Monosialotetrahexosy-1 ganglioside attenuates diabetes-associated cerebral ischemia/reperfusion injury through suppression of the endoplasmic reticulum stress-induced apoptosis

Rehabilitation report of 2 cases of spinal cord ischemic injury after intra-aortic repair

RATIONALE

Spinal cord ischemia injury is a serious complication after intra-aortic surgery, with a low incidence but high disability rate. However, patients often do not receive comprehensive treatment in the early stages of the disease. Therefore, active neurological intervention is needed to protect and prevent spinal cord ischemia during and after surgery. In this paper, rehabilitation program and imaging data of 2 cases with spinal cord ischemic injury are presented and discussed regarding causes, prevention and acute treatment with this disease, which could be referred by clinicians.

PATIENT CONCERNS

Case report 1: A 69-year-old male patient underwent aortic arch aneurysm and thoracic endovascular aortic repair (coated stent) was performed under general anesthesia. Complete paralysis of both lower limbs, constipation, and urinary retention occurred after surgery and was subsequently referred to our rehabilitation department. Case report 2: A man aged 41 years experienced sudden chest pain with no dizziness or headache. Weakness of both lower limbs gradually appeared over 30 minutes with subsequent loss of consciousness. He was diagnosed with aortic dissection and underwent aortic stent implantation. Inpatient rehabilitation began systematically 3 months after discharge.

DIAGNOSES

The 2 patients were diagnosed with paraplegia and spinal cord ischemic injury.

INTERVENTIONS

The patients received strength and transfer training, sensory input, health mission, and activities of daily living.

OUTCOMES

Patient 1 returned home without assistive devices and patient 2 returned home with wheelchair.

LESSONS

Perioperative spinal cord protection is directly related to postoperative quality of life. Once the symptoms of spinal cord ischemic injury occur, cerebrospinal fluid drainage should be performed as soon as possible to increase mean arterial pressure. At the same time, methylprednisolone, ganglioside, anticoagulation, vasodilator drugs, and symptomatic supportive treatments are required. Intercostal artery and subclavian artery are reconstructed if necessary. Symptom stability flags referral to commence rehabilitation. Repetitive functional training is necessary to help patients return to the family and society as soon as possible.

GM1 Ameliorates Neuronal Injury in Rats after Cerebral Ischemia and Reperfusion: Potential Contribution of Effects on SPTBN1-mediated Signaling

Monosialoganglioside GM1 (GM1) has long been used as a therapeutic agent for neurological diseases in the clinical treatment of ischemic stroke. However, the mechanism underlying the neuroprotective function of GM1 is still obscure until now. In this study, we investigated the effects of GM1 in ischemia and reperfusion (I/R) brain injury models. Middle cerebral artery occlusion and reperfusion (MCAO/R) rats were treated with GM1 (60 mg·kg-1·d-1, tail vein injection) for 2 weeks. The results showed that GM1 substantially attenuated the MCAO/R-induced neurological dysfunction and inhibited the inflammatory responses and cell apoptosis in ischemic parietal cortex. We further revealed that GM1 inhibited the activation of NFκB/MAPK signaling pathway induced by MCAO/R injury. To explore its underlying mechanism of the neuroprotective effect, transcriptome sequencing was introduced to screen the differentially expressed genes (DEGs). By function enrichment and PPI network analyses, Sptbn1 was identified as a node gene in the network regulated by GM1 treatment. In the MCAO/R model of rats and oxygen-glucose deprivation and reperfusion (OGD/R) model of primary culture of rat cortical neurons, we first found that SPTBN1 was involved in the attenuation of I/R induced neuronal injury after GM1 administration. In SPTBN1-knockdown SH-SY5Y cells, the treatment with GM1 (20 μM) significantly increased SPTBN1 level. Moreover, OGD/R decreased SPTBN1 level in SPTBN1-overexpressed SH-SY5Y cells. These results indicated that GM1 might achieve its potent neuroprotective effects by regulating inflammatory response, cell apoptosis, and cytomembrane and cytoskeleton signals through SPTBN1. Therefore, SPTBN1 may be a potential target for the treatment of ischemic stroke.

Ganglioside GM1 and the Central Nervous System

GM1 is one of the major glycosphingolipids (GSLs) on the cell surface in the central nervous system (CNS). Its expression level, distribution pattern, and lipid composition are dependent upon cell and tissue type, developmental stage, and disease state, which suggests a potentially broad spectrum of functions of GM1 in various neurological and neuropathological processes. The major focus of this review is the roles that GM1 plays in the development and activities of brains, such as cell differentiation, neuritogenesis, neuroregeneration, signal transducing, memory, and cognition, as well as the molecular basis and mechanisms for these functions. Overall, GM1 is protective for the CNS. Additionally, this review has also examined the relationships between GM1 and neurological disorders, such as Alzheimer's disease, Parkinson's disease, GM1 gangliosidosis, Huntington's disease, epilepsy and seizure, amyotrophic lateral sclerosis, depression, alcohol dependence, etc., and the functional roles and therapeutic applications of GM1 in these disorders. Finally, current obstacles that hinder more in-depth investigations and understanding of GM1 and the future directions in this field are discussed.

