Minocycline Reduces the Severity of Autonomic Dysreflexia after Experimental Spinal Cord Injury

Unbiased multitissue transcriptomic analysis reveals complex neuroendocrine regulatory networks mediated by spinal cord injury-induced immunodeficiency

BACKGROUND

Spinal cord injury (SCI), which causes loss of sensory and motor function in the body below the level of injury, is a devastating disease of the central nervous system. SCI leads to severe secondary immunosuppression, called SCI-induced immunodeficiency syndrome (SCI-IDS), which is characterized by increased susceptibility to infection and further exacerbates neurological dysfunction. Several studies have suggested that SCI-IDS is an independent risk factor for poor neurological prognosis. SCI-IDS predominantly occurs following injury above the T5 levels and eventually leads to systemic immune failure, possibly via the sympathetic-adrenal medullary axis and the hypothalamic‒pituitary‒adrenal (HPA) axis. However, the mechanism remains unclear.

METHODS AND OBJECTIVES

The concentrations of adrenocorticotropic hormone and cortisol in plasma, as well as changes in sympathetic activity (blood pressure and catecholamine levels in plasma), were assessed in rats in the high-level (T3) spinal cord injury (T3-SCI) group and the low-level (T10) spinal cord injury (T10-SCI) group. Second, the differential regulation of the gene network between the sympathetic-adrenal medullary axis and the HPA axis was explored by histology and multitissue transcriptomics, and the neuroendocrine-immune network associated with SCI-IDS was further elucidated.

RESULTS

The spleen and thymus gland, which are secondary immune organs, were significantly atrophied in rats in the T3-SCI group, and the white pulp of the spleen was significantly atrophied. The level of cortisol, which is mediated by the adrenal glands, was markedly elevated, but norepinephrine levels were markedly decreased. There was no difference in adrenocorticotropic hormone expression between any of the groups. The transcriptome analysis results showed that the downregulated differentially expressed genes (DEGs) in the T3-SCI group were enriched in the GO term immunoregulation, indicating that splenic immune function was markedly impaired after high-level SCI. The upregulated DEGs in the hypothalamus (hub genes: Nod2, Serpine1, Cebpb, Nfkbil1, Ripk2, Zfp36, Traf6, Akap8, Gfer, Cxcl10, Tnfaip3, Icam1, Fcgr2b, Ager, Dusp10, and Mapkapk2) were significantly enriched in inflammatory pathways, and the downregulated genes (hub genes: Grm4, Nmu, P2ry12, rt1-bb1, Oprm1, Zfhx2, Gpr83, and Chrm2) were enriched in pathways related to inhibitory Gi-mediated G protein-coupled receptor (Gi-GPCR) neurons and neuropeptide changes. The upregulated genes in the adrenal glands (hub genes: Ciart, per2, per3, cry1, and cry2) were enriched in cortisol secretion and circadian rhythm changes, and the downregulated genes (hub genes: IL7r, rt1-bb, rt1-bb1, rt1-da, rt1-ba, cd74, cxcr3, vcam1, ccl5, bin1, and IL8) were significantly enriched in MHC-mediated immune responses.

CONCLUSIONS

To explore the possible mechanism underlying SCI-IDS, this study assessed the differential regulation of the gene network associated with neuroendocrine immunity after SCI. Progressive neuroinflammation spreads after injury, and neurotransmission through Gi-mediated G protein-coupled receptors in the HPA axis and neuropeptide production by the hypothalamus are inhibited. Disruption of the connection between the hypothalamus and the adrenal glands causes autonomous regulation of the adrenal glands, disturbance of circadian rhythm and finally hypercortisolemia, leading to general suppression of peripheral adaptive immunity. Neuraxial nerve inflammation caused by SCI persists indefinitely, blocking nerve repair; persistent system-wide immunosuppression in the periphery results in increased susceptibility to infection, leading to poor neurological prognosis.

