Additive effect of heat on the UVB-induced tyrosinase activation and melanogenesis via ERK/p38/MITF pathway in human epidermal melanocytes.

Heat is known as an environmental factor that causes significant skin pigmentation, but its effects on melanogenesis have been poorly studied. It has been shown that mitogen-activated protein kinase (MAPK) is involved in ultraviolet B (UVB) and stress-induced melanogenesis in melanocytes. In this study, we investigated the effects of heat and UVB, on melanocyte melanogenesis, differentiation, and MAPK phosphorylation. The results showed that heat (1 h at 40 °C for 5 days) increased cell dendrites, enlarged cell bodies, and induced extracellular signal-regulated kinases (ERK)/p38/MITF activation but did not influence melanogenesis of human epidermal melanocytes from skin phototype III. UVB irradiation (20 mJ/cm(2) for 5 days) induced melanogenesis and c-jun N-terminal kinases (JNK)/p38/MITF/tyrosinase activation in melanocytes from skin phototype III. UVB combined with heat resulted in much more significant tyrosinase activation and melanogenesis as compared with UVB alone in melanocytes from skin phototype III. Furthermore, heat treatment and UVB irradiation induced JNK, ERK, and p38 activation but not melanogenic and morphological changes in melanocytes from skin phototype I. These findings suggested that heat promoted melanocyte differentiation, probably via heat-induced ERK/p38/MITF/activation. Furthermore, heat had an additive effect on the UVB-induced tyrosinase activation and melanogenesis. These results provide a new clue for dermatologists for the treatment of hypopigmented skin disease with heat combined with UVB irradiation.

[Effects of bradykinin on the proliferation, apoptosis and differentiation of human keratinocytes].

OBJECTIVE: To investigate the effects of bradykinin (BK) on the proliferation, apoptosis and differentiation of human keratinocyte (HKC) and the underlying mechanisms. METHODS: HKCs were cultured together with 1 x 10(-4) - 1 x 10(-9) mol/L of BK. With methyl thiotetrazole (MTT) and trypan blue staining it was shown that the BK in dose of 1 x 10(-4) mol/L possessed most powerful inhibitory effect, and the survival rate of HKC was 69.3%. Therefore, BK was employed in the dose of 1 x 10(-4) mol/L in the following studies. When the growth of HKCs reached the logarithmic phase, BK in the concentration of 1 x 10(-4) mol/L was added, and it was categorized as the test group (E). HKCs without BK served as the control group (C). The cell cycle and apoptosis were detected by flow cytometry after being cultured for 24 and 48 hours. The change in intracellular calcium [Ca(2+)](i) was determined by means of laser scanning confocal microscopy with calcium fluorescence probe Fluo-3/AM technique. The expression of HKC differentiation labeling protein keratin10 (K10) and involucrin were detected with Strept Avidin-Biotin Complex (SABC) immunocytochemical assay. RESULTS: The cell ratio in G0/G1 phase in E group increased by 34.57% while in S phase decreased by 58.91% in reference to that in C group. The G1/S phase switching of HKCs was obviously inhibited by BK, and apoptosis was stimulated (apoptotic rate of 15.34% in E group vs 5.60% in C group, P < 0.05). The [Ca(2+)](i) increased transiently in HKCs by 163.0% in E group after 3 minutes of BK activation and decreased thereafter in reference to that in C group. The K10 expression in HKC was down-regulated in E group with positive cell rate of 2.20%, which was lower than that of C group (6.89%, P < 0.05). CONCLUSION: The cell cycle process of HKC could be inhibited by high concentration of BK with increased apoptosis and an increase in [Ca(2+)](i), which might be the mechanism of inhibition of growth of HKC in vitro. Furthermore, the epithelial regeneration and HKC differentiation can also be inhibited by BK.

[Effects of all-trans-retinoic acid, acitretin and tazarotene on apoptosis and Bax/Bcl-2 expressions of human melanoma cells A375 and the significance].

OBJECTIVE: To investigate the effects of all-trans retinoic acid (ATRA), acitretin and tazarotene on apoptosis and Bax/Bcl-2 protein expressions of human melanoma A375 cells. METHODS: The effects of retinoids on apoptosis and Bax/Bcl-2 protein expressions of A375 cells in vitro were examined. Apoptosis analysis with double staining with annexin V-FITC and PI was performed using flow cytometer. SABC immunocytochemistry was employed for detection of Bax/Bcl-2 protein expressions. RESULTS: At the concentration of 1 x 10(-5) mol/L, ATRA, acitretin and tazarotene all induced apoptosis of A375 cells with apoptosis ratio of 5.03% (P<0.05), 13.42% (P<0.05) and 2.88% (P>0.05), respectively, and acitretin induced more significant apoptosis than the other two agents (P<0.05). In addition, all the three agents significantly increased the number of cells positive for Bax expression and decreased the number of cells expressing Bcl-2 (P<0.05), among which acitretin had the strongest effects. CONCLUSIONS: ATRA, acitretin and tazarotene mediate apoptosis of A375 cells possibly through, at least partially, the mitochondrial pathway. Acitretin may be utilized as a valuable alternative for treating melanoma.