Dietary PUFA supplements reduce memory deficits but not CA1 ischemic injury in rats

Selective estrogen receptor activation prior to global cerebral ischemia in female rats impacts microglial activation and anxiety-like behaviors without effects on CA1 neuronal injury

Estrogen receptor (ER) activation by 17-ß estradiol (E2) can attenuate neuronal injury and behavioral impairments following global cerebral ischemia (GCI) in rodents. This study sought to further examine the discrete roles of ERs through characterization of the effects of selective ER activation on post-ischemic pro-inflammatory microglial activation, hippocampal neuronal injury, and anxiety-like behaviors. Forty-six ovariectomized (OVX) adult female Wistar rats received daily s.c injections (100 μg/kg/day) of propylpyrazole triol (PPT; ERα agonist), diarylpropionitrile (DPN; ERβ agonist), G-1 (G-protein coupled ER agonist; GPER), E2 (activating all receptors), or vehicle solution (VEH) for 21 days. After final injection, rats underwent GCI via 4-vessel occlusion (n=8 per group) or sham surgery (n=6, vehicle injections). The Open Field Test (OFT), Elevated Plus Maze (EPM), and Hole Board Test (HBT) assessed anxiety-like behaviors. Microglial activation (Iba1, CD68, CD86) in the basolateral amygdala (BLA), CA1 of the hippocampus, and paraventricular nucleus of the hypothalamus (PVN) was determined 8 days post-ischemia. Compared to sham rats, Iba1 activation and CA1 neuronal injury were increased in all ischemic groups except DPN-treated rats, with PPT-treated ischemic rats also showing increased PVN Iba1-ir expression. Behaviorally, VEH ischemic rats showed slightly elevated anxiety in the EPM compared to sham counterparts, with no significant effects of agonists. While no changes were observed in the OFT, emotion regulation via grooming in the HBT was increased in G-1 rats compared to E2 rats. Our findings support selective ER activation to regulate post-ischemic microglial activation and coping strategies in the HBT, despite minimal impact on hippocampal injury.

Menhaden fish oil attenuates postpartum depression in rat model via inhibition of NLRP3-inflammasome driven inflammatory pathway

Background and aim

Postpartum depression (PPD) is a familiar problem which is associated with about 10–20% of women after child delivery. Fish oil (FO) has a therapeutic potentials to many diseases including mood disorders. However, there is paucity of data on the effects of FO supplementation on PPD rat model. Hence, this study aimed at investigating the potentials of FO in ameliorating depressive-like behaviors in PPD rat by evaluating the involvement of NLRP3-inflammasome.

Experimental procedure

Thirty six virgin adult female rats (n = 6) were randomly divided into six groups; Group 1–3 were normal control (NC), Sham (SHAM) and ovariectomized group (OVX) respectively whereas group 4–6 were PPD rats forced-fed once daily with distilled water (PPD), fish oil (PPD + FO; 9 g/kg) and Fluoxetine (PPD + FLX; 15 mg/kg) respectively from postpartum day 1 and continued for 10 consecutive days. Rats behaviors were evaluated on postpartum day 10 through open field test (OFT) and forced swimming test (FST), followed by biochemical analysis of NLRP3 inflammasome proteins pathway in their brain and determination of neutrophil to lymphocyte ratio (NLR).

Results

PPD-induced rats exhibited high immobility and low swimming time in FST with increased inflammatory status; NLR, IL-1β and NFкB/NLRP3/caspase-1 activity in their hippocampus. However, administration of FO or fluoxetine reversed the aforementioned abnormalities.

Conclusion

In conclusion, 10 days supplementation with FO ameliorated the depressive-like behaviors in PPD rats by targeting the NFкB/NLRP3/caspase-1/IL-1β activity. This has shed light on the potential of NLRP3 as a therapeutic target in treatment of PPD in rats.

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Pioneer study on 10 days effect of Menhaden fish oil in post partum depression rat model.

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Menhaden fish oil attenuates post partum depression in rat model.

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Menhanden fish oil acted through NLRP3 inflammasome pathways.

Models and methods for conditioning the ischemic brain

BACKGROUND

In the last decades the need to find new neuroprotective targets has addressed the researchers to investigate the endogenous molecular mechanisms that brain activates when exposed to a conditioning stimulus. Indeed, conditioning is an adaptive biological process activated by those interventions able to confer resistance to a deleterious brain event through the exposure to a sub-threshold insult. Specifically, preconditioning and postconditioning are realized when the conditioning stimulus is applied before or after, respectively, the harmul ischemia.

