Key Nuclear Transcription Factor Research Articles

Sirtuins, aging and diseases

SIR2 and related genes (sirtuins) are NAD-dependent deacetylases that link metabolism, protein acetylation and aging in a variety of species. Sirtuins are also involved in the longevity conferred by dietary or calorie restriction (CR). The mammalian sirtuins SIRT1-7 are involved in changes in stress resistance and metabolism that are triggered by CR, which not only extends life span, but also protects against many diseases of aging. In this talk, I will describe how mamamlian SIRT1 impacts tissue metabolism and diseases by deacetylating nuclear transcription factors that govern key physiological pathways. I will also describe new data from several labs showing that the mitochondrial sirtuin SIRT3 suppresses reactive oxygen species (ROS) in mitochondria and thus links sirtuins, calorie restriction, ROS, mitochondria and aging. The effect of SIRT3 on mitochondrial generated ROS further regulates the key nuclear transcription factor HIF-1α, and may thus govern the metabolic reprogramming (Warburg effect) in cancer. Finally, I will touch upon recent progress in trying to understand the mechanism of action of SIRT1-activating compounds, which are currently in numerous human clinical trials. Supported by NIA & Glenn Foundation for Medical Research. LG consults for Sirtris/GSK.

The relationship between hypoxia-inducible factor-1α and cartilage degeneration in osteoarthritis: a review

Osteoarthritis is one of the most common diseases seen in clinical practice. Cartilage survives in the hypoxic microenvironment. Hypoxia-inducible factor-1α (HIF-1α) is a key nuclear transcription factor which mediates the hypoxic response of cells. HIF-1α gene is an important regulator for the adaptation of articular cartilage to the hypoxic environment. It is important for formation of articular cartilage, energy metabolism and matrix synthesis. If the HIF-1α gene is knocked out, the cartilage can not maintain their normal morphology and function, which may lead to cartilage degeneration, and result in diseases such as osteoarthritis. Chinese herbal medicines can regulate the expression of HIF-1α gene and supply a therapy method for osteoarthritis. In this paper, the authors review the situation of the correlation between HIF-1α and osteoarthritis cartilage degeneration examined in recent years.

Diesel exhaust particulate extracts inhibit transcription of nuclear respiratory factor-1 and cell viability in human umbilical vein endothelial cells

Endothelial dysfunction precedes cardiovascular disease and is accompanied by mitochondrial dysfunction. Here we tested the hypothesis that diesel exhaust particulate extracts (DEPEs), prepared from a truck run at different speeds and engine loads, would inhibit genomic estrogen receptor activation of nuclear respiratory factor-1 (NRF-1) transcription in human umbilical vein endothelial cells (HUVECs). Additionally, we examined how DEPEs affect NRF-1-regulated TFAM expression and, in turn, Tfam-regulated mtDNA-encoded cytochrome c oxidase subunit I (COI, MTCO1) and NADH dehydrogenase subunit I (NDI) expression as well as cell proliferation and viability. We report that 17β-estradiol (E(2)), 4-hydroxytamoxifen (4-OHT), and raloxifene increased NRF-1 transcription in HUVECs in an ER-dependent manner. DEPEs inhibited NRF-1 transcription, and this suppression was not ablated by concomitant treatment with E(2), 4-OHT, or raloxifene, indicating that the effect was not due to inhibition of ER activity. While E(2) increased HUVEC proliferation and viability, DEPEs inhibited viability but not proliferation. Resveratrol increased NRF-1 transcription in an ER-dependent manner in HUVECs, and ablated DEPE inhibition of basal NRF-1 expression. Given that NRF-1 is a key nuclear transcription factor regulating genes involved in mitochondrial activity and biogenesis, these data suggest that DEPEs may adversely affect mitochondrial function leading to endothelial dysfunction and resveratrol may block these effects.

Rapid effects of novel phytoandrogen adjuvant therapy (PAT) on metabolic health: a gender, age and BMI matched case-control study

