Effects of palmitoylethanolamide on release of mast cell peptidases and neurotrophic factors after spinal cord injury

Harnessing the anti-inflammatory potential of palmitoylethanolamide

Palmitoylethanolamide (PEA) is a peroxisome proliferator-activated receptor alpha (PPAR-α) ligand that exerts anti-inflammatory, analgesic and neuroprotective actions. PEA is synthetized from phospholipids through the sequential actions of N-acyltransferase and N-acylphosphatidylethanolamine-preferring phospholipase D (NAPE-PLD), and its actions are terminated by its hydrolysis by two enzymes, fatty acid amide hydrolase (FAAH) and N-acylethanolamine-hydrolysing acid amidase (NAAA). Here, we review the impact of PEA administration in inflammatory and neurodegenerative settings and the differential role of FAAH and NAAA in controlling PEA levels. Recent studies with NAAA inhibitors put forth this enzyme as capable of increasing PEA levels in vivo in inflammatory processes, and identified it as an interesting target for drug discovery research. Thus, PEA hydrolysis inhibitors could constitute potential therapeutic alternatives in chronic inflammatory and neurodegenerative diseases.

Intracisternal injection of palmitoylethanolamide inhibits the peripheral nociceptive evoked responses of dorsal horn wide dynamic range neurons

Endogenous palmitoylethanolamide (PEA) has a key role in pain modulation. Central or peripheral PEA can reduce nociceptive behavior, but no study has yet reported a descending inhibitory effect on the neuronal nociceptive activity of Aδ- and C-fibers. This study shows that intracisternal PEA inhibits the peripheral nociceptive responses of dorsal horn wide dynamic range cells (i.e., inhibition of Aδ- and C-fibers), an effect blocked by spinal methiothepin. These results suggest that a descending analgesic mechanism mediated by the serotonergic system could be activated by central PEA.

Palmitoylethanolamide in CNS health and disease

The existence of acylethanolamides (AEs) in the mammalian brain has been known for decades. Among AEs, palmitoylethanolamide (PEA) is abundant in the central nervous system (CNS) and conspicuously produced by neurons and glial cells. Antihyperalgesic and neuroprotective properties of PEA have been mainly related to the reduction of neuronal firing and to control of inflammation. Growing evidence suggest that PEA may be neuroprotective during CNS neurodegenerative diseases. Advances in the understanding of the physiology and pharmacology of PEA have potentiated its interest as useful biological tool for disease management. Several rapid non-genomic and delayed genomic mechanisms of action have been identified for PEA as peroxisome proliferator-activated receptor (PPAR)-α dependent. First, an early molecular control, through Ca(+2)-activated intermediate- and/or big-conductance K(+) channels opening, drives to rapid neuronal hyperpolarization. This is reinforced by the increase of the inward Cl(-) currents due to the modulation of the gamma aminobutyric acid A receptor and by the desensitization of the transient receptor potential channel type V1. Moreover, the gene transcription-mediated mechanism sustains the long-term anti-inflammatory effects, by reducing pro-inflammatory enzyme expression and increasing neurosteroid synthesis. Overall, the integration of these different modes of action allows PEA to exert an immediate and prolonged efficacious control in neuron signaling either on inflammatory process or neuronal excitability, maintaining cellular homeostasis. In this review, we will discuss the effect of PEA on metabolism, behavior, inflammation and pain perception, related to the control of central functions and the emerging evidence demonstrating its therapeutic efficacy in several neurodegenerative diseases.

Mast cells, glia and neuroinflammation: partners in crime?

Glia and microglia in particular elaborate pro-inflammatory molecules that play key roles in central nervous system (CNS) disorders from neuropathic pain and epilepsy to neurodegenerative diseases. Microglia respond also to pro-inflammatory signals released from other non-neuronal cells, mainly those of immune origin such as mast cells. The latter are found in most tissues, are CNS resident, and traverse the blood-spinal cord and blood-brain barriers when barrier compromise results from CNS pathology. Growing evidence of mast cell-glia communication opens new perspectives for the development of therapies targeting neuroinflammation by differentially modulating activation of non-neuronal cells that normally control neuronal sensitization - both peripherally and centrally. Mast cells and glia possess endogenous homeostatic mechanisms/molecules that can be up-regulated as a result of tissue damage or stimulation of inflammatory responses. Such molecules include the N-acylethanolamine family. One such member, N-palmitoylethanolamine is proposed to have a key role in maintenance of cellular homeostasis in the face of external stressors provoking, for example, inflammation. N-Palmitoylethanolamine has proven efficacious in mast-cell-mediated experimental models of acute and neurogenic inflammation. This review will provide an overview of recent progress relating to the pathobiology of neuroinflammation, the role of microglia, neuroimmune interactions involving mast cells and the possibility that mast cell-microglia cross-talk contributes to the exacerbation of acute symptoms of chronic neurodegenerative disease and accelerates disease progression, as well as promoting pain transmission pathways. We will conclude by considering the therapeutic potential of treating systemic inflammation or blockade of signalling pathways from the periphery to the brain in such settings.

