APP Regulates NGF Receptor Trafficking and NGF-Mediated Neuronal Differentiation and Survival

β-amyloid precursor protein (APP) is a key factor in Alzheimer''s disease (AD) but its physiological function is largely undetermined. APP has been found to regulate retrograde transport of nerve growth factor (NGF), which plays a crucial role in mediating neuronal survival and differentiation. Herein, we reveal the mechanism underlying APP-mediated NGF trafficking, by demonstrating a direct interaction between APP and the two NGF receptors, TrkA and p75NTR. Downregulation of APP leads to reduced cell surface levels of TrkA/p75NTR and increased endocytosis of TrkA/p75NTR and NGF. In addition, APP-deficient cells manifest defects in neurite outgrowth and are more susceptible to Aβ-induced neuronal death at physiological levels of NGF. However, APP-deficient cells show better responses to NGF-stimulated differentiation and survival than control cells. This may be attributed to increased receptor endocytosis and enhanced activation of Akt and MAPK upon NGF stimulation in APP-deficient cells. Together, our results suggest that APP mediates endocytosis of NGF receptors through direct interaction, thereby regulating endocytosis of NGF and NGF-induced downstream signaling pathways for neuronal survival and differentiation.     

Tryptanthrin Inhibits Angiogenesis by Targeting the VEGFR2-Mediated ERK1/2 Signalling Pathway

Angiogenesis is a key step for tumour growth and metastasis, and anti-angiogenesis has been proposed as an important strategy for cancer therapy. Tryptanthrin is a weakly basic alkaloid isolated from the dried roots of medicinal indigo plants and has been shown to possess anti-tumour activities on various cancer cell types. This study aims to investigate the in vitro and in vivo anti-angiogenic activities of tryptanthrin and to unravel its underlying molecular action mechanisms. Our results show that tryptanthrin inhibited the in vitro proliferation, migration, and tube formation of the human microvascular endothelial cells (HMEC-1) in a concentration-dependent manner and significantly suppressed angiogenesis in Matrigel plugs in mice. Mechanistic studies indicated that tryptanthrin reduced the expression of several pro-angiogenic factors (Ang-1, PDGFB and MMP2). Tryptanthrin was also found to suppress the VEGFR2-mediated ERK1/2 signalling pathway in HMEC-1 cells and molecular docking simulation indicated that tryptanthrin could bound to the ATP-binding site of VEGFR2. Collectively, the present study demonstrated that tryptanthrin exhibited both in vitro and in vivo anti-angiogenic activities by targeting the VEGFR2-mediated ERK1/2 signalling pathway and might have therapeutic potential for the treatment of angiogenesis-related diseases.     

Real-Time Fluorescence Loop Mediated Isothermal Amplification for the Detection of Acinetobacter baumannii

Background

Detection of Acinetobacter baumannii has been relying primarily on bacterial culture that often fails to return useful results in time. Although DNA-based assays are more sensitive than bacterial culture in detecting the pathogen, the molecular results are often inconsistent and challenged by doubts on false positives, such as those due to system- and environment-derived contaminations. In addition, these molecular tools require expensive laboratory instruments. Therefore, establishing molecular tools for field use require simpler molecular platforms. The loop-mediated isothermal amplification method is relatively simple and can be improved for better use in a routine clinical bacteriology laboratory. A simple and portable device capable of performing both the amplification and detection (by fluorescence) of LAMP in the same platform has been developed in recent years. This method is referred to as real-time loop-mediated isothermal amplification. In this study, we attempted to utilize this method for rapid detection of A. baumannii.

Methodology and Significant Findings

Species-specific primers were designed to test the utility of this method. Clinical samples of A. baumannii were used to determine the sensitivity and specificity of this system compared to bacterial culture and a polymerase chain reaction method. All positive samples isolated from sputum were confirmed to be the species of Acinetobacter by 16S rRNA gene sequencing. The RealAmp method was found to be simpler and allowed real-time detection of DNA amplification, and could distinguish A. baumannii from Acinetobacter calcoaceticus and Acinetobacter genomic species 3. DNA was extracted by simple boiling method. Compared to bacterial culture, the sensitivity and specificity of RealAmp in detecting A. baumannii was 98.9% and 75.0%, respectively.

Conclusion

The RealAmp assay only requires a single unit, and the assay positivity can be verified by visual inspection. Therefore, this assay has great potential of field use as a molecular tool for detection of A. baumannii.     

Salt-Restriction-Spoon Improved the Salt Intake among Residents in China

Objective

To evaluate the effect of an improved salt-restriction spoon on the attitude of salt-restriction, the using rate of salt-restriction-spoon, the actual salt intake, and 24-hour urinary sodium excretion (24HUNa).

Design

A community intervention study.

Setting

Two villages in Beijing.

Participants

403 local adult residents being responsible for home cooking.

Intervention

Participants were randomly assigned to the intervention group or the control group. Those in the intervention group were provided with an improved salt-restriction-spoon and health education, and were informed of their actual salt intake and 24HUNa. Not any intervention was given to those in the control group.

