NS-398 and Piroxicam Suppress UVB-induced Activator Protein 1 Activity by Mechanisms Independent of Cyclooxygenase-2

Abstract

Cyclooxygenases (COX) are rate-limiting enzymes that catalyze the conversion of arachidonic acid to prostaglandins, which are involved in many physiological and pathophysiological responses. COX-2, one of two isoforms of COX, was recently found to play an important role in carcinogenesis in many cell and tissue types. COX-2 inhibitors, which belong to the family of nonsteroidal anti-inflammatory drugs, are believed to be effective in many biological activities such as tumor chemoprevention because of their inhibition of COX-2. However, in the present study we found that both piroxicam, a general COX inhibitor, and NS-398, a COX-2 selective inhibitor, effectively suppressed the activation of transcription factor activator protein 1 (AP-1) induced by ultraviolet B (UVB) or 12-O-tetradecanoylphorbol-13-acetate in mouse epidermal JB6 cells. These COX-2 inhibitors could also inhibit 12-O-tetradecanoylphorbol-13-acetate-induced cell transformation. UVB significantly increased AP-1 activity in Cox-2 ؊/؊ fibroblasts transfected with an AP-1 luciferase reporter gene, and this increase was blocked by NS-389 or piroxicam. In JB6, Cox-2 ؊/؊ , or wild-type Cox-2 ؉/؉ cells, both NS-398 and piroxicam inhibited UVB-induced phosphorylation of c-Jun NH 2 -terminal kinases, the kinases that activate the AP-1/c-Jun complex. Based on our results, we propose that the inhibition of AP-1 activity by COX-2 inhibitors NS-398 or piroxicam may occur by a mechanism that is independent of COX-2. Cyclooxygenases (COX)1 are rate-limiting enzymes that catalyze the conversion of arachidonic acid to prostaglandins, which are involved in many normal and pathophysiological responses (1-3). Of the two known COX enzymes, COX-1 is expressed in nearly all cells, whereas COX-2 is primarily considered an inducible immediate-early gene product (4). COX-2 is suggested to play an important role in tumorigenesis because of epidemiological evidence showing that various types of cancers and transformed cells tend to overexpress COX-2 constitutively (5-10). Moreover, the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA), epidermal growth factor, and ultraviolet (UV) irradiation can induce COX-2 protein expression in many tissues including the epidermis of skin and also in epidermal keratinocytes (11).COX inhibitors are known to function through the inhibition of the COX enzymes. However, other potential mechanisms are still being considered (12). COX inhibitors were reported to protect neurons against hypoxia/reperfusion through mechanisms independent of COX (13). We and others have shown that nonsteroidal anti-inflammatory drugs can block mitogeninduced transcription activator protein 1 (AP-1) activity and transactivation (14). Considering the important role of AP-1 in tumoroigensis, the inhibition of AP-1 is likely to be one of the major mechanisms involved in nonsteroidal anti-inflammatory drugs chemopreventive effects.The aim of this study was to determine whether a COX-2 highly selective inhibitor, N-(2-cyclohexyloxy-4-nitrophenyl) methanesulfonami...

Curcumin inhibits the expression of COX-2 in UVB-irradiated human keratinocytes (HaCaT) by inhibiting activation of AP-1: p38 MAP kinase and JNK as potential upstream targets

“…Consistent with these, through the present study, we have demonstrated that curcumin also effectively inhibits the expressions of COX-2 mRNA and protein induced by UVB irradiation in a human keratinocyte cell line HaCaT, which seems to be, to our knowledge, the first report. Accordingly, the expression of COX-2 has been shown to be affected by various intracellular signaling proteins such as p38 MAPK and JNK (Goel et al, 2001;Surh et al, 2001;Liu et al, 2003;Lin et al, 2004;Kang et al, 2004). Interestingly, it has been recently shown that UVB induces the expression of COX-2 by activation of p38 MAPK in HaCaT cells (Chen et al, 2001) or by activations of p38 MAPK and JNK in artificial epidermis (Mahns et al, 2004).…”

Eicosapentaenoic acid inhibits UV-induced MMP-1 expression in human dermal fibroblasts

“…After incubation for 10 h, nuclear extracts were prepared using a modification of the method described by Liu et al (19). Briefly, cells were lysed with lysis buffer (25 mM HEPES, pH 7.8, 50 mM KCl, 1 mM DTT, 20 g/ml aprotinin, 20 g/ml leupeptin, and 5 mM PMSF) containing 0.5% Nonidet P-40, cytosol fractions were removed by centrifugation, and nuclear pellets were solubilized with extraction buffer (25 mM HEPES, pH 7.8, 500 mM KCl, 1 mM DTT, 20 g/ml aprotinin, 20 g/ml leupeptin, and 5 mM PMSF) containing 1% Nonidet P-40.…”

RETRACTED: The effect of 2′,4′,7‐trihydroxyisoflavone on ultraviolet‐induced matrix metalloproteinases‐1 expression in human skin fibroblasts

“…After incubation for 10 h, nuclear extracts were prepared using a modification of the method described by Liu et al [14]. Briefly, cells were lysed with lysis buffer (25 mM HEPES, pH 7.8, 50 mM KCl, 1 mM DTT, 20 lg/ml aprotinin, 20 lg/ml leupeptin, and 5 mM PMSF) containing 0.5% Nonidet P-40 (NP-40), cytosol fractions were removed by centrifugation, and nuclear pellets were solubilized with extraction buffer (25 mM HEPES, pH 7.8, 500 mM KCl, 1 mM DTT, 20 lg/ml aprotinin, 20 lg/ml leupeptin, and 5 mM PMSF) containing 1% Nonidet P-40 (NP-40).…”