The glycosphingolipid GM1 binds cholera toxin (CT) on host cells and carries it retrograde from the plasma membrane (PM) through endosomes, the trans-Golgi (TGN), and the endoplasmic reticulum (ER) ...to induce toxicity. To elucidate how a membrane lipid can specify trafficking in these pathways, we synthesized GM1 isoforms with alternate ceramide domains and imaged their trafficking in live cells. Only GM1 with unsaturated acyl chains sorted efficiently from PM to TGN and ER. Toxin binding, which effectively crosslinks GM1 lipids, was dispensable, but membrane cholesterol and the lipid raft-associated proteins actin and flotillin were required. The results implicate a protein-dependent mechanism of lipid sorting by ceramide structure and provide a molecular explanation for the diversity and specificity of retrograde trafficking by CT in host cells.
Display omitted
► Cells sort the glycosphingolipid GM1 by the structure of its ceramide domain (76/89) ► Only unsaturated GM1 ceramides sort retrograde all the way to the ER (64/78) ► GM1 is the vehicle that carries cholera toxin from plasma membrane to ER (61/74) ► Flotillin, cholesterol, and actin are required for GM1 sorting (55/64)
Chinnapen et al. examine how membrane lipids are sorted in mammalian cells and how the membrane glycosphingolipid GM1 can direct cholera toxin trafficking from cell surface into the ER of host cells to cause disease. Their results implicate a protein-dependent mechanism of sorting GM1, determined by its unsaturated ceramide domain.
INTRODUCTION: Traumatic brain injury (TBI) induces immediate mechanical injury, including diffuse axonal shearing and myelin degradation. Epidemiological studies suggest a single, severe TBI ...initiates progressive neurodegeneration, including extensive white matter injury and culminating in long-term cognitive decline. While underlying mechanisms remain undefined, the degree of chronic inflammation correlates with delayed white matter tract damage after TBI. METHODS: Immune cell infiltration and activation was measured using preparative and analytical flow cytometry after controlled cortical impact, a pre-clinical model of focal penetrating injury, in adult mice. To assess T cell priming, APCs pulsed with myelin or isolated after experimental TBI were co-cultured with naÏve splenic T cells. Progressive neurodegeneration was assessed by histology and magnetic resonance imaging at eight weeks post-injury. RESULTS: Peripheral macrophages predominated as APCs within the CNS parenchyma after severe TBI. Myelin-pulsed APCs or APCs isolated after experimental TBI efficiently primed naÏve T cells ex vivo, generating myelin-reactive Th1/Th17 cells. Activity of the master metabolic regulator AMPK, previously shown to promote counter-inflammatory immune polarization, was decreased in myeloid cells after injury. Treatment with metformin, an AMPK activator, restored myeloid AMPK activity and attenuated neurodegenerative changes at eight weeks post-TBI. CONCLUSIONS: TBI-induced immunometabolic dysregulation allows generation of auto-reactive T cells that may contribute to chronic inflammation and progressive neurodegeneration. Metabolic reprogramming of myeloid cells via metformin restores AMPK activity and reduces progressive white matter loss after TBI, representing a potential therapeutic intervention to mitigate long-term consequences of TBI.
Background
Epilepsy, a disease characterized by recurrent seizures, is a common chronic neurologic condition. Antiepileptic drugs (AED) are the mainstay of treatment for epilepsy. Vagus nerve ...stimulation (VNS) surgery is an adjuvant therapy for the treatment of drug refractory epilepsy (DRE). VNS revision and implant removal surgeries remain common.
Methods
Using a single neurosurgeon data registry for epilepsy surgery, we retrospectively analyzed a total of 824 VNS surgeries. Patients were referred to two Level IV Comprehensive Epilepsy centers (from 08/1997 to 08/2022) for evaluation. Patients were divided into four groups: new device placement, revision surgery, removal surgery, and battery replacement for end-of-life of the generator. The primary endpoint was to analyze the reasons that led patients to undergo revision and removal surgeries. The time period from the index surgery to the removal surgery was also calculated.
