The intracellular domain of sortilin interacts with Amyloid precursor protein and regulates its lysosomal and lipid raft trafficking

The processing of Amyloid precursor protein (APP) is multifaceted, comprising of protein transport, internalization and sequential proteolysis. However, the exact mechanism of APP intracellular trafficking and distribution remains unclear. To determine the interaction between sortilin and APP and the effect of sortilin on APP trafficking and processing, we studied the binding site and its function by mapping experiments, colocalization, coimmunoprecipitation and sucrose gradient fractionation. We identified for the first time that sortilin interacts with APP at both N- and C-terminal regions. The sortilin-FLVHRY (residues 787-792) and APP-NPTYKFFE (residues 759-766) motifs are crucial for the C-terminal interaction. We also found that lack of the FLVHRY motif reduces APP lysosomal targeting and increases APP distribution in lipid rafts in co-transfected HEK293 cells. These results are consistent with our in vivo data where sortilin knockout mice showed a decrease of APP lysosomal distribution and an increase of APP in lipid rafts. We further confirmed that overexpression of sortilin-FLVHRY mutants failed to rescue the lysosomal degradation of APP. Thus, our data suggests that sortilin is implicated in APP lysosomal and lipid raft targeting via its carboxyl-terminal F/YXXXXF/Y motif. Our study provides new molecular insights into APP trafficking and processing.Miao Yang, Balaji Virassamy, Swarna Lekha Vijayaraj, Yoon Lim, Khalil Saadipour, Yan- Jiang Wang, Yan-Chuang Han, Jin-Hua Zhong, Carlos R. Morales, Xin-Fu Zho

Dysregulation of neuronal iron homeostasis as an alternative unifying effect of mutations causing familial Alzheimer's disease

The overwhelming majority of dominant mutations causing early onset familial Alzheimer's disease (EOfAD) occur in only three genes, PSEN1, PSEN2, and APP. An effect-in-common of these mutations is alteration of production of the APP-derived peptide, amyloid ß (Aß). It is this key fact that underlies the authority of the Amyloid Hypothesis that has informed Alzheimer's disease research for over two decades. Any challenge to this authority must offer an alternative explanation for the relationship between the PSEN genes and APP. In this paper, we explore one possible alternative relationship - the dysregulation of cellular iron homeostasis as a common effect of EOfAD mutations in these genes. This idea is attractive since it provides clear connections between EOfAD mutations and major characteristics of Alzheimer's disease such as dysfunctional mitochondria, vascular risk factors/hypoxia, energy metabolism, and inflammation. We combine our ideas with observations by others to describe a "Stress Threshold Change of State" model of Alzheimer's disease that may begin to explain the existence of both EOfAD and late onset sporadic (LOsAD) forms of the disease. Directing research to investigate the role of dysregulation of iron homeostasis in EOfAD may be a profitable way forward in our struggle to understand this form of dementia

p75NTR ectodomain is a physiological neuroprotective molecule against amyloid-beta toxicity in the brain of Alzheimer's disease

In Alzheimer's disease (AD), neurodegenerative signals such as amyloid-beta (Aβ) and the precursors of neurotrophins, outbalance neurotrophic signals, causing synaptic dysfunction and neurodegeneration. The neurotrophin receptor p75 (p75NTR) is a receptor of Aβ and mediates Aβ-induced neurodegenerative signals. The shedding of its ectodomain from the cell surface is physiologically regulated; however, the function of the diffusible p75NTR ectodomain (p75ECD) after shedding remains largely not known. Here, we show that p75ECD levels in cerebrospinal fluid and in the brains of Alzheimer's patients and amyloid-beta precursor protein (APP)/PS1 transgenic mice were significantly reduced, due to inhibition of the sheddase-tumor necrosis factor-alpha-converting enzyme by Aβ. Restoration of p75ECD to the normal level by brain delivery of the gene encoding human p75ECD before or after Aβ deposition in the brain of APP/PS1 mice reversed the behavioral deficits and AD-type pathologies, such as Aβ deposit, apoptotic events, neuroinflammation, Tau phosphorylation and loss of dendritic spine, neuronal structures and synaptic proteins. Furthermore, p75ECD can also reduce amyloidogenesis by suppressing β-secretase expression and activities. Our data demonstrate that p75ECD is a physiologically neuroprotective molecule against Aβ toxicity and would be a novel therapeutic target and biomarker for AD.X-Q Yao, S-S Jiao, K Saadipour, F Zeng, Q-H Wang, C Zhu, L-L Shen, G-H Zeng, C-R Liang, J Wang, Y-H Liu, H-Y Hou, X Xu, Y-P Su, X-T Fan, H-L Xiao, L-F Lue, Y-Q Zeng, B Giunta, J-H Zhong, DG Walker, H-D Zhou, J Tan, X-F Zhou, and Y-J Wan

