Mineralocorticoid receptor blockade improves diastolic function independent of blood pressure reduction in a transgenic model of RAAS overexpression

There is emerging evidence that aldosterone can promote diastolic dysfunction and cardiac fibrosis independent of blood pressure effects, perhaps through increased oxidative stress and inflammation. Accordingly, this investigation was designed to ascertain if mineralocorticoid receptor blockade improves diastolic dysfunction independently of changes in blood pressure through actions on myocardial oxidative stress and fibrosis. We used young transgenic (mRen2)27 [TG(mRen2)27] rats with increases in both tissue ANG II and circulating aldosterone, which manifests age-related increases in hypertension and cardiac dysfunction. Male TG(mRen2)27 and age-matched Sprague-Dawley rats were treated with either a low dose (～1 mg·kg(-1)·day(-1)) or a vasodilatory, conventional dose (～30 mg·kg(-1)·day(-1)) of spironolactone or placebo for 3 wk. TG(mRen2)27 rats displayed increases in systolic blood pressure and plasma aldosterone levels as well as impairments in left ventricular diastolic relaxation without changes in systolic function on cine MRI. TG(mRen2)27 hearts also displayed hypertrophy (left ventricular weight, cardiomyoctye hypertrophy, and septal wall thickness) as well as fibrosis (interstitial and perivascular). There were increases in oxidative stress in TG(mRen2)27 hearts, as evidenced by increases in NADPH oxidase activity and subunits as well as ROS formation. Low-dose spironolactone had no effect on systolic blood pressure but improved diastolic dysfunction comparable to a conventional dose. Both doses of spironolactone caused comparable reductions in ROS/3-nitrotryosine immunostaining and perivascular and interstitial fibrosis. These data support the notion mineralocorticoid receptor blockade improves diastolic dysfunction through improvements in oxidative stress and fibrosis independent of changes in systolic blood pressure.     

Angiotensin II-mediated oxidative stress promotes myocardial tissue remodeling in the transgenic (mRen2) 27 Ren2 rat

Angiotensin II (ANG II) contributes to cardiac remodeling, hypertrophy, and left ventricular dysfunction. ANG II stimulation of the ANG type 1 receptor (AT(1)R) generates reactive oxygen species via NADPH oxidase, which facilitates this hypertrophy and remodeling. This investigation sought to determine whether cardiac oxidative stress and cellular remodeling could be attenuated by in vivo AT(1)R blockade (AT(1)B) (valsartan) or superoxide dismutase/catalase mimetic (tempol) treatment in a rodent model of chronically elevated tissue levels of ANG II, the transgenic (mRen2) 27 rat (Ren2). Ren2 rats overexpress the mouse renin transgene with resultant hypertension, insulin resistance, proteinuria, and cardiovascular damage. Young (6-7 wk old) male Ren2 and age-matched Sprague-Dawley rats were treated with valsartan (30 mg/kg), tempol (1 mmol/l), or placebo for 3 wk. Heart tissue NADPH oxidase (NOX) activity and immunohistochemical analysis of subunits NOX2, Rac1, and p22(phox), heart tissue malondialdehyde, and insulin-stimulated protein kinase B (Akt) activation were measured. Structural changes were assessed with cine MRI, transmission electron microscopy, and light microscopy. Increases in septal wall thickness and altered systolic function (cine MRI) were associated with perivascular fibrosis and increased mitochondria in Ren2 on light and transmission electron microscopy (P < 0.05). AT(1)B, but not tempol, reduced blood pressure (P < 0.05); significant improvements were seen with both AT(1)B and tempol on NOX activity, subunit expression, malondialdehyde, and insulin-mediated activation/phosphorylation of Akt (each P < 0.05). Collectively, these data suggest cardiac oxidative stress-induced structural and functional changes are driven, in part, by AT(1)R-mediated increases in NADPH oxidase activity.     

