miR‑21‑5p ameliorates hyperoxic acute lung injury and decreases apoptosis of AEC II cells via PTEN/AKT signaling in rats

Hyperoxia can Induce Lung Injury by Upregulating AECII Autophagy and Apoptosis Via the mTOR Pathway

Oxygen therapy is a crucial medical intervention, but it is undeniable that it can lead to lung damage. The mTOR pathway plays a pivotal role in governing cell survival, including autophagy and apoptosis, two phenomena deeply entwined with the evolution of diseases. However, it is unclarified whether the mTOR pathway is involved in hyperoxic acute lung injury (HALI). The current study aims to clarify the molecular mechanism underlying the pathogenesis of HALI by constructing in vitro and in vivo models using H2O2 and hyperoxia exposure, respectively. To investigate the role of mTOR, the experiment was divided into five groups, including normal group, injury group, mTOR inhibitor group, mTOR activator group, and DMSO control group. Western blotting, Autophagy double labeling, TUNEL staining, and HE staining were applied to evaluate protein expression, autophagy activity, cell apoptosis, and pathological changes in lung tissues. Our data revealed that hyperoxia can induce autophagy and apoptosis in Type II alveolar epithelial cell (AECII) isolated from the treated rats, as well as injuries in the rat lung tissues; also, H2O2 stimulation increased autophagy and apoptosis in MLE-12 cells. Noticeably, the experiments performed in both in vitro and in vivo models proved that the mTOR inhibitor Rapamycin (Rapa) functioned synergistically with hyperoxia or H2O2 to promote AECII autophagy, which led to increased apoptosis and exacerbated lung injury. On the contrary, activation of mTOR with MHY1485 suppressed autophagy activity, consequently resulting in reduced apoptosis and lung injury in H2O2-challenged MLE-12 cells and hyperoxia-exposed rats. In conclusion, hyperoxia caused lung injury via mTOR-mediated AECII autophagy.

MAP3K19 Promotes the Progression of Tuberculosis-Induced Pulmonary Fibrosis Through Activation of the TGF-β/Smad2 Signaling Pathway

Tuberculosis-induced pulmonary fibrosis (PF) is a chronic, irreversible interstitial lung disease, which severely affects lung ventilation and air exchange, leading to respiratory distress, impaired lung function, and ultimately death. As previously reported, epithelial-mesenchymal transition (EMT) and fibrosis in type II alveolar epithelial cells (AEC II) are two critical processes that contributes to the initiation and progression of tuberculosis-related PF, but the underlying pathological mechanisms remain unclear. In this study, through performing Real-Time quantitative PCR (RT-qPCR), Western blot, immunohistochemistry, and immunofluorescence staining assay, we confirmed that the expression levels of EMT and fibrosis-related biomarkers were significantly increased in lung tissues with tuberculosis-associated PF in vivo and Mycobacterium bovis Bacillus Calmette-Guérin (BCG) strain-infected AEC II cells in vitro. Besides, we noticed that the mitogen-activated protein kinase 19 (MAP3K19) was aberrantly overexpressed in PF models, and silencing of MAP3K19 significantly reduced the expression levels of fibronectin, collagen type I, and alpha-smooth muscle actin to decrease fibrosis, and upregulated E-cadherin and downregulated vimentin to suppress EMT in BCG-treated AEC II cells. Then, we uncovered the underlying mechanisms and found that BCG synergized with MAP3K19 to activate the pro-inflammatory transforming growth factor-beta (TGF-β)/Smad2 signal pathway in AEC II cells, and BCG-induced EMT process and fibrosis in AEC II cells were all abrogated by co-treating cells with TGF-β/Smad2 signal pathway inhibitor LY2109761. In summary, our results uncovered the underlying mechanisms by which the MAP3K19/TGF-β/Smad2 signaling pathway regulated EMT and fibrotic phenotypes of AEC II cells to facilitate the development of tuberculosis-associated PF, and these findings will provide new ideas and biomarkers to ameliorate tuberculosis-induced PF in clinic.

