Evidence for the role of mitogen-activated protein kinase signaling pathways in the development of spinal cord injury

Investigating the Role of Buzhong Yiqi Decoction on Neurogenic Bladder with Network Pharmacology, Molecular Docking, and In Vitro Assays

Buzhong Yiqi decoction (BZYQD) is a traditional Chinese medicine prescription for treating neurogenic bladder (NB). However, the underlying pharmacological mechanism remains unclear. This study aims to clarify the related molecular mechanism. Molecular structure information and targets of core components of BZYQD were obtained from Traditional Chinese Medicines Systems Pharmacology Platform (TCMSP) and SwissTargetPrediction databases. Genes involved in NB were obtained from Comparative Toxicogenomics Database, DisGeNet, GeneCards, and Online Mendelian Inheritance in Man databases. The hub targets of BZYQD in NB treatment were identified by protein-protein interaction (PPI) network analysis with STRING platform and analyzed by gene ontology analysis and the Kyoto Encyclopedia of Genes and Genomics pathway enrichment analysis. Molecular docking was used to verify the binding affinity between the hub targets and the bioactive components of BZYQD. Subsequently, the neuroprotective and anti-inflammatory effects of main bioactive components of BZYQD were investigated with in vitro assays. A total of 131 candidate compounds and 925 predicted target genes were screened. PPI network analysis suggested that ESR1, EGFR, HSP90AA1, MAPK3, AKT1, and CASP3 were the hub targets. BZYQD treatment was associated with hypoxia inducible factor-1 (HIF-1) signaling pathway. Dehydroglyasperin C (DGC), N-cis-feruloyltyramine, shinpterocarpin (SHI), gancaonin M, and glyasperin B, as the main bioactive components of BZYQD, had good binding affinity with hub target proteins. DGC and SHI treatment could significantly inhibit the injury of neurons and inflammatory response of microglia stimulated by oxidized low-density lipoprotein (ox-LDL), respectively. In summary, BZYQD and its main bioactive components DGC and SHI show good potential to ameliorate the symptoms of NB.

MAP kinase inhibitor PD98059 regulates Th1, Th9, Th17, and natural T regulatory cells in an experimental autoimmune encephalomyelitis mouse model of multiple sclerosis

Experimental autoimmune encephalitis (EAE), an animal model of multiple sclerosis (MS), provides significant insights into the mechanisms that initiate and drive autoimmunity. MS is a chronic autoimmune disease of the central nervous system, characterized by inflammatory infiltration associated with demyelination. T lymphocyte cells play a crucial role in MS, whereas natural T regulatory (nTreg) cells prevent autoimmune inflammation by suppressing lymphocyte activity. This study sought to investigate the role of PD98059, a selective MAP kinase inhibitor, in Th1, Th9, Th17, and nTreg cells using the SJL/J mouse model of EAE. Following EAE development, the mice were intraperitoneally administered PD98059 (5 mg/kg for two weeks) daily. We evaluated the effects of PD98059 on Th1 (IFN-γ and T-bet), Th9 (IL-9 and IRF4), Th17 (IL-17A and RORγT), and nTreg (FoxP3 and Helios) cells in the spleen using flow cytometry. Moreover, we explored the effects of PD98059 on the IFN-γ, T-bet, IL-9, IRF4, IL-17A, RORγT, FoxP3, and Helios mRNA and protein levels in brain tissues using qRT-PCR and Western blot analyses. PD98059 treatment significantly decreased the proportion of CD4+IFN-γ+, CD4+T-bet+, CD4+IL-9+, CD4+IRF4+, CD4+IL-17A+, CD4+RORγT+, CD4+IL-17A+, and CD4+RORγT+ cells while increasing that of CD4+FoxP3+ and CD4+Helios+ cells. In addition, PD98059 administration decreased the mRNA and protein levels of IFN-γ, T-bet, IL-9, IRF4, IL-17A, and RORγT but increased those of FoxP3 and Helios in the brain tissue of EAE mice. Our findings suggest that PD98059 corrects immune dysfunction in EAE mice, which is concurrent with the modulation of multiple signaling pathways.

Deciphering the Molecular Mechanism of Escin against Neuropathic Pain: A Network Pharmacology Study

Background

Escin is the main active component in Aesculus hippocastanum. It has been demonstrated that escin has anti-inflammatory properties. This study combined the methods of network pharmacology, molecular docking, and molecular dynamics to explore the molecular mechanism of escin against neuropathic pain (NP).

Methods

The Swiss Target Prediction and the Pharm Mapper database were employed for predicting the targets of escin. Also, the candidate targets of NP were gathered via the databases including Therapeutic Targets, DisGeNet, GeneCards, DrugBank, and OMIM. Subsequently, the network of protein-protein interaction was screened for the key targets by the software Cytoscape 3.8.0. Then, the intersection of these targets was analysed by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment. Additionally, we further investigated the ligand-target interactions by molecular docking and molecular dynamics simulations.

Results

In total, 94 escin targets were predicted by network pharmacology. Among them, SRC, MMP9, PTGS2, and MAPK1 were the core candidate targets. Subsequently, the analysis of GO and KEGG enrichment revealed that escin affected NP by regulating protein kinase C, MAP kinase, TRP channels, the T-cell receptors signaling pathway, and the TNF signaling pathway. The results of molecular docking and molecular dynamics simulation confirmed that escin not only had a strong binding activity with the four core target proteins but also stably combined in 50 ns.

