N-docosahexaenoylethanolamine reduces neuroinflammation and cognitive impairment after mild traumatic brain injury in rats

Abstract At present, there is a growing interest in the study of the neurotropic activity of polyunsaturated fatty acids ethanolamides (N-acylethanolamines). N-docosahexaenoylethanolamine (DHEA, synaptamide) is an endogenous metabolite and structural analogue of anandamide, a widely studied endocannabinoid derived from arachidonic acid. The results of this study demonstrate that DHEA, when administered subcutaneously (10 mg/kg/day, 7 days), promotes cognitive recovery in rats subjected to mild traumatic brain injury (mTBI). In the cerebral cortex of experimental animals, we analyzed the dynamics of Iba-1-positive microglia activity changes and the expression of pro-inflammatory markers (IL1β, IL6, CD86). We used immortalized mouse microglial cells (SIM-A9) to assess the effects of DHEA on LPS-induced cytokines/ROS/NO/nitrite, as well as on CD206 (anti-inflammatory microglia) and the antioxidant enzyme superoxide dismutase (SOD) production. In vivo and in vitro experiments showed that DHEA: (1) improves indicators of anxiety and long-term memory; (2) inhibits the pro-inflammatory microglial cells activity; (3) decrease the level of pro-inflammatory cytokines/ROS/NO/nitrites; (4) increase CD206 and SOD production. In general, the results of this study indicate that DHEA has a complex effect on the neuroinflammation processes, which indicates its high therapeutic potential

Monoacylglycerol lipase inhibitor JZL184 improves behavior and neural properties in Ts65Dn mice, a model of down syndrome.

Genetic alterations or pharmacological treatments affecting endocannabinoid signaling have profound effects on synaptic and neuronal properties and, under certain conditions, may improve higher brain functions. Down syndrome (DS), a developmental disorder caused by triplication of chromosome 21, is characterized by deficient cognition and inevitable development of the Alzheimer disease (AD) type pathology during aging. Here we used JZL184, a selective inhibitor of monoacylglycerol lipase (MAGL), to examine the effects of chronic MAGL inhibition on the behavioral, biochemical, and synaptic properties of aged Ts65Dn mice, a genetic model of DS. In both Ts65Dn mice and their normosomic (2N) controls, JZL184-treatment increased brain levels of 2-arachidonoylglycerol (2-AG) and decreased levels of its metabolites such as arachidonic acid, prostaglandins PGD2, PGE2, PGFα, and PGJ2. Enhanced spontaneous locomotor activity of Ts65Dn mice was reduced by the JZL184-treatement to the levels observed in 2N animals. Deficient long-term memory was also improved, while short-term and working types of memory were unaffected. Furthermore, reduced hippocampal long-term potentiation (LTP) was increased in the JZL184-treated Ts65Dn mice to the levels observed in 2N mice. Interestingly, changes in synaptic plasticity and behavior were not observed in the JZL184-treated 2N mice suggesting that the treatment specifically attenuated the defects in the trisomic animals. The JZL184-treatment also reduced the levels of Aβ40 and Aβ42, but had no effect on the levels of full length APP and BACE1 in both Ts65Dn and 2N mice. These data show that chronic MAGL inhibition improves the behavior and brain functions in a DS model suggesting that pharmacological targeting of MAGL may be considered as a perspective new approach for improving cognition in DS

Working memory: performance in Y-maze.

<p>A. The baseline rate of spontaneous alternations in Y-maze was lower in the vehicle-treated Ts65Dn vs. 2N mice, reflecting an impairment of working memory. JZL184-treatment had no effect on the performance of both 2N and Ts65Dn mice suggesting no effect on working memory. B. The number of ‘arm entries’ during the Y-maze test was greater in vehicle-treated Ts65Dn vs. 2N mice reflecting increased locomotion of Ts65Dn mice. JZL184-treatment reduced this parameter to the levels seen in 2N animals.</p

Effect of chronic JZL184 treatment on the brain levels of endocannabinoids and their metabolites.

<p>The values are given in percents of the ‘2N Veh’ group.</p>a)<p>p<0.001. Significant difference vs. ‘2N Veh’ group.</p>b)<p>p<0.001. Significant difference vs. ‘Ts65Dn Veh’ group.</p><p>Effect of chronic JZL184 treatment on the brain levels of endocannabinoids and their metabolites.</p

Effects of ZL184-treatment on locomotor activity (A-C) and thigmotactic behavior (D-F).

<p>In the vehicle-treated animals, locomotor activity was significantly increased in Ts65Dn vs. 2N mice. This can be seen from the increased ambulatory distance (A) and ambulatory time (B) and decreased resting time (C) of Ts Veh vs. 2N Veh group. Treatment with JZL184 (8 mg/kg) restored these locomotion parameters to control levels. In addition, Ts65Dn mice exhibited increased thigmotactic behavior which can be seen from an increased percentage of ambulatory distance (D), ambulatory time (E), and resting time (F) on the arena periphery. JZL184 treatment had no effect on these parameters.</p

Long-term potentiation in the CA1 region of hippocampal slices of Ts65Dn and 2N mice.

<p>A: In the vehicle-treated animals, LTP was smaller in Ts65Dn vs. 2N slices. Scale bars: 1 mV; 2 ms. B: In the JZL184-treated mice, there was no difference between the Ts65Dn vs. 2N slices. C: Quantification of the data. JZL184-treatment increased LTP in Ts65Dn mice.</p

Levels of Aβ species in brain samples of mice treated with JZL184 or vehicle.

<p>A: Levels of Aβ40 were significantly increased in the vehicle-treated Ts65Dn vs. 2N mice. JZL184-treatment reduced the levels of Aβ40 in both Ts65Dn and 2N samples. B: Levels of Aβ42 were also greater in Ts65Dn vs 2N samples and were reduced by the JZL184-treatment.</p

Long-term memory: Novel object recognition with the retention period of 24 hours.

<p>A: Time of object exploration during acquisition. There was no difference between the groups, and no effect of JZL184-treatment on the exploration time. B: Testing phase. Left: Time of object exploration during testing was smaller in vehicle-treated Ts65Dn vs. 2N mice. There was no such difference between the JZL184-treated Ts65Dn and 2N groups. Right: Discrimination index was smaller in the vehicle-treated Ts65Dn vs. 2N mice. JZL184-treatment significantly increased the discrimination index in Ts65Dn mice, but had no effect on the performance of their 2N littermates.</p

Short-term memory: Novel place recognition with the retention period of 10 min.

<p>A: Time spent investigating objects during acquisition. There was no difference between the groups. B: Testing phase. Left: Time spent investigating objects during testing. Vehicle-treated Ts65Dn mice spent less time investigating the objects than their littermate 2N controls. There was no such difference in the JZL-treated groups. Right: Discrimination index was smaller in both vehicle- and JZL-treated Ts65Dn vs. 2N groups. Thus, short-term memory was not affected by the JZL184-treatment.</p