The systemic inflammatory response after spinal cord injury damages lungs and kidneys

A Comprehensive Proteomic and Bioinformatic Analysis of Human Spinal Cord Injury Plasma Identifies Proteins Associated with the Complement Cascade and Liver Function as Potential Prognostic Indicators of Neurological Outcome

Spinal cord injury (SCI) is a major cause of disability, with complications postinjury often leading to lifelong health issues with the need for extensive treatment. Neurological outcome post-SCI can be variable and difficult to predict, particularly in incompletely injured patients. The identification of specific SCI biomarkers in blood may be able to improve prognostics in the field. This study has utilized proteomic and bioinformatic methodologies to investigate differentially expressed proteins in plasma samples across human SCI cohorts with the aim of identifying candidate prognostic biomarkers and biological pathway alterations that relate to neurological outcome. Blood samples were taken, following informed consent, from American Spinal Injury Association impairment scale (AIS) grade C "improvers" (those who experienced an AIS grade improvement) and "nonimprovers" (no AIS change) and AIS grade A and D at <2 weeks ("acute") and ∼3 months ("subacute") postinjury. The total protein concentration from each sample was extracted, with pooled samples being labeled and nonpooled samples treated with ProteoMiner™ beads. Samples were then analyzed using two 4-plex isobaric tag for relative and absolute quantification (iTRAQ) analyses and a label-free experiment for comparison before quantifying with mass spectrometry. Data are available via ProteomeXchange with identifiers PXD035025 and PXD035072 for the iTRAQ and label-free experiments, respectively. Proteomic datasets were analyzed using OpenMS (version 2.6.0). R (version 4.1.4) and, in particular, the R packages MSstats (version 4.0.1) and pathview (version 1.32.0) were used for downstream analysis. Proteins of interest identified from this analysis were further validated by enzyme-linked immunosorbent assay. The data demonstrated proteomic differences between the cohorts, with the results from the iTRAQ approach supporting those of the label-free analysis. A total of 79 and 87 differentially abundant proteins across AIS and longitudinal groups were identified from the iTRAQ and label-free analyses, respectively. Alpha-2-macroglobulin, retinol-binding protein 4 (RBP4), serum amyloid A1, peroxiredoxin 2 (PRX-2), apolipoprotein A1, and several immunoglobulins were identified as biologically relevant and differentially abundant, with potential as individual candidate prognostic biomarkers of neurological outcome. Bioinformatics analyses revealed that the majority of differentially abundant proteins were components of the complement cascade and most interacted directly with the liver. Many of the proteins of interest identified using proteomics were detected only in a single group and therefore have potential as binary (present or absent) biomarkers, RBP4 and PRX-2 in particular. Additional investigations into the chronology of these proteins and their levels in other tissues (cerebrospinal fluid in particular) are needed to better understand the underlying pathophysiology, including any potentially modifiable targets. Pathway analysis highlighted the complement cascade as being significant across groups of differential functional recovery.

Peripheral immune reactions following human traumatic spinal cord injury: the interplay of immune activation and suppression

Traumatic spinal cord injury (SCI) damages the nerve tissue of the spinal cord, resulting in loss of motor and/or sensory functions at and below the injury level. SCI provokes a long-lasting immune response that extends beyond the spinal cord and induces changes in the composition and function of the peripheral immune system. Seemingly contradictory findings have been observed, as both systemic immune activation, including inflammation and autoimmunity, and immune suppression have been reported. Differences in the levels and functions of various cell types and components of both the innate and adaptive immune system supporting these changes have been described at (sub)acute and chronic stages post-injury. Further research is needed for a more comprehensive understanding of the peripheral immune reactions following SCI, their possible correlations with clinical characteristics, and how these immune responses could be targeted to facilitate the therapeutic management of SCI. In this review, we provide an overview of the current literature discussing changes in the peripheral immune system and their occurrence over time following a traumatic SCI.

Targeting foamy macrophages by manipulating ABCA1 expression to facilitate lesion healing in the injured spinal cord

Spinal cord injury (SCI) triggers a complex cascade of events, including myelin loss, neuronal damage, neuroinflammation, and the accumulation of damaged cells and debris at the injury site. Infiltrating bone marrow derived macrophages (BMDMϕ) migrate to the epicenter of the SCI lesion, where they engulf cell debris including abundant myelin debris to become pro-inflammatory foamy macrophages (foamy Mϕ), participate neuroinflammation, and facilitate the progression of SCI. This study aimed to elucidate the cellular and molecular mechanisms underlying the functional changes in foamy Mϕ and their potential implications for SCI. Contusion at T10 level of the spinal cord was induced using a New York University (NYU) impactor (5 g rod from a height of 6.25 mm) in male mice. ABCA1, an ATP-binding cassette transporter expressed by Mϕ, plays a crucial role in lipid efflux from foamy cells. We observed that foamy Mϕ lacking ABCA1 exhibited increased lipid accumulation and a higher presence of lipid-accumulated foamy Mϕ as well as elevated pro-inflammatory response in vitro and in injured spinal cord. We also found that both genetic and pharmacological enhancement of ABCA1 expression accelerated lipid efflux from foamy Mϕ, reduced lipid accumulation and inhibited the pro-inflammatory response of foamy Mϕ, and accelerated clearance of cell debris and necrotic cells, which resulted in functional recovery. Our study highlights the importance of understanding the pathologic role of foamy Mϕ in SCI progression and the potential of ABCA1 as a therapeutic target for modulating the inflammatory response, promoting lipid metabolism, and facilitating functional recovery in SCI.

Disrupted autonomic pathways in spinal cord injury: Implications for the immune regulation

Spinal Cord Injury (SCI) disrupts critical autonomic pathways responsible for the regulation of the immune function. Consequently, individuals with SCI often exhibit a spectrum of immune dysfunctions ranging from the development of damaging pro-inflammatory responses to severe immunosuppression. Thus, it is imperative to gain a more comprehensive understanding of the extent and mechanisms through which SCI-induced autonomic dysfunction influences the immune response. In this review, we provide an overview of the anatomical organization and physiology of the autonomic nervous system (ANS), elucidating how SCI impacts its function, with a particular focus on lymphoid organs and immune activity. We highlight recent advances in understanding how intraspinal plasticity that follows SCI may contribute to aberrant autonomic activity in lymphoid organs. Additionally, we discuss how sympathetic mediators released by these neuron terminals affect immune cell function. Finally, we discuss emerging innovative technologies and potential clinical interventions targeting the ANS as a strategy to restore the normal regulation of the immune response in individuals with SCI.

Treadmill training improves lung function and inhibits alveolar cell apoptosis in spinal cord injured rats

Secondary lung injury after SCI is a major cause of patient mortality, with apoptosis playing a key role. This study aimed to explore the impact of treadmill training and miR145-5p on the MAPK/Erk signaling pathway and apoptosis in rats with complete SCI. SD rats were used to establish T10 segmental complete SCI models and underwent treadmill training 3, 7, or 14 days postinjury. Various techniques including arterial blood gas analysis, lung wet/dry weight ratio, HE staining, immunofluorescence staining, immunohistochemical staining, qRT-PCR, and Western blotting were employed to assess alterations in lung function and the expression levels of crucial apoptosis-related factors. In order to elucidate the specific mechanism, the impact of miR145-5p on the MAPK/Erk pathway and its role in apoptosis in lung cells were confirmed through miR145-5p overexpression and knockdown experiments. Following spinal cord injury (SCI), an increase in apoptosis, activation of the MAPK/Erk pathway, and impairment of lung function were observed in SCI rats. Conversely, treadmill training resulted in a reduction in alveolar cell apoptosis, suppression of the MAPK/Erk pathway, and enhancement of lung function. The gene MAP3K3 was identified as a target of miR145-5p. The influence of miR145-5p on the MAPK/Erk pathway and its impact on apoptosis in alveolar cells were confirmed through the manipulation of miR145-5p expression levels. The upregulation of miR145-5p in spinal cord injury (SCI) rats led to a reduction in MAP3K3 protein expression within lung tissues, thereby inhibiting the MAPK/Erk signaling pathway and decreasing apoptosis. Contrarily, rats with miR145-5p knockdown undergoing treadmill training exhibited an increase in miR145-5p expression levels, resulting in the inhibition of MAP3K3 protein expression in lung tissues, suppression of the MAPK/Erk pathway, and mitigation of lung cell apoptosis. Ultimately, the findings suggest that treadmill training may attenuate apoptosis in lung cells post-spinal cord injury by modulating the MAP3K3 protein through miR145-5p to regulate the MAPK/Erk signaling pathway.

