Pre-treatment with the synthetic antioxidant T-butyl bisphenol protects cerebral tissues from experimental ischemia reperfusion injury

Phenolic Compounds of Therapeutic Interest in Neuroprotection

The number of elderly people is projected to double in the next 50 years worldwide, resulting in an increased prevalence of neurodegenerative diseases. Aging causes changes in brain tissue homeostasis, thus contributing to the development of neurodegenerative disorders. Current treatments are not entirely effective, so alternative treatments or adjuvant agents are being actively sought. Antioxidant properties of phenolic compounds are of particular interest for neurodegenerative diseases whose psychopathological mechanisms strongly rely on oxidative stress at the brain level. Moreover, phenolic compounds display other advantages such as the permeability of the blood-brain barrier (BBB) and the interesting molecular mechanisms that we reviewed in this work. We began by briefly outlining the physiopathology of neurodegenerative diseases to understand the mechanisms that result in irreversible brain damage, then we provided an overall classification of the phenolic compounds that would be addressed later. We reviewed in vitro and in vivo studies, as well as some clinical trials in which neuroprotective mechanisms were demonstrated in models of different neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS), Alzheimer's disease (AD), Parkinson's disease (PD), ischemia, and traumatic brain injury (TBI).

Endoplasmic Reticulum Stress and the Unfolded Protein Response in Cerebral Ischemia/Reperfusion Injury

Ischemic stroke is an acute cerebrovascular disease characterized by sudden interruption of blood flow in a certain part of the brain, leading to serious disability and death. At present, treatment methods for ischemic stroke are limited to thrombolysis or thrombus removal, but the treatment window is very narrow. However, recovery of cerebral blood circulation further causes cerebral ischemia/reperfusion injury (CIRI). The endoplasmic reticulum (ER) plays an important role in protein secretion, membrane protein folding, transportation, and maintenance of intracellular calcium homeostasis. Endoplasmic reticulum stress (ERS) plays a crucial role in cerebral ischemia pathophysiology. Mild ERS helps improve cell tolerance and restore cell homeostasis; however, excessive or long-term ERS causes apoptotic pathway activation. Specifically, the protein kinase R-like endoplasmic reticulum kinase (PERK), activating transcription factor 6 (ATF6), and inositol-requiring enzyme 1 (IRE1) pathways are significantly activated following initiation of the unfolded protein response (UPR). CIRI-induced apoptosis leads to nerve cell death, which ultimately aggravates neurological deficits in patients. Therefore, it is necessary and important to comprehensively explore the mechanism of ERS in CIRI to identify methods for preserving brain cells and neuronal function after ischemia.

Favorable Effects of Astaxanthin on Brain Damage due to Ischemia- Reperfusion Injury

BACKGROUND

Activated inflammation and oxidant stress during cerebral ischemia reperfusion injury (IRI) lead to brain damage. Astaxanthin (ASX) is a type of carotenoid with a strong antioxidant effect.

OBJECTIVE

The aim of this study was to investigate the role of ASX on brain IRI.

METHODS

A total of 42 adult male Sprague-Dawley rats were divided into 3 groups as control (n=14) group, IRI (n=14) group and IRI + ASX (n=14) group. Cerebral ischemia was instituted by occluding middle cerebral artery for 120 minutes and subsequently, reperfusion was performed for 48 hours. Oxidant parameter levels and protein degradation products were evaluated. Hippocampal and cortex cell apoptosis, neuronal cell count, neurological deficit score were evaluated.

RESULTS

In the IRI group, oxidant parameter levels and protein degradation products in the tissue were increased compared to control group. However, these values were significantly decreased in the IRI + ASX group (p<0.05). There was a significant decrease in hippocampal and cortex cell apoptosis and a significant increase in the number of neuronal cells in the IRI + ASX group compared to the IRI group alone (p<0.05). The neurological deficit score which was significantly lower in the IRI group compared to the control group was found to be significantly improved in the IRI + ASX group (p<0.05).

