Sulfur Containing Tyrosine Analogs Can Cause Selective Melanocytotoxicity Involving Tyrosinase-Mediated Apoptosis

Abstract

Sulfur-containing tyrosine analogs such as 4-S-cysteaminylphenol (4-S-CAP) and its N-acetyl derivative, N-acetyl-4-S-CAP, are tyrosinase substrates and can cause selective cytotoxicity or cell death of melanocytes and melanoma cells. It is not clear, however, if the cytotoxicity derives from a cytostatic or cytocidal effect. The latter can also be either apoptotic or necrotic. This paper summarizes our attempt to clarify the nature of melanocytotoxicity and cell death by using a new derivative of 4-S-CAP, N-propionyl-4-S-CAP (NPr-CAP). The i.p. administration of NPr-CAP caused marked depigmentation of black hair follicles in C57 mice. At 12 h postadministration of NPr-CAP, follicular melanocytes showed histochemical and morphologic features indicative of apoptosis by TdT-mediated dUTP-biotin nick end labeling (TUNEL) staining and electron microscopy. The agarose gel electrophoresis of DNA from drug-treated melan a2 cells, an immortal melanocyte line of C57 black mice, showed the nucleosomal DNA ladder pattern. NPr-CAP caused irreversible cytotoxicity in melan a2 and the effect was inhibited by a tyrosinase inhibitor, phenylthiocarbamide. The tyrosinase-mediated cytotoxicity of NPr-CAP was further confirmed by the decreased viability of COS 7 monkey-kidney cells, which expressed a level of high tyrosinase activity through transfection of human tyrosinase cDNA. NPr-CAP, however, also transiently inhibited the proliferation of melan c cells, a control tyrosinase-negative albino melanocyte line, and vector-transfected COS 7 cells. Thus, the major process of NPr-CAP-mediated melanocytotoxicity involves cytocidal apoptosis associated with active tyrosinase. In addition, there is transient, nontyrosinase-mediated cytostatic cytotoxicity.

Melanoma-Targeted Chemothermotherapy andIn SituPeptide Immunotherapy through HSP Production by Using Melanogenesis Substrate, NPrCAP, and Magnetite Nanoparticles

“…The selective disintegration of melanocytes which is mediated by apoptotic cell death can be seen as early as in 12 hr after a single ip administration. None of surrounding keratinocytes or fibroblasts showed such membrane degeneration and cell death [31, 32] (Figure 3). …”

“…The melanogenesis-related cytotoxicity primarily derives from tyrosinase-mediated formation of dopaquinone and other quinone intermediates, which produce ROSs such as superoxide and H 2 O 2 [4, 31, 32, 51]. This unique biological property of melanin intermediates not only causes cell death, but also may produce immunogenic properties.…”

N-propionyl-4-S-cysteaminylphenol induces apoptosis in B16F1 cells and mediates tumor-specific T-cell immune responses in a mouse melanoma model

“…Administration of a melanin precursor such as 4-Scysteaminylphenol to black mice resulted in depigmentation of hair follicles, possibly by the selective disintegration of melanocytes in the hair bulb [10,14,[20][21][22]. NPr-4-S-CAP exerts strong cytotoxicity toward melanoma cells, in which melanin synthesis is highly elevated [8,9,11].…”

“…They have been shown to be good substrates for tyrosinase [4][5][6] and to be selectively incorporated into melanoma cells, causing cytotoxicity against them and melanocytes [7][8][9][10][11]. However, it remains unclear whether NPr-4-S-CAP can induce cell death associated with the induction of host immune responses resulting in the tumor suppression in vivo.…”

Melanogenesis Exploitation and Melanoma Nanomedecine: Utilization of Melanogenesis Substrate, NPrCAP for Exploiting Melanoma-Targeting Drug and its Conjugation with Magnetite Nanoparticles for Developing Melanoma Chemo-Thermo-Immunotherapy

“…to black C57BL/6 mice, it caused depigmentation of black hair follicles which was found to be derived from selective apoptotic disintegration of follicular melanocytes [47]. Melanin intermediates produce reactive oxygen species such as superoxide and H 2 O 2 [5,47,48]. This unique biological property of melanin intermediates not only causes cell death, but also may produce immunogenic properties.…”