Tumor necrosis factor α stimulates expression and secretion of urokinase plasminogen activator in human dental pulp cells

MicroRNA-181b attenuates lipopolysaccharide-induced inflammatory responses in pulpitis via the PLAU/AKT/NF-κB axis

OBJECTIVE

This study aimed to investigate the role and underlying mechanisms of microRNA (miRNA)-181b in the inflammatory response in pulpitis.

METHODS

Quantitative reverse-transcription polymerase chain reaction (qRT-PCR), fluorescence in situ hybridization (FISH), and immunofluorescence techniques were used to determine the miRNA-181b and urokinase-type plasminogen activator (PLAU) expression levels in inflamed human dental pulp tissues (HDPTs) and lipopolysaccharide (LPS)-stimulated human dental pulp cells (hDPCs). The targets of miRNA-181b were identified and confirmed using a bioinformatics analysis, RNA sequencing, and dual-luciferase gene reporter assays. The effect of miRNA-181b or PLAU on proinflammatory cytokine expression in hDPCs was examined using qRT-PCR and western blotting. RNA sequencing was conducted to examine the signaling pathways implicated in miRNA-181b-mediated pulpitis. Western blotting and qRT-PCR were used to determine the miRNA-181b /PLAU/AKT/NF-κB signaling axis in pulpitis. A rat pulpitis model was created to observe the histopathological changes in the dental pulp tissue after the topical application of miRNA-181b agomir.

RESULTS

A significant decrease in miRNA-181b and an increase in PLAU were observed in HDPTs compared to the healthy controls, and these two factors showed a negative correlation. MiRNA-181b directly targeted PLAU. The miRNA-181b inhibitor resulted in a significant upregulation of IL-1β, IL-6 and TNF-α, whereas the knockdown of PLAU reversed this proinflammatory effect. Conversely, PLAU overexpression prevented the anti-inflammatory effects of the miRNA-181b mimics. Mechanistically, miRNA-181b inhibited the AKT/NF-κB pathway by targeting PLAU. In vivo application of the miRNA-181b agomir to inflamed pulp tissue alleviated inflammation.

CONCLUSION

MiRNA-181b targets PLAU, negatively regulating pro-inflammatory cytokine expression via the AKT/NF-κB signaling pathway.

Effects of transforming growth factor-β1 on plasminogen activation in stem cells from the apical papilla: role of activating receptor-like kinase 5/Smad2 and mitogen-activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK) signalling

AIM

To study the effects of TGF-β1 on the plasminogen activation (PA) system of stem cells from the apical papilla (SCAP) and its signalling.

METHODOLOGY

SCAP cells were isolated from the apical papilla of immature permanent teeth extracted for orthodontic reasons. They were exposed to various concentration of TGF-β1 with/without pretreatment and coincubation by SB431542 (ALK/Smad2/3 inhibitor), or U0126 (MEK/ERK inhibitor). MTT assay, Western blotting and enzyme-linked immunosorbent assay (ELISA) were used to detect their effects on cell viability, and the protein expression of plasminogen activator inhibitor-1 (PAI-1), urokinase-type plasminogen activator (uPA), uPA receptor (uPAR) and their secretion. The paired Student's t-test was used for statistical analysis.

RESULTS

TGF-β1 significantly stimulated PAI-1 and soluble uPAR (suPAR) secretion of SCAP cells (P < 0.05), whereas uPA secretion was inhibited. Accordingly, TGF-β1 induced both PAI-1 and uPAR protein expression of SCAP cells. SB431542 (an ALK5/Smad2/3 inhibitor) pretreatment and coincubation prevented the TGF-β1-induced PAI-1 and uPAR of SCAP. U0126 attenuated the TGF-β1-induced expression/secretion of uPAR, but not PAI-1 in SCAP. SB431542 reversed the TGF-β1-induced decline of uPA.

CONCLUSIONS

TGF-β1 may affect the repair/regeneration activities of SCAP via differential increase or decrease of PAI-1, uPA and uPAR. These effects induced by TGF-β1 are associated with ALK5/Smad2/3 and MEK/ERK activation. Elucidation the signalling pathways and effects of TGF-β1 is useful for treatment of immature teeth with open apex by revascularization/revitalization procedures and tissue repair/regeneration.

Contribution of the TNF-α (Tumor Necrosis Factor-α)-TNF-Rp55 (Tumor Necrosis Factor Receptor p55) Axis in the Resolution of Venous Thrombus

Objective- Deep vein thrombosis results from a combination of risk factors including genetic conditions, obesity, drugs, pregnancy, aging, and malignancy. We examined pathophysiological roles of the TNF-α (tumor necrosis factor-α)-TNF-Rp55 (tumor necrosis factor receptor p55) axis in thrombus resolution using Tnfrp55^-/- (TNF-Rp55-deficient) mice. Approach and Results- On ligating the inferior vena cava of wild-type (WT) mice, venous thrombi formed and grew progressively until 5 days but shrunk to <50% of the thrombus weight at day 14. Concomitantly, inferior vena cava ligation enhanced intrathrombotic gene expression of Tnfa and Tnfrp55, and intrathrombotic macrophages expressed both TNF-α and TNF-Rp55 proteins. In Tnfrp55^-/- mice treated with the same manner, thrombus formed at a similar rate for 5 days, but shrinking was delayed compared with WT mice. Moreover, the blood flow recovery in thrombosed inferior vena cava was suspended in Tnfrp55^-/- mice compared with WT mice. Intrathrombotic Plau (urokinase-type plasminogen activator), Mmp2 (matrix metalloproteinase 2), and Mmp9 (matrix metalloproteinase 9) mRNA expression was significantly reduced in Tnfrp55^-/- mice, compared with WT ones. Supportingly, the administration of anti-TNF-α antibody or TNF-α inhibitor (etanercept) delayed the thrombus resolution in WT mice. Furthermore, TNF-α treatment enhanced gene expression of Plau, Mmp2, and Mmp9 in WT macrophages but not Tnfrp55^-/- macrophages. These effects were significantly suppressed by ERK (extracellular signal regulated kinase) and NF-κB (nuclear factor-kappa B) inhibitors. Therefore, the lack of TNF-Rp55 has detrimental roles in the thrombus resolution by suppressing PLAU, MMP-2, and MMP-9 expression. In contrast, TNF-α administration accelerated thrombus resolution in WT but not Tnfrp55^-/- mice. Conclusions- The TNF-α-TNF-Rp55 axis may have essential roles in the resolution of venous thrombus in mice.