Background and Aim: The human androgen receptor (AR) is a key nuclear transcription factor that controls expression of genes involved in anabolism - such as musculoskeletal remodelling and body fat mobilisation to ATP energy production – processes which directly impact aspects of metabolic health. This study evaluates the adjuvant effects of orally administered AR-modulating phytoandrogens and suprahormonal lipidic augmenters (SuHLAs) combined with an integrative weight-healthcare regimen of polyvalent pharmacotherapy (hypoglycemic, lipid modifying and anti-inflammatory) and mild lifestyle intervention, over intervals of 2-4 weeks. Method: The total intention-to-treat (ITT) population consisted solely of women (N = 15) and were screened at baseline for metabolic health status, assessed via arterial blood pressure (BP), body fat (BF), lean muscle mass (LMM), body mass index (BMI), waist circumference (WC) and waist-to-hip ratio (WHR). This gender matched ITT population were then stratified into two treatment groups that were age and BMI matched: 1) patients opting for a metabolic health program (control group, n = 5, mean BMI = 26.6 kg/m2, mean age = 45 years), and 2) patients treated with a metabolic health program plus phytoandrogen adjuvant therapy (PAT group, n=10, mean BMI = 26.5 kg/m2, mean age = 44 years). Results: After treatments averaging 2.8 weeks (control group) and 2.9 weeks (PAT group), mean systolic and diastolic BPs in the total ITT population were lowered by 5 mmHg and 4 mmHg respectively, from 116/79 ±4 mmHg to 111/74 ±2 mmHg (P =0.05). Mean BF showed negligible loss of 0.2% (P >0.05) in the control group, in contrast to a highly significant reduction of 0.8% in the PAT group (P 0.1). Both treatment groups showed comparable improvement in BMI, WC and WHR. The control group had mean reductions of -0.25 kg/m2 (BMI, P <0.05), -2 cm (WC, P <0.05) and -0.03 (WHR, P<0.05), while the PAT group showed reductions of -0.35 kg/m2 (BMI, P =0.01), -3 cm (WC, P =0.01) and -0.03 (WHR, P =0.01). Measured against the top WHR bracket, odds ratios (ORs) for WHR-associated risk for diabetes, hypertension or dyslipidemia (WHR ≥0.9, OR 5.4) in the control and PAT groups were lower by 19% (WHR =0.88 ±0.02, OR 4.38) and 48% (WHR =0.83 ±0.01, OR 2.81) respectively. Conclusion: Oral phytoandrogenic SuHLAs therapy can rapidly potentiate aspects of AR-mediated anabolism within a low intensity metabolic health program. Secondarily, in contrast to physiological androgens and anabolic steroids, phytoandrogenic modulators of the AR in this study did not aggravate arterial tension. This is the first casecontrol report on the pharmacologic use of true phytoandrogens (cognate ligands of the AR) and SuHLAs to aid metabolic competency.

Increased levels of hypoxia‐inducible factor‐1α are associated with Bcl‐xL expression, tumor apoptosis, and clinical outcome in chondrosarcoma

Hypoxia-inducible factor (HIF)-1α is a key nuclear transcription factor that regulates the cellular response to hypoxia, and is important for solid tumor growth and survival. However, the underlying role of HIF-1α in human chondrosarcoma has not been well characterized. This study aims to investigate the expression patterns of HIF-1α in chondrosarcoma, and its association with clinicopathologic features, Bcl-xL expression, apoptosis index (AI), and overall survival of patients with chondrosarcoma. Our results shown that the protein levels of HIF-1α were increased, and the mRNA and protein levels of Bcl-xL were also increased in SW1353 cells under hypoxic conditions. In eight patients with chondrosarcoma, increased expression of HIF-1α and Bcl-xL was detected in chondrosarcoma tissues compared with the paired adjacent normal tissues. Of 34 archival specimens of chondrosarcomas, 20 (58.8%) showed high HIF-1α protein expression as compared to benign cartilage tumors. Increased HIF-1α expression was correlated with a higher pathological grade and MSTS stage of chondrosarcoma. Moreover, HIF-1α expression was significantly associated with Bcl-xL expression and AI. More significantly, the survival rate of patients with HIF-1α high tumors was significantly lower than that of patients with HIF-1α low tumors. These findings suggest that increased HIF-1α levels mediated up-regulation of Bcl-xL play a prominent role in evasion of apoptosis and tumor progression, and can be predictive for the prognosis in human chondrosarcoma.