Main Outcome Measures

The scores on the variables of Health Belief Model, the using rate of salt-restriction-spoon, the actual salt intake, and 24HUNa.

Analysis

Covariance analyses, Chi-square tests, Student’s t tests, and repeated measures analyses of variance.

Results

After 6 months of intervention, the intervention group felt significantly less objective barriers, and got access to significantly more cues to action as compared to the control group. The using rate and the correctly using rate of salt-restriction-spoon were significantly higher in the intervention group. The daily salt intake decreased by 1.42 g in the intervention group and by 0.28 g in the control group, and repeated measures analysis of variance showed significant change over time (F = 7.044, P<0.001) and significant difference between groups by time (F = 2.589, P = 0.041). The 24HUNa decreased by 34.84 mmol in the intervention group and by 33.65 mmol in the control group, and repeated measures analysis of variance showed significant change over time (F = 14.648, P<0.001) without significant difference between groups by time (F = 0.222, P = 0.870).

Conclusions

The intervention effect was acceptable, therefore, the improved salt-restriction-spoon and corresponding health education could be considered as an alternative for salt reduction strategy in China and other countries where salt intake comes mainly from home cooking.     

Functional Roles of the Non-Catalytic Calcium-Binding Sites in the N-Terminal Domain of Human Peptidylarginine Deiminase 4

This study investigated the functional roles of the N-terminal Ca²⁺ ion-binding sites, in terms of enzyme catalysis and stability, of peptidylarginine deiminase 4 (PAD4). Amino acid residues located in the N-terminal Ca²⁺-binding site of PAD4 were mutated to disrupt the binding of Ca²⁺ ions. Kinetic data suggest that Asp155, Asp157 and Asp179, which directly coordinate Ca3 and Ca4, are essential for catalysis in PAD4. For D155A, D157A and D179A, the k _cat/K _m,BAEE values were 0.02, 0.63 and 0.01 s⁻¹mM⁻¹ (20.8 s⁻¹mM⁻¹ for WT), respectively. Asn153 and Asp176 are directly coordinated with Ca3 and indirectly coordinated with Ca5 via a water molecule. However, N153A displayed low enzymatic activity with a k _cat value of 0.3 s⁻¹ (13.3 s⁻¹ for wild-type), whereas D176A retained some catalytic power with a k _cat of 9.7 s⁻¹. Asp168 is the direct ligand for Ca5, and Ca5 coordination by Glu252 is mediated by two water molecules. However, mutation of these two residues to Ala did not cause a reduction in the k _cat/K _m,BAEE values, which indicates that the binding of Ca5 may not be required for PAD4 enzymatic activity. The possible conformational changes of these PAD4 mutants were examined. Thermal stability analysis of the PAD4 mutants in the absence or presence of Ca²⁺ indicated that the conformational stability of the enzyme is highly dependent on Ca²⁺ ions. In addition, the results of urea-induced denaturation for the N153, D155, D157 and D179 series mutants further suggest that the binding of Ca²⁺ ions in the N-terminal Ca²⁺-binding site stabilizes the overall conformational stability of PAD4. Therefore, our data strongly suggest that the N-terminal Ca²⁺ ions play critical roles in the full activation of the PAD4 enzyme.     

Serum Uric Acid and Non-Alcoholic Fatty Liver Disease in Non-Diabetic Chinese Men

Increased serum uric acid (SUA) levels may be involved in the development of non-alcoholic fatty liver disease (NAFLD) in men presenting with metabolic syndrome (MetS) and/or insulin resistance. We aimed to determine the independent relationship between SUA and NAFLD in non-diabetic Chinese male population, and to explore the determinants of SUA levels among indexes of adiposity, lipid, and genotypes pertaining to triglycerides metabolism, inflammation, oxidative stress, and SUA concentrations. A total of 1440 men, classified depending on the presence of ultrasonographically detected NAFLD, underwent a complete healthy checkup program. Genotypes were extracted from our previously established genome-wide association study database. After adjusting for age, smoking, drinking, body mass index, homeostasis model assessment of insulin resistance, C-reactive protein, creatinine, alanine aminotransferase (ALT) and components of metabolic syndrome, the odds ratio for NAFLD, comparing the highest with the lowest SUA quartile, was 2.81 (95% confidence interval 1.66–4.76). A stepwise multivariate linear regression analysis (R² = 0.238, P<0.001) retained age, waist circumference, serum creatinine, triglycerides, the Q141K variant in ABCG2 (rs2231142) and NAFLD as significant predictors of SUA levels (all P<0.001). Besides, ALT and Met196Arg variant in TNFRSF1B (rs1061622) additionally associated with SUA among individuls with NAFLD. Our data suggest that in Chinese men, elevated SUA is significantly associated with NAFLD, independent of insulin resistance and other metabolic disorders, such as central obesity or hypertriglyceridemia. Meanwhile, among subjects with NAFLD, index of liver damage, such as elevated ALT combined with genetic susceptibility to inflammation associated with increased SUA levels.     

