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Background: Recently, the expression of proteinase-activated receptor 2 (PAR2) has been
shown to be essential for activin receptor-like kinase 5 (ALK5)/SMAD-mediated signaling and cell
migration by transforming growth factor (TGF)-β1. However, it is not known whether activation
of non-SMAD TGF-β signaling (e.g., RAS–RAF–MEK–extracellular signal-regulated kinase (ERK)
signaling) is required for cell migration and whether it is also dependent on PAR2. Methods: RNA
interference was used to deplete cells of PAR2, followed by xCELLigence technology to measure
cell migration, phospho-immunoblotting to assess ERK1/2 activation, and co-immunoprecipitation
to detect a PAR2–ALK5 physical interaction. Results: Inhibition of ERK signaling with the MEK
inhibitor U0126 blunted the ability of TGF-β1 to induce migration in pancreatic cancer Panc1 cells.
ERK activation in response to PAR2 agonistic peptide (PAR2–AP) was strong and rapid, while it was
moderate and delayed in response to TGF-β1. Basal and TGF-β1-dependent ERK, but not SMAD
activation, was blocked by U0126 in Panc1 and other cell types indicating that ERK activation is
downstream or independent of SMAD signaling. Moreover, cellular depletion of PAR2 in HaCaT
cells strongly inhibited TGF-β1-induced ERK activation, while the biased PAR2 agonist GB88 at 10
and 100 µM potentiated TGF-β1-dependent ERK activation and cell migration. Finally, we provide
evidence for a physical interaction between PAR2 and ALK5. Our data show that both PAR2–APand TGF-β1-induced cell migration depend on ERK activation, that PAR2 expression is crucial for
TGF-β1-induced ERK activation, and that the functional cooperation of PAR2 and TGF-β1 involves a
physical interaction between PAR2 and ALK5
Bloodstream infections caused by Streptococcus pneumoniae induce strong inflammatory and procoagulant cellular responses and affect the endothelial barrier of the vascular system. Bacterial virulence determinants, such as the cytotoxic pore-forming pneumolysin, increase the endothelial barrier permeability by inducing cell apoptosis and cell damage. As life-threatening consequences, disseminated intravascular coagulation followed by consumption coagulopathy and low blood pressure is described. With the aim to decipher the role of pneumolysin in endothelial damage and leakage of the vascular barrier in more detail, we established a chamber-separation cell migration assay (CSMA) used to illustrate endothelial wound healing upon bacterial infections. We used chambered inlets for cell cultivation, which, after removal, provide a cell-free area of 500 μm in diameter as a defined gap in primary endothelial cell layers. During the process of wound healing, the size of the cell-free area is decreasing due to cell migration and proliferation, which we quantitatively determined by microscopic live cell monitoring. In addition, differential immunofluorescence staining combined with confocal microscopy was used to morphologically characterize the effect of bacterial attachment on cell migration and the velocity of gap closure. In all assays, the presence of wild-type pneumococci significantly inhibited endothelial gap closure. Remarkably, even in the presence of pneumolysin-deficient pneumococci, cell migration was significantly retarded. Moreover, the inhibitory effect of pneumococci on the proportion of cell proliferation versus cell migration within the process of endothelial gap closure was assessed by implementation of a fluorescence-conjugated nucleoside analogon. We further combined the endothelial CSMA with a microfluidic pump system, which for the first time enabled the microscopic visualization and monitoring of endothelial gap closure in the presence of circulating bacteria at defined vascular shear stress values for up to 48 h. In accordance with our CSMA results under static conditions, the gap remained cell free in the presence of circulating pneumococci in flow. Hence, our combined endothelial cultivation technique represents a complex in vitro system, which mimics the vascular physiology as close as possible by providing essential parameters of the blood flow to gain new insights into the effect of pneumococcal infection on endothelial barrier integrity in flow.
Background: Cold atmospheric plasma (CAP) is increasingly used in the field of oncology.
Many of the mechanisms of action of CAP, such as inhibiting proliferation, DNA breakage, or the
destruction of cell membrane integrity, have been investigated in many different types of tumors.
In this regard, data are available from both in vivo and in vitro studies. Not only the direct treatment
of a tumor but also the influence on its blood supply play a decisive role in the success of the therapy
and the patient’s further prognosis. Whether the CAP influences this process is unknown, and the
first indications in this regard are addressed in this study. Methods: Two different devices, kINPen
and MiniJet, were used as CAP sources. Human endothelial cell line HDMEC were treated directly
and indirectly with CAP, and growth kinetics were performed. To indicate apoptotic processes,
caspase-3/7 assay and TUNEL assay were used. The influence of CAP on cellular metabolism
was examined using the MTT and glucose assay. After CAP exposure, tube formation assay was
performed to examine the capillary tube formation abilities of HDMEC and their migration was
messured in separate assays. To investigate in a possible mutagenic effect of CAP treatment,
a hypoxanthine-guanine-phosphoribosyl-transferase assay with non malignant cell (CCL-93) line was
performed. Results: The direct CAP treatment of the HDMEC showed a robust growth-inhibiting
effect, but the indirect one did not. The MMT assay showed an apparent reduction in cell metabolism
in the first 24 h after CAP treatment, which appeared to normalize 48 h and 72 h after CAP application.
These results were also confirmed by the glucose assay. The caspase 3/7 assay and TUNEL assay
showed a significant increase in apoptotic processes in the HDMEC after CAP treatment. These results
were independent of the CAP device. Both the migration and tube formation of HDMEC were
significant inhibited after CAP-treatment. No malignant effects could be demonstrated by the CAP
treatment on a non-malignant cell line.