Age increases reactive oxygen species production in macrophages and potentiates oxidative damage after spinal cord injury

Bibliometric analysis of the inflammation expression after spinal cord injury: current research status and emerging frontiers

STUDY DESIGN

Bibliometric analysis.

OBJECTIVE

To analyze literature on inflammatory expression following spinal cord injury, highlighting development trends, current research status, and potential emerging frontiers.

SETTING

Not applicable.

METHODS

Articles were retrieved using terms related to spinal cord injury and inflammatory responses from the Web of Science Core Collection, covering January 1, 1980, to May 23, 2024. Tools like CiteSpace and VOSviewer assessed the research landscape, evaluating core authors, journals, and contributing countries. Keyword co-occurrence analyses identified research trends.

RESULTS

A total of 2504 articles were retrieved, showing a consistent increase in publications. The Journal of Neurotrauma had the highest publication volume and influence. The most prolific author was Cuzzocrea S, with Popovich PG having the highest H-index. China led in the number of publications, followed closely by the United States, which had the highest impact and extensive international collaboration. Research mainly focused on nerve function recovery, glial scar formation, and oxidative stress. Future research is expected to investigate cellular autophagy, vesicular transport, and related signaling pathways.

CONCLUSION

The growing interest in inflammation caused by spinal cord injury is evident, with current research focusing on oxidative stress, glial scar, and neurological recovery. Future directions include exploring autophagy and extracellular vesicles for new therapies. Interdisciplinary research and extensive clinical trials are essential for validating new treatments. Biomarker discovery is crucial for diagnosis and monitoring, while understanding autophagy and signaling pathways is vital for drug development. Global cooperation is needed to accelerate the application of scientific findings, improving spinal cord injury treatment.

Z-ligustilide provides a neuroprotective effect by regulating the phenotypic polarization of microglia via activating Nrf2-TrxR axis in the Parkinson's disease mouse model

The polarization phenotype of microglia is critical in the progression of Parkinson's disease (PD). Molecules that can polarize microglia toward the M2 phenotype represent a promising class of compounds for anti-PD medications. Z-ligustilide (ZLG) is a naturally occurring enol ester with diverse pharmacological properties, especially in neuroprotection. For the first time, we investigated the effect of ZLG on anti-PD and elucidated its underlying mechanism. The results primarily showed that ZLG attenuated motor deficits in mice and prevented the loss of dopaminergic neurons in the substantia nigra. Mechanistically, ZLG alleviates oxidative stress-induced apoptosis of microglia by triggering the endogenous antioxidant system. Besides, ZLG modulated phenotypic polarization of the microglia through the activation of the Nrf2-TrxR axis, leading to microglia polarization towards the M2 phenotype. Taken together, our research showed that ZLG is a prospective therapy candidate for PD by altering microglia polarization and restoring redox equilibrium through the Nrf2-TrxR axis.

Nrf2 Signaling Pathway: Focus on Oxidative Stress in Spinal Cord Injury

Spinal cord injury (SCI) is a serious, disabling injury to the central nervous system that can lead to motor, sensory, and autonomic dysfunction below the injury plane. SCI can be divided into primary injury and secondary injury according to its pathophysiological process. Primary injury is irreversible in most cases, while secondary injury is a dynamic regulatory process. Secondary injury involves a series of pathological events, such as ischemia, oxidative stress, inflammatory events, apoptotic pathways, and motor dysfunction. Among them, oxidative stress is an important pathological event of secondary injury. Oxidative stress causes a series of destructive events such as lipid peroxidation, DNA damage, inflammation, and cell death, which further worsens the microenvironment of the injured site and leads to neurological dysfunction. The nuclear factor erythrocyte 2-associated factor 2 (Nrf2) is considered to be a key pathway of antioxidative stress and is closely related to the pathological process of SCI. Activation of this pathway can effectively inhibit the oxidative stress process and promote the recovery of nerve function after SCI. Therefore, the Nrf2 pathway may be a potential therapeutic target for SCI. This review deeply analyzed the generation of oxidative stress in SCI, the role and mechanism of Nrf2 as the main regulator of antioxidant stress in SCI, and the influence of cross-talk between Nrf2 and related pathways that may be involved in the pathological regulation of SCI on oxidative stress, and summarized the drugs and other treatment methods based on Nrf2 pathway regulation. The objective of this paper is to provide evidence for the role of Nrf2 activation in SCI and to highlight the important role of Nrf2 in alleviating SCI by elucidating the mechanism, so as to provide a theoretical basis for targeting Nrf2 pathway as a therapy for SCI.

Non-resolving neuroinflammation regulates axon regeneration in chronic spinal cord injury

Chronic spinal cord injury (SCI) lesions retain increased densities of microglia and macrophages. In acute SCI, macrophages induce growth cone collapse, facilitate axon retraction away from lesion boundaries, as well as play a key role in orchestrating the growth-inhibitory glial scar. Little is known about the role of sustained inflammation in chronic SCI, or whether chronic inflammation affects repair and regeneration. We performed transcriptional analysis using the Nanostring Neuropathology panel to characterize the resolution of inflammation into chronic SCI, to characterize the chronic SCI microenvironment, as well as to identify spinal cord responses to macrophage depletion and repopulation using the CSF1R inhibitor, PLX-5622. We determined the ability for macrophage depletion and repopulation to augment axon growth into chronic lesions both with and without regenerative stimulation using neuronal-specific PTEN knockout (PTEN-KO). PTEN-KO was delivered with spinal injections of retrogradely transported adeno associated viruses (AAVrg's). Both transcriptional analyses and immunohistochemistry revealed the ability for PLX-5622 to significantly deplete inflammation around and within chronic SCI lesions, with a return to pre-depleted inflammatory densities after treatment removal. Neuronal-specific transcripts were significantly elevated in mice after inflammatory repopulation, but no significant effects were observed with macrophage depletion alone. Axon densities significantly increased within the lesion after PLX-5622 treatment with a more consistent effect observed in mice with inflammatory repopulation. PTEN-KO did not further increase axon densities within the lesion beyond effects induced by PLX-5622. We identified that PLX-5622 increased axon densities within the lesion that are histologically identified as 5-HT+and CGRP+, both of which are not robustly transduced by AAVrg's. Our work identified that increased macrophage/microglia densities in the chronic SCI environment may be actively retained by homeostatic mechanisms likely affiliated with a sustained elevated expression of CSF1 and other chemokines. Finally, we identify a novel role of sustained inflammation as a prospective barrier to axon regeneration in chronic SCI.

Biomimetic nanoplatform with anti-inflammation and neuroprotective effects for repairing spinal cord injury in mice

Regeneration in the therapeutics of spinal cord injury (SCI) remains a challenge caused by the hyperinflammation microenvironment. Nanomaterials-based treatment strategies for diseases with excellent therapeutic efficacy are actively pursued. Here, we develop biodegradable poly (lactic-co-glycolic acid) nanoparticles (PLGA) obtained by loading celastrol (pCel) for SCI thrapy. Cel, as an antioxidant drug, facilitated reactive oxygen species (ROS) scavenging, and decreased the generation of pro-inflammatory cytokines. To facilitate its administration, pCel is formulated into microspheres by oil-in-water (O/W) emulsion/solvent evaporation technique. The constructed pCel can induced polarization of macrophages and obviously improved lipopolysaccharide (LPS) and interferon-γ (IFN-γ)-induced mitochondrial dysfunction, and increased neurite length in PC12 cells and primary neurons. In vivo experiments revealed that pCel regulated the phenotypic polarization of macrophages, prevented the release of pro-inflammatory cytokines, promoted myelin regeneration and inhibited scar tissue formation, and further improve motor function. These findings indicated that the neuroprotective effect of this artificial biodegradable nanoplatform is benefit for the therapy of SCI. This research opens an exciting perspective for the application of SCI treatment and supports the clinical significance of pCel.

