PP2ACα of Alveolar Macrophages Is a Novel Protective Factor for LPS-Induced Acute Respiratory Distress Syndrome

Saturated fatty acids stimulate cytokine production in tanycytes via the PP2Ac-dependent signaling pathway

The hypothalamic tanycytes are crucial for free fatty acids (FFAs) detection, storage, and transport within the central nervous system. They have been shown to effectively respond to fluctuations in circulating FFAs, thereby regulating energy homeostasis. However, the precise molecular mechanisms by which tanycytes modulate lipid utilization remain unclear. Here, we report that the catalytic subunit of protein phosphatase 2 A (PP2Ac), a serine/threonine phosphatase, is expressed in tanycytes and its accumulation and activation occur in response to high-fat diet consumption. In vitro, tanycytic PP2Ac responds to palmitic acid (PA) exposure and accumulates and is activated at an early stage in an AMPK-dependent manner. Furthermore, activated PP2Ac boosts hypoxia-inducible factor-1α (HIF-1α) accumulation, resulting in upregulation of an array of cytokines. Pretreatment with a PP2Ac inhibitor, LB100, prevented the PA-induced elevation of vascular endothelial growth factor (VEGF), fibroblast growth factor 1 (FGF1), hepatocyte growth factor (HGF), and dipeptidyl peptidase IV (DPPIV or CD26). Our results disclose a mechanism of lipid metabolism in tanycytes that involves the activation of PP2Ac and highlight the physiological significance of PP2Ac in hypothalamic tanycytes in response to overnutrition and efficacious treatment of obesity.

Analysing transcriptomic signatures and identifying potential genes for the protective effect of inactivated COVID-19 vaccines

Inactivated vaccines are one of the most effective strategies for controlling the coronavirus disease 2019 (COVID-19) pandemic. However, the response genes for the protective effect of inactivated vaccines are still unclear. Herein, we analysed the neutralization antibody responses elicited by vaccine serum and carried out transcriptome sequencing of RNAs isolated from the PBMCs of 29 medical staff receiving two doses of the CoronaVac vaccine. The results showed that SARS-CoV-2 neutralization antibody titers varied considerably among individuals, and revealed that many innate immune pathways were activated after vaccination. Furthermore, the blue module revealed that NRAS, YWHAB, SMARCA5, PPP1CC and CDC5L may be correlated with the protective effect of the inactivated vaccine. Additionally, MAPK1, CDC42, PPP2CA, EP300, YWHAZ and NRAS were demonstrated as the hub genes having a significant association with vaccines. These findings provide a basis for understanding the molecular mechanism of the host immune response induced by inactivated vaccines.

Immunotherapy strategies and prospects for acute lung injury: Focus on immune cells and cytokines

Acute lung injury/acute respiratory distress syndrome (ALI/ARDS) is a disastrous condition, which can be caused by a wide range of diseases, such as pneumonia, sepsis, traumas, and the most recent, COVID-19. Even though we have gained an improved understanding of acute lung injury/acute respiratory distress syndrome pathogenesis and treatment mechanism, there is still no effective treatment for acute lung injury/acute respiratory distress syndrome, which is partly responsible for the unacceptable mortality rate. In the pathogenesis of acute lung injury, the inflammatory storm is the main pathological feature. More and more evidences show that immune cells and cytokines secreted by immune cells play an irreplaceable role in the pathogenesis of acute lung injury. Therefore, here we mainly reviewed the role of various immune cells in acute lung injury from the perspective of immunotherapy, and elaborated the crosstalk of immune cells and cytokines, aiming to provide novel ideas and targets for the treatment of acute lung injury.

Protein phosphatases in TLR signaling

Toll-like receptors (TLRs) are critical sensors for the detection of potentially harmful microbes. They are instrumental in initiating innate and adaptive immune responses against pathogenic organisms. However, exaggerated activation of TLR receptor signaling can also be responsible for the onset of autoimmune and inflammatory diseases. While positive regulators of TLR signaling, such as protein serine/threonine kinases, have been studied intensively, only little is known about phosphatases, which counterbalance and limit TLR signaling. In this review, we summarize protein phosphorylation events and their roles in the TLR pathway and highlight the involvement of protein phosphatases as negative regulators at specific steps along the TLR-initiated signaling cascade. Then, we focus on individual phosphatase families, specify the function of individual enzymes in TLR signaling in more detail and give perspectives for future research. A better understanding of phosphatase-mediated regulation of TLR signaling could provide novel access points to mitigate excessive immune activation and to modulate innate immune signaling.

