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AbstractThe anterior cingulate cortex (ACC) processes the affective component of pain, whereas the primary somatosensory cortex (S1) is involved in its sensory-discriminative component. Injection of morphine in the ACC has been reported to be analgesic, and endogenous opioids in this area are required for pain relief. Mu opioid receptors (MORs) are expressed in both ACC and S1; however, the identity of MOR-expressing cortical neurons remains unknown. Using the Oprm1-mCherry mouse line, we performed selective patch clamp recordings of MOR+ neurons, as well as immunohistochemistry with validated neuronal markers, to determine the identity and laminar distribution of MOR+ neurons in ACC and S1. We found that the electrophysiological signatures of MOR+ neurons differ significantly between these 2 areas, with interneuron-like firing patterns more frequent in ACC. While MOR+ somatostatin interneurons are more prominent in ACC, MOR+ excitatory neurons and MOR+ parvalbumin interneurons are more prominent in S1. Our results suggest a differential contribution of MOR-mediated modulation to ACC and S1 outputs. We also found that females had a greater density of MOR+ neurons compared with males in both areas. In summary, we conclude that MOR-dependent opioidergic signaling in the cortex displays sexual dimorphisms and likely evolved to meet the distinct function of pain-processing circuits in limbic and sensory cortical areas.

Summary: The ability of the mammalian brain to maintain spatial representations of external or internal information for short periods of time has been associated with sustained neuronal spiking and reverberatory neural network activity in the medial entorhinal cortex. Here, we show that conditional genetic deletion of netrin-1 or the netrin receptor deleted-in-colorectal cancer (DCC) from forebrain excitatory neurons leads to deficits in short-term spatial memory. We then demonstrate that conditional deletion of either netrin-1 or DCC inhibits cholinergic persistent firing and show that cholinergic activation of muscarinic receptors expressed by entorhinal cortical neurons promotes persistent firing by recruiting DCC to the plasma membrane. Together, these findings indicate that normal short-term spatial memory function requires the synergistic actions of acetylcholine and netrin-1.

Chronic pain is a significant global socioeconomic burden with limited long-term treatment options. The intractable nature of chronic pain stems from two primary factors: the multifaceted nature of pain itself and an insufficient understanding of the diverse physiological mechanisms that underlie its initiation and maintenance, in both the peripheral and central nervous systems. The development of novel non-opioidergic analgesic approaches is contingent on our ability to normalize the dysregulated nociceptive pathways involved in pathological pain processing. The anterior cingulate cortex (ACC) stands out due to its involvement in top-down modulation of pain perception, its abnormal activity in chronic pain conditions, and its contribution to cognitive functions frequently impaired in chronic pain states. Here, we review the roles of the monoamines dopamine (DA), norepinephrine (NE), serotonin (5-HT), and other neuromodulators in controlling the activity of the ACC and how chronic pain alters their signaling in ACC circuits to promote pathological hyperexcitability. Additionally, we discuss the potential of targeting these monoaminergic pathways as a therapeutic strategy for treating the cognitive and affective symptoms associated with chronic pain.

Despite the high prevalence of chronic pain as a disease in our society, there is a lack of effective treatment options for patients living with this condition. Gene therapies using recombinant AAVs are a direct method to selectively express genes of interest in target cells with the potential of, in the case of nociceptors, reducing neuronal firing in pain conditions. We designed a recombinant AAV vector expressing cargos whose expression was driven by a portion of the SCN10A (NaV1.8) promoter, which is predominantly active in nociceptors. We validated its specificity for nociceptors in mouse and human dorsal root ganglia and showed that it can drive the expression of functional proteins. Our viral vector and promoter package drove the expression of both excitatory or inhibitory DREADDs in primary human DRG cultures and in whole cell electrophysiology experiments, increased or decreased neuronal firing, respectively. Taken together, we present a novel viral tool that drives expression of cargo specifically in human nociceptors. This will allow for future specific studies of human nociceptor properties as well as pave the way for potential future gene therapies for chronic pain.