Prognostic Value of Malondialdehyde (MDA) in the Temporal Progression of Chronic Spinal Cord Injury

Background: Oxidative stress is a major signature of spinal cord injury (SCI). The altered levels of various oxidative stress markers have been demonstrated in acute and chronic SCI. However, the variation of these markers in patients with chronic SCI depending on the time since the initial injury has not been explored yet. Objective: Our aim was to measure plasma levels of malondialdehyde (MDA), a marker of lipid peroxidation in patients with SCI stratified in different periods of suffering the injury (0–5 years, 5–10 years, and more than 10 years). Patients and methods: This cross-sectional study enrolled patients with SCI (N = 105) from different periods of the lesion and healthy control (HC) subjects (N = 38): short period (SCI SP, N = 31, time of evolution less than 5 years); early chronic (SCI ECP, N = 32, time of evolution 5–15 years); and late chronic (SCI LCP, N = 42, time of evolution more than 15 years). The plasma levels of MDA were measured using a commercially available colorimetric assay. Results: Patients with SCI had significantly higher plasma levels of MDA than HC subjects. Receiver operating characteristic (ROC) curve analysis for plasma MDA levels in patients with SCI demonstrated areas under the curve (AUC) of 1 (HC vs. SCI-SP); 0.998 (HC vs. SCI-ECP); and 0.964 (HC vs. SCI-LCP). Additionally, three ROC curves were used to compare the different concentrations of MDA between the subgroups of patients with SCI, and the resulting AUCs were: 0.896 (SCI-SP vs. SCI-ECP); 0.840 (SCI-ECP vs. SCI-LCP); and 0.979 (SCI-SP vs. SCI-LCP). Conclusion: Plasma concentration of MDA can be considered as an oxidative stress biomarker to assess the prognosis of SCI in chronic stages.

Differential effects of NOX2 and NOX4 inhibition after rodent spinal cord injury

Reactive oxygen species (ROS) are a contributing factor to impaired function and pathology after spinal cord injury (SCI). The NADPH oxidase (NOX) enzyme is a key source of ROS; there are several NOX family members, including NOX2 and NOX4, that may play a role in ROS production after SCI. Previously, we showed that a temporary inhibition of NOX2 by intrathecal administration of gp91ds-tat immediately after injury improved recovery in a mouse SCI model. However, chronic inflammation was not affected by this single acute treatment, and other NOX family members were not assessed. Therefore, we aimed to explore the effect of genetic knockout (KO) of NOX2 or acute inhibition of NOX4 with GKT137831. A moderate SCI contusion injury was performed in 3 month old NOX2 KO and wild-type (WT) mice, who received no treatment or GKT137831/vehicle 30 minutes post-injury. Motor function was assessed using the Basso Mouse Scale (BMS), followed by evaluation of inflammation and oxidative stress markers. NOX2 KO mice, but not GKT137831 treated mice, demonstrated significantly improved BMS scores at 7, 14, and 28 days post injury (DPI) in comparison to WT mice. However, both NOX2 KO and GKT137831 significantly reduced ROS production and oxidative stress markers. Furthermore, a shift in microglial activation toward a more neuroprotective, anti-inflammatory state was observed in KO mice at 7 DPI and a reduction of microglial markers at 28 days. While acute alterations in inflammation were noted with GKT137831 administration, this was not sustained through 28 days. In vitro analysis also showed that while GKT137831 reduced ROS production by microglia, it did not translate to changes in pro-inflammatory marker expression within these cells. These data demonstrate that NOX2 and NOX4 play a role in post-injury ROS, but a single dose of NOX4 inhibitor fails to enhance long-term recovery.

Effects of NADPH Oxidase Isoform-2 (NOX2) Inhibition on Behavioral Responses and Neuroinflammation in a Mouse Model of Neuropathic Pain

NADPH oxidase isoform-2 (NOX2) has been implicated in the pathophysiology of neuropathic pain (NP), mostly through the modulation of neuroinflammation. Since it is also accepted that some neuroimmune mechanisms underlying NP are sex-dependent, we aimed to evaluate the effects of early systemic treatment with the NOX2-selective inhibitor (NOX2i) GSK2795039 on behavioral responses and spinal neuroinflammation in spared nerve injury (SNI)-induced NP in male and female mice. Mechanical sensitivity was evaluated with the von Frey test, while general well-being and anxiety-like behavior were assessed with burrowing and light/dark box tests. Spinal microglial activation and cytokines IL-1β, IL-6, and IL-10, as well as macrophage colony-stimulating factor (M-CSF) were evaluated by immunofluorescence and multiplex immunoassay, respectively. NOX2i treatment reduced SNI-induced mechanical hypersensitivity and early SNI-induced microglial activation in both sexes. SNI-females, but not males, showed a transient reduction in burrowing activity. NOX2i treatment did not improve their burrowing activity, but tendentially reduced their anxiety-like behavior. NOX2i marginally decreased IL-6 in females, and increased M-CSF in males. Our findings suggest that NOX2-selective inhibition may be a potential therapeutic strategy for NP in both male and female individuals, with particular interest in females due to its apparent favorable impact in anxiety-like behavior.

Inflammatory Microenvironment-Responsive Nanomaterials Promote Spinal Cord Injury Repair by Targeting IRF5

Spinal cord injury (SCI) involves excessive inflammatory responses, which are characterized by the existence of high levels of proinflammatory M1 macrophages rather than prohealing M2 macrophages, and oxidative stress. Interferon regulatory factor 5 (IRF5) is a promising therapeutic target in regulation of macrophage reprogramming from the M1 to M2 phenotype. However, knockdown of IRF5 expression mediated by small interfering RNA (siRNA) is limited by instability and poor cellular uptake. In the present study, polyethylenimine-conjugated, diselenide-bridged mesoporous silica nanoparticles are tailored to regulate macrophage polarization by controllably delivering siRNA to silence IRF5. The MSN provides reactive oxygen species (ROS)-responsive degradation and release, while polyethylenimine-function offers efficient loading of siRNA-IRF5 and enhanced endosome escape. As a consequence, the intelligent nanomaterial effectively transfects the siRNA-IRF5 with its remaining high stability and bioactivity, thereby effectively regulating the M1-to-M2 macrophage conversion in vitro and in vivo. Importantly, administration of the functional nanomaterial in crush SCI mice suppresses excessive inflammation, enhances neuroprotection, and promotes locomotor restoration. Collectively, the ROS-responsive nanomedicine provides a gene silencing strategy for regulating macrophage polarization and oxidative balance in SCI repair.

Improving translatability of spinal cord injury research by including age as a demographic variable

Pre-clinical and clinical spinal cord injury (SCI) studies differ in study design, particularly in the demographic characteristics of the chosen population. In clinical study design, criteria such as such as motor scores, neurological level, and severity of injury are often key determinants for participant inclusion. Further, demographic variables in clinical trials often include individuals from a wide age range and typically include both sexes, albeit historically most cases of SCI occur in males. In contrast, pre-clinical SCI models predominately utilize young adult rodents and typically use only females. While it is often not feasible to power SCI clinical trials to test multi-variable designs such as contrasting different ages, recent pre-clinical findings in SCI animal models have emphasized the importance of considering age as a biological variable prior to human experiments. Emerging pre-clinical data have identified case examples of treatments that diverge in efficacy across different demographic variables and have elucidated several age-dependent effects in SCI. The extent to which these differing or diverging treatment responses manifest clinically can not only complicate statistical findings and trial interpretations but also may be predictive of worse outcomes in select clinical populations. This review highlights recent literature including age as a biological variable in pre-clinical studies and articulates the results with respect to implications for clinical trials. Based on emerging unpredictable treatment outcomes in older rodents, we argue for the importance of including age as a biological variable in pre-clinical animal models prior to clinical testing. We believe that careful analyses of how age interacts with SCI treatments and pathophysiology will help guide clinical trial design and may improve both the safety and outcomes of such important efforts.

Microglia dynamics in aging-related neurobehavioral and neuroinflammatory diseases

Microglia represent the first line of immune feedback in the brain. Beyond immune surveillance, they are essential for maintaining brain homeostasis. Recent research has revealed the microglial cells' spatiotemporal heterogeneity based on their local and time-based functions in brain trauma or disease when homeostasis is disrupted. Distinct "microglial signatures" have been recorded in physiological states and brain injuries, with discrete or sometimes overlapping pro- and anti-inflammatory functions. Microglia are involved in the neurological repair processes, such as neurovascular unit restoration and synaptic plasticity, and manage the extent of the damage due to their phenotype switching. The versatility of cellular phenotypes beyond the classical M1/M2 classification, as well as the double-edge actions of microglia in neurodegeneration, indicate the need for further exploration of microglial cell dynamics and their contribution to neurodegenerative processes. This review discusses the homeostatic functions of different microglial subsets focusing on neuropathological conditions. Also, we address the feasibility of targeting microglia as a therapeutic strategy in neurodegenerative diseases.

