Docosahexaenoic acid complexed to albumin provides neuroprotection after experimental stroke in aged rats

Research Progress on the Mechanisms of Central Post-Stroke Pain: A Review

Central Post-Stroke Pain (CPSP) is a primary sequelae of stroke that can develop in the body part corresponding to the cerebrovascular lesion after stroke, most typically after ischemic stroke but also after hemorrhagic stroke. The pathogenesis of CPSP is currently unknown, and research into its mechanism is ongoing. To summarize current research on the CPSP mechanism and provide guidance for future studies. Use "central post-stroke pain," "stroke AND thalamic pain," "stroke AND neuropathic pain," "post-stroke thalamic pain" as the search term. The search was conducted in the PubMed and China National Knowledge Infrastructure databases, summarizing and classifying the retrieved mechanism studies. The mechanistic studies on CPSP are extensive, and we categorized the included mechanistic studies and summarized them in terms of relevant pathway studies, relevant signals and receptors, relevant neural tissues, and described endoplasmic reticulum stress and other relevant studies, as well as summarized the mechanisms of acupuncture treatment. Studies have shown that the pathogenesis of CPSP involves the entire spinal-thalamo-cortical pathway and that multiple substances in the nervous system are involved in the formation and development of CPSP. Among them, the relevant receptors and signals are the hotspot of research, and the discovery and exploration of different receptors and signals have provided a wide range of therapeutic ideas for CPSP. As a very effective treatment, acupuncture is less studied regarding the analgesic mechanism of CPSP, and further experimental studies are still needed.

Unsaturated Fatty Acids and Their Immunomodulatory Properties

Oils are an essential part of the human diet and are primarily derived from plant (or sometimes fish) sources. Several of them exhibit anti-inflammatory properties. Specific diets, such as Mediterranean diet, that are high in ω-3 polyunsaturated fatty acids (PUFAs) and ω-9 monounsaturated fatty acids (MUFAs) have even been shown to exert an overall positive impact on human health. One of the most widely used supplements in the developed world is fish oil, which contains high amounts of PUFAs docosahexaenoic and eicosapentaenoic acid. This review is focused on the natural sources of various polyunsaturated and monounsaturated fatty acids in the human diet, and their role as precursor molecules in immune signaling pathways. Consideration is also given to their role in CNS immunity. Recent findings from clinical trials utilizing various fatty acids or diets high in specific fatty acids are reviewed, along with the mechanisms through which fatty acids exert their anti-inflammatory properties. An overall understanding of diversity of polyunsaturated fatty acids and their role in several molecular signaling pathways is useful in formulating diets that reduce inflammation and increase longevity.

Marine-derived n-3 fatty acids therapy for stroke

BACKGROUND

Currently, with stroke burden increasing, there is a need to explore therapeutic options that ameliorate the acute insult. There is substantial evidence of a neuroprotective effect of marine-derived n-3 polyunsaturated fatty acids (PUFAs) in animal models of stroke, leading to a better functional outcome.

OBJECTIVES

To assess the effects of administration of marine-derived n-3 PUFAs on functional outcomes and dependence in people with stroke.

SEARCH METHODS

We searched the Cochrane Stroke Trials Register (last searched 31 May 2021), the Cochrane Central Register of Controlled Trials (CENTRAL; 2021, Issue 5), MEDLINE Ovid (from 1948 to 31 May 2021), Embase Ovid (from 1980 to 31 May 2021), CINAHL EBSCO (Cumulative Index to Nursing and Allied Health Literature; from 1982 to 31 May 2021), Science Citation Index Expanded ‒ Web of Science (SCI-EXPANDED), Conference Proceedings Citation Index-Science - Web of Science (CPCI-S), and BIOSIS Citation Index. We also searched ongoing trial registers, reference lists, relevant systematic reviews, and used the Science Citation Index Reference Search.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) comparing marine-derived n-3 PUFAs to placebo or open control (no placebo) in people with a history of stroke or transient ischaemic attack (TIA), or both.

DATA COLLECTION AND ANALYSIS

At least two review authors independently selected trials for inclusion, extracted data, assessed risk of bias, and used the GRADE approach to assess the certainty of the body of evidence. We contacted study authors for clarification and additional information on stroke/TIA participants. We conducted random-effects meta-analysis or narrative synthesis, as appropriate. The primary outcome was efficacy (functional outcome) assessed using a validated scale, for example, the Glasgow Outcome Scale Extended (GOSE) dichotomised into poor or good clinical outcome, the Barthel Index (higher score is better; scale from 0 to 100), or the Rivermead Mobility Index (higher score is better; scale from 0 to 15). Our secondary outcomes were vascular-related death, recurrent events, incidence of other type of stroke, adverse events, quality of life, and mood.

MAIN RESULTS

We included 30 RCTs; nine of them provided outcome data (3339 participants). Only one study included participants in the acute phase of stroke (haemorrhagic). Doses of marine-derived n-3 PUFAs ranged from 400 mg/day to 3300 mg/day. Risk of bias was generally low or unclear in most trials, with a higher risk of bias in smaller studies. We assessed results separately for short (up to three months) and longer (more than three months) follow-up studies. Short follow-up (up to three months) Functional outcome was reported in only one pilot study as poor clinical outcome assessed with the GOSE (risk ratio (RR) 0.78, 95% confidence interval (CI) 0.36 to 1.68, P = 0.52; 40 participants; very low-certainty evidence). Mood (assessed with the GHQ-30, lower score better) was reported by only one study and favoured control (mean difference (MD) 1.41, 95% CI 0.07 to 2.75, P = 0.04; 102 participants; low-certainty evidence). We found no evidence of an effect of the intervention for the remainder of the secondary outcomes: vascular-related death (two studies, not pooled due to differences in population, RR 0.33, 95% CI 0.01 to 8.00, P = 0.50, and RR 0.33, 95% CI 0.01 to 7.72, P = 0.49; 142 participants; low-certainty evidence); recurrent events (RR 0.41, 95% CI 0.02 to 8.84, P = 0.57; 18 participants; very low-certainty evidence); incidence of other type of stroke (two studies, not pooled due to different type of index stroke, RR 6.11, 95% CI 0.33 to 111.71, P = 0.22, and RR 0.63, 95% CI 0.25 to 1.58, P = 0.32; 58 participants; very low-certainty evidence); and quality of life (physical component, MD -2.31, 95% CI -4.81 to 0.19, P = 0.07, and mental component, MD -2.16, 95% CI -5.91 to 1.59, P = 0.26; 1 study; 102 participants; low-certainty evidence). Adverse events were reported by two studies (57 participants; very low-certainty evidence), one trial reporting extracranial haemorrhage (RR 0.25, 95% CI 0.04 to 1.73, P = 0.16) and the other one reporting bleeding complications (RR 0.32, 95% CI 0.01 to 7.35, P = 0.47). Longer follow-up (more than three months) One small trial assessed functional outcome with both the Barthel Index for activities of daily living (MD 7.09, 95% CI -5.16 to 19.34, P = 0.26), and the Rivermead Mobility Index for mobility (MD 1.30, 95% CI -1.31 to 3.91, P = 0.33) (52 participants; very low-certainty evidence). We carried out meta-analysis for vascular-related death (RR 1.02, 95% CI 0.78 to 1.35, P = 0.86; 5 studies; 2237 participants; low-certainty evidence) and fatal recurrent events (RR 0.69, 95% CI 0.31 to 1.55, P = 0.37; 3 studies; 1819 participants; low-certainty evidence). We found no evidence of an effect of the intervention for mood (MD 1.00, 95% CI -2.07 to 4.07, P = 0.61; 1 study; 14 participants; low-certainty evidence). Incidence of other type of stroke and quality of life were not reported. Adverse events (all combined) were reported by only one study (RR 0.94, 95% CI 0.56 to 1.58, P = 0.82; 1455 participants; low-certainty evidence).