Conclusions

Our study revealed that escin acts on the core targets SRC, MMP9, PTGS2, MAPK1, and associated enrichment pathways to alleviate neuronal inflammation and regulate the immune response, thus exerting anti-NP efficacy. This study provided innovative ideas and methods for the promising treatment of escin in relieving NP.

Warm acupuncture therapy alleviates neuronal apoptosis after spinal cord injury via inhibition of the ERK signaling pathway

PURPOSE

Warm acupuncture (WA) therapy has been applied to treat spinal cord injury (SCI), but the underlying mechanism is unclear. The current study attempted to explore the WA therapy on neuronal apoptosis of SCI and the relationship with the extracellular signal-regulated kinase (ERK) signaling pathway.

METHODS

The rat SCI models were established by the impact method. SCI rat models were subjected to WA treatment at Dazhui (GV14) and Jiaji points (T10), Yaoyangguan (GV3), Zusanli (ST36), and Ciliao (BL32). The rat SCI models were established by the impact method. WA and U0126 treatments were performed on the SCI rats. Motor function and neuronal apoptosis were detected. The relative mRNA of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and interleukin-6 (IL-6), the phosphorylation level of ERK 1/2 and levels of B-cell lymphoma-2 (Bcl-2), BCL2-Associated X (Bax), and caspase-3 in spinal cord tissue were tested.

RESULTS

After WA treatment, the Basso, Beattie & Bresnahan locomotor rating scale (BBB scale) of SCI rats in the WA treatment was significantly raised from 7 to 14 days after SCI. WA and U0126 treatment significantly diminished apoptotic cells and preserved the neurons in the injured spinal cord. WA and U0126 treatment alleviated the production of inflammatory cytokines in the spinal cord. The distinct increase of p-ERK 1/2 induced by SCI was reversed in WA and U0126 treatment groups. WA and U0126 treatment augmented the level of Bcl-2 and reversed the elevated cleaved caspase-3 protein level after SCI.

CONCLUSION

Our study demonstrated that WA might be associated with the downregulation of the ERK signaling pathway. In summary, our findings indicated that WA promotes the recovery of SCI via the protection of nerve cells and the prevention of apoptosis. Meanwhile, the anti-apoptotic effect of WA might be associated with the downregulation of the ERK signaling pathway, which could be one of the mechanisms of WA in the treatment of SCI.

Mitogen-activated protein kinase inhibitor PD98059 improves neuroimmune dysfunction in experimental autoimmune encephalomyelitis in SJL/J mice through the inhibition of nuclear factor-kappa B signaling in B cells

Multiple sclerosis (MS) is a severe autoimmune disease leading to demyelination, followed by consequent axonal degeneration, causing sensory, motor, cognitive, and visual symptoms. Experimental autoimmune encephalomyelitis (EAE) is the most well-studied animal model of MS. Most current MS treatments are not completely effective, and severe side effects remain a great challenge. In this study, we report the therapeutic efficacy of PD98059, a potent mitogen-activated protein kinase inhibitor, on proteolipid protein (PLP)_139-151-induced EAE in SJL/J mice. Following the induction of EAE, mice were intraperitoneally treated with PD98059 (5 mg/kg for 14 days) daily from day 14 to day 28. This study investigated the effects of PD98059 on C-C motif chemokine receptor 6 (CCR6), CD14, NF-κB p65, IκBα, GM-CSF, iNOS, IL-6, TNF-α in CD45R⁺ B lymphocytes using flow cytometry. Furthermore, we analyzed the effect of PD98059 on CCR6, CD14, NF-κB p65, GM-CSF, iNOS, IL-6, and TNF-α mRNA and protein expression levels using qRT-PCR analysis in brain tissues. Mechanistic investigations revealed that PD98059-treated in mice with EAE had reduced CD45R⁺CCR6⁺, CD45R⁺CD14⁺, CD45R⁺NF-κB p65⁺, CD45R⁺GM-CSF⁺, CD45R⁺iNOS⁺, CD45R⁺IL-6⁺, and CD45R⁺TNF-α⁺ cells and increased CD45R⁺IκBα⁺ cells compared with vehicle-treated control mice in the spleen. Moreover, downregulation of CCR6, CD14, NF-κB p65, GM-CSF, iNOS, IL-6, and TNF-α mRNA expression level was observed in PD98059-treated mice with EAE compared with vehicle-treated control mice in the brain tissue. The results of this study demonstrate that PD98059 modulates inflammatory mediators through multiple cellular mechanisms. The results of this study suggest that PD98059 may be pursued as a therapeutic agent for the treatment of MS.

Using Network Pharmacology and Animal Experiment to Investigate the Therapeutic Mechanisms of Polydatin against Vincristine-Induced Neuropathic Pain

Background

Polydatin (PD) is the primary active compound in Polygonum cuspidatum Sieb and has been demonstrated to exert anti-inflammatory and neuroprotective activities. In the present study, we aimed to explore the therapeutic mechanisms of PD against chemotherapy-induced neuropathic pain.

Methods

The putative targets of PD were obtained from the CTD and SwissTargetPrediction databases. Neuropathic pain- and VIN-related targets were collected from the CTD and GeneCards databases. Subsequently, the intersection targets were obtained using the Venn tool, and the protein-protein interaction (PPI) was constructed by the STRING database. GO and KEGG enrichment analyses were performed to investigate the biological functions of the intersection targets. Further, a rat model of VIN-induced neuropathic pain was established to confirm the reliability of the network pharmacology findings.