Astaxanthin-folic acid combined treatment potentiates neuronal regeneration and functional recovery after brachial plexus avulsion and reimplantation

Brachial plexus avulsion (BPA), which commonly occurs in neonatal birth injuries and car accidents, severely disrupts spinal cord segments and nerve roots. Avulsion is usually located in the transitional zone at the junction of spinal nerve roots and starting point of the spinal cord, which places heavy disability burdens on patients due to sensory and motor function loss in the innervated areas. Primary mechanical injuries and secondary pathogenesis, such as inflammatory infiltration and oxidative stress, lead to inefficient management and poor prognosis. Astaxanthin (AST) has a strong ability to bleach singlet oxygen and capture free radicals, quench singlet oxygen and trap free radicals, and folic acid (FC) can effectively inhibit the inflammatory response. This study aimed to investigate the therapeutic effects of AST and FC on BPA. The 24 h after BPA was considered the acute phase of the injury, and the combination of AST and FC had the best therapeutic effect due to the synergistic effect of AST’s antioxidant and FC’s anti-inflammatory properties. At 6 weeks after BPA, AST-FC promoted the recovery of biceps motor functions, increased myofiber diameter, enlarged the amplitude of musculocutaneous nerve-biceps compound action potential, and improved Terzis grooming test (TGT) scores. Meanwhile, more functional ventral horn motor neurons in the spinal cord were maintained. In conclusion, AST-FC combined therapy has a potential role in the clinical management of BPA since it can effectively alleviate oxidative stress and the inflammatory response in the acute phase of BPA, increase the survival rate of neurons, and promote neuronal regeneration and recovery of motor functions in the late stage of BPA.

Ferulic acid alleviates retinal neovascularization by modulating microglia/macrophage polarization through the ROS/NF-κB axis

Inflammation plays a pivotal role in ischemia-induced retinal neovascularization. Targeting microglia/macrophage-based neuroinflammation presents a promising therapeutic strategy. Ferulic acid (FA), a natural and active ingredient in plants, exerts favorable anti-oxidative and anti-inflammatory activities. In this study, we investigated the inhibitory effect of FA against hypoxia-induced retinal angiogenesis using cultured retinal vascular endothelial cells and an oxygen-induced retinopathy mouse (OIR) model. The immunoregulatory effect of FA on microglia/macrophage polarization was evaluated by detecting the expression of specific markers for both pro-inflammatory “M1” and anti-inflammatory “M2” phenotypes using co-immunostaining and polymerase chain reaction assays. The underlying molecular mechanism upon FA treatment was also explored. The results showed that FA supplement markedly inhibited retinal pathological angiogenesis both in vivo and in vitro. In addition, FA switched microglia/macrophage polarization from “M1” towards “M2” phenotype and alleviated the inflammatory response. Mechanically, the anti-angiogenic and anti-inflammatory properties of FA were mainly due to blockade of the ROS/NF-κB pathway. Our data demonstrated an anti-angiogenic effect of FA through regulating M1-to-M2 microglia/macrophage polarization, suggesting a potential therapeutic strategy for retinal neovascular diseases.

Notoginsenoside R1 alleviates spinal cord injury by inhibiting oxidative stress, neuronal apoptosis, and inflammation via activating the nuclear factor erythroid 2 related factor 2/heme oxygenase-1 signaling pathway

The secondary injury plays a vital role in the development of spinal cord injury (SCI), which is characterized by the occurrence of oxidative stress, neuronal apoptosis, and inflammatory response. Notoginsenoside R1 (NGR1) has been involved in the modulation of antioxidative stress and anti-inflammatory response. However, its roles in SCI-induced injury are still unknown. We explored the therapeutic effect of NGR1 and its underlying mechanism after SCI by using behavioral, biochemical, and immunohistochemical techniques. The administration of NGR1 after SCI enhanced the neurological function, and mitigated tissue damage and motor neuron loss than those in SCI + vehicle group. Meanwhile, significantly increased expression of Nrf2 protein and HO-1 protein was found in the SCI + NGR1 group compared with those in the SCI + vehicle group. In addition, the inhibitory effects of oxidative stress, apoptotic neuron ratio, and neuronal inflammation in the SCI + NGR1 group can be partially reversed when the Nrf2/HO-1 signaling pathway was inhibited by ML385. Our results indicate that the administration of NGR1 can attenuate oxidative stress, neuronal apoptosis, and inflammation by activating the Nrf2/HO-1 signaling pathway after SCI, thereby improving neurological function.

Genistein Protects against Spinal Cord Injury in Mice by Inhibiting Neuroinflammation via TLR4-Mediated Microglial Polarization

Objective

The present study was designed to study the effect of genistein on spinal cord injury (SCI) in mice and to explore its underlying mechanisms.

Methods

We established SCI mouse model, and genistein was administered for treatment. We used the Basso, Beattie, and Bresnahan (BBB) exercise rating scale to evaluate exercise recovery, and the detection of spinal cord edema was done using the wet/dry weight method. Apoptosis was determined by TUNEL staining, and inflammation was evaluated by measuring inflammatory factors by an ELISA kit. The expression of M1 and M2 macrophage markers was determined using flow cytometry, and the expression of proteins was detected using immunoblotting.

Results

Genistein treatment not only improved the BBB score but also reduced spinal cord edema in SCI mice. Genistein treatment reduced apoptosis by increasing Bcl2 protein expression and decreasing Bax and caspase 3 protein expression. It also reduced the expression of inflammatory cytokines (TNF-α, IL-1β, IL-6, and IL-8) in the SCI area of SCI mice. Flow cytometry analysis indicated that genistein treatment significantly decreased the ratio of M1 macrophages (CD45+/Gr-1-/CD11b+/iNOS+) and increased the ratio of M2 macrophages (CD45+/Gr-1-/CD11b+/Arginase 1+) in the SCI area of SCI mice on the 28th day after being treated with genistein. We also found that genistein treatment significantly decreased the expression of TLR4, MyD88, and TRAF6 protein in the SCI area of SCI mice on 28th day after being treated with genistein.

Conclusion

Our findings suggested that genistein exerted neuroprotective action by inhibiting neuroinflammation by promoting the activation of M2 macrophages, and its underlying mechanisms might be related to the inhibition of the TLR4-mediated MyD88-dependent signaling pathway.

Immunoglobulin G is Increased in the Injured Spinal Cord in a Sex and Age Dependent Manner

There are limited studies examining age and sex as biological variables in the pathophysiology of spinal cord injury (SCI). The use of older animals and sex-balanced groups in SCI models is increasingly prioritized to better match clinical demographics. Including older animals in SCI studies is technically challenging, and outcomes are unpredictable with respect to biological and treatment responses. Incidental discoveries that are unrelated to the question under investigation often emerge while including age and sex as biological variables. When probing tissue homogenates on Western blots of 4- and 14-month-old (MO) mice, we identified a sex- and age-dependent increase in immunoglobulin G (IgG) within the spinal cords of older, 14-MO mice acutely after SCI, with females having more IgG compared with males. We further probed to determine whether differences in hemorrhage exist between sexes or ages by evaluating hemoglobin within spinal homogenates. Differences in hemoglobin between sexes and ages were not consistently observed. Because IgG was elevated in an age- and sex-dependent manner without of evidence of differences in hemorrhage, our findings point to potential pre-existing differences in IgG within mouse plasma in an age- and sex-dependent manner. This report has identified age- and sex-dependent differences in infiltrating IgG into the injured spinal cord environment that may affect injury and recovery processes. Our findings highlight that systemic contributions to SCI can be sex- and age-dependent and illustrate the value of reporting incidental discoveries.