AUTHORS' CONCLUSIONS

We are very uncertain of the effect of marine-derived n-3 PUFAs therapy on functional outcomes and dependence after stroke as there is insufficient high-certainty evidence. More well-designed RCTs are needed, specifically in acute stroke, to determine the efficacy and safety of the intervention. Studies assessing functional outcome might consider starting the intervention as early as possible after the event, as well as using standardised, clinically relevant measures for functional outcomes, such as the modified Rankin Scale. Optimal doses remain to be determined; delivery forms (type of lipid carriers) and mode of administration (ingestion or injection) also need further consideration.

MicroRNA-27a-3p relieves inflammation and neurologic impairment after cerebral ischemia reperfusion via inhibiting LITAF and the TLR4/NF-κB pathway

Cerebral ischemia reperfusion (CIR) affects microRNA (miR) expression and causes substantial inflammation. Here, we investigated the influence and underlying mechanism of miR-27a-3p in rats with CIR. Firstly, Biliverdin treatment relieved cerebral infarction and decreased the levels of serum interleukin (IL)-1β, IL-6 and TNF-α. Through our previous study, we found key miR-27a-3p and its targeted gene LITAF might involve in the molecular mechanism of CIR. Then, the regulation between miR-27a-3p and LITAF was verified by the temporal miR-27a-3p and LITAF expression profiles and luciferase assay. Moreover, intracerebroventricular injection of the miR-27a-3p mimic significantly decreased the LITAF, TLR4, NF-κB and IL-6 levels at 24h post-surgery, whereas miR-27a-3p inhibitor reversed these effects. Furthermore, miR-27a-3p mimic could relieve cerebral infarct and neurologic deficit after CIR. In addition, injection of miR-27a-3p mimic decreased neuronal damage induced by CIR. Taken together, our results suggest that miR-27a-3p protect against CIR by relieving inflammation, neuronal damage and neurologic deficit via regulating LITAF and the TLR4/NF-κB pathway.

Association between GFAP-positive astrocytes with clinically important parameters including neurological deficits and/or infarct volume in stroke-induced animals

The effect of GFAP-positive astrocytes, as positive or negative factors on stroke complications such as infarct volume and neurological deficits is currently under debate. This review was aimed to evaluate and compare the frequency of studies that showed a positive or negative relationship between astrocyte activation with the improvement of neurological deficits and/or the decrease of infarct volume. In addition, we reviewed two possible causes of differences in results including timepoint of stroke and stroke severity. Time of GFAP assessment was considered as time point and type of stroke induction and duration of stroke as stroke severity. According to our review in the most relevant English-language studies in the PubMed, Web of Science, and Google Scholar databases from 2005 to 2020, the majority of studies (77 vs. 28) showed a negative coincidence or correlation between GFAP-positive cells with neurological improvement as well as between GFAP-positive cells with infarct volume reduction. In most reviewed studies, GFAP expression was reported as a marker related to or coinciding with worse neurological function, or greater infarct volume. However, there were also studies that showed helpful effects of GFAP-positive cells on neurological function or stroke lesion. Although there are some elucidations that the difference in these findings is due to the time point of stroke and stroke severity, our review did not confirm these interpretations.

Nutraceuticals in the Prevention of Neonatal Hypoxia-Ischemia: A Comprehensive Review of their Neuroprotective Properties, Mechanisms of Action and Future Directions

Neonatal hypoxia-ischemia (HI) is a brain injury caused by oxygen deprivation to the brain due to birth asphyxia or reduced cerebral blood perfusion, and it often leads to lifelong limiting sequelae such as cerebral palsy, seizures, or mental retardation. HI remains one of the leading causes of neonatal mortality and morbidity worldwide, and current therapies are limited. Hypothermia has been successful in reducing mortality and some disabilities, but it is only applied to a subset of newborns that meet strict inclusion criteria. Given the unpredictable nature of the obstetric complications that contribute to neonatal HI, prophylactic treatments that prevent, rather than rescue, HI brain injury are emerging as a therapeutic alternative. Nutraceuticals are natural compounds present in the diet or used as dietary supplements that have antioxidant, anti-inflammatory, or antiapoptotic properties. This review summarizes the preclinical in vivo studies, mostly conducted on rodent models, that have investigated the neuroprotective properties of nutraceuticals in preventing and reducing HI-induced brain damage and cognitive impairments. The natural products reviewed include polyphenols, omega-3 fatty acids, vitamins, plant-derived compounds (tanshinones, sulforaphane, and capsaicin), and endogenous compounds (melatonin, carnitine, creatine, and lactate). These nutraceuticals were administered before the damage occurred, either to the mothers as a dietary supplement during pregnancy and/or lactation or to the pups prior to HI induction. To date, very few of these nutritional interventions have been investigated in humans, but we refer to those that have been successful in reducing ischemic stroke in adults. Overall, there is a robust body of preclinical evidence that supports the neuroprotective properties of nutraceuticals, and these may represent a safe and inexpensive nutritional strategy for the prevention of neonatal HI encephalopathy.

Low serum albumin levels predict poor outcome in patients with acute ischaemic stroke or transient ischaemic attack

BACKGROUND

To examine the relationship of serum albumin with poor functional outcome and mortality in patients with acute ischaemic stroke (AIS) or transient ischaemic attack (TIA), and perform a meta-analysis to summarise the association.

METHODS

We analysed data from the Third China National Stroke Registry (CNSR-Ⅲ). Patients were divided into four groups based on serum albumin levels at admission. The outcomes included poor functional outcome (modified Rankin Scale (mRS) score of 3 to 6) and mortality at 3 months and 1 year. Multiple logistic regression models and Cox regression models were used to evaluate the association, respectively. We used a fixed-effect model to calculate the risk ratio for poor functional outcome and a random-effect model for mortality in the meta-analysis.