The secretome of macrophages has a differential impact on spinal cord injury recovery according to the polarization protocol

Introduction

The inflammatory response after spinal cord injury (SCI) is an important contributor to secondary damage. Infiltrating macrophages can acquire a spectrum of activation states, however, the microenvironment at the SCI site favors macrophage polarization into a pro-inflammatory phenotype, which is one of the reasons why macrophage transplantation has failed.

Methods

In this study, we investigated the therapeutic potential of the macrophage secretome for SCI recovery. We investigated the effect of the secretome in vitro using peripheral and CNS-derived neurons and human neural stem cells. Moreover, we perform a pre-clinical trial using a SCI compression mice model and analyzed the recovery of motor, sensory and autonomic functions. Instead of transplanting the cells, we injected the paracrine factors and extracellular vesicles that they secrete, avoiding the loss of the phenotype of the transplanted cells due to local environmental cues.

Results

We demonstrated that different macrophage phenotypes have a distinct effect on neuronal growth and survival, namely, the alternative activation with IL-10 and TGF-β1 (M(IL-10+TGF-β1)) promotes significant axonal regeneration. We also observed that systemic injection of soluble factors and extracellular vesicles derived from M(IL-10+TGF-β1) macrophages promotes significant functional recovery after compressive SCI and leads to higher survival of spinal cord neurons. Additionally, the M(IL-10+TGF-β1) secretome supported the recovery of bladder function and decreased microglial activation, astrogliosis and fibrotic scar in the spinal cord. Proteomic analysis of the M(IL-10+TGF-β1)-derived secretome identified clusters of proteins involved in axon extension, dendritic spine maintenance, cell polarity establishment, and regulation of astrocytic activation.

Discussion

Overall, our results demonstrated that macrophages-derived soluble factors and extracellular vesicles might be a promising therapy for SCI with possible clinical applications.

System failure: Systemic inflammation following spinal cord injury

Spinal cord injury (SCI) affects hundreds of thousands of people in the United States, and while some effects of the injury are broadly recognized (deficits to locomotion, fine motor control, and quality of life), the systemic consequences of SCI are less well-known. The spinal cord regulates systemic immunological and visceral functions; this control is often disrupted by the injury, resulting in viscera including the gut, spleen, liver, bone marrow, and kidneys experiencing local tissue inflammation and physiological dysfunction. The extent of pathology depends on the injury level, severity, and time post-injury. In this review, we describe immunological and metabolic consequences of SCI across several organs. Since infection and metabolic disorders are primary reasons for reduced lifespan after SCI, it is imperative that research continues to focus on these deleterious aspects of SCI to improve life span and quality of life for individuals with SCI.

Sprouting of afferent and efferent inputs to pelvic organs after spinal cord injury

Neural plasticity occurs within the central and peripheral nervous systems after spinal cord injury (SCI). Although central alterations have extensively been studied, it is largely unknown whether afferent and efferent fibers in pelvic viscera undergo similar morphological changes. Using a rat spinal cord transection model, we conducted immunohistochemistry to investigate afferent and efferent innervations to the kidney, colon, and bladder. Approximately 3-4 weeks after injury, immunostaining demonstrated that tyrosine hydroxylase (TH)-labeled postganglionic sympathetic fibers and calcitonin gene-related peptide (CGRP)-immunoreactive sensory terminals sprout in the renal pelvis and colon. Morphologically, sprouted afferent or efferent projections showed a disorganized structure. In the bladder, however, denser CGRP-positive primary sensory fibers emerged in rats with SCI, whereas TH-positive sympathetic efferent fibers did not change. Numerous CGRP-positive afferents were observed in the muscle layer and the lamina propria of the bladder following SCI. TH-positive efferent inputs displayed hypertrophy with large diameters, but their innervation patterns were sustained. Collectively, afferent or efferent inputs sprout widely in the pelvic organs after SCI, which may be one of the morphological bases underlying functional adaptation or maladaptation.

Cervical spinal cord injury leads to injury and altered metabolism in the lungs

High-cervical spinal cord injury often disrupts respiratory motor pathways and disables breathing in the affected population. Moreover, cervically injured individuals are at risk for developing acute lung injury, which predicts substantial mortality rates. While the correlation between acute lung injury and spinal cord injury has been found in the clinical setting, the field lacks an animal model to interrogate the fundamental biology of this relationship. To begin to address this gap in knowledge, we performed an experimental cervical spinal cord injury (N = 18) alongside sham injury (N = 3) and naïve animals (N = 15) to assess lung injury in adult rats. We demonstrate that animals display some early signs of lung injury two weeks post-spinal cord injury. While no obvious histological signs of injury were observed, the spinal cord injured cohort displayed significant signs of metabolic dysregulation in multiple pathways that include amino acid metabolism, lipid metabolism, and N-linked glycosylation. Collectively, we establish for the first time a model of lung injury after spinal cord injury at an acute time point that can be used to monitor the progression of lung damage, as well as identify potential targets to ameliorate acute lung injury.

Specific Blood RNA Profiles in Individuals with Acute Spinal Cord Injury as Compared with Trauma Controls

Background

Spinal cord injury (SCI) is known to cause a more robust systemic inflammatory response than general trauma without CNS injury, inducing severe secondary organ damage, especially the lung and liver. Related studies are principally focused on the mechanisms underlying repair and regeneration in the injured spinal cord tissue. However, the specific mechanism of secondary injury after acute SCI is widely overlooked, compared with general trauma.

Methods

Two datasets of GSE151371 and GSE45376 related to the blood samples and spinal cord after acute SCI were selected to identify the differentially expressed genes (DEGs). In GSE151371, functional enrichment analysis on specific DEGs of blood samples was performed. And the top 15 specific hub genes were identified from intersectional genes between the specific upregulated DEGs of blood samples in GSE151371 and the upregulated DEGs of the spinal cord in GSE45376. The specific functional enrichment analysis and the drug candidates of the hub genes and the miRNAs-targeted hub genes were also analyzed and predicted.

Results

DEGs were identified, and a total of 64 specific genes were the intersection of upregulated genes of the spinal cord in GSE45376 and upregulated genes of human blood samples in GSE151371. The top 15 hub genes including HP, LCN2, DLGAP5, CEP55, HMMR, CDKN3, PRTN3, SKA3, MPO, LTF, CDC25C, MMP9, NEIL3, NUSAP1, and CD163 were calculated from the 64 specific genes. Functional enrichment analysis of the top 15 hub genes revealed inflammation-related pathways. The predicted miRNAs-targeted hub genes and drug candidates of hub genes were also performed to put forward reasonable treatment strategies.

Conclusion

The specific hub genes of acute SCI as compared with trauma without CNS injury were identified. The functional enrichment analysis of hub genes showed a specific immune response. Several predicted drugs of hub genes were also obtained. The hub genes and the predicted miRNAs may be potential biomarkers and therapeutic targets and require further validation.

SIRT1: A promising therapeutic target for chronic pain

Chronic pain remains an unresolved problem. Current treatments have limited efficacy. Thus, novel therapeutic targets are urgently required for the development of more effective analgesics. An increasing number of studies have proved that sirtuin 1 (SIRT1) agonists can relieve chronic pain. In this review, we summarize recent progress in understanding the roles and mechanisms of SIRT1 in mediating chronic pain associated with peripheral nerve injury, chemotherapy‐induced peripheral neuropathy, spinal cord injury, bone cancer, and complete Freund's adjuvant injection. Emerging studies have indicated that SIRT1 activation may exert positive effects on chronic pain relief by regulating inflammation, oxidative stress, and mitochondrial dysfunction. Therefore, SIRT1 agonists may serve as potential therapeutic drugs for chronic pain.

Treadmill training improves respiratory function in rats after spinal cord injury by inhibiting the HMGB1/TLR-4/NF-κB signaling pathway

OBJECTIVE

To investigate the effects of treadmill training on lung injury and HMGB1/TLR4/NF-κB after spinal cord injury (SCI) in rats.

METHODS

A total of 108 female SD rats were randomly divided into three groups: sham operation group, SCI brake group, and SCI exercise group. The rats in the SCI exercise group began treadmill running training on the 3rd day after the operation. The rats in the SCI brake group underwent braking treatment. The lung tissues were obtained on the 3rd, 7th, and 14th days after exercise. Locomotor functional recovery was determined using the BBB scores and inclined plane test. Respiratory function was determined via abdominal aortic blood gas analysis. HE staining was used to detect pathological changes in rat lung tissue. RNA sequencing was used to identify differentially expressed genes at different phases in each group of lung tissues. HMGB1, TLR4, and NF-κB in lung tissue were detected using immunohistochemistry and immunofluorescence. Detection of HMGB1 levels in serum, spinal cord tissues and lung tissues by ELISA. HMGB1, TLR4, NF-κB, IL-1β, IL-6, TNF-α mRNA, and protein expression levels were detected via qRT PCR and western blot.

