Network activity in the brain is associated with a transient increase in extracellular K+ concentration. The excess K+ is removed from the extracellular space by mechanisms proposed to involve ...Kir4.1‐mediated spatial buffering, the Na+/K+/2Cl− cotransporter 1 (NKCC1), and/or Na+/K+‐ATPase activity. Their individual contribution to K+o management has been of extended controversy. This study aimed, by several complementary approaches, to delineate the transport characteristics of Kir4.1, NKCC1, and Na+/K+‐ATPase and to resolve their involvement in clearance of extracellular K+ transients. Primary cultures of rat astrocytes displayed robust NKCC1 activity with K+o increases above basal levels. Increased K+o produced NKCC1‐mediated swelling of cultured astrocytes and NKCC1 could thereby potentially act as a mechanism of K+ clearance while concomitantly mediate the associated shrinkage of the extracellular space. In rat hippocampal slices, inhibition of NKCC1 failed to affect the rate of K+ removal from the extracellular space while Kir4.1 enacted its spatial buffering only during a local K+o increase. In contrast, inhibition of the different isoforms of Na+/K+‐ATPase reduced post‐stimulus clearance of K+ transients. The astrocyte‐characteristic α2β2 subunit composition of Na+/K+‐ATPase, when expressed in Xenopus oocytes, displayed a K+ affinity and voltage‐sensitivity that would render this subunit composition specifically geared for controlling K+o during neuronal activity. In rat hippocampal slices, simultaneous measurements of the extracellular space volume revealed that neither Kir4.1, NKCC1, nor Na+/K+‐ATPase accounted for the stimulus‐induced shrinkage of the extracellular space. Thus, NKCC1 plays no role in activity‐induced extracellular K+ recovery in native hippocampal tissue while Kir4.1 and Na+/K+‐ATPase serve temporally distinct roles. GLIA 2014;62:608–622
Main Points
Kir4.1 and Na+/K+−ATPase serve distinct roles in recovery of activity‐induced K+o in hippocampus.
The α2β2 Na+/K+−ATPase is specifically geared for controlling K+o.
NKCC1 is not involved in stimulus‐induced shrinkage of the extracellular space.
Highlights • This study compares the dynamics of cells’ survival and stroke progression in two widely used mouse models of stroke. • The photothrombotic stroke (PH) is not necessarily a good ...substitute for the standard middle cerebral artery occlusion. • The PH stroke shows delays in cellular response to damage, higher inflammation and increased immune cells infiltration. • These data are critical to understand the exact targets and temporal window of intervention for therapy in human stroke.
Children with familial dysautonomia (FD) are smaller and grow more slowly than the general population. It is unknown whether this abnormal growth is due to comorbidities that patients with FD live ...with, or if it is a direct effect of the disease-causing homozygous ELP-1 mutations. Here, we created growth curves for weight, height, and body mass index (BMI) in male and female children with FD to monitor the nutritional status of patients with FD. We used the New York University (NYU) FD Registry which includes data from 680 individuals with FD who were followed longitudinally since birth. We generated sex-specific FD growth charts for three age ranges (birth to 36 months, 2 to 20 years, and 2 to 40 years) and compared them to the general population. We generated Kaplan-Meier curves to test the hypothesis that FD patients with low BMI had shorter survival than the rest of the cohort. Growth charts generated from 591 individuals with FD show that these patients grow more slowly, reach less height, and gain less weight than the general population. The impact of FD on height was more pronounced in girls than in boys. However, both groups showed markedly low weights, which resulted in low BMI. Low weight, but not height, is already evident at birth. In a subpopulation of FD patients, we found that treatment with growth hormone or spinal fusion surgery helped patients achieve the expected growth characteristic of FD patients, but these treatments did not lead FD patients to achieve the growth pattern of the general population. Contrary to our hypothesis, low BMI had no impact on patient survival. Pediatric patients with FD have lower height, weight, and BMI compared to the general pediatric population, but this does not appear to affect survival. Growth curves specific to the FD population are an important tool to monitor growth and nutritional status in pediatric patients with FD when the general population growth curves are of limited use.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Traumatic spinal cord injury is characterized by an immediate, irreversible loss of tissue at the lesion site, as well as a secondary expansion of tissue damage over time. Although secondary injury ...should, in principle, be preventable, no effective treatment options currently exist for patients with acute spinal cord injury (SCI). Excessive release of ATP by the traumatized tissue, followed by activation of high-affinity P2X7 receptors, has previously been implicated in secondary injury, but no clinically relevant strategy by which to antagonize P2X7 receptors has yet, to the best of our knowledge, been reported. Here we have tested the neuroprotective effects of a systemically administered P2X7R antagonist, Brilliant blue G (BBG), in a weight-drop model of thoracic SCI in rats. Administration of BBG 15 min after injury reduced spinal cord anatomic damage and improved motor recovery without evident toxicity. Moreover, BBG treatment directly reduced local activation of astrocytes and microglia, as well as neutrophil infiltration. These observations suggest that BBG not only protected spinal cord neurons from purinergic excitotoxicity, but also reduced local inflammatory responses. Importantly, BBG is a derivative of a commonly used blue food color (FD&C blue No. 1), which crosses the blood-brain barrier. Systemic administration of BBG may thus comprise a readily feasible approach by which to treat traumatic SCI in humans.
