Ashida M, Bito T, Budiyanto A, Ichihashi M, Ueda M
Division of Dermatology, Clinical Molecular Medicine, Faculty of Medicine, Kobe University Graduate School of Medicine, Kobe, Japan.
Exp Dermatol. 2003 Aug;12(4):445-52. doi: 10.1034/j.1600-0625.2003.00101.x.
Because selective inhibition of cyclooxygenase-2 (COX-2) suppressed the induction of skin tumors in mice by UV and as UV has been shown to induce expression of COX-2 in skin and cells, COX-2 may be crucial for photocarcinogenesis of the skin. We studied the mechanism of UVB-induced expression of COX-2 focusing on the signal transduction pathway involved. Hydrogen peroxide (H2O2) treatment of HaCaT cells induced expression of COX-2 and pretreatment with the antioxidant N-acetylcysteine (NAC) partly inhibited the UVB-induced expression of COX-2 protein in HaCaT cells, suggesting that oxidative stress contributes to COX-2 induction. To examine the signaling pathways involved in the UVB-induced expression of COX-2 in HaCaT cells, we analysed the expression of COX-2 protein after treatment with various inhibitors of signaling molecules. Inhibition of EGFR by a specific inhibitor and by a neutralizing antibody suppressed the induction of COX-2 expression by UV. Although a neutralizing antibody to transforming growth factor-alpha (TGF-alpha) suppressed COX-2 expression induced by TGF-alpha, it did not suppress COX-2 expression by UV, indicating that a direct activation of EGFR is involved. Treatment of cells at low temperature (4 degrees C) inhibited UVB-induced JNK activation, but it did not inhibit COX-2 expression by UV. Inhibitors of MEK, p38 MAP kinase and PI3-kinase, suppressed the induction of COX-2 expression by UV. In contrast, an erbB-2 inhibitor augmented the UVB-induced increase of COX-2 protein. These data indicate that oxidative stress in association with activation of EGFR, ERK, p38 MAP kinase, and PI3-kinase plays crucial roles in the UVB induction of expression of COX-2.
由于选择性抑制环氧化酶-2（COX-2）可抑制紫外线诱导的小鼠皮肤肿瘤形成，且紫外线已被证明可诱导皮肤和细胞中COX-2的表达，因此COX-2可能在皮肤光致癌作用中起关键作用。我们研究了紫外线B（UVB）诱导COX-2表达的机制，重点关注相关的信号转导途径。用过氧化氢（H2O2）处理人永生化角质形成细胞（HaCaT细胞）可诱导COX-2表达，用抗氧化剂N-乙酰半胱氨酸（NAC）预处理可部分抑制UVB诱导的HaCaT细胞中COX-2蛋白的表达，这表明氧化应激有助于COX-2的诱导。为了研究参与UVB诱导HaCaT细胞中COX-2表达的信号通路，我们在用各种信号分子抑制剂处理后分析了COX-2蛋白的表达。用特异性抑制剂和中和抗体抑制表皮生长因子受体（EGFR）可抑制紫外线诱导的COX-2表达。虽然针对转化生长因子-α（TGF-α）的中和抗体可抑制TGF-α诱导的COX-2表达，但它不能抑制紫外线诱导的COX-2表达，这表明涉及EGFR的直接激活。在低温（4℃）下处理细胞可抑制UVB诱导的应激活化蛋白激酶（JNK）激活，但不抑制紫外线诱导的COX-2表达。丝裂原活化蛋白激酶（MEK）、p38丝裂原活化蛋白激酶和磷脂酰肌醇-3激酶（PI3-激酶）的抑制剂可抑制紫外线诱导的COX-2表达。相反，erbB-2抑制剂增强了UVB诱导的COX-2蛋白增加。这些数据表明，与EGFR、细胞外信号调节激酶（ERK）、p38丝裂原活化蛋白激酶和PI3-激酶激活相关的氧化应激在UVB诱导的COX-2表达中起关键作用。