A drug-free nanozyme for mitigating oxidative stress and inflammatory bowel disease

Inflammatory bowel disease (IBD) is an incurable disease of the gastrointestinal tract with a lack of effective therapeutic strategies. The proinflammatory microenvironment plays a significant role in both amplifying and sustaining inflammation during IBD progression. Herein, biocompatible drug-free ceria nanoparticles (CeNP-PEG) with regenerable scavenging activities against multiple reactive oxygen species (ROS) were developed. CeNP-PEG exerted therapeutic effect in dextran sulfate sodium (DSS)-induced colitis murine model, evidenced by corrected the disease activity index, restrained colon length shortening, improved intestinal permeability and restored the colonic epithelium disruption. CeNP-PEG ameliorated the proinflammatory microenvironment by persistently scavenging ROS, down-regulating the levels of multiple proinflammatory cytokines, restraining the proinflammatory profile of macrophages and Th1/Th17 response. The underlying mechanism may involve restraining the co-activation of NF-κB and JAK2/STAT3 pathways. In summary, this work demonstrates an effective strategy for IBD treatment by ameliorating the self-perpetuating proinflammatory microenvironment, which offers a new avenue in the treatment of inflammation-related diseases.

A Biomaterial Model to Assess the Effects of Age in Vascularization

As humans age, there is an increased risk for developing age-associated diseases. Many of these diseases, such as cardiovascular disease, involve dysfunction in the vasculature. Cardiovascular disease stems from endothelial cell dysfunction and reduction in vascularization. Macrophages, prominent innate immune cells involved in orchestrating inflammation and wound healing, have a significant influence on vascularization. While much recent work has investigated the crosstalk between endothelial cells and macrophages, it is still not well defined. The interactions between the cell types are even less understood in specific disease states such as advanced age. Understanding how age influences macrophage/endothelial cell interaction is essential for understanding cardiovascular disease development in the elderly. In the polyethylene glycol (PEG)-based hydrogel system, we model the effects of age on vascularization by encapsulating endothelial cells, pericytes, and human donor macrophages. We created a biomaterial model system in which macrophages, either from young (<35 years old) or old (>65 years old) donors, interact with the modeled vasculature, termed microvessels. Confocal image analysis of vessel density, vessel length, and branch points were used to quantify microvessel growth depending on the age of the macrophage donor. Alongside this, soluble factor secretion and gene expression were evaluated using ELISA and NanoString to showcase biological mechanisms based on the age of each donor. Endothelial cells cultured with macrophages from old donors have reduced microvessel density. There also is reduced soluble factor secretion by the macrophages from old donors, which likely influenced microvessel growth. Altogether, we establish our PEG-based hydrogel vascular model as a system to evaluate patient-specific cell function as well as proposed mechanisms for how age influences microvessels.

The killifish visual system as an in vivo model to study brain aging and rejuvenation

Worldwide, people are getting older, and this prolonged lifespan unfortunately also results in an increased prevalence of age-related neurodegenerative diseases, contributing to a diminished life quality of elderly. Age-associated neuropathies typically include diseases leading to dementia (Alzheimer's and Parkinson's disease), as well as eye diseases such as glaucoma and age-related macular degeneration. Despite many research attempts aiming to unravel aging processes and their involvement in neurodegeneration and functional decline, achieving healthy brain aging remains a challenge. The African turquoise killifish (Nothobranchius furzeri) is the shortest-lived reported vertebrate that can be bred in captivity and displays many of the aging hallmarks that have been described for human aging, which makes it a very promising biogerontology model. As vision decline is an important hallmark of aging as well as a manifestation of many neurodegenerative diseases, we performed a comprehensive characterization of this fish's aging visual system. Our work reveals several aging hallmarks in the killifish retina and brain that eventually result in a diminished visual performance. Moreover, we found evidence for the occurrence of neurodegenerative events in the old killifish retina. Altogether, we introduce the visual system of the fast-aging killifish as a valuable model to understand the cellular and molecular mechanisms underlying aging in the vertebrate central nervous system. These findings put forward the killifish for target validation as well as drug discovery for rejuvenating or neuroprotective therapies ensuring healthy aging.

FGF21 alleviates chronic inflammatory injury in the aging process through modulating polarization of macrophages

Previous studies reported that FGF21 prolongs life span and delays the body senescence, but the mechanism is not clear. The present study was designed to investigate the effects of FGF21 on hepatic senescence in aging mice and further research the mechanism. The 14-month-old male mice were administered with PBS, FGF21 or metformin once daily for 6 months. Results showed that FGF21 alleviated liver injury and inhibited accumulation of senescence markers SASP, P53 and P16 in the livers of aging mice. Subsequently we found that the aging mice treated by FGF21 showed transition of type 1 macrophages (M1) to type 2 macrophages (M2) in the livers. Next, we used THP-1 macrophages triggered by LPS to study effects of FGF21 on macrophages. Macrophages triggered by LPS exhibited features of M1, but the addition of FGF21 decreased the expression of M1 markers, and promoted the macrophages to exhibit features of M2. Results showed that the effects of FGF21 on macrophages were associated with the AMPK pathway. After adding AMPK inhibitor, the effects of FGF21 were inhibited, which was associated with the NF-κB signaling pathway. Finally, co-culturing differentiated macrophages and hepatocytes, we found that the large amount of pro-inflammatory factors such as IL-6 promoted hepatocyte senescence, which exhibited enhanced P53, P16 and β-galactosidase. This was contrary to hepatocytes co-cultured with macrophages treated by FGF21. These results indicate that FGF21 alleviates hepatic senescence injury by modulating the polarization of macrophages through the AMPK /NF-κB signaling pathway.

Localised delivery of quercetin by thermo-sensitive PLGA-PEG-PLGA hydrogels for the treatment of brachial plexus avulsion

Accumulating evidence indicates that oxidative stress and inflammation are implicated in brachial plexus avulsion (BPA). Quercetin has anti-inflammatory, anti-oxidant, anti-apoptotic, and neuroprotective properties. This study investigated the therapeutic efficacy of a temperature-sensitive poly(D,L-lactide-co-glycolide)-poly(ethylene-glycol)-poly(D,L-lactide-co-glycolide) (PLGA-PEG-PLGA) hydrogel sustained-release system of quercetin in BPA. In situ injections of the hydrogel loaded with different concentrations of quercetin were conducted in a rat model of BPA. Significantly reduced reactive oxygen species and interleukin-6 levels in the injured spinal cord 24 h post-surgery, increased number of anterior horn motor and functional neurons in the spinal cord 6 weeks post-surgery, thickened biceps muscle fibres and enlarged endplate area with clear structure, reduced demyelinated peripheral nerves, and significantly increased Terzis grooming test scores were found in the groups with 50 or 100 mg/mL quercetin-loaded hydrogels compared with the control and blank hydrogel groups. In conclusion, the temperature-sensitive quercetin loaded PLGA-PEG-PLGA hydrogel sustained-release system can alleviate oxidative damage and inflammation in the spinal cord, increase neuron survival rate, and promote nerve regeneration and motor function recovery in rats with early BPA. The findings suggest that this drug-loaded hydrogel has potential applications in the clinical treatment of BPA.

Curcumin Can Activate the Nrf2/HO-1 Signaling Pathway and Scavenge Free Radicals in Spinal Cord Injury Treatment

Spinal cord injury (SCI) is a devastating event that often leads to permanent neurological deficits. Evidence from emerging studies has implicated oxygen-derived free radicals and high-energy oxidants as mediators of secondary SCI. Therefore, targeting these mediators using antioxidants could be beneficial for the disease. Several signaling pathways, such as the nuclear factor erythroid-2-related factor 2/heme oxygenase 1 (Nrf2/HO-1), have been associated with the regulation of some pathophysiological features of SCI. Curcumin is a plant medicinal agent whose diverse pharmacological properties have been extensively investigated and reported, notably its ability to curtail inflammatory damage by inhibiting the nuclear factor-κ-light-chain-enhancer of activated B cells. In this review, we analyze the role of curcumin in activating Nrf2/HO-1 and scavenging free radicals to repair SCI. With its minimal side effects, curcumin could be a potential therapy for SCI treatment.

Acute inflammatory profiles differ with sex and age after spinal cord injury

Background

Sex and age are emerging as influential variables that affect spinal cord injury (SCI) recovery. Despite a changing demographic towards older age at the time of SCI, the effects of sex or age on inflammation remain to be elucidated. This study determined the sex- and age-dependency of the innate immune response acutely after SCI.

