SALM1 controls synapse development by promoting F-actin/PIP2-dependent Neurexin clustering.

Synapse development requires spatiotemporally regulated recruitment of synaptic proteins. In this study, we describe a novel presynaptic mechanism of cis-regulated oligomerization of adhesion molecules that controls synaptogenesis. We identified synaptic adhesion-like molecule 1 (SALM1) as a constituent of the proposed presynaptic Munc18/CASK/Mint1/Lin7b organizer complex. SALM1 preferentially localized to presynaptic compartments of excitatory hippocampal neurons. SALM1 depletion in excitatory hippocampal primary neurons impaired Neurexin1ß- and Neuroligin1-mediated excitatory synaptogenesis and reduced synaptic vesicle clustering, synaptic transmission, and synaptic vesicle release. SALM1 promoted Neurexin1ß clustering in an F-actin- and PIP2-dependent manner. Two basic residues in SALM1's juxtamembrane polybasic domain are essential for this clustering. Together, these data show that SALM1 is a presynaptic organizer of synapse development by promoting F-actin/PIP2-dependent clustering of Neurexin.

SynaptoPAC, an optogenetic tool for induction of presynaptic plasticity.

Optogenetic manipulations have transformed neuroscience in recent years. While sophisticated tools now exist for controlling the firing patterns of neurons, it remains challenging to optogenetically define the plasticity state of individual synapses. A variety of synapses in the mammalian brain express presynaptic long-term potentiation (LTP) upon elevation of presynaptic cyclic adenosine monophosphate (cAMP), but the molecular expression mechanisms as well as the impact of presynaptic LTP on network activity and behavior are not fully understood. In order to establish optogenetic control of presynaptic cAMP levels and thereby presynaptic potentiation, we developed synaptoPAC, a presynaptically targeted version of the photoactivated adenylyl cyclase bPAC. In cultures of hippocampal granule cells of Wistar rats, activation of synaptoPAC with blue light increased action potential-evoked transmission, an effect not seen in hippocampal cultures of non-granule cells. In acute brain slices of C57BL/6N mice, synaptoPAC activation immediately triggered a strong presynaptic potentiation at mossy fiber synapses in CA3, but not at Schaffer collateral synapses in CA1. Following light-triggered potentiation, mossy fiber transmission decreased within 20 min, but remained enhanced still after 30 min. The optogenetic potentiation altered the short-term plasticity dynamics of release, reminiscent of presynaptic LTP. Our work establishes synaptoPAC as an optogenetic tool that enables acute light-controlled potentiation of transmitter release at specific synapses in the brain, facilitating studies of the role of presynaptic potentiation in network function and animal behavior in an unprecedented manner. Read the Editorial Highlight for this article on page 270.

Neurological counterparts of hyponatremia: pathological mechanisms and clinical manifestations.

Hyponatremia, defined as a serum sodium concentration <135 mEq/L, represents the most frequent electrolyte disorder in older hospitalized patients. Early recognition of hyponatremia is mandatory, since it represents an independent risk factor that increases hospital mortality by 40 %. Delayed correction of hyponatremia may worsen brain edema, resulting in different degrees of neural damage. However, an overly rapid correction of serum sodium levels can lead to osmotic demyelination syndrome (ODS), a dreadful neurological picture. In recent years, hyponatremia and ODS have received growing attention both in terms of clinical management and pathophysiology, leading to the discovery of new drugs and treatment algorithms. In this review, we recapitulate the pathogenetic background, clinical manifestations, and treatment guidelines of hyponatremia, focusing on the neurological alterations. Neurological symptoms may be neglected when they manifest as early signs of mild hyponatremia, while brain damage can irremediably affect patients' conditions in the context of ODS.

Renal dysfunction in acute congestive heart failure: a common problem for cardiologists and nephrologists.

The term acute heart failure (AHF) refers to a clinical syndrome with typical symptoms and signs, in which a structural or functional heart abnormality leads to defective oxygen delivery. The term cardiorenal syndrome has been proposed to outline the strict interplay between cardiac and renal function. In the setting of acute cardiac decompensation, acute kidney injury (AKI) is generally referred to as cardiorenal syndrome type 1. In this review, we summarize the fundamental pathophysiological aspects of both AHF and AHF-related AKI. We also review the latest therapeutic options, including both pharmacological ones, such as loop diuretics, potassium-sparing diuretics and vaptans, and non-pharmacological ones, such as ultrafiltration, and their impact on patients' outcome. We discuss the pathophysiology of diuretic resistance, a common occurrence in these patients, reviewing the available strategies to treat it and highlighting how a close collaboration between cardiologists and nephrologists is frequently crucial for the management of this complication. Finally, we discuss three new promising non-pharmacological tools for the prevention of AHF recurrence, including two methods that exploit sympathetic denervation and one technique that acts by increasing vagal tone.

Blended practical learning in compliance with COVID-19 social distancing.