RESULTS

A total of 13 618 patients were enrolled. During the 3-month follow-up period, compared with 40 to 44.9 g/L group, patients in <35 g/L group had an increased risk of poor functional outcome and mortality (adjusted OR 1.37 (95% CI 1.12 to 1.67); adjusted HR 2.13 (95% CI 1.41 to 3.23)). The relationship in per 10 g/L decreased serum albumin with prognosis was consistently inversed (adjusted OR 1.17 (95% CI 1.01 to 1.35); adjusted HR 1.86 (95% CI 1.30 to 2.64)). Also, low serum albumin levels were independently correlated with clinical outcomes at 1 year. In the meta-analysis, the OR for poor functional outcome pooled 3 studies per 1 g/L decrease was 1.03 (95% CI 1.02 to 1.05), and the HR for mortality pooled 5 studies was 1.07 (95% CI 1.03 to 1.11).

CONCLUSIONS

Low serum albumin levels predict poor functional outcome and mortality in patients with AIS or TIA.

Acute Injection of Omega-3 Triglyceride Emulsion Provides Very Similar Protection as Hypothermia in a Neonatal Mouse Model of Hypoxic-Ischemic Brain Injury

Therapeutic hypothermia (HT) is a currently accepted treatment for neonatal asphyxia and is a promising strategy in adult stroke therapy. We previously reported that acute administration of docosahexaenoic acid (DHA) triglyceride emulsion (tri-DHA) protects against hypoxic-ischemic (HI) injury in neonatal mice. We questioned if co-treatment with HT and tri-DHA would achieve synergic effects in protecting the brain from HI injury. Neonatal mice (10-day old) subjected to HI injury were placed in temperature-controlled chambers for 4 h of either HT (rectal temperature 31–32°C) or normothermia (NT, rectal temperature 37°C). Mice were treated with tri-DHA (0.375 g tri-DHA/kg bw, two injections) before and 1 h after initiation of HT. We observed that HT, beginning immediately after HI injury, reduced brain infarct volume similarly to tri-DHA treatment (~50%). Further, HT delayed 2 h post-HI injury provided neuroprotection (% infarct volume: 31.4 ± 4.1 vs. 18.8 ± 4.6 HT), while 4 h delayed HT did not protect against HI insult (% infarct volume: 30.7 ± 5.0 vs. 31.3 ± 5.6 HT). HT plus tri-DHA combination treatment beginning at 0 or 2 h after HI injury did not further reduce infarct volumes compared to HT alone. Our results indicate that HT offers similar degrees of neuroprotection against HI injury compared to tri-DHA treatment. HT can only be provided in tertiary care centers, requires intense monitoring and can have adverse effects. In contrast, tri-DHA treatment may be advantageous in providing a feasible and effective strategy in patients after HI injury.

Acute injection of a DHA triglyceride emulsion after hypoxic-ischemic brain injury in mice increases both DHA and EPA levels in blood and brain✰

We recently reported that acute injection of docosahexaenoic acid (DHA) triglyceride emulsions (tri-DHA) conferred neuroprotection after hypoxic-ischemic (HI) injury in a neonatal mouse stroke model. We showed that exogenous DHA increased concentrations of DHA in brain mitochondria as well as DHA-derived specialized pro-resolving mediator (SPM) levels in the brain. The objective of the present study was to investigate the distribution of emulsion particles and changes in plasma lipid profiles after tri-DHA injection in naïve mice and in animals subjected to HI injury. We also examined whether tri-DHA injection would change DHA- and eicosapentaenoic acid (EPA)-derived SPM levels in the brain. To address this, neonatal (10-day-old) naïve and HI mice were injected with radiolabeled tri-DHA emulsion (0.375 g tri-DHA/kg bw), and blood clearance and tissue distribution were analyzed. Among all the organs assayed, the lowest uptake of emulsion particles was in the brain (<0.4% recovered dose) in both naïve and HI mice, while the liver had the highest uptake. Tri-DHA administration increased DHA concentrations in plasma lysophosphatidylcholine and non-esterified fatty acids. Additionally, treatment with tri-DHA after HI injury significantly elevated the levels of DHA-derived SPMs and monohydroxy-containing DHA-derived products in the brain. Further, tri-DHA administration increased resolvin E2 (RvE2, 5S,18R-dihydroxy-eicosa-6E,8Z,11Z,14Z,16E-pentaenoic acid) and monohydroxy-containing EPA-derived products in the brain. These results suggest that the transfer of DHA through plasma lipid pools plays an important role in DHA brain transport in neonatal mice subjected to HI injury. Furthermore, increases in EPA and EPA-derived SPMs following tri-DHA injection demonstrate interlinked metabolism of these two fatty acids. Hence, changes in both EPA and DHA profile patterns need to be considered when studying the protective effects of DHA after HI brain injury. Our results highlight the need for further investigation to differentiate the effects of DHA from EPA on neuroprotective pathways following HI damage. Such information could contribute to the development of specific DHA-EPA formulations to improve clinical endpoints and modulate potential biomarkers in ischemic brain injury.

Molecular profile of the rat peri-infarct region four days after stroke: Study with MANF

The peri-infarct region after ischemic stroke is the anatomical location for many of the endogenous recovery processes; however, -the molecular events in the peri-infarct region remain poorly characterized. In this study, we examine the molecular profile of the peri-infarct region on post-stroke day four, a time when reparative processes are ongoing. We used a multiomics approach, involving RNA sequencing, and mass spectrometry-based proteomics and metabolomics to characterize molecular changes in the peri-infarct region. We also took advantage of our previously developed method to express transgenes in the peri-infarct region where self-complementary adeno-associated virus (AAV) vectors were injected into the brain parenchyma on post-stroke day 2. We have previously used this method to show that mesencephalic astrocyte-derived neurotrophic factor (MANF) enhances functional recovery from stroke and recruits phagocytic cells to the peri-infarct region. Here, we first analyzed the effects of stroke to the peri-infarct region on post-stroke day 4 in comparison to sham-operated animals, finding that strokeinduced changes in 3345 transcripts, 341 proteins, and 88 metabolites. We found that after stroke, genes related to inflammation, proliferation, apoptosis, and regeneration were upregulated, whereas genes encoding neuroactive ligand receptors and calcium-binding proteins were downregulated. In proteomics, we detected upregulation of proteins related to protein synthesis and downregulation of neuronal proteins. Metabolomic studies indicated that in after stroke tissue there is an increase in saccharides, sugar phosphates, ceramides and free fatty acids and a decrease of adenine, hypoxantine, adenosine and guanosine. We then compared the effects of post-stroke delivery of AAV1-MANF to AAV1-eGFP (enhanced green fluorescent protein). MANF administration increased the expression of 77 genes, most of which were related to immune response. In proteomics, MANF administration reduced S100A8 and S100A9 protein levels. In metabolomics, no significant differences between MANF and eGFP treatment were detected, but relative to sham surgery group, most of the changes in lipids were significant in the AAV-eGFP group only. This work describes the molecular profile of the peri-infarct region during recovery from ischemic stroke, and establishes a resource for further stroke studies. These results provide further support for parenchymal MANF as a modulator of phagocytic function.