RESULTS

Motor and respiratory functions significantly decreased after SCI (P<0.05). However, locomotion and respiratory functions were significantly improved after treadmill training intervention (P < 0.05). HE staining showed that interstitial thickening, inflammatory cells, and erythrocyte infiltration occurred in lung tissue of rats after SCI (P<0.05). Moreover, inflammatory reaction in lung tissue was significantly reduced after treadmill training intervention (P<0.05). A total of 428 differentially expressed mRNAs [(|log2(FC)| > 2, P < 0.05)] were identified in the intersection of the three groups. KEGG analysis identified five enriched signal pathways, including NF-kappa B. ELISA results showed that treadmill training could significantly reduce the levels of HMGB1 in serum, spinal cord tissue and lung tissue that were elevated after SCI (P < 0.05). Immunohistochemistry, immunofluorescence, qRT PCR, and Western blot showed that HMGB1, TLR4, IL-1β, IL-6, TNF-α, and NF-κB expressions were significantly up-regulated at the 3rd, 7th and 14th days after SCI, compared with the sham operation group. Besides, inflammatory cytokines were significantly lower in the SCI exercise group than in the SCI brake group at all time points after intervention (P < 0.05).

CONCLUSION

Treadmill training alleviates lung tissue inflammation and promotes recovery of motor and respiratory functions by inhibiting the HMGB1/TLR4/NF-κB signaling pathway after SCI in rats.

Tracking Antioxidant Status in Spinal Cord Injured Rodents: A Voltammetric Method Suited for Clinical Translation

BACKGROUND

Spinal cord injury (SCI) triggers a signalling cascade that produces oxidative stress and damages the spinal cord. Voltammetry is a clinically accessible technique to detect, monitor, and guide correction of this potentially reversible secondary injury mechanism. Voltammetry is well suited for clinical translation because the method is inexpensive, simple, rapid, and portable. Voltammetry relies on the measurement of anodic current from a reagent-free, electrochemical reaction on the surface of a small electrode.

METHODS

The present study tested the use of new disposable carbon nanotube based screen printed electrodes (CNT-SPE) for the voltammetric measurement of antioxidant current (AC). Spinal cord, cerebrospinal fluid, and plasma were obtained from Sprague-Dawley rats after SCI. Locomotor function after SCI was assessed by using the Basso, Beattie, Bresnahan (BBB) score.

RESULTS

The more severe SCI caused a decline in spinal cord AC₄₁₉ at 10 minutes (P < 0.05), 4 hours (P < 0.0001), and 1 day (P < 0.01) after injury compared with sham controls. It also caused a decline in plasma AC₃₇₅ at 1 (P < 0.001) and 3 days (P < 0.05) after injury compared with their pre-injury baseline. Spinal cord AC₄₁₉ correlated with plasma AC₃₇₅ (r = 0.49, P < 0.01) and BBB score (r = 0.66, P < 0.0001) at 1 day after SCI.

CONCLUSIONS

AC measured by CNT-SPE demonstrated a time- and severity-dependent decline after SCI. Plasma AC could serve as a surrogate marker for spinal cord AC.

Spinal cord injury: a study protocol for a systematic review and meta-analysis of microRNA alterations

BACKGROUND

Spinal cord injury (SCI) is a devastating condition with no current neurorestorative treatments. Clinical trials have been hampered by a lack of meaningful diagnostic and prognostic markers of injury severity and neurologic recovery. Objective biomarkers and novel therapies for SCI represent urgent unmet clinical needs. Biomarkers of SCI that objectively stratify the severity of cord damage could expand the depth and scope of clinical trials and represent targets for the development of novel therapies for acute SCI. MicroRNAs (miRNAs) represent promising candidates both as informative molecules of injury severity and recovery, and as therapeutic targets. miRNAs are small, regulatory RNA molecules that are tissue-specific and evolutionarily conserved across species. miRNAs have been shown to represent powerful predictors of pathology, particularly with respect to neurologic disorders.

METHODS

Studies investigating miRNA alterations in all species of animal models and human studies of acute, traumatic SCI will be identified from PubMed, Embase, and Scopus. We aim to identify whether SCI is associated with a specific pattern of miRNA expression that is conserved across species, and whether SCI is associated with a tissue- or cell type-specific pattern of miRNA expression. The inclusion criteria for this study will include (1) studies published anytime, (2) including all species, and sexes with acute, traumatic SCI, (3) relating to the alteration of miRNA after SCI, using molecular-based detection platforms including qRT-PCR, microarray, and RNA-sequencing, (4) including statistically significant miRNA alterations in tissues, such as spinal cord, serum/plasma, and/or CSF, and (5) studies with a SHAM surgery group. Articles included in the review will have their titles, abstracts, and full texts reviewed by two independent authors. Random effects meta-regression will be performed, which allows for within-study and between-study variability, on the miRNA expression after SCI or SHAM surgery. We will analyze both the cumulative pooled dataset, as well as datasets stratified by species, tissue type, and timepoint to identify miRNA alterations that are specifically related to the injured spinal cord. We aim to identify SCI-related miRNA that are specifically altered both within a species, and those that are evolutionarily conserved across species, including humans. The analyses will provide a description of the evolutionarily conserved miRNA signature of the pathophysiological response to SCI.

DISCUSSION

Here, we present a protocol to perform a systematic review and meta-analysis to investigate the conserved inter- and intra-species miRNA changes that occur due to acute, traumatic SCI. This review seeks to serve as a valuable resource for the SCI community by establishing a rigorous and unbiased description of miRNA changes after SCI for the next generation of SCI biomarkers and therapeutic interventions.

TRIAL REGISTRATION

The protocol for the systematic review and meta-analysis has been registered through PROSPERO: CRD42021222552 .

β2 Integrin CD11d/CD18: From Expression to an Emerging Role in Staged Leukocyte Migration

CD11d/CD18 is the most recently discovered and least understood β2 integrin. Known CD11d adhesive mechanisms contribute to both extravasation and mesenchymal migration – two key aspects for localizing peripheral leukocytes to sites of inflammation. Differential expression of CD11d induces differences in monocyte/macrophage mesenchymal migration including impacts on macrophage sub-set migration. The participation of CD11d/CD18 in leukocyte localization during atherosclerosis and following neurotrauma has sparked interest in the development of CD11d-targeted therapeutic agents. Whereas the adhesive properties of CD11d have undergone investigation, the signalling pathways induced by ligand binding remain largely undefined. Underlining each adhesive and signalling function, CD11d is under unique transcriptional control and expressed on a sub-set of predominately tissue-differentiated innate leukocytes. The following review is the first to capture the nearly three decades of CD11d research and discusses the emerging role of CD11d in leukocyte migration and retention during the progression of a staged immune response.

Spinal Cord Injury Increases Pro-inflammatory Cytokine Expression in Kidney at Acute and Sub-chronic Stages

Accumulating evidence supports that spinal cord injury (SCI) produces robust inflammatory plasticity. We previously showed that the pro-inflammatory cytokine tumor necrosis factor (TNF)α is increased in the spinal cord after SCI. SCI also induces a systemic inflammatory response that can impact peripheral organ functions. The kidney plays an important role in maintaining cardiovascular health. However, SCI-induced inflammatory response in the kidney and the subsequent effect on renal function have not been well characterized. This study investigated the impact of high and low thoracic (T) SCI on C-fos, TNFα, interleukin (IL)-1β, and IL-6 expression in the kidney at acute and sub-chronic timepoints. Adult C57BL/6 mice received a moderate contusion SCI or sham procedures at T4 or T10. Uninjured mice served as naïve controls. mRNA levels of the proinflammatory cytokines IL-1β, IL-6, TNFα, and C-fos, and TNFα and C-fos protein expression were assessed in the kidney and spinal cord 1 day and 14 days post-injury. The mRNA levels of all targets were robustly increased in the kidney and spinal cord, 1 day after both injuries. Whereas IL-6 and TNFα remained elevated in the spinal cord at 14 days after SCI, C-fos, IL-6, and TNFα levels were sustained in the kidney only after T10 SCI. TNFα protein was significantly upregulated in the kidney 1 day after both T4 and T10 SCI. Overall, these results clearly demonstrate that SCI induces robust systemic inflammation that extends to the kidney. Hence, the presence of renal inflammation can substantially impact renal pathophysiology and function after SCI.

