Binding activity of H-Ras is necessary for in vivo inhibition of ASK1 activity

H-Ras is well known as one of the essential components of Ras/Raf/MEK/ERK cascade, which is a critical prosurvival signaling mechanism in most eukaryotic cells. Ras targets Raf/MEK/ERK cascade by integrating and transmitting extracellular signals from growth factor receptors to Raf, leading to the propagation of signals to modulate a serious of cellular survival events. Apoptosis signal-regulating kinasel (ASK1) serves as a general mediator of cell death because it is responsive to a variety of death signals. In this study, we found that H-Ras interacted with ASK1 to cause the inhibition of both ASK1 activity and ASKl-induced apoptosis in vivo, which was reversed only partially by addition of RafS621 A, an antagonist of Raf, whereas MEK inhibitor, PD98059, and PI3K inhibitor, LY294002, did not disturb the inhibitory effect of H-Ras on ASK-1-induced apoptosis. Furthermore, by means of immunoprecipitate and kinase assays, we demonstrated that the interaction between H-Ras and ASK1 as well as the inhibition of ASKI activity were dependent on the binding activity of H-Ras. These results suggest that a novel mechanism may be involved in H-Rasmediated cell survival in addition to the well established MEK/ERK and PI3K/Akt kinase-dependent enhancement of cell survival.     

The effects of 7-dehydrocholesterol on the structural properties of membranes

Smith-Lemli-Opitz syndrome, a congenital and developmental malformation disease, is typified by abnormal accumulation of 7-dehydrocholesterol (7DHC), the immediate precursor of cholesterol (CHOL), and depletion thereof. Knowledge of the effect of 7DHC on the biological membrane is, however, still fragmentary. In this study, large-scale atomistic molecular dynamics simulations, employing two distinct force fields, have been conducted to elucidate differences in the structural properties of a hydrated dimyristoylphosphatidylcholine bilayer due to CHOL and 7DHC. The present series of results indicate that CHOL and 7DHC possess virtually the same ability to condense and order membranes. Furthermore, the condensing and ordering effects are shown to be strengthened at increasing sterol concentrations.     

2-Phenyl-9H-purine-6-carbonitrile derivatives as selective cathepsin S inhibitors

Starting from previously disclosed equally potent cathepsin K and S inhibitor 4-propyl-6-(3-trifluoromethylphenyl)pyrimidine-2-carbonitrile 1, a novel 2-phenyl-9H-purine-6-carbonitrile scaffold was identified to provide potent and selective cathepsin S inhibitors.     

Genetic Analysis of the Relationship between Bone Mineral Density and Low-Density Lipoprotein Receptor-Related Protein 5 Gene Polymorphisms

Background

A number of studies have examined the association between the polymorphisms of the low-density lipoprotein receptor-related protein 5 gene (LRP5), but previous results have been inconclusive. Thus we performed a meta-analysis of studies on the association between the LRP5 polymorphisms and bone mineral density (BMD) to assess their pooled effects.

Methods

Published literature from PubMed, EMBASE and ISI web of science were searched for eligible publications. Weighted mean difference (WMD) and 95% confidence interval (CI) was calculated using fixed- or random-effects model.

Results

A total of 19 studies with 25773 subjects were considered in this meta-analysis. Of them, 17 examined the association between the A1330V polymorphism and BMD, 8 were focused on the V667M polymorphism, and 2 analyzed the Q89R polymorphism. Individuals with the A1330V AA genotype showed significantly higher BMD than those with the AV/VV genotypes [at lumbar spine (LS): WMD = 0.02g/cm², 95% CI = 0.01-0.03, P < 10^-4; at femur neck (FN): WMD = 0.01g/cm², 95% CI = 0.00-0.02, P = 0.01] or VV genotype (at LS: WMD = 0.02g/cm², 95% CI = 0.01-0.04, P = 0.01). Significant associations were also detected in the analysis for V667M (VV vs. VM/MM: WMD at LS = 0.02g/cm², 95% CI = 0.02-0.03, P < 10^-5; WMD at FN = 0.01g/cm², 95% CI = 0.01-0.02, P = 0.0002). As for Q89R, subjects with the QQ genotype tended to have higher BMD than those with the QR/RR genotypes at FN (WMD = 0.03g/cm², 95% CI = 0.01-0.05, P = 0.005).