Refocusing the Brain: New Approaches in Neuroprotection Against Ischemic Injury

A new era for neuroprotective strategies is emerging in ischemia/reperfusion. This has forced to review the studies existing to date based in neuroprotection against oxidative stress, which have undoubtedly contributed to clarify the brain endogenous mechanisms, as well as to identify possible therapeutic targets or biomarkers in stroke and other neurological diseases. The efficacy of exogenous administration of neuroprotective compounds has been shown in different studies so far. However, something must be missing to get these treatments successfully applied in the clinical environment. Here, the mechanisms involved in neuronal protection against physiological level of ROS and the main neuroprotective signaling pathways induced by excitotoxic and ischemic stimuli are reviewed. Also, the endogenous ischemic tolerance in terms of brain self-protection mechanisms against subsequent cerebral ischemia is revisited to highlight how the preconditioning has emerged as a powerful tool to understand these phenomena. A better understanding of endogenous defense against exacerbated ROS and metabolism in nervous cells will therefore aid to design pharmacological antioxidants targeted specifically against oxidative damage induced by ischemic injury, but also might be very valuable for translational medicine.

Brain targeting with docosahexaenoic acid as a prospective therapy for neurodegenerative diseases and its passage across blood brain barrier

Docosahexaenoic acid (DHA, 22:6n-3) is the main omega-3 polyunsaturated fatty acid in brain tissues necessary for common brain growth and function. DHA can be provided to the body through two origins: an exogenous origin, from direct dietary intakes and an endogenous one, from the bioconversion of the essential α-linolenic acid (ALA, 18:3n-3) in the liver. In humans, the biosynthesis of DHA from its precursor ALA is very low. A reduction in the cerebral amount of DHA is detected in patients suffering from neurodegenerative diseases such as Alzheimer's and Parkinson's diseases. Considering the vital functions of DHA for the brain, new methodologies to target the brain with DHA offers encouraging perceptions in the improvement of precautionary and therapeutic approaches for neurodegenerative diseases. The aim of the present review was to provide better understanding of the cerebral uptake of DHA in different form including free fatty acids, Lysophosphatidylcholines LysoPC-DHA as well as structured phospholipids. First, we explored the special structure of the blood-brain barrier BBB, BBB being a physical and metabolic barrier with restrictive properties. Then, we discussed the incorporation of DHA into the membrane phospholipids of the brain, the neuroprotective and therapeutic effect of DHA for neurological diseases.

Cannabinoid Receptor Agonist WIN55, 212-2 Adjusts Lipid Metabolism in a Rat Model of Cardiac Arrest

The objective of this study was to investigate the effects of pharmacologically induced hypothermia with WIN55, 212-2 (WIN)on postresuscitation myocardial function, microcirculation, and metabolism-specific lipids in a rat cardiac arrest (CA) model. Ventricular fibrillation was electrically induced and untreated for 6 minutes in 24 Sprague-Dawley rats weighing 450-550 g. Cardiopulmonary resuscitation including chest compression and mechanical ventilation was then initiated and continued for 8 minutes, followed by defibrillation. At 5 minutes after restoration of spontaneous circulation (ROSC), animals were randomized into four groups: (1) normothermia with vehicle (NT); (2) physical hypothermia with vehicle (PH); (3) WIN55, 212-2 with normothermia (WN); and (4) WIN55, 212-2 with hypothermia (WH). For groups of WN and WH, WIN was administered by continuous intravenous infusion with a syringe pump for 4 hours. PH started at 5 minutes after resuscitation. NT maintained core temperature at 37°C ± 0.2°C with the aid of a heating blanket. Hypothermia groups maintained temperature at 33°C ± 0.5°C for 4 hours after ROSC. There was a significant improvement in myocardial function as measured by ejection fraction, cardiac output, and myocardial performance index in animals treated with WH and PH beginning at 1 hour after start of infusion. In the WH and PH groups, buccal microcirculation was significantly improved compared with NT and WN. Plasma at pre-CA and ROSC 4 hours was harvested for lipid metabolism. The WH group appeared to be closer to baseline than the other groups in lipid metabolism. lysophosphatidylcholine (LPC) 18:2, free fatty acid (FFA) 22:6, and ceramide (CER) (24:0) changed significantly among the lipidomic data compared with NT (p < 0.05). Postresuscitation hypothermia improved myocardial function and microcirculation. WH-mediated lipid metabolism had the best metabolic outcome to bring back the animals to normal metabolism, which may be protective to improve outcomes of CA. LPC 18:2, FFA 22:6, and CER (24:0) may be important predictors of outcomes of CA.

Marine-derived n-3 fatty acids therapy for stroke

BACKGROUND

Currently, with stroke burden increasing, there is a need to explore therapeutic options that ameliorate the acute insult. There is substantial evidence of a neuroprotective effect of marine-derived n-3 polyunsaturated fatty acids (PUFAs) in experimental stroke, leading to a better functional outcome.

OBJECTIVES

To assess the effects of administration of marine-derived n-3 PUFAs on functional outcomes and dependence in people with stroke.Our secondary outcomes were vascular-related death, recurrent events, incidence of other type of stroke, adverse events, quality of life, and mood.

SEARCH METHODS

We searched the Cochrane Stroke Group trials register (6 August 2018), the Cochrane Central Register of Controlled Trials (CENTRAL; Issue 1, January 2019), MEDLINE Ovid (from 1948 to 6 August 2018), Embase Ovid (from 1980 to 6 August 2018), CINAHL EBSCO (Cumulative Index to Nursing and Allied Health Literature; from 1982 to 6 August 2018), Science Citation Index Expanded ‒ Web of Science (SCI-EXPANDED), Conference Proceedings Citation Index-Science - Web of Science (CPCI-S), and BIOSIS Citation Index. We also searched ongoing trial registers, reference lists, relevant systematic reviews, and used the Science Citation Index Reference Search.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) comparing marine-derived n-3 PUFAs to placebo or open control (no placebo) in people with a history of stroke or transient ischaemic attack (TIA), or both.

