Palmitoylethanolamide Modulation of Microglia Activation: Characterization of Mechanisms of Action and Implication for Its Neuroprotective Effects

Abstract

Palmitoylethanolamide (PEA) is an endogenous lipid produced on demand by neurons and glial cells that displays neuroprotective properties. It is well known that inflammation and neuronal damage are strictly related processes and that microglia play a pivotal role in their regulation. The aim of the present work was to assess whether PEA could exert its neuroprotective and anti-inflammatory effects through the modulation of microglia reactive phenotypes. In N9 microglial cells, the pre-incubation with PEA blunted the increase of M1 pro-inflammatory markers induced by lipopolysaccharide (LPS), concomitantly increasing those M2 anti-inflammatory markers. Images of microglial cells were processed to obtain a set of morphological parameters that highlighted the ability of PEA to inhibit the LPS-induced M1 polarization and suggested that PEA might induce the anti-inflammatory M2a phenotype. Functionally, PEA prevented Ca2+ transients in both N9 cells and primary microglia and antagonized the neuronal hyperexcitability induced by LPS, as revealed by multi-electrode array (MEA) measurements on primary cortical cultures of neurons, microglia, and astrocyte. Finally, the investigation of the molecular pathway indicated that PEA effects are not mediated by toll-like receptor 4 (TLR4); on the contrary, a partial involvement of cannabinoid type 2 receptor (CB2R) was shown by using a selective receptor inverse agonist.

Hexarelin Modulation of MAPK and PI3K/Akt Pathways in Neuro-2A Cells Inhibits Hydrogen Peroxide—Induced Apoptotic Toxicity

“…The number of cells in each field was used for normalizing data of skeleton analysis, which in turn was used to quantify endpoints and process length [ 28 , 29 ], since the loss of ramifications is a typical characteristic of morphological cytoskeletal changes in apoptosis. Briefly, Analyze Skeleton Plugin was applied to skeleton images obtained after a series of ImageJ plugin protocols of original photomicrographs, as described in Material and Methods, and shown in Figure 12.…”

“…Fractal dimension (D) is an index of cell complexity pattern which is used to identify cellular forms ranging from simple rounded to complex branched (Figure 13B) [ 29 , 30 ]. As shown in Figure 6 A, H 2 O 2 significantly decreased D ( p < 0.001) compared with the control, indicating a reduced branch complexity, according to skeleton analysis.…”

“…The lacunarity values of cells treated with 100 µM H 2 O 2 alone, which ranged from 0.12 to 0.38, were significantly smaller than those of the control group. Lacunarity is a property of the soma based on the heterogeneity or translational and rotational invariance in a shape (Figure 13C); lower lacunarity values indicate a loss of shape heterogeneity [ 29 , 30 ]. Hexarelin antagonized the effects of H 2 O 2 , since cells treated with their combination showed values ranging 0.33 to 0.67, significantly greater ( p < 0.001) compared to those treated with H 2 O 2 alone ( Figure 6 B).…”

Successful and Unsuccessful Brain Aging in Pets: Pathophysiological Mechanisms behind Clinical Signs and Potential Benefits from Palmitoylethanolamide Nutritional Intervention

“…These anti-inflammatory and neuroprotective effects are likely due to the ability of PEA to interact with the endocannabinoid system [223] and partially involve the CB2 receptor [222]. Under some circumstances, PEA may potentiate the actions of the canonical endocannabinoids, AEA and 2-AG, by increasing their levels [224].…”

N-acylethanolamine regulation of TLR3-induced hyperthermia and neuroinflammatory gene expression: A role for PPARα

“…N-acylethanolamine acid amidase (NAAA) is a further metabolic pathway for OEA and PEA, inhibition of which elicits potent immunosuppressive effects ( Alhouayek et al, 2015 ; Piomelli et al, 2020 ; Skaper et al, 2015 ; Solorzano et al, 2009 ). PEA reduces TLR4-induced increases in TNF-α production and IL-6 and iNOS expression in macrophages ( Li et al, 2012 ; Solorzano et al, 2009 ) and inhibits TLR4-induced pro-inflammatory M1 microglia while augmenting anti-inflammatory M2a microglia ( D'Aloia et al, 2021 ). OEA decreased TLR4-induced increases in expression of pro-inflammatory cytokines iNOS and COX-2 in macrophages ( Fan et al, 2014 ; Yang et al, 2016 ).…”