Conclusion

This meta-analysis demonstrated that the LRP5 polymorphisms may be modestly associated with BMD of LS and FN.     

Mangiferin aglycone attenuates radiation-induced damage on human intestinal epithelial cells

Recent studies suggest that mangiferin aglycone (norathyriol) has great potential as a novel radioprotector without any known toxic side effects. In this study, we assessed the protective effects of mangiferin aglycone against radiation-induced injuries on normal human intestinal epithelial cells (HIECs), while using mangiferin as a reference compound. The in vitro experiments showed that pretreatment of either mangiferin aglycone or mangiferin could inhibit cytotoxic effects of ionizing irradiation (IR) on HIECs. Cellular changes were estimated by measuring cell viability, clonogenic surviving rate, and apoptotic rate. Compared to mangiferin, we found mangiferin aglycone had greater radioprotective effects of mangiferin aglycone on HIECs. It has been demonstrated that the cytotoxicity of ionizing radiation relates to its capacity to induce DNA damage. In view of this, we monitored DNA double-strand breaks (DSBs) using γH2AX foci formation to test whether mangiferin aglycone and mangiferin could modulate genotoxic effects of radiation. It shows that mangiferin aglycone could eliminate 46.8% of the total DSBs of the cells exposed to 2 Gy IR, which is significantly better than mangiferin. Complementing earlier results from our group, it appears possible to conclude that mangiferin aglycone presents potential useful effects on IR-induced damage and may be a better radioprotective agent than mangiferin therapeutically.     

Resveratrol downregulates acute pulmonary thromboembolism-induced pulmonary artery hypertension via p38 mitogen-activated protein kinase and monocyte chemoattractant protein-1 signaling in rats

AimsIn the present study, we explored the hypothesis that initiation of PH involves the upregulation of monocyte chemoattractant protein-1 (MCP-1) in acute PTE. We evaluated the effects of resveratrol and the role of p38 mitogen-activated protein kinase (MAPK) in this process.Main methodsA rat model of acute PTE was established by infusion of an autologous blood clot into the pulmonary artery through a polyethylene catheter. Rats were randomly divided into 1, 4, and 8 hour time groups. Resveratrol, C1142 (a rodent chimeric mAb that neutralizes rat MCP-1) or SB203580 (a p38MAPK specific inhibitor) was administered to the animals beginning 1 h prior to the start of the acute PTE protocol. At each time point, the mean pulmonary artery pressure (mPAP), mRNA and protein expressions of MCP-1 were measured. The phosphorylation of p38 MAPK (p-pMAPK) was also detected.Key findingsAcute PTE elicited significant increases in mean pulmonary artery pressure (mPAP), and up-regulated the expression of monocyte chemoattractant protein-1 (MCP-1) and phosphorylation of p38 mitogen-activated protein kinase (p-p38 MAPK). Administration of C1142 markedly reduced mPAP. Furthermore, pre-treatment of rats with resveratrol significantly reduced mPAP and down-regulated the expression of MCP-1, which was associated with robustly suppressed acute PTE-induced p-p38MAPK expression.SignificanceThese findings suggested that MCP-1 was involved in the formation of acute PTE-induced PH, and resveratrol down-regulated the expression of MCP-1 by inhibiting acute PTE-induced p-p38MAPK activation, which contributed to the decrease in PH.     

An Antagonism Joint Action of Lead and Di-2-Ethylhexyl Phthalate Explains an Improved Ability of Learning and Memory after Combined Exposure in Weaning Rats

Lead and di-2-ethylhexyl phthalate (DEHP) are widely distributed in the environment, and their neurotoxicity has caused a widespread concern. The complexity of environmental exposure provides the possibility of their combined exposure. The present study aims to describe a joint neurotoxicity and clarify the potential mechanism after combined exposure to lead and DEHP. A 2 × 3 factorial design was used to analyze either single effects or their interaction by a subchronic lead and DEHP exposure model of the male weaning rats. Similar to the previous study, lead or DEHP single exposure showed an increased neurotoxicity. Interestingly, our neurobehavioral test showed the rats in the combined exposure groups had a better ability of learning and memory compared with the single-exposure ones. It seemed to reflect an antagonism joint action in neurotoxicity after combined exposure. The content of dehydroepiandrosterone (DHEA) in serum and the mRNA level of brain-derived neurotrophic factor (Bdnf) in the hippocampus showed a similar trend to the ability of learning and memory. However, there was insufficient evidence to support the joint action on some indexes of oxidative stress such as malondialdehyde (MDA), the ratio of reduced glutathione(GSH) to oxidized glutathione(GSSG), γglutamylcysteine synthetase (γ-GCS), glutathione-s transferase (GST), and nuclear factor E2-related factor 2 (Nrf2) mRNA expression in the hippocampus. In a word, our current study reminded a unique antagonism joint action of neurotoxicity after combined exposure to lead and DEHP, which may contribute to understanding some shallow mechanism of the joint toxicity due to the complexity of environmental pollutant exposure.