DATA COLLECTION AND ANALYSIS

At least two review authors independently selected trials for inclusion, extracted data, assessed risk of bias, and used the GRADE approach to assess the quality of the body of evidence. We contacted study authors for clarification and additional information on stroke/TIA participants. We conducted random-effects meta-analysis or narrative synthesis, as appropriate. The primary outcome was efficacy (functional outcome) assessed using a validated scale e.g. Glasgow Outcome Scale Extended (GOSE) dichotomised into poor or good clinical outcome, Barthel Index (higher score is better; scale from 0 to 100) or Rivermead Mobility Index (higher score is better; scale from 0 to 15).

MAIN RESULTS

We included 29 RCTs; nine of them provided outcome data (3339 participants). Only one study included participants in the acute phase of stroke (haemorrhagic). Doses of marine-derived n-3 PUFAs ranged from 400 mg/day to 3300 mg/day. Risk of bias was generally low or unclear in most trials, with a higher risk of bias in smaller studies. We assessed results separately for short (up to three months) and longer (more than three months) follow-up studies.Short follow-up (up to three months)Functional outcome was reported in only one pilot study as poor clinical outcome assessed with GOSE (risk ratio (RR) 0.78, 95% confidence interval (CI) 0.36 to 1.68; 40 participants; very low quality evidence). Mood (assessed with GHQ-30, lower score better), was reported by only one study and favoured control (mean difference (MD) 1.41, 95% CI 0.07 to 2.75; 102 participants; low-quality evidence).We found no evidence of an effect of the intervention for the remainder of the secondary outcomes: vascular-related death (two studies, not pooled due to differences in population, RR 0.33, 95% CI 0.01 to 8.00, and RR 0.33, 95% CI 0.01 to 7.72; 142 participants; low-quality evidence); recurrent events (RR 0.41, 95% CI 0.02 to 8.84; 18 participants; very low quality evidence); incidence of other type of stroke (two studies, not pooled due to different type of index stroke, RR 6.11, 95% CI 0.33 to 111.71, and RR 0.63, 95% CI 0.25 to 1.58; 58 participants; very low quality evidence); and quality of life (physical component mean difference (MD) -2.31, 95% CI -4.81 to 0.19, and mental component MD -2.16, 95% CI -5.91 to 1.59; one study; 102 participants; low-quality evidence).Adverse events were reported by two studies (57 participants; very low quality evidence), one trial reporting extracranial haemorrhage (RR 0.25, 95% CI 0.04 to 1.73) and the other one reporting bleeding complications (RR 0.32, 95% CI 0.01 to 7.35).Longer follow-up (more than three months)One small trial assessed functional outcome with both Barthel Index (MD 7.09, 95% CI -5.16 to 19.34) for activities of daily living, and Rivermead Mobility Index (MD 1.30, 95% CI -1.31 to 3.91) for mobility (52 participants; very low quality evidence). We carried out meta-analysis for vascular-related death (RR 1.02, 95% CI 0.78 to 1.35; five studies; 2237 participants; low-quality evidence) and fatal recurrent events (RR 0.69, 95% CI 0.31 to 1.55; three studies; 1819 participants; low-quality evidence).We found no evidence of an effect of the intervention for mood (MD 1.00, 95% CI -2.07 to 4.07; one study; 14 participants; low-quality evidence). Incidence of other type of stroke and quality of life were not reported.Adverse events (all combined) were reported by only one study (RR 0.94, 95% CI 0.56 to 1.58; 1455 participants; low-quality evidence).

AUTHORS' CONCLUSIONS

We are very uncertain of the effect of marine-derived n-3 PUFAs therapy on functional outcomes and dependence after stroke as there is insufficient high-quality evidence. More well-designed RCTs are needed, specifically in acute stroke, to determine the efficacy and safety of the intervention.Studies assessing functionality might consider starting the intervention as early as possible after the event, as well as using standardised clinically-relevant measures for functional outcomes, such as the modified Rankin Scale. Optimal doses remain to be determined; delivery forms (type of lipid carriers) and mode of administration (ingestion or injection) also need further consideration.

Bone Marrow Stromal Cells With Exercise and Thyroid Hormone Effect on Post-Stroke Injuries in Middle-aged Mice

Introduction:

Based on our previous findings, the treatment of stem cells alone or in combination with thyroid hormone (T₃) and mild exercise could effectively reduce the risk of stroke damage in young mice. However, it is unclear whether this treatment is effective in aged or middle-aged mice. Therefore, this study designed to assess whether combination of Bone Marrow Stromal Cells (BMSCs) with T₃ and mild treadmill exercise can decrease stroke complications in middle-aged mice.

Methods:

Under laser Doppler flowmetry monitoring, transient focal cerebral ischemia was produced by right Middle Cerebral Artery Occlusion (MCAO) for 45 min followed by 7 days of reperfusion in middle-aged mice. BMSCs (1×10⁵) were injected into the right cerebral ventricle 24 h after MCAO, followed by daily injection of triiodothyronine (T₃) (20 μg/100 g/d SC) and 6 days of running on a treadmill. Infarct size, neurological function, apoptotic cells and expression levels of Glial Fibrillary Acidic Protein (GFAP) were evaluated 1 week after stroke.

Results:

Post-ischemic treatment with BMSCs or with T₃ and or mild treadmill exercise alone or in combination did not significantly change neurological function, infarct size, and apoptotic cells 7 days after ischemia in middle-aged mice (P>0.05). However, the expression of GFAP significantly reduced after treatment with BMSCs and or T₃ (P<0.01).

Conclusion:

Our findings indicate that post-stroke treatment BMSCs with exercise and thyroid hormone cannot reverse neuronal damage 7 days after ischemia in middle-aged mice. These findings further support that age is an important variable in stroke treatment

Post-stroke administration of omega-3 polyunsaturated fatty acids promotes neurovascular restoration after ischemic stroke in mice: Efficacy declines with aging

Post-stroke treatment with omega-3 polyunsaturated fatty acids (n-3 PUFAs) may be a promising therapy in young animals but this has not been tested in aged subjects, a population at most risk of ischemic stroke. Herein we examined the therapeutic efficacy of n-3 PUFAs after distal middle cerebral artery occlusion (dMCAO) in young (10-12 weeks old) and aged (18 months old) mice. Post-ischemic mice were randomly assigned to 4 groups that received: 1) regular food with low content of n-3 PUFAs, 2) intraperitoneal docosahexaenoic acid (DHA, a major component of n-3 PUFAs) injections, 3) Fish oil (FO, containing high concentration of n-3 PUFAs) dietary supplement, or 4) combined treatment with DHA and FO dietary supplement. Long-term neurorestoration induced by n-3 PUFA post-stroke administration and its underlying mechanism(s) were analyzed up to 35 days after dMCAO. Aged mice showed more severe neurological deficits than young mice after dMCAO with histological lesions extended to the striatum. Notably, post-stroke treatment with combined DHA injections and FO dietary supplementation was more effective in reducing brain injury and improving sensorimotor function in aged mice than either treatment alone, albeit to a lesser extent than in the young mice. Unlike the improvement in spatial cognitive function observed in young mice, the combined treatment regimen failed to improve cognitive function in aged mice. The reduction in stroke-induced neurological deficits with n-3 PUFA post-treatment was associated with enhanced angiogenesis, oligodendrogenesis, neuron survival and white matter restoration. Together, these results indicate that the neurological benefits of n-3 PUFA administration after stroke extend to older animals and are associated with improved neuronal survival and brain remodeling, therefore suggesting that post-stroke administration of n-3 PUFAs is a viable clinically relevant treatment option against stroke.

