Yael Herzog

The neuropilins: multifunctional semaphorin and VEGF receptors that modulate axon guidance and angiogenesis.

The neuropilin-1 (np1) and neuropilin-2 (np2) receptors function as receptors for the axon guidance factors belonging to the class-3 semaphorin subfamily. In addition, both neuropilins are able to bind to certain heparin-binding splice forms of vascular endothelial growth factor (VEGF), indicating that both neuropilins have roles in the cardiovascular system as well. Gene targeting experiments indicate that np1 does indeed function as an important modulator of VEGF function during vasculogenesis and angiogenesis, but the role of np2 in the cardiovascular system has not been studied in detail as yet. This review focuses on the neuropilins, their interactions, and their biological roles in the nervous and cardiovascular systems.

Differential expression of neuropilin-1 and neuropilin-2 in arteries and veins

Neuropilin-1 (np1) and neuropilin-2 (np2) are receptors for class-3 semaphorins and for several isoforms of VEGF. We have cloned and characterized two chick isoforms of np2 cDNA. Expression patterns of np1, np2, and ephrin-B2 were compared in the developing vascular system of 24-72 h old chick embryos. We show for the first time that np2 is expressed in blood vessels in vivo from the earliest stages of their formation. In contrast to ephrin-B2, both np1 and np2 are expressed in blood islands of 24 h old chick embryos. At 48-72 h, np1 expression is localized preferentially in arteries with an expression pattern that resembles that of ephrin-B2. In contrast, np2 is expressed preferentially in veins. Thus, neuropilins may play a role in determining the arterial or venous identity of blood vessels.

The interaction of Neuropilin-1 and Neuropilin-2 with tyrosine-kinase receptors for VEGF.

The Neuropilin-1 (NRP1) and Neuropilin-2 (NRP2) receptors were initially described as receptors for axon guidance factors belonging to the class-3 Semaphorin sub-family. Subsequently, it was found the Neuropilins also function as receptors for some forms of vascular endothelial growth factor (VEGF). VEGF165 binds to both NRP1 and to NRP2 but VEGF121, does not bind to either of these receptors. VEGF145 on the other hand, binds to NRP2 but not to NRP1. Additional VEGF family members such as the heparin binding form of placenta growth factor (PlGF-2) and VEGF-B bind to NRP1, and it was also shown that both PlGF-2 and VEGF-C bind to NRP2. The intracellular domains of the Neuropilins are short, and do not suffice for independent transduction of biological signals subsequent to Semaphorin or VEGF binding. It was shown that both Neuropilins can form complexes with receptors belonging to the Plexin family, and that such Plexin/Neuropilin complexes are able to transduce signals following the binding of class-3 Semaphorins to Neuropilins. The VEGF165 induced proliferation and migration of cells that express the VEGF tyrosine-kinase receptor VEGFR2 is enhanced in the presence of NRP1, suggesting that Neuropilins may also form complexes with VEGF tyrosine-kinase receptors such as VEGFR2. However, it is not yet clear whether VEGFR2 and NRPI form complexes and contrasting results have been reported with regard to this issue. In contrast, it was recently reported by two laboratories that Neuropilins can form complexes with the second tyrosine-kinase receptor of VEGF, VEGFR1. However, the biological function of these complexes is still unclear.

Phosphatidylserine containing ω-3 fatty acids may improve memory abilities in non-demented elderly with memory complaints: a double-blind placebo-controlled trial.

Background: Phosphatidylserine (PS) may have beneficial effects on cognitive functions. We evaluated the efficacy of a novel preparation of PS containing ω–3 long-chain polyunsaturated fatty acids attached to its backbone (PS-DHA) in non-demented elderly with memory complaints. Methods: 157 participants were randomized to receive either PS-DHA or placebo for 15 weeks. Efficacy measures, assessed at baseline and endpoint, included the Rey Auditory Verbal Learning Test, Rey Complex Figure Test, and a computerized cognitive battery. Clinicians’ Global Impression of Change was assessed following 7 and 15 weeks of treatment. Results: 131 participants completed the study although 9 were excluded from the efficacy analysis due to protocol violation. At endpoint, verbal immediate recall was significantly improved in the PS-DHA group compared to the placebo group. Post-hoc analysis revealed that a subset of participants with relatively good cognitive performance at baseline had significant treatment-associated improvements in immediate and delayed verbal recall, learning abilities, and time to copy complex figure. These favorable results were further supported by responder analysis. Conclusions: The results indicate that PS-DHA may improve cognitive performance in non-demented elderly with memory complaints. Post-hoc analysis of subgroups suggests that participants with higher baseline cognitive status were most likely to respond to PS-DHA. The results of this exploratory study should be followed up by additional studies aimed at confirming the present tentative conclusions.