Proteomics reveals new salt responsive proteins associated with rice plasma membrane

The signaling processes in plants that initiate cellular responses to biotic and abiotic factors are believed to be located in the plasma membrane (PM). A better understanding of the PM proteome response to environmental stresses might lead to new strategies for improving stress-tolerant crops. A sub-cellular proteomics approach was applied to monitor changes in abundance of PM-associated protein in response to salinity, a key abiotic stress affecting rice productivity worldwide. Proteome was extracted from a root plasma-membrane-rich fraction of a rice salt tolerant variety, IR651, grown under saline and normal conditions. Comparative two-dimensional electrophoresis revealed that 24 proteins were differentially expressed in response to salt stress. From these, eight proteins were identified by mass spectrometry analysis. Most of the proteins identified are likely to be PM-associated and are known to be involved in several important mechanisms of plant adaptation to salt stress. These include regulation of PM pumps and channels, membrane structure, oxidative stress defense, signal transduction, protein folding, and the methyl cycle. To investigate the correlation between mRNA and protein level in response to salinity, we performed quantitative Real-Time PCR analysis of three genes that were salt responsive at the protein level, including 1,4-Benzoquinone reductase, a putative remorin and a hypersensitive induced response protein. No concordance was detected between the changes in levels of gene and protein expression. Our results indicate that the proteomics approach is suitable for expression analysis of membrane associated proteins under salt stress.     

Testing two chromosome doubling agents for in vitro tetraploid induction on ginger lilies,Hedychium gardnerianum Shepard ex Ker Gawl. and Hedychium coronarium J. Koenig

In Vitro Cellular & Developmental Biology - Plant - Polyploidization can be a way to produce new varieties in vegetatively propagated species where options on increasing genetic variability are...     

Chromatin-Based Classification of Genetically Heterogeneous AMLs into Two Distinct Subtypes with Diverse Stemness Phenotypes

1. Download high-res image (195KB)
2. Download full-size image

     

The potential of plant systems to break the HIV‐TB link

Tuberculosis (TB) and human immunodeficiency virus (HIV) can place a major burden on healthcare systems and constitute the main challenges of diagnostic and therapeutic programmes. Infection with HIV is the most common cause of Mycobacterium tuberculosis (Mtb), which can accelerate the risk of latent TB reactivation by 20‐fold. Similarly, TB is considered the most relevant factor predisposing individuals to HIV infection. Thus, both pathogens can augment one another in a synergetic manner, accelerating the failure of immunological functions and resulting in subsequent death in the absence of treatment. Synergistic approaches involving the treatment of HIV as a tool to combat TB and vice versa are thus required in regions with a high burden of HIV and TB infection. In this context, plant systems are considered a promising approach for combatting HIV and TB in a resource‐limited setting because plant‐made drugs can be produced efficiently and inexpensively in developing countries and could be shared by the available agricultural infrastructure without the expensive requirement needed for cold chain storage and transportation. Moreover, the use of natural products from medicinal plants can eliminate the concerns associated with antiretroviral therapy (ART) and anti‐TB therapy (ATT), including drug interactions, drug‐related toxicity and multidrug resistance. In this review, we highlight the potential of plant system as a promising approach for the production of relevant pharmaceuticals for HIV and TB treatment. However, in the cases of HIV and TB, none of the plant‐made pharmaceuticals have been approved for clinical use. Limitations in reaching these goals are discussed.     

Salinity tolerance of Aegilops cylindrica genotypes collected from hyper-saline shores of Uremia Salt Lake using physiological traits and SSR markers

Uremia Salt Lake, in North West Iran, has a hyper-saline water. A rare highly salinity-tolerant grass species, Aegilops cylindrica grows along its shores. Salinity tolerance of 44 genotypes of Ae. cylindrica, mainly collected from the Lake, was evaluated under control and 400 mM NaCl conditions using the physiological traits of plant height, dry weight, proline content, Na⁺ and K⁺ concentrations as well as K⁺/Na⁺ ratio. To evaluate the association between microsatellite (EST-SSR and SSR) markers and salinity tolerance, 35 primer pairs were used. Results showed a significant variation in the 44 genotypes studied in terms of their traits except for proline content. Ten most salinity-tolerant genotypes were identified based on their ability to survive, to produce the highest dry weight, and to sustain the least leaf Na⁺ concentration under salinity stress. The very high negative correlation found between Na⁺ concentration and salinity tolerance revealed the importance of individual or a combination of Na⁺ exclusion and excretion mechanisms contributing to the hyper-salinity tolerance of these genotypes. Clustering analysis based on marker data divided the 44 studied genotypes into two groups that were consistent with their saline and non-saline geographical areas. Results of molecular markers showed that four microsatellite markers (Xgwm312, Xwmc170, Xgwm291 and Xgwm410) generated a distinguished banding pattern in ten most salinity-tolerant genotypes. These results supported previous reports on their linkage with Na⁺ exclusion genes (HKT1;5 and HKT1;4) in wheat, which provided further evidence of usefulness of both genes and the linked markers to the salinity tolerance of the halophytic grass family species.     

