Propofol protects against blood-spinal cord barrier disruption induced by ischemia/reperfusion injury

Propofol alleviates spinal cord ischemia-reperfusion injury by preserving PI3K/AKT/GIT1 axis

Spinal cord ischemia-reperfusion injury (SCIRI) is a major contributor to neurological damage and mortality associated with spinal cord dysfunction. This study aims to explore the possible mechanism of Propofol and G-protein-coupled receptor-interacting protein 1 (GIT1) in regulating SCIRI in rat models. SCIRI rat models were established and injected with Propofol, over expression of GIT1 (OE-GIT1), or PI3K inhibitor (LY294002). The neurological function was assessed using Tarlov scoring system, and Hematoxylin & Eosin (H&E) staining was applied to observe morphology changes in spinal cord tissues. Cell apoptosis, blood-spinal cord barriers (BSCB) permeability, and inflammatory cytokines were determined by TdT-mediated dUTP Nick-End Labeling (TUNEL) staining, evans blue (EB) staining, and enzyme-linked immuno sorbent assay (ELISA), respectively. Reverse transcription-quantitative polymerase chain reaction and western blot were used to detect the expression levels of GIT1, endothelial nitric oxide synthase (eNOS), PI3K/AKT signal pathway and apoptosis-related proteins. SCIRI rats had decreased expressions of GIT1 and PI3K/AKT-related proteins, whose expressions can be elevated in response to Propofol treatment. LY294002 can also decrease GIT1 expression levels in SCIRI rats. Propofol can attenuate neurological dysfunction induced by SCIRI, decrease spinal cord tissue injury and BSCB permeability in addition to suppressing cell apoptosis and inflammatory cytokines, whereas further treatment by LY294002 can partially reverse the protective effect of Propofol on SCIRI. Propofol can activate PI3K/AKT signal pathway to increase GIT1 expression level, thus attenuating SCIRI in rat models.

White Cord Syndrome: A Treatment Dilemma

Spinal cord reperfusion injury following decompressive surgery is extremely rare. This complication is known as white cord syndrome (WCS). A 61-year-old male presented with chronic neck stiffness associated with left C6/C7 radiculopathy and numbness. Magnetic resonance imaging (MRI) of the cervical spine reported a severely narrowed left C6/C7 neural exit canal. C6/C7 anterior cervical decompression and fusion (ACDF) was performed. There was no significant intraoperative injury. On postoperative day 6, the patient developed bilateral C8 numbness, which started post-operation. He was treated for surgical site inflammation and was prescribed prednisolone and amitriptyline. However, his condition progressively worsened. At postoperative six weeks, there was right hemisensory loss, right triceps atrophy, and positive right Lhermitte's and Hoffman's tests. This subsequently progressed to right C7 weakness and bilateral lower limb radiculopathy at postoperative eight weeks. Postoperative MRI of the cervical spine revealed a new focal gliosis/edema within the spinal cord at C6/C7. The patient was treated conservatively with pregabalin and was referred for rehabilitation. Early diagnosis and treatment initiation are crucial in the management of WCS. Surgeons should be aware of this potential complication and counsel patients on the risk prior to surgery. Magnetic resonance imaging (MRI) remains the gold standard in the diagnosis of WCS. The current mainstay of treatment is high-dose steroids, intraoperative neurophysiological monitoring, and early recognition of postoperative WCS.

Blood-Spinal Cord Barrier: Its Role in Spinal Disorders and Emerging Therapeutic Strategies

The blood-spinal cord barrier (BSCB) has been long thought of as a functional equivalent to the blood-brain barrier (BBB), restricting blood flow into the spinal cord. The spinal cord is supported by various disc tissues that provide agility and has different local immune responses compared to the brain. Though physiologically, structural components of the BSCB and BBB share many similarities, the clinical landscape significantly differs. Thus, it is crucial to understand the composition of BSCB and also to establish the cause–effect relationship with aberrations and spinal cord dysfunctions. Here, we provide a descriptive analysis of the anatomy, current techniques to assess the impairment of BSCB, associated risk factors and impact of spinal disorders such as spinal cord injury (SCI), amyotrophic lateral sclerosis (ALS), peripheral nerve injury (PNI), ischemia reperfusion injury (IRI), degenerative cervical myelopathy (DCM), multiple sclerosis (MS), spinal cavernous malformations (SCM) and cancer on BSCB dysfunction. Along with diagnostic and mechanistic analyses, we also provide an up-to-date account of available therapeutic options for BSCB repair. We emphasize the need to address BSCB as an individual entity and direct future research towards it.

