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Objective To evaluate effects of ascorbic acid on proliferative activity of cultured melanocytes in vitro, as well as on H2O2?induced oxidative injury in melanocytes. Methods The optimal concentration of ascorbic acid solution and median lethal dose of H2O2 solution were determined by CCK?8 assay for the following experiment. Cultured melanocytes were classified into the control group, ascorbic acid group, H2O2 group and combination group. During the first 24 hours, the control group and H2O2 group were treated with M254 medium, while the ascorbic acid group and combination group with ascorbic acid solution. During an additional 24?hour period, the control group and ascorbic acid group were treated with M254 medium, while the H2O2 group and combination group with H2O2 solution at the median lethal dose. After 48?hour treatment, CCK?8 assay and flow cytometry were performed to determine the survival rate and apoptosis rate of melanocytes, respectively, in the 4 groups. Biochemical methods were used to evaluate the superoxide dismutase(SOD)activity and determine the malondialdehyde(MDA)concentration, and fluores?cent staining was conducted to detect the level of reactive oxygen species(ROS)in the control group, H2O2 group and combination group. Results The optimal concentration of ascorbic acid solution was 1 000μmol/L, and the median lethal dose of H2O2 solution was 300 μmol/L. The cell survival rate, apoptosis rate, SOD activity, MDA concentration and ROS fluorescence intensity in the control group were 100% ± 4.99%, 6.90% ± 0.87%, 54.71 ± 4.75 U/mgprot, 263.39 ± 20.17 nmol/mgprot and 342.16 ± 27.36 respectively. Compared with the control group, H2O2 solution could significantly increase the cell apoptosis rate(16.47%± 1.07%), SOD activity(103.62 ± 10.44 U/mgprot), MDA concentration(493.70 ± 31.36 nmol/mgprot)and intracellular ROS fluorescence intensity (782.48 ± 36.25), but decrease the survival rate of melanocytes (39.07% ± 2.94%), while ascorbic acid solution markedly down?regulated the H2O2?induced apoptosis (11.83%± 0.95%), SOD activity(76.73 ± 5.20 U/mgprot), MDA concentration(371.82 ± 23.05 nmol/mgprot) and ROS level (475.64 ± 52.18), but increased the cell survival rate (74.31% ± 5.53%). Conclusion Ascorbic acid solution at the concentration of 1 000 μmol/L can not only promote proliferative activity of melanocytes, but also protect melanocytes from H2O2?induced oxidative injury.
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ObjectiveTo investigate the effect of heat treatment combined with narrow band ultraviolet B(NB-UVB) on cultured normal human melanocytes in vitro.MethodsMelanocytes were isolated from the foreskin of normal human,cullured in vitro,and irradiated with NB-UVB of different doses(20,30,50,70,90,120 and 180 mJ/cm2).Then,MTT assay was performed to evaluate the proliferation and activity of melanocytes to determine the optimal dose of UVB for the next experiment.Melanocytes were classified into 3 groups to be treated with heat at 42 ℃ for 1 hour (heat group),irradiated with UVB at 50 mJ/cm2 (UVB group),or irradiated with UVB at 50 mJ/cm2 followed by heat treatment at 42 ℃ for 1 hour (combination group),daily for 3 successive days; those receiving no treatment served as the control.After 24-hour culture following the last treatment,tyrosinase activity was evaluated with L-dopa as the substrate,melanin content was detected by NaOH assay,and cell cycle stages were determined by flow cytometry.ResultsNB-UVB irradiation decreased the viability of melanocytes in a dose-dependent manner,and the optimum dose of UVB was 50 mJ/cm2.The tyrosinase activity of melanocytes was 0.244 ± 0.018 and 0.310 ± 0.015 respectively in the UVB group and combination group,and increased by 3.8％ (P ＜ 0.05) and 31.9％ (P ＜ 0.05) respectively compared with the control group (0.235 ± 0.018); the melanin content was 0.201 ± 0.016 and 0.286 ± 0.019,respectively in the UVB group and combination group,and increased by 17.5％ (P ＜ 0.05 ) and 67.3％ (P ＜ 0.05) compared with the control group (0.171 ± 0.016).In comparison with the control group,the percentage of melanocytes in G1 phase was decreased by 23.94％ in the UVB group(P＜ 0.05) and 33.51％ in the combination group(P ＜ 0.05),while that in S phase and G2 phase increased by 15.35％ (P ＜ 0.05 ) and 11.93％ (P ＜ 0.05),respectively in the UVB group,and 17.76％ (P ＞ 0.05) and 16.08％ (P ＞ 0.05),respectively in the heat group.ConclusionHeat treatment and NB-UVB can synergistically enhance the tyrosinase activity and accelerate melanogenesis,proliferation and differentiation,of melanocytes.