Essential role of Nrf2 in protection against hydroquinone- and benzoquinone-induced cytotoxicity

Benzene is a well-established human carcinogen. Benzene metabolites hydroquinone (HQ) and benzoquinone (BQ) are highly reactive molecules capable of producing reactive oxygen species and causing oxidative stress. In this study, we investigated the role of the Nrf2, a key nuclear transcription factor that regulates antioxidant response element (ARE)-containing genes, in defense against HQ- and BQ-induced cytotoxicity in cultured human lung epithelial cells (Beas-2B). When the cells were exposed to HQ or BQ the activity of an ARE reporter was induced in a dose-dependent manner, meanwhile Nrf2 protein levels were elevated and accumulated in the nucleus. Increased expression of well-known Nrf2-dependent proteins including NQO1, GCLM, GSS and HMOX was also observed in the HQ/BQ-treated cells. Moreover, transient overexpression of Nrf2 conferred protection against HQ- and BQ-induced cell death, whereas knockdown of Nrf2 by small interfering RNA resulted in increased apoptosis. We also found that the increased susceptibility of Nrf2-knockdown cells to HQ and BQ was associated with reduced glutathione levels and loss of inducibility of ARE-driven genes, suggesting that deficiency of Nrf2 impairs cellular redox capacity to counteract oxidative damage. Altogether, these results suggest that Nrf2-ARE pathway is essential for protection against HQ- and BQ-induced toxicity.

Nuclear factor κB‐associated inflammation mediates impaired vascular endothelial function in non‐diabetic middle‐aged and older overweight/obese men

Healthy middle‐aged/older (MA/O) sedentary men demonstrate vascular endothelial dysfunction with increased endothelial expression of nuclear factor‐kappa B (NFκB), a key proinflammatory nuclear transcription factor. However, there is no direct evidence that NFκB‐associated vascular inflammation mediates endothelial dysfunction in MA/O adults. High doses of Salsalate (4500 mg/d; therapeutic [plasma] 22.2 ± 1.7 mg/100ml, mean ± SE), an aspirin‐like agent that inhibits NFκB, was ingested for 4 days (randomized, placebo‐controlled, double‐blind crossover design) by 10 non‐diabetic overweight or obese MA/O men (62 ± 2 y; BMI 31.4 ± 2 kg/m2) with low‐grade inflammation (plasma C‐reactive protein 2.0 ± 0.7 mg/L). Salsalate reduced total (−30%: 0.42 ± 0.07 vs. 0.60 ± 0.09 intensity/HUVEC intensity, P=0.03) and nuclear (−23%: 128 ± 25 vs. 167 ± 24 total intensity, P=0.06) expression of NFκB p65 in vascular endothelial cells (quantitative immunofluorescence), and increased endothelium‐dependent dilation (EDD, brachial artery flow‐mediated dilation) by 100% (6.2 ± 0.6 vs. 3.1 ± 0.6%, P&lt;0.001) without affecting endothelium‐independent dilation (brachial artery dilation to sublingual nitroglycerin) (19.5 ± 2.2 vs. 19.3 ± 1.6%, P=0.80). These results support the idea that NFκB‐associated vascular inflammation mediates endothelial dysfunction in MA/O overweight/obese men. NIH AG006537, AG013038, AG022241

Rosiglitazone, a peroxisome proliferator-activated receptor-γ agonist, prevents hyperoxia-induced neonatal rat lung injury in vivo

Molecular disruption of homeostatic alveolar epithelial-mesenchymal interactions results in transdifferentiation of alveolar interstitial lipofibroblasts to myofibroblasts. Although this process was suggested to be a central molecular event in the pathogenesis of bronchopulmonary dysplasia (BPD), so far it has been only demonstrated in vitro; whether it also occurs in vivo is unknown. Our objectives were to determine if exposure to hyperoxia results in pulmonary alveolar lipo-to-myofibroblast transdifferentiation in vivo, and whether treatment with a potent peroxisome proliferator-activated receptor gamma (PPARgamma) (the key lipogenic fibroblast nuclear transcription factor) agonist, rosiglitazone, prevents this process. Newborn Sprague Dawley rat pups were exposed to control (21% O2), hyperoxia alone (95% O2 for 24 hr), or hyperoxia with rosiglitazone (95% O2 for 24 hr + rosiglitazone, 3 mg/kg, administered intraperitoneally) conditions. Subsequently, pups were sacrificed, and lung tissue was analyzed by morphometry, and by reverse transcription-polymerase chain reaction, Western hybridization, and immunohistochemistry for the expression of key lipogenic and myogenic markers. We observed a significant decrease in the expression of lipogenic markers, and a significant increase in the expression of myogenic markers in the hyperoxia-alone group. These hyperoxia-induced morphologic, molecular, and immunohistochemical changes were almost completely prevented by rosiglitazone. This is the first evidence of in vivo lipo-to-myofibroblast transdifferentiation and its almost complete prevention by rosiglitazone, prompting us to conclude that administration of PPARgamma agonists may be a novel, effective strategy to prevent the hyperoxia-induced lung molecular injury that has been implicated in the pathogenesis of BPD.

