Developmental synaptic regulator,TWEAK/Fn14 signaling,is a determinant of synaptic function in models of stroke and neurodegeneration

Identifying molecular mediators of neural circuit development and/or function that contribute to circuit dysfunction when aberrantly reengaged in neurological disorders is of high importance. The role of the TWEAK/Fn14 pathway, which was recently reported to be a microglial/neuronal axis mediating synaptic refinement in experience-dependent visual development, has not been explored in synaptic function within the mature central nervous system. By combining electrophysiological and phosphoproteomic approaches, we show that TWEAK acutely dampens basal synaptic transmission and plasticity through neuronal Fn14 and impacts the phosphorylation state of pre- and postsynaptic proteins in adult mouse hippocampal slices. Importantly, this is relevant in two models featuring synaptic deficits. Blocking TWEAK/Fn14 signaling augments synaptic function in hippocampal slices from amyloid-beta–overexpressing mice. After stroke, genetic or pharmacological inhibition of TWEAK/Fn14 signaling augments basal synaptic transmission and normalizes plasticity. Our data support a glial/neuronal axis that critically modifies synaptic physiology and pathophysiology in different contexts in the mature brain and may be a therapeutic target for improving neurophysiological outcomes.

Neural circuit patterning, refinement, and plasticity are enabled by the dynamic strengthening, weakening, and pruning of chemical synapses in response to circuit activity. However, synapse loss and reduced plasticity are early hallmarks of chronic neurological disorders such as autism, schizophrenia and Alzheimer’s disease (AD) (1–3). It is therefore hypothesized that the underlying molecular mechanisms of pruning, although normally balanced in health, are dysregulated in disease. Particularly interesting is the notion that the mechanisms responsible for the reduction in functional synapses in disease reflect the aberrant reactivation of pathways important for synapse elimination in development. For example, in an AD model, synapse elimination was shown to be mediated by the complement pathway in the hippocampus (HC), reflecting aberrant reactivation of complement-dependent synapse elimination that occurs in the dorsal lateral geniculate nucleus (dLGN) of the thalamus during visual development (4). In such a paradigm, the reactivation of developmental mechanisms enables pathways that can act universally across different ages, circuits, and brain regions. Thus, the mechanisms underlying normal circuit development and their potential reactivation as key contributors to neurological diseases are areas of deep interest.In addition to chronic neurological disorders, circuitry changes also occur in acute ischemic stroke, the second leading cause of death worldwide and a cause of debilitating long-term disability. Interruptions in blood flow that deprive neurons of oxygen and nutrients result in significant cell death, followed by deficits in neurophysiological activity that are associated with poor motor recovery (5). Remarkably, the adult brain can undergo some degree of spontaneous poststroke recovery, apparently by engaging neuroplasticity mechanisms including remapping, synaptogenesis, and synaptic strengthening (5, 6). Despite these adaptations, over half of ischemic stroke patients fail to recover completely and continue to experience persistent long-term disability (7). The underlying signaling pathways that regulate synaptic physiology after stroke are an active topic of investigation.TNF-like weak inducer of apoptosis (TWEAK) protein, originally discovered as a cytokine produced by macrophages (8), signals through its injury-inducible transmembrane receptor, FGF-inducible molecule-14 (Fn14) (9). Consequently, the function of TWEAK/Fn14 signaling was elucidated as a driver of tissue remodeling in contexts of injury and disease in a variety of organ systems (10). Recently, findings have suggested a role for the TWEAK/Fn14 pathway in the central nervous system (CNS). Namely, several compelling observations indicate that TWEAK signaling through Fn14 might be a key molecular modulator of synaptic function in contexts of neurological challenge. TWEAK and Fn14 are up-regulated in the CNS in AD (11, 12, 13 and SI Appendix, Fig. S6A) and after ischemic stroke in humans and mice (14–16). Importantly, TWEAK/Fn14 signaling was also recently shown to be a pathway necessary for synapse maturation during experience-dependent visual development. Light-induced up-regulation of Fn14 in thalamocortical excitatory neurons and corresponding up-regulation of TWEAK in microglia mediate the elimination of weak synapses and strengthening of remaining synapses in the dLGN (17, 18). Indeed, the communication between neurons and supporting microglia has emerged as a key mechanism regulating neuronal circuitry, with microglia deploying their ramified processes to continuously survey and refine synapses in response to neural activity. Interestingly, TWEAK expression has also been shown to be microglia-enriched in the mouse cortex (19), suggesting that it may play a role in multiple brain regions. Thus, like the complement pathway, the TWEAK/Fn14 pathway could be an important regulator of synapse biology in visual development which is re-engaged and acts generally in different ages and brain regions to contribute to pathology.The involvement of TWEAK/Fn14 signaling in synapse physiology or pathophysiology outside of the developing visual system is unknown. We considered it to be a strong candidate modifier of synaptic function in adults given that Fn14 is up-regulated and required for synaptic refinement in experience-dependent visual development, and TWEAK and Fn14 are up-regulated in contexts of neurological injury/disease, suggesting that the TWEAK/Fn14 system is tuned to periods of substantial change in neuronal activity levels or environment (e.g., eye opening, ischemic stroke). We employed HC slices to test the hypothesis that the TWEAK/Fn14 pathway regulates synaptic function in adult mice and in different disease contexts and delineate its mechanism of action. Herein, we reveal that TWEAK, through neuronal Fn14, mediates acute dampening of basal synaptic transmission and synaptic plasticity in hippocampal slices from mature mice. Furthermore, we demonstrate that TWEAK/Fn14 signaling broadly impacts the phosphorylation state of critical synaptic proteins, suggesting a general role in synapse modulation. Finally, we show that pathway deficiency or pharmacological inhibition of TWEAK/Fn14 signaling augments synaptic transmission and plasticity in amyloid-beta (Aβ)–overexpressing mice and post ischemic stroke animals, two model systems featuring synaptic functional deficits. Thus, our results support that TWEAK/Fn14 constitutes a synaptic regulatory pathway with therapeutic potential for CNS disorders in the adult brain.     