Spinal cord injury: molecular mechanisms and therapeutic interventions

Spinal cord injury (SCI) remains a severe condition with an extremely high disability rate. The challenges of SCI repair include its complex pathological mechanisms and the difficulties of neural regeneration in the central nervous system. In the past few decades, researchers have attempted to completely elucidate the pathological mechanism of SCI and identify effective strategies to promote axon regeneration and neural circuit remodeling, but the results have not been ideal. Recently, new pathological mechanisms of SCI, especially the interactions between immune and neural cell responses, have been revealed by single-cell sequencing and spatial transcriptome analysis. With the development of bioactive materials and stem cells, more attention has been focused on forming intermediate neural networks to promote neural regeneration and neural circuit reconstruction than on promoting axonal regeneration in the corticospinal tract. Furthermore, technologies to control physical parameters such as electricity, magnetism and ultrasound have been constantly innovated and applied in neural cell fate regulation. Among these advanced novel strategies and technologies, stem cell therapy, biomaterial transplantation, and electromagnetic stimulation have entered into the stage of clinical trials, and some of them have already been applied in clinical treatment. In this review, we outline the overall epidemiology and pathophysiology of SCI, expound on the latest research progress related to neural regeneration and circuit reconstruction in detail, and propose future directions for SCI repair and clinical applications.

Immune response following traumatic spinal cord injury: Pathophysiology and therapies

Traumatic spinal cord injury (SCI) is a devastating condition that is often associated with significant loss of function and/or permanent disability. The pathophysiology of SCI is complex and occurs in two phases. First, the mechanical damage from the trauma causes immediate acute cell dysfunction and cell death. Then, secondary mechanisms of injury further propagate the cell dysfunction and cell death over the course of days, weeks, or even months. Among the secondary injury mechanisms, inflammation has been shown to be a key determinant of the secondary injury severity and significantly worsens cell death and functional outcomes. Thus, in addition to surgical management of SCI, selectively targeting the immune response following SCI could substantially decrease the progression of secondary injury and improve patient outcomes. In order to develop such therapies, a detailed molecular understanding of the timing of the immune response following SCI is necessary. Recently, several studies have mapped the cytokine/chemokine and cell proliferation patterns following SCI. In this review, we examine the immune response underlying the pathophysiology of SCI and assess both current and future therapies including pharmaceutical therapies, stem cell therapy, and the exciting potential of extracellular vesicle therapy.

Molecular approaches for spinal cord injury treatment

Injuries to the spinal cord result in permanent disabilities that limit daily life activities. The main reasons for these poor outcomes are the limited regenerative capacity of central neurons and the inhibitory milieu that is established upon traumatic injuries. Despite decades of research, there is still no efficient treatment for spinal cord injury. Many strategies are tested in preclinical studies that focus on ameliorating the functional outcomes after spinal cord injury. Among these, molecular compounds are currently being used for neurological recovery, with promising results. These molecules target the axon collapsed growth cone, the inhibitory microenvironment, the survival of neurons and glial cells, and the re-establishment of lost connections. In this review we focused on molecules that are being used, either in preclinical or clinical studies, to treat spinal cord injuries, such as drugs, growth and neurotrophic factors, enzymes, and purines. The mechanisms of action of these molecules are discussed, considering traumatic spinal cord injury in rodents and humans.

Pathophysiology and Therapeutic Approaches for Spinal Cord Injury

Spinal cord injury (SCI) is a disabling condition that disrupts motor, sensory, and autonomic functions. Despite extensive research in the last decades, SCI continues to be a global health priority affecting thousands of individuals every year. The lack of effective therapeutic strategies for patients with SCI reflects its complex pathophysiology that leads to the point of no return in its function repair and regeneration capacity. Recently, however, several studies started to uncover the intricate network of mechanisms involved in SCI leading to the development of new therapeutic approaches. In this work, we present a detailed description of the physiology and anatomy of the spinal cord and the pathophysiology of SCI. Additionally, we provide an overview of different molecular strategies that demonstrate promising potential in the modulation of the secondary injury events that promote neuroprotection or neuroregeneration. We also briefly discuss other emerging therapies, including cell-based therapies, biomaterials, and epidural electric stimulation. A successful therapy might target different pathologic events to control the progression of secondary damage of SCI and promote regeneration leading to functional recovery.

