Effect of cyclopentanone prostaglandin 15-deoxy-delta12,14PGJ2 on early functional recovery from experimental spinal cord injury

Bioactive Lipid Mediators in the Initiation and Resolution of Inflammation after Spinal Cord Injury

Neuroinflammation is a prominent feature of the response to CNS trauma. It is also an important hallmark of various neurodegenerative diseases in which inflammation contributes to the progression of pathology. Inflammation in the CNS can contribute to secondary damage and is therefore an excellent therapeutic target for a range of neurological conditions. Inflammation in the nervous system is complex and varies in its fine details in different conditions. It involves a wide variety of secreted factors such as chemokines and cytokines, cell adhesion molecules, and different cell types that include resident cell of the CNS, as well as immune cells recruited from the peripheral circulation. Added to this complexity is the fact that some aspects of inflammation are beneficial, while other aspects can induce secondary damage in the acute, subacute and chronic phases. Understanding these aspects of the inflammatory profile is essential for developing effective therapies. Bioactive lipids constitute a large group of molecules that modulate the initiation and the resolution of inflammation. Dysregulation of these bioactive lipid pathways can lead to excessive acute inflammation, and failure to resolve this by specialized pro-resolution lipid mediators can lead to the development of chronic inflammation. The focus of this review is to discuss the effects of bioactive lipids in spinal cord trauma and their potential for therapies.

Endothelial PPARγ Is Crucial for Averting Age-Related Vascular Dysfunction by Stalling Oxidative Stress and ROCK

Aging plays a significant role in the progression of vascular diseases and vascular dysfunction. Activation of the ADP-ribosylation factor 6 and small GTPases by inflammatory signals may cause vascular permeability and endothelial leakage. Pro-inflammatory molecules have a significant effect on smooth muscle cells (SMC). The migration and proliferation of SMC can be promoted by tumor necrosis factor alpha (TNF-α). TNF-α can also increase oxidative stress in SMCs, which has been identified to persuade DNA damage resulting in apoptosis and cellular senescence. Peroxisome proliferator-activated receptor (PPAR) acts as a ligand-dependent transcription factor and a member of the nuclear receptor superfamily. They play key roles in a wide range of biological processes, including cell differentiation and proliferation, bone formation, cell metabolism, tissue remodeling, insulin sensitivity, and eicosanoid signaling. The PPARγ activation regulates inflammatory responses, which can exert protective effects in the vasculature. In addition, loss of function of PPARγ enhances cardiovascular events and atherosclerosis in the vascular endothelium. This appraisal, therefore, discusses the critical linkage of PPARγ in the inflammatory process and highlights a crucial defensive role for endothelial PPARγ in vascular dysfunction and disease, as well as therapy for vascular aging.

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.

Peroxisome proliferator-activated receptor γ (PPARγ): A master gatekeeper in CNS injury and repair

Peroxisome proliferator-activated receptor γ (PPARγ) is a widely expressed ligand-modulated transcription factor that governs the expression of genes involved in inflammation, redox equilibrium, trophic factor production, insulin sensitivity, and the metabolism of lipids and glucose. Synthetic PPARγ agonists (e.g. thiazolidinediones) are used to treat Type II diabetes and have the potential to limit the risk of developing brain injuries such as stroke by mitigating the influence of comorbidities. If brain injury develops, PPARγ serves as a master gatekeeper of cytoprotective stress responses, improving the chances of cellular survival and recovery of homeostatic equilibrium. In the acute injury phase, PPARγ directly restricts tissue damage by inhibiting the NFκB pathway to mitigate inflammation and stimulating the Nrf2/ARE axis to neutralize oxidative stress. During the chronic phase of acute brain injuries, PPARγ activation in injured cells culminates in the repair of gray and white matter, preservation of the blood-brain barrier, reconstruction of the neurovascular unit, resolution of inflammation, and long-term functional recovery. Thus, PPARγ lies at the apex of cell fate decisions and exerts profound effects on the chronic progression of acute injury conditions. Here, we review the therapeutic potential of PPARγ in stroke and brain trauma and highlight the novel role of PPARγ in long-term tissue repair. We describe its structure and function and identify the genes that it targets. PPARγ regulation of inflammation, metabolism, cell fate (proliferation/differentiation/maturation/survival), and many other processes also has relevance to other neurological diseases. Therefore, PPARγ is an attractive target for therapies against a number of progressive neurological disorders.

