial-to-mesenchymal transition in rat lungs exposed to hyperoxia

Oxygen therapy is widely used in clinical practice; however, prolonged hyperoxia exposure may result in hyperoxic acute lung injury (HALI). In this study, we investigated the role of FAM134B in hyperoxia-induced apoptosis, cell proliferation, and epithelial-to-mesenchymal transition (EMT) using RLE-6TN cells and rat lungs. We also studied the effect of CeO2-NPs on RLE-6TN cells and lungs following hyperoxia exposure. FAM134B was inhibited in RLE-6TN cells and rat lungs following hyperoxia exposure. Overexpressing FAM134B promoted cell proliferation, and reduced EMT and apoptosis following hyperoxia exposure. FAM134B activation increased ER-phagy, decreased apoptosis, improved lung structure damage, and decreased collagen fiber deposition to limit lung injury. These effects could be reversed by PI3K/AKT pathway inhibitor LY294002. Additionally, CeO2-NPs protected RLE-6TN cells and lung damage following hyperoxia exposure by ameliorating impaired ER-phagy. Therefore, FAM134B restoration is a potential therapeutic target for the HALI. Moreover, CeO2-NPs can be used for the treatment of HALI.

Regulation of immune responses to infection through interaction between stem cell-derived exosomes and toll-like receptors mediated by microRNA cargoes

Infectious diseases are among the factors that account for a significant proportion of disease-related deaths worldwide. The primary treatment approach to combat microbial infections is the use of antibiotics. However, the widespread use of these drugs over the past two decades has led to the emergence of resistant microbial species, making the control of microbial infections a serious challenge. One of the most important solutions in the field of combating infectious diseases is the regulation of the host's defense system. Toll-like receptors (TLRs) play a crucial role in the first primary defense against pathogens by identifying harmful endogenous molecules released from dying cells and damaged tissues as well as invading microbial agents. Therefore, they play an important role in communicating and regulating innate and adaptive immunity. Of course, excessive activation of TLRs can lead to disruption of immune homeostasis and increase the risk of inflammatory reactions. Targeting TLR signaling pathways has emerged as a new therapeutic approach for infectious diseases based on host-directed therapy (HDT). In recent years, stem cell-derived exosomes have received significant attention as factors regulating the immune system. The regulation effects of exosomes on the immune system are based on the HDT strategy, which is due to their cargoes. In general, the mechanism of action of stem cell-derived exosomes in HDT is by regulating and modulating immunity, promoting tissue regeneration, and reducing host toxicity. One of their most important cargoes is microRNAs, which have been shown to play a significant role in regulating immunity through TLRs. This review investigates the therapeutic properties of stem cell-derived exosomes in combating infections through the interaction between exosomal microRNAs and Toll-like receptors.

MALAT1 DEREPRESSES MIR-433-3P-MEDIATED RPTOR SUPPRESSION TO IMPAIR AUTOPHAGY AND DRIVE PYROPTOSIS IN ENDOTOXEMIA

ABSTRACT

Objective: Autophagy elevation in endotoxemia plays a protective role by negatively regulating the pyroptosis of vascular endothelial cells, but the molecular mechanisms are still poorly understood. The present study aimed to identify the mechanism underlying autophagy and pyroptosis in endotoxemia. Methods: Bioinformatics analysis and whole-gene transcriptome sequencing prediction were used to identify the endotoxemia-related lncRNA-miRNA-mRNA axis of interest. Human umbilical vein endothelial cells (HUVECs) were activated by lipopolysaccharide (LPS) to mimic the inflammatory environment encountered in endotoxemia. Autophagy and pyroptosis of LPS-treated HUVECs were assessed in response to the knockdown of MALAT1 (metastasis-associated lung adenocarcinoma transcript 1)/miR-433-3p (miRNA-433-3p)/RPTOR (regulatory-associated protein of mTOR). The binding affinity of MALAT1, miR-433-3p, and RPTOR was detected by RNA pull-down and luciferase activity assays. The endothelial cell-specific RPTOR knockout mice were developed and rendered septic using LPS induction to verify the role of RPTOR in autophagy, pyroptosis, and inflammatory response in vivo . Results: The in vitro experiments indicated that LPS could stimulate HUVECs to highly express RPTOR, and its knockdown enhanced cellular autophagy and restricted pyroptosis to curb inflammatory responses. Mechanically, MALAT1 is competitively bound to miR-433-3p to release RPTOR expression, thereby promoting pyroptosis and aggravating endotoxemia. In vivo experiments further confirmed that the knockdown of RPTOR activated autophagy and curtailed pyroptosis in septic mice. Conclusion: MALAT1 is highly expressed in endotoxemia. MALAT1 promotes RPTOR expression by competitively absorbing miR-433-3p, inhibits LPS-activated HUVEC cell autophagy, promotes cell death, enhances LPS-induced inflammatory activation of vascular endothelial cells, and ultimately promotes the progression of endotoxemia.

BCL6 attenuates hyperoxia-induced lung injury by inhibiting NLRP3-mediated inflammation in fetal mouse

BACKGROUND

The transcriptional repressor B-cell lymphoma 6 (BCL6) has been reported to inhibit inflammation. So far, experimental evidence for the role of BCL6 in bronchopulmonary dysplasia (BPD) is lacking. Our study investigated the roles of BCL6 in the progression of BPD and its downstream mechanisms.

METHODS

Hyperoxia or lipopolysaccharide (LPS) was used to mimic the BPD mouse model. To investigate the effects of BCL6 on BPD, recombination adeno-associated virus serotype 9 expressing BCL6 (rAAV9-BCL6) and BCL6 inhibitor FX1 were administered in mice. The pulmonary pathological changes, inflammatory chemokines and NLRP3-related protein were observed. Meanwhile, BCL6 overexpression plasmid was used in human pulmonary microvascular endothelial cells (HPMECs). Cell proliferation, apoptosis, and NLRP3-related protein were detected.

RESULTS

Either hyperoxia or LPS suppressed pulmonary BCL6 mRNA expression. rAAV9-BCL6 administration significantly inhibited hyperoxia-induced NLRP3 upregulation and inflammation, attenuated alveolar simplification and dysregulated angiogenesis in BPD mice, which were characterized by decreased mean linear intercept, increased radical alveolar count and alveoli numbers, and the upregulated CD31 expression. Meanwhile, BCL6 overexpression promoted proliferation and angiogenesis, inhibited apoptosis and inflammation in hyperoxia-stimulated HPMECs. Moreover, administration of BCL6 inhibitor FX1 arrested growth and development. FX1-treated BPD mice exhibited exacerbation of alveolar pathological changes and pulmonary vessel permeability, with upregulated mRNA levels of pro-inflammatory cytokines and pro-fibrogenic factors. Furthermore, both rAAV9-BCL6 and FX1 administration exerted a long-lasting effect on hyperoxia-induced lung injury (≥4 wk).

CONCLUSIONS

BCL6 inhibits NLRP3-mediated inflammation, attenuates alveolar simplification and dysregulated pulmonary vessel development in hyperoxia-induced BPD mice. Hence, BCL6 may be a target in treating BPD and neonatal diseases.

ROS-mediated MAPK activation aggravates hyperoxia-induced acute lung injury by promoting apoptosis of type II alveolar epithelial cells via the STAT3/miR-21-5p axis

Inhibition of type II alveolar epithelial (AE-II) cell apoptosis is a critical way to cure hyperoxia-induced acute lung injury (HALI). It has been reported that miR-21-5p could reduce H2O2-induced apoptosis in AE-II cells. However, the upstream molecular mechanism remains unclear. Herein, we established a cellular model of HALI by exposing AE-II cells to H2O2 treatment. It was shown that miR-21-5p alleviated H2O2-induced apoptosis in AE-II cells. ROS inhibition decreased apoptosis of H2O2-evoked AE-II cells via increasing miR-21-5p expression. In addition, ROS induced MAPK and STAT3 phosphorylation in H2O2-treated AE-II cells. MAPK inactivation reduces H2O2-triggered AE-II cell apoptosis. MAPK activation inhibits miR-21-5p expression by promoting STAT3 phosphorylation in H2O2-challenged AE-II cells. Furthermore, STAT3 activation eliminated MAPK deactivation-mediated inhibition on the apoptosis of AE-II cells under H2O2 condition. In conclusion, ROS-mediated MAPK activation promoted H2O2-triggered AE-II cell apoptosis by inhibiting miR-21-5p expression via STAT3 phosphorylation, providing novel targets for HALI treatment.

The mechanism of action of Ophiocordyceps sinensis mycelia for prevention of acute lung injury based on non-targeted serum metabolomics

Ophiocordyceps sinensis is a fungus with medicinal value in treating lung diseases, but no study has reported how to prevent acute lung injury using this fungus. The mice were divided into normal, model, positive control, and O. sinensis groups to observe lung histopathological sections and transmission electron microscopy, along with liquid chromatography-mass spectrometry and hematoxylin and eosin (H&E) staining to closely identify structural differences resulting from destruction between the groups. The results of the H&E staining showed that, compared with the normal group, the model group showed alveolar collapse. Compared with the model group, the infiltration of inflammatory cells in the alveolar cavity of the O. sinensis group was significantly reduced. Mitochondrial plate-like cristae were observed in type II alveolar cells of the normal group, with normal coloration of the mitochondrial matrix. Type II alveolar cells in the model group showed obvious edema. The statuses of type II alveolar cells in the O. sinensis and positive groups were similar to that in the normal group. Twenty-nine biomarkers and 10 related metabolic pathways were identified by serum metabolomics screening. The results showed that O. sinensis mycelia had a significant effect on the prevention of lipopolysaccharide-induced inflammation.