Targeting inflammation: new therapeutic approaches in chronic kidney disease (CKD)

Chronic inflammation and oxidative stress, features that are closely associated with nuclear factor (NF-κB) activation, play a key role in the development and progression of chronic kidney disease (CKD). Several animal models and clinical trials have clearly demonstrated the effectiveness of angiotensin-converting enzyme inhibitor (ACEI) or angiotensin receptor blocker (ARB) therapy to improve glomerular/tubulointerstitial damage, reduce proteinuria, and decrease CKD progression, but CKD treatment still represents a clinical challenge. Bardoxolone methyl, a first-in-class oral Nrf-2 (nuclear factor erythroid 2-related factor 2) agonist that until recently showed considerable potential for the management of a range of chronic diseases, had been shown to improve kidney function in patients with advanced diabetic nephropathy (DN) with few adverse events in a phase 2 trial, but a large phase 3 study in patients with diabetes and CKD was halted due to emerging toxicity and death in a number of patients. Instead, palmitoylethanolamide (PEA) a member of the fatty acid ethanolamine family, is a novel non-steroidal, kidney friendly anti-inflammatory and anti-fibrotic agent with a well-documented safety profile, that may represent a potential candidate in treating CKD probably by a combination of pharmacological properties, including some activity at the peroxisome proliferator activated receptor alpha (PPAR-α). The aim of this review is to discuss new therapeutic approaches for the treatment of CKD, with particular reference to the outcome of two therapies, bardoxolone methyl and PEA, to improve our understanding of which pharmacological properties are responsible for the anti-inflammatory effects necessary for the effective treatment of renal disease.

Metabolomics uncovers dietary omega-3 fatty acid-derived metabolites implicated in anti-nociceptive responses after experimental spinal cord injury

Chronic neuropathic pain is a frequent comorbidity following spinal cord injury (SCI) and often fails to respond to conventional pain management strategies. Preventive administration of docosahexaenoic acid (DHA) or the consumption of a diet rich in omega-3 polyunsaturated fatty acids (O3PUFAs) confers potent prophylaxis against SCI and improves functional recovery. The present study examines whether this novel dietary strategy provides significant antinociceptive benefits in rats experiencing SCI-induced pain. Rats were fed control chow or chow enriched with O3PUFAs for 8weeks before being subjected to sham or cord contusion surgeries, continuing the same diets after surgery for another 8 more weeks. The paw sensitivity to noxious heat was quantified for at least 8weeks post-SCI using the Hargreaves test. We found that SCI rats consuming the preventive O3PUFA-enriched diet exhibited a significant reduction in thermal hyperalgesia compared to those consuming the normal diet. Functional neurometabolomic profiling revealed a distinctive deregulation in the metabolism of endocannabinoids (eCB) and related N-acyl ethanolamines (NAEs) at 8weeks post-SCI. We found that O3PUFAs consumption led to a robust accumulation of novel NAE precursors, including the glycerophospho-containing docosahexaenoyl ethanolamine (DHEA), docosapentaenoyl ethanolamine (DPEA), and eicosapentaenoyl ethanolamine (EPEA). The tissue levels of these metabolites were significantly correlated with the antihyperalgesic phenotype. In addition, rats consuming the O3PUFA-rich diet showed reduced sprouting of nociceptive fibers containing CGRP and dorsal horn neuron p38 mitogen-activated protein kinase (MAPK) expression, well-established biomarkers of pain. The spinal cord levels of inositols were positively correlated with thermal hyperalgesia, supporting their role as biomarkers of chronic neuropathic pain. Notably, the O3PUFA-rich dietary intervention reduced the levels of these metabolites. Collectively, these results demonstrate the prophylactic value of dietary O3PUFA against SCI-mediated chronic pain.

