Fas and FasL Expression in the Spinal Cord Following Cord Hemisection in the Monkey

Necroptosis pathway emerged as potential diagnosis markers in spinal cord injury

The present research focused on identifying necroptosis-related differentially expressed genes (NRDEGs) in spinal cord injury (SCI) to highlight potential therapeutic and prognostic target genes in clinical SCI. Three SCI-related datasets were downloaded, including GSE151371, GSE5296 and GSE47681. MSigDB and KEGG datasets were searched for necroptosis-related genes (NRGs). Differentially expressed genes (DEGs) and NRGs were intersected to obtain NRDEGs. The MCC algorithm was employed to select the first 10 genes as hub genes. A protein-protein interaction (PPI) network related to NRDEGs was developed utilizing STRING. Several databases were searched to predict interactions between hub genes and miRNAs, transcription factors, potential drugs, and small molecules. Immunoassays were performed to identify DEGs using CIBERSORTx. Additionally, qRT-PCR was carried out to verify NRDEGs in an animal model of SCI. Combined analysis of all datasets identified 15 co-expressed DEGs and NRGs. GO and KEGG pathway analyses highlighted DEGs mostly belonged to pathways associated with necroptosis and apoptosis. Hub gene expression analysis showed high accuracy in SCI diagnosis was associated with the expression of CHMP7 and FADD. A total of two hub genes, i.e. CHMP7, FADD, were considered potential targets for SCI therapy.

Availability of neuregulin-1beta1 protects neurons in spinal cord injury and against glutamate toxicity through caspase dependent and independent mechanisms

Spinal cord injury (SCI) causes sensorimotor and autonomic impairment that partly reflects extensive, permanent loss of neurons at the epicenter and penumbra of the injury. Strategies aimed at enhancing neuronal protection are critical to attenuate neurodegeneration and improve neurological recovery after SCI. In rat SCI, we previously uncovered that the tissue levels of neuregulin-1beta 1 (Nrg-1β1) are acutely and persistently downregulated in the injured spinal cord. Nrg-1β1 is well-known for its critical roles in the development, maintenance and physiology of neurons and glia in the developing and adult spinal cord. However, despite this pivotal role, Nrg-1β1 specific effects and mechanisms of action on neuronal injury remain largely unknown in SCI. In the present study, using a clinically-relevant model of compressive/contusive SCI in rats and an in vitro model of glutamate toxicity in primary neurons, we demonstrate Nrg-1β1 provides early neuroprotection through attenuation of reactive oxygen species, lipid peroxidation, necrosis and apoptosis in acute and subacute stages of SCI. Mechanistically, availability of Nrg-1β1 following glutamate challenge protects neurons from caspase-dependent and independent cell death that is mediated by modulation of mitochondria associated apoptotic cascades and MAP kinase and AKT signaling pathways. Altogether, our work provides novel insights into the role and mechanisms of Nrg-1β1 in neuronal injury after SCI and introduces its potential as a new neuroprotective target for this debilitating neurological condition.

Mesenchymal stem cell derived EVs mediate neuroprotection after spinal cord injury in rats via the microRNA-21-5p/FasL gene axis

Spinal cord injury (SCI) represents a relatively common type of motor system trauma. While the SCI patient will experience varying degrees of paraplegia and quadriplegia, which severely affects their quality of life, a heavy burden is also placed on the family and society as a whole. The exact pathogenic mechanisms underlying this condition remain unknown and no specific treatments are currently available. Findings from recent studies have shown that mesenchymal stem cells (MSCs), derived from extracellular vesicles (EVs) can reduce apoptosis, inflammation and promote angiogenesis after SCI. However, the mechanisms through which EVs exert these effects have yet to be identified, indicating the necessity for further investigation. In the present study, we report that treatment with MSCs-EVs significantly improved functional recovery and attenuated lesion size and apoptosis in a rat model of SCI. These MSCs-EVs were found to be directed to the spinal injury site and mainly incorporated into neurons within the lesioned site of the spinal cord. Tandem Mass Tags quantitative proteomics was applied to compare protein changes after SCI and MSCs-EVs treatment. A total of 883 differential proteins were identified, many of which being associated with apoptosis and inflammation. Subsequently, miRNA contents of MSCs-EVs were determined using qRT-PCR, with the result that miR-21-5p was one of the most highly expressed miRNA in these MSCs-EVs. Moreover, inhibition of miR-21-5p in MSCs-EVs significantly reversed the beneficial effects of MSCs-EVs on motor function and apoptosis, an effect which was associated with modulating FasL expression. The data suggest that modulation of the MSCs-EVs miR-21-5p/FasL gene axis may serve as a promising strategy for clinical treatment of SCI and other neurological diseases.

Minocycline impedes mitochondrial-dependent cell death and stabilizes expression of hypoxia inducible factor-1α in spinal cord injury

INTRODUCTION

One of the crucial mechanisms following spinal cord injury is mitochondria-associated cell death. Minocycline, an anti-inflammatory drug, is well known to impede mitochondrial cell death. However, there has been no study on the effect of minocycline linking Fas cell surface death receptor (FAS)-mediated cell death and hypoxia inducible factor (HIF-1α), the targets involved in mitochondrial cell death.