Loss of IGFBP2 mediates alveolar type 2 cell senescence and promotes lung fibrosis

Accumulation of senescent cells contributes to age-related diseases including idiopathic pulmonary fibrosis (IPF). Insulin-like growth factor binding proteins (IGFBPs) regulate many biological processes; however, the functional contributions of IGFBP2 in lung fibrosis remain largely unclear. Here, we report that intranasal delivery of recombinant IGFBP2 protects aged mice from weight loss and demonstrated antifibrotic effects after bleomycin lung injury. Notably, aged human-Igfbp2 transgenic mice reveal reduced senescence and senescent-associated secretory phenotype factors in alveolar epithelial type 2 (AEC2) cells and they ameliorated bleomycin-induced lung fibrosis. Finally, we demonstrate that IGFBP2 expression is significantly suppressed in AEC2 cells isolated from fibrotic lung regions of patients with IPF and/or pulmonary hypertension compared with patients with hypersensitivity pneumonitis and/or chronic obstructive pulmonary disease. Altogether, our study provides insights into how IGFBP2 regulates AEC2-cell-specific senescence and that restoring IGFBP2 levels in fibrotic lungs can prove effective for patients with IPF.

The antimicrobial peptide LK2(6)A(L) exhibits anti-inflammatory activity by binding to the myeloid differentiation 2 domain and protects against LPS-induced acute lung injury in mice

Acute lung injury (ALI) is a life-threatening disease that is generally attributable to an uncontrolled inflammatory response in the lung, but there is a lack of effective treatments. At present, regulating the inflammatory response has become an important strategy for treating ALI. In the present study, LK2(6)A(L), a peptide derived from the natural antimicrobial peptide temporin-1CEa, inhibited lipopolysaccharide (LPS)-induced expression of tumor necrosis factor alpha (TNF-α), interleukin-6 (IL-6), and NO in RAW264.7 cells. Herein, the anti-inflammatory mechanism of LK2(6)A(L) was investigated. The RNA-sequencing (RNA-seq) results showed that LK2(6)A(L) significantly inhibited the TLR4-mediated NF-κB and MAPK signaling pathways in LPS-induced RAW264.7 cells. The results of co-immunoprecipitation (Co-IP), pull-down experiment, confocal laser scanning microscopy, and surface plasmon resonance (SPR) suggested that MD2 was the direct target of LK2(6)A(L). Chemical inhibition of MD2 and its knockdown abolished the anti-inflammatory effect of LK2(6)A(L). Molecular dynamic simulation indicated that LK2(6)A(L) could bind to the active domain of the MD2 hydrophobic pocket via six hydrogen bonds. The truncated peptides were designed based on analysis of the molecular docking of LK2(6)A(L) to MD2. The truncated peptide IS-7 showed strong affinity to MD2 and a remarkable inhibitory effect on pro-inflammatory factors that was comparable to the effect of LK2(6)A(L). Finally, LK2(6)A(L) and IS-7 relieved inflammatory symptoms and lung tissue destruction in the ALI mouse model. Overall, our study suggested that LK2(6)A(L) showed promising anti-inflammatory activity by targeting MD2, and the amino acid domain 7-13 was an important area that binds with MD2 and also an anti-inflammatory active region. LK2(6)A(L) and IS-7 may be potential new treatments for ALI and other acute inflammatory diseases.

AMPK-driven Macrophage Responses Are Autophagy Dependent in Experimental Bronchopulmonary Dysplasia

The pathogenesis of bronchopulmonary dysplasia (BPD) remains incompletely understood. Recent studies suggest insufficient AMP-activated protein kinase (AMPK) activation as a potential cause of impaired autophagy in rodent and nonhuman primate models of BPD. Impaired autophagy is associated with enhanced inflammatory signaling in alveolar macrophages (AMs) and increased severity of murine BPD induced by neonatal hyperoxia exposure. The goal of this study was to determine the role of autophagy and AMPK activation in macrophage responses in murine BPD. C57BL/6J mice were exposed to neonatal hyperoxia starting on postnatal day (P)1 and treated with the AMPK activator 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR) between P3 and P6. Mice were euthanized on P7, and markers of AMPK activation and autophagy were assessed by immunoblotting. Alveolarization was assessed using radial alveolar counts, mean linear intercept measurements, and quantification of alveolar septal myofibroblasts. Relative mRNA expression of M1-like and M2-like genes was assessed in AMs isolated from BAL fluid from wild-type, LysMCre--Becn1fl/fl, and LysMCre+-Becn1fl/fl mice after neonatal hyperoxia exposure. AICAR treatment resulted in AMPK activation and induction of autophagic activity in whole-lung and BAL cell lysates and attenuated hyperoxia-induced alveolar simplification in neonatal lungs. AICAR-treated control but not Beclin1-deficient AMs demonstrated significantly decreased expression of M1-like markers and significantly increased expression of M2-like markers. In conclusion, pharmacologic activation of AMPK by AICAR resulted in induction of autophagy and played a protective role, at least in part, through attenuation of proinflammatory signaling in AMs via autophagy-dependent mechanisms in a murine model of BPD.

OGG1 in the Kidney: Beyond Base Excision Repair

8-Oxoguanine DNA glycosylase (OGG1) is a repair protein for 8-oxoguanine (8-oxoG) in eukaryotic atopic DNA. Through the initial base excision repair (BER) pathway, 8-oxoG is recognized and excised, and subsequently, other proteins are recruited to complete the repair. OGG1 is primarily located in the cytoplasm and can enter the nucleus and mitochondria to repair damaged DNA or to exert epigenetic regulation of gene transcription. OGG1 is involved in a wide range of physiological processes, such as DNA repair, oxidative stress, inflammation, fibrosis, and autophagy. In recent years, studies have found that OGG1 plays an important role in the progression of kidney diseases through repairing DNA, inducing inflammation, regulating autophagy and other transcriptional regulation, and governing protein interactions and functions during disease and injury. In particular, the epigenetic effects of OGG1 in kidney disease have gradually attracted widespread attention. This study reviews the structure and biological functions of OGG1 and the regulatory mechanism of OGG1 in kidney disease. In addition, the possibility of OGG1 as a potential therapeutic target in kidney disease is discussed.

CircRNA, lncRNA, and mRNA profiles of umbilical cord blood exosomes from preterm newborns showing bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) represents a multifactorial chronic pulmonary pathology and a major factor causing premature illness and death. The therapeutic role of exosomes in BPD has been feverishly investigated. Meanwhile, the potential roles of exosomal circRNAs, lncRNAs, and mRNAs in umbilical cord blood (UCB) serum have not been studied. This study aimed to detect the expression profiles of circRNAs, lncRNAs, and mRNAs in UCB-derived exosomes of infants with BPD. Microarray analysis was performed to compare the RNA profiles of UCB-derived exosomes of a preterm newborn with (BPD group) and without (non-BPD, NBPD group) BPD. Then, circRNA/lncRNA-miRNA-mRNA co-expression networks were built to determine their association with BPD. In addition, cell counting kit-8 (CCK-8) assay was used to evaluate the proliferation of lipopolysaccharide (LPS)-induced human bronchial epithelial cells (BEAS-2B cells) and human umbilical vein endothelial cells (HUVECs). The levels of tumor necrosis factor (TNF)-α and interleukin (IL)-1β in LPS-induced BEAS-2B cells and HUVECs were assessed through Western blot analysis. Then, quantitative reverse transcription-polymerase chain reaction assay was used to evaluate the expression levels of four differentially expressed circRNAs (hsa_circ_0086913, hsa_circ_0049170, hsa_circ_0087059, and hsa_circ_0065188) and two lncRNAs (small nucleolar RNA host gene 20 (SNHG20) and LINC00582) detected in LPS-induced BEAS-2B cells or HUVECs. A total of 317 circRNAs, 104 lncRNAs, and 135 mRNAs showed significant differential expression in UCB-derived exosomes of preterm infants with BPD compared with those with NBPD. Gene Ontology (GO) enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses were conducted to examine differentially expressed exosomal circRNAs, lncRNAs, and mRNAs. The results showed that the GO terms and KEGG pathways mostly involving differentially expressed exosomal RNAs were closely associated with endothelial or epithelial cell development. In vitro, CCK-8 and Western blot assays revealed that LPS remarkably inhibited the viability and promoted inflammatory responses (TNF-α and IL-1β) of BEAS-2B cells or HUVECs. The expression levels of circRNAs hsa_circ_0049170 and hsa_circ_0087059 were upregulated in LPS-induced BEAS-2B cells; the expression level of hsa_circ_0086913 was upregulated and that of hsa_circ_0065188 was downregulated in LPS-induced HUVECs. Moreover, the expression level of lncRNA SNHG20 was upregulated and that of LINC00582 was downregulated in LPS-induced BEAS-2B cells. Further, 455 circRNA/lncRNA-miRNA-mRNA interaction networks were predicted, including hsa_circ_0086913/hsa-miR-103a-3p/transmembrane 4 L six family member 1 (TM4SF1) and lncRNA-SNHG20/hsa-miR-6720-5p/spermine synthase (SMS) networks, which may take part in BPD.