Anti-Inflammatory Effects of Omega-3 Fatty Acids in the Brain: Physiological Mechanisms and Relevance to Pharmacology

Classically, polyunsaturated fatty acids (PUFA) were largely thought to be relatively inert structural components of brain, largely important for the formation of cellular membranes. Over the past 10 years, a host of bioactive lipid mediators that are enzymatically derived from arachidonic acid, the main n-6 PUFA, and docosahexaenoic acid, the main n-3 PUFA in the brain, known to regulate peripheral immune function, have been detected in the brain and shown to regulate microglia activation. Recent advances have focused on how PUFA regulate the molecular signaling of microglia, especially in the context of neuroinflammation and behavior. Several active drugs regulate brain lipid signaling and provide proof of concept for targeting the brain. Because brain lipid metabolism relies on a complex integration of diet, peripheral metabolism, including the liver and blood, which supply the brain with PUFAs that can be altered by genetics, sex, and aging, there are many pathways that can be disrupted, leading to altered brain lipid homeostasis. Brain lipid signaling pathways are altered in neurologic disorders and may be viable targets for the development of novel therapeutics. In this study, we discuss in particular how n-3 PUFAs and their metabolites regulate microglia phenotype and function to exert their anti-inflammatory and proresolving activities in the brain.

Bioactive lipids as new class of microglial modulators: When nutrition meets neuroimunology

Within the central nervous system the traditional role of microglia has been in brain infection and disease, phagocytosing debris and secreting factors to modify disease progression. More recently, microglia have been found to be important for normal brain development, circuit refinement, and synaptic plasticity in ways that were previously unsuspected. Hence, the brain innate immune system appears to be key in all situations, ranging from physiology to pathology. This unique feature of microglia is established by the wide array of receptors it is equipped with to sense molecular patterns. This includes receptors to most if not all neurotransmitters, neuromodulators and purines. We here review novel, yet extensive literature on a new class of microglia modulators, namely bioactive fatty acids. These lipids are issued from metabolism of nutrients and can cross the blood brain barrier to reach the CNS. They appear to be direct modulators of microglial activity, triggering/inhibiting inflammatory processes or enhancing/inhibiting the ability of these cells to respond to hazardous agents.

Sirt1 mediates improvement in cognitive defects induced by focal cerebral ischemia following hyperbaric oxygen preconditioning in rats

Hyperbaric oxygen preconditioning (HBO-PC) has been proposed as a safe and practical approach for neuroprotection in ischemic stroke. However, it is not known whether HPO-PC can improve cognitive deficits induced by cerebral ischemia, and the mechanistic basis for any beneficial effects remains unclear. We addressed this in the present study using rats subjected to middle cerebral artery occlusion (MCAO) as an ischemic stroke model following HBO-PC. Cognitive function and expression of phosphorylated neurofilament heavy polypeptide (pNF-H) and doublecortin (DCX) in the hippocampus were evaluated 14 days after reperfusion and after short interfering RNA-mediated knockdown of sirtuin1 (Sirt1). HBO-PC increased pNF-H and DCX expression and mitigated cognitive deficits in MCAO rats. However, these effects were abolished by Sirt1 knockdown. Our results suggest that HBO-PC can protect the brain from injury caused by ischemia-reperfusion and that Sirt1 is a potential molecular target for therapeutic approaches designed to minimize cognitive deficits caused by cerebral ischemia.

Transient cerebral ischemia induces albumin expression in microglia only in the CA1 region of the gerbil hippocampus

Albumin, the most abundant plasma protein, is known to exhibit a neuroprotective effect in animal models of focal and global cerebral ischemia. In the present study, the expression and immunoreactivity of albumin was examined in the hippocampus following 5 min of transient cerebral ischemia in gerbils. Albumin immunoreactivity was observed in microglia of the CA1 hippocampal region 2 days post-ischemic insult, and it was significantly increased at 4 days following ischemia-reperfusion. In addition, at 4 days post-ischemic insult, albumin-immunoreactive microglia were abundant in the stratum pyramidale of the CA1 region. The present results demonstrated that albumin was newly expressed post-injury in microglia in the CA1 region, suggesting ischemia-induced neuronal loss. Albumin expression may therefore be associated with ischemia-induced delayed neuronal death in the CA1 region following transient cerebral ischemia.

Concussions, Traumatic Brain Injury, and the Innovative Use of Omega-3s

Traumatic brain injury (TBI), with its diverse heterogeneity and prolonged secondary pathogenesis, remains a clinical challenge. Clinical studies thus far have failed to identify an effective treatment strategy when a combination of targets controlling aspects of neuroprotection, neuroinflammation, and neuroregeneration is needed. Omega-3 fatty acids (n-3FA) offer the advantage of this approach. Although further clinical trial research is needed, there is a growing body of strong preclinical evidence and clinical experience that suggests that benefits may be possible from aggressively adding substantial amounts of n-3FA to optimize the nutritional foundation of TBI, concussion, and postconcussion syndrome patients. Early and optimal doses of n-3FA, even in a prophylactic setting, have the potential to improve outcomes from this potentially devastating problem. With evidence of unsurpassed safety and tolerability, n-3FA should be considered mainstream, conventional medicine, if conventional medicine can overcome its inherent bias against nutritional, nonpharmacologic therapies.

Role of Antioxidants in Neonatal Hypoxic-Ischemic Brain Injury: New Therapeutic Approaches

Hypoxic-ischemic brain damage is an alarming health and economic problem in spite of the advances in neonatal care. It can cause mortality or detrimental neurological disorders such as cerebral palsy, motor impairment and cognitive deficits in neonates. When hypoxia-ischemia occurs, a multi-faceted cascade of events starts out, which can eventually cause cell death. Lower levels of oxygen due to reduced blood supply increase the production of reactive oxygen species, which leads to oxidative stress, a higher concentration of free cytosolic calcium and impaired mitochondrial function, triggering the activation of apoptotic pathways, DNA fragmentation and cell death. The high incidence of this type of lesion in newborns can be partly attributed to the fact that the developing brain is particularly vulnerable to oxidative stress. Since antioxidants can safely interact with free radicals and terminate that chain reaction before vital molecules are damaged, exogenous antioxidant therapy may have the potential to diminish cellular damage caused by hypoxia-ischemia. In this review, we focus on the neuroprotective effects of antioxidant treatments against perinatal hypoxic-ischemic brain injury, in the light of the most recent advances.

