mmu-miR-374b-5p modulated inflammatory factors via downregulation of C/EBP β/NF-κB signaling in Kupffer cells during Echinococcus multilocularis infection

BACKGROUND

Alveolar echinococcosis (AE) is an important infectious disease caused by the metacestode larvae of Echinococcus multilocularis, seriously threatening global public health security. Kupffer cells (KCs) play important roles in liver inflammatory response. However, their role in hepatic alveolar echinococcosis has not yet been fully elucidated.

METHODS

In this study, qRT-PCR was used to detect the expression level of miR-374b-5p in KCs. The target gene of miR-374b-5p was identified through luciferase reporter assays and loss of function and gains. Critical genes involved in NFκB signaling pathway were analyzed by qRT-PCR and western blot.

RESULTS

This study reported that miR-374b-5p was significantly upregulated in KCs during E. multilocularis infection and further showed that miR-374b-5p was able to bind to the 3'-UTR of the C/EBP β gene and suppressed its expression. The expression levels of NF-κBp65, p-NF-κBp65 and pro-inflammatory factors including iNOS, TNFα and IL6 were attenuated after overexpression of miR-374b-5p while enhanced after suppression of miR-374b-5p. However, the Arg1 expression level was promoted after overexpression of miR-374b-5p while suppressed after downregulation of miR-374b-5p. Additionally, increased protein levels of NF-κBp65 and p-NF-κBp65 were found in the C/EBP β-overexpressed KCs.

CONCLUSIONS

These results demonstrated that miR-374b-5p probably regulated the expression of inflammatory factors via C/EBP β/NF-κB signaling. This finding is helpful to explore the mechanism of inflammation regulation during E. multilocularis infection.

C/EBP β Mediates the Aberrant Inflammatory Response and Cell Cycle Arrest in Lps-stimulated Human Renal Tubular Epithelial Cells by Regulating NF-κB Pathway

BACKGROUND AND AIMS

The main cause of sepsis-induced Acute kidney injury (AKI) is acute infection after surgery and subsequent progression. However, the mechanism by which AKI is caused and developed from sepsis are not completely known. Herein, we determined the role of CCAAT/enhancer-binding protein β (C/EBP β) in sepsis-induced AKI METHODS: C/EBP β expression was up or down-regulated in LPS-stimulated human renal tubular epithelial cells in vitro by recombinant adenoviruses or siRNA. Subsequent analyses included the test of TNF-α and IL-6 levels by ELISA, cell cycle assay by flow cytometry.

RESULTS

C/EBP β was aberrantly expressed in renal tubular epithelial HK-2 cells exposed to LPS. C/EBP β overexpression significantly enhanced, but C/EBP β silencing obviously decreased the production and secretion of inflammatory cytokines TNF-α and IL-6 induced by LPS stimulus in HK-2 cells. And the cell cycle arrest of HK-2 cells induced by LPS was also enhanced after C/EBP β overexpression while attenuated after C/EBP β silencing. Consistent pattern of changes in Cyclin D1 and p21 expression were observed in LPS-stimulated HK-2 cells after C/EBP β silencing and C/EBP β overexpression. Additionally, the increased p-NF-κB levels induced by LPS were found to be obviously decreased after C/EBP β silencing in HK-2 cells. And the enhanced TNF-α and IL-6 secretion as well as cell cycle arrest by C/EBP β overexpression were blocked by BAY11-7082 inhibitor of NF-κB pathway.

CONCLUSIONS

C/EBP β could mediate the LPS-induced aberrant inflammatory response and cell cycle arrest in tubular epithelial cells by NF-κB pathway.

Blocking C/EBP β protects vascular endothelial cells from injury induced by intermittent hypoxia

BACKGROUND

Intermittent hypoxia (IH) can damage endothelial cells and lead to apoptosis in obstructive sleep apnea-hypopnea syndrome (OSAHS). Hypoxia induces apoptosis in endothelial cells via upregulation of endothelin-1 (ET-1) and hypoxia inducible factor-1 alpha (HIF-1α) plays a key role in the hypoxic stress response.

PURPOSE

We investigated an approach to diminish the negative effect of HIF-1α while maintaining its protective effect.