MiR-124-3p helps to protect against acute respiratory distress syndrome by targeting p65

Background: Acute respiratory distress syndrome (ARDS) is a severe form of acute lung injury that has a high mortality rate and leads to substantial healthcare costs. MicroRNA-124-3p (miR-124-3p) helps to suppress inflammation during a pulmonary injury. However, its mechanism of action is largely unknown, and its role in ARDS remains to be determined.

Methods: Mice and NR8383 cells were exposed to lipopolysaccharides (LPS) to induce ARDS, and their miR-124-3p levels were determined. After a miRNA agomir was administrated to the mice, their pulmonary injuries were evaluated by H&E staining and assays for peripheral inflammatory cytokine levels. The direct interaction between miR-124-3p and p65 was predicted, and then confirmed by a luciferase activity assay. The role played by miRNA-124-3p in regulating p65 expression was further examined by transfection with its agomir, and its role in cell apoptosis was investigated by observing the effects of miRNA overexpression in vitro and in vivo.

Results: After exposure to LPS, there was a consistent decrease in miR-124-3p expression in the lungs of mice and in NR8383 cells. After treatment with the miR-124-3p agomir, the degrees of pulmonary injury (e.g. alveolar hemorrhage and interstitial edema), and the increases in IL-1β, IL-6, and TNF-α levels induced by LPS were significantly attenuated. Overexpression of miR-124-3p in NC8383 cells and lung tissues significantly suppressed LPS-induced p65 expression and cell apoptosis.

Conclusions: These results suggest that miR-124-3p directly targeted p65, and thereby decreased the levels of inflammation and pulmonary injury in a mouse model of ARDS.

Phosphatases in toll-like receptors signaling: the unfairly-forgotten

Over the past 2 decades, pattern recognition receptors (PRRs) have been shown to be on the front line of many illnesses such as autoimmune, inflammatory, and neurodegenerative diseases as well as allergies and cancer. Among PRRs, toll-like receptors (TLRs) are the most studied family. Dissecting TLRs signaling turned out to be advantageous to elaborate efficient treatments to cure autoimmune and chronic inflammatory disorders. However, a broad understanding of TLR effectors is required to propose a better range of cures. In addition to kinases and E3 ubiquitin ligases, phosphatases emerge as important regulators of TLRs signaling mediated by NF-κB, type I interferons (IFN I) and Mitogen-Activated Protein Kinases signaling pathways. Here, we review recent knowledge on TLRs signaling modulation by different classes and subclasses of phosphatases. Thus, it becomes more and more evident that phosphatases could represent novel therapeutic targets to control pathogenic TLRs signaling. Video Abstract.

BAY11-7082 inhibits the expression of tissue factor and plasminogen activator inhibitor-1 in type-II alveolar epithelial cells following TNF-α stimulation via the NF-κB pathway

Pulmonary inflammation strongly promotes alveolar hypercoagulation and fibrinolytic inhibition. NF-κB signaling regulates the expression of molecules associated with coagulation and fibrinolytic inhibition in type-II alveolar epithelial cells (AECII) stimulated by lipopolysaccharide. However, whether TNF-α-induced alveolar hypercoagulation and fibrinolysis inhibition is also associated with the NF-κB pathway remains to be determined. The aim of the present study was to determine whether BAY11-7082, an inhibitor of the NF-κB pathway, inhibits the expressions of tissue factor (TF) and plasminogen activator inhibitor-1 (PAI-1) in AECⅡ in response to TNF-α. Rat AECII were treated with BAY11-7082 for 24 h and stimulated with TNF-α for 1 h. The expression of TF and PAI-1 were determined using western blotting and reverse transcription-quantitative PCR. The concentrations of TF and PAI-1 in culture supernatant were also measured by ELISA. Moreover, levels of NF-κB p65 (p65), phosphorylated (p)-p65 (p-p65), inhibitor of NF-κB α (IκBα) and p-IκBα were also evaluated. Immunofluorescence was used to detect p65 levels in cell nuclei. TNF-α significantly promoted TF and PAI-1 expression either at the mRNA or protein level in AECII cells. Concentrations of TF and PAI-1 in supernatant also significantly increased upon TNF-α stimulation. Furthermore, TNF-α upregulated the levels of p-IκBα, p65, and p-p65 in the cytoplasm. Immunofluorescence analysis indicated that TNF-α increased p65 translocation from the cytoplasm to the nucleus. However, AECII pre-treated with BAY11-7082 expressed lower levels of TF and PAI-1 following TNF-α treatment. Levels of p-IκBα, p65 and p-p65 in the cytoplasm also decreased, and translocation of p65 from cytoplasm into the nucleus was inhibited by BAY11-7082 pretreatment. These findings suggest that BAY11-7082 improves the hypercoagulation and fibrinolytic inhibition induced by TNF-α in alveolar epithelial cells via the NF-κB signaling pathway. BAY11-7082 might represent a therapeutic option for alveolar hypercoagulation and fibrinolytic inhibition in acute respiratory distress syndrome.