The Relationship between Polyamines and Hormones in the Regulation of Wheat Grain Filling

The grain weight of wheat is strongly influenced by filling. Polyamines (PA) are involved in regulating plant growth. However, the effects of PA on wheat grain filling and its mechanism of action are unclear. The objective of the present study was to investigate the relationship between PAs and hormones in the regulation of wheat grain filling. Three PAs, spermidine (Spd), spermine (Spm), and putrescine (Put), were exogenously applied, and the grain filling characteristics and changes in endogenous PA and hormones, i.e., indole-3-acetic acid (IAA), zeatin (Z) + zeatin riboside (ZR), abscisic acid (ABA), ethylene (ETH) and gibberellin 1+4 (GAs), were quantified during wheat grain filling. Exogenous applications of Spd and Spm significantly increased the grain filling rate and weight, but exogenous Put had no significant effects on these measures. Exogenous Spd and Spm significantly increased the endogenous Spd, Spm, Z+ZR, ABA, and IAA contents and significantly decreased ETH evolution in grains. The endogenous Spd, Spm and Z+ZR contents were positively and significantly correlated with the grain filling rate and weight of wheat, and the endogenous ETH evolution was negatively and significantly correlated with the wheat grain filling rate and weight. Based upon these results, we concluded that PAs were involved in the balance of hormones that regulated the grain filling of wheat.     

Single Intraperitoneal Injection of Monocrotaline as a Novel Large Animal Model of Chronic Pulmonary Hypertension in Tibet Minipigs

Objective

The purpose of this study was to establish an animal model of chronic pulmonary hypertension with a single-dose intraperitoneal injection of monocrotaline (MCT) in young Tibet minipigs, so as to enable both invasive and noninvasive measurements and hence facilitate future studies.

Methods

Twenty-four minipigs (8-week-old) were randomized to receive single-dose injection of 12.0 mg/kg MCT (MCT group, n = 12) or placebo (control group, n = 12 each). On day 42, all animals were evaluated for pulmonary hypertension with conventional transthoracic echocardiography, right heart catheterization (RHC), and pathological changes. Findings of these studies were compared between the two groups.

Results

At echocardiography, the MCT group showed significantly higher pulmonary arterial mean pressure (PAMP) compared with the controls (P<0.001). The pulmonary valve curve showed v-shaped signals with reduction of a-waves in minipigs treated with MCT. In addition, the MCT group had longer pulmonary artery pre-ejection phases, and shorter acceleration time and ejection time. RHC revealed higher mean pulmonary arterial pressure (mPAP) in the MCT group than in the control group (P<0.01). A significant and positive correlation between the mPAP values and the PAMP values (R = 0.974, P<0.0001), and a negative correlation between the mPAP and ejection time (R = 0.680, P<0.0001) was noted. Pathology demonstrated evidence of pulmonary vascular remodeling and higer index of right ventricular hypertrophy in MCT-treated minipigs.

Conclusion

A chronic pulmonary hypertension model can be successfully established in young minipigs at six weeks after MCT injection. These minipig models exhibited features of pulmonary arterial hypertension that can be evaluated by both invasive (RHC) and noninvasive (echocardiography) measurements, and may be used as an easy and stable tool for future studies on pulmonary hypertension.     

Novel PRRT2 mutations in paroxysmal dyskinesia patients with variant inheritance and phenotypes

Paroxysmal dyskinesias (PDs) are a group of episodic movement disorders with marked variability in clinical manifestation and potential association with epilepsy. PRRT2 has been identified as a causative gene for PDs, but the phenotypes and inheritance patterns of PRRT2 mutations need further clarification. In this study, 10 familial and 21 sporadic cases with PDs and PDs‐related phenotypes were collected. Genomic DNA was screened for PRRT2 mutations by direct sequencing. Seven PRRT2 mutations were identified in nine (90.0%) familial cases and in six (28.6%) sporadic cases. Five mutations are novel: two missense mutations (c.647C>G/p.Pro216Arg and c.872C>T/p.Ala291Val) and three truncating mutations (c.117delA/p.Val41TyrfsX49, c.510dupT/p.Leu171SerfsX3 and c.579dupA/p.Glu194ArgfsX6). Autosomal dominant inheritance with incomplete penetrance was observed in most of the familial cases. In the sporadic cases, inheritance was heterogeneous including recessive inheritance with compound heterozygous mutations, inherited mutations with incomplete parental penetrance and de novo mutation. Variant phenotypes associated with PRRT2 mutations, found in 36.0% of the affected cases, included febrile convulsions, epilepsy, infantile non‐convulsive seizures (INCS) and nocturnal convulsions (NC). All patients with INCS or NC, not reported previously, displayed abnormalities on electroencephalogram (EEG). No EEG abnormalities were recorded in patients with classical infantile convulsions and paroxysmal choreoathetosis (ICCA)/paroxysmal kinesigenic dyskinesia (PKD). Our study further confirms that PRRT2 mutations are the most common cause of familial PDs, displaying both dominant and recessive inheritance. Epilepsy may occasionally occur in ICCA/PKD patients with PRRT2 mutations. Variant phenotypes INCS or NC differ from classical ICCA/PKD clinically and electroencephalographically. They have some similarities with, but not identical to epilepsy, possibly represent an overlap between ICCA/PKD and epilepsy .