The enhanced IL-18 production by UVB irradiation requires ROI and AP-1 signaling in human keratinocyte cell line (HaCaT) q Daeho Cho, b,1 Jae Seung Kang, a,1 Jong Hoon Park, b Young-In Kim, a Eunsil Hahm, a Junechul Lee, a Yoolhee Yang, b Junho Jeon, c Hyunkeun Song, c Hyunjeong Park, d Taesung Kim, e Saic Pang, f Chul-Woo Kim, g Young Il Hwang, a and Wang Jae Lee a, * a Department of Anatomy and Tumor Immunity Medical Research Center, Seoul National University College of Medicine, 28 Yongon-dong Chongno-gu, Seoul 110-799, Republic of Korea b Department of Life Science, Sookmyung WomenÕs University c Laboratory of Immunology, KRIBB d Department of Dermatology, St. MaryÕs Hospital, The Catholic University of Korea e College of Pharmacy, Chonnam National University f Department of Plastic Surgery, College of Medicine, Choongbook National University g Department of Pathology, Seoul National University College of Medicine Received 26 September 2002 Abstract Based on our recent observation that enhanced IL-18 expression positively correlates with malignant skin tumors, such as SCC and melanoma, we examined the possible role of UVB, known to be associated with skin cancer development, in the enhancement of IL-18 production using primary human epidermal keratinocytes and human keratinocyte cell line HaCaT. After cells were exposed to UVB irradiation in vitro, IL-18 production was examined by Northern blot analysis and ELISA, and it was found that IL-18 production is enhanced by UVB irradiation in a dose- and time-dependent manner. In addition, we confirmed that it is functionally active form of IL-18 using the inhibitor of caspase-1. The effect of UVB irradiation was blocked by antioxidant, N-acetyl-L -cysteine (NAC), which suggested the involvement of reactive oxygen intermediates (ROI) in the signal transduction of UVB irradiation- enhanced IL-18 synthesis. We also found that UVB irradiation increased AP-1 binding activity by using EMSA with AP-1-specific oligonucleotide. Furthermore, inhibitors of UVB-induced AP-1 activity, such as PD98059, blocked enhanced IL-18 production, indicating that AP-1 activation is required for UVB-induced IL-18 production. Taken together, our results suggest that UVB ir- radiation-enhanced IL-18 production is selectively mediated through the generation of ROI and the activation of AP-1. Ó 2002 Elsevier Science (USA). All rights reserved. Keywords: IL-18; UVB; AP-1 element; Keratinocyte IL-18 is a known IFN-c-inducing factor and is an 18kDa cytokine produced by lipopolysaccharide-acti- vated macrophages or Kupffer cells [1]. IL-18 acts on the immune system to increase IFN-c production from T H 1 and NK cells, to augment NK cell cytotoxicity, and to activateTh1cellproliferation[2].Inadditiontoactivated macrophagesorKupffercells,IL-18isproducedbymany different types of cells and tissues, including epidermal keratinocytes, the adrenal cortex, and the brain [3,4]. Recently, it has been reported that IL-18 is secreted by B16 murine melanoma cell line and that this endog- enous IL-18 is involved in the immune escape of murine melanoma cells. Furthermore, ex vivo studies suggest that enhanced IL-18 expression is positively correlated with malignant skin tumors, such as squamous cell carcinoma (SCC) and melanoma, indicating the impor- tant roles of IL-18 in the malignancy of skin tumors [5,6]. Additionally, a recent report showed that IL-18 Biochemical and Biophysical Research Communications 298 (2002) 289–295 www.academicpress.com BBRC q Abbreviations: UVB, ultaviolet B; AP-1, activator protein-1; NAC, N-acetyl-L-cystein, ROI, reactive oxygen intermediates. * Corresponding author. Fax: +82-2-745-9528. E-mail address: kinglee@snu.ac.kr (Wang. J. Lee). 1 Contributed equally to this work. 0006-291X/02/$ - see front matter Ó 2002 Elsevier Science (USA). All rights reserved. PII:S0006-291X(02)02433-6