Results

A total of 46 intersection targets were identified as potential therapeutic targets, mainly related to neuroinflammation. KEGG pathway analysis indicated that the IL-17 signaling pathway was involved in the mechanism of the antinociceptive effect of PD. PPI network analysis indicated that RELA, IL-6, TP53, MAPK3, and MAPK1 were located at crucial nodes in the network. Additionally, PD exerted an antinociceptive effect by increasing the nociceptive threshold. The results of qRT-PCR, western blot, and immunohisochemistry indicated that PD inhibited the IL-6, TP53, and MAPK1 levels in VIN-induced neuropathic pain rats.

Conclusions

Overall, this research provided evidence that suppressing inflammatory signaling pathways might be a potential mechanism action of PD's antinociceptive effect against VIN-induced neuropathic pain.

Injection of Cerium Oxide Nanoparticles to Treat Spinal Cord Injury in Rats

This study investigated the effects of local injection of cerium oxide nanoparticles (CeONPs) in a rat spinal cord injury (SCI) model. Thirty-six adult male Wistar rats were divided into 4 groups: controls (healthy animals), sham (laminectomy), SCI (laminectomy+SCI induction), and treatment (laminectomy+SCI induction+intrathecal injection of CeONPs immediately after injury). SCI was induced using an aneurysm clip at the T12-T13 vertebral region. Motor performance and pain threshold tests were performed weekly; H&E staining and measurement of cavity sizes were performed 6 weeks after injury. The expression of granulocyte colony-stimulating factor (GCSF), P44/42 MAPK, P-P44/42 MAPK, Tau, myelin-associated glycoprotein(MAG) was evaluated after 6 weeks by Western blot. The Basso, Beattie, and Bresnahan locomotor scoring scales improved in animals receiving CeONPs compared with SCI animals. The cavity sizes were less in the treatment group. GCSF expression was similar in the animals receiving CeONPs compared with the SCI group but the expression of ERK1/ERK2 and phospho-ERK was lower than in the SCI group. Expression levels of Tau and MAG were significantly increased in treated animals compared to the SCI group. These data indicate that the use of CeONPs may improve motor functional recovery in SCI.

Using Network Pharmacology to Systematically Decipher the Potential Mechanisms of Jisuikang in the Treatment of Spinal Cord Injury

Objective

To identify the potential pharmacological targets of Jisuikang (JSK) for the treatment of spinal cord injury (SCI) using network pharmacology.

Methods

The bioactive compounds of JSK herbs and their corresponding potential SCI targets were obtained from three traditional Chinese medicine (TCM) databases. SCI-related therapeutic target genes were obtained from the Comparative Toxicogenomics Database and the GeneCards Database. The common target genes between the JSK compounds and SCI-related therapeutic targets were screened using GO/KEGG functional enrichment and protein-protein interaction (PPI) analyses to identify hub genes and their categories of biological function. Gene expression distribution and receiver operating characteristic curve (ROC) analyses were used to identify probable SCI-related target genes. Molecular docking was used to quantify molecular interactions between target genes and the bioactive compounds of JSK.

Results

A total of 183 JSK bioactive compounds and 197 target genes for the treatment of SCI were screened and assessed. The target genes were enriched primarily in drug metabolism and in inflammation-related biological processes. Ten genes with statistical significance were identified as therapeutic SCI-related target genes of JSK. Molecular docking experiments demonstrated that the proteins of these 10 genes docked with binding energies of less than −5 kcal/mol with the bioactive compounds in JSK.

Conclusion

This study showed that the anti-SCI effects of JSK may be mediated through numerous bioactive components, multiple gene targets, and inflammation-related pathways and provided potential novel targets for directed therapies for treating SCI. These results provide a foundation for further experimental investigations into treatment options for SCI.

Diagnostic Markers and Molecular Dysregulation Mechanisms in the Retinal Pigmented Epithelium and Retina of Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is a chronic and progressive macular degeneration disease, which can also lead to serious visual loss. In our research, we aim to efficiently identify biomarkers relevant for AMD diagnosis. We collected the gene expression data of retinal segmented epithelium (RPE) and retina tissues of GSE29801 and GSE135092 and performed differential expression analysis. The differentially expressed genes (DEGs) related to the RPE and retina in the two sets of data were identified and enriched by intersection analysis. A PPI network was constructed for intersection genes, and the top 20 genes with the largest connectivity in the network were selected as candidate genes. The LASSO model was used to identify key genes from candidate genes, and the nomogram and ROC curve were used to evaluate the diagnostic ability of key genes. We identified 464 intersection genes associated with RPE and 509 intersection genes associated with retina. The TGF-beta signaling pathway was enriched by RPE-related DEGs, while oxidative phosphorylation was enriched by retina-related DEGs. Among the candidate genes of RPE, the LASSO model identified 7 key genes. MAPK1 and LUM can predict the clinical diagnosis of AMD. Among the candidate genes of retina, the LASSO model identified four key genes. PTPN11 has the highest predictive diagnostic value. The results suggest that the imbalance mechanism of RPE in AMD may be related to the TGF-beta signaling pathway, and the imbalance mechanism of the retina may be related to oxidative phosphorylation. MAPK1 and LUM are potential diagnostic markers of RPE, and PTPN11 is a potential diagnostic marker of the retina. Also, our results provide a theoretical basis for better understanding the molecular mechanisms of AMD onset and treatment in the future.

