Regulatory Effects of Heat on Normal Human Melanocyte Growth and Melanogenesis: Comparative Study with UVB

Abstract

Although energy-rich ultraviolet B (UVB) is considered to be primarily responsible for most of the effects associated with solar radiation, small energy recorded as heat appears to contribute to the biologic effects of solar radiation on the skin. We compared the effects of heat and UVB on normal human melanocyte functions. In monolayer culture the following was found. (i) Heat-treated melanocytes showed an increased dendricity and exhibited a larger cell body compared with nontreated melanocytes. (ii) After multiple treatments with UVB (20 mJ per cm2, 312 nm) or heat (42 degrees C for 1 h) for 3 d, melanocytes had a lower survival than nontreated melanocytes, but they resumed proliferation within 6 d in the same manner as seen in control. (iii) The expression levels of cell cycle regulators, p53 and p21 proteins, were increased after multiple treatments with UVB or heat. (iv) The tyrosinase (dopa-oxidase) activity per cell was increased after the multiple treatments with UVB or heat. (v) The number of dopa-positive melanocytes in coculture with keratinocytes in epithelial sheets was greatly increased by UVB or heat treatments. (vi) Similarly, the increased number of tyrosinase-related protein 1 positive melanocytes was seen in skin equivalents after UVB (100 mJ per cm2) or heat (42 degrees C for 1 h) treatments for 7 d. These results suggest that heat shares significant biologic activities with UVB in melanocyte functions. These results could be considered as one of the protective or adaptive responses of the skin pigmentary system to the environment.

Melanogenesis and antioxidant defense system in normal human melanocytes cultured in the presence of chlorpromazine

“…Their results have also shown that the tyrosinase activity in human melanocytes increased slightly after UVB and heat treatments, by 2.0% and 5.0%, respectively. The authors suggest that heat may share significant biologic activities with UVB in melanocyte functions and conclude that these reactions could be considered as one of the protective or adaptive responses of the skin pigmentary system to the environment (Nakazawa et al, 1998). Our earlier studies have also shown the down-regulation in melanogenesis when the cells were exposed to increasing concentrations of the tested substances (Beberok et al, 2013;Wrześniok et al, 2013a,b).…”

“…The small increase of melanogenesis was also stated by other authors. Nakazawa et al (1998) reported the regulatory effects of heat on normal human melanocytes functions, such as the inhibition of melanocyte growth, the upregulation of p21 and p53 expressions, and the stimulation of melanogenesis by increasing the number of DOPA-and TRP1-positive melanocytes in coculture with keratinocytes. Their results have also shown that the tyrosinase activity in human melanocytes increased slightly after UVB and heat treatments, by 2.0% and 5.0%, respectively.…”

Diosgenin inhibits melanogenesis through the activation of phosphatidylinositol-3-kinase pathway (PI3K) signaling

“…Diosgenin has been shown to exert anti-proliferative and proapoptotic actions on rheumatoid arthritis synoviocytes or on cancer cells in vitro Briganti et al, 2003;Oka et al, 1996) and in vivo , as well as differentiating effects (Nakazawa et al, 1998). However, the effect of diosgenin on pigmentation has not yet been elucidated.…”

“…This compound has been reported to have various biological effects in vivo (Cullen, 1998;Ortonne and Nordlund, 1998). Moreover, at an appropriate dose, diosgenin has been shown to exert anti-proliferative and proapoptotic actions on rheumatoid arthritis synoviocytes (Liagre et al, 2004) or on cancer cells in vitro Briganti et al, 2003;Oka et al, 1996) and in vivo , and also exerts differentiating effects (Nakazawa et al, 1998). It is also the starting material for the synthesis of a number of hormonal products such as dehydroepiandrosterone (Scott et al, 2001) (Fig.…”

Investigations on normal human adult epidermal melanoytes

“…Data indicate that UVB can influence the expression of TRP-1 [60,61]. Repeated UVB irradiation induced TRP-1 expression in melanocyte-keratinocyte co-culture [62]. In our experiments, direct UVB exposure caused a decrease in TRP-1 mRNA expression in melanocytes.…”