Glia and mast cells as targets for palmitoylethanolamide, an anti-inflammatory and neuroprotective lipid mediator

Glia are key players in a number of nervous system disorders. Besides releasing glial and neuronal signaling molecules directed to cellular homeostasis, glia respond also to pro-inflammatory signals released from immune-related cells, with the mast cell being of particular interest. A proposed mast cell-glia communication may open new perspectives for designing therapies to target neuroinflammation by differentially modulating activation of non-neuronal cells normally controlling neuronal sensitization-both peripherally and centrally. Mast cells and glia possess endogenous homeostatic mechanisms/molecules that can be upregulated as a result of tissue damage or stimulation of inflammatory responses. Such molecules include the N-acylethanolamines, whose principal family members are the endocannabinoid N-arachidonoylethanolamine (anandamide), and its congeners N-stearoylethanolamine, N-oleoylethanolamine, and N-palmitoylethanolamine (PEA). A key role of PEA may be to maintain cellular homeostasis when faced with external stressors provoking, for example, inflammation: PEA is produced and hydrolyzed by microglia, it downmodulates mast cell activation, it increases in glutamate-treated neocortical neurons ex vivo and in injured cortex, and PEA levels increase in the spinal cord of mice with chronic relapsing experimental allergic encephalomyelitis. Applied exogenously, PEA has proven efficacious in mast cell-mediated experimental models of acute and neurogenic inflammation. This fatty acid amide possesses also neuroprotective effects, for example, in a model of spinal cord trauma, in a delayed post-glutamate paradigm of excitotoxic death, and against amyloid β-peptide-induced learning and memory impairment in mice. These actions may be mediated by PEA acting through "receptor pleiotropism," i.e., both direct and indirect interactions of PEA with different receptor targets, e.g., cannabinoid CB2 and peroxisome proliferator-activated receptor-alpha.

Mast cell-glia axis in neuroinflammation and therapeutic potential of the anandamide congener palmitoylethanolamide

Communication between the immune and nervous systems depends a great deal on pro-inflammatory cytokines. Both astroglia and microglia, in particular, constitute an important source of inflammatory mediators and may have fundamental roles in central nervous system (CNS) disorders from neuropathic pain and epilepsy to neurodegenerative diseases. Glial cells respond also to pro-inflammatory signals released from cells of immune origin. In this context, mast cells are of particular relevance. These immune-related cells, while resident in the CNS, are able to cross a compromised blood-spinal cord and blood-brain barrier in cases of CNS pathology. Emerging evidence suggests the possibility of mast cell-glia communication, and opens exciting new perspectives for designing therapies to target neuroinflammation by differentially modulating the activation of non-neuronal cells normally controlling neuronal sensitization-both peripherally and centrally. This review aims to provide an overview of recent progress relating to the pathobiology of neuroinflammation, the role of glia, neuro-immune interactions involving mast cells and the possibility that glia-mast cell interactions contribute to exacerbation of acute symptoms of chronic neurodegenerative disease and accelerated disease progression, as well as promotion of pain transmission pathways. Using this background as a starting point for discussion, we will consider the therapeutic potential of naturally occurring fatty acid ethanolamides, such as palmitoylethanolamide in treating systemic inflammation or blockade of signalling pathways from the periphery to the brain in such settings.

Palmitoylethanolamide reduces early renal dysfunction and injury caused by experimental ischemia and reperfusion in mice

This study was designed to assess a protective effect of palmitoylethanolamide (PEA) in the development of inflammation after ischemia-reperfusion injury of the kidney. Moreover, to suggest a possible mechanism, renal ischemia-reperfusion was performed in mice with targeted disruption of peroxisome proliferator-activated receptor α (PPAR-α) gene (PPAR-αKO) to explain whether the observed PEA effect was dependent on PPAR-α pathway. Peroxisome proliferator-activated receptor-αKO and littermate wild-type controls (PPAR-αWT) were subjected to bilateral renal artery occlusion (30 min) and reperfusion (6 h) and received PEA (10 mg/kg i.p.) 15 min before release of clamps. Serum and urinary indicators of renal dysfunction and tubular and reperfusion injury were measured, specifically serum urea, creatinine, aspartate aminotransferase and γ-glutamyl transferase, and creatinine clearance. In addition, renal sections were used for histological scoring of renal injury and for immunologic evidence of nitrotyrosine formation, poly[adenosine diphosphate-ribose] (PAR), and adhesion molecules expression. The oxidative stress-sensitive nuclear factor κB signaling pathway was also investigated by Western blot analysis. Kidney myeloperoxidase activity and malondialdehyde levels were measured for assessment of polymorphonuclear leukocyte cell infiltration and lipid peroxidation, respectively. Apoptotic mechanisms were also investigated. Moreover, the infiltration and activation of mast cells were explored. In vivo, PEA administration during ischemia significantly reduced the increase in (i) creatinine, γ-glutamyl transferase, aspartate aminotransferase; (ii) nuclear translocation of nuclear factor κB p65; (iii) kidney myeloperoxidase activity and malondialdehyde levels; (iv) nitrotyrosine, PAR, and adhesion molecules expression; (v) the infiltration and activation of mast cells; and (vi) apoptosis. Our results clearly demonstrate that PEA significantly attenuated the degree of renal dysfunction, injury, and inflammation caused by ischemia-reperfusion injury. Moreover, the positive effects of PEA were at least in part dependent on PPAR-α pathway.