CONCLUSION

This study provided a systematic perspective on UCB-derived exosomal circRNAs and lncRNAs and laid an important foundation for further investigating the potential biological functions of exosomal circRNAs and lncRNAs in BPD.

WHAT IS KNOWN

• BPD represents a multifactorial chronic pulmonary pathology and a major factor causing premature illness and death. • The therapeutic role of exosomes in BPD has been feverishly investigated, and exosomal RNAs were ignored.

WHAT IS NEW

• The profiles of UCB-derived exosomal circRNAs, lncRNAs, and mRNAs were performed. • Several differentially expressed circRNAs and lncRNAs were identified in LPS-induced BEAS-2B cells and HUVECs.

Contribution of IL-38 in Lung Immunity during Pseudomonas Aeruginosa-induced Pneumonia

OBJECTIVE

Interleukin-38 (IL-38), a new type of cytokine, is involved in processes such as tissue repair, inflammatory response, and immune response. However, its function in pneumonia caused by Pseudomonas aeruginosa (P. aeruginosa) is still unclear.

METHODS

In this study, we detected circulating IL-38 and cytokines such as IL-1β, IL-6, IL-17A, TNF-α, IL-8, and IL-10 in adults affected by early stage pneumonia caused by P. aeruginosa. Collected clinical data of these patients, such as the APACHE II score, levels of PCT, and oxygenation index when they entering the ICU. Using P. aeruginosa-induced pneumonia WT murine model to evaluate the effect of IL-38 on Treg differentiation, cell apoptosis, survival, tissue damage, inflammation, and bacterial removal.

RESULTS

In clinical research, although IL-38 is significantly increased during the early stages of clinical P. aeruginosa pneumonia, the concentration of IL-38 in the serum of patients who died with P. aeruginosa pneumonia was relatively lower than that of surviving patients. It reveals IL-38 may insufficiently secreted in patients who died with P. aeruginosa pneumonia. Besides, the serum IL-38 level of patients with P. aeruginosa pneumonia on the day of admission to the ICU showed significantly positive correlations with IL-10 and the PaO2/FiO2 ratio but negative correlations with IL-1β, IL-6, IL-8, IL-17, TNF-α, APACHE II score, and PCT In summary, IL-38 might be a molecule for adjuvant therapy in P. aeruginosa pneumonia. In experimental animal models, first recombinant IL-38 improved survival, whereas anti-IL-38 antibody reduced survival in the experimental pneumonia murine model. Secondly, IL-38 exposure reduced the inflammatory response, as suggested by the lung injury, and reduced cytokine levels (IL-1β, IL-6, IL- 17A, TNF-α, and IL-8, but not IL-10). It also increased bacterial clearance and reduced cell apoptosis in the lungs. Furthermore, IL-38 was shown to reduce TBK1 expression in vitro when naive CD4+ T lymphocytes were differentiated to Tregs and played a protective role in P. aeruginosa pneumonia.

CONCLUSIONS

To summarize, the above findings provide additional insights into the mechanism of IL-38 in the treatment of P. aeruginosa pneumonia.

Hyperoxia Induces Ferroptosis and Impairs Lung Development in Neonatal Mice

Oxygen is often required to treat newborns with respiratory disorders, and prolonged exposure to high oxygen concentrations impairs lung development. Ferroptosis plays a vital role in the development of many diseases and has become the focus of treatment and prognosis improvement for related diseases, such as neurological diseases, infections, cancers, and ischemia-reperfusion injury. Whether ferroptosis participates in the pathogenesis of hyperoxia-induced lung injury remains unknown. The aims of this study are to determine the effects of hyperoxia on lung ferroptosis and development in neonatal mice. Newborn C57BL/6 mice were reared in either room air (RA) or hyperoxia (85% O₂) at postnatal days 1–7. On postnatal days 3 and 7, the lungs were harvested for histological and biochemical analysis. The mice reared in hyperoxia exhibited significantly higher Fe²⁺, malondialdehyde, and iron deposition and significantly lower glutathione, glutathione peroxidase 4, and vascular density than did those reared in RA on postnatal days 3 and 7. The mice reared in hyperoxia exhibited a comparable mean linear intercept on postnatal day 3 and a significantly higher mean linear intercept than the mice reared in RA on postnatal day 7. These findings demonstrate that ferroptosis was induced at a time point preceding impaired lung development, adding credence to the hypothesis that ferroptosis is involved in the pathogenesis of hyperoxia-induced lung injury and suggest that ferroptosis inhibitors might attenuate hyperoxia-induced lung injury.

Resveratrol inhibits cell apoptosis by suppressing long noncoding RNA (lncRNA) XLOC_014869 during lipopolysaccharide-induced acute lung injury in rats

Background

Acute lung injury (ALI) is a common clinical complication with a high mortality rate. Resveratrol (Res) has been shown to protect against ALI, but the role of long noncoding RNAs (lncRNAs) in this process is still unclear.

Methods

Male rats (n=20) aged 7–8 weeks were randomly divided into four groups: control, lipopolysaccharide (LPS), LPS + Res, and LPS + dexamethasone (Dexa). Intragastric administration of Res (0.5 mg/kg) or Dexa (1.5 mg/kg) was performed 1 h before intraperitoneal injection of LPS (5 mg/kg). Lung tissue, serum, and bronchoalveolar lavage fluid were sampled 6 h after LPS treatment for inflammatory factor detection, pathological detection, lncRNA sequencing and bioinformatical analysis, and TdT-mediated dUTP Nick-End Labeling. Quantitative real time polymerase chain reaction and western blotting were used to verify the sequencing results. LPS, Res, and RNA interference were used in rat alveolar epithelial cells experiments to confirm the protective of Res/lncRNA against ALI.

Results

Res pretreatment inhibited lung injury and the increase of inflammatory cytokines induced by LPS. The differentially expressed lncRNAs and mRNAs (P<0.05 and |fold change| >2) were mainly involved in the signaling pathway of immunity, infection, signaling molecules and interactions. Among the lncRNAs and mRNAs, 26 mRNAs and 23 lncRNAs had high levels in lungs treated with LPS but decreased with Res, and 17 mRNAs and 27 lncRNAs were at lower levels in lungs treated with LPS but increased with Res. lncRNA and adjacent mRNA analysis showed that lncRNAs XLOC_014869 and the adjacent gene Fos, and the possible downstream genes Jun and Faslg were increased by LPS, but these changes were attenuated by Res. Pretreatment with Res reduced LPS-induced lung tissue apoptosis. Similarly, Res treatment and knockdown of lncRNA XLOC_014869 reduced LPS-induced apoptosis and the levels of Fos, c-Jun, and Fas-L.

Conclusions

Res can inhibit the increase of lncRNAs XLOC_014869 caused by LPS stimulation and inhibit lung cell apoptosis. These effects may be due to lncRNA XLOC_014869 mediation of the pro-apoptotic factors (Fos, c-Jun, and Fas-L).

Chitin-Derived AVR-48 Prevents Experimental Bronchopulmonary Dysplasia (BPD) and BPD-Associated Pulmonary Hypertension in Newborn Mice

Bronchopulmonary dysplasia (BPD) is the most common complication of prematurity and a key contributor to the large health care burden associated with prematurity, longer hospital stays, higher hospital costs, and frequent re-hospitalizations of affected patients through the first year of life and increased resource utilization throughout childhood. This disease is associated with abnormal pulmonary function that may lead to BPD-associated pulmonary hypertension (PH), a major contributor to neonatal mortality and morbidity. In the absence of any definitive treatment options, this life-threatening disease is associated with high resource utilization during and after neonatal intensive care unit (NICU) stay. The goal of this study was to test the safety and efficacy of a small molecule derivative of chitin, AVR-48, as prophylactic therapy for preventing experimental BPD in a mouse model. Two doses of AVR-48 were delivered either intranasally (0.11 mg/kg), intraperitoneally (10 mg/kg), or intravenously (IV) (10 mg/kg) to newborn mouse pups on postnatal day (P)2 and P4. The outcomes were assessed by measuring total inflammatory cells in the broncho-alveolar lavage fluid (BALF), chord length, septal thickness, and radial alveolar counts of the alveoli, Fulton’s Index (for PH), cell proliferation and cell death by immunostaining, and markers of inflammation by Western blotting and ELISA. The bioavailability and safety of the drug were assessed by pharmacokinetic and toxicity studies in both neonatal mice and rat pups (P3-P5). Following AVR-48 treatment, alveolar simplification was improved, as evident from chord length, septal thickness, and radial alveolar counts; total inflammatory cells were decreased in the BALF; Fulton’s Index was decreased and lung inflammation and cell death were decreased, while angiogenesis and cell proliferation were increased. AVR-48 was found to be safe and the no-observed-adverse-effect level (NOAEL) in rat pups was determined to be 100 mg/kg when delivered via IV dosing with a 20-fold safety margin. With no reported toxicity and with a shorter half-life, AVR-48 is able to reverse the worsening cardiopulmonary phenotype of experimental BPD and BPD-PH, compared to controls, thus positioning it as a future drug candidate.

