Palmitoylethanolamide stimulation induces allopregnanolone synthesis in C6 Cells and primary astrocytes: involvement of peroxisome-proliferator activated receptor-α

Efficacy and safety of palmitoylethanolamide as an adjunctive treatment for acute mania: A randomized, double-blind, placebo-controlled trial

AIM

Palmitoylethanolamide is an endogenous fatty acid amide with neuroprotective and anti-inflammatory actions. We performed a randomized, double-blind, placebo-controlled clinical trial to investigate the efficacy and safety of palmitoylethanolamide combination therapy in acute mania.

METHODS

Patients in the acute phase of mania were assigned into two parallel groups given either lithium (blood level of 0.8-1.1 mEq/L) and risperidone 3 mg plus palmitoylethanolamide 600 mg or placebo twice per day for 6 weeks. All participants were assessed with the Young Mania Rating Scale (YMRS), Hamilton Depression Rating Scale (HDRS), and Extrapyramidal Symptom Rating Scale (ESRS) at baseline and at weeks 1, 2, 4, and 6.

RESULTS

A total of 63 patients (32 in palmitoylethanolamide and 31 in placebo groups) completed the trial. We found a significant effect for time×treatment interaction on the YMRS score (F = 5.22, d.f. = 2.34, P= 0.004) from baseline to study end point. Results from independent t test showed a significantly greater decrease in YMRS scores in the palmitoylethanolamide group, compared with the placebo group, from baseline to weeks 4 and 6 (P= 0.018 and P= 0.002, respectively). There was no significant difference between palmitoylethanolamide and placebo groups based on ESRS scores or ESRS changes in scores (P>0.05).

CONCLUSIONS

Our findings provide preliminary evidence that palmitoylethanolamide is an effective adjunctive medication that improves manic symptoms and overall clinical status in acute episodes of mania. However, larger sample sizes and more extended follow-up therapy are needed in future studies to confirm our findings.

PPARα Signaling: A Candidate Target in Psychiatric Disorder Management

Peroxisome proliferator-activator receptors (PPARs) regulate lipid and glucose metabolism, control inflammatory processes, and modulate several brain functions. Three PPAR isoforms have been identified, PPARα, PPARβ/δ, and PPARγ, which are expressed in different tissues and cell types. Hereinafter, we focus on PPARα involvement in the pathophysiology of neuropsychiatric and neurodegenerative disorders, which is underscored by PPARα localization in neuronal circuits involved in emotion modulation and stress response, and its role in neurodevelopment and neuroinflammation. A multiplicity of downstream pathways modulated by PPARα activation, including glutamatergic neurotransmission, upregulation of brain-derived neurotrophic factor, and neurosteroidogenic effects, encompass mechanisms underlying behavioral regulation. Modulation of dopamine neuronal firing in the ventral tegmental area likely contributes to PPARα effects in depression, anhedonia, and autism spectrum disorder (ASD). Based on robust preclinical evidence and the initial results of clinical studies, future clinical trials should assess the efficacy of PPARα agonists in the treatment of mood and neurodevelopmental disorders, such as depression, schizophrenia, and ASD.

Palmitoylethanolamide dampens neuroinflammation and anxiety-like behavior in obese mice

High-fat diet (HFD) consumption leads to obesity and a chronic state of low-grade inflammation, named metainflammation. Notably, metainflammation contributes to neuroinflammation due to the increased levels of circulating free fatty acids and cytokines. It indicates a strict interplay between peripheral and central counterparts in the pathogenic mechanisms of obesity-related mood disorders. In this context, the impairment of internal hypothalamic circuitry runs in tandem with the alteration of other brain areas associated with emotional processing (i.e., hippocampus and amygdala). Palmitoylethanolamide (PEA), an endogenous lipid mediator belonging to the N-acylethanolamines family, has been extensively studied for its pleiotropic effects both at central and peripheral level. Our study aimed to elucidate PEA capability in limiting obesity-induced anxiety-like behavior and neuroinflammation-related features in an experimental model of HFD-fed obese mice. PEA treatment promoted an improvement in anxiety-like behavior of obese mice and the systemic inflammation, reducing serum pro-inflammatory mediators (i.e., TNF-α, IL-1β, MCP-1, LPS). In the amygdala, PEA increased dopamine turnover, as well as GABA levels. PEA also counteracted the overactivation of HPA axis, reducing the expression of hypothalamic corticotropin-releasing hormone and its type 1 receptor. Moreover, PEA attenuated the immunoreactivity of Iba-1 and GFAP and reduced pro-inflammatory pathways and cytokine production in both the hypothalamus and hippocampus. This finding, together with the reduced transcription of mast cell markers (chymase 1 and tryptase β2) in the hippocampus, indicated the weakening of immune cell activation underlying the neuroprotective effect of PEA. Obesity-driven neuroinflammation was also associated with the disruption of blood-brain barrier (BBB) in the hippocampus. PEA limited the albumin extravasation and restored tight junction transcription modified by HFD. To gain mechanistic insight, we designed an in vitro model of metabolic injury using human neuroblastoma SH-SY5Y cells insulted by a mix of glucosamine and glucose. Here, PEA directly counteracted inflammation and mitochondrial dysfunction in a PPAR-α-dependent manner since the pharmacological blockade of the receptor reverted its effects. Our results strengthen the therapeutic potential of PEA in obesity-related neuropsychiatric comorbidities, controlling neuroinflammation, BBB disruption, and neurotransmitter imbalance involved in behavioral dysfunctions.