Neuropathic Pain models caused by damage to central or peripheral nervous system

Neuropathic Pain (NP) is a painful condition which is a direct consequence of a lesion or disease affecting the somatosensory system with symptoms like allodynia, hyperalgesia. It has complex pathogenesis as it involves several molecular signaling pathways, thus numerous reliable animal models are crucial to understand the underlying mechanism of NP and formulate effective management therapy. Some models like spinal cord injury, chronic constriction injury, spinal nerve ligation, chemotherapy induced peripheral neuropathy, diabetes-induced NP and many more are discussed. This review contains an overview of the procedures followed to induce neuropathy and specific characteristics of that particular model. Some new techniques like spared nerve ligation, have omitted the limitation of methods not presently used where complete nerve damage occurs. Since animal models provide a window to experienced symptoms and physiology and impact the translation of bench discoveries to the bedside, the reporting, interpretation and comparison of these models is necessary because slight variation in procedure of model generation can drastically alter the results. The development of novel, but rational analgesic drugs to alleviate this intractable pain demands elucidation of molecular mechanisms of NP for which different types of animal models have been established.

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.

15-Lipoxygenase metabolites of α-linolenic acid, [13-(S)-HPOTrE and 13-(S)-HOTrE], mediate anti-inflammatory effects by inactivating NLRP3 inflammasome

The ratio of ω-6 to ω-3 polyunsaturated fatty acids (PUFAs) appears to be critical in the regulation of various pathophysiological processes and to maintain cellular homeostasis. While a high proportion of dietary intake of ω-6 PUFAs is associated with various inflammatory disorders, higher intake of ω-3 PUFAs is known to offer protection. It is now well established that beneficial effects of ω-3 PUFAs are mediated in part by their oxygenated metabolites mainly via the lipoxygenase (LOX) and cyclooxygenase (COX) pathways. However, the down-stream signaling pathways that are involved in these anti-inflammatory effects of ω-3 PUFAs have not been elucidated. The present study evaluates the effects of 15-LOX metabolites of α-linolenic acid (ALA, ω-3 PUFA) on lipopolysaccharide (LPS) induced inflammation in RAW 264.7 cells and peritoneal macrophages. Further, the effect of these metabolites on the survival of BALB/c mice in LPS mediated septic shock and also polymicrobial sepsis in Cecal Ligation and Puncture (CLP) mouse model was studied. These studies reveal the anti-inflammatory effects of 13-(S)-hydroperoxyoctadecatrienoic acid [13-(S)-HPOTrE] and 13-(S)-hydroxyoctadecatrienoic acid [13-(S)-HOTrE] by inactivating NLRP3 inflammasome complex through the PPAR-γ pathway. Additionally, both metabolites also deactivated autophagy and induced apoptosis. In mediating all these effects 13-(S)-HPOTrE was more potent than 13-(S)-HOTrE.

PPARγ and the Innate Immune System Mediate the Resolution of Inflammation

The resolution of inflammation is an active and dynamic process, mediated in large part by the innate immune system. Resolution represents not only an increase in anti-inflammatory actions, but also a paradigm shift in immune cell function to restore homeostasis. PPARγ, a ligand activated transcription factor, has long been studied for its anti-inflammatory actions, but an emerging body of literature is investigating the role of PPARγ and its ligands (including thiazolidinediones, prostaglandins, and oleanolic acids) in all phases of resolution. PPARγ can shift production from pro- to anti-inflammatory mediators by neutrophils, platelets, and macrophages. PPARγ and its ligands further modulate platelet and neutrophil function, decreasing trafficking, promoting neutrophil apoptosis, and preventing platelet-leukocyte interactions. PPARγ alters macrophage trafficking, increases efferocytosis and phagocytosis, and promotes alternative M2 macrophage activation. There are also roles for this receptor in the adaptive immune response, particularly regarding B cells. These effects contribute towards the attenuation of multiple disease states, including COPD, colitis, Alzheimer's disease, and obesity in animal models. Finally, novel specialized proresolving mediators-eicosanoids with critical roles in resolution-may act through PPARγ modulation to promote resolution, providing another exciting area of therapeutic potential for this receptor.

