Panos G. Ziros

The bone-specific transcriptional regulator Cbfa1 is a target of mechanical signals in osteoblastic cells.

A primary goal of bone research is to understand the mechanism(s) by which mechanical forces dictate the cellular and metabolic activities of osteoblasts, the bone-forming cells. Several studies indicate that osteblastic cells respond to physical loading by transducing signals that alter gene expression patterns. Accumulated data have documented the fundamental role of the osteoblast-specific transcription factor Cbfa1 (core-binding factor) in osteoblast differentiation and function. Here, we demonstrate that low level mechanical deformation (stretching) of human osteoblastic cells directly up-regulates the expression and DNA binding activity of Cbfa1. This effect seems to be fine tuned by stretch-triggered induction of distinct mitogen-activated protein kinase cascades. Our novel finding that activated extracellular signal-regulated kinase mitogen-activated protein kinase physically interacts and phosphorylates endogenous Cbfa1 in vivo (ultimately potentiating this transcription factor) provides a molecular link between mechanostressing and stimulation of osteoblast differentiation. Elucidation of the specific modifiers and cofactors that operate in this mechanotranscription circuitry will contribute to a better understanding of mechanical load-induced bone formation which may set the basis for nonpharmacological intervention in bone loss pathologies.

Brown adipose tissue responds to cold and adrenergic stimulation by induction of FGF21.

Fibroblast growth factor-21 (FGF21) is a pleiotropic protein involved in glucose, lipid metabolism and energy homeostasis, with main tissues of expression being the liver and adipose tissue. Brown adipose tissue (BAT) is responsible for cold-induced thermogenesis in rodents. The role of FGF21 in BAT biology has not been investigated. In the present study, wild-type C57BL/6J mice as well as a brown adipocyte cell line were used to explore the potential role of cold exposure and β3-adrenergic stimulation in the expression of FGF21 in BAT. Our results demonstrate that short-term exposure to cold, as well as β3-adrenergic stimulation, causes a significant induction of FGF21 mRNA levels in BAT, without a concomitant increase in FGF21 plasma levels. This finding opens new routes for the potential use of pharmaceuticals that could induce FGF21 and, hence, activate BAT thermogenesis.

Differential Expression of MicroRNAs in Adipose Tissue after Long-Term High-Fat Diet-Induced Obesity in Mice

Obesity is a major health concern worldwide which is associated with increased risk of chronic diseases such as metabolic syndrome, cardiovascular disease and cancer. The elucidation of the molecular mechanisms involved in adipogenesis and obesogenesis is of essential importance as it could lead to the identification of novel biomarkers and therapeutic targets for the development of anti-obesity drugs. MicroRNAs (miRNAs) have been shown to play regulatory roles in several biological processes. They have become a growing research field and consist of promising pharmaceutical targets in various fields such as cancer, metabolism, etc. The present study investigated the possible implication of miRNAs in adipose tissue during the development of obesity using as a model the C57BLJ6 mice fed a high-fat diet. C57BLJ6 wild type male mice were fed either a standard (SD) or a high-fat diet (HFD) for 5 months. Total RNA was prepared from white adipose tissue and was used for microRNA profiling and qPCR. Twenty-two of the most differentially expressed miRNAs, as identified by the microRNA profiling were validated using qPCR. The results of the present study confirmed previous results. The up-regulation of mmu-miR-222 and the down-regulation of mmu-miR-200b, mmu-miR-200c, mmu-miR-204, mmu-miR-30a*, mmu-miR-193, mmu-miR-378 and mmu-miR-30e* after HFD feeding has also been previously reported. On the other hand, we show for the first time the up-regulation of mmu-miR-342-3p, mmu-miR-142-3p, mmu-miR-142-5p, mmu-miR-21, mmu-miR-146a, mmu-miR-146b, mmu-miR-379 and the down-regulation of mmu-miR-122, mmu-miR-133b, mmu-miR-1, mmu-miR-30a*, mmu-miR-192 and mmu-miR-203 during the development of obesity. However, future studies are warranted in order to understand the exact role that miRNAs play in adipogenesis and obesity.