COVID-19 pandemic has imposed great changes in everyday life. Starting from January 2020, Humanitas University proposed to students digital instruction for continuing medical education, in particular, concerning practical activities. The latter, defined as Professionalizing activities, were transformed into complete online learning. From September 2020, in accordance to the imposed rules of social distancing, we modified the approach to Professionalizing activities. Despite following the new constrains, we came up with a blend online and face-to-face education program. The Kirkpatrick's evaluation model has been followed for validation of the project. Two ad hoc satisfaction questionnaires have been proposed to evaluate the project. Different approaches to blended learning have been described in literature; however, we propose a new method application, which fits to the post-pandemic era, with the purpose of sharing our experience in the field. Advantages and limitations are described. According to students, the overall satisfaction was rated 6.8, while tutors evaluated it with 7.4. The qualitative analysis of data confirms the advantage of the blended learning activities in order to guarantee a continuation of the clinical curriculum. Although it highlighted the necessity for, an increased technical support and an improvement in organization of the meetings. Blended learning is becoming more accepted among academic communities because it combines "the best of both worlds." However, its effectiveness depends on several factors. With our approach, we propose a method, specifically designed to make effective this kind of teaching, which can be considered essential in the pandemic era we are facing.

Different cardiovascular responses to hemodialysis-induced fluid depletion and blood pressure compliance.

BACKGROUND: On the basis of cardiovascular compliance, hemodialysis (HD) patients can be classified as hypotension prone (HP) or hypotension resistant (HR). METHODS: We compare the hemodynamic behavior and myocardial performances in 6 HP and 6 HR patients before and after an isolated ultrafiltration (IU) session removing 3% of total body water. RESULTS: HP show higher basal plasma angiotensin II levels during IU (p<0.01), whereas angiotensin II remained unchanged in HR patients (p<0.001 between groups). The percentage changes of plasma volume (PV) was similar in the 2 groups. A significant reduction of cardiac index was observed only in the HP group (p<0.001 between groups). The mean values of heart rate remained significantly higher, whereas total peripheral resistances significantly fell in the HP in comparison with the HR group (p<0.001 between groups). During IU, the mean arterial pressure (MAP) changes were -10 +/- 3 mm Hg in the HP vs. -3.3 +/- 2 mm Hg in the HR group (p<0.001). Echocardiography data were collected before and after IU. All enrolled patients presented left ventricular hypertrophy; following IU, HP patients showed a reduction of mean left ventricular diameter (p<0.01), left atrial diameters and right atrial diameter, and a change in percentage of right atrium ejection fraction (p<0.001, p<0.01). CONCLUSIONS: In comparison with HR patients, HP patients before and after IU showed a defective arteriovenous tone adjustment to the PV changes, with a hemodynamic picture of abnormal sympathetic stimulation. Moreover, a reduced cardiac preload with both atrial and ventricular underfilling in these patients is at risk for a sudden drop in MAP.

Publisher Correction: Propagation of hippocampal ripples to the neocortex by way of a subiculum-retrosplenial pathway.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Propagation of hippocampal ripples to the neocortex by way of a subiculum-retrosplenial pathway.

Bouts of high frequency activity known as sharp wave ripples (SPW-Rs) facilitate communication between the hippocampus and neocortex. However, the paths and mechanisms by which SPW-Rs broadcast their content are not well understood. Due to its anatomical positioning, the granular retrosplenial cortex (gRSC) may be a bridge for this hippocampo-cortical dialogue. Using silicon probe recordings in awake, head-fixed mice, we show the existence of SPW-R analogues in gRSC and demonstrate their coupling to hippocampal SPW-Rs. gRSC neurons reliably distinguished different subclasses of hippocampal SPW-Rs according to ensemble activity patterns in CA1. We demonstrate that this coupling is brain state-dependent, and delineate a topographically-organized anatomical pathway via VGlut2-expressing, bursty neurons in the subiculum. Optogenetic stimulation or inhibition of bursty subicular cells induced or reduced responses in superficial gRSC, respectively. These results identify a specific path and underlying mechanisms by which the hippocampus can convey neuronal content to the neocortex during SPW-Rs.

Potassium channel-based optogenetic silencing.

Optogenetics enables manipulation of biological processes with light at high spatio-temporal resolution to control the behavior of cells, networks, or even whole animals. In contrast to the performance of excitatory rhodopsins, the effectiveness of inhibitory optogenetic tools is still insufficient. Here we report a two-component optical silencer system comprising photoactivated adenylyl cyclases (PACs) and the small cyclic nucleotide-gated potassium channel SthK. Activation of this 'PAC-K' silencer by brief pulses of low-intensity blue light causes robust and reversible silencing of cardiomyocyte excitation and neuronal firing. In vivo expression of PAC-K in mouse and zebrafish neurons is well tolerated, where blue light inhibits neuronal activity and blocks motor responses. In combination with red-light absorbing channelrhodopsins, the distinct action spectra of PACs allow independent bimodal control of neuronal activity. PAC-K represents a reliable optogenetic silencer with intrinsic amplification for sustained potassium-mediated hyperpolarization, conferring high operational light sensitivity to the cells of interest.