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.

Inhibitory effect of topical adelmidrol on antigen-induced skin wheal and mast cell behavior in a canine model of allergic dermatitis

BACKGROUND

Adelmidrol is a semisynthetic derivative of azelaic acid and analogue of the anti-inflammatory compound palmitoylethanolamide (PEA). Based upon its physicochemical properties, adelmidrol is suitable for topical application. The main objective of the present study was to evaluate the efficacy of a topical adelmidrol emulsion on early and late inflammatory responses in hypersensitive dogs. Repeated intradermal injections of Ascaris suum extract were performed in both lateral thoracic areas of six conscious hypersensitive Beagle dogs, topically treated during 8 consecutive days. Adelmidrol (2%) was applied to one side and vehicle to the other. 24 hours after the last antigen challenge, two biopsies (adelmidrol- and vehicle-treated side) were obtained for each dog at the antigen injection site.

RESULTS

A significant reduction in the antigen-induced wheal areas was observed on the 4th and 7th day of adelmidrol treatment. Moreover, cutaneous mast cell numbers were significantly decreased in biopsies obtained after 8 consecutive days of topical adelmidrol treatment.

CONCLUSIONS

The results obtained in the present study show that topical treatment with adelmidrol might represent a new therapeutic tool in controlling the early and late allergic inflammatory skin responses in companion animals.

Administration of palmitoylethanolamide (PEA) protects the neurovascular unit and reduces secondary injury after traumatic brain injury in mice

Traumatic brain injury (TBI) is a major cause of preventable death and morbidity in young adults. This complex condition is characterized by significant blood brain barrier leakage that stems from cerebral ischemia, inflammation, and redox imbalances in the traumatic penumbra of the injured brain. Recovery of function after TBI is partly through neuronal plasticity. In order to test whether treatments that enhance plasticity might improve functional recovery, a controlled cortical impact (CCI) in adult mice, as a model of TBI, in which a controlled cortical impactor produced full thickness lesions of the forelimb region of the sensorimotor cortex, was performed. Once trauma has occurred, combating these exacerbations is the keystone of an effective TBI therapy. The endogenous fatty acid palmitoylethanolamide (PEA) is one of the members of N-acyl-ethanolamines family that maintain not only redox balance but also inhibit the mechanisms of secondary injury. Therefore, we tested whether PEA shows efficacy in a mice model of experimental TBI. PEA treatment is able to reduced edema and brain infractions as evidenced by decreased 2,3,5-triphenyltetrazolium chloride staining across brain sections. PEA-mediated improvements in tissues histology shown by reduction of lesion size and improvement in apoptosis level further support the efficacy of PEA therapy. The PEA treatment blocked infiltration of astrocytes and restored CCI-mediated reduced expression of PAR, nitrotyrosine, iNOS, chymase, tryptase, CD11b and GFAP. PEA inhibited the TBI-mediated decrease in the expression of pJNK and NF-κB. PEA-treated injured animals improved neurobehavioral functions as evaluated by behavioral tests.

Therapeutic utility of palmitoylethanolamide in the treatment of neuropathic pain associated with various pathological conditions: a case series

Palmitoylethanolamide (PEA), an endogenous fatty acid amide, has been demonstrated to bind to a receptor in the cell nucleus - the peroxisome proliferator-activated receptor - and performs a great variety of biological functions related to chronic and neuropathic pain and inflammation, as has been demonstrated in clinical trials. These include peripheral neuropathies such as diabetic neuropathy, chemotherapy-induced peripheral neuropathy, carpal tunnel syndrome, sciatic pain, osteoarthritis, low-back pain, failed back surgery syndrome, dental pains, neuropathic pain in stroke and multiple sclerosis, chronic pelvic pain, postherpetic neuralgia, and vaginal pains. Probably due to the fact that PEA is an endogenous modulator as well as a compound in food, such as eggs and milk, no serious side effects have been reported, nor have drug-drug interactions. This article presents a case series describing the application and potential efficacy and safety of PEA in the treatment of various syndromes associated with chronic pain that is poorly responsive to standard therapies.