AIMS AND RESULTS

The present review will describe the most common methods to induce brain conditioning, with particular regards to surgical, physical exercise, temperature-induced and pharmacological approaches. It has been well recognized that when the subliminal stimulus is delivered after the ischemic insult, the achieved neuroprotection is comparable to that observed in models of ischemic preconditioning. In addition, subjecting the brain to both preconditioning as well as postconditioning did not cause greater protection than each treatment alone.

CONCLUSIONS

The last decades have provided fascinating insights into the mechanisms and potential application of strategies to induce brain conditioning. Since the identification of intrinsic cell-survival pathways should provide more direct opportunities for translational neuroprotection trials, an accurate examination of the different models of preconditioning and postconditioning is mandatory before starting any new project.

Postischemic fish oil treatment restores long-term retrograde memory and dendritic density: An analysis of the time window of efficacy

We reported that fish oil (FO) prevented the loss of spatial memory caused by transient, global cerebral ischemia (TGCI), provided the treatment covered the first days prior to and after ischemia. Continuing these studies, trained rats were subjected to TGCI, and FO was administered for 10days, with a time window of efficacy (TWE) of 4, 8 or 12h post-ischemia. Retrograde memory was assessed up to 43days after TGCI. In another experiment, ischemic rats received FO with a 4- or 12-h TWE, and dendritic density was assessed in the hippocampus and cerebral cortex. The brain lipid profile was evaluated in sham-operated and ischemic rats that were treated with FO or vehicle with a 4-h TWE. Ischemia-induced retrograde amnesia was prevented by FO administration that was initiated with either a 4- or 8-h TWE. Fish oil was ineffective after a 12-h TWE. Independent of the TWE, FO did not prevent ischemic neuronal death. In the hippocampus, but not cerebral cortex, TGCI-induced dendritic loss was prevented by FO with a 4-h TWE but not 12-h TWE. The level of docosahexaenoic acid almost doubled in the hippocampus in ischemic, FO-treated rats (4-h TWE). The data indicate that (i) the anti-amnesic effect of FO can be observed with a TWE of up to 8h, (ii) the stimulation of dendritic neuroplasticity may have contributed to this effect, and (iii) DHA in FO may be the main active constituent in FO that mediates the cognitive and neuroplasticity effects on TGCI.

Omega-3 Fatty Acids: Possible Neuroprotective Mechanisms in the Model of Global Ischemia in Rats

Background. Omega-3 (ω3) administration was shown to protect against hypoxic-ischemic injury. The objectives were to study the neuroprotective effects of ω3, in a model of global ischemia. Methods. Male Wistar rats were subjected to carotid occlusion (30 min), followed by reperfusion. The groups were SO, untreated ischemic and ischemic treated rats with ω3 (5 and 10 mg/kg, 7 days). The SO and untreated ischemic animals were orally treated with 1% cremophor and, 1 h after the last administration, they were behaviorally tested and euthanized for neurochemical (DA, DOPAC, and NE determinations), histological (Fluoro jade staining), and immunohistochemical (TNF-alpha, COX-2 and iNOS) evaluations. The data were analyzed by ANOVA and Newman-Keuls as the post hoc test. Results. Ischemia increased the locomotor activity and rearing behavior that were partly reversed by ω3. Ischemia decreased striatal DA and DOPAC contents and increased NE contents, effects reversed by ω3. This drug protected hippocampal neuron degeneration, as observed by Fluoro-Jade staining, and the increased immunostainings for TNF-alpha, COX-2, and iNOS were partly or totally blocked by ω3. Conclusion. This study showed a neuroprotective effect of ω3, in great part due to its anti-inflammatory properties, stimulating translational studies focusing on its use in clinic for stroke managing.