Mechanisms Mediating the Regulation of Peroxisomal Fatty Acid Beta-Oxidation by PPARα

In mammalian cells, two cellular organelles, mitochondria and peroxisomes, share the ability to degrade fatty acid chains. Although each organelle harbors its own fatty acid β-oxidation pathway, a distinct mitochondrial system feeds the oxidative phosphorylation pathway for ATP synthesis. At the same time, the peroxisomal β-oxidation pathway participates in cellular thermogenesis. A scientific milestone in 1965 helped discover the hepatomegaly effect in rat liver by clofibrate, subsequently identified as a peroxisome proliferator in rodents and an activator of the peroxisomal fatty acid β-oxidation pathway. These peroxisome proliferators were later identified as activating ligands of Peroxisome Proliferator-Activated Receptor α (PPARα), cloned in 1990. The ligand-activated heterodimer PPARα/RXRα recognizes a DNA sequence, called PPRE (Peroxisome Proliferator Response Element), corresponding to two half-consensus hexanucleotide motifs, AGGTCA, separated by one nucleotide. Accordingly, the assembled complex containing PPRE/PPARα/RXRα/ligands/Coregulators controls the expression of the genes involved in liver peroxisomal fatty acid β-oxidation. This review mobilizes a considerable number of findings that discuss miscellaneous axes, covering the detailed expression pattern of PPARα in species and tissues, the lessons from several PPARα KO mouse models and the modulation of PPARα function by dietary micronutrients.

Ultramicronized Palmitoylethanolamide (um-PEA): A New Possible Adjuvant Treatment in COVID-19 patients

The Coronavirus Disease-19 (COVID-19) pandemic has caused more than 100,000,000 cases of coronavirus infection in the world in just a year, of which there were 2 million deaths. Its clinical picture is characterized by pulmonary involvement that culminates, in the most severe cases, in acute respiratory distress syndrome (ARDS). However, COVID-19 affects other organs and systems, including cardiovascular, urinary, gastrointestinal, and nervous systems. Currently, unique-drug therapy is not supported by international guidelines. In this context, it is important to resort to adjuvant therapies in combination with traditional pharmacological treatments. Among natural bioactive compounds, palmitoylethanolamide (PEA) seems to have potentially beneficial effects. In fact, the Food and Drug Administration (FDA) authorized an ongoing clinical trial with ultramicronized (um)-PEA as an add-on therapy in the treatment of Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) infection. In support of this hypothesis, in vitro and in vivo studies have highlighted the immunomodulatory, anti-inflammatory, neuroprotective and pain-relieving effects of PEA, especially in its um form. The purpose of this review is to highlight the potential use of um-PEA as an adjuvant treatment in SARS-CoV-2 infection.

Looking for a Treatment for the Early Stage of Alzheimer's Disease: Preclinical Evidence with Co-Ultramicronized Palmitoylethanolamide and Luteolin

BACKGROUND

At the earliest stage of Alzheimer's disease (AD), although patients are still asymptomatic, cerebral alterations have already been triggered. In addition to beta amyloid (Aβ) accumulation, both glial alterations and neuroinflammation have been documented at this stage. Starting treatment at this prodromal AD stage could be a valuable therapeutic strategy. AD requires long-term care; therefore, only compounds with a high safety profile can be used, such as the new formulation containing palmitoylethanolamide and luteolin (co-ultra PEALut) already approved for human use. Therefore, we investigated it in an in vivo pharmacological study that focused on the prodromal stage of AD.

METHODS

We tested the anti-inflammatory and neuroprotective effects of co-ultra PEALut (5 mg/Kg) administered for 14 days in rats that received once, 5 µg Aβ_(1-42) into the hippocampus.

RESULTS

Glial activation and elevated levels of proinflammatory mediators were observed in Aβ-infused rats. Early administration of co-ultra PEALut prevented the Aβ-induced astrogliosis and microgliosis, the upregulation in gene expression of pro-inflammatory cytokines and enzymes, as well as the reduction of mRNA levels BDNF and GDNF. Our findings also highlight an important neuroprotective effect of co-ultra PEALut treatment, which promoted neuronal survival.

CONCLUSIONS

Our results reveal the presence of cellular and molecular modifications in the prodromal stage of AD. Moreover, the data presented here demonstrate the ability of co-ultra PEALut to normalize such Aβ-induced alterations, suggesting it as a valuable therapeutic strategy.

The Novel Role of PPAR Alpha in the Brain: Promising Target in Therapy of Alzheimer's Disease and Other Neurodegenerative Disorders

Peroxisome proliferator activated receptor alpha (PPAR-α) belongs to the family of ligand-regulated nuclear receptors (PPARs). These receptors after heterodimerization with retinoid X receptor (RXR) bind in promotor of target genes to PPAR response elements (PPREs) and act as a potent transcription factors. PPAR-α and other receptors from this family, such as PPAR-β/δ and PPAR-γ are expressed in the brain and other organs and play a significant role in oxidative stress, energy homeostasis, mitochondrial fatty acids metabolism and inflammation. PPAR-α takes part in regulation of genes coding proteins that are involved in glutamate homeostasis and cholinergic/dopaminergic signaling in the brain. Moreover, PPAR-α regulates expression of genes coding enzymes engaged in amyloid precursor protein (APP) metabolism. It activates gene coding of α secretase, which is responsible for non-amyloidogenic pathway of APP degradation. It also down regulates β secretase (BACE-1), the main enzyme responsible for amyloid beta (Aβ) peptide release in Alzheimer Diseases (AD). In AD brain expression of genes of PPAR-α and PPAR-γ coactivator-1 alpha (PGC-1α) is significantly decreased. PPARs are altered not only in AD but in other neurodegenerative/neurodevelopmental and psychiatric disorder. PPAR-α downregulation may decrease anti-oxidative and anti-inflammatory processes and could be responsible for the alteration of fatty acid transport, lipid metabolism and disturbances of mitochondria function in the brain of AD patients. Specific activators of PPAR-α may be important for improvement of brain cells metabolism and cognitive function in neurodegenerative and neurodevelopmental disorders.