Direct Injection of Hydrogels Embedding Gold Nanoparticles for Local Therapy after Spinal Cord Injury

In this study, we created a hydrogel composed of glycol chitosan (gC) and oxidized hyaluronate (oHA). Gold nanoparticles (GNPs) were conjugated with ursodeoxycholic acid (UDCA). The GNP-UDCA complex was embedded into gC-oHA (CHA) hydrogels to form a CHA-GNP-UDCA gel. This CHA-GNP-UDCA gel was injected once into an epicenter of an injured region in SCI rats. Near-infrared (NIR) irradiation was then applied to the lesion as a means of local therapy. To optimize the viscosity for injection into a lesion, several volume ratios of gC and oHA were investigated using scanning electron microscopy and a rotating rheometer. The optimally synthesized CHA-GNP-UDCA gel under NIR irradiation suppressed the production of inflammatory cytokines in vitro. In addition, the optimized CHA-GNP-UDCA gel under NIR irradiation inhibited the cystic cavity of the lesion and significantly improved the hindlimb function. The production of inflammatory cytokines following SCI was significantly inhibited in the CHA-GNP-UDCA gel + NIR group. CHA-GNP-UDCA gels with NIR irradiation can therefore have therapeutic effects for those with spinal cord injuries.

Inhibition of ERK1/2 phosphorylation attenuates spinal cord injury induced astrocyte activation and inflammation through negatively regulating aquaporin-4 in rats

The extracellular signal-regulated kinase (ERK) pathway has been reported to play a pivotal role in mediating spinal cord injury (SCI) progression. The present study aimed to investigate the effects of phosphorylated ERK1/2 (p-ERK1/2) inhibition on SCI-induced astrocyte activation and inflammation and its possible mechanism in rats. Here, female Sprague-Dawley rats were randomly assigned to four groups: (1) Sham group, (2) SCI group, (3) TGN-020 group (aquaporin-4, AQP4, blocking agent), (4) PD98059 group (ERK blocking agent). A well SCI model was established by compressing the thoracic vertebra 10 level (weight 35 g, time 5 min) in rats. Western blotting and immunofluorescence staining were used to measure the expression of associated proteins after SCI. HE staining and Nissl staining were performed to detect the morphological changes of spinal cords and the number of surviving neurons following SCI, respectively. The Basso-Beattie-Bresnahan open-field rating scale was used to evaluate functional locomotor recovery following SCI in rats. Our results demonstrated that SCI significantly induced the upregulation of aquaporin-4, p-ERK1/2, glial fibrillary acidic protein, proliferating cell nuclear antigen, and proinflammatory cytokines (tumor necrosis factor-α, interleukin-6 and interleukin-1β). However, treatment with TGN-020 or PD98059 could effectively inhibit astrocyte proliferation and proinflammatory cytokine release, preserve the number of surviving ventral horn neurons, and subsequently improve the locomotor function of rats after SCI. Interestingly, the SCI-induced elevation of AQP4 expression was downregulated by p-ERK1/2 inhibition, suggesting that blocking ERK1/2 phosphorylation could attenuate astrocyte activation and inflammatory processes through negative regulation of AQP4. Therefore, p-ERK1/2 blockade may be employed as a therapeutic target for SCI.

Roles of extra-cellular signal-regulated protein kinase 5 signaling pathway in the development of spinal cord injury

Background:

In consideration of characteristics and functions, extra-cellular signal-regulated protein kinase 5 (ERK5) signaling pathway could be a new target for spinal cord injury (SCI) treatment. Our study aimed to evaluate the roles of ERK5 signaling pathway in secondary damage of SCI.

Methods:

We randomly divided 70 healthy Wistar rats into five groups: ten in the blank group, 15 in the sham surgery + BIX02188 (sham + B) group, 15 in the sham surgery + dimethyl sulfoxide (DMSO; sham + D) group, 15 in the SCI + BIX02188 (SCI + B) group, and 15 in the SCI + DMSO (SCI + D) group. BIX02188 is a specific inhibitor of the ERK5 signaling pathway. SCI was induced by the application of vascular clips (with the force of 30 g) to the dura on T10 level, while rats in the sham surgery group underwent only T9-T11 laminectomy. BIX02188 or DMSO was intra-thecally injected at 1, 6, and 12 h after surgery or SCI. Spinal cord samples were taken for testing at 24 h after surgery or SCI.

Results:

Expression of phosphorylated-ERK5 (p-ERK5) significantly increased after SCI. Application of BIX02188 indeed inhibited ERK5 signaling pathway and reduced the degree of spinal cord tissue injury, neutrophil infiltration and proinflammatory cytokine expression, nuclear factor-κB (NF-κB) activation and apoptosis (measured by TdT-mediated 2′-deoxyuridine 5′-triphosphate nick-end labeling, expression of Fas-ligand, BCL2-associated X [Bax], and B-cell lymphoma-2 [Bcl-2]). Double immunofluorescence revealed activation of ERK5 in neurons and microglia after SCI.

Conclusion:

ERK5 signaling pathway was activated in spinal neurons and microglia, contributing to secondary injury of SCI. Moreover, inhibition of ERK5 signaling pathway could alleviate the degree of SCI, which might be related to its regulation of infiltration of inflammatory cells and release of inflammatory cytokines, expression of NF-κB and cell apoptosis.

Systemic 7,8-Dihydroxyflavone Treatment Protects Immature Retinas Against Hypoxic-Ischemic Injury via Müller Glia Regeneration and MAPK/ERK Activation

Purpose

Perinatal hypoxic-ischemic (HI) injury causes significant damages in the immature retina. The brain-derived neurotrophic factor is well known for its neuroprotective role but has limited clinical applications. A selective agonist of tyrosine kinase receptor B, 7,8-dihydroxyflavone (DHF), is a powerful therapeutic tool, when administered systemically. However, it remains unclear whether DHF treatment can protect the immature retinas against HI injury.

