Chronic administration of ethyl docosahexaenoate decreases mortality and cerebral edema in ischemic gerbils

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.

Omega 3 Fatty Acids: Novel Neurotherapeutic Targets for Cognitive Dysfunction in Mood Disorders and Schizophrenia?

An increasing body of evidences from preclinical as well as epidemiological and clinical studies suggest a potential beneficial role of dietary intake of omega-3 fatty acids for cognitive functioning. In this narrative review, we will summarize and discuss recent findings from epidemiological, interventional and experimental studies linking dietary consumption of omega-3 fatty acids to cognitive function in healthy adults. Furthermore, affective disorders and schizophrenia (SZ) are characterized by cognitive dysfunction encompassing several domains. Cognitive dysfunction is closely related to impaired functioning and quality of life across these conditions. Therefore, the current review focues on the potential influence of omega-3 fatty acids on cognition in SZ and affective disorders. In sum, current data predominantly from mechanistic models and animal studies suggest that adjunctive omega-3 fatty acid supplementation could lead to improved cognitive functioning in SZ and affective disorders. However, besides its translational promise, evidence for clinical benefits in humans has been mixed. Notwithstanding evidences indicate that adjunctive omega-3 fatty acids may have benefit for affective symptoms in both unipolar and bipolar depression, to date no randomized controlled trial had evaluated omega-3 as cognitive enhancer for mood disorders, while a single published controlled trial suggested no therapeutic benefit for cognitive improvement in SZ. Considering the pleiotropic mechanisms of action of omega-3 fatty acids, the design of well-designed controlled trials of omega-3 supplementation as a novel, domain-specific, target for cognitive impairment in SZ and affective disorders is warranted.

Sexual maturation of the Mongolian gerbil (Meriones unguiculatus): a histological, hormonal and spermatic evaluation

This study determined the phases of sexual development of the male Mongolian gerbil (Meriones unguiculatus) based on an integrative analysis of testicular morphology, hormonal data and sperm parameters. Male gerbils were analysed at 1, 7, 14, 21, 28, 35, 42, 50, 60, 70, 90, 100 and 120 days of age. Body, testicular and epididymal weights increased up to Day 70, 60 and 90, respectively. The impuberal phase, characterised by the presence of gonocytes, extended until Day 14. The prepubertal period lasted until Day 42, when puberty was achieved and a drastic increase in serum testosterone levels, mature adult Leydig cells and elongated spermatids was observed. Gerbils at 60 days of age showed a remarkable number of spermatozoa in the testis, epididymidis caput/corpus and cauda, and at Day 70 the maximum daily sperm production was reached. However, the gerbil may be considered sexually mature only from Day 90 onward, when sperm reserves become stable. The total transit time of spermatozoa along the epididymis of sexually mature gerbils was 11 days, with 1 day in the caput/corpus and 10 days in the cauda. These data cover a lacuna regarding the reproductive parameters of this rodent and provide foundations for its use in testicular toxicology studies.

Cornel iridoid glycoside reduces infarct size measured by magnetic resonance imaging and improves neurological function after focal cerebral ischemia in rats

OBJECTIVE

To investigate the effect of cornel iridoid glycoside (CIG), an ingredient extracted from traditional Chinese herb Cornus offificinalis, on neurological function and infarct size in rats as measured by magnetic resonance imaging (MRI) after ischemic stroke.

METHODS

Sprague-Dawley rats were divided into three group: control (n=11), model (n=20) and CIG (n=16) groups. Rats in the model and CIG groups underwent 90-min middle cerebral artery occlusion (MCAO) followed by reperfusion. Their neurological defect was measured by using a modified neurological severity score (mNSS). T2-weighted MRI (T2-MRI) of the brain was performed in vivo from 2 to 28 days after MCAO. The infarct volume in the brain was also measured using 2,3,5-triphenyltetrazolium chloride (TTC) staining 28 days after stroke.

RESULTS

CIG, 60 mg/(kg day), administered by oral gavage starting from 6 h after the onset of MCAO improved neurological function at 7, 14, 21, and 28 days post occlusion (P<0.05 orP<0.01) and decreased mortality. The infarct volumes computed from the T2-MR images were reduced in the CIG-treated group compared with the model group at 7, 14 and 28 days after MCAO (P<0.05); and the rate at which the infarct volume decreased from 2 to 28 days was higher in the CIG-treated group than that in the model group (P<0.05). The infarct volumes measured by TTC staining were also decreased 28 days after stroke (P<0.05).

CONCLUSION

CIG treatment, starting from 6 h after MCAO, reduced infarct size in the brain as measured by MRI and improved neurological function 2-28 days after focal cerebral ischemia in rats, suggesting that CIG could be a clinical application in improving stroke treatment.