MATERIAL AND METHODS

Male Sprague Dawley rats (N = 15, divided into three groups) were subjected to traumatic spinal cord injury and were injected with minocycline (n = 5) (90 mg/kg and later a 45 mg/kg dose twice a day (every 12 h)). Injection with sterile PBS in injured animals served as the vehicle (n = 5) and another group comprised healthy animals (n = 5). TUNEL assay was used to quantify cell death. The release of Smac/Diablo, cytochrome-c (cyt-c), HIF-1α, FAS ligand (FASL) and tumour necrosis factor-α (TNF-α) was measured using ELISA. Expression of HIF-1α, FASL and other cell death associated factors was quantified at the mRNA and protein level and confirmed with immunohistochemistry.

RESULTS

There was a marked reduction in the HIF-1α and FASL expression levels in the minocycline-treated group compared to the vehicle. The reduction of HIF-1α and FASL was associated with other factors linked to cell death (Smac/Diablo, cyt-c, TNF-α, p53, caspase-8 and BH3 interacting domain death agonist (BID)) (p < 0.5; *p < 0.05 vs. vehicle group, **p < 0.01 vs. vehicle group).

CONCLUSIONS

The present study focuses on the investigation of minocycline in inhibiting mitochondria-associated cell death by modulating FASL and HIF-1α expression, which are seemingly interlinked mechanisms contributing to cell death.

Role of Caspase-8 and Fas in Cell Death After Spinal Cord Injury

Spinal cord injury (SCI) causes the death of neurons and glial cells due to the initial mechanical forces (i.e., primary injury) and through a cascade of secondary molecular events (e.g., inflammation or excitotoxicity) that exacerbate cell death. The loss of neurons and glial cells that are not replaced after the injury is one of the main causes of disability after SCI. Evidence accumulated in last decades has shown that the activation of apoptotic mechanisms is one of the factors causing the death of intrinsic spinal cord (SC) cells following SCI. Although this is not as clear for brain descending neurons, some studies have also shown that apoptosis can be activated in the brain following SCI. There are two main apoptotic pathways, the extrinsic and the intrinsic pathways. Activation of caspase-8 is an important step in the initiation of the extrinsic pathway. Studies in rodents have shown that caspase-8 is activated in SC glial cells and neurons and that the Fas receptor plays a key role in its activation following a traumatic SCI. Recent work in the lamprey model of SCI has also shown the retrograde activation of caspase-8 in brain descending neurons following SCI. Here, we review our current knowledge on the role of caspase-8 and the Fas pathway in cell death following SCI. We also provide a perspective for future work on this process, like the importance of studying the possible contribution of Fas/caspase-8 signaling in the degeneration of brain neurons after SCI in mammals.

WITHDRAWN: Minocycline an antimicrobial agent attenuates the mitochondrial dependent cell death and stabilizes the expression of HIF-1α in spinal cord injury

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Does repair of spinal cord injury follow the evolutionary theory?

Lower vertebrates, such as fish and amphibians, and higher vertebrates in embryonic development can acquire complete regeneration of complex body structures, including the spinal cord, an important part of the central nervous system. However, with species evolution and development, this regenerative capacity gradually weakens and even disappears, but the cellular and molecular mechanisms remain poorly understood. We explored the differences in mechanisms of spinal cord regeneration capability between lower and higher vertebrates, investigated differences in their cellular and molecular mechanisms and between the spinal cord structures of lower vertebrates and mammals, such as rat and monkey, to search for theoretical evidence and therapeutic targets for nerve regeneration in human spinal cord.

P45 forms a complex with FADD and promotes neuronal cell survival following spinal cord injury

Fas-associated death domain (DD) adaptor (FADD), a member of the DD superfamily, contains both a DD and a death effector domain (DED) that are important in mediating FAS ligand-induced apoptotic signaling. P45 is a unique member of the DD superfamily in that it has a domain with sequence and structural characteristics of both DD and DED. We show that p45 forms a complex with FADD and diminishes Fas-FADD mediated death signaling. The DED of FADD is required for the complex formation with p45. Following spinal cord injury, transgenic mice over-expressing p45 exhibit increased neuronal survival, decreased retraction of corticospinal tract fibers and improved functional recovery. Understanding p45-mediated cellular and molecular mechanisms may provide insights into facilitating nerve regeneration in humans.

Region-specific expression of Dickkopf-like1 in the adult brain. Abbreviated title: Dkkl1 in the adult brain

In the adult, the dickkopf family member Dickkopf-like1 (Dkkl1) has been described as a testicular protein involved in the regulation of spermatocyte apoptosis. However, microarray studies additionally suggested that Dkkl1 regulation is involved in various tumors including high grade gliomas. Since investigations of Dkkl1 in the adult central nervous system are lacking, we analyzed Dkkl1 expression in the adult mouse brain and found a region specific expression pattern with a profoundly high cortical expression. Analysis of transgenic mice in which the lacZ gene was inserted into the Dkkl1 locus further pointed to NeuN-positive neurons as the main source of Dkkl1 in the normal adult brain. In Dkkl1(-/-) mutant mice, gross brain morphology as well as hippocampal and cortical lamination appeared normal. Similarly, neuronal density in cortical layer V was not altered. Thus, Dkkl1 may not be essential for normal brain organization, but could exert import functions during pathological conditions such as tumorigenesis and cancer progression.