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Ultraviolet (UV) irradiation causes cellular oxidative stress. Under redox imbalance, Keap1-dependent Nrf2 degradation is minimal. In this study, we examined the role of Ca 2+ in Nrf2 homeostasis after UVB irradiation using human dermal fibroblasts. UVB irradiation stimulates 12-lipoxygenase and the product 12-hydroxyeicosatetraenoic acid then activates TRPV1 increasing the cell's cytosolic Ca 2+ concentration. UVB irradiation induced reactive oxygen species generation and apoptosis are inhibited in the absence of Ca 2+ or in the presence of either a 12-lipoxygenase inhibitor or a TRPV1 inhibitor during and after UVB irradiation. Thus, the Ca 2+ increase via TRPV1 is a critical factor in UVB irradiation induced oxidative stress. UVB irradiation induces a Ca 2+ dependent Nrf2 degradation and thus activation of TRPV1 with 12-hydroxyeicosatetraenoic acid also decreasing Nrf2 levels. UVB irradiation induced Nrf2 degradation is inhibited by co-treatment of cells with W-7, cyclosporin A, SB-216763 or MG-132, which are inhibitors of calmodulin, calcineurin, GSK3β and the proteasome, respectively. Furthermore, UVB irradiation in parallel induces GSK3β dephosphorylation in a Ca 2+ dependent manner. Co-immunoprecipitation showed that UVB irradiation induces an increase in Nrf2 phosphorylation, an increase in the binding of β-TrCP and Nrf2, and an increase in Nrf2 ubiquitination; these effects are all Ca 2+ dependent. These findings suggest that UVB irradiation induced GSK3β activation in a Ca 2+ dependent manner, which then stimulates the phosphorylation and ubiquitination of Nrf2 via β-TrCP. Indeed, silencing of β-TrCP was found to inhibit UVB irradiation-induced oxidative stress, Nrf2 degradation and apoptosis, while it had no effect on the Ca 2+ increase. Taken together, our results suggest that a Ca 2+ influx via TRPV1 is responsible for UVB irradiation-induced Nrf2 degradation and that modulation of the Ca 2+ -calmodulin-calcineurin-GSK3β-Nrf2-β-TrCP-Cullin-1 pathway may explain Ca 2+ dependent Nrf2 degradation., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Increased matrix metalloproteinase 1 (MMP-1) expression is a feature of photo-aged skin. We investigated the effects of baicalein and sulphoraphane on ultraviolet B (UVB) irradiation-induced MMP-1 expression and apoptosis using human dermal fibroblasts. UVB irradiation not only increased MMP-1 expression, but also caused apoptosis. Both baicalein and sulphoraphane protected cells from UVB irradiation-induced apoptosis, but only baicalein inhibited MMP-1 expression. UVB irradiation activated 12-lipoxygenase, and its product, 12-hydroxyeicosatetraenoic acid, activated TRPV1 channels. The resulting UVB irradiation-induced Ca 2+ increase was blocked by the 12-lipoxygenase inhibitor baicalein and the TRPV1 blocker capsazepine, but not by the Nrf2 inducer sulphoraphane. UVB irradiation also increased ROS generation and decreased Nrf2 protein levels. UVB irradiation-induced MMP-1 expression was blocked by the Ca 2+ chelator BAPTA, by capsazepine and by TRPV1 silencing. However, induction was unaffected by the antioxidant N-acetylcysteine. ERK phosphorylation and JNK phosphorylation were induced by UVB irradiation, but only ERK phosphorylation was Ca 2+ sensitive. Increased MMP-1 expression was blocked by PD98059, but not by SP600125. Thus, increased MMP-1 expression is mediated by increased cytosolic Ca 2+ and ERK phosphorylation. UVB irradiation-induced ROS generation is also Ca 2+ sensitive, and UVB irradiation-induced apoptosis is caused by increased ROS. Thus, baicalein, by blocking the UVB irradiation-induced cytosolic Ca 2+ increase, protects cells from UVB irradiation-induced MMP-1 expression and apoptosis. In contrast, sulphoraphane, by decreasing cellular ROS, protects cells from only UVB-induced apoptosis. Thus, targeting 12-lipoxygenase may provide a therapeutic approach to improving the health of photo-aged human skin., (© 2019 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Thrombospondin (TSP)-1, a potent angiogenesis inhibitor, has