Resveratrol upregulates Egr-1 expression and activity involving extracellular signal-regulated protein kinase and ternary complex factors

The MEK-ERK-Egr-1 axis and its regulation in cardiovascular disease

Cardiovascular disease (CVD) is the primary cause of morbidity and mortality in the Western world. Multiple molecular and cellular processes underpinning the pathogenesis of CVD are regulated by the zinc finger transcription factor and product of an immediate-early gene, early growth response-1 (Egr-1). Egr-1 regulates multiple pro-inflammatory processes that underpin the manifestation of CVD. The activity of Egr-1 itself is influenced by a range of post-translational modifications including sumoylation, ubiquitination and acetylation. Egr-1 also undergoes phosphorylation by protein kinases, such as extracellular-signal regulated kinase (ERK) which is itself phosphorylated by MEK. This article reviews recent progress on the MEK-ERK-Egr-1 cascade, notably regulation in conjunction with factors and agents such as TET2, TRIB2, MIAT, SphK1, cAMP, teneligliptin, cholinergic drugs, red wine and flavonoids, wogonin, febuxostat, docosahexaenoic acid and AT1R blockade. Such insights should provide new opportunity for therapeutic intervention in CVD.

Regulation of c-Fos gene transcription by stimulus-responsive protein kinases

The basic region leucin zipper (bZIP) protein c-Fos constitutes together with other bZIP proteins the AP-1 transcription factor complex. Expression of the c-Fos gene is regulated by numerous extracellular signaling molecules including mitogens, metabolites, and ligands for receptor tyrosine kinases, G protein-coupled receptors, and cytokine receptors. Here, we analyzed the effects of the stimulus-responsive MAP kinases ERK1/2 (extracellular signal-regulated protein kinase), JNK (c-Jun N-terminal protein kinase) and p38 protein kinase on transcription of the c-Fos gene. We used chromatin-integrated c-Fos promoter-luciferase reporter genes containing inactivating point mutations of DNA binding sites for distinct transcription factors. ERK1/2, JNK, and p38 protein kinases were specifically activated following expression of either a mutant of B-Raf, a truncated version of mitogen-activated/extracellular signal responsive kinase kinase kinase-1 (MEKK1), or a mutant of MAP kinase kinase-6 (MKK6), respectively. The results show that the DNA binding sites for serum response factor (SRF) and for the ternary complex factor (TCF) are of major importance for stimulating c-Fos promoter activity by MAP kinases. ERK1/2 and p38-induced stimulation of the c-Fos promoter additionally required the DNA binding site for the transcription factor AP-1. Mutation of the DNA binding site for STAT had no or only a small effect on c-Fos promoter activity. We conclude that MAP kinases do not activate distinct transcription factors involving distinct genetic elements. Rather, these kinases mainly target SRF and TCF proteins, leading to an activation of transcription of the c-Fos gene via the serum response element.

Chromatin-embedded reporter genes: Quantification of stimulus-induced gene transcription

Receptors and ion channels expressed on the cell surface ensure proper communication between the cells and the environment. In multicellular organism, stimulus-regulated gene transcription is the basis for communication with the environment allowing individual cells to respond to stimuli such as nutrients, chemical stressors and signaling molecules released by other cells of the organism. Hormones, cytokines, and mitogens bind to receptors and ion channels and induce intracellular signaling cascades involving second messengers, kinases, phosphatases, and changes in the concentration of particular ions. Ultimately, the signaling cascades reach the nucleus. Transcription factors are activated that respond to cellular stimulation and induce changes in gene transcription. Investigating stimulus-transcription coupling combines cell biology with genetics. In this review, we discuss the molecular biology of stimulus-induced transcriptional activators and their responsiveness to extracellular and intracellular signaling molecules and to epigenetic regulators. Stimulus-induced gene expression is measured by several methods, including detection of nuclear translocation of transcription factors, phosphorylation or DNA binding. In this article, we emphasize that the most reliable method to directly measure transcriptional activation involves the use of chromatin-embedded reporter genes.

