We provide herein several lines of evidence to substantiate that folic acid (or folate) is a micronutrient capable of functioning as a novel redox regulator on hepatocellular carcinoma. First, we uncovered that folate deficiency could profoundly downregulate two prominent anti-apoptotic effectors including survivin and glucose-regulated protein-78. Silencing of either survivin or glucose-regulated protein-78 via small interfering RNA interfering technique established that both effectors could serve as reactive oxygen species sinker proteins. Second, folate deficiency-triggered oxidative-nitrosative stress could strongly induce endoplasmic reticulum stress that in turn could provoke cellular glutathione depletion through the modulation of the following two crucial events: (1) folate deficiency could strongly inhibit Bcl-2 expression leading to severe suppression of the mitochondrial glutathione pool and (2) folate deficiency could also profoundly inhibit two key enzymes that governing cellular glutathione redox regulation including γ-glutamylcysteinyl synthetase heavy chain, a catalytic enzyme for glutathione biosynthesis, and mitochondrial isocitrate dehydrogenase 2, an enzyme responsible for providing nicotinamide adenine dinucleotide phosphate necessary for regenerating oxidized glutathione disulfide back to glutathione via mitochondrial glutathione reductase. Collectively, we add to the literature new data to strengthen the notion that folate is an essential micronutrient that confers a novel role to combat reactive oxygen species insults and thus serves as a redox regulator via upregulating reactive oxygen species sinker proteins and averting mitochondrial glutathione depletion through proper maintenance of redox homeostasis via positively regulating glutathione biosynthesis, glutathione transporting system, and mitochondrial glutathione recycling process.

In mammalian cells, stress-induced expression of heat shock protein is controlled by heat shock factor 1 (HSF1). However, HSF1 functions as a regulator of additional genes. In this study, we observed that heat treatment effectively induced expression of Fas. Using bioinformatics, a high affinity and functional HSF1-binding element within the -1996/-1985 oligonucleotide of the 5'-flanking region of the Fas gene was found, and was determined by electrophoretic mobility shift assay and chromatin immunoprecipitation assay. Exogenous expression of a constitutively activative HSF1, induced Fas gene transcription and protein synthesis in the absence of heat stress. Moreover, RNA interference-mediated HSF1 gene-silencing attenuated Fas expression in a heat-induced model. Our results suggested that HSF1 is an important transcription factor of Fas gene.

No abstract