Reduction of ischemic brain injury by administration of palmitoylethanolamide after transient middle cerebral artery occlusion in rats

Stroke is the third leading cause of death and the leading cause of long-term disability in adults. Current therapeutic strategies for stroke, including thrombolytic drugs, such as tissue plasminogen activator offer great promise for the treatment, but complimentary neuroprotective treatments are likely to provide a better outcome. To counteract the ischemic brain injury in mice, a new therapeutic approach has been employed by using palmitoylethanolamide (PEA). PEA is one of the members of N-acyl-ethanolamine family maintain not only redox balance but also inhibit the mechanisms of secondary injury on ischemic brain injury. Treatment of the middle cerebral artery occlusion (MCAo)-induced animals with PEA reduced edema and brain infractions as evidenced by decreased 2,3,5-triphenyltetrazolium chloride (TTC) staining across brain sections. PEA-mediated improvements in tissues histology shown by reduction of lesion size and improvement in apoptosis level (assayed by Bax and Bcl-2) further support the efficacy of PEA therapy. We demonstrated that PEA treatment blocked infiltration of astrocytes and restored MCAo-mediated reduced expression of PAR, nitrotyrosine, iNOS, chymase, tryptase, growth factors (BDNF and GDNF) and GFAP. PEA also inhibited the MCAo-mediated increased expression of pJNK, NF-κB, and degradation of IκB-α. PEA-treated injured animals improved neurobehavioral functions as evaluated by motor deficits. Based on these findings we propose that PEA would be useful in lowering the risk of damage or improving function in ischemia-reperfusion brain injury-related disorders.

The role of the immune system in the generation of neuropathic pain

Persistent pain is a sequela of several neurological conditions with a primary immune basis, such as Guillain-Barré syndrome and multiple sclerosis. Additionally, diverse forms of injury to the peripheral or the central nervous systems--whether traumatic, metabolic, or toxic--result in substantial recruitment and activation of immune cells. This response involves the innate immune system, but evidence also exists of T-lymphocyte recruitment, and in some patient cohorts antibodies to neuronal antigens have been reported. Mediators released by immune cells, such as cytokines, sensitise nociceptive signalling in the peripheral and central nervous systems. Preclinical data suggest an immune pathogenesis of neuropathic pain, but clinical evidence of a central role of the immune system is less clear. An important challenge for the future is to establish to what extent this immune response initiates or maintains neuropathic pain in patients and thus whether it is amenable to therapy.

Neuroprotective activities of palmitoylethanolamide in an animal model of Parkinson's disease

The biochemical and cellular changes that occur following treatment with 1-methyl-4-phenyl-1,2,3,6-tetrahyropyridine (MPTP) are remarkably similar to that seen in idiopathic Parkinson's disease (PD). PD is characterized by the degeneration of dopaminergic nigrostriatal neurons, which results in disabling motor disturbances. Activation of glial cells and the consequent neuroinflammatory response is increasingly recognized as a prominent neuropathological feature of PD. There is currently no effective disease-modifying therapy. Targeting the signaling pathways in glial cells responsible for neuroinflammation represents a promising new therapeutic approach designed to preserve remaining neurons in PD. Chronic treatment with palmitoylethanolamide (PEA, 10 mg/kg, i.p.), initiated 24 hr after MPTP injection (20 mg/kg), protected against MPTP-induced loss of tyrosine hydroxylase positive neurons in the substantia nigra pars compacta. Treatment with PEA reduced MPTP-induced microglial activation, the number of GFAP-positive astrocytes and S100β overexpression, and protected against the alterations of microtubule-associated protein 2a,b-, dopamine transporter-, nNOS- positive cells in the substantia nigra. Furthermore, chronic PEA reversed MPTP-associated motor deficits, as revealed by the analysis of forepaw step width and percentage of faults. Genetic ablation of peroxisome proliferator activated receptor (PPAR)-α in PPAR-αKO mice exacerbated MPTP systemic toxicity, while PEA-induced neuroprotection seemed be partially PPARα-dependent. The effects of PEA on molecules typically involved in apoptotic pathways were also analyzed. Our results indicate that PEA protects against MPTP-induced neurotoxicity and the ensuing functional deficits even when administered once the insult has been initiated.

