Expression Of Tyrosinase-related Protein-1 Research Articles

효소(Protopectinase) 처리한 대두가 세포내 멜라닌 생성에 미치는 영향

본 연구에서는 효소처리 한 대두추출물의 항산화 및 미백효과를 확인하기 위하여 DPPH 및 hydroxyl radical 포착활성을 측정하였고, 멜라닌 생성의 첫 단계인 tyrosinase 활성, mouse melanoma B16BL6 세포 생존율 및 TRP-1, TRP-2 발현 저해활성을 측정하였다. 또한 기존의 기계적 마쇄 가공한 대두추출물과 효소처리 가공한 대두추출물의 항산화 및 미백효과를 비교 조사하였다. 효소처리 한 대두추출물의 DPPH radical 소거능과 hydroxyl radical 소거능이 마쇄처리 한 추출물보다 높았으며, 특히 효소처리군이 마쇄군에 비하여 20% 이상 높은 항산화력을 나타내었다. 또한 마쇄군에 비하여 효소처리군이 tyrosinase와 TRP-1, TRP-2의 더 높은 활성 억제능을 보였다. 이는 대두가 B16BL6 melanoma 세포의 tyrosinase 단백질의 활성을 저해시킴으로써 멜라닌 생성을 억제하는데 효과적임을 의미하는 동시에 효소처리에 의하여 대두의 영양소의 손실이 더 적었음을 나타낸다. 결론적으로 효소처리에 의한 대두 추출물은 항산화 활성과 미백 효과가 우수하여 기능성 화장품의 천연 소재로서 활용가능성이 매우 높은 것으로 사료된다.

Anti-Melanogenesis Effect ofGlechoma hederaceaL. Extract on B16 Murine Melanoma Cells

Glechoma hederacea L. (Labiatae) has been used in folk medicine to treat various ailments for centuries. We investigated the effects of G. hederacea extract on melanogenesis in B16 melanoma cells. It significantly reduced both the cellular melanin content and tyrosinase activity in a concentration-dependent manner. An MTT assay did not reveal any obvious cytotoxicity. Furthermore, we found that G. hederacea extract decreased tyrosinase and microphthalmia-associated transcription factor protein expression, but did not inhibit tyrosinase-related protein-1 and tyrosinase-related protein-2 expression. RT-PCR analysis indicated that the antimelanogenic effect of G. hederacea extract might be due to inhibition of tyrosinase gene transcription. Moreover, this effect is regulated via suppression of microphthalmia-associated transcription factor protein expression. Our data indicate that G. hederacea extract inhibits melanin synthesis in B16 melanoma cells but is not cytotoxic. Hence it might prove a useful therapeutic agent for treating hyperpigmentation and an effective component of whitening cosmetics.

Inhibition of melanogenesis and antioxidant properties of Magnolia grandiflora L. flower extract

BackgroundMagnolia grandiflora L. flower is wildly used in Asian as a traditional herbal medication. The purpose of the study was to investigate the antimelanogenic and antioxidant properties of Magnolia grandiflora L. flower extract. In the study, the inhibitory effects of M. grandiflora L. flower extract on mushroom tyrosinase, B16F10 intracellular tyrosinase activity and melanin content were determined spectrophotometrically. Meanwhile, the antioxidative capacity of the flower extract was also investigated.ResultsOur results revealed that M. grandiflora L. flower extract inhibit mushroom tyrosinase activity (IC50 =11.1%; v/v), the flower extract also effectively suppressed intracellular tyrosinase activity (IC50 = 13.6%; v/v) and decreased the amount of melanin (IC50 = 25.6%; v/v) in a dose-dependent manner in B16F10 cells. Protein expression level of tyrosinase and tyrosinase-related protein 1 (TRP-1) were also decreased by the flower extract. Additionally, antioxidant capacities such as ABTS+ free radical scavenging activity, reducing capacity and total phenolic content of the flower extract were increased in a dose-dependent pattern.ConclusionsOur results concluded that M. grandiflora L. flower extract decreased the expression of tyrosinase and TRP-1, and then inhibited melanogenesis in B16F10 cells. The flower extract also show antioxidant capacities and depleted cellular reactive oxygen species (ROS). Hence, M. grandiflora L. flower extract could be applied as a type of dermatological whitening agent in skin care products.