Effect of clarithromycin on nuclear factor-kappa B and transforming growth factor-beta in chronic rhinosinusitis.

Long-term, low-dose macrolide therapy is effective in the treatment of chronic rhinosinusitis. It is believed that macrolide antibiotics produce this benefit through an anti-inflammatory effect. In this study, the effect of clarithromycin treatment on the expression of transforming growth factor (TGF)-beta and the key pro-inflammatory nuclear transcription factor, NF-kappa B, was examined in vitro and in vivo. In vitro: nasal mucosa was obtained from 10 patients with chronic sinusitis and was cultured for 24 hours in the presence of clarithromycin or control. Cellular expression of TGF-beta and NF-kappa B was determined by immunohistochemistry. In vivo: 10 patients with chronic rhinosinusitis were treated for 3 months with clarithromycin. Nasal mucosal biopsies were taken pre- and posttreatment. Cellular expression of TGF-beta and NF-kappa B was again determined by immunohistochemistry. Clarithromycin, when applied to nasal biopsies in vitro, reduced cellular expression of TGF-beta and NF-kappa B. Nasal biopsies taken before and after clarithromycin treatment showed no differences in cellular expression of NF-kappa B or TGF-beta. Clarithromycin can reduce cellular expression of TGF-beta and NF-kappa B when applied in vitro, but its action during clinical therapy is less clear. Clarithromycin is capable of inhibiting pro-inflammatory cytokines in vitro, and reductions of TGF-beta and NF-kappa B may represent additional mechanisms by which macrolides reduce inflammation in chronic airway disease. Discrepancies between the actions of clarithromycin on nasal biopsies in vitro and after clinical therapy warrant further investigation.

Endogenous env elements: partners in generation of pathogenic feline leukemia viruses.

Feline leukemia viruses (FeLVs), which are replication-competent oncoretroviruses of the domestic cat species, are contagiously transmitted in natural environments. They are capable of inducing either acute antiproliferative disease or, after prolonged latency, lymphoid malignancies in this animal population. Current knowledge of the recombinational events between infectious FeLV and noninfectious endogenously inherited FeLV-like elements is reviewed, and the potential role of the derived recombinant viruses in pathogenesis is discussed. Major observations made are as follows: (1) Up to three fourths of the exogenous FeLV envelope glycoprotein (SU), beginning from the N-terminal end, can be replaced by sequences from an endogenous FeLV to produce biologically active chimeric FeLVs. The in vitro replication efficiency or cell tropism of the recombinants appears to be influenced by the amount of SU sequences replaced by the endogenous partner, as well as by the locus of origin of the endogenous sequences. (2) Generation of FeLV recombinants in tissue culture cells corresponds closely to the findings from natural tumors. There is direct evidence, based on molecular genetic analysis, for the prevalence of recombinant proviruses in naturally arising FeLV-induced lymphomas. (3) Certain recombinants harboring an altered primary neutralizing epitope in the middle of SU corresponding to the endogenous FeLV sequence can evade immunity developed against common FeLV infection. In several other recombinants, the epitope sequence is found to be frequently mutated during the process of recombination. (4) FeLV variants with altered epitope, although they may not be efficient in replication in vivo, apparently are capable of causing focal infection in target organs. Evidence is also presented that when coinfected with an exogenous FeLV, the epitope sequence in the variants is reverted to the exogenous type, providing an explanation why this sequence is found to be conserved in all natural isolates of FeLV. (5) A prototype chimeric polyprotein containing most of the SU from the endogenous source is abnormally processed and becomes trapped in the endoplasmic reticulum. A functional consequence of such trapping is interference with specific FeLV infection. (6) Some recombinants, while only poorly replicating in the host, may have the ability to infect target erythroid progenitor cells for the induction of strong cytopathic effect. (7) Some other recombinants appear to potentiate lymphomagenesis by exogenous FeLV and others to acquire properties to infect CNS endothelial cells, an event that could potentially be related to FeLV-induced neuropathogenicity. (8) Of multiple recombinant viruses, a specific recombinant species was found to occur in each of the three cats examined in which lymphoma was experimentally induced, and it was exclusively seen in one of these cats. This recombinant FeLV may potentially be a candidate for strong leukemogenic function. In addition to commonly encountered virus envelope changes, another prominent viral factor involved in tumorigenesis is mutated FeLV transcription regulatory sequences, most frequently with enhancer duplication or triplication. Although only a limited amount of information is available in the area of insertional mutagenesis in FeLV neoplastic disease, activation of certain key nuclear transcription factor genes has been documented.