The role of calcium, calcium-activated K+ channels, and tyrosine/kinase in psoralen-evoked responses in human melanoma cells

Abstract

Abstract8-Methoxy psoralen (8-MOP) exerts a short-term (24 h) mitogenic action, and a long-term (48-72 h) anti-proliferative and melanogenic action on two human melanoma cell lines, SK-Mel 28 and C32TG. An increase of intracellular calcium concentration was observed by spectrofluorometry immediately after the addition of 0.1 mM 8-MOP to both cell lines, previously incubated with calcium probe fluo-3 AM (5 µM). The intracellular Ca 2+ chelator BAPTA/AM (1 µM) blocked both early (mitogenic) and late (anti-proliferative and melanogenic) 8-MOP effects on both cell lines, thus revealing the importance of the calcium signal in both short-and long-term 8-MOP-evoked responses. Long-term biological assays with 5 and 10 mM tetraethylammonium chloride (TEA, an inhibitor of Ca 2+ -dependent K + channels) did not affect the responses to psoralen; however, in 24-h assays 10 mM TEA blocked the proliferative peak, indicating a modulation of Ca 2+ -dependent K + channels by 8-MOP. No alteration of cAMP basal levels or forskolin-stimulated cAMP levels was promoted by 8-MOP in SKMel 28 cells, as determined by radioimmunoassay. However, in C32TG cells forskolin-stimulated cAMP levels were further increased in the presence of 8-MOP. In addition, assays with 1 µM protein kinase C and calcium/calmodulin-dependent kinase inhibitors, Ro 31-8220 and KN-93, respectively, excluded the participation of these kinases in the responses evoked by 8-MOP. Western blot with antibodies anti-phosphotyrosine indicated a 92% increase of the phosphorylated state of a 43-kDa band, suggesting that the phosphorylation of this protein is a component of the cascade that leads to the increase of tyrosinase activity.

Effect of xanthotoxin (8-methoxypsoralen) on the anticonvulsant activity of classical antiepileptic drugs against maximal electroshock-induced seizures in mice

“…Xanthotoxin has been reported to block ATP-dependent potassium channels [39] and to modulate calcium-dependent potassium channels [40]. It is widely known that potassium channels are drug targets for therapeutic intervention in many diseases, including epilepsy [41,42].…”

Comparative bioinformatics analyses and profiling of lysosome-related organelle proteomes

“…Inhibition of these pumps affects melanin production and melanosome-specific protein trafficking [46]. Several solute carrier (SLC) family members and chloride channel proteins 5 and 7, all associated with ion control, may play additional roles in the regulation of melanin-producing enzymes, such as tyrosinase and tyrosinase related protein 1 [47]. The role of iron in reducing the amount of dopamine oxidation intermediates and enhancing the formation of melanin (the final product of dopamine oxidation), suggests that iron can protect cells by accelerating the conversion of dopamine oxidation intermediates to less toxic products [48].…”

Gamma-Aminobutyric Acid (GABA) Inhibits α-Melanocyte-Stimulating Hormone-Induced Melanogenesis through GABAA and GABAB Receptors

“…B16F10 melanoma cells (5 × 10 4 cells/mL) were cultured in serum-free DMEM media for 24 h and pretreated with the indicated concentrations of GABA (0–20 mM) in the presence or absence of 500 ng/mL α-MSH for 15 min [ 43 ]. In a parallel experiment, bicuculline or CGP 46381 was pretreated 2 h before treatment with GABA and/or α-MSH.…”