Docosahexaenoic acid improves behavior and attenuates blood-brain barrier injury induced by focal cerebral ischemia in rats

BACKGROUND

Ischemic brain injury disrupts the blood-brain barrier (BBB) and then triggers a cascade of events, leading to edema formation, secondary brain injury and poor neurological outcomes. Recently, we have shown that docosahexaenoic acid (DHA) improves functional and histological outcomes following experimental stroke. However, little is known about the effect of DHA on BBB dysfunction after cerebral ischemia-reperfusion injury. The present study was designed to determine whether DHA protects against BBB disruption after focal cerebral ischemia in rats.

METHODS

Physiologically-controlled SD rats received 2 h middle cerebral artery occlusion (MCAo). DHA (5 mg/kg) or vehicle (saline) was administered I.V. at 3 h after onset of MCAo. Fluorometric quantitation of Evans Blue dye (EB) was performed in eight brain regions at 6 h, 24 h or 72 h after MCAo. Fluorescein isothiocynate (FITC) - dextran leakage and histopathology was evaluated on day 3 after stroke.

RESULTS

Physiological variables were stable and showed no significant differences between groups. DHA improved neurological deficits at 24 h, 48 h and 72 h and decreased EB extravasation in the ischemic hemisphere at 6 h (by 30%), 24 h (by 48%) and 72 h (by 38%). In addition, EB extravasation was decreased by DHA in the cortex and total hemisphere as well. FITC-dextran leakage was reduced by DHA treatment on day 3 by 68% compared to the saline group. DHA treatment attenuated cortical (by 50%) and total infarct volume (by 38%) compared to vehicle-treated rats on day 3 after stroke.

CONCLUSIONS

DHA therapy diminishes BBB damage accompanied with the acceleration of behavioral recovery and attenuation of the infarct volume. It is reasonable to propose that DHA has the potential for treating focal ischemic stroke in the clinical setting.

Neuroinflammation and neurodegeneration in adult rat brain from binge ethanol exposure: abrogation by docosahexaenoic acid

Evidence that brain edema and aquaporin-4 (AQP4) water channels have roles in experimental binge ethanol-induced neurodegeneration has stimulated interest in swelling/edema-linked neuroinflammatory pathways leading to oxidative stress. We report here that neurotoxic binge ethanol exposure produces comparable significant effects in vivo and in vitro on adult rat brain levels of AQP4 as well as neuroinflammation-linked enzymes: key phospholipase A2 (PLA2) family members and poly (ADP-ribose) polymerase-1 (PARP-1). In adult male rats, repetitive ethanol intoxication (3 gavages/d for 4 d, ∼9 g/kg/d, achieving blood ethanol levels ∼375 mg/dl; “Majchrowicz” model) significantly increased AQP4, Ca⁺²-dependent PLA2 GIVA (cPLA2), phospho-cPLA2 GIVA (p-cPLA2), secretory PLA2 GIIA (sPLA2) and PARP-1 in regions incurring extensive neurodegeneration in this model—hippocampus, entorhinal cortex, and olfactory bulb—but not in two regions typically lacking neurodamage, frontal cortex and cerebellum. Also, ethanol reduced hippocampal Ca⁺²-independent PLA2 GVIA (iPLA2) levels and increased brain “oxidative stress footprints” (4-hydroxynonenal-adducted proteins). For in vitro studies, organotypic cultures of rat hippocampal-entorhinocortical slices of adult age (∼60 d) were ethanol-binged (100 mM or ∼450 mg/dl) for 4 d, which augments AQP4 and causes neurodegeneration (Collins et al. 2013). Reproducing the in vivo results, cPLA2, p-cPLA2, sPLA2 and PARP-1 were significantly elevated while iPLA2 was decreased. Furthermore, supplementation with docosahexaenoic acid (DHA; 22:6n-3), known to quell AQP4 and neurodegeneration in ethanol-treated slices, blocked PARP-1 and PLA2 changes while counteracting endogenous DHA reduction and increases in oxidative stress footprints (3-nitrotyrosinated proteins). Notably, the PARP-1 inhibitor PJ-34 suppressed binge ethanol-dependent neurodegeneration, indicating PARP upstream involvement. The results with corresponding models support involvement of AQP4- and PLA2-associated neuroinflammatory pro-oxidative pathways in the neurodamage, with potential regulation by PARP-1 as well. Furthermore, DHA emerges as an effective inhibitor of these binge ethanol-dependent neuroinflammatory pathways as well as associated neurodegeneration in adult-age brain.

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.

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.

