Taurine resumed neuronal differentiation in arsenite-treated N2a cells through reducing oxidative stress,endoplasmic reticulum stress,and mitochondrial dysfunction

The goal of the study is to investigate the preventive effect of taurine against arsenite-induced arrest of neuronal differentiation in N2a cells. Our results revealed that taurine reinstated the neurite outgrowth in arsenite-treated N2a cells. Meanwhile, arsenite-induced oxidative stress and mitochondrial dysfunction as well as degradation of mitochondria DNA (mtDNA) were also inhibited by co-treatment of taurine. Since oxidative stress and mitochondrial dysfunction is closely associated with endoplasmic reticulum (ER) stress, we further examined indicators of ER stress, 78 kDa glucose-regulated protein (GRP78), and C/EBP-homologous protein (CHOP) protein expression. The results demonstrated that taurine significantly reduced arsenite-induced ER stress in N2a cells. In the parallel experiment, arsenite-induced disruption of intracellular calcium homeostasis was also ameliorated by taurine. The proven bio-function of taurine preserved a preventive effect against deleteriously cross-talking between oxidative stress, mitochondria, and ER. Overall, the results of the study suggested that taurine reinstated neuronal differentiation by inhibiting oxidative stress, ER stress, and mitochondrial dysfunction in arsenite-treated N2a cells.     

Top3α Is Required during the Convergent Migration Step of Double Holliday Junction Dissolution

Although Blm and Top3α are known to form a minimal dissolvasome that can uniquely undo a double Holliday junction structure, the details of the mechanism remain unknown. It was originally suggested that Blm acts first to create a hemicatenane structure from branch migration of the junctions, followed by Top3α performing strand passage to decatenate the interlocking single strands. Recent evidence suggests that Top3α may also be important for assisting in the migration of the junctions. Using a mismatch-dHJ substrate (MM-DHJS) and eukaryotic Top1 (in place of Top3α), we show that the presence of a topoisomerase is required for Blm to substantially migrate a topologically constrained Holliday junction. When investigated by electron microscopy, these migrated structures did not resemble a hemicatenane. However, when Blm is together with Top3α, the dissolution reaction is processive with no pausing at a partially migrated structure. Potential mechanisms are discussed.     

Direct cocktail analysis of drug discovery compounds in pooled plasma samples using liquid chromatography-tandem mass spectrometry

Direct plasma injection technology coupled with a LC-MS/MS assay provides fast and straightforward method development and greatly reduces the time for the tedious sample preparation procedures. In this work, a simple and sensitive bioanalytical method based on direct plasma injection using a single column high-performance liquid chromatography (HPLC) and tandem mass spectrometry (MS/MS) was developed for direct cocktail analysis of double-pooled mouse plasma samples for the quantitative determination of small molecules. The overall goal was to improve the throughput of the rapid pharmacokinetic (PK) screening process for early drug discovery candidates. Each pooled plasma sample was diluted with working solution containing internal standard and then directly injected into a polymer-coated mixed-function column for sample clean-up, enrichment and chromatographic separation. The apparent on-column recovery of six drug candidates in mouse plasma samples was greater than 90%. The single HPLC column was linked to either an atmospheric pressure chemical ionization (APCI) or electrospray ionization (ESI) source as a part of MS/MS system. The total run cycle time using single column direct injection methods can be achieved within 4 min per sample. The analytical results obtained by the described direct injection methods were comparable with those obtained by semi-automated protein precipitation methods within +/- 15%. The advantages and challenges of using direct single column LC-MS/MS methods with two ionization sources in combination of sample pooling technique are discussed.     

Circulating Matrix Metalloproteinase-2 and -9 Enzyme Activities in the Children with Ventricular Septal Defect

Ventricular septal defect (VSD) is the most common form of congenital heart diseases. Matrix metalloproteinases (MMPs) are a family of zinc-dependent endopeptidases involved in causal cardiac tissue remodeling. We studied the changes of circulating MMP-2 and MMP-9 activities in the patients with VSD severity and closure. There were 96 children with perimembranous VSD enrolled in this study. We assigned the patients into three groups according to the ratio of VSD diameter/diameter of aortic root (Ao). They were classified as below: Trivial (VSD/Ao ratio ≤ 0.2), Small (0.2 < VSD/Ao ≤ 0.3) and Median (0.3 < VSD/Ao) group. Plasma MMP-2 and MMP-9 activities were assayed by gelatin zymography.There was a significant higher MMP-2 activity in the VSD (Trivial, Small and Median) groups compared with that in Control group. The plasma MMP-9 activity showed a similar trend as the findings in MMP-2 activity. After one year follow-up, a significant difference in the MMP-9 activity was found between VSD spontaneous closure and non-closure groups. In conclusion, a positive trend between the severity of VSD and activities of MMP-2 and MMP-9 was found. Our data imply that MMP-2 and MMP-9 activities may play a role in the pathogenesis of VSD.     