Ischemic brain injury in diabetes and endoplasmic reticulum stress

Diabetes is a widespread disease characterized by high blood glucose levels due to abnormal insulin activity, production, or both. Chronic diabetes causes many secondary complications including cardiovascular disease: a life-threatening complication. Cerebral ischemia-related mortality, morbidity, and the extent of brain injury are high in diabetes. However, the mechanism of increase in ischemic brain injury during diabetes is not well understood. Multiple mechanisms mediate diabetic hyperglycemia and hypoglycemia-induced increase in ischemic brain injury. Endoplasmic reticulum (ER) stress mediates both brain injury as well as brain protection after ischemia-reperfusion injury. The pathways of ER stress are modulated during diabetes. Free radical generation and mitochondrial dysfunction, two of the prominent mechanisms that mediate diabetic increase in ischemic brain injury, are known to stimulate the pathways of ER stress. Increased ischemic brain injury in diabetes is accompanied by a further increase in the activation of ER stress. As there are many metabolic changes associated with diabetes, differential activation of the pathways of ER stress may mediate pronounced ischemic brain injury in subjects suffering from diabetes. We presently discuss the literature on the significance of ER stress in mediating increased ischemia-reperfusion injury in diabetes.

Gangliosides in the Brain: Physiology, Pathophysiology and Therapeutic Applications

Gangliosides are glycosphingolipids highly abundant in the nervous system, and carry most of the sialic acid residues in the brain. Gangliosides are enriched in cell membrane microdomains ("lipid rafts") and play important roles in the modulation of membrane proteins and ion channels, in cell signaling and in the communication among cells. The importance of gangliosides in the brain is highlighted by the fact that loss of function mutations in ganglioside biosynthetic enzymes result in severe neurodegenerative disorders, often characterized by very early or childhood onset. In addition, changes in the ganglioside profile (i.e., in the relative abundance of specific gangliosides) were reported in healthy aging and in common neurological conditions, including Huntington's disease (HD), Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), stroke, multiple sclerosis and epilepsy. At least in HD, PD and in some forms of epilepsy, experimental evidence strongly suggests a potential role of gangliosides in disease pathogenesis and potential treatment. In this review, we will summarize ganglioside functions that are crucial to maintain brain health, we will review changes in ganglioside levels that occur in major neurological conditions and we will discuss their contribution to cellular dysfunctions and disease pathogenesis. Finally, we will review evidence of the beneficial roles exerted by gangliosides, GM1 in particular, in disease models and in clinical trials.

The role of sphingolipids in endoplasmic reticulum stress

The endoplasmic reticulum (ER) is an important intracellular compartment in eukaryotic cells and has diverse functions, including protein synthesis, protein folding, lipid metabolism and calcium homeostasis. ER functions are disrupted by various intracellular and extracellular stimuli that cause ER stress, including the inhibition of glycosylation, disulphide bond reduction, ER calcium store depletion, impaired protein transport to the Golgi, excessive ER protein synthesis, impairment of ER-associated protein degradation and mutated ER protein expression. Distinct ER stress signalling pathways, which are known as the unfolded protein response, are deployed to maintain ER homeostasis, and a failure to reverse ER stress triggers cell death. Sphingolipids are lipids that are structurally characterized by long-chain bases, including sphingosine or dihydrosphingosine (also known as sphinganine). Sphingolipids are bioactive molecules long known to regulate various cellular processes, including cell proliferation, migration, apoptosis and cell-cell interaction. Recent studies have uncovered that specific sphingolipids are involved in ER stress. This review summarizes the roles of sphingolipids in ER stress and human diseases in the context of pathogenic events.

GM1 Ganglioside Is A Key Factor in Maintaining the Mammalian Neuronal Functions Avoiding Neurodegeneration

Many species of ganglioside GM1, differing for the sialic acid and ceramide content, have been characterized and their physico-chemical properties have been studied in detail since 1963. Scientists were immediately attracted to the GM1 molecule and have carried on an ever-increasing number of studies to understand its binding properties and its neurotrophic and neuroprotective role. GM1 displays a well balanced amphiphilic behavior that allows to establish strong both hydrophobic and hydrophilic interactions. The peculiar structure of GM1 reduces the fluidity of the plasma membrane which implies a retention and enrichment of the ganglioside in specific membrane domains called lipid rafts. The dynamism of the GM1 oligosaccharide head allows it to assume different conformations and, in this way, to interact through hydrogen or ionic bonds with a wide range of membrane receptors as well as with extracellular ligands. After more than 60 years of studies, it is a milestone that GM1 is one of the main actors in determining the neuronal functions that allows humans to have an intellectual life. The progressive reduction of its biosynthesis along the lifespan is being considered as one of the causes underlying neuronal loss in aged people and severe neuronal decline in neurodegenerative diseases. In this review, we report on the main knowledge on ganglioside GM1, with an emphasis on the recent discoveries about its bioactive component.