CONCLUSION

Astaxanthin protects the brain from oxidative damage and reduces neuronal deficits due to IRI injury.

Dietary Fe3O4 Nanozymes Prevent the Injury of Neurons and Blood-Brain Barrier Integrity from Cerebral Ischemic Stroke

Cerebral ischemic stroke stimulates excessive reactive oxygen species, which lead to blood-brain-barrier disruption, neuron death, and aggravated cerebral infarction. Thus, it is critical to develop an antioxidant strategy for stroke treatment. Herein, we report a dietary strategy to promote stroke healing using iron oxide (Fe₃O₄) nanoparticles with intrinsic enzyme-like activities. We find that Fe₃O₄ nanozymes exhibit triple enzyme-like activities, peroxidase, catalase, and superoxide dismutase, thus potentially possessing the ability to regulate the ROS level. Importantly, intragastric administration of PEG-modified Fe₃O₄ nanozymes significantly reduces cerebral infarction and neuronal death in a rodent model following cerebral ischemic stroke. Ex vivo analysis shows that PEG-modified Fe₃O₄ nanozymes localize in the cerebral vasculature, ameliorate local redox state with decreased malondialdehyde and increased Cu/Zn SOD, and facilitate blood-brain-barrier recovery by elevating ZO-1 and Claudin-5 in the hippocampus. Altogether, our results suggest that dietary PEG-modified Fe₃O₄ nanozymes can facilitate blood-brain-barrier reconstruction and protect neurons following ischemic stroke.

Apigenin-7-O-β-D-(-6"-p-coumaroyl)-glucopyranoside treatment elicits a neuroprotective effect through GSK-3β phosphorylation-mediated Nrf2 activation

The current study was designed to seek the role of the glycogen synthase kinase-3β (GSK-β)-regulated NF-E2-related factor 2 (Nrf2) pathway in the antioxidant effect induced by Apigenin-7-O-β-D-(-6”-p-coumaroyl)-glucopyranoside (APG). Rat primary cultured cortical neurons were challenged by oxygen and glucose deprivation/reoxygenation (OGD/R) and then treated with APG. Cell viability, phosphorylation of GSK-β at Ser9 and nuclear expression of Nrf2 were measured. Male Sprague Dawley rats challenged by 2-h middle cerebral artery occlusion were treated with 50 mg/kg APG, and the neurological score, infarct volume, phosphorylation of GSK-3β and nuclear expression of Nrf2 were analyzed. The neuroprotective effect of APG and the expression levels of antioxidant enzymes and oxidative products were also examined in the presence and absence of Nrf2-siRNA and PI3K inhibitors. APG reduced the apoptotic proportion, attenuated LDH release and increased cell viability, and in vivo, APG improved neurological scores and reduced infarct volume. APG increased GSK-3β phosphorylation and Nrf2 nuclear translocation, while these effects were prevented by PI3K inhibitors or Nrf2-siRNA treatment in both OGD/R cell cultures and ischemic/reperfusion rats. These findings reveal that GSK-3β phosphorylation-mediated Nrf2 activation is involved in the neuroprotective effect of APG.

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.

Neuroprotective effect of total flavonoids from Ilex pubescens against focal cerebral ischemia/reperfusion injury in rats