Established and Emerging Therapies in Acute Spinal Cord Injury

Acute spinal cord injury (SCI) is devastating for patients and their caretakers and has an annual incidence of 20–50 per million people. Following initial assessment with appropriate physical examination and imaging, patients who are deemed surgical candidates should undergo decompression with stabilization. Earlier intervention can improve neurological recovery in the post-operative period while allowing earlier mobilization. Optimized medical management is paramount to improve outcomes. Emerging strategies for managing SCI in the acute period stem from an evolving understanding of the pathophysiology of the injury. General areas of focus include ischemia prevention, reduction of secondary injury due to inflammation, modulation of the cytotoxic and immune response, and promotion of cellular regeneration. In this article, we review established, emerging, and novel experimental therapies. Continued translational research on these methods will improve the feasibility of bench-to-bedside innovations in treating patients with acute SCI.

Spinal cord injury impairs cardiac function due to impaired bulbospinal sympathetic control

Spinal cord injury chronically alters cardiac structure and function and is associated with increased odds for cardiovascular disease. Here, we investigate the cardiac consequences of spinal cord injury on the acute-to-chronic continuum, and the contribution of altered bulbospinal sympathetic control to the decline in cardiac function following spinal cord injury. By combining experimental rat models of spinal cord injury with prospective clinical studies, we demonstrate that spinal cord injury causes a rapid and sustained reduction in left ventricular contractile function that precedes structural changes. In rodents, we experimentally demonstrate that this decline in left ventricular contractile function following spinal cord injury is underpinned by interrupted bulbospinal sympathetic control. In humans, we find that activation of the sympathetic circuitry below the level of spinal cord injury causes an immediate increase in systolic function. Our findings highlight the importance for early interventions to mitigate the cardiac functional decline following spinal cord injury.

By combining experimental models with prospective clinical studies, the authors show that spinal cord injury causes a rapid reduction in cardiac function that precedes structural changes, and that the loss of descending sympathetic control is the major cause of reduced cardiac function following spinal cord injury.

The Minocycline Ameliorated the Synaptic Plasticity Impairment in Vascular Dementia

Chronic cerebral hypoperfusion (CCH) leads to vascular dementia with progressive hippocampal damage and cognitive impairments. In the present study, we compared early and late Minocycline (MINO) treatment on cognitive function, long and short-term synaptic-plasticity following CCH. We used bilateral common carotid arteries occlusion model (2VO) for induction of hypoperfusion. Male Sprague-Dawley rats were divided into 5 following groups (each having 2 subgroups): 2VO + V (vehicle), 2VO+MINO-E (early treatment of MINO on days 0 to 3 after 2VO), 2VO+MINO-L (late-treatment on days 21 to 32 after 2VO), control, and sham. Passive-avoidance (PA) and radial arm maze (RAM) tests were used to investigate learning and memory. Long term and short term synaptic plasticity were assessed by field potential recording, the brains were removed after recording and preserved for histological study to count pyramidal cells in CA1 region.Cerebral hypoperfusion could impair memory performance, synaptic plasticity, and basal synaptic transmission (BST) along with hippocampal cell loss. Thus, we found a significant reduction in step-through latency (STL) of PA test with a higher number of working and reference errors in RAM in CCH rats. However, only late treatment with MINO improved memory performance, synaptic plasticity, hippocampal cell loss, and increased neurotransmitter pool (NP) in CCH rats, but early treatment could not produce long-lasting beneficial effects 32 days after 2VO. MINO may improve synaptic plasticity and memory performance in hypo-perfused rats directly and indirectly by increasing NP and/or suppressing inflammatory factors, respectively.

