Intracellular signaling pathways involved in cell growth inhibition of human umbilical vein endothelial cells by melatonin

Abstract

Melatonin, an indolamine mainly produced in the pineal gland, has received a great deal of attention in the last decade because of its oncostatic effects, which are due to its immunomodulatory, antiproliferative, antioxidant and its possible antiangiogenesis properties. Herein, we document its antiproliferative action on human umbilical vein endothelial cells (HUVECs). Moreover, the possible cell signaling pathways when melatonin inhibited HUVEC proliferation were explored in this study. Primary HUVECs were isolated, cultured, purified and identified before the studies were performed. HUVECs were found to possess G-protein-coupled membrane receptors for melatonin (MT1 and MT2) and also nuclear melatonin receptors (RORalpha and RORbeta, especially RORbeta). No obvious expression of RORgamma was found. We investigated the membrane receptors and several intracellular signaling pathways including mitogen-activated protein kinases (MAPK)/extracellular signal-related kinases (ERK), phosphoinositol-3-kinase (PI3K)/Akt and protein kinases C (PKC) involved in antiproliferative action of melatonin on HUVECs. The blockade of these pathways using special inhibitors decreased cell growth. Furthermore, the constitutive activation of nuclear factor kappa B (NF-kappaB) contributed to the proliferation of HUVECs. High concentrations of melatonin inhibited both NF-kappaB expression and its binding ability to DNA, possibly through inactivation of ERK/Akt /PKC pathways. Taken together, high concentrations of melatonin markedly reduced HUVEC proliferation; the antiproliferative action of melatonin was closely correlated with following pathway: melatonin receptors/ERK/PI3K/Akt/PKC/ NF-kappaB.

Melatonin signaling in mouse cerebellar granule cells with variable native MT1 and MT2 melatonin receptors

“…We found that in MT1/MT2 CGC, melatonin inhibited ERK and Akt kinases. This is similar to the recently reported action of melatonin on ERK and Act in nonneuronal cells that express both MT1 and MT2 receptors (Cui et al, 2008). On the other hand, previous work has shown that in cells which express only MT1 receptors, melatonin stimulates ERK (Bordt et al, 2001;Chan et al, 2002).…”

“…In these latter conditions, melatonin also inhibited the phosphorylation (i.e., activity) of serine/threonine kinase Akt (also known as protein kinase B) (Cui et al, 2008).…”

“…In cells expressing only MT1 receptors, melatonin increases the activity (i.e., phosphorylation) of extracellular-signal-regulated kinase (ERK), a member of the mitogen-activated protein kinases (MAPKs) (Bordt et al, 2001;Chan et al, 2002), whereas in cells expressing both MT1 and MT2 receptors, melatonin inhibited ERK phosphorylation (Cui et al, 2008). In these latter conditions, melatonin also inhibited the phosphorylation (i.e., activity) of serine/threonine kinase Akt (also known as protein kinase B) (Cui et al, 2008).…”

Inhibition of ERK1/2 Signaling Pathway is Involved in Melatonin's Antiproliferative Effect on Human MG-63 Osteosarcoma Cells

“…MAPK and Akt signaling pathways play a critical role in melatonin-induced antiproliferative events in other cells [4][5][6][7][8][9][10][11][12]. To determine whether MAPK and Akt signaling pathways are involved in the antiproliferative action of melatonin in MG-63 cells, the expression of MAPK components and Akt was evaluated using the western blot method.…”

“…Mitogen-activated protein kinase (MAPK) and Akt signaling pathways are responsible for melatonin's antiproliferative actions in some cells, including human umbilical vein endothelial cells [4], human fibroblast-like synoviocyte [5], hepatocarcinoma HepG2 cells [6], human melanoma SK-MEL-1 cells [7], rat glioma cells [8,9], human breast adenocarcinoma MCF-7 cells [10,11], and human osteoblasts [12]. The MAPK family mainly consists of extracellular signal-regulated kinase (ERK1/2), p38, and c-Jun N-terminal kinase (JNK).…”