Effects of TGF-β1 on plasminogen activation in human dental pulp cells: Role of ALK5/Smad2, TAK1 and MEK/ERK signalling

Transforming growth factor-β1 (TGF-β1) plays an important role in the pulpal repair and dentinogenesis. Plasminogen activation (PA) system regulates extracellular matrix turnover. In this study, we investigated the effects of TGF-β1 on PA system of dental pulp cells and its signalling pathways. Dental pulp cells were treated with different concentrations of TGF-β1. MTT assay, reverse transcription-polymerase chain reaction, Western blotting and enzyme-linked immunosorbant assay (ELISA) were used to detect the effect of TGF-β1 on cell viability, mRNA and protein expression of urokinase-type plasminogen activator (uPA), uPA receptor (uPAR), plasminogen activator inhibitor-1 (PAI-1) as well as their secretion. The phosphorylation of Smad2 and TAK1 was analysed by Pathscan ELISA or Western blotting. Cells were pretreated with SB431542 (ALK5/Smad2/3 inhibitor), 5z-7-oxozeaenol (TAK1 inhibitor) and U0126 (MEK/ERK inhibitor) for examining the related signalling. TGF-β1 slightly inhibited cell growth that was reversed by SB431542. TGF-β1 upregulated both RNA and protein expression of PAI-1 and uPAR, whereas it downregulated uPA expression. Accordingly, TGF-β1 stimulated PAI-1 and soluble uPAR (suPAR) secretion of pulp cells, whereas uPA secretion was inhibited. TGF-β1 induced the phosphorylation of Smad2 and TAK1. In addition, SB431542, 5z-7-oxozeaenol and U0126 attenuated the TGF-β1-induced secretion of PAI-1 and suPAR. These results indicate that TGF-β1 is possibly involved in the repair/regeneration and inflammatory processes of dental pulp via regulation of PAI-1, uPA and uPAR. These effects of TGF-β1 are related to activation of ALK5/Smad2, TAK1 and MEK/ERK signalling pathways. Clarifying the signal transduction for the effects of TGF-β1 is helpful for pulpo-dentin regeneration and tissue engineering. Copyright © 2016 John Wiley & Sons, Ltd.

Plasmin and plasminogen induce macrophage reprogramming and regulate key steps of inflammation resolution via annexin A1

Inflammation resolution is an active process that functions to restore tissue homeostasis. The participation of the plasminogen (Plg)/plasmin (Pla) system in the productive phase of inflammation is well known, but its involvement in the resolution phase remains unclear. Therefore, we aimed to investigate the potential role of Plg/Pla in key events during the resolution of acute inflammation and its underlying mechanisms. Plg/Pla injection into the pleural cavity of BALB/c mice induced a time-dependent influx of mononuclear cells that were primarily macrophages of anti-inflammatory (M2 [F4/80^high Gr1^- CD11b^high]) and proresolving (Mres [F4/80^med CD11b^low]) phenotypes, without changing the number of macrophages with a proinflammatory profile (M1 [F4/80^low Gr1⁺ CD11b^med]). Pleural injection of Plg/Pla also increased M2 markers (CD206 and arginase-1) and secretory products (transforming growth factor β and interleukin-6) and decreased the expression of inducible nitric oxide synthase (M1 marker). During the resolving phase of lipopolysaccharide (LPS)-induced inflammation when resolving macrophages predominate, we found increased Plg expression and Pla activity, further supporting a link between the Plg/Pla system and key cellular events in resolution. Indeed, Plg or Pla given at the peak of inflammation promoted resolution by decreasing neutrophil numbers and increasing neutrophil apoptosis and efferocytosis in a serine-protease inhibitor-sensitive manner. Next, we confirmed the ability of Plg/Pla to both promote efferocytosis and override the prosurvival effect of LPS via annexin A1. These findings suggest that Plg and Pla regulate several key steps in inflammation resolution, namely, neutrophil apoptosis, macrophage reprogramming, and efferocytosis, which have a major impact on the establishment of an efficient resolution process.

Relevance of the plasminogen system in physiology, pathology, and regeneration of oral tissues - From the perspective of dental specialties

Plasmin is a proteolytic enzyme that is crucial in fibrinolysis. In oral tissues, the plasminogen system plays an essential role in physiological and pathological processes, which in addition to fibrinolysis include degradation of extracellular matrix, inflammation, immune response, angiogenesis, tissue remodeling, cell migration, and wound healing. Oral tissues reveal a change in the plasminogen system during pathological processes such as periodontitis, peri-implantitis, or pulpitis, as well as in response to mechanical load. The plasminogen system is also a key element in tissue regeneration. The number of studies investigating the plasminogen system in dentistry have grown continuously in recent years, highlighting its increasing relevance in dental medicine. In this review, we present the diverse functions of the plasminogen system in physiology and its importance for dental specialists in pathology and regeneration. We thus provide an overview of the current knowledge on the role of the plasminogen system in the different fields of dentistry, including endodontics, orthodontics, periodontics, and oral surgery.