Gangliosides: Treatment Avenues in Neurodegenerative Disease

Gangliosides are cell membrane components, most abundantly in the central nervous system (CNS) where they exert among others neuro-protective and -restorative functions. Clinical development of ganglioside replacement therapy for several neurodegenerative diseases was impeded by the BSE crisis in Europe during the 1990s. Nowadays, gangliosides are produced bovine-free and new pre-clinical and clinical data justify a reevaluation of their therapeutic potential in neurodegenerative diseases. Clinical experience is greatest with monosialo-tetrahexosyl-ganglioside (GM1) in the treatment of stroke. Fourteen randomized controlled trials (RCTs) in overall >2,000 patients revealed no difference in survival, but consistently superior neurological outcomes vs. placebo. GM1 was shown to attenuate ischemic neuronal injuries in diabetes patients by suppression of ERK1/2 phosphorylation and reduction of stress to the endoplasmic reticulum. There is level-I evidence from 5 RCTs of a significantly faster recovery with GM1 vs. placebo in patients with acute and chronic spinal cord injury (SCI), disturbance of consciousness after subarachnoid hemorrhage, or craniocerebral injuries due to closed head trauma. In Parkinson's disease (PD), two RCTs provided evidence of GM1 to be superior to placebo in improving motor symptoms and long-term to result in a slower than expected symptom progression, suggesting disease-modifying potential. In Alzheimer's disease (AD), the role of gangliosides has been controversial, with some studies suggesting a "seeding" role for GM1 in amyloid β polymerization into toxic forms, and others more recently suggesting a rather protective role in vivo. In Huntington's disease (HD), no clinical trials have been conducted yet. However, low GM1 levels observed in HD cells were shown to increase cell susceptibility to apoptosis. Accordingly, treatment with GM1 increased survival of HD cells in vitro and consistently ameliorated pathological phenotypes in several murine HD models, with effects seen at molecular, cellular, and behavioral level. Given that in none of the clinical trials using GM1 any clinically relevant safety issues have occurred to date, current data supports expanding GM1 clinical research, particularly to conditions with high, unmet medical need.

Pathophysiology of Ganglioside GM1 in Ischemic Stroke: Ganglioside GM1: A Critical Review

Ganglioside GM1 is a member of the ganglioside family which has been used in many countries and is thought of as a promising alternative treatment for preventing several neurological diseases, including cerebral ischemic injury. The therapeutic effects of GM1 have been proved both in neonates and in adults following ischemic brain damage; however, its clinical efficacy in patients with ischemic stroke is still uncertain. This review examines the recent knowledge of the neuroprotective properties of GM1 in ischemic stroke, collected in the past two decades. We conclude that GM1 may have potential for stroke treatment, although we need to be cautious in respect of its complications.

CCAAT/enhancer binding protein homologous protein knockdown alleviates hypoxia-induced myocardial injury in rat cardiomyocytes exposed to high glucose

Diabetic patients are more sensitive to ischemic injury than non-diabetics. Endoplasmic reticulum (ER) stress has been reported to be closely associated with the pathophysiology of ischemic injury in diabetes. The aim of the present study was to investigate the mechanisms involved in the progression of diabetes complicated by myocardial infarction (MI) and further verify the role of CCAAT/enhancer binding protein (C/EBP)-homologous protein (CHOP) using an in vitro model of diabetes/MI. The rats were exposed to 65 mg/kg streptozotocin (STZ) and left anterior descending (LAD) coronary artery ligation. ST-segment elevation, heart rate, left ventricular systolic pressure (LVSP) and LV end-diastolic pressure (LVEDP) were measured. Serum creatinine kinase-MB (CK-MB) and cardiac troponin T (cTnT) levels were examined by ELISA. Infarct size and apoptosis were measured by triphenyltetrazolium chloride staining and terminal deoxynucleotidyl-transferase-mediated dUTP nick end labeling assay. Pathological changes were evaluated by hematoxylin and eosin staining. H9c2 cells were used to establish an in vitro model of diabetes complicated by MI. Following CHOP knockdown, cell viability, cell cycle distribution and apoptosis were examined by Cell Counting Kit-8 assay, flow cytometry and Hoechst staining. Glucose-regulated protein 78 (GRP78), CHOP, B-cell lymphoma 2 (Bcl-2), Bcl-2-associated X protein (Bax), endoplasmic reticulum oxidoreductase 1 (Ero1)-α, Ero1β and protein disulfide isomerase (PDI) levels in both myocardial tissues and H9c2 cells were determined by western blotting. In the present study, diabetes complicated by MI promoted ST-segment elevation and myocardial apoptosis, increased infarct size, induced pathological changes and elevated LVEDP, CK-MB, cTnT, GRP78, CHOP, Bax, Ero1α, Ero1β and PDI; however, it decreased heart rate, LVSP and Bcl-2. Additionally, high glucose combined with hypoxic treatment reduced cell viability, induced cell cycle arrest at G1 phase, promoted cell apoptosis, and activated the GRP78/CHOP and Ero1/PDI signaling pathways, which were reversed by CHOP knockdown. Thus, CHOP may be an effective therapeutic target for the treatment of diabetes complicated by MI.