The function role of ubiquitin proteasome pathway in the ER stress-induced AECII apoptosis during hyperoxia exposure

Background Bronchopulmonary dysplasia (BPD) is a major cause of mortality and morbidity in premature infants, characterized by alveolar dysplasia and pulmonary microvascular remodeling. In the present study, we have investigated the functional roles of ubiquitin proteasome pathway (UPP) in BPD, and its relationship with endoplasmic reticulum stress (ERS) mediated type II alveolar epithelial cell (AECII) apoptosis. Methods A hyperoxia-induced BPD rat model was constructed and the pathologic changes of lung tissues were evaluated by hematoxylin–eosin staining. Cell apoptosis and protein expression were determined by TUNEL assay and Western blotting, respectively. Further reagent kit with specific fluorescent substrate was utilized to measure the activity of 20 s proteasome. Meanwhile, AECII were cultured in vitro and exposed to hyperoxia. AECII apoptosis were measured by flow cytometry. In contrast, MG132 treatment was induced to explore UPP during hyperoxia exposure on AECII apoptosis and ERS sensors expression. Results A significant increase in apoptosis and total ubiquitinated proteins expression were observed in BPD rats and AECII culture, and the change of UPP was associated with ERS. In order to confirm the role of UPP in AECII apoptosis of BPD, AECII cells were treated by MG132 with the concentration of 10 μmol/L under hyperoxia exposure. We found that the proteins expression of glucose-regulated protein 78 (GRP-78), PKR-like ER kinase (PERK), activating transcription factor 4 (ATF4), activating transcription factor 6 (ATF6) and C/EBP homologous protein (CHOP), as well as AECII apoptosis were increased following MG132 treatment. Furthermore, the relatively up-regulated in the levels of total ubiquitinated proteins expression and 20 s proteasome activity were correlated with increased ERS sensors expression. Conclusions Our findings indicate that UPP may participate in the ERS-induced AECII apoptosis under hyperoxia condition.

18β-Glycyrrhetinic Acid Protectes Neonatal Rats with Hyperoxia Exposure Through Inhibiting ROS/NF-κB/NLRP3 Inflammasome

Bronchopulmonary dysplasia (BPD) is a common devastating pulmonary complication in preterm infants. Oxygen supplementation is a lifesaving therapeutic measure used for premature infants with pulmonary insufficiency. However, oxygen toxicity is a significant trigger for BPD, and oxidative stress-induced inflammatory responses, in turn, worsens the oxidative toxicity resulting in lung injury and arresting of lung development. Glycyrrhiza radix is commonly used in the medicine and food industries. 18β-Glycyrrhetinic acid (18β-GA), a primary active ingredient of Glycyrrhiza radix, has a powerful anti-oxidative and anti-inflammatory effects. This study aimed to determine whether 18β-GA has protective effects on neonatal rats with hyperoxia exposure. Newborn Sprague-Dawley rats were kept in either 21% (normoxia) or 80% O2 (hyperoxia) continuously from postnatal day (PN) 1 to 14. 18β-GA was injected intragastrically at 50 or 100 mg/kg body weight once a day from PN 1 to 14. We examined the body weights and alveolar development, and measured ROS level and the markers of pulmonary inflammation. Mature-IL-1β and NF-κB pathway proteins, and the NLRP3 inflammasome, were assessed; concurrently, caspase-1 activity was measured. Our results indicated that hyperoxia resulted in alveolar simplification and decreased bodyweight of neonatal rats. Hyperoxia exposure increased ROS level and pulmonary inflammation, and activated NF-κB and the NLRP3 inflammasome. 18β-GA treatment decreased ROS level, inhibited the activation of NF-κB and the NLRP3 inflammasome, decreased pulmonary inflammation, improved alveolar development, and increased the bodyweight of neonatal rats with hyperoxia exposure. Our study demonstrates that 18β-GA protects neonatal rats with hyperoxia exposure through inhibiting ROS/NF-κB/NLRP3 inflammasome.