Minocycline Pretreatment Prevents Blood-Brain Barrier Disruption in Septic Rats

INTRODUCTION

The aim of the study was to explore the mechanism by which minocycline protects the blood-brain barrier (BBB) in septic rats.

METHODS

A sepsis rat model was generated in healthy, male Sprague-Dawley rats by cecal ligation and puncture (CLP). The rats were randomly divided into four groups and treated as follows: sham-operated plus normal saline (Sham + S group), CLP plus normal saline (CLP + S group), CLP plus minocycline pretreatment (CLP + M1 group), and CLP plus minocycline treatment (CLP + M2 group). Rats in the CLP + M1 group received 45 mg/kg minocycline by intraperitoneal injection every 12 h for 72 h. Rats in the Sham + S and CLP + S groups were injected with the same volume of normal saline every 12 h for 72 h. Rats in the CLP + M2 group were intraperitoneally injected with 45 mg/kg minocycline immediately after CLP and once every 12 h for 72 h. All rats were sacrificed at 72 h after operation. Tumor necrosis factor α and interleukin 6 levels, the expression of ionized calcium-binding adaptor molecule-1 (Iba-1), and the permeability of the BBB were measured. The expression of matrix metalloproteinases-9 (MMP-9) and the tight junction proteins zonula occludens-1 (ZO-1) and occludin was detected by Western blot. In addition, Evans blue (EB) staining, immunohistochemistry, and ELISA analysis were carried out.

RESULTS

Minocycline pretreatment significantly inhibited microglial activation, decreased the sepsis-induced expression of MMP-9, increased the expression of ZO-1 and occludin, and improved the permeability of the BBB. Minocycline treatment failed to inhibit microglial activation, decrease the sepsis-induced expression of MMP-9, increase the expression of ZO-1 or occluding, or improve the permeability of the BBB.

CONCLUSIONS

Minocycline pretreatment can effectively improve the altered permeability of the BBB caused by sepsis. The mechanism may be related to the inhibition of microglial activation and MMP-9 expression and increased expression of ZO-1 and occludin.

Beyond the lesion site: minocycline augments inflammation and anxiety-like behavior following SCI in rats through action on the gut microbiota

Background

Minocycline is a clinically available synthetic tetracycline derivative with anti-inflammatory and antibiotic properties. The majority of studies show that minocycline can reduce tissue damage and improve functional recovery following central nervous system injuries, mainly attributed to the drug’s direct anti-inflammatory, anti-oxidative, and neuroprotective properties. Surprisingly the consequences of minocycline’s antibiotic (i.e., antibacterial) effects on the gut microbiota and systemic immune response after spinal cord injury have largely been ignored despite their links to changes in mental health and immune suppression.

Methods

Here, we sought to determine minocycline’s effect on spinal cord injury-induced changes in the microbiota-immune axis using a cervical contusion injury in female Lewis rats. We investigated a group that received minocycline following spinal cord injury (immediately after injury for 7 days), an untreated spinal cord injury group, an untreated uninjured group, and an uninjured group that received minocycline. Plasma levels of cytokines/chemokines and fecal microbiota composition (using 16s rRNA sequencing) were monitored for 4 weeks following spinal cord injury as measures of the microbiota-immune axis. Additionally, motor recovery and anxiety-like behavior were assessed throughout the study, and microglial activation was analyzed immediately rostral to, caudal to, and at the lesion epicenter.

Results

We found that minocycline had a profound acute effect on the microbiota diversity and composition, which was paralleled by the subsequent normalization of spinal cord injury-induced suppression of cytokines/chemokines. Importantly, gut dysbiosis following spinal cord injury has been linked to the development of anxiety-like behavior, which was also decreased by minocycline. Furthermore, although minocycline attenuated spinal cord injury-induced microglial activation, it did not affect the lesion size or promote measurable motor recovery.

Conclusion

We show that minocycline’s microbiota effects precede its long-term effects on systemic cytokines and chemokines following spinal cord injury. These results provide an exciting new target of minocycline as a therapeutic for central nervous system diseases and injuries.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-021-02123-0.