The encoding of noxious stimuli into action potential firing is largely mediated by nociceptive free nerve endings. Tissue inflammation, by changing the intrinsic properties of the nociceptive endings, leads to nociceptive hyperexcitability and thus to the development of inflammatory pain. Here, we showed that tissue inflammation–induced activation of the mammalian target of rapamycin complex 2 (mTORC2) triggers changes in the architecture of nociceptive terminals and leads to inflammatory pain. Pharmacological activation of mTORC2 induced elongation and branching of nociceptor peripheral endings and caused long-lasting pain hypersensitivity. Conversely, nociceptor-specific deletion of the mTORC2 regulatory protein rapamycin-insensitive companion of mTOR (Rictor) prevented inflammation-induced elongation and branching of cutaneous nociceptive fibers and attenuated inflammatory pain hypersensitivity. Computational modeling demonstrated that mTORC2-mediated structural changes in the nociceptive terminal tree are sufficient to increase the excitability of nociceptors. Targeting mTORC2 using a single injection of antisense oligonucleotide against Rictor provided long-lasting alleviation of inflammatory pain hypersensitivity. Collectively, we showed that tissue inflammation–induced activation of mTORC2 causes structural plasticity of nociceptive free nerve endings in the epidermis and inflammatory hyperalgesia, representing a therapeutic target for inflammatory pain.

Germline mutations that activate genes in the canonical RAS/MAPK signaling pathway are responsible for rare human developmental disorders known as RASopathies. Here, we analyzed the molecular determinants of Costello syndrome (CS) using a mouse model expressing HRAS p.G12S, patient skin fibroblasts, hiPSC-derived human cardiomyocytes, a HRAS p.G12V zebrafish model, and human fibroblasts expressing lentiviral constructs carrying HRAS p.G12S or HRAS p.G12A mutations. The findings revealed alteration of mitochondrial proteostasis and defective oxidative phosphorylation in the heart and skeletal muscle of CS mice that were also found in the cell models of the disease. The underpinning mechanisms involved the inhibition of the AMPK signaling pathway by mutant forms of HRAS, leading to alteration of mitochondrial proteostasis and bioenergetics. Pharmacological activation of mitochondrial bioenergetics and quality control restored organelle function in HRAS p.G12A and p.G12S cell models, reduced left ventricle hypertrophy in CS mice, and diminished the occurrence of developmental defects in the CS zebrafish model. Collectively, these findings highlight the importance of mitochondrial proteostasis and bioenergetics in the pathophysiology of RASopathies and suggest that patients with CS may benefit from treatment with mitochondrial modulators.

Ventriculocoronary arterial connections are typically found in patients with pulmonary atresia with an intact ventricular septum. This report describes a case of ventriculocoronary arterial connections in a patient with pulmonary atresia with a ventricular septal defect. Our case supports recent data suggesting a primary coronary artery developmental anomaly in pulmonary atresia. (Level of Difficulty: Advanced.)

Copyright of Archives of Cardiovascular Diseases is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Background Pulmonary valve replacement (PVR) often is performed in adults with repaired tetralogy of Fallot (TOF). For patients who have tricuspid regurgitation (TR), tricuspid valve (TV) repair associated to PVR is still debated. Objective We sought to evaluate perioperative factors related to TV repair when performed at the time of PVR in patients with repaired TOF. Methods We retrospectively reviewed 104 patients with repaired TOF (or its equivalent) who underwent PVR (2002-2014). Results Mean age at initial complete correction and at PVR was 20.1 ± 17.2 months and 26.3 ± 9.5 years, respectively. Forty-one patients had significant preoperative TR: 24 were moderate (group M) and 17 were severe (group S). A total of 16 TV repair were performed (8 for each group). Moderate and severe tricuspid regurgitation observed in the first year following the initial complete repair were significantly associated with severe TR at PVR ( P < .001). In group M patients, TR was improved regardless of TV repair, whereas, in group S, residual significant TR was reported in 7 patients who did not have TV repair. No cases were observed for patients who underwent concomitant TV repair ( P = .002). Among these patients with residual significant TR, 2 needed a tricuspid valve replacement. The functional status (New York Heart Association classification) of group S patients was significantly improved by concomitant TV repair. Conclusions In adults with repaired TOF, TV repair is a safe procedure when performed at the time of PVR. If, at mid-term follow-up, there is probably no benefit of TV repair when preoperative TR is moderate, TV repair may improve both tricuspid valve function and functional status of the patients in case of severe preoperative TR. [ABSTRACT FROM AUTHOR]