Hyperoxia-Exposed Lung Injury Upregulates DVL-1 Protein Expression And Activates Wnt/β-Catenin Signaling Pathway in Newborn Rat Lung

Background: Bronchopulmonary dysplasia (BPD) is a serious and lifelong pulmonary disease in premature neonates, which has an influence on a quarter of premature newborns. Wingless/integrated(Wnt)/β-catenin signaling pathway affects lung cell differentiation and lung tissue structure, and is abnormal activation in the lungs of rats with pulmonary fibrosis. Method: Newborn rats were subjected to hyperoxia-exposure, histopathological changes in lung tissues were evaluated through Immunohistochemistry (IHC), Dishevelled (DVL-1) and signaling pathways were detected through western blotting and real-time PCR. Results: Contrasting with the normoxic lungs, hyperoxia-exposed lungs demonstrated larger alveoli, less alveoli and thicker alveolar septa, and the number of alveoli reduced obviously, alveoli enlarged seriously in hyperoxia group. SOD activity was decreased (7 th day: P < 0.05; 14 th day: P < 0.01), and MDA was increased (7 th day: P < 0.05; 14 th day: P < 0.01) after hyperoxia exposure. Protein and mRNA expression levels of β-catenin, DVL-1, Ctnnbl1 and Cyclin D1 were upregulated by hyperoxia exposure on 7 th day( P < 0.01) and 14 th day( P < 0.01). Conclusion: We confirmed the positive role of DVL-1 and Wnt/β-catenin signaling pathway in promoting BPD under hyperoxia conditions, and provided promising therapeutic targets in the future.

High-mobility group box1 peptide ameliorates bronchopulmonary dysplasia via suppressing inflammation and fibrosis in a mouse model

Bronchopulmonary dysplasia (BPD) is a chronic lung disorder that affect approximately 40% of preterm infants, with no established curative therapy. The administration of mesenchymal stem cells (MSCs) to BPD patients has shown promising outcomes. Previously, we demonstrated that a synthesized peptide originating from high mobility group box-1 protein (HMGB1) induces a regenerative cascade through activating endogenous MSCs. Here, we tested whether the HMGB1 peptide can ameliorate BPD-related lung injury. In a mouse BPD model established via hyperoxia exposure, three shots of HMGB1 peptide significantly improved survival and suppressed inflammation and fibrosis in the lung. Single-cell RNA-sequencing of the lung further showed that the peptide significantly suppressed a hyperoxia-induced inflammatory signature in macrophages and fibrotic signature in fibroblasts. These changes in the transcriptome were also confirmed at the protein level. Taken together, our data show that treatment with the HMGB1 peptide suppressed inflammation and fibrosis, thus preventing BPD progression. This study serves as a foundation for the development of new effective therapies for BPD.

The Function Role of Ubiquitin Proteasome Pathway in the ER Stress-induced AECII Apoptosis during Hyperoxia Exposure

Backgroud: Bronchopulmonary dysplasia (BPD) is a major cause of mortality and morbidity in premature infants, characterized by alveolar dysplasia and pulmonary microvascular remodeling. In the present study, we have investigated the functional roles of ubiquitin proteasome pathway (UPP) in BPD, and its relationship with endoplasmic reticulum stress (ER stress, ERS) mediated AECII apoptosis. Methods: A hyperoxia-induced BPD rat model was constructed and the pathologic changes of lung tissues were evaluated by Hematoxylin-Eosin staining. Cell apoptosis and protein expression were determined by TUNEL assay and Western blotting, respectively. Further reagent kit with specific fluorescent substrate was utilized to measure the activity of 20s proteasome. Meanwhile, AECII were cultured in vitro and exposed to hyperoxia. AECII apoptosis were measured by flow cytometry. In contrast, MG132 treatment was induced to explore ubiquitin proteasome pathway during hyperoxia exposure on AECII apoptosis and ERS sensors expression.Results: A significant increase in apoptosis and total ubiquitinated proteins expression were observed in BPD rats and AECII culture, and the change of UPP was associated with ERS. In order to confirm the role of UPP in AECII apoptosis of BPD, AECII cells were treated by MG132 with the concentration of 10 μmol/L under hyperoxia exposure. We found that the proteins expression of GRP-78, PERK, ATF4, ATF6 and CHOP, as well as AECII apoptosis were increased following MG132 treatment. Furthermore, the relatively up-regulated in the levels of total ubiquitinated proteins expression and 20S proteasome activity were correlated with increased ERS sensors expression. Conclusions: Our findings indicate that UPP may participate in the ERS-induced AECII apoptosis under hyperoxia condition.