Lipocalin 2 as a Putative Modulator of Local Inflammatory Processes in the Spinal Cord and Component of Organ Cross talk After Spinal Cord Injury

Lipocalin 2 (LCN2), an immunomodulator, regulates various cellular processes such as iron transport and defense against bacterial infection. Under pathological conditions, LCN2 promotes neuroinflammation via the recruitment and activation of immune cells and glia, particularly microglia and astrocytes. Although it seems to have a negative influence on the functional outcome in spinal cord injury (SCI), the extent of its involvement in SCI and the underlying mechanisms are not yet fully known. In this study, using a SCI contusion mouse model, we first investigated the expression pattern of Lcn2 in different parts of the CNS (spinal cord and brain) and in the liver and its concentration in blood serum. Interestingly, we could note a significant increase in LCN2 throughout the whole spinal cord, in the brain, liver, and blood serum. This demonstrates the diversity of its possible sites of action in SCI. Furthermore, genetic deficiency of Lcn2 (Lcn2^-/-) significantly reduced certain aspects of gliosis in the SCI-mice. Taken together, our studies provide first valuable hints, suggesting that LCN2 is involved in the local and systemic effects post SCI, and might modulate the impairment of different peripheral organs after injury.

Anti-Inflammatory Activity of Melatonin: a Focus on the Role of NLRP3 Inflammasome

Melatonin is a hormone of the pineal gland that contributes to the regulation of physiological activities, such as sleep, circadian rhythm, and neuroendocrine processes. Melatonin is found in several plants and has pharmacological activities including antioxidant, anti-inflammatory, hepatoprotective, cardioprotective, and neuroprotective. It also has shown therapeutic efficacy in treatment of cancer and diabetes. Melatonin affects several molecular pathways to exert its protective effects. The NLRP3 inflammasome is considered a novel target of melatonin. This inflammasome contributes to enhanced level of IL-1β, caspase-1 activation, and pyroptosis stimulation. The function of NLRP3 inflammasome has been explored in various diseases, including cancer, diabetes, and neurological disorders. By inhibiting NLRP3, melatonin diminishes inflammation and influences various molecular pathways, such as SIRT1, microRNA, long non-coding RNA, and Wnt/β-catenin. Here, we discuss these molecular pathways and suggest that melatonin-induced inhibition of NLRP3 should be advanced in disease therapy.

Improving Diagnostic Workup Following Traumatic Spinal Cord Injury: Advances in Biomarkers

PURPOSE OF REVIEW

Traumatic spinal cord injury (SCI) is a life-changing event with drastic implications for patients due to sensorimotor impairment and autonomous dysfunction. Current clinical evaluations focus on the assessment of injury level and severity using standardized neurological examinations. However, they fail to predict individual trajectories of recovery, which highlights the need for the development of advanced diagnostics. This narrative review identifies recent advances in the search of clinically relevant biomarkers in the field of SCI.

RECENT FINDINGS

Advanced neuroimaging and molecular biomarkers sensitive to the disease processes initiated by the SCI have been identified. These biomarkers range from advanced neuroimaging techniques, neurophysiological readouts, and molecular biomarkers identifying the concentrations of several proteins in blood and CSF samples. Some of these biomarkers improve current prediction models based on clinical readouts. Validation with larger patient cohorts is warranted. Several biomarkers have been identified-ranging from imaging to molecular markers-that could serve as advanced diagnostic and hence supplement current clinical assessments.

Neutrophil, Extracellular Matrix Components, and Their Interlinked Action in Promoting Secondary Pathogenesis After Spinal Cord Injury

Secondary pathogenesis following primary mechanical damage to the spinal cord is believed to be the ultimate reason for the limitation of currently available therapies. Precisely, the complex cascade of secondary events-mediated scar formation is the sole hurdle in the recovery process due to its inhibitory effect on axonal regeneration, plasticity, and remyelination. Neutrophils initiate this secondary injury along with other extracellular matrix components such as matrix metalloproteinase (MMPs), and chondroitin sulfate proteoglycans (CSPGs). Together, they mediate inflammation, necrosis, apoptosis, lesion, and scar formation at the injury site. Activated neutrophil releases several proteases, cytokines, and chemokines that cause complete tissue destruction. Thus, neutrophil activation and infiltration in the acute phase of injury act as a roadmap for inducing tissue destruction. MMPs, are extracellular proteolytic enzymes that degrade the ECM proteins, increases vascular permeability, and are predominantly released by neutrophils. These MMPs, in turn, cleave NG2 proteoglycan, a subtype of CSPG, into the active form. This active or shed form is involved in both the fibrotic as well as glial scar formation. Since neutrophils and ECM components are closely associated with each other in pathological conditions. Herein, we emphasize the interaction of neutrophils and their influence on ECM protein expression during the acute and chronic phases to identify a promising targets for designing a therapeutic approach in spinal cord injury.

Restoring neuro-immune circuitry after brain and spinal cord injuries

Neuro-immune interactions are essential for our body's defense and homeostasis. Anatomical and physiological analyses have shown that the nervous system comprises multiple pathways that regulate the dynamics and functions of immune cells, which are mainly mediated by the autonomic nervous system and adrenal signals. These are disturbed when the neurons and circuits are damaged by diseases of the central nervous system (CNS). Injuries caused by stroke or trauma often cause immune dysfunction by abrogation of the immune-regulating neural pathways, which leads to an increased risk of infections. Here, I review the structures and functions of the neural pathways connecting the brain and the immune system, and the neurogenic mechanisms of immune dysfunction that emerge after CNS injuries. Recent technological advances in manipulating specific neural circuits have added mechanistic aspects of neuro-immune interactions and their dysfunctions. Understanding the neural bases of immune control and their pathological processes will deepen our knowledge of homeostasis and lead to the development of strategies to cure immune deficiencies observed in various CNS disorders.

What Makes a Successful Donor? Fecal Transplant from Anxious-Like Rats Does Not Prevent Spinal Cord Injury-Induced Dysbiosis

Spinal cord injury (SCI) causes gut dysbiosis and an increased prevalence of depression and anxiety. Previous research showed a link between these two consequences of SCI by using a fecal transplant from healthy rats which prevented both SCI-induced microbiota changes and the subsequent development of anxiety-like behaviour. However, whether the physical and mental state of the donor are important factors in the efficacy of FMT therapy after SCI remains unknown. In the present study, rats received a fecal transplant following SCI from uninjured donors with increased baseline levels of anxiety-like behaviour and reduced proportion of Lactobacillus in their stool. This fecal transplant increased intestinal permeability, induced anxiety-like behaviour, and resulted in minor but long-term alterations in the inflammatory state of the recipients compared to vehicle controls. There was no significant effect of the fecal transplant on motor recovery in rehabilitative training, suggesting that anxiety-like behaviour did not affect the motivation to participate in rehabilitative therapy. The results of this study emphasize the importance of considering both the microbiota composition and the mental state of the donor for fecal transplants following spinal cord injury.

Routinely Measured Hematological Markers Can Help to Predict American Spinal Injury Association Impairment Scale Scores after Spinal Cord Injury

Neurological outcomes following spinal cord injury (SCI) are currently difficult to predict. While the initial American Spinal Injury Association Impairment Scale (AIS) grade can give an estimate of outcome, the high remaining degree of uncertainty has stoked recent interest in biomarkers for SCI. This study aimed to assess the prognostic value of routinely measured blood biomarkers by developing prognostic models of AIS scores at discharge and 12 months post-injury. Routine blood and clinical data were collected from SCI patients (n = 417), and blood measures that had been assessed in less than 50% of patients were excluded. Outcome neurology was obtained from AIS and Spinal Cord Independence Measure III (SCIM-III) scores at discharge and 12 months post-injury, with motor (AIS) and sensory (AIS, touch and prick) abilities being assessed individually. Linear regression models with and without elastic net penalization were created for all outcome measures. Blood measures associated with liver function, such as alanine transaminase, were found to add value to predictions of SCIM-III at discharge and 12 months post-injury. Further, components of a total blood count, including hemoglobin, were found to add value to predictions of AIS motor and sensory scores at discharge and 12 months post-injury. These findings corroborate the results of our previous preliminary study and thus provide further evidence that routine blood measures can add prognostic value in SCI and that markers of liver function are of particular interest.

Acute IL-1RA treatment suppresses the peripheral and central inflammatory response to spinal cord injury

BACKGROUND

The acute phase response (APR) to CNS insults contributes to the overall magnitude and nature of the systemic inflammatory response. Aspects of this response are thought to drive secondary inflammatory pathology at the lesion site, and suppression of the APR can therefore afford some neuroprotection. In this study, we examined the APR in a mouse model of traumatic spinal cord injury (SCI), along with its relationship to neutrophil recruitment during the immediate aftermath of the insult. We specifically investigated the effect of IL-1 receptor antagonist (IL-1RA) administration on the APR and leukocyte recruitment to the injured spinal cord.