Nrf2 activation protects the liver from ischemia/reperfusion injury in mice

OBJECTIVE

To investigate the role of Nrf2 in the pathogenesis of hepatic ischemia-reperfusion (I/R) injury.

BACKGROUND

Hepatic I/R injury is a serious complication that leads to liver failure after liver surgery. NF-E2-related factor 2 (Nrf2) is a transcription factor that plays a critical role in protecting cells against oxidative stress. Therefore, it is suggested that Nrf2 activation protects the liver from I/R injury.

METHODS

Wild-type and Nrf2-deficient mice were treated with 15-deoxy-Δ(12,14)-prostaglandin J2 (15d-PGJ2), or a vehicle. Subsequently, these mice were subjected to 60-minute hepatic 70% ischemia, followed by reperfusion. Liver and blood samples were collected to evaluate liver injury and mRNA expressions.

RESULTS

After hepatic I/R, Nrf2-deficient livers exhibited enhanced tissue damage; impaired GSTm1, NQO1, and GCLc inductions; disturbed redox state; and aggravated tumor necrosis factor α mRNA expression in comparison with wild-type livers. 15d-PGJ2 treatment protected the livers of wild-type mice from I/R injury via increased expressions of GSTm1, NQO1, and GCLc; maintained redox status; and decreased tumor necrosis factor α induction. These effects induced by 15d-PGJ2 were not seen in the livers of Nrf2(-/-) mice and were not annulled by peroxisome proliferator-activated receptor γ antagonist in Nrf2(+/+) mice, suggesting that the protective effect of 15d-PGJ2 is mediated by Nrf2-dependent antioxidant response.

CONCLUSIONS

Nrf2 plays a critical role in the mechanism of hepatic I/R injury and would be a new therapeutic target for preventing hepatic I/R injury during liver surgery.

A hydrogen sulfide-releasing cyclooxygenase inhibitor markedly accelerates recovery from experimental spinal cord injury

Spinal cord trauma causes loss of motor function that is in part due to the ensuing inflammatory response. Hydrogen sulfide (H2S) is a potent, endogenous anti-inflammatory and neuroprotective substance that has been explored for use in the design of novel nonsteroidal anti-inflammatory drugs. In the current study, we evaluated the potential beneficial effects of ATB-346 [2-(6-methoxynapthalen- 2-yl)-propionic acid 4-thiocarbamoyl-phenyl ester], an H2S-releasing derivative of naproxen, in a murine model of spinal cord injury (SCI). SCI was induced in mice by spinal cord compression, produced through the application of vascular clips to the dura via a T5 to T8 laminectomy. ATB-346, naproxen (both at 30 μmol/kg), or vehicle was orally administered to the mice 1 and 6 h after SCI and once daily thereafter for 10 d. Motor function [Basso Mouse Scale (BMS) of locomotion] improved gradually in the mice treated with naproxen. However, those treated with ATB-346 exhibited a significantly more rapid and sustained recovery of motor function, achieving greater than double the increase in locomotion score of the naproxen group by the 10th day of treatment. ATB-346 also significantly reduced the severity of inflammation (proinflammatory cytokines, apoptosis of neural tissue, and nitrosative stress) that characterized the secondary effects of SCI. Again, the effects of ATB-346 were superior to those of naproxen for several parameters. These results showed marked beneficial effects of an H2S-releasing derivative of naproxen in an animal model of SCI, significantly enhancing recovery of motor function, possibly by reducing the secondary inflammation and tissue injury that characterizes this model. The combination of inhibition of cyclooxygenase and delivery of H2S may offer a promising alternative to existing therapies for traumatic injury.

Molecular evidence for the involvement of PPAR-δ and PPAR-γ in anti-inflammatory and neuroprotective activities of palmitoylethanolamide after spinal cord trauma

Background

Palmitoylethanolamide (PEA) is an endogenous fatty acid amide displaying anti-inflammatory and analgesic actions. Moreover, several data have suggested that PEA reduced inflammation and tissue injury associated with spinal cord trauma and showed a regulatory role for peroxisome proliferator-activated receptor (PPAR)-α signaling in the neuroprotective effect of PEA. However, several other mechanisms could explain the anti-inflammatory and anti-hyperalgesic effects of PEA, including the activation of PPAR-δ and PPAR-γ. The aim of the present study was to carefully investigate the exact contribution of PPAR-δ and PPAR-γ in addition to PPAR-α, in the protective effect of PEA on secondary inflammatory damage associated with an experimental model of spinal cord injury (SCI).