Advancements in understanding the role of microRnas in regulating macrophage polarization during acute lung injury

Acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) is a critical and life-threatening illness that causes severe dyspnea, and respiratory distress and is often caused by a variety of direct or indirect factors that damage the alveolar epithelium and capillary endothelial cells, leading to inflammation factors and macrophage infiltration. Macrophages play a crucial role in the progression of ALI/ARDS, exhibiting different polarized forms at different stages of the disease that control the disease outcome. MicroRNAs (miRNA) are conserved, endogenous, short non-coding RNAs composed of 18-25 nucleotides that serve as potential markers for many diseases and are involved in various biological processes, including cell proliferation, apoptosis, and differentiation. In this review, we provide a brief overview of miRNA expression in ALI/ARDS and summarize recent research on the mechanism and pathways by which miRNAs respond to macrophage polarization, inflammation, and apoptosis. The characteristics of each pathway are also summarized to provide a comprehensive understanding of the role of miRNAs in regulating macrophage polarization during ALI/ARDS.

Roles of exosomes and exosome-derived miRNAs in pulmonary fibrosis

Pulmonary fibrosis is a chronic, progressive fibrosing interstitial lung disease of unknown etiology that leads rapidly to death. It is characterized by the replacement of healthy tissue through an altered extracellular matrix and damage to the alveolar structure. New pharmacological treatments and biomarkers are needed for pulmonary fibrosis to ensure better outcomes and earlier diagnosis of patients. Exosomes are nanoscale vesicles released by nearly all cell types that play a central role as mediators of cell-to-cell communication. Moreover, exosomes are emerging as a crucial factor in antigen presentation, immune response, immunomodulation, inflammation, and cellular phenotypic transformation and have also shown promising therapeutic potential in pulmonary fibrosis. This review summarizes current knowledge of exosomes that may promote pulmonary fibrosis and be utilized for diagnostics and prognostics. In addition, the utilization of exosomes and their cargo miRNAs as novel therapeutics and their potential mechanisms are also discussed. This review aims to elucidate the role of exosomes in the pathogenesis of pulmonary fibrosis and paves the way for developing novel therapeutics for pulmonary fibrosis. Further in-depth research and clinical trials on this topic are encouraged in the future.

PTEN: An Emerging Potential Target for Therapeutic Intervention in Respiratory Diseases

Phosphatase and tensin homolog deleted on chromosome 10 (PTEN) is a potent tumor suppressor that regulates several key cellular processes, including proliferation, survival, genomic integrity, migration, and invasion, via PI3K-dependent and independent mechanisms. A subtle decrease in PTEN levels or catalytic activity is implicated not only in cancer but also in a wide spectrum of other diseases, including various respiratory diseases. A systemic overview of the advances in the molecular and cellular mechanisms of PTEN involved in the initiation and progression of respiratory diseases may offer novel targets for the development of effective therapeutics for the treatment of respiratory diseases. In the present review, we highlight the novel findings emerging from current research on the role of PTEN expression and regulation in airway pathological conditions such as asthma/allergic airway inflammation, pulmonary hypertension (PAH), chronic obstructive pulmonary disease (COPD), idiopathic pulmonary fibrosis (IPF), and other acute lung injuries (ALI). Moreover, we discuss the clinical implications of PTEN alteration and recently suggested therapeutic possibilities for restoration of PTEN expression and function in respiratory diseases.

miR-142-5p Encapsulated by Serum-Derived Extracellular Vesicles Protects against Acute Lung Injury in Septic Rats following Remote Ischemic Preconditioning via the PTEN/PI3K/Akt Axis

This study intends to investigate the effects of miR-142-5p encapsulated by serum-derived extracellular vesicles (EVs) on septic acute lung injury (ALI) following remote ischemic preconditioning (RIPC) through a PTEN-involved mechanism. ALI was induced in rats by lipopolysaccharide (LPS) injection, 24 h before which RIPC was performed via the left lower limb. Next, the binding affinity between miR-142-5p and PTEN was identified. EVs were isolated from serum and injected into rats. The morphology of lung tissues, pulmonary edema, and inflammatory cell infiltration into lung tissues were then assessed, and TNF-α and IL-6 levels in serum and lung tissues were measured. The results indicated that RIPC could attenuate ALI in sepsis. miR-142-5p expression was increased in serum, lung tissues, and serum-derived EVs of ALI rats following RIPC. miR-142-5p could target PTEN to activate the PI3K/Akt signaling pathway. miR-142-5p shuttled by serum-derived EVs reduced pulmonary edema, neutrophil infiltration, and TNF-α and IL-6 levels, thus alleviating ALI in LPS-induced septic rats upon RIPC. Collectively, serum-derived EVs-loaded miR-142-5p downregulated PTEN and activated PI3K/Akt to inhibit ALI in sepsis following RIPC, thus highlighting potential therapeutic molecular targets against ALI in sepsis.