Methods

Postnatal (P) day 7 rat pups were intraperitoneally injected with DHF or vehicle 2 hours before and 18 hours after being subjected to HI injury. The outcomes were assessed at various timepoints after injury by electroretinography and histologic examinations. Neurogenesis was assessed by double-labeling of retinal sections with 5-bromo-2'-deoxyuridine and different neuronal markers.

Results

At P8, 24-hours postinjury, brain-derived neurotrophic factor mRNA levels in the retina decreased significantly. DHF treatment partially protected immature retinas at both histologic and functional levels between P14 and P30 but did not prevent apoptosis, inflammation, or damage of the blood-retinal barrier (BRB) at P8. On the other hand, DHF treatment promoted the survival of proliferating inner retinal cells, including Müller glia, and enhanced their transdifferentiation to bipolar cells at P17. Moreover, DHF treatment rescued the levels of extracellular signal-regulated kinase (ERK) phosphorylation, which were significantly decreased after injury. The neuroprotective effects of DHF were markedly eliminated by inhibition of ERK phosphorylation.

Conclusions

Early systemic DHF treatment has neuroprotective effects against HI injury in immature retinas, possibly via promoting neurogenesis through the tyrosine kinase receptor B/ERK signaling pathway.

Chinese Abstract.

Fire Needle Acupuncture Regulates Wnt/ERK Multiple Pathways to Promote Neural Stem Cells to Differentiate into Neurons in Rats with Spinal Cord Injury

BACKGROUND & OBJECTIVE

NSCs therapy is considered one of the most potential methods for spinal cord injury (SCI).

METHODS

We build the SCI model rats to investigate the therapeutic effect of fire needle acupuncture in improving the locomotor function of SCI rats and its possible mechanism. BBB scale was used for the motor ability of rats. The expression of Nestin, NSE, Gal-C, and GFAP was detected by immunohistochemistry. Wnt, GSK3β, β-catenin, ERK1/2, CyclinD1, and ngn1 were detected by western blot and PCR. The BBB score of both model group (1.20±0.94, 3.12±0.67, 5.34±1.57, 7.12±1.49) and fire needle group (1.70±0.58, 4.50±1.63, 7.53±2.41, 9.24±0.63) gradually increased after SCI. Furthermore, at d10 and d14, the fire needle group showed a significantly high score compared with that in model group at the same time (P<0.05). Fire needle increased Nestin, NSE, and Gal-C expression inhibited GFAP expression after SCI. Also, fire needle could up-regulate Wnt3a, GSK3β, β-catenin, and ngn1, and down-regulate ERK1/2, cyclinD1 gene and protein expression.

CONCLUSION

In conclusion, fire needle could improve lower limb locomotor function of SCI rats. Also, fire needles could promote endogenous NSCs proliferation differentiating into neurons, and the mechanism might be mediated by promoting the activation of Wnt/β-catenin and inhibiting the overexpression of ERK.

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

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

PPAR-α Modulates the Anti-Inflammatory Effect of Melatonin in the Secondary Events of Spinal Cord Injury

Melatonin is the principal secretory product of the pineal gland, and its role as an immunomodulator is well established. Recent evidence shows that melatonin is a scavenger of oxyradicals and peroxynitrite and reduces the development of inflammation and tissue injury events associated with spinal cord trauma. Previous results suggest that peroxisome proliferator-activated receptor α (PPAR-α), a nuclear receptor protein that functions as a transcription factor activated by fatty acids, plays a role in control of secondary inflammatory process associated with spinal cord injury (SCI).With the aim to characterize the role of PPAR-α in melatonin-mediated anti-inflammatory activity, we tested the efficacy of melatonin (30 mg/kg) in an experimental model of spinal cord trauma, induced in mice, by the application of vascular clips (force of 24 g) to the dura via a four-level T5-T8 laminectomy, and comparing mice lacking PPAR-α (PPAR-α KO) with wild-type (WT) mice.The results obtained indicate that melatonin-mediated anti-inflammatory activity is weakened in PPAR-α KO mice, as compared to WT controls. In particular, melatonin was less effective in PPAR-α KO, compared to WT mice, as evaluated by inhibition of the degree of spinal cord inflammation and tissue injury, neutrophil infiltration, pro-inflammatory cytokine expression, nuclear factor κB (NF-κB) activation, and inducible nitric oxide synthase (iNOS) expression. This study indicates that PPAR-α can contribute to the anti-inflammatory activity of melatonin in SCI.

Tocotrienol alleviates inflammation and oxidative stress in a rat model of spinal cord injury via suppression of transforming growth factor-β

In recent years accumulating evidence has indicated that tocotrienol exhibits an oxidation resistance function, decreased cholesterol function, inhibits cancer function and has unique physiological functions, including anti-inflammatory, anti-apoptotic and anti-oxidative properties. The present study investigated the effect of tocotrienols on spinal cord injury (SCI) by evaluating oxidative stress, inflammation and inducible nitric oxide synthase (iNOS) in rats. A rat model of SCI was induced by operation. SCI rats were treated with 120 mg/kg/day tocotrienol once a day for eight consecutive weeks. Functional recovery following SCI was measured by using the Basso Beattie Bresnahan (BBB) locomotor rating scale. Then the volume of spinal cord contusions was measured following induction of SCI in the rats. In SCI rats, serum malondialdehyde, superoxide dismutase, catalase, glutathione peroxidase, nuclear factor-κB p65 unit, tumor necrosis factor-α, interleukin (IL)-1β and IL-6 levels were analyzed using respective commercial immunoassay kits. Firstly, iNOS, transforming growth factor (TGF)-β, collagen type IV and fibronectin protein expression levels, in addition to iNOS activity and plasma nitric oxide (NO) production in SCI rats was analyzed using western blot analysis, commercial kits and Griess reagent, respectively. Tocotrienol treatment elevated BBB scores and contused volume in the SCI rats. Tocotrienol protected against SCI with reduced oxidative stress and inflammation, and inhibited iNOS protein expression iNOS activity and plasma NO production in rats. In addition, treatment with tocotrienols suppressed TGF-β, collagen type IV and fibronectin protein expression levels in SCI rats. These results suggest that tocotrienols protect SCI, and suppress oxidative stress, inflammation and iNOS in this model of SCI through TGF-β, collagen type IV and fibronectin signaling pathways.