been shown to exert different biological functions on various cell types. Here, we investigate the role of TSP-1 in tumor-stroma reaction, which is mainly characterized by fibroblast activation to create a permissive microenvironment for tumor progression. Immunohistochemistry examinations in the human surgical specimens have shown that a downregulation of TSP-1 during the progression of cervical carcinogenesis was accompanied by an emergence in the upregulation of stroma markers, alpha-smooth muscle actin (alpha-SMA) and desmin. Transfection of SiHa cervical cancer cells with a plasmid expressing the TSP-1 protein exhibited antiangiogenic activity in vitro and resulted in reduced tumor growth in severe combined immunodeficiency (SCID) mice, which was accompanied by a decrease in tumor vascularization and lower expressions of alpha-SMA and desmin than those in the vector controls. Transfection with TSP-1 and purified TSP-1 added to NIH3T3 cells did not alter the protein levels of alpha-SMA and desmin but significantly inhibited matrix metalloprotease-2 activity. Transforming growth factor-beta (TGF-beta), a major factor in the activation of fibroblasts, increased alpha-SMA and desmin expression and the ability of cell migration and invasion in NIH3T3 cells. The increased migration ability and the invasive ability into tumor cluster of TGF-beta-treated NIH3T3 cells were dose dependently inhibited by TSP-1. In contrast, ectopic TSP-1 expression in SiHa cells has little effect on the invasive ability of the NIH3T3 cells. Together, our findings demonstrate a novel role of TSP-1 to inhibit tumor-stroma reaction that could be attributed to the blockage of activated fibroblasts from invading cancer cells.

Copper is more likely than iron to generate reactive oxygen species (ROS) in a redox reaction due to its higher electrochemical reactivity. This study examined the effect of a newly synthesized Cu2+ binding compound, (E)‐2‐(4‐(dimethylamino)phenylimino)methyl)quinolin‐8‐ol (DPMQ), on ultraviolet B (UVB) irradiation–induced cytotoxicity in human dermal fibroblasts. DPMQ induced Cu2+ influx as effectively as disulfiram, a Cu2+ ionophore anticancer drug. However, disulfiram induced ROS generation, mitochondrial dysfunction, and apoptosis in fibroblasts in a Cu2+‐dependent manner, whereas DPMQ was not only nontoxic, but protected cells against UVB irradiation–induced apoptosis in a Cu2+‐independent manner. UVB irradiation induced a Ca2+‐dependent increase in ROS generation, a decrease in Nrf2 levels, and activation of the mitochondrial apoptotic pathway, and these effects were prevented by DPMQ, which also increased Nrf2 nuclear translocation in a Cu2+‐independent manner. UVB irradiation activated 12‐lipoxygenase and 12‐hydroxyeicosatetraenoic acid (12‐HETE), a product of 12‐lipoxygenase, activated the TRPV1 channel. DMPQ did not act as a Ca2+ chelator, but inhibited the cytosolic Ca2+ increase induced by 12‐HETE or capsaicin, but not that induced by bradykinin or ATP. Blockade of Ca2+ influx by pharmacological inhibition or silencing of the TRPV1 channel or chelation of cytosolic Ca2+ inhibited the UVB irradiation–induced Nrf2 reduction, ROS generation, mitochondrial dysfunction, and apoptosis. Taken together, our results suggest that Ca2+ influx via the TRPV1 channel is responsible for UVB irradiation–induced cytotoxicity and that DPMQ protects cells against UVB irradiation by inhibiting the TRPV1 channel and stabilizing Nrf2, and could thus be a potentially useful compound for the treatment of free radical‐induced diseases. Treatment of cells with ultraviolet B (UVB) irradiation results in increased reactive oxygen species (ROS) generation and decreased Nrf2 levels by a mechanism involving lipoxygenase stimulation and TRPV1 channel activation. Increased ROS results in mitochondrial dysfunction and apoptosis. DPMQ inhibits the TRPV1 channel and scavenges ROS, and hence protects cells against UVB irradiation–induced cytotoxicity, whereas disulfiram induces copper influx and increases ROS generation, and therefore causes apoptosis. [ABSTRACT FROM AUTHOR]