Methods

Male and female mice of ages 4- and 14-month-old received T9 contusion SCI and the proportion of microglia, monocyte-derived macrophages (MDM), and neutrophils surrounding the lesion were determined at 3- and 7-day post-injury (DPI) using flow cytometry. Cell counts of microglia and MDMs were obtained using immunohistochemistry to verify flow cytometry results at 3-DPI. Microglia and MDMs were separately isolated using fluorescence-activated cell sorting (FACS) at 3-day post-injury (DPI) to assess RNA expression of 27 genes associated with activation, redox, and debris metabolism/clearance.

Results

Flow cytometry revealed that being female and older at the time of injury significantly increased MDMs relative to other phagocytes, specifically increasing the ratio of MDMs to microglia at 3-DPI. Cell counts using immunohistochemistry revealed that male mice have more total microglia within SCI lesions that can account for a lower MDM/microglia ratio. With NanoString analyses of 27 genes, only 1 was differentially expressed between sexes in MDMs; specifically, complement protein C1qa was increased in males. No genes were affected by age in MDMs. Only 2 genes were differentially regulated in microglia between sexes after controlling for false discovery rate, specifically CYBB (NOX2) as a reactive oxygen species (ROS)-associated marker as well as MRC1 (CD206), a gene associated with reparative phenotypes. Both genes were increased in female microglia. No microglial genes were differentially regulated between ages. Differences between microglia and MDMs were found in 26 of 27 genes analyzed, all expressed higher in MDMs with three exceptions. Specifically, C1qa, cPLA2, and CD86 were expressed higher in microglia.

Conclusions

These findings indicate that inflammatory responses to SCI are sex-dependent at both the level of cellular recruitment and gene expression.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-021-02161-8.

The Caveolin-1 Scaffolding Domain Peptide Reverses Aging-Associated Deleterious Changes in Multiple Organs

Aging is a progressive, multifactorial, degenerative process in which deleterious changes occur in the biochemistry and function of organs. We showed that angiotensin II (AngII)-induced pathologies in the heart and kidney of young (3-month-old) mice are suppressed by the caveolin-1 scaffolding domain (CSD) peptide. Because AngII mediates many aging-associated changes, we explored whether CSD could reverse pre-existing pathologies and improve organ function in aged mice. Using 18-month-old mice (similar to 60-year-old humans), we found that >5-fold increases in leakage of serum proteins and >2-fold increases in fibrosis are associated with aging in the heart, kidney, and brain. Because tyrosine phosphorylation of cell junction proteins leads to the loss of microvascular barrier function, we analyzed the activation of the receptor tyrosine kinase PDGFR and the nonreceptor tyrosine kinases c-Src and Pyk2. We observed 5-fold activation of PDGFR and 2- to 3-fold activation of c-Src and Pyk2 in aged mice. Treatment with CSD for 4 weeks reversed these pathologic changes (microvascular leakage, fibrosis, kinase activation) in all organs almost down to the levels in healthy, young mice. In studies of heart function, CSD reduced the aging-associated increase in cardiomyocyte cross-sectional area and enhanced ventricular compliance in that echocardiographic studies demonstrated improved ejection fraction and fractional shortening and reduced isovolumic relation time. These results suggest that versions of CSD may be developed as treatments for aging-associated diseases in human patients based on the concept that CSD inhibits tyrosine kinases, leading to the inhibition of microvascular leakage and associated fibrosis, thereby improving organ function. SIGNIFICANCE STATEMENT: The caveolin-1 scaffolding domain (CSD) peptide reverses aging-associated fibrosis, microvascular leakage, and organ dysfunction in the heart, kidneys, and brain via a mechanism that involves the suppression of the activity of multiple tyrosine kinases, suggesting that CSD can be developed as a treatment for a wide range of diseases found primarily in the aged.

Insight into the roles of melatonin in bone tissue and bone‑related diseases (Review)

Bone‑related diseases comprise a large group of common diseases, including fractures, osteoporosis and osteoarthritis (OA), which affect a large number of individuals, particularly the elderly. The progressive destruction and loss of alveolar bone caused by periodontitis is a specific type of bone loss, which has a high incidence and markedly reduces the quality of life of patients. With the existing methods of prevention and treatment, the incidence and mortality of bone‑related diseases are still gradually increasing, creating a significant financial burden to societies worldwide. To prevent the occurrence of bone‑related diseases, delay their progression or reverse the injuries they cause, new alternative or complementary treatments need to be developed. Melatonin exerts numerous physiological effects, including inducing anti‑inflammatory and antioxidative functions, resetting circadian rhythms and promoting wound healing and tissue regeneration. Melatonin also participates in the health management of bone and cartilage. In the present review, the potential roles of melatonin in the pathogenesis and progression of bone injury, osteoporosis, OA and periodontitis are summarized. Furthermore, the high efficiency and diversity of the physiological regulatory effects of melatonin are highlighted and the potential benefits of the use of melatonin for the clinical prevention and treatment of bone‑related diseases are discussed.

The Roles of Superoxide on At-Level Spinal Cord Injury Pain in Rats

Background: In the present study, we examined superoxide-mediated excitatory nociceptive transmission on at-level neuropathic pain following spinal thoracic 10 contusion injury (SCI) in male Sprague Dawley rats. Methods: Mechanical sensitivity at body trunk, neuronal firing activity, and expression of superoxide marker/ionotropic glutamate receptors (iGluRs)/CamKII were measured in the T7/8 dorsal horn, respectively. Results: Topical treatment of superoxide donor t-BOOH (0.4 mg/kg) increased neuronal firing rates and pCamKII expression in the naïve group, whereas superoxide scavenger Tempol (1 mg/kg) and non-specific ROS scavenger PBN (3 mg/kg) decreased firing rates in the SCI group (* p < 0.05). SCI showed increases of iGluRs-mediated neuronal firing rates and pCamKII expression (* p < 0.05); however, t-BOOH treatment did not show significant changes in the naïve group. The mechanical sensitivity at the body trunk in the SCI group (6.2 ± 0.5) was attenuated by CamKII inhibitor KN-93 (50 μg, 3.9 ± 0.4) or Tempol (1 mg, 4 ± 0.4) treatment (* p < 0.05). In addition, the level of superoxide marker Dhet showed significant increase in SCI rats compared to the sham group (11.7 ± 1.7 vs. 6.6 ± 1.5, * p < 0.05). Conclusions: Superoxide and the pCamKII pathway contribute to chronic at-level neuropathic pain without involvement of iGluRs following SCI.

Rational Design and Biological Application of Antioxidant Nanozymes

Nanozyme is a type of nanostructured material with intrinsic enzyme mimicking activity, which has been increasingly studied in the biological field. Compared with natural enzymes, nanozymes have many advantages, such as higher stability, higher design flexibility, and more economical production costs. Nanozymes can be used to mimic natural antioxidant enzymes to treat diseases caused by oxidative stress through reasonable design and modification. Oxidative stress is caused by imbalances in the production and elimination of reactive oxygen species (ROS) and reactive nitrogen species (RNS). This continuous oxidative stress can cause damage to some biomolecules and significant destruction to cell structure and function, leading to many physiological diseases. In this paper, the methods to improve the antioxidant properties of nanozymes were reviewed, and the applications of nanozyme antioxidant in the fields of anti-aging, cell protection, anti-inflammation, wound repair, cancer, traumatic brain injury, and nervous system diseases were introduced. Finally, the future challenges and prospects of nanozyme as an ideal antioxidant were discussed.

Progenitor cell therapy for acquired pediatric nervous system injury: Traumatic brain injury and acquired sensorineural hearing loss

While cell therapies hold remarkable promise for replacing injured cells and repairing damaged tissues, cell replacement is not the only means by which these therapies can achieve therapeutic effect. For example, recent publications show that treatment with varieties of adult, multipotent stem cells can improve outcomes in patients with neurological conditions such as traumatic brain injury and hearing loss without directly replacing damaged or lost cells. As the immune system plays a central role in injury response and tissue repair, we here suggest that multipotent stem cell therapies achieve therapeutic effect by altering the immune response to injury, thereby limiting damage due to inflammation and possibly promoting repair. These findings argue for a broader understanding of the mechanisms by which cell therapies can benefit patients.