A Post-stroke Therapeutic Regimen with Omega-3 Polyunsaturated Fatty Acids that Promotes White Matter Integrity and Beneficial Microglial Responses after Cerebral Ischemia

White matter injury induced by ischemic stroke elicits sensorimotor impairments, which can be further deteriorated by persistent proinflammatory responses. We previously reported that delayed and repeated treatments with omega-3 polyunsaturated fatty acids (n-3 PUFAs) improve spatial cognitive functions and hippocampal integrity after ischemic stroke. In the present study, we report a post-stroke n-3 PUFA therapeutic regimen that not only confers protection against neuronal loss in the gray matter but also promotes white matter integrity. Beginning 2 h after 60 min of middle cerebral artery occlusion (MCAO), mice were randomly assigned to receive intraperitoneal docosahexaenoic acid (DHA) injections (10 mg/kg, daily for 14 days), alone or in combination with dietary fish oil (FO) supplements starting 5 days after MCAO. Sensorimotor functions, gray and white matter injury, and microglial responses were examined up to 28 days after MCAO. Our results showed that DHA and FO combined treatment-facilitated long-term sensorimotor recovery and demonstrated greater beneficial effect than DHA injections alone. Mechanistically, n-3 PUFAs not only offered direct protection on white matter components, such as oligodendrocytes, but also potentiated microglial M2 polarization, which may be important for white matter repair. Notably, the improved white matter integrity and increased M2 microglia were strongly linked to the mitigation of sensorimotor deficits after stroke upon n-3 PUFA treatments. Together, our results suggest that post-stroke DHA injections in combination with FO dietary supplement benefit white matter restoration and microglial responses, thereby dictating long-term functional improvements.

Delayed Docosahexaenoic Acid Treatment Combined with Dietary Supplementation of Omega-3 Fatty Acids Promotes Long-Term Neurovascular Restoration After Ischemic Stroke

Prophylactic dietary intake of omega-3 polyunsaturated fatty acids (n-3 PUFAs) has been shown to remarkably ameliorate ischemic brain injury. However, the therapeutic efficacy of n-3 PUFA administration post-stroke, especially its impact on neurovascular remodeling and long-term neurological recovery, has not been fully characterized thus far. In this study, we investigated the effect of n-3 PUFA supplementation, as well as in combination with docosahexaenoic acid (DHA) injections, on long-term stroke outcomes. Mice were subjected to transient middle cerebral artery occlusion (MCAO) before randomly assigned to four groups to receive the following: (1) low dose of n-3 PUFAs as the vehicle control, (2) intraperitoneal DHA injections, (3) n-3 PUFA dietary supplement, or (4) combined treatment of (2) and (3). Neurological deficits and brain atrophy, neurogenesis, angiogenesis, and glial scar formation were assessed up to 28 days after MCAO. Results revealed that groups 2 and 3 showed only marginal reduction in post-stroke tissue loss and attenuation of cognitive deficits. Interestingly, group 4 exhibited significantly reduced tissue atrophy and improved cognitive functions compared to groups 2 and 3 with just a single treatment. Mechanistically, the combined treatment promoted post-stroke neurogenesis and angiogenesis, as well as reduced glial scar formation, all of which significantly correlated with the improved spatial memory in the Morris water maze. These results demonstrate an effective therapeutic regimen to enhance neurovascular restoration and long-term cognitive recovery in the mouse model of MCAO. Combined post-stroke DHA treatment and n-3 PUFA dietary supplementation thus may be a potential clinically translatable therapy for stroke or related brain disorders.

Neuroprotection and antioxidants

Ischemia as a serious neurodegenerative disorder causes together with reperfusion injury many changes in nervous tissue. Most of the neuronal damage is caused by complex of biochemical reactions and substantial processes, such as protein agregation, reactions of free radicals, insufficient blood supply, glutamate excitotoxicity, and oxidative stress. The result of these processes can be apoptotic or necrotic cell death and it can lead to an irreversible damage. Therefore, neuroprotection and prevention of the neurodegeneration are highly important topics to study. There are several approaches to prevent the ischemic damage. Use of many modern therapeutical methods and the incorporation of several substances into the diet of patients is possible to stimulate the endogenous protective mechanisms and improve the life quality.

Nrf2/antioxidant defense pathway is involved in the neuroprotective effects of Sirt1 against focal cerebral ischemia in rats after hyperbaric oxygen preconditioning

Sirtuin 1 (Sirt1) is a class III histone deacetylase involved in neuroprotection induced by hyperbaric oxygen preconditioning (HBO-PC) in animal models of ischemia. However, the underlying mechanisms remain to be illustrated. In the present study, rats exposed to middle cerebral artery occlusion (MCAO) were used to establish an ischemic stroke model. The infarct volume ratio, neurobehavioral score, and expressions of Sirt1, nuclear factor erythroid 2-related factor 2 (Nrf2), heme oxygenase 1 (HO-1), and superoxide dismutase 1 (SOD1) were evaluated at 7 days after reperfusion, and the level of malondialdehyde (MDA) was used to assess oxidative stress. HBO-PC increased the expression of Sirt1 and reduced infarct volume ratio and neurobehavioral deficit in MCAO rats. Meanwhile, HBO-PC also increased expression of Nrf2, HO-1, and SOD1 and decreased MDA content. Furthermore, either Sirt1 or Nrf2 knockdown by short interfering RNA (siRNA) inhibited the expression of Nrf2, HO-1, and SOD1 and eliminated the neuroprotective effects of HBO-PC. Taken together, the results suggest that the Nrf2/antioxidant defense pathway is involved in the long lasting neuroprotective effects of Sirt1 induced by HBO-PC against transient focal cerebral ischemia.

Plasma non-esterified docosahexaenoic acid is the major pool supplying the brain

Despite being critical for normal brain function, the pools that supply docosahexaenoic acid (DHA) to the brain are not agreed upon. Using multiple kinetic models in free-living adult rats, we first demonstrate that DHA uptake from the plasma non-esterified fatty acid (NEFA) pool predicts brain uptake of DHA upon oral administration, which enters the plasma NEFA pool as well as multiple plasma esterified pools. The rate of DHA loss by the brain is similar to the uptake from the plasma NEFA pool. Furthermore, upon acute iv administration, although more radiolabeled lysophosphatidylcholine (LPC)-DHA enters the brain than NEFA-DHA, this is due to the longer plasma half-life and exposure to the brain. Direct comparison of the uptake rate of LPC-DHA and NEFA-DHA demonstrates that uptake of NEFA-DHA into the brain is 10-fold greater than LPC-DHA. In conclusion, plasma NEFA-DHA is the major plasma pool supplying the brain.

