The Effect Of Cyclooxygenase On The Formation Of The Dendrites Induced By UVB Irradiation And Its Mechanisms

The color of human skin is variety, melanin plays a decisive role in thisphenomenon. The process of pigmentation is very sophisticated and theprocess should be divided into four steps melanin synthetic in melanosomes,melanosomes transport along dendrites, transport to keratinocytes anddegradation in keratinocytes. The process of melanosomes transport fromperinuclear to keratinocytes is known as melanosomes transfer.In the process of pigmentation, dendritic plays an extremely important role in melanin transportation. Scott study found, RhoA and Rac1, small GTP enzymes of Rho family, especially plays an important role inmelanocyte dendrite formation. Rac-1can induced the formation and extension of dendrites, and RhoA has the opposite effects. We found UVB irradiation can stimulate melanocytes to form more dendrite throughthe expression of Rac1and RhoA previously, however, mechanism of the UVB irradiation regulating the formation of dendrites is not clear. Recent studies have shown that COX-2inhibitors could inhibit themigration of endothelial cells depended on Cdc42/Rac1. Besides, NS-398, thespecific inhibitor of COX-2, could cause the decline of the cell’s invasiveness,indicating that COX-2and Cdc42/Rac1were the most important molecularsin disappearing of cell’s filipodium and declining of invasiveness in vitrocaused by NSAIDs. These studies also suggested that COX could play a rolein the formation of dendrites.Methods:The PIG1cells, a immortalized human epidermal melanocytes cell strain,were cultured. Then divide the cells to5groups:①The control group;②100mJ/cm~2UVB irradiation group;③100mJ/cm~2UVB irradiation group+ASA;④100mJ/cm~2UVB irradiation group+NS-398;⑤100mJ/cm~2UVBirradiation group+SC-560. The changes of dendritics of melanocytesbetween different groups in morphology were observed under a microscope；The proteins and RNAs were extracted to analysis the expression of COX-1,COX-2, Rac1and RhoA by Western blot and PT-PCR.Results:1. After100mJ/cm~2UVB irradiation, the mRNA and the protein expressionof COX-1and COX-2in PIG1cells increased markedly;2. Both of100μmol/LASAand30μmol/LNS-398can inhibit formation andextension of the PIG1’s dendrites induced by UVB irradiation, but10μmol/LSC-560has no obvious inhibition on the formation and extension of dendrites.3. When the concentration is50~150μmol/L, ASA could turnover the highexpression of Rac1and low expression of RhoA induced by UVB irradiationin PIG1cells in a dose-dependent manner. Both of ASA（100μmol/L）and NS-398（30μmol/L）could inhibit the Rac-1’s high expression and RhoA’slow expression, however, SC-560did not have similar effect.Conclusion:1. UVB irradition could increase the expression of COX-1and COX-2inmelanocytes;2. Cyclooxygenase plays an important role in the formation and extensionof dendrites induced by UVB, and COX-2played a dominant role.