Alpha-linolenic acid given as enteral or parenteral nutritional intervention against sensorimotor and cognitive deficits in a mouse model of ischemic stroke

Stroke is a leading cause of disability and death worldwide. Numerous therapeutics applied acutely after stroke have failed to improve long-term clinical outcomes. An emerging direction is nutritional intervention with omega-3 polyunsaturated fatty acids acting as disease-modifying factors and targeting post-stroke disabilities. Our previous studies demonstrated that the omega-3 precursor, alpha-linolenic acid (ALA) administrated by injections or dietary supplementation reduces stroke damage by direct neuroprotection, and triggering brain artery vasodilatation and neuroplasticity. Successful translation of putative therapies will depend on demonstration of robust efficacy on common deficits resulting from stroke like loss of motor control and memory/learning. This study evaluated the value of ALA as adjunctive therapy for stroke recovery by comparing whether oral or intravenous supplementation of ALA best support recovery from ischemia. Motor and cognitive deficits were assessed using rotarod, pole and Morris water maze tests. ALA supplementation in diet was better than intravenous treatment in improving motor coordination, but this improvement was not due to a neuroprotective effect since infarct size was not reduced. Both types of ALA supplementation improved spatial learning and memory after stroke. This cognitive improvement correlated with higher survival of hippocampal neurons. These results support clinical investigation establishing therapeutic plans using ALA supplementation.

Consumption of a high n-3 polyunsaturated fatty acid diet during gradual mild physiological stress in rats

n-3 Polyunsaturated fatty acids (n-3PUFAs) may be beneficial for anxiety and depression under stressful conditions. Studies however, typically utilise physical or sudden physiological stress, while gradual physiological stress is also relevant to human conditions. Using deoxycorticosterone acetate (DOCA) administration to induce gradual physiological stress, this study investigated the impact of n-3PUFAs under gradual physiological stress in rats. Animals (aged 2 months) (N=8-12/group) received daily injections of DOCA or vehicle and were concurrently fed a high n-3PUFA or control diet for eight weeks. Behavioural measures were taken throughout. Behavioural tests and physiological measures were conducted after six and eight weeks respectively. DOCA administration decreased plasma renin, plasma proteins and relative adrenal weight, and increased water intake, relative kidney weight, and anxiety in the open field. These findings demonstrate disruptions to the renin-angiotensin-aldosterone system, a result of mild physiological stress, that also impact on anxiety behaviours. No effects of n-3PUFAs were found.

Enriched endogenous omega-3 fatty acids in mice protect against global ischemia injury

Transient global cerebral ischemia, one of the consequences of cardiac arrest and cardiovascular surgery, usually leads to delayed death of hippocampal cornu Ammonis1 (CA1) neurons and cognitive deficits. Currently, there are no effective preventions or treatments for this condition. Omega-3 (ω-3) PUFAs have been shown to have therapeutic potential in a variety of neurological disorders. Here, we report that the transgenic mice that express the fat-1 gene encoding for ω-3 fatty acid desaturase, which leads to an increase in endogenous ω-3 PUFAs and a concomitant decrease in ω-6 PUFAs, were protected from global cerebral ischemia injury. The results of the study show that the hippocampal CA1 neuronal loss and cognitive deficits induced by global ischemia insult were significantly less severe in fat-1 mice than in WT mice controls. The protection against global cerebral ischemia injury was closely correlated with increased production of resolvin D1, suppressed nuclear factor-kappa B activation, and reduced generation of pro-inflammatory mediators in the hippocampus of fat-1 mice compared with WT mice controls. Our study demonstrates that fat-1 mice with high endogenous ω-3 PUFAs exhibit protective effects on hippocampal CA1 neurons and cognitive functions in a global ischemia injury model.

Fish oil provides a sustained antiamnesic effect after acute, transient forebrain ischemia but not after chronic cerebral hypoperfusion in middle-aged rats

We reported that fish oil (FO) abolishes retrograde amnesia consistently following transient global cerebral ischemia (TGCI) in young rats, provided it covered the first days prior to and after ischemia. Here, we further evaluated whether FO given post-ischemia in older rats (15-18 months old) is equally effective in facilitating memory recovery. We also tested whether the antiamnesic effect of FO observed after TGCI can be reproduced after chronic cerebral hypoperfusion (CCH). FO (300 mg/kg docosahexaenoic acid [DHA]) was delivered orally 4h after TGCI and continued once per day for 9 days. In the CCH group, FO treatment began soon after the first stage of 4-VO/ICA and continued daily for 43 days. Two weeks after surgery, the animals were tested for retrograde memory performance across 5 weeks. Both TGCI and CCH caused persistent memory impairment and hippocampal and cortical neurodegeneration. TGCI-induced retrograde amnesia was reversed by FO, an effect that was sustained for at least 5 weeks after discontinuing treatment. In contrast, the memory deficit caused by CCH remained unchanged after FO treatment. Both hippocampal and cortical damage was not alleviated by FO. We conclude that the FO-mediated antiamnesic effect following TGCI can be extended to older rats, even when the treatment begins 4h postischemia. Such efficacy was not reproduced after CCH. Therefore, the present results support the notion that FO may have therapeutic utility in treating learning/memory dysfunction after acute/transient cerebral ischemia and suggest that such benefits may not apply when a state of chronic cerebrovascular insufficiency is present.

