Distinct effects of AMPAR subunit depletion on spatial memory.

Pharmacological studies established a role for AMPARs in the mammalian forebrain in spatial memory performance. Here we generated global GluA1/3 double knockout mice (Gria1/3-/-) and conditional knockouts lacking GluA1 and GluA3 AMPAR subunits specifically from principal cells across the forebrain (Gria1/3ΔFb). In both models, loss of GluA1 and GluA3 resulted in reduced hippocampal GluA2 and increased levels of the NMDAR subunit GluN2A. Electrically-evoked AMPAR-mediated EPSPs were greatly diminished, and there was an absence of tetanus-induced LTP. Gria1/3-/- mice showed premature mortality. Gria1/3ΔFb mice were viable, and their memory performance could be analyzed. In the Morris water maze (MWM), Gria1/3ΔFb mice showed profound long-term memory deficits, in marked contrast to the normal MWM learning previously seen in single Gria1-/- and Gria3-/- knockout mice. Our results suggest a redundancy of function within the pool of available ionotropic glutamate receptors for long-term spatial memory performance.

Perceptions of heart failure symptoms, disease severity, treatment decision-making, and side effects by patients and cardiologists: a multinational survey in a cardiology setting.

PURPOSE: Explore the extent to which heart failure (HF) symptoms and side effects of HF treatment experienced by patients are recognized by cardiologists, and concordance between patient-cardiologist perceptions of HF severity and patients' contributions to treatment decision-making. METHODS: A multinational, cross-sectional survey of cardiologists and patients with HF was conducted. Patient-record forms (PRFs) were completed by cardiologists for consecutive consulting patients with HF, who completed a patient self-completion questionnaire (PSC). Responses from PRFs with an associated PSC were analyzed to compare patient- and cardiologist-reported occurrences of HF symptoms and treatment side effects, patient-perceived severity of HF and cardiologists' perceived risk of death within 12 months, and patient input into treatment decisions. Concordance was calculated as the number of response agreements between PSCs and PRFs for total number of matched pairs. Over- or underreporting of symptoms and side effects by cardiologists relative to patient-reported occurrences were calculated. RESULTS: Overall, 2,454 patient-cardiologist pairs were identified. High levels of concordance between matched pairs were observed for the occurrence of reported HF symptoms (93%), side effects (77%-98%) and degree of patient input into treatment decisions (74%); for perceived HF severity, concordance was 54%. Most symptoms (except dyspnea when active and fatigue/weakness, experienced by >50% of patients) were underreported by cardiologists. Of patients reporting to have been informed by their cardiologist that their HF was mild, 28% were perceived by their cardiologist to have a moderate-high/very high risk of death within 12 months. Treatment choice was not discussed with almost a third of patients. When discussed, 94% of patients (n=1,540) reported the cardiologist made the final decision. Cardiologists more often under- than overreported the occurrence of side effects reported by patients. CONCLUSION: Improved patient-cardiologist dialogue and shared decision-making is required for optimizing patient care and outcomes in HF.

Care pathways and treatment patterns for patients with heart failure in China: results from a cross-sectional survey.

PURPOSE: The objective of this study was to describe the clinical care pathways, management and treatment patterns, and hospitalizations for patients with heart failure (HF) in China. SUBJECTS AND METHODS: A cross-sectional survey of cardiologists and their patients with HF was conducted. Patient record forms were completed by 150 cardiologists for 10 consecutive patients. Patients for whom a patient record form was completed were invited to complete a patient self-completion questionnaire. RESULTS: Most of the 1,500 patients (mean [SD] age 66 [10] years; 55% male) included in the study received care in tier-2 and -3 hospitals in large cities. Cardiologists were responsible for initial consultation, diagnosis, and treatment of patients with HF. The use of guideline-recommended diagnostics was high. However, guideline-recommended double- and triple-combination therapy was received by only 51% and 18% of patients, respectively. In total, 20% of patients with HF reported that they were not consulted on the choice of therapy. Concordance was high (≥80%) between matched cardiologist and patient pairs for the occurrence of side effects, while cardiologists more often under- than overreported the occurrence of side effects of treatment reported by patients. CONCLUSION: The management of HF was predominantly overseen by cardiologists. The use of diagnostic tests was high, but the use of guideline-recommended treatment was low in this population. Improved communication between patients and cardiologists is essential to optimize treatment decision making and to increase awareness of treatment side effects.