Copyright of Archives of Cardiovascular Diseases is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Archives of Cardiovascular Diseases is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Archives of Cardiovascular Diseases is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Archives of Cardiovascular Diseases is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Objective: To investigate and measure the functional significance of altered P2Y12 expression in the context of human microglia activation. Methods: We performed in vitro and in situ experiments to measure how P2Y12 expression can influence disease-relevant functional properties of classically activated (M1) and alternatively activated (M2) human microglia in the inflamed brain. Results: We demonstrated that compared to resting and classically activated (M1) human microglia, P2Y12 expression is increased under alternatively activated (M2) conditions. In response to ADP, the endogenous ligand of P2Y12, M2 microglia have increased ligand-mediated calcium responses, which are blocked by selective P2Y12 antagonism. P2Y12 antagonism was also shown to decrease migratory and inflammatory responses in human microglia upon exposure to nucleotides that are released during CNS injury; no effects were observed in human monocytes or macrophages. In situ experiments confirm that P2Y12 is selectively expressed on human microglia and elevated under neuropathologic conditions that promote Th2 responses, such as parasitic CNS infection. Conclusion: These findings provide insight into the roles of M2 microglia in the context of neuroinflammation and suggest a mechanism to selectively target a functionally unique population of myeloid cells in the CNS.

Supplemental Digital Content is available in the text. [ABSTRACT FROM AUTHOR]

Background After congenital heart surgery, delayed sternal closure (DSC) can be used electively to aid in hemodynamic and respiratory stability in the initial postoperative period. Risk factors for DSC have been previously determined for neonates. The purpose of our study was to determine risk factors that may predict the need for DSC in children < 1 year. Patients and methods We retrospectively reviewed records of children < 1 year who underwent open-heart surgery in our institution over a period of 5 years. The criteria for DSC were hemodynamic instability, deterioration of the central venous saturation, metabolic status and/or high ventilatory pressures. In total, 283 patients underwent open-heart surgery during the period and 89 (31.4%) had DSC. Mean age was 3.8 months (± 3.3) and mean weight was 4.8 kg (± 1.8). The major congenital heart diseases encountered were ventricular septal defect ( n = 80), tetralogy of Fallot ( n = 41) and transposition of the great arteries ( n = 38). Ten patients (3.5%) needed sternal reopening during the first postoperative 24 h. Thirteen patients (4.6%) died after the surgery. Results Cardiopulmonary bypass (CPB) time was significantly longer in children who had DSC (189 min ± 68 versus 130 min ± 44, P < 0.001). Among the studied factors, use of hypothermia, preoperative use of prostaglandin, preexistent renal insufficiency, pulmonary hypertension and cyanosis were significantly associated with DSC ( r = 0.406, P < 0.001; r = 0.335, P < 0.001; r = 0.250, P < 0.001; r = 0.164, P = 0.006; respectively). Multivariate analysis determined an age < 7 days, long CPB time, preoperative mechanical ventilation and renal insufficiency as independent risk factors for DSC. The best cut-off value was 147 min (se = 75%, sp = 70%, AUC = 0.79) for CPB time. Conclusion Small age at surgery, long CPB time and altered preoperative condition are highly at risk for DSC in children < 1 year. Further studies are needed to develop a predictive model for the anticipation of sternal closure in this population. [ABSTRACT FROM AUTHOR]