Chronic Oral Palmitoylethanolamide Administration Rescues Cognitive Deficit and Reduces Neuroinflammation, Oxidative Stress, and Glutamate Levels in A Transgenic Murine Model of Alzheimer's Disease

N-palmitoylethanolamide (PEA) is a lipid mediator belonging to the class of the N-acylethanolamine. Products containing PEA, also in ultramicronized formulation (um-PEA), are already licensed for use in humans for its analgesic and anti-inflammatory properties, and demonstrated high safety and tolerability. Preclinical studies indicate that PEA, especially in the ultramicronized form, could be a potential therapeutic agent for Alzheimer's disease (AD). In this study, we evaluated the neuroprotective and antioxidant effects of chronic (three months) um-PEA administration in an animal model of AD (3×Tg-AD mice). For translation purposes, the compound has been orally administered. Cognitive performance as well as biochemical markers [(interleukin-16 (IL-16) and tumor necrosis factor- (TNF-)] levels, reactive oxygen species (ROS) production, synaptophysin and glutamate levels) have been evaluated at the end of um-PEA treatment. The results indicate that orally administered um-PEA was adsorbed and distributed in the mice brain. The chronic treatment with um-PEA (100 mg/kg/day for three months) rescued cognitive deficit, restrained neuroinflammation and oxidative stress, and reduced the increase in hippocampal glutamate levels observed in 3×Tg-AD mice. Overall, these data reinforce the concept that um-PEA exerts beneficial effects in 3×Tg-AD mice. The fact that PEA is already licensed for the use in humans strongly supports its rapid translation in clinical practice.

Effects of the glial modulator palmitoylethanolamide on chronic pain intensity and brain function

Background: Chronic neuropathic pain (NP) is a complex disease that results from damage or presumed damage to the somatosensory nervous system. Current treatment regimens are often ineffective. The major impediment in developing effective treatments is our limited understanding of the underlying mechanisms. Preclinical evidence suggests that glial changes are crucial for the development of NP and a recent study reported oscillatory activity differences within the ascending pain pathway at frequencies similar to that of cyclic gliotransmission in NP. Furthermore, there is evidence that glial modifying medications may be effective in treating NP. The aim of this Phase I open-label clinical trial is to determine whether glial modifying medication palmitoylethanolamide (PEA) will reduce NP and whether this is associated with reductions in oscillatory activity within the pain pathway.

Methods: We investigated whether 6 weeks of PEA treatment would reduce pain and infra-slow oscillatory activity within the ascending trigeminal pathway in 22 individuals (17 females) with chronic orofacial NP.

Results: PEA reduced pain in 16 (73%) of the 22 subjects, 11 subjects showed pain reduction of over 20%. Whilst both the responders and non-responders showed reductions in infra-slow oscillatory activity where orofacial nociceptor afferents terminate in the brainstem, only responders displayed reductions in the thalamus. Furthermore, functional connections between the brainstem and thalamus were altered only in responders.

Conclusion: PEA is effective at relieving NP. This reduction is coupled to a reduction in resting oscillations along the ascending pain pathway that are likely driven by rhythmic astrocytic gliotransmission.

Stimulation of Peroxisome Proliferator-Activated Receptor-α by N-Palmitoylethanolamine Engages Allopregnanolone Biosynthesis to Modulate Emotional Behavior

BACKGROUND

The endocannabinoid and neurosteroid systems regulate emotions and stress responses. Activation of peroxisome proliferator-activated receptor (PPAR)-α by the endocannabinoid congener N-palmitoylethanolamine (PEA) regulates pathophysiological systems (e.g., inflammation, oxidative stress) and induces peripheral biosynthesis of allopregnanolone, a gamma-aminobutyric acidergic neurosteroid implicated in mood disorders. However, effects of PPAR-α on emotional behavior are poorly understood.

METHODS

We studied the impact of PPAR-α activation on emotional behavior in a mouse model of posttraumatic stress disorder. Neurosteroid levels before and after PEA treatment were measured by gas chromatography-mass spectrometry in relevant brain regions of socially isolated versus group-housed mice exposed to the contextual fear conditioning test, elevated plus maze test, forced swim test, and tail suspension test. Neurosteroidogenic enzyme levels were quantified in hippocampus by Western blot.

RESULTS

PEA administered in a model of conditioned contextual fear reconsolidation blockade facilitated fear extinction and fear extinction retention and induced marked antidepressive- and anxiolytic-like effects in socially isolated mice with reduced brain allopregnanolone levels. These effects were mimicked by the PPAR-α synthetic agonists, fenofibrate and GW7647, and were prevented by PPAR-α deletion, PPAR-α antagonists, and neurosteroid-enzyme inhibitors. Behavioral improvements correlated with PEA-induced upregulation of PPAR-α, neurosteroidogenic enzyme expression, and normalization of corticolimbic allopregnanolone levels.