Burden of heart failure on patients from China: results from a cross-sectional survey.

PURPOSE: Little evidence exists on the burden that chronic heart failure (HF) poses specifically to patients in China. The objective of this study, therefore, was to describe the burden of HF on patients in China. MATERIALS AND METHODS: A cross-sectional survey of cardiologists and their patients with HF was conducted. Patient record forms were completed by 150 cardiologists for 10 consecutive patients. Patients for whom a patient record form was completed were invited to complete a patient questionnaire. RESULTS: Most of the 933 patients (mean [SD] age 65.8 [10.2] years; 55% male; 80% retired) included in the study received care in tier 2 and 3 hospitals in large cities. Patients gave a median score of 4 on a scale from 1 (no disruption) to 10 (severe disruption) to describe how much HF disrupts their everyday life. Patients in paid employment (8%) missed 10% of work time and experienced 29% impairment in their ability to work due to HF in the previous week. All aspects of patients' health-related quality of life (QoL) were negatively affected by their condition. Mean ± SD utility calculated by the 3-level 5-dimension EuroQol questionnaire was 0.8±0.2, and patients rated their health at 70.3 (11.5) on a 100 mm visual analog scale. Patients incurred costs associated with HF treatment, travel, and professional caregiving services. CONCLUSION: HF is associated with poor health-related QoL and considerable disruption in patients' lives. Novel and improved therapies are needed to reduce the burden of HF on patients and the health care system.

Burden of heart failure on caregivers in China: results from a cross-sectional survey.

PURPOSE: Family and friends play a pivotal role in caring for patients with heart failure (HF); however, evidence of the impact of caregiving is limited. The objectives of this study were to describe the burden of caregiving on informal caregivers of patients with chronic HF in China. MATERIALS AND METHODS: A cross-sectional survey of cardiologists, their patients with HF, and those patients' caregivers was conducted. Patient record forms were completed by 150 cardiologists for 10 consecutive patients. Caregivers of these patients were invited to complete a questionnaire. RESULTS: Overall, 458 caregivers completed a questionnaire (mean ± standard deviation age 60.1±10.6 years; 60% female; 77% spouses; 74% retired). Caregivers spent a mean of 24.5 (16.9) hours caregiving per week, and a third reported a reduction in their social activity, time for themselves, or time for family. Caregivers in employment took several days off work in the past 3 months owing to caregiving, sometimes resulting in reduced income. Up to 79% of caregivers reported an impact on their physical or emotional well-being, and 57% reported deterioration in their objective health status. Inconsistencies stemming from differences in the three-level five-dimension EuroQol questionnaire and HF Caregiver Questionnaire were observed for the impact of caregiving on caregivers' health-related quality of life. CONCLUSION: Assisting patients with HF is associated with caregiver burden. Addressing the needs of caregivers may help to promote their continued support and improve patient outcomes.

Early insights into the characteristics and evolution of clinical parameters in a cohort of patients prescribed sacubitril/valsartan in Germany.