Hemorheology and vascular reactivity in patients with diabetes mellitus type 2

The study aimed to investigate the hemorheological parameters in patients with diabetes mellitus type 2 and to estimate their relationship with the cerebral and cutaneous blood flow and their responses to postural changes. The basic hemorheological constituents: hematocrit (Ht), fibrinogen (Fib), whole blood (WBV) and plasma viscosity (PV) were examined in 20 patients with diabetes mellitus type 2 and in 10 healthy age and sex matched controls. Blood flow velocity in the middle cerebral artery (MCA) was measured by transcranial Doppler monitoring at rest and during 5-min head-up tilt. Also laser Doppler-recorded tiptoe skin blood flow was investigated and venoarteriolar reflex perfusion responses to postural impact was monitored. Significant increase of Fib and WBV at shear rates of 0.0237 s(-1) to 128.5 s(-1) in the patients in comparison to controls was found. The postural challenge caused decrease of the cerebral blood flow velocity and increase of the resistance index (RI) in the diabetic patients. The initial mean skin perfusion values of the tiptoes and the venoarteriolar constriction response indices were significantly higher in the diabetes group. In the patients with diabetes mellitus type 2 the increased blood viscosity values were associated with impaired cerebrovascular and peripheral vascular responces.     

Effect of chromium on the insulin resistance in patients with type II diabetes mellitus

INTRODUCTION: Chromium deficiency in diabetic patients is a debatable problem. The prevailing opinion suggests the presence of low serum concentrations in such patients and therefore an early, long-term addition of chromium to the standard therapy is recommended. PURPOSE: The aim of the present study was to evaluate the effect of chromium on the insulin resistance in diabetic patients with type II diabetes mellitus. MATERIAL AND METHODS: We have studied a total of 34 overweight patients with type II diabetes mellitus, who were distributed in two study sub-groups--patients with very good metabolic control and patients with bad control. For sixty days the patients of both groups received 30 microg of chromium picolinate as food additive. We measured the serum concentration of chromium (using atom-absorption methods), immune-reactive insulin and the insulin resistance index at baseline and at the end of the two-month period. RESULTS: The serum concentrations of chromium was significantly lower in diabetic patients than in the healthy individuals used as controls (2.18 +/- 0.87 nmol/l versus 4.03 +/- 0.96 nmol/l; p < 0.001). We found a significant decrease of the immune-reactive insulin and the insulin resistance index after a two-month application of chromium 30 microg daily (1 tablet of chrome picolinate). The effects of this trace element are analysed in the light of an improved first phase of secretion of insulin or facilitated post-receptor insulin sensibility as a way of potentiating the insulin action. CONCLUSION: Chromium included early in the complex therapy of diabetes is beneficial in the reduction of the degree of insulin resistance.     