METHODS

Human umbilical vein endothelial cells (HUVECs) were subjected to sustained hypoxia (SH) or IH for 24 h, and the responses of HIF-1α, CCAAT/enhancer binding protein beta (C/EBP β), and endothelin-1 (ET-1) were assessed by western blotting. A luciferase reporter system was employed to verify the potential binding site (transcription factor binding site, TFBS) for C/EBP β in the ET-1 promoter. The specificity of regulation of ET-1 by HIF-1α via C/EBP β was evaluated by a lentiviral system. The effects of silencing of C/EBP β on IH-induced apoptosis, vascular endothelial growth factor (VEGF) protein levels, proliferation, and in vitro tube formation were studied.

RESULTS

We found that IH significantly increased HIF-1α, C/EBP β, and ET-1 in HUVECs. Knockdown of HIF-1α or C/EBP β inhibited the upregulation of ET-1 induced by IH. Blocking C/EBP β impaired IH-induced apoptosis but did not affect VEGF expression, proliferation, or in vitro tube formation. C/EBP β was shown to mediate increased ET-1 transcription by HIF-1α through the TFBS, 5'-GTTGCCTGTTG-3', in ET-1 promoter.

CONCLUSION

Silencing of C/EBP β can suppress apoptosis but does not affect the protective role of HIF-1α in the hypoxic stress response.

Osthole inhibits pancreatic cancer progression by directly exerting negative effects on cancer cells and attenuating tumor-infiltrating M2 macrophages

Pancreatic cancer has remained a major cause of cancer-related deaths. A hallmark of pancreatic cancer is extensive stromal reactions, resulting in a unique tumor microenvironment, especially the involvement of macrophages. These tumor-educated cells limit the efficacy of chemotherapy. Therefore, it is necessary to identify an effective treatment strategy. In this study, we aimed to explore the anti-tumor and immunomodulatory effects of osthole on pancreatic cancer. We found that osthole suppressed Panc 02 cell migration and proliferation and induced apoptosis as shown in vitro. Osthole also attenuated the development of pancreatic cancer in mice by inhibiting tumor-infiltrating M2 macrophages in our study. Additionally, osthole inhibited the polarization of primary bone marrow cells into M2 macrophages and inhibited the expression of MRC1, CCL22 and TGF-β in the M2 polarization process in vitro. Detection of the related signaling pathways revealed that osthole exerted immunomodulatory effects on M2 macrophages by down-regulating p-STAT6 and the p-ERK1/2-C/EBP β axis. These results indicated that osthole has effective anti-tumor and immunomodulatory effects on pancreatic cancer.

The role of C/EBPβ phosphorylation in modulating membrane phospholipids repairing in LPS-induced human lung/bronchial epithelial cells

Acute lung injury/acute respiratory distress syndrome (ALI/ARDS) is a common critical emergency with high mortality in clinical practice. The key mechanism of ALI/ARDS is that the excessive inflammatory response damages the integrity of alveolar and bronchial cell membrane and thus affects their basic function. Phospholipids are the main component of cell membranes. Phospholipase A2 (PLA2), which catalyzes the cleavage of membrane phospholipids, is the most important inflammatory mediator of ALI. However, clara cell secretory protein 1 (CCSP1), an endogenous PLA2 inhibitor can increase the self-defense of membrane phospholipids. Thus, CCSP1 up-regulation and PLA2 inhibition constitutes an effective method for ensuring the stability of membrane phospholipids and for the treatment of ALI/ARDS. In the present study, we developed an in vitro model of ALI via lipopolysaccharide (LPS) stimulation of a human bronchial epithelial cell line, BEAS-2B, and assessed the mRNA and protein levels of CCSP1 and PLA2 in the model cells. The results demonstrated LPS induction inhibited the transcription and protein expression of CCSP1, but only the protein level of membrane associated PLA2 was increased, suggesting that in the in vitro ALI model, abnormally regulated CCSP1 transcription plays a crucial role in the damage of cell membrane. To find out the reason that CCSP1 expression was decreased in the ALI model, we predicted, by means of bioinformatics, putative transcription factors which would bind to CCSP1 promoter, examined their background and expression, and found that a transcription factor, CCAAT/enhancer binding protein β (C/EBP β), was correlated with the transcription of CCSP1 in the in vitro ALI model, and its phosphorylation in the model was decreased. CHIP-PCR and luciferase reporter assay revealed that C/EBP β bound to CCSP1 promoter and facilitated its transcription. Therefore, we conclude that there is a C/EBP β/CCSP1/PLA2 pathway in the in vitro ALI model. The study of underlying mechanism show that the activity of C/EBP β depends on its phosphorylation:LPS stimulation reduced C/EBP β phosphorylation and suppressed the transcription of CCSP1 in BEAS-2B cells, which resulted in enhanced PLA2 and the consequent membrane damage. And further study shows that overexpression of CDK2(Cyclindependent kinase 2), promoted the phosphorylation of C/EBP β and inhibited PLA2 through the C/EBP β/CCSP1/PLA2 pathway, so as to attenuate membrane damage. The significance of this study lies in that artificial C/EBP β phosphorylation regulation may ease the membrane damage in ALI and improve membrane repair.