N-3 polyunsaturated fatty acids in animal models with neuroinflammation: An update

Neuroinflammation is a characteristic of a multitude of neurological and psychiatric disorders. Modulating inflammatory pathways offers a potential therapeutic target in these disorders. Omega-3 polyunsaturated fatty acids have anti-inflammatory and pro-resolving properties in the periphery, however, their effect on neuroinflammation is less studied. This review summarizes 61 animal studies that tested the effect of omega-3 polyunsaturated fatty acids on neuroinflammatory outcomes in vivo in various models including stroke, spinal cord injury, aging, Alzheimer's disease, Parkinson's disease, lipopolysaccharide and IL-1β injections, diabetes, neuropathic pain, traumatic brain injury, depression, surgically induced cognitive decline, whole body irradiation, amyotrophic lateral sclerosis, N-methyl-D-aspartate-induced excitotoxicity and lupus. The evidence presented in this review suggests anti-neuroinflammatory properties of omega-3 polyunsaturated fatty acids, however, it is not clear by which mechanism omega-3 polyunsaturated fatty acids exert their effect. Future research should aim to isolate the effect of omega-3 polyunsaturated fatty acids on neuroinflammatory signaling in vivo and elucidate the mechanisms underlying these effects.

Omega-3 polyunsaturated fatty acids and brain aging

PURPOSE OF REVIEW

The literature on the influence of dietary omega-3 polyunsaturated fatty acid (ω-3 PUFA) on brain aging has grown exponentially during the last decade. Many avenues have been explored but no global picture or clear evidence has emerged. Experimental studies have shown that ω-3 PUFA is involved in many neurobiological processes that are involved in neurotransmission and neuroprotection, indicating that these PUFAs may prevent age-related brain damage. Human studies have revealed only a weak link between ω-3 PUFA status and cognitive aging, whereas interventional studies have yet to confirm it. The purpose of this review is to analyze the developments in the area during the last 2 years.

RECENT FINDINGS

Human brain MRI studies have confirmed previous findings that ω-3 PUFA can protect the brain during aging; two intervention studies obtained clear evidence. We also analyzed the experimental data clarifying the involvement of ω-3 PUFA in neurotransmission, neuroprotection (including prevention of peroxidation, inflammation, and excitotoxicity), and neurogenesis, thereby helping the brain cope with aging.

SUMMARY

These recent human and experimental studies provide support for and clarification of how ω-3 PUFA protect against brain aging and highlight the main lines for future research.

Involvement of GPR40, a long-chain free fatty acid receptor, in the production of central post-stroke pain after global cerebral ischemia

Central post-stroke pain (CPSP), one of the complications of cerebral ischemia and neuropathic pain syndrome, is associated with specific somatosensory abnormalities. Although CPSP is a serious problem, detailed underlying mechanisms and standard treatments for CPSP are not well established. In this study, we assessed the role of GPR40, a long-chain fatty acid receptor, showing anti-nociceptive effects, in CPSP. We also examined the role of astrocytes in CPSP due to their effects in mediating the release of polyunsaturated fatty acids, which act as potential GPR40 ligands. The aim of this study was to determine the interactions between CPSP and astrocyte/GPR40 signaling. Male ddY mice were subjected to 30 min of bilateral carotid artery occlusion (BCAO). The development of hind paw mechanical hyperalgesia was measured after BCAO using the von Frey test. Neuronal damage was estimated by histological analysis on day 3 after BCAO. The thresholds for hind paw mechanical hyperalgesia were significantly decreased on days 1-28 after BCAO when compared with those of pre-BCAO assessments. BCAO-induced mechanical hyperalgesia was significantly decreased by intracerebroventricular injection of docosahexaenoic acid or GW9508, a GPR40 agonist; furthermore, these effects were reversed by GW1100, a GPR40 antagonist. The expression levels of glial fibrillary acidic protein, an astrocytic marker, and some free fatty acids were significantly decreased 5h after BCAO, although no effects of BCAO were noted on hypothalamic GPR40 protein expression. Our data show that BCAO-induced mechanical hyperalgesia is possible to be regulated by astrocyte activation and stimulation of GPR40 signaling.

The late phase of post-stroke neurorepair in aged rats is reflected by MRI-based measures

Non-invasive criteria determining the progress of brain healing are especially important in aging, providing a case-specific therapeutic strategy in populations with dysregulated neurorepair mechanisms. We hypothesized that temporal evolution of magnetic resonance imaging (MRI) of T2 tissue relaxation values correlate with neurological severity scores (NS), and provide a robust indicator of healing in the aging brain after stroke. Pre-treatment of aged rats with brain-only proton irradiation was undertaken to pre-condition the inflammatory system. Irradiation was performed 10days prior to right middle cerebral artery occlusion (MCAO) for 50min (MCAO+Rad). Control rats included naïve (no ischemia, no radiation), irradiated-only (Rad), irradiated ischemic, or ischemic-only (MCAO). MRI and NS were obtained at 3, 14 and 28days post-stroke. At 28days post-stroke, immunofluorescence for visualizing blood vessels (Von Willebrand factor; vWF), neurons (neuronal nuclear antigen; NeuN), astrocytes (glial fibrillary acidic protein; GFAP), activated microglia/macrophages (ionized calcium-binding adapter molecule 1, Iba1), T-lymphocytes (CD3), phagocytes (ED1) and apoptotic cells (caspase-3) was assessed. We found a positive T2-NS correlation in irradiated, ischemic rats that corresponded to late-stage brain recovery. Late-stage brain recovery was characterized by improved neovascularization, formation of glio-vascular complexes (visualized by GFAP/vWF) and enhanced neuronal viability (by NeuN/caspase-3) in the peri-lesional zone. The immune response plateaued at the late stage of repair as evidenced by significantly decreased expression (41.7%) and distribution of phagocytes (phagocytic rim decreased 44.6%). We also found reduced infiltration of T-lymphocytes (CD3) in the brain and normalization of blood lymphocytes. The observed T2-NS correlations may provide a simple MRI-based criterion for recognition of regenerative brain transformation in aged patients following stroke. Selective activation of innate immunity and accelerated transition from pro-inflammatory to pro-healing macrophage phenotypes induced by localized brain irradiation is a potential mechanism for enhancing repair ability in the elderly.