OBJECTIVES: This study aimed to provide early insights into sacubitril/valsartan (sac/val) prescription patterns and the demographic and clinical characteristics of patients prescribed sac/val in primary care and cardiology settings in Germany. METHODS: The study used electronic medical records from the German IMS® Disease Analyzer database. Patients with ≥1 prescription for sac/val during 1 January-31 December 2016 (n = 1643) were identified and followed up for ≤12 months from first prescription. Patients with ≥1 heart failure (HF) diagnosis during the study period, ≥1 additional HF diagnosis in the full history of the database, and ≥1 prescription for an angiotensin-converting enzyme inhibitor or angiotensin receptor blocker and a ß-blocker during the study period, without a prescription for sac/val (n = 25,264), were included as a reference cohort. Changes in clinical parameters in the 12 months before and after sac/val initiation were investigated and compared with those from the PARADIGM-HF study. RESULTS: The characteristics of patients prescribed sac/val more closely resembled those of patients enrolled in PARADIGM-HF (e.g. younger age, higher proportion of men than women, lower systolic blood pressure) than patients in the reference cohort. Most patients were initiated on the lowest dose of sac/val irrespective of clinical setting. Significant decreases (p < 0.001) in NT-proBNP and glycated haemoglobin levels were observed following sac/val initiation. CONCLUSIONS: Patients prescribed sac/val had similar baseline demographics and clinical characteristics to those from PARADIGM-HF, and most patients were initiated on the lowest dose. Changes in clinical parameters before and after initiation mirrored findings from the PARADIGM-HF study.

Differential effects of BDNF and neurotrophin 4 (NT4) on endocytic sorting of TrkB receptors.

Neurotrophins are a family of growth factors playing key roles in the survival, development, and function of neurons. The neurotrophins brain-derived neurotrophic factor (BDNF) and NT4 both bind to and activate TrkB receptors, however, they mediate distinct neuronal functions. The molecular mechanism of how TrkB activation by BDNF and NT4 leads to diverse outcomes is unknown. Here, we report that BDNF and NT4 lead to differential endocytic sorting of TrkB receptors resulting in diverse biological functions in cultured cortical neurons. Fluorescent microscopy and surface biotinylation experiments showed that both neurotrophins stimulate internalization of TrkB with similar kinetics. Exposure to BDNF for 2-3 h reduced the surface pool of TrkB receptors to half, whereas a longer treatment (4-5 h) with NT4 was necessary to achieve a similar level of down-regulation. Although BDNF and NT4 induced TrkB phosphorylation with similar intensities, BDNF induced more rapid ubiquitination and degradation of TrkB than NT4. Interestingly, TrkB receptor ubiquitination by these ligands have substantially different pH sensitivities, resulting in varying degrees of receptor ubiquitination at lower pH levels. Consequently, NT4 was capable of maintaining longer sustained downstream signaling activation that correlated with reduced TrkB ubiquitination at endosomal pH. Thus, by leading to altered endocytic trafficking itineraries for TrkB receptors, BDNF and NT4 elicit differential TrkB signaling in terms of duration, intensity, and specificity, which may contribute to their functional differences in vivo. The neurotrophins, brain-derived neurotrophic factor (BDNF) and neurotrophin-4 (NT4), both bind to and activate TrkB receptors, however, they mediate distinct neuronal functions. Here, we propose that BDNF and NT4 lead to differential endocytic sorting of TrkB receptors resulting in diverse biological functions. BDNF induces more rapid ubiquitination and degradation of TrkB than NT4. Consequently, NT4 is capable of maintaining more sustained signaling downstream of TrkB receptors.

CLK2 inhibition ameliorates autistic features associated with SHANK3 deficiency.

SH3 and multiple ankyrin repeat domains 3 (SHANK3) haploinsufficiency is causative for the neurological features of Phelan-McDermid syndrome (PMDS), including a high risk of autism spectrum disorder (ASD). We used unbiased, quantitative proteomics to identify changes in the phosphoproteome of Shank3-deficient neurons. Down-regulation of protein kinase B (PKB/Akt)-mammalian target of rapamycin complex 1 (mTORC1) signaling resulted from enhanced phosphorylation and activation of serine/threonine protein phosphatase 2A (PP2A) regulatory subunit, B56ß, due to increased steady-state levels of its kinase, Cdc2-like kinase 2 (CLK2). Pharmacological and genetic activation of Akt or inhibition of CLK2 relieved synaptic deficits in Shank3-deficient and PMDS patient-derived neurons. CLK2 inhibition also restored normal sociability in a Shank3-deficient mouse model. Our study thereby provides a novel mechanistic and potentially therapeutic understanding of deregulated signaling downstream of Shank3 deficiency.