Mitochondria exert age-divergent effects on recovery from spinal cord injury

The extent that age-dependent mitochondrial dysfunction drives neurodegeneration is not well understood. This study tested the hypothesis that mitochondria contribute to spinal cord injury (SCI)-induced neurodegeneration in an age-dependent manner by using 2,4-dinitrophenol (DNP) to uncouple electron transport, thereby increasing cellular respiration and reducing reactive oxygen species (ROS) production. We directly compared the effects of graded DNP doses in 4- and 14-month-old (MO) SCI-mice and found DNP to have increased efficacy in mitochondria isolated from 14-MO animals. In vivo, all DNP doses significantly exacerbated 4-MO SCI neurodegeneration coincident with worsened recovery. In contrast, low DNP doses (1.0-mg/kg/day) improved tissue sparing, reduced ROS-associated 3-nitrotyrosine (3-NT) accumulation, and improved anatomical and functional recovery in 14-MO SCI-mice. By directly comparing the effects of DNP between ages we demonstrate that mitochondrial contributions to neurodegeneration diverge with age after SCI. Collectively, our data indicate an essential role of mitochondria in age-associated neurodegeneration.

Neuroinflammation, oxidative stress and their interplay in neuropathic pain: Focus on specialized pro-resolving mediators and NADPH oxidase inhibitors as potential therapeutic strategies

Neuropathic pain (NP) is a chronic condition that results from a lesion or disease of the nervous system, greatly impacting patients' quality of life. Current pharmacotherapy options deliver inadequate and/or insufficient responses and thus a significant unmet clinical need remains for alternative treatments in NP. Neuroinflammation, oxidative stress and their reciprocal relationship are critically involved in NP pathophysiology. In this context, new pharmacological approaches, aiming at enhancing the resolution phase of inflammation and/or restoring redox balance by targeting specific reactive oxygen species (ROS) sources, are emerging as potential therapeutic strategies for NP, with improved efficacy and safety profiles. Several reports have demonstrated that administration of exogenous specialized pro-resolving mediators (SPMs) ameliorates NP pathophysiology. Likewise, deletion or inhibition of the ROS-generating enzyme NADPH oxidase (NOX), particularly its isoforms 2 and 4, results in beneficial effects in NP models. Notably, SPMs also modulate oxidative stress and NOX also regulates neuroinflammation. By targeting neuroinflammatory and oxidative pathways, both SPMs analogues and isoform-specific NOX inhibitors are promising therapeutic strategies for NP.

Protein kinase inhibitors in traumatic brain injury and repair: New roles of nanomedicine

Traumatic brain injury (TBI) causes physical injury to the cell membranes of neurons, glial and axons causing the release of several neurochemicals including glutamate and cytokines altering cell-signaling pathways. Upregulation of mitogen associated protein kinase (MAPK) and extracellular signal-regulated kinase (ERK) occurs that is largely responsible for cell death. The pharmacological blockade of these pathways results in cell survival. In this review role of several protein kinase inhibitors on TBI induced oxidative stress, blood-brain barrier breakdown, brain edema formation, and resulting brain pathology is discussed in the light of current literature.

Aging-Exacerbated Acute Axon and Myelin Injury Is Associated with Microglia-Derived Reactive Oxygen Species and Is Alleviated by the Generic Medication Indapamide

Age is a critical risk factor for many neurologic conditions, including progressive multiple sclerosis. Yet the mechanisms underlying the relationship are unknown. Using lysolecithin-induced demyelinating injury to the mouse spinal cord, we characterized the acute lesion and investigated the mechanisms of increased myelin and axon damage with age. We report exacerbated myelin and axon loss in middle-aged (8-10 months of age) compared with young (6 weeks of age) female C57BL/6 mice by 1-3 d of lesion evolution in the white matter. Transcriptomic analysis linked elevated injury to increased expression of Cybb, the gene encoding the catalytic subunit of NADPH oxidase gp91phox. Immunohistochemistry in male and female Cx₃cr1 ^CreER/+ :Rosa26 ^tdTom/+ mice for gp91phox revealed that the upregulation in middle-aged animals occurred primarily in microglia and not infiltrated monocyte-derived macrophages. Activated NADPH oxidase generates reactive oxygen species and elevated oxidative damage was corroborated by higher malondialdehyde immunoreactivity in lesions from middle-aged compared with young mice. From a previously conducted screen for generic drugs with antioxidant properties, we selected the antihypertensive CNS-penetrant medication indapamide for investigation. We report that indapamide reduced superoxide derived from microglia cultures and that treatment of middle-aged mice with indapamide was associated with a decrease in age-exacerbated lipid peroxidation, demyelination and axon loss. In summary, age-exacerbated acute injury following lysolecithin administration is mediated in part by microglia NADPH oxidase activation, and this is alleviated by the CNS-penetrant antioxidant, indapamide.SIGNIFICANCE STATEMENT Age is associated with an increased risk for the development of several neurologic conditions including progressive multiple sclerosis, which is represented by substantial microglia activation. We demonstrate that in the lysolecithin demyelination model in young and middle-aged mice, the latter group developed greater acute axonal and myelin loss attributed to elevated oxidative stress through NADPH oxidase in lineage-traced microglia. We thus used a CNS-penetrant generic medication used in hypertension, indapamide, as we found it to have antioxidant properties in a previous drug screen. Following lysolecithin demyelination in middle-aged mice, indapamide treatment was associated with decreased oxidative stress and axon/myelin loss. We propose indapamide as a potential adjunctive therapy in aging-associated neurodegenerative conditions such as Alzheimer's disease and progressive multiple sclerosis.

Considerations for Studying Sex as a Biological Variable in Spinal Cord Injury

In response to NIH initiatives to investigate sex as a biological variable in preclinical animal studies, researchers have increased their focus on male and female differences in neurotrauma. Inclusion of both sexes when modeling neurotrauma is leading to the identification of novel areas for therapeutic and scientific exploitation. Here, we review the organizational and activational effects of sex hormones on recovery from injury and how these changes impact the long-term health of spinal cord injury (SCI) patients. When determining how sex affects SCI it remains imperative to expand outcomes beyond locomotor recovery and consider other complications plaguing the quality of life of patients with SCI. Interestingly, the SCI field predominately utilizes female rodents for basic science research which contrasts most other male-biased research fields. We discuss the unique caveats this creates to the translatability of preclinical research in the SCI field. We also review current clinical and preclinical data examining sex as biological variable in SCI. Further, we report how technical considerations such as housing, size, care management, and age, confound the interpretation of sex-specific effects in animal studies of SCI. We have uncovered novel findings regarding how age differentially affects mortality and injury-induced anemia in males and females after SCI, and further identified estrus cycle dysfunction in mice after injury. Emerging concepts underlying sexually dimorphic responses to therapy are also discussed. Through a combination of literature review and primary research observations we present a practical guide for considering and incorporating sex as biological variable in preclinical neurotrauma studies.

The effects of mouse strain and age on a model of unilateral cervical contusion spinal cord injury

There are approximately 1.2 million people currently living with spinal cord injury (SCI), with a majority of cases at the cervical level and half involving incomplete injuries. Yet, as most preclinical research has been focused on bilateral thoracic models, there remains a disconnect between bench and bedside that limits translational success. Here, we profile a clinically relevant model of unilateral cervical contusion injury in the mouse (30kD with 0, 2, 5, or 10 second dwell time). We demonstrate sustained behavioral deficits in performance on grip strength, cylinder reaching, horizontal ladderbeam and CatWalk automated gait analysis tasks. Beyond highlighting reliable parameters for injury assessment, we also explored the effect of mouse strain and age on injury outcome, including evaluation of constitutively immunodeficient mice relevant for neurotransplantation and cellular therapy testing. Comparison of C57Bl/6 and immunodeficient Rag2gamma(c)-/- as well as Agouti SCIDxRag2Gamma(c)-/- hybrid mouse strains revealed fine differences in post-injury ipsilateral grip strength as well as total number of rearings on the cylinder task. Differences in post-SCI contralateral forepaw duty cycle and regularity index as measured by CatWalk gait analysis between the two immunodeficient strains were also observed. Further, assessment of young (3–4 months old) and aging (16–17 months old) Rag2gamma(c)-/- mice identified age-related pre-injury differences in strength and rearing that were largely masked following cervical contusion injury; observations that may help interpret previous results in aged rodents as well as human clinical trials. Collectively, the work provides useful insight for experimental design and analysis of future pre-clinical studies in a translational unilateral cervical contusion injury model.

