Effect Of UVB Irradiation On Melanosomes Transfer And Molecular Mechanism

Human skin color is mainly affected by pigmentation. It not only determines colors of skin, hair and eyes, but it also can protect skin from UV excessive exposure. This process is complicated. The first, assemble melanosome and melanogenesis;The second, melanosomes transfer to the end of dendrites;The third, melanosomes deliver into keratinocytes. The last, redistribution and degradation. The process that melanosomes transfer from nuclear to the end of dendrites and deliver to keratinocytes can be called melanosomes transfer. Research shows that melanosomes transfer plays an extremely important role in skin pigmentation. But its mechanism has yet to be fully understood. UVB irradiation can lead to pigmentation. UVB biological effect intensity is 800～1000 times stronger than UVA. Research proves that UVB radiation can cause skin pigmentation. UVB radiation can promote melanocytes proliferation, stimulate melanogenesis. UVB can promote melanosomes transfer on epidermal equivalents. Melanosomes can distribute in basal layer and stratum corneum.This suggested that UVB radiation can promote melanosomes transfer.But the mechanism is not clear. Therefore, our objective is to investigate the effect of UVB irradiation on the transfer of melanosomes into keratinocytes and molecular mechanism .Objective: to investigate the effect of UVB irradiation on the transfer of melanosomes into keratinocytes and molecular mechanism . Method: In this study, we chosen the Ultraviolet phototherapy instrument which was used in clinical treatment frequently at present.And the cultured human epidermal melanocytes in vitro were irradiated. Morphology change of PIG1 cells was observed by light microscopy; MTT assay was used to record cellular activity. the change of the number and the length of dendrites was detected by statistics. The mRNA expression of Rac1,RhoA,PAR-2 and F-actin was performed using real time RT-PCR. The protein expression of Rac1,RhoA,PAR-2 and F-actin was assayed by western blotting.Results:1. The influence of different energies of UVB radiation on proliferation activity of PIG1 cells.24h afer UVB radiation, the proliferation activity was higher than before at the energy of 50 and 100mJ/cm~2.The proliferation activity was lower than before at the energy of 200mJ/cm~2.It has a downtrend with energy increased.48h after UVB radiation , Cell activity can recover with a certain degree at the energy of 100 mJ/cm~2. It has a downtrend when the energy was higher than 400mJ/cm~2.2.The influence of UVB radiation on morphology change of PIG1 cells; Because UVB radiation of 100mJ/ cm~2 energy could increase cell activity stably,we observe morphology change at 48h after UVB radiation of 100mJ/ cm~2 energy.①Controls:PIG1 cells grow into logarithmic phase quickly .and in good condition. The dendrites were multiple branching. It is in a good condition and has a good refraction. UVB radiations: After UVB irradiation, the number of PIG1 cells was increased and the length of dendrites was extended significantly.②The influence of UVB radiation on dendrites of PIG1 cells; The length of dendrites was extended and the number of dendrites was increased significantly.3. Time regularity of mRNA expression and protein level of Tyr were observed The expression was increased significantly at 24h after been irradiated. It may increase gradually with the increasing of time.4. The effect of UVB irradiation on melanogenesis was observed according to the fluorescent intensity by labeling the melanosomal matrix protein gp100. The fluorescent intensity was strongest at 48h after been irradiated at energy of 100mJ/cm~2.5. The mRNA expression of F-actin,Rac1,RhoA and PAR-2 were tested by fluorescent quantitative real-time RT-PCR. The mRNA expression of F-actin,Rac1 and PAR-2 were enhanced, while the expression of RhoA was inhibited.6. The protein expression of F-actin,Rac1,RhoA and PAR-2 was assayed by western blotting. The protein expression of F-actin,Rac1 and PAR-2 were enhanced, while the expression of RhoA was inhibited.Major conclusions:1.UVB irradiation can increase the cytoactive of PIG1 cells at the irradiated dosage (100mJ/cm~2). UVB irradiation can promote the proliferation activity of PIG1 cells. When the energy was greater than 100mJ/cm~2, the inhibition on melanocyte activity by the UVB irradiation may increase gradually with the increasing of the energy density. However, inhibition of UVB irradiation is not a continuing nature. Melanocyte activity can enhance reboundly at some point in time. 2. Within the energy range which not affects the cell viability, UVB irradiation can promote the proliferation activity of PIG1 cells and extend the dendrites of PIG1.3.UVB irradiation can impact mRNA expression and protein level of Tyr. The expression was increased significantly at 24h after been irradiated. It may increase gradually with the increasing of time.4.The effect of UVB irradiation on melanogenesis was observed according to the fluorescent intensity by labeling the melanosomal matrix protein gp100. The irradiation of 100mJ/cm~2 could stimulate melanogenesis significantly at 48h after been irradiated.5. UVB irradiation can promote the expression of Rac1,F-actin and PAR-2. while the expression of RhoA was inhibited.