Effect of xanthoxylin on melanin content and melanogenic protein expression in B16F10 melanoma

Background: Reduced production of melanin and decreased or absence of melanocytes leads to various hypopigmentation disorders. Melanin synthesis is regulated by melanogenic proteins such as tyrosinase, tyrosinase-related protein 1 (TRP-1) and tyrosinase-related protein 2 (TRP -2), as well as their transcription factors. Objectives: This study elucidated the effects of xanthoxylin on melanin content, dendriticity, melanogenic protein expression and its signal transduction pathways in mouse B16F10 melanoma cells (B16F10 cells). Methods: Melanin production of B16F10 cells was measured by using a melanin content assay. The effect of xanthoxylin on the dendriticity of B16F10 cells was determined by a melanocyte dendricity assay. RT-PCR was used to investigate the effects of xanthoxylin on the melanogenic protein expression. Results: We found that xanthoxylin increased melanin production, number of dendrites, tyrosinase, and microphthalmia-associated transcription factor (MITF) expression in cultured B16F10 cells. In addition, PKA and PKC inhibitor decreased melanin production, tyrosinase, and MITF expression in xanthoxylin-treated cells. However, xanthoxylin did not inhibit TRP-1 and TRP-2 expression. Conclusion: These results indicated that xanthoxylin induces melanogenesis mainly via cAMP-mediated PKA activation. Other signaling pathways may also play a role in xanthoxylin-induced melanogenesis. Keywords: Melanocyte, melanin, xanthoxylin

홍화자, 향부자, 형개 추출물의 미백효과에 관한 연구

본 연구에서는 3가지 홍화자, 향부자, 형개 추출물의 미백효과를 연구하였다. 멜라닌 생성 첫 단계인 tyrosinase 억제활성과 멜라닌 생성 억제효과를 측정한 결과, 홍화자 에탄올 추출물이 tyrosinase 활성과 B16F10 melanoma 세포의 멜라닌 생성 억제하였다. 그 결과, 홍화자 추출물은 B16F10 melanoma 세포에서 melanogenesis 따른 tyrosinase 형성 억제에 따른 멜라닌 합성 관련 인자 MITF, tyrosinase, TRP-1, TRP-2 의 발현을 억제함에 따라 홍화자 추출물의 미백효과를 확인하였다. 따라서 홍화자는 미백효과를 가진 천연 기능성 재료로서 가능성이 매우 높은 것으로 판단된다. The objective of the present study was to evaluate the skin depigmentation effect of the extracts of three herbs, Carthamus tinctorius seed, Cyperus rotundus and Schizonepeta tenuifolia. Their effects on tyrosinase and melanin synthesis inhibitory action were assessed. We found that the C. tinctorius seed ethanol extracts reduced the tyrosinase activity and melanin formation of B16F10 melanoma cells. The C. tinctorius seed suppressed the expression in microphthalmia associated transcription factor (MITF), tyrosinase, tyrosinase related protein 1 (TRP-1), and tyrosinase related protein 2 (TRP-2) in B16F10 melanoma cells. These results show that C. tinctorius seed inhibited melanogenesis on the B16F10 melanoma cell. The underlying mechanism of C. tinctorius seed whitening activity may be the inhibition of tyrisinase, MITF, tyrosinase, TRP-1, and TRP-2 expression. The results suggested that C. tinctorius seed has considerable potential as a natural functional ingredient with a depigmentation effect.