Methods

SCI was induced in mice through a spinal cord compression by the application of vascular clips (force of 24 g) to the dura via a four-level T5 to T8 laminectomy, and PEA (10 mg/kg, intraperitoneally, 1 and 6 hours after SCI) was injected into wildtype mice and into mice lacking PPAR-α (PPAR-αKO). To deepen the ability of specific PPAR-δ and PPAR-γ antagonists to reverse the effect of PEA, mice were administered GSK0660 or GW9662, 30 minutes before PEA injection.

Results

Genetic ablation of PPAR-α in mice exacerbated spinal cord damage, while PEA-induced neuroprotection seemed be abolished in PPARαKO mice. Twenty-four hours after spinal cord damage, immunohistological and biochemical studies were performed on spinal cord tissue. Our results indicate that PPAR-δ and PPAR-γ also mediated the protection induced by PEA. In particular, PEA was less effective in PPAR-αKO, GSK0660-treated or GW9662-pretreated mice, as evaluated by the degree of spinal cord inflammation and tissue injury, neutrophil infiltration, proinflammmatory cytokine, inducible nitric oxide synthase expression and motor function. PEA is also able to restore PPAR-δ and PPAR-γ expression in spinal cord tissue.

Conclusion

This study indicates that PPAR-δ and PPAR-γ can also contribute to the anti-inflammatory activity of PEA in SCI.

Peroxisome proliferator-activated receptor-γ agonist rosiglitazone reduces secondary damage in experimental spinal cord injury

OBJECTIVE

To investigate the neuroprotective effects of rosiglitazone in a rat traumatic spinal cord injury (SCI) model.

METHODS

Adult Sprague-Dawley rats (n = 12/group) underwent laminectomy (sham), SCI, SCI and rosiglitazone treatment (2 mg/kg twice daily for 7 days), or SCI and saline injection (vehicle). SCI was induced via dural application of an aneurysm clip. Spinal cord apoptosis and levels of tumour necrosis factor-α (TNFα), interleukin (IL)-1β, myeloperoxidase (MPO) and the apoptosis-associated proteins B-cell leukaemia/lymphoma 2 (Bcl-2) and Bcl-2 associated X protein (Bax) were examined 24 h after SCI. Locomotor function was evaluated 3, 7, 10, 14 and 21 days after SCI.

RESULTS

At 24 h after SCI, apoptosis and TNFα, IL-1β and MPO concentrations were significantly lower in the rosiglitazone group than in the vehicle and SCI groups. SCI resulted in an increase in Bax and a decrease in Bcl-2, which was reversed by rosiglitazone treatment. Rats in the rosiglitazone group had significantly better functional recovery than those in the vehicle and SCI groups.

CONCLUSION

Rosiglitazone significantly improved functional recovery, probably via attenuation of the local inflammatory reaction and reduced apoptosis.

PGJ(2) provides prolonged CNS stroke protection by reducing white matter edema

Few clinically effective approaches reduce CNS-white matter injury. After early in-vivo white matter infarct, NFκB-driven pro-inflammatory signals can amplify a relatively small amount of vascular damage, resulting in progressive endothelial dysfunction to create a severe ischemic lesion. This process can be minimized by 15-deoxy-Δ(12,14)-prostaglandin J2 (PGJ(2)), an analog of the metabolically active PGD(2) metabolite. We evaluated PGJ(2)'s effects and mechanisms using rodent anterior ischemic optic neuropathy (rAION); an in vivo white matter ischemia model. PGJ(2) administration systemically administered either acutely or 5 hours post-insult results in significant neuroprotection, with stereologic evaluation showing improved neuronal survival 30 days post-infarct. Quantitative capillary vascular analysis reveals that PGJ(2) improves perfusion at 1 day post-infarct by reducing tissue edema. Our results suggest that PGJ(2) acts by reducing NFκB signaling through preventing p65 nuclear localization and inhibiting inflammatory gene expression. Importantly, PGJ(2) showed no in vivo toxicity structurally as measured by optic nerve (ON) myelin thickness, functionally by ON-compound action potentials, on a cellular basis by oligodendrocyte precursor survival or changes in ON-myelin gene expression. PGJ(2) may be a clinically useful neuroprotective agent for ON and other CNS infarcts involving white matter, with mechanisms of action enabling effective treatment beyond the currently considered maximal time for intervention.

