Transforming growth factor ß2 (TGF-ß2)-induced connective tissue growth factor (CTGF) expression requires sphingosine 1-phosphate receptor 5 (S1P5) in human mesangial cells.

Transforming growth factor ß2 (TGF-ß2) is well known to stimulate the expression of pro-fibrotic connective tissue growth factor (CTGF) in several cell types including human mesangial cells. The present study demonstrates that TGF-ß2 enhances sphingosine 1-phosphate receptor 5 (S1P5) mRNA and protein expression in a time and concentration dependent manner. Pharmacological and siRNA approaches reveal that this upregulation is mediated via activation of classical TGF-ß downstream effectors, Smad and mitogen-activated protein kinases. Most notably, inhibition of Gi with pertussis toxin and downregulation of S1P5 by siRNA block TGF-ß2-stimulated upregulation of CTGF, demonstrating that Gi coupled S1P5 is necessary for TGF-ß2-triggered expression of CTGF in human mesangial cells. Overall, these findings indicate that TGF-ß2 dependent upregulation of S1P5 is required for the induction of pro-fibrotic CTGF by TGF-ß. Targeting S1P5 might be an attractive novel approach to treat renal fibrotic diseases.

FTY720 and two novel butterfly derivatives exert a general anti-inflammatory potential by reducing immune cell adhesion to endothelial cells through activation of S1P(3) and phosphoinositide 3-kinase.

Sphingosine-1-phosphate (S1P) is a key lipid regulator of a variety of cellular responses including cell proliferation and survival, cell migration, and inflammatory reactions. Here, we investigated the effect of S1P receptor activation on immune cell adhesion to endothelial cells under inflammatory conditions. We show that S1P reduces both tumor necrosis factor (TNF)-α- and lipopolysaccharide (LPS)-stimulated adhesion of Jurkat and U937 cells to an endothelial monolayer. The reducing effect of S1P was reversed by the S1P1+3 antagonist VPC23019 but not by the S1P1 antagonist W146. Additionally, knockdown of S1P3, but not S1P1, by short hairpin RNA (shRNA) abolished the reducing effect of S1P, suggesting the involvement of S1P3. A suppression of immune cell adhesion was also seen with the immunomodulatory drug FTY720 and two novel butterfly derivatives ST-968 and ST-1071. On the molecular level, S1P and all FTY720 derivatives reduced the mRNA expression of LPS- and TNF-α-induced adhesion molecules including ICAM-1, VCAM-1, E-selectin, and CD44 which was reversed by the PI3K inhibitor LY294002, but not by the MEK inhibitor U0126.In summary, our data demonstrate a novel molecular mechanism by which S1P, FTY720, and two novel butterfly derivatives acted anti-inflammatory that is by suppressing gene transcription of various endothelial adhesion molecules and thereby preventing adhesion of immune cells to endothelial cells and subsequent extravasation.