Pulmonary delivery of siRNA against acute lung injury/acute respiratory distress syndrome

The use of small interfering RNAs (siRNAs) has been under investigation for the treatment of several unmet medical needs, including acute lung injury/acute respiratory distress syndrome (ALI/ARDS) wherein siRNA may be implemented to modify the expression of pro-inflammatory cytokines and chemokines at the mRNA level. The properties such as clear anatomy, accessibility, and relatively low enzyme activity make the lung a good target for local siRNA therapy. However, the translation of siRNA is restricted by the inefficient delivery of siRNA therapeutics to the target cells due to the properties of naked siRNA. Thus, this review will focus on the various delivery systems that can be used and the different barriers that need to be surmounted for the development of stable inhalable siRNA formulations for human use before siRNA therapeutics for ALI/ARDS become available in the clinic.

Mechanism of Adipose-Derived Mesenchymal Stem Cell-Derived Extracellular Vesicles Carrying miR-21-5p in Hyperoxia-Induced Lung Injury

Hyperoxia-induced lung injury (HILI) tends to develop bronchopulmonary dysplasia. Adipose-derived mesenchymal stem cell (ADMSC)-derived extracellular vesicles (EVs) hold great promise in alleviating lung injury. This study explored the mechanism of ADMSC-EVs in HILI. ADMSC-EVs were isolated and identified. The murine and cell models of HILI were established. HILI mice and cells were pre-treated with ADMSC-EVs. The lung dry/wet ratio, pathological structure, apoptosis, and inflammation of HILI mice were measured. The viability, apoptosis, and oxidative stress of HILI cells were measured. The internalization of EVs in lung and cells was observed by fluorescence labeling. The binding relationships between miR-21-5p and SKP2, and Nr2f2 and C/EBPα were analyzed. The binding of SKP2 and Nr2f2 and the Nr2f2 ubiquitination level were detected. ADMSC-EVs exerted preventive effects on HILI mice, evidenced by reduced lung dry/wet ratio, inflammation, and apoptosis in HILI mice. In vitro, EVs enhanced HILI cell viability and reduced apoptosis, inflammation, and oxidative stress. EVs carried miR-21-5p into lung cells to upregulate miR-21-5p expression and thereby target SKP2. SKP2 bound to Nr2f2 and promoted its ubiquitination degradation. EVs inhibited the binding of Nr2f2 and C/EBPα and further suppressed C/EBPα transcription. Collectively, ADMSC-EVs carrying miR-21-5p alleviated HILI via the SKP2/Nr2f2/C/EBPα axis. Role and mechanism of adipose-derived mesenchymal stem cell-derived extracellular vesicles in hyperoxia-induced lung injury. ADMSC-EVs upregulated miR-21-5p expression in cells by carrying miR-21-5p into lung cells, thereby promoting the binding of miR-21-5p and SKP2 mRNA, inhibiting the expression of SKP2, reducing the ubiquitination level of Nr2f2, increasing the expression of Nr2f2, promoting the binding of Nr2f2 and the C/EBPα promoter, upregulating C/EBPα mRNA level, and eventually alleviating HILI.

