Intracellular Signaling Mechanisms Leading to Synergistic Effects of Endothelin-1 and Stem Cell Factor on Proliferation of Cultured Human Melanocytes

Abstract

We previously reported that activation of mitogenactivated protein kinase (MAPK) is involved in the mitogenic stimulation of normal human melanocytes (NHMC) by endothelin-1 (ET-1). In the present study, we determined signaling mechanisms upstream of MAPK activation that are involved in ET-1 stimulation and their synergism with stem cell factor (SCF). Pretreatment of cultured NHMC with ET B receptor antagonists, pertussis toxin, a specific phospholipase C inhibitor (U73122), or a protein kinase C inhibitor (calphostine) blocked a transient tyrosine phosphorylation of MAPK induced by ET-1, whereas the addition of a calcium chelator (BAPTA) failed to inhibit that tyrosine phosphorylation of MAPK. Treatment with ET-1 and SCF together synergistically increased DNA synthesis, which was accompanied by synergism for MAPK phosphorylation. The time course of inositol 1,4,5-trisphosphate formation revealed that there is no difference in the level of inositol 1,4,5-trisphosphate stimulated by ET-1 ؉ SCF or by ET-1 alone. Evaluations of the serine phosphorylation of MEK and Raf-1 activity showed a synergistic effect in SCF ؉ ET-1-treated NHMC. Stimulation with SCF ؉ ET-1 induced a more rapid and stronger tyrosyl phosphorylation of proteins corresponding to p52 and p66 Shc than did stimulation with SCF only, and this was accompanied by a stronger association of tyrosinephosphorylated Shc with Grb2. Interestingly, a more rapid and marked tyrosine phosphorylation of c-kit was also detected in NHMC-treated with SCF ؉ ET-1 than NHMC treated with SCF only. These data indicate that the synergistic cross-talk between SCF and ET-1 signaling is initiated through the pathway of tyrosine phosphorylation of c-kit, which results in the enhanced formation of the Shc-Grb 2 complex which leads in turn to the synergistic activation of the Ras/Raf-1/MEK/MAP kinase loop.

Inhibitory Mechanism of an Extract of Althaea officinalis L. on Endothelin-1-Induced Melanocyte Activation.

“…DAG has been reported to activate MAPK via protein kinase C. The action of ET-1 is transmitted to stimulate cell proliferation mainly via MAPK. 9,20) The present study showed that the extract of A. officinalis did not affect the intracellular signal transduction pathway located upstream of calcium mobilization, i.e., the binding of ET-1 to the ET B R on NHMC or the production of IP 3 . In contrast, the ET-1-induced activation of MAPK was inhibited by the extract.…”

Growth factors rescue cutaneous melanoma cells from apoptosis induced by knockdown of mutated (V600E) B-RAF

“…The latter cells responded to exogenous bFGF by activation of ERK1,2, although this activation did not reach the same level as in the control cells ( Figure 4b). These data suggest that bFGF rescues cells with reduced Several growth factors other than bFGF have been implicated in proliferation and survival of melanocytes and/or melanoma development, including HGF, SCF, and ET-1 (Imokawa et al, 2000;Li et al, 2001;Satyamoorthy et al, 2001). In a colony formation assay, 10 ng/ml human recombinant HGF was as effective as 100 ng/ml bFGF in rescuing FM55-M2 cells from the cell death induced by suppression of V600E B-RAF ( Figure 5).…”

Inhibition of melanogenesis by Gaillardia aristata flower extract

“…The mechanism of epidermal hyper-pigmentation occurs by the increased expression level of ET-1 and SCF, or the decreased expression of TNF-α and IL-6. In particular, SCF and ET-1 are germane to the hyper-pigmentary mechanism by UVB-induced melanin synthesis [26][27][28][29][30]. Presently, GAE inhibited SCF-stimulated pigmentation in human epidermal equivalents.…”