METHODS

Adult female C57BL/6 mice underwent either a 70kD contusive SCI, or sham surgery, and tissue was collected at 2, 6, 12, and 24 hours post-operation. For IL-1RA experiments, SCI mice received two intraperitoneal injections of human IL-1RA (100mg/kg), or saline as control, immediately following, and 5 hours after impact, and animals were sacrificed 6 hours later. Blood, spleen, liver and spinal cord were collected to study markers of central and peripheral inflammation by flow cytometry, immunohistochemistry and qPCR. Results were analysed by two-way ANOVA or student's t-test, as appropriate.

RESULTS

SCI induced a robust APR, hallmarked by elevated hepatic expression of pro-inflammatory marker genes and a significantly increased neutrophil presence in the blood, liver and spleen of these animals, as early as 2 hours after injury. This peripheral response preceded significant neutrophil infiltration of the spinal cord, which peaked 24 hours post-SCI. Although expression of IL-1RA was also induced in the liver following SCI, its response was delayed compared to IL-1β. Exogenous administration of IL-1RA during this putative therapeutic window was able to suppress the hepatic APR, as evidenced by a reduction in CXCL1 and SAA-2 expression as well as a significant decrease in neutrophil infiltration in both the liver and the injured spinal cord itself.

CONCLUSIONS

Our data indicate that peripheral administration of IL-1RA can attenuate the APR which in turn reduces immune cell infiltration at the spinal cord lesion site. We propose IL-1RA treatment as a viable therapeutic strategy to minimise the harmful effects of SCI-induced inflammation.

Altered physiology of gastrointestinal vagal afferents following neurotrauma

The adaptability of the central nervous system has been revealed in several model systems. Of particular interest to central nervous system-injured individuals is the ability for neural components to be modified for regain of function. In both types of neurotrauma, traumatic brain injury and spinal cord injury, the primary parasympathetic control to the gastrointestinal tract, the vagus nerve, remains anatomically intact. However, individuals with traumatic brain injury or spinal cord injury are highly susceptible to gastrointestinal dysfunctions. Such gastrointestinal dysfunctions attribute to higher morbidity and mortality following traumatic brain injury and spinal cord injury. While the vagal efferent output remains capable of eliciting motor responses following injury, evidence suggests impairment of the vagal afferents. Since sensory input drives motor output, this review will discuss the normal and altered anatomy and physiology of the gastrointestinal vagal afferents to better understand the contributions of vagal afferent plasticity following neurotrauma.

Prognostic value of early leukocyte fluctuations for recovery from traumatic spinal cord injury

BACKGROUND

Acute traumatic spinal cord injury (SCI) induces a systemic immune response involving circulating white blood cells (WBCs). How this response is influenced by overall trauma severity, the neurological level of injury and/or correlates with patient outcomes is poorly understood. The objective of this study was to identify relationships between early changes in circulating WBCs, injury characteristics and long-term patient outcomes in individuals with traumatic SCI.

METHODS

We retrospectively analysed data from 161 SCI patients admitted to Brisbane's Princess Alexandra Hospital (exploration cohort). Logistic regression models in conjunction with receiver operating characteristic (ROC) analyses were used to assess the strength of specific links between the WBC response, respiratory infection incidence and neurological outcomes (American Spinal Injury Association Impairment Scale (AIS) grade conversion). An independent validation cohort from the Trauma Hospital Berlin, Germany (n = 49) was then probed to assess the robustness of effects and disentangle centre effects.

RESULTS

We find that the extent of acute neutrophilia in human SCI patients is positively correlated with New Injury Severity Scores but inversely with the neurological outcome (AIS grade). Multivariate analysis demonstrated that acute SCI-induced neutrophilia is an independent predictor of AIS grade conversion failure, with an odds ratio (OR) of 4.16 and ROC area under curve (AUC) of 0.82 (P < 0.0001). SCI-induced lymphopenia was separately identified as an independent predictor of better recovery (OR = 24.15; ROC AUC = 0.85, P < 0.0001). Acute neutrophilia and increased neutrophil-lymphocyte ratios were otherwise significantly associated with respiratory infection presentation in both patient cohorts.

CONCLUSIONS

Our findings demonstrate the prognostic value of modelling early circulating neutrophil and lymphocyte counts with patient characteristics for predicting the longer term recovery after SCI.

Splenic sympathetic signaling contributes to acute neutrophil infiltration of the injured spinal cord

Background

Alterations in the immune system are a complication of spinal cord injury (SCI) and have been linked to an excessive sympathetic outflow to lymphoid organs. Still unknown is whether these peripheral immune changes also contribute for the deleterious inflammatory response mounted at the injured spinal cord.

Methods

We analyzed different molecular outputs of the splenic sympathetic signaling for the first 24 h after a thoracic compression SCI. We also analyzed the effect of ablating the splenic sympathetic signaling to the innate immune and inflammatory response at the spleen and spinal cord 24 h after injury.

Results

We found that norepinephrine (NE) levels were already raised at this time-point. Low doses of NE stimulation of splenocytes in vitro mainly affected the neutrophils’ population promoting an increase in both frequency and numbers. Interestingly, the interruption of the sympathetic communication to the spleen, by ablating the splenic nerve, resulted in reduced frequencies and numbers of neutrophils both at the spleen and spinal cord 1 day post-injury.

Conclusion

Collectively, our data demonstrates that the splenic sympathetic signaling is involved in the infiltration of neutrophils after spinal cord injury. Our findings give new mechanistic insights into the dysfunctional regulation of the inflammatory response mounted at the injured spinal cord.

Age as a determinant of inflammatory response and survival of glia and axons after human traumatic spinal cord injury

Despite the shift in the demographics of traumatic spinal cord injury (SCI) with increased proportion of injuries in the elderly, little is known on the potential effects of old age on the pathobiology of SCI. Since there is an assumption that age adversely affects neural response to SCI, this study examines the clinically relevant question on whether age is a key determinant of inflammatory response, oligodendroglial apoptosis and axonal survival after traumatic SCI. This unique study includes post-mortem spinal cord tissue from 64 cases of SCI (at cervical or high-thoracic levels) and 38 control cases without CNS injury. Each group was subdivided into subgroups of younger and elderly individuals (65 years of age or older at the SCI onset). The results of this study indicate that age at the SCI onset does not adversely affect the cellular inflammatory response to, oligodendroglial apoptosis and axonal survival after SCI. These results support the conclusion that elderly individuals have similar neurobiological responses to SCI as younger people and, hence, treatment decisions should be based on an assessment of the individual patient and not an arbitrary assumption that "advanced age" should exclude patients with an acute SCI from access to advanced care and translational therapies.

Cognitive Dysfunction in Persons with Chronic Spinal Cord Injuries

Cognitive dysfunction (CD) is pervasive in individuals who have chronic spinal cord injuries (SCI). Although classically associated with concomitant traumatic brain injuries, many other causes have been proposed, including premorbid neuropsychological conditions, mood disorders, substance abuse, polypharmacy, chronic pain and fatigue, sleep apnea, autonomic dysregulation, post-intensive care unit syndrome, cortical reorganizations, and neuroinflammation. The consequences of CD are likely widespread, affecting rehabilitation and function. CD in those with SCI should be recognized, and potentially treated, in order to provide the best patient care.

Traumatic Spinal Cord Injury and the Gut Microbiota: Current Insights and Future Challenges

Individuals with traumatic spinal cord injury (SCI) suffer from numerous peripheral complications in addition to the long-term paralysis that results from disrupted neural signaling pathways. Those living with SCI have consistently reported gastrointestinal dysfunction as a significant issue for overall quality of life, but most research has focused bowel management rather than how altered or impaired gut function impacts on the overall health and well-being of the affected individual. The gut-brain axis has now been quite extensively investigated in other neurological conditions but the gastrointestinal compartment, and more specifically the gut microbiota, have only recently garnered attention in the context of SCI because of their vast immunomodulatory capacity and putative links to infection susceptibility. Most studies to date investigating the gut microbiota following SCI have employed 16S rRNA genomic sequencing to identify bacterial taxa that may be pertinent to neurological outcome and common sequalae associated with SCI. This review provides a concise overview of the relevant data that has been generated to date, discussing current understanding of how the microbial content of the gut after SCI appears linked to both functional and immunological outcomes, whilst also emphasizing the highly complex nature of microbiome research and the need for careful evaluation of correlative findings. How the gut microbiota may be involved in the increased infection susceptibility that is often observed in this condition is also discussed, as are the challenges ahead to strategically probe the functional significance of changes in the gut microbiota following SCI in order to take advantage of these therapeutically.