Gypenoside XVII protects against spinal cord injury in mice by regulating the microRNA‑21‑mediated PTEN/AKT/mTOR pathway

Gypenoside XVII (GP‑17), one of the dominant active components of Gynostemma pentaphyllum, has been studied extensively and found to have a variety of pharmacological effects, including neuroprotective properties. However, the neuroprotective effects of GP‑17 against spinal cord injury (SCI), as well as its underlying mechanisms of action remain unknown. The present study aimed to investigate the effects of GP‑17 on motor recovery and histopathological changes following SCI and to elucidate the mechanisms underlying its neuroprotective effects in a mouse model of SCI. Motor recovery was evaluated using the Basso, Beattie and Bresnahan (BBB) locomotor rating scale. Spinal cord edema was detected by the wet/dry weight method. H&E staining was performed to examine the effect of GP‑17 on spinal cord damage. Inflammatory response production was assessed by ELISA. Candidate miRNAs were identified following the integrated analysis of the Gene Expression Omnibus (GEO) dataset GSE67515. Western blot analysis was also performed to detect the expression levels of associated proteins. The results revealed that GP‑17 treatment improved functional recovery, and suppressed neuronal apoptosis and the inflammatory response in the mouse model of SCI. Moreover, it was observed that miR‑21 expression was downregulated following SCI, whereas it was upregulated following the administration of GP‑17. The inhibition of miR‑21 eliminated the protective effects of GP‑17 on SCI‑induced neuronal apoptosis and the inflammatory response. In addition, phosphatase and tensin homologue (PTEN), a key molecule in the activation of the protein kinase B (AKT)/mammalian target of rapamycin (mTOR) pathway, was identified as a target of miR‑21, and PTEN expression was downregulated by GP‑17 through miR‑21. Furthermore, the PTEN/AKT/mTOR pathway was inactivated by SCI, whereas it was re‑activated by GP‑17 through the regulation of miR‑21 in mice with SCI. On the whole, the findings of the present study suggest that GP‑17 plays a protective role in SCI via regulating the miR‑21/PTEN/AKT/mTOR pathway.

miR-21-5p Suppresses Mitophagy to Alleviate Hyperoxia-Induced Acute Lung Injury by Directly Targeting PGAM5

Hyperoxia-induced acute lung injury (HALI) is a severe side effect of refractory hypoxemia treatment, for which no effective therapeutic strategy is available. Here, we found that the lung miR-21-5p level was significantly decreased in the rats subjected to hyperoxia. Further, we presented evidence that miR-21-5p was a crucial regulator of mitophagy and mitochondrial dysfunction. Moreover, it proved that miR-21-5p regulated hyperoxia-induced mitophagy and mitochondrial dysfunction by directly binding to the target gene PGAM5. In conclusion, for the first time, we found that miR-21-5p could directly suppress mitophagy and mitochondrial damage during HALI formation.

Sufentanil attenuates inflammation and oxidative stress in sepsis-induced acute lung injury by downregulating KNG1 expression

The present study aimed to investigate the effects of sufentanil on sepsis-induced acute lung injury (ALI), and identify the potential molecular mechanisms underlying its effect. In order to achieve this, a rat sepsis model was established. Following treatment with sufentanil, the lung wet/dry (W/D) weight ratio was calculated. Histopathological analysis was performed via hematoxylin and eosin staining. Levels of inflammatory factors in bronchoalveolar lavage fluid were determined via ELISA. Furthermore, malondialdehyde (MDA) content and the activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) in tissue homogenates were assessed using commercial kits. Western blot analysis was performed to determine kininogen-1 (KNG1) protein expression. In addition, alveolar epithelial type II cells (AEC II) were stimulated with lipopolysaccharide (LPS) to mimic ALI. The levels of inflammation and oxidative stress were evaluated following overexpression of KNG1. Protein expression levels of nuclear factor-κB (NF-κB) and nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) signaling were determined via western blot analysis. The results of the present study demonstrated that sufentanil alleviated histopathological injury and the W/D ratio in lung tissue. Following treatment with sufentanil, levels of inflammatory factors also decreased, accompanied by decreased concentrations of MDA, and increased activities of SOD, CAT and GSH-Px. Notably, KNG1 was decreased in lung tissues following treatment with sufentanil. Furthermore, overexpression of KNG1 attenuated the inhibitory effects of sufentanil on LPS-induced inflammation and oxidative stress in AEC II. Sufentanil markedly downregulated NF-κB expression, while upregulating Nrf2 and HO-1 expression levels, which was reversed following overexpression of KNG1. Taken together, the results of the present study suggested that sufentanil may alleviate inflammation and oxidative stress in sepsis-induced ALI by downregulating KNG1 expression.