CONCLUSIONS

This evidence supports a previously unknown role for PPAR-α in behavior regulation and suggests new strategies for the treatment of neuropsychopathologies characterized by deficient neurosteroidogenesis, including posttraumatic stress disorder and major depressive disorder.

The Potential Benefits of Palmitoylethanolamide in Palliation: A Qualitative Systematic Review

Palmitoylethanolamide (PEA) is a nutraceutical endocannabinoid that was retrospectively discovered in egg yolks. Feeding poor children with known streptococcal infections prevented rheumatic fever. Subsequently, it was found to alter the course of influenza. Unfortunately, there is little known about its pharmacokinetics. Palmitoylethanolamide targets nonclassical cannabinoid receptors rather than CB1 and CB2 receptors. Palmitoylethanolamide will only indirectly activate classical cannabinoid receptors by an entourage effect. There are a significant number of prospective and randomized trials demonstrating the pain-relieving effects of PEA. There is lesser evidence of benefit in patients with nonpain symptoms related to depression, Parkinson disease, strokes, and autism. There are no reported drug-drug interactions and very few reported adverse effects from PEA. Further research is needed to define the palliative benefits to PEA.

Benefits of Fenofibrate in prenatal valproic acid-induced autism spectrum disorder related phenotype in rats

Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder with two major behavioral symptoms i.e. repetitive behavior and social-communication impairment. The unknown etiology of ASD is responsible for the difficulty in identifying the possible therapeutic modulators for ASD. Valproic acid (VPA) is an anticonvulsant drug in both human and rodents with teratogenic effects during pregnancy. Therefore, prenatal exposure of VPA induced autism spectrum disorder like phenotypes in both human and rodents. Peroxisome proliferator-activated receptor-alpha (PPAR-α) is widely localized in the brain. This research investigates the utility of fenofibrate, a selective agonist of PPAR-α in prenatal VPA-induced experimental ASD in Wistar rats. The prenatal VPA has induced social impairment (three chambers social behavior apparatus), repetitive behavior (Y-maze), hyperlocomotion (actophotometer), anxiety (elevated plus maze) and low exploratory activity (hole board test). Also, prenatal VPA treated rats have shown higher levels of oxidative stress (increased in thiobarbituric acid reactive species and decreased in reduced glutathione level) and inflammation (increased in interleukin-6, tumor necrosis factor-α and decreased in interleukin-10) in the cerebellum, brainstem and prefrontal cortex. Treatment with fenofibrate significantly attenuated prenatal VPA-induced social impairment, repetitive behavior, hyperactivity, anxiety, and low exploratory activity. Furthermore, fenofibrate also decreased the prenatal VPA-induced oxidative stress and inflammation in brain regions. Hence, it may be concluded that fenofibrate may provide neurobehavioral and biochemical benefits in prenatal VPA-induced autism phenotypes in rats.

Modulation of the Oxidative Stress and Lipid Peroxidation by Endocannabinoids and Their Lipid Analogues

Growing evidence supports the pivotal role played by oxidative stress in tissue injury development, thus resulting in several pathologies including cardiovascular, renal, neuropsychiatric, and neurodegenerative disorders, all characterized by an altered oxidative status. Reactive oxygen and nitrogen species and lipid peroxidation-derived reactive aldehydes including acrolein, malondialdehyde, and 4-hydroxy-2-nonenal, among others, are the main responsible for cellular and tissue damages occurring in redox-dependent processes. In this scenario, a link between the endocannabinoid system (ECS) and redox homeostasis impairment appears to be crucial. Anandamide and 2-arachidonoylglycerol, the best characterized endocannabinoids, are able to modulate the activity of several antioxidant enzymes through targeting the cannabinoid receptors type 1 and 2 as well as additional receptors such as the transient receptor potential vanilloid 1, the peroxisome proliferator-activated receptor alpha, and the orphan G protein-coupled receptors 18 and 55. Moreover, the endocannabinoids lipid analogues N-acylethanolamines showed to protect cell damage and death from reactive aldehydes-induced oxidative stress by restoring the intracellular oxidants-antioxidants balance. In this review, we will provide a better understanding of the main mechanisms triggered by the cross-talk between the oxidative stress and the ECS, focusing also on the enzymatic and non-enzymatic antioxidants as scavengers of reactive aldehydes and their toxic bioactive adducts.

A Pharmacological Rationale to Reduce the Incidence of Opioid Induced Tolerance and Hyperalgesia: A Review

Chronic pain is an important health and social problem. Misuse and abuse of opioids in chronic non-cancer pain management seem to be a huge problem, in some countries. This could probably affect the normal use of such analgesics in patients in need of them. Basic and clinical researches should find the solution to mitigate the potential damage. Dysregulation of mast cell and microglia activation plays an important role in the pathogenesis and management of chronic pain. Persistent mast cell activation sensitizes nociceptors and initiates central nervous system inflammatory processes, involving microglial cell activation and sensitization of spinal somatosensory neurons. Exposure of mast cells and microglia to opioids is well known to provoke activation of these non-neuronal immune cell populations, thereby contributing to an exacerbation of pro-inflammatory and pro-nociceptive processes and promoting, over the long-term, opioid-induced hyperalgesia and tolerance. This review is intended to provide the reader with an overview of the role for these non-neuronal cells in opioid-induced chronic pain and tolerance as a consequence of prolonged exposure to these drugs. In addition, we will examine a potential strategy with the aim to modulate opioid-induced over-activation of glia and mast cells, based on endogenous defense mechanisms and fatty acid amide signaling molecules.