Health Benefits of Resveratrol in Kidney Disease: Evidence from In Vitro and In Vivo Studies

Different diseases and disorders that affect the kidneys include, but are not limited to, glomerulonephritis, diabetic nephropathy, polycystic kidney disease, kidney stones, renal fibrosis, sepsis, and renal cell carcinoma. Kidney disease tends to develop over many years, making it difficult to identify until much later when kidney function is severely impaired and undergoing kidney failure. Although conservative care, symptom management, medication, dialysis, transplantation, and aggressive renal cancer therapy are some of the current strategies/approaches to kidney disease treatment, new preventative targeted therapies are needed. Epidemiological studies have suggested that a diet rich in fruits and vegetables is associated with health benefits including protection against kidney disease and renal cancer. Resveratrol, a polyphenol found in grapes and berries, has been reported to have antioxidant, anti-inflammatory, antidiabetic, hepatoprotective, neuroprotective, and anti-cancer properties. The current review summarizes the existing in vitro and in vivo animal and human studies examining the nephroprotective effects of resveratrol.

Resveratrol stimulates c-Fos gene transcription via activation of ERK1/2 involving multiple genetic elements

The polyphenol resveratrol is found in many plant and fruits and is a constituent of our diet. Resveratrol has been proposed to have chemopreventive and anti-inflammatory activities. On the cellular level, resveratrol activates stimulus-regulated transcription factors. To identify resveratrol-responsive elements within a natural gene promoter, the molecular pathway leading to c-Fos gene expression by resveratrol was dissected. The c-Fos gene encodes a basic region leucine zipper transcription factor and is a prototype of an immediate-early gene that is regulated by a wide range of signaling molecules. We analyzed chromatin-integrated c-Fos promoter-luciferase reporter genes where transcription factor binding sites were destroyed by point mutations or deletion mutagenesis. The results show that mutation of the binding sites for serum response factor (SRF), activator protein-1 (AP-1) and cAMP response element binding protein (CREB) significantly reduced reporter gene transcription following stimulation of the cells with resveratrol. Inactivation of the binding sites for signal transducer and activator of transcription (STAT) or ternary complex factors did not influence resveratrol-regulated c-Fos promoter activity. Thus, the c-Fos promoter contains three resveratrol-responsive elements, the cAMP response element (CRE), and the binding sites for SRF and AP-1. Moreover, we show that the transcriptional activation potential of the c-Fos protein is increased in resveratrol-stimulated cells, indicating that the biological activity of c-Fos is elevated by resveratrol stimulation. Pharmacological and genetic experiments revealed that the protein kinase ERK1/2 is the signal transducer that connects resveratrol treatment with the c-Fos gene.

Differential Effects of Resveratrol on the Expression of Brain-Derived Neurotrophic Factor Transcripts and Protein in the Hippocampus of Rat Brain

BACKGROUND

The induction of brain-derived neurotrophic factor (BDNF) expression in the hippocampus has shown to play a role in the beneficial effects of resveratrol (RSV) on the learning and memory. The BDNF gene has a complicated structure with eight 5' noncoding exons (I-IXa), each of which can splice to a common coding exon (IX) to form a functional transcript. Estrogens increase levels of BDNF transcripts in the hippocampus of rats. The aim of this study was to evaluate the effects of the phytoestrogen, RSV, on the splicing pattern of BDNF transcripts and on the pro-BDNF protein in the hippocampi of mother rats and their embryos.

METHODS

RSV (60 or 120 mg/kg BW/day) was administered orally to pregnant rats from days 1 to 20 of gestation. Hippocampi of adults and embryos were dissected 24 h after the last administration of RSV. Extracts from hippocampi were subject to quantitative (q) RT-PCR and Western blotting to assess splicing pattern of the BDNF transcripts and levels of pro-BDNF protein, respectively.