The Specific Connexin 43–Inhibiting Peptide Gap26 Improved Alveolar Development of Neonatal Rats With Hyperoxia Exposure

Bronchopulmonary dysplasia (BPD) is a common devastating pulmonary complication in preterm infants. Alveolar maldevelopment is the crucial pathological change of BPD highly associated with oxidative stress–mediated excessive apoptosis. Cellular injury can be propagated and amplified by gap junction (GJ)–mediated intercellular communication. Connexin 43 (Cx43) is the most ubiquitous and critical GJ protein. Gap26 is a specific Cx43 mimic peptide, playing as a Cx43-GJ inhibitor. We hypothesized that Cx43-GJ was involved in alveolar maldevelopment of BPD via amplifying oxidative stress signaling and inducing excessive apoptosis. Neonatal Sprague Dawley rats were kept in either normoxia (21% O2) or hyperoxia (85% O2) continuously from postnatal day (PN) 1 to 14 in the presence or absence of Gap26. Moreover, RLE-6TN cells (type II alveolar epithelial cells of rats) were cultured in vitro under normoxia (21% O2) or hyperoxia (85% O2). RLE-6TN cells were treated by N-acetyl cysteine (NAC) (a kind of reactive oxygen species (ROS) scavenger) or Gap26. Morphological properties of lung tissue are detected. Markers associated with Cx43 expression, ROS production, the activity of the ASK1-JNK/p38 signaling pathway, and apoptotic level are detected in vivo and in vitro, respectively. In vitro, the ability of GJ-mediated intercellular communication was examined by dye-coupling assay. In vitro, our results demonstrated ROS increased Cx43 expression and GJ-mediated intercellular communication and Gap26 treatment decreased ROS production, inhibited ASK1-JNK/p38 signaling, and decreased apoptosis. In vivo, we found that hyperoxia exposure resulted in increased ROS production and Cx43 expression, activated ASK1-JNK/p38 signaling, and induced excessive apoptosis. However, Gap26 treatment reversed these changes, thus improving alveolar development in neonatal rats with hyperoxia exposure. In summary, oxidative stress increased Cx43 expression and Cx43-GJ–mediated intercellular communication. And Cx43-GJ–mediated intercellular communication amplified oxidative stress signaling, inducing excessive apoptosis via the ASK1-JNK/p38 signaling pathway. The specific connexin 43–inhibiting peptide Gap26 was a novel therapeutic strategy to improve the alveolar development of BPD.

Effect of antibiotic-induced intestinal dysbacteriosis on bronchopulmonary dysplasia and related mechanisms

Background Modification of the gut microbiota by antibiotics may influence the disease susceptibility and immunological responses. Infants in the neonatal intensive care unit (NICU) subjected to frequent antibiotics and oxygen therapies, which may give rise to local and systemic inflammatory reactions and progression of bronchopulmonary dysplasia (BPD). This study aimed to investigate the role of intestinal dysbacteriosis by antibiotic therapy before hyperoxia exposure in the progression of BPD. Methods Mice had been exposed to hyperoxia (85% O2) since postnatal day 3 until day 16 for the BPD model establishment, treated with antibiotics from postnatal day 2 until day 8. Treated mice and appropriate controls were harvested on postnatal day 2 or 10 for 16S rRNA gene sequencing, or postnatal day 17 for assessment of alveolar morphometry and macrophages differentiation. Results Antibiotic-induced intestinal dysbacteriosis before hyperoxia exposure gave rise to deterioration of BPD evidenced by reduced survival rates and alveolarization. Moreover, antibiotic-induced intestinal dysbacteriosis resulted in increased M1 macrophage maker (iNOS) and decreased M2 macrophage maker (Arg-1) levels in lung homogenates. Conclusion Broad-spectrum antibiotic-induced intestinal dysbacteriosis may participate in BPD pathogenesis via alteration of the macrophage polarization status. Manipulating the gut microbiota may potentially intervene the therapy of BPD.