     

Spatial patterns of soil and ecosystem respiration regulated by biological and environmental variables along a precipitation gradient in semi-arid grasslands in China

Precipitation is a key environmental factor in determining ecosystem structure and function. Knowledge of how soil and ecosystem respiration responds to climate change (e.g., precipitation) and human activities (e.g., grazing or clipping) is crucial for assessing the impacts of climate change on terrestrial ecosystems and for improving model simulations and predictions of future global carbon (C) cycling in response to human activities. In this study, we examined the spatial patterns of soil and ecosystem respiration along a precipitation gradient from 167.7 to 398.1 mm in a semi-arid grassland. Our results showed that soil and ecosystem respiration increased linearly with increasing mean annual precipitation. The trends were similar to those of shoot biomass, litter and soil total C content along the precipitation gradient. Our results indicated that precipitation was the primary controlling factor in determining the spatial pattern of soil and ecosystem respiration in semi-arid grasslands in China. The linear/nonlinear relationships in this study describing the variations of the ecosystem carbon process with precipitation can be useful for model development, parameterization and validation at the regional scale to improve predictions of how carbon processes in grasslands respond to climate change, land use and grassland management.     

Asparaginase Potentiates Glucocorticoid-Induced Osteonecrosis in a Mouse Model

Osteonecrosis is a common dose-limiting toxicity of glucocorticoids. Data from clinical trials suggest that other medications can increase the risk of glucocorticoid-induced osteonecrosis. Here we utilized a mouse model to study the effect of asparaginase treatment on dexamethasone-induced osteonecrosis. Mice receiving asparaginase along with dexamethasone had a higher rate of osteonecrosis than those receiving only dexamethasone after 6 weeks of treatment (44% vs. 10%, P = 0.006). Similarly, epiphyseal arteriopathy, which we have shown to be an initiating event for osteonecrosis, was observed in 58% of mice receiving asparaginase and dexamethasone compared to 17% of mice receiving dexamethasone only (P = 0.007). As in the clinic, greater exposure to asparaginase was associated with greater plasma exposure to dexamethasone (P = 0.0001). This model also recapitulated other clinical risk factors for osteonecrosis, including age at start of treatment, and association with the systemic exposure to dexamethasone (P = 0.027) and asparaginase (P = 0.036). We conclude that asparaginase can potentiate the osteonecrotic effect of glucocorticoids.     

HIV Nef-mediated CD4 down-regulation is adaptor protein complex 2 dependent

Nef is a crucial viral protein for HIV to replicate at high titers and in the development of AIDS. One Nef function is down-regulating CD4 from the cell surface, which correlates with Nef-enhanced viral pathogenicity. Nef down-regulates CD4 by linking CD4 to clathrin-coated pits. However, the mechanistic connection between the C-terminal dileucine motif of Nef and the component(s) of the clathrin-coated pits has not been pinpointed. In this report we used two AP-2 complex-specific inhibitors: a dominant negative mutant of Eps15 (Eps15DIII) that binds to the alpha subunit of AP-2 complex and a small interference RNA that is specific for the mu2 subunit of AP-2 complex. We show that both HIV Nef- and SIV Nef-mediated CD4 down-regulations were profoundly blocked by the synergistic effect of Eps15DIII and RNA interference of AP-2 expression. The results demonstrate that HIV/SIV Nef-mediated CD4 down-regulation is AP-2 dependent. We also show that the PMA-induced CD4 down-regulation was blocked by these two inhibitors. Therefore, PMA-induced CD4 down-regulation is also AP-2 dependent. The results demonstrate that, like the tyrosine sorting motif-dependent endocytosis (for which the transferrin receptor and the epidermal growth factor receptor are the two prototypes), dileucine sorting motif-dependent endocytosis of Nef and CD4 are also AP-2 dependent.