The changes of microRNA expression profiles and tyrosinase related proteins in MITF knocked down melanocytes

Microphthalmia-associated transcription factor (MITF) is a master regulator in melanocyte proliferation, development, survival and melanoma formation. In melanocyte dysfunction disease, it is observed that the expressions of MITF, tyrosinase (TYR), tyrosinase related protein 1 (TYRP1) and tyrosinase related protein 2 (TYRP2)/dopachrome tautomerase (DCT) are changed, the consequence of which remains unclear. In this study, we focused on the change of microRNA (miRNA) profiles and Tyrosinase Related Proteins (TRPs) in MITF knocked down melanocytes. For the first time, we assayed the MITF-KD miRNA profiles using a miRNA microarray and found that hsa-miR-1225-3p, hsa-miR-634, hsa-miR-197, hsa-miR-766, hsa-miR-574-5p and hsa-miR-328 were upregulated, and hsa-miR-720 and hsa-miR-1308 were downregulated in MITF knocked down melanocytes. These miRNAs were validated by miRNA real time qPCR. These miRNA potential targets, especially the TRPs, were analyzed according to the miRNA database (Sanger Center). By TargetScan prediction, the hsa-miR-634 and hsa-miR-328 have poorly conserved sites on TYR and hsa-miR-197 have poorly conserved sites on TYR1. Through qPCR and western blotting we found that the expression of TYR and TYRP1 were dramatically decreased and the expression of TYRP2 was increased in MITF knocked down melanocytes (MITF-KD). These results suggested that the miRNAs may be involved in MITF regulation of TYR, TYRP1 and TYRP2, which provides a new clue for understanding the role of miRNAs in melanocyte dysfunctional disease.

Ascorbic acid increases the activity and synthesis of tyrosinase in B16F10 cells through activation of p38 mitogen-activated protein kinase

Ascorbic acid, a potential antioxidant, is known to inhibit melanogenesis. However, there are conflicting findings that ascorbic acid has very low stability and acts as a pro-oxidant, eventually increasing proliferation and melanin content in melanoma cells. In the present study, we explored the effects of ascorbic acid on the activity and expression of tyrosinase and melanin pigmentation in the presence and absence of α-melanocyte-stimulating hormone (α-MSH) using B16F10 melanoma cells. The mechanism by which ascorbic acid stimulated the expression of tyrosinase was also investigated. No inhibitory effect on melanin content was observed in ascorbic acid-treated cells, regardless of the presence of α-MSH. Ascorbic acid stimulated the activity and expression of tyrosinase and increased the expression of melanogenic regulatory factors, such as tyrosinase-related protein-1 (TRP-1), dihydroxyphenylalaminechrome tautomerase (TRP-2), and microphthalmia-associated transcription factor (MITF). Ascorbic acid also induced phosphorylation of p38 mitogen-activated protein kinase (MAPK). The inhibition of p38 MAPK pathway by SB203580 led to the suppression of tyrosinase, TRP-1, and TRP-2 expression in cells treated with ascorbic acid. Combined treatment with N-acetyl-L: -cysteine and/or desferrioxamine mesylate attenuated the stimulating effect of ascorbic acid on tyrosinase activation in the cells. Collectively, ascorbic acid stimulates tyrosinase activity and expression in B16F10 cells via activation of p38 MAPK signaling and subsequent up-regulation of MITF, tyrosinase, and TRP expression.

Aromatic-turmerone inhibits α-MSH and IBMX-induced melanogenesis by inactivating CREB and MITF signaling pathways

This study investigated the anti-melanogenic effect of aromatic (ar)-turmerone on alpha-melanocyte stimulating hormone (α-MSH) and 3-isobuty-1-methxlzanthine (IBMX)-induced tyrosinase (Tyr), tyrosinase-related protein 1 (TRP-1), and tyrosinase-related protein 2 (TRP-2) expression in B16F10 melanoma cells. We demonstrated that ar-turmerone inhibits α-MSH and IBMX-induced melanin synthesis and tyrosinase activity. Data also showed that ar-turmerone inhibits the expression of tyrosinase, TRP-1, and TRP-2 in α-MSH- and IBMX-stimulated B16F10 cells. In addition, ar-turmerone exhibits stronger anti-melanogenic effects than curcumin. Furthermore, ar-turmerone strongly inhibited α-MSH- and IBMX-induced microphthalmia-associated transcription factor by suppressing the activity of cyclic adenosine monophosphate (cAMP)-responsive element binding protein in α-MSH-stimulated B16F10 cells. Our data revealed that ar-turmerone is a novel, effective, anti-melanogenic agent that functions by downregulating tyrosinase, Trp-1, and Trp-2 gene expression. Therefore, ar-turmerone may be a useful therapeutic agent for treating hyperpigmentation disorders, such as freckles and melasma, and as a beneficial additive in whitening cosmetics.