Ammonia is a ubiquitous waste product of protein metabolism that can accumulate in numerous metabolic disorders, causing neurological dysfunction ranging from cognitive impairment to tremor, ataxia, ...seizures, coma and death. The brain is especially vulnerable to ammonia as it readily crosses the blood-brain barrier in its gaseous form, NH3, and rapidly saturates its principal removal pathway located in astrocytes. Thus, we wanted to determine how astrocytes contribute to the initial deterioration of neurological functions characteristic of hyperammonemia in vivo. Using a combination of two-photon imaging and electrophysiology in awake head-restrained mice, we show that ammonia rapidly compromises astrocyte potassium buffering, increasing extracellular potassium concentration and overactivating the Na(+)-K(+)-2Cl(-) cotransporter isoform 1 (NKCC1) in neurons. The consequent depolarization of the neuronal GABA reversal potential (EGABA) selectively impairs cortical inhibitory networks. Genetic deletion of NKCC1 or inhibition of it with the clinically used diuretic bumetanide potently suppresses ammonia-induced neurological dysfunction. We did not observe astrocyte swelling or brain edema in the acute phase, calling into question current concepts regarding the neurotoxic effects of ammonia. Instead, our findings identify failure of potassium buffering in astrocytes as a crucial mechanism in ammonia neurotoxicity and demonstrate the therapeutic potential of blocking this pathway by inhibiting NKCC1.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Traumatic brain injury (TBI) is not only a leading cause for morbidity and mortality in young adults (Bruns and Hauser, Epilepsia 44(Suppl 10):210,
2003
), but also a leading cause of seizures. ...Understanding the seizure-inducing mechanisms of TBI is of the utmost importance, because these seizures are often resistant to traditional first- and second-line anti-seizure treatments. The early post-traumatic seizures, in turn, are a contributing factor to ongoing neuropathology, and it is critically important to control these seizures. Many of the available anti-seizure drugs target gamma-aminobutyric acid (GABA
A
) receptors. The inhibitory activity of GABA
A
receptor activation depends on low intracellular Cl
−
, which is achieved by the opposing regulation of Na
+
–K
+
–Cl
−
cotransporter 1 (NKCC1) and K
+
–Cl
−
–cotransporter 2 (KCC2). Up-regulation of NKCC1 in neurons has been shown to be involved in neonatal seizures and in ammonia toxicity-induced seizures. Here, we report that TBI-induced up-regulation of NKCC1 and increased intracellular Cl
−
concentration. Genetic deletion of NKCC1 or pharmacological inhibition of NKCC1 with bumetanide suppresses TBI-induced seizures. TGFβ expression was also increased after TBI and competitive antagonism of TGFβ reduced NKKC1 expression, ameliorated reactive astrocytosis, and inhibited seizures. Thus, TGFβ might be an important pathway involved in NKCC1 up-regulation after TBI. Our findings identify neuronal up-regulation of NKCC1 and its mediation by TGFβ, as a potential and important mechanism in the early post-traumatic seizures, and demonstrate the therapeutic potential of blocking this pathway.
In this study, we investigated whether the ability of Eph receptor signaling to mediate cell repulsion is antagonized by fibroblast growth factor receptor (FGFR) activation that can promote cell ...invasion. We find that activation of FGFR1 in EphB2-expressing cells prevents segregation, repulsion, and collapse responses to ephrinB1 ligand. FGFR1 activation leads to increased phosphorylation of unstimulated EphB2, which we show is caused by down-regulation of the leukocyte common antigen-related tyrosine phosphatase receptor that dephosphorylates EphB2. In addition, FGFR1 signaling inhibits further phosphorylation of EphB2 upon stimulation with ephrinB1, and we show that this involves a requirement for the mitogen-activated protein kinase (MAPK) pathway. In the absence of activated FGFR1, EphB2 activates the MAPK pathway, which in turn promotes EphB2 activation in a positive feedback loop. However, after FGFR1 activation, the induction of Sprouty genes inhibits the MAPK pathway downstream of EphB2 and decreases cell repulsion and segregation. These findings reveal a novel feedback loop that promotes EphB2 activation and cell repulsion that is blocked by transcriptional targets of FGFR1.