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CDK2 over-expression promotes C/EBPβ phosphorylation and improves membrane repair through C/EBPβ/CCSP/PLA2 pathway in ALI.

CCAAT/Enhancer-Binding Protein β Mediates the Killing of Toxoplasma gondii by Inducing Autophagy in Nonhematopoietic Cells

Autophagy is a main defense strategy by which infected host cells can virtually induce the killing of parasite, including Toxoplasma gondii. However, the regulatory mechanisms of autophagy in T. gondii-infected nonhematopoietic cells are still unknown. Emerging evidence indicates that CCAAT/enhancer-binding protein β (C/EBP β) is associated with the regulation of autophagy. Herein, we hypothesized that C/EBP β plays roles in inducing autophagy in nonhematopoietic cells. Expression of C/EBP β was aberrantly regulated in endothelial cells and retinal pigment epithelial cells challenged by T. gondii. Inhibition of C/EBP β reduced the killing of T. gondii in nonhematopoietic cells, whereas C/EBP β overexpression resulted in the enhancement of killing of T. gondii as well as the increase in autophagy in infected cells. Furthermore, the mammalian target of rapamycin (mTOR) activation was found to be reduced by C/EBP β overexpression, but increased by C/EBP β inhibition. The increase in T. gondii killing induced by C/EBP β overexpression was blocked by the mTOR activator phosphatidic acid and was increased by the inhibitor AZD8055. In conclusion, we demonstrate that C/EBP β expression is increased in nonhematopoietic cells infected by T. gondii, resulting in the activation of autophagy in host cells by inhibiting mTOR pathway.

C/EBP β Mediates Endoplasmic Reticulum Stress Regulated Inflammatory Response and Extracellular Matrix Degradation in LPS-Stimulated Human Periodontal Ligament Cells

Periodontitis is an oral inflammatory disease that not only affects the integrity of local tooth-supporting tissues but also impacts systemic health. A compositional shift in oral microbiota has been considered as the main cause of periodontitis; however, the potential mechanism has not been fully defined. Herein, we investigated the role of CCAAT/enhancer-binding protein β (C/EBP β), a member of the C/EBP family of transcription factors, in human periodontal ligament cells (hPDLCs) exposed to Porphyromonas gingivalis (P. gingivalis) lipopolysaccharide (LPS). RT-PCR and Western blotting analysis showed that the expression of C/EBP β was significantly increased in hPDLCs stimulated with LPS stimuli. Overexpression of C/EBP β by the recombinant adenoviral vector pAd/C/EBP β markedly increased the expression of the pro-inflammatory cytokines IL-6 and IL-8, and matrix metalloproteinases (MMP)-8 and -9 in hPDLCs in response to LPS. Furthermore, the activation of endoplasmic reticulum (ER) stress was confirmed in LPS-stimulated hPDLCs by measuring the expression of the ER stress marker molecules protein kinase-like ER kinase (PERK), eIF2α, GRP78/Bip, and C/EBP homologous protein (CHOP). The ER stress inhibitor salubrinal repressed, but inducer tunicamycin enhanced, the production of IL-6, IL-8, MMP-8, and MMP-9 in hPDLCs. Additionally, ER stress inducer tunicamycin significantly increased the expression level of C/EBP β in hPDLCs. Blocking of C/EBP β by siRNA resulted in a significant decrease in the secretion of IL-6 and IL-8 and expression of MMP-8 and MMP-9 induced by tunicamycin treatment in hPDLCs. Taken together, ER stress appears to play a regulatory role in the inflammatory response and extracellular matrix (ECM) degradation in hPDLCs in response to LPS stimuli by activating C/EBP β expression. This enhances our understanding of human periodontitis pathology.