Nrf-2 overexpression in mesenchymal stem cells reduces oxidative stress-induced apoptosis and cytotoxicity

The most prominent capabilities of mesenchymal stem cells (MCSs) which make them promising for therapeutic applications are their capacity to endure and implant in the target tissue. However, the therapeutic applications of these cells are limited due to their early death within the first few days following transplantation. Therefore, to improve cell therapy efficacy, it is necessary to manipulate MSCs to resist severe stresses imposed by microenvironment. In this study, we manipulated MSCs to express a cytoprotective factor, nuclear factor erythroid-2 related factor 2 (Nrf2) to address this issue. Full-length human Nrf2 cDNA was isolated and TOPO cloned into TOPO cloning vector and then transferred to gateway adapted adenovirus expression vector by LR recombination reaction. Afterwards, the Nrf2 bearing recombinant virus was prepared in appropriate mammalian cell line and used to infect MSCs. The viability and apoptosis of the Nrf2 expressing MSCs were evaluated following hypoxic and oxidative stress conditions. Transient expression of Nrf2 by MSCs protected them against cell death and the apoptosis triggered by hypoxic and oxidative stress conditions. Nrf2 also enhanced the activity of SOD and HO-1. These findings could be used as a strategy for prevention of graft cell death in MSC-based cell therapy. It also indicates that management of cellular stress responses can be used for practical applications.     

Detection and quantification of Lyme spirochetes using sensitive and specific molecular beacon probes

Background  

Lyme disease, caused by Borrelia burgdorferi, affects a large number of people in both the USA and Europe. The mouse is a natural host for this spirochete and is widely used as a model system to study Lyme pathogenesis mechanisms. Since disease manifestations often depend upon the spirochete burden in a particular tissue, it is critical to accurately measure the bacterial number in infected tissues. The current methods either lack sensitivity and specificity (SYBR Green), or require independent analysis of samples in parallel to quantitate host and bacterial DNA (TaqMan). We have developed a novel molecular beacon-based convenient multiplex real-time quantitative PCR assay to identify and detect small numbers of B. burgdorferi in infected mouse tissues.     

Ralstonia eutropha as a biocatalyst for desulfurization of dibenzothiophene

The potential of Ralstonia eutropha as a biocatalyst for desulfurization of dibenzothiophene (DBT) was studied in growing and resting cell conditions. The results of both conditions showed that sulfur was removed from DBT which accompanied by the formation of 2-hydroxybiphenyl (2-HBP). In growing cell experiments, glucose was used as an energy supplying substrate in initial concentrations of 55 mM (energy-limited) and 111 mM (energy-sufficient). The growing cell behaviors were quantitatively described using the logistic equation and maintenance concept. The results indicated that 2-HBP production was higher for the energy-sufficient cultures, while the values of the specific growth rate and the maintenance coefficient for these media were lower than those of the energy-limited cultures. Additionally, the kinetic studies showed that the half-saturation constant for the energy-limited cultures was 2 times higher than the energy-sufficient ones where the inhibition constant (0.08 mM) and the maximum specific DBT desulfurization rate (0.002 mmol g_cell ⁻¹ h⁻¹) were almost constant. By defining desulfurizing capacity (D _DBT) including both the biomass concentration and time to reach a particular percentage of DBT conversion, the best condition for desulfurizing cell was determined at 23% g_cell L⁻¹ h⁻¹ which corresponded with the resting cells that were harvested at the mid-exponential growth phase.