Pharmacokinetic-pharmacodynamic influence of N-palmitoylethanolamine, arachidonyl-2'-chloroethylamide and WIN 55,212-2 on the anticonvulsant activity of antiepileptic drugs against audiogenic seizures in DBA/2 mice

We evaluated the effects of ACEA (selective cannabinoid (CB)₁ receptor agonist), WIN 55,212-2 mesylate (WIN; non-selective CB₁ and CB₂ receptor agonist) and N-palmitoylethanolamine (PEA; an endogenous fatty acid of ethanolamide) in DBA/2 mice, a genetic model of reflex audiogenic epilepsy. PEA, ACEA or WIN intraperitoneal (i.p.) administration decreased the severity of tonic-clonic seizures. We also studied the effects of PEA, WIN or ACEA after co-administration with NIDA-41020 (CB₁ receptor antagonist) or GW6471 (PPAR-α antagonist) and compared the effects of WIN, ACEA and PEA in order to clarify their mechanisms of action. PEA has anticonvulsant features in DBA/2 mice mainly through PPAR-α and likely indirectly on CB₁ receptors, whereas ACEA and WIN act through CB₁ receptors. The co-administration of ineffective doses of ACEA, PEA and WIN with some antiepileptic drugs (AEDs) was examined in order to identify potential pharmacological interactions in DBA/2 mice. We found that PEA, ACEA and WIN co-administration potentiated the efficacy of carbamazepine, diazepam, felbamate, gabapentin, phenobarbital, topiramate and valproate and PEA only also that of oxcarbazepine and lamotrigine whereas, their co-administration with levetiracetam and phenytoin did not have effects. PEA, ACEA or WIN administration did not significantly influence the total plasma and brain levels of AEDs; therefore, it can be concluded that the observed potentiation was only of pharmacodynamic nature. In conclusion, PEA, ACEA and WIN show anticonvulsant effects in DBA/2 mice and potentiate the effects several AEDs suggesting a possible therapeutic relevance of these drugs and their mechanisms of action.

Palmitoylethanolamide protects mice against 6-OHDA-induced neurotoxicity and endoplasmic reticulum stress: In vivo and in vitro evidence

Several pathogenetic factors have been involved in the onset and progression of Parkinson's disease (PD), including inflammation, oxidative stress, unfolded protein accumulation, and apoptosis. Palmitoylethanolamide (PEA), an endogenous N-acylethanolamine, has been shown to be a neuroprotective and anti-inflammatory molecule, acting as a peroxisome proliferator activated receptor (PPAR)-α agonist. In this study we investigated the effects of PEA on behavioral alterations and the underlying pathogenic mechanisms in the 6-hydroxydopamine (6-OHDA)-induced model of PD in male mice. Additionally, we showed the involvement of PPAR-α in PEA protective effect on SH-SY5Y neuroblastoma against 6-OHDA damage. Here, we report that PEA (3-30mg/kg/days.c.) improved behavioral impairments induced by unilateral intrastriatal injection of 6-OHDA. This effect was accompanied by a significant increase in tyrosine hydroxylase expression at striatal level, indicating PEA preserving effect on dopaminergic neurons. Moreover, we found a reduction in the expression of pro-inflammatory enzymes, i.e. inducible nitric oxide synthase and cyclooxygenase-2, a modulation between pro- and anti-apoptotic markers, suggestive of PEA capability in controlling neuroinflammation and cell death. Interestingly, PEA also showed protective scavenging effect, through superoxide dismutase induction, and dampened unfolding protein response, interfering on glucose-regulated protein 78 expression and PERK-eIF2α pathway. Similar data were found in in vitro studies, where PEA treatment was found to rescue SH-SY5Y neuroblastoma cells from 6-OHDA-induced damage and death, partly by inhibiting endoplasmic reticulum stress detrimental response. Therefore, PEA, counteracting the pathogenetic aspects involved in the development of PD, showed its therapeutic potential, possibly integrating current treatments correcting dopaminergic deficits and motor dysfunction.

TSPO-ligands prevent oxidative damage and inflammatory response in C6 glioma cells by neurosteroid synthesis

Translocator protein 18kDa (TSPO) is predominantly located in the mitochondrial outer membrane, playing an important role in steroidogenesis, inflammation, cell survival and proliferation. Its expression in central nervous system, mainly in glial cells, has been found to be upregulated in neuropathology, and brain injury. In this study, we investigated the anti-oxidative and anti-inflammatory effects of a group of TSPO ligands from the N,N-dialkyl-2-phenylindol-3-ylglyoxylamide class (PIGAs), highlighting the involvement of neurosteroids in their pharmacological effects. To this aim we used a well-known in vitro model of neurosteroidogenesis: the astrocytic C6 glioma cell line, where TSPO expression and localization, as well as cell response to TSPO ligand treatment, have been established. All PIGAs reduced l-buthionine-(S,R)-sulfoximine (BSO)-driven cell cytotoxicity and lipid peroxidation. Moreover, an anti-inflammatory effect was observed due to the reduction of inducible nitric oxide synthase and cyclooxygenase-2 induction in LPS/IFNγ challenged cells. Both effects were blunted by aminoglutethimide (AMG), an inhibitor of pregnenolone synthesis, suggesting neurosteroids' involvement in PIGA protective mechanism. Finally, pregnenolone evaluation in PIGA exposed cells revealed an increase in its synthesis, which was prevented by AMG pre-treatment. These findings indicate that these TSPO ligands reduce oxidative stress and pro-inflammatory enzymes in glial cells through the de novo synthesis of neurosteroids, suggesting that these compounds could be potential new therapeutic tools for the treatment of inflammatory-based neuropathologies with beneficial effects possibly comparable to steroids, but potentially avoiding the negative side effects of long-term therapies with steroid hormones.

