A new copper ionophore DPMQ protects cells against ultraviolet B irradiation by inhibiting the TRPV1 channel.

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 Cu 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 Cu influx as effectively as disulfiram, a Cu ionophore anticancer drug. However, disulfiram induced ROS generation, mitochondrial dysfunction, and apoptosis in fibroblasts in a Cu -dependent manner, whereas DPMQ was not only nontoxic, but protected cells against UVB irradiation-induced apoptosis in a Cu -independent manner. UVB irradiation induced a Ca -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 Cu -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 Ca chelator, but inhibited the cytosolic Ca increase induced by 12-HETE or capsaicin, but not that induced by bradykinin or ATP. Blockade of Ca influx by pharmacological inhibition or silencing of the TRPV1 channel or chelation of cytosolic Ca inhibited the UVB irradiation-induced Nrf2 reduction, ROS generation, mitochondrial dysfunction, and apoptosis. Taken together, our results suggest that Ca 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.