Background Although ventricular septal defect (VSD) is one of the most common congenital heart disease, this defect is not so frequent in adults because of early surgery and spontaneous closure. Complications such as aortic insufficiency, infectious endocarditis or supraventricular arrhythmia are classically described. Purpose The main objective of this study was to determine the outcome of adult patients who were operated for VSD after childhood. Methods We conducted an observational, retrospective and multicenter study including patients operated for VSD from the age of 18 years, over a 15-year period (2000–2015). Overall survival and occurrence of adverse events were analyzed. Results Seventy-three patients were included. Mean age was 37.47 ± 2.1 years with a male predominance (62%). Type 2 VSDs were the most common type encountered. After surgery, overall survival was 92% with a mean follow-up of 6 years. Excluding events occurring during the early postoperative period, overall survival was significantly better in patients operated for isolated VSD than in patients operated for VSD associated with other cardiac injuries (95% versus 92%, P = 0.02). Early postoperative complications were found in 14% of patients (principally atrioventricular block requiring early postoperative permanent pacing). Aortic cross clamp and cardiopulmonary bypass time were significantly lower in patients operated for isolated VSD than in patients with associated lesion. Conclusion As morbi-mortality is low, surgical closure of VSD in adults is not a high-risk intervention. Survival of patients with isolated VSD is better than that of patients with associated cardiac lesions. This last finding advocates for early surgery before the apparition of complications. [ABSTRACT FROM AUTHOR]

The article discusses French Prime Minister Georges Clemenceau and his relations with Japan during World War I. Focus is given to Clemenceau's efforts in getting the Japanese Empire to send troops to Europe to fight alongside the Triple-Entente, an alliance including the Russian Empire, France, and Great Britain. His reasons for a Japanese intervention, the reception of his arguments by Russia and Great Britain, and Japan's interests in the war are mentioned.

Background Although coarctation of the aorta could be suspected prenatally, the diagnosis is not certain before birth and remains difficult in the neonatal period especially when ductus arteriosus is open. 2D strain, a recent echocardiographic tool to assess myocardial performance, allows the early detection of abnormal myocardial deformation. Objective The aim of this study was to assess the accuracy of left ventricular 2D strain to predict aortic coarctation in neonates with patent ductus arteriosus. Patients and Methods This was a single centre prospective study. Neonates with patent ductus arteriosus and prenatal/postnatal suspicion of isthmic coarctation were included. Left ventricular (LV) 2D strain was performed for each patient. Patients were divided into three groups: those who developed coarctation (group 1, n=9), those who had normal aorta after ductal closure (group 2, n=10), and a control group of healthy neonates with patent ductus arteriosus (group 3, n=20). Results The median age of gestation was 38+4 weeks of amenorrhea and the median birth weight was 3.088kg. The inter observer agreement was good for the assessment of LV 2D strain. Although radial strain was significantly decreased in group 1 (17.76 vs 40.19 in group 2, p<0.001), there was only a trend in the alteration of longitudinal and circumferential strain (-16.34 vs -16.84, p=0.059 & -10.41 vs – 13.88, p=0.053 respectively). Conclusion LV 2D strain seems to be effective for the early diagnosis of aortic coarctation before the ductus arteriosus closes. [ABSTRACT FROM AUTHOR]

Background Intra-aortic balloon pump (IABP) is a commonly used method of temporary circulatory support in adults. Despite the availability of paediatric size balloons, the use of IABP in children is currently not widespread. Aims To describe our practice of IABP in children and to review its indications. Methods Single-centre retrospective study. We reviewed the medical records of all paediatric patients (<18 years) who were supported with IABP from April 2010 to April 2015. We compare our practice with those reported in Pubmed (37 articles). Results During this period 7 patients (6 boys) had a circulatory support with IABP. Mean age was 12.1 years (10-14) and mean weight was 46.1kg (30-61). All were mechanically ventilated and received inotropic support at the time of IABP deployment. 2 IABP were started before surgery to treat acute heart failure (1 myocarditis and 1 ischemic condition). The major indication for IABP was postoperative hemodynamic deterioration (n=5). 4 of them were related to suboptimal cardioplegia in a context of left ventricular hypertrophy. Mean duration of IABP support was 7.1 days (2-13). All IABP catheters were inserted through the common femoral artery. No local complication was reported. All IABP were inserted by an intensivist without surgical help. Conclusion IABP is a feasible method in children with acute left ventricular failure. By improving diastolic perfusion of the coronary arteries, IABP is effective especially in case of myocardial ischemia. This life-saving technique has to be associated to conventional medical treatment of refractory low cardiac output. Sometimes, IABP may be an alternative for effective mechanical circulatory support. [ABSTRACT FROM AUTHOR]