Metabolic and Inflammatory Adaptation of Reactive Astrocytes: Role of PPARs

Astrocyte-mediated inflammation is associated with degenerative pathologies such as Alzheimer's and Parkinson's diseases and multiple sclerosis. The acute inflammation and morphological and metabolic changes that astrocytes develop after the insult are known as reactive astroglia or astrogliosis that is an important response to protect and repair the lesion. Astrocytes optimize their metabolism to produce lactate, glutamate, and ketone bodies in order to provide energy to the neurons that are deprived of nutrients upon insult. Firstly, we review the basis of inflammation and morphological changes of the different cell population implicated in reactive gliosis. Next, we discuss the more active metabolic pathways in healthy astrocytes and explain the metabolic response of astrocytes to the insult in different pathologies and which metabolic alterations generate complications in these diseases. We emphasize the role of peroxisome proliferator-activated receptors isotypes in the inflammatory and metabolic adaptation of astrogliosis developed in ischemia or neurodegenerative diseases. Based on results reported in astrocytes and other cells, we resume and hypothesize the effect of peroxisome proliferator-activated receptor (PPAR) activation with ligands on different metabolic pathways in order to supply energy to the neurons. The activation of selective PPAR isotype activity may serve as an input to better understand the role played by these receptors on the metabolic and inflammatory compensation of astrogliosis and might represent an opportunity to develop new therapeutic strategies against traumatic brain injuries and neurodegenerative diseases.

Finasteride Has Regionally Different Effects on Brain Oxidative Stress and Acetylcholinesterase Activity in Acute Thioacetamide-Induced Hepatic Encephalopathy in Rats

Finasteride (FIN) inhibits neurosteroid synthesis and potentially improves the course of hepatic encephalopathy (HE). This study aimed to investigate the effects of FIN on brain oxidative stress and acetylcholinesterase (AchE) activity in acute thioacetamide-induced HE in rats. Male Wistar rats were divided into groups: 1. control; 2. thioacetamide-treated group (TAA; 900 mg/kg); 3. finasteride-treated group (FIN; 150 mg/kg); 4. group treated with FIN and TAA (FIN+TAA). Daily doses of FIN (50 mg/kg) and TAA (300 mg/kg) were administered intraperitoneally during three days and in FIN+TAA group FIN was administered 2h before every dose of TAA. FIN pretreatment prevented TAA-induced rise in malondialdehyde level in the cortex due to restoration of catalase activity and increased expression of superoxide dismutase 1 (SOD1) and induced an increase in malondialdehyde level in the thalamus due to reduction of glutathione peroxidase (GPx) and glutathione reductase (GR) activity. Although FIN pretreatment did not affect malondialdehyde level in hippocampus and caudate nucleus, hippocampal SOD1 expression was higher (p<0.05) and GR activity lower in FIN+TAA vs. TAA group (p<0.05). GPx activity was lower in caudate nucleus in FIN+TAA vs. TAA group (p<0.01). FIN pretreatment prevented TAA-induced rise in AchE activity in the thalamus and caudate nucleus and AchE activity correlates inversely in the thalamus (p<0.05) and positively in caudate nucleus (p<0.01) with malondialdehyde level. FIN has regionally selective effects on oxidative stress and AchE activity in the brain in acute TAA-induced HE in rats. The prooxidant role of FIN in the thalamus may be causally linked with inhibition of AchE.

Antineuropathic profile of N-palmitoylethanolamine in a rat model of oxaliplatin-induced neurotoxicity

Neurotoxicity is a main side effect of the anticancer drug oxaliplatin. The development of a neuropathic syndrome impairs quality of life and potentially results in chemotherapy dose reductions and/or early discontinuation. In the complex pattern of molecular and morphological alterations induced by oxaliplatin in the nervous system, an important activation of glia has been preclinically evidenced. N-Palmitoylethanolamine (PEA) modulates glial cells and exerts antinociceptive effects in several animal models. In order to improve the therapeutic chances for chemotherapy-dependent neuropathy management, the role of PEA was investigated in a rat model of oxaliplatin-induced neuropathy (2.4 mg kg^-1 daily, intraperitoneally). On day 21, a single administration of PEA (30 mg kg^-1 i.p.) was able to reduce oxaliplatin-dependent pain induced by mechanical and thermal stimuli. The repeated treatment with PEA (30 mg kg^-1 daily i.p. for 21 days, from the first oxaliplatin injection) prevented lowering of pain threshold as well as increased pain on suprathreshold stimulation. Ex vivo histological and molecular analysis of dorsal root ganglia, peripheral nerves and spinal cord highlighted neuroprotective effects and glia-activation prevention induced by PEA repeated administration. The protective effect of PEA resulted in the normalization of the electrophysiological activity of the spinal nociceptive neurons. Finally, PEA did not alter the oxaliplatin-induced mortality of the human colon cancer cell line HT-29. The efficacy of PEA in neuropathic pain control and in preventing nervous tissue alteration candidates this endogenous compound as disease modifying agent. These characteristics, joined to the safety profile, suggest the usefulness of PEA in chemotherapy-induced neuropathy.