Acute spinal cord injury: Pathophysiology and pharmacological intervention (Review)

Spinal cord injury (SCI) is one of the most debilitating of all the traumatic conditions that afflict individuals. For a number of years, extensive studies have been conducted to clarify the molecular mechanisms of SCI. Experimental and clinical studies have indicated that two phases, primary damage and secondary damage, are involved in SCI. The initial mechanical damage is caused by local impairment of the spinal cord. In addition, the fundamental mechanisms are associated with hyperflexion, hyperextension, axial loading and rotation. By contrast, secondary injury mechanisms are led by systemic and cellular factors, which may also be initiated by the primary injury. Although significant advances in supportive care have improved clinical outcomes in recent years, a number of studies continue to explore specific pharmacological therapies to minimize SCI. The present review summarized some important pathophysiologic mechanisms that are involved in SCI and focused on several pharmacological and non‑pharmacological therapies, which have either been previously investigated or have a potential in the management of this debilitating injury in the near future.

Noninvasive Neuroprosthesis Promotes Cardiovascular Recovery After Spinal Cord Injury

Spinal cord injury (SCI) leads to severe impairment in cardiovascular control, commonly manifested as a rapid, uncontrolled rise in blood pressure triggered by peripheral stimuli-a condition called autonomic dysreflexia. The objective was to demonstrate the translational potential of noninvasive transcutaneous stimulation (TCS) in mitigating autonomic dysreflexia following SCI, using pre-clinical evidence and a clinical case report. In rats with SCI, we show that TCS not only prevents the instigation of autonomic dysreflexia, but also mitigates its severity when delivered during an already-triggered episode. Furthermore, when TCS was delivered as a multisession therapy for 6 weeks post-SCI, the severity of autonomic dysreflexia was significantly reduced when tested in the absence of concurrent TCS. This treatment effect persisted for at least 1 week after the end of therapy. More importantly, we demonstrate the clinical applicability of TCS in treatment of autonomic dysreflexia in an individual with cervical, motor-complete, chronic SCI. We anticipate that TCS will offer significant therapeutic advantages, such as obviating the need for surgery resulting in reduced risk and medical expenses. Furthermore, this study provides a framework for testing the potential of TCS in improving recovery of other autonomic functions such lower urinary tract, bowel, and sexual dysfunction following SCI.

Advances in immunotherapy for the treatment of spinal cord injury

Spinal cord injury (SCI) is a leading cause of morbidity and disability in the world. Over the past few decades, the exact molecular mechanisms describing secondary, persistent injuries, as well as primary and transient injuries, have attracted massive attention to the clinicians and researchers. Recent investigations have distinctly shown the critical roles of innate and adaptive immune responses in regulating sterile neuroinflammation and functional outcomes after SCI. In past years, some promising advances in immunotherapeutic options have efficaciously been identified for the treatment of SCI. In our narrative review, we have mainly focused on the new therapeutic strategies such as the maturation and apoptosis of immune cells by several agents, mesenchymal stem cells (MSCs) as well as multi-factor combination therapy, which have recently provided novel ideas and prospects for the future treatment of SCI. This article also illustrates the latest progress in clarifying the potential roles of innate and adaptive immune responses in SCI, the progression and specification of prospective immunotherapy and outstanding issues in the area.

Sumatriptan improves the locomotor activity and neuropathic pain by modulating neuroinflammation in rat model of spinal cord injury

OBJECTIVES

To investigate the therapeutic effects of sumatriptan in a rat model of spinal cord injury (SCI) and possible anti-inflammatory and analgesic mechanisms underlying this effect.