EGCG promotes PRKCA expression to alleviate LPS-induced acute lung injury and inflammatory response

Acute lung injury (ALI), which could be induced by multiple factors such as lipopolysaccharide (LPS), refer to clinical symptoms of acute respiratory failure, commonly with high morbidity and mortality. Reportedly, active ingredients from green tea have anti-inflammatory and anticancer properties, including epigallocatechin-3-gallate (EGCG). In the present study, protein kinase C alpha (PRKCA) is involved in EGCG protection against LPS-induced inflammation and ALI. EGCG treatment attenuated LPS-stimulated ALI in mice as manifested as improved lung injury scores, decreased total cell amounts, neutrophil amounts and macrophage amounts, inhibited the activity of MPO, decreased wet-to-dry weight ratio of lung tissues, and inhibited release of inflammatory cytokines TNF-α, IL-1β, and IL-6. PRKCA mRNA and protein expression showed to be dramatically decreased by LPS treatment while reversed by EGCG treatment. Within LPS-stimulated ALI mice, PRKCA silencing further aggravated, while PRKCA overexpression attenuated LPS-stimulated inflammation and ALI through MAPK signaling pathway. PRKCA silencing attenuated EGCG protection. Within LPS-induced RAW 264.7 macrophages, EGCG could induce PRKCA expression. Single EGCG treatment or Lv-PRKCA infection attenuated LPS-induced increases in inflammatory factors; PRKCA silencing could reverse the suppressive effects of EGCG upon LPS-stimulated inflammatory factor release. In conclusion, EGCG pretreatment inhibits LPS-induced ALI in mice. The protective mechanism might be associated with the inhibitory effects of PRKCA on proinflammatory cytokine release via macrophages and MAPK signaling pathway.

miR34a: a novel small molecule regulator with a big role in bronchopulmonary dysplasia

Preterm infants with bronchopulmonary dysplasia (BPD), characterized by pulmonary inflammation leading to impaired alveolarization and vascular dysregulation, have an increased risk of abnormal lung function in infancy, childhood, and adulthood. These include a heightened risk of pulmonary hypertension, and respiratory illnesses. MicroRNAs (miRNAs) are known to disrupt normal lung development and function by interrupting alveolarization and vascularization resulting in the development of BPD. Among the various miRs involved in BPD, miR34a has been shown to have a significant role in BPD pathogenesis. Targeting miR34a or its downstream targets may be a promising therapeutic intervention for BPD. In this review, we summarize the data on cellular arrest, proliferation, differentiation, epithelial-mesenchymal transition, mitochondrial dysfunction, and apoptosis impacted by miR34a in the development of BPD pulmonary phenotypes while predicting the future perspective of miR34a in BPD.

SIRT1-Related Signaling Pathways and Their Association With Bronchopulmonary Dysplasia

Bronchopulmonary dysplasia (BPD) is a chronic and debilitating disease that can exert serious and overwhelming effects on the physical and mental health of premature infants, predominantly due to intractable short- and long-term complications. Oxidative stress is one of the most predominant causes of BPD. Hyperoxia activates a cascade of hazardous events, including mitochondrial dysfunction, uncontrolled inflammation, reduced autophagy, increased apoptosis, and the induction of fibrosis. These events may involve, to varying degrees, alterations in SIRT1 and its associated targets. In the present review, we describe SIRT1-related signaling pathways and their association with BPD. Our intention is to provide new insights into the molecular mechanisms that regulate BPD and identify potential therapeutic targets for this debilitating condition.

Autophagy markers as mediators of lung injury-implication for therapeutic intervention

Lung injury is characterized by inflammatory processes demonstrated as loss of function of the pulmonary capillary endothelial and alveolar epithelial cells. Autophagy is an intracellular digestion system that work as an inducible adaptive response to lung injury which is a resultant of exposure to various stress agents like hypoxia, ischemia-reperfusion and xenobiotics which may be manifested as acute lung injury (ALI), acute respiratory distress syndrome (ARDS), chronic lung injury (CLI), bronchopulmonary dysplasia (BPD), chronic obstructive pulmonary disease (COPD), asthma, ventilator-induced lung injury (VILI), ventilator-associated lung injury (VALI), pulmonary fibrosis (PF), cystic fibrosis (CF) and radiation-induced lung injury (RILI). Numerous regulators like LC3B-II, Beclin 1, p62, HIF1/BNIP3 and mTOR play pivotal role in autophagy induction during lung injury possibly for progression/inhibition of the disease state. The present review focuses on the critical autophagic mediators and their potential cross talk with the lung injury pathophysiology thereby bringing to limelight the possible therapeutic interventions.

Impaired Autophagic Activity Contributes to the Pathogenesis of Bronchopulmonary Dysplasia. Evidence from Murine and Baboon Models

Bronchopulmonary dysplasia (BPD) is a common and serious complication associated with preterm birth. The pathogenesis of BPD is incompletely understood, and there is an unmet clinical need for effective treatments. The role of autophagy as a potential cytoprotective mechanism in BPD remains to be fully elucidated. In the present study, we investigated the role and regulation of autophagy in experimental models of BPD. Regulation and cellular distribution of autophagic activity during postnatal lung development and in neonatal hyperoxia-induced lung injury (nHILI) were assessed in the autophagy reporter transgenic GFP-LC3 (GFP-microtubule-associated protein 1A/1B-light chain 3) mouse model. Autophagic activity and its regulation were also examined in a baboon model of BPD. The role of autophagy in nHILI was determined by assessing lung morphometry, injury, and inflammation in autophagy-deficient Beclin 1 heterozygous knockout mice (Becn1^+/-). Autophagic activity was induced during alveolarization in control murine lungs and localized primarily to alveolar type II cells and macrophages. Hyperoxia exposure of neonatal murine lungs and BPD in baboon lungs resulted in impaired autophagic activity in association with insufficient AMPK (5'-AMP-activated protein kinase) and increased mTORC1 (mTOR complex 1) activation. Becn1^+/- lungs displayed impaired alveolarization, increased alveolar septal thickness, greater neutrophil accumulation, and increased IL-1β concentrations when exposed to nHILI. Becn1^+/- alveolar macrophages isolated from nHILI-exposed mice displayed increased expression of proinflammatory genes. In conclusion, basal autophagy is induced during alveolarization and disrupted during progression of nHILI in mice and BPD in baboons. Becn1^+/- mice are more susceptible to nHILI, suggesting that preservation of autophagic activity may be an effective protective strategy in BPD.

LncRNA-NEF regulated the hyperoxia-induced injury of lung epithelial cells by FOXA2

INTRODUCTION

Hyperoxia-induced injury is a common form of damage in lung tissues, which could lead to bronchopulmonary dysplasia (BPD) in newborns. Recent studies have discovered that FOXA2 played a substantial role in protecting lung tissues from various injuries and lncRNA-NEF could activate the expression of FOXA2. However, it is unclear whether lncRNA-NEF could alleviate hyperoxia-caused damage of lung tissues by activating FOXA2.

MATERIAL AND METHODS

In this study, we used the lentivirus to establish the lncRNA-NEF overexpression RLE-6TN and MLE-12 cells. After that, the lentivirus was also used to knockdown the expression of FOXA2 in the two lncRNA-NEF overexpression cells. ELISA was performed to detect the levels of TNF-α, IL-1β and IL-6. The production of ROS, SOD, MDA and LDH was determined with the commercial kits. The apoptosis rates of these cells were measured with the flow cytometry.

RESULTS

The secretion of TNF-α, IL-1β and IL-6 was inhibited in RLE-6TN and MLE-12 cells after the overexpression of lncRNA-NEF. Furthermore, the production of ROS, MDA and LDH was also suppressed after the upregulation of lncRNA-NEF. The promotion of lncRNA-NEF also restricted the hyperoxia-induced apoptosis. However, the knockdown of FOXA2 abolished all the inhibitory effects exerted by lncRNA-NEF.

CONCLUSION

LncRNA-NEF regulated hyperoxia-caused inflammatory response, oxidative damage and apoptosis of RLE-6TN and MLE-12 cells by affecting the expression of FOXA2.

Autophagy Augmentation to Alleviate Immune Response Dysfunction, and Resolve Respiratory and COVID-19 Exacerbations

The preservation of cellular homeostasis requires the synthesis of new proteins (proteostasis) and organelles, and the effective removal of misfolded or impaired proteins and cellular debris. This cellular homeostasis involves two key proteostasis mechanisms, the ubiquitin proteasome system and the autophagy–lysosome pathway. These catabolic pathways have been known to be involved in respiratory exacerbations and the pathogenesis of various lung diseases, such as chronic obstructive pulmonary disease (COPD), cystic fibrosis (CF), idiopathic pulmonary fibrosis (IPF), acute lung injury (ALI), acute respiratory distress syndrome (ARDS), and coronavirus disease-2019 (COVID-19). Briefly, proteostasis and autophagy processes are known to decline over time with age, cigarette or biomass smoke exposure, and/or influenced by underlying genetic factors, resulting in the accumulation of misfolded proteins and cellular debris, elevating apoptosis and cellular senescence, and initiating the pathogenesis of acute or chronic lung disease. Moreover, autophagic dysfunction results in an impaired microbial clearance, post-bacterial and/or viral infection(s) which contribute to the initiation of acute and recurrent respiratory exacerbations as well as the progression of chronic obstructive and restrictive lung diseases. In addition, the autophagic dysfunction-mediated cystic fibrosis transmembrane conductance regulator (CFTR) immune response impairment further exacerbates the lung disease. Recent studies demonstrate the therapeutic potential of novel autophagy augmentation strategies, in alleviating the pathogenesis of chronic obstructive or restrictive lung diseases and exacerbations such as those commonly seen in COPD, CF, ALI/ARDS and COVID-19.