PINK1 Mediates the Protective Effects of Thyroid Hormone T3 in Hyperoxia-induced Lung Injury

Introduction: Hyperoxia can lead to respiratory failure and death. Our previous work demonstrates that oxidant and mitochondrial injury plays a critical role in hyperoxia-induced acute lung injury (HALI). Recently, thyroid hormone has been demonstrated to promote mitochondrial survival in other models of lung injury, but its role in hyperoxia is unknown. Methods: Adult WT mice were pretreated with nebulized triiodothyronine (T3, 40 μg/kg) for 1 or 3 days, or with propylthiouracil (PTU, 100 μg/kg), for 3 days. Following pretreatment, WT mice underwent 72 hours of hyperoxia exposure. WT and PINK1-/- mice were pretreated with nebulized T3 (40 μg/kg) for 3 days or no pretreatment prior to 72h continuous hyperoxia exposure. Bronchoalveolar lavage (BAL), histological changes in cellular composition, and type I cytokine induction were assessed. Lung lysates for mitochondrial cellular bioenergetics markers were analyzed by Western blot. Results: Hyperoxia caused a significant increase in BAL total cell counts and lung cellular infiltrates. Administration of PTU enhanced HALI, while T3 attenuated HALI, inflammation, and oxidants in WT mice. T3 pretreatment increased mitochondrial biogenesis/fusion/mitophagy and decreased ER stress and apoptosis. PINK1-/- mice were more susceptible to hyperoxia than WT mice. Notably, pretreatment with T3 did not attenuate HALI in PINK1-/- mice. T3 pretreatment also increased mitochondrial anti-ROS potential, improved mitochondrial bioenergetics and mitophagy, and attenuated mitochondria-regulated apoptosis, all in a PINK1-dependent manner. Conclusions: Our results highlight a novel protective role for PINK1 in mediating the cytoprotective effects of thyroid hormone in HALI. Therefore, thyroid hormone may represent a potential therapy for ALI.

Prenatal Maternal Lipopolysaccharide and Mild Newborn Hyperoxia Increase Intrapulmonary Airway but Not Vessel Reactivity in a Mouse Model

Maternal infection is a risk for preterm delivery. Preterm newborns often require supplemental oxygen to treat neonatal respiratory distress. Newborn hyperoxia exposure is associated with airway and vascular hyperreactivity, while the complications of maternal infection are variable. In a mouse model of prenatal maternal intraperitoneal lipopolysaccharide (LPS, embryonic day 18) with subsequent newborn hyperoxia (40% oxygen × 7 days) precision-cut living lung slices were used to measure intrapulmonary airway and vascular reactivity at 21 days of age. Hyperoxia increased airway reactivity to methacholine compared to room air controls. Prenatal maternal LPS did not alter airway reactivity in room air. Combined maternal LPS and hyperoxia exposures increased airway reactivity vs. controls, although maximal responses were diminished compared to hyperoxia alone. Vessel reactivity to serotonin did not significantly differ in hyperoxia or room air; however, prenatal maternal LPS appeared to attenuate vessel reactivity in room air. Following room air recovery, LPS with hyperoxia lungs displayed upregulated inflammatory and fibrosis genes compared to room air saline controls (TNFαR1, iNOS, and TGFβ). In this model, mild newborn hyperoxia increases airway but not vessel reactivity. Prenatal maternal LPS did not further increase hyperoxic airway reactivity. However, inflammatory genes remain upregulated weeks after recovery from maternal LPS and newborn hyperoxia exposures.