METHODS

Using an aneurysm mini-clip model of contusive SCI, T9-10 laminectomies were performed for 60 male rats. Animals were divided into six experimental groups (n = 10 per group) as follows: a minocycline administered positive control group, a saline-vehicle negative control group, a sham-operated group, and three experimental groups which received separate doses of sumatriptan (0.1, 0.3 and 1 mg/kg). Behavioural assessments were used to evaluate locomotor activity and neuropathic pain for 28 days. At the end of the study, spinal cord tissues were collected from sacrificed animals for histopathological analysis. Levels of calcitonin gene-related peptide (CGRP) and two pro-inflammatory cytokines (tumor necrosis factor [TNF]-α and interleukin [IL]-1β) were assessed by the enzyme-linked immunosorbent assay (ELISA).

RESULTS

Sumatriptan significantly (P < 0.001) improved the locomotor activity in SCI group. Sumatriptan was also more effective than the positive control, i.e. minocycline (0.3 mg/kg). Additionally, sumatriptan and minocycline similarly attenuated the mechanical and thermal allodynia in SCI (P < 0.001). TNF-α, IL-1β and CGRP levels in sumatriptan- and minocycline-treated groups significantly (P < 0.001) decreased compared to controls. Histopathological analysis also revealed a markedly improvement in hemorrhage followed by inflammatory cell invasion, neuronal vacuolation, and cyst formation in both sumatriptan- and minocycline-treated groups compared to control animals.

CONCLUSIONS

Sumatriptan improves functional recovery from SCI through its anti-inflammatory effects and reducing pro-inflammatory and pain mediators.

Neuroimmune System as a Driving Force for Plasticity Following CNS Injury

Following an injury to the central nervous system (CNS), spontaneous plasticity is observed throughout the neuraxis and affects multiple key circuits. Much of this spontaneous plasticity can elicit beneficial and deleterious functional outcomes, depending on the context of plasticity and circuit affected. Injury-induced activation of the neuroimmune system has been proposed to be a major factor in driving this plasticity, as neuroimmune and inflammatory factors have been shown to influence cellular, synaptic, structural, and anatomical plasticity. Here, we will review the mechanisms through which the neuroimmune system mediates plasticity after CNS injury. Understanding the role of specific neuroimmune factors in driving adaptive and maladaptive plasticity may offer valuable therapeutic insight into how to promote adaptive plasticity and/or diminish maladaptive plasticity, respectively.

Minocycline attenuates testicular damages in a rat model of ischaemia/reperfusion (I/R) injury

Testicular torsion is a serious urological disease leading to testicular damage. This study aimed to assess the effect of minocycline on testicular ischaemia/reperfusion (I/R) injury caused by testicular torsion/detorsion. Male adult Wistar rats (n = 32) were assigned into four groups of sham, I/R, I/R + minocycline and minocycline. I/R injury was induced by two sets of surgical operations, including the rotation of the left testis (720°, counterclockwise), followed by detorsion after 4 hr. The administration of minocycline was carried out 30 min before detorsion and then continued for 8 weeks. At the end of the 8th week, rats were killed and sampling was done. Johnson's score, the height of seminiferous tubule epithelium, the mean seminiferous tubule diameter, as well as biochemical parameters, SOD, GPx and CAT, were significantly enhanced in the I/R + minocycline group compared with the I/R group. The administration of minocycline led to a marked decrease in expression levels of Caspase-3, Bax, IL-1β and TNF-α genes, and a remarkable increase in expression levels of Bcl-2, 3β-HSD and 17β-HSD3 genes compared with the I/R group. Administration of minocycline could also reduce the rate of germ cell apoptosis (TUNEL staining). Hence, minocycline was useful in the management of testicular torsion/detorsion.