Minor and major complications of arthroscopic synovectomy of the knee joint performed by rheumatologist

The aim of the study was to analyze the type and incidence of major and minor complications resulting from arthroscopy with arthroscopic synovectomy of the knee joint performed by rheumatologist in different rheumatological diseases. METHODS: In a prospective study the incidence of complications in arthroscopic subtotal synovectomy with subsequent tidal flow lavage was analyzed in 201 rheumatic patients. The arthroscopic synovectomies were performed by one team of rheumatologists in the operation room of the University Clinic of Rheumatology in the town of Plovdiv for a period of 8-9 years. RESULTS: The major complications related to the arthroscopic synovectomy included septic arthritis (0.5%) and rupture of the joint capsule with edema of the thigh and leg (1.5%). The minor postarthroscopic complications were infection of the operative skin incision (2.0%), hemarthrosis (3.5%), severe postoperative pain (1.5%) and gout relapse (0.5%). Complete recovery was achieved after complications were treated and the result of the synovectomy was not compromised. CONCLUSION: Arthroscopic synovectomy of the knee joint performed by rheumatologist in in-patients involves low risk of complications among which minor operative and postoperative ones are prevalent. These do not compromise near and late results of the arthroscopic synovectomy.     

Guggulsterone and bexarotene induce secretion of exosome‐associated breast cancer resistance protein and reduce doxorubicin resistance in MDA‐MB‐231 cells

Many breast cancer cells acquire multidrug resistance (MDR) mediated by ABC transporters such as breast cancer resistance protein (BCRP/ABCG2). Here we show that incubation of human breast cancer MDA‐MB‐231 cells with farnesoid X receptor antagonist guggulsterone (gug) and retinoid X receptor agonist bexarotene (bex) elevated ceramide, a sphingolipid known to induce exosome secretion. The gug+bex combination reduced cellular levels of BCRP to 20% of control cells by inducing its association and secretion with exosomes. Exogenous C6 ceramide also induced secretion of BCRP‐associated exosomes, while siRNA‐mediated knockdown or GW4869‐mediated inhibition of neutral sphingomyelinase 2 (nSMase2), an enzyme generating ceramide, restored cellular BCRP. Immunocytochemistry showed that ceramide elevation and concurrent loss of cellular BCRP was prominent in Aldefluor‐labeled breast cancer stem‐like cells. These cells no longer excluded the BCRP substrate Hoechst 33342 and showed caspase activation and apoptosis induction. Consistent with reduced BCRP, ABC transporter assays showed that gug+bex increased doxorubicin retention and that the combination of gug+bex with doxorubicin enhanced cell death by more than fivefold. Taken together, our results suggest a novel mechanism by which ceramide induces BCRP secretion and reduces MDR, which may be useful as adjuvant drug treatment for sensitizing breast cancer cells and cancer stem cells to chemotherapy.     

Cost accounting methodologies in price setting of acute inpatient services in Hungary

On the basis of documentary analysis and interviews with decision makers, this paper discusses the cost accounting methodologies used for price setting of inpatient services in the Hungarian health care system focusing on sector of acute inpatient care, which is financed through the Hungarian adaptation of Diagnosis Related Groups since 1993. Hungary has a quite sophisticated DRG system, which had a deep impact on the efficiency of the acute inpatient care sector. Nevertheless, the system requires continuous maintenance, where the cooperation of hospitals, as well as the minimisation of political influence are critical success factors.     

Analysis of exhaled breath condensate in a mixed population of psittacine birds

Collection of exhaled breath condensate (EBC) and the measurement of inflammatory markers contained therein (eg, hydrogen peroxide [H2O2], leukotriene B4 [LTB4], and pH) have been reported to be noninvasive tools for the investigation of respiratory disease in various species. In this study, the EBC of clinically healthy psittacine birds (n = 15) and psittacine birds with respiratory tract disease (n = 19) was examined, and inflammatory markers contained in the EBC were analyzed and compared. Awake birds were placed in an acrylic container from which the outflow passed through a condensation system that collected the EBC. All samples were analyzed for pH, H2O2, and LTB4. The mean values for each of these components, as well as the mean volume of the total EBC, measured from the apparently healthy birds did not differ significantly from those measured in birds with signs of respiratory tract disease. However, LTB4 in the EBC of diseased birds was higher than that of the apparently healthy birds and showed a trend toward significance. The study demonstrated the establishment of a standardized method for collecting and analyzing EBC in psittacine birds and a measurement protocol for pH, H2O2, and LTB4.