Regulation of melanocyte pivotal transcription factor MITF by some other transcription factors

The microphthalmia transcription factor (MITF) is discussed as the master gene for melanocytic survival and a key transcription factor regulating the expression of tyrosinase (TYR), tyrosinase-related protein-1 (TRP-1), and tyrosinase-related protein-2 (TRP-2). MITF is influenced in a complex manner by a large number of different extracellular and intracellular proteins. Many transcription factors are able to modulate the expression and/or transcriptional activity of MITF in vivo. In this review, we summarize these transcription factors that regulate MITF and their interactions. The Sry-related HMG box 10 (SOX10) can directly transactivate the MITF gene and cooperate with MITF to activate TRP-2 expression. The Paired box 3 (PAX3) can increase MITF expression by binding to its promoter and simultaneously prevent MITF from activating downstream genes by competition for enhancer occupancy. Activated signal transducer and activator of transcription 3 (STAT3) and protein inhibitor of activated STAT3 (PIAS3) are able to regulate transcriptional activity of MITF through their interaction. Activated cAMP response element binding protein (CREB) can bind the cAMP response element to increase the MITF gene expression. MITF expression can also be initiated by lymphoid-enhancing factor-1 (LEF-1) and be temporally facilitated by the synergy of LEF-1 and MITF. Both immunoglobulin transcription factor-2 (ITF2) and forkhead-box transcription factor D3 (FOXD3) can negatively regulate MITF expression. All the above-mentioned transcription factors constitute a regulatory network that precisely modulates the MITF.

GILT regulates CD4+ T cell tolerance (100.28)

Abstract Regulating the balance between T cell activation and tolerance is essential for stimulating an anti-tumor immune response and in controlling autoimmunity. We have shown that gamma-interferon-inducible lysosomal thiol reductase (GILT) is required for efficient MHC class II-restricted processing of an epitope from the melanoma antigen tyrosinase-related protein 1 (TRP1). Using CD4+ TRP1-specific T cell receptor transgenic mice, here we demonstrate a novel function for GILT in the regulation of TRP1-specific T cell tolerance. TRP1-specific T cells are centrally deleted in mice expressing both GILT and TRP1 on the RAG-/- background. In contrast, CD4+ T cells develop in the absence of either GILT or TRP1. GILT’s role in central tolerance is supported by GILT and TRP1 expression in thymic stromal cells. Although TRP1-specific CD4+ T cells escape thymic deletion in the absence of GILT, they are tolerant to TRP1 and do not induce vitiligo. TRP1-specific T cells from GILT-deficient mice initially divide in response to antigen, but fail to produce substantial levels of IFN-γ and IL-2. Tolerance is partially mediated by CD25+Foxp3+ regulatory T (Treg) cells. There is an increased percentage of TRP1-specific Treg cells in GILT-deficient compared to TRP1-deficient mice, and Treg cell depletion allows GILT-deficient TRP1-specific CD4+ T cells to induce vitiligo. These studies highlight a critical role for GILT in shaping the CD4+ T cell repertoire.