Plasma pentraxin-3 as a marker of bioincompatibility in hemodialysis patients.

INTRODUCTION: Hemodialysis (HD)-induced inflammation has a pathogenetic role in patients with end-stage renal disease (ESRD). The aim of the present study was to assess whether pentraxin-3 (PTX3) could be a reliable biomarker of HD-induced inflammation and of membrane biocompatibility. METHODS: We prospectively enrolled 31 HD patients. Blood samples for determining PTX3, C-reactive protein (CRP), leukocytes and neutrophils were drawn from the arterial needle, before dialysis after the long dialysis-free interval (time 0), at the end of the index session (time 1) and before the next dialysis session (time 2). In 22 of 31 patients, 30 minutes after start of dialysis, PTX3 and CRP plasma levels were measured in blood collected from both the arterial and venous lines (time A - time V) of the dialyzer. In 7 of 22 patients intracellular PTX3 levels in neutrophils were measured at the end of session. RESULTS: PTX3 venous levels were significantly increased at the end of the index session compared with baseline and in blood samples drawn from the venous line compared with the arterial line of the dialyzer. At time 1, a reduction of intracellular PTX3 in neutrophils was noticed. In contrast, CRP plasma levels were stable during the HD session. CONCLUSIONS: Our findings suggest that PTX3, which is rapidly produced by several cell types and released by neutrophils upon stimulation, could be a biomarker of HD-induced inflammation and of blood-membrane bioincompatibility.

Impact of large regenerative, low grade and high grade dysplastic nodules in hepatocellular carcinoma development.

BACKGROUND/AIMS: The natural outcome of ultrasound-detected macronodules in cirrhosis is still poorly understood. In this study we assessed the incidence and predictors of malignant transformation in a prospective study of 90 consecutive ultrasound-detected macronodules in cirrhosis. METHODS: Macronodules classification was based on recently proposed histological criteria. Extranodular large (LCC) and small cell changes were also evaluated. The follow-up included ultrasound and serum alfa-fetoprotein determination every 3 months. Independent predictors of hepatocellular carcinoma were evaluated by Cox proportional hazards regression analysis. RESULTS: During a mean follow-up of 33 months, 28 (31%) nodules transformed into hepatocellular carcinoma. The incidence of hepatocellular carcinoma per 100 person-years of follow-up was 11.3%, with a malignant transformation rate of 3.5, 15.5, 31 and 48.5% at 1, 2, 3, and 5 years respectively. High-grade dysplastic nodules (HGDN) (hazard risk=2.4; CI 95%=1.1-5.0) and LCC (hazard risk=3.1; CI 95%=1.2-7.8) were independent predictors of malignant transformation. Eight additional hepatocellular carcinomas developed outside the original lesions raising the overall malignant transformation rate to 40% while 15 macronodules (17%) became undetectable at ultrasound (US). CONCLUSIONS: Macronodules characterize a cirrhotic subpopulation with high risk of hepatocellular carcinoma. HGDN and LCC are strong predictors of malignant transformation; subjects with simultaneous presence of both these two conditions are at highest risk of cancer development. The management of cirrhotics with macronodules should be based on morphologic features detected on liver microsamples.

Iron reduction and sustained response to interferon-alpha therapy in patients with chronic hepatitis C: results of an Italian multicenter randomized study.

OBJECTIVES: It has been suggested that iron depletion improves the response to interferon in patients with chronic hepatitis C. We aimed to evaluate whether iron reduction by phlebotomy before interferon improves the rate of virological sustained response in previously untreated noncirrhotic patients. METHODS: One hundred fourteen hepatitis C virus (HCV) RNA positive patients with hepatic iron concentrations of > or =700 microg/g dry wt (men) and > or =500 microg/g dry wt (women), stratified according to HCV genotype and gamma-glutamyltransferase values, were randomly allocated to interferon alone (6 MU three times a week) (group A) or to phlebotomy until iron depletion followed by interferon (6 MU three times a week) (group B). After 4 months dosage was reduced to 3 MU three times a week for another 8 months. RESULTS: Virological sustained response was observed in 25 patients (22%), nine (15.8%, 95% CI = 7.5-27.9) of group A and 16 (28.1%, 95% CI = 17.0-41.6) of group B. At univariate analysis the variables associated with the response were HCV genotypes 2-3, normal gamma-glutamyltransferase, higher levels of baseline ALT, normal ALT values, and negativity for HCV-RNA at the 3rd month of therapy. At multivariate analysis, genotype and ALT levels at enrollment maintained their association with the response. A trend toward a better response to interferon was observed in patients who received phlebotomy (odds ratio = 2.32, 95% CI = 0.96-6.24, p = 0.082). Patients with hepatic iron concentration of < or = 1100 microg/g dry wt had a trend toward a higher rate of virological sustained response (p = 0.059) when submitted to treatment B. CONCLUSION: Iron removal by phlebotomy is able to improve the rate of response to interferon, especially in patients with lower hepatic iron deposits; it could be useful as adjuvant therapy to new therapeutic modalities.