Inverse Association of N-Terminal Pro-B-Type Natriuretic Peptide with Metabolic Syndrome in Patients with Congestive Heart Failure

Background

Metabolic syndrome has been shown to be associated with lower levels of plasma N-terminal pro-B-type natriuretic peptide (Nt-proBNP) in the general population. We sought to elucidate the relationship between Nt-proBNP and components of metabolic syndrome in patients with congestive heart failure (CHF).

Methods

Fasting blood samples were obtained from 93 patients in our institution. Plasma levels of Nt-proBNP and other biochemical data were measured. The New York Heart Association (NYHA) classification system (I-IV) was used to define the functional capacity of CHF. Metabolic syndrome and its components were defined using diagnostic criteria from the International Diabetes Federation.

Results

Forty-nine patients (52.7%) had CHF. There was a positive correlation between plasma Nt-proBNP levels and NYHA functional capacity in CHF patients. Plasma Nt-proBNP levels increased significantly with each increasing NYHA class of the disease. The prevalence of metabolic syndrome in CHF patients was higher than that in patients without CHF. Most importantly, we found that plasma Nt-proBNP levels were lower in CHF patients with metabolic syndrome attributable to inverse relationships between plasma Nt-proBNP and body mass index (β = −0.297), plasma triglyceride (β = −0.286) and homeostasis model assessment of insulin resistance (HOMA-IR; β = −0.346). Fasting glucose to insulin ratio (FGIR, an insulin sensitivity index) was positively associated with plasma Nt-proBNP levels (β = 0.491), and was the independent predictor of plasma Nt-proBNP levels in CHF patients.

Conclusions

Plasma Nt-proBNP levels are inversely associated with metabolic syndrome in CHF patients. Reduced plasma Nt-proBNP levels in CHF patients may lead to impaired lipolysis and metabolic function, and may contribute to the development of metabolic syndrome in CHF patients.     

Aliskiren Attenuates Steatohepatitis and Increases Turnover of Hepatic Fat in Mice Fed with a Methionine and Choline Deficient Diet

Background & Aims

Activation of the renin-angiotensin-system is known to play a role in nonalcoholic steatohepatitis. Renin knockout mice manifest decreased hepatic steatosis. Aliskiren is the first direct renin inhibitor to be approved for clinical use. Our study aims to evaluate the possible therapeutic effects and mechanism of the chronic administration of aliskiren in a dietary steatohepatitis murine model.

Methods

Male C57BL/6 mice were fed with a methionine and choline-deficient (MCD) diet to induce steatohepatitis. After 8 weeks of feeding, the injured mice were randomly assigned to receive aliskiren (50 mg_·kg^-1 per day) or vehicle administration for 4 weeks. Normal controls were also administered aliskiren (50 mg_·kg^-1 per day) or a vehicle for 4 weeks.

Results

In the MCD mice, aliskiren attenuated hepatic steatosis, inflammation and fibrosis. Aliskiren did not change expression of lipogenic genes but increase turnover of hepatic fat by up-regulating peroxisome proliferator-activated receptor α, carnitine palmitoyltransferase 1a, cytochrome P450-4A14 and phosphorylated AMP-activated protein kinase. Furthermore, aliskiren decreased the hepatic expression of angiotensin II and nuclear factor κB. The levels of oxidative stress, hepatocyte apoptosis, activation of Kupffer cells and hepatic stellate cells, and pro-fibrotic markers were also reduced in the livers of the MCD mice receiving aliskiren.

Conclusions

Aliskiren attenuates steatohepatitis and fibrosis in mice fed with a MCD diet. Thus, the noted therapeutic effects might come from not only the reduction of angiotensin II but also the up-regulation of fatty acid oxidation-related genes.