The fatty acid amide hydrolase inhibitor URB597 exerts anti-inflammatory effects in hippocampus of aged rats and restores an age-related deficit in long-term potentiation

BACKGROUND

Several factors contribute to the deterioration in synaptic plasticity which accompanies age and one of these is neuroinflammation. This is characterized by increased microglial activation associated with increased production of proinflammatory cytokines like interleukin-1β (IL-1β). In aged rats these neuroinflammatory changes are associated with a decreased ability of animals to sustain long-term potentiation (LTP) in the dentate gyrus. Importantly, treatment of aged rats with agents which possess anti-inflammatory properties to decrease microglial activation, improves LTP. It is known that endocannabinoids, such as anandamide (AEA), have anti-inflammatory properties and therefore have the potential to decrease the age-related microglial activation. However, endocannabinoids are extremely labile and are hydrolyzed quickly after production. Here we investigated the possibility that inhibiting the degradation of endocannabinoids with the fatty acid amide hydrolase (FAAH) inhibitor, URB597, could ameliorate age-related increases in microglial activation and the associated decrease in LTP.

METHODS

Young and aged rats received subcutaneous injections of the FAAH inhibitor URB597 every second day and controls which received subcutaneous injections of 30% DMSO-saline every second day for 28 days. Long-term potentiation was recorded on day 28 and the animals were sacrificed. Brain tissue was analyzed for markers of microglial activation by PCR and for levels of endocannabinoids by liquid chromatography coupled to tandem mass spectrometry.

RESULTS

The data indicate that expression of markers of microglial activation, MHCII, and CD68 mRNA, were increased in the hippocampus of aged, compared with young, rats and that these changes were associated with increased expression of the proinflammatory cytokines interleukin (IL)-1β and tumor necrosis factor-α (TNFα) which were attenuated by treatment with URB597. Coupled with these changes, we observed an age-related decrease in LTP in the dentate gyrus which was partially restored in URB597-treated aged rats. The data suggest that enhancement of levels of endocannabinoids in the brain by URB597 has beneficial effects on synaptic function, perhaps by modulating microglial activation.

Microglia and mast cells: two tracks on the road to neuroinflammation

One of the more important recent advances in neuroscience research is the understanding that there is extensive communication between the immune system and the central nervous system (CNS). Proinflammatory cytokines play a key role in this communication. The emerging realization is that glia and microglia, in particular, (which are the brain's resident macrophages), constitute an important source of inflammatory mediators and may have fundamental roles in CNS disorders from neuropathic pain and epilepsy to neurodegenerative diseases. Microglia respond also to proinflammatory signals released from other non-neuronal cells, principally those of immune origin. Mast cells are of particular relevance in this context. These immunity-related cells, while resident in the CNS, are capable of migrating across the blood-spinal cord and blood-brain barriers in situations where the barrier is compromised as a result of CNS pathology. Emerging evidence suggests the possibility of mast cell-glia communications and opens exciting new perspectives for designing therapies to target neuroinflammation by differentially modulating the activation of non-neuronal cells normally controlling neuronal sensitization, both peripherally and centrally. This review aims to provide an overview of recent progress relating to the pathobiology of neuroinflammation, the role of microglia, neuroimmune interactions involving mast cells, in particular, and the possibility that mast cell-microglia crosstalk may contribute to the exacerbation of acute symptoms of chronic neurodegenerative disease and accelerate disease progression, as well as promote pain transmission pathways. We conclude by considering the therapeutic potential of treating systemic inflammation or blockade of signaling pathways from the periphery to the brain in such settings.

Multimodal stepped care approach with acupuncture and PPAR-α agonist palmitoylethanolamide in the treatment of a patient with multiple sclerosis and central neuropathic pain

Central neuropathic pain is a common debilitating symptom in patients with multiple sclerosis. Side effects of analgesics often limit reaching therapeutic dosages. In this case report, a 61-year-old woman with chronic central neuropathic pain due to multiple sclerosis is described. Acupuncture could only partly and temporarily reduce the pain. However, after adding the natural compound palmitoylethanolamide, a glial modulator and peroxisome proliferator-activated receptor-α agonist, pain reduction was more pronounced and the interval between acupuncture sessions could be increased. A multimodal stepped care approach is demonstrated, with acupuncture and palmitoylethanolamide both influencing non-neuronal cells, such as activated glial cells, which are key factors in the development and maintenance of neuropathic pain.