sphingosine-kinase and Brain-Injuries

The pathogenic processes of brain injury after intracerebral hemorrhage (ICH) have not yet been fully elucidated. Increasing evidence suggests that ferroptosis activation aggravates injury after ICH, but the underlying mechanism remains unclear. Sphingosine kinase 1 (Sphk1) is a key enzyme in the regulation of sphingosine metabolism involved in the ferroptosis pathway, but its role in ICH needs clarification. In this study, transcriptional changes in ICH patients were assessed by microarray data, exposing Sphk1 as a highly upregulated gene during ICH. Furthermore, Sphk1 chemical inhibitors and siRNA were used to inhibit ICH-induced Sphk1 upregulation in in vivo and in vitro models, showing that Sphk1 inhibition after protects against ferroptosis and attenuates secondary brain injury and cell death. Mechanistically, this study unveiled that sphingosine kinase 1/sphingosine 1-phosphate/extracellular-regulated protein kinases/phosphorylated extracellular-regulated protein kinases (Sphk1/S1p/ERK/p-ERK) pathway is responsible for regulation of ferroptosis leading to secondary brain injury and cell death following ICH. Collectively, this study demonstrates that ferroptosis is closely associated with ICH, and that Sphk1 has a critical role in this lethal process. These results suggest a novel unique and effective therapeutic approach for ICH prevention and treatment.

Topics: Brain Injuries; Cerebral Hemorrhage; Ferroptosis; Humans; Phosphotransferases (Alcohol Group Acceptor); Sphingosine

Allicin, one of the main biologically active compounds derived from garlic, has been shown to exert various pharmacological activities and is considered to have therapeutic potential for many pathologic conditions. In the present study, we investigated the potential post-ischemic neuroprotective effects of allicin and its underlying mechanisms. Using a rat middle cerebral artery occlusion (MCAO) model, we found that intraperitoneal treatment with 50 mg/kg allicin significantly reduced brain infarct volume, attenuated cerebral edema and decreased the neurological deficit score. Allicin treatment also diminished TUNEL positive cells and inhibited the activation of caspase-3 after MCAO. These protective effects could be observed even if the administration was delayed to 6 h after injury. In addition, we evaluated the in vitro protective effects of allicin against oxygen glucose deprivation (OGD) induced neuronal injury in primary cultured cortical neurons. Allicin (50 μM) increased neuronal viability, decreased lactate dehydrogenase (LDH) release and inhibited apoptotic neuronal death after OGD. These protective effects could be observed even if the administration was delayed to 4 h after injury. Furthermore, allicin significantly increased the expression of sphingosine kinases 2 (Sphk2) both in vivo and in vitro. Pretreatment with the Sphk2 inhibitor ABC294640 partially reversed the protective effects of allicin against MCAO and OGD injury, indicating that an Sphk2-mediated mechanism was involved in allicin-induced protection in our models. The combination of findings suggests that post-injury administration of allicin has potential as a neuroprotective strategy for ischemic stroke.

Topics: Animals; Brain Injuries; Brain Ischemia; Cell Survival; Cells, Cultured; Cerebral Cortex; Disulfides; Drug Administration Schedule; Enzyme Activation; Male; Phosphotransferases (Alcohol Group Acceptor); Rats; Rats, Sprague-Dawley; Sulfinic Acids

In addition to immediate brain damage, traumatic brain injury (TBI) initiates a cascade of pathophysiological events producing secondary injury. The biochemical and cellular mechanisms that comprise secondary injury are not entirely understood. Herein, we report a substantial deregulation of cerebral sphingolipid metabolism in a mouse model of TBI. Sphingolipid profile analysis demonstrated increases in sphingomyelin species and sphingosine concurrently with up-regulation of intermediates of de novo sphingolipid biosynthesis in the brain. Investigation of intracellular sites of sphingosine accumulation revealed an elevation of sphingosine in mitochondria due to the activation of neutral ceramidase (NCDase) and the reduced activity of sphingosine kinase 2 (SphK2). The lack of change in gene expression suggested that post-translational mechanisms are responsible for the shift in the activities of both enzymes. Immunoprecipitation studies revealed that SphK2 is complexed with NCDase and cytochrome oxidase (COX) subunit 1 in mitochondria and that brain injury hindered SphK2 association with the complex. Functional studies showed that sphingosine accumulation resulted in a decreased activity of COX, a rate-limiting enzyme of the mitochondrial electron transport chain. Knocking down NCDase reduced sphingosine accumulation in mitochondria and preserved COX activity after the brain injury. Also, NCDase knockdown improved brain function recovery and lessened brain contusion volume after trauma. These studies highlight a novel mechanism of secondary TBI involving a disturbance of sphingolipid-metabolizing enzymes in mitochondria and suggest a critical role for mitochondrial sphingosine in promoting brain injury after trauma.

Topics: Alkaline Ceramidase; Animals; Brain; Brain Injuries; Electron Transport Complex IV; Humans; Male; Mice; Mice, Knockout; Mitochondria; Nerve Tissue Proteins; Phosphotransferases (Alcohol Group Acceptor); Sphingosine

Isoflurane, a volatile anesthetic agent, has been recognized for its potential neuroprotective properties and has antiapoptotic effects. We examined whether isoflurane posttreatment is protective against early brain injury after subarachnoid hemorrhage and determined whether this effect needs sphingosine-related pathway activation.. Controlled in vivo laboratory study.. Animal research laboratory.. One hundred seventy-nine 8-wk-old male CD-1 mice weighing 30-38 g.. Subarachnoid hemorrhage was induced in mice by endovascular perforation. Animals were randomly assigned to sham-operated, subarachnoid hemorrhage-vehicle, and subarachnoid hemorrhage+2% isoflurane. Neurobehavioral function and brain edema were evaluated at 24 and 72 hrs. The expression of sphingosine kinase, phosphorylated Akt, and cleaved caspase-3 was determined by Western blotting and immunofluorescence. Neuronal cell death was examined by terminal deoxynucleotidyl transferase-mediated uridine 5'-triphosphate-biotin nick end-labeling staining. Effects of a sphingosine kinase inhibitor N, N-dimethylsphingosine or a sphingosine 1 phosphate receptor inhibitor VPC23019 on isoflurane's protective action against postsubarachnoid hemorrhage early brain injury were also examined.. Isoflurane significantly improved neurobehavioral function and brain edema at 24 hrs but not 72 hrs after subarachnoid hemorrhage. At 24 hrs, isoflurane attenuated neuronal cell death in the cortex, associated with an increase in sphingosine kinase 1 and phosphorylated Akt, and a decrease in cleaved caspase-3. The beneficial effects of isoflurane were abolished by N, N-dimethylsphingosine and VPC23019.. Isoflurane posttreatment delays the development of postsubarachnoid hemorrhage early brain injury through antiapoptotic mechanisms including sphingosine-related pathway activation, implying its use for anesthesia during acute aneurysm surgery or intervention.

Topics: Animals; Apoptosis; Brain Edema; Brain Injuries; Isoflurane; Lysophospholipids; Male; Mice; Neuroprotective Agents; Phosphotransferases (Alcohol Group Acceptor); Random Allocation; Signal Transduction; Sphingosine; Subarachnoid Hemorrhage