Site-Specific and Time-Dependent Activation of the Endocannabinoid System after Transection of Long-Range Projections

Abstract

BackgroundAfter 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).MethodsIn 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).ResultsUsing 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.ConclusionNeuronal 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.

Intrinsic Up-Regulation of 2-AG Favors an Area Specific Neuronal Survival in Different In Vitro Models of Neuronal Damage

“…Interestingly, we observed no alteration in the amount of CB 1 protein in the DG 24 hpl, the primary target of 2-AG [31]. Recent reports found a decrease in CB 1 by internalization or downregulation after prolonged 2-AG stimulation in coronal brain section by [ 35 S] GTPγS binding [61].…”

“…We focused on intrinsic 2-AG regulation after a model of long range projection damage, the perforant pathway transaction in OHSC. This model was described in detail recently [31] allowing clear differentiation of anterograde (DG), retrograde (EC) and more distant area (CA1) changes induced by axonal injury of long range projections without leading to neuronal cell death. At the direct axonal lesion site no changes of 2-AG were observed.…”

“…Lipid extraction has been carried out as previously described [30], [31]. Briefly, 70 µl ice cold H 2 O was added to the sample prior to homogenation by a mixer mill 400 (Retsch, Haan, Germany) for 90 sec at 25 Hz.…”

Effects of parabolic flight and spaceflight on the endocannabinoid system in humans

“…Other structurally related fatty acids, such as palmitoylethanolamide and oleoylethanolamide, are part of the same chemical group, the N-acylethanolamines, but bind as well to other receptors, such as the transient receptor potential vanilloid type 1 receptor system or the G-protein-coupled receptor GPR55, and have potentiated effects (entourage effects) on anand amide (Ryberg et al, 2007;Ho et al, 2008;Kallendrusch et al, 2012).…”

Daytime-Dependent Changes of Cannabinoid Receptor Type 1 and Type 2 Expression in Rat Liver

“…Intensities of individual protein bands were normalized against the vinculin signal. The specificity of CB 1 antibody was given as reported earlier [ 73 , 74 ].…”