Slitrk5 Mediates BDNF-Dependent TrkB Receptor Trafficking and Signaling.

Recent studies in humans and in genetic mouse models have identified Slit- and NTRK-like family (Slitrks) as candidate genes for neuropsychiatric disorders. All Slitrk isotypes are highly expressed in the CNS, where they mediate neurite outgrowth, synaptogenesis, and neuronal survival. However, the molecular mechanisms underlying these functions are not known. Here, we report that Slitrk5 modulates brain-derived neurotrophic factor (BDNF)-dependent biological responses through direct interaction with TrkB receptors. Under basal conditions, Slitrk5 interacts primarily with a transsynaptic binding partner, protein tyrosine phosphatase δ (PTPδ); however, upon BDNF stimulation, Slitrk5 shifts to cis-interactions with TrkB. In the absence of Slitrk5, TrkB has a reduced rate of ligand-dependent recycling and altered responsiveness to BDNF treatment. Structured illumination microscopy revealed that Slitrk5 mediates optimal targeting of TrkB receptors to Rab11-positive recycling endosomes through recruitment of a Rab11 effector protein, Rab11-FIP3. Thus, Slitrk5 acts as a TrkB co-receptor that mediates its BDNF-dependent trafficking and signaling.

Atg4b-dependent autophagic flux alleviates Huntington's disease progression.

The accumulation of aggregated mutant huntingtin (mHtt) inclusion bodies is involved in Huntigton's disease (HD) progression. Medium sized-spiny neurons (MSNs) in the corpus striatum are highly vulnerable to mHtt aggregate accumulation and degeneration, but the mechanisms and pathways involved remain elusive. Here we have developed a new model to study MSNs degeneration in the context of HD. We produced organotypic cortico-striatal slice cultures (CStS) from HD transgenic mice mimicking specific features of HD progression. We then show that induction of autophagy using catalytic inhibitors of mTOR prevents MSNs degeneration in HD CStS. Furthermore, disrupting autophagic flux by overexpressing Atg4b in neurons and slice cultures, accelerated mHtt aggregation and neuronal death, suggesting that Atg4b-dependent autophagic flux influences HD progression. Under these circumstances induction of autophagy using catalytic inhibitors of mTOR was inefficient and did not affect mHtt aggregate accumulation and toxicity, indicating that mTOR inhibition alleviates HD progression by inducing Atg4b-dependent autophagic flux. These results establish modulators of Atg4b-dependent autophagic flux as new potential targets in the treatment of HD.

Slitrks as emerging candidate genes involved in neuropsychiatric disorders.

Slitrks are a family of structurally related transmembrane proteins belonging to the leucine-rich repeat (LRR) superfamily. Six family members exist (Slitrk1-6) and all are highly expressed in the central nervous system (CNS). Slitrks have been implicated in mediating basic neuronal processes, ranging from neurite outgrowth and dendritic elaboration to neuronal survival. Recent studies in humans and genetic mouse models have led to the identification of Slitrks as candidate genes that might be involved in the development of neuropsychiatric conditions, such as obsessive compulsive spectrum disorders and schizophrenia. Although these system-level approaches have suggested that Slitrks play prominent roles in CNS development, key questions remain regarding the molecular mechanisms through which they mediate neuronal signaling and connectivity.

Enhanced erythropoiesis in Hfe-KO mice indicates a role for Hfe in the modulation of erythroid iron homeostasis.