Background Levosimendan is an inodilator agent belonging to the family of calcium sensitizer agents. Its positive inotropic and vasodilating properties make it interesting for the treatment of heart failure. Although this inotropic drug is increasingly used in children, a special license is still needed to obtain it in several countries. Aims To report our experience of levosimendan and to analyse its effects in children. Methods It was a single-centre retrospective study. From January 2010 to December 2014, all paediatric patients who received at least one perfusion of levosimendan were included. Levosimendan was administered as continuous infusions at a dose of 0.2 µg/kg/min for 24 hours without any loading dose. Medical records were analyzed for each patient. Results More than 200 patients received levosimendan during the period and more than 300 infusions were performed. No side effect was reported. Levosimendan significantly improved BNP level. Indications of levosimendan infusion were: 1) treatment of postoperative hemodynamic deterioration, 2) preoperative conditioning, 3) treatment of acute heart failure (myocardial ischemia, myocarditis, decompensated cardiomyopathies), 4) treatment of chronic heart failure (cardiomyopathies and failing Fontan). Conclusion Because of the long half-life of its active metabolite, levosimendan has a prolonged effect lasting for up to 7 to 9 days after discontinuation of a 24-hour infusion. Using this drug, the potential of arrhythmia is reduced as total intracellular calcium levels are not raised. This inodilator agent is safe and effective for the treatment of heart failure in children and must be part of the conventional therapeutic arsenal. [ABSTRACT FROM AUTHOR]

Background Animal studies showed that levosimendan protects cardiomyocytes against apoptotic cell death in acute viral myocarditis. In addition to its inotropic properties, levosimendan seems to prevent the detrimental effects of oxidative stress and to limit cardiomyocyte loss. Aim To analyze the outcome of children who received levosimendan for acute or fulminant viral myocarditis. Patients and methods Retrospective single center study covering the period 2007- 2013. All children (<18 years) with viral myocarditis were treated, in association with epinephrine and/or milrinone, with a 24-hours infusion of levosimendan. Clinical, biological and echocardiographic evolutions were analyzed. Results Between 2007 and 2013, 18 successive children were treated, 9 for acute myocarditis and 9 for fulminant myocarditis (according to the international clinicopathological classification). Median age was 4 years (1.1-11) and median weight was 15kg (10-40). BNP level significantly decreased 48 hours after the beginning of the infusion (4599ng/L [2698-9266] vs 1928ng/L [848-4557], p=0.05). No dialysis was necessary. Among the fulminant myocarditis group, 1 patient (11%) required early mechanical circulatory support with a limitation of care due to severe neurologic complications. 13 patients (72%) recovered a LVEF >55% (100% for the acute myocarditis group). 1 patient had heart transplantation 18 months later. Conlusion In our experience, levosimendan was efficient for the inotropic support of acute and fulminant viral myocarditis. We believe that its cardioprotective effect enabled us to limit the use of mechanical assistance (only 11% of the fulminant forms) and allowed a recovering of the cardiac function for the majority of the patients. Although further clinical studies are needed to confirm these data, levosimendan should be systematically considered for the treatment of these critical patients. [ABSTRACT FROM AUTHOR]