Quercetin Inhibits α‐MSH‐stimulated Melanogenesis in B16F10 Melanoma Cells

Quercetin is known to inhibit tyrosinase activity and melanin production in melanocytes. However, several reports suggest that quercetin has different and opposite effects on melanogenesis. This study examined the precise effects of quercetin on melanogenesis using cell-free assay systems and melanocytes. Quercetin inhibited the monophenolase and diphenolase activities of tyrosinase, and melanin synthesis in cell-free assay systems. Quercetin induced mild stimulation of the tyrosinase activity and dihydroxyphenylalaminechrome tautomerase (TRP-2) expression but only at low concentrations (<20 μm) in B16F10 melanoma cells. In contrast, the addition of 50 μm quercetin to the cells led to a significant decrease in the activity and synthesis of tyrosinase, as well as a decrease in the expression of tyrosinase-related protein-1 and TRP-2 proteins, regardless of the presence or absence of α-melanocyte stimulating hormone (α-MSH). Quercetin also reduced the intracellular cAMP and the phosphorylated protein kinase A levels in α-MSH-stimulated B16F10 cells. Moreover, quercetin (20 μm) diminished the expression and activity of tyrosinase, and melanin content in cultured normal human epidermal melanocytes. These effects were not related to its cytotoxic action. Although the in vivo effects of quercetin are still unclear, these results suggest that quercetin could play important roles in controlling melanogenesis.

Beta-carboline alkaloids harmaline and harmalol induce melanogenesis through p38 mitogen-activated protein kinase in B16F10 mouse melanoma cells

Melanin synthesis is regulated by melanocyte specific enzymes and related transcription factors. β-carboline alkaloids including harmaline and harmalol are widely distributed in the environment including several plant families and alcoholic beverages. Presently, melanin content and tyrosinase activity were increased in melanoma cells by harmaline and harmalol in concentration- and time-dependent manners. Increased protein levels of tyrosinase, tyrosinase-related protein-1 (TRP-1), and TRP-2 were also evident. In addition, immunofluorescence and Western blot analyses revealed harmaline and harmalol increased cAMP response element binding protein phosphorylation and microphthalmia-associated transcription factor expression. In addition to studying the signaling that leads to melanogenesis, roles of the p38 MAPK pathways by the harmaline and harmalol were investigated. Harmaline and harmalol induced time-dependent phosphorylation of p38 MAPK. Harmaline and harmalol stimulated melanin synthesis and tyrosinase activity, as well as expression of tyrosinase and TRP-1 and TRP-2 indicating that these harmaline and harmalol induce melanogenesis through p38 MAPK signaling.

정공피 추출물의 항산화 활성 및 미백효과에 관한 연구

본 연구에서는 정공피 물 추출물의 미백 효과를 확인하기 위하여 항산화 효능을 검증하였고, 멜라닌 생성의 첫 단계인 tyrosinase 활성, mouse melanoma B16BL6 세포 생존율 및 TRP-1, TRP-2 mRNA 발현 정도를 측정하였다. 정공피 물 추출물은 DPPH 및 hydroxy 라디칼 소거 작용을 통하여 높은 항산화 효능을 나타내었고, tyrosinase, TRP-1, TRP-2의 활성을 효과적으로 억제하는 것을 확인하였다. 이는 정공피 물 추출물이 직접적으로 B16BL6 melanoma 세포의 tyrosinase 단백질의 활성을 저해시킴으로써 멜라닌 생성을 억제하는데 효과적임을 의미한다. 결론적으로 정공피 추출물은 항산화 활성과 미백 효과가 우수하여 기능성 화장품의 천연 소재로서 활용 가능성이 매우 높은 것으로 판단된다.

TRP‐ing off the p53 apoptotic switch

TRP‐ing off the p53 apoptotic switch

Effect of Palmitoleic Acid on Melanogenic Protein Expression in Murine B16 Melanoma

