Melatonin Effects on the Cytoskeletal Organization of MDCK and Neuroblastoma N1E‐115 Cells

Abstract

Despite the fact that many physiological and pharmacological actions of melatonin (MEL) have been described, its mechanism of action at the subcellular level remains unclear. It has been suggested that MEL has effects on cellular processes that involve microfilaments and microtubules. In the present study MEL effects on the cytoskeleton were evaluated in MDCK and N1E-115 cells in which the microfilaments have been shown to participate in cell morphology and dome formation (MDCK) and the microtubules in neurite outgrowths. After one day of culture with 10(-11)-10(-7) M MEL MDCK cells showed an increase in the number of elongated cells. After four days with the hormone, an increase in the incidence of MDCK cells contacting neighboring cells through long cytoplasmic elongations was observed. Actin antibody stain showed the appearance of thicker fluorescent fibres beneath the cell membrane and over the nucleus in the MEL treated cells. An increase in dome formation in confluent cells was also observed. In N1E-115 cells MEL (10(-13)-10(-5) M) induced an increase in cell with neurite processes. Neurite outgrowth is clearly seen at 24 h after plating. MEL-treated cells grow in clusters with neurites forming intricate networks. Antitubulin antibody stain showed long fluorescent neurites in the N1E-115 MEL-treated cells. A decrease in N1E-115 neurite formation was observed with either serotonin or 6-hydroxymelatonin (6OH-MEL). However, the number of MDCK cells with cytoplasmic elongations was decreased only after 6OH-MEL. We conclude that MEL action at the cellular level involves a modification of the cytoskeletal organization.

New genes associated with schizophrenia in neurite formation: a review of cell culture experiments

“…[44][45][46] Hormones like estrogens, cortisol, growth hormone, melatonin, T3 and T4 also participate in neuritogenesis as extrinsic factors as well. [47][48][49][50][51] The extracellular environment influences neuronal differentiation through tenascins, hyaluronan and the adhesion molecules collagen and laminin among others. [52][53][54] Several types of receptors such as Trk interact with the environment of the neuron, inducing cell membrane changes mediated by increases in calcium and other second messenger events 55,56 that result in neurite protrusion.…”

Melatonin induction of filamentous structures in non-neuronal cells that is dependent on expression of the human mt1 melatonin receptor

“…Recent work has confirmed that the mt1 receptor signals through two inhibitory G␣ proteins (G i2 and G i3 ) that attenuate adenylyl cyclase activity and one stimulatory G␣ protein (G q/11 ) that increases phospholipase C activity [Brydon et al, 1999]. The possibility exists however, that the signaling actions of melatonin could also be due to receptorindependent processes that directly affect calmodulin [Poffenbarger and Fuller, 1976;Cardinali and Freire, 1975;Benitez-King et al, 1990] as melatonin is a small lipophilic molecule capable of traversing the plasma membrane.…”

“…To date, what is known about the effects of melatonin at the level of cellular and cytoskeletal structure is that treatment of MDCK, SK-N-SH, and N1E-115 cells with melatonin results in an increase in the number of cells with neurite processes (N1E-115 or SK-N-SH) or "domes" (MDCK) and in an increase in the number of microtubules within these cells [Benitez-King et al, 1990;Melendez et al, 1996;Cos et al, 1996]. Melatonin has also been shown to increase the levels of polymerized tubulin in N1E-115 cells [Melendez et al, 1996].…”

Melatonin Involvement in Immunity and Cancer

“…In fact, calcium and calmodulin are involved in processes conferring stability to DNA in proliferating neoplastic cells [108] and melatonin was seen to act as a Ca 2+ -calmodulin antagonist, either directly by interacting with key target enzymes or indirectly via specific protein kinases [109,110].…”