Results
The median age of patients undergoing any type of surgery was 34 years. The primary reason for revision surgeries was device malfunction, followed by patients’ cosmetic dissatisfaction. There was no statistical sex-difference in revision surgeries. The median age and body mass index (BMI) of patients who underwent revision surgery were 38 years and 26, respectively. On the other hand, the primary reason for removal was lack of efficacy, followed again by cosmetic dissatisfaction. The survival analysis showed that 43% of VNS device remained in place for 5 years and 50% of the VNS devices were kept for 1533 days or 4.2 years.
Conclusions
VNS therapy is safe and well-tolerated. VNS revision and removal surgeries occur in less than 5% of cases. More importantly, attention to detail and good surgical technique at the time of the index surgery can increase patient satisfaction, minimize the need for further surgeries, and improve acceptance of the VNS technology.
To compare the impact of different management strategies on diagnosis of new-onset mental health disorders (MHDs) in patients with vestibular schwannoma (VS) and health care utilization at 1-year ...follow-up.
MarketScan databases were queried using the International Classification of Diseases, Ninth Revision and Tenth Revision and Current Procedural Terminology, Fourth Edition, 2000–2020. We included patients ≥18 years old with a diagnosis of VS who underwent clinical observation, surgery, or stereotactic radiosurgery (SRS) with at least 1 year of follow-up. We looked at health care outcomes and MHDs at 3-month, 6-month, and 1-year follow-up.
The database search identified 23,376 patients. Of these, 94.2% (n = 22,041) were managed conservatively with clinical observation at the initial diagnosis, and 2% (n = 466) underwent surgery. The surgery cohort had the highest incidence of new-onset MHDs followed by SRS and clinical observation cohorts at 3 months (surgery: 17%; SRS: 12%; clinical observation: 7%), 6 months (surgery: 20%; SRS: 16%; clinical observation: 10%), and 12 months (surgery: 27%; SRS: 23%; clinical observation: 16%) (P < 0.0001). The median difference in combined payments between patients with and without MHDs was highest in the surgery cohort followed by SRS and clinical observation cohorts at all time points (12 months: surgery: $14,469; SRS: $10,557; clinical observation: $6439; P = 0.0002).
Compared with clinical observation only, patients who underwent surgery for VS were 2 times more likely and patients who underwent SRS were 1.5 times more likely to develop MHDs with corresponding increase in health care utilization at 1-year follow-up.
Stroke continues to be a major public health issue resulting in high mortality and severe long-term disability. Carotid endarterectomy (CEA) plays an important role in the prevention of ischemic ...stroke. Complications associated with CEA can be life threatening and prompt recognition is crucial. In this report, we present a patient who presented to the hospital with progressive headache, 2 weeks following CEA. He was neurologically intact and hypertensive. Non-contrast head computed tomography (CT) scan showed convexity subarachnoid hemorrhage (SAH). He was found to have a left internal carotid artery dissection. Patients who present to the hospital following CEA with headache and hypertension benefit from a non-contrast head CT scan. The presence of SAH can be a warning sign of cerebral hyperperfusion syndrome. Carotid artery dissection is also a disease entity that can occur in the post-operative period. Prompt recognition and treatment is crucial for the management of these disease entities.
Abstract only
The goal is to develop technology using glycosphingolipids for oral or nasal administration of therapeutic peptides. We recently discovered that the structure of the ceramide domain of ...the ganglioside GM1 dictates intracellular trafficking in epithelial cells. GM1‐ceramides with short or unsaturated fatty acids enter the recycling endosome where they are sorted to multiple destinations including to the basolateral cell surface by transcytosis. GM1‐ceramides with saturated fatty acid chains do not enter these pathways. Here, we test whether GM1 with short‐ or unsaturated chain ceramides can be harnessed as vehicles for transepithelial delivery of bioactive peptides. We linked GM1 to stable versions of the therapeutic hormone glucagon‐like peptide‐1 (GLP‐1). The function of the peptide remained intact in the fusion molecules. The GLP1‐GM1 fusions with short or unsaturated fatty acids were incorporated into apical cell membranes, trafficked into the recycling endosome, and reached the basolateral membrane of polarized epithelial cells. The GLP1‐GM1 fusions with long saturated fatty acid were not sorted into these pathways. Thus, ceramide‐based intra‐cellular trafficking may have clinical utility for delivery of therapeutic cargo by transcytosis across epithelial barriers at mucosal surface. The source of research support is from the NIH/NIDDK R21.
PDF