Melanogenesis is a well-known physiological response of human skin that may occur because of exposure to ultraviolet light, for genetic reasons, or due to other causes. In our efforts to find new skin lightening agents, palmitoleic acid was investigated for its ability to inhibit melanogenesis. In this study, palmitoleic acid's effect on melanin formation was assessed. Results indicated that palmitoleic acid was shown to down-regulate melanin content in a dose-dependent pattern. To clarify the target of palmitoleic acid action in melanogenesis, we performed Western blotting for tyrosinase, tyrosinase-related protein-1 (TRP-1), TRP-2, and microphthalmia-associated transcription factor (MITF), which are key melanogenic enzymes. Palmitoleic acid inhibited tyrosinase, TRP-2, and MITF expressions in a dose-dependent manner. However, it did not inhibit TRP-1 expression. In order to assess its usefulness in future cosmetic product applications, the cytotoxic effects of the palmitoleic acid were also determined by colourimetric MTT assays using human keratinocyte HaCaT cells. Palmitoleic acid exhibited no cytotoxicity at 500 muM in a human cell line. Therefore, this study suggests that palmitoleic acid is a candidate anti-melanogenic agent, and it might be effective in hyperpigmentation disorders.

Antigenic profiles of individual-matched pairs of primary and melanoma metastases

A unique collection of individual-matched pairs of primary and melanoma metastases were studied immunohistochemically with a panel of 6 monoclonal antibodies directed to gp-100, pigmentation-associated antigen, tyrosinase-related protein, human leukocyte antigen DR, MAA-1, and MAA-2 (high molecular weight melanoma-associated antigens). The antigenic profile of immunoreactive pigment cells was compared with the stage of tumor progression. Our data show consistent antigenic profiles of primary melanomas and their metastases within the same patient. Expression of tyrosinase-related protein and pigmentation-associated antigen was observed in the radial growth phase of primary melanomas but showed diminished or complete loss of expression in the vertical growth phase and in metastatic melanomas. HLA-DR was negative in the most primary lesions, but melanoma cells and a larger proportion of immunoreactive cells were observed at the metastatic site. The melanoma-associated antigens MAA-1 and MAA-2 were expressed throughout tumor progression. Although no clear distinction could be made between primary and secondary melanoma lesions for both melanoma-associated antigens, there was a profound variability in the topographical antigen distribution when compared with HLA-DR. The loss of expression of pigmentation-associated antigen and tyrosinase-related protein in the vertical growth phase of the primary lesions and metastatic melanomas did not reach statistical significance but still may be related to tumor progression. This indicates that primary melanomas can be distinguished from their metastases by evaluation of the antigenic profile and in this respect facilitate the recognition of tumor progression stages.

Melanoma Progression Despite Infiltration by In Vivo-primed TRP-2–specific T Cells

Many antigens recognized by tumor-reactive cytotoxic CD8+ T cells are self-antigens. Tyrosinase-related protein 2 (TRP-2) is a melanogenic enzyme expressed by both melanocytes and melanomas that is reported to be a candidate melanoma rejection antigen. To study the role of self-reactive CD8+ T cells in tumor immunity and autoimmunity, we generated mice that bear a T-cell receptor transgene (TCR Tg) specific for the TRP-2(180-188) epitope. TRP-2 TCR Tg mice did not spontaneously develop depigmentation despite systemic expression of TRP-2 in the skin. Peripheral T cells from these TCR Tg mice exhibited a naive phenotype and proliferated in response to TRP-2 in vitro. In addition, transfer of in vitro-activated Tg T cells reduced B16 pulmonary tumor burden, but not subcutaneous tumors. We next sought to determine the in vivo responses of the Tg T cells to endogenous and tumor-derived TRP-2. Adoptive transfer of naive TCR Tg T cells into wild-type C57BL/6 mice, in combination with a TRP-2-pulsed dendritic cell vaccine, induced proliferation of the Tg T cells and resulted in migration of the Tg T cells into a subcutaneous B16 melanoma tumor. Although these tumor-infiltrating Tg T cells remained reactive against TRP-2, they did not reduce growth of the primary subcutaneous tumor; similarly, these in vivo-primed effector cells had no significant effect on the growth of pulmonary nodules. These data demonstrate that despite in vivo priming, tumor-infiltrating T cells may fail to reduce tumor burden. Determining the basis for the inability of the tumor microenvironment to sustain effective antitumor responses will be critical for designing newer, more potent antitumor immunotherapies.