MicroRNA-377-3p released by mesenchymal stem cell exosomes ameliorates lipopolysaccharide-induced acute lung injury by targeting RPTOR to induce autophagy

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are the severe lung damage and respiratory failure without effective therapy. However, there was a lack of understanding of the mechanism by which exosomes regulate autophagy during ALI/ARDS. Here, we found lipopolysaccharide (LPS) significantly increased inflammatory factors, administration of exosomes released by human umbilical cord mesenchymal stem cells (hucMSCs) successfully improved lung morphometry. Further studies showed that miR-377-3p in the exosomes played a pivotal role in regulating autophagy, leading to protect LPS induced ALI. Compared to exosomes released by human fetal lung fibroblast cells (HFL-1), hucMSCs-exosomes overexpressing miR-377-3p more effectively suppressed the bronchoalveolar lavage (BALF) and inflammatory factors and induced autophagy, causing recoveration of ALI. Administration of miR-377-3p expressing hucMSCs-exosomes or its target regulatory-associated protein of mTOR (RPTOR) knockdown significantly reduced ALI. In summary, miR-377-3p released by hucMSCs-exosomes ameliorated Lipopolysaccharide-induced acute lung injury by targeting RPTOR to induce autophagy in vivo and in vitro.

Hyperoxia reduces STX17 expression and inhibits the autophagic flux in alveolar type II epithelial cells in newborn rats

Supplemental oxygen therapy can be life-saving for premature infants. Our previous study revealed a defect in the autophagic flux in the lung tissues of neonatal rats with hyperoxia-induced bronchopulmonary dysplasia (BPD), but the underlying mechanism remains unknown. Moreover, there are few innovative treatments that can completely alter the course of BPD. The present study examined the expression of Syntaxin 17 (STX17), a protein necessary for autophago-some-lysosome binding, in alveolar type II (AT-II) epithelial cells of neonatal rats with BPD. Neonatal Sprague-Dawley rats were randomly exposed to elevated O₂ levels [fraction of inspired oxygen (FiO₂), 0.8; model group] or normal room air (FiO₂, 0.21; control group), and the expression levels of STX17, autophagy-related [Microtubule-associated protein 1A/1B-light chain 3B (LC3B)-II, p62, lysosomal-associated membrane protein 1)] and apoptosis-related (cleaved caspase3) mRNA and proteins were examined in lung tissues. Moreover, the expression levels of the aforementioned proteins were measured in isolated primary AT-II cells cultured in vitro under hyperoxic conditions in the presence or absence of pharmacological modulators of autophagy. Transmission electron microscopy identified that AT-II cell apoptosis and autophagosome aggregation were elevated in the lungs of BPD rats compared with control rats on postnatal day 7. STX17 mRNA and protein expression levels were decreased in lung tissue and isolated AT-II cells as early as postnatal day 3 in BPD rats, while the expression levels of LC3B-II, p62 and cleaved caspase3 were increased, reaching a peak on postnatal day 7. This early reduction in STX17 expression, followed by increased expression in autophagy- and apoptosis-related proteins, was also observed in isolated AT-II cells exposed to hyperoxia in vitro. However, treatment with the autophagy inducers rapamycin or LiCl eliminated the hyperoxia-induced reduction in STX17, partially restored the autophagy flux and increased the survival of AT-II cells exposed to hyperoxia. Collectively, these results indicated that STX17 expression in AT-II cells was reduced in the early stages of BPD in neonatal rats and may be related to the subsequent hyperoxia-induced block in autophagic flux.

Chitin Analog AVR-25 Prevents Experimental Bronchopulmonary Dysplasia

Infants born extremely preterm are at a high risk of developing bronchopulmonary dysplasia (BPD) which is characterized by large, simplified alveoli, increased inflammation, disrupted and dysregulated vasculogenesis, decreased cell proliferation, and increased cell death in the lungs. Due to lack of specific drug treatments to combat this condition, BPD and its long-term complications have taken a significant toll of healthcare resources. AVR-25, a novel immune modulator experimental compound, was able to partially recover the pulmonary phenotype in the hyperoxia-induced experimental mouse model of BPD. We anticipate that AVR-25 will have therapeutic potential for managing human BPD.

Genetic Approaches to Bronchopulmonary Dysplasia

Bronchopulmonary dysplasia (BPD) remains a common and challenging complication of prematurity, with limited effective strategies at the neonatologist's disposal. Throughout the years, our understanding of this complex syndrome has broadened. Instead of solely attributing this disease to the effects of prematurity and injuries to the lung from mechanical ventilation, it is now accepted to be a multifactorial disease. Recent research efforts have focused on investigating the gene-environment interactions that may influence an infant's susceptibility toward the development of BPD. So far, success has been limited but promising, offering hope that in the future, novel therapies will be available to ameliorate the risk for BPD.

Cilostazol alleviate nicotine induced cardiomyocytes hypertrophy through modulation of autophagy by CTSB/ROS/p38MAPK/JNK feedback loop

Nicotine is proved to be an important factor for cardiac hypertrophy. Autophagy is important cell recycling system involved in the regulation of cardiac hypertrophy. Cilostazol, which is often used in the management of peripheral vascular disease. However, the effects of cilostazol on nicotine induced autophagy and cardiac hypertrophy are unclear. Here, we aim to determine the role and molecular mechanism of cilostazol in alleviating nicotine-induced cardiomyocytes hypertrophy through modulating autophagy and the underlying mechanisms. Our results clarified that nicotine stimulation caused cardiomyocytes hypertrophy and autophagy flux impairment significantly in neonatal rat ventricular myocytes (NRVMs), which were evidenced by augments of LC3-II and p62 levels, and impaired autophagosomes clearance. Interestingly, cathepsin B (CTSB) activity decreased dramatically after stimulation with nicotine in NRVMs, which was crucial for substrate degradation in the late stage of autophagy process, and cilostazol could reverse this effect dramatically. Intracellular ROS levels were increased significantly after nicotine exposure. Meanwhile, p38MAPK and JNK were activated after nicotine treatment. By using ROS scavenger N-acetyl-cysteine (NAC) could reverse the effects of nicotine by down-regulation the phosphorylation of p38MAPK and JNK pathways, and pretreatment of specific inhibitors of p38MAPK and JNK could restore the autophagy impairment and cardiomyocytes hypertrophy induced by nicotine. Moreover, CTSB activity of lysosome regained after the treatment with cilostazol. Cilostazol also inhibited the ROS accumulation and the activation of p38MAPK and JNK, which providing novel connection between lysosome CTSB and ROS/p38MAPK/JNK related oxidative stress pathway. This is the first demonstration that cilostazol could alleviate nicotine induced cardiomyocytes hypertrophy through restoration of autophagy flux by activation of CTSB and inhibiting ROS/p38/JNK pathway, exhibiting a feedback loop on regulation of autophagy and cardiomyocytes hypertrophy.

Small Molecule Inhibitor Adjuvant Surfactant Therapy Attenuates Ventilator- and Hyperoxia-Induced Lung Injury in Preterm Rabbits

Background

Invasive mechanical ventilation (IMV) has become one of the mainstays of therapy in NICUs worldwide, as a result of which premature babies with extremely low birth weight have been able to survive. Although lifesaving, IMV can result in lung inflammation and injury. Surfactant therapy is considered a standard of care in preterm infants with immature lungs. Recently, small molecule inhibitors like siRNAs and miRNAs have been used for therapeutic purposes. Ddit3 (CHOP), Ang2 and miR34a are known to be upregulated in experimental lung injury. We wanted to test whether inhibitors for these molecules (CHOP siRNA, Ang2 siRNA, and miR34a antagomir) if used alone or with a combination with surfactant (Curosurf^®) would help in reducing ventilation and hyperoxia-induced injury in an experimental lung injury model.

Methods

Preterm rabbits born by cesarean section were intratracheally instilled with the three small molecule inhibitors with or without Curosurf^® prior to IMV and hyperoxia exposure. Prior to testing the inhibitors in rabbits, these small molecule inhibitors were transfected in mouse lung epithelial cells (MLE12 and AECII) and delivered to neonatal mouse pups intranasally as a proof of concept that surfactant (Curosurf^®) could be used as an effective vehicle for administration of such drugs. Survival, pulmonary function tests, histopathology, immunostaining, quantitative PCR and western blotting were done to see the adjuvant effect of surfactant with these three small molecule inhibitors.

Results

Our data shows that Curosurf^® can facilitate transfection of small molecules in MLE12 cells with the same and/or increased efficiency as Lipofectamine. Surfactant given alone or as an adjuvant with small molecule inhibitors increases survival, decreases IMV and hyperoxia-induced inflammation, improves pulmonary function and lung injury scores in preterm rabbit kits.

Conclusion

Our study shows that Curosurf^® can be used successfully as an adjuvant therapy with small molecule inhibitors for CHOP/Ang2/miR34a. In this study, of the three inhibitors used, miR34a inhibitor seemed to be the most promising compound to combat IMV and hyperoxia-induced lung injury in preterm rabbits.

Anti-fibrosis activity of quercetin attenuates rabbit tracheal stenosis via the TGF-β/AKT/mTOR signaling pathway

AIMS

This study aimed to explore the possible mechanism of trauma-induced laryngotracheal stenosis and potential protective and therapeutic efficacy of quercetin on trauma-induced laryngotracheal stenosis.

