hTCEpi cells stratify, differentiate, and desquamate similar to normal human corneal epithelium. Further study of the hTCEpi cell line may be valuable in studying the molecular mechanisms regulating corneal epithelial cell differentiation and desquamation.
Estrogens are potent neuroprotective hormones and mitochondria are the site of cellular life-death decisions. As such, it is not surprising that we and other have shown that estrogens have remarkable effects on mitochondrial function. Herein we provide evidence for a primary effect of estrogens on mitochondrial function, achieved in part by the import of estrogen receptor β (ERβ) into the mitochondria where it mediates a number of estrogen actions on this vital organelle. ERβ is imported into the mitochondria, through tethering to cytosolic chaperone protein and/or through direct interaction with mitochondrial import proteins. In the mitochondria, ERβ can affect transcription of critical mitochondrial genes through the interaction with estrogen response elements (ERE) or through protein-protein interactions with mitochondrially imported transcription factors. The potent effects of estrogens on mitochondrial function, particularly during mitochondrial stress, argues for a role of estrogens in the treatment of mitochondrial defects in chronic neurodegenerative diseases like Alzheimer's disease (AD) and Parkinson's disease (PD) and more acute conditions of mitochondrial compromise, like cerebral ischemia and traumatic brain injury.
Abstract4-Hydroxynonenal (4-HNE) has been suggested to be involved in stress-induced signaling for apoptosis. In present studies, we have examined the effects of 4-HNE on the intrinsic apoptotic pathway associated with p53 in human retinal pigment epithelial (RPE and ARPE-19) cells. Our results show that 4-HNE causes induction, phosphorylation, and nuclear accumulation of p53 which is accompanied with down regulation of MDM2, activation of the pro-apoptotic p53 target genes viz. p21 and Bax, JNK, caspase3, and onset of apoptosis in treated RPE cells. Reduced expression of p53 by an efficient silencing of the p53 gene resulted in a significant resistance of these cells to 4-HNE-induced cell death. The effects of 4-HNE on the expression and functions of p53 are blocked in GSTA4-4 over expressing cells indicating that 4-HNE-induced, p53-mediated signaling for apoptosis is regulated by GSTs. Our results also show that the induction of p53 in tissues of mGsta4 (-/-) mice correlate with elevated levels of 4-HNE due to its impaired metabolism. Together, these studies suggest that 4-HNE is involved in p53-mediated signaling in in vitro cell cultures as well as in vivo that can be regulated by GSTs.
D, L-Sulforaphane (SFN), a synthetic analogue of broccoli-derived L-isomer, is a highly promising cancer chemopreventive agent substantiated by inhibition of chemically-induced cancer in rodents and prevention of cancer development and distant site metastasis in transgenic mouse models of cancer. SFN is also known to inhibit growth of human cancer cells in association with cell cycle arrest and reactive oxygen species-dependent apoptosis, but the mechanism of these cellular responses to SFN exposure is not fully understood. Because 4-hydroxynonenal (4-HNE), a product of lipid peroxidation (LPO), the formation of which is regulated by hGSTA1-1, assumes a pivotal role in oxidative stress-induced signal transduction, the present study investigated its contribution in growth arrest and apoptosis induction by SFN using HL60 and K562 human leukemic cell lines as model. The SFN-induced formation of 4-HNE was suppressed in hGSTA1-1 over expressing cells, which also acquired resistance to SFN-induced cytotoxicity, cell cycle arrest, and apoptosis. While resistance to SFN-induced cell cycle arrest by ectopic expression of hGSTA1-1 was associated with changes in levels of G2/M regulatory proteins, resistance to apoptosis correlated with increased Bcl-xL/Bax ratio, inhibition of nuclear translocation of AIF, and attenuated cytochrome c release in cytosol. The hGSTA1-1 over expressing cells showed enhanced cytoplasmic export of Daxx, nuclear accumulation of transcription factors Nrf2 and HSF1, and up regulation of their respective client proteins, γ-GCS and HSP70. These findings not only reveal a central role of 4-HNE in cellular responses to SFN but also reaffirm that 4-HNE contributes to oxidative stress mediated signaling.
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