Dementia, Depression, and Associated Brain Inflammatory Mechanisms after Spinal Cord Injury

Evaluation of the chronic effects of spinal cord injury (SCI) has long focused on sensorimotor deficits, neuropathic pain, bladder/bowel dysfunction, loss of sexual function, and emotional distress. Although not well appreciated clinically, SCI can cause cognitive impairment including deficits in learning and memory, executive function, attention, and processing speed; it also commonly leads to depression. Recent large-scale longitudinal population-based studies indicate that patients with isolated SCI (without concurrent brain injury) are at a high risk of dementia associated with substantial cognitive impairments. Yet, little basic research has addressed potential mechanisms for cognitive impairment and depression after injury. In addition to contributing to disability in their own right, these changes can adversely affect rehabilitation and recovery and reduce quality of life. Here, we review clinical and experimental work on the complex and varied responses in the brain following SCI. We also discuss potential mechanisms responsible for these less well-examined, important SCI consequences. In addition, we outline the existing and developing therapeutic options aimed at reducing SCI-induced brain neuroinflammation and post-injury cognitive and emotional impairments.

Effect of physical stimulation (gingival massage) on age-related changes in gingival microcirculation

The decline in circulatory function with aging may be alleviated by a combination of gingival massage (physical stimulation) and mechanical cleaning. Several studies have reported the systemic effect of physical stimulation on various parts of the body, including its therapeutic effect on pain in the neck and shoulders that becomes evident with age, and improvement in blood circulation. In contrast, few studies have reported on the changes in gingival microcirculation induced by gingival massage, while no previous study has evaluated the effect of gingival microcirculation on age-related changes in the hemodynamics of the oral cavity. This study aimed to investigate how gingival massage affects age-related changes in gingival microcirculation. Male Wistar rats (7-week, 6-month and 1-year old) were prepared for a gingival massage group and a control group. Mechanical stimulation was applied on the maxillary molar gingiva for 5 seconds twice a week for 4 weeks. Subsequently, gingival reactive hyperemia was measured using a laser Doppler flowmeter. In addition, morphological analyses were also performed by hematoxylin and eosin and Indian ink staining and a vascular resin cast model. Base Flow, maximum response (Peak), and time required for the maximum response to halve (T1/2) were reduced in 1-year-old rats compared with the other age groups. In the mechanical stimulated group, T1/2 was increased in 7-week, 6-month, and 1-year-old rats, and total blood flow (Mass) was increased in 6-month and 1-year-old rats. In addition, clear blood vessel networks and loop-like revascularization were only observed in the mechanical stimulated group. Changes in age-related decline in gingival microcirculatory function and vascular construction were reported in this study, and the results suggested that gingival massage activates both the functional and morphological aspects of gingival microcirculation and may be effective for maintaining oral health.

Does Dysregulation of Redox State Underpin the Decline of Innate Immunity with Aging?

Significance: Antibacterial defense invokes the innate immune system as a first responder, with neutrophils phagocytozing and forming neutrophil extracellular traps around pathogens in a reactive oxygen species (ROS)-dependent manner. Increased NOX2 activity and mitochondrial ROS production in phagocytic, antigen-presenting cells (APCs) affect local cytokine secretion and proteolysis of antigens for presentation to T cells at the immune synapse. Uncontrolled oxidative post-translational modifications to surface and cytoplasmic proteins in APCs during aging can impair innate immunity. Recent Advances: NOX2 plays a role in the maturation of dendritic cells, but paradoxically NOX2 activity has also been shown to promote viral pathogenicity. Accumulating evidence suggests that a reducing environment is essential to inhibit pathogen proliferation, facilitate antigenic processing in the endosomal lumen, and enable an effective immune synapse between APCs and T cells. This suggests that the kinetics and location of ROS production and reducing potential are important for effective innate immunity. Critical Issues: During aging, innate immune cells are less well able to phagocytoze, kill bacteria/viruses, and process proteins into antigenic peptides-three key steps that are necessary for developing a specific targeted response to protect against future exposure. Aberrant control of ROS production and impaired Nrf2-dependent reducing potential may contribute to age-associated immune decline. Future Directions: Local changes in redox potential may be achieved through adjuvant formulations to improve innate immunity. Further work is needed to understand the timing of delivery for redox modulators to facilitate innate immune cell recruitment, survival, antigen processing and presentation activity without disrupting essential ROS-dependent bacterial killing.

Microglia and macrophage metabolism in CNS injury and disease: The role of immunometabolism in neurodegeneration and neurotrauma

Innate immune responses, particularly activation of macrophages and microglia, are increasingly implicated in CNS disorders. It is now appreciated that the heterogeneity of functions adopted by these cells dictates neuropathophysiology. Research efforts to characterize the range of pro-inflammatory and anti-inflammatory phenotypes and functions adopted by microglia and macrophages are fueled by the potential for inflammatory cells to both exacerbate neurodegeneration and promote repair/disease resolution. The stimulation-based, M1/M2 classification system has emerged over the last decade as a common language to discuss macrophage and microglia heterogeneity across different fields. However, discontinuities between phenotypic markers and function create potential hurdles for the utility of the M1/M2 system in the development of effective immunomodulatory therapeutics for neuroinflammation. A framework to approach macrophage and microglia heterogeneity from a function-based phenotypic approach comes from rapidly emerging evidence that metabolic processes regulate immune cell activation. This concept of immunometabolism, however, is only beginning to unfold in the study of neurodegeneration and has yet to receive much focus in the context of neurotrauma. In this review, we first discuss the current views of macrophage and microglia heterogeneity and limitations of the M1/M2 classification system for neuropathological studies. We then review and discuss the current literature supporting metabolism as a regulator of microglia function in vitro. Lastly, we evaluate the evidence that metabolism regulates microglia and macrophage phenotype in vivo in models of Alzheimer's disease (AD), stroke, traumatic brain injury (TBI) and spinal cord injury (SCI).

The Influence of Neuron-Extrinsic Factors and Aging on Injury Progression and Axonal Repair in the Central Nervous System

In the aging western population, the average age of incidence for spinal cord injury (SCI) has increased, as has the length of survival of SCI patients. This places great importance on understanding SCI in middle-aged and aging patients. Axon regeneration after injury is an area of study that has received substantial attention and made important experimental progress, however, our understanding of how aging affects this process, and any therapeutic effort to modulate repair, is incomplete. The growth and regeneration of axons is mediated by both neuron intrinsic and extrinsic factors. In this review we explore some of the key extrinsic influences on axon regeneration in the literature, focusing on inflammation and astrogliosis, other cellular responses, components of the extracellular matrix, and myelin proteins. We will describe how each element supports the contention that axonal growth after injury in the central nervous system shows an age-dependent decline, and how this may affect outcomes after a SCI.

Aging alters Hv1-mediated microglial polarization and enhances neuroinflammation after peripheral surgery

Perioperative neurocognitive disorders have been widely recognized as common adverse events after surgical intervention. Aging is one of the most important independent risk factors for worsened cognitive outcome, and this deterioration is linked to exacerbated microglia-mediated neuroinflammation in the aged brain. Under pathological stimulation, microglia are capable of polarizing toward proinflammatory M1 and anti-inflammatory M2 phenotypes. In the present study, we examined how aging affects microglial responses and neuroinflammation following peripheral surgery. Adult (2-3 months) and aged (18 months old) male C57/BL6 mice were subjected to tibial fracture or sham surgery. Aged mice exhibited higher level of tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) in the hippocampus. The expression of synaptic protein synaptophysin (SYP) was also markedly reduced in the aged brain after the surgery. Both adult and aged mice showed significant increases in M1 microglial polarization (CD16/32). In contrast, tibial fracture surgery induced a decreased M2 microglial polarization (CD206, Ym1/2, Arg1) in aged brain but enhanced M2 microglial polarization in adult brain. Aged mice have upregulated voltage-gated proton channel (Hv1) and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase subunit expression compared with adult mice. The percentage of CD16/32-positive M1 microglia colabeling with Hv1 was higher in aged mice after tibial fracture surgery. Thus, Hv1/NADPH oxidase upregulation in the aged brain may shift the dynamic equilibrium of microglial activation toward M1 polarization and exaggerate postoperative neuroinflammatory responses after peripheral surgical intervention.