MAIN METHODS

The expression and activity of fibrotic factors [interleukin (IL)-6, IL-8, autophagy related 5 (ATG5), collagen (COL)-1, tumor growth factor (TGF)-β COL-3, microtubule-associated proteins 1A/1B light chain 3A (LC3), and vascular endothelial growth factor (VEGF)] and fibrotic signaling mediators [mammalian target of rapamycin (mTOR) and phosphorylated AKT (pAKT)] were detected by real-time quantitative PCR (qRT-PCR), ELISA, Western blot, and immunohistochemical staining, respectively, in the lipopolysaccharide (LPS)-induced WI-38 (a human embryonic lung fibroblast cell line) cellular fibrotic model and a trauma-induced rabbit tracheal stenosis model, with and without quercetin treatment.

KEY FINDINGS

Pre-treatment with quercetin significantly reversed the LPS-induced upregulation of pro-fibrotic factors (IL-6, IL-8, COL-1, COL-3, LC3) and fibrotic signaling mediators (mTOR and AKT), and it induced the downregulation of ATG5 in the WI-38 cells. Furthermore, the anti-fibrotic activity of quercetin was confirmed in the trauma-induced rabbit tracheal stenosis model. Thus, the nasogastric administration of quercetin attenuated the tracheal stenosis of the rabbit tracheal stenosis model, in addition to effectively reversing an increase in pro-fibrotic factors (VEGF, IL-6, TGF-β, COL-1, and COL-3) and fibrotic signaling mediators (mTOR and AKT), as well as downregulating ATG5 of the rabbit tracheal stenosis model.

SIGNIFICANCE

Quercetin exhibits anti-fibrotic activity by inhibiting pro-fibrotic factors and AKT/mTOR signaling pathway, in addition to activating autophagy activity. This study provided experimental evidence supporting the application of quercetin in tracheal stenosis, clinically.

[Expression of microRNA-495-5p in preterm infants with bronchopulmonary dysplasia: a bioinformatics analysis]

OBJECTIVE

To study the expression of microRNA-495-5p (miRNA-495-5p) in the serum of preterm infants with bronchopulmonary dysplasia (BPD) based on a bioinformatics analysis, and to provide a theoretical basis for further research on the association between miRNA-495-5p and BPD.

METHODS

A total of 40 preterm infants who were admitted to the neonatal intensive care unit from January 2015 to December 2016 were enrolled. Among these infants, 20 with early clinical manifestations of BPD were enrolled as the BPD group, and 20 without such manifestations were enrolled as the control group. Peripheral blood samples were collected. The miRNA microarray technique was used to screen out differentially expressed miRNAs in serum between the two groups. RT-PCR was used for validation of results. TargetScan, miRDB, and miRWalk databases were used to predict the target genes of miRNA-495-5p. The DAVID database was used to perform gene ontology (GO) analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis of the target genes.

RESULTS

Compared with the control group, the BPD group had a significant increase in the expression of miRNA-495-5p in serum (P<0.05). A total of 117 target genes of miRNA-495-5p were predicted by the above three databases and they were involved in several molecular functions (including transcriptional regulatory activity, transcriptional activation activity, and transcription cofactor activity), biological processes (such as metabolic regulation, DNA-dependent transcriptional regulation, and vascular pattern), and cell components (including nucleoplasm, membrane components, and insoluble components) (P<0.05). As for signaling pathways, these genes were significantly enriched in the mTOR signaling pathway (P<0.05).

CONCLUSIONS

MiRNA-495-5p may be involved in the development and progression of BPD by regulating angiogenesis, stem cell differentiation, apoptosis, and autophagy, which provides clues for further research on the role and functional mechanism of miRNA-495-5p in BPD.

Acid Sphingomyelinase Inhibition Attenuates Cell Death in Mechanically Ventilated Newborn Rat Lung

RATIONALE

Premature infants subjected to mechanical ventilation (MV) are prone to lung injury that may result in bronchopulmonary dysplasia. MV causes epithelial cell death and halts alveolar development. The exact mechanism of MV-induced epithelial cell death is unknown.

OBJECTIVES

To determine the contribution of autophagy to MV-induced epithelial cell death in newborn rat lungs.

METHODS

Newborn rat lungs and fetal rat lung epithelial (FRLE) cells were exposed to MV and cyclic stretch, respectively, and were then analyzed by immunoblotting and mass spectrometry for autophagy, apoptosis, and bioactive sphingolipids.

MEASUREMENTS AND MAIN RESULTS

Both MV and stretch first induce autophagy (ATG 5-12 [autophagy related 5-12] and LC3B-II [microtubule-associated proteins 1A/1B light chain 3B-II] formation) followed by extrinsic apoptosis (cleaved CASP8/3 [caspase-8/3] and PARP [poly(ADP-ribose) polymerase] formation). Stretch-induced apoptosis was attenuated by inhibiting autophagy. Coimmunoprecipitation revealed that stretch promoted an interaction between LC3B and the FAS (first apoptosis signal) cell death receptor in FRLE cells. Ceramide levels, in particular C16 ceramide, were rapidly elevated in response to ventilation and stretch, and C16 ceramide treatment of FRLE cells induced autophagy and apoptosis in a temporal pattern similar to that seen with MV and stretch. SMPD1 (sphingomyelin phosphodiesterase 1) was activated by ventilation and stretch, and its inhibition prevented ceramide production, LC3B-II formation, LC3B/first apoptosis signal interaction, caspase-3 activation, and, ultimately, FLRE cell death. SMPD1 inhibition also attenuated ventilation-induced autophagy and apoptosis in newborn rats.

CONCLUSIONS

Ventilation-induced ceramides promote autophagy-mediated cell death, and identifies SMPD1 as a potential therapeutic target for the treatment of ventilation-induced lung injury in newborns.

The Changes of Twist1 Pathway in Pulmonary Microvascular Permeability in a Newborn Rat Model of Hyperoxia-Induced Acute Lung Injury

Background: Bronchopulmonary dysplasia (BPD) is a chronic lung disease in preterm infants, which is characterized by alveolar and vascular dysplasia and increased vascular permeability. Hyperoxia is a critical factor in the pathogenesis of BPD, hyperoxia-induced acute lung injury (HALI) model has similar pathological manifestations as human BPD, therefore, may provide insight into the pathogenesis of human BPD. Studies have shown that Twist1 regulates pulmonary vascular permeability of LPS-induced lung injury through the Ang-Tie2 pathway. However, the effect of Twist1 pathway on vascular permeability in HALI has not been reported. Methods: We randomly exposed newborn rats to the room air or hyperoxia for 14 days. Lung histopathology, immunofluorescence, vascular permeability, mRNA and protein expression was assessed on day 1,7,14. Results: Our results verified that hyperoxia caused alveolar and vascular developmental disorders and increased pulmonary vascular permeability, which was consistent with previous findings. In hyperoxia-exposed rat lungs, the expressions of Twist1, Ang1, Tie1, Tie2, and pTie2 were significantly reduced, whereas the expression of Ang2 was significantly increased. Next, we observed a significant down-regulation of the Akt/Foxo1 pathway. Conclusion: In HALI, the pulmonary microvascular permeability was increased, accompanied by changes in Twist1-Tie2 pathway which combined to Angs, and downregulation of Tie1 and Akt/Foxo1 pathway.

TREM-1 Attenuates RIPK3-mediated Necroptosis in Hyperoxia-induced Lung Injury in Neonatal Mice

Hyperoxia-induced injury to the developing lung, impaired alveolarization, and dysregulated vascularization are critical factors in the pathogenesis of bronchopulmonary dysplasia (BPD); however, mechanisms for hyperoxia-induced development of BPD are not fully known. In this study, we show that TREM-1 (triggering receptor expressed on myeloid cells 1) is upregulated in hyperoxia-exposed neonatal murine lungs as well as in tracheal aspirates and lungs of human neonates with respiratory distress syndrome and BPD as an adaptive response to survival in hyperoxia. Inhibition of TREM-1 function using an siRNA approach or deletion of the Trem1 gene in mice showed enhanced lung inflammation, alveolar damage, and mortality of hyperoxia-exposed neonatal mice. The treatment of hyperoxia-exposed neonatal mice with agonistic TREM-1 antibody decreased lung inflammation, improved alveolarization, and was associated with diminished necroptosis-regulating protein RIPK3 (receptor-interacting protein kinase 3). Mechanistically, we show that TREM-1 activation alleviates lung inflammation and improves alveolarization through downregulating RIPK3-mediated necroptosis and NLRP3 (nucleotide-binding oligomerization domain-like receptor containing pyrin domain 3) inflammasome activation in hyperoxia-exposed neonatal mice. These data show that activating TREM-1, enhancing angiopoietin 1 signaling, or blocking the RIPK3-mediated necroptosis pathway may be used in new therapeutic interventions to control adverse effects of hyperoxia in the development of BPD.

Hyperoxia causes miR199a-5p-mediated injury in the developing lung

BACKGROUND

Hyperoxia-induced acute lung injury (HALI) is characterized by increased permeability and infiltration of inflammatory cells, impairment of alveolar development, and compromised lung function. Recent evidence has determined that microRNAs (miRs) are implicated in hyperoxia-induced lung injury, including bronchopulmonary dysplasia (BPD). However, the expression profile and functional role of miR199a-5p in developing lungs have not been reported.