Introduction Cardiopulmonary bypass can be responsible for post-operative left ventricular dysfunction. As conventional echographic parameters are not reliable in the post-operative period, we assessed left ventricular function by 2D strain. The main objective of this study was to evaluate the peri-operative feasibility and reliability of 2D strain. The second objective was to assess the impact of aortic cross-clamp duration on echographic parameters. Methods 33 pediatric patients (<18 years) with congenital heart disease undergoing cardiac surgery with cardiopulmonary bypass were included in this prospective single center study. Daily echocardiography was performed from the day before surgery to the sixth post-operative day. Left ventricular ejection fraction (Teichholz and Simpson) and 2D strain (longitudinal, circumferential and radial) were measured. The cohort was then divided into three groups according to aortic cross-clamp duration (<30 min for group 1, 30-80 min for group 2, >80 min for group 3). Results Mean age and weight were 4 years [2-6] and 15kg [10-20]. Mean duration of aortic cross-clamp was respectively 22 min, 56 min and 101 min in groups 1, 2 and 3. Longitudinal, circumferential and radial strains were feasible in 91%, 95% and 95% of the cases respectively, which was similar to conventional parameters (97%). The reliability of 2D strain measurements was better than the one of conventional parameters (intra and inter-observer correlation coefficients: 0.916, p<0.001 and 0.885 p<0.001 for longitudinal strain versus 0.156, p=0.538 and 0.064, p=0.800 for Simpson). The means of longitudinal and circumferential strains over time were significantly different between the three groups (p<0,001) whereas there was no difference for Simpson measurements (p=0,617). Conclusion 2D strain is feasible and more reproducible than echographic parameters in the post-operative period. Post-operative evolution of 2D strain is linked to aortic cross-clamp duration. [ABSTRACT FROM AUTHOR]

Abstract The receptor deleted in colorectal cancer (DCC) and its ligand netrin-1 are essential for axon guidance during development and are expressed by neurons in the mature brain. Netrin-1 recruits GluA1-containing α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs) and is critical for long-term potentiation (LTP) at CA3-CA1 hippocampal Schaffer collateral synapses, while conditional DCC deletion from glutamatergic neurons impairs hippocampal-dependent spatial memory and severely disrupts LTP induction. DCC co-fractionates with the detergent-resistant component of postsynaptic density, yet is enriched in axonal growth cones that differentiate into presynaptic terminals during development. Specific presynaptic and postsynaptic contributions of DCC to the function of mature neural circuits have yet to be identified. Employing hippocampal subregion-specific conditional deletion of DCC, we show that DCC loss from CA1 hippocampal pyramidal neurons resulted in deficits in spatial memory, increased resting membrane potential, abnormal dendritic spine morphology, weaker spontaneous excitatory postsynaptic activity, and reduced levels of postsynaptic adaptor and signaling proteins; however, the capacity to induce LTP remained intact. In contrast, deletion of DCC from CA3 neurons did not induce detectable changes in the intrinsic electrophysiological properties of CA1 pyramidal neurons, but impaired performance on the novel object place recognition task as well as compromised excitatory synaptic transmission and LTP at Schaffer collateral synapses. Together, these findings reveal specific pre- and post-synaptic contributions of DCC to hippocampal synaptic plasticity underlying spatial memory.

P2X receptors constitute a gene family of cation channels gated by extracellular ATP. They mediate fast ionotropic purinergic signaling in neurons and non-excitable cell types in vertebrates. The highly calcium-permeable P2X4 subtype has been shown to play a significant role in cardiovascular physiology, inflammatory responses and neuro-immune communication. We previously reported the discovery of a P2X4-selective antagonist, the small organic compound BX430, with submicromolar potency for human P2X4 receptors and marked species-dependence (Ase et al., 2015). The present study investigates the molecular basis of P2X4 inhibition by the non-competitive blocker BX430 using a structural and functional approach relying on mutagenesis and electrophysiology. We provide evidence for the critical contribution of a single hydrophobic residue located in the ectodomain of P2X4 channel subunits, Ile312 in human P2X4, which determines blockade by BX430. We also show that the nature of this extracellular residue in various vertebrate P2X4 orthologs underlies their specific sensitivity or resistance to the inhibitory effects of BX430. Taking advantage of high-resolution crystallographic data available on zebrafish P2X4, we used molecular dynamics simulation to model the docking of BX430 on an allosteric binding site around Ile315 (zebrafish numbering) in the ectodomain of P2X4. We also observed that the only substitution I312D (human numbering) that renders P2X4 silent by itself has also a profound silencing effect on all other P2X subtypes tested when introduced at homologous positions. The generic impact of this aspartate mutation on P2X function indicates that the pre-TM2 subregion involved is conserved functionally and defines a novel allosteric inhibitory site present in all P2X receptor channels. This conserved structure-channel activity relationship might be exploited for the rational design of potent P2X subtype-selective antagonists of therapeutic value.