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.

Micronized palmitoylethanolamide reduces the symptoms of neuropathic pain in diabetic patients

The present study evaluated the effectiveness of micronized palmitoylethanolamide (PEA-m) treatment in reducing the painful symptoms experienced by diabetic patients with peripheral neuropathy. PEA-m, a fatty acid amide of the N-acylethanolamine family, was administered (300 mg twice daily) to 30 diabetic patients suffering from painful diabetic neuropathy. Before treatment start, after 30 and 60 days the following parameters were assessed: painful symptoms of diabetic peripheral neuropathy using the Michigan Neuropathy Screening instrument; intensity of symptoms characteristic of diabetic neuropathic pain by the Total Symptom Score; and intensity of different subcategories of neuropathic pain by the Neuropathic Pain Symptoms Inventory. Hematological and blood chemistry tests to evaluate metabolic control and safety were also performed. Statistical analysis (ANOVA) indicated a highly significant reduction in pain severity (P < 0.0001) and related symptoms (P < 0.0001) evaluated by Michigan Neuropathy Screening instrument, Total Symptom Score, and Neuropathic Pain Symptoms Inventory. Hematological and urine analyses did not reveal any alterations associated with PEA-m treatment, and no serious adverse events were reported. These results suggest that PEA-m could be considered as a promising and well-tolerated new treatment for symptomatology experienced by diabetic patients suffering from peripheral neuropathy.

Voluntary running in young adult mice reduces anxiety-like behavior and increases the accumulation of bioactive lipids in the cerebral cortex

Combinatorial therapies using voluntary exercise and diet supplementation with polyunsaturated fatty acids have synergistic effects benefiting brain function and behavior. Here, we assessed the effects of voluntary exercise on anxiety-like behavior and on total FA accumulation within three brain regions: cortex, hippocampus, and cerebellum of running versus sedentary young adult male C57/BL6J mice. The running group was subjected to one month of voluntary exercise in their home cages, while the sedentary group was kept in their home cages without access to a running wheel. Elevated plus maze (EPM), several behavioral postures and two risk assessment behaviors (RABs) were then measured in both animal groups followed immediately by blood samplings for assessment of corticosterone levels. Brains were then dissected for non-targeted lipidomic analysis of selected brain regions using gas chromatography coupled to mass spectrometry (GC/MS). Results showed that mice in the running group, when examined in the EPM, displayed significantly lower anxiety-like behavior, higher exploratory and risky behaviors, compared to sedentary mice. Notably, we found no differences in blood corticosterone levels between the two groups, suggesting that the different EPM and RAB behaviors were not related to reduced physiological stress in the running mice. Lipidomics analysis revealed a region-specific cortical decrease of the saturated FA: palmitate (C16:0) and a concomitant increase of polyunsaturated FA, arachidonic acid (AA, omega 6-C20: 4) and docosahexaenoic acid (DHA, omega 3-C22: 6), in running mice compared to sedentary controls. Finally, we found that running mice, as opposed to sedentary animals, showed significantly enhanced cortical expression of phospholipase A2 (PLA2) protein, a signaling molecule required in the production of both AA and DHA. In summary, our data support the anxiolytic effects of exercise and provide insights into the molecular processes modulated by exercise that may lead to its beneficial effects on mood.

Spinal cord injury induced changes of nuclear receptors PPARα and LXRβ and modulation with oleic acid/albumin treatment

In previous studies with animal models of spinal cord injury (SCI) pharmacological activation of peroxisome proliferator activated receptors (PPAR) and liver X receptors (LXR) were used to reduce tissue damage and promote behavioral recovery in animal models. We have studied the endogenous expression of the transcription factors PPARα and LXRβ in the chronic stage after SCI in rats. The immunohistochemical investigation revealed a long lasting increase in the level of PPARα in white matter in the vicinity of the lesion site. The source of this signal was identified in a subpopulation of astrocytes outside of the glial scar area. Intrathecal injections of oleic acid/albumin reduced the lesion-induced PPARα immunoreactivity. In addition, ependymal cells displayed a prominent PPARα signal in the non-injured spinal cord, and continued to express the receptor as they proliferated and migrated within the damaged tissue. The nuclear receptor LXRβ was detected at similar levels after SCI as in sham operated animals. We found high levels of immunoreactivity in the gray matter, while in the white matter it was present in subpopulations of astrocytes and oligodendrocytes. Macrophages that had accumulated within the center of the lesion contained LXRβ in their cell nuclei. Possible endogenous functions of PPARα and LXRβ after SCI are discussed, specifically the control of fatty acid and cholesterol metabolism and the regulation of inflammatory reactions.

Blocking the peroxisome proliferator-activated receptor (PPAR): an overview

Peroxisome proliferator-activated receptors (PPARs) have been studied extensively over the last few decades and have been assessed as molecular targets for the development of drugs against metabolic disorders. A rapid increase in understanding of the physiology and pharmacology of these receptors has occurred, together with the identification of novel chemical structures that are able to activate the various PPAR subtypes. More recent evidence suggests that moderate activation of these receptors could be favorable in pathological situations due to a decrease in the side effects brought about by PPAR agonists. PPAR partial agonists and antagonists are interesting tools that are currently used to better elucidate the biological processes modulated by this family of nuclear receptors. Herein we present an overview of the various molecular structures that are able to block each of the PPAR subtypes, with a focus on promising therapeutic applications.