METHODS

The present study was undertaken to explore the role of miR199a-5p in developing mice lungs and human neonates. We exposed neonatal mice for 7 days, mouse lung epithelial cells (MLE12), mouse lung endothelial cells (MLECs), and macrophages (RAW246.7), to hyperoxia at different time points.

RESULTS

Our results demonstrated enhanced miR199a-5p expression in hyperoxia-exposed mice lungs and cells, as well as in tracheal aspirates of infants developing BPD, with significant reduction in the expression of its target, caveolin-1. Next, we observed that miR199a-5p-mimic worsens HALI as evidenced by increased inflammatory cells, cytokines, and lung vascular markers. Conversely, miR199a-5p-inhibitor treatment attenuated HALI.

CONCLUSION

Thus, our findings suggest that miR199a-5p is a potential target for attenuating HALI pathophysiology in the developing lung. Moreover, miR199a-5p-inhibitor could be part of a novel therapeutic strategy for improving BPD in preterm neonates.

Autophagy is required for lung development and morphogenesis

Bronchopulmonary dysplasia (BPD) remains a major respiratory illness in extremely premature infants. The biological mechanisms leading to BPD are not fully understood, although an arrest in lung development has been implicated. The current study aimed to investigate the occurrence of autophagy in the developing mouse lung and its regulatory role in airway branching and terminal sacculi formation. We found 2 windows of epithelial autophagy activation in the developing mouse lung, both resulting from AMPK activation. Inhibition of AMPK-mediated autophagy led to reduced lung branching in vitro. Conditional deletion of beclin 1 (Becn1) in mouse lung epithelial cells (Becn1Epi-KO), either at early (E10.5) or late (E16.5) gestation, resulted in lethal respiratory distress at birth or shortly after. E10.5 Becn1Epi-KO lungs displayed reduced airway branching and sacculi formation accompanied by impaired vascularization, excessive epithelial cell death, reduced mesenchymal thinning of the interstitial walls, and delayed epithelial maturation. E16.5 Becn1Epi-KO lungs had reduced terminal air sac formation and vascularization and delayed distal epithelial differentiation, a pathology similar to that seen in infants with BPD. Taken together, our findings demonstrate that intrinsic autophagy is an important regulator of lung development and morphogenesis and may contribute to the BPD phenotype when impaired.

Iloprost attenuates hyperoxia-mediated impairment of lung development in newborn mice

Cyclooxygenase-2 (COX-2/PTGS2) mediates hyperoxia-induced impairment of lung development in newborn animals and is increased in the lungs of human infants with bronchopulmonary dysplasia (BPD). COX-2 catalyzes the production of cytoprotective prostaglandins, such as prostacyclin (PGI2), as well as proinflammatory mediators, such as thromboxane A2. Our objective was to determine whether iloprost, a synthetic analog of PGI2, would attenuate hyperoxia effects in the newborn mouse lung. To test this hypothesis, newborn C57BL/6 mice along with their dams were exposed to normoxia (21% O2) or hyperoxia (85% O2) from 4 to 14 days of age in combination with daily intraperitoneal injections of either iloprost 200 µg·kg-1·day-1, nimesulide (selective COX-2 antagonist) 100 mg·kg-1·day-1, or vehicle. Alveolar development was estimated by radial alveolar counts and mean linear intercepts. Lung function was determined on a flexiVent, and multiple cytokines and myeloperoxidase (MPO) were quantitated in lung homogenates. Lung vascular and microvascular morphometry was performed, and right ventricle/left ventricle ratios were determined. We determined that iloprost (but not nimesulide) administration attenuated hyperoxia-induced inhibition of alveolar development and microvascular density in newborn mice. Iloprost and nimesulide both attenuated hyperoxia-induced, increased lung resistance but did not improve lung compliance that was reduced by hyperoxia. Iloprost and nimesulide reduced hyperoxia-induced increases in MPO and some cytokines (IL-1β and TNF-α) but not others (IL-6 and KC/Gro). There were no changes in pulmonary arterial wall thickness or right ventricle/left ventricle ratios. We conclude that iloprost improves lung development and reduces lung inflammation in a newborn mouse model of BPD.

miR-34b-5p inhibition attenuates lung inflammation and apoptosis in an LPS-induced acute lung injury mouse model by targeting progranulin

Inflammation and apoptosis play important roles in the initiation and progression of acute lung injury (ALI). Our previous study has shown that progranulin (PGRN) exerts lung protective effects during LPS-induced ALI. Here, we have investigated the potential roles of PGRN-targeting microRNAs (miRNAs) in regulating inflammation and apoptosis in ALI and have highlighted the important role of PGRN. LPS-induced lung injury and the protective roles of PGRN in ALI were first confirmed. The function of miR-34b-5p in ALI was determined by transfection of a miR-34b-5p mimic or inhibitor in intro and in vivo. The PGRN level gradually increased and subsequently significantly decreased, reaching its lowest value by 24 hr; PGRN was still elevated compared to the control. The change was accompanied by a release of inflammatory mediators and accumulation of inflammatory cells in the lungs. Using bioinformatics analysis and RT-PCR, we demonstrated that, among 12 putative miRNAs, the kinetics of the miR-34b-5p levels were closely associated with PGRN expression in the lung homogenates. The gain- and loss-of-function analysis, dual-luciferase reporter assays, and rescue experiments confirmed that PGRN was the functional target of miR-34b-5p. Intravenous injection of miR-34b-5p antagomir in vivo significantly inhibited miR-34b-5p up-regulation, reduced inflammatory cytokine release, decreased alveolar epithelial cell apoptosis, attenuated lung inflammation, and improved survival by targeting PGRN during ALI. miR-34b-5p knockdown attenuates lung inflammation and apoptosis in an LPS-induced ALI mouse model by targeting PGRN. This study shows that miR-34b-5p and PGRN may be potential targets for ALI treatments.

[Effect of prone positioning on respiratory function in very preterm infants undergoing mechanical ventilation]

OBJECTIVE

To explore the effect of prone positioning on respiratory function in very preterm infants undergoing mechanical ventilation.

METHODS

A total of 83 very preterm infants treated with mechanical ventilation were enrolled in the study and were randomly assigned to supine group and prone group. Four infants withdrew from the study and 79 infants completed treatment and observation (37 in the supine group and 42 in the prone group). Infants in both groups were mechanically ventilated in a volume assist-control mode. Infants in the prone group were ventilated in the supine position for 4 hours and in the prone position for 2 hours. Ventilator parameters, arterial blood gas analysis, and vital signs were recorded before grouping, every 6 hours in the supine group, and every hour after conversion into the prone position in the prone group, respectively.

RESULTS

Fraction of inspired oxygen (FiO2), peak inspiratory pressure, mean inspiratory pressure, and duration of ventilation were significantly lower in the prone group than in the supine group (P<0.05); there were no significant differences in tidal volume or positive end-expiratory pressure between the two groups (P>0.05). The prone group had a significantly higher PO2/FiO2 ratio but significantly lower oxygenation index and respiratory rate than the supine group (P<0.05). There were no significant differences in arterial oxygen tension, pH, base excess, heart rate, or mean blood pressure between the two groups (P>0.05).

CONCLUSIONS

Alternating ventilation between the prone position and supine position can improve oxygenation function, decrease the fraction of inspired oxygen, and shorten the duration of mechanical ventilation in very preterm infants undergoing mechanical ventilation.

[Effect of prone positioning on respiratory function in very preterm infants undergoing mechanical ventilation]

OBJECTIVE

To explore the effect of prone positioning on respiratory function in very preterm infants undergoing mechanical ventilation.

METHODS

A total of 83 very preterm infants treated with mechanical ventilation were enrolled in the study and were randomly assigned to supine group and prone group. Four infants withdrew from the study and 79 infants completed treatment and observation (37 in the supine group and 42 in the prone group). Infants in both groups were mechanically ventilated in a volume assist-control mode. Infants in the prone group were ventilated in the supine position for 4 hours and in the prone position for 2 hours. Ventilator parameters, arterial blood gas analysis, and vital signs were recorded before grouping, every 6 hours in the supine group, and every hour after conversion into the prone position in the prone group, respectively.

RESULTS

Fraction of inspired oxygen (FiO²), peak inspiratory pressure, mean inspiratory pressure, and duration of ventilation were significantly lower in the prone group than in the supine group (P<0.05); there were no significant differences in tidal volume or positive end-expiratory pressure between the two groups (P>0.05). The prone group had a significantly higher PO²/FiO² ratio but significantly lower oxygenation index and respiratory rate than the supine group (P<0.05). There were no significant differences in arterial oxygen tension, pH, base excess, heart rate, or mean blood pressure between the two groups (P>0.05).

CONCLUSIONS

Alternating ventilation between the prone position and supine position can improve oxygenation function, decrease the fraction of inspired oxygen, and shorten the duration of mechanical ventilation in very preterm infants undergoing mechanical ventilation.

Autophagy inducers restore impaired autophagy, reduce apoptosis, and attenuate blunted alveolarization in hyperoxia-exposed newborn rats

AIM

Autophagy is a common process during development. Abnormal autophagy can impact cell apoptosis. Previous studies have shown that apoptosis is present during bronchopulmonary dysplasia (BPD). However, there is no consensus on the level of coexisting autophagy. This study was designed to investigate the role of autophagy and the effects of autophagy inducers in a BPD model.

