Chia-Li Yu

Narrow-band ultraviolet-B stimulates proliferation and migration of cultured melanocytes.

Abstract:u2002 Narrow‐band ultraviolet‐B (UVB) radiation is an effective treatment for vitiligo vulgaris. However, the mechanisms of narrow‐band UVB in inducing repigmentation of vitiligo lesions are not thoroughly clarified. The purpose of our study was to investigate the effects of narrow‐band UVB irradiation on melanocyte proliferation and migration in vitro. Our results showed that the cell counts as well as [3H]thymidine uptake of melanocytes were significantly enhanced by narrow‐band UVB‐irradiated keratinocyte supernatants. In these supernatants, a significant increase in basic fibroblast growth factor (bFGF) and in endothelin‐1 (ET‐1) release was observed. bFGF is a natural mitogen for melanocytes, whereas ET‐1 can stimulate DNA synthesis in melanocytes. This stimulatory effect of melanocyte proliferation by supernatants derived from narrow‐band UVB‐irradiated keratinocytes was significantly reduced by a selective endothelin‐B (ET‐B) receptor antagonist (BQ788), suggesting an essential role of ET‐1 on melanocyte proliferation. Our results of time‐lapse microphotography revealed a stimulatory effect of narrow‐band UVB irradiation on melanocyte migration. Focal adhesion kinase (FAK) plays a pivotal role in cell migration. Phosphorylated FAK (p125FAK) expression on melanocyte was enhanced by narrow‐band UVB irradiation. In this study, narrow‐band UVB irradiation stimulated a significant increase in matrix metalloproteinase‐2 (MMP‐2) activity in melanocyte supernatants. Narrow‐band UVB‐irradiation‐induced migration of melanocytes was significantly annihilated by the addition of p125FAK inhibitor (herbimycin‐A) or MMP‐2 inhibitor (GM6001). These results suggest that p125FAK and MMP‐2 activity play important roles in narrow‐band UVB‐induced migration of melanocytes. Our results provide a theoretical basis for the effectiveness of narrow‐band UVB irradiation in treating vitiligo.

Differential effects of arsenic on cutaneous and systemic immunity: focusing on CD4+ cell apoptosis in patients with arsenic-induced Bowen's disease

Bowens disease (BD), a carcinoma in situ of the skin, has been identified as an early lesion in arsenic carcinogenesis. Patients with arsenic-induced Bowens disease (As-BD) showed both cutaneous and systemic immune dysfunctions. We set out to evaluate the interactions between keratinocytes and lymphocytes in the context of As-BD carcinogenesis. Our results showed that As-BD lesions demonstrated a significant dermal CD4+ cell, an essential regulator of proper tumor immunity, undergoing apoptosis. In addition, it was found that the As-BD patients have lower percentage of peripheral CD4+ cells as compared with control subjects. However, the CD4+ cells from As-BD patients were less susceptible to arsenic-induced apoptosis, due to reduced tumor necrosis factor receptor 1 expression. Interestingly, arsenic was found to induce Fas expression on CD4+ cells and increase the soluble Fas ligand (sFasL) production from keratinocytes. This sFasL-containing keratinocyte supernatant was able to induce comparable CD4+ cell apoptosis for both patients and controls. Using immunofluorescent staining, increased FasL was observed in keratinocytes of As-BD lesions and Fas was expressed among infiltrating CD4+ cells. Our findings suggested that systemically, the percentage of CD4+ cells was decreased in the peripheral blood of As-BD patients. These residual CD4+ cells were less susceptible to arsenic-induced apoptosis. However, once infiltrated into the As-BD lesions, the selective CD4+ cell apoptosis might be mediated by FasL from keratinocytes. This additional tumor-anti-immune phenomenon present in the cutaneous environment provides a reasonable explanation for frequent occurrence of arsenic cancers in the skin.

