1.Protease-activated receptor 4-mediated Ca2+ signaling in mouse lung alveolar epithelial cells.
Ando S1, Otani H, Yagi Y, Kawai K, Araki H, Nakamura T, Fukuhara S, Inagaki C. Life Sci. 2007 Aug 16;81(10):794-802. Epub 2007 Aug 17.
Protease-activated receptor (PAR)-4 is a recently identified low-affinity thrombin receptor that plays a pathophysiological role in many types of tissues including the lung. Here, we showed for the first time that PAR4 mRNA and protein are expressed on primary cultured mouse lung alveolar epithelial cells by reverse transcriptase-polymerase chain reaction (RT-PCR) and immunocytochemical analyses. In a fura 2-AM-loaded single epithelial cell, stimulation with thrombin (1 U/ml) and a PAR4 agonist peptide (AYPGKF-NH(2), 1-100 microM) increased intracellular Ca(2+) concentration ([Ca(2+)](i)), which consisted of an initial peak phase followed by a slowly decaying delayed phase, while a PAR1 agonist peptide, TFLLR-NH(2) (1-100 microM), induced a transient increase in [Ca(2+)](i). AYPGKF-NH(2) (10 microM)-induced [Ca(2+)](i) response was attenuated by a PAR4 antagonist peptide (tcY-NH(2)), a phospholipase C inhibitor, U-73122 (1-10 microM) or a Ca(2+)-ATPase inhibitor, thapsigargin (1 microM).
2.TNF increases expression of IL-4 and PARs in mast cells.
Zhang H1, Yang H, He S. Cell Physiol Biochem. 2010;26(3):327-36. doi: 10.1159/000320556. Epub 2010 Aug 24.
Tumor necrosis factor (TNF) is a proinflammatory cytokine which has been shown to be actively involved in the pathogenesis of allergic inflammation. However, little is known of the effects of TNF on cytokine secretion and protease activated receptor (PAR) expression in mast cells. In the present study, we examined potential influence of TNF on IL-4 and IL-12 release from P815 cells and PAR expression in P815 cells by using flow cytometry analysis, quantitative real time PCR, ELISA and cellular activation of signaling ELISA (CASE) techniques. The results showed that TNF induced up to 2.7-fold increase in IL-4, but not IL-12 release from P815 cells, and PAR-2 antagonist peptide FSLLRY-NH(2) and PAR-4 antagonist peptide trans-cinnamoyl (tc)-YPGKF-NH(2) did not affect TNF induced IL-4 release. Approximately up to 2.4 and 2.3 fold increases in expression of PAR-2 and PAR-4 were observed when cells were incubated with TNF. Pretreatment of cells with TNF for 60 min enhanced trypsin and tryptase induced PAR-2 expression by 2.