METHOD

A total of 100 newborn Sprague-Dawley rats were randomly assigned to model and control groups. BPD models were established by hyperoxic induction(FiO₂ 0.80). Some of them were treated with autophagy-inducing agents.

RESULT

As compared to the control group, more autophagic bodies were found within Type II alveolar epithelial cells (AT-II cells) under transmission electron microscopy (TEM) in the model group at 3 d . These autophagic bodies were also accompanied by apoptotic bodies and expression of both bodies peaked at 7 d. As shown by TdT-mediated dUTP nick end labeling (TUNEL), there were more apoptotic cells in the model group than in the control group. Protein expression levels of LC3B-II, p62, Lamp1, and cleaved Caspase-3 increased with increased hyperoxic exposure time. No significant differences were observed in the mRNA expression levels of LC3B, p62, and Lamp1. After introducing an autophagy inducer, either rapamycin or lithium chloride, the radial alveolar count (RAC) value of BPD model group increased as compared with placebo group, the thickness of alveolar septum decreased, while apoptosis decreased.

CONCLUSION

Reduced autophagy resulting from blocked autophagy flow may be a key link in the pathogenesis of BPD. By enhancing repressed autophagy, apoptosis could be reduced and alveolar development improved.

Early gestational mesenchymal stem cell secretome attenuates experimental bronchopulmonary dysplasia in part via exosome-associated factor TSG-6

BACKGROUND

Mesenchymal stem cells (MSCs) are promising tools for the treatment of human lung disease and other pathologies relevant to newborn medicine. Recent studies have established MSC exosomes (EXO), as one of the main therapeutic vectors of MSCs in mouse models of multifactorial chronic lung disease of preterm infants, bronchopulmonary dysplasia (BPD). However, the mechanisms underlying MSC-EXO therapeutic action are not completely understood. Using a neonatal mouse model of human BPD, we evaluated the therapeutic efficiency of early gestational age (GA) human umbilical cord (hUC)-derived MSC EXO fraction and its exosomal factor, tumor necrosis factor alpha-stimulated gene-6 (TSG-6).

METHODS

Conditioned media (CM) and EXO fractions were isolated from 25 and 30 weeks GA hUC-MSC cultures grown in serum-free media (SFM) for 24 h. Newborn mice were exposed to hyperoxia (> 95% oxygen) and were given intraperitoneal injections of MSC-CM or MSC-CM EXO fractions at postnatal (PN) day 2 and PN4. They were then returned to room air until PN14 (in a mouse model of severe BPD). The treatment regime was followed with (rh)TSG-6, TSG-6-neutralizing antibody (NAb), TSG-6 (si)RNA-transfected MSC-CM EXO and their appropriate controls. Echocardiography was done at PN14 followed by harvesting of lung, heart and brain for assessment of pathology parameters.

RESULTS

Systemic administration of CM or EXO in the neonatal BPD mouse model resulted in robust improvement in lung, cardiac and brain pathology. Hyperoxia-exposed BPD mice exhibited pulmonary inflammation accompanied by alveolar-capillary leakage, increased chord length, and alveolar simplification, which was ameliorated by MSC CM/EXO treatment. Pulmonary hypertension and right ventricular hypertrophy was also corrected. Cell death in brain was decreased and the hypomyelination reversed. Importantly, we detected TSG-6, an immunomodulatory glycoprotein, in EXO. Administration of TSG-6 attenuated BPD and its associated pathologies, in lung, heart and brain. Knockdown of TSG-6 by NAb or by siRNA in EXO abrogated the therapeutic effects of EXO, suggesting TSG-6 as an important therapeutic molecule.

CONCLUSIONS

Preterm hUC-derived MSC-CM EXO alleviates hyperoxia-induced BPD and its associated pathologies, in part, via exosomal factor TSG-6. The work indicates early systemic intervention with TSG-6 as a robust option for cell-free therapy, particularly for treating BPD.

RIPK3 promotes sepsis-induced acute kidney injury via mitochondrial dysfunction

Sepsis causes acute kidney injury (AKI) in critically ill patients, although the pathophysiology remains unclear. The receptor-interacting protein kinase-3 (RIPK3), a cardinal regulator of necroptosis, has recently been implicated in the pathogenesis of human disease. In mice subjected to polymicrobial sepsis, we demonstrate that RIPK3 promotes sepsis-induced AKI. Utilizing genetic deletion and biochemical approaches in vitro and in vivo, we identify a potentially novel pathway by which RIPK3 aggravates kidney tubular injury independently of the classical mixed lineage kinase domain-like protein-dependent (MLKL-dependent) necroptosis pathway. In kidney tubular epithelial cells, we show that RIPK3 promotes oxidative stress and mitochondrial dysfunction involving upregulation of NADPH oxidase-4 (NOX4) and inhibition of mitochondrial complex I and -III, and that RIPK3 and NOX4 are critical for kidney tubular injury in vivo. Furthermore, we demonstrate that RIPK3 is required for increased mitochondrial translocation of NOX4 in response to proinflammatory stimuli, by a mechanism involving protein-protein interactions. Finally, we observed elevated urinary and plasma RIPK3 levels in human patients with sepsis-induced AKI, representing potential markers of this condition. In conclusion, we identify a pathway by which RIPK3 promotes kidney tubular injury via mitochondrial dysfunction, independently of MLKL, which may represent a promising therapeutic target in sepsis-induced AKI.

The kinetics of autophagy in the lung following acute spinal cord injury in rats

BACKGROUND CONTEXT

Lung injury is a major cause of respiratory complications following an acute spinal cord injury (ASCI), which are associated with a high mortality rate. Autophagy has been shown to be involved in a variety of lung diseases; however, whether autophagy is activated in the lung following ASCI remains unknown.

PURPOSE

The objective of this study was to investigate the induction of autophagy in the lung after ASCI.

STUDY DESIGN

This is an experimental animal study of ASCI investigating kinetics of autophagy in the lung following ASCI.

METHODS

One hundred and forty-four rats (N=144) were divided into two groups: (1) a sham (n=72) and (2) an injury group (n=72). Allen's method was used to induce an injury at the level of the 10th thoracic vertebra. Rats were sacrificed at 6, 12, 24, 48, and 72 hours, 1 week, and 2 weeks after surgery. Lung pathology and apoptosis were assessed to determine the level of damage in the lung. LC3, RAB7, P62, and Beclin 1 were used to detect the induction of autophagy. The study was funded by the Natural Science Foundation of China (NSFC,81272172); National Key Specialty Construction of Clinical Projects of China (#2013-544). The funder of the present study had no capacity to influence the scholarly conduct of the research, interpretation of results, or dissemination of study outcomes.

RESULTS

In the injury group, pathologic changes (i.e., pulmonary congestion, hemorrhage, inflammatory exudation, and alveolar collapse) occurred within the lung tissue within 72 hours after ASCI. Apoptosis of the lung cells gradually increased and peaked 72 hours after ASCI. Within 24 hours of ASCI, LC3 expression decreased, recovered, and gradually increased from 24 hours to 72 hours. As RAB7 decreased, P62 increased, and the ratio of RAB7/LC3 significantly decreased.

CONCLUSIONS

After ASCI, autophagy in the injured lung underwent dynamic changes, as early autophagosome formation decreased and late autophagosomes accumulated; thus, autophagy is in a state of inhibition.

Exosomal microRNA predicts and protects against severe bronchopulmonary dysplasia in extremely premature infants

Premature infants are at high risk for developing bronchopulmonary dysplasia (BPD), characterized by chronic inflammation and inhibition of lung development, which we have recently identified as being modulated by microRNAs (miRNAs) and alterations in the airway microbiome. Exosomes and exosomal miRNAs may regulate cell differentiation and tissue and organ development. We discovered that tracheal aspirates from infants with severe BPD had increased numbers of, but smaller, exosomes compared with term controls. Similarly, bronchoalveolar lavage fluid from hyperoxia-exposed mice (an animal model of BPD) and supernatants from hyperoxia-exposed human bronchial epithelial cells (in vitro model of BPD) had increased exosomes compared with air controls. Next, in a prospective cohort study of tracheal aspirates obtained at birth from extremely preterm infants, utilizing independent discovery and validation cohorts, we identified unbiased exosomal miRNA signatures predictive of severe BPD. The strongest signal of reduced miR-876-3p in BPD-susceptible compared with BPD-resistant infants was confirmed in the animal model and in vitro models of BPD. In addition, based on our recent discovery of increased Proteobacteria in the airway microbiome being associated with BPD, we developed potentially novel in vivo and in vitro models for BPD combining Proteobacterial LPS and hyperoxia exposure. Addition of LPS led to a larger reduction in exosomal miR 876-3p in both hyperoxia and normoxia compared with hyperoxia alone, thus indicating a potential mechanism by which alterations in microbiota can suppress miR 876-3p. Gain of function of miR 876-3p improved the alveolar architecture in the in vivo BPD model, demonstrating a causal link between miR 876-3p and BPD. In summary, we provide evidence for the strong predictive biomarker potential of miR 876-3p in severe BPD. We also provide insights on the pathogenesis of neonatal lung disease, as modulated by hyperoxia and microbial product-induced changes in exosomal miRNA 876-3p, which could be targeted for future therapeutic development.