In hereditary hemochromatosis, mutations in HFE lead to iron overload through abnormally low levels of hepcidin. In addition, HFE potentially modulates cellular iron uptake by interacting with transferrin receptor, a crucial protein during erythropoiesis. However, the role of HFE in this process was never explored. We hypothesize that HFE modulates erythropoiesis by affecting dietary iron absorption and erythroid iron intake. To investigate this, we used Hfe-KO mice in conditions of altered dietary iron and erythropoiesis. We show that Hfe-KO mice can overcome phlebotomy-induced anemia more rapidly than wild-type mice (even when iron loaded). Second, we evaluated mice combining the hemochromatosis and ß-thalassemia phenotypes. Our results suggest that lack of Hfe is advantageous in conditions of increased erythropoietic activity because of augmented iron mobilization driven by deficient hepcidin response. Lastly, we demonstrate that Hfe is expressed in erythroid cells and impairs iron uptake, whereas its absence exclusively from the hematopoietic compartment is sufficient to accelerate recovery from phlebotomy. In summary, we demonstrate that Hfe influences erythropoiesis by 2 distinct mechanisms: limiting hepcidin expression under conditions of simultaneous iron overload and stress erythropoiesis, and impairing transferrin-bound iron uptake by erythroid cells. Moreover, our results provide novel suggestions to improve the treatment of hemochromatosis.

Slitrk5 deficiency impairs corticostriatal circuitry and leads to obsessive-compulsive-like behaviors in mice.

Obsessive-compulsive disorder (OCD) is a common psychiatric disorder defined by the presence of obsessive thoughts and repetitive compulsive actions, and it often encompasses anxiety and depressive symptoms. Recently, the corticostriatal circuitry has been implicated in the pathogenesis of OCD. However, the etiology, pathophysiology and molecular basis of OCD remain unknown. Several studies indicate that the pathogenesis of OCD has a genetic component. Here we demonstrate that loss of a neuron-specific transmembrane protein, SLIT and NTRK-like protein-5 (Slitrk5), leads to OCD-like behaviors in mice, which manifests as excessive self-grooming and increased anxiety-like behaviors, and is alleviated by the selective serotonin reuptake inhibitor fluoxetine. Slitrk5(-/-) mice show selective overactivation of the orbitofrontal cortex, abnormalities in striatal anatomy and cell morphology and alterations in glutamate receptor composition, which contribute to deficient corticostriatal neurotransmission. Thus, our studies identify Slitrk5 as an essential molecule at corticostriatal synapses and provide a new mouse model of OCD-like behaviors.

Variant brain-derived neurotrophic factor (Val66Met) alters adult olfactory bulb neurogenesis and spontaneous olfactory discrimination.

Neurogenesis, the division, migration, and differentiation of new neurons, occurs throughout life. Brain derived neurotrophic factor (BDNF) has been identified as a potential signaling molecule regulating neurogenesis in the subventricular zone (SVZ), but its functional consequences in vivo have not been well defined. We report marked and unexpected deficits in survival but not proliferation of newly born cells of adult knock-in mice containing a variant form of BDNF [a valine (Val) to methionine (Met) substitution at position 66 in the prodomain of BDNF (Val66Met)], a genetic mutation shown to lead to a selective impairment in activity-dependent BDNF secretion. Utilizing knock-out mouse lines, we identified BDNF and tyrosine receptor kinase B (TrkB) as the critical molecules for the observed impairments in neurogenesis, with p75 knock-out mice showing no effect on cell proliferation or survival. We then localized the activated form of TrkB to a discrete population of cells, type A migrating neuroblasts, and demonstrate a decrease in TrkB phosphorylation in the SVZ of Val66Met mutant mice. With these findings, we identify TrkB signaling, potentially through activity dependent release of BDNF, as a critical step in the survival of migrating neuroblasts. Utilizing a behavioral task shown to be sensitive to disruptions in olfactory bulb neurogenesis, we identified specific impairments in spontaneous olfactory discrimination, but not general olfactory sensitivity or habituation to olfactory stimuli in BDNF mutant mice. Through these observations, we have identified novel links between genetic variant BDNF and adult neurogenesis in vivo, which may contribute to significant impairments in olfactory function.