Docosahexaenoic acid confers enduring neuroprotection in experimental stroke

Recently we demonstrated that docosahexaenoic acid (DHA) is highly neuroprotective when animals were allowed to survive during one week. This study was conducted to establish whether the neuroprotection induced by DHA persists with chronic survival. Sprague-Dawley rats underwent 2h of middle cerebral artery occlusion (MCAo) and treated with DHA or saline at 3h after MCAo. Animals received neurobehavioral examination (composite neuroscore, rota-rod, beam walking and Y maze tests) followed by ex vivo magnetic resonance imaging and histopathology at 3 weeks. DHA improved composite neurologic score beginning on day 1 by 20%, which persisted throughout weeks 1-3 by 24-41% compared to the saline-treated group. DHA prolonged the latency in rota-rod on weeks 2-3 by 162-178%, enhanced balance performance in the beam walking test on weeks 1 and 2 by 42-51%, and decreased the number of entries in the Y maze test by 51% and spontaneous alteration by 53% on week 2 compared to the saline-treated group. DHA treatment reduced tissue loss (computed from T2-weighted images) by 24% and total and cortical infarct volumes by 46% and 54% compared to the saline-treated group. These results show that DHA confers enduring ischemic neuroprotection.

Fish oil provides robust and sustained memory recovery after cerebral ischemia: influence of treatment regimen

We previously reported that long-term treatment with fish oil (FO) facilitates memory recovery after transient, global cerebral ischemia (TGCI), despite the presence of severe hippocampal damage. The present study tested whether this antiamnesic effect resulted from an action of FO on behavioral performance itself, or whether it resulted from an anti-ischemic action. Different treatment regimens were used that were distinguished from each other by their initiation or duration with regard to the onset of TGCI and memory assessment. Naive rats were trained in an eight-arm radial maze, subjected to TGCI (4-VO model, 15 min), and tested for memory performance up to 6 weeks after TGCI. Fish oil (docosahexaenoic acid, 300 mg/kg/day) was given orally according to one of the following regimens: regimen 1 (from 3 days prior to ischemia until 4 weeks post-ischemia), regimen 2 (from 3 days prior to ischemia until 1 week post-ischemia), and regimen 3 (from week 2 to week 5 post-ischemia). When administered according to regimens 1 and 2, FO abolished amnesia completely. This effect persisted for at least 5 weeks after discontinuing the treatment. Such an effect did not occur, however, in the group treated according to regimen 3. Hippocampal and cortical damage was not alleviated by FO. The present results demonstrate that FO-mediated memory recovery (or preservation) following TGCI is a reproducible, robust, and long-lasting effect. Moreover, such an effect was found with a relatively short period of treatment, provided it covered the first days prior to and after ischemia. This suggests that FO prevented amnesia by changing some acute, ischemia/reperfusion-triggered process and not by stimulating memory performance on its own.

Expression of Bcl-2 and Bax after hippocampal ischemia in DHA + EPA treated rats

To determine the impact of ω3 fatty acids on post-ischemic expression of pro- and anti-apoptotic proteins in hippocampus, male rats were received 10 or 100 mg/kg [Docosahexaenoic acid (DHA) + Ecosapentaenoic acid (EPA); gavage; 21 days before ischemia to 2-10 days after ischemia]. Global cerebral ischemia reperfusion (IR) was performed using the four-vessel occlusion model; ischemia 8 min and reperfusion 6, 48 h and 10 days. IR increased Bcl-2 and Bax expression after 48 h (p < 0.05 and p < 0.01 vs. sham) and 10 days (only Bax; p < 0.05), without significant difference with DHA + EPA groups after 6 h. But after 48 h expression of Bcl-2 increased (p < 0.05 vs. IR) and Bax decreased (p < 0.05). At day 10 after ischemia expression of Bax in DHA + EPA acid groups was less than IR (p < 0.05) and in 100 mg/kg DHA + EPA group Bcl-2 expression was more than IR (p < 0.05). These data suggested that long-term gavage with DHA + EPA increase hippocampal neurons survival for days after ischemia, revealed by increased Bcl-2 and decreased Bax expressions.