Morphological maladaptations in sympathetic preganglionic neurons following an experimental high-thoracic spinal cord injury

Spinal cord injury (SCI) disrupts the supraspinal vasomotor pathways to sympathetic preganglionic neurons (SPNs) leading to impaired blood pressure (BP) control that often results in episodes of autonomic dysreflexia and orthostatic hypotension. The physiological cardiovascular consequences of SCI are largely attributed to the plastic changes in spinal SPNs induced by their partial deafferentation. While multiple studies have investigated the morphological changes in SPNs following SCI with contrasting reports. Here we investigated the morphological changes in SPNs rostral and caudal to a high thoracic (T3) SCI at 1-, 4- and 8-weeks post injury. SPNs were identified using Nicotinamide adenine dinucleotide hydrogen phosphate-diaphorase (NADPH- diaphorase) staining and were quantified for soma size and various dendritic measurements. We show that rostral to the lesion, soma size was increased at 1 week along with increased dendritic arbor. The total dendritic length was also increased at chronic stage (8 weeks post SCI). Caudal to the lesion, the soma size or dendritic lengths did not change with SCI. However, dendritic branching was enhanced within a week post SCI and remained elevated throughout the chronic stages. These findings demonstrate that SPNs undergo significant structural changes form sub-acute to chronic stages post-SCI that likely determines their functional consequences. These changes are discussed in context of physiological cardiovascular outcomes post-SCI.

Lentivirus-mediated downregulation of α-synuclein reduces neuroinflammation and promotes functional recovery in rats with spinal cord injury

BACKGROUND

The prognosis of spinal cord injury (SCI) is closely related to secondary injury, which is dominated by neuroinflammation. There is evidence that α-synuclein aggregates after SCI and that inhibition of α-synuclein aggregation can improve the survival of neurons after SCI, but the mechanism is still unclear. This study was designed to investigate the effects of α-synuclein on neuroinflammation after SCI and to determine the underlying mechanisms.

METHOD

A T3 spinal cord contusion model was established in adult male Sprague-Dawley rats. An SNCA-shRNA-carrying lentivirus (LV-SNCA-shRNA) was injected into the injury site to block the expression of α-synuclein (forming the SCI+KD group), and the SCI and sham groups were injected with an empty vector. Basso-Beattie-Bresnahan (BBB) behavioural scores and footprint analysis were used to detect motor function. Inflammatory infiltration and myelin loss were measured in the spinal cord tissues of each group by haematoxylin-eosin (HE) and Luxol Fast Blue (LFB) staining, respectively. Immunohistochemistry, Western blot analysis, and RT-qPCR were used to analyse protein expression and transcription levels in the tissues. Immunofluorescence was used to determine the morphology and function of glial cells and the expression of matrix metalloproteinase-9 in the central canal of the spinal cord. Finally, peripheral serum cytokine levels were determined by enzyme-linked immunosorbent assay.

RESULTS

Compared with the SCI group, the SCI+KD group exhibited reduced inflammatory infiltration, preserved myelin, and functional recovery. Specifically, the early arrest of α-synuclein inhibited the pro-inflammatory factors IL-1β, TNF-α, and IL-2 and increased the expression of the anti-inflammatory factors IL-10, TGF-β, and IL-4. The neuroinflammatory response was regulated by reduced proliferation of Iba1+ microglia/macrophages and promotion of the shift of M1-polarized Iba1+/iNOS+ microglia/macrophages to M2-polarized Iba1+/Arg1+ microglia/macrophages after injury. In addition, compared with the SCI group, the SCI+KD group also exhibited a smaller microglia/astrocyte (Iba1/GFAP) immunostaining area in the central canal, lower MMP-9 expression, and improved cerebrospinal barrier function.

CONCLUSION

Lentivirus-mediated downregulation of α-synuclein reduces neuroinflammation, improves blood-cerebrospinal barrier function, promotes functional recovery, reduces microglial activation, and promotes the polarization of M1 microglia/macrophages to an M2 phenotype to confer a neuroprotective immune microenvironment in rats with SCI.

Transcriptomic analysis of α-synuclein knockdown after T3 spinal cord injury in rats

Background

Endogenous α-synuclein (α-Syn) is involved in many pathophysiological processes in the secondary injury stage after acute spinal cord injury (SCI), and the mechanism governing these functions has not been thoroughly elucidated to date. This research aims to characterize the effect of α-Syn knockdown on transcriptional levels after SCI and to determine the mechanisms underlying α-Syn activity based on RNA-seq.