MicroRNA‑138‑5p regulates the development of spinal cord injury by targeting SIRT1

MicroRNAs (miRs) play an important role in the development and progression of spinal cord injury (SCI). The role of miR-138-5p in SCI was investigated in the present study. The anti-inflammatory effects of miR-138-5p and underlying mechanisms were investigated in an SCI rat model and in vitro model. Reverse transcription-quantitative PCR (RT-qPCR) was used to examine the expression of miR-138-5p in the SCI in vivo and in vitro models, as well as patients with SCI; it was found that miR-138-5p was significantly upregulated in SCI. Bioinformatics and dual-luciferase reporter assays were performed to predict and confirm the binding sites between miR-138-5p and the 3′untranslated region of sirtuin 1 (SIRT1). Then, the expression of SIRT1 was detected via RT-qPCR and western blotting, indicating downregulation of SIRT1 in SCI. PC12 cells were transfected with miR-138-5p inhibitor, inhibitor control or miR-138-5p inhibitor + SIRT1 small interfering RNA for 48 h, and then subjected to lipopolysaccharide (100 ng/ml) treatment for 4 h. Then, MTT assay, flow cytometry and ELISA experiments were performed to analyze cell viability, apoptosis, and the levels of tumor necrosis factor-α, interleukin (IL)-1β and IL-6. Findings suggested that downregulation of miR-138-5p increased PC12 cell viability, inhibited cell apoptosis and attenuated proinflammatory responses, which may result in amelioration of SCI. However, all these effects were reversed by SIRT1 knockdown. Finally, it was observed that miR-138-5p altered the related protein expression of the PTEN/AKT pathway. These results indicated that miR-138-5p could regulate inflammatory responses and cell apoptosis in SCI models by modulating the PTEN/AKT signaling pathway via SIRT1, thus playing an important role in the development of SCI. Collectively, the present study demonstrated that miR-138-5p may be a novel therapeutic target for the treatment of SCI.

Hepatic dysfunction after spinal cord injury: A vicious cycle of central and peripheral pathology?

The liver is essential for numerous physiological processes, including filtering blood from the intestines, metabolizing fats, proteins, carbohydrates and drugs, and regulating iron storage and release. The liver is also an important immune organ and plays a critical role in response to infection and injury throughout the body. Liver functions are regulated by autonomic parasympathetic innervation from the brainstem and sympathetic innervation from the thoracic spinal cord. Thus, spinal cord injury (SCI) at or above thoracic levels disrupts major regulatory mechanisms for hepatic functions. Work in rodents and humans shows that SCI induces liver pathology, including hepatic inflammation and fat accumulation characteristic of a serious form of non-alcoholic fatty liver disease (NAFLD) called non-alcoholic steatohepatitis (NASH). This hepatic pathology is associated with and likely contributes to indices of metabolic dysfunction often noted in SCI individuals, such as insulin resistance and hyperlipidemia. These occur at greater rates in the SCI population and can negatively impact health and quality of life. In this review, we will: 1) Discuss acute and chronic changes in human and rodent liver pathology and function after SCI; 2) Describe how these hepatic changes affect systemic inflammation, iron regulation and metabolic dysfunction after SCI; 3) Describe how disruption of the hepatic autonomic nervous system may be a key culprit in post-injury chronic liver pathology; and 4) Preview ongoing and future research that aims to elucidate mechanisms driving liver and metabolic dysfunction after SCI.

Protective effects of 3,4-dihydroxyphenylethanol on spinal cord injury-induced oxidative stress and inflammation

3,4-Dihydroxyphenylethanol (DOPET) is a potent antioxidant polyphenolic compound. In this study, our objective was to investigate the underlying mechanism of the neuroprotective role of DOPET in attenuating spinal cord injury (SCI). Initially, SCI was induced by performing surgical laminectomy on the rats at T10-T12 level. Then, the neurological function-dependent locomotion was measured using Basso Beattie Bresnahan score, which declined in the SCI-induced group. Increased antioxidant levels such as superoxide dismutase, glutathione peroxidase, and glutathione along with other parameters such as increased lipid peroxidation (LPO) and myeloperoxidase (MPO) activities were all observed in the SCI group. Levels of proinflammatory cytokines such as tumor necrosis factor-α and interleukin-1β were upregulated in the serum and spinal cord tissue as observed on the immunoblot. Interestingly, protein levels of apoptotic markers such as Bax, cleaved caspase 3 and RT-PCR analysis-based mRNA level of pro-inflammatory cytokine, nuclear factor- κ activated B cells (NF-κB) were significantly upregulated in the spinal cord tissue. Nonetheless, antiapoptotic factor such as B-cell lymphoma 2 (Bcl-2) protein expression was downregulated in the same group. However, on administering 10 mg/kg of DOPET, the neuronal function was rescued, antioxidants were restored back to the normal levels, LPO and MPO activities were reduced in conjunction with downregulated levels of proinflammatory cytokines and apoptotic markers in the SCI group. These findings show that DOPET could potentially target multiple signalling pathways to combat SCI.

A Preliminary Cohort Study Assessing Routine Blood Analyte Levels and Neurological Outcome after Spinal Cord Injury

There is increasing interest in the identification of biomarkers that could predict neurological outcome following a spinal cord injury (SCI). Although initial American Spinal Injury Association (ASIA) Impairment Scale (AIS) grade is a good indicator of neurological outcome, for the patient and clinicians, an element of uncertainty remains. This preliminary study aimed to assess the additive potential of routine blood analytes following principal component analysis (PCA) to develop prognostic models for neurological outcome following SCI. Routine blood and clinical data were collected from SCI patients (n = 82) and PCA used to reduce the number of blood analytes into related factors. Outcome neurology was obtained from AIS scores at 3 and 12 months post-injury, with motor (AIS and total including all myotomes) and sensory (AIS, touch and pain) abilities being assessed individually. Multiple regression models were created for all outcome measures. Blood analytes relating to “liver function” and “acute inflammation and liver function” factors were found to significantly increase prediction of neurological outcome at both 3 months (touch, pain, and AIS sensory) and at 1 year (pain, R² increased by 0.025 and total motor, R² increased by 0.016). For some models “liver function” and “acute inflammation and liver function” factors were both significantly predictive, with the greatest combined R² improvement of 0.043 occurring for 3 month pain prediction. These preliminary findings support ongoing research into the use of routine blood analytes in the prediction of neurological outcome in SCI patients.

Activity/exercise-induced changes in the liver transcriptome after chronic spinal cord injury

Multi-organ dysfunction is a major complication after spinal cord injury (SCI). In addition to local injury within the spinal cord, SCI causes major disruption to the peripheral organ innervation and regulation. The liver contains sympathetic, parasympathetic, and small sensory axons. The bi-directional signaling of sensory dorsal root ganglion (DRG) neurons that provide both efferent and afferent information is of key importance as it allows sensory neurons and peripheral organs to affect each other. SCI-induced liver inflammation precedes and may exacerbate intraspinal inflammation and pathology after SCI, which may be modulated by activity and exercise. In this study, we collected comprehensive gene expression data through RNA sequencing of liver tissue from rats with chronic SCI to determine the effects of activity and exercise on those expression patterns. The sequenced data are of high quality and show a high alignment rate to the Rn6 genome. Gene expression is demonstrated for genes associated with known liver pathologies. UCSC Genome Browser expression tracks are provided with the data to facilitate exploration of the samples.

AICD: an integrated anti-inflammatory compounds database for drug discovery

Systemic or local inflammation drives the pathogenesis of various human diseases. Small compounds with anti-inflammatory properties hold great potential for clinical translation. Over recent decades, many compounds have been screened for their action against inflammation-related targets. Databases that integrate the physicochemical properties and bioassay results of these compounds are lacking. We created an “Anti-Inflammatory Compounds Database” (AICD) to deposit compounds with potential anti-inflammation activities. A total of 232 inflammation-related targets were recruited by the AICD. Gene set enrichment analysis showed that these targets were involved in various human diseases. Bioassays of these targets were collected from open-access databases and adopted to extract 79,781 small molecules with information on chemical properties, candidate targets, bioassay models and bioassay results. Principal component analysis demonstrated that these deposited compounds were closely related to US Food and Drug Administration-approved drugs with respect to chemical space and chemical properties. Finally, pathway-based screening for drug combination/multi-target drugs provided a case study for drug discovery using the AICD. The AICD focuses on inflammation-related drug targets and contains substantial candidate compounds with high chemical diversity and good drug-like properties. It could be serviced for the discovery of anti-inflammatory medicines and can be accessed freely at http://956023.ichengyun.net/AICD/index.php.

Macrophage centripetal migration drives spontaneous healing process after spinal cord injury

Traumatic spinal cord injury (SCI) brings numerous inflammatory cells, including macrophages, from the circulating blood to lesions, but pathophysiological impact resulting from spatiotemporal dynamics of macrophages is unknown. Here, we show that macrophages centripetally migrate toward the lesion epicenter after infiltrating into the wide range of spinal cord, depending on the gradient of chemoattractant C5a. However, macrophages lacking interferon regulatory factor 8 (IRF8) cannot migrate toward the epicenter and remain widely scattered in the injured cord with profound axonal loss and little remyelination, resulting in a poor functional outcome after SCI. Time-lapse imaging and P2X/YRs blockade revealed that macrophage migration via IRF8 was caused by purinergic receptors involved in the C5a-directed migration. Conversely, pharmacological promotion of IRF8 activation facilitated macrophage centripetal movement, thereby improving the SCI recovery. Our findings reveal the importance of macrophage centripetal migration via IRF8, providing a novel therapeutic target for central nervous system injury.