A method for quantifying melanosome transfer efficacy from melanocytes to keratinocytes in vitro

Several different in vivo and in vitro bioassays are used to evaluate melanosome transfer efficacy from melanocytes to keratinocytes. However, these methods are complicated and time consuming. Here, we report on a simple, rapid, direct, and reliable in vitro method for observing the process of melanosome transfer from melanocytes to keratinocytes. First, we selected and tested a melanoma cell line RPMI-7951 that can normally synthesize melanin and transfer from mature melanosomes to keratinocytes in vitro. We cocultured these cells with a human ovarian teratoma transformed epidermal carcinoma cell line, which is also capable of accepting melanosomes transferred from melanocytes, as in normal keratinocytes. The cells were cocultured for 24-72 h and double labeled with FITC-conjugated antibody against the melanosome-associated protein TRP-1, and with Cy5-conjugated antibody against the keratinocyte-specific marker keratin 14. The cells were examined by fluorescence microscope and flow cytometry. Melanosome transfer from melanocytes to keratinocytes increased in a time-dependent manner. To verify the accessibility of this method, the melanosome transfer inhibitor, a serine protease inhibitor, 4-(2-aminoethyl) benzenesulfonyl fluoride hydrochloride, and a melanosome transfer stimulator, alpha-melanocyte-stimulating hormone, were added. The serine protease inhibitor decreased melanosome transfer, and alpha-melanocyte-stimulating hormone increased melanosome transfer, in a dose-dependent manner. In conclusion, this is a simple, rapid, and effective model system to quantify the melanosome transfer efficacy from melanocytes to keratinocytes in vitro.

Tumor progression despite the presence of functional tumor‐infiltrating CD8+ T cells

Many of the antigens recognized by tumor‐reactive cytotoxic CD8+ T cells are self‐antigens. Tyrosinase‐related protein 2 (TRP‐2) is a melanosomal enzyme expressed by both normal melanocytes and melanomas that is believed to be a candidate melanoma rejection antigen. To study the role of self‐reactive CD8+ T cells in tumor immunity and autoimmunity, we generated T cell receptor transgenic (TCR Tg) mice which bear a TCR transgene specific for TRP‐2 (180–188). TRP‐2 TCR Tg mice did not develop depigmentation despite systemic expression of TRP‐2 in the skin and their T cells exhibit a naïve phenotype: CD44low, CD62hi and CD69 and CD25 negative. Furthermore, endogenous TRP‐2 expression has no effect on the TRP‐2 specific CD8+ T cells development and antigen responsiveness. Using a system of Tg T cell adoptive transfer into wild‐type C57BL/6 mice, we have observed that in vitro‐activated TRP‐2‐specific CD8+ T cells reduced B16/BL6 pulmonary nodules. However, provision of a TRP‐2‐pulsed dendritic cell vaccine induced proliferation of the Tg T cells resulting in migration to the subcutaneous tumor. These tumor‐infiltrating Tg T cells remained reactive to TRP‐2 for at least 15 days after vaccination but did not reduce tumor growth. Thus, these findings demonstrate that tumors can evade functional anti‐tumor immune responses. Our on‐going studies will test whether priming these tumor‐reactive T cells in the presence of various cytokine regimens will sufficiently enhance their cytotoxic capacity to induce more potent tumor immunity.

Inhibitory Effects of Macelignan Isolated from Myristica fragrans HOUTT. on Melanin Biosynthesis

The aim of this study was to investigate the in vitro inhibitory effects of macelignan isolated from Myristica fragrans HOUTT. on melanogenesis and its related enzymes such as tyrosinase, tyrosinase-related protein-1 (TRP-1), and tyrosinase-related protein-2 (TRP-2) in melan-a murine melanocytes. The IC50 values of macelignan for melanogenesis and tyrosinase were 13 microM and 30 microM, respectively, while those of arbutin as a positive control were 990 microM and 660 microM, respectively. In Western blot analysis, macelignan also significantly decreased tyrosinase, TRP-1, and TRP-2 protein expression. These results indicate that macelignan effectively inhibits melanin biosynthesis and thus could be employed as a new skin-whitening agent.