The MEK inhibitor PD98059 attenuates growth inhibition and death in gallic acid-treated Calu-6 lung cancer cells by preventing glutathione depletion

Abstract

Abstract. Gallic acid (Ga) is widely distributed in various plants and foods and has various biological effects. in this study, we investigated the effects of mitogen-activated protein kinase (MeK, JnK or p38) inhibitors on Ga-induced calu-6 lung cancer cell death in relation to reactive oxygen species (roS) and glutathione (GSH) levels. Ga inhibited the growth of calu-6 cells and induced apoptosis and/or necrosis accompanied by the loss of mitochondrial membrane potential (MMP; ∆ψ m ). roS levels and the number of GSH-depleted cells were observed to be increased at 24 h. MeK inhibitor suppressed cell growth inhibition, death, MMP (∆ψ m ) loss and GSH depletion induced by Ga, but failed to suppress the increase in roS levels. JnK inhibitor also somewhat suppressed cell growth inhibition, MMP (∆ψ m ) loss and GSH depletion induced by Ga, and limited the increase in roS levels. By contrast, p38 inhibitor mildly enhanced Ga-induced cell growth inhibition, MMP (∆ψ m ) loss and the increase in roS levels. in conclusion, MeK inhibitor suppressed Ga-induced cell growth inhibition and death in calu-6 cells. This was related to the prevention of GSH depletion. IntroductionGallic acid (Ga; 3,4,5-triphydroxyl-benzoic acid) is a polyhydroxylphenolic compound that is widely distributed in various plants, fruits and other foods (1), and is very well absorbed by humans (2). Various biological effects of Ga have been reported, including anti-bacterial (3), anti-viral (4) and anti-inflammatory activities (5). The major point of interest in Ga is related to its anti-cancer activity, which has been reported in various cancer cells, including prostate (6), lung (7,8), gastric, colon, breast, cervical and esophageal cancer (9). apoptosis induced by Ga is associated with oxidative stress derived from reactive oxygen species (roS), mitochondrial dysfunction and an increase in intracellular ca 2+ levels (10,11). controversially, Ga has been suggested to have both pro-oxidant and antioxidant properties depending on iron or H 2 o 2 levels in medium and plasma (12,13).There are currently three well-known mitogen-activated protein kinases (MaPKs): extracellular signal regulated kinase (erK1/2), c-Jun n-terminal kinase/stress-activated protein kinase (JnK/SaPK) and p38 kinase (14). each MaP kinase pathway has relatively different upstream activators and specific substrates (15). Multiple lines of evidence demonstrate that JnK and p38 are strongly activated by roS or by a mild oxidative shift in the intracellular thiol/disulfide redox state, leading to apoptosis (16,17). roS are also known to induce erK phosphorylation and to activate the erK pathway (18). in most instances, erK activation has a pro-survival rather than a pro-apoptotic effect (19). Since variations in the level of roS and differences in the function of MAPKs as influenced by ROS may have opposite effects in even the same type of cells, the relationship between roS and MaPKs in terms of cell survival or cell death signaling requires further clarification.understanding the tox...

Low concentration of formononetin promotes proliferation of estrogen receptor-positive cells through an ERα-miR-375-PTEN-ERK1/2-bcl-2 pathway

“…The MEK inhibitor PD98059 has been widely used to evaluate involvement of the ERK1/2 signaling pathway. PD98059 inhibits phosphorylation of MEK, inactivates the oncogene bcl-2, and ultimately increases apoptosis of cancer cells [ 41 , 42 ]. Our results demonstrate that formononetin decreases the amount of late apoptotic cells and elevates bcl-2 protein expression, both of which were reversed by the addition of PD98059 and the miR-375 inhibitor.…”