Therapeutic targets and nanomaterial-based therapies for mitigation of secondary injury after spinal cord injury

Spinal cord injury (SCI) and the resulting neurological trauma commonly result in complete or incomplete neurological dysfunction and there are few effective treatments for primary SCI. However, the following secondary SCI, including the changes of microvasculature, inflammatory response and oxidative stress around the injury site, may provide promising therapeutic targets. The advances of nanomaterials hold promise for delivering therapeutics to alleviate secondary SCI and promote functional recovery. In this review, we highlight recent achievements of nanomaterial-based therapy, specifically targeting blood-spinal cord barrier disruption, mitigation of the inflammatory response and lightening of oxidative stress after spinal cord injury.

Ischemia-Reperfusion Injury After Posterior Cervical Laminectomy

Ischemia-reperfusion injury is a rare but serious complication encountered after spinal decompression surgery. This is only the 11th case reported in the literature. There is no current mainstay of treatment; however, several therapies have been studied. This case presents a patient with myelomalacia who underwent posterior laminectomy and developed diffuse cord edema with postoperative quadriplegia. Ischemia-reperfusion injury is believed to be mediated by oxidative and nitrosative stress leading to protein degradation and lipid peroxidation. It is characterized by myelomalacia in a chronically ischemic spinal cord and hyperintensity on T2-weighted MRI after decompression. Treatment has involved steroids and rehabilitation, and outcomes have ranged from minor improvement to full recovery. Novel treatment options have shown promise in animal models.

Propofol-induced MiR-20b expression initiates endogenous cellular signal changes mitigating hypoxia/re-oxygenation-induced endothelial autophagy in vitro

Certain miRNAs can attenuate hypoxia/re-oxygenation-induced autophagic cell death reported in our previous studies, but how these miRNAs regulate the autophagy-related cellular signaling pathway in preventing cell death is largely unknown. In the current study, the autophagy-related miRNAs of hsa-miR-20b were investigated in an in vitro model of hypoxia/re-oxygenation-induced endothelial autophagic cell death. Of these, miR-20b was found to be the most important miRNA which targeted on the key autophagy kinase ULK1 and inhibited hypoxia/re-oxygenation injury-induced autophagy by decreasing both autophagosomes and LC3I to II transition rate and P62 degradation. These processes were reversed by the transfection of an miR-20b inhibitor. Re-expression of ULK1 restores miR-20b-inhibited autophagy. Propofol, a commonly used anesthetic, promoted miR-20b and METTL3 expression and attenuated endothelial autophagic cell death. The inhibited endogenous expression of miR-20b or silenced METTL3 diminished the protective effect of propofol and accentuated autophagy. Additionally, METTL3 knockdown significantly inhibited miR-20b expression but up-regulated pri-miR-20b expression. Together, our data shows that propofol protects against endothelial autophagic cell death induced by hypoxia/re-oxygenation injury, associated with activation of METTL3/miR-20b/ULK1 cellular signaling.

Ubiquitin and endogenous antioxidant enzymes participate in neuroprotection of the rabbit spinal cord after ischemia and bradykinin postconditioning