Ilex pubescens is commonly used in traditional Chinese medicine to treat cardiovascular and cerebrovascular diseases, such as coronary artery disease and stroke. However, the underlying mechanisms remain to be fully elucidated. The aim of the present study was to investigate the effects of Ilex pubescens total flavonoids (IPTF) on neuroprotection and the potential mechanisms in a rat model of focal cerebral ischemia/reperfusion (I/R) injury. Rats were pretreated with intragastric administration of IPTF at doses of 200 and 100 mg/kg for 5 days; middle cerebral artery occlusion surgery was then performed to induce cerebral I/R injury. Neurological deficits were determined using the 5‑point neurological function score evaluation system, brain infarct sizes were determined by 2,3,5‑triphenyltetrazolium chloride staining and alterations in brain histology were determined by hematoxylin and eosin staining. The neurological deficit score, the infarcted area and the brain tissue pathological injury were significantly reduced when the rats were pretreated with IPTF. In addition, inflammatory mediators and neurotrophic factors in the brain were investigated. IPTF pretreatment decreased the activities of total nitric oxide synthase (TNOS), induced NOS (iNOS) and constitutive NOS (cNOS), and the levels of nitric oxide (NO), interleukin‑1β (IL‑1β) and tumor necrosis factor‑α (TNF‑α), however, it increased the levels of IL‑10 in brain tissues. Furthermore, pretreatment with IPTF also increased the protein expressions of brain‑derived neurotrophic factor, glial cell‑derived neurotrophic factor and vascular endothelial growth factor, when compared with the model group. In conclusion, the results of the present study demonstrated that IPTF has a neuroprotective effect against focal cerebral I/R injury in rats. The mechanism may be associated with the decreased production of certain proinflammatory cytokines including NO, IL‑1β, TNF‑α, TNOS, iNOS and cNOS, the increased production of the anti‑inflammatory cytokine IL‑10 and the increased secretion of neurotrophic factors.

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.

Vitamin D3 Reduces Tissue Damage and Oxidative Stress Caused by Exhaustive Exercise

Exhaustive exercise results in inflammation and oxidative stress, which can damage tissue. Previous studies have shown that vitamin D has both anti-inflammatory and antiperoxidative activity. Therefore, we aimed to test if vitamin D could reduce the damage caused by exhaustive exercise. Rats were randomized to one of four groups: control, vitamin D, exercise, and vitamin D+exercise. Exercised rats received an intravenous injection of vitamin D (1 ng/mL) or normal saline after exhaustive exercise. Blood pressure, heart rate, and blood samples were collected for biochemical testing. Histological examination and immunohistochemical (IHC) analyses were performed on lungs and kidneys after the animals were sacrificed. In comparison to the exercise group, blood markers of skeletal muscle damage, creatine kinase and lactate dehydrogenase, were significantly (P < 0.05) lower in the vitamin D+exercise group. The exercise group also had more severe tissue injury scores in the lungs (average of 2.4 ± 0.71) and kidneys (average of 3.3 ± 0.6) than the vitamin D-treated exercise group did (1.08 ± 0.57 and 1.16 ± 0.55). IHC staining showed that vitamin D reduced the oxidative product 4-Hydroxynonenal in exercised animals from 20.6% to 13.8% in the lungs and from 29.4% to 16.7% in the kidneys. In summary, postexercise intravenous injection of vitamin D can reduce the peroxidation induced by exhaustive exercise and ameliorate tissue damage, particularly in the kidneys and lungs.

Role of Natural Stilbenes in the Prevention of Cancer

Natural stilbenes are an important group of nonflavonoid phytochemicals of polyphenolic structure characterized by the presence of a 1,2-diphenylethylene nucleus. Stilbenes have an extraordinary potential for the prevention and treatment of different diseases, including cancer, due to their antioxidant, cell death activation, and anti-inflammatory properties which associate with low toxicity under in vivo conditions. This review aims to discuss various approaches related to their mechanisms of action, pharmacological activities in animal models and humans, and potential chemoprevention in clinical studies. The biological activity of natural stilbenes is still incompletely understood. Furthermore, after administration to animals or humans, these molecules are rapidly metabolized. Thus pharmacokinetics and/or activities of the natural structures and their metabolites may be very different. Novel drug formulations have been postulated in order to improve stability and bioavailability, to minimize side effects, and to facilitate interaction with their domains in target proteins. These pharmacological improvements should lead stilbenes to become effective candidates as anticancer drugs.