Treatment With 2-BFI Attenuated Spinal Cord Injury by Inhibiting Oxidative Stress and Neuronal Apoptosis via the Nrf2 Signaling Pathway

Previous reports showed that 2-(-2-benzofuranyl)-2-imidazoline (2-BFI) has antioxidant, anti-inflammatory and anti-apoptotic effects on neuroprotection in numerous disorders. However, the precise mechanisms remain elusive. The nuclear factor c factor 2 (Nrf2)/antioxidant response element (ARE) signaling pathway plays an important and essential role in the antioxidant and anti-inflammatory responses of the cell. Therefore, the purpose of this study was to investigate the potential neuroprotective effects of 2-BFI in a rat model of spinal cord injury (SCI) and to determine whether its neuroprotective effects are associated with the activation of Nrf2. To test this hypothesis, we examined the potential roles of 2-BFI in SCI models which were established in rats using a clip-compression injury method. Our results showed that treatment with 2-BFI twice daily improved locomotion recovery from SCI, which increased Nrf2 expression in both neurons and astrocytes, meanwhile, the level of heme oxygenase-1 (HO-1) also significantly enhanced. In addition, after the treatment with 2-BFI increased levels of superoxidase dismutase (SOD) and glutathione peroxidase (GPx) indicated the antioxidant effect of the drug. Furthermore, the upregulation of Bcl-2 and downregulation of Bax and caspase-3 implied antiapoptotic effects on neuroprotection of 2-BFI, which were verified by the Fluoro-Jade B (FJB) staining and TUNEL staining. Collectively, these results add to a growing body of evidence supporting that 2-BFI may attenuate SCI mediated by activation of the Nrf2/HO-1 signaling pathway.

Wnt Glycation Inhibits Canonical Signaling

Glycation occurs as a non-enzymatic reaction between amino and thiol groups of proteins, lipids, and nucleotides with reducing sugars or α-dicarbonyl metabolites. The chemical reaction underlying is the Maillard reaction leading to the formation of a heterogeneous group of compounds named advanced glycation end products (AGEs). Deleterious effects have been observed to accompany glycation such as alterations of protein structure and function resulting in crosslinking and accumulation of insoluble protein aggregates. A substantial body of evidence associates glycation with aging. Wnt signaling plays a fundamental role in stem cell biology as well as in regeneration and repair mechanisms. Emerging evidence implicates that changes in Wnt/β-catenin pathway activity contribute to the aging process. Here, we investigated the effect of glycation of Wnt3a on its signaling activity. Methods: Glycation was induced by treatment of Wnt3a-conditioned medium (CM) with glyoxal (GO). Effects on Wnt3a signaling activity were analyzed by Topflash/Fopflash reporter gene assay, co-immunoprecipitation, and quantitative RT-PCR. Results: Our data show that GO-treatment results in glycation of Wnt3a. Glycated Wnt3a suppresses β-catenin transcriptional activity in reporter gene assays, reduced binding of β-catenin to T-cell factor 4 (TCF-4) and extenuated transcription of Wnt/β-catenin target genes. Conclusions: GO-induced glycation impairs Wnt3a signaling function.

Inhibition of NOX2 signaling limits pain-related behavior and improves motor function in male mice after spinal cord injury: Participation of IL-10/miR-155 pathways

NADPH oxidase (NOX2) is an enzyme that induces reactive oxygen species (ROS) and serves as a switch between the pro-inflammatory and neurorestorative microglial/macrophage phenotypes; such changes play an important role in neuropathic pain and motor dysfunction. Increased NOX2 expression after spinal cord injury (SCI) has been reported, and inhibition of NOX2 improves motor function. However, the underlying mechanisms of NOX2 in post-traumatic pain and motor deficit remain unexplored. In the present study, we report that depletion of NOX2 (NOX2^-/-) or inhibition of NOX2 using NOX2ds-tat significantly reduced mechanical/thermal cutaneous hypersensitivity and motor dysfunction after moderate contusion SCI at T10 in male mice. Western blot (WB, 3 mm lesion area) and immunohistochemistry (IHC) showed that SCI elevates NOX2 expression predominantly in microglia/macrophages up to 8 weeks post-injury. Deletion of NOX2 significantly reduced CD11b⁺/CD45^hiF4/80⁺ macrophage infiltration at 24 h post-injury detected by flow cytometry and 8-OHG⁺ ROS production at 8 weeks post-injury by IHC in both lesion area and lumbar enlargement. NOX2 deficiency also altered microglial/macrophage pro-inflammatory and anti-inflammatory balance towards the neurorestorative response. WB analysis showed robust increase of Arginase-1 and YM1 proteins in NOX2^-/- mice. Furthermore, qPCR analysis showed significant up-regulation of anti-inflammatory cytokine IL-10 levels in NOX2^-/- mice, associated with reduced microRNA-155 expression. These findings were confirmed in CD11b⁺ microglia/macrophages isolated from spinal cord at 3 days post-injury. Taken together, our data suggest an important role for IL-10/miR-155 pathway in regulating NOX2-mediated SCI-dysfunction. Thus, specific targeting of NOX2 may provide an effective strategy for treating neurological dysfunction in SCI patients.

Emerging targets for reprograming the immune response to promote repair and recovery of function after spinal cord injury

PURPOSE OF REVIEW

In adult mammals, a traumatic spinal cord injury (SCI) elicits a chronic unregulated neuroinflammatory response accompanied by seemingly paradoxical suppression of systemic immunity. These SCI-induced changes in immune function contribute to poor neurological outcomes and enhanced morbidity or mortality. Nonspecific anti-inflammatory or proinflammatory therapies are ineffective and can even worsen outcomes. Therefore, recent experimental SCI research has advanced the understanding of how neuroimmune cross-talk contributes to spinal cord and systemic pathology.

RECENT FINDINGS

It is now appreciated that the immune response caused by injury to the brain or spinal cord encompasses heterogeneous elements that can drive events on the spectrum between exacerbating pathology and promoting tissue repair, within the spinal cord and throughout the body. Recent novel discoveries regarding the role and regulation of soluble factors, monocytes/macrophages, microRNAs, lymphocytes and systemic immune function are highlighted in this review.

SUMMARY

A more nuanced understanding of how the immune system responds and reacts to nervous system injury will present an array of novel therapeutic opportunities for clinical SCI and other forms of neurotrauma.

Reducing age-dependent monocyte-derived macrophage activation contributes to the therapeutic efficacy of NADPH oxidase inhibition in spinal cord injury

OBJECTIVE

The average age at the time of spinal cord injury (SCI) has increased to 43 years old. Middle-aged mice (14 months old, MO) exhibit impaired recovery after SCI with age-dependent increases in reactive oxygen species (ROS) production through NADPH oxidase (NOX) along with pro-inflammatory macrophage activation. Despite these aging differences, clinical therapies are being examined in individuals regardless of age based upon preclinical data generated primarily using young animals (∼4 MO). Our objective is to test the extent to which age affects SCI treatment efficacy. Specifically, we hypothesize that the effectiveness of apocynin, a NOX inhibitor, is age-dependent in SCI.

METHODS

Apocynin treatment (5 mg/kg) or vehicle was administered 1 and 6 h after moderate T9 contusion SCI (50kdyn IH) and then daily for 1 week to 4 and 14 MO mice. Locomotor and anatomical recovery was evaluated for 28 days. Monocyte-derived macrophage (MDM) and microglial activation and ROS production were evaluated at 3 and 28 days post-injury.

RESULTS

Apocynin improved functional and anatomical recovery in 14 but not 4 MO SCI mice. Apocynin-mediated recovery was coincident with significant reductions in MDM infiltration and MDM-ROS production in 14 MO SCI mice. Importantly, microglial activation was unaffected by treatment.

CONCLUSION

These results indicate that apocynin exhibits age-dependent neuroprotective effects by blocking excessive neuroinflammation through NOX-mediated ROS production in MDMs. Further, these data identify age as a critical regulator for SCI treatment efficacy and indicate that pharmacologically reduced macrophage, but not microglia, activation and ROS production reverses age-associated neurological impairments.