NLRX1 Enhances Glutamate Uptake and Inhibits Glutamate Release by Astrocytes

Uptake of glutamate from the extracellular space and glutamate release to neurons are two major processes conducted by astrocytes in the central nervous system (CNS) that protect against glutamate excitotoxicity and strengthen neuronal firing, respectively. During inflammatory conditions in the CNS, astrocytes may lose one or both of these functions, resulting in accumulation of the extracellular glutamate, which eventually leads to excitotoxic neuronal death, which in turn worsens the CNS inflammation. NLRX1 is an innate immune NOD-like receptor that inhibits the major inflammatory pathways. It is localized in the mitochondria and was shown to inhibit cell death, enhance ATP production, and dampen oxidative stress. In the current work, using primary murine astrocyte cultures from WT and Nlrx1^-/- mice, we demonstrate that NLRX1 potentiates astrocytic glutamate uptake by enhancing mitochondrial functions and the functional activity of glutamate transporters. Also, we report that NLRX1 inhibits glutamate release from astrocytes by repressing Ca²⁺-mediated glutamate exocytosis. Our study, for the first time, identified NLRX1 as a potential regulator of glutamate homeostasis in the CNS.

Degeneration of white matter and gray matter revealed by diffusion tensor imaging and pathological mechanism after spinal cord injury in canine

AIM

Exploration of the mechanism of spinal cord degeneration may be the key to treatment of spinal cord injury (SCI). This study aimed to investigate the degeneration of white matter and gray matter and pathological mechanism in canine after SCI.

METHODS

Diffusion tensor imaging (DTI) was performed on canine models with normal (n = 5) and injured (n = 7) spinal cords using a 3.0T MRI scanner at precontusion and 3 hours, 24 hours, 6 weeks, and 12 weeks postcontusion. The tissue sections were stained using H&E and immunohistochemistry.

RESULTS

For white matter, fractional anisotropy (FA) values significantly decreased in lesion epicenter, caudal segment 1 cm away from epicenter, and caudal segment 2 cm away from epicenter (P = 0.003, P = 0.004, and P = 0.013, respectively) after SCI. Apparent diffusion coefficient (ADC) values were initially decreased and then increased in lesion epicenter and caudal segment 1 cm away from epicenter (P < 0.001 and P = 0.010, respectively). There are no significant changes in FA and ADC values in rostral segments (P > 0.05). For gray matter, ADC values decreased initially and then increased in lesion epicenter (P < 0.001), and overall trend decreased in caudal segment 1 cm away from epicenter (P = 0.039). FA values did not change significantly (P > 0.05). Pathological examination confirmed the dynamic changes of DTI parameters.

CONCLUSION

Diffusion tensor imaging is more sensitive to degeneration of white matter than gray matter, and the white matter degeneration may be not symmetrical which meant the caudal degradation appeared to be more severe than the rostral one.

Early Systemic Alterations in Severe Spinal Cord Injury: An Experimental Study on the Impact of Injury Level on Renal Function

STUDY DESIGN

An experimental model of spinal cord injury (SCI) intended to characterize changes in renal function.

OBJECTIVE

The aim of this study was to evaluate the possible influence of SCI level on renal function during spinal shock.

SUMMARY OF BACKGROUND DATA

SCI triggers multiple systemic and metabolic alterations. Among them, renal dysfunction stands out. Although several variables have been related to its extent, the impact of the cord injury level on renal function has not been clearly stated, particularly during the spinal shock.

METHODS

Anesthetized adult Sprague-Dawley rats were subjected to severe spinal cord contusion at low (T8) and high (T1) thoracic levels using the weight-drop method. Glomerular filtration rate (GFR) and tubular secretion (TS) were estimated 24 hours after injury, using a validated method based on the determination of plasma concentrations of iopamidol and p-aminohippuric acid by high-performance liquid chromatography.

RESULTS

GFR, fell to 33% (95% CI [24%, 43%]) and 10% (8%, 13%) of the sham-injured controls, whereas TS, decreased to 59% (95% CI [47%, 71%]), and 25% (18%, 32%) of the sham-injured controls, in T8 and T1 injury levels, respectively. Comparisons between cords injured and control rats, as well as between low and high-injured levels, were statistically significant (P < 0.01).

CONCLUSION

Renal dysfunction occurs early after severe SCI. The damage is greater in high compared to low injuries. These findings could have important implications in the acute management of patients with high thoracic and cervical injuries, especially in pharmacotherapy using drugs eliminated by the kidney.

LEVEL OF EVIDENCE

N/A.

Investigation of Microbiota Alterations and Intestinal Inflammation Post-Spinal Cord Injury in Rat Model

Although there has been a significant amount of research focused on the pathophysiology of spinal cord injury (SCI), there is limited information on the consequences of SCI on remote organs. SCI can produce significant effects on a variety of organ systems, including the gastrointestinal tract. Patients with SCI often suffer from severe, debilitating bowel dysfunction in addition to their physical disabilities, which is of major concern for these individuals because of the adverse impact on their quality of life. Herein, we report on our investigation into the effects of SCI and subsequent antibiotic treatment on the intestinal tissue and microbiota. For that, we used a thoracic SCI rat model and investigated changes to the microbiota, proinflammatory cytokine levels, and bacterial communication molecule levels post-injury and gentamicin treatment for 7 days. We discovered significant changes, the most interesting being the differences in the gut microbiota beta diversity of 8-week SCI animals compared to control animals at the family, genus, and species level. Specifically, 35 operational taxonomic units were enriched in the SCI animal group and three were identified at species level; Lactobacillus intestinalis, Clostridium disporicum, and Bifidobacterium choerinum. In contrast, Clostridium saccharogumia was identified as depleted in the SCI animal group. Proinflammatory cytokines interleukin (IL)-12, macrophage inflammatory protein-2 (MIP-2), and tumor necrosis factor alpha were found to be significantly elevated in intestinal tissue homogenate 4 weeks post-SCI compared to 8-weeks post-injury. Further, levels of IL-1β, IL-12, and MIP-2 significantly correlated with changes in beta diversity 8-weeks post-SCI. Our data provide a greater understanding of the early effects of SCI on the microbiota and gastrointestinal tract, highlighting the need for further investigation to elucidate the mechanism underlying these effects.

Time-dependent changes in paw carrageenan-induced inflammation above and below the level of low thoracic spinal cord injury in rats

STUDY DESIGN

This was an animal study.

OBJECTIVES

Local inflammation is attenuated below high thoracic SCI, where innervation of major lymphoid organs is involved. However, whether inflammatory responses are affected after low thoracic SCI, remains undetermined. The aim of this study was to characterize the influence of low thoracic SCI on carrageenan-induced paw swelling in intact and paralyzed limbs, at acute and subacute stages.

SETTING

University and hospital-based research center, Mexico City, Mexico.

METHODS

Rats received a severe contusive SCI at T9 spinal level or sham injury. Then, 1 and 15 days after lesion, carrageenan or vehicle was subcutaneously injected in forelimb and hindlimb paws. Paw swelling was measured over a 6-h period using a plethysmometer.

RESULTS

Swelling increased progressively reaching the maximum 6 h post-carrageenan injection. Swelling increase in sham-injured rats was approximately 130% and 70% compared with baseline values of forelimbs and hindlimbs, respectively. Paws injected with saline exhibited no measurable swelling. Carrageenan-induced paw swelling 1-day post-SCI was suppressed in both intact and paralyzed limbs. Fifteen days post-injury, the swelling response to carrageenan was completely reestablished in forelimbs, whereas in hindlimbs it remained significantly attenuated compared with sham-injured rats.

CONCLUSIONS

SCI at low spinal level affects the induced swelling response in a different way depending on both, the neurological status of challenged regions and the stage of injury. These findings suggest that neurological compromise of the main immunological organs is not a prerequisite for the local swelling response to be affected after injury.

The kinetics of autophagy in the lung following acute spinal cord injury in rats

BACKGROUND CONTEXT

Lung injury is a major cause of respiratory complications following an acute spinal cord injury (ASCI), which are associated with a high mortality rate. Autophagy has been shown to be involved in a variety of lung diseases; however, whether autophagy is activated in the lung following ASCI remains unknown.

PURPOSE

The objective of this study was to investigate the induction of autophagy in the lung after ASCI.