Summary: Dynamic trafficking of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid glutamate receptors (AMPARs) to synapses is critical for activity-dependent synaptic plasticity underlying learning and memory, but the identity of key molecular effectors remains elusive. Here, we demonstrate that membrane depolarization and N-methyl-D-aspartate receptor (NMDAR) activation triggers secretion of the chemotropic guidance cue netrin-1 from dendrites. Using selective genetic deletion, we show that netrin-1 expression by excitatory neurons is required for NMDAR-dependent long-term potentiation (LTP) in the adult hippocampus. Furthermore, we demonstrate that application of exogenous netrin-1 is sufficient to trigger the potentiation of excitatory glutamatergic transmission at hippocampal Schaffer collateral synapses via Ca2+-dependent recruitment of GluA1-containing AMPARs, promoting the maturation of immature or nascent synapses. These findings identify a central role for activity-dependent release of netrin-1 as a critical effector of synaptic plasticity in the adult hippocampus. : Glasgow et al. demonstrate depolarization- and NMDAR-dependent secretion of netrin-1 from the dendrites of hippocampal neurons. They report that genetic deletion of netrin-1 from excitatory neurons impairs hippocampal synaptic plasticity and that netrin-1 application is sufficient to trigger the potentiation of excitatory synaptic transmission via the insertion of GluA1 AMPARs. Keywords: CA1 pyramidal neurons, long-term potentiation, axon guidance, AMPA receptor trafficking, GluR1, deleted-in-colorectal cancer, DCC

Neurotrophins activate intracellular signaling pathways necessary for neuronal survival, growth and apoptosis. The most abundant neurotrophin in the adult brain, brain-derived neurotrophic factor (BDNF), is first synthesized as a proBDNF precursor and recent studies have demonstrated that proBDNF can be secreted and that it functions as a ligand for a receptor complex containing p75NTR and sortilin. Activation of proBDNF receptors mediates growth cone collapse, reduces synaptic activity, and facilitates developmental apoptosis of motoneurons but the precise signaling cascades have been difficult to discern. To address this, we have engineered, expressed and purified HBpF-proBDNF, an expression construct containing a 6X-HIS tag, a biotin acceptor peptide (BAP) sequence, a PreScission™ Protease cleavage site and a FLAG-tag attached to the N-terminal part of murine proBDNF. Intact HBpF-proBDNF has activities indistinguishable from its wild-type counterpart and can be used to purify proBDNF signaling complexes or to monitor proBDNF endocytosis and retrograde transport. HBpF-proBDNF will be useful for characterizing proBDNF signaling complexes and for deciphering the role of proBDNF in neuronal development, synapse function and neurodegenerative disease.

Lewy bodies (LBs), α-synuclein-enriched intracellular inclusions, are a hallmark of Parkinson's disease (PD) pathology, yet a cellular model for LB formation remains elusive. Recent evidence indicates that immune dysfunction may contribute to the development of PD. In this study, we found that induced pluripotent stem cell (iPSC)-derived human dopaminergic (DA) neurons form LB-like inclusions after treatment with α-synuclein preformed fibrils (PFFs) but only when coupled to a model of immune challenge (interferon-γ or interleukin-1β treatment) or when co-cultured with activated microglia-like cells. Exposure to interferon-γ impairs lysosome function in DA neurons, contributing to LB formation. The knockdown of LAMP2 or the knockout of GBA in conjunction with PFF administration is sufficient for inclusion formation. Finally, we observed that the LB-like inclusions in iPSC-derived DA neurons are membrane bound, suggesting that they are not limited to the cytoplasmic compartment but may be formed due to dysfunctions in autophagy. Together, these data indicate that immune-triggered lysosomal dysfunction may contribute to the development of PD pathology., (© 2024. The Author(s), under exclusive licence to Springer Nature America, Inc.)