Nrf2 Represses FGF21 During Long-Term High-Fat Diet–Induced Obesity in Mice

OBJECTIVE Obesity is characterized by chronic oxidative stress. Fibroblast growth factor 21 (FGF21) has recently been identified as a novel hormone that regulates metabolism. NFE2-related factor 2 (Nrf2) is a transcription factor that orchestrates the expression of a battery of antioxidant and detoxification genes under both basal and stress conditions. The current study investigated the role of Nrf2 in a mouse model of long-term high-fat diet (HFD)-induced obesity and characterized its crosstalk to FGF21 in this process. RESEARCH DESIGN AND METHODS Wild-type (WT) and Nrf2 knockout (Nrf2-KO) mice were fed an HFD for 180 days. During this period, food consumption and body weights were measured. Glucose metabolism was assessed by an intraperitoneal glucose tolerance test and intraperitoneal insulin tolerance test. Total RNA was prepared from liver and adipose tissue and was used for quantitative real-time RT-PCR. Fasting plasma was collected and analyzed for blood chemistries. The ST-2 cell line was used for transfection studies. RESULTS Nrf2-KO mice were partially protected from HFD-induced obesity and developed a less insulin-resistant phenotype. Importantly, Nrf2-KO mice had higher plasma FGF21 levels and higher FGF21 mRNA levels in liver and white adipose tissue than WT mice. Thus, the altered metabolic phenotype of Nrf2-KO mice under HFD was associated with higher expression and abundance of FGF21. Consistently, the overexpression of Nrf2 in ST-2 cells resulted in decreased FGF21 mRNA levels as well as in suppressed activity of a FGF21 promoter luciferase reporter. CONCLUSIONS The identification of Nrf2 as a novel regulator of FGF21 expands our understanding of the crosstalk between metabolism and stress defense.

Gene transfer into human hematopoietic progenitor cells with an episomal vector carrying an S/MAR element

Episomally maintained self-replicating systems present attractive alternative vehicles for gene therapy applications. Recent insights into the ability of chromosomal scaffold/matrix attachment regions (S/MARs) to mediate episomal maintenance of genetic elements allowed the development of a small circular episomal vector that functions independently of virally encoded proteins. In this study, we investigated the potential of this vector, pEPI-eGFP, to mediate gene transfer in hematopoietic progenitor cell lines and primary human cells. pEPI-eGFP was episomally maintained and conferred sustained eGFP expression even in nonselective conditions in the human cell line, K562, as well as in primary human fibroblast-like cells. In contrast, in the murine erythroleukemia cell line, MEL, transgene expression was silenced through histone deacetylation, despite the vectors episomal persistence. Hematopoietic semisolid cell colonies derived from transfected human cord blood CD34+ cells expressed eGFP, albeit at low levels. After 4 weeks, the vector is retained in approximately 1% of progeny cells. Our results provide the first evidence that S/MAR-based plasmids can function as stable episomes in primary human cells, supporting long-term transgene expression. However, they do not display universal behavior in all cell types.

Simvastatin activates Keap1/Nrf2 signaling in rat liver

Some of the statins’ pleiotropic actions have been attributed to their antioxidant activity. The Nrf2 transcription factor controls the expression of a number of protective genes in response to oxidative stress. In the present study, wistar rats, primary hepatocytes as well as ST2 cells, were employed to explore the potential role of Nrf2 in mediating the reported antioxidant effects of statins. Simvastatin triggered nuclear translocation of Nrf2 in rat liver and in primary rat hepatocytes in a mevalonate-dependent and cholesterol-independent way. In liver, nuclear extracts from simvastatin-treated rats, the DNA-binding activity of Nrf2, was significantly increased and the mRNA of two known targets of Nrf2 (HO-1 and GPX2) was induced. In ST2 cells stably transfected with constructs bearing Nrf2-binding site (antioxidant responsive element), simvastatin enhanced Nrf2-mediated transcriptional activity in a mevalonate-dependent and cholesterol-independent fashion. In conclusion, activation of Keap1/Nrf2 signaling pathway by simvastatin might provide effective protection of the cell from the deleterious effects of oxidative stress.

