Activation of Protease-Activated Receptor 2 Induces VEGF Independently of HIF-1

Abstract

BackgroundHuman adipose stem cells (hASCs) can promote angiogenesis through secretion of proangiogenic factors such as vascular endothelial growth factor (VEGF). In other cell types, it has been shown that induction of VEGF is mediated by both protease activated receptor 2 (PAR2) and hypoxia inducible factor 1(HIF-1). The present study hypothesized that PAR2 stimulation through activation of kinase signaling cascades lead to induction of HIF-1 and secretion of VEGF.Methodology/Principal FindingsImmunohistochemistry revealed the expression of PAR2 receptors on the surface of hASCs. Blocking the PAR2 receptors with a specific antibody prior to trypsin treatment showed these receptors are involved in trypsin-evoked increase in VEGF secretion from hASCs. Blocking with specific kinase inhibitors suggested that that activation of MEK/ERK and PI3-kinase/Akt pathways are involved in trypsin-eveoked induction of VEGF. The effect of the trypsin treatment on the transcription of VEGF peaked at 6 hours after the treatment and was comparable to the activation observed after keeping hASCs for 24 hours at 1% oxygen. In contrast to hypoxia, trypsin alone failed to induce HIF-1 measured with ELISA, while the combination of trypsin and hypoxia had an additive effect on both VEGF transcription and secretion, results which were confirmed by Western blot.ConclusionIn hASCs trypsin and hypoxia induce VEGF expression through separate pathways.

Mast Cells Density Positive to Tryptase Correlate with Microvascular Density in both Primary Gastric Cancer Tissue and Loco-Regional Lymph Node Metastases from Patients That Have Undergone Radical Surgery

“…Tryptase is an agonist of PAR-2 in vascular ECs that stimulates their proliferation. Signaling via PAR-2 on ECs elicits activation of the major members of the MAPK phosphorylation family and contributes to proliferation of ECs and angiogenesis [23,24,25,26,27,28,29,30,31,32,47,48,49,50,51]. …”

Pharmacological inhibition of PAR2 with the pepducin P2pal-18S protects mice against acute experimental biliary pancreatitis

“…An explanation for our surprising observation is not immediately obvious, but it is tempting to speculate that it 1) may indicate that there exists "cross talk" or dimerization between PAR2 and the bile acid receptor Gpbar1 and/or 2) PAR2 inhibition interferes with Gpbar1 signaling in acinar cells. Such transactivation has been shown to exist between PAR2 and epidermal growth factor (4), vascular endothelial growth factor (25), or PAR1 (8,26). Future studies will be needed to test these hypotheses and to define the mechanisms by which P2pal-18S inhibits bile acidinduced acinar cell calcium changes.…”

Discrete adipose-derived stem cell subpopulations may display differential functionality after in vitro expansion despite convergence to a common phenotype distribution

“…The transcriptional activation of lineage-specific differentiation genes, including PPAR-γ2, Sox9, and Osteocalcin, and the reference genes, including cyclophilin A (PPIA) and tyrosine 3/tryptophan 5-monooxygenase activation protein (YWHAZ), was carried out as described previously [16, 44]. Briefly, total RNA was isolated using the Aurum Total RNA Mini Kit (Bio-Rad, Copenhagen, Denmark) and the purity and concentration were determined spectrophotometrically using the Agilent RNA 6000 Nano kit (Agilent Technologies, Waldbronn, Germany).…”

“…They were found expressed to a high degree, minimally around 60%, but not completely [14–16], thus leaving open a question of the significance of subpopulations with different surface repertoire. In the face of wide acceptance of this basic profile, attempts have been made to identify additional markers that would be associated with ASC stemness.…”