RESULTS

RSV (120 mg/kg BW/day) caused a statistically significant increase in the expression levels of BDNF exons III, IV and IX, but not the exon I in the hippocampi of adult rats (P≤0.05). Levels of pro-BDNF protein remained unchanged in the hippocampal tissues from both adult and embryonic rats treated by RSV (60 or 120 mg/kg BW/day).

CONCLUSION

Our results showed that RSV differentially activates promoters of the BDNF gene in the hippocampus of pregnant rats, but fails to affect the pro-BDNF level neither in adult nor in the embryonic hippocampal tissues.

Resveratrol-Mediated Repression and Reversion of Prostatic Myofibroblast Phenoconversion

Background

Resveratrol, a phytoalexin found in berries, peanuts, grapes, and red wine, inhibits oxidation, inflammation, and cell proliferation and collagen synthesis in multiple cell types and or animal models. It represses collagen deposition in the vasculature, heart, lung, kidney, liver, and esophagus in animal models and may have some utility as an anti-fibrotic. Recent studies have shown that increased collagen deposition and tissue stiffness in the peri-urethral area of the prostate are associated with lower urinary tract dysfunction (LUTD) and urinary obstructive symptoms. The aim of this study was to determine whether Resveratrol might be useful to inhibit or revert TGFβ- and/or CXCL12-mediated myofibroblast phenoconversion of prostate fibroblasts in vitro, and therefore whether the use of anti-fibrotic therapeutics might be efficacious for the treatment of LUTD.

Methods

Primary prostate and lung tissues were explanted and fibroblast monolayers expanded in vitro. Primary and N1 immortalized prostate stromal fibroblasts, as well as primary fibroblasts cultured from a normal lung and one affected by idiopathic pulmonary fibrosis (IPF) for comparison, were grown in serum–free defined media supplemented with vehicle, TGFβ or CXCL12, pre- or post-treatment with Resveratrol, and were evaluated using immunofluorescence for alpha smooth muscle actin (αSMA) and collagen I (COL1) protein expression and assessed for cell proliferation, apoptosis, and COL1 and EGR1 transcript expression.

Results

This study showed that low concentrations of Resveratrol (≤50 μM) had no effect on N1 or primary prostate fibroblast cell proliferation, apoptosis, or COL1 or EGR1 gene transcription but repressed and reversed myofibroblast phenoconversion. As expected, these same effects were observed for IPF lung fibroblasts though higher levels of Resveratrol (≥100uM) were required. Taken together, these data suggest that, like lung fibroblasts, prostate fibroblast to myofibroblast phenoconversion can be both repressed and reversed by Resveratrol treatment. Thus, anti-fibrotic therapeutics might be efficacious for the treatment of LUTD.

Resveratrol stimulates cyclic AMP response element mediated gene transcription

SCOPE

Many intracellular effects have been attributed to resveratrol, a polyphenolic phytoalexin found in grapes and in other plants, including the direct regulation of transcription. Here, we have analyzed the impact of resveratrol on gene transcription regulated by the cyclic AMP response element (CRE).

METHODS AND RESULTS

Transcription of a chromatin-embedded reporter gene with CREs in its regulatory region was significantly elevated in resveratrol-treated 293 human embryonic kidney cells, hepatoma cells and neural stem cells. The CRE thus functions as resveratrol-responsive element. The polyphenols quercetin and naringenin also stimulated CRE-mediated gene transcription, but not in the range of resveratrol. The polyphenol curcumin, in contrast, had no effect upon CRE-regulated transcription. In addition, resveratrol stimulation upregulated the transcriptional activation potentials of the CRE-binding proteins (CREB) and activating transcription factor 2 (ATF2).

CONCLUSION

CREB exhibits cytoprotective activity by stimulating CRE-regulated genes, while ATF2 has been identified as a tumor suppressor. The fact that resveratrol upregulates CRE-mediated gene transcription and enhances the transcriptional activation potentials of CREB and ATF2 suggests that cytoprotective and tumor suppressive activities of resveratrol may rely-at least in part-on the stimulation of CREB- and ATF2-controlled target genes.