Ceramide induces MMP-9 expression through JAK2/STAT3 pathway in airway epithelium

BACKGROUND

Ceramide, a bioactive lipid, plays an essential role in the development of several pulmonary inflammatory diseases. Matrix metallopeptidase 9 (MMP-9) regulates the synthesis and degradation of extracellular matrix, and is associated with airway remodeling and tissue injury. This study was conducted to investigate the effects and underlying mechanisms of ceramide on MMP-9 expression in airway epithelium.

METHODS

BEAS-2B cells, normal human bronchial epithelium cell lines, were pretreated with AG490, a selective janus tyrosine kinase 2 (JAK2) inhibitor, or Stattic, a selective signal transducer and activator of transcription 3 (STAT3) inhibitor. The cells were then stimulated with C6-ceramide. The levels of MMP-9 were determined by ELISA and real-time quantitative PCR (RT-qPCR). JAK2, phosphorylated JAK2 (p-JAK2), STAT3, and phosphorylated STAT3 (p-STAT3) expression was examined by Western blotting. BALB/c mice were pretreated with AG490 or Stattic before intratracheally instillated with C6-ceramide. Pathological changes in lung tissues were examined by Hematoxylin and Eosin staining, Periodic-acid Schiff staining, and Masson's trichrome staining. MMP-9, JAK2, p-JAK2, STAT3, and p-STAT3 expression in the lung tissues was examined by Western blotting.

RESULTS

The expression of MMP-9, p-JAK2 and p-STAT3 in BEAS-2B cells was significantly increased after the treatment of C6-ceramide. Furthermore, the increased expression of MMP-9 induced by C6-ceramide was inhibited by AG490 and Stattic. Similar results were obtained in the lung tissues of C6-ceramide-exposed mice which were treated with AG490 or Stattic.

CONCLUSIONS

Ceramide could up-regulate MMP-9 expression through the activation of the JAK2/STAT3 pathway in airway epithelium. Targeted modulation of the ceramide signaling pathway may offer a potential therapeutic approach for inhibiting MMP-9 expression. This study points to a potentially novel approach to alleviating airway remodeling in inflammatory airway diseases.

Increased α-synuclein oligomerization is associated with decreased activity of glucocerebrosidase in the aging human striatum and hippocampus

Aging is associated with an increased risk for Parkinson's disease and dementia with Lewy bodies, in which α-synuclein (α-syn) oligomerization plays key pathogenic roles. Here, we show that oligomeric α-syn levels increase with age in the human brain and are accompanied by a decrease in the activity of glucocerebrosidase (GCase), a lysosomal enzyme whose dysfunction is linked to the accumulation of oligomeric α-syn. The inverse relationship between oligomeric α-syn levels and GCase activity was more evident in brain regions susceptible to neurodegeneration (i.e., the striatum and hippocampus) than those that are less vulnerable (i.e., the cerebellum and occipital cortex). GCase could potentially regulate α-syn oligomerization, as demonstrated by the decrease in oligomeric α-syn levels caused by a GCase agonist. In vitro experiments showed that GCase activity was more potently inhibited by oligomeric than monomeric α-syn in the lysosome-enriched fractions isolated from brain tissues and cultured neuronal cells. Alterations in oligomeric α-syns and their association with GCase in aging brains may explain the vulnerability of certain brain regions to neurodegeneration in Parkinson's disease and dementia with Lewy bodies.

Protein phosphatase 2A as a therapeutic target in inflammation and neurodegeneration

Protein phosphatase 2A (PP2A) is a highly complex heterotrimeric enzyme that catalyzes the selective removal of phosphate groups from protein serine and threonine residues. Emerging evidence suggests that it functions as a tumor suppressor by constraining phosphorylation-dependent signalling pathways that regulate cellular transformation and metastasis. Therefore, PP2A-activating drugs (PADs) are being actively sought and investigated as potential novel anti-cancer treatments. Here we explore the concept that PP2A also constrains inflammatory responses through its inhibitory effects on various signalling pathways, suggesting that PADs may be effective in the treatment of inflammation-mediated pathologies.