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ObjectiveTo explore the effects of heat treatment and ultraviolet B (UVB) radiation alone or in combination on the expression of heat shock protein (HSP) 72 in human epidermal melanocytes.Methods Melanocytes were obtained from human foreskin,and subjected to primary culture.After 3 to 5 passages,the melanocytes were classified into 4 groups:control group (receiving no treatment),heat treatment group (treated with heat at 42 ℃ for 1 hour every day for 3 days),UVB group(irradiated with UVB at 50 mJ/cm2 daily for 3days),combination group(treated with heat at 42 ℃ for 1 hour followed by irradiation with UVB at 50 mJ/cm2daily for 3 days).After another 2- to 6-hour culture following the last treatment,melanocytes were collected and subjected to real time PCR and Western blot for the detection of HSP72 mRNA and protein expression,respectively.ResultsThe mRNA and protein expressions of HSP72 were significantly higher in the heat treatment group and combination group than in the control group (mRNA:6.584 ± 0.871 and 7.269 ± 0.454 vs.0.975 ± 0.089,both P ＜ 0.001; protein:2.022 ± 0.058 and 2.080 ± 0.045 vs.0.532 ± 0.033,both P ＜ 0.001 ),but was similar between the UVB group and control group (mRNA:0.832 ± 0.084 vs.0.975 ± 0.089,P ＞ 0.05;protein:0.546±0.021 vs.0.532 ± 0.033,P ＞ 0.05).The ANOVA of factorial design showed that neither heat treatment nor UVB irradiation had interaction effect on the mRNA or protein expression of HSP72 (F =2.106,1.399 respectively,both P ＜ 0.05).ConclusionsHeat treatment can cause an increase in the expression of HSP72,which may enhance the function of melanocytes and protect melanocytes from UVB induced damage.
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ObjectiveTo observe the increasing effect of infrared irradiation on tyrosinase activity and melanin content in cultured normal human epidermal melanocytes in vitro and to explore the optimal dose of infrared irradiation.MethodsEpidermal melanocytes were isolated from normal human foreskin tissue,and subjected to primary culture.Methyl thiazolyl tetrazolium(MTT) assay was performed to evaluate the effect of different doses(0,20,60,80,100,140,240,320 J/cm2)of infrared light on the proliferation of melanocytes and to select the optimal irradiation dose.Then,melanocytes were irradiated with infrared light at the optimal dose for 3 consecutive days followed by the determination of tyrosinase activity,melanin content,and cell cycle via dopa oxidation assay,NaOH solubilization method and flow cytometry,respectively.ResultsThe best intervention dose of infrared light was 80 J/cm2.The tyrosinase activity(A492 nm) and melanin content(A492 nm)were 0.3601 ± 0.0301 and 0.2748 ± 0.0243 respectively in melanocytes after irradiation with infrared light of 80 J/cm2 for 3 days,significantly higher than those in unirradiated melanocytes(0.3114 ± 0.0341,0.2325 ±0.0254,respectively,both P ＜ 0.05),with an increase rate of 15.64％ and 18.19％ respectively.Cell cycle analysis revealed a decline in cell percentage in G1 phase(P ＜ 0.01 ) but a concomitant increase in cell percentage in G2 and S phase (both P ＜ 0.05) in irradiated melanocytes compared with unirradiated melanocytes.ConclusionsThe optimal dose of infrared light is 80 J/cm2 for the irradiation of melanocytes,and this dose of infrared light can increase melanin content,tyrosinase activity,differentiation and proliferation of melanocytes.
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Objective To investigate the effect of heat treatment on the proliferation of, melanin synthesis and tyrosinase activity in cultured normal human melanocytes. Methods Normal human foreskin tissue was obtained by sterile circumcision and melanocytes were harvested by using methods for epidermal cell culture. Basic fibroblast growth factor (bFGF) was utilized as the primary mitogen to establish the culture system of normal human epidermal melanocytes. Masson-Fontana staining was proformed to identify melanocytes.Third-passage melanocytes were treated with hyperthermia at various temperatures (39 ℃, 41 ℃, 42 ℃, 43 ℃ and 45℃) for 1 hour a day for consecutive 3 days followed by the measurement of cell viability with MTT assay. The hyperthermia at optimized temperature was used to treat fourth-passage melanocytes for 1 hour a day for consecutive 3 days; subsequently, the tyrosinase activity were detected with L-Dopa as the substrate, and melanin content was determined in heat-treated and untreated (control) melanocytes. Results The hyperthermia at 42 ℃ exhibited the strongest promotive effect on the proliferation of melanocytes among these 5 hyperthermia conditions. After treatment with hyperthermia at 42 ℃ for 1 hour a day for consecutive 3 days, melanocytes showed an increment in tyrosinase activity by 36.4% and melanin synthesis by 78% compared with the untreated melanocytes (both P＜0.05). Conclusions Heat treatment can enhance the proliferation of cultured human melanocytes, promote their melanin synthesis and tyrosinase activity.