Propionic Acidemia (PA) is characterized by the accumulation of propionic acid (PPA), its toxic derivatives, and ammonia. The disease causes multiorgan damage, especially in heart, pancreas, and ...brain; seizures and intellectual disability are often described. Some PA children also show autism spectrum disorders (ASD). In this study, we have compiled data from 62 individuals from the Propionic Acidemia International Patient Registry and compared it to the published literature on the prevalence of autism in PA. The PA registry shows a significant proportion of ASD diagnoses that is consistent with the combined prevalence reported in the literature. It also shows that ASD in PA is gender balanced and it is diagnosed at older ages (median age 8 years) than in the national registry for autism (median age 4.3 years), which raises the possibility, among others, of PA specific risk factors affecting the natural history of ASD. Data from patient registries provide valuable information on studying the mechanisms involved in a rare disease, although more outreach effort must be done to increase participation and consistency in data entry.
The destruction of the World Trade Center (WTC) on September 11, 2001 (9/11) released large amounts of toxic dusts and fumes into the air that exposed many community members who lived and/or worked ...in the local area. Many community members, defined as WTC survivors by the federal government, developed lower respiratory symptoms (LRS). We previously reported the persistence of these symptoms in patients with normal spirometry despite treatment with inhaled corticosteroids and/or long-acting bronchodilators. This report expands upon our study of this group with the goal to identify molecular markers associated with exposure and heterogeneity in WTC survivors with LRS using a selected plasma biomarker approach. Samples from WTC survivors with LRS (
= 73, WTCS) and samples from healthy control participants of the NYU Bellevue Asthma Registry (NYUBAR,
= 55) were compared. WTCS provided information regarding WTC dust exposure intensity. Hierarchical clustering of the linear biomarker data identified two clusters within WTCS and two clusters within NYUBAR controls. Comparison of the WTCS clusters showed that one cluster had significantly increased levels of circulating matrix metalloproteinases (MMP1, 2, 3, 8, 12, 13), soluble inflammatory receptors (receptor for advanced glycation end-products-RAGE, Interleukin-1 receptor antagonist (IL-1RA), suppression of tumorigenicity (ST)2, triggering receptor expressed on myeloid cells (TREM)1, IL-6Ra, tumor necrosis factor (TNF)RI, TNFRII), and chemokines (IL-8, CC chemokine ligand- CCL17). Furthermore, this WTCS cluster was associated with WTC exposure variables, ash at work, and the participant category workers; but not with the exposure variable WTC dust cloud at 9/11. A comparison of WTC exposure categorial variables identified that chemokines (CCL17, CCL11), circulating receptors (RAGE, TREM1), MMPs (MMP3, MMP12), and vascular markers (Angiogenin, vascular cell adhesion molecule-VCAM1) significantly increased in the more exposed groups. Circulating biomarkers of remodeling and inflammation identified clusters within WTCS and were associated with WTC exposure.
The purpose of this study was to assess the effectivity of upfront kilovoltage intraoperative radiotherapy (IORT) as a boost in high-risk early-stage breast cancer patients from an international ...pooled cohort.
Patients from four centers in three different countries were retrospectively screened. Those with a minimum 1-year follow-up were included. Cumulative local (LR), regional (RR), and distant metastasis rates (DM) were analyzed. Additionally, the estimated overall survival (OS) was assessed. The Cox regression analysis was performed to identify failure predicting factors.
A total of 653 patients from centers in Peru, Spain, and Germany were included. The median follow-up was 55 (12-180) months, and age was 58 (27-86) years. Clinical tumor (T) staging was T1 65.85%, T2 30.17%, and T3 3.98%. Positive margins were found in 7.9% and
component in 20.06%. The median IORT dose was 20 (6-20). The median time from IORT to EBRT was 74.5 (13-364) days. An overall 3.4% (n = 22) of patients developed local recurrence at some point during follow-up. The 12-, 60-, and 120-month cumulative LR were 0.3%, 2.3%, and 7.9%, respectively. After multivariate analysis, only age <50 remained to be a significant prognostic factor for local recurrence (HR 0.19, 95% CI 0.08-0.47; p < 0.05). The 10-year estimated OS was 81.2%.
Upfront boost with IORT yields similar local control outcomes to those EBRT-based reports. Results from prospective trials, regarding toxicity, cosmesis, and effectivity are awaited to confirm these findings.
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