Temporospatial expression of fibulin-1 after acute spinal cord injury in rats

OBJECTIVE

Fibulin-1 is a matricellular protein that plays important roles in motility inhibition in a variety of cells and blocks the proliferation of cultured neural stem cells. The biological function of fibulin-1 in the spinal cord has not been fully elucidated.

METHODS

To clarify the expressions and possible functions of fibulin-1 in spinal cord injury (SCI), we performed an acute spinal cord contusion injury model in adult rats. Our work studied the temporospatial expression patterns of fibulin-1.

RESULTS

Western blot analysis revealed that fibulin-1 levels significantly increased 5 days after spinal cord contusion. Immunohistochemistry confirmed an increased number of fibulin-1 immunopositive cells about 2 mm from the lesion site. Moreover, double immunofluorescence labeling suggested that these changes were especially prominent in neurons and microglia.

CONCLUSION

These findings suggest that fibulin-1 may be involved in neuronal apoptosis and microglial activation after SCI.

Role of melatonin in traumatic brain injury and spinal cord injury

Brain and spinal cord are implicated in incidences of two of the most severe injuries of central nervous system (CNS). Traumatic brain injury (TBI) is a devastating neurological deficit involving primary and secondary injury cascades. The primary and secondary mechanisms include complex consequences of activation of proinflammatory cytokines, cerebral edema, upregulation of NF-κβ, disruption of blood-brain barrier (BBB), and oxidative stress. Spinal cord injury (SCI) includes primary and secondary injury cascades. Primary injury leads to secondary injury in which generation of free radicals and oxidative or nitrative damage play an important pathophysiological role. The indoleamine melatonin is a hormone secreted or synthesized by pineal gland in the brain which helps to regulate sleep and wake cycle. Melatonin has been shown to be a versatile hormone having antioxidative, antiapoptotic, neuroprotective, and anti-inflammatory properties. It has a special characteristic of crossing BBB. Melatonin has neuroprotective role in the injured part of the CNS after TBI and SCI. A number of studies have successfully shown its therapeutic value as a neuroprotective agent in the treatment of neurodegenerative diseases. Here in this review we have compiled the literature supporting consequences of CNS injuries, TBI and SCI, and the protective role of melatonin in it.

MEK inhibition reduces glial scar formation and promotes the recovery of sensorimotor function in rats following spinal cord injury

The aim of this study was to investigate the effect of U0126 on the formation of glial scars following spinal cord injury (SCI) in a rat model. Ninety adult female Sprague-Dawley rats were divided randomly into sham injury (group I), SCI (group II) and U0126 treatment (group III) groups, and functional outcome was observed during the 4 weeks following the injury. The P1 and N1 latencies and P1-N1 amplitudes of somatosensory-evoked potentials (SEPs) were collected one day prior to surgery, on the day of surgery and 14 and 28 days postoperatively. The expression levels of glial fibrillary acidic protein (GFAP) and vimentin (Vim) were assessed 14 and 28 days post-injury. Treatment with U0126 significantly increased locomotor function from the second week until 4 weeks post-SCI. At 14 and 28 days subsequent to the injury, the number of cells that were positive for GFAP expression in the U0126-treated group was significantly reduced and the GFAP-positive cells were observed to be smaller, with a reduced prominence and pale staining. Moreover, the area of glial scarring was smaller compared with that of the SCI controls. Inhibitors of MEK may reduce glial scar formation by suppressing the proliferation of astrocytes, and may improve hindlimb motor function.

Inhibition of EGFR/MAPK signaling reduces microglial inflammatory response and the associated secondary damage in rats after spinal cord injury

Background

Emerging evidence indicates that reactive microglia-initiated inflammatory responses are responsible for secondary damage after primary traumatic spinal cord injury (SCI); epidermal growth factor receptor (EGFR) signaling may be involved in cell activation. In this report, we investigate the influence of EGFR signaling inhibition on microglia activation, proinflammatory cytokine production, and the neuronal microenvironment after SCI.

Methods

Lipopolysaccharide-treated primary microglia/BV2 line cells and SCI rats were used as model systems. Both C225 and AG1478 were used to inhibit EGFR signaling activation. Cell activation and EGFR phosphorylation were observed after fluorescent staining and western blot. Production of interleukin-1beta (IL-1β) and tumor necrosis factor alpha (TNFα) was tested by reverse transcription PCR and ELISA. Western blot was performed to semi-quantify the expression of EGFR/phospho-EGFR, and phosphorylation of Erk, JNK and p38 mitogen-activated protein kinases (MAPK). Wet-dry weight was compared to show tissue edema. Finally, axonal tracing and functional scoring were performed to show recovery of rats.