Putative role of prostaglandin receptor in intracerebral hemorrhage

Each year, approximately 795,000 people experience a new or recurrent stroke. Of all strokes, 84% are ischemic, 13% are intracerebral hemorrhage (ICH) strokes, and 3% are subarachnoid hemorrhage strokes. Despite the decreased incidence of ischemic stroke, there has been no change in the incidence of hemorrhagic stroke in the last decade. ICH is a devastating disease 37–38% of patients between the ages of 45 and 64 die within 30 days. In an effort to prevent ischemic and hemorrhagic strokes we and others have been studying the role of prostaglandins and their receptors. Prostaglandins are bioactive lipids derived from the metabolism of arachidonic acid. They sustain homeostatic functions and mediate pathogenic mechanisms, including the inflammatory response. Most prostaglandins are produced from specific enzymes and act upon cells via distinct G-protein coupled receptors. The presence of multiple prostaglandin receptors cross-reactivity and coupling to different signal transduction pathways allow differentiated cells to respond to prostaglandins in a unique manner. Due to the number of prostaglandin receptors, prostaglandin-dependent signaling can function either to promote neuronal survival or injury following acute excitotoxicity, hypoxia, and stress induced by ICH. To better understand the mechanisms of neuronal survival and neurotoxicity mediated by prostaglandin receptors, it is essential to understand downstream signaling. Several groups including ours have discovered unique roles for prostaglandin receptors in rodent models of ischemic stroke, excitotoxicity, and Alzheimer disease, highlighting the emerging role of prostaglandin receptor signaling in hemorrhagic stroke with a focus on cyclic-adenosine monophosphate and calcium (Ca²⁺) signaling. We review current ICH data and discuss future directions notably on prostaglandin receptors, which may lead to the development of unique therapeutic targets against hemorrhagic stroke and brain injuries alike.

Anti-inflammatory effect of simvastatin in an experimental model of spinal cord trauma: involvement of PPAR-α

BACKGROUND

Statins such as simvastatin are inhibitors of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase used in the prevention of cardiovascular disease. In addition to their cholesterol-lowering activities, statins exert pleiotropic anti-inflammatory effects, which might contribute to their beneficial effects on lipid-unrelated inflammatory diseases. Recently it has been demonstrated that the peroxisome proliferator-activated receptor (PPAR)-α mediates anti-inflammatory effects of simvastatin in vivo models of acute inflammation. Moreover, previous results suggest that PPAR-α plays a role in control of secondary inflammatory process associated with spinal cord injury (SCI).

METHODS

With the aim to characterize the role of PPAR-α in simvastatin activity, we tested the efficacy of simvastatin (10 mg/kg dissolved in saline i.p. 1 h and 6 h after the trauma) in an experimental model of SCI induced in mice by extradural compression of the spinal cord (T6-T7 level) using an aneurysm clip with a closing force of 24 g via a four-level T5-T8 laminectomy, and comparing mice lacking PPAR-α (PPAR-α KO) with wild type (WT) mice. In order to elucidate whether the effects of simvastatin are due to activation of the PPAR-α, we also investigated the effect of a PPAR-α antagonist, GW6471 (1 mg/kg administered i.p. 30 min prior treatment with simvastatin) on the protective effects of on simvastatin.

RESULTS

Results indicate that simvastatin activity is weakened in PPAR-α KO mice, as compared to WT controls. In particular, simvastatin was less effective in PPAR-α KO, compared to WT mice, as evaluated by inhibition of the degree of spinal cord inflammation, neutrophil infiltration, nitrotyrosine formation, pro-inflammmatory cytokine expression, nuclear factor (NF)-κB activation, inducible nitric-oxide synthase (iNOS) expression, and apoptosis. In addition we demonstrated that GW6471 significantly antagonized the effect of the statin and thus abolished the protective effect.

CONCLUSIONS

This study indicates that PPAR-α can contribute to the anti-inflammatory activity of simvastatin in SCI.