Contemplation on Competency-based Curriculum in Medical Education

Introduction: One of the approaches to explaining the relationship between education and the world of work, and reducing the gap between students’ knowledge and their professional needs is competency-based curriculum. Due to its unique characteristics, competency-based curriculum has been noticed recently by educational systems of various countries especially in medical education. Given the importance of competency approach in medical education, this paper attempts to explain this approach. Methods: This paper is a review study. The keywords competence, competency, competency-based curriculum and learning outcomes in the field of medical education were used for searching through the databases of Sagepub, ProQuest, Google Scholar, Magiran and SID from 1990-2014. Results:A total of 52 publications were reviewed. Graduates’ professional needs are of great importance in competency-based curriculum in medical education and elements of the curriculum and competency models are closely tied with these needs in any field. Conclusion: The quality of the educational system could be improved by recognition of the competency approach, the characteristics and elements of the curriculum in this approach, and also the process of designing and planning competency-based curriculum and its implementation

Effect of Short-term Forced Exercise on Naloxone Induced Withdrawal Symptoms in Morphine Addicted Male Rats

ABSTRACT: Introduction & Objective: Opioid dependence has been causing limitation in usage of morphine and other opioid drugs in pain control. The aim of this study was to assess the effect of short-term forced exercise on withdrawal syndrome in morphine addicted male rats. Materials & Methods: This experimental study was done in the physiology research center of Ahwas Jondishapour University of Medical Sciences. Twenty four young male Wistar rats, weighing 200-300gr, were randomly divided into four groups: no addiction and no exercise, no addiction and exercise, addiction and no exercise and addiction and exercise. The exercise groups underwent treadmill forced exercise for ten days. The first five days morphine was administrated (ip) twice daily with increasing dose (5، 10، 20، 40, 50 mg/kg) to addicted groups. Also single dose (50mg/kg) of morphine was administrated to them on the 10th day of exercise. After administration of naloxone hydrochloride the withdrawal symptoms were evaluated for 5 minutes. The findings of this study were analyzed by SPSS software and One- way ANOVA (Tukey) test. Results: The findings of this study showed that the withdrawal symptoms was elevated in exercise and addicted groups in comparison with control group (p<0.05 , p<0.01). However, most of withdrawal symptoms decreased in addicted and exercise group in comparison with addicted and no exercise group (p<0.01, p<0.001). Conclusion: The exercise could increase endogenous opioid and withdrawal symptoms in animals but reduce withdrawal symptoms in addicted and exercise groups compared to addicted and no exercise group. Its mechanism might be related to down regulation and low sensitivity of opioid receptor

Preventive effect of grapefruit juice (Citrus Paradisi Macf.) on morphine withdrawal symptome in male rats

Background & Objective: Addiction to opiates such as morphine is one of major public health problems. It has been shown that in addicted animals, administration of antioxidant agents such as vitamin C can reduce the withdrawal symptoms (WDS). The aim of this study was to evaluate the preventional effect of grapefruit juice (Citrus Paradisi Macf.) on withdrawal symptoms in rats. Materials & Methods: In this experimental study, Sixteen male Wistar rats (250-300g) randomly divided into two groups (n=8). All animals were addicted by intraperitoneal (i.p) injection of morphine (the 1-3 days: 10 mg/kg, the 4-6 days: 20 mg/kg and the 7-9 days 40 mg/kg daily) for 9 days. The first group received 2 ml Citrus Paradisi Macf. orally 1 hour before morphine administration. The sham group received 2 ml of normal saline. Naloxone (10mg/kg, s.c) was administrated 45 minutes after of an additional dose of morphine (40 mg/kg) in the tenth day for withdrawal symptoms inducing. Then withdrawal symptoms such as frequency of wet-dog shaking, teeth chattering, defecation and penis licking were evaluated for 30 minutes. Results: All withdrawal symptoms including frequency of wet-dog shaking, teeth chattering, defecation and penis licking were reduced in the Citrus Paradisi Macf. group in comparison with the sham group significantly (p<0.05). Conclusion: Our results showed that presumably antioxidant activity of Citrus Paradisi Macf. can reduce withdrawal symptoms. Although the exact mechanisms of its effect in brain need to be elucidate

Effects of Ascorbic Acid on the Amplitude of Ventral Tegmental Area Field Action Potential in Morphine-Exposed Rats (An Electrophysiology Study)