Results

EGFR phosphorylation was found to parallel microglia activation, while EGFR blockade inhibited activation-associated cell morphological changes and production of IL-1β and TNFα. EGFR blockade significantly downregulated the elevated MAPK activation after cell activation; selective MAPK inhibitors depressed production of cytokines to a certain degree, suggesting that MAPK mediates the depression of microglia activation brought about by EGFR inhibitors. Subsequently, seven-day continual infusion of C225 or AG1478 in rats: reduced the expression of phospho-EGFR, phosphorylation of Erk and p38 MAPK, and production of IL-1β and TNFα; lessened neuroinflammation-associated secondary damage, like microglia/astrocyte activation, tissue edema and glial scar/cavity formation; and enhanced axonal outgrowth and functional recovery.

Conclusions

These findings indicate that inhibition of EGFR/MAPK suppresses microglia activation and associated cytokine production; reduces neuroinflammation-associated secondary damage, thus provides neuroprotection to SCI rats, suggesting that EGFR may be a therapeutic target, and C225 and AG1478 have potential for use in SCI treatment.

Effects of mitogen-activated protein kinase signaling pathway inhibition on the development of cerulein-induced acute pancreatitis in mice

OBJECTIVES

Extracellular signal-regulated kinase (ERK) influences a number of pathways in all cells. The ERK cascade has long been known to be central to the activation of cellular processes such as proliferation, differentiation, and oncogenic transformation. The mitogen-activated protein (MAP) serine/threonine family of protein kinases, of which ERK is a member, is evolutionarily conserved and is activated by a mechanism that includes protein kinase cascades. The aim of this study was to investigate the effects of PD98059 [2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one], a highly selective inhibitor of MAP/ERK kinase 1 (MEK1) activation, on the development of acute pancreatitis.

METHODS

Pancreatitis was induced by intraperitoneal injection of cerulein (hourly × 5, 50 μg/kg) and PD98059 (10 mg/kg, 10% dimethylsulfoxide, intraperitoneally) was administrated 1 and 3 hours after cerulein administration.

RESULTS

Cerulein injection resulted in acute necrotizing pancreatitis. On the contrary, pancreatitis histological features, amylase, lipase, pancreas edema, and immunohistochemical staining for leukocyte adhesion molecules, transforming growth factor β, and apoptosis-related proteins were found reduced in PD98059-treated mice.

CONCLUSIONS

We propose that this study could help to clarify the role of MAPK in the regulation of the inflammatory process as acute pancreatitis.

Pregabalin as a neuroprotector after spinal cord injury in rats: biochemical analysis and effect on glial cells

As one of trials on neuroprotection after spinal cord injury, we used pregabalin. After spinal cord injury (SCI) in rats using contusion model, we observed the effect of pregabalin compared to that of the control and the methylprednisolone treated rats. We observed locomotor improvement of paralyzed hindlimb and body weight changes for clinical evaluation and caspase-3, bcl-2, and p38 MAPK expressions using western blotting. On histopathological analysis, we also evaluated reactive proliferation of glial cells. We were able to observe pregabalin's effectiveness as a neuroprotector after SCI in terms of the clinical indicators and the laboratory findings. The caspase-3 and phosphorylated p38 MAPK expressions of the pregabalin group were lower than those of the control group (statistically significant with caspase-3). Bcl-2 showed no significant difference between the control group and the treated groups. On the histopathological analysis, pregabalin treatment demonstrated less proliferation of the microglia and astrocytes. With this animal study, we were able to demonstrate reproducible results of pregabalin's neuroprotection effect. Diminished production of caspase-3 and phosphorylated p38 MAPK and as well as decreased proliferation of astrocytes were seen with the administration of pregabalin. This influence on spinal cord injury might be a possible approach for achieving neuroprotection following central nervous system trauma including spinal cord injury.

Effect of Apocynin, an inhibitor of NADPH oxidase, in the inflammatory process induced by an experimental model of spinal cord injury

NADPH-oxidase is an enzyme responsible for reactive oxygen species production, and inhibition of this enzyme represents an attractive therapeutic target for the treatment of many diseases. The aim of this study was to investigate the effects of Apocynin, NADPH-oxidase inhibitor, in the modulation of secondary injury in the spinal cord. The injury was induced by application of vascular clips to the dura via a four-level T5-T8 laminectomy in mice. Treatment with Apocynin 1 and 6 h after the trauma significantly decreased (1) the degree of spinal cord inflammation and tissue injury, (2) neutrophil infiltration, (3) adhesion molecule expression, (4) nuclear transcription factor-κB expression, (5) nitrotyrosine and poly-ADP-ribose formation, (6) pro-inflammatory cytokines production, (7) apoptosis and (8) mitogen-activated protein kinase activation. Moreover, Apocynin significantly ameliorated the loss of limb function (evaluated by motor recovery score). Thus, it is proposed that Apocynin may be useful in the treatment of inflammation associated with spinal cord trauma.

Effect of PD98059, a selective MAPK3/MAPK1 inhibitor, on acute lung injury in mice

The aim of the present study is to evaluate the contribution of mitogen-activated protein kinase 1-3 MAPK3/MAPK1) in a model of acute lung inflammation in mice. Injection of carrageenan into the pleural cavity of mice elicited an acute inflammatory response characterized by: accumulation of fluid containing a large number of neutrophils (PMNs) in the pleural cavity, infiltration of PMNs in lung tissues and subsequent adhesion molecule expression (I-CAM and P-selectin), lipid peroxidation, and increased production of tumour necrosis factor-alpha, (TNF-alpha) and interleukin-1beta (IL-1beta). Furthermore, carrageenan induced lung apoptosis (Bax and Bcl-2 expression) as well as nitrotyrosine formation, NF-kB activation, and pJNK expression, as determined by immunohistochemical analysis of lung tissues and the degree of lung inflammation and tissue injury (histological score). Administration of PD98059, an inhibitor of MAPK3/MAPK1 (10 mg/kg) 1 h after carrageenan caused a reduction in all the parameters of inflammation measured. Thus, based on these findings we propose that inhibitors of the MAPK3/MAPK1 signaling pathways, such as PD98059, may be useful in the treatment of various inflammatory diseases.