The acute administration of eicosapentaenoic acid is neuroprotective after spinal cord compression injury in rats

The aim of the present study was to investigate the effects of treatment with eicosapentaenoic acid (EPA) after spinal cord compression injury in adult rats. Saline or EPA (250 nmol/kg) was administered intravenously 30 min after compression injury. Locomotor recovery was assessed daily using the BBB open-field locomotor score. One week after injury, animals were sacrificed and the spinal cord tissue containing the compression epicenter, and the adjacent rostral and caudal segments, was immunostained using specific markers for neurons, oligodendrocytes, axonal injury, and macrophages/microglia. Administration of EPA resulted in decreased axonal injury and increased neuronal and oligodendrocyte survival, in the lesion epicenter and adjacent tissue. The behavioural assessment mirrored the neuroprotective effects and showed a significantly improved functional recovery in animals treated with EPA compared to the saline-treated controls over the 7-day period. These observations suggest that EPA has neuroprotective properties when administered after spinal cord trauma.

PPARγ agonist rosiglitazone is neuroprotective after traumatic spinal cord injury via anti-inflammatory in adult rats

Spinal cord injury (SCI) results in the loss of function below the lesion. Secondary injury following the primary impact includes a number of biochemical and cellular alterations leading to tissue necrosis and cell death. Peroxisome proliferator-activated receptor-γ (PPARγ) is a ligand-activated transcription factor of nuclear hormone receptor superfamily. Thiazolidinedione rosiglitazone is a potent agonist of PPARγ which is shown to induce neuroprotection in animal models of focal ischemia and traumatic brain injury. SCI is induced by the application of vascular clips (force of 24 g) to the dura via a four-level T(5)-T(8) laminectomy. To gain a better insight into the mechanism of action of the anti-inflammatory effects of rosiglitazone, the following end points of the inflammatory process were evaluated: (1) spinal cord inflammation and tissue injury (histological score); (2) neutrophil infiltration (myeloperoxidase activity); (3) apoptosis (terminal deoxynucleotidyl transferase-mediated UTP end labeling staining and electron microscopy); (4) proinflammatory cytokines TNF-α and IL-β; (5) PPARγ, HSP70 and HSP27 expressions. To elucidate whether the protective effects of rosiglitazone were mediated via the estrogen receptors, we investigated the effect of a PPARγ antagonist, GW9662, on the protective effects of rosiglitazone. GW9662 significantly antagonized the effect of the rosiglitazone and abolished the protective effect against SCI. Taken together, our results clearly demonstrate that administration of rosiglitazone after SCI reduces the development of inflammation and tissue injury associated with spinal cord trauma.

Activation of metabotropic glutamate receptor 5 improves recovery after spinal cord injury in rodents

OBJECTIVE

Activation of metabotropic glutamate receptor 5 (mGluR5) has neuroprotective properties in vitro and has been reported to limit postischemic lesion volume in vivo. Previously, mGluR5 has been identified on microglia in vitro, but the effects of mGluR5 activation on inflammation in vivo or on recovery after spinal cord injury is unknown.

METHODS

Rats received intrathecal infusion of the selective mGluR5 agonist (RS)-2-chloro-5-hydroxyphenylglycine (CHPG) for 7 days after moderate impact spinal cord injury at T9. Complementary studies examined CHPG effects on activated spinal microglia cultures.

RESULTS

Functional motor recovery was significantly increased by CHPG treatment up to 28 days after injury, with improvements in weight bearing, step taking, and coordination of stepping behavior. CHPG treatment significantly reduced lesion volume and increased white matter sparing at 28 days after injury. Administration of CHPG attenuated microglial-associated inflammatory responses in a dose-dependent fashion, including expression of ED1, Iba-1, Galectin-3, NADPH oxidase components, tumor necrosis factor-alpha, and inducible nitric oxide synthase. Because mGluR5 is expressed by microglial cells in the rat spinal cord, such effects may be mediated by direct action on microglial cells. mGluR5 stimulation also reduced microglial activation and decreased microglial-induced neurotoxicity in spinal cord microglia cultures; the latter effects were blocked by the selective mGluR5 antagonist MTEP.

INTERPRETATION

These data demonstrate that mGluR5 activation can reduce microglial-associated inflammation, suggesting that the protective effects of mGluR5 agonists may reflect this action. Ann Neurol 2009;66:63-74.