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.

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.

Palmitoylethanolamide protects against the amyloid-β25-35-induced learning and memory impairment in mice, an experimental model of Alzheimer disease

Alzheimer disease (AD) is the most common form of neurodegenerative dementia. Amyloid-β deposition, neurofibrillary tangle formation, and neuro-inflammation are the major pathogenic mechanisms that in concert lead to memory dysfunction and decline of cognition. Palmitoylethanolamide (PEA) is the naturally occurring lipid amide between palmitic acid and ethanolamine. Despite its clear role in inflammation and pain control, only limited in vitro evidence exist about a role for PEA in neurodegenerative diseases. Here we describe the neuroprotective activities of PEA in mice injected intracerebroventricularly with amyloid-β 25-35 (Ab25-35) peptide (9 nmol). We used spatial and non-spatial memory tasks to evaluate learning and memory dysfunctions. Ab25-35 injection significantly impaired spontaneous alternation performances, water maze spatial reference and working-like memory, and novel object recognition test. PEA was administered once a day (3-30 mg/kg, subcutaneously), starting 3 h after Ab25-35, for 1 or 2 weeks. PEA reduced (10 mg/kg) or prevented (30 mg/kg) behavioral impairments induced by Ab25-35 injection. PEA failed to rescue memory deficits induced by Ab25-35 injection in peroxisome proliferator-activated receptor-α (PPAR-α) null mice. GW7647 (2-(4-(2-(1-cyclohexanebutyl)-3-cyclohexylureido)ethyl)phenylthio)-2-methylpropionic acid; 5 mg/kg per day), a synthetic PPAR-α agonist, mimicked the effect of PEA. Acute treatment with PEA was ineffective. According with the neuroprotective profile of PEA observed during behavioral studies, experimental molecular and biochemical markers induced by Ab25-35 injection, such as lipid peroxidation, protein nytrosylation, inducible nitric oxide synthase induction, and caspase3 activation, were reduced by PEA treatment. These data disclose novel findings about the therapeutic potential of PEA, unrevealing a previously unknown therapeutic possibility to treat memory deficits associated with AD.

Site-specific and time-dependent activation of the endocannabinoid system after transection of long-range projections

Background

After focal neuronal injury the endocannabinioid system becomes activated and protects or harms neurons depending on cannabinoid derivates and receptor subtypes. Endocannabinoids (eCBs) play a central role in controlling local responses and influencing neural plasticity and survival. However, little is known about the functional relevance of eCBs in long-range projection damage as observed in stroke or spinal cord injury (SCI).

Methods

In rat organotypic entorhino-hippocampal slice cultures (OHSC) as a relevant and suitable model for investigating projection fibers in the CNS we performed perforant pathway transection (PPT) and subsequently analyzed the spatial and temporal dynamics of eCB levels. This approach allows proper distinction of responses in originating neurons (entorhinal cortex), areas of deafferentiation/anterograde axonal degeneration (dentate gyrus) and putative changes in more distant but synaptically connected subfields (cornu ammonis (CA) 1 region).

Results

Using LC-MS/MS, we measured a strong increase in arachidonoylethanolamide (AEA), oleoylethanolamide (OEA) and palmitoylethanolamide (PEA) levels in the denervation zone (dentate gyrus) 24 hours post lesion (hpl), whereas entorhinal cortex and CA1 region exhibited little if any changes. NAPE-PLD, responsible for biosynthesis of eCBs, was increased early, whereas FAAH, a catabolizing enzyme, was up-regulated 48hpl.

Conclusion

Neuronal damage as assessed by transection of long-range projections apparently provides a strong time-dependent and area-confined signal for de novo synthesis of eCB, presumably to restrict neuronal damage. The present data underlines the importance of activation of the eCB system in CNS pathologies and identifies a novel site-specific intrinsic regulation of eCBs after long-range projection damage.

Implication of allopregnanolone in the antinociceptive effect of N-palmitoylethanolamide in acute or persistent pain

We investigated the involvement of de novo neurosteroid synthesis in the mechanisms underlying the analgesic and antihyperalgesic effects of N-palmitoylethanolamine (PEA) in two models of acute and persistent pain, the formalin test and carrageenan-induced paw edema. The pivotal role of peroxisome proliferator-activated receptor (PPAR)-α in the antinocifensive effect of PEA was confirmed by the lack of this effect in PPAR-α-null mice. PEA antinociceptive activity was partially reduced when the animals were treated with aminoglutethimide or finasteride, implying that de novo neurosteroid synthesis is involved in the effect of PEA. Accordingly, in the spinal cord, the allopregnanolone (ALLO) levels were increased by PEA treatment both in formalin- and carrageenan-exposed mice, as revealed by gas chromatography-mass spectrometry. In agreement with those data, in both pain models, PEA administration in challenged mice specifically restored the expression of two proteins involved in neurosteroidogenensis, the steroidogenic acute regulatory protein (StAR) and cytochrome P450 side-chain cleavage (P450scc) in the ipsilateral horns of spinal cord, without affecting their expression in the contralateral side. These results provide new information about the involvement of de novo neurosteroid synthesis in the modulation of pain behavior by PEA.

Steroidogenic acute regulatory protein expression in the central nervous system

Locally produced neurosteroids are proposed to have many functions in the central nervous system. The identification of the steroidogenic acute regulatory protein in steroid-producing neural cells provides a new tool to understand the sites, regulation, and importance of their synthesis.