N-Arachidonoyl-l-Serine is Neuroprotective after Traumatic Brain Injury by Reducing Apoptosis

Abstract

N-arachidonoyl-L-serine (AraS) is a brain component structurally related to the endocannabinoid family. We investigated the neuroprotective effects of AraS following closed head injury induced by weight drop onto the exposed fronto-parietal skull and the mechanisms involved. A single injection of AraS following injury led to a significant improvement in functional outcome, and to reduced edema and lesion volume compared with vehicle. Specific antagonists to CB2 receptors, transient receptor potential vanilloid 1 (TRPV1) or large conductance calcium-activated potassium (BK) channels reversed these effects. Specific binding assays did not indicate binding of AraS to the GPR55 cannabinoid receptor. N-arachidonoyl-L-serine blocked the attenuation in phosphorylated extracellular-signal-regulated kinase 1/2 (ERK) levels and led to an increase in pAkt in both the ipsilateral and contralateral cortices. Increased levels of the prosurvival factor Bcl-xL were evident 24 hours after injury in AraS-treated mice, followed by a 30% reduction in caspase-3 activity, measured 3 days after injury. Treatment with a CB2 antagonist, but not with a CB1 antagonist, reversed this effect. Our results suggest that administration of AraS leads to neuroprotection via ERK and Akt phosphorylation and induction of their downstream antiapoptotic pathways. These protective effects are related mostly to indirect signaling via the CB2R and TRPV1 channels but not through CB1 or GPR55 receptors.

Cannabinoids in Neurodegenerative Disorders and Stroke/Brain Trauma: From Preclinical Models to Clinical Applications

“…In the case of TBI, damage is most commonly caused either by closed (concussion) or open head injury (stab wound). The cannabinoids having beneficial effects in these models included 1) dexanabinol (HU-211) [8][9][10][11], which is a synthetic compound having a chemical structure of a classic cannabinoid but no activity at cannabinoid receptors; 2) nonselective synthetic cannabinoid agonists such as HU-210, the active enantiomer of HU-211 [12], WIN 55,212-2 [13,14], TAK-937 [15,16], and BAY 38-7271 [17,18]; 3) phytocannabinoids such as Δ 9 -tetrahydrocannabinol (Δ 9 -THC) [19], which binds not only CB 1 R and CB 2 R, but also cannabidiol (CBD), which has no affinity at these receptors but was highly active against brain ischemia [20][21][22]; 4) endocannabinoids such as 2-arachidonoylglycerol (2-AG), in particular in TBI induced by closed head injury [23][24][25], but also in experimental ischemia [26], and also anandamide [27] and its related signaling lipids palmitoylethanolamide (PEA) [28], oleoylethanolamide [27], and N-arachidonoyl-L-serine (AraS) [29]; and 5) selective CB 2 R targeting ligands such as O-3853, O-1966, and JWH-133 [30][31][32][33][34][35]. Most of these studies were conducted with the cannabinoid administered at least after the cytotoxic insult [12-19, 21-26, 28-35].…”

“…Most of these studies were conducted with the cannabinoid administered at least after the cytotoxic insult [12-19, 21-26, 28-35]. In most cases, the benefits obtained with these cannabinoid-related compounds (e.g., improved neurological performance, reduced infarct size, edema, BBB disruption, inflammation and gliosis, and control of immunomodulatory responses) involved the activation of CB 1 R (e.g., HU-210 [12], WIN55,212-2 [13,14], TAK-937 [15,16], BAY 38-7271 [17,18], Δ 9 -THC [19], and PEA [36]) and/or CB 2 R (e.g., AraS [29], O-3853, O-1966, and JWH-133 [30][31][32][33][34][35] mice with a genetic deficiency in CB 1 R or, to a lesser extent, CB 2 R. For example, CB 1 -/-mice showed increased infarct size and neurological deficits after tMCAO, concomitant with a reduction in cerebral blood flow and NMDA excitotoxicity [37], and a similar greater vulnerability was also found in TBI models [24], then supporting the protective role of CB 1 R against both pathological conditions. In the case of CB 2 -/-mice, results were controversial, with a study reporting larger cerebral infarction and a worsened neurological function after tMCAO [30], but others describing no differences using permanent MCAO [32,33], despite the notable effects found in pharmacological experiments with compounds selectively activating the CB 2 R [30][31][32][33][34][35].…”

“…In addition, their strong anti-inflammatory profile appears to be one of the most consistent mechanisms leading to reduction of the lesion, by actions affecting resident, vascular, and peripheral cells. It is also important to remark that the benefits of certain cannabinoids in acute stroke and TBI also involve effects on other pharmacological targets, such as the blockade of NMDA receptors (e.g., HU-211 [8][9][10][11]), the activation of 5-HT 1A receptors (e.g., CBD [20][21][22]), and the activation of transient receptor potential vanilloid-type 1 receptors (e.g., PEA [36] and AraS) [29]). It is also possible that part of these beneficial effects may be related to the hypothermic effects of cannabinoids, but it is well known that such effects are CB 1 R-mediated [12,38,39].…”

Humanin Derivatives Inhibit Necrotic Cell Death in Neurons

“…On the basis of the results obtained in vitro, the next step was to assess the protective activity of AGA(C8R)-HNG17 against necrotic cell death in vivo, by using moderate TBI as a model (34,41). In moderate TBI, necrosis was shown to be the predominant mechanism of cellular destruction (42).…”

“…Based on the in vitro results, we next extended our study to include the in vivo model of necrosis-related diseases. Peptide-protective activities were evaluated by using mice to model TBI (34,41), where necrosis is a major cell death pathway under moderate trauma conditions (42). The TBI model uses a weight-drop device that is designed to deliver a standard blow to the cranium, resulting in a controlled cerebral injury.…”