Melatonin Induces Apoptotic Cell Death via p53 in LNCaP Cells

Abstract

In this study, we examined whether melatonin promotes apoptotic cell death via p53 in prostate LNCaP cells. Melatonin treatment significantly curtailed the growth of LNCaP cells in a dose-and time-dependent manner. Melatonin treatment (0 to 3 mM) induced the fragmentation of poly(ADPribose) polymerase (PARP) and activation of caspase-3, caspase-8, and caspase-9. Moreover, melatonin markedly activated Bax expression and decreased Bcl-2 expression in dose increments. To investigate p53 and p21 expression, LNCaP cells were treated with 0 to 3 mM melatonin. Melatonin increased the expressions of p53, p21, and p27. Treatment with mitogen-activated protein kinase (MAPK) inhibitors, PD98059 (ERK inhibitor), SP600125 (JNK inhibitor) and SB202190 (p38 inhibitor), confirmed that the melatonin-induced apoptosis was p21-dependent, but ERK-independent. W ith the co-treatment of PD98059 and melatonin, the expression of p-p53, p21, and MDM2 did not decrease. These effects were opposite to the expression of p-p53, p21, and MDM2 observed with SP600125 and SB202190 treatments. Together, these results suggest that p53-dependent induction of JNK/p38 MAPK directly participates in apoptosis induced by melatonin.

Melatonin triggers p53Ser phosphorylation and prevents DNA damage accumulation

“…Most importantly, this does not pair with p53-mediated pro-survival effects, as melatonin does not counteract apoptosis induced by chemotherapy (Supplementary Figures S2 and S3A-D). One study demonstrated that 1 mM melatonin induces p53 phosphorylation at Ser-15 and apoptosis in androgensensitive LNCaP prostate cancer cells (Kim and Yoo, 2010). The concentration of melatonin used in this study is far higher than both physiological levels (1 mM vs 1 nM) and levels reached when melatonin is used to treat sleep disorders or as an adjuvant for anticancer therapy (Vakkuri et al, 1985;Kane et al, 1994;Markantonis et al, 2008), in which the highest concentration is 0.5 mM.…”

“…Melatonin treatment induces the accumulation of heavily phosphorylated p53 protein (Kim and Yoo, 2010). This occurs at a specific p53 residue (Ser-15) (Kim and Yoo, 2010) that has been shown to have a critical role in orchestrating p53-reponse upon DNA-damaging agents (Lakin and Jackson, 1999;Helton and Chen, 2007). In response to DNA damage, different kinases, including ATM and p38 MAPK, phosphorylate p53 at Ser-15 residue.…”

“…The outcome of this is either p53 accumulation or destabilization, resulting in potentiating or impairing its tumor-suppressor activities. Melatonin treatment induces the accumulation of heavily phosphorylated p53 protein (Kim and Yoo, 2010). This occurs at a specific p53 residue (Ser-15) (Kim and Yoo, 2010) that has been shown to have a critical role in orchestrating p53-reponse upon DNA-damaging agents (Lakin and Jackson, 1999;Helton and Chen, 2007).…”

“…Evidence shows that p38 MAPK phosphorylates p53 at Ser-15 residue (She et al, 2000;Kim and Yoo, 2010). To assess whether melatonin-induced p53 phosphorylation occurs through p38 kinase activity, we first checked p38 MAPK expression levels after adding melatonin.…”

Sulfite exposure-induced hepatocyte death is not associated with alterations in p53 protein expression

“…Serine 15 of p53 has been reported to be a key phosphorylation target during DNA damage (Santoro et al, 2012). Melatonin was found to induce apoptosis by phosphorylating p53 at serine 15 and increasing the expression of downstream signals such as Mdm2 and p21 in LNCaP human prostate cancer cells (Kim and Yoo, 2010).…”