Introduction & Objective: Evidences have indicated that the Ventral Tegmental Area (VTA) is the major source of dopamine (DA) neurons projecting to cortical and limbic regions involved in cognitive and motivational aspects of addiction. Also, studies have indicated that the Ascorbic acid (vitamin C) can reduce the dependency symptoms of opioids such as morphine via effect of activity on dopaminergic neuron in VTA. For this reason, the aim of this study was to assess the effects of ascorbic acid on the amplitude of Ventral Tegmental Area field action potential in morphine-exposed rats. Materials & Methods: Forty male Wistar’s rats were used in this experimental study conducted at Yasuj University of Medical Sciences in 2010. Animals were randomly divided into four groups after electrode implantation and recovery period: 1. No- Vit C and No-Addicted group (nVitC.nA) 2. Vit C and No-Addicted group (VitC.nA) 3. No- Vit C and Addicted group (nVitCA) 4.Vit C and Addicted (VitC.A), The Vit C groups received 500 mg/kg of Vit C during 20 days. For addicted groups morphine was administrated once daily for 20 days. In the 20th day, the field potential recording was accomplished. Two-way ANOVA was used for data analysis followed by the Tukey test for post hoc analysis. Results were considered significant at P < 0.05. Results: This study shows the exposure to morphine declined the power of Delta and Beta bands (p<0.05) and Vit C solely enhance power of Theta and Beta (p<0.05, p<0.001) in VTA nuclei. Furthermore, Vit C could alter power of some bands which were affected by morphine. Therefore it seems that Vit C has an increasing effects on them (p<0.05). Conclusion: Although the effect of Vit C on power of the VTA bands is not well known, but it is supposed that this phenomenon can be related to alteration in activity of dopaminergic neuron in the brain

Cellular trafficking of amyloid precursor protein in amyloidogenesis physiological and pathological significance

The accumulation of excess intracellular or extracellular amyloid beta (Aβ) is one of the key pathological events in Alzheimer's disease (AD). Aβ is generated from the cleavage of amyloid precursor protein (APP) by beta secretase-1 (BACE1) and gamma secretase (γ-secretase) within the cells. The endocytic trafficking of APP facilitates amyloidogenesis while at the cell surface, APP is predominantly processed in a non-amyloidogenic manner. Several adaptor proteins bind to both APP and BACE1, regulating their trafficking and recycling along the secretory and endocytic pathways. The phosphorylation of APP at Thr668 and BACE1 at Ser498, also influence their trafficking. Neurotrophins and proneurotrophins also influence APP trafficking through their receptors. In this review, we describe the molecular trafficking pathways of APP and BACE1 that lead to Aβ generation, the involvement of different signaling molecules or adaptor proteins regulating APP and BACE1 subcellular localization. We have also discussed how neurotrophins could modulate amyloidogenesis through their receptors.Noralyn Basco Mañucat-Tan, Khalil Saadipour, Yan-Jiang Wang, Larisa Bobrovskaya and Zhou Xin-F

Cumulus Cell Role on Mouse Germinal Vesicle Oocyte Maturation, Fertilization, and Subsequent Embryo Development to Blastocyst Stage In Vitro

Objective: The purpose of this study is to investigate the effect of cumulus cells on maturation,fertilization and subsequent development of mouse germinal vesicle oocytes.Materials and Methods: A total of 470 germinal vesicle (GV) oocytes were obtained from26 ovaries of 3- 4 week old ICR female mice 48 hours after injection of 5 IU pregnant mareserum gonadotropin (PMSG). Collected oocytes were divided into two groups; group I: GVoocytes without cumulus cells (denuded oocyte), group II: GV oocytes with cumulus cells(cumulus-oocyte complex). The oocytes in both groups were cultured in TCM-199 mediumsupplemented with 10% fetal bovine serum (FBS) for 22- 24 hours in a humidified atmosphereof 5% CO2 in air at 37°C. Oocyte maturation was scored under inverted microscope.To do in vitro fertilization, matured oocytes from each group were placed in T6 mediumand capacitated spermatozoa were added. Then the fertilized oocytes were cultured andassessed for cleavage to the 2-cell stage 24 hours and production of blastocyst 120 hoursafter fertilization. Data was analyzed by chi-square test and differences in the values wereconsiderable significant when p<0.05.Results: Maturation, fertilization, cleavage and blastocyst rates in denuded oocytes were:76.32%, 57.49%, 51.15% and 19.14% respectively. In the cumulus-oocyte complex rateswere: 89.41%, 80.76%, 75.58% and 45.62% respectively; all in the cumulus-oocyte complexwere significantly higher than those of denuded oocytes (p<0.05).Conclusion: The present study indicates that cumulus cells have important role duringmaturation, fertilization and subsequent embryo development to the blastocyst stage