Neuropilin-2 is a novel marker expressed in pancreatic islet cells and endocrine pancreatic tumours.

Neuropilin‐2 (NP‐2) is a cell surface transmembrane protein originally characterized as a receptor for the type 3 semaphorins, and more recently for a number of vascular endothelial growth factor (VEGF) isoforms. NP‐2 expression has been recently localized to a subset of neuroendocrine cells in the gastrointestinal tract. The aim of this study was to define the expression pattern of NP‐2 in normal pancreatic islets and to determine the utility of NP‐2 expression as a diagnostic marker of pancreatic endocrine tumours. Paraffin‐embedded tissue sections from 30 endocrine pancreatic tumours (EPTs) and from normal pancreas were immunostained with a rabbit polyclonal antibody generated towards NP‐2. Nineteen of the tumours were hormonally functional (nine insulinomas, nine gastrinomas, and one glucagonoma). The NP‐2 staining pattern was correlated with islet cell hormone expression. In addition, NP‐2 expression was evaluated in other normal neuroendocrine tissues and neuroendocrine neoplasms. In normal pancreas, NP‐2 stained a distinct subset of islet cells situated primarily at the islet periphery. Double immunohistochemical staining revealed co‐localization with glucagon‐expressing cells. Moderate to strong NP‐2 staining was present in 27 of 30 EPTs. Serial staining of the pancreatic tumours with insulin, gastrin, glucagon, pancreatic polypeptide (PP) or somatostatin did not reveal a distinct pattern of co‐localization. NP‐2 expression was not detected in neuroendocrine cells outside the gastroenteropancreatic system, or in their corresponding neoplasms, except for focal staining in one bronchial carcinoid tumour. In conclusion, the vast majority of EPTs examined expressed NP‐2, suggesting its utility as a diagnostic marker for these tumours. The function of NP‐2 in islet cell biology or tumourigenesis remains to be elucidated. Copyright

Segregation of arterial and venous markers in subpopulations of blood islands before vessel formation

The neuropilin‐1 (np1) and the neuropilin‐2 (np2) receptors bind vascular endothelial growth factor (VEGF) and class‐3 semaphorins. They form complexes with VEGF tyrosine‐kinase receptors or alternatively with type‐A plexins to transduce respective VEGF or semaphorin signals. We have compared the expression patterns of np1, np2, plexin‐A1, and plexin‐A2 in the emerging vasculature of chick embryos. Double in situ hybridization reveals that six‐somite embryos contain intermingled extraembryonic blood island (BI) subpopulations that express np1 or np2 as well as a BI subpopulation that coexpresses both neuropilins. In 13‐somite embryos, which already contain an extraembryonic vascular plexus, the expression of np1 and np2 is segregated between the arterial and venous parts of the plexus, despite the absence of blood flow. However, the arterial marker ephrin‐B2 was not yet expressed in the plexus at this stage. In 26‐somite embryos, which possess a functional vascular system, np1 and np2 are differentially expressed in arteries and veins as previously reported. At this stage, posterior BIs expressing np2 appear to undergo fusion to form the posterior sinus vein and its tributaries, suggesting that the venous identity of these veins may be established before their formation. The neuropilin coreceptor plexin‐A2 was expressed in extraembryonic veins but not in extraembryonic arteries. In contrast, within the embryo, plexin‐A2 expression was observed in the dorsal aorta as well as in the cardinal vein. Semaphorin‐3F (s3f), an np2 ligand, bound to np2‐expressing cells in 26‐somite embryos regardless of the presence or absence of plexin‐A1 or plexin‐A2. Of interest, even though s3f binds to np1 in vitro, np1‐expressing arteries fail to bind s3f in whole‐mount binding experiments. Developmental Dynamics 232:1047–1055, 2005.

The effect of phosphatidylserine-containing omega-3 fatty acids on memory abilities in subjects with subjective memory complaints: a pilot study

Objective: To evaluate for the first time the efficacy of safe-sourced phosphatidylserine-containing omega-3 long chain polyunsaturated fatty acid (PS-omega-3) in improving memory abilities. Methods: PS-omega-3 was administered daily for 6 weeks to eight elderly volunteers with subjective memory complaints. The Cognitive Drug Research test battery was used to assess the effect on their cognitive abilities. Results: PS-omega-3 supplementation resulted in 42% increase in the ability to recall words in the delayed condition. Conclusion: PS-omega-3 may have a favorable effect on memory in subjects with subjective memory complaints. PS-omega-3 may serve as a safe alternative to phosphatidylserine extracted from bovine cortex.