The aim of this study was to investigate neuroprotective effect of bradykinin postconditioning on the rabbit spinal cord after 20 min of ischemia and 3 days of reperfusion. Bradykinin was administered by single i.p. application at 1, 6, 12 or 24 h after ischemia. Assessment of neurological function of hind limbs (Tarlov score) was estimated. Quantitative analysis was evaluated by Fluoro Jade B method, NeuN and ubiquitin immunohistochemistry in anterior horn neurons of the spinal cord. Histomorphologically distribution of ubiquitin and endogenous antioxidant enzymes (SOD1, SOD2, catalase) immunoreaction was described. Bradykinin postconditioning showed decreased number of degenerated neurons, increased number of surviving neurons and increase in number of ubiquitin positive neurons in all bradykinin postconditioned groups versus ischemia/reperfusion group. According to our results bradykinin postconditioning applied 24 h after ischemia significantly decreased (p < 0.001) number of degenerated neurons versus ischemia/reperfusion group. The least effective time window for bradykinin postconditioning was at 12 h after ischemia. Tarlov score was significantly improved (p < 0.05) in groups with bradykinin postconditioning applied 1, 6 or 24 h after ischemia versus ischemia/reperfusion group. Tarlov score in group with bradykinin application 12 h after ischemia was significantly decreased (p < 0.05) versus sham control group. Neuronal immunoreaction of ubiquitin, SOD1, SOD2 and catalase influenced by bradykinin postconditioning was dependent on neuronal survival or degeneration. In conclusion, bradykinin postconditioning showed protective effect on neurons in anterior horns of the rabbit spinal cord and improved motor function of hind limbs.

Late-onset "white cord syndrome" in an elderly patient after posterior cervical decompression and fusion: a case report

Introduction

In 2013, a rare early complication following cervical decompression the so-called "white cord syndrome" (WCS) was described for first time. This designation was given on the basis of the postoperative appearance of intramedullary hypertense areas in T2-MRI, resulting in devastating neurological damage. To our knowledge, only three cases of WCS have been published; we hereby present the fourth case, but the first one with late-onset presentation of this syndrome.

Case presentation

A 79-year-old male patient with Nurick grade 3 CSM was referred to our institution. He had already had a double-level C4-C6 anterior cervical decompression and fusion (ACDF) 2 years ago in another institution. The patient underwent posterior decompression from C3 to C6 plus C2-C7 lateral mass screw fusion. Within the first 24 h following surgery, he gradually developed C6 incomplete paraplegia (ASIA B). Cervical MRI disclosed a hypertensive signal in T2-weighted sequences at C6-C7 levels and the diagnosis of WCS was suspected. Revision surgery was made 30 h following our first surgery, with wider posterior decompression accompanied by intravenous methylprednisolone. The patient's neurologic status was improved, but the final neurologic outcome was worse (Nurick 4) than the preoperative status and subsequently did not change at all.

Discussion

To the best of our knowledge, this is the first report of a late-onset WCS and the fourth case of WCS per se. Spine surgeons should be aware of this rare but serious complication. We highlight possible risk factors and review the literature on the hypotheses about the pathophysiology of WCS.

Propofol improved hypoxia-impaired integrity of blood-brain barrier via modulating the expression and phosphorylation of zonula occludens-1

Aims

Hypoxia may damage blood‐brain barrier (BBB). The neuroprotective effect of propofol has been reported. We aimed to identify whether and how propofol improved hypoxia‐induced impairment of BBB integrity.

Methods

Mouse brain microvascular endothelial cells (MBMECs) and astrocytes were cocultured to establish in vitro BBB model. The effects of hypoxia and propofol on BBB integrity were examined. Further, zonula occludens‐1 (ZO‐1) expression and phosphorylation, hypoxia‐inducible factor‐1α (HIF‐1α) and vascular endothelial growth factor (VEGF) expression, intracellular calcium concentration and Ca²⁺/calmodulin‐dependent protein kinase II (CAMKII) activation were measured.

Results

Hypoxia‐impaired BBB integrity, which was protected by propofol. Hypoxia‐reduced ZO‐1 expression, while induced ZO‐1 phosphorylation. These effects were attenuated by propofol. The expression of HIF‐1α and VEGF was increased by hypoxia and was alleviated by propofol. The hypoxia‐mediated suppression of ZO‐1 and impaired BBB integrity was reversed by HIF‐α inhibitor and VEGF inhibitor. In addition, hypoxia increased the intracellular calcium concentration and induced the phosphorylation of CAMKII, which were mitigated by propofol. The hypoxia‐induced phosphorylation of ZO‐1 and impaired BBB integrity was ameliorated by calcium chelator and CAMKII inhibitor.

Conclusion

Propofol could protect against hypoxia‐mediated impairment of BBB integrity. The underlying mechanisms may involve the expression and phosphorylation of ZO‐1.