Foxo1 Attenuates NaF-Induced Apoptosis of LS8 Cells through the JNK and Mitochondrial Pathways

Abstract

Fluoride-induced ameloblast apoptosis is a key event in dental fluorosis development. Forkhead box o1 (Foxo1) is a transcription factor involved in cell apoptosis. The present study aims to investigate the effect of Foxo1 on ameloblast apoptosis induced by fluoride in vitro and to explore its possible mechanism. Ameloblast-like cells (LS8 cells) were exposed to various concentrations of NaF for up to 48 h. Foxo1 activation was modulated using lentiviral vectors, and cell apoptosis was measured by flow cytometry. The expression levels of Foxo1, c-Jun N-terminal kinase (JNK), and some well-known regulators of the mitochondrial pathway of apoptosis (cytoplasmic cytochrome c, cleaved caspase-9, cleaved caspase-3, Bcl-2, and Bax) were detected by quantitative real-time PCR, western blot, and immunofluorescence assay. The results showed significantly decreased expression and increased phosphorylation of Foxo1 in NaF-treated LS8 cells. Further investigation revealed that forced Foxo1 activation with lentiviral vectors attenuated NaF-induced apoptosis of LS8 cells, markedly decreasing protein levels of cytoplasmic cytochrome c, cleaved caspase-9, and cleaved caspase-3 while increasing the Bcl-2/Bax ratio and JNK expression level. These findings suggest that Foxo1 attenuated NaF-induced apoptosis of LS8 cells via inhibiting the mitochondrial pathway and activating JNK.

Daidzein induces choriocarcinoma cell apoptosis in a dose-dependent manner via the mitochondrial apoptotic pathway

“…Equol, which is a metabolite of daidzein, induces apoptosis in SMMC-7721 human hepatocellular carcinoma cells through the intrinsic and endoplasmic reticulum stress pathways (26). Caspase-9 and the Bcl-2/Bax ratio are commonly used activity markers of the mitochondrial apoptotic pathway (43)(44)(45). In the present study, western blotting was used to detect these markers, revealing that the cleavage of caspase-9 increased and the ratio of Bcl-2/Bax decreased in both cell lines in a dose-dependent manner, which indicated that daidzein-induced apoptosis was mediated via the mitochondrial apoptotic pathway.…”

JNK signaling in cancer cell survival

“…Recent studies have proposed potential molecular mechanisms underlying the prosurvival function of JNK, including autophagy . JNK can induce autophagy and counteract cancer cell apoptosis . In addition, a tumor immune evasion mechanism may be involved .…”

“…| 2091 apoptosis. 59 In addition, a tumor immune evasion mechanism may be involved. 60,61 JNK activates compensatory cell proliferation to maintain the balance between cancer cell death and survival.…”

“…Nuclear factor kappa B (NF‐κB), p38, and JNK share common upstream activators and may act synergistically to regulate cancer cell survival . The role of JNK in promoting cancer cell survival involves autophagy, as JNK can induce autophagy to counteract apoptosis . Extensive evidence supports that JNK‐mediated prosurvival autophagy promotes cancer cell resistance to chemotherapy, and recent studies suggest the involvement of tumor immune evasion in this process .…”

Fluoride Induces Apoptosis in Mammalian Cells: In Vitro and In Vivo Studies

“…5 and 8 days of continuous exposure revealed genetic damage and morphological alterations indicative of apoptosis by transmission electron microscopy as depicted by loss of cell-to-cell contact, nuclear chromatin condensation and apoptotic bodies (70). At the molecular level, rats treated with fluoride at 10 mg/kg for 5 weeks showed that caspase-9 and caspase-3, and the gene expressions of Bax were significantly increased (71).…”