sphingosine-1-phosphate and pyrazolanthrone

We conducted this experimental study to analyze the relationship between sphingosine-1-phosphate (S1P)-induced mitogen-activated protein (MAP) kinase pathways and keloid formation. We collected samples of the normal tissue and the keloid tissue from 10 normal healthy individuals and 12 patients with keloid scars, respectively. Then, we compared the level of sphingosine-1-phosphate receptor (S1PR1/S1PR2) mRNA/protein expression between the normal tissue and the keloid tissue. Moreover, we also compared the level of S1PR protein expression, that of S1P-induced COL1A1 (collagen Type I, α-1 chain) expression, that of S1P-induced JNK/ERK phosphorylation, that of S1P-induced COL1A1 expression following the treatment with 30 μM PD98059 (ERK inhibitor) or 30 μM SP600125 (JNK inhibitor) and that of S1P-induced COL1A1 expression following the treatment with W146 (S1PR1 inhibitor) or JTE013 (S1PR2 inhibitor) between the normal fibroblasts and the keloid fibroblasts. We found that the level of S1PR1/S1PR2 mRNA/protein expression was significantly higher in the keloid tissue as compared with the normal tissue. Our results also showed that the level of S1P-induced COL1A1 expression and that of S1P-induced JNK/ERK phosphorylation were significantly higher in the keloid fibroblasts as compared with the normal ones (P < 0.05). Furthermore, there were significant decreases in the level of S1P-induced COL1A1 expression when the keloid fibroblasts were treated with 30 μM SP600125 or 30 μM PD98059 and that of S1P-induced COL1A1 expression when the treated with 100 nM W146 or 100 nM JTE013 (P < 0.05). Our results indicate that S1P-induced signal transduction is associated with increased collagen synthesis via S1PR-mediated signaling pathways in the keloid tissue.

Topics: Adult; Anilides; Anthracenes; Cell Line; Collagen Type I; Collagen Type I, alpha 1 Chain; Female; Fibroblasts; Flavonoids; Humans; Keloid; Lysophospholipids; Male; MAP Kinase Signaling System; Middle Aged; Mitogen-Activated Protein Kinases; Organophosphonates; Phosphorylation; Pyrazoles; Pyridines; Signal Transduction; Sphingosine; Sphingosine-1-Phosphate Receptors; Young Adult

We showed previously that TNF-α down-regulates the Na+/K+ ATPase in HepG2 cells. This work was undertaken to study the role of ceramide and its metabolites in TNF-α action. Treating HepG2 cells with the cytokine in presence of an inhibitor of sphingomyelinase, abrogated the effect of TNF-α on the ATPase. To confirm the involvement of ceramide or its metabolites, cells were incubated with exogenous ceramide. Ceramide reduced time-dependently the activity of the ATPase and its effect disappeared in presence of CAY 10466 or SHKI, respective inhibitors of ceramidase and spingosine kinase, suggesting that ceramide acts via sphingosine or sphingosine-1-phosphate (S1P). However, HepG2 cells treated with exogenous sphingosine showed a higher Na+/K+ ATPase activity inferring that S1P is the one responsible for the down-regulatory effect of TNF-α and ceramide. This hypothesis was confirmed by the observed inhibitory effect of exogenous S1P on the pump, which was maintained when JNK and NF-κB were inhibited separately or simultaneously. The concurrent, but not individual inhibition of the kinase and transcription factor in the absence of S1P imitated the effect of S1P. It was concluded that S1P down-regulates the ATPase by inhibiting both JNK and NF-κB. This conclusion was supported by the observed decrease in the phosphorylation of c-jun and the enhanced protein expression of IκB and lower NK-KB activity.

Topics: Aniline Compounds; Anthracenes; Apoptosis; Benzylidene Compounds; Cell Line; Ceramides; Hep G2 Cells; Humans; I-kappa B Proteins; JNK Mitogen-Activated Protein Kinases; Lysophospholipids; NF-kappa B; Phosphotransferases (Alcohol Group Acceptor); Proline; Sodium-Potassium-Exchanging ATPase; Sphingomyelin Phosphodiesterase; Sphingosine; Thiocarbamates; Tumor Necrosis Factor-alpha

Ultraviolet B (UVB) is known to induce apoptosis in human melanocytes. Here we show the cytoprotective effect of sphingosine-1-phosphate (S1P) against UVB-induced apoptosis. We also show that UVB-induced apoptosis of melanocytes is mediated by caspase-3 activation and poly(ADP-ribose) polymerase (PARP) cleavage, and that S1P prevents apoptosis by inhibiting this apoptotic pathway. We further investigated three major mitogen-activated protein (MAP) kinases after UVB irradiation. UVB gradually activated c-Jun N-terminal kinase (JNK) and p38 MAP kinase, while extracellular signal-regulated protein kinase (ERK) was inactivated transiently. Blocking of the p38 MAP kinase pathway using SB203580 promoted cell survival and inhibited the activation of caspase-3 and PARP cleavage. These results suggest that p38 MAP kinase activation may play an important role in the UVB-induced apoptosis of human melanocytes. To explain this cytoprotective effect, we next examined whether S1P could inhibit UVB-induced JNK and p38 MAP kinase activation. However, S1P was not found to have any influence on UVB-induced JNK or p38 MAP kinase activation. In contrast, S1P clearly stimulated the phosphorylation of ERK, and the specific inhibition of the ERK pathway using PD98059 abolished the cytoprotective effect of S1P. Based on these results, we conclude that the activation of p38 MAP kinase plays an important role in UVB-induced apoptosis, and that S1P may show its cytoprotective effect through ERK activation in human melanocytes.

Topics: Anthracenes; Apoptosis; Caspase 3; Caspase Inhibitors; Caspases; Cell Survival; Cytoprotection; Dose-Response Relationship, Radiation; Enzyme Activation; Flavonoids; Humans; Imidazoles; JNK Mitogen-Activated Protein Kinases; Korea; Lysophospholipids; Melanocytes; Mitogen-Activated Protein Kinases; p38 Mitogen-Activated Protein Kinases; Poly(ADP-ribose) Polymerase Inhibitors; Poly(ADP-ribose) Polymerases; Pyridines; Sphingosine; Ultraviolet Rays