Protective effects of eicosapentaenoic acid on genotoxicity and oxidative stress of cyclophosphamide in mice

The aim of this article is to elucidate the mechanism by which eicosapentaenoic acid (EPA) acts against cyclophosphamide (CP)-induced effects. The prevalence of micronuclei, the extent of lipid peroxidation, and the status of the antioxidant enzymes, superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX) in both liver and serum of mice were used as intermediate biomarkers of chemoprotection. Lipid peroxidation and associated compromised antioxidant defenses (CAT and GPX) in CP treated mice were observed in the liver, serum, and were accompanied by increased prevalence of micronuclei in bone marrow. The number of MN was significantly different (p < 0.01) between the groups treated with CP (group III, IV, V, VI) and the solvent control (group II) (3.2 ± 0.7‰). There was a dose-dependent reduction in formation CP induced micronuclei by treatment with 100, 200, or 300 mg EPA/kg BW mice. Activities of SOD, CAT, and extent of lipid peroxidation were statistically different in liver cells of mice exposed to EPA only with CP compared with the CP group (group III). The present findings imply that EPA may be a potential antigenotoxic, antioxidant and chemopreventive agent and could be used as an adjuvant in chemotherapeutic applications.

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.

Differentiation of Leydig cells in the Mongolian gerbil

Information on postnatal Leydig cell (LC) differentiation in the Mongolian gerbil has been unavailable. Therefore, current investigation was designed to examine LC lineage differentiationin this rodent, from birth to adulthood. Gerbil testes at 1 day, 1-7 weeks (w), 2 and 3 months of age were conventionally processed by light and transmission electron microscopy. Immunocytochemistry for specific markers of steroidogenic enzymes, namely 3beta-hydroxysteroid dehydrogenase (3beta-HSD) and 11beta-hydroxysteroid steroid dehydrogenase 1 (11beta-HSD1) and also for androgen receptor (AR) was performed. The establishment of adult Leydig cell populations (ALC) during testis maturation in the gerbil follows the pattern previously described in other mammalian species, with the four progressive stages of differentiation. The LC progenitors were identified at second w by 3beta-HSD expression; the first newly formed ALC were recognized at fourth w whereas immature ALC appeared at fifth w. The latter were recognized by abundance of cytoplasmic lipid, in addition to expression of 11beta-HSD1 and intense nuclear AR immunoreaction. Mature ALC in gerbil exhibited irregular eccentric nuclei and a cytoplasmic canaliculus in the perinuclear area. Only one third of mature ALC in adult gerbils showed a high expression of 11beta-HSD1 and AR expression was highly variable among them. In conclusion, the process of differentiation of ALC population in gerbil follows the pattern previously established for other rodents. However, the resulting mature ALC are strikingly different due their singular asymmetric morphology and presence of a cytoplasmic canaliculus and as well as their functional heterogeneity.

Versatile roles of docosahexaenoic acid in the prenatal brain: from pro- and anti-oxidant features to regulation of gene expression

Docosahexaenoic acid (DHA) is the most ubiquitous polyunsaturated fatty acid (FA) in brain tissue. It is selectively esterified to amino phospholipids (PL) and therefore it is highly prevalent at the cytofacial site of the plasma membrane where it may specifically participate in intracellular events. A highly selective DHA accumulation prior to birth is the result of maternal supply via the placenta through a bio-magnification process. Supplements of DHA via the intra-amniotic route to the fetal rat increase brain DHA levels and also confer neuroprotection to fetuses subjected to global ischemic stress. The protective effect has been attributed to an enhanced free radical scavenging capacity of DHA. Dietary deprivation of linolenic acid (LNA) during the perinatal life on the other hand, resulted in losses of DHA from cerebral PLs [M. Schiefermeier, E. Yavin, n-3 deficient and DHA-enriched diets during critical periods of the developing prenatal rat brain, J. Lipid Res. 43 (2002) 124-131]. LNA deprivation also caused changes in a number of gene markers the identification of which was attained by a labor-intensive suppression subtractive hybridization protocol using mRNA from 2-week-old postnatal brains [E. Yakubov, P. Dinerman, F. Kuperstein, S. Saban, E. Yavin, Improved representation of gene markers on microarray by PCR-select subtracted cDNA targets, Mol. Brain Res. 137 (2005) 110-118]. Most notable was a remarkable elevation of dopamine (DA) receptor (D1 and D2) genes as evaluated by quantitative RT-PCR, SDS-PAGE gel electrophoresis and immunochemical staining [F. Kuperstein, E. Yakubov, P. Dinerman, S. Gil, R. Eylam, N. Salem Jr., E. Yavin, Overexpression of dopamine receptor genes and their products in the postnatal rat brain following maternal n-3 FA dietary deficiency, J. Neurochem. 95 (2005) 1550-1562]. Over-expression of DA receptors has been attributed to a compensatory mechanism resulting from impairment in DA neurotransmitter production, storage and processing. In conclusion, DHA is a versatile molecule with a wide range of actions spanning from participation in cellular oxidative processes and intracellular signaling to modulatory roles in gene expression and growth regulation.