Growth hormone attenuates the transcriptional activity of Runx2 by facilitating its physical association with Stat3β

We document that GH controls osteoblast function by modulating the biological activity of the osteospecific transcription factor Runx2. Evidence is provided for a physical interaction between Runx2 and Stat3β, which is enhanced by GH and downregulates the transcriptional properties of this key osteogenic regulator.

Loop-Mediated Isothermal Amplification (LAMP) for the Detection of Salmonella in Food

Salmonella infection represents a considerable global burden, with significant health and economic impacts. Salmonellosis is most often attributed to the consumption of contaminated foods such as poultry, beef, pork, eggs, milk, seafood, nut products, and fresh produce. Increased public awareness related to food-borne contamination resulted in greater efforts to develop more sensitive, rapid, and inexpensive methods of pathogens detection. Loop-mediated isothermal amplification (LAMP) constitutes a promising solution for rapid diagnosis of food-borne pathogens and is increasingly been applied for the specific diagnosis of different pathogens, Salmonella included. We have reviewed the application of LAMP for the specific detection of Salmonella in food matrices, compared with conventional culture techniques, and in terms of applicability, food matrices, type of assays, target genes, assay temperature, time and equipment, specificity, sensitivity, and robustness. The pros and cons of Salmonella LAMP assays are presented. The potential of LAMP for the development of new on-site diagnostics for the food and agricultural industries and its use as a routine Salmonella screening tool are discussed. Salmonella-specific LAMP assays are expected to provide a very robust, innovative, and powerful molecular diagnostic method for food safety testing services and public health authorities.

Simvastatin lowers reactive oxygen species level by Nrf2 activation via PI3K/Akt pathway

The beneficial effects of HMG-CoA (3-hydroxy-3-methyl-glutaryl-CoA) reductase inhibitors (statins) have been attributed not only to their cholesterol lowering effect but also to their pleiotropic actions and especially to their anti-oxidant activity. Nrf2 (NF-E2-related factor 2) is a transcription factor that orchestrates the transcriptional response of cells to oxidative stressors and electrophilic xenobiotics. In this study, primary mouse embryonic fibroblasts from wild type or Nrf2 knock out C57BL6J mice and ST-2 cells were used to investigate the implication of Nrf2 in the mediation of the anti-oxidant effects of statins and the possible involvement of PI3K/Akt pathway in this process. We show for the first time that simvastatin lowers reactive oxygen species (ROS) by activating Nrf2 through the PI3K/Akt pathway.

Growth hormone/JAK-STAT axis signal-transduction defect. A novel treatable cause of growth failure.

Primary cultured fibroblasts of four patients with idiopathic short stature and severe growth delay, which displayed normal growth hormone receptor expression presented a reduced ability for activation of signal transducer and activator of transcription‐3 (STAT3). Impaired STAT3 activation was accompanied by cell‐cycle arrest at the Go /G1 phase. Increased levels of the cyclin‐dependent kinase inhibitor, p21WAF/CIPI, and reduced levels of cyclins were also detected in these patients. High concentrations of human growth hormone (1000 ng·mL−1) added to the culture medium induced activation of STAT3 and reduced the levels of p21WAF/CIPI in the fibroblasts of the four idiopathic short stature children. Treatment of these children with exogenous human growth hormone significantly augmented their growth velocity. Overall, our study provides the first evidence linking the idiopathic short stature phenotype with a functional aberration in the growth hormone signal transduction cascade which can be successfully overcome by exposure to high doses of growth hormone.