Result

The establishment of a rat model of lentiviral vector-mediated knockdown of α-Syn in Sprague-Dawley rats with T3 spinal cord contusion (LV_SCI group). The results of the RNA-seq analysis showed that there were 337 differentially expressed genes (DEGs) between the SCI group and the LV_SCI group, and 153 DEGs specific to LV_SCI between the (SCI vs LV_SCI) and (SCI vs CON) comparisons. The top 20 biological transition terms were identified by Gene ontology (GO) analysis. The Kyoto Gene and Genomic Encyclopedia (KEGG) analysis showed that the LV_SCI group significantly upregulated the cholinergic synaptic & nicotine addiction and the neuroactive ligand receptor interaction signaling pathway. Enriched chord analysis analyzes key genes. Further cluster analysis, gene and protein interaction network analysis and RT-qPCR results showed that Chrm2 and Chrnb2 together significantly in both pathways. The proliferation of muscarinic cholinergic receptor subtype 2 (Chrm2) and nicotinic cholinergic receptor subtype β2 (Chrnb2), and the neurogenesis were elevated in the injury site of LV_SCI group by immunofluorescence. Further by subcellular localization, the LV_SCI group enhanced the expression of Chrnb2 at the cell membrane.

Conclusion

Knockdown of α-Syn after SCI enhance motor function and promote neurogenesis probably through enhancing cholinergic signaling pathways and neuroreceptor interactions. This study not only further clarifies the understanding of the mechanism of knockdown of α-Syn on SCI but also helps to guide the treatment strategy for SCI.

The Blood Pressure Pendulum following Spinal Cord Injury: Implications for Vascular Cognitive Impairment

Cognitive impairment following spinal cord injury (SCI) has received considerable attention in recent years. Among the various systemic effects of SCI that contribute towards cognitive decline in this population, cardiovascular dysfunction is arguably one of the most significant. The majority of individuals with a cervical or upper-thoracic SCI commonly experience conditions called orthostatic hypotension and autonomic dysreflexia, which are characterized by dangerous fluctuations in systemic blood pressure (BP). Herein, we review the potential impact of extreme BP lability on vascular cognitive impairment (VCI) in individuals with SCI. Albeit preliminary in the SCI population, there is convincing evidence that chronic hypotension and hypertension in able-bodied individuals results in devastating impairments in cerebrovascular health, leading to VCI. We discuss the pertinent literature, and while drawing mechanistic comparisons between able-bodied cohorts and individuals with SCI, we emphasize the need for additional research to elucidate the mechanisms of cognitive impairment specific to the SCI population. Lastly, we highlight the current and potential future therapies to manage and treat BP instability, thereby possibly mitigating VCI in the SCI population.

Snx27 Deletion Promotes Recovery From Spinal Cord Injury by Neuroprotection and Reduces Macrophage/Microglia Proliferation

Sorting nexin 27 (SNX27) is an endosome-associated cargo adaptor that is involved in various pathologies and development of neurological diseases. However, the role of SNX27 in spinal cord injury (SCI) remains unclear. In this study, we found that SNX27 was up-regulated in injured mice spinal cords by western blot and immunofluorescence. A comparative analysis of Basso mouse scale (BMS), footprint test and corticospinal tract (CST) tracing in Snx27 ^+/+ and Snx27 ^+/- mice revealed that haploinsufficiency of SNX27 ameliorated the clinical symptoms of SCI. Based on the results of western blot and immunofluorescence, mechanistically, we found that SNX27 deficiency suppresses apoptotic caspase-3 induced neuronal death. In addition, SNX27 haploinsufficiency lowers the infiltration and activation of macrophage/microglia by suppressing their proliferation at the SCI lesion site. Together, these results suggest that down-regulation of SNX27 is a potential therapy targeting both acute neuronal death and chronic neuroinflammation, and promoting nerve repair after SCI.