STUDY DESIGN

This is an experimental animal study of ASCI investigating kinetics of autophagy in the lung following ASCI.

METHODS

One hundred and forty-four rats (N=144) were divided into two groups: (1) a sham (n=72) and (2) an injury group (n=72). Allen's method was used to induce an injury at the level of the 10th thoracic vertebra. Rats were sacrificed at 6, 12, 24, 48, and 72 hours, 1 week, and 2 weeks after surgery. Lung pathology and apoptosis were assessed to determine the level of damage in the lung. LC3, RAB7, P62, and Beclin 1 were used to detect the induction of autophagy. The study was funded by the Natural Science Foundation of China (NSFC,81272172); National Key Specialty Construction of Clinical Projects of China (#2013-544). The funder of the present study had no capacity to influence the scholarly conduct of the research, interpretation of results, or dissemination of study outcomes.

RESULTS

In the injury group, pathologic changes (i.e., pulmonary congestion, hemorrhage, inflammatory exudation, and alveolar collapse) occurred within the lung tissue within 72 hours after ASCI. Apoptosis of the lung cells gradually increased and peaked 72 hours after ASCI. Within 24 hours of ASCI, LC3 expression decreased, recovered, and gradually increased from 24 hours to 72 hours. As RAB7 decreased, P62 increased, and the ratio of RAB7/LC3 significantly decreased.

CONCLUSIONS

After ASCI, autophagy in the injured lung underwent dynamic changes, as early autophagosome formation decreased and late autophagosomes accumulated; thus, autophagy is in a state of inhibition.

Spinal cord injury modulates the lung inflammatory response in mechanically ventilated rats: a comparative animal study

Mechanical ventilation (MV) is widely used in spinal injury patients to compensate for respiratory muscle failure. MV is known to induce lung inflammation, while spinal cord injury (SCI) is known to contribute to local inflammatory response. Interaction between MV and SCI was evaluated in order to assess the impact it may have on the pulmonary inflammatory profile. Sprague Dawley rats were anesthetized for 24 h and randomized to receive either MV or not. The MV group included C4-C5 SCI, T10 SCI and uninjured animals. The nonventilated (NV) group included T10 SCI and uninjured animals. Inflammatory cytokine profile, inflammation related to the SCI level, and oxidative stress mediators were measured in the bronchoalveolar lavage (BAL). The cytokine profile in BAL of MV animals showed increased levels of TNF-α, IL-1β, IL-6 and a decrease in IL-10 (P = 0.007) compared to the NV group. SCI did not modify IL-6 and IL-10 levels either in the MV or the NV groups, but cervical injury induced a decrease in IL-1β levels in MV animals. Cervical injury also reduced MV-induced pulmonary oxidative stress responses by decreasing isoprostane levels while increasing heme oxygenase-1 level. The thoracic SCI in NV animals increased M-CSF expression and promoted antioxidant pulmonary responses with low isoprostane and high heme oxygenase-1 levels. SCI shows a positive impact on MV-induced pulmonary inflammation, modulating specific lung immune and oxidative stress responses. Inflammation induced by MV and SCI interact closely and may have strong clinical implications since effective treatment of ventilated SCI patients may amplify pulmonary biotrauma.

Serum MicroRNAs Reflect Injury Severity in a Large Animal Model of Thoracic Spinal Cord Injury

Therapeutic development for spinal cord injury is hindered by the difficulty in conducting clinical trials, which to date have relied solely on functional outcome measures for patient enrollment, stratification, and evaluation. Biological biomarkers that accurately classify injury severity and predict neurologic outcome would represent a paradigm shift in the way spinal cord injury clinical trials could be conducted. MicroRNAs have emerged as attractive biomarker candidates due to their stability in biological fluids, their phylogenetic similarities, and their tissue specificity. Here we characterized a porcine model of spinal cord injury using a combined behavioural, histological, and molecular approach. We performed next-generation sequencing on microRNAs in serum samples collected before injury and then at 1, 3, and 5 days post injury. We identified 58, 21, 9, and 7 altered miRNA after severe, moderate, and mild spinal cord injury, and SHAM surgery, respectively. These data were combined with behavioural and histological analysis. Overall miRNA expression at 1 and 3 days post injury strongly correlates with outcome measures at 12 weeks post injury. The data presented here indicate that serum miRNAs are promising candidates as biomarkers for the evaluation of injury severity for spinal cord injury or other forms of traumatic, acute, neurologic injury.

Changes in Gene Expression and Metabolism in the Testes of the Rat following Spinal Cord Injury

Spinal cord injury (SCI) results in devastating changes to almost all aspects of a patient's life. In addition to a permanent loss of sensory and motor function, males also will frequently exhibit a profound loss of fertility through poorly understood mechanisms. We demonstrate that SCI causes measureable pathology in the testis both acutely (24 h) and chronically up to 1.5 years post-injury, leading to loss in sperm motility and viability. SCI has been shown in humans and rats to induce leukocytospermia, with the presence of inflammatory cytokines, anti-sperm antibodies, and reactive oxygen species found within the ejaculate. Using messenger RNA and metabolomic assessments, we describe molecular and cellular changes that occur within the testis of adult rats over an acute to chronic time period. From 24 h, 72 h, 28 days, and 90 days post-SCI, the testis reveal a distinct time course of pathological events. The testis show an acute drop in normal sexual organ processes, including testosterone production, and establishment of a pro-inflammatory environment. This is followed by a subacute initiation of an innate immune response and loss of cell cycle regulation, possibly due to apoptosis within the seminiferous tubules. At 1.5 years post-SCI, there is a chronic low level immune response as evidenced by an elevation in T cells. These data suggest that SCI elicits a wide range of pathological processes within the testes, the actions of which are not restricted to the acute phase of injury but rather extend chronically, potentially through the lifetime of the subject. The multiplicity of these pathological events suggest a single therapeutic intervention is unlikely to be successful.

Experimental Traumatic Brain Injury Induces Bone Loss in Rats

Few studies have investigated the influence of traumatic brain injury (TBI) on bone homeostasis; however, pathophysiological mechanisms involved in TBI have potential to be detrimental to bone. The current study assessed the effect of experimental TBI in rats on the quantity and quality of two different weight-bearing bones, the femur and humerus. Rats were randomly assigned into either sham or lateral fluid percussion injury (FPI) groups. Open-field testing to assess locomotion was conducted at 1, 4, and 12 weeks post-injury, with the rats killed at 1 and 12 weeks post-injury. Bones were analyzed using peripheral quantitative computed tomography (pQCT), histomorphometric analysis, and three-point bending. pQCT analysis revealed that at 1 and 12 weeks post-injury, the distal metaphyseal region of femora from FPI rats had reduced cortical content (10% decrease at 1 week, 8% decrease at 12 weeks; p < 0.01) and cortical thickness (10% decrease at 1 week, 11% decrease at 12 weeks p < 0.001). There was also a 23% reduction in trabecular bone volume ratio at 1 week post-injury and a 27% reduction at 12 weeks post-injury in FPI rats compared to sham (p < 0.001). There were no differences in bone quantity and mechanical properties of the femoral midshaft between sham and TBI animals. There were no differences in locomotor outcomes, which suggested that post-TBI changes in bone were not attributed to immobility. Taken together, these findings indicate that this rat model of TBI was detrimental to bone and suggests a link between TBI and altered bone remodeling.

Gut dysbiosis impairs recovery after spinal cord injury

Kigerl et al. show that spinal cord injury causes profound changes in gut microbiota and that these changes in gut ecology are associated with activation of GALT immune cells. They show that feeding mice probiotics after SCI confers neuroprotection and improves functional recovery.

The trillions of microbes that exist in the gastrointestinal tract have emerged as pivotal regulators of mammalian development and physiology. Disruption of this gut microbiome, a process known as dysbiosis, causes or exacerbates various diseases, but whether gut dysbiosis affects recovery of neurological function or lesion pathology after traumatic spinal cord injury (SCI) is unknown. Data in this study show that SCI increases intestinal permeability and bacterial translocation from the gut. These changes are associated with immune cell activation in gut-associated lymphoid tissues (GALTs) and significant changes in the composition of both major and minor gut bacterial taxa. Postinjury changes in gut microbiota persist for at least one month and predict the magnitude of locomotor impairment. Experimental induction of gut dysbiosis in naive mice before SCI (e.g., via oral delivery of broad-spectrum antibiotics) exacerbates neurological impairment and spinal cord pathology after SCI. Conversely, feeding SCI mice commercial probiotics (VSL#3) enriched with lactic acid–producing bacteria triggers a protective immune response in GALTs and confers neuroprotection with improved locomotor recovery. Our data reveal a previously unknown role for the gut microbiota in influencing recovery of neurological function and neuropathology after SCI.