Alterations of Mitogenic Responses of Mononuclear Cells by Arsenic in Arsenical Skin Cancers

We have studied the endemic occurrence of chronic arsenism in a limited area on the southwest coast of Taiwan. The effects of arsenic on the mitogenic responses of mononuclear cells (MNC) derived from patients with arsenical skin cancers in that area were evaluated. The subjects enrolled in this study included patients with 1) Bowens disease, 2) arsenical skin cancers (basal cell carcinoma and squamous cell carcinoma), 3) non‐arsenical skin cancers (basal cell carcinoma and squamous cell carcinoma), 4) nasopharyngeal cancer and 5) healthy controls from endemic and non‐endemic areas. Phytohemagglutinin (PHA) stimulated [3H]thymidine incorporation in MNC in all groups except the arsenical skin cancer group. However, when a low concentration of As2O3 (2.5 × 10−7 M) was added to PHA‐stimulated MNC, a tremendous amplification of the uptake of [3H]thymidine was noticed in patients with arsenical skin cancer. In this study, this phenomenon did not occur in cancers not related to arsenic. This result shows that arsenical carcinomas are hyperreactive to its specific etiology—arsenic. Arsenic seems to play a role as a co‐stimulant of PHA similar to interleukin‐1.

Pigmentation in Basal Cell Carcinoma Involves Enhanced Endothelin-1 Expression

Abstract:u2002 Basal cell carcinoma (BCC) is the most prevalent malignant skin tumor. In Asian patients, marked pigmentation in BCC lesions is often observed. Recently, endothelins (ETs) have been implicated to participate in the pigmentation process of BCC. Therefore, we set out to investigate the involvement of ET in the pigmentation process of BCC and the potential regulators in the pigmentation pathway. We explored the effects of an established BCC cell line on melanocytes. The growth factor profiles of BCC culture supernatant and effects of supernatant on melanocytes were documented. Potential regulators involved in the pigmentation pathway were also studied. The immunohistochemical staining of pigmented and non‐pigmented BCC specimens was performed to confirm our in vitro findings. Our results showed that BCC supernatant contained significant amount of ET‐1, basic fibroblast growth factor, and nerve growth factor. Furthermore, BCC supernatant stimulated melanin formation of cultured melanocytes. Addition of ET‐receptor antagonist abrogated the melanogenic effect of BCC supernatant on melanocytes. Introduction of UVB irradiation decreased the ET‐1 secretion by BCC cells. Immunohistochemical staining of the pigmented facial BCC specimens showed prominent expression of ET‐1 on pigmented BCC, while the non‐pigmented facial BCC specimens showed little ET‐1 reactivity. Tumor necrosis factor‐alpha (TNF‐α) staining showed little expression on BCC specimens, regardless of pigmentation status. In summary, our results indicate that enhanced ET‐1 expression in pigmented BCC plays an important role in the hyperpigmentation of this tumor. Moreover, this enhanced ET‐1 cascade showed little correlation with UV irradiation and TNF‐α expression in our study.

Immunological dysfunction in chronic arsenic exposure: From subclinical condition to skin cancer

Exposure to arsenic is a global health issue. Long‐term arsenic exposure may associate with various cancers and many other pathological effects. Over 100 million people worldwide are exposed to arsenic particularly in countries such as Bangladesh, Chile, China, India, Mexico, Taiwan and the USA. Drinking of water contaminated with arsenic is the major route of human exposure. Skin lesions are considered to be the most common adverse effects associated with chronic arsenic exposure. Skin lesions usually develop with the latency period spanning more than 20 years from first exposure. Arsenic‐induced Bowens disease, the most frequently encountered carcinoma in situ resulting from chronic arsenic exposure, is characterized by multiple and recrudescent lesions. Long‐term arsenic exposure results in impaired immunity in susceptible individuals. In the prenatal stage, enhanced placental inflammatory responses and reduced placental T cells by arsenic may result in decreased thymic size and functions in newborns. In childhood, arsenic exposure may reduce peripheral CD4+ cells and interleukin‐2 secretion which leads to susceptibility to opportunistic infections. There was an impairment of macrophage function and oxidative DNA damage of peripheral polymorphonuclear leukocytes in adults with skin lesions. In arsenic‐induced Bowens disease lesions, a decrease in the number and functions of Langerhans cells and, in parallel, a selective CD4+ cell apoptosis was noticed. These findings provide scientific evidence for understanding the phenomenon of arsenic‐induced immune escape in the early stage of carcinogenesis and a reasonable explanation for multiple and recrudescent arsenic cancers in the skin.