Involvement of ERK2 in traumatic spinal cord injury

Activation of extracellular signal-regulated protein kinase 1/2 (ERK1/2) are implicated in the pathophysiology of spinal cord injury (SCI). However, the specific functions of individual ERK isoforms in neurodegeneration are largely unknown. We investigated the hypothesis that ERK2 activation may contribute to pathological and functional deficits following SCI and that ERK2 knockdown using RNA interference may provide a novel therapeutic strategy for SCI. Lentiviral ERK2 shRNA and siRNA were utilized to knockdown ERK2 expression in the spinal cord following SCI. Pre-injury intrathecal administration of ERK2 siRNA significantly reduced excitotoxic injury-induced activation of ERK2 (p < 0.001) and caspase 3 (p < 0.01) in spinal cord. Intraspinal administration of lentiviral ERK2 shRNA significantly reduced ERK2 expression in the spinal cord (p < 0.05), but did not alter ERK1 expression. Administration of the lentiviral ERK2 shRNA vector 1 week prior to severe spinal cord contusion injury resulted in a significant improvement in locomotor function (p < 0.05), total tissue sparing (p < 0.05), white matter sparing (p < 0.05), and gray matter sparing (p < 0.05) 6 weeks following severe contusive SCI. Our results suggest that ERK2 signaling is a novel target associated with the deleterious consequences of spinal injury.

The P2Y-like receptor GPR17 as a sensor of damage and a new potential target in spinal cord injury

Upon central nervous system injury, the extracellular concentrations of nucleotides and cysteinyl-leukotrienes, two unrelated families of endogenous signalling molecules, are markedly increased at the site of damage, suggesting that they may act as 'danger signals' to alert responses to tissue damage and start repair. Here we show that, in non-injured spinal cord parenchyma, GPR17, a P2Y-like receptor responding to both uracil nucleotides (e.g. UDP-glucose) and cysteinyl-leukotrienes (e.g. LTD4 and LTC4), is present on a subset of neurons and of oligodendrocytes at different stages of maturation, whereas it is not expressed by astrocytes. GPR17 immunoreactivity was also found on ependymal cells lining the central canal that still retain some of the characteristics of stem/progenitor cells during adulthood. Induction of spinal cord injury (SCI) by acute compression resulted in marked cell death of GPR17+ neurons and oligodendrocytes inside the lesion followed by the appearance of proliferating GPR17+ microglia/macrophages migrating to and infiltrating into the lesioned area. Moreover, 72 h after SCI, GPR17+ ependymal cells started to proliferate and to express GFAP, suggesting their activation and 'de-differentiation' to pluripotent progenitor cells. The in vivo knock down of GPR17 by an antisense oligonucleotide strategy during SCI induction markedly reduced tissue damage and related histological and motor deficits, thus confirming the crucial role played by this receptor in the early phases of tissue damage development. Taken together, our findings suggest a dual and spatiotemporal-dependent role for GPR17 in SCI. At very early times after injury, GPR17 mediates neuronal and oligodendrocyte death inside the lesioned area. At later times, GPR17+ microglia/macrophages are recruited from distal parenchymal areas and move toward the lesioned zone, to suggest a role in orchestrating local remodelling responses. At the same time, the induction of the stem cell marker GFAP in GPR17+ ependymal cells suggests initiation of repair mechanisms. Thus, GPR17 may act as a 'sensor' of damage that is activated by nucleotides and cysteinyl-leukotrienes released in the lesioned area, and could also participate in post-injury responses. Moreover, its presence on spinal cord pre-oligodendrocytes and precursor-like cells suggests GPR17 as a novel target for therapeutic manipulation to foster remyelination and functional repair in SCI.

Melatonin reduces stress-activated/mitogen-activated protein kinases in spinal cord injury

Permanent functional deficits following spinal cord injury (SCI) arise from both mechanical injury and from secondary tissue reactions involving inflammation. The mitogen-activated protein kinases (MAPKs) play a critical role in cell signaling and gene expression. MAPK family includes three major members: extracellular signal regulated kinase (ERK), p38, and c-Jun N-terminal kinase (JNK), representing three different signaling cascades. Moreover, various studies have clearly shown that high-mobility group box 1 (HMGB1) protein is implicated as a putative danger signal involved in the pathogenesis of a variety of inflammatory conditions including autoimmunity, cancer, trauma and hemorrhagic shock, and ischemia-reperfusion injury. Recently, we have reported that the pineal secretory product melatonin exerts important anti-inflammatory effects in an experimental model of SCI induced by the application of vascular clips (force of 24 g) to the dura after a four-level T5-T8 laminectomy. However, no reports are available on the effect of melatonin on MAPK signaling pathways and HMGB1 expression in SCI. The aim of the present study was to evaluate whether the melatonin protective effect observed in SCI is related to the regulation of MAPK signaling pathways and HMGB1 in mice. In this study we demonstrate the efficacy of treatment with the melatonin in SCI in mice in reducing (a) motor recovery, (b) activation of MAPKs p38, JNK and ERK1/2, (c) tumor necrosis factor-alpha expression, and (d) expression of HMGB1. We propose that melatonin's ability to reduce SCI in mice is also related to a reduction in MAPK signaling pathways and HMGB1 expression.