The effect of soybean-derived phosphatidylserine on cognitive performance in elderly with subjective memory complaints: a pilot study

Objective To evaluate the efficacy and safety of soybean-derived phosphatidylserine (SB-PS) (300 mg/day) in improving cognitive performance in elderly with memory complaints, following a short duration of 12 weeks’ SB-PS administration. Methods SB-PS was administered daily for 12 weeks to 30 elderly volunteers with memory complaints (age range 50–90 years). Cognitive performance was determined by a computerized test battery and by the Rey Auditory Verbal Learning Test (Rey-AVLT). Physical examination and blood safety parameters were part of the extensive safety analysis of PS that was performed. Results The computerized test results showed that SB-PS supplementation significantly increased the following cognitive parameters: memory recognition (P = 0.004), memory recall (P = 0.006), executive functions (P = 0.004), and mental flexibility (P = 0.01). The Rey-AVLT indicated that, following SB-PS administration, total learning and immediate recall improved significantly (P = 0.013 and P = 0.007, respectively). Unexpected results from the safety tests suggested that SB-PS significantly reduces both systolic (P = 0.043) and diastolic (P = 0.003) blood pressure. SB-PS consumption was well tolerated and no serious adverse events were reported during the study. Conclusion This exploratory study demonstrates that SB-PS may have favorable effects on cognitive function in elderly with memory complaints. In addition, the study suggests that SB-PS is safe for human consumption and may serve as a safe alternative to phosphatidylserine extracted from bovine cortex. These results encourage further extended studies in order to establish the safety and efficacy of SB-PS treatment.

Phosphatidylserine Containing Omega-3 Fatty Acids May Improve Memory Abilities in Nondemented Elderly Individuals with Memory Complaints: Results from an Open-Label Extension Study

Background: The present study is an open-label extension (OLE) aimed at evaluating the effect of 100 mg/day of phosphatidylserine enriched with docosahexaenoic acid (PS-DHA) on cognitive performance in nondemented elderly individuals with memory complaints. Methods: From the participants who completed the core study, 122 continued with a 15-week OLE. Efficacy was assessed using a computerized tool and the Clinical Global Impression of Change (CGI-C) rating scale. Results: A significant improvement in sustained attention and memory recognition was observed in the PS-DHA naïve group, while the PS-DHA continuers maintained their cognitive status. Additionally, a significant improvement in CGI-C was observed in the naïve group. Conclusions: The results demonstrate that consumption of 100 mg/day of PS-DHA might be associated with improving or maintaining cognitive status in elderly subjects with memory complaints.

Safety of phosphatidylserine containing omega-3 fatty acids in non-demented elderly: a double-blind placebo-controlled trial followed by an open-label extension

BackgroundPhosphatidylserine (PS) is a naturally occurring phospholipid present in the inner leaflet of mammalian plasma membranes. Administration of PS extracted from bovine cortex (BC-PS), which contains high levels of omega-3 long chain polyunsaturated fatty acid (LC-PUFA) attached to its backbone, resulted in positive effects on brain functions such as learning and memory. Recently, a novel marine-sourced PS with omega-3 LC-PUFA attached to its backbone was developed (PS-DHA). In the present study, we evaluated the safety profile of the novel PS preparation in non-demented elderly with memory complaints. The efficacy study of this novel formulation indicated that PS-DHA may ameliorate cognitive deficits in non-demented elderly population.Methods157 non-demented elderly participants with memory complaints were randomized to receive either PS-DHA (300 mg PS/day) or placebo for 15 weeks. Standard biochemical and hematological safety parameters, blood pressure and heart rate were evaluated at baseline and endpoint. 122 participants continued into an open-label extension for additional 15 weeks, in which they all consumed PS-DHA (100 mg PS/day) and were evaluated for their blood pressure, heart rate and weight at endpoint. Adverse events were monitored throughout the double-blind and open-label phases.Results131 participants completed the double-blind phase. No significant differences were found in any of the tested safety parameters between the study groups, or within each group. 121 participants completed the open-label phase. At the end of this phase, there was a reduction in resting diastolic blood pressure and a slight weight gain among participants who consumed PS-DHA for 30 weeks.ConclusionsThe results of this study indicate that consumption of PS-DHA at a dosage of 300 mg PS/day for 15 weeks, or 100 mg PS/day for 30 weeks, is safe, well tolerated, and does not produce any negative effects in the tested parameters.Trial registrationclinicaltrials. gov, identifier: NCT00437983